122519-60-2Relevant academic research and scientific papers
(Trimethylphosphine)cobalt(I) complexes: Reactions of CoBr(PMe3)3 with the terminal alkynes HC≡C-t-Bu, HC≡CPr, and HC≡CPh. X-ray structure of [Co(C≡C-t-Bu)(HC=CH-t-Bu)(MeCN)(PMe3)3]BPh 4
Habadie, Nouzzha,Dartiguenave, Michèle,Dartiguenave, Yves,Britten, James F.,Beauchamp, André L.
, p. 2564 - 2569 (2008/10/08)
CoBr(PMe3)3 reacted with the terminal alkynes HC≡C-t-Bu, HC≡CPr, and HC≡CPh under mild conditions in polar solvents. With HC≡C-t-Bu and HC≡CPr, (σ-alkynyl)(σ-alkenyl)cobalt(III) products [Co(C≡CR)(CH=CHR)(MeCN)(PMe3)3]BPh4 (R = t-Bu, 1; R = Pr, 2) formed in two steps: oxidative addition of the alkyne to the cobalt center and then insertion of the second alkyne into the Co-H bond. The reaction is regioselective, giving only the trans-alkenyl isomer with the alkyne substituent in β-position of cobalt. The structure of 1 was determined by X-ray diffraction (P21/c, a = 22.139 A?, b = 10.315 A?, c = 24.265 A?, β = 121.57°, Z = 4, R = 0.035 for 4428 observed Mo Kα? reflections). The unit cell contains BPh4- anions and distorted octahedral Co(III) complex cations. The metal is bonded to three roughly coplanar PMe3 ligands in a mer arrangement, with the fourth corner in the same plane occupied by a trans-tert-butylvinyl ligand. The bonds perpendicular to this plane are formed with MeCN and a tert-butylacetylide ligand. The Co-(C≡C) and Co-(CH≡CH) bonds occupy cis corners, and their lengths are 1.869 (4) and 1.985 (3) A?, respectively. HC≡CPh reacted differently, yielding four new species: a phoephonium salt, [Me3PCH2CH(OMe)Ph]BPh4, a cobalt(I) complex, [Co(HC≡CPh)(MeCN)(PMe3)3]BPh4, and two cobalt(III) species, CoH(C≡CPh)2(PMe3)3 and [Co(C≡CPh)2(PMe3)4]BPh4. A reaction scheme is proposed whereby the second alkyne molecule, once bonded to cobalt, would undergo successive nucleophilic attacks by methanol and by trimethylphosphine. Alkyne polymerization was never observed in these systems under the present conditions.
