Reactions of diphosphineplatinum(II) oxalate complexes with phenylacetylene. Formation of phenylalkynylplatinum complexes

[Pt(C₂O₄)(dppe)] reacts thermally with PhCCH to produce [Pt(CCPh)₂(dppe)], which has been prepared by alternative routes. Similar treatment of [Pt(C₂O₄)(dppm)] initially produces [Pt(CCPh)₂(dppm)], which rearranges to give cis,cis-[Pt₂(CCPh)₄(μ-dppm)₂]. Reaction of [PtCl₂(dppm)] with PhCCH/KOH/18-crown-6, or with (PhCC)SnMe₃, gives [Pt(CCPh)₂(dppm)], which may be converted to the cis,cis-dimer by addition of oxalic acid. Ultraviolet irradiation or refluxing with a trace amount of dppm converts [Pt(CCPh)₂(dppm)] to trans,trans-[Pt₂(CCPh)₄(μ-dppm)₂], but the cis,cis-dimer is stable under these conditions. [Pt(C₂O₄)L₂] (L = PPh₃, PEt₃) complexes also react thermally with PhCCH to yield [Pt(CCPh)₂L₂] species.     

Homogeneous hydrogenation of alk-1-enes and alkynes catalyzed by the 1-[Ir(CO)(PhCN)(PPh3)]-7-C6H5-1,7-(σ-C2B10H10) complex

The complex [Ir(σ-carb)(CO)(PhCN)(PPh₃)], where carb = -7-C₆H₅-1,2C₂B₁₀H₁₀, was found to be an effective catalyst for homogeneous hydrogenation of terminal olefins and acetylenes at room temperature and atmospheric or subatmospheric hydrogen pressure. Internal olefins are not hydrogenated, but simple alk-1-enes are readily converted into the corresponding alkanes. Isomerization of the double bond catalyzed by the metal complex occurs at very small extent. Catalytic hydrogenation of olefins having carboxylate substituents on the unsaturated carbon atoms is prevented by the formation of thermally stable chelate hydridoalkyl complexes of the type I$\text{(H)}$(σ-CHRCHR′C(O)OR″) (σ-carb)(CO)(PPh₃)]. Acetylenes are hydrogenated to alkenes. The alk-1-enes formed in the hydrogenation of the alkynes HCCR in turn undergo the more slow reactions either of hydrogenation to alkanes or isomerization to internal olefins which cannot be further hydrogenated. Hydrogenation of alkynes of the type RCCR′ is stereospecifically cis, yielding cis- olefins. Catalyzed cis → trans isomerization reaction of these internal olefins occurs only to a negligeable extent.     

Coordinatively unsaturated alkyne complexes: synthesis of mono and bis-alkyne complexes of tungsten (II)

[WBr₂(CO₄]_n reacts with alkynes to give complexes [WBr₂CO(RCCR)₂]₂ (1) (R = R′ = Me, Et, Ph; R = Me, R′ = Ph), which react with nucleophiles L{L = CNBu^t, PPh₃, or P(OMe)₃} to give monoalkyne derivatives (WBr₂(CO)(RCCR′)L₂](2). An intermediate bis-alkyne adduct [WBr₂CO(MeCCMe)₂(CNBu^t)] (3) was isolated in the reaction of [WBr₂CO(MeCCMe)₂]₂ with CNBu^t illustrating that cleavage of the dimer (1) is the first stage in these reactions.     

Aryl- and acetylene-nickel(I) complexes

Reduction of various pentafluorophenylnickel(II) complexes in the presence of phosphines gives unstable nickel(I) compounds but Ni(C₆F₅)(CO)₂(PPh₃)₂ is isolated in the presence of CO. Similar NiR(CO)₂(PPh₃)₂ (R = C₆F₅,C₆Cl₅, 2,3,5,6-C₆Cl₄H) are obtained by reaction of the halogenonickel(I) complex with MgRBr or LiR. Reduction of NiX₂L₂ in the presence of acetylenes gives [NiXL₂]₂(μ-PhCCR) (R = H, X = Cl and R = Ph, X = Cl, Br) when L = P-n-Bu₃ but only NiX(PPh₃)₃ are recovered when L = PPh₃. No reaction with the alkyne is observed for [NiX(PPh₃)₂]_n but [NiCl(PPh₃)]_n reacts with RCCR′ to give paramagnetic NiCl(PPh₃)(CRCR′) (R = Ph, R′= H, COOEt), diamagnetic [NiCl(PPh₃)]₂(μ-PhCCPh) and cyclotrimerization when R = R′ = COOMe. Chemical and structural behaviour of the new nickel(I) complexes is described.     

Improved syntheses of Ru(CO)2 (O3SCF3)2 (bidentate) complexes and their conversion into new [Ru(CO)2 (bidentate)2]2+ complexes

Reaction of the complexes Ru(CO)₂Cl₂L [L = 2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen)] with trifluoromethanesulphonic acid under carefully controlled conditions yields Ru[cis-(CO)₂] [cis-(O₃SCF₃)₂] (bidentate complexes. From reactions of the trifluoromethanesulphonates with the appropriate bidentate ligands, the new complexes [cis-Ru(CO)₂-L(L′)]²⁺ (L as above; L′ = 4,4′-dimethyl-2,2′-bipyridyl or 4,4′-diisopropyl-2,2′-bipyridyl) as well as the known [_cis-Ru(CO)₂L₂]²⁺ and [cis-Ru(CO)₂bpy(phen)]²⁺ have been prepared.     

Activation of CH bonds in acetylene and terminal alkynes by rhodium(I) species. Crystal structure of cis-(ethynyl)hydride [(NP3)Rh(H)(CCH)]BPh4·1.5C4H8O (NP3 = N(CH2CH2PPh2)3)

The 16-electron fragment (NP₃)Rh⁺ inserts in a highly stereospecific manner across CH bonds from acetylene and 1-alkynes to give the octahedral cis-(alkynyl)hydrides [(NP₃)Rh(H)(CCR)]BPh₄ (R = H, Ph, COOEt). The structure of the cis-(ethynyl)hydride [(NP₃)Rh(H)(CCH)]BPh₄ · 1.5 THF has been established by X-ray diffraction. The trigonal bipyramidal rhodium(I) complex [(NP₃)RhH], reacts with terminal alkynes to give H₂ and the neutral σ-acetylides [(NP₃)Rh(CCR)] (R = Ph, COOEt). These undergo metathesis between terminal alkynes and the σ-acetylide ligand through a mechanism involving consecutive breaking and making of CH bonds.     

Reversible alkin-addition an rp-verbrückte carbonyleisen-cluster

The clusters (μ₃-RP)₂Fe₃(CO0₉ (1) photochemically add alkines R′CCR′ across their bridging phosphorus centers to yield (μ₃-η⁴-RPCR′CR′PR)Fe₃(CO)₉ (2). Thermal activation of 2 opens two different reaction channels: Complezes 2 may split into R′CCR′ and 1 in a thermally induced reversion of their photoinitiated formation reaction: in another pathway they may lose Fe(CO)₃ to yield (μ₂-η²-(PFe)RPCR′CR′PR)Fe₂(CO)₆ (3). Complex 3 is an Fe₂(CO)₆ derivative of the butterfly type with the μ₂-bridging phosphorus centers linked by an R′CCR′ moeity. The reverse transformation 3 → 2 is induced by Fe₂(CO)₉ as an “Fe(CO)₃” source.Compounds 2 undergo a CO substitution reaction with R′CCR′ to give (μ₃-η²- RPCR′CR′PR)(μ₃-η²-R′CCR′)Fe₃(CO)₇ (4) which, upon heating, also transforms into 3. The above reactions 1 ⇋ 2 ⇋ 3 and 2 → 4 → 3 ⇋ 2 present a rare example of a complete closed set of cluster transformations. An analogous subset of reactions is also verified for the arsenic homologues 1, 2 and 4.     

Insertionsreaktionen von Bis(η-cyclopentadienyl)hydridorhenium mit monosubstituierten Acetylenen

Bis(η-cyclopentadienyl)hydridorhenium Cp₂ReH undergoes stereospecific trans insertion reactions when treated with monosubstituted acetylenes HCCR (R  CO₂Me, CN, CF₃). The cis alkenyl complexes Cp₂Re[η¹-(Z)-CHCHR] thus formed isomerize thermally or under acid catalysis to produce the trans isomers Cp₂Re[η¹-(E)-CHCHR]. When Cp₂ReH adds to HCCCOMe only the trans isomer is observed. The regiospecific β-addition of Cp₂ReH contrasts with the α-addition of Cp₂MoH₂ and Cp₂WH₂. The insertion of acetylenes HCCR′ into the metalcarbon bond of some alkenyl complexes Cp₂Re[η¹-(E)-CHCHR] affords butadienyl complexes Cp₂Re[η¹-{(1E,3E)-CHCHR′CHCHR&}] (R,R′  COMe, CO₂Me). The (E,E)-configuration of these compounds is deduced from ³J(¹³-C¹H) coupling constants.     

Übergangsmetall-Carbin-Komplexe: CIII. Aktivierung von Ethylisocyanid an elektronenreichen Metallzentren; Synthese von einkernigen Wolfram-Aminocarbin-Komplexen des Typs Tp′(CO)2 WCN(R)Et (R  Me,Et)

A large-scale, high-yield synthesis of the aminocarbyne complexes Tp′(CO)₂WCN(R)Et (5: R  Me; 6: R  Et) [Tp′ = hydridotris(3,5-dimethylpyrazol-1-yl)borate] is reported, starting from Tp′W(CO)₃I (2). The first step of the synthetic procedure involves thermal decarbonylation of 2 with EtNC to give cis-Tp′W(CO)₂(CNEt)I (3). Complex 3 is then reduced with Na/Hg to give the metallate Na[Tp′W(CO)₂(CNEt)] (4). Finally, complex 4 is alkylated with RI (R  Me, Et) exclusively at the isocyanide nitrogen to give the aminocarbyne complexes 5 and 6. In contrast, the metallates Na[(η⁵-C₅R′₅)W(CO)₂(CNEt)] (R′  H, Me) undergo alkylation with RI at the metal centre to afford the W^II alkyl complexes cis/trans-(η-C₅R′₅)W(CO)₂(CNEt)R. This difference in reactivity is ascribed to the steric demands of the Tp′ ligand, which shields the metal centre from the incoming electrophile.     

A new synthesis of platinum—carbon bonds

Syntheses of cis-[PtCl(CH₂COCH₃)(PEt₃)₂], cis-[PtCl(CH₂NO₂) (PEt₃)₂], and trans-[Pt(CCPh)₂ (PEt₃)₂] are described. The procedure involves reaction of cis-[PtCl₂(PEt₃)₂] with Ag₂O and acidic CH bonds to precipitate AgC1 and generate a PtC bond. The method may represent a new general route to platinum—carbon bonds.     

Kinetische und mechanistische untersuchungen von übergansmetallkomplex-reaktionen: XXI. Einfluss von zentralmetall,trans-X-ligand und carbinsubstituent auf die MCO-dissoziation in carbin-komplexen des typs trans-X(CO)4MCR

The influence of the central metal atom, the trans-X ligand, and the carbyne substituent R on the MCO dissociation step of seventeen different carbyne complexes, trans-(CO)₄MCR (X = Cl, Br, I, SePh; M = Cr, W; R = Me, aryl, NEt₂), in 1,1,2-trichloroethane was studied by means of the substitution of one CO ligand by PPh₃. All complexes react with PPh₃ according to the first-order rate equation: — d[complex]/dt = k[complex]. The activation enthalpies ΔH³ are in the range 97–116 kJ mol⁻¹, the activation entropies ΔS³ are 34 to 72 J mol⁻¹ K⁻¹. The reaction rate, (i) is virtually independent of the electronic properties of R, (ii) decreases slightly with increasing steric requirements of R, (iii) increases strongly in the series trans-X = I, Br, Cl, SePh, and (iv) is faster for chromium complexes than for analogous tungsten compounds by a factor of ca. 30 to 50. There is no general correlation between the rate constants k and the CO force constants k(CO). The variation in the reaction rate is essentially determined by the different levels of stabilization of energy in the transition state. The thermolysis of carbyne complexes is also initiated by CO dissociation. The rate of thermolysis when [CO] = 0 is equal to the rate of CO/PPh₃ substitution; it decreases rapidly with increasing CO concentration in the solution; and when [CO] = constant it increases significantly with increasing concentration of the complex. A mechanistic scheme is proposed for the thermolysis which involves three different reaction pathways for the coordinatively unsaturated fragment X(CO)₃MCR formed by CO dissociation from trans-X(CO)₄MCR: readdition of CO, monomolecular decomposition, and reaction with trans-X(CO)₄MCR.     

Platinum and rhodium complexes in which diphenylphosphino(methylthio)methane acts as a monodentate,chelated or bridging ligand

Reaction of [PtCl₂(cod)] with Ph₂PCH₂SCH₃ yields cis-[PtCl₂(Ph₂PCH₂-SCH₃)₂] which, on treatment with AgBF₄, is converted to [PtC](Ph₂PCH₂SCH₃)₂]-BF₄, in which one of the ligands is chelated. With [Pt(dba)₂], cis-[Pt(Cl₂(Ph₂PCH₂-SCH₃)₂] reacts to give the platinum(I) complex [Pt₂Cl₂(μ-Ph₂PCH₂SCH₃)₂], which contains a platinum-platinum bond. The terminal chlorides may be replaced by iodide, but the complex is cleaved by carbon monoxide. [Rh₂(μ-Cl)₂(CO)₄] reacts with Ph₂PCH₂SCH₃ to produce [Rh₂Cl₂(CO)₂(μ-Ph₂PCH₂SCH₃)₂], whereas with Ph₂PCH₂CH₂SCH₃ it yields [RhCl(CO)(Ph₂PCH₂CH₂SCH₃)]. A ligand exchange reaction occurs between cis-[PtCl₂(Ph₂SCH₃)₂] and [Rh₂(μ-Cl)₂(CO)₄] to give cis-[PtCl₂(CO)(Ph₂PCH₂SCH₃)] and [Rh₂Cl₂(CO)₂(μ-Ph₂PCH₂SCH₃)₂].     

The formation of alkyne and alkynyl complexes by reaction of 1-alkynes with trans-[M(N2)2(PH2PCH2CH2PPh2)2] (M  Mo OR W) and with [Mo(Ph2PCH2PPh2)3]: X-ray structure of trans-[Mo(CCPh)2(PH2PCH2CH2PPh2)2]

Reaction of RCCH (R  Ph, CO₂Meor CO₂Et) with trans-[M(N₂)₂(dppe)₂] (M  Mo or W; dppe  Ph₂PCH₂CH₂PPh₂) or [Mo(dppm)₃] (dppm  Ph₂PCH₂PPh₂) gives the alkyne complexes [M(RCCH)₂(diphos)₂] (diphos  dppe, M  Mo, R = Ph; dihpos  dppm, M  Mo, R  Ph or CO₂Me) and the alkynyl complexes trans-[M(cCR)₂(dppe)₂], [MH₂(CCR)₂ (dppe)₂] (M  Mo or W. R  Ph, CO₂Me or CO₂Et) and cis-[WH(CCCO₂Me)(dppe)₂]: the X-ray structure of trans-[Mo(CCPh)₂(dppe)₂] is reported.     

Synthetic and electrochemical studies on alkynyl complexes of iron and ruthenium

Cyclic voltammetric studies on a series of alkynyl complexes [M(CCR)L₂(η- C₅R′₅)] (M = Fe or Ru; R = Ph, Bu_n or Bu_t; L = CO or P-donor ligand; R′ = H or Me) reveal a one-electron oxidation at a glassy carbon electrode in dichloromethane. The chemical reversibility of the oxidation process is dependent upon all four variables (M, L, R and W) considered in this investigation.     

Syntheses of σ-cyclobut-1-en-3-onyl complexes by cycloaddition of ketenes to some transition metal alkynyl complexes

Reactions of ketenes (R¹R²CCO) with (η⁵-C₅H₅)Ni(PPh₃)CCR (I) and (η⁵-C₅H₅)Fe(CO)(L)CCR (III, L = CO and PPh₃) give σ-cyclobut-1-en-3-onyl complexes, {(η⁵-C₅H₅)Ni(PPh₃)$\text{CC(R)COC}$}R¹R² (VI) and (η⁵-C₅H₅)Fe(CO)(L)$\text{CC(R)COC}$R¹R² (IX)}, (2 + 2) cycloaddition products, in good yields. The σ-cyclobutenonyl complexes also can be prepared by the reaction of I and III with acyl chlorides in the presence of triethylamine.     

Complexation d'iminopyridines par le sel de zeise: voie d'access a des conjugues estradiol-cis-dichloro platine. Etude structure du complexe cis-PtCl2[C5H4NCH2NC(CH3)C6H4OH],H2O

In order to synthesize penta- and hexa-gonal platinum(II) metallocycles, bidentate ligands such as iminopyridines (L) have been prepared and characterized. The (2-pyridyl)CHNR¹ and (2-pyridyl)CH₂NCR¹R² ligands react with Zeise's salt to afford directly the pentagonal chelates PtCl₂L. Their structure and the cis-stereo-chemistry were shown by the usual spectroscopic methods and for cis-PtCl₂[C₅H₄NCH₂NC(CH₃)C₆H₄OH],H₂O by an X-ray diffraction study. On the other hand, the (2-pyridyl)(CH₂)₂NCR¹R² ligands do not afford the expected hexagonal metallocycles; instead, after complexation at the nitrogen atom of the imine they give rise to the (2-pyridyl)ethylamine complex formed after hydrolysis of the coordinated ligands. Complexes trans-[ethylene][(2-pyridyl)(CH₂)₂NCR¹R²]PtCl₂ represent when R¹ is estradiol a model for “cytotoxic with delayed activity”.     

Alkinylphosphinhaltige substitutionsprodukte von chrom- und wolfram-hexacarbonyl

The photochemical preparation of [M(CO)₅(P(CCC₆H₅)_n(C₆H₅)_3-n], cis-[M(CO)₄(PCCC₆H₅)_n(C₆H₅)_3-n] (M = Cr, W; n = 1,2,3) and fac-[Cr(CO)₃(P(CCC₆H₅)(C₆H₅)₃] by the corresponding substitution reactions of the hexacarbonyls is described. The IR and Raman spectra of the complexes in the region of the ν(CO) and ν(CC) vibrations and the ³¹P NMR spectra are discussed.     

The reactivity of Cp2V2(CO)5 towards alkynes

The chemistry of Cp₂V₂(CO)₅ (I) with alkynes is reported. In non-coordinating solvents, I reacts with large, electron-poor alkynes to give the cyclobutadiene complexes CpV(CO)₂(C₄R₄), which are not formed from photolysis of CpV(CO)₄ in the presence of alkyne. Smaller, more basic alkynes give simple monomeric adduct products of the type CpV(CO)₂(RCCR). This latter product is the only one obtained if coordinating solvents are employed. It is demonstrated that coupling to form the cyclobutadiene ligand occurs on the dimer. The dimeric intermediate, produced at low temperature and observed at low temperature by IR and NMR, is believed to have the formula Cp₂V₂(CO)₄(μ-RCCR) (X).Cp₂V₂(CO)₅ is active as a catalyst precursor in the photochemical hydrogenation of diphenyl acetylene to cis-stilbene. The mechanism appears to proceed through a Cp₂V₂(CO)₄(alkyne) intermediate.     

ÜbergangsmetallCarbin-Komplexe: LXXXVI. Synthese mono-, bis-, und tris-Trimethylphosphan-substituierter Diethylaminocarbin-Komplexe des Wolframs

The reaction of trans-I(CO)₄WCNEt₂ (I) with a slight excess of PMe₃ results in the replacement of one carbonyl group to give mer-I(CO)₃(PMe₃)WCNEt₂ (II). Complex II reacts at room temperature with additional PMe₃ under CO replacement to give a mixture of cis- and trans-dicarbonyl-I(CO)₂(PMe₃)₂WCNEt₂ (III, IV). Complexes III and IV, which can be separated by column chromatography, isomerize slowly at room temperature, the thermodynamic equilibrium favouring the more stable trans complex IV. The cis isomer III can be obtained from I(CO)₂py₂WCNEt₂ (V) and PMe₃. Another CO ligand can be eliminated from III or IV by an excess of PMe₃ in boiling hexane and gives mer-I(CO)(PMe₃)₃WCNEt₂ (VI). Moreover complex VI can be prepared by oxidative decarbonylation from III or IV by iodine and subsequent reduction of the intermediate, an isolable, seven-coordinated carbyne complex formulated as (I)₃(CO)(PMe₃)₂WCNEt₂ (VII), by two equivalents of PMe₃.     

Chelates formed by a constrained bis(diphenylphosphino)xylene; the crystal structures of [FeCl2(anphos)] and [RhCl(CO)(anphos-monoxide)]

The indan derived diphosphine, cis-1,3-(diphenylphosphino)indan (anphos) is synthesised by the addition of Ph₂P(BH₃)Li to cis-1,3-dibromoindan followed by deprotection with diethylamine. Anphos readily forms the bicyclic chelates [RhCl(CO)(anphos)], [PtCl₂(anphos)], [PtCl(Me)(anphos)] and [FeCl₂(anphos)]. The crystal structures of [FeCl₂(anphos)] and the monoxide complex, [RhCl(CO)(anphosO)] have been determined. Reaction of the diphosphine with [Rh(acac)(CO)₂] under moderate hydroformylation conditions catalysed the formation of 1-heptanal and branched aldehydes from 1-hexene in a ratio of 1.5:1.