Synthesis, Characterization, and Spectroscopy of Dipyridocatecholate Complexes of Platinum

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Abstract
Several new complexes containing 1,10-phenanthroline-5,6-diolate (dipyridocatecholate, dpcat2-) ligand are reported. The complex (dpcat)Pt(dbbpy) (4; dbbpy = di-tert-butylbipyridine) was synthesized from Cl2Pt(dbbpy) and dpcat2-. The reaction of (dpcat)Pt(dbbpy) with Cl2Pt(PhCN)2 yielded Cl2Pt(dpcat)Pt(dbbpy) (5). The latter complex was reacted with 3,4-dimercaptotoluene (toluenedithiolate, tdt2-), 3,5-di-tert-butylcatecholate (dbcat2-), and dpcat2- to give (tdt)Pt(dpcat)Pt(dbbpy) (6), (dbcat)Pt(dpcat)Pt(dbbpy) (7), and (dpcat)Pt(dpcat)Pt(dbbpy) (8), respectively. All of these complexes containing Pt(diimine)(diolate) centers display intense absorption bands in the 500−600 nm range. However, excitation at these wavelengths does not result in photoemission similar to that seen for closely related Pt(diimine)(dithiolate) complexes. The absorption bands of the dinuclear species are unsymmetrical, possibly indicating isolated but overlapping transitions for the two chromophores in each complex. The complex (dpcat)Pt(dbbpy) was found to react with (dbbpy)2RuCl2 and NH4PF6 to yield [(dbbpy)2Ru(dpcat)Pt(dbbpy)](PF6)2 (10). A connectivity structure of this compound confirms the structural arrangement and the role of dpcat as a bridging ligand between a square planar Pt(II) center and an octahedral Ru(II) moiety. In an analogous synthesis, the trinuclear complex [(dbbpy)2Ru(dpcat)Pt(dpcat)Pt((dbbpy)](PF6)2 (11) was obtained by reacting (dpcat)Pt(dpcat)Pt(dbbpy) with (dbbpy)2RuCl2 and NH4PF6. The complex [(dbbpy)2Ru(dpcat)Pt(dbbpy)](PF6)2 displays absorption bands associated with individual Ru and Pt centers and photoemission that arises from Ru(diimine)32+. A trinuclear complex (dbcat)Co{(dpcat)Pt(dbbpy)}2 (9) was also obtained from the reaction of (dpcat)Pt(dbbpy) and Co4(dbsq)8 (dbsq = di-tert-butylsemiquinone).