Conversion between Doubly and Triply Carboxylate Bridged Bis(ethylzinc) Complexes and Formation of the (μ-Oxo)tetrazinc Carboxylate [Zn[subscript 4]O(Ar[superscript Tol]CO[subscript 2)[subscript 6]]

Abstract

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 [Zn[subscript 2](Ar[superscript Tol]CO[subscript 2])[subscript 2](Et)[subscript 2](THF)[subscript 2]] (1), [Zn[subscript 2](Ar[superscript Tol]CO[subscript 2])[subscript 3](Et)(THF)] (2), and diethylzinc (Ar[superscript Tol] = 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 [Zn[subscript 4]O(Ar[superscript Tol]CO[subscript 2])[subscript 6]] (3).