Things intelligent undead are immune to (that are relevant to this question):
Any spell, spell-like ability, supernatural ability, or extraordinary ability that has the mind-affecting descriptor
Any spell or spell-like ability belonging to the charm, compulsion, pattern, or phantasm subschool
Any supernatural or extraordinary ability that produces a charm, compulsion, pattern, or phantasm effect (as stated specifically in that ability's description)
Morale bonuses
Things unintelligent undead are immune to (that are relevant to this question):
All of the above
Diplomacy checks
Since neither the skill descriptions of Bluff and Diplomacy nor the undead traits make mention of not using social skills against intelligent undead, it's assumed that this is allowed. (While you could make the argument that you can Bluff a mindless undead, why would it care what you have to say?)
If this seems a bit unintuitive, think of it this way: Seduction and persuasion are about convincing a vampire to agree with you. Mind-affecting abilities are about forcing a vampire to agree with you (magically or at least supernaturally), to which they're immune.