Metallaborane reactions

The volatile, air-sensitive Hquid species (CH3)2AlB3Hg and (CH3)2GaB3Hg are prepared by the direct reaction of the corresponding main group metal hahde and salts of the [B3Hg] ion, in the absence of solvent (178). The reaction of (CH3)2AlB3Hg and A1(BH 3 results in the species (BH 2AlB3Hg. These small metallaboranes are fluxional in solution and have limited thermal stability at room temperature. 

A series of divalent lanthanide metal metallaborane derivatives have been prepared by the redox reaction of metallic lanthanides and boron hydrides and by the metathesis reaction of boron hydride salts with LnC where Ln = Sm, Eu, Yb (181,182). The species (CH3CN)6Yb [(p,-H)2B - H12],... 

Metallaboranes containing M—B CT-bonds can be prepared by nucleophilic displacement reactions (183) and oxidative addition (184) of B—H and B-Br bonds to metal centers. For example, the reaction of IrCl(CO)[P(CH3)3]2 and 1- or 2-BrB5H8 results in 2-[IrBi (CO)-[P(CH3)3]2B5H8] in which the B5H8 polyhedron serves as ligand for the metal. 

An important method for the synthesis of carbaboranes is the reaction of a borane cluster with an alkyne. However, an analogous reaction of a metallaborane cluster with an alkyne is not commonly used to prepare metallacarbaborane clusters. Equation (21) illustrates one example. 

Reactions between a metallaborane and alkyne are not always predictable. For example, itio-l,2-(Cp Rh)2B3H7 catalyzes the cyclotrimerization of alkynes rather than undergoing insertion of the alkyne into the cluster cage. ... 

Thermal, Photochemical, and Redox Reactions of Borane and Metallaborane Clusters with Applications to Molecular Electronics... 

Photochemical transformations are widely employed in both organic and organoinetallic chemistry and have been extensively used as synthetic strategies for the formation of a variety of new compounds.1 Part of our recent research has focused upon an exploration of the photochemical reactions of borane and metallaborane clusters. As a contextual setting for these photochemical studies, we have also explored several aspects of the thermal and redox chemistry of these clusters. In this paper, we present a summary of our recent work on the thermal, photochemical, and redox reactions of borane and metallaborane clusters. In addition, recent work directed toward the application of these clusters to several aspects of molecular electronics will be presented. 

On a study visit to Notre Dame, Yasushi Nishihara observed that the reaction of BH3THF with [Cp CoCl]2 was facile and lead to the formation of metallaboranes, e.g., 2,4-... 

The synthesis of metallaboranes in quantity permits the examination of reaction chemistry and we have already described a considerable number of reactions of chroma-,27, 281 29, 30 molybda-,20 ruthena-,15, cobalta-,31 and rhodaboranes.13 This work constitutes a true study of the effects of the transition metal on chemistry as the metal ancillary ligand (Cp ) is unchanged. Space does not permit more than a single example that serves to illustrate the type of new chemistry that has been revealed by these new metallaboranes. 

---