No 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.

This paper focuses on ferrocene-based secondary diphosphines of the type [Fe{η-CH(PHR)}] with P-substituents of distinctly different steric and electronic properties, namely methyl, neopentyl (Np), tert-butyl, phenyl and 3,5-bis(trifluoromethyl)phenyl (XyF). The reaction of [Fe{η-CH(PHPh)}] (H1a) and [Fe{η-CH(PHt-Bu)}] (H1b) with n-BuLi in the presence of TMEDA afforded lithium diphosphides of the type [Li(μ-1)(TMEDA)], which contain a cyclic non-planar LiP core. The analogous reactions of [Fe{η-CH(PHMe)}] (H1c) and [Fe{η-CH(PHNp)}] (H1d) furnished dimeric aggregates exhibiting a ladder-type LiP motif, viz. [Li(μ-1c)(TMEDA)] and [Li(μ-1d)(TMEDA)]. H1e (R = XyF) did not afford a stable lithium diphosphide. A Brønsted metathesis with Zr(NMe) was possible with the aryl-substituted compounds H1a and H1e, leading to products of the type [{Zr(NMe)}(μ-1)]. In contrast, the alkyl-substituted congeners H1b-H1d were inert towards Zr(NMe). The reaction of [Fe{η-CH(PHR)}] with nickelocene afforded intractable mixtures of numerous products in the case of H1c and H1e. In the other three cases, compounds of the type [(NiCp)(μ-1)] were isolated. For H1b and H1d a two-stepped reaction via a phosphino-phosphido intermediate of the type [NiCp(H1)] was observed, which could be isolated and fully characterised in the case of [NiCp(H1b)].