Oxidative Addition of X-H (X ) C, N, O) Bonds to [Ir(PMe3) 4]Cl and Catalytic Hydration of Acetonitrile Using its Peroxo Derivative, [Ir(O2)(PMe3)4]Cl, as Catalyst Precursor

Article abstract of DOI:10.1021/om9000633

The reactions of [Ir(PMe₃)₄]Cl (1) with a variety of substrates (acetonitrile, p-aminobenzonitrile, p-cyanophenol) containing a nitrile group were examined. Cleavage of the X-H bonds occurred selectively over the coordination of the

Full text of DOI:10.1021/om9000633

2904
Organometallics 2009, 28, 2904–2914
Oxidative Addition of X-H (X ) C, N, O) Bonds to [Ir(PMe3)4]Cl
and Catalytic Hydration of Acetonitrile Using its Peroxo Derivative,
[Ir(O2)(PMe3)4]Cl, as Catalyst Precursor
Marco G. Crestani,*,† Andreas Steffen,‡ Alan M. Kenwright,‡ Andrei S. Batsanov,‡
Judith A. K. Howard,‡ and Todd B. Marder*,‡
Facultad de Qu´ımica, UniVersidad Nacional Auto´noma de Me´xico, Me´xico, D.F. 04510, Mexico, and
Department of Chemistry, Durham UniVersity, South Road, Durham, DH1 3LE, U.K.
ReceiVed January 27, 2009
The reactions of [Ir(PMe3)4]Cl (1) with a variety of substrates (acetonitrile, p-aminobenzonitrile,
p-cyanophenol) containing a nitrile group were examined. Cleavage of the X-H bonds occurred selectively
over the coordination of the CN moiety in those substrates, and compounds derived from the corresponding
X-H (X ) C, N, O) oxidative addition reaction, namely, cis-[IrH(CH2CN)(PMe3)4]Cl (2), cis-
[IrD(CD2CN)(PMe3)4]Cl (3), cis-[IrH(p-NHC6H4CN)(PMe3)4]Cl (4), and cis-[IrH(p-OC6H4CN)(PMe3)4]Cl
(6), were obtained. X-ray diffraction studies have confirmed the structures of 3 and 4. In the case of 6,
the compound trans-[IrClH(PMe3)4][p-OC6H4CN] (5b), resulting from exchange of Cl and p-OC6H4CN
anions between inner and outer sphere, was also formed, and the solid-state structure (5b · HOC6H4CN),
obtained by X-ray diffraction, contained the hydrogen-bonded NCC6H4O · · · H · · · OC6H4CN anion. The
salt [Ir(PMe3)4][BPh4] (7) was also prepared, characterized by X-ray diffraction and reacted with
p-HOC6H4CN. Reaction of 1 with acetamide, the product of acetonitrile hydration, was undertaken to
gain insight into the nitrile hydration process, and the single-crystal structure of the N-H bond cleavage
product, cis-[IrH(NHC(O)Me)(PMe3)4]Cl (8), was determined by X-ray diffraction. The peroxo compound
derived from reaction of 1 with O2, [Ir(O2)(PMe3)4]Cl (9), was prepared, characterized by X-ray diffraction,
and used as a catalyst precursor for the hydration of acetonitrile using the protio and deuterio mixtures
of substrates, CH3CN/H2O (A), CD3CN/D2O (B), CD3CN/H2O (C), and CH3CN/D2O (D). Catalysis
occurred cleanly at 140 °C, giving dn-acetamides; the formation of these was monitored by 1H and 13C{1H}
NMR spectroscopy and GC/MS. In situ 31P{1H} NMR spectroscopic studies during catalysis confirmed
the formation of OdPMe3.
and mild conditions has been proposed4,5 as a particularly
important alternative for the nitrile hydration process to address
Introduction
The coordination and reactivity of nitriles with low-valent
late transition metal complexes is of interest because catalytic
hydration of nitriles to amides remains a challenging goal.1 The
conversion of nitriles into amides by conventional acid/base
strategies usually requires harsh conditions2 and remains
impractical for most purposes due to conversion and selectivity
issues,3 and even more so, due to serious concerns regarding
the extensive formation of salts that result from the neutralization
of the reaction media, which may account for up to ca. 70 wt
% of total wastes.4a The development of catalytic reactions that
employ transition metal complexes as catalysts under neutral
these issues, and a considerable amount of effort has been
expended in this direction.1b The majority of these efforts,
however, have not succeeded in achieving catalysis,1-6 and as
a result, most of the existing literature concerning transition-
metal-promoted hydration of nitriles still refers to stoichiometric
reactions.1a,b
Relevant to the nitrile hydration, the reactivity of organoni-
triles with nickel complexes has been examined by Garcia and
Jones et al.7 In this instance, the formation of organometallic
compounds containing side-on bound RCt N groups, η2-
coordinated8 to Ni(0), has been well established by spectroscopic
and structural studies including X-ray crystallographic studies
of an extensive number of compounds bearing aryl,7i,j
heteroaryl,7i and alkyl substituents.7g The reactivity of the
* Corresponding authors. E-mail: todd.marder@durham.ac.uk (T.B.M.);
crestanigutierrez@yahoo.com.mx (M.G.C.).
† Universidad Nacional Auto´noma de Me´xico.
‡ Durham University.
(1) For recent reviews on metal-mediated and metal-catalyzed hydration
of nitriles, see: (a) Kukushkin, V. Y.; Pombeiro, A. J. L. Inorg. Chim. Acta
2005, 358, 1–21. (b) Bokach, N. A.; Kukushkin, V. Y. Russ. Chem. ReV.
2005, 74, 153–170. (c) Kukushkin, V. Y.; Pombeiro, A. J. L. Chem. ReV.
2002, 102, 1771–1802.
(2) Smith, M. B.; March, J. AdVanced Organic Chemistry: Reactions,
Mechanisms, and Structure, 5th ed.; John Wiley and Sons, Inc.: New York,
2001; pp 1179-1180.
(3) The rate of hydrolysis of the amide to the corresponding carboxylic
acid is usually greater than that of the precursor nitrile to the amide, therefore
making their straightforward synthesis by conventional acid/base conditions
difficult. See: Chin, J. Acc. Chem. Res. 1991, 24, 145–152.
(4) (a) Murahashi, S.-I.; Takaya, H. Acc. Chem. Res. 2000, 33, 225–
233. (b) Murahashi, S.-I.; Sasao, S.; Saito, E.; Naota, T. J. Org. Chem.
1992, 57, 2521–2523.
(5) (a) Goto, A.; Endo, K.; Saito, S. Angew. Chem. Int Ed. 2008, 47,
3607–3609. (b) Cadierno, V.; Francos, J.; Gimeno, J. Chem.-Eur. J. 2008,
14, 6601–6605. (c) Leung, C. W.; Zheng, W.; Zhou, Z.; Lin, Z.; Lau, C. P.
Organometallics 2008, 27, 4957–4969. (d) Oshiki, T.; Yamashita, H.;
Sawada, K.; Utsunomiya, M.; Takahashi, K.; Takai, K. Organometallics
2005, 24, 6287–6290. (e) Breno, K. L.; Pluth, M. D.; Tyler, D. R.
Organometallics 2003, 22, 1203–1211.
(6) For the use of enzymes as catalysts for this reaction see: Mart´ınkova´,
L.; Mylerova´, V. Curr. Org. Chem. 2003, 7, 1279–1295.
10.1021/om9000633 CCC: $40.75
2009 American Chemical Society
Publication on Web 04/14/2009

OxidatiVe Addition of X-H (X ) C, N, O) to [Ir(PMe3)4]Cl
Organometallics, Vol. 28, No. 9, 2009 2905
Scheme 1. Reaction of [Ir(PMe3)4]Cl (1) with CH3CN and
CD3CN
coordinated nitriles toward the addition of water was investi-
gated,7d,e and as a result, the feasibility of a catalytic process
using Ni(0) catalyst precursors for the hydration of benzonitrile
and acetonitrile7e and the aryl-dinitriles 1,2-, 1,3-, and 1,4-
terephthalonitrile7d has been demonstrated. A related study
concerned the preparation of η2-coordinated imines of formula
[(dippe)Ni(η2-C(Ph)(H)dN(R)] (R ) fluorinated benzene ring),9
resembling an [(L2)Ni(η2-C(R)(OH)dNH)] intermediate pro-
posed in the catalytic hydration process, a result of the N,N-
dihydro-C-oxo-biaddition of water.2,10 The σ-coordination and
C-C bond cleavage of nitriles at rhodium11 and iridium12
centers has been observed by the groups of Brookhart and
Bergman, and the possibility of η2-coordination has been
suggested in reaction intermediates. Of additional relevance, the
formation of Ir(III) carboxamides, [Cp*(PMe3)Ir(Ph)(NHC-
(O)R)], has been reported to occur via a bimetallic reaction
between [Cp*(PMe3)Ir(Ph)(OH)] and [Cp*(PMe3)Ir(Ph)-
(NCR)]+;13 the formation of the latter compound occurred as a
result of reaction between [Cp*(PMe3)Ir(Ph)(OTf)] and a
number of aromatic (R ) -C6H4CH3, -C6H5, and -C6H4CF3)
and aliphatic (R ) -CH3, -CH(Ph)2) nitriles. Competing C-H
activation was observed to take place when attempting the
reaction with acetonitrile instead of aromatic nitriles. The use
of [Cp*(PMe3)Ir(Ph)(OH)] in the additional presence of aceta-
mide, however, showed the C-H bond activation to be
overcome by N-H bond cleavage; the iridium carboxamide
[Cp*(PMe3)Ir(Ph)(NHC(O)Me)] and a stoichiometric amount
of water were obtained selectively under these conditions. The
formation of -NHC(O)R complexes is envisaged as being key
to the overall metal-mediated or catalytic conversion of an
organonitrile into a free carboxamide, and thus the synthesis of
such intermediates is relevant. In the latter case, however,
formation of free carboxamides was not achieved in catalysis
even using excess water and high temperatures, and thus,
protonolysis of bound carboxamides using HCl was required
to release the free amides.
We envisaged [Ir(PMe3)4]Cl (1) to be of potential use in the
study of the nitrile hydration reaction because the [Ir(PMe3)4]+
cation is known14a to oxidatively add water, giving the cis-
hydrido-hydroxy cation [IrH(OH)(PMe3)4]+, and also to activate
acetonitrile. Thus, previous studies of reactions of Ir(I)/Rh(I)
systems with acetonitrile by English and Herskovitz14b dem-
onstrated not only the C-H oxidative addition of CH3CN to 1
and to [Ir(Et2PC2H4PEt2)2]Cl but also the formal carboxylation
of the CH2CN moiety with CO2. The present work provides a
more detailed characterization, by high-field NMR spectroscopy
and X-ray diffraction studies, of the product of CH3CN C-H
oxidative addition to 1. We also explored 1, as well as the more
electrophilic peroxo compound [Ir(O2)(PMe3)4]Cl (9), for the
nitrile hydration reaction and show that the latter compound, at
a low loading of 0.1 mol %, is a useful catalyst precursor for
the hydration of acetonitrile using stoichiometric amounts of
water. First, we describe studies of the oxidative addition of
C-H, N-H, and O-H bonds to 1.
(7) (a) Ates¸in, T. A.; Li, T.; Lachaize, S.; Brennessel, W. W.; Garc´ıa,
J. J.; Jones, W. D. J. Am. Chem. Soc. 2007, 129, 7562–7569. (b) Acosta-
Ram´ırez, A.; Mun˜oz-Herna´ndez, M.; Jones, W. D.; Garc´ıa, J. J. Organo-
metallics 2007, 26, 5766–5769. (c) Acosta-Ram´ırez, A.; Flores-Gaspar, A.;
Mun˜oz-Herna´ndez, M.; Are´valo, A.; Jones, W. D.; Garc´ıa, J. J. Organo-
metallics 2007, 26, 1712–1720. (d) Criso´stomo, C.; Crestani, M. G.; Garc´ıa,
J. J. J. Mol. Catal. A: Chem. 2007, 266, 139–148. (e) Crestani, M. G.;
Are´valo, A.; Garc´ıa, J. J. AdV. Synth. Catal. 2006, 348, 732–742. (f) Acosta-
Ram´ırez, A.; Mun˜oz-Herna´ndez, M.; Jones, W. D.; Garc´ıa, J. J. J.
Organomet. Chem. 2006, 691, 3895–3901. (g) Garc´ıa, J. J.; Are´valo, A.;
Brunkan, N. M.; Jones, W. D. Organometallics 2004, 23, 3997–4002. (h)
Brunkan, N. M.; Brestensky, D. M.; Jones, W. D. J. Am. Chem. Soc. 2004,
126, 3627–3641. (i) Garc´ıa, J. J.; Brunkan, N. M.; Jones, W. D. J. Am.
Chem. Soc. 2002, 124, 9547–9555. (j) Garc´ıa, J. J.; Jones, W. D.
Organometallics 2000, 19, 5544–5545. (k) Crestani, M. G.; Garc´ıa, J. J. J.
Mol. Catal. A: Chem. 2009, 299, 26–36.
(8) For a review concerning coordination modes of nitriles to transition
metals, see: (a) Michelin, R. A.; Mozzon, M.; Bertani, R. Coord. Chem.
ReV. 1996, 147, 299–338. (b) For a relevant series of studies involving
tungsten(IV) nitrile complexes exhibiting both σ- and η2-coordination
modes, see: Cross, J. L.; Garrett, A. D.; Crane, T. W.; White, P. S.;
Templeton, J. L. Polyhedron 2004, 23, 2831–2840. (c) For a theoretical
study concerning the relative stability and switching of an end-on
coordinated acetonitrile molecule in [HCo(L)3(η1-Nt C-Me)] (L ) CO, PH3,
PPh3, PMe3, 1,2-bis(dimethylphosphine)ethane, and an N-heterocyclic
carbene) into the corresponding side-on coordinated compound [HCo(L)3(η2-
N,C-NCMe)], depending on the particular ligand used, see: Huo, C.-F.; Zeng,
T.; Li, Y.-W.; Beller, M.; Jiao, H. Organometallics 2005, 24, 6037–6042.
(9) Iglesias, A. L.; Mun˜oz-Herna´ndez, M.; Garc´ıa, J. J. J. Organomet.
Chem. 2007, 692, 3498–3507.
(10) The reduction of π-bound nitriles yielding π-bound imines using
tungsten(II) complexes of the type [W(CO)(acac)(η2-N,C-NCR)] (acac )
acetylacetonate, R ) Ph, Me) has recently been reported: Jackson, A. B.;
Khosla, C.; Gaskins, H. E.; White, P. S.; Templeton, J. L. Organometallics
2008, 27, 1322–1327.
(11) (a) Taw, F. L.; Mueller, A. H.; Bergman, R. G.; Brookhart, M.
J. Am. Chem. Soc. 2003, 125, 9808–9813. (b) Taw, F. L.; White, P. S.;
Bergman, R. G.; Brookhart, M. J. Am. Chem. Soc. 2002, 124, 4192–4193.
(12) Klei, S. R.; Tilley, T. D.; Bergman, R. G. Organometallics 2002,
21, 4648–4661.
Results and Discussion
Reactions of [Ir(PMe3)4]Cl (1) with CH3CN and CD3CN.
Stoichiometric C-H and C-D oxidative addition was observed
when 1 was dissolved in neat CH3CN and CD3CN, respectively,
at room temperature (Scheme 1).14b
In both cases, the stoichiometric activation of a corresponding
C-H or C-D bond occurred in preference to the coordination
of the -CN moiety, and thus, the hydrido σ-alkyl compounds
cis-[IrH(CH2CN)(PMe3)4]Cl (2) and cis-[IrD(CD2CN)(PMe3)4]Cl
(3) were obtained in high purity and reasonable isolated yield
(56% and 54%) as air-stable, white solids upon crystallization
from neat CH3CN or CD3CN solutions, respectively, by addition
of toluene.14
Compounds 2 and 3 exhibit an octahedral geometry around
the Ir center, the corresponding hydride (1H NMR: δ -13.18,
2
2
2
ddt, JH-P-trans ) 132 Hz, JH-P-cis-a ) 20 Hz, JH-P-cis-b ) 16
Hz) and deuteride (2H{1H} NMR: δ -13.12 br dq, 2JD-P-trans
)
2
20 Hz, JD-P-cis ) 3 Hz) moieties occupying positions cis to
(13) Tellers, D. M.; Ritter, J. C. M.; Bergman, R. G. Inorg. Chem. 1999,
38, 4810–4818.
coordinated CH2CN and CD2CN, respectively, as expected for

2906 Organometallics, Vol. 28, No. 9, 2009
Crestani et al.
octahedral geometry around iridium.16 Details of the molecular
structure in the solid state will be deferred to a later section
(Vide infra).
The C-H/C-D activation of acetonitrile described above
proceeds very quickly, and we did not observe any precoordi-
nation of the nitrile to the metal center via π- or σ-bonding in
NMR experiments. This leaves the question of a feasible
bonding mode prior to C-H bond activation or a possible
hydration reaction of nitriles at iridium open, and therefore, we
investigated the coordination properties of p-substituted ben-
zonitriles, p-XC6H4CN (X ) CF3, F, Me, OH, OMe, and NH2),
with increasingly negative Hammett σp values, to 1, thus
avoiding competing C-H activation at the R-position.
Reaction of 1 with p-Aminobenzonitrile: Formation of
cis-[IrH(p-NHC6H4CN)(PMe3)4]Cl (4). In situ NMR spectro-
scopic studies of the reactions of 1 with a series of benzonitriles
with para subtituents X ) CF3, F, Me, and OMe showed no
evidence for interaction of the nitrile moiety with the iridium
center. However, in the case of p-aminobenzonitrile, N-H
oxidative addition occurred, and the product 4 was thus obtained
as an air- and moisture-stable white solid in 41% yield (Scheme
2).
The bound -NH- fragment of compound 4 appeared as a
1
broad singlet at δ 2.0 in the H NMR spectrum, upfield from
Figure 1. (Top) Molecular structure of 3 · 2H2O (here and hence-
forth, thermal ellipsoids are drawn at the 50% probability level).
(Bottom) Details of the hydrogen-bonding network involving the
Cl anion and two water molecules.
the respective free ligand (δ 4.3). Four separate doublets of
doublets for the aromatic protons appeared at δ 7.23, 7.01, 6.60,
and 6.51, the free ligand exhibiting only two doublets at δ 7.35
and 6.62. Importantly, the replacement of one NH proton by
the Ir center breaks the 2-fold symmetry of the p-aminoben-
zonitrile moiety, and the observation of four sharp aromatic
a concerted oxidative addition process. The deuteride moiety
displayed a trans coupling of 20 Hz, 6.6 times smaller than
that displayed by the hydride, consistent with the ratio of γH/
γD of 6.51.15
proton and four C-H carbon signals in the H and 13C{1H}
1
NMR spectra, respectively, indicates a lack of rotation about
the N-C bond, consistent with a trigonal-planar nitrogen
involved in strong π-conjugation with the aromatic ring. This
is probably enhanced by the presence of the p-CN π-acceptor
group as well as by the potentially destabilizing π-interaction
of the N-lone pair with the filled t2g orbitals on the d6-Ir(III)
center, resulting in a push-pull interaction across the arene ring.
The 13C NMR chemical shift of the aryl carbon attached to the
CN group appears shielded by ca. 8 ppm from its position in
the free p-aminobenzonitrile, consistent with a considerable
amount of negative charge being located at this center.
The 31P NMR spectrum of 4 confirmed the presence of the
phosphine trans to the hydride as a broad doublet at δ -55.8
(2JP-H-trans ) 139 Hz), the other two phosphorus environments
appearing as broad multiplets at δ -45 (trans-PMe3) and -57.3
(PMe3 trans to -NHC6H4CN).
The 31P and 31P{1H} NMR spectra of both compounds are
consistent with the presence of four phosphines in three
environments in an octahedral cis-IrP4XY geometry. In the case
2
of 2, the signal for the P trans to the hydride displays a JP-H
coupling of 132 Hz in the 31P NMR spectrum, matching the
value obtained from the 1H NMR spectrum. While the 31P{1H}
NMR spectrum of 3 displays a complex multiplet for the P trans
2
2
to D, due to the near equivalence of the JP–D and two JP-P
values, the 31P{1H + 2H} NMR spectrum simplified to a well-
resolved quartet with JP-P of 20 Hz. Single crystals of
2
compound 3 were obtained and characterized by X-ray crystal-
lography (see Figure 1, Tables 1 and S1), confirming the
(14) (a) Milstein, D.; Calabrese, J. C.; Williams, I. D. J. Am. Chem.
Soc. 1986, 108, 6387–6389. (b) English, A. D.; Herskovitz, T. J. Am. Chem.
Soc. 1977, 99, 1648–1649. For a later system involving the activation of a
C-H bond of (CH2(CN)2) by [Ir(H)(PMe3)4] under stoichiometric condi-
tions, see: (c) Behr, A.; Herdtweck, E.; Herrmann, W. A.; Keim, W.;
Kipshagen, W. Organometallics 1987, 6, 2307–2313. For an additional
report concerning the activation of R-CH bonds of nitriles using ruthenium,
see (d) Murahashi, S.-I.; Naota, T.; Taki, H.; Mizuno, M.; Takaya, H.;
Komiya, S.; Mizuho, Y.; Oyasato, N.; Hiraoka, M.; Hirano, M.; Fukuoka,
A. J. Am. Chem. Soc. 1995, 117, 12436–12451. For other reports concerning
the stoichiometric cleavage of activated R-protons using iridium complexes
of the type [Ir(PMe3)4]+ or its methyl analogue [Ir(PMe3)4Me] (ref 14d),
consult: (e) Dahlenburg, L.; Hache, R. Inorg. Chim. Acta 2003, 350, 77–
85. (f) Thorn, D. L.; Tulip, T. H. Organometallics 1982, 1, 1580–1586. (g)
Thorn, D. L. Organometallics 1982, 1, 197–204. (h) Thorn, D. L. J. Am.
Chem. Soc. 1980, 102, 17109–7110. For two additional reports describing
The solid-state structure of compound 4 was confirmed by
single-crystal X-ray diffraction (Figure 2, Tables 1 and S1).
Reaction of [Ir(PMe3)4]Cl (1) with p-Cyanophenol. The
addition of p-cyanophenol to a stirred THF/hexane suspension
of 1 led to the precipitation of a 1:1 mixture of cis-
[IrClH(PMe3)4][p-OC6H4CN] (5a) and trans-[IrClH(PMe3)4][p-
OC6H4CN] (5b). After three weeks at room temperature, this
ratio shifted completely in favor of the cis compound (Scheme
3).
1
The identity of the compounds has been confirmed by H
and 31P{1H} NMR spectroscopy, HRMS, and elemental analysis.
the formation of
a platinum(II) hydrido σ-alkyl complex, [Pt(H)-
(CH2CN)(PPh3)2], see: (i) Del Pra, A.; Forselini, E.; Bombieri, G.; Michelin,
R. A.; Ros, R. J. Chem. Soc., Dalton Trans. 1979, 1862. (j) Ros, R.;
Michelin, R. A.; Belluco, U.; Zanotti, G.; Del Pra, A.; Bombieri, G. Inorg.
Chim. Acta 1978, 29, L187–L188.
(16) Crystals of 3 were grown in air, leading to incorporation of water
molecules in the lattice. Repeated efforts to grow single crystals of 2 and
3 under an inert atmosphere were unsuccessful, suggesting that incorporation
of H2O may be required for crystal growth.
(17) Blum, O.; Carmielli, R.; Martin, J. M. L.; Milstein, D. Organo-
metallics 2000, 19, 4608–4612.
(15) The magnetogyric ratios of 1H and 2H (γH and γD) are 26.7522128
and 4.10662791 × 107 rad T-1 s-1, respectively. See, e.g.: http://
www.webelements.com/webelements/elements/text/H/nucl.html.

OxidatiVe Addition of X-H (X ) C, N, O) to [Ir(PMe3)4]Cl
Organometallics, Vol. 28, No. 9, 2009 2907
Table 1. Selected Bond Distances (Å)
3
4
5b
7
8
9a
9b
Ir-P(1)
Ir-P(2)
Ir-P(3)
Ir-P(4)
Ir-Cl
Ir-C(1)
Ir-N(1)
Ir-D/H
Ir-O(1)
Ir-O(2)
O(1)-O(2)
2.3536(9)
2.3254(8)
2.3447(8)
2.3897(9)
2.3428(8)
2.2966(8)
2.3491(8)
2.3817(9)
2.3460(4)
2.3291(4)
2.2963(7)
2.3056(7)
2.2874(7)
2.3034(8)
2.3388(7)
2.2975(6)
2.3564(7)
2.3969(6)
2.3667(7)
2.2778(7)
2.2833(6)
2.3596(7)
2.361(1)
2.298(1)
2.287(1)
2.356(1)
2.4950(5)
1.45(3)
2.177(3)
1.49(4)
2.121(2)
1.61
2.098(2)
1.64(3)
2.056(2)
2.064(2)
1.475(3)
2.057(3)
2.073(3)
1.481(5)
Scheme 2. Oxidative Addition of an N-H Bond of
p-Aminobenzonitrile to 1
Scheme 3. Reaction of [Ir(PMe3)4]Cl (1) with p-Cyanophenol
Leading to Two Isomers
The HRMS-ES+ spectrum displayed a peak at m/z of 531.11557
1
Da for the [IrHCl(PMe3)4]+ cation. The H NMR spectrum
displayed a doublet of quartets centered at δ -11.8 (2JH-P-trans
) 148 Hz, 2JH-P-cis ) 18 Hz) for the hydride of 5a and a quintet
at δ -21.66 (2JH-P-cis ) 15 Hz) for the trans compound 5b in
accordance with a publication by Milstein et al.17 The two
isomers are further distinguished by their 31P NMR spectrum,
2
2
5a displaying signals at δ -45.15 (dt, JP-P ) 19 Hz, JP-P
)
2
2
11 Hz), δ -46.90 (t, JP-P ) 19 Hz), and δ -53.60 (td, JP-P
) 19 Hz, JP-P ) 11 Hz), while 5b gives rise to a singlet at δ
2
-45.42. Single crystals of 5b · HOC6H4CN · THF suitable for
X-ray diffraction were obtained after recrystallization from THF;
the structure (Figure 3) shows the phenolate anion being
stabilized by a second molecule of 4-cyanophenol via hydrogen
bonding.
Interestingly, unlike the experiment involving p-aminoben-
zonitrile, the reaction with p-cyanophenol did not yield the
primary X-H oxidative addition product. The initial ratio of
compounds 5a and 5b might result from either protonation of
the iridium complex 1 followed by coordination of the chloride
anion or oxidative addition of p-cyanophenol and subsequent
anion substitution. However, the H NMR spectrum of the
1
reaction mixture showed traces of an additional product giving
rise to a doublet of quartets at δ -11.2 (2JH-P-trans ) 148 Hz,
2JH-P-cis ) 18 Hz) and a quintet at δ -20.59 (2JH-P-cis ) 15
Hz). In addition, small amounts of another cation were observed
in the HRMS at m/z ) 614.17392, suggesting partial Cl/p-
Figure 3. Molecular structure of 5b · HOC6H4CN · THF. Primed
atoms are generated by 2-fold axes, double-primed by an inversion
center.
Figure 2. Molecular structure of 4 · CD3CN (note the absence of
hydrogen bonding to the NH group).

2908 Organometallics, Vol. 28, No. 9, 2009
Crestani et al.
Figure 4. Molecular structure of 7 · THF, showing one of the alternative positions of the THF molecule. Primed atoms are generated by the
2-fold axis.
Scheme 4. Iridium-Mediated N-H Bond Cleavage of
OC6H4CN anion exchange leading to the [IrH(p-OC6H4CN)-
Acetamide
(PMe3)4] cation. This reaction has been carried out several times,
and in some cases, we were able to detect cis-[IrH(p-
OC6H4CN)(PMe3)4]Cl (6) as the major product (ca. 75%) giving
rise to a doublet of quartets at δ -11.04 (2JH-P-trans ) 144 Hz,
2JH-P-cis ) 19 Hz) in the 1H NMR spectrum and a signal in the
HRMS at m/z ) 614.17392. Whatever the small differences in
the conditions of the experiments were is not clear, but it is
feasible that a concentration effect or traces of water might
influence the reaction pathway through, e.g., hydrogen bonding,
as has been found in the crystal (Figure 3) obtained from a
understand the origin of the H/D scrambling, we also examined
reaction mixture employing 2 equiv of p-cyanophenol.
the reactivity of 1 toward acetamide.
Synthesis of [Ir(PMe3)4][BPh4] (7). In order to investigate
N-H Oxidative Addition of Acetamide to 1. The reaction
further the oxidative addition reaction of p-cyanophenol to the
of acetamide with 1 at room temperature, in THF suspension
cation [Ir(PMe3)4]+ and the influence of the counterion, we
(Scheme 4), resulted in the cleavage of an N-H bond in prefer-
prepared and fully characterized [Ir(PMe3)4][BPh4] (7) and
ence to a C-H bond in the same molecule, the activation of
reacted it with p-HOC6H4CN.
the former being envisioned as the reverse of the final step in
the catalytic hydration of acetonitrile.18 The reaction required
The addition of Na[BPh4] to a stirred suspension of 1 in THF
led to the quantitative formation of 7. Single crystals of 7
suitable for X-ray diffraction were obtained after recrystallization
from THF/hexanes, and the structure is shown in Figure 4.
72 h, after which time, cis-[IrH(NHC(O)Me)(PMe3)4]Cl (8) was
1
isolated as a white, air-stable solid in 55% yield. Its H NMR
spectrum displayed a broad signal centered at δ 3.9 and a sharp
singlet at δ 1.95, consistent with a bound -NH and a -CH3
group of the coordinated -NHC(O)Me moiety. The chemical
shift for the -NH fragment is shielded from the corresponding
-NH2 protons in free acetamide (δ 6.1, 5.9).
The Ir-H resonance was observed at δ -11.3 as a broad
doublet; coupling to the cis-phosphines was not resolved. The
31P{1H} NMR spectrum of 8 confirmed the presence of three
phosphorus environments consistent with a cis octahedral
geometry. The structure of compound 8, cocrystallized with a
water molecule, was obtained by X-ray diffraction studies
(Figure 5, Tables 1 and S1).
Compound 8 should be the last key intermediate in the
iridium-mediated hydration reaction of acetonitrile and provides
various possible pathways for H/D exchange, i.e., protonation
of the metal-bound nitrogen by H2O or CD3CN, exchange of
the hydrido ligand at iridium prior to reductive elimination, etc.
Unfortunately, the reaction of 7 with p-HOC6H4CN is very
unselective and led to several unidentified products. The NMR
experiments indicate that the counterion [BPh4]- is partially
involved and is thus not completely innocent.
Although we could not find evidence for Ct N coordination
of benzonitriles to 1, and acetonitrile undergoes C-H bond
activation, we nonetheless examined 2 and 3 as potential catalyst
precursors for the hydration of acetonitrile. In preliminary NMR
experiments, with 10 mol % loading of cis-[IrH(CH2CN)-
(PMe3)4]Cl (2) or cis-[IrD(CD2CN)(PMe3)4]Cl (3) in d3-aceto-
nitrile/H2O (molar ratio 1:1) at 120 °C, the formation of
acetamide, the hydration product of CD3CN, was observed
together with stoichiometric amounts of OPMe3 with respect
to the iridium complex. Interestingly, 13C NMR spectroscopic
and GC/MS investigations clearly indicated incorporation of
protons at the methyl group in the final product, as well as
incorporation of deuterium at the nitrogen in acetamide, leading
to a distribution of several dn-acetamides. In addition, the GC/
MS also revealed that the CD3CN solvent undergoes H/D
exchange with H2O under the above-mentioned conditions. The
same behavior was found on employment of 1 as catalyst
precursor for the reaction of acetonitrile with water. In order to
The observed C-H and N-H bond activation of acetonitrile
and of the hydration reaction product acetamide, respectively,
(18) For the use of [Cp*(PMe3)Ir(Ph)(OH)] in reactions involving the
preparation of a series of carboxamido complexes, including one with
acetamide, see ref 13.

OxidatiVe Addition of X-H (X ) C, N, O) to [Ir(PMe3)4]Cl
Organometallics, Vol. 28, No. 9, 2009 2909
metric unit of 4 contains one molecule of deuterated acetonitrile,
forming a weak hydrogen bond, C-D · · · Cl (D · · · Cl 2.69 Å).
Surprisingly, the -NH group forms no hydrogen bond in the
presence of good potential acceptors.
The cation in each case shows a distorted cis-octahedral
coordination of Ir and approximate local mirror symmetry (plane
“m” through Ir, P(2), P(4), and C(1) or N(1) atoms). The
positions of hydride (deuteride in 3) ligands were revealed in
the electron density map (and in 3 and 8 also refined by least-
squares) to lie in this plane within experimental error. Ir-P
distances are consistent with the succession of trans-influence,
H/D > PMe3 > CH2CN > NHC(O)Me. In 3, the linear
C(1)C(2)N group is syn to the deuteride ligand but is rotated
out of the m plane by 9° to the side of P(3). The CD2-CN
bond distance (1.451(4) Å) is typical of that found for alkyl-
CH2CN derivatives (mean 1.465(7) Å),21 and the Ir-C (2.177(3)
Å) bond is slightly longer than in [(Me3P)4Ir(H)Me]-
[CpMo(CO)3] (2.04(2) Å),22 PPN[(OC)2Ir(CH2CN)2] (2.138(8)
Å),23 and [(Me3P)4Ir(H)CH2OH]PF6 (2.134(5) Å).14a In cation
8, the planar acetamido ligand forms a dihedral angle of 15°
with the m plane. The N(1)-C(1) bond is shorter (1.322(3) Å)
and the C(1)-O(1) bond longer (1.262(3) Å) than in R-NH-
C(O)Me analogues, e.g., with R ) 1-adamantyl (1.345(2) and
1.235(2) Å, respectively)24 or R ) 4-fluorocuban-1-yl (1.336(1)
and 1.234(1) Å),25 indicating a shift toward the +NdC-O-
structure. In cation 4, the angle between the m plane and the
benzene ring plane equals 10°, the coordination plane of the
N(1) atom being inclined to these planes by 4° and 6°,
respectively. The arene ring shows a significant quinoid distor-
tion, the C(2)-C(3) and C(5)-C(6) bonds being ca. 0.03 Å
shorter than the remaining four C-C bonds (mean 1.377(3) vs
1.410(4) Å). The only structurally characterized p-NC-C6H4NHR
derivative with an unconjugated R group, bis(4-cyanophenyl)-
cyclohexanediamine,26 shows a similar difference in the ring
bond distances (∆ ) 0.031, esd 0.005 Å) as well as C(ar)-NH
and C(ar)-CN distances (1.362(4) and 1.433(5) Å) similar to
those in 4 (1.354(3) and 1.433(3) Å), and consistent with a
degree of C(ar)-NH multiple bond character resulting in the
lack of rotation about this bond in solution, Vide supra. Two
iridium complexes (five- and six-coordinate) with PhNH
ligands27 also show marginal quinoidal distortions (∆ ) 0.018,
esd 0.003 Å); the Ir-N bond in the six-coordinate (PCP)Ir(H)-
(NHPh)(CO) is trans to the Ir-C σ-bond and is slightly longer
(2.142(2) Å) than in 4.
Figure 5. Molecular structure of cis-[IrH(NHC(O)Me)(PMe3)4]Cl
(8) · H2O.
providing possibilities for H/D exchange, led us to investigate
the synthesis and catalytic properties of a more electrophilic
Ir(III) species incapable of undergoing oxidative addition and
thus potentially favoring coordination of nitrile Ct N groups.
Reaction of [Ir(PMe3)4]Cl (1) with O2. Bubbling dry
dioxygen for a period of 4 h through an orange THF suspension
of 1 gave cis-[Ir(O2)(PMe3)4]Cl (9) as a white precipitate, which
was recrystallized from CH3CN/Et2O and isolated in 82% yield.
The green-yellow crystals were suitable for X-ray diffraction,
and crystal structures were obtained for two different pseudo-
polymorphs (a and b), as shown in Figures 6 and 7. It is
noteworthy that when the product is dried in Vacuo, it is
colorless, while a solvent effect leads to the colored crystals.
Scheme 5 illustrates the reaction; the formation of d6 complexes
with formula [M(L)4(O2)]+ (M ) Co, Rh, Ir)19 containing η2-
coordinated dioxygen,14d and their analogues, [M(L2)2(O2)]+ (M
) Rh, Ir),20 is well-known.
Discussion of the Crystal Structures of 3, 4, 5b, and
7-9. Crystal data and other experimental details are listed in
Table S1, and selected bond distances are given in Table 1.
The single crystals for X-ray diffraction studies were grown
by solvent diffusion of toluene/acetonitrile mixtures without
precautions to eliminate exposure to air; thus, incorporation of
water molecules in the crystal lattice was observed in several
cases. This finding underlines the stability of the products to
oxygen and water at ambient temperature.
The asymmetric units in crystals of 3, 4, and 8 (Figures 1, 2,
and 5) contain one complex cation and one chloride anion. That
of 3 also contains two water molecules, which, with the anions,
form an infinite hydrogen-bonded double chain [ribbon] parallel
to the crystal axis x (Figure 1, bottom). The asymmetric unit of
8 contains one water molecule; the cations related via the
inversion center (1/2, 0, 1/2) are linked by a pair of hydrogen-
bonded bridges, N-H · · · Cl · · · H-O-H · · · O(1). The asym-
In the structure of 5b (Figure 3), the cation is situated on a
crystallographic 2-fold axis (passing through the Ir, Cl, and
hydride H atoms) and thus has a distorted trans-octahedral
coordination. The p-NCC6H4O- anion and its symmetrical
equivalent via an inversion center must be linked by a hydrogen
bond (and thus constitute a {(NCC6H4O)2H}- monoanion), as
indicated by the short O · · · O′′ distance of 2.438(3) Å, cf.
2.471(5) Å in [PhOHOPh]NBu428 and 2.44 Å in [(p-OC6H4O)(p-
HOC6H4OH)](NH2Et2)2.29 Indeed, a peak of electron density
(19) (a) Lanci, M. P.; Brinkley, D. W.; Stone, K. L.; Smirnov, V. V.;
Roth, J. P. Angew. Chem., Int. Ed. 2005, 44, 7273–7276. (b) Ziegler, T.
Inorg. Chem. 1985, 24, 1547–1552. (c) Norman, J. G., Jr.; Ryan, P. B.
Inorg. Chem. 1982, 21, 3555–3557. (d) Nolte, M.; Singleton, E. Acta
Crystallogr. 1976, B32, 1838–1841. (e) de Bruin, B.; Peters, T. P. J.; Wilting,
J. B. M.; Thewissen, S.; Smits, J. M. M.; Gal, A. W. Eur. J. Inorg. Chem.
2002, 2671–2680.
(20) (a) Vigalok, A.; Shimon, L. J. W.; Milstein, D. J. Chem. Soc., Chem.
Commun. 1996, 1673–1674. (b) Wang, J.-C.; Chou, L.-Y.; Hsien, W.-Y.;
Liu, L.-K. Acta Crystallogr. 1994, C50, 879–882. (c) Nolte, M.; Singleton,
E.; Laing, M. J. Chem. Soc., Dalton Trans. 1976, 19, 1979–1984. (d) Nolte,
M. J.; Singleton, E.; Laing, M. J. Am. Chem. Soc. 1975, 97, 6396–6400.
(e) Terry, N. W., III; Amma, E. L.; Vaska, L. J. Am. Chem. Soc. 1972, 94,
653–655. (f) McGinnety, J. A.; Payne, N. C.; Ibers, J. A. J. Am. Chem.
Soc. 1969, 91, 6301–6310. (g) McGinnety, J. A.; Ibers, J. A. J. Chem. Soc.,
Chem. Commun. 1968, 5, 235–237.
(21) Cambridge Structural Database, November 2007 release, see: Allen,
F. H.; Taylor, R. Chem. Soc. ReV. 2004, 33, 463–475.
(22) Dahlenburg, L.; Hache, R. Inorg. Chim. Acta 2003, 350, 77–85.
(23) Porta, F.; Ragaini, F.; Cenini, S.; Demartin, F. Organometallics
1990, 9, 929–935.
(24) Prohl, H.-H.; Blaschette, A.; Jones, P. G. Acta Crystallogr. 1997,
C53, 1434–1436.
(25) Irngartinger, H.; Strack, S.; Gredel, F.; Dreuw, A.; Della, E. W.
Eur. J. Org. Chem. 1999, 1253–1257.
(26) Anthony, S. P.; Radhakrishnan, T. P. Chem. Commun. 2004, 1058–
1059.
(27) Kanzelberger, M.; Zhang, X.; Emge, T. J.; Goldman, A. S.; Zhao,
J.; Incarvito, C.; Hartwig, J. F. J. Am. Chem. Soc. 2003, 125, 13644–13645.

2910 Organometallics, Vol. 28, No. 9, 2009
Crestani et al.
Figure 6. Molecular structure of 9a · 3CH3CN, showing the disorder of the acetonitrile of crystallization.
(hydride) ligand, in 5b the four phosphine ligands adopt a
peculiar pseudotetrahedral arrangement. With respect to a plane
perpendicular to the 2-fold (i.e., Cl-Ir-H) axis and passing
through the Ir atom, P(1) and its symmetric equivalent P(1′)
are tilted by 0.45 Å toward the Cl atom, while P(2) and P(2′)
are tilted by 0.26 Å toward the hydride ligand. In either case,
one methyl group of the phosphine ligand is eclipsed with the
ligand (H or Cl) from which the phosphine is tilted away.
The asymmetric unit of 7 contains two symmetrically
nonequivalent [Ir(PMe3)4]+ cations, both Ir atoms lying on a
crystallographic 2-fold axis. The THF molecule is disordered
between two positions related via the same axis, while the
[BPh4]- anion occupies a general position (Figure 4). The crystal
is isomorphous with that of [Rh(PMe3)4][BPh4] · 1/2C6H6.31 The
metal coordination is distorted from square-planar toward
tetrahedral, with pseudo-trans angles P(1)-Ir(1)-P(1′) 158.55(4)°,
P(2)-Ir(1)-P(2′) 160.40(4)°, P(3)-Ir(2)-P(3′) 152.82(4)°,
P(4)-Ir(2)-P(4′) 158.87(4)° considerably reduced from 180°.
However, in [Ir(PMe3)4]PF6 (the only nonchelated IrP4 complex
reported previously), these angles are even smaller, 149.3(1)°
and 150.3(1)°; thus the coordination must be fairly responsive
to outer-sphere influences.
Figure 7. Molecular structure of 9b · H2O · CH3CN.
Scheme 5. Formation of the Peroxo Compound
cis-[Ir(O2)(PMe3)4]Cl (9)
Crystallizations of 9 gave two pseudopolymorphs, both
containing one cation and one anion per asymmetric unit, that
of 9a contains three molecules of acetonitrile (two of them
disordered), and that of 9b, one acetonitrile and one water
molecule. Thus, incidentally, 9b has exactly the composition
for the catalytic process. The anions and water molecules are
hydrogen-bonded into an infinite chain (spiraling around the 21
screw axis) to which the acetonitrile molecules are attached
through weak C-H · · · O and C-H · · · Cl hydrogen bonds. The
cations in 9a and 9b have essentially identical geometries, which
could be described as trigonal-bipyramidal, with the Ir, P(2),
P(3), O(1), and O(2) atoms lying in the equatorial plane,
although, as the P(2)-Ir-P(3) angle ) 94.63(2)° in 9a and
99.66(4)° in 9b, a distorted octahedral description seems more
appropriate. As usual, “axial” Ir-P bonds are longer than
“equatorial” ones. Compared with the isostructural cation
[Ir(O2)(PMe2Ph)4]+, Ir-P distances in 9 are shorter by ca. 0.03
was located at the inversion center and successfully refined as
a hydrogen atom. The THF molecule of crystallization is located
on a crystallographic 2-fold axis.
Complex 5b is the third structurally characterized IrHP4Cl
complex and the second one with a trans-configuration, after
[HIr(depe)2C1]+[CH(CN)2]-.30 While in the latter complex the
angles at Ir deviate little from octahedral, and in the cations of
3, 4, and 8 adjacent phosphines are tilted toward the smallest
(28) Goddard, R.; Hertzog, H. M.; Reetz, M. T. Tetrahedron 2002, 58,
7847–7850.
(29) Mahmoud, M. M.; Wallwork, S. C. Acta Crystallogr. 1991, C47,
1434–1438.
(30) Behr, A.; Herdtweck, E.; Herrmann, W. A.; Keim, W.; Kipshagen,
W. Organometallics 1987, 6, 2307–2313.
(31) Nolte, M. J.; Singleton, E. Acta Crystallogr. 1976, C32, 1838–
1841.

OxidatiVe Addition of X-H (X ) C, N, O) to [Ir(PMe3)4]Cl
Organometallics, Vol. 28, No. 9, 2009 2911
Scheme 6. Nucleophilic Attack of Water at a Nitrile Group
Coordinated to an Ir(III) Center
Å, but the geometry of dioxygen bonding is essentially the same,
confirming the absence of straightforward structural relation-
ships.32
Catalysis Experiments. The peroxo compound cis-
[Ir(O2)(PMe3)4]Cl (9) was employed as catalyst precursor at 0.l
mol % loading for the reaction of acetonitrile with water at 140
°C for 200 h to yield acetamide with >800 turnovers and an
isolated yield of 82%. The activity of the iridium catalyst in
terms of TON is comparable to those of nickel, platinum, and
palladium systems using phosphines as auxiliary ligands. A
series of experiments were subsequently conducted at 1 mol %
catalyst loading to gain insight into the reaction mechanism.
The experiments included the reagent combinations CH3CN/
H2O (A), CD3CN/D2O (B), CD3CN/H2O (C), and CH3CN/D2O
(D).
In the same manner as the original run to yield acetamide
(A), perdeuterated d5-acetamide can be obtained on employment
of CD3CN and D2O (B) as demonstrated by GC/MS and 13C
NMR spectroscopy (see Figure S3). Interestingly, the reactions
of CD3CN/H2O (C) and CH3CN/D2O (D) did not give the
expected single products CD3C(O)NH2 and CH3C(O)ND2, but
rather a statistical distribution of various isotopomers of
acetamide with different deuterium content ranging from d0 to
d5 was observed. The GC/MS results indicate for C that d3-
acetamide and for D, that d2-acetamide were major products
with ca. 32% abundance, although further signals at (1 mass
units appear with 21-27% abundance (see Figures S5 and S7).
The resonances in the 13C NMR spectra at δ 21.5 for the
acetamide methyl group produced in reactions C and D show
overlapping singlets, triplets, quintets, and septuplets with
coupling constants of 1JC-D ) 20 Hz, thus proving the presence
of CH3, CH2D, CHD2, and CD3 groups in the final products.
Substantial evidence for competitive C-H and C-D activation
of acetonitrile and therefore a feasible explanation for the above-
mentioned observations was obtained on investigation of the
reaction mixtures by 13C NMR spectroscopy and GC/MS. The
resonance at δ 0.8 for the CH3/CD3 group in “unreacted”
acetonitrile appears as several overlapping multiplets. The GC/
MS indicates for run D CH2DCN (m/z ) 42) and CHD2CN
(m/z ) 43) as the major species, although loss of deuterium
from CD3CN to give CD2CN (m/z ) 42) as a fragment ion
cannot be entirely excluded. The data for experiment C show,
besides CH2DCN as the major isotopomer, further deuterium
incorporation pointing to the presence of CHD2CN and CD3CN
(see Figures S6 and S8). In an in situ 31P NMR spectrum of a
catalytic reaction mixture, the formation of OdPMe3 was
observed together with the formation of an {Ir(PMe3)3} species
displaying a doublet at δ -33.8 (2JP-P ) 20 Hz) and a triplet
at δ -51.0 (2JP-P ) 20 Hz) in addition to signals for other
species in small quantities. The 1H NMR spectrum of the
reaction mixture displayed several resonances in the hydride
region between δ -11 and -25. It is feasible that during the
catalytic conversion an Ir(I) species is generated that undergoes
C-H/C-D/O-H/O-D activation of acetonitrile and water,
promoting the H/D exchange. Milstein et al. reported the
formation of cis-[IrH(OH)(PMe3)4]PF6 upon addition of water
to [Ir(PMe3)4]PF6.14a The high basicity of the hydroxo ligand
leads to H/D exchange to give cis-[IrH(OD)(PMe3)4]PF6. We
have shown in this publication that [Ir(PMe3)4]Cl is also capable
of activating the N-H bond in acetamide, and thus an
intermediate iridium hydrido-acetamido complex would provide
another route for H/D incorporation at the amino group of the
Scheme 7. Nitrile Insertion into the Metal Hydroxo Bond
(Left) or External Attack of Hydroxide on Coordinated
Nitrile (Right)
initial product. Further evidence supporting the existence of an
Ir(I) species capable of C-H/O-H activation, and hence
scrambling, arises from the above-mentioned preliminary NMR
experiments reacting [Ir(PMe3)4]Cl (1), cis-[IrH(CH2CN)-
(PMe3)4]Cl (2), or cis-[IrD(CD2CN)(PMe3)4]Cl (3) with water
in CD3CN at elevated temperature, giving dn-acetamide accord-
1
ing to H NMR and 13C NMR spectroscopy and GC/MS. In
both experiments the formation of OdPMe3 was observed,
although no O2 was present, and thus water must be the source
of the oxygen atom.
Various general mechanisms for the hydration of nitriles are
possible, two of which involve nucleophilic attack of water upon
coordination of the nitrile group or insertion into a metal-hydroxo
bond, aspects of which are illustrated in Schemes 6 and 7. End-
on coordination of the nitrile group should be favored at a
coordinatively unsaturated Ir(III) center, not being able to
undergo facile oxidative addition, which could be formed by
either dissociation of phosphine ligands or intramolecular
reaction of the PMe3 with the oxygen bound to the metal at
elevated temperature, forming OdPMe3 and an electrophilic
(32) Blum, O.; Calabrese, J. C.; Frolow, F.; Milstein, D. Inorg. Chim.
Acta 1990, 174, 149–151.

2912 Organometallics, Vol. 28, No. 9, 2009
Crestani et al.
over and vacuum transferred from calcium hydride. THF-d8 and
D2O were purchased from Cambridge Isotope Laboratories and were
also deoxygenated using the freeze-pump-thaw method. All
deuterated organic solvents were stored over 3 Å molecular sieves
in a glovebox for at least 24 h prior to their use. [Ir(PMe3)4]Cl (1)
was prepared following the literature procedure,34 p-aminoben-
zonitrile (98%), p-tolunitrile (98%), p-fluorobenzonitrile (99%), and
acetamide (99%) were purchased from Alfa-Aesar, Avocado, or
Lancaster, and p-methoxybenzonitrile (99%) and p-cyanophenol
(95%) were purchased from Aldrich. All other chemicals, filter aids,
and chromatographic materials were reagent grade and were used
as received. 1H (399.9 or 499.8 MHz), 31P, 31P{1H} (161.9 or 202.3
MHz), and 13C{1H} (100.6 or 125.7 MHz) NMR spectra were
recorded at ambient temperature using Varian Mercury-400, Bruker
Avance-400, or Varian Inova-500 spectrometers; all 2H{1H} (76.7
MHz) and 31P{1H+2H} (202.3 MHz) NMR spectra were recorded
using the latter spectrometer. 1H NMR chemical shifts are reported
relative to TMS and were referenced via residual proton resonances
of the corresponding deuterated solvent, while 13C{1H} NMR
spectra are reported relative to TMS using the carbon signals of
the deuterated solvent. 31P{1H} and 31P NMR spectra are reported
relative to external 85% H3PO4. 2H NMR experiments are reported
relative to TMS and were referenced via the residual deuterium
resonance in the corresponding protio solvent. The NMR samples
in this work were handled under nitrogen or argon using Wilmad
NMR tubes equipped with J. Young valves unless otherwise
specified. Unit mass and high-resolution mass spectrometric (MS
and HRMS, respectively) determinations were obtained by means
of electrospray (ES+) using acetonitrile solutions and a Thermo-
Finnigan LTQ FT spectrometer. Elemental analyses were obtained
using an Exeter Analytical Inc. CE-440 elemental analyzer. GC/
MS analyses were performed using a LECO-Pegasus 4D equipped
with an Agilent 6890N gas chromatograph and a time-of-flight mass
analyzer or using an Agilent 6890N gas chromatograph equipped
with an Agilent 5973 mass selective detector operating in EI mode.
Structure Determinations. Full spheres of diffraction data were
measured at T ) 120 K on Bruker 3-circle diffractometers with
CCD area detectors SMART 1K (for 3, 4, 7, 8, and 9a) or SMART
6K (for 5b), or a Rigaku R-Axis SPIDER diffractometer with
cylindrically curved imaging plate (for 9b), using graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å) and Cryostream
(Oxford Cryosystems) open-flow N2 cryostats. Data were corrected
for absorption by a semiempirical method based on Laue equivalents
(3, 4) or by numerical integration based on crystal face-indexing
(5b, 7, 8, 9a, and 9b) using the SADABS program35 (for 9b,
NUMABS36). The structures were solved by Patterson (3, 8, 9a)
or direct methods and refined by full-matrix least-squares against
F2 of all data, using SHELXTL software.37 Non-hydrogen atoms
were refined in anisotropic approximation (isotropic for disordered
carbon atoms in 9b). All deuterium atoms in 3, H atoms bonded to
Ir (except in 4), N or O (except in 9b) atoms were refined in isotopic
approximation. Methyl groups were treated as rigid bodies, and
other H atoms were treated using a “riding” model.
Ir(III) cation (Scheme 6). The insertion reaction might yield an
Ir(I) species after reductive elimination of the acetamide
(Scheme 7), in turn participating in the various H/D exchange
mechanisms. The latter case can proceed via two different
reaction pathways, one involving dissociation of a hydroxo
ligand and the formation of an iridium dication with subsequent
nucleophilic attack of OH- on coordinated nitrile, the other
occurring by dissociation of PMe3 and intramolecular migration
of the OH- ligand to the coordinated nitrile. Both pathways
would give the same intermediate I (Scheme 7) after tautomerism.
As mentioned above, the reactions of 1 with degassed water
in CD3CN and 2 or 3 in degassed H2O/CD3CN also produce
OdPMe3, giving rise to a different mechanism of phosphine
oxidation involving water as the oxygen source instead of cis-
[Ir(O2)(PMe3)4]Cl (9).33 The great variety of different feasible
mechanisms for metal-mediated H/D exchange and for the
catalytic hydration of the nitrile makes it very difficult to
determine the reaction pathways and the active species. How-
ever, we have prepared and investigated cis-[Ir(O2)(PMe3)4]Cl
(9) as an air- and moisture-stable catalyst precursor that
generates in situ an active catalyst for the hydration of
acetonitrile to give acetamide.
Conclusions
In this paper we report reactions of the electron-rich complex
[Ir(PMe3)4]Cl (1) with nitriles, in which the employment of
CH3CN and p-X-C6H4CN (X ) HO, H2N) led to C-H/O-H/
N-H activation, with no spectroscopic evidence for nitrile
coordination to the metal center. An NMR spectroscopic
investigation of the reactions of other para-substituted benzoni-
triles p-X-C6H4CN (X ) CF3, F, Me, OMe) with 1 also did not
show any evidence of nitrile coordination. We reacted 1 with
acetamide, the product of acetonitrile hydration, to gain insight
into the nitrile hydration process, and we isolated the N-H
oxidative
addition
product
cis-[IrH(NHC(O)Me)-
(PMe3)4]Cl (8), which can be seen as being a model for the
penultimate intermediate in the catalytic process.
The iridium complexes 1, 2, and 3, as well as the peroxo
derivative cis-[Ir(O2)(PMe3)4]Cl (9), were catalyst precursors
for acetonitrile hydration at 140 °C, with 9 giving up to 800
turnovers under the conditions examined. The activity of the
iridium catalyst is comparable to those of nickel, ruthenium,
palladium, and platinum systems using phosphines as auxiliary
ligands. The reaction of CH3CN with D2O and CD3CN with
H2O using 9 as catalyst precursor led to acetamides containing
0-5 D per molecule, indicative of H/D scrambling. NMR
spectroscopic follow-up of the reaction also revealed C-H/D
scrambling in the acetonitrile.
cis-[IrH(CH2CN)(PMe3)4]Cl (2). [Ir(PMe3)4]Cl (1) (0.050 g,
0.094 mmol) was dissolved in acetonitrile (1 mL) and stirred at
room temperature overnight. The orange solution turned pale
yellow. Addition of toluene precipitated the product as a white,
crystalline solid, which was collected by filtration, washed with
Et2O (3 × 10 mL), and dried overnight in Vacuo. Yield: 0.030 g
(56.6%). Anal. Calcd (%) for C14H39ClIrNP4: C, 29.34; H, 6.86;
N, 2.44. Found: C, 29.07; H, 6.92; N, 2.19. HRMS-ES+: calcd for
C14H39191IrNP4 ([M]+) 536.16336 Da, found 536.16334 Da. NMR
Experimental Section
General Considerations. Unless otherwise noted, all manipula-
tions were performed using standard Schlenk and glovebox
techniques under an inert atmosphere. An Innovative Technology
Inc. glovebox was used under nitrogen (BOC), and VAC and
MBraun gloveboxes were used under argon (Praxair). All protio
solvents (Fisher Scientific and J.T. Baker) were reagent grade and
were dried and deoxygenated using an Innovative Technology Inc.
Pure-Solv 400 solvent purification system; THF was also distilled
from purple benzophenone ketyl solutions. Water was purified by
distillation and was deoxygenated using the freeze-pump-thaw
method. CH3CN and CD3CN were purchased from Aldrich, refluxed
2
(CD3CN): 1H δ 1.75 (d, JH-P ) 3 Hz, 18H, mutually trans
(34) Herskovitz, T. Inorg. Synth. 1982, 99–103.
(35) Sheldrick, G. M. SADABS 2006/1; Bruker-Nonius AXS: Madison,
WI, 2006.
(33) Grushin, V. V.; Alper, H. Organometallics 1993, 12, 1890–1901.
(36) NUMABS; Rigaku Inc.: Tokyo, Japan, 2007.

OxidatiVe Addition of X-H (X ) C, N, O) to [Ir(PMe3)4]Cl
Organometallics, Vol. 28, No. 9, 2009 2913
2
phosphines), 1.74 (d, JH-P ) 2 Hz, 9H, PMe3 trans to hydride),
precipitate formed, which was collected by filtration and dried in
Vacuo to give a white solid. Yield: 125 mg (100%). cis-
[IrClH(PMe3)4][p-OC6H4CN] (5a), NMR (CD3CN): 1H δ 7.10 (br
d, JH-H ) 9 Hz, 2H, Ar), 6.18 (br d, JH-H ) 9 Hz, 2H, Ar), 1.8 (br
d, 2JH-P ) 10 Hz, 9H, PMe3 trans to chloride), 1.74 (vt, JH-P ) 4
1.46 (d, 2JH-P ) 8 Hz, 9H, PMe3 trans to CH2CN), 1.27 (tdd, J1 )
2
9 Hz, J2, J3 ) 6 Hz, 2H, CH2CN), -13.2 (ddt, JH-P-trans ) 132
Hz, JH-P-cis-a ) 21 Hz, JH-P-cis-b ) 16 Hz, 1H, Ir-H); 13C{1H} δ
2
2
133.24 (br d, 3JC-P-trans ) 11 Hz, CN), 23.76 (ddd, 1JC-P ) 35 Hz,
3JC-P-cis-a ) 4 Hz, JC-P-cis-b ) 2 Hz, PMe3 trans to hydride), 21.1
3
2
Hz, 18H, PMe3, mutually trans phosphines), 1.56 (dd, JH-P ) 8
1
3
3
3
4
(tdt, JC-P, JC-P-trans-PMe3 ) 20 Hz, JC-P-cis-a ) 3 Hz, JC-P-cis-b
)
Hz, JH-H ) 1 Hz, 9H, PMe3, trans to hydride), -11.8 (dq,
2 Hz, mutually trans phosphines), 18.75 (dq, 1JC-P ) 29 Hz, 3JC-P
2JH-P-trans ) 148 Hz, 2JH-P-cis ) 18 Hz, 1H, Ir-H); 31P{1H} δ -45.2
2
2
2
) 2 Hz, PMe3 trans to CH2CN), -32.9 (br d, JC-P-trans ) 60 Hz,
(td, JP-P ) 20 Hz, JP-P ) 11 Hz, 1P, PMe3 trans to Cl), -46.9
CH2CN); 31P δ -53.4 (br m, mutually trans phosphines), -59.2
2
2
(t, JP-P ) 20 Hz, 2P, mutually trans PMe3), -53.6 (td, JP-P
20 Hz, JP-P ) 11 Hz, PMe3 trans to H). trans-[IrClH(PMe3)4]-
[p-OC6H4CN] (5b), NMR (CD3CN): H δ 7.10 (br d, J ) 9 Hz,
)
2
(br m, PMe3 trans to CH2CN), -60.5 (br d, JP-H-trans ) 132 Hz,
2
PMe3 trans to hydride); 31P{1H} δ -53.4 (t, J ) 20 Hz, mutually
trans phosphines), -59.2 (dt, J1 ) 18 Hz, J2 ) 20 Hz, PMe3 trans
to CH2CN), -60.55 (dt, J1 ) 18 Hz, J2 ) 20 Hz, PMe3 trans to
hydride).
1
2H, Ar), 6.18 (br d, JH-H ) 9 Hz, 2H, Ar), 1.69 (s, PMe3), -21.87
2
(quint, JH-P-cis ) 15 Hz, 1H, Ir-H); 31P{1H} δ -45.4 (s, PMe3).
Anal. Calcd (%) for C19H41NClIrOP4: C 35.03, H 6.35, N 2.15.
Found: C 34.57, H 6.27, N 2.47. HRMS-ES+: calcd for
C12H3735Cl193IrP4 ([M]+) 531.11583, found 531.11557.
cis-[IrD(CD2CN)(PMe3)4]Cl (3). [Ir(PMe3)4]Cl (1) (0.050 g,
0.094 mmol) was dissolved in CD3CN (1 mL) and stirred at room
temperature overnight. The orange solution turned pale yellow.
Addition of toluene precipitated the product as a white, crystalline
solid, which was collected by filtration, washed with Et2O (3 × 10
mL), and dried overnight in Vacuo. Yield: 0.030 g (54.7%). Anal.
Calcd (%) for C14H36D3ClIrNP4: C, 29.19; H, 7.35, N, 2.43. Found:
C, 29.14; H, 6.85; N, 2.14. MS-ES+: 541 Da ([M]+). NMR
[Ir(PMe3)4][BPh4] (7). [Ir(PMe3)4]Cl (1) (60 mg, 0.113 mmol)
and Na[BPh4] (39 mg, 0.113 mmol) were suspended in THF (2.5
mL) and stirred overnight at room temperature. A dark red solution
with a colorless precipitate formed. After filtration, the volatiles
were removed in Vacuo, and the red residue was redissolved in
THF (2 mL). Slow diffusion of hexane into the solution yielded a
(CD3CN): 1H δ 1.75 (d, JH-P ) 4 Hz, 18H, mutually trans
2
1
phosphines), 1.74 (d, 2JH-P ) 2 Hz, 9H, PMe3 trans to deuteride),
1.45 (d, 2JH-P ) 8 Hz, 9H, PMe3 trans to CD2CN); 2H{1H} δ 1.23
(br s, 2D, CD2), -13.1 (br dq, 2JD-P-trans ) 20 Hz, 2JD-P-cis ) 3 Hz,
red, crystalline solid. Yield: 63 mg (68%). NMR (THF-d8): H δ
7.27 (br m, 8H, Ar), 6.85 (br t, JH-H ) 9 Hz, 8H, Ar), 6.70 (br t,
JH-H ) 9 Hz, 4H, Ar), 1.54 (br s, 36H, PMe3); 31P{1H} δ -27.1
(s, PMe3). Anal. Calcd (%) for C36H56BIrP4: C 52.97, H 6.92.
Found: C 51.84, H 6.94.
1D, Ir-D); 13C{1H} δ 133.2 (br d, JC-P-trans ) 11 Hz, CN), 23.7
3
1
1
(d, JC-P ) 35 Hz, PMe3 trans to deuteride), 21.1 (vt, JC-P
,
)
3JC-P-trans ) 20 Hz, mutually trans phosphines), 18.7 (d, JC-P
1
cis-[IrH(NHC(O)Me)(PMe3)4]Cl (8). Acetamide (0.006 g, 0.094
mmol) was added to a stirred suspension of 1 (0.050 g, 0.094 mmol)
in THF (1 mL). The orange suspension turned pale white, and after
72 h, the resulting white residue was dissolved in situ by dropwise
addition of acetonitrile and crystallized by careful addition of
toluene. The crystalline solid was collected by filtration, washed
with THF (3 × 20 mL), and vacuum-dried overnight. Yield: 0.030
g (54.7%). Anal. Calcd (%) for C14H41ClIrNOP4: C, 28.45; H, 6.99,
N, 2.37. Found: C, 28.80; H, 7.11; N, 2.36. HRMS-ES+: calcd for
C14H41191IrNOP4 ([M]+) 554.17392 Da, found 554.17394 Da. NMR
(CD3CN): 1H δ 3.9 (br s, 1H, NH), 1.95 (br s, 3H, Me), 1.7 (br d,
2JH-P ) 9 Hz, 9H, PMe3 trans to hydride), 1.6 (vt, 2JH-P, 4JH-P-trans
) 4 Hz, 18H, mutually trans phosphines), 1.5 (br d, 2JH-P ) 8 Hz,
9H, PMe3 trans to NHC(O)Me), -11.3 (br d, 2JH-P-trans ) 143 Hz,
30 Hz, PMe3 trans to CD2CN), -32.9 (br m, CD2); 31P δ -52.5
(br m, mutually trans phosphines), -58.3 (br m, PMe3 trans to
CD2CN), -59.6 (br m, PMe3 trans to deuteride); 31P{1H} δ -52.5
(t, J ) 20 Hz, mutually trans phosphines), -58.3 (q, J ) 20 Hz,
PMe3 trans to -CD2CN), -59.6 (tq, J1 ) J2 ) 20 Hz, PMe3 trans
to deuteride); 31P{1H + 2H}: δ -52.5 (t, J ) 20 Hz, mutually trans
phosphines), -58.3 (q, J ) 20 Hz, PMe3 trans to CD2CN), -59.6
(q, J ) 20 Hz, PMe3 trans to deuteride).
cis-[IrH(p-NHC6H4CN)(PMe3)4]Cl (4). To a stirred suspension
of 1 (0.050 g, 0.094 mmol) in THF (1 mL) was added p-
aminobenzonitrile (0.011 g, 0.094 mmol) at room temperature. The
mixture was left to react overnight, and the precipitate gradually
turned from orange to white. CH3CN was added to dissolve the
precipitate, which crystallized upon addition of toluene. Yield: 0.025
g (41%). Anal. Calcd (%) for C19H42ClIrN2P4: C, 35.10; H, 6.51,
N, 4.31. Found: C, 35.32; H, 6.48; N, 4.94. HRMS-ES+: calcd for
C19H42191IrN2P4 ([M]+) 613.18991 Da, found 613.19043 Da. NMR
3
1H, Ir-H); 13C{1H} δ 175.2 (br d, JC-P-trans ) 4 Hz, CdO), 25.7
(d, 4JC-P-trans ) 5 Hz, Me), 23.5 (br dm, 1JC-P ) 43 Hz, PMe3 trans
to hydride), 20.6 (vtd, 1JC-P ) 3JC-P-trans ) 20 Hz, 3JC-P-cis ) 4 Hz,
mutually trans phosphines), 19.0 (d, 1JC-P ) 29 Hz, PMe3 trans to
NHC(O)Me); 31P δ -45.7 (br m, mutually trans phosphines), -56.6
(br m, PMe3 trans to NHC(O)Me), -57.3 (br m, PMe3 trans to
hydride); 31P{1H} δ -45.7 (m, mutually trans phosphines), -56.64
(overlapping m, PMe3 trans to NHC(O)Me), -57.3 (overlapping
m, PMe3 trans to hydride).
1
(CD3CN): H δ 7.23 (dd, JH-H ) 9, 2 Hz 1H, Ar), 7.01 (dd, JH-H
) 9, 2 Hz, 1H, Ar), 6.60 (dd, JH-H ) 9, 2 Hz, 1H, Ar), 6.51 (dd,
JH-H ) 9, 2 Hz, 1H, Ar), 2.24 (br s, 1H, NH), 1.77 (d, 2JH-P ) 10
2
Hz, 9H, PMe3 trans to hydride), 1.6 (d, JH-P ) 8 Hz, 9H, PMe3
2
4
trans to NHC6H4CN), 1.56 (vt, JH-P, JH-P-trans ) 4 Hz, 18H,
2
mutually trans phosphines), -11.52 (dq, JH-P-trans ) 139 Hz,
Preparation of [Ir(O2)(PMe3)4]Cl (9). 1 (0.050 g, 0.094 mmol)
was suspended in THF (50 mL), and dry dioxygen (Linde-Praxair)
was bubbled through the stirred suspension for a period of 3 h.
The reaction mixture was stirred for a further 24 h, and the orange
suspension turned colorless. The volatiles were evaporated in Vacuo,
and the gray residue was recrystallized from acetonitrile/Et2O to
yield green-yellow crystals suitable for X-ray analysis. Upon drying
in Vacuo, a white solid was obtained. Yield: 227 mg (82%). Anal.
Calcd (%) for C12H36ClIrO2P4: C, 25.56; H, 6.43. Found: C, 25.75;
H, 6.32. HRMS-ES+: calcd for C12H36191IrO2P4 ([M]+) 527.12664
2JH-P-cis ) 18 Hz, 1H, Ir-H); 13C{1H} δ 161.7 (s, C, Ar), 135.1 (s,
CH, Ar), 133.7 (s, CH, Ar), 123.2 (s, CN), 115.6 (s, CH, Ar), 115.2
1
(s, CH, Ar), 91.5 (s, C, Ar), 23.45 (d, JC-P ) 41 Hz, PMe3 trans
to hydride), 20.6 (vtd, 1JC-P, 3JC-P-trans ) 20 Hz, 3JC-P-cis ) 34 Hz,
mutually trans phosphines), 18.0 (d, 1JC-P ) 29 Hz, PMe3 trans to
NHC6H4CN); 31P δ -45 (br m, mutually trans phosphines), -55.8
2
(br d, JP-H-trans ) 139 Hz, PMe3 trans to hydride), -57.3 (br m,
PMe3 trans to NHC6H4CN); 31P{1H} δ -45 (br t, JP-P ) 20 Hz,
mutually trans phosphines), -55.8 (q, JP-P ) 20 Hz, PMe3 trans
to hydride), -57.3 (q, JP-P ) 20 Hz, PMe3 trans to NHC6H4CN).
cis- and trans-[IrClH(PMe3)4][p-OC6H4CN] (5a/5b). [Ir(PMe3)4]-
Cl (1) (102 mg, 0.192 mmol) and p-hydroxybenzonitrile (23 mg,
0.193 mg) were suspended in a mixture of THF and hexane (0.5
mL/1 mL) and stirred at room temperature overnight. A white
1
2
Da, found 527.12671 Da. NMR (CD3CN): H δ 1.76 (d, JH-P
10 Hz, 18H, PMe3 trans to oxygen), 1.46 (vt, 2JH-P, 4JH-P-trans ) 4
Hz, 18H, mutually trans phosphines); 13C{1H} δ 21.26 (d, 1JC-P
)
)
1
3
38 Hz, PMe3 trans to oxygen), 13.58 (vt, JC-P ) JC-P-trans ) 20

2914 Organometallics, Vol. 28, No. 9, 2009
Crestani et al.
Hz, mutually trans phosphines); 31P{1H} δ -27.62 (t, J ) 16 Hz,
PMe3 trans to oxygen), -51.25 (t, J ) 16 Hz, mutually trans
phosphines).
1.84 (overlapping br m, CHD2/CH2D); 13C{1H} δ 175.40 (s, CdO),
21.45 (overlapping m, 1JC-D ) 20 Hz, CH2D/CHD2/CD3). GC/MS:
mass ) 60 (Int.(%) ) 8), 61 (Int.(%) ) 21), 62 ([M]+, Int.(%) )
32), 63 (Int.(%) ) 27), 64 (Int.(%) ) 11). (D) CD3CN/D2O, overall
conversion ) 67.3%, TON ) 699 cycles, TOF ) 3.5 cycles/h.
Catalysis Experiments. NMR tubes equipped with J Young
valves were charged with 9 (0.0054 g, 0.0096 mmol, 0.1 mol %),
CH3CN or CD3CN (9.6 mmol), and H2O or D2O (9.6 mmol). The
sealed tubes were heated to 140 °C in a silicone oil bath and
periodically monitored by NMR spectroscopy over a period of
200 h, at which point substantive crystallization of acetamide
produced in situ hampered the acquisition of NMR spectra at
ambient temperature. Acetamide was recovered from the tubes in
the air, dissolving the products in acetone and filtering them through
a small bed of silica. The solvent was evaporated, and the remaining
white solid was left to dry overnight.
CD3C(O)ND2, GC/MS: 64 ([M]+, Int.(%)
) 100). NMR
(D2O+CD3CN): 13C{1H} δ 175.42 (s, CdO), 21.09 (sept, 1JC-D
20 Hz, CD3).
)
Acknowledgment. The authors thank CONACYT (grant
F80606) and DGAPA-UNAM (grant IN202907-3) for their
support of this work. M.G.C. also thanks CONACYT for a
Ph.D. grant and PCQ-UNAM and DGEP-UNAM for travel
support. This work was also supported by the DAAD (A.S.).
We thank Mr. I. McKeag for assistance in obtaining some
of the NMR spectra, Mrs. J. Dostal for elemental analysis,
Dr. A. Are´valo for technical assistance, and Mr. R. Barrios-
Francisco for helpful discussions. We are also grateful to
Prof. J. J. Garcia (UNAM) for helpful discussions and for
allowing M.G.C. to visit Durham to carry out aspects of this
research. The authors thank the referees for their very helpful
and detailed comments, which improved the quality of the
paper.
(A) CH3CN/H2O, conversion ) 81.5%, TON ) 846 cycles, TOF
) 4.2 cycles/h. MeC(O)NH2. GC/MS: 59 ([M]+). (B) CH3CN/
D2O, overall conversion ) 74.8%, TON ) 777 cycles, TOF ) 3.9
1
cycles/h. NMR (D2O+MeCN): H δ 7.88 (br s, NH), 7.15 (br s,
NH), 2.37 (s, Me), 2.36 (t, 2JH-D ) 2 Hz, CH2D), 2.35 (br m, CHD2);
13C{1H} δ 176.01 (s, CdO), 175.95 (s, CdO), 22.29 (q, 3JC-D ) 4
1
3
Hz, Me), 22.02 (tq, JC-D ) 20 Hz, JC-D ) 4 Hz, CH2D), 21.86
(overlapping m, CHD2/CD3). GC/MS: 59 (Int.(%) ) 6), 60 (Int.(%)
) 20), 61 ([M]+, Int.(%) ) 32), 62 (Int.(%) ) 27), 63 (Int.(%) )
12), 64 (Int.(%) ) 3). (C) CD3CN/H2O, overall conversion )
85.1%, TON ) 884 cycles, TOF ) 4.4 cycles/h. NMR
1
(CD3CN+H2O): H δ 7.33 (br s, 1H, NH), 6.64 (br s, 1H, NH),
Supporting Information Available: This material is available
free of charge via the Internet at http://pubs.acs.org.
(37) Sheldrick, G. M. SHELXTL, Version 6.14; Bruker AXS: Madison,
WI, 2003.
OM9000633