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The syntheses of the new triple-decker complexes [(triphos)Co(μ,η 3:3 -P 3 )Ru(triphos)](BPh 4 ) 2 ; ( CoP 3 Ru )(BPh 4 ) 2 , [(triphos)Co(μ,η 3:3 -P 3 )Os(triphos)](BPh 4 ) 2 ; ( CoP 3 Os )(BPh 4 ) 2 and [(triphos)Ru(μ,η 3:3 -P 3 )Ru(triphos)]PF 6 ·(CH 3 ) 2 CO; ( RuP 3 Ru )PF 6 ·(CH 3 ) 2 CO, three new members of the [(tripod)M(μ-P 3 )M′(tripod)] n+ ( MP3M ′ n+ ) family are described. The structure of the homodinuclear complex ( RuP 3 Ru )PF 6 ·(CH 3 ) 2 CO is also reported. This latter compound has a structure similar to that of the other members of the series and shows an M⋯M separation among the longest hitherto found in these compounds. An electrochemical study shows that they are stable in various oxidation states with a VEN value ranging between 28 and 34. A reasoning around the redox data shows a progressive shift of two pairs of redox processes, corresponding to the VEN variation 30/31-31/32 and 32/33-33/34, which almost rigidly moves in the cathode direction as the overall charge of the homoelectronic compound decreases.

The reaction of trans-[RhCl(CO)(dppm)]2 with P4 carried out at room temperature showed that bimetallic cooperation resulted in the cleavage of P4, giving a μ,η2-P2 (μ-κ2:κ2-P2) ligand coordinated to the two metal centres. The new complex cis-[Rh2(CO) 2(μ-dppm)2(μ,η2-P2)] has been fully characterised in solution by NMR spectroscopy and in the solid state by single-crystal X-ray diffraction. The Rh-Rh distance of 2.723(18) A is consistent with the presence of a metal-metal single bond, which was supported by theoretical analysis showing that the HOMO of the complex has metal-metal bond character. A literature survey revealed that, in most cases, the P 2 unit acts as a P24- ligand, and also in the case at hand the diphosphenyl ligand behaves as an eight-electron donor with all the π* combinations occupied and donates into four empty metal combinations. The new complex cis-[Rh2(CO)2(μ-dppm) 2(μ,η2-P2)], obtained by activation of white phosphorus under mild conditions, was fully characterised in solution by NMR spectroscopy and in the solid state by single-crystal X-ray diffraction. The P2 unit acts as an eight-electron donor with all the π* combinations occupied and donates into four empty metal combinations, as described by theoretical analysis. Copyright

Reaction of the acidic tungsten(II) hydride 2 with the nickel(II) pincer complex 1 in either THF or toluene after an initial dihydrogen bonding (DHB) interaction led to the formation of the Ni-W bimetallic species 3 (see picture). The first example of DHB between two metal hydrides with opposite polarity was analyzed by NMR and IR spectroscopy, X-ray crystallography, and DFT calculations.

The novel iridium(III) hydride [(kappa(3)-P,P,P-NP(3))IrH(3)] [NP(3) = N(CH(2)CH(2)PPh(2))(3)] was synthesized and characterized by spectroscopic methods and X-ray crystallography. Its reactivity with strong (HBF(4)) and medium-strength [the fluorinated alcohols 1,1,1-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP)] proton donors was investigated through low-temperature IR and multinuclear NMR spectroscopy. In the case of the weak acid TFE, the only species observed in the 190-298 K temperature range was the dihydrogen-bonded adduct between the hydride and the alcohol, while with the stronger acid HBF(4), the proton transfer was complete, giving rise to a new intermediate [(kappa(3)-P,P,P-NP(3))IrH(4)](+). With a medium-strength acid like HFIP, two different sets of signals for the intermediate species were observed besides dihydrogen bond formation. In all cases, the final reaction product at ambient temperature was found to be the stable dihydride [(kappa(4)-NP(3))IrH(2)](+), after slow molecular dihydrogen release. The nature of the short-living species was investigated with the help of density functional theory calculations at the M05-2X//6-31++G(df,pd) level of theory.

The reaction of [CpOs(PPh 3 ) 2 Cl] (1) with one equivalent of white phosphorus in the presence of AgOTf (OTf = triflate, OSO 2 CF 3 ) as chloride scavenger affords the stable metal complex [CpOs(PPh 3 ) 2 (η 1 -P 4 )]OTf (2), which contains the tetrahedral P 4 η 1 -bond to the CpOs(PPh 3 ) 2 metal fragment. Addition of [CpRu(PPh 3 ) 2 (OTf)] to 2 yields the heterobimetallic species [{CpRu(PPh 3 ) 2 }[CpOs(PPh 3 ) 2 )}(μ,η 1:1 -P 4 )](OTf) 2 (3), in which the tetrahedral P 4 is bound to two different metal fragments through two phosphorus atoms. The compounds have been characterized by elemental analysis, IR and NMR spectroscopy, and their crystal structures have been determined by X-ray diffraction. The coordinated P 4 , at variance with the free ligand, reacts with an excess amount of water in thf under mild conditions to yield several products, most of which have been characterized.

A new family of rhodium and iridium compounds with the bulky tris(ortho-methoxyphenyl) phosphine (PAn3) was synthesized and characterized by NMR methods. The X-ray crystal structures of RhCl(PAn3)(COD) (1) and Ir[(PBz3)(PAn3)(COD)]PF6 (4) have been determined. A stabilizing agostic interaction has been crystallographically observed in both compounds, due to the steric hindrance of the ortho-substituted phosphine ligand and its presence has been associated to the fluxional behavior shown by the complexes on the NMR timescale in solution. Iridium complexes containing PBz3 and/or PAn3 have been evaluated as catalyst precursors for the hydrogenation of trans-cinnamaldehyde (CNA), and their activities have also been compared to those of other iridium complexes containing bulky phosphine ligands, such as PTol3 (tris-ortho-tolyl-phosphine). The catalytic experiments show that irrespectively of the phosphine combination, all of the evaluated catalysts prevalently hydrogenate the C C moiety. However, the product selectivity can be tuned by changing either the substrate/catalyst ratio or the phosphine ligand at the metal center. The catalyst with PAn3 proved to be more efficient and also gave higher yields of the enol product, indicating that stereoelectronic effects are responsible for the changes in selectivity.

The proton transfer from substituted phenols (ArOH = p -nitrophenol, p -nitophenyl-aza-phenol) to the ruthenium dihydride complex [(PP 3 )RuH 2 ], where PP 3 = P(CH 2 CH 2 PPh 2 ) 3 , was studied by variable temperature UV–visible spectroscopy in dichloromethane, THF, THF/CH 3 OH and THF/CH 3 CN mixtures, showing a significant influence of the polarity and/or the proton donating/proton accepting properties of the solvent on the position of the proton transfer equilibrium. The formation of ion pairs stabilized by hydrogen bonding between the non-classical cation [(PP 3 )RuH(η 2 -H 2 )] + and the homoconjugated anion [ArOHOAr] − was determined in low-polar media. The increase of the media polarity has been proved to favor the proton transfer leading to the dissociation of hydrogen bonded ion pairs [{(PP 3 ) RuH(η 2 -H 2 )} + ⋯{ArOHOAr} − ]. Under comparable media polarity, the presence of a protic solvent in the mixture greatly favors the proton transfer due to the additional H-bonding with solutes. The structural, energetic and electronic features of the dihydrogen bonded adducts and of the proton transfer products were investigated by means of DFT/B3LYP calculations on the model dihydride [{P(CH 2 CH 2 PH 2 ) 3 }RuH 2 ] using CH 3 OH or CF 3 OH as proton donors. The specific and non-specific influence of the media properties on the dihydrogen bonding and proton transfer was studied by introducing the second protic (proton donor or solvent) molecule in the model system or by CPCM calculations. The additional participation of external molecules, from either the solvent or the alcohol, strengthens remarkably the dihydrogen bonded adducts and eases the proton transfer process.

New rhodium and iridium complexes, with the formula [MCl(PBz 3 )(cod)] [M = Rh ( 1 ), Ir ( 2 )] and [M(PBz 3 ) 2 (cod)]PF 6 [M = Rh ( 3 ), Ir ( 4 )] (cod = 1,5-cyclooctadiene), stabilized by the tribenzylphosphine ligand (PBz 3 ) were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The addition of pyridine to a methanol solution of 1 or 2 , followed by metathetical reaction with NH 4 PF 6 , gave the corresponding derivatives [M(py)(PBz 3 )(cod)]PF 6 [M = Rh ( 5 ), Ir ( 6 )]. At room temperature in CHCl 3 solution, 4 converted spontaneously to the ortho -metallated complex [IrH(PBz 3 )(cod){η 2 - P , C -(C 6 H 4 CH 2 )PBz 2 }]PF 6 ( 7 ) as a mixture of cis / trans isomers via intramolecular C–H activation of a benzylic phenyl ring. The reaction of 3 or 4 with hydrogen in coordinating solvents gave the dihydrido bis(solvento) derivative [M(H) 2 (S) 2 (PBz 3 ) 2 ]PF 6 (M = Rh, Ir; S = acetone, acetonitrile, THF), that transformed into the corresponding dicarbonyls [M(H) 2 (CO) 2 (PBz 3 ) 2 ]PF 6 by treatment with CO. Analogous cis -dihydrido complexes [M(H) 2 (THF) 2 (py)(PBz 3 ) 2 ]PF 6 (M = Rh, Ir) were observed by reaction of the py derivatives 5 and 6 with H 2 .

The ortho-palladation of the iminophosphane ligand 6-phenyl-2-[(2,6-diisopropylphenyl)imino]pyridine (HL) with Pd(OAc)2 and PdCl2(PhCN)2 in benzene yields the neutral Pd–C,N,N pincer complexes Pd(OAc)(κ3-C,N,N-L) (1) and PdCl(κ3-C,N,N-L) (2), respectively. In the presence of NaBAr′4 [Ar′ = 3,5-(CF3)2C6H3], 2 reacts in CH2Cl2 with MeCN, PPh3, or PH[o-MeO(C6H4)]2 to give the cationic palladium(II) pincer complexes [Pd(CH3CN)(κ3-C,N,N-L)]BAr′4 (3), [Pd(PPh3)(κ3-C,N,N-L)]BAr′4 (4) and {Pd[PH(o-MeOC6H4)2](κ3-C,N,N-L)}BAr′4 (5), respectively. Complexes 1–5 have been characterized by multinuclear NMR and IR spectroscopy. The solid-state structures of 1 and 2 have been determined by single-crystal X-ray diffraction techniques. Both the neutral compounds 1 and 2 and the cationic derivatives 3, 4, and 5 were tested as catalyst precursors for the Suzuki cross-coupling of 4-bromo- and 4-chloroacetophenone with phenylboronic acid. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

A new family of Cs- and C1-symmetric 2,6-bis(imino)pyridyl ligands has been synthesised. These ligands, which differ from their known counterparts in the contemporaneous presence of alkyl and aryl substituent at the ketimine nitrogen atoms, form stable, five-coordinate complexes with FeCl2 and CoCl2. All ligands and catalysts have been fully characterised both in the solid state and in solution. A single-crystal X-ray analysis of [CoCl2{2-[CMe=N−(2,6-dimethylphenyl)]-6-(CMe=N−C6H11)C5H3N}]·H2O shows the metal centre to adopt a highly distorted square-pyramidal geometry. In combination with methylaluminoxane (MAO), both iron and cobalt compounds act as effective and selective (> 99%) catalysts for the oligomerisation of ethylene to a Schulz−Flory distribution of α-olefins, with the α factor ranging from 0.61 to 0.91. The iron catalysts exhibit TOFs as high as 7·105 mol C2H4 (mol of cat × h)−1 and are much more active than their cobalt analogues. Experiments at different ethylene pressures with the iron catalysts showed that both the propagation rate and the chain transfer rate are first order in ethylene pressure. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2003)

The rhenium(III) dichloride complex [ReCl2(η4-NP3)]Cl (1) was prepared from [ReCl3(CH3CN)(PPh3)2] by treatment with the tripodal tetradentate ligand N(CH2CH2PPh2)3 (NP3) in ethanol. The reaction of 1 with LiAIH4 in THF gave the rhenium(III) trihydride [ReH3(η4-NP3)] (2), which was converted into the rhenium(V) tetrahydride [ReH4(η4-NP3)]BPha4 (3) by protonation in CH2Cl2 with HBF4·OMe2, followed by a metathetical reaction with NaBPh4. The classical polyhydride nature of 2 and 3, as well as the overall molecular structures in solution, were determined by NMR spectroscopy, 1H NMR relaxation, and IR spectroscopy. The polyhydride complexes 2 and 3 are stereochemically nonrigid in solution, and the thermodynamic parameters associated with the fluxional processes were determined by variable-temperature NMR studies. A single-crystal X-ray analysis of 3 has shown the complex cation [ReH4 (qη4-NP3)]+ to be eight- coordinated by the four donor atoms of NP3 and by four terminal hydride ligands in a distorted dodecahedral geometry. An in situ IR study in CH2Cl2 has shown that the protonation of 3 occurs regioselectively at the metal center with no formation of a dihydrogen complex. Kinetic hydrogen bond products of the formula [(qη4NP3)H3Re··· HOR] (ROH = C2H5OH, CFH2CH2OH, CF3CH2OH) were intercepted by IR spectroscopy at low temperature. The thermodynamic parameters associated with the formation of the hydrogen bond adducts were determined by either IR spectroscopy applying the logansen equation or van't Hoff plots of the formation constant vs. temperature.

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.

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...

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...

This work reports the catalytic reduction, via hydrogen-transfer from propan-2-ol, of various α , β -unsaturated ketones or unsymmetrical ketones in the presence of [Ir(COD)(OMe)] 2 and the chiral aminodiphosphine ligands ( R )-PhC * H(Me)N(CH 2 CH 2 PR 2 ) 2 (R=Ph, Cy) and ( R )-(Et)C * H(Me)N(CH 2 CH 2 PPh 2 ) 2 . In general, these catalyst systems show good activity but modest enantioselectivity. Both the chemoselectivity and the enantioselectivity for the reduction of α , β -unsaturated ketones to optically pure allylic alcohols depend on the nature of the substituent(s) at either the carbon stereocentre or the phosphorus substituents.

Two novel Ru-II hydrides containing the tripodal polyphosphine ligand NP3 (N(CH2CH2PPh2)(3)) have been prepared and characterized: (kappa(4)-NP3)Ru(H)(2) (1) and [(kappa(4)-NP3)Ru(H)(eta(2)-H-2)] BAr4Cl (2; Ar-Cl = 3,5-dichlorophenyl, C6H3Cl2). The classical and nonclassical nature of the hydride ligand in 1 and 2, respectively, has been confirmed by solution NMR studies and single-crystal X-ray diffraction. The reaction of 1 and 2 with excess ammonia borane (NH3 center dot BH3, AB) has been analyzed experimentally through variable-temperature multinuclear (B-11, P-31, H-1) NMR spectroscopy, kinetic rate measurements, and kinetic isotope effect determination with deuterated AB isotopologues. Both complexes are active in AB dehydrogenation, with release of two H-2 equivalents per AB equivalent, with concomitant polyborazylene and cyclic polyaminoborane formation as the final "spent fuel". A DFT modeling of the AB first dehydrogenation step has been finally performed, at the M06//6-31G* level of theory. The combination of the kinetic and computational data reveals that the initial AB activation step is different for the two catalysts: a simultaneous B-H/N-H activation occurs in the presence of 1, whereas the N-H activation only is the rate-determining step if 2 is employed as a catalyst.

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...

The complexes formed by the ions Co2+, Ni2+, Cu2+, and Zn2+ with the ligand propane-1,2,3-triamine (L1) in 0.15 mol dm−3 aqueous NaCl at 25 °C have been studied by potentiometry and calorimetry (ligand to metal molar ratio, 1–3; pH range from 3.0 to 6.5–11.0). Stability constants have been obtained from potentiometric data by means of the least-squares program HYPERQUAD for the following species: [M(L1)]2+ and [MH(L1)]3+ for all four metal cations; [M(L1)2]2+ and [MH(L1)2]3+ for Ni2+, Cu2+, and Zn2+; [MH2(L1)2]4+ for Ni2+ and Cu2+; and [M(OH)(L1)]+ for Cu2+ only. Stabilities increase in the order Zn 1 have approximately the same stability as the corresponding ones formed by the related triamines 2-methyl (2-methylamine) propane-1,3-diamine (L3) and 2-ethyl (2-methylamine)propane-1,3-diamine (L4). The stability constants have been used to obtain, from the calorimetric titration experiments, the formation enthalpies of all the metal complexes except those for cobalt(II) as well as the corresponding entropy changes. The thermodynamic quantities are compared with the corresponding values previously found for L3, in order to derive information about the coordination ability of the ligand. The analysis suggests that the unprotonated ligand forms a fac-tridentate complex in most cases, but for some species, such as [Cu(L1)2]2+, [CuH(L1)2]3+, and [Zn(L1)]2+, the thermodynamic quantities indicate that at least one of the nitrogen atoms of the triamine is either loosely bonded or not coordinated to the metal ion. A gas-phase molecular mechanics analysis shows that the strain energies of the fac-[Co(L1)2]2+ and -[Ni(L1)2]2+ symmetrical (s) and unsymmetrical (u) isomers are very similar. If the same solvation energy is assumed for the two isomers, each isomer will be present in roughly equal amounts in solution. Keywords: propane-1,2,3-triamine, potentiometry, calorimetry, complexation, cobalt, nickel, copper, zinc.

Combining variable-temperature infrared and NMR spectroscopic studies with quantum-chemical calculations (density functional theory (DFT) and natural bond orbital) allowed us to address the problem of competition between MH (M = transition metal) and BH hydrogens as proton-accepting sites in dihydrogen bond (DHB) and to unravel the mechanism of proton transfer to complex (PP3)RuH(η(1)-BH4) (1, PP3 = κ(4)-P(CH2CH2PPh2)3). Interaction of complex 1 with CH3OH, fluorinated alcohols of variable acid strength [CH2FCH2OH, CF3CH2OH, (CF3)2CHOH (HFIP), (CF3)3COH], and CF3COOH leads to the medium-strength DHB complexes involving BH bonds (3-5 kcal/mol), whereas DHB complexes with RuH were not observed experimentally. The two proton-transfer pathways were considered in DFT/M06 calculations. The first one goes via more favorable bifurcate complexes to BHterm and high activation barriers (38.2 and 28.4 kcal/mol in case of HFIP) and leads directly to the thermodynamic product [(PP3)RuHeq(H2)](+)[OR](-). The second pathway starts from the less-favorable complex with RuH ligand but shows a lower activation barrier (23.5 kcal/mol for HFIP) and eventually leads to the final product via the isomerization of intermediate [(PP3)RuHax(H2)](+)[OR](-). The B-Hbr bond breaking is the common key step of all pathways investigated.

The hydration of phenylacetylene in the presence of the complex mer,trans-(PNP)RuCl2(PPh3) in THF at 60 °C leads to the cleavage of the C−C triple bond with formation of the carbonyl complex fac,cis-(PNP)RuCl2(CO) and toluene [PNP = CH3CH2CH2N(CH2CH2PPh2)2]. A study under different experimental conditions, the use of model and isotope labeling experiments, and the detection of several intermediates, taken altogether, show that the C−C bond cleavage reaction comprises a number of steps, among which the most relevant to the mechanism are 1-alkyne to vinylidene tautomerism, conversion of a vinylidene ligand to hydroxycarbene by intramolecular attack of water, deprotonation of hydroxycarbene to σ-acyl, deinsertion of CO from the acyl ligand, and hydrocarbon elimination by protonation of the metal-alkyl moiety. The following intermediate species have been isolated and characterized: the vinylidene fac,cis-(PNP)RuCl2{CC(H)Ph}, the (aquo)(σ-alkynyl) complex fac-(PNP)RuCl(C⋮CPh)(OH2), and the (benzyl)carbonyl me...

Catalytic dehydrogenation of ammonia-borane (NH3·BH 3, AB) and dimethylamine borane (NHMe2·BH 3, DMAB) by the PdII complex [(tBuPCP)Pd(H 2O)]PF6 [tBuPCP = 2,6-C6H 3(CH2PtBu2)2] leads to oligomerization and formation of spent fuels of general formula cyclo-[BH 2-NR2]n (n = 2,3; R = H, Me) as reaction byproducts, while one equivalent of H2 is released per amine-borane equivalent. The processes were followed through multinuclear (31P, 1H, 11B) variable temperature NMR spectroscopy; kinetic measurements on the hydrogen production rate and the relative rate constants were also carried out. One non-hydridic intermediate could be detected at low temperature, whose chemical nature was explored through a DFT modeling of the reaction mechanism, at the M06//6-31+G(d,p) computational level. The computational output was of help to propose a reliable mechanistic picture of the process. This journal is © 2013 The Royal Society of Chemistry.

The structure consists of discrete neutral molecules of [RuCl 2 (PPh 3 )(PNP)] [PNP = CH 3 CH 2 CH 2 N(CH 2 CH 2 PPh 2 ) 2 ] and dichloromethane solvent molecules. In the molecular structure of the complex a Ru II metal centre is pseudo-octahedrally coordinated by a meridional tridentate PNP ligand, by two Cl ligands trans to each other, and by a triphenylphosphine ligand. The latter ligand is trans to the N-atom donor of the amino-diphosphine.

According to low-temperature UV-Vis spectroscopy data, the two-step protonation of iron subgroup metal hydrides [{P(CH2CH2PPh2)3}MH2] (M = Fe, Ru, Os) with p-nitrophenol includes the formation of ion pairs stabilized by a hydrogen bond between the cationic dihydrogen complex and the phenolate anion. The trend of the extent of proton transfer appeared to be aperiodic, FeI ≪ OsI < RuI, in contrast to the previously obtained sequence of the proton-acceptor capacity of the hydride ligand, which increases down the group.

The complex [(PP 3 )OsH(N 2 )]BPh 4 is a catalyst precursor for the regio- and stereoselective dimerization of HCCR (RPh, SiMe 3 ) to ( Z )-1,4-disubstituted-but-3-en-l-ynes (PP 3 P(CH 2 CH 2 PPh 2 ) 3 ). In the presence of H 2 O or C 2 H 5 OH, the catalytic reaction with HCCSiMe 3 selectively gives but-3-en-l-ynyl-trimethyisilane. A detailed study under different experimental conditions, the detection of some intermediates, and the use of isolated complexes in independent reactions, taken altogether, permit mechanistic conclusions which account for the observed products. A key-role is played by (vinylidene)σ-alkynyl complexes which transform into η 3 -butenynyl derivatives via intramolecular CC bond formation. The Os(II) η 3 -butenynyl complexes are likely reagents in the rate determining step of the catalytic cycle, and produce free ( Z )-1,4-disubstituted-but-3-en-l-ynes upon σ-bond metathesis reaction with HCCR. The 16-electron fragments [(PP 3 )OsX] + (X  H, Cl, CCR) are capable of promoting the 1-alkyne to vinylidene tautomerism. In particular, the (vinylidene)hydride [(PP 3 )OsH{CC(H)-SiMe 3 }]BPh 4 has been isolated and properly characterized. Since the stoichiometric reaction of the latter compound with HCCSiMe 3 gives vinyltrimethylsilane, the formation of (vinylidene)hydride species is suggested to be an effective step, alternative to 1-alkyne insertion, in the reduction of 1-alkynes to alkenes assisted by hydrido metal complexes.

Reaction of the pincer hydride complex ((tBu)PCP)Ni(H) [(tBu)PCP = 2,6-C(6)H(3)(CH(2)P(t)Bu(2))(2)] with BH(3)·thf in THF at 190 K generates the corresponding borohydride complex ((tBu)PCP)Ni(BH(4)). The kinetically stable (but thermodynamically unstable) species undergoes reversible borane loss. The related fluoride complex ((tBu)PCP)Ni(F) shows the same reactivity towards BF(3)·Et(2)O, producing ((tBu)PCP)Ni(BF(4)) as the main final product. The processes were followed through multinuclear NMR spectroscopy and DFT calculations, at the M06//6-31+G(d,p) level of theory.

The cis-hydride-η 2 -dihydrogen complex [(PP 3 )OsH(η 2 -H 2 )]BPh 4 , PP 3 =P(CH 2 CH 2 PPh 2 ) 3 , has been prepared by either protonation of the dihydride [(PP 3 )OsH 2 ] or reaction of the novel dinitrogen complex [(PP 3 )OsH(N 2 )]BPh 4 with H 2 . The nonclassical structure of 4 has been established in solution by variable-temperaturc NMR spectroscopy ( 1 H, 31 P), T 1 measurements, and J(HD) values.

Fe(II) and Fe(I) σ-alkynyl complexes of the general formula ((PP 3 )Fe(C≡CR)] n+ (n=1, 0) have been synthesized as BPh 4 - salts or neutral molecules and characterized by chemical, spectroscopic, X-ray, and electrochemical techniques (R=Ph, SiMe 3 , n-C 3 H 7 , n-C 5 H 11 ; CMe 3 ; PP 3 =P(CH 2 CH 2 PPh 2 ) 3 ]. All of the compounds undergo electron-transfer reactions that encompass Fe(0), Fe(I), Fe(II), and Fe(III) oxidation states of the metal

The dichloride ((PP{sub 3})RuCl{sub 2}) (1) is selectively transformed into ((PP{sub 3})Ru(H)({eta}{sup 1}-BH{sub 4})) (2), ((PP{sub 3})Ru(H)Cl) (3), and ((PP{sub 3})Ru(H){sub 2}) (4) by reaction with NaBH{sub 4}, LiHBEt{sub 3}, and LiAlH{sub 4}, respectively (PP{sub 3} = P(CH{sub 2}CH{sub 2}PPh{sub 2}){sub 3}). Complex 2 is fluxional on the NMR time scale in ambient-temperature solutions due to equilibration of the BH{sub 4}{sup {minus}} hydrogens through cleavage of the Ru-H{sub b}-B bridge and interconversion of H{sub t} by rotation. The hydride-tetrahydroborate complex exhibits amphoteric nature: it reacts with protic acids, yielding the cis-hydride dihydrogen complex ((PP{sub 3})Ru(H)({eta}{sup 2}-H{sub 2}))Y (Y = PF{sub 6}, 6a; BPh{sub 4}, 6b), and with bases such as PEt{sub 3} or KO{sup t}Bu, converting to the dihydride 4. The latter compound can be obtained also by thermal decomposition of 2 in refluxing toluene or benzene. Complexes 6a,b can be prepared by reaction of the dihydride 4 with protic acids. In the solid state and in solution at low temperature ((PP{sub 3})Ru(H)({eta}{sup 2}-H{sub 2})){sup +} is octahedral, and the hydride and dihydrogen ligands occupy mutually cis positions. At ambient temperature in solution the complex is trigonal-bipyramidal and the equilibration of the hydrogens might proceed through an H{sub 3} unitmore » occupying an axial position trans to the bridgehead phosphorus atom of PP{sub 3}. 36 refs., 6 figs., 2 tabs.« less

The novel iridium(III) hydride [(kappa(3)-P,P,P-NP(3))IrH(3)] [NP(3) = N(CH(2)CH(2)PPh(2))(3)] was synthesized and characterized by spectroscopic methods and X-ray crystallography. Its reactivity with strong (HBF(4)) and medium-strength [the fluorinated alcohols 1,1,1-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP)] proton donors was investigated through low-temperature IR and multinuclear NMR spectroscopy. In the case of the weak acid TFE, the only species observed in the 190-298 K temperature range was the dihydrogen-bonded adduct between the hydride and the alcohol, while with the stronger acid HBF(4), the proton transfer was complete, giving rise to a new intermediate [(kappa(3)-P,P,P-NP(3))IrH(4)](+). With a medium-strength acid like HFIP, two different sets of signals for the intermediate species were observed besides dihydrogen bond formation. In all cases, the final reaction product at ambient temperature was found to be the stable dihydride [(kappa(4)-NP(3))IrH(2)](+), after slow molecular dihydrogen release. The nature of the short-living species was investigated with the help of density functional theory calculations at the M05-2X//6-31++G(df,pd) level of theory.

The comparison of the very similar compounds (Ph(3)P)(2)Pt(mu-S)(2)Pt(PPh(3))(2) (1) and (Ph(2)PyP)(2)Pt(mu-S)(2)Pt(PPh(2)Py)(2) (2) raises intriguing questions about the reliability of the reported Pt(2)S(2) core in 1, where the Pt-S bonds are the shortest ever reported. Also, the trans-annular S center dot center dot center dot S separation of 2.69 angstrom is surprisingly shorter in 1 than in 2 (3.01 angstrom), but no incipient coupling between two S(2-) bridges seems reasonable in this case. Various considerations lead to reformulate 1 as [(Ph(3)P)(2)Pt(mu-OH)(2)Pt(PPh(3))(2)](BF(4))(2), 3. The sets of cell parameters for 1 and 3 are not equal but two axes match, and the volume of 1 is exactly double. Simple matrices may be constructed to interconvert the direct and reciprocal crystalline cells, thus corroborating their identity of the compounds. It is concluded that, in the structure solution of 1, some atoms were either neglected (BF(4)(-) counterions) or ill identified (sulfido in place of hydroxo bridges), while the structure of 3 was solved by collecting only one-half of the possible reflections (hence, also the different space groups). A new preparation, crystallization and X-ray structure of 3 confirms the above points and dismisses any other theoretical conjecture about two electronically different Pt(2)S(2) cores in 1 and 2.

Ammonia borane (AB, NH3·BH3) was activated selectively on the boron hydrogen atoms by [Ir(dppm)2]OTf, as shown by variable-temperature 31P, 11B and 1H NMR studies, to yield cis- and trans-[Ir(H)2(dppm)2]OTf dihydrides. X-ray crystal structures of these complexes were obtained. DFT calculations suggest the key reaction intermediate to be a Lewis base (L) stabilised adduct, cis-[Ir(H)(BH2·L)(dppm)2]+(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The dichloride ((PP{sub 3})RuCl{sub 2}) (1) is selectively transformed into ((PP{sub 3})Ru(H)({eta}{sup 1}-BH{sub 4})) (2), ((PP{sub 3})Ru(H)Cl) (3), and ((PP{sub 3})Ru(H){sub 2}) (4) by reaction with NaBH{sub 4}, LiHBEt{sub 3}, and LiAlH{sub 4}, respectively (PP{sub 3} = P(CH{sub 2}CH{sub 2}PPh{sub 2}){sub 3}). Complex 2 is fluxional on the NMR time scale in ambient-temperature solutions due to equilibration of the BH{sub 4}{sup {minus}} hydrogens through cleavage of the Ru-H{sub b}-B bridge and interconversion of H{sub t} by rotation. The hydride-tetrahydroborate complex exhibits amphoteric nature: it reacts with protic acids, yielding the cis-hydride dihydrogen complex ((PP{sub 3})Ru(H)({eta}{sup 2}-H{sub 2}))Y (Y = PF{sub 6}, 6a; BPh{sub 4}, 6b), and with bases such as PEt{sub 3} or KO{sup t}Bu, converting to the dihydride 4. The latter compound can be obtained also by thermal decomposition of 2 in refluxing toluene or benzene. Complexes 6a,b can be prepared by reaction of the dihydride 4 with protic acids. In the solid state and in solution at low temperature ((PP{sub 3})Ru(H)({eta}{sup 2}-H{sub 2})){sup +} is octahedral, and the hydride and dihydrogen ligands occupy mutually cis positions. At ambient temperature in solution the complex is trigonal-bipyramidal and the equilibration of the hydrogens might proceed through an H{sub 3} unitmore » occupying an axial position trans to the bridgehead phosphorus atom of PP{sub 3}. 36 refs., 6 figs., 2 tabs.« less

Reaction of white phosphorus with [(triphos)Re(CO)2(OTf)] (1) in dichloromethane affords the new tetraphosphorus complex [(triphos)Re(CO)2(η1-P4)](OTf) (2) [triphos = MeC(CH2PPh2)3; OTf = OSO2CF3]. Compound 2 reacts with a second equivalent of 1 to give the binuclear complex [{(triphos)Re(CO)2}2(μ,η1,η1-P4)](OTf)2 (3) in which a tetrahedro-P4 ligand behaves as tethering unit between two [(triphos)Re(CO)2]+ moieties. Complexes 2 and 3 represent the first soluble metal complexes of the tetraphosphorus molecule where the P4 ligand has not undergone any major modification.

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

Chlorophosphine gold(I) compounds [Au(PR 3 )Cl] (R = Et, Ph) have been used as reagents for distinguishing classical from nonclassical structures in a family of dihydrides or dihydrogen complexes of iron, cobalt, rhodium and iridium stabilized by the tripodal polyphosphine PP 3 [PP 3 = P(CH 2 CH 2 PPh 2 ) 3 ]. Novel mixed transition-metal gold hydrides, including the first iron—gold species, are described.

Regioselective formation of 2-(benzoyloxy)propene results from the addition of benzoic acid to propyne in the presence of the trigonal-bipyramidal Rh(I) monohydrides [(PPh 3 )RhH] (1) and [(NP 3 )RhH] (2, PP 3 =P(CH 2 CH 2 PPh 2 ) 3 , NP 3 =N(CH 2 CH 2 PPh 2 ) 3 ). The reactions are catalytic under relatively mild conditions (catalyst to substrate ratio 1:100, toluene, 100 o C). A detailed experimental study on the reactions of 1 and 2 with carboxylic acids, 1-alkynes, or carboxylic acid/1-alkyne mixtures has allowed us to draw a catalysis cycle involving the 16-electron fragments [(L)Rh] + as catalysts (L=PP 3 , NP 3 ). The catalytic behavior of the precursors 1 and 2 has been compared and contrasted with those of the isostructural and isoelectronic derivatives [(L)Rh(C≡CPh), [(L)RhCl], and [(PP 3 )RhMe]. The novel vinylphosphonium complex [(Ph 2 PCH 2 CH 2 ) 2 P(CH 2 CH 2 PPh 2 )Rh{C=C(H)Ph}(O 2 CPh) has been synthesized and fully characterized by IR and 1 H and 34 P{ 1 H} NMR techniques

The trigonal-bipyramidal Rh(I) vinylidene complexes ((NP{sub 3})Rh=C=C(H)(R)){sup +} have been prepared by treatment of the neutral {sigma}-acetylides ((NP{sub 3})Rh(C{triple bond}CR)) with strong protic acids and isolated as BPh{sub 4}{sup {minus}} or PF{sub 6}{sup {minus}} salts (NP{sub 3} = N(CH{sub 2}CH{sub 2}PPh{sub 2}){sub 3}; R = Ph, CO{sub 2}Et). Reaction of the vinylidene complexes with nucleophiles such as NEt{sub 3}, MeLi, and PhLi leads to deprotonation to restore the parent {sigma}-acetylide compounds. When the vinylidene complexes are treated with NaBH{sub 4} or LiHBEt{sub 3}, the acid-base reaction competes with the nucleophilic addition of H{sup {minus}} to the vinylidene C{sub {alpha}} atom to form the alkenyl derivatives ((E)-(NP{sub 3})Rh(CH=C(H)R)). Two-electron oxidation of the vinylidene complexes by controlled-potential electrolysis results in the deprotonation of the vinylidene ligand. When O{sub 2} is bubbled into CH{sub 2}Cl{sub 2} solutions of the vinylidene complexes, the Rh(III) hydroxide acetylide compounds ((NP{sub 3})Rh(OH)(C{triple bond}CR))BPh{sub 4} are obtained in ca. 60% yield because of extensive decomposition of the starting compounds. For R = Ph, an appreciable amount of phenol is found. Thermal decomposition of the vinylidene complexes in refluxing THF produces H{sub 2} and the paramagnetic Rh(II) derivatives ((NP{sub 3})Rh(C{triple bond}CR)){sup +}. Unlike the NP{sub 3} {sigma}-acetylides, the PP{submore » 3} analogues (PP{sub 3} = P(CH{sub 2}CH{sub 2}PPh{sub 2}){sub 3}) react with strong acids in THF or CH{sub 2}CL{sub 2} to form unusual examples of vinylphosphonium compounds of formula (((Ph{sub 2}PCH{sub 2}CH{sub 2}){sub 2}P(CH{sub 2}CH{sub 2}PPh{sub 2}))Rh(C=C(H)C(O)R))BPh{sub 4}.« less

Removal of one chloride ligand from the aminocarbene fac -[(PNP)RuCl 2 (C&{N(H)Ph}{CH 2 Ph})] in THF followed by treatment with phenylacetylene yields the ruthenium(II) complex mer -[(PNP)RuCl{C=C(H)Ph}(C{N(H)Ph}{CH 2 Ph})]PF 6 ( 4 ). Complex 4 represents the first example of a transition metal complex with the simultaneous coordination of vinylidene and carbene ligands.