Μ-vinylidene Complexes Research Articles

Chemistry of vinylidene complexes X. Synthesis and characterization of the vinylidene bridged complexes Cp(CO) 2MnPt(μ-CCHPh)(PP) with chelating diphosphine ligands PPdppm, dppe or dppp at the platinum atom

The binuclear μ-vinylidene complex Cp(CO) 2MnPt(μ-CCHPh)(PPh 3) 2 reacts with diphosphines PP Ph 2P(CH 2) n PPh 2, where n=1 (dppm), 2 (dppe) or 3 (dppp), at room temperature to give new complexes of the type Cp(CO) 2MnPt(μ-CCHPh)(PP) with chelating disphosphine ligands PP at the Pt atom in quantitative yields. All complexes are characterized by IR and 1H, 13C and 31P NMR spectra. The influence of the nature of the ligands at the Pt atom on the bonding between Pt and the semi-bridging carbonyl group is discussed.

Organic chemistry of dinuclear metal centres. Part 12. Synthesis, X-ray crystal structure, and reactivity of the di-µ-alkylidene complex [Ru2(CO)2(µ-CHMe)(µ-CMe2)(η-C5H5)2]: alkylidene linking

Upon treatment with methyl-lithium followed by HBF4·OEt2 a carbon monoxide ligand of the µ-alkylidene complex [Ru2(CO)2(µ-CO)(µ-CMe2)(η-C5H5)2](1) is converted into µ-ethylidyne, giving [Ru2(CO)2(µ-CMe)(µ-CMe2)(η-C5H5)2]+(2). This is deprotonated readily by water to form the µ-vinylidene complex [Ru2(CO)2(µ-CCH2)(µ-CMe2)(η-C5H5)2](3), which quantitatively regenerates (2) with HBF4·OEt2. Addition of NaBH4 to (2) results in hydride attack on µ-CMe to yield the di-µ-alkylidene complex [Ru2(CO)2(µ-CHMe)(µ-CMe2)(η-C5H5)2](4) as cis and trans isomers. The structure of the trans isomer has been established by X-ray diffraction. Crystals are triclinic, space group P, with Z= 2 in a unit cell for which a= 8.474(2), b= 7.802(3), c= 12.989(5)A, α= 99.42(3), β= 96.96(3), and γ= 107.73(3)°. The structure was solved by heavy-atom methods and refined to R 0.026 (R′ 0.031) for 4 092 independent intensities. A ruthenium–ruthenium single bond of 2.701(1)A is symmetrically bridged by ethylidene [mean Ru–C 2.079(3)] and isopropylidene [mean Ru–C 2.107(3)A] ligands to form an approximately planar Ru2C2 ring with a non-bonding Me2C··CHMe distance of 3.20 A. Upon thermolysis the alkylidenes link to evolve Me2CCHMe, Me2CHCHCH2, and Et(Me)CCH2. The absence of C4 and C6 hydrocarbons indicates that the alkylidene coupling occurs intramolecularly, and the electronic and stereochemical requirements of this process are discussed. Unlike mono-µ-alkylidene complexes, [Ru2(CO)2(µ-CO)(µ-CR2)(η-C5H5)2], the cis and trans forms. of (4) do not interconvert thermally below 145 °C, but u.v. irradiation effects a slow trans to cis isomerisation. U.v. irradiation of (4) in the presence of dimethyl acetylenedicarboxylate promotes ethylidene–alkyne linking to form [Ru2(CO)(µ-CMe2){µ-C(CO2Me)C(CO2Me)CHMe}(η-C5H5)2], but with ethyne both of the alkylidenes are lost and the ruthenium–ruthenium double-bonded complex [Ru2(µ-CO)(µ-C2H2)(η-C5H5)2] is produced.

Organic chemistry of dinuclear metal centres—X. Dimerization of allene at a diruthenium centre; X-ray crystal structure of [Ru 2(CO) 2{ (μ-C(Me)CHCH 2CCH 2)}(η-C 5Me 5) 2

Photolysis of [Ru 2(CO) 4(η-C 5R 5 2] (R = H or Me) in the presence of allene yields complexes [(η-C 5R 5)(CO) 2RuCH 2C(CH 2)C(CH 2)CH 2Ru(CO) 2(η-C 5R 5)] and [Ru 2(CO) 2{(μ-C(Me)CHCH 2CCH 2)}(η-C 5Me 5) 2], containing dimers of allene derived by C(2)C(2) and C(1)C(1) coupling, respectively. The molecular structure of [Ru 2(CO) 2 (μ-C(Me)CHCH 2)CCH 2(η-C 5Me 5) 2] has been determined by X-ray diffraction. The structure was solved by heavy-atom methods and refined by least-squares to give a final R 0.047 for 4678 unique, observed diffractometer data. Crystals are monoclinic, space group P2 1 / c, with Z = 8 in a unit cell of dimensions a = 10.403(8), b = 28.804(27), c = 19.882(18) Å, β = 117.14(6)°. The molecule is based on a trans-(η-C 5Me 5)(CO)RuRu(CO)(η-C 5Me 5) unit with one terminal and one semi-bridging carbonyl ligand This unit is bridged by a linear MeCCHCH 2CCH 2 six-carbon chain which is η 2-bound to one ruthenium through two σ-bonds, making a metallacyclopentene ring, and to the other through an η 2-interaction of an exocyclic double bond. The formation of the allene dimer products is attributed to the attack of Ru(CO) 2(η-C 5R 5) radicals upon the C(1) or C(2) carbon of allene, followed by dimerization of the radicals so formed. The μ-allene species [Ru 2(CO) 2(μ-CH 2CCH 2)(η-C 5H 5) 2] is obtained by photolysis of the μ-vinylidene complex [Ru 2(CO) 3(μ-CCH 2)(η-C 5H 5) 2] in acetonitrile, followed by the addition of diazomethane.

Chemistry of vinylidene complexes. V. The ligand substitution reactions at the platinum atom in complexes Cp(CO) 2MnPt(μ-CCHPh)L 2

The dimetal μ-vinylidene complexes Cp(CO) 2-MnPt(μ-CCHPh)L 2 (L = PPh 3 or P(OPr i) react with nucleophylic molecules (phosphines, phosphites or CO), without cleavage of a dimetallacycle, to afford the products of substitution of platinum-bound terminal ligands with geometry depending on the nature of an entering ligand. The reaction of Cp(CO) 2MnPt(μ-CCHPh)(PPh 3) 2 and P(OPr i) gives Cp(CO) 2MnPt(μ-CCHPh)[P(OPr i) 3] 2 and Cp(CO) 2- MnPt(μ-CCHPh)[P(OPr i) 3](PPh 3) with the P(OPr i) 3 group cis to the μ-C atom. The latter is also formed by treating Cp(CO) 2MnPt(μ-CCCHPh)[P(OPr i) 3] 2 with PPh 3, and as a result of the ligand exchange reaction between bis-phosphine and bis-phosphite compounds. The last ligand redistribution process is reversible, and an equilibrium between all three of the above complexes exists in solution. Treatment of Cp(CO)MnPt(μ-CCHPh)L 2 with Co 2(CO) 8 yields the tricarbonyl complexes Cp(CO) 2- MnPt(μ-CCHPh)(L)(CO) with the platinum-bound Co group trans to μ-C. All studied reactions are stereoselective, and no mixed-ligand complexes isomeric to the above species have been detected. The IR and 1H, 13P NMR spectra of the new complexes are discussed.

Übergangsmetall—methylen-komplexe: LXI. Übergangsmetall—vinyliden-komplexe: Neuartige synthese aus diazoalken-vorstufen

The diazoolefines of composition N 2CCR 2 (R/R = CH 3/CH 3 and(-CH 2-) 5) are suitable precursors of the corresponding vinylidene ligands CCR 2. Thus, treatment of the RhRh complex [(η 5-C 5Me 5)Rh(μ-CO)] 2 ( 1) with the N-nitrosourethanes 2a and 2b, resp., in the presence of lithium t-butoxide yields the otherwise inaccessible μ-vinylidene complexes (μ-CCR 2)[(η 5-C 5Me 5)Rh(CO)] 2 (R = CH 3 ( 3a), R,R = (-CH 2-) 5 ( 3b)). The analogous cobalt compound (μ-CCMe 2)[(η 5-C 5Me 5)Co(CO)] 2 ( 5a) is obtained similarly. This procedure extends the well-documented diazoalkane method for the synthesis of μ-alkylidene complexes to the less stable diazoalkenes. A single-crystal X-ray diffraction study of the dimethylvinylidene derivative 3a shows the CMe 2 ligand to adopt an almost symmetrically metal-bridging position ( d(RhC) 197.8(1) and 204.3(1) pm), with a rhodium-rhodium single bond completing a three-membered Rh 2C-metallacycle ( d(RhRh) 268.4(0) pm) analogous with cyclopropane.

Übergangsmetall—methylen-komplexe: LIX. Ein neues darstellungsverfahren für vinyliden-komplexe

The diazo olefins N 2CCR 2 (R/R = CH 3/CH 3 and (CH 2) 5, respectively), generated in situ from the corresponding cyclic N-nitrosourethanes 2a, 2b, are suitable precursors for the corresponding vinylidene ligands ‖CCR 2. Thus, treatment of the RhRh complex [(η 5-C 5Me 5)Rh(μ-CO)] 2 ( 1) with 2a, 2b in the presence of lithium ethoxide yields the otherwise inaccessible μ-vinylidene complexes (μ-CCR 2)[(η 5-C 5Me 5)Rh(CO)] 2 ( 3a, 3b). This procedure extends the well-documented diazoalkane method for synthesis of μ-alkylidene complexes to the less stable diazoalkenes*

Protonation of allenylidene- and vinylidene-manganese complexes. Crystal and molecular structure of [Cp(CO) 2MnCCHCPh 2] + BF 4t

The cyclopentadienylmanganese carbonyl complexes with terminal allenylidene ligands, Cp(CO) 2MnCCCR 2 (R = Bu t, Ph), are protonated by HX acids (X = Cl, BF 4, CF 3COO) yielding cationic vinylcarbyne complexes of the type [Cp(CO) 2MnCCHCR 2] +X −. One of these, with R = Ph, X = BF 4, was characterized by X-ray crystallography. The MnC bond of 1.665 Å in it is the shortest one known to date. The binuclear μ-vinylidene complexes, [Cp(CO) 2,Mn] 2CCHR′ (R′ = Ph, COOMe) are also protonated at the β-carbon atom of the vinylidene ligand.

Organic chemistry of binuclear metal centres. Part 6. µ-Vinylidene and µ-ethylidyne diruthenium complexes: crystal structures of cis-[Ru2(CO)2(µ-CO)(µ-CCH2)(η-C5H5)2] and cis-[Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2][BF4

The dimetallacycles [Ru2(CO)(µ-CO){µ-C(O)C2HR}(η-C5H5)2](R = H or Ph) isomerise in boiling toluene to the µ-vinylidene complexes [Ru2(CO)2(µ-CO)(µ-CCHR)(η-C5H5)2], shown by a deuterium-labelling experiment to involve an intramolecular hydrogen shift. Protonation of the µ-CCH2 complex with HBF4·OEt2 gives the µ-ethylidyne species [Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2][BF4], which deprotonates readily when treated with water, triethylamine, or methyl-lithium; with NaBH4 the cation is attacked by hydride to produce the µ-ethylidyne complex [Ru2(CO)2(µ-CO)(µ-CHMe)(η-C5H5)2]. Successive addition of methyl-lithium and HBF4·OEt2 to [Ru2(CO)4(η-C5H5)2] also yields the complex [Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2][BF4], whose subsequent conversion to [Ru2(CO)2(µ-CO)(µ-CCH2)(η-C5H5)2] or [Ru2(CO)2(µ-CO)(µ-CHMe)(η-C5H5)2] provides an excellent route to these complexes. Similar successive addition of phenyl-lithium, HBF4·OEt2, and NaBH4 to [Ru2(CO)4(η-C5H5)2] gives [Ru2(CO)2(µ-CO)(µ-CHPh)(η-C5H5)2] in high yield. The molecular structures of cis-[Ru2(CO)2(µ-CO)(µ-CCH2)(η-C5H5)2] and cis-[Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2][BF4] have been determined by X-ray diffraction studies. Crystals of both compounds are monoclinic, space group P21/n with Z= 4 and unit-cell dimensions a= 8.620(6), b= 15.712(9), c= 10.844(8)A, β= 92.57(4)° and a= 9.121(2), b= 9.724(3), c= 20.666(6)A, β= 106.42(3)° respectively. The structures were solved by heavy-atom methods and refined by least squares to give final residuals R of 0.051 and 0.026 for 2 503 and 3 044 unique, observed, diffractometer data respectively. Both cis-[Ru2(CO)2(µ-CO)(µ-CCH2)(η-C5H5)2] and cis-[Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2]+ show approximate Cs symmetry in the solid state, with Ru–Ru single bond distances of 2.696(1) and 2.714(1)A respectively. In both cases each ruthenium atom is co-ordinated by terminal carbonyl and η-cyclopentadienyl ligands in addition to bridging carbonyl and hydrocarbon (vinylidene and ethylidyne) groups. The geometry and orientation of the bridging vinylidene ligand is consistent with a C–C bond order of two [C–C 1.326(11)A] and contact carbon bonding to the Ru2 fragment via donor and acceptor interactions of σ and π symmetry in the Ru2C plane. The µ-ethylidyne ligand in cis-[Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2][BF4] shows average Ru–C distances shorter than those of the η-vinylidene ligand in cis-[Ru2(CO)2(µ-CO)(µ-CCH2)(η-C5H5)2][1.937(4)vs. 2.030(7)A], and has a longer C–C distance [1.462(6)A] consonant with a C(sp)-C(sp3) single bond. These geometric features, and the reactivity of the cationic µ-ethylidyne complex towards nucleophiles, are explained in terms of a simple molecular orbital model.

Sequential conversion of ethyne into μ-vinylidene, μ-methylcarbyne and μ-methylcarbene at a di-ruthenium centre: X-ray structures of [Ru 2(CO) 2(μ-CO) (μ-CCH 2) (η-C 5H 5) 2] and [Ru 2(CO) 2(μ-CO) (μ-CCH 3) (η-C 5H 5) 2] [BF 4

The ethyne-derived demetallocycle [Ru 2(CO) (μ-CO){μ-C(O)C 2H 2}(η-C 5H 5) 2 isomerises in boiling toluene to yield the μ-vinylidene complex [Ru 2(CO) 2(μ-CO)(μ-CCH 2) (η-C 5H 5) 2], which on protonation with dry HBF 4 provides the μ-carbyne complex [Ru 2(CO) 2(μ-CO)(μ-CCH 3)(η-C 5H 5) 2][BF 4]; the structure of each product has been determined by X-ray diffraction. The μ-carbyne cation is attacked by hydride to produce the μ-methylcarbene complex [Ru 2(CO) 2(μ-CO)(μ-CHCH 3)(η-C 5H 5) 2].