Carbon-carbon coupling on tetrahedral iridium clusters: X-ray molecular structures and multinuclear NMR studies of the two isomeric forms of [Ir-4(CO)(6)(mu(3)-eta(2)-HCCPh)(mu(2)-eta(4)-C4H2Ph2)(mu-PPh2)(2)]

摘要

The reactions of [HIr4(CO)(9)(Ph(2)PCequivalent toCPh)(mu-PPh2)] (1) or [Ir-4(CO)(8)(mu(3)-eta(2)-HCCPh)(p-PPh2)(2)] (2) with HCequivalent toCPh gave two isomeric forms of [Ir-4(CO)(6)(mu(3)-eta(2)-HCCPh)(mu(2)-eta(4)-C4H2Ph2)(mu-PPh2)(2)] (3 and 4) in good yields as the only products. These compounds were characterized with analytical and spectroscopic data including H-1, C-13 and P-31 NMR (1 and 2D) spectroscopy and their molecular structures were established by X-ray diffraction studies. Compounds 3 and 4 exhibit the same distorted butterfly metal polyhedral arrangement of metal atoms with two mu-PPh2 that occupy different positions in the structures of the two isomers. Both molecules contain a HCCPh ligand bonded in a mu(3)-eta(2)-// mode to one of the wings of the butterfly and a metallacyclic ring, which resulted from head-to-tail coupling, in the case of [Ir-4(CO)(6)(mu(3)-eta(2)-HCCPh){mu(2)-eta(4)-(H)CC(Ph)C(H)C(Ph)}(mu-PPh2)(2)] (3) and tail-to-tail coupling, in that of [Ir-4(CO)(6)(mu(3)-eta(2)-HCCPh){mu(2)-eta(4)-(H)CC(Ph)C(Ph)C(H)}(mu-PPh2)(2)] (4), and which is linked to two metal atoms of the second wing of the butterfly. (C) 2004 Elsevier B.V. All rights reserved.