Reduction–oxidation properties of organotransition-metal complexes. Part 16. Nitrosyl-bridged dicobalt complexes [{Co(η-NO)(η-C5R5)}2]z(R = H or Me, z= 0 to +2) and [CO2(µ-CO)(µ-NO)(η-C5Me5)2]z(z= 0 or +1): synthesis, electrochemistry, and relative reactivity

Abstract

The complex [Co(CO)₂(η-C₅H₅)] reacts with [NO][PF₆] in refluxing CH₂Cl₂ to give paramagnetic [{Co(µ-NO)(η-C₅H₅)}₂][PF₆](1), electrochemical studies on which reveal reduction to [{Co(µ-NO)(η-C₅H₅)}₂] and oxidation to [{Co(µ-NO)(η-C₅H₅)}₂]²⁺; ferrocenium ion oxidation of the neutral dimer provides a second route to (1). With [Co(CO)₂(η-C₅Me₅)], [NO][PF₆] gives [Co₂(µ-CO)(µ-NO)(η-C₅Me₅)₂][PF₆](2) which is chemically and electrochemically reduced to paramagnetic [CO₂(µ-CO)(µ-NO)(η-C₅Me₅)₂](3). Complex (2) and NO gas give the complex [{Co(µ-NO)(η-C₅Me₅)}₂][PF₆](4) which is reduced to [{Co(µ-NO)(η-C₅Me₅)}₂](5) by K[BH(CHMeEt)₃]. Electrochemical studies on complex (4) show one-electron reduction to (5) and oxidation to [{Co(µ-NO)(η-C₅Me₅)}₂]²⁺(6) which may be made from (2) and [NO][PF₆]. Complex (1) reacts with cyclo-octene (L) and Ag[PF₆] to give [CoL(NO)(η-C₅H₅)][PF₆], with PPh₃ to give [{Co(µ-NO)(η-C₅H₅)}₂] and [Co(PPh₃)(NO)(η-C₅H₅)][PF₆], and with CNC₆H₃Me₂-2,6 to give [Co(CNC₆H₃Me₂-2,6)₃(NO)] and [Co₂(CNC₆H₃Me₂-2,6)₂(µ-NO)(η-C₅H₅)₂][PF₆].