Ambi-Valence Taken Literally: Ruthenium vs Iron Oxidation in (1,1 '-Diphosphinoferrocene)ruthenium(II) Hydride and Chloride Complexes as Deduced from Spectroelectrochemistry of the Heterodimetallic "Mixed-Valent" Intermediates

作者：Sixt Torsten; Sieger Monika; Krafft Michael J; Bubrin Denis; Fiedler Jan; Kaim Wolfgang^*

来源：Organometallics, 2010, 29(21): 5511-5516.

DOI：10.1021/om1004258

Combining two different redox-active organometallic moieties, we prepared the compounds [(Cym)-RuCl(dpf)](PF(6)), with Cym = p-cymene = 1-isopropyl-4-methylbenzene, and the diphosphinoferrocenes (dpf) 1,1'-bis(diphenylphosphino)ferrocene (dppf; complex 3), 1,1'-bis(diisopropylphosphino)ferrocene (dippf; complex 4), and 1,1'-bis(diethylphosphino)ferrocene (depf; complex 5) as well as the structurally characterized hydride complex [(C(5)Me(5))RuH(dippf)] (2). In contrast to the case for 2, with an approximately staggered ferrocene conformation, the chloride complexes 3-5 exhibit a syn-periplanar ferrocene arrangement, due to a Cl center dot center dot center dot H(C(5)H(4)) interaction in the solid and in solution. The related new compounds [(Cym)RuH(dppf)](PF(6)) (6) and trinuclear (mu-dpf)[(Cym)RuCl(2))](2) (7-9) were also obtained and identified by (1)H and (31)P NMR spectroscopy. The redox behavior of 2-6 and of the known [(C(5)Me(5))RuH(dppf)] (1) was investigated using cyclic voltammetry, spectroelectrochemistry in the UV/vis/near-IR and ER regions, and, in part, by EPR. The first oxidation of the areneruthenium compounds 3-6 occurs reversibly at the ferrocene site, while the reduction proceeds via an ECE two-electron pattern under chloride dissociation. These results are compared to those obtained for the pentamethylcyclopentadienide/hydride complexes 1 and 2, which demonstrate unambiguously the ruthenium center as the site of the first electron loss. The different results for the two kinds of heterodimetallic d(5)/d(6) mixed-valent intermediates, Fe(II)Ru(III) for 1(+) and 2(+) and Fe(III) Ru(II) for 3(+) -6(+), are discussed with respect to the possible uses of such heterodinuclear systems in H(2) conversion catalysis.

• 出版日期2010-11-8