SHELXT - integrated space-group and crystal-structure determination

Raising the (metastable) bar: 100% photo-switching in [Pd(Bu4dien)(η1-N̲O2)]+ approaches ambient temperature

Rapid, fully-reversible photo-switching is observed under near-ambient conditions for the first time in crystals of a novel palladium–nitrite linkage isomer.

Sterically-constrained tripodal phosphorus-bridged tris-pyridyl ligands

Substituents in the 6-position of the 2-pyridyl rings (py′) of neutral tris-pyridyl phosphanes of the type P(2-py′)₃ constrain the coordination sphere of metal ions and provide promising 6-electron capping ligands.

Aluminum complexes containing salicylbenzoxazole ligands and their application in the ring-opening polymerization of rac-lactide and ε-caprolactone

Two series of aluminum complexes supported by salicylbenzoxazole ligands were successfully synthesized and applied as active initiators for the ring-opening polymerization of rac-LA and ε-CL.

Iron(ii) β-ketiminate complexes as mediators of controlled radical polymerisation

A series of novel iron(ii) β-ketiminate complexes have been prepared and screened in styrene and methyl methacrylate CRP.

3d transition metal complexes with a julolidine–quinoline based ligand: structures, spectroscopy and optical properties

Five new complexes of a julolidine–quinoline based ligand with 3d transition metals have been synthesised and structurally characterised.

Bis(amido) rare-earth complexes coordinated by tridentate amidinate ligand: synthesis, structure and catalytic activity in the polymerization of isoprene and rac-lactide

Rare-earth bis(amides) {2-[Ph₂Р(O)]C₆H₄NC(tBu)N(2,6-Me₂C₆H₃)}Ln(N(SiMe₃)₂)₂ (Ln = Y, Nd, La) coordinated by tridentate amidinate ligand were synthesized, structurally characterized and evaluated as catalysts for isoprene and rac-lactide polymerizations.

Water-soluble β-aminobisulfonate building blocks for pH and Cu2+ indicators

Two phenyl β-aminobisulfonate ligands characterised by UV-visible absorption, EPR and ¹H NMR spectroscopy exhibit evidence for binding with Cu²⁺ in water and methanol.

A water-soluble Pd(ii) complex with a terpyridine ligand: experimental and molecular modeling studies of the interaction with DNA and BSA; and in vitro cytotoxicity investigations against five human cancer cell lines

[Pd(4-OHPh-tpy)Cl]Cl was prepared. The complex interacts with DNA via a combination of covalent, intercalation, and hydrogen bonding interactions.

Short contacts of the sulphur atoms of a 1,2,3,5-dithiadiazolyl dimer with triphenylstibine: first co-crystal with an aromatic compound

Co-crystallization of aromatic compounds with neutral dithiadiazolyl dimers has not previously succeeded. There is great scope here for crystal engineering using mutually compatible components.

Reversible cyclometalation at RhI as a motif for metal–ligand bifunctional bond activation and base-free formic acid dehydrogenation

The first example of base-free catalytic dehydrogenation of formic acid using reversible cyclometalation at Rh(i) is discussed, using a combination of experimental and computational methods.

Ru(ii)-p-cymene complexes containing esters of chiral d/l-phenylalanine derived aroylthiourea ligands for enantioselective reduction of pro-chiral ketones

The chiral Ru(ii)-p-cymene complexes are efficient catalysts for the enantioselective reduction of ketones to chiral alcohols.

Complexes of the tripodal phosphine ligands PhSi(XPPh2)3(X = CH2, O): synthesis, structure and catalytic activity in the hydroboration of CO2

The coordination chemistry of Fe²⁺, Co²⁺and Cu⁺ions was explored with the ligands PhSi{CH₂PPh₂}₃(1) and PhSi{OPPh₂}₃(2), so as to evaluate the impact of the electronic properties of the tripodal phosphorus ligands on the structure and reactivity of the corresponding complexes.

Water induced spin-crossover behaviour and magneto-structural correlation in octacyanotungstate(iv)-based iron(ii) complexes

The SCO is mainly tuned by the octahedral distortion of the [FeN₆] core caused by intermolecular hydrogen bonds, and there is an exact correlation between SCO behavior and the amount of lattice water molecules existing in the crystal.

Hydrothermal synthesis, structures and properties of two uranyl oxide hydroxyl hydrate phases with Co(ii) or Ni(ii) ions

Two new iso-structured uranyl oxide hydroxyl hydrate phases with hydroxyl Co²⁺or Ni²⁺ions at the interlayers have been synthesised under hydrothermal conditions and structurally characterised.

Synthesis, structure, magnetic and magnetocaloric properties of a series of {CrIII4LnIII} complexes

Magnetic properties and magnetocaloric effect of rare heterometallic Cr(iii)–Ln(iii) complexes are reported.

Steric versus electronic factors in metallacarborane isomerisation: nickelacarboranes with 3,1,2-, 4,1,2- and 2,1,8-NiC2B9 architectures and pendant carborane groups, derived from 1,1′-bis(o-carborane)

Nickelacarborane derivatives of 1,1′-bis(o-carborane) allow comment on the factors important in the isomerisation of metallacarboranes.

Bis-(benzothiazol-2-yl)-amines and their metal amides: a structural comparison in the solid state

A series of functionalised bis-(benzothiazol-2-yl)-amine ligands and the related dimethylaluminium amides were synthesised and characterised. The solid state structural comparison reveals various coordination motifs, specific folding parameters and hydrogen bonding patterns in detail and guide the way to future Janus head ligand design.

Self-assembly hydrogen-bonded supramolecular arrays from copper(II) halogenobenzoates with nicotinamide:Structure and EPR spectra‡

Nicotinamide was employed as a supramolecular reagent in the synthesis of six new copper(II) bromo-, iodo-, fluoro- and dibromobenzoate complexes. Structures of [Cu(2-Brbz)

Exploring the reactivity of manganese(III) complexes with diphenolate-diamino ligands in rac-lactide polymerization

Manganese(III) complexes of tetradentate diphenolate-diamino (NNOO(2-)) ligands were prepared from aerobic reaction of MnCl2 with the respective ligands in basic methanolic solution. Methoxide complexes (NNOO)Mn(OMe)(MeOH)0-1 were obtained for three ligands, while others only provided the respective chloride complexes (NNOO)Mn(Cl)(MeOH). Complexes were analyzed by X-ray diffraction studies and octahedral complexes showed evidence of Jahn-Teller distortions. Magnetic moments determined in MeOD were indicative of high-spin Mn(III)-d(4) complexes (μeff = 4.2-4.6μB). Methoxide complexes were active in the coordination-insertion polymerization of rac-lactide (130 °C, 0.33-1.0 mol% catalyst loading) to yield atactic polylactic acid with moderate molecular weight control. Polymerization activity was reduced, but not suppressed by the presence of protic impurities. Chloride complexes showed less activity and only in the presence of external alcohol, indicative of an activated-monomer mechanism.

Synthesis of New 2-Halo-2-(1H-tetrazol-5-yl)-2H-azirines via a Non-Classical Wittig Reaction

The synthesis and reactivity of tetrazol-5-yl-phosphorus ylides towards N-halosuccinimide/TMSN₃ reagent systems was explored, opening the way to new haloazidoalkenes bearing a tetrazol-5-yl substituent. These compounds were obtained as single isomers, except in one case. X-ray crystal structures were determined for three derivatives, establishing that the non-classical Wittig reaction leads to the selective synthesis of haloazidoalkenes with (Z)-configuration. The thermolysis of the haloazidoalkenes afforded new 2-halo-2-(tetrazol-5-yl)-2H-azirines in high yields. Thus, the reported synthetic methodologies gave access to important building blocks in organic synthesis, vinyl tetrazoles and 2-halo-2-(tetrazol-5-yl)-2H-azirine derivatives.

Compressed Corannulene in a Molecular Cage

Self-assembled coordination cages can be employed as a molecular press, where the bowl-shaped guest corannulene (C20H10) is significantly flattened upon inclusion within the hydrophobic cavity. This is demonstrated by the pairwise inclusion of corannulene with naphthalene diimide as well as by the dimer inclusion of bromocorannulene inside the box-like host. The compressed corannulene structures are unambiguously revealed by single-crystal X-ray analysis.

Group 6 metal pentacarbonyl complexes of air-stable primary, secondary, and tertiary ferrocenylethylphosphines

The synthesis and characterization of a series of Group 6 metal pentacarbonyl complexes of air stable primary, secondary, and tertiary phosphines containing ferrocenylethyl substituents are reported [M(CO)5L: M = Cr, Mo, W; L = PH2(CH2CH2Fc), PH(CH2CH2Fc)2, P(CH2CH2Fc)3]. The structure and composition of the complexes were confirmed by multinuclear NMR spectroscopy, IR and UV-Vis absorption spectroscopy, mass spectrometry, X-ray crystallography, and elemental analysis. The solid-state structural data reported revealed trends in M-C and M-P bond lengths that mirrored those of the atomic radii of the Group 6 metals involved. UV-Vis absorption spectroscopy and cyclic voltammetry highlighted characteristics consistent with electronically isolated ferrocene units including wavelengths of maximum absorption between 435 and 441 nm and reversible one-electron (per ferrocene unit) oxidation waves between 10 and -5 mV relative to the ferrocene/ferrocenium redox couple. IR spectroscopy confirmed that the σ donating ability of the phosphines increased as ferrocenylethyl substituents were introduced and that the tertiary phosphine ligand described is a stronger σ donor than PPh3 and a weaker σ donor than PEt3, respectively.

Structural and IR-spectroscopic characterization of magnesium acesulfamate

Magnesium acesulfamate, Mg(C4H4NO4S)2·6H2O, was prepared by the reaction of acesulfamic acid and magnesium carbonate in aqueous solution, and characterized by elemental analysis. Its crystal structure was determined by single crystal X-ray diffraction methods. The substance crystallizes in the triclinic space group P1̅ with one molecule per unit cell. The FTIR spectrum of the compound was also recorded and is briefly discussed. Some comparisons with other simple acesulfamate and saccharinate salts are also made.

Intramolecular C-C Bond Coupling of Nitriles to a Diimine Ligand in Group 7 Metal Tricarbonyl Complexes

Dissolution of M(CO)3(Br)(L(Ar)) [L(Ar) = (2,6-Cl2-C6H3-NCMe)2CH2] in either acetonitrile [M = Mn, Re] or benzonitrile (M = Re) results in C-C coupling of the nitrile to the diimine ligand. When reacted with acetonitrile, the intermediate adduct [M(CO)3(NCCH3)(L(Ar))]Br forms and undergoes an intramolecular C-C coupling reaction between the nitrile carbon and the methylene carbon of the β-diimine ligand.

Electronic Structure of a Mixed-Metal Fluoride-Centered Triangle Complex: A Potential Qubit Component

A novel fluoride-centered triangular-bridged carboxylate complex, [Ni2Cr(μ3-F)(O2C(t)Bu)6(HO2C(t)Bu)3] (1), is reported. Simple postsynthetic substitution of the terminal pivalic acids in 1 with pyridine and 4-methylpyridine led to the isolation of [Ni2Cr(μ3-F)(O2C(t)Bu)6(C5H5N)3] (2) and [Ni2Cr(μ3-F)(O2C(t)Bu)6((4-CH3)C5H4N)3] (3). Structural and magnetic characterizations carried out on the series reveal a dominating antiferromagnetic interaction between the nickel and chromium centers leading to an S = (1)/2 ground state with a very unusual value of geff = 2.48.

Dithio- and Diselenophosphinate Thorium(IV) and Uranium(IV) Complexes: Molecular and Electronic Structures, Spectroscopy, and Transmetalation Reactivity

We report a comparison of the molecular and electronic structures of dithio- and diselenophosphinate, (E2PR2)(1-) (E = S, Se; R = (i)Pr, (t)Bu), with thorium(IV) and uranium(IV) complexes. For the thorium dithiophosphinate complexes, reaction of ThCl4(DME)2 with 4 equiv of KS2PR2 (R = (i)Pr, (t)Bu) produced the homoleptic complexes, Th(S2P(i)Pr2)4 (1S-Th-(i)Pr) and Th(S2P(t)Bu2)4 (2S-Th-(t)Bu). The diselenophosphinate complexes were synthesized in a similar manner using KSe2PR2 to produce Th(Se2P(i)Pr2)4 (1Se-Th-(i)Pr) and Th(Se2P(t)Bu2)4 (2Se-Th-(t)Bu). U(S2P(i)Pr2)4, 1S-U-(i)Pr, could be made directly from UCl4 and 4 equiv of KS2P(i)Pr2. With (Se2P(i)Pr2)(1-), using UCl4 and 3 or 4 equiv of KSe2P(i)Pr2 yielded the monochloride product U(Se2P(i)Pr2)3Cl (3Se-U(iPr)-Cl), but using UI4(1,4-dioxane)2 produced the homoleptic U(Se2P(i)Pr2)4 (1Se-U-(i)Pr). Similarly, the reaction of UCl4 with 4 equiv of KS2P(t)Bu2 yielded U(S2P(t)Bu2)4 (2S-U-(t)Bu), whereas the reaction with KSe2P(t)Bu2 resulted in the formation of U(Se2P(t)Bu2)3Cl (4Se-U(tBu)-Cl). Using UI4(1,4-dioxane)2 and 4 equiv of KSe2P(t)Bu2 with UCl4 in acetonitrile yielded U(Se2P(t)Bu2)4 (2Se-U-(t)Bu). Transmetalation reactions were investigated with complex 2Se-U-(t)Bu and various CuX (X = Br, I) salts to yield U(Se2P(t)Bu2)3X (6Se-U(tBu)-Br and 7Se-U(tBu)-I) and 0.25 equiv of [Cu(Se2P(t)Bu2)]4 (8Se-Cu-(t)Bu). Additionally, 2Se-U-(t)Bu underwent transmetalation reactions with Hg2F2 and ZnCl2 to yield U(Se2P(t)Bu2)3F (6) and U(Se2P(t)Bu2)3Cl (4Se-U(tBu)-Cl), respectively. The molecular structures were analyzed using (1)H, (13)C, (31)P, and (77)Se NMR and IR spectroscopy and structurally characterized using X-ray crystallography. Using the QTAIM approach, the electronic structure of all homoleptic complexes was probed, showing slightly more covalent bonding character in actinide-selenium bonds over actinide-sulfur bonds.

Mometasone furoate revisited, or how did the hydrate get in the bottle?

The redetermined structure of 9α,21-dichloro-11β,17α-dihydroxy-16α-methyl-3,20-dioxopregna-1,4-dien-17-yl furan-2-carboxylate monohydrate, C27H32Cl2O7·H2O, at 100 K has triclinic (P1) symmetry. The structure displays O—H...O hydrogen bonding, which gives rise to infinite sheets extending parallel to the [110] plane. The previously published structure [Chenet al.(2005).J. Pharm. Sci.94, 2496–2509] was determined at room temperature and no significant anomalous signal was present. Data for the structure presented in this study were collected at low temperature and the absolute configuration could be established based solely on anomalous diffraction. Another point of interest is that the structure determined in this study is that of the monohydrate, even though the crystal was harvested from a bottle of nasal spray that was supposed to contain exclusively crystals of the anhydrous form.

Crystal structure of di-aqua-bis-(2,6-di-methyl-pyrazine-κN)bis-(thio-cyanato-κN)cobalt(II) 2,5-di-methyl-pyrazine tris-olvate

In the crystal structure of the title compound, [Co(NCS)2(C6H8N2)2(H2O)2]·3C6H8N2, the Co(II) cation is coordinated by two terminally N-bound thio-cyanate anions, two water mol-ecules and two 2,6-di-methyl-pyrazine ligands, forming a discrete complex with a slightly distorted octa-hedral N4O2 coordination environment. The asymmetric unit contains one Co(II) cation and three halves of 2,5-di-methyl-pyrazine solvate mol-ecules, all entities being completed by inversion symmetry, as well as one thio-cyanate anion, an aqua ligand and a 2,6-di-methyl-pyrazine ligand, all in general positions. In the crystal, discrete complexes are arranged in a way that cavities are formed where the noncoordinating 2,5-di-methyl-pyrazine mol-ecules are located. The coordination of the latter to the metal is prevented due to the bulky methyl groups in vicinal positions to the N atoms, leading to a preferential coordination through the 2,6-di-methyl-pyrazine ligands. The complex mol-ecules are linked by O-H⋯N hydrogen bonds between the water H atoms and the N atoms of 2,5-di-methyl-pyrazine solvent mol-ecules, leading to a layered structure extending parallel to (100).

Crystal structure of (5Z)-5-(2-hy-droxy-benzyl-idene)-1,3-thia-zolidine-2,4-dione

The title compound, C10H7NO3S, crystallizes with four independent mol-ecules in the asymmetric unit with slightly different conformations; the dihedral angles between the six- and five-membered rings are 2.6 (1), 1.09 (9), 8.6 (1) and 6.2 (1)°. In the crystal, mol-ecules are linked by O-H⋯O and N-H⋯O hydrogen bonds, forming sheets lying parallel to (101).

Crystal structure of phenyl N-(4-nitro-phen-yl)carbamate

The asymmetric unit of the title compound, C13H10N2O4, contains two independent mol-ecules (A and B). The dihedral angle between the aromatic rings is 48.18 (14)° in mol-ecule A and 45.81 (14)° in mol-ecule B. The mean plane of the carbamate N-C(=O)-O group is twisted slightly from the attached benzene and phenyl rings, making respective dihedral angles of 12.97 (13) and 60.93 (14)° in A, and 23.11 (14) and 59.10 (14)° in B. In the crystal, A and B mol-ecules are arranged alternately through N-H⋯O hydrogen bonds and C-H⋯π inter-actions, forming chains along the a axis. The chains are further linked by C-H⋯O hydrogen bonds into a double-chain structure.

Crystal structure of 2-amino-4-(4-meth-oxy-phen-yl)-4H-benzo[g]chromene-3-carbo-nitrile

In the title compound, C21H16N2O2, the naphthalene fragment is twisted slightly, as indicated by the dihedral angle of 3.2 (2)° between the two six-membered rings. The pendant 4-meth-oxy-phenyl ring makes a dihedral angle of 86.08 (6)° with the central six-membered ring of the 4H-benzo[g]chromene ring system. In the crystal, mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers which are linked into chains propagating in the b-axis direction by N-H⋯O hydrogen bonds.

Crystal structure of (4-meth-oxy-phen-yl)[(4-meth-oxy-phen-yl)phospho-nato]dioxidophosphate(1-) 2-amino-6-benzyl-3-eth-oxy-carbon-yl-4,5,6,7-tetra-hydro-thieno[2,3-c]pyridin-6-ium

The asymmetric unit of the title mol-ecular salt, C17H21N2O2S(+)·C14H15O7P2 (-), comprises two cations and two anions. Each cation features an intra-molecular N-H⋯O hydrogen bond, which closes an S(6) ring; in each case the hydro-pyridine ring adopts a half-chair conformation. In the anions, the dihedral angles between the aromatic rings are 64.1 (2) and 54.9 (2)°. In each case, the diphosphate groups are close to eclipsed [C-P⋯P-C pseudo-torsion angles = 11.6 (2) and -19.3 (2)°]. One of the meth-oxy groups in each anion is disordered over two orientations in a 0.539 (18):0.461 (18) ratio in one anion and 0.82 (2):0.18 (2) in the other. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the components into [100] chains. Numerous C-H⋯O inter-actions cross-link the chains into a three-dimensional network.

Crystal structure of 3-benzyl-1-[(cyclo-hexyl-idene)amino]-thio-urea

The conformation of the title compound, C14H19N3S, is partially determined by an intra-molecular N-H⋯N hydro-gen-bond inter-action, although the N-H⋯N angle of 108° is quite small. The cyclo-hexyl-idene ring has a chair conformation and its mean plane is inclined to the benzene ring by 46.30 (8)°. In the crystal, mol-ecules are linked by pairs of N-H⋯S hydrogen bonds, forming inversion dimers, with an R 2 (2)(8) ring motif. The dimers are reinforced by pairs of C-H⋯S hydrogen bonds, and are linked by further weak C-H⋯S hydrogen bonds, forming chains propagating along [100].

Crystal structures of two bis-(iodo-meth-yl)benzene derivatives: similarities and differences in the crystal packing

The isomeric derivatives 1,2-bis-(iodo-meth-yl)benzene, (I), and 1,3-bis-(iodo-meth-yl)benzene (II), both C8H8I2, were prepared by metathesis from their di-bromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bis-ects the C-C bond between the two iodo-methyl substituents. The packing in (I) relies solely on C-H⋯I hydrogen bonds supported by weak parallel slipped π-π stacking inter-actions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C-H⋯I hydrogen bonds are also found in the packing of (II), type II, I⋯I halogen bonds [I⋯I = 3.8662 (2) Å] and C-H⋯π contacts feature prominently in stabilizing the three-dimensional structure.

Crystal structure of 4-[(E)-(4-hy-droxy-benzyl-idene)amino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one

The asymmetric unit of the title compound, C18H17N3O2, comprises three independent mol-ecules (1, 2 and 3). In mol-ecule 1, the dihedral angles between the pyrazolone ring and the pendant phenyl and hydroxybenzene rings are 54.43 (6) and 28.72 (6)°, respectively. The corresponding data for mol-ecule 2 are 86.84 (6) and 25.69 (5)°, respectively, and for mol-ecule 3 are 47.41 (7) and 17.09 (7)°, respectively. The three mol-ecules feature an intra-molecular C-H⋯O inter-action, which closes an S(6) ring in each case. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, which generate [100] chains incorporating all three asymmetric mol-ecules. Two weak C-H⋯O interactions connect three independent molecules to each other along the c-axis direction.

Crystal structure of 4-benzyl-2H-benzo[b][1,4]thia-zin-3(4H)-one

In the title compound, C15H13NOS, the thia-zine ring adopts a twisted boat conformation and the dihedral angle between the aromatic rings is 86.54 (4)°. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions, resulting in chains along [010].

Crystal structure of tris-(N-methyl-salicylaldiminato-κ(2) N,O)vanadium(III)

The structure of the title complex, [V(C8H8NO)3], comprises neutral and discrete complexes, in which the V(III) cation is coordinated by three anionic N-methyl-alicylaldiminate ligands within a slightly distorted mer-N3O3 octa-hedral geometry. In the crystal structure, the mol-ecules are linked via C-H⋯O hydrogen bonds into supra-molecular chains that extend along the c axis.

Crystal structure of {bis-[(1H-benzimid-azol-2-yl-κN (3))meth-yl]sulfane}dichloridomercury(II)

In the asymmetric unit of the title compound, [HgCl2(C16H14N4S)], the Hg(II) cation is linked to two Cl atoms and two imidazole N atoms of the chelating bis-[(1H-benzimidazol-2-yl)meth-yl]sulfane ligand, forming a slightly distorted tetra-hedral environment. The substitued imidazole rings of the ligand are almost perfectly planar [with maximum deviations of 0.017 (3) and 0.012 (3) Å] and form a dihedral angle of 42.51 (5)°. The crystal packing can be described as alternating layers parallel to (010). In this arrangement, N-H⋯Cl hydrogen bonds between the N-H groups of the benzimidazole moieties and chloride ligands are responsible for the formation of the chain-like packing pattern along [010] exhibiting a C(6) graph-set motif.

Crystal structure of tris-(μ-bis-{4-[(pyridin-2-yl-methyl-idene)amino]-phen-yl}methane-κ(4) N,N':N'',N''')dizinc tetra-kis-(tetra-fluorido-borate) aceto-nitrile tris-olvate

The asymmetric unit of the title compound, [Zn2(C25H20N4)3](BF4)4·3CH3CN, consists of one dinuclear Zn(II) complex cation with a triple-helical [Zn2 L 3](4+) motif (L is bis-{4-[(pyridin-2-yl-methyl-idene)amino]-phen-yl}methane), four BF4 (-) anions and three CH3CN solvent mol-ecules. The Zn⋯Zn separation is 11.3893 (14) Å and the ligands wrap around the two Zn(II) atoms, forming a triple helix as defined by the Zn-N-N-Zn torsion angles of 104.05 (18), 99.06 (19) and 101.40 (19)°. The Zn-N(pyrid-yl) distances in the octahedral ZnN6 coordination sphere are in the range 2.128 (5)-2.190 (5) Å and the Zn-N(imine) distances are in the range 2.157 (5)-2.277 (5) Å.