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Biomedical subjects

Craig A Grapperhaus

Publications and source records attributed to Craig A Grapperhaus.

6 recordsLinked to original sources
PubMed2003

Synthesis and characterization of N2S3X-Fe models of iron-containing nitrile hydratase.

A series of iron complexes based on the pentadentate ligand 4,7-bis(2'-methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane), (bmmp-TASN)(2)(-), have been synthesized and characterized as models of iron-containing nitrile hydratase (NHase). The chloro derivative [(bmmp-TASN)Fe(III)Cl].0.5EtOH (1) contains a labile chloride which facilitates synthesis of related complexes via substitution reactions. Complex 1 is high-spin, g = 4.28. Addition of NEt(4)CN with 1 in CH(2)Cl(2) results in the cyanide ligated complex [(bmmp-TASN)Fe(III)CN] x 0.5EtOH (2), which shows a single intense nu(CN) band at 2083 cm(-)(1) in the IR region. Complex 2 is low-spin, g(1) = 2.31, g(2) = 2.16, and g(3) = 1.96. Under basic conditions complex 1 affords a mu-oxo bridged dimeric Fe(III) complex [(bmmp-TASN)Fe(III)](2)O (3), which shows an intense band at 799 cm(-)(1). Complex 3 was recrystallized from CH(2)Cl(2)/hexane solution in the triclinic space group P1, with a = 10.5486(15) A, b = 13.0612(19) A, c = 8.1852(12) A, alpha = 96.923(2) degrees, beta = 112.729(2) degrees, gamma = 81.048(2) degrees, and Z = 1. Density functional theory (DFT) calculations of the previously communicated iron-nitrosyl complex [(bmmp-TASN)Fe(III)(NO)][BPh(4)] (4) (Inorg. Chem. 2002, 41, 1039-1041) reveal that the HOMO region is dominated by Fe-S bonding. Complexes 1-4 display irreversible or quasi-reversible reductions in the cyclic voltammograms. All of the iron complexes and the zinc derivative, (bmmp-TASN)Zn (5), display an irreversible oxidation. Complex 5 was crystallized in the monoclinic space group P2(1)/n with a = 9.5759(6) A, b = 20.9790(13) A, c = 10.7113(7) A, beta = 91.283(1) degrees, and Z = 4.

Crystallography, X-Ray↗
PubMed2002

Dichloromethane alkylates a trithiolato-ruthenium complex to yield a methylene-bridged thioether core. Synthesis and structural comparison to the thiolato-ruthenium precursor.

The previously reported triphosphino/trithiolato-ruthenium anion, [tris-(2-diphenylphosphinothia-phenolato)ruthenium(II)](-), [Ru(DPPBT)(3)](-), has been isolated as the PPN salt (PPN = bis(triphenylphosphoranylidene) ammonium), 1, from chlorobenzene/ether as light-orange crystalline plates, and the X-ray crystal structure has been determined. In dichloromethane, the cis positioned thiolates are alkylated by solvent yielding the methylene-bridged triphosphino/dithioether/thiolato complex [(bis-(2-diphenylphosphinothiaphenolato)methane)(2-diphenyl-phosphinothiaphenolato)ruthenium(II)]chloride, [Ru((DPPBT)(2)CH(2))(DPPBT)]Cl (2). Dichloromethane solutions of 1 layered with hexanes yield 2 as orange cubes. The ruthenium-sulfur bond distances in the alkylated, thioether product are slightly shorter than in the thiolate precursor. Within 2, the iron-thioether bond distances are comparable to the iron-thiolate distances.

Journal Article↗
PubMed2002

Unique reactivity of a tetradentate N(2)S(2) complex of nickel: intermediates in the production of sulfur oxygenates.

Complex 1 [(N,N'-dimethyl-N,N'-bis(2-sulfanylethyl)ethylenediamine)nickel(II)], previously shown to react with H(2)O(2) to produce the fully oxygenated disulfonate 5 [diaqua(N,N'-dimethyl-N,N'-bis(2-sulfonatoethyl)ethylenediamine)nickel(II)], has been explored in detail to explain the observed reactivity of this compound and to discern intermediates in the oxygenation reaction. Reaction of 1 with 1 equiv of methyl iodide results in the monomethylated square-planar nickel complex 2 [[(N,N'-dimethyl-N-(2-sulfanylethyl)-N'-(2-methylthioethyl)(ethylenediamine)nickel(II)] iodide], while a slight excess of methyl iodide results in the dimethylated complex 3 [diiodo(N,N'-dimethyl-N,N'-bis(2-methylthioethyl)ethylenediamine)nickel(II)], an X-ray structure of which has shown that the nickel ion is in an octahedral N(2)S(2)I(2) environment. Crystal data of 3: monoclinic, a = 8.865(3) A, b = 14.419(4) A, c = 14.389(6) A, beta = 100.19(3) degrees, V = 1810.2(12) A(3), space group P2(1)/n, Z = 4. The equatorial positions are occupied by the two cis-amine N-atoms and the coordinated iodides, while the axial positions are occupied by the thioether sulfur atoms. In organic solvents, the dithiolate complex 1 reacts with molecular oxygen or H(2)O(2) to produce the mixed sulfinato/thiolato complex 4 [(N,N'-dimethyl-N-(2-sulfanylethyl)-N'-(2-sulfinatoethyl)(ethylenediamine)nickel(II)], and the fully oxidized product 5. X-ray analysis of complex 4 reveals a square-planar geometry in which the nickel ion is coordinated by two cis-amine nitrogens, one thiolate sulfur donor, and one sulfinato sulfur donor. Crystal data of 4: orthorhombic, a = 11.659(2) A, b = 13.119(3) A, c = 16.869(3) A, V = 2580.2(9) A(3), space group Pbca, Z = 8. This complex is the only intermediate in the oxygenation reaction that could be isolated, and it is shown to be further reactive toward O(2) to yield the fully oxidized product 5. For a better understanding of the reactivity observed for 4, DFT calculations have been undertaken, which show a possible reaction path toward the fully oxidized product 5.

Journal Article↗
PubMed2002

cis-Dioxocyclam.

Molecules of 1,4,8,11-tetraazacyclotetradecane-5,7-dione, or cis-dioxocyclam, C(10)H(20)N(4)O(2), lie across mirror planes in space group Cmca; the crystal structure reveals interleaved columns of cis-dioxocyclam molecules along the 2(1) screw axis parallel to the crystallographic b axis. The columns are interconnected in a chain-like arrangement by an amido hydrogen-bonding network (N* * *O = 2.816 A) and an amino hydrogen-bonding network (N* * *N = 3.193 A). The intracolumn spacing is 9.02 A.

Journal Article↗
PubMed2002

First [Fe-NO](6) complex with an N(2)S(3)Fe-NO core as a model of NO-inactivated iron-containing nitrile hydratase. Are thiolates and thioethers equivalent donors in low-spin iron complexes?

The spectroscopic and structural properties of [(bmmp-TASN)FeNO]BPh(4) (1) (bmmp-TASN = 4,7-bis(2'-methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane) have been determined and are compared with the nitric oxide inactivated form of iron-containing nitrile hydratase, NHase(dark). [(bmmp-TASN)FeNO]BPh(4) is prepared from the addition of NO to (bmmp-TASN)FeCl followed by addition of sodium tetraphenylborate. [(bmmp-TASN)FeNO]BPh(4) crystallizes from acetonitrile-methanol solutions upon ether vapor diffusion as dark blue plates in the monoclinic space group P2(1)/c with a = 11.9521(14) A, b = 11.3238(13) A, c = 26.624(3) A, beta = 98.280(2), and Z = 4. The nu(NO) stretching frequency of 1856 cm(-)(1) and the Mössbauer parameters, delta = 0.06 mm/s and DeltaE(q) = 1.75 mm/s, compare favorably with those of NHase(dark). The similarities of the iron-sulfur bond distances to the thiolate, 2.284(2) A and 2.291(2) A, versus thioether, 2.285(2) A, are attributed to the low-spin configuration of the iron. The relationship between this structural observation and the spectroscopic properties of the complex are discussed.

Binding Sites↗