Further studies on the chemistry of molybdenyl adducts of [Pt 2(μ-S)2(PPh3)4]: Hydrolysis, condensation and ligand exchange processes

Abstract

Reaction of [Pt2(μ-S)2(PPh3) 4] with [MoO2(acac)2] in methanol gives the known five-coordinate Mo(VI) adduct [Pt2(μ-S)2(PPh 3)4MoO2(OMe)]+ isolated as its PF6 -, BPh4 - and [Mo 8O26]4- salts; the latter was structurally characterised, the polymolybdate anion being the uncommon γ form. Hydrolysis of [Pt2(μ-S)2(PPh3) 4MoO2(OMe)]+ in wet dichloromethane initially produces [Pt2(μ-S)2(PPh3) 4MoO2(OH)]+ and subsequently the bright yellow oxo-bridged dimolybdenum species [{Pt2(μ-S)2(PPh 3)4MoO2}2O]2+, structurally characterised as its tetraphenylborate salt, and found to contain two five-coordinate molybdenum centres. [{Pt2(μ-S) 2(PPh3)4MoO2}2O] 2+ can be prepared directly from [Pt2(μ-S) 2(PPh3)4] and [MoO2(acac) 2] in wet MeCN. Slow reconversion to [Pt2(μ-S) 2(PPh3)4MoO2(OMe)]+ occurs when [{Pt2(μ-S)2(PPh3) 4MoO2}2O]2+ is dissolved in methanol. [Pt2(μ-S)2(PPh3) 4MoO2(OMe)]+ undergoes alkoxide exchange in dichloromethane-alcohol solutions to give [Pt2(μ-S) 2(PPh3)4MoO2(OR)]+ species (R = e.g. n-octyl). These reactions are easily monitored using electrospray ionisation mass spectrometry. © 2011 Elsevier B.V.