Vanadium cyclopentadienyls

Insertions of isocyanide into niobium-carbon bonds follow a path similar to that with vanadium, resulting in the formation of the 7]2-iminoacyl complexes, which can then be involved in further chemistry.175 176 The reaction of acetone with cyclopentadienyl complex 110 under a carbon monoxide atmosphere gives the if -acetone compound 111. Complex 111 subsequently undergoes either stepwise insertion of two isocyanides via 112 or double insertion of the isocyanide to give complex 113 (Scheme 48).177... 

The Tp hgands (i.e., tris(pyrazolyl)borates or scorpionates [13]) are close analogs to the Cp hgands (i.e., -cyclopentadienyl), and in connection with the chemistry of the Tp Cr complexes mentioned above, a recent example of O2-binding from vanadium chemistry is of interest, even though it is formally not organometalhc chemistry Reaction of the V(IV) complex... 

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. 

The ESR spectra of a series of triarylboron anion radicals have been determined and show selective line-broadening effects (95). The radical anions of diborane, generated in an argon matrix at 77 K by irradiation with a-rays have been studied by ESR (121). The vanadium-aluminum complex obtained on mixing dichlorobis(7r-cyclopentadienyl)vanadium with ethylaluminum dichloride, a system that catalyzes the polymerization of ethylene to give a polymer with good characteristics, has been characterized by ESR and ultraviolet studies (44). 

The successful acylation of ferrocene set off a vigorous research effort that has resulted in the establishment of the present field of metallocene chemistry, ir- Cyclopentadienyl compounds of ruthenium, osmium, manganese, vanadium, and chromium also exhibit certain aromatic-type reactions in varying degrees. These metallocenes thus represent a new class of heterocyclic compounds in which transition metals, akin to nitrogen, oxygen, and sulfur in classical heterocycles, not only are an integral part of the structure but actually participate directly in many reactions. 

The MWDs of polyolefins produced with some soluble catalysts such as Cp2TiCl2 (Cp = cyclopentadienyl anion)/ A1(C2H5)2C154) and VCljAlfC Hj Cl55) were found to be expressed by Eq. (13). As will be shown in later sections, various soluble catalysts based on titanium and vanadium compounds yield polymers with Q values (Kfw/Mn) near 2.0, indicating that the polymerization of olefin with the respective soluble catalyst proceeds on uniform (homogeneous) active centers. 

Bis(cyclopentadienyl)bis(pentafluorophenyl)zirconium, 3824 Bis(cyclopentadienyldinitrosylchromium), 3269 Bis(cyclopentadienyl)hexafluoro-2-butynechromium, 3629 Bis(cyclopentadienyl)lead, 3288 Bis(cyclopentadienyl)magnesium, 3271 Bis(cyclopentadienyl)manganese, 3272 Bis(cyclopentadienyl)niobium tetrahydroborate, 3318 Bis(cyclopentadienyl)pentafluorophenylzirconium hydroxide, 3696 Bis(cyclopentadienyl)phenylvanadium, 3698 Bis(cyclopentadienyl)titanium selenate, 3287 Bis(cyclopentadienyl)tungsten diazide oxide, 3279 Bis(cyclopentadienyl)vanadium diazide, 3280 Bis(cyclopentadienyl)zirconium, 3290 Bis(l,2-diaminoethane)diaquacobalt(III) perchlorate, 1787 Bis(l,2-diaminoethane)dichlorocobalt(III) chlorate, 1780 Bis(l,2-diaminoethane)dichlorocobalt(III) perchlorate, 1781 c/i-Bisf 1,2-diaminoethane)dinitrocobalt(III) iodate, 1782 Bis(l,2-diaminoethane)dinitrocobalt(III) perchlorate, 1778 Bis(l,2-diaminoethane)hydroxooxorhenium(V) perchlorate, 1785 Bis(l, 2-diaminopropane)-ds-dichlorochromium(III) perchlorate, 2609 1,10-Bis(diazonio)decaboran(8)ate, 0197... 

Bis(cyclopentadienyl)vanadium(II) complexes applications, 5, 39 coordination compounds, 5, 37 vanadocenes, 5, 36... 

Mixed-sandwich complexes with cyclodextrins, 12, 787 iridium cyclopentadienyl complexes, 7, 368 with nickel, synthesis and reactivity, 8, 160 with vanadium, 5, 47... 

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