Transition-metal carbonyl complexes

Trifluorophosphine and carbon monoxide readily undergo ligand-exchange reactions in their transition metal complexes. The close similarity in bonding characteristics of the two ligands toward transition metals has been discussed extensively in several review articles (72,174,272) and the evidence will not be repeated here. Extensive vibrational spectroscopic studies have been made on mixed carbonyl-PF3 metal complexes (72,174) and force constant calculations have been carried out in some cases. 

More recently, the volatility of metal-PF3 complexes, metal carbonyls, and mixed PF3-CO compounds has enabled UV photoelectron spectroscopic studies to be carried out (see Section V), and the data 

Several 19F and 31P NMR studies of mixed PF3-CO transition metal complexes have appeared and the fluxional nature of five-coordinated complexes such as [Fe(PF3)5 II(CO)11] and [CoR/(PF3)4 (CO) ] were among the first examples of this structural type to be studied in detail. So far, structural data are available only for [Mo(PF3)(CO)5] from an electron diffraction study in the gas phase (47). 

Synthetic routes to these complexes are summarized in Table XIII, which also lists the spectroscopic studies that have been made on this class of complexes. The action of PF3 or CO usually under pressure with simultaneous UV irradiation on metal carbonyls or metal trifluorophos-phine complexes, respectively, is of general applicability (method A). More recently, photolysis using a KrF laser has also been utilised, e.g., 

Often because of the close similarity in volatility and solubility of the mixed carbon trifluorophosphine metal complexes the best separative method involves gas chromatography. Vapor pressures and enthalpy of sublimation data for the complexes [M(PF3)(CO)5] (M = Cr, W) are comparable with the values for the corresponding hexacarbonyl complexes. 

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Therefore bonding in PdSiO may be compared to that in typical transition metal carbonyl complexes. 

To date, most of the photochemical data available for transition metal complexes comes from condensed phase studies (1). Recently, the primary photochemistry of a few model transition metal carbonyl complexes has been investigated in gas phase (5.). Studies to date indicate that there are many differences between the reactivity of organometallic species in gas phase (5.6) as conq>ared with matrix (7-10) or solution (11-17) environments. In most cases studied, photoexcitation of isolated transition metal... 

Salmain, M., Vessieres, A., Butler, I., and Jaouen, G. (1991) N-Succinimidyl (4-pentynoate)hexacarbon yldicobalt A transition-metal carbonyl complex having similar uses to the Bolton-Hunter reagent. Bioconjugate Chem. 2, 13-15. 

In these mixtures the catena-tvistibines are by far the most abundant chain species and even under favorable conditions [excess of cyc/6>-(RSb) ] the caten -tetrastibines form only as minor components. Nevertheless, recently the selective extraction and stabilization of these tetrastibines in the coordination sphere of a transition metal carbonyl complex was achieved by reacting mixtures of distibines and cyclostibines with... 

Pensak and McKinney (28) [PM], using this method, have recently reported a systematic study of first-row transition metal carbonyl complexes for which experimental bond distances and angles were reliably reproduced, along with key bond dissociation energies. 

Bodner, G.M., May, M.P., and McKinney, L.E., A Fourier transform carbon-13 NMR study of the electronic effects of phosphorus, arsenic, and antimony ligands in transition-metal carbonyl complexes, Inorg. Chem., 19, 1951, 1980. 

Vibrational Spectra of Transition Metal Carbonyl Complexes Linda M. Haines and M. H. Stiddard... 

Supercritical fluids allow the formation of species that cannot be made in conventional solvents. For example, rj2-H2 complexes have been generated by direct reaction of hydrogen with a transition metal carbonyl complex [10]. In order to isolate these compounds, a continuous flow reactor was used and such compounds could be isolated with surprising ease. 

CO Loss from Transition Metal Carbonyl Complexes... 

High pressure infrared (HP IR) spectroscopy has now been used for over 30 years for the study of homogeneous transition metal catalysed processes. The technique is particularly useful for reactions involving carbon monoxide, for which transition metal carbonyl complexes are key intermediates in the catalytic mechanisms. Such complexes have one or more strong r(CO) absorptions, the frequencies and relative intensities of which provide information about the geometry and electronic character of the metal center. As well as probing the metal species, HP IR spectroscopy can also be used to monitor the depletion and formation of organic reactants and products if they have appropriate IR absorptions. 

The facility of 1H-azepines to form transition metal carbonyl complexes was realized soon after they were first synthesized. Variable temperature HNMR studies on the tricarbonyliron complex formed either by photolysis of 1-ethoxycarbonyl-l//-azepine with tricarbonyliron in THF, or by heating the azepine with nonacarbonyldiiron in hexane, demonstrated that it undergoes rapid reversible valence tautomerism and that there is considerable restricted rotation about the N—CO bond (B-69MI51600). The molecular geometry of the complex has been determined by X-ray analysis (see Section 5.16.2.2). 

Jahn, H. A. Teller, E. Proc. Roy. Soc. bond. A 1937, 161, 220-235. Mckinlay, R. G. Paterson, M. J. The Jahn-Teller Effect in Binary Transition Metal Carbonyl Complexes. In The Jahn-Teller Effect Fundametals and Implications for Physics and Chemistry , Eds. Koppel, H. Yarkony,... 

Hi) Formation of transition metal carbonyl complexes Ashe and Colburn have reported (77JA8099) the synthesis of molybdenum carbonyl complexes of arsenin and antimonin but were unable to prepare bismin complexes because of its lability (Scheme 23). As expected for electron-rich aromatic compounds, both formed six-electron 7r-complexes (113) by a ligand displacement mechanism. Arsenin also forms a two-electron complex (114) analogous to those formed by pyridine, whereas antimonin did not give a similar complex under the conditions of this reaction. 

MAIN GROUP-TRANSITION METAL CARBONYL COMPLEXES... 

Metal carbonyl anions react with main group halides and oxides to yield a number of main-group transition-metal carbonyl complexes in good yields. These complexes serve as starting materials for a number of higher nuclearity cluster complexes. 

Main group-transition metal carbonyl complexes 221... 

Cyclopropylcarbene complexes of the type L M=C(XR )R2 (X = O, S R1 = alkyl, aryl R2 = cyclopropyl) having a stabilizing heteroalkyl (XR1) group on the electrophilic carbene ligand (Scheme 3) have found widespread application in organic synthesis. These so-called Fischer carbene complexes are best known via their group 6 transition metal carbonyl complexes (CO)5M=(OR )R2(M = Cr, Mo, W)132. Much less abundant are the Schrock-type cyclopropylcarbene complexes L M=CR R2 where no heteroatom is bound to the carbene carbon atom133. 

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