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Cationic heteroleptic Ni(ii) complexes of dithiocarbamate and phosphine ligands : synthesis, characterization and proton reduction study

Pal, Sarvesh Kumar LU ; Mishra, Anjali LU ; Mishra, Gaurav Kumar ; Hansson, Ruben LU ; Jaiswal, Vishal ; Nordlander, Ebbe LU ; Lisensky, George LU ; Singh, Amrendra Kumar LU ; Singh, Nanhai and Lama, Prem , et al. (2026) In Dalton Transactions
Abstract

Three cationic heteroleptic Ni(ii) dithiocarbamate complexes ([Ni(L)(L′)n]PF6, n = 1 or 2) were synthesized and characterized to explore the relationship between diphosphine chelate ring size and their electrocatalytic activity for hydrogen production. These complexes (1–3) feature a common dithiocarbamate ligand (L) and varied diphosphine ligands (L′): dppm (1), dppe (2), and dppp (3). Single-crystal X-ray analysis showed a distorted square pyramidal geometry for 1 and square planar geometries for 2 and 3 around the NiP2S2 core. Electrochemical studies revealed a small variation in redox potentials (ΔE1/2 ≈ 60 mV), suggesting a weak electronic effect of ligands from dppm (1) to... (More)

Three cationic heteroleptic Ni(ii) dithiocarbamate complexes ([Ni(L)(L′)n]PF6, n = 1 or 2) were synthesized and characterized to explore the relationship between diphosphine chelate ring size and their electrocatalytic activity for hydrogen production. These complexes (1–3) feature a common dithiocarbamate ligand (L) and varied diphosphine ligands (L′): dppm (1), dppe (2), and dppp (3). Single-crystal X-ray analysis showed a distorted square pyramidal geometry for 1 and square planar geometries for 2 and 3 around the NiP2S2 core. Electrochemical studies revealed a small variation in redox potentials (ΔE1/2 ≈ 60 mV), suggesting a weak electronic effect of ligands from dppm (1) to dppp (3). However, a significant difference in catalytic half-wave potentials (ΔEcat/2 ≈ 200 mV in 4 mM CH3COOH) indicates a strong influence of the P–Ni–P bite angles. The catalytic activity of the complexes is significantly influenced by the chelate ring size and their P–Ni–P bite angles, which follow the trend 92.07(4)° (3) > 86.84(6)° (2) > 75.24(3)° (1). The enhanced electrocatalytic performance of 3 with a low overpotential (∼600 mV), a high turnover frequency (∼706 s−1), and faradaic efficiency (88%) is attributed to the conformational flexibility of the six-membered chelate ring in 3 due to the dppp ligand. Both experimental data and DFT calculations support an ECEC mechanism for the HER catalysed by heteroleptic Ni(ii) complexes with the formation of Ni(iii)–H intermediate species.

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Contribution to journal
publication status
epub
subject
in
Dalton Transactions
publisher
Royal Society of Chemistry
external identifiers
  • scopus:105029308362
ISSN
1477-9226
DOI
10.1039/d5dt02840j
language
English
LU publication?
yes
id
40b87965-dd34-49f9-a229-bd4bad6aa813
date added to LUP
2026-02-20 12:00:02
date last changed
2026-02-20 12:00:35
@article{40b87965-dd34-49f9-a229-bd4bad6aa813,
  abstract     = {{<p>Three cationic heteroleptic Ni(ii) dithiocarbamate complexes ([Ni(L)(L′)<sub>n</sub>]PF<sub>6</sub>, n = 1 or 2) were synthesized and characterized to explore the relationship between diphosphine chelate ring size and their electrocatalytic activity for hydrogen production. These complexes (1–3) feature a common dithiocarbamate ligand (L) and varied diphosphine ligands (L′): dppm (1), dppe (2), and dppp (3). Single-crystal X-ray analysis showed a distorted square pyramidal geometry for 1 and square planar geometries for 2 and 3 around the NiP<sub>2</sub>S<sub>2</sub> core. Electrochemical studies revealed a small variation in redox potentials (ΔE<sub>1/2</sub> ≈ 60 mV), suggesting a weak electronic effect of ligands from dppm (1) to dppp (3). However, a significant difference in catalytic half-wave potentials (ΔE<sub>cat/2</sub> ≈ 200 mV in 4 mM CH<sub>3</sub>COOH) indicates a strong influence of the P–Ni–P bite angles. The catalytic activity of the complexes is significantly influenced by the chelate ring size and their P–Ni–P bite angles, which follow the trend 92.07(4)° (3) &gt; 86.84(6)° (2) &gt; 75.24(3)° (1). The enhanced electrocatalytic performance of 3 with a low overpotential (∼600 mV), a high turnover frequency (∼706 s<sup>−1</sup>), and faradaic efficiency (88%) is attributed to the conformational flexibility of the six-membered chelate ring in 3 due to the dppp ligand. Both experimental data and DFT calculations support an ECEC mechanism for the HER catalysed by heteroleptic Ni(ii) complexes with the formation of Ni(iii)–H intermediate species.</p>}},
  author       = {{Pal, Sarvesh Kumar and Mishra, Anjali and Mishra, Gaurav Kumar and Hansson, Ruben and Jaiswal, Vishal and Nordlander, Ebbe and Lisensky, George and Singh, Amrendra Kumar and Singh, Nanhai and Lama, Prem and Kumar, Kamlesh}},
  issn         = {{1477-9226}},
  language     = {{eng}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Dalton Transactions}},
  title        = {{Cationic heteroleptic Ni(ii) complexes of dithiocarbamate and phosphine ligands : synthesis, characterization and proton reduction study}},
  url          = {{http://dx.doi.org/10.1039/d5dt02840j}},
  doi          = {{10.1039/d5dt02840j}},
  year         = {{2026}},
}