# How to Calculate Number of Metal-Metal Bonds and Number of Bonds per Atom

## Number of M-M Bonds & Number of Bonds per Atom Calculator

Total number of valence electrons (X) in the complex = Number of valence electrons in the metal + Electrons from each ligand + Charge (use table).

Find out number of Metals in Complex (N)

Now, the number of M-M bonds in Complex = [N × 18) − X] ÷ 2

Now, number of Bond per Atom = 18 − (X/N)

**Note:** 'X' divided by 'N' gives the number of electrons per metal atom. If this number comes out to be 18 it implies there are no metal-metal bonds; for 17, there will be one M-M bond and if it is 16, there will be two M-M bonds and so on.

### The Mo−Mo bond order in [(η^{5}- C_{5}H_{5})Mo(CO)_{2}]_{2} which obeys the 18- electron rule is GATE: 2021

Answer: Total Valence Electron (X) = (5 × 2) + (6 × 2) + (4 × 2) = 30

Number of Metals in Complex (N) = 2

Now, the number of M-M bonds in Complex = [N × 18) − X] ÷ 2

or, Mo−Mo bond order in [(η^{5}- C_{5}H_{5})Mo(CO)_{2}]_{2} = (2 × 18) − 30] ÷ 2 = 3

### The number of metal-metal bonds in [Mo_{2}(CH_{3}CO_{2})_{4}] complex is GATE: 2022

Answer: Total Valence Electron (X) = (6 × 2) + (4 × 4) = 28

Number of Metals in Complex (N) = 2

Now, the number of M-M bonds in Complex = [N × 18) − X] ÷ 2

or, Number of Mo−Mo bonds in [Mo_{2}(CH_{3}CO_{2})_{4}] = (2 × 18) − 28] ÷ 2 = 4

### The number of metal-metal bonds in [Co_{2}Fe_{2}(CO)_{11}(µ^{4}-PPh)_{2}] is CSIR:NET/JRF: June 2016

Answer: Total Valence Electron (X) = 14 + 16 + 22 + 8 = 64

Number of Metals in Complex (N) = 4

So, the Number of M−M bonds in [Co_{2}Fe_{2}(CO)_{11}(µ^{4}-PPh)_{2}] = (4 × 18) − 64] ÷ 2 = 4

### The W-W bond order in [W(n^{5}-C_{5}H_{5})(µ-Cl)(CO)_{2}]_{2} is CSIR:NET/JRF: Dec. 2015

Answer: Total Valence Electron (X) = 12 + 10 + 6 + 8 = 36

Number of Metals in Complex (N) = 2

So, the Number of M−M bonds in [W(n^{5}-C_{5}H_{5})(µ-Cl)(CO)_{2}]_{2} = (2 × 18) − 36] ÷ 2 = 0

### The number of metal-metal bonds in [Ni_{2}(CO)_{6}]^{2-} that are consistent with 18 electron rule respectively are CSIR:NET/JRF: June 2014

Answer: Total Valence Electron (X) = 20 + 12 + 2 = 34

Number of Metals in Complex (N) = 2

So, the Number of M−M bonds in [Ni_{2}(CO)_{6}]^{2-} = (2 × 18) − 34] ÷ 2 = 1

### The number of metal-metal bonds in [Ir_{4}(CO)_{12}] is CSIR:NET/JRF: June 2013

Answer: Total Valence Electron (X) = 36 + 24 = 60

Number of Metals in Complex (N) = 4

So, the Number of M−M bonds in [Ir_{4}(CO)_{12}] = (4 × 18) − 60] ÷ 2 = 6

### The number of metal-metal bonds in [W_{2}(OPh)_{6}] is CSIR:NET/JRF: June 2013

Answer: Total Valence Electron (X) = 12 + 18 = 30

Number of Metals in Complex (N) = 2

So, the Number of M−M bonds in [W_{2}(OPh)_{6}] = (2 × 18) − 30] ÷ 2 = 3

### In the cluster [Co_{3}(CH)(CO)_{9}] obeying 18 electron rule, the number of metal-metal bonds are CSIR:NET/JRF: Dec. 2012

Answer: Total Valence Electron (X) = (3 × 9) + 2 + (9 × 2) = 27 + 2 + 18 = 47

Number of Metals in Complex (N) = 3

So, the Number of M−M bonds in [Co_{3}(CH)(CO)_{9}] = (3 × 18) − 47] ÷ 2 = 3.5 (Considered as 3)

### The number of metal-metal bonds in the dimers, [CpFe(CO)(NO)]_{2} and [CpMo(CO)_{3}]_{2} respectively are CSIR:NET/JRF: Dec. 2011

Answer:

[CpFe(CO)(NO)]_{2} Complex:

Total Valence Electron (X) = [5 + 8 + 2 + 3] × 2 = 18 × 2 = 36

Number of Metals in Complex (N) = 2

So, the Number of M−M bonds in [CpFe(CO)(NO)]_{2} = (2 × 18) − 36] ÷ 2 = 0

[CpMo(CO)_{3}]_{2} Complex:

Total Valence Electron (X) = [5 + 6 + (2 × 3)] × 2 = 17 × 2 = 34

Number of Metals in Complex (N) = 2

So, the Number of M−M bonds in [CpMo(CO)_{3}]_{2} = (2 × 18) − 34] ÷ 2 = 1

### Calculate the number of metal meta bonds in the following complexes:

1. [Fe_{2}(CO)_{4}]^{2-}

2. [Co_{3}(CH)(CO)_{9}]

3. [Ni_{2}(CO)_{6}]^{2+}

4. [(η^{5}-C_{5}H_{5})Fe(CO)]_{2}

5. [Ru_{2}Cl_{4}(CO)_{4}]

6. [Ag_{4}(CN)_{4}]

7. [Cr_{2}O_{7}]^{2-}

8. [Mn_{2}(CO)_{10}]

9. dimer [Mn_{2}(CO)_{10}]

10. [Ru_{3}(CO)_{12}]

11. [Ti_{2}Cl_{8}]^{2-}

12. [Fe(CO)(PPh_{3})]_{2}

13. [Co_{4}(CO)(C_{5}H_{5})]_{4}

14. [V_{2}O_{5}]

Answer | ||||||
---|---|---|---|---|---|---|

1- 1 | 2- 0 | 3- 2 | 4- 0 | 5- 2 | 6- 3 | 7- 0 |

8- 1 | 9- 1 | 10- 3 | 11- 2 | 12- 0 | 13- 4 | 14- 0 |