Iridium olefin complexes bearing dialkylamino/amido PNP pincer ligands: Synthesis, reactivity, and solution dynamics

Article abstract of DOI:10.1021/om800423u

The reaction of [IrCl(COE)₂]₂ (1, COE = cyclooctene) with pincer ligand HN (CH₂CH₂PⁱPr ₂)₂ ((PNP)^H) and AgPF₆ gives iridium(I) amino olefin complex [Ir(COE)

Full text of DOI:10.1021/om800423u

708
Organometallics 2009, 28, 708–718
Iridium Olefin Complexes Bearing Dialkylamino/amido PNP Pincer
Ligands: Synthesis, Reactivity, and Solution Dynamics†
Anja Friedrich, Rajshekhar Ghosh, Roman Kolb, Eberhardt Herdtweck, and
Sven Schneider*
Department Chemie, Technische UniVersita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching b. Mu¨nchen, Germany
ReceiVed May 9, 2008
The reaction of [IrCl(COE)2]2 (1, COE ) cyclooctene) with pincer ligand HN(CH2CH2PiPr2)2 ((PNP)H)
and AgPF6 gives iridium(I) amino olefin complex [Ir(COE)(PNP)H]PF6 (3COE-PF6). Without anion
exchange, the stability of 3COE-Cl is highly solvent dependent. In benzene or THF a mixture of amido
complex [Ir(COE)(PNP)] (4COE), [IrHCl2(PNP)H] (5), and [IrHCl(C8H13)(PNP)H] (6) with a vinylic
cyclooctenyl ligand is obtained. A pathway is proposed that includes concurrent trapping of intramolecular
C-H versus intermolecular N-H activation products. 3L-PF6 (L ) C2H4, C3H6, CO) are prepared by
olefin substitution. Deprotonation with KOtBu gives the corresponding amido complexes [IrL(PNP)] (4L;
L ) COE, C2H4, CO). Reversible COE C-H activation is proposed to account for the fluxional behavior
of 3COE-PF6 in solution as compared with the structural rigidity of 4COE, which points toward strong
NfIr π-donation in the amido complexes.
increasing CPCPfIr π-donation due to a destabilizing filled-filled
CPCP-Ir repulsion. However, the influence of strongly π-donat-
ing auxiliary ligands, such as amides, on C-H bond activation
reactions is not well examined. Ozerov and co-workers have
recently studied halobenzene C-H and C-X oxidative addition
to the diarylamido pincer fragment (PNP′)Ir (PNP′ ) N(C6H3-4-
Me-2-PiPr2)2; Figure 1, B).6a Milstein and co-workers have
demonstrated, that the backbone methylene groups of pyridine-
based pincer complex [(PNP*)Ir(COE)]+ (PNP* ) C5H3N-
(CH2PtBu2)2; COE ) cyclooctene) can be reversibly deproto-
nated. The resulting isolable amido complex adds benzene across
the ligand backbone under mild conditions.6c
This example illustrates the utilization of a cooperating
ligand, which undergoes reversible chemical transformations
during the crucial bond activation steps.8 In catalysis, this
concept has been applied successfully to transfer hydrogenation
of polar double bonds EdCRR′ (E ) O, NR′′), where the
heterolytic activation of H2 by Ru amido complexes was coined
bifunctional catalysis.9 Gru¨tzmacher and co-workers recently
used iridium amido complexes for highly efficient transfer
hydrogenation with benzochinone as hydrogen acceptor.10 The
proposed catalytic cycle comprises stepwise N-H deprotona-
tion, one-electron oxidation, and H-transfer from the alcohol
substrate and was therefore compared with the galactose oxidase
catalyzed dehydrogenation of primary alcohols. Furthermore,
they were able to isolate the oxidation product of a rhodium(I)
amide, which was described as a metal-stabilized persistent
aminoyl radical cation.11
Introduction
In the past years, late transition metal complexes bearing
pincer ligands have been utilized in numerous stoichiometric
and catalytic reactions, such as Heck coupling,1 alkane dehy-
drogenation,2 N-H activation,3 or olefin hydroamination.4 5
,
With group 9 metals, particularly diphosphino pincers have
proven to be effective ligands supporting intermolecular C-H
activation reactions.2,6 Recently, Krogh-Jespersen et al. exam-
ined theoretically and experimentally the thermodynamics of
RH (R ) H, aryl, alkyl) oxidative addition to (p-R′-PCP)IrL
(p-R′-PCP ) 4-R′-C6H2-2,6-(CH2PR′′2)2; L ) no ligand, CO,
H2), rationalizing the results in terms of CPCP-Ir MO interac-
tions.7 Variation of the para aryl substituent R′ showed that
RH addition to the parent (p-R′-PCP)Ir fragment is favored by
† Dedicated to Prof. Dr. h.c. mult. W. A. Herrmann on the occasion of
his 60th birthday.
* Corresponding author. E-mail: sven.schneider@ch.tum.de.
(1) (a) Ohff, M.; Ohff, A.; van der Boom, M. E.; Milstein, D. J. Am.
Chem. Soc. 1997, 119, 11687.
(2) Goldman, A. S.; Renkema, K. B.; Czerw, M.; Krogh-Jespersen, K.
In ActiVation and Functionalization of C-H Bonds; Goldberg, K. I.,
Goldman, A. S., Eds.; ACS Symposium Series 885; American Chemical
Society: Washington, DC, 2004; pp 198-215.
(3) (a) Kanzelberger, M.; Zhang, X.; Emge, T. J.; Goldman, A. S.; Zhao,
J.; Incarvito, C.; Hartwig, J. F. J. Am. Chem. Soc. 2003, 125, 13644. (b)
Zhao, J.; Goldman, A. S.; Hartwig, J. F. Science 2005, 307, 1080. (c) Sykes,
A. C.; White, P.; Brookhart, M. Organometallics 2006, 25, 1664. (d) Fafard,
C. D.; Adhikari, D.; Foxman, B. M.; Mindiola, D. J.; Ozerov, O. V. J. Am.
Chem. Soc. 2007, 129, 10318.
(4) (a) Michael, F. E.; Cochran, B. M. J. Am. Chem. Soc. 2006, 128,
4246. (b) Cochran, B. M.; Michael, F. E. J. Am. Chem. Soc. 2008, 130,
2786.
(5) van der Boom, M. E.; Milstein, D. Chem. ReV. 2003, 103, 1759.
(6) For recent examples see: (a) Fan, L.; Parkin, S.; Ozerov, O. V. J. Am.
Chem. Soc. 2005, 127, 16772. (b) Feller, M.; Karton, A.; Leitus, G.; Martin,
J. M. L.; Milstein, D. J. Am. Chem. Soc. 2006, 128, 12400. (c) Ben-Ari,
E.; Leitus, G.; Shimon, L. J. W.; Milstein, D. J. Am. Chem. Soc. 2006,
128, 15390. (d) Kloek, S. M.; Heinekey, M.; Goldberg, K. I. Organome-
tallics 2006, 25, 3007. (e) Whited, M. T.; Grubbs, M. T. J. Am. Chem.
Soc. 2008, 130, 5874.
(8) Gru¨tzmacher, H. Angew. Chem. 2008, 120, 1838; Angew. Chem.,
Int. Ed. 2008, 47, 1814.
(9) Noyori, R.; Ohkuma, T. Angew. Chem. 2001, 113, 40; Angew. Chem.,
Int. Ed. 2001, 40, 40. (b) Clapham, S. E.; Hadzovic, A.; Morris, R. H.
Coord. Chem. ReV. 2004, 248, 2201. (c) Muniz, K. Angew. Chem. 2005,
117, 6780; Angew. Chem., Int. Ed. 2005, 44, 6622.
(10) Ko¨nigsmann, M.; Donati, N.; Stein, D.; Scho¨nberg, H.; Harmer,
J.; Sreekanth, A.; Gru¨tzmacher, H. Angew. Chem. 2007, 119, 3637; Angew.
Chem., Int. Ed. 2007, 46, 3567.
(11) Bu¨ttner, T.; Geier, J.; Frison, G.; Harmer, J.; Calle, C.; Schweiger,
A.; Scho¨nberg, H.; Gru¨tzmacher, H. Science 2005, 307, 235.
(7) Krogh-Jespersen, K.; Czerw, M.; Zhu, K.; Singh, B.; Kanzelberger,
M.; Darji, N.; Achord, P. D.; Renkema, K. B.; Goldman, A. S. J. Am. Chem.
Soc. 2002, 124, 10797.
10.1021/om800423u CCC: $40.75
2009 American Chemical Society
Publication on Web 01/14/2009

Iridium Olefin Complexes
Organometallics, Vol. 28, No. 3, 2009 709
Figure 1. Amido chelate ligands used with group 9 metals.
Given this recent interest in late metal amido complexes for
heterolytic and homolytic bond activation, the chemistry of
group 9 amides is not well developed. Based on the pioneering
work of Fryzuk,12 Caulton described the synthesis of disilyla-
mido complexes (Figure 1, A),13 and Ozerov and co-workers
utilized diarylamido pincers (Figure 1, B and C).6a,14 However,
complexes with more π-basic dialkylamido ligands are particu-
larly scarce, presumably due to the intrinsic tendency to undergo
ꢀ-H elimination.15 Some rare examples are the rhodium and
iridium complexes with biscycloheptatrienylamido- and biscy-
cloheptatrienyldiamido-based chelate ligands developed by the
Gru¨tzmacher group (Figure 1, D and E).11,16 Recently, Abdur-
Rashid, Gusev, and co-workers used bis(2-phophinoethyl)amido
and 2-phosphinoethyl-2-aminoethylamido ligands to stabilize
the iridium(III) amides [Ir(H)2(PNP)] (PNP ) N(CH2CH2PiPr2)2)
and [Ir(H)2(PNN)] (PNN ) iPr2PCH2CH2NCH2CH2NEt2) (F).17
Both complexes are highly active catalysts for the transfer
hydrogenation of ketones with 2-propanol and the postulated
Noyori-Morris-type mechanism was recently confirmed in a
theoretical examination.18 However, no PNP iridium(I) com-
plexes were reported.
In this article we describe the synthesis and reaction pathways
toward a new class of iridium(I) amino and amido complexes
bearing the pincer ligands HN(CH2CH2PiPr2)2 ((PNP)H) and
N(CH2CH2PiPr2)2 (PNP). Ligand N-H activation, vinylic olefin
C-H activation, solution dynamics, and amino/amido bonding
to the metal, which distinguish this ligand type from related
diphosphine pincers, will be discussed.
Results
1. Reaction of [IrCl(COE)2]2 (1) with (PNP)H: Solvent
Influence. Clarke et al. reported that the reaction of [Ir-
Cl(COE)2]2 (1, COE ) cyclooctene) with (PNP)H in 2-propanol
at 80 °C results in the formation of [Ir(H)2Cl(PNP)H] (2)
(Scheme 1).17a However, monitoring the reaction of 1 with
(PNP)H in 2-propanol at room temperature by 31P NMR
spectroscopy we observed quantitative formation of iridium(I)
amino olefin complex [Ir(COE)(PNP)H]Cl (3COE-Cl) by com-
parison with 3COE-PF6, which was synthesized and fully
characterized upon anion exchange (Vide infra). To avoid
hydride transfer from the solvent, the reaction was carried out
in benzene, resulting in a 1:1 mixture of iridium(I) amido
complex [Ir(COE)(PNP)] (4COE) and iridium(III) hydride
[IrHCl2(PNP)H] (5) (Scheme 1). Furthermore, C-H activation
product [IrHCl(C8H13)(PNP)H] (6) with a vinylic cyclooctenyl
ligand was observed as a minor product in around 15% yield.
5 is easily isolated by extraction of 4COE and 6 with pentane.
While 4COE was synthesized and fully characterized on another
route (Vide infra), 6 could not be isolated and was characterized
from this mixture by multinuclear NMR.
(12) (a) Fryzuk, M. D.; MacNeil, P. A. Organometallics 1983, 2, 355.
(b) Fryzuk, M. D.; MacNeil, P. A. Organometallics 1983, 2, 682. (c) Fryzuk,
M. D.; MacNeil, P. A.; Rettig, S. J. Organometallics 1985, 4, 1145. (d)
Fryzuk, M. D.; MacNeil, P. A.; Rettig, S. J. J. Am. Chem. Soc. 1985, 107,
6708. (e) Fryzuk, M. D.; MacNeil, P. A.; Rettig, S. J. Organometallics
1986, 5, 2469. (f) Fryzuk, M. D.; MacNeil, P. A.; McManus, N. T.
Organometallics 1987, 6, 882. (g) Fryzuk, M. D.; MacNeil, P. A.; Rettig,
S. J. J. Am. Chem. Soc. 1987, 109, 2803. (h) Fryzuk, M. D.; Bhangu, K.
J. Am. Chem. Soc. 1988, 110, 961. (i) Fryzuk, M. D.; Huang, L.; McManus,
N. T.; Paglia, P.; Rettig, S. J.; White, G. S. Organometallics 1992, 11,
1979. (j) Fryzuk, M. D.; Gao, X.; Joshi, K.; MacNeil, P. A.; Massey, R. L.
J. Am. Chem. Soc. 1993, 115, 10581. (k) Fryzuk, M. D.; Gao, X.; Rettig,
S. J. J. Am. Chem. Soc. 1995, 117, 3106.
(13) (a) Ingleson, M.; Fan, H.; Pink, M.; Tomaszewski, J.; Caulton, K. G.
J. Am. Chem. Soc. 2006, 128, 1804. (b) Ingleson, M. J.; Fullmer, B. C.;
Buschhorn, D. T.; Fan, H.; Pink, M.; Huffman, J. C.; Huffman, J. C.;
Caulton, K. G. Inorg. Chem. 2008, 47, 407. (c) Verat, A. Y.; Pink, M.;
Fan, H.; Tomaszewski, J.; Caulton, K. G. Organometallics 2008, 27, 166.
(14) (a) Ozerov, O. V.; Guo, C.; Papkov, V. A.; Foxman, B. M. J. Am.
Chem. Soc. 2004, 126, 4792. (b) Weng, W.; Guo, C.; Moura, C.; Yang, L.;
Fowman, B. M.; Ozerov, O. V. Organometallics 2005, 24, 3487. (c) Gatard,
S.; C¸ elenligil-C¸ etin, R.; Foxman, B. M.; Ozerov, O. V. J. Am. Chem. Soc.
2006, 128, 2808.
2. Reaction of [IrCl(COE)2]2 (1) with (PNP)H: Mecha-
nistic Studies. Monitoring the reaction of 1 with (PNP)H in C6D6
(15) Bryndza, H. E.; Tam, W. Chem. ReV. 1988, 88, 1163.
(16) (a) Maire, P.; Bu¨ttner, T.; Breher, F.; Le Floch, P.; Gru¨tzmacher,
H. Angew. Chem. 2005, 117, 6477; Angew. Chem., Int. Ed. 2005, 44, 6318.
(b) Maire, P.; Breher, F.; Gru¨tzmacher, H. Angew. Chem. 2005, 117, 6483;
Angew. Chem., Int. Ed. 2005, 44, 6325. (c) Maire, P.; Breher, F.; Scho¨nberg,
H.; Gru¨tzmacher, H. Organometallics 2005, 24, 3207. (d) Maire, P.;
Ko¨nigsmann, M.; Sreekanth, A.; Harmer, J.; Schweiger, A.; Gru¨tzmacher,
H. J. Am. Chem. Soc. 2006, 128, 6578.
1
by 31P and H NMR reveals that multiple intermediates are
formed over the course of 2 days at room temperature (Figure
2). As in 2-propanol, 3COE-Cl represents the first major
intermediate. The large downfield 1H chemical shift of the broad
(17) (a) Clarke, Z. E.; Maragh, P. T.; Dasgupta, T. P.; Gusev, D. G.;
Lough, A. J.; Abdur-Rashid, K. Organometallics 2006, 25, 4113. (b)
Choualeb, A.; Lough, A. J.; Gusev, D. G. Organometallics 2007, 26, 5224.
(18) Bi, S.; Xie, Q.; Zhao, X.; Zhao, Y.; Kong, X. J. Organomet. Chem.
2008, 693, 633.

710 Organometallics, Vol. 28, No. 3, 2009
Friedrich et al.
Scheme 2. Proposed Pathway for the Formation of 4COE, 5,
and 6 from 3COE-Cl (iridium species in square brackets are
not fully characterized)
Figure 2. 31P NMR spectra of the reaction of 1 with (PNP)H in
C6D6.
Scheme 1. Reaction of [IrCl(COE)2]2 (1) with HN(CH2CH2PiPr2)2
(PNP)H in 2-Propanol17a and Benzene, Respectively
These results show that 3COE-Cl is initially formed in the
reaction of 1 with (PNP)H, but is not stable in nonprotic solvents,
such as benzene or THF, slowly reacting toward 4COE, 5, and
6. Accordingly, 3COE-PF6 reacts with chloride sources such as
[PPh4]Cl or [NnBu3(CH2Ph)]Cl in C6H6 or THF to give an
equimolar amount of 4COE and 5 in combination with cycloocte-
nyl complex 6, the latter in a slightly higher yield (approximately
20%). Based on the intermediates found for this reaction a
pathway is proposed (Scheme 2).
To check for the viability of the model in Scheme 2, the
kinetics of the reaction of 3COE-PF6 with chloride were studied
by 31P NMR spectroscopy. Kinetic experiments were conducted
at 295 and 300 K in THF due to a lack of a suitable water-free
chloride source that was soluble enough in benzene at the initial
concentration [3COE-PF6]0 ) 57.7 mM, and even in THF the
equimolar amount of [NnBu3(CH2Ph)]Cl was not fully soluble.20
However, plots of ln [3COE-PF6] versus time (Figure 3) were
linear over three half-lifes with kobs at 3.2 × 10-3 min-1 (298
K) and 4.5 × 10-3 min-1 (300 K), indicating that preequilibria
signal assigned to the N-H proton in 3COE-Cl (9.57 ppm/C6D6)
relative to 3COE-PF6 (4.72 ppm/C6D6) indicates hydrogen
bonding,presumablytothechloridecounteranion.[IrHCl(COE)(P-
NP)H]Cl (7-Cl) is observed as an intermediate in an early stage
of the reaction sequence, decaying quickly. Two further
intermediates, 8 and 9, that could not be prepared independently
are observed by NMR.19 However, the 1H NMR spectrum of 8
strongly resembles complex 6, indicating a vinylic cyclooctenyl
ligand. On the other hand, between 3.5 and 8 ppm 9 features
only a signal assignable to an N-H proton. The 1H NMR signals
for the hydride ligands of 8 (-23.39 ppm) and 9 (-23.66 ppm)
are very close to each other and slightly downfield from 5
(-24.73 ppm) and 6 (-24.40 ppm). Therefore, we tentatively
assign 8 and 9 to structures that are isomers of the final products
6 and 5, respectively, with the hydride ligands in 8 and 9 in
trans position to the (PNP)H amine donor and not trans to a
chloride ligand as in 5 and 6.
such as dissolution of [NnBu3(CH2Ph)]Cl or formation of a 3COE
-
Cl precomplex are fast versus the decay of 3COE-Cl. Addition
of COE did not affect kobs. The concentrations of 3COE-Cl, 4COE
,
5, 6, 7-Cl, 8, and 9 were fitted to the model outlined in Scheme
2 featuring a reasonable correlation of the simulation with
experimental results (Figure 3 and Supporting Information).
3. Syntheses of Stable Iridium PNP Complexes. The
reaction of 1 with (PNP)H in the presence of AgPF6 or NaBPh4
gives [Ir(COE)(PNP)H]X (3COE-X; X ) PF6, BPh4), which are
stable in organic solvents (Scheme 3). Likewise, olefin com-
plexes [Ir(L)(PNP)H]X (L ) C2H4 (3C2H4-X), C3H6 (3C3H6-X);
X ) PF6, BPh4) can be prepared upon in situ olefin exchange
in high yield. Facile substitution of ethylene versus CO gives
(19) Selected NMR data of 8 (C6D6, rt, [ppm]): 1H NMR (399.78 MHz)
δ-23.39 (t, 2JHP ) 14.4 Hz, 1H, Ir-H), 2.94 (t, 3JHH ) 5.5 Hz, 2H, IrCCH2),
3.83 (br, 1H, NH), 6.27 (t, 3JHH ) 8.6 Hz, 1H, dCH). 31P{1H} NMR (161.8
MHz): δ 25.8 (s, PiPr2). Selected NMR data of 9 (C6D6, rt, [ppm]): 1H
NMR (399.78 MHz): δ-23.66 (t, 2JHP ) 13.6 Hz, 1H, Ir-H), 6.36 (br, 1H,
NH). 31P{1H} NMR (161.8 MHz): δ 27.7 (s, PiPr2).
(20) The solubility of [NnBu3CH2Ph]Cl in d8-THF at 295 K was derived
by NMR spectroscopy (10 mM).

Iridium Olefin Complexes
Organometallics, Vol. 28, No. 3, 2009 711
Figure 3. (Top) Decay of 3COE-Cl in THF at 298 and 300 K. (Bottom) Concentration vs time plot of the reaction of 3COE-PF6 with [NnBu3(CH2Ph)]Cl
in THF at 300 K with experimental (crosses) and fitted (lines) concentrations based on the proposed pathway in Scheme 2.
carbonyl complex [Ir(CO)(PNP)H]X (3CO-X; X ) PF6, BPh4).
Oxidative addition of HCl to 3COE-PF6 affords iridium(III)
complex [IrHCl(COE)(PNP)H]PF6 (7-PF6) in moderate yield.
The six-coordinate iridium(III) amino complexes 5, 6, and
7-PF6 feature similar solution NMR spectra for the (PNP)H
chelate as 2.17a The singlet in the 31P NMR spectrum, four H
1
Clean N-deprotonation of 3L-X (L ) COE, C2H4, CO) is
obtained by the reaction with KOtBu in THF, giving rise to
[IrL(PNP)] (4L) (Scheme 4). The highly air-sensitive amido
complexes 4L are very soluble in nonpolar organic solvents such
as benzene and pentane.
4. Spectroscopic Characterization. The iridium(I) amino
complexes 3L-PF6 (L ) COE, C2H4, C3H6, CO) exhibit N-H
stretching frequencies in the IR spectra between 3223 and 3210
cm-1, which are much closer to that of the free ligand (3285
cm-1) compared with the octahedral iridium(III) complexes
[IrH3(PNP)H] (3140 cm-1),17a 2 (3171 cm-1),17a and 5 (3130
cm-1). While N-H · · · H-Ir hydrogen bonding was proposed
for [IrH3(PNP)H],17a N-H · · · Cl-Ir hydrogen bonding could
account for the low N-H stretching vibration in 2 and 5. The
CO stretching vibration of 3CO-PF6 was observed at 1976 cm-1.
Deprotonation of the pincer ligand results in a strong batho-
chromic shift of this band (4CO: 1908 cm-1), indicating a large
increase of electron density at the metal center.
NMR peaks in the methyl region (doublets of virtual triplets),
and two 1H NMR signals assignable to methyne groups indicate
a meridional arrangement of the (PNP)H pincer ligand with two
sets of chemically inequivalent isopropyl substituents, each
bearing diastereotopic methyl groups, respectively. Accordingly,
four signals can be assigned to the ethylene backbone protons,
which appear as complex multiplets owing to the complex
ABCDXX′ spin system. The hydride chemical shifts of 5
(-24.73 ppm) and 6 (-24.40 ppm) suggest a trans arrangement
to a chloride ligand, and that of 7-PF6 (-17.83 ppm) indicates
a location trans to the olefin, as a result of HCl cis oxidative
addition to 3COE-PF6.21 The NMR signals for the cyclooctenyl
ligand of 6 are in agreement with vinylic C-H activation
featuring the vinylic proton at 6.06 ppm and the olefinic carbon
atoms at 124.0 and 134.7 ppm, respectively.
(21) (a) Blake, D. M.; Kubota, M. Inorg. Chem. 1970, 9, 989. (b)
Johnson, C. E.; Eisenberg, R. J. Am. Chem. Soc. 1985, 107, 6531.

712 Organometallics, Vol. 28, No. 3, 2009
Friedrich et al.
Scheme 3. Syntheses of Iridium PNP Amino Complexes
(MX ) AgPF6, NaBPh4; L ) C2H4, C3H6)
Figure 4. Methyl region of the 1H-ROESY NMR spectrum of 3C3H6
PF6.
-
Scheme 4. Synthesis of Iridium PNP Amido Complexes (X
) PF6, BPh4; L ) COE, C2H4, CO)
Figure 5. (Top) 31P NMR spectrum of 3C3H6-PF6 in d6-acetone at
183 K. (Bottom) 31P NMR spectrum of 3COE-PF6 in d8-THF at 173
K.
Solution NMR spectra of iridium(I) amino complexes 3C2H4
-
nitrogen inversion was not observed for 3COE-PF6, the 15N
PF6, 3COE-PF6, and 3CO-PF6 resemble those of iridium(III)
complexes 5, 6, and 7-PF6 with respect to the number and
coupling pattern of the (PNP)H ligand signals, suggesting Cs
symmetry on the NMR time scale. In contrast to this, propylene
complex 3C3H6-PF6 features two sharp doublets in the 31P NMR
spectrum with a typical trans 2JPP coupling constant (307 Hz).
1
chemical shift (δ ) -318.8 ppm, H-15N HSQC) in d8-THF
shows a small coordination shift relative to the free ligand (δ
23
) -331.2 ppm, H-15N HMBC), indicating weak nitrogen
1
coordination to the metal.24 Furthermore, the 3COE-PF6 JH-N
1
coupling constant (-72 Hz) suggests the absence of strong
M · · · H-N interactions.25,26
1
Furthermore, H and 13C signals for the (PNP)H ligand are in
To further elucidate the fluxional behavior of 3COE-PF6, the
amino olefin complexes were studied by VT NMR. Cooling of
a 3C2H4-PF6 solution in d6-acetone to -90 °C does not result in
broadening of the 31P and 1H NMR peaks. However, propylene
complex 3C3H6-PF6 exhibits successive broadening of the two
31P NMR doublets with coalescence of the downfield signal at
around -80 °C (Figure 5, Supporting Information). Low-
temperature 31P NMR of 3COE-PF6 in d6-acetone reveals that
the sharp room-temperature signal splits at around -65 °C into
two broad peaks, as would be expected for freezing olefin
rotation (Supporting Information). However, cooling below -90
°C in d8-THF results in further splitting of the 31P NMR signals,
resulting in a complex pattern of broad peaks at -100 °C,
similar to 3C3H6-PF6 (Figure 5). Between +25 and -100 °C,
no peaks assignable to hydrides were found by 1H NMR
agreement with the absence of the virtual plane, indicating
hindered propylene rotation for 3C3H6-PF6. This interpretation
is further backed by a 1H-ROESY spectrum, where the doublet
signal for the propylene methyl group (1.51 ppm) exhibits strong
cross-peaks only with two of the eight chemically inequivalent
pincer methyl groups (Figure 4).
The mirror symmetry found for 3COE-PF6 at room temperature
indicates fluxional behavior at room temperature on the NMR
time scale. Addition of 0.5 equiv of COE to a solution of 3COE
-
PF6 in d8-THF at room temperature does not result in broadening
1
of the free (5.63 ppm) or bound (3.54 ppm) olefin H NMR
signals, respectively. Furthermore, a 1H-EXSY NMR spectrum
at room temperature does not indicate slow olefin exchange
(Supporting Information).22 As in 3C2H4-PF6, four sharp peaks
for the 3COE-PF6 backbone ethylene bridges suggest high barriers
for inversion of the pyramidal amine nitrogen atom. However,
the effect of amine inversion can be demonstrated by fast N-H
proton exchange: Addition of 1 equiv of p-methylphenol to the
corresponding amido complex 4COE (Vide infra) results in C2V
symmetry on the NMR time scale owing to fast O-H/N-H
proton exchange. Cooling to -60 °C slows the equilibrium and
the signals for 3COE-OC7H7 and 4COE are observed. While
(23) No signal was found in the 1H-15N HSQC NMR spectrum of
(PNP)H, presumably due to rapid N-H exchange on the NMR time scale.
(24) Mason, J. Chem. ReV. 1981, 81, 205.
(25) The 1JHN coupling constant of HNMe2 was reported to be-67 Hz:
Alei M., Jr.; Florin, A. E.; Litchman, W. M.; O’Brien, J. F. J. Phys. Chem.
1971, 75, 932.
(26) (a) Pregosin, P. S.; Ru¨egger, H.; Wombacher, F.; van Koten, G.;
Grove, D. M.; Wehman-Ooyevaar, I. C. M. Magn. Reson. Chem. 1992, 30,
548. (b) Lee, J. C., Jr.; Mu¨ller, B.; Pregosin, P.; Yap, G. P. A.; Rheingold,
A. L.; Crabtree, R. H. Inorg. Chem. 1995, 34, 6295. (c) Yao, W.; Eisenstein,
O.; Crabtree, R. H. Inorg. Chim. Acta 1997, 254, 105.
(22) Perrin, C. L.; Dwyer, T. J. Chem. ReV. 1990, 90, 935.

Iridium Olefin Complexes
Organometallics, Vol. 28, No. 3, 2009 713
Figure 6. DIAMOND plot of 5 in the crystal (one of the two
independent molecules) with thermal ellipsoids drawn at the 50%
probability level. Hydrogen atoms other than H1 and H20 are
omitted for clarity.
Table 1. Selected Bond Lengths and Angles of 217a and 5
(corresponding values for the second crystallographically
independent molecule in parentheses) in the Crystal
5
217a
Bond Lengths (Å)
Figure 7. DIAMOND plot of the 3C2H4-PF6 (above) and 3CO-PF6
(below) cations in the crystal, respectively, with thermal ellipsoids
drawn at the 50% probability level. Calculated hydrogen atoms are
omitted for clarity.
a
a
Ir1-H20
Ir1-Cl1
Ir1-Cl2
Ir1-N1
Ir1-P1
1.41(7) (1.30(7))
2.386(1) (2.385(1))
2.524(2) (2.521(1))
2.091(4) (2.082(4))
2.296(2) (2.291(2))
2.293(2) (2.298(2))
2.70 (2.63)
Ir1-H1Ir
Ir1-H2Ir
Ir1-Cl1
Ir1-N1
Ir1-P1
Ir1-P2
1.36(5)
1.63(5)
2.506(1)
2.187(3)
2.276(1)
2.276(1)
2.58(7)
Table 2. Selected Bond Lengths and Angles of 3C2H4-PF6, 3CO-PF6,
4C2H4, and 4CO (corresponding values for the second
crystallographically independent molecule in parentheses) in the
Crystal
Ir1-P2
H1 · · · Cl2
H1N · · · Cl1a
Bond Angles (deg)
Cl2-Ir1-N1
Cl1-Ir1-Cl2
N1-Ir1-Cl1
P1-Ir1-P2
85.6(1) (84.1(1))
Cl1-Ir-N1
86.8(1)
91(2)
178(2)
167.19(4)
3C2H4-PF6 3CO-PF6
4C2H4
4CO
a
92.71(5) (94.40(5))
176.9(1) (178.5(1))
165.81(5) (167.22(5))
Cl1-Ir-H2Ir
N1-Ir1-H2Ir
P2-Ir1-P2
a
Bond Lengths (Å)
2.131(4) 2.121(6) 1.99(2)
2.304(1) 2.297(2) 2.277(5)
2.303(1) 2.300(2) 2.264(5)
2.145(6) 1.804(7) 2.10(2)
Ir1-N1
Ir1-P1
2.035(4) (2.028(4))
2.284(1) (2.287(1))
2.281(1) (2.293(1))
1.839(7) (1.818(6))
a H1Ir: hydride trans to Cl1; H2Ir: hydride trans to N1; H1N: N-H.
spectroscopy, but all 1H NMR peaks exhibit very strong
Ir1-P2
Ir1-C20
Ir1-C21
C20-C21
broadening with half-widths at -100 °C of up to 40 Hz.
2.144(6)
1.355(9)
2.17(2)
1.42(3)
Furthermore, the sharp 31P and 19F NMR signals of the 3COE
PF6 counteranion remain unchanged down to -100 °C.
-
Bond Angles (deg)
NMR spectra of ethylene amido complexes 4C2H4 and 4CO
are in agreement with C2V symmetry, implying planarization of
the dialkylamido backbone on the NMR time scale. On the other
hand, NMR spectra of 4COE indicate the loss of the mirror plane
defined by N, Ir, and the olefinic carbon atoms, resulting in
two sharp 31P NMR doublets with a 2JPP trans coupling constant
of 373 Hz. No peak broadening of these signals was observed
upon heating to 100 °C in d8-toluene.
P1-Ir1-P2
166.63(4) 166.75(6) 165.49(18) 165.89(5) (164.06(5))
N1-Ir1-C20 159.5(2) 179.8(3) 158.8(8)
177.0(2) (177.9(3))
N1-Ir1-C21 163.7(2)
Ir1-C20-O1
162.4(7)
178.6(7)
179.3(4) (178.4(4))
Ir1-N1-C2 113.4(3) 113.7(4) 122.4(12) 121.0(3) (122.6(3))
Ir1-N1-C4 114.6(3) 114.7(4) 124.8(13) 122.8(4) (122.5(4))
C2-N1-C4 111.3(4) 109.9(6) 109.5(15) 112.4(4) (110.0(4))
molecular structure in the solid state (Figure 7, Table 2). The
cations feature distorted square-planar coordinated iridium
centers with (PNP)H bite angles of 166.63(4)° (3C2H4-PF6) and
166.75(6)° (3CO-PF6), respectively. The Ir1-H1 distances
(3C2H4-PF6: 2.47(6) Å; 3CO-PF6: 2.54 Å) and Ir1-N-H1 angles
(3C2H4-PF6: 104(4)°; 3CO-PF6: 106°) are not indicative of an
intramolecular M · · · H-N interaction. The large Ir1-N1 dis-
tances (3C2H4-PF6: 2.131(4) Å; 3CO-PF6: 2.121(6) Å) are in
agreement with strong ethylene and CO trans-influences and
weak coordinative NfM bonding. The olefinic CdC bond
length in 3C2H4-PF6 (C20-C21: 1.355(9) Å) is very close to
the equilibrium CdC distance experimentally found for free
ethylene (1.334 Å).27
5. X-ray Crystal Structure Determinations. 3C2H4-PF6,
3CO-PF6, 4C2H4, 4CO, and 5 were characterized by single-crystal
X-ray diffraction. Repeated crystallization attempts for 3COE
-
PF6 and 3COE-BPh4 resulted in heavily disordered crystals.
However, the constitution and conformation of the (PNP)H
backbone in the 3COE-BPh4 cation were confirmed to be
analogous to 3C2H4-PF6 and 3CO-PF6 (Supporting Information).
The molecular structure of complex 5 (Figure 6, Table 1) in
the solid state strongly resembles that of dihydrido chloro
compound 2, which was reported by Clarke et al.17a As a major
difference, the Ir-N1 bond is considerably shorter in 5 (∆DIr-N
) 0.1 Å), owing to the weaker trans-influence of chloride
compared with a hydride ligand. The metal center in 5 is located
in a slightly distorted octahedral coordination geometry with a
(PNP)H chelate bite angle of 165.81(5)°. Further distortion arises
from bending of Cl2 toward amine proton H1 (Cl2-Ir1-N1:
85.6(1)°) indicative of H1 · · · Cl2 hydrogen bonding (H1 · · · Cl2:
2.70 Å), which is in agreement with IR spectroscopic results.
For iridium(I) amino complexes 3L-PF6 (L ) C2H4, CO) the
structural assignments in solution are in agreement with the
The molecular structures of amido complexes 4C2H4 and 4CO
in the solid state (Figure 8, Table 2) confirm planarization of
the amido nitrogen atom (sum of the bond angles around N1:
357° (4C2H4), 356° (4CO)). Furthermore, covalent amido bonding
results in significantly shorter Ir1-N1 bonds (4C2H4: 1.99(2) Å;
4
CO: 2.035(4) Å) as compared with the corresponding amino
(27) Duncan, J. L. Mol. Phys. 1974, 28, 1177.

714 Organometallics, Vol. 28, No. 3, 2009
Friedrich et al.
first-order rate was observed for 3COE-Cl. The rate law for 3COE
Cl, according to the model, is given by
-
r(3COE-Cl) ) -k1[3COE-Cl]-k2[3COE-Cl]-k3[3COE-Cl] +
k-3[HCl][4COE]-k4[HCl][3COE-Cl] (1)
This rate becomes pseudo first order assuming steady-state
conditions for cHCl, which is reasonable, as both oxidative
addition of HCl to iridium(I) (k4) and protonation of amido
complex 4COE (k-3) should be fast with respect to N-H
deprotonation (k3) as was found in the simulation, as well.
Accordingly, calculated cHCl is very small, remaining below 7
× 10-4 M throughout the course of the reaction. Hence, kobs
for the decay of 3COE-Cl (4.5 × 10-3 min-1 at 300 K) marks
an upper limit for the rates of the formation of C-H activation
products 6 and 8, with calculated values for k1 and k2 of 1.4 ×
10-3 and 1.0 × 10-3 min-1, respectively. It is unlikely for C-H
activation and trapping of the vinyl hydride by Cl- to proceed
concerted, and intermediates such as a five-coordinate hydrido
vinyl species are most reasonable. However, the absence of COE
exchange for 3COE-PF6 suggests that three-coordinate [Ir(P-
NP)H]+ is not involved.
Iridium vinyl hydrides have been reported for several
stoichiometric and catalytic alkene functionalization reactions,
such as alkane dehydrogenation,31 olefin dimerization,32 or
catalytic vinylic H/D exchange.33 As usually the η2-olefin
complexes are the thermodynamically favored isomers, they
cannot be direct intermediates for thermal vinylic C-H activa-
tion in these cases, and separate transition states must account
for π-complexation and C-H oxidative addition during the
interaction of the metal with an incoming olefin.34 Stable vinyl
hydrides were typically obtained with sterically encumbered
auxiliary ligands and alkenes or by trapping of five-coordinate
vinyl hydrides with a sixth ligand.2,31,35 For cyclooctene, iridium
complexes resulting from both vinylic35c,36 and allylic37 C-H
activation are known. In a system related to ours, Milstein
reported that the reaction of 1 with the pyridine-based pincer
ligand (PNP*) gave hydrido vinyl complex [IrHCl(C8H13)-
(PNP*)].35c
Figure 8. DIAMOND plot of 4C2H4 (above) and 4CO (below; one
of the two independent molecules) in the crystal, respectively, with
thermal ellipsoids drawn at the 50% probability level. Hydrogen
atoms are omitted for clarity.
complexes. Most other bond lengths and angles around the metal
centers in 4C2H4 and 4CO are close to those found in the
respective amino complexes, indicating structural flexibility of
the ethylene-bridged pincer ligand. The CdC distance in 4C2H4
is considerably longer compared with 3C2H4-PF6 (∆DCdC ) 0.07
Å), pointing toward strong Mfolefin back-bonding in the amido
complex. Accordingly, the angle φ of the plane defined by the
metal and the ethylene carbon atoms (Ir1, C20, and C21) with
the square-planar coordination polyhedron (Ir1, P1, and N1) is
closer to ideal 90° (3C2H4-PF6: 72.3(4)°; 4C2H4: 82.7(14)°).
Unfortunately, the quality of the 4C2H4 crystal structure does
not permit localization of the olefinic protons on the electron
density map to compare pyramidalization of C20/C21 as a
diagnostic tool for their hybridization.
(30) (a) Gupta, M.; Hagen, C.; Flesher, R. J.; Kaska, W. C.; Jensen,
C. M. Chem. Commun. 1996, 2083. (b) Goldman, A. S.; Ghosh, R. In
Handbook of C-H Transformations - Applications in Organic Synthesis;
Dyker, G., Ed.; Wiley-VCH: New York, 2005; pp 616-621.
Discussion
1. Reactivity and Fluxional Behavior of 3COE-PF6. Scheme
2 shows our proposed model for the formation of 4COE, 5, and
6 from 3COE-Cl in nonprotic solvents. The reaction scheme can
be broken down in two principle pathways: (1) C-H activation
of the COE ligand and trapping by nucleophilic attack of the
chloride at the iridium center; (2) chloride base assisted N-H
activation and intermolecular HCl oxidative addition. This model
explains the observed solvent dependence, as efficient solvation
of the chloride ion via hydrogen bonding with protic solvents
both increases the barrier to nucleophilic attack and reduces its
basicity.28 It should be pointed out that we have no indication
for intramolecular N-H activation, contrasting with other PEP
(E ) N, C) pincer ligands, such as HN(RC6H3PR2)2,
CH2(C2H4PR2)2, or C6H4(m-CH2PR2)2, where E-H oxidative
addition is typically observed with IrI precursors.14a,29,30 Given
the complexity of the proposed model, it is interesting that a
(31) Kanzelberger, M.; Singh, B.; Czerw, M.; Krogh-Jespersen, K.;
Goldman, A. S. J. Am. Chem. Soc. 2000, 122, 11017.
(32) Alvarado, Y.; Boutry, O.; Gutierrez, E.; Monge, A.; Nicasio, M. C.;
Poveda, M. L.; Perez, P. J.; Ruiz, C.; Bianchini, C.; Carmona, E. Chem.-
Eur. J. 1997, 3, 860.
(33) Torres, F.; Sola, E.; Martin, M.; Lopez, J. A.; Lahoz, F. J.; Oro,
L. A. J. Am. Chem. Soc. 1999, 121, 10632.
(34) (a) Stoutland, P. O.; Bergman, R. G. J. Am. Chem. Soc. 1985, 107,
4581. (b) Stoutland, P. O.; Bergman, R. G. J. Am. Chem. Soc. 1988, 110,
5732. (c) Bell, T. W.; addleton, D. M.; McCamley, A.; Partridge, M. G.;
Perutz, R. N.; Willner, H. J. Am. Chem. Soc. 1990, 112, 9212. (d) Bianchini,
C.; Barbaro, P.; Meli, A.; Peruzzini, M.; Vacca, A.; Vizza, F. Organome-
tallics 1993, 12, 2505. (e) Bell, T. W.; Brough, S.-A.; Partridge, M. G.;
Perutz, R. N.; Rooney, A. D. Organometallics 1993, 12, 2933. (f) Smith,
K. M.; Poli, R.; Harvey, J. N. Chem.-Eur. J. 2001, 7, 1679.
(35) Examples: (a) Werner, H.; Dirnberger, T.; Schulz, M. Angew. Chem.
1988, 100, 993; Angew. Chem., Int. Ed. Engl. 1988, 27, 948. (b) Ghosh,
C. K.; Hoyano, J. K.; Krentz, R.; Graham, W. A. G. J. Am. Chem. Soc.
1989, 111, 5480. (c) Hermann, D.; Gandelman, M.; Rozenberg, H.; Shimon,
L. J. W.; Milstein, D. Organometallics 2002, 21, 812.
(36) (a) Fernandez, M. J.; Rodriguez, M. J.; Oro, L. A.; Lahoz, F. J.
J. Chem. Soc., Dalton Trans. 1989, 2073. (b) Iimura, M.; Evans, D. R.;
Flood, T. C. Organometallics 2003, 22, 5370.
(37) (a) Tanke, R. S.; Crabtree, R. H. Inorg. Chem. 1989, 28, 3444. (b)
Peters, J. C.; Feldman, J. D.; Tilley, T. D. J. Am. Chem. Soc. 1999, 121,
9871. (c) Budzelaar, P. H. M.; Moonen, N. N. P.; de Gelder, R.; Smits,
J. M. M. Eur. J. Inorg. Chem. 2000, 753. (d) Ortmann, D. A.; Gevert, O.;
Laubender, M.; Werner, H. Organometallics 2001, 20, 1776. (e) Turculet,
L.; Feldman, J. D.; Tilley, T. D. Organometallics 2004, 23, 2488.
(28) (a) Regan, C. K.; Craig, S. L.; Brauman, J. I. Science 2002, 296,
2245. (b) Vayner, G.; Houk, K. N.; Jorgensen, W. L.; Brauman, J. I. J. Am.
Chem. Soc. 2004, 126, 9054. (c) Bordwell, F. G. Acc. Chem. Res. 1988,
21, 456.
(29) Crocker, C.; Empsall, H. D.; Errington, R. J.; Hyde, E. M.;
McDonald, W. S.; Markham, R.; Norton, M. C.; Shaw, B. L.; Weeks, B.
J. Chem. Soc., Dalton Trans. 1982, 1217.

Iridium Olefin Complexes
Organometallics, Vol. 28, No. 3, 2009 715
Table 3. CO Stretching Vibrations of trans-Diphosphine Carbonyl
Scheme 5. Proposed Switchable C-H Activation for
3COE-PF6 and 4COE
Iridium(I) Complexes
complex
νCO [cm-1
]
ref
[Ir(CO){HN(CH2CH2PiPr2)2}]PF6
[Ir(CO){C5H3N(CH2PtBu2)2]PF6
[Ir(CO){C6H3(OPtBu2)2}]
[Ir(CO)Cl(PiPr3)2]
1976
1962
1949
1935
1930
1930
1920
1908
this work
40
41
42
12e
43
44
this work
accessible, the increase in Ir-olefin binding strength prevents
the olefin complexes from rearrangement. The conjugate acid/
base pair 3COE-PF6 and 4COE therefore represents an unprec-
edented example of metal complexes with switchable vinylic
olefin C-H activation by de/protonation of the pincer auxiliary
ligand (Scheme 5).
[Ir(CO){N(SiMe2CH2PiPr2)2}]
[Ir(CO){N(C6MeH3PiPr2)2}]
[Ir(CO){C6H3(CH2PiPr2)2}]
[Ir(CO){N(CH2CH2PiPr2)2}]
We hoped for the fluxional behavior of 3COE-PF6 to provide
further information. NMR spectroscopic characterization sug-
gests rigid olefin binding for 3C3H6-PF6. Furthermore, the
molecular structure of 3C2H4-PF6 in the crystal features the olefin
Conclusions
i
In conclusion, we described the synthesis of a new class of
iridium(I) amino and amido complexes bearing the PNP pincer
ligand N(CH2CH2PiPr2)2. The instability of 3COE-Cl in nonprotic
solvents is attributed to both anion-assisted N-H deprotonation
and trapping of vinylic C-H activation products. No indications
for M · · · H-N interactions or intramolecular N-H oxidative
addition were found. Our results suggest that 3COE-PF6 is a rare
example of an olefin complex that exhibits a fast equilibrium
with a vinyl hydride isomer at room temperature on the NMR
time scale, accounting at least in part for the observed
fluxionality. Unfortunately, other dynamic processes on the
pincer ligand seem to be coupled, preventing the extraction of
quantitative data. On the other hand, the structural rigidity of
the corresponding amido complex 4COE is attributed to strong
olefin binding, which is reinforced by the N-Ir-olefin 3c-4e
π-interaction and illustrates the electron-rich character of the
Ir(PNP) fragment. Using the olefin ligand as a probe for Ir-N
bonding, this interpretation renders 3COE-PF6/4COE an interesting
system that features switchable C-H activation upon de/
protonation of the pincer ligand.
embedded in the cavity formed by the Pr substituents with
several close contacts to the pincer ligand. Therefore, for
sterically more stressed 3COE-PF6 rapid olefin rotation seems
unlikely as the origin of the fluxional behavior.38 Olefin
exchange, anion coordination, and amine inversion can further
be excluded. Unfortunately, low-temperature NMR of 3COE
-
PF6 remains inconclusive. However, a similarly complex pattern
in the 31P NMR and very broad 1H NMR peaks were found for
the (PNP)H ligand signals of 3C3H6-PF6, which is not fluxional
at room temperature with respect to the olefin moiety. On the
basis of the observed reactivity of 3COE-Cl, we suggest that the
fluxionality of 3COE-PF6 can be explained with rapid, reversible
vinylic C-H activation of the COE ligand. The lack of
observable hydride signals in the 1H NMR at any temperatures
indicates that the equilibrium must be shifted toward the olefin
complex. However, further dynamic processes, e.g., isopropyl
rotation or hemilability of the nitrogen donor, seem to be
freezing in the same temperature range, so that quantitative
kinetic data could not be extracted.
2. Comparison of Amino and Amido Complexes. In
contrast to 3COE-PF6, amido complex 4COE features rigid olefin
binding up to 100 °C on the NMR time scale. Since sterics
should be comparable in these complexes, electronic factors
must mainly account for the different behavior. The CO
stretching vibrations of 3COE-PF6 and 4CO are at the far ends of
a range of iridium(I) diphosphine carbonyl complexes (Table
3), suggesting a substantial increase in electron density at the
metal center upon deprotonation of the (PNP)H nitrogen. Further
indication is provided by the large increase in olefinic CdC
bond distance upon N-deprotonation of the ethylene amino
complex (3C2H4-PF6/4C2H4: ∆DCdC ) 0.07 Å). Almost identical
olefinic 13C upfield shifts (3C2H4-PF6/4C2H4: ∆δ13C ) 22.1 ppm;
3COE-PF6/4COE: ∆δ13C ) 20.8 ppm) suggest comparable effects
on COE binding.39
Experimental Section
Materials and Synthetic Methods. All experiments were carried
out under an atmosphere of argon using Schlenk and glovebox
techniques. The solvents were dried over Na/benzophenone/
tetraglyme (benzene) or Na/benzophenone (THF), distilled under
argon, and deoxygenated prior to use. Deuterated solvents were
dried by distillation from Na/K alloy (C6D6 and d8-THF), stirring
over 4 Å molecular sieves, and distillation from B2O3 (d6-acetone)
or distillation from CaH2 (CD2Cl2), respectively, and deoxygenated
by three freeze-pump-thaw cycles. KOtBu and cyclooctene were
purchased from VWR and sublimed (KOtBu)/distilled (cyclooctene)
prior to use. Ethene 2.7 (Messer Griesheim), propylene 2.8 (Gerling,
Holz + Co.), and iridiumtrichloride hydrate (ABCR) were used as
45
purchased. HN(CH2CH2PiPr2)2 and [IrCl(COE)2]2 (1)46 were
Therefore, we attribute the structural rigidity of 4COE, as
compared with 3COE-PF6, to strong IrfCOE back-bonding. The
electron density at the metal will be strongly enhanced by
repulsive π-interaction of the amido lone pair with a filled metal
d-orbital, which is involved in IrfLtrans (L ) olefin, CO) back-
bonding, as well. Although the higher electron density in the
amido complexes should make IrIII thermodynamically more
prepared as reported in the literature.
Analytical Methods. Elemental analyses were obtained from
the Microanalytical Laboratory of Technische Universita¨t Mu¨nchen.
The IR spectra were recorded on a Jasco FT/IR-460 PLUS
(40) Kloeck, S. M.; Heinekey, M.; Goldberg, K. I. Organometallics 2006,
25, 3007.
(41) Go¨ttker-Schnetmann, I.; White, P. S.; Brookhart, M. Organome-
tallics 2004, 23, 1766.
(42) Faraone, F.; Piraino, P.; Pietropaolo, R. J. Chem. Soc., Dalton Trans.
(38) Activation parameters for hypothetical olefin rotation for 3COE
-
PF6 were estimated by line-shape analysis of the 31P NMR signals to be in
the range of ∆Gq ≈ 37 kJ · mol-1
.
1973, 1625.
300
(39) Although rationalization of metal-olefin bonding on the basis of
pure 13C olefin coordination shifts has been discussed controversially, within
closely related systems it is justified to use ∆δ13C values as a qualitative
indicator for relative Mfolefin back-bonding: (a) Thoennes, D. J.; Wilkins,
C. L.; Trahanovsky, W. S. J. Magn. Reson. 1974, 13, 18. (b) Evans, J.;
Norton, J. R. Inorg. Chem. 1974, 13, 3042. (c) Clark, P. W.; Hanisch, P.;
Jones, A. J. Inorg. Chem. 1979, 18, 2067.
(43) Whithead, M. T.; Grubbs, R. H. J. Am. Chem. Soc. 2008, 130, 5874.
(44) Rybtchinski, B.; Ben-David, Y.; Milstein, D. Organometallics 1997,
16, 3786.
(45) Danopoulos, A. A.; Wills, A. R.; Edwards, P. G. Polyhedron 1990,
9, 2413.
(46) Onderlinden, A. L.; van der Ent, A. Inorg. Chim. Acta 1972, 6,
420.

716 Organometallics, Vol. 28, No. 3, 2009
Friedrich et al.
Table 4. Crystallographic Data for [Ir(C2H4)(PNP)H][PF6] (3C2H4-PF6), [Ir(CO)(PNP)H][PF6] (3CO-PF6), [Ir(C2H4)(PNP)] (4C2H4), [Ir(CO)(PNP)]
(4CO), and [IrHCl2(PNP)H] (5)
3C2H4-PF6
3CO-PF6
4C2H4
4CO
5
formula
fw
C18H41F6IrNP3
670.65
C17H37F6IrNOP3
670.61
C18H40IrNP2
524.67
C17H36IrNOP2
524.63
C16H38Cl2IrNP2
569.53
color/habit
red/fragment
0.18 × 0.20 × 0.25
monoclinic
P21/c (no. 14)
8.7145(4)
15.9371(5)
18.3834(9)
90
96.488(4)
90
2536.81(19)
4
yellow/fragment
0.05 × 0.18 × 0.46
monoclinic
P21/c (no. 14)
8.6581(1)
15.6096(2)
18.5711(2)
90
94.818(1)
90
2501.01(5)
4
yellow/plate
0.05 × 0.25 × 0.33
triclinic
yellow/plate
0.02 × 0.25 × 0.25
triclinic
colorless/fragment
0.20 × 0.33 × 0.38
triclinic
cryst dimens (mm3)
cryst syst
j
j
j
space group
a, Å
b, Å
c, Å
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
8.967(2)
10.632(3)
12.933(4)
70.12(2)
83.63(2)
70.30(2)
1091.6(6)
2
7.6119(4)
13.5411(7)
21.8518(12)
78.202(4)
80.638(4)
73.614(4)
2102.0(2)
4
11.8102(4)
14.2081(5)
14.5239(4)
101.423(3)
101.801(3)
106.574(3)
2199.45(14)
4
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
T, K
173
1.756
5.502
1328
153
1.781
5.583
1320
193
1.596
6.261
524
173
1.658
6.506
1040
153
1.720
6.457
1128
Dcalcd, g cm-3
µ, mm-1
F(000)
θ range, deg
index ranges (h, k, l)
no. of rflns collected
no. of indep rflns/Rint
no. of obsd rflns (I > 2σ(I))
no. of data/restraints/params
R1/wR2 (I > 2σ(I))a
R1/wR2 (all data)a
GOF (on F2)a
largest diff peak and hole (e Å-3
3.98-26.79
(11, (20, (23
34 278
5346/0.069
4723
5346/0/290
0.0317/ 0.0632
0.0393/0.0655
1.100
2.99-25.30
(10, (18, (22
29 964
4554/0.046
3506
4554/0/270
0.0360/0.0893
0.0535/0.1038
1.075
3.71-22.46
(9, (11, (13
4107
2078/0.106
1671
2078/0/207
0.0523/0.1278
0.0689/0.1350
0.988
3.90-26.79
(9, (17, (27
36 155
8863/0.073
6818
8863/0/413
0.0301/0.0724
0.0405/0.0741
0.903
2.81-25.38
(14, (17, (17
39 372
7989/0.026
6440
7989/0/421
0.0256/0.0506
0.0445/0.0632
1.202
)
+1.21/-1.26
+2.78/-1.03
+1.13/-1.08
+1.21/-1.86
+2.77/-1.21
a
2
2
2
R1 ) ∑(|Fo| - |Fc|)/∑|Fo|; wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo )2]}1/2; GOF ) {∑[w(Fo - Fc2)2]/(n - p)}1/2
.
spectrometer as Nujol mulls between KBr plates. NMR spectra were
recorded on Jeol Lambda 400, Bruker DPX 400, Bruker DMX 500,
and Bruker DMX 600 spectrometers at room temperature and were
calibrated to the residual proton resonance and the natural abun-
gously by using NaBPh4 instead of AgPF6 (yield 90%). The
1
cation exhibits identical H, 13C, and 31P NMR spectra to those
in 3COE-PF6.
[Ir(C2H4)(PNP)H][PF6] (3C2H4-PF6). Ethylene is bubbled through
a suspension of 1 (0.402 g, 0.449 mmol) in acetone (10 mL) at
-30 °C until a clear colorless solution occurs. Consecutively a
solution of AgPF6 (0.215 g, 0.850 mmol) in acetone (5 mL) and a
solution of HN(CH2CH2PiPr2)2 (0.260 g, 0.851 mmol) in acetone
(5 mL) are added at -30 °C. The resulting red suspension is
warmed to rt and filtered. Precipitation with pentane gives a red
oil, which is redissolved in THF, filtered, and precipitated with
diethyl ether and pentane. 3C2H4-PF6 is obtained as a red crystalline
product upon filtration, washing with diethyl ether, and drying in
Vacuo. Yield: 0.403 g (0.601 mmol; 67%). Anal. Calcd for
C18H41F6IrNP3 (670.65): C, 32.24; H, 6.16; N, 2.09. Found: C,
32.56; H, 5.81; N, 2.07. IR (cm-1): ν ) 3210 (N-H). NMR (d6-
dance 13C resonance of the solvent (C6D6, δH ) 7.16 and δC
)
128.1 ppm; d6-acetone, δH ) 2.05 and δC ) 29.8 + 206.3 ppm;
d8-THF, δH ) 1.73 + 3.58 ppm and δC ) 25.4 + 67.6 ppm). 31P
NMR NMR chemical shifts are reported relative to external
phosphoric acid (δ 0.0 ppm). 15N NMR shifts are given relative
to MeNO2 by referencing with external 15N-urea in d6-dmso (δ
-302.1 ppm). Signal multiplicities are abbreviated as s (singlet),
d (doublet), t (triplet), vt (virtual triplet), sp (septet), m
(multiplet), br (broad).
Syntheses. [Ir(COE)(PNP)H][PF6] (3COE-PF6). HN(CH2CH2PiPr2)2
(0.142 g; 0.466 mmol) is added to a solution of 1 (0.200 g; 0.223
mmol) and AgPF6 (0.118 g; 0.466 mmol) in THF (5 mL) and stirred
for 30 min. After filtration the orange product is precipitated with
pentanes, washed twice with pentanes, and dried in Vacuo. Yield:
0.229 g (0.377 mmol; 84%). Anal. Calcd for C24H51F6IrNP3
(752.80): C, 38.29; H, 6.83; N, 1.86. Found: 38.28; H, 7.11; N,
1.91. IR (cm-1): ν ) 3215 (N-H). NMR (d6-acetone, rt, [ppm])
1H NMR (399.8 MHz): δ 1.20 (dvt, 3JHH ) 6.7 Hz, JPH ) 6.7 Hz,
6H, CH3), 1.28 (dvt, 3JHH ) 6.7 Hz, JPH ) 6.7 Hz, 6H, CH3), 1.34
1
3
acetone, rt, [ppm]) H NMR (399.78 MHz): δ 1.19 (dvt, JHH
)
7.2 Hz, JHP ) 7.2 Hz, 6H, CH3), 1.25 (m, 18H, CH3), 1.95 (m, 2H,
PCH2), 2.35 (m, 2H, PCH2), 2.45 (m, 2H, CH(CH3)2), 2.58 (m,
3
2H, CH(CH3)2), 2.75 (m, 2H, NCH2), 2.88 (t, JHH ) 4.0 Hz, 4H,
C2H4), 3.45 (m, 2H, NCH2), 5.70 (br, 1H, NH). 13C{1H} NMR
(100.6 MHz): δ 17.8 (s, CH3), 17.9 (s, CH3), 18.7 (s, CH3), 18.9
(s, CH3), 23.9 (vt, JCP ) 14.6 Hz, CH(CH3)2), 25.0 (vt, JCP ) 13.0
Hz, PCH2), 25.3 (vt, JCP ) 13.1 Hz, CH(CH3)2), 31.9 (s, C2H4),
57.1 (s, NCH2). 31P{1H} NMR (161.8 MHz): δ 49.0 (s, PiPr2),
3
(dvt, JHH ) 8.6 Hz, JPH ) 7.3 Hz, 6H, CH3), 1.35 (2H, CH2COE),
3
1.40 (dvt, JHH ) 7.3 Hz, JPH ) 8.6 Hz, 6H, CH3), 1.49 (m, 4H,
CH2COE), 1.64 (m, 4H, CH2COE), 1.88 (m, 2H, PCH2), 2.25-2.32
-143.6 (sp, 1JPF ) 707 Hz, PF6). [Ir(C2H4)(PNP)H][BPh4] (3C2H4
-
3
(m, 4H, PCH2 + CH2COE), 2.41 (spvt, JHH ) 7.0 Hz, JPH ) 2.8
BPh4) can be prepared analogously by using NaBPh4 instead of
Hz, 2H, CH(CH3)2), 2.54 (spvt, 3JHH ) 7.0 Hz, JPH ) 2.8 Hz, 2H,
CH(CH3)2), 2.70 (m, 2H, NCH2), 3.33 (m, 2H, NCH2), 3.62 (br,
2H, CHCOE), 5.35 (br, 1H, NH). 13C{1H} NMR (100.6 MHz): δ
16.9 (s, CH3), 18.5 (s, CH3), 18.9 (s, CH3), 24.3 (vt, JCP ) 13.8
AgPF6 (yield 81%). The cation exhibits identical H, 13C, and 31P
1
NMR spectra to those in 3C2H4-PF6.
[Ir(C3H6)(PNP)H][PF6] (3C3H6-PF6). 1 (0.200 g, 0.223 mmol)
is suspended in THF (10 mL) at -80 °C and propylene bubbled
through the solution for 20 min. After addition of
HN(CH2CH2PiPr2)2 (0.136 g, 0.445 mmol) and AgPF6 (0.113 g,
0.446 mmol) the solution is stirred for 1 h at -80 °C. Upon addition
of pentane the crude product is precipitated, filtered off, and
redissolved in THF. After filtration the product was precipitated as
orange microcrystals with pentane, filtered off, and dried in Vacuo.
Hz, CH(CH3)2), 24.5 (vt, JCP ) 14.5 Hz, PCH2), 25.7 (vt, JCP
)
13.0 Hz, CH(CH3)2), 26.3 (s, CH2COE), 31.6 (s, CH2COE), 33.8 (s,
2
CH2COE), 52.3 (s, CHCOE), 55.8 (d, JCP ) 2 Hz, NCH2). 31P {1H}
NMR (161.8 MHz): δ 43.1 (s, PiPr2), -143.6 (sp, 1JPF ) 707 Hz,
PF6). Assignments were confirmed by a 1H-1H COSY spectrum.
[Ir(COE)(PNP)H][BPh4] (3COE-BPh4) can be prepared analo-

Iridium Olefin Complexes
Organometallics, Vol. 28, No. 3, 2009 717
2
4
Yield: 0.169 g (0.249 mmol; 55%). Anal. Calcd for C19H43F6IrNP3
(684.68): C, 33.33; H, 6.33; N, 2.05. Found: C, 32.83; H, 6.15; N,
(dd, JCP ) 5.3 Hz, JCP ) 3.8 Hz, NCH2). 31P{1H} NMR (161.8
MHz): δ 49.9 (d, JPP ) 373 Hz, PiPr2), 53.6 (d, JPP ) 373 Hz,
PiPr2). Assignments were confirmed by 1H-1H COSY and 1H-13C
HETCOR spectra.
2
2
1
2.02. IR (cm-1): ν ) 3220 (N-H). NMR (d8-THF, rt, [ppm]) H
NMR (399.78 MHz): δ 1.09-1.14 (m, 9H, 3 × PCHCH3), 1.17
[Ir(C2H4)(PNP)] (4C2H4). KOtBu (0.011 g; 0.096 mmol) in THF
(5 mL) is added to a solution of 3C2H4-BPh4 (0.081 g; 0.096 mmol)
in 5 mL of THF at 0 °C. The yellow solution is stirred for 1 h, and
the solvent evaporated and extracted with pentanes. Evaporation
of the solvent gives 4C2H4 as a yellow, microcrystalline solid. Yield:
0.036 g (0.069 mmol; 72%). Anal. Calcd for C18H40IrNP2 (524.68):
C, 41.20; H, 7.68; N, 2.68. Found: C, 40.80; H, 7.16; N 2.66. NMR
(C6D6, rt, [ppm]) 1H NMR (399.78 MHz): δ 1.04 (dvt, 3JHH ) 7.2
Hz, JHP ) 7.2 Hz, 12H, CH3), 1.16 (dvt, 3JHH ) 7.2 Hz, JHP ) 7.2
Hz, 12H, CH3), 1.34 (m, 4H, PCH2), 1.64 (m, 2H, CH(CH3)2), 1.91
(dd, 3JHH ) 5.6 Hz, 3JHP ) 10.6 Hz, 3H, PCHCH3), 1.28 (dd, 3JHH
3
3
) 5.6 Hz, JHP ) 10.0 Hz, 3H, PCHCH3), 1.35 (dd, JHH ) 5.3
Hz, 3JHP ) 9.7 Hz, 3H, PCHCH3), 1.42 (dd, 3JHH ) 6.5 Hz, 3JHP
)
12.3 Hz, 3H, PCHCH3), 1.44 (dd, 3JHH ) 5.6 Hz, 3JHP ) 11.2 Hz,
3
3H, PCHCH3), 1.51 (d, JHH ) 4.7 Hz, 3H, H2C)CHCH3),
1.93-2.10 (m, 3H, 3 × PCH2), 2.22 (m, 2H, 1 × PCH2
+
PCHMe2), 2.38 (dsp, 3JHP ) 5.0 Hz, 3JHH ) 5.3 Hz, 1H, PCHMe2),
2.47-2.62 (m, 4H, 1 × H2CdCHMe + 2 × NCH2 + PCHMe2),
3
3
2.71 (dsp, JHP ) 5.6 Hz, JHH ) 5.3 Hz, 1H, PCHMe2), 2.95 (dt,
3JHH ) 7.9 Hz, JHP ) 5.3 Hz, 1H, H2CdCHMe), 3.34 (dm, JHP
3
3
3
3
(t, JHH ) 4.4 Hz, 4H, C2H4), 1.92 (m, 2H, CH(CH3)2), 3.40 (m,
) 29.0 Hz, 1H, 1 × NCH2), 3.49 (dm, JHP ) 27.8 Hz, 1H, 1 ×
4H, NCH2). 13C{1H} NMR (100.6 MHz): δ 9.8 (s, C2H4), 17.7 (s,
CH3), 19.0 (s, CH3), 23.9 (vt, JCP ) 13.0 Hz, CH(CH3)2), 26.9 (vt,
JCP ) 12.2 Hz, PCH2), 65.1 (vt, JCP ) 4.6 Hz, NCH2). 31P{1H}
NMR (161.8 MHz): δ 55.6 (s, PiPr2).
NCH2), 3.72 (m, 1H, H2CdCHMe), 5.09 (br, 1H, NH). 13C{1H}
NMR (100.6 MHz): δ 16.7 (s, PCHCH3), 16.8 (s, PCHCH3), 17.0
(s, PCHCH3), 17.2 (s, 2 × PCHCH3), 17.4 (s, PCHCH3), 18.6 (d,
2JPC ) 3.1 Hz, PCHCH3), 19.0 (d, 2JPC ) 2.3 Hz, PCHCH3), 22.5
[Ir(CO)(PNP)] (4CO). KOtBu (0.009 g, 0.080 mmol) is added
to a solution of 3CO-[PF6] (0.041 g, 0.062 mmol) in THF (5 mL)
and stirred for 1 h at rt. The solvent is evaporated in Vacuo and the
residue extracted with pentane, filtered, and evaporated to give a
yellow solid. Yield: 0.032 g (0.061 mmol; 98%). Anal. Calcd for
C17H36IrNOP2 (524.64): C, 38.92; H, 6.92; N, 2.67. Found: 39.43;
H, 6.28; N, 2.38. IR (cm-1): ν ) 1908 (CO). NMR (C6D6, rt, [ppm])
1
1
(s, H2CdCHCH3), 23.7 (d, JCP ) 20.7 Hz, PCH2), 25.2 (dd, JCP
3
1
) 21.4 Hz, JCP ) 5.7 Hz, CH(CH3)2), 26.3 (dd, JCP ) 21.4 Hz,
3JCP ) 4.6 Hz, CH(CH3)2), 32.7 (s, H2CdCHCH3), 42.3 (s,
2
2
H2CdCHCH3), 56.1 (t, JPC ) 3.8 Hz, NCH2), 57.0 (t, JPC ) 3.1
Hz, NCH2). One PCH2 and two CH(CH3)2 13C signals are
superimposed with one of the solvent signals. 31P{1H} NMR (161.8
MHz): δ 50.6 (d, JPP ) 307 Hz, PiPr2), 47.5 (d, JPP ) 307 Hz,
2
2
1H NMR (399.78 MHz) δ ) 1.02 (dvt, JHH ) 7.2 Hz, JHP ) 7.2
3
PiPr2), -143.7 (sp, JPF ) 711 Hz, PF6).
1
Hz, 12H, CH3), 1.23 (dvt, 3JHH ) 8.8 Hz, JHP ) 6.8 Hz, 12H, CH3),
1.81 (tt, 3JHH ) 6.6 Hz, JHP ) 4.4 Hz, 4H, PCH2), 1.97 (spvt, 3JHH
) 7.0 Hz, JHP ) 3.0 Hz, 4H, CH(CH3)2), 3.32 (tvt, 3JHH ) 6.4 Hz,
JHP ) 8.8 Hz, 4H, NCH2). 13C{1H} NMR (100.6 MHz): δ ) 18.2
(s, CH3), 19.5 (s, CH3), 26.2 (vt, JCP ) 15 Hz, CH(CH3)2), 27.1
(vt, JCP ) 13 Hz, PCH2), 63.0 (vt, JCP ) 5.0 Hz, NCH2), 187.8 (t,
2JCP ) 9.0 Hz, CO). 31P{1H} NMR (161.8 MHz): δ 80.7 (s, PiPr2).
[IrHCl2(PNP)H] (5). HN(CH2CH2PiPr2)2 (0.102 g; 0.339 mmol)
is added to a solution of 1 (0.147 g; 0.164 mmol) in benzene (10
mL) and stirred overnight. The solvent is evaporated in Vacuo and
the residue washed with pentanes to give a white solid, which is
dried in Vacuo. Yield: 0.092 g (0.162 mmol; 49%). Anal. Calcd
for C16H38Cl2IrNP2 (569.55): C, 33.74; H, 6.72; N, 2.46. Found:
33.23; H, 6.59; N, 2.22. IR (cm-1): ν ) 3130 (N-H), 2195 (Ir-H).
NMR (C6D6, rt, [ppm]) H NMR (399.8 MHz): δ -24.73 (t, JHP
) 12.8 Hz, 1H, IrH), 0.97 (dvt, 3JHH ) 7.6 Hz, JPH ) 6.8 Hz, 6H,
CH3), 1.11 (dvt, 3JHH ) 6.8 Hz, JPH ) 6.8 Hz, 6H, CH3), 1.42 (m,
12H, CH3, PCH2, NCH2), 1.78 (dvt, 6H, 3JHH ) 7.6 Hz, JPH ) 7.6
Hz, CH3), 1.99 (m, 2H, CH(CH3)2), 2.56 (m, 2H, CH(CH3)2), 3.27
(m, 2H, NCH2), 5.11 (br, 1H, NH). 13C{1H} NMR (100.6 MHz):
δ 17.9 (s, CH3), 19.0 (s, CH3), 19.4 (s, CH3), 20.1 (s, CH3), 24.2
(vt, JCP ) 13.7 Hz, CH(CH3)2), 25.9 (vt, JCP ) 13.8 Hz, CH(CH3)2),
29.4 (vt, JCP ) 12.2 Hz, PCH2), 59.3 (s, NCH2). 31P{1H} NMR
(161.8 MHz): δ 27.1 (s, PiPr2).
[Ir(CO)(PNP)H][PF6] (3CO-PF6). CO is bubbled through a
solution of 3C2H4-PF6 (0.136 g, 0.203 mmol) in THF (10 mL) at rt
until a yellow, clear solution is obtained. After filtration 3CO-PF6
precipitates upon addition of diethyl ether and pentane as a yellow
crystalline product, which is filtered off, washed with pentane, and
dried in Vacuo. Yield: 0.130 g (0.194 mmol; 95%). Anal. Calcd
for C17H37F6IrNOP3 (670.61): C, 30.45; H, 5.56; N, 2.09. Found:
C, 31.20; H, 5.47; N, 2.05. IR (cm-1): ν ) 3223 (N-H), 1976 (s,
CO). NMR (C6D6, rt, [ppm]) 1H NMR (399.78 MHz): δ 0.81 (dvt,
3JHH ) 7.2 Hz, JHP ) 7.2 Hz, 6H, CH3), 0.87 (dvt, 3JHH ) 7.2 Hz,
JHP ) 7.2 Hz, 12H, CH3), 0.91 (dvt, 3JHH ) 7.2 Hz, JHP ) 7.2 Hz,
3
12H, CH3), 1.06 (dvt, JHH ) 7.6 Hz, JHP ) 7.2 Hz, 6H, CH3),
1.78 (m, 6H, PCH2 + NCH2), 2.09 (m, 4H, CH(CH3)2), 3.46 (m,
2H, NCH2), 4.79 (br, 1H, NH). 13C{1H} NMR (100.6 MHz): δ
18.0 (s, CH3), 18.2 (s, CH3), 18.9 (s, CH3), 19.0 (s, CH3), 24.2 (vt,
1
2
JCP ) 12.2 Hz, CH(CH3)2), 25.9 (vt, JCP ) 16.1 Hz, PCH2), 26.6
2
(vt, JCP ) 15.2 Hz, CH(CH3)2), 55.6 (s, NCH2), 180.8 (t, JCP
)
8.0 Hz, CO). 31P{1H} NMR (161.8 MHz): δ 69.8 (s, PiPr2), -142.53
1
(sp, JPF ) 712 Hz, PF6).
[Ir(COE)(PNP)] (4COE). KOtBu (0.015 g, 0.133 mmol) is added
to a solution of 3COE-[PF6] (0.100 g, 0.133 mmol) in THF (5 mL)
and stirred for 2 h at rt. The solvent is evaporated in Vacuo and the
residue extracted with pentane, filtered, and evaporated in Vacuo
to give an orange-yellow solid. Yield: 0.058 g (0.95 mmol; 72%).
Anal. Calcd for C24H50IrNP2 (606.83): C, 47.50; H, 8.31; N, 2.31.
Reaction of 3COE-PF6 with [PPh4]Cl: NMR Characteri-
zation of 6. A suspension of 3COE-PF6 (0.016 g; 0.021 mmol) and
[PPh4]Cl (0.008 g, 0.021 mmol) in THF (2 mL) is stirred at room
temperature for 36 h, resulting in a mixture of 4COE, 5, and 6 by
31P NMR. After evaporation of the solvent the residue is extracted
with pentanes and filtered. Upon evaporation of the extract, a
mixture of 4COE and 6 is obtained, which could not be further
separated. NMR data of [IrHCl(C8H13)(PNP)H] (6): 1H NMR
(399.78 MHz, C6D6): δ -24.40 (t, 2JHP ) 15.0 Hz, 1H, IrH), 0.95
(dvt, 3JHH ) 6.4 Hz, JPH ) 6.4 Hz, 6H, CH3), 1.21 (m, 12H, CH3),
1
Found: 47.03; H, 8.42; N, 2.28. NMR (C6D6, rt, [ppm]) H NMR
3
(399.78 MHz): δ 1.03 (m, 12H, 4 × CH3), 1.19 (dd, JHH ) 7.6
3
3
3
Hz, JHP ) 12.8 Hz, 6H, 2 × CH3), 1.31 (dd, JHH ) 7.2 Hz, JHP
) 12.8 Hz, 6H, 2 × CH3), 1.42 (m, 2H, CHdCHCH2), 1.59 (m,
6H, PCH2 + CH2COE), 1.73 (dt, 2JHP ) 7.2 Hz,3JHH ) 6.8 Hz, 2H,
PCH2), 1.82 (m, 2H, CH2COE) 1.97 (m, 6H, 4 × CH(CH3)2
+
)
CH2COE), 2.40 (m, 4H, CHdCHCH2 + HCdCH), 3.32 (dt, 3JHP
14.6 Hz,3JHH ) 6.7 Hz, 2H, NCH2), 3.43 (dt, 3JHP ) 16.5 Hz,3JHH
) 6.1 Hz, 2H, NCH2). 13C{1H} NMR (100.6 MHz): δ 17.7 (s, CH3),
2
2
3
17.9 (s, CH3), 19.2 (d, JCP ) 2.3 Hz, CH3), 20.2 (d, JCP ) 4.5
1.34 (dvt, JHH ) 6.6 Hz, JPH ) 6.6 Hz, 6H, CH3), 1.53 (m, 2H,
Hz, CH3), 23.5 (dd, JCP ) 20.7 Hz,3JCP ) 5.4 Hz, CH(CH3)2),
1
NCH2), 1.67 (m, 4H, PCH2, CH2COE), 1.82 (m, 4H, CH2COE), 1.96
(m, 2H, CH2COE), 2.11 (m, 2H, CH(CH3)2), 2.40 (m, 6H, PCH2,
25.8 (dd, 1JCP ) 17.0 Hz,3JCP ) 7.0 Hz, CH(CH3)2), 26.1 (dd, 1JCP
3
1
3
) 24.0 Hz, JCP ) 3.1 Hz, PCH2), 27.5 (s, CH2COE), 28.9 (d, JCP
) 22.1 Hz, PCH2), 31.5 (s, HCdCH), 33.7 (s, CH2COE), 35.3 (m,
CHdCHCH2), 63.6 (dd, 2JCP ) 3.8 Hz,4JCP ) 2.3 Hz, NCH2), 64.6
NCH2, IrC)CHCH2), 3.08 (t, JHH ) 6.0 Hz, 2H, IrCCH2), 3.20
(m, 2H, CH(CH3)2), 4.00 (br, 1H, NH), 6.06 (t, 3JHH ) 7.7 Hz, 1H,
dCH).13C{1H} NMR (100.6 MHz): δ 18.8 (s, CH3), 19.1 (s, CH3),

718 Organometallics, Vol. 28, No. 3, 2009
Friedrich et al.
19.5 (s, CH3), 20.0 (s, CH3), 24.5 (vt, JCP ) 13.4 Hz, CH(CH3)2),
Specific Details: 3C2H4-PF6: An empirical absorption correction
was performed using the PLATON DELABS procedure (Tmin )
1
25.7 (vt, JCP ) 12.2 Hz, CH(CH3)2), 27.3 (s, CH2COE), 27.7 (s,
CH2COE), 28.5 (s, CH2COE) 29.7 (s, CH2COE), 31.2 (s, IrCdCHCH2),
0.116, Tmax ) 0.372). The amine and ethylene hydrogen positions
could be located from difference Fourier syntheses and were allowed
to refine freely. All other hydrogen atoms were placed in calculated
positions and refined using a riding model (dC-H ) 0.98, 0.99, and
1.00 Å and Uiso(H) ) 1.2Ueq(C) or 1.5Ueq(C)). 3CO-PF6: All hydrogen
atoms were placed in calculated positions and refined using a riding
31.6 (s, PCH2), 41.0 (s, IrCCH2), 54.1 (s, NCH2), 124.0 (t, 2JCP
)
9.2 Hz, IrC), 134.7 (s, IrCdCH). 31P{1H} NMR (161.8 MHz): δ
24.4 (s). Assignments were confirmed by 1H-1H COSY and
1H-13C HSQC spectra.
[IrHCl(COE)(PNP)H][PF6] (7-PF6). HCl (0.1 M in Et2O; 0.50
mL; 0.05 mmol) is added to a suspension of 3COE-PF6 (0.038 g;
0.050 mmol) in toluene (3 mL) at -20 °C. After 1 h the solution
is filtered at -20 °C and the product precipitated by addition of
pentanes to give colorless 7-PF6. Yield: 0.016 g (20 µmol; 40%).
model (dC-H ) 0.98, 0.99, and 1.00 Å, dN-H 0.93 Å, and Uiso(H)
)
1.2Ueq(C/N) or 1.5Ueq(C)). 4C2H4: A numerical absorption correction
after crystal shape optimization was performed using the programs
XSHAPE and XRED (Tmin ) 0.157, Tmax ) 0.470). Twinning and
the overall crystal quality required setting the resolution limit to
0.93 Å. All hydrogen atoms were placed in calculated positions
and refined using a riding model (dC-H ) 0.98, 0.99, and 1.00 Å
and Uiso(H) ) 1.2Ueq(C) or 1.5Ueq(C)). 4CO: A numerical absorption
correction after crystal shape optimization was performed using
the programs XSHAPE and XRED (Tmin ) 0.228, Tmax ) 0.769).
All hydrogen atoms were placed in calculated positions and refined
1
2
NMR (C6D6, rt, [ppm]) H NMR (399.8 MHz): δ -17.83 (t, JHP
) 10.8 Hz, 1H, IrH), 0.69 (dvt, 3JHH ) 6.7 Hz, JPH ) 6.7 Hz, 6H,
CH3), 0.75 (dvt, 3JHH ) 7.0 Hz, JPH ) 7.0 Hz, 6H, CH3), 0.79 (dvt,
3JHH ) 7.0 Hz, JPH ) 7.3 Hz, 6H, CH3), 1.05 (dvt, 3JHH ) 8.9 Hz,
JPH ) 7.6 Hz, 6H, CH3), 1.12-1.34 (m, 8H, CH2COE), 1.45 (m,
2H, CH(CH3)2), 1.47 (m, 2H, NCH2), 1.57 (m, 2H, CH2COE), 1.87
(m, 2H, PCH2), 1.64 (m, 4H, CH2COE), 2.33 (m, 2H, CH2COE), 2.80
(m, 2H, PCH2), 2.89-3.09 (m, 4H, CH(CH3)2 + NCH2), 4.06 (br,
2H, CHCOE), 5.67 (br, 1H, NH). 31P{1H} NMR (161.8 MHz): δ
23.3 (s, PiPr2), -142.5 (sp, 1JPF ) 707 Hz, PF6). Assignments were
using a riding model (dC-H ) 0.98, 0.99, and 1.00 Å and Uiso(H)
)
1.2Ueq(C) or 1.5Ueq(C)). Two crystallographic independent molecules
were found in the unit cell. 5: The hydride hydrogen positions could
be located from difference Fourier syntheses and were allowed to
refine freely. All other hydrogen atoms were placed in calculated
positions and refined using a riding model (dC-H of 0.98, 0.99, and
1.00 Å, dN-H 0.93 Å, and Uiso(H) ) 1.2Ueq(C/N) or 1.5Ueq(C)). Two
crystallographically independent molecules were found in the unit
cell. Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publica-
tion no. CCDC-715654 (3C2H4-PF6), CCDC-715652 (3CO-PF6),
CCDC-715655 (4C2H4), CCDC-715653 (4CO), and CCDC-715651
(5). Copies of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
(+44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
confirmed by H-1H COSY NMR.
1
Kinetic Experiments. Equimolar amounts (20.2 µmol) of 3COE
-
PF6 and [NnBu3(CH2Ph)]Cl were dissolved in THF (0.35 mL) in a
J-Young NMR tube equipped with a sealed capillary of phosphoric
acid as internal standard. The reaction was followed recording
31P{1H} NMR spectra every 10 min in the inverse-gated mode to
avoid NOE buildup. The relaxation delay (15 s) was chosen as
>5T1, as derived by 31P NMR inversion recovery experiments of
pure samples. Data analysis was performed using the program
package COPASI.47
X-ray Crystal-Structure Determinations. General. Crystal data
and details of the structure determination are presented in Table 4.
Suitable single crystals for the X-ray diffraction studies were grown
by diffusion of pentane into THF solutions (3C2H4-PF6, 3CO-PF6,
5) or slow cooling of saturated pentane solutions to -35 °C (4C2H4
,
Acknowledgment. The authors thank Prof. W. A. Herrmann
for generous support and G. Kummerlo¨we and P. Kaden for
recording 15N NMR spectra. S.S. is grateful to the DFG for
a grant within the Emmy-Noether Programm (SCHN950/2-
1), and R.G. would like to thank the Alexander von
Humboldt Foundation for a fellowship.
4
CO). Crystals were stored under perfluorinated ether, transferred
in a Lindemann capillary, fixed, and sealed. Preliminary examina-
tions and data collection were carried out with area detecting
systems and graphite-monochromated Mo KR radiation (λ )
0.71073 Å). The unit cell parameters were obtained by full-matrix
least-squares refinements during the scaling procedures. Data
collection was performed at low temperatures (Oxford Cryosys-
tems), and each crystal measured with a couple of data sets in
rotation scan modus with either ∆ꢁ/∆ω ) 1.0° or 2.0°. Intensities
were integrated and the raw data were corrected for Lorentz,
polarization, and, arising from the scaling procedure, latent decay
and absorption effects. The structures were solved by a combination
of direct methods and difference Fourier syntheses. All non-
hydrogen atoms were refined with anisotropic displacement pa-
rameters. Full-matrix least-squares refinements were carried out by
minimizing ∑w(Fo- Fc2)2 with the SHELXL-97 weighting scheme
and stopped at shift/err < 0.002. The final residual electron density
maps showed no remarkable features. Neutral atom scattering
factors for all atoms and anomalous dispersion corrections for the
non-hydrogen atoms were taken from International Tables for
Crystallography. All calculations were performed on an Intel
Pentium 4 PC, with the WinGX system, including the programs
PLATON, SIR92, and SHELXL-97.48
Supporting Information Available: 2D NMR spectra, kinetic
fit results, and crystallographic information for complexes 3COE
-
BPh4. This material is available free of charge via the Internet at
http://pubs.acs.org.
OM800423U
(48) (a) Data Collection Software and Data Processing Software for Stoe
IPDS 2T diffractometer, X-ARERA, Version 1.26; Stoe & Cie: Darmstadt,
Germany, 2004. (b) Data Processing Software for Stoe IPDS 2T diffrac-
tometer, XRED, XSHAPE, Version 1.26; Stoe & Cie: Darmstadt, Germany,
2004. (c) CrysAlis Data Collection Software and Data Processing Software
for Oxford Xcalibur diffractometer, Version 1.171; Oxford Diffraction Ltd.:
Oxfordshire, U.K., 2005. (d) Farrugia, L. J. WinGX (Version 1.70.01
January 2005). J. Appl. Crystallogr. 1999, 32, 837-838. (e) Altomare, A.;
Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla, M. C.; Polidori, G.;
Camalli, M. SIR92. J. Appl. Crystallogr. 1994, 27, 435–436. (g) Interna-
tional Tables for Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1992; Vol. C, Tables 6.1.1.4,
4.2.6.8, and 4.2.4.2. (h) Spek, A. L. PLATON, A Multipurpose Crystal-
lographic Tool; Utrecht University: Utrecht, The Netherlands, 2001. (i)
Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen: Go¨ttingen, Germany,
1998.
(47) Hoops, S.; Sahle, S.; Gauges, R.; Lee, C.; Pahle, J.; Simus, N.;
Singhal, M.; Xu, L.; Mendes, P.; Kummer, U. Bioinformatics 2006, 22,
3067.