Organomonophosphines in Pt(η³-X¹X²X³)(PR₃), (X = N¹, N², N³; S¹, S², S³; or Te¹, Te², Te³) Derivatives: Structural Aspects

Abstract

This paper covers nineteen Pt(II) complexes of the composition Pt(η³-X¹X²X³)(PR₃), (X = N¹, N², N³; S¹, S², S³; or Te¹, Te², Te³). These complexes crystallized in three crystal classes: triclinic (eleven examples), monoclinic (six examples), and orthorhombic (two examples). Each tridentate ligand creates two metallocyclic rings with common N², S², or Te² donor ligands of the types N¹C₂N²C₂N³, N¹C₂N²NC₂N³, S¹C₂S²C₂S³, S¹C₃S²C₃S³, and Te¹CNTe²NCTe³. The homotridentate ligand with monodentate PR₃ ligand builds up a distorted square planar geometry about Pt(II) atoms. The degree of distortion ranges from 0.029 to 0.092, and the reason for the distortion is discussed. There is an example that contains two crystallographically independent molecules within the same crystal. This is a classic example of distortion isomerism.

1. Introduction

The coordination chemistry of platinum covers a huge number, as shown by a survey covering the crystallographic and structural data of almost two thousand monomeric examples [1,2,3]. Research activity in this field is always very active, and one of the reasons is the biological activity of platinum complexes [4]. Organophosphines as soft donor ligands are very useful for building a wide variety of platinum complexes. Much attention has been paid to organophosphines ligands in the chemistry of platinum. There have been numerous structural studies published of such complexes that were classified and analyzed [5]. Another review covers structural data of numerous platinum(II) coordination complexes with inner coordination spheres: PtP₄, PtP₃X (X = H, F, O, N, Cl, S, Br or I), and PtP₂X₂ (X – H, F, O, N, CN or B), in which P-donor ligands are monodentate organomonophosphines [6]. There are also numerous structures of Pt(II) complexes with organodiphosphines [7].

The aim of this paper is to analyze structural data of Pt(η³-X¹X²X³)(PR₃) (X = N¹, N², N³; S¹, S², S³; or Te¹, Te², Te³) complexes, where PR₃ represents the ligand coordination via the P atom.

2. Pt(η³-X¹X²X³)(PR₃) Derivatives

Pt(η³-X¹X²X³)(PR₃) derivatives are divided into three groups, classified and discussed in this paper, namely Pt(η³-N¹N²N³)(PR₃), Pt(η³-S¹S²S³)(PR₃), and Pt(η³-Te¹Te²Te³)(PR₃) derivatives; their X-ray data are gathered in

Table 1. Structural data for Pt (η³-N¹N²N³)(PR₃) derivatives ^a.

Pt (η3-N1N2N3)(PR3)	Crystal cl. Space gr. z	a [Å] b [Å] c [Å]	α [°] β [°] γ [°]	Chromophore (Chelate Rings) τ4	Pt-L b [Å]	L-Pt-L b [°]	Ref.
[Pt{η3-C31H30F6N4O8S2}. (PPh3)] [Pt{η3-C17H28N3}(PPh3)]. CH2Cl	tr P$\stackrel{-}{1}$ 2 tr P$\stackrel{-}{1}$ 2	11.925 14.820 17.550 11.135(2) 11.462(2) 13.808(2)	94.77 103.02 111.67 80.18(2) 81.74(2) 88.27(2)	PtN3P (N1C2N2C2N3) 0.080 PtN3P (N1C2N2C2N3) 0.089	N1 2.017 N2 2.040 N3 2.038 P 2.266 N1 1.996 N2 2.035 N3 2.032 P 2.268	N1,N2 79.8(4) c N2,N3 79.2(3) c N1,N3 160.4 N1,P 104.0 N3,P 96.9(2) N2,P 170.8 N1,N2 78.5 N2,N3 78.2 N1,N3 156.5 N1,P 97.3 N3,P 106.1 N2,P 172.2	[8,9]
[Pt{η3-C13H5F6N5}. (PPh3)]	tr P$\stackrel{-}{1}$ 2	9.142 10.264 16.507	103.04 103.07 99.68	PtN3P (N1C2N2C2N3) 0.075	N1 2.011 N2 2.024 N3 2.015 P 2.257	N1,N2 79.0 c N2,N3 78.9 N1,N3 157.8 N1,P 102.7 N3,P 99.5 N2,P 175.1	[10]
[Pt{η3-C25H19N5}(PPh3)]. 3CH2Cl2 (at 223 k)	m P21/n 4	6.068(0) 8.323(0) 33.868(0)	90.86(0)	PtN3P (N1C2N2C2N3) 0.070	N1 2.015 N2 2.017 N3 1.996 P 2.253	N1,N2 79.2 c N2,N3 79.3 c N1,N3 158.4 N1,P 96.9 N3,P 104.6 N2,P 176.2	[11]
[Pt{η3-C29H33N7}(PPh3)]. CH2Cl2 (at 223 k)	tr P$\stackrel{-}{1}$ 2	11.926(0) 13.052(0) 14.258(0)	97.75(0) 102.93(0) 95.73(0)	PtN3P (N1C2N2C2N3) 0.070	N1 2.012 N2 2.036 N3 2.009 P 2.244	N1,N2 78.9 c N2,N3 78.9 c N1,N3 157.7 N1,P 99.9 N3,P 102.2 N2,P 177.1	[11]
[Pt{η3-C30H35N5}(PPh3)] (at 223 k)	tr P$\stackrel{-}{1}$ 2	11.005(0) 12.424(0) 15.305(0)	75.50(0) 82.31(0) 87.08(0)	PtN3P (N1C2N2C2N3) 0.067	N1 2.009 N2 2.022 N3 2.010 P 2.243	N1,N2 79.1 c N2,N3 78.8 c N1,N3 157.5 N1,P 99.4 N3,P 102.3 N2,P 178.4	[11]
[Pt{η3-C12H6F6N7O}(PPh3)] (at 223 k)	tr P$\stackrel{-}{1}$ 2	7.952(0) 11.542(0) 16.515(0)	76.83(0) 83.35(0) 89.27(0)	PtN3P (N1C2N2C2N3) 0.077	N1 2.015 N2 2.031 N3 2.035 P 2.263	N1,N2 78.0 c N2,N3 78.4 c N1,N3 156.4 N1,P 97.6 N3,P 105.9 N2,P 175.7	[12]
[Pt{η3-C18H23N7O}(PPh3)] (at 223 k)	m P21/n 4	13.371(0) 17.428(0) 15.657(0)	114.69(0)	PtN3P (N1C2N2C2N3) 0.081	N1 2.016 N2 2.026 N3 2.008 P 2.256	N1,N2 78.4 c N2,N3 78.5 c N1,N3 156.9 N1,P 98.4 N3,P 104.6 N2,P 173.9	[12]
[Pt{η3-C22H15N7O}(PPh3)] (at 223 k)	m C2/6 8	24.786(0) 30.842(0) 10.313(0)	101.98(0)	PtN3P (N1C2N2C2N3) 0.072	N1 2.006 N2 2.033 N3 2.012 P 2.269	N1,N2 78.0 c N2,N3 78.3 c N1,N3 156.3 N1,P 101.2 N3,P 102.4 N2,P 177.8	[12]
[Pt{η3-C17H21N7}(PPh3)] (at 223 k)	tr P$\stackrel{-}{1}$ 4	15.098(0) 16.025(0) 17.125(0)	114.45(0) 94.20(0) 112.02(0)	PtN3P (N1C2N2C2N3) 0.078	N1 2.022 N2 2.021 N3 2.010 P 2.263	N1,N2 78.5 c N2,N3 78.7 c N1,N3 157.0 N1,P 101.0 N3,P 101.9 N2,P 174.8	[12]
[Pt{η3-C11H3F6N7}(PPh3)] (at 223 k)	m P21/n 4	17.477(0) 7.859(0) 22.016(0)	112.64(0)	PtN3P (N1C2N2C2N3) 0.076	N1 2.027 N2 2.037 N3 2.012 P 2.275	N1,N2 78.3 c N2,N3 78.5 c N1,N3 156.8 N1,P 105.9 N3,P 97.7 N2,P 175.7	[12]
[Pt{η3-C15H11N3}(PPh3)]. 2SO3CF3 e (at 173 k)	tr P$\stackrel{-}{1}$ 4	9.054(7) 19.936(14) 22.196(16)	111.04(1) 99.18(1) 99.74(1)	PtN3P (N1C2N2C2N3) 0.070 PtN3P (N1C2N2C2N3) 0.082	N1 2.043 N2 1.978 N3 2.052 P 2.276 N1 2.057 N2 1.975 N3 2.040 P 2.288	N1,N2 79.6 c N2,N3 80.0 c N1,N3 159.2 N1,P 101.8 N3,P 98.8 N2,P 175.4 N1,N2 79.9 c N1,N3 79.3 c N1,N3 158.5 N1,P 103.2 N3,P 98.1 N2,P 172.0	[13]
[Pt{η3-C11H3F6N7}. {P(CH3)Ph2}] (at 223 k)	tr P$\stackrel{-}{1}$ 2	7.892(0) 10.614(0) 16.050(0)	90.75(0) 97.77(0) 108.22(0)	PtN3P (N1C2N2C2N3) 0.068	N1 2.005 N2 2.032 N3 2.006 P 2.256	N1,N2 78.6 c N2,N3 79.2 c N1,N3 157.7 N1,P 100.0 N3,P 102.2 N2,P 177.9	[14]
[Pt{η3-C15H11N3}{P(η1-C14H19O5)Ph2}].2SO3CF3. 2Me2CO (at 223 k)	m C2/c 4	31.541(4) 17.658(4) 24.072(4)	121.50(0)	PtN3P (N1C2N2C2N3) 0.068	N1 1.918(16) N2 2.000(1) N3 2.097(10) P 2.287(3)	N1,N2 79.8(5) c N2,N3 79.5(3) c N1,N3 158.7(5) N1,P 97.9(3) N3,P 103.0(3) N2,P 176.6(3)	[15]
[Pt{η3-C12H10N4}(PPh3)] (at 100 k)	or P212121 6	10.417(0) 13.328(0) 18.299(0)		PtN3P (N1C2N2NC2N3) 0.034	N1 1.984 N2 2.025 N3 1.964 P 2.255	N1,N2 81.7 c N2,N3 89.6 d N1,N3 170.6 N1,P 93.0 N3,P 96.3 N2,P 177.2	[16]

^a Where more than one chemically equivalent distance or angle is present, the mean value is tabulated. The first number in parentheses is e.s.d., and the second is the maximum deviation from the mean; ^b the chemical identity of a coordinate atom or ligand is specified in these columns; ^c five-membered metallocyclic ring; ^d six-membered metallocyclic ring; ^e there are two crystallographically independent molecules.

,

Table 2. Structural data for Pt(η³-S¹S²S³)(PPh₃) derivatives ^a.

Pt(η3-S1S2S3)(PPh3)	Crystal cl. Space gr. z	a [Å] b [Å] c [Å]	α [°] β [°] γ [°]	Chromophore (Chelate Rings) τ4	Pt-L b [Å]	L-Pt-L b [°]	Ref.
[Pt{η3-S(C6H4)S(C6H4)S}. (PPh3)]	m P21/n 4	8.990(1) 11.393(3) 25.587(3)	9093(1)	PtS3P (S1C2S2C2S3) 0.051	S1 2.312(1) S2 2.287(1) S3 2.312(1) P 2.261(1)	S1,S2 87.69(4) S2,S3 87.08(4) S1,S3 163.92(3) S1,P 94.40(1) S3,P 90.76(4) S2,P 177.85(4)	[17]
[Pt{η3-MeS(CH2)3S(CH2)3. SMe}(PPh3)]BF4	tr P$\stackrel{-}{1}$ 2	13.266(3) 11.315(2) 13.970(2)	106.04(2) 84.95(2) 86.56(2)	PtS3P (S1C3S2C3S3) 0.035	S1 2.330(2) S2 2.339(2) S3 2.338(2) P 2.332(2)	S1,S2 87.1(2) c S2,S3 89.5(2) c S1,S3 176.3(2) S1,P 91.1(2) S3,P 92.3(2) S2,P 171.0(2)	[18]

^a Where more than one chemically equivalent distance or angle is present, the mean value is tabulated. The first number in parentheses is e.s.d., and the second is the maximum deviation from the mean; ^b the chemical identity of coordinate atom or ligand is specified in these columns; ^c six-membered metallocyclic ring.

and

Table 3. Structural data for Pt(η³-Te¹Te²Te³)(PPh₃) derivatives ^a.

Pt(η3-S1S2S3)(PPh3)	Crystal cl. Space gr. z	a [Å] b [Å] c [Å]	α [°] β [°] γ [°]	Chromophore (Chelate Rings) τ4	Pt-L b [Å]	L-Pt-L b [°]	Ref.
[Pt{η3-C10H8N2Te3}(PPh3)]	m C2/c 4	39.040(7) 13.261(4) 11.943(1)	93.85(1)	PtTe3P (Te1CNTe2NCTe3) 0.044	Te1 2.5940(7) Te2 2.5752(2) Te3 2.570(2) P 2.282(2)	Te1,Te2 92.83(2) c Te2,Te3 92.56(2) c Te1,Te3 172.74(2) Te1,P 86.10(5) Te3,P 89.29(6) Te2,P 171.40(2)	[19]
[Pt{η3-C12H12N2Te3}(PPh3)]. C6H6	tr P$\stackrel{-}{1}$ 2	12.300(12) 15.251(8) 10.029(7)	107.38(3) 99.51(6) 83.25(4)	PtTe3P (Te1CNTe2NCTe3) 0.029	Te1 2.588(3) Te2 2.569(2) Te3 2.612(3) P 2.283(3)	Te1,Te2 91.59(6) c Te2,Te3 91.40(7) c Te1,Te3 173.99(11) Te1,P 90.40(10) Te3,P 86.99(10) Te2,P 17.56(9)	[19]

^a Where more than one chemically equivalent distance or angle is present, the mean value is tabulated. The first number in parentheses is e.s.d., and the second is the maximum deviation from the mean; ^b the chemical identity of coordinate atom or ligand is specified in these columns; ^c five-membered metallocyclic ring.

, respectively.

2.1. Pt(η³-N¹N²N³)(PR₃) Type

There were fifteen complexes of such types which crystallized in three crystal classes: triclinic (nine examples), monoclinic (four examples), and orthorhombic (two examples) (see Table 1). In [Pt(η³-C₁₂H₁₀N₄)(PPh₃)] (at 100 K) (see Figure 1) [16], the tridentate ligand creates two dissimilar rings. Five- and six-membered complexes of the N¹C₂N²NC₂N³ type had values of respective angles of 81.7° (N¹-Pt-N²) and 89.6° (N²-Pt-N³). The values of the remaining L-Pt-L bind angles opened in the order 93.0° (N¹-Pt-P) < 96.3° (N³-Pt-P) < 170.6° (N¹-Pt-N³) < 177.2° (N²-Pt-P). The Pt-L bond distance elongated in the order 1.964 Å (Pt-N³, trans to N¹) < 1.984 Å (Pt-N¹) < 2.025 Å (Pt-N², trans to P) < 2.255 Å (Pt-P).

In the remaining fourteen Pt(η³-N¹N²N³) (Pt) complexes (see Table 1), a distorted square planar geometry around each Pt(II) atom was built up by η³-N¹N²N³ with monodentate Pt ligands. Each tridentate donor ligand formed a pair of five-membered metallocyclic rings of the N¹C₂N²C₂N³ type, with total mean values of the respective angles of 78.8° (N¹-Pt-N²) and 79.9° (N²-Pt-N³). The remaining L-Pt-L bond angles opened in the order (total mean values) 100.5° (N¹-Pt-P) < 102.9° (N³-Pt-P) < 157.2° (N³-Pt-N³) < 176.0° (N²-Pt-P). The Pt-L bond distance elongated in the order (total mean values) 2.013 Å (Pt-N³, trans to N¹) < 2.017 Å (Pt-N¹) < 2.018 Å (Pt-N², trans to P) < 2.265 Å (Pt-P).

2.2. Pt(η³-S¹S²S³)(PR₃) Type

Monoclinic [Pt{η³-S(C₆H₄)S(C₆H₄)S}(PPh₃)](PPh₃)] [17] and triclinic [Pt{η³-MeS(CH₂)₃S(CH₂)₃SMe}(PPh₃)].BF₄ [18] are the only examples of such a type (Table 2). The structure of the cation is shown in Figure 2 [18]. The tridentate ligand formed a pair of six-membered metallocyclic rings with a common S² atom of the monoclinic S¹C₂S²C₂S³ and triclinic S¹C₃S²C₃S³ type. The values of the respective angles were 87.69(4)° (S¹-Pt-S²) and 87.08(4)° (S²-Pt-S³) in monoclinic and in triclinic were 87.1(2)° (S¹-Pt-S²) and 89.5(2)° (S²-Pt-S³).

The remaining L-Pt-L bond angles opened in the order 91.1(2)° (S¹-Pt-P) < 92.3(2)° (S³-Pt-P) < 171.0(2)° (S²-Pt-P) < 176.3(2)° (S¹-Pt-S³). The Pt-L bond distance elongated in the order 2.330(2) Å (Pt-S¹, trans to S³) < 2.332(2) Å (Pt-P, trans to S²) < 2.338(2) Å (Pt-S³) < 2.339(2) Å (Pt-S²). The monodentate PPh₃ ligand completed a distorted squared planar geometry around the Pt(II) atom.

2.3. Pt(η³-Te¹Te²Te³)(PR₃) Type

There were two complexes of such a type; monoclinic [Pt{η³-C₁₀H₈N₂Te₃}(PPt₃)] and triclinic [Pt{η³-C₁₂H₁₂N₂Te₃}(PPh₃)]C₆H₆ [19] (see Table 3). The structure of the former is shown in Figure 3. Each tridentate ligand formed a pair of five-membered metallocyclic rings of the Te¹CNTe²NCTe³ type with the values of the respective angles of 92.8° (Te¹-Pt-Te²) and 92.5° (Te²-Pt-Te³) in monoclinic; in triclinic they were 91.6° and 91.4°. The remaining L-Pt-L bond angles opened in the order 81.1° (Te¹-Pt-P) < 89.3° (Te³-Pt-P) < 171.4° (Te²-Pt-P) < 171.172.27° (Te¹-Pt-Te³) in monoclinic, and in triclinic the order of 87.0° (Te³-Pt-P) < 90.4° (Te¹-Pt-P) < 174.0° (Te¹-Pt-Te³) < 175.5° (Te²-Pt-P).

The Pt-L bond distance elongated in the order 2.282(2) Å (Pt-P, trans to Te²) < 2.5720(2) Å (Pt-Te³, trans to Te¹) < 2.5752(2) Å (Pt-Te²) < 2.5940(7) Å (Pt-Te¹) (in monoclinic); in triclinic, the order was 2.283(3) Å (Pt-P, trans to Te²) < 2.569(2) Å (Pt-Te²) < 2.588(3) Å (Pt-Te¹, trans to Te³) < 2.612(3) Å (Pt-Te³). The monodentate PPh₃ completed a distorted square-planar geometry around the Pt(II) atoms.

3. Conclusions

This paper includes nineteen monomeric Pt(II) complexes with the composition of (Pt (η³-X¹X²X³)(R₃), (X = N, S or Te)). These complexes crystallized in three classes: triclinic (eleven examples), monoclinic (six examples), and orthorhombic (two examples). Based on tridentate ligands, these complexes could be divided into three sub-groups. In each sub-group, the Pt-L bond distance (mean values) with sums of Pt-L(x4) bond distances were:

Pt(η³-N¹ N² N³)(PR₃);

PtN₃P: 2.017 Å (Pt-N¹, trans to N³); 2.018 Å (Pt-N², trans to P); 2.013 Å (Pt-N³); 2.265 Å (Pt-P); Σ 8.313 Å (see Table 1);

Pt(η³-S¹ S² S³)(PR₃);

PtS₃P: 2.330 Å (Pt-S¹, trans to S³); 2.339 Å (Pt-S², trans to P); 2.338 Å (Pt-S³); 2.332 Å (Pt-P); Σ 9.339 Å (see Table 2);

Pt(η³-Te¹ Te² Te³)(PR₃);

PtTe₃P: 2.591 Å (Pt-Te¹, trans to Te³); 2.572 Å (Pt-Te², trans to P); 2.592 Å (Pt-Te³); 2.283 Å (Pt-P); Σ 10.038 Å (see Table 3).

The total mean values of Pt-L(x4) bond distances grew with the value of the covalent radius of coordinated atoms in the sequence 8.313 Å (0.73 Å, N) (PtN₃P) < 9.339 (1.02 Å, S) (PtS₃P) < 10.038 Å (1.36 Å, Te) (PtTe³P).

Each tridentate ligand formed two metallocyclic rings with common N², S², or Te² of the following types, with the mean value of L-Pt-L bond angles:

5 + 5, rings N¹C₂N²C₂N³ 78.8° (N¹-Pt-N²) and 78.9° (N²-Pt-N³);

5 + 5, rings S¹C₂S²C₂S³ 87.69(4)° (S¹-Pt-S²) and 87.08(4)° (S²-Pt-S³)

5 + 5, rings Te¹CNTe²NCTe³ 92.1° (Te¹-Pt-Te²) and 92.0° (Te²-Pt-Te³);

5 + 6, rings N¹C₂N²NC₂N³ 81.7° (N¹-Pt-N²) and 89.6° (N²-Pt-N³);

6 + 6, rings S¹C₃S²C₃S³ 87.1° (S¹-Pt-S²) and 89.5° (S²-Pt-S³).

In transition metal complexes, the oxidation state plays a leading role in the geometry formed, and platinum is no exception. In four coordinates, Pt(II) prefers a square-planar geometry. The utility of a simple metric to assess the molecule shape and degree of distortion as well as exemplify best the τ₄ parameter for a perfect square-planar geometry is provided by the equation introduced by [20].

$${\tau }_4=\frac{360-(\alpha +\beta )}{360} \mathrm{f}\mathrm{o}\mathrm{r} \mathrm{s}\mathrm{q}\mathrm{u}\mathrm{a}\mathrm{r}\mathrm{e} \mathrm{p}\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{a}\mathrm{r}, \mathrm{a}\mathrm{n}\mathrm{d}$$

$${\tau }_4=\frac{360-(\alpha +\beta )}{141} \mathrm{f}\mathrm{o}\mathrm{r} \mathrm{t}\mathrm{e}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{h}\mathrm{e}\mathrm{d}\mathrm{r}\mathrm{a}\mathrm{l}.$$

The values of τ₄ ranged from 0.00 for the perfect square-planar geometry to 1.00 for a perfect tetrahedral geometry, since 360 − 2(109.5) = 141.

There is a cooperative effect between the size of the metallocyclic rings and donor atoms and the distortion of square-planar geometry around the Pt(II) atom. The distortion diminishes when the size of the metallocyclic rings grows, and the covalent radius increases as 0.75 Å (N) < 1.02 Å (S) < 1.31 Å (Te) of donor atoms, as can be seen:

5 + 5, rings 0.068 (τ₄) 78.8° (N¹C₂N²C₂N³) < 0.053 (τ₄) 81.4° (S¹C₂S²C₂S³) < 0.036 (τ₄) 92.0° (Te¹CNTe²NCTe³);

5 + 5, rings 0.068 (τ₄) 78.8° (N¹C₂N²C₂N³);

5 + 6, rings 0.034 (τ₄) 81.7° and 84.6° (N¹C₂N²C₂N³);

5 + 5, rings 0.053 (τ₄) 87.4° S¹C₂S²C₂S³;

6 + 6, rings 0.035 (τ₄₎) 87.1° and 89.54.6° S¹C₃S²C₃S³.

Monoclinic [Pt{η³-C₁₅H₁₁N₃}(PPh₃)].SO₃CF₃ (at 173 k) [13] contains two crystallographically independent molecules within the same crystal (Table 1). These two molecules are different from each other by the degree of distortion, with values of τ₄ 0.070 and 0.082. They are a classic example of a distortion isomerism [21].