Selenium and tellurium donor ligands

Only after the publication of CCC (1987) were well-characterized coordination compounds of the. s-block elements containing bonds to Se or Te described. As a rule selenium or tellurium donor 

Direct insertion of elemental Se into the Li—C bond of (THF)3LiC(SiMe3)3 in DME produces (DME)LiSeC(SiMc3)3. The related centrosymmetric dimer [(DME)LiSeSi(SiMe3)3]2 has also been structurally characterized (Li—Se = 2.57, 2.62 Interestingly, Te is displaced from 

Use of the analogous germanium (TFIF)2LiTeGe(SiMe3)3 reagent gives only intractable materials when treated with Se.  

Lithiation of HSe(2,4,6-(Me3C)3C6H2) with BuLi in the presence of one equivalent of THF produces [Li(THF)Se(2,4,6-(Me3C)3C6H2)]3. The molecule has a Li3Se3 core, with pyramidal coordination at Se and almost planar Li coordination (sum of angles around Li = 355-360°).  

Reaction of the sterically encumbered silylselanol HSeSi(SiMe3)3 with either Bu2Mg or the bis(trimethylsilyl)amides of Ca, Sr, and Ba in the presence of Lewis bases yields crystalline alkaline-earth selenolates. The Mg selenolate has been crystallized as a tris((dimethylphosphino)-methyl)-t-butylsilane complex, whereas the Ca, Sr, and Ba complexes have been isolated as TMEDA adducts. The magnesium complex is constructed around a six-membered P—Mg— P— C—S—C-ring that is puckered in a chair conformation. The strontium complex has Sr— Se = 2.94A with a linear Se—Sr—Se core.  

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Complexes with sulfur, selenium, and tellurium donor ligands 959... 

COMPLEXES OF GOLD(IH) WITH SULFUR, SELENIUM AND TELLURIUM DONOR LIGANDS... 

Oxygen, Sulfur, Selenium, and Tellurium Donor Ligands 6.01.6.1 Oxygen... 

Pentahalides form essentially 1 1 adducts with sulfur, selenium, and tellurium donors, including phosphine sulfides and selenides. IR, Raman (see Raman Spectroscope, and NMR studies of the complexes formed with mixed-donor 0,S ligands showed bonding to occur via sulfur exclusively. The ionic [NbCl4()] -S2R2)][NbCle] complexes are volatile and act as a single-source precursor to mixed-Nb2 05/NbS2 films... 

Complexes of group VIB elements with sulfur or selenium donor atoms are mainly concerned with complexes of selenium(II), tellurium(II) and tellurium(IV). The structural chemistry of complexes of selenium and tellurium with sulfur- and selenium-containing ligands has been well reviewed in the recent past.11... 

This section of the coverage of palladium(II) coordination chemistry will concentrate on complexes of the more common, usually unidentate ligands containing sulfur, selenium or tellurium donor atoms coverage of the vast number of chelate complexes of bi- or multi-dentate ligands will be limited but the reader will find references to most classes of palladium(II) chelate complexes and these will provide an entry into the literature. 

Selenium and tellurium ligands Halogens as ligands Mixed donor atom ligands... 

The 0x0 (0 ) ligand is dominant in the coordination chemistry of osmium, participating in the VIII to IV oxidation states inclusive. The tetroxide OSO4 is the single most important compound of osmium OSO4 and the recently discovered [0s04] ion arc tetrahedral. The /ra 5-[0=0s —O] osmyl moiety displays an extensive chemistry, comparable with that of the uranyl 0=U=0 unit, and there is an extensive and unique cyclic oxo-ester chemistry (p. 584). There is surprisingly little information on hydroxo, aqua, sulfato, nitrato or phosphato complexes, but much recent work has been carried out on carboxylato species, and clearly much work remains to be done on the O-donor chemistry of the element. There are a reasonable number of sulfur-donor complexes but few with selenium or tellurium. 

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