title: Synthesis, Characterization, and Electrochemistry of Ruthenium Porphyrins Containing a Nitrosyl Axial Ligand.
abstract: Two ruthenium nitrosyl porphyrins have been synthesized and characterized by spectroscopic and electrochemical methods. The investigated compounds are represented as [(TPP)Ru(NO)(H(2)O)]BF(4) and (TPP)Ru(NO)(ONO) where TPP is the dianion of 5,10,15,20-tetraphenylporphyrin. (TPP)Ru(NO)(ONO) crystallizes in the tetragonal space group I4, with a = 13.660(1) Å, c = 9.747(1) Å, V = 1818.7(3) Å(3), and Z = 2, 233 K. The most chemically interesting feature of the structure is that the nitrosyl and O-bound nitrito groups are located axial and trans to one another. Both complexes undergo an irreversible reduction at the metal center which is accompanied by dissociation of the axial ligand trans to NO. The addition of 1-10 equiv of pyridine to [(TPP)Ru(NO)(H(2)O)]BF(4) in CH(2)Cl(2) containing 0.1 M TBAP leads to the formation of [(TPP)Ru(NO)(py)](+), a species which is reversibly reduced at E(1/2) = -0.29 V. The electrochemical data indicate that (TPP)Ru(NO)(ONO) can also be converted to [(TPP)Ru(NO)(py)](+) in CH(2)Cl(2) solutions containing pyridine but only under specific experimental conditions. This reaction does not involve a simple displacement of the ONO(-) axial ligand from (TPP)Ru(NO)(ONO) but occurs after reduction of (TPP)Ru(NO)(ONO) to (TPP)Ru(NO)(py) followed by reoxidation to [(TPP)Ru(NO)(py)](+).
authors.affiliation: Department of Chemistry, University of Houston, Houston, Texas 77204-5641, Dipartimento di Scienze e Tecnologie Chimiche, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Rome, Italy, and Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, Oklahoma 73019.
authors.forename: Karl M.
authors.initials: KM
authors.lastname: Kadish
authors.forename: Victor A.
authors.initials: VA
authors.lastname: Adamian
authors.forename: Eric Van
authors.initials: EV
authors.lastname: Caemelbecke
authors.forename: Zheng
authors.initials: Z
authors.lastname: Tan
authors.forename: Pietro
authors.initials: P
authors.lastname: Tagliatesta
authors.forename: Paola
authors.initials: P
authors.lastname: Bianco
authors.forename: Tristano
authors.initials: T
authors.lastname: Boschi
authors.forename: Geun-Bae
authors.initials: GB
authors.lastname: Yi
authors.forename: Masood A.
authors.initials: MA
authors.lastname: Khan
authors.forename: George B.
authors.initials: GB
authors.lastname: Richter-Addo