The compound W(O)Cl2(CO)(PMePh2)2 has n (CO) at 2006 cm-1. Would you predict for W(S)Cl2...

The compound W(O)Cl₂(CO)(PMePh₂)₂ has n (CO) at 2006 cm^-1. Would you predict for W(S)Cl₂(CO)(PMePh₂)₂ to be at higher or lower energy? Explain briefly. (See J. C. Bryan, S. J. Geib, A. L. Rheingold, J. M. Mayer, J. Am. Chem. Soc., 1987, 109, 2826.)