181037-28-5Relevant articles and documents
Titanium complexes stabilized by N-(tert-hydrocarbyl)anilide ligation: A synthetic investigation
Johnson, Adam R.,Davis, William M.,Cummins, Christopher C.
, p. 3825 - 3835 (2008/10/08)
The complexes Ti(NRArF)2(NMe2)2 (4, R = C(CD3)2CH3, ArF = 2,5-C6H3FMe), Ti(NRArF)2-(NMe2)(I) (5), Ti(NRArF)2(NMe2)(CH2SiMe 3) (6), and Ti(NRArF)2(I)(CH2SiMe3) (7) have been synthesized in 77, 71, 70, and 84percent yield, respectively, in a four step sequence of alternating salt elimination and dimethylamide deprotection steps. The complex Ti(NRAr)(I)2(OAr′) (11, Ar = 3,5-C6H3Me2, Ar′ = 2,6-C6H3iPr2) was prepared in 65percent yield via the complexes Ti-(NRAr)(NMe2)3 (9) and Ti(NRAr)(NMe2)2(OAr′) (10), which were generated in situ, spectroscopically characterized, and not isolated. The complexes Ti(NR′Ar)(NMe2)3 (12, R′ = C(CD3)2Ph, Ti(NR′Ar)(NMe2)2(OAr″) (13, Ar″ = 2,6-C6H3tBu2), and Ti(NR′Ar)(NMe2)(OAr″)-(I) (14) were prepared in 83, 83, and 95percent isolated yield, respectively, via a salt-elimination, protonolysis, and dimethylamide deprotection sequence. Treatment of 14 with (i) neopentyllithium, (ii) thermolysis at 65°C, and (iii) excess methyl iodide at 70°C led to the isolation in 62percent yield of the cyclometallated compound Ti(NR′Ar)(O-2,6-C6H3[tBu][CMe 2CH2](I) (17) via an intermediate neopentyl complex (15) which was not isolated. The titanium(III) "ate" complex (ArR′N)2Ti(μ-Cl)2Li(TMEDA)n (18, TMEDA = Me2NCH2CH2NMe2, n = ca. 3) was isolated in 80percent yield as green crystals upon treatment of TiCl3(THF)3 (THF = tetrahydrofuran) with 2 equiv of Li(NR′Ar)(OEt2) in a THF/TMEDA mixture. Chloroform treatment of the ate complex 18 led to the titanium(IV) dichloride Ti(NR′Ar)2Cl2 (19). The titanium(III) ate complex (ArRN)2Ti(μ-Cl)2Li(TMEDA) (20) was isolated in 57percent yield in a manner analogous to the preparation of 18. Alkylation of 20 with LiCH(SiMe3)2 led to the mixed amido-alkyl titanium(III) complex Ti(NRAr)2(CH[SiMe3]2) (21) in 72percent isolated yield. A single-crystal X-ray diffraction study carried out for 21 revealed an η3 bonding mode for one of the NRAr ligands and a typical η1 bonding mode for the other. The diamagnetic dimeric complex (μ-NCPhCPhN)[Ti(NRAr)2(CH[SiMe3]2)]2 (23) was obtained in 82percent yield via the blue benzonitrile adduct Ti(NRAr)2(CH[SiMe3]2)(NCPh) (22), which was not isolated. A robust green pivalonitrile adduct Ti(NRAr)2(CH[SiMe3]2)(NCCMe3) (24) was observed upon treatment of 21 with pivalonitrile. Addition of azidotrimethylsilane to 24 delivered the titanium(IV) azido complex Ti(NRAr)2(CH[SiMe3]2)(N3) (25) in 37percent isolated yield. Treatment of 21 with 0.5 equiv of I2 in benzene provided Ti(NRAr)2(CH[SiMe3]2)(I) (26) in 68percent yield.
