Question

choose the correct answer

C-O in [Fe(CO)6]2+ have stretching bands higher in energy than those in free CO? Due to positively transition metal decreases the electrons toward oxygen. As result of that, bond between oxygen and carbon become stronger and the stretching of bond requires lower frequency. Due to positively transition metal decreases the electrons toward oxygen. As result of that, bond between oxygen and carbon become weaker and the stretching of bond requires higher energy. Due to positively transition metal decreases the electrons toward oxygen. As result of that, bond between oxygen and carbon become stronger and the stretching of bond requires longer wavelength. Due to positively transition metal decreases the electrons toward oxygen. As result of that, bond between oxygen and carbon become stronger and the stretching of bond requires higher energy. 20 : 12 JI > >> Identify the species that does not follow 18e rule: A) [Mn(n-C5H5)(CO)2] B) [Cu(n-C5H5)(CO)] C) [Cr(n5-C6H5CO) 31 D) (N5-C5H5)(CO)4] A&C&D A&C A&B B&D

Answer 1

1. When a metal carbonyl has positive charge on it, the metal has deficiency of electrons due to which it shows the tendency to pull electrons. Also the tendency of metal to CO $\pi$ ^* back bonding decreases. This shortens and strengthens the CO bond and hence the CO bond order and stretching frequency increases. Also the stretching bands have higher energy than in free CO.

So the correct option is D.

2. A. Total number of valence electrons = Mn (7) + $\eta$ ⁵ C₅H₅ (5) + (CO)₂ (2 x 2 = 4)

= 7 + 5 + 4 = 16

B. Total number of valence electrons = Cu (11) + $\eta$ ⁵ C₅H₅ (5) + (CO)(2)

= 11 + 5 + 2 = 18

C. Total number of valence electrons = Cr (6) + $\eta$ ⁵ C₅H₅ (5) + (CO)₃ (2 x 3 = 6)

= 6 + 5 + 6 = 17

D. Total number of valence electrons = V (5) + $\eta$ ⁵ C₅H₅ (5) + (CO)₄ (2 x 4 = 8)

= 5 + 5 + 8 = 18

A and C do not follow 18 electron rule.