Synthetic and Computational Studies of Thiocarbonyl/σ-Organyl Coupling Reactions

Abstract

The reactions of a range of coordinatively unsaturated σ-organyl thiocarbonyl complexes with 1,4,7-trithiacyclononane ([9]aneS 3 ) have been investigated, leading in some but not all cases to migratory insertive coupling of thiocarbonyl and σ-organyl ligands. Thus, under ambient conditions, the reaction of [RuRCl(CS)(PPh 3 ) 2 ] (R ) C(CO 2 Me)dCHCO 2 Me, C(CtCPh)dCHPh, C 6 H 5 ) with [9]aneS 3 provides σ-organyl complexes [RuR(CS)(PPh 3 )([9]aneS 3 )] + . On heating, the species [Ru(C 6 H 5 )(CS)(PPh 3 )([9]aneS 3 )] + converts to the thiobenzoyl complex [Ru(η 2 -SCPh)(PPh 3 )([9]aneS 3 )] + . Similarly the silyl complex [RuCl(SiMe 2 OEt)-(CS)(PPh 3 ) 2 ] with [9]aneS 3 provides [Ru(SiMe 2 OEt)(CS)(PPh 3 )([9]aneS 3 )] + . However, the styryl and stilbenyl complexes [Ru(CRdCHPh)Cl(CS)(PPh 3 ) 2 ] (R ) H, Ph) under similar conditions provide dihapto thioacyl derivatives [Ru(η 2 -SCCRdCHPh)(PPh 3 )([9]aneS 3 )] + . The osmium species [Os(CHdCHC 6 H 4 Me-4)Cl(CS)-(BTD)(PPh 3 ) 2 ] (BTD ) 2,1,3-benzothiadiazole), however, yields only the nonmigrated product [Os(CHdCHC 6 -H 4 Me-4)(CS)(PPh 3 )([9]aneS 3 )] + . Migratory insertion is not induced by other sulfur donor ligands, e.g., Cy 3 PCS 2 (Cy ) cyclohexyl) and Na[S 2 CNMe 2 ], which provide the complexes [Ru(CHdCH 2 )(S 2 CPCy 3 )-(CS)(PPh 3 ) 2 ] + and [Ru(CHdCHPh)(S 2 CNMe 2 )(CS)(PPh 3 ) 2 ], respectively. The reactivity of different ligands (R) toward thiocarbonyl migratory insertion in [Ru(R)(CS)(PPh 3 )([9]aneS 3 )] + 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 π-orbital of the ligand.

Synthesis and Reactivities of Polyhydrido Osmium Arylsilyl Complexes Prepared from OsH3Cl(PPh3)3

“…Reactions of silanes with transition-metal complexes are of interest because their relevance to Si–H bond activation, − the structural properties of polyhydrides, , and catalytic hydrosilylation reactions. − In the area of osmium chemistry, reactions of silanes have been reported with Os(0) mononuclear and cluster complexes, Os­(II) halo, , hydride, and alkyl/aryl complexes, − Os­(IV) hydride , and halohydride complexes, and OsO 4 …”

Photochemical Alkyne Insertions into the Iron–Thiocarbonyl Bond of [Fe2(CS)(CO)3(Cp)2]

“…Compared to CO, thiocarbonyl ligands display an enhanced propensity for entering into migratory insertion reactions, but this behavior is mostly restricted to sigma alkyl or aryl complexes . Insertion involving alkynes and CS would likely proceed through alkynyl or alkenyl intermediates, which remain difficult to observe, although these species are proposed as intermediates in the formation of metallacyclobutenethiones, metallabenzenes, or cyclopentadienethione complexes . Conversely, migratory insertion reaction involving bridging CS takes advantage of the stabilization provided by multisite coordination and provides a unique opportunity to observe CS–RCCR coupling as well as the resulting bridging thiocarbonyl–alkenyl fragment.…”

“…Conversely, migratory insertion reaction involving bridging CS takes advantage of the stabilization provided by multisite coordination and provides a unique opportunity to observe CS–RCCR coupling as well as the resulting bridging thiocarbonyl–alkenyl fragment. Indeed, this latter molecular fragment is unique in terms of composition and coordination mode, in that few similarities can be envisaged with mononuclear complexes containing α,β-unsaturated thioacyl (thiocinnamoyl complexes) , and, to a lesser extent, with thioketene bridging diiron complexes …”

Synthesis and Reactivity of Phosphinocarbyne Complexes

“…64 The single most relevant structural study however involves the bimetallic bridging thiotoluyl complex [WRu(μ-SCC 6 H 4 Me-4)(CO) 4 (Tp)(Cb)] (Cb = η 5 -C 2 B 9 H 11 ), 65 Both the positively mesomeric effect of amino substituents on thiocarbamoyls (Chart 4) 67 and the coordination of a second metal center to the sulfur atom might be expected to have a significant effect on the metallathiirene geometry given that substituent mesomeric effects play a role in both the facility and the thermodynamics of thiocarbonyl migratory insertion processes. 68 In practice, the geometric features of the MCS ring in 4) Å). Thus, coordination of the Lewisacidic "CbRu(CO) 2 " unit appears to result in a modest contraction of the WCS metallacycle.…”