Fe₂(CO)₉ is diamagnetic.Which of the following reasons is correct?

1. Presence of one CO as bridge group

2. Presence of monodentate ligand

3. Metal-metal(Fe-Fe) bond in molecule

4. Resonance hybridization of CO

The compound that is not  $\mathrm{\pi }$-bonded organometallic compound is :

1. K[PtCl₃(${\eta }^{\mathit{2}}$-C₂H₄)]

2. Fe(${\eta }^5$-C₅H₅)₂

3. Cr(${\eta }^6$-C₆H₆)₂

4. (CH₃)₄Sn

Ferrocene is :

1. Fe(${\eta }^{\mathit{5}}$-C₅H₅)₂

2. Fe(${\eta }^2$-C₅H₅)₂

3. Cr(${\eta }^{\mathit{5}}$-C₅H₅)₅

4. Os(${\eta }^{\mathit{5}}$-C₅H₅)₂

$\pi$ bonding is not involved in

1. Ferrocene

2. Dibenzene Chromium

3. Zeise's Salt

4. Grignard Reagent

The co-ordination number of Fe in Ferrocene is : 

1. 2

2. 5

3. 6

4. 10

Correct increasing order for the wavelengths of absorption in the visible region for the complexes of Co³⁺ is : 

(1)  $[\mathrm{Co}{\left(\mathrm{en}\right)}_3{]}^{3+}$ , $[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6{]}^{3+}$ , $[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{]}^{3+}$

(2)  $[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{]}^{3+}$ , $[\mathrm{Co}{\left(\mathrm{en}\right)}_3{]}^{3+}$, $[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6{]}^{3+}$

(3)  $[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{]}^{3+}$, $[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6{]}^{3+}$, $[\mathrm{Co}{\left(\mathrm{en}\right)}_3{]}^{3+}$  

(4)  $[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6{]}^{3+}$,$[\mathrm{Co}{\left(\mathrm{en}\right)}_3{]}^{3+}$, $[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{]}^{3+}$ 

An example of a sigma bonded organometallic compound is:

1. Grignard's reagent

2. Ferrocene

3. Cobaltocene

4. Ruthenocene

Iron carbonyl, $\mathrm{Fe}{\left(\mathrm{CO}\right)}_5$, is classified as:

The  complex ion that does not expected to absorb visible light is:

1. $\left[Ni\right(CN{)}_4{]}^{\mathrm{2-}}$

2. $\left[Cr\right(N{H}_3{)}_6{]}^{3+}$

3. $\left[Fe\right(H_{2}O{)}_6{]}^{2+}$

4. $\left[Ni\right(H_{2}O{)}_6{]}^{2+}$

The shape of Fe(CO)₅ is: