Alkenyl Complexes Research Articles

Reactions of a Transient Carbonyl(chloro)(hydrido)ruthenium(II) Complex with Ethylene, Alkynes, and CO; Chemistry of the New Anion [Ru2 (CO)4 Cl5

A 97% yield of [Ru3 (CO)12 ] (2) in 20 minutes is obtained simply by treating [Ru(CO)3 Cl2 (thf)] with KOH under CO (1 atm). The reduction to Ru0 can be explained in terms of the facile reductive elimination of HCl from the transient hydrido complex 1. Though elusive, the latter can be intercepted by olefins or alkynes to produce trappable alkyl or alkenyl complexes such as 3 and 4.█ denotes a vacant coordination site.

Transformations of alkynyl ligands at iron centres: alkenyl formation via addition of PPh3 and enyne generation via head-to-head coupling and addition of benzene

Thermolysis of Fe2(CO)6(µ-PPh2)(µ-C2But) affords the binuclear alkenyl complex Fe2(CO)5(µ-PPh2)(µ-o-Ph2PC6H4CCHBut) and the trinuclear arene complex Fe3(CO)4(µ3-o-PhPC6H4PPh){µ3-C(But)CCHCBut-η6-C6H5} both resulting from a number of novel transformations including C–C bond formation and C–H and C–P bond cleavage and reformation.

Cluster-Mediated Conversion of Diphenylacetylene into α-Phenylcinnamaldehyde. Construction of a Catalytic Hydroformylation Cycle Based on Isolated Intermediates

The present paper deals with a rational attempt to achieve the hydroformylation of diphenylacetylene onto a hydrido triruthenium cluster complex incorporating the 2-(methylamino)pyridyl group (abbreviation: MeNpy) as a hemilabile ancillary ligand [note: in all species discussed below, the bridgehead μ2-N atom is linked to the centers labeled as Ru(1) and Ru(2), whereas the pyridyl nitrogen is bound to Ru(3)]. The complex Ru3(μ-H)(μ-MeNpy)(CO)9 (1) is shown to react cleanly with diphenylacetylene to give the alkenyl complex Ru3(μ-MeNpy)(μ-PhCCHPh)(CO)8 (2), the structure of which is reported. The reaction of 2 with 1 equiv of PPh3 proceeds to completion within less than 3 min at 25 °C, giving two propenoyl complexes, namely, Ru3(μ-MeNpy)(μ-OC−PhCCHPh)(PPh3)(CO)7 (3) (48% yield) and Ru3(μ-MeNpy)(μ-OC−PhCCHPh)(PPh3)2(CO)6 (4) (19% yield), both fully characterized by spectroscopic methods and X-ray analysis. Complex 3 is an adduct of 2 with PPh3. The incorporation of the phosphine has caused a migratory CO insertion of the alkenyl group. The phosphine occupies an equatorial coordination site on Ru(1), in cis position relative to the nitrogen atom of the amido bridge. The newly formed propenoyl group occupies an equatorial bridging position across the Ru(1)−Ru(3) edge, with the acyl oxygen bound to Ru(1), in cis position relative to both the bridgehead nitrogen atom and the phosphine. The molecular structure of the second propenoyl compound, Ru3(μ-MeNpy)(μ-OC−PhCCHPh)(PPh3)2(CO)6 (4), is formally derived from the previous one, 3, by a simple substitution of an equatorial CO of Ru(2) by PPh3. The use of a 2-fold amount of phosphine for the above reaction modifies only slightly the relative abundance of 3 (30%) and 4 (44%). This indicates that 3 is not the kinetic product of the reaction between 2 and a phosphine. Further reaction of 4b with CO induces loss of one PPh3 and incorporation of two CO ligands. This produces the open 50e cluster Ru3(μ-MeNpy)(μ-OC−PhCCHPh)(PPh3)(CO)8 (5), in which the bridging propenoyl group now spans the open edge Ru(1)−Ru(2) (the remaining phosphine occupies an equatorial site cis to the acyl oxygen). Treatment of 2b with CO (1 atm, 25 °C, 20 min) also promotes migratory CO insertion, giving the 50e propenoyl complex Ru3(μ-MeNpy)(μ-OC−PhCCHPh)(CO)9 (6b), whose structure has been determined. The propenoyl group spans the open edge Ru(1)−Ru(2). Although stable in CO-saturated solutions under CO atmosphere, the complex reverts rapidly to 2 within 30 s under inert atmosphere. Treatment of 6 with CO/H2 gas mixtures under ambient conditions produces α-phenylcinnamaldehyde with concomitant recovery of 1, showing that the hydroformylation of diphenylacetylene can be achieved in a stepwise manner through the cyclic reaction sequence 1 → 2 → 6 → 1. Under nonoptimized catalytic conditions, the amount of α-phenylcinnamaldehyde obtained corresponds to about eight cycles. The metal-containing species recovered in the reactor through the catalytic runs is isolated and formulated as the bimetallic carboxamido complex [Ru{−C(O)−MeNpy}(CO)3]2 (7). Thus, it appears that deactivation of the system has taken place via CO insertion into the metal−amide bond.

Synthesis and Reactivity of Ferrocenecarboxylate Ruthenium(II) Complexes. Catalytic Synthesis of a Ferrocenecarboxylic Enol Ester

Summary: New ferrocenecarboxylate ruthenium(II) complexes were obtained from the reaction of [RuClH(CO)(PPh3)3] with ferrocenecarboxylic acid or its sodium salt. The reaction of alkenyl complexes [Ru(O2C(C5H4)Fe(C5H5))(CR‘CRH)(CO)(PPh3)2] with CO and catalytic synthesis of the phenylethyleneferrocenecarboxylic ester have been studied.

Understanding the Preference for the Coplanarity of Alkenyl and Carbonyl Ligands in η1-Alkenyl Transition-Metal Complexes: A Simple Molecular Orbital Approach and ab Initio Calculations

The preference for coplanarity of alkenyl and carbonyl ligands in η1-alkenyl transition-metal complexes can be understood in terms of a simple molecular orbital model in which the nonbonding metal t2g orbitals interact with the π* orbitals of these ligands. Such back-bonding interactions are most favorable when the alkenyl and carbonyl ligands are coplanar, as all three t2g orbitals are utilized by the ligands. Optimized geometries obtained from ab initio calculations for a variety of ruthenium alkenyl complexes show the preference for alkenyl−carbonyl planarity when only one or two carbonyl ligands are present in the complex. In these complexes the energy required to rotate the alkenyl ligand is calculated to be approximately 7 kcal/mol, while in complexes with three or more carbonyl ligands this energy decreases due to competition by carbonyl ligands for favorable back-bonding interactions. This competition effectively rules out any preferential alkenyl−carbonyl arrangement, and instead steric interacti...

Hydrogen Transfer in Pt-Mo Heterodinuclear Hydride Complexes Promoted by Alkynes

Abstract Reactions of a Pt-Mo heterodinuclear hydride complex, (dpe)HPt-MoCp(CO)3 with alkynes at room temperature lead to facile reductive elimination giving HMoCp(CO)3 accompanied by the formation of Pt(alkyne)(dpe). When terminal alkynes are employed, further Markovnikov addition of HMoCp(CO)3 to the coordinated alkyne takes place to give new heterodinuclear alkenyl complexes (dpe)(μ-H2C=CR)Pt-MoCp(μ-CO)(CO).

Insertion Reactions of Alkynes into the Ru−H Bond of Indenylruthenium(II) Hydride Complexes. Mechanism of the Reaction of Phenylacetylene with [RuH(η5-C9H7)(dppm)] (dppm = Bis(diphenylphosphino)methane)

The indenyl complexes [RuX(η5-C9H7)(dppm)] (dppm = bis(diphenylphosphino)methane, X = H, D) react with phenylacetylene to give the products of syn addition [Ru{(E)-CHCXPh}(η5-C9H7)(dppm)] in toluene, in the temperature range 40−80 °C. The indenyl complexes [RuH(η5-C9H7)LL‘] (L = L‘ = PMe2Ph; L = PPh3, L‘ = PMe2Ph; L = PPh3, L‘ = PMe3; LL‘ = dppe) and [RuH(η5-Me3C9H4)(CO)(PPh3)] and the cyclopentadienyl complex [RuH(η5-C5H5)(dppm)] do not react with PhC⋮CH, even under more forcing conditions. The complexes [RuH(η5-C9H7)LL‘] (LL‘ = dppe; LL‘ = dppm; L = L‘ = PMe2Ph; L = PPh3, L‘ = PMe3; L = PPh3, L‘ = PMe2Ph) and the indenyl-substituted complexes [RuH(η5-Me3C9H4)(CO)(PR3)] (PR3 = PPh3, PiPr3) react with dimethyl acetylenedicarboxylate to give the alkenyl derivatives [Ru{(E)-C(CO2Me)CH(CO2Me)}(η5-C9H7)LL‘] and [Ru{(E)-C(CO2Me)CH(CO2Me)}(η5-Me3C9H4)(CO)(PR3)], respectively, in diethyl ether under reflux. The reaction of [RuH(η5-C9H7)LL‘] with methyl propiolate yields the α-metalated alkenyl complexes [Ru{C(CO2Me)CH2}(η5-C9H7)LL‘] (LL‘ = dppe, dppm; L = L‘ = PMe2Ph; L = PPh3, L‘ = PMe3) in refluxing diethyl ether. A kinetic study has been carried out for the reaction of the complexes [RuX(η5-C9H7)(dppm)] with phenylacetylene in toluene, by 1H and 31P{1H} NMR spectroscopy. The reactions are first order with respect to the ruthenium complex and to the alkyne. The hydride and the deuteride complexes react at the same rate; intermediates are not detectable neither by kinetic studies nor by spectroscopy. The activation parameters, from rate measurements in the range 40−60 °C, are as follows: ΔH⧧ = 17 ± 2 kcal mol-1, ΔS⧧ = −21 ± 4 cal mol-1 K-1. An associative mechanism is proposed for the reaction, which involves the formation of an intermediate from the ruthenium complex and the alkyne under rate-determining steady-state conditions, followed by fast hydride migration and product formation. Due to the lack of reactivity of the analogous cyclopentadienyl complex [RuH(η5-C5H5)(dppm)], the reaction represents a case of indenyl effect. On the other hand, the indenyl and the cyclopentadienyl complexes react at comparable rates with the activated alkyne methyl propiolate.

Addition of Organolithium Nucleophiles to the Diiron Allenyl Complex [Fe2(CO)6(μ-PPh2){μ-η1:η2α,β-(H)CαCβCγH2}]: Synthesis and Characterization of Organodiiron-Coordinated β,γ-Unsaturated Ketones

The binuclear allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1:η2α,β-(H)CαCβCγH2}] (1) has been prepared, and its reactivity with organolithium nucleophiles is described. Prop-2-yne bromide reacts with [Fe2(CO)7(μ-PPh2)]-Na+, via an SN2 mechanism, to give [Fe2(CO)6(μ-PPh2){μ-η1:η2α,β-(H)CαCβCγH2}], the first example of a phosphido-bridged allenyl complex. The molecular structure of [Fe2(CO)6(μ-PPh2){μ-η1:η2-(H)CαCβCγH2}] (1) was determined by single-crystal X-ray diffraction and shows that the allenyl ligand is coordinated through Cα−Cβ. Variable-temperature 1H and 13C NMR studies reveal a high-energy exchange process that equilibrates the diastereotopic allenyl protons, presumably via a zwitterionic intermediate, as well as two independent trigonal rotations that act to exchange the carbonyl ligands on each unique Fe(CO)3 group. Complex 1 reacts with organolithium reagents (RLi; R = Me, nBu, Ph, C4H3S), via allenyl−carbonyl−nucleophile coupling, to afford the binuclear β,γ-unsaturated ketones [Fe2(CO)5{P(OMe)3}(μ-PPh2)(μ-η1:η2-{RC(O)CH2}CCH2)] (R = Me, 3a; nBu, 3b; Ph, 3c; C4H3S, 3d), and a single-crystal X-ray structure determination of 3a was undertaken to confirm the connectivity of the hydrocarbyl ligand. The most likely mechanism for the formation of 3a−d involves nucleophilic attack of R- at CO to give an acylate intermediate followed by migration of RCO to Cα of the allenyl and protonation of the resulting enolate to give the unstable alkenyl complexes [Fe2(CO)5(μ-PPh2)(μ-η1(C):η1(C):η2(C)-{RC(O)CH2}CCH2)] (R = Me, 2a; Bu, 2b; Ph, 2c; C4H3S, 2d). Finally, substitution of the metal-coordinated ester carbonyl in 2a−d with trimethylphosphite affords 3a−d as stable crystalline products.

The Effect of N-Donor Ligands on the Reaction of Ruthenium Hydrides with 1-Alkynes

Neutral ruthenium hydrides Ru(CO)ClH(L)(PPh3)2 bearing one N-donor ligand react with 1-alkynes at 23 °C to yield neutral alkenyl complexes Ru(CO)Cl(CHCHR)(L)(PPh3)2. Under similar conditions, cationic hydrido complexes [Ru(CO)H(L)2(PPh3)2]PF6 with pyridine-type N-donor ligands yield alkynyl complexes [Ru(CO)(CH≡CHR)(L)2(PPh3)2]PF6 as a result of the reaction of the intermediate labile alkenyl with a second molecule of alkyne. Under more forcing conditions, 1-alkynyl complexes could also be prepared from the neutral ruthenium hydrides. Cationic ruthenium hydrides with bidentate N-donor ligands are unreactive toward 1-alkynes. Neutral alkenyl complexes Ru(CO)Cl(CHCHR)(L)(PPh3)2 (R = p-MeC6H4, CMe3; L = pyridine, isoquinoline) reacted smoothly with 1-alkynes to afford the corresponding σ-alkynyl ruthenium derivatives Ru(CO)Cl(C≡CR)(L)(PPh3)2.

Diiron σ-π alkenyl complexes: crystal structures of cis-[Fe 2(CO) 4(μ-RCCH 2)(μ-PPh 2)(μ-dppm)], (R  Ph, CH 2OH), trans-[Fe 2(CO) 4(μ-HCCHPh)(μ-PPh 2)(μ-dppm)] and the α,β-unsaturated acyl complex trans-[Fe 2(CO) 4{μ-OCC(Ph)CH 2}(μ-PCy 2)(μ-dppm)

Insertion of phenylethyne into cis-[Fe 2(CO) 4(μ-H)(μ-CO)(μ-PPh 2)(μ-dppm)] 1a affords isomers cis-[Fe 2(CO) 4(μ-PhCCH 2)(μ-PPh 2)(μ-dppm)] 2a and trans-[Fe 2(CO) 4(μ-HCCHPh)(μ-PPh 2)(μ-dppm)] 2b which differ in both the regioselectivity of the alkyne insertion (α and β) and the relative orientations of the phosphido and diphosphine ligands ( cis and trans) respectively. In contrast, reaction with trans-[Fe 2(CO) 4(μ-H)(μ-CO)(μ-PCy 2)(μ-dppm)] 1b appears to give only the α-substituted product trans-[Fe 2(CO) 4(μ-PhCCH 2)(μ-PCy 2)(μ-dppm)] 3a, however, thermolysis of the crude reaction mixture leads to the low yield isolation of the α,β-unsaturated acyl complex trans-[Fe 2(CO) 4{μ-OCC(Ph)CH 2)}(μ-PCy 2)(μ-dppm)] 4, formally resulting from Co insertion into the unidentified β-substituted isomer. Reaction of 1a with propargyl alcohol affords chromatographically separable isomers cis-[Fe 2(CO) 4{μ-C(CH 2OH)CH 2}(μ-PPh 2(μ-dppm)] 5a and trans-[Fe 2(CO) 4{μ-HCCH(CH 2OH)}(μ-PPh 2)(μ-dppm)] 5b, while with 1b an inseparable mixture of trans-[Fe 2(CO) 4{μ-C(CH 2OH)CH 2}(μ-PCy 2)(μ-dppm)] 6a and trans-[Fe 2(CO) 4{μ-HCCH(CH 2OH)}(μ-PCy 2)(μ-dppm)] 6b results. Complexes 2a, 2b, 4 and 5a have been characterised by single crystal X-ray diffraction analyses. All μ-alkenyl complexes undergo ‘windshield-wiper’ fluxionality on the NMR timescale, with free energies of activation varying dramatically, an effect which can be correlated with the mode of binding of the alkenyl ligand in the solid state.

A reductive rearrangement of iron acetylide hydride complexes

Iron acetylide hydride complexes of the type [Fe(H)(CCR)(dmpe) 2 ] [dmpe = 1,2-bis(dimethylphosphino)ethane] react with anions in a methanol solution to form substituted alkenyl complexes; the crystal structure of trans-FeN 3 (CHCHPh)(dmpe) 2 ] is presented.

Reactivity of Silylated Dinuclear Iron−Platinum Acyl Complexes: Formation of μ-Vinylidene Complexes and Crystal Structures of the Acyl Complex [(OC)3{(MeO)3Si}Fe(μ-dppm)Pt{C(O)Me}(t-BuNC)] and the μ-Vinylidene Complex [(OC)3Fe{μ-CC(H)Ph}(μ-dppm)Pt(PPh3)

Addition of RNC to the heterobimetallic acyl complex [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppm)Pt{C(O)Me}] (1a), which displays a μ−η2-Si−O bridge, afforded the isonitrile adducts [(OC)3{(MeO)3Si}Fe(μ-dppm)Pt{C(O)Me}(C⋮NR)] (3a R = t-Bu, 3b R = 2,6-xylyl). Upon treatment of a CH2Cl2 solution of 1a with MeO2CC⋮CCO2Me (DMAD), alkyne insertion into the Pt−C bond gave the alkenyl complex [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppm)Pt{(MeO2C)CC(CO2Me)C(O)Me}] 4. The isonitrile adducts [(OC)3{(MeO)3Si}Fe(μ-dppm)Pt{(MeO2C)CC(O2Me)C(O)Me}(C⋮NR)] (5a R = t-Bu, 5b R = 2,6-xylyl)] were isolated after addition of RNC. A more complex reaction occurred when phenylacetylene or tert-butylacetylene were reacted with 1a. The iron-bound Si(OMe)3 group and the organic ligand coordinated on platinum were eliminated, and the vinylidene-bridged complexes [(OC)3Fe{μ-CC(H)R}(μ-dppm)Pt(CO)] (6a R = Ph, 6b R = t-Bu, 6c R = n-Bu) were obtained. The loosely Pt-bound CO ligand of 6a−c was readily displaced by PPh3, P(OMe)3, or 2,6-xylyl isonitrile yielding the substitution products [(OC)3Fe{μ-CC(H)R}(μ-dppm)Pt(L)] (7a R = Ph, L = PPh3; 7b R = t-Bu, L = PPh3; 7c R = t-Bu, L = P(OMe)3; 7d R = t-Bu, L = 2,6-xylylNC). The heterobimetallic phenyl complex [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppm)Pt(Ph)] (8) was obtained by reaction of K[Fe{Si(OMe)3}(CO)3(η1-dppm)] with a cold THF solution of [PtCl(Ph)(1,5-COD)]. The μ−η2-Si−O bridge is readily opened under a CO atmosphere to give the CO adduct [(OC)3Fe{Si(OMe)3}(μ-dppm)Pt(CO)(Ph)] (9), which unexpectedly does not insert CO into the Pt−phenyl bond. This complex reversibly loses the CO ligand under reduced pressure to regenerate 8. All complexes have been studied by multinuclear NMR spectroscopy. The solid state structures of complexes 3a and 7a have been determined by single-crystal X-ray diffraction.

Synthesis of “Phosphine Tethered” η2-Allene and μ-η1:η2-Alkenyl Complexes: Facile P−Cα Bond Formation and C−H Activation Reactions of Bis(diphenylphosphino)methane with [Fe2(CO)6(μ-ER){μ-η1:η2α,β-(H)CαCβCγH2}] (E = PPh, R = Ph; E = S, R = tBu)

The phosphido-bridged diiron allenyl complex [Fe2(CO)6(μ-PPh2){μ-η1:η2α,β-(H)CαCβCγH2}] (1) reacts with dppm to afford, in the first instance, [Fe2(CO)6(μ-PPh2){η1(P):η2(C)-Ph2PCH2PPh2(H)CCCH2}] (3), which contains a novel η1(P):η2(C)-dppm-functionalized allene. A single-crystal X-ray study reveals 3 to be derived from 1 by nucleophilic attack of dppm at Cα with metal−metal bond cleavage and internuclear migration of CO. Upon standing in toluene [Fe2(CO)6(μ-PPh2){η1(P):η2(C)-Ph2PCH2PPh2(H)CCCH2}] (3) slowly decarbonylates to afford the unusual σ-π-alkenyl complex [Fe2(CO)5(μ-PPh2){μ-η1(P):η1(C):η2(C)-Ph2PCHPPh2(H)CCCH3}] (4), containing a metal- and carbon-coordinated bis(diphenylphosphino)methanide ligand. Overall, the transformation of 3 into 4 requires activation of a dppm methylene C−H bond, hydrogen migration to Cγ together with metal−metal bond formation, and loss of CO. Surprisingly, [Fe2(CO)6(μ-StBu){μ-η1:η2α,β-(H)CαCβCγH2}] and dppm react to afford high yields of the isomeric alkenyl complexes [F...

Iridapyrrole Complexes via Formal 3 + 2 Cycloaddition of Iridium Alkenyls to Acetonitrile

Under appropriate conditions, the bis(ethylene) derivative Tp*Ir(C2H4)2 (Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate) reacts with MeCN to provide the Ir(III) complex Tp*Ir(CHCH2)(C2H5)(NCMe) (1). In the presence of catalytic amounts of water, 1 undergoes intramolecular coupling of the vinyl and acetonitrile ligands, with formation of a compound (2a) that contains a delocalized, five-membered iridapyrrole ring. This unusual cycloaddition reaction can be extended to other related alkenyl complexes of iridium.

Carbon−Carbon Coupling and Carbon−Hydrogen Activation Reactions in Bis(triisopropylphosphine)osmium Complexes

Reaction of the alkenyl complex OsCl(E-CHCHPh)(CO)(PiPr3)2 (1) with phenyllithium gives OsH{C6H4-2-(E-CHCHPh)}(CO)(PiPr3)2 (2). The structure of 2 (isomer 2a) has been determined by X-ray diffraction: triclinic, P1, a = 9.230(1) A, b = 10.092(1) A, c = 18.525(2) A, α = 88.667(7)°, β = 87.172(7)°, γ = 71.110(6)°, V = 1630.6(3), Z = 2, R (F, Fo ≥ 4σ(Fo)) = 4.01, wR (F2, all reflections) = 9.94%. The geometry around the osmium can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying two relative trans positions. The remaining perpendicular plane is formed by the carbonyl and the 2-(E-1‘-styryl)phenyl ligands mutually trans disposed, the hydride ligand and one olefinic hydrogen of the 2-(E-1‘-styryl)phenyl ligand, which shows an agostic interaction with the osmium atom (distance 2.05(7) A). The solutions of 2 show equilibria between the agostic isomer (2a) and a nonagostic isomer (2b). The thermodynamic magnitudes involved in the equilibrium as well as the activation p...

Intramolecular addition of monomeric arylcopper entities across an alkyne grouping in a complex of type [( η5-C 5H 4SiMe 3) 2 Ti(CCSiMe 3) 2]CuR; X-ray structure of [( η5-C 5H 4SiMe 3) 2Ti(CCSiMe 3) μ-CC(SiMe 3)(C 6H 3(CH 2NMe 2) 2-2,6) Cu

The tetranuclear heteroleptic arylcopper aggregate [Cu 4R 2Br 2] (RC 6H 3(CH 2NMe 2) 2-2,6) reacts with the organometallic 1,4-diyne [( η 5-C 5 H 4SiMe 3) 2Ti(CCSiMe 3) 2), 1, to give equivalent amounts of known [ 1 · CuBr], and the novel 1,1- bis-metalla alkenyl complex η 5- C 5 SiMe 3) 2 Ti( C CSiMe 3)μ- C C( SiMe 3)( R) Cu, 6 , that is the result of intramolecular addition of a CuC bond across the alkyne triple bond.

Syntheses of carbene and alkenyl derivatives of palladium. Solid-state structures of {(Me 2NCS 2) Pd(PEt 3) [η 1−C(N(CH 3) C(CH 3) 3) CH 3]}BPh 4 and {(Me 2NCS 2)Pd(PEt 3)[η 1−C(NHC(CH 3) 3)CH 3]}PF 6 · Et 2O

The reaction of tBuNC and (Me 2NCS 2)Pd(PEt 3)CH 3 yields Mc 2NCS 2)Pd(PEt 3)[η 1-C(NC(CH 3) 3)CH 3]. Reaction of this amino acyl complex with [(CH 3) 3O]BF 4 yields, after anion exchange, {(Me 2NCS 2)Pd(PEt 3)[η 1-C(N(CH 3)C(CH 3)C(CH 3) 3]}BPh 4. An analogous reaction with NH 4PF 6 yields 2)Pd(PEt 3)[η 1-C(NHC(CH 3) 3)CGG 3]}PF 6. Both of these carbene complexes have been characterized crystallographically. Crystal data: Pd(PEt 3)[η 1C(N(CH 3C(CH 3]}BPH 4 triclinic, P 1a = 12.253(12) A ̊ b = 14.422(5) A ̊ c = 11.564(5) A, α = 97.38(3)°, β = 93.04(6)°, γ = 85.21(5)°, V= 2018 A ̊ 3, Z = 2, T = 298 K, R(F) = 7.6%; {(Me 2NCS 2)Pd(PEt 3)[η 1C(NHC(CH 3) 3 · Et 2O triclinic, P 1, a = 12.844(2) A ̊ b = 15.247(2) A ̊ , c = 8.312(2) A ̊ , α = 105.60(1)°, β = 101.67(2)°, γ = 90.20(1)°, V = 1533 A ̊ 3, Z = 2, T = 298 K, R(F) = 5.4% . In both complexes the overall coordination geometry is approximately planar about both the palladium atom and carbene carbon atom, and these two planes are perpendicular. Reaction of Pd(PEt 3[η 1C(N(N(CH 3)C(CH 3) with LiCH 3 results in deprotonation at the β-carbon yielding Pd(PEt 3)[η 1-C(N(CH 3)C(CH and this reaction is reversed with HBF 4 · Et 2O. The reaction of LiC(OCH 2CH 3-CH 2 with (Me 2NCS 2)Pd(PEt 3)Cl yields (Me 2NCS 2)Pd(PEt 3)[η 1C(OCH 2CH 3)CH 2]. This alkenyl complex reacts with BH 3 in ethanol to yield S 2)Pd(PEt 3)[η 1CH(OCH 2CH CS 2)Pd(PEt 3)[η 1-C(OCH 2CH also forms in the reaction of (Me 2NCS 2)Pd(PEt 3)H and HCq̊ along with both geometric isomers of S 2)Pd(PEt 3[η 1CHCH(OCGH 2CH 3,Reaction of phenylacetylene and (Me 2NCS 2)Pd (PEt 3)H yields mainly dNCS 2)Pd(PEt 3{η 1C(PH)C with small amounts of one of the other regioisomers present.

Nucleophilic additions to the chiral rhenium alkene complexes [Re(η5-C5H5)(NO)(PPh3)(H2CCHR)]BF4(R = H, Me, CH2CH2Me, Ph or CH2Ph): regio-, diastereo- and enantio-selectivities

Reactions of alkene complexes [Re(η5-C5H5)(NO)(PPh3)(H2CCHR)]BF41(R = H a, Me b, CH2CH2Me c, Ph d or CH2Ph e) and LiCuMe2 in tetrahydrofuran (thf) at –80 °C gave the primary, β-branched alkyl complexes [Re(η5-C5H5)(NO)(PPh3)(CH2CHMeR)]2(79–99%). No secondary alkyl complexes derived from additions to the unsubstituted CH2 termini were detected. Product diastereomer and enantiomer ratios matched those of the reactants. Thus, the additions are regiospecific, diastereospecific and enantiospecific. A chemical correlation involving [Re(η5-C5H5)(NO)(PPh3){CH2CH(CD3)Me}] and a crystal structure determination [(SR,RS)-2e·0.5C6H14] show that attack occurs on the CC face anti to the rhenium. Reactions of 1a or 1b(in thf) with NaOMe–MeOH gave predominantly the 2-methoxyalkyl complexes [Re(η5-C5H5)(NO)(PPh3){CH2CH(OMe)R}](R = H 4a or Me 4b)(92–97%). Analogous reactions of 1c or 1d gave 81–77:19–23 mixtures of 4c or 4d and the alkenyl complexes (E)-[Re(η5-C5H5)(NO)(PPh3)(CHCHR)](85–71%). A similar reaction of 1e gave mainly the allyl complex [Re(η5-C5H5)(NO)(PPh3)(CH2CHCHPh)].

A general method of generating agostic interaction between RuIIand C–H bonds of tert-butyl, methyl, aryl, heterocyclic or alkenyl groups using azine phosphines

Treatment of [RuCl2(PPh3)3]2 with the azine phosphine Z,E-PPh2CH2C(But)N–NC(Me)But3a, derived from MeC(O)But, gave the δ-agostic tert-butyl complex mer,trans-[RuCl2(PPh3){PPh2CH2C(But)N–NC(Me)But}]4a, in which all nine hydrogens of the tert-butyl group are agostically interacting with ruthenium on the NMR time-scale at 20°C. The analogous δ-agostic tert-butyl complex mer,trans-[RuCl2(PPh3){PPh2CH2C(But)N–NC(H)But}]4b was also prepared. Treatment of 2 with the symmetrical azine diphosphine Z,Z-PPh2CH2C(But)N–NC(But)CH2PPh25 gave the δ-agostic tert-butyl complex mer,trans-[RuCl2(PPh3){PPh2CH2C(But)N–NC(But)CH2PPh2}]6, in which one of the PPh2 groups is unco-ordinated. Treatment of 2 with the azine phosphine Z,E-PPh2CH2C(But)N–NC10H167, derived from pinacolone–fenchone mixed azine, gave the δ-agostic methyl complex mer,trans-[RuCl2(PPh3){PPh2CH2C(But)N–NC10H16}]8, in which the methyl group (C10H3) in the 1-position of the fenchone residue interacts with ruthenium (fenchone = 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one). The unsymmetrical camphor azine monophosphine Z,Z-PPh2C10H15N–NC10H169 also gave a similar δ-agostic methyl complex mer,trans-[RuCl2(PPh3){PPh2-C10H15N–NC10H16}]10(camphor = 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one). Treatment of 2 with the azine Z,E-PPh2CH2C(But)N–NCH(C6H4NMe2-4)11a, derived from 4-dimethylaminobenzaldehyde, gave the δ-agostic complex mer,trans-[RuCl2(PPh3){PPh2CH2C(But)N–NCH(C6H4NMe2-4)}]12a, in which the hydrogens in the 2 and 6 positions of the aryl group are agostically interacting with ruthenium. Similarly, the azines 11b and 11c, derived from 4-methoxybenzaldehyde or 4-nitrobenzaldehyde, gave the δ-agostic complexes 12b and 12c, respectively. Treatment of 2 with the azine 13, derived from 1-methylpyrrole-2-carbaldehyde, gave the δ-agostic complex 14, in which the hydrogen in the 3-position of the heterocyclic group is agostically interacting with ruthenium. Treatment of 2 with the azine 15, derived from benzylideneacetone, gave the δ-agostic alkenyl complex 16. Proton, 31P-{1H} and some 13C-{1H} NMR data are given.

Synthesis, electrosynthesis and structural studies of bis(silylcyclopentadienyl) niobium complexes with acetylene ligands

The reduction of [Nb(η 5-C 5H 4SiMe 3) 2Cl 2] ( 1) with one equivalent of sodium amalgam (10%) in the presence of acetylenes yields [Nb(η 5-C 5H 4SiMe 3) 2Cl(η 2-RC 1CR 2)], (R 1 = H, R 2 = COOMe, 3c; R 1 = Me, R 2 = COOMe, 3d; R 1 = R 2 COOMe, 3e) The structural characterization of these compounds has been carried out by NMR spectroscopy. The reduction of the (acetylene)niobium(V) complexes [Nb(η 5-C 5H 4SiMe 3) 2Cl(η 2-R 1CCR 2)] with one equivalent of sodium amalgam (10%) gives the paramagnetic niobium(IV) complexes [Nb(η 5-C 5H 4SiMe 3) 2(η 2-R 1CCR 2)] (R 1 = R 2 = Ph, 4a; R 1 = H, R 2 = Ph, 4b; R 1 = H, R 2 = COOMe, 4c; R 1 = Me, R 2 = COOMe, 4d; R 1 = R 2 = COOMe, 4e), which have been characterized by ESR spectroscopy. However, electroreduction of 1 in the presence of the acetylenes gives the complexes 3 or 4 depending both on the nature of the acetylene and on the experimental conditions. In the electrolysis of 1 in the presence of acetylenes c or d a slow production of 4c and 4d, respectively, occurs to yield the alkenyl complexes [Nb(η 5-C 5H 4SiMe 3) 2Cl(η 1-R 1C = CHR 2)], 4'c and 4'd. Finally, the addition of HCl to solutions of 4a gives a mixture of 1 and cis-stilbene.