Metal complexes of N(4)-substituted analogues of the antiviral drug methisazone {1-methylisatin thiosemicarbazone}

1-Methylisatin N(4)-methyl- and N(4)-dimethylthiosemicarbazone, HMIs4M and HMIs4DM, respectively, and their cobalt(II), nickel(II) and copper(II) complexes have been prepared and characterized, by elemental analyses, molar conductivities, magnetic susceptibilities and by spectral methods: i.r., u.v.-vis.-n.i.r., n.m.r. and e.s.r. The two thiosemicarbazones, upon loss of the N(2)H, coordinate as monoanions via the azomethine nitrogen and thiolato sulfur atoms, as well as the isatin oxygen {i.e. except for [Cu(MIs4M)₂] and [Cu(MIs4DM)₂]} to give complexes of the general formula [M(MIs)₂] and [M(MIs)Cl] where M = Co^II, Ni^II and Cu^II and MIs = both HMIs4M and HMIs4DM. The preparation with HMIs4DM and nickel(II) chloride formed [Ni(MIs4DM)₂] rather than [Ni(MIs4DM)Cl]. Copper(II) bromide yielded complexes with low magnetic susceptibilities, which are considered to be binuclear {i.e. [Cu(MIs4M)Br]₂ and [Cu(MIs4DM)Br]₂}.