Ligands chalcogen bridging

Chalcogen-bridged di-iron species functioning i bidcntate ligand... 

The use of silylated chalcogen reagents in the synthesis of chalcogen-bridged metal clusters has produced a remarkable number of complexes with a variety of structural types. The nuclearities and structures of these complexes can be highly dependent on the reaction conditions, the steric demands of the ancillary and/or chalcogenolate ligands, as well as the ratio M E. Complexes... 

Chalcogen Bridged D ansition Metal Clusters with i/ -Cydopentadienyl, /13-Allyl, and CO Ligands... 

Y. Takashima, Y. Nakayama, K. Watanabe, T. Itono, N. Ueyama, A. Nakamura, H. Yasuda, A. Harada, J. Okuda, Polymerizations of cyclic esters catalyzed by titanium complexes having chalcogen-bridged chelating diaryloxo ligands. Macromolecules 35 (2002) 7538-7544. 

Complexes with Chalcogen Bridging Ligands 6.17.2.4.1 Complexes with oxygen bridging ligands... 

Unlike reactive diatomic chalcogen-nitrogen species NE (E = S, Se) (Section 5.2.1), the prototypical chalcogenonitrosyls HNE (E = S, Se) have not been characterized spectroscopically, although HNS has been trapped as a bridging ligand in the complex (HNS)Fc2(CO)6 (Section 7.4). Ab initio molecular orbital calculations at the self-consistent field level, with inclusion of electron correlation, reveal that HNS is ca. 23 kcal mof more stable than the isomer NSH. There is no low-lying barrier that would allow thermal isomerization of HNS to occur in preference to dissociation into H -1- NS. The most common form of HNS is the cyclic tetramer (HNS)4 (Section 6.2.1). 

Figure 27 Oxidative addition of the organochalcogen compounds to low-valent transition metal centers most often resulting in the cleavage of the chalcogen-chalcogen bond and the formation of mono- or dinuclear complexes with anionic bridging or terminal RE- (E = Se, Te) ligands.

Also, Yam and Cheung [62] have carried out the synthesis of a series of novel polynuclear mercury(II) diimine complexes with bridging chalcogenate ligands and studied their luminescence and electrochemical properties. 

Figure 1.74 Gold (I)—Cold (III) complexes with bridging chalcogen ligands.

Formation of polynuclear compounds with chalcogen atoms as bridging ligands between metal atoms is a characteristic feature of chalcogen metal carbonyl complexes. Such polynuclear complexes, in which often an additional metal-metal bond is assumed so as to account for the diamagnetism, have become known in increasing numbers because of the work of various research groups, and it is neither possible nor is it within the scope of this article to review this subject here. Only a few of our own results will be mentioned herein. 

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