Syntheses, structural determination, and electrochemistry of Ru-2(Fap)(4)Cl and Ru-2(Fap)(4)(NO)Cl

Ru-2(Fap)(4)Cl and Ru-2(Fap)(4)(NO)Cl, where Fap is the 2-(2-fluoroanilino) pyridinate anion, were synthesized, and their structural, electrochemical, and spectroscopic propel-ties were characterized. Ru-2(Fap)(4)Cl, which was obtained by reaction between Ru-2(O2CCH3)(4)Cl and molten HFap, crystalliz es in the monoclinic space group P2(1)/c. With a = 11.2365(4) Angstrom, b = 19.9298(8) Angstrom, c = 19.0368(7) Angstrom. beta = 90.905(1)degrees and Z = 4. The presence of three unpaired electrons on the Ru-2(5+) core and th e 2.2862(3) Angstrom Ru-Ru bond length for Ru-2(Fap)(4)Cl are consistent wi th the electronic configuration (sigma)(2)(pi)(4)(delta)(2)(pi*)(2)(delta*) (1). The reaction between Ru-2(Fap)(4)Cl and NO gas yields Ru-2(Fap)(4)(NO) Cl, which crystallizes in the orthorhombic space group Pbca, with a = 10.04 68(6) Angstrom, b = 18.8091-(10) W, c = 41.7615(23) Angstrom, and Z = 8. Th e Ru-Ru bond length of Ru-2(Fap)(4)(NO)Cl is 2.4203(8) Angstrom, while its N-O bond length and Ru-N-O bond angle are 1.164(8) Angstrom and 155.8(6)deg rees, respectively. Ru-2(Fap)(4)(NO)Cl can be formulated as a formal Ru2(II ,II)(NO+) complex with a linear Ru-N-O group. and the proposed electronic c onfiguration for this compound is (sigma)(2)(pi)(4)(delta)(2)(pi*)(3)(delta *)(1). The binding of NO to Ru-2(Fap)(4)Cl leads to some structural changes of the Ru-2(Fap)(4) framework and a stabilization of the lower oxidation s tates of the diruthenium unit. Also, IR spectroelectrochemical studies of R u,(Fap)l(NO)CI show that NO remains bound to the complex upon reduction and that the first reduction involves the addition of an electron on the dirut henium core and not on the NO axial ligand.