Hemilabile Thioether Ligands Based on Pyrimidine and/or Pyridine Derivatives that Interconvert between N,S‐ and N‐Coordination in Congested Ruthenium(II) Complexes

Abstract

The thioether ligands L [L = 2-pyridylmethyl 2Ј-pyridyl sulfide (L 1 ), 2-pyridylmethyl 2Ј-pyrimidyl sulfide (L 2 ) and 2-pyr-investigations show that these potentially tridentate ligands act as N,S-bidentate species, to form a five-membered RuSCCN(Ru-N) ring, and in certain cases, as N-monodentate species coordinated to the ruthenium through the 2-pyridylmethyl group. The N,S-chelated species contain chiral sulfur and ruthenium atoms with (R) and (S), and Δ and Λ configurations, respectively. Two invertomers and two sets of NMR signals in the slow-exchange region are expected. However, the low-temperature 1 H NMR spectra show that sulfur inver-

Dynamic Stereochemical Behaviour of Congested Ruthenium(II) Complexes Containing Asymmetric Thioether Ligands Based on Pyridine and Pyrimidine

“…These data indicate that dps, 4mdps and 5mdps act as N,N-chelate ligands. [12][13][14][15][16][17] These findings were confirmed by subsequent 1 H and 13 C NMR spectroscopic studies.…”

“…[4,[6][7][8]11] Some years ago, studying the coordination chemistry of thioethers based on pyridine or pyrimidine, we found that these usually N,N-bidentate donors [12] often show N,S che-lation towards congested ruthenium substrates. [13][14][15][16][17] The resultant complexes display dynamic stereochemical rearrangements associated with inversion at the sulfur atom coordinated to the ruthenium, [14] the restricted rotation of the pendant ring [15] and the exchange between different coordination modes. [17] NMR spectroscopic studies by us were performed to elucidate the mechanisms of these processes.…”

“…[13][14][15][16][17] The resultant complexes display dynamic stereochemical rearrangements associated with inversion at the sulfur atom coordinated to the ruthenium, [14] the restricted rotation of the pendant ring [15] and the exchange between different coordination modes. [17] NMR spectroscopic studies by us were performed to elucidate the mechanisms of these processes. Inversion of the sulfur centre and restricted rotation were studied when potentially bidentate ligands were used, [14,15] whereas the exchange between different coordination modes was observed when thioethers, which are generally asymmetrical and potentially tridentate, were used.…”

“…Inversion of the sulfur centre and restricted rotation were studied when potentially bidentate ligands were used, [14,15] whereas the exchange between different coordination modes was observed when thioethers, which are generally asymmetrical and potentially tridentate, were used. [17] In the last case, different types of bonding groups show different bond strengths, and the thioethers may act as hemilabile ligands with dissociation and recoordination of weakly bound groups.…”

“…For the compounds [17] [Ru(N,N-diimmine) 2 L 1 ][PF 6 ] 2 [diimmine = 2-pyrimidyl sulfide, 2,2Ј-bis(5-ethylpyrimidyl) sulfide; L 1 = 2-pyridylmethyl 2Ј-pyridyl sulfide, 2-pyridylmethyl 2Ј-pyrimidyl sulfide (pps) and 2-(4-methylpyrimidyl) 2Ј-pyridylmethyl sulfide (mps)] only two exchanging species were observed. In the major species, L 1 was N pyridine ,S-chelated, and in the minor species, L 1 was N pyridine monodentate.…”