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The complex [NiCl2{Ph2POCH2oxMe2}] (Ph2POCH2oxMe2 ) 2-((diphenylphosphinooxy) methyl)-4,4-dimethyl-4,5-dihydrooxazole) 14 has been synthesized by reaction of solid [NiCl2(DME)] (DME ) 1,2-dimethoxyethane) with a CH2Cl2 solution of the P,N ligand. X-ray diffraction studies on its red crystals established the mononuclear nature of the complex 14a, whose metal center has a distorted tetrahedral coordination geometry. Recrystallization of 14a from a toluene-pentane/CH2Cl2 solution at temperatures below 253 K afforded green crystals of the dinuclear, chloride-bridged, formula isomer complex 14b. Conversion of 14b to 14a was observed as a function of temperature, both in the solid-state and in solution. Together with other Ni(II) complexes containing a chelating P,N ligand of the type phosphinoor phosphinito-oxazoline or phosphino-thiazoline, 14a has been evaluated as precatalyst in the oligomerization of ethylene, with AlEtCl2 or MAO as cocatalyst, or propylene, with MAO as cocatalyst. With AlEtCl2 as activator (6 equiv), the catalytic activities with ethylene were generally modest and [NiCl2{Ph2PCH2ox}] (Ph2PCH2ox ) 2-((diphenylphosphinooxy)methyl)-4,5-dihydrooxazole) 1 was the most active, with turnover frequencies (TOF) up to 7.9 × 104 mol of C2H4 (mol Ni × h)-1, whereas 14a, activated with 2 equiv of AlEtCl2, was the most selective for ethylene dimers (up to 96%) and 1-butene (up to 22%). With MAO as cocatalyst, complex 1 was again the most active, with TOF values up to 23 × 104 mol of C2H4 (mol Ni × h)-1. The highest selectivity for butenes was observed with complex [NiCl2{Ph2PCH2thiazMe2}] 3. With propylene, TOFs up to 3.3 × 104 mol of C3H6 (mol Ni × h)-1 were obtained with [NiCl2{Ph2POCH2pyridine}] 8 and selectivities for C6 products higher than 98.5% were observed with precatalysts 3, [NiCl2{t-Bu2POCH2pyridine}] 9, and 14a.

In this paper are described the synthesis, characterization, and coordinating properties of a new potentially pentadentate nitrogen ligand, CyAr2N5, that combines in the same molecular structure 2,6-bis(imino)-pyridine and (imino)pyridine moieties. This ligand reacts with 1 or 2 equiv of anhydrous MCl2 (M ) Fe, Co) to give paramagnetic mononuclear or homodinuclear complexes of the formula CyAr2N5MCl2 and CyAr2N5M2Cl4. In the dinuclear complexes, one metal center is five-coordinate, while the other is fourcoordinate. Ligand and metal complexes have been characterized, both in the solid state and in solution, by a variety of techniques, including single-crystal X-ray diffraction analyses, magnetic susceptibility determinations, IR, vis-NIR, 1H NMR, and X-band EPR spectroscopies. On activation by methylaluminoxane (MAO) in toluene, the FeII and CoII complexes generate effective catalysts for the oligomerization of ethylene to R-olefins with productivities and Schulz-Flory parameters depending on the type and number of the coordinated metals. In an attempt to rationalize the surprisingly high activity of the CoII precursors, and in particular that of the dinuclear derivative CyAr2N5Co2Cl4, which is 4 times higher than that of the mononuclear analogue CyAr2N5CoCl2, a CoII complex has been synthesized where the supporting ligand is sterically similar to CyAr2N5, yet it contains only the three nitrogen donor atoms of the 2,6-bis-(imino)pyridine moiety. From this study, it is concluded that all five nitrogen atoms of CyAr2N5 play an active role under catalytic conditions, even when the precursor contains a free (imino)pyridine moiety.

The position of the sulfur atom in the thienyl group of 6-(thienyl)-2-(imino)pyridine ligands strongly affects the catalytic activity of the corresponding tetrahedral high-spin dihalide CoII complexes in the oligomerization of ethylene to -olefins upon activation with methylaluminoxane (MAO). Complexes with the sulfur atom in the 3-position of the thienyl ring catalyze the selective conversion of ethylene to 1-butene, while catalysts containing thien-2-yl groups give C4 C14 alfa-olefins. In situ EPR experiments showed the occurrence of a spin state changeover with the formation of low-spin CoII species upon activation of the catalyst precursors by MAO. DFT calculations suggest that only thien-2-yl rings allow for the coordination of the sulfur atom to the cobalt center in the MAO-activated systems.

The iridium complexes [Ir(PBz3)2(COD)]PF6 and [Ir(py)(PBz3)(COD)]PF6 are effective catalyst precursors for the homogeneous hydrogenation of N-(β-naphthylmethylene)aniline (NβNA) to naphthalene-2-ylmethylphenylamine (PBz3 = tribenzylphosphine; COD = 1,5-cyclooctadiene; py = pyridine). For comparative purposes, other iridium and rhodium catalysts modified with either PBz3 or PPh3 have been tested as catalysts for NβNA hydrogenation. A kinetic study of this reaction catalyzed by [Ir(PBz3)2(COD)]PF6, [Ir(py)(PBz3)(COD)]PF6, and [Rh(PPh3)2(COD)]PF6, together with in situ NMR experiments, has led us to propose catalytic cycles for the three precursors.

Some rhodium(I) complexes of the general formula [Rh(P-P)(COD)]X were synthesized and characterized by multinuclear NMR spectroscopy (COD ) cyclocta-1,5-diene; P-P ) 1,1¢-bis(diphenylphosphino)ferrocene, dppf, X ) BPh4, PF6; P-P ) 1,1¢-bis(diphenylphosphino) ruthenocene, dppr, X ) BPh4; P-P ) 1,1¢-bis(diphenylphosphino)osmocene, dppo, X ) BPh4, PF6; P-P ) 1,1¢-bis(diphenylphosphino)octamethylferrocene, dppomf, X ) BAr¢4; P-P ) (1,1¢-bis(di(o-isopropylphenyl)phosphino)ferrocene, o-iPr-dppf, X ) BAr¢4). These complexes were employed as catalyst precursors for the hydroformylation of 1-hexene in THF either in standard autoclaves or in high-pressure (HP) NMR tubes and IR cells. All catalysts exhibited good activity (TOFs ranging from 700 to 1000 mol aldehyde (mol cat)-1 h-1) and moderate regioselectivity in n-heptanal (67-74%). Irrespective of the rhodium precursor, the HP-NMR experiments under catalytic conditions showed the formation of kinetic dicarbonyl products at room temperature, which were independently prepared by reaction of the COD precursors with 1 bar CO in THF. Square-planar dicarbonyl complexes containing two cis carbonyl groups were obtained with the dppf and dppomf ligands, while the precursors with the dppr, dppo, and o-iPr-dppf ligands gave trigonal-bipyramidal dicarbonyl complexes with the equatorial positions occupied by two carbonyl groups and by the metallocene metal atom. The complexes [Rh(CO)2(dppf)]PF6 and [Rh(CO)2(dppo)]PF6 were isolated in the solid state and characterized by single-crystal X-ray analysis. On increasing gradually the temperature of the HP-NMR hydroformylation experiments, the dppf, dppr, and dppo dicarbonyl complexes disappeared. Formed in their place were neutral fivecoordinate hydride(dicarbonyl) complexes RhH(CO)2(P-P) that exist in solution as two rapidly equilibrating geometric isomers. The reaction of the o-iPr-dppf precursor with syngas at 60 °C gave a trigonal-bipyramidal dicarbonyl complex with a dative Fe-Rh bond, while the dppomf complex decomposed to various CO-containing rhodium complexes. Unlike HPNMR spectroscopy, HP-IR spectroscopy showed no kinetic product at any stage of the catalytic reactions. Also, HP-IR spectroscopy allowed us to distinguish the ee and ea geometric isomers of the hydride(dicarbonyl) resting states with dppf, dppr, and dppo. Irrespective of the temperature, o-iPr-dppf formed a stable dicarbonyl complex as a result of the catalytic reaction, while the dppomf dicarbonyl was unstable under hydroformylation conditions, converting into phosphine-free carbonyl Rh compounds.

Palladium(II) complexes with the formula [Pd(H2O)(OTs)(P-P)]OTs, where P-P is 1,1‘-bis(dimethylphosphino)ferrocene (dmpf), 1,1‘-bis(diethylphosphino)ferrocene (depf), or 1,1‘-bis(diisopropylphosphino)ferrocene (dippf), have been synthesized and used to catalyze the carbonylation of ethylene in MeOH, water, or a 1/1 water/1,4-dioxane mixture. In MeOH, the reactions catalyzed by the dmpf and depf complexes gave alternating polyketone (alt-E-CO), while methyl propanoate and 3-pentanone were selectively produced with the dippf catalyst. The last catalyst was inactive in aqueous solvent. In contrast, the dmpf and depf catalysts were active in either water or water/1,4-dioxane for the copolymerization of CO with ethylene. These two catalysts were efficient also for the terpolymerization of CO with ethylene and propene in MeOH or water/1,4-dioxane. Operando high-pressure NMR experiments and in situ reactions with model compounds have provided useful information to rationalize the activity and selectivity of the ...

The mechanism of the Pd-catalyzed cross-coupling reaction between tributyltin acetylides and metal iodides has been investigated with the use of a model Mo precursor bearing a ligand with appropriate steric and electronicproperties. This study has allowed us to intercept the tetrametallic Pd 2 -Mo 2 complex Ph(Bu)P(η 5 -C 5 H 4 )Mo(CO) 3 Pd(μ-I) 2 PdMo(CO) 3 (η 5 -C 5 H 4 )-P(Ph)Bu, which is a precursor to the catalytically active solvento complex Ph(Bu)P(η 5 -C5H4)Mo(CO)3PdI(DMF). Both complexes play a key role in Pd-catalyzed cross-coupling reactions between tributyltin acetylides and metal iodides, leading to metal-σ-alkynyls. The catalytic cycle for such a reaction has been further elucidated, especially with regard to the role of the ligands in the metal iodide for the stabilization and/or detection of the intermediates as well as for the formation of the M-alkynyl product.

The reaction in MeOH between the bis-chelate complex [Pd(dppe)2](OAc)2 and Pd(OAc)2 to give the monochelate product Pd(OAc)2(dppe) is assisted by free acetate ion, and its rate is proportional to the concentrations of both reagents (dppe = 1,2-bis(diphenylphosphino)ethane). The aggregation of Pd(OAc)2 in CH2Cl2 and the low dielectric constant of this solvent are proposed to be important factors in accelerating the formation of Pd(OAc)2(dppe) in CH2Cl2.

The Pd(II) methyl complexes [Pd(Me)(MeCN)(P-P)]PF6 are effective catalyst precursors for the alternating copolymerization of carbon monoxide with ethene in CH2Cl2 (P-P ) 1,3- bis(diphenylphosphino)propane (dppp), meso-2,4-bis(diphenylphosphino)pentane (meso-bdpp), rac-2,4-bis(diphenylphosphino)pentane (rac-bdpp)). The productivity in high molecular weight polyketones within 30 min follows the ligand order dppp > meso-bdpp > rac-bdpp. All the methyl precursors exhibit comparable values of both intrinsic activity and energy barriers to migratory insertions [Pd(Me)(CO), Pd(COMe)(C2H4)] as well as opening of â-chelates [Pd- (CH2CH2C(O)Me)(P-P)]+ by CO. It is concluded that the presence and/or stereochemistry of methyl groups in the 1,3-positions of dppp do not exert a significant influence on the propagation rate of the copolymerization reaction in CH2Cl2. High-pressure NMR studies under catalytic conditions show the occurrence of chain transfer by protonolysis with adventitious water to give í-hydroxo compounds [Pd(í-OH)(P-P)]2 2+. With time, the bischelates [Pd(P-P)2]2+ are the only species visible on the NMR time scale. Independent copolymerization reactions in CH2Cl2 with either í-OH or bis-chelate precursors show that both resting states can reenter the catalysis cycle to give alternating polyketones with productivities increasing in the orders [Pd(í-OH)(rac-bdpp)]2 2+ < [Pd(í-OH)(meso-bdpp)]2 2+ < [Pd(í-OH)(dppp)]2 2+, and [Pd(rac-bdpp)2]2+ < [Pd(dppp)2]2+ < [Pd(meso-bdpp)2]2+. On the basis of the batch reactions and in situ NMR experiments it is suggested that both í-hydroxo and bis-chelate compounds contribute appreciably to determine the overall productivity of the methyl precursors [Pd(Me)(MeCN)(P-P)]+ in CH2Cl2. The bis-chelates are also active catalysts for the CO/ethene copolymerization in MeOH with productivities that increase in the ligand order dppp , rac-bdpp < meso-bdpp.

Several palladium(II) complexes with 1,1‘-bis(diphenylphosphino)octamethylferrocene (dppomf) and its oxidized form 1,1‘-bis(diphenylphosphino)octamethylferrocenium (dppomf+) have been synthesized and characterized by spectroscopic and electrochemical methods. For comparative purposes, analogous Pd(II) derivatives with 1,1‘-bis(diphenylphosphino)ferrocene (dppf) have been also prepared. Single-crystal X-ray analyses have been carried out for the square-planar mononuclear compounds [Pd(H2O)2(dppf)](OTf)2 and [Pd(H2O)2(dppomf)](OTf)2 and for the binuclear complex [Pd(μ-OPF2O)(dppomf+)]2(BF4)4·6CH2Cl2 in which two [Pd(dppomf+)]3+ moieties are held together by the oxygen atoms of two bridging PO2F2- groups derived from the oxidative degradation of PF6- ions. Selected dppf and dppomf Pd(II) complexes have been employed as catalyst precursors for the methoxycarbonylation of ethene (600 psi, 1:1 CO/C2H4, 85 °C). It has been found that dppomf generates selective catalysts for the production of methyl propanoate, w...

Reaction of the rhenium(I) allenylidene complex [Re{C=CCPh 2 }(CO) 2 (triphos)]OTf (1; triphos = MeC(CH 2 PPh 2 ) 3 , OTf = OSO 2 CF 3 ) with thiophenol, 2-thionaphthol, or allyl mercaptan gave selectively the α,β-unsaturated thiocarbene complexes [Re{C(SR)CH=CPh 2 }-(CO) 2 (triphos)]OTf(R = Ph (2), α-naphthyl (3), CH 2 CH=CH 2 (4)). A reversible reaction was observed for PhSH in DMSO at 80 °C. Compounds 2 and 3 have been found to react with sodium alkoxides, yielding the kinetic thioallenyl products [Re{C(SR)=C=CPh 2 }(CO) 2 -(triphos)] (R = Ph (6a), α-naphthyl (7a)). These equilibrated in room-temperature solution with the thermodynamic thioalkynyl products [Re{C≡CC(SR)Ph 2 }(CO) 2 (triphos)] (R = Ph (6b), α-naphthyl (7b)) to give stationary states (6a/6b, 40/60; 7a/7b, 20/80). Deprotonation of the thioallyl complex 4 gave the stable allenyl derivative [Re{C(SCH 2 CH=CH 2 )=C=CPh 2 }'-(CO) 2 (triphos)] (8). Ammonia, aniline, and propargylamine each reacted with 1 to give the azoniabutadienyl compounds [Re{C(=NHR)CH=CPh 2 }(CO) 2 (triphos)]OTf (R = H (9), Ph (10), CH 2 C≡CH (11)) via N-H bond addition across the C α =C β double bond. NMR spectroscopy showed the γ-alkynylammonium complex [Re{C≡CCPh 2 (NH 3 )}(CO) 2 (triphos)]OTf(12) to be a transient intermediate along the reaction of 1 with ammonia. Treatment of 10 or 11 with sodium methoxide resulted in the selective deprotonation of the nitrogen atom to give the azabutadienyl compounds [Re{C(=NR)CH=CPh 2 }(CO) 2 (triphos)] (R = Ph (13), CH 2 C≡CH (14)). The molecular structure of the azoniabutadienyl complex 11 was determined by a single-crystal X-ray analysis. The geometry around the rhenium center conforms to a slightly distorted octahedron, with the polyphosphine sitting on a face of the coordination polyhedron. In keeping with the azoniabutadienyl structure, the Re-C,, bond length is 2.151(7) A, and the C α -N distance is 1.300(9) A.

The Ru(II) complex [(sulphos)Ru(NCMe)3](OSO2CF3) (1) has been immobilized on partially dehydroxylated high-surface-area silica via hydrogen-bonding interactions between the silanol groups of the support and the SO3- groups from both the sulphos ligand and the triflate counteranion (sulphos = -O3S(C6H4)CH2C(CH2PPh2)3). Compound 1 has been authenticated in the solid state by a single-crystal X-ray analysis and in solution by NMR spectroscopy, while its silica-grafted form [(sulphos)Ru(NCMe)3](OSO2CF3)/SiO2 (1/SiO2) has been characterized by DRIFT and CP MAS 31P NMR studies. The supported hydrogen-bonded (SHB) complex 1/SiO2 is an effective and selective catalyst for the hydrogenation of benzylideneacetone to benzylacetone and of benzonitrile to benzylidenebenzylamine in n-octane. No appreciable ruthenium leaching into the hydrocarbon phase was observed in either case. Analogous hydrogenation reactions catalyzed by either the aqueous-biphase catalyst 1 in water/n-octane or the homogeneous analogue [(triphos)...

The new optically pure C1-symmetric diphosphine ligand (R)-(R)-3-benzyl-2,4-bis(diphenylphosphino) pentane (BDPBzP) has been synthesized by enantioselective reduction of 3-benzyl-2,4-pentanedione with [((S)-BINAP)Ru(p-cymene)Cl]Cl, followed by the reaction of potassium diphenylphosphide with the bis(mesylate) intermediate (S)-(S)-PhCH2CH(CH- (OMs)CH3)2. The Ru(II) complexes [(BDPBzP)Ru(p-cymene)I]Iâ2CH2Cl2 (5), [(BDPBzP)- (DMSO)Ru(í-Cl)3RuCl(BDPBzP)] (6a), and [(BDPBzP)RuCl(CH3CN)3]OTf (7) have been prepared and characterized by multinuclear NMR spectroscopy. The p-cymene complex 5 has been authenticated by a single-crystal X-ray analysis. All Ru(II) complexes are effective catalyst precursors for the enantioselective hydrogenation of acetylacetone to (R)-(R)-2,4- pentanediol. The best catalytic performance in terms of enantioselective discrimination (ee's up to 99%) has been observed for the dimer 6a. An in situ high-pressure NMR study in catalytic conditions has shown that the nonclassical polyhydride dimer [(BDPBzP)(è2- H2)ClRu(í-H)2RuCl(è2-H2)(BDPBzP)] is the only species observed all over the catalytic cycle. The monohydrogenated intermediate (R)-4-hydroxypentan-2-one is obtained in appreciable yields only at low temperature or low conversion. The relative yields and ee's of the monoand dihydrogenated products are consistent with the effect of a double stereodifferentiation process.

The optically pure 2,6-bis(imino)pyridyl ligands (R)-2,6-bis{1-[α-methylbenzylimine]ethyl}pyridine [(R)-2,6-py(NCHMePh)2] and (S)-2,6-bis{1-(1-naphthyl)ethylimine]ethyl}pyridine [(S)-2,6-py(NCHMeNaph)2] have been prepared by condensation of 2,6-diacetylpyridine with (R)-(+)-α-methylbenzylamine and (S)-(−)-1-(1-naphthyl)ethylamine, respectively. These two ligands and others bearing different substituents on the imine nitrogen atoms (i.e., c-C6H11, C6H5, 2,6-Me2Ph) form, in combination with ruthenium(II) fragments, efficient catalysts for the cyclopropanation of styrene with ethyl diazoacetate (EDA). The catalyst precursors have the general formula RuCl2(PPh3){2,6-py(NR)2} (R = Cy,1; Ph, 6; CHMeNaph, 7; CHMePh, 8). It is generally found that the catalytic activity increases with the size of the substituents on the imine nitrogen atoms. Consistently, the solvento complex RuCl2{2,6-py(N(2,6-Me2Ph2)2}·CH2Cl2 is the most efficient in the series. Best results in terms of activity, diastereoselectivity, and enant...

The hydroformylation of 1-hexene with syngas (40 bar of 1:1 CO/H2) in the presence of the catalyst precursor RhH(CO)(PPh3)3 has been studied by high-pressure NMR spectroscopy in a 10 mm sapphire tube equipped with a Ti-alloy valve. Except for RhH(CO)2(PPh3)2, no direct observation of labile intermediates involved in the catalytic cycle has been detected; however as many as four rhodium resting states have been seen, and some factors controlling their formation/interconversion/inhibition have been identified. The information gathered from this in situ investigation is particularly relevant to a better understanding of the inhibiting action of the CO pressure as well as the positive action of PPh3 addition.

The complex [(triphos)(CO)2Re(OTf)] (1) reacts with disubstituted propargyl alcohols HC⋮CCR(R‘)OH in CH2Cl2 at room temperature (R = R‘ = Ph, Me; R = Ph, R‘ = Me), to give either allenylidene deriv...

Various primary amines and NH3 have been found to react in THF with the Ru(II) vinylidene complex fac,cis-[(PNP)RuCl2{CC(H)Ph}], affording aminocarbene derivatives of the general formula fac,cis-[(PNP)RuCl2{C(NHR)(CH2Ph)}] (PNP = CH3CH2CH2N(CH2CH2PPh2)2; R = CH3CH2CH2, Ph, cyclo-C6H11, (R)-(+)-CH(Me)(Ph), (R)-(−)-CH(Me)(Et), (S)-(−)-CH(Me)(1-naphthyl), H). With piperidine as the starting material, the tertiary aminocarbene fac,cis-[(PNP)RuCl2{C(NC5H10)(CH2Ph)}] has been obtained. The aminocarbene complexes are formed through an unforeseen mechanism in which 2 equiv of amine is involved: one serves to deprotonate the vinylidene Cβ carbon atom, while the other coordinates the metal center and then brings about an intramolecular nucleophilic attack onto the Cα carbon atom of a σ-phenylethynyl ligand. The (phenylethynyl)amine intermediates have been isolated and characterized. The aminocarbene derivative fac,cis-[(PNP)RuCl2{C(NH(S)-(−)-CH(Me)(1-naphthyl))(CH2Ph)}] has been authenticated by a single-crystal X...

Various five-coordinate ruthenium(II) complexes of the general formula RuCl2L, where L is a chiral triphosphine ligand, have been tested as catalyst precursors for the cyclopropanation of styrene u...

The orthometalated dihydride complex fac-exo-(R)-[IrH2{C6H4C*H(Me)N(CH2CH2PPh2)2}] is an effective catalyst precursor for the enantioselective hydrogenation of 2-methylquinoxaline (MeQ) to 2-methyl-1,2,3,4-tetrahydroquinoxaline (MeTHQ) with ee's up to 90% (5 bar of H2, MeOH, 100 °C). In-situ high-pressure NMR spectroscopy in catalytic conditions shows that the catalytically active species is generated by deorthometalation rather than by H2 reductive elimination. 1H NMR spectroscopy also suggests that the two CN groups in MeQ are hydrogenated at comparable rates.

On activation by MAO the CoII pyridinimine dichloride complex CoCl2N2Ph catalyzes the unprecedented enchainment of one norbornene molecule with two ethylene molecules to give exo-2,exo-3 ethyl-viny...

The reaction of [(triphos)RuH(BH4)] (1) in THF with KOBut yields the novel trihydride complex K[(triphos)RuH3] (2) and BH2OBut (triphos = MeC(CH2PPh2)3). The ruthenate complex 2 can also be synthesized by hydrogenation (30 bar of H2) in THF of the tris(acetonitrile) complex [(triphos)Ru(NCMe)3](BPh4)2 (3) in the presence of a 5-fold excess of BH2OBut at 40 °C. This reaction produces a mixture of NH2Et, NHEt2, NEt3, and NH3 as a result of MeCN hydrogenation, followed by amine redistribution reactions. Compound 2 is isolated in analytically pure form as [K(C12H24O6)][(triphos)RuH3] (2a) by recrystallization from THF/n-hexane in the presence of 18-crown-6 ether. In the presence of a strong base such as KOBut, both 1 and 3 are effective catalyst precursors for the homogeneous hydrogenolysis of benzo[b]thiophene (BT) to 2-ethylthiophenol (ETP) in THF under mild reaction conditions (≥70 °C, 30 bar of H2). The hydrogenolysis rate increases with the concentration of the base, which, depending on the catalyst prec...

The ruthenium(II) (tetrahydroborate)hydride complex [(triphos)RuH(BH4)] (1) reacts with benzo[b]thiophene (BT) in THF at 40 °C yielding, after 3 h, a mixture of four different compounds: [(triphos)RuH{BH3(o-S(C6H4)CH2CH3)}] (2), [(triphos)Ru{η4-S(C6H4)CH(CH3)}] (3), [(triphos)RuH(μ-S(C6H4)CH2CH3)2HRu(triphos)] (4), and [(triphos)RuH(μ-BH4)HRu(triphos)]+ (5+) (triphos = MeC(CH2PPh2)3). After two further hours of reaction, 3 disappears and is completely converted to 4. Further heating at 40 °C does not change the product composition (2, 4, and 5+ in a 4:1.3:3 ratio). A variety of independent reactions with isolated compounds have been performed with the aim of elucidating the mechanism of the C−S insertion/hydrogenation of BT to the 2-ethylthiophenolate ligand. The μ-thiolate complex 4 reacts in THF with dihydrogen (≥160 °C, 30 bar H2) or with HBF4·OEt2 (20 °C) yielding ethylbenzene and 2-ethylthiophenol, respectively. No reaction occurs with LiHBEt3. All of the reactions and new complexes reported have be...

Photolysis of [(PP3)RuH2] (PP3 = P(CH2CH2PPh2)3) (1) in THF at 23 °C under an inert atmosphere (N2, Ar, or He) in the presence of thiophene (T) or ethyl 2-thiophenecarboxylate (2-CO2EtT) gives the ...

The new chiral aminodiphosphine ligands (R)- and (S)-sec-butylbis(2-(diphenylphosphino)ethyl)amine, (R)- and (S)-sec-butylbis(2-(dicyclohexylphosphino)ethyl)amine, and (R)- and (S)-(α-methylbenzyl)bis(2-(dicyclohexylphosphino)ethyl)amine have been synthesized from optically pure (R)-(−)- and (S)-(+)-sec-butylamine or (R)-(+)- and (S)-(−)-(α-methylbenzyl)amine. The reactions between these PNP* ligands and [Ir(COD)(OMe)]2 have been investigated in either aprotic or protic solvents (COD = cycloocta-1,5-diene). Depending on the substituents at either the carbon stereocenter or the phosphorus donors, iridium products with different structures and/or stabilities are obtained. Among the new complexes, there are monohydride, dihydride, and trihydride species. It is observed that (i) cyclohexyl substituents on the phosphorus donors favor the formation of complexes where the PNP* ligand adopts a meridional conformation; (ii) phenyl groups attached to the carbon stereocenter lead to the formation of thermodynamicall...

A number of new chiral bis(ferrocenyl)−triphosphine ligands have been synthesized by the reaction of cyclohexylphosphine with different chiral ferrocenyl aminophosphines in hot acetic acid. The thioether ligand bis{(S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl} sulfide has been similarly prepared by the reaction of (S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl acetate with either (S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl mercaptan or (S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl mercaptan sodium salt. All the above reactions proceed with retention of configuration on the side-chain stereocenters of the starting materials. Monomeric Ru(II) complexes containing either chloride or acetonitrile coligands have been prepared with all the chiral tridentate ligands. Both the new ligands and the ruthenium complexes have been characterized by multinuclear NMR spectroscopy. The structure of [(S)-(R)-Pigiphos]RuCl2·2CH2Cl2 ((S)-(R)-Pigiphos = bis{(S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl}cycloh...

The complexes [M(COD)(PPh3)2]PF6 (M = Rh, 1a; Ir, 1b) are highly efficient precatalysts for the homogeneous hydrogenation of benzo[b]thiophene (BT) to 2,3-dihydrobenzo[b]thiophene (DHBT). Both complexes react rapidly with BT and H2 to produce the corresponding [M(H)2(η1(S)-BT)2(PPh3)2]PF6 (M = Rh, 2a; Ir, 2b), which enter the catalytic cycle. In the case of Ir, the catalysis is more conveniently carried out by use of 2b, which is stable enough to be isolated pure. Kinetic and mechanistic studies of BT hydrogenation were carried out by using 1a and 2b as the catalyst precursors in 1,2-dichloroethane solution at 40 °C. For both complexes, the reaction proceeds according to the rate law r = kcat [M] [H2], where kcat = k1K3/(1 + K3[H2]). All of the experimental data are consistent with a general mechanism in which the transfer of the hydrides to coordinated BT in [M(H)2(η2(CC)-BT)(PPh3)2]PF6 is the rate-determining step of the catalytic cycle. The complex [Ir(H)2(η1(S)-DHBT)2(PPh3)2]PF6 was obtained as a stab...

[RuH(CH3CN)(NP3)]OTf effectively catalyzes the dimerization of both aliphatic and aromatic alkynes to give (Z)-enynes in high regio- and stereoselectivity. The catalytic system can tolerate a number of functional groups, which allows for its use in organic and aqueous medium.

The fragment [(triphos)IrH], generated in situ by thermolysis of (triphos)Ir(H)2(C2H5) in THF, reacts with dinaphtho[2,1-b:1‘,2‘-d]thiophene (DNT) at temperatures higher than 100 °C to give a temperature-invariant 3:2 mixture of the two diastereomeric C−S insertion products (triphos)IrH(η2(C,S)-C20H12S) (3a,b; triphos = MeC(CH2PPh2)3). In the temperature range from 70 to 100 °C, the reaction gives kinetic mixtures of the C−S insertion products and of the complex (triphos)IrH(η2-C20H12S) (2), which is suggested to contain an intact DNT molecule bound to iridium via a double bond from a naphthyl ring. Complex 2 in THF transforms into 3a,b even at 70 °C. Hydrogenation of 3a,b (30 atm of H2, 60 °C) in THF gives the dihydride thiolate complex (triphos)Ir(H)2(SC20H13), which is protonated by strong acids, converting to the dimer [(triphos)IrH(μ-SC20H13)2HIr(triphos)](BPh4)2. The latter compound is straightforwardly obtained by reaction of 3a,b with protic acids. The complex (triphos)RhH3 (6) reacts with DNT (TH...

C1-symmetric[2,6-bis(imino)pyridyl]irondichloride complexes can form on activation by MAO highly active catalysts for the one-pot transformation of ethylene into mixtures of linear homopolymer and alpha-olefins with a Schulz-Flory distribution.

The oligomerization of ethylene to α-olefins has been obtained by MAO activation of tetrahedral CoII complexes of iminopyridines substituted in the 6-position of the pyridine ring by thiophen-2-yl, furan-2-yl, or phenyl groups. An intriguing heteroatom effect has been noticed on both activity and selectivity, together with a change in the CoII spin state upon activation of the dichloride precursors with MAO.

published in Aduance A C S Abstracts, April 15, 1994. 0276-7333/94/2313-2010~04.50/0 mechanism governs cyclotrimerization at all of these varied catalytic centers. The evidence for various mechanisms has been thoroughly reviewed by Wigley,l with particular reference to low-valent early (electropositive) transition metal centers. We have reported2 a series of studies where acetylene cyclotrimerization is effected at 25 "C by catalyst precursors containing the (triphos)Ir+ substructure (triphos = MeC(CH2PPh2)s). At the same time, we have reported on

[(triphos)Ir(H){sub 2}(C{sub 2}H{sub 5})] (1) is thermally activated toward ligand displacement yielding a reactive, 16 electron intermediate. Reactions of this intermediate with ethene, styrene, benzene, and phenylacetylene was investigated under purely thermolytic conditions and under the influence of photochemical activation. Potential reaction mechanisms for the thermal and photochemical reactions are presented.

A p-styrenyl substituent attached to the ligand framework allows the diphosphine moiety -(C6H4)CH2-OCH2C(CH3)(CH2PPh2)2 to be introduced as a pendant group in cross-linked styrene/divinylbenzene matrixes via free-radical copolymerization. In conjunction with rhodium(I), the POLYDIPHOS material forms an effective heterogeneous catalyst for the hydrogenation of benzylideneacetone to benzylacetone and of quinoline to a mixture of 1,2,3,4-tetrahydroquinoline, 5,6,7,8-tetrahydroquinoline, and decahydroquinoline. The homogeneous behavior of related 1,3-bis(diphenylphosphino)- propane rhodium complexes is different in both activity and selectivity.

The iridacyclopropane complex [(triphos)IR(Cl)(C 2 H 4 )] is the starting point to synthesize a number of stable iridium complexes containing various combinations of participative ligands such as hydride, ethylene, alkyls and heteroalkyls, alkynes, and carbon monoxide: Ir(H)(C 2 H 4 ), Ir(H) 2 (C 2 H 4 ), Ir(C 2 H 5 )(C 2 H 4 ), Ir(CO) 2 , Ir(H)(C 2 H 5 )(CO), Ir(H) 2 (CO), Ir(H) 2 (CH 2 CH 2 PEt 3 ), Ir(H) 3 , Ir(H) 2 (C 2 H 5 ), Ir(H) 2 (C 3 H 7 ), Ir(C 2 H 4 ) 2 , Ir(RC≡CR), IrH(μ-H) 2 HIr, and IrH(μ-Cl) 2 HIr. Due to the tripodlike structure of the ligand MeC(CH 2 PPh 2 ) 3 (triphos), all the complexes invariably exhibit a facial arrangement of the phosphorus and non-phosphorus ligands

Depending on the metal to ethyne ratio, the reaction of [(triphos)RhCl(C 2 H 4 )] (1;triphos=MeC-(CH 2 PPh 2 ) 3 ) with ethyne forms either the binuclear complex [(triphos)Rh(μ-Cl)(μ-η 2 ,η 2 -C 2 H 2 )Rh(triphos)]Cl (2) or the mononuclear rhodacyclopentadiene complex [(triphos)RhCl(η 2 -C 4 H 4 )] (3). The crystal structure of the complex cation [(triphos)Rh(μ-Cl)(μ-η 2 ,η 2 -C 2 H 2 )Rh(triphos)] + (2 + ) has been determined by X-ray methods. Complex 2 + undergoes two-electron oxidation by chemical or electrochemical methods

Reactions de HC=CR (R=CO 2 Et; Ph,n-C 5 H 11 ) avec le complexe [(PP 3 )CoH] PP 3 =P(CH 2 CH 2 PPh 2 ) 3 . La reaction est influencee par differents facteurs comme la concentration molaire, le substituant del'alcyne, la temperature

The number, the disposition, and the nature of the substituents play an important role in determining the product composition of the reactions between the trihydride ((triphos)RhH{sub 3}) (1) and mono- or 1,2-disubstituted alkenes (triphos = MeC(CH{sub 2}PPh{sub 2}){sub 3}). In particular, alkenes bearing electron-withdrawing substituents such as CO{sub 2}R or Ph stabilize cis hydride {eta}{sup 2}-alkene complexes of the formula ((triphos)Rh-(H)({eta}{sup 2}-alkene)), whereas electron-rich alkenes do not form {eta}{sup 2} adducts but are hydrogenated to alkanes by 1. Alkynes are more easily hydrogenated by 1 than comparable alkenes. The crystal structure of ((triphos)Rh(H)({eta}{sup 2}-DMFU)){center dot}C{sub 4}H{sub 9}OH has been determined by x-ray methods (DMFU = dimethyl fumarate).

The reaction of HC≡CR (R=CO 2 Et, Ph, n−C 3 H 7 , n−C 5 H 11 , SiMe 3 ) with the Rh(I) monohydrides [(NP 3 )Rh(H] (1) and [(PP 3 )RhH] (2) in THF is influenced by a number of factors, including stoichiometry, alkyne substituent, and temperature (NP 3 =N(CH 2 CH 2 PPh 2 ) 3 ; PP 3 =P(CH 2 CH 2 PPh 2 ) 3 ). The stereospecific addition of 1-alkynes to either 1 or 2 is interpreted in terms of a concerted mechanism