- Synthesis, structure, and reactivity of the formaldehyde complex [(η-C5H5)Re(NO)(PPh3)(η 2-H2C=O)]+PF6-
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Reaction of [(η5-C5H5)Re(NO)(PPh3)(=CH 2)]+PF6- with C6H5I+-O- gives formaldehyde complex [(η5-C5H5)Re(NO)(PPh 3)(η2-H2C=O)]+PF 6- (1, 83%), which is characterized by X-ray crystallography. The η2-H2C=O ligand adopts a conformation such that overlap of its π* orbital with the rhenium fragment HOMO is maximized, and its oxygen terminus is syn to the PPh3. Extended Hu?ckel MO calculations on model compound [(η5-C5H5)Re(NO)(PH3)(η 2-H2C=O)]+ predict a similar conformational energy minimum. Complex 1 slowly reacts with CD3CN (18 days, 25°C) to give [(η5-C5H5)Re(NO)(PPh3)(CD 3CN)]+PF6- (2-d3, 67-92%) and rapidly reacts with NaI (acetone, 25°C) to precipitate [(η5-C5H5)Re(NO)(PPh 3)(η2-H2C=O)]+I- (3, 68%). Addition of 3 to CH3OH rapidly gives (η5-C5H5)Re(NO)(PPh3)(I) (4, 65%). Unlike previously synthesized (neutral) η2-H2C=O complexes, 1 undergoes nucleophilic additions but not well-defined electrophilic additions. Thus, addition of PR3 to 1 gives [(η5-C5H5)Re(NO)(PPh3)(OCH 2PR3)]+PF6- (5, R = Ph, 89%; 6, R = Me, 85%). Reaction of 1 with formyl complex (η5-C5H5)Re(NO)(PPh3)(CHO) gives methoxide complex (η5-C5H5)Re(NO)(PPh3)(OCH 3) (7, 52%) and [(η5-C5H5)Re(NO)(PPh3)(CO)] +PF6-. Attempted addition of (η5-C5H5)Co(CO)(PMe3) to 1 in acetone-d6 gives [(η5-C5H5)Re(NO)(PPh 3)(η1-(CD3)2C=O)] +PF6- (8-d6). The relationship of this chemistry to metal-catalyzed reactions involving formaldehyde is discussed.
- Buhro, William E.,Georgiou, Savas,Fernández, Jesús M.,Patton, Alan T.,Strouse, Charles E.,Gladysz
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p. 956 - 965
(2008/10/08)
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