How to properly free the memory allocated by placement new?

Question

I've been reading somewere that when you use placement new then you have to call the destructor manually.

Consider the folowing code:

   // Allocate memory ourself
char* pMemory = new char[ sizeof(MyClass)];

// Construct the object ourself
MyClass* pMyClass = new( pMemory ) MyClass();

// The destruction of object is our duty.
pMyClass->~MyClass();

As far as I know operator delete normally calls the destructor and then deallocates the memory, right? So why don't we use delete instead?

delete pMyClass;  //what's wrong with that?

in the first case we are forced to set pMyClass to nullptr after we call destructor like this:

pMyClass->~MyClass();
pMyClass = nullptr;  // is that correct?

BUT the destructor did NOT deallocate memory, right? So would that be a memory leak?

I'm confused, can you explain that?