Substitution chemistry of MM quadruply bonded complexes (M = Mo or W) supported by the anion of 2-hydroxy-6-methylpyridine

The compounds M(2)(mhp)(4), where M = Mo or W and mhp is the anion formed from deprotonation of 2-hydroxy-6-methylpyridine, are shown to react with carboxylic acids RCOOH to give an equilibrium mixture of products M(2)(O(2)CR)(n)(mhp)(4-n) where R = 2-thienyl and phenyl. The equilibrium can be moved in favor of M(2)(O(2)CR)(4) by the addition of excess acid or by the favorable crystallization of these products. The latter provides a facile synthesis of the W(2)(O(2)CR)(4) compound where R = 9-anthracene. Reactions involving 2,4,6-triisopropyl benzoic acid, TiPBH, yield M(2)(TiPB)(2)(mhp)(2) compounds as thermodynamic products. Reactions involving Me(3)OBF(4) (1 and 2 equiv.) yield the complexes Mo(2)(mhp)(3)(CH(3)CN)(2)BF(4) and Mo(2)(mhp)(2)(CH(3)CN)(4)(BF(4))(2), respectively. The latter compound has been structurally characterized and shown to have mirror symmetry with two cis mhp ligands: MoMo = 2.1242(5) A, Mo-O = 2.035(2) A, Mo-N(mhp) = 2.161(2) A, and Mo-N(CH(3)CN) = 2.160(3) and 2.170(3) A. Reactions involving Mo(2)(mhp)(3)(CH(3)CN)(2)(2+) and Mo(2)(mhp)(2)(CH(3)CN)(4)(2+) with (n)Bu(4)NO(2)CMe (1 and 2 equiv.) yield the complexes Mo(2)(mhp)(3)(O(2)CMe) and Mo(2)(mhp)(2)(O(2)CMe)(2) which are shown to be kinetically labile to ligand scrambling. Reactions between Mo(2)(mhp)(3)(CH(3)CN)(2)(+)BF(4)(-) (2 equiv.) and [(n)Bu(4)N(+)](2)[O(2)C-X-CO(2)](2-) yielded dimers of dimers [Mo(2)(mhp)(3)](2)(micro-O(2)C-X-CO(2)] where X = nothing, 2,5- or 3,4-thienyl and 1,4-C(6)H(4). Reactions between Mo(2)(mhp)(2)(CH(3)CN)(4)(2+)(BF(4)(-))(2) and tetra-n-butylammonium oxalate and terephthalate yield compounds [Mo(mhp)(2)bridge](n) which by MALDI-TOF MS are proposed to be a mixture of molecular squares (n = 4) and triangles (n = 3) along with minor products of [Mo(2)(mhp)(3)](2)(bridge) and Mo(2)(mhp)(4) that arise from ligand scrambling.     

Group 9 Chalcogenometalates

The compounds [K(18-crown-6)](3)[Ir(Se(4))(3)] (1), [K(2.2.2-cryptand)](3)[Ir(Se(4))(3)].C(6)H(5)CH(3) (2), and [K(18-crown-6)(DMF)(2)][Ir(NCCH(3))(2)(Se(4))(2)] (3) (DMF = dimethylformamide) have been prepared from the reaction of [Ir(NCCH(3))(2)(COE)(2)][BF(4)] (COE = cyclooctene) with polyselenide anions in acetonitrile/DMF. Analogous reactions utilizing [Rh(NCCH(3))(2)(COE)(2)][BF(4)] as a Rh source produce homologues of the Ir complexes; these have been characterized by (77)Se NMR spectroscopy. [NH(4)](3)[Ir(S(6))(3)].H(2)O.0.5CH(3)CH(2)OH (4) has been synthesized from the reaction of IrCl(3).nH(2)O with aqueous (NH(4))(2)S(m)(). In the structure of [K(18-crown-6)](3)[Ir(Se(4))(3)] (1) the Ir(III) center is chelated by three Se(4)(2)(-) ligands to form a distorted octahedral anion. The structure contains a disordered racemate of the Deltalambdalambdalambda and Lambdadeltadeltadelta conformers. The K(+) cations are pulled out of the planes of the crowns and interact with Se atoms of the [Ir(Se(4))(3)](3)(-) anion. [K(2.2.2-cryptand)](3)[Ir(Se(4))(3)].C(6)H(5)CH(3) (2) possesses no short K.Se interactions; here the [Ir(Se(4))(3)](3)(-) anion crystallizes as the Deltalambdalambdadelta/Lambdadeltadeltalambda racemate. In the crystal structure of [K(18-crown-6)(DMF)(2)][Ir(NCCH(3))(2)(Se(4))(2)] (3), the K(+) cation is coordinated by an 18-crown-6 ligand and two DMF molecules and the anion comprises an octahedral Ir(III) center bound by two chelating Se(4)(2)(-) chains and two trans acetonitrile groups. The [Ir(Se(4))(3)](3)(-) and [Rh(Se(4))(3)](3)(-) anions undergo conformational transformations as a function of temperature, as observed by (77)Se NMR spectroscopy. The thermodynamics of these transformations are: [Ir(Se(4))(3)](3)(-), DeltaH = 2.5(5) kcal mol(-)(1), DeltaS = 11.5(2.2) eu; [Rh(Se(4))(3)](3)(-), DeltaH = 5.2(7) kcal mol(-)(1), DeltaS = 24.7(3.0) eu.     

Formation and coordination modes of the C4E4 moiety (E = COOMe) bound to two palladium(II) moieties

The transmetallation of the palladacyclopentadiene complex Pd{C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy) with the dicationic Pd(II) complex [Pd(bipy)(CH(3)CN)(2)][BF(4)](2) afforded a terminally σ-palladated diene complex [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy)(2)(CH(3)CN)(2)][BF(4)](2). It was revealed by X-ray crystallographic analysis that replacement of the acetonitrile ligands in a terminally σ-palladated diene complex with PPh(3) ligands resulted in the conformation change of the σ-palladated diene moiety from skewed s-cis to planar s-trans. Treatment of a bis-triphenylphosphine dipalladium complex [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2) with dimethoxyacetylene dicarboxylate (DMAD) (1 equiv.) in acetonitrile resulted in the insertion of DMAD to the Pd-Pd bond to afford [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)}(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2). Addition of the second DMAD gave the ylide-type complex [Pd(2){μ-η(2):η(3)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)(PPh(3))}(PPh(3))(2)(CH(3)CN)(3)][PF(6)](2) of which the structure was determined by X-ray crystallographic analysis.     

Synthesis,crystal structure,and magnetic properties of mu-hydroxo-bis[pentakis(acetonitrile)chromium(III)] tetrafluoroborate: an acetonitrile analogue to "acid rhodo"

The reaction of [Cr(NCCH(3))(6)](2+) with dioxygen in acetonitrile (MeCN) solution acidified with HBF(4) gave red crystals of the binuclear complex [(CH(3)CN)(5)Cr(OH)Cr(NCCH(3))(5)](BF(4))(5) (1). From the X-ray crystal structure of 1, the Cr-O-Cr angle was found to be 147.5(2) degrees. Magnetic susceptibility measurements of 1 showed an antiferromagnetic coupling between the two chromium(III) centers with a triplet energy J = 35.9(1) cm(-1). On redissolution of 1 in MeCN, the hydroxo bridge was deprotonated, and a green solution of the complex [(CH(3)CN)(5)CrOCr(NCCH(3))(5)](4+) formed. The electronic absorption spectrum of this solution is very similar to the spectrum of the classical complex [(H(3)N)(5)CrOCr(NH(3))(5)](4+) with intense bands in the UV and near-UV region. From the temperature dependence of the absorption spectrum near 12900 cm(-1), the triplet energy J was found to be 1067(19) cm(-1). The acidity of the hydroxo bridge in 1 is very high with an acid dissociation constant K(a) > 1 M.     

Synthesis, characterization, and photoresponsive properties of a series of Mo(IV)-Cu(II) complexes

Six Mo(IV)-Cu(II) complexes, [Cu(tpa)](2)[Mo(CN)(8)]·15H(2)O (1, tpa = tris(2-pyridylmethyl)amine), [Cu(tren)](2)[Mo(CN)(8)]·5.25H(2)O (2, tren = tris(2-aminoethyl)amine), [Cu(en)(2)][Cu(0.5)(en)][Cu(0.5)(en)(H(2)O)][Mo(CN)(8)]·4H(2)O (3, en = ethylenediamine), [Cu(bapa)](3)[Mo(CN)(8)](1.5)·12.5H(2)O (4, bapa = bis(3-aminopropyl)amine), [Cu(bapen)](2)[Mo(CN)(8)]·4H(2)O (5, bapen = N,N'-bis(3-aminopropyl)ethylenediamine), and [Cu(pn)(2)][Cu(pn)][Mo(CN)(8)]·3.5H(2)O (6, pn = 1,3-diaminopropane), were synthesized and characterized. Single-crystal X-ray diffraction analyses show that 1-6 have different structures varying from trinuclear clusters (1-2), a one-dimensional belt (3), two-dimensional grids (4-5), to a three-dimensional structure (6). Magnetic and ESR measurements suggest that 1-6 exhibit thermally reversible photoresponsive properties on UV light irradiation through a Mo(IV)-to-Cu(II) charge transfer mechanism. A trinuclear compound [Cu(II)(tpa)](2)[Mo(V)(CN)(8)](ClO(4)) (7) was synthesized as a model of the photoinduced intermediate.     

Synthesis and reactions of group 6 metal half-sandwich complexes of 2,2-dicyanoethylene-1,1-dichalcogenolates [(Cp*)M[E(2)C=C(CN)(2)](2)]-(M = Mo,W; E = S,Se)

A series of group 6 transition metal half-sandwich complexes with 1,1-dichalcogenide ligands have been prepared by the reactions of Cp*MCl(4)(Cp* = eta(5)-C(5)Me(5); M = Mo, W) with the potassium salt of 2,2-dicyanoethylene-1,1-dithiolate, (KS)(2)C=C(CN)(2) (K(2)-i-mnt), or the analogous seleno compound, (KSe)(2)C=C(CN)(2) (K(2)-i-mns). The reaction of Cp*MCl(4) with (KS)(2)C=C(CN)(2) in a 1:3 molar ratio in CH(3)CN gave rise to K[Cp*M(S(2)C=C(CN)(2))(2)] (M = Mo, 1a, 74%; M = W, 2a, 46%). Under the same conditions, the reaction of Cp*MoCl(4) with 3 equiv of (KSe)(2)C=C(CN)(2) afforded K[Cp*Mo(Se(2)C=C(CN)(2))(2)] (3a) and K[Cp*Mo(Se(2)C=C(CN)(2))(Se(Se(2))C=C(CN)(2))] (4) in respective yields of 45% and 25%. Cation exchange reactions of 1a, 2a, and 3a with Et(4)NBr resulted in isolation of (Et(4)N)[Cp*Mo(S(2)C=C(CN)(2))(2)] (1b), (Et(4)N)[Cp*W(S(2)C=C(CN)(2))(2)] (2b), and (Et(4)N)[Cp*Mo(Se(2)C=C(CN)(2))(2)] (3b), respectively. Complex 4 crystallized with one THF and one CH(3)CN molecule as a three-dimensional network structure. Inspection of the reaction of Cp*WCl(4) with (KSe)(2)C=C(CN)(2) by ESI-MS revealed the existence of three species in CH(3)CN, [Cp*W(Se(2)C=C(CN)(2))(2)]-, [Cp*W(Se(2)C=C(CN)(2))(Se(Se(2))C=C(CN)(2))]-, and [Cp*W(Se(Se(2))C=C(CN)(2))(2)]-, of which [Cp*W(Se(2)C=C(CN)(2))(Se(Se(2))C=C(CN)(2))]-(5) was isolated as the main product. Treatment of 2a with 1/4 equiv of S(8) in refluxing THF resulted in sulfur insertion and gave rise to K[Cp*W(S(2)C=C(CN)(2))(S(S(2))C=C(CN)(2))](6), which crystallized with two THF molecules forming a three-dimensional network structure. 6 can also be prepared by refluxing 2a with 1/4 equiv of S(8) in THF. 3a readily added one Se atom upon treatment with 1 mol of Se powder in THF to give 4 in high yield, while the treatment of 3a or 4 with 2 equiv of Na(2)Se in THF led to formation of a dinuclear complex [(Cp*Mo)(2)(mu-Se)(mu-Se(Se(3))C=C(CN)(2))] (7). The structure of 7 consists of two Cp*Mo units bridged by a Se(2-) and a [Se(Se(3))C=C(CN)(2)](2-) ligand in which the triselenido group is arranged in a nearly linear way (163 degrees). The reaction of 2a with 2 equiv of CuBr in CH(3)CN yielded a trinuclear complex [Cp*WCu(2)(mu-Br)(mu(3)-S(2)C=C(CN)(2))(2)] (8), which crystallized with one CH(3)CN and generated a one-dimensional chain polymer through bonding of Cu to the N of the cyano groups.     

Homologous series of redox-active, dinuclear cations [M(2)(O(2)CCH(3))(2)(pynp)(2)](2+) (M = Mo, Ru, Rh) with the bridging ligand 2-(2-pyridyl)-1,8-naphthyridine (pynp)

A homologous series of dinuclear compounds with the bridging ligand 2-(2-pyridyl)-1,8-naphthyridine (pynp) has been prepared and characterized by X-ray crystallographic and spectroscopic methods. [Mo(2)(O(2)CCH(3))(2)(pynp)(2)][BF(4)](2) x 3CH(3)CN (1) crystallizes in the monoclinic space group P2(1)/c with a = 15.134(5) A, b = 14.301(6) A, c = 19.990(6) A, beta = 108.06(2) degrees, V = 4113(3) A(3), and Z = 4. [Ru(2)(O(2)CCH(3))(2)(pynp)(2)][PF(6)](2) x 2CH(3)OH (2) crystallizes in the monoclinic space group C2/c with a = 14.2228(7) A, b = 20.3204(9) A, c = 14.1022(7) A, beta = 95.144(1) degrees, V = 4059.3(3) A(3), and Z = 4. [Rh(2)(O(2)CCH(3))(2)(pynp)(2)][BF(4)](2) x C(7)H(8) (3) crystallizes in the monoclinic space group C2/c with a = 13.409(2) A, b = 21.670(3) A, c = 13.726(2) A, beta = 94.865(2) degrees, V = 3973.9(8) A(3), and Z = 4. A minor product, [Rh(2)(O(2)CCH(3))(2)(pynp)(2)(CH(3)CN)(2)][BF(4)][PF(6)] x 2CH(3)CN (4), was isolated from the mother liquor after crystals of 3 had been harvested; this compound crystallizes in the triclinic space group, P1 with a = 12.535(3) A, b = 13.116(3) A, c = 13.785(3) A, alpha = 82.52(3) degrees, beta = 77.70(3) degrees, gamma = 85.76(3) degrees, V = 2193.0(8) A(3), and Z = 2. Compounds 1-3 constitute a convenient series for probing the influence of the electronic configuration on the extent of mixing of the M-M orbitals with the pi system of the pynp ligand. Single point energy calculations performed on 1-3 at the B3LYP level of theory lend insight into the bonding in these compounds and allow for correlations to be made with electronic spectral data. Although purely qualitative in nature, the values for normalized change in orbital energies (NCOE) of the frontier orbitals before and after reduction are in agreement with the observed differences in reduction potentials as determined by cyclic voltammetry.     

Synthesis, structures, and reactivity of weakly coordinating anions with delocalized borate structure: the assessment of anion effects in metallocene polymerization catalysts.

The formation of adducts of tris(pentafluorophenyl)borane with strongly coordinating anions such as CN(-) and [M(CN)(4)](2)(-) (M = Ni, Pd) is a synthetically facile route to the bulky, very weakly coordinating anions [CN[B(C(6)F(5))(3)](2)](-) and [M[CNB(C(6)F(5))(3)](4)](2-) which are isolated as stable NHMe(2)Ph(+) and CPh(3)(+) salts. The crystal structures of [CPh(3)][CN[B(C(6)F(5))(3)](2)] (1), [CPh(3)][ClB(C(6)F(5))(3)] (2), [NHMe(2)Ph](2)[Ni[CNB(C(6)F(5))(3)](4)].2Me(2)CO (4b.2Me(2)CO), [CPh(3)](2)[Ni[CNB(C(6)F(5))(3)](4)].2CH(2)Cl(2) (4c.2CH(2)Cl(2)), and [CPh(3)](2)[Pd[CNB(C(6)F(5))(3)](4)].2CH(2)Cl(2) (5c.2CH(2)Cl(2)) are reported. The CN stretching frequencies in 4 and 5 are shifted by approximately 110 cm(-1) to higher wavenumbers compared to the parent tetracyano complexes in aqueous solution, although the M-C and C-N distances show no significant change on B(C(6)F(5))(3) coordination. Zirconocene dimethyl complexes L(2)ZrMe(2) [L(2) = Cp(2), SBI = rac-Me(2)Si(Ind)(2)] react with 1, 4c or 5c in benzene solution at 20 degrees C to give the salts of binuclear methyl-bridged cations, [(L(2)ZrMe)(2)(mu-Me)][CN[B(C(6)F(5))(3)](2)] and [(L(2)ZrMe)(2)(mu-Me)](2)[M[CNB(C(6)F(5))(3)](4)]. The reactivity of these species in solution was studied in comparison with the known [[(SBI)ZrMe](2)(mu-Me)][B(C(6)F(5))(4)]. While the latter reacts with excess [CPh(3)][B(C(6)F(5))(4)] in benzene to give the mononuclear ion pair [(SBI)ZrMe(+).B(C(6)F(5))(4)(-)] in a pseudo-first-order reaction, k = 3 x 10(-4) s(-1), [(L(2)ZrMe)(2)(mu-Me)][CN[B(C(6)F(5))(3)](2)] reacts to give a mixture of L(2)ZrMe(mu-Me)B(C(6)F(5))(3) and L(2)ZrMe(mu-NC)B(C(6)F(5))(3). Recrystallization of [Cp' '(2)Zr(mu-Me)(2)AlMe(2)][CN[B(C(6)F(5))(3)](2)] affords Cp' '(2)ZrMe(mu-NC)B(C(6)F(5))(3) 6, the X-ray structure of which is reported. The stability of [(L(2)ZrMe)(2)(mu-Me)](+)X(-) decreases in the order X = [B(C(6)F(5))(4)] > [M[CNB(C(6)F(5))(3)](4)] > [CN[B(C(6)F(5))(3)](2)] and increases strongly with the steric bulk of L(2) = Cp(2) < SBI. Activation of (SBI)ZrMe(2) by 1 in the presence of AlBu(i)(3) gives extremely active ethene polymerization catalysts. Polymerization studies at 1-7 bar monomer pressure suggest that these, and by implication most other highly active ethene polymerization catalysts, are strongly mass-transport limited. By contrast, monitoring propene polymerization activities with the systems (SBI)ZrMe(2)/1/AlBu(i)(3) and CGCTiMe(2)/1/AlBu(i)(3) at 20 degrees C as a function of catalyst concentration demonstrates that in these cases mass-transport limitation is absent up to [metal] approximately 2 x 10(-5) mol L(-1). Propene polymerization activities decrease in the order [CN[B(C(6)F(5))(3)](2)](-) > [B(C(6)F(5))(4)](-) > [M[CNB(C(6)F(5))(3)](4)](2-) > [MeB(C(6)F(5))(3)](-), with differences in activation barriers relative to [CN[B(C(6)F(5))(3)](2)](-) of DeltaDeltaG = 1.1 (B(C(6)F(5))(4)(-)), 4.1 (Ni[CNB(C(6)F(5))(3)](4)(2-)) and 10.7-12.8 kJ mol(-)(1) (MeB(C(6)F(5))(3)(-)). The data suggest that even in the case of very bulky anions with delocalized negative charge the displacement of the anion by the monomer must be involved in the rate-limiting step.     

Encapsulation of cyanometalates by a tris-macrocyclic ligand tricopper(II) complex: syntheses, structural variation, and magnetic exchange coupling pathways

The reaction of [M(CN)(6)](3-) (M = Cr(3+), Mn(3+), Fe(3+), Co(3+)) and [M(CN)(8)](4-/3-) (M = Mo(4+/5+), W(4+/5+)) with the trinuclear copper(II) complex of 1,3,5-triazine-2,4,6-triyltris[3-(1,3,5,8,12-pentaazacyclotetradecane)] ([Cu(3)(L)](6+)) leads to partially encapsulated cyanometalates. With hexacyanometalate(III) complexes, [Cu(3)(L)](6+) forms the isostructural host-guest complexes [[[Cu(3)(L)(OH(2))(2)][M(CN)(6)](2)][M(CN)(6)]][M(CN)(6)]30 H(2)O with one bridging, two partially encapsulated, and one isolated [M(CN)(6)](3-) unit. The octacyanometalates of Mo(4+/5+) and W(4+/5+) are encapsulated by two tris-macrocyclic host units. Due to the stability of the +IV oxidation state of Mo and W, only assemblies with [M(CN)(8)](4-) were obtained. The Mo(4+) and W(4+) complexes were crystallized in two different structural forms: [[Cu(3)(L)(OH(2))](2)[Mo(CN)(8)]](NO(3))(8)15 H(2)O with a structural motif that involves isolated spherical [[Cu(3)(L)(OH(2))](2)[M(CN)(8)]](8+) ions and a "string-of-pearls" type of structure [[[Cu(3)(L)](2)[M(CN)(8)]][M(CN)(8)]](NO(3))(4) 20 H(2)O, with [M(CN)(8)](4-) ions that bridge the encapsulated octacyanometalates in a two-dimensional network. The magnetic exchange coupling between the various paramagnetic centers is characterized by temperature-dependent magnetic susceptibility and field-dependent magnetization data. Exchange between the CuCu pairs in the [Cu(3)(L)](6+) "ligand" is weakly antiferromagnetic. Ferromagnetic interactions are observed in the cyanometalate assemblies with Cr(3+), exchange coupling of Mn(3+) and Fe(3+) is very small, and the octacoordinate Mo(4+) and W(4+) systems have a closed-shell ground state.     

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.     

Dehydration reaction of hydroxyl substituted alkenes and alkynes on the Ru(2)S(2) complex

A variety of inter- and intramolecular dehydration was found in the reactions of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)(mu-S(2))](CF(3)SO(3))(4) (1) with hydroxyl substituted alkenes and alkynes. Treatment of 1 with allyl alcohol gave a C(3)S(2) five-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)CH(2)CH(OCH(2)CH=CH(2))S]](CF(3)SO(3))(4) (2), via C-S bond formation after C-H bond activation and intermolecular dehydration. On the other hand, intramolecular dehydration was observed in the reaction of 1 with 3-buten-1-ol giving a C(4)S(2) six-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2) [mu-SCH(2)CH=CHCH(2)S]](CF(3)SO(3))(4) (3). Complex 1 reacts with 2-propyn-1-ol or 2-butyn-1-ol to give homocoupling products, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCR=CHCH(OCH(2)C triple bond CR)S]](CF(3)SO(3))(4) (4: R = H, 5: R = CH(3)), via intermolecular dehydration. In the reaction with 2-propyn-1-ol, the intermediate complex having a hydroxyl group, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OH)S]](CF(3)SO(3))(4) (6), was isolated, which further reacted with 2-propyn-1-ol and 2-butyn-1-ol to give 4 and a cross-coupling product, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OCH(2)C triple bond CCH(3))S]](CF(3)SO(3))(4) (7), respectively. The reaction of 1 with diols, (HO)CHRC triple bond CCHR(OH), gave furyl complexes, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SSC=CROCR=CH]](CF(3)SO(3))(3) (8: R = H, 9: R = CH(3)) via intramolecular elimination of a H(2)O molecule and a H(+). Even though (HO)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OH) does not have any propargylic C-H bond, it also reacts with 1 to give [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)C(=CH(2))C(=C=C(CH(3))(2))]S](CF(3)SO(3))(4) (10). In addition, the reaction of 1 with (CH(3)O)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OCH(3)) gives [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(2)][mu-S=C(C(CH(3))(2)OCH(3))C=CC(CH(3))CH(2)S][Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)]](CF(3)SO(3))(4) (11), in which one molecule of CH(3)OH is eliminated, and the S-S bond is cleaved.     

Supramolecular structural variations with changes in anion and solvent in silver(I) complexes of a semirigid, bitopic tris(pyrazolyl)methane ligand

The bitopic ligand p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2) (pz = pyrazolyl ring) that contains two tris(pyrazolyl)methane units connected by a semirigid organic spacer reacts with silver(I) salts to yield [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgX)(2)]( infinity ), where X = CF(3)SO(3)(-) (1), SbF(6)(-) (2), PF(6)(-) (3), BF(4)(-) (4), and NO(3)(-) (5). Crystallization of the first three compounds from acetone yields [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgCF(3)SO(3))(2)]( infinity ) (1a), [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgSbF(6))(2)[(CH(3))(2)CO](2)]( infinity ) (2b), and [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)AgPF(6)]( infinity ) (3a), where the stoichiometry for the latter compound has changed from a metal:ligand ratio of 2:1 to 1:1. The structure of 1a is based on helical argentachains constructed by a kappa(2)-kappa(1) coordination to silver of the tris(pyrazolyl)methane units. These chains are organized into a tubular 3D structure by cylindrical [(CF(3)SO(3))(6)](6)(-) clusters that form weak C-H...O hydrogen bonds with the bitopic ligand. The same kappa(2)-kappa(1) coordination is present in the structure of 2a, but the structure is organized by six different tris(pyrazolyl)methane units from six ligands bonding with six silvers to form a 36-member argentamacrocycle core. The cores are organized in a tubular array by the organic spacers where each pair of macrocycles sandwich six acetone molecules and one SbF(6)(-) counterion. The structure of 3a is based on a kappa(2)-kappa(0) coordination mode of each tris(pyrazolyl)methane unit forming a helical coordination polymer, with two strands organized in a double stranded helical structure by a series of C-H...pi interactions between the central arene rings. Crystallization of 2-4 from acetonitrile yields complexes of the formula [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)[(AgX)(2)(CH(3)CN)(n)]]( infinity ) where n = 2 for X = SbF(6)(-) (2b), X = PF(6)(-) (3b) and n = 1 for X = BF(4)(-) (4b). All three structures contain argentachains formed by a kappa(2)-kappa(1) coordination mode of the tris(pyrazolyl)methane units linked by the organic spacer and arranged in a 2D sheet structure with the anions sandwiched between the sheets. Crystallization of 5 from acetonitrile yields crystals of the formula [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgNO(3))(2)(CH(3)CN)(4)]( infinity ), where the nitrate is bonded to the silver. The argentachains, again formed by kappa(2)-kappa(1) coordination, are arranged in W-shaped sheets that have an overall configuration very different from 2b-4b. Treating [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgSbF(6))(2)]( infinity ) with a saturated aqueous solution of KPF(6) or KO(3)SCF(3) slowly leads to complete exchange of the anion. Crystallization of a sample that contains an approximately equal mixture of SbF(6)(-)/PF(6)(-) from acetonitrile yields [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)[Ag(2)(PF(6))(0.78(1))(SbF(6))(1.22(1))(CH(3)CN)(2)][(CH(3)CN)(0.25) (C(4)H(10)O)(0.25)]]( infinity ), a compound with a sheet structure analogous to 2b-4b. Crystallization of the same mixture from acetone yields [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgSbF(6))[(CH(3))(2)CO](1.5)]( infinity ), where the metal-to-ligand ratio is 1:1 and the [C(pz)(3)] units are kappa(2)-kappa(0) bonded forming a coordination polymer. The supramolecular structures of all species are organized by a combination of C-H...pi, pi-pi, or weak C-H-F(O) hydrogen bonding interactions.     

Hybrid cluster-cages formed via cyanometalate condensation: Cs subset Co(4)Ru(6)S(2)(CN)(12), Co(4)Ru(9)S(6)(CN)(9), and Rh(4)Ru(9)S(6)(CN)(9) frameworks

Condensation of cyanometalates and cluster building blocks leads to the formation of hybrid molecular cyanometalate cages. Specifically, the reaction of [Cs subset [CpCo(CN)(3)](4)[CpRu](3)] and [(cymene)(2)Ru(3)S(2)(NCMe)(3)]PF(6) produced [Cs subset [CpCo(CN)(3)](4)[(cymene)(2)Ru(3)S(2)][CpRu](3)](PF(6))(2), Cs subset Co(4)Ru(6)S(2)(2+). Single-crystal X-ray diffraction, NMR spectroscopy, and ESI-MS measurements show that Cs subset Co(4)Ru(6)S(2)(2+ ) consists of a Ru(4)Co(4)(CN)(12) box fused with a Ru(3)S(2) cluster via a common Ru atom. The reaction of PPN[CpCo(CN)(3)] and 0.75 equiv of [(cymene)(2)(MeCN)(3)Ru(3)S(2)](PF(6))(2) in MeCN solution produced [[CpCo(CN)(3)](4)[(cymene)(2)Ru(3)S(2)](3)](PF(6))(2), Co(4)Ru(9)S(6)(2+). Crystallographic analysis, together with NMR and ESI-MS measurements, shows that Co(4)Ru(9)S(6)(2+ ) consists of a Ru(3)Co(4)(CN)(9) "defect box" core, wherein each Ru is fused to a Ru(3)S(2) clusters. The analogous condensation using [CpRh(CN)(3)](-) in place of [CpCo(CN)(3)](-) produced the related cluster-cage Rh(4)Ru(9)S(6)(2+). Electrochemical analyses of both Co(4)Ru(9)S(6)(2+) and Rh(4)Ru(9)S(6)(2+) can be rationalized in the context of reduction at the cluster and the Co(III) subunits, the latter being affected by the presence of alkali metal cations.     

Fluoride-ion acceptor properties of WSF4: synthesis, characterization, and computational study of the WSF5(-) and W2S2F9(-) anions and 19F NMR spectroscopic characterization of the W2OSF9(-) anion

The new [N(CH(3))(4)][WSF(5)] salt was synthesized by two preparative methods: (a) by reaction of WSF(4) with [N(CH(3))(4)][F] in CH(3)CN and (b) directly from WF(6) using the new sulfide-transfer reagent [N(CH(3))(4)][SSi(CH(3))(3)]. The [N(CH(3))(4)][WSF(5)] salt was characterized by Raman, IR, and (19)F NMR spectroscopy and [N(CH(3))(4)][WSF(5)]·CH(3)CN by X-ray crystallography. The reaction of WSF(4) with half an aliquot of [N(CH(3))(4)][F] yielded [N(CH(3))(4)][W(2)S(2)F(9)], which was characterized by Raman and (19)F NMR spectroscopy and by X-ray crystallography. The WSF(5)(-) and W(2)S(2)F(9)(-) anions were studied by density functional theory calculations. The novel [W(2)OSF(9)](-) anion was observed by (19)F NMR spectroscopy in a CH(3)CN solution of WOF(4) and WSF(5)(-), as well as CH(3)CN solutions of WSF(4) and WOF(5)(-).     

Tetradentate selenium ligand as a building block for homodinuclear complexes of Pd(II) and Ru(II) having seven membered rings or bis-pincer coordination mode: high catalytic activity of Pd-complexes for Heck reaction

1,2,4,5-Tetrakis(phenyselenomethyl)benzene (L) has been synthesized by reaction of in situ generated PhSe(-) with 1,2,4,5-tetrakis(bromomethyl)benzene in N(2) atmosphere. Its first bimetallic complexes and a bis-pincer complex having compositions [(η(3)-C(3)H(5))(2)Pd(2)(L)][ClO(4)](2) (1) [Pd(2)(C(5)H(5)N)(2)(L)][BF(4)](2) (2) and [(η(6)-C(6)H(6))(2)Ru(2)(L)Cl(2)][PF(6)](2) (3) have been synthesized by reacting L with [Pd(η(3)-C(3)H(5))Cl](2), [Pd(CH(3)CN)(4)][BF(4)](2) and [(η(6)-C(6)H(6))(2)RuCl(2)](2) respectively. The structures of ligand L and its all three complexes have been determined by X-ray crystallography. In 1 and 3, ligand L forms with two organometallic species seven membered chelate rings whereas in 2 it ligates in a bis-pincer coordination mode. The geometry around Pd in 1 or 2 is close to square planar whereas in 3, Ru has pseudo-octahedral half sandwich "Piano-Stool" geometry. The Pd-Se bond distances are in the ranges 2.4004(9)-2.4627(14) ? and follow the order 1 > 2, whereas Ru-Se bond lengths are between 2.4945(16) and 2.5157(17) ?. The 1 and 2 have been found efficient catalysts for Heck reaction of aryl halides with styrene and methyl acrylate. The 2 is superior to 1. The TON and TOF values (per Pd) are up to ~47500 and ~2639 h(-1) respectively.     

Preparation and characterization of the argentates: [Ag[P(CF(3))(2)](2)](-), [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-) (M = Cr, W), and [Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)](-): X-ray crystal structure of [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)

The first example of a mononuclear diphosphanidoargentate, bis[bis(trifluoromethyl)phosphanido]argentate, [Ag[P(CF(3))(2)](2)](-), is obtained via the reaction of HP(CF(3))(2) with [Ag(CN)(2)](-) and isolated as its [K(18-crown-6)] salt. When the cyclic phosphane (PCF(3))(4) is reacted with a slight excess of [K(18-crown-6)][Ag[P(CF(3))(2)](2)], selective insertion of one PCF(3) unit into each silver phosphorus bond is observed, which on the basis of NMR spectroscopic evidence suggests the [Ag[P(CF(3))P(CF(3))(2)](2)](-) ion. On treatment of the phosphane complexes [M(CO)(5)PH(CF(3))(2)] (M = Cr, W) with [K(18-crown-6)][Ag(CN)(2)], the analogous trinuclear argentates, [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-), are formed. The chromium compound [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)] crystallizes in a noncentrosymmetric space group Fdd2 (No. 43), a = 2970.2(6) pm, b = 1584.5(3) pm, c = 1787.0(4), V = 8.410(3) nm(3), Z = 8. The C(2) symmetric anion, [Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)](-), shows a nearly linear arrangement of the P-Ag-P unit. Although the bis(pentafluorophenyl)phosphanido compound [Ag[P(C(6)F(5))(2)](2)](-) has not been obtained so far, the synthesis of its trinuclear counterpart, [K(18-crown-6)][Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)], was successful.     

Studies of a series of [Ni(P(R)2N(Ph)2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production: substituent variation at the phosphorus atom of the P2N2 ligand

A series of [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes containing the cyclic diphosphine ligands [P(R)(2)N(Ph)(2) = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(P(Bn)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) and [Ni(P(n-Bu)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(P(Bn)(2)N(Ph)(2))(2)] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(P(Cy)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2), all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H(2) in acidic acetonitrile solutions. The heterolytic cleavage of H(2) by [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(P(R)(2)N(Ph)(2))(2)](BF(4)) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H(2), suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate.     

A study of structural and bonding variations in the homologous series [Mo(2)(CN)(6)(dppm)(2)](n-) (n = 2, 1, 0)

Reaction of Mo(2)Cl(4)(dppm)(2) (dppm = bis(diphenylphosphino)methane) with 6 equiv of [n-Bu(4)N][CN] or [Et(4)N][CN] in dichloromethane yields [n-Bu(4)N](2)[Mo(2)(CN)(6)(dppm)(2)] (1) and [Et(4)N](2)[Mo(2)(CN)(6)(dppm)(2)] (2), respectively. The corresponding one- and two-electron oxidation products [n-Bu(4)N][Mo(2)(CN)(6)(dppm)(2)] (3) and Mo(2)(CN)(6)(dppm)(2) (4)were prepared by reactions of 1 with the oxidant NOBF(4). Single-crystal X-ray structures of 2.2CH(3)CN, 3.2CH(3)CN.2H(2)O, and 4.2CH(3)NO(2) were performed, and the results confirmed that all three complexes contain identical ligand sets with trans dppm ligands bisecting the Mo(2)(mu-CN)(2)(CN)(4) equatorial plane. The binding of the bridging cyanide ligands is affected by the oxidation state of the dimolybdenum core as evidenced by an increase in side-on pi-bonding overlap of the mu-CN in going from 1 to 4. The greater extent of pi-donation into Mo orbitals is accompanied by a lengthening of the Mo-Mo distance (2.736(1) A in Mo(2)(II,II) (2), 2.830(1) A in Mo(2)(II,III) (3), and 2.936(1) A in Mo(2)(III,III) (4)). A computational study of the closed-shell members of this homologous series, [Mo(2)(CN)(6)(dppm)(2)](n)() (n = 2-, 0), indicates that the more pronounced side-on pi-donation evident in the X-ray structure of 4 leads to significant destabilization of the delta orbital and marginal stabilization of the delta() orbitals with respect to nearly degenerate delta and delta orbitals in the parent compound, 2. The loss of delta contributions combined with the reduced orbital overlap due to higher charges on molybdenum centers in oxidized complexes 3 and 4 is responsible for the observed increase in the length of the Mo-Mo bond.     

How to make a major shift in a redox potential: ligand control of the oxidation state of dimolybdenum units

A compound reported earlier (Polyhedron 1989, 8, 2339) as (Bu(n)()(4)N)(2)H(2)[Mo(2)[Mo(CO)(4)(PhPO(2))(2)](2)] has been reexamined. We find that the hydrogen atoms in this formula are not present. Therefore, the complex must be considered as having a central triply bonded Mo(2)(6+) unit, instead of a quadruply bonded Mo(2)(4+) unit. Our conclusion is based on a variety of experimental evidence, including X-ray crystal structures of four crystal forms, as well as the neutron crystal structure of one. This explains the relatively long Mo-Mo bond lengths found in the range 2.1874(7)-2.2225(7) A and the absence of a delta --> delta transition in the visible spectrum. From electrochemistry we also find that the diphosphonate ligand has such an exceptional ability to stabilize higher oxidation states that even common solvents such as CH(2)Cl(2) and C(2)H(5)OH readily oxidize the Mo(2)(4+) unit that is introduced from the Mo(2)(O(2)CCH(3))(4) or [Mo(2)(O(2)CCH(3))(2)(NCCH(3))(6)](BF(4))(2) employed in the preparation. The only chemically reversible wave at E(1/2) = -1.54 V vs Ag/AgCl corresponds to the reduction process Mo(2)(6+) --> Mo(2)(5+).     

Si(SiMe3)3]3Ge9M(CO)3(-) (M=Cr, Mo, W): coordination chemistry with metalloid clusters

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-)1 can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. So the reaction of 1 with Cr(CO)(3)(CH(3)CN)(3) leads to a cluster enlargement where the chromium atom is incorporated into the cluster core. Here further applications of 1 as a flexible ligand in coordination chemistry are presented where the reaction of 1 with Mo(CO)(3)(EtCN)(3) and W(CO)(3)(CH(3)CN)(3) leads to [(CO)(3)MoGe(9)R(3)](-)4 and [(CO)(3)WGe(9)R(3)](-)5 respectively (R = Si(SiMe(3))(3)), showing that 1 can indeed be used as a flexible ligand in coordination chemistry. Structural and electronic properties of the Ge(9)M clusters 4 and 5 are discussed as well as mechanistic aspects of their formation.