Preparation and structural features of new dialkylamino-substituted cyclopropenylidenepentacarbonylchromium complexes

The (2-ethoxy-3-dimethylaminocyclopropenylidene)pentacarbonylchromium complex 2 was prepared from dimethylaminoacetylene in 78% yield. It reacted with dimethylamine and diethylamine at room temperature to give quantitative yields of the bis(dialkylamino)cyclopropenylidene complexes 3a,b. The structural data and 13C-NMR chemical shifts of 2 and 3b show interesting differences relating to the different donor abilities of alkoxy and dialkylamino groups.