Interconversion and Reactivity of Two Heterometallic Tin-Containing Cuboidal Clusters from [Mo(3)S(4)(H(2)O)(9)](4+): X-ray Structure of the Single Cube with an Mo(3)SnS(4) Core

The Mo(3)SnS(4)(6+) single cube is obtained by direct addition of Sn(2+) to [Mo(3)S(4)(H(2)O)(9)](4+). UV-vis spectra of the product (0.13 mM) in 2.00 M HClO(4), Hpts, and HCl indicate a marked affinity of the Sn for Cl(-), with formation of the more strongly yellow [Mo(3)(SnCl(3))S(4)(H(2)O)(9)](3+) complex complete in as little as 0.050 M Cl(-). The X-ray crystal structure of (Me(2)NH(2))(6)[Mo(3)(SnCl(3))S(4)(NCS)(9)].0.5H(2)O has been determined and gives Mo-Mo (mean 2.730 ?) and Mo-Sn (mean 3.732 ?) distances, with a difference close to 1 ?. The red-purple double cube cation [Mo(6)SnS(8)(H(2)O)(18)](8+) is obtained by reacting Sn metal with [Mo(3)S(4)(H(2)O)(9)](4+). The double cube is also obtained in approximately 50% yield by BH(4)(-) reduction of a 1:1 mixture of [Mo(3)SnS(4)(H(2)O)(10)](6+) and [Mo(3)S(4)(H(2)O)(9)](4+). Conversely two-electron oxidation of [Mo(6)SnS(8)(H(2)O)(18)](8+) with [Co(dipic)(2)](-) or [Fe(H(2)O(6)](3+) gives the single cube [Mo(3)SnS(4)(H(2)O)(12)](6+) and [Mo(3)S(4)(H(2)O)(9)](4+) (up to 70% yield), followed by further two-electron oxidation to [Mo(3)S(4)(H(2)O)(9)](4+) and Sn(IV). The kinetics of the first stages have been studied using the stopped-flow method and give rate laws first order in [Mo(6)SnS(8)(H(2)O)(18)](8+) and the Co(III) or Fe(III) oxidant. The oxidation with [Co(dipic)(2)](-) has no [H(+)] dependence, [H(+)] = 0.50-2.00 M. With Fe(III) as oxidant, reaction steps involving [Fe(H(2)O)(6)](3+) and [Fe(H(2)O)(5)OH](2+) are implicated. At 25 degrees C and I = 2.00 M (Li(pts)) k(Co) is 14.9 M(-)(1) s(-)(1) and k(a) for the reaction of [Fe(H(2)O)(6)](3+) is 0.68 M(-)(1) s(-)(1) (both outer-sphere reactions). Reaction of Cu(2+) with the double but not the single cube is observed, yielding [Mo(3)CuS(4)(H(2)O)(10)](5+). A redox-controlled mechanism involving intermediate formation of Cu(+) and [Mo(3)S(4)(H(2)O)(9)](4+) accounts for the changes observed.     

Crystal structures and magnetic properties of 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)-containing copper(II) complexes

Four new copper(II) complexes of formula [Cu(2)(tppz)(dca)(3)(H(2)O)].dca.3H(2)O (1), [Cu(5)(tppz)(N(3))(10)](n)() (2), [[Cu(2)(tppz)(N(3))(2)][Cu(2)(N(3))(6)]](n)() (3), and [Cu(tppz)(N(3))(2)].0.33H(2)O (4) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and dca = dicyanamide anion] have been synthesized and structurally characterized by X-ray diffraction methods. The structure of complex 1 is made up of dinuclear tppz-bridged [Cu(2)(tppz)(dca)(3)(H(2)O)](+) cations, uncoordinated dca anions, and crystallization water molecules. The copper-copper separation across bis-terdentate tppz is 6.5318(11) A. Complex 2 is a sheetlike polymer whose asymmetric unit contains five crystallographically independent copper(II) ions. These units are building blocks in double chains in which the central part consists of a zigzag string of copper atoms bridged by double end-on azido bridges, and the outer parts are formed by dinuclear tppz-bridged entities which are bound to the central part through single end-on azido bridges. The chains are furthermore connected through weak, double out-of-plane end-on azido bridges, yielding a sheet structure. The intrachain copper-copper separations in 2 are 6.5610(6) A across bis-terdentate tppz, 3.7174(5) and 3.8477(5) A across single end-on azido bridges, and from 3.0955(5) to 3.2047(7) A across double end-on azido bridges. The double dca bridge linking the chains into sheets yields a copper-copper separation of 3.5984(7) A. The structure of 3 consists of centrosymmetric [Cu(2)(tppz)(N(3))(2)](2+) and [Cu(2)(N(3))(6)](2)(-) units which are linked through axial Cu.N(azido) (single end-on and double end-to-end coordination modes) type interactions to afford a neutral two-dimensional network. The copper-copper separations within the cation and anion are is 6.5579(5) A (across the bis-terdentate tppz ligand) and 3.1034(6) A (across the double end-on azido bridges), whereas those between the units are 3.6652(4) A (through the single end-on azido group) and 5.3508(4) A (through the double end-to-end azido bridges). The structure of complex 4 is built of neutral [Cu(tppz)(N(3))(2)] mononuclear units and uncoordinated water molecules. The mononuclear units are grouped by pairs to give a rather short copper-copper separation of 3.9031(15) A. The magnetic properties of 1-4 have been investigated in the temperature range 1.9-300 K. The magnetic behavior of complexes 1 and 4 is that of antiferromagnetically coupled copper(II) dimers with J = -43.7 (1) and -2.1 cm(-)(1) (4) (the Hamiltonian being H = -JS(A).S(B)). An overall ferromagnetic behavior is observed for complexes 2 and 3. Despite the structural complexity of 2, its magnetic properties correspond to those of magnetically isolated tppz-bridged dinuclear copper(II) units with an intermediate antiferromagnetic coupling (J = -37.5 cm(-)(1)) plus a ferromagnetic chain of hexanuclear double azido-bridged copper(II) units (the values of the magnetic coupling within and between the hexameric units being +61.1 and +0.0062 cm(-)(1), respectively). Finally, the magnetic properties of 3 were successfully analyzed through a model of a copper(II) chain with regular alternating of three ferromagnetic interactions, J(1) = +69.4 (across the double end-on azido bridges in the equatorial plane), J(2) = +11.2 (through the tppz bridge), and J(3) = +3.4 cm(-)(1) (across the single end-on azido bridge).     

Betaine-induced assembly of neutral infinite columns and chains of linked silver(I) polyhedra with embedded acetylenediide

Ten polymeric silver(I) double salts containing embedded acetylenediide: [(Ag2C2)2(AgCF3CO2)9(L1)3] (1), [(Ag2C2)2(AgCF3CO2)10(L2)3]H2O (2), [(Ag2C2)(AgCF3CO2)4(L3)(H2O)]0.75 H2O (3), [(Ag2C2)(1.5)(AgCF3CO2)7(L4)2] (4), [(Ag2C2)(AgCF3CO2)7(L5)2(H2O)] (5), [(Ag2C2) (AgC2F5CO2)7(L1)3(H2O)] (6), [(Ag2C2)(AgCF3CO2)7(L1)3(H2O)]2 H2O (7), [(Ag2C2)(AgC2F5CO2)6(L3)2] (8), [(Ag2C2)2(AgC2F5CO2)12(L4)2(H2O)4]H2O (9), and [(Ag2C2)(AgCF3CO2)6(L3)2(H2O)]H2O (10) have been isolated by varying the types of betaines, the perfluorocarboxylate ligands employed, and the reaction conditions. Single-crystal X-ray analysis has shown that 1-4 all have a columnar structure composed of fused silver(I) double cages, with C2(2-) species embedded in its stem and an exterior coat comprising anionic and zwitterionic carboxylates. For 5 and 6, single silver(I) cages are linked into a beaded chain through both types of carboxylate ligands. In 7, two different coordination modes of L1 connect the silver(I) polyhedra into a chain. For 8, the mu(2)-O,O' coordination mode of L3 connects the silver(I) double cages into a chain. Compound 9 exhibits a two-dimensional architecture generated from the cross-linkage of double cages by C2F5CO2-, L4, and [Ag2(C2F5CO2)2] units. Similar to 9, 10 is also a two-dimensional structure, which is formed by connecting the chains of linked double cages through [Ag2(CF3CO2)2] bridging.     

Flexible and shape-selective guest binding at Cu(II) axial sites in 1-dimensional Cu(II)-1,2-bis(4-pyridyl)ethane coordination polymers

A series of guest-binding Cu(II) coordination polymers, {[Cu(bpetha)2(acetone)2].2PF6}n (bpetha = 1,2-bis(4-pyridyl)ethane) (1), {[Cu(bpetha)2(DMF)2].2PF6}n (2), {[Cu(bpetha)(2)(MeCN)(2)].2PF6.2MeCN}n (3), {[Cu(bpetha)2(H2O)2].2PF6.3THF.2H2O}n (4), {[Cu(bpetha)2(H2O)2].2PF6.3dioxane}n (5), and {[Cu(bpetha)2(H2O)2].2PF6.2-PrOH.2H2O}n (6), have been synthesized and crystallographically characterized. Their framework stabilities and guest-exchange properties have also been investigated. All compounds form a similar framework motif, a "double chain", in which the bpetha ligands bridge Cu(II) centers to form 1-D [Cu(bpetha)2]n double chains. A variety of Lewis base guest molecules, such as H2O, acetone, DMF, MeCN, THF, dioxane, and 2-PrOH, are incorporated into the assembly of the 1-D double chains. These chains flexibly change their forms of assembly in a guest-dependent manner. Interestingly, acetone, DMF, and MeCN guests with a carbonyl or cyanide group coordinate directly to the axial sites of the Cu(II) centers; in contrast, THF, dioxane, and 2-PrOH guests with an ether or alcohol group are incorporated into the frameworks not via coordination bonds but via weak interactions (hydrogen bonds and van der Waals forces). This selectivity is probably due to steric effects at coordinated oxygen or nitrogen atoms of the guests. Crystal-to-crystal transformations triggered by guests are observed, during which guests coordinated to the Cu(II) axial sites are readily removed and replaced by other guests.     

Dimers of and tautomerism between 2-pyrimidinethiol and 2(1H)-pyrimidinethione: a density functional theory (DFT) study

Density functional theory (BLYP, B3LYP, B3P86, B3PW91) with the 6-31+G(d,p), 6-311+G(d,p), and cc-pVTZ basis sets has been used to calculate structural parameters, relative energies, and vibrational spectra of 2-pyrimidinethiol (1) and 2(1H)-pyrimidinethione (2) and their hydrogen-bonded homodimers (C(2) 3, C(2h) [4](double dagger), C(2h) 5), monohydrates, and dihydrates and a heterodimer (6). Several transition state structures proposed for the tautomerization process have also been examined. At the B3PW91/6-311+G(d,p)//B3PW91/6-31+G(d,p) level of theory 2-pyrimidinethiol (1) is predicted to be 3.41 kcal/mol more stable (E(rel)) than 2(1H)-pyrimidinethione (2) in the gas phase and 2 is predicted to be 6.47 kcal/mol more stable than 1 in aqueous medium. An unfavorable planar intramolecular strained four center transition state (TS1) for the tautomerization of 1 and 2 in the gas-phase lies 29.07 kcal/mol higher in energy than 2-pyrimidinethiol (1). The C(2) 2-pyrimidinethiol dimer (3) is 6.84 kcal/mol lower in energy than the C(2) homodimer transition state structure ([11](double dagger)) that connects dimers 3 and 4. Transition state [11](double dagger) provides a facile pathway for tautomerization between 1 and 2 in the gas phase (monomer-dimer promoted tautomerization). The hydrogen bonded 2-pyrimidinethiol- - -H(2)O and 2-pyrimidinethiol- - -2H(2)O structures are predicted to be 1.27 and 1.55 kcal/mol, respectively, higher in energy than 2(1H)-pyrimidinethione- - -H(2)O and 2(1H)-pyrimidinethione- - -2H(2)O. Water promoted tautomerization via cyclic transition states involving one water molecule (TS- - -H(2)O, [12](double dagger)) and two water molecules (TS- - -2H(2)O, [13](double dagger)) lie 11.42 and 11.44 kcal/mol, respectively, higher in energy than 2-pyrimidinethiol- - -H(2)O and 2-pyrimidinethiol- - -2H(2)O. Thus, the hydrated transition states [12](double dagger) and [13](double dagger) are involved in the tautomerism between 1 and 2 in aqueous medium.     

Three-, two-, and one-dimensional metal phosphonates based on [hydroxy(4-pyridyl)methyl]phosphonate: M{(4-C5H4N)CH(OH)PO3}(H2O) (M = Ni, Cd) and Gd{(4-C5H4N)CH(OH)P(OH)O2}3.6H2O

Based on the [hydroxy(4-pyridyl)methyl]phosphonate ligand, three compounds with formula Ni{(4-C(5)H(4)N)CH(OH)PO(3)}(H(2)O) (1), Cd{(4-C(5)H(4)N)CH(OH)PO(3)}(H(2)O) (2), and Gd{(4-C(5)H(4)N)CH(OH)P(OH)O(2)}(3).6H(2)O (3) have been synthesized under hydrothermal conditions. The crystal data for 1 are as follows: orthorhombic, space group Pbca, a = 8.7980(13) A, b = 10.1982(15) A, and c = 17.945(3) A. For 2 the crystal data are as follows: monoclinic, space group C2/c, a = 23.344(6) Angstroms, b = 5.2745(14) Angstroms, c = 16.571(4) Angstroms, and beta = 121.576(4) degrees. The crystal data for 3 are as follows: rhombohedral, space group R, a = 22.2714(16) Angstroms, b = 22.2714(16) Angstroms, and c = 9.8838(11) Angstroms. Compound 1 adopts a three-dimensional pillared layered structure in which the inorganic layers made up of corner-sharing {NiO(5)N} octahedra and {CPO(3)} tetrahedra are connected by pyridyl groups. A two-dimensional layer structure is found in compound 2, which contains alternating inorganic double chains and pyridyl rings. Compound 3 has a one-dimensional chain structure where the Gd atoms are triply bridged by O-P-O linkages. The pyridyl nitrogen atom in 3 remains uncoordinated and is involved in the interchain hydrogen bonds. Magnetic susceptibility studies of 1 and 3 reveal that weak ferromagnetic interactions are mediated between Ni(II) centers in compound 1. For compound 3, the behavior is principally paramagnetic.     

The bis-phenyltin-substituted, lone-pair-containing tungstoarsenate [(C(6)h(5)Sn)(2)as(2)W(19)O(67)(H(2)O)](8)(-)

The bis-phenyltin-substituted, lone-pair-containing tungstoarsenate [(C(6)H(5)Sn)(2)As(2)W(19)O(67)(H(2)O)](8)(-) (1) has been synthesized and characterized by multinuclear NMR, IR, and elemental analysis. Single-crystal X-ray analysis was carried out on (NH(4))(7)Na[(C(6)H(5)Sn)(2)As(2)W(19)O(67)(H(2)O)].17.5H(2)O (NH(4)(-1), which crystallizes in the monoclinic system, space group P2(1)/c, with a = 18.3127(17) A, b = 24.403(2) A, c = 22.965(2) A, beta = 106.223(2) degrees, and Z = 4. Polyanion 1 consists of two B-alpha-(As(III)W(9)O(33)) Keggin moieties linked via a WO(H(2)O) fragment and two SnC(6)H(5) groups leading to a sandwich-type structure with nominal C(2)(v) symmetry. Polyanion 1 is stable in solution as indicated by the expected 6-line pattern (4:4:4:4:2:1) in (183)W NMR and the expected (119)Sn, (13)C, and (1)H NMR spectra. Synthesis of 1 was accomplished by reaction of C(6)H(5)SnCl(3) and K(14)[As(2)W(19)O(67)(H(2)O)] in a 2:1 molar ratio in aqueous acidic medium (pH 2). In the solid-state structure of NH(4)(-1, neighboring polyanions are weakly bound via W-O-Na bonds leading to chains which interact with each other via the phenyl rings resulting in a 2-D assembly.     

Diorganodiselenides and zinc(II) organoselenolates containing (imino)aryl groups of type 2-(RN=CH)C6H4

Several new diorganodiselenides containing (imino)aryl groups, [2-(RN[double bond, length as m-dash]CH)C(6)H(4)](2)Se(2) [R = Me(2)NCH(2)CH(2) (4), O(CH(2)CH(2))(2)NCH(2)CH(2) (5), PhCH(2) (6), 2',6'-(i)Pr(2)C(6)H(3) (7)] were obtained by reacting [2-{(O)CH}C(6)H(4)](2)Se(2) (3) with RNH(2). Treatment of the diselenides 6 and 7 with stoichiometric amounts of K-selectride or Na resulted in isolation of the selenolates K[SeC(6)H(4)(CH[double bond, length as m-dash]NCH(2)Ph)-2] (9) and Na[SeC(6)H(4)(CH[double bond, length as m-dash]NC(6)H(3)(i)Pr(2)-2',6')-2] (10), respectively. The reaction of potassium selenolates with anhydrous ZnCl(2) (2:1 molar ratio) gave Zn[SeC(6)H(4)(CH=NCH(2)Ph)-2](2) (11) and Zn[SeC(6)H(4)(CH[double bond, length as m-dash]NC(6)H(3)(i)Pr(2)-2',6')-2](2) (12). When the dark green solution obtained from diselenide 7 and an excess of Na (after removal of the unreacted metal) was reacted with anhydrous ZnCl(2) a carbon-carbon coupling reaction occurred and the 9,10-(2',6'-(i)Pr(2)C(6)H(3)NH)(2)C(14)H(10) (8) species was obtained. The compounds were investigated in solution by multinuclear NMR ((1)H, (13)C, (77)Se, including 2D and variable temperature experiments) and by mass spectrometry. The molecular structures of 6, 8, 11 and 12 were established by single-crystal X-ray diffraction. All compounds are monomeric in the solid state. In the diselenide 6 the (imino)aryl group acts as a (C,N)-ligand resulting in a distorted T-shaped coordination geometry of type (C,N)SeX (X = Se). For the zinc complexes 11 and 12 the (Se,N) chelate pattern of the selenolato ligands results in tetrahedral Zn(Se,N)(2) cores.     

Interplay of cubic building blocks in (et6-arene)ruthenium-containing tungsten and molybdenum oxides

A series of molybdenum and tungsten organometallic oxides containing [Ru(arene)]2+ units (arene =p-cymene, C6Me6) was obtained by condensation of [[Ru(arene)Cl2]2] with oxomolybdates and oxotungstates in aqueous or nonaqueous solvents. The crystal structures of [[Ru(eta6-C6Me6]]4W4O16], [[Ru(eta6-p-MeC6H4iPr]]4W2O10], [[[Ru-(eta6-p-MeC6H4iPr)]2(mu-OH)3]2][[Ru(eta6-p-MeC6H4iPr)]2W8O28(OH)2[Ru(eta6-p-MeC6H4iPr)(H2O)]2], and [[Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) have been determined. While the windmill-type clusters [[Ru(eta6-arene)]4(MO3)4(mu3-O)4] (M = Mo, W; arene =p-MeC6H4iPr, C6Me6), the face-sharing double cubane-type cluster [[Ru(eta6-p-MeC6H4iPr)]4(WO2)2(mu3-O)4(mu4-O)2], and the dimeric cluster [[Ru(eta6-p-MeC6H4iPr)(WO3)3(mu3-O)3(mu3-OH)Ru(eta6-pMeC6H4iPr)(H2O)]2(mu-WO2)2]2- are based on cubane-like units, [(Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) are more properly described as lacunary Lindqvist-type polyoxoanions supporting three ruthenium centers. Precubane clusters [[Ru(eta6-arene)](MO3)2(mu-O)3(mu3-O)]6- are possible intermediates in the formation of these clusters. The cluster structures are retained in solution, except for [[Ru(eta6-p-MeC6H4iPr)]4Mo4O16], which isomerizes to the triple-cubane form.     

Enhancement of the Curie temperature by isomerization of diarylethene (DAE) for an organic-inorganic hybrid system: Co4(OH)7(DAE)0.5.3H2O

Intercalation of an organic photochromic molecule into layered magnetic systems may provide multifunctional properties such as photomagnetism. To build up a photosensitive multifunctional magnet, an organic-inorganic hybrid system coupled with a photochromic diarylethene anion, 2,2'-dimethyl-3,3'-(perfluorocyclopentene-1,2-diyl)bis(benzo[b]thiophene-6-sulfonate) (DAE), and cobalt LDHs (layered double hydroxides), Co4(OH)7(DAE)0.5.3H2O, was synthesized by the anion exchange reaction between Co2(OH)3(CH3COO).H2O and DAE. In the dark and under UV-irradiated (313 nm) conditions, Co4(OH)7(DAE)0.5.3H2O with open and closed forms of DAE were obtained, respectively. The magnetic susceptibility measurements elucidated ferromagnetic intra- and interlayer interactions and Curie temperatures of TC = 9 and 20 K for cobalt LDHs with the open and closed forms of DAE, respectively. The enhancement of the Curie temperature from 9 to 20 K by substitution of the open form of DAE with the closed form of DAE as an intercalated molecule is attributed to the delocalization of the pi-electrons in the closed form of DAE, which enhances the interlayer magnetic interaction. The enhancement of the interlayer magnetic interaction induced by the delocalization of pi-electrons in intercalated molecules is strongly supported by the fact that the Curie temperature (26.0 K) of cobalt LDHs with (E,E)-2,4-hexadienedioate having a conjugated pi-electron system is enormously higher than that (7.0 K) of the cobalt LDHs with hexanedioate. By UV irradiation at 313 nm, Co4(OH)7(DAE)0.5.3H2O shows the photoisomerization of DAE from the open form to the closed one in the solid state, which leads to the enhancement of Curie temperature.     

Polar symmetry and intercalation of new multilayered hybrid molybdates: [M2(pzc)2(H2O)x][Mo5O16] (M = Co, Ni)

The layered molybdate [M2(pzc)2(H2O)x][Mo5O16] (I: M = Ni, x = 5.0; II: M = Co, x = 4.0; pzc = pyrazinecarboxylate) hybrid solids were synthesized via hydrothermal reactions at 160-165 degrees C. The structures were determined by single-crystal X-ray diffraction data for I (Cc, Z = 4; a = 33.217(4) A, b = 5.6416(8) A, c = 13.982(2) A, beta = 99.407(8) degrees , and V = 2585.0(6) A3) and powder X-ray diffraction data for II (C2/c, Z = 4; a = 35.42(6) A, b = 5.697(9) A, c = 14.28(2) A, beta = 114.95(4) degrees , and V = 2614(12) A3). The polar structure of I contains new [Ni2(pzc)2(H2O)5]2+ double layers that form an asymmetric pattern of hydrogen bonds and covalent bonds to stair-stepped [Mo5O16]2- sheets, inducing a net dipole moment in the latter. In II, however, the [Co2(pzc)2(H2O)4]2+ double layers have one less coordinated water and subsequently exhibit a symmetric pattern of covalent and hydrogen bonding to the [Mo5O16]2- sheets, leading to a centrosymmetric structure. Thermogravimetric analyses and powder X-ray diffraction data reveal that I can be dehydrated and rehydrated with from 0 to 6.5 water molecules per formula unit, which is coupled with a corresponding contraction/expansion of the interlayer distances. Also, the dehydrated form of I can be intercalated by approximately 4.3 H2S molecules per formula unit, but the intercalation by pyridine or methanol is limited to less than one molecule per formula unit.     

Reduction of tris(benzene-1,2-dithiolate)molybdenum(VI) by water. A functional mo-hydroxylase analogue system

Mo(VI)(S(2)C(6)H(4))(3) reacts cleanly and completely with H(2)O in THF to afford [H(3)O](+)[Mo(V)(S(2)C(6)H(4))(3)](-). Kinetic data were fit by the rate equation -d[Mo(VI)(S(2)C(6)H(4))(3)]/dt = k[Mo(VI)(S(2)C(6)H(4))(3)]/[H(3)O(+)], which is consistent with a coupled electron-proton transfer mechanism involving a coordinated H(2)O molecule. The Mo(VI)(S(2)C(6)H(4))(3) reduction is accelerated by the presence of PPh(3) and affords OPPh(3). (18)O isotope tracing shows that H(2)O is the source of oxygen transferred to PPh(3).     

Facile Ni(II)/ketoxime-mediated conversion of organonitriles into imidoylamidine ligands. Synthesis of imidoylamidines and acetyl amides

Treatment of alkyl nitriles with NiX(2).6H(2)O (X = Cl, NO(3)) and 2-propanone oxime, followed by (X = Cl) addition of [i-Pr(4)N](NO(3)) for precipitation of the product, resulted in the formation of amidinium nitrates [RC([double bond]NH(2))NH(2)](NO(3)) (R = Me, Et, n-Pr). The reaction went to another direction with NiX(2).2H(2)O, i.e., the reaction between neat RCN (R = Me, Et, n-Pr, i-Pr, n-Bu, CH(2)Cl, CH(2)C(6)H(4)OMe-p) and NiCl(2).2H(2)O/2-propanone oxime (other ketoximes can also be used) gave the (imidoylamidine)Ni(II) complexes [Ni[N(H)[double bond]C(R)NHC(R)[double bond]NH](2)](2+) (1(2+)-7(2+)). The latter were isolated in good yields (65-91%) as the bis-chloride salts 1.Cl(2)-6.Cl(2) and the mixed salt 7.(Cl)(p-MeOC(6)H(4)CH(2)CO(2)). Remarkably, the latter transformation does not proceed at all if NiCl(2).2H(2)O or the ketoxime are taken alone. Liberation of imidoylamidines was performed for one alkyl-containing complex [2.Cl(2)] and one benzyl-containing complex [7.(Cl)(p-MeOC(6)H(4)CH(2)CO(2))], by (i) addition of HBF(4).Et(2)O to the acetonitrile solution of the complexes to yield [N(H)[double bond]C(R)NHC(R)[double bond]NH].2HBF(4) (R = Et 8 and R = CH(2)C(6)H(4)OMe-p 9) or (ii) substitution for ethanediamine (en) with following precipitation of the complex [Ni(en)(3)]Cl(2) with formation of free N(H)[double bond]C(R)NHC(R)[double bond]NH (R = Et 10 and R = CH(2)C(6)H(4)OMe-p 11). In contrast to the liberation in nonaqueous media, treatment of 2.Cl(2) and 7.(Cl)(p-MeOC(6)H(4)CH(2)CO(2)) with Na(2)EDTA.2H(2)O in water-methanol solutions led to substitution and hydrolysis to furnish the acyl amides [EtC([double bond]O)](2)NH (12) and [p-MeOC(6)H(4)CH(2)C([double bond]O)](2)NH (13). Alternatively, 12 and 13 were obtained by hydrolysis of 10 and 11 in water at pH ca. 8.5. It was shown that the oxime complexes trans-[NiCl(2)(C(4)H(8)C[double bond]NOH)(4)] (14) or cis-[Ni(O,O-NO(3))(2)(C(4)H(8)C[double bond]NOH)(2)] (15) can be intermediates in the formation of amidines and imidoylamidines. The sequence of the Ni(II)/oxime mediated formation of (imidoylamidine)Ni complexes and liberation (or hydrolytic liberation) of the ligands opens up a novel, facile and environmentally benign route to imidoylamidines and acyl amides.     

Structural evolution and magnetic properties of Co(II) coordination polymers varied from 1D to 3D constructed by 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene

Seven Co(II) coordination polymers, [Co(btx)(3)(H(2)O)(2)](ClO(4))(2)·(btx)·2H(2)O (1), [Co(btx)(3)(H(2)O)(2)](BF(4))(2)·(btx)·2H(2)O (2), [Co(btx)(2)(H(2)O)(2)](NO(3))(2)·2H(2)O (3), [Co(btx)(2)Cl(2)] (4), [Co(btx)(BA)(2)(H(2)O)(2)]·2HBA (5), [Co(btx)(IPA)] (6) and [Co(3)(btx)(3)(BTA)(2)(H(2)O)(2)] (7) (btx = (1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), HBA = benzoic acid, H(2)IPA = isophthalic acid, H(3)BTA = benzene-1,3,5-tricarboxylic acid), have been hydrothermally synthesized and characterized. 1 and 2 are isostructural and show a 1D Co-μ(2)-btx-Co chain structure, in which btx acts as both a bridging and terminal ligand. 3 is also a 1D chain structure but different from 1 and 2. The Co(II) ions are bridged by double μ(2)-btx to form Co(2)-btx(2) rings, which were further connected into 1D chains by sharing the Co(II) ions of the rings. 4 exists as a 2D grid with (4,4) topology structure. When aromatic acid was introduced to the synthetic system, three other coordination polymers 5-7 were obtained. In 5, the 1D chain is as that of 1, except that the terminal ligand was replaced by BA(-). 6 shows a two-fold parallel interpenetration framework featuring a 6-c uninodal net with (3(3),4(6),5(5),6) Schlafli topological symbol. 7 is an interesting 3D framework, which contains a 2-nodal net motif with the unprecedented (3(6),4(2),5(6),6)(3(9),4(9),5(3))(2) topology structure. The influence of the varieties of the structures and magnetic properties are studied and discussed in detail.     

Synthesis and characterization of high nuclearity iron(III) phosphonate molecular clusters

Three new phosphonic acid ligands (4- (t)butylphenyl phosphonic acid, 3,5-dimethylphenyl phosphonic acid, and diphenylmethylphosphonic acid) have been synthesized and employed in search of high molecularity iron(III) clusters. The cluster compounds are characterized by single crystal X-ray diffraction and magnetic measurements. The solvothermal reaction of FeCl 3.6H 2O with diphenylacetic acid and p- (t)butylphenyl phosphonic acid resulted in an unprecedented dodecanuclear cluster [Fe 12(mu 2-O) 4(mu 3-O) 4(O 2CCHPh 2) 14(4- (t)buPhPO 3H) 6]( 1) having a double butterfly like core structure. [Fe 12(mu 2-O) 4(mu 3-O) 4(O 2CPh) 14(C 10H 17PO 3H) 6]( 2), another dodecanuclear cluster having core structure similar to 1, has been synthesized in a reaction between [Fe 3O(O 2CPh) 6(H 2O) 3]Cl and camphylphosphonic acid in the presence of triethylamine at ambient condition. 3,5-Dimethylphenyl phosphonic acid on reacting solvothermally with an oxo-centered iron triangle [Fe 3O(O 2CCMe 3) 6(H 2O) 3]Cl gives a nonanuclear cluster [Fe 9(mu 3-O) 4(O 3PPh(Me) 2) 3(O 2CCMe 3) 13]( 3) having icosahedral type core structure where three positions of the iron atoms have been replaced by phosphorus. Another nonanuclear [Fe 9(O) 3(OH) 3(O 3PCHPh 2) 6(O 2CCMe 3) 6(H 2O) 9] ( 4), having a distorted cylindrical core structure, has been synthesized in a similar solvothermal reaction between [Fe 3O(O 2CCMe 3) 6(H 2O) 3]Cl and biphenylmethyl phosphonic acid. All compounds are characterized by IR spectra, elemental analysis, as well as single crystal X-ray analysis. Magnetic measurements for all the compounds reveal that there are antiferromagnetic interactions between the metal centers.     

(M4H3X)2B2O2: hydrometal complexes (M = Ni, Mg) containing double tetracoordinate planar nonmetal centers (X = C, N)

Geometrical optimizations and electronic structural analyses of the -O(2)B(2)- bridged hydrometal complexes (M(4)H(3)C)(2)B(2)O(2) and (M(4)H(3)N)(2)B(2)O(2)(2+) (M = Ni, Mg) containing double tetracoordinate planar nonmetals (TPN) have been performed using the density functional theory at the B3LYP/6-311+G(d,p) level. Theoretical evidence of the possibility of double TPN centers coexisting in one planar molecule is presented.     

Synthesis, structure, and magnetic properties of (6-9)-nuclear Ni(II) trimethylacetates and their heterospin complexes with nitroxides

New polynuclear nickel trimethylacetates [Ni6(OH)4(C5H9O2)8(C5H10O2)4] (6), [Ni7(OH)7(C5H9O2)7(C5H10O2)6(H2O)] x 0.5 C6H14 x 0.5 H2O (7), [Ni8(OH)4(H2O)2(C5H9O2)12] (8), and [Ni9(OH)6(C5H9O2)12(C5H10O2)4] x C5H10O2 x 3 H2O (9), where C5H9O2 is trimethylacetate and C5H10O2 is trimethylacetic acid, have been found. Their structures were determined by X-ray crystallography. Because of their high solubility in low-polarity organic solvents, compounds 6-9 reacted with stable organic radicals to form the first heterospin compounds based on polynuclear Ni(II) trimethylacetate and nitronyl nitroxides containing pyrazole (L(1)-L(3)), methyl (L(4)), or imidazole (L(5)) substituent groups, respectively, in side chain [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L(1))2(H2O)] x 0.5 C6H14 x H2O (6+1a), [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L2)2(H2O)] x H2O (6+1b), [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L(3))2(H2O)] x H2O (6+1c), [Ni6(OH)3(C5H9O2)9(C5H10O2)4(L(4))] x 1.5 C6H14 (6'), and [Ni4OH)3(C5H9O2)5(C5H10O2)4(L(5))] x 1.5 C7H8 (4). Their structures were also determined by X-ray crystallography. Although Ni(II) trimethylacetates may have varying nuclearity and can change their nuclearity during recrystallization or interactions with nitroxides, this family of compounds is easy to study because of its topological relationship. For any of these complexes, the polynuclear framework may be derived from the [Ni6] polynuclear fragment {Ni6(mu4-OH)2(mu3-OH)2(mu2-C5H9O2-O,O')6(mu2-C5H9O2-O,O)(mu4-C5H9O2-O,O,O',O')(C5H10O2)4}, which is shaped like an open book. On the basis of this fragment, the structure of 7-nuclear compounds (7 and 6+1a-c) is conveniently represented as the result of symmetric addition of other mononuclear fragments to the four Ni(II) ions lying at the vertexes of the [Ni6] open book. The 9-nuclear complex is formed by the addition of trinuclear fragments to two Ni(II) ions lying on one of the lateral edges of the [Ni6] open book. This wing of the 9-nuclear complex preserves its structure in another type of 6-nuclear complex (6') with the boat configuration. If, however, two edge-sharing Ni(II) ions are removed from [Ni6] (one of these lies at a vertex of the open book and the other, on the book-cover line), we obtain a 4-nuclear fragment recorded in the molecular structure of 4. Twinning of this 4-nuclear fragment forms highly symmetric molecule 8, which is a new chemical version of cubane.     

Preparation and Properties of the Corner-Shared Double Cube [Mo(6)BiS(8)(H(2)O)(18)](8+) as a Derivative of [Mo(3)S(4)(H(2)O)(9)](4+) in Aqueous Acidic Solutions

The reaction of [Mo(3)S(4)(H(2)O)(9)](4+) with Bi(III) in the presence of BH(4)(-) (rapid), or with Bi metal shot (3-4 days), gives a heterometallic cluster product. The latter has been characterized as the corner-shared double cube [Mo(6)BiS(8)(H(2)O)(18)](8+) by the following procedures. Analyses by ICP-AES confirm the Mo:Bi:S ratio as 6:1:8. Elution from a cation-exchange column by 4 M Hpts (Hpts = p-toluenesulfonic acid), but not 2 M Hpts (or 4 M HClO(4)), is consistent with a high charge. The latter is confirmed as 8+ from the 3:1 stoichiometries observed for the oxidations with [Co(dipic)(2)](-) or [Fe(H(2)O)(6)](3+) yielding [Mo(3)S(4)(H(2)O)(9)](4+) and Bi(III) as products. Heterometallic clusters [Mo(6)MS(8)(H(2)O)(18)](8+) are now known for M = Hg, In, Tl, Sn, Pb, Sb, and Bi and are a feature of the P-block main group metals. The color of [Mo(6)BiS(8)(H(2)O)(18)](8+) in 2.0 M Hpts (turquoise) is different from that in 2.0 M HCl (green-blue). Kinetic studies (25 degrees C) for uptake of a single chloride k(f) = 0.80 M(-)(1) s(-)(1), I = 2.0 M (Hpts), and the high affinity for Cl(-) (K > 40 M(-)(1)) exceeds that observed for complexing at Mo. A specific heterometal interaction of the Cl(-) not observed in the case of other double cubes is indicated. The Cl(-) can be removed by cation-exchange chromatography with retention of the double-cube structure. Kinetic studies with [Co(dipic)(2)](-) and hexaaqua-Fe(III) as oxidants form part of a survey of redox properties of this and other clusters. The Cl(-) adduct is more readily oxidized by [Co(dipic)(2)](-) (factor of approximately 10) and is also more air sensitive.     

Electrochemistry of niobium(V) in sulfuric and methanesulfonic acids: formation of the Nb3O2(SO4)6(H2O)(3)(5-) cluster and designed electrochemical generation of "Nb3O2" core clusters by double potential pulse electrolysis

The electrochemical and spectroelectrochemical properties of niobium(V) and the Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) cluster in sulfuric acid and methanesulfonic acid were investigated using cyclic voltammetry, constant potential electrolysis, and spectroelectrochemistry. These chemical systems were suitable to probe the formation of "Nb(3)O(2)" core trinuclear clusters. In 9 M H(2)SO(4) the cluster Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) exhibited a reversible 1-electron reduction peak at E(pc) = -1.30 V vs Hg/Hg(2)SO(4) electrode, as well as a 4-electron irreversible oxidation peak at E(pa) = -0.45 V. Controlled potential reduction at E = -1.40 V produced the green Nb(3.33+) cluster anion Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(6-). In 12 M H(2)SO(4) Nb(V) displayed two reduction peaks at E(pc) = -1.15 V and E(pc) = -1.30 V. It was determined that the first process involves a quasi-reversible 2-electron reduction. After reduction of Nb(V) to Nb(III) the following chemical step involves formation of [Nb(III)](2) dimer, which further reacts with Nb(V) to produce the Nb(3)O(2)(SO(4))(6(H(2)O)(3)(5-) cluster (ECC process). The second reduction peak at E(pc) = -1.30 V corresponds to further 2-electron reduction of Nb(III) to Nb(I). The electrogenerated Nb(I) species also chemically reacts with starting material Nb(V) to produce additional [Nb(III)](2). In 5 M H(2)SO(4), the rate of the second chemical step in the ECC process is relatively slower and reduction of Nb(V) at E = -1.45 V/-1.2 V produces a mixture of Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) and [Nb(III)](2) dimer. [Nb(III)](2) can be selectively oxidized by two 2-electron steps at E = -0.65 V to Nb(V). However, if the oxidation is performed at E = -0.86 V, the product is Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-). A double potential pulse electrolysis waveform was developed to direct the reduction of Nb(V) toward selective formation of the Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) cluster. Proper application of dc-voltage pulses alternating between E(1) = -1.45 V and E(2) = -0.86 V yields only the target trinuclear cluster. Analogous double potential pulse electrolysis of Nb(V) in methanesulfonic acid generates the "Nb(3)O(2)" core cluster Nb(3)O(2)(CH(3)SO(3))(6)(H(2)O)(3)(+).     

Lanthanide-3d cyanometalate chains Ln(III)-M(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb; M=Fe) with the tridentate ligand 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz): evidence of ferromagnetic interactions for the Sm(III)-M(III) compounds (M=Fe, Cr)

A series of cyanide-bridged chain mixed Fe(III)/Ln(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb) complexes with the tridentate ligand 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) used as a capping group has been prepared. Reactions of tptz and LnCl3 with K3Fe(CN)6 yield a family of air-stable 1-D compounds {[Pr(tptz)(H2O)4Fe(CN)6].8H2O}infinity, {[Nd(tptz)(H2O)4Fe(CN)6].8H2O}infinity, {[Sm(tptz)(H2O)4Fe(CN)6].8H2O}, {[Eu(tptz)(H2O)4Fe(CN)6].6H2O}infinity, {[Gd(tptz)(H2O)4Fe(CN)6].6H2O}infinity, and {[Tb(tptz)(H2O)4Fe(CN)6].8H2O}infinity. Temperature dependent magnetic susceptibility studies of reveal that in , the Sm(III) and Fe(III) ions are ferromagnetically coupled with 3-D ordering occurring below 3.5 K. The appearance of the frequency dependent out-of-phase signal is explained in terms of an ordering with a spin glass-like behavior. To compare the magnetic behavior of with related compounds, {[Sm(tptz)(H2O)4Co(CN)6].8H2O}infinity and {[La(tptz)(DMF)(H2O)3Fe(CN)6].5H2O}infinity, {[Sm(tmphen)(DMF)3(H2O)Fe(CN)6].2H2O}infinity, {[Sm(tmphen)2(H2O)2Fe(CN)6].MeOH.13H2O}infinity and {[Sm(tmphen)2(H2O)2Cr(CN)6].MeOH.9H2O}infinity with 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) were also prepared.