Metallacycle Expansion by Alkyne Insertion. Chemistry of a New Family of Ruthenium Organometallics

Abstract

Acetylene and phenylacetylene reacts with carbonylchloro[4-methyl-6-((R-imino)methyl)phenolato-C,O]bis(triphenylphosphine)ruthenium(II), Ru(RL 1 )(PPh 3 ) 2 (CO)Cl (3), affording the inserted product carbonylchloro[2-vinyl-4-methyl-6-((R-imino)methyl)phenolato-C,O]bis-(triphenylphosphine)ruthenium(II), Ru(RL 2 ,X)(PPh 3 ) 2 (CO)Cl ( 4), in virtually quantitative yield. The X-ray structures of 4b (R ) X ) Ph) and 4g (R ) Et, X ) H) have revealed the presence of distorted-octahedral RuC 2 P 2 ClO coordination spheres. In the conversion 3 f 4, the Ru(C,O) chelate ring expands from four-membered to six-membered. The insertion of phenylacetylene is regiospecific, and a reaction model implicating initial Ru-O cleavage and steric control is proposed. The Ru-O bond in 4 is significantly shorter (by ∼0.14 Å) and stronger than that in 3. This is reflected in the lowering of the ruthenium(III)ruthenium(II) reduction potential by ∼200 mV. The uncoordinated Schiff base moiety in 4 is present in the hydrogen-bonded iminium-phenolato zwitterionic form, as revealed by the N‚‚‚O distance as well as by IR and NMR data.

Ruthenium(III) Cyclometalates Obtained by Site‐Specific Orthometallation and Their Reactivity with Nitric Oxide: Photoinduced Release and Estimation of NO Liberated from the Ruthenium Nitrosyl Complexes

“…This peak disappeared after shaking the NMR sample solution in D 2 O, which supported the presence of an exchangeable proton in the -OH functional group ( Figure S14). [11,23] These data supported a dissociation of the Ru-O Ph bond during NO coordination in 1a.…”

Zwitterionic Organometallates

“…This complex could be described by the zwitterionic structure 38, featuring an NH⋅⋅⋅O hydrogen bond. [67] Scheme 16 Milstein and co-workers reported that a non-zwitterionic Pt IV complex produced by intramolecular C-H activation of a neutral Pt II complex undergoes spontaneous stabilization through intramolecular proton-transfer to a pendant amino group to give the zwitterionic Pt II complex 39 (Scheme 17). [68] Scheme 17…”

Synthesis, characterization and photophysical properties of quinolin-8-olato chelated osmium(II) organometallics bearing a pendant imine-phenol motif and electrogeneration of trivalent analogue

“…We are scrutinizing the reactivity of these compounds. It has been found that different alkynes undergoes facile insertion into the Ru-C bond of the fourmembered ruthenium metallacycles leading to two carbon expansion [20][21][22] whereas the osmium analogue remains unreactive. Upon treatment with isonitrile ruthenium system undergoes halide substitution as well as insertion into the Ru-O bond and the resultant product then exhibits aryl migration and C-C bond formation [23,24] while in case of osmium system isonitrile simply displaced bromide ligand furnishing the cationic complexes which are isolated as salts [25].…”