205746-73-2Relevant academic research and scientific papers
Chelating diamide complexes of titanium: New catalyst precursors for the highly active and living polymerization of α-olefins
Scollard, John D.,McConville, David H.,Vittal, Jagadese J.,Payne, Nicholas C.
, p. 201 - 214 (2008/10/09)
The reaction of RHN(CH2)3NHR (la,b) (a, R = 2,6-(i)Pr2C6H3; b, R = 2,6-Me2C6H3) with 2 equiv of BuLi followed by 2 equiv of ClSiMe3 yields the silylated diamines R(Me3Si)N(CH2)3N(SiMe3)R (3a,b). The reaction of 3a,b with TiCl4 yields the dicholoride complexes [RN(CH2)3NRITiCl2 (4a,b) and two equiv of ClSiMe3. An X-ray study of 4a (P21/n, a = 9.771(1) A, b = 14.189(I) A, c = 21.081(2) A, β = 96.27(1)°, V = 2905.2(5) A3, Z = 4, T= 25°C, R = 0.0701, Rω, = 0.1495) revealed a distorted tetrahedral geometry about titanium with the aryl groups lying perpendicular to the TiN2-plane. Compounds 4a,b react with 2 equiv of MeMgBr to give the dimethyl derivatives [RN(CH2)3NR]TiMe2 (5a,b). An X-ray study of 5b (P222i, a = 8.0955(10) A, b = 15.288(4) A, c - 16.909(3) A, V= 2092.8(7) A3, Z= 4, T= 23°C, R = 0.0759, Rω = 0.1458) again revealed a distorted tetrahedral geometry about titanium with titanium-methyl bond lengths of 2.100(9) A and 2.077(9) A. These titanium dimethyl complexes are active catalysts for the polymerization of 1-hexene, when activated with methylaluminoxane (MAO). Activities up to 350,000 g of poly(1-hexene)/mmol catalyst. h were obtained in neat I-hexene. These systems actively engage in chain transfer to aluminum. Equimolar amounts of 5a or 5b and B(C6F5)3 catalyze the living aspecific polymerization 1-hexene. Polydispersities (Mω/M(n)) as low as 1.05 were measured. Highly active living systems are obtained when 5a is activated with {Ph3C}+[B(C6F5)4]-. A primary insertion mode (1,2 insertion) has been assigned based on both the initiation of the polymer chain and its purposeful termination with iodine.
