Isonitrile Insertion into the Ru−O Bond and Migratory C−C Bond Formation. Novel Organoruthenium Imidic Ester and Acyl Species

Abstract

Organometallics of type [Ru(C 6 H 2 O-2-CHNHC 6 H 4 R-3-Me-5)(PPh 3 ) 2 (CO)(Cl)], 3 (R ) H, Me, OMe, Cl), incorporating a four-membered C,O chelate ring smoothly react with CNBu t in benzene solution affording the yellow-colored organoruthenium imidic ester hydrochloride system [Ru(C 6 H 2 OCN(Bu t )HCl-2-CHNC 6 H 4 R-3-Me-5)(PPh 3 ) 2 (CO)(CNBu t )], 4, in which a fivemembered C,C chelate ring is present. While stable in the solid state, 4 is spontaneously reactive in solution, furnishing the red-colored chelate [Ru(C 6 H 2 (CO-1)O-2-CHNHC 6 H 4 R-3-Me-5)(PPh 3 ) 2 (CNBu t )(Cl)], 5, incorporating five-membered acyl-phenolato C,O chelation. Chloride elimination from 5 by excess CNBu t furnishes [Ru(C 6 H 2Characteristic spectral features of the families are reported. A notable electrochemical feature is that the Ru(III)/Ru(II) reduction potential increases with increasing number of carbon atoms in the coordination sphere: 5 < 6 + < 4. The X-ray structures of 4(Me), 5(H), and [6(Me)]Cl‚2CH 2 Cl 2 are reported. The equatorial coordination planes are RuC 4 , RuC 2 OCl, and RuC 3 O, respectively, the axis being uniformly defined by the trans RuP 2 fragment. Both 5(H) and 6(Me) + display iminium-phenolato N-H‚‚‚O hydrogen bonding, while in 4(Me), N-H‚‚‚Cl and C-H‚‚‚O hydrogen bondings are present. In the transformation 3 f 4, one CNBu t molecule displaces the chloride ligand and another inserts into the Ru-O bond, generating a chelated imidic ester function. In 4(Me) the Ru-CO bond (1.891(8) Å) lying trans to the imidic ester carbon is ∼0.1 Å longer than that in the precursor complex 3(Me). The Ru-C(aryl) distance is also longer in 4(Me) by 0.04 Å. Thus both the bonds are activated by isonitrile insertion and the transformation 4 f 5 occurs spontaneously with C-C bond formation via aryl migration attended with isonitrile elimination, the reaction following first-order kinetics. The activation parameters determined for the 4(Cl) f 5(Cl) reaction are ∆H q , 18.72(1.00) kcal mol -1 , and ∆S q , -17.89(3.20) eu, implying that the transition state is ordered but with an excess of net bond breaking over net bond formation. Logarithmic rate constants are found to vary linearly with the Hammett constant of the R substituent, consistent with nucleophilic aryl migration.

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

“…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]. It is indeed found that ruthenium metallacycle is smoothly converted to the acyl system upon reaction with carbon monoxides under ambient conditions whereas the osmium analogue did not lead to insertion and afforded only an unreactive cisdicarbonyl complex [26].…”

Metallacycle Expansion via butadiyne/octadiyne Insertion into a Four-membered Ruthenium Organometallic

“…The reactivity of (1) is under scrutiny. Isocyanides [6] and alkynes [7] promote metallacycle expansion but bidentate monoanionic r-donor reagents such as carboxylates [8], palmitate and terephthalate [9], nitrate and nitrite [10], thioxanthate [11], pyridine-2-thiolate [12] invariably form a fourmembered chelate ring, electroneutral a-diimine ligand [13], and 8-hydroxyquinoline [14] undergoes fivemembered chelation.…”

Synthesis, Structure, and Properties of Biimidazole‐Chelated Arylruthenium Complexes

“…Alkynes and isocyanides promote metallacycle expansion [5,6,8,15,16] but bidentate monoanionic σ-donor reagents such as carboxylates, nitrate, nitrite, xanthate, and pyridine-2-thiolate invariably form a four-membered chelate ring.…”

“…The cation and anion in the complex are engaged in N−H···F and C−H···F hydrogen bonding, generating a centrosymmetric dimer in the lattice. One of the hydrogen bonds, characterized by H···F, 2.03 (8) Å and N−H···F, 166(2)°, is particularly strong. Solutions of 2 absorb near 400 nm and emit near 460 nm with quantum yields and lifetimes of ca.…”

“…Another relevant plane (plane B) is the metallated aldimine ring defined by Ru, C(1) to C (8), N(1), O(1) (mean deviation 0.03 Å ). The two planes are noncoplanar as highlighted in 7, the dihedral angle between them is 34.5°.…”