Cyclometallation reactions of N-(benzylidene)benzylamines with palladium compounds

The cyclometallation of p-RC₆H₄CHNCH₂C₆H₂, (R = H, Cl, NO₂) by PdX₂ (X = Cl, AcO) has been studied.In every case the cyclometallation occurs with formation of a five-membered ring containing the methine group. The structure of these compounds [$\text{PdX(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHN}$CH₂C₆H₅)]₂, derived from ¹H NMR spectra, are different from those reported previously. Reaction of these compounds with PEt₃ gives the compounds [PdX(p-RC₆H₃CHNCH₂C₆H₅)(PEt₃)₂] but with an excess of PPh₃ only the complexes [$\text{PdX(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHN}$CH₂C₆H₅)(PPh₃)] are formed.     

1H n.m.r. conformational studies of glycyl-L-phenylalanine and L-phenylalanyl-glycine dipeptides and their complexes with palladium (II)

The conformations of Gly-Phe and Phe-Gly dipeptides and those of their complexes with the Pd(II) ion has been established by means of ¹H n.m.r. spectra over various pH ranges. In the most stable rotamer of both dipeptides the bulkiest groups, i.e. carboxylate (or carbonyl) and the aromatic ring, are in trans position to each other. In the 1:1 molar ratio complexes, the dipeptides are the tridentate ligands within the 3–10 pH region. In the predominant conformer the aromatic ring lies over the complex plane, which suggests its interaction with the metal ion. At pH above 13, the carboxyl group becomes non-coordinated. The dipeptides are then bidentate and the most stable rotamers are the same as those found for the metal-free ligands, i.e. the carboxyl or carbonyl group is in the trans position to the aromatic ring. The glycine chelate ring in the Pd(II) Gly-Phe complex is planar up to pH 10 and its distortion from planarity follows when the ligand becomes bidentate.     

1H n.m.r. studies of palladium(II) complexes of 2,9-dimethyl-1,10-phenanthroline and 8-hydroxyquinoline

Summary The structures in solution of a series of palladium(II) complexes have been determined by¹H n.m.r. and i.r. spectroscopy. Dicyanobis-(8-hydroxyquinoline)palladium(II) has acis-square-planar configuration, the unidentate 8-hydroxyquinoline molecules bonding to Pd through the nitrogen atoms. Dicyanobis-(2,9-dimethyl-1,10-phenanthroline)-palladium(II) has acis-square planar arrangement about Pd with respect to the nitrogen atoms of the two heterocyclic ligands. The cyanide groups bond to the two apical positions apparently giving rise to a six-coordinate PdlI atom. Dihalo-2,9-dimethyl-1,10-phenanthrolinepalladium(II) (X = Cl, Br, I) exhibits the usualcis-square-planar arrangement of Pd^II, whereas the halobis-(2,9-dimethyl-1,10-phenanthroline) - palladium(II) ion (X = Cl, Br) has a trigonal bipyramidal structure with the halogen atom in the trigonal plane.     

Synthesis and N.m.r. studies of bis-trisubstituted phosphine platinum(o) and palladium(o) complexes with push-pull olefins

Summary Platinum(0) and palladium(0) complexes of the type: P₂M(R₁R₂C=CR₃R₄) (P=trisubstituted phosphine; R₁, R₂, R₃ and R₄ are different groups having electron acceptor or electron donor properties; M=Pt or Pd) with so called pushpull olefins, have been prepared and characterized. In some cases unusual patterns in the n.m.r. spectra of olefinic protons were observed. The spectra were analyzed by computer simulation and general rules for ABMX patterns for this type of complexes are given.     

Proton n.m.r. spin-tickling studies of 13C-labeled compounds. The correlation of J(C,H) and J(H,H)

A tabulation has been compiled for twenty ¹³C? H coupling constants of various carboxylic acids and includes ²J(C,H), ³J(C,H) and ⁴J(C,H) values of olefins (both cis and trans); ³J(C,H), ⁴J(C,H) and ⁵J(C,H) values of aromatics; ³J(C,H) and ⁴J(C,H) values of acetylenes; and ²J(C,H) and ³J(C,H) values of rigid aliphatics. This tabulation has been completed in the present study by the spin-tickling proton n.m.r. study of ¹³C-carboxyl-endo-1,2,3,4,7,7-hexachloronorbornene-5-carboxylic acid, which has established that the ²J(C,H) value is negative and the ³J(C,H) values (both cis and trans) are positive in this system. A plot of these twenty J(C,H) values vs the corresponding J(H,H) values of geometrically equivalent model systems (where there is a proton in place of a carboxyl group) gives a correlation coefficient of 0·975 (with a slope of 0·62), indicating that carbon–proton and proton–proton couplings operate by similar mechanisms throughout this broad series of structural types.     

Cyclometallation ofN,N-dimethyl-3-furancarbothioamide with palladium(II), platinum(II), ruthenium(II) and rhodium(III)

Summary N, N-Dimethyl-3-furancarbothioamide (Hbft) was cyclometallated with Li₂PdCl₄, K₂PtCl₄, RuCl₂(CO)₃, and RhCl (PBu₃)₂ (PBu₃=tri-n-butylphosphine) to give, respectively, PdCl(bft), PtCl(bft), RuCl(bft)(CO)₂, and RhCl₂ (bft)(PBu₃)₂. These and some of their derivatives were characterized spectroscopically. Cyclometallation occurs regioselectively at position 2 of the furan ring to give a five-membered metallaheterocycle, along with Secoordination of the thioamide group. When the position 2 of the furan ring is blocked by a methyl group,N, N-dimethyl-2-methyl-3-furancarbothioamide (Hmft) is, in similar conditions, cyclopalladated at the N–Me substituout of the thioamide group, the furan ring being left intact. Position 4 of the furan ring of both Hbft and Hmft is unreactive toward cyclometallation.     

Cyclometallation of a pyrrole ring of 2-(1-pyrrolyl)pyridine with palladium(II) and rhodium(III)

2-(1-Pyrrolyl)pyridine (Hplp) is cyclometallated with lithium tetrachloropalladate(II) and hexahalogenotetrakis(tri-n-butylphosphine)dirhodium(III) to give [PdCl(plp)]₂ and [RhX₂(plp(PBu₃)₂] (X = Cl, Br; PBu₃ = tri-n-butylphosphine), respectively, where deprotonated plp is coordinated via the pyridine-N and pyrrole-2C atoms forming a five-membered metallacycle. [PdCl(plp)]₂ reacts with pyridine (py) and with PBu₃ to form the adducts [PdCl(plp)L] (L = py, PBu₃) and with acetylacetone (Hacac) to afford the complex [Pd(plp)(acac)]. Metathesis of [RhCl₂(plp)(PBu₃)₂] with excess lithium iodide gives a mixed halogeno complex [RhClI(plp)(PBu₃)₂]. These complexes are characterized spectroscopically.     

Silver(I), palladium(II), platinum(II) and platinum (IV) complexes with isoorotate and 2-thioisoorotate ligands: synthesis,i.r. and n.m.r. spectra,thermal behaviour and antimicrobial activity

Summary From the reaction of isoorotic and 2-thioisoorotic acids with Ag^I, Pd^II, Pt^II and Pt^IV ions, twelve new complexes containing the uracil ligand in either monoor dianionic forms have been isolated and studied by conductivity measurements, i.r. and n.m.r. spectroscopies, and by thermal methods (t.g. and d.s.c.). From the data obtained, tentative molecular structures are suggested for each complex. The most common coordination mode of both acids involves formation of a six-membered chelate ring through the exocyclic O(4) atom and an oxygen of the carboxylate group. The antimicrobial activity of these compounds against several bacteria and yeast has also been assayed. It is noticeable that PdCl(H₂CU)py complex is active againstPseudomonas sp. andMicrococcus sp. at MIC values lower than 50 g cm^–3.     

Complexes of aminobenzylamines. part II. Complexes ofo-aminobenzylamine with palladium(II) and platinum(II)

Summary The reactions of K₂[MX₄] (M = Pd^II or Pt^II and X = Cl or Br) witho-aminobenzylamine (o-aba) have been studied in neutral aqueous solutions. Two types of complexes were isolated from these studies: [MLX₂] and [ML₂]X₂. Elemental analyses, conductivity measurements, i.r. and visible spectra suggest polymeric structures for [MLX₂] with the ligand,o-aba = L, acting as a bridge, and/or mononuclear structures for [ML₂]X₂.     

Structural and spectral studies of palladium(II) and platinum(II) complexes derived from N,N,N,N-tetradentate macrocyclic ligands

Palladium(II) and platinum(II) complexes having the general composition [M(L)] X2 (where M=Pd(II) and Pt(II), L=3,4,12,13-tetraphenyl-2,5,11,14,19,20-hexaaza tricyclo [13.3.1.1.(6-10)] cosa-1(19), 2,4,6,8,10,(20),11,13,15,17-decaene (L1); 3,4,13,14-tetraphenyl-2,5,12,15-tetraaza tricyclo [11,0,0,(6-11)] cosa-1(16),2,4,7,9,6(11),12,14,17, 19-decaene (L2); 2,3,8,9-tetraphenyl-1,4,7,10-tetraaza cyclododeca-1,3,7,9-tetraene (L3) and X=Cl(-)) have been synthesized. The ligands were characterized on the basis of elemental analyses, IR, 1H NMR and EI mass spectral studies while that of the complexes were characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, and electronic spectral techniques. All the complexes were found to be diamagnetic. The structures consist of monomeric units in which the Pd(II) and Pt(II) atoms exhibit square planar geometry.     

Carbonyl complexes of manganese(I) with pyridazine: Synthesis and1H n.m.r. study

Summary Three new pyridazine complexes of manganese(I): [MnBr(pyr)₂(CO)₃] (1), [Mn(pyr)(CO)₅][ClO₄] (2) and [Mn(pyr)₃(CO)₃][ClO₄] (3) (pyr=pyridazine) have been prepared and their i.r. and variable-temperature¹H n.m.r. spectra investigated.     

Coordination compounds of palladium(II) and platinum(II) with benzotriazoles

Summary The nitrogen-donor ligands 1-methylbenzotriazole (1Mebta), 5-methylbenzotriazole (5MebtaH), 5-chlorobenzotriazole (5ClbtaH) and 5-nitrobenzotriazole (5NO₂btaH) react with palladium(II) and platinum(II) to give cis-[PdL₂Cl₂], cis-[PtL₂Cl₂] (L = 1Mebta, 5MebtaH, 5ClbtaH or 5NO₂btaH), [Pt(5ClbtaH)₄]Cl₂, [Pd-(5MebtaH)Cl₂]₂, [Pd(5ClbtaH)Cl₂]₂ and [Pd(5NO₂btaH)-Cl₂]₂. The complexes were characterized by physicochemical and spectroscopic methods. The benzotriazoles act as monodentate ligands binding through N(3). Monomeric square planar structures are assigned for the 12 complexes and [Pt(5ClbtaH)₄]Cl₂ in the solid state. Centrosymmetric, chloro-bridged, dinuclear square planar structures of C_2h symmetry are proposed for the 11 palladium(II) compounds.     

Chemical and spectroscopic studies of a new palladium(II) complex with N -acetyl-L-cysteine

Chemical and spectroscopic studies of a new palladium(II) N-acetyl-L-cysteine complex are described. Elemental analyses for the solid complex are consistent with the formula [Pd(C₅H₈NO₃S)₂]?·?H₂O or [Pd(NAC)₂]?·?H₂O. Solid-state ¹³C nuclear magnetic resonance (NMR), UV–Visible (UV–Vis) and infrared (IR) spectroscopic analyses are consistent with coordination of the ligand to palladium(II) through the nitrogen and sulfur atoms in a square-planar geometry. Thermogravimetric and differential thermal analyses confirmed the composition; final residue was identified as metallic palladium.     

Ternary complexes of palladium(II) and selected amines

Summary The formation and equilibria of the binary and ternary palladium(II) complexes of diethylenetriamine (dien) with other selected amines have been investigated. The results of pH titration measurements allowed the calculation of equilibrium constants, characteristic for the binary and ternary complexes formed. The concentration distribution of various complex species was evaluated and the chelation mode ascertained by conductivity measurements.     

Synthesis, spectral and thermal studies on dicarboxylate-bridged palladium(II) coordination polymers. Part I

The synthesis and thermal behavior of the new [Pd(fum)(bipy)] _n ·2nH₂O (1), [Pd(fum)(bpe)] _n ·nH₂O (2) and [Pd(fum)(pz)] _n ·3nH₂O (3) {bipy = 4,4′-bipyridine, bpe = 1,2-bis(4-pyridyl)ethene and pz = pyrazine} fumarate complexes are described in this work as well their characterization by IR and ¹³C CPMAS NMR spectroscopies. TG curves showed that the compounds released organic ligands and lattice water molecules in the temperature range of 46–491 °C. In all the cases, metallic palladium was identified as the final residue.     

N.m.r. studies of complexes of molybdenum(VI) with tartaric acid in aqueous solution

Summary Complex formation between molybdate ions and R,R-(+)-tartaric acid has been studied in aqueous solution, and to a limited extent in DMSO, over a range of concentrations and pH at 298K, using¹H and¹³C n.m.r. techniques. Only four main species are evident; two, which have Mo: L ratios of 11 and 12, are bondedvia a carboxylic oxygen atom and an adjacent hydroxyl oxygen atom. The 12 species forms stereospecifically. The other two main species contain bridging tartaric acid molecules, and a 22 species, also formed stereo-specifically in solution, have been isolated and characterised in the solid state. A limited number of experiments with racemic acid and meso-tartaric acid indicate that only a few species are formed in these systems and with a good deal of stereospecificity also.     

Cyclometallation of 2-(2-thienyl)pyridine and 2-(3-thienyl)pyridine with palladium(II), rhodium(III) and ruthenium(II)

Summary 2-(2-Thienyl)pyridine [H(2-tp)] and 2-(3-thienyl)pyridine [H(3-tp)] react with lithium tetrachloropalladate(II), hexachlorotetrakis(tri-n-butylphosphine) dirhodium(III), and tetrachlorohexacarbonyldiruthenium(II) to give [PdCl(C-N)]₂-(CN=2-tp and 3-tp), [RhCl₂(C-N)PBu₃]₂ (C-N = 2-tp and 3-tp), and [RuCl(2-tp)(CO)₂]₂, respectively. Some bromo analogues are also prepared. These complexes react with pyridine and tri-n-butylphosphine to give adducts in which 2-tp is chelated through pyridine-N and thiophene-3-C and 3-tp through pyridine-N and thiophene-2-C atoms. The structures of these complexes are similar to those of the corresponding complexes of cyclometallated 2-phenylpyridine.     

Selenium oxoanion compounds of palladium(II)

Three new palladium compounds, PdSeO3, PdSe2O5, and Na2Pd(SeO4)2, containing selenium oxoanions of both Se(IV) and Se(VI) have been prepared under mild hydrothermal conditions. PdSe2O5 and Na2Pd(SeO4)2 both possess one-dimensional structures. Within the structure of PdSe2O5, [PdO4] square planar building blocks are joined together through diselenite, Se2O52-, anions, and form a zigzag chain along the c axis. In Na2Pd(SeO4)2, [PdO4] units are connected by two selenate, SeO42-, anions, and extend along the a axis to form a [Pd(SeO4)2]2- chain. Na+ cations reside in the space between the [Pd(SeO4)2]2- chains and act as counter cations. Unlike above two compounds, PdSeO3 exhibits a layered structure. In the structure of PdSeO3, [PdO4] units are connected to each other by corner-sharing and form a zigzag chain along the b axis. The chains are further joined together by tridentate selenite, SeO32-, anions to form layers in the [ab] plane that stack along the c axis. Crystallographic data: (193 K; Mo Kalpha, lambda=0.71073 A): PdSeO3, monoclinic, space group P21/m, a=3.8884(5) A, b=6.4170(8) A, c=6.1051(7) A, beta=96.413(2) degrees, V=151.38(3) A3, Z=2; PdSe2O5, monoclinic, space group C2/c, a=12.198(2) A, b=5.5500(8) A, c=7.200(1) A, beta=107.900(2) degrees , V=463.8(1) A3, Z=4; Na2Pd(SeO4)2, triclinic, space group P, a=4.9349(11) A, b=5.9981(13) A, c=7.1512 (15) A, alpha=73.894(4) degrees, beta=86.124(4) degrees, gamma=70.834(4) degrees, V=192.03(7) A3, Z=1.