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

Depending on the reaction conditions, different products are obtained from the reaction of CoCl 2 with CH 3 C(CH 2 PPh 2 ) 3 (triphos), including the low-spin complexes [(triphos)Co(μ-Cl) 2 Co(triphos)] 2+ ( 1 2+ ) and [(triphos)CoCl 2 ] ( 3 ), their solid-state structures being determined by X-ray methods. In solution, additionally, a four-coordinate high-spin complex [(η 2 -triphos)CoCl 2 ] ( 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) 2 MCl 2 ] (M = Fe ( 5 ), Co ( 6 )). Reactions with Lewis bases L yield complexes of the rare type [(triphos)CoCl(L)] + (L = CO ( 7 + ), PMe 3 ( 8 + ), NH 3 ( 9 + ), CH 3 CN ( 10 + )). One-electron reduction of 3 leads to the previously prepared pseudotetrahedral [(triphos)Co I Cl] complex 11, and one-electron oxidation to the novel trigonal-bipyramidal low-spin complex [(triphos)Co III Cl 2 ] + ( 12 + ).