Carbyne Complexes Research Articles

Reactions of cationic carbyne complexes of manganese and rhenium with metal carbonyl anions

Treatment of [(η-C5H5)(OC)2MnCC6H5]BBr4 1 and [(η-C5H5)(OC)2ReCC6H5]BBr4 2 with the carbonyl monoanion [Mn(CO)5]– 3 in THF at low temperature afforded the ketenyl bridged complexes [Mn2{µ-C(CO)C6H5}(CO)6(η-C5H5)] 6 and [ReMn{µ-C(CO)C6H5}(CO)6(η-C5H5)] 7 respectively. The analogous reactions of complexes 1 and 2 with [Co(CO)4]– 4 gave corresponding ketenyl bridged complexes [MnCo{µ-C(CO)C6H5}(CO)5(η-C5H5)] 8 and [ReCo{µ-C(CO)C6H5}(CO)5(η-C5H5)] 9 respectively. Complexes 1 and 2 reacted with the carbonyl dianion [W(CO)5]2– 5 to give the dimetal carbene bridged complexes [MnW{µ-C(H)C6H5}(CO)7(η-C5H5)] 10 and [ReW{µ-C(H)C6H5}(CO)7(η-C5H5)] 11 respectively. The structures of complexes 6, 9 and 11 have been established by X-ray diffraction studies.

Syntheses and reactions of the carbyne complexes, M(CR)Cl(CO)(PPh 3) 2 (M=Ru, Os; R=1-naphthyl, 2-naphthyl). The crystal structures of [Os(C-1-naphthyl)(CO) 2(PPh 3) 2]ClO 4, Os(CH-2-naphthyl)Cl 2(CO)(PPh 3) 2, and Os(2-naphthyl)Cl(CO) 2(PPh 3) 2

Treatment of the dichlorocarbene-containing complex, Os(CCl 2)Cl 2(CO)(PPh 3) 2 with two equivalents of 1-naphthyllithium or two equivalents of 2-naphthyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine (tmeda) gives the corresponding carbyne-containing complexes Os(CR)Cl(CO)(PPh 3) 2 (R=1-naphthyl ( 1); R=2-naphthyl ( 2)). Similar treatment of Ru(CCl 2)Cl 2(CO)(PPh 3) 2 with two equivalents of phenyllithium or 1-naphthyllithium yields Ru(CR)Cl(CO)(PPh 3) 2 (R=Ph ( 3); R=1-naphthyl ( 4)). When 1, 2, 3 and 4 are carbonylated in the presence of AgClO 4 the corresponding carbyne-containing cations [M(CR)(CO) 2(PPh 3) 2]ClO 4 are formed (M=Os, R=1-naphthyl ( 5); M=Os, R=2-naphthyl ( 6); M=Ru, R=Ph ( 7); M=Ru, R=1-naphthyl ( 8)). When Ru(CPh)Cl(CO)(PPh 3) 2 is added to an acetonitrile solution containing two equivalents of AgClO 4 in the absence of CO the complex [Ru(CPh{AgOClO 3})(NCMe)(CO)(PPh 3) 2]ClO 4 ( 9) can be isolated. Addition of LiCl to 9 yields the complex Ru(CPh{AgCl})Cl(CO)(PPh 3) 2 ( 10). The acids HX react with the neutral carbyne complexes 1, 2, 3 or 4 to form the corresponding carbene complexes M(CHR)ClX(CO)(PPh 3) 2 (M=Os, R=1-naphthyl, X=Cl ( 11); M=Os, R=2-naphthyl, X=Cl ( 12); M=Ru, R=Ph, X=Cl ( 13); M=Ru, R=1-naphthyl, X=Cl ( 14); M=Os, R=1-naphthyl, X=ClO 4 ( 15); M=Os, R=1-naphthyl, X=F ( 16)). Treatment of complexes 1 or 2 with PhICl 2 leads to corresponding monochlorocarbene-containing complexes Os(CClR)Cl 2(CO)(PPh 3) 2 (R=1-naphthyl ( 17); R=2-naphthyl ( 18)) which subsequently rearrange on addition of aqueous base to give the σ-naphthyl, dicarbonyl complexes OsRCl(CO) 2(PPh 3) 2 (R=1-naphthyl ( 19); R=2-naphthyl ( 20)). The single crystal X-ray structures of [Os(C-1-naphthyl)(CO) 2(PPh 3) 2]ClO 4, Os(CH-2-naphthyl)Cl 2(CO)(PPh 3) 2, and Os(2-naphthyl)Cl(CO) 2(PPh 3) 2 have been determined.

Dearomatization of Furan: Elementary Transformations of η2-Coordinated Furan Complexes of Pentaammineosmium(II)

A series of complexes has been prepared of the form [Os(NH3)5(4,5-η2-L)]2+ where L = furan and various alkylated furans. These heterocycle complexes were surveyed for their reactivity with various electrophiles (e.g., acids, silyl triflate, N-methylacetonitrilium triflate, acetals, aldehydes, and Michael acceptors). Electrophilic addition to C(3) results in an unstable reaction intermediate, a 4,5-η2-3H-furanium species, that leads to complexes of 4,5-η2-3-substituted furans, 2,3-dihydrofurans, C(5)-substituted 2-oxoalkenes, cyclic vinyl ethers, or osmium carbyne complexes. The specific reactivity displayed by the η2-furan complexes strongly depends on the presence and location of alkyl substituents and their ability to stabilize η2-vinyl cation intermediates resulting from C(5)−O bond cleavage. In all cases investigated, the addition of an electrophile at C3 occurs anti to osmium coordination.

Mechanism of the Formation of Carbyne Complexes of Rhenium upon Protonation of Vinylidene Precursors

The reactions of trans-[ReX(CCHR)(dppe)2] with [NHEt3][BPh4] to form the carbyne complexes trans-[ReX(⋮CCH2R)(dppe)2]+ (X = Cl; R = Ph, C6H4Me-4, But, CO2Me, CO2Et; X = F; R = CO2Et; dppe = Ph2PCH2CH2PPh2) have been studied by stopped-flow spectrophotometry and shown to proceed via three pathways whose relative contribution depends on the nature of R and X. The most direct pathway involves regiospecific protonation at the β-carbon of the vinylidene. However, under some conditions initial protonation at the metal to form [Re(H)X(CCHR)(dppe)2]+ is more rapid, and this hydride subsquently rearranges to form the carbyne by an intramolecular pathway or by protonation of [Re(H)X(CCHR)(dppe)2]+ at the β-carbon of the vinylidene ligand to give [Re(H)X(⋮CCH2R)(dppe)2]2+, which then undergoes deprotonation to form [ReX(⋮CCH2R)(dppe)2]+. For the R = C6H5 or C6H4Me-4 complexes, kinetic analysis indicates that all three pathways occur, whereas for the bulky R = But analogue, the pathways that involve direct addition t...

Electrophilic Addition to η2-Aldehyde Complexes of Pentaammineosmium(II): The Formation of Fischer Carbyne Complexes via η2-Aldehydium Intermediates

A series of η2-aldehyde complexes of pentaammineosmium(II) of the form [Os(NH3)5(L)](OTf)2 (L = formaldehyde (1), acetaldehyde (2), trimethylacetaldehyde (3), benzaldehyde (4), and crotonaldehyde (5), OTf = trifluoromethanesulfonate) are prepared and characterized. Treatment of these η2-bound aldehyde complexes with CH3OTf affords Fischer carbyne complexes 14−18 with typical yields ranging from 25−92%. Protonation (HOTf/MeCN) or methylation (MeOTf/DME) of many of these aldehyde complexes afford O-protonated or O-methylated η2-aldehydium intermediates, respectively, which over time convert to the corresponding carbyne complex. The chemistry of olefin-coordinated α,β-unsaturated aldehyde complexes is also explored.

Synthesis and Decomposition of Alkyl Complexes of Tungsten(IV) That Contain a [(Me3SiNCH2CH2)3N]3- Ligand

The synthesis of a variety of tungsten alkyl complexes of the type [N3N]WR ([N3N]3- = [(Me3SiNCH2CH2)3N]3-; R = Me, Et, Bu, CH2Ph, CH2SiMe3, CH2CMe3, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopentenyl) was attempted by alkylation of [N3N]WCl complexes. Only the methyl, phenyl, and cyclopentenyl complexes could be isolated. The susceptibility of the [N3N]WR complexes is similar to that of [N3N]WCl; the effective moment is depressed as a consequence of a combination of spin−orbit effects and low-symmetry ligand-field components that result in zero-field splitting of the d2 ground-state spin triplet. No linear alkyl complexes could be observed as a consequence of α,α-dehydrogenation to give molecular hydrogen and alkylidyne complexes, [N3N]W⋮CR‘. [N3N]W(cyclopropyl) evolves ethylene in a first-order process to give [N3N]W⋮CH, while [N3N]W(cyclobutyl) is converted into the 1-tungstacyclopentene complex, [N3N]W(CHCH2CH2CH2), as confirmed in an X-ray study. [N3N]W(CHCH2CH2CH2) decomposes readily in a first-order manner to give [N3N]W⋮CCH2CH2CH3. An attempt to prepare [N3N]W(cyclopentyl) led to formation of [N3N]W(cyclopentylidene)(H), as confirmed in an X-ray study. NMR studies suggest that [N3N]W(cyclopentylidene)(H) is in equilibrium with [N3N]W(cyclopentyl) where ΔH° = 11.8(6) kcal mol-1 and ΔS° = 33(2) eu or Keq ≈ 0.1 at 46 °C. From these and other data it is concluded that the rate constant for α elimination in [N3N]M(cyclopentyl) is approximately the same for Mo and W. The [N3N]W(cyclopentenyl) complex is unstable, decomposing to give a complex containing a “bent imido” ligand, [(Me3SiNCH2CH2)2(NCH2CH2)N]W(1-(trimethylsilyl)cyclopentene), as confirmed in an X-ray study.

Syntheses, Spectroscopy, and Redox Properties of Fluoro−Carbyne and Derived Fluoro−Vinylidene Complexes of Rhenium and of Analogous Chloro Complexes

The fluoro− or chloro−carbyne complexes trans-[ReX(≡CCH2R)(dppe)2][BF4] (X = F (1), R = H (1a), But (1b), CO2Me (1c), CO2Et (1d), Ph (1e), or C6H4Me-4 (1f); X = Cl (2), R = H (2a), But (2b), CO2Me (2c), CO2Et (2d), Ph (2e), or C6H4Me-4 (2f); dppe = Ph2PCH2CH2PPh2) have been prepared by a single-pot reaction, in THF and under sunlight, of the appropriate 1-alkyne (HC≡CR) with trans-[ReCl(N2)(dppe)2] and [NH4][BF4] in the presence or in the absence, respectively, of Tl[BF4]. With the exception of the less acidic tert-butylcarbyne complexes (1b and 2b), these complexes are deprotonated by [Bu4N]OH to give the corresponding vinylidene complexes trans-[ReX(CCHR)(dppe)2] (X = F (3) or Cl (4)) which, by treatment with HBF4, regenerate the carbyne complexes. This route is more convenient for the synthesis of the chloro−carbyne complexes 2 from the vinylidenes 4, the latter being then prepared upon reaction of the dinitrogen complex with HC≡CR in toluene under sunlight. The electrochemical behavior of complexes 1−4 has been investigated by cyclic voltammetry and controlled potential electrolysis in aprotic media and at a Pt electrode. These complexes undergo single-electron reversible oxidations at half-wave oxidation potentials in the range from 1.39 to 1.48 (1, 2) and −0.35 to 0.25 (3, 4) V vs SCE. The corresponding electrochemical PL and EL ligand parameters have been estimated for the carbyne (PL = 0.21−0.24 V, EL ca. 1.2 V vs NHE) and the vinylidene (PL = −0.27 to −0.13 V, EL = 0.50−0.62 V vs NHE) ligands and discussed in terms of redox potential−structure relationships. The former ligands behave as remarkably strong π-electron acceptors and undergo cathodically induced C−H bond cleavage to give the corresponding vinylidenes. Both the carbyne and the vinylidene ligands are effectively stabilized by the trans-fluoride ligand, although it presents, relative to chloride, a slightly stronger destabilizing effect on the HOMO in these complexes.

Synthesis and Characterization of Tungsten Alkenyl−Carbyne and Alkenyl−Ketenyl Complexes Containing Dithio Ligands. X-ray Crystal Structure and MO Analyses of [(dppe){κ3(S,C,S)-S2CPCy3}W⋮CCHC(CH2)3CH2][BF4

The reaction = 1,2-bis(diphenylphosphino)ethane; n = 1 (1a), 4 (1b)) with S2CPCy3 in methanol for 10 min affords = 1 (2a), 4 (2b)). Similarly, the = 1 (3a), 4 (3b)) have been prepared by the reaction with [NBu4][S2P(OEt)2]. When 1a and 1b are reacted with S2CPCy3 in methanol for 24 h, the = 1 (4a), 4 (4b)) are formed. Moreover, when 1a and 1b are reacted with NaS2CNR2 (R = Me, Et), the formed (R = Me, n = 1 (5a), 4 (5b); R = Et, n = 1 (5c), 4 (5d)) subsequent to the coupling between the carbyne group and carbon monoxide. IR and 1H, 31P, and 13C NMR data are reported for all of the species. The molecular structure of compound 4a, determined by X-ray diffraction methods, shows that the S2CPCy3 ligand is bound to the metal in a pseudoallylic κ3(S,C,S) fashion. The metal coordination is completed by the W⋮C triple bond of the alkenyl−carbyne group and by two additional W−P bonds. Since the metal center in 4a is formally a deficient 16-electron species and since the synthetic route has clearly indicated that an additional CO ligand is preferentially rejected by the metal, a reasonable interpretation of the bonding has been sought by means of EHMO calculations. Not only has the coexistence between the dithiocarboxylate and the carbyne ligands been elucidated, but also the strength of the W−S bonds is accounted for in comparison with the weaker W−S bonds observed in other saturated W complexes containing a κ3(S,C,S) dithio ligand. Finally, qualitative theoretical considerations are presented for the different behavior of the dithiocarbamate ligand.

Transition‐Metal‐Substituted Acylphosphanes and Phosphaalkenes, 35 Unprecedented Coupling of a Transition‐Metal Carbyne and a Methylene Phosphane Moiety – Structure of [Tp'(CO)2W=CP=C(NEt2)2] [Tp = HB (3,5‐Me2HC3N2)3

AbstractCondensation of [Tp](CO)2 Mčl] [1: M = Mo; 2: W; Tp] HB (3,5‐Me2HC2N2)3] with the inverse phosphaalkenes Me3 Sip=C(NR2)2 (3a: R = Me; 3b: Et) affords the novel phosphaalkenyl carbyne complexes [Tp](CO)2M.C–P=C(NR2)2] (a, b) (M = Mo; R = Me, Et) and 5a, b (M = W; R = Me, Et), which have been characterized by IR, 1H‐, 13C‐ and 31P‐NMR spectroscopy. In additon, the molecular structure of 5 has been elucidated by a single‐crystal X‐ray structure determination.

Convenient Synthesis of W(⋮CR)X3(dme) Compounds from W(⋮CR)(OBut)3 Triple-Bond Metathesis Products

Tungsten−alkylidyne complexes of the type W(⋮CR)X3(dme) (R = But, Prn, Ph; X = Cl, Br; dme = 1,2-dimethoxyethane) are prepared in 77−87% yields from reactions between W(⋮CR)(OBut)3 and BX3 in the p...

Diffusional and Internal Rotation in Single and Linked Trinuclear Bis(carbyne) Cluster Complexes Determined by (13)C NMR Relaxation Time Measurements.

Carbon-13 NMR relaxation times have been measured as a function of temperature for a family of bis(carbyne) cluster complexes: (CpCo)(3)(&mgr;(3)-CPh)(2) (1a), (CpCo)(3)(&mgr;(3)-CH)(&mgr;(3)-CPh) (1b), and X(1,4-C(6)H(4))Y with X = Y = (CpCo)(3)(&mgr;(3)-CPh)(&mgr;(3)-C-) (2); X = (CpCo)(3)(&mgr;(3)-CPh)(&mgr;(3)-C-), Y = -C&tbd1;CPh (3); or X = Y = -C&tbd1;CPh (4). These molecules can be regarded as symmetric top molecules in which the phenyl rings are adjacent to zero, one, or two Cp(3)Co(3) metal cluster units. Molecular rotational diffusion coefficients about the different axes of the molecules (D( perpendicular)and D(s)) obtained from the relaxation times indicate that the motions of the molecules are highly anisotropic. Rapid internal rotation of the phenyl rings described by the rotation rates R contributes significantly to that anisotropy. Phenyl rings adjacent to an alkyne group rotate at a rate comparable to that of free benzene whereas phenyl rings bound to a (CpCo)(3) group through a &mgr;(3)-carbyne ligand show significantly reduced rates of rotation. The observed difference in rotation rates is believed to be due primarily to steric interactions between phenyl rings and their substituents.

Synthesis of Boryl Metal Complexes with Additional Agostic Stabilization by Hydroboration of Fischer Carbyne Complexes

Synthesis of Boryl Metal Complexes with Additional Agostic Stabilization by Hydroboration of Fischer Carbyne Complexes

Tungstaarsirenes: Synthesis and Structure of η2-Arsinocarbene Complexes of Tungsten [(η5-C5H5)(CO)2WC(R)AsPh2][PF6

The reaction of the carbyne complexes (η5-C5H5)(CO)2W⋮CR (R = Me, Ph, Tol) with chlorodiphenylarsine, Ph2AsCl, provides in the presence of thallium hexafluorophosphate the novel cationic η2-arsinocarbene complexes [(η5-C5H5)(CO)2WC(R)AsPh2][PF6] (2a−c) in high yields. The constitution of the new tungstaarsacyclopropene complexes was determined by spectroscopic investigation and, in the case of the 4-methylphenyl-substituted compound 2c, additionally by X-ray single-crystal structure determination.

Metalcarbon multiple bonds: synthesis, structure, and electrochemistry of chromium aminocarbyne and phenylcarbyne complexes bearing phosphine or alkyl isonitrile ligands

The synthesis, structure and cyclic voltammetry studies of neutral and cationic chromium carbyne complexes bearing phosphine or alkyl isonitrile ligands are reported. Treatment of cis-X(CO) 2(pic) 2CrCN iPr 2 (pic: 4-methylpyridine) ( 1a: X  Cl; 1b: X  Br) with two equivalents of PMe 3 and PMe 2Ph, or one equivalent of 1,2-bis(diphenylphosphino)ethatne (dppe) affords the aminocarbyne complexes cis-Cl(CO) 2(PMe 3) 2CrCN iPr 2 ( 2a). cis-Cl(CO) 3(dppe)CrCN iPr 2 ( 2b) and cis-Br(CO) 2(PMe 2Ph) 2CrCN 1Pr 2 ( 2e) respectively. In comparison, reaction of 1a with two equivalents of P(OMe) 3 gives selectively the trans-isomer Cl(CO) 2[P(OMe) 3] 2CrCN 1Pr 2 ( 3). Complex 2c is converted with TIPF 6 and PMe 2Ph to the cationic aminocarbyne complex [ fac-(PMe 2Ph) 3(CO) 2CrCN 1Pr 2][PF 6] ( 4). Similarly, the cationic phenylcarbyne complex [ fac-[ tBuNC) 3 (CO) 2CrCph][PF 6] ( 6a) is obtained from cis-Br(CO) 2( tBuNC) 2CrCPh ( 5a), TIPF 6 and tBuNC, Treatment of 1a with four equivalents of isopropyl isonitrile affords the cationic aminocarbyne complex [ cis-( iPrNC) 4(CO)CrCN iPr 2]Cl ( 9a), which is converted with TIPF 6 to [ cis-( iPrNC) 4(CO)CrCN iPr 2][PF 6] ( 9b). Comparative cyclic voltammetry studies of the aminocarbyne complexes 2a, 2c, 4, cis-Br(CO) 2( tBuNC) 2CrCN iPr 2 ( 5b), [ fac-( tBuNC) 3(CO) 2CrCN iPr 2][PF 6] ( 6b), mer-Br( tBuNC) 3(CO)CrCN iPr 2 ( 7), [ cis-( tBuNC) 4(CO)CrCN iPr 2][PF 6] ( 8b), [( tBuNC) 5CrCN iPr 2IPF 6] ( 10) and the phenylcarbyne complexes 5a and 6a are reported. The crystal structures of the aminocarbyne complexes 2a and 2c are described.

Carborane Complexes of Ruthenium: Reactions of [Ru(THF)(CO)2(η5-7,8-R2-7,8-C2B9H9)] (R = H or Me) with Alkylidyne Complexes of Molybdenum and Tungsten

The complex [Ru(THF)(CO)2(η5-7,8-C2B9H11)] (1a, THF = tetrahydrofuran) reacts with the alkylidyne reagents [M(⋮CC6H4Me-4)(CO)2(η5-C5H5)] (M = Mo or W) to give the compounds [MRu(μ-CC6H4Me-4)(CO)4(η5-7,8-C2B9H11)(η5-C5H5)] (M = W (2a), Mo (2b)), which readily isomerize to the species [MRu(CO)4{σ,η5-9-CH(C6H4Me-4)-7,8-C2B9H10}(η5-C5H5)] (M = W (3a), Mo (3b)). The structure of 3b was established by X-ray diffraction. The Mo(CO)2(η5-C5H5) fragment is attached to the closo-RuC2B9 framework by a Mo−Ru bond and a three-center two-electron B−H⇀Mo linkage involving a boron atom in an α site in the CCBBB ring ligating the ruthenium. The CH(C6H4Me-4) moiety bridges between the Ru(CO)2 group and the B atom located in the other α site in the CCBBB ring. The oxo complex [WRuO{μ-σ,η5-9-CH(C6H4Me-4)-7,8-C2B9H10}(CO)2(η5-C5H5)] (4a) is a side product in the formation of 3a, and it also was characterized by X-ray diffraction. Treatment of the species 3 with PMe3 affords the zwitterionic compounds [MRu(CO)4{η5-9-CH(PMe3)(C6H4Me-4)-7,8-C2B9H10}(η5-C5H5)] (M = W (5a), Mo (5b)). A single-crystal X-ray diffraction study of 5a revealed that the (OC)2W−Ru(CO)2 unit is bridged by the nido-9-CH(PMe3)(C6H4Me-4)-7,8-C2B9H10 group. The open C2B3 face is pentacoordinated to the Ru atom, and there is an exopolyhedral B−H⇀W bond involving a Bα atom in the CCBBB ring. The other Bα site carries the CH(PMe3)(C6H4Me-4) substituent. Reactions between the ruthenium reagent [Ru(THF)(CO)2(η5-7,8-Me2-7,8-C2B9H9)] (1b) and [W(⋮CC6H4Me-4)(CO)2(η5-C5H5)] gave [WRuO{μ-σ,η5-7,8-Me2-10-CH(C6H4Me-4)-7,8-C2B9H8}(CO)2(η5-C5H5)] (4b), [WRu(μ-H){μ-η5,η‘5-7,8-Me2-9-C5H4-10-CH2(C6H4Me-4)-7,8-C2B9H7}(CO)5] (6a), and [WRu{μ-σ,η5-2,7-Me2-8-CH2(C6H4Me-4)-9-C(H)O-2,7-C2B9H6}(CO)4(η5-C5H5)] (7a) that were separated by column chromatography. The corresponding reaction between 1b and [W(⋮CC6H4Me-2)(CO)2(η5-C5H5)] afforded [WRuO{μ-σ,η5-7,8-Me2-n-CH(C6H4Me-2)-7,8-C2B9H8}(CO)2(η5-C5H5)] (n = 9 (4c), 10 (4d)) and [WRu{μ-σ,η5-2,7-Me2-8-CH2(C6H4Me-2)-9-C(H)O-2,7-C2B9H6}(CO)4(η5-C5H5)] (7b). Treatment of 1b with [Mo(⋮CC6H4Me-n)(CO)2(η5-C5H5)] (n = 4 or 2) yielded [MoRu(μ-H){μ-η5,η‘5-7,8-Me2-9-C5H4-10-CH2(C6H4Me-n)-7,8-C2B9H7}(CO)5] (n = 4 (6b), 2 (6c)). The structures of 4b, 6b, and 7b were established by X-ray diffraction. In 6b, the (OC)3Mo(μ-H)Ru(CO)2 unit is bridged by a 7,8-Me2-9-C5H4-10-CH2(C6H4Me-4)-7,8-C2B9H7 moiety, a structure resulting from a linking of C5H5 and nido-C2B9 groups. The C5 ring is η5-coordinated to the molybdenum, while the open CCBBB face of the carborane cage is similarly attached to the ruthenium. In complex 7b, a nido-2,7-Me2-8-CH2(C6H4Me-2)-9-C(H)O-2,7-C2B9H6 cage system bridges the Ru−W bond with an η5-CB4 ring coordinated to the Ru atom and with the cage joined to the W atom by a B−W bond. In addition, the C(H)O group forms a second bridge linking the cage to the tungsten, with the latter coordinated by the formyl O atom.

Synthesis, Spectroscopic Characterization, and Reactivity of the Unusual Five-Coordinate Hydrido−Vinylidene Complex OsHCl(CCHPh)(PiPr3)2: Precursor for Dioxygen Activation

The hydrido−carbyne complex OsHCl2(CCH2Ph)(PiPr3)2 (1) reacts with sodium methoxide in 1:1 molar ratio to give the five-coordinate hydrido−vinylidene OsHCl(CCHPh)(PiPr3)2 (2), which affords [OsHCl(CCH2Ph)(H2O)(PiPr3)2]BF4 (3) by reaction with HBF4·H2O. The spectroscopic data obtained for 2 indicate that in solution, it is a mixture of two conformers in equilibrium. The thermodynamic magnitudes involved in the equilibrium as well as the activation parameters for the conversion between them were determined by 1H NMR spectroscopy in toluene-d8. The values obtained were ΔH° = −0.7 (±0.1) kcal mol-1, ΔS° = −2.3 (±0.6) cal K-1 mol-1 , ΔH⧧ = 11.0 (±0.2) kcal mol-1 and ΔS⧧ = 3.2 (±0.6) cal K-1 mol-1. At room temperature under argon, complex 2 is stable in the solid state and in solution. However in the presence of air, it activates molecular oxygen to give the dioxo−styryl compound OsCl{(E)-CHCHPh}(O)2(PiPr3)2 (4), which has been characterized by X-ray diffraction analysis. The geometry around of the osmium atom ...

Site-selective substitution and vinylidene–alkylidyne–vinylidene interconversion in dimolybdenum–ruthenium clusters

The thermal reaction of the dimolybdenum–ruthenium vinylidene clusters [Mo 2 Ru(µ 3 -CCHR)(CO) 7 (η-C 5 H 5 ) 2 ] (R = H 1a, Me 1b, Ph 1c or CO 2 Me 1d) with the tertiary phosphine PPh 2 Me afforded the monosubstituted complexes [Mo 2 Ru(µ 3 -CCHR)(CO) 6 (PPh 2 Me)(η-C 5 H 5 ) 2 ] 2a–2d in excellent yields. The products exist as single isomers in which site-selective substitution of a CO ligand has occurred exclusively at the ruthenium atom. The crystal structure of 2b has been determined by X-ray diffraction; the geometry of the vinylidene ligand is identical to that previously found in the parent compound 1b, but a slightly different pattern of semi-bridging carbonyls is present. The reactions of 1a and 1b with diphenylphosphine are more complex. Depending on the stoichiometry and conditions employed, three different types of cluster have been isolated: the substitution product [Mo 2 Ru(µ 3 -CCH 2 )(CO) 6 (PPh 2 H)(η-C 5 H 5 ) 2 ] 2e; the 46-electron monophosphido compounds [Mo 2 Ru(µ 3 -CCH 2 R)( µ-PPh 2 )(CO) 5 (η-C 5 H 5 ) 2 ] 3a, 3b and the saturated bis(phosphido) species [Mo 2 Ru(µ 3 -CCHR)(µ- PPh 2 ) 2 (CO) 4 (η-C 5 H 5 ) 2 ] 4a, 4b. Separate experiments have established that these products are formed sequentially, thus demonstrating the conversion of the initial vinylidene into an alkylidyne ligand and then back to a vinylidene. The structures of 3b and 4a have been confirmed by X-ray diffraction, showing that the phosphido groups bridge one or both of the Mo–Ru edges respectively.

One-dimensional alignment of organometallic donor–acceptor compounds via coordination polymerization. Synthesis and structures of [W(CC6H4X-4)(OBut)3] ∞ (X = NMe2, SMe)

Metal–alkylidyne complexes of the type W(CC 6 H 4 X-4)(OBu t ) 3 (X = NMe 2 , SMe), which are analogues of classic organic donor–acceptor compounds, form infinite-chain structures in the solid state through weak intermolecular dative bonds between the tungsten and donor atoms.

Theoretical study of the metathesis-like reaction between ditungsten hexaalkoxides and alkynes †

Density-functional calculations have been carried out on a metathesis-like reaction between W2(OR)6 (R = alkyl) and alkynes to give tungsten alkylidyne complexes. Two possible pathways have been taken into consideration: (i) a parallel approach between the reactants to give 1,2-ditungstenacyclobutadiene; (ii) a perpendicular approach to yield a ditungstenatetrahedrane which then flattens giving a 1,3-ditungstenacyclobutadiene. The electronic structure of the compounds involved in the reaction, as well as several energy profiles corresponding to the formation and decomposition of these species, have been investigated in order to study the thermodynamics and kinetics of the metathesis-like reaction. The inclusion of relativistic effects is crucial in order to understand how the reaction proceeds.

Thioacyl complexes of molybdenum and tungsten

The reactions of a range of alkylidyne complexes of molybdenum and tungsten [M(CR)L n ] with 2-methylthiirane provide the first thioacyl complexes [M(η 2 -SCR)L n ] of these elements, which serve as precursors for complexes bearing dithiocarboxylate, thioselenocarboxylate, thiolatocarbene and α-thioalkyl ligands and thioacyl-bridged binuclear complexes.