Synthesis, Characterization and Redox Behaviour of Mono‐ and Dicarbonyl Phosphane Rhenium(I) Complexes Bearing N‐, N,N‐ and N,O‐Type Ligands

New mono‐ and dicarbonyl phosphane Re I complexes [ReCl(L) 2 (CO)(PPh 3 ) 2 ] {L = 3,5‐Me 2 ‐Hpz ( 3 ), quin ( 4 )} and [Re(L) n (CO) 2 (PPh 3 ) 2 ][BPh 4 ] m {L = pz/Hpz, n = 2, m = 0 ( 2 ); L = 4,7‐Ph 2 ‐phen, n = 1, m = 1 ( 5 ); L = 2‐Me‐dipic, n = 1, m = 0 ( 6 )} were prepared by reaction of the dinitrogen Re I precursor [ReCl(N 2 )(CO) 2 (PPh 3 ) 2 ] ( 1 ), in refluxing methanol or methanol/benzene mixture, with 3,5‐dimethylpyrazole (3,5‐Me 2 ‐Hpz), quinoline (quin), pyrazole (Hpz), 4,7‐diphenyl‐1,10‐phenanthroline (4,7‐Ph 2 ‐phen) and dipicolinic acid (H 2 dipic), respectively, with esterification of the latter in 6 to afford the 2‐methoxycarbonyl‐6‐pyridinecarboxylate (2‐Me‐dipic) moiety. Complexes 2 – 6 were characterized by IR spectroscopy, 1 H‐, 31 P{ 1 H}‐ and 13 C{ 1 H} NMR spectroscopy, FAB‐MS, cyclic voltammetry, elemental analyses and single‐crystal X‐ray diffraction (for 2 , 5 and 6 ) analyses which indicate mutually trans triphenylphosphane ligands. The redox behaviour of the obtained complexes in solution was studied, and the Lever electrochemical ligand parameter E L was determined, for the first time, for 4,7‐Ph 2 ‐phen. Compounds 2 – 6 represent the first examples of mono ‐ and dicarbonyl Re complexes bearing these types of ligands.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)