I'm considering the following reaction:
CO + Mo(CO)5
I think this is an example of a dissociative mechanism because an associative mechanism would lead to a 20-electron complex, making it unstable because it isn't in agreement with the 18-electron rule. But I'm a bit confused because if it is dissociative, then wouldn't Mo(CO)5
form an unstable intermediate because it would be a 16-electron complex?
I'm pretty sure it's dissociative because there's a similar example with W(CO)6
to form W(CO)5
), but wouldn't this lead to the same problem? I first thought that the solvent might temporarily interact with the intermediate to stabilise it before the pip ligand interacts, but the reaction is in toluene and I'm not sure if it can do η2
as well as η6
- I would say that it does because I know benzene can do η2
bonding, but I'm not sure if the methyl group in toluene would change this.
Any help would be greatly appreciated!