Synthesis and structures of aluminum alkanethiolate complexes

The homoleptic aluminum thiolate complex [Al(mu-S-t-Bu)(S-t-Bu)(2)](2) was prepared by reacting AlBr(3) with NaS-t-Bu while the analogous 2-propanethiolate complex [Al(mu-S-i-Pr)(S-i-Pr)(2)](2) was synthesized by reacting AlH(3)(OEt(2)) with i-PrSH. In the solid state, the dimers have tetrahedral Al atoms and anti-Al(mu-SR)(2)Al four-member rings. The attempted synthesis of [Al(mu-S-t-Bu)(S-t-Bu)(2)](2) by reacting Al(N-i-Pr(2))(3) with t-BuSH in THF solvent yielded the thermally stable THF adduct Al(S-t-Bu)(3)(THF). The same reaction in diethyl ether solvent produced a mixture of [Al(mu-mgr;-S-t-Bu)(S-t-Bu)(2)](2) and the salt [i-Pr(2)NH(2)][Al(S-t-Bu)(4)]. In the solid-state structure of the salt, the anion [Al(S-t-Bu)(4)](-) has a distorted tetrahedral geometry. Reactions of [Al(NMe(2))(3)](2) and AlH(3)(NMe(2)Et) with the alkanethiols yielded stable amine adducts Al(SR)(3)(R'NMe(2)) (R = i-Pr or t-Bu; R' = H or Et). The ligand adducts Al(S-i-Pr)(3)(HNMe(2)) and Al(S-t-Bu)(3)(THF) have distorted trigonal pyramidal geometries in the solid state. Three of the new compounds, [Al(mu-S-i-Pr)(S-i-Pr)(2)](2) and Al(SR)(3)(HNMe(2)) (R = i-Pr or t-Bu), are viable precursor candidates for the chemical vapor deposition of aluminum sulfide films because they are thermally stable, volatile liquids at moderate temperatures.     

Iron silylamide-grafted periodic mesoporous silica

The surface chemistry of a series of well-defined metalorganic ferrous and ferric iron complexes on periodic mesoporous silica (PMS) was investigated. In addition to literature known Fe(II)[N(SiMe(3))(2)](2)(THF), Fe(II)[N(SiPh(2)Me(2))(2)](2), and Fe(III)[N(SiMe(3))(2)](2)Cl(THF), the new complexes [Fe(II){N(SiHMe(2))(2)}(2)](2) and Fe(III)[N(SiHMe(2))(2)](3)(μ-Cl)Li(THF)(3) were employed as grafting precursors. Selection criteria for the molecular precursors were the molecular size (monoiron versus diiron species), the oxidation state of the iron center (II versus III), and the functionality of the silylamido ligand (e.g., built-in spectroscopic probes). Hexagonal channel-like MCM-41 and cubic cage-like SBA-1 were chosen as two distinct PMS materials. The highest iron load (12.8 wt %) was obtained for hybrid material [Fe(II){N(SiHMe(2))(2)}(2)](2)@MCM-41 upon stirring the reaction mixture iron silylamide/PMS/n-hexane for 18 h at ambient temperature. Size-selective grafting and concomitantly extensive surface silylation were found to be prominent for cage-like SBA-1. Here, the surface metalation is governed by the type of iron precursor, the pore size, the reaction time, and the solvent. The formation of surface-attached iron-ligand species is discussed on the basis of diffuse reflectance infrared Fourier transform (DRIFT) and electron paramagnetic resonance (EPR) spectroscopy, nitrogen physisorption, and elemental analysis.     

Iron-arylimide clusters [Fe(m)()(NAr)(n)Cl(4)](2)(-) (m,n = 2, 2; 3, 4; 4, 4) from a ferric amide precursor: synthesis,characterization, and comparison to Fe-S chemistry

Tetrahedral FeCl[N(SiMe(3))(2)](2)(THF) (2), prepared from FeCl(3) and 2 equiv of Na[N(SiMe(3))(2)] in THF, is a useful ferric starting material for the synthesis of weak-field iron-imide (Fe-NR) clusters. Protonolysis of 2 with aniline yields azobenzene and [Fe(2)(mu-Cl)(3)(THF)(6)](2)[Fe(3)(mu-NPh)(4)Cl(4)] (3), a salt composed of two diferrous monocations and a trinuclear dianion with a formal 2 Fe(III)/1 Fe(IV) oxidation state. Treatment of 2 with LiCl, which gives the adduct [FeCl(2)(N(SiMe(3))(2))(2)](-) (isolated as the [Li(TMEDA)(2)](+) salt), suppresses arylamine oxidation/iron reduction chemistry during protonolysis. Thus, under appropriate conditions, the reaction of 1:1 2/LiCl with arylamine provides a practical route to the following Fe-NR clusters: [Li(2)(THF)(7)][Fe(3)(mu-NPh)(4)Cl(4)] (5a), which contains the same Fe-NR cluster found in 3; [Li(THF)(4)](2)[Fe(3)(mu-N-p-Tol)(4)Cl(4)] (5b); [Li(DME)(3)](2)[Fe(2)(mu-NPh)(2)Cl(4)] (6a); [Li(2)(THF)(7)][Fe(2)(mu-NMes)(2)Cl(4)] (6c). [Li(DME)(3)](2)[Fe(4)(mu(3)-NPh)(4)Cl(4)] (7), a trace product in the synthesis of 5a and 6a, forms readily as the sole Fe-NR complex upon reduction of these lower nuclearity clusters. Products were characterized by X-ray crystallographic analysis, by electronic absorption, (1)H NMR, and M?ssbauer spectroscopies, and by cyclic voltammetry. The structures of the Fe-NR complexes derive from tetrahedral iron centers, edge-fused by imide bridges into linear arrays (5a,b; 6a,c) or the condensed heterocubane geometry (7), and are homologous to fundamental iron-sulfur (Fe-S) cluster motifs. The analogy to Fe-S chemistry also encompasses parallels between Fe-mediated redox transformations of nitrogen and sulfur ligands and reductive core conversions of linear dinuclear and trinuclear clusters to heterocubane species and is reinforced by other recent examples of iron- and cobalt-imide cluster chemistry. The correspondence of nitrogen and sulfur chemistry at iron is intriguing in the context of speculative Fe-mediated mechanisms for biological nitrogen fixation.     

Dinuclear cyano complexes of cobalt(III) and Iron(III) containing noninnocent 1,2,4,5-tetrakis(2-pyridinecarboxamido)benzene bridging ligands

Two new dinucleating ligands 1,2,4,5-tetrakis(2-pyridinecarboxamido)benzene, H(4)(tpb), and 1,2,4,5-tetrakis(4-tert-butyl-2-pyridinecarboxamido)benzene, H(4)(tbpb), have been synthesized, and the following dinuclear cyano complexes of cobalt(III) and iron(III) have been isolated: Na(2)[Co(III)(2)(tpb)(CN)(4)] (1); [N(n-Bu)(4)](2)[Co(III)(2)(tbpb)(CN)(4)] (2); [Co(III)(2)(tbpb(ox2))(CN)(4)] (3); [N(n-Bu)(4)](2)[Fe(III)(2)(tpb)(N(3))(4)] (4); [N(n-Bu)(4)](2)[Fe(III)(2)(tpb)(CN)(4)] (5); [N(n-Bu)(4)](2)[Fe(III)(2)(tbpb)(CN)(4)] (6). Complexes 2-4 and 6 have been structurally characterized by X-ray crystallography at 100 K. From electrochemical and spectroscopic (UV-vis, IR, EPR, M?ssbauer) and magnetochemical investigations it is established that the coordinated central 1,2,4,5-tetraamidobenzene entity in the cyano complexes can be oxidized in two successive one-electron steps yielding paramagnetic (tbpb(ox1))(3)(-) and diamagnetic (tbpb(ox2))(2)(-) anions. Thus, complex 6 exists in five characterized oxidation levels: [Fe(III)(2)(tbpb(ox2))(CN)(4)](0) (S = 0); [Fe(III)(2)(tbpb(ox1))(CN)(4)](-) (S = (1)/(2)); [Fe(III)(2)(tbpb)(CN)(4)](2)(-) (S = 0); [Fe(III)Fe(II)(tbpb)(CN)(4)](3)(-) (S = (1)/(2)); [Fe(II)(2)(tbpb)(CN)(4)](4)(-) (S = 0). The iron(II) and (III) ions are always low-spin configurated. The electronic structure of the paramagnetic iron(III) ions and the exchange interaction of the three-spin system [Fe(III)(2)(tbpb(ox1))(CN)(4)](-) are characterized in detail. Similarly, for 2 three oxidation levels have been identified and fully characterized: [Co(III)(2)(tbpb)(CN)(4)](2)(-) (S = 0); [Co(III)(2)(tbpb(ox1))(CN)(4)](-) (S = (1)/(2)); [Co(III)(2)(tbpb(ox2))(CN)(4)](0). The crystal structures of 2 and 3 clearly show that the two electron oxidation of 2 yielding 3 affects only the central tetraamidobenzene part of the ligand.     

Methanolysis and phenolysis routes to Fe6, Fe8, and Fe1) complexes and their magnetic properties: a new type of Fe8 ferric wheel

Alcoholysis of preformed tetranuclear and hexanuclear iron(III) clusters has been employed for the synthesis of four higher-nuclearity clusters. Treatment of [Fe(4)O(2)(O(2)CMe)(7)(bpy)(2)](ClO(4)) with phenol affords the hexanuclear cluster [Fe(6)O(3)(O(2)CMe)(9)(OPh)(2)(bpy)(2)](ClO(4)) (1). Reaction of [Fe(6)O(2)(OH)(2)(O(2)CR)(10)(hep)(2)] (R = Bu(t) or Ph) with PhOH affords the new "ferric wheel" complexes [Fe(8)(OH)(4)(OPh)(8)(O(2)CR)(12)] [R = Bu(t) (2) or Ph (3)]. Complexes 2 and 3 exhibit the same structure, which is an unprecedented type for Fe(III). In contrast, treatment of [Fe(6)O(2)(OH)(2)(O(2)CBu(t))(10)(hep)(2)] with MeOH leads to the formation of [Fe(10)(OMe)(20)(O(2)CBu(t))(10)] (4), which exhibits the more common type of ferric wheel seen in analogous complexes with other carboxylate groups. Solid-state variable-temperature magnetic susceptibility measurements indicate spin-singlet ground states for complexes 2 and 4. The recently developed semiempirical method ZILSH was used to estimate the pairwise exchange parameters (J(AB)) and the average spin couplings S(A)[empty set].S(B)[empty set] between the Fe(III) centers, providing a clear depiction of the overall magnetic behavior of the molecules. All exchange interactions between adjacent Fe(III) atoms are antiferromagnetic.     

Reaction of (mu-oxo)diiron(III) core with CO2 in N-methylimidazole: formation of mono(mu-carboxylato)(mu-oxo)diiron(III) complexes with N-methylimidazole as ligands

Several iron(III) complexes with N-methylimidazole (N-MeIm) as the ligand have been synthesized by using N-MeIm as the solvent. Under anaerobic conditions, [Fe(N-MeIm)(6)](ClO(4))(3) (1) reacts with stoichiometric amounts of water in N-MeIm to afford the (mu-oxo)diiron(III) complex, [Fe(2)(mu-O)(N-MeIm)(10)](ClO(4))(4) (3). Exposure of a solution of 3 in N-MeIm to stoichiometric and excess CO(2) gives rise to the (mu-oxo)(mu-carboxylato)diiron(III) species [Fe(2)(mu-O)(mu-HCO(2))(N-MeIm)(8)](ClO(4))(3) (4) and the methyl carbonate complex [Fe(2)(mu-O)(mu-CH(3)OCO(2))(N-MeIm)(8)](ClO(4))(3) (5), respectively. Formation of the formato-bridged complex 4 upon fixation of CO(2) by 3 in N-MeIm is unprecedentated. Methyl transfer from N-MeIm to a bicarbonato-bridged (mu-oxo)diiron(III) intermediate appears to give rise to 5. Complex 3 is a good starting material for the synthesis of (mu-oxo)mono(mu-carboxylato)diiron(III) species [Fe(2)(mu-O)(mu-RCO(2))(N-MeIm)(8)](ClO(4))(3) (where R = H (4), CH(3) (6), or C(6)H(5) (7)); addition of the respective carboxylate ligand in stoichiometric amount to a solution of 3 in N-MeIm affords these complexes in high yields. Attempts to add a third bridge to complexes 4, 6, and 7 to form the (mu-oxo)bis(mu-carboxylato)diiron(III) species result in the isolation of the previously known triiron(III) mu-eta(3)-oxo clusters [[Fe(mu-RCO(2))(2)(N-MeIm)](3)O](ClO(4)) (8). The structures of 3, 4, 6, and 7 allow one, for the first time, to inspect the various features of the [Fe(2)(mu-O)(mu-RCO(2))](3+) moiety with no strain from the ligand framework.     

A novel mu(4)-oxo bridged copper tetrahedron derived by self-assembly: first example of double helical bis(tridentate) coordination of a hexadentate amine phenol ligand

In methanol, the reaction of Cu(ClO(4))(2).6H(2)O and the hexadentate amine phenol ligand (H(2)bahped) in the presence of triethylamine affords a tetranuclear copper(II) complex having the formula [Cu(4)(mu(4)-O)(bahped)(2)](ClO(4))(2). The X-ray structure of this complex shows a tetrahedral central [Cu(II)(4)(mu(4)-O)]unit coordinated to two hexadentate bridging (via the central ethylenediamine part) ligands. The compound is the first example of a mu(4)-oxo tetranuclear copper(II) complex without any bridging ligand along the six tetrahedral edges. Variable-temperature magnetic data clearly show an S(t) = 0 spin ground state for antiferromagnetic interactions between four (2)B(2) copper(II) ions in a dimer of dimers.     

Molecular [(fe(3))-(fe(3))] and [(fe(4))-(fe(4))] coordination cluster pairs as single or composite arrays

The synthesis of molecular cluster pairs is a challenge for coordination chemists due to the potential applications of these species in molecular spintronics or quantum computing. The ligand H(4)L, 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-2-methoxybenzene, has been successfully used to obtain a series of such complexes using the basic Fe(III) trinuclear carboxylates as starting materials. Synthetic control has allowed the isolation of the two molecular cluster pairs that form the composite [Fe(4)O(2)(PhCO(2))(6)(H(2)L)(pz)](2)[Fe(3)O(PhCO(2))(5)(py)(H(2)L)](2) (1). The dimers of trinuclear units, [Fe(3)O(PhCO(2))(5)(H(2)O)(H(2)L)](2) (2) and [Fe(3)O(o-MePhCO(2))(5)(H(2)L)(py)](2) (3), and the dimers of tetranuclear units, [Fe(4)O(2)(PhCO(2))(6)(H(2)L)(pz)](2) (4) and [Fe(4)O(2)(o-MePhCO(2))(6)(H(2)L)(pz)](2) (5), are presented here. The magnetic properties of the reported aggregates show that they are pairs of semi-independent clusters weakly interacting magnetically as required for two-qubit quantum gates.     

Synthesis and reactions of triphenylsilanethiolato complexes of manganese(II), iron(II), cobalt(II), and nickel(II)

Reactions of Fe[N(SiMe(3))(2)](2) with 1 and 2 equiv of Ph(3)SiSH in hexane afforded dinuclear silanethiolato complexes, [Fe(N(SiMe(3))(2))(mu-SSiPh(3))](2) (1) and [Fe(SSiPh(3))(mu-SSiPh(3))](2) (2), respectively. Various Lewis bases were readily added to 2, generating mononuclear adducts, Fe(SSiPh(3))(2)(L)(2) [L = CH(3)CN (3a), 4-(t)BuC(5)H(4)N (3b), PEt(3) (3c), (LL) = tmeda (3d)]. From the analogous reactions of M[N(SiMe(3))(2)](2) (M = Mn, Co) and [Ni(NPh(2))(2)](2) with Ph(3)SiSH in the presence of TMEDA, the corresponding silanethiolato complexes, M(SSiPh(3))(2)(tmeda) [M = Mn (4), Co (5), Ni (6)], were isolated. Treatment of 3a with (PPh(4))(2)[MoS(4)] or (NEt(4))(2)[FeCl(4)] resulted in formation of a linear trinuclear Fe-Mo-Fe cluster (PPh(4))(2)[MoS(4)(Fe(SSiPh(3))(2))(2)] (7) or a dinuclear complex (NEt(4))(2)[Fe(2)(SSiPh(3))(2)Cl(4)] (8). On the other hand, the reaction of 3a with [Cu(CH(3)CN)(4)](PF(6)) gave a cyclic tetranuclear copper cluster Cu(4)(SSiPh(3))(4) (9), where silanethiolato ligands were transferred from iron to copper. Silicon-sulfur bond cleavage was found to occur when the cobalt complex 5 was treated with (NBu(4))F in THF, and a cobalt-sulfido cluster Co(6)(mu(3)-S)(8)(PPh(3))(6) (10) was isolated upon addition of PPh(3) to the reaction system. The silanethiolato complexes reported here are expected to serve as convenient precursors for sulfido cluster synthesis.     

Neutral and ionic aluminum,gallium, and indium compounds carrying two or three terminal ethynyl groups

The syntheses of the ionic compounds [Li(+).2 dioxane (2,6-iPr(2)C(6)H(3)N(SiMe(3))Al(C triplebond CSiMe(3))(3))(-)].0.75 dioxane (1), [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))Ga(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (2), and [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))In(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiC triplebond CSiMe(3) are reported. The neutral ethynyl compounds Br-Al(C triplebond CtBu)(2).2 THF (4), Cl-Ga(C triplebond CtBu)(2).THF (5), Cl-In(C triplebond CtBu)(2).2 THF (6), Al(C triplebond CtBu)(3).C[N(Me)CMe](2) (7), Ga(C triplebond CtBu)(3).dioxane (8), and In(C triplebond CtBu)(3).NEt(3) (9) have been obtained in good yields from the reaction of AlBr(3), GaCl(3), and InCl(3) with LiC triplebond CtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(C triplebond CPh)(3).NMe(3) (10) and Ga(C triplebond CPh)(3).NMe(3) (11) have been prepared by the reaction of AlH(3).NMe(3) or GaH(3).NMe(3) with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units.     

Self-assembly and redox modulation of the cavity size of an unusual rectangular iron thiolate aryldiisocyanide metallocyclophane

The decarbonylation reaction of ferric carbonyl dicationic [Cp(2)Fe(2)(μ-SEt)(2)(CO)(2)](BF(4))(2) [1(BF(4))(2)] carried out in refluxing acetonitrile affords a binuclear iron-sulfur core complex [Cp(2)Fe(2)(μ-SEt)(2)(CH(3)CN)(2)](BF(4))(2) [2(BF(4))(2)] containing two acetonitrile coordinated ligands. The treatment of 2(BF(4))(2) with 2 equiv of the 1,4-diisocyanobenzene (1,4-CNC(6)H(4)NC) results in the formation of the diisocyanide complex [Cp(2)Fe(2)(μ-SEt)(2)(1,4-CNC(6)H(4)NC)(2)](BF(4))(2) [3(BF(4))(2)]. The rectangular tetranuclear iron thiolate aryldiisocyanide metallocyclophane complex [Cp(4)Fe(4)(μ-SEt)(4)(μ-1,4-CNC(6)H(4)NC)(2)](BF(4))(4) [4(BF(4))(4)] has been synthesized by a self-assembly reaction between equimolar amounts of 2(BF(4))(2) and 1,4-diisocyanobenzene or by a stepwise route involving mixing of a 1:1 molar ratio of complexes 2(BF(4))(2) and 3(BF(4))(2). Chemical reduction of 4(BF(4))(4) by KC(8) was observed to produce the reduction product 4(BF(4))(2). The spectroscopic and electrochemical properties of the iron-sulfur core complexes 1(PF(6))(2), 3(BF(4))(2), 4(BF(4))(4), and 4(BF(4))(2) were determined. Finally, differences between the redox control cavities of rectangular tetranuclear iron thiolate aryldiisocyanide complexes are revealed by a comparison of the X-ray crystallographically determined structures of complexes 4(BF(4))(4) and 4(BF(4))(2).     

Proton control of oxidation and spin state in a series of iron tripodal imidazole complexes

Reaction of iron salts with three tripodal imidazole ligands, H(3)(1), H(3)(2), H(3)(3), formed from the condensation of tris(2-aminoethyl)amine (tren) with 3 equiv of an imidazole carboxaldehyde yielded eight new cationic iron(III) and iron(II), [FeH(3)L](3+or2+), and neutral iron(III), FeL, complexes. All complexes were characterized by EA(CHN), IR, UV, M?ssbauer, mass spectral techniques and cyclic voltammetry. Structures of three of the complexes, Fe(2).3H(2)O (C(18)H(27)FeN(10)O(3), a = b = c = 20.2707(5), cubic, I3d, Z = 16), Fe(3).4.5H(2)O (C(18)H(30)FeN(10)O(4.5), a = 20.9986(10), b = 11.7098(5), c = 19.9405(9), beta = 109.141(1), monoclinic, P2(1)/c), Z = 8), and [FeH(3)(3)](ClO(4))(2).H(2)O (C(18)H(26)Cl(2)FeN(10)O(9), a = 9.4848(4), b = 23.2354(9), c = 12.2048(5), beta = 111.147(1) degrees, monoclinic, P2(1)/n, Z = 4) were determined at 100 K. The structures are similar to one another and feature an octahedral iron with facial coordination of imidazoles and imine nitrogen atoms. The iron(III) complexes of the deprotonated ligands, Fe(1), Fe(2), and Fe(3), are low-spin while the protonated iron(III) cationic complexes, [FeH(3)(1)](ClO(4))(3) and [FeH(3)(2)](ClO(4))(3), are high-spin and spin-crossover, respectively. The iron(II) cationic complexes, [FeH(3)(1)]S(4)O(6), [FeH(3)(2)](ClO(4))(2), [FeH(3)(3)](ClO(4))(2), and [FeH(3)(3)][B(C(6)H(5))(4)](2) exhibit spin-crossover behavior. Cyclic voltammetric measurements on the series of complexes show that complete deprotonation of the ligands produces a negative shift in the Fe(III)/Fe(II) reduction potential of 981 mV on average. Deprotonation in air of either cationic iron(II) or iron(III) complexes, [FeH(3)L](3+or2+), yields the neutral iron(III) complex, FeL. The process is reversible for Fe(3), where protonation of Fe(3) yields [FeH(3)(3)](2+).     

Coordination algorithms control molecular architecture: [CuI4(L2)4]4+ grid complex versus [MII2(L2)2X4]y+ side-by-side complexes (M=Mn,Co, Ni,Zn; X=solvent or anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3

The synthesis and characterisation of a pyridazine-containing two-armed grid ligand L2 (prepared from one equivalent of 3,6-diformylpyridazine and two equivalents of p-anisidine) and the resulting transition metal (Zn, Cu, Ni, Co, Fe, Mn) complexes (1-9) are reported. Single-crystal X-ray structure determinations revealed that the copper(I) complex had self-assembled as a [2 x 2] grid, [Cu(I) (4)(L2)(4)][PF(6)](4).(CH(3)CN)(H(2)O)(CH(3)CH(2)OCH(2)CH(3))(0.25) (2.(CH(3)CN)(H(2)O)(CH(3)CH(2)OCH(2)CH(3))(0.25)), whereas the [Zn(2)(L2)(2)(CH(3)CN)(2)(H(2)O)(2)][ClO(4)](4).CH(3)CN (1.CH(3)CN), [Ni(II) (2)(L2)(2)(CH(3)CN)(4)][BF(4)](4).(CH(3)CH(2)OCH(2)CH(3))(0.25) (5 a.(CH(3)CH(2)OCH(2)CH(3))(0.25)) and [Co(II) (2)(L2)(2)(H(2)O)(2)(CH(3)CN)(2)][ClO(4)](4).(H(2)O)(CH(3)CN)(0.5) (6 a.(H(2)O)(CH(3)CN)(0.5)) complexes adopt a side-by-side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [Fe(II)(L2)(3)][Fe(III)Cl(3)OCl(3)Fe(III)].CH(3)CN (7.CH(3)CN). A more soluble salt of the cation of 7, the diamagnetic complex [Fe(II)(L2)(3)][BF(4)](2).2 H(2)O (8), was prepared, as well as two derivatives of 2, [Cu(I) (2)(L2)(2)(NCS)(2)].H(2)O (3) and [Cu(I) (2)(L2)(NCS)(2)] (4). The manganese complex, [Mn(II) (2)(L2)(2)Cl(4)].3 H(2)O (9), was not structurally characterised, but is proposed to adopt a side-by-side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side-by-side complexes: J=-21.6 cm(-1) and g=2.17 for S=1 dinickel(II) complex [Ni(II) (2)(L2)(2)(H(2)O)(4)][BF(4)](4) (5 b) (fraction monomer 0.02); J=-7.6 cm(-1) and g=2.44 for S= 3/2 dicobalt(II) complex [Co(II) (2)(L2)(2)(H(2)O)(4)][ClO(4)](4) (6 b) (fraction monomer 0.02); J=-3.2 cm(-1) and g=1.95 for S= 5/2 dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7.H(2)O gave J=-75 cm(-1) and g=1.81 for the S= 5/2 diiron(III) anion (fraction monomer=0.025). These parameters are lower than normal for Fe(III)OFe(III) species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7.H(2)O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. M?ssbauer measurements at 77 K confirmed that there are two iron sites in 7.H(2)O, a low-spin iron(II) site and a high-spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5 b, 6 b and 8 and this showed that multiple redox processes are a feature of all of them.     

Pyridazine-bridged copper(I) complexes of bis-bidentate ligands: tetranuclear [2 x 2] grid versus dinuclear side-by-side architectures as a function of ligand substituents

Eight bis-bidentate Schiff-base ligands, derived from 3,6-diformylpyridazine and substituted amino-benzenes, have been prepared. A variety of electron donating/withdrawing and/or sterically demanding/undemanding substituents were employed. Two ligands and five of the six pure copper(I) complexes have been structurally characterised. The sterically unhindered ligand derived from 3,5-difluoroaniline, (m,m-F), was almost completely flat whereas the very sterically hindered ligand derived from trimethylaniline, (o,o,p-Me), was severely twisted. The only dinuclear side-by-side complex obtained, [Cu(I)(2)((o-Ph))(2)](PF(6))(2), was of the ligand derived from 2-aminobiphenyl. All five of the other complexes are believed to be [2 x 2] tetranuclear grid complexes, and this was unequivocally shown to be the case for four of these complexes, [Cu(I)(4)((p-Me))(4)](PF(6))(4), [Cu(I)(4)((o,p-Me))(4)](PF(6))(4), [Cu(I)(4)((m,m-F))(4)](PF(6))(4) and [Cu(I)(4)((m,m-Cl))(4)](PF(6))(4). In all cases the copper(I) centres are substantially distorted from tetrahedral, with the most severe distortion present in the side-by-side complex. In the absence of any special effects, tetracopper(I) [2 x 2] grid architectures are observed to be the favored outcome for 1 : 1 reactions of these bis-bidentate ligands with copper(I) ions. Only when the aromaticity of the ligand was extended by employing a phenyl substituent on the phenyl rings, (o-Ph), did a dicopper(I) side-by-side architecture result. Cyclic voltammetry in acetone revealed that the free ligands did not undergo reduction until potentials below -0.8 V, whereas between three and four reversible one electron reductions were observed, between +0.16 and -0.71 vs. AgCl/Ag, for the tetranuclear copper(I) [2 x 2] grid complexes. The redox potentials observed for these complexes are highly dependent on the nature of the ligand phenyl ring substituent(s). The side-by-side complex had one irreversible reduction process, E(pc)ca.-0.5 V.     

Redox-noninnocence of the S,S'-coordinated ligands in bis(benzene-1,2-dithiolato)iron complexes

The electronic structures of complexes of iron containing two S,S'-coordinated benzene-1,2-dithiolate, (L)(2)(-), or 3,5-di-tert-butyl-1,2-benzenedithiolate, (L(Bu))(2)(-), ligands have been elucidated in depth by electronic absorption, infrared, X-band EPR, and Mossbauer spectroscopies. It is conclusively shown that, in contrast to earlier reports, high-valent iron(IV) (d(4), S = 1) is not accessible in this chemistry. Instead, the S,S'-coordinated radical monoanions (L(*))(1)(-) and/or (L(Bu)(*))(1)(-) prevail. Thus, five-coordinate [Fe(L)(2)(PMe(3))] has an electronic structure which is best described as [Fe(III)(L)(L(*))(PMe(3))] where the observed triplet ground state of the molecule is attained via intramolecular, strong antiferromagnetic spin coupling between an intermediate spin ferric ion (S(Fe) = (3)/(2)) and a ligand radical (L(*))(1)(-) (S(rad) = (1)/(2)). The following complexes containing only benzene-1,2-dithiolate(2-) ligands have been synthesized, and their electronic structures have been studied in detail: [NH(C(2)H(5))(3)](2)[Fe(II)(L)(2)] (1), [N(n-Bu)(4)](2)[Fe(III)(2)(L)(4)] (2), [N(n-Bu)(4)](2)[Fe(III)(2)(L(Bu))(4)] (3); [P(CH(3))Ph(3)][Fe(III)(L)(2)(t-Bu-py)] (4) where t-Bu-py is 4-tert-butylpyridine. Complexes containing an Fe(III)(L(*))(L)- or Fe(III)(L(Bu))(L(Bu)(*))- moiety are [N(n-Bu)(4)][Fe(III)(2)(L(Bu))(3)(L(Bu)(*))] (3(ox)()), [Fe(III)(L)(L(*))(t-Bu-py)] (4(ox)()), [Fe(III)(L(Bu))(L(Bu)(*))(PMe(3))] (7), [Fe(III)(L(Bu))(L(Bu)(*))(PMe(3))(2)] (8), and [Fe(III)(L(Bu))(L(Bu)(*))(PPr(3))] (9), where Pr represents the n-propyl substituent. Complexes 2, 3(ox)(), 4, [Fe(III)(L)(L(*))(PMe(3))(2)] (6), and 9 have been structurally characterized by X-ray crystallography.     

Homoleptic 1-D iron selenolate complexes-synthesis, structure, magnetic and thermal behaviour of (1)(∞)[Fe(SeR)2] (R=Ph, Mes)

The first examples of polymeric homoleptic iron chalcogenolato complexes (1)(∞)[Fe(SePh)(2)] and (1)(∞)[Fe(SeMes)(2)] (Ph = phenyl = C(6)H(5), Mes = mesityl = C(6)H(2)-2,4,6-(CH(3))(3)) have been both prepared by reaction of [Fe(N(SiMe(3))(2))(2)] with two equivalents of HSeR (R = Ph, Mes) while (1)(∞)[Fe(SePh)(2)] was found to be also easily accessible through reactions of either FeCl(2), Fe(OOCCH(3))(2) or FeCl(3) with PhSeSiMe(3) in THF. In the crystal, the two compounds form one-dimensional chains with bridging selenolate ligands comprising distinctly different Fe-Se-Fe bridging angles, namely 71.15-72.57° in (1)(∞)[Fe(SePh)(2)] and 91.80° in (1)(∞)[Fe(SeMes)(2)]. Magnetic measurements supported by DFT calculations reveal that this geometrical change has a pronounced influence on the antiferromagnetic exchange interactions of the unpaired electrons along the chains in the two different compounds with a calculated magnetic exchange coupling constant of J = -137 cm(-1) in (1)(∞)[Fe(SePh)(2)] and J = -20 cm(-1) in (1)(∞)[Fe(SeMes)(2)]. In addition we were able to show that the ring molecule [Fe(SePh)(2)](12) which is a structural isomer of (1)(∞)[Fe(SePh)(2)] behaves magnetically similar to the latter one. Investigations by powder XRD reveal that the ring molecule is only a metastable intermediate which converts in THF completely to form (1)(∞)[Fe(SePh)(2)]. Thermal gravimetric analysis of (1)(∞)[Fe(SePh)(2)] under vacuum conditions shows that the compound is thermally labile and already starts to decompose above 30 °C in a two step process under cleavage of SePh(2) to finally form at 250 °C tetragonal PbO-type FeSe. The reaction of (1)(∞)[Fe(SePh)(2)] with the Lewis base 1,10-phenanthroline yielded, depending on the conditions, the octahedral monomeric complexes [Fe(SePh)(2)(1,10-phen)(2)] and [Fe(1,10-phen)(3)][Fe(SePh)(4)].     

Synthesis and crystal structure of unprecedented oxo/hydroxo-bridged polynuclear gallium(III) aqua complexes

Two new polynuclear oxo/hydroxo-bridged polynuclear gallium(III) aqua complexes are obtained upon treatment of Ga(3+)(aq) with pyridine: the supramolecular compound of macrocyclic cavitand cucurbit[6]uril with gallium complex containing 32 metal atoms [Ga(32)(mu(4)-O)(12)(mu(3)-O)(8)(mu(2)-O)(7)(mu(2)-OH)(39)(H(2)O)(20)](PyH subsetC(36)H(36)N(24)O(12))(3)(NO(3))(6).53H(2)O (1) and the tridecanuclear complex [Ga(13)(mu(3)-OH)(6)(mu(2)-OH)(18)(H(2)O)(24)](NO(3))(15).12H(2)O (2). It follows that two modes of nucleation exist when Ga(3+)(aq) is hydrolyzed: one around the tetrahedral GaO(4) units (complex 1) and the other around the octahedral GaO(6) units (complex 2). This is the first time that polynuclear oxo/hydroxo-bridged aqua complexes of Ga(III) have been isolated without the use of other ligands to control or block olygomerization.     

Trithiotungsten(VI) complexes having phosphine-thiolate hybrid ligands: synthesis and cluster forming reactions with CuBr, FeCl(2), and [Fe(CH(3)CN)(6)](ClO(4))(2)

Five-coordinated trithiotungsten complexes (PPh(4))[(dmsp)W(S)(3)] (1a) and (PPh(4))[(dpsp)W(S)(3)] (1b) (R(2)PCH(2)CH(2)S(-); R = Me (dmsp-)), Ph (dpsp-))) were synthesized by addition of Hdmsp and Hdpsp to a THF solution of (PPh(4))[(EtS)W(S)(3)]. Treatment of 1a with CuBr in the presence of PPh(3) in CH(3)CN afforded a WCu(2) cluster (dmsp)WS(3)Cu(2)(PPh(3))(2)Br (2). The reaction of 1a with 1 equiv of FeCl(2) went smoothly to generate a 1:1 adduct (PPh(4))[(dmsp)WS(3)(FeCl(2))] (3), while 3 did not react further with excess FeCl(2). On the other hand, 3 was found to react with [Fe(CH(3)CN)(6)](ClO(4))(2), giving rise to an unusual tetranuclear cluster, [(dmsp)WS(3)](2)Fe(2)Cl (4), while the reaction of 1a with 2 equiv of [Fe(CH(3)CN)(6)](ClO(4))(2) led to a cyclic octanuclear cluster [(dmsp)WS(3)Fe](4) (5). Although the oxidation states of W(VI), Cu(I), and Fe(II) are retained in 2 and 3, reduction of the metal ions occurs in the formation of 4 and 5. All the complexes reported in this paper were structurally characterized by X-ray analysis. It is anticipated that the new type of trithiotungsten complexes, 1a and 1b, will serve as potential synthons for various heterometallic sulfide clusters.     

Iron(II) complexes with tetradentate bis(aminophenolate) ligands: synthesis and characterization, solution behavior, and reactivity with O(2)

Tetradentate bis(aminophenolate) ligands H(2)salan(X) and H(2)bapen(X) (where X refers to the para-phenolate substituent = H, Me, F, Cl) react with [Fe{N(SiMe(3))(2)}(2)] to form iron(II) complexes, which in the presence of suitable donor ligands L (L = pyridine or THF) can be isolated as the complexes [Fe(salan(X))(L)(2)] and [Fe(bapen(X))(L)(2)]. In the absence of donor ligands, either mononuclear complexes, for example, [Fe(salan(tBu,tBu))], or dinuclear complexes of the type [Fe(salan(X))](2) are obtained. The dynamic coordination behavior in solution of the complexes [Fe(salan(F))(L)(2)] and [Fe(bapen(F))(L)(2)] has been investigated by VT (1)H and (19)F NMR spectroscopy, which has revealed equilibria between isomers with different ligand coordination topologies cis-α, cis-β and trans. Exposure of the iron(II) salan(X) complexes to O(2) results in the formation of oxo-bridged iron(III) complexes of the type [{Fe(salan(X))}(2)(μ-O)] or [{Fe(salan(X))(L)}(2)(μ-O)]. The lack of catalytic activity of the iron(II) salan and bapen complexes in the oxidation of cyclohexane with H(2)O(2) as the oxidant is attributed to the rapid formation of stable and catalytically inactive oxo-bridged iron(III) complexes.     

Solvothermal synthesis and characterization of polyselenidoarsenate salts of transition metal complex cations

The polyselenidoarsenates [Fe(phen)(3)][As(2)Se(6)] (1), [Zn(phen)(dien)][As(2)Se(6)]·2phen (2), [{Mn(phen)(2)}(2)(μ-η(2),η(2)-AsSe(4))](2)[As(2)Se(6)]·H(2)O (3), and [Ni(phen)(3)][As(2)Se(2)(μ-Se(3))(μ-Se(5))] (4) (dien = diethylenetriamine and phen = 1,10-phenanthroline) were prepared by the reaction of As(2)O(3), Se, dien, and phen in the presence of transition metals in a methanol solvent under solvothermal conditions. Compounds 1-3 consist of [As(2)Se(6)](2-) anions with [Fe(phen)(3)](2+), [Zn(phen)(dien)](2+), and [{Mn(phen)(2)}(2)(μ-η(2),η(2)-AsSe(4))](+) complex counter cations, respectively. The [As(2)Se(6)](2-) anion is formed from two As(III)Se(3) trigonal pyramids linked through two Se-Se bonds. Compound 3 is the first example of a mixed-valent selenidoarsenate(III,V) and exhibits the coexistence of As(III)Se(3) trigonal pyramidal and As(V)Se(4) tetrahedral units. Compound 4 is composed of a helical chain of [As(2)Se(2)(μ-Se(3))(μ-Se(5))(2-)](∞) and octahedral [Ni(phen)(3)](2+) cations. The [As(2)Se(2)(μ-Se(3))(μ-Se(5))(2-)](∞) chain is constructed from AsSe(+) units alternatively linked by μ-Se(3)(2-) and μ-Se(5)(2-) bridging ligands. When the structures of compounds 1-4 are compared, the transition metal ions show different structural directing effects during the synthesis of arsenic polyselenides in methanol. Compounds 1, 2, 3, and 4 exhibit semiconducting properties with band gaps of 1.88, 2.29, 1.82, and 2.01 eV, respectively.