Complexes heterobimetallic

2 Heterobimetallic Complexes. - A collection of Ti-based acetylide tweezer compounds in which Cu, Cu and Au, HgX2 and CuMe (which has 

Complexes like 139 have been prepared and contain planar four-coordinate carbon atoms. The zwitterionic early-late transition metal bimetallic species 140 has been synthesised and characterised. Little information about the structure, other than connectivity, could be inferred due to the poor nature of the crystallographic data. Heterobimetallic compounds such as 141 have been synthesised and fully characterised. Strong negative solvatachroism was observed along with high first-order hyperpolarisability The compound 142 has been prepared and crystallographically characterised. The role of planar 

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The nitrogen atom in ri -pyrrolylmanganesetricarbonyl forms a donor-acceptor bond with transition metals. Complexes in which the pyrrolyl ring behaves as a tt ligand for the manganese atom and n-donor for the other metal were synthesized 12 (M = Mn, Re) [78JOM(157)431]. The binuclear heterobimetallic complexes... 

Without question, the most significant advance in the use of sulfur-centered nucleophiles was made by Shibasaki, who discovered that 10 mol% of a novel gallium-lithium-bis(binaphthoxide) complex 5 could catalyze the addition of tert-butylthiol to various cyclic and acyclic meso-epoxides with excellent enantioselectiv-ities and in good yields (Scheme 7.11) [21], This work builds on Shibasaki s broader studies of heterobimetallic complexes, in which dual activation of both the electrophile and the nucleophile is invoked [22]. This method has been applied to an efficient asymmetric synthesis of the prostaglandin core through an oxidation/ elimination sequence (Scheme 7.12). 

Structures of the Heterobimetallic Complex AgAu(MTP)2. Inorganica Chimica Acta, 334, 376. 

Blackie, M.A.L., Beagley, P., Chibale, K., Clarkson, C., Moss, J.R. and Smith, P.J. (2003) Synthesis and antimalarial activity in vitro of new heterobimetallic complexes Rh and Au derivatives of chloroquine and a series of ferrocenyl-4-amino-7-chloroquinolines. Journal of Organometallic Chemistry, 688(1-2), 144-152. 

Very few mixed heterobimetallic complexes which contain an alkali metal and a group 14 which are metal not directly bonded to one another have been structurally characterized. Wright and co-workers, in developing a series... 

Heterobimetallic complexes that induce reactions at significantly faster rates than (or notably different product selectivities from) monometallic derivatives are probably genuine cluster catalysts. 

Hartner and Schwartz [24] studied long-chain alkylidene-bridged heterobimetallic complexes and found that the addition of Cp2Zr(H)Cl to neohexenylborane 23 gave the new boron—zirconium complex 24 (Scheme 7.7). 

A novd example of a catalytic enantioselective domino process1201 is the inter-intramolecular nitro-aldol reaction described by Shibasaki et al which generates substituted indanones. As catalyst a praseodym-heterobimetallic complex with binaph-thol as chiral ligand is employed. Treatment of keto-aldehyde 41 with nitromethane in the presence of the catalyst 46 at -40 °C and successive warming to room temperature affords diredly the produd 42 in an overall yield of 41 % and 96 % ee after several recrystallizations (scheme 9). As intermediates the nitromethane adduct 43 and the hemiacetal 44 can be proposed. In a second aldol reaction 44 leads to 45 which isomerizes to the thermodynamically more stable epimer 42. 

Our preliminary attempts to obtain a basic chiral rare earth complex have led us to create several new chiral heterobimetallic complexes which catalyze various types of asymmetric reactions. The rare earth-alkali metal-tris(l,f-bi-2-naphthoxide) complexes (LnMB, where Ln = rare earth, M = alkali metal, and B = l,l -bi-2-naphthoxide) have been efficiently synthesized from the corresponding metal chloride and/or alkoxide,13,41 and the structures of the LnMB complexes have been unequivocally... 

Scheme 7. Catalytic asymmetric reactions promoted by heterobimetallic complexes.

Moreover, these rare earth heterobimetallic complexes can be utilized for a variety of efficient catalytic asymmetric reactions as shown in Scheme 7 Next we began with the development of an amphoteric asymmetric catalyst assembled from aluminum and an alkali metal.1171 The new asymmetric catalyst could be prepared efficiently from LiAlH4 and 2 mol equiv of (R)-BINOL, and the structure was unequivocally determined by X-ray crystallographic analysis (Scheme 8). This aluminum-lithium-BINOL complex (ALB) was highly effective in the Michael reaction of cyclohexenone 75 with dibenzyl malonate 77, giving 82 with 99% ee and 88 % yield at room temperature. Although LLB and... 

K. Yamada, S. J. Harwood, H. Groger, M. Shibasaki, The First Catalytic Asymmetric Nitro-Mannich-Type Reaction Promoted by a New Heterobimetallic Complex, Angew. Chem, 1999, 38, 3504-3506. 

In addition to the systems mentioned already, a range of other heterobimetallic complexes in... 

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