A correlation study: 13C, 17O, 29Si and 31P NMR chemical shifts and approximate CO stretching force constants for cis-disubstituted molybdenum carbonyl complexes

Abstract The 13 C, 17 O, 29 Si and 31 P NMR spectral properties of cis -Mo(CO) 4 (PPh 2 X) 2 , where X is Cl, OMe, 4-MeC 6 H 4 O, NH 2 , NHMe, NHCH 2 CH 2 NH 2 , NHCH 2 CH 2 NMe 2 , 4-MeC 6 H 4 NH, SEt, OSiMe 3 or NHSiMe 3 and of cis -Mo(CO) 4 )(PPh 2 YPPh 2 ), where Y is NMeCH 2 CH 2 CH 2 NMe, NHSiMe 2 NH, NHSiMePhNH, OSiMe 2 O, or OSiMePhO and of cis -[Mo(CO) 4 (PPh 2 O) 2 ] 2 Si have been determined. Good to excellent correlations between the 13 C and 17 O chemical shifts of carbonyl ligands trans to the phosphorus donor ligands are found. Only poor correlations are seen between 13 C and 17 C chemical shifts for carbonyl ligands cis to the two phosphine substituted carbonyl groups. Based on only seven samples, 29 Si and 13 C of trans carbonyl ligands also correlate well. Correlations of chemical shift data with approximate CO stretching force constants are fair to good depending upon the selection of data. In particular, much better correlations are noted in almost all instances when complexes with monodentate ligands and bidentate ligands are examined separately.