cis-Bis(phosphine)platinum(II) complexes with pyrimidyl nucleobases. Synthesis, characterization, and crystal structures of cis-(1-methylthyminato-N3)(N,N-dimethylformamide-O)(1,1'-bis(diphenylphosphino)ferrocene)platinum(II) tetrafluoroborate-dichloromethane, [(dppf)Pt(1-MeTy(-H))(DMF)]BF4.cntdot.C