79703-04-1Relevant articles and documents
Photochemistry of organometallic halide complexes. Mechanisms for the formation of ionic products
Pan, Xiong,Philbin, Cecelia E.,Castellani, Michael P.,Tyler, David R.
, p. 671 - 676 (2008/10/08)
The photochemical reactions of the Mn(CO)5X (X = Cl, Br, I), CpMo(CO)3X (X = Cl, I), and CpFe(CO)2I complexes with various ligands were investigated with an emphasis on determining how ionic products form in these reactions. Two pathways account for the formation of ionic products: (1) M-X heterolysis and (2) metal-metal-bonded dimer formation followed by subsequent disproportionation. The metal-metal-bonded dimer may form via a secondary photolysis of a M-CO-loss photoproduct, via M-X heterolysis, or via a minor M-X homolysis pathway, followed by coupling of two metal radicals. CpMo(CO)3X reacts photochemically with a variety of ligands to give substitution products, but ionic products form only with pyridine and DMSO. With pyridine, the following sequence of reactions was found to yield ionic products: (1) CpMo(CO)3Cl →hν CpMo(CO)3 + Cl; (2) 2CpMo(CO)3 → Cp2Mo2(CO)6; (3) Cp2Mo2(CO)6 →hν CpMo(CO)3- + CpMo(CO)3py+. (Reaction 3 is the photochemical disproportionation of Cp2Mo2(CO)6 described previously by us.) The CpMo(CO)3X complexes are the only halides studied for which some M-X homolysis occurs; however, homolysis of the Mo-X bond is very inefficient: Φ = 9 × 10-4. For CpMo(CO)3X in DMSO, the only ionic product is CpMo(CO)2(DMSO)2+, formed by the following route: CpMo(CO)3Cl + DMSO →hν CpMo(CO)2(DMSO)Cl →hν CpMo(CO)2DMSO+ + Cl- → CpMo(CO)2(DMSO)2+. Ionic products form in the photochemical reactions of Mn(CO)5X complexes via the following route involving initial Mn-CO bond dissociation: Mn(CO)5X →hν Mn2(CO)8X2 →hν MnX2 + 3CO + 1/2 Mn2(CO)10. Photochemical disproportionation of the Mn2(CO)10 complex then occurs. Ionic products also form in the photochemical reactions of the CpFe(CO)2I complex via the intermediate formation of the metal-metal-bonded dimer, followed by disproportionation of this species. In this case, however, the dimer is formed by initial heterolysis of the Fe-I bond (CpFe(CO)2I →hν CpFe(CO)2+ + I-) followed by the sequence of reactions in Scheme II.
PHOTOCHEMISTRY OF METAL-METAL BONDED COMPOUNDS. 1. ISOLATION AND X-RAY MOLECULAR STRUCTURE ANALYSES OF ORTHOMETALATED TRIPHENYL PHOSPHITE MANGANESE CARBONYL DERIVATIVES AND REACTION MECHANISMS OF ORTHOMETALATION FROM PHOTODEGRADATION OF MANGANESE CARBONYL DERIVATIVES WITH Sn-Mn BOND.
Onaka,Kondo,Furuichi,Toriumi,Ito
, p. 87 - 94 (2007/10/02)
Photochemical degradation of a series of tin-manganese bonded complexes was studied. The apparent reactivity of the tin-manganese bond toward UV irradiation is interpreted on the basis of absorption spectra of relevant complexes and available emissions from the light source. Two kinds of orthometalated products were obtained from photolysis of Me//3Sn-Mn(CO)//3 left bracket P(OPh)//3 right bracket //2 in benzene. Various kinds of experiments suggest that their photochemical reactions proceed through homolytic cleavage of the Sn-Mn bond in the initial stage and the resulting 15-electron intermediates abstract hydrogen from the triphenyl phosphite moiety. Molecular structures of the two kinds of orthometalated products, as clarified by X-ray structure analyses, are described.
