Carbene complexes charge distributions

Charge Distributions. Mulliken population analyses have been used to calculate approximate charge distributions in a number of carbene complexes (see, for example, Refs. 10 and 12) and several conclusions can be drawn ... 

Charge. The small amount of charge distribution data for carbyne complexes (based on Mulliken population analyses) indicates that the metal-carbon bond is generally polarized Ms+—C5- and that the carbyne carbon is always more negative than adjacent carbonyl carbons (28,30). These conclusions are directly analogous to those derived for carbene complexes. 

Fig. 3.17. Two reactions that demonstrate the stereospecificity of Rh-catalyzed cis-cyclo-propanations of electron-rich alkenes. — The zwitterionic resonance form A turns out to be a better presentation of the electrophilic character of rhodium-carbene complexes than the (formally) charge-free resonance form B or the zwit-ter-ionic resonance form (not shown here) with the opposite charge distribution ( adjacent to the C02Me groups, on Rh) rhodium-carbene complexes preferentially react with electron-rich alkenes.

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