Synthesis and X-ray crystal structure of the novel hydridocarbonyl cluster [NEt4][Re4(\u3bc-H)5(CO)14]

The reaction between [Re3(\u3bc-H)3(CO)10(NCMe)2] and [ReH2(CO)4]- affords the novel hydridocarbonyl cluster [Re4(\u3bc-H)5(CO)14]-. Its NEt4+ salt has been investigated by X-ray analysis; the crystals are monoclinic, space group P21/n, with a = 14.038(6), b = 15.152(5), c = 15.501(6) \uc5, \u3b2 = 101.79(3)\ub0, and Z = 4. The structure was solved and refined on the basis of 3 169 significant counter data, to a final R value of 0.031. The anion contains a butterfly metallic skeleton [Re-Re bond lengths 3.206(1)-3.247(1) \uc5] with all the edges bridged by hydride ligands. The most unusual feature is the absence of ligands bridging the wing tips of the butterfly cluster