The 1H NMR spectrum of isatH in deuterated DMSO showed signals at 6.9(d), 7.06(t), 7.5(t), 7.61(d) ppm due to protons of the benzene ring and a signal at 10.98(s) ppm due to proton of NH group [3]. The 1H NMR spectrum of PPh3 showed multiplets in the range of 6.93–7.24 ppm. 1H NMR spectra of the molybdenum complex exhibited two broad singlet signals at 11.02 and 10.86 ppm due to NH and appearance of a new doublet signal at 9.05 ppm due to one proton in the isatin phenyl ring, in addition to the shifts of isatin and PPh3 as a result of coordination. The ratios of the signals at 11.02 and 10.86 ppm were of (1:3) and 2:1 for molybdenum and tungsten complexes, respectively, suggesting that the complex present in two-tautomeric structure. The appearance of the new signal and change in the chemical shift of NH proton is essentially related to the presence of the PPh3 and its effect on the chemical shifts of the isatin protons. This shift may be due to mutual anisotropic deshielding between the phenyl group of PPh3 and one proton of the benzene ring of isatin which can affect the signal of NH. This effect is due to magnetic field through space and not through chemical bond by inductive effect [10]. This indicates the possibility of exchange between CO and PPh3 groups in the solution in the axial position [11, 12] . X-ray studies of cis-RuCl2(trpy)(PPh3); where trpy=terpyridine, showed that the PPh3 has two phenyl rings parallel to the trpy while the third phenyl ring nearly perpendicular to the external pyridine of trpy and this lead to low-field shift of the parallel pyridine proton by 1.09 ppm. This was not observed for trans-RuCl2(tepy)(PPh3) [13]. From the spectroscopic data, we can conclude that the complexes can exist in mer- and fac-isomers in solution as shown in Scheme 2.