The complex [PtMe2(9N3)], 1, 9N3 = 1,4,7-triazacyclononane, undergoes protonation by triflic acid and, reversibly, even by methanol to form the cationic complex [PtHMe2(9N3)]+, 2, which is thermally stable up to 190 °C in the solid state as the triflate salt. Oxidation of 1 or 2 by H2O2 or by H2O/O2 gives the hydroxy complex [Pt(OH)Me2(9N3)]+, which can be reversibly protonated to the aqua complex [Pt(OH2)Me2(9N3)]2+.

A hydrido(methyl)(carbene)platinum(IV) complex, using a stabilized Arduengo carbene, has been formed and characterized at low temperature by NMR. The electron-rich carbene complex [PtMe2{C3H2N2(CH2-2-py)2}] reacts with MeX (X = I or CF3SO3) to give [PtMe3{C3H2N2(CH2-2-py)2}]X and is protonated at low temperature to give [PtHMe2{C3H2N2(CH2-2-py)2}]X, X = CF3SO3, BF4, or CF3CO2. At room temperature [PtHMe2{C3H2N2(CH2-2-py)2}]+ undergoes irreversible reductive elimination of methane and dimerizes to give a binuclear bis{methyl(carbene)platinum(II)} complex cation [Pt2Me2{C3H2N2(CH2-2-py)2}2]2+.

The effect of changing the bite angle of the dipyridyl ligand LL on the reactivity of the dimethylplatinum-(II) complexes [PtMe 2 (LL)] has been studied, by comparing complexes with the ligands LL ) di-2pyridylamine (DPA) or di-2-pyridyl ketone (DPK), which form a six-membered chelate ring, to compounds with 2,2′-bipyridyl derivatives, which form a five-membered chelate ring. The complex [PtMe 2 (DPA)] undergoes easy oxidative addition of methyl iodide to give the corresponding platinum(IV) complex [PtIMe 3 (DPA)]. Both [PtMe 2 (DPA)] and [PtMe 2 (DPK)] are protonated by acids HX at low temperature to give the hydridodimethylplatinum(IV) complexes [PtHXMe 2 (NN)] and [PtH(S)Me 2 (NN)]X (S ) solvent), which can exist in two isomeric forms with H trans to X or N. The structure of the complex [PtHClMe 2 (DPK)] was determined crystallographically. In a solution containing excess CD 3 OD, extensive hydrogen/deuterium exchange occurs into the methylplatinum groups and methane product at low temperature, indicating very easy reversibility of the exchange between hydridomethylplatinum(IV) and (methane)platinum(II) complexes. The hydridomethylplatinum(IV) complexes reductively eliminate methane at room temperature in solution but have significantly higher thermal stability and undergo more extensive H-D exchange than when NN ) 2,2′-bipyridyl. The reaction of [PtMe 2 (DPA)] with excess HCl gave [PtCl 2 (DPA)], and the reaction of [PtMe 2 (DPK)] with excess CF 3 SO 3 H gave the aqua complex [Pt(OH 2 ) 2 (DPK)](CF 3 SO 3 ) 2 or the binuclear hydroxo complex [Pt 2 (µ-OH) 2 (DPK) 2 ](CF 3 SO 3 ) 2 , depending on the experimental conditions.

The flexible, unsymmetrical triamine ligands NNN ) N,N,N′-trimethyl-N′-(2-pyridylmethyl)ethylenediamine (PICO), N-benzyl-N′,N′-dimethyl-N-(2-picolyl)ethylenediamine (BPICO), and N,N′,N′′-pentamethyldiethylenetriamine (PMDETA) act as bidentate ligands in forming square-planar dimethylplatinum(II) complexes cis-[PtMe 2 (NNN)]. These complexes undergo oxidative addition with MeI to give the platinum(IV) complexes fac-[PtMe 3 (NNN)]I, in which the ligand NNN is fac-tridentate in [PtMe 3 (NNN)]I when NNN ) PICO or BPICO, but in equilibrium with bidentate NNN in [PtIMe 3 (NNN)] when NNN ) PMDETA. Protonation of the complexes cis-[PtMe 2 (NNN)] gave the corresponding dimethyl(hydrido)platinum(IV) complexes, [PtHMe 2 (NNN)]X (X ) BF 4 -, CF 3 SO 3 -, CF 3 CO 2 -), often as a mixture of isomers whose structures were deduced from the NMR spectra. These hydridoplatinum-(IV) complexes undergo reductive elimination of methane to give the methylplatinum(II) complexes [PtMe(NNN)]X, in which NNN is a mer-tridentate ligand, with the rate of reaction for NNN ) PMDETA > PICO, BPICO. In all cases, H/D exchange experiments indicate reversibility of the protonation and methyl(hydride) to methane complex steps in the reaction sequence.

The dimethylplatinum(II) complex [PtMe2(Me3TACN)] (Me3TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane) reacts easily with Me3SnCl, Me2SnCl2, or HX (X = CF3CO2, CF3SO3, BF4) to give the thermally stable cationic dimethyl platinum(IV) complexes [Pt(SnMe3)Me2(Me3TACN)]+, [Pt(SnMe2Cl)Me2(Me3TACN)]+, or [PtHMe2(Me3TACN)]+. The complexes [PtMe2(Me3TACN)] and [PtHMe2(Me3TACN)]+ are oxidized by moist air to give the hydroxo complex [PtMe2(OH)(Me3TACN)]+, which can then be protonated reversibly to form the aqua complex [PtMe2(OH2) (Me3TACN)]2+. The structures of the hydroxo complex [PtMe2(OH)(Me3TACN)]+, as both the BF[Formula: see text] or CF3SO[Formula: see text] salt, and of the mixed hydroxo, aqua complex [PtMe2(OH)(Me3TACN)][PtMe2(OH2)(Me3TACN)][BF4]3 have been determined and the complexes are shown to display interesting hydrogen bonding. Key words: platinum, oxidation, organometallic, tin, hydride.