Regina H.A. Santos

The reactivity of five-coordinate Ru(II) (1,4-bis(diphenylphosphino)butane) complexes with the N-donor ligands: ammonia, pyridine, 4-substituted pyridines, 2,2′-bipyridine, bis(o-pyridyl)amine, 1,10-phenanthroline, 4,7-diphenylphenanthroline and ethylenediamine

Abstract A series of Ru(II)(1,4-bis(diphenylphosphino)butane)(L)2 complexes was synthesized from [RuCl2(dppb) l2 (μ-dppb) or RuCl2 (dppb)- (PPh3); dppb = Ph2P(CH2)4PPH2, L = NH3, pyridine (py), 4-aminopyridine (4-NH2py), 4-cyanopyridine (4-CNpy), 4-dimethylaminopyridine (4-Me2Npy), 4-methylpyridine (4-Mepy), 4-phenylpyridine (4-Phpy), 4-vinylpyridine (4-Phy) and N-methylimidazole (Melm) and L2 = 2,2′-bipyridine (bipy), bis(o-pyridyl)amine (bpa), 1,10-phenanthroline (phen), 4,7-diphenylphenanthroline (or bathophenanthroline, batho) and ethylenediamine (en). The complexes were characterized by elemental analysis, cyclic voltametry, UV-Vis, NMR and IR spectroscopies. The structures of trans-RuCl2(dppb) (py)2 (3), cis-RuCl2(dppb)(bipy) (4) and cis-RuCl2(dppb) (phen) (5) were established by X-ray crystallographic analyses. Crystals of trans-3, cis-4-CH2Cl2 and cis-5-solvate are all monoclinic, space group P21/c, with Z=4; a = 12.946 (2), b = 14.204(3), c = 18.439(4) A , β = 90.08(2)° for trans-3; a=10.694(6), b=18.485(6), c=18.632(7) A , β = 90.26(3)° for cis-4·CH2Cl2; a = 17.094 (1), b = 9.923(2), c = 21.905(2) A , β = 98.883 (6)° for cis-5 solvate. The structures were solved by the heavy atom Patterson method and were refined by full-matrix least-squares procedures to R=0.069, 0.071 and 0.036 (Rw = 0.069, 0.076 and 0.039) for 1957, 4165 and 4824 reflections with l ≥ 3σ (l), respectively.

Nitrosyl ruthenium complexes with general formula [RuCl3(NO)(PP)] (PP = {PPh2(CH2)nPPh2}, n = 1–3 and {PPh2-CHPPh2}). X-ray structure of [RuCl3(NO){PPh2(CH2)3PPh2}]

Abstract Ruthenium(II) complexes with general formula [RuCl3(NO)(PP)] were obtained in the solid state, where PP = PPh2(CH2)nPPh2 (n = 1) and PPh2-Ch = CH-PPh2. The 31P NMR spectra of these compounds measured in CH2Cl2 showed only singlets, consistent with a fac configuration containing two equivalent phosphorus atoms. However the X-ray diffraction data show that the [RuCl3(NO){PPh2(CH2)3PPh2}] complex crystallizes in a mer configuration, where one of the phosphorus atoms is trans to the NO group, in a slightly distorted octahedral geometry.

The adsorption of 2‚ 2’: 6’‚ 2’’-terpyridine‚ 4’-(5-mercaptopentyl)-2‚ 2’: 6’‚ 2’’-terpyridinyl‚ and perchlorate on silver and copper surfaces monitored by SERS

Abstract The adsorption of 2,2′:6′,2″-terpyridine on Ag and Cu electrode surfaces has been studied by using surface enhanced Raman spectroscopy (SERS). Two types of surface complexes have been found on a silver electrode: the first one is stable near the open circuit potential, having bonding between tpy and silver active site analogous to the AgN bonding in the [AgI(tpy)Cl]·2H2O complex; and the second one is stable in the −0.1 to −0.5 V (Ag/AgCl) potential range, where the interaction between tpy and silver active site is similar to the CuN bonding in the [CuII(tpy)Cl2] complex. The SERS spectra of 4′-(5-mercaptopentyl)-2,2′:6′,2″-terpyridinyl (tpy–SH) have shown an increase in the relative intensity of the mercaptopentyl moiety bands and a band at 310 cm−1, assigned to the AgS stretching, indicating an adsorption through the S atom. In addition, using the Raman results of different copper perchlorate salts obtained with different hydration degrees, it has been possible to characterize the adsorption of perchlorate anion on silver electrode and the kind of coordination in the [CuII(tpy)(H2O)(ClO4)]ClO4 and [CuII(tpy)(H2O)(ClO4)2] complexes.

Diimine copper(II) complexes as building blocks for microporous catalytic materials

Abstract New copper(II) complexes with tridentate diimine ligands, containing imidazolate-bridging groups, have been prepared as precursors of supramolecular-coordination-chemistry-based assemblies, designed to act as oxidation catalysts. These complexes were isolated as mono-, di- and polymeric or cyclic supramolecular species. In solution, solvent- and pH-dependent equilibria between the mono- and dinuclear complexes, or the mono- and the corresponding polymeric species were detected. Those species were characterized by different spectroscopic techniques (UV/Vis, IR, Raman and EPR), and the X-ray crystallographic structure was determined for one of them. The catalytic activity of the dinuclear and polymeric species in the oxidation of phenol substrates by molecular oxygen were verified, by monitoring the corresponding quinone formation. Cyclic hexa- or tetranuclear copper(II) species, exhibiting imidazolate-bridge groups between the copper centres, were observed to be better catalysts then the analogous dinuclear ones, mainly due the interaction of the substrate with the catalyst hydrophobic cavity. A modulation of the cavity size seems strongly affect the reactivity of these systems.

Self-assembly of Pd(II) pyrazolyl complexes to 1-D hydrogen-bonded coordination polymers

This work describes the synthesis and characterization of two novel Pd(II) pyrazolyl complexes of the type (PdX2(HdmPz)2)n {XSCN � (1), N3 � (2); HdmPz � 3,5-dimethylpyrazole} that self-assemble through NH NCS or NH NNN hydrogen bonds to yield infinite one-dimensional chains, as confirmed by single crystal X-ray study on 1. The expected solid state polymeric structure for 2 is slowly broken up in CHCl3 solution, leading to an equilibrium mixture of cis and trans- (Pd(N3)2(HdmPz)2) monomers, as demonstrated by time-dependent IR and NMR studies. # 2003 Elsevier Science B.V. All rights reserved.

Crystallographic and spectroscopic studies on palladium(II) complexes containing pyrazole and thiocyanate ligands

Mononuclear palladium(II) complexes containing both pyrazole-type ligands and thiocyanate, of general formula [Pd(SCN)2(L)2] {L = pyrazole (HPz) and 1-phenyl-3-methylpyrazole (phmPz)} have been prepared and characterized by elemental analysis, i.r. and n.m.r. spectroscopy and by single crystal X-ray diffraction methods. The Pd atom in these structures lies on the crystallographic inversion center; in a square-planar coordination geometry made by two sulfur and two nitrogen atoms of the ligands, both in trans positions.

Organotin(IV) Derivatives of 2-Acetylpyridine-N(4)-Phenylthiosemicarbazone, HAP4P, and 2-Hydroxyacetophenone-N(4)-Phenylthiosemicarbazone, H2DAP4P: Crystal and Molecular Structure of [SnMe2(DAP4P)] and [SnBu2(DAP4P)]

The reactions of 2-acetylpyridine-N(4)-phenylthiosemicarbazone, HAP4P, and 2-hydroxyacetophenone-N(4)-phenylthiosemicarbazone, H2DAP4P, with R4-mSnXm (m = 2, 3; R = Me, nBu, Ph and X = Cl, Br) led to the formation of hexa- and penta-coordinated organotin(IV) complexes, which were studied by microanalysis, IR, 1H-NMR and Mossbauer spectroscopies. The molecular structures of [SnMe2(DAP4P)] and [SnnBu2(DAP4P)] were determined by single-crystal X-ray diffraction studies. In the compounds [SnClMe2(AP4P)] and [SnBrMe2(AP4P)], the deprotonated ligand AP4P- is N,N,S-bonded to the Sn(IV) atoms, which exhibit strongly distorted octahedral coordination. The structures of [SnMe2(DAP4P)] and [SnnBu2(DAP4P)] revealed that the DAP4P2- anion acts as a O,N,S-tridentate ligand. In these cases, the Sn(IV) atoms adopt a strongly distorted trigonal bipyramidal configuration where the azomethine N and the two C atoms are on the equatorial plane while the O and the S atoms occupy the axial positions.

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF DICHLOROBIS (1-PHENYL-3-METHYLPYRAZOLE) PALLADIUM(II) AND DIAZIDOBIS (1-PHENYL-3-METHYLPYRAZOLE) PALLADIUM(II)

Abstract Mononuclear pyrazolyl Pd(II) complexes of the type [PdX 2(phmPz)2] (X = Cl−, N− 3) have been prepared. The 1-phenyl-3-methylpyrazole displaces acetonitrile from [PdCl2(CH3CN)2] to form [PdCl2(phmPz)2] (phmPz=1-phenyl-3-methylpyrazole) (1). [Pd(N3)2(phmPz)2] (2) could be obtained by metathesis from [PdCl2(CH3CN)2] or by substitution of the chloride in (1) by the azide ion. Both complexes were characterized by elemental analysis, infrared spectroscopy, 1H and 13C NMR and by single crystal X-ray diffraction. The coordination geometry around Pd(II) in these complexes is nearly square-planar, with the ligands in a trans configuration.

CYCLOADDITION REACTION OF THE AZIDO-BRIDGED CYCLOMETALLATED COMPLEX [Pd(dmba)N3]2 WITH CS2. CRYSTAL AND MOLECULAR STRUCTURE OF DI(μ, N,S-l,2,3,4-THIATRIAZOLE-5-THIOLATE)BIS[(N,N-DIMETHYLBENZYL-AMINE-C2,N)PALLADIUM(II)]

Abstract The 1,3-dipolar cycloaddition of carbon disulfide to the coordinated azide in the cyclometal-lated compound [Pd(dmba)(N3)]2 (1), dmba = N,N-dimethylbenzylamine, was investigated. The compound obtained di(μ, N, S-l,2,3,4-thiatriazole-5-thiolate)-bis[(N,N-dimethylbenzylamine-C2, N)palladium(II)] (2), was characterized by IR spectroscopy and X-ray diffraction. Complex (2) is dimeric with the two [Pd(N,N-dimethylbenzylamine)] moieties being connected by the two vicinal bridging N, S-l,2,3,4-thiatriazole-5-thiolate anions in a square-planar coordination for the palladium atoms.

Synthesis and solid-state structural characterization of bis (thiocyanatemercury)tetracarbonyliron

Abstract The bis (thiocyanatemercury)tetracarbonyliron, [Fe(CO)4(HgSCN)2], was prepared from [Fe(CO) 5] and Hg(SCN)2, and studied by IR spectroscopy and X-ray diffraction. The compound crystallizes in the tetragonal space group I4,1/a. The unit cell, with dimensions of a = 13.778(3), c = 13.234(3) A, V = 2512.3(9) A3, contains four molecules. The iron atom is octahedrally coordinated by four carbonyl groups and two mercury atoms in cis positions. The coordination of the mercury atoms is distorted square-planar, since, besides mercury-iron and mercury—sulphur bonds, there are also mercury—mercury and mercury-nitrogen interactions. The FeHg distance is 2.506(5)A and the HgFeHg angle is 78.0(1)°.