Organometallic Aqua Complexes, III. Olefin Aqua Complexes of Rhodium(I)

Abstract

Abstract Dehalogenation of halide precursors [(olefin)RhCl] 2 [olefin = ethylene, 1,5‐cyclooctadiene (COD], norbornadiene (NBD), 2,3‐dimethylbutadiene (DMB)] in water gave the respective cis ‐diolefin aqua ions, characterized by NMR spectroscopy in solution. Attempted isolation of the tosylate salt [(COD)Rh‐(H 2 O) 2 ]OTs yielded crystals of (COD)Rh(H 2 O)(η 1 ‐OTs) characterized by X‐ray structural analysis. [(NBD]Rh(H 2 O) 2 ]SbF 6 in the presence of adventitious toluene decomposed into [(NBD])Rh(η 6 ‐toluene)]SbF 6 and [(NBD] 2 Rh]SbF 6 , both complexes were isolated and structurally characterized. Ethylene exchange in [(C 2 H 4 ) 2 Rh(H 2 O) 2 ] + is fast with k 2 of the order of 10 4 –10 5 s ‐1 · M ‐1 . The rate constant for water exchange in [CODRh(H 2 O) 2 ] + is estimated as 10 4 s ‐1 (ΔDL G ≈︁ 25 kJ/mol) at 173 K.