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Tantalum complexes arene

The tantalum(V) calix[4]arene complex 44 provides an interesting scaffold for the construction of an j -PhC2C=CPh ligand upon reaction with an excess of phenylethynyllithium (Scheme 10). The coupling reaction is presumed to proceed via bis-alkynyl 45, which is subsequently attacked at the a-carbon of one of the acetylide ligands to give anion 46, isolated as its lithium salt. The addition of a further equivalent of LiC CPh is probably prohibited by orbital constraints. ... [Pg.105]

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... [Pg.76]

Inter- and intramolecular (cyclometallation) reactions of this type have been ob-.served, for instance, with titanium [408,505,683-685], hafnium [411], tantalum [426,686,687], tungsten [418,542], and ruthenium complexes [688], Not only carbene complexes but also imido complexes L M=NR of, e.g., zirconium [689,690], vanadium [691], tantalum [692], or tungsten [693] undergo C-H insertion with unactivated alkanes and arenes. Some illustrative examples are sketched in Figure 3.37. No applications in organic synthesis have yet been found for these mechanistically interesting processes. [Pg.121]

The unsubstituted para-t-butyl calixarenes themselves complex metals via their aryloxide groups. Since aryloxide complexes are frequently oligomeric, the simple calixarenes do not give monomeric complexes. Aryloxides are hard ligands, therefore they readily form complexes with oxo-philic hard metal ions such as alkali metals, early transition metals, lanthanides, and actinides. Complexation is often inferred because the calixarene acts as a carrier for the metal ion from an aqueous to an organic phase. With the /wa-/-butylcalix[ ]arenes in alkaline solution, a value of n = 6 gives the best carrier for lithium(I), sodium(I), and potassium(I), with a value of n 8 giving the best carrier for rubidium(I) and caesium(I).15,16 Titanium(IV) complexes have been characterized,17-19 as well as those of niobium(V) and tantalum(V).20-22 These complexes are classified as... [Pg.488]

Binuclear complexes of naphthalene (VIII) and of benzene (IX) with [Os(NH3)5]2+ and [Ru(NH3)5]2+ moieties were reported by Taube et al. (19), in which anti- //-1,2-rj2 3,4- 2) coordination of the arene is present. This bonding mode was first observed by Pasman et al. (20) in the binuclear Rhenium complex X. Wolczanski et al. (21) obtained complex XI from the mononuclear complex [Ta(0—Si Bu3)3 2-(N,C)-pyridine ] and benzene. Each tantalum atom is bound unsymmetrically to one C=C bond of benzene with a weak interaction to a third carbon atom the bonding may be described as a distorted tj3-enyl. In the dinuclear cobalt complex XII, the xylene functions as a bis(enyl)-ligand (12,22). [Pg.189]

The reduction of a tantalum alkoxide with sterically demanding ligands [(RO)2TaCl3] (R = 2,6-PriC6H3) by sodium amalgam in the presence of 2-butyne gives a dewar-benzene complex which can be seen as a model for the last intermediate in the cyclotrimerization of alkynes to arenes see equation (49). It... [Pg.416]

There is some material of relevance in a review on niobium and tantalum coordination chemistry. 1 The thermal reactions of the ions M" " (M = Ta, Nb, NbO, NbN) with arenes in the gas phase results in cleavage of the arenes to form metallacyclopentadiene ion complexes via retro-alkyne cyclotrimerization mechanisms. ... [Pg.206]

Vanadium, Niobium, Tantalum and Zirconium Mixed sandwich complexes of vanadium containing arene rings have been described in two reports. The bisindenylbisvanadium complex (41) has been structurally characterised and contains a metal-metal bond length of 2.35A. The complex is formed in the reductive... [Pg.369]


See other pages where Tantalum complexes arene is mentioned: [Pg.172]    [Pg.2055]    [Pg.329]    [Pg.144]    [Pg.2640]    [Pg.2947]    [Pg.329]    [Pg.2946]    [Pg.341]    [Pg.2055]    [Pg.254]    [Pg.435]    [Pg.182]    [Pg.44]    [Pg.46]    [Pg.49]    [Pg.70]    [Pg.452]    [Pg.148]    [Pg.707]    [Pg.2055]   
See also in sourсe #XX -- [ Pg.60 ]




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