Transition metals carbenes

The diazo function in compound 4 can be regarded as a latent carbene. Transition metal catalyzed decomposition of a diazo keto ester, such as 4, could conceivably lead to the formation of an electron-deficient carbene (see intermediate 3) which could then insert into the proximal N-H bond. If successful, this attractive transition metal induced ring closure would accomplish the formation of the targeted carbapenem bicyclic nucleus. Support for this idea came from a model study12 in which the Merck group found that rhodi-um(n) acetate is particularly well suited as a catalyst for the carbe-noid-mediated cyclization of a diazo azetidinone closely related to 4. Indeed, when a solution of intermediate 4 in either benzene or toluene is heated to 80 °C in the presence of a catalytic amount of rhodium(n) acetate (substrate catalyst, ca. 1000 1), the processes... 

Keywords Azolium salts AJ-heterocydic carbenes transition metal complexes asymmetric catalysis... 

Since there are many more carbene-transition-metal complexes known than main-group adducts this chapter is organized by the synthetic methods that lead to the complexes rather than by the metal itself, Applications of these complexes to catalysis and materials science will be discussed in separate chapters of this article. 

Stable Carbene-Transition Metal Complexes Applications in Catalysis.. . 358... 

Compounds with multiple bonds between a transition metal and group-14 elements as the heavier analogues of carbenes — transition metal complexes of the type (CO)sCr-EH2 (E = C to Sn) — have been calculated at the DFT level by Jacobsen and Ziegler117. The authors report the equilibrium geometries and the transition metal-E bond dissociation... 

With the 1964 paper by Fischer and Maasbol [25], published 27 years earlier than the seminal report by Arduengo, the era of carbene-transition metal chemistry began. Between the middle of 1964 and the end of 1973 (when Fischer presented his Nobel Lecture) more than 50 papers were published from Fischer s... 

Sanderson MD, Kamplain JW, Bielawski CW (2006) Quinone-annulated N-heterocyclic carbene-transition-metal complexes observation of jt-back-bonding using FT-IR spectroscopy and cyclic voltammetry. J Am Chem Soc 128 16514-16515... 

Lappert MF, Maskell RK. (1984) Carbene transition metal complexes as hydrosilylation... 

Figure 1.1 Bonding in Fischer, Wanziick-Arduengo and Schrock carbene transition metal complexes.

Note The formation of bridging versus chelating bis-carbene transition metal complexes is a function of tether length, reaction temperature, steric demand of wingtip groups and the order of the addition of counter anions. 

Figure 3.121 Synthesis of Janus (back-to-back) bis-carbene transition metal complexes.

N-HeterocycHc carbene transition metal complexes for catalysis in aqueous media 12CSR7032. 

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