cas 12078-25-0, DICARBONYLCYCLOPENTADIENYLCOBALT

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METHOD OF SELECTIVELY FORMING COBALT METAL LAYER BY USING COBALT COMPOUND, AND METHOD OF FABRICATING SEMICONDUCTOR DEVICE BY USING COBALT COMPOUND
A method of selectively forming a cobalt metal layer includes supplying a cobalt compound represented by Chemical Formula (1) onto a substrate that includes a wiring line of a late transition metal and an isolation film adjacent thereto, and supplying a reducing gas to selectively form a cobalt metal layer on the wiring line,
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Paragraph 0157-0161

(2021/02/05)

Anodic reaction of CO(η5-C5H5)(CO) (PPh3): An oxidatively induced ligand exchange involving a 17 e -/18 e- redox pair
Unlike a number of other monocarbonyl-substituted complexes CoCp(CO)L (Cp = (η5-C5H5)), chemical oxidation of the L = triphenylphosphine derivative CoCp(CO)(PPh3), 1, is known to give, in the absence of added PPh3, the disubstituted phosphine complex [CoCp(PPh3)2]+ rather than the simple 17-electron radical cation 1+. Electrochemistry of 1 in CH 2Cl2/[NBu4][B(C6F5) 4] (E1/2(1/1+) = -0.38 V vs ferrocene) shows that the favored anodic products depend on the concentration of 1. At low concentrations (e.g., 10-4 M) and on the cyclic voltammetry time scale, the radical cation 1+ dominates, but at higher concentrations and longer reaction times, a quantitative mixture of CoCp(CO)2 and [CoCp(PPh3)2]+ is produced in an overall half-electron process. On the basis of cyclic voltammetry, chronoamperometry, bulk electrolysis, and IR spectroelectrochemistry, a radical-substrate mechanism is proposed involving the reaction of 1+ with 1 to give transient [Co2Cp2(CO) 2(PPh3)2]+. This putative dimer radical cation intermediate may be viewed as an odd-electron analogue of the intermediates that have previously been invoked by Kochi, Atwood, and others to explain ligand-transfer reactions between cation/anion pairs of organometallic complexes.
Nafady, Ayman,Geiger, William E.
p. 4276 - 4281
(2010/12/20)

Reactions of early-late heterobimetallics with oxiranes: New examples for cooperative reactivity
In the reaction of oxiranes and cobalt-containing early-late heterobimetallic (ELHB) compounds isolated or prepared in situ, acyl-cobalt complexes, Y3MEOCHRCH2C(O)Co(CO)4 (1, ME = Ti, Zr, Hf), were ob
Sisak, Attila,Halmos, Erzsébet
p. 1817 - 1824
(2008/02/04)

Characterization and reactions of previously elusive 17-electron cations: Electrochemical oxidations of (C6H6)Cr(CO)3 and (C5H5)Co(CO)2 in the presence of [B(C6F5)4]
The electrochemical oxidations of (C6H6)Cr(CO)3, 1, and (C5H5)Co(CO)2, 2, when carried out in CH2Cl2/[NBu4][B(C6F5)4], allow the physical or chemical characterization of the 17-electron cations 1+ and 2+ at room temperature. The generation of 1+ on a synthetic time scale permits an electrochemical switch process involving facile substitution of CO by PPh3 as a route to (C6H6)Cr(CO)2PPh3. The radical 2+ undergoes a second-order reaction to give a product assigned as the metal-metal bonded dimer dication [Cp2Co2(CO)4]2+. The new anodic chemistry of these often-studied 18-electron compounds is made possible by increases in the solubility and thermal stability of the cation radicals in media containing the poorly nucleophilic anion [B(C6F5)4]-, TFAB. Copyright
Camire, Nicole,Nafady, Ayman,Geiger, William E.
p. 7260 - 7261
(2007/10/03)

Facial coordination of cyclooctatetraene to a Co2Ni triangle in a heterometallic trinuclear cluster complex
Reaction of [(η-C5H5)NiCo3(CO)9] (5) with 1,3,5,7-cyclooctatetraene or 1,4-(SiMe3)2C8H6, respectively, yields the complexes [Co2Ni(CO)6(μ3/
Wadepohl, Hubert,Gebert, Stefan,Merkel, Rüdiger,Pritzkow, Hans
p. 142 - 147
(2007/10/03)

Reactions of the μ-alkyne-dicobalt complexes [Co2(CO)6(μ-CF3-CC-R)] (R=CF3, H) with [Co2Cp2(μ-SMe)2]: Substitution and insertion leading to novel thiolato-alkyne tetra- and trico
The bis(μ-thiolato)dicobalt complex [Co2Cp2(μ-SMe)2] (1) reacts with alkyne-cobalt complexes [Co2(CO)6(μ-F3CCCR)] (2) to give tri- and tetranuclear cobalt cluster compounds. When R=CF3
Muir, Kenneth W.,Rumin, René,Pétillon, Fran?ois Y.
p. 110 - 118
(2007/10/03)

An electron-transfer induced migratory insertion reaction originating from a 19-electron cobaltacyclic anion
The cyclopentadienyl cobaltafluorenyl carbonyl complex Cp(CO)CoC12H8 (3) is reduced in THF in a one-electron irreversible process. The reduction products include the fluorenone radical anion, Fl-, which is proposed to arise through migratory insertion of the CO ligand into the metallacyclic Co-C bond of the 19-electron complex 3-. Electrochemical and IR analyses show that bulk electrolysis under N2 gives 1/3 equiv. each of Fl- and CpCo(CO)2 and 2/3 equiv. of a 17-electron anion [CpCoC12H8]- (2-) Under CO the yield of Fl- is quantitative. The insertion product is also formed when the reduction of the analogous phosphine complex Cp(PPh3)CoC12H8 is performed under CO. An equilibrium between 17- and 19-electron compounds is postulated to account for the synthetic and voltammetric observations. When the cobaltacycle Cp(PPh3)CoC4Ph4 (5) is reduced under carbon monoxide, the CO-insertion product is the π-cyclopentadienone complex CpCo(η4-C4Ph4O) (8). (C) 2000 Elsevier Science S.A.
Morneau, Andre,Donovan-Merkert, Bernadette T.,Geiger, William E.
p. 96 - 101
(2008/10/08)

Pentamethylcyclopentadienylbis(ethene)iron - a 17e Halfsandwich Complex with Easily Displaceable Ethene Ligands
The new room temperature stable halfsandwich complex Cp*Fe(tmeda)Cl (2) has been synthesized by the 1:1 reaction of FeCl2(thf)1.5 with LiCp* in a mixture of THF and TMEDA at -30 deg C. 2 is an ideal starting material for the synthesis of a wide range of new iron complexes.Treatment of 2 with lithium sand in THF in the presence of COD are ethene followed by the addition of TMEDA yields the ferrates (3) or (4).By delithiation with dichloroethane, 3 and 4 can be transformed into the novel 17e iron complexes Cp*Fe(cod) (5) and Cp*Fe(C2H4)2 (6). 6 is extremely labile.Since the ethene ligands can be easily displaced, the title compound is a synthetically valuable source of the Cp*Fe fragment.Whereas the photochemically generated 17e dicarbonyl species CpFe(CO)2 rapidly recombines to give the dimer 2, the isoelectronic 6 is stable in ethene saturated pentane for several days at 0 deg C.Without the stabilizing effect of ethene (in pure pentane or under vacuum), 6 loses ethene to give the dinuclear complex (Cp*Fe)2(C2H4)2 (8) irreversibly.The structure of 8 has been characterized by X-ray analysis. - Keywords: Bis(ethene)iron, Halfsandwich, Dinuclear Iron Complex
Jonas, Klaus,Klusmann, Peter,Goddard, Richard
p. 394 - 404
(2007/10/02)

A novel metallacycle, 1,2,5,3-cobaltadithiazole. Formation, structure, and properties of (η5-cyclopentadienyl or η5-pentamethylcyclopentadienyl)(1-phenylmethanimine-N,1-dithiolato)cobalt(III)
(η5-Cyclopentadienyl)(1-phenylmethanimine-N,1-dithiolato)cobalt(III), 5-C5R5)> (1a: R = H or 1b: R = CH3), which contain a 1,2,5,3-cobaltadithiazole ring were synthesized in the reactions of 5-C5R5)Ln> Ln = (CO)2 or 1,5-cyclooctadiene) with two types of heterocyclic compounds: (1) compounds with a partial structure of -S-N=C(Ph)-S- or with similar structures; and (2) compounds which give benzonitrile sulfide on thermolysis or photolysis.The crystals of 1b are orthorhombic of space group P2,2,2 with a = 14.936 Angstroem, b = 14.262 Angstroem, c = 8.078 Angstroem and Z = 4.The structure was solved and refined to R = 0.038 and Rw = 0.040 by using 3981 independent reflections.The structure of 1,2,5,3-cobaltadithiazole is similar to that of 1,2,5-cobaltadithiolenes.The 1,2,5,3-cobaltadithiazole ring is almost planar and perpendicular to cp*.The cobaltadithiazoles undergo a reversible one electron reduction which is ascribed to the process from CoIII to CoII.The halfwave potential of -1.34 V versus Ag0.1 mol dm-3 AgClO4 for the reduction of 1b is less negative than that of the cobaltadithiolene with a similar structure.This shows that the nitrogen atom in the ring attracts electrons and causes the cobaltadithiazole ring to be electron-dificient. Key words: 1,2,5,3-Cobaltadithiazole; Metallacycle; Cobalt; Dithiolate
Kato, Akihiro,Tono, Masaki,Hisamatsu, Naoki,Nozawa, Sho-hei,Ninomiya, Kazuo,et al.
p. 313 - 322
(2007/10/02)

Late Metal Metallacyclobutene Chemistry: Conversion to η4-Vinylketene, η4-Vinylketenimine, and Furan Products
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O'Connor, Joseph M.,Ji, Hong-Li,Rheingold, Arnold L.
p. 9846 - 9847
(2007/10/02)

(Bicyclohepta-1,3-dienyl)cobalt(I) Complexes
Three isomeric bicycloheptadienes 1-3 are compared by semiempirical calculations.Experimental attempts directed to the synthesis of derivatives of 1 are described.The synthesis, properties and some reactions of (η5-bicyclohepta-1,3-dienyl)(η4-cycloocta-1,5-diene)cobalt(I) (22), including an X-ray crystal structure determination of the reaction product with diphenylethyne, the tetraphenylcyclobutadiene complex 30, are presented.Key Words: Bicyclohepta-1,3-dienyl complexes / Calculations, semiempirical / Alkyne trimerization / Cobalt complexes
Angermund, Klaus P.,Betz, Peter,Butenschoen, Holger
p. 713 - 724
(2007/10/02)

Cobalt isocyanide complexes
The synthesis and properties of mono and bis-isocyanide complexes of cobalt(I), CpCoLL', are described, together with migration reactions involving the isocyanide and the cyclopentadienyl ligand.
Beaumont, Ian,Wright, Anthony H.
p. C11 - C14
(2007/10/02)

Organometallic clusters with face-capping arene ligands. 4. Tris(cyclopentadienylcobalt) clusters with μ3-alkenyl- and μ3-alkylbenzenes
The (CpCo)3(μ3-(1-alkenyl)benzene) clusters 5a,b and 6a,b are prepared from CpCo(C2H4)2 (3) and α-methylstyrene, β-methylstyrene, 1,1-diphenylethylene, and stilbene. From 3 and 4-methoxystilbene a mixture of the coordination isomers of (CpCo)3(μ3-4-methoxystilbene) (7a,b) is obtained. (CpCo)3(μ3-1,1-diphenylpropene) (10) is formed from 1,1-diphenylpropene and CpCo(C6Me6) (4). Styrene and 3 do not give a μ3-styrene cluster, but (CpCo)3(μ3-4-methylstyrene) (8) and (CpCo)3(μ3-4-methoxystyrene) (9) are isolated in good yield from the reaction of 3 and the corresponding substituted styrenes. Allylbenzene, 4-methoxy(allyl)benzene, and 4-phenyl-1-butene are catalytically rearranged by 3 or 4 to the (1-alkenyl)benzene derivatives. By reaction of the further ligands with 3 molar equiv of 3 the (CpCo)3(μ3-(1-alkenyl)arene) complexes 5b, 11, and 12 are formed. The X-ray crystal structures of 5b and 6a have been determined. Crystal data: 5b, monoclinic, P21, a = 8.725 (5) A?, b = 7.542 (5) A?, c = 15.151 (6) A?, β = 103.17 (4)°, Z = 2, R = 0.026, Rw = 0.027 (w = σ-2(F)) with 2893 reflections; 6a·0.5C7H8, triclinic, P1, a = 8.734 (4) A?, b = 11.470 (5) A?, c = 12.791 (6) A?, α = 85.37 (3)°, β = 83.81 (3)°, γ = 83.52 (3)°, Z = 2, R = 0.043, Rw = 0.038 (w = σ-2(F)) with 5795 reflections. The face-capping arene rings in both compounds are coplanar with the (CpCo)3 triangles and adopt a staggered orientation. Bond length alternation within the μ3-η2:η2:η 2-coordinated arene rings is only slight, with a mean difference of 0.03 A? between longer and shorter carbon-carbon bonds. In solution rotation of the arenes on top of the (CpCo)3 triangles takes place, which can be frozen out at low temperature. The chemical reactivity of the title compounds is low. The μ3-arene ligands cannot be displaced by other arenes or by two-electron donors. Bromination, hydrosilylation, and cyclopropanation of the exocyclic alkenyl group of 5b cannot be achieved. However, catalytic hydrogenation of 5b to give (CpCo)3(μ3-n-propylbenzene) (18) proceeds readily. The relationship of the μ3-arene clusters to the metal surface adsorption states of benzene is discussed.
Wadepohl, Hubert,Büchner, Klaus,Herrmann, Michael,Pritzkow, Hans
p. 861 - 871
(2008/10/08)

Synthetic and structural studies on (η5:η5-fulvalene)bimetallic compounds derived from (η5:η5-fulvalene)dithallium
A reaction between halide-free solutions of dihydrofulvalene and thallium ethoxide has produced (η5 : η5-fulvalene)dithallium (1) in 85-100percent yield.Reactions of 1 with carbonyl halides of cobalt, rhodium, iridium, manganese and rhenium produce corresponding homobimetallic fulvalene metal carbonyls (2, 5, 9-11) in yields of 52-94percent.The rhodium complex (η5 : η5-C10H8)Rh2(CO)4 (5) reacted with trimethylamine-N-oxide dihydrate to form a tricarbonyl derivative (η5 : η5-C10H8)Rh2(μ-CO)(CO)2 (6) that contained a bridging carbonyl group and a rhodium-rodium bond.The bridging carbonyl substituent could be replaced by a bridging methylene group by reaction of 6 with N-methyl-N-nitrosourea.Tetra(η2-ethylene)-, bis(η4-1,2,5,6-cyclooctadiene)-, and bis(η4-1,2,5,6-cyclooctatetraene)(η5 : η5-fulvalene)dirhodium (12-14) have been prepared in high yields by reactions of 1 with the corresponding chloro(diolefin)rhodium dimers.Variable temperature 1H NMR studies on the tetraethylene complex 12 demonstrated that the ethylene ligands are fluxional, with ΔG+ 65 +/- 1 KJ/mol.Photolysis of 14 with two equivalents of (η2-C2H4)2(η5-C5H5)Rh has afforded the tetranuclear complex bis 5-cyclo-pentadienyl)rhodium(μ-cyclooctatetraene)>(η5 : η5-fulvalene)dirhodium (15) in 27percent yield.The single crystal X-ray structures of 2,5,10, and 12 have been carried out.Each consists of an η5 : η5-fulvalene dianion bridging two metal centers which lie on opposite sides on the fulvalene plane.In each case the formula unit resides around a crystallographic center of inversion. 2 and 5 are isostructural crystallizing in the monoclinic space group P21/c with a 7.938(6), b 8.223(7),c 10.884(8) Angstroem, β 109.34(4)deg, and Dcalc 1.77 gcm-3 for Z = 2 (2) and a 8.149(1), b 8.420(1), c 10.498(4) Angstroem, β 107.27(2)deg and Dcalc 2.15 gcm-3 for Z = 2 (5).The average M-C(η5) and M-CO distances are Co-C(η5) 2.10(2) Angstroem, Co-CO 1.734(6) Angstroem (2) and Rh-C(η5) 2.27(3) Angstroem, Rh-CO 1.864(3) Angstroem (5). 10 is monoclinic P21/n with a 10.366(6), b 6.986(4), c 11.910(5) Angstroem, β 115.07(4)deg and Dcalc 1.73 gcm-3 for Z = 2.The average Mn-C(η5) and Mn-CO distances are 2,115(5) and 1.802(6) Angstroem, respectively. 12 is triclinic, P1, with a 8.068(1), b 9.998(4), c 11.509(3) Angstroem α 67.48(2), β 69.01(2), χ 80.51(3)deg and Dcalc 1.85 gcm-1 for Z = 2.There are two unique molecular units each residing around a crystallographic center of inversion.The two differ by a small rotation of the Rh(C2H4)2 fragments.The average Rh-C(η5) and Rh-C(η2) separations are 2.25(3) and 2.129(9) Angstroem, respectively.
Rausch, Marvin D.,Spink, W. Craig,Conway, Brian G.,Rogers, Robin D.,Atwood, Jerry L.
p. 227 - 252
(2007/10/02)

Reaction of mesitylenetetracobaltnonacarbonyl with 2. Syntheses and structures of the clusters C5H5(CO)2MoCo3(CO)6(μ-CO)3 and (C5H5)2(CO)3Mo2Co2(CO)4(μ-CO)3
Interaction of (mesitylene)Co4(CO)9 (I) with 2 (II) has been shown to result in a mixture of clusters Cp(CO)2MoCo3(CO)6(μ-CO)3 (III) and Cp2(CO)3Mo2Co2(CO)4(μ-CO)3 (IV).Complexes III and IV have also been obtained by an independent synthesis fr
Kaganovich, V. S.,Slovokhotov, Yu. L.,Mironov, A. V.,Struchkov, Yu. T.,Rybinskaya, M. I.
p. 339 - 350
(2007/10/02)

Synthesis and reactivity of titanium/cobalt complexes with Ti-O-C-Co bridges
Reactions between titanium metallocene dicarbonyls and dicobalt octacarbonyl were investigated and found to give a variety of Ti/Co complexes depending on the reaction conditions. Reaction between Cp2Ti(CO)2 and Co2(CO)8 in nondonor solvents led to the formation of the known Cp2Ti[OCCo3(CO)9]2 via a novel redox/cluster-building process. However, reaction between Cp2Ti(CO)2 and Co2(CO)8 in tetrahydrofuran led to the formation of the ionic compound [Cp2Ti(THF)2][Co(CO)4]. A mechanism in which isocarbonyl bridge formation is required to build the cluster compounds is proposed. Reaction between Cp*2Ti(CO)2 (Cp* = pentamethylcyclppentadienyl) and Co2(CO)8 yields the Ti(IV) isocarbonyl-bridged complex Cp*2Ti[OCCo(CO)3]2 from toluene but gives the paramagnetic Ti(III) dinier [Cp*2TiOCCo(CO)3]2 from hexane solution. Reactions of the above Ti/Co complexes with triphenylphosphine induce inner-sphere electron transfer from Co to Ti to take place via the isocarbonyl bridge.
Merola, Joseph S.,Campo, Kathryn S.,Gentile, Robert A.
p. 2950 - 2954
(2008/10/08)

Low-valent cyanocobaltate chemistry. 3. Reactions of [(η5-C5H5)Co(CN)(CO)]- with electrophiles, nucleophiles, and redox agents. Synthesis of new (η5-cyclopentadienyl)cobalt cyanide complexes
Details of the syntheses and reactivity of (K-crown)[Cp(CN)(CO)] (1a) (crown = 18-crown-6 ether), PPN[Cp(CN)(CO)] (1b), (K-crown)[CpCo(CN)PPh3] (4), and (K-crown)[CpCo(CN)2] (10a) are presented. Compound 1a is readily formed by reaction of CpCo(CO)2 with cyanide in aprotic media. Reaction of CpCo(CO)2 with excess cyanide under forcing conditions results in the dissociation of cyclopentadienide anion instead of [CpCo(CN)2]2- formation. Although the [CpCo(CN)2]2- anion appears to be extremely basic and reactive, an impure form can be isolated by the low-temperature reduction of 10a in DMF. The electrophiles acetyl chloride, benzyl bromide, and methyl fluorosulfate do not react with 1a to form isocyanides but unexpectedly produce CpCo(CO)2 and a variety of Co(II) and Co(III) compounds. The pathways that culminate in these products are suggested to originate from an initial one-electron transfer yielding the intermediate [Cp(CN)(CO)]. Treatment of 1a or 1b with tosyl chloride yields [CpCo-(CN)2(η1-SO2C6H 4CH3)]- and cyanide-bridged cyclopentadienylcobalt(III) polymers, while 1a or 1b reacts cleanly with R3SnCl reagents to form the expected isocyanide complexes. Hg(CN)2 oxidizes 1 to CpCo(CN)3-. Acyl chlorides lacking α-hydrogens react with 1 to produce novel bis(acyl isocyanide) complexes CpCo-(CNCOR)2 in low yields. The spectroscopic characterization of these compounds is presented, and the nature of the cyanide ligand's influence on low-valent metal centers is discussed.
Carter, Stephen J.,Stuhl, Louis S.
p. 1909 - 1918
(2008/10/08)

Gas-phase ligand substitution reactions with (OC)Fe(NO)2.-', (OC)2Co(NO).-, (η3-C3H5)Co(CO)2.-, (C3H5)Co(CO)3.-, and CpCo(CO)2.-
Three 17-electron transition-metal complex negative ions LM(CO)x-1.- ((OC)Fe(NO)2.-, (OC)2Co(NO).-, and (η3-C3H5)Co(CO)2.-) and two parent molecular anion radicals LM(CO)x.- ((C3H5)Co(CO)3.- and CpCo(CO)2.-) were generated by electron impact on the corresponding LM(CO)x complexes in the gas phase. The ion-molecule reactions of these five metal complex negative ions were studied with the neutral molecules PF3, PMe3, NO, SO2, olefins with electron-donating and -withdrawing vinyl substituents, acetone and certain fluorinated derivatives, biacetyl, O2, CO, and CS2. In general, the LM(CO)x-1.- complexes and CpCo(CO)2.- reacted by ligand substitution involving the associative mechanism. In many cases, the product ions of adduct formation and ligand substitution were directly observed in the same reaction. These ligand substitution reactions appear to take advantage of the abbility of the NO, η3-C3H5, and Cp ligands to reduce their hapticities as the neutral ligand bonds to the metal. The reaction of (C3H5)Co(CO)3.- with PF3 occurred by fragmentation of the allyl radical. This latter result was considered to occur by radical β-fragmentation of the excited acyl complex [C3H5C(=O)Co(CO)2(PF3) .-]* formed by CO insertion into the Co-allyl bond. Both parent molecular anion radicals were observed to undergo electron transfer with several of the neutral substrates yielding EA((η3-C3H5)Co(CO)3) = EA(CpCo(CO)2) = 0.62 ± 0.1 eV; EA(η3-C3H5)Co(CO)2) = 0.9 ± 0.2 eV was also measured. The results of the reactions of the parent LM(CO)x.- species with the neutral ligands were consistent with their structures having a 17-electron configuration about the metal with η3-Cp and η1-C3H5 ligands.
McDonald, Richard N.,Schell, Philip L.
p. 1806 - 1820
(2008/10/08)

Carbon-carbon bond-forming reactions of cobaltacyclopentene/cobaltaoxanorbornadiene complexes with isocyanides, carbon monoxide, and alkynes
Reaction of (η5-C5H5)Co[C(R)C(CO2CH 3)CH(CO2CH3)CH(CO2CH 3)][P(C6H5)3] (R = C6H5, 2a; R = CO2CH3, 2b) with isocyanides, CO, and diphenylacetylene (DPA) afforded 1-amino-1,3-cyclopentadienes, cyclopent-2-enones, and (η5-C5H5)Co(η 4-1,3-cyclohexadiene) complexes, respectively. The related [2.2.1]-metallabicyclic cobaltaoxanorbornadiene complexes 1a and 1b reacted with the same reagents to afford identical products. Reactions with isocyanides and CO proceeded in two distinct steps: (1) co-ordination of the reactant to cobalt to form a new ligand-substituted cobaltacyclopentene complex and (2) insertion of the reactant into the metallacycle, followed by reductive elimination. Intermediates were not detected in the reactions with DPA. However, the isolation of isomeric η4-cis-5,6-dicarbomethoxy-1,3-cyclohexadiene complexes with CpCo coordinated on different faces of the diene suggested the intermediacy of a metallacycloheptadiene complex. Kinetic measurements established that the reaction of 1a with DPA was first order with respect to both reagents. A rate constant for the reaction of 2a with DPA was calculated from our data and the known equilibrium constant between 2a, 1a, and P(C6H5)3. The agreement of the calculated rate with a published rate for the reaction confirmed that 1a is the kinetically significant intermediate in the carbon-carbon bond-forming reactions of 2a.
Scozzafava, Maryrose,Stolzenberg, Alan M.
p. 1073 - 1083
(2008/10/08)

DERIVATE DES BOROLS VIII. (η5-BOROL)COBALT-KOMPLEXE
A large variety of (η5-borole)cobalt complexes have been prepared starting with μ-(CO)25-C4H4BR)>2(Co-Co) (IIIa: R = Me, IIIb: R = Ph), including inter alia, the sandwich complexes CpCo(η5-C4H4BR) (VIIa, b), the triple-decked complexes μ-(η5-C4H4BR)5-C4H4BR)>2 (VIIIa, b) and μ-(η5-C4H4BR)(FeCp)5-C4H4BR)> (X, R = Ph), the dinuclear complex μ-(CO)25-C4H4BPh)>(Fe-Co) (IX), and salts M5-C4H4BR)2> (XVa, b: M = Na; XVIa, b: M = NMe4; XVII: M = Cs, R = Ph).The anions 5-C4H4BR)2>(-) readily undergo stacking reactions to form multiple-decked complexes such as the triple-decked compounds μ-(η5-C4H4BR)(5-C4H4BR)> (XIIa, b), μ-(η5-C4H4BR)>5-C4H4BR)> (XVIII), 5-C4H4BPh)5-C4H4BPh)>> (XX), and the quadruple-decker complex Ru5-C4H4BR)Co(η5-C4H4BR)>2 (XXI).The monofacially bound η5-borole ligands in VIIb and VIIIb sohw regiospecific H/D exchange, at the α position of the boron, on treatment with CF3CO2D at room temperature.VIIb undergoes a Friedel-Crafts substitution to give the 2-acetyl derivative XXIV with MeCOCl/SnCl4 in CH2Cl2 at room temperature.The structure of VIIIa, as determined by X-ray diffraction studies is that of a typical triple-decker compound with nearly coplanar rings.The three borole rings form a helix with torsional angles of 59.8 and 72.2 degree.All intra-ring bond distances of the central ligand are longer than those of the outer ligands.The metal-ligand interaction is somewhat stronger for the outer ligands than for the central ligand.
Herberich, G. E.,Hessner, B.,Saive, R.
p. 9 - 28
(2007/10/02)

Electrochemical oxidation and reduction of methylene-bridged complexes of manganese, cobalt, and rhodium
The oxidation and reduction of a series of alkylidene-bridged dimetallic compounds containing Mn, Co, or Rh have been studied by electrochemical and spectroscopic techniques. Oxidation results in production of a cation radical whose stability depends on the identity of the metal in the complex and the nature of the bridge substituent. Among the dirhodium complexes, the one having bridging carbonyl groups gives the most stable cation. The cobalt and rhodium compounds are susceptible to attack by nucleophiles, and all cations decompose to give mononuclear products. One-electron reduction gives detectable anions in the case of Co and Rh compounds, but these anion radicals rapidly decompose. It is concluded that both oxidation and reduction weaken the M-C-M triangle, consistent with the description of these compounds as dimetallacyclopropanes.
Geiger, William E.,Gennett, Thomas,McVicar, William K.,Herrmann, Wolfgang A.
p. 1634 - 1639
(2008/10/08)

Cobalt carbene complexes from (butadiene)zirconocene and (cyclopentadienyl)cobalt carbonyls: An example of a nonnucleophilic synthesis of Fischer-type carbene complexes
The (s-cis-/s-trans-η4-butadiene)zireonocene equilibrium mixture (17/15 = 55/45) reacts with CpCo(CO)2 at ambient temperature to give the metallacyclic Fischer-type carbene complex Cp2Zr(C4H6) (OC=)Co(CO)Cp, 20. The (s-trans-diene)metallocene complex reacts much faster with the metal carbonyl than the more nucleophilic (s-cis-C4H6) ZrCp2 isomer. The product of this nonnucleophilic carbene complex forming reaction, 20, was characterized by X-ray diffraction. It crystallizes in the space group P21/c with cell constants a = 7.824 (2), b = 15.753 (4), and c = 15.121 (3) A? and β = 99.26 (2)°. Complex 20 is characterized by a rather short Co-C(carbene) bond length of 1.815 (4) A?. At ambient temperature in solution 20 rapidly equilibrates with the starting components Cp2Zr(butadiene) and CpCo(CO)2. At equilibrium the carbene complex is favored by 85/15. Substitution of a Cl on the Cp ring of the CpCo moiety shifts the equilibrium ratio further to the side of the zirconoxycarbene complex: (η5-C5H5)2Zr-(C 4H6)(OC=)Co(CO)(η5-C5H 4Cl) ? Cp2Zr(butadiene) + (η5-C5H4Cl)Co(CO)2 (>98/2).
Erker, Gerhard,Lecht, Rainer,Petersen, Jeffrey L.,B?nnemann, Helmut
p. 1962 - 1967
(2008/10/08)

DV-Xα calculations, UV-PE spectra, and redox properties of nitrosyl-bridged binuclear cobalt complexes
The electronic structure of two cobalt dimers containing bridging nitrosyl groups, (μ-NO)2[Co(μ5-C5H5)] 2 (I) and (μ-NO)(μ-CO)[Co(μ5-C5H5)]2 (II), has been investigated by vapor-phase UV photoelectron (PE) spectroscopy and electrochemical techniques. The information obtained by the two experimental approaches was fit together in a unique bonding picture by DV-Xα quantum mechanical calculations. The UV-PE spectrum of I is consistent with a bent (μ-NO)2Co2 core in the vapor phase, in contrast with the planar core observed in the solid state. The theoretical calculations predict a direct Co-Co interaction for the bent geometry, at variance with the planar one where no charge accumulation between the metal atoms is computed. The bonding scheme emerging from the calculations is consistent with the redox behavior of both I and II. Both complexes were found to undergo reversible one-electron-transfer processes revealing the existence of the redox couples I0/1-, I1+/0, I2+/1+, II0/1-, and II1+/0. Except reduction of II, either removal or addition of electrons resulted, however, in bridge splitting follow-up reaction. Bridge cleavage in I- is a consequence of the filling of the strongly antibonding Co-NO LUMO, while in I2+ it arises from the large decrease of the dπ(Co) →*(NO) back-bonding owing to the high positive charge on the metal atoms. The observed reaction mode of II+ into 15-electron [CoCp(CO)]+ and 17-electron CoCp(NO) fragments has been tentatively attributed to a charge polarization effect consequent to the presence of two different bridging groups. Otherwise, kinetic factors were found to merely rationalize the unstability of intermediate I+.
Pilloni, Giuseppe,Zecchin, Sandro,Casarin, Maurizio,Granozzi, Gaetano
p. 597 - 606
(2008/10/08)

CARBONYLCOBALT(I) COMPLEXES. THE CRYSTAL AND MOLECULAR STRUCTURE OF (Co(CO)(dppm)2)ClO4
New anionic carbonylcobalt(I) complexes (X2Co(CO)2(PPh3))(PR4) (X=Cl, PR4=PBzPh3 (I); X=Br, PR4=PEtPh3 (II)) have been prepared by reduction of the cobalt(II) halides with NaBH4 in the presence of PPh3 and the phosphonium salt PR4X.Cleavage of halide bridges in dimeric or polymeric (XCo(PPh3)2)n and (XCo(PPh3))n gives the neutral dicarbonyl derivatives XCo(CO)2(PPh3)2.Treatment of ClCo(CO)2(PPh3)2 with alkylating agents gives the known ?- and η-organocobalt(I) derivatives, and reactions with TlClO4 in the presence of various amounts of different mono- and bi-dentate phosphines give the cationic tricarbonyl (Co(CO)3(PPh3)2)(+), dicarbonyl (Co(CO)2(PMePh2)3)(+) and monocarbonyl (Co(CO)L4)(+) complexes (L4=4P(OMe)3, 2 dppe and 2 dppm).The dppm complex crystallizes in the monoclinic space group P21/c with a 17.895(6), b 10.751(2), c 24.687(4) angstroem, β 98.92(1) deg, and Dcalc 1.35 g cm-3 for Z=4.A final R value of 0.077 (Rw=0.061), based on 2656 observed reflections, was obtained.The cobalt atom exhibits a distored trigonal bipyramidal geometry.The perchlorate anion is severely disordered or freely rotating.
Carriedo, C.,Gomez-Sal, P.,Royo, P.,Martinez-Carrera, S.,Garcia-Blanco, S.
p. 79 - 90
(2007/10/02)

THE REACTIONS OF COMPLEXES WITH NUCLEOPHILES
The extent of the reaction of with CO in chloroform at ca. 20 deg C and 1 atmosphere pressure is markedly dependent on X.Thus when X = CL the reductive elimination of the tin(IV) halide, SnCl4, is complete within 30 minutes and is formed almost quantitatively but reversibly.When X = I no detectable reaction takes place, but when X = Br an intermediate situation is observed, with both reagent and product present in the reation mixture.On the other hand, te principal reactions of with both (PhO)3P and Ph3P (L) are CO substitutions to give .A limited amount of reductive elimination to give and may occur, but because it is reversible these side-products soon disappear.The course of the reactions of with CO depends on the PIII ligand L, and on X.Thus when L = (PhO)3P and X = Br the sole product is but when L = Ph3P and X = Br and then some are formed. does not appear to react with CO.When (X = Cl or Br) are dissolved in donor solvents such as tetrahydrofuran, acetone or acetonitrile, some reversible formation of takes place, but the sole isolable products have the empirical formulae .With pyridine (py) or 2,2'-bipyridyl (bipy), these last give blue and brown respectively.
Murray, Paul T.,Manning, A. R.
p. 219 - 224
(2007/10/02)

Formation and reactivity of halogen derivatives of (η5-cyclopentadienyl)thallium
Reactions of chloro-, bromo-, or iodocyclopentadiene, generated in ethyl ether solution from cyclopentadienylthallium and N-halosuccinimides or iodine, with thallous ethoxide has afforded the respective (halocyclopentadienyl)thallium compounds in 72-96% yield. (Chlorocyclopentadienyl)thallium can also be formed in good yield from chlorocyclopentadiene, thallium(I) chloride, and potassium hydroxide in aqueous solution. These new reagents have served as convenient intermediates in the formation of the following compounds: (η5-C5H4X)2Fe (X = Cl, Br); (η5-C5H5)(η5-C 5H4Cl)TiCl2; (η5-C5H4Cl)2TiCl2; (η5-C5H4X)Mn(CO)3 (X = Cl, Br); (η5-C5H4X)Co(CO)2 (X = Cl, Br, I); (η5-C5H4Cl)Rh(CO)2; (η5-C5H4Cl)2Ni; and (η5-C5H4Cl)Cu[P(C2H 5)3]. A reaction between (η5-C5H4Br)Co(CO)2 and n-butyllithium in ethyl ether solution at -78 °C has generated (η5-C5H4Li)Co(CO)2, which reacts with carbon dioxide and with acetone to produce (η5-C5H4CO2H)Co(CO)2 and [η5-C5H4C(CH3) 2OH]Co(CO)2, respectively.
Conway, Brian G.,Rausch, Marvin D.
p. 688 - 693
(2008/10/08)

BASISCHE METALLE. LII. SYNTHESE VON CARBENOID- UND YLIDCOBALT(III)-KOMPLEXEN AUS SUBSTITUTIONSLABILEN COBALT(I)-VORSTUFEN
The cyclopentadienylcobalt(I) compounds C5H5Co(PMe3)P(OR)3 (R=Me, Et, Pri) and C5H5Co(C2H4)L (L=PMe3, P(OMe)3, CO) are prepared by ligand substitution starting from C5H5Co(PMe3)2 and C5H5Co(C2H4)2.Whereas the reaction of C5H5Co(PMe3)P(OMe)3 with CH2Br2 mainly gives Br, the dihalogenocobalt(III) complexes C5H5CoX2(PMe3) (X=Br, I) are obtained from C5H5Co(CO)PMe3 and CH2X2.Treatment of C5H5Co(CO)PMe3 or C5H5Co(C2H4)PMe3 with CH2ClI at low temperatures produces a mixture of C5H5CoCH2Cl(PMe3)I and C5H5CoCl(PMe3)I, which can be separated due to their different solubilities.The same reaction in the presence of ligand L gives the carbenoidcobalt(III) compounds PF6 in nearly quantitative yields.If NEt3 is used as the Lewis base, the ylide complexes PF6 (X=Br, I) are obtained.The PF6 salts of the dications 2+ (L=PMe3, P(OMe)3, CNMe) and 2+ are prepared either from + and L, or more directly from C5H5Co(CO)PMe3, CH2X2 and PMe3 or P(OMe)3, respectively.The synthesis of C5H5CoCH2OMe(PMe3)I is also described.
Hofmann, L.,Werner, H.
p. 141 - 156
(2007/10/02)

Direct Metal Exchange in Germylidyne Tricobalt Clusters
The reactions of the clusters RGeCo3(CO)9 (1, R=Me, Ph, tBu) and of their subsequent products with the metal exchange reagents 2, 2, 2, and Na2Fe(CO)4 were investigated.From 1 and 2 (M=Mo, W) the clusters RGeCo2MCp(CO)8 (4, 5) were formed, with 2 rearrangements occured, and only for R=tBu with Na2Fe(CO)4 the compound tBuGeCo2Fe(CO)9H (6) was obtained.Starting from the clusters tBuGeCo2MCp(CO)8 (4c, 5c) further metal exchange yielded the corresponding mixed metal clusters with CoMo2, CoMoW, CoMoNi, and CoMoFe frameworks.In the clusters LnM-GeCo3(CO)9 (11) with Ln=Cp(CO)3Mo, Cp(CO)3W, Cp(CO)2Fe, (CO)4Co, and CpCONi metal exchange with 2 replaced either the external organometal unit or the Co(CO)3 unit in the cluster.Among the resulting products were the new compounds LnM-GeCo2MoCp(CO)8 (12) with LnM=Cp(CO)3Mo, Cp(CO)3W, and Cp(CO)2Fe.Crystal structure determinations were performed for tBuGeCoMoFeCp(CO)8H (10) and Cp(CO)3WGeCo2MoCp(CO)8 (12b).
Gusbeth, Petra,Vahrenkamp, Heinrich
p. 1770 - 1781
(2007/10/02)

REARRANGEMENT OF ETHYLENE TO HYDRIDO AND ETHYLIDYNE LIGANDS AND FORMALDEHYDE DECARBONYLATION IN THE SYNTHESIS OF (η5-C5H5)4Co4> DERIVATIVES. CRYSTAL STRUCTURE OF 5-C5H5)4Co4(μ3-CO)2>
Rearrangement of ethylene to hydrido and ethylidyne ligands bonded to two faces of the tetrahedral skeleton (Cp=η5-C5H5) in 3-H)(μ3-CCH3)> was observed upon heating a hexane solution of ; treatment of with formaldehyde gave 3-CO)2>, the X-ray structure of which is reported.
Gambarotta, Sandro,Floriani, Carlo,Chiesi-Villa, Angiola,Guastini, Carlo
p. C6 - C10
(2007/10/02)

μ3-Silylidyne Heterometal Clusters
The silylidyne tricobalt clusters RSiCo3(CO)9 (1, R = Me, Ph, p-Tol) proved to be too sensitive for the conversion to mixed metal clusters by the reported metal exchange procedures.Therefore for the purpose of cluster construction the functional complexes RSiH2 - MLn (2 - 7, MLn = CrCp(CO)3, MoCp(CO)3, WCp(CO)3, Mn(CO)5, FeCp(CO)2, Co(CO)4) were prepared from RSiH2Br (R = Me, Ph) and carbonyl metalates.Their reaction with Co2(CO)8 produced the open trinuclear complexes R(MLn)SiCo2(CO)7 (8 - 10) only for MLn = MoCp(CO)3, WCp(CO)3, and FeCp(CO)2.Subsequent thermolysis resulted in the case of MLn = MoCp(CO)3 and WCp(CO)3 in the mixed metal clusters RSiCo2MCp(CO)8 (11, 12, M = Mo, W).
Gusbeth, Petra,Vahrenkamp, Heinrich
p. 1143 - 1153
(2007/10/02)

SYNTHESES OF MIXED TRANSITION METAL CLUSTERS CONTAINING THE COORDINATED PHOSPHAALKYNE tBuCP
Syntheses of the phosphaalkyne complexes 5-C5H5)2(tBuCP)> and 5-C5H5)(CO)3(tBuCP)> are described.Adducts of the latter with and 5-C5H5)> are also reported.The reactions
Bartsch, Rainer,Nixon, John F.,Sarjudeen, Nigel
p. 267 - 272
(2007/10/02)

Buildup of Germylidyne-bridged Tri- and Tetranuclear Clusters
Reaction of organogermanium trihalides with KCo(CO)4 yields the trinuclear clusters RGeCo3(CO)9 (1, R=Me, Ph, tBu) as well as the new tetranuclear clusters (RGe)2Co4(CO)11 (3, R=Ph, tBu).The dinuclear complexes LnM-GeI2-MLn (4-6, MLn=FeCp(CO)2, Co(CO)4, NiCpCO) resulting from insertion of GeI2 into metal-metal bonds react with KCo(CO)4 to form the clusters Ln-GeCo3(CO)9 (7-9).Metal exchange reactions produce the hetero tetranuclear clusters (tBuGe)2Co3(CO)8M'Ln (10, 11, M'Ln=MoCp(CO)2, NiCp).Crystal structure analyses were performed for Cp(CO)2Fe-GeCo3(CO)9 (7) and (tBuGe)2Co3(CO)8NiCp (11).
Gusbeth, Petra,Vahrenkamp, Heinrich
p. 1746 - 1757
(2007/10/02)

Carbon-Carbon Bond Formation in Dinuclear Dialkyl Complexes. Reactions of 2 (R = CH3, CH2CH3, CH2CF3) and (C11H10)Co2(CO)2(CH3)2 with Carbon Monoxide and Triphenylphosphine
The full details of the synthesis, thermal decomposition, and carbonylation of dialkyldicobalt dimers 2 are reported.The dinuclear dimethyl complex 2a gives acetone and cobalt clusters on thermal decomposition; the very sensitive mononuclear complex CpCo(CO)Me2 (7a) can be detected as an intermediate.The bis(trifluoroethyl) complex 2 (2c) rearranges to 7c (R = CH2CF3), which does not go on to ketone and can be isolated.Carbonylation of the dinuclear dimethyl and diethyl complexes 2a and 2b proceeds even more cleanly to ketones, giving a quantitative yield of CpCo(CO)2 as the final organometallic product.However, this reaction proceeds by a mechanism different from that of the thermal decomposition.In the carbonylation an initial very rapid reaction leads to the diacyl complex 2; this goes on to ketone at a rate faster than can be attributed to 7.Crossover experiments provide strong evidence that complexes 2a, 2b, and 2c are in rapid equilibrium with small amounts of the paramagnetic, 17-electron monomers CpCo(CO)R.The corresponding complex (C11H10)Co2(CO)2Me2 (13a), containing a bridging ligand in which two Cp rings are connected by a CH2 group, has also been synthesized.This material is more stable than 2a; it undergoes carbonylation to acetone only at temperatures near 70 deg C.It reacts with PPh3 at 25 deg C but instead of leading to ketone gives the rearranged product (14).The PPh3 + 13 14 reaction is reversible at room temperature, with an equilibrium constant of 33 M-1.Kinetic studies on this system are consistent with a mechanism involving the reversible formation of a transient intermediate which can be trapped by PPh3.Taken together, the results require that at least three chemical pathways are accessible to complexes of type 2: reversible cleavage to paramagnetic monomers, alkyl transfer from one cobalt atom to another, and carbonylation to give dinuclear diacyl complexes, which can rapidly proceed on to form ketone.
Schore, Neil E.,Ilenda, Casmir S.,White, Mary Ann,Bryndza, Henry E.,Matturro, Michael G.,Bergman, Robert G.
p. 7451 - 7461
(2007/10/02)

Efficient syntheses of new fulvalene-bridged carbonyl complexes of cobalt, ruthenium, chromium, molybdenum, and tungsten
A variety of new dimetallafulvalene carbonyl complexes have been prepared by slow addition of cold purified dihydrofulvalene in heptane to boiling solutions of metal carbonyls. Reaction of Co2(CO)8 with dihydrofulvalene allows efficient preparation of (η5:η5-C10H8)(CO) 4Co2. Ru3(CO)12, Cr(NCEt)3(CO)3, Mo(CO)6, and W(NCEt)3(CO)3 react to form the intramolecularly metal-metal bonded complexes (η5:η5-C10H8)(CO) 4Ru2 and (η5:η5-C10H8)(CO) 6M2 (M = Cr, Mo, and W). Attempts to generate the analogous iron complexes were unsuccessful. Reaction of a mixture of Ru3(CO)12 and Mo(CO)6 with dihydrofulvalene affords a better than statistical yield of the mixed metal-metal bonded complex (η5:η5-C10H8)(CO) 5MoRu.
Vollhardt, K. Peter C.,Weidman, Timothy W.
p. 82 - 86
(2008/10/08)

Synthesis, crystal and molecular structure, and reactions of the bridging vinylidenedicobalt complex (μ-CCH2)(CpCoCO)2. Reaction with molybdenum hydrides to give a heteronuclear cluster complex
The first unsubstituted dicobalt μ-vinylidene complex (μ-CCH2)(CpCoCO)2 (1) has been synthesized and characterized by X-ray diffraction. 1 is readily protonated by HBF4 at the β-carbon to yield an isolable μ-ethylidyne salt, 2, which in turn is reduced by NaBH4 to give the corresponding μ-ethylidene complex 3. Complex 3 is also formed on treatment of 1 with H2 at 60°C, but under these conditions competitive hydrogenolysis of 3 to ethane occurs. Reaction of 1 with CpMo(CO)2(L)H (L = CO, PPh3) affords the mixed-metal cluster 4 in good yield, in a rational and potentially general route to μ-carbyne trinuclear systems. Possible mechanisms are briefly discussed.
Jacobsen, Eric N.,Bergman, Robert G.
p. 329 - 331
(2008/10/08)

UEBERGANGSMETALL-METHYLEN-KOMPLEXE. LII. SYNTHESEKONZEPTE ZUM AUFBAU HETERODINUCLEARER METALL-METALL-MEHRFACHBINDUNGEN
Novel heterodinuclear metal-metal multiple bonds are accessible by simple high-yield metal-metal coupling reactions: the cobalt-iridium complex (η5-C5H5)Co(μ-CO)2Ir(η5-C5Me5) (Me=CH3; 3) is formed as the main product from the reactio
Herrmann, Wolfgang A.,Barnes, Craig E.,Serrano, Ricardo,Koumbouris, Basile
p. C30 - C34
(2007/10/02)

Photochemical synthesis and structure of (μ-η4-syn-1,3-butadlene )(μ-carbonyl)bis(η5-cyclopentadienyl)dicobalt(Co-Co), a dinuclear butadiene complex
Irradiation of (η4-1,3-butadiene)(η5-C5H 5)Co in the presence of (η5-C5H5)Co(CO)2 results in the title compound, the first dinuclear parent η4-butadiene complex adopting a syn configuration to be characterized by X-ray crystallography.
King Jr., Joseph A.,Vollhardt, K. Peter C.
p. 684 - 686
(2008/10/08)

Synthesis and Reaction Chemistry of a New Class of μ-Alkylidene Dicobalt Complexes. Crystal and Molecular Structure of (μ-Methylene)bis5-(methylcyclopentadienyl)carbonylcobalt>
Threatment of Na2 with gem-diiodoalkanes (RR'CI2, R = H, alkyl) leads to a class of dinuclear μ-alkyliidene complexes containing two adjacent cobalt atoms.Cis and trans isomers were observed in certain of these materials, as well as bridging and terminal carbonyls, depending upon the substituents located at the alkylidene carbon.Complexes having two alkyl substituents attached to this carbon lose one CO ligand, leading to stable unsaturated μ-alkylidene complexes.The molecular structure of (μ-(methylcyclopentadienyl)carbonylcobalt> (11) was determined by X-ray diffraction (R = 2.82percent).The crystals were triclinic (space group P1), with unit cell parameters a = 8.0592 Angstroem, b = 9.5160 Angstroem, c = 9.9330 Angstroem, α = 69.678 deg, β = 74.769 deg, and γ = 83.704 deg.At elevated temperatures dimers 10 (M, M' = Co; R = H, R' = neopentyl) and 13 (M = Co; M' = Rh; R, R' = H) undergo cis-trans isomerization at a rate which is rapid on the NMR time scale.Treatment of 1 (M,M' = Co; R,R' = H) with 11 or CpRh(CO)2 leads to metal-metal exchange reactions, resulting in the formation of heteronuclear (Co-Rh) μ-alkylidene complexes. 1 reacts with ethylene to give propene and CpCo(CO)(C2H4).Mechanistic studies have demonstrated that this process is autocatalytic, and addition of other ligands (e.g., CO, C2F4, propene) retards the rate of the reaction by scavenging the unsaturated cobalt complexes which function as the autocatalysts.Finally, thermolysis of internal or disubstituted alkylidene complexes 2, 5, and 7 causes a novel rearrangement in which the dicobalt moiety migrates to the end of the alkylidene carbon chain, generating terminal alkylidene complexes having the same number of carbon atoms.Labeling studies have demonstrated that both sequential 1,2 metal shift (leading to alkene ? complexes) and allylic C-H activation (leding to ?-allyl complexes) are involved as steps in this rearrangement.
Theopold, Klaus H.,Bergman, Robert G.
p. 464 - 475
(2007/10/02)

Kinetics and Mechanism of Decomposition of a Benzodicobaltacyclohexene: Reversible Dinuclear Elimination of o-Xylylene via a Dimetalla-Diels-Alder Reaction
A detailed mechanistic study of several reactions of the first dimetallacyclohexene, (η5-Cp)2Co2(μ-CO)2(μ-o-xylylene) (1), is described.The predominant reaction pathway is proposed to involve reversible cleavage of 1 In Diels-Alder fashion, into free o-xylylene (3) and the metal-metal double-bonded dimer 9.Several lines of evidence support this conclusion.Crossover experiments demonstrated that loss of 3 from 1 in its reaction with PPhMe2 to give dinuclear monophosphine adduct 2 is a dinuclear elimination process that leaves the cobalt-cobalt bond intact.Kinetic studies showed that sufficiently high concentrations of several ligands (phosphines, bis(methylcyclopentadienyl) metal-metal double-bonded dimer 10, or dimethyl acetylenedicarboxylate (DMAD)) induce decomposition of 1 at the same maximum rate, to give monophosphine adduct 2, bis(methylcyclopentadienyl)dimetallacyclohexene 5, or dinuclear DMAD adduct 16, respectively.Both the phosphine and DMAD reactions exhibited falloff in the observed rates of decomposition at lower ligand concentration.On the basis of the proposal that 1 was in thermal equilibrium with two reactive intermediates (3 and 9), theoretical results suggested, and were experimentally confirmed, that at low DMAD concentration the fallof in decomposition rate could be eliminated by lowering the concentration of 1, to again induce decomposition at the previously observed maximum rate.An Arrenius plot of data collected in this limiting rate regime, representing the rate of the retro-dimetalla-Diels-Alder reaction,gave ΔH = 24.3 kcal/mol and ΔS = +12.1 eu.Preparative reactions of double-bonded dimer 9 with two different o-xylylene precursors gave moderate yields of metallacycle 1, providing additional evidence for the forward dimetalla-Diels-Alder reaction.A minor reaction pathway, thermal decomposition of 1 to CpCo(o-xylylene) (12) and CpCo(CO)2 (13), was also observed.Evidence is presented suggesting that it is mechanistically related to the major decomposition pathway operating in other dinuclear dicobalt systems, involving intramolecular alkyl to cobalt migration.
Hersh, William H.,Bergman, Robert G.
p. 5846 - 5859
(2007/10/02)

Synthesis, Crystal and Molecular Structures, and Reactions of a Benzodicobaltacyclohexene, a Thermally Derived Mononuclear o-Xylylene Complex, and an Unsymmetrical Phosphine-Derived Dinuclear Complex
Alkylation of Na2 (Cp = η5-cyclopentadienyl) with α,α'-dibromo-o-xylene gives bis(μ-carbonyl)(μ-o-xylylene)bis5-cyclopentadienyl)cobalt>(Co-Co) (1), the first dimetallacycloxene.The X-ray crystal structure of the derivative analogue 8 hyving η5-methylcyclopentadienyl rings was solved (2371 reflections; R = 2.64percent; space group P; a = 9.1045 (11), b = 9.5465 (13), c = 11.8147 (16) Angstroem; α = 83.730 (11) deg; β = 81.414 (10) deg, γ = 63.392 (10) deg; Z = 2, dcalcd = 1.598 g/cm3) and shows a six-membered ring containing two cobalt atoms with a Co-Co ''single bond'' length of 2.438 Angstroem; the dimetallacycle ring adopts a boat conformation with a folding angle of 58.5 deg.Compound 1 undergoes slow decomposition at room temperature in solution to give CpCo(CO)2 (10) and new complex (η5-cyclopentadienyl)(η4-o-xylylene)cobalt (11).The crystal structure of 11 (1370 reflections; R = 3.90percent; space group Pbca; a = 7.6286 (40), b = 11.6094 (16), c = 23.7196 (24) Angstroem; Z = 8, dcalcd = 1.443 g/cm3) is that of a diene complex in which the o-xylylene ligand consists of a delocalized butadiene portion and a nonaromatic six-membered carbocycle.Photolysis of 1 also leads to 10 and 11 as primary products.Carbonylation of mononuclear o-xylylene complex 11 at 70 deg C gives 10 and the CO insertion product 2-indanone (13).Carbonylation of 1 yields 10 and dimers 14 and 15 of free o-xylylene (4).Reactions of 1 with phosphines and phosphites (L) also give 14 and 15 as well as CpCo(CO)L (16), but the unstable dinuclear intermediate 17, proposed to be Cp2Co2(μCO)2(L), was detected in the phosphine reactions.This material can also be prepared from the dinuclear compound 2 (3) and phosphines.Compound 17 (L = PMe3) decomposes via parallel first and second-order pathways in the presence of PMe3, while 17 (L = PPh3) decomposes primarily via a first-order pathway in the presence of PPh3.The X-ray crystal structure of an analogue of 17, (MeCp)2Co2(μ-CO)2(PPhMe2) (20), was determined (2664 reflections; R = 2.76percent; space group P21/c; a = 10.0035 (14), b = 14.0816 (13), c = 14.4761 (18) Angstroem; β = 92.042 (11) deg; Z = 4, dcalcd = 1.533 g/cm3) and indicates the presence of a Co-Co ''single bond'' (2.416 Angstroem); the phosphine is bound to one of the cobalt atoms, and the two carbonyls are semibridging, with the closer contacts being to the cobalt atom not bound to phosphine.
Hersh, William H.,Hollander, Frederick J.,Bergman, Robert G.
p. 5834 - 5846
(2007/10/02)

METALLORGANISCHE LEWIS-SAEUREN; METALLKOMPLEXE MIT SCHWACH KOORDINIERTEN ANIONISCHEN LIGANDEN. XII. REAKTIONEN VON (?-C5H5)(CO)3MoX (X- = BF4-, PF6-, AsF6-, SbF6-) MIT METHYL-CARBONYL-KOMPLEXEN SOWIE MIT COBALTOCEN, NICKELOCEN UND (?-C5H5)Co(CO)2. STRUKTUR VON...
The acyl-bridged complexes 2-, η2-COCH2Ph)Mo(CO)2(?-C5H5)>+ BF4- (2b),2-, η1-COCH3)Mo(CO)3(?-C5H5)>+ SbF6- (4) besides other products have been obtained from the reaction of (?-C5H5)(CO)3MoX (X-= BF4-, SbF6-) with (?-C5H5)(CO)3MoCH2Ph and (?-C5H5)(CO)2FeCH3, respectively.The X-ray structure of 4 has been determinated.Hydrine and methyl transfer occurs in the reaction of (?-C5H5)(CO)3MoFBF3 with (CO)5MCH3 (M = Mn, Re) to give 2H>+ BF4-, (?-C5H5)(CO)3MoCH3 and (CO)5MFBF3. (?-C5H5)(CO)3MoFBF3 reacts with (?-C5H5)Co(CO)2 to give a 1:1 adduct, whereas with M(?-C5H5)2 (M = Ni, Co) redox reactions have been observed.
Suenkel, Karlheinz,Nagel, Ulrich,Beck, Wolfgang
p. 227 - 244
(2007/10/02)

Stereochemistry of Metallacycle Formation in the Double Alkylation of Bis(triphenylphosphine)nitrogen(1+) Bis(η5-cyclopentadienyl)bis(μ-carbonyl)dicobaltate with α,γ-Diiodoalkanes
Alkylation of the dinuclear cobalt radical anion 4 with 1,3-diiodopentane yields three new matallacycles: a methyldicobaltacyclopentane (11) and cis and trans isomers of an α,α'-dimethyldicobaltacyclopentane (6c and 6t).Alkylation of 4 with either of the diastereomeric 2,4-diiodopentanes meso-7 and dl-7 yields identical ratios of 6c and 6t.Control studies demonstrate that neither starting diiodide isomerization nor product isomerization can account for this product mixture.This is evidence that at least one of the two alkylation steps proceeds via electron transfer.In contrast, alkylation of 4 with a mixture of (2R,3R)- and (2S,3S)-1,3-diiodobutane-2-d (syn-12-d) proceeds stereoselectively: a 1:5 ratio of syn/anti metallacycles 11-d is formed.We conclude that the first (intermolecular) step in the double alkylation proceeds by initial electron transfer while the second (cyclization) step proceeds predominantly by SN2 displacement or by a partly stereospecific electron transfer process of the type recently postulated in certain photosolvolysis reactions.
Yang, Gilbert K.,Bergman, Robert G.
p. 6045 - 6052
(2007/10/02)

REACTIVE ORGANOMETALLIC COMPOUNDS FROM METALLOCENES.
Metallocenes can be converted into reactive organometallic compounds having readily accessible coordination sites by removing one or both of the C//5H//5-ligands: two types of reaction are discussed by which this can be achieved. Aspects to be covered include the synthesis of (C//5H//5)Co(C//2H//4)//2 and its application as a catalyst precursor for the cobalt-catalyzed alkyne cyclooligomerization and the cotrimerization of alkynes and nitriles. Also reported are the alkali metal cobaltates M//A left bracket Co(C//2H//4)//4 right bracket and M//A left bracket Co(cod)//2 right bracket (M//A equals alkali metal) which can be used as starting materials for the preparation of new catalysts for the hydrogenation of olefins and arenes. Finally, a series of novel binuclear complexes of Co, Fe and V is presented that are the first examples in which eta **6 -arene ligands are bonded to two metal centers.
Jonas
p. 63 - 80
(2008/10/08)

Synthese und Reaktionen von η5-Cyclopentadienylbis(ethen)cobalt
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Jonas, Klaus,Deffense, Etienne,Habermann, Dietrich
p. 729
(2007/10/02)

CoCpBr INTERMEDIATES IN THE CYCLOPENTADIENYLATION OF CoBr2 WITH NaCp
Reaction of CoBr2 and NaCp (Cp = η5-C5H5) at low temperature followed by addition of a diene or acetylene gives the complexes CoCp(diene).The scope and mechanism of this novel reaction have been investigated.
Koelle, U.,Sistig, F.,Gersdorf, J.
p. 253 - 258
(2007/10/02)

Mixed Metal Clusters: Metal Exchange via Dinuclear (Cylopentadienyl)metal Carbonyls
In the tetrahedral cobalt cluster MeCCo3(CO)9 (2a) by means of the dinuclear (cyclopentadienyl)metal carbonyls 2 (1, M = Mo, W, Fe, Ni) one Co(CO)3 unit can be replaced by an isoelectronic unit CpM(CO)n.The best exchange reagent 2 yields the corresponding mixed Co2Ni and Co3Ni clusters, resp. also with other YCCo3(CO)9 clusters (2, Y = Ph, p-Tol, F) and with Co4(CO)12.Thus, by combination of this method with the previously described organometal dimethylarsenide method from YCCo3(CO)9 (2, Y = Me, Ph) the clusters YCCoMoNiCp2(CO)5 (16) with three different metal atoms are obtained.Under modified reaction conditions twofold metal exchange in MeCCo3(CO)9 yields the cluster MeCCoMo2Cp2(CO)7 (15) and in PhCCo2MoCp(CO)8 yields the cluster PhCMoNi2Cp3(CO)2 (17).Of the CoMoNi compound 16a and the MoNi2 compound 17 the molecular structures were determined.
Beurich, Harald,Blumhofer, Roland,Vahrenkamp, Heinrich
p. 2409 - 2422
(2007/10/02)

Synthesis, crystal and molecular structure, and chemistry of (μ-trimethylene)bis(η-cyclopentadienyl)bis(aμ-carbonyl)dicobalt, a five-membered dlcobaltacycle
Treatment of Na[CpCo(CO)]2 with l,n-dihaloalkanes leads in certain cases to double alkylation, giving dinuclear metallacycles containing two adjacent cobalt atoms. This paper reports the synthesis and study of several such systems and an in-depth investigation of the five-membered dimetallacycle 1 prepared from 1,3-diiodopropane. The molecular structure of 1 was determined by X-ray diffraction, using 1016 reflections (R = 2.47). The crystals were orthorhombic (space group Fdd2), with unit-cell parameters a = 16.7983 ?, b = 45.576 ?, c = 6.9565 ?. The complex has an open envelope ring structure, with a dihedral angle of 32.9°; the Co-Co bond distance is 2.413 ?. Thermolysis of 1 (80-100°) gives cyclopropane and propene. Reaction of 1 with CO or phosphines (L) occurs at lower temperature, leading to a product distribution which is dependent upon the concentration of L. At low [L], the reaction leads to cyclopropane mixed with a small amount of propene and CpCo(L)(CO). High [L] produces CpCo(L)(CO) and mononuclear metallacyclopentanones 6, 7, or 8 depending on the entering ligand. Thermolysis of the metallacyclopentanones leads again to cyclopropane and propene rather than to cyclobutanone. Kinetic and isotope labeling studies on the reaction of 1 with dative ligands suggest a mechanism involving initial formation of dicobaltacyclohexanones A and B. B then is postulated to rearrange to a mononuclear carbonylmetallacyclobutane complex (C) which can either eliminate C3 hydrocarbons or undergo CO insertion, leading to metallacyclopentanone.
Theopold, Klaus H.,Bergman, Robert G.
p. 1571 - 1579
(2008/10/08)

Reactions of (η5-cyclopentadienyl)cobalt(III) alkyls with cobalt(I) phosphines and iron carbonyls. Evidence for direct η5-cyclopentadienyl and trimethylphosphine group transfer between metal centers
We have found that (η 5-rnethylcyclopentadienyl)(triphenylphosphine)dimethylcobalt(III) (1) undergoes intermolecular cyclopentadienyl ligand exchange with (η5-cyclopentadienyl)bis(triphenylphosphine)cobalt(I) (2). The unsubstituted c
Bryndza,Bergman
p. 2988 - 2991
(2008/10/08)

Darstellung und Thermolyse P2Me4-verbrueckter Mehrkern-Carbonylcomplexe
Chain-like trinuclear complexes 3 and 5 with a M - P - P - M' - P - P - M framework (M, M' = carbonyl metal units, P - P = P2Me4) were prepared from metal carbonyls and the monofunctional organometallic Lewis bases M - MP2Me4 in the ratio 1:2 or from metall carbonyls and the bifunctional Lewis base (CO)4Cr(P2Me4)2 in the ratio 2:1.They as well as the analogous dinuclear complexes with M - P - P - M' framework were thermolysed in sealed tubes with the intention to obtain new M - M' bonded polynuclear complexes.Under mild conditions the thermolysis resulted mainly in ligand exchange whereby also six-membered ring complexes with M(P - P)2M' frameworks were formed.Under more vigorous conditions in addition besides increasing decomposition also ligand fragmentations were observed which led to simple complexes or those with metal - metal bonds.As new complexes with hetero metal - metal bonds (CO)4Cr(μ-PMe2)2 - MnCpCO and (CO)4Cr(μ-PMe2)2Ni(CO)2 were isolated.We consider the new compound Fe2(CO)4(PMe2)4 to contain a Fe - Fe bond, one P2Me4, and two PMe2 bridges.
Trenkle, Armin,Vahrenkamp, Heinrich
p. 1366 - 1381
(2007/10/02)

Nitrosyl-bridged Cyclopentadienyl-cobalt and -rhodium Cations
(M = Co or Rh, R = H or Me) and + afford + (3) and then + (4) which decarbonylates to give + (5); complex (4) undergoes reversible nitrosyl-bridge cleavage with alken
Clamp, Sara,Connelly, Neil G.,Payne, John D.
p. 897 - 899
(2007/10/02)