A controversy about a proton transfer (PT) from a water molecule to the sulfate ion is presented in theoretical studies of isolated MgSO4 center dot 6H(2)O systems in the forms of contact (CIP) and solvent-share (SIP) ion pairs. Calculations with different methods and basis sets were performed without and with solvation. The results show that a PT may occur in a system without solvation; however, the no proton transfer (NPT) structure is also stable. The formation of either PT or NPT depends on the starting location and orientation of the sixth water molecule. In particular, we find that solvation favors NPT formation.