Substitution reactions of rhenium–chloride bonds in [Re 2(DMAA) 4Cl 2], (DMAA=2′,6′-dimethylacetanilido); synthesis and characterisation of [Re 2(DMAA) 4X 2] (X=NCO, NCS, N 3) and [Re 2(DMAA) 4L n][SbF 6] 2 ( n=2, L=pyridine; n=1, L=4,4′-bipyridine)

Abstract

Substitution of chloride ligands in [Re 2(DMAA) 4Cl 2] ( 1), (DMAA=2′,6′-dimethylacetanilido) in a mixture of dichloromethane–methanol affords [Re 2(DMAA) 4X 2] complexes with X=[N 3] −, 2·CH 2Cl 2, [SCN] −, 3, or [NCO] −, 4·CH 2Cl 2 in yields of 84, 72 and 76%, respectively. The reaction of 1 and Ag[SbF 6] in air affords [Re 2(DMAA) 4(H 2O) 2][SbF 6] 2 ·H 2O, 5·H 2O (71%). The aquo ligands in 5 can be displaced by pyridine or 4,4′-bipyridine to produce [Re 2(DMAA) 4(pyridine) 2][SbF 6] 2 ( 6) (68%), and [Re 2(DMAA) 4(4,4′-bipyridine)][SbF 6] 2 ·CH 2Cl 2 ( 7) (42%). All new compounds were characterised with C, H and N chemical analysis, FTIR and, except for 7, 1H and 13C NMR spectroscopies. Additionally, single crystal X-ray crystallography was used to establish the molecular structures of 2·CH 2Cl 2 and 3·0.83CHCl 3. Principal distances and angles are: rhenium–rhenium distances in 2 and 3 of 2.2477(3) and 2.2324(5) Å, respectively; rhenium to azido nitrogen distances in 2 of 2.158(5) and 2.166(6) Å, and rhenium to isothiocyanato nitrogen distances in 3 of 2.208(8) and 2.210(6) Å; essentially linear azido and isothiocyanato ligands with NNN angles of 178.4(10) and 179.1(9)° and NCS angles of 177.9(10) and 179.7(9)°, and ReNX angles (X=N for 2 and C for 3) of the rhenium pseudo-halide bonds of 139.8(6) and 128.6(5)° in 2 and 151.9(7) and 169.1(9)° in 3, respectively.