Initial steps of the interaction of Ru3(CO)12, Fe3(CO)12, Fe2Ru(CO)12 and H2FeRu3(CO)13 clusters with hydrated alumina surfaces have been studied by FT-IR spectroscopy combined with data handling procedures. The first stage of the interaction is a pure physisorption. At the second stage the metal-metal bonds split producing a large variety of mobile subcarbonyls. In the case of Fe3(CO)12 the subcarbonyls form molecular Fe(CO)5, while at the bimetallic clusters they form molecular Fe- (CO)5 and Ru3(CO)12. Fe(CO)5 loses CO ligands producing Fe2+ and Fe3+ anchored ions. Ru3(CO)12, through further intermediate subcarbonyls, slowly decomposes into incipient anchored species RuO- (CO)2, RuII(CO)2 and RuIII(CO)2. 相似文献
The electronic structure of H2M3(CO)9S clusters (M = Ru, Os) is discussed on the basis of their He I and He II excited gas-phase photoelectron spectra and on the basis of CNDO quantum mechanical calculations. The PE data clearly demonstrate the cleavage of two direct MM interactions by operation of the bridging hydrides, giving rise to three-center two-electron MHM levels. The μ3-S bonding mode has been described in detail and compared with previous results on related μ3-CY cluster derivatives. The CNDO results on Ru3(CO)9S=, HRu3(CO)9S? and H2Ru3(CO)9S indicate that the μ3-S—cluster interaction is mostly independent of the presence of the bridging hydrides. 相似文献
The reactions of the complexes Fe3(CO)12, H2FeRu3(CO)13, H2Ru4(CO)13 and CpNiRu3(H)3(CO)9 with 2(diphenylphosphino)ethyl-triethoxysilane give considerable yields of the complexes Fe3(CO)10L2 (1), H2FeRu3(CO)10L2 (2), Ru4(CO)10L3 (3) and CpNiRu3(H)3(CO)7L2 (4) where L = Ph2PCH2CH2Si(OEt)3. The complexes (1-3) have been characterized by analytical and spectroscopic techniques. The structure of (4) has been determined by X-ray analysis. The presence of a phosphine containing the -Si(OEt)3 group has been exploited for grafting complexes (3) and (4) on the mesoporous SBA-15 and the resulting inorganic-organometallic materials have been characterized by means of ICP-MS, FT-IR, DR-UV-vis spectroscopy, XRD and textural analysis. 相似文献
As known, on hydrated alumina support the Ru3(CO)12 cluster quickly decomposes into monometallic subcarbonyls. By FT-IR spectroscopy combined with data handling procedures, the structure and thermal behaviour of the bimetallic systems of Fe2Ru(CO)12/ Al2O3 and H2FeRu3(CO)13 together with that of Ru3(CO)12 have been studied. At the end of an interaction with the hydrated alumina surface, iron ruthenium bimetallic clusters decompose into identical ruthenium anchored surface species RuA RuIII(CO)2, RuBRuII(CO)2 and RuCRu0(CO)2, like pure ruthenium clusters, and no CO bonded to iron has been detected RuB and RuC are stable in a wide temperature range (300–500 K) and they can be interconverted by oxidation and reduction. RuA is less stable (300–400 K). These main molecule-like species, anchored onto uniform sites of the surface, are accompanied by mobile subcarbonyls and stable monocarbonylic species, which occupy a large variety of different sites. 相似文献
Density functional theory has been used to explore possible homoleptic binuclear Cr carbonyls Cr2(CO)n (n = 11, 10, 9, and 8) using the pure DFT method BP86 and the hybrid Hartree-Fock DFT method B3LYP. The binuclear Cr2(CO)11 is computed to be thermodynamically unstable with respect to dissociation into mononuclear fragments in contrast to the experimentally known Cr2(CO)10(μ-H)−. This may account for the failure to synthesize Cr2(CO)11 as a stable compound. Optimized structures for the formally unsaturated Cr2(CO)10 are a singlet with two four-electron donor bridging CO groups and no formal metal-metal bonding and a triplet with no bridging CO groups and a CrCr double bond similar to the OO bond in O2. The more highly unsaturated homoleptic binuclear chromium carbonyls Cr2(CO)9 and Cr2(CO)8 are computed to be stable with respect to dissociation into mononuclear fragments in contrast to Cr2(CO)11 and Cr2(CO)10. The optimized structure for Cr2(CO)9 is a singlet Cr2(CO)6(μ-CO)3 with a short metal-metal distance (∼2.3 Å) consistent with the Cr≡Cr triple bond required for an 18-electron configuration for each Cr atom. The global minimum for Cr2(CO)8 is a closely related Cr2(CO)5(μ-CO)3 structure derived from the Cr2(CO)6(μ-CO)3 global minimum by loss of one of the terminal CO groups with little change in the Cr≡Cr distance. Higher energy minima for Cr2(CO)8 include two different Cr2(CO)6(μ-CO)2 structures, one formulated with two four-electron donor μ-CO groups bridging two Cr(CO)3 groups and the other with similar μ-CO groups bridging a Cr(CO)4 and a Cr(CO)2group. 相似文献
The geometries and thermochemistry of Re2(NO)4(CO)n (n?=?4, 3, 2, 1, 0) structures isovalent with the binuclear cobalt carbonyls Co2(CO)n+4 have been examined using density functional theory. Eight low-energy Re2(NO)4(CO)4 structures, all with formal Re–Re single bonds, lie within 6 kcal mol?1 of the global minimum. These eight structures include unbridged structures as well as structures with two bridging NO groups but no structures with bridging CO groups. Similarly, five low-energy Re2(NO)4(CO)3 structures, all with formal Re=Re double bonds, lie within 6 kcal mol?1 of the global minimum. Again these five structures include unbridged structures as well as structures with one or two bridging NO groups but no structures with bridging CO groups. The Re2(NO)4(CO)n (n?=?4, 3) appear to be fluxional systems similar to the well-known Co2(CO)8 for which doubly bridged and unbridged structures have approximately the same energies. The lowest energy Re2(NO)4(CO)2 structures have formal Re=Re double bonds including a structure with a five-electron donor bridging η2-μ-NO group. Isomeric Re2(NO)4(CO)2 structures with formal Re≡Re triple bonds lie approximately ～10 kcal mol?1 above the global minimum. For the more highly unsaturated Re2(NO)4(CO) and Re2(NO)4 systems, the lowest energy structures have formal Re≡Re triple bonds of length ～2.6 Å. Higher energy Re2(NO)4(CO) structures have shorter Re–Re distances of length ～2.5 Å suggesting formal quadruple bonds.
Graphical Abstract The geometries and thermochemistry of Re2(NO)4(CO)n (n?=?4, 3, 2, 1, 0) structures isovalent with the binuclear cobalt carbonyls Co2(CO)n+4 have been examined using density functional theory. A number of energetically closely spaced Re2(NO)4(CO)4 and Re2(NO)4(CO)3 structures are found, including unbridged and NO-bridged structures but no CO-bridged structures. The Re2(NO)4(CO)n (n?=?2, 1, 0) systems provide examples of Re–Re multiple bonds of orders ranging from 2 to 4.
Low temperature NMR spectroscopy has been used to characterize the mixtures formed in the oligomerization reactions of the unsaturated complex [Re2(μ-H)2(CO)8] (1), promoted by hydrido-carbonyl rhenates. Three families of chain clusters, constituted by Re(CO)4 units connected through Re(μ-H)Re interactions, have been obtained. The first one, of general formula [(CO)5Re-{HRe(CO)4}2n+1]−, was formed using [HRe2(CO)9]− as promoter. The nature of the products was confirmed by 13C NMR of 13CO enriched samples. The formation of Re6 and Re8 chain clusters was recognized. The other two families have general formula [H-{HRe(CO)4}2n]− and [H-{HRe(CO)4}2n+1]− and were obtained using as initiators [HB(sBu)3]− or [H2Re(CO)4]−, respectively. Mixtures of oligomers with mean chain lengths higher than 10 have been observed. The addition of a strong acid caused H2 evolution, leading back to the “monomer” 1. For all the three families, each oligomerization step was reversible, with the longer oligomers favoured at the lowest temperatures, where, however, the reactions were very slow, usually preventing the attainment of the equilibrium. Variable temperature NMR spectra revealed a dynamic process involving the terminal H2Re(CO)4 moiety(ies), that simultaneously exchanges terminal/bridging hydrides and the carbonyls trans to them (ΔG# 41-44 kJ mol−1). At room temperature, the more hydrogen-rich chain clusters also underwent dehydrogenation/cyclization reactions. 相似文献
IR spectra of crystal, solution and pseudo-gas phases (argon and nitrogen matrices) of Fe2Ru(CO)12 and of crystal and solution phases of Fe3(CO)12 were recorded. By quantitative data-handling procedures, structures and bond angles for bridging carbonyls were estimated. Fe2Ru(CO)12 in crystal has a bridging structure analogous to that of Fe3(CO)12, with two bridged carbonyls and C2v or pseudo-C2v symmetry. In solution, both samples contain the same carbonyl bridged structure of C2v symmetry,just as in pseudo- gas phase; the latter, however, contains other bridged molecules of unknown structures, too. 相似文献
The 13C and 15SN NMR spectra of eleven cis-Fe(S2CNRR′)2(CO)2 complexes, where R and R′ are organic substituents, have been measured at ambient temperature in CDCl3 (0.08–0.16 M). The 13C absorptions for the carbonyl ligands correlate well with the force constants for the CO stretching vibrations in CHCl3 solution. Each of the parameters (13CO absorption and kcis for CO) correlate well with the aqueous solution pKa for+H2NRR′, corrected for the phenyl-containing substituents, high pKa values corresponding to high 13CO absorptions and low kcis CO force constants. [p ]Evidence was found in the 13C NMR spectra for hindered rotation about the CN bond in S2CNC2 in complexes with higher pKa(corr) values and in the 13C spectra of the corresponding thiuram disulfides. [p ]The 15N (natural abundance) NMR spectra for each of the complexes was determined. Each revealed a single sharp absorption in a region of the 15N NMR spectrum which indicates substantial CN double bond character, as one would expect for coordinated dithiocarbamate ligands. 相似文献
A paramagnetic binuclear molybdenum(V) thioglycolate of composition Mo2(L)5(H2O)2 (H2L = CH2SHCOOH, thioglycolic acid) has been synthesized by direct reduction of molybdenum(VI) oxide hydrate (MoO3 · H2O) with thioglycolic acid in an argon atmosphere. Based on the combined results of elemental analysis, EPR, IR 1H NMR, electronic spectra, magnetic susceptibility, cyclic voltametry and x-ray photoelectron spectral measurements, it is concluded that in the title compound, both the molybdenum atoms are in pentavalent state with octahedral coordination through both sulphur and oxygen atoms of thioglycolic acid and water molecules. The two molybdenum ions have slightly different coordination environments due to bridging thioglycolate ions. 相似文献
The lowest energy structure for Mn2(BF)(CO)10 is predicted to consist of two Mn(CO)5 groups bridged by a BF group without a manganese-manganese bond. This structure is related to the stable compounds Mn2(μ-BX)(CO)10 (X = Cl, Br) and [(η5-C5H5)Ru(CO)2]2(μ-BF), which have been synthesized and characterized by X-ray crystallography. The following principles determine the lowest energy structures of the Mn2(BF)(CO)n (n = 9, 8, 7, 6) derivatives: (1) two-electron donor bridging μ-BF groups are highly favorable; (2) four-electron donor bridging η2-μ-BF groups are not found and thus appear to be highly unfavorable. Thus the lowest energy structure of Mn2(BF)(CO)9 is a doubly bridged structure with bridging CO and BF groups, in contrast to the experimentally observed unbridged structure of Mn2(CO)10. The lowest energy structures of Mn2(BF)(CO)8 have either a four-electron donor η2-μ-CO group or a two-electron donor bridging BF group. Similarly the lowest energy structures of the more highly unsaturated Mn2(BF)(CO)n (n = 7, 6) are singlet (for n = 7) or triplet (for n = 6) states in which the BF group is a bridging rather than a terminal ligand. 相似文献
Formation of the linear chain ruthenium and osmium carbonyls by successive linkage of mononuclear [M(CO)4Cl2] units and by opening trinuclear clusters [M3(CO)12] and [FeM2(CO)12] (M = Ru, Os) with chlorine gas have been studied by computational DFT methods. Energetically the formation of dinuclear [M2(CO)8Cl2] from [M(CO)4Cl2] units is the most demanding step. The following chain growth by adding new mononuclear units proceeds more easily with nearly constant energy per step. Cluster opening by chlorine gas to obtain trinuclear [M3(CO)12Cl2] is a facile reaction for both ruthenium and osmium clusters as well as for mixed metal clusters. Mixed metal clusters [FeOs2(CO)12] and [FeRu2(CO)12] open preferably between iron-osmium or iron-ruthenium bonds producing linear trinuclear Fe-M-M-type of compound. In the case of mixed metal Os-Ru clusters, the cleavage of Os-Ru bond is not clearly preferred. Fragmentation of the cluster to shorter units cis(Cl)-[M(CO)4Cl2] or [M2(CO)8Cl2] with equatorial chlorides is highly favorable and competes with the cluster opening. No preferences on the bond type (Os-Ru, Os-Os, or Ru-Ru) that are broken can be found in the case of mixed metal Os-Ru clusters. 相似文献
Theoretical studies on the binuclear cyclopentadienyliron carbonyl thiocarbonyl derivatives Cp2Fe2(CO)2(μ-CS)(μ-CO) and Cp2Fe2(CO)2(μ-CS)2 indicate that the trans and cis isomers are nearly degenerate in energy, consistent with experiment. Structures with bridging CS groups are of lower energy than corresponding structures with bridging CO groups. The corresponding unbridged Cp2Fe2(CS)(CO)3 and Cp2Fe2(CS)2(CO)2 isomers are predicted to lie 11 and 16 kcal/mol, respectively, above their global minima, indicating increasing activation energies for the cis/trans interconversion as bridging CO groups are replaced by bridging CS groups. The unsaturated species Cp2Fe2(μ-CS)(μ-CO)2 and Cp2Fe2(μ-CS)2(μ-CO) are predicted to have triply bridged triplet spin state structures with FeFe double bonds of lengths 2.26 Å, analogous to the experimentally known triplet (Me5C5)2Fe2(μ-CO)3. However, low-lying singlet Cp2Fe2(CS)(CO)2 and Cp2Fe2(CS)2(CO) structures with four-electron donor bridging η2-μ-CS groups and formal Fe-Fe single bonds are also found. The lowest lying Cp2Fe2(CS)(CO) and Cp2Fe2(CS)2 structures have two bridging groups and very short FeFe distances of ∼2.14 Å, suggesting formal triple bonds. Several higher energy four-electron donor η2-μ-CS bridged structures are also found for Cp2Fe2(CS)(CO) and Cp2Fe2(CS)2. In addition, singlet and triplet structures are found for Cp2Fe2(CS)2 in which the two CS ligands have coupled to form a bridging SCCS group with a carbon-carbon bond. Only a η2-μ-CS bridged singlet structure is predicted for Cp2Fe2(CS), rather than the normal bridged structure with a FeFe quadruple bond such as that predicted for the carbonyl analog Cp2Fe2(CO). 相似文献
The fragmentation pathways of (η3-C3H4X)FeCO)2NO, (σ-C3H4X)Fe(CO)2(NO)L, (η3-C3H4X)Fe(CO)(NO)L, (σ-C3H4X)Fe(CO)2(NO)L′, (η3- C3H4X)Fe(CO)(NO)L′, (σ-C3H5)M(CO)5, (η3-C3H5)M(CO)4, (σ-CH2CHC(Me)2)Mn(CO)5, (η3-CH2 CHC(Me)2)Mn(CO)4, (X=2-Cl; L=PPh3; L′= P(OMe)3; M=Mn, Re) have been investigated by mass spectrometry. In the σ derivatives the molecular ion loses CO or the allylic ligand, while in the η3 derivative loss of a CO group is the only fragmentation mode of the molecular ion. Electron impact as well as methane chemical ionization mass spectra have been reported. Kinetic energy release of selected metastable ions indicates that a σ → η3 rearrangement reaction occurs. 相似文献
By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L = (OH)C6H4(CH3)CN(CH2)3NC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV-Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (1) and the red [Cu4(μ-L)2(μ1,1-N3)2(N3)2(H2O)2] (2) crystals show that the coordination environment of the two μ-phenoxo and μ1,1-azido bridged isomorphous tetranuclear CuII complexes are slightly different. Thus, both complexes are formed by very similar building units, although with a significant variation in the bridging Cu-O(phenoxo)-Cu and Cu-N(azido)-Cu bond angles. The consequences of these structural variations on the magnetic properties have been investigated from both the experimental and theoretical points of view by variable temperature magnetic measurements and DFT calculations. 相似文献
The reactions of Fe(CO)3(R-DAB; R1, H(4e)) (1a: R = i-Pr, R1 = H; 1b: R = t-Bu, R1 = H; 1c: R = c-Hex, R1 = H; 1e: R = p-Tol, R1 = H; 1f: R = i-Pr, R1 = Me) with Ru3(CO)12 and of Ru(CO)3(R-DAB; R1, H(4e)) (2a: R = i-Pr, R1 = H; 2d: R = CH(i-Pr)2, R1 = H) with Fe2(CO)9 in refluxing heptane both afforded FeRu(CO)6(R-DAB; R1, H(6e)) (3) in yields between 50 and 65%.The coordination mode of the ligand has been studied by a single crystal X-ray structure determination of FeRu(CO)6(i-Pr-DAB(6e)) (3a). Crystals of 3a are monoclinic, space group P21/a, with four molecules in a unit cell of dimensions: a = 22.436(3), b = 8.136(3), c = 10.266(1) Å and β = 99.57(1)°. The structure was refined to R = 0.049 and Rw = 0.052 using 3045 reflections above the 2.5σ(I) level. The molecule contains an FeRu bond of 2.6602(9) Å, three terminally bonded carbonyls to Fe, three terminally bonded carbonyls to Ru and bridging 6e donating i-Pr-DAB ligand. The i-Pr-DAB ligand is coordinated to Ru via N(1) and N(2) occupying an apical and equatorial site respectively (RuN(1) = 2.138(4) RuN(2) = 2.102(3) Å). The C(2)N(2) moiety of the ligand is η2-coordinated to Fe with C(2) in an apical and N(2) in an equatorial site (FeC(2) = 2.070(5) and FeN(2) = 1.942(3) Å).The 1H and 13C NMR data indicate that in all FeRu(CO)6(R-DAB(6e)) complexes (3a to 3f) exclusively η2-CN coordination to the Fe atom and not to the Ru atom is present irrespective of whether 3 was prepared by reaction of Fe(CO)3(R-DAB(4e)) (1) with Ru3(CO)12 or by reaction of Ru(CO)3(R-DAB(4e)) (2) with Fe2(CO)9. In the case of FeRu(CO)6(i-Pr-DAB; Me, H(6e)) (3f) the NMR data show that only the complex with the C(Me)N moiety of the ligand σ-N coordinated to the Ru atom and the C(H)N moiety η2-coordinated to the Fe atom was formed. Variable temperature NMR experiments up to 140 °C showed that the α-diimine ligand in 3a is stereochemically rigid bonded.FeRu(CO)6(R-DAB(6e)) (3a and 3e) reacted with allene to give FeRu(CO)5(R-DAB(4e))(C3H4) (4a and 4e). A single crystal X-ray structure determination of FeRu(CO)5(i-Pr-DAB(4e))(C3H4) (4a) was performed. Crystals of 4a are triclinic, space group P1, with two molecules in a unit cell of dimensions: a = 9.7882(7), b = 12.2609(9), c = 8.3343(7) Å, α = 99.77(1)°, β = 91.47(1)° and γ = 86.00(1)°. The structure was refined to R = 0.028 and Rw = 0.043 using 4598 reflections above the 2σ(I) level. The molecule contains an FeRu bond of 2.7405(7) Å and three terminally bonded carbonyls to iron. Two carbonyls are terminally bonded to the Ru atom together with a chelating 4e donating i-Pr-DAB ligand [RuN = 2.110(1) (mean)]. The allene ligand is coordinated in an η3-allylic fashion to the Fe atom while the central carbon of the allene moiety is σ-bonded to the Ru atom (FeC(14) = 2.166(3), FeC(15) = 1.970(2), FeC(16) = 2.127(3) and RuC(15) = 2.075(2) Å). The 1H and 13C NMR data show that in solution the coordination modes of the R-DAB and the allene ligands are the same as in the solid state.Thermolysis reactions of 3a with R-DAB or carbodiimides gave decomposition and did not afford C(imine)C(reactant) coupling products. Thermolysis reactions of 3a with M3(CO)12 (M = Ru, Os) and Me3NO gave decomposition. When the reaction of 3a with Me3NO was performed in the presence of dimethylacetylenedicarboxylate (DMADC) the known complex FeRu(CO)4(i-Pr-DAB(8e))(DMADC) (5a) was formed in low yield. In 5a the R-DAB ligand is in the 8e coordination mode with both the imine bonds η2-coordinated to iron. The acetylene ligand is coordinated in a bridging fashion, parallel with the FeRu bond. 相似文献
Various Cr, Mo and W carbonyl complexes of a tridentate ligand containing N and P as donor atoms, bis(2-(diphenylphosphino)ethyl)benzylamine (DPBA), have been synthesized. Reaction of M(CO)6 (M = Cr, Mo and W) with DPBA in a 1:1 mole ratio in toluene or xylene, resulted in the formation of facial and meridional complexes of the type [M(CO)3(DPBA)] (M = Cr, Mo and W). Interaction of Cr(CO)6 or Mo(CO)6 with DPBA and PPh3 in toluene yielded complexes of the composition [Cr(CO)3(DPBA)(PPh3)] and [Mo(CO)2(DPBA)(PPh3)], respectively. However reaction of W(CO)6 with DPBA and PPh3 yielded only [W(CO)3(DPBA)]. Reaction of Cr(CO)6 with DPBA and 1,2-bis(diphenylphosphino)ethane(diphos) in toluene for 24 h resulted in the formation of a mixed ligand complex, [Cr(CO)4(DPBA)(diphos)] where both the ligands coordinate to the metal atom through only one of their donor atoms. A unique binuclear complex of the composition [Mo(CO)2(DPBA)(diphos)]2 resulted, with the tridentate ligand DPBA acting as a bidentate bridging ligand, by the reaction of Mo(CO)6 with DPBA and diphos in refluxing xylene for 24 h. All the complexes are characterized by elemental analysis and infrared spectra. The 31P{1H} and 1H NMR spectral data of the complexes gave valuable information in elucidating the structures of the complexes. The ligand DPBA has found to behave in a triligate monometallic, biligate monometallic, monoligate monometallic and biligate bimetallic manner. 相似文献
The tetrametallic compound [Ir4(μ-1,2-S2C6H4)2(μ-H)2H6(PiPr3)4(NCMe)] (1) has been obtained by treatment of the reactive cationic complex [IrH2(PiPr3)(NCMe)3]BF4 with the benzene-1,2-dithiolate anion. In the solid state, this tetrametallic compound exhibits an irregular nearly planar metal skeleton with the two dithiolate anions bridging the four metal centres from the same side of the tetrametallic plane. Even though all iridium atoms coordinate one PiPr3 ligand, two bridging S atoms and, at least, two hydrides, they show different electronic and coordination environments. This unusual structure is maintained in solution, even after substitution of the labile acetonitrile ligand by other Lewis bases such as ethylene or carbon monoxide. 相似文献
The three-component system consisting of Co4(CO)12, Co2(CO)8 and HCo(CO)4 was analyzed by means of IR spectroscopy. A quantitative method was developed in order to enable the precise calculation of the concentrations of all three compounds simultaneously. The quantitative analysis was based upon the intensity of the bridging CO stretching bands at 1858 cm−1 (A2) and 1867 cm−1 (A1) of the polynuclear carbonyls, and the terminal CO symmetric stretching band of HCo(CO)4 at 2116 cm−1 (A3). The mathematical expression for the concentrations of the three compounds required the precise knowledge of at least one of the four extinction coefficients of either Co4(CO)12, ϵJ1 and ϵJ2 or Co2(CO)8, ϵK1 and ϵK2. The reference extinction coefficient was ϵK2, because Co2(CO)8 was employed as the starting compound in all experiments performed in this study. In order to determine the extinction coefficient of HCo(CO)4 at 2116 cm−1, ϵ3, intensities of this band were plotted as function of the corresponding concentrations of HCo(CO)4, which were calculated by means of the three- component system method; from the slope of the straight line ϵ3 could be directly calculated. 相似文献
The structures and relative energies of the As2Co2(CO)n (n = 6, 5, 4) derivatives are predicted by density functional theory to be analogous to those of the corresponding H2C2Co2(CO)n derivatives. Thus As2Co2(CO)6 is predicted to have three carbonyls on one cobalt atom eclipsed relative to the three carbonyls on the other cobalt atom. The corresponding As2Co2(CO)6 structure with a staggered rather than eclipsed arrangement of the Co(CO)3 units is a transition state rather than a genuine minimum. For As2Co2(CO)5 the structure in which an equatorial group is removed from the As2Co2(CO)6 structure and a singly bridged As2Co2(CO)4(μ-CO) structure are predicted to have essentially the same energies, within <2 kcal/mol. A higher energy As2Co2(CO)5 structure by 9 ± 2 kcal/mol is derived from the As2Co2(CO)6 structure by removal of an axial carbonyl group. The two unbridged As2Co2(CO)5 structures correspond to those observed experimentally in the photolysis of As2Co2(CO)6 in Nujol matrices at low temperatures. In such photolysis experiments the higher energy isomer is produced initially and then converted to the lower energy isomer upon annealing. A singly bridged structure was found for As2Co2(CO)4. The analogous structure was not observed in the previous work with H2C2Co2(CO)4. However, such a H2C2Co(CO)3(μ-CO) structure is found here for the acetylene complex. This singly bridged structure is predicted to lie 1.9 kcal/mol below the H2C2Co2(CO)44-1S structure by the BP86 method but 3.5 kcal/mol above the latter by the B3LYP method. In addition to the singly bridged As2Co2(CO)4 structure, the same six unbridged structures were located for As2Co2(CO)4 that were previously found for H2C2Co2(CO)6. 相似文献
