Conclusion: Mental events and properties are not brain events and properties.

P1: Mental events and properties (such as my thought of Kansas City) are not located in space.
P2: Brain events and properties are located in space.
Therefore, (C) Mental events and properties are not brain events and properties. (from P1 and P2 by the indiscernibility of identicals)

Clarification:

II says: If M is B, then whatever is true of M is true of B and vice versa.

But is true of brain events that they are in space and it is not true of mental events that they are in space.

So, it is not true that whatever is true or mental events is true of brain events and vice versa.

So, by modus tollens, mental events are not brain events.