Syntheses, structural determination, and electrochemistry of Ru2(Fap)4Cl and Ru2(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, crystallizes 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 the 2.2862(3) Angstrom Ru-Ru bond length for Ru-2(Fap)(4)Cl are consistent with 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 = 10.0468(6) Angstrom, b = 18.8091-(10) W, c = 41.7615(23) Angstrom, and Z = 8. The 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)degrees, 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 configuration 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 states of the diruthenium unit. Also, IR spectroelectrochemical studies of Ru,(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 diruthenium core and not on the NO axial ligand.