= Solution
\b[The terminal nitrosyls are linear in both proposed electron-precise structures; the formal M–M bond orders are V–V double and Fe–Fe single.] Use three-electron terminal linear NO donors, three-electron $\mu_2$-NO bridges, and five-electron neutral Cp donors in covalent counting.
For the <vanadium> dimer the two <metal> fragments together contain
$$
N_{\rm frag}=2(5)_{\rm V}+2(5)_{\rm Cp}+2(3)_{\rm terminal\ NO}+2(3)_{\mu\rm NO}=32.
$$
A <metal>–<metal> bond of order $b$ adds $b$ to each local count, so $32+2b=36$ gives \b[$b=2$] and 18 <electrons> per V. For an ionic cross-check, Cp is $-1$, each linear terminal NO is conventionally NO$^+$, and each bridge is represented as NO$^-$. Thus
$$
2x-2+2-2=0,\qquad\boxed{x_{\rm V}=+1,\quad d^4.}
$$
Each V then has $4+6_{\rm Cp}+2_{\rm terminal\ NO}+4_{\rm two\ bridges}+2_{\rm V=V}=18$ <electrons>.
The <iron> species is \b[monoanionic], and $\mathrm L^-$ is a <pyrazolate> bridge binding through its two <nitrogens>. This is a four-electron donor overall in ionic counting, or three overall in neutral counting. The carbonyl bridge supplies two <electrons> overall. The covalent fragment total is consequently
$$
N_{\rm frag}=2(8)_{\rm Fe}+4(3)_{\rm terminal\ NO}+2_{\mu\rm CO}+3_{\mu\rm L}+1_{\rm anion}=34.
$$
Therefore $34+2b=36$ gives \b[$b=1$]. In the formal NO$^+$ description,
$$
2x+4-1=-1,\qquad\boxed{x_{\rm Fe}=-2,\quad d^{10}.}
$$
Each Fe receives $10+4_{\rm two\ NO}+2_{\rm pyrazolate\ N}+1_{\mu\rm CO}+1_{\rm Fe-Fe}=18$ <electrons>. The negative formal <oxidation state> follows from the chosen nitrosyl assignment and the overall charge; omitting that charge would change the count.
Bent terminal NO ligands would supply fewer neutral-count <electrons> and demand much higher formal M–M bond orders to attain 18-electron counts. The linear assignments give the ordinary double and single bond solutions. Since NO is a <non-innocent ligand>, these <oxidation states> are formal bookkeeping limits, not measured <metal> charges; actual nitrosyl bending and M–M bond strengths require structural and spectroscopic evidence.<Principles of structure, bonding, and reactivity for metal nitrosyl complexes by John H. Enemark and Richard D. Feltham>[Coordination Chemistry Reviews 13, pp. 339–406; formal nitrosyl assignments and distinction from actual electron distribution]{ref}
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