Diamine Bis(phenolate) M(III) (Y, Ti) Complexes: Synthesis, Structures, and Reactivity

Abstract

Reactions of titanium and yttrium trichlorides with 1 equiv of the sodium or potassium salts of the diamine bis(phenolate) H 2 tBu2 O 2 NN′ (Me 2 NCH 2 CH 2 -(CH 2 -2-HO-3,5-C 6 H 2 t Bu 2 ) 2 ) led to formation of [TiCl( tBu2 O 2 NN′)(L)] (L = THF, 1; py, 2 ) and [YCl( tBu2 O 2 NN′)(DME)], 3 . Reactions of 1 or 3 with MCH 2 -(2-NMe 2 )C 6 H 4 and with M[2-(CH 2 NMe 2 )C 6 H 4 ] (M = Li, K) led to [Ti( tBu2 O 2 NN′)(κ 2 -(CH 2 C 6 H 4 NMe 2 ))], 5, [Y( tBu2 O 2 NN′)(κ 2 -(CH 2 C 6 H 4 NMe 2 ))], 6, and [Y( tBu2 O 2 NN′)(κ 2 -(C 6 H 4 CH 2 NMe 2 ))], 7 . [Y( tBu2 O 2 NN′)N(SiMe 3 ) 2 ], 4, was obtained from 3 and KN(SiMe 3 ) 2, whereas [(Y( tBu2 O 2 NN′)(CH 2 SiMe 3 )) 2 (μ 4 -O)(μ 3 -Li) 2 ], 8, formed from reaction of 3 and LiCH 2 SiMe 3 . The reaction of 7 with 1 equiv of CH 3 CN gave [Y( tBu2 O 2 NN′)(NC(CH 3 )C 6 H 4 CH 2 NMe 2 )], 10, which displays a chelating ketimide ligand formed by nitrile insertion in the Y−Ph bond. Further reaction with CH 3 CN led to [Y( tBu2 O 2 NN′)(κ 2 -(N(H)C(CH 3 )C(H)C(C 6 H 4 CH 2 NMe 2 )N(H)], 9, the formation of which involves an imine−enamine tautomerism followed by a second nitrile insertion and 1,3-hydrogen shift. The reaction of 1 with CH 3 CN gave [TiCl( tBu2 O 2 NN′)(NCCH 3 )], which upon heating converts to a new paramagnetic species that is likely a chloride-bridged Ti(III) dimer. The EPR study performed reveals that bis(phenolate) Ti(III) complexes do not promote nitrile coupling reactions by electron transfer. The solid state molecular structures of 1 − 9 revealed that in all the complexes the bis(phenolate) ligand is coordinated to the metal center by the two oxygen atoms and the two nitrogen atoms with trans phenolate arrangement.