- Comparative Photochemistry of Tricarbonyl(η5-cyclopentadienyl)methyl- and -ethyl-molybdenum and -tungsten in Poly(vinyl chloride) Film Matrices at 12-298 K
-
The photoreactions of 5-C5H5)(CO)3(CH3)> and 5-C5H5)(CO)3(C2H5)> complexes (M = Mo or W) in poly(vinyl chloride) (pvc) film matrices over a wide temperature range have been monitored using i.r. spectroscopy.At 298 K the methyl complexes dealkylate on irradiation (λ > 300 nm) to form 5-C5H5)(CO)3Cl>, 5-C5H5)(CO)3H>, and 5-C5H5)2(CO)6>.Photolysis at 12 K leads primarily to the formation of 5-C5H5)(CO)2(CH3)>.In the case of molybdenum, M-CH3 bond cleavage also occurs at 12 K and the complexes 5-C5H5)(CO)3Cl> and 5-C5H5)(CO)3H> are generated on warming the matrices.Photolysis of 5-C5H5)(CO)3(C2H5)> at 12 K proceeds with the formation of 5-C5H5)(CO)2(C2H5)> which rearranges photochemically or thermally to form trans-5-C5H5)(CO)2(C2H4)H>.The cis-ethylene-hydride complex is also observed for tungsten at temperatures below ca. 50 K.At 298 K, photolysis of 5-C5H5)(CO)3(C2H5)> leads directly to trans-5-C5H5)(CO)2(C2H4)H> which reacts further to form 5-C5H5)(CO)3H>, 5-C5H5)(C0)2(C2H4)Cl>, 5-C5H5)(CO)3Cl>, and 5-C5H5)2(CO)6>.However, on photolysis of 5-C5H5)(CO)3(C2H5)> at 298 K the main product observed is with trace amounts of 5-C5H5)(CO)3H>, 5-C5H5)(CO)3Cl>, and 5-C5H5)2(CO)6>.
- Hooker, Richard H.,Rest, Antony J.
-
-
Read Online
- Triphenylarsine derivatives of cyclopentadienyl-molybdenum carbonyls
-
C5H5Mo(CO)2AsPh3Cl (I) reacts with benzonitrile in the presence of AlCl3 to form +AlCl4-, which has been isolated as the PF6- salt II.Reaction of this ionic complex with n-butyllithium did not yield a methyleneamine complex by nucleophilic attack at the coordinated nitrile, but gave a mixture of 2 (III) and (C5H5)2Mo2(CO)5(AsPh3) (IV).When dichloromethane was used to extract the crude mixture, C5H5Mo(CO)2(AsPh3)Cl was an additional product.The outcome of the reaction is rationalised in terms of initial formation of III, which was shown separately to be formed with C5H5Mo(CO)3Cl from IV.When a solution of III was heated or III was reduced with sodium amalgam or lithium methoxide IV was formed together with carbonylfree decomposition products.IV was formed to reacts with dichloromethane to form I and C5H5Mo(CO)3Cl.
- Clark, J. Andrew,Kilner, Melvyn
-
-
Read Online
- Reactivity of the metallophosphines (Cp = η-C5H5, M = Mo, W) towards alkynes. X-Ray crystal structure of >
-
The mononuclear phosphido complexes (Cp = η-C5H5; M = Mo, W) react with the electron deficient alkynes methyl propiolate (HCCCO2Me) and dimethyl acetylenedicarboxylate (DMAD, MeO2CCCCO2Me) to give the metallacyclic complexes 1=C(R2)CO)> (R1 = H, CO2Me; R2 = CO2Me), which contain a five-membered chelate ring formed by the linking of the phosphido group, the alkyne, and one CO ligand.The molybdenum phosphido complex, though not the tungsten, also reacts with phenylacetylene to give the corresponding metallacycle , which has been characterized by a single crystal X-ray structure determination.This complex can also be produced by the action of PPh2Cl on the dinuclear μ-acetylide LiCPh)(CO)4>.
- Adams, Harry,Bailey, Neil A.,Day, Andrew N.,Morris, Michael J.,Harrison, Mary M.
-
-
Read Online
- Low-temperature photochemistry of (η5-C5H5)Mo(CO)3Mn(CO) 5: Identification of an unexpectedly stable coordinatively unsaturated heterodinuclear carbonyl complex
-
The low-temperature photochemistry of (η5-C5H5)Mo(CO)3Mn(CO) 5 has been investigated in rigid methylcyclohexane at 93 K. Irradiation at either 313 or 366 nm results in loss of CO as the only photoreaction, and the relative efficiency of CO loss in the glass was established as Φ313/Φ366 ≈ 15, with Φdiss = 10-3 at 313 nm. The origin of photoejected CO (Mo or Mn) cannot be established by a selective 13CO labeling of the starting complex because 13C NMR shows rapid scrambling of CO at 298 K. IR and UV-vis measurements made after the glass was warmed and cooled establish that two isomers of the CO loss product exist, and the more unstable isomer undergoes rapid thermal conversion to the more stable isomer upon melting the glass. No significant wavelength dependence on the product distribution is observed, indicating that both isomers are formed from the decay of the same excited state. The structure of the more stable isomer of (η5-C5H5)MoMn(CO)7 features six terminal CO ligands and one bridging CO as deduced from the IR spectrum and is assigned a structure featuring a bridging CO, (η5-C5H5)Mo(CO) 2(μ-CO)Mn(CO)4. The less stable isomer of (η5-C5H5)MoMn(CO)7 is formulated as having a μ-η1, η2-CO. Both isomers react with CO in fluid methylcyclohexane to yield (η5-C5H5)Mo(CO)3Mn(CO) 5. At 298 K (η5-C5H5)MoMn(CO)7 reacts with CO to quantitatively yield (η5-C5H5)Mo(CO)3Mn(CO) 5 with a rate constant of 1.4 × 102 M-1 s-1. Kinetic measurements were made to determine the activation parameters (ΔH? = 24.0 ± 2 kJ mol-1 and ΔS? = -140 ± 20 J mol-1 K-1) for the reaction of the more stable isomer of (η5-C5H5)MoMn(CO)7 with CO, and the results indicate that the rate is controlled by a large entropic contribution.
- Pope, Keith R.,Wrighton, Mark S.
-
p. 2321 - 2325
(2008/10/08)
-
- Bi- and triheteronuclear complexes of uranium and group VI transition metals
-
The new heterobimetallic compounds Cp3U[OCM(CO)2Cp′] containing uranium and group VI transition metals are synthesized from Cp3UCl and Na[M(CO)3Cp′] or from Cp3UCH3 and H[M(CO)3Cp′] (M = Mo, W; Cp = C5H5; Cp′ = C5H5 or C5Me5). In a same manner, the trimetallic Cp2U[OCMo(CO) 2Cp]2 is obtained starting from Cp2U(NEt2)2 and H[Mo(CO)3Cp]. All these complexes exhibit low CO stretching frequencies characteristic of isocarbonyl linkages between uranium and Mo or W atoms.
- Dormond, Alain,Moise, Claude
-
p. 595 - 598
(2008/10/08)
-