Synthesis and crystal and molecular structure of tris-µ-(t-butyl isocyanide)-tris(t-butyl isocyanide)-triangulo-triplatinum

Abstract

Reaction of t-butyl isocyanide with bis(cyclo-octa-1,5-diene)platinum gives the orange crystalline complex [Pt₃(Bu^tNC)₆] in essentially quantitative yield. Methyl, ethyl, and cyclohexyl isocyanides react with [Pt(1,5-C₈H₁₂)₂] in a similar manner to give [Pt₃(RNC)₆](R = Me, Et, or C₆H₁₁). The structural identity of [Pt₃(Bu^tNC)₆] has been established by analysis of single-crystal X-ray data recorded at room temperature on a four-circle diffractometer. The complex is monoclinic, space group P2₁/n, Z= 4, a= 18.213(7), b= 11.811 (5), c= 21.996(6)Å, β= 110·21(3)°. Using 3 543 reflections, the refinement has converged to R 0.057 (R′0.070). The molecule contains an essentially equilateral triangle of platinum atoms each of which carries a terminal isocyanide ligand, with the remaining three isocyanide groups bridging the sides of the triangle. The former are effectively linear and the latter bent [CNC(mean) 132.7°]. The platinum atoms and the six attached carbon atoms are effectively coplanar with maximum deviation 0.08 Å. Hydrogen-1 and ¹³C n.m.r. studies between room temperature and 120 °C reveal that [Pt₃(Bu^tNC)₆] undergoes dynamic behaviour via an intermolecular process involving terminal and bridge isocyanide site exchange catalysed by free ligand.