New Synthetic Methods for η5-Cyclopentadienyl Nickel(III) Dithiolene Complexes Derived from Nickelocene

Abstract

The reactions of nickelocene with the neutral square-planar metal dithiolene complexes [M(S2C2(R1)(R2))2] gave the η5-cyclopentadienyl nickel(III) dithiolene complexes [CpNi(S2C2(R1)(R2))] (R1, R2 = Ph (2); R1 = Ph, R2 = H (3); R1, R2 = Me (4)) in 58−62% yields. The monoanions of the square-planar dithiolene complexes [M(S2C2(R1)(R2))2]- reacted with nickelocenium to form [CpNi(S2C2(R1)(R2))] (R1, R2 = COOMe (5) or CN (6)) in 67% or 68% yield, respectively, when the R1 and R2 substituents are electron-withdrawing groups. The CpNi dithiolene complexes 3 and 5 were also obtained by the thermal reactions or photoreactions of nickelocene with 1,3-dithiol-2-one or 1,3-dithiol-2-thione derivatives, [EC(S2C2(R1)(R2))] (E = O, S; R1 = Ph, R2 = H; R1, R2 = COOMe). The most efficient synthetic method for the CpNi dithiolene complex was the reaction of the hexacoordinated platinum dithiolene complex [Pt(S2C2Ph2)2(dppe)] (dppe = bis(diphenylphosphino)ethane) with nickelocene (96% yield for complex 2). The structure of complex 6 was determined by X-ray crystal structure analysis. The electronic and ESR properties of the CpNi dithiolene complexes 2−6 were investigated.