Highly Electrophilic Half-Sandwich Group 4 Metallacarborane Alkyls. C−H/C−O Activation and Alkyne Insertion Reactions at Neutral Metal Complexes

Treatment of 7-Me2N(H)CH2CH2-7,8-C2B9H11
with M(CH2SiMe3)4 in toluene gave the C−H activation
products [η1:σ:η5-{MeN(CH2)CH2CH2}C2B9H10]M(CH2SiMe3)(THF) (M = Zr (1), Hf (2)). Insertion of diphenylacetylene into the azametallacyclopropane in 2 and
subsequent elimination of SiMe4 afforded a new metallacyclic complex, [σ:σ:η1:η5-{(CH2)[(CH2)PhCCPh]N(CH2CH2)C2B9H10}]Hf(THF) (3). Reaction of Zr(CH2Ph)4 with
7-Me2N(H)CH2CH2-7,8-C2B9H11 in DME generated a
C−H/C−O activation product, [{η1:σ:η5-[MeN(CH2)CH2CH2]C2B9H10}Zr(μ:η1-OCH2CH2OCH3)]2 (4). These results demonstrated that neutral half-sandwich metallacarborane alkyls have characteristics of electrophilic
metal alkyls.