Unsaturated Metal Carbonyl Research Articles

Into the Role of Unsaturated Trinuclear Metal Carbonyls in the Formation of [M3(2,3-bpp)(CO)10] with M=Ru, Os: A DFT Stability Analysis and Electronic Structure

Into the Role of Unsaturated Trinuclear Metal Carbonyls in the Formation of [M3(2,3-bpp)(CO)10] with M=Ru, Os: A DFT Stability Analysis and Electronic Structure

Joshua S. Figueroa

Joshua S. Figueroa

High‐Level Ab Initio Calculations of Molecular Properties of Chromium Monocarbonyl, CrCO

Chromium monocarbonyl (CrCO) is the simplest unsaturated transition metal carbonyl, and ab initio methods that include a dynamic electron correlation effect are necessary to calculate the molecular properties of CrCO. We employed post Hartree–Fock ab initio methods with various all‐electron basis sets to calculate the molecular properties of CrCO including the molecular structures, vibrational frequencies, and bond dissociation energy. The methods including triple excitation and a quadruple‐ζ level basis set are required to reasonably describe the molecular properties of CrCO. We found that the most efficient combination of theoretical method and basis set for this weakly interacting system is the unrestricted coupled‐cluster singles and doubles with perturbative triples (UCCSD(T)) with the Sapporo‐DKH3‐QZP basis set.

Excited States of the Nickel Carbonyls Ni(CO) and Ni(CO)4: Challenging Molecules for Electronic Structure Theory.

We apply a wide range of correlated electronic structure approaches to the excited states of Ni(CO)4 and Ni(CO) as model complexes of saturated and unsaturated transition metal carbonyls respectively to understand the performance of each method, in addition to setting benchmark data for these metal carbonyls. In particular, we apply the coupled-cluster linear response hierarchy, complete-active-space self-consistent field theory, N-electron valence state multireference perturbation theory, Monte Carlo configuration interaction, and time-dependent density functional theory with a range of functionals and basis sets. We find that although the systems can qualitatively be described by a single configuration, electron correlation effects are sufficiently strong to give large single amplitudes in cluster expansions, which cause spurious solutions to the response equations for the intermediate CCn methods. DFT also performs well if care is taken to choose an appropriate functional, although for Ni(CO) several popular functionals give the incorrect ground spin-state, depending on the amount of Hartree-Fock exchange.

Dynamic Rotation of Bridging Aryl Ligands in Unsaturated Metal Carbonyl Cluster Complexes

Variable-temperature NMR studies of the compound Os3(CO)10(μ-η 1 -C6H5)(μ-AuPPh3 )( 1) have revealed a dynamic process of hindered rotation of the bridging phenyl ligand about the metalmetal bond. The activation parameters for the process, ΔH ⧧ = 73.33(42) kJ/mol and ΔS ⧧ = �2.66(1.25) J/(K mol), were determined by analysis of variable-temperature 1 H NMR spectra. A density functional theory analysis has provided a mechanism that involves a shift of the ligand out of the bridging position with the formation of an agostic interaction of one of the ortho-positioned CH bonds of the phenyl ring to the neighboring metal atom. The related compound Os3(CO)10(μ-η 1 -Py)(μ-AuPPh3 )( 2; Py = 2-C15H9) was synthesized and was found to exhibit a similar rotation of the bridging pyrenyl ligand about the metalmetal bond: ΔH ⧧ = 70.93(61) kJ/mol and ΔS ⧧ = �6.98(1.83) J/(K mol).

Ruthenium and osmium carbonyl nitrosyl complexes: Matrix infrared spectra and density functional calculations for M(CO)2(NO)2 and M(CO)(NO) (M = Ru, Os)

Laser-ablated ruthenium or osmium atom reactions with CO and NO mixtures in solid argon produce unsaturated metal carbonyl nitrosyls including M(CO)(NO) and 18-electron configuration M(CO)2(NO)2 molecules (M=Ru, Os). The observed absorption bands of reaction products are identified by isotopic substitution, isotopic ratios and isotopic distributions (13CO, 15NO, and mixtures). DFT (B3LYP and BP86) vibrational fundamental calculations reproduce observed frequencies and isotopic shifts very well. The bonding and reaction mechanism are discussed.

Prospects for Three-Electron Donor Boronyl (BO) Ligands and Dioxodiborene (B2O2) Ligands as Bridging Groups in Binuclear Iron Carbonyl Derivatives

Recent experimental work (2010) on (Cy(3)P)(2)Pt(BO)Br indicates that the oxygen atom of the boronyl (BO) ligand is more basic than that in the ubiquitous CO ligand. This suggests that bridging BO ligands in unsaturated binuclear metal carbonyl derivatives should readily function as three-electron donor bridging ligands involving both the oxygen and the boron atoms. In this connection, density functional theory shows that three of the four lowest energy singlet Fe(2)(BO)(2)(CO)(7) structures have such a bridging η(2)-μ-BO group as well as a formal Fe-Fe single bond. In addition, all four of the lowest energy singlet Fe(2)(BO)(2)(CO)(6) structures have two bridging η(2)-μ-BO groups and formal Fe-Fe single bonds. Other Fe(2)(BO)(2)(CO)(n) (n = 7, 6) structures are found in which the two BO groups have coupled to form a bridging dioxodiborene (B(2)O(2)) ligand with B-B bonding distances of ~1.84 Å. All of these Fe(2)(μ-B(2)O(2))(CO)(n) structures have long Fe···Fe distances indicating a lack of direct iron-iron bonding. One of the singlet Fe(2)(BO)(2)(CO)(7) structures has such a bridging dioxodiborene ligand with cis stereochemistry functioning as a six-electron donor to the pair of iron atoms. In addition, the lowest energy triplet structures for both Fe(2)(BO)(2)(CO)(7) and Fe(2)(BO)(2)(CO)(6) have bridging dioxodiborene ligands with trans stereochemistry functioning as a four-electron donor to the pair of iron atoms.

Addition of Alkyl Radicals to Transition-Metal-Coordinated CO: Calculation of the Reaction of [Ru(CO)5] and Related Complexes and Relevance to Alkane Carbonylation

Electronic structure methods have been used to study the transition state and products of the reaction between alkyl radicals and CO coordinated in transition-metal complexes. At the B3LYP DFT level, methyl addition to a carbonyl of [Ru(CO)5] or [Ru(CO)3(dmpe)] is calculated to be about 6 kcal/mol more exothermic than addition to free CO. In contrast, methyl addition to [Mo(CO)6] is 12 kcal/mol less exothermic than addition to CO, while the reaction enthalpy of methyl addition to [Pd(CO)4] is comparable to that of free CO. Related results are obtained at the CCSD-T level and for the reactions of the cyclohexyl radical. The transition state for these reactions is characterized by significant distortion of the geometry of the reactant complex, which include lengthening and bending of the M-CO bond, but with negligible C-C bond formation. Accordingly, the activation energy for addition to coordinated carbonyls is 2-10 kcal/mol greater than that of addition to free CO. Additional calculations were also carried out on representative unsaturated metal carbonyls. The calculated results afford an understanding of the mechanism of previously reported photochemical alkane carbonylation systems utilizing d(8)-ML5 metal carbonyls as cocatalysts. In particular, it is strongly indicated that such systems operate via direct attack by an alkyl radical at a CO ligand, a reaction that has not previously been proposed.

Octacarbonyldivanadium: a highly unsaturated binuclear metal carbonyl

The first structural characterization of the highly unsaturated octacarbonyldivanadium, V2(CO)8, is reported using density functional theory (DFT) with the B3LYP and BP86 functionals. Various combinations of vanadium–vanadium multiple bonding, four-electron bridging CO groups, and metal electron configurations less than the 18-electron rare gas configuration are found to accommodate the high unsaturation implied by the V2(CO)8 stoichiometry. Thus, the global minimum for V2(CO)8 is a C2h structure (1) with two four-electron bridging CO groups and a vanadium–vanadium distance of 2.896 (B3LYP) or 2.858 Å (BP86), suggestive of a V–V single bond and thus 16-electron configurations for the vanadium atoms. The next lowest-lying structure (2) for V2(CO)8 at 10.6 (B3LYP) or 12.5 kcal mol−1 (BP86) above the global minimum (1) also has C2h symmetry with two bridging CO groups, but a much shorter vanadium–vanadium distance of 2.440 (B3LYP) or 2.460 Å (BP86), suggestive of a V≡V triple bond. Of similar energy to 2 is a D4d unbridged structure (3) for V2(CO)8 with an extremely short vanadium–vanadium distance of 1.941 (B3LYP) or 1.967 Å (BP86), consistent with, but not proving, the presence of the quintuple bond required to give each vanadium atom the favored 18-electron rare gas electronic configuration. The one other optimized structure for V2(CO)8 within 27 kcal mol−1 of the global minimum and without any imaginary vibrational frequencies is a highly unsymmetrical Cs structure (6) with three very unsymmetrical bridging CO groups and a vanadium–vanadium distance of 2.615 (B3LYP) or 2.509 Å (BP86), suggestive of a V=V double bond.

Detection of free nickel monocarbonyl, NiCO: rotational spectrum and structure.

Unsaturated transition metal carbonyls are important in processes such as organometallic synthesis, homogeneous catalysis, and photochemical decomposition of organometallics. In particular, a metal monocarbonyl offers a zeroth-order model for interpreting the chemisorption of a CO molecule on a metal surface in catalytic activation processes. Quite large numbers of theoretical papers have appeared which predict spectroscopic and structural properties of transition metal carbonyls. The nickel monocarbonyl NiCO has been one of the metal carbonyls most extensively studied by the theoretical calculations. At least 50 theoretical studies have been published on this simplest transition metal carbonyl up to the present time. However, experimental evidence of NiCO is much more sparse than theoretical predictions, and the actual structure of NiCO has never been determined by any experimental methods. This Communication reports the first preparation of free nickel monocarbonyl and observation of its rotational transitions. The NiCO molecule was generated by the sputtering reaction of a Ni cathode in the presence of CO. The accurate bond lengths of Ni-C and C-O were experimentally determined from isotopic data and were compared with the theoretical predictions for the first time.

Reactions of Laser-Ablated Mo and W Atoms, Cations, and Electrons with CO in Excess Neon: Infrared Spectra and Density Functional Calculations on Neutral and Charged Unsaturated Metal Carbonyls

Laser-ablated Mo and W atoms react with CO in excess neon to give the same unsaturated M(CO)3,4,5 carbonyls observed from photodissociation of M(CO)6. The observed neon matrix fundamentals for these M(CO)3,4,5 species bridge previous argon matrix and gas phase values. The M(CO)2 dicarbonyls absorb at 1895.2 and 1884.5 cm-1, and the MCO monocarbonyls absorb at 1881.2 and 1859.9 cm-1 for Mo and W, respectively. The M(CO)1,2+ cations and M(CO)1,2- anions are observed as the ablation process also provides cations and electrons. Density functional theory calculations support the product identifications and vibrational assignments.

Ultrafast Dynamics of Transition Metal Carbonyls. 3. Intracluster Chemistry in [Cr(CO)6]n

We report on one-color femtosecond−pump/probe experiments applied to homogeneous chromium hexacarbonyl clusters which are prepared in a molecular beam. The pump pulse initiates bimolecular intra-cluster reactions by ultrafast photodissociation of a CO ligand from Cr(CO)6 in a 1T1u metal-to-ligand charge-transfer state. The resulting reaction products are detected mass-selectively after multiphoton ionization by the probe pulse. In contrast to nanosecond multiphoton ionization (Peifer, W. R.; Garvey, J. F. Int. J. Mass Spectrom. Ion Processes 1990 102, 1), which exclusively leads to appearance of the Cr+ mass peak, a number of novel species which may serve as interesting model systems for catalysis and surface chemistry are detected. In addition to mononuclear fragments, metal cluster ions, and coordinatively unsaturated polynuclear metal carbonyls, metal oxides and carbides are observed in the femtosecond mass spectra. The appearance of these species can be rationalized by formation of asymmetric π-bridging CO ligands in the neutral manifold. The dynamics extracted from the transients of different reaction products is interpreted using concepts of surface and inorganic cluster chemistry. Ultrafast metal−metal bond formation on a time scale much faster than our laser pulse width (ca. 150 fs) can be observed. Site exchange of CO from terminal to bridging positions on the picosecond time scale is proposed to occur in coordinatively unsaturated polynuclear metal carbonyls. Experiments at different center wavelengths (280 and 262.5 nm) reveal energy-dependent reaction channels which are closed when exciting the clusters at 280 nm. When exciting at 262.5 nm, impulsive formation of the corresponding products and decay on the picosecond time scale is observed.

Photochemistry of (η6-arene)Mo(CO)3 and the Role of Alkane Solvents in Modifying the Reactions of Coordinatively Unsaturated Metal Carbonyl Fragments

The reactions of (η6-arene)Mo(CO)2(Sol) and M(CO)5(Sol) with CO have been studied in a range of alkane solvents (Sol), and the kinetic and activation parameters have been determined (M = Cr, Mo, or W). For M = Cr the ΔH⧧ is constant (22 ± 2 kJ mol-1), while the ΔS⧧ term becomes less negative as the alkane chain length increases. For the larger metals the variation in kinetic and activation parameters is less significant. Solvent displacement by CO involves an interchange mechanism for the Cr system, while for Mo or W complexes the mechanism is more associative in character. The photochemistry of (η6-arene)Mo(CO)3 (arene = benzene, mesitylene, p-xylene, or hexamethylbenzene) compounds was investigated by laser flash photolysis, supported by matrix isolation and time-resolved infrared spectroscopy (TRIR). In contrast to the behavior to the analogous (η6-arene)Cr(CO)3, it is found that the efficiency for photochemical expulsion of CO from (η6-mesitylene)Mo(CO)3 is markedly wavelength dependent (ΦCO = 0.587, ...

Nature of the Carbonyl Semibridge Bond in Coordinatively Unsaturated Metal Carbonyl Compounds. Solvated and Semibridged Forms in Photolysis of MM'(CO)10 (M, M' = Mn, Re) in 3-Methylpentane

Nature of the Carbonyl Semibridge Bond in Coordinatively Unsaturated Metal Carbonyl Compounds. Solvated and Semibridged Forms in Photolysis of MM'(CO)10 (M, M' = Mn, Re) in 3-Methylpentane

Transient Infrared Spectroscopy as a Probe of Coordinatively Unsaturated Metal Carbonyls in the Gas Phase

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransient Infrared Spectroscopy as a Probe of Coordinatively Unsaturated Metal Carbonyls in the Gas PhaseEric WeitzCite this: J. Phys. Chem. 1994, 98, 44, 11256–11264Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://doi.org/10.1021/j100095a005RIGHTS & PERMISSIONSArticle Views222Altmetric-Citations62LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Insertion reactions of metal carbonyl anions with methyl formate in the gas phase as revealed by 13C- and D-labeling

The gas-phase reactions of coordinatively unsaturated metal carbonyl anions (M(CO) − n, M = Cr, Mn, Fe, Co; n = 0–3 and Co(CO) nNO −, n = 0–2) with unlabeled and D- and 13C-labeled methyl formate have been studied with Fourier transform ion cyclotron resonance mass spectrometry. The reactions proceed in most instances by loss of one or more CO molecules from the collision complex. In the reactions of the dicarbonyl and tricarbonyl anions with H 13COOCH 3, part of the eliminated carbon monoxide molecules contain the label revealing the occurrence of initial insertion of the metal center into the bonds adjacent to the carbonyl function of the substrate with formation of five- or six-coordinate intermediates, respectively. In addition, the Mn(CO) − 3, Fe(CO) − 2, and Co(CO) − 2 ions react by the loss of methanol and a [C,H 2,O] neutral species. The D- and 13C-labeling show that methanol is expelled in a reductive elimination from a five- or six-coordinate species, whereas the [C,H 2,O] loss is a more complex process possibly involving the competing losses of formaldehyde and CO + H 2. In the reaction of Fe(CO) − 3 with H 13COOCH 3, a facile consecutive exchange of all three CO ligands of the reactant ion for 13CO is observed. This novel reaction appears to involve initial insertion into the H 13COOCH 3-bond followed by facile hydrogen shifts from the formyl ligand to a CO ligand prior to the loss of unlabeled methyl formate.

The initial photochemical process of triosmiumdodecacarbonyl adsorbed on the surface of silica as studied by picosecond diffuse reflectance laser photolysis and matrix isolation

The transient absorption spectrum of the coordinatively unsaturated trinuclear osmium carbonyl cluster Os 3(CO) 11 adsorbed on the surface of silica was observed for the first time by the ps time-resolved diffuse reflectance laser photolysis of Os 3(CO) 12. The present results demonstrated that Os 3(CO) 11 is the photoprimary product responsible for the net oxidative addition of surface hydroxyls to Os 3(CO) 12 adsorbed on the surface of silica to form the surface attached trinuclear species HOs 3(CO) 10-OSi. It was revealed that the addition of surface hydroxyls to Os 3(CO) 11 is completed within the time of our instrumental response (⩽35 ps), which is comparable to the coordination of solvent to coordinatively unsaturated metal carbonyls.

Formation of a stabilized coordinatively unsaturated metal carbonyl cluster, H2Ru4(CO)12, by photochemical reaction of H2Ru4(CO)13 adsorbed on the surface of silica

The photochemical formation of coordinatively unsaturated metal carbonyl clusters on the surface of metal oxide supports has the potential of leading to interesting new materials that can be used as selective catalysts. In line with the authors' work on this theme, the photochemical reaction of dihydrotetraruthenium tridecacarbonyl, H[sub 2]Ru[sub 4](CO)[sub 13], adsorbed on the surface of silica was investigated by DRS UV-visible, FT-IR, and EXAFS spectroscopies. When irradiated by UV-visible light, H[sub 2]Ru[sub 4](CO)[sub 13] loses one carbon monoxide ligand, producing selectively a coordinatively unsaturated H[sub 2]Ru[sub 4](CO)[sub 12] on the surface of silica. The initial photoproduct, H[sub 2]Ru[sub 4](CO)[sub 12], is interacting weakly with surface hydroxyl groups, which are the only functionality available to act as a stabilizing ligand, and the dissociated carbon monoxide is lost from the surface. This process prevents secondary reactions, thus leading to the selective formation and stabilization of the coordinatively unsaturated H[sub 2]Ru[sub 4](CO)[sub 12], which is unstable in solutions and undergoes secondary reactions. 20 refs., 4 figs., 2 tabs.

Branching ratios and bond dissociation energies from the excimer laser photolysis of group 6 metal carbonyls

Photolysis of the group 6 (Cr, Mo, W) metal carbonyls in the gas phase, at excimer laser wavelengths, may lead to more than one primary product. Branching ratios between these products have been measured as a function of photolysis wavelength, buffer gas pressure, and temperature using time-resolved infrared spectroscopy. The results are modeled using a sequential dissociation mechanism in which branching ratios are determined by competition between unimolecular dissociation and collisional relaxation. The sensitivity of the results to thermochemical input parameters and assumptions concerning energy disposal mechanisms is discussed. Under qualified assumptions the branching ratio measurements provide estimates for CO bond dissociation energies for coordinatively unsaturated metal carbonyls. For Mo and W the individual bond dissociation energies are close to the average values but for Cr the first three ligands coordinated are significantly less strongly bound than the last three. This finding is discussed in terms of recent ab initio calculations on bonding in metal carbonyls.

A study of the thermal and photochemical reactions of the group 6 metal carbonyls with organic polymer supports

The synthesis of organic polymers containing metal carbonyl moieties is described. The reaction of [Mo(CO) 4(bipy)] with poly-4-vinylpyridine proceeds smoothly to give [Mo(CO) 3(bipy)(poly-4-vinylpyridine)] which has a fac configuration. The thermal chemistry of a variety of polymer-bound metal carbonyl compounds is also presented, as is evidence for the formation of [W(CO) 4(poly-4-vinylpyridinestyrene)] from [W(CO) 5(poly-4-vinylpyridinestyrene)]. Included is evidence for the decarbonylation of polymer-bound metal compounds resulting in polymers which contain fully decarbonylated metal centres. Preliminary photochemical investigations indicate the generation of active coordinatively unsaturated metal carbonyl species in polymer matrices at low temperatures.