title: Reduced and Superreduced Diplatinum Complexes.
abstract: A d(8)-d(8) complex [Pt2(μ-P2O5(BF2)4](4-) (abbreviated Pt(pop-BF2)(4-)) undergoes two 1e(-) reductions at E1/2 = -1.68 and Ep = -2.46 V (vs Fc(+)/Fc) producing reduced Pt(pop-BF2)(5-) and superreduced Pt(pop-BF2)(6-) species, respectively. The EPR spectrum of Pt(pop-BF2)(5-) and UV-vis spectra of both the reduced and the superreduced complexes, together with TD-DFT calculations, reveal successive filling of the 6pσ orbital accompanied by gradual strengthening of Pt-Pt bonding interactions and, because of 6pσ delocalization, of Pt-P bonds in the course of the two reductions. Mayer-Millikan Pt-Pt bond orders of 0.173, 0.268, and 0.340 were calculated for the parent, reduced, and superreduced complexes, respectively. The second (5-/6-) reduction is accompanied by a structural distortion that is experimentally manifested by electrochemical irreversibility. Both reduction steps proceed without changing either d(8) Pt electronic configuration, making the superreduced Pt(pop-BF2)(6-) a very rare 6p(2) σ-bonded binuclear complex. However, the Pt-Pt σ bonding interaction is limited by the relatively long bridging-ligand-imposed Pt-Pt distance accompanied by repulsive electronic congestion. Pt(pop-BF2)(4-) is predicted to be a very strong photooxidant (potentials of +1.57 and +0.86 V are estimated for the singlet and triplet dσ*pσ excited states, respectively).
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Tania V
authors.initials: TV
authors.lastname: Darnton
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Hunter
authors.affiliation: Occidental College , Los Angeles, California 90041, United States.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hill
authors.affiliation: J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences , Dolejškova 3, CZ-182 23 Prague, Czech Republic.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Záliš
authors.affiliation: J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences , Dolejškova 3, CZ-182 23 Prague, Czech Republic.|School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London E1 4NS, United Kingdom.
authors.forename: Antonín
authors.initials: A
authors.lastname: Vlček
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray