New cationic palladium (II) and rhodium (I) complexes of [Ph2PCH2C(Ph)N(2,6-Me2C6H3)]

Treatment of the bulky iminophosphine ligand [Ph₂PCH₂C(Ph)N(2,6-Me₂C₆H₃)] (L) with [M(CH₃CN)₂(ligand)]⁺ⁿ, where for M = Pd(II): ligand = η³-allyl, n = 1, and for M = Rh(I), ligand: 2(C₂H₄), 2(CO) or cod, n = 0, yields the mono-cationic iminophosphine complexes [Pd(η³-C₃H₅)(L)][BF₄] (1), [Rh(cod)(L)][BF₄] (2), [Rh(CO)(CH₃CN)(L)][BF₄] (3), and cis-[Rh(L)₂][BF₄] (4). All the new complexes have been characterised by NMR spectroscopy and X-ray diffraction. Complex 1 shows moderate activity in the copolymerisation of CO and ethene but is inactive towards Heck coupling of 4-bromoacetophenone and n-butyl acrylate.     

Palladium(II) complexes containing a bulky pyridinyl N-heterocyclic carbene ligand: Preparation and reactivity

Coordination chemistry of a pyridine imidazole-2-ylidene ligand (pyN ˆC) with sterically hindered substituents toward palladium(II) metal ions has been investigated. The palladium carbene complex [(C-pyN ˆC)Pd(η³-allyl)Cl] (3) is prepared via the transmetallation from the corresponding silver carbene complexes with [ClPd(η³-allyl)]₂. Upon the abstraction of chloride, coordination of pyridinyl-nitrogen becomes feasible to form [C,N-(pyN ˆC)Pd(η³-allyl)](BF₄) (4). Ligand substitution reaction of 4 with triphenylphosphine results in the formation of [(C-pyN ˆC)Pd(PPh₃)(η³-allyl)](BF₄)], which the pyridinyl-nitrogen donor is substituted by the phosphine. This palladium complex appears to be base sensitive. Treatment of 4 with t-butoxide causes the decomposition to yield the metal nano-particles. Furthermore, de-complexation of 4 takes place under hydrogen atmosphere to generate the carbene precursor, 1-(6-mesityl-2-picolyl)-3-mesitylimidazolium salt. Nevertheless, the palladium complex 4 shows good catalytic activity on the Suzuki-Miyaura and Mizoroki-Heck reactions.     

Regioselective synthesis of trifluoromethyl group containing allylic amines by palladium-catalyzed allylic amination and sequential isomerization

The palladium-catalyzed regioselective allylic amination of the α-trifluoromethyl group-substituted allyl acetate has been accomplished using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/DPPF as catalysts. The selective formation of the γ-product was attained in the presence of Pd(OAc)₂/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF₄/DPPF. We also succeeded in the regioselective synthesis of the enantiomerically enriched aminated product from chiral allyl acetate using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/(S)-BINAP. Furthermore, we found that kinetic resolution had occurred during the isomerization step from the γ-type product to the α-type product by the [Pd(π-allyl)(cod)]BF₄/(S)-BINAP catalyst.     

Preparation and characterisation of mononuclear Pd(II) complexes with 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) ligand: Spectroscopy studies and crystal structure of trans-[Pd(SCN)2(bddo)]

Mononuclear palladium(II) complexes containing a pyrazole-thioether ligand, with general formula trans-[Pd(X)₂(bddo)] (X = CN⁻ (1), SCN⁻ (2) or N₃⁻ (3); bddo = 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane), have been prepared. Similar reactivity carried out with pyridine or triphenylphosphine has been assayed. When pyridine is used, a mixture of [Pd(bddo)(py)₂](BF₄)₂ ([4](BF₄)₂) and [Pd(bddo)](BF₄)₂ is obtained. When triphenylphosphine is used, only [Pd(bddo)](BF₄)₂ is obtained. The complexes have been characterised by elemental analyses, conductivity measurements, IR and NMR spectroscopies. X-ray crystal structure of trans-[Pd(SCN)₂(bddo)] (2) is presented. In this complex the metal atom is coordinated by the two azine nitrogen atoms of the pyrazole rings and two SCN⁻ anions in trans disposition.     

Substitution reactions of [MBr(π allyl)(CO)2(LL)] complexes (M = Mo,W; L-L = 2,2 -bipyridine 1,2-bis(diphenylphosphine)ethane) with xanthates and dithiocarbamates

The complexes [MBr(π-allyl)(CO)₂(bipy)] (M = Mo, W, bipy = 2,2′-bipyridine) react with alkylxanthates (M^IRxant), and N-alkyldithiocarbamates (M^IRHdtc) (M^I = Na or K), yielding complexes of general formula [M(S,S)- (π-allyl)(CO)₂(bipy)] (M = Mo, (S,S) = Rxant (R = Me, Et, t-Bu, Bz), RHdtc (R = Me, Et); M = W, (S,S) = Extant). A monodentate coordentate coordination of the (S,S) ligand was deduced from spectral data. The reaction of [MoBr(π-allyl)(CO)₂(bipy)] with MeHdtc and Mexant gives the same complexes whether pyridine is present or not. The complexes [Mo(S,S)(π-allyl)(CO)₂(bipy)] ((S,S) = MeHdtc, Mexant) do not react with an excess of (S,S) ligand and pyridine.No reaction products were isolated from reaction of [MoBr(π-allyl)(CO)₂(dppe)] with xanthates or N-alkyldithiocarbamates.     

Synthesis and characterization of palladium(II) complexes with chiral aminophosphine ligands: Catalytic behaviour in asymmetric hydrovinylation. Crystal structure of cis-[PdCl2(PPh((R)-NHCHCH3Ph)2)2]

Optically active ligands of type Ph₂PNHR (R = (R)-CHCH₃Ph, (a); (R)-CHCH₃Cy, (b); (R)-CHCH₃Naph, (c)) and PhP(NHR)₂ (R = (R)-CHCH₃Ph, (d); (R)-CHCH₃Cy, (e)) with a stereogenic carbon atom in the R substituent were synthesized. Reaction with [PdCl₂(COD)₂] produced [PdCl₂P₂] (1) (P = PhP(NHCHCH₃Ph)₂), whose molecular structure determined by X-ray diffraction showed cis disposition for the ligands. All nitrogen atoms of amino groups adopted S configuration. The new ligands reacted with allylic dimeric palladium compound [Pd(η³-2-methylallyl)Cl]₂ to gave neutral aminophosphine complexes [Pd(η³-2-methylallyl)ClP] (2a-2e) or cationic aminophosphine complexes [Pd(η³-2-methylallyl)P₂]BF₄ (3a-3e) in the presence of the stoichiometric amount of AgBF₄. Cationic complexes [Pd(η⁴3-2-methylallyl)(NCCH₃)P]BF₄ (4a-4e) were prepared in solution to be used as precursors in the catalytic hydrovinylation of styrene. ³¹P NMR spectroscopy showed the existence of an equilibrium between the expected cationic mixed complexes 4, the symmetrical cationic complexes [Pd(η³-2-methylallyl)P₂]BF₄ (3) and [Pd(η³-2-methylallyl)(NCCH₃)₂]BF₄ (5) coming from the symmetrization reaction. The extension of the process was studied with the aminophosphines (a-e) as well as with nonchiral monodentate phosphines (PCy₃ (f), PBn₃ (g), PPh₃ (h), PMe₂Ph (i)) showing a good match between the extension of the symmetrization and the size of the phosphine ligand. We studied the influence of such equilibria in the hydrovinylation of styrene because the behaviour of catalytic precursors can be modified substantially when prepared ‘in situ’. While compounds 3 and bisacetonitrile complex 5 were not active as catalysts, the [Pd(η³-2-methylallyl)(η²-styrene)₂]⁺ species formed in the absence of acetonitrile showed some activity in the formation of codimers and dimers. Hydrovinylation reaction between styrene and ethylene was tested using catalytic precursors solutions of [Pd(η³-2-methylallyl)LP]BF₄ ionic species (L = CH₃CN or styrene) showing moderate activity and good selectivity. Better activities but lower selectivities were found when L = styrene. Only in the case of the precursor containing Ph₂PNHCHCH₃Ph (a) ligand was some enantiodiscrimination (10%) found.     

Microwave‐Assisted Synthesis and Transformations of Cationic CpRu(II)(naphthalene) and CpRu(II)(naphthoquinone) Complexes

Details of the direct synthesis of cationic Ru(II)(η⁵‐Cp)(η⁶‐arene) complexes from ruthenocene using microwave heating are reported. Developed for the important catalyst precursor [Ru(II)(η⁵‐Cp)(η⁶‐1‐4,4a,8a‐naphthalene)][PF₆] reaction time could be shortened from three days to 15 min. The method was extended to [Ru(II)(η⁶‐benzene)(η⁵‐Cp)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐toluene)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐mesitylene)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐hexamethylbenzene)][PF₆], [Ru(II)(η⁵Cp)(η⁶‐indane)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐2,6‐dimethylnaphthalene)][PF₆], and [Ru(II)(η⁵‐Cp)(η⁶‐pyrene)][PF₆]. 1‐methylnaphthalene and 2,3‐dimethylnaphthalene afforded mixtures of regioisomeric complexes. [Ru(Cp)(CH₃CN)₃][PF₆], derived from the naphthalene precursor provided access to the cationic RuCp complexes of naphthoquinone, tetralindione, 1,4‐dihydroxynaphthalene, and 1,4‐dimethoxynaphthalene. Reduction of the tetralindione complex afforded selectively the endo,endo diol derivative. X‐Ray structures of five complexes are reported.     

Protonation of palladium(II)-allyl and palladium(0)-olefin complexes containing 2-pyridyldiphenylphosphine

The pendant nitrogen atom of the Ph₂PPy ligand in the Pd(II)-allyl complexes [PdCl(η³-2-CH₃-C₃H₄)(Ph₂PPy)] (1) and [Pd(η³-2-CH₃-C₃H₄)(Ph₂PPy)₂]BF₄ (3) has been protonated with methanesulfonic acid to afford the corresponding pyridinium salts [PdCl(η³-2-CH₃-C₃H₄)(Ph₂PPyH)](CH₃SO₃) (1a) and [Pd(η³-2-CH₃-C₃H₄)(Ph₂PPyH)₂](CH₃SO₃)₂(BF₄) (3a).Protonation strongly influences the ¹H and ¹³C NMR spectral parameters of the allyl moieties of 1a and 3a whose signals resonate at lower fields with respect to the parent species indicating that upon protonation Ph₂PPy becomes a weaker σ-donor and a stronger Π-acceptor. The allyl moiety, which in 1 is static, becomes dynamic in 1a, the observed syn-syn and anti-anti exchange being due to deligation of the protonated phosphine from the metal centre. Treatment of complex 3 with diethylamine in the presence of fumaronitrile gives the new Pd(0)-olefin complex [Pd(η²-fumaronitrile)(PPh₂Py)₂] (4) which has been characterized by elemental analysis and NMR spectroscopy. Low temperature protonation of 4 with methanesulfonic acid leads to the bis-protonated species [Pd(η²-fumaronitrile)(Ph₂PPyH)₂](CH₃SO₃)₂ (4a) which is stable only at temperatures <0 °C.     

Synthesis,Structure, and 2D-NMR Studies of Novel Chiral (η3-Allyl)palladium(II) Complexes Containing the Bidentate Ligand Sparteine

Novel cationic allylpalladium (II) comp, exes containing the alkaloid (?)sparteine ( 1 ) as a bidentate ligand have been prepared. Two of them, [η³(cyclohex-2-enyl)] (sparteine)palladium(II) hexafluorophosphate([Pd(η³-C₆ H₉)(sparteine)][PF₆] 3b ) and (sparteine)[η³-(1,1,3-triphenylallyl)] palladium (II) trifluorophosphate ([Pd(η³-Ph₂CCHCHPh)(sparteine)][sparteine)] [CF³SO₃]; ( 3c ) were characterized by X-ray diffraction. The application of 2D-NMR methods (COSY and NOESY)affords a correlation between the solid-state and solution structures for complex 3c .     

Isolation and crystallographic characterization of solvate- and anion-stabilized PCP pincer complexes of palladium(II)

Pincer PCP-Pd(II) complex [PdCl(PCP)] (1) (PCP = ^?CH(CH₂CH₂PPh₂)₂) reacts with AgNO₃ to give [Pd(NO₃)(PCP)] (2). Similar reaction with AgBF₄ gives the aqua complex [Pd(OH₂)(PCP)][BF₄] (3) and the dinuclear complex [{Pd(PCP)}₂(μ-Cl)][BF₄] (4) with singly bridging chloro ligand. All new complexes were characterized by NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. Complex 1 and the triflate complex [Pd(OTf)(PCP)] (5) are active towards Suzuki–Miyaura coupling between aryl bromides and phenyl boronic acid.     

Cationic (fluoromesityl)palladium(II) complexes

Halide abstraction from [Pd(μ-Cl)(Fmes)(NCMe)]₂ (Fmes = 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl) with TlBF₄ in CH₂Cl₂/MeCN gives [Pd(Fmes)(NCMe)₃]BF₄, which reacts with monodentate ligands to give the monosubstituted products trans-[Pd(Fmes)L(NCMe)₂]BF₄ (L = PPh₃, P(o-Tol)₃, 3,5-lut, 2,4-lut, 2,6-lut; lut = dimethylpyridine), the disubstituted products trans-[Pd(Fmes)(NCMe)(PPh₃)₂]BF₄, cis-[Pd(Fmes)(3,5-lut)₂(NCMe)]BF₄, or the trisubstituted products [Pd(Fmes)L₃]BF₄ (L = CN^tBu, PHPh₂, 3,5-lut, 2,4-lut). Similar reactions using bidentate chelating ligands give [Pd(Fmes)(L-L)(NCMe)]BF₄ (L-L = bipy, tmeda, dppe, OPPhPy₂-N,N′, (OH)(CH₃)CPy₂-N,N′). The complexes trans-[Pd(Fmes)L₂(NCMe)]BF₄ (L = PPh₃, tht) (tht = tetrahydrothiophene) and [Pd(Fmes)(L-L)(NCMe)]BF₄ (L-L = bipy, tmeda) were obtained by halide extraction with TlBF₄ in CH₂Cl₂/MeCN from the corresponding neutral halogeno complexes trans-[Pd(Fmes)ClL₂] or [Pd(Fmes)Cl(L-L)]. The aqua complex trans-[Pd(Fmes)(OH₂)(tht)₂]BF₄ was isolated from the corresponding acetonitrile complex. Overall, the experimental results on these substitution reactions involving bulky ligands suggest that thermodynamic and kinetic steric effects can prevail affording products or intermediates different from those expected on purely electronic considerations. Thus,water, whether added on purpose or adventitious in the solvent, frequently replaces in part other better donor ligands, suggesting that the smaller congestion with water compensates for the smaller M-OH₂ bond energy.     

Structural Chemistry of Chiral Complexes. NMR and X-ray studies on Rh1 compounds of (S)-1-[bis(p-methylphenyl)phosphino]-2-[(p-methoxybenzyl)amino]-3-methylbutane

The Rh¹(diolefin)complexes [Rh(nbd)( 2 )][PF₆] [Rh(1,5-cod)( 2 )][PF₆], and [Rh((Z)-α -acetamidocinnamic acid)( 2 )][PF₆] ( 2 = the chiral P,N-ligand (S)-1-[bis(p-methylphenyl)phospino]-2-[p-methoxybenzyl)amino]-3-methylbutane have been prepared and characterized. These complexes exit as a mixture of isomers arising from different five-membered-ring conformations and diastereoisomers due to both the prochiral nitrogen and olefin ligands. The three-dimensional solutions structures of these complexes have been studied with the specific aim of understanding how the chiral pocket is built. Aspects of the exchange dynamics and their possible relevance to homogeneous hydrogenation are discussed The solid-state structure for the nbd complex, [Rh(nbd)( 2 )][PF₆], as well as detailed one- and two-dimensional ³¹P-, ¹³C-, and ¹H-NMR results are presented.     

(η3-allyl)palladium(II) catalysts for the addition polymerization of norbornene derivatives with functional groups

Cycloaliphatic polyolefins with functional groups were prepared by the Pd(II)-catalyzed addition polymerization of norbornene derivatives. Homo- and copolymers containing repeating units based on bicyclo[2.2.1] hept-5-en-2-ylmethyl decanoate (endo/exo-ratio = 80/20), bicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester (exo/endo = 80/20), bicyclo[2.2.1]hept-5-ene-2-methanol (endo/exo = 80/20), and bicyclo[2.2.1]hept-5-ene-2-carboxylic acid (100% endo) were prepared in 49–99% yields with {(η³-allyl)Pd(BF₄)} and {(η³-allyl)Pd(SbF₆)} as catalysts. The catalyst containing the hexafluoroantimonate ion was slightly more active than the tetrafluoroborate based Pd-complex.     

Tuning the hemilabile behaviour of a thioether–pyrazole ligand on Pd(II) complexes with diphosphines

The coordination mode of thioether–pyrazole ligand, 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane (bdtp) and 1,8-bis-(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) ligands, in Pd(II) complexes containing a diphosphine ligand is determined by subtle changes in size of the bridge between the two phosphorus atoms. The ¹H NMR and ³¹P{¹H} NMR at variable temperature in acetonitrile solution prove that the hemilabile character of the bdtp ligand depend on the diphosphine ligand. Thus, while in [Pd(bdtp)(dppe)](BF₄)₂ [1](BF₄)₂ the thioether group not participate in the Pd(II) coordination sphere, two isomers with different coordination (P₂N₂ vs P₂NS) are in equilibrium in [Pd(bdtp)(dppp)](BF₄)₂ [2](BF₄)₂ acetonitrile solution. For complexes [Pd(bddo)(dppe)](BF₄)₂ [3](BF₄)₂ and [Pd(bddo)(dppp)](BF₄)₂ [4](BF₄)₂, only the coordination N,N is observed.     

Tuning the hemilabile behaviour of a thioether–pyrazole ligand on Pd(II) complexes with diphosphines

The coordination mode of thioether–pyrazole ligand, 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane (bdtp) and 1,8-bis-(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) ligands, in Pd(II) complexes containing a diphosphine ligand is determined by subtle changes in size of the bridge between the two phosphorus atoms. The ¹H NMR and ³¹P{¹H} NMR at variable temperature in acetonitrile solution prove that the hemilabile character of the bdtp ligand depend on the diphosphine ligand. Thus, while in [Pd(bdtp)(dppe)](BF₄)₂ [1](BF₄)₂ the thioether group not participate in the Pd(II) coordination sphere, two isomers with different coordination (P₂N₂ vs P₂NS) are in equilibrium in [Pd(bdtp)(dppp)](BF₄)₂ [2](BF₄)₂ acetonitrile solution. For complexes [Pd(bddo)(dppe)](BF₄)₂ [3](BF₄)₂ and [Pd(bddo)(dppp)](BF₄)₂ [4](BF₄)₂, only the coordination N,N is observed.     

Effect of 5-Me substituent(s) on the catalytic activity of palladium(II) 2,2-bipyridine complexes in CO/4-tert-butylstyrene copolymerization

The coordination of two 5-substituted-2,2^′-bipyridines L (L¹=5-methyl-2,2^′-bipyridine, L²=5,5^′-dimethyl-2,2^′-bipyridine) to palladium was studied. The neutral complexes [Pd(L)Cl₂] and [Pd(L)(Me)Cl], and the cationic complexes obtained after chlorine abstraction [Pd(L)₂][BAr^′₄]₂ and [Pd(L)(Me)(NCMe)][BAr^′₄] (Ar^′=3,5-(CF₃)₂-C₆H₃), respectively, were isolated and characterized by NMR and FAB mass spectroscopy. The complex [Pd(L²)(L³)][BAr^′₄]₂ (L³=2,2^′-bipyridine) bearing different ligands, was prepared for comparison purposes. The activity of the monocationic and dicationic complexes as catalytic precursors in the CO/4-tert-butylstyrene copolymerization was compared with that of related well-known catalysts containing the unsubstituted 2,2^′-bipyridine as nitrogen ligand, to evaluate the influence of the substituents in 5- and 5,5^′-position. The presence of one or two substituents on the nitrogen ligand has a positive effect on productivity using both types of precursors. No influence was observed on the polymer properties in terms of molecular weight and tacticity. Analysis of the reactivity of the methyl-palladium complexes towards carbon monoxide shows further differences depending on the nitrogen ligand.     

Mixed N-heterocycles/N-heterocyclic carbene palladium(II) allyl complexes as precatalysts for direct arylation of azoles with aryl bromides

A series of mixed N-heterocycles/N-heterocyclic carbene palladium(II) allyl complexes with general formula [(NHC)Pd(η³-allyl)]₂(μ₂-N-heterocycles)(BF₄)₂ were prepared in one pot based on anion metathesis of (NHC)Pd(η³-allyl)Cl complexes and then ligand replacement with N-heterocycles [N-heterocycles?=?pyrazine (pyz), 4,4′-bipyridine (bpy) and trans-4,4′-bipyridylethylene (bpe)]. The solid-state structures shown dinuclear structures with two palladium(II) centers holding together by bridged N-heterocycles. Initially investigation of the obtained complexes as precatalysts for direct CH bond arylation of azoles with aryl bromides was carried out.     

Structural and kinetic effects of chloride ions in the palladium-catalyzed allylic substitutions

Addition of ligands to [Pd(η³-RCHCHCH₂)(μ-Cl)]₂ or chloride ions to cationic [(η³-RCHCHCH₂)PdL₂]⁺BF₄⁻ induces the formation of neutral complexes η¹-RCHCHCH₂PdClL₂ (R=H with L=(4-ClC₆H₄)₃P, (4-CH₃C₆H₄)₃P, (4-CF₃C₆H₄)₃P or L₂=1,2-bis(diphenylphosphino)butane (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppf); R=Ph with L=(4-ClC₆H₄)₃P), instead of the expected cationic complexes [(η³-RCHCHCH₂)PdL₂]⁺Cl⁻. In the presence of chloride ions, the reaction of morpholine with the cationic complexes [(η³-allyl)Pd(PAr₃)₂]⁺BF₄⁻ (Ar=4-ClC₆H₄, 4-CH₃C₆H₄) goes slower and involves both cationic [(η³-allyl)Pd(PAr₃)₂]⁺ and neutral η¹-allyl-PdCl(PAr₃)₂ complexes as reactive species in equilibrium with Cl⁻. The cationic complex is more reactive than the neutral one. However, their relative contribution in the reaction strongly depends on the chloride concentration, which controls their relative concentration. The neutral η¹-allyl-PdCl(PAr₃)₂ may become the major reactive species at high chloride concentration. Consequently, [Pd(η³-allyl)(μ-Cl)]₂ associated with ligands or cationic [(η³-allyl)PdL₂]⁺BF₄⁻, used indifferently as precursors in palladium-catalyzed allylic substitutions, are not equivalent. In both situations, the mechanism of the Pd-catalyzed allylic substitution depends on the concentration of the chloride ions, delivered by the precursor or purposely added, that determines which species, [(η³-allyl)PdL₂]⁺ or/and η¹-allyl-PdClL₂ are involved in the nucleophilic attack with consequences on the rate of the reaction and probably on its regioselectivity. Consequently, the chloride ions of the catalytic precursors [Pd(η³-allyl)(μ-Cl)]₂ must not be considered as ‘innocent’ ligands.     

The molecular structure of a three-coordinate palladium(II)-styrene complex [Pd(η5-C5H5)(PEt3)(styrene)]BF4

The molecular structure of a three-coordinate palladium(II)-styrene complex, [Pd(η⁵-C₅H₅)(PEt₃)(styrene)]BF₄ has been determined by means of X-ray diffraction. The crystal belongs to the monoclinic system, space group P2₁/c, with four formula units in a cell of dimensions: a 10.229(3), b 11.262(3), c 18.760(5) Å and β 103.77(2)°. The structure was solved by the heavy atom method, and refined by the least-squares procedure to R = 0.050 for 3635 observed reflections. The palladium atom is surrounded by the cyclopentadienyl group, the triethylphosphine ligand and the olefinic bond of styrene in the cationic complex. In the palladiumstyrene bonding, the olefinic bond is inclined by 77.3° to the coordination plane defined by the Pd and P atoms and the center of the cyclopentadienyl ring (PdC(1) 2.176(6), PdC(2) 2.234(5) and C(1)C(2) 1.369(8) Å).     

Palladium complexes of 8-(di-tert-butylphosphinooxy) quinoline

The preparation of the new ligand 8-(di-tert-butylphosphinooxy)quinoline (1) and the palladium derivatives [PdCl₂(1)] (2), [Pd(η³-all)(1)]⁺ [all = C₃H₅ (3a), 1-PhC₃H₄ (3b) and 1,3-Ph₂C₃H₃ (3c)] and [Pd(η²-ol)(1)] [ol = dimethyl fumarate (4a) and fumaronitrile (4b)] is reported. The cationic species 3a-3c have been isolated as salts. The complex 3a(BF₄) is obtained either from the reaction of 1 with [Pd(μ-Cl)(η³-C₃H₅)]₂ or from the reaction of ClP(CMe₃)₂ with [Pd(η³-C₃H₅)(8-oxyquinoline)], followed in both cases by chloride abstraction with NaBF₄. In the complexes, the ligand 1 is P,N chelated to the central metal, as shown by the X-ray structural analysis of 3a(BF₄). At 25 °C in solution, 3a(BF₄) and 3b(BF₄) undergo a fast η³−η¹−η³ dynamic process which brings about a syn-anti exchange only for the allylic protons cis to phosphorus, while for 4a and 4b a slow rotation of the olefin around its bond axis to palladium takes place. The complexes 2 and 3a(BF₄) are efficient catalyst precursors in the coupling of the phenylboronic acid with aryl bromides and chlorides.