Why are Sonogashira reactions moisture sensitive?

Exemple, aryl halide + TMS-acetylene in NEt3 + Pd[PPh3]2Cl2 or Pd[PPh3]4:


The reaction does not form water at any time so its presence wouldn't shift the equilibrium. Neither TMS-acetylene or the aryl halide are subject to react with water. This would signify that the Palladium catalyst is moisture sensitive. Yet, Palladium can not be oxidized by water as oxidative addition of water isn't possible (OA of OH extremely rare) and beta hydrogen elimination to form Pd=OH seems impossible?


Hope someone will be able to enlighten me.


