TY - JOUR
T1 - Electron transfer behavior of pincer-type {RhNO}8 complexes
T2 - Spectroscopic characterization and reactivity of paramagnetic {RhNO}9 complexes
AU - Pellegrino, Juan
AU - Gaviglio, Carina
AU - Milstein, David
AU - Doctorovich, Fabio
PY - 2013/11/11
Y1 - 2013/11/11
N2 - The electrochemistry of the {RhNO}8 complexes [Rh(PCP tBu)(NO)][BF4] (1+), [Rh(PCP tBuCH2)(NO)][BF4] (2+), and Rh(PCPtBu)(NO)Cl (3) was studied. Both four-coordinate complexes 1+ and 2+ exhibit a reversible reduction within the CH2Cl2 solvent window. Nevertheless, the chemical or electrochemical reduction of 1+ and 2+ in CH 2Cl2 led to the formation of the five-coordinate {RhNO}8 complexes 3 and Rh(PCPtBuCH2)(NO)Cl (4), respectively, through chloride abstraction from CH2Cl 2 by the one-electron-reduced {RhNO}9 species [Rh(PCP tBu)(NO)]• (1•) and [Rh(PCP tBuCH2)(NO)]• (2•), as has been observed for many other 17-electron paramagnetic complexes. The new complex 4 was fully characterized by multinuclear NMR techniques, IR, X-ray diffraction, CV, UV-vis, and elemental analysis. On the other hand, the five-coordinate complexes 3 and 4 show only one irreversible oxidation in CH2Cl2 and two irreversible reductions in THF. The {RhNO}9 complex 1• could be obtained quantitatively by one-electron reduction of 1+ with cobaltocene in nonchlorinated solvents and was characterized by IR, EPR, and 1H NMR in solution. Activation of carbon-halogen bonds by complex 1• was observed by studying the reactivity of 1• with some aryl halides, giving in all cases the {RhNO}8 Rh(PCPtBu)(NO)X (X = Cl -, 3, or X = I-, 6) as the only rhodium complex, while a complex with coordination of the aryl moiety was not observed as a stable final product in any case. The fate of the aryl organic radicals could be determined in some cases. In addition, DFT calculations were performed to elucidate the electronic structure of 1• and to support the observed reactivity.
AB - The electrochemistry of the {RhNO}8 complexes [Rh(PCP tBu)(NO)][BF4] (1+), [Rh(PCP tBuCH2)(NO)][BF4] (2+), and Rh(PCPtBu)(NO)Cl (3) was studied. Both four-coordinate complexes 1+ and 2+ exhibit a reversible reduction within the CH2Cl2 solvent window. Nevertheless, the chemical or electrochemical reduction of 1+ and 2+ in CH 2Cl2 led to the formation of the five-coordinate {RhNO}8 complexes 3 and Rh(PCPtBuCH2)(NO)Cl (4), respectively, through chloride abstraction from CH2Cl 2 by the one-electron-reduced {RhNO}9 species [Rh(PCP tBu)(NO)]• (1•) and [Rh(PCP tBuCH2)(NO)]• (2•), as has been observed for many other 17-electron paramagnetic complexes. The new complex 4 was fully characterized by multinuclear NMR techniques, IR, X-ray diffraction, CV, UV-vis, and elemental analysis. On the other hand, the five-coordinate complexes 3 and 4 show only one irreversible oxidation in CH2Cl2 and two irreversible reductions in THF. The {RhNO}9 complex 1• could be obtained quantitatively by one-electron reduction of 1+ with cobaltocene in nonchlorinated solvents and was characterized by IR, EPR, and 1H NMR in solution. Activation of carbon-halogen bonds by complex 1• was observed by studying the reactivity of 1• with some aryl halides, giving in all cases the {RhNO}8 Rh(PCPtBu)(NO)X (X = Cl -, 3, or X = I-, 6) as the only rhodium complex, while a complex with coordination of the aryl moiety was not observed as a stable final product in any case. The fate of the aryl organic radicals could be determined in some cases. In addition, DFT calculations were performed to elucidate the electronic structure of 1• and to support the observed reactivity.
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U2 - 10.1021/om4008746
DO - 10.1021/om4008746
M3 - Article
AN - SCOPUS:84887714387
VL - 32
SP - 6555
EP - 6564
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 21
ER -