New advances in homoleptic organotransition-metal compounds: The case of perhalophenyl ligands†
Abstract
Homoleptic derivatives of formula [M(C6X5)n]z− (X = F, Cl) have been prepared and isolated for every first-row transition metal as well as for several of the heavier ones. The stoichiometry attained in each case (n ranging between 2 and 6) can be understood considering the tendency of a given metal ion to compensate its coordinative and electronic unsaturation, while not incurring severe interligand repulsive effects. The molecular structures associated with each stoichiometry seem, in turn, to be governed by electronic rather than steric factors. Most of these [M(C6X5)n]z− compounds are unsaturated, open-shell organometallic species, not fulfilling the 18-electron (or Effective Atomic Number) rule. This behaviour can be attributed to the absence of π stabilising