Synthesis of tetra-and penta-nuclear platinum–osmium carbido-cluster complexes from non-carbido-precursors: X-ray structural studies on [Os3Pt (µ-H)2(µ4-C)(CO)10{P(cyclo-C6H11)3}],[Os3Pt2(µ-H)2(µ5-C)(µ-CO)(CO)9{P(cyclo-C6H11)3}2], and [Os3Pt2(µ-H)(µ5-C)(µ-OMe)(µ-CO)(CO)9{P(cyclo-C6H11)3}2]

Abstract

The reaction between the compounds [Os₃(µ-H)(µ₃-CH)(CO)₁₀] and [Pt(C₂H₄)₂{P(cyclo-C₆H₁₁)₃}] in toluene at 80 °C affords two cluster complexes, one containing a single platinum atom [Os₃Pt(µ-H)2(µ₄-C)(CO)₁₀{P(C₆H₁₁)₃}](1), and the other two platinum atoms, [Os₃Pt₂(µ-H)₂(µ₄-C)(µCO)(CO)₉{P(C₆H₁₁)₃}₂](2). Both have been characterised by single-crystal X-ray diffraction studies. Compound (1) contains a triangle of osmium atoms [Os–Os 2.828(1)–2.906(1)Å], with the Pt atom bonded to one osmium [Os(2)–Pt 2.764(1)Å]. The carbido-carbon atom is irregularly bonded [1.90(2)–2.21(2)Å] to all four metal atoms. Each osmium atom is ligated by three terminal carbonyl ligands, whilst the platinum atom is bonded to a terminal carbonyl group and a P(cyclo-C₆H₁₁)₃ moiety. Two hydrido-ligands bridge the Os(1)–Os(3) and Os(1)-Os(2) vectors. Compound (2) contains a square-planar arrangement comprising two osmium and two platinum atoms with the third osmium atom [Os(3)] bridging the Os(1)–Os(2) edge. The angle between the planes Os(1)Os(2)Pt(1)Pt(2) and Os(1)Os(2)Os(3) is 76.4°. The carbido-carbon atom is approximately equidistant [2.065(11)T–2.120(10)Å] from all five metal atoms, and the metal–metal separations are Os–Os 2.855(1)–2.917(1), Os–Pt 2.929(1)–2.935(1), and Pt(1)–Pt(2) 2.716(1)Å. Each osmium atom carries three terminal carbonyl ligands, whilst the platinum atoms are symmetrically bridged by a carbonyl ligand, and each is ligated by a P(cyclo-C₆H₁₁)₃ group. The two hydrido-ligands bridge equivalent edges [Os(1)–Os(3) and Os(2)–Os(3)]. The n.m.r. data (¹H, ¹³C-{¹H}, and ³¹P-{¹H}) are all consistent with the structures established in the solid state. Treatment of [Pt(C₂H₄)₂{P(cyclo-C₆H₁₁)₃}] with [Os₃(µ-H)(µ-COMe)(CO)₁₀] in toluene at ambient temperatures affords a pentanuclear metal complex [Os₃Pt₂(µ-H)(µ₅-C)(µ-OMe)(µ-CO)(CO)₉{P(C₆H₁₁)₃}₂](3), the structure of which was again determined by single-crystal X-ray diffraction. Two platinum and two osmium atoms are arranged in a ‘buckled’ square with the third osmium atom [Os(3)] metal–metal bonded only to Os(1). As in (2), the carbido–metal distances are approximately equal [2.075(22)–2.144(20)Å]. Moreover, the metal–metal distances Os–Os [2.813(1)–2.853(1)Å] and Os–Pt [2.891(1)–2.941(1)Å] are rather similar to those in (2) but the Pt–Pt distance [2.668(1)Å] is noticeably shorter. In (3) each osmium atom carries three terminal carbonyl ligands, while a single carbonyl group asymmetrically bridges the two platinum atoms [Pt–µ-CO 2.032(23) and 1.968(20)Å]. Each platinum bears a P(cyclo-C₆H₁₁)₃ group, with the hydrido-ligand bridging the shorter of the two Pt–Os edges [Pt(1)–Os(1)]. The n.m.r. spectra are consistent with the structure established in the solid state though some dynamic behaviour is evident.