Ti imido

The first monomeric Ti-imido complex reported was the structurally characterized complex Ti(NP(S)Ph2)Cl2(NC5H5)3 (Ti-N= 1.720(2) A) by Roesky et al.119 Subsequently they showed that reaction of (SiMe3)2NP(S)Pr2 with TiCl4 in MeCN yielded the dimeric species (Ti(/u-NP(S)Pr12)Cl2(MeCN))2 in which the imido groups bridge the two Ti centers.120... 

Addition of 2 equiv. of primary amines RNH2 to a suspension of Cp TiCl3 and phosphoalkynes P=CR in toluene at room temperature gives azaphosphatitanacyclobutane derivatives (Scheme 218). The mechanism of the formation of these complexes is thought to proceed via Ti-imido intermediates.595... 

In 1999, Doye disclosed that dimethyltitanocene is a catalyst widely applicable to intermolecular hydroamination of alkynes with primary aryl- and alkylamines [302]. In the case of unsymmetrically substituted alkynes, the reaction occurs with high re-gioselectivity, forming the anti-Markovnikov products exclusively (Scheme 14.127). Kinetic studies suggest that the reaction mechanism involves the formation of a Ti-imido complex as the catalytically active species. Doye further developed a tandem Ti-catalyzed protocol of alkyne hydroamination and imine reduction, affording secondary amines in a fully catalytic one-pot reaction [303]. 

Titanium imido complexes supported by amidinate ligands form an interesting and well-investigated class of early transition metal amidinato complexes. Metathetical reactions between the readily accessible titanium imide precursors Ti( = NR)Cl2(py)3 with lithium amidinates according to Scheme 84 afforded either terminal or bridging imido complexes depending on the steiic bulk of the amidinate anion. In solution, the mononuclear bis(pyridine) adducts exist in temperature-dependent, dynamic equilibrium with their mono(pyiidine) homologs and free pyridine. 

The Cp Ti(amidinate) fragment provides a particularly useful platform for the synthesis of novel titanium imido complexes and the study of their unusual reactivity. Numerous single-, double-, and cross-coupling and imido-transfer reactions were investigated using these compounds. The synthetic routes leading to CpTi and Cp Ti amidinate derivatives are outlined in Scheme... 

Reversible pyridine dissociation yields the non-Lewis base stabilized imido complex [Cp(NHAr) Ti=NAr] (54). This coordinatively unsaturated species undergoes a [2 + 2] cycloaddition reaction with allene to give an azatitanocyclobutane (55), which is then protonated to the /mamido complex. Elimination of enamine occurs followed by isomerization to the energetically more favorable imine. 

With R = R = Ph and using complexes 1 or 2a, the central N -N single bond of the azine is cleaved by both metals. In this case, the bis(imido) complexes 81 were formed, treatment of which with complexes such as CpCo(C2H2)2 can give heterobimetallic bis(alkylideneamido)-bridged complexes such as 82. Mach has used this concept for the reaction of methyl-substituted titanocenes with acetoneazine. With 3, monomeric Ti(III) complexes 83 and, after activation of the methyl groups, coupled products such as 84 could be obtained [44],... 

The metathetical reaction of C02 with metal (Ti(IV), U(V)) arylimido-complexes led to an arylisocyanate and a metal-oxo species [4g, 115a]. In these processes, which take place under very mild conditions (ambient temperature and pressure), the metal center acts as the sink for unrequired oxygen. A common feature which characterizes these transformations from a mechanistic point of view is the intermediate formation of a metal carbimato-species through the [2+2] cycloaddition of C02 with the metal-imido complex (Scheme 6.23). By cycloreversion, the four-membered aza-metalla-cycle then converts into isocyanate and a stable metal-oxo complex. These processes, at least formally, are reminiscent of the reaction of imino-phosphoranes with C02 to give isocyanates and carbodiimides [115b,c]. 

Amidinato-amido chloro complexes, with Ti(IV), 4, 335-336 Amidinato-imido titanium complexes, synthesis, 4, 431 -32 Amidinato ligands... 

Dibenzyl complexes with calcium, strontium, barium, 2, 120 with Ti(IV), 4, 343, 4, 349 with Zr(IV), 4, 783, 4, 785-786 with Zr(IV) mono-Cp complexes, 4, 833 Dibenzylgallium azides, for semiconductor growth, 12, 17 Dibenzyl imido complexes, with Ti(IV), 4, 352-353 Dibenzyl phosphoranimino carbenes, with Zr(IV), 4, 798 Dibenzyl titanasilsesquioxanes, synthesis, 4, 493 Dibenzyo-tetramethyltetraaza[14]-annulenes, with Zr(IV),... 

Imidazolium ligands, in Rh complexes, 7, 126 Imidazolium salts iridium binding, 7, 349 in silver(I) carbene synthesis, 2, 206 Imidazol-2-ylidene carbenes, with tungsten carbonyls, 5, 678 (Imidazol-2-ylidene)gold(I) complexes, preparation, 2, 289 Imidazopyridine, in trinuclear Ru and Os clusters, 6, 727 Imidazo[l,2-a]-pyridines, iodo-substituted, in Grignard reagent preparation, 9, 37—38 Imido alkyl complexes, with tantalum, 5, 118—120 Imido-amido half-sandwich compounds, with tantalum, 5,183 /13-Imido clusters, with trinuclear Ru clusters, 6, 733 Imido complexes with bis-Gp Ti, 4, 579 with monoalkyl Ti(IV), 4, 336 with mono-Gp Ti(IV), 4, 419 with Ru half-sandwiches, 6, 519—520 with tantalum, 5, 110 with titanium(IV) dialkyls, 4, 352 with titanocenes, 4, 566 with tungsten... 

Imido-nitrido complexes, with mono-Cp Ti(IV), 4, 425-426 Imido-supporting ligands, in molybdenum complexes alkenes, 5, 535 alkynes, 5, 548... 

Bulky titanium alkylamido complexes are capable of equilibrating with aliphatic and aromatic hydrocarbons via concerted 1,2-elimination/l,2-addition processes a Ti=NR imido species is formed as a transient intermediate. Kinetic parameters suggest a four-center transition state with an almost linear NHR arrangement 122... 

Imido zwitterionic titanium complexes, Ti=NAr[CH3B(C6F5)3], undergo reaction with carbon dioxide to give isocyanates and symmetrical carbodiimides via a ligand metathesis... 

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