Ligand Substitution Reactions on Aquapentachloro‐ and Hexachloroplatinic Acid — Synthesis and Characterization of Tetrachloroplatinum(IV) Complexes with Heterocyclic N, N Donors

Reactions of aquapentachloroplatinic acid, (H 3 O)[PtCl 5 (H 2 O)]·2(18C6)·6H 2 O ( 1 ) (18C6 = 18‐crown‐6), and H 2 [PtCl 6 ]·6H 2 O ( 2 ) with heterocyclic N , N donors (2, 2′‐bipyridine, bpy; 4, 4′‐di‐ tert ‐butyl‐2, 2′‐bipyridine, t Bu 2 bpy; 1, 10‐phenanthroline, phen; 4, 7‐diphenyl‐1, 10‐phenanthroline, Ph 2 phen; 2, 2′‐bipyrimidine, bpym) afforded with ligand substitution platinum(IV) complexes [PtCl 4 (N∩N)] (N∩N = bpy, 3a ; t Bu 2 bpy, 3b ; Ph 2 phen, 5 ; bpym, 7 ) and/or with protonation of N , N donor yielding (R 2 phenH) 2 [PtCl 6 ] (R = H, 4a ; Ph, 4b ) and (bpymH) + ( 8 ). With UV irradiation Ph 2 phen and bpym reacted with reduction yielding platinum(II) complexes [PtCl 2 (N∩N)] (N∩N = Ph 2 phen, 6 ; bpym, 9 ). Identities of all complexes were established by microanalysis as well as by NMR ( 1 H, 13 C, 195 Pt) and IR spectroscopic investigations. Molecular structures of [PtCl 4 (bpym)]·MeOH ( 7 ) and [PtCl 2 (Ph 2 phen)] ( 6 ) were determined by X‐ray diffraction analyses. Differences in reactivity of bpy/bpym and phen ligands are discussed in terms of calculated structures of complexes [PtCl 5 (N∩N)] — with monodentately bound N , N ligands (N∩N = bpy, 10a ; phen, 10b ; bpym, 10c ).