Acceptor CF3PCPH pincer reactivity with (PPh3) 3Ir(CO)H

Article abstract of DOI:10.1039/c1dt10952a

The syntheses of Ir(i) and Ir(iii) complexes incorporating the electron-withdrawing pincer ligand (1,3-C₆H₄(CH ₂P(CF₃)₂)₂) (CF₃PCPH) with (PPh₃)₃Ir(CO)H and subsequent chemistry are reported. Under ambient conditions, reaction of 1 equiv. CF₃PCPH with (PPh₃)₃Ir(CO)H gave the mono-bridged complex [Ir(CO)(PPh₃)₂(H)]₂(μ-CF₃PCPH) (1). Reaction of (PPh₃)₃Ir(CO)H with excess CF ₃PCPH and MeI gave the doubly-bridged complex [Ir(CO)(PPh ₃)(H)]₂(μ-CF₃PCPH)₂ (2), whereas the tetrameric oligomer [Ir(CO)(PPh₃)(H)]₄(μ-CF ₃PCPH)₄ (2-sq) was obtained from a 1:1 ligand:metal mixture in benzene in the presence of excess MeI. At higher temperatures (165 °C) the reaction of CF₃PCPH with (PPh₃) ₃Ir(CO)H afforded the 5-coordinate Ir(i) complex (CF ₃PCP)Ir(CO)(PPh₃) (3). Complex 3 shows mild catalytic activity for the decarbonylation of 2-naphthaldehyde in refluxing diglyme (162 °C). The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt10952a

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PAPER
Acceptor CF PCPH pincer reactivity with (PPh3)3Ir(CO)H†
3
Jeramie J. Adams, Navamoney Arulsamy and Dean M. Roddick*
Received 20th May 2011, Accepted 13th July 2011
DOI: 10.1039/c1dt10952a
The syntheses of Ir(I) and Ir(III) complexes incorporating the electron-withdrawing pincer ligand
(1,3-C6H4(CH2P(CF3)2)2) (CF PCPH) with (PPh3)3Ir(CO)H and subsequent chemistry are reported.
3
Under ambient conditions, reaction of 1 equiv. CF PCPH with (PPh3)3Ir(CO)H gave the mono-bridged
3
CF
complex [Ir(CO)(PPh3)2(H)]2(m-CF PCPH) (1). Reaction of (PPh3)3Ir(CO)H with excess PCPH and
3
3
MeI gave the doubly-bridged complex [Ir(CO)(PPh3)(H)]2(m-CF PCPH)2 (2), whereas the tetrameric
3
oligomer [Ir(CO)(PPh3)(H)]4(m-CF PCPH)4 (2-sq) was obtained from◦a 1 : 1 ligand : metal mixture in
3
benzene in the presence of excess MeI. At higher temperatures (165 C) the reaction of CF PCPH with
3
(PPh3)3Ir(CO)H afforded the 5-coordinate Ir(I) complex (CF PCP)Ir(CO)(PPh3) (3). Complex 3 shows
3
mild catalytic activity for the decarbonylation of 2-naphthaldehyde in refluxing diglyme (162 ◦C).
planar complex trans-(PPh3)2Ir(CO)(H), which is reactive to-
Introduction
ward PCP pincer ligands. Reaction of (PPh3)3Ir(CO)(H) with
Interest in iridium(I) pincer-type RPCP (R = Me, iPr, tBu)
and resorcinol-derived tBuPOCOP complexes continues owing to
their applications as active homogeneous alkane dehydrogenation
catalysts.1–4 We have recently reported the metallation and co-
ordination behavior of Ir(I) and Ir(III) centers with the strongly
◦
iPrPCPH at 60 C readily affords trans-(iPrPCP)Ir(CO)(H)2.6 Mil-
stein has proposed a mechanism to account for the forma-
tion of trans-(iPrPCP)Ir(CO)(H)2 involving the sequential dis-
placement of Ph3P groups to form monomeric unmetallated
CF
3
(iPrPCPH)Ir(CO)(H)(Ph3P). In contrast, reacting
PCPH with
CF
3
p-accepting ligand C6H4(CH2P(CF3)2)2
(
PCPH) to give 4-
(PPh3)3Ir(CO)(H) at ambient temperature for 2 h resulted in
and 5-coordinate (CF PCP)Ir(I) and 6-coordinate ( PCP)Ir(III)
complexes.5 These acceptor pincer systems differ significantly
from donor PCP systems, with an increased tendency toward
coordinative saturation and non-meridional pincer coordination.
CF
3
3
conversion to the CF PCPH-bridged dimer [Ir(CO)(PPh3)2(H)]2(m-
3
CF
3
PCPH) (1) (Scheme 1). The reaction was optimized by scav-
enging released triphenylphosphine: reaction of (PPh3)3Ir(CO)(H)
CF
3
with
PCPH in the presence of excess MeI resulted in the
As part of our initial efforts to access (CF PCP)Ir chemistry, a
3
formation of Ph3PMe+I- and clean formation of 1 after 2 h at
ambient temperature. This phosphine alkylation strategy has been
employed by us previously in the synthesis of CpRu(dfepe)Cl,7 and
exploits the relatively low nucleophilicity of (Rf)2PR phosphines
and their inertness toward phosphonium salt formation compared
to donor phosphine ligands.
range of iridium(I) precursors were surveyed. Milstein reported the
◦
reaction of (PPh3)3Ir(H)(CO) with iPrPCPH at 60 C to generate
trans-(iPrPCP)Ir(CO)H2.6 In this paper, we report the correspond-
CF
3
ing chemistry of (PPh3)3Ir(H)(CO) with
PCPH. Under mild
CF
3
conditions, both dimeric and tetrameric unmetallated PCPH-
bridged products are formed. At elevated temperatures pincer
metallation takes place to form the 5-coordinate Ir(I) complex
The 31P NMR spectrum of 1 exhibits two resonances at 38.7
and 15.0 ppm (2JPP = 141 Hz) in a 1 : 2 ratio, assigned as
CF
CF
3
3
CF
3
(
PCP)Ir(CO)(PPh3). ( PCP)Ir(CO)(PPh3) exhibits reasonable
the bridging
PCPH and Ph3P ligands, respectively. Complex
catalytic activity for the decarbonylation of 2-naphthaldehyde.
coupling observed for the 38.7 ppm resonance is due to fluorine
and phosphorus PPh3 coupling, whereas the Ph3P resonance at
15.0 ppm is a simple doublet due to coupling to a single CF PCPH
3
Results and discussion
phosphorus. A diagnostic doublet of triplets (2JPH = 30 Hz, 2JPH
18 Hz) is observed for the H hydride resonance, consistent with
=
1
Reactivity of CF PCPH with (PPh3)3Ir(CO)(H)
3
CF
3
cis phosphine coupling to the
PCPH and Ph3P ligands. The
1
The Ir(I) precursor (PPh3)3Ir(CO)(H) readily undergoes PPh3
dissociation in solution to give the 4-coordinate d8 square
appearance of only one doublet benzylic H resonance at 3.36
ppm (2JHH = 9.0 Hz) and a single 19F CF3 doublet at -59.8
(2JPF = 60 Hz) confirms mirror symmetry across the
PCPH
CF
3
ligand. A single n(CO) band was observed at 1960 cm-1. Bridg-
Department of Chemistry, University of Wyoming, Box 3838, Laramie,
Wyoming, 82071, USA
† CCDC reference numbers 826940–826942. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt10952a
ing CF PCPH complexes [PtMe2]2(m- PCPH)2 and [(cod)IrCl(m-
CF
3
3
CF
3
PCPH)]n have been observed by our group as pre-metallation
intermediates.5a,8 Bridging unmetallated PCPH binding modes
10014 | Dalton Trans., 2011, 40, 10014–10019
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Scheme 1
in [(cod)Rh(Cl]2(m-PhPCPH) and [(PhPCP)Rh(H)Cl]2(m-PhPCPH)
have also been reported.9
During the course of the reaction to produce 1, a small amount
CF
3
of the doubly-bridged
PCPH dimer [(Ph3P)Ir(H)(CO)]2(m-
CF
3
PCPH)2 (2) was observed and subsequently removed by recrys-
tallization. 2 was prepared in reasonable yield by increasing the
equivalents of CF PCPH used and increasing the reaction time from
3
CF
2 to 48 h. Key 31P NMR features for 2 are a PCPH multiplet
3
at 34.7 ppm and a Ph3P triplet at 11.0 ppm which integrates as
1
2 : 1. A diagnostic H for the hydride ligand in 2 appears as a
2
triplet of doublets at -11.88 (2JPH = 26 Hz, JPH = 16 Hz). The
n(CO) for 2 is 1992 cm-1, 32 cm-1 higher than observed for 1
and consistent with decreased electron density due to PPh3 loss
and replacement by CF PCPH. n(CO) values for both 1 and 2 are
3
Fig. 1 Molecular structure of [(PPh3)Ir(H)(CO)]2(m-CF PCPH)2 (2) with
3
considerably higher than n(CO) reported for the parent complex
(PPh3)3Ir(CO)H (1930 cm-1).10 Solutions of 1 slowly decompose to
form 2 under ambient air in a CH2Cl2–methanol solution, together
with the formation of OPPh3, which was identified by 31P NMR.
The degree of aggregation of 2 in the solid state is sensitive to
crystallization conditions. Recrystallization of 2 from CH2Cl2–
MeOH gave a doubly-bridged dimer, as determined by X-ray
diffraction (Fig. 1). Crystals grown by slow evaporation from
an NMR scale reaction between (PPh3)3Ir(CO)(H), one equiv.
50% thermal ellipsoids. All hydrogens and several CF3 groups are omitted
for clarity. Selected bond lengths (A): Ir(1)–P(1): 2.2369(14), Ir(1)–P(2):
˚
2.2401(13), Ir(1)–P(3): 2.3170(13), Ir(1)–C(25): 1.925(6), C(25)–O(1):
1.140(7), Ir(2)–P(4): 2.2405(14), Ir(2)–P(5): 2.2302(14), Ir(2)–P(6):
2.3242(13), Ir(2)–C(26): 1.922(6), C(26)–O(2): 1.134(7). Selected bond
angles (◦): P(1)–Ir(1)–P(2): 120.15(5), P(1)–Ir(1)–P(3): 119.98(5),
P(2)–Ir(1)–P(3): 114.21(5), C(25)–Ir(1)–P(1): 97.14(19), C(25)–Ir(1)–P(1):
97.14(19), C(25)–Ir(1)–P(2): 99.36(18), C(25)–Ir(1)–P(3): 97.41(18),
P(5)–Ir(2)–P(4): 119.10(5), P(5)–Ir(2)–P(6): 113.18(5), P(4)–Ir(2)–P(6):
121.87(5), C(26)–Ir(1)–P(4): 97.57(19), C(26)–Ir(1)–P(5): 99.03(19),
C(26)–Ir(1)–P(6): 97.72(19).
CF
3
PCPH, and excess MeI in benzene, however, produced the
tetrameric square [(Ph3P)Ir(H)(CO)]4(m-CF PCPH)4 (2-sq) (Fig.
2). In both cases the
3
CF
3
PCPH : metal ratio is 1 : 1 and the
metal coordination environment is essentially identical. The key
difference between the syntheses of 1 and 2-sq is the time of
reaction: 1 is favored over a shorter timescale (2 h), whereas at
phosphine carbonyl complex (CF PCP)Ir(CO)(PPh3) (3) is ob-
3
tained, whereas the 6-coordinate Ir(III) dihydride complex trans-
(iPrPCP)Ir(CO)(H)2 is formed using iPrPCPH. Insight into this
difference is provided by our previous report of facile elimination
CF
3
longer times (48 h) the remaining 0.5 equiv. of free
incorporated to form the tetrameric complex.
PCPH is
PCPH with (PPh3)3Ir(CO)H occurs ~75 ◦C
CF
3
of H2 from the dihydride complex trans-(CF PCP)Ir(CO)(H)2
3
Metallation of
higher than reported for iPrPCPH, and the nature of the product
and the unusual stability of 5-coordinate (CF PCP)Ir(CO)(L)2
3
CF
3
products.5b Formation of trans-(CF PCP)Ir(CO)(H)2, in the
3
formed is also distinct: for
This journal is
PCPH, the 5-coordinate Ir(I)
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CF3
Fig.
3
Molecular structure of
(
PCP)Ir(CO)(PPh3) (3) with
50% thermal ellipsoids. Hydrogen atoms are omitted for clarity.
˚
3
Selected bond lengths (A): Ir(1)–P(1): 2.2290(5); Ir(1)–P(2): 2.2268(5);
Fig.
2
Molecular structure of [(PPh3)Ir(H)(CO)]4(m-CF PCPH)4
Ir(1)–P(3): 2.3734(4); Ir(1)–C(1): 2.1318(17); Ir(1)–C(13): 1.9036(19);
C(13)–O(1): 1.138(2). Selected bond angles (◦): P(1)–Ir(1)–P(2):
(2-sq) with 50% thermal ellipsoids. All hydrogens and selected
fluorine atoms are omitted for clarity. Selected bond lengths (A):
˚
128.042(18);
P(1)–Ir(1)–P(3):
114.577(16);
P(2)–Ir(1)–P(3):
Ir(1)–C(25): 1.920(8), Ir(1)–P(2): 2.222(2), Ir(1)–P(1): 2.241(2),
Ir(1)–P(3): 2.332(2), Ir(1)–Ir(2): 9.3530(5), Ir(2)–C(26): 1.935(8),
Ir(2)–P(6): 2.228(2), Ir(2)–P(4): 2.246(2), Ir(2)–P(5): 2.326(2). Selected
bond angles (◦): C(25)–Ir(1)–P(2): 97.0(2), C(25)–Ir(1)–P(1): 98.7(2),
P(2)–Ir(1)–P(1): 118.71(7), C(25)–Ir(1)–P(3): 94.1(2), P(2)–Ir(1)–P(3):
119.26(7), P(1)–Ir(1)–P(3): 118.09(7), C(26)–Ir(2)–P(6): 97.9(2),
C(26)–Ir(2)–P(4): 98.4(2), P(6)–Ir(2)–P(4): 119.14(7), C(26)–Ir(2)–P(5):
92.5(2): P(6)–Ir(2)–P(5): 119.71(7), P(4)–Ir(2)–P(5): 117.59(7).
110.783(16); C(13)–Ir(1)–C(1): 171.79(7); C(13)–Ir(1)–P(1): 99.65(6);
C(13)–Ir(1)–Pt(2): 98.61(6); C(1)–Ir(1)–P(1): 76.79(5); C(1)–Ir(1)–P(2):
78.34(5).
doublets (2JHH = 16 Hz), and the appearance of separate CF3
19F multiplets at -55.2 and -62.2 ppm. A single n(CO) band is
observed at 2011 cm-1.
CF
3
reaction of
PCPH with (PPh3)3Ir(CO)H would lead to rapid
Reactivity of (CF PCP)Ir(CO)(PPh3) (3) with MeI
3
H2 loss and trapping by Ph3P.
It is not known whether the singly- or doubly-bridged complexes
2 or 1 are direct metallation precursors for 3. 3◦1P spectra of a
While methyl iodide is used in the syntheses of compounds 1 and
2 to sequester released Ph3P at ambient temperature, subsequent
mixture of (PPh3)3Ir(CO)(H) and CF PCPH at 150 C in mesitylene
thermal reaction of (CF PCP)Ir(CO)(PPh3) with MeI also occurs.
3
3
after 1 h show a 16 : 1 : 2 mixture of 1 : 2 : 3. After 3 h a 1 : 1 mixture
of 1 : 3 is observed with only a trace amount of 2, and after 48 h
the reaction mixture shows 95+% conversion to 3 and only a
trace amount of 1. Preparative scale optimization for complex
3 was accomplished by refluxing (PPh3)3Ir(CO)(H) with 1 equiv.
Reaction of 3 with excess CH3I (~60 equiv.) was monitored by 31
P
NMR. Quantitative conversion to a single product was achieved
after 1 h at 155 ◦C in mesitylene; thermolysis at 100 ◦C resulted in
90% conversion to the same product after 25.5 h. The product is
tentatively formulated as the anionic Ir(III) diiodide complex cis-
CF
CF
-
+
1
3
3
PCPH in mesitylene for 48 h, followed by Ph3P sequestration
(
PCP)Ir(CH3)(I)2 Ph3PMe (4) (Scheme 2). H NMR spectra
using excess MeI at ambient temperature for 2 h.
show diastereotopic benzylic protons at 4.23 and 3.74 ppm (2JHH
=
=
=
CF
3
3
31P spectra of 3 show a
PCP multiplet at d 51.1 and a
17 Hz, JPH = 5 Hz), and an Ir–CH3 triplet at 1.60 ppm (3JPH
characteristic Ph3P triplet at d -0.9 (2JPP = 144 Hz). A loss
6 Hz). A diagnostic methyl doublet appears at 2.74 ppm (2JPH
of symmetry across the meridional (CF PCP)Ir plane has been
13 Hz) due to the Ph3PMe+ cation. A trace amount of the MeI
3
confirmed by X-ray diffraction (Fig. 3) and is reflected in 1H NMR
spectra, which show a diastereotopic pair of benzyl methylene
oxidative addition product (CF PCP)Ir(CO)MeI (5) was identified
3
by 1H NMR.5b The intermediacy of complex 5 in the formation of
Scheme 2
10016 | Dalton Trans., 2011, 40, 10014–10019
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(1)
˚
˚
4 is consistent with the results of a separate experiment: reaction◦of
P bond lengths average 2.235 A, 0.09 A less than the Ir–PPh3 bond
lengths.
CF
+ -
3
(
PCP)Ir(CO)MeI with one equiv. MePPh3 I in C6D6 at 100 C
CF
CF
3
3
formed 4 in ~70% yield after 3 h. Under the sealed NMR tube
conditions employed, the build-up of released CO established a
1 : 2.5 equilibrium ratio of 3 to 4.
(
PCP)Ir(CO)(PPh3) (3) has Ir–P
PCP bond lengths av-
˚
eraging 2.228 A, on the lower end of the Ir–P range for other
5-coordinate (CF PCP)Ir(L1)(L2) complexes [L1 = L2 = CO, dfmp
3
((C2F5)2PMe); L1 = C2H4 and L2 = PhCN, and (CF PCP)Ir(LL),
3
where LL = cod, and (C2F5)2PCH2CH2P(C2F5)2] which average
2.252 A. 3 has a P–Ir–P pincer angle of 128.042(18)◦ that
5b
Aldehyde decarbonylation studies
˚
◦
falls between reported values for (CF PCP)Ir(CO)2 (130.3 ) and
3
Stoichiometric aldehyde decarbonylation using Rh(PPh3)3Cl11 has
been made catalytic by suitable tuning of the metal coordination
environment: The complexes (dppp)RhCl, [(Me3P)(CO)RhCl]2,
and (cod)Ir(PPh3)Cl are currently the most active neutral ho-
mogenous catalysts for aldehyde decarbonylation under relatively
mild conditions.12,13 Stoichiometric decarbonylation of alkyl for-
mates and alkynyl aldehydes has also been recently carried out
using the PCP containing motif (tBuPCP)Rh(N2).14 The ability
◦
CF
3
(
PCP)Ir(P(C2F5)2Me)2 (124.2 ).
Summary
Metallation of the strong p-acceptor pincer ligand precursor
CF
3
PCPH occurs under more rigorous thermal conditions than
the donor iPrPCPH to give the 5-coordinate Ir(I) complex
of the (CF PCP)Ir(I) fragment to undergo oxidative addition
3
CF
3
(
PCP)Ir(CO)(PPh3) instead of a dihydride complex analogous
trans-(iPrPCP)Ir(CO)(H)2. Formation of complex 3 is assumed
and reversible Ir(I) 4- and 5-coordination (including facile CO
dissociation from (CF PCP)Ir(CO)2) suggested the possibility of
5b
3
CF
3
to be preceded by bridging
PCPH intermediates such as 1
catalytic aldehyde decarbonylation by (CF PCP)Ir(CO)(PPh3).
3
and 2. The formation of the dimeric unmetallated pincer 2
Monitoring the reaction of (CF PCP)Ir(CO)(PPh3) (5 mol%)
3
CF
3
closely parallels the reaction of
PCPH with the platinum
with 2-naphthaldehyde in refluxing diglyme (152 ◦C, 590 torr)
by 1H NMR showed 1.5 equiv. naphthylene formed after 6 h
(0.25 TO/h) and 4.5 equiv. after 24 h (0.19 TO/h) (eqn (1)).
After 24 h the major metal species observed was > 95% 3 and
precursor (cod)Pt(Me)2 to form cis-[(m-CF PCPH)PtMe2]2: both
systems accommodate bridging PCPH groups with cis phosphine
coordination at each metal center. The catalytic activity of 3 for
the decarbonylation of 2-naphthaldehyde suggests that the tuning
of (CF PCP)Ir(CO)(L) by suitable variation of L may lead to more
efficient catalysts for decarbonylation and related processes.15
8
3
CF
3
ca. 3% of uncoordinated
PCPH was identified by 19F NMR.
3
Catalytic activity over longer timescales was not examined. Under
similar conditions in diglyme, complex 3 has lower activity than
RhCl3·3H2O/dppp (0.75 TO/h) and [Ir(cod)(m-Cl)]2/PPh3: (3.07
TO/h).
Experimental section
General procedures
Crystallographic studies
All manipulations were conducted under N2 or vacuum using
high-vacuum line and glovebox techniques unless otherwise noted.
All ambient pressure chemistry was carried out under a pressure
of approximately 590 torr (elevation ~2195 m). All solvents
were dried using standard procedures and stored under vacuum.
Aprotic deuterated solvents used in NMR experiments were dried
CF
3
Hydride ligands for the doubly-bridged
PCPH complexes
[(PPh3)Ir(H)(CO)]2(m-CF PCPH)2 (2) and [(PPh3)Ir(H)(CO)]4(m-
3
CF
3
PCPH)4 (2-sq) were not located, but presumably (based on
2
cis JPH couplings) are trans to the carbonyl ligands in both
structures. The resulting metal coordination geometries are dis-
torted trigonal bipyramidal with equatorial phosphine ligands
˚
over activated 3 A molecular sieves. Elemental analyses were
CF
3
(two
PCPH groups, one Ph3P) and axial CO and hydride
performed by Columbia Analytical Services. NMR spectra were
obtained with a Bruker DRX-400 instrument using 5 mm NMR
tubes fitted with Teflon valves (Chemglass, CG-–512). 31P spectra
were referenced to an 85% H3PO4 external standard. 19F spectra
were referenced to CF3CO2CH2CH3 (d -75.32) and CF3C6H5
external standards. CO gas was purchased from Airgas and used
without further purification. All other reagents were purchased
from Aldrich and were used without further purification. The
ligands. Two of the three P–Ir–P angles about each iridium
center for 2 are nearly ideal, ranging between 119.10(5)–121.87(5)◦
with the remaining P–Ir–P angle (subtended by Ph3P and one
CF
3
of the
PCPH ends) somewhat compressed at 114.21(5) and
113.18(5)◦. Interestingly, the P–Ir–P angles for the tetramer 2-sq
all fall between 117.59(7) and 119.71(7)◦ and reflect an easing of
intramolecular steric interactions and adoption of a less distorted
trigonal bipyramidal coordination environment. In keeping with
CF
3
PCPH and (PPh3)3Ir(CO)H were prepared according to litera-
previous perfluoralkyl-substituted phosphine trends, CF PCPH Ir–
ture methods.8,10
3
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[Ir(CO)(PPh3)2(H)]2(l-CF PCPH) (1)
temperature MeI (1 mL) was added and the reaction mixture
3
+
was stirred for 2 h. MePPh3 I- was filtered off and the filtrate
(PPh3)3Ir(H)(CO) (0.300 g, 0.298 mmol), CF PCPH (92 ml, 0.145 g,
0.328 mmol), and excess CH3I (1 mL) were dissolved in 20 mL
of C6H6 and stirred for 2 h at ambient temperature, during which
3
was evaporated to dryness to give a white residue. The residue
was triturated with hexanes and the resulting white solid was
collected (0.308 g, 56% yield). Crystals suitable for single crystal
X-ray diffraction were grown by the slow evaporation from a 1 : 2
CH2Cl2 : hexanes solution. Anal. Calcd for C31H22P3F12O1Ir: C,
40.26%; H, 2.51%. Found: C, 40.08%; H, 2.38%. 1H NMR (C6D6,
400.13 MHz, 20 ◦C): d 7.10 (m, 6H; PPh3), 6.92 (m, 9H, PPh3), 6.70
(t, 3JHH = 8 Hz, 1H, p-C6H3(CH2P(CF3)2)2), 6.54 (d, 3JHH = 8 Hz,
2H; m-C6H3(CH2P(CF3)2)2), 3.35 (m, 2H; C6H3(CH2P(CF3)2)2),
time white MePPh3 I- precipitated. MePPh3 I- was removed by
filtration and the filtrate was evaporated to dryness to give a
white residue. The residue was triturated with hexanes, and the
resulting white solid was collected. The product was purified by
dissolving in dichloromethane (ca. 3 mL) and ethanol (ca. 15 mL)
and slowly removing the dichloromethane under vacuum to give a
white microcrystalline precipitate (0.180 g, 65% yield). Anal. Calcd
for C86H70P6F12O2Ir2: C, 53.35%; H, 3.65%.◦Found: C, 52.98%; H,
+
+
2
2.37 (d, JHH = 16 Hz, 2H; C6H3(CH2P(CF3)2)2). 31P{H} NMR
(C6D6, 161.97 MHz, 20 ◦C): d 50.0 (m, 2P; C6H3(CH2P(CF3)2)2),
-2.4 (t, 2JPP = 144 Hz, 1P; PPh3). 19F NMR (C6D6, 376.50 MHz,
20 ◦C): d -58.0 (m, 6F, CF3), -65.1 (m, 6F, CF3). IR (CH2Cl2,
cm-1): n(CO) = 2011 cm-1.
1
3.65%. H NMR (C6D6, 400.13 MHz, 20 C): d 7.48 (br. s, 1H;
C6H4(CH2P(CF3)2)2), 7.29 (m, 24H; ortho PPh3 H’s), 6.94 (m, 39H;
overlapping para, meta PPh3 H’s and C6H4(CH2P(CF3)2)2), 3.36 (d,
2JHP = 9 Hz, 4H; C6H4(CH2P(CF3)2)2), -10.95 (dt, 2JPH = 30, 18 Hz,
2H; IrH). 31P{H} NMR (C6D6, 161.97 MHz, 20 ◦C): d 38.7 (tsep,
cis-(CF PCP)Ir(CH3)(I)2 MePPh3 (4)
-
+
3
2
2JPP = 141 Hz, JPF = 66 Hz, 2P; C6H4(CH2P(CF3)2)2), 15.0 (d,
◦
2JPP = 141 Hz, 4P, PPh3). 19F NMR (C6D6, 376.50 MHz, 20 C):
A 5 mm NMR tube was charged with 26 mg (0.028 mmol)
of 3, 61 equiv. (0.244 g, 0.11 mL) of MeI, and 0.5 mL of
C6D6. The reaction mixture was heated to 100 ◦C and moni-
tored by NMR. After 25.5 h conversion to ~90% 4 and ~10%
d -61.3 (d, 2JPF = 64 Hz, 12F; CF3). IR (CH2Cl2, cm-1): n(CO) =
1960 cm-1.
CF
3
(
PCP)Ir(CH3)(CO)I had occurred. 1H NMR (C6D6, 400.13
[(PPh3)Ir(H)(CO)]2(l-CF PCPH)2 (2)
3
MHz, 20 ◦C): d 7.23–7.12 (m, 15H; CH3P(C6H5)3), 6.88 (d, 3JHH
8 Hz, 2H, m-C6H3(CH2P(CF3)2)2), 6.80 (t, JHH = 8 Hz, 1H; p-
C6H3(CH2P(CF3)2)2), 4.26 (dt, JHH = 17 Hz, JPH = 5 Hz, 2H;
C6H3(CH2P(CF3)2)2), 3.78 (dt, JHH = 17 Hz, JPH = 4 Hz, 2H;
=
(PPh3)3Ir(H)(CO) (0.200 g, 0.198 mmol), CF PCPH (92 ml, 0.145 g,
0.328 mmol) and 1 mL MeI were dissolved in 20 mL of benzene
and the solution was stirred at room temperature for 48 h.
MePPh3 I- precipitated and was removed by filtration. The filtrate
was evaporated to dryness to give a white residue which was
dissolved in 5 mL of dichloromethane and 20 mL of MeOH. The
product was precipitated by reducing the volume of the solution
under vacuum to about 5 mL to give a white microcrystalline
solid which was collected by filtration (0.095 g, 50% yield).
Anal. Calcd for C62H48P6F24O2Ir2: C, 40.17%; H, 2.61%. Found:
C, 40.19%; H, 2.80%. 1H NMR (C6D6, 400.13 MHz, 20 ◦C):
d 7.32 (m, 12H; PPh3), 7.22 (s, 2H; C6H4(CH2P(CF3)2)2), 7.04
3
3
2
3
2
3
+
2
C6H3(CH2P(CF3)2)2), 2.77 (d, JHP = 13 Hz, 3H; CH3P(C6H5)3),
1.63 (t, JPH = 6 Hz, 3H; Ir-CH3). 31P{H} NMR (C6D6, 161.97
3
MHz, 20 ◦C): d 45.9 (X portion of an A6A6¢XX¢ spin system (due
to 4JFP π 0), 2P; C6H3(CH2P(CF3)2)2), 22.9 (s, 1P; CH3P(C6H5)3 ).
+
19F NMR (C6D6, 376.50 MHz, 20 ◦C): d -50.3 (m, 6F, CF3), -51.3
(m, 6F, CF3).
Reaction of (CF PCP)Ir(CH3)(CO)(I) with MePPh3 I
+
-
3
3
A 5 mm NMR tube was charged with 37 mg (0.056 mmol) of
(t, JHH = 8 Hz, 6H; p-PPh3), 6.95 (m, 12H; PPh3), 6.89 (d,
CF
3
3JHH = 8 Hz, 4H; C6H4(CH2P(CF3)2)2), 6.80 (t, JHH = 8 Hz, 2H;
3
(
PCP)Ir(CO), 0.15 mL (2.41 mmol) of MeI, and 0.5 mL of C6D6
and was allowed to stand for 24 h to give quantitative conversion
C6H4(CH2P(CF3)2)2), 3.29 (m, 8H; C6H4(CH2P(CF3)2)2), -11.88
to (CF PCP)Ir(CH3)(CO)I, as judged by NMR.5b The volatiles were
(td, 2JPH = 26, 16 Hz, 2H; IrH). 31P{H} NMR (C6D6, 161.97 MHz,
3
removed and 22 mg (0.054 mmol) of MePPh3 I- and 0.5 mL of
+
◦
20 C): d 34.7 (m, 4P, CF PCPH), 11.8 (t, JPP = 120 Hz, 2P, PPh3).
2
3
C6D6 were added and the mixture was warmed to 100 ◦C. A
◦
19F NMR (C6D6, 376.50 MHz, 20 C): d -58.5 (m, 12F, PCF3),
1 : 2.5 mixture of (CF PCP)Ir(CH3)(CO)I to 4 was reached after
-59.5 (m, 12F, PCF3). IR (CH2Cl2, cm-1): n(CO) = 1992 cm-1.
3
3 h. No further conversion to 4 was achieved after heating for
24 h, presumably due to an equilibrium established with evolved
CO.
[(Ph3P)Ir(H)(CO)]4(l-CF PCPH)4 (2-sq)
3
A 5 mm NMR tube was charged with (PPh3)3Ir(CO)H (0.015 g,
0.015 mmol), PCPH (4.6 ml, 0.0074 g, 0.016 mmol), 40 equiv.
MeI and 0.5 mL C6D6 and allowed to stand undisturbed for
48 h, giving a colorless solution and MePPh3 I- as a white
CF
3
Decarbonylation of 2-naphthaldehyde using
CF
3
(
PCP)Ir(CO)(PPh3) (3)
+
In a typical experiment 3 (0.025 mmol, 0.023 g) and 2-
naphthaldehyde (0.50 mmol, 0.078 g) were dissolved in 1 mL
of unpurified degassed diglyme, and the reaction mixture was
refluxed (152 ◦C at 580 torr) under flowing N2 for 6 or 24 h,
then cooled to ambient temperature. Turnovers were quantified
precipitate. Solution NMR spectra for 2-sq were identical to 2.
Suitable crystals suitable for X-ray diffraction were grown by slow
evaporation of the C6D6 solution.
CF
3
(
PCP)Ir(CO)(PPh3) (3)
by integration of product naphthylene resonances against CF PCP
3
CF
3
(PPh3)3Ir(H)(CO) (0.600 g, 0.595 mmol) and
PCPH (184 ml,
aryl protons. 31P and 19F NMR identified 3 as the major (>95%)
CF
CF
3
3
0.290 g, 0.656 mmol) were dissolved in 15 mL of mesitylene and
the solution was refluxed under N2 for 24 h. After cooling to room
(
PCP)Ir species with a small amount (~3%) of
PCPH
observed by 19F NMR.
10018 | Dalton Trans., 2011, 40, 10014–10019
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X-ray crystallography
and A. S. Goldman, J. Am. Chem. Soc., 2004, 126, 13044; (e) K. Krogh-
Jespersen, M. Czerw, K. Zhu, B. Singh, M. Kanzelberger, N. Darji, P.
D. Achord, K. B. Renkema and A. S. Goldman, J. Am. Chem. Soc.,
2002, 124, 10797; (f) K. Krogh-Jespersen, M. Czerw, N. Summa, K. B.
Renkema, P. D. Achord and A. S. Goldman, J. Am. Chem. Soc., 2002,
124, 11404.
3 (a) S. Kundu, Y. Choliy, G. Zhuo, R. Ahuja, T. J. Emge, R.
Warmuth, M. Brookhart, K. Krogh-Jespersen and A. S. Goldman,
Organometallics, 2009, 28, 5432; (b) I. Goettker-Schnetmann, P. White
and M. Brookhart, J. Am. Chem. Soc., 2004, 126, 1804.
4 B. L. Dietrich, K. I. Goldberg, D. M. Heinekey, T. Autrey and J. C.
Linehan, Inorg. Chem., 2008, 47, 8583.
The X-ray diffraction data for complexes 2, 2-sq, and 3 were
measured at 150 K on a Bruker SMART APEX II CCD area
detector system equipped with a graphite monochromator and a
Mo-Ka fine-focus sealed tube operated at 1.5 kW power (50 kV, 30
mA). Crystals were attached to glass fibers or cryoloops (Hampton
Research Corp.) using Paratone N oil. Collection and refinement
details are included in the supplementary material.
5 (a) J. J. Adams, A. Lau, N. Arulsamy and D. M. Roddick,
Organometallics, 2011, 30, 689; (b) J. J. Adams, N. Arulsamy and D. M.
Roddick, Organometallics, 2011, 30, 697.
6 B. Rybtchinski, Y. Ben-David and D. Milstein, Organometallics, 1997,
16, 3786.
7 M. S. Keady, J. D. Koola, A. C. Ontko, R. K. Merwin and D. M.
Roddick, Organometallics, 1992, 11, 3417.
Acknowledgements
We thank the National Science Foundation (CHE-0457435) and
DOE/EPSCoR (DE-FG02-05ER46185) for financial support.
8 J. J. Adams, A. Lau, N. Arulsamy and D. M. Roddick, Inorg. Chem.,
2007, 46, 11328.
9 J. Yao, W. T. Wong and G. Jia, J. Organomet. Chem., 2000, 598, 228.
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15 For example, (CF PCP)Ir(CO)2 is a more active 2-naphthaldehyde
3
decarbonylation catalyst (~1.2 TO h-1, diglyme reflux). J. J. Adams,
and D. M. Roddick, manuscript in preparation.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10014–10019 | 10019
©