Mixed unsymmetric oxadiazoline and/or imine platinum(ii) complexes

Abstract

Iminoacylation of acetone oxime Me₂CNOH 2 upon reaction with trans-[PtCl₂(NCCH₂CO₂Me)₂] 1 and [2 + 3] cycloaddition of acyclic nitrone ⁻O⁺N(Me)C(H)(C₆H₄Me-4) 3 to a nitrile ligand in 1 lead to the formation of mono-imine trans-[PtCl₂(imine-a)(NCCH₂CO₂Me)] 4 [imine-a = NHC(CH₂CO₂Me)ONCMe₂] and mono-oxadiazoline trans-[PtCl₂(oxadiazoline-a)(NCCH₂CO₂Me)] 6 [oxadiazoline-a = NC(CH₂CO₂Me)ON(Me)C(H)(C₆H₄Me-4)] unsymmetric mixed ligand complexes, respectively, as the main products. Reactions of 6 or 4 with acetone oxime 2, cyclic nitrone ⁻O⁺NCHCH₂CH₂CMe₂8 or N,N-diethylhydroxylamine 11 give access, in moderate to good yields, to the unsymmetric mixed ligand oxadiazoline and/or imine complexes trans-[PtCl₂(oxadiazoline-a)(imine-a)] 9, trans-[PtCl₂(oxadiazoline-a)(oxadiazoline-b)] 10 [oxadiazoline-b = NC(CH₂CO₂Me)ONC(H)CH₂CH₂CMe₂], trans-[PtCl₂(imine-a)(imine-b)] 12 [imine-b = NHC(CH₂CO₂Me)ONEt₂] or trans-[PtCl₂(imine-a)(oxadiazoline-b)] 13. The cis mono-imine mixed ligand complex cis-[PtCl₂(imine-a)(NCCH₂CO₂Me)] 4a is the major product from the reaction of cis-[PtCl₂(NCCH₂CO₂Me)₂] 1a with the oxime 2, while the di-imine compound cis-[PtCl₂(imine-a)₂] 5a is a minor product. Reaction of cis-[PtCl₂(imine-a)(NCCH₂CO₂Me)] 4a with N,N-diethylhydroxylamine 11 or the cyclic nitrone 8 affords, in good yields, the unsymmetric mixed ligand complexes cis-[PtCl₂(imine-a)(imine-b)] 12a or cis-[PtCl₂(imine-a)(oxadiazoline-b)] 13a, respectively. All these complexes were characterized by elemental analyses, IR and ¹H, ¹³C and ¹⁹⁵Pt NMR spectroscopies, and FAB⁺-MS. The X-ray structural analysis of trans-[PtCl₂{NHC(CH₂CO₂Me)ONCMe₂}(NCCH₂CO₂Me)] 4 is also reported.