The reactivity of antimony and bismuth N,C,N-pincer compounds toward K[BEt3H] - the formation of heterocyclic compounds vs. element-element bonds vs. stable terminal Sb-H bonds

The oxidative addition of CF3SO3CH2Si(CH3)(3) ((NpOTf)-O-Si) toward organopnictogen(i) N,C,N-pincer compounds, i.e. [2,6-(DippN 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 CH)(2)C6H3]E (1-E, where E = Sb, Bi; Dipp = 2,6-iPr(2)C(6)H(3)) produced compounds [2,6-(DippNCH)(2)C6H3]E(Np-Si)(OTf) (2-E, where E = Sb, Bi). By analogy, the in situ reduction of [2,6-(Me2NCH2)(2)C6H3]ECl2 (3-E, where E = Sb, Bi) followed by treatment with (NpOTf)-O-Si or MeI gave compounds [2,6-(Me2NCH2)(2)C6H3]E(R)(X) (R/X = Np-Si/OTf 4-E, where E = Sb, Bi; R/X = Me/I 5-Sb). The reactivity of these compounds toward 1 eq. of K[BEt3H] was examined showing remarkable differences depending both on the ligand backbone and the pnictogen used. Thus in the case of 2-E, the addition of the hydride across the imino-function was achieved thereby yielding azapnicta-heterocyclic compounds [2-(DippNCH(2))-6-(DippNCH)C6H3]E(Np-Si) (6-E, where E = Sb, Bi). The same reaction of 4-Bi produced dibismuthine {[2,6-(Me2NCH2)(2)C6H3]Bi(Np-Si)}(2) (7-Bi), but in the case of 4/5-Sb the analogous distibines {[2,6-(Me2NCH2)(2)C6H3]Sb(R)}(2) (R = Np(Si)7-Sb, Me 8-Sb) were not formed directly and hydrides [2,6-(Me2NCH2)(2)C6H3]Sb(R)H (R = Np(Si)9-Sb, Me 10-Sb) could be isolated instead. Nevertheless, heating of both 9-Sb and 10-Sb led to an activation of a labile Sb-H bond and the formation of distibines 7/8-Sb.