Synthesis, Characterization, and Spectroscopy of Dipyridocatecholate Complexes of Platinum

Several new complexes containing 1,10-phenanthroline-5,6-diolate (dipyridocatecholate, dpcat(2)(-)) ligand are reported. The complex (dpcat)Pt(dbbpy) (4; dbbpy = di-tert-butylbipyridine) was synthesized from Cl(2)Pt(dbbpy) and dpcat(2)(-). The reaction of (dpcat)Pt(dbbpy) with Cl(2)Pt(PhCN)(2) yielded Cl(2)Pt(dpcat)Pt(dbbpy) (5). The latter complex was reacted with 3,4-dimercaptotoluene (toluenedithiolate, tdt(2)(-)), 3,5-di-tert-butylcatecholate (dbcat(2)(-)), and dpcat(2)(-) 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)(2)RuCl(2) and NH(4)PF(6) to yield [(dbbpy)(2)Ru(dpcat)Pt(dbbpy)](PF(6))(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)(2)Ru(dpcat)Pt(dpcat)Pt((dbbpy)](PF(6))(2) (11) was obtained by reacting (dpcat)Pt(dpcat)Pt(dbbpy) with (dbbpy)(2)RuCl(2) and NH(4)PF(6). The complex [(dbbpy)(2)Ru(dpcat)Pt(dbbpy)](PF(6))(2) displays absorption bands associated with individual Ru and Pt centers and photoemission that arises from Ru(diimine)(3)(2+). A trinuclear complex (dbcat)Co{(dpcat)Pt(dbbpy)}(2) (9) was also obtained from the reaction of (dpcat)Pt(dbbpy) and Co(4)(dbsq)(8) (dbsq = di-tert-butylsemiquinone).