Unusual Me-O Bond Cleavage in a Metalated Crown-Ether: X-ray Molecular Structure of (5-Methoxy-4,6-dimethyl-1,3-xylylene-2-one)-15 Crown-4 Complex of Pentamethylcyclopentadienyl Iridium.
The reaction of [(C(5)Me(5))Ir(Solvent)(3)][BF(4)](2) (1) with (2,5-dimethoxy-4,6-dimethyl-1,3-xylylene)-15 crown-4 (2) affords the metalated crown-ether complex [(eta(5)-C(5)Me(5))Ir(eta(6)-C(18)H(28)O(6))][BF(4)](2) (3) in 88% yield. Complex 3 undergoes a facile Me-O bond cleavage to give the related semiquinone form of the metalated crown-ether [(eta(5)-C(5)Me(5))Ir(eta(5)-C(17)H(25)O(6))][BF(4)] (4). A single-crystal X-ray structure determination of complex 4 is reported. Complex 4 crystallizes in the monoclinic space group P2(1)/m with a = 8.187(5) Å, b = 17.193(4) Å, and c = 10.900(3) Å, alpha = 90 degrees, beta = 109.68(1) degrees, gamma = 90 degrees, and Z = 2. The structure provides us with valuable information about the nature of the eta(5)-semiquinone form of the metalated crown-ether and reveals that, surprisingly, the Me-O unit close to the crown chain is the one that undergoes hydrolysis. A rationale consistent with the experimental results is advanced.
Amouri
H.
H
NMR Services of École Nationale Supérieure de Chimie de Paris, URA CNRS 403, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05, France.
Vaissermann
J.
J
Rager
M. N.
MN
Besace
Y.
Y