Diaminocarbene and Phosphonium Ylide Ligands: A Systematic Comparison of their Donor Character.
The coordinating properties of the diaminocarbene (A) and phosphonium ylide (B) ligand types have been investigated systematically through a test family of C,C-chelating ligands containing two moieties of either kind. The overall character of ο-CHAB ligands (a + b = 2) has been analyzed from the lR...
| Published in: | Journal of the American Chemical Society Vol. 130; no. 26; pp. 8406 - 8414 |
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| Main Authors: | , , , , |
| Format: | Article |
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American Chemical Society
7/2/2008
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| Subjects: | |
| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=33113260&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 33113260 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 7/2/2008 vid: 130 iid: 26 pid: 997 pub: American Chemical Society artinfo: ui: 33113260 10.1021/ja801159v ppf: 8406 ppct: 8 formats: tig: atl: Diaminocarbene and Phosphonium Ylide Ligands: A Systematic Comparison of their Donor Character. aug: au: Canac, Yves Lepetit, Christine Abdalilah, Mohammed Duhayon, Carine Chauvin, Remi affil: Laboratoire de Chimie de Coordination (LCC) of CNRS, 205 route de Narbonne, 31077 Toulouse cedex 4, France su: Ligands (Chemistry) Carbenes Hydrogen-ion concentration Spectrum analysis Optical diffraction sug: subj: Ligands (Chemistry) Carbenes Hydrogen-ion concentration Spectrum analysis Optical diffraction ab: The coordinating properties of the diaminocarbene (A) and phosphonium ylide (B) ligand types have been investigated systematically through a test family of C,C-chelating ligands containing two moieties of either kind. The overall character of ο-CHAB ligands (a + b = 2) has been analyzed from the lR CO stretching frequencies of isostructural complexes [(η²CHAB)Rh(CO)][TfO]. The test moieties A = NCHN(Me)C and B = PhPCH were first considered. While the ligands bearing at least one diaminocarbene end (AA, a = 2 and AB, a = 1) could be generated (and trapped by complexation), the bis-ylide case BB (a = 0) proved to be awkward: treatment of the dication CH(PPhMe) with n-BuLi indeed lead to the Schmidbaur's carbodiphosphorane PhPCPPhMe, through an unprecendented ylidopentacoordinated phosphorane which could be fully characterized by NMR techniques. The bis-ylide ligand type CHB could however be generated by bridging the phosphonium methyl groups by a methylene link (B = (PPhCH)CH), preventing the formation of the analogous highly strained carbodiphosphorane. The three complexes [(η²-CHAB)Rh(CO)][TfO] were fully characterized, including by X-ray diffraction analysis and Rh NMR spectroscopy. Comparison of their lR spectra indicated that the A type bis-NHC ligand is less donating than the hybrid AB type, which is itself less donating than the B type bis-ylide ligand. The excellent linear variation of the VCO frequencies vs a (= 0, 1, 2) shows that the coordinating moieties act in a pseudoindependent way. This was confirmed by DFT calculations at the B3PW91/6-31G**/LANL2DZ*(Rh) level, It is therefore demonstrated that a phosphonium ylide ligand is a stronger donor than a diaminocarbene ligand. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2008 holdings: @attributes: islocal: N |
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