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(κ1-dppm)] and [Pt(bhq)Ar(κ1-dppm)], in which
the dppm ligands are monodentate, or in a 2:1 ratio to give the symmetrical
binuclear complexes [{Pt(ppy)Ar}2(μ-dppm)] and [{Pt(bhq)Ar}2(μ-dppm)], in which the dppm ligands are bridging bidentate.
Most remarkably, the reaction of [Pt(ppy)Ar(SMe2)] with
[Pt(bhq)Ar′(κ1-dppm)] or of [Pt(bhq)Ar′(SMe2)] with [Pt(ppy)Ar(κ1-dppm)] occurs selectively
to give the unsymmetrical bridged complexes [(ppy)ArPt(μ-dppm)PtAr′(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 π-stacking.