Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Rhenium ligands

In inert systems such as technetium and rhenium, ligand substitution reactions-including solvolysis-proceed under virtually irreversible conditions. Thus, the nature of the reaction center, the nature of the leaving group, and the nature and position of the other ligands in the complex affect the rates and activation parameters in a complicated manner. Most substitution reactions take place via interchange mechanisms. This is not too surprising when the solvent is water - or water-like - and where, in order to compete with the solvent,... [Pg.272]

The average experimental values are equal to 3.681, 2.404, and 2.451 A. The rhenium-rhenium distances are well reproduced and the rhenium-ligand distances are slightly longer than the experimental ones (the difference does not exceed 1.5%). The experimental data show that the structure of the rhenium core remains unchanged for all closed shell clusters. At the same time, it has been reported that the Re-Cl distances strongly depend on the nature of the counter-cation in the salt. This shows that the rhenium-apical ligand bonds are very sensitive to the effects of environment. Our calculations in gas phase do not take into account the crystal... [Pg.391]

Polynuclear Carbonyls. Several stmctures consist of dinuclear metal carbonyls as shown in stmctures (4)—(6). The metal atoms in Mn2(CO) Q, as also for technetium and rhenium, are held together by a metal—metal bond and the compound contains 10 terminal CO ligands, five coordinated to each atom. The CO ligands of Mn2(00) 0 adopt a staggered configuration as illustrated in stmcture... [Pg.63]

The parent ligand forms complexes of the type [M(CO)5(HNSO)][AsF6] (M = Mn, Re) (Eq. 9.11). ° The rhenium complex can also be prepared by nucleophilic displacement of F from coordinated NSF using MesSnOH as the source of... [Pg.170]

The difference between the two extremes is essentially that, in the former, the Re retains its valence electrons in its d orbitals whereas in the latter it loses 6 of them to delocalized ligand orbitals. In either case paramagnetism is anticipated since rhenium has an odd number of valence electrons. The magnetic moment of 1.79 BM corresponding to 1 unpaired electron, and esr evidence showing that this electron is situated predominantly on the ligands, indicates that an intermediate oxidation state is involved... [Pg.1055]

The chemistry of technetium(II) and rhenium(II) is meagre and mainly confined to arsine and phosphine complexes. The best known of these are [MCl2(diars)2], obtained by reduction with hypophosphite and Sn respectively from the corresponding Tc and Re complexes, and in which the low oxidation state is presumably stabilized by n donation to the ligands. This oxidation state, however, is really best typified by manganese for which it is the most thoroughly studied and, in aqueous solution, by far the most... [Pg.1058]

Cp(CO)2Re(THF) forms the complex 105 upon reaction with thiophene (89JA8753, 910M2436). Similar species are known for 2- and 3-methyl-, 2,5-dimethyl, and tetramethylthiophene (91IC1417). Thiophene in 105 is S-coordi-nated, and the sulfur atom is pyramidal. Treatment of 105 with Fc2(CO)9 produces 106, where the thiophene ligand is bridge-coordinated via the sulfur atom to rhenium and four carbon atoms of the dienic system with iron (the coordination mode). The pyramidal nature of the sulfur atom is preserved. The -coordination of thiophene separates the dienic and sulfur counterparts of the ligand and decreases the TT-electron delocalization, which leads to the enhanced basicity of the sulfur atom. [Pg.17]

Ligand induced redox reactions of low oxidation state rhenium halides and related systems in non-aqueous solvents. R. A. Walton, Prog. Inorg. Chem., 1976, 21, 105-127 181). [Pg.38]

The only technetium complex has been reported (226) is [Tc(CO)4(R2dtc)]. There appear to be few reports of rhenium or technetium complexes with 1,1-dithiolato ligands. [Pg.236]

The dinuclear rhenium disulfido complex with n,rj -S2 ligands (ReCp )2(/U-S2)2 (Cp =7j -C5Me4Et) (type IIa2 complex in Fig. 2) undergoes an insertion reaction of acetylene and ethylene into the S-S bond according to Scheme 57. [Pg.190]

R = SiMe3) ligand. Apparently, the loss of a CO ligand on each rhenium atom causes the bis(N,M )-chelated complex (13) to rearrange to a cube (14). [Pg.147]

The vast majority of phosphine/phosphite-substituted products involve F-ligand ligation at late transition metals. In contrast, phosphite ligands displaced rhenium-coordinated CO or acetylene in [RePt3(/i-dppm)3(CO)3(L)l", - which are the... [Pg.57]


See other pages where Rhenium ligands is mentioned: [Pg.98]    [Pg.323]    [Pg.151]    [Pg.74]    [Pg.102]    [Pg.15]    [Pg.163]    [Pg.164]    [Pg.164]    [Pg.164]    [Pg.335]    [Pg.917]    [Pg.1057]    [Pg.1058]    [Pg.1062]    [Pg.89]    [Pg.43]    [Pg.120]    [Pg.226]    [Pg.32]    [Pg.196]    [Pg.197]    [Pg.195]    [Pg.219]    [Pg.209]    [Pg.210]    [Pg.275]    [Pg.233]    [Pg.15]    [Pg.194]    [Pg.58]    [Pg.67]    [Pg.72]    [Pg.98]    [Pg.120]   
See also in sourсe #XX -- [ Pg.150 ]




SEARCH



© 2024 chempedia.info