Formation and Reactions of Ring-Substituted Derivatives of (η5-Cyclopentadienyl)dicarbonylnitrosylchromium

Friedel-Crafts acylation of (η5-cyclopentadienyl)dicarbonylnitrosylchromium (1) produces the corresponding ketones and esters in good yield. Hydrolysis of [η5-((methylthio)carbonyl)cyclopentadienyl]dicarbonylnitrosylchromium gives (η5-carboxycyclopentadienyl)dicarbonylnitrosylchromium (pKa = 5.1) in 50% yield. Reduction of ketone derivatives of 1 with sodium borohydride produces the corresponding secondary alcohols in high yield, whereas reduction with lithium aluminum chloride-aluminum chloride leads to products of hydrogenolysis in 55-65% yield. High yields of tertiary alcohols have been obtained by treating ketone derivatives of 1 with alkyl or aryl Grignard reagents. Dehydration of [η5-(l-hydroxy-l-methylethyl)cyclopentadienyl]dicarbonylnitrosylchromium produces (η5-isopropenylcyclopentadienyl)dicarbonylnitrosylchromium in 81 % yield. (η5-Ethynylcyclopentadienyl)dicarbonylnitrosylchromium has been prepared by reaction of (η5-acetylcyclopentadienyl) dicarbonylnitrosylchromium with phosphorus oxychloride in dimethylformamide, followed by decomposition of the resulting chloro aldehyde in refluxing basic dioxane solution.