Thiocarbonyl and Selenocarbonyl Complexes

Cyclooctene complexes [Mcp(CO)2 (cyclooctene)] are utilized for preparation of thiocarbonyl and selenocarbonyl complexes [see reactions (2.176) and (2.177) ... 

Thiocarbonyl and selenocarbonyl metal complexes are generally prepared from carbon disulfide, CS2 thiophosgene, CSCI2 and carbon diselenide, CSc2, as well as from transition metal complexes such as metal carbonyls. Commonly, triphenyl-phosphine is utilized to eliminate sulfur or selenium ... 

G. R. Clark, K. Marsden, W. R. Roper, and L. J. Wright, Carbonyl, Thiocarbonyl, Selenocarbonyl, and Tellurocarbonyl Complexes Derived from a Dihalocarbene Complex of Osmium, J. Am. Chem. Soc. 102, 1206-1207 (1980). 

Several diatomic ligands similar to CO are worth brief mention. Two of these, CS (thio-carbonyl) and CSe (selenocarbonyl), are of interest in part for purposes of comparison with CO. In most cases, synthesis of CS and CSe complexes is somewhat more difficult than for analogous CO complexes, because CS and CSe do not exist as stable, free molecules and do not, therefore, provide a ready ligand source.Therefore, the comparatively small number of such complexes should not be viewed as an indication of their stability. Thiocarbonyl complexes are also of interest as possible intermediates in certain sulfur transfer reactions in the removal of sulfur from natural fuels. In recent years, the chemistry of complexes containing these ligands has developed more rapidly as avenues for their synthesis have been devised. 

Thiocarbonyls CS and selenocarbonyls CSe are instable, but stabilized by complexation. In bridged bimetallic complexes containing both CO and CS, CS is the bridging ligand. 

Only ca. 200 metal thiocarbonyls are known following the initial discovery of trans-RhX(CS)(PPh3)2 and RhX3(CS)(PPh3)2 (X = Cl, Br). Metal selenocarbonyls are even rarer with fewer than 20 complexes being identified since the isolation of (> -Cp)Mn(CO)2(CSe) and cis-RuCl2(CO)(CSe)(PPh3)2 This is due to the instability of the diatomic CS and CSe species compared to CO CS is only stable as a monomer... 

High yields of Cr(CO)5(CX) (X = S, Se) are obtained by displacement of the arene ligands in (>/ -arene)Cr(CO)2(CX) with CO under 10 kPa . Reduction of CljCS by (tetraphenylporpinato)iron(II) in the presence of Fe powder leads to the five-coordinated species, (tetraphenylporphinato)(thiocarbonyl)iron(II) . The same complex, as well as the analogous selenocarbonyl derivative, can also be obtained by the decomposition of Fe(II) porphyrin thio- and selenocarbene species . 

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