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

The reaction between [Re3(μ-H)3(CO)10(NCMe)2] and [ReH2(CO)4]- affords the novel hydridocarbonyl cluster [Re4(μ-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) Å, β = 101.79(3)°, 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) Å] 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.