摘要:
The iron(II) hydride dimers [(LFe)-Fe-R(mu-H)(2)FeLR] (L-Me = 2,4-bis(2,6-diisopropylphenylimino)pent-3-yl; L-tBu = 2,2,6,6-tetramethyl-3,5-bis(2,6-diisopropylphenylimino)hept-4-yl) abstract hydrocarbyl groups from BR'(3) (R' = Et, Ph) to give (LFeR)-Fe-R' and (LFe)-Fe-R(mu-H)(2)BR'(2). Mechanistic studies with R = R' = Me are consistent with a process in which the hyride dimer opens one Fe-H bond, and subsequent B-H bond formation is concerted with dissociation of an Fe-H unit. Cleavage of boron-carbon bonds is likely to proceed at least in part from transient quaternary borate anions formed through disproportionation of HBEt3-. In a separate bond-breaking reaction, (LFe)-Fe-Me(mu-H)(2)BEt2 reacts with N2H4 to form a 1:1 adduct, which has been crystallographically characterized. Upon heating, it ejects H-2 from the bridging hydrides and cleaves the N-N bond to form the diaminoborate complex (LFe)-Fe-Me(mu-NH2)(2)BEt2. These novel bond-breaking reactions are facilitated by the low coordination number at the iron(II) center.