Substituent effects in the hydrosilylation of coordinated dinitrogen in a ditantalum complex: Cleavage and functionalization of N-2

resumo

The dinitrogen complex ([NPN]Ta)(2)(mu(1)-eta(2):eta(2)-N-2)(mu-H)(2), 1, (where [NPN] = (PhNSiMe2CH2)(2)PPh) undergoes hydrosilylation with primary and secondary alkyl- and arylsilanes, giving a new N-Si bond and a new terminal tantalum hydride derived from one Si-H unit. Various primary silanes can be employed to give isolable complexes of the general formula ([NPN]TaH)(mu-N-N-SiHnR3-n)(mu-H)(2)(Ta[NPN]) (5, R=Bu, n = 2; 9, R=Ph, n = 2). Analogous complexes featuring secondary silanes are not isolable, because these products, and 5 and 9, are uniformly unstable toward reductive elimination of bridging hydrides as H-2, followed by cleavage of the N-N bond to give ([NPN]TaH)(mu-N)(mu-N-SiHnR3-n)(Ta[NPN]) (6, R=Bu, n = 2; 10, R=Ph, n = 2; 15, R=Ph, n = 1; 16, R=Ph and Me, n = 1). The bridging nitrido ligand in these complexes is itself a substrate for a second hydrosilylation when n = 2, and schemes leading to Ta(IV) complexes of the general formula ([NPN]Ta)(2)(mu-N-SiH2R)(mu-N-SiH2R') via elimination of H-2 are reported (4, R=R' = Bu; 12, R=Bu, R' = Ph; 13, R=Bu, R' = CH2CH2SiH3). At this point, the general reaction manifold for these compounds ramifies, with distinct outcomes occurring for different R groups-[NPN] ligand amide migration from Ta to RSi affords 11, ([NPN]Ta(mu-NSiH2Ph)(mu-NSiH2Ph)Ta[NPN]), whereas stable complex 6 rearranges to give 7, ([NP(C6H4)N]Ta(BuSiH2N-mu-SiHBu-mu-N)Ta[NPN]) in the presence of excess silane. Ethanediylbissilane reacts with 1 to give 14, ([NP(C6H4)N]Ta(N-SiH2CH2CH2Si(H)-mu-N)Ta[NPN]), isostructural to 7.

palavras-chave

N BOND-CLEAVAGE; SIDE-ON; METAL-COMPLEXES; TRIAMIDOAMINE COMPLEXES; CATALYTIC-REDUCTION; MOLECULAR NITROGEN; TERMINAL ALKYNES; END-ON; MOLYBDENUM; LIGAND

categoria

Chemistry

autores

MacKay, BA; Munha, RF; Fryzuk, MD

nossos autores

Grupos

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