Mechanistic studies on the reductive cyclooligomerisation of CO by U(III) mixed sandwich complexes; the molecular structure of [(U(eta-C8H6{Si(i)Pr3-1,4}2)(eta-Cp*)]2(mu-eta1:eta1-C2O2)

The stoichiometric reaction of 1 equiv of CO with [(U(eta-C8H6{SiiPr3-1,4}2)(eta-Cp*)] affords the linear diuranium ynediolate complex [(U(eta-C8H6{SiiPr3-1,4}2)(eta-Cp*)]2(mu-eta1:eta1-C2O2) which does not react with further CO to give the deltate derivative [(U(eta-C8H6{SiiPr3-1,4}2)(eta-Cp*)]2(mu-eta1:eta2-C3O3). Spectroscopic and computational studies suggest a plausible mechanism for the formation of the deltate complex, in which a "zig-zag" diuranium ynediolate species is the key intermediate.     

Synthesis and characterization of Pr(III), Nd(III) and Er(III) complexes with 2,6-pyridinedimethanol

The reactions of Ln(NO₃)₃?6H₂O (Ln=Pr, Nd or Er) with the potentially tridentate O,N,O chelating ligand 2,6-pyridinedimethanol (H₂pydm) in a 1:2 M ratio were investigated, and complexes with the formula [Ln(H₂pydm)₂(NO₃)₂](NO₃) (Ln=Pr or Nd) (1 and 2) and [Er(H₂pydm)₃](NO₃)₃ (3) were isolated. The compounds contain 10-coordinate Pr(III) and Nd(III) ions that crystallize in the triclinic space group P-1 while the 9-coordinate Er(III) complex crystallizes in the monoclinic system (P2₁/n). A new lanthanide complex, [Pr(H₂pydm)₃](Cl)₃?DMF (4), has been synthesized by reaction of PrCl₃?6H₂O and H₂pydm. The nine-coordinate Pr(III) is bound to three H₂pydm ligands. X-ray crystal structures of 1–4 reveal that the ligand coordinates tridentate via the pyridyl nitrogen and the two hydroxyl oxygens. The electronic absorption spectra of 1–4 show 4f–4f transitions.     

The influence of phosphane coligands on the nuclearity of rhodium(I) 4-thiolatobenzoic acid complexes

[RhCl(PR3)3] (R = Ph, Et) reacts with the potassium salt of 4-mercaptobenzoic acid to give a mixture of the monomeric and dimeric complexes, [Rh(SC6H4COOH)(PR3)3] and [{Rh(-SC6H4COOH)(PR3)2}2], respectively. With the labile PPh3 coligand, the dimer is the major product, while for the electron-richer coligand PEt3, the equilibrium is easily shifted to the monomer by the addition of excess PEt3. Phosphane dissociation and dimerization could be prevented by using the chelating coligand PPh(C2H4PPh2)2. [{Rh(-SC6H4COOH)(PPh3)2}2] (2b), [Rh(SC6H4COOH)(PEt3)3] (3a), and [Rh(SC6H4COOH){PPh(C2H4PPh2)2}] (4) were fully characterized by nuclear magnetic resonance and infrared spectroscopy, mass spectrometry, and elemental analysis. The molecular structures of 2b and 4 were determined by X-ray structure analysis. In solution, the lability of the phosphane ligands leads to the decomposition of 2b. One of the decomposition products, namely, the mixed-valent complex [{RhIRhIII(-SC6H4COO)(-SC6H4COOH)(SC6H4COOH)(PPh3)3}2] (5), was characterized by X-ray structural analysis. The dinuclear rhodium(III) complex [{Rh(-SC6H4COO)(SC6H4COOH)(PEt3)2}2] (6) was shown to be a byproduct in the synthesis of 3a, and this demonstrates the reactivity of the rhodium(I) complexes toward oxidative addition. The structurally characterized complexes 2b, 4, 5, and 6 show hydrogen bonding of the free carboxyl groups.     

Synthesis and characterization of neutral ligand-bridged binuclear dialkylcobalt(III) complexes

A series of neutral ligand-bridged binuclear dialkylcobalt(III) chelates has been prepared. Chelate systems based on monoanions of dimethylglyoxime (dm     

Metal complexes of selenophosphinates from reactions with (R2PSe)2Se: [M(R2PSe2)n] (M = Zn(II), Cd(II), Pb(II), In(III), Ga(III), Cu(I), Bi(III), Ni(II); R = (i)Pr, Ph) and [Mo(V)2O2Se2(Se2P(i)Pr2)2

The reactions of bis(dialkylselenophosphinyl)selenide with a series of metals have been investigated: synthesis of several metal selenophosphinate complexes and their structures are reported.     

Synthesis and structural characterisation of new Re(III) complexes using aldimines of α-amino acids as coligands

Complexes of the general formula [Re^III(L)Cl(PPh₃)₂] have been synthesised by reacting H₂L and [ReOCl₃(PPh₃)₂] in ethanol. Here H₂L represents imines of α-amino acids (glycine, l-alanine, l-valine, l-phenylalanine) derived from salicylaldehyde and naphthaldehyde. The crystal structure of one complex has been determined. The complexes are mononuclear, paramagnetic and display paramagnetic ¹H NMR in CDCl₃ solution. Their spectral and redox properties are scrutinised.     

Stable and tunable phosphorescent neutral cyclometalated Au(III) diaryl complexes

A series of novel luminescent cyclometalated Au(III) neutral complexes of the type cis-[(N(∧)C)AuL] [N(∧)C = 2-phenylpyridine (ppy), L = 1,1'-biphenyl (1)] and cis-[(N(∧)C)AuL(2)] [N(∧)C = 2-phenylpyridine (ppy), L = C(6)H(5) (2), C(6)F(5) (3), C(6)H(4)-CF(3)-p (4), 2-C(4)H(3)S (5)]; [N(∧)C = 2-(2-thienyl)pyridine (thpy), L = C(6)H(5) (6), C(6)F(5) (7)]; [N(∧)C = 2-(5-methyl-2-thienyl)pyridine (5 m-thpy), L = C(6)F(5) (8)] were successfully synthesized. The X-ray crystal structures of all compounds except 3 have been determined. These complexes were found to show long-lived emission in solution at room temperature. The emission origins of the complexes have been tentatively assigned to be derived from triplet states predominantly bearing intraligand (IL) character with some perturbation from the metal center. Density functional theory (DFT) calculations were performed to evaluate the stability associated with the complexes and TD-DFT calculations to ascertain the nature of the excited state. Variation of the cyclometalated ligands in the complexes readily leads to the tuning of the nature of the lower energy emissive states.     

Arsenic(III) halide complexes with acyclic and macrocyclic thio- and selenoether coligands: synthesis and structural properties

The preparations of the new complexes [AsBr(3)[MeS(CH(2))(2)SMe]], [AsX(3)([9]aneS(3))] (X = Cl, Br or I; [9]aneS(3) = 1,4,7-trithiacyclononane), [AsCl(3)([14]aneS(4))] ([14]aneS(4) = 1,4,8,11-tetrathiacyclotetradecane), [AsX(3)([8]aneSe(2))] ([8]aneSe(2) = 1,5-diselenacyclooctane), [(AsX(3))(2)([16]aneSe(4))] ([16]aneSe(4) = 1,5,9,13-tetraselenacyclohexadecane), and [(AsBr(3))(2)([24]aneSe(6))] ([24]aneSe(6) = 1,5,9,13,17,21-hexaselenacyclotetracosane) are described. These are obtained from direct reaction of the appropriate AsX(3) and 1 mol equiv of the thio- or selenoether ligand in anhydrous CH(2)Cl(2) (or thf for X = I) solution. The products have been characterized by microanalysis and IR and (1)H NMR spectroscopy. In solution they are extensively dissociated, reflecting the weak Lewis acidity of AsX(3). Reaction of AsX(3) with MeSe(CH(2))(2)SeMe or MeC(CH(2)EMe)(3) (E = S or Se) gave only oils. Treatment of PCl(3) or PBr(3) with Me(2)S, MeE(CH(2))(2)EMe, or [9]aneS(3) failed to give solid complexes, and there was no evidence from NMR spectroscopy for any adduct formation in solution. The crystal structures of the first series of thioether and selenoether complexes of As(III) are described: [AsBr(3)[MeS(CH(2))(2)SMe]], C(4)H(10)AsBr(3)S(2), a = 10.2818(6) A, b = 7.8014(5) A, c = 14.503(1) A, beta = 102.9330(2) degrees, monoclinic, P2(1)/c, Z = 4; [AsI(3)[MeS(CH(2))(2)SMe]], C(4)H(10)AsI(3)S(2), a = 9.1528(1) A, b = 11.5622(2) A, c = 12.0939(2) A, beta = 93.863(1) degrees, monoclinic, P2(1)()/n, Z = 4; [AsCl(3)([9]aneS(3))], C(6)H(12)AsCl(3)S(3), a = 17.520(4) A, b = 17.520(4) A, c = 16.790(7) A, tetragonal, I4(1)cd, Z = 16; [AsCl(3)([14]aneS(4))], C(10)H(20)AsCl(3)S(4), a = 13.5942(2) A, b = 7.7007(1) A, c = 18.1270(3) A, beta = 111.1662(5) degrees, monoclinic, P2(1)()/n, Z = 4; [(AsCl(3))(2)([16]aneSe(4))], C(12)H(24)As(2)Cl(6)Se(4), a = 9.764(3) A, b = 13.164(1) A, c = 10.627(2) A, beta = 114.90(1) degrees, monoclinic, P2(1)()/n, Z = 2; [(AsBr(3))(2)([16]aneSe(4))], C(12)H(24)As(2)Br(6)Se(4), a = 10.1220(1) A, b = 13.4494(2) A, c = 10.5125(2) A, beta = 113.49(2) degrees, monoclinic, P2(1)()/n, Z = 2. [AsBr(3)[MeS(CH(2))(2)SMe]] and [AsI(3)[MeS(CH(2))(2)SMe]] reveal discrete mu(2)-halo As(2)X(6) dimeric structures involving distorted octahedral As(III), with the dithioether ligand chelating. [AsCl(3)([9]aneS(3))] adopts a discrete molecular distorted octahedral geometry with the thioether behaving as a weakly coordinated fac-capping ligand. [AsCl(3)([14]aneS(4))] forms an infinite sheet involving two mu(2)-chloro ligands on each As but bridging to two distinct As centers. Each macrocycle coordinates to two adjacent As centers via one S atom, giving a cis-octahedral Cl(4)S(2) donor set at As(III). The structures of [(AsCl(3))(2)([16]aneSe(4))] and [(AsBr(3))(2)([16]aneSe(4))] adopt 2-dimensional sheet structures with mu(2)-dihalo As(2)X(6) dimers cross-linked by mu(4)-tetraselenoether macrocycles, giving a disorted cis-X(4)Se(2) donor set at each As center. These species are compared with their antimony(III) and bismuth(III) analogues where appropriate.     

Conformational isomers of neutral trans-di­nitro­cobalt(III) complexes

The reaction of Co(acac)₃ with N-(2-amino­ethyl)-1,3-propane­di­amine in the presence of NaNO₂ results in the preparation of an unexpected di­nitro­cobalt(III) compound, (11-amino-4-methyl-5,8-di­aza­undeca-2,4-dien-2-olato-κ⁴­N^5,8,11,O)-di­nitrocobalt(III), [Co(C₁₀H₂₀N₃O)(NO₂)₂], containing the tetra­dentate anion of 11-amino-4-methyl-5,8-diazaundeca-2,4-dien-­2-ol. Two isomers of the compound were obtained by recrystallization of the crude product. In one isomer, the two trans nitro groups are staggered, and in the other they are eclipsed.     

Schiff base derivatives of lanthanons,La(III), Pr(III), Nd(III) and Sm(III) complexes of bifunctional tetradentateSchiff base

Reactions of La(III), Pr(III), Nd(III) or Sm(III) nitrate with bifunctional tetradentateSchiff base, [o-HOC₆H₄C(CH₃): :NCH₂]₂, having the donor system HO–N–N–OH in 12 molar ratio have been investigated and found to yield new derivatives of the type [Ln(SBH₂)₂](NO₃)₃ [whereLn=La(III), Pr(III), Nd(III) or Sm(III) andSBH₂=Schiff base molecule, [o-HOC₆H₄C(CH₃) : NCH₂]₂. On the basis of elemental analyses, conductivity and magnetic measurements and infrared spectra, plausible structures for the resulting complexes have been indicated.     

Chromium(III) complexes of 2-amino-benzothiazole

The following chromium(III) complexes of 2-amino-benzothiazole (L) were prepared and studied: CrCl₂(OH)L.H₂O, CrCl₃L₃.xS (xS = 2H₂O, MeOH) CrBr₃L₂, Cr₂(SO₄)₃L₃.3H₂O and Cr(NO₃)₃L₃.3H₂O. Infrared spectra show that in these complexes the ligand is coordinated through the aminic nitrogen atom. Electronic spectra indicate a normal six-coordination.     

4f-4f absorption spectra of nine-coordinate Pr (III) and Nd (III) complexes in different environments

Absorption spectroscopic studies on the mixed-ligand complexes of Pr (III) and Nd (III) with 2,2'-bipyridyl and thiocyanate in pyridine, DMSO, DMF and methanol are presented. The oscillator strengths for the hypersensitive and non-hypersensitive transitions have been calculated and variation in the oscillator strength and band shapes with respect to solvent type is rationalized in terms of solvent structures and coordinating properties. A comparison is made with 1,10-phenanthroline complexes and has been shown that bpy is a weaker ligand than phen for these ions. Pyridine has been found most effective in promoting 4f-4f intensity and the increase in the oscillator strength in this solvent is due to dynamic ligand polarization mechanism.     

Antimony(III) and bismuth(III) halide complexes of 2-methyl-benzoxazole

In the antimony(III) and bismuth(III) complexes of 2-methyl-benzoxazole: SbX₃·L (X = Cl, Br), SbI₃·2.5L, MX₃·L·H₂O (M = Sb, X = I; M = Bi, X = Cl, Br), SbCl₄·HL, SbBr₅·2HL, BiCl₅·2HL. Bi₂X₉·3HL (X = Br, I) the ligand is O-bonded to the metal.     

Unique crown thioether complexes of f elements: the crystal structure of U(III) and La(III) complexes of 1,4,7-trithiacyclononane

The crystal structures of the first U(III) complex of a crown thioether and of its La(III) analog have been determined; a stronger M-S interaction is observed for U(III) with respect to La(III) and Ce(III) in solution and in the solid state.     

Facile and reproducible syntheses of bis(dialkylselenophosphenyl)-selenides and -diselenides: X-ray structures of ((i)Pr2PSe)2Se, ((i)Pr2PSe)2Se2 and (Ph2PSe)2Se

Facile and reproducible methods for the syntheses of bis(di-iso-propylselenophosphinyl)selenide ((i)Pr2PSe)2Se (1), bis(di-iso-propylselenophosphinyl)diselenide ((i)Pr2PSe)2Se2 (2) and bis(di-phenylselenophosphinyl)selenide (Ph2PSe)2Se (3) is reported.     

Phenylarsenic(III) complexes of 2-(2-hydroxyphenyl)benzothiazolines

Equimolar reactions of PhAs(OMe)₂ (prepared in situ) and 2-(2-hydroxyphenyl)benzothiazolines LH₂ give the addition products PhAs(OMe)₂LH₂, while equimolar reactions of PhAsCl₂ with Na₂L yield substitution products PhAsL. All these derivatives have been characterized by elemental analyses and their plausible structures have been established on the basis of physico-chemical, IR, and NMR (¹H and ¹³C) spectral studies. © 2003 Wiley Periodicals, Inc. 15:92–96, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.10220