Richard A. Newmark

Complete analysis of the 31P and 19F NMR spectra of [(PF3)3Mo(CO)3]†

The product of the reaction of PF3 gas with cycloheptatriene molybdenum tricarbonyl to give [(PF3)3Mo(CO)3] was originally studied by IR and NMR spectroscopy and the product was described as the mer isomer based on the appearance of the CO stretching peaks in the IR spectra. This was unexpected since the starting organometallic must have the carbonyl groups in a fac configuration. The high‐field 19F and 31P NMR spectra have now been completely analyzed by computer simulation and are best described by a mixture of mer and fac isomers. The values of the 2J(PP) and 1J(PF) coupling constants are in line with those from earlier measurements on cis‐ and trans‐[(PF3)2Mo(CO)4]. The fine structure in the spectrum of the fac molecule can only be reproduced by inclusion of a long range, non‐zero, 4J(FF′) coupling of 5.7 Hz between trans fluorine atoms. The gas‐phase fluorine NMR spectrum run at three temperatures confirmed the presence of both fac and mer isomers in about the same ratio as in solution. Copyright