A trans‐Dimethyl Derivative of Octahedral Ti^IV: Alkylation and Arylation of Ti^IV‐Schiff Base Complexes

Abstract

Table I. Metathesis of I-octene with hetero-and homogeneous carbene and carbyne tungsten(v1) complexes. x = turnovers per minute (mol 1-octenei mol W). Starting concentration I-octene :W = 10' : I . 80-Turnover [Yo] at 69°C at 122°C a) Heterogeneous catalysts Si0,/[C12W=CHtBu] Si02i[Np2W=CHtBu] b) Homogeneous catalysts [Cl,(dme)W=CfBu] [(tBuO),W=CtBu] [Np,W=CtBu] [ ( I B U O )~( P~O )~W = C H~B U ] S~O~/ [ (~B U O )~W = C H I B U ] 30 200 60 140 260 830 5 50 1 5 0 0 0 0the alkoxy ligands by strongly electron-withdrawing perfluoroalkoxy or imido ligands. In this way, the electronegative character of the W center is increased, favoring addition of olefins to the W=C bond so that metathesis can more readily occur. A similar effect is clearly also achieved by coordination on the S O 2 surface. The heterogeneous carbene complexes can be stored at -30°C for several weeks without loss of catalytic activity. After one week at 20"C, SiO,/[Np,W=CHtBu] still had its original activity.Alkene isomerization becomes significant only when the molar ratio W : I-octene becomes greater, i.e. with decreasing I-octene concentration. A similar behavior has been observed for the heterogeneous bimetallic catalysts prepared from carbene or carbyne tungsten(0) complexes and the reduced Phillips catalyst.''-31Carbene tungsten complexes in high oxidation states have long been postulated to be the catalytically active species in the metathesis of olefins by heterogeneous tungsten catalysts.'"' The results reported here support this theory and make it possible to study these catalysts systematically.The chemistry of the titanium-carbon bond is still having a major impact in organometallic chemistry for both metal-induced stoichiometric". and catalytic transformat i o n~. '~~] Many of its characteristics are, however, associated with the presence of cyclopentadienyl ligands at a tetrahedrally coordinated metal center.[3c' Since the chemical behavior of the Ti-C bond towards substrates is largely affected by the steric and electronic constraints imposed by the ancillary ligands, we turned our attention to a rigid ligand, such as salen [salen = N,N'-ethylenebis(salicy1ideneiminato) dianion], whose use has many precedents, almost exclusively in the organometallic chemistry of cob a l t (~~~) . [~] Several organic derivatives of early transition metals with tetradentate ligands have been reported recently.L5,61 ITi(salen)Cl,] l L 7 I seemed to be an excellent starting material for tives. CI I 1, [Ti(salen)C12] y 3 the preparation of organometallic derivaa ) LiMe 2 (alkylation at the metal) I (metal reduction and b) PhMgBr 1 THF ~ formation of an organometallic titaniurn(lll) compound) I 1 C) MesMgBr (alkvlation at the metal toluene or dtoxane and at the imino group) Ph I Mes I I thf I Mes 2, [ T i (~o l e n ) ( M e )~] 3, [(Ph)Ti(solen)(thf)] 4, [Ti(solenMes)(Mes)] Scheme I. Mes = 2,4,6-Me,C6H2. The arrows indicate the possible alkylation sites in 1 .

Alkylation and arylation of dichloro[N,N′-ethylenebis(salicylideneiminato)]titanium(IV)

“…x / a 2606(2) 2835( 7) 1773( 7) 3363( 10) 2478( 13) 1761(9) 3 340( 7) 3362( 7) 3852( 7) 4320( 7) 4299( 7) 3808 (7) the low-angle reflections no corrections for secondary extinction were deemed necessary. Solution and refinement were based on the observed reflections.…”

Polymerization of ethylene and propene promoted by binaphthyl-bridged Schiff base complexes of titanium

“…This has been traced to the fact that the imine unit(s) readily undergo inter-or intra-molecular reduction, i.e. 1,2-migratory insertion (1,2-MI) with metal-bound alkyl ligands [2], the imine nitrogen is so transformed into an anionic donor which coordinates to the metal occupying a potential polymerization site.…”

Di-μ-hydroxo-κ4O:O-bis[aquatris(triphenylsilanolato-κO)zirconium(IV)] toluene solvate

“…The chemistry of group 4 metal complexes containing inorganic donor sets, viz. O or N donor sites, is much less developed because the coordination chemistry of these compounds is much more complicated than that of metallocene derivatives (Britovsek et al, 1999;Tajima & Kunioka, 1968;Gibson et al, 1998;Shah et al, 1996;Horton & de With, 1996;Tinkler et al, 1996;Baumann et al, 1997;Scollard & McConville, 1996;Walther et al, 1996;Sobota et al, 1997;Floriani et al, 1989;North et al, 1998;Solari et al, 1992;Murugavel et al, 1996).…”