Syntheses of lanthanide monochloride and monoborohydride complexes supported by bridged bis(guanidinate) ligand and the use of borohydride complexes in polymerization of cyclic esters

Zhang, Xingmin; Wang, Chuanyong; Xue, Mingqiang; Zhang, Yong; Yao, Yingming; Shen, Qi

doi:10.1016/j.jorganchem.2012.05.011

Cited by 21 publications

(9 citation statements)

References 50 publications

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“…The lengths of the covalent Ln(1)–N(5) bond ( 3 : 2.295(3) Å; 4 : 2.389(3)–2.408(4) Å) are comparable with those in the formerly described amido yttrium [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]Y(2,6‐Pr i 2 C 6 H 3 NH)DME (2.237(4) Å), {(3,5‐Me 2 C 3 HN 2 ) 3 B}Y[κ 3 ‐(4‐NH=(C 8 N 2 H 4 )(2‐NHC 6 H 4 ))]{(Me 2 N) 3 P=O} (2.309(5) Å) and neodymium complexes [3,5‐Bu t 2 ‐2‐O‐C 6 H 2 CH=N‐C 5 H 4 N] 2 NdN(SiMe 3 ) 2 (2.385(3) Å), [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]Nd(2,6‐Pr i 2 C 6 H 3 NH)DME (2.342(7) Å), [{(NC 5 H 4 )NHCH 2 (3,5‐Bu t 2 ‐C 6 H 2 ‐2‐OH)}NdN(SiMe 3 ) 2 (THF)] 2 (2.372(3) Å) . The Ln–N amidinate distances in 3 and 4 are somewhat different (κ 4 ‐NNOO‐ligand 2.378(3)–2.379(3) Å ( 3 ), 2.473(2)–2.483(2) Å ( 4 ); κ 2 ‐NN‐ligand 2.21(2)–2.45(2) Å, average 2.34(6) Å ( 3 ), 2.415(5)–2.487(4) Å, average 2.46(2) Å ( 4 )), but are comparable with the corresponding values measured in the related seven‐coordinate yttrium amidinate complexes [{1,3‐C 6 H 4 (NC(Ph)NSiMe 3 ) 2 } 3 Y(THF)Y(µ‐Cl)Li(THF) 3 ] (2.341(6), 2.455(6) Å), [Y{ o ‐CH 3 O‐C 6 H 4 NC(Ph)N(SiMe 3 )}Cl 2 (THF) 2 ] 2 (2.384(2), 2.375(2) Å), [(2,6‐Et 2 C 6 H 3 N) 2 C(4‐Me‐C 6 H 4 )] 2 Y(THF)(Cl)(µ‐Cl)Li(THF) 3 (2.402(6)–2.464(5) Å), [1,8‐C 10 H 6 {NC(Bu t )N‐2,6‐Me 2 ‐C 6 H 3 } 2 ]YCl(DME) (2.331(1)–2.369(1) Å) [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]YCl(DME) (2.360(3)–2.379(3) Å) and seven‐coordinate neodymium complexes (2.385(2)–2.604(7) Å) , . The C–N bond lengths within the amidinate fragments in 3 and 4 fall into a narrow interval ( 3 : 1.321(8)–1.333(9) Å, 4 : 1.313(4)–1.333(9) Å) thus being indicative of delocalization of the negative charge over the NCN fragments.…”

Section: Resultssupporting

confidence: 66%

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

et al. 2019

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Amido [Bu t C(NC 6 H 4 -2-OMe) 2 ] 2 LnN(SiMe 3 ) 2 (Ln = Y (3), Nd (4)) and borohydrido complexes [Bu t C(NC 6 H 4 -2-OMe) 2 ] 2 LnBH 4 (Ln = Y (5), Nd (6)) coordinated by new amidinate ligand bearing two pendant anisolyl groups are synthesized. According to X-ray analysis in complexes 3 and 4 one amidinate ligand is coordinated to the Ln 3+ cation in a bidentate fashion (κ 2 -NN), while the second one is tetradentate (κ 4 -NNOO). At the same time in borohydrido neodymium complex 6 the amidin-[a] G. A. Razuvaev

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Section: Resultssupporting

confidence: 66%

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

et al. 2019

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“…Noteworthy, given that 4 – 7 are bisborohydride compounds, this corresponded to the full conversion of nearly 4000 equiv of CL per rare earth metal center, a ratio rarely achieved in the ROP of CL mediated by rare earth borohydride derivatives . To our knowledge, only one successful experiment was reported at such a high [CL] 0 /[BH 4 ] 0 value, namely, 5000, with the monoborohydride neodymium complex [( i Pr(SiMe 3 )NC(N i Pr)N(CH 2 ) 3 NC(N i Pr)N(SiMe 3 ) i Pr)Nd(BH 4 )(DME)] ( M n,NMR = 228 000 g·mol –1 , Đ M = 1.45) . The control of the polymerization obtained from 4 – 7 in terms of experimental/theoretical molar mass values agreement ( M n,SEC and M n,NMR vs M n,theo ) and of rather narrow dispersity values was generally observed throughout the rare earth series.…”

Section: Resultsmentioning

confidence: 99%

“…50 To our knowledge, only one successful experiment was reported at such a high [CL] 0 /[BH 4 ] 0 value, namely, 5000, with the monoborohydride neodymium complex [( i Pr-(SiMe 3 )NC(N i Pr)N(CH 2 ) 3 NC(N i Pr)N(SiMe 3 ) i Pr)Nd(BH 4 )-(DME)] (M n,NMR = 228 000 g•mol −1 , Đ M = 1.45). 90 The control of the polymerization obtained from 4−7 in terms of experimental/theoretical molar mass values agreement (M n,SEC and M n,NMR vs M n,theo ) and of rather narrow dispersity values was generally observed throughout the rare earth series. The PCL molar mass values fall in the range M n,NMR = 8300−92 700 g•mol −1 , while the Đ M = 1.12−1.55 values fall in the lower range of typical data reported for trivalent rare earth borohydride initiators (Đ M = 1.16−1.83).…”

Section: ■ Introductionmentioning

confidence: 83%

β-Diketiminate Rare Earth Borohydride Complexes: Synthesis, Structure, and Catalytic Activity in the Ring-Opening Polymerization of ε-Caprolactone and Trimethylene Carbonate

2014

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International audienceThe synthesis of a series of divalent and trivalent β-diketiminate borohydrides [(dipp)2NacNacLn(BH4)(THF)2] ((dipp)2NacNac = (2,6-C6H3iPr2)NC(Me)CHC(Me)N(2,6-C6H3iPr2); Ln = Sm, Eu, Yb) and [(dipp)2NacNacLn(BH4)2(THF)] (Ln = Sc, Sm, Dy, Yb, Lu) is reported. All compounds were obtained by salt metathesis in THF from [(dipp)2NacNacK] and the corresponding homoleptic divalent and trivalent borohydrides [Ln(BH4)2(THF)2] (Ln = Sm, Eu, Yb), [Sc(BH4)3(THF)2], and [Ln(BH4)3(THF)3] (Ln = Sm, Dy, Yb, Lu), respectively. The complexes were fully characterized, and their solid-state structures were established by single-crystal X-ray diffraction. In both the divalent and trivalent compounds, the BH4– groups coordinate in a κ3(H) mode to the metal. Only in the lutetium complex [(dipp)2NacNacLu(BH4)2(THF)] does one BH4– group coordinate in a κ3(H) mode, whereas the other one coordinates as κ2(H). This kind of mixed κ2/κ3(H) coordination mode is rare. The application of the divalent and trivalent compounds as initiators in the ring-opening polymerization (ROP) of ε-caprolactone (CL) and trimethylene carbonate (TMC) was investigated. All complexes afforded a generally well-controlled ROP of both of these cyclic esters. High molar mass poly(ε-caprolactone) diols (Mn,NMR < 92 700 g mol–1, ĐM = 1.51) and α-hydroxy,ω-formate telechelic poly(trimethylene carbonate)s (Mn,NMR < 16 000 g mol–1, ĐM = 1.59) were thus synthesized under mild operating conditions

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“…A range of different ligand frameworks that support these metal catalysts have been described. Ancillary ligands based on anionic phenoxide donors further supported by neutral, potentially hemilabile donors such as amines and ethers have been very popular in these studies . Nitrogen-based ligands in the form of β - diketiminates or weakly donating sulfonamides and phosphinamides also proved to be highly effective frameworks for metal complexes that facilitated the controlled ROP of lactides .…”

Section: Introductionmentioning

confidence: 99%

Diamido-Ether Actinide Complexes as Initiators for Lactide Ring-Opening Polymerization

et al. 2013

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International audienceThe synthesis and characterization of a series of new diamido-ether actinide(IV) alkoxide complexes are reported. Addition of 2 equiv of LiOiPr to [tBuNON]ThCl5Li3*DME ([tBuNON]2- = [(tBuNSiMe2)2O]2-) in toluene gives [tBuNON]Th(OiPr)3Li*DME (1-DME). Recrystallization of 1-DME from diethyl ether gives [tBuNON]Th(OiPr)3Li*Et2O (1-Et2O). The addition of 2 equiv of LiOiPr to {[tBuNON]UCl2}2 gives {[tBuNON]U(OiPr)2}2 (2). If KOtBu is used instead, the product is {[tBuNON]U(OtBu)}2 (3). The reaction of 2 equiv of KOtBu with [iPr2PhNCOCN]ThCl2*DME ([iPr2PhNCOCN]2- = [(2,6-iPr2PhNCH2CH2)2O]2-) gives [iPr2PhNCOCN]Th(OtBu)2 (4), while addition of 1 equiv of KOtBu to [iPr2PhNCOCN]UCl3Li*THF results in [iPr2PhNCOCN]U(OtBu)Cl (5). Complexes 1-5 as well as the previously reported diamido actinide dialkyl complexes [tBuNON]An(CH2SiMe3)2 (An = Th (6), U (7)) and [iPr2PhNCOCN]An(CH2SiMe3)2 (An = Th (8), U (9)) were evaluated as initiators for the ring-opening polymerization (ROP) of l-lactide (l-LA) and racemic lactide (rac-LA). It was established that complexes 1-8 were capable of producing poly(l-LA) (PLLA) under mild conditions within relatively short periods of time. Diisopropoxide complex 2 polymerized up to 500 equiv of l-LA in 90 min at 30 °C, with moderate to good control over the molecular weight features (values of Mw/Mn with this complex are typically 1.5 or below). The hydrocarbyl complexes 6-8 also proved active under the same conditions, with 7 showing a similar ability to control the ROP with monomer loadings up to 500 equiv. PLLAs prepared with initiators 1-5 and 6-8 have been characterized by end-group analysis via NMR and MALDI-TOF MS, which indicate clearly that the diamido ligand does not participate as an initiating group in the ROP process and that the alkoxide and alkyl moieties, respectively, are the only initiating groups. When it was applied to mediate the ROP of rac-LA, 2 yielded heterotactically enriched PLA (Pr values up to 0.73 in THF)

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Syntheses of lanthanide monochloride and monoborohydride complexes supported by bridged bis(guanidinate) ligand and the use of borohydride complexes in polymerization of cyclic esters

Cited by 21 publications

References 50 publications

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

β-Diketiminate Rare Earth Borohydride Complexes: Synthesis, Structure, and Catalytic Activity in the Ring-Opening Polymerization of ε-Caprolactone and Trimethylene Carbonate

Diamido-Ether Actinide Complexes as Initiators for Lactide Ring-Opening Polymerization

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