Titanium imido complexes of pendant arm functionalised benzamidinate ligands
Abstract
Reactions of the lithiated pendant arm functionalised benzamidinates Li{Me2NCH2CH2NC(Ph)NSiMe3} and Li{Me2NCH2CH2CH2NC(Ph)NSiMe3} with the compounds [Ti(NR)Cl2(py)3]
(R =
tBu, 2,6-Me2C6H3, 2,6-iPr2C6H3) afforded five-coordinate [Ti(NR){Me2NCH2CH2NC(Ph)NSiMe3}Cl]
1–3 and [Ti(NR){Me2NCH2CH2CH2NC(Ph)NSiMe3}Cl]
4–6, respectively. Reaction of [Ti(NtBu){Me2NCH2CH2CH2NC(Ph)NSiMe3}Cl]
4 with C6F5NH2 gave elimination of tBuNH2 and the corresponding perfluoroarylimido complex 7. The X-ray crystal structures of [Ti(NtBu){Me2NCH2CH2NC(Ph)NSiMe3}Cl]
1 and [Ti(N-2,6-R2C6H3){Me2NCH2CH2CH2NC(Ph)NSiMe3}Cl]
(R = Me 5 or iPr 6) have been determined. Reaction of either 1 or 4 with H2N-2,6-Me2C6H3 in C6D6 afforded the corresponding arylimido compounds 2 and 5, but this route is not amenable to easy scale-up. For better evaluation of the effects of the pendant NMe2 donor group in 1–6, the bis(pyridine) compound [Ti(NtBu){MeCH2CH2NC(Ph)NSiMe3}Cl(py)2]
9 was prepared from Li{MeCH2CH2NC(Ph)NSiMe3}
8 and [Ti(NtBu)Cl2(py)3]. The compounds 1–3 with two-carbon pendant arms are quite sensitive to adventitious protonation, and the X-ray crystal structures of the products of two such reactions, namely [Ti2{Me2NCH2CH2NC(Ph)N(H)SiMe3}2(NtBu)2Cl2(μ-Cl)2]
10 and [Ti2(N-2,6-C6H3Me2)2Cl2(μ-O){Me2NCH2CH2NC(Ph)N(H)SiMe3}2]
11, have been determined. Both possess