The metal-mediated coupling between coordinated EtCN in the platinum(II) and platinum(IV) complexes cis- and trans-[PtCl2(EtCN)(2)], trans-[PtCl4(EtCN)(2)], a mixture of cis/trans-[PtCl4(EtCN)(2)] or [Ph3PCH2Ph][PtCln(EtCN)] (n = 3, 5), and dialkyl- and dibenzylhydroxylamines R2NOH (R = Me, Et, CH2Ph, CH2C6Cl-P) proceeds smoothly in CH2O2 at 20-25 degrees C and the subsequent workup allowed the isolation of new imino, species [PtCln{NH=C(Et)-ONR2}(2)] (n = 2, R = Me, cis-1 and trans-1; Et, cis-2 and trans-2; CH2Ph, cis-3 and trans-3; CH2C6H4Cl-p, cis-4 and trans-4; n = 4, R = Me, trans-9; Et, trans-10; CH2Ph, trans-11; CH2C6H4Cl-p, trans-12) or [Ph3PCH2Ph]-[PtCln{NH=C(Et)ONR2}] (n = 3, R = Me, 5; Et, 6; CH2Ph, 7; CH2C6H4Cl-p, 8; n = 5, R = Me, 13; Et, 14; CH2Ph, 15; CH2C6Cl-p, 16) in excellent to good (95-80%) isolated yields. The reduction of the Pt(IV) complexes 9-16 with the ylide Ph3P=CHCO2Me allows the synthesis of Pt(II) species 1-8. The compounds 1-16 were characterized by elemental analyses (C, H, N), FAB-MS, IR, H-1, C-13{H-1}, and P-31 {H-1} NMR (the latter for the anionic type complexes 5-8 and 13-16) and by X-ray crystallography for the Pt(II) (cis-1, cis-2, and trans-4) and Pt(IV) (15) species. Kinetic studies of addition of R2NOH (R = CH2C6H4Cl-P) to complexes [Ph3PCH2Ph][(PtCl3)-Cl-parallel to(EtCN)] and [Ph3PCH2Ph][(PtCl5)-Cl-IV(EtCN)] by the H-1 NMR technique revealed that both reactions are first order in (p-CIC6H4CH2)(2)NOH and Pt(II) or Pt(IV) complex, the second-order rate constant k(2) being three orders of magnitude larger for the Pt(IV) complex. The reactions are intermolecular in nature as proved by the independence of k(2) on the concentrations of added EtC&3bond; N and Cl-. These data and the calculated values of Delta H-double dagger and Delta S-double dagger are consistent with the mechanism involving the rate-limiting nucleophilic attack of the oxygen Of (p-ClC6H4CH2)(2)NOH at the sp-carbon of the C&3bond; N bond followed by a fast proton migration.