Effects of sulphur substituents on the geometries of dipalladium μ-thiolato complexes: Crystal structures of Pd 2Cl 2(μ-Cl)(μ-SR)(PMe 3) 2 (R  Me, t-Bu and Ph) and Pd 2Cl 2(μ-SPh) 2(PEt 3) 2

Abstract

The mono(μ-alkylthiolato) complexes, cis-Pd 2Cl 2(μ-Cl)(μ-SR)(PMe 3) 2 (R  Me, 1; t-Bu, 2) are obtained as the exclusive products of the reaction of acetone solutions of trans-[PdCl(μ-Cl)(PMe 3)] 2 with the corresponding thiols at 25°C, whereas reaction with stoichiometric amounts of thiophenol gives mixtures of cis-Pd 2Cl 2(μ-Cl)(μ-SPh)(PMe 3) 2 ( 3) and trans-Pd 2Cl 2(μ-SPh) 2(PMe 3) 2 ( 5). Reaction of trans-[PdCl(μ-Cl)(PR 3)] 2 with thiophenol in a 1 : 2 stoichiometry gives exclusively trans-Pd 2Cl 2(μ-SPh) 2(PR 3) 2 (R = Et, 4; Me, 5). The molecular structures of 1, 2, 3·CH 2Cl 2 and 4 have been determined by X-ray diffraction. Complexes 1 and 2 have non-planar geometries with dihedral angles of 140 and 146°, respectively, between the coordination planes of the palladium atoms. By contrast, the μ-arylthiolato complexes are planar with dihedral angles of 180° between the coordination planes of the palladium atoms. The PdS bond distances 2.262(2)–2.272(2) Å in complexes 1 and 2 are significantly shorter than the PdS distances in 3, 2.288(2) and 2.301(2) Å, indicating enhanced metal-sulphur bonding in the alkylthiolato complexes. The bent geometries of the alkylthiolato complexes as well as the dichotomy of cis and trans phosphine geometries preferred by M 2Cl 2(μ-SR) 2(PR′ 3) 2 (M = Pd, Pt) alkylthiolato and arylthiolato complexes, respectively, are discussed in view of the enhanced sulphur-metal donor interactions in the alkylthiolato complexes. The isolation of mono(μ-thiolato) complexes from the reaction of trans-[PdCl(μ-Cl)(PMe 3)] 2 with alkylthiols and not arylthiols is also accounted for by the additional stabilization of the metal-sulphur bonds in the alkylthiolato complexes. Crystallographic data : for 1, orthorhombic, Pbc2 1, Z = 4, a = 11.630(6), b = 11.667(3), c = 12.816(4) Å, V = 1739(1) Å 3, ϱ calc. = 1.980 g cm −3; for 2, orthorhombic, P2 1 cn, Z = 4, a = 8.158(3), b = 10.345(3), c = 24.106(6) Å, V = 2035(1) Å 3, ϱ calc. = 1.830 g cm −3; for 3·CH 2Cl 2, monoclinic C2/2, Z = 8, a = 27.38(1), b = 11.477(9), c = 16.506(7) Å, β = 124.12(3)°, V = 4294(4) Å 3, ϱ calc. = 1.924 g cm −3; for 4, triclinic P 1 , Z = 2, a = 8.694(5), b = 9.570(6), c = 10.203(7) Å, α = 68.72(5), β = 76.86(5), γ = 85.27(5)°, V = 770.3(8) Å 3, ϱ calc. = 1.592 g cm −3.