Structure of a Transition Metal Complex with a Terminal Dicyanovinylidene Ligand, MoCl(π-C₅H₅)[C=C(CN)₂[P(OCH₃)₃]₂

The structure of (dicyanovinylidene)(π-cyclopentadienyl)-trans-bis(trimethyl phosphite)chloromolybdenum(II), MoCl(π- C₅H₅)[C=C(CN)₂][P(OCH₃)₃]₂, has been determined from three-dimensional X-ray data collected by counter methods. The clear orange compound crystallizes in space group C_2h⁵-P2₁/n of the monoclinic system with four molecules in a unit cell of dimensions a = 9.127 (2) Å, b = 18.515 (2) Å, c = 12.923 (2) Å, and β = 91.56 (1)°. The observed and calculated densities are 1.51 (2) and 1.58 g cm^-3, respectively. Full-matrix least-squares refinement led to a final value of the conventional R index (on F) of 0.043 for the 3037 reflections having F²> 3σ(F²). The structure consists of discrete monomers. The coordination geometry about the metal is distorted square pyramidal. The π-cyclopentadienyl ligand occupies the apical position while the dicyanovinylidene, chloro, and trimethyl phosphite ligands occupy the basal plane. The molybdenum atom is located 0.779 (3) Å from the basal plane. The trans trimethyl phosphite ligands are disordered. Some important bond distances (in Å) are as follows: Mo-C(dicyanovinylidene), 1.833 (6); Mo-P(1), 2.461 (2); Mo-P(2), 2.470 (2); Mo-Cl, 2.467 (1). An interesting feature of the structure is that the nearly planar dicyanovinylidene ligand is bent (Mo-C(1)-C(2) = 166.6(4)°) toward the apical cyclopentadienyl ring which, in its own right, is tilted toward the dicyanovinylidene ligand. These structural features are consistent with an attractive “through-space” ligand-ligand interaction, as well as with an asymmetric metal-ligand π-back-bonding interaction.