Mass spectrometry of π-complexes of transition metals : XII. Ferrocenyl and cymantrenyl derivatives of chalcones

The main processes of the electron-impact induced fragmentation of the ferrocenyl and cymantrenyl analogues of chalcones RCOCH=CHR′ (R, R′ = C₅H₄FeC₅H₅, C₅H₄Mn(CO)₃, or aryl) involve a cleavage of the metalligand bond. A “chalcone” mode of fragmentation is weakly pronounced, due to the fact that the positive charge is localized preferably on the metal atom.     

Dynamics of photochemical reactions: Simulation by quantum calculations for transition metal hydrides

The photodissociation dynamics of some organometallic molecules in the lowest repulsive electronically states are reported for the following concurrent primary reactions: (i) the homolysis of a metal–hydrogen bond vs. the heterolytic loss of a carbonyl ligand in HCo(CO)₄; (ii) the photoinduced elimination of molecular hydrogen vs. the loss of a carbonyl ligand in H₂Fe(CO)₄; and (iii) the photoinduced elimination of molecular hydrogen vs. the loss of a mesithylene ligand in H₂Os(CO)Mes (Mes = C₆H₃(CH₃))₃. The dynamics are simulated quantum mechanically using a time-dependent wavepacket propagation technique on potential energy surfaces obtained from CASSCF /CCI calculations for HCo(CO)₄ and H₂Fe(CO)₄ and from SCF -INO /MRCI calculations for H₂Os(CO)Mes. This approach gives a rather detailed view of some important elementary processes that contribute to the photochemistry of these complexes. The nature of the photoactive excited states is determined without ambiguity, as well as the time scales, the branching ratio of the different primary dissociation pathways, and some features of the absorption spectra. © 1994 John Wiley & Sons, Inc.     

Electron-impact studies of organometallic molecules—X. Some simple transition metal fluorocarbon complexes

The mass spectra of several fluoroalkyl, fluoroalkenyl and fluoroacyl complexes of manganese, rhenium, iron and ruthenium carbonyls are described. After loss of carbonyl groups, fluoroalkyl compounds eliminate an olefin, with formation of metal halide species. A trifluorovinyl complex shows a novel elimination of a carbon atom to give an ion postulated to be a difluorocarbene-metal fluoride; the occurrence of difluorocarbene-metal ions in the spectra of some related complexes is also discussed. The spectra of the acyl complexes show little evidence of elimination of the acyl carbonyl group; the major process is fission of the CO? R_f bond with loss of a fluoroalkyl radical and formation of the cationic metal carbonyl, e.g. π-C₅H₅M(CO)₃⁺ (M ? Fe or Ru). The relevance of thermal or photochemical model reactions to processes occurring in the mass spectrometer is discussed.     

On the role of the indenyl effect in controlling intramolecular hydride transfer in iron carbonyl complexes

Density functional theory reveals multiple pathways for intramolecular hydride transfer in the cyclopentadienyl and indenyl species (η⁵-C₅H₅)Fe(CO)₃H and (η⁵-C₉H₇)Fe(CO)₃H. The ability of the indenyl ligand to undergo facile η⁵- to η³-‘ring slippage’ stabilises the isomer where the hydride is bonded directly to the metal, which opens up a low-energy pathway for hydride transfer from CO to metal.     

Electron-impact studies of organometallic molecules—VII. Some transition metal complexes derived from 3,3,3-trifluoroprop-1-yne

The mass spectra of ten complexes derived from 3,3,3-trifluoroprop-1-yne, namely (CF₃C?CH)CO₂(CO)₆, (CF₃C?CH) [π? C₅H₅Ni]₂, (CF₃C?CH)₃Co₂(CO)₄, CF₃CH₂C[Co(CO)₃]₃, are discussed in terms of their structures. The major processes observed can be satisfactorily explained in terms of (i) loss of carbonyl groups, if present; (ii) loss of one fluorine atom from the parention (iii) elimination of neutral metal fluorides, with ligand transfer reactions in the case of the iron complexes; (iv) elimination of neutral fluorocarbon molecules.     

Reactions of (η5-C5H5)Fe(CO)2(η1-C5H5) with phosphorus donor ligands

The course of the reaction of (η⁵-C₅H₅)Fe(CO)₂(η¹-C₅H₅) with phosphorus donor ligands depends strongly on the nature of the ligand; products derived from an Arbuzov-like rearrangement or from reduction have been found as well as the expected simple substitution product. The dynamic PMR behavior of (η⁵-C₅H₅)Fe(CO) (P(OPh)₃) (η¹-C₅H₅) has been examined.     

The reactivity of complexed carbocycles : XII. Neutral dimetallic complexes with bridging cyclooctatetraene. X-ray structure of μ-[1–4:5–8η-cyclooctatetraene]cyclopentadienylcobalt-tricarbonylmolybdenum (CoMo)

The reaction of CpCoC₈H₈ with (diglyme)Mo(CO)₃, (CH₃CN)₃Cr(CO)₃ and (DMF)₃W(CO)₃ yields dimetallic complexes CpCoC₈H₈M(CO)₃ which contain bridging fluctional cyclooctatetraene. The electron deficiency of the Mo(CO)₃ groups relative to CpCo is believed to be balanced by a π-donor metal—metal bond. This is indicated by an unusually low absorption band in the IR spectrum, and by the X-ray structure of the CoMo dimer, which shows a shortened MoCO bond trans to the metal—metal bond. A further product is the nonfluctional dimer CpCoC₈H₈Mo(CO)₄, in which cyclooctatetraene retains a rigid “tub” conformation. Reaction of C₈H₈Fe(CO)₃ with (diglyme)Mo(CO)₃ also yields a dimeric product (CO)₃FeC₈H₈Mo(CO)₃ with a fluctional bridge ligand.     

Acylation of pyrrolyltricarbonylmanganese. Structure of the acylation product

The acylation of pyrrolyltricarbonylmanganese (PTM) is studied. The reaction proceeds in an unusual manner; introduction of an acetyl group into the α-position of the PTM pyrrolyl ligand is accompanied by extensive rearrangement of bonds resulting in the formation of a binuclear complex (π-C₄H₄N)Mn(CO)₃(CH₃COC₄H₃N)Mn(CO)₃ (I)Coordination of the acetylpyrrolyl ligand to the manganese atom is of the chelate type and involves atoms of heterocyclic nitrogen and of acetyl oxygen. The ligand, therefore, is not a five-electron but a three-electron donor. The manganese atom is additionally coordinated to three carbonyl groups and one molecule of the initial PTM (by a donor—acceptor bond through a nitrogen atom), thus acquiring a 18-electron shell. A scheme for complex I formation is proposed.     

A kinetic and spectroscopic study of the interaction between a M(CO)5 (M=Cr, W) fragment and ethyl diazoacetate

The reaction between Cr(CO)₅[C₆H₆] and ethyl diazoacetate (EDA) has been studied using the technique of laser flash photolysis. Results indicate that the Cr(CO)₅ fragment reacts very rapidly with the EDA ligand. Low temperature spectroscopic studies suggest that in the case of W(CO)₅, and by analogy also in the case of Cr(CO)₅, the initial adduct between the pentacarbonyl fragment and EDA is one where the oxygen atom of the diazocarbonyl ligand is bound to the metal center. This kinetic product is then converted to a thermodynamically favored complex which is tentatively assigned as the nitrogen bound W(CO)₅-EDA complex that appears to be stable at r.t.     

Mass spectra of organometallic compounds—IX: Compounds with metal-metal bonds

The mass spectra of the following compounds have been investigated: (i) The organotin derivatives (CH₃)₃SnMo(CO)₃C₅H₅ and (CH₃)₃SnNCW(CO)₅; (ii) The mercury derivatives Hg[Mn(CO)₅]₂, Hg[Co(CO)₄]₂, Hg[Mo(CO)₃C₅H₅]₂ and ClHgMo(CO)₃C₅H₅; (iii) The polynuclear cyclopentadienyl metal derivatives [C₅H₅Ru(CO)₂]₂, [C₅H₅Cr(CO)₃]₂, [C₅H₅Cr(NO)₂]₂ and [C₅H₅Fe-CO]₄; (iv) The trinuclear cobalt carbonyl derivatives YCCo₃(CO)₉ (Y = Cl and CH₃); (v) The binuclear triene-iron carbonyl derivatives C₄H₄Fe₂(CO)₆ and C₈H₁₀Fe₂(CO)₆. The mass spectra of the trimethyltin derivatives exhibited stepwise loss of methyl groups as well as of carbonyl groups. The mass spectra of the mercury derivatives exhibited the facile loss of mercury. The mass spectrum of [C₅H₅Cr(CO)₃]₂ indicated a very weak chromium-chromium bond since it exhibited no ion containing two chromium atoms. The mass spectrum of the nitrosyl derivative [C₅H₅Cr(NO)₂]₂ exhibited the stepwise loss of its four nitrosyl groups. The mass spectrum of [C₅H₅FeCO]₄ was rather complex and exhibited a variety of unusual processes including eliminations of neutral Fe and C₅H₅Fe fragments. Unusual ions observed in the mass spectrum of CH₃CCo₃(CO)₉ include the bare polymetallic ions [Co_n]⁺ (n = 3 and 2). Many examples of the elimination of neutral CO, C₂H₂ and H₂ fragments were noted in this work.     

Cumulated double bond systems as ligands : V. Dialkylsulfurdiimine compounds M(CO)4(RNSNR) (M = Cr,Mo, W) and M(CO)5(RNSNR) (M = Cr,W); structural,spectroscopic and fluxional properties.

The preparation and properties are reported of M(CO)₄(RNSNR) (M = Cr, Mo, W; R = i-Pr, t-Bu), in which the ligand is bidentate and in the trans,trans configuration, and of M(CO)₅(RNSNR) (M = CR, W; R = Et, i-Pr) in which the sulfurdiimine is monodentate and in the cis,trans configuration. In both cases the ligand is linked to the metal atom via the N-atom(s). With M(CO)₅(MeNSNMe) a second isomer is found in which the sulfurdiimine is probably bonded via the S-atom to the metal. All the pentacarbonyl compounds are fluxional; this is attributed to a gliding movement of the metal atom along the NSN system.Both W(CO)₄(t-BuNSN-tBu) and W(CO)₅(MeNSNMe) show vibronic coupling of metal to ligand charge transfer transitions with sulfurdiimine vibrations, as shown with Resonance Raman, but only for W(CO)₅(MeNSNMe) also with the symmetric mode of the equatorial carbonyl groups. The metalsulfurdiimine bond appears to be weak for M(CO)₅(RNSNR), but strong for M(CO)₄(RNSNR).     

Übergangsmetall-substituierte phosphane,arsane und stibane : XXV. C5H5(CO)2[P(OMe)3]M-substituierte dioxaphospholane und dioxarsolane; stereochemische evidenz für den intermolekularen ablauf einer isomerisierung unter methylgruppenverschiebung

2-C₅H₅(CO)₂[P(OMe)₃]Mo(W)-substituted 4,4,5,5-tetramethyl-1,3,2-dioxarsolanes and -dioxaphospholanes (Ia–Ic) are obtained from C₅H₅(CO)₃M derivatives via CO/P(OMe)₃ exchange. In all cases the phosphite ligand appears trans to the σ-bonded arsenic heterocycle, which prefers a conformation with the transition metal group in an axial position. The dioxaphospholane-metal (Ia) undergoes isomerization with alkyl migration at 0°C, which due to stereochemical reasons can only occur by an intermolecular mechanism.     

Rearrangements accompanying the fragmentation of ionized 1-phenylalkan-1-ols

Some aspects of the fragmentation sequence of 1-phenylalkan-1-ols (C₆H₅CH(OH)R), which consists of the loss of R˙ followed by the elimination of CO and subsequently of H₂, are discussed. Labelling studies and collision activation data of reference compounds allow a mechanism to be proposed for this rearrangement.     

A zwitterionic triosmium cluster bearing a metallated azulene ligand coordinated perpendicularly as an alkylidene bridge

The cluster [Os₃(CO)₁₀(MeCN)₂] reacts readily with azulene in refluxing cyclohexane to give the oxidative addition product [Os₃(μ-H)(μ₂-η¹-C₁₀H₇)(CO)₁₀] 1 which was shown by its X-ray crystal structure to contain the C₅ ring of the azulenyl ligand bonded through a single carbon atom at the 1-position. We propose that the compound is zwitterionic, with the 7-membered ring a tropylium cation and the 5-membered ring coordinated as a μ-alkylidene to the metal cluster, which carries a formal negative charge. Thermal loss of one CO ligand leads by further oxidative addition to the known cluster [Os₃(μ-H)₂(μ₃-η¹:η¹:η¹-C₁₀H₆)(CO)₉] 2.     

Stereoselektive Hydrid-Addition an von N-Methylbenzimidchlorid abgeleitete Carbenchelatkomplexe

Upon reaction with NaBH₄ the carbene chelates [C₅H₅(CO)_xMC(C₆H₅N(CH₃)C(C₆H₅)N(CH₃)]PF₆ (I,M = Mo, x = 2; II,M = Fe, x = 1) are reduced at the carbene carbon with formation of the neutral compounds C₅H₅(CO)_xMC(H)(C₆H₅)N(CH₃)C(C₆H₅)N(CH₃) (III and IV). Depending on the orientation of the incoming H substituent with respect to the C₅H₅ ligand two different isomers A and B are obtained which can be separated by column chromatography. Whereas the H^? addition to the Fe compound II is almost stereospecific (formation of 95% IVB), the stereoselectivity of the H^? addition to the Mo compound I is influenced by a competitive metal centered rearrangement of III in opposite direction. The approach to the equilibrium IIIA/IIIB 85/15 can be measured by ¹H NMR spectroscopy (ΔG³₃₂₈ 26.6 kcal/mol).     

Double Carbonyl Substitution in [BrMn(CO)5]: Reaction with Benzoylhydrazine and Synthesis of fac‐[Mn(Br)(CO)3(BHD)]·2THF (BHD = OC(Ph)—NH—NH2)

[BrMn(CO)₅] reacts with benzoylhydrazine in THF occurring substitution of two CO groups by a Metal‐ligand ring to give fac‐[Mn(Br)(CO)₃(BHD)]·2THF (BHD = C₆H₅CONHNH₂). The novel compound shows a distorted octahedral arrangement at the manganese atom, with three nearly linear carbonyl ligands in a fac arrangement, illustrating another example that the CO group in position trans to the bromine ligand in [BrMn(CO)₅] presents the most intensive metal‐CO backbonding effect of all the CO groups of the parent complex, leading to the formation of a facial (and not meridional) isomer, even in the presence of a bidentate ligand like benzydrazide. X‐ray measures of yellow crystals showed that the title complex belong to space group P2₁/c, with the asymmetric unit containing one crystallographically independent [Mn(Br)(CO)₃(BHD)] complex and two tetrahydrofurane solvate molecules. The new compound represents heretofore the unique occurrence of the complexing single bidentate ligand ‐O=C(Ph)‐N(H)‐N(H)₂‐ with an octahedral coordination at the Mn^I atom supported chiefly by carbonyl groups.     

Binuclear metal carbonyl dab complexes : II. The syntheses and coordination properties of Mn(CO)5M′(CO)3DAB (M′ = Mn,Re; DAB = 1,4-diazabutadiene)

Mn(CO)₅M′(CO)₃DAB complexes (M′ = Mn, Re; DAB = R₁N=C(R₂)-C(R′₂)=NR₁) can be easily obtained from the reaction between Mn(CO)₅^? and M′(CO)₃X(DAB) (M′ = Mn, Re; X = Cl, Br, I). The complexes are formed by a nucleophilic mechanism, while a redistribution is responsible for the formation of a small amount of Mn₂(CO)₁₀.A diastereotopic effect can be observed in the ¹H and ¹³C NMR spectra of complexes having isopropyl groups attached to the DAB ligand skeleton. A comparison is made with mononuclear complexes of the same symmetry, and the chemical shift differences for the methyl groups strongly depend on the substituent on the central metal responsible for the asymmetry.The low temperature enhancement of the σ → σ^★ transition localised on the metal—metal bond, which is normally observed for this type of compounds, was not observed for the Mn(CO)₅M′(CO)₃(DAB) complexes. The metal—metal bond can be activated by irradiating at the wave lengths associated with the CT transitions between the metal and the DAB ligand. Metal—metal bond cleavage occurs and Mn₂(CO)₁₀ is formed.     

Molecular structure of π-C5H5NiFe(CO)3Ph3PCCH

The mixed metal complex π-C₅H₅NiFe(CO)₃Ph₃PCCH, obtained from the reaction of π-C₅H₅Ni(PPh₃)CCH with Fe₂(CO)₉, is shown by an X-ray diffraction study to contain the ethynyltriphenylphosphonium group as the bridging ligand. Based on this structure, new reactions of [Ph₃PCCPh]Br with some organometallic compounds have been attempted from which π-C₅H₅NiFe(CO)₃(Ph₃PC₂Ph) and CoFe(CO)₆(Ph₃PC₂Ph) can be obtained.     

A Bimetallic Iron–Nickel Cluster from the Reaction of Nickelocene with a Pentairon Carbonyl Carbide Cluster Complex

The new bimetallic Fe–Ni carbide containing cluster complex, Fe₄Ni(Cp)₂(CO)₁₀(μ₅-C), 4 was afforded by metal–metal exchange and metal cluster rearrangement processes in the reaction of Fe₅(μ₅-C)(CO)₁₅, 1, with NiCp₂ at 80 °C. A minor product Fe₅(Cp)₂(CO)₁₀(μ₅-C), 5, was also obtained from this reaction which contains no nickel and is a di-Cp substituted derivative of 1. Both compounds were characterized by a combination of IR, ¹H NMR, mass spectrometry, elemental and single crystal X-ray diffraction analyses. Compound 4 consists of an open Fe₄Ni(μ₅-C) cluster framework with a carbide ligand where one iron atom bridges a butterfly arrangement of one nickel and three iron atoms.     

Mass spectrometry of metal compounds: II—mass spectrometric studies of [CF3EMn(CO)4]2, [CF3EFe(CO)3]2 (E = S,Se), CF3SeFe(CO)2C5H5 and CF3SCr(NO)2C5H5

The electron impact induced mass spectra of [CF₃SMn(CO)₄]₂, [CF₃SeMn(CO)₄]₂, [CF₃SFe(CO)₃]₂, [CF₃SeFe(CO)₃]₂, CF₃SeFe(CO)₂C₅H₅ and CF₃SCr(NO)₂C₅H₅ are reported. These compounds exhibit weak molecular ion peaks and undergo preferential loss of CO or NO groups. The CO or NO free fragments suffer typical loss of ECF₂(E = S, Se) with the simultaneous shift of F from carbon to metal. The ions [FFeC₅H₅]⁺ and [FCrC₅H₅]⁺ in the spectra of the cyclopentadienyl compounds prefer expulsion of π-cyclopentadienyls. The pyrolysis effects on the spectra of the compounds have been studied. An increase in temperature eases the expulsion of ECF₂ groups from all the compounds and favors the formation of [Fe(C₅H₅)₂]⁺ and [Cr(C₅H₅)₂]⁺ in the cyclopentadienyl compounds.