Conversion between Doubly and Triply Carboxylate Bridged Bis(ethylzinc) Complexes and Formation of the (μ-Oxo)tetrazinc Carboxylate [Zn4O(ArTolCO2)6]

Ethylzinc 2,6-bis­(p-tolyl)­benzoate converts between two forms in solution. Through NMR spectroscopic techniques and X-ray crystallography, the species in equilibrium were identified as [Zn2(ArTolCO2)2(Et)2(THF)2] (1), [Zn2(ArTolCO2)3(Et)­(THF)] (2), and diethylzinc (ArTol = 2,6-bis­(p-tolyl)­phenyl). The equilibrium provides a model for understanding the speciation between doubly and triply m-terphenylcarboxylate bridged diiron­(II) and mononuclear iron­(II) complexes. Evidence is presented for the occurrence of coordinatively unsaturated trigonal zinc species in solution. Both 1 and 2 decompose in air to form the T-symmetric oxozinc carboxylate [Zn4O­(ArTolCO2)6] (3).