Titanium acac complexes

Employing silyated quadridentate Schiff bases, e.g. 0,0 -bis(trimethylsilyl)-JV,JV -ethylenebis(salicylideneimine),105 a range of titanium(IV) complexes Ti(j/5-C5H5)(salen)L (25 L = Cl, OMe, SMe, NMe2, SnPh3, acac) have been prepared. 

Treatment of the thermally stable, formally divalent bis(alkoxide)titanium alkyne complexes, (Pr 0)2Ti( 7Z-RC=CR) (R = Et, Pr, p-Me-C(,H4),222 with aryl iodides in the presence of Ni(COD)2 (COD = 1,5-cyclooctadiene) affords the corresponding cross-coupled products.223 Other catalysts such as Ni(acac)2 (acac = acetylacetonate), Pd(OAc)2, and Pd(PPh3)4 promote the reaction but are significantly less active. As anticipated, aryl iodides undergo cross-coupling more effectively than the corresponding bromides, chlorides, and triflates. 

Other transition-metal oxidants can convert alkenes to epoxides. The most useful procedures involve /-butyl hydroperoxide as the stoichiometric oxidant in combination with vanadium, molybdenum, or titanium compounds. The most reliable substrates for oxidation are allylic alcohols. The hydroxyl group of the alcohol plays both an activating and a stereodirecting role in these reactions. /-Butyl hydroperoxide and a catalytic amount of VO(acac)2 convert allylic alcohols to the corresponding epoxides in good yields.44 The reaction proceeds through a complex in which the allylic alcohol is coordinated to... 

Titanium can be inserted into a porphyrin by heating TiPh2Cl2, TiO(acac)2 or TiCL, in high boiling solvents.17 The complex is isolated as TiO(Por), which serves as a precursor of halide derivatives.36 The reaction of an oxotitanium porphyrin with benzoyl peroxide or hydrogen peroxide gives a peroxy compound (v(0—O) 895 cm-1). X-Ray structure analyses confirmed the triangular side-on structure with the O—O bond ( 1.45 A) parallel to one of the —Ti—directions. 

This can be achieved by using the cis molybdenum(VI)dioxo ion instead of titanium(IV). In this ion two comers of the octahedron at the molybdenum are already blocked by oxygen atoms and only two catechol units can be bound to the metal. Thus, reaction of ligand 3-H4 with MoC>2(acac)2 in the presence of potassium carbonate leads to a mononuclear macrocydic complex [3Mo0212 in which a loop-type conformation is stabilized at the peptide (Scheme 1.3.3) [23]. (Similar... 

The binuclear titanium complex Cp2TiCl(/x-0)TiCl(acac)2 is formed by the reaction of Gp2TiCl2 with 2 equiv. of 2,4-pentanedione in the presence of NEt3 in CH3CN at room temperature. Its molecular structure has been determined by X-ray diffraction. On activation with LiBu11, the compound catalyzes the reaction of phenylsilane with aldehydes to give O-silylation products.1531... 

The fragment CpTi(acac)S2 is considered as an S-donor metalloligand that supports the binuclear moiety Ir2(CO)4 in the complex CpTi(acac)(/i3-S)2[Ir(CO)2]2, which is obtained upon carbonylation of CpTi(acac)(//3-S)2[Ir(diolefin)2]2. In this Tilr2 system the titanium fragment, as a metalloligand, exerts important steric and electronic influences on the reactivity of the Ir metal toward electrophiles. Thus, the reactivity of this complex with iodine, alkyl iodides, and activated acetylenes has been studied.1798... 

The reaction of titanium alkoxides with acetylacetone leads to several molecular compounds. [TiO(acac)2]2 is formed in the presence of an excess of acetylacetone or upon hydrolysis of Ti(acac)2(OR)2. Single crystals have been isolated, and x-ray diffraction experiments show dimers with sixfold coordinated Ti atoms linked through oxygen atoms. Strongly complexing acac ligands cannot be hydrolyzed easily, and condensation does not go any further (Fig. 8) [35]. 

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