Group 14 elements carbene

It is often difficult to deduce from the restricted experimental data the main trends in reactivity. Theoretical calculations could give the needed information to fill these gaps. In other words, they could be used to sometimes interpolate scarce experimental data, e.g. in studying substituent effects. To examine general trends in the series of Group 14 elements carbene analogs, data for silylenes and even for carbenes are presented in this section for some cases. 

M. F. Lappert, R S. Rowe, The Role of Group 14 Elements Carbene Analogues in Transition Metal Chemistry", Coord Chem. Rev. 1990,100,267. 

Low-coordinate species of the main group elements of the second row such as carbenes, olefins, carbonyl compounds (ketones, aldehydes, esters, amides, etc.), aromatic compounds, and azo compounds play very important roles in organic chemistry. Although extensive studies have been devoted to these species not only from the physical organic point of view but also from the standpoints of synthetic chemistry and materials science, the heavier element homologues of these low-coordinate species have been postulated in many reactions only as reactive intermediates, and their chemistry has been undeveloped most probably due to... 

Reactions of stable nucleophilic carbenes with main group element compounds have recently been reviewed Garmalt, C. J. Cowley, A. H. 

One example is known for the transfer of an NHC from a main-group element to a transition metal The NHC adduct of BH3 was reported to transfer the carbene to [Mn(CO)5Br]. ... 

The first group 13 (IIIA) element-carbene complex to be reported was an imi-dazol-2-ylidene-alane complex (Scheme 8.23). Based on NMR data, it was suggested that the imidazole fragment has an electronic structure that is intermediate between those of the free carbene and imidazolium ion. The use of an imidazol-2-... 

A wide variety of cyclopropenylium metal cations has been prepared and studied over the past two decades, ranging from main group elements (Li, Mg) through transition metal -complexes (Fe, Mn, Pd, Pt). Extensive NMR studies suggest that the metal carbene... 

The synthetic potential of silicon substituents in organic and organometallic chemistry has by far not been fully exploited, which is evidenced by the numerous contributions in this chapter. This is examplified for the description of the silyl group as a substituent and as a functional group in carbene and carbenoid chemistry, for the function of the trimethylsilyl substituent in the synthesis of low-valent compounds containing elements ofgroup 15 andfor the influence of a supersilyl ligand to a phosphorous center. 

Recently, significant progress has been made in the characterization of main group adducts of these carbenes. This chapter will deal only with carbene compounds of the main group elements reported since 1993 and excludes transition metal carbene compounds (such compounds may be found in the article Carbene Complexes). 

Summary Trimethyl- and triisopropyl-silyl diazomethane derivatives have been used for the synthesis of new types of diazo derivatives including those featuring a heavier main-group element or a transition metal directly bound to the diazo-carbon. They are also precursors to a variety of stable nitrilimines and carbodiimides, and stable pseudo-diazoalkenes and carbenes. (Phosphino)(silyl)carbenes have been used in the synthesis of new types of heterocycle including some stable four-7c-electron four-membered derivatives. 

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