Platinum(II) Diimine Complexes with Halide/Pseudohalide Ligands and Dangling Trialkylamine or Ammonium Groups

A series of platinum­(II) complexes with the formulas Pt­(diimine)­(pip2NCNH2)­(L)2+ [pip2NCNH2+ = 2,6-bis­(piperidiniummethyl)­phenyl cation; L = Cl, Br, I, NCS, OCN, and NO2; diimine = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2phen), and 5,5′-ditrifluoromethyl-2,2′-bipyridine (dtfmbpy)] were prepared by the treatment of Pt­(pip2NCN)­Cl with a silver­(I) salt followed by the addition of the diimine and halide/pseudohalide under acidic conditions. Crystallographic data as well as 1H NMR spectra establish that the metal center is bonded to a bidentate phenanthroline and a monodentate halide/pseudohalide. The pip2NCNH2+ ligand with protonated piperidyl groups is monodentate and bonded to the platinum through the phenyl ring. Structural and spectroscopic data indicate that the halide/pseudohalide group (L–) and the metal center in Pt­(phen)­(pip2NCNH2)­(L)2+ behave as Brønsted bases, forming intramolecular NH···L/NH···Pt interactions involving the piperidinium groups. A close examination of the 10 structures reported here reveals linear correlations between N–H···Pt/L angles and H···Pt/L distances. In most cases, the N–H bond is directed toward the Pt–L bond, thereby giving the appearance that the proton bridges the Pt and L groups. In contrast to observations for Pt­(tpy)­(pip2NCN)+ (tpy = 2,2′;6′,2″-terpyridine), the electrochemical oxidation of deprotonated adducts, Pt­(diimine)­(L)­(pip2NCN), is chemically and electrochemically irreversible.