Article,

Structures and redox properties of metal complexes of the electron-deficient diphosphine chelate ligand R,R-quinoxP

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Organometallics, 27 (2): 218--223 (2008)
DOI: 10.1021/om700755y

Abstract

The air-stable chiral diphosphine chelate ligand R,R-qinoxP (L; 2,3-bis(tert-butylmethylphosphino)quinoxaline) as developed by Imamoto et al. (2005). L was used to obtain the crystallog. characterized complexes (L)PtCl2 (1), (L)PdCl2 (2), and (L)Re(CO)3Cl (3). Coordination occurs via the P donor atoms, as indicated by crystal structures and NMR studies; the quinoxaline N donors do not participate in any coordination to the metals. The stereochem. arrangements obsd. illustrate the enantioselectivity reported for catalysis involving complexes of L. Electron acceptance by the quinoxaline heterocycle is responsible not only for the improved stability of L toward air but also for rather facile redn. of the complexes to the persistent radical anions 1·-and 3·- In contrast, the redn. to 2·- proceeds irreversibly even at 243 K in the absence of excess chloride. EPR, UV-vis, and IR spectroelectrochem. was used, when possible, to establish the spin location in the quinoxaline p system with rather small contributions from the metals or the P nuclei. on SciFinder(R)

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