Synthesis, characterization, and X-ray structures of three iridium(III)-hydrido-cyclometallated-imine complexes, including the first reported hydrido(n1-imine)-Ir complex

Article abstract of DOI:10.1139/V07-153

Reactions of cis,trans,cis-[Ir(H)₂(PPh₃) ₂(solv)₂]PF₆ (solv = MeOH or Me₂CO) with the imines HN=CPh₂, (o-HOC₆H₄)C(Me)= NCH₂Ph, and PhC(H)=N(p-F-C

Full text of DOI:10.1139/V07-153

253
Synthesis, characterization, and X-ray structures
of three iridium(III)-hydrido-cyclometallated-imine
complexes, including the first reported hydrido-
(␩1-imine)-Ir complex
Fabio Lorenzini, Paolo Marcazzan, Brian O. Patrick, and Brian R. James
Abstract: Reactions of cis,trans,cis-[Ir(H)2(PPh3)2(solv)2]PF6 (solv = MeOH or Me2CO) with the imines HN=CPh2, (o-
HOC6H4)C(Me)=NCH2Ph, and PhC(H)=N(p-F-C6H4) in MeOH or acetone under Ar give the complexes
[IrH{NH=C(Ph)(o-C6H4)}(NH=CPh2)(PPh3)2]PF6 (3), [IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)(PPh3)2]PF6, where solv =
MeOH (4) or Me2CO (4a), and [IrH{N(p-F-C6H4)=CH(o-C6H4)}(Me2CO)(PPh3)2]PF6 (5a), which have been isolated
and characterized. The imine (C6F5)C(H)=NPh is unreactive toward the Ir precursors. The X-ray structures of 3,
2
4·2MeOH, and 5a·1/2Me2CO show an η -N,C-imine moiety coordinated via the N atom and an orthometallated-C atom.
1
Complex 3, which contains both an orthometallated imine and an η -imine, is the first structurally characterized
1
hydrido-(η -imine)-Ir complex. Comparisons are made with data for the corresponding Rh systems.
Key words: iridium, hydride complexes, imines, fluoroimines, phosphine complexes, orthometallation, crystallography,
NMR spectroscopy.
Résumé : Les réactions du cis,trans,cis-[Ir(H)2(PPh3)(solv)2]PF6 (solv = MeOH ou Me2CO) avec les imines
HN=CPh2, (o-HOC6H4)C(Me)=NCH2Ph et PhC(H)=N(p-F-C6H4), en solution dans le MeOH ou l’acétone, sous une
atmosphère d’argon, conduit à la formation des complexes [IrH{NH=C(Ph)(o-C6H4)}(NH=CPh2)(PPh3)2]PF6 (3),
[IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)(PPh3)2]PF6 dans lequel solv = MeOH (4) ou Me2CO (4a) et [IrH{N(p-F-
C6H4)=CH(o-C6H4)}(Me2CO)(PPh3)2]PF6 (5a) qui ont été isolés et caractérisés. L’imine (C6F5)CH=NPh n’est pas réac-
tive vis-à-vis les précurseurs Ir. Les structures des composés 3, 4·2MeOH et 5a·1/2Me2CO telles que déterminées par
2
diffraction des rayons X ont permis de montrer la présence d’une portion η -N,C-imine coordinée par le biais de
l’atome d’azote et d’un atome de carbone orthométallé. Le complexe 3 qui comporte une imine orthométallée ainsi
1
1
qu’une η -imine est le premier complexe hydrido-(η -imine)-Ir à être caractérisée d’un point de vue structural. On a
effectué des comparaisons avec des données pour les systèmes correspondants du rhodium.
Mots-clés : iridium, complexes d’hydrure, imines, fluoroimines, complexes de phosphine, organométallation,
cristallographie, spectroscopie RMN.
[Traduit par la Rédaction] Lorenzini et al. 260
Introduction
poisoning by the amine product. The studies on the Ir sys-
tems, because of their lack of catalytic activity, have been
more limited than those on the Rh systems. With imines
containing an aryl moiety at the imine-C atom, the Ir precur-
sor has generally formed (at 1:1 imine/Ir stoichiometries)
monohydrido-IrIII species via orthometallation at an ortho-C
Since 2003, we have published 10 papers (1), including
one review (2), on the hydrogenation of imines catalyzed by
the Rh- and Ir-bis(triphenylphosphine) precursor complexes
[M(cod)(PPh3)2]PF6 (M = Rh, Ir; cod = 1,5-cyclooctadiene).
Much diverse imine-coordination chemistry has been un-
veiled, important parameters being the structure and physical
nature (solid or liquid) of the imine, the imine:metal
stoichiometry, the presence of trace water, the nature of the
solvent, use of an inert or an H2 atmosphere, and catalyst
1
atom of an assumed [trans-Ir(PPh3)2(η -imine)(solv)]+
intermediate, where solv = MeOH or Me2CO (3); this ‘stan-
dard’ chemistry is illustrated in Scheme 1. With use of ex-
cess of the imine PhCH2N=CHPh, the presence of trace
water results in Ir-promoted hydrolysis of the imine and the
generated benzylamine simply replaces the coordinated sol-
vent of the orthometallated species (3). This new paper re-
ports on the reactions of the Ir precursor with three imines,
HN=CPh2 (Im1), (o-HOC6H4)C(Me)=NCH2Ph (Im2), and
PhC(H)=N(p-F-C6H4) (Im3) (see Scheme 2), and notes the
non-reactivity of (C6F5)C(H)=NPh (Im4). The imines Im1
and Im2 were chosen for comparison with their known reac-
tivity toward the corresponding Rh precursor species (1),
while the fluoro-substituted imines were used in the hope
Received 5 November 2007. Accepted 10 December 2007.
Published on the NRC Research Press Web site at
canjchem.nrc.ca on 15 February 2008.
F. Lorenzini, P. Marcazzan, B.O. Patrick, and
B.R. James.1 Department of Chemistry, The University of
British Columbia, Vancouver, BC V6T 1Z1, Canada.
1Corresponding author (e-mail: brj@chem.ubc.ca).
Can. J. Chem 86: 253–260 (2008)
doi:10.1139/V07-153
© 2008 NRC Canada

254
Can. J. Chem Vol. 86, 2008
Scheme 1. Formation of IrIII-cyclometallated-imine complexes (R, R′ = aryl or alkyl). [Ir(cod)(PPh3)2]+ under H2 is known to generate
cis,trans,cis-[Ir(H)2(PPh3)2(solv)2]+ (solv = Me2CO or MeOH (refs. 3, 4)).
+ PF6–
+ PF6–
+ PF6–
solv
Ir
PPh3
Ir
solv
PPh3
H
PPh3
imine,
1 equiv.
PPh3
N
H
H
solv
R
solv
Ph3P
Ir
R
N
Ph3P
-H2, -solv
H
C
R'
(ortho-CH)
Scheme 2. Reactions of cis,trans,cis-[Ir(H)2(PPh3)2(solv)2]PF6 (solv = MeOH (2) or Me2CO (2a)) with the imines Im1, Im2, and Im3
1
to form the complexes [IrH{NH=C(Ph)(o-C6H4)}(η -NH=CPh2)(PPh3)2]PF6 (3), [IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)(PPh3)2]PF6
(solv = MeOH (4) or Me2CO (4a)), and [IrH{N(p-C6H4-F)=CH(o-C6H4)}(solv)(PPh3)2]PF6 (solv = MeOH (5) or Me2CO (5a)). Im4
showed no reactivity.
Imine, - H2
solv, Ar
H2, solv
- cod
[Ir(H)2(PPh3)2(solv)2]PF6
[Ir(cod)(PPh3)2]PF6
3, 4, 4a, 5, 5a
1
solv = MeOH (2), Me2CO (2a)
c
i
PF6
j
i
b
a
h
d
e
c
c
f
OH
g
b
a
PF6
d
e
b
a
PF6
h
d
NH
Ph3P
CH3
e
Ir
H
Ir
PPh3
N
N
F
H
Ph3P
Ph3P
H
m
o
Ir
n
o
PPh3
PPh3
H
N
l
m
p
H
solv
solv
k
l
3
solv = MeOH (4), Me2CO (4a)
solv = MeOH (5), Me2CO (5a)
m
m
n
F
F
NH
OH
H
N
H
CH3
F
F
N
N
F
F
Im1
Im3
Im2
Im4
2
that the product might be a monometallic η -C=N (π-bonded)
species because electron-withdrawing substituents appear to
favour side-on bonding of imines (5). Such species have not
been detected in metal complex-catalyzed hydrogenation
of imines and whether they play a mechanistic role (as do
π-bonded olefins in catalyzed olefin hydrogenations) is an
important, unanswered question (6). We find, in fact, that
Im1, Im2, and Im3 all form hydrido-orthometallated species
akin to those shown in Scheme 1, although in the Im1 prod-
uid imine HN=CPh2 was a Sigma-Aldrich product, while the
solid imines (o-HOC6H4)C(Me)=NCH2Ph, PhC(H)=N(p-F-
C6H4), and (C6F5)C(H)=NPh were synthesized previously in
this laboratory (7a); recent papers by other groups have also
described the syntheses of the solid imines, which involve
condensation of the ketones or aldehydes with the appropri-
ate amine (7b, 7c).
The [Ir(cod)(PPh3)2]PF6 complex (1) was prepared ac-
cording to a literature procedure (8) using IrCl3·3H2O pur-
chased from Colonial Metals Inc. Acetone and MeOH
(Fisher Scientific) were dried over K2CO3 and Mg/I2, re-
spectively, and distilled under N2. Acetone-d6, CD2Cl2, and
CD3OD (Cambridge Isotope Laboratory) were used as re-
1
uct the solvent has been replaced by a second η -bonded
Im1. The product from the Im1 reaction corresponds to that
found earlier for the Rh system (1b); however, the structure
1
presented is the first reported for a hydrido-η -imine com-
plex of Ir. The product from the Im2 reaction is different
from that of the corresponding Rh system, which does not
give an orthometallated product (1a). Comparisons between
the Ir and Rh reactions with Im3 and Im4 systems are also
mentioned.
1
ceived for measuring 31P{1H}, 13C{1H}, and H NMR spec-
tra at rt on a Bruker AV400 spectrometer. When necessary,
atom assignments were made by means of 1H-13C{1H}
1
(HSQC and HMBC) and H-31P{1H} (HSQC and HMBC)
NMR correlation spectroscopies. Residual protonated spe-
cies in the deuterated solvents were used as internal refer-
ences (δ: 2.05 q for acetone-d6; δ: 5.32 t for CD2Cl2; and δ:
3.31 q and 4.87 s for CD3OD). All shifts are reported in ppm
(s = singlet, d = doublet, t = triplet, q = quintet, spt =
septet, m = multiplet, br = broad), relative to external SiMe4
or 85% aq. H3PO4, with J values in Hz. Solid samples of the
synthesized complexes were stored at rt under Ar; elemental
Experimental
All manipulations and synthetic procedures were per-
formed at room temperature (rt, ~20 °C) under an atmo-
sphere of dry Ar or extra-dry H2 (from Praxair, Edmonton,
Alta.) as stated, using standard Schlenk techniques. The liq-
© 2008 NRC Canada

Lorenzini et al.
255
analyses were performed on a Carlo Erba 1108 analyzer.
ESI-MS were acquired in the positive ion mode on a Bruker
Esquire LC ion-trap mass spectrometer equipped with an
electrospray ion source; solvents used were acetone/MeOH
or CH2Cl2/MeOH, and the sample solution of concentration
~25–50 µmol/L was infused into the ion source by a syringe
pump at a flow-rate of 700 µL/h. MALDI-MS were obtained
on a Bruker Biflex IV MALDI-TOF spectrometer equipped
with a nitrogen laser. The samples were dissolved in ace-
tone/MeOH or CH2Cl2/MeOH and dithranol was used as
matrix. The sample solutions (~1 mg/mL) and the matrix
(20 mg/mL) were mixed in a ratio of 1:1 to 1:10, and 1 µL
of the mixture was deposited onto the sample target; these
spectra were acquired in the positive reflection mode with
delay extraction by averaging 100 laser shots, and were cali-
brated externally using peptides. MS data are reported as m/z
values. IR spectra were measured with a Thermo Nicolet
FT-IR Nexus spectrometer using either a KBr pellet or a so-
lution, as stated.
(16 mg, 0.069 mmol) in acetone (1.0 mL) and subsequent
stirring of the mixture at rt for 1 h generated a yellow solu-
tion. Addition of Et2O (20.0 mL) precipitated a yellow pow-
der that was collected, washed with Et2O (2 × 10 mL), and
dried in vacuo; the product is 4a (51 mg, 72% yield). IR
(KBr, cm–1): 3057 (νO-H), 2195 (νIr-H), 1587, 1579 (νC=N). IR
(acetone, cm–1): 2034 (νIr-H), 1581 (νC=N). 1H NMR (acetone-
2
d6) (see Scheme 2 for atom-labeling) δ: –15.48 (t, 1H, JHP
=
17.6, IrH), 8.94 (br s, 1H, OH), 7.51 (m, 5H, CH2C6H5),
7.39 (m, 15H, PC6H5), 7.27 (t, 1H, 3JHHa ~ 3JHHc ~ 7.3, Hb),
3
7.04 (m, 15H, PC6H5), 6.49 (d, 1H, JHHb ~ 7.2, Hc),
3
6.28 (d, 1H, JHHb ~ 7.4, Ha), 5.50 (br s, 2H, NCH2), 2.09
(br s, 3H, CH3), 2.09 (br m, 6H, (CH3)2CO). 13C{1H} NMR
(acetone-d6) δ: 183.26 (s, C(H)=N), 159.20 (s, Cd), 136.52
(s, C-OH), 134.25 (m, PC6H5), 133.31 (s, Ca), 132.71 (m,
CH2C6H5), 128.59 (m, PC6H5), 127.94 (s, Cb), 110.83 (s,
Cc), 56.99 (s, CH2Ph) 20.66 (s, CH3); the Ce signal could not
be assigned. 31P{1H} NMR (acetone-d6) δ: 17.91 (s, PPh),
1
–142.64 (spt, JPF = 707.3, PF6). MALDI-MS: 942 [M-PF6-
Me2CO]+, 679 [M – H-PF6-Me2CO-PPh3]+.
X-ray quality, yellow prism crystals of 4·2MeOH, as well
as a yellow precipitate of 4, were obtained at ~273 K from a
saturated MeOH (2.0 mL) solution of 4a; 4 was washed with
Et2O and dried in vacuo. Anal. calcd. for C52H49N4O2F6P3Ir
(4): C 55.81, H 4.41, N, 1.25; found: C 55.89, H 4.94, N
1.22.
[IrH{NH=C(Ph)(o-C6H4)}(HN=CPh2)(PPh3)2]PF6 (3)
A red suspension of [Ir(cod)(PPh3)2]PF6 (1) (61 mg,
0.063 mmol) in MeOH (1.8 mL) was reacted with 1 atm H2
at rt to generate immediately a brown solution containing
cis,trans,cis-[Ir(H)2(PPh3)2(MeOH)2]PF6 (2) (3, 4). HN=CPh2
(Im1) (22.0 µL, 0.127 mmol) in MeOH (0.5 mL) was then
added under H2. Stirring the mixture at rt for 90 min resulted
in precipitation of a yellow solid that was collected, washed
with Et2O (3 × 5 mL), and dried in vacuo (63 mg, 82%
yield). IR (KBr, cm–1): 3429 (νN-H), 2132 (νIr-H), 1589, 1560
(νC=N). IR (CH2Cl2, cm–1): 3340 (νN-H), 2195 (νIr-H), 1583,
[IrH{N(p-F-C6H4)=CH(o-C6H4)}(Me2CO)(PPh3)2]PF6
(5a)
A red solution of 1 (25 mg, 0.026 mmol) in acetone-d6 (or
acetone) (1.0 mL) was treated as above with H2 to form a
solution of 2a. Addition under Ar of PhC(H)=N(p-F-C6H4)
(Im3) (6 mg, 0.030 mmol) in acetone-d6 (or acetone)
(0.5 mL) at rt resulted in a yellow solution into which slow
diffusion of Et2O generated overnight a yellow, crystalline
powder (5a) and X-ray quality, yellow plate crystals of
5a·1/2Me2CO. The powder (5a) was collected, washed with
Et2O (3 × 5 mL), and dried in vacuo (24 mg, 83% yield). IR
(KBr, cm–1): 2206 (νIr-H), 1599 (νC=N). IR (CH2Cl2, cm–1):
1
1568 (νC=N). H NMR (CD2Cl2) (see Scheme 2 for atom-
2
labeling) δ: –15.80 (t, 1H, JHP = 14.1, IrH), 10.21 (s,
3
HN=C(o-C6H4)), 9.98 (s, HN=CPh2), 7.58 (t, 1H, JHHi
~
3
7.6, Hj), 7.43 (d, 1H, JHH = 7.3, Hd), 7.39–7.06 (m, 38H,
3
PC6H5, Hi, Hm, Hn), 6.86 (d, 2H, JHH = 7.7, Hl or Ho), 6.75
3
3
3
3
(t, 1H, JHHa ~ JHHc ≅ 7.3, Hb), 6.65 (t, 1H, JHHb ~ JHHd
~
=
3
3
7.2, Hc), 6.56 (d, 1H, JHH = 7.5, Ha), 6.37 (d, 2H, JHH
7.6, Hh), 6.28 (d, 2H, JHH = 7.5, Hl or Ho). 13C{1H} NMR
(CD2Cl2) δ: 189.40 (s, NH=C(o-C6H4)), 179.32 (s,
HN=CPh2), 151.59 (s, Cf), 147.32 (s, Ce), 142.04 (s, Cd),
137.97 (s, Ck or Cp), 137.01 (s, Ck or Cp), 134.69 and
131.88-127.93 (m, PC6H5, Ci, Cm, Cn), 133.82 (s, Ca),
131.18 (s, Cc), 129.86 (s, Cj), 129.43 (s, Cl or Co), 128.65 (s,
Ch), 128.64 (s, Cl or Co), 121.23 (s, Cb); the Cg signal could
not be assigned. 31P{1H} NMR (CD2Cl2) δ: 16.93 (s, PPh),
3
1
2217 (νIr-H), 1599, 1587 (νC=N). H NMR (acetone-d6) (see
2
Scheme 2 for atom-labeling) δ: –16.98 (t, 1H, JHP = 15.8,
IrH), 8.15 (br s, 1H, C(H)=N), 7.49 (m, 6H, C6H4F, Ha, Hd),
7.40–7.30, 7.19–7.09 (m, 30H, PC6H5), 6.87 (br t, 1H, Hb or
3
4
Hc), 6.55 (dt, 1H, JHH ~ 7.6, JHH ~ 1.2, Hb or Hc). 13C{1H}
NMR (acetone-d6) δ: 175.07 (s, C(H)=N), 146.88 (s, Ce),
131.43 (m, PC6H5), 129.42 (s, Cb or Cc), 128.84 (m, C6H4F,
–143.70 (spt, JPF = 712.0, PF6). ESI-MS: 1080 [M+], 899
1
Ca, Cd), 126.69 (m, PC6H5), 119.39 (s, Cb or Cc). 31P{1H}
[M+-NH=C(Ph)(o-C6H4)]. Anal. calcd. for C62H52N2F6P3Ir: C
60.83, H 4.28, N 2.29; found: C 60.87, H 4.30, N 2.18.
Yellow, X-ray quality tablet crystals of 3 were grown at rt
by diffusion of Et2O into a CH2Cl2 solution (1.5 mL) of the
complex (25 mg, 20.4 mmol).
1
NMR (acetone-d6) δ: 17.69 (s, PPh), –142.64 (spt, JPF
=
707.3, PF6). MALDI-MS: 917 [M-H-PF6-Me2CO]+. Anal.
calcd. for C52H48NOF7P3Ir: C 55.71, H 4.32, N 1.25; found:
C 55.37, H 4.18, N, 1.25.
Attempted reactions with (C6F5)C(H)=NPh (Im4)
[IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)(PPh3)2]PF6;
solv = MeOH (4), Me2CO (4a)
A red suspension of 1 (60 mg, 0.062 mmol) in acetone
(1.0 mL) was reacted with 1 atm H2 at rt to form a brown
solution of cis,trans,cis-[Ir(H)2(PPh3)2(Me2CO)2]PF6 (2a).2
Addition under Ar of (o-HOC6H4)C(Me)=NCH2Ph (Im2)
Solutions of 2 and 2a (and the corresponding species with
solv = CD3OD and acetone-d6, see Scheme 2) were made in
the appropriate solvents as described above, but using a
smaller quantity of 1 (15 mg, 0.016 mmol) in 0.5 mL of the
respective solvents. No rt reactions over several hours were
seen on addition of Im4 (5 mg, 0.017 mmol), the NMR spec-
2 All the complexes labelled with an ‘a’ have coordinated acetone.
© 2008 NRC Canada

256
Can. J. Chem Vol. 86, 2008
Table 1. Crystal data for complexes 3, 4·2MeOH, and 5a·1/2Me2CO.
Crystal
3
4·2MeOH
5a·1/2Me2CO
Empirical formula
C62H52N2F6P3Ir
C54H57N4O4F6P3Ir
C53.5H49NO1.5F7P3Ir
Formula weight
Crystal system
Space group
1224.17
Orthorhombic
Pna21 (no. 33)
1183.12
Monoclinic
P21/n (no. 14)
1148
Monoclinic
P21/c (no. 14)
Crystal size (mm3)
0.10 × 0.18 × 0.35
27.947(1)
18.5418(7)
12.0971(5)
90.0
90.0
90.0
6268.6(4)
4
1.297
0.12 × 0.20 × 0.50
12.1301(5)
13.4827(7)
31.115(2)
90.00
95.718(2)
90.00
5063.4(4)
4
0.05 × 0.20 × 0.40
23.6030(10)
14.8451(7)
28.2107(14)
90.00
92.489(2)
90.00
9875.4(8)
8
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
Volume (Å3)
Z
Dcalcd. (mg m–3)
1.552
1.544
Abs. µ (mm–1)
F(000)
2.260
2456.00
2.800
2384.00
2.868
4592.00
Reflections collected
Unique reflections [R(int)]
No. of variables
GoF on F2
40 584
13 043 [0.051]
64 532
12 067 [0.051]
643
129 567
15 224 [0.097]
1212
673
1.05
1.03
1.20
Final R indices (I > 2σ(I))
R1 0.064,a wR2 0.126b
R1 0.048,a wR2 0.065b
R1 0.111,a wR2 0.195b
Max. diff. peak/hole (e Å–3)
3.84, –2.87
0.99, –1.12
3.87, –5.27
aR1 = Σ||Fo| – |Fc||/Σ|Fo|.
2
2
bwR2 = [Σ(w(Fo – Fc2)2)/Σw(Fo )2]1/2
.
tra revealing the presence of only 2 or 2a. 1H NMR
Results and discussion
2
(CD3OD) δ: –29.46 (t, 1H, JHP = 17.1, IrH). 31P{1H} NMR
(CD3OD) δ: 27.16 (s, PPh), –143.32 (spt, 1JPF = 707.5, PF6).
The new complexes [IrH{NH=C(Ph)(o-C6H4)}(HN=CPh2)-
(PPh3)2]PF6 (3), [IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)-
(PPh3)2]PF6, where solv = MeOH (4) or Me2CO (4a), and
[IrH{N(p-F-C6H4)=CH(o-C6H4)}(Me2CO)(PPh3)2]PF6 (5a),
were obtained by reaction of cis,trans,cis-[Ir(H)2(PPh3)2
(solv)2]PF6 (solv = MeOH (2) or Me2CO (2a)) with the
imine, with co-production of H2 (Scheme 2); the complexes
are of the well-documented hydrido-orthometallated-imine
type (Scheme 1). Such complexes have been characterized
for many metals (certainly for all the platinum metals; see
following and ref. 12), and continue to attract attention be-
cause of their wide range of applicability in areas that in-
clude asymmetric synthesis, functionalization of C–H bonds,
C-C coupling reactions, and biological systems (13).
Complex 3 was readily obtained in 82% yield from reac-
tion in MeOH of 2 with 2 equiv. of benzophenone imine
(HN=CPh2, Im1), and was fully characterized by X-ray anal-
ysis, elemental analysis, and NMR, IR, and MS data. Our
group recently isolated the analogous Rh complex with
essentially the same structure (see later), but the Rh species
2
1H NMR (acetone-d6) δ: –27.68 (t, 1H, JHP = 15.9, IrH).
31P{1H} NMR (acetone-d6) δ: 28.89 (s, PPh), –142.62 (spt,
1JPF = 707.4, PF6). These NMR data are in accord with liter-
ature values (3, 4).
X-ray crystallographic analyses of 3, 4·2MeOH, and
5a·1/2Me2CO
Measurements were made at 173(1) K on a Bruker X8
APEX diffractometer using graphite-monochromated Mo-K
α radiation (λ = 0.71073 Å); data were collected and inte-
grated using the Bruker SAINT software package (9) and
were corrected for absorption effects using the multi-scan
technique (SADABS) (10) with minimum and maximum
transmission coefficients of 0.551 and 0.798, respectively,
for 3, 0.434 and 0.715 for 4·2MeOH, and 0.549 and 0.866
for 5a·1/2Me2CO. The data were corrected for Lorentz and
polarization effects, and the structures were solved by direct
methods (11). For 3, one phenyl ring appears to be disor-
dered over 2 sites; the 2 rings were thus refined using mild
restraints with the major fragment refined anisotropically
and the minor fragment isotropically. Located in difference
maps and refined isotropically were the imine-H of the
orthometallated imine of 3, and the hydride and the H-atoms
of the OH groups of the coordinated MeOH and the C6H3
ring of 4. The hydrides of 3 and 5a were not located and
were thus not included in the models. All other H-atoms of
the complexes were placed in calculated positions and were
not refined. Some of the crystallographic data are given in
Table 1, while selected bond lengths and angles are given in
Table 2.
1
was formed more slowly via cis-[Rh(PPh3)2(η -
NH=CPh2)2]PF6 in which one imine ligand subsequently un-
dergoes orthometallation (1b). No intermediates were de-
tected in the Ir system, the stronger Ir-H bond (vs. Rh-H)
presumably promoting the metallation step (14).
The reaction of 2 with (o-HOC6H4)C(Me)=NCH2Ph (Im2)
in MeOH resulted in a mixture of products that could not be
separated. However, a successful isolation of complex 4 was
achieved by carrying out a 1:1 reaction of 2a with Im2 in
acetone and then recrystallizing the resulting isolated ace-
tone analogue (4a) from MeOH. Complex 4a, obtained in
© 2008 NRC Canada

Lorenzini et al.
257
Table 2. Selected bond lengths and angles for 3, 4·2MeOH, and 5a·1/2Me2CO.
3
4·2MeOH
5a·1/2Me2COa
Bond lengths (Å)
Ir(1)—C(1)
Ir(1)—N(1)
Ir(1)—N(2)
Ir(1)—P(1)
Ir(1)—P(2)
N(1)—C(7)
C(14)—N(2)
Bond angles (°)
2.018(7)
2.138(6)
2.132(6)
2.3308(19)
2.331(2)
1.296(9)
1.265(9)
Ir(1)—C(1)
Ir(1)—H(1)
Ir(1)—N(1)
Ir(1)—O(2)
Ir(1)—P(1)
Ir(1)—P(2)
C(7)—N(1)
1.998(3)
1.27(4)
Ir(2)—C(53)
Ir(2)—N(2)
Ir(2)—O(2)
Ir(2)—P(3)
Ir(2)—P(4)
C(59)—N(2)
2.082(15)
2.157(12)
2.154(10)
2.332(4)
2.316(4)
1.294(18)
2.151(3)
2.237(2)
2.3320(8)
2.3310(8)
1.299(4)
C(1)-Ir(1)-N(1)
C(1)-Ir(1)-N(2)
C(1)-Ir(1)-P(1)
C(1)-Ir(1)-P(2)
N(1)-Ir(1)-N(2)
N(1)-Ir(1)-P(1)
N(1)-Ir(1)-P(2)
N(2)-Ir(1)-P(1)
N(2)-Ir(1)-P(2)
P(1)-Ir(1)-P(2)
C(14)-N(2)-Ir(1)
C(7)-N(1)-H(1n)
Ir(1)-N(1)-H(1n)
78.7(3)
177.1(3)
87.3(2)
89.6(2)
98.6(2)
92.21(16)
92.40(17)
91.70(16)
91.58(16)
173.88(7)
134.7(5)
127(4)
C(1)-Ir(1)-H(1)
C(1)-Ir(1)-N(1)
C(1)-Ir(1)-O(2)
C(1)-Ir(1)-P(1)
C(1)-Ir(1)-P(2)
H(1)-Ir(1)-N(1)
H(1)-Ir(1)-O(2)
H(1)-Ir(1)-P(1)
H(1)-Ir(1)-P(2)
N(1)-Ir(1)-O(2)
N(1)-Ir(1)-P(1)
N(1)-Ir(1)-P(2)
O(2)-Ir(1)-P(1)
O(2)-Ir(1)-P(2)
P(1)-Ir(1)-P(2)
C(34)-O(2)-Ir(1)
95.9(16)
78.27(11)
178.07(10)
88.04(8)
88.95(8)
173.8(16)
84.6(16)
88.6(15)
76.7(15)
101.26(10)
93.26(7)
100.84(7)
90.12(6)
92.98(6)
164.67(3)
122.7(2)
C(53)-Ir(2)-N(2)
C(53)-Ir(2)-O(2)
C(53)-Ir(2)-P(3)
C(53)-Ir(2)-P(4)
N(2)-Ir(2)-O(2)
N(2)-Ir(2)-P(3)
N(2)-Ir(2)-P(4)
O(2)-Ir(2)-P(3)
O(2)-Ir(2)-P(4)
P(3)-Ir(2)-P(4)
Ir(2)-O(2)-C(102)
79.3(5)
170.4(5)
87.3(4)
88.3(4)
91.1(4)
94.6(3)
97.2(3)
94.5(3)
92.0(3)
166.37(14)
137.6(13)
118(4)
aData for one of the two molecules in the asymmetric unit.
72% yield, was well characterized by NMR, MS, and IR
data, but a satisfactory elemental analysis could not be ob-
tained, possibly because of the variable acetone solvate con-
tent; complex 4 as a yellow powder gave a good elemental
analysis for a non-solvated species, while the crystal con-
tained two MeOH solvates per molecule as determined by
X-ray analysis (see later).
Of note, the rate of formation of 4a appears to be depend-
ent on the water content of the solvent (acetone or metha-
nol); in the synthetic work carried out in dried solvents,
reaction was complete in ~1 h, but the reaction of 2a with
Im2, as monitored by 31P{1H} NMR spectroscopy in non-
dried acetone-d6, took ~13 d for completion (Fig. S1, δP:
28.89 for 2a and 17.91 for 4a).2 Presumably, water competes
with the solvent for a coordination site in 2a and (or) 4a and
somehow impedes the reaction, although there was no direct
evidence for the presence of any aquo species.
Reaction of 2a with PhC(H)=N(p-F-C6H4) (Im3) at ~1:1
stoichiometry in acetone led to the isolation of 5a in 83%
yield as a mixture of a yellow powder and crystals after slow
diffusion of Et2O into the solution of 5a; higher yields were
obtained when a 2:1 ratio of Im3/Ir was used. Elemental
analysis of the powder corresponded to unsolvated 5a, while
X-ray analysis of the crystal revealed one-half an acetone
solvate per molecule (see below). NMR, MS, and IR data
were in accord with the solid state structure. The formation
of 5a is apparently a reversible process as evidenced by
monitoring under H2 an acetone-d6 solution of isolated 5a by
31P{1H} NMR spectroscopy (Fig. S2)3: the δP 17.69 reso-
nance of 5a decays over a week and is partially replaced by
the δP 28.89 signal of the Ir-dihydride (2a, where solv = ace-
tone-d6). Of note, no formation of 5 (the MeOH/CD3OD an-
alogue of 5a) was evident when 2 (solv = CD3OD) was
reacted with ~1 mol equiv. of Im3 in CD3OD at rt; in situ
31P{1H} NMR spectra over several hours revealed only the
δP 27.16 resonance of 2, although over the period of a week
this was replaced completely by broad singlets at δP 21.00
and 19.68 due to unidentified species (at an Im3:Ir ratio of 2,
~15% of 5 was formed over a week as evidenced by a reso-
nance at δP 17.66). The complications detected by the NMR
experiments may again be symptomatic of water impurity in
the deuterated solvents and stresses the need for dry solvents
in the synthetic procedures.
As monitored by 31P{1H} NMR spectroscopy, there was
no reaction at rt of 2 or 2a with (C6F5)C(H)=NPh (Im4) in
the respective solvents at imine:Ir ratios up to 2.
The X-ray structures of the cations of 3, 4·2MeOH, and
5a·1/2Me2CO are shown in Figs. 1–3, and some geometrical
2 Supplementary data for this article are available on the journal Web site (canjchem.nrc.ca) or may be purchased from the Depository of Un-
published Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 3710. For more in-
formation on obtaining material refer to cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC numbers 670430–670432 contain the
crystallographic data for this manuscript. These data can be obtained, free of charge, via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax +44 1223 336033; or de-
posit@ccdc.cam.ac.uk).
© 2008 NRC Canada

258
Can. J. Chem Vol. 86, 2008
Fig. 1. Structure of the [IrH{NH=C(Ph)(o-C6H4)}(HN=CPh2)(PPh3)2]+
cation of 3, with 50% probability ellipsoids.
Fig. 3. Structure of one of the two almost identical molecules of
the [IrH{N(p-C6H4-F)=CH(o-C6H4)}(Me2CO)(PPh3)2]+ cation of
5a, with 50% probability ellipsoids.
showing νIr-H 2034–2217 cm–1) unequivocally establish its
presence in all three complexes. (Solid state and solution IR
data for νC=N for 3–5, νN-H for 3, and νO-H for 4 are also
noted). The hydride resonances are very similar to those we
found earlier for an analogue of 5a synthesized in the same
manner but using PhC(H)=NCH2Ph (3). The imine-NH pro-
Fig. 2. Structure of the [IrH{PhCH2N=C(Me)(o-C6H3OH)}-
(MeOH)(PPh3)2]+ cation of 4, with 50% probability ellipsoids.
1
ton singlets for 3, at δ 9.98 (for the η -imine) and 10.21 (for
2
the η -imine), are close to the values reported for the same
imine (Im1) similarly coordinated at RuII and OsII (15) but
are ~3 ppm to lower field than those of the Rh analogue
[RhH{NH=C(Ph)(o-C6H4)}(HN=CPh2)(PPh3)2]PF6
(1b).
Measurements of 2D HSQC, HMBC 31P{1H}/1H, and 2D
HSQC, HMBC 13C{1H}/1H NMR spectra have allowed for
1
assignment of all the H NMR resonances of 3, 4, and 5a.
The 31P{1H} NMR spectra of 3, 4a, and 5a each show a
sharp singlet in the δ 18–17 region for the trans-phosphines,
–
and a septet at δ ~–143 for the PF6 anion. Mass spectral
data for complex 3 show the mass fragment of the intact cat-
ion, while the highest fragments seen for 4a and 5a corre-
spond to [IrH{N(CH2Ph)=C(Me)(o-C6H3OH)}(PPh3)2]+ and
[Ir{N(p-F-C6H4)=CH(o-C6H4)}(PPh3)2]+, respectively.
The five-membered planar metallocycle ring within the
1
parameters are listed in Table 2. Complexes 3 and 4·2MeOH
crystallize with one molecule in the asymmetric unit, while
5a·1/2Me2CO crystallizes as two almost identical, crystallo-
graphically independent molecules with one molecule of
free acetone in the asymmetric unit. The structures of the
three distorted octahedral IrIII cations exhibit similar fea-
tures, all having five coordination sites occupied by the
complexes is essentially coplanar with the η -N atom of the
second imine in 3, the O-C of the MeOH in 4·2MeOH, and
the O-C-C2 unit of the Me2CO in 5a. The N-Ir-C angle of
the metallocycle of all three structures (79.3°–78.3°) is very
similar to those found in other cyclometallated imine com-
plexes of IrIII (3) and also, for example, of RhIII (16) and
OsII (17). The trans-PPh3 ligands are bent slightly towards
the hydride as indicated by P-Ir-P angles of 164.7° to 173.9°
and other angles at the Ir centre (Table 2); all such hydrido-
bis(phosphine)-orthometallated-imine complexes of Ir (3)
and Rh (1b, 16) systems display such bending. The Ir-O-C
angles of the coordinated MeOH in 4 and coordinated ace-
tone in 5a are 122.7° and 137.6°, respectively.
2
same arrangement of ligands: an η -imine moiety coordi-
nated via the imine-N atom and the orthometallated-C atom
(Cortho), a hydride trans to the N-atom, and trans-PPh3 lig-
ands cis to the hydride (cf. Scheme 1), and, while 4 and 5a
respectively have MeOH or Me2CO coordinated trans to
1
C
ortho, 3 has a second imine, η -coordinated. The hydride at-
tached to the heavy metal centre was successfully located by
The Ir—P, Ir—N, and Ir—Cortho bond lengths (and the
1
2
X-ray analysis only for 4, but H NMR data (a high-field
C=N bond lengths for the η -C,N-imine) for the three com-
2
triplet at δH –17 to –15 with JHP ~ 14–18 Hz, and IR data
plexes are in the range found previously for the closely re-
© 2008 NRC Canada

Lorenzini et al.
259
lated orthometallated-imine species [IrH{PhCH2N=CH(o-
C6H4)}(PPh3)2L]PF6, where L = Me2CO or PhCH2NH2 (3).
The geometry of the orthometallated benzophenone ligand
of 3 is also very similar to that of the same ligand within the
Rh analogue of 3 (1b) and within complexes of RuII (15d)
Our previous studies have shown that isolated Ir-
cyclometallated-imine complexes are stable toward H2 in ac-
etone or MeOH solution at ambient conditions and are not
effective for catalytic hydrogenation of the imine (3, 30),
and this has been confirmed recently by the Zaragosa group
(31). The new complexes 3–5 are similarly inactive. In gen-
eral, cyclometallated-imine Rh complexes can become active
catalysts in MeOH, when they undergo partial reductive
elimination of the cyclometallated imine (the reverse of
orthometallation — cf. the intermediate shown in Scheme 1)
1
and OsII (17). The C=N bond length of the η -NH=CPh2 of 3
is about 0.2 Å shorter than that of the corresponding Rh
1
complex (1b) and those found in other RhI- and RhIII-(η -
imine) complexes (18).
As far as we are aware, complex 3 is the first structurally
1
1
to generate a solvated η -imine species that does react with
characterized Ir(η -imine) complex, where the imine is a
H2 (2, 16a). The Rh analogues of 3 (1b) and 5a4 are inactive
toward H2, while the Rh analogue of 4 (or 4a) is unknown
(see earlier), and the Ir and Rh complexes derived from Im3
in MeOH are not characterized.
‘standard one’, i.e., containing only alkyl, aryl, or hydrogen
substituents at the imine-C and -N atoms; however, other
1
such Ir(η -imine) complexes have been isolated, including
benzophenone systems (19). Complex 3 is also a relatively
1
rare example of a hydrido-η -imine species; except for the
Rh analogue of 3 mentioned above (1b), all the other exam-
Conclusions
1
ples are η -benzophenone derivatives of Ru or Os (15).
There is, of course, a vast literature on Ir complexes with
Following our earlier work on the reactions between im-
ines and cis,trans,cis-[Rh(H)2(PPh3)2(solv)2]+ (solv = MeOH
or Me2CO), this article describes reactions of the imines
with the corresponding Ir precursor species. The selected
imines are HN=CPh2, (o-HOC6H4)C(Me)=NCH2Ph, and
PhC(H)=N(p-F-C6H4), the last one being chosen with the
1
‘non-standard’ η -N=C < moieties within a range of ligands
such as imine-ethers, iminols, and amidines (20), diimines
(21), pyrazoles (22), imidazoles (22), oxazolines (23),
oxazolones (24), anthranil (25), and creatinine (26).
The ketimine Im2, containing an o-OH substituent in the
imine-C phenyl group, forms complex 4, a typical hydrido-
orthometallated species akin to those we report here and
elsewhere (3); however, this is the first type of such a com-
plex derived from this ketimine. In complexes of CuII (27),
RuII (28), and VIV (29), the ketimine is chelated via the N-
atom and the alkoxy-O atom from the hydroxy group. In
recent work, on an analogous study of this imine with
cis,trans,cis-[Rh(H)2(PPh3)2(MeOH)2]PF6 (or cis-[Rh(PPh3)2
(MeOH)2]PF6), we isolated an unique type of zwitterionic
2
aim of possibly favouring formation of an η -C=N (π-
bonded) species. However, in each case, the product is a
2
hydrido species containing an η -N,C-imine moiety coordi-
nated via the N atom and an orthometallated-C atom. With
benzophenone imine, the product contains also a second
1
imine that is η -N coordinated, the product proving to be the
1
first reported, structurally characterized hydrido-(η -imine)-
Ir complex. The Ir complexes are inactive as precursor hy-
drogenation catalysts for the imines. Comparisons are made
with the products formed in the corresponding Rh systems
and significant differences are noted.
4
complex, namely [Rh{η -(C6H4O)(–)C(Me)=N(+)(H)CH2Ph}-
(PPh3)2]PF6, in which the ketimine is coordinated via the C4
part of the o-hydroxy-arene moiety in a quinoid form; this
tautomer is generated via proton transfer from the O-atom to
the N-atom within the molecular, benzenoid form. Presum-
ably, the strength of the Ir–H bond again promotes the ortho-
metallation.
Acknowledgment
We thank the Natural Sciences and Engineering Research
Council of Canada (NSERC) for financial support via a Dis-
covery Grant.
Complex 5a formed from Im3 is again a typical hydrido-
orthometallated species, but we are unaware of any other
such structures with this fluorinated imine. Of note, however,
a recent structure with this imine, Ni[iPr2P(CH2)2PiPr2]-
[PhC(H)=N(p-F-C6H4)], reveals the π-bonded Im3 (5), and
indeed this report prompted us to investigate the reactivity of
this particular imine toward Ir. The strength of the Ir–H
bond again likely favours formation of 5a. Of major interest,
in a cursory study we have found that the reaction of Im3
with the Rh analogue of 2a forms only a trace of a hydrido-
orthometallated species, and the major product has yet to be
identified.3 The fluoro-aldimine (C6F5)C(H)=NPh (Im4) was
unreactive toward 2, 2a, or the corresponding Rh species;
the reactivity of Im4 toward the Ni precursor used for the
Im3 reaction, [Ni{iPr2P(CH2)2PiPr2}]2(µ-H)2, was not re-
ported (5). We continue studies with variation of the
fluoroimine and the phosphine ligand in the hope of achiev-
ing an appropriate electronic and steric environment for for-
mation of a π-bonded imine-Ir or -Rh complex.
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