Synthesis and Crystal Structure of a New Guanidinatoaluminium Complex and Its Utility in the Meerwein-Ponndorf-Verley Reduction

The treatment of pyrrolidine (C4H8NH) with sequentially trimethylaluminum and carbodiimide CyN=C=NCy in a molar ratio of 1:1:1 in the presence of O-2 afforded a new guanidinatoaluminum complex, [{(C4H8N)C(NCy)(2)}AlMe(mu-OMe)](2) (1), which was characterized by elemental analyses, H-1, C-13 NMR spectra and single-crystal X-ray diffraction analysis. Complex 1 crystallizes in monoclinic, space group P2(1)/c with a = 9.8330(9), b = 8.5786(8), c = 24.159(2) angstrom, beta = 92.927(2)degrees, V= 2035.3(3) angstrom(3), D-c = 1.141 g cm(-3), F(000) = 768 and mu = 0.110 mm(-1). In addition, complex 1 was used to catalyze the Meerwein-Ponndorf-Verley (MPV) reduction and 1 as a pre-catalyst at low catalyst loadings (5 mol%) exhibited good catalytic activity for the reduction of a series of aldehydes to the corresponding alcohols in good yields (conv. up to 99%).