Electrophilic addition to eta(2)-aldehyde complexes of pentaamineosmium(II): The formation of Fischer carbyne complexes via eta(2)-aldehydium intermediates

Spera ML; Chen HY; Moody MW; Hill MM; Harman WD

Journal of the American Chemical Society, Vol.119, No.52, 12772-12778, 1997

Spera ML, Chen HY, Moody MW, Hill MM, Harman WD

A series of eta(2)-aldehyde complexes of pentaammineosmium(II) of the form [Os(NH3)(5)(L)](OTf)(2) (L = formaldehyde (1), acetaldehyde (2), trimethylacetaldehyde (3), benzaldehyde (4), and crotonaldehyde (5), OTf = trifluoromethanesulfonate) are prepared and characterized. Treatment of these eta(2)-bound aldehyde complexes with CH3OTf affords Fischer carbyne complexes 14-18 with typical yields ranging from 25-92%. Protonation (HOTf/MeCN) or methylation (MeOTf/DME) of many of these aldehyde complexes afford O-protonated or O-methylated eta(2)-aldehydium intermediates, respectively, which over time convert to the corresponding carbyne complex. The chemistry of olefin-coordinated alpha,beta-unsaturated aldehyde complexes is also explored.