Synthesis and metal carbonyl complexes of cis,cis-1,3,5-triisocyanocyclohexane, an unusual tridentate ligand

Relatively little is known about the coordination chemistry of multidentate isocyanide ligands as compared to their monodentate analogues.2 The synthesis and reactions of a series of alkyl238239 and aryl240 diisocyanide ligands were recently investigated. We wish to report herein the synthesis and chemical properties of an unusual tridentate triisocyanide ligand, cis, cis-1, 3, 5-triisocyanocyclohexane (triNC), which is potentially capable of coordinating to a triangular array of three metal-metal-bonded atoms. The ligand may assume either of two forms: A or B. In form A the NC groups.all axial and the three carbon atoms describe an equilateral triangle whose edge is about 2.5 Å. Molecular models indicate that this distance is comparable to metal-metal bond lengths in triangular arrays of metal atoms in many metal carbonyl clusters. Form A of triNC is related to the bidentate 1, 3-diisocyanopropane (bridge) ligand which is known to bridge two interacting Rh atoms in the Rh2(bridge)42+ complexes.3 These considerations suggested that triNC may be capable of coordinating to and perhaps stabilizing triangular arrays of metal atoms in simple M3 clusters or in larger polyhedra with triangular faces.