1361315-74-3Relevant academic research and scientific papers
Site selectivity and reversibility in the reactions of titanium hydrazides with Si-H, Si-X, C-X and H+ reagents: Ti=Nα 1,2-silane addition, Nβ alkylation, Nα protonation and σ-bond metathesis
Tiong, Pei Jen,Nova, Ainara,Schwarz, Andrew D.,Selby, Jonathan D.,Clot, Eric,Mountford, Philip
, p. 2277 - 2288 (2012/03/22)
We report a combined experimental and computational comparative study of the reactions of the homologous titanium dialkyl- and diphenylhydrazido and imido compounds Cp*Ti{MeC(NiPr)2}(NNR2) (R = Me (1) or Ph (2)) and Cp*Ti{MeC(NiPr)2}(NTol) (3) with silanes, halosilanes, alkyl halides and [Et3NH][BPh 4]. Compound 1 underwent reversible Si-H 1,2-addition to TiN α with RSiH3 (experimental ΔH ca. -17 kcal mol-1), and irreversible addition with PhSiH2X (X = Cl, Br). DFT found that the reaction products and certain intermediates were stabilised by β-NMe2 coordination to titanium. The Ti-D bond in Cp*Ti{MeC(NiPr)2}(D){N(NMe2)SiD 2Ph} underwent σ-bond metathesis with BuSiH3 and H2. Compound 1 reacted with RR′SiCl2 at N α to transfer both Cl atoms to Ti; 2 underwent a similar reaction. Compound 3 did not react with RSiH3 or alkyl halides but formed unstable TiNα 1,2-addition or Nα protonation products with PhSiH2X or [Et3NH][BPh 4]. Compound 1 underwent exclusive alkylation at Nβ with RCH2X (R = H, Me or Ph; X = Br or I) whereas protonation using [Et3NH][BPh4] occurred at Nα. DFT studies found that in all cases electrophile addition to Nα (with or without NMe2 chelation) was thermodynamically favoured compared to addition to Nβ. The Royal Society of Chemistry 2012.
