A palladacyclic N-heterocyclic carbene system used to probe the donating abilities of monoanionic chelators

作者：Yan, Xuechao; Feng, Rui; Yan, Chunhui; Lei, Peng; Guo, Shuai^*; Han Vinh Huynh^*

来源：Dalton Transactions, 2018, 47(23): 7830-7838.

DOI：10.1039/c8dt01618f

• BOND-FORMING REACTIONS
• C-13 NMR-SPECTROSCOPY
• PALLADIUM(II) COMPLEXES
• CATALYTIC-ACTIVITIES
• NHC-LIGANDS
• ELECTRONIC-PROPERTIES
• TRICARBENE LIGAND
• C-C
• ARYL
• 1,2,3-TRIAZOLYLIDENES

A series of NHC-containing [(CN)-N-boolean AND]- or [(CC)-C-boolean AND']-type palladacyclic complexes of the general formula [PdBr(Pr-i(2)-bimy)((LX)-X-boolean AND)] (5-8, 11, 12, Pr-i(2)-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) have been synthesized and fully characterized. Using these complexes, the donating abilities of monoanionic chelators were probed for the first time. The [(CN)-N-boolean AND]-type palladacycles 5-8 were prepared from acetato-bridged dipalladium complexes [Pd(mu-CH3COO)((CN)-N-boolean AND)](2) (1-4) and Pr-i(2)-bimy center dot H(+)Br(-)as precursors. In the case of the [(CC)-C-boolean AND']-type NHC palladacycles (11, 12), the hetero-bis(NHC) complexes trans-[PdBr2(Pr-i(2)-bimy)(trz)] (8, 9, trz = 1,2,3-triazolin-5-ylidene) containing the Pr-i(2)-bimy probe were first prepared followed by acetate-assisted cyclopalladations. The C-13(carbene) NMR signals of the Pr-i(2)-bimy ligands in all complexes (i.e. HEP and HEP2 values) are found to rationally reflect the donating abilities of the incorporated trz or [(LX)-X-boolean AND]-type chelators with the exception of the Bzpy ligand (Bzpy = 2-(2-pyridinylmethyl)phenyl-C,N). This has been attributed to its larger bite angle, the resulting varied coordination geometry and the lack of electronic delocalization between the two donor units. The donicities of [(LX)-X-boolean AND]-type chelators studied in this work were found to surpass those of all other bidentate ligands evaluated by HEP2 thus far.

• 出版日期2018-6-21
• 单位首都师范大学