SYNTHESIS AND PROPERTIES OF CHIRAL RHENIUM ETHER COMPLEXES OF THE FORMULA [(ETA-5-C5H5)RE(NO)(PPH3)(OR2)]+X-

Reaction of the dichloromethane complex [(η5−C5H5)Re(NO)(PPh3)(ClCH2Cl)]+BF4−(2+BF4−; in CH2C12) and tetrahydrofuran gives [η5−C5H5)Re(NO)(PPh3)(THF)]+BF4−(5+BF4−; 91% after workup). Reaction of 2+BF4−and methyl ether gives [tf-C5H5)Re(NO)(PPh3)(OMe2)]+BF4−(4+BF4−, characterized in situ). Ethyl ether and 2+BF4−react to give [(η5−C5H5)Re-(NO)(PPh3)(OEt2)]+BF4−(3+BF4−), but not under preparatively useful conditions. Reaction of the hydride complex (η5−C5H5)Re(NO)(PPh3)(H) (6), Ph3C+PF6−, and tetrahydrofuran gives 5+PF6−(90%). Reaction of 6, Ph3C+PF6−, and ethyl ether gives 3+PF6−(93%). Reactions of alkoxide complexes (η5−C5H5)Re(NO)(PPh3)(OR) and oxonium salts R3O+X−(R = Et, Me) in CH2C12give ethers R2O and ether complexes 3+X−/4+X−in quantitative NMR yields. These and other data show that tetrahydrofuran, methyl ether, and ethyl ether have higher thermodynamic binding affinities than dichloromethane for the metal fragment [(η5−C5H5)Re(NO)(PPh3)]+and that the oxygen lone-pair basicity in (η5−C5H5)Re(NO)(PPh3)(OR) is greater than that in R2O. © 1990, American Chemical Society. All rights reserved.