Heterobimetallic complexes composed of bismuth and lithium carboxylates as polyurethane catalysts – alternatives to organotin compounds

Levent, Emre; Sala, Oliver; Wilm, Lukas F. B.; Löwe, Pawel; Dielmann, Fabian

doi:10.1039/d1gc00446h

Cited by 9 publications

(9 citation statements)

References 57 publications

(69 reference statements)

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“…A previous study by Arnould et al showed similar catalytic efficiency of bismuth neodecanoate compared to a Sn catalyst, in particular dioctyltin dilaurate [34]. Meanwhile, Levent et al showed only moderate activity of several bismuth carboxylates towards the isocyanate/alcohol reaction, but that it can be improved using heterobimetallic complexes with lithium carboxylate [20]. Therefore, isocyanate conversion suggests that bismuth triflate is a strong candidate to substitute tin-based catalysts, and it appears to have better performance than other bismuth-based catalysts.…”

Section: Resultsmentioning

confidence: 98%

“…However, its high toxicity has limited its applicability in several sectors, such as packaging and biomedical [14,15]. Thus, research efforts are focused on the use of alternative organo [6,16,17], or metal catalysts [11,[18][19][20][21][22][23][24][25]. Among the different metal catalysts, the most studied complexes are based in iron [19,[21][22][23], copper [21,24], zinc [19,22,23], titanium [19,21,22], cobalt [21,22] and zirconium [22,25].…”

Section: Introductionmentioning

confidence: 99%

“…For example, bismuth sub-salicylate has been used for more than 100 years as a gastrointestinal drug, and bismuth oxide as well as bismuth sub-carbonate have long traditions as ingredients of ointments [27]. Additionally, bismuth carboxylates have been shown to be good alternatives for PU systems [18,28], but their catalytic activity can be insufficient for many applications and can require their combination with other metal catalysts, such as lithium carboxylates [20]. Furthermore, the sensitivity of some bismuth catalysts to water could limit their applicability in PU foams.…”

Section: Introductionmentioning

confidence: 99%

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Use of Novel Non-Toxic Bismuth Catalyst for the Preparation of Flexible Polyurethane Foam

et al. 2021

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Foam products are one of the largest markets for polyurethane (PU) and are heavily used in many sectors. However, current PU formulations use highly toxic and environmentally unfriendly production processes. Meanwhile, the increasing environmental concerns and regulations are intensifying the research into green and non-toxic products. In this study, we synthesized flexible polyurethane foam (PUF) using different weight percentages (0.025%, 0.05% and 0.1%) of a non-toxic bismuth catalyst. The bismuth-catalyzed foams presented a well evolved cellular structure with an open cell morphology. The properties of the bismuth-catalyzed flexible PUF, such as the mechanical, morphological, kinetic and thermal behaviors, were optimized and compared with a conventional tin-catalyzed PUF. The bismuth-catalyst revealed a higher isocyanate conversion efficiency than the stannous octoate catalyst. When comparing samples with similar densities, the bismuth-catalyzed foams present better mechanical behavior than the tin-catalyzed sample with similar thermal stability. The high solubility of bismuth triflate in water, together with its high Lewis acidity, have been shown to benefit the production of PU foams.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Use of Novel Non-Toxic Bismuth Catalyst for the Preparation of Flexible Polyurethane Foam

et al. 2021

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“…The environmentally benign nature of bismuth compounds offers access to novel sustainable materials and led to developments, e.g., in catalysis, medicine, radiopaque additives, and electronics [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Among the starting materials used for the synthesis of solid-state materials, bismuth(III) nitrate pentahydrate is one of the most common and readily available compounds.…”

Section: Introductionmentioning

confidence: 99%

Deposition of Nanosized Amino Acid Functionalized Bismuth Oxido Clusters on Gold Surfaces

et al. 2022

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Bismuth compounds are of growing interest with regard to potential applications in catalysis, medicine, and electronics, for which their environmentally benign nature is one of the key factors. One thing that currently hampers the further development of bismuth oxido-based materials, however, is the often low solubility of the precursors, which makes targeted immobilisation on substrates challenging. We present an approach towards the solubilisation of bismuth oxido clusters by introducing an amino carboxylate as a functional group. For this purpose, the bismuth oxido cluster [Bi38O45(NO3)20(dmso)28](NO3)4·4dmso (dmso = dimethyl sulfoxide) was reacted with the sodium salt of tert-butyloxycabonyl (Boc)-protected phenylalanine (L-Phe) to obtain the soluble and chiral nanocluster [Bi38O45(Boc–Phe–O)24(dmso)9]. The exchange of the nitrates by the amino carboxylates was proven by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, as well as elemental analysis and X-ray photoemission spectroscopy. The solubility of the bismuth oxido cluster in a protic as well as an aprotic polar organic solvent and the growth mode of the clusters upon spin, dip, and drop coating on gold surfaces were studied by a variety of microscopy, as well as spectroscopic techniques. In all cases, the bismuth oxido clusters form crystalline agglomerations with size, height, and distribution on the substrate that can be controlled by the choice of the solvent and of the deposition method.

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“…1,[34][35][36][37][38][39][40][41][42] A key reaction involved in polymer formation is alcoholysis via the HNCO species to produce carbamates. 42,43 The rate of this reaction can be significantly modified in many ways by changing substituents on the RNCO or ROH reactants, [44][45][46] autocatalysis of the reactants, [47][48][49][50][51][52] solvent selection, 50 or via other more efficiently designed catalysts [53][54][55][56] such as organotin. 57,58 It is well established that HNCO will react with water across either the N − − C or C − − O bonds, producing carbamate and imidic acid, respectively.…”

Section: Introductionmentioning

confidence: 99%

Catalyzed Reaction of Isocyanates (RNCO) with Water

Wolf¹,

Vandezande

Schaefer³

2021

Preprint

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The reactions between substituted isocyanates (RNCO) and other small molecules (e.g. water, alcohols, and amines) are of significant industrial importance, particularly for the development of novel polyurethanes and other useful polymers. We present very high-level ab initio computations on the HNCO + H2O reaction, with results targeting the CCSDT(Q)/CBS//CCSD(T)/cc-pVQZ level of theory. Our results affirm that hydrolysis can occur across both the N=C and C=O bonds of HNCO via concerted mechanisms to form carbamate or imidic acid with 0 K enthalpy barrier heights of 38.5 and 47.5 kcal mol^-1 A total of 24 substituted RNCO + H2O reactions were studied. Geometries obtained with a composite method and refined with CCSD(T)/CBS single point energies determine that substituted RNCO species have a significant influence on these barrier heights, with an extreme case like fluorine lowering both barriers by close to 20 kcal mol^-1 and most common alkyl substituents lowering both by approximately 4 kcal mol^-1. Natural Bond Orbital (NBO) analysis provides evidence that the predicted barrier heights are strongly associated with the occupation of the in-plane C-O* orbital of the RNCO reactant. Key autocatalytic mechanisms are considered in the presence of excess water and RNCO species. Additional waters (one or two) are predicted to lower both barriers significantly at the CCSD(T)/aug-cc-pV(T+d)Z level of theory with strongly electron withdrawing RNCO substituents also increasing these effects, similar to the uncatalyzed case. The 298 K Gibbs energies are only marginally lowered by a second catalyst water molecule, indicating that the decreasing 0 K enthalpy barriers are offset by the loss of translational entropy with more than one catalyst water. Two-step 2RNCO + H2O mechanisms are characterized for the formation of carbamate and imidic acid. The second step of these two pathways exhibits the largest barrier and presents no clear pattern with respect to substituent choice. Our results indicate that an additional RNCO molecule might catalyze imidic acid formation but have less influence on the efficiency of carbamate formation. We expect that these results lay a firm foundation for the experimental study of substituted isocyanates and their relationship to the energetic pathways of related systems.

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Heterobimetallic complexes composed of bismuth and lithium carboxylates as polyurethane catalysts – alternatives to organotin compounds

Abstract: Organotin compounds are important catalysts for the synthesis of polyurethanes consisting of aliphatic isocyanates and polyols. Due to their toxicity, however, it has been a long-standing goal to develop more...

Cited by 9 publications

References 57 publications

Use of Novel Non-Toxic Bismuth Catalyst for the Preparation of Flexible Polyurethane Foam

Use of Novel Non-Toxic Bismuth Catalyst for the Preparation of Flexible Polyurethane Foam

Deposition of Nanosized Amino Acid Functionalized Bismuth Oxido Clusters on Gold Surfaces

Catalyzed Reaction of Isocyanates (RNCO) with Water

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