Kinetic study of oxygen exchange in hexakis(carbonyl)rhenium hexafluorophosphate with water (oxygen-17)

Kump, Robin L.; Todd, Lee J.

doi:10.1021/ic50225a027

Cited by 13 publications

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“…The relative rates of 17 O exchange between the carbon monoxide of 1 , 2 , and 3 and the bulk water can be understood on the basis of the electrophilic character of the carbon atom in the different complexes, since the exchange is believed to occur by a nucleophilic attack at a carbon atom by H 2 O, , forming a ruthenacarboxylic acid intermediate (see Scheme ) . The Ru−C σ-bond is formed from an unshared pair of electrons located on the carbon atom; an increase in this donation will result in a decrease in electron density on the carbon.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2000

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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.

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Section: Resultsmentioning

confidence: 99%

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

et al. 2000

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“…38 Later, a 17 O NMR study provided quantitative data. 39 The oxygen exchange on [Re(CO) 6 ]PF 6 in H 2 O/CH 3 CN was assumed to obey the following rate law: rate ) k CO [Re(CO) 6 + ][H 2 O] 2 with k CO 305 ) (5.84 ( 0.90) × 10 -4 M -2 s -1 . A similar oxygen exchange has also been reported for [(CO) x Ru(H 2 O) 6-x ] 2+ complexes (x ) 1-3), where the rates increase with increasing x.…”

Section: Discussionmentioning

confidence: 99%

“…Since the report by Muetterties, showing that [Re(CO) 6 ] + exchanges its O atom with water without being decomposed, this reaction has been qualitatively studied by IR . Later, a 17 O NMR study provided quantitative data . The oxygen exchange on [Re(CO) 6 ]PF 6 in H 2 O/CH 3 CN was assumed to obey the following rate law: rate = k CO [Re(CO) 6 + ][H 2 O] 2 with = (5.84 ± 0.90) × 10 -4 M -2 s -1 .…”

Section: Discussionmentioning

confidence: 99%

“…Generally, it is assumed that the oxygen exchange on carbonyl ligands in the presence of water proceeds via a so-called metallacarboxylic acid, which is the result of nucleophilic attack of H 2 O (or OH - ) on the C atom of the carbonyl ligand. − An electron-depleted carbonyl will therefore be more prone for nucleophilic attack than a carbonyl experiencing a strong π back-bonding. Among the complexes discussed here, [(CO) 3 Ru(H 2 O) 3 ] 2+ has one of the highest frequencies and is also the complex with the fastest exchange .…”

Section: Discussionmentioning

confidence: 99%

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Relevance of the Ligand Exchange Rate and Mechanism offac-[(CO)₃M(H₂O)₃]⁺(M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals

et al. 2006

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The water exchange process on fac-[(CO)3Mn(H2O)3]+ and fac-[(CO)3Tc(H2O)3]+ was kinetically investigated by 17O NMR as a function of the acidity, temperature, and pressure. Up to pH 6.3 and 4.4, respectively, the exchange rate is not affected by the acidity, thus demonstrating that the contribution of the monohydroxo species fac-[(CO)3M(OH)(H2O)2] is not significant, which correlates well with a higher pKa for these complexes compared to the homologue fac-[(CO)3Re(H2O)3]+ complex. The water exchange rate K298ex/s(-1) (DeltaHex double dagger/kJ mol(-1); DeltaSex double dagger/J mol(-1) K(-1); DeltaV double dagger/cm3 mol-1) decreases down group 7 from Mn to Tc and Re: 23 (72.5; +24.4; +7.1) > 0.49 (78.3; +11.7; +3.8) > 5.4 x 10(-3) (90.3; +14.5; -). For the Mn complex only, an O exchange on the carbonyl ligand could be measured (K338co = 4.3 x 10(-6) s(-1)), which is several orders of magnitude slower than the water exchange. In the case of the Tc complex, the coupling between 17O (I = 5/2) and 99Tc (I = 9/2) nuclear spins has been observed (1J99Tc,17O = 80 +/- 5 Hz). The substitution of water in fac-[(CO)3M(H2O)3]+ by dimethyl sulfide (DMS) is slightly faster than that by CH3CN: 3 times faster for Mn, 1.5 times faster for Tc, and 1.2 times faster for Re. The pressure dependence behavior is different for Mn and Re. For Mn, the change in volume to reach the transition state is always clearly positive (water exchange, CH3CN, DMS), indicating an Id mechanism. In the case of Re, an Id/Ia changeover is assigned on the basis of reaction profiles with a strong volume maximum for pyrazine and a minimum for DMS as the entering ligand.

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“…It is our aim to initiate a programme which allows the thermal study of metal carbonyls through techniques such as TG and DSC to complement other established methods such as calorimetry [28,29], flash photolysis [30], IR [31], NM R [17][18][19] and mass spectroscopic techniques [32] which are used extensively in kinetic and mechanistic investigations. We wish to report as part of a series of thermal studies on organometallic complexes, the monosubstituted pentacarbonyl M(CO)5(dppm ) where M = Cr, Mo, and W. The dppm in these molecules functions as a monodentate ligand despite its bidentate potential.…”

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Thermal degradation of the transition metal carbonyl complexes

Chan¹,

Hor²,

Chiam³

et al. 1987

Journal of Thermal Analysis

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Kinetic study of oxygen exchange in hexakis(carbonyl)rhenium hexafluorophosphate with water (oxygen-17)

Cited by 13 publications

References 1 publication

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

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

Relevance of the Ligand Exchange Rate and Mechanism offac-[(CO)₃M(H₂O)₃]⁺(M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals

Thermal degradation of the transition metal carbonyl complexes

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Kinetic study of oxygen exchange in hexakis(carbonyl)rhenium hexafluorophosphate with water (oxygen-17)

Cited by 13 publications

References 1 publication

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

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

Relevance of the Ligand Exchange Rate and Mechanism offac-[(CO)3M(H2O)3]+(M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals

Thermal degradation of the transition metal carbonyl complexes

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Relevance of the Ligand Exchange Rate and Mechanism offac-[(CO)₃M(H₂O)₃]⁺(M = Mn, Tc, Re) Complexes for New Radiopharmaceuticals