Several cobalt nitrosyl porphyrins of the form (T(p/m-X)PP)Co(NO) (p/m-X = p-OCH(3) (1), p-CH(3) (2), m-CH(3) (3), p-H (4), m-OCH(3) (5), p-OCF(3) (6), p-CF(3) (7), p-CN (8)) have been synthesized in 30-85% yields by reaction of the precursor cobalt porphyrin with nitric oxide. Compounds 1-7 were also prepared by reaction of the precursor cobalt porphyrin with nitrosonium tetrafluoroborate followed by reduction with cobaltocene. Compounds 1-8 have been characterized by elemental analysis, IR and (1)H NMR spectroscopy, mass spectrometry, and UV-vis spectrophotometry. They are diamagnetic and display nu(NO) bands in CH(2)Cl(2) between 1681 and 1695 cm(-)(1). The molecular structure of 1, determined by a single-crystal X-ray crystallographic analysis, reveals a Co-N-O angle of 119.6(4) degrees. Crystals of 1 are monoclinic, P2/c, with a = 15.052(1) Å, b = 9.390(1) Å, c = 16.274(2) Å, beta = 111.04(1) degrees, V = 2146.8(4) Å(3), Z = 2, T = 228(2) K, D(calcd) = 1.271 g cm(-)(3), and final R1 = 0.0599 (wR2 = 0.1567, GOF = 1.054) for 3330 "observed" reflections with I >/= 2sigma(I). Cyclic voltammetry studies in CH(2)Cl(2) reveal that compounds 1-7 undergo two reversible oxidations and two reversible reductions at low temperature. This is not the case for compound 8, which undergoes two reversible reductions but an irreversible oxidation due to adsorption of the oxidized product onto the electrode surface. Combined electrochemistry-infrared studies demonstrate that each of the compounds 1-7 undergoes a first oxidation at the porphyrin pi ring system and a first reduction at either the metal center or the nitrosyl axial ligand. The formulation for the singly oxidized products of compounds 1-7 as porphyrin pi-cation radicals was confirmed by the presence of bands in the 1289-1294 cm(-)(1) region (for compounds 1-5), which are diagnostic IR bands for generation of tetraarylporphyrin pi-cation radicals.

Ruthenium and osmium porphyrins of the form (por)M(CO) (por = octaethylporphyrinato dianion (OEP), tetratolylporphyrinato dianion (TTP)) react with thionitrites (RSNO) and isoamyl nitrite (RONO) to give the (por)M(NO)(SR) and (por)M(NO)(OR) addition products. Reaction of S-nitroso-N-acetyl-l-cysteine methyl ester with (TPP)Fe(THF)2 (TPP = tetraphenylporphyrinato dianion) gives (TPP)Fe(NO) in high yield. The related reaction of isoamyl nitrite with [(TPP)Fe(THF)2]+ gives the nitrosyl alcohol product [(TPP)Fe(NO)(HO-i-C5H11)]+. The solid state structures of (OEP)Ru(NO)(NACysMe-S) (NACysMe = N-acetyl-l-cysteinate methyl ester), (TTP)Os(NO)(S-i-C5H11), and [(TPP)Fe(NO)(HO-i-C5H11)]+ have been determined by X-ray diffraction.

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)](+).

Diethylnitrosamine reacts with [(TPP)Fe(THF)(2)]ClO(4) (TPP = 5,10,15,20-tetraphenylporphyrinato dianion) in toluene to generate the bis-nitrosamine complex, [(TPP)Fe(Et(2)NNO)(2)]ClO(4), in 96% isolated yield. The related [(TTP)Fe(Et(2)NNO)(2)]SbF(6) (TTP = 5,10,15,20-tetra-p-tolylporphyrinato dianion) complex is prepared in 70% isolated yield via a similar reaction in CH(2)Cl(2). Reaction of [(TPP)Fe(Et(2)NNO)(2)]ClO(4) in CH(2)Cl(2) with NO gas results in the displacement of one of the Et(2)NNO ligands to give the air-sensitive and thermally sensitive [(TPP)Fe(NO)(Et(2)NNO)]ClO(4) derivative. Reaction of (OEP)Ru(CO) (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinato dianion) with NOBF(4) in CH(2)Cl(2) gives [(OEP)Ru(NO)(H(2)O)]BF(4) as the final isolated product (after exposure to air) in 71% isolated yield. The aqua ligand is then displaced by Et(2)NNO in CH(2)Cl(2) to give [(OEP)Ru(NO)(Et(2)NNO)]BF(4) in 82% isolated yield. The valence isoelectronic (OEP)Ru(CO)(Et(2)NNO) compound is prepared in 71% isolated yield by the addition of excess Et(2)NNO to (OEP)Ru(CO) in CH(2)Cl(2). The nitrosyl amine complex [(OEP)Ru(NO)(HNEt(2))]BF(4) is prepared (i) in 78% yield by diethylamine addition to [(OEP)Ru(NO)(H(2)O)]BF(4) or (ii) in 71% isolated yield by diethylamine addition to [(OEP)Ru(NO)(Et(2)NNO)]BF(4). The osmium nitrosamine complexes, (TTP)Os(CO)(Et(2)NNO) and (OEP)Os(CO)(Et(2)NNO), are prepared in 74% and 66% yields, respectively, by diethylnitrosamine addition to the precursor (porphyrin)Os(CO) compounds in CH(2)Cl(2). The nitrosyl [(OEP)Os(NO)(Et(2)NNO)]BF(4) derivative is prepared in quantitative yield (by IR and (1)H NMR spectroscopy) by the reaction of (OEP)Os(CO)(Et(2)NNO) with NOBF(4). Labeling studies using (15)NOBF(4), Et(2)N(15)NO, and Et(2)NN(18)O have been used to assign the nitrosyl and nitrosamine bands in the IR spectra of several of the complexes. The solid-state structures of [(TPP)Fe(THF)(2)]ClO(4), [(TPP)Fe(Et(2)NNO)(2)]ClO(4), [(OEP)Ru(NO)(H(2)O)]BF(4), (OEP)Ru(CO)(Et(2)NNO), and (TTP)Os(CO)(Et(2)NNO) have also been determined by single-crystal X-ray diffraction. The Et(2)NNO ligands display a rare eta(1)-O binding mode in all three nitrosamine complexes.