In metal carbonyl derivatives

The metal-n-cyclopenladienyl bond is somewhat stronger in n-cyclo-pentadienyl derivatives than the metal-carbon bond in metal carbonyl derivatives. However, stepwise loss of 7t-cyclopentadienyl ligands occurs in the mass spectra of 7t-cyclopentadienyl derivatives 24>. The following fragmentation of ferrocene is particularly important because of the occurrence of ferrocene as a pyrolysis product in numerous mass spectra ... 

The possibility of ir-bond interactions in metal carbonyl derivatives of phosphorus compounds has received little attention in the literature, and experiments with purely ir-bonding ligands are to some extent limited by the difficulty of introducing them into carbonyl complexes. The (T-inductive effect of a ligand L on its neighbours in an octahedral complex [LM(C0)5] has been assumed to be isotropic (that is equal for ligands cis and trans to L), but there is no symmetry requirement that this should be so. Thus, at present, it is not known whether... 

Sometimes mercury derivatives formed in the preparation of alkali metal carbonyls by reduction with sodium amalgam are potential contaminants in metal carbonyl derivatives prepared from the resulting sodium compounds. Moreover, in large-scale preparations the quantity of mercury required for the dilute amalgams can be very large and thus inconvenient. It is possible to avoid the presence of mercury in reductions of metal carbonyls such as Mn2(CO)io and Co2(CO)g by the use of lithium wire in tetrahydrofuran 38). 

Mossbauer spectroscopy has not been noted in this report for some years, so it was of some interest to find that Ishiguro and co-workers have produced Sb, Fe and spectra in a detailed study on antimony-transition metal bonds in metal carbonyl derivatives of tertiary stibines. Finally, in this section, Beyer and Leary comment on energy-resolved collision-induced dissociation of Fc2(CO)/ (y = 1-9). 

The preparation of 5-ACETYL-l,2,3,4,5-PENTAMETHYLCYCLO-PENTADIENE is of value in the synthesis of pentamethyleyclo-pentadiene and many pentamethylcyclopentadienyl metal carbonyl derivatives that are more soluble in organic solvents than those derived from cyclopentadiene. Simple preparations of 5,6-DIHYDRO-2-PYRAN-2-0NE and 2-//-PYRAN-2-ONE make these hitherto rather inaccessible intermediates available for cycloaddition and other reactions. The already broad scope of the Michael reaction has been widened further by including an efficient preparation of ETHYL (E)-3-NITROACRYLATE. Workers in the field of heterocyclic chemistry will find a simplified method for the preparation of 2,3,4,5-TETRA-HYDROPYRIDINE of help. 

The Importance of Reactions of Oxygen Bases with Metal Carbonyl Derivatives in Catalysis... 

In many instances it is not necessary to isolate the acetonitrile complex or to carry out the reaction in acetonitrile. The use of amine oxide as a means of displacing carbonyl groups in metal carbonyls is well documented, and reaction proceeds smoothly with the carbonyl in the presence of a variety of ligands—e.g., ethylene or pyridine—to yield the monosubstituted derivatives. The advantage of the acetonitrile adducts is the stability of the compounds and the reactivity of the amine oxide toward acidic ligands. 

The IR spectra of a variety of metal carbonyl derivatives (and [Fe(CN)5NO]2— and NJ salts) under high pressure. Little change in CO symmetry is generally observed... 

Thallium(i) salts have long been used in reactions with organic and organometallic halide complexes as a means of activating the halide by removal as insoluble T1X. However, the thallium ions proved not to be innocent bystanders, and numerous examples were reported in COMC (1995) where the metal-bound thallium complexes were formed. Deliberate reactions of thallium(i) and thallium(m) salts with metal carbonyl anions have yielded a variety of complexes of the form T1 MLJ3. In the past decade, new examples of metal carbonyl derivatives of thallium have been prepared (see Table 2). In addition, the propensity for Tl+ to form adducts with 16-electron noble metal complexes has been exploited. 

Whereas a large number of metal-sulfur clusters are present in nature, carbonyl clusters are exclusively products of chemical synthesis. They have been widely used in industrial catalytic processes17 and some of these processes are triggered by the redox aptitude of these species.lc g As for the metal-sulfur clusters, we will briefly discuss their structures and their propensity to donate/accept electrons in order of increasing nuclearity. We will consider only homonuclear and homoleptic metal-carbonyl derivatives. However, it is noted that heteronuclear derivatives are gaining considerable interest due to the synergistic effect of metal-metal bonds possessing a polar character.lc,ld... 

The fragmentation of metal carbonyl derivatives is characterized by successive loss of carbonyl groups, but in some cases all possible losses of CO are not observed. For [(CoF6)2PFe(CO)3]2, in addition to the parent ion, there are peaks corresponding to the loss of 1, 2, 3, 5, and 6-carbonyl groups, but for reasons which are not clear, the loss of 4 is not observed (90) (Fig. 5). 

Several cyclopentadienyl(alkyl)metal carbonyl derivatives have reacted with acetylenes. In some examples, insertion reactions may also be involved, although the mechanisms have not been investigated. Cyclopentadienyl(methyl)iron dicarbonyl with diphenylacetylene gave a 10% yield of cyclopen tadienyltetra-phenylcyclopentadienyliron 71). 

In the course of a study of the formation of fluorophosphoranes from chloro-phosphines (22) we observed one exception in the compound chloromethyldi-chlorophosphine, which reacted smoothly with antimony trifluoride to give the flammable fluorophosphine, C1CH2PF2, under conditions where many other chloro-phosphines were invariably converted into fluorophosphoranes. As this fluorophosphine is readily available, its interaction with a metal carbonyl derivative was studied, and cycloheptatriene molybdenum tricarbonyl, obtained from the reaction of molybdenum hexacarbonyl with cycloheptatriene (I, 2), was chosen as a starting compound. 

Caution. Pentacarbonylmethylrhenium is a volatile metal carbonyl derivative. Metal carbonyls usually are very toxic and must be handled in a well-ventilated hood. 

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