J . Am. Chem. SOC.1993, l l S , 2323-2334
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one-electron reduction is essentially metal-based and results in a more traditional 19e-d9 complex lacking a high degree of delocalization onto the cyclooctatetraene ring, just as is obtained, for example, with simple metal-diolefin compounds.65
Acknowledgment. W.E.G. is grateful for the support of the National Science Foundation under CHE86-03728 and CHE91-16332. We thank Thomas C.Richards for obtaining the new ESR spectrum of CpCo(l,3-C8H,)'-.
(65) Leading references to dVr-hydrocarbon complexes may be found in refs 25,54, 58, and 59. Note that the possibility of electron-transfer-induced isomerization of a metal-cyclooctadiene bond is raised in refs 11b, 25, and in Baghdadi, J.; Bailey, N. A,; Dowding, A. S.; White, C. J . Chem. SOC., Chem. Commun. 1992, 170.
Note Added in Proof. Koelle et al., in ref 48c, have recently interpreted the DR spectra of in a C ~ C ~ ( C , H . , , ) matrix in terms of a metal dxz ground state, with the d y ~level l m g just below.
Synthesis, Structure, and Spectroscopic Properties of Chiral Rhenium Aromatic Aldehyde Complexes [ (q5-C5H5)Re( NO)( PPh3)(O=CHAr)]+X-: Equilibria between 7r and cr Aldehyde Binding Modes N. Quirk Mindez, Jeffery W. Seyler, A. M. Arif, and J. A. Gladysz* Contribution from the Department of Chemistry, University of Utah, Salt Lake City, Utah 841 12. Received September 24, 1992 Abstract: Reactions of [($-C,H5)Re(NO)(PPh,)(ClCH2Cl)]+BF4and ArCHO (Ar = a, C6F5;b, 4-C6H4CF3;c, 3-C6H4CF3; d, 3-C6H,OCH,; e, 2-C,H,OCH,; f, 4-C&C1; g, 4-C6H4F; h, 1 -naphthyl; i, C6Hs;. j, 3,4,5-C6Hz(OCH3)3; k, ~ - C ~ H ~ C ~ H S ; 1, 4-C&CH,; m, 2,4-C6H,(OCH,),; n, 3,4-C6H3(OCH,),; 0, 4-C6H40CH3)give aromatic aldehyde complexes [(+C,H5)Re(NO)(PPh3)(O=CHAr)]+BF4(4a-o+BF4-, 80-97%). IR analyses (CH2CI2,26 "C) show 4a-o+BF4- to be >96:
