JOURNAL OF MAGNETIC RESONANCE 33, 149-157 (1979) Carbon-13 and Oxygen-17 NMR Spectra of Some Arenechromium(0) Tricarbonyls and Their Monothiocarbonyl Derivatives* DANIELCOZAK,IIANS.BUTLER,ANDJAMES P. HICKEY Department of Chemistry, McGill University, Montreal, Quebec, Canada H3A 2K6 AND LEEJ.TODD Department of Chemistry, Indiana University, Bloomington, Indiana 47401 Received March 10, 1978 The 13C and “0 NMR spectra of a series of arenechromium(0) complexes, (n6- CeHe-,R,) Cr(CO),(CX) (R= H, Cl, Me, OMe, NH*, NMes, COaMe; X= 0, S; n = O-3). have been measured at 30°C in CHzClz solution. Linear regression analyses relating the observed i3C and “0 chemical shifts of the CO and CS ligands with the approximate primary CX stretching force constants, k cx, indicate a definite correlation only for S(13CO) vs koo. The much poorer correlations for S(i3CS) and 6(C”O) suggest that these chemical shifts are not influenced by the same factors as 6(‘3CO). In contrast to 13C and “0 NMR studies on other substituted metal carbonyls, replacement of a CO group by CS in (n6-CeH6-nR,)Cr(CO)3 produces an upfield shift in 6(i3CO) and a downfield shift in 6(C”O). This difference is attributed to the greater net electron- withdrawing capacity of CS compared to CO in the Cr(CO),(CS) moiety. The 13C and I’0 carbonyl shielding values exhibit opposite trends on going from 0 to S in CX and on changing the electronegativity of R in the C6HswnRn ring [with the exception of the aniline (R = NHs) derivatives]. INTRODUCTION There has been considerable interest lately in the comparative properties of isoelectronic transition metal thiocarbonyls and carbonyls, since it is evident that CS is a better cr donor and 7~acceptor ligand than CO (1). However, while there have been extensive 13C NMR studies reported for metal carbonyls [for recent views, see Ref. (Z)], there are relatively few 6(r3CS) data for metal thiocarbonyls in the literature: M(CO),(CS) (M = Cr, W) (3), (q’-C5H#l’(CO)2(CS) (M’ = Mn, Re) (4, and [(q5-C5H5)Fe(CO)(CS)L]+ (5). We now report the results of a detailed examination of the 13C NMR spectra of some arenechromium(0) thiocarbonyl complexes, (q6-C6H6-,R,)CR(CO)2(CS) (R = H, Cl, Me, OMe, NH*, NMe2, C02Me; n = O-3), and the corresponding tricarbonyl complexes. The I70 NMR chemical shifts of the carbonyl ligands for most of these complexes have also been * Taken in part from the Ph.D. Thesis of D.C., McGill University, 1977; presented in part at the 59th Canadian Chemical Conference, London, Ontario, June 1976. t Present address: Anorganisch-chemisches Institut der Technichen Universitat Miinchen, Munich, West Germany. 149 0022-2364/79/010149-09$02.00/0 Copyright @ 1979 by Academic Press, Inc. All rights of reproduction in any form reserved. Printed in Great Britain