Reaction of the Pt­(II) complexes [PtMe2(pbt)], 1a, (pbt = 2-(2-pyridyl)­benzothiazole) and [PtMe­(C^N)­(PPh2Me)] [C^N = deprotonated 2-phenylpyridine (ppy), 1b, or deprotonated benzo­[h]­quinoline (bhq), 1c] with benzyl bromide, PhCH2Br, is studied. The reaction of 1a with PhCH2Br gave the Pt­(IV) product complex [PtBr­(CH2Ph)­Me2(pbt)]. The major trans isomer is formed in a trans oxidative addition (2a), while the minor cis products (2a′ and 2a″) resulted from an isomerization process. A solution of Pt­(II) complex 1a in the presence of benzyl bromide in toluene at 70 °C after 7 days gradually gave the dibromo Pt­(IV) complex [Pt­(Br)2Me2(pbt)], 4a, as determined by NMR spectroscopy and single-crystal XRD. The reaction of complexes 1b and 1c with PhCH2Br gave the Pt­(IV) complexes [PtMeBr­(CH2Ph)­(C^N)­(PPh2Me)] (C^N = ppy; 2b; C^N = bhq, 2c), in which the phosphine and benzyl ligands are trans. Multinuclear NMR spectroscopy ruled out other isomers. Attempts to grow crystals of the cycloplatinated­(IV) complex 2b yielded a previously reported Pt­(II) complex [PtBr­(ppy)­(PPh2Me)], 3b, presumably from reductive elimination of ethylbenzene. UV–vis spectroscopy was used to study the kinetics of reaction of Pt­(II) complexes 1a–1c with benzyl bromide. The data are consistent with a second-order SN2 mechanism and the first order in both the Pt complex and PhCH2Br. The rate of reaction decreases along the series 1a ≫ 1c > 1b. Density functional theory calculations were carried out to support experimental findings and understand the formation of isomers.

The starting complex [Pt(Me)(DMSO)(pbz)], (1, (pbz = 2-(2pyridyl)benzimidazolate) was prepared by a known method using the 1 reaction of [Pt(Me) 2 (DMSO) 2 ], A, with Hpbz at room temperature. Reaction of 1 with an equivalent of a phosphine ligand gave the neutral mononuclear complexes [Pt(Me)(L)(pbz)], )] ( 2, (L = PPh 3 ) or and 3, (L =PPh 2 Me). Reaction of 1 with 0.5 equivalent of the linear diphosphine 1,1'-bis(diphenylphosphino)acetylene (dppac) gave the binuclear complex [Pt 2 (Me) 2 (μ-dppac)(pbz) 2 ], 4. All Each the complexes were was fully characterized by NMR spectroscopy, X-ray crystallography and mass spectrometry. The photophysical properties of the complexes were investigated in under different conditions and interpretation was, supported by TD-DFT calculations. The low-lying transitions in the absorption and emission spectra were assigned as having LLCT/MLCT (ligand to ligand charge transfer/metal-to-ligand charge transfer) character. We also describe the luminescence properties of [Pt(Me)(PPh 3 ) (ppy)], 7, and [Pt(Me)(PPh 2 Me)(ppy)], 8, (ppy is 2-phenylpyridinate), the (N^C  ) analogues of 2 and 3.

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The reaction of complex [Pt(Me)(DMSO)(pbz)], 1, (pbz = 2-(2-pyridyl)benzimidazolate) with [PtMe(Cl)(DMSO)2], B, followed by addition of bis(diphenylphosphino)acetylene (dppac), gave the novel tetranuclear platinum complex [Pt4Me4(µ-dppac)2(pbz)2Cl2], 2, bearing both the pbz and dppac ligands. In this structure, the pbz ligands act as both chelating and bridging to stabilize the tetraplatinum framework. The tetranuclear Pt(II) complex was fully characterized by NMR spectroscopy, X-ray crystallography and mass spectrometry and its electronic structure was investigated and supported by DFT calculations.

Number: 97012633 and 990144222-(2 0 -Pyridyl)benzimidazole (Hpbz), containing both C-H and N-H bonds available for activation, has been investigated to elucidate which bond is activated upon coordination to the Pt(II) precursor complex (PtMe 2 (DMSO) 2 ), 1.On the basis of density functional theory (DFT), Hpbz is predicted to react with 1 through N-H bond activation of the benzimidazole ring in preference to C-H bond activation of the pyridine ring. The reasons for this difference in selectivity are discussed based on the energy barrier needed for N-H versus C-H bond activation. The DFT results are in agreement with experimental findings in which reaction of Hpbz with 1 at room temperature leads to N-H bond activation to give (PtMe(pbz-κ 2 -N,N)(DMSO)), 2. The kinetic and mechanistic study of the reaction between Hpbz and 1 shows that the reaction occurs through substitution of one DMSO by the nitrogen atom of pyridine ring of Hpbz to give (PtMe 2 (Hpbz-κ 1 N)(DMSO)), followed by N-H activation and release of methane to form 2.