Reactions of [RuCl₂(PPh₃)₃] with Nitron and with the “Enders Carbene”: Access to Ruthenium(III) NHC Complexes

Abstract

The reactions of [RuCl2(PPh3)3] with the “Enders carbene” 1,3,4-triphenyl-1,2,4-triazol-5-ylidene (1) and the “instant carbene” Nitron (2) respectively afforded the RuII chelates [RuCl(3)(PPh3)2] (3 = 3,4-diphenyl-1-o-phenylene-1,2,4-triazol-5-ylidene) and [RuCl(4)(PPh3)2] (4 = 4-phenyl-3-phenylamino-1-o-phenylene-1,2,4-triazol-5-ylidene) in a process involving the ortho metalation of the 1-Ph group of the respective carbene ligand. It proved possible to synthesize [RuCl(3)(PPh3)2] more conveniently in higher yield by using the stable carbene precursor 5-methoxy-1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazole (MeO-1-H) instead of the free carbene 1 in the presence of triethylamine to trap the HCl generated by the ortho metalation. Aerobic oxidation of the RuII chelates in the presence of chloride ions furnished [RuCl2(3)(PPh3)2] and [RuCl2(4)(PPh3)2], which are rare examples of RuIII NHC complexes. The crystal structures of all four complexes were determined by single-crystal X-ray diffraction studies. In addition, the crystal structure of the hydrochloride of Nitron was also determined. In the RuII chelates, the pentacoordinate metal center is in a distorted-square-pyramidal environment with the carbon atom of the ortho-metalated 1-Ph group occupying the apical position. The coordination sphere of the RuIII chelates is complemented by a second chlorido ligand, which is positioned trans to this carbon atom.

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

“…One face of this core is occupied by the three benzylic substituents, leaving the other face open for the chloride anion which is held in place by two N–H···Cl hydrogen bonds, one of them being very short ( d (H···Cl) = 2.11(2) Å, d (N···Cl) = 3.060(1) Å) and linear and the other one much longer and non-linear. Short N–H···Cl hydrogen bonds have also been found in the crystal structures of related compounds, such as II ·HCl·CH 3 OH ( d (H···Cl) = 2.36 Å, d (N···Cl) = 3.15 Å [35]) and a 2-phenylamino-1,3,4-thiadiazolium chloride (2.05/3.00 Å [36]). In the packing arrangement of the crystal, the chloride ions are found in anion channels oriented along the 2 1 screw axis parallel to the crystallographic a -axis of the orthorhombic unit cell (space group P 2 1 2 1 2 1 ).…”

Ruthenium(II) complexes of some simple classic amine ligands

“…reagent. This situation has led others [18][19][20] to focus often on the isolation of such triphenylphosphine-containing products. Therefore, the possibility of the formation of a highly-soluble [Ru (Dien)(Dien*) PPh 3 ] 2+ complex (Dien* denotes a "dangling" [21] Dien) should not be discounted.…”

Crystal structure of (1,4-diphenyl-4H-1,2,4-triazol-3-yl)phenylamine difluorophosphate, and a survey of the difluorophosphate anion (PO2F2 −)

“…Nitron has been utilized as a reagent for gravimetric analysis of the nitrate anion ('Busch's reagent'; Busch, 1905) from slightly acidic solutions under formation of the salt C 20 H 17 N 4 + ÁNO 3 À . In recent years, inexpensive Nitron was rediscovered as a stable N-heterocyclic carbene (Fä rber et al, 2012) that can be reacted with several coinage or other noble metals to yield corresponding metal complexes (Hitzel et al, 2014;Thie et al, 2016). The Nitron salt of difluorophosphoric acid, C 20 H 17 N 4 + ÁPO 2 F 2 À (III) was reported by Lange more than 90…”

“…The structure of the hydrochloride methanol solvate of Nitron(NITLEJ;Hitzel et al, 2014) is the most similar in comparison to I because it shows no direct coordination to a metal and is not derivatized. In (Nitron) + Cl À Á CH 3 OH, the central triazole ring is co-planar with only one phenyl ring (attached to N2).…”