Synthesis and Reactivity of 1,2- and 1,3-Diphosphanes that Contain Four Chiral Rhenium Fragments: Architecturally Novel Tetrametallo-DMPE and -DMPP Species that are Unprivileged Ligands for Enantioselective Catalysis

• Published in: European Journal of Inorganic Chemistry 2005-08, Vol.2005 (15), p.2983-2998
• Main Authors: Kromm, Klemenz, Eichenseher, Sandra, Prommesberger, Markus, Hampel, Frank, Gladysz, J. A.
• Format: Article
• Language: English
• Subjects: Chiral diphosphane; Hydrogenation; Hydrosilylation; Phosphane oxide; Rhenium; Rhodium
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200500254

Reactions of enantiopure (S)‐[(η5‐C5H5)Re(NO)(PPh3)(=CH2)]+ PF6– [(S)‐2] and PH2CH2(CH2)nCH2PH2 (0.5 equiv.) give (SReSRe)‐[(η5‐C5H5)Re(NO)(PPh3){CH2PH2CH2(CH2)nCH2PH2CH2}(Ph3P)(ON)Re(η5‐C5H5)]2+ 2PF6– [n = 0/1, (SReSRe)‐3/4; 65–62/77–58 %]. Reaction of racemic 2 (BF4– salt) and PH2(CH2)2PH2 (0.5 equiv.) gives the meso and rac diastereomers of 3 (BF4– salts) in 28 % and 38 % yields after crystallization. Treatments of (SReSRe)‐3/4 with tBuOK and then (S)‐2 give the tetrarhenium complexes (SReSReSReSRe)[{(η5‐C5H5)Re(NO)(PPh3)(CH2)}2{PHCH2(CH2)nCH2PH}{(CH2)(Ph3P)(ON)Re(η5‐C5H5)}2]2+ 2PF6– [n = 0/1, (SReSReSReSRe)‐7/8; 89–88/98–87 %]. The crystal structure of(SReSReSReSRe)‐7 is determined and its conformation analyzed. Reactions of (SReSReSReSRe)‐7/8 and tBuOK give air‐sensitive diphosphanes (SReSReSReSRe)‐{(η5‐C5H5)Re(NO)(PPh3)(CH2)}2{PCH2(CH2)nCH2P}{(CH2)(Ph3P)(ON)Re(η5‐C5H5)}2 [n = 0/1, (SReSReSReSRe)‐9/10; 92/62 %]. Additions of (a) PhIO give the corresponding dioxides (72/62 %), and (b) [Rh(NBD)2]+ PF6– give the corresponding chelates [(P–P)Rh(NBD)]+ PF6– (75/82 %) (NBD = norbornadiene). These catalyze hydrogenations of protected dehydroamino acids and hydrosilylations of propiophenone with only modest enantioselectivities. Similar results are obtained when (SReSReSReSRe)‐9/10 are applied in rhodium‐catalyzed conjugate additions of aryl boronic acids, or palladium‐catalyzed allylic alkylations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)