C-13 AND O-17 NMR-SPECTRA OF SOME ARENECHROMIUM(0) TRICARBONYLS AND THEIR MONOTHIOCARBONYL DERIVATIVES

The 13C and 17O NMR spectra of a series of arenechromium(0) complexes, (η-6C6H6-nRn) Cr(CO)2)(CX) (R = H, Cl,Me, OMe, NH2, NME2, CO2Me; X = O, S; n = 0-3), have been measured at 30°C in CH2Cl2 solution. Linear regression analyses relating the observed 13C and 17O chemical shifts of the CO and CS ligands with the approximate primary CX stretching force constants, kCX indicate a definite correlation only for δ(13CO) vs kCO. The much poorer correlations for δ(13CS) and δ(C17O) suggest that these chemical shifts are not influenced by the same factors as δ(13CO). In contrast to 13C and 17O NMR studies on other substituted metal carbonyls, replacement of a CO group by CS in (η6-C6H6-nRn)Cr(CO)3 produces an upfield shift in δ(13CO) and a downfield shift in δ(C17O). This difference is attributed to the greater net electron-withdrawing capacity of CS compared to CO in the Cr(CO)2(CS) moiety. The 13C and 17O carbonyl shielding values exhibit opposite trends on going from O to S in CX and on changing the electronegativity of R in the C6H6-nRn ring [with the exception of the aniline (R = NH2) derivatives]. © 1979.