Biguanide Complexes of Boron and Aluminum

Abstract

In search of an alternative to the dominant industrial processes, facilitated mostly by transition metal catalytic systems, current economic and environmental aspects are leading to a growing interest in the chemistry and application of main group element-based catalysts and materials. Mono- and dinuclear boron and aluminum complexes bearing a biguanide ligand (substituted 4,6-dimethoxypyrimidin-2-yl-guanidinate; L) were prepared by deprotonation of LH2 with BH3Me2S, BF3Et2O, Me3Al or Me2AlCl or, in some cases, by transmetallation reactions of the lithium complex. Complexes were characterized by multinuclear NMR and sc-XRD analyses. Two coordination isomers, where the central atoms can occur both in four- and six-membered N,N’-chelate ring, were found for homobimetallic aluminum and boron biguanide com-plexes. Thorough study was performed to understand the formation and isomerization process, where a thermally and kinetically conducted isomerization was explored. The relative Gibbs free energies of optimized structures as well as hypothetical arrangements were calculated and compared in order to support the described isomerization. The activity of selected complexes was tested in the Ring-Opening Polymerization (ROP) of rac-lactide. While the boron complexes are inactive, dimethylaluminum species show moderate activity and good control over the polymer mass and dispersity after co-initiation by iPrOH. Furthermore, the species turned out as effective in promoting hydroboration of unsaturated C-C bonds.

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BibTeX

@article{vlk2026biguanide,
  title = {{Biguanide Complexes of Boron and Aluminum}},
  author = {Lukáš Vlk and Tomáš Chlupatý and Alena Hoffmannová and Zdeňka Růžičková and Aleksandra Szymańska and Benjamin Théron and Raluca Malacea-Kabbara and Pierre Le Gendre and Jędrzej Walkowiak and Aleš Růžička},
  journal = {Inorganic Chemistry},
  year = {2026},
  month = jun,
  doi = {10.1021/acs.inorgchem.6c00595},
  url = {https://hal.science/hal-05839721v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Biguanide Complexes of Boron and Aluminum
AU  - Lukáš Vlk
AU  - Tomáš Chlupatý
AU  - Alena Hoffmannová
AU  - Zdeňka Růžičková
AU  - Aleksandra Szymańska
AU  - Benjamin Théron
AU  - Raluca Malacea-Kabbara
AU  - Pierre Le Gendre
AU  - Jędrzej Walkowiak
AU  - Aleš Růžička
PY  - 2026
DA  - 2026/06/04
JO  - Inorganic Chemistry
DO  - 10.1021/acs.inorgchem.6c00595
UR  - https://hal.science/hal-05839721v1
AB  - In search of an alternative to the dominant industrial processes, facilitated mostly by transition metal catalytic systems, current economic and environmental aspects are leading to a growing interest in the chemistry and application of main group element-based catalysts and materials. Mono- and dinuclear boron and aluminum complexes bearing a biguanide ligand (substituted 4,6-dimethoxypyrimidin-2-yl-guanidinate; L) were prepared by deprotonation of LH2 with BH3Me2S, BF3Et2O, Me3Al or Me2AlCl or, in some cases, by transmetallation reactions of the lithium complex. Complexes were characterized by multinuclear NMR and sc-XRD analyses. Two coordination isomers, where the central atoms can occur both in four- and six-membered N,N’-chelate ring, were found for homobimetallic aluminum and boron biguanide com-plexes. Thorough study was performed to understand the formation and isomerization process, where a thermally and kinetically conducted isomerization was explored. The relative Gibbs free energies of optimized structures as well as hypothetical arrangements were calculated and compared in order to support the described isomerization. The activity of selected complexes was tested in the Ring-Opening Polymerization (ROP) of rac-lactide. While the boron complexes are inactive, dimethylaluminum species show moderate activity and good control over the polymer mass and dispersity after co-initiation by iPrOH. Furthermore, the species turned out as effective in promoting hydroboration of unsaturated C-C bonds.
SN  - 0020-1669
SN  - 1520-510X
ER  -

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