Electrophile-Promoted Carbon−Sulfur Bond Cleavage in η2-Thiophene Complexes of Pentaammineosmium(II)

• Published in: Journal of the American Chemical Society Vol. 119; no. 38; pp. 8843 - 8851
• Main Authors: Spera, Michael L, Harman, W. Dean
• Format: Journal Article
• Language: English
• Published: American Chemical Society 24-09-1997
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja970941k

Several S-alkylthiophenium complexes of the type [Os(NH3)5(4,5-η2-L)](OTf)3 (where L = S-alkylthiophenium, S-methylbenzo[b]thiophenium) are prepared by alkylation of the corresponding thiophene complexes. The S-alkylthiophenium species are proposed to undergo rapid and reversible cleavage of the C5−S bond, forming highly electrophilic metallacyclopropene intermediates. Although not directly observable, these vinyl cation intermediates may be trapped with both anionic and neutral nucleophiles affording η2-4-(alkylthio)-1,3-butadiene complexes. Treatment of selected 4-(alkylthio)-1,3-butadiene complexes with an oxidant (e.g., DDQ) affords the organic ligand in good yield.