Trimethylphosphine-cobalt(I) complexes. crystal and molecular structure of the (nonbornadiene)tris(trimethylphosphine)cobalt(I) tetraphenylborate complex, [Co(η 4-C 7H 8)(PMe 3) 3[BPh 4

Abstract

Reaction of CoBr(PMe 3) 3 with norbornadiene, a non-conjugated diene, in presence of NaBPh 4 gives rise to a high yield of the [Co(η 4-C 7H 8)(PMe 3) 3]BPh 4 complex. Its cyrstal structure has been determined by X-ray diffraction techniques. The compound belongs to the orthorhombic space group Pmn2 1, with a 15.114(11), b 10.006(7), c 12.316(11) Å) and Z  2 formula units per cell. The structure was solved from a set of 1482 nonzero Mo- K α reflections collected at 170 K and refined to R  0.047. The crystal consists of discrete BPh 4 − anions and [Co(PMe 3) 3− (norbornadiene)] + cations. The BPh 4 − ion sits on the crystallographic mirror plane and it is not disordered. The complex cation is involved in a two-fold disorder in which two individuals are related by the crystallographic mirror plane. In addition, one of the phosphines shows two-fold oreientation disorder of the methyl groups about the CoP bond. The complex cation has no crystallographic symmetry of its own. Its environment is best described as a distorted square pyramid (mean L apicalCoL basal 103.6°), with one of the PMe 3 Ligands (CoP(1) 2.290(3) Å) occupying the apical position. Norbornadiene spans two adjacent basal sites (Comid |2.010(10) and 1.935(11) Å), whereas the two remaining basal sites are occupied by PMe 3 molecules (CoP(2) 2.243(2), CoP(3) 2.182(3) Å). Multinuclear NMR studies (183–293 K) show that the complex is stereochemically non-rigid in this temperature range.