Reactions of decakis(isopropylisocyanide)dicobalt(II) complexes with tertiary phosphine ligands

Abstract

Reaction of [Co 2(CNCHMe 2) 10]X 4· nH 2O (XClO 4, BF 4) with triarylphosphines and substituted trialkylphosphines produces disubstituted Co(I) complexes, [Co(CNCHMe 2) 3(PR 3) 2]X; R  C 6H 5, C 6H 4Cl- p, C 6H 4OMe- p, CH 2C 6H 5, NMe 2, CH 2CH 2CN. These reduction/ligand-substitution reactions are analogous to those of [Co(CNCMe 3) 4H 2O](ClO 4) 2. Reaction with unsubstituted trialkylphosphines produces Co(III) complexes, [Co(CNCHMe 2) 4(PR 3) 2]X 3; R  C 4H 9-n, C 6H 13-n; in disproportionation reaction from which the Co(I) complex is not recovered: [CO 2(CNCHMe 2) 10]X 4+4PR 3 → [Co(CNR) 4(PR 3) 2]X 3+ [Co(CNR) 3(PR 3) 2]X+3CNR. Solution properties (ν(  NC), electronic spectra, Λ M) are compared for CNCHMe 2 and CNCMe 3 complexes. The Co(I) complexes are 1:1 electrolytes in CH 3CN, CH 3NO 2, CH 3C(O)CH 3 and CH 2Cl 2; the Co(III) complexes are 3:1 electrolytes in CH 3CN and CH 3NO 2, but exhibit increasing ion-pairing in acetone and CH 2Cl 2. The ν( NC) suggest decreasing π *-acceptance in the order: CNCHMe 2 ⪢ P(C 6H 4Cl- p) 3 > P(C 6H 5) 3 ≥ P(CH 2CH 2CN) 3 > P(C 6H 4OMe- p) 3 > P(CH 2Ph) 3 > P(NMe 2) 3. Solution structure for [Co(CNCHMe 2) 3(PR 3) 2]X is believed to be distorted trigonal bipyramidal, but rigorous D 4h for [Co(CNCHMe 2) 4(PR 3) 2]X 3.