In your first sentence:
[Whom we expect to be delivering the presentation] is absent.
In the second
The desire to fight is [what we believe to be planted in his mind].
The noun clause includes everything that acts like a noun when considered together. "Whom we expect to be delivering the presentation" all relates to the subject of the sentence (the unnamed 'person whom').
In the second sentence the object of the sentence is a thing (a noun) represented by the words "what we believe to be planted in his mind". Every word in that clause relates to that 'thing'.
As Colin Fine said before me, these are complex sentences.
As you know, a noun clause will begin with a relative pronoun (which, who, what, etc) and must include a verb and a subject.
In each of your sentences 'the verb' is a more complex arrangement than a standard single word. They are verb phrases.
expect to be delivering
believe to be planted
As to the role the infinitive is playing - certain verbs can be followed by an infinitive construction to complete their meaning, and these are such cases. 'Expect' and 'believe' are often - perhaps usually - not enough to convey a full meaning on their own. So we can 'expect to ...' or 'believe to ...' something to add more information. More detail here. Add the passive voice on top of that, and you have 'expect to be delivering' and 'believe to be planted'.