Cyclopentadienyl complexes of iron

The isotopic method has been used in conjunction with a flow apparatus by Stranks, to measure the exchange between the cyclopentadienyl complexes of iron (III) and iron (II) in methanol. Separation was based on the insolubility of Fe(C5H5) in petroleum ether at —80 °C. Using Fe(II) and Fe(III) 10 M and short reaction times ( msec), a rate coefficient 8.7 x 10 l.mole .sec at — 75 °C was obtained. The rate of exchange in the presence of chloride ions and inert electrolytes was found to be more rapid. Calculations using Marcus Theory showed reasonable agreement with the experimental observations. In deuterated acetone, line broadening measurements have led to an estimate of this rate coefficient of > 10 l.mole . sec at 26 °C. 

Other rate processes studied include isopropyl group rotation, (529) restricted rotations in phosphine derivatives of cyclopentadienyl complexes of iron and nickel, (530) and ring and nitrogen inversion in (en) complexes of praseodymium. (531) Molecular geometries of molecules in solution can be accurately determined from NMR spectra of the molecules oriented in a nematic phase of a liquid crystalline solvent. The effect of Eu(dpm), on the nematic phase spectrum of pyridine has been examined. The pyridine geometry is unaffected by the LSR. The observed LIS values can be separated into isotropic and anisotropic components. (532)... 

A number of (phosphanylalkyl)cyclopentadienyl complexes of iron and ruthenium were prepared by... 

The Fe—Si bond distances in compounds 3M and 3, 226.4 pm and 228.1 pm respectively, are essentially smaller than the value for the sum of the covalent radii (Z r = 235 pm) and are among the shortest Fe—Si bond lengths observed to date. They do correspond, however, to the general trend observed for relevant bond distances in other cyclopentadienyl complexes of iron [202-206]. The Fe—C and C—O bond distances lie within the range observed for other such measured bond lengths. 

The bis-TT-cyclopentadienyl complexes of iron, cobalt and titanium(Il) chloride may be prepared similarly [23, 24]. 

Another convenient method of preparing this Jt-complex of iron is a two-step process in which the first step involves preparation of cyclopentadienyl Grignard reagent, such as 2,4-cyclopentadienylmagnesium bromide CsHsMgBr which may then be combined with ferric chloride to yield dicyclopen tadienyl iron ... 

Iron cyclopentadienyl complexes of 3-(2-chlorophenyl)propanones are cyclized with hydrazine into 1,4-dihydrocinnoline complexes, demetalated with sodium amide to give 3- or 3,4-disubstituted cinnolines (70-80%) (Scheme 29) (88JHC1107). 

We studied allyliron tricarbonyl halides obtained earlier by Plowman and Stone (427) and by others (428, 429). The compounds were taken because (1) they are complexes of iron, the metal whose cyclopentadienyl derivatives were under thorough study in our laboratories, and (2) octahedral 77-allyl complexes were scarcely known at that time, so it was challenging to compare them with the square-planar 77-allyl complexes which were extensively studied in the USSR as well as elsewhere. 

On the other hand, the cyclopentadienyl derivatives of iron(II), Fe(rj -CsH5)R(CO)2, molybdenum(II), Mo(r -C5H5)R(CO)3, and MR(CO)5, M = Mn, Re, react with sulfur dioxide giving initially the 0-sulfinato complexes, which then rearrange to the S-bonded linkage isomers . ... 

Half-Sandwich Complexes of Iron and Tungsten with Silanol-Functionalized Cyclopentadienyl Ligand ... 

CYCLOPENTADIENYL-FUNCTIONALIZED N-HETEROCYCLIC CARBENE COMPLEXES OF IRON AND NICKEL... 

Many 7i-cyclopentadienyl complexes may be prepared from the reaction of alkali metal cyclopentadienides with ammonia-soluble transition metal salts such as nitrates and thiocyanates in liquid ammonia (2-30). The amine complexes, [M(NH3) ] (C5H5)2, lose ammonia when heated in vacuo, and the uncharged dicyclopentadienyl complexes of iron, cobalt, nickel, chromium, and manganese are obtained. 

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

Experimental Procedure 3.1.2. Preparation of an Iron Vinylidene Complex by Electrophilic Abstraction Carbonyl(Ti -cyclopentadienyl)(dimethylvinylidene)-(triphenylphosphine)iron tetrafluoroborate... 

Reactions of cyclopentadienyl- and (pentmethylcyclopentadienyl)iron dicarbonyl 2-alkynyl complexes as well as cyclopentadienylmolybdenum tricarbonyl 2-alkynyl complexes with 4,5-diphenyl-3,6-dihydro-l,2-dithiin 1-oxide 111 were shown to yield transition metal-substituted five-membered ring thiosulfinate esters 112 in moderate to excellent yields (Scheme 27) <19910M2936, 1989JA8268>. These reactions are formal [3-1-2] cycloadditions. When... 

The first metal-olefin complex was reported in 1827 by Zeise, but, until a few years ago, only palladium(II), platinum(Il), copper(I), silver(I), and mercury(II) were known to form such complexes (67, 188) and the nature of the bonding was not satisfactorily explained until 1951. However, recent work has shown that complexes of unsaturated hydrocarbons with metals of the vanadium, chromium, manganese, iron, and cobalt subgroups can be prepared when the metals are stabilized in a low-valent state by ligands such as carbon monoxide and the cyclopentadienyl anion. The wide variety of hydrocarbons which form complexes includes olefins, conjugated and nonconjugated polyolefins, cyclic polyolefins, and acetylenes. 

---