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 and
2B 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[Co
2(salophen)
2Na
2(THF)
6](
4) and[Co
2(MeOsalophen)
2Na
2(THF)
4](
6), respectively. However, such cobalt(II)centers be
have 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)(H
2O)](
11), and [Co(MeOsalophen)(COOMe)(H
2O)] (
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 CO
2adducts[Co(salophen)NaCO
2(THF)] (
13)and [Co(MeOsalophen)NaCO
2(THF)](
14). Crystallographic data:
2 istriclinic,space group
P,
a = 14.651(1) Å,
b = 15.355(1) Å,
c = 11.671(11),
hars/alp
ha.gif" BORDER=0> = 105.70(1)
,
hars/beta2.gif" BORDER=0 ALIGN="middle"> = 102.66(1)
,
hars/gamma.gif" BORDER=0 >=97.65(1)
,
Z = 2, and
R = 0.044;
4 is monoclinic, space group
P2
1/
c,
a =11.270(2) Å,
b = 17.594(3) Å,
c=16.606(3) Å,
hars/alp
ha.gif" BORDER=0> =
hars/gamma.gif" BORDER=0 > = 90
,
hars/beta2.gif" BORDER=0 ALIGN="middle"> = 90.45(2)
,
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),
hars/alp
ha.gif" BORDER=0> = 106.28(3)
,
hars/beta2.gif" BORDER=0 ALIGN="middle"> = 101.17(3)
,
hars/gamma.gif" BORDER=0 > = 103.04(3)
,
Z = 1, and
R =0.057.