Five‐Membered Ruthenacycles: Ligand‐Assisted Alkyne Insertion into 1,3‐N,S‐Chelated Ruthenium Borate Species

Abstract

Building upon previous work, the chemistry of [(η -p-cymene)Ru{P(OMe) OR}Cl ], (R=H or Me) has been extended with [H B(mbz) ] (mbz=2-mercaptobenzothiazolyl) using different Ru precursors and borate ligands. As a result, a series of 1,3-N,S-chelated ruthenium borate complexes, for example, [(κ -N,S-L)PR Ru{κ -H,S,S'-H B(L) }], (2 a-d and 2 a'-d'; R=Ph, Cy, OMe or OPh and L=C H NS or C H NS ) and [Ru{κ -H,S,S'-H B(L) } ], (3 L=C H NS, 3' L=C H NS ) were isolated upon treatment of [(η -p-cymene)RuCl PR ], 1 a-d (R=Ph, Cy, OMe or OPh) with [H B(mp) ] or [H B(mbz) ] ligands (mp=2-mercaptopyridyl). All the Ru borate complexes, 2 a-d and 2 a'-d' are stabilized by phosphine/phosphite and hemilabile N,S-chelating ligands. Treatment of these Ru borate species, 2 a'-c' with various terminal alkynes yielded two different types of five-membered ruthenacycle species, namely [PR {C H S -(E)-N-C=CH(R')}Ru{κ -H,S,S'-H B(L) }], (4-4'; R=Ph and R'=CO Me or C H NO ; L=C H NS ) and [PR {C H NS-(E)-S-C=CH(R')}Ru{κ -H,S,S'-H B(L) }], (5-5', 6 and 7; R=Ph, Cy or OMe and R'=CO Me or C H NO ; L=C H NS ). All these five-membered ruthenacycle species contain an exocyclic C=C moiety, presumably formed by the insertion of a terminal alkyne into the Ru-N and Ru-S bonds. The new species have been characterized spectroscopically and the structures were further confirmed by single-crystal X-ray diffraction analysis. Theoretical studies and chemical-bonding analyses established that charge transfer occurs from phosphorus to ruthenium center following the trend PCy.