Phenyl bridges

The X-ray structure of the bis(l,4,7-trithiacyclononane) zinc shows an unusual S6 thioether-coordinated zinc center.540 A rare monodentate thioether donor is observed in a phenyl-bridged zinc dimer that has been structurally characterized with a tetrahydrothiophene coordinated to each zinc center.541... 

A DFT study was performed in order to determine the structures of phenylcalcium hydride and its magnesium analog in donor solvents.391 A dimeric phenylcalcium hydride was found to be the most stable species in solution, but monomers or tetramers cannot be excluded at very low or very high concentrations. Hydride bridging is favored over phenyl bridging, and a coordination number of six is predicted to be dominant in solution. 

A series of analogues of the original PHOX catalyst, in which the phenyl bridge is attached to C(4) instead of C(2) of the oxazoline ring (15, Fig. 29.3), were recently synthesized [14]. These catalysts were used to hydrogenate a number of substrates, including a range of 1-phenylbutenoic acids, with >90% ee. 

PyrPHOX catalysts 25 (Fig. 29.12) [25], with a pyrrole instead of a phenyl bridge, showed selectivity which was comparable to - and in some cases better than - that of the PHOX catalysts 14. 

For the aluminum systems so far described, only the monomer-dimer equilibrium has been observed. For very bulkyl R groups, the monomer predominates for small alkyls, cyclopropyl, and phenyl-bridged species, the symmetrical dimer is the stable form. When the phenylethynyl group is present, this equilibrium is complicated further by the additional feature arising from the different possible types of bridge bonds, which may be described in the following manner ... 

Fig. 29 Extension of the face bridging, C3-symmetric ligand 44 that forms M4L4 tetrahedron 47. Introduction of rigid phenyl bridges in ligand 50 preserves the necessary rigidity to form tetrahedron 51 [154], whereas introduction of a flexible methylene bridge results in the formation of mononuclear M1L1 complex 52 [156]...

Barigelletti F et al (1993) Luminescence properties of rigid rod-like binuclear ruthenium(II)-osmium(II) terpyridine complexes - electronic interaction through phenyl bridges. JCS Chem Commun 942-944... 

Recently, new insight into detailed mechanisms of photochemical processes in donor-acceptor pairs (DA) has emerged. To study the role of bridge energy levels on electron transfer rates, a series of rod-like donor-bridge-acceptor (D-B-A) molecules in which a 4-aminonaphthalene-l,8-imide (ANI) electron donor is linked to a 1,8 4,5-naphthalenediimide acceptor (NI) via the 1,4 positions on a phenyl bridge was... 

It is reasouable to expect that the use of rigid 60° angular buildiug blocks with 180° liuear linking units would provide triangular structures. Indeed, this has been demonstrated by the self-assembly of 4,7-phenanthroline and the linear phenyl-bridged bis-palladium complex, which yields the triangle (26). ... 

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