Spectral, crystallographic, theoretical and antibacterial studies of palladium(II)/platinum(II) complexes with unsymmetric diphosphine ylides

The reaction of alpha-keto-stabilized diphosphine ylides [Ph2P(CH2)(n)PPh2C(H)C(O)C6H4-p-CN] (n = 1 (Y-1); n = 2 (Y-2)) with dibromo(1,5-cyclooctadiene) palladium(II)/platinum(II) complexes, [Pd/PtBr2(cod)], in equimolar ratio gave the new cyclometalated Pd(II) and Pt(II) complexes [Br2Pd(kappa(2)-Y-1)] (1), [Br2Pt(kappa(2)-Y-1)] (2), [Br2Pd(kappa(2)-Y-2)] (3) and [Br2Pt(kappa(2)-Y-2)] (4). These compounds were screened in a search for novel antibacterial agents and characterized successfully using Fourier transfer infrared and NMR (H-1, C-13 and P-31) spectroscopic methods. Also, the structures of complexes 1 and 2 were characterized using X-ray crystallography. The results showed that the P,C-chelated complexes 1 and 2 have structures consisting of five-membered rings, while 3 and 4 have six-membered rings, formed by coordination of the ligand through the phosphine group and the ylidic carbon atom to the metal centre. Also, a theoretical study of the structures of complexes 1-4 was conducted at the BP86/def2-SVP level of theory. The nature of metal-ligand bonds in the complexes was investigated using energy decomposition analyses (EDA) and extended transition state combined with natural orbitals for chemical valence analyses. The results of EDA confirmed that the main portions of Delta E-int, about 57-58%, in the complexes are allocated to Delta E-elstat

Neutral and Cationic Rare Earth Metal Alkyl and Benzyl Compounds with the 1,4,6-Trimethyl-6-pyrrolidin-1-yl-1,4-diazepane Ligand and Their Performance in the Catalytic Hydroamination/Cyclization of Aminoalkenes

A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L) was prepared. Reacting L with trialkyls M(CH2SiMe3)3(THF)2 (M = Sc, Y) and tribenzyls M(CH2Ph)3(THF)3 (M = Sc, La) yielded trialkyl complexes (L)M(CH2SiMe3)3 (M = Sc, 1; M = Y, 2) and tribenzyl complexes (L)M(CH2Ph)3 (M = Sc, 3; M = La, 4). Complexes 1 and 2 can be converted to their corresponding ionic compounds [(L)M(CH2SiMe3)2(THF)][B(C6H5)4] (M = Sc, Y) by reaction with [PhNMe2H][B(C6H5)4] in THF. Complexes 3 and 4 can be converted to cationic species [(L)M(CH2Ph)2]+ by reaction with [PhNMe2H][B(C6F5)4] in C6D5Br in the absence of THF. The neutral complexes 1-4 and their cationic derivatives were studied as catalysts for the hydroamination/cyclization of 2,2-diphenylpent-4-en-1-amine and N-methylpent-4-en-1-amine reference substrates and compared with ligand-free Sc, Y, and La neutral and cationic catalysts. The most effective catalysts in the series were the cationic L-yttrium catalyst (for 2,2-diphenylpent-4-en-1-amine) and the cationic lanthanum systems (for N-methylpent-4-en-1-amine). For the La catalysts, evidence was obtained for release of L from the metal during catalysis.

Novel bis-arene (Sandwich) Complexes with NO\u3csup\u3e+\u3c/sup\u3e Acceptor. Isolation, X-ray Crystallography and Electronic Structure

The unusual charge-transfer complexes of various arene donors (ArH) with the nitrosonium cation (NO+) resulting from bimolecular [1 ∶ 1] associations can be extended at suitably high ArH concentrations to termolecular processes leading to the analogous [2 ∶ 1] complexes. Spectral analyses of the intense color changes accompanying the arene interaction with NO+ provide optimum conditions for the isolation of pure crystalline ternary complexes. Single crystal X-ray crystallographic determinations establish the unique sandwich structure consisting of the NO moiety interposed (parallel) between a pair of cofacial arene donors—reminiscent of the well-known transition metal sandwich complexes with aromatic ligands. The electronic structure associated with the arene binding to NO in the ternary complex is analyzed by the application of the semi-empirical LCAO molecular-orbital methodology and the Mulliken (charge-transfer) formulation of the electronic (UV–VIS–NIR) transitions. The resultant evaluation of the electronic coupling (matrix) elements HAB indicates strong donor/acceptor interactions of the frontier orbitals of the arene donor (HOMO) and nitrosonium acceptor (LUMO) that are only slightly less than those extant in the corresponding binary [1 ∶ 1] complexes

Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2’:6’,2’’-terpyridine ligand: implications for actinide(III) /lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2’:6’,2’’-terpyridine (CyMe4-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of the 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO22+) ion were obtained by X-ray crystallographic analysis, and showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. 1H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligand

Activation of Tri(2-Furyl)Phosphine at a Dirhenium Centre: Formation of Phosphido-Bridged Dirhenium Complexes

Reaction of tri(2-furyl)phosphine (PFu3) with [Re2(CO)10−n(NCMe)n] (n = 1, 2) at 40 °C gave the substituted complexes [Re2(CO)10−n(PFu3)n] (1 and 2), the phosphines occupying axial position in all cases. Heating [Re2(CO)10] and PFu3 in refluxing xylene also gives 1 and 2 together with four phosphido-bridged complexes; [Re2(CO)8−n(PFu3)n(μ-PFu2)(μ-H)] (n = 0, 1, 2) (3–5) and [Re2(CO)6(PFu3)2(μ-PFu2)(μ-Cl)] (6) resulting from phosphorus–carbon bond cleavage. A series of separate thermolysis experiments has allowed a detailed reaction pathway to be unambiguously established. A similar reaction between [Re2(CO)10] and PFu3 in refluxing chlorobenzene furnishes four complexes which include 1, 2, 6 and the new binuclear complex [Re2(CO)6(η1-C4H3O)2(μ-PFu2)2] (7). All new complexes have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction studies

A combinatorial non-positive curvature I: weak systolicity

We introduce the notion of weakly systolic complexes and groups, and initiate regular studies of them. Those are simplicial complexes with nonpositive-curvature-like properties and groups acting on them geometrically. We characterize weakly systolic complexes as simply connected simplicial complexes satisfying some local combinatorial conditions. We provide several classes of examples --- in particular systolic groups and CAT(-1) cubical groups are weakly systolic. We present applications of the theory, concerning Gromov hyperbolic groups, Coxeter groups and systolic groups.Comment: 35 pages, 1 figur