Structure and reactivity of new iridium complexes with bis(oxazoline)- phosphonito ligands

Article abstract of DOI:10.1021/ic901579u

The synthesis and characterization of novel iridium(I) complexes bearing a neutral bis(oxazoline)phosphonite ligand, NOPON^Me2 (I), are reported. Numerous Ir(I) complexes have been isolated in high yields and characterized by spectroscopy and X-ray diffraction. [Ir(μ-CI)(COd)]₂ (cod = 1,5-cyclooctadiene) reacted with I to give the air-sensitive complex [IrCl(cod)(NOPON^Me2)] (1), which shows broad ¹H and ¹³C{1H} NMR signals due to dynamic exchange equilibria involving the cod and the NOPON^Me2 ligands. Reaction between a solution of 1 and CO afforded the carbonyl complex [IrCl(CO)(NOPON^Me2)] (2), whose solid-state structure has been determined by X-ray diffraction. Cationic complexes have been obtained by using NaBAr^F (BAr^F = B[3,5-(CF₃)₂C₆H₃]₄) as a chloride abstractor. The complex [Ir(cod)(NOPON^Me2)]BAr^F (3) displays a mononuclear structure in the solid state with ligand I acting as a bidentate P,N chelating ligand. This complex is a precatalyst for the hydrogenation of alkenes. Oxidative addition of H2 to 3 occurred either in solution or in the solid-state and this reaction allowed the isolation of the 32 electron, dinuclear dihydridobridged iridium(lll) complex [IrH(μ-H) (NOPON^Me2)]₂(BAr^F)₂ (4), in which the NOPON^Me2 ligands exhibit a facial coordination mode. It contains only hydrides as bridging ligands and the Ir₂(μ-H)₂ unit can be viewed as containing a formal Ir - Ir double bond or two 3c - 2e bonds. Complex 3 has also been reacted with CO in solution and in the solid state, and this yielded the dicarbonyl derivative [Ir(CO)₂(NOPON ^Me2)]BAr^F (5). A transmetalation reaction between 3 and [PdCl₂(NCPh)₂] afforded the cationic Pd(II) complex [PdCI(NOPON^Me2)]BAr^F (6), which has been structurally characterized.

Full text of DOI:10.1021/ic901579u

Inorg. Chem. 2009, 48, 11415–11424 11415
DOI: 10.1021/ic901579u
Structure and Reactivity of New Iridium Complexes with
Bis(Oxazoline)-Phosphonito Ligands
Riccardo Peloso,† Roberto Pattacini, Catherine S. J. Cazin,‡ and Pierre Braunstein*
ꢀ
Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Universite de Strasbourg,
4 Rue Blaise Pascal, F-67070 Strasbourg Cedex, France. †Present address: Instituto de Investigaciones
´
´
ꢀ
Quımicas-Departamento de Quımica Inorganica, Universidad de Sevilla-Consejo Superior de Investigaciones
‡
´
ꢀ
Cientıficas, Avda. Americo Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain. Present address: School of
Chemistry, University of St Andrews, North Haugh, St. Andrews, KY16 9ST, U.K.
Received August 7, 2009
The synthesis and characterization of novel iridium(I) complexes bearing a neutral bis(oxazoline)phosphonite ligand,
NOPONMe (I), are reported. Numerous Ir(I) complexes have been isolated in high yields and characterized by
2
spectroscopy and X-ray diffraction. [Ir(μ-Cl)(cod)]2 (cod = 1,5-cyclooctadiene) reacted with I to give the air-sensitive
1
complex [IrCl(cod)(NOPONMe )] (1), which shows broad H and 13C{1H} NMR signals due to dynamic exchange
2
equilibria involving the cod and the NOPONMe ligands. Reaction between a solution of 1 and CO afforded the carbonyl
2
complex [IrCl(CO)(NOPONMe )] (2), whose solid-state structure has been determined by X-ray diffraction. Cationic
2
complexes have been obtained by using NaBArF (BArF = B[3,5-(CF3)2C6H3]4) as a chloride abstractor. The complex
[Ir(cod)(NOPONMe )]BAr (3) displays a mononuclear structure in the solid state with ligand I acting as a bidentate P,N
F
2
chelating ligand. This complex is a precatalyst for the hydrogenation of alkenes. Oxidative addition of H2 to 3 occurred
either in solution or in the solid-state and this reaction allowed the isolation of the 32 electron, dinuclear dihydrido-
F
Me2
bridged iridium(III) complex [IrH(μ-H)(NOPONMe )]2(BAr )2 (4), in which the NOPON ligands exhibit a facial
2
coordination mode. It contains only hydrides as bridging ligands and the Ir2(μ-H)2 unit can be viewed as containing a
formal Ir-Ir double bond or two 3c-2e bonds. Complex 3 has also been reacted with CO in solution and in the solid
F
state, and this yielded the dicarbonyl derivative [Ir(CO)2(NOPONMe )]BAr (5). A transmetalation reaction between 3
2
F
and [PdCl2(NCPh)2] afforded the cationic Pd(II) complex [PdCl(NOPONMe )]BAr (6), which has been structurally
2
characterized.
Introduction
donor ligands have been found to be highly efficient catalytic
systems for a number of organic reactions, such as asym-
metric hydrogenation of alkenes,6,7 hydrogenation of tri- and
tetrasubstituted olefins,8 alkylation of amines,9 and forma-
tion of C-C bonds.10 Most of these catalysts contain
phosphine-, phosphonite-, or phosphoramidite functional-
ities combined with nitrogen donor moieties, usually pyri-
dine or oxazoline rings, the latter being particularly con-
venient in asymmetric catalysis because of an easy access
to enantiopure synthons. Surprisingly, to the best of our
knowledge, only one iridium complex containing N,P,N
chelating ligands has been described to date.11 Moreover,
Phosphonite and phosphine ligands bearing oxazoline
moieties have attracted much interest in the fields of inor-
ganic and organometallic chemistry because they contain
both soft (P) and hard (N) donor atoms, a feature which
often allows ligand hemilability in their metal complexes and
can facilitate elementary steps involved in homogeneous
catalysis.1-5 Despite the considerable number of publications
dealing with iridium complexes and their catalytic properties,
in particular for hydrogenation and dehydrogenation reac-
tions, the coordination chemistry of polyfunctional ligands
applied to iridium complexes is far from being exhaustively
studied. In this context, iridium complexes containing P, N
(6) Cui, X.; Burgess, K. Chem. Rev. 2005, 105, 3272.
(7) Lu, W.-J.; Chen, Y.-W.; Hou, X.-L. Angew. Chem., Int. Ed. 2008, 47,
10133.
(8) Wustenberg, B.; Pfaltz, A. Adv. Synth. Catal. 2008, 350, 174.
(9) Blank, B.; Madalska, M.; Kempe, R. Adv. Synth. Catal. 2008, 350,
749.
(10) Carmona, D.; Ferrer, J.; Lorenzo, M.; Lahoz, F. J.; Dobrinovitch,
I. T.; Oro, L. A. Eur. J. Inorg. Chem. 2005, 1657.
(11) Camerano, J. A.; Casado, M. A.; Ciriano, M. A.; Tejel, C.; Oro, L. A.
Chem.-Eur. J. 2008, 14, 1897.
*To whom correspondence should be addressed. E-mail: braunstein@
unistra.fr.
(1) Slone, C. S.; Weinberger, D. A.; Mirkin, C. A. Prog. Inorg. Chem.
1999, 48, 233.
(2) Helmchen, G.; Pfaltz, A. Acc. Chem. Res. 2000, 33, 336.
(3) Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. 2001, 40, 680.
(4) Braunstein, P. J. Organomet. Chem. 2004, 689, 3953.
(5) Speiser, F.; Braunstein, P.; Saussine, L. Acc. Chem. Res. 2005, 38, 784.
r
2009 American Chemical Society
Published on Web 11/02/2009
pubs.acs.org/IC

11416 Inorganic Chemistry, Vol. 48, No. 23, 2009
Peloso et al.
iridium complexes containing tridentate ligands, such as
tris(pyrazolyl)borates and PCP pincer ligands, are well-
known to be active in challenging catalytic reactions, such
as C-H activation12 and alkane dehydrogenation.13 For
these reasons, the synthesis of new iridium complexes bearing
neutral N,P,N ligands was felt of interest not only for
academic interest but also because of the catalytic potential
of such complexes.
the methyl protons (at 1.81, 1.75, 1.21, and 1.17 ppm).
The presence of a single AB spin system for the methylene
protons of the NOPONMe ligand suggests that the oxazo-
2
line moieties are symmetrically coordinated to the metal
center or that they are involved in a fast exchange on the
NMR time scale. Similarly, only four signals for the methyl
protons are observed. For comparison, the 1H NMR
spectrum of the free ligand displays a similar sets of signals,
namely, an AB system for the diastereotopic CH2 protons
and four signals for the methyl groups.14 The signals due to
the vinyl protons of the cod ligand are instead very broad,
suggesting a fluxional behavior of the cyclooctadiene
molecule. This prompted us to perform variable tempera-
ture NMR experiments. Two different equilibria appear to
exist in the coordination environment of the metal, which
involve the cod and the oxazoline moieties, respectively. In
particular, a comparison between the 1H NMR spectra of 1
at 25 °C and at -30 °C reveals that the broad signal
(5.6-3.2 ppm) due to the cod CHdCH protons is split
into two signals at 5.20 and 3.52 ppm, which could
correspond to the vinyl protons of the free and coordinated
double bonds, respectively. As far as the resonances of the
CH2 protons of the oxazoline moieties are concerned, the
two sharp doublets of the AB spin system change signifi-
cantly by decreasing the temperature from 25 to -20 °C
(see Figure S-1 of the Supporting Information). One of the
two doublets becomes a broad signal, and two of the
signals assigned to the methyl groups broaden. A more
complex 1H NMR spectrum at low temperature is consis-
tent with the lower symmetry of the rigid structure of the
complex in which the two oxazoline moieties are inequi-
valent. The infrared spectrum of 1 displays an absorption
of medium intensity at 1662 cm-1 assigned to the CdN
stretching vibration, which is very close to that of the free
ligand. Some interesting information about the molecular
structure of 1 in the solid state could be inferred from its far
IR spectrum. In particular, the absorption at 304 cm-1
suggests the presence of an Ir-Cl bond. In the absence of
single crystals suitable for X-ray diffraction, the molecular
structure of the compound can only be suggested on the
In 2001, we reported on the synthesis of the bis-
(oxazoline)phosphonite ligand NOPONMe (I) and the unu-
2
sual stabilization of its Pd(II) η1-allyl complexes.14 The
complex [RuCl2(NOPONMe )] and its carbonyl adduct,
2
[RuCl2(CO)(NOPONMe )], were also described together with
2
some complexes containing an isopropyl-substituted analo-
gue of the NOPONMe ligand.15 More recently, the NO-
2
PONMe ligand has been employed for the preparation of
2
Co(II),16 Ni(II),17 and Fe(II)18 complexes, which have also
been tested in the catalytic oligomerization of ethylene. These
studies highlighted the versatility of the NOPONMe ligand
2
and prompted us to explore its chemistry toward Ir(I) and
Ir(III). Herein, we report on the synthesis, characterization,
and reactivity of new iridium complexes bearing the NO-
PONMe ligand.
2
Results and Discussion
The reaction between NOPONMe and the iridium(I)
2
precursor complex [Ir(μ-Cl)(cod)]2 (cod = 1,5-cycloocta-
diene) in CH2Cl2 resulted in the formation of an orange,
air-sensitive compound, exhibiting high solubility in chlori-
nated and aromatic solvents and moderate solubility in
saturated hydrocarbons. This product could be purified by
extraction of the crude in pentane followed by evaporation of
the solvent. Evidence for the formation of a new complex
1
basis of spectroscopic data. The H NMR spectra have
shown that the cod ligand is still present in the complex and
of formula [IrCl(cod)(NOPONMe )] (1) was obtained by
2
that the NOPONMe ligand is coordinated through the
2
multinuclear magnetic resonance (NMR) and infrared
(IR) spectroscopy, matrix-assisted laser desorption ioniza-
tion-time-of-flight (MALDI-TOF) mass spectrometry, and
elementalanalysis. In particular, the31P{1H} NMR spectrum
of 1 in CDCl3 shows a high-field shift of the phosphorus
phosphorus and the oxazoline nitrogen atoms, the latter
being probably involved in a fast exchange about the metal
center consistent with the documented hemilability of the
NOPONMe ligand.14 We suggest that a dynamic exchange
2
takes place in solution between the uncoordinated CdC
double bond of the cod ligand and an oxazoline moiety (1a/
1b in Scheme 1), as indicated by the 1H NMR spectra of 1 at
variable temperatures. Moreover, the far IR spectrum and
the high solubility of 1 in solvents of low polarity indicate
that the compound is neutral, with the chloride ligand
bound to the metal. Dissociation of the chloride anion in
chloroform or dichloromethane to give the cationic species
resonance from 150.5 ppm for uncoordinated NOPONMe to
2
103.2 ppm for 1. The 1H NMR of 1 in CDCl3 exhibits three
sets of sharp signals due to the phenyl protons (8.0-7.3 ppm),
an AB spin system for the CH2 protons of the oxazoline
moieties (at 3.97 and 3.85 ppm), and four singlets for
(12) Slugovc, C.; Padilla-Martinez, I.; Sirol, S.; Carmona, E. Coord.
Chem. Rev. 2001, 213, 129.
(13) Goldman, A. S.; Roy, A. H.; Huang, Z.; Ahuja, R.; Schinski, W.;
Brookhart, M. Science 2006, 312, 257.
(14) Braunstein, P.; Naud, F.; Dedieu, A.; Rohmer, M.-M.; DeCian, A.;
Rettig, S. J. Organometallics 2001, 20, 2966.
(15) Braunstein, P.; Naud, F.; Pfaltz, A.; Rettig, S. J. Organometallics
2000, 19, 2676.
[Ir(cod)(NOPONMe )]þ appears unlikely, considering that
2
the fragment [IrCl(NOPONMe )] was unambiguously ob-
2
served by MALDI-TOF analysis of a dichloromethane
solution of 1. The MALDI-TOF MS spectrum of 1 shows
þ
two main peaks at m/z = 721.35 [193Ir(cod)(NOPONMe )]
2
and 719.34 [191Ir(cod)(NOPONMe )] þ and a third one at
þ
2
(16) Braunstein, P.; Kermagoret, A. Dalton Trans. 2008, 585.
(17) Kermagoret, A.; Tomicki, F.; Braunstein, P. Dalton Trans. 2008,
2945.
m/z = 648.28 [193Ir35Cl(NOPONMe )] , which is consistent
2
(18) Speiser, F.; Braunstein, P.; Saussine, L. Dalton Trans. 2004, 1539.
with the proposed formulation for the compound.

Article
Inorganic Chemistry, Vol. 48, No. 23, 2009 11417
Scheme 1. Solid-State and Solution Structures of 1 Discussed in the
Text
Scheme 2. Synthesis of Complex 2
Figure 1. ORTEPofcomplex2in2 CH2Cl2 with ellipsoidsdrawn at the
50% probability level. Solvent moleculesand hydrogenatoms are omitted
for clarity.
3
˚
The data available for 1 are consistent with a neutral,
Table 1. Selected Bond Distances (A) and Angles (deg) for [IrCl(CO)(NO-
pentacoordinated Ir(I) complex in the solid state,19,20
PONMe )] (2) in 2 CH2Cl2
2
3
with the NOPONMe ligand acting as a tridentate ligand
2
Ir(1)-P(1)
Ir(1)-N(1)
Ir(1)-C(23)
Ir(1)-Cl(1)
C(23)-O(5)
2.1735(19)
2.142(6)
1.855(9)
2.4015(19)
1.12(1)
C(4)-N(1)
C(4)-O(4)
C(12)-N(2)
C(12)-O(3)
1.278(9)
1.324(10)
1.282(9)
1.365(9)
(Scheme 1, structure a) and the cod as a two electron donor,
although this is very rarely encountered.21 A pentacoordi-
nated diolefinic complex with a chelating NOPONMe ligand
2
(Scheme 1, structure b) is not consistent with the solution
data, which indicates the presence of an uncoordinated CdC
double bond. Although the spectroscopic data do not strictly
rule out the possibility of a tetracoordinated Ir(I) species
C(23)-Ir(1)-N(1)
C(23)-Ir(1)-P(1)
N(1)-Ir(1)-Cl(1)
Ir(1)-C(23)-O(5)
177.3(3)
88.6(2)
92.94(15)
178.2(7)
N(1)-Ir(1)-P(1)
C(23)-Ir(1)-Cl(1)
P(1)-Ir(1)-Cl(1)
90.14(16)
88.5(2)
175.51(7)
(Scheme 1, structure c) where one arm of the NOPONMe
2
ligand is popping on and off, this appears less likely in view of
173.0 ppm in the 13C{1H} NMR spectrum of the compound
is in agreement with a coordinated CO molecule. Spectro-
scopic evidence for the asymmetric coordination of the
the strong propensity for the cod and NOPONMe ligands to
2
occupy the coordination sites available, i.e., to favor penta-
coordination around the Ir(I) center.
NOPONMe ligand has been previously discussed in the case
2
Upon treatment of complex 1 with CO at 1 atm pressure, a
new compound was selectively obtained in high yield
(Scheme 2). The presence of a coordinated CO molecule
was clearly indicated by a strong absorption at 1989 cm-1 in
the solid-state IR spectrum. The Ir-Cl stretching vibration
of Pd(II) complexes.14
A single crystal X-ray structure determination confirmed
the hypotheses drawn on the basis of the spectroscopic data
and allowed us to unambiguously identify the product as the
neutral complex [IrCl(CO)(NOPONMe )] (2), see Figure 1.
2
gives rise to an absorption at 290 cm ,
-1 22 which disappears
The crystals were grown from CH2Cl2/Et2O and contain one
molecule of dichloromethane per complex. Selected bond
distances and angles are listed in Table 1.
after treatment of the compound with LiBr in acetone
solution (substitution of the Ir-Cl bond by an Ir-Br bond).
The two CdN stretching absorptions at 1656 and 1608 cm-1
are in agreement with a P, N-bidentate behavior of the
The iridium atom lies in a slightly distorted square-planar
environment as shown by the P(1)-Ir(1)-Cl(1) and N(1)-
Ir(1)-C(23) bond angles of 175.51(7) and 177.3(3)°, respec-
tively. The six-membered ring formed by the bidentate
NOPONMe ligand and the presence of a pendant oxazoline
2
group (the CdN stretching vibration of the free ligand occurs
at 1661 cm-1) or with the CdN groups being coordinated in
different chemical environments. These data are also consis-
tent with the 1H and13C{1H} NMR spectra. Inparticular, the
1H NMR spectrum exhibits two sets of signals for the AB
spin system of the CH2 protons and eight signals due to the
methyl groups, thus confirming the nonequivalence of the
two oxazoline arms, even in solution. Moreover, the singlet at
NOPONMe ligand upon coordination adopts a boat con-
2
formation with a N(1)-Ir(1)-P(1) angle of 90.14(16)°. The
CdN bond distances in the coordinated and dangling oxazo-
line rings are not significantly different, whereas the NC-O
bond in the free oxazoline moiety is slightly longer than in the
coordinated one. The metal-phosphorus distance is shorter
than those reported for similar Ir(I) complexes.9,23 As ex-
pected on the basis of the weaker trans influence of the
nitrogen donor compared to the phosphorus donor, the
carbonyl ligand occupies the position trans to the coordi-
nated oxazoline ring.
(19) Shivakumar, M.; Gangopadhyay, J.; Chakravorty, A. Polyhedron
2001, 20, 2089.
(20) (a) Frazier, J. F.; Merola, J. S. Polyhedron 1992, 11, 2917. (b) Oro,
L. A.; Carmona, D.; Esteruelas, M. A.; Foces-Foces, C.; Cano, F. H.
J. Organomet. Chem. 1983, 258, 357.
(21) Prinz, M.; Veiros, L. F.; Calhorda, M. J.; Romao, C. C.; Herdtweck,
€
E.; Kuhn, F. E.; Herrmann, W. J. Organomet. Chem. 2006, 691, 4446.
(22) Schramm, K. D.; Tulip, T. H.; Ibers, J. A. Inorg. Chem. 1980, 19,
(23) Zhu, S.-F.; Xie, J.-B.; Zhang, Y.-Z.; Li, S.; Zhou, Q.-L. J. Am. Chem.
Soc. 2006, 128, 12886.
3183.

11418 Inorganic Chemistry, Vol. 48, No. 23, 2009
Scheme 3. Synthesis of Complex 3
Peloso et al.
Figure 2. ORTEP of complex 3 in 3 0.5C6H6 with ellipsoids drawn at
3
Complex 1 was reacted with NaBArF (BArF = B[3,5-(C-
the 40% probability level. The anion, solvent molecules, and hydrogen
atoms are omitted for clarity.
F3)2C6H3]4) in CH2Cl2 in order to obtain the corresponding
F
cationic complex [Ir(cod)(NOPONMe )]BAr (3). The latter
2
˚
has also been prepared by reacting in situ [Ir(μ-Cl)(cod)]2,
Table 2. Selected Bond Distances (A) and Angles (deg) for [Ir(cod)(NO-
PONMe )]BArF (3) in 3 0.5C6D6
a
F
2
NOPONMe , and NaBAr (Scheme 3). Both reaction proce-
2
3
dures led to a red-orange, air-stable compound, which is
soluble in chlorinated solvents and ethers, slightly soluble in
aromatic solvents, and insoluble in saturated hydrocarbons.
In the 31P{1H} NMR spectrum of 3, a downfield shift of 7.4
ppm is observed with respect to the neutral compound 1,
which is consistent with a decreased electron-density at the
metal.
Ir(1)-P(1)
Ir(1)-N(1)
Ir(1)-C(23)
Ir(1)-C(24)
Ir(1)-C(27)
Ir(1)-C(28)
2.2351(16)
2.127(5)
2.229(6)
2.265(6)
2.151(6)
2.143(6)
C(23)-C(24)
C(27)-C(28)
C(12)-N(2)
C(12)-O(4)
C(4)-N(1)
C(4)-O(2)
1.364(9)
1.404(9)
1.256(8)
1.388(7)
1.290(7)
1.327(7)
N(1)-Ir(1)-P(1)
84.23(14)
93.1(3)
N(1)-Ir(1)-
C(23/24)
C(23/24)-
Ir(1)-C(27/28)
96.7(3)
85.8(3)
The 1H and 13C{1H} NMR spectra of 3 are affected by a
significant fluxionality of the ligands about the metal center.
With the exception of the signals due to the phenyl ring and
the BArF- anion, all signals are very broad. This prompted us
to perform variable temperature 1H NMR experiments. At
-10 °C, eight singlets in the methyl region were identified,
which is in agreement with a bidentate behavior of the
C(27/28)-Ir(1)-P(1)
a C(23/24) and C(27/28) represent the middle of the cod double bonds,
respectively.
THF, dichloromethane, or chloroform was exposed to 1 atm
of hydrogen at room temperature. The reaction could be
visually monitored by a color change from red-orange to pale
yellow, which occurred within a few minutes. Moreover, pure
3 reacted quickly with H2 even in the solid state to afford a
pale yellow powder. The reaction between 3 and H2 was also
studied in situ by multinuclear NMR spectroscopy in THF-
d8 solution. 31P{1H} NMR spectroscopy demonstrated that,
upon exposure to H2, complex 3 is quantitatively and
selectively converted into a new compound with appearance
NOPONMe ligand. In the IR spectrum of 3, the two bands
2
at 1671 and 1605 cm-1 were attributed to the stretching
vibrations of the CdN bonds of the uncoordinated and
coordinated oxazoline rings, respectively.14 After record-
ing the NMR spectra of 1 in C6D6, 1 equiv of NaBArF
was added. Formation of single crystals of [Ir(cod)-
F
(NOPONMe )]BAr 0.5C6D6 suitable for X-ray diffraction
2
3
studies occurred within minutes. This confirmed the coordi-
nation of both cod and NOPONMe ligands to the metal
2
1
of a singlet at 123.8 ppm. The H NMR spectrum of the
center, which lies in a distorted square planar environment, if
the two double bonds of the cyclooctadiene, one nitrogen
atom of an oxazoline ring, and the phosphorus atom are
considered (see Figure 2). Selected bond distances and angles
for 3 are listed in Table 2.
complex shows two sets of signals due to the oxazoline rings,
namely, two AB spin systems for the CH2 protons and eight
resonances in the methyl region. Moreover, a doublet at
-25.99 ppm (2JPH = 15.0 Hz) indicates unambiguously the
presence of a metal hydride, in a 1:1 ratio with the ligand.
Some signals in the CH2 and vinyl regions are likely to be
attributed to partially hydrogenated cyclooctadiene in solu-
tion, free or bound to the metal. In this context, some Ir(III)
hydrides bearing alkyl substituents have been previously
reported.24-27 Such species could explain the presence of
several resonances in the methylene region. The reaction was
carried out again in CD2Cl2 and monitored by NMR
Similarly to the carbonyl derivative 2, the six-membered
ring formed by the bidentate NOPONMe ligand and the
2
iridium atom adopts a boat conformation with a N(1)-
Ir(1)-P(1) angle of 84.23(14)°. Some differences between the
two oxazoline moieties are noteworthy. In particular, the
coordinated oxazoline ring shows a slightly longer CdN
bond distance and a significantly shorter NC-O bond
distance compared to the dangling oxazoline ring. The Ir-
˚
C bond distances range from 2.143(6) to 2.265(6) A and the
(24) Barbaro, P.; Bianchini, C.; Meli, A.; Peruzzini, M.; Vacca, A.; Vizza,
F. Organometallics 1991, 10, 2227.
(25) Bianchini, C.; Casares, J. A.; Masi, D.; Meli, A.; Pohl, W.; Vizza, F.
J. Organomet. Chem. 1997, 541, 143.
(26) Li, X.; Appelhans, L. N.; Faller, J. W.; Crabtree, R. H. Organo-
metallics 2004, 23, 3378.
(27) Hermann, D.; Gandelman, M.; Rozenberg, H.; Shimon, L. J. W.;
Milstein, D. Organometallics 2002, 21, 812.
shortest Ir-C bonds are located, as expected, in positions
trans to the nitrogen donor atom. Similarly, the cycloocta-
diene CdC bond distance trans to the nitrogen atom is longer
than the other one.
The reactivity of 3 toward CO and H2 was investigated. A
rapid reaction took place when a red-orange solution of 3 in

Article
Inorganic Chemistry, Vol. 48, No. 23, 2009 11419
Scheme 4. Synthesis of the Tetrahydride Complex 4a
a For the bonding within the Ir2(μ-H)2 moiety, see the text.
spectroscopy, which gave the same results as those obtained
in THF. The dinuclear structure drawn for 4 in Scheme 4
corresponds to that determined in the solid state by
X-ray diffraction (see below). The dinuclear Ir(III) hydride
F
complex [IrH(μ-H)(NOPONMe )]2(BAr )2 (4 4CH2Cl2) se-
2
3
Figure 3. ORTEP of the cationic complex of 4 in 4 4CH2Cl2 with
3
parated out as a crystalline solid from a concentrated
ellipsoids drawn at the 50% probability level (methyl groups, solvent
molecules, and anion are omitted for clarity). The symmetry operation
generating equivalent atoms (i): -x, -y, -z.
dichloromethane solution of 3 under H2 (Scheme 4).
The molecular structure of this air-sensitive complex was
determined by X-ray diffraction. In order to isolate 4 in
higher yields, the reaction between 3 and H2 was also
performed in pentane and in the solid state. Both procedures
afforded a pale yellow air-sensitive solid, which was analyzed
by NMR spectroscopy and found to be identical to the
compound observed by reacting 3 with H2 in CD2Cl2 or
THF-d8. Dissolution of 4 led to decomposition and thus
evidence for the presence of dinuclear 4 in solution could not
be obtained. The fact that only one hydride resonance was
observed in solution, which corresponds to one hydride per
ligand, suggests that the dinuclear species forms only in the
solid state by slow crystallization, a mononuclear Ir(III)
monohydride being the main product in solution but its
instability (see above) prevented its characterization. To the
best of our knowledge, 4 represents only the second example
of a structurally characterized iridium complex containing a
tridentate N,P,N donor ligand (see Figure 3). The first
complex of this type containeda modified scorpionate ligand,
namely, a hybrid pyrazolyl/phosphane anionic ligand.11
Although hydrido-bridged dinuclear iridium complexes
are well-known, the metal centers are usually bridged by
additional ligand(s), such as diphosphines,28-30 chlorides,31
N-donor ligands,32-36 or oxygen based linkers.37 It is
noteworthy that complex 4 is one of the few iridium hy-
drides complexes in which the bridging ligands are all
˚
Table 3. Selected Bond Distances (A) and Angles (deg) for [IrH(μ-H)-
F
(NOPONMe )]2(BAr )2 (4) in 4 4CH2Cl2
2
3
Ir(1)-Ir(1)i
Ir(1)-N(1)
Ir(1)-P(1)
2.7651(5)
2.273(5)
2.1628(15)
Ir(1)-N(2)
N(1)-C(4)
N(2)-C(12)
2.142(5)
1.279(8)
1.274(7)
N(1)-Ir(1)-P(1)
N(2)-Ir(1)-P(1)
N(1)-Ir(1)-N(2)
88.92(13)
89.54(14)
94.29(19)
N(1)-Ir(1)-Ir(1)i
P(1)-Ir(1)-Ir(1)i
N(2)-Ir(1)-Ir(1)i
98.95(12)
133.21(4)
135.03(14)
hydrides: according to the Cambridge Structural Database
(CSD), structurally relevant precedents appear limited to
[{(Ph2PCH2CH2PPh2)Ir(H)}2(μ-H)3]BF4,38a [{Cp*(PMe3)(H)-
Ir}2(μ-H)}]2PF6,38b [(Cp*Ir)2(μ-H)3]ClO4,38c [{(C2F6)2PCH2-
CH2P(C2F6)2}(H)2Ir(μ-H)]2,38d
[(PhBP3)Ir(H)(μ-H)]2,38e
[(Cp*Ir)(CO)(μ-H)]2[BArF]2,38f and [(Cp*Ir)(Cl)(μ-H)]2.38f Se-
lected bond distances and angles are listed in Table 3. This
dicationic complex has 32 valence electrons, like [Ir2(μ-η2-
2þ 38f
O2CR)(μ-H)2H2(PPh3)4]þ,37 [(Cp*Ir)(CO)(μ-H)]2
,
or
[(Cp*Ir)(Cl)(μ-H)]2,38f and like them could be considered as
containing a formal Ir-Ir double bond, which would satisfy the
18 electron rule. However, it remains clear that electronic
delocalization occurs within the Ir2(μ-H)2 unit, and this is
represented in Scheme 4 by two 3c-2e bonds.
The cationic unit contains a crystallographic inversion
center. The data are consistent with the presence of terminal
and bridging hydride ligands, as indicated in the drawings
(see Experimental Section). The Ir-Ir bond distance of
(28) Fujita, K.; Nakaguma, H.; Hamada, T.; Yamaguchi, R. J. Am.
Chem. Soc. 2003, 125, 12368.
(29) Fujita, K.; Takahashi, Y.; Nakaguma, H.; Hamada, T.; Yamaguchi,
R. J. Organomet. Chem. 2008, 693, 3375.
(30) Takahashi, Y.; Nonogawa, M.; Fujita, K.-i.; Yamaguchi, R. Dalton
Trans. 2008, 3546.
(31) White, C.; Oliver, A. J.; Maitlis, P. M. J. Chem. Soc., Dalton Trans.
1973, 1901.
(32) Arita, H.; Ishiwata, K.; Kuwata, S.; Ikariya, T. Organometallics
2008, 27, 493.
(33) Martin, M.; Sola, E.; Tejero, S.; Lopez, J. A.; Oro, L. A. Chem.-Eur.
J. 2006, 12, 4057.
(34) Tejel, C.; Ciriano, M. A.; Millaruelo, M.; Lopez, J. A.; Lahoz, F. J.;
Oro, L. A. Inorg. Chem. 2003, 42, 4750.
(35) Jimenez, M. V.; Sola, E.; Caballero, J.; Lahoz, F. J.; Oro, L. A.
Angew. Chem., Int. Ed. 2002, 41, 1208.
˚
2.7651(5) A is slightly longer that in the above-mentioned
complexes which contained anionic ancillary ligands, in
contrast to NOPONMe . The coordination spheres of the
2
metal centers constitute two edge-sharing octahedra. The
NOPONMe ligands adopt a facial arrangement with the
2
phosphorus atoms in equatorial positions. The two terminal
hydrides occupy the remaining apical positions, while the two
(38) (a) Wang, H. H.; Pignolet, L. H. Inorg. Chem. 1980, 19, 1470. (b)
Burns, C. J.; Rutherford, N. M.; Berg, D. J. Acta Crystallogr., Sect. C: Cryst.
Struct. Commun. 1987, 43, 229. (c) Stevens, R. C.; McLean, M. R.; Wen, T.;
Carpenter, J. D.; Bau, R.; Koetzle, T. F. Inorg. Chim. Acta 1989, 161, 223.
(d) Schnabel, R. C.; Carroll, P. S.; Roddick, D. M. Organometallics 1996, 15,
655. (e) Feldman, J. D.; Peters, J. C.; Tilley, T. D. Organometallics 2002, 21,
4050. (f) Meredith, J. M.; Goldberg, K. I.; Kaminsky, W.; Heinekey, D. M.
Organometallics 2009, 28, 3546.
(36) Sola, E.; Torres, F.; Jimenez, M. V.; Lopez, J. A.; Ruiz, S. E.; Lahoz,
F. J.; Elduque, A.; Oro, L. A. J. Am. Chem. Soc. 2001, 123, 11925.
(37) Esteruelas, M. A.; Garcia, M. P.; Lahoz, F. J.; Martin, M.; Modrego,
~
J.; Onate, E.; Oro, L. A. Inorg. Chem. 1994, 33, 3473.

11420 Inorganic Chemistry, Vol. 48, No. 23, 2009
Peloso et al.
bridging hydrides lie in the equatorial plane. The Ir-N bond
Scheme 5. Synthesis and Proposed Molecular Structure of Complex 5
˚
distances of 2.142(5) and 2.273(5) A for the equatorial and
apical bonds, respectively, are consistent with the stronger
transinfluence of theapicalhydride compared to thebridging
hydride. The N-Ir-P bond angles of 88.92(13) and
89.54(14)° for the equatorial and apical positions, respec-
tively, are slightly distorted from the expected 90°.
Complex 4 seemed to be a good candidate for alkane
transfer dehydrogenation catalysis. Therefore, a suspension
of 3 was treated with hydrogen in cyclooctane in the presence
of 50 equiv of tert-butylethylene (as a potential hydrogen
acceptor), in order to eliminate the coordinated cod ligand
and generate a reactive, coordinatively unsaturated Ir(III)
complex. The orange suspension turned quickly pale yellow
and it was then heated at 150 °C. Decomposition occurred
within a few minutes as indicated by the formation of a black
precipitate. Similar experiments were carried out in the
absence of tert-butylethylene, at lower temperatures (up to
100 °C), or in the presence of H2. Dehydrogenation of the
cyclooctane to cycloctene was never detected by gas chroma-
tography (GC) analysis. However, we noted that the tert-
butylethylene, which was added to the reaction as a potential
hydrogen acceptor, had been hydrogenated to tert-butyl-
ethane when the reaction was performed under 1 atm H2.
This hence led to catalytic studies of 3 for the hydrogenation
of olefinic substrates such as cis-cyclooctene, 1-octene, 1-
methylcyclohexene, and 2-cyclohexen-1-one. Catalytic de-
tails are given in Table S-1 (Supporting Information). The
experiments showed that the activity of the catalyst depends
significantly on the accessibility of the CdC double bond in
the substrate, i.e., on the degree of substitution of the alkene.
High activities were observed in the hydrogenation of mono-
substituted double bonds, such as 1-octene. The introduction
of a conjugated electron-withdrawing group in the substrate
did not seem to significantly affect the activity of the catalyst,
as observed by comparing the hydrogenation reaction of cyclo-
octene and 2-cyclohexene-1-one. The best results were obtained
for 1-octene in chlorobenzene (60 °C, 1.5 bar H2, 2 h, turnover
number 900). For comparison, complex 1 was also tested in
hydrogenation catalysis but showed a much lower activity.
A solution of 3 in dichloromethane was reacted with 1 atm
of CO at room temperature and, similarly to the reaction with
H2, the reaction took place also in the solid state to afford a
yellow powder. The product of the reaction was isolated,
analyzed by NMR and IR spectroscopic methods, and
suggests that the two oxazoline arms are symmetrically
coordinated to the metal, likely to be pentacoordinated as
observed in several trigonal bipyramidal iridium complexes
bearing two carbonyl ligands,39 which have been known for
some time.40 The spectroscopic data are consistent with a mer
arrangement of the NOPONMe ligand with the two nitrogen
2
atoms in the apical positions and the phosphorus in the
equatorial plane. Consequently, the two CO molecules
should occupy two equatorial positions, in agreement with
the presence of two absorption bands in the IR spectrum of
the compound and with one signal due to the carbon atom of
the CO in the 13C{1H} NMR spectrum. Compound 5 could
also be synthesized from the carbonyl compound 2 under CO
by addition of 1 equiv of NaBArF (Scheme 5).
The availability of an uncoordinated oxazoline ring in
complex 3 prompted us to attempt the synthesis of poly-
nuclear complexes, where the NOPONMe might act as a
2
bridging ligand between two metal centers. Hence, we reacted
2 equiv of 3 with 1 equiv of [PdCl2(NCPh)2] in CDCl3. The
31P{1H} NMR spectrum of the crude showed two sharp
signals at 115.6 and 110.7 ppm, thus indicating that a new
compound had formed (δP = 115.5 ppm) but that some
iridium complex 3 remained unreacted. Slow evaporation of
the solvent from the NMR tube yielded some pale yellow
crystals, which were identified by X-ray diffraction as the
F
Pd(II) cationic complex [PdCl(NOPONMe )]BAr (6). Thus,
2
transfer of the ligand from Ir(I) to Pd(II) had occurred, in
preference to the formation of a heteronuclear complex.
Subsequently, compound 6 was directly prepared by reac-
tion of [PdCl2(NCMe)2] with NOPONMe in dichloro-
2
methane followed by addition of NaBArF (Scheme 6). The
X-ray structure of 6 CHCl3 in the solid state shows that the
3
metal center lies in an approximately square-planar coordi-
nation environment in which the NOPONMe ligand acts as a
2
identified as the cationic complex [Ir(CO)2(NOPONMe )]-
2
tridentate chelating ligand (see Figure 4). A terminal chloride
completes the coordination on palladium. Selected bond
distances and angles for 6 are reported in Table 4.
BArF (5). The presence of coordinated CO molecules was
indicatedby two absorptionsof medium intensity at2096 and
2038 cm-1 in the solid-state IR spectrum of 5 (a weaker band
at 2009 cm-1 is probably due to solid-state effects since it
disappears when the spectrum is recorded in ether solution)
and further confirmed by the 13C{1H} NMR of the complex,
which exhibits a doublet due to the coordinatedCO ligands at
173.9 ppm (2JPC = 60.9 Hz). The 31P{1H} NMR spectrum
displays a singlet at 116.5 ppm, downfield shifted by about 6
ppm with respect to complex 3. The NMR spectra of this
compound contain only sharp signals, thus indicating that
the substitution of the cyclooctadiene ligand by two CO
molecules has resulted in an important decrease of the
fluxionality of the ligands around the metal center. In
The structural features of the coordinated NOPONMe
2
ligand are very similar to those in the dicationic complex
14
[Pd(NCMe)(NOPONMe )](BF4)2, and the bond distances
2
involving the Pd atom are slightly longer than in this com-
plex. This can be ascribed to the decrease in the overall charge
of the cation from þ2 to þ1.
Conclusions
Coordination complexes of Ir(I) containing the bis-
(oxazoline)phosphonite ligand NOPONMe have been de-
2
scribed and their reactivity toward H2 and CO investigated.
1
particular, the H NMR spectrum of 5 exhibits two sharp
(39) Fernandez, M. J.; Esteruelas, M. A.; Oro, L. A.; Apreda, M. C.;
Foces-Foces, C.; Cano, F. H. Organometallics 1987, 6, 1751.
(40) Payne, N. C.; Ibers, J. A. Inorg. Chem. 1969, 8, 2714.
doublets for the CH2 protons of the NOPONMe (AB spin
2
system) and four singlets for the methyl protons. This

Article
Inorganic Chemistry, Vol. 48, No. 23, 2009 11421
Scheme 6. Synthesis of Complex 6
Figure 4. ORTEP of complex 6 in 6 CHCl3 with ellipsoids drawn at the
3
Complexes containing cod as the ancillary ligand, namely,
the neutral complex 1 and its cationic analogue 3, exhibit a
significant fluxionality in solution due to fast exchange
equilibria about the metal, which are facilitated by the
50% probability level. The anion, solvent molecules, and hydrogen atoms
are omitted for clarity.
˚
Table 4. Selected Bond Distances (A) and Angles (deg) for [PdCl(NOPO-
NMe )]BArF (6) in 6 CHCl3
2
hemilabile behavior of the NOPONMe ligand. The cyclo-
3
2
octadiene molecule could be easily displaced by exposing
solutions of 1 and 3 to carbon monoxide (1 atm) at room
temperature, which afforded the monocarbonyl derivative 2
and the dicarbonyl derivative 5, respectively. The molecular
structures of 2 and 3 have been elucidated by X-ray diffrac-
tion analyses and display distorted square planar geometries.
Addition of dihydrogen to the cationic complex 3 was
achieved in pentane or in the solid state and has allowed
the isolation of 4, a 32 electron, dinuclear cationic complex of
Ir(III), which shows two unusual features, namely, the
presence of only hydrides as bridging ligands and a Ir2(μ-
H)2 unit which can be viewed as containing a formal Ir-Ir
double bond or two 3c-2e bonds. Furthermore, this com-
plex is, to the best of our knowledge, only the second example
of a structurally characterized iridium complex containing an
N,P,N chelating ligand. Despite the chelating behavior of the
Pd(1)-Cl(1)
Pd(1)-P(1)
Pd(1)-N(1)
Pd(1)-N(2)
2.3667(12)
2.1811(12)
2.049(4)
C(10)-N(1)
C(10)-O(2)
C(18)-N(2)
C(18)-O(4)
1.289(6)
1.328(6)
1.281(6)
1.328(6)
2.068(4)
N(2)-Pd(1)-Cl(1)
N(1)-Pd(1)-P(1)
P(1)-Pd(1)-Cl(1)
96.78(11)
82.79(11)
167.19(5)
N(2)-Pd(1)-P(1)
N(1)-Pd(1)-Cl(1)
N(1)-Pd (1)-N(2)
90.05(11)
90.97(11)
171.90(15)
multiple bond correlation (HMBC) experiments. IR spectra
were recorded in the region 4000-100 cm-1 on a Nicolet 6700
FT-IR spectrometer equipped with a Smart Orbit ATR acces-
sory (Ge or diamond crystals). Elemental analyses were per-
ꢀ
formed by the “Service de microanalyse”, Universite de
Strasbourg. Electrospray mass spectra (ESI-MS) were recorded
on a microTOF (Bruker Daltonics, Bremen, Germany) instru-
ment using nitrogen as the drying agent and nebulizing gas, and
MALDI-TOF analyses were carried out on a Bruker AutoflexII
TOF/TOF (Bruker Daltonics, Bremen, Germany), using dithra-
nol (1,8,9-trihydroxyanthracene) as a matrix. Yields of the metal
complexes are based on iridium. GC analyses were performed
on a Thermoquest GC8000 Top Series gas chromatograph using
a HP Pona column (50 m, 0.2 mm diameter, 0.5 μm film
thickness). [Ir(μ-Cl)(cod)]2 was purchased from UMICORE
and used as received. [PdCl2(NCPh)2],41 [PdCl2(NCMe)2],42
NOPONMe ligand in 3, it was readily transferred to Pd(II) as
2
a transmetalation reaction occurred when 3 was reacted with
[PdCl2(NCPh)2]. Complex 3 was shown to catalyze the
hydrogenation of CdC double bonds and this occurred
chemoselectively in the case of 2-cyclohexene-1-one as a
substrate. The versatility of the coordination modes of the
NOPONMe ligand to transition metals was further evidenced
2
NOPONMe
and Na[B(3,5-(CF3)2C6H3)4]43 were prepared
14
2
,
in this work. Thus, it can behave as a P, N chelate or as a N, P,
N tridentate donor, occupying facial or meridional coordina-
tion sites in octahedral metal complexes.
according to literature methods. Other chemicals were commer-
cially available and used as received.
Synthesis of [IrCl(cod)(NOPONMe )] (1). The complex [Ir(μ-
2
Cl)(cod)]2 (203 mg, 0.302 mmol) was dissolved in a solution of
NOPONMe (254 mg, 0.605 mmol) in CH2Cl2 (5 mL), and the
2
Experimental Section
reaction mixture was stirred overnight at room temperature.
The solution was concentrated under reduced pressure to 1 mL,
and pentane was added (100 mL) to afford a suspension. After
the pale red solid was filtered and washed with pentane (3 ꢀ 100
mL), the combined filtrates were evaporated under reduced
pressure to give a yellow-orange powder which was dried under
vacuum. Yield: 270 mg (58%). Selected IR absorptions (pure,
diamond attenuated total reflectance (ATR)): 2963 mw, 1662 m,
1260 s, 1108 s, 1017 vs, 968 s, 798 vs, 749 m, 697 m, 304 (Ir-Cl)
General Considerations. All operations were carried out using
standard Schlenk techniques under inert atmosphere. Solvents
were dried, degassed, and freshly distilled prior to use. THF and
Et2O were dried over sodium/benzophenone. CH2Cl2 was dis-
˚
tilled from CaH2. CD2Cl2, CDCl3, and C6D6 were dried over 4 A
molecular sieves, degassed by freeze-pump-thaw cycles, and
stored under argon. THF-d8 was used as received. Unless
otherwise stated, NMR spectra were recorded at room tempera-
ture on a Bruker AVANCE 300 spectrometer (1H, 300 MHz;
13C, 75.47 MHz; 19F, 282.4 MHz; 31P, 121.5 MHz) or on a
Bruker AVANCE 400 spectrometer (1H, 400 MHz; 13C, 100.60
MHz, 31P, 162.0 MHz,) and referenced using the residual proton
solvent (1H) or solvent (13C) resonance. Assignments are based
on DEPT135, correlation spectroscopy (COSY), heteronuclear
multiple quantum coherence (HMQC), and heteronuclear
1
cm-1. H NMR (300.13 MHz, CDCl3): δ 7.95-7.87 (m, 2H,
o-aryl), 7.41-7.38 (m, 3H, m- and p-aryl), 5.2-3.2 (vbr, 4H, CH
(41) Anderson, G. K.; Lin, M. Inorg. Synth. 1990, 28, 60.
(42) Wimmer, F. L.; Wimmer, S.; Castan, P.; Puddephatt, R. J. Inorg.
Synth. 1992, 29, 185.
(43) Yakelis, N. A.; Bergman, R. G. Organometallics 2005, 24, 3579.

11422 Inorganic Chemistry, Vol. 48, No. 23, 2009
Peloso et al.
2
cod), 3.97 and 3.85 (AB spin system, JHH = 8.1 Hz, 4H,
was filtered to remove NaCl, and the volume of the solution was
reduced to 3 mL. Addition of pentane afforded an orange-red
precipitate, which was collected by filtration, washed with
pentane (3 ꢀ 15 mL), and dried under vacuum. Yield: 940 mg
(0.594 mmol, 92%). Selected IR absorptions (pure, diamond
ATR): 1671 vw, 1605 w, 1353 m, 1276 vs, 1165 m, 1129 vs, 1022
w, 993 w, 965 w, 682 w cm-1. 1H NMR (300.13 MHz, CDCl3): δ
7.73 (br, 8H, o-BArF), 7.62-6.47 (m, 9H, overlapping CH aryl
and p-BArF), 5.38 (vbr, 2H, CH cod), 4.5-3.0 (m, 6H, over-
OCH2), 2.40-2.15 (m, 4H, CH2 cod), 2.05-1.85 (m, 4H, CH2
cod), 1.81 (s, 6H, OC(CH3)(CH3)), 1.75 (s, 6H, OC(CH3)(CH3)),
1.21 (s, 6H, NC(CH3)(CH3)), 1.17 (s, 6H, NC(CH3)(CH3)) ppm.
13C{1H} NMR (75.5 MHz, CDCl3): δ 166.9 (d, 3JPC = 3.7 Hz,
1
2
CdN), 137.0 (d, JPC = 71.5 Hz, ipso-aryl), 131.6 (d, JPC
=
4
15.8 Hz, o-aryl), 130.9 (d, JPC = 2.3 Hz, p-aryl), 127.9 (d,
3JPC = 11.8 Hz, m-aryl), 79.4 (s, OC(CH3)2), 79.3 (s, OCH2),
67.3 (s, NC(CH3)2), 31.5 (br, CH2 cod), 28.3 (d, 3JPC = 4.5 Hz,
OC(CH3)(CH3)), 28.1 (s, NC(CH3)(CH3)), 27.8 (s, NC(CH3)-
(CH3)), 27.0 (d, 3JPC = 5.5 Hz, OC(CH3)(CH3)) ppm. 31P{1H}
lapping CH2 NOPONMe and CH cod), 3.0-0.1 (m, 32H, over-
2
lapping CH2 cod and CH3) ppm. 13C{1H} NMR (75.5
MHz, CDCl3): δ 161.7 (q, 1JBC = 49.8 Hz, ipso-BArF), 134.8 (s,
NMR (121.5 MHz, CDCl3): δ 103.2 (s) ppm. MALDI-TOF
2
o-BArF), 134.6 (d, JPC = 69.4 Hz, ipso-aryl), 132.8 (d,
þ
MS: m/z (%) 721.35 (100) [1þ93Ir(cod)(NOPONMe )] , 719.34
2
2
4JPC = 2.4 Hz, p-aryl), 130.1 (d, JPC = 14.9 Hz, o-aryl),
(60) [19þ1Ir(cod)(NOPONMe )] , 648.28 (15) [193Ir35Cl(NOPO-
2
129.3 (d, 3JPC = 11.6 Hz, m-aryl), 128.9 (qq, 2JCF = 31.6 Hz,
3JBC = 2.9 Hz, CCF3), 124.6 (q, 1JCF = 272.5 Hz, CF3), 117.5
(sept, 3JCF = 3.9 Hz, p-BArF), 27.8 (s, CH3), 27.4 (s, CH3) ppm.
31P{1H} NMR (121.5 MHz, CDCl3): δ 110.7 (s) ppm. 19F{1H}
NMe )] . Anal. Calcd for C30H45ClIrN2O4P CH2Cl2: C, 44.26;
2
3
H, 5.63; N, 3.33. Found: C, 43.86; H, 5.66; N, 3.73.
Synthesis of [IrCl(CO)(NOPONMe )] (2). The complex [Ir(μ-
2
Cl)(cod)]2 (200 mg, 0.298 mmol) was dissolved in a solution of
NOPONMe (250 mg, 0.595 mmol) in CH2Cl2 (5 mL) placed in a
2
NMR (282.4 MHz, CDCl3): -62.8 ppm. MALDI-TOF MS:
m/z (%) 720.73 (100) [1þ93Ir(cod)(NOPONMe )] , 718.71 (52)
þ
2
Schlenk tube. After 4 h, the flask was filled with CO. The orange
solution quickly became pale yellow. The solution was concen-
trated to 1 mL, and pentane was added. The compound [IrCl-
(CO)(NOPONMe2)] precipitated as a pale yellow solid which
was collected by filtration and dried under vacuum. Yield: 277
mg (69%). Selected IR absorptions (pure, germanium ATR):
1989 vs, 1656 w, 1608 m, 1327 w, 1153 m, 1116 m, 973 ms, 751
2
[
191Ir(cod)(NOPONMe )] . Anal. Calcd for C62H57BF24Ir-
N2O4P: C, 47.01; H, 3.63; N, 1.77. Found: C, 47.04; H, 3.59;
N, 1.92. Crystals suitable for X-ray diffraction were formed
by addition of excess Na[B(3,5-(CF3)2C6H3)4] to a solution of
1 in C6D6.
Reaction of [Ir(cod)(NOPONMe )][B(3,5-(CF3)2C6H3)4] with
2
H2: Isolation of [IrH(μ-H) (NOPONMe )]2[B(3,5-(CF3)2C6H3)4]2
ms, 290 (Ir-Cl) cm-1 1H NMR (300.13 MHz, CDCl3): δ
.
2
(4) in the Solid State. Compound 3 (40 mg, 0.025 mmol) was
dissolved in THF-d8 (0.45 mL) in a NMR tube under Ar and
placed in a Schlenk flask, which has been evacuated and filled
with hydrogen. The solution quickly turned pale yellow. 1H
NMR (300.13 MHz, THF-d8): δ 7.97-7.80 (m, 10H, o-aryl and
o-BArF), 7.58-7.51 (m, 7H, m-, p-aryl, and p-BArF), 4.64 and
4.19 (AB spin system, 2H, 2JHH = 8.9 Hz, OCH2), 4.35 and 3.94
(AB spin system, 2H, 2JHH = 8.6 Hz, OCH2), 1.84 (s, 3H, CH3),
1.82 (s, 3H, CH3), 1.76 (s, 3H, CH3), 1.66 (s, 3H, CH3), 1.44 (s,
3H, CH3), 1.41 (s, 3H, CH3), 1.32 (s, 3H, CH3), 1.11 (s, 3H,
CH3), -25.99 (d, 1H, 2JPH = 15.0, Ir-H) ppm. 13C{1H} NMR
(75.5 MHz, CDCl3): δ 167.5 (d, 3JPC = 7.9 Hz, CdN), 165.7 (d,
8.00-7.93 (m, 2H, o-aryl), 7.48-7.36 (m, 3H, m- and p-aryl),
4.25 and 4.07 (AB spin system, JHH = 8.2 Hz, 2H, OCH2
2
coordinated oxazoline), 4.19 and 3.97 (AB spin system, 2JHH
=
8.0 Hz, 2H, OCH2 uncoordinated oxazoline), 1.94 (s, 3H, OC-
(CH3)(CH3) coordinated oxazoline), 1.87 (s, 3H, NC(CH3)-
(CH3) coordinated oxazoline), 1.78 (s, 3H, OC(CH3)(CH3)
uncoordinated oxazoline), 1.71 (s, 3H, NC(CH3)(CH3) coordi-
nated oxazoline), 1.68 (s, 3H, OC(CH3)(CH3) uncoordinated
oxazoline), 1.61 (s, 3H, OC(CH3)(CH3) coordinated oxazoline),
1.50 (s, 3H, NC(CH3)(CH3) uncoordinated oxazoline), 1.24 (s,
3H, NC(CH3)(CH3) uncoordinated oxazoline) ppm. 13C{1H}
NMR (75.5 MHz, CDCl3): δ 173.0 (s, CO), 172.8 (s, CdN
uncoordinated oxazoline), 166.8 (s, CdN coordinated oxazo-
line), 140.4 (d, 1JPC = 108 Hz, ipso-aryl), 131.3 (d, 4JPC = 2.0
1
3JPC = 4.8 Hz, CdN), 160.0 (q, JBC = 49.8 Hz, ipso-BArF),
135.6 (d, 2JPC = 95.15 Hz, ipso-aryl), 132.8 (s, o-BArF), 130.7 (d,
4JPC = 2.3 Hz, p-aryl), 128.6 (d, 2JPC = 16.1 Hz, o-aryl), 127.2
Hz, p-aryl), 130.8 (d, 2JPC = 14.8 Hz, o-aryl), 128.0 (d, 3JPC
=
11.8 Hz, m-aryl), 83.2 (s, OCH2 coordinated oxazoline), 79.2 (s,
OCH2 uncoordinated oxazoline), 72.7 (s, NC(CH3)2 coordi-
nated oxazoline), 67.8 (s, NC(CH3)2 uncoordinated oxazoline),
30.1 (s, 3H, OC(CH3)(CH3) coordinated oxazoline), 29.2 (d,
3JCP = 7.1 Hz, 3H, OC(CH3)(CH3) uncoordinated oxazoline),
28.8 (s, NC(CH3)(CH3) uncoordinated oxazoline), 28.6 (s, 3H,
NC(CH3)(CH3) coordinated oxazoline), 27.6 (s, 3H, NC(CH3)-
(CH3) uncoordinated oxazoline), 27.1 (s, OC(CH3)(CH3) co-
ordinated oxazoline), 26.9 (s, OC(CH3)(CH3) uncoordinated
oxazoline), 25.4 (s, 3H, NC(CH3)(CH3) coordinated oxazoline)
ppm, signals of OC(CH3)2 are masked by the peak of CDCl3.
31P{1H} NMR (121.5 MHz, CDCl3): δ 102.1 (s) ppm. ESI-MS:
m/z (%) 682.157 (100) [193Ir35ClN2O5PC23H32Li]þ, 680.154 (59)
(qq, 2JCF = 31.5 Hz, 3JBC = 2.8 Hz, CCF3), 126.5 (d, 3JPC
=
13.1 Hz, m-aryl), 122.7 (q, 1JCF = 272.5 Hz, CF3), 115.4 (sept,
3JCF = 3.9 Hz, p-BArF), 77.9 (s, unassigned), 77.7 (d, J = 7.8
Hz, unassigned), 77.3 (s, OCH2), 76.4 (d, J = 6.1, unassigned),
75.9 (s, OCH2), 73.4 (d, J = 1.3 Hz, unassigned), 72.6 (s,
OC(CH3)2), 71.3 (s, OC(CH3)2), 68.5 (s, NC(CH3)2), 67.9 (s,
NC(CH3)2), 60.8 (s), 29.0-21.0 (m, CH3) ppm. 31P{1H} NMR
(162.0 MHz, CD2Cl2): δ 123.8 (s) ppm. 19F{1H} NMR (282.4
MHz, CDCl3): -65.7 ppm. The same reaction was carried out in
CH2Cl2 (50 mg of 3 in 5 mL). After a few hours, colorless single
crystals of [Ir(μ-H)H(NOPONMe )]2[B(3,5-(CF3)2C6H3)4]2
2
formed, whose structure was determined by X-ray diffraction
to be that of a dinuclear complex, 4, too unstable in solution to
be analyzed.
[
191Ir35ClN2O5PC23H32Li]þ, 641.132 (10) [193IrN2O5PC23H33]þ.
Anal. Calcd for C23H34ClIrN2O5P: C, 40.79; H, 5.06; N, 4.14.
Found: C, 40.49; H, 5.04; N, 3.78. Crystals suitable for X-ray
diffraction were grown by slow diffusion of Et2O in a concen-
trated solution of the compound in CH2Cl2.
Synthesis of [Ir(NOPON)(CO)2][B(3,5-(CF3)2C6H3)4] (5). An
orange solution of 3 (150 mg, 0.095 mmol) in CH2Cl2 (10 mL)
was treated with CO at 1 atm. The solution quickly turned
yellow. The solvent was evaporated under reduced pressure. The
resulting yellow solid was washed with pentane (2 ꢀ 3 mL) and
dried under vacuum. Yield: 115 mg (0.075 mmol, 79%). Selected
IR absorptions (pure, germanium ATR): 2096 m, 2038 m, 2009
w, 1663 vw, 1610 mw, 1354 ms, 1276 vs, 1122 vs cm-1. 1H NMR
(300.13 MHz, CDCl3): δ 7.75-7.45 (m, 17H, aromatic protons),
4.08 and 3.99 (AB spin system, 2JHH = 8.8 Hz, 2H, OCH2), 1.82
(s, 6H, OC(CH3)(CH3)), 1.70 (s, 6H, OC(CH3)(CH3)), 1.26 (s,
6H, NC(CH3)(CH3)), 1.07 (s, 6H, NC(CH3)(CH3)) ppm. 13C-
{1H} NMR (75.5 MHz, CDCl3): 173.9 (d, 2JPC = 60.9 Hz, CO),
Synthesis of [Ir(cod)(NOPONMe )][B(3,5-(CF3)2C6H3)4] (3).
2
The complex [Ir(μ-Cl)(cod)]2 (218 mg, 0.325 mmol) was dis-
solved in a solution of NOPONMe (272 mg, 0.647 mmol) in
2
CH2Cl2 (15 mL), and the solution was stirred for 1 h at room
temperature. Solid Na[B(3,5-(CF3)2C6H3)4] (580 mg, 0.654
mmol) was added and the orange solution rapidly turned red.
The suspension was allowed to stir overnight at room tempera-
ture. The solvent was removed by evaporation under reduced
pressure, and Et2O (20 mL) was added. The resulting suspension

Article
Inorganic Chemistry, Vol. 48, No. 23, 2009 11423
Table 5. Crystal Data and Structure for 2 CH2Cl2, 3 0.5(C6H6), 4 4(CH2Cl2), and 6 CHCl3
3
3
3
3
2 CH2Cl2
3
3 0.5C6H6
3
4 4CH2Cl2
3
6 CHCl3
3
formula
C23H33ClIrN2-
O5P CH2Cl2
761.06
monoclinic
C2/c
173 (2)
40.250(2)
9.0131(5)
17.7372(5)
90
C62H57IrBF24N2-
O4P 0.5(C6H6)
1623.13
monoclinic
P21/c
173 (2)
13.7530(3)
23.6740(7)
24.5963(6)
90
122.268 (2)
90
C
108H94B2F48Ir2N4-
O8P2 4(CH2Cl2)
C
54H45BClF24N2-
O4PPd CHCl3
1544.92
3
3
3
3
Mr/g mol -1
crystal system
space group
T/K
3295.54
triclinic
P1
173 (2)
12.4044(11)
14.6314(10)
18.9398(17)
71.857(4)
79.532(3)
87.282(5)
3212.0(5)
1
monoclinic
C2/c
173 (2)
19.0888(3)
18.4791(3)
36.2002(7)
90
100.196(1)
90
12567.7 (4)
8
˚
a/A
˚
b/A
˚
c/A
R/deg
β/deg
γ/deg
113.674(2)
90
5893.0(5)
8
3
˚
V/A
Z
6771.5 (3)
4
crystal size/mm
Dcalcd/g cm-3
μ/mm-1
0.08 ꢀ 0.08 ꢀ 0.04
0.15 ꢀ 0.14 ꢀ 0.09
0.14 ꢀ 0.12 ꢀ 0.07
0.35 ꢀ 0.32 ꢀ 0.30
1.716
4.89
1.592
2.11
1.704
2.39
1.633
0.61
θ max/deg
Rint
26.5
0.0458
26.0
0.0754
30.1
0.0948
27.5
0.0678
final R indices
[I > 2σ(I)]
no. of measd,
independent, and
obsvd reflns
R indices all data
R1 = 0.0472
wR2 = 0.1191
10 079, 6109, 4497
R1 = 0.0526
wR2 = 0.1114
35 689, 13 281, 8171
R1 = 0.0702
wR2 = 0.1516
19 854, 19 854, 13 784
R1 = 0.0642
wR2 = 0.1726
38 471, 14 298, 8344
R1 = 0.0770
wR2 = 0.1447
1.049
R1 = 0.1095
wR2 = 0.1258
0.999
R1 = 0.1207
wR2 = 0.1738
1.069
R1 = 0.1278
wR2 = 0.2241
0.995
S on F2
R1 = Σ Fo| - |Fc /|Σ(Fo); wR2 = Σw(Fo2 - Fc2)2]/Σ [w(Fo2)2]]1/2
.
169.8 (d, 3JPC = 5.2 Hz, CdN), 161.7 (q, 1JBC = 49.8 Hz, ipso-
BArF), 134.8 (s, o-BArF), 134.2 (d, 4JPC = 2.6 Hz, p-aryl), 132.0
(d, 1JPC = 83.7 Hz, ipso-aryl), 130.6 (d, 2JPC = 15.8 Hz, o-aryl),
129.7 (d, 3JPC = 13.0 Hz, m-aryl), 128.9 (qq, 2JCF = 31.6 Hz,
3JBC = 2.9 Hz, CCF3), 124.6 (q, 1JCF = 272.5 Hz, CF3), 117.5
3JPC = 7.1 Hz, OC(CH3)(CH3)) ppm. 31P{1H} NMR (121.5
MHz, CDCl3): δ 115.6 (s) ppm. 19F{1H} NMR (282.4 MHz,
CDCl3): -62.8 ppm. MALDI-TOF MS: m/z (%) 564.99 (50)
þ
þ
108Pd37Cl(NOPONMe )] , 562.99 (95) [106Pd37Cl(NOPONMe )]
2
2
[
þ
and [108Pd35Cl(NOPONMe )] , 561.00 (100) [106Pd35Cl(NOP-
2
(sept, JCF = 3.9 Hz, p-BArF), 83.3 (d, JPC = 9.7 Hz, OC-
ONMe )] , 526.03 (45) [106Pd(NOPONMe )] . Anal. Calcd for
C54H45BClF24N2O4PPd: C, 45.5; H, 3.18; N, 1.97. Found: C,
43.66 ; H, 3.73; N, 1.90 (no better carbon analysis could be
obtained, despite several attempts). Crystals suitable for X-ray
diffraction were obtained in an NMR tube by slow evaporation
of CDCl3 from the solution of 1.
3
2
þ
þ
2
2
(CH3)2), 80.4 (s, OCH2), 70.1 (s, NC(CH3)2), 28.8 (d, 3JPC = 6.0
=
Hz, OC(CH3)(CH3)), 28.2 (s, NC(CH3)(CH3)), 27.6 (d, 3JPC
5.1 Hz, OC(CH3)(CH3)), 27.5 (s, NC(CH3)(CH3)) ppm. 31P{1H}
NMR (121.5 MHz, CDCl3): δ 116.5 (s) ppm. 19F{1H} NMR
(282.4 MHz, CDCl3): -62.8 ppm. MALDI-TOF MS: m/z (%)
þ
641.13 (25) [193Ir(CO)(NOPONMe ) - H] , 613.þ15 (100) [193Ir-
2
X-ray Crystal Structure Analyses of 2 CH2Cl2, 3 0.5(C6H6),
3
3
(NOPONMe )] , 611.15 (60) [191Ir(NOPONMe )] . Anal. Calcd
for C56H47BF24IrN2O6P: C, 43.85; H, 3.09; N, 1.83. Found: C,
43.41; H, 3.21; N, 1.71.
þ
2
2
4 4(CH2Cl2), and 6 CHCl3. Suitable crystals for the X-ray
3
3
analysis of all compounds were obtained as described above.
The intensity data were collected at 173(2) K on a Kappa
CCD diffractometer44 (graphite monochromated Mo KR radia-
Synthesis of [PdCl(NOPON)][B(3,5-(CF3)2C6H3)4] (6). Solid
[PdCl2(NCMe)2] (80 mg, 0.308 mmol) was dissolved in a CH2Cl2
˚
tion, λ = 0.710 73 A). Crystallographic and experimental details
solution of NOPONMe (130 mg, 0.309 mmol) to give a pale
for the structures are summarized in Table 5. The structures
were solved by direct methods (SHELXS-97) and refined by
full-matrix least-squares procedures (based on F2, SHELXL-
97)45 with anisotropic thermal parameters for all the non-
hydrogen atoms. The hydrogen atoms were introduced
into the geometrically calculated positions (SHELXS-97 proce-
dures) and refined riding on the corresponding parent
atoms. Details about the structure refinements are summarized
below.
2
yellow solution. After 1 h, NaBArF (274 mg, 0.309 mmol) was
added. The mixture was stirred overnight at room temperature
and then filtered to remove NaCl. The solvent was evaporated
under reduced pressure, and the resulting pale yellow powder
was washed with pentane (2 ꢀ 5 mL), collected by filtration, and
dried under vacuum. Yield: 420 mg (94%). Selected IR absorp-
tions (pure, diamond ATR): 1612 mw, 1376 s, 1276 vs, 1161 s,
1
1123 vs, 991 m, 973 m, 716 m cm-1. H NMR (300.13 MHz,
CDCl3): δ 7.75-7.35 (m, 17H, aromatic protons), 4.35 and 4.14
(AB spin system, JHH = 9.0 Hz, 2H, OCH2), 2.30 (s, 6H,
=
In the crystals of 2 CH2Cl2, the dichloromethane molecule
3
2
was found disordered in two positions with equal occupancy
factors. The disorder is probably higher, but attempts to find
a satisfactory model failed. This molecule was then refined
with restrained isotropic parameters and restrained C-Cl
OC(CH3)(CH3)), 1.76 (s, 6H, NC(CH3)(CH3)), 1.68 (d, 3JPH
2.0 Hz, 6H, OC(CH3)(CH3)), 1.47 (s, 6H, NC(CH3)(CH3)) ppm.
13C{1H} NMR (75.5 MHz, CDCl3): δ 171.9 (d, 3JPC = 10.4 Hz,
CdN), 161.7 (q, 1JBC = 49.9 Hz, ipso-BArF), 135.5 (d, 4JPC
=
and Cl Cl distances. The C18 atom is close to this dis-
3 3 3
3.0 Hz, p-aryl), 134.8 (s, o-BArF), 130.1 (d, 3JPC = 14.6 Hz, m-
aryl), 129.6 (d, 4JPC = 16.2 Hz, o-aryl), 128.9 (qq, 2JCF = 31.6
Hz, 3JBC = 2.9 Hz, CCF3), ipso-aryl masked by CCF3 signals,
order and it has been refined with restrained anisotropic
parameters.
1
3
124.6 (q, JCF = 272.5 Hz, CF3), 117.5 (sept, JCF = 3.9 Hz,
(44) Nonius. Kappa CCD Reference Manual; Nonius BV: Delft, The
Netherlands, 1998.
(45) Sheldrick, G. M. SHELX-97 Program for Crystal Structure Refine-
p-BArF), 83.5 (s, OCH2), 83.2 (d, JPC = 5.0 Hz, OC(CH3)2),
72.7 (s, NC(CH3)2), 29.9 (d, JPC = 3.5 Hz, OC(CH3)(CH3)),
28.2 (s, NC(CH3)(CH3)), 26.9 (s, NC(CH3)(CH3)), 24.9 (d,
2
3
€
€
ment; University of Gottingen: Gottingen, Germany, 1997.

11424 Inorganic Chemistry, Vol. 48, No. 23, 2009
Peloso et al.
In the crystals of 3 0.5(C6H6), the CF3 groups of the BArF
from the Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif
3
anion were found severely disordered, the images having the
carbon atom in common. In each of the three disordered CF3
groups, the fluorine atoms were introduced in two calculated
positions, tilted by 60°, and refined riding to the parent carbon
(SHELXL AFIX 128). The two images have unequal occupancy
factor. The F atoms were then refined with restrained aniso-
tropic parameters. The benzene molecule was found disordered
in two positions around the symmetry center, having no atom in
common. The solvent was refined isotropically with ideal geo-
metry (SHELXL AFIX 66).
General Procedure for the Hydrogenation Experiments. In a
10 mL Schlenk tube, compound 3 (7.7 mg, 4.86 μmol)
and 1-octene (0.46 mL, 293 μmol) were dissolved in PhCl
(1 mL). The solution was degassed under vacuum (freeze-
pump-thaw), and the Schlenk tube was connected to a hydro-
gen generator through its stopcock and refilled with 1.5 atm
of hydrogen. The solution was then heated at 60 °C and stirred
for 2 h. The hydrogen feed was always provided by the hydro-
gen generator. After removal of the catalyst by means of a
silica column, the solution was diluted with ether and analy-
zed by gas chromatography using 1-heptene as an internal
standard.
An anion disorder similar to that found in 3 0.5(C6H6) was
observed in 4 4CH2Cl2. The refinement was performed with
restrains similar to those applied for 3 0.5(C6D6). In addition,
3
3
3
one of the two dichloromethane molecules was refined with
restrained C-Cl distances and anisotropic parameters. The two
hydrides were found in the ΔF2 maps. They were then refined
Acknowledgment. The Centre National de la Recherche
˚
with Ir-H distances restrained to 1.8 A.
ꢁ
Scientifique (CNRS), the Ministere de l’Enseignement
The aforementioned disorder of the BArF anion was also
present in 6 CHCl3. One of the CF3 groups was disordered in
two positions having the carbon atom in common and was
refined with equal anisotropic displacements and with re-
strained geometrical parameters. A MULTISCAN46,47 absorp-
ꢀ
ꢀ
Superieur et de la Recherche (Paris), and the Universite de
Strasbourg are gratefully acknowledged for support. We also
thank Dr. Lydia Brelot for the crystal structure determination of
6, Shaofeng Liu and Marc Mermillon-Fournier for experimen-
tal assistance, and a referee for suggestions.
3
tion correction was applied to all compounds except 6 CHCl3.
3
CCDC 740920-740923 contain the supplementary crystal-
lographic data for this paper that can be obtained free of charge
Supporting Information Available: Data for hydrogenation of
alkenes with 3, 1H NMR spectra of 1 at variable temperatures,
and CIF files. This material is available free of charge via the
Internet at http://pubs.acs.org.
(46) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.
(47) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.