Carbodiimide Insertion into Organoaluminum Compounds and Thermal Rearrangement of the Products

Chang, Cheng‐Wei Tom; Chung-Sheng, Hsiung; Su, Huey‐Jen; Srinivas, B.; Chiang, Michael Y.; Lee, Gene‐Hsiang; Wang, Yu

doi:10.1021/om970392r

Cited by 62 publications

(48 citation statements)

References 44 publications

(49 reference statements)

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“…The Al-C bond lengths for the compounds 2 and 3 lie between 1.949(6) Å and 1.962(3) Å, these values are similar to the reported values of Al-C bond lengths. [6][7][8][9][10][11][12][13] The Al-I bond distances in 4 Al1-I1 is 2.507(2) Å and Al1-I2 is 2.521(2) Å which are well in agreement with the reported values. [6][7][8][9][10][11][12][13] The bite angles of the bridged bis-guanidine ligands N1-Al1-N2, which are 68.75 (16), 69.33 (10) and 71.19 (19) • 4 for 2-4, respectively.…”

Section: Crystallographic Informationsupporting

confidence: 90%

“…7 i) Metallation of neutral guanidines with aluminum alkyls; ii) Salt metathesis reaction of alkali guanidinates with AlX 3 (X = halide); iii) Addition of Al-N bond of Al 2 (NMe 2 ) 6 to carbodiimide. 12 By employing the first method, guanidinates of aluminum complexes were prepared. Metallation of neutral bis-guanidines with AlR 3 (R = alkyl) afforded the guanidinates of aluminum alkyl complexes.…”

Section: Synthesis and Spectroscopic Characterizationmentioning

confidence: 99%

“…5 To date, several examples of mononuclear guanidinato aluminum complexes, including aluminum alkyls and halides are known in the literature. [6][7][8][9][10][11][12][13] Recent reports suggest that dinuclear aluminum complexes are more important precursors for ring opening polymerization (ROP) of cyclic esters (e.g., lactide and ε-caprolactone), cyclic ethers (e.g., cyclohexne oxide (CHO) and propylene oxide (PO)) than their monometallic counterparts. [14][15][16] Despite the prominent role of cooperative effect between two aluminum centers, synthesis and catalytic application of well-characterized dinuclear aluminum complexes remain scarce.…”

Section: Introductionmentioning

confidence: 99%

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Bimetallic aluminum alkyl and iodide complexes stabilized by a bulky bis-guanidinate ligand

et al. 2018

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A series of bulky bis-guanidine ligands such as L 1 (2H), L 2 (2H) and L 3 (2H), where L = {ArNCNAr} 2 {μ-N(C 2 H 4) 2 N}, for L 1 (2H) (Ar = 2, 6-Me 2-C 6 H 3), L 2 (2H) (Ar = 2, 4, 6-Me 3-C 6 H 2) and (L 3 (2H)) (Ar = 2, 6-i Pr 2-C 6 H 3) have been utilized to synthesize four-membered dinuclear aluminum heterocycles. Deprotonation of L 1−3 (2H) (1.0 equiv.) upon treatment with trimethyl aluminum (2.1 equiv.) in toluene led to the formation of bimetallic aluminum alkyls: [L 1 (AlMe 2) 2 ] (1), [L 2 (AlMe 2) 2 ] (2) and [L 3 (AlMe 2) 2 ] (3). Aluminum halide complex i.e., [L 3 (AlI 2) 2 ](4) was obtained by the reaction of compound 3 with four equivalents of molecular iodine in toluene at 80 • C, in which alkyl-halide exchange occurred. All the compounds (1-4) were confirmed by multinuclear (1 H and 13 C) magnetic resonance spectroscopy. Furthermore, compounds 2-4 were confirmed by single crystal X-ray structural analysis. All the compounds 1-4 display the expected number of signals in the 1 H and 13 C NMR spectra and are consistent with their compositions. The solid state structures of 1-4 reveal that each aluminum center is bonded to the monoanionic guanidinate ligand in N ,N-chelated fashion and the other two sites are occupied by alkyl or halide ligands, resulting in a distorted tetrahedral geometry.

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Section: Crystallographic Informationsupporting

confidence: 90%

Section: Synthesis and Spectroscopic Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bimetallic aluminum alkyl and iodide complexes stabilized by a bulky bis-guanidinate ligand

et al. 2018

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“…Alkyl or amido complexes of main group, lanthanide, or early-transition elements react with carbodiimides giving amidininato [32][33][34][35] or guanidinato derivatives, [33,34,[36][37][38][39] respectively; some of these have found applications. [35,37,40] Insertion reactions of carbodiimides into an M À C (M= metal) of other organometallic compounds [41] or into an M À H bond [42] have also been reported.…”

mentioning

confidence: 99%

Reactivity of ortho‐Substituted Aryl–Palladium Complexes towards Carbodiimides, Isothiocyanates, Nitriles, and Cyanamides

Vicente

Abad

López-Sáez

et al. 2009

Chemistry A European J

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Complexes [Pd(C(6)H(3)XH-2-R'-5)Y(N;N)] (X=O, NH; Y=Br, I; R'=H, NO(2); N;N=N,N,N',N'-tetramethylethylenediamine (tmeda), 2,2'-bipyridine (bpy), 4,4'-di-tert-butyl-2,2'-bipyridine (dtbbpy)) react with RN=C=E (E=NR, S) or RC identical withN (R=alkyl, aryl, NR''(2)) and TlOTf (OTf=CF(3)SO(3)) to give, respectively, 1) products of the insertion of the C=E group into the C--Pd bond, protonation of the N atom, and coordination of X to Pd, [Pd{kappa(2)-X,E-(XC(6)H(3){EC(NHR)}-2-R'-4)}(N;N)]OTf or [Pd(kappa(2)-X,N-{ZC(6)H(3)(NH=CR)-2-R'-4})(N;N)]OTf, or products of the coordination of carbodiimides and OH addition, [Pd{kappa(2)-C,N-(C(6)H(4){OC(NR)}NHR-2)}(bpy)]OTf; or 2) products of the insertion of the C identical withN group to Pd and N-protonation, [Pd(kappa(2)-X,N-{XC(6)H(3)(NH=CR)-2-R'-4})(N;N)]OTf.

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“…33,34 Junk et al also reported the synthesis of a dimethylaluminium complex featuring the bulky N,N¢-bis (2,6-diisopropylphenyl)-4-toluamidinate ligand. 35 To the best of our knowledge, most of the amidinate aluminium complexes were explored mainly for studying the synthetic methodologies, 30,31,[33][34][35][36][37][38][39][40][41][42][43][44][45] as catalysts for olefin polymerization, [46][47][48][49] or for other non-catalytic applications, 50 and have not yet been used as initiators for the ROP of cyclic esters such as lactides and e-caprolactone. Due to the high Lewis acidity of the unsaturatedly coordinated metal center which should facilitate the coordination and activation of substrates, it is conceivable that amidinate aluminium complexes may possess catalytic activity for the ROP of lactide.…”

Section: Introductionmentioning

confidence: 99%

Amidinate aluminium complexes: synthesis, characterization and ring-opening polymerization of rac-lactide

Qian

Liu

2010

Dalton Trans.

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A series of aluminium alkyl complexes {PhC(NR')(NR'')}AlR(2) (4a-n, R' = 2,6-(i)Pr(2)C(6)H(3), 2,6-Me(2)C(6)H(3); R'' = aryl groups with various ortho-, para- or meta-substituents, tert-butyl; R = methyl, ethyl) bearing non-symmetrically N-substituted benzamidinate ligands were synthesized via the reaction of trialkylaluminium and the corresponding benzamidine proligands. Complex 5 bearing symmetric amidinate ligand was also obtained for comparison purposes. The X-ray diffraction studies of complexes 4b, 4c and 5 show in each case a distorted tetrahedral geometry around the aluminium center. All the amidinate aluminium complexes were found to catalyze the ring-opening polymerization (ROP) of rac-lactide with moderate activities. The steric and electronic characteristics of the ancillary ligands have a significant influence on the polymerization performance of the corresponding aluminium complexes. The introduction of electron-withdrawing substituents at the ortho-positions of N-phenyl ring of the ligands resulted in an obvious increase in catalytic activity. Complex 4b showed the highest activity among the investigated aluminium complexes due to the high electrophilicity of the metal center induced by the ortho-chloro substituents on the phenyl ring. The existence of ortho-substituents of small steric bulkiness is also beneficial for the increase of activity of these catalysts. However, further increase of steric hindrance of the ligands by introducing bulky ortho-substituents onto the phenyl moieties resulted in a decrease of activity and an increase in the isotactic bias of the obtained polylactides. The broad molecular weight distributions (PDI = 1.13-2.02) of the polymer samples indicated that the ROP of rac-lactide initiated by these complexes was not well-controlled.

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Carbodiimide Insertion into Organoaluminum Compounds and Thermal Rearrangement of the Products

Cited by 62 publications

References 44 publications

Bimetallic aluminum alkyl and iodide complexes stabilized by a bulky bis-guanidinate ligand

Bimetallic aluminum alkyl and iodide complexes stabilized by a bulky bis-guanidinate ligand

Reactivity of ortho‐Substituted Aryl–Palladium Complexes towards Carbodiimides, Isothiocyanates, Nitriles, and Cyanamides

Amidinate aluminium complexes: synthesis, characterization and ring-opening polymerization of rac-lactide

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