Pyridines with osmium carbenes

Instead of adding 4-substituted pyridine ligands trans to the carbene ligand, the complexes Os(CHR XTTP) (R = SiMe3, C02Et) add these donors to the carbene carbon atom with formation of an ylide species. This reaction is not observed for Os(CR2XTTP) with R = Ph [313c]. Nevertheless, the diphenylcar-bene or trimethylsilylmethylene osmium porphyrins crystallize as Os(CRR )-(TTP)THF with a THF molecule in trans position. 

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