Electrochemical behavior of S,S-bridged adducts of square planar metalladithiolene complexes [M(S2C2Ph2)2](M=Ni, Pd, and Pt) |
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| Authors: | Mitsushiro Nomura |
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| Institution: | Department of Chemistry, Faculty of Science and Technology, Sophia University, 7-1, Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan |
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| Abstract: | The electrochemical behavior of the S,S′-bridged adducts of square planar metalladithiolene complexes was investigated by using cyclic voltammetry and electrochemical spectroscopies (visible, near-IR, and ESR). The norbornene-bridged S,S′-adduct Ni(S2C2Ph2)2(C7H8)] (2a; C7H8=norbornene) formed by Ni(S2C2Ph2)2] (1a) and quadricyclane (Q) was dissociated by an electrochemical reduction, and anion 1a− and norbornadiene (NBD) were formed. Q was isomerized to NBD in the overall reaction. The o-xylyl-bridged S,S′-adduct Ni(S2C2Ph2)2(CH2)2(C6H4)] (3a; (CH2)2(C6H4)=o-xylyl) was also dissociated by an electrochemical reduction, and this reaction gave the o-xylyl radical (o-quinodimethane). The reduction of complex 3a in the presence of excess o-xylylene dibromide underwent the catalytic formation of o-quinodimethane. The butylene-bridged S,S′-adduct Ni(S2C2Ph2)2(CH2)4] (4a; (CH2)4=butylene) was stable on an electrochemical reduction. The lifetimes of reduced species of these adducts 2a-4a were influenced by the stability of the eliminated group (stability: NBD > o-xylyl radical (o-quinodimethane) > butylene radical). Therefore, the reduced species are stable in the sequence 4a− > 3a− > 2a−. Although the palladium complex Pd(S2C2Ph2)2] (1b) was easier to reduce than the nickel complex 1a or the platinum complex Pt(S2C2Ph2)2] (1c), their S,S′-adducts were easier to reduce in the order of Ni adduct > Pd adduct > Pt adduct. |
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| Keywords: | Metalladithiolene Electrochemistry Reduction Addition Elimination |
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