Condensation of Fe<sub>2</sub>(SH)<sub>2</sub>(CO)<sub>6</sub>, acetaldehyde, and (NH<sub>4</sub>)<sub>2</sub>CO<sub>3</sub> affords the methyl-substituted azadithiolate Fe<sub>2</sub>[(SCHMe)<sub>2</sub>NH](CO) <sub>6</sub> (1). The complex exists mainly ∼95%) as the meso diastereomer, but the d,l diastereoisomers could be detected. DFT calculations predict that the meso isomer would be 2.5 kcal/mol more stable than the d,l isomer due to conventional nonbonding interactions between the methyl groups and the ring hydrogen atoms. Crystallographic analysis of meso-1 confirms that the two methyl groups are equatorial, constraining the diferraazadithiolate bicycle to a conformation that desymmetrizes the diiron center. The lowered symmetry is confirmed by the observation of two <sup>13</sup>C NMR signals in the FeCO region under conditions of fast turnstile rotation at the Fe(CO)<sub>3</sub> groups. The pK<sub>a</sub> value of the amine in 1 is 7.89 (all pK<sub>a</sub>'s determined in MeCN solution), which is similar to a redetermined value for Fe<sub>2</sub>[(SCH<sub>2</sub>)<sub>2</sub>NH](CO)<sub>6</sub> (2, pK <sub>a</sub> = 7.98) and only slightly less basic than the tertiary amine Fe<sub>2</sub>[(SCH<sub>2</sub>)<sub>2</sub>NMe](CO)<sub>6</sub> (pK<sub>a</sub> = 8.14). Substitution of 1 with PMe<sub>3</sub> proceeded via the intermediacy of two isomers of Fe<sub>2</sub>[(SCHMe)<sub>2</sub>NH](CO)<sub>5</sub>(PMe <sub>3</sub>), affording Fe<sub>2</sub>[(SCHMe)<sub>2</sub>NH](CO) <sub>4</sub>(PMe<sub>3</sub>)<sub>2</sub> (3). <sup>31</sup>P NMR spectra confirm that the two PMe<sub>3</sub> ligands in 3 are nonequivalent, consistent with the desymmetrizing effect of the dithiolate. The pK<sub>a</sub> value of the amine in 3 was found to be 11.3. Using triphenylphosphine, we prepared Fe<sub>2</sub>[SCHMe)<sub>2</sub>NH](CO)<sub>5</sub>(PPh<sub>3</sub>) as a single regioisomer. © 2008 American Chemical Society.
Stanley, J.L., Heiden, Z.M., Rauchfuss, T.B., Wilson, S.R., De Gioia, L., & Zampella, G. (2008). Desymmetrized diiron azadithiolato, carbonyls: A step toward modeling the iron-only hydrogenases. ORGANOMETALLICS, 27(1), 119-125.
Citazione: | Stanley, J.L., Heiden, Z.M., Rauchfuss, T.B., Wilson, S.R., De Gioia, L., & Zampella, G. (2008). Desymmetrized diiron azadithiolato, carbonyls: A step toward modeling the iron-only hydrogenases. ORGANOMETALLICS, 27(1), 119-125. |
Tipo: | Articolo in rivista - Articolo scientifico |
Carattere della pubblicazione: | Scientifica |
Titolo: | Desymmetrized diiron azadithiolato, carbonyls: A step toward modeling the iron-only hydrogenases |
Autori: | Stanley, JL; Heiden, ZM; Rauchfuss, TB; Wilson, SR; De Gioia, L; Zampella, G |
Autori: | |
Data di pubblicazione: | 2008 |
Lingua: | English |
Rivista: | ORGANOMETALLICS |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1021/om7009599 |
Appare nelle tipologie: | 01 - Articolo su rivista |