Photoassisted alkane activation under CO atmosphere: Observation of aldehyde, alkene, and activated alkane

Abstract

Direct observation of carbonylated and dehydrogenated products from cyclohexane was made via in situ FTIR monitored reaction of half-sandwich iridium dicarbonyl metal centers under carbon monoxide atmosphere. Variation of pressure in semibatch experiments allows for the detection of aldehydes as well as alkene. Changing atmosphere from carbon monoxide to compressed air resulted in ketone formation. Initial product detection was made via GC-MS and pure component IR spectra of the individual products was made possible through recently developed chemometrics- Band Target Entropy Minimization (BTEM). This also allowed for detection degradation products and previously unobserved metal carbonyl species were observed. BTEM also allowed for previously unobserved unseen details in the pure component spectra of the common activated alkane intermediate. Further confirmation of product identity was provided through spectroscopic comparison (IR and NMR) and gas Chromatographic (GC-FID) comparison of samples obtained through experiment and those commercially available. It can be concluded that iridium half-sandwich complexes can be used to promote carbonylation of saturated alkanes under photoirradiation.