SYNTHESIS AND CHARACTERIZATION OF TRIS(ALKYLISOCYANIDE) BIS(TRIARYL-PHOSPHINE)COBALT(II) COMPLEXES

A series of complexes having the general formula, [Co(CNR) 3 (PR 3 ) 2 ]X 2 , X = ClO 4 , BF 4 with CNR = CNCMe 3 , CNCHMe 2 , CNC 6 H 11 . CNCH 2 Ph and PR 3 = PPh 3 , P(C 6 H 4 Me-p) 3 , P(C 6 H 4 OMe-p) 3 has been synthesized and characterized. Synthesis can be achieved by reaction of [Co(CNR) 4 (AsPh 3 ) 2 ]X 2 complexes with controlled excess of PR 3 ligands, and by AgClO 4 /AgBF 4 oxidation of the [Co(CNR) 3 (PR 3 ) 2 ]X complexes. The latter procedure is preferable. Alternate syntheses of the [Co(CNR) 3 (PR 3 ) 2 ]X complexes have also been employed. Five-coordinate Co(II) complexes have not been obtained using CNCMe 3 with P(C 6 H 4 Me-p) 3 ligands, CNCH 2 Ph with P(C 6 H 4 OMe-p) 3 ligands, or CNC 4 H 9-n with PPh 3 ligands. [Co(CNC-Me 3 ) 3 {P(C 6 H 4 Cl-p) 3 } 2 ]ClO 4 produced only [Co{CNCMe 3 ) 4 H 2 O](ClO 4 ) 2 upon forced oxidation with excess AgClO 4 . [Co(CNR) 3 (PR 3 ) 2 ]X 2 complexes appear to undergo varying degrees of distortion from regular (i.e., D 3h symmetry) axially-disubstituted trigonal bipyramidal coordination in the solid state, as evidenced by v(-N°C) IR patterns, but to assume regular trigonal bipyramidal coordination in solution. Effective magnetic moments indicate one-electron paramagnetism, and solution electronic spectra are compatible with trigonal bipyramidal coordination.