Ruthenium Arene Derivatives with PN Hemilabile Ligands. P−C Cleavage and Phosphine to Phosphinite Transformation

Abstract

Complexes of formula [RuCl 2 (arene)(κ 1 -dpim)] (dpim ) 2-(diphenylphosphino)-1-methylimidazole) (arene ) p-cymene, 1a; C 6 H 6 , 1b) were prepared by the reaction of [RuCl 2 (pcymene)] 2 or [RuCl 2 (C 6 H 6 )(CH 3 CN)] with dpim. Complexes 1a and 1b were structurally characterized by NMR spectroscopy and X-ray diffraction. The reaction of these precursors with BF 4salts led, in dichloromethane, to cationic complexes of formula [RuCl(arene)(κ 2dpim)]BF 4 (arene ) p-cymene, 2a; C 6 H 6 , 2b). However, in methanol the products were unexpected phosphinite derivatives of the type [RuCl(arene)(HImMe){κ 1 -PPh 2 (OMe)}]A (A ) BF 4 , arene ) p-cymene, 3a; C 6 H 6 , 3b; A ) BPh 4 , arene ) p-cymene, 3d) (ImMe ) methylimidazole). This transformation implies the existence of an easy P-C bond cleavage and phosphine functionalization with methanol at room temperature. The precursors 1a,b or the analogous derivative with 2-(diphenylphosphino)pyridine (PPh 2 py), [RuCl 2 (p-cymene)-(κ 1 -PPh 2 py)], 1c, reacted with HBF 4 to give cationic derivatives by protonation of the imidazole or the pyridine fragment, [RuCl 2 (arene)(κ 1 -PNH)]BF 4 (PNH ) dpimH, arene ) p-cymene, 4a; C 6 H 6 , 4b; PNH ) PPh 2 pyH, arene ) p-cymene, 4c). In these compounds the existence of an asymmetric and bifurcated hydrogen bond NH‚‚‚Cl 2 has been structurally determined (even by X-ray studies for 4a,b). Complexes 2a and 4a also yield the corresponding and analogous phosphinite derivatives in the presence of methanol-d 4 but at a markedly slower rate. NMR and spectrophotometric studies provided information concerning the formation of the phosphinite derivatives. It was concluded that the phosphine is not functionalized if it is not coordinated and that, very probably, a methanol solvatesintermediate between 1a and 2asparticipates in the P-C bond cleavage and allows the aforementioned transformation. Some preliminary catalytic tests involving the transfer hydrogenation of cyclohexanone and the hydrogenation of phenylacetylene have also been carried out.

Cytotoxicity of ruthenium(II) piano-stool complexes with imidazole-based PN ligands

“…[32,[34][35][36][37] All reactions were carried out in Schlenk tubes under an atmosphere of dry nitrogen using anhydrous solvents purified according to standard procedures. All chemicals were purchased from commercial sources and used as received.…”

“…4). The ruthenium atom is coordinated by 2a/b in the chelating κ [31,35,[47][48][49] and complexes [(cym)Ru(N-N)Cl] + with diammino ligands [31,50,51] .…”

Ruthenium piano-stool complexes bearing imidazole-based PN ligands

“…All calculations were carried out using the program Olex2. 41 Important crystallographic data and refinement details are summarised in 43 We synthesised several series of imidazole-based phosphine ligands in the last few years for biomimetic model complexes and metallo-drugs. 33,34,44,45,46,47 Here, these ligands as well as some new PN ligands, as depicted in Figure 1, were used in CpRu-complexes, which should catalyse the hydration of alkynes.…”

Bond Activation in Iron(II) and Nickel(II) Complexes of Polypodal Phosphanes

“…The reaction proceeds by insertion of the metal into a C-H bond of the ligand, and usually deactivates the catalyst. A less frequently observed type of side reaction is metal insertion into a C-P bond of the ligand, sometimes initiated by the solvent, which acts as a nucleophile [3]. We recently described what appears to be the first solvent-induced C-P bond cleavage in an alkylphosphane ligand [4,5].…”