Sodium, cyclopentadienyl complexes

Solutions of complex compound cyclopentadienyl-dititana in hexane and sodium cyclopentadienyl complex have high catalytic activity. Films with a metallic luster can be obtained by slowly removing the solvent from the formed gel polyacetylene in vacuum. It is assumed that the active complex has a tetrahedral structure. Polymerization mechanism is similar to the mechanism of olefin polymerization on catalyst Ziegler-Natta. Obtained at -80°C cis-polyacetylene films after doping had a conductivity of 240 (Ohm-cm" ). 

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). 

Roesky introduced bis(iminophosphorano)methanides to rare earth chemistry with a comprehensive study of trivalent rare earth bis(imino-phosphorano)methanide dichlorides by the synthesis of samarium (51), dysprosium (52), erbium (53), ytterbium (54), lutetium (55), and yttrium (56) derivatives.37 Complexes 51-56 were prepared from the corresponding anhydrous rare earth trichlorides and 7 in THF and 51 and 56 were further derivatised with two equivalents of potassium diphenylamide to produce 57 and 58, respectively.37 Additionally, treatment of 51, 53, and 56 with two equivalents of sodium cyclopentadienyl resulted in the formation of the bis(cyclopentadienly) derivatives 59-61.38 In 51-61 a metal-methanide bond was observed in the solid state, and for 56 this was shown to persist in solution by 13C NMR spectroscopy (8Ch 17.6 ppm, JYc = 3.6 2/py = 89.1 Hz). However, for 61 the NMR data suggested the yttrium-carbon bond was lost in solution. DFT calculations supported the presence of an yttrium-methanide contact in 56 with a calculated shared electron number (SEN) of 0.40 for the yttrium-carbon bond in a monomeric gas phase model of 56 for comparison, the yttrium-nitrogen bond SEN was calculated to be 0.41. 

The compound Na[Tc3(CO)9(OMe)4] prepared by the incomplete carbonylation of sodium pertechnetate in methanol shows promises as an important reagent for the future. It has been used to prepare LTc(CO)3, Tc2(CO)io, and various arene and cyclopentadienyl complexes (see Arene Complexes and Cydopentadienyl). The reaction conditions for these syntheses are moderately mild. 

Sodium cyclopentadienyl-dicarbonylferrate 96 and tetrafluoroboric acid react with oxiranes to give olefins with the same stereostructure, after decomposition of the iron-alkene complex. With 96, diaryl and dialkyloxiranes are transformed to the olefins with inversion, by thermal decomposition of the intermediate alkoxide. Oxiranes interact with CF3C(0)I to yield olefins with the same geometry via a 3-iodotrifluoroacetate. ... 

The THF in UCI2H2BPZ2THF could easily be replaced by pyridine, giving a dark blue compound. Treatment of a solution of the THF complex in toluene with sodium cyclopentadienyl gave a red-brown solution whose UV/vis spectrum was different from that of the U(III)cyclopentadienyl THF adduct though Still characteristic of a U(III) compound. The same reaction in THF solution, however, did yield a U/f sHslsTHF solution 290). 

Cyclopentadienyl complexes, as previously discussed, are exceptionally numerous and have been the subject of extensive study. Several routes are available for introducing this ligand into a metal complex. One approach is to react a metal compound with the cyclopentadienide ion, C5H5. This ion can be purchased as the sodium salt in solution it can also be prepared by the following two-step process. 

Treatment of 5-phenyl-l,3-thiaselenole-2-thione (51) with sodium ethoxide in the presence of the cyclopentadienyl complex [Co(cp)l2CO] in ethanol also results in ring opening with formation of the stable cobalt cyclopentadienyl complex (52) (Equation (6)) <89BCJ3266>. 

O-Methylation of mandelic acid leads to the enantiomers of a-methoxy-M-phcnylacetic acid (10), which are also commercially available. This methylation without noticeable racemiza-tion was achieved with diazomethane, using aluminum tris(tert-butanoate) as catalyst8. Alternatively, dimethyl sulfate/ sodium hydroxide has been used15, as described in detail for the racemic compound10. The acids have been used for the construction of quite sophisticated chiral auxiliaries, e.g., a rhodium cyclopentadienyl complex (Section 7.2.2.), and for chiral dienes applied in both normal and inverse Diels-Alder reactions (Section D.1.6.1.1.1.). Chiral dienes, e.g., 1, for normal Diels -Alder reactions were prepared by pyrolysis (460 C) of a tricyclic precursor cstcrified with (S)-O-methylmandeloyl chloride or with the free acid and dicyclohexylcarbodiimide/4-dimethylaminopyridine11 -13. 

The tris(cyclopentadienyl) complexes of the rare earths were the first compounds discovered and the most intensively investigated class of organometallic compounds of these elements. They were reported for the first time in 1954 by Wilkinson and Birmingham, and generally prepared by reaction of anhydrous rare earth trichlorides with sodium cyclopentadienide in tetrahydrofuran at room temperature and isolated by sublimation of the crude products in vacuum at about 220°C (Wilkinson and Birmingham, 1954 Krasnova et al., 1971) ... 

When trans-halo-tetracarbonylcarbyne complexes of molybdenum and tungsten, X(CO)4M=CR, are treated with sodium cyclopentadienyl, not only the displacement of the halide, but an additional elimination of two carbonyl ligands is observed, affording dicarbonyl(rj -cyclopenta-dienyl)carbyne complexes [2,3]. A different synthetic approach converts vinylidene ligands into carbyne ligands to yield comparable bisdimethylphosphite substituted complexes of molybdenum [4]. 

Bis(cyclopentadienyl)complexes have been isolated for the elements of the First Transition Series from vanadium to nickel inclusive and also for ruthenium and osmium. The most general method of preparation is to treat an anhydrous halide of the metal with sodium cyclopentadienide in tetrahydrofuran under an atmosphere of nitrogen or argon. 

The Group VIII cyclopentadienyl complexes of formula CpM(NO) (M = Ni, Pd, Pt) have all been synthesized. The nickel complex is best prepared from nickelocene and nitric oxide, and a method for the preparation of the nickelocene m situ without its isolation has been described (56). The palladium complex can be prepared from [Pd(NO)Cl] and sodium cyclopentadienide (23) and the platinum complex from Pt2(CO)2Cl4 and sodium cyclopentadienide and nitric oxide (22). The microwave (13) and infrared spectra (18) of CpNi(NO) have received detailed study, and the electronic structure of the complex is discussed in an early paper (77). 

Alkali metal cyclopentadienide salts are important reagents in organometallic chemistry, having been used to prepare innumerable cyclopentadienyl complexes. Potassium cyclopentadienide, KCp, is usually made by deprotonation of cyclo-pentadiene with potassium metal either in organic solvents such as THF and benzene or in liquid ammonia, or by deprotonation with KH" or KOH. The analogous sodium compound, NaCp, was reported by the groups of Fischer and... 

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