Imidazole Side Chain Of Single-atom Bridged Cyclopentadienyl Ligand And The Iv Vice Family Transition Metallocene Complexes Of Synthetic Research

One novel type of imidazole one-atom bridged cyclopentadienyl ligands and its reaction withâ…£B salts has been established,as well as the studies of their synthesis,structural and reactive activity.The synthetic route of this novel imidazole one-atom bridged cyclopentadienyl ligands has been thoroughly studied.Treatment 1-diethoxylmethylimidazole(1) and 1-dimethoxylmet hylimidazole(5) with 6,6-diphenyl fulvene(2),6-monopehylfulvene(11) has been shown to afford pure ligands C₅H₅CR₂-(2-C₃H₃N₂)(R₂=Ph,Ph;Ph,H(4),(12) respectively).The novel bidentate ligands are finally characterized.Reaction of ligands(4),(12) with n-BuLi afford the corresponding dilithium salt,(7),(14).Dilithium salt LiC₅H₄CR₂-(2-C₃H₂N₂Li)(R₂=Ph,Ph;7) has been isolated in pure state as an adduct with 2 molecules of THF.Crystal and molecular structure of 7·2THF has been established by X-ray diffraction analysis.For this compound, an interesting case of organolithium compound catenation provided byη⁵-Cp-Li^(CN=2) -N(imidazolide) intermolecular interactions has been found.A brief quantum-chemical modeling for(7) revealed a good match of the observed and calculated structural parameters for theη⁵-Cp-Li^(CN=2)-N(imidazolide) moiety and outlined considerableÏ€-interaction within this fragment.An interesting n-BuLi invoked rearrangement of 1-diethoxymethyl-1H-imidazole(1) or 1-dimethoxylmethyl-1H-imidazole(5) into their 2-isomers(17) and(20) has been observed. The suggested method allows to prepare 2-1H-imidazole carbaldehyde(18)(quantitative acidic hydrolysis of(17) and/or(20)) in a cheap and convenient way comparatively to the literature synthetic routines.Compound(18) is rather a useful pharmaceutical intermediate(20 $/g).Attempts to prepare the ligand(F) under various base conditions proved to be a failure.Under the gas chromatograph column conditions,compound(17) has been proved to undergo a quantitative conversion into 4,8-diethoxy-3a,4,7a,8-tetrahydro-1,3a,5,7a-tetraza-s-i ndacenes[19a(4RS,8RS)- and 19b(4R,8S)-diastereomers].Crystal and molecular structures of(17) and 19(b) have been established by X-ray diffraction analysis.For compound(13),NMR-time scale slow-limit tautomeric rearrangement has been observed.Crystal structure of(13) has been established by X-ray diffraction analysis.Attempts to develop an alternative route to the 1H-imidazol-2-yl side-chain functionalized cyclopentadienes(C) failed.Reaction of dilithium salt(7) with the Group 4 metal tetrahalides,ZrCl₄·2THF and TiCl₄, has been studied.Formation of supposedly polymeric products has been postulated in this case.Treatment of bidentate ligands(12 and 4) with Ti(NEt₂)₄(9) in toluene at 80-90℃has been shown to lead to pure {[2-η⁵-cyclopenta-2,4-dienyl]-mono(or di-) phenylmethyl] -1H-imidazole-κN]}bis(N,N-diehtylamido)titaniums(+4),C₂₃H₃₂N₄Ti(15) and C₃₉H₃₇N₄Ti (10) in 60 and 50%yields,respectively.Crystal structure of(15) has been established by X-ray diffraction analysis.The Ti-linked amido-nitrogen atoms of NEt₂ and imidazole groups have been proved to possess planar environments what is indicative of an additionalÏ€-donation from all of the amido-type groups towards the Ti-center.Thus,the titanium atom in(15) formally possesses an 18e^- shell,that presents a rather untypical phenomenon in Ti(â…£) organochemistry.Generally,it possesses an 16 e^- shell.