Metal-assisted coupling of oximes and nitriles: a synthetic, structural and theoretical study

Abstract

or Ph(NH 2 )] to give the corresponding iminoacylated product [Ph 3 PCH 2 Ph][PtCl 5 {HN᎐ ᎐ C(Et)ON᎐ ᎐ CR 1 R 2 }]. All compounds were characterized by elemental analyses, FAB mass spectrometry, IR and 1 H, 13 C-{ 1 H}, 31 P-{ 1 H} and 195 Pt NMR spectroscopies. A crystal structure determination of [Ph 3 PCH 2 Ph][PtCl 5 {NH᎐ ᎐ C(Et)ON᎐ ᎐ C(C 9 H 16 )}] disclosed amidine one-end rather than the N,N-bidentate co-ordination mode of the N-donor ligand. The iminoacylation by oximes was investigated by ab initio methods (at RHF level using quasi-relativistic pseudopotentials for platinum) for [PtCl 5 (NCMe)] Ϫ which were also applied to the related neutral platinum() [PtCl 4 (NCMe) 2 ] and platinum() [PtCl 2 (NCMe) 2 ] complexes. The calculations included geometry optimization of the starting and final complexes, location of possible transition states for the reaction discussed and intrinsic reaction coordinate calculations for one reaction. The results obtained provided an interpretation, on the basis of kinetic (activation energies) and thermodynamic (reaction energies) effects, for the order of reactivity observed [neutral Pt IV > anionic Pt IV > neutral Pt II ] and indicated that a mechanism based on nucleophilic addition of the protic nucleophile (undeprotonated oxime), to form a transition state with a four-membered NCOH ring, is energetically favoured relative to the alternative one involving prior deprotonation of the oxime, unless base-catalysed conditions are operating. Scheme 1 Reactions of Pt IV -bound organonitriles with oximes and nitrones.

Substitution Kinetics of [Fe(PDT/PPDT)n(phen)m]2+(n≠m;n,m= 1,2) with 2,2′-Bipyridine, 1,10-Phenanthroline, and 2,2′,6,2″-Terpyridine

“…The energy of HOMO and LUMO are associated with the electron‐donating and electron‐accepting abilities of the complexes, respectively . The complexes with smaller HOMO–LUMO energy gap are reactive and kinetically labile . This is also the case in the present study, where the HOMO–LUMO energy gap gradually decreases from complex 1 to 4 as the reactivity increases.…”

Copper(I)-Catalyzed 1,3-Dipolar Cycloaddition of Ketonitrones to Dialkylcyanamides: A Step toward Sustainable Generation of 2,3-Dihydro-1,2,4-oxadiazoles

“…We have successfully used this approach in studies of similar metal-assisted and metal-free 1,3-dipolar CA reactions of nitrones to isocyanides 20 and nitriles, 21 and metal-assisted coupling of oximes and nitriles. 22…”

Triphenylbenzylphosphonium trichloro(propiononitrile)platinate(II)

“…As part of our interest in the reactivity of metal-activated nitriles toward nucleophilic addition (Kukushkin & Pombeiro, 2002), we have performed two kinetic studies devoted to the addition of such HON-nucleophiles as N,N-dialkylhydroxylamines (Luzyanin et al, 2005) and oximes (Luzyanin et al, 2006) to Pt-bound organonitriles. The known complex [Ph 3 PCH 2 Ph][PtCl 3 (EtCN)], (I), (Kuznetsov et al, 2000) has been chosen as a convenient starting material for these studies because it has only one nitrile ligand, in contrast to the more common [PtCl 2 (RCN) 2 ], and can be easily prepared in a pure form. Here we report the molecular structure of (I), determined by a single-crystal X-ray diffraction analysis.…”