Synthesis and Crystal Structure of Tris(4-nitrophenyl isocyanide)bis(diethyl phenylphosphonite)cobalt(I) Perchlorate

The syntheses of five-coordinate cobalt(I) complexes of the type [Co(4-NO2C6H4NC)5-x(PhP(OEt)2)x]ClO4 (x = 2 or 3) obtained by reaction at room temperature of 4-nitrophenyl isocyanide with cobalt(II) chloride and diethyl phenylphosphonite is reported. The compounds were characterized on the basis of their chemical and physical properties (conductivities and infrared, electronic, and 1H NMR spectra). The crystal and molecular structure of tris(4-nitrophenyl isocyanide)bis(diethyl phenylphosphonite)cobalt(I) perchlorate, [Co(4-NO2C6H4NC)3(PhP(OEt)2)2]ClO4, has been determined by single-crystal x-ray analysis and refined, with full-matrix least squares using anisotropic temperature parameters for all atoms, to R = 0.072 on F2. The crystals are monoclinic, space group P21/c (C2h5), with a = 13.085 (5) Å, b = 10.826 (4) Å, c = 33.019 (8) Å, β = 91.92 (3)°, and Z = 4. The coordinated polyhedron around the cobalt atom has the shape of a slightly distorted trigonal bipyramid with isocyanide ligands in the equatorial positions. The average Co-C and Co-P distances (1.80 and 2.175 Å, respectively) clearly indicate strong double-bond character. Distortions around the phosphorus atoms are compared with those found in Ni(II) and Fe(II) complexes with the same phosphonite ligand and correlated to the M-P ir interaction. © 1976, American Chemical Society. All rights reserved.