Photoisomerization and other reactions of dimethylplatinum(IV) complexes with iminodiacetate and (methylimino)diacetate

The ligands L 2-, RN(CH 2CO 2 -) 2 (R = CH 3, H), react with a solution of [{Pt(CH 3) 2(OH) 2}·1.5H 2O] n in alkali to give initially Pt(CH 3) 2(OH) 2(L-N,O) 2- in which the ligand coordinates bidentate trans to the methyl groups. Ring closure to form Pt-(CH 3) 2(OH)(L-N,O,O′) - is very slow under alkaline conditions, but is much faster in acid solution, to give Pt(CH 3) 2(H 2O)(L-N,O,O′) (N trans to methyl). fac-Pt(CH 3) 2Br(H 2O) 3 + with LH - gives Pt(CH 3) 2Br(L-N,O,O′) - (N trans to methyl). Irradiation with a mercury lamp causes facile isomerization to the isomer with N trans to bromide. This reaction occurs without dissociation of L 2-. A side reaction at high pH produces Pt(CH 3) 2(OH)(L-N,O,O′) - (N trans to hydroxide). The colorless aqua complexes Pt(CH 3) 2(H 2O)(L) are photoisomerized much less efficiently than the pale yellow bromo complexes. Thermal isomerizations are very much slower