1215877-01-2Relevant academic research and scientific papers
Steering S-H and N-H bond activation by a stable N-heterocyclic silylene: Different addition of H2S, NH3, and organoamines on a Silicon(II) ligand versus its Si(II)→Ni(CO)3 complex
Meltzer, Antje,Inoue, Shigeyoshi,Praesang, Carsten,Driess, Matthias
, p. 3038 - 3046 (2010/05/01)
The strikingly different behavior of the ylide-like, N-heterocyclic silylene LSI: (5: L = CH[(C=CH2)CMe(NAr)2]; Ar = 2,6- iPrC6H3) versus its LSi→Ni(CO)3 complex 13 to activate E-H bonds (E = S, N) of small molecules is reported. Remarkably, conversion of 5 with hydrogen sulfide leads exclusively to the first isolable silathioformamide, L′Si(=S)H (16: L′ ) CH[C(Me)NAr]2; Ar ) 2,6-iPrC6H3) with a donorsupported Si=S double bond and four-coordinate silicon. The latter result demonstrates the unusual ambivalent reactivity of 5 by combining two modes of reactivity involving S-H bond activation and subsequent 1,4- and 1,1-addition, respectively. In addition, 5 can serve as a ligand with well-balanced σ-donor and π-acceptor capabilities toward transition metals. This has been demonstrated by the isolable [Ni0(arene)] complexes 12a-e (arene ) MenC 6H6-n, n = 0-3), which are ideal precursors for the formation of the corresponding Ni(CO)3 complex 13. The latter activates a S-H bond in hydrogen sulfide, too, but the presence of the Ni(CO)3 moiety governs the formation of the complex 17, bearing an unprecedented β-diketiminate silicon(II) thiol ligand: L′Si(SH): (L′ ) CH[C(Me)NAr]2; Ar ) 2,6-iPrC6H3). Likewise, the Si(II)→Ni(CO)3 coordination in 13 steers exclusively 1,4-addition of ammonia, isopropylamine, and phenylhydrazine onto the silylene ligand 5, leading to the corresponding β-diketiminate silicon(II) amide or hydrazide complexes L′Si(NHR)→Ni(CO)3 (23a-c: R ) H, iPr, N(H)Ph). IR measurements reveal that the carbonyl stretching frequencies of the Ni(CO)3 moiety in 23a-c are shifted to even lower wavenumbers in comparison to those of NHCs or phosphines. In other words, the β-diketiminate silicon(II) amide ligands in 23a-c represent the strongest donors in the series of N-heterocyclic silylenes reported as yet.
