The 150-year history of organometallic chemistry has led to the conventional view that transition metal alkyls, without ligands like phosphines or cyclopentadienyl groups, are too labile for use in organic chemistry. Over the last decade, however, our group has reexamined the properties of such alkyls and has uncovered a gratifying array of decomposition pathways leading to important organic transformations (Eur. J. Org. Chem. 2005, 2657-2670). The following processes are finding unique and significant applications in organic synthesis: 1) reductive elimination in R₂ME₂leading to ME₂ reagents; 2) metal-hydride elimination from R₂ME₂ to produce hydrometallating agent, H₂ME₂; 3) direct epimetallation of pi-bonded substrates by ME₂; 4) transfer epimetallation of pi-bonded substrates by R₂ME₂; 5) metallation of hydrocarbon acids by R₂ME₂; 6) rearrangement of R₂Zr(OEt)₂ derivatives leading to new C—C bonds; and 7) the cleavage of C—C bonds of the type, Ar₂CH—CHAr₂, by R₂Zr(OEt)₂.

The structural factors in R₂ME₂ derivatives and the specific experimental conditions favoring certain modes of reaction offer valuable evidence on the prevailing reaction intermediates and mechanisms. Such processes can involve polar, radical or even radical-ion carbon-metal bond scissions. Striking experimental observations include the following: a) donor solvents such as THF favor reductive elimination (path 1) over metal-hydride elimination (path 2); b) the LiE by-product from producing R₂Me₂ from ME₄ and two equiv. RLi can greatly alter the reactivity of R₂ME₂; and c) transfer epititanation by R₂TiE₂ proceeds faster and more efficiently than direct epititanation by TiE₂. Such evidence not only permits great insight into the prevailing reaction mechanism but allows for some steering of such decompositions toward a desired organic transformation.