Oxidorhenium(V) and Rhenium(III) Complexes with m ‐Terphenyl Isocyanides

Reactions of the sterically encumbered m ‐terphenyl isocyanides CNAr Dipp2 (Dipp = 2,6‐diisopropylphenyl) and CNAr Mes2 (Mes = 2,4,6‐trimethylphenyl) with (NBu 4 )[ReOCl 4 ] in CH 2 Cl 2 form stable complexes of the composition (NBu 4 )[ReOCl 3 (CNAr R )] or [ReOCl 3 (CNAr R ) 2 ] depending on the amount of isocyanide added. In the [ReOCl 3 (CNAr R ) 2 ] complexes, cis coordination of the two isocyanides is observed for CNAr Mes2 , while the sterically more demanding CNAr DIPP2 ligands are found in trans positions. The rhenium(III) species [ReCl 3 (PPh 3 )(CNAr Mes2 ) 2 ] was obtained from the reaction of [ReOCl 3 (PPh 3 ) 2 ] and CNAr Mes2 . The ν(CN) IR frequencies measured for the Re V complexes appear at higher wavenumbers than for the uncoordinated isocyanides, which suggests a low degree of backdonation into anti ‐bonding orbitals of these ligands.