Borane-Tethered Heteroscorpionate Zinc Catalysts for the Hydroboration of Carbon Dioxide, Isocyanates, Esters and Nitriles

14/03/2025

This work describes the synthesis, characterization and catalytic hydroboration activity of a family of zinc bis(κ2-borohydride) complexes containing borane-functionalized heteroscorpionate ligands. The new zinc bis(κ2-borohydride) complexes with R-substituted bis(3,5-dimethylpyrazolyl)methane ligands with or without borane functionalities [(L1–4)Zn(BH4)2]1–4 (1, R = H; 2, R = CH2CH[double bond, length as m-dash]CH2; 3, R = CH2CH2CH2(9-borabicyclo[3.3.1]nonane) or CH2CH2CH2(9-BBN); 4, R = CH2CH2CH2BCy2) were synthesized by reacting the corresponding dichloride complexes [(L1–4)ZnCl2] with two equivalents of NaBH4 in THF. The new complexes were characterized by NMR spectroscopy, FTIR spectroscopy and elemental analysis, while complex 3 was characterized by single-crystal X-ray diffraction. The borane-functionalized complexes 3 and 4 catalyzed the hydroboration of CO2 at 1 bar pressure, an array of isocyanates and esters and the dihydroboration of a set of nitriles with pinacolborane (HBPin) at catalyst loadings of 1 mol% and temperature of 60 °C in yields of 32–99%. In the cases of CO2 and isocyanates, the methylated products (along with PinBOBPin) were preferred after 16 h. The catalytic reactions utilizing 1 mol% of the unfunctionalized complexes 1 and 2 achieved yields in the range of 7–24%, an average 4-fold decrease in catalytic activities, confirming that the catalytic intermediates benefit from the intra- or intermolecular stabilization of incorporated boranes.

Autores da comunidade :

• 

  T

  Tiago Filipe Carpinteiro Cruz

  ist165790

  Afiliações e fontes

  IST

  Instituto Superior Técnico

• 

  L

  Luís Filipe Coelho Veiros

  ist12434

  Afiliações e fontes

  IST > CQE

  Centro de Química Estrutural

  IST > DEQ

  Departamento de Engenharia Química

VoR - Versão publicada

Royal Society of Chemistry

https://pubs.rsc.org/en/content/articlelanding/2025/dt/d4dt03363a

Dalton Transactions

4244

4254

54

10

1477-9234

10.1039/D4DT03363A

001414248700001

chemical-sciences - Química

eng - Inglês

CC-BY - CC-BY