The Rare Earth Metal Organic Compounds Of Sulfur And Ene Imine Activation

Insertion of unsaturated substrates into metal-ligand bond is a fundamental reaction in various metal-promoted functionality transformations. During the last two decades, considerable attention has been devoted to organolanthanide chemistry on exploring new insertions through choice of appropriate substrates. The related information is now being extensively used in organic synthesis and catalysis. As part of a continuing effort in our laboratory toward the development of new insertions of organolanthanide compounds and their application in organic synthesis, the present thesis investigated insertions of elemental sulfur and heteroallenes into lanthanide-ligand bond. In brief, we have developed 5 new types of reactions and synthesized 40 new organolanthanide complexes and 13 new organic compounds, among which 49 were structurally determined through X-ray single crystal diffraction analysis.1. Activation of alkyl and aryl lanthanide complexes with guanidinate coligands on elemental sulfur was studied. Sulfur atom smoothly inserted into Ln-C bond of [(Me3Si)2NC(NCy)2]2LnBn to form the corresponding thiolate complexes {[(Me3Si)2NC(NCy)2]2Ln(μ-SBn)}2 [Ln=Er (2-3-Er), Y (2-3-Y)]. Moreover, the in situ generated bis(guanidinate) lanthanide n-butyl and phenyl complexes could also react with elemental sulfur to give the insertion products {[(Me3Si)2NC(NCy)2]2Ln(μ-SR)}2 [R=nBu, Ln=Y (2-5-Y), Er (2-5-Er); R=Ph, Ln =Er (2-6-Er), Yb (2-6-Yb)] in high yields. However, only disulfide complexes {[(Me3Si)2NC(NCy)2]2Ln}2(μ-η2:η2-S2) [Ln=Er (2-4-Er), Yb (2-4-Yb)] were isolated in the reaction of [(Me3Si)2NC(NCy)2]2LntBu with S8.2-4-Er could also be prepared by reaction of 2-3-Er with S8. To the best of our knowledge, the synthesis of thiolate complexes containing guanidinate coligand has no precedent. It is noted that these thiolate and disulfide complexes would be difficult to prepare by classical metathetical reactions employing thiols as starting materials.2. Treatment of [Cp2Ln(μ-Me)]2 and Cp2LnPh with Ph2C=C=NtBu or PhCH=C=N'Bu gave the insertion products Cp2Ln[tBuNC(R')CRPh] [R=Ph, R'= Me, Ln=Y (3-1-Y), Er (3-1-Er), Yb (3-1-Yb); R=Ph, R'=Ph, Ln=Y (3-2-Y), Er (3-2-Er), Yb (3-2-Yb); R=H, R'= Me, Ln=Y (3-3-Y), Er (3-3-Er), Yb (3-3-Yb); R =H, R'=Ph, Ln=Y (3-4-Y), Er (3-4-Er), Yb (3-4-Yb)], which represent the first example of ketenimine insertion into transition metal-carbon bond and provide an efficient method for the synthesis of organolanthanides with 1-azaallyl ligands. Furthermore, it has been found that the bonding mode of the aza-allyl to a metal depends on the natures of substituents and metals. A novelη4-bonding mode of the aryl-substituted aza-allyl to a metal is observed.3. In contrast to methyl and phenyl complexes, bis(cyclopentadienyl) lanthanide tert-butyl complexes reacted with Ph2C=C=NtBu to give the Ln-H bond insertion products Cp2Ln[tBuNCHCPh2] (Ln=Y (4-1-Y), Er (4-1-Er)), while under the same conditions bis(cyclopentadienyl) lanthanide tert-butyl complexes reacted with CyN=C=NCy to give the Ln-C(tBu) bond insertion products Cp2Ln[(CyN)2CtBu] (Ln =Y (4-3-Y), Er (4-3-Er)). It is noteworthy that reaction of huge steric 2,6-iPr2C6H3NCNC6H3iPr2-2,6 with the same complexes also afforded the Ln-H bond insertion products Cp2Ln[(ArN)2CH] (Ln=Y (4-5-Y), Er (4-5-Er)). To elucidate the probable mechanism of the formation of 4-5, we examined the reaction of [Cp2LnH] with CyN=C=NCy, wherein the expected Ln-H bond insertion products Cp2Ln[(CyN)2CH] (Ln=Y (4-4-Y), Er (4-4-Er)) were obtained. It is clear that the steric factor makes a favorable transformation of tert-butyl complexes to hydrides. To the best of our knowledge, insertions of ketenimines and carbodiimides into the Ln-H bond haven't been reported before, which offer a new method for the synthesis of organolanthanideα-substituted 1-azaallyls and formamidinates, respectively.4.3-3-Ln and 3-4-Ln reacted with phenyl isocyanate to form the Ln-N bond insertion products Cp2Ln{OC[N(tBu)C(R)CHPh]NPh}(THF) (R=Me, Ln=Er (5-1-Er), Yb (5-1-Yb); R=Ph, Ln=Er (5-2-Er), Yb (5-2-Yb)). The reaction of 3-3-Ln and CO2 followed by crystallizing in THF in the presence of HMPA gave also the Ln-N bond insertion products Cp2Ln{OC[N(tBu)C(Me)CHPh]O}(HMPA) (Ln= Er(5-3-Er),Yb(5-3-Yb)). Metal-depended selectivity was observed in reaction of 3-4-Er and 3-4-Yb with CO2. The former gave the Ln-N bond insertion product (Cp2Er)2{μ-η1:η1-OC[N(tBu)C(Ph)CHPh]O}2 (5-4-Er), while the latter provided the Ln-C bond insertion product (Cp2Yb)2{μ-η1:η2-OC[CH(Ph)C(Ph)NtBu]O}2 (5-5-Yb). The subtle change of reactivity of 1-azaallyl lanthanide complexes described herein was not investigated before and will provide valuable information for design of new sequence insertion reactions of organolanthanide complexes.5. In contrast to the reaction of organolanthanide alkyls with PhCH=C=NtBu, it is found that treatment of PhCH=C=NtBu with tBuLi gave the H atom abstraction product other than Li-C bond insertion one. The resulting lithiated aza-allene readily reacted with PhCH=C=NtBu or other unsaturated substrates to give various interesting products depending on reaction stoichiometry. For example, the reaction oftBuLi with PhCH=C=NtBu in 1:1 or 0.5:1 provided dimeric cyclobutenimine dilithium salt (6-1) or cyclobutenimine lithium salt (6-2) respectively. Ortho-C-H bond activation of phenyl group was observed in compound 6-1 which reacted with diaryl ketone to form ortho-phenyl derivatization products 2-(2-tert-butyl-3-phenyl-4-tert-butyliminocyclobut-1-enyl)phenyl-diarylmethanol (aryl=Ph,6-3; p-tolyl,6-4). In order to capture the intermediate [LiC(Ph)=C=NtBu], the reaction of tBuLi with 1 equiv of PhCH=C=NtBu and subsequently with 2 equiv of PhCN was examined through careful control of the addition rate of PhCH=C=NtBu. Aminopyrimidine lithium salt (6-5) was obtained, which underwent hydrolysis to form N-tert-butyl-4-amino-2,5,6-triphenylpyrimidine (6-6). Similar product N-tert-butyl-4-amino-2,6-di(4-Cl-phenyl)-5-phenylpyrimidine (6-7) or N-tert-butyl-4-amino-2,6-di(3-Cl-phenyl)-5-phenylpyrimidine (6-8) was obtained when PhCN was replaced by 4-Cl-C6H4CN or 3-Cl-C6H4CN. The reaction of PhCH=C=NtBu with 0.5 equiv of tBuLi and subsequently with 0.5 equiv of various aroyl chlorides gave a series of multisubstituted aminopyrans 6-9-6-13. Some of the key intermediates in the formation process of 6-1 were successfully verified.