Synthesis, Electrochemistry and Crystal Structure of the [Ni36Pt4(CO)45]6-and [Ni37Pt4(CO)46]6-Hexaanions

The [Ni36Pt4(CO)45]6-and [Ni37Pt4(CO)46]6-clusters have been obtained in mixture upon reaction in acetonitrile of [Ni6(CO)12]2-salts with K2PtCl4in a 2.5:1 molar ratio. The two hexaanions were indistinguishable by spectroscopic techniques. Crystallization of their trimethylbenzylammonium salts led to crystals of composition 0.5[NMe3CH2Ph]6[Ni36Pt4(CO)45]-0.5[NMe3CH2Ph]6[Ni37Pt4(CO)46] · C3H8O, hexagonal,space group P63(No. 173), a = 17.853(9), c = 27.127(13) Å, Z = 2; final R = 0.057. The metal core of the [Ni36Pt4(CO)45]6-anion consists of a Pt4tetrahedron fully encapsulated in a shell of 36 Ni atoms belonging to a very distorted and incomplete V5tetrahedron. The [Ni37Pt4(CO)46]6-hexaanion derives from the former by capping the unique triangular face of the metal polyhedron with an additional Ni(CO) fragment. The [ Ni36Pt4(CO)45]6--[Ni37Pt4(CO)46]6-mixture is rapidly degraded to the known [Ni9Pt3(CO)21]4-cluster by exposure to carbon monoxide. Its reaction with protic acids initially affords the corresponding [H6-nNi36Pt4(CO)45]n--[H6-nNi37Pt4(CO)46]n-(n = 5, 4) derivatives, and eventually leads to rearrangement to the known [H6-nNi38Pt6(CO)48]n-species. Both [Ni36Pt4(CO)45]6--[Ni37Pt4(CO)46]6-and [HNi36Pt4(CO)45]5--[HNi37Pt4(CO)46]5-mixtures have been chemically and electrochemically reduced to their corresponding [Ni36Pt4(CO)45]n--[Ni37Pt4CO)46]n-(n = 7-9) and [HNi36Pt4(CO)45]n--[HNi37Pt4(CO)46]n-(n = 6-8) mixtures.