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Colin A Kilner

Publications and source records attributed to Colin A Kilner.

At least 19 recordsLinked to original sources
PubMed2006

Polyhedral monocarbaborane chemistry. Some C-phenylated seven, eight, nine, ten, eleven and twelve-vertex species.

Some synthetic and structural systematics for monocarbaboranes, using the C-phenylated motif as the example, are investigated. The 10-vertex [6-Ph-nido-6-CB(9)H(11)](-) anion 1, from reaction of PhCHO with B(10)H(14) in KOH/H(2)O, is a useful entry synthon into C-phenyl monocarbaborane chemistry. Treatment of anion 1 with Na/thf yields the 10-vertex [1-Ph-closo-1-CB(9)H(9)](-) anion 2a, whereas treatment of anion 1 with iodine in alkaline solution yields the isomeric 10-vertex [2-Ph-closo-2-CB(9)H(9)](-) anion 2b, which isomerises quantitatively to 2a on heating under reflux in DME. Thermolysis of anion 1 yields the 9-vertex [4-Ph-closo-4-CB(8)H(8)](-) anion 5, whereas treatment of anion 1 with FeCl(3)/HCl gives neutral 9-vertex [4-Ph-arachno-4-CB(8)H(13)] 3. Compound 3 gives neutral 9-vertex [1-Ph-nido-1-CB(8)H(11)] 4 in refluxing toluene, and gives the 7-vertex [2-Ph-closo-2-CB(6)H(6)](-) anion 7 and the 8-vertex [1-Ph-closo-1-CB(7)H(7)](-) anion 6 in refluxing toluene with NEt(3). Reaction of 1 with [BH(3)(thf)] yields the 11-vertex [7-Ph-nido-7-CB(10)H(12)](-) anion 8 which can be converted to the 12-vertex [1-Ph-closo-1-CB(11)H(11)](-) anion 10 using [BH(3)(SMe(2))]; alternatively, anion 1 yields anion 10 directly on treatment with [BH(3)(NEt(3))]. Treatment of anion 8 with I(2)/KOH yields the 11-vertex [2-Ph-closo-2-CB(10)H(10)](-) anion 9. The structures of anions 1, 2a, 2b, 5, 6, 7, 8, 9 and 10 have been established by single-crystal X-ray diffraction analyses of their [NEt(4)](+) salts, and those of neutral 3 and 4 estimated by DFT calculations at the B3LYP/6-31G* level; similar calculations have also been applied to the new anionic closo species 2a, 2b, 5, 6, 7, 9 and 10. Crystals of the [NEt(4)](+) salt of the [2-Ph-closo-2-CB(6)H(6)](-) anion 7 required synchrotron X-radiation for sufficient diffraction intensity for molecular-structure elucidation. The syntheses are in principle generally applicable to give extensive derivative C-aryl and C-alkyl chemistries.

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PubMed2006

Homoleptic zinc(II) complexes with first and second coordination shells of 5-tert-butylpyrazole.

Reaction of hydrated Zn[NO3]2 or Zn[BF4]2 with four or more equivalents of 3{5}-tert-butylpyrazole (L(tBu)) yields [Zn(L(tBu))4]X2 (X- = NO3- or BF4-). The nitrate complex contains C2-symmetric four-coordinate zinc(II) centers with a slightly flattened tetrahedral geometry, and each nitrate anion hydrogen bonds to two pyrazole N-H groups. Similar reactions with Zn[ClO4]2 or ZnCl2 in the presence of 2 equiv of AgPF6 or AgSbF6 yield instead [{Zn(L(tBu))4}(L(tBu))4][ClO4]2 and [{Zn(L(tBu))4}(L(tBu))2]Y2 (Y- = PF6- or SbF6-). Crystals of [{Zn(L(tBu))4}(L(tBu))4][ClO4]2 are composed of discrete [{Zn(L(tBu))4}(L(tBu))4]2+ supramolecules that are formed from N-H...N hydrogen bonding between zinc-bound and uncoordinated pyrazole rings. The [{Zn(L(tBu))4}(L(tBu))4]2+ moieties are linked into planar 4(4) nets by hydrogen bonding to bridging ClO4- anions. The ClO4- ions are almost perfectly encapsulated in near-spherical cavities of approximate dimensions 5.0 x 5.0 x 4.5 A that are formed by two interlocked supramolecular dications. Similarly, [{Zn(L(tBu))4}(L(tBu))2][PF6]2 crystallizes as discrete supramolecules in the crystal with the PF6- anions occupying a shallow bowl-shaped cavity on the surface of the complex that is formed by two zinc-bound and one uncoordinated pyrazole ligands. (1)H NMR and IR studies of [{Zn(L(tBu))4}(L(tBu))4][ClO4]2 in CD2Cl2 imply that the second-sphere L(tBu) ligands dissociate from the [Zn(L(tBu))4]2+ center in this solvent and that free and metal-bound L(tBu) are in rapid chemical exchange.

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PubMed2006

Macropolyhedral boron-containing cluster chemistry. Cluster opening and B-frame rearrangement in the reaction of B(16)H(20) with [{(IrCl(2)(eta(5)-C(5)Me(5))}(2)]. Synchrotron X-ray structures of [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(17)Cl] and [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(15)Cl].

Products from the reaction of + nido ten-vertex : nido eight-vertex, B(16)H(20) with [{(IrCl(2)(eta(5)-C(5)Me(5))}(2)] and tmnd show unanticipated rearrangement of the starting {B(16)} skeleton, as exhibited by + nido ten-vertex : nido ten-vertex, [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(17)Cl] which has a {B(2)} edge conjunction and by + nido ten-vertex : nido eleven-vertex, [(eta(5)-C(5)Me(5))(2)Ir(2)B(16)H(15)Cl] which has a {B(3)} face conjunction.

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PubMed2006

An unusual example of a linearly coordinated acetone ligand in a six-coordinate iron(II) complex.

The title compound, acetonediaqua[2,6-bis(3-tert-butylpyrazol-1-yl)pyridine]iron(II) bis(tetrafluoroborate) acetone disolvate, [Fe(C19H25N5)(C3H6O)(H2O)2](BF4)(2).2C3H6O, contains a C2-symmetric six-coordinate complex dication, with an acetone ligand in its equatorial plane that is linearly coordinated by symmetry (Fe-O=CMe2=180 degrees). This is a consequence of close steric contacts between the coordinated carbonyl group and the two distal tert-butyl substituents on the tridentate ligand.

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PubMed2006

Macropolyhedral boron-containing cluster chemistry. A synthetic approach via the auto-fusion of [6,9-(SMe2)2-arachno-B10H12].

In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1 in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe2)-nido-B10H12] 2 (30%), but also the two two-cluster species [6,9-(SMe2)2-arachno-B10H11-1-(6-nido-B10H13)] 3 (20%) and [1,6-(nido-B10H13)2] 6 (ca. 0.5%) and the two three-cluster species [6,9-(SMe2)2-arachno-B10H10-1,5-(6-nido-B10H13)2] 4 (5%), characterized crystallographically, and [6,9-(SMe2)2-arachno-B10H10-1,3-(6-nido-B10H13)2] 5 (<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe2)-nido-B10H12] 2 is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe2)2-arachno-B10H12] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre--linked two-cluster compounds as starting substrates, two-cluster [5-(SMe2)-4-(2-nido-B10H13)-nido-B10H11] 7 (0.6%) has been isolated from the reaction of SMe2 with [1,5-(nido-B10H13)2], other identified products being compound 1 (39%) and compound 3 (10.5%).

Journal Article↗
PubMed2005

Structural diversity in iron(II) complexes of 2,6-di(pyrazol-1-yl)pyridine and 2,6-di(3-methylpyrazol-1-yl)pyridine.

The syntheses, magnetochemistry and crystallography of [Fe(L1)2]I0.5[I3]1.5 (1), [Fe(L1)2][Co(C2B9H11)2]2 (2) and [Fe(L2)2][SbF6]2 (3) (L1 = 2,6-di(pyrazol-1-yl)pyridine; L2 = 2,6-di(3-methylpyrazol-1-yl)pyridine) are described. Compounds 1 and 3 are high-spin between 5-300 K. For 1, this reflects a novel variation of an angular Jahn-Teller distortion at the iron centre, which traps the molecule in its high-spin state. No such distortion is present in 3; rather, the high-spin nature of this compound may reflect ligand conformational strain caused by an intermolecular steric contact in the crystal lattice. Compound 2 exhibits a gradual high --> low spin transition upon cooling with T(1/2) = 318 +/- 3 K, that is only 50% complete. This reflects the presence of two distinct, equally populated iron environments in the solid. One of these unique iron centres adopts the same angular structural distortion shown by 1 and so is trapped in its high-spin state, while the other, which undergoes the spin-crossover, has a more regular coordination geometry. In contrast with 3, the solvated salts [Fe(L2)2][BF4]2 x 4 CH3CN and [Fe(L2)2][ClO4]2 x (CH3)2CO both undergo gradual thermal spin-transitions centred at 175 +/- 3 K.

Cations↗
PubMed2005

Copper(II) complexes of thioether-substituted salcyen and salcyan derivatives and their silver(I) adducts.

New syntheses are reported of 5-tert-butyl-2-hydroxy-3-methylsulfanylbenzaldehyde, 5-tert-butyl-2-hydroxy-3-phenylsulfanyl-benzaldehyde, and salcyen (H(2)L(1)-H(2)L(3)) and salcyan (H(2)L(4)-H(2)L(6))-type ligands derived from these aldehydes and from 5-tert-butyl-2-hydroxybenzaldehyde. The complexes [CuL](L(2-)=[L(1)](2-)-[L(6)](2-)) bearing sulfanyl substituents each show two distinct voltammetric ligand-based oxidations under the same conditions, the first of which is chemically reversible. The first oxidation product is much longer lived by coulometry for the salcyen than for the salcyan ligand complexes, despite the latter having a substantially lower oxidation potential. The lifetimes of all the ligand oxidation products in this system are substantially smaller than for similar compounds derived from 3,5-di(tert-butyl)-2-hydroxybenzaldehyde (Dalton Trans., 2004, 2662). Attempted chemical oxidation of the Schiff base compounds using AgBF(4) yielded instead stable silver(i) adducts. A crystal structure of one such compound showed that the Ag atom was coordinated in a slightly bent geometry by the two ligand sulfanyl groups, with two additional long-range Ag...O interactions to the phenoxide donors. EPR spectra showed that some of these silver adducts dimerise in CH(2)Cl(2), probably through basal, apical intermolecular Cu-O...Cu bridging. In contrast the parent copper(ii) complexes are all monomeric in this solvent by EPR.

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PubMed2005

An unusual zinc-promoted decomposition of a bis(2-{pyrid-2-yl}ethyl)amine derivative.

The complex [ZnBr(2)L(1)] (L(1) = ferrocenylmethyl-bis[2-{pyrid-2-yl}ethyl]amine) contains bidentate L(1) by crystallography and NMR spectroscopy and decomposes during recrystallization from CH(2)Cl(2)/pentane via both C-N bond cleavage and formation steps. Other [MBr(2)L(1)] (M = Co, Ni, Cu) compounds do not undergo this reaction and contain L(1) bound in the more usual tridentate coordination mode.

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PubMed2005

2-[Bis(pyrazol-1-yl)methyl]-4-tert-butyl-6-(phenylsulfanyl)phenol.

The title compound, C23H24N4OS, contains a highly asymmetric bifurcated intramolecular hydrogen bond between the hydroxy group and two pyrazole N atoms. The compound associates into centrosymmetric dimers in the crystal through two unique C-H...pi interactions, which are in turn linked into a (6,3)-network through an additional intermolecular C-H...N hydrogen bond.

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PubMed2005

A structural, magnetic and Mössbauer spectroscopic study of an unusual angular Jahn-Teller distortion in a series of high-spin iron(II) complexes.

Single crystal X-ray structures and susceptibility data are described for six homoleptic iron(II) complex salts, of 2,6-di(pyrazol-1-yl)pyridine or a 3,3"-disubstituted derivative of it. Zero field Mossbauer spectroscopic data for four of the complexes, and one previously reported analogue, are also discussed. Four of these compounds exhibit an unusual angular Jahn-Teller distortion towards C(2) symmetry to differing degrees, while the other two exhibit structures close to the "ideal" D(2d) symmetry for this ligand set. This structural distortion has two components: a twisting of the plane of one ligand relative to the other about the N{pyridine}-Fe-N{pyridine} vector, so that the two ligands are no longer perpendicular; and a rotation of one ligand about the Fe ion, so that the N{pyridine}-Fe-N{pyridine} angle < 180 degrees. Susceptibility data show that all the complexes are fully high-spin between 5 and 300 K, but yield an unusually wide range of zero-field splitting parameters for the different compounds of between 2.6 and 13.4 cm(-1). Magnetostructural correlations suggest that a low value of |D| is diagnostic for a high degree of "rotation" distortion. The Mossbauer spectra imply that an increased quadrupole splitting might also be diagnostic for the presence of the angular distortion.

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PubMed2005

The capture of dioxygen, carbon monoxide and sulfur dioxide by [(PMe2Ph)4Pt2B10H10].

The metal-metal bond in [(PMe2Ph)4Pt2B10H10], from reaction of [PtCl2(PMe2Ph)2] or PMe2Ph with [(PMe2Ph)2PtB10H12], very readily, and readily reversibly, takes up atmospheric O2 to give the peroxidic dioxygen-dimetallaborane complex [(PMe2Ph)4(O2)Pt2B10H10], which has Pt-Pt 2.7143(3), Pt-O 2.141(4) and 2.151(4), and O-O 1.434(6)A. The {Pt2O2} bonding mode is fluxional. Compound irreversibly takes up CO to give the bridging-carbonyl-dimetallaborane complex [(PMe2Ph)4(CO)Pt2B10H10] which has a CO vector radial to the cluster, with Pt-Pt 2.7488(3), Pt-C 2.104(6) and 2.113(6), and C-O 1.163(6)A; CO readily displaces O2 from to give 3. SO2 similarly reacts with either or to give [(PMe2Ph)4(SO2)Pt2B10H10], which has tetrahedral sulfur, with Pt-Pt 2.8194(4), Pt-S 2.350(2) and 2.381(3), and S-O 1.470(8)A and 1.477(9)A.

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PubMed2005

Copper(II) complexes of tridentate pyridylmethylethylenediamines: role of ligand steric hindrance on DNA binding and cleavage.

Copper(II) complexes of three linear unsymmetrical tridentate ligands viz. N-methyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L1), N,N-dimethyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L2) and N,N-dimethyl-N'-((6-methyl)pyrid-2-ylmethyl)ethylenediamine (L3) have been isolated and characterized by elemental analysis, electronic absorption and EPR spectroscopy and cyclic and differential pulse voltammetry. Of these complexes [Cu(L2)Cl2] and [Cu(L3)Cl2] have been structurally characterized by X-ray crystallography. The [Cu(L2)Cl2] complex crystallizes in the monoclinic space group P2(1)/n with a=11.566(2) A, b=7.369(1) A, c=15.703(3) A, alpha=90 degrees , beta=109.68(8) degrees , gamma=90 degrees and Z=4 while [Cu(L3)Cl2] crystallizes in the triclinic space group P1 with a=9.191(2) A, b=12.359(3) A, c=14.880(3) A, alpha=79.61(13) degrees , beta=86.64(13) degrees , gamma=87.28(8) degrees and Z=2. The coordination geometries around copper (II) in these two complexes are best described as trigonal bipyramidal distorted square based pyramidal (TBDSBP). The distorted CuN3Cl basal plane in them is comprised of three nitrogen atoms of the meridionally coordinated ligand and a chloride ion and the axial position is occupied by the other chloride ion. The interaction of these complexes with Calf Thymus DNA (CT DNA) has been studied by using absorption, emission and circular dichroic spectral methods, thermal denaturation studies, viscometry and cyclic and differential pulse voltammetry. A strong blueshift in the ligand field band and a redshift in the ligand based bands of the copper(II) complexes on binding to DNA imply a covalent mode of DNA binding of the complexes, which involves coordination of most possibly guanine N7 nitrogen of DNA to form a CuN4 chromophore. This is supported by studying the interaction of the complexes with N-methylimidazole (N-meim), guanosine monophosphate (GMP), adenosine monophosphate (AMP) and cytidine (cytd) by ligand field and EPR spectral methods, which indicate the formation of a CuN4 chromophore only in the case of the more basic N-meim and GMP. The DNA melting curves obtained in the presence of copper(II) complexes reveal a monophasic and irreversible melting of the DNA strands and the high positive DeltaTm values (12-21 degrees C) also support the formation of strong Cu-N bonds by the complexes with DNA, leading to intra- and/or interstrand crosslinking of DNA. Competitive ethidium bromide (EthBr) binding studies show that the L2 and L3 complexes are less efficient than the L1 complex in quenching EthBr emission, which is consistent with their forming DNA crosslinking preventing the displacement of the DNA-bound EthBr. A very slight decrease in relative viscosity of DNA is observed on treating the L1 and L2 complexes with CT DNA; however, a relatively significant decrease is observed for the L3 complex suggesting that the length of the DNA fiber is shortened. DNA cleavage experiments show that all the complexes induce the cleavage of pBR322 plasmid DNA, the complex of L1 being more efficient than those of sterically hindered L2 and L3 ligands.

Animals↗
PubMed2004

Monocarbaborane anion chemistry. [COOH], [CH2OH] and [CHO] units as functional groups on ten-vertex monocarbaborane anionic compounds.

B(10)H(14) reacts with para-C(6)H(4)(CHO)(COOH) in aqueous KOH solution to give the [nido-6-CB(9)H(11)-6-(C(6)H(4)-para-COOH)](-) anion 1, which undergoes cage closure with iodine in alkaline solution to give the [closo-2-CB(9)H(9)-2-(C(6)H(4)-para-COOH)](-) anion 2. Upon heating, anion 2 rearranges to form the [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-COOH)](-) anion 3. Similarly, B(10)H(14) with glyoxylic acid OHCCOOH in aqueous KOH gives the [arachno-6-CB(9)H(13)-6-(COOH)](-) anion 4, which undergoes cage closure with iodine in alkaline solution to give the [closo-2-CB(9)H(9)-2-(COOH)](-) anion 5. Upon heating, anion 5 rearranges to give the [closo-1-CB(9)H(9)-1-(COOH)](-) anion 6. Reduction of the [COOH] anions 3 and 6 with diisobutylaluminium hydride gives the [CH(2)OH] hydroxy anions [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CH(2)OH)](-) and [closo-1-CB(9)H(9)-1-(CH(2)OH)](-) 8 respectively. The [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CH(2)OH)](-) anion 7 can also be made via isomerisation of the [closo-2-CB(9)H(9)-2-(C(6)H(4)-para-CH(2)OH)](-) anion 9, in turn obtained from the [nido-6-CB(9)H(11)-6-(C(6)H(4)-para-CH(2)OH)](-) anion 10, which is obtained from the reaction of B(10)H(14) with terephthaldicarboxaldehyde, C(6)H(4)-para-(CHO)(2), in aqueous KOH solution. Oxidation of the hydroxy anions 7 and 8 with pyridinium dichromate gives the aldehydic [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CHO)](-) anion 11 and the aldehydic [closo-1-CB(9)H(9)-1-(CHO)](-) anion 12 respectively, characterised as their 2,4-dinitrophenylhydrazone derivatives, the [closo-1-CB(9)H(9)-1-C(6)H(4)-para-CH=N-NHC(6)H(3)(NO(2))(2)](-) anion 13 and the [closo-1-CB(9)H(9)-1-CH=N-NHC(6)H(3)(NO(2))(2)](-) anion respectively.

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PubMed2004

Reactions of copper(II) salts with 3[5]-tert-butylpyrazole: double-cubane complexes with bound exogenous anions, and a novel pyrazole coordination mode.

Reaction of CuX(2) (X(-)=Cl(-), Br(-), NO(3) (-)), NaOH, and 3[5]-tert-butylpyrazole (Hpz(tBu)) in a 1:1:2 molar ratio in MeOH at 293 K for three days affords [[Cu(3)(Hpz(tBu))(6)(mu(3)-X)(mu(3)-OH)(3)](2)Cu]X(6) (X(-)=Cl(-), 1; X(-)=Br(-), 2; X(-)=NO(3)(-), 3) in moderate yields. These compounds contain a centrosymmetric, vertex-sharing double-cubane [[Cu(3)(Hpz(tBu))(6)(mu(3)-X)(mu(3)-OH)(3)](2)Cu](6+) core, surrounded by a belt of six hydrogen-bonded X(-) ions. For 1 and 2, the ring of guest anions has near C(3) symmetry, that is slightly distorted owing to the axis of Jahn-Teller elongation at the central Cu ion. For 3 only, the NO(3)(-) guest ions are crystallographically disordered, reflecting their poor complimentarity with complex host. A similar reaction employing CuF(2) yields [[Cu(3)(Hpz(tBu))(4)(mu-pz(tBu))(2)(mu-F)(2)(mu(3)-F)](2)]F(2) (4), whose structure contains a cyclic hexacopper core with approximate C(2v) symmetry. Finally, an analogous reaction using Cu(NCS)(2) gives a mixture of trans-[Cu(NCS)(2)(Hpz(tBu))(2)] (5) and [Cu(2)(NCS)(2)(mu-pz(tBu))(2)(mu-Hpz(tBu))(Hpz(tBu))(2)] (6). The latter compound contains a Hpzt(Bu) ligand bridging the two Cu ions in an unusual kappa(1),mu-coordination mode. The variable temperature magnetic properties of 1-3 show antiferromagnetic behavior, leading to a S=1/2 ground state in which the seven copper(II) ions are associated into three mutually independent distinct spin systems. In confirmation of this interpretation, Q-band EPR spectra of solid 1 and 2 at 5 K also demonstrate a S= 1/2 spin system and exhibit hyperfine coupling to three (63,65)Cu nuclei. Unusually, the coupling is manifest as an eight-line splitting of the parallel feature, rather than the usual 10 lines. This has been rationalized by a spin-projection calculation, and results from the relative magnitudes of coupling to the three Cu nuclei. UV/Vis and mass spectrometric data show that 1-4 decompose to lower nuclearity species in solution.

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PubMed2004

Tris[4-(1H-pyrazol-3-yl)-3-azabut-3-enyl]amine iron(II) diperchlorate monohydrate.

In the title complex, [Fe(C(18)H(24)N(10))](ClO(4))(2).H(2)O, the complex cation adopts a capped trigonal antiprismatic stereochemistry, with a long Fe-amine interaction [2.7468 (16) A]. The Fe centre in the asymmetric unit is fully high-spin at 100 K. Hydrogen bonding assembles dimeric units, which are then linked by further hydrogen bonding into chains running parallel to the crystallographic a axis.

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