This contribution reports the synthesis and characterization of the ylide complexes Cp’2Th[OC(CH2-t-Bu)C-(PR3)O](C1) (Cp‘ = η5-C5Me5; R = Me, Ph) formed by the carbonylation of Cp’2Th(Cl)(η2-COCH2-t-Bu) (1) in the presence of phosphines. Isotopic tracer studies with 13CO indicate that the labeled carbon atom is incorporated regiospecifically at the ylide a-carbon atom position. The carbonylation of 1 to yield the enedionediolate Cp’2Th(Cl)(η2-COCH2-t-Bu) (2) or the ylide complexes was found to obey a second-order rate law where rate = KPCO; k = 1.50 (5) X 10-5 min-1 torr-1for both carbonylations at 30.8 °C. The rate of formation of the ylide complexes was also found to be independent of solvent, phosphine concentration, and type of phosphine used. The carbonylation of 1 is therefore inferred to involve a rate-determining coupling of CO with the acyl to yield an intermediate ketene or ketene-like complex. The reaction of acyl 1 or Cp’2Th-(Cl)(η2-COCH2Ph) with a variety of isocyanides (RNC; R = t-Bu, C6H11, 2,6-Me2C6H3) results in the formation of ketenimine complexes of the type Cp’2Th[OC(CH2-t-Bu)CNR](Cl) and Cp/2Th[OC(CH2Ph)CNR](Cl). Addition of a second equivalent of isocyanide yields simple adducts of the type Cp/2Th[OC(CH2-t-Bu)CNR](CNR)(Cl) and Cp’2Th[OC(CH2Ph)CNR]-(CNR)(C1). These new complexes have been fully characterized by standard techniques and the ketenimine Cp’2Th(Cl)-[OC(CH2-t-Bu)(CN-2,6-Me2C6H3)] by single-crystal X-ray diffraction. Under the appropriate conditions, the N-aryl complexes suffer secondary reactions in which the η2-acyl ultimately undergoes coupling with 2 equiv of isocyanide to yield acetylindolate and acetylindoleninate derivatives. The η2-acyl was also found to undergo coupling with 1 equiv of diphenylketene to yield the complex Cp/2Th[OC(CH2-t-Bu)C(CPh2)O](Cl). These coupling products have been fully characterized by conventional analytical and structural methodology. The mechanistic and reactivity results of this study are discussed in terms of the anchored Fischer carbene-like character of actinide η2-acyls and the mechanism by which the carbonylation of 1 yields the enedionediolate 2.
ASJC Scopus subject areas
- Colloid and Surface Chemistry