Beckman Institute, California Institute of Technology , Pasadena, California 91125, United States.
Occidental College , Los Angeles, California 90041, United States.
J Am Chem Soc. 2016 May 4;138(17):5699-705. doi: 10.1021/jacs.6b02559. Epub 2016 Apr 18.
A d(8)-d(8) complex Pt2(μ-P2O5(BF2)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).
一个 d(8)-d(8) 配合物 Pt2(μ-P2O5(BF2)4（简称 Pt(pop-BF2)(4-)) 在 E1/2 = -1.68 和 Ep = -2.46 V（相对于 Fc(+)/Fc）处经历两次 1e(-)还原，分别生成还原的 Pt(pop-BF2)(5-)和超还原的 Pt(pop-BF2)(6-)物种。Pt(pop-BF2)(5-)的 EPR 光谱和还原和超还原配合物的 UV-vis 光谱，以及 TD-DFT 计算，揭示了 6pσ 轨道的连续填充，伴随着 Pt-Pt 键合相互作用的逐渐增强，并且由于 6pσ 离域，在两次还原过程中 Pt-P 键也逐渐增强。母体、还原和超还原配合物的 Mayer-Millikan Pt-Pt 键序分别计算为 0.173、0.268 和 0.340。第二次（5-/6-）还原伴随着结构变形，这在电化学不可逆性中得到了实验证实。两个还原步骤都不改变 d(8)Pt 电子构型，使超还原的 Pt(pop-BF2)(6-)成为非常罕见的 6p(2)σ 键合双核配合物。然而，Pt-Pt σ 键合相互作用受到相对较长的桥连配体施加的 Pt-Pt 距离的限制，同时伴随着排斥的电子拥挤。Pt(pop-BF2)(4-)预计是一种非常强的光氧化剂（单重态和三重态 dσ*pσ 激发态的电势分别估计为 +1.57 和 +0.86 V）。
