Imido transfer from bis(imido)ruthenium(VI) porphyrins to hydrocarbons: Effect of imido substituents, C-H bond dissociation energies, and Ru VI/V reduction potentials

Article abstract of DOI:10.1021/ja0542789

[Ru^VI(TMP)(NSO₂R)₂] (SO₂R = Ms, Ts, Bs, Cs, Ns; R = p-C₆H₄OMe, p-C₆H ₄Me, C₆H₅, p-C₆H₄-Cl, p-C₆H₄NO₂, respectively) and [Ru ^VI(Por)(NTs)₂] (Por = 2,6-Cl₂TPP, F ₂₀-TPP) were prepared by the reactions of [Ru^II(Por)(CO)] with Phl=NSO₂R in CH₂Cl₂. These complexes exhibit reversible Ru^VI/V couple with E_1/2 = -0.41 to -0.12 V vs Cp₂Fe^+/10 and undergo imido transfer reactions with styrenes, norbornene, cis-cyclooctene, indene, ethylbenzenes, cumene, 9,10-dihydroanthracene, xanthene, cyclohexene, toluene, and tetrahydrofuran to afford aziridines or amides in up to 85% yields. The second-order rate constants (k₂) of the aziridination/amidation reactions at 298 K were determined to be (2.6 ± 0.1) × 10^-5 to 14.4 ± 0.6 dm³ mol^-1 s^-1, which generally increase with increasing Ru^VI/V reduction potential of the imido complexes and decreasing C-H bond dissociation energy (BDE) of the hydrocarbons. A linear correlation was observed between log K (K is the k₂ value divided by the number of reactive hydrogens) and BDE and between log k₂ and E_1/2(Ru^VI/V); the linearity in the former case supports a H-atom abstraction mechanism. The amidation by [Ru^VI(TMP)(NNs) ₂] reverses the thermodynamic reactivity order cumene > ethylbenzene/toluene, with K(3° C-H)/K(2° C-H) = 0.2 and K(3° C-H)/K(1° C-H) = 0.8.

Full text of DOI:10.1021/ja0542789

Published on Web 11/02/2005
Imido Transfer from Bis(imido)ruthenium(VI) Porphyrins to
Hydrocarbons: Effect of Imido Substituents, C-H Bond
Dissociation Energies, and RuVI/V Reduction Potentials
Sarana Ka-Yan Leung, Wai-Man Tsui, Jie-Sheng Huang,* Chi-Ming Che,*
Jiang-Lin Liang, and Nianyong Zhu
Contribution from the Department of Chemistry and Open Laboratory of Chemical Biology of
the Institute of Molecular Technology for Drug DiscoVery and Synthesis,
The UniVersity of Hong Kong, Pokfulam Road, Hong Kong
Received June 29, 2005; E-mail: cmche@hku.hk; jshuang@hku.hk
Abstract: [RuVI(TMP)(NSO2R)2] (SO2R ) Ms, Ts, Bs, Cs, Ns; R ) p-C6H4OMe, p-C6H4Me, C6H5, p-C6H4-
Cl, p-C6H4NO2, respectively) and [RuVI(Por)(NTs)2] (Por ) 2,6-Cl2TPP, F20-TPP) were prepared by the
reactions of [RuII(Por)(CO)] with PhIdNSO2R in CH2Cl2. These complexes exhibit reversible RuVI/V couple
with E1/2 ) -0.41 to -0.12 V vs Cp2Fe+/0 and undergo imido transfer reactions with styrenes, norbornene,
cis-cyclooctene, indene, ethylbenzenes, cumene, 9,10-dihydroanthracene, xanthene, cyclohexene, toluene,
and tetrahydrofuran to afford aziridines or amides in up to 85% yields. The second-order rate constants
(k2) of the aziridination/amidation reactions at 298 K were determined to be (2.6 ( 0.1) × 10-5 to 14.4 (
0.6 dm3 mol-1 s-1, which generally increase with increasing RuVI/V reduction potential of the imido complexes
and decreasing C-H bond dissociation energy (BDE) of the hydrocarbons. A linear correlation was observed
between log k′ (k′ is the k2 value divided by the number of reactive hydrogens) and BDE and between log
k2 and E1/2(RuVI/V); the linearity in the former case supports a H-atom abstraction mechanism. The amidation
by [RuVI(TMP)(NNs)2] reverses the thermodynamic reactivity order cumene > ethylbenzene/toluene, with
k′(3° C-H)/k′(2° C-H) ) 0.2 and k′(3° C-H)/k′(1° C-H) ) 0.8.
Introduction
The chemistry of metal-catalyzed aziridination of alkenes and
amidation of C-H bonds using iminoiodane (PhIdNSO2R),
“PhI(OAc)2 + NH2SO2R”, or “PhIO + NH2SO2R” as nitrogen
source, as depicted in reactions 1 and 2 (Figure 1), has expanded
dramatically in the past decade.1-26 Such catalytic processes
are increasingly attractive as a synthetic route to aziridines or
amides. The widely believed involvement of reactive metal
imido (or nitrene) intermediates (M)NSO2R species) in reac-
(1) (a) Breslow, R.; Gellman, S. H. J. Chem. Soc., Chem. Commun. 1982,
1400. (b) Breslow, R.; Gellman, S. H. J. Am. Chem. Soc. 1983, 105, 6728.
(c) Yang, J.; Weinberg, R.; Breslow, R. Chem. Commun. 2000, 531.
(2) (a) Mansuy, D.; Mahy, J.-P.; Dureault, A.; Bedi, G.; Battioni, P. J. Chem.
Soc., Chem. Commun. 1984, 1161. (b) Mahy, J.-P.; Bedi, G.; Battioni, P.;
Mansuy, D. J. Chem. Soc., Perkin Trans. 2 1988, 1517. (c) Mahy, J. P.;
Bedi, G.; Battioni, P.; Mansuy, D. Tetrahedron Lett. 1988, 29, 1927. (d)
Mahy, J. P.; Bedi, G.; Battioni, P.; Mansuy, D. New J. Chem. 1989, 13,
651.
(3) (a) Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J. Org. Chem. 1991, 56,
6744. (b) Evans, D. A.; Faul, M. M.; Bilodeau, M. T.; Anderson, B. A.;
Barnes, D. M. J. Am. Chem. Soc. 1993, 115, 5328. (c) Evans, D. A.; Faul,
M. M.; Bilodeau, M. T. J. Am. Chem. Soc. 1994, 116, 2742.
(4) Li, Z.; Quan, R. W.; Jacobsen, E. N. J. Am. Chem. Soc. 1995, 117, 5889.
(5) (a) Mu¨ller, P.; Baud, C.; Jacquier, Y.; Moran, M.; Na¨geli, I. J. Phys. Org.
Chem. 1996, 9, 341. (b) Mu¨ller, P.; Baud, C.; Jacquier, Y. Tetrahedron
1996, 52, 1543. (c) Na¨geli, I.; Baud, C.; Bernardinelli, G.; Jacquier, Y.;
Moran, M.; Mu¨ller, P. HelV. Chim. Acta 1997, 80, 1087. (d) Mu¨ller, P.;
Baud, C.; Na¨geli, I. J. Phys. Org. Chem. 1998, 11, 597. (e) Mu¨ller, P.;
Baud, C.; Jacquier, Y. Can. J. Chem. 1998, 76, 738. (f) Mu¨ller, P.; Fruit,
C. Chem. ReV. 2003, 103, 2905. (g) Fruit, C.; Mu¨ller, P. Tetrahedron:
Asymmetry 2004, 15, 1019. (h) Fruit, C.; Mu¨ller, P. HelV. Chim. Acta 2004,
87, 1607.
Figure 1. Metal-catalyzed aziridination of alkenes and amidation of C-H
bonds using iminoiodane (PhIdNSO2R), “PhI(OAc)2 + NH2SO2R”, or
“PhIO + NH2SO2R” as nitrogen source. These processes are proposed to
involve M)NSO2R intermediates.
tions 1 and 2 places great importance on the investigation of
their chemistry, particularly with regard to imido transfer
(8) (a) So¨dergren, M. J.; Alonso, D. A.; Andersson, P. G. Tetrahedron:
Asymmetry 1997, 8, 3563. (b) So¨dergren, M. J.; Alonso, D. A.; Bedekar,
A. V.; Andersson, P. G. Tetrahedron Lett. 1997, 38, 6897. (c) Bertilsson,
S. K.; Tedenborg, L.; Alonso, D. A.; Andersson, P. G. Organometallics
1999, 18, 1281. (d) Brandt, P.; So¨dergren, M. J.; Andersson, P. G.; Norrby,
P.-O. J. Am. Chem. Soc. 2000, 122, 8013.
(6) (a) Nishikori, H.; Katsuki, T. Tetrahedron Lett. 1996, 37, 9245. (b)
Kohmura, Y.; Katsuki, T. Tetrahedron Lett. 2001, 42, 3339.
(7) Harm, A. M.; Knight, J. G.; Stemp, G. Tetrahedron Lett. 1996, 37, 6189.
9
10.1021/ja0542789 CCC: $30.25 © 2005 American Chemical Society
J. AM. CHEM. SOC. 2005, 127, 16629-16640
16629

A R T I C L E S
Leung et al.
reactions with alkenes and imido insertion into C-H bonds,
which could provide valuable insight into the mechanism of
metal-catalyzed aziridination/amidation reactions.
limiting formation of carboradical intermediates in the imido
transfer reactions.30b
To gain further insight into the mechanism of alkene
aziridination and C-H bond amidation, it would be of interest
to examine the effect of reduction potentials of metal imido
complexes and C-H bond dissociation energies (BDEs) of
hydrocarbons on the reaction rate constants. Such driVing force
dependence of rate constants, to our knowledge, has not hitherto
been reported in metal imido chemistry, nor haVe electrochemi-
cal studies on reactiVe M)NSO2R complexes been reported in
the literature. In metal oxo chemistry, Bruice,35a Che,35b and
co-workers examined the effect of reduction potentials of metal
oxo complexes on the rate constants of alkene epoxidation
reactions; Mayer and co-worker demonstrated the importance
of BDE to the reaction rate constants of C-H bond oxidations.36
In view of the analogy between oxo and imido groups, an
important issue to be addressed is whether the results obtained
for metal oxo complexes can be extended to metal imido
complexes.
On the other hand, imido groups have tunable steric hindrance
and can be much bulkier than oxo groups, rendering C-H bond
amidation by metal imido complexes to encounter larger steric
hindrance than C-H bond oxidation by metal oxo complexes.
Consequently, by replacing an oxo group with an imido group,
it may be possible to reverse the thermodynamic reactivity order
3° > 2° > 1° C-H bonds without the need of altering the steric
hindrance of auxiliary ligands. This unique approach to reversal
of the relative reactivity of 3° versus 2° versus 1° C-H bonds
has rarely been investigated.30b
While a variety of iron,1,2,12,22 manganese,1,2,6,12 cop-
per,3,4,7-9,11,13-17,20,23-26 ruthenium,10a-g,j,k dirhodium,5,10h,i,18,19
and silver21 complexes have been demonstrated to be efficient
catalysts for reactions 1 and/or 2, isolation or spectroscopic
identification of putative M)NSO2R species remains a serious
challenge. In fact, well characterized M)NSO2R complexes are
sparse, including [MoVIOn(NTs)2-n(Et2dtc)2] (n ) 0, 1),27,28a,b
[Tp′(CO)2W(NTs)][I3],28c,29 [RuVI(Por)(NTs)2],10f,30 and [OsVI-
(Por)(NTs)2],31 of which only [RuVI(Por)(NTs)2] can undergo
alkene aziridination and C-H bond amidation.10f,30
Imido transfer reactions with alkenes have also been known
for a few other types of metal imido complexes, including
[OsVIIIO4-n(NBut)n] (n ) 1-3)32 and [OsVIIIO3(NR)]32c for
oxyamination or diamination of alkenes, [MnV(TMP)(NCOCF3)-
(OOCCF3)] for aziridination of cyclooctene,28d,33 and [(dtbpe)-
NidN(2,6-Pri2C6H3)] for aziridination of ethylene.28e,34
Direct mechanistic studies on alkene aziridination and C-H
bond amidation reactions of reactive metal imido complexes
are rare. In a previous work,30b the reactions of [RuVI(TPP)-
(NTs)2] 28f with styrenes, norbornene, cyclohexene, cyclooctene,
ethylbenzenes, and cumene were examined through kinetic
studies. The observed effect of 1e oxidation potential of alkenes
and the effect of para-substituents of styrenes or ethylbenzenes
on rate constants, along with kinetic isotope effect, support rate-
(9) (a) D´ıaz-Requejo, M. M.; Pe´rez, P. J.; Brookhart, M.; Templeton, J. L.
Organometallics 1997, 16, 4399. (b) D´ıaz-Requejo, M. M.; Belderra´ın, T.
R.; Nicasio, M. C.; Trofimenko, S.; Pe´rez, P. J. J. Am. Chem. Soc. 2003,
125, 12078. (c) Mairena, M. A.; D´ıaz-Requejo, M. M.; Belderra´ın, T. R.;
Nicasio, M. C.; Trofimenko, S.; Pe´rez, P. J. Organometallics 2004, 23,
253.
(10) (a) Lai, T.-S.; Kwong, H.-L.; Che, C.-M.; Peng, S.-M. Chem. Commun.
1997, 2373. (b) Au, S.-M.; Zhang, S.-B.; Fung, W.-H.; Yu, W.-Y.; Che,
C.-M.; Cheung, K.-K. Chem. Commun. 1998, 2677. (c) Zhou, X.-G.; Yu,
X.-Q.; Huang, J.-S.; Che, C.-M. Chem. Commun. 1999, 2377. (d) Yu, X.-
Q.; Huang, J.-S.; Zhou, X.-G.; Che, C.-M. Org. Lett. 2000, 2, 2233. (e)
Au, S.-M.; Huang, J.-S.; Che, C.-M.; Yu, W.-Y. J. Org. Chem. 2000, 65,
7858. (f) Liang, J.-L.; Huang, J.-S.; Yu, X.-Q.; Zhu, N.; Che, C.-M. Chem.s
Eur. J. 2002, 8, 1563. (g) Liang, J.-L.; Yuan, S.-X.; Huang, J.-S.; Yu, W.-
Y.; Che, C.-M. Angew. Chem., Int. Ed. 2002, 41, 3465. (h) Liang, J.-L.;
Yuan, S.-X.; Chan, P. W. H.; Che, C.-M. Org. Lett. 2002, 4, 4507. (i)
Liang, J.-L.; Yuan, S.-X.; Chan, P. W. H.; Che, C.-M. Tetrahedron Lett.
2003, 44, 5917. (j) Liang, J.-L.; Yuan, S.-X.; Huang, J.-S.; Che, C.-M. J.
Org. Chem. 2004, 69, 3610. (k) He, L.; Chan, P. W. H.; Tsui, W.-M.; Yu,
W.-Y.; Che, C.-M. Org. Lett. 2004, 6, 2405.
(11) (a) Dauban, P.; Dodd, R. H. Tetrahedron Lett. 1998, 39, 5739. (b) Dauban,
P.; Dodd, R. H. J. Org. Chem. 1999, 64, 5304. (c) Dauban, P.; Dodd, R.
H. Org. Lett. 2000, 2, 2327. (d) Dauban, P.; Sanie`re, L.; Tarrade, A.; Dodd,
R. H. J. Am. Chem. Soc. 2001, 123, 7707. (e) Duran, F.; Leman, L.; Ghini,
A.; Burton, G.; Dauban, P.; Dodd, R. H. Org. Lett. 2002, 4, 2481. (f)
Dauban, P.; Dodd, R. H. Synlett 2003, 1571. (g) Sanie`re, L.; Leman, L.;
Bourguignon, J.-J.; Dauban, P.; Dodd, R. H. Tetrahedron 2004, 60, 5889.
(12) Simonato, J.-P.; Pe´caut, J.; Scheidt, W. R.; Marchon, J.-C. Chem. Commun.
1999, 989.
(13) (a) Halfen, J. A.; Hallman, J. K.; Schultz, J. A.; Emerson, J. P.
Organometallics 1999, 18, 5435. (b) Halfen, J. A.; Uhan, J. M.; Fox, D.
C.; Mehn, M. P.; Que, L., Jr. Inorg. Chem. 2000, 39, 4913. (c) Halfen, J.
A.; Fox, D. C.; Mehn, M. P.; Que, L., Jr. Inorg. Chem. 2001, 40, 5060.
(14) Adam, W.; Roschmann, K. J.; Saha-Mo¨ller, C. R. Eur. J. Org. Chem. 2000,
557.
(19) (a) Padwa, A.; Stengel, T. Org. Lett. 2002, 4, 2137. (b) Padwa, A.; Flick,
A. C.; Leverett, C. A.; Stengel, T. J. Org. Chem. 2004, 69, 6377.
(20) Comba, P.; Merz, M.; Pritzkow, H. Eur. J. Inorg. Chem. 2003, 1711.
(21) (a) Cui, Y.; He, C. J. Am. Chem. Soc. 2003, 125, 16202. (b) Cui, Y.; He,
C. Angew. Chem., Int. Ed. 2004, 43, 4210.
(22) Avenier, F.; Latour, J.-M. Chem. Commun. 2004, 1544.
(23) Xu, J.; Ma, L.; Jiao, P. Chem. Commun. 2004, 1616.
(24) Leca, D.; Toussaint, A.; Mareau, C.; Fensterbank, L.; Lacoˆte, E.; Malacria,
M. Org. Lett. 2004, 6, 3573.
(25) Han, H.; Bae, I.; Yoo, E. J.; Lee, J.; Do, Y.; Chang, S. Org. Lett. 2004, 6,
4109.
(26) Amisial, L. D.; Dai, X.; Kinney, R. A.; Krishnaswamy, A.; Warren, T. H.
Inorg. Chem. 2004, 43, 6537.
(27) Harlan, E. W.; Holm, R. H. J. Am. Chem. Soc. 1990, 112, 186.
(28) Abbreviations: (a) Ts ) p-toluenesulfonyl; (b) Et2dtc ) N,N-diethyldithio-
carbamate; (c) Tp′ ) hydridotris(3,5-dimethyl-1-pyrazolyl)borate; (d) TMP
) 5,10,15,20-tetramesitylporphyrinato(2-); (e) dtbpe ) 1,2-bis(di-tert-
butylphosphino)ethane; (f) TPP ) 5,10,15,20-tetraphenylporphyrinato-
(2-); (g) Ms ) p-methoxybenzenesulfonyl; (h) Bs ) benzenesulfonyl; (i)
Cs ) p-chlorobenzenesulfonyl; (j) Ns ) p-nitrobenzenesulfonyl; (k) 2,6-
Cl2TPP ) 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinato(2-); (l) F20-
TPP ) 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-); (m) TTP
) 5,10,15,20-tetrakis(p-tolyl)porphyrinato(2-); (n) 4-Cl-TPP ) 5,10,15,-
20-tetrakis(p-chlorophenyl)porphyrinato(2-); (o) 4-OMe-TPP ) 5,10,15,-
20-tetrakis(p-methoxyphenyl)porphyrinato(2-); (p) OEP ) 2,3,7,8,12,13,-
17,18-octaethylporphyrinato(2-); (q) Por* ) 5,10,15,20-tetrakis{(1S,4R,5R,
8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl}por-
phyrinato(2-).
(29) Pe´rez, P. J.; White, P. S.; Brookhart, M.; Templeton, J. L. Inorg. Chem.
1994, 33, 6050.
(30) (a) Au, S.-M.; Fung, W.-H.; Cheng, M.-C.; Che, C.-M.; Peng, S.-M. Chem.
Commun. 1997, 1655. (b) Au, S.-M.; Huang, J.-S.; Yu, W.-Y.; Fung, W.-
H.; Che, C.-M. J. Am. Chem. Soc. 1999, 121, 9120.
(15) Llewellyn, D. B.; Adamson, D.; Arndtsen, B. A. Org. Lett. 2000, 2, 4165.
(16) (a) Sanders, C. J.; Gillespie, K. M.; Bell, D.; Scott, P. J. Am. Chem. Soc.
2000, 122, 7132. (b) Gillespie, K. M.; Crust, E. J.; Deeth, R. J.; Scott, P.
Chem. Commun. 2001, 785. (c) Gillespie, K. M.; Sanders, C. J.;
O’Shaughnessy, P.; Westmoreland, I.; Thickitt, C. P.; Scott, P. J. Org.
Chem. 2002, 67, 3450.
(17) Taylor, S.; Gullick, J.; McMorn, P.; Bethell, D.; Page, P. C. B.; Hancock,
F. E.; King, F.; Hutchings, G. J. J. Chem. Soc., Perkin Trans. 2 2001,
1714.
(31) Au, S.-M.; Fung, W.-H.; Huang, J.-S.; Cheung, K.-K.; Che, C.-M. Inorg.
Chem. 1998, 37, 6564.
(32) Selected examples: (a) Sharpless, K. B.; Patrick, D. W.; Truesdale, L. K.;
Biller, S. A. J. Am. Chem. Soc. 1975, 97, 2305. (b) Chong, A. O.; Oshima,
K.; Sharpless, K. B. J. Am. Chem. Soc. 1977, 99, 3420. (c) Patrick, D. W.;
Truesdale, L. K.; Biller, S. A.; Sharpless, K. B. J. Org. Chem. 1978, 43,
2628. (d) Mun˜iz, K.; Nieger, M.; Mansikkama¨ki, H. Angew. Chem., Int.
Ed. 2003, 42, 5958.
(18) (a) Espino, C. G.; Wehn, P. M.; Chow, J.; Du Bois, J. J. Am. Chem. Soc.
2001, 123, 6935. (b) Guthikonda, K.; Du Bois, J. J. Am. Chem. Soc. 2002,
124, 13672. (c) Wehn, P. M.; Lee, J.; Du Bois, J. Org. Lett. 2003, 5, 4823.
(d) Fiori, K. W.; Fleming, J. J.; Du Bois, J. Angew. Chem., Int. Ed. 2004,
43, 4349. (e) Espino, C. G.; Fiori, K. W.; Kim, M.; Du Bois, J. J. Am.
Chem. Soc. 2004, 126, 15378.
(33) Groves, J. T.; Takahashi, T. J. Am. Chem. Soc. 1983, 105, 2073.
(34) Waterman, R.; Hillhouse, G. L. J. Am. Chem. Soc. 2003, 125, 13350.
(35) (a) Garrison, J. M.; Ostovic´, D.; Bruice, T. C. J. Am. Chem. Soc. 1989,
111, 4960. (b) Che, C.-M.; Li, C.-K.; Tang, W.-T.; Yu, W.-Y. J. Chem.
Soc., Dalton Trans. 1992, 3153.
(36) Bryant, J. R.; Mayer, J. M. J. Am. Chem. Soc. 2003, 125, 10351.
9
16630 J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005

Imido Transfer from Bis(imido)ruthenium(VI) to Hydrocarbons
A R T I C L E S
Scheme 1
It was previously reported that the efficiency of dirhodium-
or copper-catalyzed alkene aziridination with PhIdNSO2R5e,8a,b
and the product yields in ruthenium-, manganese-, dirhodium-,
Previous preparation of [RuVI(Por)(NTs)2] from reaction 3
led to the isolation of [RuVI(Por)(NTs)2] with Por ) TPP,30b
TTP,28m,30b 4-Cl-TPP,28n,30b 4-OMe-TPP,28°,30b OEP,28p,30b and
Por*.10f,28q The applicability of this reaction to a wide variety
of porphyrin ligands and different SO2R groups is remarkable,
which demonstrates the generality of this synthetic route to bis-
(arenesulfonylimido)ruthenium(VI) porphyrins.
The above [RuVI(Por)(NSO2R)2] complexes are diamagnetic
and have the following spectral features in common: (i) the
mass spectra each show a prominent peak attributable to the
parent ion [M]+; (ii) the NMR pyrrolic proton (Hâ) signals and
the IR “oxidation state marker” bands30b are comparable to those
of the corresponding [RuVI(Por)O2];37 (iii) the axial SO2R groups
give substantially upfield shifted 1H NMR signals compared to
those in NH2SO2R; and (iv) the UV-vis spectra exhibit red
shifted Soret and â bands compared with the corresponding
[RuII(Por)(CO)] counterpart.
For [RuVI(TMP)(NSO2R)2], the Hâ signals (δ ) 8.67-8.71
ppm) and the â bands (535-536 nm) do not significantly vary
among the R groups p-C6H4OMe, p-C6H4Me, C6H5, p-C6H4Cl,
and p-C6H4NO2. A small blue shift upon increasing electron-
withdrawing strength of the R group is reflected from the Soret
bands at 422, 421, 420, 419, and 416 nm for R ) p-C6H4OMe,
p-C6H4Me, C6H5, p-C6H4Cl, and p-C6H4NO2, respectively.
Possibly, such a blue shift arises from a decrease in π-donor
strength of the imido ligand.
In the case of [RuVI(Por)(NTs)2], the Hâ chemical shift
increases along TMP f 2,6-Cl2TPP f F20-TPP ligands (δ )
8.67, 8.83, 9.01 ppm, respectively). The Soret and â bands of
[RuVI(2,6-Cl2TPP)(NTs)2] (422 and 534 nm) are similar to,
whereas those of [RuVI(F20-TPP)(NTs)2] (418 and 528 nm) are
or copper-catalyzed aziridination/amidation with “PhI(OAc)2 +
11d-g
NH2SO2R”10e-g,18 or “PhIO + NH2SO2R”,
markedly
depend on the electronic properties of the R groups. However,
the origin of these observations is unclear. A possible reason is
the tuning of the reactivity of the putative “M)NSO2R” species
by R groups. Therefore, examination of the effect of imido
substituents on the rate constants of the alkene aziridination and
C-H bond amidation by isolable metal imido complexes is of
importance.
In the present work, we report the preparation of a series of
[RuVI(Por)(NSO2R)2] complexes bearing various SO2R groups
and porphyrin ligands, along with their reactivities and elec-
trochemistry. By varying the substituent R or porphyrin ligand
of [RuVI(Por)(NSO2R)2], a tuning of the E1/2(RuVI/V) value over
a range of -0.41 to -0.12 V vs Cp2Fe+/0 was observed. The
effect of C-H bond dissociation energies, RuVI/V reduction
potentials, and imido substituents on reaction rate constants,
together with the relative reactivity of 3° versus 2° versus 1°
C-H bonds in their amidation by [RuVI(Por)(NSO2R)2], has
been examined.
Results
Synthesis and Characterization. Scheme 1 depicts the new
RudNSO2R complexes prepared in this work. Reaction of [RuII-
28d
(TMP)(CO)]
with 4 equiv of PhIdNSO2R, wherein SO2R
) Ms,28g Ts,28a Bs,28h Cs,28i and Ns,28j afforded the correspond-
ing [RuVI(TMP)(NSO2R)2] (reaction 3 in Scheme 1). A similar
reaction of [RuII(Por)(CO)] for Por ) 2,6-Cl2TPP28k and F20-
TPP28l with PhIdNTs in CH2Cl2 gave [RuVI(2,6-Cl2TPP)(NTs)2]
and [RuVI(F20-TPP)(NTs)2]. All these imido complexes were
isolated in about 70% yields.
(37) (a) Groves, J. T.; Quinn, R. Inorg. Chem. 1984, 23, 3844. (b) Leung, W.-
H.; Che, C.-M. J. Am. Chem. Soc. 1989, 111, 8812. (c) Ho, C.; Leung,
W.-H.; Che, C.-M. J. Chem. Soc., Dalton Trans. 1991, 2933.
9
J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005 16631

A R T I C L E S
Leung et al.
Table 1. Half-Wave Potentials (V vs Cp2Fe+/0) of
blue shifted from, the corresponding bands of [RuVI(TMP)-
(NTs)2]. These phenomena are reminiscent of those observed
for the [RuII(Por)(CO)] counterparts.
[RuVI(Por)(NSO2R)2] in CH2Cl2 Containing 0.1 M [NBun4]PF6 (Scan
Rate ) 100 mV s-1
)
reduction
oxidation
III
1
[RuVI(F20-TPP)(NTs)2] exhibits almost identical H NMR
complex
I
II
spectrum to that of [OsVI(F20-TPP)(NTs)2],38 the latter has been
structurally characterized by X-ray crystallography.38 19F NMR
spectrum of [RuVI(F20-TPP)(NTs)2] (δ ) -135.5, -150.7,
-161.1 ppm for the o-, p-, m-F of the meso-pentafluorophenyl
groups, respectively) reveals that the two o-F (and m-F as well)
of each meso-pentafluorophenyl group have the same chemical
shift, consistent with the symmetric axial coordination in the
complex.
[RuVI(TMP)(NMs)2]
[RuVI(TMP)(NTs)2]
[RuVI(TMP)(NBs)2]
[RuVI(TMP)(NCs)2]
[RuVI(TMP)(NNs)2]
[RuVI(TPP)(NTs)2]
-0.41
-0.38
-0.34
-0.27
-0.12
-0.27
-0.34
-0.12
-1.51
-1.54
-1.58
-1.46
-1.61
-1.45
-1.27
-1.12
0.61
0.62
0.67
0.69
0.75
0.69
0.80
1.18
[RuVI(2,6-Cl2TPP)(NTs)2]
[RuVI(F20-TPP)(NTs)2]
Stability. Like previously reported [RuVI(Por)(NTs)2],30b the
[RuVI(Por)(NSO2R)2] prepared in this work are stable for at least
several hours in highly purified CH2Cl2 solution at room
temperature under an inert atmosphere. The stability of these
imido complexes in aerobic solutions is considerably lower and
increases with the electron-donating and/or sterically demanding
strength of the porphyrin ligand and the electron-donating
strength of the R groups. For example, in CH2Cl2 solution open
to air at room temperature, [RuVI(F20-TPP)(NTs)2], [RuVI(TPP)-
(NTs)2], [RuVI(TMP)(NNs)2], [RuVI(TMP)(NTs)2], and [RuVI-
(TMP)(NMs)2] (concentrations ≈5 × 10-4 M) exhibited ap-
preciable decomposition after about 0.25, 0.5, 1.5, 3, and 3.5
h, respectively, as revealed by UV-vis spectroscopy. Attempts
to isolate [RuVI(F20-TPP)(NNs)2] in a pure form have not been
successful. This complex, which features a Hâ signal (δ ) 9.20
ppm) and Soret and â bands (413 and 528 nm, respectively)
comparable to those of [RuVI(F20-TPP)(NTs)2] and exhibits the
parent ion cluster peak at m/z 1474, could be generated in situ
from the reaction of [RuII(F20-TPP)(CO)] with PhIdNNs in CH2-
Cl2.
Upon prolonged standing in aerobic solution, [RuVI(TMP)-
(NSO2R)2] gradually converted into nitrido complexes [RuVI-
(TMP)(N)(NHSO2R)] (like the conversion of [RuVI(TMP)-
(NTs)2] to [RuVI(TMP)(N)(NHTs)] 39a), different from the
formation of nitrosyl ruthenium porphyrins in an aerobic solution
of [RuVI(Por)(O)(NBut)] upon standing.39b For the other [RuVI-
(Por)(NSO2R)2] complexes, their degradation products in aerobic
solutions have not been identified yet.
Electrochemistry. The cyclic voltammograms of [RuVI-
(TMP)(NSO2R)2] (SO2R ) Ms, Ts, Bs, Cs, Ns) and [RuVI(Por)-
(NTs)2] (Por ) TPP, 2,6-Cl2TPP, F20-TPP) in CH2Cl2 solutions
each exhibit two reversible or quasi-reversible reduction couples
I and II, together with one reversible oxidation couple III; the
corresponding half-wave potentials (vs Cp2Fe+/0) are listed in
Table 1, and a typical cyclic voltammogram is depicted in Figure
2a. There are also two irreversible waves, IV and V, in each of
the cyclic voltammograms. However, if the scan was reversed
at the potential immediately after the cathodic wave of the first
reduction (I), the irreversible wave V disappeared (Figure 2b),
regardless of whether the initial scan was in the anodic or
cathodic direction. It is likely that the irreversible wave V stems
from the species generated by the irreversible reduction IV.
The cyclic voltammogram of [RuVI(TMP)O2] was also
recorded, which is shown in Figure 2c for comparison. This
Figure 2. Cyclic voltammograms of [RuVI(TMP)(NMs)2] (a and b) and
[RuVI(TMP)O2] (c) in CH2Cl2 at a scan rate of 100 mV s-1. The potential
E is versus 0.1 M Ag/AgNO3 in MeCN.
complex exhibits one reversible oxidation couple similar to that
of [RuVI(TMP)(NSO2R)2]. However, the reduction of [RuVI-
(TMP)O2] is irreversible and occurs at a potential markedly more
cathodic than those of [RuVI(TMP)(NSO2R)2].
Reactions with Hydrocarbons. (i) Product Analysis. We
examined the stoichiometric reactions of [RuVI(TMP)(NSO2R)2]
(SO2R ) Ms, Ts, Bs, Cs, Ns) and [RuVI(Por)(NTs)2] (Por )
2,6-Cl2TPP, F20-TPP) with a series of hydrocarbons in CH2Cl2
containing pyrazole (Hpz, 2% w/w).40 These reactions, like those
of [RuVI(TPP)(NTs)2],30b resulted in alkene aziridination or C-H
bond amidation, accompanied by formation of [RuIV(Por)-
(NHSO2R)(pz)] (reactions 4 and 5 in Schemes 2 and 3). Several
(40) In the presence of pyrazole, the reactions of hydrocarbons with the [RuVI
-
(Por)(NSO2R)2] reported in this work are simple processes, as revealed by
the appearance of isosbestic points in the UV-vis spectral changes during
the reactions (no isosbestic points were observed in the absence of pyrazole).
Because pyrazole itself was not found to react with these imido complexes
on the time scale of their reactions with hydrocarbons, its role here could
be the trapping of transient intermediates generated from the attack of [RuVI-
(Por)(NSO2R)2] by hydrocarbons.
(38) Li, Y.; Huang, J.-S.; Zhou, Z.-Y.; Che, C.-M. J. Am. Chem. Soc. 2001,
123, 4843.
(39) (a) Leung, S. K.-Y.; Huang, J.-S.; Liang, J.-L.; Che, C.-M.; Zhou, Z.-Y.
Angew. Chem., Int. Ed. 2003, 42, 340. (b) Huang, J.-S.; Sun, X.-R.; Leung,
S. K.-Y.; Cheung, K.-K.; Che, C.-M. Chem.sEur. J. 2000, 6, 334.
9
16632 J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005

Imido Transfer from Bis(imido)ruthenium(VI) to Hydrocarbons
A R T I C L E S
Scheme 2
Scheme 3
of the [RuIV(Por)(NHSO2R)(pz)] complexes, namely, [RuIV(F20-
TPP)(NHTs)(pz)] and [RuIV(TMP)(NHSO2R)(pz)] (SO2R ) Ms,
Cs, Ns), were isolated, and the structure of [RuIV(TMP)(NHCs)-
(pz)] was determined by X-ray crystallography (see Table 2 and
Figure 3).
An interesting feature in the structure of [RuIV(TMP)(NHCs)-
(pz)] is the large dihedral angle between the axial phenyl plane
and the porphyrin plane (about 55°), probably resulting from a
steric interaction between the amido phenyl group and the
porphyrin meso-mesityl groups (see the space-filling structure
in the upper right corner of Figure 3). In previously reported
crystal structures of [RuIV(Por)(NHTs)(pz)] (Por ) TPP,30a OEP
30b) and [OsVI(Por)(NTs)2] (Por ) TPP,31 F20-TPP38) bearing
sterically unencumbered porphyrin ligands, such planes are
9
J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005 16633

A R T I C L E S
Leung et al.
Table 2. Crystal Data and Structure Refinement for
[RuIV(TMP)(NHCs)(pz)]‚5H2O
Table 3. Stoichiometric Imido Transfer Reactions of
[RuVI(Por)(NSO2R)2] with Hydrocarbons in CH2Cl2 Containing
Pyrazole (2% w/w) at 298 K
formula
Mr
crystal system
space group
a, Å
C65H60ClN7O2SRu‚5H2O
[RuVI(Por)(NSO2R)2]
1229.87
monoclinic
P21/n
18.363(4)
19.578(4)
19.987(4)
90
113.78(3)
90
2568
6575(2)
4
1.243
0.365
1.27-25.23
14635
yield
(%)
entry
Por
SO2R
substrate
product
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
TMP
TMP
TMP
TMP
Ms
Ts
Bs
Cs
Ns
Ts
Ts
Ns
Ns
Ns
Ns
Ns
Ns
Ns
Ns
Ms
Ts
Bs
Cs
Ns
Ts
Ts
Ns
Ns
Ns
Ns
Ns
Ns
Ts
Ts
Ts
styrene
styrene
styrene
styrene
styrene
styrene
styrene
p-methylstyrene
p-methoxystyrene
p-chlorostyrene
p-trifluoromethylstyrene
p-nitrostyrene
norbornene
1
1
1
1
1
1
1
2
3
4
5
6
7
8
9
10
10
10
10
10
10
10
11
12
13
14
15
16
17
17
17
73
77
72
75
82
72
78
83
85
80
83
80
78
75
68
71
72
70
72
75
70
71
75
73
65
82
75
22
40
53
68
b, Å
c, Å
R, deg
â, deg
γ, deg
F(000)
V, Å3
TMP
2,6-Cl2TPP
F20-TPP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
2,6-Cl2TPP
F20-TPP
TMP
TMP
TMP
TMP
TMP
TMP
TPP
TMP
2,6-Cl2TPP
Z
F
calc, Mg m-3
µ(Mo KR), mm-1
θ range, deg
reflections collected
independent reflections
parameters
cis-cyclooctene
indene
5801
384
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene
p-methoxyethylbenzene
cumene
final R indices (I > 2σ(I))
R1 ) 0.09, wR2 ) 0.24
goodness-of-fit
0.98
largest diff. peak/hole, e Å-3
0.824/-0.689
almost parallel to each other (possibly due to π-π interactions).
The Ru-N(NHSO2R) distance (2.00(1) Å), N(NHSO2R)-Ru-
N(pz) angle (172.4(4)°), and S-N-Ru angle (138.6(7)°) in
[RuIV(TMP)(NHCs)(pz)] are comparable to those in [RuIV(TPP)-
(NHTs)(pz)] (2.025(11) Å, 176.2(4)°, 136.4(7)°)30a and [RuIV-
(OEP)(NHTs)(pz)] (2.020(6) Å, 173.1(2)°, 135.6(3)°).30b
After reaction with [RuVI(TMP)(NSO2R)2], the alkenes
p-XC6H4CHdCH2 (X ) H, Me, OMe, Cl, CF3, NO2), nor-
bornene, cis-cyclooctene, and indene were converted into the
corresponding aziridines 1-9 in 68-85% yields (Scheme 2 and
entries 1-15 in Table 3), whereas ethylbenzenes p-XC6H4CH2-
CH3 (X ) H, OMe), cumene, 9,10-dihydroanthracene, xanthene,
cyclohexene, and toluene were converted into the corresponding
9,10-dihydroanthracene
xanthene
cyclohexene
toluene
tetrahydrofuran
tetrahydrofuran
tetrahydrofuran
amides 10-16 in 22-82% yields (Scheme 3 and entries 16-
28 in Table 3). In almost all cases, the main byproduct was
NH2SO2R (SO2R ) Ms, Ts, Bs, Cs, or Ns, depending on the
Figure 3. Structure of [RuIV(TMP)(NHCs)(pz)] with omission of hydrogen atoms (thermal ellipsoid probability level: 30%). A space-filling representation
of the structure (with hydrogen atoms) viewed along the N2‚‚‚N4 axis is shown in the upper right corner. Selected bond distances (Å): Ru1-N1 2.037(9),
Ru1-N2 2.034(9), Ru1-N3 2.042(9), Ru1-N4 2.010(9), Ru1-N5 2.00(1), Ru1-N6 2.07(1), N5-S1 1.57(1), C57-S1 1.78(2), S1-O1 1.443(9), S1-O2
1.462(9). Selected bond angles (deg): N5-Ru1-N6 172.4(4), S1-N5-Ru1 138.6(7), C57-S1-N5 104.3(7).
9
16634 J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005

Imido Transfer from Bis(imido)ruthenium(VI) to Hydrocarbons
A R T I C L E S
Table 4. Second-Order Rate Constants (k2) for Imido Transfer
imido complex), with the total yield of the aziridine/amide and
NH2SO2R close to 100%.
Reactions of [RuVI(Por)(NSO2R)2] with Hydrocarbons in CH2Cl2
Containing Pyrazole (2% w/w) at 298 K
We also examined the reaction of [RuVI(Por)(NTs)2] (Por )
TPP, TMP, 2,6-Cl2TPP) with tetrahydrofuran, which afforded
the amidation product 17 (Scheme 3) in 40-68% yields (entries
29-31, Table 3). Amidation of tetrahydrofuran with PhIdNTs
catalyzed by [RuII(Por)(CO)] to give 17 has been reported,10d
but no corresponding amidation of this substrate by a well
characterized metal imido complex has previously been known.
(ii) Kinetic Studies. The reactions of [RuVI(TMP)(NSO2R)2]
(SO2R ) Ms, Ts, Bs, Cs, Ns) and [RuVI(Por)(NTs)2] (Por )
2,6-Cl2TPP, F20-TPP) with hydrocarbons in CH2Cl2 solution
containing pyrazole (2% w/w) were monitored by UV-vis
spectrophotometry under the conditions similar to those reported
for [RuVI(TPP)(NTs)2].30b In general, isosbestic UV-vis spectral
changes have been observed (see, for example, Figures S1-S5
in Supporting Information), with the final spectra essentially
identical to those of [RuIV(Por)(NHSO2R)(pz)]. Control experi-
ments revealed no appreciable reaction of the imido complexes
with pyrazole on the time scale of the kinetic studies.
[RuVI(Por)(NSO2R)2]
Por SO2R
k2
(dm3 mol-1 s-
)
×
103
1
entry
substrate
1
2
3
4
5
6
7
8
9
TMP
Ms
Ts
Bs
Cs
Ns
styrene
styrene
styrene
styrene
styrene
styrene
styrene
styrene
1.47 ( 0.07
3.0 ( 0.2
TMP
TMP
TMP
TMP
4.2 ( 0.2
11.5 ( 0.6
83 ( 4
2,6-Cl2TPP Ts
4.4 ( 0.2
F20-TPP
TPP
Ts
Ts
Ns
Ns
Ns
Ns
Ns
Ns
Ns
Ns
Ns
Ms
Ts
Bs
Cs
Ns
Ns
56 ( 3
9.0 ( 0.1a
141 ( 5
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
TMP
p-methylstyrene
p-methoxystyrene
p-fluorostyrene
p-chlorostyrene
p-trifluoromethylstyrene
p-nitrostyrene
norbornene
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
1520 ( 70
105 ( 5
69 ( 3
9.7 ( 0.5
7.2 ( 0.3
1.26 ( 0.06
1.32 ( 0.07
27 ( 2
cis-cyclooctene
indene
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene
ethylbenzene-d10
ethylbenzene
ethylbenzene
ethylbenzene
p-methoxyethylbenzene
cumene
0.30 ( 0.02
0.33 ( 0.02
0.53 ( 0.03
0.61 ( 0.03
2.4 ( 0.1
Pseudo-first-order rate constants, kobs, were determined by
the method described in previous work.30b The kobs values
correlate linearly with the hydrocarbon concentrations (see, for
example, Figures S6-S9 in Supporting Information). From the
kobs versus hydrocarbon concentration plots, the second-order
rate constants, k2, were determined and listed in Table 4.
0.50 ( 0.02
0.57 ( 0.03
13.8 ( 0.7
3.60 ( 0.07a
19.7 ( 0.9
0.029 ( 0.002
0.032 ( 0.001
0.048 ( 0.002
0.074 ( 0.003
0.25 ( 0.01
10.9 ( 0.5
1.5 ( 0.1a
130 ( 6
2,6-Cl2TPP Ts
F20-TPP
TPP
TMP
TMP
TMP
TMP
TMP
TMP
F20-TPP
TPP
TMP
F20-TPP
TMP
TMP
F20-TPP
TMP
F20-TPP
TMP
F20-TPP
TMP
TMP
TMP
Ts
Ts
Ns
Ms
Ts
Bs
Cs
Ns
Ts
Ts
Ns
Ts
Ns
Ns
Ts
Ns
Ts
Ns
Ts
Ms
Ts
Bs
Cs
Ns
Discussion
cumene
cumene
cumene
cumene
cumene
cumene
Metal imido complexes are important metal-ligand multiply
bonded species known in the literature.41 Despite the extensive
studies on their chemistry,41 only a few types of these
compounds have been found to react with hydrocarbons to afford
aziridines, amines, or amides (see Introduction), a reactivity
analogous to the extensively investigated oxo transfer reactions
of metal oxo complexes.42 The present work provides a number
of new metal imido complexes that are reactive toward alkene
aziridination and C-H bond amidation reactions, of which
[RuVI(TMP)(NSO2R)2] with SO2R ) Ms, Ts, Bs, Cs, and Ns
bearing p-OMe, -Me, -H, -Cl, and -NO2 substituents, respec-
tively, constitute a unique series of well-defined metal imido
complexes suitable for examining the various factors governing
imido transfer reactions. Prior to this work, the imido groups
in the well characterized M)NSO2R complexes27,29-31 are
exclusively NTs; in the cases of other metal imido complexes,32-34
the examples with para-substituted imido ligands that are
reactive toward hydrocarbons remain unreported.
9,10-dihydroanthracene
9,10-dihydroanthracene
xanthene
p-nitroethylbenzene
xanthene
600 ( 30
8100 ( 400
0.96 ( 0.05
14400 ( 600
64 ( 3
fluorene
fluorene
104 ( 4
13.6 ( 0.8
48 ( 2
0.026 ( 0.001
0.046 ( 0.002
0.074 ( 0.003
0.15 ( 0.01
0.93 ( 0.04
0.13 ( 0.01
7.1 ( 0.3
cyclohexene
cyclohexene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
TMP
TMP
2,6-Cl2TPP Ts
F20-TPP
TPP
Ts
Ts
Ms
Ts
Bs
Cs
Ns
0.48 ( 0.02
0.56 ( 0.02
0.86 ( 0.04
1.50 ( 0.08
2.30 ( 0.09
10.3 ( 0.5
1.8 ( 0.1
TMP
TMP
TMP
TMP
TMP
tetrahydrofuran
tetrahydrofuran
tetrahydrofuran
tetrahydrofuran
tetrahydrofuran
tetrahydrofuran
tetrahydrofuran
Redox Behavior of [RuVI(Por)(NSO2R)2]. Under electro-
chemical conditions, [RuVI(TMP)(NSO2R)2] with SO2R ) Ms,
Ts, Bs, Cs, and Ns undergo oxidation at E1/2 ) 0.61-0.75 V
vs Cp2Fe+/0 (Table 1). The potentials of this reversible oxidation
couple are comparable to that of the oxidation of [RuVI(TMP)-
O2] (Figure 2c, E1/2 ) 0.69 V vs Cp2Fe+/0), revealing a
porphyrin-centered oxidation.43 In accord with this assignment,
the oxidation potentials of [RuVI(Por)(NTs)2] for Por ) TMP,
TPP, 2,6-Cl2TPP, and F20-TPP (E1/2 ) 0.62-1.18 V, Table 1)
increase with the electron-withdrawing strength of peripheral
substituent on the porphyrin ligands. As expected, oxidation of
the electron-deficient F20-TPP ligand occurs at a markedly more
anodic potential.
2,6-Cl2TPP Ts
TPP Ts
20 ( 1
a From ref 30b.
1), which markedly depend on the R groups and are much more
anodic than those of the porphyrin-centered reduction.44 We
assign this reduction to the following electrode reaction:
[RuVI(Por)(NSO2R)2] y+e
\
z [RuV(Por)(NSO2R)2]-
-e
The first reduction couple of [RuVI(Por)(NSO2R)2] has E1/2
values in the range of -0.41 to -0.12 V vs Cp2Fe+/0 (Table
The reVersible RuVI/V reduction of [RuVI(Por)(NSO2R)2] con-
trasts with the irreVersible RuVI/V reduction at Ep,c ) -1.05 V
9
J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005 16635

A R T I C L E S
Scheme 4
Leung et al.
vs Cp2Fe+/0 observed for [RuVI(TMP)O2] (see Figure 2c),
suggesting that [RuV(Por)(NSO2R)2]- is more stable than the
respective [RuV(Por)O2]- under the electrochemical conditions.
The reduction couple with E1/2 ) -1.12 to -1.61 V vs
Cp2Fe+/0 for [RuVI(Por)(NSO2R)2] (Table 1) should be attributed
to a porphyrin-centered reduction. Indeed, in the case of [RuVI-
(Por)(NTs)2] (Por ) TMP, TPP, 2,6-Cl2TPP, F20-TPP), the
potentials of this reduction couple increase with the electron-
withdrawing strength of peripheral substituent on the porphyrin
ligands, like those of the porphyrin-centered oxidation.
reason is that the meso-aryl rings in 2,6-Cl2TPP are perpen-
dicular to the porphyrin ring, whereas the nonsubstituted meso-
phenyl rings and the porphyrin ring in TPP are more in plane
and thus more in resonance. By altering porphyrin ligands
among TMP, TPP, 2,6-Cl2TPP, and F20-TPP, a change of up to
260 mV in E1/2(RuVI/V) was observed.
Combining the above dependence of E1/2(RuVI/V) on imido
substituents and porphyrin ligands, one would expect that there
could be an overall tuning of the E1/2(RuVI/V) of [RuVI(Por)-
(NSO2R)2] by about 560 mV through changing both the imido
groups and porphyrin ligands.
The RuVI/V reduction of [RuVI(TMP)(NSO2R)2] occurs at a
more anodic potential than that of [RuVI(TMP)O2] (cf. Figure
2b,c), indicating that the RuVI ion in the arenesulfonylimido
complexes is more electron-deficient than that in the dioxo
counterpart.
It can be seen from Table 1 that the E1/2(RuVI/V) of [RuVI-
(TMP)(NSO2R)2] increases with the electron-withdrawing strength
of the R substituent. The electron-donating or -withdrawing
property of the R group would affect the π-donor strength of
imido group and thus the E1/2(RuVI/V) value. In this work, we
found that for a given porphyrin ligand, such as TMP, the
E
1/2(RuVI/V) could be tuned by about 300 mV when the R group
Effects of Imido Substituents, C-H Bond Dissociation
Energies, and RuVI/V Reduction Potentials on k2 for Alkene
Aziridination or C-H Bond Amidation by [RuVI(Por)-
(NSO2R)2]. We propose that the imido transfer reactions of
[RuVI(Por)(NSO2R)2] with alkenes or C-H bonds proceed by
a mechanism as shown in Scheme 4, which is based on the
previous mechanistic studies using [RuVI(TPP)(NTs)2].30b In-
deed, the substituent effect on the rate constants for the reaction
of para-substituted styrenes with [RuVI(TMP)(NNs)2] is similar
to that with [RuVI(TPP)(NTs)2], as is evident from the compa-
changes from p-C6H4OMe to p-C6H4NO2.
Changing the porphyrin ligand also affects the E1/2 of RuVI/V
couple, as reflected by the data in Table 1. The more anodic
E
1/2(RuVI/V) of [RuVI(F20-TPP)(NTs)2] is consistent with the
electron-deficient nature of the F20-TPP (compared with the
other porphyrin ligands). The more cathodic E1/2(RuVI/V) of
[RuVI(2,6-Cl2TPP)(NTs)2] than that of [RuVI(TPP)(NTs)2] seems
unusual, which cannot be clearly rationalized yet. A possible
(41) For reviews, see: (a) Nugent, W. A.; Haymore, B. L. Coord. Chem. ReV.
1980, 31, 123. (b) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple
Bonds; Wiley-Interscience: New York, 1988. (c) Wigley, D. E. Prog. Inorg.
Chem. 1994, 42, 239. (d) Eikey, R. A.; Abu-Omar, M. M. Coord. Chem.
ReV. 2003, 243, 83.
(42) Selected examples: (a) Samsel, E. G.; Srinivasan, K.; Kochi, J. K. J. Am.
Chem. Soc. 1985, 107, 7606. (b) Groves, J. T.; Watanabe, Y. J. Am. Chem.
Soc. 1986, 108, 507. (c) Groves, J. T.; Stern, M. K. J. Am. Chem. Soc.
1988, 110, 8628. (d) Garrison, J. M.; Bruice, T. C. J. Am. Chem. Soc.
1989, 111, 191. (e) Arasasingham, R. D.; He, G.-X.; Bruice, T. C. J. Am.
Chem. Soc. 1993, 115, 7985. (f) Khenkin, A. M.; Hill, C. L. J. Am. Chem.
Soc. 1993, 115, 8178. (g) Stultz, L. K.; Binstead, R. A.; Reynolds, M. S.;
Meyer, T. J. J. Am. Chem. Soc. 1995, 117, 2520. (h) Kaizer, J.; Klinker, E.
J.; Oh, N. Y.; Rohde, J.-U.; Song, W. J.; Stubna, A.; Kim, J.; Mu¨nck, E.;
Nam, W.; Que, L., Jr. J. Am. Chem. Soc. 2004, 126, 472.
+
rable F+ values of the log krel versus σp plot for [RuVI(TPP)-
(NTs)2] (F+ ) -1.1)30b and [RuVI(TMP)(NNs)2] (F+ ) -1.4,
Figure S10) and from the similar linearity of log krel versus (σmb
,
σJJ ) plots,45 where σJJ• is a radical constant, in both cases (see
ref 30b and Figure S11). The kinetic isotope effect for the
amidation of ethylbenzene by [RuVI(TMP)(NNs)2] (kH/kD ) 4.8,
cf. entries 22 and 23 in Table 4) is comparable to that for the
amidation of hydrocarbons by [RuVI(TPP)(NTs)2] (kH/kD ) 6.1-
11).30b
•
Inspection of the results in Tables 1 and 4 reveals the
following effects on the k2 of the imido transfer reactions.
(43) Chen, C.-Y.; Cheng, S.-H.; Su, Y. O. J. Electroanal. Chem. 2000, 487,
51.
(44) Li, Y.; Huang, J.-S.; Xu, G.-B.; Zhu, N.; Zhou, Z.-Y.; Che, C.-M.; Wong,
K.-Y. Chem.sEur. J. 2004, 10, 3486.
(45) Jiang, X.-K. Acc. Chem. Res. 1997, 30, 283.
9
16636 J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005

Imido Transfer from Bis(imido)ruthenium(VI) to Hydrocarbons
A R T I C L E S
The higher reactivity of [RuVI(TMP)(NNs)2] than that of
[RuVI(TMP)(NSO2R)2] with the other R groups toward aziri-
dination of styrene correlates with the higher efficiency of
copper-catalyzed aziridination of alkenes with PhIdNNs than
with other PhIdNSO2R nitrogen sources.5e,8a,b
(ii) Effect of C-H Bond Dissociation Energies (BDEs).
Mayer and co-worker established that C-H bond oxidation by
metal oxo complexes involving a H-atom abstraction mechanism
exhibits linear correlation between log k′ (k′ is the k2 value
divided by the number of reactive hydrogens) and BDE.36 In
this work, the C-H bond amidation by [RuVI(F20-TPP)(NTs)2]
features k′ values in the order
xanthene > 9,10-dihydroanthracene > fluorene >
cyclohexene > cumene > ethylbenzene > toluene
similar to the case of C-H bond oxidation by metal oxo
complexes.36 There is also a linear correlation between log k′
and BDE (Figure 5). This supports the H-atom abstraction
mechanism proposed previously.30b
The larger k′ for cumene (3° C-H) than for ethylbenzene
(2° C-H) (k′(3° C-H)/k′(2° C-H) ) 1.6) in the C-H bond
amidation by [RuVI(F20-TPP)(NTs)2] should be noted. Previous
work30b showed that the amidation by [RuVI(TPP)(NTs)2] (k′-
(3° C-H)/k′(2° C-H) ) 0.84) reverses the thermodynamic
reactivity order cumene > ethylbenzene, opposite to the C-H
bond oxidation by [RuVI(TPP)O2] (k′(3° C-H)/k′(2° C-H) )
2.9).37c As depicted in Table 4, the C-H bond amidation by
[RuVI(F20-TPP)(NTs)2] is faster than by [RuVI(TPP)(NTs)2].
Remarkably, [RuVI(TMP)(NNs)2], which is less reactive than
[RuVI(TPP)(NTs)2] and bears a sterically demanding TMP
ligand, gives a k′(3° C-H)/k′(2° C-H) value of 0.2 for cumene
and ethylbenzene, and the k′ for cumene is even smaller than
for toluene (1° C-H) (k′(3° C-H)/k′(1° C-H) ) 0.8). Except
for the unusually small k′ value for cumene, there is a linear
correlation between log k′ and BDE for the C-H bond
amidation by [RuVI(TMP)(NNs)2] (Figure 5).
•
Figure 4. Plots of (a) log krel versus σp+ and (b) log krel versus (σmb, σJJ
)
at 298 K for aziridination of styrene by [RuVI(TMP)(NSO2R)2].
(i) Effect of Imido Substituents. For the reactions of [RuVI-
(TMP)(NSO2R)2] with styrene, the k2 values are in the SO2R
order
Ms < Ts < Bs < Cs < Ns
(cf. entries 1-5 in Table 4), and on going from SO2R ) Ms to
Ns, the reaction becomes about 56 times faster. This is
remarkable considering the relatively remote location of the
OMe/NO2 groups of Ms/Ns from the reaction site. The increase
in k2 with the electron-withdrawing strength of the imido
substituents reflects the electrophilic nature of the imido groups,
in agreement with the electrophilicity of such groups reflected
(iii) Effect of RuVI/V Reduction Potentials. From the
E
1/2(RuVI/V) values of [RuVI(TMP)(NSO2R)2] (SO2R ) Ms, Ts,
Bs, Cs, Ns) and the k2 values for the reactions of these
complexes with styrene, the increase in E1/2(RuVI/V) correlates
with the increase in k2 values. The reaction of styrene with [RuVI-
(TPP)O2] gave a smaller k2 value ((4.3 ( 0.3) × 103)37c than
with [RuVI(TPP)(NTs)2] (k2 ) (9.0 ( 0.1) × 103),30b in
accordance with the more cathodic RuVI/V reduction potential
of the former.
In a previous work,30b we reported that, for the reaction of
[RuVI(TPP)(NTs)2] with various alkenes, the plot of log k2 versus
the E1/2 values of the 1e oxidation potentials of alkenes exhibits
a good linearity with a slope of -1.7 V-1, corresponding to a
slope of R ) 0.1 in the conventional Bronsted plot (log k2 vs
log Keq).30b
by the negative F+ value of the log krel versus σp plot for the
+
imido transfer from [RuVI(TPP)(NTs)2] or [RuVI(TMP)(NNs)2]
to para-substituted styrenes.
A linear correlation was observed between log krel and the
σp+ of the para-substituents of the imido groups (Figure 4a, F+
) 1.1). Plotting log krel against (σmb, σJJ ) results in a much
•
•
better linearity than against σp+ (Figure 4b, Fmb ) 0.99, FJJ
)
1.3). This seems to provide additional support for the rate-
limiting formation of a radical intermediate in the reaction.45
However, it remains unclear how the para-substituents of the
imido groups interact with the radical center.
For the reactions of [RuVI(TMP)(NSO2R)2] with ethylben-
zene, cumene, toluene, and tetrahydrofuran, the k2 also increases
with the electron-withdrawing strength of the R groups (cf.
entries 18-22, 28-32, 44-48, and 52-56 in Table 4), but the
rate increase from SO2R ) Ms to Ns in these cases is smaller,
with k2(Ns)/k2(Ms) ≈ up to 36.
The present work allows examination of the effect of driving
force on the rate constants of imido transfer to a given
hydrocarbon. There is a linear correlation between log k2 and
E
1/2(RuVI/V) for the reactions of styrene with [RuVI(TMP)-
(NSO2R)2] (Figure 6a). The slope of the log k2 versus E1/2 plot
is 5.9 V-1, corresponding to a slope of R ) 0.35 in the
conventional Bronsted plot. In contrast, the epoxidation of
styrene or norbornene by metal oxo complexes features log k2
versus E1/2 plots with larger slopes of 9-14 V-1 35
.
9
J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005 16637

A R T I C L E S
Leung et al.
Figure 5. Plots of log k′ versus BDE for reactions of [RuVI(TMP)(NNs)2] and [RuVI(F20-TPP)(NTs)2] with hydrocarbons.
comparable to the slope of 5.9 V-1 for the reaction of styrene
with [RuVI(TMP)(NSO2R)2] (Figure 6a).
Reactions of [RuVI(Por)(NTs)2] (Por ) TMP, 2,6-Cl2TPP,
TPP, F20-TPP) with styrene, cumene, ethylbenzene, tetrahydro-
furan, or toluene have k2 values in the order
TMP < 2,6-Cl2TPP < TPP < F20-TPP
This is in agreement with the E1/2(RuVI/V) of [RuVI(Por)(NTs)2],
which increases along TMP f 2,6-Cl2TPP f TPP f F20-TPP
(Table 1). Notably, on going from TMP to F20-TPP, the reaction
of [RuVI(Por)(NTs)2] with styrene and ethylbenzene becomes
about 19 and 42 times faster, respectively. Tetrahydrofuran
contains activated R-C-H bonds and reacts with [RuVI(Por)-
(NTs)2] more rapidly than ethylbenzenes (cf. entries 19 vs 53,
24 vs 57, and 26 vs 58 in Table 4). The k2 for the amidation of
tetrahydrofuran is about 23-fold larger for [RuVI(TPP)(NTs)2]
than for [RuVI(TMP)(NTs)2], in contrast to the about 11-fold
larger k2 value for amidation of ethylbenzene by [RuVI(TPP)-
(NTs)2] than by [RuVI(TMP)(NTs)2], indicating a stronger
dependence of imido transfer rates on the porphyrin substituents
in the case of tetrahydrofuran.
Figure 6. Plots of log k2 versus E1/2(RuVI/V) for reactions of [RuVI(TMP)-
(NSO2R)2] with (a) styrene, (b) tetrahydrofuran, (c) ethylbenzene, (d)
toluene, and (e) cumene.
The different R values obtained for the reactions of [RuVI-
(TPP)(NTs)2] with various alkenes30b and for the reactions of
styrene with different [RuVI(TMP)(NSO2R)2] suggest the pres-
ence of perpendicular contribution to the overall slope R, which
approximately follows the equation35a
[RuVI(TMP)(NCs)2] and [RuVI(TPP)(NTs)2] have essentially
the same E1/2(RuVI/V) value (-0.27 V vs Cp2Fe+/0, Table 1).
Thus, in the absence of steric effect, the reactions of these two
imido complexes with a given hydrocarbon should exhibit
similar k2 values. We found that the steric effect in styrene
aziridination by [RuVI(Por)(NSO2R)2] is small, with the k2 for
[RuVI(TMP)(NCs)2] ((11.5 ( 0.6) × 103, entry 4 in Table 4)
comparable to that for [RuVI(TPP)(NTs)2] ((9.0 ( 0.1) × 103).30b
Including [RuVI(TPP)(NTs)2], [RuVI(2,6-Cl2TPP)(NTs)2], [RuVI-
(F20-TPP)(NTs)2], as well as [RuVI(TMP)(NSO2R)2] (SO2R )
Ms, Ts, Bs, Cs, Ns) in the log k2 versus E1/2(RuVI/V) plot for
styrene aziridination gives a fairly good linearity (Figure S12);
the obtained slope (5.5 V-1) is similar to that (5.9 V-1) for
[RuVI(TMP)(NSO2R)2] (SO2R ) Ms, Ts, Bs, Cs, Ns) (Figure
6a).
R ) ø ( 0.5(τ - 1)
where ø is the progress of the reaction along the reaction
coordinate, and τ is the “tightness” of the transition state.
Through this equation and from the above two R values, we
estimated the ø and τ values to be 0.225 and 0.75, respectively,
which might imply that the transition state of the imido transfer
reaction is earlier and more “tight” than that of the oxo transfer
reaction of [CrV(Por)O]+ with alkenes (ø ) 0.37, τ ) 0.63).35a
For amidation of cumene, ethylbenzene, tetrahydrofuran, or
toluene by different [RuVI(TMP)(NSO2R)2], the log k2 versus
Upon replacing [RuVI(TMP)(NCs)2] with [RuVI(TPP)(NTs)2],
the k2 becomes about 3-, 6-, 9-, and 20-fold larger for amidation
of toluene, ethylbenzene, tetrahydrofuran, and cumene, respec-
E
1/2(RuVI/V) plots (Figure 6b-e) also exhibit a good linearity,
with slopes of 3.3, 3.1, 4.2, and 5.2 V-1, respectively,
9
16638 J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005

Imido Transfer from Bis(imido)ruthenium(VI) to Hydrocarbons
A R T I C L E S
(0.05 mmol) and PhIdNSO2R (0.2 mmol) in freshly distilled CH2Cl2
(8 mL) was stirred for 5 min at room temperature under argon. The
reaction mixture was passed through a short column of neutral alumina
with CH2Cl2 as eluent. The first band was collected, and the solvent
was removed in vacuo, affording the desired product as a dark purple
solid in about 70% yield.
[RuVI(TMP)(NMs)2]. Anal. Calcd for C70H66N6O6RuS2: C, 67.13;
H, 5.31; N, 6.71. Found: C, 67.01; H, 5.12; N, 6.58. UV-vis (3.86 ×
10-6 M, CH2Cl2): λmax/nm (log ꢀ) 422 (5.24), 536 (4.31), 566 (3.55).
IR (KBr, cm-1): 1017 (“oxidation state marker” band). 1H NMR (300
MHz, CD2Cl2): δ Hâ 8.70 (8H, s), Hm(eq) 7.33 (8H, s), p-Me(eq) 2.66
(12H, s), o-Me(eq) 1.84 (24H, s), Hm(ax) 5.87 (4H, d, J ) 8.9 Hz),
Ho(ax) 4.91 (4H, d, J ) 8.9 Hz), OMe(ax) 3.47 (6H, s). ESMS (CH2-
Cl2): m/z 1252 [M]+, 896 [M - NMs - Ms]+.
tively (cf. entries 47 vs 51, 21 vs 26, 55 vs 58, and 31 vs 34 in
Table 4). This can be rationalized by the increasing steric effect
along the series toluene (1° C-H) f ethylbenzene, tetrahy-
drofuran (2° C-H) f cumene (3° C-H). The substantial 20-
fold increase in k2 value for cumene reveals that steric effect
could significantly affect the amidation of the 3° C-H bond.
On the basis of the studies described above, it can be
envisaged that [RuVI(F20-TPP)(NNs)2] bearing electron-deficient,
sterically unencumbered F20-TPP ligand and having strongly
electron-withdrawing NO2 substituent on the imido group should
exhibit a high reactivity toward hydrocarbons. Such a complex
has not been obtained in pure form but could be generated in
situ from reaction of [RuII(F20-TPP)(CO)] with PhIdNNs in
CH2Cl2 as mentioned above. Indeed, the reaction of the in situ
generated [RuVI(F20-TPP)(NNs)2] with any of the hydrocarbons
in Tables 3 and 4 is too fast to be monitored by UV-vis
spectrophotometry. Preliminary examination of the [RuII(F20-
TPP)(CO)]-catalyzed amidation of cyclohexane and decalin with
PhIdNNs in CH2Cl2 at 40 °C with a catalyst:(PhIdNNs):
substrate molar ratio of 1:50:5000 afforded the amidation
products in 14 and 24% yield (based on the amount of consumed
PhIdNNs), respectively (for decalin, a mixture of two isomers
in 2.2:1 ratio was obtained); no amidation products could be
detected if PhIdNNs was replaced with PhIdNTs.
[RuVI(TMP)(NTs)2]. Anal. Calcd for C70H66N6O4RuS2: C, 68.88;
H, 5.45; N, 6.89. Found: C, 68.92; H, 5.38; N, 6.60. UV-vis (5.29 ×
10-6 M, CH2Cl2): λmax/nm (log ꢀ) 421 (5.24), 536 (4.33), 566 (3.63).
IR (KBr, cm-1): 1017 (“oxidation state marker” band). 1H NMR (300
MHz, CD2Cl2): δ Hâ 8.67 (8H, s), Hm(eq) 7.30 (8H, s), p-Me(eq) 2.62
(12H, s), o-Me(eq) 1.80 (24H, s), Hm(ax) 6.17 (4H, d, J ) 8.3 Hz),
Ho(ax) 4.81 (4H, d, J ) 8.3 Hz), Me(ax) 1.88 (6H, s). ESMS (CH2-
Cl2): m/z 1220 [M]+, 896 [M - NTs - Ts]+.
[RuVI(TMP)(NBs)2]. Anal. Calcd for C68H62N6O4RuS2: C, 68.49;
H, 5.24; N, 7.05. Found: C, 68.32; H, 5.08; N, 6.97. UV-vis (1.14 ×
10-5 M, CH2Cl2): λmax/nm (log ꢀ) 420 (5.24), 536 (4.28), 566 (3.87).
IR (KBr, cm-1): 1017 (“oxidation state marker” band). 1H NMR (300
MHz, CD2Cl2): δ Hâ 8.69 (8H, s), Hm(eq) 7.31 (8H, s), p-Me(eq) 2.63
(12H, s), o-Me(eq) 1.81 (24H, s), Hp(ax) 6.80 (2H, t, J ) 7.5 Hz),
Hm(ax) 6.39 (4H, t, J ) 7.9 Hz), Ho(ax) 4.93 (4H, d, J ) 7.4 Hz).
ESMS (CH2Cl2): m/z 1192 [M]+, 896 [M - NBs - Bs]+.
Conclusion
(i) [RuVI(Por)(NSO2R)2] is isolable for a series of SO2R
groups and porphyrin ligands. This unique class of metal imido
complexes readily undergo imido transfer reactions with hy-
drocarbons, affording aziridines or amides in good yields. (ii)
The reactivity of [RuVI(Por)(NSO2R)2] toward hydrocarbons is
remarkably affected by the electronic properties of the remote
para-substituents of SO2R groups; the imido substituent having
a larger electron-withdrawing strength results in a higher
reactivity. (iii) In terms of the effect of imido substituents, the
attack of the imido groups toward alkene double bonds is
electrophilic, which complements previous results obtained from
the effect of alkene substituents.30b (iv) For the amidation of
hydrocarbons by [RuVI(Por)(NSO2R)2], the second-order rate
constants correlate with C-H bond dissociation energies,
providing additional evidence for the H-atom abstraction
mechanism proposed in previous work.30b (v) [RuVI(Por)-
(NSO2R)2] shows RuVI/V reduction at a potential considerably
more anodic than [RuVI(Por)O2]; more strongly electron-
withdrawing imido groups lead to more anodic reduction
potentials. The RuVI/V reduction of [RuVI(Por)(NSO2R)2] is
reversible, whereas that of [RuVI(TMP)O2] is irreversible. There
is a linear correlation between log k2 and the E1/2(RuVI/V) of
[RuVI(Por)(NSO2R)2] for their reaction with styrene, cumene,
ethylbenzene, tetrahydrofuran, or toluene (a more anodic
[RuVI(TMP)(NCs)2]. Anal. Calcd for C68H60Cl2N6O4RuS2: C, 64.75;
H, 4.79; N, 6.66. Found: C, 64.53; H, 4.71; N, 6.58. UV-vis (5.25 ×
10-6 M, CH2Cl2): λmax/nm (log ꢀ) 419 (5.24), 535 (4.27), 565 (3.54).
IR (KBr, cm-1): 1016 (“oxidation state marker” band). 1H NMR (300
MHz, CD2Cl2): δ Hâ 8.69 (8H, s), Hm(eq) 7.31 (8H, s), p-Me(eq) 2.62
(12H, s), o-Me(eq) 1.80 (24H, s), Hm(ax) 6.38 (4H, d, J ) 8.7 Hz),
Ho(ax) 4.87 (4H, d, J ) 8.7 Hz). ESMS (CH2Cl2): m/z 1262 [M]+,
896 [M - NCs - Cs]+.
[RuVI(TMP)(NNs)2]. Anal. Calcd for C68H60N8O8RuS2: C, 63.68;
H, 4.72; N, 8.74. Found: C, 63.33; H, 4.61; N, 8.54. UV-vis (2.89 ×
10-6 M, CH2Cl2): λmax/nm (log ꢀ) 416 (5.24), 535 (4.21), 565 (3.68).
IR (KBr, cm-1): 1017 (“oxidation state marker” band). 1H NMR (300
MHz, CD2Cl2): δ Hâ 8.71 (8H, s), Hm(eq) 7.34 (8H, s), p-Me(eq) 2.65
(12H, s), o-Me(eq) 1.83 (24H, s), Hm(ax) 7.27 (4H, d, J ) 8.8 Hz),
Ho(ax) 5.18 (4H, d, J ) 8.8 Hz). ESMS (CH2Cl2): m/z 1282 [M]+,
896 [M - NNs - Ns]+.
[RuVI(2,6-Cl2TPP)(NTs)2]. Anal. Calcd for C58H34Cl8N6O4RuS2: C,
52.47; H, 2.58; N, 6.33. Found: C, 52.50; H, 2.45; N, 6.18. UV-vis
(5.30 × 10-6 M, CH2Cl2): λmax/nm (log ꢀ) 422 (5.24), 534 (4.26). IR
1
(KBr, cm-1): 1018 (“oxidation state marker” band). H NMR (400
MHz, CD2Cl2): δ Hâ 8.83 (8H, s), Hm,p(eq) 7.87 (12H, m), Hm(ax)
6.23 (4H, d, J ) 8.2 Hz), Ho(ax) 4.86 (4H, d, J ) 8.3 Hz), Me(ax)
1.94 (6H, s). ESMS (CH2Cl2): m/z 1328 [M]+, 1004 [M - NTs -
Ts]+.
[RuVI(F20-TPP)(NTs)2]. Anal. Calcd for C58H22F20N6O4RuS2: C,
49.34; H, 1.57; N, 5.95. Found: C, 49.65; H, 1.82; N, 6.21. UV-vis
(6.1 × 10-6 M, CH2Cl2): λmax/nm (log ꢀ) 418 (5.40), 528 (4.38), 558
(3.84). IR (KBr, cm-1): 1019 (“oxidation state marker” band). 1H NMR
(300 MHz, CD2Cl2): δ Hâ 9.01 (8H, s), Hm(ax) 6.28 (4H, d, J ) 8.1
Hz), Ho(ax) 4.82 (4H, d, J ) 8.2 Hz), Me(ax) 1.99 (6H, s). 19F NMR
(376 MHz, CD2Cl2): δ o-F -135.5 (8F, d, J ) 20 Hz), p-F -150.7
(4F, t, J ) 21 Hz), m-F -161.1 (8F, t, J ) 22 Hz). ESMS (CH2Cl2):
m/z 1412 [M]+, 1088 [M - NTs - Ts]+.
E
1/2(RuVI/V) corresponds to a higher reactivity). (vi) Amidation
of hydrocarbons by [RuVI(Por)(NSO2R)2] features larger steric
effect than the aziridination of styrene by the same imido
complex. Manipulation of the steric hindrance of the imido
complexes can reverse the relative amidation reactivity of 3°
versus 2°/1° C-H bonds.
Experimental Section
Preparation of [RuVI(Por)(NSO2R)2]. These complexes were
prepared by a modification of the procedure reported previously for
the preparation of [RuVI(Por)(NTs)2].30b A mixture of [RuII(Por)(CO)]
[RuVI(F20-TPP)(NNs)2]. This complex was prepared in situ by
stirring a solution of [RuII(F20-TPP)(CO)] (0.05 mmol) and PhIdNNs
(0.2 mmol) in CH2Cl2 (8 mL) for 5 min at room temperature under
9
J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005 16639

A R T I C L E S
Leung et al.
1
argon. UV-vis (CH2Cl2): λmax/nm 413 (Soret), 528. H NMR (300
MHz, CD2Cl2): δ Hâ 9.20 (8H, s), Hm(ax) 7.42 (4H, d, J ) 8.7 Hz),
Ho(ax) 5.15 (4H, d, J ) 8.7 Hz). ESMS (CH2Cl2): m/z 1474 [M]+,
1088 [M - NNs - Ns]+.
[RuIV(F20-TPP)(NHTs)(pz)]. Anal. Calcd for C54H19F20N7O2RuS:
C, 49.48; H, 1.46; N, 7.48. Found: C, 49.20; H, 1.76; N, 7.75. UV-
vis (6.21 × 10-6 M, CH2Cl2): λmax/nm (log ꢀ) 407 (5.18), 525 (4.15).
IR (KBr, cm-1): 1015 (“oxidation state marker” band). 1H NMR (300
MHz, CDCl3): δ Hâ -15.0 (8H, s), Hm(ax) 12.3 (2H, s), Ho(ax) 4.8
(2H, s), Me(ax) 11.8 (3H, s) (the pz signals were not located). FAB
MS: m/z 1312 [M + H]+, 1244 [M - pz]+, 1074 [M - NHTs - pz]+.
X-ray Crystal Structure Determination of [RuIV(TMP)(NHCs)-
(pz)]‚5H2O. A diffraction-quality crystal (0.25 × 0.2 × 0.06 mm3),
obtained by slow evaporation of a CHCl3-MeOH solution (1:3 v/v) at
room temperature for 3 days, was mounted on a glass fiber for data
collection at 28 °C on a MAR diffractometer with a 300 mm image
plate detector using graphite-monochromatized Mo KR radiation (λ )
0.71069 Å) (2° oscillation, 66 images at 120 mm distance and 600 s
exposures). The images were interpreted and intensities integrated by
using DENZO.46 The structure was solved by direct methods employing
SIR-9747 on PC and expanded by Fourier cycles and refined by full-
matrix least-squares using SHELXL-97.48 A crystallographic asym-
metric unit consists of one formula unit. In the least-squares refinement,
Ru, S, Cl, O, and N atoms in the molecule were refined anisotropically
and other non-hydrogen atoms isotropically. The positions of H-atoms
were calculated based on riding mode with thermal parameters equal
to 1.2 times that of the associated C atoms and participated in the
calculation of the final R indices.
Stoichiometric Alkene Aziridination and C-H Bond Amidation
by [RuVI(Por)(NSO2R)2]. These reactions were performed under argon
using standard Schlenk techniques. A typical procedure is given as
follows: To a solution of substrate (1 or 2 mmol) in CH2Cl2 (2 mL) in
a Schlenk tube (10 mL) were added [RuVI(Por)(NSO2R)2] (0.05 mmol)
and pyrazole (2% w/w). The mixture was stirred for 3 h. After removal
of solvent in vacuo, a mixture of n-pentane and Et2O (5:1 v/v, 20 mL)
was added, resulting in the formation of a reddish-purple precipitate.
The precipitate was found to be [RuIV(Por)(NHSO2R)(pz)] (yield: about
65%), which was collected by filtration and washed with n-pentane.
The filtrate containing organic products was evaporated to dryness,
and the residue was dissolved in ethyl acetate and purified by
chromatography. The organic products were identified as described in
Supporting Information.
[RuIV(TMP)(NHMs)(pz)]. Anal. Calcd for C66H63N7O3RuS: C,
69.82; H, 5.59; N, 8.64. Found: C, 69.62; H, 5.85; N, 8.90. UV-vis
(4.05 × 10-6 M, CH2Cl2): λmax/nm (log ꢀ) 414 (5.26), 529 (4.20), 560
(3.95, sh). IR (KBr, cm-1): 1010 (“oxidation state marker” band). 1H
NMR (300 MHz, CD2Cl2): δ Hâ -17.5 (8H, s), Hm(eq) 6.17 (8H, d),
p-Me(eq) 2.04 (12H, s), o-Me(eq) 1.55 (24H, s), Hm(ax) 10.9 (2H, s),
Ho(ax) 5.0 (2H, s), p-OMe(ax) 4.65 (3H, s), pz -25.0 (1H, s) and -27.7
(1H, s) (the signal of the ortho proton was not located). FAB MS: m/z
1136 [M + H]+, 1068 [M - pz]+, 882 [M - NHMs - pz]+.
[RuIV(TMP)(NHCs)(pz)]. Anal. Calcd for C65H60ClN7O2RuS: C,
68.49; H, 5.31; N, 8.60. Found: C, 68.43; H, 5.30; N, 8.43. UV-vis
(4.39 × 10-6 M, CH2Cl2): λmax/nm (log ꢀ) 413 (5.29), 528 (4.23), 561
(3.99, sh). IR (KBr, cm-1): 1009 (“oxidation state marker” band). 1H
NMR (400 MHz, CD2Cl2): δ Hâ -18.6 (8H, s), Hm(eq) 6.16 (8H, d),
p-Me(eq) 2.04 (12H, s), o-Me(eq) 1.57 (24H, s), Hm(ax) 11.9 (2H, s),
Ho(ax) 5.1 (2H, s), pz -25.8 (1H, s) and -27.8 (1H, s) (the signal of
the ortho proton was not located). ESMS (CH2Cl2): m/z 1139 [M]+,
1072 [M - pz]+, 882 [M - NHCs - pz]+.
[RuIV(TMP)(NHNs)(pz)]. Anal. Calcd for C65H60N8O4RuS: C,
67.87; H, 5.26; N, 9.74. Found: C, 68.05; H, 5.09; N, 9.54. UV-vis
(5.73 × 10-6 M, CH2Cl2): λmax/nm (log ꢀ) 411 (5.05), 531 (3.93), 560
(3.69). IR (KBr, cm-1): 1010 (“oxidation state marker” band). 1H NMR
(300 MHz, CD2Cl2): δ Hâ -19.7 (8H, s), Hm(eq) 6.11 (8H, d), p-Me-
(eq) 2.00 (12H, s), o-Me(eq) 1.56 (24H, s), Hm(ax) 12.7 (2H, s), Ho-
(ax) 5.1 (2H, s), pz -26.8 (1H, s) and -28.8 (1H, s) (the signal of the
ortho proton was not located). ESMS (CH2Cl2): m/z 1150 [M]+, 1083
[M - pz]+, 882 [M - NHNs - pz]+.
Kinetic Studies. These were performed by following the procedures
reported previously.30b
Acknowledgment. This work was supported by The Uni-
versity of Hong Kong, the Hong Kong Research Grants Council
(HKU7011/04P), University Development Fund of the Hong
Kong University, and the University Grants Committee of the
Hong Kong SAR of China (Area of Excellent Scheme, AoE/
P-10/01).
Supporting Information Available: General Experimental
Section, characterization of aziridination/amidation products,
Figures S1-S12, and CIF file for the X-ray crystal structure of
[RuVI(TMP)(NHCs)(pz)]‚5H2O. This material is available free
of charge via the Internet at http://pubs.acs.org.
JA0542789
(46) Otwinowski, Z.; Minor, W. In Methods in Enzymology, Vol. 276:
Macromolecular Crystallography, Part A; Carter, C. W., Jr., Sweet, R.
M., Eds.; Academic Press: New York, 1997; p 307.
(47) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.;
Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1999, 32, 115.
(48) Sheldrick, G. M. SHELXL-97. Program for the Refinement of Crystal
Structures. University of Go¨tingen: Go¨ttingen, Germany, 1997.
9
16640 J. AM. CHEM. SOC. VOL. 127, NO. 47, 2005