The approximate positions of $v_{\mathrm{co}}$ bands $\left(\mathrm{cm}^{-1}\right)$ in the solid-state infrared spectrum and the Fe-Fe bond order in $\left[\mathrm{Fe}\left(\eta^{5}-\mathrm{C}_{5} \mathrm{H}_{5}\right)(\mu-\mathrm{CO})(\mathrm{CO})\right]_{2}$ (non-centrosymmetric) respectively, are 13
(c)$(2020,1980)$ and one
(d)(2143) and one
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
(2020, 1980, 1800 cm⁻¹) and an Fe–Fe single bond (a).