Methylcyclopentadienyl complex

All these complexes react further with CO2 to form the corresponding N,0-bound carbamate complexes, which, in turn, extrude Bu NCO (above —25 °C for the methylcyclopentadienyl complexes and at room temperature in the case of the... 

A titanium complex with a pyrazolylborate ligand was studied by Campbell and Malanga [19]. Similarities between the cyclopentadienyl ligand and the hydridotris(pyrazolyl)borate ligand have been noted for transition metal complexes. Catalyst efficiencies are much lower than those of the analogous penta-methylcyclopentadienyl complexes. 

Green and Pardy prepared [Co(Ti -C5Me4Et)(Ti -C2H4)2] by the sodium-amalgam reduction of [ CoCl2(T) -CjMc4Et) ] under ethylene (toluene, 110°)- The penta-methylcyclopentadienyl complex described here offers several advantages it is a crystalline solid rather than an oil compounds derived from [Co(-n -CsMes)(V 2114)2] by displacement of ethylene are frequently solids also and the H nmr is simpler. 

After evaporation of ammonia the compounds remain as solvate complexes Cp2Ln(NH3). However, heating of them in vacuum at 120-200°C leads to complete removing of NH3. The methylcyclopentadienyl complex (MeC5H4)2Yb(DME) has been prepared similarly [26], Samarium complexes can not be used in this route since samarium does not dissolve in liquid ammonia. 

The first isolable alkenetitanium complex, the bis(pentamethylcyclopentadienyl)-titanium—ethylene complex 5, was prepared by Bercaw et al. by reduction of bis(penta-methylcyclopentadienyl)titanium dichloride in toluene with sodium amalgam under an atmosphere of ethylene (ca. 700 Torr) or from ( (n-C5Mc5)2Ti 2(fJ-N2)2 by treatment with ethylene [42], X-ray crystal structure analyses of 5 and of the ethylenebis(aryloxy)trimethyl-phosphanyltitanium complex 6 [53] revealed that the coordination of ethylene causes a substantial increase in the carbon—carbon double bond length from 1.337(2) A in free ethylene to 1.438(5) A and 1.425(3) A, respectively. Considerable bending of the hydrogen atoms out of the plane of the ethylene molecule is also observed. By comparison with structural data for other ethylene complexes and three-membered heterocyclic compounds, the structures of 5 and 6 would appear to be intermediate along the continuum between a Ti(11)-ethylene (4A) and a Ti(IV)-metallacyclopropane (4B) (Scheme 11.1) as... 

This reaction exclusively leads to hydrides where hydrogen is cis to silicon or germanium and which are identical to those obtained by oxidative addition of Si-H or Ge-H complexes to (i/ -methylcyclopentadienyl)tricarbonylmanganese. 

The compounds Ln(C5H5)2Cl also have been made only with the lanthanides above samarium (772). These compounds are stable in the absence of air and moisture, sublime near 200 °C, are insoluble in non-polar solvents, and exhibit room temperature magnetic moments near the free ion values (772, 113). The chloride ion may be replaced by a variety of anions including methoxide, phenoxide, amide and carboxylate. Some of these derivatives are considerably more air-stable than the chloride — the phenoxide is reported to be stable for days in dry air. Despite their apparent stability, little is known about the physical properties of these materials. The methyl-substituted cyclopentadiene complexes are much more soluble in non-polar solvents than the unsubstituted species. Ebulliometric measurements on the bis(methylcyclopentadienyl)lanthanide(III) chlorides indicated the complexes are dimeric in non-coordinating solvents (772). A structmre analysis of the ytterbium member of this series has been completed (714). The crystal and molecular parameters of this and related complexes are compared in Table 5. 

Due to low solubility in hydrocarbon solvents at low temperatures, [(>75-C5H5)Mo(CO)3]2 is not well suited for photoreactions. In order to increase the solubility, the methylcyclopentadienyl derivative, [(t/5-CH3C5H4)-Mo(CO)3]2 (102), has been used. After photoreaction with la-lc and It in n-pentane solution, the reaction mixtures contain two products each, di-nuclear tricarbonylbis(f/5-methylcyclopentadienyl)( /4-diene)molybdenum (103) and dicarbonyl-t -enyl- 5-methylcyclopentadienylmolybdenum complexes (104) (141) [Eq. (56)]. 

Extensive efforts have also been made to develop olefin polymerisation catalysts based on metallocenes with only one ligand of the cyclopentadienyl type. Ethylene-,dimethylsilylene- or tetramethyldisilylene-bridged mono(l-tetra -methylcyclopentadienyl), mono(l-indenyl) or mono(9-fluorenyl)-amidotita-nium complexes, such as dimethylsilylene(l-tetramethylcyclopentadienyl)(t-butyl)amidotitanium dichloride [Me2Si(Me4Cp)N(/-Bu)TiCl2] (Figure 3.10), have recently attracted both industrial and scientific interest as precursors for methylaluminoxane-activated catalysts, which polymerise ethylene and copolymerise ethylene with 1-butene, 1-hexene and 1-octene [30,105,148-152]. 

It is interesting that the [ (CHsIskTi, 14-electron metallocene car-benoid even inserts into the hydrocarbon-like C—H bond of a penta-methylcyclopentadienyl ligand. Significantly, however, the reaction is reversible, whereas with bis(T)-cyclopentadienyl) systems the formation of complex hydrides (Sections II,A,1 and 2) seems to be an irreversible pro-... 

A number of unsaturated substances, such as ketone, azobenzene, imine, a-diimine, carbodi-imide, nitrile, CO2, and so on can be reduced by divalent samarium complexes. For example, reaction of bi(methylcyclopentadienyl) samarium complex with carbodiimide generates, via reducing-coupling reaction, the first structurally characterized bimetallic oxalamidino complex (Figure 8.34) [114]. 

The method is not limited to the formation of this particular complex. Numerous other ones have been prepared by the same general procedure. In place of bis(cyclo-pentadienyl)nickel(II) one may employ the corresponding bis(methylcyclopentadienyl)nickel(II) with no change in procedure. 

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