Thermodynamics of metal [sbnd]ligand bond formation : XXXII. Lewis acidity of phenyl-zinc and -cadmium compounds

Abstract

Thermodynamic data have been obtained by calorimetric titration in toluene at 30°C for the formation of adducts of Ph 2Cd and Ph 2Zn with heterocyclic bases. Cd readily becomes 4-coordinate, forming very stable 1/1 adducts with o-phen, bipy or tmed and both 1/1 and2/1 adducts with 4-methylpyridine. Zn prefers to become 3-coordinate, forming very stable adducts (Ph 2Zn) 2B with phen, bipy or tmed; only phen forms a 1/1 adduct and its enthalpy of formation is little greater. With 4-methylpyridine a stable1/1 adduct is formed, but addition of further base is incomplete even with a large excess of base.