Structures, Physicochemical Properties, and Reactivities of Cobalt(II) Complexes Supported by a Homoscorpionate (Tris(pyrazolyl)borate) Ligand TpPh,Me

The coordination chemistry of a mononuclear cobalt complex supported by the monoanionic hydrotris­(pyrazolyl)­borate tridentate ligand [TpPh,Me] containing substituted phenyl groups at the 3-position of the pyrazole rings and methyl groups at the 5-position of the pyrazole rings is examined. The Co­(II) halide complex [TpPh,Me]­CoCl (1) serves as a precursor to the organometallic species [TpPh,Me]­CoMe (2), [TpPh,Me]­CoCH2SiMe3 (3), [TpPh,Me]­CoCH2CH­(Me)2 (4), [TpPh,Me]­Co­(CH2)2Me (5), [TpPh,Me]­CoEt (6), [TpPh,Me]­Co­(CH2)5Me (7), and [TpPh,Me]­Co­(CH2)3Me (8). All of the cobalt­(II) organometallic complexes have been characterized by X-ray crystallography, NMR spectroscopy, FT-IR, and elemental analysis. The X-ray crystallographic analyses reveal that complexes 2–6 and 8 have slightly distorted tetrahedral structures. Solution-state magnetic susceptibility measurements of all complexes in C6D6 indicate that they all have 3/2 ground states. The reaction of 1 with tBuLi and iPrMgCl in hexane under N2 results in the production of the i-butyl and n-propyl complexes 4 and 5, respectively, in ∼56% yield. These isomerizations and exchange reactions of the alkyl group proceed via formation of a Co–H species, as determined by trapping experiments.