Homoleptic complexes titanium

The homoleptic (see Homoleptic Compound) titanium diene complex (j " -r-BuCH=CHCH=CHBu-t)2Ti (11) has been prepared by the condensation ofelectron-beam vaporized titanium with an excess of 1,4-di-t-butylbuta-1,3-diene" (see Metal Vapor Synthesis of Transition Metal Compounds). The bis-diene dmpe complex Ti(dmpe)( " -C4H6)2Ti (12) has been prepared by the reduction of TiCl4(dmpe) with Na/Hg in the presence of butadiene, and by the reduction of TiCLi with CH2=CHLi in the presence of dmpe. ... 

The addition of a base, typically ammonia, to mixtures of transition metal halides and alcohols allows the synthesis of homoleptic alkoxides and phenoxides for a wide range of metals. Anhydrous ammonia was first used in the preparation of titanium alkoxides where the reaction is forced to completion by the precipitation of ammonium chloride.41 Although useful for the synthesis of simple alkoxides and phenoxides of Si, Ge, Ti, Zr, Hf, V, Nb, Ta and Fe, as well as a number of lanthanides,42-47 the method fails to produce pure /-butoxides of a number of metals.58 Presumably, secondary reactions between HC1 and Bu OH take place. However, mixing MC14(M = Ti, Zr) with the Bu OH in the presence of pyridine followed by addition of ammonia proves successful, giving excellent yields of the M(OBul)4 complexes.59... 

No homoleptic isocyanide complexes of niobium, tantalum, titanium, zirconium, and halfnium have yet been synthesized. The vanadium cation... 

Homoleptic tetrazincates, characteristics, 2, 346 Homoleptic titanium(III) complexes, with -ligands, 4, 282 Homoleptic trizincates, characteristics, 2, 345 Homoleptic vanadium(III) alkyl complexes synthesis and structure, 5, 12 VMes3 reactivity, 5, 12... 

Mixed-metal alkoxide complexes of thallium are also known. For example, Sn(/u-t-BuO)3Tl has both Sn(II) and T1(I) ions." The thallium site is unreactive as a donor for metal carbonyls. However, as indicated earlier, the indium(I) site of the indium analogue shows Lewis-base character. The Sn(IV)/Tl(I) mixed alkoxide [Sn(EtO)eTl2] exists as a one-dimensional polymer. This adduct reacts quantitatively with SnCl2 to form the homoleptic, mixed-valent [Sn2(OEt)6]n. Thallium-titanium double alkoxides have been synthesized using thallium alkoxide as one of the starting materials. ... 

The homoleptic, bis(trispyrazolylborate)titanium(ll) complex, Tp2Ti (Tp = trispyrazolylborate 203), has been prepared by reaction of 2 equiv. of KTp with TiCl2(TMEDA) (TMEDA = Ar,Ar,Ar, A -tetrarncthylcthylcncdiarninc).122 The dark red, paramagnetic compound has idealized /)v/ symmetry in the solid state and is easily oxidized to the corresponding Ti(m) derivative both electrochemically and chemically with AgPF, 204. Two-electron oxidation to Ti(rv) chalcogenido complexes has been accomplished with pyridine-N-oxide as well as with elemental sulfur and selenium (205, Scheme 31). 

In 2013, Schafer s group [22b] reported titanium bis(amidate) and bis(pyridonate) complexes for the homopolymerization of rac-lactide and e-caprolactone, and also the formation of a random copolymer of the two. These complexes form pseudo-octahedral six-coordinate species, which were characterized in the solid state. Complexes were synthesized by first installing 2 equiv. of the ligand on homoleptic TifNMe ) followed by protonolysis of dimethylamido ligands with 2 equiv. of alcohol (Figure 19). 

The trinuclear [ClCu Zr2(OPr )9 ] has the [CuZr(jU3-OPr )2(jU,-OPr )3] core similar to the analogous titanium complex. The homoleptic Cu(i)Zr(iv) complex has a different structure [Cu2Zr2(OPr )io] containing the confacial bi-octahedral Zr2(OPr )9 unit into which the Cu2(/u,-OPr ) group is inserted by the copper atoms bridging with terminal isopropoxo ligands on each Zr. The (/i-OPr ) Cu(/i-OPr ) system has a hnear O-Cu-0... 

This example shows the extreme influence of the nature of each of the substituents at P on the stabilization of the gem-dianion as well as on the formation of carbene complexes. Most recently, we were able to synthesize either the monocarbene or the homoleptic biscarbene of titanium using dianion 7Li2 (route A) [93]. In 2009, a related class of pincer ligand was developed by Martin-Vaca, Bourissou et al. who used route B to obtain the first example of indenylidene complexes of Zr (Scheme 29) [94]. Here also, the corresponding isolable dianionic ligands are not accessible. It is to be noted here that the in situ coordination/deprotonation required forcing conditions (ca. 100°C for several hours). 

As discussed in Sect. 5, the intermolecular hydroamination of alkynes catalyzed by group 4 metal complexes is a well-documented process. The less challenging intramolecular transformation can be achieved efficiently with various titanium-based catalysts [51, 125-130]. The cyclization proceeds analogously to the rare earth metal-catalyzed process with exclusive ej o-selectivity and often requires elevated temperatures. However, the homoleptic titanium tetraamide Ti(NMe2)4 catalyzes the cyclization of both terminal and internal aminoalkynes at room temperature (7) [126, 127]. 

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