Tetrahedral, Highly Coordinatively Unsaturated 14e (Fe) and 15e (Co) Hydrocarbyl Complexes Bearing Hydrotris(pyrazolyl)borato Ligands (TpR‘), TpR‘M−R (M = Fe, Co, Ni)

A series of hydrocarbyl complexes supported only by hydrotris(pyrazolyl)borato ligands (TpR‘ = 3,5-diisopropylpyrazolyl (TpiPr2) and 3,4,5-trimethylpyrazolyl derivatives (TpMe3)), TpR‘M−R (M/R/R‘ = Ni/η3-allyl/iPr2 (2iPr2Ni), Co/η3-allyl/iPr2 (2iPr2Co), Fe/η1-allyl/iPr2 (2iPr2Fe), Ni/η3-prenyl/iPr2 (3iPr2Ni), Co/η1-p-methylbenzyl/iPr2 (4iPr2Co), Fe/η1-p-methylbenzyl/iPr2 (4iPr2Fe), Co/η1-p-methylbenzyl/Me3 (4Me3Co), Fe/η1-p-methylbenzyl/Me3 (4Me3Fe), Co/η1-α-naphthylmethyl/iPr2 (5iPr2Co), Co/η1-ethyl/iPr2 (6iPr2Co), Fe/η1-ethyl/iPr2 (6iPr2Fe)) is prepared by reaction of the corresponding precursors, TpiPr2M−Cl (M = Fe (1iPr2Fe), Co (1iPr2Co), Ni (1iPr2Ni)) or TpMe3M(κ2-X) (M/X = Co/NO3 (1‘Me3Co), Fe/OAc (1‘Me3Fe)), with appropriate Grignard reagents. η1-Hydrocarbyl complexes are obtained when M = Fe, Co, and the thermally unstable η1-ethylnickel derivative 6iPr2Ni is characterized via conversion to the acyl derivative TpiPr2Ni(CO)C(O)Et (12). Characterization by a combination of various spectroscopic meth...