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

• Published in: Inorganica Chimica Acta 2001-07, Vol.319 (1), p.137-146
• Main Authors: Zechmann, Cecilia A., Boyle, Timothy J., Rodriguez, Mark A., Kemp, Richard A.
• Format: Article
• Language: English
• Subjects: Alkoxide complexes; Crystal Structures; Magnesium complexes; Siloxide complexes
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(01)00447-9

A series of sterically hindered Mg(OR) 2, [OR=OC(CH 3)(C 6H 5) 2 (DPE), and OSi(C 6H 5) 3 (TPS)] were synthesized from the reaction of Mg(Bu) 2 with 2 HOR in a variety of solvents. The resultant products were crystallographically characterized as Mg 3(μ 3-DPE)(μ-DPE) 3(DPE) 2 ( 1), Mg[(μ-TPS) 2Mg(TPS)] 2 ( 2), [Mg(μ-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 centers are in a triangular arrangement and are bound by a single μ 3-DPE, three μ-DPE, and two terminal DPE ligands. Two of the three Mg cations are tetrahedrally (Td) coordinated while the remaining metal center adopts a trigonal pyramidal geometry. In contrast, 2 displays a more linear arrangement of the Mg centers supported by four μ-TPS and two terminal TPS ligands. Two of the Mg cations adopt trigonal planar arrangements while the remaining central Mg exhibits a distorted Td geometry. For the dinuclear complexes ( 3– 6), each metal possesses a Td geometry satisfied by two μ-OR, one terminal OR, and one coordinated solvent. 1H NMR characterization indicates that 1 is likely fluxional in solution while 2– 5 remain intact in solution and 6 is disrupted by pyridine to yielding a monomer. The reaction of Mg(Bu) 2 with 2 HOR [OR=OC(CH 3)(C 6H 5) 2 (DPE), and OSi(C 6H 5) 3 (TPS)] led to the characteization of Mg 3(μ 3-DPE)(μ-DPE) 3(DPE) 2 ( 1, shown), Mg[(μ-TPS) 2Mg(TPS)] 2 ( 2), [Mg(μ-DPE)(DPE)(solv)] 2 (solv=THF, 3; py, 4), and [Mg(TPS) 2(solv)] 2 (solv=THF, 5; py, 6). The nuclearity is controlled by solvent and ligand choice. In solution, 1 is fluxional, 2– 5 remain intact and 6 is disrupted by pyridine to yield a monomer.