Molecular precursors to gallium oxide thin films

The donor-functionalised alkoxides [Et(2)Ga(OR)](2)(R = CH(2)CH(2)NMe(2)(1), CH(CH(2)NMe(2))(2)(2), CH(2)CH(2)OMe (3), CH(CH(3))CH(2)NMe(2)(4), C(CH(3))(2)CH(2)OMe (5)) were synthesised by the 1:1 reaction of Et(3)Ga with ROH in hexane or dichloromethane at room temperature. Reaction of Et(3)Ga with excess ROH in refluxing toluene resulted in the isolation of a 1:1 mixture of [Et(2)Ga(OR)](2) and the ethylgallium bisalkoxide [EtGa(OR)(2)](R = CH(2)CH(2)NMe(2)(6) or CH(CH(3))CH(2)NMe(2)(7)). X-ray crystallography showed that compound 6 is monomeric and this complex represents the first structurally characterised monomeric gallium bisalkoxide. Homoleptic gallium trisalkoxides [Ga(OR)(3)](2) were prepared by the 1:6 reaction of [Ga(NMe(2))(3)](2) with ROH (R = CH(2)CH(2)NMe(2)(8), CH(CH(3))CH(2)NMe(2)(9), C(CH(3))(2)CH(2)OMe (10)). The decomposition of compounds 1, 4, 5 and 8 were studied by thermal gravimetric analysis. Low pressure CVD of 1 and 5 resulted in the formation of thin films of crystalline Ga(2)O(3).     

Two new terpyridine dimanganese complexes: a manganese(III,III) complex with a single unsupported oxo bridge and a manganese(III,IV) complex with a dioxo bridge. Synthesis, structure, and redox properties

Two new terpyridine dimanganese oxo complexes [Mn(2)(III,IV)(mu-O)(2)(terpy)(2)(CF(3)CO(2))(2)](+) (3) and [Mn(2)(III,III)(mu-O)(terpy)(2)(CF(3)CO(2))(4)] (4) (terpy = 2,2':6,2' '-terpyridine) have been synthesized and their X-ray structures determined. In contrast to the corresponding mixed-valent aqua complex [Mn(2)(III,IV)(mu-O)(2)(terpy)(2)(H(2)O)(2)](3+) (1), the two Mn atoms in 3 are not crystallographically equivalent. The neutral binuclear monooxo manganese(III,III) complex 4 exhibits two crystallographic forms having cis and trans configurations. In the cis complex, the two CF(3)CO(2)(-) ligands on each manganese adopt a cis geometry to each other; one CF(3)CO(2)(-) is trans to the oxygen of the oxo bridge while the second is cis. In the trans complex, the two coordinated CF(3)CO(2)(-) have a trans geometry to each other and are cis to the oxo bridge. The electrochemical behavior of 3 in organic medium (CH(3)CN) shows that this complex could be oxidized into its corresponding stable manganese(IV,IV) species while its reduced form manganese(III,III) is very unstable and leads by a disproportionation process to Mn(II) and Mn(IV) complexes. Complex 4 is only stable in the solid state, and it disproportionates spontaneously in CH(3)CN solution into the mixed-valent complex 3 and the mononuclear complex [Mn(II)(terpy)(2)](2+) (2), thereby preventing the observation of its electrochemical behavior.     

Titanium, zinc and alkaline-earth metal complexes supported by bulky O,N,N,O-multidentate ligands: syntheses, characterisation and activity in cyclic ester polymerisation

The reactions of the bulky amino-bis(phenol) ligand Me(2)NCH(2)CH(2)N[CH(2)-3,5-Bu(t)(2)-C(6)H(2)OH-2](2)(1-H(2)) with Zn[N(SiMe(3))(2)](2)(4), [Mg[N(SiMe(3))(2)](2)](2)(5) and Ca[N(SiMe(3))(2)](2)(THF)(2)(6) yield the complexes 1-Zn, 1-Mg and 1-Ca in good yields. The X-ray structure of 1-Ca showed the complex to be dimeric, with calcium in a distorted octahedral coordination geometry. Five of the positions are occupied by an N(2)O(3) donor set, while the sixth is taken up by an intramolecular close contact to an o-Bu(t) substituent, a rare case of a Ca...H-C agostic interaction (Ca...H distances of 2.37 and 2.41 Angstroms). Another sterically hindered calcium complex, Ca[2-Bu(t)-6-(C(6)F(5)N=CH)C(6)H(3)O](2)(THF)(2).(C(7)H(8))(2/3)(7), was prepared by reaction of 6 with the iminophenol 2-Bu(t)-6-(C(6)F(5)N=CH)C(6)H(3)OH (3-H). According to the crystal structure 7 is monomeric and octahedral, with trans THF ligands. The complex Ti[N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)O-2](2)[CH(2)CH(2)NMe(2)]](OPr(i))(2)(2-Ti) was prepared by treatment of Ti(OPr(i)(4)) with the new amino-bis(phenol) Me(2)NCH(2)CH(2)N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)OH-2](2)(2-H(2)). The reduction of 2-Ti with sodium amalgam gave the titanium(III) salt Ti[N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)O-2](2)[CH(2)CH(2)NMe(2)]](OPr(i))(2).Na(THF)(2)(8). A comparison of the X-ray structures of 2-Ti and 8 showed that the additional electron in 8 significantly reduced the intensity of the pi-bonding from the oxygen atoms of the isopropoxide groups to titanium. 1-Ca and 8 were active initiators for the ring-opening polymerisation of epsilon-caprolactone (up to 97% conversion of 200 equivalents in 2 hours) and yielded polymers with narrow molecular weight distributions.     

Electronic structure of iron chlorins: characterization of bis(l-valine methyl ester)(meso-tetraphenylchlorin)iron(III)triflate and bis(l-valine methyl ester)(meso-tetraphenylchlorin)iron(II)

The synthesis and characterization of the two iron chlorin complexes [Fe(III)(TPC)(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2)))(2)]CF(3)SO(3) (1) and Fe(II)(TPC)[(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2))](2) (2) are reported. The crystal structure of complex 1 has been determined. The X-ray structure shows that the porphyrinate rings are weakly distorted. The metal-nitrogen distances to the reduced pyrrole N(4), 2.034(4) A, and to the pyrrole trans to it N(2), 2.012(4) A, are longer than the distances to the two remaining nitrogens [N(1), 1.996(4) A, and N(3), 1.984(4) A], leading to a core-hole expansion of the macrocycle due to the reduced pyrrole. The (1)H NMR isotropic shifts at 20 degrees C of the different pyrrole protons of 1 varied from -0.8 to -48.3 ppm according to bis-ligated complexes of low-spin ferric chlorins. The EPR spectrum of [Fe(TPC)(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2)))(2)]CF(3)SO(3) (1) in solution is rhombic and gives the principal g values g(1) = 2.70, g(2) = 2.33, and g(3) = 1.61 (Sigmag(2) = 15.3). These spectroscopic observations are indicative of a metal-based electron in the d(pi) orbital for the [Fe(TPC)(NH(2)CH(CO(2)CH(3))(CH(CH(3))(2)))(2)]CF(3)SO(3) (1) complex with a (d(xy))(2)(d(xz)d(yz))(3) ground state at any temperature. The X-ray structure of the ferrous complex 2 also shows that the porphyrinate rings are weakly distorted. The metal-nitrogen distances to the reduced pyrrole N(4), 1.991(5) A, and to the pyrrole trans to it N(2), 2.005(6) A, are slightly different from the distances to the two remaining nitrogens [N(1), 1.988(5) A, and N(3), 2.015(5) A], leading to a core-hole expansion of the macrocycle due to the reduced pyrrole.     

The synthesis of W-O-W μ-oxo clusters by hydrolysis of tungsten aminoalkoxides and their structural characterisation

The tungsten aminoalkoxides W(O)(OPr(i))(3)L [L = dmae, OCH(2)CH(2)NMe(2) (1); bdmap, OCH(CH(2)NMe(2))(2) (2); tdmap, OC(CH(2)NMe(2))(3) (3)] have been synthesised. Controlled hydrolysis of 1-3 has allowed isolation of W(4)O(4)(μ-O)(6)(dmae)(4) (4), W(4)O(4)(μ-O)(4)(OPr(i))(4)(bdmap)(4) (5), W(6)O(6)(μ-O)(9)(tdmap)(6) (6), W(4)O(4)(μ-O)(6)(tdmap)(4) (7), W(4)O(4)(μ-O)(6)(tdmap)(4)·4H(2)O (7a), all of which have been characterised by X-ray crystallography. 4, 7, 7a each embody a W(4)O(6) core with adamantane structure, 5 incorporates a folded W(4)O(4) square and 6 has a trigonal prismatic W(6)O(9) at its heart. 7 decomposes in air at to give orthorhombic WO(3), while 1-3 decomposed under an autogenerated pressure (Reaction under Autogenic Pressure at Elevated Temperatures, RAPET) to form mixtures of carbon-coated WO(x) needles and carbon spherules.     

Ligand-modification effects on the reactivity, solubility, and stability of organometallic tantalum complexes in water

Tantalum complexes [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NMe(2))=CH)py}] (4) and [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NH(2))=CH)py}] (5), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ(3)-N,O,O-(OCH(2))(OCH)py}] (Cp* = η(5)-C(5)Me(5)) with HC≡CCH(2)NMe(2) and HC≡CCH(2)NH(2), respectively. The reactions of [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(Ph)=CH)py}] (2) and [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(SiMe(3))=CH)py}] (3) with triflic acid (1:2 molar ratio) rendered the corresponding bis-triflate derivatives [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(OCHC(Ph)=CH(2))py}] (6) and [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(OCHC(SiMe(3))=CH(2))py}] (7), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water-soluble cationic complex [TaCp*(OTf){κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NHMe(2))=CH)py}]OTf (8). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H(2)O){κ(3)-N,O,O-(OCH(2))(OCHC(CH(2)NHMe(2))=CH(2))py}](OTf)(2) (9). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ(4)-C,N,O,O-(OCH(2))(HOCHC(CH(2)NHMe(2))=CH)py}](OTf)(2) (10), which afforded the corresponding protonolysis derivative [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(HOCHC(CH(2)NHMe(2))=CH(2))py}](OTf) (11) in solution. Complex 8 reacted with CNtBu and potassium 2-isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13, respectively. The molecular structures of complexes 5, 7, and 10 were established by single-crystal X-ray diffraction studies.     

Alkynyldiphenylphosphine d8 (Pt, Rh, Ir) complexes: contrasting behavior toward cis-[Pt(C6F5)2(THF)2

The synthesis and characterization of a series of mononuclear d(8) complexes with at least two P-coordinated alkynylphosphine ligands and their reactivity toward cis-[Pt(C(6)F(5))(2)(THF)(2)] are reported. The cationic [Pt(C(6)F(5))(PPh(2)C triple-bond CPh)(3)](CF(3)SO(3)), 1, [M(COD)(PPh(2)C triple-bond CPh)(2)](ClO(4)) (M = Rh, 2, and Ir, 3), and neutral [Pt(o-C(6)H(4)E(2))(PPh(2)C triple-bond CPh)(2)] (E = O, 6, and S, 7) complexes have been prepared, and the crystal structures of 1, 2, and 7.CH(3)COCH(3) have been determined by X-ray crystallography. The course of the reactions of the mononuclear complexes 1-3, 6, and 7 with cis-[Pt(C(6)F(5))(2)(THF)(2)] is strongly influenced by the metal and the ligands. Thus, treatment of 1 with 1 equiv of cis-[Pt(C(6)F(5))(2)(THF)(2)] gives the double inserted cationic product [Pt(C(6)F(5))(S)mu-(C(Ph)=C(PPh(2))C(PPh(2))=C(Ph)(C(6)F(5)))Pt(C(6)F(5))(PPh(2)C triple-bond CPh)](CF(3)SO(3)) (S = THF, H(2)O), 8 (S = H(2)O, X-ray), which evolves in solution to the mononuclear complex [(C(6)F(5))(PPh(2)C triple-bond CPh)Pt(C(10)H(4)-1-C(6)F(5)-4-Ph-2,3-kappaPP'(PPh(2))(2))](CF(3) SO(3)), 9 (X-ray), containing a 1-pentafluorophenyl-2,3-bis(diphenylphosphine)-4-phenylnaphthalene ligand, formed by annulation of a phenyl group and loss of the Pt(C(6)F(5)) unit. However, analogous reactions using 2 or 3 as precursors afford mixtures of complexes, from which we have characterized by X-ray crystallography the alkynylphosphine oxide compound [(C(6)F(5))(2)Pt(mu-kappaO:eta(2)-PPh(2)(O)C triple-bond CPh)](2), 10, in the reaction with the iridium complex (3). Complexes 6 and 7, which contain additional potential bridging donor atoms (O, S), react with cis-[Pt(C(6)F(5))(2)(THF)(2)] in the appropriate molar ratio (1:1 or 1:2) to give homo- bi- or trinuclear [Pt(PPh(2)C triple-bond CPh)(mu-kappaE-o-C(6)H(4)E(2))(mu-kappaP:eta(2)-PPh(2)C triple-bond CPh)Pt(C(6)F(5))(2)] (E = O, 11, and S, 12) and [(Pt(mu(3)-kappa(2)EE'-o-C(6)H(4)E(2))(mu-kappaP:eta(2)-PPh(2)C triple-bond CPh)(2))(Pt(C(6)F(5))(2))(2)] (E = O, 13, and S, 14) complexes. The molecular structure of 14 has been confirmed by X-ray diffraction, and the cyclic voltammetric behavior of precursor complexes 6 and 7 and polymetallic derivatives 11-14 has been examined.     

Group-4 eta(1)-pyrrolyl complexes incorporating N,N-di(pyrrolyl-alpha-methyl)-N-methylamine

Syntheses and properties of group-4 complexes incorporating the tridentate, dianionic ligand N,N-(dipyrrolyl-alpha-methyl)-N-methylamine, dpma, have been investigated. Addition of 1 equiv of H(2)dpma to Ti(NMe(2))(4) and Zr(NMe(2))(4) results in transamination with 2 dimethylamides providing Ti(NMe(2))(2)(dpma) and Zr(NMe(2))(2)(NHMe(2))(dpma), respectively. Addition of 2 equiv of H(2)dpma to Zr(NMe(2))(4) and Hf(NMe(2))(4) results in production of the homoleptic complexes Zr(dpma)(2) and Hf(dpma)(2). Conversely, treatment of Ti(NMe(2))(4) with 2 equiv of H(2)dpma does not provide Ti(dpma)(2), which was available by addition of 2 Li(2)dpma to TiCl(4). The properties of the isostructural series M(dpma)(2) were investigated by single crystal X-ray diffraction, cyclic voltammetry, (14)N NMR, and other techniques. By (14)N NMR, it was found that the pyrrolyl resonance chemical shift changes approximately linearly with the electronegativity of the metal center, which was attributed to pi-interaction between the pyrrolyl nitrogen lone pair and the metal. Other complexes produced during this study include Ti(CH(2)SiMe(3))(NMe(2))(dpma), TiCl(2)(THF)(dpma), and Ti(OCH(2)CF(3))(2)(THF)(dpma). Two isomers for Ti(CH(2)SiMe(3))(NMe(2))(dpma) were isolated and characterized.     

Systematic preparation of Mo 2 4+ building blocks for supramolecular assemblies

The preparation of additional and useful building blocks for the construction of supramolecular entities with quadruply bonded Mo(2)(4+) units has been explored, and five new mixed-ligand complexes with three types of ligands and various basicities are reported. The ligands used were the DAniF (N,N'-di-p-anisylformamidinate) anion, the acetate anion, and neutral acetonitrile molecules. The formamidinate ligands are the least labile, and the acetonitrile molecules are the most labile. This difference as well as a relatively strong trans directing influence by the formamidinate anions in ligand substitution reactions allows designed synthesis of various mixed-ligand building blocks, including rare pairs of cis and trans isomers. The new compounds are cis-Mo(2)(DAniF)(2)(O(2)CCH(3))(2) (1), trans-Mo(2)(DAniF)(2)(O(2)CCH(3))(2) (2), trans-[Mo(2)(DAniF)(2)(O(2)CCH(3))(CH(3)CN(eq)())(2)]BF(4) (3), trans-[Mo(2)(DAniF)(2)(CH(3)CN(eq)())(4)](BF(4))(2) (4), and [Mo(2)(O(2)CH(3))(CH(3)CN(eq)())(6)(CH(3)CN(ax)())](BF(4))(3) (5), where eq and ax designate equatorial and axial ligands, respectively. A comparison with some previously synthesized complexes is given along with a discussion of the overall reactivity of all compounds.     

Gallium oxide thin films from the AACVD of [Ga(NMe2)3]2 and donor functionalised alcohols

Thin films of Ga(2)O(3) have been produced from [Ga(NMe(2))(3)](2) and ROH (R = CH(2)CH(2)NMe(2), CH(CH(2)NMe(2))(2), CH(CH(3))CH(2)NMe(2), CH(2)CH(2)OMe and C(CH(3))(2)CH(2)OMe) by aerosol assisted chemical vapour deposition on glass. Transparent, unreflective films were obtained at a deposition temperature of 550 degrees C using toluene as solvent. The gallium oxide films were analyzed by Scanning electron microscopy (SEM), Raman spectroscopy, wavelength dispersive analysis of X-rays (WDX) and X-ray photoelectron spectroscopy (XPS). The gallium oxide films obtained were X-ray amorphous. Gas-sensing experiments indicated that the films showed an n-type response to ethanol at a variety of temperatures.     

New diamide-diamine ligands and their zirconium and hafnium dichloride and bis(dimethylamide) complexes

The multigram syntheses of the protio ligands (2-NC(5)H(4))CH(2)N(CH(2)CH(2)NHSiMe(2)R)(2) (R = Me, H(2)N(2)NN' 3; R = (t)Bu, H(2)N(2)NN() 4) are described via reactions of the previously reported (2-NC(5)H(4))CH(2)N(CH(2)CH(2)NH(2))(2) (1). A new synthesis of 1 is reported starting from 2-aminomethylpyridine and N-tosylaziridine, proceeding via (2-NC(5)H(4))CH(2)N(CH(2)CH(2)NHTs)(2) (2). Reaction of H(2)N(2)NN' or H(2)N(2)NN* with (n)BuLi gives good yields of the dilithiated derivatives Li(2)N(2)NN' and Li(2)N(2)NN*. Reaction of H(2)N(2)NN' or H(2)N(2)NN* with [MCl(2)(CH(2)SiMe(3))(2)(Et(2)O)(2)] gives the cis-dichloride complexes [MCl(2)(L)] (L = N(2)NN', M = Zr 7 or Hf 8; L = N(2)NN(), M = Zr 9). The corresponding reactions of H(2)N(2)NN' or H(2)N(2)NN* with [Zr(NMe(2))(4)] afford the bis(dimethylamide) derivatives [Zr(NMe(2))(2)(L)] (L = N(2)NN' 10 or N(2)NN* 11). All of these protonolysis reactions proceed smoothly and in good yields. Attempts to prepare the titanium complexes [Ti(X)(2)(N(2)NN')] (X = Cl or NMe(2)) were unsuccessful. The X-ray crystal structures of (2-NC(5)H(4))CH(2)N(CH(2)CH(2)NHTs)(2).EtOH, [ZrCl(2)(N(2)NN')].0.5C(6)H(6), [Zr(NMe(2))(2)(N(2)NN')], and [Zr(NMe(2))(2)(N(2)NN*)] are reported.     

Chiral fluorous dialkoxy-diamino zirconium complexes: synthesis and use in stereospecific polymerization of 1-hexene

New catalysts for the isospecific polymerization of 1-hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy-diamino ligands [OC(CF(3))(2)CH(2)N(Me)(CH(2))(2)N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(2)NO)(2-)] and [OC(CF(3))(2)CH(2)N(Me)(1R,2R-C(6)H(10))N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(Cy)NO)(2-)] have been developed. The chiral fluorous diamino-diol [(ON(Cy)NO)H(2), 2] was prepared by ring-opening of the fluorinated oxirane (CF(3))(2)COCH(2) with (R,R)-N,N'-dimethyl-1,2-cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH(2)Ph)(4)] and [Ti(OiPr)(4)] precursors to give the corresponding dialkoxy complexes [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3) and [Ti(OiPr)(2)(ON(Cy)NO)] (4), respectively. An X-ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (Lambda-3 and Delta-3), both of which adopt a distorted octahedral structure with trans-O, cis-N, and cis-CH(2)Ph ligands. The two diastereomers Lambda-3 and Delta-3 adopt a C(2)-symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH(2)Ph)(ON(2)NO)(THF)(n)](+) (n=0, anion=[B(C(6)F(5))(4)](-), 5; n=1, anion=[PhCH(2)B(C(6)F(5))(3)](-), 6) and [Zr(CH(2)Ph)(ON(Cy)NO)(THF)](+)[PhCH(2)B(C(6)F(5))(3)](-) (7) were generated from the neutral parent precursors [Zr(CH(2)Ph)(2)(ON(2)NO)] (H) and [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3), and their possible structures were determined on the basis of (1)H, (19)F, and (13)C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (Lambda-3/Delta-3 mixture), when activated with B(C(6)F(5))(3) or [Ph(3)C](+)[B(C(6)F(5))(4)](-), catalyze the polymerization of 1-hexene with overall activities of up to 4500 kg PH mol Zr(-1) h(-1), to yield isotactic-enriched (up to 74 % mmmm) polymers with low-to-moderate molecular weights (M(w)=4800-47 200) and monodisperse molecular-weight distributions (M(w)/M(n)=1.17-1.79).     

Aerosol assisted chemical vapor deposition of In2O3 films from Me3In and donor functionalized alcohols

The reaction of Me3In and ROH (R = CH2CH2NMe2, CH(CH3)CH2NMe2, C(CH3)2CH2OMe, CH2CH2OMe) in toluene under aerosol assisted chemical vapor deposition (AACVD) conditions leads to the production of indium oxide thin films on glass. The indium oxide films were deposited at 550 degrees C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. This CVD technique offers a rapid, convenient route to In2O3, which presumably involves the in situ formation of dimethylindium alkoxides, of the type [Me2InOR]2. In order to identify compounds present in the aerosol mist, the solution-phase reaction between Me3In and ROH (R = CH2CH2NMe2, C(CH3)2CH2OMe, CH(CH3)CH2NMe2, CH(CH2NMe2)2) at room temperature in toluene was carried out. Dimeric indium alkoxides, of the type [Me2In(OR)]2, were isolated, and their structures were determined by X-ray crystallography.     

Metal ion-controlled self-assembly using pyrimidine hydrazone molecular strands with terminal hydroxymethyl groups: a comparison of Pb(II) and Zn(II) complexes

Metal complexation studies were performed with the ditopic pyrimidine-hydrazone (pym-hyz) strand 6-hydroxymethylpyridine-2-carboxaldehyde (2-methyl-pyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) and Pb(ClO(4))(2)·3H(2)O, Pb(SO(3)CF(3))(2)·H(2)O, Zn(SO(3)CF(3))(2), and Zn(BF(4))(2) to examine the ability of 1 to form various supramolecular architectures. X-ray crystallographic and NMR studies showed that coordination of the Pb(II) salts with 1 on a 2:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2) resulted in the linear complexes [Pb(2)1(ClO(4))(4)] (2), [Pb(2)1(ClO(4))(3)(H(2)O)]ClO(4) (3), and [Pb(2)1(SO(3)CF(3))(3)(H(2)O)]SO(3)CF(3) (4). Two unusually distorted [2 × 2] grid complexes, [Pb1(ClO(4))](4)(ClO(4))(4) (5) and [Pb1(ClO(4))](4)(ClO(4))(4)·4CH(3)NO(2) (6), were formed by reacting Pb(ClO(4))(2)·6H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2). These grids formed despite coordination of the hydroxymethyl arms due to the large, flexible coordination sphere of the Pb(II) ions. A [2 × 2] grid complex was formed in solution by reacting Pb(SO(3)CF(3))(2)·H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN as shown by (1)H NMR, microanalysis, and ESMS. Reacting the Zn(II) salts with 1 on a 2:1 metal/ligand ratio gave the linear complexes [Zn(2)1(H(2)O)(4)](SO(3)CF(3))(4)·C(2)H(5)O (7) and [Zn(2)1(BF(4))(H(2)O)(2)(CH(3)CN)](BF(4))(3)·H(2)O (8). (1)H NMR studies showed the Zn(II) and Pb(II) ions in these linear complexes were labile undergoing metal ion exchange. All of the complexes exhibited pym-hyz linkages in their cisoid conformation and binding between the hydroxymethyl arms and the metal ions. No complexes were isolated from reacting either of the Zn(II) salts with 1 on a 1:1 metal/ligand ratio, due to the smaller size of the Zn(II) coordination sphere as compared to the much larger Pb(II) ions.     

Synthesis of zinc trisubstituted hydrazido complexes and ortho-metalation of 4-(dimethylamino)pyridine

The zinc hydrazide complexes [EtZn(N(SiMe(3))NMe(2))](2), [EtZn(N(Me)NMe(2))](4), and Zn(3)Et(4)(N(Et)NMe(2))(2) were synthesized by allowing excess hydrazine, HN(R)NMe(2), to react with diethyl zinc. The product of the reaction between ZnEt(2) and HN(i-Pr)NMe(2)ortho-metalated 4-(dimethylamino)pyridine (DMAP) at room temperature, producing the complex Zn[(NC(5)H(3)-p-NMe(2))ZnEt(N(i-Pr)NMe(2))](2). At elevated temperatures, Zn(3)Et(4)(N(Et)NMe(2))(2) also ortho-metalated DMAP, but [EtZn(N(Me)NMe(2))](4) did not. Single-crystal X-ray diffraction studies revealed that the hydrazide ligands in [EtZn(N(SiMe(3))NMe(2))](2) act as bridging mono-hapto amide ligands, and in Zn(3)Et(4)(N(Et)NMe(2))(2) and Zn[(NC(5)H(3)-p-NMe(2))ZnEt(N(i-Pr)NMe(2))](2) the hydrazide ligands are di-hapto.     

NMR spectroscopic and X-ray crystallographic study of methylcobalt(III) compounds with saturated amine ligands

The (13)C chemical shifts of methylcobalt(III) compounds with saturated amine ligands in cis positions to the methyl group and a monodentate ligand, L = CN(-), NH(3), NO(2)(-), N(3)(-), H(2)O, or OH(-), in the trans position are reported. The amine ligands used, 1,2-ethanediamine (en), 1,3-propanediamine (tn), N,N'-bis(2-aminoethyl)-1,3-propanediamine (2,3,2-tet), N,N'-bis(3-aminopropyl)-1,2-ethanediamine (3,2,3-tet), and 1,4,8,11-tetraazacyclotetradecane (cyclam), all exert an apparent cis influence on the (13)C resonance signal of the coordinated methyl group. In the trans-[Co(en)(2)(CH(3))(L)](n+) series the (15)N resonance frequency of the coordinated en has also been measured. The influence of L on the en (15)N chemical shifts is reverse the influence on the methyl (13)C chemical shifts except in the case of L = NO(2)(-), which affects a further deshielding of the amine nitrogen nucleus. The methyl (1)J(CH) coupling constants in the trans-[Co(en)(2)(CH(3))(L)](n+) series range from 128.09 Hz (L = CN(-)) to 134.11 Hz (L = H(2)O). The crystal structures of trans-[Co(en)(2)(CH(3))(ClZnCl(3))], trans-[Co(3,2,3-tet)(CH(3))(N(3))]ClO(4), trans,trans-[(CH(3))(en)(2)Co(CN)Co(en)(2)(CH(3))](PF(6))(3)(CH(3)CN), and cis-[Co(en)(2)(CH(3))(NH(3))]ZnCl(4) were determined from low-temperature X-ray diffraction data.     

Substitution reactions of [Ru(dppe)(CO)(H(2)O)(3)][OTf](2)

The labile nature of the coordinated water ligands in the organometallic aqua complex [Ru(dppe)(CO)(H(2)O)(3)][OTf](2) (1) (dppe = Ph(2)PCH(2)CH(2)PPh(2); OTf = OSO(2)CF(3)) has been investigated through substitution reactions with a range of incoming ligands. Dissolution of 1 in acetonitrile or dimethyl sulfoxide results in the facile displacement of all three waters to give [Ru(dppe)(CO)(CH(3)CN)(3)][OTf](2) (2) and [Ru(dppe)(CO)(DMSO)(3)][OTf](2) (3), respectively. Similarly, 1 reacts with Me(3)CNC to afford [Ru(dppe)(CO)(CNCMe(3))(3)][OTf](2) (4). Addition of 1 equiv of 2,2'-bipyridyl (bpy) or 4,4'-dimethyl-2,2'-bipyridyl (Me(2)bpy) to acetone/water solutions of 1 initially yields [Ru(dppe)(CO)(H(2)O)(bpy)][OTf](2) (5a) and [Ru(dppe)(CO)(H(2)O)(Me(2)bpy)][OTf](2) (6a), in which the coordinated water lies trans to CO. Compounds 5a and 6a rapidly rearrange to isomeric species (5b, 6b) in which the ligated water is trans to dppe. Further reactivity has been demonstrated for 6b, which, upon dissolution in CDCl(3), loses water and coordinates a triflate anion to afford [Ru(dppe)(CO)(OTf)(Me(2)bpy)][OTf] (7). Reaction of 1 with CH(3)CH(2)CH(2)SH gives the dinuclear bridging thiolate complex [[(dppe)Ru(CO)](2)(mu-SCH(2)CH(2)CH(3))(3)][OTf] (8). The reaction of 1 with CO in acetone/water is slow and yields the cationic hydride complex [Ru(dppe)(CO)(3)H][OTf] (9) via a water gas shift reaction. Moreover, the same mechanism can also be used to account for the previously reported synthesis of 1 upon reaction of Ru(dppe)(CO)(2)(OTf)(2) with water (Organometallics 1999, 18, 4068).     

Zirconium complexes incorporated with asymmetrical tridentate pincer type mono- and di-anionic pyrrolyl ligands: mechanism and reactivity as catalytic precursors

The reactions of Zr(NR(2))(4) (1, R = Me; 2, R = Et) with an asymmetrical tridentate pincer type pyrrole ligand precursor [C(4)H(2)NH(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))] and treatment of the derivatives with either PhNCS or PhNCO have been carried out and characterized. Reacting Zr(NR(2))(4) (1, R = Me; 2, R = Et) with [C(4)H(2)NH(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))] generates Zr[C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NMe(2))](NR(2))(2) (3, R = Me; 4, R = Et) in high yield along with the elimination of 2 equiv of dimethylamine or diethylamine, respectively. Interestingly, while changing the solvent from Et(2)O to CH(2)Cl(2), the complex Zr[C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NMe(2))][C(4)H(2)N(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))]Cl (5) is produced by undergoing C-Cl bond cleavage. Furthermore, reaction of either 3 or 4 with 1 or 2 equiv of PhNCS or PhNCO yields Zr[C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NMe(2))](NMe(2))[PhNC(NMe(2))S] (6), Zr[C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NMe(2))](NEt(2))[PhNC(NEt(2))O] (7) and Zr[C(4)H(2)N(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))][PhNC(NEt(2))O](3) (8), respectively. All the aforementioned complexes were characterized by (1)H and (13)C NMR spectrometry and the molecular structures of 5, 6, and 8 have been determined by single-crystal X-ray diffractometry. Complexes 4, 5, and 7 initiated the ethylene polymerization in the presence of MAO as the co-catalyst.     

Synthesis and catalytic activity of group 5 metal amides with chiral biaryldiamine-based ligands

A new series of group 5 metal amides have been prepared from the reaction between V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) and chiral ligands, (R)-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (1H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (2H(2)), (R)-6,6'-dimethyl-2,2'-bis(mesitoylamino)-1,1'-biphenyl (3H(2)), (R)-2,2'-bis(mesitylenesulfonylamino)-6,6'-dimethyl-1,1'-biphenyl (4H(2)), (R)-2,2'-bis(diphenylthiophosphoramino)-1,1'-binaphthyl (5H(2)), (R)-2,2'-bis[(3-tert-butyl-2-hydroxybenzylidene)amino]-6,6'-dimethyl-1,1'-biphenyl (6H(2)), (R)-2,2'-bis[(3,5-di-tert-butyl-2-hydroxybenzylidene)amino]-6,6'-dimethyl-1,1'-biphenyl (7H(2)), (R)-2,2'-bis[(3-tert-butyl-2-hydroxybenzylidene)amino]-1,1'-binaphthyl (8H(2)), (S)-2-(mesitoylamino)-2'-(dimethylamino)-1,1'-binaphthyl (9H), and (R)-2-(mesitoylamino)-2'-(dimethylamino)-6,6'-dimethyl-1,1'-biphenyl (10H), which are derived from (R) or (S)-2,2'-diamino-1,1'-binaphthyl, and (R)-2,2'-diamino-6,6'-dimethyl-1,1'-biphenyl, respectively. Treatment of V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) with 1 equiv of C(2)-symmetric amidate ligands 1H(2), 2H(2), 3H(2), 4H(2), and 5H(2), or Schiff base ligands 6H(2), 7H(2) and 8H(2) at room temperature gives, after recrystallization from a benzene, toluene or n-hexane solution, the vanadium amides (1)V(NMe(2))(2) (11), (2)V(NMe(2))(2) (14), (3)V(NMe(2))(2) (17), (5)V(NMe(2))(2) (22), (6)V(NMe(2))(2) (23) and (7)V(NMe(2))(2) (24), and niobium amides (1)Nb(NMe(2))(3) (12), (2)Nb(NMe(2))(3) (15), (3)Nb(NMe(2))(3) (18), (4)Nb(NMe(2))(3) (20) and [2-(3-Me(3)C-2-O-C(6)H(3)CHN)-2'-(N)-C(20)H(12)][2-(Me(2)N)(2)CH-6-CMe(3)-C(6)H(3)O]NbNMe(2)·C(7)H(8) (25·C(7)H(8)), and tantalum amides (1)Ta(NMe(2))(3) (13), (2)Ta(NMe(2))(3) (16), (3)Ta(NMe(2))(3) (19) and (4)Ta(NMe(2))(3) (21) respectively, in good yields. Reaction of V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) with 2 equiv of C(1)-symmetric amidate ligands 9H or 10H at room temperature gives, after recrystallization from a toluene or n-hexane solution, the chiral bis-ligated vanadium amides (9)(2)V(NMe(2))(2)·3C(7)H(8) (27·3C(7)H(8)) and (10)V(NMe(2))(2) (28), and chiral bis-ligated metallaaziridine complexes (10)(2)M(NMe(2))(η(2)-CH(2)NMe) (M = Nb (29), Ta (30)) respectively, in good yields. The niobium and tantalum amidate complexes are stable in a toluene solution at or below 160 °C, while the vanadium amidate complexes degrade via diemthylamino group elimination at this temperature. For example, heating the complex (2)V(NMe(2))(2) (14) in toluene at 160 °C for four days leads to the isolation of the complex [(2)V](2)(μ-NMe(2))(2) (26) in 58% yield. These new complexes have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 12, 13, and 15-30 have further been confirmed by X-ray diffraction analyses. The vanadium amides are active chiral catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to good yields with good ee values (up to 80%), and the tantalum amides are outstanding chiral catalysts for the hydroaminoalkylation, giving chiral secondary amines in good yields with excellent ee values (up to 93%).     

T-shaped platinum boryl complexes: synthesis and structure

A series of cationic T-shaped 14-electron boryl complexes of the type trans-[(Cy(3)P)(2)Pt{B(X)X'}](+) (X=Br; X'=ortho-tolyl, tBu, NMe(2), piperidyl, Br; XX'=(NMe(2))(2), catecholato) were synthesized by halide abstraction from trans-[(Cy(3)P)(2)Pt(Br){B(X)X'}] (Cy=cyclohexyl) with Na[BAr(f) (4)] (Ar(f)=3,5-(CF(3))(2)C(6)H(3)), K[B(C(6)F(5))(4)], or Na[BPh(4)]. X-ray diffraction studies were performed on all compounds, revealing a subtle correlation between the trans-influence of the boryl moiety and the Pt--H and Pt--C separations. However, no notable agostic C--H interaction with the platinum center was detected. trans-[(Cy(3)P)(2)Pt(BCat)](+) (Cat=catecholato), the complex with the shortest Pt--H and Pt--C distances, was treated with Lewis bases (L), forming compounds of the type trans-[(Cy(3)P)(2)Pt(L)(BCat)](+), thus proving a decisive influence of the degree of trans-influence exerted by the boryl ligands on the chemical reactivity of the title complexes. Another point that was investigated and clarified is the different behavior of trans-[(Cy(3)P)(2)Pt(Br){B(Br)Mes}] (Mes=mesityl) towards K[B(C(6)F(5))(4)] with formation of the borylene species trans-[(Cy(3)P)(2)Pt(Br)(BMes)](+).