14096-06-1Relevant academic research and scientific papers
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.
Spontaneous and Induced Homolysis of Bis(triphenylphosphine)octacarbonyldimanganese (Mn-Mn)
Poee, Anthony,Sekhar, Chandra V.
, p. 4874 - 4883 (2007/10/02)
Kinetic studies show that the complex Mn2(CO)8(PPh3)2 reacts thermally by two paths with C2H2Cl4, C16H33I, O2, NO, P(OEt)3, and P-n-Bu3 in decalin or cylcohexane.Reactions with CO or P(OPh)3 proceed only by one of these paths.The two paths are approximately equal importance and both show a very close fit to the same, rather complex, form of rate equation.The equation is quite inconsistent with any form of rate-determining dissociation, but it is consistent with two forms of reversible homolysis, one spontaneous and one induced.The latter involves initial, reversible formation of a reactive isomer of Mn2(CO)8(PPh3)2 which undergoes homolysis when attacked by a sufficiently reactive reagent.Both paths are therefore operative in reactions with the more reactive reagents, but reactions with CO and P(OPh)3 proceed only via spontaneous homolysis because these reagents are evidently unable to induce homolysis of the reactive isomer of the complex.A possible structure for the reactive isomer is one formed by metal migration, i.e., it can be formulated as (Ph3P)(OC)4Mn(μ-CO)Mn(CO)3(PPh3) which contains a bridging CO ligand, no Mn-Mn bond, and a vacant coordination site on one Mn atom.Attack at this site by suitably active reagents is postulated to lead to fragmentation.These results show that behavior previously thought to be uniquely indicative of spontaneous homolysis could also be explained by reversible homolysis induced by the reactant after isomerization of the complex.Rate constants are derived for halogen transfer from C2H2Cl4 or C16H33I to .Mn(CO)4(PPh3) and for nucleophilic displacement of PPh3 from .Mn(CO)4(PPh3) by P(OPh)3, P(OEt)3, and CO.
Haloalkyl Complexes of the Transition Metals. Part 3. Reactions of Some Chloromethyl and Methoxymethyl Complexes of Molybdenum, Tungsten, Manganese, Rhenium, Iron, and Rutenium with Some Tertiary Phosphine and Related Ligands
Pelling, Simon,Botha, Cheryl,Moss, John R.
, p. 1495 - 1502 (2007/10/02)
The reactions of some chloromethyl transition-metal complexes with PPh3 have been investigated.For M'= Fe(η5-C5H5)(CO)2 or W(η5-C5H5)(CO)3, cationic ylide complexes of the type (1+) have been isolated, whereas for M'= Mn(CO)5 or Mo(η5-C5H5)(CO)3, chloro-complexes were obtained and for M'= Re(CO)5 or Ru(η5-C5H5)(CO)2, no ligand products were found under the reaction conditions used.The reactions have been investigated in methanol and acetonitrile.The reactions of 5-C5H5)(CO)2(CH2Cl)> with other ligands (L) have also been studied; cationic ylide complexes 5-C5H5)(CO)2(CH2L)>(1+) have been obtained for L = PMe2Ph, PMePh2, PEt2Ph, PEtPh2, or AsPh3 and disubstituted cationic complexes 5-C5H5)(CO)L2>(1+) where L = PMe3, PMe2Ph, PEt2Ph, or PEtPh2.Possible mechanisms for these reactions are discussed.The reactions of some methoxymethyl complexes with PPh3 are also described.
