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

摘要

Building upon previous work, the chemistry of [(h6-p-cymene)Ru{P(OMe)_2OR}Cl_2], (R=H or Me) has been extended with [H_2B(mbz)_2]~- (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, [(k~2-N,S-L)PR_3Ru{k~3-H,S,S'-H_2B(L)_2}], (2a-d and 2a'- d'; R=Ph, Cy, OMe or OPh and L=C_5H_4NS or C7H_4NS_2) and [Ru{k~3-H,S,S'-H_2B(L)_2}_2], (3: L=C_5H_4NS, 3': L=C_7H_4NS_2) were isolated upon treatment of [(η~6-p-cymene)RuCl_2PR_3], 1a-d (R=Ph, Cy, OMe or OPh) with [H_2B(mp)_2]~- or [H_2B(mbz)_2]~- ligands (mp=2-mercaptopyridyl). All the Ru borate complexes, 2a-d and 2a'-d' are stabilized by phosphine/phosphite and hemilabile N,S-chelating ligands. Treatment of these Ru borate species, 2a'-c' with various terminal alkynes yielded two different types of five-membered ruthenacycle species, namely [PR_3{C7H_4S_2-(E)-N-C=CH(R')}Ru{k~3-H,S,S'- H_2B(L)_2}], (4-4'; R=Ph and R'=CO_2Me or C_6H_4NO_2; L= C_7H_4NS_2) and [PR_3{C_7H_4NS-(E)-S-C=CH(R')}Ru{k~3-H,S,S'- H_2B(L)_2}], (5-5', 6 and 7; R=Ph, Cy or OMe and R'=CO_2Me or C_6H_4NO_2; L=C_7H_4NS_2). 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_3