Chemical redox reactions of multiply-bonded dirhenium phosphine complexes of the M(,2)L(,8) and M... more Chemical redox reactions of multiply-bonded dirhenium phosphine complexes of the M(,2)L(,8) and M(,2)L(,10) structural types have been carried out using cobaltocene and nitrosonium hexafluorophosphate as the reductant and oxidant, respectively. The systems that were studied are those which were found to exhibit electrochemically reversible oxidations or reductions as determined by the cyclic voltammetry technique. The series Re(,2)Cl(,4)(PMe(,2)Ph)(,4) (\u27n+) (n = 0, 1, or 2) was prepared using NOPF(,6) and was studied structurally in order to ascertain the relationship between bond distance and formal metal-metal bond order. Another series of dirhenium complexes was prepared by the one-electron oxidation and one-electron reduction of the doubly-bonded complex Cl(,2)Re((mu)-Cl)(,2)((mu)-dppm)(,2)ReCl(,2) to give Re(,2)Cl(,6)(dppm)(,2) (\u271+,1-). Both of the latter ions are examples of the rarely encountered M-M bond order of 1.5. The quadruply-bonded complexes Re(,2)Cl(,6)(PR(,3))(,2) (PR(,3) = PEt(,3), P-n-Pr(,3), PMePh(,2) or PEtPh(,2)) and Re(,2)(O(,2)CR)(,4)Cl(,2) (R = C(,3)H(,7), CMe(,3), or C(,6)H(,5)) were reduced by Cp(,2)Co to give the paramagnetic salts ((eta)(\u275)-C(,5)H(,5))(,2)Co Re(,2)Cl(,6)(PR(,3))(,2) and ((eta)(\u275)-C(,5)H(,5))(,2)Co Re(,2)(O(,2)CR)(,4)Cl(,2) . The reduction of Re(,2)Cl(,5)- (PMe(,2)Ph(,2))(,3) to give ((eta)(\u275)-C(,5)H(,5))(,2)Co Re(,2)Cl(,5)(PMePh(,2))(,3) and its oxida- tion to Re(,2)Cl(,5)(PMePh(,2))(,3) PF(,6) have also been accomplished. These results demonstrate that mixed halide-phosphine complexes of Re(,2)(\u27n+) (n = 6, 5, or 4) exhibit the most extensive redox chemistry of any class of multiply-bonded dimetal species. The reactions of carbon monoxide with dirhenium complexes containing monodentate phosphine ligands have been explored. The series Re(,2)Cl(,4)(PMe(,2)Ph)(,4) (PF(,6))(,n) (n = 0, 1, or 2) reacts with CO to yield monomeric ReCl(CO)(,2)(PMe(,2)Ph)(,3), ReCl(CO)(,3)(PMe(,2)Ph)(,2) and ReCl(,3)(CO)(PMe(,2)Ph)(,3), resulting from M-M bond cleavage. The complex Re(,2)Cl(,4)(dppm)(,2), which contains the bridging bidentate phosphine bis(diphenylphosphino)methane, reacts with CO to yield Re(,2)Cl(,4)(dppm)(,2)(CO)(,n) (n = 1 or 2). These results provide, for the first time, evidence as to the nature of the intermediates that are formed in the cleavage of the electron-rich triple bond ((sigma)(\u272)(pi)(\u274)(delta)(\u272)(delta)*(\u272) configuration) by (pi)-acceptor ligands. The interesting biscarbonyl complex Re(,2)Cl(,4)(dppm)(,2)(CO)(,2) reacts with L = RCN and RNC in the presence of TIPF(,6) to yield Re(,2)Cl(,3)(dppm)(,2)(CO)(,2)(L) PF(,6). These species can be reduced by Cp(,2)Co to give the corresponding neutral compounds. The latter constitute the first examples of complexes that contain the Re(,2)(\u273+) core
ABSTRACT The interplay of metal orbitals in metal TCNQ (7,7,8,8-tetracyanoquinodimethane) and DCN... more ABSTRACT The interplay of metal orbitals in metal TCNQ (7,7,8,8-tetracyanoquinodimethane) and DCNQI (N,N′-dicyanoquinonediimine) complexes is investigated on the basis of molecular orbital calculations. For the M(TCNQ) materials, where M = Na, K, Rb, Cs, Tl, Cu, and Ag, the conductivity decreases with the increase in dimerization. Some Cu compounds, however, exhibit uniform columns and higher conducting properties, for which hybridization of the Cu 3d orbitals with the organic radicals is expected. The energy level of Tl 6s is slightly more separated from the TCNQ LUMO, but could potentially mediate similar metal–organic interactions. A simple analytical energy band model is proposed to evaluate the hybridization of the metal orbitals, providing the criteria to form a closed Fermi surface. Accordingly, semiconducting and comparatively high-conducting states of many Cu and Tl TCNQ complexes with uniform columns are to be regarded as a Mott insulating state rather than a Peierls insulating state.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Chemical redox reactions of multiply-bonded dirhenium phosphine complexes of the M(,2)L(,8) and M... more Chemical redox reactions of multiply-bonded dirhenium phosphine complexes of the M(,2)L(,8) and M(,2)L(,10) structural types have been carried out using cobaltocene and nitrosonium hexafluorophosphate as the reductant and oxidant, respectively. The systems that were studied are those which were found to exhibit electrochemically reversible oxidations or reductions as determined by the cyclic voltammetry technique. The series Re(,2)Cl(,4)(PMe(,2)Ph)(,4) (\u27n+) (n = 0, 1, or 2) was prepared using NOPF(,6) and was studied structurally in order to ascertain the relationship between bond distance and formal metal-metal bond order. Another series of dirhenium complexes was prepared by the one-electron oxidation and one-electron reduction of the doubly-bonded complex Cl(,2)Re((mu)-Cl)(,2)((mu)-dppm)(,2)ReCl(,2) to give Re(,2)Cl(,6)(dppm)(,2) (\u271+,1-). Both of the latter ions are examples of the rarely encountered M-M bond order of 1.5. The quadruply-bonded complexes Re(,2)Cl(,6)(PR(,3))(,2) (PR(,3) = PEt(,3), P-n-Pr(,3), PMePh(,2) or PEtPh(,2)) and Re(,2)(O(,2)CR)(,4)Cl(,2) (R = C(,3)H(,7), CMe(,3), or C(,6)H(,5)) were reduced by Cp(,2)Co to give the paramagnetic salts ((eta)(\u275)-C(,5)H(,5))(,2)Co Re(,2)Cl(,6)(PR(,3))(,2) and ((eta)(\u275)-C(,5)H(,5))(,2)Co Re(,2)(O(,2)CR)(,4)Cl(,2) . The reduction of Re(,2)Cl(,5)- (PMe(,2)Ph(,2))(,3) to give ((eta)(\u275)-C(,5)H(,5))(,2)Co Re(,2)Cl(,5)(PMePh(,2))(,3) and its oxida- tion to Re(,2)Cl(,5)(PMePh(,2))(,3) PF(,6) have also been accomplished. These results demonstrate that mixed halide-phosphine complexes of Re(,2)(\u27n+) (n = 6, 5, or 4) exhibit the most extensive redox chemistry of any class of multiply-bonded dimetal species. The reactions of carbon monoxide with dirhenium complexes containing monodentate phosphine ligands have been explored. The series Re(,2)Cl(,4)(PMe(,2)Ph)(,4) (PF(,6))(,n) (n = 0, 1, or 2) reacts with CO to yield monomeric ReCl(CO)(,2)(PMe(,2)Ph)(,3), ReCl(CO)(,3)(PMe(,2)Ph)(,2) and ReCl(,3)(CO)(PMe(,2)Ph)(,3), resulting from M-M bond cleavage. The complex Re(,2)Cl(,4)(dppm)(,2), which contains the bridging bidentate phosphine bis(diphenylphosphino)methane, reacts with CO to yield Re(,2)Cl(,4)(dppm)(,2)(CO)(,n) (n = 1 or 2). These results provide, for the first time, evidence as to the nature of the intermediates that are formed in the cleavage of the electron-rich triple bond ((sigma)(\u272)(pi)(\u274)(delta)(\u272)(delta)*(\u272) configuration) by (pi)-acceptor ligands. The interesting biscarbonyl complex Re(,2)Cl(,4)(dppm)(,2)(CO)(,2) reacts with L = RCN and RNC in the presence of TIPF(,6) to yield Re(,2)Cl(,3)(dppm)(,2)(CO)(,2)(L) PF(,6). These species can be reduced by Cp(,2)Co to give the corresponding neutral compounds. The latter constitute the first examples of complexes that contain the Re(,2)(\u273+) core
ABSTRACT The interplay of metal orbitals in metal TCNQ (7,7,8,8-tetracyanoquinodimethane) and DCN... more ABSTRACT The interplay of metal orbitals in metal TCNQ (7,7,8,8-tetracyanoquinodimethane) and DCNQI (N,N′-dicyanoquinonediimine) complexes is investigated on the basis of molecular orbital calculations. For the M(TCNQ) materials, where M = Na, K, Rb, Cs, Tl, Cu, and Ag, the conductivity decreases with the increase in dimerization. Some Cu compounds, however, exhibit uniform columns and higher conducting properties, for which hybridization of the Cu 3d orbitals with the organic radicals is expected. The energy level of Tl 6s is slightly more separated from the TCNQ LUMO, but could potentially mediate similar metal–organic interactions. A simple analytical energy band model is proposed to evaluate the hybridization of the metal orbitals, providing the criteria to form a closed Fermi surface. Accordingly, semiconducting and comparatively high-conducting states of many Cu and Tl TCNQ complexes with uniform columns are to be regarded as a Mott insulating state rather than a Peierls insulating state.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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