Imido−Titanium/Molybdenum Heterobimetallic Systems. Switching from η⁶-Arene to Fischer-Type Aminocarbene Complexes by Tuning Reactivity Conditions

Abstract

Two types of bimetallic titanium/molybdenum systems are described: the first possesses unprecedented η6-arene-imido groups, while the second has Fischer-type aminocarbene ligands bridging the two metals. The (η6-arene)−Mo imido−Ti complex Ti[N(η6-Ar)Mo(CO)3]Cl2(NHMe2)2 (2; Ar = 2,6- i Pr2-C6H3) has been prepared through the reaction of (η6-ArNH2)Mo(CO)3 (3) and TiCl2(NMe2)2. The alternative route from 2 and Ti(NMe2)4/Me3SiCl also afforded 1, but it was contaminated with a small amount of Ti(NAr)Cl2(NHMe2)2 (1). The reaction between the dimeric complexes {Ti(μ-NAr)(NMe2)2}2 and Mo(CO)6 gave complex mixtures of products, among which the Fischer-type aminocarbene complex [(CO)5Mo{C(NMeCH2NMe2)O}Ti(N-2,6-Pr i 2-C6H3)(NMe2)(NHMe2)] (4) could be characterized. The formation of 4 resulted from the nucleophilic attack of the amido −NMe2 to the carbonyl that afforded the titanoxy aminocarbene linker between the Mo and the Ti centers, followed by a subsequent C−H activation of a methyl group of the aminocarbene and C,N coupling with an amido ligand on titanium. Treatment of Ti(NMe2)4 with 1 equiv of Mo(CO)6 produced the titanoxy aminocarbene [(CO)5Mo{C(NMe2)O}Ti(NMe2)3] (5), while in the presence of 1 equiv of ArNH2 the imido complex [(CO)5Mo{C(NMe2)O}Ti(N-2,6-Pr i 2-C6H3)(NMe2)(NHMe2)2] (6) is formed. The molecular structures of 1−6 have been determined by X-ray diffraction.

Titanium–Imido Complexes with Pendant Groups – Synthesis, Characterization, and Evaluation of Their Role as Precatalysts for Ethylene Polymerization

“…The N imido –Ti–Cl angles are in the range 107–115°, and theN imido –Ti–N angles are in the range 94–100°. The distances and angles associated with the titanium center and the ligands are comparable to those found in other [M(=NR)Cl 2 (NHMe 2 ) 2 ] complexes (M = Ti,24,25,27V22,23). The complexes exhibit a short Ti–N imido distance of 1.6979(16) for O 1 , 1.700(2) for S 1 , and 1.701(3) Å for S 2 , and the imido linkage is almost linear [Ti–N imido –C ipso 175.72(14), 174.6(2), and 166.9(2)° in O 1 , S 1 , and S 2 , respectively].…”

“…The imido–titanium complexes were prepared according to our general procedure for easy access to various titanium– and vanadium–imido compounds of the type [M(=NR)Cl 2 (NHMe 2 ) 2 ] 19,22–25. In a one‐pot synthesis, a toluene solution of Ti(NMe 2 ) 4 was treated with 1 equiv.…”

Reactive Heterobimetallic Complex Combining Divalent Ytterbium and Dimethyl Nickel Fragments

“…This particular case was extensively studied in terms of the tandem-reaction catalysts, where, for example, one metal is the source of one reaction, the other of a second one, and the substrate undergoes two chemical transformations in one pot [9–12]. Another elegant use of the bimetallic complexes is found in the chemical cooperation between both metal fragments, allowing a reactivity that would not occur efficiently with only one of these taken separately [13]. The recent interest in photochemically active bimetallic complexes is witness to these developments [14,15].…”

Homo- and Co-Polymerization of Ethylene with Cyclic Olefins Catalyzed by Phosphine Adducts of (Imido)vanadium(IV) Complexes

“…Extensive studies have been carried out with first row metals (particularly Ti, V, and Cr). Several examples of (imido)­Ti­(IV) complexes have been reported. , Cr­(VI) complexes bearing two dianionic supporting imido ligands have been also investigated , for the possibility of developing a homogeneous, well-defined catalytic system, analogous to the widespread heterogeneous Phillips catalyst. Dianionic imido ligands have been employed also with group 5 metals; for these metals in the +5 oxidation state, the isolobal analogy with group 4 metallocenes is reached with a monoanionic supporting ligand in addition to the dianionic imido ligand.…”