Reaction of K 2 [Pt I I Cl 4 ] with 2-propanone oxime in water gives the complexes cis-[Pt I I Cl 2 (Me 2 C = NOH) 2 ] and [Pt I I Cl 3 -(Me 2 C = NOH)] - , the latter one isolated as the tetra(n-butylammonium) salt upon addition of [(n-Bu) 4 N][HSO 4 ] to the solution separated from the former complex. [(n-Bu) 4 N][PtCl 3 (Me 2 C = NOH)] crystallizes from water in the orthorhombic space group Pbcn with a = 13.773(3), b = 21.794(5), c = 8.7460(10) 9; V = 2625.3(9) 9 3 , Z = 4, and ρ(calc) = 1.561 g cm - 3 . Other anionic-type oxime complexes, Q[PtX 3 (RR C = NOH)] where Q = (n-Bu) 4 N, X = Br, R = R = Me; Q = Ph 3 PCH 2 Ph, X = Cl, R = R = Me, R = Me, R = Et, RR = C 4 H 8 and C 5 H 1 0 , were prepared analogously. Reactions of [(n-Bu) 4 N][PtCl 3 (Me 2 C = NOH)] or a mixture of Me 2 C = NOH and K 2 [PtCl 4 ] with concentrated (about 36%) aqueous HCl lead to the oxidation of Pt(II) species and concurrent reductive hydrolysis of the oxime to give (NH 4 ) 2 [Pt I V Cl 6 ] and either [(n-Bu) 4 N] 2 [Pt I V Cl 6 ] or K 2 [Pt I V Cl 6 ].