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

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-iPr2-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-Pri2-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-Pri2-C6H3)(NMe2)(NHMe2)2] (6) is formed. The molecular structures of 1−6 have been determined by X-ray diffraction.