SYNTHESIS, STRUCTURE, AND REACTIVITY OF ETA-2-1,3-DIENE AND ENYNE COMPLEXES OF THE CHIRAL RHENIUM LEWIS-ACID [(ETA-5-C5H5)RE(NO)(PPH3)]+ - OZONOLYSIS WITHIN A METAL COORDINATION SPHERE
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abstract
Reaction of [(5-C5H5)Re(NO)(PPh3)(ClC6H5)]+BF4 (1) and trans-piperylene at room temperature (RT) gives [(5-C5H5)Re(NO)(PPh3)(2-H2CCHCHCHCH3)]+BF4 (2a; 72%) as a 63:37 mixture of RS,SR/RR,SS diastereomers. At 95 C, (8990):(ll10) mixtures are obtained (8488%). No linkage isomers with coordinated CHCHCH3 moieties are observed. Reaction of 1 and isoprene (RT) gives [(5-C5H5)Re(NO)(PPh3)(H2CCHC(CH3)CH2)]+BF4 (90%) as a 65:15:7:13 mixture of isomers. At 95 C, 95:2:1:2 mixtures are obtained (>99%). The major products have coordinated H2CCH moieties ((RS,SR)/(RR,SS)2b); the minor products have coordinated C(CH3)CH2 moieties. Reactions of 1 or the corresponding dichloromethane complex and vinylacetylene (RT) give (717):(935):(6144):(234) mixtures of the RS,SR and RR,SS diastereomers of alkene complex [(5-C5H5)Re(NO)(PPh3)(2-H2CCHCCH)]+BF4 and the sc and ac Re(CC) rotamers of alkyne complex [(5-C5H5)Re(NO)PPh3)(H2CCH-2-CCH)]+BF4. Ozonolyses of 2a and 2b cleave the free CC moieties to give alkene complexes of acrolein and methyl vinyl ketone (7973%). The crystal structure of (RS,SR)2a. shows an s-trans diene conformation. Other structural features of the preceding compounds are analyzed. Rationales for the kinetic and thermodynamic binding selectivities are given. 1993, American Chemical Society. All rights reserved.
