Orientation and Restricted Rotation of Lopsided N-Donor Heterocyclic Bioligands in Octahedral Ruthenium Complexes

Abstract

In order to analyze the roles of steric and electrostatic factors in determining the orientation and dynamic behavior of benzimidazole-type ligands in Ru II (dimethyl sulfoxide) complexes, compounds of the general formula RuX 2 (dmso-S) 2−n (CO) n (L) 2 [X = Cl, Br; L = 1,5,6-trimethylbenzimidazole (Me 3 Bzm), benzimidazole (Bzm); n = 0−2] with cis and trans arrangements of the X ligands, have been prepared and structurally characterized both in solution and in the solid state, by NMR and X-ray techniques, respectively. New descriptors, based on the torsion angles about the Ru−N bonds, are introduced for a more efficient definition of the head-tohead (HH) and head-to-tail (HT) orientations of the heterocyclic nitrogen bases. Similar descriptors, based on the torsion angles about the Ru−S bonds, are used to define the orientation of the dimethyl sulfoxide ligands. The experi- [a] We recently reported that restricted rotation about RuϪN bonds in octahedral complexes of the type cis,cis,cis-RuCl 2 (dmso-S) 2 (L1)(L2) [9] (L1 trans to Cl, L2 trans to dmso-S; Scheme 1) allows assessment of the relative ori-

Half-sandwich RuII[9]aneS3 complexes structurally similar to antitumor-active organometallic piano-stool compounds: Preparation, structural characterization and in vitro cytotoxic activity

“…The RuAN coordination distances of 2.141(4) Å are comparable with the mean value of those found in the benzimidazole (Bzm) derivative trans,cis,cis-[RuCl 2 (dmso-S) 2 (Bzm) 2 ] (RuAN = 2.128(3), 2.155(3) Å ) [23] and also with those detected in the pyrazole (pzH) complex trans,cis,cis-[RuCl 2 (dmso-S) 2 (pzH) 2 ] (RuAN = 2.133(2), 2.124(2) Å ) [12], making allowance for the e.s.d.'s. On the other hand, the RuAN distances are significantly elongated with respect to those of ca.…”

Synthesis and Reactivity of Ru-, Os-, Rh-, and Ir-Halide−Sulfoxide Complexes

“…In other words, compound 9 (and 11 too) under mild reaction conditions selectively replaces two cis dmso-S ligands. 92,97 Conversely, when the above reactions are performed at higher temperature, complex 9 behaves like 8 and yields preferentially the thermodynamically more stable cis,cis,cis isomer.…”

“…For example, for each complex selective replacement of all the dmso-O ligands with N-donor ligands L such as pyridine was achieved under mild conditions, yielding complexes such as cis,cis,cis-RuCl 2 (dmso-S) 2 (L)(CO), trans,cis,cis-RuCl 2 -(L) 2 (CO) 2 , and cis,fac-RuCl 2 (CO) 3 (L) (Scheme 47). 97,335 In particular, 34 was found to be a very useful building block in the construction of several supramolecular adducts with pyridylporphyrins, including molecular squares. [339][340][341][342][343][344][345][346] It should be noted that the substitution reactions of the Ru(II)-dmso carbonyls can be sometimes accompanied by geometrical isomerization, as in the case of 26, which, upon replacement of the dmso-O trans to CO with L, yields selectively cis,cis,cis-RuCl 2 (dmso-S) 2 (L)(CO) complexes in which CO (previously trans to dmso) is trans to a Cl (Scheme 47).…”

Trans–cis–cis-[RuCl2(DMSO)2(2-amino-5-methyl-thiazole)2], (PMRu52), a novel ruthenium(II) compound acting as a strong inhibitor of cathepsin B

“…PMRu52 can be obtained starting from either II or III, under the same reaction conditions, with nearly equal yields; this possibility was already stated by other authors 15 working with different ligands. Notably, it was previously reported that cis-[RuCl 2 (DMSO) 4 ] and trans-[RuCl 2 (DM-SO) 4 ] typically react with excess azole heterocycles to produce six-coordinate complexes of the general formula RuCl 2 (DMSO) 2 (azole) 2 , where azole = imidazole, 4-nitroimidazole, dimethylimidazole, benzimidazole, 1,5,6-trimethylbenzimidazole, pyrazole and indazole (often as individual isomers) [21][22][23][24][25][26].…”