| Abstract
| - Intramolecular electronic communication has been observedin diiron complexes of the type ER2[(η5-C5H4)Fe(L2)Me]2 (L2 = dppe; ER2 = CH2 (1a),SiMe2 (2a), GeMe2 (3a), SnMe2 (4a)) for the first time. The resolutionbetween two reversible waves increases in the order 1a< 2a< 3a< 4a.The related ferrocenyl (Fc) complexes (η5-C5H5)Fe(L2)ER2Fc exhibited Fe−Ebond cleavage upon electrochemical oxidation; however, in the absenceof a bridge, two reversible redox processes are observed.
- Cyclic voltammetric studies on ER2[(η5-C5H4)Fe(L2)Me]2 (L2 = dppe; ER2 = CH2 (1a), SiMe2 (2a),GeMe2 (3a), SnMe2 (4a)) revealed two well-resolved reversible waves (1E1/2 = −0.33 V, 2E1/2 = −0.20 V (for 1a); 1E1/2 = −0.35 V, 2E1/2 = −0.21 V (for2a); 1E1/2 = −0.36V, 2E1/2 = −0.23 V (for 3a); 1E1/2 = −0.36V, 2E1/2 = −0.22 V (for 4a)) in CH2Cl2, suggesting electroniccommunication between two iron centers, which is seen for the firsttime in this family of organometallic complexes. The resolution betweentwo reversible waves increases in the order 1a< 2a< 3a< 4a; however, coordinatingsolvents such as pyridine, PhCN, DMSO, and DMF decreased these interactions,attributable to the stabilization of cationic species formed afterthe first oxidation. UV/vis spectroelectrochemistry of 1a−4a revealed two distinct absorbance patternsfor both redox processes and reflected the stepwise oxidation. Homobimetalliccomplexes containing ferrocenyl groups, (η5-C5H5)Fe(L2)ER2Fc (ER2 = none, L2 = cis-dppen(5a); ER2 = SiMe2, L2 = cis-dppen (6a), dppm (6b); ER2 = GeMe2, L2 = cis-dppen (7a),dppm (7b); ER2 = SntBu2, L2 = dmpe (8a); Fc= (η5-C5H4)Fe(η5-C5H5)), were preparedand studied in terms of electrochemistry. The cyclic voltammogramof 5a exhibited two well-resolved one-electron reversiblewaves at 1E1/2 = −0.21V and 2E1/2 = 0.58 V corresponding to oxidation of the Fe(P−P) and Fciron atoms, respectively. Other complexes in this series (6a/6b,7a/7b, 8a) containing direct Fe−E−Fc (E = Si,Ge, Sn) bridging units were not stable under electrochemical conditions,and rupture of the Fe−E bonds was observed.
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