The number of metal-metal bonds in the dimers, $[\mathrm{CpFe}(\mathrm{CO})(\mathrm{NO})]_{2}$ and $\left[\mathrm{CpMo}(\mathrm{CO})_{3}\right]_{2}$ respectively, are
(a)two and two
(b)two and three
(c)one and two
(d)zero and one
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
[CpFe(CO)(NO)]₂ reaches 18 e through bridging CO/NO with no Fe–Fe bond; [CpMo(CO)₃]₂ needs one Mo–Mo bond (5 + 6 + 6 = 17 per Mo).