Assembly of Symmetrical or Unsymmetrical Cyclometalated Organoplatinum Complexes through a Bridging Diphosphine Ligand

The cyclometalated complexes [Pt(ppy)Ar(SMe2)] or [Pt(bhq)Ar(SMe2)], where ppyH = 2-phenylpyridine, bhqH = benzo[h]quinoline, and Ar = 4-tolyl or 4-anisyl, react with bis(diphenylphosphino)methane, dppm, in a 1:1 ratio to give the corresponding complexes [Pt(ppy)Ar(kappa(1)-dppm)] and [Pt(bhq)Ar(kappa(1)-dppm)], in which the dopm ligands are monodentate, or in a 2:1 ratio to give the symmetrical binuclear complexes [{Pt(ppy)Ar}(2)(mu-dppm)] and [{Pt(bhq)Ar}(2)(mu-dppm)], in which the dppm ligands are bridging bidentate. Most remarkably, the reaction of [Pt(ppy)Ar(SMe2)] with [Pt(bhq)Ar-t(kappa(1)-dppm)] or of [Pt(bhq)Ar-t(SMe2)] with [Pt(ppy)Ar(kappa(1)-dppm)] occurs selectively to give the unsymmetrical bridged complexes [(ppy)ArPt(kappa-dppm)PtArt(bhq)]. An example of each structural type has been characterized crystallographically, and it is shown that some of the bhq complexes undergo supramolecular self-assembly through pi-stacking.