Synthesis and structural characterisation of some tetrahedral platinum–gold cluster compounds containing the sulphur dioxide ligand

Abstract

The compound [Pt₃Au(µ-CO)₃{P(C₆H₁₁)₃}₄] PF₆ has been synthesised from [Pt₃(µ-CO)₃{P(C₆H₁₁)₃}₃] and [AuCl{P(C₆H₁₁)₃}] in the presence of TIPF₆. It reacts with SO₂ to give a tetrahedral platinum–gold cluster compound [Pt₃Au(µ-CO)₂(µ-SO₂){P(C₆H₁₁)₃}₄] PF₆(1) in which one of the CO ligands of the starting material has been replaced by SO₂. Compound (1) crystallises in the orthorhombic space group Pn2₁a with four formula units in a cell of dimensions a= 18.671(4), b= 19.618(3), and c= 28.162(4)Å. The compound [Pt₃(µ-SO₂)₃{P(C₆H₁₁)₃}₃] reacts with [AuCl{P(C₆H₄F-p)₃}] to give the tetrahedral platinum–gold cluster compound [Pt₃Au(µ-SO₂)₂(µ-Cl){P(C₆H₁₁)₃}₃{P(C₆H₄F-p)₃}](2) in which one of the SO₂ligands of the starting triangulo-cluster has been replaced by a bridging chloride. Compound (2) crystallises in the monoclinic space group P2₁/n with four formula units in a cell of dimensions a= 25.490(4), b= 25.855(6), c= 13.819(4)Å, and β= 96.98(2)°. The bonded bridging ligand atoms are approximately coplanar with the metal triangles whilst the metal–phosphine bonds point towards the centre of the metal tetrahedron. N.m.r. studies, ³¹P-{¹H} and ¹⁹⁵Pt-{¹H}, suggest that the solid-state structures are retained in solution for both compounds. The reaction of [Pt₃(µ-SO₂)₃{P(C₆H₁₁)₃}₃] with [AuCl{P(C₆H₁₁)₃}] in the presence of TIPF₆gives [Pt₃Au(µ-SO₂)₃{P(C₆H₁₁)₃}₄] PF₆ which may be converted into (1) by reaction with CO. The compound [Pt₃(µ-SO₂)₃{P(C₆H₁₁)₃}₃] reacts with [AuCl{P(C₆H₄F-p)₃}] to give [Pt₃Au(µ-SO₂)₃{P(C₆H₁₁)₃}₃{P(C₆H₄F-p)₃}] PF₆ which may be converted into (2) with NMe₄Cl. The compound [Pt₃Au(µ-SO₂)₃{P(C₆H₁₁)₃}₃{P(C₆H₄F-p)₃}] PF₆ and its chloride-bridged derivative (2) represent the first examples of compounds formed where [Au(PR₃)]⁺ and [AuCl(PR₃)] have been added to the same cluster compound. These studies indicate the occurrence of 54- and 56-electron tetrahedral Pt₃Au clusters analogous to the 42- and 44-electron triangular parent clusters.