Syntheses of pentamethylcyclopentadienylcobalt(III) compounds and reactions of [Co(C5Me5)(solvent)3]X2(solvent = acetonitrile or acetone, X = BF4or PF6)

Abstract

The complexes [Co(C₅Me₅)I₂L][L = PMe₂Ph, P(OPh)₃, or CNBu^t] and [Co(C₅Me₅)IL₂]I (L = CNBu^t) are prepared by reaction of [{Co(C₅Me₅)l₂}_n] with the appropriate Lewis base, L. The preparation and properties of [Co(C₅Me₅)(solvent)_n]X₂[solvent = NCMe, n= 3, X = PF₆(6); solvent = OCMe₂, n believed to be 3, X = PF₆(8a) or BF₄(8b)] are described including the rapid solvolysis of the hexafluorophosphate anion of (8a). Reaction of the complexes (6) or (8) with the appropriate small ligand L yields [Co(C₅Me₅)L₃]²⁺[L = P(OMe)₃, P(OEt)₃, pyridine, or CNBu^t] whereas larger ligands with (6) give [Co(C₅Me₅)(NCMe)₂L]²⁺[L = PMe₂Ph, P(OPh)₃, or PPh₃]. One equivalent of 1,10-phenanthroline (phen) and MeCN react with (6) to give [Co(C₅Me₅)(phen)(NCMe)]²⁺ whereas excess of phen gives [Co(phen)₃]²⁺; a similar displacement of the C₅Me₅ ligand occurs when [Co(C₅Me₅)I₂(CO)] reacts with Ag[PF₆] in dimethyl sulphoxide to give [Co(OSMe₂)_n][PF₆]₂. These reactions have been contrasted with those of the analogous complexes [M(C₅Me₅)(solvent)_n][PF₆]₂(M = Rh or lr).