The metalla-Pinner reaction between Pt(iv)-bound nitriles and alkylated oxamic and oximic forms of hydroxamic acids

Abstract

The nitrile ligands in the platinum(IV) complexes trans-[PtCl₄(RCN)₂] (R = Me, Et, CH₂Ph) and cis/trans-[PtCl₄(MeCN)(Me₂O)] are involved in a metalla-Pinner reaction with N-methylbenzohydroxamic acid (N-alkylated form of hydroxamic acid, hydroxamic form; F1), PhC(O)N(Me)OH, to achieve the imino species [PtCl₄{NHC(R)ON(Me)C(O)Ph}₂] (1–3) and [PtCl₄{NHC(Me)ON(Me)C(O)Ph}(Me₂O)] (7), respectively. Treatment of trans-[PtCl₄(RCN)₂] (R = Me, Et) and cis/trans-[PtCl₄(MeCN)(Me₂O)] with the O-alkylated form of a hydroxamic acid (hydroximic form), i.e. methyl 2,4,6-trimethylbenzohydroximate, 2,4,6-(Me₃C₆H₂)C(OMe)NOH (F2A), allows the isolation of [PtCl₄{NHC(R)ONC(OMe)(2,4,6-Me₃C₆H₂)}₂] (5, 6) and [PtCl₄{NHC(Me)ONC(OMe)(2,4,6-Me₃C₆H₂)}(Me₂O)] (8), correspondingly. In accord with the latter reaction, the coupling of nitriles in trans-[PtCl₄(EtCN)₂] with methyl benzohydroximate, PhC(OMe)NOH (F2B), gives [PtCl₄{NHC(Et)ONC(OMe)Ph}₂] (4). The addition proceeds faster with the hydroximicF2, rather than with the hydroxamic form F1. The complexes 1–8 were characterized by C, H, N elemental analyses, FAB⁺ mass-spectrometry, IR, ¹H and ¹³C{¹H} NMR spectroscopies. The X-ray structure determinations have been performed for both hydroxamic and hydroximic complexes, i.e. 2 and 6, indicating that the imino ligands are mutually trans and they are in the E-configuration.