Six-membered [C,N] cyclopalladated sym N,N¡äspan>,N¡å-tri(4-tolyl)guanidines: Synthesis, reactivity studies and structural aspects
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- 作者：Palani Elumalai ; Natesan Thirupathi ; Munirathinam Nethaji
- 关键词：Palladacycle ; Guanidine ; Bridge-splitting reaction ; n&ndash ; ¦Ð Conjugation
- 刊名：Journal of Organometallic Chemistry
- 出版年：2013
- 出版时间：1 October, 2013
- 年：2013
- 卷：741-742
- 期：Complete
- 页码：141-147
- 全文大小：974 K
文摘
Six-membered [C,N] cyclopalladated sym N,N¡ä,N¡å-tri(4-tolyl)guanidines, [(ArNH)<sub>2sub>Cscript> script>NAr] (sym?= symmetrical; Ar?=?4-MeC<sub>6sub>H<sub>4sub>; LH<sub>2sub><sup>4-tolylsup>) of the types [(C,N)Pd(¦Ì-OC(O)R)]<sub>2sub> (<strong class=""boldFont"">1strong> and <strong class=""boldFont"">2strong>), [(C,N)Pd(¦Ì-Br)]<sub>2sub> (<strong class=""boldFont"">3strong>), cis-[(C,N)PdLBr] (<strong class=""boldFont"">4strong>-<strong class=""boldFont"">7strong>), and [(C,N)Pd(acac)] (<strong class=""boldFont"">8strong>) were prepared in high yield by established methods with a view aimed at understanding the influence of the 4-tolyl substituent of the guanidine moiety upon the solution behaviour of <strong class=""boldFont"">1strong>-<strong class=""boldFont"">8strong>. The composition of <strong class=""boldFont"">1strong>-<strong class=""boldFont"">8strong> was confirmed by elemental analysis, IR, and NMR spectroscopy, and mass spectrometry. The molecular structures of <strong class=""boldFont"">1strong>-<strong class=""boldFont"">6strong> were determined by single-crystal X-ray diffraction. Palladacycles <strong class=""boldFont"">1strong>-<strong class=""boldFont"">3strong> exist as a dimer in transoid conformation in the solid state while <strong class=""boldFont"">4strong>-<strong class=""boldFont"">6strong> exist as a monomer with cis configuration around the palladium atom as the Lewis base is placed cis to the Pd-C bond due to antisymbiosis. The NMR spectra of <strong class=""boldFont"">1strong>-<strong class=""boldFont"">8strong> revealed the presence of a single isomer in solution and this spectral feature is ascribed to the rapid inversion of the six-membered ¡°[C,N]Pd¡± ring due to the presence of sterically less hindered and more symmetrical 4-tolyl substituent in the script> script>NAr unit of the guanidine moiety.