Substitution of chloride in [PtCl2(PEt3)2] by the chiral anionic ligand [Mo(CO)5(PPhH)]- to give mixed platinum-molybdenum compounds and a 31P{1H} NMR analysis of their fluxionality. X-ray crystal structure of [PtCl(PEt3)2

Article abstract of DOI:10.1016/S0277-5387(96)00403-2

Deprotonation of the primary phosphine complex [Mo(CO)₅(PPhH₂)] generated [Mo(C-O)₅(PPhH)]^-, a chiral anionic ligand which reacted readily with cis-or trans-[PtCl₂(PEt₃)₂] via facile nucleophilic substitution of one or both chloride ligands to afford trans-[PtCl(PEt₃)₂(μ-PPhH){Mo(CO)₅}] (1) and cis- and trans-[Pt(PEt₃)₂(μ-PPhH)₂{Mo(CO) ₅}₂] (2), respectively. These are rare examples of heterometallic complexes containing primary phosphido bridges. Compound 1 can be described either as the square-planar Pt^II complex with the anionic ligand PPhH{Mo(CO)₅}^- or as the Pt-Mo phosphido-bridged dimer trans-[PtCl(PEt₃)₂(μ-PPhH){Mo(CO)₅}]. As a phosphido-bridged heterobimetallic 1 possesses an exceptionally large Pt-P-Mo angle [120.9(1)°] reflecting the long Pt-Mo nonbonding interaction (4.5 A). Compound 2 can correspondingly be described either as a phosphido-bridged PtMo₂ trimer or a square-planar arrangement of two neutral PEt₃ and two anionic PPhH{Mo(CO)₅} ligands at Pt. The low-temperature ³¹P{¹H} NMR spectrum of 1 showed several ABXY spin systems together with their associated ABXYM (M = ¹⁹⁵Pt) counterparts and variable-temperature studies revealed the dynamic interconversion of several rotametric isomers arising from restricted rotation about the Pt-Pμ bond. The ³¹P{¹H} NMR spectrum of trans-2 shows its two possible RR/SS and meso diastereoisomers, the latter existing in clearly identifiable rotameric forms which interconvert slowly at -75°C. We note very different values between ²J(P-P) and ¹J(¹⁹⁵Pt-P) for the anionic ligands [PPhH{Mo(CO)₅}]^- and PEt₃, unattributable to bond length variation but which must reflect reduced s-orbital contribution to the Pt-P bond of the anionic phosphines PPhH{Mo(CO)₅}.