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Crucial Influence of the Intramolecular Hydrogen Bond on the Coordination Mode of RC(S)NHP(S)(O i Pr) 2 in Homoleptic Complexes with Ni II
Author(s) -
Babashkina Maria G.,
Safin Damir A.,
Srebro Monika,
Kubisiak Piotr,
Mitoraj Mariusz P.,
Bolte Michael,
Garcia Yann
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201200890
Subject(s) - chemistry , deprotonation , homoleptic , intramolecular force , crystallography , thiourea , metal , conformational isomerism , hydrogen bond , crystal structure , stereochemistry , molecule , ion , organic chemistry
Abstract Reaction of the deprotonated N ‐thiophosphorylated thioureas RC(S)NHP(S)(O i Pr) 2 [R = EtNH ( HL I ), i PrNH ( HL II ), Et 2 N ( HL III ), 2,5‐Me 2 C 6 H 3 NH ( HL IV ), 4‐Me 2 NC 6 H 4 NH ( HL V )] with Ni II leads to complexes of the formula [NiL I–V 2 ] . The molecular structures of the complexes in the solid were elucidated by single‐crystal X‐ray diffraction analysis. In the complexes, the metal atom is found to be in a square‐planar trans ‐ N 2 S 2 ( [NiL II,IV 2 ] ) environment formed by the C=S sulfur atoms and the P–N nitrogen atoms, or in a square‐planar trans ‐ S 2 S′ 2 ( [NiL I,III 2 ] ) environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands. Reaction of deprotonated N ‐thiophosphorylated thiourea HL V with NiCl 2 leads to violet [Ni(L‐1,3‐ N , S ) 2 ] or dark violet [Ni(L‐1,5‐ S , S′ ) 2 ]·(CH 3 ) 2 C=O crystals that were isolated by recrystallization from a mixture of CH 2 Cl 2 or acetone, respectively, and n ‐hexane. DFT calculations confirmed that the [Ni(L I,II,IV,V ‐ N , S ) 2 ] conformers are more stable (by 5–7 kcal/mol) than [Ni(L I,II,IV,V ‐ S , S′ ) 2 ] , whereas [Ni(L III ‐ N , S ) 2 ] is less stable (by 7–9 kcal/mol) than [Ni(L III ‐ S , S′ ) 2 ] . The main reason for higher stability of the 1,3‐ N , S versus 1,5‐ S , S′ isomers is the formation of intramolecular N–H ··· S=P hydrogen bonds. The same hydrogen bonds are impossible in complex [NiL III 2 ] . In solution, complex [NiL III 2 ] has revealed an exclusively 1,5‐ S , S′ coordination, whereas compounds [NiL I,II,IV,V 2 ] reveal at least two isomers in the 1 H and 31 P{ 1 H} NMR spectra. The major species is assigned to the 1,3‐ N , S ‐coordinated isomer, and the minor signals are assigned to the 1,5‐ S , S′ isomer, which was confirmed by UV/Vis spectroscopic results. The electrochemical measurements reveal reversible one‐electron reduction and irreversible oxidations both assigned to ligand‐centred processes. Ligand‐based oxidation processes agree well with TD‐DFT results.