Complexes of Cobalt(II) Chloride with the Tripodal Trisphosphane triphos:  Solution Dynamics, Spin-Crossover, Reactivity, and Redox Activity

Abstract

Depending on the reaction conditions, different products are obtained from the reaction of CoCl2 with CH3C(CH2PPh2)3 (triphos), including the low-spin complexes [(triphos)Co(μ-Cl)2Co(triphos)]2+ (1 2+) and [(triphos)CoCl2] (3), their solid-state structures being determined by X-ray methods. In solution, additionally, a four-coordinate high-spin complex [(η2-triphos)CoCl2] (2) is present, its concentration relative to that of 3 depending on the solvent and the temperature. The reactivity of these species toward Lewis acids is investigated leading to the novel heterodinuclear complexes [(triphos)Co(μ-Cl)2MCl2] (M = Fe (5), Co (6)). Reactions with Lewis bases L yield complexes of the rare type [(triphos)CoCl(L)]+ (L = CO (7 +), PMe3 (8 +), NH3 (9 +), CH3CN (10 +)). One-electron reduction of 3 leads to the previously prepared pseudotetrahedral [(triphos)CoICl] complex 11, and one-electron oxidation to the novel trigonal-bipyramidal low-spin complex [(triphos)CoIIICl2]+ (12 +).

Magnetic Interaction in Dinuclear Triphos−Cobalt Complexes with Co···Co Separations of 8 and 10 Å

“…The small energy difference and activation barrier between square-pyramidal and trigonal-bipyramidal distorted triphosϪCo complexes has been experimentally shown by EPR [24] as well as by the fact that in one case both conformational isomers have been isolated in the solid state. [33] This is consistent with the assumption that neither the total energy nor the energy gap of the frontier orbitals change significantly during the distortion. Therefore unlike the CuϪCu dimers [2] [7] the singletϪtriplet splitting in CoϪCo dimers of the type described in this work appears relatively insensitive towards this geometrical distortion.…”

Highly Selective Cobalt‐Catalyzed Hydrovinylation of Styrene

“…[21] The P À Co bond lengths of~2.3-2.4 are in the typical range observed for Co(II)-phosphine complexes. [22] The Xantphos ligand backbone is close to planar, significantly different as observed in various other metal complexes bearing this particular ligand scaffold. [23] The Co À O distances of~2.9-3.0 are considerably shorter than the sum of the ionic radii (3.55 ), which might suggest some weak bonding interaction with the oxygen atom, while this does not lead to a very large P À Co À P angle.…”

Reductive Activation of Tripod Cobalt Compounds: Oxidative Addition of H−H, P−H, and Sn−H Functions

“…On the other hand, it is well-known that templates L 3 Co (L ϭ PMe 3 ) [3] also possess a rich chemistry with Co in lower oxidation states. A possible entry into the chemistry of low-valent [tripodCo] compounds is the reduction of easily accessible [tripodCo II ] compounds such as tripodCoCl 2 (1) (Scheme 1), [4] by electropositive metals. Using zinc powder as the reductant, [5] the Co I compound tripodCoCl (2), is produced, [4,6] which in itself allows access to the chemistry of [tripodCo I ] derivatives.…”

“…A possible entry into the chemistry of low-valent [tripodCo] compounds is the reduction of easily accessible [tripodCo II ] compounds such as tripodCoCl 2 (1) (Scheme 1), [4] by electropositive metals. Using zinc powder as the reductant, [5] the Co I compound tripodCoCl (2), is produced, [4,6] which in itself allows access to the chemistry of [tripodCo I ] derivatives. [5] Reduction of 1 with Na/Hg has been found to produce tripodCo(N 2 )Cotripod (3).…”