The preparation, analysis, and reactions of novel, highly stereoselective cyclopentadienyldialkoxyallyltitanium reagents, available in both enantiomeric forms, are described. Chiral monochlorotitanates are readily prepared from CpTiCl 3 or Cp.TiCl 3 and chiral 1,4-diols, which in turn are obtained from tartrate ester acetals by Grignard addition. The resulting stable seven-membered titanacycles have been analyzed by 1 H, 13 C, and 49 Ti NMR spectroscopy. The structures of two representatives, the complexes 15 and 20, are confirmed by X-ray diffraction

Enantioselective syntheses with titanium carbohydrate complexes. Part 7. Enantioselective allyltitanation of aldehydes with cyclopentadienyldialkoxyallyltitanium complexes

Scorpionates represent one of the most versatile types of tridentate ligand that can coordinate to a wide variety of elements, e.g. from early to late transition metals, and the coordination chemistry of these systems has developed greatly in recent years. This Perspective gives an account of studies on the following aspects: (1) the preparative methods for a new class of heteroscorpionate [RR′C(pz)2] ligand derived from bis(pyrazol-1-yl)methane and (2) the description of metal complexes containing these ligands, examples of which incorporate a range of different metals from the Periodic Table.

Heteroscorpionate ligands based on bis(pyrazol-1-yl)methane: design and coordination chemistry.

Pentamethylcyclopentadienylgallium (Cp*Ga): Alternative Synthesis and Application as a Terminal and Bridging Ligand in the Chemistry of Chromium, Iron, Cobalt, and Nickel†

Fluorinated half-sandwich complexes of titanium, such as CpTiF3, show an increase in activity of up to a factor of 50 compared to chlorinated compounds. In a temperature range of 10−70 °C the excess of methylaluminoxane (MAO) can be reduced to an Al:Ti ratio of 300. The highest melting point of 277 °C can be obtained using pentamethylcyclopentadienyltitanium trifluoride Cp*TiF3. This fluorinated complex affords polymers with a significantly higher molecular weight than with the chlorinated compound. Alkyl substitution of the cyclopentadienyl ligand can increase the activity.

Fluorinated Half-Sandwich Complexes as Catalysts in Syndiospecific Styrene Polymerization

An organotitanium(IV) compound, TiCl3OCH2CF3, 1, was found to polymerize n-hexyl isocyanate to high yields and without the formation of cyclic trimer. CpTiCl2L (L = −OCH2CF3, −N(CH3)2, −CH3), 2−4, respectively, likewise polymerized n-hexyl isocyanate but also polymerized isocyanates in the presence of donor solvents and isocyanates possessing donor functional groups, activated olefins, and strained olefins. The activity of the organotitanium(IV) catalysts decreased with increasing steric bulk about the metal center and increasing electron donation to the metal center from the ligands. The polymerization of n-hexyl isocyanate using organotitanium(IV) compounds is living. The PDIs of PHIC synthesized using catalysts 1−4 were found to range from 1.05 to 1.2. The molecular weight of the polymer formed in polymerizations of n-hexyl isocyanate using catalysts 1−4 varied linearly as a function of the monomer-to-initiator ratio and the percent conversion of the polymerization. Polymerizations using 2 can be endca...

Living organotitanium(IV)-catalyzed polymerizations of isocyanates

(C5Me5)SiMe3 as a mild and effective reagent for transfer of the C5Me5 ring: an improved route to monopentamethylcyclopentadienyl trihalides of the group 4 elements

The reaction between (C5Me5)SiMe3 and group 4 element tetrahalides MX4 (M  Ti, X  Cl, Br, I; M  Zr and Hf, X  Cl) gives the corresponding (η5-C5Me5)MX3 derivatives in nearly quantitative yields in a one-step procedure without the need for further purification.

(C5Me5)SiMe3 as a Mild and Effective Reagent for Transfer of the C5Me5 Ring: An Improved Route to Monopentamethylcyclopentadienyl Trihalides of the Group 4 Elements.

Gerardo Hidalgo Llinás

Papers

(C5Me5)SiMe3 as a mild and effective reagent for transfer of the C5Me5 ring: an improved route to monopentamethylcyclopentadienyl trihalides of the group 4 elements

(C5Me5)SiMe3 as a Mild and Effective Reagent for Transfer of the C5Me5 Ring: An Improved Route to Monopentamethylcyclopentadienyl Trihalides of the Group 4 Elements.