Reactivity of bimetallic dibridged complexes Cp2Ta(H)(μ-H)(μ-PMe2)M′(CO)4 (M′ = Cr, Mo, W) toward two-electron donor ligands L (L = PR3, Me2P(CH2)nPMe2).: Synthesis of linear trinuclear chain complexes Cp2Ta(H)2(μ-PMe2)M′(CO)4(Me2P(CH2)2PMe2)Cr(CO)5 (M′ = Mo, W)

The reaction of the heterobimetallic phosphido-and hydride-bridged complexes Cp2TaH(mu-H)(mu-PMe2)M'(CO)(4) (M' = Cr, Mo, W) (1-3) with phosphines (L = PPh2Me, PMe2Ph) or diphosphines (L = dmpm, dmpe) leads to Cp2Ta(H)(2)(mu-PMe2)M'(CO)(4)(L) (1a, 1b, c, d-3b, c, d) with L regiospecifically coordinated to M'. Except for L = PPh,Me, the reaction is stereospecific, since a cis arrangement (with respect to the PMe2 bridge) on the M' site is obtained. The new compounds Cp2Ta(H)(2)(mu-PMe2)M' (CO)(4)(Me2P(CH2)(2)PMe2) (M' = Mo, W) are able to bind [Cr(CO)(5)] fragments affording the linear trinuclear chain compounds Cp2Ta(H)(2)(mu-PMe2)M'(CO)(4)(Me2P(CH2)(2)PMe2) (Cr(CO)(5)) (4, 5). All new complexes have been fully characterized by NMR and IR spectroscopy, and by their elemental analyses. (C) 1997 Elsevier Science Ltd.