Reactivity of frustrated Lewis pairs with BOC protected diazocarboxylates: FLP capture of diazene.

Reactions of ( t BuO 2 CN) 2 with FLPs are examined. B(C 6 F 5 ) 3 interacts with the carbonyl oxygen atoms inducing loss of CH 2 CMe 2 ; however, in the presence of basic donors, the protons are intercepted affording the salts [Hbase] 2 [((C 6 F 5 ) 3 BO 2 CN) 2 ] (base = t Bu 3 P 1, NC 5 H 2 Ph 3 2, HNC 5 H 6 Me 4 3). In contrast, in the presence of ( o -Tol) 3 P, a proton transfers to the diazo-N atom affording ( o -Tol) 3 PN(CO 2 t Bu)NHB(C 6 F 5 ) 3 4. Further addition of B(C 6 F 5 ) 3 to 4 prompts loss of olefin CH 2 CMe 2 and CO 2 affording ( o -Tol) 3 PNHNHB(C 6 F 5 ) 3 5. The course of these reactions is examined by extensive DFT calculations. The nature of 5 is consistent with the FLP reduction of a diazene fragment.