Structure and Reactivity of Aquacarbonylruthenium(II) Complexes. An X-ray and Oxygen-17 NMR Study

Abstract

3 ](ClO 4 ) 2 (3), the 17 O exchange between the bulk water and the carbonyl oxygens have been studied by 17 O NMR spectroscopy, and the X-ray crystallographic structures of 1 and 2 have been determined. The water exchange of equatorially and axially coordinated water molecules on 1 and 2 follow an I d mechanism and are characterized by k eq 298 (s -1 ), ∆H q (kJ/mol), and ∆S q (J/(mol K)) of (2.54 ( 0.05) × 10 -6 , 111.6 ( 0.4, and 22.4 ( 1 (1-eq); (3.54 ( 0.02) × 10 -2 and 81 (1-ax); (1.58 ( 0.14) × 10 -7 , 120.3 ( 2, and 28.4 ( 4 (2-eq); and (4.53 ( 0.08) × 10 -4 , 97.9 ( 1, and 19.3 ( 3 (2-ax). The observed reactivities correlate with the strength of the Ru-OH 2 bonds, as expressed by their length obtained by X-ray studies: 2.079 (1-eq), 2.140 (1-ax), 2.073 (2-eq), and 2.110 (2-ax) Å. 3 is strongly acidic with a pK a of -0.14 at 262 K. Therefore, the acid-dependent water exchange can take place through 3 or Ru(CO) 3 (H 2 O) 3 OH + with an estimated k eq 298 of 10 -4 /10 -3 s -1 and k OH 262 of 0.053 ( 0.006 s -1 . The 17 O exchange rate between the bulk water and the carbonyl oxygens increases from 1 to 2 to 3. For 1 an upper limit of 10 -8 s -1 was estimated. For 2, no acid dependence of k Ru CO between 0.1 and 1 m Htos was observed. At 312.6 K, in 0.1 and 1 m Htos, k Ru CO ) (1.18 ( 0.03) × 10 -4 . For the tricarbonyl complex, the exchange can proceed through 3 or Ru(CO) 3 (H 2 O) 2 OH + with k Ru CO and k RuOH CO of, respectively, 0.003 ( 0.002 and 0.024 ( 0.003 s -1 , with a ruthenacarboxylic acid intermediate.

Ligand exchange and complex formation kinetics studied by NMR exemplified on fac-[(CO)3M(H2O)]+ (M=Mn, Tc, Re)

“…28). Fixing K a to the value determined from the water exchange (pK a = 1.2), exchange rate constants for oxygen exchange on fac-[(CO) 2 [43,61] and [(CO) n Ru(H 2 O) 6−n ] + [37]. …”

Structure of the Triaquatricarbonylrhenium(I) Cation and Its Conjugate Base

“…There are, in fact, only a limited number of elucidated structures of aquacarbonyl complexes in the chemical literature, and only four structures with exclusively water and carbon monoxide as ligands. [14][15][16][17] We have discovered that crystals containing 1 + are surprisingly easy to prepare. We now report the first crystal structures of salts of 1 + and the formal appearance of its conjugate base, Re-(CO) 3 (OH)(H 2 O) 2 2 in a crystal structure.…”

Oxygen-17 NMR spectroscopy: Basic principles and applications (Part I)

“…C and17 O NMR chemical shifts (ppm) of the mono, bis, and tris ruthenium carbonyl aqua complexes[607].À192 [RuCO(H 2 O-eq) 4 (H 2 O-ax)](tos) 2 À155 À29 358 206 cis-[Ru(CO) 2 (H 2 O-eq) 2 (H 2 Oax) 2 ](tos) 2 fac À ½RuðCOÞ 3 ðH 2 OÞ 3 ðCIO 4 Þ 2 a tos À = p-toluenesulfonate anion. b 2 M HClO 4 .…”