Structure of trans-M(CO)(C₄N₃)(PPh₃)₂.1.5C₆H₆ (M = Ir and Rh): the pyramidal geometry of the tricyanomethanide anion (C₄N₃ ⁻)

Abstract

The crystal structures of two tricyanomethanide (TCM) complexes have been determined. Compound In both cases the TCM ligand is coordinated to the metal, near linearly through nitrogen, and both metal centers have a distorted square-planar geometry. In the RT structure, the geometry of TCM is planar with one set of unusually large displacement parameters for one of the cyano groups. In the LT structure of (1), these large anisotropic displacement parameters were resolved into halfpopulated C and N sites of disordered cyano groups. The geometry of TCM is thus slightly, pyramidal, with the central C atoms lying 0.115 A out of the plane defined by the three C atoms (C1, C2, C431) bonded to it.

Crystal structures and magnetic properties of the interpenetrating rutile-related compounds M(tcm)2 [M = octahedral, divalent metal; tcm− = tricyanomethanide, C(CN)3−] and the sheet structures of [M(tcm)2(EtOH)2] (M = Co or Ni)

“…14 Crystal structure studies of simple salts of tcm Ϫ with NH 4 ϩ , 15 Na ϩ 16 and K ϩ 17 and of other derivatives involving either unco-ordinated 18 or monodentate 19 tcm Ϫ generally reveal an essentially planar tcm Ϫ ; one notable exception is [Ir(CO)(tcm)(PPh 3 ) 2 ], which shows a distortion towards pyramidal geometry. 20 The anion tcm Ϫ appeared to offer considerable promise as a building block for infinite co-ordination networks because it is robust, stable under a variety of conditions, easily synthesized as a variety of salts, 21 its planar, trigonal geometry appears to be fairly rigid, and it co-ordinates to metal centres readily on account of its negative charge and good terminal nitrogen donors. We have already reported a range of new co-ordination polymers in which both tcm Ϫ and various co-ligands act simultaneously as connecting units.…”