Palladium organyls

A completely different type of amphotropic materials is made up by various metal or-ganyls, such as the linear ones illustrated by the di-palladium organyl 45, the twinned rod-like organyl 47, or the disc-like orga-nyls 48 and 49 (Figs. 30 to 32). These and related metallomesogens exhibit thermo-... 

Figure 31. Molecular structures of the twinned rod-like palladium organyl 47 [159] and the disc-like analogue 48 [149, 156]. The ringed lateral substituents of 48 are responsible for the change of the mesomorphic behavior M = Pd or Pt, X=C1, Br, 1 (47) or X = C1, Br, I, SCN, N3 (48).

Tetra - palladium organyl charge transfer complexes... 

Dinuclear palladium organyls with a discoid molecular shape constitute a class of electron donor compounds displaying an unusual and complex phase behavior with TNF as a strong electron acceptor [64] (see Fig. 7). The mesomorphism of these meso-gens, exhibiting monotropic nematic discotic phases in their pure forms, in TNF-CT... 

Figure 7. Schematic phase diagrams of the di-nuclear palladium organyls 5 a, c, and d with TNF as the electron acceptor [64] Cr crystalline, Np nematic discotic, Coli, columnar hexagonal mesophase (o intramolecular ordered), Iso isotropic liquid (see footnote I in Sec. 3 commenting on the nomenclature of columnar mesophases). Shaded areas mark bi-phasic regions.

Phase diagrams similar to those of type 5 pallado-nematogens with TNF are also observed for a related series of dinuclear palladium organyls with hexyloxy instead of the hexyl chains [20] and for similar dinu-clear platinum organyls [65]. 

An alternative way [25] to obtain a chiral nematic discotic phase is simply the use of a chiral organic solvent, e.g. the hydrocarbon R-(+)-Iimonene, in which, for example, an achiral, slightly folded disclike di-palladium organyl is dissolved. 

This collection contains one platinum and four palladium organyls (7a and 7b-7e, respectively) as well as an azacyclic cobalt(II) complex (8). Whereas the five pure metal organyls 7a-7e meh between 73 and 96°C and show only a monotropic No phase, the cobah(II) compound 8 does exhibit the Ncoi phase enantiotropically at lower temperatures, between 30 and 60°C. The metal-free precursor ligand of 8 is not mesomorphic [63] ... 

Strained palladacycloalkanolates (cyclopropanes and cyclobutanes) undergo carbon elimination to yield c-palladium organyls. ... 

Scheme8.11. Palladium-catalyzed homocoupling and reduction of organyl halides, carbonates, and triflates [57, 94, 104, 108,109].

Brase, S. and de Meijre, A., Palladium-catalyzed Coupling of Organyl Halides to Alkenes - the Heck Reaction , in Metal-catalyzed Cross-coupling Reactions, Wiley-VCH, Weinheim, 1998, pp. 99-166. 

S. Brase and A. de Meijere, Palladium-Catalyzed Coupling of Organyl Halides to Alkenes—The Heck Reaction, in Metal-Catalyzed Cross-Coupling Reactions, (F. Diederich, P. J. Stang, Eds.), Wiley-VCH, Weinheim, 1998, 99-154. 

Palladium Catalyzed Coupling of Organyl Halides to Alkenes - The... 

Brase, S., De Meijere, A. Palladium-catalyzed coupling of organyl halides to alkenes - the Heck reaction, in Metal-Catalyzed Cross-... 

Praefcke and co-workers have carried out important research on macroheterocyclic tetrapalladium" " and tetraplatinum organyls 118 and 119, derived from polycatenar bis(imine)phenylene, and the nematogenic bis(imine)-stilbenylene ligands. These [M4(/r -X)4L2] complexes were prepared by ort4o-metallation of the appropriate diimine with palladium acetate or di-/r-chloro-bis-[(77 -2-methylallyl)platinum], followed by an acidic treatment to form the chloro-bridged compormds. The other complexes were obtained by ion-exchange reactions with KBr, KI, and... 

Palladium appears to be the most versatile metal for catalytic reactions in organic synthesis. Most prominent are cross-coupling reactions between compounds with sp or sp C-X bonds and metal organyls. Moreover, a large number of palladium-mediated reactions for C-H bond activation has been described. In most cases, palladium(O) displays the catalytically active species. However,... 

Indirect evidence for an activation step is found in the ability of pre-synthesized, stable, pentacoordinate silanes to transfer an organyl group onto palladium. Two examples are the use of catecholsilanes for alkenyl transfer and the use of TBAT as a phenylating reagent (Figure 7.1) [16, 74]. Yet there are also indications from earlier work with fluoride-activated fluorosilanes of how pentacoordinate silanes could play a role in the reaction. 

Once generated by carbopalladation of alkenes, palladium o-organyl can undergo a variety of different transformations (Figure 5-7). ... 

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