Titanium clusters

Wu H, Desai S R and Wang L S 1996 Electronic structure of small titanium clusters emergence and evolution of the 3d band Phys. Rev. Lett. 76 212... 

Reetz, M.T., Quaiser, S.A., and Merk, C., Electrochemical preparation of nanostructured titanium clusters characterization and use in Mcmurry-type coupling reactions, Chem. Ben, 129, 741, 1996. 

Beller et al. have shown for the first time that palladium colloids are effective catalysts for the olefination of aryl bromides (Heck reaction). Reetz et al. have studied Suzuki and Heck reactions catalyzed by preformed palladium clusters and palladium/nickel bimetallic clusters and further progress was achieved by Reetz and Lohmert using propylene carbonate stabilized nanostructured palladium clusters as catalysts in Heck reactions. In addition, the use of nanostructured titanium clusters in McMurry-type coupling reactions has been demonstrated by Reetz et... 

Self-supported chiral titanium clusters were prepared by mixing the ligand and titanium alkoxide in anhydrous toluene, followed by addition of a small amount of water (Scheme 7.22). In some cases, the cluster was completely insoluble in the reaction medium, especially in the case of 30. The cyanation works well with this heterogeneous catalyst, which was reused many times with no significant loss of activity. Additional experiments revealed that no appreciable amount of chiral catalyst had leached into the solution and the enantioselectivity came only from the solid catalyst. 

Strecker reaction A robust heterogeneous self-supported chiral titanium cluster (SCTC) catalyst applied both in batch and continuous mode [44] enabled imine cyanation as well as a three-component Strecker reaction using the corresponding aldehydes and amines under continuous flow conditions in a PBR giving aminonitriles enantiomeric excess values of up to 98%. 

Seayad, A.M., Ramalingam, B., Chai, C.LL, Li, C., Garland, M.V., and Yoshinaga, K. (2012) Self-supported chiral titanium cluster (SCTC) as a robust catalyst for the asymmetric cyanation of imines under batch and continuous flow at room temperature. Chem. Eur. J., 18, 5693-5700. doi 10.1002/chem.201200528... 

Product ion scan, where Ql is set to aUow only the target precursor ion mass to enter the cell, while Q2 scans to measure all the product ions formed in the cell, including controUed cluster ion analysis. An example of this is the use of NH3 gas to create cluster ions of an analyte such as titanium. By allowing only Ti through Ql, only titanium cluster complex ions are formed in the cell, and not other potentially interfering transition metal cluster ions as with a traditional coUision/reaction cell. 

A titanium(O) colloid, prepared by the reduction of TiCU with KBEtsH, has been used in the synthesis of indoles [260]. Nanostructured titanium clusters, produced electrochemically by using a titanium sacrificial anode as the metal source and Bu4NBr in THF as the electrolyte and stabilizer, were found to induce olefin-forming McMurry-type coupling of oxoamides, aromatic aldehydes, and ketones [261]. 

Geometry optimization was performed on the discrete cluster unit to eliminate the effects of crystal packing and interactions with titanium ions. The calculations were carried out in local spin density approximation using a SPARTAN 5.0.3 package (Wavefanction, Inc., Irvine, CA 92612 USA). 

Figure 16. Mass distribution of TimCj clusters generated from the reactions of titanium with CH4. Note the "super magic" peak corresponding to TisCu. Taken with permission from ref. 92.

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