Organometallic chemistry of diphosphazanes. Part 7. Platinum(II), palladium-(o), -(I) and -(II) complexes of RN[P(OPh)2]2(R = Me or Ph)

The reactions of [MCl2(cod)](M = Pd or Pt, cod = cycloocta-1,5-diene) with RN[P(OPh)2]2[R = Me (L1) or Ph (L2)] afford the chelate complexes [MCl2L1] and [MCl2L2]. The dinuclear palladium(O) complex, [Pd2L13] has been synthesized by starting from [Pd2(dba)3](dba = dibenzylideneacetone). Redox condensation of [Pd2(dba)3] and [PdCl2(PhCN)2] in the presence of the diphosphazane ligands gives the dinuclear palladium(I) complexes [Pd2Cl2L12] and [Pd2Cl2L22]. The structures of the complexes have been deduced from 1H and 31P NMR spectroscopic data. Single-crystal X-ray diffraction studies confirm the structures of [Pd2L13] and [Pd2Cl2L22].

Palladium(II) chloride complexes of bis(pyrazolyl)cyclotriphosphazenes

Reactions of the bis(3,5-dimethylpyrazolyl)cyclotriphosphazene derivatives gem-N3P3(MeNCH(2)CH(2)O)(2)(dmp)(2) (1) and nongeminal cis-N3P3(OPh)(4)(dmp)(2) (2) with PdCl2 afford complexes of the type [PdCl2.(L)] (L = 1 or 2). In these complexes, the phosphazenes act as bidentate NN-donor ligands with the two pyrazolyl pyridinic nitrogen atoms bonded to the metal, thus forming a six- and an eight-membered chelate ring, respectively. The structures of 2 and [PdCl2.(2)] (4) have been confirmed by single-crystal X-ray diffraction. Crystal data for 2: a = 16.759(2) Angstrom, b = 10.788(3) Angstrom, c = 19.635(9) Angstrom, beta = 101.61(3)degrees, P2(1/c), Z = 4, R = 0.038 for 4688 reflections with F > 5 sigma(F). Crystal data for 4: a = 9.701(3) Angstrom, b = 24.853(4) Angstrom, c = 15.794(4) Angstrom, beta = 101.46(2)degrees, P2(1/n), Z = 4, R = 0.030 for 5416 reflections with F > 5 sigma(F).

Spectroscopie de complexes plans carrés de platine(II) et de palladium(II) en fonction de la température et de la pression : structure et énergie

Les interactions entre des complexes de platine (II) ou de palladium (II) ont une grande influence sur une grande gamme de propriétés chimiques et physiques. Ces propriétés peuvent être étudiées par plusieurs méthodes spectroscopiques comme la spectroscopie Raman, d’absorption, d’émission et de réflectivité diffuse. L’empilement de molécules a un effet important sur les propriétés spectroscopiques de plusieurs composés des éléments de transition. La spectroscopie est très utile pour comprendre les effets intermoléculaires majeurs de plusieurs composés inorganiques. Les complexes plan-carré de platine(II) et de palladium(II) sont très intéressants à cause de leur grande quantité d’effets intermoléculaires et intramoléculaires. Des mesures avec des variations de pression (entre 1 bar et 40 kbar) et de température (entre 80 K et 300 K) ont été effectuées sur ces complexes. La structure à l’état fondamental des composés de platine(II) et de palladium(II) a un effet important sur la spectroscopie de luminescence. Des complexes avec des donneurs axiaux mènent à un effet de déplacement du maximum d’émission vers de plus basses énergies avec l’augmentation de pression. Des complexes similaires sans composante axiale ont un maximum d’émission qui se déplace vers des plus hautes énergies. Ces effets sont explorés à l’aide de plusieurs composés incluant une série de complexes pinceur qui ont démontré des déplacements entre -1 cm-1/kbar et -30 cm-1/kbar. Le changement du type d’émission causé par un changement de pression ou de température est aussi observable. Un complexe de platine(II) montre un changement d’une transition centrée sur le ligand à pression ambiante à une transition de type transfert de charge à plus haute pression. La combinaison de l’information cristallographique et spectroscopique donne de l’information quantitative sur les variations de la structure et des niveaux électroniques de plusieurs complexes.

Spectroscopie sous pression de complexes plans carrés de palladium(II) et de platine(II) : effets intra- et intermoléculaires

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

The crucial importance of agostic interactions in intermediates formed in propylene polymerization using neutral salicyladiminato palladium(II) and nickel complexes as catalysts

The structures of intermediates formed in propylene polymerisation using neutral salicyladiminato palladium(II) and nickel(II) complexes as catalysts have been investigated using density functional theory. Calculations show that all low energy intermediates contain agostic interactions either between the metal and a hydrogen from the added propylene forming four- or five-membered chelate rings, or, when a phenyl ring is present, between the metal and an aromatic C-C bond. The agostic interactions with the metal are concomitant with changes in ligand dimensions and electronic properties. In particular when a metal to hydrogen bond is formed, there is a lengthening of the C-H bond. Significant differences are found for the agostic interactions with palladium and nickel in that for Pd there is a clear preference for specific intermediates but for Ni there are several different structures with similar energies which are likely to lead to a greater variety of products on further polymerisation. (c) 2007 Elsevier B.V. All rights reserved.

Palladium(II) and platinum(II) complexes with tridentate iminophosphine ligands; synthesis and structural studies

The previously synthesised Schiff-base ligands 2-(2-Ph2PC6H4N = CH) - R' - C6H3OH (R' = 3-OCH3, HL1; 5-OCH3, HL2; 5-Br, HL3; 5-Cl, HL4) were prepared by a faster, more efficient route involving a microwave assisted co-condensation of 2-(diphenylphosphino) aniline with the appropriate substituted salicylaldehyde. HL1-4 react directly with (MCl2)-Cl-II (M = Pd, Pt) or (PtI2)-I-II(cod) affording neutral square-planar complexes of general formula [(MCl)-Cl-II(eta(3)-L1-4)] (M = Pd, Pt, 1 - 8) and [(PtI)-I-II(eta(3)-L1-4)] (M = Pd, Pt, 9 - 12). Reaction of complexes 1 - 4 with the triarylphosphines PR3 (R = Ph, p-tolyl) gave the novel ionic complexes [Pd-II(PR3)(eta(3)- L1-4)] ClO4 (13 - 20). Substituted platinum complexes of the type [Pt-II(PR3)(eta(3)- L1-4)] ClO4 (R = P(CH2CH2CN)(3) 21 - 24) and [Pt-II( P(p-tolyl)(3))(eta(3)-L-3,L-4)] ClO4 ( 25 and 26) were synthesised from the appropriate [(PtCl)-Cl-II(eta(3)-L1-4)] complex (5 - 8) and PR3. The complexes are characterised by microanalytical and spectroscopic techniques. The crystal structures of 3, 6, 10, 15, 20 and 26 were determined and revealed the metal to be in a square-planar four-coordinate environment containing a planar tridentate ligand with an O, N, P donor set together with one further atom which is trans to the central nitrogen atom.

Coordination modes of 3-aminosalicylic and 3-hydroxyanthranilic acids in palladium(II), platinum(II) and rhenium(V) complexes. The crystal structure of cis-[Pt(HsalNH)(PPh3)(2)] (.) 0.25C(2)H(5)OH

New Pd(II), Pt(II) and Re(V) complexes of 3-aminosalicylic acid (H(2)salNH(2)) and 3-hydroxyantranilic acid (HantOH) have been prepared, cis-[Pt (HsalNH)(PPh3)(2)] center dot 0.25C(2)H(5)OH (1), trans-[PdCl(salNH(2))(PPh3)(2)](2), trans-[ReOI2(HsalNH(2))(PPh3)] center dot (CH3)(2)CO (3), cis-[Pt(HantO)(PPh3)(2)] (4), trans-[PdCl(antOH)(PPh3)(2)] center dot 4H(2)O (5), [PdCl(antOH)(bipy)] center dot C2H5OH (6), [PdCl2(HantOH)(2)] (7) and trans-[ReOI(HantO)(PPh3)(2)] center dot (CH3)(2)CO (8). The crystal structure of complex I was determined showing chelation of HsalNH(2-) through the adjacent nitrogen and oxygen atoms of the amino and phenolate groups. Infrared and H-1 NMR spectroscopic data for the complexes are presented. (c) 2005 Elsevier Ltd. All rights reserved.

Synthesis, X-ray structure and electrochemical characterization of palladium(II) bearing ferrocenyldiphenylphosphine complexes

Four new complexes, [PdX(κ2-2-C6R4PPh2)(PPh2Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh2Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ2-2-C6F4PPh2)(μ-I)(μ-2-C6F4PPh2)PdI(PPh2Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1–4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh2Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh2Fc; subsequently, the metal–phosphorus bond is cleaved, leading to free PPh2Fc+, which undergoes further chemical and electrochemical reactions.

Thermal decomposition of palladium(II) pyrazolyl complexes. Part I

The thermal behavior of simple and mixed pyrazolyl complexes [PdCl2(phmPz)(2)] (1),[Pd(N-3)(2)(phmPz)(2)] (2), [Pd(SCN)(2)(phmPz)(2)] (3), and [Pd(N-3)(SCN)(phmPz)(2)] (4) (phmPz: 1-phenyl-3-methylpyrazole) has been investigated by means of thermogravimetry (TG) and differential thermal analysis (DTA). From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 4 < 2 < 3 < 1. The final products of the thermal decompositions were characterized as metallic palladium (Pd-0). (C) 2004 Elsevier B.V. All rights reserved.

Thermal decomposition of palladium(ii) pyrazolyl complexes: Part II

Thermal behavior of pyrazolyl complexes [PdCl2(HPz)2] (1), [PdCl2(HdmPz)2] (2), [Pd(SCN)2(HPz) 2] (3), [Pd(SCN)2(HdmPz)2] (4), [Pd(N 3)2(HdmPz)2] (5), [Pd(PzNHCO)2] (6) and [Pd(dmPzNHCO)2] (7) (HPz=pyrazole, HdmPz=3,5-dimethylpyrazole) has been studied by TG and DTA. In general, the thermal stability of [PdX 2(HL)2] (HL=HPz, HdmPz) compounds varies in the following order: HdmPz>HPz as well, according to the trends X=Cl ->SOT->NNN-. Except for 5, the [PdX 2(HL)2] complexes showed higher thermal stability than the 6 and 7 chelates. No stable intermediates were isolated during the thermal decompositions because of the overlapping degradation processes. The final products of the thermal decompositions were identified as metallic palladium by X-ray powder diffraction. © 2005 Akadémiai Kiadó, Budapest.

trans-Dichloro-bis-(arylazoimidazole)palladium(II): Synthesis, Structure, Photoisomerization, and DFT Calculation

Reaction between PdCl2 and 1-alkyl-2-(arylazo)imidazole (RaaiR') or 1-alkyl-2-(naphthyl-alpha/beta-azo)imidazole (alpha/beta-NaiR') under reflux in ethanol has isolated complexes of compositions Pd(RaaiR')(2)Cl-2 (5, 6) and Pd(alpha/beta-NaiR')(2)Cl-2 (7, 8). The X-ray structure determination of one of the molecules, Pd(alpha-NaiBz)(2)Cl-2 (7c), has reported a trans-PdCl2 configuration, and alpha-NaiBz acts as monodentate N(imidazole) donor ligand. The spectral (IR, UV-vis, H-1 NMR) data support the structure. UV light irradiation (light source: Perkin-Elmer LS 55 spectrofluorimeter, Xenon discharge lamp, lambda = 360-396 nm) in a MeCN solution of the complexes shows E-to-Z isomerization of the coordinated azoimidazole unit. The reverse transformation, Z-to-E, is very slow with visible light irradiation. Quantum yields (phi(E-Z)) of E-to-Z isomerization are calculated, and phi is lower than that of the free ligand but comparable with those of Cd(II) and Hg(II) complexes of the same ligand. The Z-to-E isomerization is a thermally induced process. The activation energy (E-a) of Z-to-E isomerization is calculated by controlled-temperature experimentation. cis-Pd(azoimidazole)Cl-2 complexes (azomidazole acts as N(imidazole) and N(azo) Chelating ligand) do not respond upon light irradiation, which supports the idea that the presence of noncoordinated azo-N to make free azo (-N=N-) function is important to reveal photochromic activity. DFT calculation of Pd(alpha-NaiBz)(2)Cl-2 (7c) has suggested that the HOMO of the molecule is constituted of Pd (32%) and Cl (66%), and hence photo excitation may use the energy of Pd and Cl instead of that of the photofunctional -N=N-Ar motif; thus, the rate of photoisomerization and quantum yield decrease versus the free ligand values.

Reactions of coordinated bivalent tetradentate schiff-base chelates of nickel (II) and palladium (II)

Reactions of N,N′-n-propylene-bis(acetylacetoneimino) metal (II), M[n-P-(AI)2], where M=Ni(II) or Pd(II), with nitrosating reagents have been investigated. Mono- and di-nitrosated complexes were obtained selectively, depending upon the concentration of the nitrosating reagents and the reaction time. In both the cases, the γ-CH group is transformed to an ambidentate isonitroso group (>C=NOH), which coordinates to the metal ion by dislodging the already coordinated carbonyl group. The factors influencing the mode of binding of the isonitroso group have been discussed. The bromination reactions of the mono-nitrosated products of M[n-P-(AI)2] and Pd (II) complexes, Pd [E/i-P-(AI)2], where E/i-P-(AI)2 is a dianion of ethylene/i-propylene-bis (acetylacetoneimine), are also reported. The reaction products have been characterized by elemental analyses, electrical conductivity molecular weight determination, and ir, pmr and electronic spectral data.