Donor-substituted CpCo-stabilized cyclobutadienes and superphanes
摘要:
RCpCoL2 complexes (L-2 = (CO)(2) or COD, R = H, CO2Me, TMS) were reacted with various alkynes substituted with chalcogen atoms adjacent to the triple bonds. These reactions yielded hetero-substituted CpCo-capped cyclobutadienes and superphanes dependent on the ring size of the corresponding cyclic diene used as starting material. Reactions in decaline afforded not only CpCo-capped cyclobutadieno superphanes, but also mixed cyclobutadieno cyclopentadienono superphanes. X-ray analyses do not indicate a significant amount of conjugation between the pi systems and the lone pairs of the heteroatoms whereas cyclic voltammetry reveals an easier oxidation when increasing the number of electron-donating heteroatoms. (C) 2004 Elsevier B.V. All rights reserved.
Synthesis and Selectivity in the Formation of Cyclophosphazene-Derived 1,3-Cyclohexadienes from Reactions of RCpCo(COD) [R = MeOC(O)] with Alkynes and Alkenes
作者:Muthiah Senthil Kumar、Ram Prakash Gupta、Anil J. Elias
DOI:10.1021/ic7024507
日期:2008.4.1
pathway for cyclohexadiene formation in CpCo catalyzedreactions. Selectivity is also observed in the formation of bisfluorophosphazene derived cyclohexadienes which stems from the fact that two P 3N 3F 5 units cannot be accommodated on vicinal carbonatoms of a carbacycle or metallacycle. Interestingly, reactions of (beta-phenylethynyl)pentafluorobenzene with [eta (5)-MeOC(O)C 5H 4]Co[COD] in the presence
已经制备了单和双氟磷腈衍生的[η(5)-环戊二烯基] [η(4)-1,3-环己二烯]钴配合物的第一实例以及三明治化合物[η(5)-羰基甲氧基环戊二烯基] [η(4) [η(5)-MeOC(O)C 5H 4] Co [COD],PhCCP 3N 3F 5和在存在或不存在额外的环烯烃或茚的情况下形成苯乙炔。这些单和双氟磷腈衍生的钴环己二烯配合物的形成为CpCo催化反应中环己二烯形成的金属环戊二烯途径提供了实验证据。在双氟磷腈衍生的环己二烯的形成中也观察到选择性,这是由于以下事实:两个P 3N 3F 5单元不能容纳在碳环或金属环的相邻碳原子上。有趣的是,在相同反应条件下,在存在和不存在外部环烯烃的条件下,(β-苯基乙炔基)五氟苯与[η(5)-MeOC(O)C 5H 4] Co [COD]的反应仅产生顺式和反式异构体。茂金属[η(5)-MeOC(O)C 5H 4] Co [eta(4)-C 4Ph
Synthesis and Properties of Donor-Acceptor-Substituted Metal-Capped Fourfold-Bridged Cyclobutadienophanes
The synthesis of the superphanes 4-8 could be achieved from (1,2,11,12-eta(4))-tricyclo[10.8.0.0(2,11)]eicosa-1, 11-diene-6,17-diyne}(eta(5)-cyclopentadienyl (15) and its methoxycarbonyl congener 14 by heating with R-CpCo(CO)(2) (R = H, CH3, (CH3)(5)). X-ray investigations on the superphanes 3, 6, and 8 reveal distances between the two cyclobutadiene units between 2.922 Angstrom (3) and 2.941 Angstrom (6). Investigations by means of cyclic voltammetry show a decrease of the first oxidation potentials with increasing number of CH3 substituents at the cyclopentadienyl ligands. The comparison between the first oxidation potentials of 2-6, 4-7, and 5-8 gives evidence for a partial charge delocalization over both CpCoCb fragments of the superphanes.
Synthesis and Properties of Donor/Acceptor-Substituted Metal-Capped Twofold-Sila-Bridged Cyclobutadieno Superphanes
Reaction of 1,6-cyclodecadiyne and 1,8-cyclotetradecadiyne with substituted CpCo(cod)
作者:Rolf Gleiter、Georg Pflaesterer
DOI:10.1021/om00029a051
日期:1993.5
The yields of CpCo-capped cyclobutadiene superphane from 1,6-cyclodecadiyne (1) and (R-C5H4)Co(cod) varies considerably with the substituents R. Electron-withdrawing substituents give yields between 35 and 45 % while electron-donating substituents give very small yields. In the case of 1,8-cyclotetradecadiyne (2) such a dependence on R is much less pronounced. The reaction between 1 and 2 and the indenyl complex (eta5-C9H7)Co(cod) is also reported.
Effect of electron-withdrawing substituents on the cobalt(I)-coordinated cyclopentadienyl ring. Spectra and diene substitution kinetics of [Co(C5H4X)(1,5-cyclooctadiene)]