Synthesis, structure, and spectroscopic properties of chiral rhenium aromatic aldehyde complexes [([eta][sup 5]-C[sub 5]H[sub 5])Re(NO)(PPh[sub 3])(O[double bond]CHAr)][sup +]X[sup [minus]]: Equilibria between [pi] and [sigma] aldehyde binding modes

Journal Article · Wed Mar 24 04:00:00 EST 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00059a029· OSTI ID:6215446

Mendez, N Q; Seyler, J W; Arif, A M; Gladysz, J A ^[1]

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1. Univ. of Utah, Salt Lake City (United States)

Reactions of [([eta][sup 5]-C[sub 5]H[sub 5])Re(NO)(PPh[sub 3])(ClCH[sub 2]Cl)][sup +]BF[sub 4][sup [minus]] and ArCHO (Ar = a, C[sub 6]F[sub 5]; b, 4-C[sub 6]H[sub 4]CF[sub 3]; c, 3-C[sub 6]H[sub 4]CF[sub 3]; d, 3-C[sub 6]H[sub 4]OCH[sub 3]; e, 2-C[sub 6]H[sub 4]OCH[sub 3]; f, 4-C[sub 6]H[sub 4]Cl; g, 4-C[sub 6]H[sub 4]F; h, 1-naphthyl; i, C[sub 6]H[sub 5]; j, 3,4,5-C[sub 6]H[sub 2](OCH[sub 3])[sub 3]; k, 4-C[sub 6]H[sub 4]C[sub 6]H[sub 5]; l, 4-C[sub 6]H[sub 4]CH[sub 3]; m, 2,4-C[sub 6]H[sub 3](OCH[sub 3])[sub 2]; n, 3,4-C[sub 6]H[sub 3](OCH[sub 3])[sub 2]; o, 4-C[sub 6]H[sub 4]OCH[sub 3]) give aromatic aldehyde complexes [([eta][sup 5]-C[sub 5]H[sub 5])Re(NO)(PPh[sub 3])(O[double bond]CHAr)][sup +]BF[sub 4][sup [minus]] (4a--o[sup +]BF[sub 4][sup [minus]], 80--97%). IR analyses (CH[sub 2]Cl[sub 2], 26[degrees]C) show 4a--o[sup +]BF[sub 4][sup [minus]] to be >96:<4 to 15:85 mixtures of [pi]/[sigma] isomers (v[sub NO] 1745--1733/1701--1692 cm[sup [minus]1]). Electron withdrawing substituents (which enhance aldehyde [pi] acidity and lower [sigma] basicity) favor the [pi] binding model. Electron donating substituents have an opposite effect. The [pi]/[sigma] ratios increase in more polar solvents and at lower temperatures. Van't Hoff plots give [Delta]H (4i,l,o[sup +]BF[sub 4][sup [minus]]; [pi] [yields] [sigma]) of 3.6, 2.8, and 1.8 kcal/mol and [Delta]S of 9.2, 9.5, and 9.1 eu. IR features unique to both binding modes, and visible absorptions characteristic of [sigma] isomers, are identified. Complex 4o[sup +]PF[sub 6][sup [minus]] crystallizes as a [sigma] isomer, with a conjugated Ar/C[double bond]O linkage, a lengthened C[double bond]O bond (1.271 (8) [angstrom]), and a 0[degrees] N-Re-O-C torsion angle. This Re-O conformation maximizes overlap of the d orbital HOMO of the rhenium fragment with C[double bond]O [pi]* orbital lobes on oxygen. 60 refs., 8 figs., 5 tabs.

• OSTI ID: 6215446
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:6; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical &amp; Spectral Procedures
400201* -- Chemical &amp; Physicochemical Properties
ALDEHYDES
AROMATICS
COMPLEXES
CRYSTALLOGRAPHY
DATA
EXPERIMENTAL DATA
INFORMATION
ISOMERS
LIGANDS
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
RESONANCE
RHENIUM COMPLEXES
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES