Oxoethoxide chlorides - Representatives of oligonuclear alkoxide complexes of gallium: Penta- and dodecanuclear molecules

Metathesis of solid GaCl3 with NaOEt/EtOH (1:3) provided, after separation of the NaCl precipitate, a solution containing oxoalkoxide chloride complexes of gallium. Residues from evacuation of the latter were redissolved in either toluene/ MeCN (solution 1) or toluene/pyridine (solution 2). Storage of the first solution provided crystals of Ga-5(mu(5)-O)(mu-OEt)(8)Cl-5 (1), and of the second solution - [Ga-12(mu(4)-O)(2)(mu(3)-O)(5)(mu-OEt)(10)-Cl12Py4]Py (2), both at room temperature and in relatively high yields. Compound 1 crystallizes as a vertically contracted tetragonal pyramid with the mu(5)-O ligand situated in the center of the equatorial plane defined by four trigonal bipyramidal coordinated gallium atoms. The axial Ga atom has octahedral coordination. All eight edges of the pyramid are capped by mu-OEt groups, and all the chloride ligands are situated in terminal positions. Crystals of [Ga-12(mu(4)-O)(mu(3)-O)(5)(mu- OEt)(10)Cl12Py4]Py (2) contain two [Ga-5(mu(4)-O)(mu(3)-O)(2)(mu-OEt)(5)- Cl5Py] fragments connected through a cyclic [Ga-4(mu(3)-O)(5)-Cl2Py2] unit with a mu(3)-O ligand in its center. Of the metal atoms, three possess tetrahedral, seven trigonal bipyramidal, and two octahedral coordination. The mass spectrum of I contains penta- and tetranuclear fragments. The spectrum of 2 contains heptameric fragments in addition to the pentanuclear fragments that are analogous to those in the spectrum of 1. The factors leading to formation of polymeric M(OR)(n) and related oligonuclear oxocomplexes are discussed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).