Bis-insertion Product Research Articles

Heteroallene Insertions into Tin(II) Alkoxide Bonds.

A series of iso-carbamate complexes have been synthesized by the reaction of [SnII(OiPr)2] or [SnII(OtBu)2] with either aryl or alkyl isocyanates, ONC-R (R = 2,4,6-trimethylphenyl (Mes), 2,6-diisopropylphenyl (Dipp), isopropyl (iPr), cyclohexyl (Cy) and tert-butyl (tBu)). In the case of aryl isocyanates, mono-insertion occurs to form structurally characterized complexes [Sn{κ2-N,O-R-NC(OiPr)O}(μ-OiPr)]2 (1: R = Mes, 2: R = Dipp) and [Sn{κ2-N,O-R-NC(OtBu)O}(μ-OtBu)]2 (3: R = Mes, 4: R = Dipp). The complicated solution-state chemistry of these species has been explored using 1H DOSY experiments. In contrast, reactions of tin(II) alkoxides with alkyl isocyanates result in the formation of bis-insertion products [Sn{κ2-N,O-R-NC(OiPr)O}2] (5: R = iPr, and 6: R = Cy) and [Sn{κ2-N,O-R-NC(OtBu)O}2] (7: R = iPr, 8: R = Cy), of which complexes 6-8 have also been structurally characterized. 1H NMR studies show that the reaction of tBu-NCO with either [Sn(OiPr)2] or [Sn(OtBu)2] results in a reversible mono-insertion. Variable-temperature 2D 1H-1H exchange spectroscopy (VT-2D-EXSY) was used to determine the rate of exchange between free tBu-NCO and the coordinated tBu-iso-carbamate ligand for the {OiPr} alkoxide complex, as well as the activation energy (Ea = 92.2 ± 0.8 kJ mol-1), enthalpy (ΔH‡ = 89.4 ± 0.8 kJ mol-1), and entropy (ΔS‡ = 12.6 ± 2.9 J mol-1 K-1) for the process [Sn(OiPr)2] + tBu-NCO ↔ [Sn{κ2-N,O-tBu-NC(OiPr)O}(OiPr)]. Attempts to form Sn(II) alkyl carbonates by the insertion of CO2 into either [Sn(OiPr)2] or [Sn(OtBu)2] proved unsuccessful. However, 119Sn{1H} NMR spectroscopy of the reaction of excess CO2 with [Sn(OiPr)2] reveals the presence of a new Sn(II) species, i.e., [(iPrO)Sn(O2COiPr)], VT-2D-EXSY (1H) of which confirms the reversible alkyl carbonate formation (Ea = 70.3 ± 13.0 kJ mol-1; ΔH‡ = 68.0 ± 1.3 kJ mol-1 and ΔS‡ = -8.07 ± 2.8 J mol-1 K-1).

Synthesis of a Ga-Stabilized As-Centered Radical and a Gallastibene by Tailoring Group 15 Element-Carbon Bond Strengths.

A convenient synthetic route to Ga-stabilized pnictogen-centered radicals and gallapnictenes by manipulation of pnictogen-carbon bond strengths is presented. Two equivalents of LGa (L = HC[C(Me)N(Dip)]2, Dip = 2,6-i-Pr2C6H3) react with CpArAsCl2 (CpAr = C5(4-t-BuC6H4)5) with formation of the arsenic-centered radical [L(Cl)Ga]2As·1. In contrast, the analogous reaction with TerSbCl2 (Ter = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) yields the gallastibene LGa═SbTer (2) containing a Ga-Sb double bond, whereas reactions of DipSbCl2 with one and two equivalents of LGa give the monoinsertion and bisinsertion products L(Cl)GaSb(ClDip) (3) and [L(Cl]Ga]2SbDip (4), respectively. 1-4 were structurally characterized by single crystal X-ray diffraction. The description of 1 as an arsenic-centered radical is consistent with results of electron paramagnetic resonance and density functional theory (DFT) studies. The π-bonding in LGa═SbTer (2) is estimated to 10.68 kcal mol-1 by variable-temperature (VT) NMR spectroscopy, and DFT studies reveal a significant π-bonding interaction between Sb and Ga.

Reactivity of Scandium β-Diketiminate Alkyl Complexes with Carbon Dioxide

The reactions of two highly air- and moisture-sensitive scandium bis(alkyls) supported by a bulky β-diketiminato (nacnac) ligand with carbon dioxide are described. [κ2-ArNC(tBu)CHC(tBu)NAr]ScR2 (Ar = 2,6-iPr2C6H3; R = CH3, 1a; R = CH2SiMe3, 1b) react rapidly with CO2 to give mixtures of mono- and bis(carboxylato) insertion products 2a/2b and 3a/3b depending on the stoichiometry and conditions of the reaction. Compound 2a (R = CH3) is a dimeric complex with bridging acetato groups, as determined by X-ray crystallography. These compounds were characterized by NMR spectroscopy, and 3a could be isolated in pure form. Treatment of these compounds with excess CO2 resulted in addition to the central carbon of the Sc(nacnac) six-membered ring and displacement of the nitrogen donors to yield dimeric scandium carboxylates 4a/4b; compound 4b was characterized by X-ray crystallography. Reactions of the nacnac scandium cations formed upon abstraction of one or two methides from 1a using B(C6F5)3 with CO2 were also explored. Although the products were qualitatively more thermally robust, eventually ligand displacement occurred in these cationic acetato complexes as well. Nevertheless, insertion products were characterizable in solution using NMR spectroscopy. Overall, this study shows the facility with which CO2 is taken up by scandium alkyls but that the nacnac ligand framework is too reactive to support chemistry aimed at catalytic conversion of CO2 into other products.

Reactivity of Cationic Terminal Borylene Complexes: Novel Mechanisms for Insertion and Metathesis Chemistry Involving Strongly Lewis Acidic Ligand Systems

The reactions of terminal borylene complexes of the type [CpFe(CO)(2)(BNR2)](+) (R = `Pr, Cy) with heteroallenes have been investigated by quantum-chemical methods, in an attempt to explain the experimentally observed product distributions. Reaction with dicyclohexylcarbodiimide (CyNCNCy) gives a bis-insertion product, in which 1 equiv of carbodiimide is assimilated into each of the Fe=B and B=N double bonds to form a spirocyclic boronium system. In contrast, isocyanates (R'NCO, R' = Ph, 2,6-wXy1, CY; XYl = C6H3Me2) react to give isonitrile complexes of the type [CpFe(CO)(2)(CNR')]+, via a net oxygen abstraction (or formal metathesis) process. Both carbodiimide and socyanate substrates are shown to prefer initial attack at the Fe=B bond rather than the B=N bond of the borylene complex. Further mechanistic studies reveal that the carbodiimide reaction ultimately leads to the bis-insertion compounds [CpFe(CO)(2)C(NCy)(2)B(NCY)(2)CNR2](+), rather than to the isonitrile system [CpFe(CO)(2)(CNCy)](+), on the basis of both thermodynamic (product stability) and kinetic considerations (barrier heights). The mechanism of the initial carbodiimide insertion process is unusual in that it involves coordination of the substrate at the (borylene) ligand followed by migration of the metal fragment, rather than a more conventional process: i.e., coordination of the unsaturated substrate at the metal followed by ligand migration. In the case of isocyanate substrates, metathesis products are competitive with those from the insertion pathway. Direct, single-step metathesis reactivity to give products containing a coordinated isonitrile ligand (i.e. [CpFe(CO)(2)(CNR')](+)) is facile if initial coordination of the isocyanate at boron occurs via the oxygen donor (which is kinetically favored); insertion chemistry is feasible when the isocyanate attacks initially via the nitrogen atom. However, even in the latter case, further reaction of the monoinsertion product so formed with excess isocyanate offers a number of facile (low energetic barrier) routes which also generate ['CpFe(CO)(2)(CNR')](+), rather than the bis-insertion product [CpFe(CO)(2)C(NR')(O)B(NR')(O)CNR2](+) (i.e., the direct analogue of the observed products in the carbodiimide reaction).

Antimony−Antimony Bond Formation by Reductive Elimination from a Hafnium Bis(stibido) Complex

The bis(stibido) complex CpCp*Hf(SbMes2)2 (2) was prepared and structurally characterized. Complex 2 reacts with 2 equiv of xylylisocyanide to give the bis-insertion product CpCp*Hf[C(SbMes2)=N(2,6-MeC6H3)]2 (4). The reaction of 2 with oxidants (I2 and O2) or donors (carbon monoxide and diphenylacetylene) or thermolysis promotes the reductive elimination of Sb2Mes4.

The reactions of dialkyl and diarylethoxysilanes with T 6 silsesquioxane cages : X-ray crystallographic studies of the mono-T 6D 1 and bis-T 6D 2 insertion ring expansion products

Successful ring-expanding insertion reactions of T 6 silsesquioxane cages using dialkyl and diarylethoxysilanes have been performed to give the first reported mixed T 6D 1 and T 6D 2 silsesquioxane cages. The reactions of hexacyclohexylsilsesquioxane (T 6) with dialkyl and diaryldiethoxysilanes give predominantly T 6D 2 bis-insertion compounds while the reaction of T 6 with dimethylethoxysilane gives one T 6D 1 mono-insertion product and various T 6D 2 bis-insertion products as isolable components. Three of the ring-expanded products are chiral and it has been shown from their X-ray crystal structures that the pairs of enantiomers, formed as racemic mixtures, co-crystallise together. As well as comparing these structures with related ones in the literature, the possible mechanism of their formation is discussed.

Borane Insertion into Group-4 Metal-to-Carbon Bonds: The Reaction of HB(C6F5)2 with (η2-Formaldehyde)zirconocene Dimer and with (Butadiene)zirconocene

(η2-Formaldehyde)zirconocene dimer (8) cleanly adds one or two molar equivalents of the borane HB(C6F5)2 by insertion of the H–[B] unit into the zirconium–carbon bond of the metallaoxirane moieties to form the mono- and bis-insertion products 16 and 17, respectively. These systems contain five-membered heterocyclic rings that are built up by connecting five different elements, namely H, B, C, O, and Zr. The bis(borane) insertion product 17 was characterized by an X-ray crystal structure analysis. (Butadiene)zirconocene reacts with HB(C6F5)2 in a similar way by insertion of the H–[B] unit into the (butadiene)C4–Zr linkage to form the metallacycle 18.

Ruthenium-catalysed ortho vinylation of aromatic ketones with alkynes; unexpected cyclopentaannulation

Abstract Ruthenium-catalysed coupling of aromatic ketones with alkynylsilanes yielded in most cases ortho vinylation adducts in high yield. The predominant stereochemistry of the newly introduced double bond was E in all but a few cases. In contrast, 1-acetylnaphthalene underwent a one-pot insertion–cyclisation sequence yielding cyclopenta[ a ]naphthalene derivatives. A bis acetylene gave both mono and bis insertion products.

C 1-insertion reactions at cyclodimeric ( η2-acetaldehyde) zirconocene complexes

Carbonylation of dimethylzirconocene, followed by treatment with zirconocene dihydride, benzyl chloride and then methyllithium, gave the ( η 2-acetaldehyde)zirconocene dimer ( 9) as a mixture of trans- and cis-isomers isolated in a 1.5:1 ratio under kinetic control and in a 1:1.7 ratio under thermodynamic control, respectively. Complexes trans- 9/ cis- 9 were treated with carbon monoxide to give the rans- 10 / cis- 10 monoinsertion products, and with isonitriles RNC (R = CH 2SiMe 3 ( a), CMe 3 ( b)) to give the mono- and bis-insertion product trans- and cis- 11(a, b) and 12(a, b), respectively. Complex 12a was characterized by X-ray diffraction. In all cases the trans / cis stereochemical information was predominantly retained in the products, which indicates that dimetallic pathways are favoured in these insertion reactions of the metallatricyclic ( η 2-aldehyde)metallocene dimers.

Reaction of (dichloro)(1,5-cyclooctadiene)platinum(II) with dimethyl diazomethylphosphonate. Crystal structure analysis of a bis-insertion product, ( R, R)-bis[chloro(dimethoxyphosphonyl)methyl]-(1,5-cyclooctadiene)platinum(II)

The reaction of dichloro(1,5-cyclooctadiene)platinum(II), 1 with dimethyl diazomethylphosphonate, 2, results in the formation of products of insertion of the carbene moiety into one or both PtCl bonds. An X-ray diffraction study of a crystal obtained from the major bis-insertion product of this reaction shows it to be ( R, R)-bis[chloro(dimethoxyphosphonyl)methylyl](1,5-cyclooetadiene)platinum(II), 5. The space group is polar indicating that spontaneous resolution has occurred upon crystallization.

Synthesis and intramolecular coupling of tantalum η 2-iminoacyl (η 2-RNCR′) and η 2-imine (η 2-RNCR′ 2) functional groups

The migratory insertion of organic isocyanides into the metal-carbon bonds of a series of tri-alkyls, Ta(OAr) 2R 3 (OAr = 2,6-dimethylphenoxide; R = CH 3, CH 2Ph), has been examined. Addition of 2,6-dimethylphenyl- or 2,6-di-isopropylphenylisocyanide (Ar′NC ⩾ 2 equivalents) results in the essentially quantitative formation of the bis-insertion products, Ta(OAr) 2(η 2-Ar′NCR) 2R ( 1). Spectroscopic as well as structural data are consistent with both iminoacyls being η 2-bound to the metal centre. In contrast, addition of tert-butylisocyanide to the tris-aryl Ta(OAr) 2Ph 3 proceeds to produce a mixed η 2-imine, η 2-iminoacyl compound Ta(OAr) 2(η 2 -Bu tNCPh 2)(η 2Bu tNCPh) ( 2). This compound is presumably formed by a second phenyl group migration taking place in an intermediate of type ( 1). All of these compounds exhibit thermal instability to varying degrees. The methyl compound Ta(OAr) 2(η 2-Ar′NCMe) 2(Me) rearranges over days at 25°C to produce a mixed amido, imido complex Ta(OAr) 2(Ar′NCMeCMe 2)(NAr′) ( 3a). This is believed to be formed by intramolecular coupling and fragmentation in an intermediate, Ta(OAr) 2(η 2-Ar′NCMe 2)(η 2-Ar′NCMe) of type ( 2). Support for this hypothesis comes from thermolysis of ( 2) to produce Ta(OAr) 2(Bu tNCPhCPh 2)(NBu t) ( 3b) which has been structurally characterized. The benzyl derivatives Ta(OAr) 2(η 2 -Ar′NCCH 2Ph) 2(CH 2Ph) also thermally produce mixed imido, amido compounds, only this time more dramatic fragmentation occurs to produce Ta(OAr) 2(Ar′NCH 2CH 2Ph)(NAr′) ( 4) and an organic fragment, PhCH 2CCPh. Structural studies confirmed this formulation. Mechanistic aspects of the reactivity of these η 2-iminoacyl and η 2-imine functionalities are discussed. Crystal data for TaC 48H 61N 2O 2 ( 3b) at −158°C are a = 21.806(5), b = 19.568(6), c = 10.078(2)Å, β = 90.63(1)°, Z = 4, d calc, = 1.358 g cm −3, in space group P2 1/ n. Of the 5642 unique intensities collected with Mo- K α, the 4790 with F> 2.33σ( F) were used in the least-squares refinement to yield R = 0.0419, R w = 0.0439. Crystal data for TaC 44H 51N 2O 2 ( 4) at −155°C are a = 12.423(5), b = 20.772(10), c = 14.840(6) Å, β = 93.27(2)°, Z = 4, d cacl = 1.426 g cm −3 in space group P2 1/ n. Of the 5004 unique intensifies collected with Mo- K α, the 3209 with F o > 3.00 σ( F) were used in the least-squares refinement to yield R = 0.0574, R w = 0.0498.

Synthesis and reactivity of alkenyl and alkynyl derivatives of permethylzirconocene and permethylhafnocene. Rearrangement of alkenyl derivatives involving β-H elimination from an sp2-hybridized carbon

The insertion of unactivated acetylenes into the metal-hydride bonds of (η 5-C 5Me 5) 2MH 2 (M = Zr, Hf) proceeds rapidly at low temperature to form mono- and/or bisinsertion products, dependent on the steric bulk of the acetylene substituents. 2-Butyne and t-butylacetylene react to form (η 5-C 5Me 5) 2M(H)(C(Me)CHMe) and (η 5-C 5Me 5) 2M(H)(CHCHCMe 3) (M = Zr, Hf). Propyne and 1-butyne react to form (η 5-C 5Me 5) 2M(CHCHCH 3) 2 (M = Zr, Hf) and (η 5-C 5Me 5) 2Zr(CHCHCH 2CH 3) 2. Phenylacetylene yields both (η 5-C 5Me 5) 2M(H)(CHCHPh) and (η 5-C 5Me 5) 2M(CHCHPh) 2 (M = Zr, Hf). To extend the study of the unsaturated carbon ligands, the bis(propynyl) complexes (η 5-C 5Me 5) 2M(CCCH 3) 2 (M = Zr, Hf) are prepared by treating (η 5-C 5Me 5) 2MCl 2 with LiCCCH 3. The reactivity of many of these complexes with carbon monoxide and dihydrogen is surveyed. The mono(2-butenyl)zirconium complex (η 5-C 5Me 5) 2Zr(H)(C(Me)CHMe) rearranges, forming the crotyl-hydride species (η 5-C 5Me 5) 2Zr(H)(η 3-C 4H 7) or, in the presence of 2-butyne, the zirconacyclopentene (η 5-C 5Me 5) 2- ZrCH 2CH(CH 2CH 3)C(CH 3)C (CH 3). The hafnium analog (η 5-C 5Me 5) 2Hf-(H)(C(Me)CHMe) also rearranges, although more slowly and less cleanly, to the analogous crotyl-hydride hafnium species. The bis(propenyl) and bis(butenyl)zirconium complexes also rearrange, forming zirconacyclopentenes (η 5-C 5Me 5) 2 ZrCH 2CH(R)CHC R and (η 5-C 5Me 5) 2 ZrCH 2CH(R)C(R)C H (R = CH 3, CH 2CH 3). The bis(propenyl)hafnium complex is stable to rearrangement. Mechanistic and kinetic studies of these transformations demonstrate the occurrence of an unusual β-hydrogen elimination from an sp 2-hybridized carbon.

Cyclopentadienyl-ruthenium and -osmium chemistry: XXVIII. Reactions and isomerisation of 1,2-bis(methoxycarbonyl)ethenyl complexes: X-ray structures of Ru{ Z)-C(CO 2Me)CH(CO 2Me)} -(CO)(PPh 3)(η-C 5H 5) · 0.5EtOH, Ru{( E)-C(CO 2Me)CH(CO 2Me)}(dppe)(η-C 5H 5) and [formula omitted]CH(CO 2Me)} - (PPh 3)(η-C 5H 5)

A reinvestigation of the reaction between C 2(CO 2Me) 2 and RuH(PPh 3) 2(η-C 5H 5) and some related complexes is reported. Initial cis addition is followed by conversion into the trans isomer. In the case of the bis-(PPh 3) complex, isomerisation is followed by chelation of the ester CO group with concomitant displacement of one PPh 3ligand. The resulting chelate complex reacts with CO or CNBu t to give the ( Z)-RuC(CO 2Me)CH(CO 2Me) complexes; the ( E)-isomer of the carbonyl complex is obtained by addition of C 2(CO 2Me) 2to RuH(CO)(PPh 3)(η-C 5H 5). The 1Hand 13C NMR spectra are not a reliable guide to assignment of the stereochemistry of the vinyl group. Other products isolated from the initial reaction are the bis-insertion product Ru{C(CO 2Me)C(CO 2Me)C(CO 2Me) CH(CO 2Me)} -(PPh 3)(η-C 5H 5) and the 1/2 PPh 3/C 2(CO 2Me) 2 adduct. The molecular structures of Ru{( Z)-C(CO 2Me)CH(CO 2Me)}(CO)(PPh 3(η-C 5H 5) · 0.5EtOH, Ru{( E)-C(C 2Me)CH(CO 2Me)}(dppe)(η-C 5H 5) and Ru{C(CO 2Me)C(CO 2Me)C(CO 2-Me) CH(CO 2Me)}(PPh 3)(η-C 5H 5) have been determined. The cis isomer is monoclinic, space group P2 1,with a 9.328(8), b 17.385(10), c 10.356(7) Å, β 101.78(3)° and Z = 2; 2107 data with I ≥ 2.5σ( I) were refined to R = 0.076 R w = 0.085. The trans isomer is triclinic, space group P 1 , with a 10.404(7) b 11.221(6), c 13.230(9) Å, α 92.67(5), β 110.56(5), γ 106.21(5)° and Z = 2; 2520 data with I ≥ 2.5σ( I) were refined to R = 0.055 R w = 0.068. The butadienyl complex is monoclinic, space group P2 1/ a, with a 19.655(8), b 8.674(4), c 21.060(5) Å, β 116.22(3)° and Z = 4; 2724 data with I ≥ 2.5σ( I) were refined to R = 0.042, R w = 0.047.

Reactions of co-ordinated ligands. Part 21. Reaction of 3,3,3-trifluoroprop-1-yne with methyl- and benzyl-dicarbonyl(η-cyclopentadienyl)iron and of hexafluorobut-2-yne with tricarbonyl(1—3-η-2-methylallyl)cobalt. Crystal and molecular structure of [1—5-η-exo-1-acetyl-2,4,6-tris(trifluoromethyl)cyclohexadienyl](η-cyclopentadienyl)iron

The u.v. irradiation of a hexane solution of 3,3,3-trifluoroprop-1-yne and [FeR(CO)2(η-C5H5)](R = Me, CH2C6H5, or C3H5) affords the vinyl complexes [Fe{C(CF3)C(H)R}(CO)2(η-C5H5)](R = Me, CH2C6H5), or C3H5) arising from cis insertion of the acetylene, and η5-pyranyl complexes [Fe{[graphic ommitted](CF3)}(–(η-C5H5)](R = Me or CH2C6H5). In the case of the methyl and benzyl system, [1–5-η-exo-1-acyl-2,4,6-tris(trifluoromethyl)cyclohexadienyl](η-cyclopentadienyl) iron complexes are also formed. An X-ray determination of the molecular structure of the acetyl compound shows that the 3,3,3-trifluoroprop-1-yne molecules have linked head to tail to form a six-membered ring of envelope conformation, with five atoms coplanar and η5-bonded to the iron atom. The cyclopentadienyl ring is likewise η5-bonded to the iron and completes a parallel-plane sandwich. The sixth carbon atom of the C6 ring bends away from the metal, and the acetyl group completes a tetrahedral arrangement around this atom, again bending away (exo configuration) in the same sense. The bond lengths in the planar portion of the C6 ring suggest extensive delocalisation. The crystals are monoclinic, space group P21/n(no. 14) with Z= 4 in a unit cell of dimensions a= 13.025(3), b= 10.432(2), c= 12.503(2)A, and β= 101.93(5)°. The structure has been solved by heavy-atom methods from 3 236 independent intensities measured on a fourcircle diffractometer and refined to R 0.056. The possible reaction paths available for the formation of these products are discussed. A reinvestigation of the reaction of hexafluorobut-2-yne with [Co(CO)3(η3-2-MeC3H4)] has afforded only the two compounds [[graphic ommitted]CH2}(CO)3] and [[graphic ommitted]CH2}(CO)3] there being no evidence for the formation of a bis-insertion product.

Reactivity of cyclopalladated complexes. Part 5. Insertion reactions of diphenylacetylene, 1-phenylprop-1-yne, and hexafluorobut-2-yne with cyclopalladated compounds. Crystal and molecular structure of chloro{3–4-η-4-[(2-dimethylaminomethyl)phenyl]-1,4-dimethyl-2,3-diphenylbuta-1,3-dienyl-C1N}palladium(II) and bromo{3–4-η-4-[(2-dimethylaminomethyl)phenyl]-2,4-dimethyl-1,3-diphenylbuta-1,3-dienyl-C1N}-palladium(II)

Reactions between disubstituted alkynes RC2R′(R = R′= Ph and R = Me, R′= Ph) and [{Pd(dmba)X}2](dmba =NN-dimethylbenzylamine, X = Cl or Br) afford bis-insertion products [Pd{(RCCR′)2C6H4CH2NMe2}X] in high yield. With MeC2Ph two isomers have been isolated, (1bα) and (1bβ). In order to establish their molecular structures, a single-crystal X-ray diffraction study has been made on the chloro-derivative of (1bβ) and the bromo-derivative of (1bα). Crystals of (1bα; X = Br) are monoclinic, space group P21/c, Z= 4, with a= 15.362(13), b= 12.368(5), c= 14.886(11)A, and β= 94.86(13)°. The structure has been refined to R 0.078 (R′ 0.105) for 2 529 independent reflections; the two acetylenes inserted into the Pd–C bond have a head-to-tail arrangement, the Pd being σ-bonded to a carbon bearing a phenyl group. Crystals of (1bβ; X = Cl) are monoclinic, space group P21, Z= 2, with a= 8.227(6), b= 16.059(33), c= 8.923(9)A, and β= 99.30(12)°. The structure has been refined to R 0.074 (R′ 0.065) for 2 077 independent reflections. The molecule shows a tail-to-tail arrangement for the two inserted acetylenes, the carbon σ-bonded to the palladium bearing a methyl group. The corresponding reaction with the 8-methylquinoline palladated dimer affords a benzenoid trimer via a bis-insertion analogue which was isolated for R = R′= Ph. Hexafluorobut-2-yne (hfb) reacts with the above palladated dimers and those formed from benzo[h]quinoline and NN-dimethyl-1-naphthylamine to give novel halide-bridged binuclear complexes with seven-membered rings. They are formed by formal insertion of one hfb unit into the Pd–C σ bond. With the naphthylamine dimer only an organic compound was isolated. The novel dimeric complexes easily afford monomeric derivatives by bridge-splitting reactions with pyridine or PPh3.

ChemInform Abstract: Copper Catalysis in the Methylenation of Arsenic Trichloride and Arsenic Tribromide.

AbstractDie Arsentrihalogenide (I) werden mit Diazomethan (II) zu den Einschiebungsprodukten (III) und (IV) in hohen Ausbeuten umgesetzt, wenn Kupferpulver als Katalysator eingesetzt und aus früheren Reaktionen wiedergewonnener Äther als Lösungsmittel verwendet wird.

Insertion reactions of hexafluorobut-2-yne, tetrafluoroethylene, and hexafluoroacetone with η5-cyclopentadienyl-iron, -ruthenium, -palladium, and -molybdenum complexes; molecular and crystal structures of [Fe2(CO){C4(CF3)4CO}(η5-C5H5)2] and [Fe{COCF2C5H5}(η5-C5H5)

Reaction (u.v. irradiation) of [{Fe(CO)2(η5-C5H5)}2] with hexafluorobut-2-yne (hfb) gives [Fe2(CO){C8F12CO}(η5-C5H5)2], structurally identified by X-ray crystallography as a ferracyclohexadienone complex. The ruthenium compound [{Ru(CO)2(η5-C5H5)}2] reacts with hfb to give [Ru{trans-C(CF3):C(CF3)H}(CO)2(η5-C5H5)], which subsequently affords the bis-insertion product [[graphic omitted](CF3)H}(CO)(η5-C5H5)]. Irradiation of [FeMe(CO)2(η5-C5H5)] and hfb affords [[graphic omited]Me(η5-C5H5)], which exists in solution as two interconverting conformers. Treatment of [MnMe(CO)5] with hfb gives the insertion product [Mn{cis-C(CF3):C(CF3)Me}(CO)5]. Reaction of [Fe(η1-C3H5)(CO)2(η5-C5H5)] with hfb gives only the cis mono-insertion product, whereas, the corresponding molybdenum system [Mo(η1-C3H5)(CO)3(η5-C5H5)]affords a bis-insertion product; the first step probably involves a trans-insertion. A second product is [Mo2(CO)4(CF3C2CF3)(η5-C5H5)2]. The photolytic reaction of [Pd(η3-C3H5)(η5-C5H5)] and hfb, in contrast with the Fe and MO systems, gives a dinuclear complex [Pd2C4(CF3)4(η3-C3H5)(η5-C5H5)]. Irradiation of hfb and [Fe(η1-C5H5)(CO)2(η5-C5H5)] gives a product corresponding to a formal (2 + 4)π addition to an unco-ordinated substituted cyclopentadiene, followed by a carbonyl insertion reaction. Tetrafluoroethylene undergoes an unusual carbon–carbon double bond cleavage on reaction with [Fe(η1-C5H5)(CO)2(η5-C5H5)] to give [Fe(COCF2C5H5)(η5-C5H5)], structurally characterised by X-ray crystallography. Hexafluoroacetone (hfa) readily reacts at low temperature with [Fe(η1-C5H5)(CO)2(η5-C5H5)] to give products, in which the hfa has formally inserted into a C–H bond on the σ-bonded C5 ring.

Copper Catalysis in the Methylenation of Arsenic Trichloride and Arsenic Tribromide

Abstract Dramatic increases in yields of methylene-insertion products in the reactions of diazomethane with arsenic trichloride and arsenic tribromide were achieved through the use of copper catalysis. Mono-and bis-insertion products, XCH2AsX2 and (XCH2)2AsX (X = C1 or Br), but no tris-halomethyl arsines were obtained. The success of the procedure depends upon the use of ether solvent reclaimed from previous reactions.