| Exploration into the reaction pathway for borane addition to pentamethylcyclopentadienyl metal halides, [Cp*MClm]n (where m = 4, n = 1; m = 2, n = 2) to form metallaboranes has been done. The reaction of Cp*WCl4 with three molar equivalents of borane (BH3·THF) results in the formation of [Cp*WCl2(μ-H)]2 and BH 2Cl. Reaction of this tungsten hydride with a stoichiometric amount of BH3·THF leads to the known final product, (Cp*W) 2B5H9. This hydride-containing product is subsequently found to be an intermediate in the pathway of borane addition to Cp*WCl 4 to form (CP*W)2B5H9.; Isolation of a metal hydride intermediate led to the investigation into the use of [Cp*MH2]2 compounds as synthons for metallaborane formation. The first metal hydride examined, [Cp*RuH2]2, is an analog of [Cp*RuCl2]2, and the latter has been shown to be successful for metallaborane formation via reaction with borane and lithium borohydride. [Cp*RuH2]2 is found to react selectively with three molar equivalents of BH3·THF to form the known (Cp*Ru)2B3H9, which in turn reacts with one molar equivalent of BH3·THF to form (Cp*Ru) 2B4H10. Reaction conditions are very mild, yields are high and no separation is required obtain pure products. The mild conditions allow for a qualitative investigation into the reaction pathway with the purpose of intermediate observation. Comparison between the known and new synthetic method for ruthenaborane formation is made.; Success in forming known metallaboranes from a metal hydride source was followed by synthesis of new metallaboranes via reaction of [Cp*FeH2 ]2 with borane. Spectroscopic characterization of the major product results in the formulation of the metallapentaborane, Cp*FeB 4H11. Reaction of this compound with Co2(CO) 8 results in metal fragment addition to give the structurally characterized (Cp*Fe)(μ-H)B4H8Co(CO)3 in good yield. In summary, the reactions of pentamethylcyclopentadieny metal hydrides [Cp*MClmHn] 2 (where M = W, m = 2, n = 1; M = Ru, m = 0, n =2; M = Fe, m = 0, n = 2) with borane (BH3·THF) are examined. This new synthetic pathway is compared to known synthetic pathways for metallaborane formation and improvements are noted. |
