65836-19-3Relevant academic research and scientific papers
(Trimethylphosphine)cobalt(I) complexes. 4. Reaction with acyclic dienes and crystal structure of (butadiene)tris(trimethylphosphine)cobalt(I) tetraphenylborate
De Carvahlo, L. C. Ananias,Pèrés, Yolande,Dartiguenave, Michéle,Dartiguenave, Yves,Beauchamp, Andrè L.
, p. 2021 - 2028 (2008/10/08)
Reaction of CoBr(PMe3)3 with butadiene, isoprene, and 2,3-dimethylbutadiene in presence of NaBPh4 yielded [Co(diene)(PMe3J3] BPh4 complexes. The crystal structure of [Co(η4-C4H6)(PMe3) 3]BPh4 has been determined by X-ray diffraction techniques. The complex crystallizes in the monoclinic system, C2/c, with a = 46.71 (2) A?, b = 15.93 (4) A?, c = 34.21 (2) A?, β = 118.69 (4)°, Z = 24, and R = 0.083 (5587 observed reflections). The structure consists of a perfectly ordered framework of BPh4 anions, in which large cavities are occupied by [Co(η4-C4H6)(PMe3) 3]+ cations. In only one-third of these cavities are the cations ordered. Two different kinds of disorder are found for the remaining cations. In the ordered cations, cobalt is in a distorted square-pyramidal environment. One of the PMe3 molecules is apical, whereas two PMe3 molecules and the butadiene ligand occupy the basal sites. The difference between the apical (2.192 (5) A?) and basal (average 2.221 (4) A?) Co-P bond lengths is significant but small. The butadiene ligand is planar within 0.5σ, and its plane makes an angle of 84.5° to the basal plane. It is symmetrically coordinated and the cobalt atom is located 0.60 A? above the basal plane. In one of the disordered cations, two isomeric forms related by a 120° rotation of the butadiene ligand about the pseudo C3 axis of the Co(PMe3)3 fragment are observed, suggesting the possibility of fluxionality in the crystal. Multinuclear NMR studies (187-295 K) show that in solution the [Co(η4-diene)(PMe3)3]BPh4 compounds do not exist as η3-allyl complexes with σ-CH2 ligand-to-cobalt interactions but retain the η4-diene structure observed in the solid state.
