Coordination chemistry of mercury-containing anticrowns. Synthesis and structures of the complexes of cyclic trimeric perfluoro-o-phenylenemercury with ethanol, THF and bis-2,2′-tetrahydrofuryl peroxide

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) is capable of reacting with ethanol to form a 1:1 complex, {[(o-C₆F₄Hg)₃](EtOH)} (2), having a pyramidal structure. The ethanol molecule in 2 is coordinated through the oxygen atom to all Hg atoms of the macrocycle. The interaction of 1 with THF followed by drying of the product obtained in vacuum also gives the corresponding pyramidal 1:1 complex {[(o-C₆F₄Hg)₃](THF)} (3). However, when a THF solution of 1 is slowly concentrated to a small volume and the resulting crystals are not dried, three cocrystallized adducts, viz., {[(o-C₆F₄Hg)₃](THF)₂} (4), {[(o-C₆F₄Hg)₃](THF)₃} (5) and {[(o-C₆F₄Hg)₃](THF)₄} (6), containing two, three and even four THF molecules, respectively, are produced. Complex 4 has a bipyramidal structure. Complexes 5 and 6 are also characterized by the presence of a bipyramidal fragment formed by two coordinated THF species. The topological analysis of the DFT-calculated function of the electron density distribution in the crystals of 2 and 3 revealed the critical points (3, −1) on each of the three Hg···O lines, which is in accord with the X-ray diffraction data indicating on the presence of the triply coordinated Lewis base molecule in both adducts. If a THF solution of 1 is held for a month at 20 °C on air under stirring, a sandwich complex of 1 with previously unknown bis-2,2′-tetrahydrofuryl peroxide (THFPO) is formed. The THFPO ligand in this sandwich, {[(o-C₆F₄Hg)₃]₂(THFPO)} (7), provides all its four oxygen atoms for the bonding to the molecules of 1. Two of these oxygen atoms, belonging to the tetrahydrofuryl moieties, are cooperatively bound each by three Hg atoms of the neighbouring macrocyclic unit whereas two others, belonging to the peroxide group, coordinate to a single Hg atom of the adjacent macrocycle.     

Coordination chemistry of anticrowns: Complexation of cyclic trimeric perfluoro-o-phenylenemercury with nitro compounds

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) is capable of reacting with nitromethane to give complex {[(o-C₆F₄Hg)₃](CH₃NO₂)} (2) containing one molecule of the nitro compound per one macrocycle molecule. In this complex, the nitromethane ligand is bound to 1 by its both oxygen atoms, one of which is simultaneously coordinated to all three Hg centres of the macrocycle while the other interacts with a single Hg centre. The complex of similar composition, {[(o-C₆F₄Hg)₃](C₆H₅NO₂)} (3), is produced in the interaction of 1 with nitrobenzene. In this complex too, the both oxygen atoms of the nitro group are involved in the bonding to the macrocycle. A distinctive feature of 3 is that here one oxygen atom of the coordinated nitro derivative is bound by only two Hg centres of 1 whereas the other interacts again with a single Hg site. The reaction of 1 with 5-nitroacenaphthene affords a 1:1 complex, {[(o-C₆F₄Hg)₃](C₁₂H₉NO₂)} (4), having a polydecker sandwich structure in the crystal. Unlike in 3, the aromatic rings of the nitroarene units in 4 are disposed virtually in parallel to the macrocycles. The nitro compound in 4 behaves again as a bidentate ligand, forming three Hg-O bonds with one of the adjacent macrocycles and a single Hg-O bond with another molecule of 1. The complex is characterized also by shortened Hg-C contacts between the Hg centres of 1 and the carbon atoms of the nitroarene moiety as well as shortened C-C contacts between the carbon atoms of the nitroarene and the macrocycle. In the interaction of 1 with 1-nitropyrene, complexes of two compositions, viz. {[(o-C₆F₄Hg)₃](C₁₆H₉NO₂)} (5) and {[(o-C₆F₄Hg)₃](C₁₆H₉NO₂)₃} (6) are formed. An X-ray diffraction study of 6 has shown that in this adduct two of three coordinated molecules of the nitro compound are located on one side of the metallacycle plane while the third nitroarene molecule is disposed on its other side. The aromatic rings of all three nitropyrene ligands in 6 are practically parallel to the mean plane of the macrocycle. In contrast to 2-4, each molecule of the nitroarene in 6 is bonded to 1 by a single oxygen atom which is coordinated only to one Hg centre. In the case of one of the nitropyrene ligands that forms much longer Hg-O bond with 1 than two others, an additional contribution to the bonding is made by shortened Hg-C contacts between the macrocycle and the carbon atoms of the aromatic pyrene core and also by shortened C-C contacts between the carbon atoms of the coordinated nitroarene and 1. The synthesized adducts are the first examples of complexes of an anticrown with nitro compounds.     

Coordination chemistry of anticrowns. Complexation of cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 with the cyanoborohydride anion [H3BCN]− and triethylamineborane Et3NBH3

As was shown by IR spectroscopy, the reaction of the three-mercury anticrown (o-C₆F₄Hg)₃ (1) with the [H₃BCN]ion in THF affords the complexes {[(o-C₆F₄Hg)₃][H₃BCN](5) and [(o-C₆F₄Hg)₃]₂[H₃BCN](6). Complex 6 was isolated from solution in the analytically pure state. According to X-ray diffraction data, complex 6 has a double-decker sandwich structure, in which the borohydride group of the [H₃BCN]^? anion is bound to one anticrown molecule by three B-H-Hg bridges, whereas the cyanide group is cooperatively coordinated by three mercury centers of another molecule 1 through the nitrogen atom. The reaction of compound 1 with triethylamineborane Et₃NBH₃ in THF affords the 1: 1 complex ～[(o-C₆F₄Hg)₃][Et₃NBH₃]～ (7). In this adduct, the binding of the aminoborane to the mercury anticrown is also accomplished by B-H-Hg bridges. The stability constants of complexes 5 and 6 in THF were determined.     

Crown compounds for anions. Sandwich complexes of cyclic trimeric perfluoro-o-phenylenemercury with hexacyanoferrate(III) and nitroprusside anions

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) is able to bind hexacyanoferrate(III) and nitroprusside anions to form complexes {[(o-C₆F₄Hg)₃]₂[Fe(CN)₆]}³⁻ and {[(o-C₆F₄Hg)₃]₂[Fe(CN)₅NO]}²⁻, respectively, which contain one anionic species per two macrocycles. According to X-ray diffraction data, the complexes have unusual sandwich structures wherein the anionic guest is located between the planes of two molecules of 1 and is coordinated to each of these through two types of Fe-C-N-Hg bridges. One type is the simultaneous coordination of a cyanide ligand to all three Hg centres of the cycle. The other type is the coordination of a cyanide group to a single Hg atom of the macrocycle. In both types, the bonding of the anionic guest with the macrocyclic host is accomplished with the participation of π-electrons of the cyanide ligands. The synthesized compounds are the first examples of host-guest complexes of a macrocyclic multidentate Lewis acid with anionic metal complexes.     

Mono- and bimetallic platinum(II) and palladium(II) complexes containing fluorinated benzothiolates

The new mononuclear palladium(II) and platinum(II) [M(p-SC₆F₄(CF₃))₂(dppe)] complexes M = Pd 1a, Pt 2a; [M(o-SC₆H₄(CF₃))₂(dppe)] M = Pd 1d, Pt 2d as well as the previously known [M(SC₆F₅)₂(dppe)] M = Pd 1b, Pt 2b and [M(p-SC₆HF₄)₂(dppe)] M = Pd 1c, Pt 2c, have been used as metalloligands for the preparation of the heteroleptic bimetallic complexes [M₂(μ-SRf)₂(dppe)₂](SO₃CF₃)₂ M = Pd, Rf = p-C₆F₄(CF₃) 3a, C₆F₅3b, p-C₆HF₄3c, o-C₆H₄(CF₃) 3d; M = Pt, Rf = p-C₆F₄(CF₃) 4a, C₆F₅4b, p-C₆HF₄4c and o-C₆H₄(CF₃) 4d. Variable temperature ¹⁹F NMR experiments show that the fluorothiolate bridged bimetallic compounds are fluxional in solution whereas mononuclear complexes are not. The solid state X-ray diffraction structures of [Pd(p-SC₆HF₄)₂(dppe)] (1c), [Pt(SC₆F₅)₂(dppe)] (2b) and [Pt(o-SC₆H₄(CF₃))₂(dppe)] (2d) show square-planar coordination around the metal centers. The solid state molecular structure of the compound [Pt₂(μ-o-SC₆H₄(CF₃))₂(dppe)₂](SO₃CF₃)₂ (4d), exhibit a planar [Pt₂(μ-S)₂] ring with the sulfur substituents in an anti configuration.     

Coordination chemistry of macrocyclic multidentate Lewis acids. Synthesis and structures of complexes of cyclic trimeric perfluoro-o-phenylenemercury with N,N-dimethylacetamide and n-butyronitrile

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ readily reacts with N,N-dimethylacetamide and n-butyronitrile to form the complexes {[(o-C₆F₄Hg)₃](MeCONMe₂)₂} and {[(o-C₆F₄Hg)₃](PrⁿCN)}, respectively. According to X-ray diffraction data, the amide ligands are located above and below the plane of the macrocycle, each being coordinated to all Hg atoms of the macrocycle through the O atom. The nitrile ligand is bound to the macrocycle through the N atom, all Hg atoms being also involved in this bonding.     

Syntheses, structures, and properties of zinc(II), cadmium(II), cobalt(II), and manganese(II) coordination polymers with tetraiodoterephthalate

The coordination chemistry of a rigid periodinated ligand, 2,3,5,6-tetraiodo-1,4-benzenedicarboxylic acid (H₂BDC-I₄), with a series of transition metal ions has been explored to afford five new coordination polymers {[M(BDC-I₄)(MeOH)₄](H₂BDC-I₄)(MeOH)₂} _n (M?=?Zn^II for 1, Cd^II for 2, Co^II for 3 and Mn^II for 4) and {[Mn(BDC-I₄)(MeOH)₄](DMF)} _n (5). All these complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, and X-ray crystallography. Single-crystal X-ray diffraction reveals that complexes 1?C4 are isostructural and have a one-dimensional chain structure. Upon the addition of the solvent DMF, the infinite linear chain array in 4 is converted to a 1-D wave-like chain motif in 5 with a different space group ( $ P\overline{1} $ for 4 and P2₁/c for 5). The difference between structures 1?C4 and 5 can be attributed to the coordination mode of carboxylate changing from trans to cis fashion. The Zn^II and Cd^II complexes 1 and 2 display similar emissions in the solid state, which essentially are intraligand transitions.     

New molecular complexes of trimeric perfluoro-ortho-phenylene mercury with heterocyclic compounds

Slow evaporation in air of the solution of trimeric perfluoro-ortho-phenylene mercury (1) and 2,1,3-benzothiadiazole (2) in THF affords a complex l.2 ₂·H₂O_0.59 (3). A complex of 1 with di(tetrahydrofur-2-yl) ether (4; probably, a THF oxidation product) with a composition of 1.4 ₂ (5) is detected as a minor admixture to 3. The structure of complexes 3 and 5 is determined by single crystal XRD. In complex 3, a molecule of 1 participates in Hg…N and π_F…H—C interactions with one molecule of 2 and in the π_F…π_H stacking interaction with another. Complex 5 is formed by Hg…O interactions with the participation of both heterocycles of a molecule of 4.     

Copper complexes of two isomeric NS2-macrocycles

Two isomeric NS₂-macrocycles incorporating a xylyl group at ortho (o -L) and meta (m -L) positions were employed and their copper complexes (1?C5) were prepared and structurally characterized. The copper(II) nitrate complexes [Cu(L)(NO₃)₂] (1: L = o -L, 2: L = m -L) for both ligands were isolated. In each case, the copper center is five-coordinated with a distorted square pyramidal geometry. Despite the overall geometrical similarity, 1 and 2 show the different ligand conformation due to the discriminated packing pattern. Reaction of o -L with copper(II) perchlorate afforded complex 3 containing two independent complex cations [Cu(o -L)(H₂O)(DMF)(ClO₄)]⁺ and [Cu(o -L)(H₂O)(DMF)]²⁺; the coordination geometry of the former is a distorted octahedron while the latter shows a distorted square pyramidal arrangement. In the reactions of copper(I) halides (I or Br), o -L gave a mononuclear complex [Cu(o-L)I] (4) with a distorted tetrahedral geometry, while m -L afforded a unique exodentate 2:1 (ligand-to-metal) complex [trans-Br₂Cu(m-L)₂] (5) adopting a trans-type square-planar arrangement.     

Reactivity and reaction pathways of alkylalkoxybenzene radical cations. Part 3. Effects of 2-alkyl substituents on the relative importance of ring-substitution over deprotonation of 2-alkyl-1,4-dimethoxybenzene radical cations

One-electron oxidation of 2-alkyl-1,4-dimethoxybenzenes 1a-f (2-alkyl=Me, Et, i-Pr, cy-C₃H₅CH₂, PhCH₂ and t-Bu) by 4-nitrobenzoyl peroxide 2 and pentaflurobenzoyl peroxide 3 was proved by the observation of great acceleration of decomposition of the peroxides at room temperature, the detection of the corresponding radical cations 1 ^+? a-f and product analysis. The product studies have disclosed that under the conditions employed (in acetonitrile at 40°C), the reaction pathways of the radical cations are greatly dependent on the nature of 2-alkyl substituents: Ring-4-nitrobenzoloxylation product at C ₅ and C ₆ were obtained exclusively in the reactions of the donors with aliphatic 2-alkyl substituents bearing at least one α-hydrogen atom, such as 1a, 1b, 1c and 1d; whereas in the case of 1e (with 2-benzyl group), both ring-substitution at C ₅ (4e) and C ₆ (5e) and deprotonation/4-nitrobenzoloxylation products 8e were isolated; from the donor without α-hydrogen atom, 1f, de-t-butylation products 12 and t-butyl 4-nitrobenzoate 13 were incorporated with ring-substitution at C ₅ (4f) and C ₆ (5f). Furthermore, the product distribution (4 over 5) is also affected by the bulkiness of 2-alkyl group. For all the electron-transfer reactions, large amounts of the benzoic acid (4-NO₂-C₆H₄COOH or C₆F₅COOH) were generated and trace amounts of de-methylation product (2-alkyl-1,4-benzoqinones 6) were also detected by ¹H NMR.     

Platinum complexes bearing 2,2′-dipyridylamine ligand

The replacement of the iodide ligands in the complex [PtI₂(dpa)] (1) (dpa is 2,2′-dipyridylamine) by silver triflate in acetonitrile afforded the compound [Pt(dpa)(MeCN)₂](SO₃CF₃)₂ (2). Homoleptic complexes [Pt(dpa)₂](X)₂ (3·(X)₂) were synthesized by the treatment of [PtI₂(dpa)] (1) with 2,2′-dipyridylamine in the presence of silver salts AgX in methanol (X = NO₃) or acetonitrile (X = SO₃CF₃). The deprotonation of the complex [3](SO₃CF₃)₂ to give the homoleptic complex [Pt(dpa-H)₂] (4) was performed by two methods, e.g., by the treatment of [3](SO₃CF₃)₂ with 2 equiv. of NaOH in methanol or by the addition of excess Et₃N to a suspension of [3](SO₃CF₃)₂ in methanol. The structures of compounds 1–4 were established by elemental analyses, high resolution electrospray ionization mass spectrometry, IR and NMR spectroscopy; the crystal structure of complexes [2](SO₃CF₃)₂, [3](NO₃)₂·H₂O, [3](SO₃CF₃)₂·2H₂O, and 4 were determined by single-crystal X-ray diffraction.     

Synthesis and characterization of palladium(II) and platinum(II) metal complexes with iminophosphine ligands: X-ray crystal structures of platinum(II) complexes and use of palladium(II) complexes as pre-catalysts in Heck and Suzuki cross-coupling reactions

The reactions of N-(2(diphenylphosphino) benzylidene) (phenyl) methanamine, Ph₂PPhNHCH₂-C₅H₄N, 1 and N-(2-(diphenylphosphino) (benzylidene) (thiophen-2-yl) methanamine, Ph₂PPhNHCH₂-C₄H₃S, 2 with MCl₂(cod) and MCl(cod)Me (M = Pd, Pt; cod = 1,5-cyclooctadiene) yield the new complexes [M(Ph₂PPhNHCH₂-C₅H₄N)Cl₂], M = Pd1a, Pt1b, [M(Ph₂PPhNHCH₂-C₅H₄N)ClMe], M = Pd1c, Pt 1d, [M(Ph₂PPhNHCH₂-C₄H₃S)Cl₂], M = Pd2a, Pt 2b, and [M(Ph₂PPhNHCH₂-C₄H₃S)ClMe], M = Pd2c, Pt 2d, respectively. The new compounds were isolated as analytically pure crystalline solids and characterized by ³¹P-, ¹H-NMR, IR spectroscopy, electro spray ionization-mass spectrometry (ESI-MS) and elemental analysis. The representative solid-state molecular structures of the platinum complexes 1b and 2b were determined using single crystal X-ray diffraction analysis and revealed that the complexes exhibit a slightly distorted square-planar geometry. Furthermore, the palladium complexes were tested as potential catalysts in the Heck and Suzuki cross-coupling reactions.     

Bimetallic amine-bridged bis(phenolate) lanthanide aryloxides and alkoxides: synthesis,characterization, and application in the ring-opening polymerization of rac-lactide and rac-β-butyrolactone

A series of neutral bimetallic lanthanide aryloxides p-C6H4[OLnL(THF)n]2 [Ln = Y(1), Yb(2), Sm(3)(n = 1) and La(4)(n = 2), L = Me2NCH2CH2N{CH2-(2-O–C6H2–tBu2-3,5)}2] and alkoxides p-C6H4CH2[OLnL(THF)]2 [Ln = Y(5), Yb(6)] supported by an amine-bridged bis(phenolate) ligand have been synthesized through one-pot reactions of Ln(C5H5)3(THF), LH2 with p-benzenediol and 1,4-benzenedimethanol, respectively. All complexes have been fully characterized by elemental analyses, single-crystal X-ray diffraction analysis, and IR and multi-nuclear NMR spectroscopy(in the cases of 1, 4 and 5). Study of their catalytic behavior revealed that, in general, all complexes are efficient initiators for the polymerization of rac-lactide(LA) and rac-β-butyrolactone(BBL), except for 3 and 4 in the case of BBL. The influence imposed by lanthanides of different ionic radii and initiating groups of different structures on the activity, controllability, and stereoselectivity of polymerization were systematically studied and compared. Highly heterotactic PLA(Pr up to 0.99) and syndiotactic PHB(Pr ≈ 0.81) with high molecular weight and narrow polydispersity formed and were automatically capped with hydroxyl functionality at both ends.     

Synthesis, Structure and Electrochemical Properties of Triarylamine Bridged Dicobaltdicarbon Tetrahedrane Clusters

The reaction of [Co₂(CO)₆(dppm)] (1) with the ethynyl substituted triarylamines [N(C₆H₄-4-C??CSiMe₃)(C₆H₄Me-4)₂] (2) or [N(C₆H₄-4-C??CSiMe₃)₂(C₆H₄Me-4)] (3) affords [{Co₂(CO)₄(dppm)}{??-(Me₃SiC₂-4-C₆H₄)N(C₆H₄Me-4)₂}] (4) or a mixture of [Co₂{??-Me₃SiC₂-4-C₆H₄N(C₆H₄-4-C??CSiMe₃)(C₆H₄Me-4)}(CO)₄(dppm)] (5) and [{Co₂(CO)₄(dppm)}₂{??-(Me₃SiC₂-4-C₆H₄)₂N(C₆H₄Me-4)}] (6), respectively. A combination of electrochemical measurements in different electrolytes, and IR and NIR spectroscopic studies of these compounds, which feature both organometallic and organic redox active groups, indicates that the cluster centres are oxidised at significantly less positive potentials than the triarylamine moieties. Reaction of 6 with one or two equivalents of [Fe(??-C₅H₄COMe)Cp]PF₆ gives [6][PF₆] _n (n?=?1, 2), which are best described in terms of cluster-localised oxidation processes. Despite the presence of the substantial differences in the first and second cluster based oxidations in 6 (up to 220?mV in CH₂Cl₂/0.1?M [NBu₄][BAr ₄ ^F ]), there is little ground state delocalisation between the cluster centres through the triarylamine bridge. The stabilisation of [6]⁺ with respect to disproportionation can be attributed to electrostatic effects.     

Hydro- and chloro-substituted silyl- and silyl-η-amido-η-tetramethylcyclopentadienyl titanium complexes

Chlorosilyl-cyclopentadienyl titanium precursors [Ti(η⁵-C₅Me₄SiMeXCl)Cl₃] (X=H 2, Cl 3) were prepared by reaction of TiCl₄ with the trimethylsilyl derivatives of the corresponding cyclopentadienes. Methylation of these compounds with MgClMe under appropriate conditions afforded the methyl complexes [Ti(η⁵-C₅Me₄SiMe₂R)XMe₂] (R=H, X=Cl 5, Me 6; R=X=Me 7). Reactions of 2 and 3 with two equivalents of LiNH^tBu afforded the ansa-silyl-η-amido compounds [Ti{η⁵-C₅Me₄SiMeX(η¹-N^tBu)}Cl₂] (X=H 8, Cl 9). Methylation of 8 gave [Ti{η⁵-C₅Me₄SiMeH(η¹-N^tBu)}Me₂] 10. Complex 9 was also obtained by reaction of 8 with BCl₃, whereas the same reaction using alternative chlorinating agents (TiCl₄, HCl) resulted in deamidation to give 2, which was also converted into 3 by reaction with BCl₃. All of the new compounds were characterized by NMR spectroscopy and the molecular structures of 2 and 4 were determined by X-ray diffraction methods.     

Dipyridyl-type ligand-directed assembly of three cobalt(II) coordinated polymers based on carboxyphenylpropionate

A series of Co(II)-H₂Cpp coordination polymers incorporating different auxiliary ligands, [Co(Cpp)(Phen)(H₂O)] (I), {[Co(Bipy)(H₂O)₄](Cpp)} _n (II), and [Co(Cpp)(Bds)(H₂O)] _n (III) (H₂Cpp = 3-(4-carboxyphenyl)propionic acid, Phen = 1,10-phenanthroline, Bipy = 4,4′-bipyridyl, and Bds = 4,4′-bipyridyl sulfide), were synthesized by the hydrothermal reaction and characterized by single crystal X-ray diffraction, elemental analysis, IR, and TG. Three complexes display from 0D to 1D different structural features under the regulation of distinguishing dipyridyl-type coligands. Complex I possesses a binuclear Co(II) motif constructed by H₂Cpp and Phen, which further developing a zipper-like 2D layer via H-bonded and π-π stacking interactions. Complex II displays straight Bipy-bridging 1D chain, and further forming a 3D supramolecular structure by hydrogen-bonded interactions. Complex III exhibits 1D double-chain collectively jointed by Cpp and Bds, which further interlinked into a 3D supramolecular architecture by H-bonded interactions.     

From straight chain to macrocyclic complexes containing mixed sulfur/nitrogen donors and coordinated 1,3-diynes

The acid-mediated reaction of [{Co₂(CO)₆(μ-η²-HOCH₂CC-)}₂] (1) with the meta- and para-substituted aminothiophenols, 3-NH₂-C₆H₄SH and 4-NH₂-C₆H₄SH, affords the straight chain species, [{Co₂(CO)₆(μ-η²-(3-NH₂-C₆H₄S)CH₂CC-)}₂] (2) and [{Co₂(CO)₆(μ-η²-(4-NH₂-C₆H₄S)CH₂CC-)}₂] (3), respectively. The molecular structure of 3 reveals the presence of two isomeric forms differing in the relative disposition of the S-aryl groups. Conversely, reaction of 1 with the ortho-substituted aminothiophenol, 2-NH₂-C₆H₄SH, furnishes the 10-membered macrocyclic species [{Co₂(CO)₆}₂{cyclo-μ-η²:μ-η²-CH₂C₂C₂CH₂SC₆H₃-NH-2}] (4) along with the linear chain complex [{Co₂(CO)₆(μ-η²-(2-NH₂-C₆H₄S)CH₂CC-)}₂] (5). On the other hand, treatment of 1 with the ortho-substituted mercaptopyridine, 2-SH-C₅H₄N, in the presence of HBF₄ gives the salt [{Co₂(CO)₆(μ-η²-(2-S-C₅H₄NH)CH₂CC-)}₂](BF₄)₂ (6a) in good yield; work-up in the presence of base affords the neutral complex [{Co₂(CO)₆(μ-η²-(2-S-C₅H₄N)CH₂CC-)}₂] (6b). Single crystal X-ray diffraction studies have been reported on 3-5 and 6a.     

Reactions of nitrosoarenes containing electron-withdrawing substituents with coordinated CO. Synthesis and structure of complexes Pd2(OAc)2(p-ClC6H4N[p-ClC6H3NO])2 and Pd2(OAc)2(o-ClC6H4N[o-ClC6H3NO])2

The reaction of tetranuclear Pd₄(μ-COOCH₃)₄(μ-CO)₄ cluster (1a) with p- and o-chloronitrosobenzenes was found to give dinuclear nitrosoamide complexes, Pd₂(OAc)₂(p-ClC₆H₄N[p-ClC₆H₃NO])₂ (4) and Pd₂(OAc)₂(o-ClC₆H₄N[o-ClC₆H₃NO])₂ (5), respectively. The formation of complexes 4 and 5 is accompanied by evolution of CO₂, resulting from oxidation of CO coordinated in cluster 1. Complexes 4 and 5 were characterized by elemental analysis and IR and ¹H NMR spectroscopy; their structures were studied by EXAFS. The reactions of dinuclear complex 4 with molecular hydrogen and CO were studied. The major products of reduction of 4 with hydrogen include metallic palladium, acetic acid, cyclohexanone, and molecular nitrogen. Treatment of complex 4 with CO under mild conditions (1 atm, 20 °C) affords p-chlorophenyl isocyanate.     

Novel coordination polymers with 1,4-di(benzimidazole-1-yl)benzene modulated by an anion: Syntheses, structures and properties

Three novel coordination polymers, {[Co(L)(SO₄)(H₂O)](CH₃OH)}_∞ (1), {[Cd(L)₂(SiF₆)](H₂O)}_∞ (2) and [Zn(L)(NO₃)₂]_∞ (3), synthesized from 1,4-di(benzimidazole-1-yl)benzene (L), have been characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction. Compounds 1–3 exhibit different structures. Complex 1 has a 3-D diamond network containing 1-D Co^II chains connected by SO ₄ ^2? · anions; 2 has a 3-D-Po framework with 1-D porous channels along the c axis; and 3 has a 1-D zig-zag chain structure with a 2-D supramolecular network based on π-π interactions. The magnetic properties of 1 and the solid state fluorescence spectra of 2 and 3 have also been explored.     

Synthesis and biological activity of Magnesium(II) complexes of heptaaza Schiff base macrocyclic ligands; 1H and 13C chemical shifts computed by the GIAO-DFT and CSGT-DFT methodologies

Two new pendant armed Schiff base macrocyclic complexes, [MgL¹](ClO₄)₂ (1), and [MgL²](ClO₄)₂ (2), have been prepared via cyclocondensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with two hexadentate hexaamines, ten and tmen, in the presence of Mg(II) ion. The ligands are 15-membered pentaaza macrocycles having two 2-aminoethyl pendant arms. The newly prepared complexes are investigated by IR, ¹H NMR, ¹³C{¹H} NMR, DEPT(135), COSY(H, H) and HMQC spectroscopic methods. The antimicrobial screening of newly prepared complexes, 1 and 2, as well as previously prepared similar complexes, [MgL³](ClO₄)₂ (3) and [MgL⁴](ClO₄)₂ (4), against Escherichia coli, Staphylococcus aureus and candidia albicans showed that the macrocyclic complexes of Mg(II) containing 15-membered pentaaza ring (1, 2 and 3) have no activity. Where as the compound 4, which contain 16-membered pentaaza ring, had remarkable inhibition zone on the culture of S. aureus and E. coli as compared with standard drugs. The ¹H and ¹³C chemical shieldings of gas phase complexes were also studied by the gauge independent atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) methods at the level of density functional theory (DFT). The computed ¹³C chemical shifts are in reasonably good agreement with the experimental data.