Poly(iminomethylene) copolymers

Copolymerization of an isocyanide giving an insoluble homopolymer with another isocyanide giving a soluble homopolymer in ethanol solution using 0.5–1% of a nickel (II) catalyst in many cases gives a soluble copolymer containing pendant groups arising from both isocyanides. Thus, methyl isocyanide, which gives an insoluble homopolymer, gives chloroform-soluble copolymers incorporating 39–44% of pendant methyl groups when copolymerized with equimolar amounts of tert-butyl isocyanide or several aryl isocyanides. Similarly, cyclohexyl isocyanide, which also gives an insoluble homopolymer, gives chloroform-soluble copolymers incorporating 43–59% of pendant cyclohexyl groups when copolymerized with equimolar amounts of several aryl isocyanides. The compositions, chloroform solubilities, and polystyrene equivalent molecular weights are given for 33 different copolymers obtained by copolymerizations of various equimolar binary mixtures of the monomers CH₃NC, (CH₃)₃CNC, cyclo-C₆H₁₁NC, C₂H₅NC, CH₃CH?CHNC,(CH₃)₂C?CHNC, 2,4,6-(CH₃)₃C₆H₂CH?CHNC, C₆H₅CH(CH₃)NC, CH₂?CHNC, (CH₃)₃CCH?CHNC, C₆H₅NC, 2- and 4-CH₃C₆H₄NC and 2-, 3-, 4-CH₃OC₆H₄NC using the nickel (II) catalyst system.     

Reaction of alkenyl carbonyl ruthenium(II) complexes with t-butyl isocyanide. Synthesis of η1-acylruthenium(II) complexes by intramolecular CO insertion

Reaction of Ru(CO)Cl(CHCHR)(PPh₃)₂ or Ru(CO)Cl(CHCHR)(PPh₃)₂L (L = py, Me₂Hpz) with 1 equivalent of t-butyl isocyanide gives the alkenyl derivatives Ru(CO)Cl(CHCHR)(PPh₃)₂(t-BuNC). When an excess of isocyanide is used, further reaction results in intramolecular CO insertion to yield η¹-acyl complexes [Ru(COCHCHR) (t-BuNC)₃(PPh₃)₂]Cl. Related complexes were obtained from [Ru(CO)(CHCHR)(MeCN)₂(PPh₃)₂]PF₆ and an excess of isocyanide.     

Studies on poly(iminomethylenes)

A variety of simple alkyl and aryl isocyanides have been polymerized using 0.5% NiCl₂ in ethanol as a catalyst. The resulting poly(iminomethylenes) have been characterized by carbon-13 NMR spectroscopy and their polystyrene-equivalent molecular weights have been determined by gel permeation chromatography. Straight chain aliphatic isocyanides having from three to ten carbon atoms in the chain form readily solyble polymers having molecular weights (M_w) in the general range 10,000 to 30,000. Neopentyl isocyanide unlike tert-butyl isocyanide forms an insoluble polymer. A number of new soluble aryl isocyanide polymers have been obtained. However, aryl isocyanides having a single alkyl substituent (CH₃, C₂H₅, CF₃) in the ortho position give only insoluble polymers, whereas aryl isocyanides having alkyl substituents in both ortho positions (e.g., 2,6-(CH₃)₂C₆H₃NC and 2,4,6-(CH₃)₃C₆H₂NC) fail to polymerize under these conditions. The highest molecular weight soluble aryl isocyanide homopolymer is obtained from 3-CH₃OC₆H₄NC(M_w = 26,000). The trimethylsilyl substituted isocyanide (CH₃)₃SiCH₂CH₂NC has been obtained from LiCH₂NC and (CH₃)SiCH₂Cl and gives a brown soluble homopolymer with a molecular weight (M_w) of 19,000.     

Ringöffnende acetylierung eines an kobalt koordinierten ringliganden vom divinylboran-typ

(C₅H₅)Co[2–6-η-(CH₃)₂Si(CHCH)₂BC₆H₅(III) is prepared photochemically from (C₅H₅)Co(CO)₂ and (CH₃)₂Si(CHCH)₂BC₆H₅ (II). Acetylation of the new complex III with CH₃COCl/AlCl₃ and subsequent hydrolysis effect ring-opening new complex III with CH₃COCl/AlCl₃ and subsequent hydrolysis effect ring-opening to give (C₅H₅)Co[(1,2-η-(cis-CH₃COCH)CH(η-CH₂CH)Si(CH₃)₂] (IV) which slowly isomerizes (ΔG^≠₂₉₆ 100 ± 2 kJ mol^?1) to the corresponding trans-isomer (V).Pure (CH₃)₂Si(CHCH)₂Sn(CH₃)₂ (I) can be obtained in preparative quantities via the new complex (CH₃)₂Si(CHCH)₂Sn(CH₃)₂ · 2 CuCl.     

Assignments of the vibrational spectra of 2,5-dimethyl-2,4-hexadiene, 4-methyl-1,3-pentadiene and (E)-2-methyl-1,3-pentadiene. Effect of the terminal and lateral methyl groups

The complete assignment of the vibrational spectra of 2,5-dimethyl-2,4-hexadiene, 4-methyl-1,3-pentadiene and (E)-2-methyl-1,3-pentadiene was obtained from a comparative analysis of their i.r. and Raman spectra (solid, liquid and gas) in the range 3200-50 cm⁻¹. It is shown that particular vibrational motions strongly interact to give rise to very characteristic modes depending on the site of methyl substitution. The comparison of our results with those of analogous shorter and larger polyenes and polyenals allows us to discuss the various local coupled motions characteristic of unsubstituted (CHCH CH)CH and methyl substituted (CHC(CH₃)CH), ((CH₃)₂CCH) or (CH₃CHCH) fragments in polyenic chains.     

π-Allylmetal chemistry.IV. Structures and equilibria in Crotylplatinum(II) complexes

Simple methods to prepare crotylplatinum(II) complexes of the type, Pt(CH₂CHCHMe)Cl(PPh₃)₂ and Pt(CH₂CHCHMe)C1L (L PPh₃, AsPh₃), are described. ¹H NMR and vibrational spectral evidence suggests that the σ-allylic form is the dominant species in a benzene solution of Pt(CH₂CHCHMe)Cl(PPh₃)₂, while in chloroform this compound has the ionic α-allyl structure with both the anti and syn-methyl isomers present. Various rate processes exhibited by Pt(CH₂CHCHMe)C1L₂ (L PPh₃ , AsPh₃) in different solvents have been discussed in terms of the structures of intermediate σ-allylic complexes and the different coordinating abilities of L.     

Synthese und kristallstrukturuntersuchung von bis[dicarbonyl(μ-trifluormethylisocyanid)-(η-pentamethylcyclopentadienyl)molybdän)], [Mo(CO)2(μ-CNCF3)(η-Cp)]2 und dessen isomerisierung zu Cp(CO)2Mo(μ-F3CNCCNCF3)Mo(CO)2Cp

Trifluoromethyl isocyanide adds to the metal—metal triple bond of bis[dicarbonyl(η-pentamethylcyclopentadienyl)molybdenum] forming Mo₂Cp₂(CO)₄(η²-μ-CNCF₃) as the first isolated product. Further addition of trifluoromethyl isocyanide at 0°C leads to the formation of [Mo(CO)₂(μ-CNCF₃)(η-Cp)]₂, which according to crystal structure analysis contains two bridging CF₃NC ligands. During the isomerization of this compound in dichloromethane solution at room temperature or in the solid state above 110°C molybdenum—molybdenum bond cleavage and carbon—carbon bond formation occurs, leading to Cp(CO)₂Mo(μ-F₃CNCCNCF₃)Mo(CO)₂Cp, which contains 1,1,1,6,6,6-hexafluoro-2,5-diaza-2,3,4-hexatriene as bridging ligand.     

Carbon-13-nuclear magnetic resonance spectra of 5-coordinate tris-olefin complexes of rhodium(I)

Studies of the ¹³C N.M.R. spectra of the series RhX[P(Ch₂CH₂CHCH₂)₃] and RhX[P(CH₂CH₂CH₂CHCH₂)₃] where x  Cl or Br have revealed that (a) the J(¹⁰³Rh-¹³C) (olefin) for the complexes studied is only $\text{1}\text{2}$ ? $\text{1}\text{3}$ that found for square-planar complexes, and (b) the fluxional character in the olefinic carbons observed for the compounds RhX[P(CH₂CH₂CHCH₂)₃] is related to the partial rotation of the olefin about the rhodium-olefin bond.     

Synthèse de complexes du tungstène,du chrome et du rhénium contenant un ligand 1,4-bidenté carbéne-alcéne

A general synthesis of alkene-carbene complexes of tungsten, chromium and rhenium, containing a six-membered ring system, is outlined and the crystal structure of two new complexes of this type, (CO)₄WC(OEt)(CH)(η²-CH₂CHCH₂) (CH₂CHCH₂) and (CO)₉Re₂(OCH₂CH₃(CH₂(CH₂(CH₂CHCH₂), is described.     

A method for γ-functionalization of tiglaldehyde via the lithio aldimine

LiCH₂CC(CH₃)CHNC₆H₁₁ reacts with carbonyl compounds to give γ capture products (HMPA present) or α capture products (no HMPA).     

Cleavage of iron2-alkenyl and iron2-alkynyl bonds by mercury(II) chloride

Reactions of HgCl₂ with η⁵-C₅H₅Fe(CO)₂R (R  CH₂CHCH₂ and CH₂C(CH₃)CH₂) in THF at 25°C rapidly afford $\text{1}\text{1}$ adducts of the two reactants. These adducts were converted to the corresponding PF₆^? salts, [η⁵-C₅H₅Fe(CO)₂(η²-CH₂C(R)CH₂HgCl)]⁺ PF₆^? (R  H and CH₃), for characterization. Slower reactions with cleavage of the ironcarbon σ bond and elimination of the R group from η⁵-C₅H₅Fe(CO)₂R occur for R  CH₂CHC(CH₃)₂, CH₂CHCHC₆H₅, and CH₂CCC₆H₅. Both elimination and $\text{1}\text{1}$ adduct formation are observed when R  CH₂CHCHCH₃. The kinetics of the cleavage reactions are presented and possible mechanisms for both cleavage and $\text{1}\text{1}$ adduct formation are discussed.     

The chemistry of the transition metalcarbon σ-bond. Insertion reactions between stannous chloride and h1-allyl and h1-propargyl complexes of h5-cyclopentadienyldicarbonyliron

The reactions between h⁵-CpFe(CO)₂R (R = CH₂CHCH₂; CH₂CMe=CH₂; CH₂CHCHMe; CH₂CHCMe₂) and stannous chloride in tetrahydrofuran afford the insertion products h⁵-CpFe(CO)₂SnCl₂R. When treated with stannous chloride in methanol or with excess stannous chloride in tetrahydrofuran, h⁵-CpFe(CO)₂CH₂CMeCH₂ affords primarily h⁵-CpFe(CO)₂SnCl₃. The allenyl, 2-butynyl or cationic isobutylene complexes (R = CHCCH₂; CH₂ CCMe; CH₂CMe⁺₂) yield only h⁵-CpFe(CO)₂SnCl₃. Stannous iodide reacts with h⁵-CpFe(CO)₂CH₂CHCH₂ in benzene to form h⁵-CpFe(CO)₂I. Plumbous chloride in methanol fails to react with the above complexes.     

Allylbutyltin halides (CH2CHCH2)SnBu3−nCln (n = 0, 1, 2, 3). Preparation,carbon-13 NMR characterization and allylstannylation ability towards ketones and aldehydes

Mixed allylbutyltin halides (CH₂CHCH₂)SnBu_3-nCl_n (n = 0–3) have been prepared, and characterized by carbon-13 NMR spectroscopy. Their ability to bring about allylstannylation of ketones and aldehydes, to form organostannoxy compounds, Bu_3-nSnCl_nOC(R′)(R″)CH₂CHCH₂, has been shown to increase on increasing the value of n, that is on increasing the acceptor ability of the tin centre.     

Synthesis and x-ray structures of some homonuclear μ-alkylidenetungsten complexes

The complexes W₂{μ-CHCHC(CH₃)₂](CO)₁₀} and W₂{μ-CHCHC(CH₃)(CH₂)₃CH₃][(CO)₁₀} have been synthesized, and an X-ray diffraction study has revealed the presence of five CO groups on each metal center. The analogy between W₂{μ-CHCHC(CH₃)₂][(CO)₉]} anda complex of W(CO)₄ and a tungstabutadiene (CO)₅WCHCHC(CCH₃)₂ prompted the synthesis of the first heteroatom-substitued μ-alkylidene complexes of tungsten, starting from conjugated Fischer-typ carbene complexes (CO)₅WC(OR)CHCHR. The X-ray structure of the complex W₂{μ-C(OEt)CHCH(CH₃)][(CO)₉]} has also been determined. In the case of the simplest conjugated compelx (CO)₅WC(OR)CHCH₂, an interesting rearrangement initiated by addition of W(CO)₅ to the terminal CC double bond giving a dinuclear complex W(CO)₅[η²-CH₂CHC(OMe)W(CO)₅] in which the two metal centers are not directly linked, has been observed.     

High-yield catalytic metathesis of alkenyl tosylates with applications in organic synthesis

Alkenyl tosylates of the type RCHCH(CH₂)_nOTs [RH, n=9; RH, n=7; and RCH₃(CH₂)₇, n=8] undergo metathesis using a WCl₆-Me₃SnCl catalyst system, producing difunctionalised alkenes of the type TsO(CH₂)_nCHCH(CH₂)_nOTs (n=7,8, and 9); examples of the use of these products in synthesis are presented.     

Preparation of siloxycarbenemanganese complexes including a chelated siloxycarbene-alkene complex

Reaction of Li{(η⁵-C₅H₄Me)Mn(CO)₂]C(O)Ph]} with one equivalent of RSiMe₂Cl yields (η⁵-C₅H₄Me)Mn(CO)₂[C(Ph)(OSiMe₂R)] for R  CH₃, CHCH₂, and CH₂CHCH₂ (1a–c, respectively). Low temperature photolysis of the vinyl derivative, 1b, results in formation of a chelated manganese siloxycarbene-alkene complex, (η⁵-C₅H₄Me)MN(CO)[C(Ph)(η²-OSiMe₂CHCH₂)]. (2). Photolysis of the allyl derivative, 1c, under similar conditions leads to uncharacterized decomposition products. Infrared, ¹H, ¹³C, and ²⁹Si NMR data are reported for these new siloxycarbenemanganese derivatives.     

Significant electrostatic effects in π-facial stereoselection of nucleophilic addition reactions to β,γ-unsaturated carbonyl compounds

The Significance of electrostatic effects on the origin of π-facial stereoselectivity in nucleophilic additions to β,γ-unsaturated carbonyl systems was shown through theoretical studies (ab initio MO calculations of transition structures for NaH + HCOCH₂CCH) and experimental results (M(BH₄)_n reduction of PhCOCH(CH₃)R (M  Na, Zn, Cd; R  C₂H₅, CHCH₂, CCH)).     

Bis(ligand)metall-komplexe von nickel,palladium und platin mit cyclischen liganden vom divinylboran-typ

Nine complexes of type ML₂ with M = Ni, Pd, Pt and L = X(CHCH)₂BC₆H₅ (X = (CH₃)₂C, (CH₃)₂Si, (CH₂)₂) are described. The X-ray structural analysis of Ni[(CH₃)₂Si(CHCH)₂BC₆H₅]₂ and the ¹H and ¹¹B NMR spectra demonstrate a sandwich-type bis(η⁵-divinylborane)metal structure with C₂ molecular symmetry. All complexes show exceptional thermal stability as compared to the corresponding bis(1,5-cyclooctadienyl)metal complexes. In the ¹H NMR spectra internal rotation of the two ligands with respect to each other is observed for two Pd complexes and the Pt complexes at room temperature.     

Metallkomplexe mit biologisch wichtigen Liganden. CLVII [1] Halbsandwich‐Komplexe mit Isocyanoacetylaminosäureestern und Isocyanoacetyldi‐ und tripeptidestern („Isocyano‐Peptide”︁)

Metal Complexes of Biologically Important Ligands, CLVII [1] Halfsandwich Complexes of Isocyanoacetylamino acid esters and of Isocyanoacetyldi‐ and tripeptide esters (?Isocyanopeptides”?) N‐Isocyanoacetyl‐amino acid esters CNCH₂C(O) NHCH(R)CO₂CH₃ (R = CH₃, CH(CH₃)₂, CH₂CH(CH₃)₂, CH₂C₆H₅) and N‐isocyanoacetyl‐di‐ and tripeptide esters CNCH₂C(O)NHCH(R¹)C(O)NHCH(R²)CO₂C₂H₅ and CNCH₂C(O)NHCH(R¹)C(O)NHCH (R²)C(O)NHCH(R³)CO₂CH₃ (R¹ = R² = R³ = CH₂C₆H₅, R² = H, CH₂C₆H₅) are available by condensation of potassium isocyanoacetate with amino acid esters or peptide esters. These isocyanides form with chloro‐bridged complexes [(arene)M(Cl)(μ‐Cl)]₂ (arene = Cp*, p‐cymene, M = Ir, Rh, Ru) in the presence of Ag[BF₄] or Ag[CF₃SO₃] the cationic halfsandwich complexes [(arene)M(isocyanide)₃]⁺X^? (X = BF₄, CF₃SO₃).     

Synthesis,characterization and vibrational investigation of divinylborinic anhydride

The new molecule divinylborinic anhydride [(CH₂CH)₂B]₂O as been prepared by the limited hydrolysis of divinylchloroborane. Characterization of the compound has included the preparation of 1 : 1 adducts with trimethylphosphine, dimethylphosphine and trimethylamine. Born-11 and carbon-13 NMR spectra have been obtained and have been interpreted in terms of mesomeric interactions between the empty boron pπ orbital and unshared pairs of electrons on oxygen as well as the pi electron system of the vinyl moiety. The Raman spectra (3500–200 cm^-1) of liquid and solid [(C₂H₃)₂B]₂O and the infrared spectra (3500–200 cm^-1) of gaseous and solid [(C₂H₃)₂B]₂O ¹ have been investigated for both the ¹⁶O and ¹⁸O isotopic species. The vibrational data indicate that the molecule possesses C₁ symmetry and a linear BOB angle.