Interest in heterobimetallic complexes stems from the promise they hold as precursors to materials, reagents in synthesis, and as new catalysts. The thesis begins by presenting the TM-H-M linkage(TM = transition metal; M = Mg, Zn, Al, Ga) and organising the full catalogue of examples for its developed understanding.
The /3-diketi minate/(trihydrido)zirconocene complexes of Mg and Zn (0 Mg•Zr and 0 Zn•Zr )are reported, creating a Mg, Zn, Al series. The Zr-H-Zn linkageis hitherto unknown, and Zr­ H-Mg has not been reported without support from alkyne or alkene bridging ligands. The new complexes show very little evidence of bridge cleavage to form the mononuclear complexes under 363 K. Such dissociation is facile in the aluminium system (MAl•Zr ) down to 193 K. The bridging unit is probed further using 1H NMR spectroscopy and OFT calculations: a 'cog' mechanism is established for the chemical exchange process between terminal and bridging hydride in both the Mg and Zn analogues. This exchange, and M11/Zr d issociat ion, are found to be easier with 0 Zn•Zr.
The reactivity differences in the M/Zr series are investigated with regards to alkene isomerisation. In the case of tightly-bound0 Mg•Zr (and the easily dissociatingMAl•Zr ), on ly the catalytic isomerisation of cycloocta-1,5-diene to cycloocta-1,3-diene is effected. However, the slightly weaker-bound 0 Zn•Zr reacts with either cyclooctadiene to give a new Zr-H-Zn complex that includes a bridging cyclooctyne ligand. It is proposed that 0 Zn•Zr has the ability to dissociateto give a spectator Zn hydride fragment and the Zr centre that is active for the on­ metal isomerisation, before later recombination. Tightly-bound 0 Mg•Zr gives the (E)-selective isomerisation of terminal alkenes to internal positions with a high ratio of alkene:alkane products across a number of substrates - MAl•Zr gives larger amounts of alkane by-products, and 0 Zn•Zr is not an active catalyst.