14e η1-Hydrocarbyliron complexes supported by hydrotris(3,5-diisopropyl-pyrazolyl)borate: the allyl complex prefers a highly coordinatively unsaturated 14e η1-structure to a 16e η3-structure‡

Coordinatively unsaturated allyl and benzyl complexes with the hydrotris(3,5-diisopropylpyrazolyl)borate ligand (TpiPr), TpiPrM–allyl (M = Ni, Co, Fe) and TpiPrFe–p-methylbenzyl, are prepared and characterized by X-ray crystallography, and the allyl ligand is coordinated to the Fe center in a η1-fashion to form a 14e species in contrast to the η3-coordination found for the Ni and Co complexes.