Half sandwich complexes of Ru(II) and complexes of Pd(II) and Pt(II) with seleno and thio derivatives of pyrrolidine: Synthesis, structure and applications as catalysts for organic reactions

Reactions of benzene based half sandwich ruthenium(II) complex with 2,6-bis((phenylseleno)methyl)pyridine: Preferential substitution of ring resulting in a catalyst of high activity for oxidation of alcohols

“…The advantages of 1 in comparisons to recently reported Ru based good catalytic species [30,33,36,[41][42][43][44][45] for oxidation of alcohols are: (i) high efficiency/yield as they are needed in less quantity and (ii) short reaction time. The half sandwich Ru(II) complexes containing chalcogenated pyrrolidine, benzotriazole, Schiff base and morpholine known to catalyze the oxidation of alcohols efficiently with NMO [23,25,46,47] (TON up to 9.8 × 10 4 ) are comparable with the present complexes (TON up to 9.7 × 10 4 ). The cyclic voltammetric experiment performed at 298 K in CH 3 CN (0.01 M NBu 4 ClO 4 as supporting electrolyte) for 1 at scan rate 100 mVs − 1 (anodic sweep) reveals an irreversible oxidation by one electron transfer with E 1/2 value 0.587 V (vs. Ag/AgCl) (see Table S3 and Fig.…”

“…The percentage yields and conversions do not differ much. The earlier work carried out on the mechanism of such catalytic oxidation suggests that Ru(IV) = O species [23,[25][26][27][28][29][30][31][32][33][34][35]46,47] are involved. On adding NMO to the solution of complex 1 the signal in its 77 Se{ 1 H} NMR spectrum goes to higher frequency ≥353 ppm.…”

“…In UV-visible spectrum, on addition of NMO to a dichloromethane solution of 1, a new shoulder at 392 nm appears which is believed [23,25,[32][33][34][35][36][37]46,47] to be due to Ru(IV) = O species, reported to be responsible for transfer of the oxygen to alcohol substrates resulting in their catalytic oxidation. IR spectrum of the residue left after evaporating off solvent from the mixture of NMO with 1, exhibits a very strong band at 845 cm − 1 (ν P-F at 839 cm − 1 is of medium intensity only), which further supports the formation of Ru (IV) = O species [23,25,28,33,[36][37][38][39][40]46,47] which is probably responsible for catalytic oxidation of alcohols. The 1 H NMR spectrum of 1 recorded after adding NMO becomes broad, indicating the formation of paramagnetic species as intermediate.…”

“Piano‐Stool” Complexes of Ruthenium(II) Designed with Arenes and N‐[2‐(Arylchalcogeno)ethyl]morpholines: Highly Active Catalysts for the Oxidation of Alcohols with N‐Methylmorpholine N‐Oxide, tert‐Butyl Hydroperoxide and Sodium Periodate and Oxychloride

“…The Ru–S bond length in the cation of 1 is 2.3815(12) Å, somewhat longer than that in 3 [2.3742(14) Å]. Both are within the range 2.3548(15)–2.4156(9) Å in which the Ru–S bond lengths of [(η 6 ‐C 6 H 6 )ruthenium(II)Cl(S,N)ligand] + , [(η 6 ‐C 6 H 6 )ruthenium(II)(S,N,Se)ligand] + , [Cp*Ru(PMe 3 ) 2 (SC 6 F 4 H)], and [Cp*Ru(NO)(SC 6 F 4 H) 2 ] are reported29–31 to fall. Complex 4 is a new example of the little known (η 6 ‐arene)(seleno ether)ruthenium(II) complex (arene = η 6 ‐C 6 H 6 or η 6 ‐ p ‐cymene) 29,30,32.…”

Palladium and half sandwich ruthenium(II) complexes of selenated and tellurated benzotriazoles: Synthesis, structural aspects and catalytic applications

“…The Rucomplexes of selenoether ligands have scantly investigated. However, Ru(II)(g 6 -benzene)-and Ru(II)(g 6 -p-cymene)-complexes of selenated pyrrolidine derivatives have been reported by our research group recently in which Ru is coordinated through Se and N forming a five membered chelate ring [38]. The 3 is another example of such Ru-selenoether complex.…”