Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Abstract

The reaction of Cp2TiPh2 with 2,2-dimethylpropane-1,3-diol proceeds with the evolution of benzene affording the bimetallic titanocene alkoxide species Cp2Ti(Ph)(p-OCH2C(CH3)2CH20)(Ph)TiCpz, 1. Complex 1 crystallizes in the monclinic space group Cc with a = 25.448(7) A, b = 8.483(s) A, c = 14.512(3) A, P = 101.52(2)", Z = 4, and V = 3070(1) A3. The structure was refined employing 1471 data with Fo > 3uF0 and 138 variables to R values of R = 0.0588 and R,,, = 0.0828. the dimeric nature of 1 is confirmed. The coordination spheres of the two Ti centres are pseudo-tetrahedral. The T i 4 u bonds were found to be 2.21(1) and 2.25(1) A. Although the phenyl substituents are directed towards each other, steric effects appear to be overcome by the approximately perpendicular orientation of the phenyl rings (in fact the angle between the planes is 81.9"). The Ti ... Ti separation in 1 is 6.725 A. The implications of the preparation of 1 regarding the mechanism of formation of early metal macrocyclic compounds are discussed. In addition, the ramifications for the synthesis of dissymmetric early metal macrocycles are considered.Key words: titanium alkoxides, alkoxide bridged, structure. Introduction Titania or zirconia are often employed as support materials for heterogeneous catalysts (1). These supports may act simply as a dispersent for the late metal centers or may play an active role in the catalytic cycle. In the latter case, such participation gives rise to the phenomenon known as strong metal-support interactions (SMSI) (1). Activation of substrate molecules by a Lewis acidic, early metal and a late metal center may account for the observed effects. We and others have investigated homogeneous systems in which early and late metals are linked in close proximity by bridging Iigands (2). Such heterobimetallics are of interest both as models for the heterogeneous catalyst systems and because of their potential as catalysts in their own right. Fewer studies have focused on simple complexes of Ti or Zr that might model the Lewis acidic, early metal centers of titania or zirconia. Several groups (3-3, have reported the syntheses and reaction chemistry of a variety of early metal alkoxide complexes. The similarity of metal-alkoxide species to metal oxides and the propriety of such species as models for metal-oxide surfaces have been considered by others (3). Much of the work to date has focused on systems in which sterically demanding alkoxy or aryloxy ligands inhibit oligomerization and yield mononuclear early metal compounds (4, 5). In our 'A complete set of supplementary material may be purchased from the Depository of Unpublished Data, CISTI, National Research Council of Canada, Ottawa, Ont., Canada KIA 0S2. initial investigations in this area, we described the specific formation of bimetallic macrocyclic Zr-alkoxide species via the reaction of dimethylzirconocene with diols (Scheme 1) (6).In this report we describe the product of the related reaction of Cp2TiPh2 with 2,2-dimethylpropanediol, i.e., Cp2Ti(Ph)(p-0CH2C(CH3)2...

Novel Aryltitanium(IV) Complexes Containing η3-NCN-Pseudofacial- and η3-NCN-Meridional-Bonded [C6H3(CH2NMe2)2-2,6]- (Abbreviated as NCN) Ligands. The Crystal Structures of [TiCl2(η3-fac-NCN)(O-i-Pr)], [TiCl(η3-mer-NCN)(O-i-Pr)(OTf)] Containing an η1-O-Bonded Triflate Anion, and the Seven-Coordinated [Ti(η3-mer-NCN)(O-i-Pr)(O

“…An obvious difference between 1a , 2 , and 3 is the Ti−O−C bond angles, which vary from 149.22(18) to 157.2(4) and 172.4(3)°, respectively. As has been proposed, the M−O bond distance and, in particular, the M−O−C bond angle in group 4 metal alkoxide complexes give an indication of the degree of M−O dπ−pπ multiple bond character in the alkoxy−metal bond. The M−O−C bond angle is influenced by the hybridization of the oxygen atom, i .…”

Reaction of the titanocene alkyne complex Cp2Ti(η2-Me3SiC2SiMe3) with methanol: Preparation and characterization of a novel trinuclear titanium complex [{Cp2Ti(OMe)}2{Ti(OMe)4}]

“…The methanolysis of 1 represents an alternative synthetic approach to the preparation of mixed-valent titanium alkoxides, which have the ability to bridge two or more metal centers to give macrocyclic metallocene derivatives [8,11], which is a prerequisite for the occurrence of short Ti-Ti-contacts. A second characteristic of interest is the high reducing power of low-valent titanium(III).…”

Titanocene derivatives containing titanium–carbon σ-bonds

“…Titanocene trifluoromethanesulfonate alcoholates Cp 2 Ti(O 3 SC-F 3 )(OR), where R = Me, Me 3 Si, Me 2 Bu t Si, are formed upon treatment of methyltitanocene trifluoromethanesulfonate with the corresponding alcohols. 265 Reactions of dimethyltitanocene with (+)-(2R,3R)-dimethyl and (+)-(2R,3R)-dibutyl tartrates 269 and reactions of diphenyltitanocene with 2,2-dimethylpropane-1,3-diol 270 yielded the binuclear complexes 154 and 155, respectively.…”