Synthetic and computational studies of thiocarbonyl/?-organyl coupling reactions(1)

Green, Jennifer C., Hector, Andrew L., Hill, Anthony F., Lin, Sibo and Wilton-Ely, James D.E.T. (2008) Synthetic and computational studies of thiocarbonyl/?-organyl coupling reactions(1). Organometallics, 27 (21), 5548-5558. (doi:10.1021/om800637y).

Abstract

The reactions of a range of coordinatively unsaturated ?-organyl thiocarbonyl complexes with 1,4,7-trithiacyclononane ([9]aneS3) have been investigated, leading in some but not all cases to migratory insertive coupling of thiocarbonyl and ?-organyl ligands. Thus, under ambient conditions, the reaction of [RuRCl(CS)(PPh3)2] (R = C(CO2Me)CHCO2Me, C(CCPh)CHPh, C6H5) with [9]aneS3 provides ?-organyl complexes [RuR(CS)(PPh3)([9]aneS3)]+. On heating, the species [Ru(C6H5)(CS)(PPh3)([9]aneS3)]+ converts to the thiobenzoyl complex [Ru(?2-SCPh)(PPh3)([9]aneS3)]+. Similarly the silyl complex [RuCl(SiMe2OEt)(CS)(PPh3)2] with [9]aneS3 provides [Ru(SiMe2OEt)(CS)(PPh3)([9]aneS3)]+. However, the styryl and stilbenyl complexes [Ru(CRCHPh)Cl(CS)(PPh3)2] (R = H, Ph) under similar conditions provide dihapto thioacyl derivatives [Ru(?2-SCCRCHPh)(PPh3)([9]aneS3)]+. The osmium species [Os(CHCHC6H4Me-4)Cl(CS)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole), however, yields only the nonmigrated product [Os(CHCHC6H4Me-4)(CS)(PPh3)([9]aneS3)]+. Migratory insertion is not induced by other sulfur donor ligands, e.g., Cy3PCS2 (Cy = cyclohexyl) and Na[S2CNMe2], which provide the complexes [Ru(CHCH2)(S2CPCy3)(CS)(PPh3)2]+ and [Ru(CHCHPh)(S2CNMe2)(CS)(PPh3)2], respectively. The reactivity of different ligands (R) toward thiocarbonyl migratory insertion in [Ru(R)(CS)(PPh3)([9]aneS3)]+ was analyzed through density functional theory. The calculated barriers agree qualitatively with experimental observations. In order to determine the electronic effect of substituents on the migrating ligand, a series of hypothetical systems with phenyl ligands varying only in the para-substituent was considered. A general trend that electron-releasing substituents on the migrating ligand promote reaction was observed. Through symmetry-adapted fragment orbital analysis, this phenomenon is determined to correlate well with the energy of the highest occupied ?-orbital of the ligand.

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Contributors

Author: Andrew L. Hector

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