Search

Four easily isolable bis-pyrrolidine-C70 regioisomers were synthesized and characterized by spectroscopic techniques. The four [70]fullerene bis-adducts were unambiguously assigned using spectroscopic techniques and X-ray crystallography, as the β-2-β, α-2-α, α-1-β and α-1-α regioisomers.

A new 30-center Ga(III)-oxy-hydroxide cation cluster was synthesized by hydrolysis of an aqueous GaCl3 solution near pH = 2.5 and crystallized using 2,6-napthalene disulfonate (NDS). The cluster has 30 metal centers and a nominal stoichiometry: [Ga30(μ4-O)12(μ3-O)4(μ3-OH)4(μ2-OH)42(H2O)16](2,6-NDS)6, where 2,6-NDS = 2,6-napthalene disulfonate This cluster augments the very small library of Group 13 clusters that have been isolated from aqueous solution and closely resembles one other Ga(III) cluster with 32 metal centers that had been isolated using curcurbit ligands. These clusters have uncommon linked Ga(O)4 centers and sets of both protonated and unprotonated μ3-oxo.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. By combining two chemical methods of purification, 4mg of purified CeLu2N at C80 was readily isolated from 500mg of carbon soot extract without the use of recycling HPLC, a method which has previously been necessary to obtain pure samples of endohedral fullerenes. In stage1, CeLu2N at C80 was selectively precipitated by virtue of its low first oxidation potential (+0.01V) and the judicious choice of MgCl2 as the Lewis acid precipitant. For stage2, we used a stir and filter approach (SAFA), which employed the electron-rich NH2 groups immobilized on silica gel to selectively bind residual endohedrals and higher cage fullerenes that were contaminants from stage1. Crystallographic analysis of CeLu2N at C80 in the co-crystal CeLu2N at Ih-C80Ni(octaethylporphyrin)2(toluene) reveals that the Ih-C80 cage is present with a pyramidalized CeLu2N unit inside.

Ag(I)-Ag(I) interactions in supramolecular structures have been achieved through the use of structural support from the ligand frames. In structures involving simple ligands like pyridine, strong π-π interaction leads to spatial ordering of the individual [Ag(L)2]+ units. In such structures anions also play a crucial role in dictating the final arrangement of the [Ag(L)2]+ synthons. In order to determine whether the anions can solely dictate the arrangement of the [Ag(L)2]+ synthons in the supramolecular structure, four Ag(I) complexes of 4-pyridylcarbinol (PyOH), namely, [Ag(PyOH)2]X (X = NO3- (1), BF4- (2), CF3SO3- (3), and ClO4- (4)) have been synthesized and structurally characterized. Gradual transformation of the extended structures observed in 1-3 eventually merges into a unique linear alignment of the [Ag(PyOH)2]+ units in 4 along the c axis, a feature that results in strong argentophilic interactions. Complex 4 is sensitive to light and is inherently less stable than the other three analogues. The structural variations in this set of extended assemblies are solely dictated by the anions, since π-π interaction between the substituted pyridine ligands is significantly diminished due to disposition of the -CH2OH substituent at the 4 position and H-bonding throughout the structure.

The structure of the title compound octa-kis-{[4-(dimethyl-amino)-pyridine](nitros-yl)[N,N'-(o-phenyl-ene)bis-(pyridine-2-carboxamidato)]manganese(II)} ethanol hepta-solvate 3.5-hydrate, [Mn(C(18)H(12)N(4)O(2))(C(7)H(10)N(2))(NO)](8)·7C(2)H(5)OH·3.5H(2)O, or 8[Mn(bpb)(DMAP)(NO)]·7EtOH·3.5H(2)O, is an unusual example of a structure with Z' = 8. The tetra-dentate bpb ligand, together with the nitrosyl and dimethyl-amino-pyridine ligands, gives rise to a distorted octa-hedral coordination environment for the Mn(II) ion. The average Mn-N((N=O)) bond length is 1.631 (13) Å. The eight mol-ecules in the asymmetric unit differ mainly in the rotation of the DMAP pyridine plane with respect to a reference plane of the Mn and three N atoms, one of which is the N atom of the NO group. The dihedral angles between the normals to these planes range from a minimum of 28.0 (2)° to a maximum of 64.2 (2)°. There are also some differences in O-H⋯O hydrogen bonding inter-actions. For example, of the sixteen C=O acceptors, there are seven different inter-actions with EtOH donors and two inter-actions with H(2)O donors. The crystal studied was found to be a two-component twin, with a 179.9° rotation about the real axis [-0.535, 0.004, 1.000]. Due to the presence of a superlattice and, consequently, the large number of weak reflections, the refinement utilized rigid solvate groups and isotropic displacement parameters for all except the Mn atoms. H atoms were not located for hydrate molecules.

The title compound, [Mn(2)O(2)(C(10)H(24)N(4))(2)](C(24)H(20)B)(2)Cl·2CH(3)CN, is a mixed-valent Mn(III)/Mn(IV) oxide-bridged mangan-ese dimer with one chloride and two tetra-phenyl-borate counter-anions. There are two non-coordinated mol-ecules of acetonitrile in the formula unit. A center of inversion is present between the two metal atoms, and, consequently, there is no distinction between Mn(III) and Mn(IV) metal centers. In the Mn(2)O(2) core, the Mn-O distances are 1.817 (3) and 1.821 (3) Å. The cyclam ligand is in the cis configuration. The chloride counter-anion resides on a center of symmetry, whereas the tetra-phenyl-borate counter-anion is in a general position. The cyclam ligand is hydrogen bonded to the acetonitrile as well as to the chloride anion. One of the phenyl rings of the anion and the acetonitrile solvent molecule are each disordered over two sets of sites.

The centrosymmetric title cluster, hexa-aquadi-μ(3)-carbonato-hexa-cyclamhexa-μ(2)-hydroxido-dodeca-μ(2)-oxido-hexa-mang-an-ese(IV)hexa-manganese(III) octa-chloride tetra-cosa-hydrate, [Mn(12)(CO(3))(2)O(12)(OH)(6)(C(10)H(24)N(4))(6)(H(2)O)(6)]Cl(8)·24H(2)O, has two μ(3)-CO(3) groups that not only bridge octahedrally coordinated Mn(III) ions but also act as acceptors to two different kinds of hydrogen bonds. The carbonate anion is planar within experimental error and has an average C-O distance of 1.294 (4) Å. The crystal packing is stabilized by O-H⋯Cl, O-H⋯O, N-H⋯Cl and N-H⋯O hydrogen bonds. Two of the four independent chloride ions are disordered over five positions, and eight of the 12 independent water mol-ecules are disordered over 21 positions.

The title compound, {[BaPt(CN)(4)(C(12)H(26)N(2)O(4))]·0.5H(2)O}(n), is a two-dimensional coordination polymer in which the sheets are oriented approximately parallel to the (01) set of crystal planes. In the crystal structure, disordered water mol-ecules (half occupancy) connect the sheets into a three-dimensional network via inter-molecular O-H⋯O hydrogen bonds. An N-H⋯N inter-action is also present. The shortest Pt⋯Pt contacts are 7.5969 (4) Å by an inversion relationship and 7.6781 (4) Å by translation along the a axis.

The structure of the title compound, poly[triaquatetra-μ-cyanido-tetracyanidobis-(1,4,10,13-tetra-oxa-7,16-diaza-cyclo-octa-deca-ne)di-barium(II)tetra-gold(I)], [Au(4)Ba(2)(CN)(8)(C(12)H(26)N(2)O(4))(2)(H(2)O)(3)](n), displays O-H⋯N hydrogen bonding between water molecules and cyano ligands and an unusual pattern of aurophilic inter-actions that yields a monomer, dimer, and trimer of [Au(CN)(2)](-) within the same crystal structure. In two of the five Au positions, the atom resides on a center of inversion. The overall arrangement is that of a coordination polymer assisted by aurophilic and hydrogen-bonded inter-actions.

The title compound, [Co(C(21)H(22)NO)(2)], crystallizes with two mol-ecules in the asymmetric unit. The coordination environments of the two Co(II) ions are distorted tetra-hedral. The primary structural difference between the two independent complex mol-ecules lies in the orientations of their adamantyl groups.

We present the inaugural synthesis of a chiral teropyrene achieved through a four-fold alkyne benzannulation catalyzed by InCl 3 , resulting in good yields. The product underwent thorough characterization using FT-Raman and FT-IR spectroscopies, demonstrating a close agreement with calculated spectra. X-ray crystallographic analysis unveiled a notable twist in the molecule's backbone, with an end-to-end twist angle of 51°, consistent with computational predictions. Experimentally determined enantiomeric inversion barriers revealed a significant energy barrier of 23 kcal/mol, facilitating the isolation of enantiomers for analysis by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopies. These findings mark significant strides in the synthesis and characterization of chiral teropyrenes, offering insights into their structural and spectroscopic properties., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report the ability to trap the dimer Au 2 (μ-dppe) 2 I 2 (dppe is 1,2-bis(diphenylphosphino)ethane) with different separations between the three-coordinate gold ions in crystalline solvates. All of these solvates ((Au 2 (μ-dppe) 2 I 2 ·4(CH 2 Cl 2 ) ( 1 ), Au 2 (μ-dppe) 2 I 2 ·2(CH 2 Cl 2 ) ( 2 ), the polymorphs α-Au 2 (μ-dppe) 2 I 2 ·2(HC(O)NMe 2 ) ( 3 ) and β-Au 2 (μ-dppe) 2 I 2 ·2(HC(O)NMe 2 ) ( 4 ), and Au 2 (μ-dppe) 2 I 2 ·4(CHCl 3 ) ( 5 )) along with polymeric {Au(μ-dppe)I} n · n (CHCl 3 ) ( 6 )) originated from the same reaction, only the solvent system used for crystallization differed. In the different solvates of Au 2 (μ-dppe) 2 I 2 , the Au···Au separation varied from 3.192(1) to 3.7866(3) Å. Computational studies undertaken to understand the flexible nature of these dimers indicated that the structural differences were primarily a result of crystal packing effects with aurophillic interactions having a minimal effect.

A section in the Acta Crystallographica Section C article by Raymond & Girolami [Acta Cryst. (2023), C79, 445-455] stated that the product of the reaction of [(Cp*Rh) 2 (μ-OH) 3 ] + (Cp* is 1,2,3,4,5-pentamethylcyclopentadiene) with 1-methylthymine (1-MT) at pH 10 and 60 °C, to synthesize the anionic component [Rh I (η 1 -N 3 -1-MT) 2 ] - , was not an Rh I complex, but rather an Ag I complex, due to the use of silver triflate (AgOTf) to remove Cl - from [Cp*RhCl 2 ] 2 to synthesize [Cp*Rh(H 2 O) 3 ](OTf) 2 , a water-soluble crystalline complex. We will clearly show that this premise, as stated, is invalid, while the authors have simply avoided several important facts, including that Cp*OH, a reductive elimination product, at pH 10 and 60 °C, was unequivocally identified, thus leading to the Rh I anionic component [Rh I (η 1 -N 3 -1-MT) 2 ] - . More importantly, AgOH, from the reaction of NaOH at pH 10 with any potentially remaining AgOTf, after the AgCl was filtered off, would be insoluble in water. Furthermore, a control experiment with the inorganic complex Rh(OH) 3 , reacting with 1-methylthymine at pH 10, provided no product, and this bodes well for a similar fate with AgOTf and 1-methylthymine, i.e. at pH 10, AgOTf would again be converted to the water-insoluble AgOH; therefore, no reaction would occur! Finally, a 1 H NMR spectroscopy experiment was carried out with synthesized and crystallized [Cp*Rh(H 2 O) 3 ](OTf) 2 in D 2 O at various pD values; at pD 8.65 no reaction took place, while at pD 13.6, and at 60 °C for 2 h, a reductive elimination reaction caused the precipitation of Cp*OH. The subsequent 1 H NMR spectrum clearly demonstrated, in the absence of any Ag I complexes, that the solution structure and the X-ray crystals in D 2 O were similar. A postulated mechanism for this novel anionic component structure, as published previously [Smith et al. (2014). Organometallics, 33, 2389-2404], will be presented, along with the experimental data, to insure the credibility of our results. We will also answer the comments in the response of Drs Raymond and Girolami to this rebuttal.

Six salts ([Au 2 (μ-dppe) 2 ](BF 4 ) 2 ·CHCl 3 , [Au 2 (μ-dppe) 2 ](BF 4 ) 2 ·1,2-Cl 2 C 2 H 4 , [Au 2 (μ-dppe) 2 ](PF 6 ) 2 ·CHCl 3 , [Au 2 (μ-dppe) 2 ](PF 6 ) 2 , [Au 2 (μ-dppe) 2 ](SbF 6 ) 2 , and [Au 2 (μ-dppe) 2 ](OTf) 2 ·2CHCl 3 ), (dppe is bis(diphenylphosphine)ethane) containing the dication, [Au 2 (μ-dppe) 2 ] 2+ , have been prepared and structurally characterized by single-crystal X-ray crystallography. Unlike the three-coordinate dppe-bridged dimers, Au 2 X 2 (μ-dppe) 2 (X = Br, I), which show considerable variation in the distance between the gold(I) ions over the range 3.0995(10) to 3.8479(3) Å in various solvates, the structure of the helical dication, [Au 2 (μ-dppe) 2 ], in the new salts is remarkably consistent with the Au···Au separation falling in the narrow range 2.8787(9) to 2.9593(5) Å. In the solid state, the six crystals display a green luminescence both at room temperature and at 77 K, which has been assigned as phosphorescence. However, solutions of the dication are not luminescent. Salts containing the analogous dication [Au 2 (μ-dppp) 2 ](PF 6 ) 2 (dppp is bis(diphenylphosphine)propane) have been prepared to determine whether the longer bridging ligand might also twist into a helical shape. These salts include [Au 2 (μ-dppp) 2 ](OTf) 2 (OTf is triflate) and three crystalline forms of [Au 2 (μ-dppp) 2 ](PF 6 ) 2 : the solvate [Au 2 (μ-dppp) 2 ](PF 6 ) 2 ·(CHCl 3 ) and two polymorphs of the unsolvated salt. None of these crystals are luminescent, but all contain a similar dication, [Au 2 (μ-dppp) 2 ] 2+ , that contains two nearly parallel, linear P-Au-P groups and a long separation between the gold ions that varies from 5.3409(4) to 5.6613(6)Å.

Terbium has been added to the list of elements that form oxide clusters inside fullerene cages. Tb 2 O@ C 2 (13333)-C 74 has been isolated as a byproduct of the electric arc synthesis of the azafullerene Tb 2 @C 79 N. Cocrystallization of Tb 2 O@ C 2 (13333)-C 74 with Ni(OEP) (where OEP is the dianion of octaethylporphyrin) in toluene yielded black needles of Tb 2 O@ C 2 (13333)-C 74 ·Ni II (OEP)·1.5C 7 H 8 that have been examined by single-crystal X-ray diffraction. The resulting structure shows that a nearly linear Tb-O-Tb unit is contained in a C 2 (13333)-C 74 , which has two sites where pentagons share an edge to form pentalene units at opposite ends of the fullerene. Unlike the usual situations where metal atoms in fullerenes that do not obey the isolated pentagon rule are situated within the folds of the pentalene units, the Tb atoms in Tb 2 O@ C 2 (13333)-C 74 are positioned to the side of the pentalene units and near-neighboring hexagons. The magnetic properties of Tb 2 O@ C 2 (13333)-C 74 have been examined starting from the experimental geometry, using ab-initio multiconfigurational methods. The computations predict that Tb 2 O@ C 2 (13333)-C 74 will show strong axiality, which would make it a single-molecule magnet with a large magnetic anisotropy barrier.

Four Schiff base ligands of the general formulas [6-( R )-2-pyridyl- N -(2'-methylthiophenyl)methylenimine] ( R L1) and 6- p -chlorophenyl-2-pyridyl- N -(2'-phenylthiophenyl)methylenimine ( R L2), where R = H, Me, p -ClPh, and their bis-ligand copper(II) and copper(I) complexes, 1 - 4 and 1' - 4' , respectively, were synthesized and characterized. The reactivities of 1 - 4 with nitric oxide (NO) gas and of 1' - 4' with solid NOBF 4 (NO + ) were examined in dry acetonitrile in the presence and absence of water (H 2 O). The results revealed that, in the absence of H 2 O , complexes 1 - 4 (or 1' - 4' ) reacts with NO (or NOBF 4 ), leading to imine C═N bond cleavage of both (or one) Schiff base(s) that generates 2 (or 1) equiv of 2-(methyl/phenyl)thiobenzenediazonium perchlorates ( 5 / 6 ) and the corresponding picolaldehyde ( R Pial) via a copper nitrosyl of a {CuNO} 10 -type intermediate. In the presence of H 2 O , the in situ formed R Pial get oxidized to the corresponding picolinic acid ( R PicH) via an in situ formed LCu I OH intermediate (LCu I + HO-NO → LCu I OH + NO + ; L = R L1/ R L2/ R Pic - and ν O-H of Cu I OH = 3650 cm -1 ) and subsequently produces, with the aid of NO + oxidant, the picolinate-ligated copper(II) complexes (i) [( H Pic) 2 Cu] ( 7 ), [( Me Pic) 4 Cu 3 (NO 3 ) 2 ] n ·H 2 O ( 8 ·H 2 O), or [( ClPh Pic) 2 Cu] ( 9 ) when NO reacts with 1 - 4 or (ii) [( R Pic)Cu II ( R L1/ R L2)] + when NO + reacts with 1' - 4' . The Cu II to Cu I reduction of [( R Pic)Cu II ( R L1/ R L2)] + is essential for C═N cleavage of the remaining R L1/ R L2 Schiff base; excess NO can do it. The X-ray structures ( 1 , 1' , 3' , 5 , 7 , and 8 ) and spectroscopic results revealed the role of Cu II/I , NO, NO + , and H 2 O, shedding light on the mechanism of C═N bond cleavage and the oxidation of pyridine-2-aldehyde to pyridine-2-carboxylic acid. The reaction of 1 with 15 NO revealed that the terminal N of the N 2 + group of 5 originates from 15 NO [ν 14 N 14 N- = 2248 cm -1 and ν 15 N 14 N- = 2212 cm -1 ].

Treatment of an open-cage fullerene, designated as MMK-9, with (Ph 3 P) 4 Pt in toluene solution at room temperature allows a (PPh 3 ) 2 Pt unit to be incorporated into the rim of the cage so that it becomes an integral part of the carbon cage skeleton. The structure of the adduct has been determined by single crystal X-ray diffraction and reveals that the platinum atom has planar PtC 2 P 2 coordination, rather than the usual η 2 -bonding to an intact C-C double bond of the fullerene.

With aromatic and aliphatic thiol-S donor Schiff base ligands, the copper-sulfur clusters, [(L1) 8 Cu I 6 Cu II 2 ](ClO 4 ) 2 ·DMF·0.5CH 3 OH ( 1 ) and [(L2) 12 Cu I 5 Cu II 11 (μ 4 -S)(μ 4 -O) 6 ](ClO 4 )·4H 2 O, respectively, have been reported ( Chem. Commun. 2017, 53, 3334); HL1/HL2 are 2-(((3-methylthiophen-2-yl)methylene)amino)benzene/ethanethiol). Complex 1 comprises a wheel shaped Cu 8 S 8 framework, made up of interlinked Cu 2 {μ-S(R)} 2 units. To understand the properties with relevance to the Cu A site and to check whether self-assembly generates similar type clusters to 1 , three complexes, [(L3) 8 Cu I 6 Cu II 2 ](ClO 4 ) 2 ·(C 2 H 5 ) 2 O·2.5H 2 O ( 2 ), [(L3 Cl ) 8 Cu I 6 Cu II 2 ](ClO 4 ) 2 ·1.25(C 2 H 5 ) 2 O·1.25CH 3 OH·2H 2 O ( 3 ), and [(L3 CF3 ) 8 Cu I 6 Cu II 2 ](ClO 4 ) 2 ·2(C 2 H 5 ) 2 O·H 2 O ( 4 ) have been synthesized with supporting ligands HL3 X (HL3 = 2-((furan-2-ylmethylene)amino)benzenethiol when X = -H; X = -Cl or -CF 3 para to thiol-S are HL3 Cl and HL3 CF3 ligands, respectively). The X-ray structures of 3 and 4 feature a similar Cu 8 S 8 architecture to 1 . The spectroscopic properties and the X-ray structures revealed that 2 - 4 are fully spin delocalized mixed valence (MV) of class-III type clusters. The structural parameters of the N 2 Cu 2 {μ-S(R)} 2 units of 3 and 4 closely resemble those of the MV binuclear Cu A site. With the aid of UV-vis-NIR, EPR, and spectroelectrochemical studies, the electronic properties of these complexes have been described in comparison with the MV model complexes and Cu A site.

The discovery of a third, non-luminescent crystalline polymorph of [(C6H11NC)2Au]PF6 is reported. Remarkably, crystals of this polymorph are sensitive to mechanical pressure or to exposure to dichloromethane vapor. In both cases, the conversion produces the yellow, green luminescent polymorph of [(C6H11NC)2Au]PF6 and not the colorless, blue luminescent polymorph.

Cocrystallization of NiII(OEP) (where OEP is the dianion of octaethylporphyrin) with C70 in p-xylene produces black plates of 12NiII(OEP)·12C70·18p-xylene (1). Single crystal X-ray diffraction at 90 K reveals that the crystal contains 42 individual, well-ordered molecules in the asymmetric unit with distinctive interactions between each NiII(OEP)/C70 pair and each pair of neighboring C70 molecules. Warming the crystal to 186 K produces a phase change so that only four NiII(OEP)/C70 sites and six p-xylene molecules are present. Under the same conditions CuII(OEP) cocrystallizes with C70 to form CuII(OEP)·C70·1.5p-xylene (2) with a much simpler structure consisting of one molecule of the porphyrin and the fullerene along with 1.5 molecules of p-xylene in the asymmetric unit. Crystallization of C70 from toluene in the presence of NiII(etioporphyrin-I) produces the black solvate 6C70·6toluene (3). It seems that C70 has a tendency to crystallize so that several orientations of the oblong molecule are present in the solid.

Non-luminescent, isostructural crystals of [(C 6 H 11 NC) 2 Au](EF 6 )·C 6 H 6 (E = As, Sb) lose benzene upon standing in air to produce green luminescent (E = As) or blue luminescent (E = Sb) powders. Previous studies have shown that the two-coordinate cation, [(C 6 H 11 NC) 2 Au] + , self-associates to form luminescent crystals that contain linear or nearly linear chains of cations and display unusual polymorphic, vapochromic, and/or thermochromic properties. Here, we report the formation of non-luminescent crystalline salts in which individual [(C 6 H 11 NC) 2 Au] + ions are isolated from one another. In [(C 6 H 11 NC) 2 Au](BArF 24 ) ((BArF 24 ) - is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) each cation is surrounded by two anions that prohibit any close approach of the gold ions. Crystallization of [(C 6 H 11 NC) 2 Au](EF 6 ) (E = As or Sb, but not P) from benzene solution produces colorless, non-emissive crystals of the solvates [(C 6 H 11 NC) 2 Au](EF 6 )·C 6 H 6 . These two solvates are isostructural and contain columns in which cations and benzene molecules alternate. With the benzene molecules separating the cations, the shortest distances between gold ions are 6.936(2) Å for E = As and 6.9717(19) Å for E = Sb. Upon removal from the mother liquor, these crystals crack due to the loss of benzene from the crystal and form luminescent powders. Crystals of [(C 6 H 11 NC) 2 Au](SbF 6 )·C 6 H 6 that powder out form a pale yellow powder with a blue luminescence with emission spectra and powder X-ray diffraction data that show that the previously characterized [(C 6 H 11 NC) 2 Au](SbF 6 ) is formed. In the process, the distances between the gold(i) ions decrease to ∼3 Å and half of the cyclohexyl groups move from an axial orientation to an equatorial one. Remarkably, when crystals of [(C 6 H 11 NC) 2 Au](AsF 6 )·C 6 H 6 stand in air, they lose benzene and are converted into the yellow, green-luminescent polymorph of [(C 6 H 11 NC) 2 Au](AsF 6 ) rather than the colorless, blue-luminescent polymorph. Paradoxically, the yellow, green-luminescent powder that forms as well as authentic crystals of the yellow, green-luminescent polymorph of [(C 6 H 11 NC) 2 Au](AsF 6 ) are sensitive to benzene vapor and are converted by exposure to benzene vapor into the colorless, blue-luminescent polymorph., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

According to the well-accepted mechanism, methyl-coenzyme M reductase (MCR) involves Ni-mediated thiolate-to-disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni-ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of Ni II complexes comprising a tridentate N 2 S donor thiol and its analogous N 4 S 2 donor disulfide ligands. These complexes demonstrate reversible Ni II -thiolate/Ni II -disulfide (both bound and unbound disulfide-S to Ni II ) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Noncoordinating anions, which generally play a subordinate role in coordination chemistry, alter the structure, the luminescence, as well as the thermochromic and vapochromic behaviors of salts of the two-coordinate cation, [(C 6 H 11 NC) 2 Au] + . Thus whereas the yellow polymorphs of [(C 6 H 11 NC) 2 Au](PF 6 ) and [(C 6 H 11 NC) 2 Au](AsF 6 ) contain single chains of cations and are vapochromic, yellow [(C 6 H 11 NC) 2 Au](SbF 6 ) does not form the same polymorph and is not vapochromic but contains two distinct chains of cations connected through aurophilic interactions. Mixed crystals such as [(C 6 H 11 NC) 2 Au](PF 6 ) 0.50 (AsF 6 ) 0.50 have been prepared by adding diethyl ether to a dichloromethane solution containing equimolar amounts of [(C 6 H 11 NC) 2 Au](PF 6 ) and [(C 6 H 11 NC) 2 Au](AsF 6 ). The initial (kinetic) product for the three combinations of anions ((PF 6 ) - /(AsF 6 ) - , (PF 6 ) - /(SbF 6 ) - , and (AsF 6 ) - /(SbF 6 ) - ) was a precipitate of fine yellow needles with a green emission, which were gradually transformed at rates that depended on the anions present into colorless crystals with a blue emission. Whereas neither polymorph of [(C 6 H 11 NC) 2 Au](PF 6 ) nor [(C 6 H 11 NC) 2 Au](SbF 6 ) is thermochromic, the colorless mixed crystal [(C 6 H 11 NC) 2 Au](PF 6 ) 0.50 (SbF 6 ) 0.50 is thermochromic and converts from blue-emitting to green-emitting at 87-95 °C. The temperature required to transform a crystal of the type [(C 6 H 11 NC) 2 Au](PF 6 ) n (AsF 6 ) 1- n from colorless (blue-emitting) to yellow (green-emitting) increases as the fraction of hexafluorophosphate ion in the crystal increases. The yellow crystals of [(C 6 H 11 NC) 2 Au](PF 6 ) 0.75 (AsF 6 ) 0.25 , [(C 6 H 11 NC) 2 Au](PF 6 ) 0.50 (AsF 6 ) 0.50 , and [(C 6 H 11 NC) 2 Au](PF 6 ) 0.25 (AsF 6 ) 0.75 are vapochromic, whereas the yellow crystals of [(C 6 H 11 NC) 2 Au](PF 6 ) 0.50 (SbF 6 ) 0.50 and [(C 6 H 11 NC) 2 Au](AsF 6 ) 0.50 (SbF 6 ) 0.50 are not.

The unsymmetrical coordination of gold(I) by 2,2'-bipyridine (bipy) in some planar, three-coordinate cations has been examined by crystallographic and computational studies. The salts [(Ph 3 P)Au(bipy)]XF 6 (X = P, As, Sb) form an isomorphic series in which the differences in Au-N distances range from 0.241(2) to 0.146(2) Å. A second polymorph of [(Ph 3 P)Au(bipy)]AsF 6 has also been found. Both polymorphs exhibit similar structures. The salts [(Et 3 P)Au(bipy)]XF 6 (X = P, As, Sb) form a second isostructural series. In this series the unsymmetrical coordination of the bipy ligand is maintained, but the gold ions are disordered over two unequally populated positions that produce very similar overall structures for the cations. Although many planar, three-coordinate gold(I) complexes are strongly luminescent, the salts [(R 3 P)Au(bipy)]XF 6 (R = Ph or Et; X = P, As, Sb) are not luminescent as solids or in solution. Computational studies revealed that a fully symmetrical structure for [(Et 3 P)Au(bipy)] + is 7 kJ/mol higher in energy than the observed unsymmetrical structure and is best described as a transition state between the two limiting unsymmetrical geometries. The Au-N bonding has been examined by natural resonance theory (NRT) calculations using the "12 electron rule". The dominant Lewis structure is one with five lone pairs on Au and one bond to the P atom, which results in a saturated (12 electron) gold center and thereby inhibits the formation of any classical, 2 e - bonds between the gold and either of the bipy nitrogen atoms. The nitrogen atoms may instead donate a lone pair into an empty Au-P antibonding orbital, resulting in a three-center, four-electron (3 c /4e) P-Au-N bond. The binuclear complex, [μ 2 -bipy(AuPPh 3 ) 2 ](PF 6 ) 2 , has also been prepared and shown to have an aurophillic interaction between the two gold ions, which are separated by 3.0747(3) Å. Despite the aurophillic interaction, this binuclear complex is not luminescent.

The averages (average deviations from the mean are given in square brackets) of uncorrected Cl-O bond distances in a perchlorate anion from an X-ray diffraction analysis of (N-{2-[bis(pyridin-2-ylmethyl)amino]ethyl}pyridine-2-carboxamidato)(nitric oxide)manganese perchlorate acetonitrile disolvate, [Mn(C 20 H 20 N 5 O)(NO)]ClO 4 ·2CH 3 CN or [Mn(PaPy 3 )(NO)]ClO 4 ·2CH 3 CN, decrease from 1.447 [4] Å at 10 K to 1.428 [4] Å at 170 K. The 10 K value is close to the neutron value (1.441 [1] Å) at 18 K. Comparisons are made with a second X-ray study at 30 K [1.444 (8) Å] and to libration-corrected, density functional theory (DFT), and Cambridge Structural Database (CSD) values.

The synthesis of pyreno[ a ]pyrene-based helicene hybrids was achieved in good yield via a four-fold alkyne benzannulation reaction that was promoted by Brønsted acid. The molecules are configurationally locked, allowing the enantiomers to be separated using chiral HPLC so that their photophysical and chiroptical properties, including circular dichroism and circularly polarized luminescence, could be studied.

Purified samples of Ho 3 N@C 2 (22010)-C 78 and Tb 3 N@C 2 (22010)-C 78 have been isolated by two distinct processes from the rich array of fullerenes and endohedral fullerenes present in carbon soot from graphite rods doped with Ho 2 O 3 or Tb 4 O 7 . Crystallographic analysis of the endohedral fullerenes as cocrystals with Ni(OEP) (in which OEP is the dianion of octaethylporphyrin) shows that both molecules contain the chiral C 2 (22010)-C 78 cage. This cage does not obey the isolated pentagon rule (IPR) but has two sites where two pentagons share a common C-C bond. These pentalene units bind two of the metal ions, whereas the third metal resides near a hexagon of the cage. Inside the cages, the Ho 3 N or Tb 3 N unit is planar. Ho 3 N@C 2 (22010)-C 78 and Tb 3 N@C 2 (22010)-C 78 use the same cage previously found for Gd 3 N@C 2 (22010)-C 78 rather than the IPR-obeying cage found in Sc 3 N@D 3h -C 78 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diastereoselective Lewis acid-mediated additions of nucleophilic alkenes to N-sulfonyl imines are reported. The canonical polar Felkin-Anh model describing additions to carbonyls does not adequately describe analogous additions to N-sulfonyl imines. Herein, we describe the development of conditions to produce both syn and anti products with high diastereoselectivity and good yields. A stereoelectronic model consistent with experimental outcomes is also proposed., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two new molecular boxes, the mono-bromo box [Au 6 (Triphos) 4 Br](SbF 6 ) 5 ⋅6(CH 2 Cl 2 ), 4 mB, and the dibromo box, [Au 6 (Triphos) 4 Br 2 ⋅H 2 O](SbF 6 ) 4 ⋅4(CH 2 Cl 2 ), 5 dB, have been prepared in crystalline form. Although constructed from non-luminescent components, both are strongly luminescent. Like its chloro counterpart, the mono-bromo box [Au 6 (Triphos) 4 Br](SbF 6 ) 5 ⋅6(CH 2 Cl 2 ), 4 mB, is mechanochromic. Under grinding, it loses its luminescence. The bromo-bridged helicate, [(μ-Br){Au 3 (Triphos) 2 } 2 ](CF 3 SO 3 ) 5 ⋅2(CH 2 Cl 2 ), 3μ-H, with a cation that is isomeric with the box [Au 6 (Triphos) 4 Br] 5+ , has also been prepared and crystallographically characterized. Unlike its chloro analogue, [(μ-Br){Au 3 (Triphos) 2 } 2 ](CF 3 SO 3 ) 5 ⋅2(CH 2 Cl 2 ) is not luminescent. Thus, the cation produced upon grinding may be the cation present in the bromo-bridged helicate, [(μ-Br){Au 3 (Triphos) 2 } 2 ](CF 3 SO 3 ) 5 ⋅2(CH 2 Cl 2 ), 3μ-H. The dibromo box, [Au 6 (Triphos) 4 Br 2 ⋅H 2 O](SbF 6 ) 4 ⋅4(CH 2 Cl 2 ), 5 dB, is not significantly mechanochromic., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carbon disulfide is cleaved by n-propyldiphenylphosphine and nickel(II) bromide in a one-step process, to form two unprecedented complexes: orange, [Ni(S 2 C 2 (P n PrPh 2 ) 2 )Br(P n PrPh 2 )]Br⋅CS 2 (1) and purple [Ni{η 2 -SC(P n PrPh 2 ) 2 }Br(P n PrPh 2 )]Br⋅0.5CS 2 (2). Orange (1) contains a dithiolene-related ligand that results from carbon-carbon bond formation, while purple (2) contains a remarkable ligand in which two n-propyldiphenylphosphine molecules have added to a carbon atom of a CS unit that is coordinated to nickel., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The mono- and di-chloroform solvates of [Au 2 (μ-1,2-bis(diphenylarsino)ethane) 2 ](AsF 6 ) 2 undergo single-crystal-to-single-crystal transformations that result in gain (over 12 hours) or slow loss (over five years) of only one chloroform molecule. The change in solvation results in changes in the structure and luminescence of the digold cation. The cation consists of a pair of slightly bent As-Au-As units that are connected through the two bridging dpae ligands and by aurophilic interactions with Au⋅⋅⋅Au contacts of 3.05152(15) Å in the disolvate or 2.9570(5) Å in the monosolvate., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The solid-state structures of seven solvates of C 60 (C 60 ·4tetrachloroethylene, C 60 ·2tetrachloroethylene, C 60 ·3benzene, C 60 · n-pentane, C 60 ·diethyl ether, C 60 ·chlorobenzene, and C 60 ·benzene·dichloromethane) were determined by single-crystal X-ray diffraction at low temperature. At 90 K, the fullerene and solvate components are generally well-ordered and do not show the orientational disorder that plagues similar structures determined at room temperature. Interactions between the solvate molecules and the fullerene and between adjacent C 60 molecules were examined and analyzed. Van der Waals and weak charge-transfer interactions are important to help to organize the individual components in these structures. The weak Lewis acid behavior of C 60 , such as when it cocrystallizes with diethyl ether or chlorinated solvents, is apparent. In addition, π-stacking interactions are prevalent. The solvates of C 60 reported here were frequently obtained from attempts to cocrystallize C 60 with another chemical compound. Although the desired cocrystals were never formed, the unincorporated molecules influenced solvate formation.

Aliphatic thiolato-S-bridged tri- and binuclear nickel(II) complexes have been synthesized and characterized as models for the Ni p site of the A cluster of acetyl coenzyme A synthase (ACS)/carbon monooxide (CO) dehydrogenase. Reaction of the in situ formed N 2 S thiol donor ligands with [Ni(H 2 O) 6 ](ClO 4 ) 2 afforded the trinuclear complexes [Ni{(L Me(S) ) 2 Ni} 2 ](ClO 4 ) 2 ·CH 3 CN (1·CH 3 CN) and [Ni{(L Br(S) ) 2 Ni} 2 ](ClO 4 ) 2 ·5H 2 O (2·5H 2 O) following self-assembly. Complexes 1 and 2 react with [Ni(dppe)Cl 2 ] and dppe [dppe = 1,2-bis(diphenylphosphino)ethane] to afford the binuclear [Ni(dppe)Ni(L Me(S) ) 2 ](ClO 4 ) 2 ·2H 2 O (3·2H 2 O) and [Ni(dppe)Ni(L Br(S) ) 2 ](ClO 4 ) 2 ·0.75O(C 2 H 5 ) 2 [4·0.75O(C 2 H 5 ) 2 ], respectively. The X-ray crystal structures of 1-4 revealed a central Ni II S 4 moiety in 1 and 2 and a Ni II P 2 S 2 moiety in 3 and 4; both moieties have a square-planar environment around Ni and may mimic the properties of the Ni p site of ACS. The electrochemical reduction of both terminal Ni II ions of 1 and 2 occurs simultaneously, which is further confirmed by the isolation of [Ni{(L Me(S) ) 2 Ni(NO)} 2 ](ClO 4 ) 2 (5) and [Ni{(L Br(S) ) 2 Ni(NO)} 2 ](ClO 4 ) 2 (6) following reductive nitrosylation of 1 and 2. Complexes 5 and 6 exhibit ν NO at 1773 and 1789 cm -1 , respectively. In the presence of O 2 , both 5 and 6 transform to nitrite-bound monomers [(L Me(S-S) )Ni(NO 2 )](ClO 4 ) (7) and [(L Br(S-S) )Ni(NO 2 )](ClO 4 ) 2 (8). The nature of the ligand modification is evident from the X-ray crystal structure of 7. To understand the origin of multiple reductive responses of 1-4, complex [(L Me(SMe) ) 2 Ni](ClO 4 ) 2 (9) is considered. The central NiS 4 part of 1 is labile like the Ni p site of ACS and can be replaced by phenanthroline. The treatment of CO to reduce 3 generates a 3 red -(CO) 2 species, as confirmed by Fourier transform infrared (ν CO = 1997 and 2068 cm -1 ) and electron paramagnetic resonance ( g 1 = 2.18, g 2 = 2.13, g 3 = 1.95, and A P = 30-80 G) spectroscopy. The CO binding to Ni I of 3 red is relevant to the ACS activity.

A method has been developed for isolating a pure sample of Er 2 C 94 from the myriad of fullerenes and endohedral fullerenes that are formed in the electric arc process. Crystallographic analysis of Er 2 C 94 in a cocrystal formed with Ni(OEP) reveals that the molecule is the carbide Er 2 C 2 @D 3 (85)-C 92 . Crystals of Er 2 C 2 @D 3 (85)-C 92 ⋅Ni(octaethylporphyrin)⋅2 C 7 H 8 are isostructural with those of Sm 2 @D 3 (85)-C 92 ⋅Ni(octaethylporphyrin)⋅2 (chlorobenzene). Comparisons are made between the four crystallographically characterized endohedrals (Er 2 C 2 @D 3 (85)-C 92 , Gd 2 C 2 @D 3 (85)-C 92 , La 2 C 2 @D 3 (85)-C 92 , and Sm 2 @D 3 (85)-C 92 ) that utilize the chiral D 3 (85)-C 92 cage., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Luminescent gold(I) complexes ([Au 6 (Triphos) 4 Cl](PF 6 ) 5 ·2(CH 3 C 6 H 5 ), [Au 6 (Triphos) 4 Cl](AsF 6 ) 5 ·8(CH 3 C 6 H 5 ), and [Au 6 (Triphos) 4 Cl](SbF 6 ) 5 ·7(CH 3 C 6 H 5 ) where Triphos = bis(2-diphenylphosphinoethyl)phenylphosphine) with a boxlike architecture have been prepared and crystallographically characterized. A chloride ion resides at the center of the box with two of the six gold(I) ions nearby. Mechanical grinding of blue luminescent crystals containing the cation, [Au 6 (Triphos) 4 Cl] 5+ , results in their conversion into amorphous solids with green emission that contain the bridged helicate cation, [μ-Cl{Au 3 (Triphos) 2 } 2 ] 5+ . A mechanism of the mechanochromic transformation is proposed. The structures of the blue-emitting helicate, [Au 3 (Triphos) 2 ](CF 3 SO 3 ) 3 ·4(CH 3 C 6 H 5 )·H 2 O, and the green-emitting bridged-helicate, [μ-Cl{Au 3 (Triphos) 2 } 2 ](PF 6 ) 5 ·3CH 3 OH have been determined by single crystal X-ray diffraction.

The proton-coupled reduction of Cu II -bound nitrite (NO 2 - ) to nitric oxide (NO 2 - + 2H + + e - → NO(g) + H 2 O), such as occurs in the enzyme copper nitrite reductase, is investigated in this work. Our studies focus on the copper(II/I) model complexes [(L2)Cu(H 2 O)Cl] (1), [(L2)Cu(ONO)] (2), [(L2)Cu(CH 3 CO 2 )] (3), and [Co(Cp) 2 ][(L2)Cu(NO 2 )(CH 3 CN] (4), where HL2 = N-[2-(methylthio)ethyl]-2'-pyridinecarboxamide. Complex 1 readily reacts with a NO 2 - anion to form the nitrito-O-bound copper(II) complex 2. Electrochemical reduction of Cu II → Cu I indicates coordination isomerization from asymmetric nitrito-κ 2 -O,O to nitro-κ 1 -N. Isolation and spectroscopic characterization of 4 support this notion of nitrite coordination isomerization (ν Cu-N ∼ 460 cm -1 ). A reduction of 2, followed by reaction with acetic acid, causes evolution of stoichiometric NO via the transient copper(II) nitrosyl species and subsequent formation of the acetate-bound complex 3. The probable copper nitrosyl intermediate [(L2)Cu(NO)(CH 3 CN)] + of the {CuNO} 10 type is evident from low-temperature UV-vis absorption (λ max = 722 nm) and electron paramagnetic resonance spectroscopy. A density functional theory (DFT)-optimized model of [(L2)Cu(NO)(CH 3 CN)] + shows end-on NO binding to Cu with Cu-N(NO) and N-O distances of 1.989 and 1.140 Å, respectively, and a Cu-N-O angle of 119.25°, consistent with the formulation of Cu II -NO • . A spin-state change that triggers NO release is observed. Considering singlet- and triplet-state electronic configurations of this model, DFT-calculated ν NO values of 1802 and 1904 cm -1 , respectively, are obtained. We present here important mechanistic aspects of the copper-mediated nitrite reduction pathway with the use of model complexes employing the ligand HL2 and an analogous phenyl-based ligand, N-[2-(methylthio)phenyl]-2'-pyridinecarboxamide (HL1).

A simple exchange reaction between [Ar iPr4 Sn(μ-Cl)] 2 (1) and sodium azide afforded the doubly bridged Sn(II) azide, [Ar iPr4 Sn(μ-N 3 )] 2 (2) (Ar iPr4 = C 6 H 3 -2,6(C 6 H 3 -2,6- i Pr 2 ) 2 ) in 85% yield. Photolysis of a diethyl ether solution of 2 for ca. 16 h yielded an azepinyl-substituted insertion product, [C 6 H 3 -2-(C 6 H 3 -2,6- i Pr 2 )-6-(C 6 H 3 N-3,7- i Pr 2 )Sn] 2 (3). The reaction of the Lewis acid, B(C 6 F 5 ) 3 (BCF), or the Lewis base, pyridine, with 2 dissociates the dimer to afford the corresponding complexed monomeric Sn(II) azide, Ar iPr4 SnN 3 BCF (4) in which BCF coordinates the α-nitrogen, or Ar iPr4 Sn(pyridine)N 3 (6) in which pyridine coordinates to the tin atom. Photolysis of 4 in diethyl ether for 12 h results in the insertion of the α-nitrogen of the azide group into one of the B-C bonds of the BCF acceptor to yield the tin(II) amide, Ar iPr4 SnN(C 6 F 5 )B(C 6 F 5 ) 2 (5). In contrast, photolysis of 6 for over 36 h afforded no apparent reaction. A highly reactive Sn nitride intermediate, Ar iPr4 Sn≡N, is proposed as part of the mechanistic pathway for the formation of 3 and 5 as a result of trapping the tin-centered radical isomers. This was effected by immediate freezing the samples of 2 or 4 after ca. 30 min of UV photolysis and recording their electron paramagnetic resonance spectra. These exhibited a rhombic g tensor of [g 1 , g 2 , g 3 ] = [2.029, 1.978, 1.933]. This radical intermediate could be related to the valence isomers of the nitride [-Sn IV ≡N] intermediate, in isomeric equilibrium with the nitrene [-Sn II -N] and nitridyl [-Sn III ═N·] forms, but with the spin density on the nitrogen being quenched, possibly by the H atom abstraction to form an S = 1/2 species of formula -Sn·═N(H).

A totally unanticipated regio- and stereoisomerically pure C 2h -symmetric trans-1-(bis-pyrrolidine)-tetra-malonate hexa-adduct of C 60 was obtained via a topologically controlled method, followed by a 1,3-dipolar cycloaddition reaction. The structures of the products were elucidated by 1 H and 13 C NMR and by X-ray crystallography. The unexpected regio- and stereoselectivity observed, supported by theoretical calculations, was found to be a consequence of malonate-pyrrolidine interactions., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bio-inspired manganese [Mn(N 5 Py)(H 2 O)(CH 3 OH)](ClO 4 ) 2 (1) and iron [Fe(N 5 Py)(H 2 O)(ClO 4 )]ClO 4 (2) complexes derived from a pentadentate ligand (N 5 Py = 2,6-bis((E)-1-phenyl-2-(pyridin-2-ylmethylene)hydrazinyl)pyridine) framework containing a N 5 binding motif were synthesized and characterized using different spectroscopic methods. The molecular structures of complexes 1 and 2 were determined by X-ray crystallography. These complexes were found to be stable under physiological conditions and exhibited an excellent superoxide dismutase (SOD) activity. The SOD activity was determined by a xanthine-xanthine oxidase-nitro blue tetrazolium assay and the IC 50 values were determined to be 1.53 and 2.09 μM, respectively.