Formation of Carbon-Carbon-Bonded Dimers in the Reduction of [CoIIsalophen] [salophen = N,N'-o-Phenylenebis(salicylideneaminato)]: Their Reactivity with Electrophiles T

详细信息    查看全文

• 作者：Stefania De Angelis ; Euro Solari ; Emma Gallo ; Carlo Floriani ; Angiola Chiesi-Villa ; and Corrado Rizzoli
• 刊名：Inorganic Chemistry
• 出版年：1996
• 出版时间：October 9, 1996
• 年：1996
• 卷：35
• 期：21
• 页码：5995 - 6003
• 全文大小：486K
• 年卷期：v.35,no.21(October 9, 1996)
• ISSN：1520-510X

文摘

The reduction of cobalt-Schiff base complexes has beenexplored as a function of the nature of the ligand.Inthe case of substituted salen complexes, reduction occurred at themetal with the formation of bifunctional Co(I)-Na complexes, while for salophen derivatives the reductivecoupling of imino groups was observed. SuchC-C bonds function as electron shuttles in chemical reductions.Reduction of [Co(MeOsalen)] (1) withNametal in THF led to a monomeric[Co(MeOsalen)Na(THF)₂] (2A) anda dimeric[{Co(MeOsalen)Na(THF)}₂](2B) compound. Compounds 2A and2B exemplify a bifunctional acid-base system with bothcenters in closeproximity. The analogous reduction of [Co(salophen)](3) and [Co(MeOsalophen)] (5) led todimeric cobalt(II)derivatives containing a bridging C-C bond across two units in[Co₂(salophen)₂Na₂(THF)₆](4) and[Co₂(MeOsalophen)₂Na₂(THF)₄](6), respectively. However, such cobalt(II)centers behave as cobalt(I), sincethe C-C bond provides a pair of electrons to the metal couple duringthe chemical reaction. Alkylation at thecobalt has been observed in complexes 4 and 6with the concomitant formation of a Co(III)-C bond in[Co(salophen)(Me)] (9),[Co(salophen)(COOMe)(THF)] (10),[Co(MeOsalophen)(Me)(H₂O)](11), and [Co(MeOsalophen)(COOMe)(H₂O)] (12).The cleavage and formation of the C-C bond linking the twosalophenunits have been observed in the reversible reactions of 4and 6 with carbon dioxide leading to the CO₂adducts[Co(salophen)NaCO₂(THF)] (13)and [Co(MeOsalophen)NaCO₂(THF)](14). Crystallographic data: 2 istriclinic,space group P, a = 14.651(1) Å,b = 15.355(1) Å, c = 11.671(11), = 105.70(1)deg.gif">, = 102.66(1)deg.gif">, =97.65(1)deg.gif">, Z = 2, and R = 0.044;4 is monoclinic, space groupP2₁/c, a =11.270(2) Å, b = 17.594(3) Å, c=16.606(3) Å, = = 90deg.gif">, = 90.45(2)deg.gif">,Z = 2, and R = 0.053; 6 istriclinic, space group P, a =11.857(4)Å, b = 12.639(4) Å, c =10.553(5), = 106.28(3)deg.gif">, = 101.17(3)deg.gif">, = 103.04(3)deg.gif">, Z = 1, and R =0.057.