Solvent-Driven P-S vs P-C Bond Formation from a Diplatinum(III) Complex and Sulfur-Based Anions

The outcome of the reaction of the Pt(III),Pt(III) complex [(C6F5)2PtIII(μ-PPh2)2PtIII(C6F5)2](Pt-Pt) (1) with the S-based anions thiophenoxide (PhS-), ethyl xanthogenate (EtOCS2-), 2-mercaptopyrimidinate (pymS-), and 2-mercaptopyridinate (pyS-) was found to be dependent on the reaction solvent. The reactions carried out in acetone led to the formation of [NnBu4][(RF)2PtII(μ-PhS-PPh2)(μ-PPh2)PtII(RF)2] (2), [NnBu4][(RF)2PtII(μ-EtOCS2-PPh2)(μ-PPh2)PtII(RF)2] (3), [NnBu4][(RF)2PtII(μ-pymS-PPh2)(μ-PPh2)PtII(RF)2] (4), and [NnBu4][(RF)2PtII(μ-pyS-PPh2)(μ-PPh2)PtII(RF)2] (5), respectively (RF= C6F5). Complexes 2-5 display new Ph2P(SL) ligands exhibiting a ΰ2-P,S bridging coordination mode, which is derived from a reductive elimination of a PPh2group and the S-based anion. Carrying out the reaction in dichloromethane afforded, in the cases of EtOCS2-and pymS-, the monobridged complexes [NnBu4][(PPh2RF)(RF)2PtII(μ-PPh2)PtII(EtOCS2)(RF)] (6) and [NnBu4][(PPh2RF)(RF)2PtII(μ-PPh2)PtII(pymS)(RF)] (7), respectively, which are derived from reductive elimination of a PPh2group with a pentafluorophenyl ring. The reaction of 1 with EtOCS2K in acetonitrile yielded a mixture of 3 and 6 as a consequence of the concurrence of two processes: (a) the formation of 3 by a reaction that parallels the formation of 3 by 1 plus EtOCS2K in acetone and (b) the transformation of 1 into the neutral complex [(PPh2RF)(CH3CN)(RF)PtII(μ-PPh2)PtII(RF)2(CH3CN)] (8), which, in turn, reacts with EtOCS2K to give 6. The 1 to 8 transformation was found to be fully reversible. In fact, dissolving 8 in acetone or dichloromethane afforded pure 1 after solvent evaporation or crystallization with n-hexane. The XRD structures of 2-4 and 6-8 were determined, and the behavior in solution of the new complexes is discussed.