36352-27-9Relevant academic research and scientific papers
KINETICS AND MECHANISM OF THE TRANSFER HYDROGENATION AND DOUBLE BOND MIGRATION OF 1-HEXENE CATALYZED BY MOLYBDENUM COMPLEXES.
Tatsumi,Shibagaki,Tominaga
, p. 19 - 32 (1984)
The mechanism of the transfer hydrogenation and double bond migration of 1-hexene catalyzed by trans-Mo(N//2)//2(dpe)//2 (dpe equals Ph//2PCH//2CH//2PPh//2) has been studied. The stoichiometric reaction of 1-hexene with MoH//4(dpe)//2 suggests that the active species for the hydrogenation is MoH//2(dpe)//2 and that for the double bond migration it is Mo(dpe)//2. The double bond migration is suppressed in the hydrogenation of 1-hexene by molecular hydrogen, with the formation of a moderate amount of hexane. The result of the reaction of Mo(C//2H//4)//2 with 2-propanol suggests that dual pathways may be available for the transfer hydrogenation.
Detection of unusual reaction intermediates during the conversion of W(N2)2(dppe)2 to W(H)4(dppe) 2 and of H2O into H2
Eguillor, Beatriz,Caldwell, Patrick J.,Cockett, Martin C. R.,Duckett, Simon B.,John, Richard O.,Lynam, Jason M.,Sleigh, Christopher J.,Wilson, Ian
, p. 18257 - 18265 (2013/01/15)
W(N2)2(dppe-κ2P)2 reacts with H2 to form WH3{Ph(C6H4)PCH 2CH2PPh2-κ2P}(dppe- κ2P) and then W(H)4(dppe-κ2P) 2. When para-hydrogen is used in this study, polarized hydride signals are seen for these two species. The reaction is complicated by the fact that trace amounts of water lead to the formation of H2, PPh 2CH2CH2Ph2P(O) and W(H) 3(OH)(dppe-κ2P)2, the latter of which reacts further via H2O elimination to form W(H)4(dppe- κ2P)2 and [WH3{Ph(C6H 4)PCH2CH2PPh2-κ2P} (dppe-κ2P)]. These studies demonstrate a role for the 14-electron intermediate W(dppe-κ2P)2 in the CH activation reaction pathway leading to [WH3{Ph(C6H 4)PCH2CH2PPh2-k2P}(dppe- k2P)]. UV irradiation of W(H)4(dppe-κ2P) 2 under H2 led to phosphine dechelation and the formation of W(H)6(dppe-k2P)(dppe-k1P) rather than H 2 loss and W(H)2(dppe-κ2P)2 as expected. Parallel DFT studies using the simplified model system W(N 2)2((Ph)HPCH2CH2PH 2-κ2P)(H2PCH2CH 2PH2-κ2P) confirm that ortho-metalation is viable via both W(dppe-κ2P)2 and W(H) 2(dppe-κ2P)2 with explicit THF solvation being necessary to produce the electronic singlet-based reaction pathway that matches with the observation of para-hydrogen induced polarization in the hydride signals of [WH3{Ph(C6H4)PCH 2CH2PPh2-κ2P}(dppe- κ2P)], W(H)3(OH)(dppe-κ2P) 2 and W(H)4(dppe-κ2P)2 during this study. These studies therefore reveal the existence of differentiated and previously unsuspected thermal and photochemical reaction pathways in the chemistry of both W(N2)2(dppe-κ2P) 2 and W(H)4(dppe-κ2P)2 which have implications for their reported role in N2 fixation.
Synthesis and reactivities of pyrrolylimido complexes of molybdenum and tungsten: Formation of pyrrole and N-aminopyrrole from molecular nitrogen
Seino, Hidetake,Ishii, Youichi,Sasagawa, Takao,Hidai, Masanobu
, p. 12181 - 12193 (2007/10/03)
Hydrazido(2-) complexes trans-[MX(NNH2)(dppe)2]+ (M = Mo, W; X = F, Cl; dppe = Ph2PCH2CH2-PPh2) and cis,mer-[WX2(NNH2)(PMe2Ph)3] (X = Cl, Br), which are readily derived from trans-[M(N2)2(dppe)2] (1) and cis-[W(N2)2(PMe2Ph)4] by protonation, condensed with 2,5-dimethoxytetrahydrofuran to afford pyrrolylimido complexes of the type trans-[MX(NNCH=CHCH=CH)(dppe)2]+ (3+) and cis,mer-[WX2(NNCH=CHCH=CH)(PMe2-Ph)3] (6), respectively. Their structures were characterized spectroscopically and further confirmed by X-ray diffraction study. Electrophilic substitution reactions at the pyrrole ring in complexes 3+ occurred selectively at the β-position to give the corresponding β-substituted pyrrolylimido complexes trans-[MX(NNCH=C(E)CH=CH)(dppe)2]+ (E = Br, CN, SO3-, COR), although only chlorination of 3+ with N-chlorosuccinimide in THF took place predominantly at the α-position. This β-regioselectivity is in sharp contrast to the α-regioselectivity of free pyrrole and is probably caused by the steric effect of the dppe ligands. Complexes 3+ were readily reduced under ambient conditions with LiAlH4 to liberate pyrrole and N-aminopyrrole in high yields. Further, the tetrahydrido complexes [MH4(dppe)2], which can be converted back into the original dinitrogen complexes 1, were recovered in moderate yields after the reduction. This accomplishes the synthetic cycle for pyrrole and N-aminopyrrole starting from the dinitrogen complexes 1. β-Heptylpyrrole was also prepared by starting from 3c+ (M = W, X = Cl) by the β-selective heptanoylation followed by the reduction with LiAlFL;. On the other hand, reduction of 6b (X = Br) with LiAlH4 predominantly produced pyrrole, whereas treatment of 6b with KOH/EtOH liberated N-aminopyrrole in a high yield.
Photophysical and Photochemical Behaviour of Tetrahydridobis(bis(1,2-diphenylphosphino)ethane)molybdenum and -tungsten: Optical Emission and Photoreduction of Alkenes
Graff, James L.,Sobieralsky, Ted J.,Wrighton, Mark S.,Geoffroy, Gregory L.
, p. 7526 - 7533 (2007/10/02)
The complexes H4M(DPPE)2 and D4M(DPPE)2 (M = Mo, W; DPPE = bis(1,2-diphenylphosphino)ethane) exhibit emission of visible light upon photoexcitation at 77 K in 2-methyltetrahydrofuran.The emission lifetime at 77 K for the W species (ca.13 μs) is shorter than for the Mo species (ca.90 μs) and is independent of whether the substance is the 1H or 2H species.The shorter lifetime for the W species is consistent with an emissive triplet state that is antibonding with respect to M-H2 interactions, since the solution photochemistry at 298 K is dominanted by H2 loss.While the lifetime of the 1H and 2H species is the same, the quantum yield of emission for M = Mo is higher for the 2H species (0.28) than for the 1H species (0.21).The data are consistent with an effect from 2H that diminished nonradiative decay from the singlet excitet state reached by direct absorption.This diminished nonradiative decay allows intersystem crossing to be more competitive, yielding the emissive triplet with higher efficiency.Irradiation of the H4M(DPPE)2 species in the presence of an alkene (e.g., 1-pentene, cis-2-pentene, 3,3-dimethyl-1-pentene, cyclopentene) results in stoichiometric reduction to form an alkane; i.e., each H4M(DPPE)2 molecule yields two molecules of alkane.Irradiation of H4M(DPPE)2 in the presence of alkene and 10 psi of H2 yielsd photoassisted alkane formation, yielding many alkane molecules per H4M(DPPE)2 initially present, as illistrated with the reduction of 1-pentene.The intriguing finding concerning the photoreduction of 1-pentene or cis-2-pentene is that the reduction occurs without detectable isomerization to cis- and trans-2-pentene or 1- and trans-2-pentene, respectively, an unprecedented results for such photoassisted alkene reduction using polyhydride precursors.
