Bridging Monodentate Ligands

Thiolate ligands also afford an interesting variety of species [156-161]. Because or their relation with the antiarthritic drug Auranofin, thiolate-goldphosphine derivatives have received great interest. The simplest structures are those in which the thiolate bridges two gold atoms and thus different compounds of stoichiometry 

These molecules are connected through only one intermolecular gold-gold contact [166]. 

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Figure 17.23 F.xamples of monodentate. ehelaiing and bridging perchlorate ligands.

Analogous to the dithiophosphate complexes, cis octahedral complexes are formed with bident-ate ligands like phenanthroline, 2,2 -bipyridine, or tmeda and trans octahedral complexes are formed with monodentate ligands like pyridine and its derivatives. Some examples are mentioned with linear bidentate ligands like 4,4 -bipyridine, which build up ID chains by bridging the [NiL2] molecules.926-933... 

The bridging PBu 2I I molecule is not as tightly bonded as other bridging bidentate ligands. This can easily be confirmed by comparing the reactivities of monodentate phosphines.832 The strength of the overall Pd2(/ -PBu 2[ I) interaction is greater than that of a terminal Pd—Bu 2H bond.832... 

Distibines react as monodentate (type 5) or bridging bidentate (type 6) ligands through donation of the lone pairs of electrons to main group or transition metal centers. Fission of the Sb-Sb bond leads to complexes with bridging R2Sb ligands (type 7, 8 and 9) (Scheme 3). 

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