Mishra Vishwesh, Thirupathi Natesan
Department of Chemistry, University of Delhi, Delhi 110 007, India.
ACS Omega. 2018 Jun 5;3(6):6075-6090. doi: 10.1021/acsomega.8b00782. eCollection 2018 Jun 30.
The reactions of -[Pt(OAc)(DMSO)] with 2 equiv of ,',″-triarylguanidines, [ArN=C(NHAr)], in toluene under reflux condition for 8 h afforded six-membered cycloplatinated guanidines, [Pt{κ(,)}(OAc){κ (ArN=C(NHAr))}] [ = symmetrical; Ar = 2-MeCH () and 2,4-MeCH ()], in 82 and 84% yields, respectively. The salt metathesis reaction of with 1 equiv of AgTFA in CHCl at room temperature (RT) afforded [Pt{κ(,)}(TFA){κ (ArN=C(NHAr))}] () in 94% yield. The reaction of -[Pt(TFA)(DMSO)] with 1 equiv of [ArN=C(NHAr)] in toluene under reflux condition for 8 h afforded six-membered cycloplatinated guanidines, [Pt{κ(,)}(TFA)(DMSO)] [Ar = 2-MeCH (), 4-MeCH (), 2,4-MeCH (), and 2-(MeO)CH ()], in ≥73% yields. The reaction of -[PtCl(PhCN)] with 2 equiv of [ArN=C(NHAr)] in toluene under reflux condition for 48 h afforded -[PtCl{ArN=C(NHAr)}] [Ar = 2-MeCH () and 2,4-MeCH ()] in 90 and 45% yields, respectively. Complexes and were separately refluxed in MeOH for 8 h to afford six-membered cycloplatinated guanidines, [Pt{κ(,)}(μ-Cl)] ( and ), in 93 and 96% yields, respectively, with concomitant formation of the respective guanidinium salts, [(ArNH)C]Cl, as the byproduct. Platinacycle was treated with 2 equiv of AgTFA in CHCl at RT to afford six-membered cycloplatinated guanidine, [Pt{κ(,)}(μ-TFA)] (), in 94% yield. The new compounds were characterized by analytical techniques and multinuclear NMR (H, C, and Pt) spectroscopy, and further, molecular structures of 10 compounds were determined by single-crystal X-ray diffraction. The structural motif in ·1/2CHCl and is novel in that it contains a planar six-membered [Pt{κ(,)}] unit and a nonplanar eight-membered [Pt{κ(,)}] ring, wherein OAc and the guanidine ligands are linked through a N-H···O hydrogen bond. The six-membered cycloplatinated structural motifs present in /·CH and ·CHCl are also unprecedented in the literature. The number and nature of solution species of new complexes were unambiguously investigated by detailed NMR studies. The critical role of anions in Pt(II) precursors upon the course of cycloplatination and thus the motifs in the products were addressed. Plausible mechanisms of cycloplatination reactions are discussed.
在甲苯中，于回流条件下，将-[Pt(OAc)(DMSO)]与2当量的',″-三芳基胍[ArN=C(NHAr)]反应8小时，分别以82%和84%的产率得到六元环铂化胍[Pt{κ(,)}(OAc){κ (ArN=C(NHAr))}] [ = 对称；Ar = 2-MeCH ()和2,4-MeCH ()]。在室温下，于CHCl中，将与1当量的AgTFA进行盐复分解反应，以94%的产率得到[Pt{κ(,)}(TFA){κ (ArN=C(NHAr))}] ()。在甲苯中，于回流条件下，将-[Pt(TFA)(DMSO)]与1当量的[ArN=C(NHAr)]反应8小时，得到产率≥73%的六元环铂化胍[Pt{κ(,)}(TFA)(DMSO)] [Ar = 2-MeCH (), 4-MeCH (), 2,4-MeCH (), 和2-(MeO)CH ()]。在甲苯中，于回流条件下，将-[PtCl(PhCN)]与2当量的[ArN=C(NHAr)]反应48小时，分别以90%和45%的产率得到-[PtCl{ArN=C(NHAr)}] [Ar = 2-MeCH ()和2,4-MeCH ()]。配合物和分别在甲醇中回流8小时，以93%和96%的产率得到六元环铂化胍[Pt{κ(,)}(μ-Cl)] (和)，同时生成相应的胍盐[(ArNH)C]Cl作为副产物。在室温下，于CHCl中，用2当量的AgTFA处理铂环[，以94%的产率得到六元环铂化胍[Pt{κ(,)}(μ-TFA)] ()。通过分析技术和多核NMR（H、C和Pt）光谱对新化合物进行了表征，此外，通过单晶X射线衍射确定了10种化合物的分子结构。·1/2CHCl和中的结构基序是新颖的，因为它包含一个平面六元[Pt{κ(,)}]单元和一个非平面八元[Pt{κ(,)}]环，其中OAc和胍配体通过N-H···O氢键相连。/·CH和·CHCl中存在的六元环铂化结构基序在文献中也是前所未有的。通过详细的NMR研究明确研究了新配合物溶液物种的数量和性质。探讨了阴离子在铂（II）前体对环铂化过程以及产物中基序的关键作用。讨论了环铂化反应的合理机制。
