US EPA

5307335 

Journal Article 

Regioselectivity in the nucleophilic functionalization of dibenzofuran, dibenzothiophene and xanthene complexes of Mn(CO)(3)(+) 

Verona, I; Gutheil, JP; Pike, RD; Carpenter, GB 

1996 

Yes 

Journal of Organometallic Chemistry
ISSN: 0022-328X
EISSN: 1872-8561 

ELSEVIER SCIENCE SA LAUSANNE 

LAUSANNE 

524 

1-2 

71-80 

10.1016/S0022-328X(96)06347-4 

WOS:A1996VZ15200009 

The cationic complexes [(eta(6)-DBF)Mn(CO)(3)]BF4, [(eta(6)-DBT)Mn(CO)(3)]BF4 and [(eta(6)-XAN)Mn(CO)(3)]PF6 (DBF = dibenzofuran, DBT = dibenzothiophene, XAN = xanthene) are prepared. These species react with carbon-based nucleophiles to form exo-substituted cyclohexadienyl complexes, Addition is found exclusively at carbons 1 and 4. The C(1)-functionalized regioisomer predominates, especially for the DBF and XAN complexes, for which 90 to > 95% selectivity is found with stabilized nucleophiles. Preference for C(1) is greatly reduced for unstabilized magnesium and lithium nucleophiles. The origin of this selectivity is discussed. Loss of the aromatic ring from the cationic complexes in the presence of CH3CN is found to be extremely facile for the DBF and DBT complexes owing to increased ease of ring slippage. Second-order rate constants for the displacement reactions with CH3CN are 4.6 +/- 0.6 x 10(-5) M(-1) s(-1) (DBF complex, 25 degrees C), 4.4 +/- 1.0 x 10(-5) M(-1) s(-1) (DBT complex, 25 degrees C) and about 1.0 x 10(-5) M(-1) s(-1) (XAN complex, 60 degrees C). A crystal structure is presented for the hydride adduct of the DBF complex, [(eta(5)-C12H9O)Mn(CO)(3)]: space group P2(1)/c, a = 15.301(2), b = 6.4422(12), c = 12.988(2) Angstrom, beta = 90.888(13)degrees, V = 1280.1(3) Angstrom(3), Z = 4, D-calc = 1.599 Mg m(-3), R = 0.0410 and wR2 = 0.0945 on 2446 reflections with F-2 > 4.0 sigma(F-2). 

manganese; arene complexes; nucleophilic addition; heterocycles