Tricobalt Cluster Research Articles

Nanoporous {Co3}-Organic framework for efficiently seperating gases and catalyzing cycloaddition of epoxides with CO2 and Knoevenagel condensation

Enhancing the catalysis of metal–organic frameworks (MOFs) by regulating inherent Lewis acid-base sites to realize the efficient seperation and chemical fixation of inert carbon dioxide (CO2) is crucial but challenging. Herein, the solvothermal self-assembly of Co2+, 5′-(4-carboxy-2-nitrophenyl)-2,2′,2′',4′,6′-pentanitro-[1,1′:3′,1′'-terphenyl]-4,4′'-dicarboxylic acid (H3TNBTB) and 4′-phenyl-4,2′:6′,4′'-terpyridine (PTP) generated a highly robust cobalt-organic framework of {[Co3(TNBTB)2(PTP)]·7DMF·6H2O}n (NUC-82). In NUC-82, the tri-core clusters of {Co3} with linear shape are bridged by TNBTB3– to form two-dimensional structure in ac plane, which is further linked by PTP to generate a three-dimensional framework with two kinds of solvent-accessible channels: rhombic-like (ca. 11.57 × 10.76 Å) along a axis and rectangular-like (ca. 7.32 × 11.56 Å) along b axis. Furthermore, it is worth emphasizing that the confined pore environments are characterized by plentiful Lewis acid-base sites of tricobalt clusters, grafted nitro groups and free pyridinyl, high specific surface area and solvent-free nano-caged windows. Activated NUC-82a owns the ultra-high ethylene (C2H2) separation performance over the mixture of C2H2/CH4 and CO2/CH4 with the selectivity of 223.1 and 44.7. Thanks to the great Lewis-acid sites as well as the large pore volume, activated NUC-82a displays the high catalytic performace on the cycloaddition of CO2 with epoxides under wield condtions such as amibient pressure. Furthermore, because of the rich Lewis base sites, NUC-82a can efficiently catalyze Knoevenagel condensation of aldehydes and malononitrile. In the above organic reactions, NUC-82a not only shows the high catalytic activity, but also exhibits the high selectivity, satifactory recyclability and easy-to-separate heterogeneity, confirming that NUC-82a is a promising catalyst. Hence, this work provides in-depth insight into the construction of multifunctional MOFs by modifying the traditional ligands with as many Lewis acid-base active sites as possible.

Dinitrogen Insertion and Cleavage by a Metal-Metal Bonded Tricobalt(I) Cluster.

Reduction of a tricobalt(II) tri(bromide) cluster supported by a tris(β-diketiminate) cyclophane results in halide loss, ligand compression, and metal-metal bond formation to yield a 48-electron CoI3 cluster, Co3LEt/Me (2). Upon reaction of 2 with dinitrogen, all metal-metal bonds are broken, steric conflicts are relaxed, and dinitrogen is incorporated within the internal cavity to yield a formally (μ3-η1:η2:η1-dinitrogen)tricobalt(I) complex, 3. Broken symmetry DFT calculations (PBE0/def2-tzvp/D3) support an N-N bond order of 2.1 in the bound N2 with the calculated N-N stretching frequency (1743 cm-1) comparable to the experimental value (1752 cm-1). Reduction of 3 under Ar in the presence of Me3SiBr results in N2 scission with tris(trimethylsilyl)amine afforded in good yield.

Organometallic derivatives of natural products: dicobalt hexacarbonyl complexes of geranyl-alkynes

Di- and tri-cobalt carbonyl clusters bearing geranyl or neryl substituents offer potential routes to novel terpenoid systems.

Chiral diphosphine derivatives of alkylidyne tricobalt carbonyl clusters – A comparative study of different cobalt carbonyl (pre)catalysts for (asymmetric) intermolecular Pauson–Khand reactions

Reaction of the tricobalt carbyne cluster [Co3(μ3-CH)(CO)9] with chiral diphosphines of the Josiphos and Walphos families affords the new clusters [Co3(μ3-CH)(CO)7(P–P∗)] in good yield (P–P∗=J004 (1), J005 (2), J007 (3), W001 (4), W003 (5)). The new alkylidyne tricobalt clusters, and the previously known [Co3(μ3-CH)(CO)7(μ-J003)], have been tested as catalysts/catalyst precursors for intermolecular Pauson–Khand cyclization, using norbornene and phenylacetylene as substrate. The diphosphine-substituted tricobalt carbonyl clusters proved to be viable catalysts/catalyst precursors that gave products in moderate to good yields, but the enantiomeric excesses were low. When the chiral diphosphine ligands were used as promoters/auxiliary ligands for the same Pauson–Khand reaction, using either [Co2(CO)8] or [Co4(CO)12] as catalyst precursors, both the overall yields and the selectivities with respect to cyclopentenone formation were significantly improved. The best results were obtained for ligands J007 and W001, with [Co4(CO)12] as pre-catalyst, where yields of 96%, and virtually 100% selectivity were obtained. However, the enantioselectivity of product formation was low or non-existent. The crystal structure of [Co3(μ3-CH)(CO)7(μ-J004)] is described. [J003=[(R)-1-{(S)-2-(dicyclohexylphosphino)-ferrocenyl} ethyldicyclohexylphosphine], J004=[(R)-1-{(S)-2-(dicyclohexylphosphino)-ferrocenyl} ethyldiphenylphosphine], J005=[(R)-1-{(S)-2-(diphenylphosphino)ferrocenyl}ethyl-di-3,5-xylylphosphine], J007=[(R)-1-{(S)-2-di-(4-methoxy-3,5-dimethylphenyl)phosphino)ferrocenyl} ethyldicyclohexylphosphine], W001=[(R)-1-{(R)-2-(2′-diphenyl phosphinophenyl)ferrocenyl} ethyldi(bis-3,5-trifluoromethylphenyl)phosphine], W003 [(R)-1-{(R)-2-(2′-diphenylphosphino-phenyl)ferrocenyl}ethyldi(3,5-xylyl)phosphine].

Unprecedented binodal (7,9)-connected network based on distinct tricobalt(ii) clusters: structure, topology and cooperative magnetism

A new Co(II)-based coordination polymer, [{Co3(ina)7.5(μ3–O)}{Co3(ina)2.5(μ3–OH)(μ–OH)(C2H5OH)(H2O)2}3]NO3·3C2H5OH·24H2O (1, also denoted as MCF-39), has been synthesized from the solvothermal reaction of cobalt(II) nitrate and the ligand isonicotinic acid (Hina) with the presence of hmq (2-(hydroxymethyl)-quinolin-8-ol) as a necessary additive. The crystal structure of 1 consists of the 7- and 9-connected trinuclear clusters, and exhibits the first highly-connected binodal network with (34·49·56·62)3(36·415·515) topology. Magnetic studies show that the spin canting and spin-glass-like behaviours were found in 1, and the cooperative effect among intra- and inter-trimer could greatly influence the bulk magnetic behaviour of the three-dimensional (3D) framework.

Synthesis, structure and spectroscopic behaviors of a five- and six-coordinated tri-cobalt(II) cluster: [(CoL) 2(OAc) 2Co]·2C 2H 5OH

A tri-nuclear cobalt(II) cluster, [(CoL) 2(OAc) 2Co]·2C 2H 5OH, has been synthesized by the reaction of cobalt(II) acetate tetrahydrate with a novel Salen-type bisoxime chelating ligand, 3,3′-dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H 2L), and characterized by elemental analyses, IR spectra, TG-DTA and molar conductances. UV–vis spectroscopic titration in methanol solution clearly indicated the exclusive formation of the 3:2 [Co 3L 2] 2+ cluster. The single-crystal X-ray diffraction determination of the Co(II) cluster shows that there are two acetate ions coordinate to three cobalt(II) ions through Co–O–C–O–Co bridges, and quadruple μ-phenoxo oxygen atoms from two [CoL] chelates also coordinate to cobalt(II) ions. Interestingly, different conformational central ions: five- and six-coordinated geometries were found in the cluster.

Chiral and achiral phosphine derivatives of alkylidyne tricobalt carbonyl clusters as catalyst precursors for (asymmetric) inter- and intramolecular Pauson–Khand reactions

Phosphine derivatives of alkylidyne tricobalt carbonyl clusters have been tested as catalysts/catalyst precursors in intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. A number of new phosphine derivatives of the tricobalt alkylidyne clusters [Co3(micro3-CR)(CO)9] (R = H, CO2Et) were prepared and characterised. The clusters [Co3(micro3-CR)(CO)9-x(PR'3)x] (PR'3 = achiral or chiral monodentate phosphine, x = 1-3) and [Co3(micro3-CR)(CO)7)(P-P)] (P-P = chiral diphosphine; 1,1'- and 1,2-structural isomers) were assayed as catalysts for intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. The phosphine-substituted tricobalt clusters proved to be viable catalysts/catalyst precursors that gave moderate to very good product yields (up to approximately 90%), but the enantiomeric excesses were too low for the clusters to be of practical use in the asymmetric reactions.

Synthesis and structural characterization of a novel tricobalt cluster with 4,4′-dichloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol

A novel chelating bisoxime ligand, 4,4′-dichloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol (H2L), and its corresponding trinuclear Co(II) cluster {[CoL(C2H5OH)]2(OAc)2Co} · 2C2H5OH (1) have been synthesized and characterized by elemental analyses, IR, 1H NMR, TG-DTA and X-ray diffraction methods. The Co(II) cluster crystallizes in the triclinic system, space group P − 1 with cell dimensions a = 9.412(2) A, b = 11.868(2) A, c = 14.280(2) A, α = 108.131(3)°, β = 108.924(3)°, γ = 97.909(2)°, V = 1382.6(4) A3, Z = 1, R1 = 0.0790, wR2 = 0.1869. In the Co(II) cluster, there are two ligand moieties (which provide N2O2 donors), two acetate ions and two ethanol molecules, which result in the formation of three slightly distorted octahedral geometries around the Co(II) ions.

Ligand chelation, P–C bond cleavage, and phenyl-group transfer in the reaction between RCCo 3(CO) 9 and 1,8-bis(diphenylphosphino)naphthalene (dppn): Syntheses and X-ray diffraction structures of PhCCo 3(CO) 4(μ-CO) 3(dppn) and PhCCo 3(CO) 8[η 1-PPh(OH)C 10H 6P(O)Ph 2

The tricobalt cluster PhCCo 3(CO) 9 ( 1) undergoes facile ligand substitution with 1,8-bis(diphenylphosphino)naphthalene (dppn) under thermal and Me 3NO activation to afford the cluster compounds PhCCo 3(CO) 8[PPh 2(1-C 10H 7)] ( 2) and PhCCo 3(CO) 4(μ-CO) 3(dppn) ( 3). Whereas thermolysis of dppn with the methylidyne-capped cluster HCCo 3(CO) 9 ( 4) yields only HCCo 3(CO) 8[PPh 2(1-C 10H 7)] ( 5) and HCCo 3(CO) 4(μ-CO) 3(dppn) (6) as isolable products, the reaction between 4 and dppn in the presence of Me 3NO furnishes the latter two clusters in addition to the phenyl-capped cluster PhCCo 3(CO) 8[η 1-PPh(OH)C 10H 6P(O)Ph 2] ( 7). The clusters 2 and 5 represent simple substitution products based on the ligand diphenyl(1-naphthyl)phosphine, while clusters 3 and 6 each possess a chelating dppn ligand and three bridging CO groups in the solid state. Oxidation of the two phosphine moieties by Me 3NO and transfer of one of the phenyl groups from the dppn ligand to the methylidyne carbon moiety in cluster 4 produces the thermally unstable cluster 7. These clusters have been characterized in solution by IR and 31P NMR spectroscopies, and the solid-state structures of 3 and 7 established by X-ray crystallography.

CO replacement in the tetrahedrane cluster MeC(O)CCo3(CO)9 by the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-l,3-dione (bpcd): Diphosphine ligand isomerization and X-ray structure of the bridged cluster MeC(O)CCo3(CO)7(bpcd)

The tricobalt cluster MeC(O)CCo3(CO)9 reacts with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-l,3-dione (bpcd) in the presence of added Me3NO to furnish the disubstituted cluster MeC(O)CCo3(CO)7(bpcd) in good yield. MeC(O)CCo3(CO)7(bpcd) has been characterized in solution by IR and NMR (1H and 31P) spectroscopies, and the solid-state structure determined by X-ray crystallography. MeC(O)CCo3(CO)7(bpcd) crystallizes in the monoclinic space group P21/c, a=14.8421(8), b=16.6162(9), c=14.9363(8) A, β=99.705(1)°, V=3630.9(3) A3, Z=4, D cacl=1.632 Mg/m3; R=0.0288, R w=0.0683 for 8618 observed reflections with I > 2σ(I). The bridging of adjacent cobalt atoms by the bpcd ligand in MeC(O)CCo3(CO)7(bpcd) is crystallographically established, and the facile isomerization of the bridging bpcd to the chelating isomer at low temperature is confirmed by VT 31P NMR measurements.

Thermolysis of the tetrahedrane cluster PhCCo3(CO)3(μ-CO)Cp2 with the unsaturated diphosphine ligands (Z)-Ph2PCH=CHPPh2 and 4,5-Bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd): Redox properties and molecular structure of PhCCo3(CO)(μ-CO)[(Z)-Ph2PCH=CHPPh2]Cp2

Thermolysis of the tricobalt cluster PhCCo3(CO)3(μ-CO)Cp2 (1) with the diphosphine ligands (Z)-Ph2PCH=CHPPh2 and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) has been examined and found to give the diphosphine-substituted clusters PhCCo3(CO)[(Z)-Ph2PCH=CHPPh2](μ-CO)Cp2 (2) and PhCCo3(CO)(bpcd)(μ-CO)Cp2 (3) in moderate yield. The new compounds 2 and 3 have been isolated and characterized in solution by IR and NMR (1H and 31P) spectroscopies. VT 31P NMR data reveal that the chelating diphosphine ligand is fluxional in solution and exhibits a rocking motion between the axial and equatorial sites that renders both phosphorus moieties identical at ambient temperature. The molecular structure of PhCCo3(CO)[(Z)-Ph2PCH=CHPPh2](μ-CO)Cp2 (2) has been determined by X-ray crystallography. PhCCo3(CO)[(Z)-Ph2PCH=CHPPh2](μ-CO)Cp2 crystallizes, as the CH2Cl2 solvate, in the monoclinic space P21/n, a = 16.822(2) A, b = 10.554(1) A, c = 23.135(3) A, β = 100.944(2)∘, V = 4032.4(8) A3, Z = 4, and dcalc = 1.537 Mg/m3; R = 0.0488, Rw = 0.0725 for 9431 reflections with I > 2σ(I). The solid-state structure of cluster 2 establishes the chelating nature of the ancillary (Z)-Ph2PCH=CHPPh2 ligand at the unique Co(CO)P2 center via coordination at an equatorial and an axial site. The redox behavior of clusters 2 and 3 has been explored by cyclic voltammetry and chronocoulometry. Each cluster reveals the presence of two one-electron oxidations of common origin due to the oxidation of a Co–Co bonding orbital. Whereas cluster 2 does not exhibit an accessible reduction process in CH2Cl2, a ligand-based one-electron reduction was found for cluster 3 given its low-lying π* LUMO associated with the bpcd ligand. The electrochemical data for clusters 2 and 3 are discussed with respect to the reported redox chemistry for this genre of tricobalt cluster and the bpcd ligand.

Studies of metal exchange reactions: the synthesis and structures of heteronuclear metal clusters containing the indenyl ligand (μ 3-CR)Co 2M(CO) 8(η 5- Ind)(R=H,CH 3,C 6H 5,COOC 2H 5; M=Mo,W)

The novel tetrahedral clusters ( μ 3-CR)Co 2M(CO) 8(η 5-Ind) (M=Mo,W; R=H, CH 3, C 6H 5, COOC 2H 5) 5– 12 containing the indenyl ligand were isolated from reactions of tricobalt clusters (μ 3-CR)Co 3(CO) 9 (R=H, CH 3, C 6H 5, COOC 2H 5) and K(η 5-Ind)M(CO) 3 (M=Mo,W) under mild conditions. The cluster complex (μ 3-CC 6H 5)CoMo 2(CO) 7(η 5-Ind)(η 5-Cp (Cp*=C 5H 4C(O)CH 3) 16 was obtained via the stepwise metal exchange reaction of complex (μ 3-CC 6H 5)Co 2Mo(CO) 8(η 5-Ind) 9 with Na(η 5-CpMo(CO) 3, but the reaction of (μ 3-CC 6H 5)Co 2Mo(CO) 8(η 5-Cp*) 15 with K(η 5-Ind)Mo(CO) 3 yielded only 9. The crystal structures of compounds 7, 9 and 13 were established by single crystal X-ray diffraction methods and show structural evidence for “slippage” of the indenyl ring.

Synthesis, structure, and formation mechanism of the halogen-bridged tricobalt clusters, [Co3Cp3(μ3-CPh)2(μ-X)]+ (X=Cl, Br, and I)

Reactions of a benzylidyne-capped tricobalt cluster, [Co3Cp3(μ3-CPh)2] (1), with halogens (X2 = Cl2, Br2, and I2) in CH2Cl2 afforded halogen-adducts of 1. The structure of four isolated salts [Co3Cp3(μ3-CPh)2(μ-Cl)]PF6·MeCN (2PF6·MeCN), [Co3Cp3(μ3-CPh)2(μ-Br)]SbF6 (3SbF6), [Co3Cp3(μ3-CPh)2(μ-I)]SbF6·CH2Cl2 (4SbF6·CH2Cl2), and [Co3Cp3(μ3-CPh)2(μ-I)]I3 (4I3) determined by X-ray diffraction can be regarded formally as halide-adducts of 12+. The halogen atom in each structure lies in the Co3 plane. The halogen-bridged Co–Co edge was elongated (in 2PF6·MeCN = 2.6072(4), in 3SbF6 = 2.6106(7), in 4SbF6·CH2Cl2 = 2.622(2), and in 4I3=2.6718(9) Å), and the Co–Co distances that had no halogen-bridge remained unchanged from the Co–Co distance of 1 (2.382(8) Å), (in 2PF6=2.4037(8) and 2.3948(7), in 3SbF6=2.3888(6) and 2.4017(7), in 4SbF6·CH2Cl2 = 2.393(2) and 2.388(1), and in 4I3=2.397(1) and 2.3868(9) Å). The UV–Vis absorption spectra of 2+, 3+, and 4+ had characteristic absorption peaks at 796, 819, and 844 nm, respectively. Cyclic voltammograms of 2PF6 in CH2Cl2 with 0.1 M nBu4NPF6 as the supporting electrolyte showed a chemically reversible oxidation (at a potential of 0.75 V versus Fc/Fc+), and an irreversible reduction wave at −0.57 V. The irreversible reduction resulted in the recovery of 1. The redox properties of 3+ and 4+ are very similar to that of 2+. Cyclic voltammetry of 1 in 0.1 M nBu4NCl/MeCN indicates that the formation of 2+ is a multi-step reaction. Initially, 1 is oxidized to 1+, and then, 1+ is coordinated by Cl− followed by immediate oxidation to 2+.

Electronic structure of a benzylidyne-capped tricobalt cluster, [Co 3Cp 3(μ 3-CPh) 2]. X-ray structures and 1H NMR paramagnetic shifts of its cation and DFT calculations of its model complex

The cationic tricobalt cluster [Co 3Cp 3(μ 3-CPh) 2] + ( 1 +) was synthesized by the electrochemical oxidation of [Co 3Cp 3(μ 3-CPh) 2] ( 1). A large structural change was observed not only in the Co–Co, but also in the Co–C(cap) bonds upon oxidation of 1 to 1ClO 4. 1H NMR paramagnetic shifts of this salt were measured in CD 2Cl 2. The π spin density on each sp 2 carbon atom was estimated to be 0.0089 ( o-Ph), −0.0012 ( m-Ph), 0.0087 ( p-Ph), and 0.0053 (Cp). These values on the phenyl carbon atoms are similar to ca. 1/25 of those of the benzyl radical. It indicates that there is significant spin density on the capping carbon atom, which is delocalized onto the benzylidyne groups from the Co 3C 2 oxidation center by π conjugation between them. These results are consistent with the e ′′ (in the idealized D 3 h symmetry) singly occupied molecular orbital (SOMO) of 1 +, and are reproduced by B3LYP-DFT calculations of a model complex, [Co 3Cp 3(μ 3-CH) 2] ( 2), and its cation.

Addition and/or oxidation in the reaction of a tricobalt cluster with silver(I) salts: synthesis, structure and solution properties of [Co 3Cp 3(μ 3-CPh) 2{μ-Ag(X)}] (X=CF 3CO 2, NO 3) and [Co 3Cp 3(μ 3-CPh) 2{μ-Ag(NCMe)}]PF 6

Reactions of the benzylidyne-capped tricobalt cluster [Co 3Cp 3(μ 3-CPh) 2] ( 1) with various silver salts have been examined. The salts of weakly- or non-coordinating anions (e.g., BF 4 − and PF 6 −) oxidize 1 in CH 2Cl 2 to form its cationic radical, 1 +. Reactions with salts of strongly coordinating anions (e.g., CF 3CO 2 − and NO 3 −) yield the silver(I) adducts of 1, [Co 3Cp 3(μ 3-CPh) 2{μ-Ag(X)}] (for X=CF 3CO 2 −: 2 and NO 3 −: 3). Even with AgBF 4 or AgPF 6, the reaction in MeCN produces a silver(I) adduct, [Co 3Cp 3(μ 3-CPh) 2{μ-Ag(NCMe)}] + ( 4 +). The Co 3Ag skeleton in the structures of 2, 3, and 4 + is similar in each compound. The Co–Co bond bridged by the Ag atom (for 2, Co–Co=2.4785(8) Å, for 3, Co–Co=2.4837(9) Å, and for 4 +, Co–Co=2.4578(7) Å) is longer than the average Co–Co bond length in 1 where 〈Co–Co〉 av=2.382(8) Å. The other Co–Co bonds in the compounds are slightly shorter than those in 1. The Co 2Ag triangle is not coplanar with the Co 3 triangle; the dihedral angles between these triangles for 2, 3 and 4 + are 162.7°, 157.7°, and 151.6°, respectively. Dissolution of 4PF 6 in CH 2Cl 2 leads to the formation of 1 + and the deposition of Ag metal. The 1H NMR spectra of 2 and 3 in CD 2Cl 2 indicate that the AgX group moves over the three Co–Co bonds. The ESR spectra in frozen acetonitrile solutions of 2, 3, and 4PF 6 show the existence of a small amount of 1 +, but the deposition of Ag metal was not observed.

Construction of a hexanuclear cluster composed of spatially separated Co3 and Ru3 units: X-ray diffraction structure of Co3(CO)9[μ3-CCO2CH2CC{HRu3(CO)9}

Treatment of the tricobalt cluster $${\text{Co}}_3 ({\text{CO}})_9 (\mu _3 - {\text{CCO}}_{\text{2}} {\text{CH}}_{\text{2}} {\text{C}} \equiv {\text{CH)}}$$ with the activated triruthenium cluster Ru3(CO)10(MeCN)2 affords the acetylide-bridged hexanuclear cluster Co3(CO)9[μ3–CCO2CH2CC{HRu3(CO)9}] in moderate yield. The new cluster was characterized in solution by IR spectroscopy and molecular structure was established by X-ray diffraction analysis. Co3(CO)9[μ3–CCO2CH2CC{HRu3(CO)9}] crystallizes in the triclinic space group P(−1), a = 8.728(1) A, b = 12.916(2) A, c = 14.663(2) A, α = 82.950(2)°, β = 82.465(2)°, γ = 86.199(2)°, V = 1624.2(4) A3, Z = 2, d calc = 2.207 mg/m3; R = 0.0263, R w = 0.0623 for 3596 observed reflections with I > 2σ(I). The coordination of the triruthenium cluster to the acetylene ligand of Co3(CO)9(μ3–CCO2CH2C≡CH) is confirmed, and the structural details associated with the acetylide-bridged triruthenium frame are contrasted with other structurally characterized Ru3 clusters bound by a 5e-acetylide ligand.

ETC and Thermal Ligand Substitution in PhCCo 3 (CO) 9 with 2,3-Bis(diphenylphosphino)- N -phenylmaleimide(bppm). X-Ray Diffraction Structure of Co 3 (CO) 6 [μ 2 ,η 2 , η 1 -C(Ph) $$$$ (O)](μ 2 -PPh 2 )

The reactivity of the bidentate ligand 2,3-bis(diphenylphosphino)-N-phenylmaleimide (bppm) with the tetrahedrane cluster PhCCo3(CO)9 under thermolysis and ETC conditions has been studied and found to ultimately give Co3(CO)6[μ2,η2,η1-C(Ph) $${\text{C}}{\text{ = }}{\text{ = }}{\text{C(PPh}}_{\text{2}} {\text{)C(O)NPhC}}$$ (O)](μ2-PPh2) as the final product. The intermediate cluster compound PhCCo3(CO)7(bppm), which was observed by IR and 31P NMR spectroscopies, readily and rapidly transforms into the product cluster under the reactions conditions. The solid-state structure of Co3(CO)6[μ2,η2,η1-C(Ph)fptt(O)](μ2-PPh$_{2})$ was unequivocally determined by X-ray crystallography. Co3(CO)6[μ2, η2, η1-C(Ph)O(O)](μ2-PPh2) crystallizes in the monoclinic space group P2(1)/n, a = 11.825(5) A, b = 31.20(1) A, c = 11.831(5) A, β = 108.720(7)°, V = 4134(7) A3, Z = 4, d calc = 1.567 Mg/m3; R = 0.0350, R w = 0.0817 for 4747 observed reflections with I > 2σ(I). The X-ray structure confirms the coupling of the benzylidyne ligand with the bppm ligand in Co3(CO)6[μ2,η2,η1-C(Ph)O(O)](μ2-PPh2). The course of the thermolysis reaction is identical to those reactions carried out with the related diphosphine ligands bma and bpcd. The utility of electron-transfer catalysis (ETC) in the preparation of PhCCo3(CO)7(bppm) is discussed relative to the reduction potential of the bppm ligand and the tricobalt cluster PhCCo3(CO)9.

2,5-Bis(diphenylmethylene)-3-cyclopentenone: a solvent-dependent cobalt cluster mediated propargyl radical coupling process

Protonation of (1,1-diphenyl-2-propyn-1-ol)Co 2(CO) 6 with HBF 4 in dichloromethane generates the expected metal-stabilized propargyl cation, and also rearranges to give the tricobalt cluster Ph 2CCH-CCo 3(CO) 9 9 . In contrast, use of THF as solvent affords the radical (Co 2(CO) 6)[HCC-CPh 2 ] 2 , which dimerizes at the methyne position; subsequent cyclization and carbonylation yields 2,5-bis-(diphenylmethylene)-3-cyclopentenone 11 . The products have been characterized by X-ray crystallography, and the scope and mechanism of the reaction are discussed.

Cyclopentadienylrhodium coordination to alkenylarenes.

Photochemical reaction of [Rh(eta-C(5)H(5))(C(2)H(4))(2)] (5) with alkenyl benzene derivatives PhC(R(1))=CHR(2) results in the formation of four types of cyclopentadienylrhodium complexes: the mononuclear ethylene eta(2)-alkenylbenzene complexes [Rh(eta-C(5)H(5))(eta-C(2)H(4))(eta(2)-PhC(R(1))=CHR(2))] 9 a (R(1)=H, R(2)=Ph), 9 b (R(1)=Ph, R(2)=H), 9 c (R(1)=CH(3), R(2)=H), the mononuclear eta(4)-alkenylbenzene complex [Rh(eta-C(5)H(5))[beta,alpha,1,2-eta-C(6)H(5)C(Ph)=CH(2)]] (10), the dinuclear mu-eta(4):eta(4)-alkenylbenzene complex [anti-[Rh(eta-C(5)H(5))](2)[mu-beta,alpha,1,2-eta:3,4,5,6-eta-C(6)H(5)C(Ph)C=CH(2)]] (11), and the dinuclear rhodaindenyl complexes [Rh(eta-C(5)H(5))[1-3,8,9-eta-[1-(eta-C(5)H(5))]-3-R(1)-1-rhodaindenyl]] 12 a (R(1)=Ph), 12 b (R(1)=CH(3)). Reaction of 5 with triisopropenylbenzene gives the dinuclear complex [[Rh(eta-C(5)H(5))](2)(mu-beta,alpha,1,2-eta:beta',alpha',4,3-eta-C(6)H(3)[C(CH(3))=CH(2)](3))] (13). In the complexes 9, only the olefinic side chain of the alkenylbenzene binds to the metal. In the complexes 10, 11, 12, and 13, an arene nucleus coordinates to rhodium as a 1,3-diene moiety (or part thereof). The rhodaindenyl complexes 12 result from C-H activation of the alkenylbenzene at the beta and ortho positions. The crystal and molecular structures of 9 a, 9 b, 10, 11, and 12 a, b were determined. The role of 9-11 and 13 as models for intermediates during alkenylbenzene-assisted self-assembly of tricobalt clusters is discussed.

Reactions of the μ-alkyne-dicobalt complexes [Co 2(CO) 6(μ-CF 3–CC–R)] (R=CF 3, H) with [Co 2Cp 2(μ-SMe) 2]: substitution and insertion leading to novel thiolato-alkyne tetra- and tricobalt clusters

The bis(μ-thiolato)dicobalt complex [Co 2Cp 2(μ-SMe) 2] ( 1) reacts with alkyne-cobalt complexes [Co 2(CO) 6(μ-F 3CCCR)] ( 2) to give tri- and tetranuclear cobalt cluster compounds. When R=CF 3 the main product is [Co 2(CO) 4(μ-CF 3C 2CF 3){μ-Co 2Cp 2(μ-SMe) 2}] ( 3) but the trinuclear cluster [Co 3Cp(CO) 4(μ-SMe) 2(μ-CF 3C 2CF 3)] ( 4) is also obtained in low yield. When R=H the products are the isomeric clusters [Co 3Cp(CO) 4(μ-SMe) 2(μ-CF 3C 2H)] ( 5 and 6), [Co 3Cp 2(CO) 3(μ-SMe)(μ-CF 3C 2CH)] ( 7) and [CpCo(CO) 2]. The solid state structures of 3 , 4, 5 and 7 have been established by X-ray analysis. The 50 electron triangular cluster 4 has weak Co–Co bonds [2.573(1), 2.800(1), 2.838(1) Å]. The alkyne ligand bridges the shortest of these bonds in perpendicular fashion. 5 and 7 contain open chain tricobalt units [Co–Co 2.39–2.57 Å] more typical of 50 electron M 3 species. In these complexes the alkyne is π-bonded to the central metal atom and σ-bonded to both terminal cobalt atoms. Variable temperature NMR indicates that 5, 6 and 7 each exist in solution as interconverting isomers which differ in the configuration at one sulphur atom. For 5 the activation parameters [Δ H ‡=64 kJ mol −1 and Δ S ‡=−85 J K −1 mol −1] were obtained spectroscopically. In the solid, molecules of 7 contain an asymmetrically bridging carbonyl [Co–C 1.833(4) and 2.050(3) Å] which is not detectable in the solution spectra.