Question

Nitrosyl ligand binds to d-metal atoms in linear and bent fashion and behaves , respectively as
A.$N{O}^{+}$ and $N{O}^{+}$
B.$N{O}^{+}$ and $N{O}^{-}$
C.$N{O}^{-}$ and $N{O}^{-}$
D.$N{O}^{-}$ and $N{O}^{+}$

Answer 1

Hint:Nitrosyl complexes or metal nitrosyl complexes are complexes which contain nitric oxide, $NO$ bonded to the transitional metal. Of the many kinds of the nitrosyl complexes, they differ both in co ligand and structure.

Complete step by step answer:
Most complexes which have $NO$ ligand may be seen or viewed as a nitrosyl cation $N{O}^{+}$ . It feeds two electrons to the metal and in return accepts electrons from the metal via back-bonding.
The $$M-N-O$$ present in nitrosyl complexes are usually linear, or have no more than $${15}^{\circ }$$ from linear. But in some complexes, however, it is noticed, especially when back-bonding is a little less important, the $$M-N-O$$ angle can strongly deviate from $${180}^{\circ }$$ .
We will see that, in $$N{O}^{+}$$ structure, there exists a triple bond between $N$ and $O^{-}$ atoms and two electrons which act as a lone pair of electrons or coordinate, so the angle between $$M-N-O$$ is $${180}^{\circ }$$
While in $$N{O}^{-}$$ structure double bond exist between $N$ and $O^{-}$ atoms while the $$4e^{\mathrm{\_}}$$ acts as two lone pairs of electrons , so only one lone pair of electron coordinate with metal atom.
Suppose for a metal $M$ the bonding with $N{O}^{+}$ goes as -

Which gives us a linear structure.
And bonding with $N{O}^{-}$ goes as –

Which gives us a bent structure.
Therefore we can conclude that for the mentioned question,
Option (B). $N{O}^{+}$ and $N{O}^{-}$ is the correct answer.

Additional information –
The linear and bent $$NO$$ ligands can be distinguished using infrared spectroscopy. Linear $$M-N-O$$ groups absorb in the range $$1650-1900c{m}^{-1}$$, where as, the bent nitrosyls tend to absorb in the range of $$1525-1690c{m}^{-1}$$. They differ in their vibrational frequencies and it reflects the differing $$N-O$$ bond orders for linear (triple bond) and bent $$NO$$ (double bond).

Note:
The bent $NO$ ligand is sometimes described as the anion, $$N{O}^{-}$$. Examples for such compounds are the organic nitroso compounds, such as nitrosobenzene. For example a complex with a bent $$NO$$ ligand is trans$$-{\left[Co{\left(en\right)}_2\left(NO\right)Cl\right]}^{+}$$