Low-Dimensional Architectures in Isomeric cis-PtCl₂{Ph₂PCH₂N(Ar)CH₂PPh₂} Complexes Using Regioselective-N(Aryl)-Group Manipulation

Abstract

The solid-state behaviour of two series of isomeric, phenol-substituted, aminomethylphosphines, as the free ligands and bound to Pt^II, have been extensively studied using single crystal X-ray crystallography. In the first library, isomeric diphosphines of the type Ph₂PCH₂N(Ar)CH₂PPh₂ [1a–e; Ar = C₆H₃(Me)(OH)] and, in the second library, amide-functionalised, isomeric ligands Ph₂PCH₂N{CH₂C(O)NH(Ar)}CH₂PPh₂ [2a–e; Ar = C₆H₃(Me)(OH)], were synthesised by reaction of Ph₂PCH₂OH and the appropriate amine in CH₃OH, and isolated as colourless solids or oils in good yield. The non-methyl, substituted diphosphines Ph₂PCH₂N{CH₂C(O)NH(Ar)}CH₂PPh₂ [2f, Ar = 3-C₆H₄(OH); 2g, Ar = 4-C₆H₄(OH)] and Ph₂PCH₂N(Ar)CH₂PPh₂ [3, Ar = 3-C₆H₄(OH)] were also prepared for comparative purposes. Reactions of 1a–e, 2a–g, or 3 with PtCl₂(η⁴-cod) afforded the corresponding square-planar complexes 4a–e, 5a–g, and 6 in good to high isolated yields. All new compounds were characterised using a range of spectroscopic (¹H, ³¹P{¹H}, FT–IR) and analytical techniques. Single crystal X-ray structures have been determined for 1a, 1b∙CH₃OH, 2f∙CH₃OH, 2g, 3, 4b∙(CH₃)₂SO, 4c∙CHCl₃, 4d∙½Et₂O, 4e∙½CHCl₃∙½CH₃OH, 5a∙½Et₂O, 5b, 5c∙¼H₂O, 5d∙Et₂O, and 6∙(CH₃)₂SO. The free phenolic group in 1b∙CH₃OH, 2f∙CH₃OH_, 2g, 4b∙(CH₃)₂SO, 5a∙½Et₂O, 5c∙¼H₂O, and 6∙(CH₃)₂SO exhibits various intra- or intermolecular O–H∙∙∙X (X = O, N, P, Cl) hydrogen contacts leading to different packing arrangements.

1. Introduction

Tertiary phosphines, and their phosphine oxides, have played an important role in the study of supramolecular and self-assembly processes [1,2,3]. Their synthetic versatility, coupled with ease of substituent modification, has no doubt played a significant contribution over the years. Hydrogen bonding interactions are routinely encountered in supramolecular ligand systems as illustrated by the elegant studies from Breit [4], Reek [5], and others [6,7]. More recently, amongst other common types of non-covalent interactions, those based on halogen bonding [8,9] and H^δ+∙∙∙H^δ− have been reported [10].

For a number of years, we [11,12,13,14,15,16], and others [17,18,19,20,21,22], have been interested in aminomethylphosphines, readily amenable by Mannich condensation reactions. Such interest stems from the relative ease of accessing P-monodentate ligands based on a P–C–N linker [11,15,16,19,20,22] or P/P-bidentate derivatives bearing a P–C–N–C–P backbone [12,13,14,17,18,19,21]. Previously, we have shown that the N-arene group can be easily tuned with, for example, various H-bonding donor/acceptor sites based on –CO₂H/OH groups [12,13,14,15,16]. In continuation of these studies, we report here our work on the regioselective positioning of amide/hydroxy and methyl groups within a series of aminomethylphosphines, both as the free ligands and when coordinated to a square-planar Pt(II) metal centre. Our rationale for introducing an –C(O)NH– group is based on the known use of this functionality in supramolecular chemistry [23] and, furthermore, the recent interest in amide-modified phosphines for their variable coordination chemistry [24,25,26], binding nitroaromatics [27], and relevance to catalysis based on Pd [28]. Our choice of metal fragment in this work, “cis-PtCl₂”, is based on its capability to support a relatively small bite angle diphosphine ligand in a cis, six-membered ring conformation, and to provide up to two “acceptor” sites for potential H-bonding [29]. For this purpose, we elected to pursue a double Mannich condensation reaction of Ph₂PCH₂OH with a series of isomeric primary amines bearing either OH/CH₃ groups and/or an amide spacer between the arene and P–C–N–C–P backbone (Chart 1).

2. Results and Discussion

2.1. Ligand Synthesis

We [11,12,13,14,15,16,29], and others [17,19,20,21,22], have previously used Mannich condensations as a versatile method for the synthesis of aminomethylphosphines. Accordingly, two equivalents of Ph₂PCH₂OH were reacted with one equivalent of the amine, for 24 h at r.t. under N₂, yielding the desired phenol-substituted ditertiary phosphines 1a–e and 3 (Scheme 1).

For 1a–e, colourless solids were isolated in 38–97% yields and found to be air stable in the solid state, but oxidise rapidly in solution. Compounds 1a–e and 3 exhibit single resonances in their ³¹P{¹H} NMR spectra (in d⁶-dmso) around δ(P) −26 ppm [12,13,14,15,29], indicating the presence of only one P^III environment. The ligands were also characterised by ¹H NMR, FT–IR, and elemental analysis (

Table 1. Selected spectroscopic and analytical data for compounds 1a–3 ^a.

Com-pound a	δ(P) b	δ(H) /OH (NH)	δ(H) /arom. H.	δ(H) /CH2	δ(H) /CH2 d	δ(H) /CH3	νOH (νNH) e	Microanalysis (CHN)
1a (79)	−27.5	8.62	7.33–7.23, 6.76, 6.69–6.57		4.15 (2.4)	2.10	3398	Calc. for C33H31NOP2, C, 76.29; H, 6.01; N, 2.70 Found, C, 76.07; H, 6.13; N, 2.78
1b (56)	−27.3	9.06	7.36–7.26, 7.15, 6.50, 6.44		3.96 (5.6)	1.74	3282	Calc. for C33H31NOP2.2MeOH, C, 72.03; H, 6.74; N, 2.40 Found, C, 72.45; H, 6.04; N, 2.58
1c (97)	−27.5	8.77	7.44–7.22, 6.86, 6.54, 6.48		4.09 (3.4)	2.12	3389	Calc. for C33H31NOP2, C, 76.29; H, 6.01; N, 2.70 Found, C, 75.99; H, 6.00; N, 2.76
1d (38)	−26.7	8.63	7.40–7.30, 6.55		4.02 (3.2)	1.96	3432	Calc. for C33H31NOP2, C, 76.29; H, 6.01; N, 2.70 Found, C, 75.53; H, 6.05; N, 2.74
1e (96)	−26.4	9.06	7.49–7.33, 6.85, 6.50, 6.27		3.88 (3.6)	2.08	3387	Calc. for C33H31NOP2.MeOH, C, 74.03; H, 6.40; N, 2.54 Found, C, 74.81; H, 5.93; N, 2.61
2a (81)	−26.0	8.15	7.77–7.19	5.06	3.62 (8.0)	1.19	-	-
2b (89)	−26.0	7.83	7.60–7.21	5.07	3.69 (3.6)	1.63	-	-
2c (88)	−26.5 c	9.34 (8.17)	7.71–7.19	5.27	3.61 (4.8)	1.63	-	-
2d (65)	−27.1	9.05 (8.68)	7.55–7.32, 6.95, 6.61, 6.41	3.69	3.81 (4.8)	2.04	3047 (3228)	Calc. for C35H34N2O2P2, C, 72.91; H, 5.94; N, 4.86 Found, C, 72.72; H, 5.95; N, 4.88
2e (80)	−27.1	9.29 (9.08)	7.46–7.35, 7.29, 6.86, 6.15	3.73	3.82 (4.4)	2.08	3178 (3317)	Calc. for C35H34N2O2P2, C, 72.91; H, 5.94; N, 4.86 Found, C, 72.71; H, 5.94; N, 4.82
2f (70)	−27.5	9.31 (9.07)	7.41–7.03, 6.94, 6.40, 6.30	3.69	3.77 (4.4)		3163 (3283)	Calc. for C34H32N2O2P2, C, 72.59; H, 5.73; N, 4.98 Found, C, 72.10; H, 5.80; N, 4.95
2g (85)	−26.8	9.09 (8.78)	7.36–7.25, 6.83, 6.53	3.61	3.72 (4.4)		3300 (3257)	Calc. for C34H32N2O2P2, C, 72.59; H, 5.73; N, 4.98 Found, C, 72.15; H, 5.72; N, 4.95
3 (53)	−27.6	9.12	7.38–7.31, 6.92, 6.30, 6.13		3.85		3376	Calc. for C32H29NOP2, C, 76.03; H, 5.78; N, 2.77 Found, C, 75.67; H, 5.71; N, 2.74

^a Isolated yields in parentheses. ^b Recorded in (CD₃)₂SO unless otherwise stated. ^c Recorded in CDCl₃. ^{d 2}J(PH) coupling in brackets. ^e Recorded as KBr discs.

). In particular, the absence of an NH resonance, in the ¹H NMR spectra, confirmed that double condensation had occurred.

The synthesis of ditertiary phosphines, containing a flexible backbone presenting extra donor/acceptor sites with additional H-bonding capability, is described here with the opportunity to enhance solid-state packing behaviour. The precursors for the synthesis of the desired functionalised ditertiary phosphines 2a–g were prepared using, in step (i), 1 equiv. of primary amine, N-carbobenzyloxyglycine (1 equiv.) and dicyclohexylcarbodiimide (DCC, 1 equiv.) in THF affording the corresponding carbamates followed by, in step (ii), treatment with Pd/C and cyclohexene in C₂H₅OH, to give the desired primary alkylamines in moderate to good yields [30,31]. Using a similar procedure to that described for 1a–e, the amide-functionalised diphosphines 2a–e were prepared in 65–89% yields by condensation using 1 equiv. of primary amine and two equiv. of Ph₂PCH₂OH at r.t. in CH₃OH (Scheme 1). Furthermore, the phenol-substituted phosphines 2f and 2g were synthesised to investigate what effect, if any, an absent methyl group on the N-arene ring displays. In the case of 2d–g, the diphosphines were obtained as solids whereas 2a–c were obtained as yellow oils that were sufficiently pure to be used in complexation studies. All compounds displayed a single ³¹P NMR resonance around δ(P) −26 ppm [12,13,14,15,29] indicating the inclusion of an amide spacer has negligible effect on the ³¹P chemical shift. Other spectroscopic and analytical data are given in Table 1.

2.2. Single Crystal X-ray Studies of 1a, 1b∙CH₃OH_, 2f∙CH₃OH, 2g, and 3

X-ray quality crystals of 1a, 1b∙CH₃OH_, 2f∙CH₃OH, 2g, and 3 were obtained by slow evaporation of a methanol solution, while for 2g diethyl ether was diffused into a deuterochloroform/methanol solution (

Table 2. Details of the X-ray data collections and refinements for compounds 1a, 1b·CH₃OH, 2f·CH₃OH, 2g, and 3.

Compound	1a	1b·CH3OH	2f·CH3OH	2g	3
Formula	C33H31NOP2	C34H35NO2P2	C35H36N2O3P2	C34H32N2O2P2	C32H29NOP2
M	519.53	551.57	594.60	562.55	505.50
Crystal dimensions	0.42 × 0.15 × 0.03	0.13 × 0.12 × 0.02	0.24 × 0.18 × 0.16	0.25 × 0.18 × 0.15	0.31 × 0.28 × 0.03
Crystal morphology and colour	Plate, colourless	Block, colourless	Block, colourless	Block, colourless	Plate, colourless
Crystal system	Monoclinic	Monoclinic	Triclinic	Monoclinic	Triclinic
Space group	P21/n	P21/c	P$\overline{1}$	Ia	P$\overline{1}$
a/Å	17.367(5)	10.3050(3)	12.6198(3)	11.6234(10)	10.5860(4)
b/Å	8.522(2)	32.8017(10)	16.2027(4)	21.7359(19)	10.7397(4)
c/Å	20.382(6)	8.5189(2)	17.8529(4)	11.6340(10)	13.4172(6)
α/°			64.0678(10)		73.1667(6)
β/°	114.673(4)	92.7318(16)	76.7403(14)	93.8717(14)	80.4518(7)
γ/°			75.5070(14)		63.1422(6)
V/Å3	2741.2(13)	2876.30(14)	3148.15(13)	2932.6(4)	1301.45(9)
Z	4	4	4	4	2
λ/Å	0.71073	0.71073	0.71073	0.71073	0.71073
Τ/Κ	150(2)	120(2)	120(2)	150(2)	150(2)
Density (calcd.)/Mg/m3	1.259	1.274	1.255	1.274	1.290
μ/mm−1	0.185	0.183	0.176	0.182	0.193
θ range/°	2.02–26.60	3.03–27.53	3.24–25.00	1.87–28.82	1.59–30.62
Measured reflections	23,525	27,247	61,330	12,577	15,576
Independent reflections	5708	6545	11,047	6586	7814
Observed reflections (F2 > 2σ(F2))	3115	5019	7559	5293	6116
Rint	0.124	0.058	0.095	0.039	0.027
R[F2 > 2σ(F2)] a	0.0743	0.0799	0.0517	0.0389	0.0441
wR2 [all data] b	0.2205	0.1650	0.1220	0.0861	0.1248
Largest difference map features/eÅ−3	1.40, −0.49	0.46, −0.52	0.38, −0.30	0.29, −0.16	0.51, −0.21

^a R = ∑||Fo| − |Fc||/∑|Fo|. ^b wR2 = [∑[w(Fo² − Fc²)²]/∑[w(Fo²)²]]^1/2.

).

The geometry around each phosphorus atom is essentially pyramidal as would be anticipated (Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5). The P^III atoms are in an anti conformation, presumably to minimise steric repulsions between the phenyl groups. The geometry about the N(1) centre is approx. pyramidal [Σ(C–N(1)–C) angles: 337.0(3)° for 1a; 335(2)° for 1b∙CH₃OH; 335.2(2)/336.6(2)° for 2f∙CH₃OH; 333.7(2)° for 2g] and approximately trigonal planar for 3 [Σ(C–N–C) = 359.05(11)°]. In 1a and 1b∙CH₃OH, the N-arene ring [C(3) > C(8)] is twisted by ca. 88° (1a) and 86° (1b∙CH₃OH) [12,32] such that it is almost perpendicular to the C(1)–N(1)–C(2) plane, whereas for 3, the twist of the C(1)–N(1)–C(2) fragment is around 9° from co-planarity with the N-arene group, apparently as a result of the intermolecular H-bonding requirements (vide infra).

2.3. Secondary Interactions in 1a, 1b∙CH₃OH, 2f∙CH₃OH, 2g, and 3

The synthons observed in the solid state for these highly modular ligands may be dictated by various factors including the nature of the ligand, the flexibility of the P–C–N–C–P backbone, the predisposition of the OH/CH₃ groups about the N-arene ring, and the solvent used in the crystallisation. In order to probe the OH/CH₃ interplay of groups, the crystal structure of 1a, with the –OH group in the ortho position with respect to the N(1) atom, is described first. Ligand 1a crystallises with an intramolecular S(5) [33,34,35] H-bonded ring with d = 2.26(5) Å [denoting the hydrogen (H) to acceptor (A) distance in an H-bond D–H···A] [36] for the O–H···N interaction (Figure 1). The intramolecular H-bonding in 1a limits the dimensionality of the packing of the diphosphine ligand. Therefore, the structure of 1a is essentially zero-dimensional (

Table 3. Selected data (D···A/Å, ∠D–H···A/°) for key inter- and intramolecular contacts for compounds 1a, 1b·CH₃OH, 2f·CH₃OH, 2g, and 3.

	1a	1b·CH3OH	2f·CH3OH a	2g	3
O–H···Nintra	2.745(4), 119(4)
O–HMeOH···Ointer O–HMeOH···OMeOH		2.844(8), 157 2.781(11), 172
O–H···Pinter		3.432(3), 173			3.4400(12), 167(2)
O–H···(O)Cinter			2.671(3), 171(3) [2.659(3), 165(3)]	2.706(4), 169(4)
N–H···Nintra			2.695(3), 114(2) [2.714(3), 117(2)]	2.748(4), 114(3)

^a Values in parentheses are for the second independent molecule.

).

Compound 3, where the −OH functional group is in the meta position with respect to the tertiary N(1) atom, aggregates in the solid state in such a way that fairly weak hydrogen bonds, O−H···P [d = 2.60(2) Å], form between symmetry-related molecules, creating dimers in which two ligands are held in an R²₂(16) H-bonding motif (Figure 2). The distance between symmetry-related nitrogen atoms is 8.257 Å. The structure of 3 shows a 0D arrangement.

Compound 1b∙CH₃OH, which contains the −OH group in a para position with respect to the N-arene, displays a similar structure to 3 with intramolecular O–H···P interactions at d = 2.60 Å. However, instead of forming dimers, there are 1D zig-zag chains in the c direction (Figure 3). The para hydroxyl oxygen acts as an acceptor for an O–H···O intermolecular H-bond from approximately alternate CH₃OH molecules of crystallisation with d = 2.05 Å. These CH₃OH molecules are 50/50 disordered with the second component H-bonding to its neighbour with d = 1.95 Å. Selected hydrogen parameters for 1b∙CH₃OH are listed in Table 3.

Compound 2f∙CH₃OH crystallises with two, similarly behaved, molecules in the asymmetric unit. A pair of H-bonded molecules, related by inversion symmetry, and with d = 1.81(3) Å for the intermolecular O–H···O interaction [1.78(3) Å for molecule 2] affords R²₂(16) ring motifs (Figure 4). The intramolecular N–H∙∙∙N S(5) H-bond motif with d = 2.25(3) Å [2.26(3) Å for molecule 2] results in an intermediate twist angle of 64.23(13)° [but a rather more perpendicular 78.70(8)° for molecule 2] between planes C(1)/N(1)/C(2) and ring C(5) > C(10) [plane C(35)/N(4)/C(36) and ring C(39) > C(44) for molecule 2]. The meta hydroxy group in 2f facilitates 0D dimer formation, as opposed to the chains observed in 2g (vida infra).

For 2g, molecules form H-bonded, 1D, zig-zag chains in the c direction via strong O–H∙∙∙O interactions with d = 1.83(5) Å (Figure 5). The intramolecular N–H∙∙∙N S(5), H-bond motif with d = 2.29(3) Å again results in an almost perpendicular twist angle of 82.09(15)° between planes C(1)/N(1)/C(2) and arene ring C(5) > C(10). The para hydroxy group promotes chain formation.

2.4. Dichloroplatinum(II) Complexes of 1a–e, 2a–g, and 3

The synthesis of P,P-chelate complexes cis-PtCl₂(1a–e) [4a–e], cis-PtCl₂(2a–g) [5a–g], and cis-PtCl₂(3) [6] (Chart 2) was achieved by stirring the ligands and PtCl₂(η⁴-cod) (1:1 ratio) in CH₂Cl₂ for 1.5 h with displacement of the cod ligand. The products were isolated in good yields as colourless solids. Downfield shifts of the ³¹P NMR resonances were observed for all complexes, with ¹J_PtP coupling constants of approx. 3400 Hz, indicative of a cis conformation [29]. This was further supported by two characteristic ν_PtCl IR vibrations in the range of 279–316 cm⁻¹ (

Table 4. Selected spectroscopic and analytical data for compounds 4a–6 ^a.

Com-pound a	δ(P) b	δ(H) /OH (NH)	δ(H) /arom. H.	δ(H) /CH2	δ(H) /CH2	δ(H) /CH3	νOH (νNH) f	νPtCl	Microanalysis (CHN)
4a (98)	−9.4 d (3424)	9.25	7.89–7.80, 7.64–7.46, 6.68, 5.90		4.21	1.93	3314	316, 289	Calc. for C33H31Cl2NOP2Pt.CH2Cl2, C, 46.91; H, 3.82; N, 1.61 Found, C, 47.07; H, 3.77; N, 1.69
4b (89)	−4.9 d (3426)	9.22	7.96–7.53, 6.96, 6.49, 6.33		4.19	1.29	3373	315, 282	Calc. for C33H31Cl2NOP2Pt, C, 50.46; H, 3.98; N, 1.78 Found, C, 50.51; H, 4.13; N, 1.83
4c (78)	−8.6 d (3436)	9.42	7.89–7.84, 7.56–7.43, 6.59, 6.30, 6.05		4.16	2.06	3433	309, 290	Calc. for C33H31Cl2NOP2Pt.0.5CH2Cl2, C, 48.96; H, 3.87; N, 1.68 Found, C, 49.42; H, 3.96; N, 1.73
4d (98)	−11.7 d (3410)	8.44	7.94–7.87, 7.78–7.62, 6.86, 6.47		4.43	2.02	3421	314, 290	Calc. for C33H31Cl2NOP2Pt, C, 50.46; H, 3.98; N, 1.78 Found, C, 50.24; H, 3.98; N, 1.85
4e (81)	−7.8 d (3421)	9.01	7.96–7.85, 7.59–7.45, 6.75, 6.27, 6.03		4.33	2.09	3416	316, 284	Calc. for C33H31Cl2NOP2Pt, C, 50.46; H, 3.98; N, 1.78 Found, C, 50.66; H, 4.61; N, 1.70
5a (89)	−9.8 d,e (3398)	9.45 (8.91)	7.84–7.80, 7.53–7.44, 6.69	3.49	4.05	2.22	3051 (3249)	305, 283	Calc. for C35H34Cl2N2O2P2Pt.0.5CH2Cl2, C, 48.63; H, 3.74; N, 3.15 Found, C, 49.00; H, 4.07; N, 3.13
5b (65)	−11.0 d (3397)	9.16 (8.61)	7.83–7.80, 7.57–7.41, 7.05, 6.48	4.03	4.03	1.80	3050 (3350)	316, 283	Calc. for C35H34Cl2N2O2P2Pt, C, 49.89; H, 4.07; N, 3.32 Found, C, 49.32; H, 4.17; N, 3.25
5c (73)	−9.9 d (3405)	9.56 (8.94)	7.85–7.77, 7.59–7.38, 6.63, 6.51	3.17	4.05	2.17	3075 (3347)	315, 290	Calc. for C35H34Cl2N2O2P2Pt, C, 49.89; H, 4.07; N, 3.32 Found, C, 49.28; H, 4.05; N, 2.91
5d (99)	−9.8 c,d (3406)	9.17 (8.90)	7.98–7.50, 6.97–6.84, 6.68, 6.73	3.20	4.66	2.13	3323 (3465)	309, 283	Calc. for C35H34Cl2N2O2P2Pt.0.5C4H10O, C, 50.52; H, 4.47; N, 3.19 Found, C, 50.91; H, 4.53; N, 3.61
5e (90)	−9.7 c,d (3406)	9.46 (9.21)	7.94–7.78, 7.54–7.42, 7.09, 6.87, 6.69	3.43	4.12	2.02	3287 (3439)	312, 286	Calc. for C35H34Cl2N2O2P2Pt, C, 49.89; H, 4.07; N, 3.32 Found, C, 49.77; H, 3.95; N, 3.38
5f (85)	−9.5 c,d (3425)	9.62 (9.36)	7.91–7.86, 7.60–7.42, 7.05, 6.83, 6.45	3.47	4.18		3053 (3312)	304, 279	Calc. for C34H32Cl2N2O2P2Pt, C, 49.29; H, 3.89; N, 3.38 Found, C, 48.98; H, 3.38; N, 3.37
5g (84)	−9.5 c,d (3405)	9.52 (9.31)	8.01–7.97, 7.70–7.61, 7.34, 6.78	3.49	4.26		3054 (3325)	311, 287	Calc. for C34H32Cl2N2O2P2Pt, C, 49.29; H, 3.89; N, 3.38 Found, C, 48.72; H, 3.66; N, 3.33
6 (89)	−4.0 d (3436)	8.45	7.45–7.05, 6.89–6.76, 6.31,		4.31		3356	311, 289	Calc. for C32H29Cl2NOP2Pt, C, 49.82; H, 3.79; N, 1.82 Found, C, 49.31; H, 3.58; N, 1.79

^a Isolated yields in parentheses. ^b Recorded in (CD₃)₂SO unless otherwise stated. ^c Recorded in CDCl₃.^{d 1}J(PtP) coupling in parentheses. ^e Recorded in CDCl₃/CD₃OD. ^f Recorded as KBr discs.

). Furthermore, compounds 4a–e, 5a–g, and 6 present ν(NH) and ν(OH) IR absorptions in the range 3050–3465 cm^–1 and also a strong band in the region of 1653–1675 cm^–1, indicative of ν(C=O amide).

2.5. Single Crystal X-ray Studies of Complexes 4b∙(CH₃)₂SO, 4c∙CHCl₃, 4d∙½Et₂O, 4e∙½CHCl₃∙½CH₃OH, 5a∙½Et₂O, 5b, 5c∙¼H₂O, 5d∙Et₂O, and 6∙(CH₃)₂SO

Detailed single crystal X-ray analysis (

Table 5. Details of the X-ray data collections and refinements for compounds 4b·(CH₃)₂SO, 4c·CHCl₃, 4d·½OEt₂, and 4e·½CHCl₃·½CH₃OH.

Compound	4b·(CH3)2SO	4c·CHCl3	4d·½OEt2	4e·½CHCl3·½CH3OH
Formula	C35H37Cl2NO2P2PtS	C34H32Cl5NOP2Pt	C35H36Cl2NO1.5P2Pt	C34H33.5Cl3.5NO1.5P2Pt
M	863.64	904.88	822.58	861.22
Crystal dimensions	0.19 × 0.02 × 0.01	0.30 × 0.18 × 0.04	0.13 × 0.06 × 0.03	0.15 × 0.04 × 0.02
Crystal morphology and colour	Needle, colourless	Plate, colourless	Lath, colourless	Needle, colourless
Crystal system	Tetragonal	Monoclinic	Monoclinic	Monoclinic
Space group	P43	P21/n	P21/c	P21/n
a/Å	11.373(3)	11.6938(4)	15.7344(6)	21.4521(4)
b/Å		16.7052(6)	17.0714(6)	12.5164(2)
c/Å	26.773(6)	18.2242(7)	13.9632(5)	24.5837(4)
α/°
β/°		99.7066(6)	92.0800(4)	92.2343(5)
γ/°
V/Å3	3463(2)	3509.1(2)	3748.2(2)	6595.78(19)
Z	4	4	4	8
λ/Å	0.71073	0.71073	0.6710	0.71073
Τ/Κ	150(2)	150(2)	150(2)	120(2)
Density (calcd.)/Mg/m3	1.657	1.713	1.458	1.735
μ/mm−1	4.391	4.500	3.425	4.666
θ range/°	1.79–26.09	1.67–31.09	1.78–31.10	2.94–27.49
Measured reflections	29,848	32,600	48,268	84,353
Independent reflections	6852	10,997	13,239	15,063
Observed reflections (F2 > 2σ(F2))	5560	8926	10,918	12,905
Rint	0.110	0.043	0.039	0.049
R[F2 > 2σ(F2)] a	0.0473	0.0303	0.0266	0.0561
wR2 [all data] b	0.1015	0.0660	0.0646	0.1202
Largest difference map features/eÅ−3	1.43, −0.91	1.29, −1.08	0.84, −0.67	1.64, −1.48

^a R = ∑||Fo| − |Fc||/∑|Fo|. ^b wR2 = [∑[w(Fo² − Fc²)²]/∑[w(Fo²)²]]^1/2.

and

Table 6. Details of the X-ray data collections and refinements for compounds 5a ½OEt₂, 5b, 5c·¼H₂O, 5d OEt₂, and 6 (CH₃)₂SO.

Compound	5a·½OEt2	5b	5c·¼H2O	5d·OEt2	6·(CH3)2SO
Formula	C37H39Cl2N2O2.50P2Pt	C35H34Cl2N2O2P2Pt	C35H34.5Cl2N2O2.25P2Pt	C39H44Cl2N2O3P2Pt	C34H35Cl2NO2P2PtS
M	879.63	842.57	842.57	916.69	849.62
Crystal dimensions	0.12 × 0.06 × 0.05	0.05 × 0.02 × 0.01	0.09 × 0.05 × 0.02	0.13 × 0.12 × 0.02	0.32 × 0.11 × 0.02
Crystal morphology and colour	Block, colourless	Plate, colourless	Plate, colourless	Plate, colourless	Needle, colourless
Crystal system	Trigonal	Monoclinic	Triclinic	Orthorhombic	Monoclinic
Space group	P32	P21/n	P$\overline{1}$	Pbcm	P21/n
a/Å	24.3688(7)	18.2384(7)	8.4021(6)	10.125(6)	9.7763(4)
b/Å		8.1955(3)	10.3896(7)	19.790(11)	13.0930(5)
c/Å	10.6567(6)	23.5809(10)	21.8810(15)	18.407(10)	25.8715(10)
α/°			92.8380(10)
β/°		111.4543(5)	97.9841(9)		95.1690(6)
γ/°			106.6253(8)
V/Å3	5480.5(4)	3280.5(2)	1804.5(2)	3688(4)	3298.1(2)
Z	6	4	2	4	4
λ/Å	0.7848	0.6910	0.6710	0.71073	0.71073
Τ/Κ	150(2)	120(2)	150(2)	150(2)	150(2)
Density (calcd.)/Mg/m3	1.599	1.706	1.559	1.651	1.711
μ/mm−1	5.266	4.225	3.561	4.077	4.609
θ range/°	3.69–33.17	1.19–31.01	2.71–30.94	2.01–25.00	1.58–30.64
Measured reflections	48,822	37,553	22,910	25,092	38,887
Independent reflections	19,298	10,642	12,184	3357	10,104
Observed reflections (F2 > 2σ(F2))	17,145	8283	10,104	2051	7753
Rint	0.071	0.063	0.053	0.1504	0.0572
R[F2 > 2σ(F2)] a	0.0542	0.0363	0.0507	0.0746	0.0356
wR2 [all data] b	0.1551	0.0842	0.1341	0.2065	0.0816
Largest difference map features/eÅ−3	1.59, −1.71	1.40, −1.47	2.34, −3.46	2.77, −1.91	1.97, −1.50

^a R = ∑||Fo| − |Fc||/∑|Fo|. ^b wR2 = [∑[w(Fo² − Fc²)²]/∑[w(Fo²)²]]^1/2.

) of complexes 4b∙(CH₃)₂SO, 4c∙CHCl₃, 4d∙½Et₂O, 4e∙½CHCl₃∙½CH₃OH, 5a∙½Et₂O, 5b, 5c∙¼H₂O, 5d∙Et₂O, and 6∙(CH₃)₂SO shows that the geometry about each Pt(II) centre is approximately square planar [P–Pt–P range 90.23(9)–96.52(3)°] (

Table 7. Selected bond distances and angles for dichloroplatinum(II) compounds 4b·(CH₃)₂SO, 4c·CHCl₃, 4d, and 4e·½CHCl_3·½CH₃OH.

Bond Length (Å)	4b·(CH3)2SO	4c·CHCl3	4d	4e·½CHCl3·½MeOH a
Pt(1)–P(1)	2.223(4)	2.2226(6)	2.2257(6)	2.2386(18) [2.2353(18)]
Pt(1)–P(2)	2.225(4)	2.2186(7)	2.2146(6)	2.2475(18) [2.2464(18)]
Pt(1)–Cl(1)	2.358(4)	2.3625(6)	2.3558(6)	2.3560(18) [2.3574(17)]
Pt(1)–Cl(2)	2.359(4)	2.3484(6)	2.3553(6)	2.3694(17) [2.3616(18)]
Bond angle (°)
Cl(1)–Pt(1)–P(1)	87.91(14)	86.12(2)	87.63(2)	87.30(7) [86.87(7)]
Cl(1)–Pt(1)–P(2)	174.97(15)	176.08(3)	175.93(2)	176.50(7) [176.84(7)]
Cl(1)–Pt(1)–Cl(2)	88.95(13)	88.68(2)	90.43(2)	88.13(7) [87.34(7)]
Cl(2)–Pt(1)–P(2)	86.71(13)	88.94(2)	85.53(2)	88.54(7) [90.04(7)]
Cl(2)–Pt(1)–P(1)	176.37(15)	174.73(2)	177.81(2)	169.14(7) [170.73(7)]
P(1)–Pt(1)–P(2)	96.35(14)	96.30(3)	96.42(2)	96.17(7) [95.95(7)]

^a Values in parentheses are for the second independent molecule.

and

Table 8. Selected bond distances and angles for dichloroplatinum(II) compounds 5a·½OEt₂, 5b, 5c·¼H₂O, 5d·OEt₂, and 6·(CH₃)₂SO.

Bond Length (Å)	5a·½OEt2 a	5b	5c·¼H2O	5d·OEt2	6·(CH3)2SO
Pt(1)–P(1)	2.233(3) [2.234(3)]	2.2172(9)	2.2268(12)	2.220(3)	2.2219(9)
Pt(1)–P(2)	2.230(3) [2.229(3)]	2.2249(9)	2.2196(12)	c	2.2288(9)
Pt(1)–Cl(1)	2.381(3) [2.378(3)]	2.3685(9)	2.347(4) b	2.348(3)	2.3421(9)
Pt(1)–Cl(2)	2.361(3) [2.365(3)	2.3425(9)	2.3638(12)	c	2.3618(10)
Bond angle (°)
Cl(1)–Pt(1)–P(1)	86.31(10) [86.48(10)]	85.73(3)	92.55(11)	89.98(12)	88.81(3)
Cl(1)–Pt(1)–P(2)	177.81(12) [177.51(12)]	176.29(3)	167.1(2)	176.96(13)	173.98(3)
Cl(1)–Pt(1)–Cl(2)	90.20(13) [90.16(13)]	89.33(3)	88.17(11)	87.38(17)	88.78(4)
Cl(2)–Pt(1)–P(2)	87.75(14) [87.51(13)]	88.31(3)	87.76(4)	89.98(12)	87.17(3)
Cl(2)–Pt(1)–P(1)	175.76(12) [175.67(12)]	174.72(3)	178.70(5)	176.96(13)	174.52(4)
P(1)–Pt(1)–P(2)	90.20(13) [95.81(11)]	96.52(3)	91.30(4)	92.62(17)	94.83(3)

^a Values in parentheses are for the second independent molecule. ^b 2-fold disorder. ^c Molecule lies on a mirror plane.

). The Pt–Cl and Pt–P bond distances are consistent with literature values [29] and the conformation of the Pt–P–C–N–C–P six-membered ring in each complex is best described as a boat. The dihedral angle measured between the P₂C₂ plane and N-arene ring least-squares planes varies between 50.98(12)° [in 6∙(CH₃)₂SO] and 90° (in 5d∙Et₂O), the difference of ca. 39° may tentatively be explained by the predisposition of the –OH group about the N-arene group and subsequent H-bonding requirements. Upon metal chelation, a degree of freedom, compared with the free ligands 1a, 1b∙CH₃OH_, 2f∙CH₃OH, 2g, and 3 has been removed, as the P–C–N–C–P backbone is locked into a specific conformation. Unfortunately, we were unable to obtain suitable X-ray quality crystals of compounds 4a and 5e–g.

Despite the ortho position of the hydroxy group in 4c∙CHCl₃, molecules do not form an intramolecular S(5) O–H∙∙∙N interaction as seen in 1a (Figure 1), instead forming a bifurcated H-bond with the two coordinated chloride ligands of an adjacent molecule (Figure 6). This generates a 1D chain, and also attracts a bifurcated H-bonded chloroform molecule. There are somewhat asymmetric distances d for H(1C) to Cl(1) and Cl(2) are 2.45(4) and 2.76(4) Å, while those from H(34) to Cl(1) and Cl(2) are 2.66 and 2.86 Å, so are also asymmetric. The twist angle between planes P(1)/P(2)/C(1)/C(2) and ring C(3) > C(8) is 84.83(8)°, so is almost perpendicular. Atoms N(1) and Pt(1) lie 0.795(4) and 0.024(2) Å away from the P(1)/P(2)/C(1)/C(2) plane, respectively. The hinge angle across the P(1)–P(2) vector is 2.51(5)°. Selected hydrogen bonding geometric parameters for 4c∙CHCl₃ are shown in

Table 9. Selected data (D···A/Å, ∠D–H···A/°) for key inter- and intramolecular contacts for compounds 4b·(CH₃)₂SO, 4c·CHCl₃, 4e·½CHCl_3·½CH₃OH, 5a·½OEt₂, 5b, 5c·¼H₂O, 5d·OEt₂, and 6·(CH₃)₂SO.

	4b·(CH3)2SO	4c·CHCl3	4e·½CHCl3 ·½CH3OH	5a·½OEt2 a	5b	5c·¼H2O	5d·OEt2	6·(CH3)2SO
O–H···(O)Cinter						3.714(14), 169
N–H···Nintra					2.711(5), 107(4)	2.776(12), 108 b
O–Hinter···OMeOH			2.624(10), 160
O–Hinter···ClPt		3.145(2), 145(3) 3.361(2), 133(3)	3.197(6), 160(9)		3.065(3), 161(5)
O–Hinter···O(CH3)2SO	2.716(17), 170							1.79(2), 173(5)
N–Hinter···ClPt				3.328(12), 145(16) 3.320(11), 159(16)			3.505(15), 138(6)
O–H···(O)Cintra				2.596(13), 157 2.610(13), 175(20)

^a Values in parentheses are for the second independent molecule. ^b For the major disorder component; 2.658(12), 117 for the minor component.

.

Compound 6∙(CH₃)₂SO, in which the –OH group is meta to the N-arene group H-bonds to the DMSO molecule of crystallisation resulting in a 0D structure (Figure 7). The distance d for this H-bond is 1.79(2) Å. The twist angle between plane P(1)/P(2)/C(1)/C(2) and ring C(3) > C(8) is 50.98(12)°. Atoms N(1) and Pt(1) lie 0.758(4) and 0.404(2) Å away from the P(1)/P(2)/C(1)/C(2) plane, respectively, so is more chair-shaped than some of the other platinum(II) complexes reported here. The hinge angle across the P(1)–P(2) vector is 11.87(13)°.

For 4d∙½Et₂O (Figure 8) a molecule of badly disordered diethyl ether, modelled by the Platon Squeeze procedure, is not shown, but is in the vicinity of the hydroxy group and may H-bond to it resulting in a 0D structure. The twist angle between plane P(1)/P(2)/C(1)/C(2) and ring C(3) > C(8) is 67.82(7)°. Atoms N(1) and Pt(1) lie 0.797(3) and 0.2378(16) Å away from the P(1)/P(2)/C(1)/C(2) plane, respectively. The hinge angle across the P(1)–P(2) vector is 9.20(9)°.

The crystal structure of 4b∙(CH₃)₂SO shows the hydroxy group H-bonding to the DMSO molecule of crystallisation (Figure 9a). The distance d for this H-bond is 1.89 Å. The twist angle between plane P(1)/P(2)/C(1)/C(2) and ring C(3) > C(8) is 72.2(4)°. Atoms N(1) and Pt(1) lie 0.781(17) and 0.180(10) Å away from the P(1)/P(2)/C(1)/C(2) plane, respectively. The hinge angle across the P(1)–P(2) vector is 8.7(6)°. Molecules form 1D, weakly H-bonded, undulating chains in the c direction via the methylene H atoms on C(1) and C(2) to a single, coordinated chloride ligand in an adjacent molecule (Figure 9b). Selected hydrogen bonding parameters for 4b∙(CH₃)₂SO are shown in Table 9.

For compound 4e∙½CHCl₃∙½CH₃OH there are two independent Pt complexes, one CH₃OH, and one CHCl₃ in the asymmetric unit. Both Pt complexes form 1D chains aligned parallel to b, but these chains are different (Figure 10). The chain involving Pt(2) forms simple O–H∙∙∙Cl H-bonds with the adjacent molecules via the para hydroxy group with d = 2.39(4) Å. For the chain involving the Pt(1)-containing molecules, the intermolecular H-bond has an inserted methanol molecule. The distances, d, are 2.32(5) and 1.82 Å for H(3)∙∙∙Cl(2) and H(1A)∙∙∙O(3), respectively. Atoms N(1)/N(2) and Pt(1)/Pt(2) lie 0.765(9)/0.798(9) and 0.424(5)/0.364(5) Å away from the P(1)/P(2)/C(1)/C(2) or P(3)/P(4)/C(34)/C(35) planes, respectively. So, as in 6∙(CH₃)₂SO, the core 6-membered Pt–P–C–N–C–P rings adopt more chair-shaped conformations. The hinge angles across the P(1)–P(2)/P(3)–P(4) vectors are 13.44(16)/12.47(16)°. The twist angles between planes P(1)/P(2)/C(1)/C(2) or P(3)/P(4)/C(34)/C(35) and rings C(3) > C(8) or C(36) > C(41) are 88.17(19)/54.62(15)°. So, while the other geometric parameters are similar between the two molecules, this twist angle is significantly different.

In 5c, the amide and ring atoms from C(4) > C(11) are disordered over two sets of almost equally occupied positions. The disorder highlights two or more chain-forming possibilities for this structure, analogous to that observed in in 4e∙½CHCl₃∙½CH₃OH, with one possibility being simple (hydroxyl)O–H∙∙∙O(amide) links (Figure 11a), while the other, shown in Figure 11b, shows an alternative, water-inserted linkage. There is also likely to be some alternation of these motifs, given the random disorder and approx. 25% occupancy observed for water atom O(3). Unlike almost all of the other structures herein, the core 6-membered Pt–P–C–N–C–P ring adopts a conformation with atoms Pt(1)/P(1)/P(1)/C(2) being in a plane and atoms C(1) and N(2) being 1.021(6) and 1.237(6) Å, respectively, away from that plane. There is no C=O∙∙∙HN intermolecular H-bonding observed between molecules. Instead, the amide NH forms a bifurcated H-bond with the two neighbouring acceptor atoms N(1) and the ortho hydroxyl O(2) with d = 2.37 and 2.28 Å, respectively, while d = 2.89 Å for H(2)∙∙∙O(1A).

In the second motif, adjacent molecules have an inserted water molecule in the H-bond pattern (Figure 11b). The amide NH again forms a bifurcated H-bond with the two neighbouring acceptor atoms N(1) and O(2X) with d = 2.14 and 2.25 Å, respectively, while d = 2.89 Å for H(2X)∙∙∙O(3), which is a little long, and d for O(3)∙∙∙O(1XA) = 2.21(3) Å, which is rather short. The distance d from water oxygen O(3) to O(1A), however, is entirely reasonable for an H-bond at 2.74 Å, suggesting a predominantly alternating pattern between the two disorder options is most likely.

Complex 5a∙½Et₂O was crystallised from a diethyl ether solution, including half a solvent molecule per complex molecule in the crystal lattice. There are two Pt complexes and two, half-occupied, Et₂O solvent molecules of crystallisation in the asymmetric unit. The packing adopted by this second complex with an ortho hydroxyl group is very different to 5c (Figure 12). Here there is no intramolecular N–H∙∙∙N H-bond, instead the ortho hydroxyl forms an intramolecular H-bond with the amide oxygen with d = 1.80 and 1.77(4) Å in the molecules containing Pt(1) and Pt(2), respectively. This does leave the two unique amide NH atoms free to form intermolecular interactions, which they do via highly asymmetric, bifurcated H-bonds with the coordinated chloride ligands on adjacent Pt complexes. From H(2) d = 2.60(11) and 2.95(13) Å to Cl(3) and Cl(4), respectively, while d = 2.52(7) and 3.12(15) Å from H(4) to Cl(1A) and Cl(2A), respectively. N(1)/N(3) and Pt(1)/Pt(2) lie 0.771(13)/0.781(14) and 0.349(8)/0.346(8) Å out of the planes P(1)/P(2)/C(1)/C(2) and P(3)/P(4)/C(37)/C(38), respectively. The twist angle between planes P(1)/P(2)/C(1)/C(2) and P(3)/P(4)/C(37)/C(38) relative to the rings C(5) > C(10) and C(41) > C(46) are 51.3(5) and 51.71(4)°, respectively. Hinge angles across P(1)–P(2) and P(3)–P(4) are 12.3(5) and 12.0(4)°, respectively. Differences between the two systems involving ortho hydroxyl groups are the position of the methyl ring substituent in the meta or para position, and the co-crystallised solvent being a small amount of water or Et₂O. Either, or both of these differences might account for the different intra- and intermolecular packing motifs observed. Selected hydrogen bonding parameters for 5a∙½Et₂O are shown in Table 9.

Molecules of 5d∙Et₂O lie on a mirror plane, passing through Pt(1), between pairs of P and Cl atoms, and including the atoms from N(1) to the terminal hydroxy-substituted ring. Again, here the amide NH is involved in the 1D chain propagation (Figure 13), forming a symmetrical bifurcated H-bond with the two coordinated chloride ligands on the adjacent molecule with d = 2.66(15) Å. Supporting this is an additional (Ar)C–H(5)∙∙∙Pt(1) interaction at 2.78 Å. The twist angle between the P(1)/P(1A)/C(1)/C(1A) plane and the ring C(4) > C(9) = 90° due to the imposed crystallographic symmetry. The hinge angle at P(1)–P(1A) = 29.5(5)°. Atoms N(1) and Pt(1) lie 0.79(2) and 0.782(14) Å away from the P(1)/P(2)/C(1)/C(2) plane, respectively. So, this is the most chair shaped core Pt–P–C–N–C–P 6-membered ring. The meta hydroxyl group is not involved in the chain propagating intermolecular interactions and points into a cleft between a pair of Ph rings. It does not make an H-bond with the solvent of crystallisation.

For compound 5b, the para position of the hydroxyl group facilitates 1D chain formation, forming an H-bond with one of the chloride ligands on an adjacent molecule with d = 2.09(6) Å (Figure 14). The amide NH here forms the familiar, but not universal, H-bond with the amine N(1) with d = 2.29(5) Å. The twist angle between the P(1)/P(2)/C(1)/C(2) plane and the ring C(5) > C(10) = 68.39(12)°. The hinge angle at P(1)–P(1A) = 4.95(10)°. Atoms N(1) and Pt(1) lie 0.810(4) and 0.164(3) Å away from the P(1)/P(2)/C(1)/C(2) plane, respectively.

3. Conclusions

In summary, we have shown that the position of the OH/CH₃ groups with respect to the N-arene, the inclusion of an amide spacer, and the solvent used in the crystallisation can dictate the solid-state packing behaviour of both non coordinated and cis-PtCl₂ bound diphosphine ligands. Unsurprisingly, the use of highly polar solvents (DMSO, CH₃OH) in this study has been shown to play an important role in disrupting packing behaviour. Our work reinforces the importance of substituent effects, not only those commonly associated with −PR₂ groups which may be alkyl or aryl based [37,38], but also those functional moieties positioned on the arene group of the central tertiary amine.

4. Materials and Methods

4.1. General Procedures

The synthesis of ligands 1a–e, 2a–g, and 3 were undertaken using standard Schlenk-line techniques and an inert nitrogen atmosphere. Ph₂PCH₂OH was prepared according to a known procedure [39]. All coordination reactions were carried out in air, using reagent grade quality solvents. The compound PtCl₂(η⁴-cod) (cod = cycloocta-1,5-diene) was prepared according to a known procedure [40]. All other chemicals were obtained from commercial sources and used directly without further purification

4.2. Instrumentation

Infrared spectra were recorded as KBr pellets on a Perkin-Elmer Spectrum 100S (4000–250 cm⁻¹ range) Fourier-Transform spectrometer. ¹H NMR spectra (400 MHz) were recorded on a Bruker DPX-400 spectrometer with chemical shifts (δ) in ppm to high frequency of Si(CH₃)₄ and coupling constants (J) in Hz. ³¹P{¹H} NMR (162 MHz) spectra were recorded on a Bruker DPX-400 spectrometer with chemical shifts (δ) in ppm to high frequency of 85% H₃PO₄. NMR spectra were measured in CDCl₃ or (CD₃)₂SO at 298 K. Elemental analyses (Perkin-Elmer 2400 CHN Elemental Analyser) were performed by the Loughborough University Analytical Service within the Department of Chemistry.

4.3. Preparation of Ligands 1a–e, 2a–g, and 3

The following general procedure was used for the synthesis of 1a–e, 2a–g, and 3. A mixture of Ph₂PCH₂OH (2 equiv.) and the appropriate amine (1 equiv.) in CH₃OH (20 mL) was stirred under N₂ for 24 h. The volume of the solution was evaporated to ca. 2–3 mL, under reduced pressure, to afford the desired ligands which were collected by suction filtration (except 2a–c) and dried in vacuo. Isolated yields in range 38–97%. Characterising details are given in Table 1.

4.4. Preparation of cis-Dichloroplatinum(II) Phosphine Complexes 4a–e, 5a–g, and 6

The following general procedure was used for the synthesis of 4a–e, 5a–g, and 6. To a solution of PtCl₂(η⁴-cod) (1 equiv.) in CH₂Cl₂ (5 mL) was added a solution of the appropriate ligand (1 equiv.) in CH₂Cl₂ (5 mL). The colourless (or pale yellow) solution was stirred for 30 min at r.t., evaporated to ca. 2–3 mL under reduced pressure, and diethyl ether (10 mL) added. The solids were collected by suction filtration and dried in vacuo. Isolated yields in range 73–99%. Characterising details are given in Table 4.

4.5. Single Crystal X-ray Crystallography

Suitable crystals of 1a, 1b∙CH₃OH, 2f·CH₃OH, and 3 were obtained by slow evaporation of a CH₃OH solution whereas 2g was obtained by vapour diffusion of Et₂O into a CDCl₃/CH₃OH solution. Crystals of 4b∙(CH₃)₂SO, 5a∙½Et₂O, 5b, and 5c∙¼H₂O were obtained by slow diffusion of Et₂O into a CDCl₃/(CH₃)₂SO/CH₃OH solution. Slow diffusion of hexanes [for 6∙(CH₃)₂SO] into a CDCl₃/(CH₃)₂SO solution or vapour diffusion of Et₂O into a CHCl₃/(CH₃)₂SO/CH₃OH [for 4c∙CHCl₃, 4e∙½CHCl₃∙½CH₃OH) or CH₂Cl₂/CH₃OH (for 5d∙Et₂O)]. Slow evaporation of a CH₂Cl₂/Et₂O/hexanes solution gave suitable crystals of 4d∙½Et₂O. Table 2, Table 5 and Table 6 summarise the key data collection and structure refinement parameters. Diffraction data for compounds 1a, 1b∙CH₃OH, 2f∙CH₃OH 3, 4b∙(CH₃)₂SO, 4c∙CHCl₃, 4d 4e∙½CHCl₃∙½CH₃OH, 5d∙Et₂O, and 6∙(CH₃)₂SO, were collected using a Bruker or Bruker-Nonius APEX 2 CCD diffractometer using graphite-monochromated Mo-K_α radiation. Data for compounds 5b and 5c∙¼H₂O, were collected using a Bruker APEX 2 CCD diffractometer using synchrotron radiation at Daresbury SRS Station 9.8 or 16.2 SMX for 5a·½Et₂O. Data for compound 2g was collected using a Bruker SMART 1000 CCD diffractometer using graphite-monochromated Mo-K_α radiation. All structures were solved by direct methods [except structures 4b∙(CH₃)₂SO, 5a∙½Et₂O, and 5b which were solved using Patterson synthesis] and refined by full-matrix least-squares methods on F². All CH atoms were placed in geometrically calculated positions and were refined using a riding model (aryl C–H 0.95 Å, methyl C–H 0.98 Å, methylene C–H 0.99 Å. Where data quality allowed, OH and NH atom coordinates and U_iso were freely refined, or refined with mild geometrical restraints; otherwise, they were placed geometrically with O/N–H = 0.84 Å. U_iso(H) values were set to be 1.2 times U_eq of the carrier atom for aryl CH and NH, and 1.5 times U_eq of the carrier atom for OH and CH₃. Throughout the text and tabulated data, where H atom geometry does not include a SU, the coordinates were constrained. Unless stated, all structural determinations proceeded without the need for restraints or disorder modelling. Where disorder was modelled it was supported with appropriate geometrical and U value restraints. In 1b∙CH₃OH, the methanol was modelled as disordered over two equally occupied sets of positions. In 2f·CH₃OH the methanol was modelled using the Platon Squeeze procedure [41]. Compound 3 was found to contain a disordered methanol and was modelled over two sets of positions, each at half weight. In 4d·½Et₂O, atoms C(1) > C(7) and N(1) were modelled with U value restraints. The Et₂O was modelled using Platon Squeeze due to significant disorder. In 4e∙½CHCl₃∙½CH₃OH the chloroform molecule was modelled over two sets of positions with major occupancy 57.1(7)% Restraints were applied to that molecule and also ring C(55) > C(60). In 5a·½Et₂O three Ph rings were modelled as disordered over two sets of positions with occupancies close to 50%. Restraints were applied to these rings and also the two half-occupancy Et₂O solvent molecules of crystallisation. In 5c∙¼H₂O, atoms Cl(1) and C(3) > C(11), O(1), O(2) and N(1) were modelled as split over two sets of positions with major occupancy 56(4) and 50.9(6)%, respectively and restraints were applied. In 5d∙Et₂O the Et₂O was modelled as a diffuse area of electron density by the Platon Squeeze procedure and restraints were applied to atoms C(1) > C(10), C(11) > C(22) and N(2) O(2). In 6∙(CH₃)₂SO the DMSO was modelled with restraints as disordered over two sets of positions with major component 71.0(5)% and with C(33) coincident for both components Programs used during data collection, refinement and production of graphics were Bruker SMART, Bruker APEX 2, SAINT, SHELXTL, COLLECT, DENZO and local programs [41,42,43,44,45,46,47,48,49,50,51]. CCDC 2101643-2101656 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures (accessed on 3 November 2021).