Well, I don't have the Player's Handbook in front of me, but looking at the SRD, it says that it attacks from the character's direction, and can flank. Since it can flank, it must have a threatened area, but since it can only attack from the character's direction, it should probably only be considered to threaten the square immediately in front of it. Other than that, I'd say that if whatever is in that square provokes an AoO, the caster can take it with the spectral hand, although that uses up his AoO for the round (or one of them, if he has Combat Reflexes).