Effects of steric/basic properties of Lewis bases on the degree of aggregation of zinc(II) pivalate complexes

A triangular [Zn3(μ3-OH)(OC(O)tBu)(μ2-κ1O:κ1O′–O2CtBu)4(3,5-lutidine)3] (1), a paddlewheel based dinuclear [Zn(μ2-κ1O:κ1O′–O2CtBu)2L]2 [L = 2,4-lutidine (2), 3,4-lutidine (3), and 2,3-lutidine (4)] and an hourglass based linear trinuclear [Zn3(μ2-κ1O:κ1O′-O2CtBu)6(pyridine)2] (5) complexes were synthesized to understand the role of subtle steric/basic properties of Lewis bases on the degree of aggregation of the products. The mononuclear Zn(OC(O)tBu)2·2H2O was also prepared in order to probe the origin of the μ3-OH moiety in complex 1. Complexes 1–5 and Zn(OC(O)tBu)2·2H2O were characterized by microanalytical, IR, TGA/DTA, solution (1H and 13C) NMR, solid-state cross-polarization magic angle spinning (CP-MAS) 13C NMR, mass spectral data and single crystal X-ray diffraction data. Complex 1 represents the first example of a discrete trinuclear zinc(II) carboxylate complex that contains a [Zn3(μ3-OH)]5+ core with zinc atoms in three distinct geometries namely a distorted tetrahedral, trigonal bipyramidal, and octahedral. A plausible mechanism for the formation of complexes 1–5 was explained with the aid of point zero charge (pzc) model.