Synthesis, Structure, Spectroscopy, and Reactivity of Oxapentadienyl−Cobalt−Phosphine Complexes<sup>,</sup>
作者:John R. Bleeke、Bryn L. Lutes、Michael Lipschutz、Donastas Sakellariou-Thompson、John Seonghyun Lee、Nigam P. Rath
DOI:10.1021/om100361a
日期:2010.11.8
The first examples of oxapentadienyl-cobalt complexes have been synthesized and structurally characterized. Treatment of (Cl)Co(PMe3)(3) with potassium oxapentadienide produces ((1,2,3-eta)-5-oxapentadienyl)Co(PMe3)(3) (1), while the reaction of (Cl)Co(PMe3)(3) with potassium 2,4-dimethyloxapentadienide generates ((1,2,3-eta)-2,4-dimethyl-5-oxapentadienyl)Co(PMe3)(3) (2). Both 1 and 2 undergo ligand substitution reactions when treated with excess carbon monoxide. Compound 1 reacts with 1 equiv of CO to produce ((1,2,3-eta)-5-oxapentadienyl)Co(PMe3)(2)(CO) (3), while 2 undergoes a double CO substitution to generate ((1,2,3-eta)-2,4-dimethyl-5-oxapentadienyl)Co(PMe3)(CO)(2) (4). Compound 3 can also be synthesized by reacting (Cl)Co(PMe3)(2)(CO)(2) with potassium oxapentadienide, but the analogous reaction involving potassium 2,4-dimethyloxapentadienide results in reduction of the cobalt starting material and production of the Co(0) dimer (CO)(PMe3)(2)Co(PMe)(2)Co(PMe3)(2)(Co) (5). Treatment of 1 with triflic acid (HO3SCF3) or methyl triflate (MeO3SCF3) results in electrophilic attack at oxygen and production of (eta(4)-butadienol)Co(PMe3)(3)+O3SCF3- (6) or (eta(4)-butadienyl methyl ether)Co(PMe3)3+O3SCF3- (7). Treatment of 2 with triflic acid or methyl triflate also results in electrophilic attack at oxygen; however, these products are unstable and rapidly lose their protonated or methylated ligands. The resulting Co(PMe3)4+O3SCF3-, generated in situ, reacts with excess carbon monoxide to produce Co(PMe3)(3)(CO)(2)+O3SCF3- (8). Compounds 1-8 have been characterized by single-crystal X-ray diffraction.