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4.2.3.4.7 Monoanionic tridentate ligand complexes

The ligand [N(CH2CH2NEt2)2n was used to prepare Tia2(N(CH2CH2NEt2)2).941'942 Crystal-lographic data was reported for the V111 analogue.

4.2.3.4.8 Tris(pyrazolyl)borate ligand complexes

The Ti111 tris(pyrazolyl)borate ligand complexes TiCl2((N2C3HMe2)3BH)(C3H2Me2N2) and [NHMe2NHMe][TiCl3((N2C3HMe2)3BH)] were prepared from TiCl3((N2C3HMe2)3BH) and hydrazines. These products were crystallographically characterized and were shown to exhibit a distorted octahedral geometry at Ti.943

4.2.3.4.9 Dianionic tridentate ligand complexes

The polydentate diamido-amine ligand [Me3SiN(CH2CH2NSiMe3)2]2~ has been used to prepare the Ti dimer Ti2(^-Cl)2(Me3SiN(CH2CH2NSiMe3)2)2 (83). Subsequent alkylation with Li[CH-(SiMe3)2] gave the monomeric species Ti(CH(SiMe3)2)(Me3SiN(CH2CH2NSiMe3)2) which was transformed to the stable diamagnetic Tin-hydride Ti2(u-H)2(Me3SiN(CH2CH2NSiMe3)2)2 upon hydrogenolysis.944

4.2.3.4.10 Dianionic tetradentate ligand complexes

The Ti111 compound, TiCl(Me4taa) (84), was isolated and transformed to a variety of organo-metallic derivatives.945

4.2.3.4.11 Porphyrin complexes

Five-coordinate Ti porphyrin complexes are known to have an affinity for oxygen-based ligands. Reaction of TiF(TPP) with Na[SMe] and methanol yielded Ti(OMe)(TPP).946

4.2.3.5 Phosphorus-based Ligand Complexes

TiCl-phosphine complexes have the tendency to form dinuclear Cl-bridged complexes. For example, the series of compounds (TiCl2L)2(^-Cl)2 (L = Pri2PCH2CH2PPri2,947 2PMe3,928 Et2PCH2CH2PEt2 and DMPE ) consist of two octahedra that share a common edge. Alternatively, two octahedra fused by a common face are exemplified by the complexes [PPh4][(TiCl2L)2 (M-Cl)3] (L = PEt3, PMe2Ph,915,948). A dissymmetric bioctahedral analogue Ti2(^-l)2I4(PMe3)4 (85) has also been reported.949 In addition, the monomeric Ti111 adducts TiCl3(THF)(Pri2PCH2CH2 PPri2)947 and TiCl3(P(SiMe3)3)2950 have been synthesized.

4.2.3.6 Oxygen-based Ligand Complexes 4.2.3.6.1 Neutral oxygen donor ligand complexes

A number of THF adducts of Ti chlorides including [Tia2(THF)4][ZnCl3(THF)],951 [TiCl2(THF)4][Sna5(THF)]952 and (Tia2(THF)2)2(M-Cl)2953 have been synthesized. Interestingly, reduction of TiCl4(THF)2 by Al in THF gave TiCl3(THF)3, while the same reaction in CH2Cl2 gave (TiCl2(THF)2)2(^-Cl)2.953 In addition, the crystal structures of TiCl2(THF)2 (M-Cl)2Li(THF)2,954'9'55 TiCl3(THF)(OC4H7CH2OH),956 and (TiCl2(C6H4(CO2Et)2))2 (m-C1)2957 have been reported.

The complex [NBu4]2[TiCl6] was reduced photochemically to the TiIII complex [NBu4] [TiCl4(THF)2]. Alternatively, this anion was prepared directly from the reaction of TiCl3(THF)3 and [NBu4]2[MgCl4].727

Aqueous TiI has been utilized as a reducing agent in a wide variety of redox reactions.958-969 In addition, a variety of tools have been employed to study Tira aqua complexes. For example, the reduction of H2O2 and O2 by [Ti(EDTA)(H2O)]~ and [Ti(H2O)6] + were studied using radical traps.970 The SCF MS-Xa method suggested that the most stable configuration of trans-[TiCl2(H2O)4]+ was with the plane of each H2O molecule oriented parallel to the Cl-Ti-Cl axis.97 Magnetization and Raman studies of the [Ti(H2O)g]3+ cation demonstrated the influence of Jahn-Teller coupling on the magnetic properties. 2 Finally, crystallographic studies have been performed on [Ti(H2O)6][C6H4MeSO3]3 and [NMe4][TiF2(H2O)4][TiF6].973,974

4.2.3.6.2 Hydroxide ligand complexes

Partial hydrolysis of Ti111 in the presence of [PPh4]Cl in acetone gave the dinuclear species [PPh4]2[Ti2-(M-Cl)Cl6(M-OH)(H2O)(OCMe2)] and the mononuclear compound TiCl3(H2O)3.975

4.2.3.6.3 Alkoxide ligand complexes

A series of Tira alkoxides with the formulas TiCl2(OR) and TiCl(OR)2 (R = Me, Et, Bu) were reported from the reactions of anhydrous TiCl3 and trialkylorthoformates. These materials were thought to be polymeric in nature.976 Reaction of TiCl3(THF)3 with Na[OC6H3But2] led to the monomeric five-coordinate Ti complex TiCl2(OC6H3But2)(THF)2, which was shown to have trigonal bipyramidal coordination geometry.977

In related work, Ti(OC6H3But2)3 was obtained from TiCl3(NMe3)2 and excess Li[OC6H3But2]. An electrochemical study showed that Ti(OC6H3But2)2X2 (X = Cl, Br) were reversibly reduced to the corresponding Tira monoanions.426 In contrast, reduction of the TiIV precursor in a non-donor solvent led to the formation of the dimer (Ti(OC6H3Ph2)2)2(^-Cl)2.978

The complex Ti(OC6H3Pri2)2Bn(ButNCBn) reacted with pyridine effecting alkyl transfer, elimination of imine, and reductive coupling of a pyridine, affording the intermediate Tira complex (Ti(OC6H3Pri2)2(NC5H5)2)2(M2-NC5H4C5H4N) (86).979

Reactions of TiCl2(TMEDA)2 with Na[OR] (R = Ph, C6H3But2) formed the trimer Ti3-(u-OPh)4(OPh)5(TMEDA)2 (87) and the dimer (Tia(OC6H3But2)2(TMEDA))2(M-OC6H3But2)2

respectively. Alternatively, the reaction of Ti(N(SiMe3)2)3 with HOC6H3Me2 gave (Ti(OC6H3Me2)2Gu-OC6H3Me2))2, while the reaction of Li[OC6H3Me2] with TiCl3(THF)3 gave the monometallic salt [Li(TMEDA)2][Ti(OC6H3Me2)4].980

Floriani and co-workers have synthesized the Ti11 complex Li3[Ti(DAG)6] (88) that contained ligand, di-o-isopropylidene-a-D-glucofuranose (DAG-). The alkoxide fragments of the glucose ligands bridged the Ti and Li atoms and gave the pseudo-octahedral geometry about Ti. 1

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