Hydrogenation of Imines Catalyzed by Trisphosphine-Substituted Molybdenum and Tungsten Nitrosyl Hydrides and Co-Catalytic Acid

作者：Chakraborty Subrata; Blacque Olivier; Fox Thomas; Berke Heinz^*

来源：Chemistry-An Asian Journal, 2014, 9(10): 2896-2907.

DOI：10.1002/asia.201402280

• hydrides
• imines
• ionic hydrogenation
• molybdenum
• tungsten

Hydride complexes Mo,W(CO)(NO)H(mer-etp(i)p) (iPr(2)PCH(2)CH(2))(2)PPh=etp(i)p) (2a,b(syn), syn and anti of NO and Ph(etp(i)p) orientions) were prepared and probed in imine hydrogenations together with co-catalytic [H(Et2O)(2)][B(C6F5)(4)] (140 degrees C, 60bar H-2). 2a,b(syn) were obtained via reduction of syn/anti-Mo,W(NO)Cl-3(mer-etp(i)p) and syn,anti-Mo,W(NO)(CO)Cl(mer-etp(i)p). [H(Et2O)(2)][B(C6F5)(4)] in THF converted the hydrides into THF complexes syn-[Mo,W(NO)(CO)(etp(i)p)(THF)][B(C6F5)(4)]. Combinations of the p-substituents of aryl imines p-(RC6H4CH)-C-1=N-p-C6H4R2 (R-1,R-2=H,F,Cl,OMe,-Np) were hydrogenated to amines (maximum initial TOFs of 1960h(-1) (2a(syn)) and 740h(-1) (2b(syn)) for N-(4-methoxybenzylidene)aniline). An ionic hydrogenation' mechanism based on linear Hammett plots (=-10.5, p-substitution on the C-side and =0.86, p-substitution on the N-side), iminium intermediates, linear P(H-2) dependence, and DKIE=1.38 is proposed. Heterolytic splitting of H-2 followed by proton before hydride' transfers are the steps in the ionic mechanism where H-2 ligand addition is rate limiting.

• 出版日期2014-10