Low-valent isocyanide complexes and clusters of palladium and platinum. Crystal structure of [Pt{C(NR)N(R)C(NR}(RNC)2](R = 2,6-Me2C6H3)

Abstract

Reduction of [PtCl2(RNC)2](R = 2,6-Me2C6H3) with sodium amalgam in the presence of isocyanide gave two clusters, [Pt3(RNC)6](1a) and [HgPt6(RNC)12](2a), and two metallocycles, [P[graphic omitted]R}(RNC)2](3a) and [P[graphic omitted] (NR)}(RNC)2](4a). In (2a) the six Pt atoms define a trigonal prism whose edges are associated with bridging and terminal isocyanide groups and the mercury atom is sandwiched by the two triangular Pt3 cores. The structure of (4a) was determined by X-ray analysis: space group Pbcn, a= 18.542(11), b= 22.702(5), c= 22.197(5)A, and Z= 8. In a similar reaction of [PdCl2(2,6-Me2C6H3NC)2], palladium analogues of (1a) and (4a) were isolated. Reduction of [MCl2(RNC)2](M = Pt or Pd) having bulky R groups 2,4-But2-6-MeC6H2 or 2,4,6-But3C6H2 gave the corresponding triangular trimetallic complexes [M3(RNC)6]. Six isocyanide molecules are bound to the metals as terminal and bridging ligands in the 2,4-di-t-butyl-6-methylphenyl isocyanide complex, and as only terminal isocyanide ligand in the 2,4,6-tri-t-butylphenyl isocyanide. Emission spectra of (2a) and the triangular palladium complexes were measured at 77 K; the former showed a fluorescence band at ca. 720 nm and the latter a phosphorescence band at ca. 640 nm.