Synthesis, characterization, and structural study of sterically hindered magnesium alkoxide and siloxide compounds

A series of sterically hindered Mg(OR)(2), [OR = OC(CH3)(C6H5)(2) (DPE), an d OSi(C6H5)(3) (TPS)] were synthesized from the reaction of Mg(Bu), with 2 HOR in a variety of solvents. The resultant products were crystallographica lly characterized as Mg-3(mu (3)-DPE)(mu -DPE)(3)(DPE)(2) (1), Mg[(mu -TPS) (2)Mg(TPS)](2) (2), [Mg(mu -DPE)(DPE)(solv)](2) (solv = THF,3; py, 4), and [Mg(TPS)(2)(solv)](2) (solv = THF, 5; py, 6). For 1, the three metal center s are in a triangular arrangement and are bound by a single mu (3)-DPE, thr ee mu -DPE, and two terminal DPE ligands. Two of the three Mg cations are t etrahedrally (Td) coordinated while the remaining metal center adopts a tri gonal pyramidal geometry. In contrast, 2 displays a more linear arrangement of the Mg centers supported by four mu -TPS and two terminal TPS ligands. Two of the Mg cations adopt trigonal planar arrangements while the remainin g central Mg exhibits a distorted Td geometry. For the dinuclear complexes (3-6), each metal possesses a Td geometry satisfied by two mu -OR, one term inal OR, and one coordinated solvent. H-1 NMR characterization indicates th at 1 is likely fluxional in solution while 2-5 remain intact in solution an d 6 is disrupted by pyridine to yielding a monomer. (C) 2001 Elsevier Scien ce B.V. All rights reserved.