[Cheese_Burgers]

Ok, so far as my understanding goes, the palladium acetate is used because it is air stable and so, it allows the ligands to be attached in situ. Yeah I'm pretty lost when I'm looking at these reaction conditions. There are a few phosphine ligands they use with 2 phosphine groups per molecule and some with only one.

Am I right that they are basically kicking off the acetates and replacing with phosphine's ligands via a transmetalation?

I'm lost.

For example if the phosphine ligand was tritertbutyl phosphine, would this result in a hexadentate palladium complex? Meh...

[salteen]

You're on the right track.  Phosphine ligands will associate with the Pd(OAc)₂ quite easily, since Pd²⁺ is electron deficient.  They do sort of "kick off" the acetates through a type of ligand exchange - it's not a transmetallation since only one metal is involved. The mechanism I most commonly encounter is something like this:

[kriggy]

For example if the phosphine ligand was tritertbutyl phosphine, would this result in a hexadentate palladium complex? Meh...

Probably not It would be more likely tetrahedral (d10 configuration of paladium) and the tris(t-but)phosphine ligand is quite huge to form octahedral complex.
btw hexadentate means that the ligand has 6 atoms which can form the bond with metal. (EDTA)

[kamiyu]

1) The phosphine is both ligand and reducing agent.

2) For di-tert-butylphosphine, it is too bulky to have normal coordination of four for palladium. bis(tert-butylphosphine) palladium (0) is stable and can be isolated. It is also commercially avalibale.