Cycloneophylplatinum Chemistry: A New Route to Platinum(II) Complexes and the Mechanism and Selectivity of Protonolysis of Platinum–Carbon Bonds

A new route to cycloneophylplatinum­(II) complexes is reported and the selectivity of protonolysis of the platinum–aryl and −alkyl bonds has been determined. Reaction of [PtCl2(SMe2)2] with neophylmagnesium chloride gives the binuclear cycloneophylplatinum­(II) complex [Pt2(CH2CMe2C6H4)2(μ-SMe2)2], 1, which is shown to exist as a mixture of syn and anti isomers. Complex 1 reacts reversibly with SMe2 to give [Pt­(CH2CMe2C6H4)­(SMe2)2], 2, and irreversibly with bidentate ligands NN = 3,4,7,8-tetramethyl-1,10-phenanthroline (phen*) or 4,4′-di-t-butyl-2,2’bipyridine (bubipy) to give the corresponding complexes [Pt­(CH2CMe2C6H4)­(phen*)], 3, and [Pt­(CH2CMe2C6H4)­(bubipy)], 4, respectively. Complex 2 reacts with HCl initially by cleavage of the aryl–platinum bond to give mostly trans-[PtCl­(CH2CMe2Ph)­(SMe2)2], which then rearranges to an equilibrium mixture with trans-[PtCl­(C6H4-2-t-Bu)­(SMe2)2], while 3 and 4 react to give [PtCl­(CH2CMe2Ph)­(phen*)] and [PtCl­(CH2CMe2Ph)­(bubipy)], which do not undergo the isomerization reaction. The protonolysis reactions occur by way of a platinum­(IV) hydride complex in each case, and the unusual reactivity of complex 2 is attributed to the ease of dissociation of the Me2S ligands.