Thiosemicarbazonates of palladium(II): The presence of methyl/phenyl substituents (R²) at C² carbon atom induces C-H activation of R¹ rings of thiosemicarbazones {R¹R²C²N³-N

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• 作者：Tarlok S. Lobana^a ; ^{tarlokslobana@yahoo.co.in} ; Poonam Kumari^a ; Ray J. Butcher^b ; Takashiro Akitsu^c ; Yoshikazu Aritake^c ; Josefina Perles^d ; Francisco J. Fernandez^e ; M. Cristina Vega^e
• 关键词：Palladium(II) ; 2-Acetylthiopheneyl&ndash ; N1&ndash ; methyl thiosemicarbazone ; 2-Acetylpyrrole&ndash ; N1&ndash ; phenyl thiosemicarbazone ; Triphenyl phosphine ; Cyclometallation
• 刊名：Journal of Organometallic Chemistry
• 出版年：2012
• 出版时间：15 March, 2012
• 年：2012
• 卷：701
• 期：Complete
• 页码：17-26
• 全文大小：1743 K

文摘

A series of palladium(II) complexes involving C-H and N-H bond activations of the R¹ rings of thiosemicarbazones {R¹(R²)C²-N³-N²(H)-C¹(S)-N¹HR³; R¹, R²: thiopheneyl, Me, H₂L¹ (R³?=?Me), H₂L² (R³?=?Ph); R¹, R²: Ph, Me, H₂L³ (R³?=?Me), H₂L⁴ (R³?=?Ph); R¹, R²: Ph, Ph, H₂L⁵ (R³?=?Me), H₂L⁶ (R³?=?Ph) and R¹, R²: pyrrole, Me, H₂L⁷ (R³?=?Me), H₂L⁸ (R³?=?Ph)} are described. Methyl group (R²) at C² carbon in H₂L¹ and H₂L² induced C-H bond activation of the thiopheneyl ring and formed cyclometallated complexes, [Pd(¦Ê³-C⁴,N³,S-L)(PPh₃)] (L?=?L¹, 1; L², 2). Similarly, phenyl rings (R¹) in H₂L³, H₂L⁴, H₂L⁵, H₂L⁶ at C² carbon have shown C-H activations forming cyclometallated complexes, [Pd(¦Ê³-C⁴,N³,S-L)(PPh₃)] (L?=?L³, 3; L⁴, 4; L⁵, 5; L⁶, 6). However, pyrrole ring did not exhibit similar C-H activation behavior, rather involved N-H activation and formed complexes, [Pd(¦Ê³-N⁴,N³,S-L)(PPh₃)] {L?=?L⁷, 7; L⁸, 8}. All these complexes have been characterized with the help of analytical data, spectroscopic techniques (IR, ¹H and ³¹P NMR), and single crystal X-ray crystallography (1, 2, 4, 5, 7 and 8). The thiosemicarbazone ligands behave as dinegative C⁴, N³, S-chelating in 1-6 and N⁴, N³, S-chelating in complexes 7 and 8. Interestingly, complexes 2, 4 and 8, with phenyl substituent at N¹ atom, have two independent molecules in their respective crystal lattices.