Synthesis and structural characterization of ruthenium complexes with 1-aryl-imidazole-2-thione

Abstract

Treatment of [RuCl 2 (PPh 3 ) 3 ] with 2 equiv. Himt MPh (Himt MPh = 1-(4-methyl-phenyl)-imidazole-2-thione) in the presence of MeONa afforded cis-[Ru(κ 2 -S,N-imt MPh ) 2 (PPh 3 ) 2 ] (1), while interaction of [RuCl 2 (PPh 3 ) 3 ] and 2 equiv. Himt MPh in tetrahydrofuran (THF) without base gave [RuCl 2 (κ 1 -S-The ruthenium hydride complexes 4a and 4b easily convert to their corresponding ruthenium chloride complexes [RuCl(κ 2 -S,N-imt MPh )(CO) (PPh 3 ) 2 ] (5a) and [RuCl(κ 2 -S,N-imt NPh )(CO)(PPh 3 ) 2 ] (5b), respectively, in refluxing CHCl 3 by chloride substitution of the RuH. Photolysis of 5a in CHCl 3 at room temperature afforded an oxidized product [RuCl 2 (κ 2 -S,N-imt MPh )(PPh 3 ) 2 ] (6). Reaction of 6 with excess [imt MPh ] À afforded 1. The molecular structures of 1·EtOH, 3·C 6 H 14 , 4b·0.25CH 3 COCH 3 , and 6·2CH 2 Cl 2 have been determined by single-crystal X-ray crystallography.

N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry

“…813 This interaction was described as a metal-to-boron dative bond, making this boron-bridged tris(imidazolin-2-thione) ligand a prominent member of the extensively studied class of ambiphilic σ-acceptor (Z-type) 33 ligands. 814−818 The same structural motif as found in 638 was realized subsequently in numerous other transition metal complexes containing iron, 819 cobalt, 820 nickel, 821,822 ruthenium, 813,823,824 rhodium, 825−827 palladium, 828 osmium, 829 iridium, 826,830,831 and platinum. 832 The related silicon-bridged tris(imidazolin-2-thione) ligand 639 was prepared by Breher and co-workers from HSiCl 3 and 3-trimethylsilyl-1-methylimidazolin-2-thione.…”

“…The molecular structure of this complex revealed octahedral and tetrahedral coordination geometries around the ruthenium and boron atoms, respectively, with a short Ru–B bond length of 2.161(5) Å (Figure ). This interaction was described as a metal-to-boron dative bond, making this boron-bridged tris­(imidazolin-2-thione) ligand a prominent member of the extensively studied class of ambiphilic σ-acceptor (Z-type) ligands. − The same structural motif as found in 638 was realized subsequently in numerous other transition metal complexes containing iron, cobalt, nickel, , ruthenium, ,, rhodium, − palladium, osmium, iridium, ,, and platinum …”

Quantifying the Donor Strength of Ligand-Stabilized Main Group Fragments

“…In recent years, it has been a matter of particular interest as to whether neutral, tricoordinate boron compounds can serve as electron-donating ligands rather than pure acceptor ligands, as they are commonly viewed. Notably, a majority of tricoordinate boron compounds of the type BR 3 are known to act as Lewis acids and σ-accepting or Z-type ligands in transition-metal complexes. − By manipulation of the R substituents in BR 3 , it is possible to cause a dramatic change in these properties: formally anionic substituents, such as hydrides, alkyls, aryls, halogenides, and most anionic N-heterocycles lead to classical Lewis acids or Z-type ligands. ,− In these cases, the vacant p z -orbital of the trigonal planar boron compound is stabilized either by π-donation of the substituents or by dimerization and the formation of two-electron, three-center bonds. Replacing one of the substituents R on boron by a neutral σ-donating and π-accepting substituent L formally results in a partially filled p z -orbital at the boron atom in BR 2 L. This ligand-stabilized boryl ligand acts as an X-type ligand and contributes one electron to a covalent bond.…”