15614-21-8Relevant articles and documents
Bimetallic anionic formyl complexes: Synthesis and properties
Tam, Wilson,Marsi, Marianne,Gladysz
, p. 1413 - 1421 (2008/10/08)
Three bimetallic anionic formyl complexes, Li+[Mn2(CO)9(CHO)]- (2), Li+[ReMn(CO)9(CHO)]- (3), and Li+[cis-Re2(CO)9(CHO)]- (4), are prepared by the reaction of Li(C2H5)3BH with the corresponding neutral metal carbonyl dimers MM′(CO)10. Whereas 2 has a half-life of ca. 8 min at room temperature, 4 is stable for days and is easily isolated as a THF solvate. When 2-4 are treated with electrophiles such as benzaldehyde, Fe(CO)5, and n-octyl iodide, hydride transfer occurs to give benzyl alcohol (after protonation), Li+[Fe(CO)4(CHO)]-, and octane, respectively. Heterobimetallic formyl 3 is a weaker hydride donor than 2 and 4. Reaction of 4 with CH3I gives CH4 (ca. 50%). However, complex reactions occur when 2 and 4 are treated with CH3SO3F and strong acids, contrary to our original report of CH4 and H2 evolution. Formyl 2 is stabilized by added (C2H5)3B and decomposes disproportionatively to Mn2(CO)10 (0.5 equiv), Li+[Mn(CO)5]- (1.0 equiv), and H2 (0.5 equiv). An initial Mn-Mn bond cleavage step is proposed. The only characterizable product from the thermolysis of 4 is Re2(CO)10, but photolysis gives Li+[Re2(CO)9(H)]-. When K+[Re2(CO)9(CHO)]- is treated with 1 equiv of K(sec-C4H9)3BH, reduction to formaldehyde (21%) and K2[Re2(CO)9] (92%) occurs.
Ground- and Excited-State Oxidation-Reduction Chemistry of (Triphenyltin)- and (Triphenylgermanium)tricarbonyl(1,10-phenanthroline)rhenium and Related Compounds
Luong, John C.,Faltynek, Robert A.,Wrighton, Mark S.
, p. 7892 - 7900 (2007/10/02)
Optical absorptions and emission spectroscopy and the photochemistry and electrochemistry are reported for complexes of the general formula R3EM(CO)3L (R = Ph or Me; E = Ge or Sn; M = Mn or Re; L = 1,10-phenanthroline, 2,2'-bipyridine, or 2,2'-biquinoline).The lowest excited state in each system results from charge-transfer, (E-M)?b -> ?*L, absorption.Several of the Re complexes (R = Ph; E = Ge or Sn; L = 2,2'-bipyridine or 1,10-phenanthroline) exhibit optical emission from the lowest excited state at 298 K in fluid solution; emission lifetimes under such conditions for these complexes are ca. 10-6 s.These excited complexes can be quenched by both electron-donor quenchers and by electron-acceptor quenchers.Detailed quenching studies of Ph3SnRe(CO)3(phen) (phen = 1,10-phenanthroline) have been carried out, and quenching obeys Stern-Volmer kinetics.Electron donors, Q, for which E(Q+/Q) is more negative than ca.+0.2 V vs.SCE quench at an essentially diffusion-controlled rate.Electron acceptors, P+, for which E(P+/P) is more positive than ca.-0.1 V vs.SCE also quench at nearly a diffusion-controlled rate.Cyclic voltammetry of the complexes in CH3CN/0.1 M ClO4 typically shows a one-electron, reversible reduction in the -1.1 to -1.7 V vs.SCE range associated with the population of the lowest available ?* orbital principally localized on L.An irreversible oxidation current peak is observed in the range +0.5 to +0.8 V vs.SCE.The M-containing oxidation product is fac-+.Consistent with the groung state electrochemistry, quenching by reversibly electron-donor quenchers (e.g., N,N,N',N'-tetramethyl-p-phenylenediamine) results in no net photoredox reaction (Φ -3) whereas quenching by reversible electron-acceptor quenchers (e.g., N,N'-dimethyl-4,4'-bipyridinium) results in net redox chemistry to reduce the quencher and to form fac-+ from the complex.The data are consistent with primary formation of R3E. and the 16-valence electron + from cleavage of the +. formed by excited-state electron transfer.Rate of +. cleavage is similar to the dissociative E-M bond cleavage induced by the (E-M)?b -> ?*L optical excitation.
