First kinetic data of the CO substitution in fac-[Re(L,L '-Bid)(CO)(3)(X)] complexes (L,L '-Bid = acacetylacetonate or tropolonate) by tertiary tot phosphines PTA and PPh3: Synthesis and crystal structures of water-soluble rhenium(I) tri- and dicarbonyl complexes with 1,3,5-triaza-7-phosphaadamantane (PTA)

摘要

fac-[Re(OH2)(3)(CO)(3)](+) reacts with acetylacetone (AcacH) at room temperature to yield factRe(Acac)(CO)(3)(OH2)] (1) under aqueous conditions 1 was isolated and reacted with the monodentate ligand, 1,3,5-triaza-7-phosphaadamantane (PTA), to form fac-[Re(Acac)(CO)(3)(PTA)] (2) in a 9:1 ratio of water and methanol. The isolated complex 2 was further reacted with an excess of PTA ligand in a 9:1 ratio of water and methanol to yield the highly soluble cis-trans-[Re(Acac)(CO)(2)(PTA)(2)] (3). The complexes have been characterized by spectroscopic techniques IR, H-1,C- 13 and P-31 NMR, as well as single crystal X-ray crystallography for 2 and 3. From the crystallographic results of 3, the formation of the cis-trans conformation was confirmed, while the P-31 NMR results further established 3 as the sole product formed. A P-31 NMR kinetic study, involving the methanol substitution of fac-[Re(CO)(3) (Acac)(CH3OH)] (4) and fac-[Re(CO)(3)(Trop)(CH3OH)] (TropH = tropolone) with PTA as entering monodentate ligand was also undertaken. The second-order rate constants (k(1)) for the forward reactions at 25.0 degrees C were respectively obtained as (35.9 +/- 0.2) x 10(-3) M-1 s(-1) and (25.1 +/- 0.8) M-1 min(-1) . In a preliminary P-31 NMR kinetic investigation of the carbonyl substitution in fac-[Re(Acac) (CO)(3)(PPh3)] by PPh3, an estimated equilibrium constant (K-est) of approximate to 5.09 was calculated for the reversible reaction.