Question 1: Rationalize the given observations:
a) On going from Fe(CO)5 to Fe(CO)3(PPh3)2, absorptions in the IR spectrum at 2025 and 2000 cm-1 are replaced by bands at 1944, 1886 and 1881 cm-1.
b) On forming IrBr(CO){η2-C2(CN)4}(PPh3)2, the unique C-C bond in C2(CN)4 lengthens from 135 to 151 pm.
c) The Tolman cone angles of PPh3 and P(p-MeC6H4)3 are 145°, however that of P(o-MeC6H4)3 is 194°.
d) A single ν(CO) band is observed for the ion [Co(CO)3(PPh3)2]+.
Question 2: List out the given in order of decreasing reactivity towards trimethylamine oxide: Mo(CO)6, [Mn(CO)6]+, Mo(CO)2(Ph2PCH2CH2PPh2)2, [Mo(CO)5]2–, Mo(CO)4(Ph2PCH2CH2PPh2),Mo(CO)3(NO)2. What physical data would you prefer to measure as an aid to ordering such complexes?
Question 3: NO+ is isoelectronic with CO and frequently replaces CO in substitution reactions; therefore it might seem the reaction below is favorable. Comment on whether the process is likely.
Mo(CO)6 + NOBF4 → [Mo(NO)6][BF4]6 + 6CO
Question 4: A complex with the empirical formula Mn3(C5H5)3(NO)4 has infrared absorptions at 1320 and 1495 cm-1 and a single peak in the 1H NMR spectrum. Draw a plausible structure.
Question 5: The product of reaction between PtCl2 and CO at high pressure and 200 °C consists of a molecular weight of 322. Determine the formula and recommend possible isomers. Comment on the probable relative MC and CO bond lengths in such isomers. Can vibrational spectroscopy be used to differentiate between isomers?