Comparative Study of Diastereoisomer Interconversion in Chiral BINOL-ate and Diamine Platinum Complexes of Conformationally Flexible NUPHOS Diphosphines
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- 作者：Simon Doherty ; Colin R. Newman ; Rakesh K. Rath ; Jan-Albert van den Berg ; Christopher Hardacre ; Mark Nieuwenhuyzen ; and Julian G. Knight
- 刊名：Organometallics
- 出版年：2004
- 出版时间：March 1, 2004
- 年：2004
- 卷：23
- 期：5
- 页码：1055 - 1064
- 全文大小：306K
- 年卷期：v.23,no.5(March 1, 2004)
- ISSN：1520-6041
文摘
A thorough and detailed study of diastereointerconversion in the chiral platinum complexes[(NUPHOS)Pt{(S)-BINOL}] (3a-e) has been undertaken and compared with the results ofa similar study with [(BIPHEP)Pt{(S)-BINOL}]. Rate data revealed that this process obeysfirst-order relaxation kinetics, and rate constants for conversion of the minor to the majordiastereoisomer have been obtained. Eyring analysis of the data gave 
H
and S valuesof 22-25 kcal mol-1 and -1 to -16 eu, respectively. In combination with computationalanalysis, these studies indicate that atropinversion most likely occurs via an on-metalpathway involving a planar seven-membered transition state. Substitution of (S)-BINOLfor (S,S)-DPEN results in a marked reduction in the barrier to atropinversion; a H valueof 17 kcal mol-1 has been determined for the conversion of 
-[(Ph4-NUPHOS)Pt{(S,S)-DPEN}]Cl2 to 
-[(Ph4-NUPHOS)Pt{(S,S)-DPEN}]Cl2, which could indicate that an alternativemechanism operates.
H and S valuesof 22-25 kcal mol-1 and -1 to -16 eu, respectively. In combination with computationalanalysis, these studies indicate that atropinversion most likely occurs via an on-metalpathway involving a planar seven-membered transition state. Substitution of (S)-BINOLfor (S,S)-DPEN results in a marked reduction in the barrier to atropinversion; a H valueof 17 kcal mol-1 has been determined for the conversion of -[(Ph4-NUPHOS)Pt{(S,S)-DPEN}]Cl2 to -[(Ph4-NUPHOS)Pt{(S,S)-DPEN}]Cl2, which could indicate that an alternativemechanism operates.