Todd Graham - Article Tetranuclear, Early−Late Heterobimetallic Complexes Bridged by the Bifunctional Phosphinoalkylcyclopentadienyl Ligands [Ph2P(CH2)nC5H4]- (n = 1, 2)

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      Todd W. Graham, Angela Llamazares, Robert McDonald,  and Martin Cowie Organometallics, 1999, 18 (17),   3502


      Reaction of   (η5-C5H4(CH2)nPPh2)2MCl2  (n = 1, M = Ti (1), Zr   (2); n = 2, M = Ti   (3), Zr (4)) with   [RhCl(CO)2]2 at −80 °C and under conditions   of high dilution yields the tetranuclear products   [(μ-η51-C5H4(CH2)nPPh2)2MCl2RhCl(CO)]2  (n = 2, M = Ti (5), Zr   (6); n = 1, M = Ti   (7), Zr (8)). Molecular weight   measurements, mass spectral data, and the X-ray structures of   5b (one isomer of 5) and of   7 confirm the tetranuclear formulations.   Compounds 5b and 7 are shown to   have two parallel Rh(I) square planes, in which these    metals are approximately 11.88 and 9.01 Å apart, respectively,   each  bridged by the metallodiphosphine ligands,   (η5-C5H4(CH2)nPPh2)2TiCl2,   which are in trans positions at each Rh. The larger   metallodiphosphine ligand (n = 2) gives rise to   additional flexibility in compounds 5 and   6,  yielding two isomers of each, which   appear to differ by a twist of the  titanocene dichloride   moiety about the metallodiphosphine backbone.  Reaction of   compound 1 with (COD)PdCl2 gives the   analogous Ti/Pd tetranuclear product   [(μ-η51-C5H4CH2PPh2)2TiCl2PdCl2]2,   which is assumed, on the basis of spectral similarities, to have   a structure like those of 7 and   8.

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