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High enantioselectivities (up to 99\u2009%\u2005<jats:italic>ee<\/jats:italic>) and excellent yields were obtained in the addition to either cyclic or acyclic substrates. The flexible biphenolic P ligands outperformed the analogous rigid binaphtholic P ligands. Variable\u2010temperature <jats:sup>31<\/jats:sup>P\u2005NMR studies revealed that the biphenolic ligands are <jats:italic>tropos<\/jats:italic> even at low temperature. Only below 190\u2005K was a coalescence observed; upon further cooling, two atropisomers were detected. The Rh homocomplexes ([Rh(L<jats:sup>a<\/jats:sup>)<jats:sub>2<\/jats:sub>]<jats:sup>+<\/jats:sup>) were also studied: in general, a single doublet (P\u2013Rh coupling) was observed in the case of the biphenolic phosphite ligands, over the temperature range 380\u2013230\u2005K, demonstrating their <jats:italic>tropos<\/jats:italic> nature in the rhodium complexes even at low temperatures. On the other hand, the phosphoramidites showed different behaviors depending on the structure of the ligand and on the nature of the rhodium source. The spectrum at 230\u2005K of the mixture of [Rh(acac)(eth)<jats:sub>2<\/jats:sub>] (eth=C<jats:sub>2<\/jats:sub>H<jats:sub>4<\/jats:sub>) with phosphite <jats:bold>6<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>O and phosphoramidite <jats:bold>19<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>N (the most enantioselective ligand combination in the conjugate addition reaction) revealed the presence of four homocomplexes (total approximately 40\u2009%: [Rh{<jats:bold>6<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>O}<jats:sub>2<\/jats:sub>], [Rh{(a<jats:italic>R<\/jats:italic>)\u2010<jats:bold>19<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>N}<jats:sub>2<\/jats:sub>], [Rh{(a<jats:italic>S<\/jats:italic>)\u2010<jats:bold>19<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>N}<jats:sub>2<\/jats:sub>], [Rh{(a<jats:italic>R<\/jats:italic>)\u2010<jats:bold>19<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>N}{(a<jats:italic>S<\/jats:italic>)\u2010<jats:bold>19<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>N}]) and one heterocomplex, [Rh{<jats:bold>6<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>O}{(a<jats:italic>R<\/jats:italic>)\u2010<jats:bold>19<\/jats:bold>\u2010P(O)<jats:sub>2<\/jats:sub>N}] (approximately 60\u2009%) In the heterocomplex, the biphenol\u2010derived phosphite is free to rotate (<jats:italic>tropos<\/jats:italic>) while the biphenol\u2010derived phosphoramidite shows a temperature\u2010dependent <jats:italic>tropos<\/jats:italic>\/<jats:italic>atropos<\/jats:italic> behavior (coalescence temperature=310\u2005K).<\/jats:p>","DOI":"10.1002\/chem.200600960","type":"journal-article","created":{"date-parts":[[2006,11,29]],"date-time":"2006-11-29T13:50:36Z","timestamp":1164808236000},"page":"1547-1558","source":"Crossref","is-referenced-by-count":77,"title":["Rh\u2010Catalyzed 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