Question

Determine whether or not the following compounds obey the eighteen electron rule;

a. H2Fe(CO)4

b). [V(CO)5H]2–

c. Mn(CO)4(NO)

d. Co(H)(N2)(PPh3)3

e. [Cr(CO)5]1–

Answer 1

a) H2Fe(CO)4

Fe = 8

2H = 2

4 CO = 4x 2 =8

total electrons = 18

it obeys 18 electron rule

b)  [V(CO)5H]2–

V = 5

5CO = 5 x 2 = 10

H = 1

-2 charge = 2

total electrons = 5 + 10 + 1 + 2 = 18

it obeys 18 electron rule

c) Mn(CO)4(NO)

Mn = 7

4CO = 4 x 2 = 8

NO = 1

total electrons = 7 + 8 + 1 = 16

it is not obeying electron rule

d)  Co(H)(N2)(PPh3)3

Co = 9

H = 1

N2 = 2

3PPh3 = 3 x 2 = 6

total electrons = 9 + 1 + 2 + 6 = 18

it obeys 18 electron rule

e) [Cr(CO)5]1–

Cr = 6

5 CO = 5 x 2 = 10

1 charge = 1

total electrons = 6 + 10 + 1 = 17

not obeys 18 electron rule.