A new twist in anion binding: metallo-helicate hosts for anionic guests

The condensation of 5-chlorocarbonyl-2,2'-bipyridine with a variety of rigid aromatic diamines, L, gave a series of new bisamido-2,2'-bipyridine based ligands (L = 4,4'-methylenediamine, L1; L = 1,1-bis(4-aminophenyl)cyclohexane, L2; L = 1,1-bis(4-amino-3,5-dimethylphenyl)cyclohexane, L3) capable of forming dinuclear triple helicate complexes on coordination to Fe(II). The reaction of various Fe(II) salts with gave: {[Fe2(L1)3](BF4)4, 1; [Fe2(L1)3](ClO4)4, 2; [Fe2(L1)3]Cl4, 3; [Fe2(L1)3](SO4)2, 4; [Fe2(L2)3](BF4)4, 5; [Fe2(L2)3]Cl4, 6; [Fe2(L3)3](BF4)4; 7; [Fe2(L3)3]Cl4, 8; and [Fe2(L3)3](SO4)2, 9, as determined by UV-Vis, IR and 1H NMR spectroscopy, electrospray mass spectrometry (ESMS) and elemental analyses. A UV-Vis complexometric titration experiment between L3 and Fe(BF4)2 established conclusively a [Fe2(L3)3]4+ product species. 1H NMR spectroscopy showed that the complexes exist as both rac-(helical) and meso-(non-helical) isomers in DMSO-d6 solution at 298 K. L1-L3 were designed such that following complexation, six amide hydrogen atoms would line an inter-strand intrahelical cavity of sufficient size to facilitate the binding of guest species within it. Indeed, ESMS studies showed characteristic peaks typical of complex-anion species in solution. Furthermore, 1H NMR titration experiments showed that anions bind within the intrahelical cavity as titration of 1, 5 and 7 with Bu4NCl showed significant downfield shifts in the amide and bipyridyl H6 proton resonances to yield a species of 1 : 2 host to guest stoichiometry. Moreover, addition of Bu4NCl to 1, 5 and 7 shifted the rac-/meso-species distribution from 1 : 2 in favour of the meso- to 100% in favour of the rac-isomer, showing that Cl- ions favour the formation of the triple helicate species in DMSO-d6 solution.     

Missing-link macrocycles: hybrid heterocalixarene analogues formed from several different building blocks

The synthesis and structural characterization of hybrid heterocalix[4]arene analogues containing pyrrole, benzene, methoxy-substituted benzene, and pyridine subunits is described. Macrocycles 1 and 2, examples of calix[2]benzene[2]pyrrole and calix[1]benzene[3]pyrrole systems, respectively, are synthesized by the condensation of pyrrole and an appropriate phenylbis(carbinol). Macrocycles 3 and 7, examples of calix[2]benzene[1]pyridine[1]pyrrole and calix[1]pyridine[3]pyrrole, respectively, are synthesized by the use of a carbene-based pyrrole-to-pyridine ring-expansion procedure. Single-crystal X-ray analysis reveals that compounds 1a, 1b, and 2b adopt 1,3-alternate conformations in the solid state, whereas compounds 3 and 7 display structures that are best described as "flattened partial cones" in terms of their conformation. (Series a refers to pure benzene-derived systems, whereas series b indicates macrocycles containing 5-methoxyphenyl subunits). In the solid state, the methoxy-functionalized macrocycles 1b and 2b, and the chloropyridine-containing macrocycle 7 exist as dimers. In the case of 1a and 7, these compounds interact with neutral solvent in the solid state. The conformations of the macrocycles in solution were explored by temperature-dependent proton NMR and NOESY spectral analysis. At 188 K, macrocycles 1a and 2a adopt flattened 1,3-alternate conformations, whereas macrocycles 3 and 7 exist in the form of flattened partial-cone conformations. Standard proton NMR titration analyses were carried out in the case of macrocycles 1a and 2a, and reveal that at least the second of these systems is capable of binding fluoride and chloride anions in CD(2)Cl(2) solution at room temperature (K(a)=571 and 17M(-1) in the case of 2a and F(-) and Cl(-), respectively).     

Simultaneous freezing of chirality and in-out conformation of a macropentacyclic cryptand by protonation

Compound 1, a cryptand-derived macropentacycle, is a flexible molecule that encompasses many conformations (symmetrical, unsymmetrical, and chiral ones) depending on the observation temperature (VT 1H NMR). Selective monoprotonation of this molecule leads to a totally unsymmetrical, rigidly chiral species in solution (1H NMR). Helical chirality and in-out conformation of monoprotonated 1 are observed in the solid state by X-ray diffraction analysis, as well as the proton location. The latter is bound to the endo bridgehead nitrogen atom and involved in hydrogen-bonding interactions with the three closest sulfurs. Significant induction of chirality is triggered by reaction of 1 with the optically active (R)-(-)-1,1'-binaphthyl-2,2'-diylphosphoric acid. It proceeds with a maximum 24% diastereomeric excess, as shown by the splitting, in the 62:38 intensity ratio, of several 1H NMR signals. These correspond to the two indistinguishable diastereomeric ion pairs: (Lambda-[1-H])((R)-(-)-BNP) and (Delta-[1-H])((R)-(-)-BNP).     

Studies on Biologically Potent Tetraazamacrocyclic Complexes of Bivalent Tin

Fourteen- to eighteen-membered tetraamide macrocyclic ligands N 4 L 1 -N 4 L 4 have been prepared by the condensation of 1,2-diaminoethane or 1,3-diaminopropane with malonic or succinic acid in the presence of condensing reagents dicyclohexylcarbodiimide and 4-dimethylaminopyridine. On reduction, these macrocyclic ligands give a new series of tetraazamacrocycles MacL 1 -MacL 4 which form complexes with tin(II) chloride. The ligands and their complexes were characterized by elemental analyses, molecular weight determinations, infrared and 1 H NMR spectral studies. The hexacoordinated state for tin has been confirmed by spectral studies. An octahedral geometry for these complexes has been proposed as the binding sites are the nitrogen atoms of the macrocycles. On the basis of the chemical composition the representation of the complexes as [Sn(MacL n )Cl 2 ] (n = 1-4) has been established. The ligands and their complexes also have been screened for their antifungal and antibacterial activities and the findings have been reported and explained.     

The proton complex of a diaza-macropentacycle: structure, slow formation, and chirality induction by ion pairing with the optically active 1,1'-binaphthyl-2,2'-diyl phosphate anion

The protonation of a sterically crowded [N2S6] macropentacycle (1) with 1 equiv of CF3SO3H in CDCl3 is slow and gives the singly (oo(+) [1 x H](+)) and doubly (o(+)o(+) [1 x 2H](2+)) protonated forms as kinetic products, the i(+)o form of [1 x H](+) being the thermodynamic product. i(+)o [1 x H](+) is C3 helically chiral in the solid state and in solution. The barrier to racemization (DeltaG(double dagger)) of the [1 x H](+) propeller is >71 kJ mol(-1). The ammonium proton is encapsulated in the tetrahedral coordination sphere provided by the endo (i) nitrogen bridgehead atom and the three proximal thioether sulfurs, which makes [1 x H](+) a proton complex. Use of the optically active acid (R)-(-)- or (S)-(+)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (BNPH) in chloroform allowed us to induce a significant diastereomeric excess (24% de), which produced a detectable ICD. The de was decreased in acetone-d6 (10%), suggesting that the sense of chirality of [1 x H](+) is controlled by ion-pair interactions. Detailed NMR studies allowed us to locate the chiral anion on the endo side of [1 x H](+), in the cavity lined by endo t-Bu groups, and to establish that the rate of anion exchange in [1 x H][(S,R)-(+/-)-BNP] was higher than the rate of propeller inversion of [1 x H](+).     

Heterodinuclear Ln[bond]Na complexes with an asymmetrical macrocyclic compartmental Schiff base

Heterodinuclear lanthanide(III)-sodium(I) complexes [LnNa(L)(Cl)(2)(CH(3)OH)] (Ln=La[bond]Nd, Sm[bond]Lu), where H(2)L is a [1+1] asymmetric compartmental macrocyclic ligand containing a N(3)O(2) Schiff base and a O(3)O(2) crown-ether-like coordination site, have been prepared and characterized by IR, (1)H, (13)C, and (23)Na NMR spectroscopy, mass spectrometry, and electron microscopy. In the solid state, the lanthanide(III) ions coordinate the Schiff-base N(3)O(2) site, and the sodium ion occupies the O(3)O(2) crownlike cavity, as shown by the X-ray crystal structures of the Nd, Eu, Gd, and Yb derivatives. In these complexes, the lanthanide(III) ion is coordinated by two chlorine atoms in the trans position and by three nitrogen and two negatively charged phenol oxygen atoms of the Schiff base, and the ion is heptacoordinated with a pentagonal bipyramidal geometry. The sodium ion is coordinated by three etheric oxygen atoms and the two phenolic oxygens that act as a bridge. A methanol molecule is also coordinated in the apical position of the resulting pentagonal pyramidal polyhedron. A detailed (1)H and (13)C NMR study was carried out in CD(3)OD for both diamagnetic and paramagnetic heterodinuclear complexes [LnNa(L)(Cl)(2)(CH(3)OH)]. The complexes are also isostructural in solution, and their structures parallel those found in the solid state. Moreover, some significative distances determined in the solid state and in solution are comparable. Finally, the potential use of these complexes as molecular probes for the selective recognition of specific metal ions has been tested. In particular, their ability to act as shift reagents and the selectivity of the O(3)O(2) site towards Li(+), Ca(2+), and K(+) were investigated by (23)Na NMR spectroscopy.     

Synthesis, structural, spectral, thermal and antimicrobial studies of palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes derived from N,N,N,N-tetradentate macrocyclic ligand

Palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes of general stoichiometry [PdL]Cl(2), [PtL]Cl(2), [Ru(L)Cl(2)]Cl and [Ir(L)Cl(2)]Cl are synthesized with a tetradentate macrocyclic ligand, derived from 2,6-diaminopyridine with 3-ethyl 2,4-pentanedione. Ligand was characterized on the basis of elemental analyses, IR, mass, and (1)H NMR and (13)C NMR spectral studies. All the complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, mass, electronic spectral techniques and thermal studies. The value of magnetic moments indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moments corresponding its one unpaired electron. The macrocyclic ligand and all its metal complexes were also evaluated in vitro against some plant pathogenic fungi and bacteria to assess their biocidal properties.     

Jørgensen complex within a molecular container: selective encapsulation of trans-[Co(en)2Cl2]+ into cucurbit[8]uril and influence of inclusion on guest's properties

The unprecedented selective encapsulation of trans-[Co(en)2Cl2]+ from the mixture of trans and cis isomers into the cavity of macrocyclic cavitand cucurbit[8]uril (C48H48N32O16, CB[8]) leads to the inclusion compound {trans-[Co(en)2Cl2]@CB[8]}Cl.17H2O (1). Single-crystal X-ray analysis, 1H NMR, and ESI-MS spectra confirm the formation of host-guest complex 1 in both solid state and solution. The geometry of the complex cation alters significantly upon inclusion, which causes appreciable hypsochromic shifts of the absorption bands of the guest complex. According to TGA data, inclusion of trans-[Co(en)2Cl2]+ dramatically stabilizes the complex toward thermal decomposition. Encapsulation of trans-[Co(en)2Cl2]+ into the CB[8] cavity also increases the stability of the metal complex toward isomerization into the cis form. The supramolecular adduct {cis-[Co(en)2(H2O)2](CB[8])6}Cl3.ca109.5H2O (2) was isolated only after prolonged heating of an aqueous solution of 1 at 120 degrees C in an evacuated tube; it was characterized by X-ray crystallography, IR, and elemental analysis.     

Synthesis and X-ray Structures of Novel Macrocycles and Macrobicycles Containing N,N-Di(pyrrolylmethyl)-N-methylamine Moiety: Preliminary Anion Binding Study

The [2 + 2] Schiff base condensation reactions between the newly synthesized dialdehyde, N,N-di(α-formylpyrrolyl-α-methyl)-N-methylamine), and ethylenediamine or p-phenylenediamine dihydrochloride readily afforded the 30- and 34-membered large size macrocycles in very high yields. Subsequent reduction reactions of these macrocycles with NaBH(4) gave the corresponding saturated macrocyclic hexaamines in good yields. The analogous reaction of the new dialdehyde with a triamine molecule afforded the [3 + 2] Schiff base macrobicycle in high yield, which was then reduced by reaction with NaBH(4) to give the saturated macrobicycle. All these compounds were characterized by spectroscopic methods. The anion binding properties of the saturated macrocycles having the ethylene and the phenylene linkers in CDCl(3) were studied by NMR titration methods. Although they have similar pyrrolic and amine NH groups their binding properties are different and interesting, owing to the conformational flexibility or rigidness rendered by the ethylene or phenylene groups, respectively. The macrocycle having the ethylene linkers binds anions in a 1:1 fashion, while the other receptor having the phenylene linkers prefers to bind anions in a sequential 1:2 fashion and has a multiple equilibria between a 1:1 and a 1:2 complexes, as shown by their binding constants, curve fittings by EQNMR, and Job plots. The X-ray structures of the 1:2 methanol, the aqua and the benzoate anion complexes of the macrocycles show two cavities in which the guests are bound, correlating with the high affinity found for the formation of stable 1:2 complexes in solution. The X-ray structure showed that the macrobicycle Schiff base adopts an eclipsed paddle-wheel shaped conformation and exhibits an out-out configuration at the bridgehead nitrogen atoms.     

From helix to macrocycle: anion-driven conformation control of π-conjugated acyclic oligopyrroles

Anion-responsive pyrrole-based linear receptor oligomers were newly synthesized and their anion-driven dynamic conformation changes were investigated. Phenylene-bridged dimers and a tetramer of dipyrrolyldiketone boron complexes as π-conjugated acyclic anion receptors formed anion-driven helical structures in the solid and solution states. In fact, single-crystal X-ray analyses of the receptor-anion complexes exhibited various helical structures, such as [1+1]- and [1+2]-type single helices and a [2+2]-type double helix according to the lengths of oligomers and the existence of terminal aryl substituents. Anion-binding modes and behaviors of the oligomers in solution state were also examined by (1)H NMR and UV/Vis spectra along with ESI-TOF MS. Differences in the binding modes were observed in the solid and solution states. The oligomers showed augmented anion-binding constants and anion-tunable electronic and optical properties in comparison with the monomer receptor. A negative cooperative effect in the tetramer was observed in the second anion binding of the [1+2]-type single helix due to electrostatic repulsion between two anions captured in the helix. Further, an anion-template coupling reaction from the linear dimer provided a receptor macrocycle, which was obtained as a Cl(-) complex with distinct electronic and optical properties. The macrocycle exhibited extremely high anion-binding constants (>10(10) m(-1) in CH(2)Cl(2)) through multiple hydrogen bonding.     

Chemistry and stereochemistry of the interaction of the water-soluble phosphine [HO(CH2)3]3P with cinnamaldehyde in aqueous media

To learn more about the bleaching action of pulps by (hydroxymethyl)phosphines, cinnamaldehyde was reacted with tris(3-hydroxypropyl)phosphine, [HO(CH2)3]3P (THPP), in aqueous solution at room temperature under argon. Self-condensation of the aldehyde into two isomeric products, 2-benzyl-5-phenyl-pent-2,4-dienal and 5-phenyl-2-(phenylmethylene)-4-pentenal, is observed; this implies initial nucleophilic attack of the phosphine at the beta-carbon of the alpha,beta-unsaturated aldehyde. Reaction in D2O gives the same products in which all but the phenyl and CHO protons are replaced by deuterons. NMR studies are consistent with carbanion formation and subsequent condensation of two phosphonium-containing aldehyde moieties to generate the products with concomitant elimination of phosphine oxide. In D2O in the presence of HCl, THPP reversibly attacks the aldehyde-C atom to form the (alpha-hydroxy)phosphonium derivative [PhCH=C(H)CH(OD)PR3]Cl (where R=(CH2)3OD), which slowly converts into the deuterated bisphosphonium salt [R3PCH(Ph)CD(H)CH(OD)PR3]Cl2 via the deuterated monophosphonium salt [R3PCH(Ph)CD(H)CHO]Cl. The phosphonium intermediates and phosphonium products in this chemistry, although having up to three chiral carbon centers, are formed with high stereoselectivity just in enantiomeric forms. In acetone-H2O (1:1 v/v), a cross-condensation of cinnamaldehyde with acetone to give 6-phenyl-3,5-hexadien-2-one is promoted by THPP via generation of OH-.     

Nonchelated d0 zirconium-alkoxide-alkene complexes

The reaction of Cp'2Zr(O(t)Bu)Me (Cp' = C5H4Me) and [Ph3C][B(C6F5)4] yields the base-free complex [Cp'2Zr(O(t)Bu)][B(C6F5)4] (6), which exists as Cp'2Zr(O(t)Bu)(ClR)+ halocarbon adducts in CD2Cl2 or C6D5Cl solution. Addition of alkenes to 6 in CD2Cl2 solution at low temperature gives equilibrium mixtures of Cp'2Zr(O(t)Bu)(alkene)+ (12a-l), 6, and free alkene. The NMR data for 12a-l are consistent with unsymmetrical alkene bonding and polarization of the alkene C=C bond with positive charge buildup at C(int) and negative charge buildup at C(term). These features arise due to the lack of d-pi* back-bonding. Equilibrium constants for alkene coordination to 6 in CD2Cl2 at -89 degrees C, K(eq) = [12][6](-1)[alkene](-1), vary in the order: vinylferrocene (4800 M(-1)) > ethylene (7.0) approximately alpha-olefins > cis-2-butene (2.2) > trans-2-butene (<0.1). Alkene coordination is inhibited by sterically bulky substituents on the alkene but is greatly enhanced by electron-donating groups and the beta-Si effect. Compounds 12a-l undergo two dynamic processes: reversible alkene decomplexation via associative substitution of a CD2Cl2 molecule, and rapid rotation of the alkene around the metal-(alkene centroid) axis.     

Reactivity of (ferrocenylmethyl)phosphine toward palladium and platinum chlorides. X-ray structure of [Pd(PH2CH2Fc)Cl(mu-PHCH2Fc)]4 (Fc = ferrocenyl), a unique complex containing a Pd4P4 cycle

The reaction of 2 equiv of the air-stable primary phosphine (ferrocenylmethyl)phosphine (PH2CH2Fc, 1) with [Pd(cod)Cl2] (Fc = ferrocenyl; cod = 1,5-cyclooctadiene) at 298 K gave the phosphanido-bridged Pd(II) tetramer [Pd(PH2CH2Fc)Cl(mu-PHCH2Fc)]4 (2), which shows an unprecedented arrangement of four Pd atoms embedded in an eight-membered Pd4P4 ring. An X-ray diffraction study showed that 2 crystallizes in the triclinic space group P with a = 17.607(7) A, b = 17.944(7) A, c = 18.792(7) A, alpha = 107.120(12) degrees, beta = 96.344(13) degrees, gamma = 117.087(15) degrees . Each molecule contains four palladium atoms in a distorted square-planar coordination formed by one chlorine and three phosphorus atoms. Two of the latter belong to bridging primary phosphanides and the remaining one is contributed by a terminal PH2CH2Fc ligand. The coordination environments of neighboring metal centers adopt an almost perpendicular mutual orientation. The reaction of 2 equiv of 1 with [Pt(cod)Cl2] at 323 K yielded the analogous Pt(II) tetramer of formula [Pt(PH2CH2Fc)Cl(mu-PHCH2Fc)]4 (3), which was fully characterized by multinuclear and dynamic NMR, IR, and elemental analyses. Single-crystal X-ray diffraction on 3 confirmed the tetranuclear arrangement in the solid state, but orientational disorder of the molecule precludes a more detailed discussion of the structure. Low-temperature NMR experiments in CD2Cl2 showed the presence of two slowly interconnecting conformers. Reaction of 1 and [M(cod)Cl2] (M = Pd or Pt) at lower temperatures (273 K for Pd, 295 K for Pt) in dichloromethane allowed the detection in solution of the mononuclear species cis-[M(PH2CH2Fc)2Cl2] (M = Pd, 4; M = Pt, 5) which, upon heating, transformed into the tetramers 2 and 3, respectively. Solid samples of 4 and 5 could be isolated after workup at low temperature and were characterized by conventional spectroscopic methods.     

Synthesis and characterization of cationic tungsten(V) methylidynes

Cationic tungsten(V) methylidynes [L4W(X)[triple bond]CH]+[B(C6F5)4]- [L = PMe3, 0.5dmpe (dmpe = Me2PCH2CH2PMe2), X = Cl, OSO2CF3] have been prepared in high yield by a one-electron oxidation of the neutral tungsten(IV) methylidynes L4W(X)[triple bond]CH with [Ph3C]+[B(C6F5)4]-. The ease and reversibility of the one-electron oxidation of L4W(X)[triple bond]CH were demonstrated by cyclic voltammetry in tetrahydrofuran (E1/2 is approximately -0.68 to -0.91 V vs Fc). The paramagnetic d1 (S = 1/2) complexes were characterized in solution by electron spin resonance (g = 2.023-2.048, quintets due to coupling to 31P) and NMR spectroscopy and Evans magnetic susceptibility measurements (mu = 2.0-2.1 muB). Single-crystal X-ray diffraction showed that the cationic methylidynes are structurally similar to the neutral precursor methylidynes. In addition, the neutral (PMe3)4W(Cl)[triple bond]CH was deprotonated with a strong base at the trimethylphosphine ligand to afford (PMe3)3(Me2PCH2)W[triple bond]CH, a tungsten(IV) methylidyne complex that features a (dimethylphosphino)methyl ligand.     

Platinum(IV) complexes with dipeptide. X-ray crystal structure, 195Pt NMR spectra, and their inhibitory glucose metabolism activity in Candida albicans

Three dipeptide complexes of the form K[Pt(IV)(dipep)Cl3] and two complexes of the form K[Pt(IV)(Hdipep)Cl4] were newly prepared and isolated. The platinum(IV) complexes containing the dipeptide were obtained directly by adding KI to H2[PtCl6] solution. The reaction using KI was rapidly completed and provided analytically pure yellow products in the form of K[Pt(dipeptide)Cl3] for H2digly, H2gly(alpha)-ala, H2alpha-alagly and H2di(alpha)-ala. The K[Pt(IV)(digly)Cl3] complex crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 10.540(3) A, b = 13.835(3) A, c = 8.123(3) A, beta = 97.01(2) degrees, Z = 4. The crystal data represented the first report of a Pt(IV) complex with a deprotonated peptide, and this complex has the rare iminol type diglycine(2-) coordinating to Pt(IV) with the bond lengths of the C2-N1 (amide) bond (1.285(13) A). The 195Pt NMR peaks of the K[Pt(IV)(dipep)Cl3] and the K[Pt(IV)(Hdipep)Cl4] complexes appeared at about 270 ppm and at about -130 ppm, respectively, and were predicted for a given set of ligand atoms. While the K[Pt(IV)(x-gly)Cl3] complexes, where x denotes the glycine or alpha-alanine moieties, were easily reduced to the corresponding platinum(II) complexes, the K[Pt(IV)(x-alpha-ala)Cl3] complexes were not reduced, but the Cl- ion was substituted for OH- ion in the reaction solution. The K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] complexes inhibited the growth of Candida albicans, and the antifungal activities were 3- to 4-fold higher than those of cisplatin. The metabolism of glucose in C. albicans was strongly inhibited by K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] but not by the antifungal agent fluconazole.     

Synthesis and structure determination of pyrazine-containing macrocyclic polyazomethines

<正>Two pyrazine-contairting macrocyclic polyazomethines 2 and 3 were synthesized by direct[2 + 2]and[3 + 3]condensation reactions between 2,2'-[pyrazine-2,3-diylbis(oxy)]dibenzaldehyde(1) and hydrazine.Both 2 and 3 were characterized by NMR, HRMS,and their structures were determined via X-ray crystal diffraction studies.     

Syntheses and characterization of oxygen/sulfur-bridged incomplete cubane-type clusters, [Mo3S4Tp3]+ and [Mo3OS3Tp3]+, and a mixed-metal cubane-type cluster, [Mo3FeS4ClTp3]. X-ray structures of [Mo3S4Tp3]Cl, [Mo3OS3Tp3]PF6, and [Mo3FeS4ClTp3

The reaction of [Mo3S4(H2O)9]4+ (1) with hydrotris(pyrazolyl)borate (Tp) ligands produced [Mo3S4Tp3]Cl x 4 H2O ([3]Cl x 4 H2O) in an excellent yield. An X-ray structure analysis of [3]Cl x 4 H2O revealed that each molybdenum atom bonded to the Tp ligand. We report four salts of 3, [3]Cl x 4 H2O, [3]tof x 2 H2O, [3]PF6 x H2O, and [3]BF4 x 2 H2O in this paper. The solubility and stability of the chloride salt in organic solvents differ completely from those of the other salts. We have also prepared a new compound, [Mo3OS3Tp3]PF6 x H2O ([4]PF6 x H2O), via the reaction of [Mo3OS3(H2O)9]4+ (2) with KTp in the presence of NH4PF6. All the molybdenum atoms bonded to Tp ligand. 1H NMR signals corresponding to nine protons bonded to three pyrazole rings in one Tp were observed in a spectrum (at 253 K) of [3]BF4 x 2 H2O. It shows that cluster 3 has a 3-fold rotation axis in CD2Cl2 solution. Twenty-one 1H NMR signals corresponding to twenty-seven protons bonded to nine pyrazole rings in three Tp ligands were observed in a spectrum (at 233 K) of [4]PF6 x H2O; obviously, 4 has no 3-fold rotation axis, in contrast to 3. The short CH...mu3S distance caused large upfield chemical shifts in the 1H NMR spectra of 3 and 4. The reaction of 3 with metallic iron in CH2Cl2 produced [Mo3FeS4XTp3] (X = Cl (5), Br (6)). X-ray structure analysis of 5 has revealed the existence of a cubane-type core Mo3FeS4. Complex 3 functions as a metal-complex ligand for preparing a novel mixed-metal complex even in nonaqueous solvents. The cyclic voltammogram of 5 shows two reversible one-electron couples (E(1/2) = -1.40 and 0.52 V vs SCE) and two irreversible one-electron oxidation processes (E(pc) = 1.54 and 1.66 V vs SCE).     

1,2,4,3,5-benzotrithiadiazepine and its unexpected hydrolysis to unusual 7H,14H-dibenzo[d,i][1,2,6,7,3,8]tetrathiadiazecine

Previously unknown 1,2,4,3,5-benzotrithiadiazepine 1 was prepared by 1:1 condensation of Ph-N=S=N-SiMe3 with S2Cl2 followed by intramolecular ortho-cyclization of [Ph-N=S=N-S-S-Cl] intermediate, and hydrolyzed in pyridine to unusual macrocyclic 7H,14H-dibenzo[d,i][1,2,6,7,3,8]tetrathiadiazecine 2.     

An acidity scale of tetrafluoroborate salts of phosphonium and iron hydride compounds in [D2]dichloromethane

Equilibrium constants (K) for reactions between acids and the conjugate base forms of a number of phosphonium salts, [HPR3][BF4], and iron hydrides, [Fe(CO)3H(PR3)2][BF4], in CD(2)Cl(2) have been determined by means of 31P and 1H NMR spectroscopy at 20 degrees C. The anchor compound chosen for pK(CD(2)Cl(2)) determinations was [HPCy3][BF4] with a pK(CD(2)Cl(2)) value of 9.7, as assigned by literature convention (Cy: cyclohexyl). A continuous scale of pK(CD(2)Cl(2)) values covering the range from 9.7 to -3 was created and correlated with the DeltaH values reported by Angelici and co-workers and literature pK(a) values. The pK(CD(2)Cl(2)) values for 15 other hydride or dihydrogen complexes of the iron group elements and of diethyl ether were also placed on this scale. The crystal structures of [Fe(CO)3H(PCy(2)Ph)2][BF4] and [Fe(CO)3(PCy(2)Ph)2] revealed that the trans-oriented, bulky, unsymmetrical phosphane ligands distort the equatorial plane of the complexes. The acidity of iron carbonyl hydrides is an important feature of the reactions of iron hydrogenase enzymes.     

Simultaneous fluoride binding to ferrocene-based heteronuclear bidentate Lewis acids

A series of micro2-fluoro-bridged heteronuclear bidentate Lewis acid complexes [K(18-crown-6)THF]+ [Fc(BMeF)(SnMe2Cl)F]- (1-2F), [K(18-crown-6)THF]+ [Fc(BMeF)(SnMe2F)F]- (1-3F), [K(18-crown-6)THF]+ [Fc(BMePh)(SnMe2Cl)F]- (2-F), and [K(18-crown-6)THF]+ [Fc(BMePh)(SnMe2F)F]- (2-2F) (Fc=1,2-ferrocenediyl) was prepared. Compounds 2-F and 2-2F were obtained as a mixture of diastereomers, which arise due to the generation of a stereocenter at boron in addition to their inherent planar chirality. All compounds have been studied in the solid state by single-crystal X-ray diffraction analysis and by multinuclear NMR spectroscopy in solution. As a result of bridging-fluoride interactions, tetrahedral boron and distorted trigonal-bipyramidal tin centers are observed. Comparison with the corresponding monofunctional ferrocenylborates further supports the bridging nature of the fluoride anion. Two-dimensional exchange spectroscopy 19F NMR studies provide evidence for facile intermolecular and intramolecular fluorine exchange processes. All complexes display reversible one-electron oxidation events at lower potentials than those of the tricoordinate ferrocenylborane precursors, which is typical of ferrocenylborate complexes.