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Jeanette A Krause Bauer

Publications and source records attributed to Jeanette A Krause Bauer.

At least 19 recordsLinked to original sources
PubMed2005

Anion-controlled nuclearity in nickel complexes with potentially dinucleating, poly(oxime) amine ligands.

Two new ligands consisting of bis(oxime) amine units tethered by a bridge have been synthesized. Their nickel chloride and nickel nitrate complexes have also been synthesized and characterized by X-ray crystallography, FTIR, mass spectrometry, and elemental analysis. One of these ligands, L1 (N,N,N',N'-tetra(1-propan-2-onyl oxime)-diamino-m-xylene), is always dinucleating, while the other ligand, L2 (N,N,N',N'-tetra(1-propan-2-onyl-oxime)-1,3-diaminopropane), shows an unusual anion dependence on the nuclearity. When nickel chloride is used, the ligand acts in a dinucleating manner and coordinates two nickels; however, when nickel nitrate is used, the ligand acts in a monodentate fashion and coordinates only one nickel. Once the mononuclear complex is formed, it is not possible to add a second nickel if Ni(NO(3))(2) is used as the nickel source; it is possible, however, to add a second nickel if NiCl(2) is used as the nickel source. The dinuclear complex can be converted to the mononuclear one by either using silver nitrate to exchange the chloride anions for nitrates or by dissolving the complex in water. Ni(2)(L1)Cl(4)(DMF)(2).DMF: orthorhombic, P2(1)2(1)2(1), a = 12.2524(11) A, b = 16.6145(15) A, c = 20.1234(19) A, V = 4096.5(6) A(3), Z = 4. [Ni(2)(L2)Cl(4)(DMF)](2).2DMF: triclinic, P-1, a = 12.5347(5) A, b = 12.5403(5) A, c = 14.3504(6) A, alpha = 67.348(1) degrees , beta = 69.705(1) degrees , gamma = 81.549(1) degrees , V = 1952.25(14) A(3), Z = 1. Ni(L2).(NO(3))(2): monoclinic, P2(1)/n, a = 9.6738(3) A, b = 30.2229(9) A, c = 15.8238(5) A, beta = 97.995(1) degrees , V = 4581.4(2) A(3), Z = 8.

Amines↗
PubMed2005

Photoenolization of 2-(2-methyl benzoyl) benzoic acid, methyl ester: effect of E photoenol lifetime on the photochemistry.

[reaction: see text] Photolysis of 3 in argon-saturated 2-propanol led to formation of 5 via intermolecular H-atom abstraction followed by lactonization. Irradiation of 4 in 2-propanol gave compounds 6 and 7 that also come from intermolecular H-atom abstraction. In contrast, photolysis of an oxygen-saturated solution of 3 in 2-propanol yields products 8, 9, and 10, which were all formed from intramolecular H-atom abstraction and trapping of the corresponding biradical with oxygen. Laser flash photolysis of 3 in methanol showed formation of biradical 3BR (lambda(max) 330 nm, and tau = 50 ns) via intramolecular H-atom abstraction as the main photoreactivity of 3. Biradical 3BR decayed into photoenols 3Z and 3E (lambda(max) 390 nm, tau = 6.5 micros and tau = 162 micros, respectively). In comparison, laser flash photolysis of 4 yielded photoenols 4Z and 4E (lambda(max) 390 nm, tau = 15 micros and tau = 3.6 ms, respectively). Thus photoenol 3E is unusually short-lived, and therefore it does not undergo the intramolecular lactonization as we have observed for the analogous photoenol 1E. Photoenol 3Z decays back to 3 via an intramolecular 1,5-H shift, whereas photoenol 3E reforms 3 efficiently via the solvent with the aid of the ortho ester group. The intramolecular lactonization of photoenols 1E and 3E must be a slow process, presumably because the photoenols are rigid and the hydroxyl group is inhibited, by intramolecular hydrogen bonding, from acquiring the correct geometry for lactonization. Thus only photoenols that are resistant to reformation of their ketone via the solvent are long-lived enough to undergo lactonization and release the alcohol moiety.

Journal Article↗
PubMed2005

Intramolecular metal...sulfur interactions of platinum(II) 1,4,7-trithiacyclononane complexes with bipyridyl ligands: the relationship between molecular and electronic structures.

Five platinum(II) 1,4,7-trithiacyclononane (ttcn) complexes with bidentate-substituted 2,2'-bipyridine ligands have been prepared and structurally characterized: [Pt(bpy)(ttcn)](PF6)2 (bpy = 2,2'-bipyridine), triclinic, P1, a = 10.2529(3) A, b = 10.7791(3) A, c = 10.7867(3) A, alpha = 83.886(1) degrees, beta = 87.565(1) degrees, gamma = 84.901(1), V = 1179.99(6) A3, Z = 2; [Pt(4,4'-dmbpy)(ttcn)](PF6)2 x CH3CN x H2O (4,4'-dmbpy = 4,4'-dimethyl-2,2'-bipyridine), triclinic, P1, a = 10.1895(3) A, b = 11.8566(4) A, c = 13.1004(4) A, alpha = 77.345(1) degrees, beta = 79.967(1) degrees, gamma = 72.341(1) degrees, V = 1461.56(8) A3, Z = 2; [Pt(5,5'-dmbpy)(ttcn)](PF6)2 (5,5'-dmbpy = 5,5'-dimethyl-2,2'-bipyridine), triclinic, P1, a = 10.6397(4) A, b = 10.8449(4) A, c = 11.2621(4) A, alpha = 90.035(1) degrees, beta = 98.061(1) degrees, gamma = 91.283(1) degrees, V = 1286.32(8) A3, Z = 2; [Pt(dbbpy)(ttcn)](PF6)2 x CH3NO2 (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine), triclinic, P1, a = 11.5422(7) A, b = 11.6100(7) A, c = 13.6052(9) A, alpha = 85.902(1) degrees, beta = 89.675(1) degrees, gamma = 74.942(1) degrees, V = 1755.90(19) A3, Z = 2; and [Pt(dtfmbpy)(ttcn)](PF6)2 x CH3CN (dtfmbpy = 5,5'-di-trifluoromethyl-2,2'-bipyridine): monoclinic, P2(1)/c, a = 13.1187(9) A, b = 20.9031(15) A, c = 11.3815(8) A, beta = 105.789(2) degrees, V = 3003.3(4) A3, Z = 4. For each salt, the platinum(II) center of the cation is bonded to two nitrogen atoms of the chelating diimine and two sulfur atoms of the thioether macrocycle. The third sulfur atom of ttcn forms a long apical interaction with the metal center (2.84-2.97 A), resulting in a flattened square pyramid structure. An examination of these and 17 other structures of platinum(II) ttcn complexes reveals a correlation between the apical Pt...S distance and the donor properties of the ancillary ligands, suggesting a means for using variations in ligand electronic properties to tune molecular structure. The room-temperature absorption spectra in acetonitrile solution show a broad and comparatively low-energy MLCT band maximizing near approximately 390 nm for the bpy and dialkyl-substituted bipyridyl derivatives. The maximum is dramatically red-shifted to 460 nm in the spectrum of the dtfmbpy complex as a result of the electron-withdrawing properties of the -CF(3) groups. The 3:1 EtOH/MeOH 77 K glassy solution emission spectra exhibit low-energy emission bands (lambdamax, 570-645 nm), tentatively assigned as originating from a lowest, predominantly spin-forbidden MLCT excited state that is stabilized by apical Pt...S interactions.

Journal Article↗
PubMed2005

Luminescent platinum(II) dimers with a cyclometallating aryldiamine ligand.

Triflate salts of three (Pt(pip2NCN))2(mu-L)2+ (pip2NCNH = 1,3-bis(piperidylmethyl)benzene) dimers bridged by a series of nitrogen-donor ligands (L = pyrazine (pyz), 1,2-bis(4-pyridyl)ethane (bpa), trans-1,2-bis(4-pyridyl)ethylene (bpe)) are reported. These complexes have been fully characterized by 1H NMR spectroscopy and elemental analysis. The X-ray crystal structures of [(Pt(pip2NCN))2(mu-pyz)](CF3SO3)2 and [(Pt(pip2NCN))2(mu-bpe)](CF3SO3)2 x 2CH2Cl2 are reported. [(Pt(pip2NCN))2(mu-pyz)](CF3SO3)2: triclinic, P, a = 12.5240(5) A, b = 14.1570(6) A, c = 14.2928(6) A, alpha = 106.458(1) degrees , beta = 92.527(1) degrees , gamma = 106.880(1) degrees , V = 2303.46(17) A(3), Z = 2. [(Pt(pip2NCN))2(mu-bpe)](CF3SO3)2 x 2CH2Cl2: monoclinic, P21/c, a = 10.1288(6) A, b = 16.3346(9) A, c = 17.4764(10) A, beta = 90.882(2) degrees , V = 2891.1(3) A3, Z = 2. These structures and solution measurements provide evidence for the strong trans-directing properties of the pip2NCN- ligand. The electronic structures of these complexes and those of the 4,4'-bipyridine (bpy) dimer, (Pt(pip2NCN))2(mu-bpy)2+, also have been investigated by UV-visible absorption and emission spectroscopies, as well as cyclic voltammetry. The accumulated data indicate that variations in the bridging ligands provide remarkable control over the electronic structures and photophysics of these complexes. Notably, the bpa dimer exhibits a broad, low-energy emission from a metal-centered 3LF excited state, whereas the bpe and bpy dimers exhibit structured emission from a lowest pyridyl-centered 3(pi-pi*) excited state. In contrast, the pyz dimer exhibits remarkably intense yellow emission tentatively assigned to a triplet metal-to-ligand charge-transfer excited state.

Journal Article↗
PubMed2005

Novel metallamacrocyclic gold(I) thiolate cluster complex: structure and luminescence of [Au9(mu-dppm)4(mu-p-tc)6](PF6)3.

The structure of a novel metallamacrocyclic phosphine gold(I) thiolate cluster, [Au9(mu-dppm)4(mu-p-tc)6](PF6)3, where dppm = bis(diphenylphosphine)methane and p-tc = p-thiocresolate, is reported and shows AuAu attractions of approximately 3.0 A and gold(I) atoms linked to thiolate and phosphine ligands in distorted trigonal and nearly linear geometries.

Journal Article↗
PubMed2004

Mu-biphenyl-2,2'-dithiolato-kappa2S:S'-bis[(triphenylphosphine-kappaP)gold(I)].

The reaction of ClAuPPh3 and 1,1'-biphenyl-2,2'-dithiol in the presence of trimethylbenzylammonium chloride and K2CO3 in a tetrahydrofuran/methanol solution gives the title complex, [Au2(C12H8S2)(C18H15P)2]. The molecule contains P-Au-S units which 'cross' with torsion angles of approximately 90 degrees [P-Au-Au-P = 86.23 (5) degrees and S-Au-Au-S = 95.62 (5) degrees]. The intra- and intermolecular Au.Au distances [3.9064 (3) and 6.3797 (5) A, respectively] are outside the range for typical Au...Au interactions. However, the Au atoms appear to be drawn together, leading to a significant bending of the P-Au-S angles [170.24 (5) and 169.52 (5) degrees].

Journal Article↗
PubMed2004

A luminescent platinum(II) 2,6-bis(N-pyrazolyl)pyridine complex.

Four platinum(II) cationic complexes were prepared with the mer-coordinating tridentate ligands 2,6-bis(N-pyrazolyl)pyridine (bpp) and 2,6-bis(3,5-dimethyl-N-pyrazolyl)pyridine (bdmpp): [Pt(bpp)Cl]Cl.H(2)O; [Pt(bdmpp)Cl]Cl.H(2)O; [Pt(bpp)(Ph)](PF(6)); [Pt(bdmpp)(Ph)](PF(6)). The complexes were characterized by (1)H NMR spectroscopy, elemental analysis, and mass spectrometry, and the structures of the bpp derivatives were determined by X-ray crystallography. [Pt(bpp)Cl]Cl.2H(2)O: monoclinic, P2(1)/n, a = 11.3218(5) A, b = 6.7716(3) A, c = 20.6501(6) A, beta = 105.883(2) degrees, V = 1522.73(11) A(3), Z = 4. The square planar cations stack in a head-to-tail fashion to form a linear chain structure with alternating Pt...Pt distances of 3.39 and 3.41 A. [Pt(bpp)(Ph)](PF(6)).CH(3)CN: triclinic, P, a = 8.3620(3) A, b = 10.7185(4) A, c = 13.4273(5) A, alpha = 96.057(1) degrees, beta = 104.175(1) degrees, gamma = 110.046(1) degrees, V = 1072.16(7) A(3), Z = 2. Cyclic voltammograms indicate all four complexes undergo irreversible reductions between -1.0 and -1.3 V vs Ag/AgCl (0.1 M TBAPF(6)/CH(3)CN), attributable to ligand- and/or metal-centered processes. By comparison to related 2,2':6',2' '-terpyridine complexes, the electrochemical and UV-visible absorption data are consistent with bpp being both a weaker sigma-donor and pi-acceptor than terpyridine. Solid samples of [Pt(bpp)(Ph)](PF(6)) at 77 K exhibit a remarkably intense, narrow emission centered at 655 nm, whereas the other three complexes exhibit only very weak emission.

Journal Article↗
PubMed2004

Tuning the electronic structures of platinum(II) complexes with a cyclometalating aryldiamine ligand.

Triflate salts of four platinum(II) pyridyl complexes with a mer-coordinating tridentate pincer ligand, pip(2)NCN(-) (pip(2)NCNH = 1,3-bis(piperidylmethyl)benzene), are reported: Pt(pip(2)NCN)(L)(+) (2, L = pyridine; 3, L = 4-phenylpyridine; 5, L = 2,6-pyridinedimethanol) and [(Pt(pip(2)NCN))(2)(micro-4,4'-bipyridine)](2+) (4). The complexes have been fully characterized by (1)H NMR spectroscopy, elemental analysis, and X-ray crystallography. Compound 2(CF(3)SO(3)(-)): triclinic, P1, a = 9.7518(6) A, b = 12.0132(8) A, c = 12.6718(9) A, alpha = 114.190(2) degrees, beta = 100.745(3) degrees, gamma = 103.545(2) degrees, V = 1247.95(14) A(3), Z = 2. Compound 3(CF(3)SO(3)(-)): monoclinic, P2(1)/c, a = 15.550(2) A, b = 9.7386(11) A, c = 18.965(3) A, beta = 92.559(7) degrees, V = 2869.1(6) A(3), Z = 4. Compound 4(CF(3)SO(3)(-))(2).1/2(CH(3))(2)CO: monoclinic, I2/a, a = 21.3316(5) A, b = 9.6526(2) A, c = 26.1800(6) A, beta = 96.4930(10) degrees, V = 5356.0(2) A(3), Z = 4. Compound 5(CF(3)SO(3)(-)).3/2CHCl(3): monoclinic, P2(1)/n, a = 17.1236(10) A, b = 9.3591(5) A, c = 21.3189(11) A, beta = 96.11(3) degrees, V = 3397.2(3) A(3), Z = 4. The accumulated data indicate that the phenyl group of pip(2)NCN(-) labilizes the trans pyridyl ligand. The electronic structures were investigated using cyclic voltammetry, as well as UV-visible absorption and emission spectroscopies. Red emission from 2 in rigid media originates from a lowest triplet ligand field excited state, whereas yellow-green emissions from 3 and 4 originate from a lowest pyridyl ligand-centered triplet pi-pi state, indicating that substitution of the pyridyl ligand results in a dramatic change in the orbital character of the emissive state.

Journal Article↗
PubMed2004

Binuclear rhenium(I) complexes with bridging [2.2]paracyclophane-diimine ligands: probing electronic coupling through pi-pi interactions.

Two pseudo-para substituted bis-diimino[2.2]paracyclophane ligands (4,16-bis(picolinaldimine)-[2.2]paracyclophane (BPPc) and 4,16-bis(methyl-picolinaldimine)-[2.2]paracyclophane (BmPPc)) were prepared by the condensation reaction of the appropriate picolinaldimine with 4,16-diamino-[2.2]paracyclophane (2). An improved synthesis of 2 from [2.2]paracyclophane also is reported. BPPc (3a): monoclinic, P2(1)/c, a = 8.2238(11) A, b = 15.336(2) A, c = 8.4532(11) A, beta = 98.578(3) degrees, V = 1054.2(2) A(3), Z = 2. To investigate the binding properties of the bis-diimino[2.2]paracyclophane ligands, binuclear rhenium(I) tricarbonyl chloride complexes [Re(CO)(3)Cl](2)(micro-BPPc) (5a) and [Re(CO)(3)Cl](2)(micro-BmPPc) (5b) were prepared and fully characterized by infrared spectroscopy, (1)H NMR spectroscopy, elemental analysis, UV-visible absorption spectroscopy, and cyclic voltammetry. Two model complexes, Re(tolyl-pyCa)(CO)(3)Cl (4) (tolyl-pyCa = N-(p-tolyl)-2-pyridinecarboxaldimine) and [Re(CO)(3)Cl](2)(micro-PBP) (6) (PBP = p-phenylenebis(picolinaldimine)), also are reported. The dimeric compounds 5 and 6 each undergo two one-electron, predominantly diimine-centered reduction processes. Spectroscopic data and comproportionation constants (5a, 23 +/- 9; 5b, 23 +/- 9; 6, 2750 +/- 540) are consistent with relatively weak interactions between the diimine groups mediated by the paracyclophane bridging group, and these results are consistent with steric and electronic factors.

Journal Article↗
PubMed2004

Emission energy correlates with inverse of gold-gold distance for various [Au(SCN)2]- salts.

A series of bis(thiocyanato)gold(I) complexes with Au-Au interactions show luminescence in the range from 500 to 670 nm. The series of salts correlates emission energy with the reciprocal of the Au-Au distance. As the Au-Au distance increases, the emission energy decreases. The ligand system provides no framework for the Au-Au interaction. The emission energy seems totally determined by the Au-Au distance.

Journal Article↗
PubMed2003

Photoaddition reactions of acetylene and butadiyne derivatives to benzodithiophene.

The photochemical [2pi +2pi] cycloaddition of dimethyl acetylenedicarboxylate to benzo[1,2-b:4,5-b']dithiophene has been used to synthesize substituted cyclobuta[b]thieno[2,3-f][1]benzothiophene. The first [2pi + 2pi] photocycloaddition reaction of a series of butadiynes to benzodithiophene is reported to yield regioselective and acetylene-substituted cyclobutene derivatives containing an aromatic thiophene moiety.

Journal Article↗
PubMed2003

Formation of a cationic gold(I) complex and disulfide by oxidation of the antiarthritic gold drug auranofin.

The mechanism of action of auranofin, an antiarthritic gold(I) drug, is unknown, but several studies suggest that oxidation may be important for its biochemical effect. Bulk electrolysis studies on auranofin [(Et(3)P)Au(TATG); TATG = 2,3,4,6-tetraacetyl-1-thio-d-glucopyranosato] at +1.2 and +1.6 V versus Ag/AgCl in 0.1 M Bu(4)NBF(4)/CH(2)Cl(2) results in n values of 0.5 and >2 electrons, respectively. Oxidation of auranofin with the mild oxidant, Cp(2)Fe(+), results in formation of disulfide and a digold(I) cation with a bridging thiolate ligand, [(Et(3)PAu)(2)(mu-TATG)](+) (1). The X-ray structure of the PMe(3) analogue, [(Me(3)PAu)(2)(mu-TATG)](NO(3)) (2), is reported. Compound 2 forms a tetranuclear cluster containing an almost perfect square of four gold atoms with Au.Au distances averaging 3.14 A. The complex crystallizes in the tetragonal space group P4(2)2(1)2 with cell constants a = 26.1758(6) A, b = 26.1758(6) A, c = 9.7781(3) A, alpha = beta = gamma = 90 degrees, V = 6699.7(3) A(3), Z = 4, R1 = 0.0644, and wR2 = 0.1152. A mechanism for oxidation of auranofin and possible biological implications are discussed.

Antirheumatic Agents↗
PubMed2003

An outer-sphere two-electron platinum reagent.

A strategy for designing cooperative outer-sphere two-electron platinum reagents is demonstrated. The novel platinum(II) complex, [Pt(tpy)(pip2NCN)][BF4] (1(BF4-)) (tpy = 2,2':6',2' '-terpyridine, pip2NCN- = 2,6-(CH2N(CH2)5)2-C6H3-), in which the metal is bonded to two pincer type ligands, has been prepared. Treatment of 1 with protic acid results in protonation of the pendant piperdyl groups, allowing for the isolation of [Pt(tpy)(pip2NCNH2)][PF6]3 (2(PF6-)3). 1H NMR spectra of 1 and 2 establish that in each complex the terpyridyl ligand is tridentate, whereas the piperdyl ligand is monodentate, bonded to platinum through the phenyl ring. The structure of the protonated complex was confirmed by an X-ray crystallographic study of crystals of 2(Cl-)3.4H2O. The cyclic voltammagram of 1 exhibits two reversible one-electron reduction waves at E degrees ' = -0.98 V and E degrees ' = -1.50 V (E degrees ' = (Epc + Epa)/2), with a DeltaEp of 65 and 61 mV, respectively. In contrast to other Pt(II) complexes, including 2, this complex also undergoes a nearly reversible two-electron oxidation process at E degrees ' = 0.40 V (DeltaEp = 43 mV, 0.01 V/s). The accumulated data are consistent with the unusual ligand architecture of 1 being capable of stabilizing and allowing for facile interconversion between the Pt(II) and Pt(IV) oxidation states.

Journal Article↗
PubMed2003

Synthesis and atructure of [meso-triarylcorrolato]silver(III).

An efficient meso-triarylcorrole synthesis is detailed, and the formation and spectroscopic properties of their diamagnetic square-planar d(8) Ag(III) complexes are described. The spectroscopic properties of the [corrolato]Ag(III) complexes are contrasted with those of the corresponding [porphyrinato]Ag(II) complexes. The oxidation state of the central metal in the corrolato complexes was inferred from their diamagnetic NMR spectra, from X-ray photoelectron spectroscopy measurements, and by single-crystal X-ray diffractometry of the [meso-tetra-p-tolylcorrolato]silver(III) complex TTCAg(III), as its toluene solvate (crystal data for C(40)H(29)N(4)Ag.C(7)H(8): monoclinic space group C2/c with a = 21.4679(19) A, b = 20.7606(19) A, c = 16.0122(11) A, beta = 93.700(4) degrees, V = 7121.5(10) A(3), Z = 8, R = 0.0453, and R(w) = 0.1131). The conformation of the corrolato ligand in the complex is slightly saddled. The Ag(III) complexes are without precedent in the coordination chemistry of corroles. The Ag(III) complexes underline the ability of meso-triarylcorroles to stabilize higher oxidation states as compared to the corresponding meso-tetraarylporphyrinato complexes.

Journal Article↗
PubMed2003

[Mu-o-phenylenebis(diphenylphosphine)-kappa2P:P']bis[chlorogold(I)], dppbz(AuCl)2.

The Au...Au distance in the title compound, [Au(2)Cl(2)(C(30)H(24)P(2))], is 2.996 (1) A, typical of an Au...Au interaction. The two P-Au-Cl arms 'cross' at the Au centers, with a Cl-Au...Au-Cl torsion angle of -63.92 (7) degrees. Only a small deviation from linearity is observed in the coordination around the Au atoms. Related phosphine-gold(I) chloride structures with intra- and intermolecular Au...Au interactions are surveyed.

Journal Article↗
PubMed2003

Structural and spectroscopic studies of nickel(II) complexes with a library of Bis(oxime)amine-containing ligands.

A library of tripodal amine ligands with two oxime donor arms and a variable coordinating or noncoordinating third arm has been synthesized, including two chiral ligands based on l-phenylalanine. Their Ni(II) complexes have been synthesized and characterized by X-ray crystallography, UV-vis absorption, circular dichroism, and FTIR spectroscopy, mass spectrometry, and room-temperature magnetic susceptibility. At least one crystal structure is reported for all but one Ni/ligand combination. All show a six-coordinate pseudo-octahedral coordination geometry around the nickel center, with the bis(oxime)amine unit coordinating in a facial mode. Three distinct structure types are observed: (1) for tetradentate ligands, six-coordinate monomers are formed, with anions and/or solvent filling out the coordination sphere; (2) for tridentate ligands, six-coordinate monomers are formed with Ni(II)(NO(3))(2), with one monodentate and one bidentate nitrate filling the remaining coordination positions; (3) for tridentate ligands, six-coordinate, bis(mu-Cl) dimers are formed with Ni(II)Cl(2), with one terminal and two bridging chlorides filling the coordination sphere. The UV-vis absorption spectra of the complexes show that the value of 10 Dq varies according to the nature of the third arm of the ligand. The trend based on the third arm follows the order alkyl/aryl < amide < carboxylate < alcohol < pyridyl < oxime.

Amines↗
PubMed2002

Oxygen reactivity of a nickel(II)-polyoximate complex.

The ligand tris(2-hydroxyiminopropyl)amine (Ox(3)H(3)) binds to nickel(II) in multiple protonation states. In the neutral state, the X-ray crystal structure of the monomeric complex [Ni(Ox(3)H(3))(NO(3))(H(2)O)](NO(3)).(H(2)O), 1, has six-coordinate pseudo-octahedral geometry, with binding of the amine and three oxime nitrogens, a nitrate, and a water. In the mono-deprotonated form, the X-ray crystal structure shows a dimer, [Ni(Ox(3)H(2))(CH(3)CN)](2)(ClO(4))(2), 2, which has bridging oximate groups and a Ni-Ni distance of 3.575 A. The fully deprotonated complex, 3, shows significantly low Ni(II) oxidation potentials at -390 and +165 mV (versus Fc(+)/Fc). Complex 3 shows reactivity when exposed to O(2), consuming multiple O(2) equivalents and turning from the purple 3 to a dark brown complex, 4. Complex 4 has an EPR spectrum consistent with Ni(III), but spin quantitation accounts for only about 10% of the total Ni, consistent with turnover of the Ni oxidation states. This Ni(II)/O(2) system oxidizes triphenylphosphine to its oxide, with incorporation of the isotopic label from O(2).

Journal Article↗