Synthesis and crystal structure of four Pd(II) complexes containing nido or closo carborane diphosphine ligands

Three Pd(II) complexes [Pd₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] · 0.25CH₂Cl₂ (1), [Pd{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] · 4CHCl₃ (2) and [PdCl₂(1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀)] (3) have been synthesized by the reactions of 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ with PdCl₂ in acetonitrile, cyanophenyl and dichloromethane, respectively. A fourth complex, [PdI₂(1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀)] (4), was obtained by a ligand exchange reaction through the substitution of the Cl⁻ of complex 3 with I⁻. All four complexes have been characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal X-ray determination showed that the carborane cage, nido for 1, 2 and closo for 3, 4, was coordinated bidentately to the Pd atom through the two P atoms, and the geometry at the Pd atom was square-planar in all the complexes.     

Synthesis,characterization and luminescence of the tetranuclear gold cluster: [Au4{7,8-(PPh2)2-7,8-C2B9H10}2(PPh3)2]

A tetranuclear gold cluster has been synthesized by the reaction of [Au(PPh₃)NO₃] with the closo carborane diphosphine 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ in THF, and characterized by elemental analysis, FT-IR, ¹H and ¹³C?NMR spectroscopy and X-ray structure determination. The cluster crystallizes in the triclinic Pī, a?=?15.118(8)?Å, b?=?16.057(9)?Å, c?=?24.284(13)?Å, α?=?80.822(9)°, β?=?79.624(8)°, γ?=?81.938(8)°, Z?=?2, R ₁?=?0.0626, wR ₂?=?0.1894. A single crystal structure determination showed that four gold atoms form a tetrahedral framework. Among these four gold atoms, two were chelated by two nido carborane diphosphine [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]^? anions coming from the degradation of the initial closo ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀, while the other two were ligated to two PPh₃ groups. The luminescence of this cluster was also investigated in dichloromethane solution at room temperature.     

Synthesis of fused dihydropyrido[e]purines via ring closing metathesis

Ring closing metathesis (RCM) of 8,9-diallylpurines or 9-butenyl-8-vinylpurines with the Grubbs 2nd generation catalyst resulted in fused 6,9- or 8,9-dihydropyrido[e]purines, respectively. The 8,9-dialkenylpurines were prepared from 8-bromopurines after 9-alkenylation and subsequent Stille coupling at C-8 with alkenylstannanes in the presence of Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂.     

Yldiide Ligands as Building Blocks for Polynuclear Coinage Metal Complexes: Metal Squares,Triangles and Chains

Yldiides have unique electronic properties and donor abilities, but as ligands in transition metal complexes they are scarcely represented in the literature. Here, the controlled synthesis of a series of polynuclear gold yldiide complexes derived from triphenyl(cyanomethyl)phosphonium bromide, [Ph₃PCH₂CN]Br, under mild conditions is described. Anionic dinuclear NBu₄[(AuX)₂{C(CN)PPh₃}] (X=Cl, C₆F₅) or trinuclear derivatives NBu₄[Au₃X₂{C(CN)PPh₃}] bearing terminal chloride or pentafluorophenyl groups and bridging yldiide ligands have been prepared. These compounds evolve in solution giving rise to the formation of an unprecedented tetrameric gold cluster, [Au₄{C(CN)PPh₃}₄], by the loss of the gold complex NBu₄[AuX₂]. This gold cluster can also be prepared in high yield by a transmetalation reaction from the analogous tetrameric silver cluster, and two geometric isomers have been characterised, their formation dependent on the synthetic route. The triphenylphosphonium cyanomethyldiide ligand has also been used to build different dinuclear and trinuclear cationic complexes bearing phosphine or diphosphine ancillary ligands and bridging yldiide moieties. Further coordination through the cyano group of the yldiide ligand gives heterometallic trinuclear or pentanuclear derivatives. Structural characterisation of many of these compounds reveals the presence of complex molecular systems stabilised by gold⋅⋅⋅gold interactions and bridging yldiide ligands.     

Synthesis and spectroscopic studies of some new metal carbonyl derivatives of 1-(2-pyridylazo)-2-naphthol

Interaction of 1-(2-pyridylazo)-2-naphthol (PAN) with [Mo(CO)₆] in air resulted in formation of the tricarbonyl oxo-complex [Mo(O)(CO)₃(PAN)], 1. The dicarbonyl complex [Ru(CO)₂(PAN)], 3, was obtained from the reaction of [Ru₃(CO)₁₂] with PAN. In presence of triphenyl phosphine (PPh₃), the reaction of PAN with either Mo(CO)₆ or Ru₃(CO)₁₂ gave [Mo(CO)₃(PAN)(PPh₃)], 2, and [Ru(CO)₂(PAN)(PPh₃)], 4. All the complexes were characterized by elemental analysis, mass spectrometry, IR, and NMR spectroscopy. The thermal properties of the complexes were also investigated by thermogravimetry.     

ortho-metallation reactions involving some triphenyl phosphite complexes of osmium

Osmium triphenylphosphine complexes, OsH₄(PPh₃)₃, OsH₂ (CO)(PPh₃)₃ and OsHCl(CO)(PPh₃)₃ react with triphenyl phosphite in boiling organic solvents to yield triphenyl phosphite derivatives which subsequently undergo ortho-metallation reactions.     

Synthesis, isomerism, and catalytic properties of chelate ruthenium copper bimetallacarborane cluster exo-closo-(Ph3P)Cu(μ-H)Ru[Ph2P(CH2)4PPh2](η5-C2B9H11), in radical polymerization of methyl methacrylate

Chelate exo-nido-ruthenacarboranes exo-5,6,10-[RuCl(Ph₂P(CH₂)₄PPh₂)]-5,6,10-(μ-H)₃-10-H-7,8-R,R′-nido-7,8-C₂B₉H₆ (R, R′ = H, PhCH₂) were synthesized by the direct method using the reaction of Cl₂Ru(PPh₃)(Ph₂P(CH₂)₄PPh₂) with [7,8-R,R′-nido-7,8-C₂B₉H₁₀][K] in benzene. Unsubstituted exo-nido-ruthenacarborane (R, R′ = H) was used in situ for the synthesis of the dinuclear Ru-Cu exo-closo cluster of the formula exo-closo-(Ph₃P)Cu(μ-H)Ru(Ph₂P(CH₂)₄PPh₂)(η⁵-C₂B₉H₁₁). The isomerism of the complex and the crystal structure were studied by NMR spectroscopy and X-ray diffraction. The catalytic activity of the cluster in the atom transfer radical polymerization of methyl methacrylate was investigated.     

Synthesis and characterization of three nickel(ii) carborane complexes containing nido- or closo-carborane diphosphine ligand

Three nickel(II) carborane complexes, [Ni₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] (1), [Ni{7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀}{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (2) and [NiBr₂{1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀}] · CH₂Cl₂ (3), have been synthesized by the reactions of 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane with NiCl₂ · 6H₂O or NiBr₂ · 6H₂O in ethanol under different conditions, respectively. For complex 1, it could also be obtained under the solvothermal condition. All the three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal analysis shows that the molecular symmetry of complex 1 is centrosymmetric, containing two same structure units - Ni(7,8-(PPh₂)₂-7,8-C₂B₉H₁₀) linked by two bridged-Cl atoms. The central square plane formed by the [Ni₂Cl₂] unit is almost parallel to the two side NiPP planes. For complex 2, the coordination environment of the Ni atom is a seriously distorted square-planar, in which two positions come from the chelating diphosphine ligand [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻ degraded from the closo species, while the other two are occupied by an unsymmetrical chelating phosphine oxide ligand [7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀]⁻. As for complex 3, the geometry at the Ni atom is a slightly distorted square-planar. The closo carborane diphosphine ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ was coordinated bidentately to the metal ion through the two phosphorus atoms, and the two Br atoms are at cis position which can fulfill the four coordination mode of the metal.     

Kinetic and mechanistic study on the thermal reactivity of stabilized phosphorus ylides,part 3: [(Acetyl)(arylcarbamoyl)methylene]triphenylphosphoranes and [(alkoxycarbonyl)(arylcarbamoyl)methylene]triphenylphosphoranes and their thiocarbamoyl analogues

A series of five [(acetyl)(arylcarbabmoyl)methylene]triphenyl‐phosphoranes 1a–e and their thiocarbamoyl analogues 2a–e , [(alkoxycarbonyl)(arylcarbamoyl)methylene]triphenylphosphoranes 3a–e and their thiocarbamoyl analogues 4a–e were prepared and fully characterized. All ylides are found under conditions of flash vacuum pyrolysis to fragment giving arylisocyanate or isothiocyanate and acetyl ylides or alkoxy ylides which undergo thermal extrusion of Ph₃PO. A kinetic study shows that these reactions are unimolecular and are of first‐order nature with no significant substituent effect. The thiocarbamoyl ylides 2 react from 4.6 to 42 times faster than their carbamoyl ylides 1 , while the thiocarbamoyl ylides 4 react from 6.6 to 20.9 times faster than their carbamoyl ylides 3 . © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 6–16, 2007     

Stereochemical aspects of base-promoted reactions of o-alkenyl substituted arylhydrazonoyl chlorides with triphenylphosphine

The title arylhydrazonoyl chlorides treated with Et₃N and PPh₃ give arylazomethyl-enetriphenylphosphoranes and, in some cases, products of intramolecular cyclization (cyclopropacinnolines and benzodiazepines). A high concentration of base and a polar solvent accelerate all the observed reactions. In the presence of PPh₃ a low reaction temperature and a non polar solvent favour the formation of the phosphoranes over the cyclization reaction. The steric configuration of phosphoranes and cyclopropacinnolines is determined by the relative stability of the two isomers.     

Phenoxide-assisted P-C bond cleavage in PdCl2(PPh3)2 under very mild conditions

PdCl₂(PPh₃)₂ reacted with NaOAr (Ar = Ph, p-tolyl) at 0 °C to afford PdCl(Ph)(PPh₃)₂, instead of PdCl(OAr)(PPh₃)₂, in 12-16% isolated yields based on Pd. The structure was confirmed by NMR and X-ray crystallography. GC-MS analysis of the reaction solution revealed that OPPh₂(OAr), OPPh(OAr)₂, and OP(OAr)₃ are formed, while NMR studies indicated that PdCl(Ph)(PPh₃)₂ is produced when PdCl(OAr)(PPh₃)₂ decomposes. The reaction of PdCl₂(PPh₃)₂ with Bu₃Sn(OC₆H₄-p-OMe) also gave PdCl(Ph)(PPh₃)₂ in 8% isolated yield. These results suggest that PdCl(OAr)(PPh₃)₂ is highly labile and the aryloxy ligand exchanges with the phenyl groups in triphenylphosphine even under very mild conditions.     

Oxorhenium(V) Complexes with 1,3,4‐Triphenyl‐1,2,4‐triazol‐5‐ylidene

Reactions of the oxorhenium(V) complexes [ReOX₃(PPh₃)₂] (X = Cl, Br) with the N‐heterocyclic carbene (NHC) 1,3,4‐triphenyl‐1,2,4‐triazol‐5‐ylidene (L^Ph) under mild conditions and in the presence of MeOH or water give [ReOX₂(Y)(PPh₃)(L^Ph)] complexes (X = Cl, Br; Y = OMe, OH). Attempted reactions of the carbene precursor 5‐methoxy‐1,3,4‐triphenyl‐4,5‐dihydro‐1H‐1,2,4‐triazole ( 1 ) with [ReOCl₃(PPh₃)₂] or [NBu₄][ReOCl₄] in boiling xylene resulted in protonation of the intermediately formed carbene and decomposition products such as [HL^Ph][ReOCl₄(OPPh₃)], [HL^Ph][ReOCl₄(OH₂)] or [HL^Ph][ReO₄] were isolated. The neutral [ReOX₂(Y)(PPh₃)(HL^Ph)] complexes are purple, airstable solids. The bulky NHC ligands coordinate monodentate and in cis‐position to PPh₃. The relatively long Re–C bond lengths of approximate 2.1Å indicate metal‐carbon single bonds.     

Solvothermal Synthesis and Characterization of Two New Nickel <Emphasis Type="Italic">Nido</Emphasis>-Carborane Diphosphine Complexes

Solvothermal synthesis method has been successfully introduced into the diphosphine carborane system, and two new nickel complexes containing nido-carborane diphosphine ligand [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻ with the formula [Ni₂(μ-Cl)(μ-OOPPh₂){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂]·CH₂Cl₂ (1) and [H₃O][NiBr₂] {7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}·C₆H₆ (2) were obtained by the reactions of 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ with NiCl₂·6H₂O or NiBr₂·6H₂O in CH₂Cl₂ under the solvothermal condition. Both of the two complexes have been characterized by the elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and single crystal X-ray diffraction. The X-ray structure analysis for these two complexes reveals the nido-nature of the carborane diphosphine ligand, indicating that the solvothermal synthesis is an efficient method for the degradation of the closo-carborane diphosphine ligand.     

Reactions Between 4-Hydroxycoumarins or 4-Hydroxy-1-Methylquinolinone and Dmad in the Presence of Phosphites. Synthesis of (Chromen-3-YL)- and (Quinolin-3-YL)-(Dialkoxyphosphoryl)Succinates

Abstract

Dimethyl (chromen-3-yl)-(dialkoxyphosphoryl)succinates are prepared from the reaction of 4-hydroxycoumarin with DMAD and P(OR)₃. 4-Hydroxy-1-methylquinolinone reacts with DMAD and P(OEt)₃ to give dimethyl (quinoline-3-yl)-(diethoxyphosphoryl)-succinate.

GRAPHICAL ABSTRACT      

Catalytic activity and visible spectroscopy of [Rh(norbornadiene)Cl]2/p-RC6H4)3P system in methanol

Summary The catalytic hydrogenation of hex-1-ene in methanolic solution with [Rh(norbornadiene)Cl]₂/(p-RC₆H₄)₃ P (R=H, Me or OMe) systems preparedin situ has been measured. The catalytic activity shows a dependence on the ageing of the catalyst precursor solution in the presence of air. A spectroscopic study (visible region) has been carried out for the system with triphenyl phosphine and shows degradation with the formation of [Rh(norbornadiene)PPh₃Cl] as an intermediate. It was demonstrated that the spectral changes and the consequent catalytic activity are due to PPh₃ loss because of the oxygen dissolved in the media.     

The stereoselective synthesis of (E)-octafluoro-1,3,5-hexatriene and (3E,5E,7E)-dodecafluoro-1,3,5,7,9-decapentaene

(E)-(1,2-Difluoro-1,2-ethenediyl)bis[tributylstannane], 3, readily undergoes a Pd(PPh₃)₄/CuI-catalyzed cross-coupling reaction with iodotrifluoroethene to yield (E)-octafluoro-1,3,5-hexatriene, 4, in high isomeric purity. (1Z,3E,5Z)-(1,2,3,4,5,6-Hexafluoro-1,3,5-hexenetriyl)bis[tributylstannane], 7, was sequentially prepared from (1Z,3E,5Z)-(1,2,3,4,5,6-hexafluoro-1,3,5-hexenetriyl)bis[triethylsilane], 5, which was prepared via a Pd(PPh₃)₄/CuI-catalyzed cross-coupling reaction of 3 with (E)-1,2-difluoro-1-iodo-2-triethylsilylethene, 6. Pd(PPh₃)₄/CuI cross-coupling of 7 with iodotrifluoroethene gave (3E,5E,7E)-dodecafluoro-1,3,5,7,9-decapentaene, 8.     

Synthesis and characterization of a cationic oxorhenium(V) complex containing the pentadentate N3O2-donor ligand bis ( N -methylsalicylideneiminopropyl)amine

The complex salt [ReO(bsa)]PF₆ (H₂bsa?=?bis(N-methylsalicylideneiminopropyl)amine) was prepared from the reaction of cis-[ReO₂I(PPh₃)₂] with H₂bsa in toluene. The dianionic pentadentate ligand bsa is coordinated to the ReO³⁺ moiety via one secondary amino and two imino nitrogens, and two anionic phenolate oxygens. The complex was characterized by spectroscopy and analytical data, and the structure has been determined by single-crystal X-ray diffraction analysis.     

Regioselective homogeneous hydrogenation of heteroaromatic nitrogen compounds by use of [RuH(CO)(NCMe)2(PPh3)2]BF4 as the precatalyst

Summary The complex [RuH(CO)(NCMe)₂(PPh₃)₂]BF₄ (1) is an efficient and regioselective catalyst precursor for the hydrogenation of polyaromatic nitrogen compounds such as quinoline (Q), isoquinoline (iQ), indole (ln), 5,6- and 7,8-benzoquinoline (BQ) and acridine (A) under relatively mild reaction conditions (125 °C, 4 atm H₂). The order of individual initial rates was: A > Q > 5,6-BQ > 7,8-BQ > ln > iQ, reflecting both steric and electronic effects. For the regioselective homogeneous hydrogenation of A to 9,10-dihydroacridine (DHA) catalysed by complex (1), a kinetic study was carried out; the experimentally determined rate law was r = k ₁ [Ru] [H₂]. These findings are consistent with a mechanism involving the hydrogenation of [RuH(CO)(A)(NCMe)(PPh₃)₂]BF₄ to yield DHA and the unsaturated species [RuH(CO)(NCMe)(PPh₃)₂]BF₄ in the rate-determining step.     

Transition metal clusters : edited by B.F.G. Johnson, John Wiley and Sons, Inc. Chichester/New York/Brisbane/Toronto, 1980, 681 pages, $ 96.50.

The complexes cis-[V(CO)₄LL] (where LL is a ditertiary phosphine), V(CO)₅PPh₃ and {V(CO)₅}₂-μ-{p-C₆H₄(PPh₂)₂} were prepared by oxidation of the corresponding anionic compounds with tropylium tetrafluoroborate. IR and selected ESR data are presented.     

Ab initio calculations on phosphorus compounds. II. Effects of disubstitution on ligand apicophilicity in phosphoranes

Geometry optimizations at the HF/3-21G(*) and HF/6-31G* levels of ab initio theory have been carried out for various isomers of model disubstituted phosphoranes PH₃XY(X, Y?OH, CH₃, NH₂, and SH). Reasonable agreement was obtained between the optimized geometries and available crystal structure data for analogous compounds. The isomers were further characterized by frequency calculations. The MP2/6-31G*//6-31G* + ZPE energy data reveal that the interactions between the ligands are relatively small (0–4 kcal mol^?1) for the most stable conformations of the isomers. Hence, for these conformations the apicophilicities (based upon monosubstituted phosphoranes) are approximately additive. The less stable PH₃XY conformations are in general transition states or higher-order saddle points, and their interligand interactions are larger in magnitude (up to 10 kcal mol^?1); the results with these conformations suggest that apicophilicities may not be as additive for some highly substituted phosphoranes. © 1993 John Wiley & Sons, Inc.