PdCl2 Complexes Research Articles

Development of a green process for poly-α-olefin based lubricants

Poly-α-olefin (PAO) based lubricants have a large share of the synlubes market and these are produced in two stages—oligomerisation of α-olefins and hydrogenation. The current industrial processes use AlCl3 and BF3 as catalysts for oligomerisation, which are polluting, hazardous and give a very wide molecular weight distribution. This study reports a green synthesis of a PAO synlube by using 1-decene as the starting material with a variety of solid acidic catalysts, mainly based on clays. The activities for oligomerisation were found to be in the following order: K10 montmorillonite clay > 20% w/w ZnCl2/K10 > 5% w/w (dodecatungstophosphoric acid, DTP)/K10 > 20% DTP/K10 > 10% AlCl3 + 10% FeCl3/K10 > S–ZrO2 > Al-pillared clay > DTP > 20% DTP/carbon. K10 clay gave a conversion of 1-decene of 73% but the selectivities towards the dimer and trimer were 88 and 12%, respectively. 20% ZnCl2/K10 led to a conversion of 68% with 100% dimer formation. The kinetics of reaction were established by using both K-10 and 20% ZnCl2/K10. Oligomerisation is controlled by intrinsic kinetics. The catalysts are reusable. Other olefins such as 1-octene and 1-dodecene were also oligomerized in the presence of 20% ZnCl2/K10. 1-Decene dimer was isolated and then in the next step hydrogenated by employing 20% w/w Ni/SiO2, 20% w/w Ni–Cu (50:50)/SiO2 and a clay anchored bipyridine–montmorillonite–PdCl2 complex as catalysts. Amongst these 20% w/w Ni/SiO2 was found to be the most active catalyst at 50 atm and 150 °C, whereas the anchored catalyst BM–Pd(II) was active at atmospheric pressure and 30 °C. Effects of various parameters were studied to arrive at a kinetic model with both the catalysts. The reactions are intrinsically kinetically controlled showing zero order in dimer concentration and first order in hydrogen partial pressure. 1-Decene based PAO with a viscosity of about 2 cSt has great many applications The hydrogenated product had a viscosity of 2.22 cSt which was found to be comparable with commercially available sample. High-speed spindle oil used in textile industry was also prepared and its performance tested.

Catalytic activity of palladium(II) complexes with tridentate nitrogen ligands in the hydrogenation of alkenes and alkynes

A series of palladium(II) complexes with the nitrogen ligands N-pyridin-2-yl- N′-pyridin-2-ylmethylene-hydrazine ( HL 1 ), and N, N-dimethyl- N′-pyridin-2-ylmethylene-ethane-1,2-diamine, ( L 2 ) have been synthesised and their catalytic activity in the hydrogenation of alkenes and alkynes in mild conditions ( P H 2 =1 atm, T=40 °C) has been studied. Ligand L 2 behaves as tridentate in the complexes Pd( L 2 )Cl 2 ( 4) and [Pd( L 2 )Cl](OTf) ( 5), whose catalytic activity is negligible in the hydrogenation of the tested substrates (styrene and phenylacetylene). The complexes Pd( L 1 )Cl ( 1) and Pd( L 1 )(OAc) ( 2) show a good catalytic activity towards styrene and phenylacetylene under homogeneous conditions. The high insolubility of the complex Pd 3( L 1 ) 2Cl 4 ( 3) prevents its use as catalyst in homogeneous hydrogenations; however, it has been employed in heterogeneous conditions, showing a very good chemo- and stereo-selectivity in the semi-hydrogenation of alkynes (phenylacetylene, diphenylacetylene and 4-octyne).

A pyridine bridged dicarbene ligand and its silver(I) and palladium(II) complexes: synthesis, structures, and catalytic applications

The potentially tridentate ligand 2,6-bis[(3-methylimidazolium-1-yl)methyl]pyridine dibromide reacts readily with silver(I) oxide in dichloromethane or dimethylsulfoxide to give a dinuclear silver(I)–carbene complex that was isolated as the tetrafluoroborate salt. Single crystal X-ray crystallography shows that each silver(I) ion is bridged by two ligands bonding through the carbene donors. Treatment of the silver(I) complex with suitable palladium(II) precursors gave the complexes PdCl[(CNC)]BF 4 and [PdMe(CNC)]BF 4 (CNC=2,6-bis[(3-methylimidazolin-2-yliden-1-yl)methyl]pyridine), in which the pyridyl and both carbene moieties are coordinated to a single palladium(II). The palladium(II) complexes have been fully characterised, including X-ray crystallography, and exhibit good activities in the Heck coupling reaction of 4-bromoacetophenone and n-butyl acrylate.

Synthesis of Palladium Benzyl Complexes from the Reaction of PdCl2[P(OPh)3]2 with Benzyl Bromide and Triethylamine: Important Intermediates in Catalytic Carbonylation

The palladium complex PdCl2(P(OPh)3)2 is reduced to Pd(P(OPh)3)4 by tertiary amines (NEt3, NPr3, NBu3) in the presence of water. The formation of aldehydes and corresponding secondary amines in this reaction has confirmed the role of amines as reducing agents. The new palladium benzyl complexes, cis-[PdBr2(CH2Ph)(P(OPh)3)][PhCH2NEt3] (1) and [PdBr(CH2Ph)(P(O-o-MeC6H4)3)]2 (2a), were obtained in one-step syntheses from PdCl2(P(OPh)3)2 or PdCl2[P(O-o-MeC6H4)3)]2, NEt3, and benzyl bromide and X-ray characterized. The air oxidation of complex 1 led to [PdBr3(P(OPh)3)][PhCH2NEt3] (4) with the abstraction of benzaldehyde.

Palladium(II) beta-agostic alkyl cations and alkyl ethylene complexes: investigation of polymer chain isomerization mechanisms.

A series of stable dialkyl complexes of Pd, (alpha-diimine)PdR2 (alpha-diimine = aryl-substituted diimine, R = n-Pr, n-Bu, i-Bu), have been prepared via Grignard alkylation of the corresponding (alpha-diimine)PdCl2 complexes. Protonation of these dialkyl species at low temperature results in loss of alkane and formation of cationic Pd beta-agostic alkyl complexes, which have been observed as intermediates in the polymerization of ethylene and propylene by these Pd catalysts. Studies of the structure and dynamic behavior of these alkyl complexes are presented, along with the results of trapping reactions of these species with ligands such as NCMe, CO, and C2H4. Trapping with ethylene results in formation of cationic alkyl ethylene complexes which model the catalyst resting state in these systems. These complexes have been used to obtain mechanistic details and kinetic parameters of several processes, including isomerization of the alkyl ethylene complexes, associative and dissociative exchange with free ethylene, and migratory insertion rates of both primary and secondary alkyl ethylene species. These studies indicate that the overall branching observed in polyethylenes produced by these Pd catalysts is governed both by the kinetics of migratory insertion and by the equilibria involving the alkyl ethylene complexes.

Neutral and Cationic Palladium(II) Complexes of a Diazapyridinophane. Structure, Fluxionality, and Reactivity toward Ethylene

The palladium complexes (t-Bu-N4)PdCl2 (1), (t-Bu-N4)PdMeCl (2), (t-Bu-N4)PdMe(NCMe)+BAr4- (3), and (t-Bu-N4)PdMe(C2H4)+BAr4- (4) [t-Bu-N4 = N,N‘-ditertiobutyl-2,11-diaza[3.3](2,6)pyridinophane, Ar = 3,5-(CF3)2-C6H3] have been synthesized and characterized by VT 1H NMR and X-ray (for 1 and 3) analysis. The macrocyclic ligand is only bi- or tridentate, both coordination modes coexisting in solution for 1 and 3. Cationic methyl-ethylene complex 4 decomposes readily through insertion of ethylene into the Pd−Me bond, and ethylene polymerization with use of 1 (in the presence of MAO) or 3 as catalysts is therefore precluded. Complexes 1, 3, and 4 are fluxional, the t-Bu-N4 ligand undergoing an η2−η3 oscillatory process (ΔG⧧ = 14.1−14.9 kcal mol-1) as well as hindered rotation of the t-Bu substituent of the coordinated amine function around the corresponding N−C bond (ΔG⧧ = 8.8−10.1 kcal mol-1).

Syntheses and Structures of New Luminescent Cyclometalated Palladium(II) and Platinum(II) Complexes: M(Bab)Cl, M(Br−Bab)Cl (M = Pd(II), Pt(II)), and Pd3Cl4(Tab)2 (Bab = 1,3-bis(7-azaindolyl)phenyl, Br−Bab = 1-Bromo-3,5-bis(7-azaindolyl)phenyl, Tab =1,3,5-tris(7-azaindolyl)phenyl)

The reactions of blue luminescent ligands 1,3-bis(7-azaindolyl)benzene (BabH), 1-bromo-3,5-bis(7-azaindolyl)benzene (Br−BabH), and 1,3,5-tris(7-azaindolyl)benzene (TabH) with K2PdCl4 and K2PtCl4 have been investigated. Five new luminescent cyclometalated palladium(II) and platinum(II) complexes Pd(Bab)Cl (1), Pt(Bab)Cl (2), Pd(Br−Bab)Cl (3), Pt(Br−Bab)Cl (4), and Pd3Cl4(Tab)2 (5) have been synthesized and fully characterized. The molecular structures of 1 and 2, and 3 and 4, are similar. There are however significant variations in the solid-state structures and luminescence of 1 and 2, and 3 and 4. EHMO calculations revealed that it is most likely that the electronic transitions in the Pt(II) complexes are π to π* transitions with significant contributions from dπ lone pairs of the Pt(II) center in the π level, and the electronic transitions in the Pd(II) complexes are either d(z2) to π* charge-transfer transitions or π to π* transitions similar to the Pt(II) complexes.

Methanofullerene-Based Palladium Bis(amino)aryl Complexes and Application in Lewis Acid Catalysis

Synthetic routes have been developed for the attachment of palladium(II) bis(amino)aryl (NCN or C6H2{CH2NMe2}2-2,6)- complexes to C60. Using diazo and Bingel addition reactions, various methanofullerene NCN-SiMe3 compounds (C60-L-NCN-SiMe3, L = C(Me), C(CO2Et)CO2CH2, and C(Me)C6H4CC) have been prepared and characterized. Electrophilic palladation of these ligands was achieved with Pd(OAc)2, leading to the corresponding C60-L-NCN·PdCl complexes. These were converted into active Lewis acid catalysts for the aldol condensation and the Michael reaction. Catalytic tests show that the activity of cationic methanofullerene NCN-palladium complexes in the aldol reaction between benzaldehyde and methyl isocyanoacetate is comparable to the parent unsupported NCN palladium complex. However, in the Michael reaction of methyl vinyl ketone and ethyl cyanoacetate, the fullerene catalysts are not only significantly slower but also undergo a deactivation/decomposition process during the reaction. Preliminary retention measurements using a nanofiltration membrane have shown 72% retention of the palladium complex C60-C(Me)-(NCN)PdCl.

ChemInform Abstract: Weakly Ligated Palladium Complexes PdCl2(RCN)2 in Piperidine: Versatile Catalysts for Sonogashira Reaction of Vinyl Chlorides at Room Temperature.

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Cyclopalladation versus hydroxylation. A case of pH dependence

1-Alkyl-2-(naphthyl-α-azo)imidazoles (NaiR, 2) (C 10H 7NNC 3H 2N 21R; R=Me ( a), Et ( b), PhCH 2 ( c)) have been reacted with Na 2PdCl 4 in MeOH or MeCN solutions of Pd(MeCN) 2Cl 2 to synthesise Pd(NaiR)Cl 2 ( 3). The reaction of Pd(OAc) 2 in boiling benzene with NaiR followed by the addition of LiCl has resulted in the synthesis of the cyclopalladated complex Pd(NaiRH)Cl ( 4). The ligand, NaiR, acts as a N, N′-bidentate chelator while NaiRH acts as a tridentate N, N′, C-cyclometallating ligand. The infrared spectra of 3 exhibit two PdCl stretches correspond to a cis-PdCl 2 geometry, and a single ν(PdCl) band in 4 suggests one PdCl bond. Cyclopalladation is supported by a single crystal X-ray crystal structural study of Pd(NaiEtH)Cl ( 4b) and the metallation takes place at C(8′)-position. The solution of Pd(NaiR)Cl 2 ( 3) is also irreversibly transformed into Pd(NaiRH)Cl ( 4) when the pH is adjusted to 4.5–6.0 by NaOAc or other bases (NaOMe, NaOH, LiOH, Li 2CO 3 etc.). At higher pH values (8–10) the reaction shows the chelative hydroxylation at the C(2′)-site to synthesise Pd(NaiRO)Cl ( 5). The structure of the hydroxylated blue product is also supported by a single crystal X-ray crystal structure of Pd(NaiEtO)Cl ( 5b). The reaction of Pd(NaiR)Cl 2 in MeCN with dilute sodium hydroxide in air, or aqueous silver nitrate under boiling conditions, or its treatment with Tollen's reagent in MeCN solution under ambient conditions has also yielded the hydroxylated product. All the compounds have been characterised by elemental analyses, IR, UV–vis and 1H-NMR data. The solution spectral behaviour has been interpreted by EHMO calculations.

Enhancement of CO Insertion into a Pd−C Bond in a Pd−Co Heterodinuclear Complex

A series of Pd-containing heterodinuclear methyl complexes, (dppe)(CH3)Pd−MLn (MLn = MoCp(CO)3, WCp(CO)3, Co(CO)4; dppe = 1,2-bis(diphenylphosphino)ethane), have been prepared by the metathetical reactions of Pd(CH3)(NO3)(dppe) with Na+[MLn]-, and the complexes were characterized by spectroscopic methods and/or X-ray structure analysis. Related Pt-containing dinuclear complexes were similarly prepared and characterized. The rate of CO insertion into a Pd−CH3 or Pt−CH3 bond was investigated using these complexes. The Pd−Co complex (dppe)(CH3)Pd−Co(CO)4 shows a high activity of CO insertion, giving (dppe)(CH3CO)Pd−Co(CO)4, and the initial rate is ca. 80 times higher than those of the analogous complex Pd(CH3)Cl(dppe). Whereas slow insertion of CO is observed in the Pt−Co complex (dppe)(CH3)Pt−Co(CO)4, no reaction takes place for Pt(CH3)Cl(dppe). It is revealed by using 13CO that CO in the Co(CO)4 fragment preferentially inserts into the Pd−CH3 bond over CO in the gas phase. The carbonyl insertion reaction in the Pd−Co heterodinuclear complex has been theoretically studied using B3LYP hybrid density functional theory to clarify its reaction mechanism and the electronic factors controlling the reaction. The calculations for a model complex, (H2PCH2CH2PH2)Pd(CH3)−Co(CO)4, have shown that the most favorable reaction path consists of methyl migration from the Pd to the Co atom, carbonyl insertion reaction on the Co atom, CO coordination to the Co atom, and acetyl migration from the Co atom to the Pd atom, which is in accord with the experimental results. The electron donation from the Pd d orbital to the bridging CO π* orbitals plays an important role in stabilizing the intermediates and transition states.

Weakly ligated palladium complexes PdCl 2(RCN) 2 in piperidine: versatile catalysts for Sonogashira reaction of vinyl chlorides at room temperature

Copper iodide and weakly ligated palladium complexes PdCl 2(RCN) 2 (R=Ph, Me) catalyzed efficiently the coupling reaction of vinyl chlorides with 1-alkynes in the presence of piperidine to give the corresponding conjugated enynes in good to excellent yields. The reaction takes place rapidly and cleanly at room temperature. Application to the synthesis of terbinafine which exhibits strong antimycotic activity has been realized.

1,2-Bis-[(5-methyl/chloro/nitro)-2-1H-benzimidazolyl]-1,2-ethanediols and their PdCl2 complexes

1,2-Bis-[(5-methyl)-2-1H-benzimidazolyl]- (L1), 1,2-bis-[(5-chloro)-2-1H-benzimidazolyl]- (L2), 1,2-bis-[(5-nitro)-2-1H-benzimidazolyl]-1,2-ethanediol (L3) and their PdCl2 complexes were synthesized and characterized by elemental analysis, molar conductivity, i.r. and 1H-n.m.r. spectra. The benzene ring substituents lead to a decrease in melting point. The methyl group reduces the solubility and the acidity of L1 and Pd(L1)Cl2, whereas the Cl and NO2 groups increase the solubility and the acidity of L2, L3, Pd(L2)Cl2 and Pd(L3)Cl2. In Pd(L1)Cl2 and Pd(L2)Cl2 complexes, the ligands act as a bidentate through two nitrogen atoms. In Pd(L3)Cl2, ligand coordination occurs through one OH group oxygen atom and one of the benzimidazole nitrogen atoms.

Chemistry of Azopyrimidines. Part III. Synthesis, Spectral Characterization and Electrochemical Studies of Arylazopyrimidine Complexes of Palladium(II) and Catecholato Derivatives

2-(Phenylazo)pyrimidine (papm), 2-(p-tolylazo)pyrimidine (p-tapm), 2-(p-chlorophenylazo)pyrimidine (p-Clpapm) are used as N,N′-chelators. They are called arylazopyrimidines and abbreviated in general as aapm (1). They were reacted with cis-Pd(MeCN)2Cl2 to yield orange-red complexes of the type Pd(aapm)Cl2 (2). Upon reaction with catechols in the presence of triethylamine (Et3N), Pd(aapm)Cl2 yielded the mixed-ligand complexes [Pd(aapm)(O,O)] where O,O = pyrocatecholate [cat, (3)], 4-tert-butylcatecholate [tbcat, (4)], 3,5-di-tert-butylcatecholate [dtbcat, (5)] and tetrachlorocatecholate [tccat, (6)]. The complexes were characterised by elemental analyses, IR spectra, UV-VIS spectra and 1H NMR spectra. The redox properties were examined with cyclic voltammetry. [Pd(aapm)(O,O)] exhibits four successive redox responses and the E12 values are highly sensitive to the nature of the substituents. The electronic spectra of [Pd(aapm)(O,O)] exhibit ligand-to-ligand charge transfer transitions and are different from those of Pd(aapm)Cl2 The band position is largely dependent on the substituent type of the catechol frame and is tentatively assigned to the 3bi (cat)→π*(aapm) transition.

ChemInform Abstract: Enantioselective Diene Cyclization/Hydrosilylation Catalyzed by Optically Active Palladium Bisoxazoline and Pyridine-Oxazoline Complexes.

A 1:1 mixture of (N−N)Pd(Me)Cl [N−N = (S,S)-4,4‘-dibenzyl-4,5,4‘,5‘-tetrahydro-2,2‘-bisoxazoline] (S,S-4a) and NaBAr4 [Ar = 3,5-C6H3(CF3)2] (5 mol %) catalyzed the asymmetric cyclization/hydrosilylation of dimethyl diallylmalonate (2) and triethylsilane at −30 °C for 48 h to form an 8.1:1 mixture of the silylated carbocycle (S,S)-trans-1,1-dicarbomethoxy-4-methyl-3-[(triethylsilyl)methyl]cyclopentane (S,S-3) (95% de, 72% ee) and dimethyl 3,4-dimethylcyclopentane-1,1-dicarboxylate (S,S-6) in 64% combined yield. In comparison, a 1:1 mixture of the palladium pyridine−oxazoline complex (N−N)Pd(Me)Cl [N−N = (R)-(+)-4-isopropyl-2-(2-pyridinyl)-2-oxazoline] (R-5b) and NaBAr4 (5 mol %) catalyzed the asymmetric cyclization/hydrosilylation of 2 and triethylsilane at −32 °C for 24 h to form carbocycle S,S-3 in 82% yield (>95% de, 87% ee) as the exclusive product. Asymmetric diene cyclization catalyzed by complex R-5b was compatible with a range of functional groups and produced carbocycles with up to 91% ee. The pro...

ChemInform Abstract: Synthesis of New Acyclic Aminophosphites and Their Chelate Complexes with Rhodium(I) and Palladium(II).

New acyclic aminophosphites (RO)2POCH2CH2NMe2 (PN) (R=Et, Pri, or adamantyl) characterized by various steric requirements of the phosphorus center were synthesized. The reactions of the aminophosphites with Pd(COD)Cl2 (COD is 1,5-cyclooctadiene) and [Rh(CO)2Cl]2 afforded the stable chelate mononuclear complexes PdCl2(PN) and RhClCO(PN), respectively. The structures of the resulting compounds were established by1H,13C, and31P NMR and IR spectroscopy, X-ray diffraction analysis, laser and plasma desorption mass spectrometry, X-ray photoelectron spectroscopy, and sedimentation analysis.

Development, Synthetic Scope, and Mechanistic Studies of the Palladium-Catalyzed Cycloisomerization of Functionalized 1,6-Dienes in the Presence of Silane

A 1:1 mixture of the π-allyl palladium complex (η3-C3H5)Pd(Cl)PCy3 (1a) and NaB[3,5-C6H3(CF3)2]4 in the presence of HSiEt3 catalyzed the cycloisomerization of diethyl diallylmalonate (2b) to form 4,4-dicarbomethoxy-1,2-dimethylcyclopentane (3b) in 98% yield with 98% isomeric purity. The procedure tolerated a range of functionality including esters, ketones, sulfones, protected alcohols, and substitution at the allylic and terminal olefinic carbon atoms. Cycloisomerization of 2b obeyed zero-order kinetics to >3 half-lives with initial formation of 1,1-dicarboethoxy-4-methyl-3-methylenecyclopentane (4b), followed by secondary isomerization to 3b. Deuterium labeling studies revealed that the conversion of 2b to 4b was accompanied by significant H/D exchange, consistent with an addition/elimination pathway coupled with facile H/D exchange of the Pd−H(D) intermediates with free silane.

Synthesis and Solid State and Solution Characterization of Mono- and Di-(η1-C) Carbamoyl−Palladium Complexes. New Efficient Palladium-Catalyzed Routes to Carbamoyl Chlorides: Key Intermediates to Isocyanates, Carbamic Esters, and Ureas

Pd complexes have been used in catalytic conversion of primary and secondary amines into isocyanates or carbamoyl chlorides, respectively. The latter have been used as intermediates for the synthesis of carbamates and ureas. The palladium-based catalytic system is very active and operates in two steps, avoiding the synthesis of phosgene (COCl2), but making use of CO and Cl2 as in phosgene chemistry. In the first step the palladium(II) complex PdCl2L2 [L2 = 2,2‘ dipyridine (dipy) or 1,10-phenantroline (phen); L = triphenylphosphine (PPh3)] reacts with the amine [NH2R, R = n-C3H7 (a), n-C4H9 (b), n-C5H11 (c); NHRR‘, NRR' = CH2(CH2)4N (d), CH2(CH2OCH2)CH2N (e)] and CO to produce the carbamoyl complexes PdCl(CONHR)L2 and PdCl(2-x)(CONRR‘)xL2 (x = 1, 2). When primary amines NH2R, (a, b, and c) are used, only monocarbamoyl complexes [PdCl(CONHR)(dipy) (1a−c), PdCl(CONHR)(phen) (2a−c), and PdCl(CONHR)(PPh3)2 (3a,b)] are isolated. Secondary amines NHRR‘ (d and e) afford both monocarbamoyl PdCl(CONRR‘)(dipy) (4d,e) and PdCl(CONRR‘)(phen) (5d,e) and dicarbamoyl complexes, Pd(CONRR‘)2(dipy) (6d,e) and Pd(CONRR‘)2(phen) (7d). 4d and 6d have been structurally characterized: they are the first example of mono- and dicarbamoyl complexes, respectively, of the same metal system for which the solid state structure is reported.The carbamoyl complexes are subsequently reacted with halogen donors (CuCl2, N-chlorosuccinimide, Cl2, I2) with elimination of the carbamoyl ligand as isocyanate (primary amines complexes 1−3) or carbamoyl chloride (secondary amines complexes 4−7) and quantitative formation of the starting Pd(II) complex. Cl2 and I2 are most effective and selective. They do not generate byproducts and allow an easy and quantitative recovery of the catalyst, making the reaction of potential utility.

CP/MAS NMR and X-ray crystallographic characterization of trans-PdX2(PPh2vinyl)2 (X = Cl, I); UV and Et2O·BF3 reaction studies, including the formation of [Pd(µ-Cl)(PPh2vinyl)2]2[BF4]2

The complexes PdCl2(PPh2vinyl)2 and PdI2(PPh2vinyl)2 have been prepared and crystallographically characterized as their trans square planar isomers. Trans-PdCl2(PPh2vinyl)2 exists in a centrosymmetric structure with a planar PdCl2P2 core whereas trans-PdI2(PPh2vinyl)2 shows no local Pd-centred symmetry and significant distortion of the PdI2P2 core from planarity. Crystallographic data is in accord with the 31P{1H} CP/MAS NMR spectra of the two complexes, which display a single resonance for the chloro-complex and two resonances for the iodo-complex. UV irradiation of CH2Cl2 solutions of PdCl2(PPh2vinyl)2 followed by re-dissolution in CDCl3 indicates no permanent chemical change. However, post-irradiation CP/MAS 31P{1H} NMR spectroscopy demonstrates the presence of trans-PdCl2(PPh2vinyl)2 in two solid state structures, plus cis-PdCl2(PPh2vinyl)2. PdI2(PPh2vinyl)2 exists only in its trans form in both solid state and solution. Irradiation results in phosphine displacement and the formation of sym-[PdI2(PPh2vinyl)]2 and free phosphine, the latter being characterized as Ph2P(O)vinyl following aerobic oxidation. PdCl2(PPh2vinyl)2 reacts in the presence of Et2O·BF3 to afford [Pd(µ-Cl)(PPh2vinyl)2]2[BF4]2 whereas PdI2(PPh2vinyl)2 is recovered in 95% yield, with the remaining material undergoing phosphine abstraction to form sym-[PdI2(PPh2vinyl)]2.Key words: palladium, phosphine, alkene, isomerization, CP/MAS.

Kinetics and mechanism of styrene hydroalkoxycarbonylation catalyzed by the complex PdCl2(Ph3P)2 in the presence of butanol

The single-factor experiment method was used to study the kinetics of styrene hydrobutoxycarbonylation catalyzed by the complex PdG2(Ph3P)2 in dioxane (383 K, [BuOH] = 1–8 mol/1). The rates of accumulation of the regioisomeric reaction products as empirical functions of CO pressure and concentrations of styrene, triphenylphosphine, and the catalyst were found. The acyl complex (PhC2H4CO)PdCl(Ph3P)2 was isolated from the reaction mixture. The assumed intermediate of an alcoholate mechanism, the (BuOOC)PdCl(Ph3P)2 complex, is not formed by the reaction of PdCl2(Ph3P)2 with CO and butanol. The set of data generally corresponds to a hydride mechanism of styrene hydrocarboxylation, which includes three key intermediates HPdCIL2-n(CO)n (n= 0–2). A change in the solvation properties of the reaction medium due to the replacement of water by butanol affects the kinetic scheme of the process.