AN UNUSUAL SPECIES FROM THE REACTION OF THE UNSATURATED ANION {[RE3(MU-H)3(CO)9(MU-3-O ... H ... NME3)]-, AND CRYSTAL AND MOLECULAR-STRUCTURE OF ITS TETRAETHYLAMMONIUM SALT}

The reactions of the unsaturated cluster anion [Re3(μ-H)4(CO)10]- with Me3NO, in a solvent of low donor ability, such as acetone or tetrahydrofuran, give three products, in a ratio which depends on the reaction conditions: two of them, the unsaturated [Re3(μ-H)4(CO)9(NMe3)]- and [Re3(μ-H)4(CO)9(ONMe3)]- species, have been characterized spectroscopically. The third has been isolated and characterized by X-ray single crystal analysis as an adduct formed by hydrogen bonding between Me3N and the triangular cluster anion [Re3(μ-H)3(CO)9(μ3-OH)]-. The crystals are monoclinic, space group P21/m, with a 8.576(3), b 20.442(4), c 8.748(3) Å, β 108.08(4)°; Z = 2. The structure was solved by Patterson and Fourier methods by use of 2085 unique reflections and refined to a final R value of 0.026. The mean ReRe and ReO(OH) bond lengths are 2.979 and 2.126 Å, respectively. The O · H · N hydrogen bond is short and almost linear (O ⋯ N 2.502(10) Å). Various experiments have demonstrated that the triply bridging OH group can, according to the reaction conditions, come either from a water molecule (present in the commercial amine oxide) or by attack of a hydridic ligand on the oxygen of a coordinated amine oxide molecule. The same adduct has been obtained starting from the dianion [Re3(μ-H)3(CO)9(μ3-O)]2-, directly by reaction with Me3NHCl or in a two step sequence of protonation to [Re3(μ-H)3(CO)9(μ3-OH)]- and subsequent treatment with Me3N.