The cluster types of [Fe5(CO)14N]− and [Co6(CO)13N]− are, respectively

Concept:

→ The given clusters are higher carbonyl clusters.

Higher carbonyl clusters refer to compounds that contain multiple carbonyl (CO) functional groups bound to a central metal atom. 

→ To determine these structures we first need to calculate skeletal electrons.

S = \(\frac{12 × N - TVE}{2}\)

where N = number of metals present in the cluster.

TVE = total valence electron

[N+1] is closo type

[N+2] is Nido type

[N+3] is arachno type

[N+4] is hypo type

Explanation:

→ [Fe5(CO)14N]− 

Fe have 8 valence electrons, CO contributes 2 electrons, N have 5 valence electrons + 1 for negative charge

TVE = 8 × 5 + 14 × 2 + 5 + 1 = 74 electrons

S = \(\frac{12 × N - TVE}{2}\)

S = \(\frac{12 \times 5 - 74}{2} = 7\)

Number of Metals present in this structure is 5, but S is 7 thus, it is N+2 type i.e., Nido

→ [Co6(CO)13N]−

Co have 9 valence electrons, CO contributes 2 electrons, N have 5 valence electrons + 1 for negative charge

TVE = 9 × 6 + 13 × 2 + 5 + 1 = 74 electrons

S = \(\frac{12 × N - TVE}{2}\)

S = \(\frac{12 \times 6 - 86}{2} = 7\)

Number of Metals present in this structure is 6, but S is 7 thus, it is N+1 type i.e., Closo.

Conclusion:
The correct answer is nido-, closo-.