Diruthenium(II,III) tetramidates as a new class of oxygenation catalysts

Abstract

Two new diruthenium(II,III) tetramidate compounds, Ru(2)(NHOCC(CH(3))(2))(4)Cl (1) and Ru(2)(NHOCCH(2)CH(3))(4)Cl (2) have been prepared and structurally characterized by X-ray crystallography. The activity of promoting sulfide oxygenation using simple oxidants such as hydrogen peroxide (H(2)O(2)) and tert-butyl hydroperoxide (TBHP) was studied. A UV-kinetics study indicated that the initial rates of 1 and 2 are comparable to the previously studied diruthenium tetracarboxylates in promoting TBHP oxygenation of methyl phenyl sulfide (MPS). Using excess oxidant and CH(3)CN as the solvent, organic sulfides MPS and diphenyl sulfide (PPS) were oxidized using 1 mol% of the catalytic species. Compound 1 is more effective than 2 in converting sulfides to sulfoxide under the same conditions. Fast conversion was achieved when the reactions were carried out in the solvent-free conditions, and the major oxidation product was the sulfoxide. The electronic structure of the title compounds was studied with DFT calculations to gain an understanding of the activation of peroxy reagents.

Synthesis, Crystal Structure, and Magnetic Properties of Amidate and Carboxylate Dimers of Ruthenium

“…However, the thermal activation in solution does not produce the complexes as has been previously observed for analogous compounds [6][7][8][9][10][11][12][13]. To achieve the substitution of the carboxylate ligands in [Ru 2 X(µ-O 2 CMe) 4 ] n (X = Cl, Br, I) by the corresponding amidate groups the presence of triethylamine and the corresponding halide salt (LiCl for 1, KBr for 2 and KI for 3) have been used in both methods [19].…”

“…In the 1-3 amidate complexes, due to the asymmetry of the amidate ligands, four linkage isomers are possible, depending on the relative coordination of the ligands [17]. However, the three complexes show a cis-RuN 2 O 2 environment similar to that observed in the other tetraamidatodiruthenium complexes described in the literature [8,9,[11][12][13]17,18]. Thus, in these complexes, each diruthenium unit resides on a center of inversion, and the asymmetric unit consists of two half dimers linked by the halide ligand, resulting in zigzag chains.…”

“…The usual method for obtaining these compounds is through a metathesis reaction of [Ru 2 Cl(µ-O 2 CMe) 4 ] with an excess of the corresponding carboxylic acid in a mixture of methanol/water (1:1) at reflux for several hours [4,5]. However, the interchange reaction of the acetate ligands by amidate groups to give the analogous [Ru 2 Cl(µ-NHOCR) 4 ] cannot be carried out under mild reaction conditions [6][7][8][9][10][11][12][13]. Johnson and Powell [14] demonstrated some years ago that the microwave activation is useful to prepare dimolybdenum compounds in short periods of time and with good yields.…”

Synthesis, Structure and Magnetic and Electrochmical Properties of Tetrakis(benzamidato)diruthenium(II,III) Tetrafluoroborate

“…The result is shown in Figure 4. The redox wave at E1/2 ((Epa + Epc)/2) = 1.12 V (vs. SCE) in the oxidation side was attributed to a Ru2 6+ /Ru2 5+ couple on referring to the CV results obtained for the Ru2 5+ complexes with amidato bridges [11- 13,18], while irreversible waves were subsequently shown at ca. −0.5 and ca.…”

“…Such spin state change from S = 3/2 to S = 1/2 has not been reported on the removal of the axial halogenide ligand from [Ru2(O2CR)4X]. Amidate ions with an N,O-donor set have also been known to work as a dinucleating bridging ligand to give a lantern-type structure [11][12][13][14][15][16][17][18][19][20][21]. One of the amidates is benzamidate (PhCONH − ), the chemical structure of which is shown in Scheme 1b.…”