Help using keyword this

Here is the problem piece of my code:

Please note that SafePointerToCats is a safe pointer (boost library)
to the Cats class, DerivedFromCats is a class that is derived from
Cats and SafePointerToDerivedFromCats is a safe pointer to
DerivedFromCats.
PointerToSomeClass is a safe pointer to SomeClass

class SomeClass
{
      private: SafePointerToCats  CatPointer;

      public: SomeClass() {}
              void setCatPointer (SafePointerToCats cat){CatPointer =
cat;}

};

//Then in some other file..

void DerivedFromCats::SomeFunction( someparameter& something,
anotherparameter& anotherthing)

{
   PointerToSomeClass PointersAreCool ( new SomeClass());
	PointersAreCool -> setCatPointer (this);
}

My hope was that this code would result in in CatPointer pointing at
the derived class.  Instead it gave a compile error.

What is wrong here?

Thanks for your help,

Paul Epstein