210700-30-4Relevant academic research and scientific papers
Monoazadiene complexes of early transition metals. 2. Syntheses and structures of titanium 1-aza-1,3-diene complexes and their reactions with ketones
Scholz, Joachim,Kahlert, Steffen,G?rls, Helmar
, p. 2876 - 2884 (2008/10/08)
The novel dark green or violet and air-sensitive 1-aza-1,3-diene titanocene complexes Cp2-Ti[N(R1)CH=C(R2)CH(Ph)] [R1 = t-Bu, R2 = H (7a); R1 = C6H4-4-Me, R2 = H (7b); R1 = c-C6H11, R2 = Me (7c)] were prepared by the complexation of the 1-aza-1,3-dienes 1a-c to the titanocene Cp2Ti generated in situ by reduction of Cp2TiCl2 with magnesium. The solid-state structure of 7c shows a bent azatitanacyclic ring with a fold angle of 130.9(4)°. A series of electron-deficient 14e 1-aza-1,3-diene titanium complexes CpTi[N(R1)CH=C(Me)-CH(Ph)]Cl [R1 = c-C6H11 (8a), t-Bu (8b), C6H4-2-Me (8c), C6H4-4-Me (8d)] has also been prepared by reduction of CpTiCl3 with magnesium in the presence of the 1-aza-1,3-dienes R1N=CHC(Me)=CH(Ph) 1c-f. These new complexes were isolated as air-sensitive brown (8a,b) or dark red (8c,d) crystals in 50-65% yield. The X-ray crystal structure of 8c revealed that the coordination geometry for the 1-aza-1,3-diene ligands has substantial σ2,π-η4-metallacyclopent-4-ene character. The 1-aza-1,3-diene complexes 8a,c,d only exhibit supine geometry as confirmed by 1H NMR spectroscopy, while 8b exists in both the conventional supine geometry and the prone geometry, which is demonstrated by quite different 1H NMR chemical shift values. Addition of 8c to 1 equiv of acetophenone gives the seven-membered metallacyclic ring system CpTi[N(C6H4-4-Me)CH=C(Me)CH(Ph)C(Me)PhO] (9), whose structure has also been characterized by NMR spectral data and by X-ray diffraction analysis. In contrast to 8c, the 1-aza-1,3-diene titanocene complex Cp2Ti[N(C-C6H11)CH=C(Me)CH-(Ph)] (7c) does not react with acetophenone even at high temperatures. ? MAD is used as an acronym for 1-aza-1,3-dienes (monoazadienes) in general. In this paper we will use MAD when N-alkyl-(￡)-cinnamaldimines (R1)N=CHC(R2)=CH(Ph) (R1 = t-Bu, C-C6H11; R2 = H, Me) or N-aryl-(E)-cinnamaldimines (R1 = C6H4-2-Me, C6H4-4-Me; R2 = H, Me) are meant.
