Platinum(iv)-mediated hydrolysis of nitriles giving metal-bound iminols

The platinum(IV) complexes cis/trans-[PtCl4(MeCN)2] and trans-[PtCl4(EtCN)2] react smoothly and under mild conditions with water, contained in non-dried commercial acetone, to afford trans-[PtCl4{N(H)C(OH)Me}2]·Me2CO (1) or trans-[PtCl4{N(H)C(OH)Et}2] (2); no hydroxide is required, in contrast to relevant platinum(II) systems, to furnish the metal-bound carboxamides which are stable in the iminol form. In non-dried acetone, reaction between trans-[PtCl4(EtCN)2] and MeC(O)NH2 gives a mixture of 1 (derived from substitution) and 2 (derived from the hydrolysis), while in non-dried dichloromethane an isomorphic mixture of cis-[PtCl4{N(H)C(OH)Me}2] and cis-[PtCl4{N(H)C(OH)Et}2], i.e.cis-[PtCl4{Z-N(H)C(OH)Me}2]0.66·cis-[PtCl4{Z-N(H)C(OH)Et}2]0.33 (3) is obtained. Complexes 1–3 were characterised by elemental analyses (C, H, N), FAB+-MS, IR, 1H- and 13C{1H}-NMR spectroscopy. Complexes 2 and 3 were also characterised by 195Pt-NMR spectroscopy. Crystal structures of 2 and 3 provide the first examples of structurally characterised platinum(IV) complexes with amides in their iminol form. The equilibrium structures for the geometrical and linkage isomers of the platinum(II) complexes [PtIICl2{N(H)C(OH)Me}2] and [PtIICl2{OC(NH2)Me}2] and the platinum(IV) compounds [PtIVCl4{N(H)C(OH)Me}2] and [PtIVCl4{OC(NH2)Me}2] were calculated at the B3PW91 level of theory and the study shows that the most stable isomers for both platinum(II) and platinum(IV) complexes are the trans-(iminol)Pt forms, in accord with the experimental results.