An investigation of the mixed-bridge dinuclear complex [Pt2(μ-S)(μ-NH2)(PPh3)4]+

The product formed by reaction of cis-[PtCl2(PPh3)2], NH3 and Na2S in ethanol, previously reported as [Pt2(μ-S)(PPh3)4], has been reinvestigated by electrospray ionisation mass spectrometry (ESI MS) and found to consist of the ethanol solvate of the well-known metalloligand [Pt2(μ-S)2(PPh3)4] together with the novel mixed-ligand complex [Pt2(μ-S)(μ-NH2)(PPh3)4]+. Upon prolonged ageing in air, a mixture of this complex with [Pt2(μ-S)(μ-O)(PPh3)4 + H]+ is observed by ESI MS. [Pt2(μ-S)(μ-NH2)(PPh3)4]+ can be prepared from cis-[PtCl2(PPh3)2] and aqueous NH3 using a stoichiometric quantity of sodium sulfide, or by reaction of [Pt2(μ-S)2(PPh3)4] with 2-chloro-1-methylpyridinium tetraphenylborate and ammonia; the complex was structurally characterised as its tetraphenylborate salt. This novel desulfurisation reaction was serendipitously discovered during investigations on the reactivity of [Pt2(μ-S)2(PPh3)4] towards 2-chloro-1-methylpyridinium iodide giving the known iodo complex [Pt2(μ-S)(μ-I)(PPh3)4]+, isolated as either the PF6− or I− salts.