Patterns in Sigma Bond Complexation

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9401739 Crabtree This project, supported by the Inorganic, Bioinorganic and Organometallic Chemistry Program, is concerned with the further development of the chemistry of X-H sigma-bonds (X=H, N, Si and its congeners, and M) coordinated to transition metals. This is a recently recognized area of organometallic chemistry for which the underlying principles are unclear; the goal of this reseach is to discover general trends across several classes of sigma-bond complexes. Among the several goals to be pursued are: generation of "stretched" dihydrogen complexes and new polyhydrogen species by steric crowding, demonstration of a change in reactivity for unsymmetrically bridged metal hydrides, and demonstration of a distinctive reactivity for sigma-bond bound N-H complexes. Techniques for detection and characterization of such compounds based upon NMR spectroscopy will be sought. %%% One of the most exciting recent developments in transition metal chemistry was the discovery that molecular hydrogen can bind to a metal complex without cleavage of the hydrogen-hydrogen bond. Professor Crabtree has played an important role in the elucidation of the factors that determine how molecular hydrogen will bind to a metal and in the development of spectroscopic techniques for determining the mode of binding. This project attempts to determine the role that such sigma-bond complexes play in transition metal chemistry of other X-H bonds. Ultimately the information obtained from this work will be important in the development of a better understanding of organometallic reaction mechanisms and may be useful in the design of more specific catalysts for industrially important reactions. ***