For each of the following pairs of metal complexes, circle the one that will have the highest CO stretching frequency. Briefly and clearly discuss your reasoning for each case.
a) Fe(CO) [P(OMe)₃]₂ -or- Cr(CO)₃(PMe₃)₂(pyridine)
b) [NbO₂(CH₃)₂(CO)] -or- RhCI(CO)(PPh₃)₂
0) Ni(CO)₃(PPh₃) -or- Fe(CO) [P(0-MeO-C6H4)₃]
d) [IrF4(CO)₂] -or- Rh(CH₃)₃(CO)₂(N=CCH₃)
e) CpMn(CO)₃ -or- CpRe(CH₂)(CH₃)₂(CO