Hydride Ion Abstraction from Titanocene Cyclic Organohydroborates, Cp₂Ti{(μ-H)₂BR₂} (R₂= C₄H₈, C₅H₁₀, C₈H₁₄), as a Function of Solvent

Hydride abstraction reactions of titanocene cyclic organohydroborate complexes CP2Ti{(mu -H)(2)BR2} (R-2 = C4H8, C5H10, C8H14) with B(C6F5)(3) were investigated as a function of solvent. It was determined that the coordinating ability of the solvent directed the course of these abstraction reactions. The reaction in toluene, a noncoordinating solvent, produced a metathesis product, CP2Ti{(mu -H)(2)B(C6F5)(2)} (1), in which the cyclic organohydroborate H2BR2 was substituted by H2B(C6F5)(2). In diethyl ether and THF, the salts [CP2TiL2] [HB(C6F5)(3)] (2, L = Et2O; 3, L = THF) consisting of titanocene cations with solvent ligands were isolated. Salt 2 is the first structurally characterized [CP2TiL2](+) cation containing diethyl ether solvent ligands. The diethyl ether molecules of the cation in 2 are weakly co ordinated and are labilized in THF and toluene. Dissolution of 2 in THF afforded 3. The complex CP2Ti{(mu -H)B(C6F5)(3)}(OEt2) (4) and the proposed 15-electron species CP2Ti{(mu -H)B(C6F5)(3)} (5) were generated through the displacement of an ether molecule from 2 by the [HB(C6F5)(3)](-) anion in toluene. Single-crystal X-ray structures of 1, 2, and 3 were determined.