RHENIUM COMPLEXES FROM ALKYNES - X-RAY CRYSTAL-STRUCTURES OF RE-2(MU-2-ETA(1),ETA(4)-C(4)PH(4))(CO)(7) AND RE(C,O-CH=C[RE(CO)(4)(NME(3))]C(OME)O)(CO)(4)

The molecular structure of Re-2(mu-2 eta(1),eta(4)-C(4)Ph(4))(CO)(7) obtained from Re-2(CO)(8)(NCMe), and C(2)Ph(2), consists of an Re-2(CO)(7) unit [Re-Re 2.874(1) Angstrom] bridged by a 2 eta(1),eta(4)-C(4)Ph(4) ligand, as proposed by earlier workers. Methyl propiolate is inserted into the Re-Re bond of Re-2(CO)(9)(NCMe), as shown by the molecular structure of the NMe(3) derivative of the product; the NMe(3) Ligand is attached to the non-chelated Re atom [Re-N 2.31(1) Angstrom].