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) H2 tBu2O2NN′ (Me2NCH2CH2-(CH2-2-HO-3,5-C6H2 tBu2)2) led to formation of [TiCl(tBu2O2NN′)(L)] (L = THF, 1; py, 2) and [YCl(tBu2O2NN′)(DME)], 3. Reactions of 1 or 3 with MCH2-(2-NMe2)C6H4 and with M[2-(CH2NMe2)C6H4] (M = Li, K) led to [Ti(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 5, [Y(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 6, and [Y(tBu2O2NN′)(κ2-(C6H4CH2NMe2))], 7. [Y(tBu2O2NN′)N(SiMe3)2], 4, was obtained from 3 and KN(SiMe3)2, whereas [(Y(tBu2O2NN′)(CH2SiMe3))2(μ4-O)(μ3-Li)2], 8, formed from reaction of 3 and LiCH2SiMe3. The reaction of 7 with 1 equiv of CH3CN gave [Y(tBu2O2NN′)(NC(CH3)C6H4CH2NMe2)], 10, which displays a chelating ketimide ligand formed by nitrile insertion in the Y−Ph bond. Further reaction with CH3CN led to [Y(tBu2O2NN′)(κ2-(N(H)C(CH3)C(H)C(C6H4CH2NMe2)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 CH3CN gave [TiCl(tBu2O2NN′)(NCCH3)], 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.

Cobalt in a Bis-β-diketiminate Environment

“…Inorganic Chemistry 34 yttrium−aryl, 35 and chromium−methyl species, 36,37 each of which form corresponding NacNac derivatives.…”

Rare-Earth Complexes Supported by Tripodal Tetradentate Bis(phenolate) Ligands: A Privileged Class of Catalysts for Ring-Opening Polymerization of Cyclic Esters

“…24 All of those alkyl complexes featured a sixcoordinated metal center in a distorted-octahedral environment, with either a THF molecule or an extra donor (i.e., amino) group embedded in the alkyl/aryl moiety, as reported by Marques, Martins, et al (Scheme 6). 19 The latter authors isolated the unusual complex Li 2 (μ 4 -O)[Y(ON(NMe 2 )-O tBu,tBu )(CH 2 SiMe 3 )] 2 from the salt metathesis reaction between LiCH 2 SiMe 3 and the chloro precursor (Scheme 7); although this could not be evidenced, the origin of the μ 4 -oxygen bridge was presumed to be THF rather than adventitious moisture, possibly via formation of an ate complex stabilized by (Li(THF) n ) + . 19 Because the active propagating species in ROP of cyclic esters is a metal alkoxide (Scheme 1), access to these types of complexes, namely Ln{ONXO R1,R2 }(OR)(donor) n in the present case, has been long highly desired.…”

Chiral Diamine Bis(phenolate) TiIV and ZrIV Complexes – Synthesis, Structures and Reactivity

“…[7] However, the only example of a chiral tripodal diamine bis(phenolate) complex reported to date is a molybdenum compound and no catalytic applications have been described. [8] As part of our research with diamine bis(phenolate) complexes of group 3, 4 and 5 metals [9] we undertook the preparation of chiral tripodal diamine bis(phenol) ligand precursors. Attempts to introduce chirality in the benzylic methylene protons were hampered by the formation of 1,3-benzoxazines.…”