[leximancer]

I'm currently trying to write up a lab report for the synthesis of dimolybdenum tetracetate Mo2(CH3COO)4.  It's a quadruple-bonded dimolybdenum core with each Mo in a +2 oxidation state.  It was synthesized from molybdenum hexacarbonyl Mo(CO)6, an excess of acetic acid, and some acetic anhydride under a nitrogen atmosphere at reflux conditions.

As far as I understand, the molybdenum gets oxidized from 0 to +2, and dimolybdenum core is formed, and the carbonyls are replaced with acetate.  But these are the questions I'm stumped on:
(1) What is the oxidizing agent?
(2) What is the role of the acetic anhydride?
(3) What is the fate of the carbonyl ligands?
(4) What is the fate of the hydrogen ion that's dissociated from the acetate, the same acetate that replaces most of the carbonyl ligands?

I've done some reading and searching, but I haven't been able to find the answer to this.

[AWK]

Very good questions. I do not know an exact answer.
But I think since Mo(CO)6 is a compound though with oxidation numer = 0, it can react with acetic acid with hydrogen and CO evolution.The driving force for thus reaction is  formation of  a strong Mo-Mo bonding (or strong complexation by acetyl groups, or both interactions). Acetic anhydride ensures absolutely anhydrous conditions.

[orpheus]

This may not answer your question, but from Mo(CO)6 + acH,  you can add HBF4/MeCN and [Me3O]+/MeCN to give the Mo(ac)4 product.

[woelen]

I think the acetic acid is the reductor, in particular, the proton, which can be split off from the acetate-group.

Mo goes from oxidation state 0 to +2 and the hydrogen from the -COOH group goes from +1 to 0. Elemental H2 is formed, together with CO from the carbonyl ligands.