Dimeric rhodium-ethylene NHC complexes as reactive intermediates for the preparation of tetra-heteroleptic NHC complexes

Olena V. Zenkina, Eric C. Keske, Ruiyao Wang, Cathleen M. Crudden*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


Dimeric rhodium complexes with various N-heterocyclic carbene (NHC) ligands have been synthesized and fully characterized. X-ray analysis unambiguously confirms the bimetallic nature of these complexes, and in all cases one molecule of ethylene is coordinated to each metal center in an η2- fashion. The Rh atoms are also coordinated to one NHC ligand and are interconnected by two μ-chlorine bridges. The dimeric nature of the complexes is most likely stabilized due to the significant steric bulk around the metal centers provided by the carbene ligands. Consistent with this, modulating the steric properties and backbone saturation of the ligands was shown to have a significant effect on the stability and geometry of the complexes. Treatment of the carbene dimers with ligands such as PPh3 results in cleavage of the dimers and a unique synthesis of tetra-heteroleptic complexes of the general formula [ClRh(NHC)(PR3)(CH2=CH2)]. The stabilities of these compounds have been assessed, and although decomposition to Wilkinson's complex is observed upon treatment with an excess of phosphine for prolonged times, the presence of the ethylene ligand provides greatly increased stability compared with the bis-phosphine analogues [ClRh(NHC)(PPh 3)2].

Original languageEnglish
Pages (from-to)6423-6432
Number of pages10
Issue number23
Publication statusPublished - 12 Dec 2011
Externally publishedYes

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