Cyclometalation of Phosphanes at Iridium(I): Interplay with Intramolecular Reductive Elimination Induced by the Strong π-Acceptor Ligands CO and NO+

Article abstract of DOI:10.1002/ejic.201500363

Reaction of [{Ir(μ-Cl)(coe)₂}₂] (1; coe = cis-cyclooctene) with 4 equiv. of PtBu₂Ph in CH₂Cl₂ at ambient temperature resulted in oxidative addition of one phosphane ligand affording the known cyclomet

Full text of DOI:10.1002/ejic.201500363

FULL PAPER
DOI:10.1002/ejic.201500363
Cyclometalation of Phosphanes at Iridium(I): Interplay
with Intramolecular Reductive Elimination Induced by the
Strong π-Acceptor Ligands CO and NO+
Hans-Christian Böttcher,*[a] Merlin Junk,[a] Peter Mayer,[a] and
Wolfgang Beck[a]
Dedicated to Professor Manfred Scheer on the occasion of his 60th birthday
Keywords: Iridium / Phosphane ligands / Cyclometalation / Oxidative addition / Reductive elimination
Reaction of [{Ir(μ-Cl)(coe)2}2] (1; coe = cis-cyclooctene) with
4 equiv. of PtBu2Ph in CH2Cl2 at ambient temperature re- known IrI complex trans-[IrCl(CO)(PtBu2Ph)2] (3). In a similar
sulted in oxidative addition of one phosphane ligand afford- manner, reacted with nitrosonium tetrafluoridoborate
the CO ligand and inversion of cyclometalation to give
1
ing the known cyclometalated IrIII complex [IrCl(H)-
(PtBu2C6H4-κ2P,C)(PtBu2Ph)] (2) in high yield. Compound 2
exhibits a coordinatively unsaturated five-coordinate 16 VE
species, and its reactivity towards strong π-acceptor ligands
is investigated. Reaction of 2 with CO resulted in addition of
affording the new complex salt [IrCl(NO)(PtBu2Ph)2][BF4] (4),
which is isoelectronic with 3. Compounds 2 and 4 were char-
acterized by spectroscopic methods as well as by X-ray crys-
tallography confirming their molecular structures.
compound 2 to generate the corresponding iridium(I) com-
plexes. This reaction was presumably induced by coordina-
tion of the strong π-acceptor ligand. In light of this finding,
we report herein the full characterization of compound 2
including its molecular structure by X-ray crystallography
along with selected studies on the reactivity of this coordi-
natively unsaturated species towards several ligands.
Introduction
Some years ago we reported the synthesis and X-ray
crystal structure of olefinic complex trans-[IrCl(coe)-
(PtBu2H)2] (coe = cis-cyclooctene), which was obtained by
treating [{Ir(μ-Cl)(coe)2}2] (1) with secondary phosphane
PtBu2H in CH2Cl2 at room temperature using a molar ratio
of Ir/P = 1:1.5.[1] These defined conditions should be
warranted since, by the use of a molar ratio of 1 Ir/P =
1:2, the formation of [IrCl(PtBu2H)3][2] is observed to some
extent. Since only a few molecular structure determinations
on trans-[IrCl(coe)(phosphane)2] complexes had been re-
ported, we were interested in examining the analogous reac-
tion of 1 with tertiary phosphane PtBu2Ph. However, our
investigations in this field resulted, unexpectedly, in facile
cyclometalation including the ortho position of the phenyl
group in one phosphane ligand affording the cyclo-
metalated, coordinatively unsaturated complex [IrCl(H)-
(PtBu2C6H4-κ2P,C)(PtBu2Ph)] (2).[3] Initially, we assumed
that the formation of a stable Ir–C bond was the driving
force in this reaction. Contrary to this finding, we observed
in reactions of 1 with strong π-acceptor ligands such as CO
and NO+ a spontaneous inversion of cyclometalation at
room temperature resulting in reductive elimination from
Results and Discussion
Treatment of 1 with PtBu2Ph (molar ratio of Ir/P = 1:1.5
and 1:2) in CH2Cl2 at room temperature resulted, in the
early stage of the reaction, in a red-brown suspension that
changed into a clear deep-red solution within 15 min. We
cannot exclude that, in this period, the expected complex
trans-[IrCl(coe)(PtBu2Ph)2] was present in the reaction mix-
ture. However, NMR investigations after a very short reac-
tion time showed that compound 2 was quickly formed
as the sole product. After 1 h, [IrCl(H)(PtBu2C6H4-
κ2P,C)(PtBu2Ph)] (2)[3] was isolated from the reaction mix-
ture as dark red crystals in good yield. Notably, treatment
of 1 with PtBu2Ph in a molar ratio of Ir/P = 1:3 using
analogous conditions resulted also exclusively in the forma-
tion of compound 2. Coordinatively saturated iridium(III)
complexes often exhibit a yellow color. In contrast to this
observation, complex 2 was intensely red-brown. This can
be presumably attributed to low-energy, metal-based elec-
[a] Department Chemie, Ludwig-Maximilians-Universität
München,
Butenandtstraße 5-13, 81377 München
E-mail: hans.boettcher@cup.uni-muenchen.de
http://www.cup.uni-muenchen.de
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tronic transitions in the HOMO–LUMO region; the intense earlier report.[3] Moreover, the very large chemical shift of
color was a first hint at the coordinatively unsaturated char- the hydrido signal into the high-field region in the 1H NMR
acter of this species. Corresponding UV/Vis absorption spectrum was indicative of such an environment.[5] Com-
bands were observed in a pentane solution of 2 (see Exp. pound 2 exhibits a valence-electron count of 16 VE and is
Sect.). Indeed, the hypothesized coordinative unsaturation therefore an electronically and coordinatively unsaturated
was ultimately confirmed by X-ray crystallographic data species.
generated using single crystals of 2 (see below). In the litera-
ture it is well established that (phosphane)iridium(I) com-
plexes bearing suitable substituents on the phosphorus
atom (e.g. phenyl groups) can undergo facile intramolecular
oxidative addition reactions under mild conditions afford-
ing products that contain cyclometalated phosphane li-
gands.[4] Complex 2 was characterized by elemental analy-
sis, NMR spectroscopy (1H, 31P and 13C) and mass spec-
trometry. Our findings corresponded well with the reported
data,[3] and we were able to collect more data in detail (see
Exp. Sect.). Correspondingly, we found better resolved sig-
1
nals in the H NMR spectrum in the region of aromatic
protons. Some broad resonances, centered at δ = 7.88 and
7.37 ppm, can be attributed to phosphane interconversions
by reversible metalation/demetalation of the ortho-hydrogen
atoms on the two different phosphane ligands as discussed
in the literature.[5] The 31P{1H} NMR spectrum of 2 in
CD2Cl2 at room temperature consists of a pattern corre-
sponding to an AX (almost AB) spin system. A trans ar-
Figure 1. ORTEP view of the molecular structure of 2 in the crys-
rangement of both phosphorus-containing ligands is clearly
tal. Displacement ellipsoids are drawn at the 50% probability level.
2
indicated by the large coupling constant JPP = 335.1 Hz.
The chemical shift of one signal in the high-field region at
δ = –11.2 ppm was an indication that the expected complex
with the constitution trans-[IrCl(coe)(PtBu2Ph)2] was not
obtained. Such a large shift to upfield values was indicative
Selected bond lengths [Å] and angles [°]: Ir1–P1 2.3248(9), Ir1–P2
2.3400(8), Ir1–C1 2.051(3), Ir1–Cl1 2.4118(9), Ir1–H1 1.42(5), P2–
C21 1.885(3), C1–C2 1.409(4), P1–C2 1.800(3), P1–C7 1.877(3),
P1–C11 1.871(3), P2–C15 1.841(3), P2–C21 1.885(3) P2–C25
1.904(3); P1–Ir1–P2 169.11(3), P1–Ir1–C1 68.38(8), Ir1–P1–C7
116.53(10), Ir1–P2–C25 116.64(9), Cl1–Ir1–C1 160.35(9), C1–Ir1–
H1, 84.6(17), P1–Ir1–H1 85.9(17), P2–Ir1–H1, 91.3(16).
1
of an ortho-metalation process.[6] The H NMR spectrum
confirmed unambiguously the presence of a phosphane be-
side a cyclometalated phosphane and a hydrido ligand in
In light of the coordinative unsaturation of species 2, we
the product. Finally, the molecular structure of 2 was examined its reactivity towards small molecules by investi-
corroborated by an X-ray diffraction study confirming that gating possible addition reactions. Thus, treatment of com-
[IrCl(H)(PtBu2C6H4-κ2P,C)(PtBu2Ph)] (2) was the sole pound 2 with carbon monoxide in CH2Cl2 at room tem-
product of this reaction. In the literature[3] it has been perature resulted spontaneously in a reaction characterized
argued that compound 2 is an intermediate in the synthesis by a color change from deep red to slightly yellow. From
of complex [Ir(H)2Cl(PtBu2Ph)2] from [{Ir(μ-Cl)(coe)2}2] the solution, pale yellow crystals in high yield were isolated
and PtBu2Ph, and that an IrI center in products derived exhibiting a very strong ν(CO) band in the IR spectrum at
from the reaction of [{Ir(μ-Cl)(olefin)2}2] with phosphane 1974 cm–1 (solid, ATR). Surprisingly, in the 31P{1H} NMR
has an exceptional ability to metalate C–H bonds. Our data spectrum (CD2Cl2) at room temperature only a singlet at δ
support the correctness of this statement, although the = 51.5 was observed. This latter circumstance was an indi-
phosphane ligands should be amenable to cyclometalation. cation that smooth addition of CO to compound 2 did not
In the case of secondary phosphane PtBu2H – as a compar- occur. These spectroscopic data alone suggested that the
ative starting point of our investigations – this was not reaction product was known compound trans-
possible.
[IrCl(CO)(PtBu2Ph)2] (3)[7] (Scheme 1). Indeed, we unam-
Compound 2 crystallized from toluene/ethanol at –30 °C biguously confirmed the identity of this species by further
as red block-like crystals belonging to the monoclinic space analytical methods (see Exp. Sect.). Comparable reactivity
group P21/c with four molecules in the unit cell. A view of has been observed in the literature only in very few cases.
the molecular structure in the crystal is depicted in Fig- Caulton and co-workers reported that the coordinatively
ure 1, selected bond lengths and angles are given in the cap- unsaturated iridium(III) complexes [Ir(H)2X(PtBu2Ph)2] (X
tion. The crystal-structure determination revealed a five-co- = halide or other anions) reacted quickly with CO.[8] Sub-
ordinate iridium(III) complex with distorted a square- sequently, the adducts with CO were able to reductively
pyramidal polyhedron shape with an apical hydrido ligand. eliminate HX, although this reaction was strongly depend-
The strong σ-donor hydrido ligand is arranged trans to the ent on the electronic properties of the coordinated ligand
empty coordination site confirming the hypothesis of the X. Interestingly, the complexes containing X = F or OPh
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quickly lost HX by spontaneous reductive elimination upon cyclometalation in the reaction of 2 with CO is more likely
reaction with CO. On the other hand, for the complexes attributable to the special bonding situation in the resulting
with X = Cl, Br, I or N3, stable iridium(III) adducts with product. IrIII complexes are less favoured to coordinate the
CO were isolated.[8]
strong π-acceptor ligand CO than are IrI compounds.
Therefore, we believe that the driving force in cyclo-
metalation inversion is provided by attainment of a pre-
ferred bonding situation for the incoming CO ligand. To
support this assertion we examined the reaction of com-
pound 2 with the strong π-acceptor ligand NO+. Thus,
treatment of equimolar amounts of compound 2 and
NO[BF4] in CH2Cl2 at room temperature resulted, after 1 h,
in a reaction with a color change from deep-red to violet-
brown. From the solution, dark red crystals could be iso-
lated in high yield. The solid exhibited a very strong ν(NO)
band in the IR spectrum (ATR) at 1873 cm–1 clearly indi-
cating coordination of the NO+ ligand in the coordination
sphere. As observed for trans-[IrCl(CO)(PtBu2Ph)2] (3) in
the 31P{1H} NMR spectrum (CD2Cl2) at room tempera-
ture, only a singlet at δ = 52.6 ppm was observed. Therefore,
also in this case, the addition of NO+ to compound 2
occurred with reductive elimination of the cyclometalated
phosphane ligand resulting in the formation of the new
compound trans-[IrCl(NO)(PtBu2Ph)2][BF4] (4) (Scheme 1).
The identity of this species was confirmed by spectroscopic
and analytical data (see Exp. Sect.), and its molecular struc-
ture was determined by X-ray diffraction analysis. Com-
pound 4 crystallized by the diffusion method from CH2Cl2/
MeOH at room temperature as red block-like crystals
Scheme 1. Synthesis of trans-[IrCl(CO)(PtBu2Ph)2] (3) and trans-
[IrCl(NO)(PtBu2Ph)2]BF4 (4).
Moreover, Caulton and co-workers reported numerous belonging to the monoclinic space group P21/c with four
studies of coordinatively unsaturated complexes bearing molecules in the unit cell. A view of the molecular structure
bulky phosphane ligands that influence steric protection of of 4 in the crystal is depicted in Figure 2; selected bond
empty coordination sites without any direct interaction lengths and angles are given in the caption. Corresponding
with the central atom beyond metal–phosphorus bonding.[9] complexes trans-[IrX(NO)(PPh3)2]+ (X = Cl, OH, OR) were
However, remarkable exceptions were reported for cyclo- described in the literature long ago;[11] however, no crystal-
metalated phosphane complexes where intramolecular C–H structure reports for this type of complex have been pub-
activations (oxidative addition) facilitate reductive elimi-
nation processes from IrIII complexes.[9] Previously, a sim-
ilar reductive elimination at an ortho-metalated hydridoirid-
ium(III) complex containing a tripodal tetraphosphorus li-
gand was reported.[10] However, in this case, a cyclo-
metalated, coordinatively saturated IrIII species bearing a
hydrido ligand underwent inversion of the cyclometalation
during reaction with carbon monoxide. The reaction de-
scribed needed rougher conditions (5 bar CO, 2 weeks at
room temperature, 80% conversion). In contrast, the reac-
tion of 2 with CO occurred spontaneously under normal
conditions and in nearly quantitative yield. The spontane-
ous reaction could be attributed to the coordinative unsatu-
ration of compound 2. We assume that, in the first step of
the reaction, addition of CO to the unsaturated complex 2
Figure 2. ORTEP view of the molecular structure of compound 4
occurred. Moreover, we think that steric hindrance should
in the crystal. Displacement ellipsoids are drawn at the 50% prob-
ability level. Selected bond lengths [Å] and angles [°]: Ir1–Cl1
not deter addition of the relatively small CO molecule to 2.
In light of this, we have some indications that acetonitrile,
for instance, adds as the ligand to 2 resulting in the corre-
sponding coordinatively saturated species. Unfortunately,
the latter species is very labile in solution, (e.g., workup
under vacuum conditions resulted in a loss of acetonitrile
2.2652(7), Ir1–P1 2.429(6), Ir1–P2 2.429(6), Ir1–N1 1.734(19), P1–
C1 1.890(2), P1–C5 1.878(3), P1–C9 1.828(2), P2–C15 1.881(2),
P2–C19 1.892(3), P2–C23 1.834(2), B1–F1 1.382(3); Cl1–Ir1–P1
90.75(2), P1–Ir1–P2 178.31(2), P1–Ir1–N1 89.71(6), Ir1–P1–C1
118.50(7), Ir1–P1–C5 106.59(8), Ir1–P1–C9 105.59(7), Ir1–P2–C15
106.56(8), Ir1–P2–C19 118.57(8), Ir1–P2–C23 105.68(8), Ir1–N1–
affording complex 2 back). Therefore, the inversion of O1 178.99(18).
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lished to date. The coordination sphere around the iridium X(PtBu2Ph)2] (X = F, OPh) reacted quickly with CO under
atom in the cationic complex can best be described as reductive-elimination conditions to afford complexes
nearly square-planar with the bulky phosphane ligands [IrH(CO)2(PtBu2Ph)] and [IrH(CO)(PtBu2Ph)2], respec-
trans-positioned relative to each other. The nitrosyl ligand tively.[8,13] Since, in the case of X = Cl, for example, a stable
exhibiting a bond angle Ir1–N1–O1 of 178.99(18)° can be addition product of IrIII with CO, namely [Ir(H)2Cl-
clearly identified as an NO+ ligand corresponding very well (CO)(PtBu2Ph)2], was isolated, we have to conclude that
to the characteristic ν(NO) band at 1873 cm–1. The P–Ir1– this reaction behavior is not directly comparable to our re-
P angle deviates from the ideal value of 180° only by 1.7°. actions described therein. We started with a compound con-
Even the Cl–Ir–N angle is close to 180° indicating an ap- taining a metalated C–H bond and, as mentioned above,
proximately square-planar coordination sphere for the IrI such a situation seemed to facilitate reductive elimination
cationic complex.
from IrIII complexes.[9,14]
The cationic complex in compound 4 can be considered
a
close relative of the isoelectronic species trans-
Experimental Section
[IrCl(CO)(PPh3)2], the well-known Vaska compound.[12]
Currently, we are working in the field of reaction studies
of 2 with other strong π-acceptor ligands and a series of
other σ-donor ligands. Here we have some indications that
the closely related compound trans-[IrCl(PF3)(PtBu2Ph)2]
can be obtained in a fashion similar to that used to access
compounds 3 and 4. Unfortunately, the complex bearing
the PF3 ligand is very unstable at room temperature in solu-
tion – a circumstance that renders more difficult its charac-
terization by NMR spectroscopic methods. Nevertheless,
we obtained preliminary X-ray crystal-structure results con-
firming the molecular structure of this species. Further-
more, we examined the reactivity of 2 towards the ligands
PMe3, PPh3 and P(OPh)3. These reactions were not easy
to investigate as indicated by the formation of mixtures of
products, which are strongly influenced by the chosen mo-
lar ratios between iridium and the incoming ligand. The
reaction solutions obtained were difficult to handle at room
temperature; transformations were often revealed using
NMR methods. Continued investigations in this field are
in progress in our laboratory. However, these studies are
challenging by virtue of the fact that, at room temperature,
facile metalation and demetalation processes must be care-
fully controlled.
General: All reactions were carried out under dry nitrogen using
standard Schlenk techniques. Reagents were purchased commer-
cially from ABCR and used without further purification. [{Ir(μ-
Cl)(coe)2}2] (1) was prepared from hydrated iridium(III) chloride
and cis-cyclooctene according to a published procedure.[15] IR
spectra were recorded from solids with a JASCO FT/IR-460 Plus
spectrometer equipped with an ATR unit. NMR spectra were ob-
tained using Jeol Eclipse 270 and 400 instruments operating at 270
and 400 (1H), 109 MHz (31P), and 68 MHz (13C), respectively.
Chemical shifts are given in ppm from SiMe4 (1H, 13C) or 85%
H3PO4 (31P). Mass spectra were recorded using a Jeol MStation
JMS-700 instrument. UV/Vis spectra were recorded with a Varian
Cary 300 double-beam spectrometer. Microanalyses (C, H, Cl, N)
were performed by the Microanalytical Laboratory of the Depart-
ment of Chemistry, LMU Munich, using a Heraeus Elementar
Vario EL instrument.
[IrCl(H)(PtBu2C6H4-κ2P,C)(PtBu2Ph)] (2): To a solution of 1
(448 mg, 0.50 mmol) in CH2Cl2 (20 mL) was added PtBu2Ph
(444 mg, 0.48 mL, 2.00 mmol) and the mixture stirred for 1 h.
During an initial time of 15 min, a red-brown suspension resulted,
which changed subsequently into a dark red solution. The solvent
was evaporated in vacuo, and n-hexane (10 mL) was added to the
residue affording a red-brown microcrystalline precipitate. The so-
lid was filtered off, washed with cold pentane (3 mL), and dried in
vacuo. Yield: 570 mg (85%). C28H46ClIrP2 (672.29): calcd. C 50.02,
H 6.90, Cl 5.27; found C 49.84, H 6.98, Cl 4.98. 31P{1H} NMR
(109 MHz, CD2Cl2, 20 °C): δ = 52.3 (d, 2JPP = 335.3 Hz, PtBu2Ph),
2
1
–11.2 (d, JPP = 335.3 Hz, PtBu2C6H4) ppm. H NMR (400 MHz,
CD2Cl2, 20 °C): δ = 7.88 (br. s, 2 H), 7.37 (t, JHH = 7.0 Hz, 1 H),
7.32 (br. s, 2 H), 6.84 (t, JHH = 8.4 Hz, 1 H), 6.67 (dt, JHH = 7.5,
JHH = 2.6 Hz, 1 H), 6.50 (dt, JHH = 7.6, 1.0 Hz, 1 H), 5.79 (dd,
Conclusions
We have investigated the reaction of [{Ir(μ-Cl)(coe)2}2]
(1) with tertiary phosphane PtBu2Ph with the aim of gener-
ating trans-[IrCl(coe)(PtBu2Ph)2]. Instead, facile ortho
metalation of one of the phenyl groups gave rise to the
formation of known cyclometalated IrIII complex
[IrCl(H)(PtBu2C6H4-κ2P,C)(PtBu2Ph)] (2). This coordina-
3
JHH = 7.8, 4.4 Hz, 1 H), 1.59 (d, JPH = 13.2 Hz, 9 H, t-C4H9),
1.47 (d, 3JPH = 14.0 Hz, 9 H, t-C4H9), 1.41 (d, 3JPH = 14.0 Hz, 9 H,
t-C4H9), 1.33 (d, 3JPH = 13.2 Hz, 9 H, t-C4H9), –42.1 (br. pseudo-t,
2
2JPH = 11.4, JPH = 11.2 Hz) ppm. 13C{1H} NMR (68 MHz,
CD2Cl2, 20 °C): δ = 150.5 (d, JPC = 40.3 Hz, C6H4), 136.9 (dd, J
tively unsaturated species reacted smoothly with the strong = 13.4, 1.9 Hz, cyclometalated C), 132.2, (d, J = 32.6 Hz, C6H4),
129. 5 (s), 128.3 (s, C6H5), 127.5 (s), 121.4 (d, 2JPC = 7.7 Hz, C6H4),
37.7 (dd, 3JPC = 18.7, 3.9 Hz, P-C-CH3), 37.2 (dd, 3JPC = 17.3, JPC
π-acceptor ligands CO and NO+ affording iridium(I)
complexes trans-[IrCl(CO)(PtBu2Ph)2] (3) and trans-
[IrCl(NO)(PtBu2Ph)2]+, respectively. Originally, we ex-
pected reactions upon addition of these small molecules.
Instead, and quite unexpectedly, inversion of cyclo-
metalation was observed. We attribute this reaction be-
havior to a better donor–acceptor situation in the resulting
iridium(I) product than is the case for the corresponding
iridium(III) complex. Caulton and co-workers reported that
3
= 2.9 Hz, P-C-CH3), 35.5 (dd, JPC = 13.9, JPC = 3.8 Hz, P-C-
CH3), 33.2 (dd, 3JPC = 14.4, JPC = 4.8 Hz, P-C-CH3), 32.3 (d, 2JPC
2
= 4.8 Hz, P-C-CH3), 30.1 (br., P-C-CH3), 30.0 (d, JPC = 2.9 Hz,
2
P-C-CH3), 29.3 (d, JPC = 1.9 Hz, P-C-CH3) ppm. MS (DEI): m/z
= 672 [M+], 636 [M+ – Cl], 580 [M+ – C4H9], 522 [M+ – 2 C4H9].
UV/Vis (pentane): λmax (ε)
= 312 (6962), 426 (3280), 486
(2375 cm–1 m–1) nm. Suitable single crystals of 2 for X-ray diffrac-
tion were obtained from toluene/ethanol solution by cooling to
coordinatively unsaturated iridium(III) complexes [Ir(H)2- –30 °C for 2 d.
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trans-[IrCl(CO)(PtBu2Ph)2] (3): Compound 2 (336 mg, 0.50 mmol)
C6H5), 40.2 (t, JPC = 9.9 Hz, CCH3), 30.9 (s, CCH3) ppm. MS
was dissolved in CH2Cl2 (20 mL), and a slow stream of carbon (DEI): m/z = 702 [M+ – BF4], 442 [M+ – BF4 – PtBu2Ph – NO].
monoxide was bubbled through the solution at room temperature
for ca. 2 min. During this time the color of the solution changed
spontaneously from deep red to nearly colorless. The mixture was
stirred under the resulting CO atmosphere for 30 min. The solution
was concentrated to dryness and the remaining residue crystallized
from CH2Cl2/MeOH affording slightly yellow crystals. Yield:
345 mg (98%). C29H46ClIrOP2 (700.30): calcd. C 49.74, H 6.62, Cl
Crystal-Structure Determination and Refinement: Crystals suitable
for X-ray crystallography of 2 and 4 were obtained as described
above. Crystals were selected by means of a polarization micro-
scope, mounted on the tip of a glass fiber, and investigated with an
OxfordXCalibur and a Bruker Nonius-Kappa CCD diffractometer,
respectively, using graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å). The structures were solved by Direct Methods (SIR97)
[16]
and refined by full-matrix least-squares calculations on F2
5.06; found C 50.02, H 6.43, N 4.93. IR (solid): ν = 1974 (vs, CO)
˜
cm–1. 31P{1H} NMR (109 MHz, CD2Cl2, 20 °C): δ = 51.5 (br. s)
(SHELXL-97).[17] Anisotropic displacement parameters were re-
fined for all non-hydrogen atoms. Details of the crystal data, data
collection, structure solution, and refinement parameters of com-
pounds 2 and 4 are summarized in Table 1. CCDC-1053539 (for 2)
and CCDC-1053540 (for 4) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
ppm. 1H NMR (270 MHz, CD2Cl2): δ = 8.13–8.06 (m, 2 H, C6H5),
7.41–7.34 (m, 3 H, C6H5), 1.54 (pseudo-t, 18 H, PC4H9) ppm.
2
13C{1H} NMR (68 MHz, CD2Cl2, 20 °C): δ = 171.8 (t, JPC
=
12.1 Hz, CO), 136.3 (m, C6H5),133.8 (t, JPC = 19.3 Hz, C6H5,
Cipso), 129.3 (s, C6H5), 126.6 (m, C6H5), 37.5 (t, JPC = 10.4 Hz,
CCH3), 30.8 (s, CCH3) ppm. MS (DEI): m/z = 700 [M+], 643 [M+
–
C4H9], 615 [M+ – C4H9 – CO], 560 [M+ – Cl – CO – C6H5].
trans-[IrCl(NO)(PtBu2Ph)2][BF4](4): Compound
2
(370 mg,
0.55 mmol) was dissolved in CH2Cl2 (20 mL), NO[BF4] (75 mg,
0.64 mmol) was added and the mixture stirred at room temperature
for 2 h resulting in a violet-brown solution. The solvent was evapo-
rated in vacuo and the residue crystallized from CH2Cl2/Et2O
affording dark red crystals suitable for X-ray diffraction. Yield:
395 mg (91%). C28H46BClF4IrNOP2 (789.10): calcd. C 42.62, H
5.88, Cl 4.49, N 1.78; found C 42.75, H 6.05, Cl 4.23, N 1.52. IR
Acknowledgments
The authors are grateful to the Department of Chemistry, Ludwig
Maximilian University Munich, for support of these investigations.
A generous loan of iridium(III) chloride hydrate from Johnson
Matthey plc., Reading, UK, is gratefully acknowledged.
(solid): ν = 1873 (s, NO) cm–1. 31P{1H} NMR (109 MHz, CD2Cl2,
˜
[1] H.-C. Böttcher, M. Graf, M. Karaghiosoff, P. Mayer, Z. Anorg.
Allg. Chem. 2007, 633, 913–916.
20 °C): δ = 52.6 (br. s) ppm. 1H NMR (270 MHz, CD2Cl2): δ =
7.97–7.93 (m, C6H5), 7.58–7.54 (m, C6H5), 1.67 (pseudo-t, 18 H,
PC4H9) ppm. 13C{1H} NMR (68 MHz, CD2Cl2, 20 °C): δ = 135.7
(m, C6H5), 132.2 (m, C6H5), 128.8 (m, C6H5), 126.9 (t, J = 21.4 Hz,
[2] H.-C. Böttcher, M. Graf, K. Merzweiler, Polyhedron 1997, 16,
341–343.
[3] A. C. Cooper, K. G. Caulton, Inorg. Chim. Acta 1996, 251, 41–
51.
[4] H.-C. Böttcher, P. Mayer, Z. Naturforsch. B 2014, 69, 1237–
1240, and references cited therein.
[5] A. C. Cooper, J. C. Huffman, K. G. Caulton, Organometallics
1997, 16, 1974–1978.
[6] P. E. Garrou, Chem. Rev. 1981, 81, 229–266.
[7] C. H. Bushweller, C. D. Rithner, D. J. Butcher, Inorg. Chem.
1984, 23, 1967–1970.
[8] A. C. Cooper, J. C. Bollinger, J. C. Huffman, K. G. Caulton,
New J. Chem. 1998, 22, 473–480.
[9] A. C. Cooper, E. Clot, J. C. Huffman, W. E. Streib, F. Maseras,
O. Eisenstein, K. G. Caulton, J. Am. Chem. Soc. 1999, 121, 97–
106, and references cited therein.
Table 1. Details of the X-ray crystal-data collection and structure
refinement for compounds 2 and 4.
2
4
Empirical formula
C28H46ClIrP2 C28H46BClF4IrNOP2
Mr
672.282
789.093
Crystal system
Space group
monoclinic
P21/c
monoclinic
P21/c
a [Å]
b [Å]
c [Å]
15.3422(7)
13.9596(6)
14.7662(6)
14.2979(6)
13.7215(6)
16.8382(7)
[10] Y. Gloaguen, L. M. Jongens, J. N. H. Reek, M. Lutz, B.
de Bruin, J. I. van der Vlugt, Organometallics 2013, 32, 4284–
4291, and references cited therein.
β [°]
115.1450(10) 93.6298(12)
V /Å3
2862.8(2)
4
3296.8(2)
4
[11] C. A. Reed, W. R. Roper, J. Chem. Soc. C 1969, 1459–1460.
[12] L. Vaska, J. Peone, Inorg. Synth. 1974, 15, 64–68.
[13] A. C. Cooper, K. Folting, J. C. Huffman, K. G. Caulton, Orga-
nometallics 1997, 16, 505–507.
Z
T [K]
100(2)
1.55982(11)
4.883
173(2)
1.58983(10)
4.272
ρcalcd. [gcm–3]
μ [mm–1]
[14] M. Aizenberg, D. Milstein, Organometallics 1996, 15, 3317–
θ range for data collection [°]
Reflections collected
Independent reflections
Rint
3.04 to 27.51 2.97 to 27.57
3322.
51303
6586
78172
7618
[15] A. van der Ent, A. L. Onderdelinden, Inorg. Synth. 1990, 28,
90–91.
[16] A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115–119.
[17] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
Received: April 8, 2015
0.0544
0.0243
0.0480
305
0.0357
0.0194
0.0419
364
R1 [I Ͼ 2σ(I)]
wR2 (all data)
Parameters
Goodness of fit on F2
1.038
1.054
Largest difference peak/hole [eÅ–3] 1.217/–0.573 1.435/–0.499
Published Online: June 22, 2015
Eur. J. Inorg. Chem. 2015, 3323–3327
3327
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