Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, 700 032, India.
Dalton Trans. 2010 Mar 14;39(10):2717-26. doi: 10.1039/b918336a. Epub 2010 Feb 2.
Chemical reactions of Pt(pap)Cl(2) [pap = 2-(phenylazo)pyridine] with the N,S-donor atom ligands, 2-alkylthioanilines (HL, (H(2)N--SR), where R = Me, -CH(2)Ph, -CH(2)-CH=CH(2)) in acetonitrile solvent under alkaline conditions yielded mixed chelate donor-acceptor complexes, Pt(pap)(HN--SR) (1(+), R = Me), [Pt(pap)(HN--S)] (2, HN--S = 2-amidothiophenolate, R = Me, -CH(2)Ph, -CH(2)-CH=CH(2)) and [Pt(pap)(RN--S)] (RN--S = 2-(N-alkyl)amidothiophenolate 3 and 4, R = -CH(2)Ph, -CH(2)-CH=CH(2)). Unusual types of 1,4-alkyl group migration associated with simultaneous S-C bond cleavage and N-C bond formation were observed for R = -CH(2)Ph, -CH(2)-CH=CH(2). However, for R = Me, only S-C bond cleavage occurred producing compound 2 at a higher temperature. Under identical experimental conditions the reaction of Pt(bpy)Cl(2) [bpy = 2,2'-bipyridine] with 2-methylthioaniline afforded Pt(bpy)(HN--SR) (5(+), R = Me) as the only product with no S-C bond activation. The complexes have been characterized by (1)H NMR, UV-vis-NIR, ESI-MS, EPR and cyclic voltammetry studies. Single-crystal X-ray structures of the complexes, [1][OTf] (OTf = trifluoromethanesulfonate), 2, 3, 4 and [5][OTf] are reported. The Pt-pap complexes (1(+) and 2-4) showed intense interligand charge transfer (ILCT) transition in the NIR-region (>800 nm). This band in the Pt-bpy analogue, 5 shifted to a much higher energy, at 545 nm. The cationic complex, [1][OTf] displayed two reversible responses at -0.21 and -0.94 V along with two irreversible anodic responses at 0.48 and 0.90 V. The molecular compounds, 2, 3 and 4 showed two reversible waves near -0.60 and -1.30 V and an irreversible anodic response near 0.5 V. The response at the anodic potential is presumably due to oxidation of 2-amidothioether/2-amidothiophenolate ligand while the reversible responses at cathodic potentials are due to successive reductions of the azo chromophore of the coordinated pap ligand. The redox processes are characterized by EPR and spectroelectrochemistry. Density-functional theory calculations were employed to confirm the structural features and to support the spectral and redox properties of the complexes.
Pt(pap)Cl(2) [pap = 2-(苯基偶氮)吡啶]与 N，S-供体原子配体 2-烷基硫代苯胺（HL，（H(2)N--SR），其中 R = Me，-CH(2)Ph，-CH(2)-CH=CH(2)) 在碱性条件下在乙腈溶剂中发生化学反应，生成混合螯合给体-受体配合物，[Pt(pap)(HN--SR)]+ (1(+)，R = Me)，[Pt(pap)(HN--S)] (2，HN--S = 2-氨硫代酚，R = Me，-CH(2)Ph，-CH(2)-CH=CH(2)) 和 [Pt(pap)(RN--S)] (RN--S = 2-(N-烷基)氨硫代酚 3 和 4，R = -CH(2)Ph，-CH(2)-CH=CH(2))。观察到 R = -CH(2)Ph，-CH(2)-CH=CH(2) 时，与同时发生的 S-C 键断裂和 N-C 键形成相关的不寻常的 1,4-烷基基团迁移类型。然而，对于 R = Me，仅发生 S-C 键断裂，在较高温度下生成化合物 2。在相同的实验条件下，Pt(bpy)Cl(2) [bpy = 2,2'-联吡啶]与 2-甲基硫代苯胺反应得到 [Pt(bpy)(HN--SR)]+ (5(+)，R = Me)作为唯一产物，没有 S-C 键活化。通过（1）H NMR、UV-vis-NIR、ESI-MS、EPR 和循环伏安法研究对配合物进行了表征。报道了配合物[1][OTf]（OTf = 三氟甲磺酸根）、2、3、4 和 [5][OTf]的单晶 X 射线结构。Pt-pap 配合物（1(+)和 2-4）在近红外区域（>800nm）显示出强烈的配体间电荷转移（ILCT）跃迁。Pt-bpy 类似物5中的该带移至更高的能量，为 545nm。阳离子配合物[1][OTf]在-0.21 和-0.94 V 附近显示出两个可逆响应，以及在 0.48 和 0.90 V 附近的两个不可逆阳极响应。分子化合物 2、3 和 4 在-0.60 和-1.30 V 附近显示出两个可逆波，在 0.5 V 附近显示出一个不可逆阳极响应。阳极电位处的响应可能归因于 2-氨硫醚/2-氨硫代酚配体的氧化，而阴极电位处的可逆响应归因于配位的 pap 配体的偶氮发色团的连续还原。氧化还原过程通过 EPR 和光谱电化学进行表征。密度泛函理论计算用于确认配合物的结构特征，并支持配合物的光谱和氧化还原性质。
