Interconversion of acetyl- and terminal-carbonyl groups on labeled (η 5-indenyl)(CO) 2Fe 13C(O)CH 3

Abstract

The 13C-labeled (95–99%) acetyl complex (η 5-In)(CO) 3Fe 13C(O)CH 3 ( 8) (In = indenyl) has been prepared by acylating In(CO) 2Fe − Na + ( 1) with CH 3 13C(O)Cl. All of the starting 1 must be consumed in this reaction (at −78°C), or 45% of the product results as In(CO)( 13CO)FeC(O)CH 3 ( 9). Once isolated, neither 8 nor mixtures of 8 and 9 further redistribute or lose this label after pressurizing under 800 atm CO, or after heating in heptane, THF, or acetonitrile solution. Treating 8 with even trace amounts of 1 or of Cp(CO) 2Fe − Na + ( 5) rapidly interconverts the acetyl and terminal carbonyls, thus transforming 8 into mixtures of 8 and 9. A mechanism is proposed that involves a labile metalla-β-diketonate In(CO)Fe(Fp-CO)(CH 3 13CO) − Na +.