The organic species isolobal to $\mathrm{[Fe(CO)_2(PPh_3)]^-}$ is
(a)$\mathrm{CH_2^+}$
(b)$\mathrm{CH^-}$
(c)$\mathrm{CH_3}$
(d)CH
Answer
Answer (as printed): D
Explanation
Fe(-1)→ d9 system 0 d9 ML3 CH For d9 –ML3, original co-ordination number will be considered as ML6. Therefore, [Fe(CO)2(PPh3)]- having three co-ordination number, missing three from original ML6 and similarly for CH, three ligands also missing from original CH4 . Hence, [Fe(CO)2(PPh3)]- is isolobal with CH but not with CH2+ (5e-) because two ligands missing from original CH4.
Explanation as extracted from the printed page; notation may be imperfect.