Synthesis of Rhodium(I) Boryl Complexes: Catalytic N–H Activation of Anilines and Ammonia

The treatment of the rhodium methyl complex [Rh(Me)(PEt3)3] (1) with diboranes B2[(OR)2]2 gave the 16-valence-electron rhodium(I) boryl complexes [Rh{B(OR)2}(PEt3)3] [2: (OR)2 = pin = pinacolato, O2C2Me4; 3: (OR)2 = cat = catecholato, O2C6H4; 4: (OR)2 = O2C5H10]. The reactions of 2 and 4 with anilines yielded the amidoboranes HN[B(OR)2](R′) [6: B(OR)2 = Bpin, R′ = C6F5; 7: B(OR)2 = Bpin, R′ = Ph; 8: B(OR)2 = BO2C5H10, R′ = Ph] and the rhodium hydrido complex [Rh(H)(PEt3)3] (5) by N–H activation. The addition of ammonia to 2 resulted in the generation of the amine HN(Bpin)2 (9) as well as 5. The amidoboranes 6, 7, and 9 can also be synthesized catalytically with turnover numbers of 10 for 9 and 8 for 6 and 7.