You run an IR on the complex RuH2(CO)2(PPh3)3. What change could you make to...?

Isotopic substitution

ν(A-B) α √1/Mr Mr is reduced mass 1/Mr = 1/MA +1/MB

Assume Force Const remains constant upon isotopic substitution

Can ignore mass of metal ν(M-H)/ν(M-D) ≈ √2 ν(M-H) = 2000 cm^-1 ν(M-D) = ~1400 cm^-1

ν(M-H) are usually weak (vibration, small dipole moment change)

Likewise ν(12-CO)/ν(13-CO)= √1.018 ν(M-C-12≡O) = 2000 cm^-1 ν(M(C-13≡O) = ~1965 cm^-1 easily picked up on a modern IR machine; indeed you can see the ν(C-13≡O) bands in the natural abundance sample. ν(C≡O) if IR allowed are intense bands (large dipole moment change). Can also use C≡O-18.

RuH2(CO)2(PPh3)3 is a nice (Wilkinson-type) catalyst for the hydrogenation of terminal alkenes and for the isomerisation of terminal alkenes to secondary alkenes. When stirred under C-13≡O it will rapidly undergo isotopic subst that can be monitored by IR.