Iridium(I) and rhodium(I) carbonyl complexes with the bis(3- tert -butylimidazol-2-ylidene)borate ligand and unusual B-H fluorination

Article abstract of DOI:10.1021/om200036w

Iridium(I) and rhodium(I) carbonyl complexes [H₂B(Im ^tBu)₂]M(CO)₂ (M = Ir, 1a; M = Rh, 1b) with the bis(3-tert-butylimidazol-2-ylidene)borate ligand have been prepared. Reactions of 1a,b with [FeCp₂][PF₆] or AgPF₆ unexpectedly yielded the B-F products [F₂B(Im^tBu)₂]M(CO) ₂ (M = Ir, 2a; M = Rh, 2b), respectively. IR peaks of the CO ligands have been used to evaluate the electronic effects of bis(3-tert-butylimidazol-2- ylidene)borate and its fluorinated derivative.

Full text of DOI:10.1021/om200036w

ARTICLE
pubs.acs.org/Organometallics
Iridium(I) and Rhodium(I) Carbonyl Complexes with the Bis(3-tert-
butylimidazol-2-ylidene)borate Ligand and Unusual B-H Fluorination
†
†
†
,†
‡
Fei Chen, Jia-Feng Sun, Tao-Yuan Li, Xue-Tai Chen,* and Zi-Ling Xue
†
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures,
School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People’s Republic of China
‡
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
S Supporting Information
b
ABSTRACT: Iridium(I) and rhodium(I) carbonyl complexes
t
2 2 2
[
H B(Im Bu) ]M(CO) (M = Ir, 1a; M = Rh, 1b) with the
bis(3-tert-butylimidazol-2-ylidene)borate ligand have been pre-
pared. Reactions of 1a,b with [FeCp ][PF ] or AgPF unex-
2
6
6
t
pectedly yielded the B-F products [F B(Im Bu) ]M(CO)
M = Ir, 2a; M = Rh, 2b), respectively. IR peaks of the CO
2
2
2
(
ligands have been used to evaluate the electronic effects of
bis(3-tert-butylimidazol-2-ylidene)borate and its fluorinated derivative.
he coordination and organometallic chemistry of N-hetero-
cyclic carbenes has been of intense interest since the
synthesis and characterization of iridium(I) and rhodium(I)
carbonyl complexes with the bis(3-tert-butylimidazol-2-ylide-
1
T
isolation of the first stable N-heterocyclic carbene (NHC),
ne)borate ligand and the unusual reactivity of the BH moiety
2
2
imidazol-2-ylidene, by Arduengo and co-workers. Many biden-
in the ligand.
tate or polydentate NHC-containing ligands have been designed
and used in the preparation of new organometallic complexes
with novel catalytic properties, among which bidentate bis-
3
’ RESULTS AND DISCUSSION
(
NHC) ligands such as bis(NHC)methylene (A, Chart 1) have
Synthesis and NMR Spectra of 1a,b. Deprotonation of the
4
t
þ -
2
attracted particular attention due to their chelating effect.
ligand precursor salt H B( BuImH) I with 2 equiv of LDA in
2
The bis(pyrazolyl)borate (Bp) ligand (B, Chart 1) has been
THF afforded the corresponding lithium complex H B-
2
5
t
widely used in coordination and organometallic chemistry. Ir
and Rh complexes supported by Bp have exhibited novel
reactivities and catalytic activities.
cases, the Bp ligand acts as an innocent and unreactive ligand
during the reaction process. However, several examples of the
functionalization of the BH moiety have been reported.
More recently, Messerle et al. reported unusual hydride substitu-
(
BuIm) Li in situ, which was then treated with [Ir(CO) Cl]
2 2 2
t
or [Rh(CO) (acac)] to obtain [H B(Im Bu) ]M(CO) (M = Ir,
2
2
2
2
5g,h,j
In most of the reported
1
a; M = Rh, 1b) in good yields (Scheme 1).
Complexes 1a,b are soluble in common organic solvents but
decompose slowly into undefined products in halogenated
5g,6
2
solvents such as CH Cl and CHCl after several days under
2
2
3
N . 1a,b also decompose slowly in solution and in the solid state
2
1
tion by X (X = F, Cl, OH) in the B-H bonds of the chelat-
ing bis(pyrazolyl)borate ligand in the ruthenium complex
after 2 weeks in air. The H NMR spectra of 1a,b do not exhibit
the 2H-imidazolium proton signal at 9.15 ppm, indicating the
7
1
3
[
RuTp(Bp)PPh3].
coordination of the carbene carbon to the metal atom. The
C
The bidentate bis(NHC) ligands bis(3-alkylimidazol-2-ylide-
NMR signals of the carbene carbon atoms in 1a,b (169.0 and
i
1
ne)dihydroborate, [H B(R-ImH) ] (R = Me, Et, Pr; C,
2
2
171.6 ppm, respectively, with J
= 45.0 Hz) are located in
Rh-C
Chart 1), which possess both the Bp framework and the strong
electron-donating ability of NHC ligands, were first reported by
Fehlhammer and co-workers in 2001. They also employed these
ligands in the preparation of Li(I), Pd(II), Pt(II), and Au(I)
11
the characteristic range reported for Ir(I)/Rh(I)-NHC com-
13
plexes. The signal of the CO carbon atom was observed at
1
1
83.2 ppm for 1a and 190.4 ppm for 1b with J
= 58.1 Hz.
Rh-C
11
The B NMR data reflect significant changes from the imida-
8
9
10
10
complexes. Since then Li(I), Ca(II), Sr(II), and Ni(II)
zolium salt (-7.60 ppm) to the carbene complexes (-3.08
ppm, 1a; -3.97 ppm, 1b), further indicating that the carbene
carbon coordinates to the metal atom.
complexes with the bis(imidazol-2-ylidene)borate ligand have
been also prepared and characterized. It is surprising that no
rhodium or iridium complex with the bis(imidazol-2-ylidene)bo-
rate ligand has been reported yet, considering that related Rh and
Ir complexes with the Bp ligand are well-known.
Reactions of 1a,b with [FeCp ][PF ] and the Formation of
2
6
2
a,b. Initially reactions of 1a,b with 2 equiv of [FeCp ][PF ]
2 6
We have continued our research in the organometallic chem-
istry of N-heterocyclic carbenes, and we report here the
Received: January 15, 2011
Published: March 14, 2011
12
r 2011 American Chemical Society
2006
dx.doi.org/10.1021/om200036w
|Organometallics 2011, 30, 2006–2011

Organometallics
ARTICLE
1
Chart 1
with J
= 24.9 Hz (2a) or 25.4 Hz (2b). Similar patterns have
F-B
been observed in the ruthenium complexes with the bis-
7
(
pyrazolyl)difluoroborate ligand.
Obviously the activation of the B-H bond occurred in this
transformation reaction. In reported examples, the B-H func-
tionalization in poly(pyrazolyl)borate metal complexes typically
requires the activation of the B-H bond via the B-H-metal
6c,14
interaction.
To gain a further insight into the mechanism of
the boron-hydride substitution, some control studies were
carried out by the reactions of 1a,b with other hexafluorophos-
phate salts such as KPF , NH PF , and 1-butyl-3-methylimida-
Scheme 1
6
4
6
zolium hexafluorophosphate. No fluoride substitution product
was obtained in Et O after 1 day of the reactions at room
2
temperature with these hexafluoroborate salts. Only the starting
material was recovered. However, when 1a,b were reacted with
AgPF or AgBF , the fluorine-substituted products 2a,b were
6
4
obtained, respectively. As in the isolation of FeCp in the
2
reactions of 1a,b with [FeCp ][PF ], the reduced byproduct
2
6
þ
Scheme 2
Ag was obtained as a gray precipitate. Since [FeCp ] and Ag(I)
2
are both Lewis acids, it is assumed that the fluorination of B-H
was facilitated by interaction of boron hydrides in
t
2 2 2 2
þ
[
H B(Im Bu) ]M(CO) (M = Ir, Rh) with the [FeCp ] or
Ag(I) cations. Due to strong metal-NHC bonding, it is quite
possible that no dissociation of the metal-NHC bond occurred
in the reaction process. Furthermore, since the two carbonyl
groups are retained in the products 2a,b, it is reasonable to
assume that no dissociation of the metal-CO bond took place in
the reactions. Therefore, the boron fluorination is probably a
were used to probe their reactivities. We had expected the
result of the direct interaction between the BH moiety and the
2
oxidation of 1a,b, as [FeCp ][PF ] is a mild one-electron
Lewis acid. Such B-H activation has been suggested by Messerle
2
6
7
oxidant. Surprisingly, the F-B substituted complexes
et al. in the reaction of [RuTp(Bp)PPh ] with AgBF . It should
3
4
t
[
F B(Im Bu) ]M(CO) (M = Ir, 2a; M = Rh, 2b) were isolated.
be pointed that B-H activation via involvement of the B-H---M
agostic interaction could not be ruled out in our case.
2
2
2
The mixture of 1a or 1b and [FeCp ][PF ] in Et O was stirred
2
6
2
at room temperature for 4 h. The unreacted [FeCp ][PF ] was
Molecular Structures of 1a,b and 2b. The molecular struc-
tures of 1a,b and 2b were confirmed by single-crystal X-ray
diffraction. Crystals suitable for X-ray diffraction studies were
obtained by recrystallization from hexane solutions at -20 °C.
The structures of 1a,b and 2b are shown in Figures 1-3, with
selected bond lengths and angles given in the captions. The
molecular structures of these complexes exhibit slightly distorted
square planar configurations around the metal center coordi-
nated by the bidentate carbene ligand and two cis-carbonyl
groups. The macrocyclic six-membered ring adopts a pseudo-
twist-boat conformation, similar to the reported complexes of the
2
6
then removed by filtration, and the filtrate was subsequently
concentrated and purified by column chromatography. Elution
with hexane first gave ferrocene, and then elution with hexane/
diethyl ether (4:1) afforded pale yellow products, which were
t
identified as [F B(Im Bu) ]M(CO) (M = Ir, 2a; M = Rh, 2b).
2
2
2
t
In the F B(Im Bu) ligand, two fluorine atoms had substituted
the two boron hydrides in H B(Im Bu) (Scheme 2).
2
2
t
2
2
In contrast to 1a,b, 2a,b are relatively stable in solution and in
the solid state. No decomposition was observed after being
placed in air for 3 weeks. 2a,b were characterized by NMR
spectroscopy, mass spectrometry, and elemental analysis. In the
8-11
bis(3-tert-butylimidazol-2-ylidene)borate ligand.
The Ir-C bond lengths in 1a (2.093(4), 2.100(5) Å) are
1
H NMR spectra of 2a,b, the imidazyl protons appear at 7.04-
carbene
11
7
.30 ppm, which is shifted by about 0.2 ppm from 1a,b. The
B
in the range of other chelated bis-imidazolylidene complexes of Ir
15
NMR data reflect significant changes from 1a (-3.08 ppm) and
complexes. The Ir-CO distances are 1.854(7) and 1.877(6) Å.
The bite angle is 83.20°. The bisimidazolylidene dihedral angle is
67.59°.
1
b (-3.97 ppm) to 2a (4.93 ppm) and 2b (5.02 ppm),
19
respectively. The F NMR spectra (470.5 MHz, CDCl )
3
showed two characteristic multiplets at -135.0 and -162.7
ppm for 2a and -135.1 and -163.5 ppm for 2b, respectively,
representing the two magnetically inequivalent fluorine atoms.
The splitting pattern of the first multiplet at -135.0 ppm (2a) or
The structural parameters of 1b and 2b are similar. The Rh-
Ccarbene bond lengths in 1b (2.094(2), 2.088(3) Å) and 2b
(2.084(2), 2.077(2) Å) are within the range of reported Rh(I)-
13a
C
bonds (1.914-2.102 Å). The Rh-CO distances are
NHC
-
135.1 ppm (2b) results from two coupling interactions. The
1.887(4) and 1.861(5) Å for 1b and 1.880(3) and 1.857(3) Å for
2b, respectively, which are slightly shorter than those in the
analogous Rh complex with a bis(NHC)methylene ligand (1.892
19
19
2
larger interaction is the geminal F- F interaction of J
0
=
F-F
19
11
8
7.0 Hz (2a) or 90.0 Hz (2b). The smaller F- B interaction
1
4f
of J
= 27.3 Hz (2a) or 28.2 Hz (2b) gives a characteristic
Å). The bite angles are 83.21° (1b) and 83.79° (2b). The
F-B
splitting pattern of 1:1:1:1. The second multiplet at -162.7
two B-F bond lengths in 2b are equivalent at 1.384(4) and
1.382(4) Å, which is close to the average B-F bond length
(1.38 Å) observed in similar fluorine-substituted borate metal
ppm (2a) or -163.5 ppm (2b) was also the result of two coupl-
1
9
19
2
ing interactions, a geminal F- F interaction with J
0
=
F-F
19
11
7,16
8
3.5 Hz (2a) or 84.1 Hz (2b) and a smaller F- B interaction
complexes.
2
007
dx.doi.org/10.1021/om200036w |Organometallics 2011, 30, 2006–2011

Organometallics
ARTICLE
Figure 1. Molecular structure of complex 1a showing 30% probability
ellipsoids. Hydrogen atoms other than those bonded to boron are
omitted for clarity. Selected bond lengths (Å) and angles (deg): Ir1-C1
Figure 3. Molecular structure of complex 2b showing 30% probability
ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Rh1-C1 = 2.084(2), Rh1-C8 =
=
2.093(4), Ir1-C8 = 2.100(5), Ir1-C15 = 1.854(7), Ir1-Cl6 =
2
.077(2), Rh1-C15 = 1.880(3), Rh1-Cl6 = 1.857(3), O1-Cl5 =
.136(4), O2-Cl6 = 1.138(4), B1-F1 = 1.384(4), B1-F2 = 1.382(4);
1
.877(6), O1-Cl5 = 1.146(9), O2-Cl6 = 1.137(7); C1-Ir-C8 =
1
83.20(18), C15-Ir1-C16 = 89.8(3), C1-Ir1-C15 = 91.8(2), C8-
C1-Rh1-C8 = 83.79(8), C15-Rh1-C16 = 89.88(13), C1-Rh1-
C15 = 94.65(11), C8-Rh1-C15 = 91.00(11), C1-Rh1-C16 =
1
Ir1-C16 = 94.8(2), C1-Ir1-C16 = 176.9(2), C8-Ir1-C15 =
69.9(3), N1-B1-N3 = 104.6(3).
1
68.05(12), C8-Rh1-C15 = 176.22(10), F1-B1-F2 = 111.0(3),
N1-B1-N3 = 106.5(2).
-
1
asymmetric and symmetric carbonyl stretches at 2044, 1974 cm
-
1
and 2053, 1986 cm in CH Cl solution, respectively. The
2
2
stretches for the iridium species 1a are of lower frequency,
indicating a higher degree of back-bonding. This result is
consistent with average bond lengths of Ir-C(O) = 1.865 Å
(
1a) vs Rh-C(O) = 1.874 Å (1b) and (Ir)C-O = 1.141 Å (1a)
vs (Rh)C-O = 1.131 Å (1b). Similar lower frequencies were
observed for 2a in comparison to those for 2b. In each case, the
asymmetric and symmetric stretches were of similar intensity, as
expected for the complexes containing two mutually cis carbo-
nyl groups. The data in Table 1 reveal that the substitution of
two fluorines in the B-H bonds has an important influence on
the electron-donating nature of bis(NHC) ligands. The IR
peaks of the CO ligands in 1a,b shift significantly to higher
frequencies in the F-substituted compounds 2a,b, thus implying
a significant reduction of the electron-donating character of the
F-substituted bidentate ligand.
Figure 2. Molecular structure of complex 1b showing 30% probability
ellipsoids. Hydrogen atoms other than those bonded to boron are
omitted for clarity. Selected bond lengths (Å) and angles (deg): Rh1-
C1 = 2.094(4), Rh1-C8 = 2.088(3), Rh1-C15 = 1.887(4), Rh1-Cl6 =
Table 1 also gives the IR data of other similar Rh or Ir
18
complexes with monoanionic bidentate ligands Bp (entries 5
4b
and 6) and bis(NHC)methylene (entry 7). 1a,b and 2a,b have
lower CO frequencies, indicating that the bis(3-tert-butylimida-
zol-2-ylidene)borate ligand has a stronger electron-donating
capacity than the monoanionic bidentate Bp ligand. Even though
the electron-donating capacity of the fluorinated derivative has
been diminished by the fluorine substitution, it is still stronger
than for the monoanionic bidentate Bp ligand. It is interesting
to note that bis(3-tert-butylimidazol-2-ylidene)dihydridobo-
rate and its fluorinated derivatives exhibit stronger electron
donating ability than their neutral analogue bis(NHC)-
methylene (entry 7).
1
.861(5), O1-Cl5 = 1.133(5), O2-Cl6 = 1.128(7); C1-Rh1-C8 =
3.21(14), C15-Rh1-C16 = 90.1(2), C1-Rh1-C15 = 94.76(17),
8
C8-Rh1-C16 = 91.31(17), C1-Rh1-C16 = 168.90(18), C8-Rh1-
C15 = 175.90(18), N1-B1-N3 = 105.1(3).
IR Spectroscopic Analysis and the Electronic Effect. The
electron-donating properties of the monodentate N-heterocyclic
carbenes have been well established by the infrared carbonyl
stretching frequencies of the metal complexes [LM(CO) Cl]
2
17
(
L = NHC, M = Rh, Ir). To obtain a direct comparison of the
electronic effect of bis(imidazol-2-ylidene)borate and other
related ligands such as bis(pyrazolyl)borate and bis(NHC)-
methylene, we measured the carbonyl stretching frequencies
of 1a,b and 2a,b and compared them to those reported, as shown
in Table 1. The infrared spectra of complexes 1a,b showed
The current work reveals unexpected fluorination of the BH2
moiety in the bis(3-tert-butylimidazol-2-ylidene)borate ligand
t
during the reactions of [H B(Im Bu) ]M(CO) (1a,b) with
2
2
2
t
[FeCp ][PF ], AgPF , or AgBF , yielding [F B(Im Bu) ]M
2
6
6
4
2
2
(CO) (2a,b), respectively. The fluorination leads to a reduction
2
2
008
dx.doi.org/10.1021/om200036w |Organometallics 2011, 30, 2006–2011

Organometallics
ARTICLE
Table 1. Carbonyl Stretching Frequencies for [M(L)(CO) ] Compounds
2
of the electron-donating ability of the bidentate ligand, as shown
in the IR frequencies of the CO ligands in 1a,b and 2a,b. Even
with this reduction, the fluorinated ligand is still a stronger
electron donor than the analogous bis(pyrazolyl)borate ligand.
the standard Schlenk techniques. Solvents were dried using conventional
19
methods and freshly distilled before use. 1-tert-Butylimidazole, the
t
þ - 11
carbene precursor salt H B( BuImH) I , and the metal precursors
2 2
2
0
21
[Ir(CO)
literature methods. LDA (2.0 M in THF), [FeCp
AgBF were purchased from Aldrich. Elemental analysis was performed
in a Perkin-Elmer 240C analytical instrument. NMR spectra were
obtained in CDCl on a Bruker AM-500 spectrometer. Chemical shifts
are given with respect to CHCl
2
Cl]
2
and [Rh(CO)
2
(acac)] were prepared according to the
2
][PF ], AgPF , and
6
6
’
EXPERIMENTAL SECTION
4
General Procedures. Unless otherwise noted, all reactions and
manipulations were performed under a dry nitrogen atmosphere using
3
1
13
3 3
/CDCl (δ( H) 7.28, δ( C) 77.0),
2
009
dx.doi.org/10.1021/om200036w |Organometallics 2011, 30, 2006–2011

Organometallics
ARTICLE
1
1
19
2
1
Et
2
O BF
3
(δ( B) 0), and CFCl
3
(δ( F) 0). Infrared spectra were
(470.5 MHz, CDCl
28.2 Hz, F ), -163.5 (dq, J
3
, 25 °C): -135.1 (dq, J
F
a
-F
b
= 90.0 Hz, J
F
a
-B
=
3
a
2
1
b
measured on a Nicolet NEXUS870 FT-IR spectrometer.
Synthesis of 1a,b. LDA (1.0 mL, 2.0 M in THF, 2.0 mmol) was
added to the ligand precursor H B( BuImH)
a
b
= 84.1 Hz, J
Fb-B= 25.4 Hz, F ). FT-IR
F -F
-
1
2 2 4 2
(CH Cl ): ν(CO) 2062, 1996 cm . Anal. Calcd for C16H24BN O Rh:
t
þ -
I
2
(388 mg, 1.0 mmol)
C, 42.32; H, 4.88; N, 12.34. Found: C, 42.30; H, 4.90; N, 12.35. MS
2
(ESI ): m/z (%) 477.08 [M þ Na] (100%), 930.83 [2M þ Na]þ
þ
þ
in 20 mL of THF, at -40 °C. The mixture was stirred for 2 h while the
temperature was increased from -40 °C to room temperature.
(13%).
[
Ir(CO) Cl] (284 mg, 0.5 mmol) or [Rh(CO) (acac)] (259 mg, 1.0
2
2
2
mmol) was then added to the reaction flask. The mixture was stirred at
room temperature for 5 h and dried under vacuum. The residue was
extracted into hexane, filtered through Celite, and dried under
vacuum to yield a yellow solid. Recrystallization from a solution of
hexane gave pure crystals suitable for elemental analysis and X-ray
’
ASSOCIATED CONTENT
Supporting Information. H, C, B, and F NMR
1
13
11
19
S
b
spectra of 1a,b and 2a,b (Figure 1S), text giving detailed X-ray
structure determination procedures, a summary of crystallo-
graphic data (Table 1S), bond lengths and bond angles (Table
2S), and CIF files giving crystallographic data for 1a,b and 2b
diffraction for 1a,b.
1
1
a: yield 38.0 mg (75%). H NMR (500 MHz, CDCl , 25 °C): δ 7.02
3
t
t
(
(
s, 2H, ring-CHdCHN- Bu), 7.01 (s, 2H, ring-CHdCHN- Bu), 3.51
(
CCDC 812810-812812). This material is available free of
13
br, 2H, BH
2
), 1.71 (s, 18H, CMe
3
). C NMR (125 MHz, CDCl
3
,
charge via the Internet at http://pubs.acs.org.
t
25 °C): 183.2 (CO), 169.0 (carbene-C), 125.3 (ring-CHdCHN- Bu),
117.2 (ring-CHdCHN- Bu), 57.0 (CMe ), 32.3 (CMe ). B NMR
t
11
3
3
’
AUTHOR INFORMATION
(
2
1
160 MHz, CDCl
3
, 25 °C): -3.08 (BH
044, 1974 cm . Anal. Calcd for C16 24BIrN
1.04. Found: C, 37.71; H, 4.68; N, 11.11.
2
). FT-IR (CH
2 2
Cl ): ν(CO)
-
1
H
4
O
2
: C, 37.87; H, 4.77; N,
Corresponding Author
*Tel: þ86 25 83597147. Fax: þ86 25 83314502. E-mail:
1
1
b: yield 32.6 mg (78%). H NMR (500 MHz, CDCl , 25 °C): δ 7.04
3
t t
xtchen@netra.nju.edu.cn.
(s, 2H, ring-CHdCHN- Bu), 6.94 (s, 2H, ring-CHdCHN Bu), 3.51
13
(br, 2H, BH
2 3 6
), 1.68 (s, 18H, CMe ). C NMR (125 MHz, benzene-d ,
5 °C): 190.4 (d, J
1
1
2
= 58.1 Hz, CO), 171.6 (d, J
= 45.0 Hz,
’ ACKNOWLEDGMENT
Rh,C
Rh,C
t
t
carbene-C), 125.4 (ring-CHdCHN- Bu), 116.8 (ring-CHdCHN- Bu),
We are grateful for financial support from the National Basic
Research Program of China (No. 2007CB925102 to X.-T.C.),
the Natural Science Grant of China (Nos. 21071078 and
11
5
(
6.4 (CMe
BH ). FT-IR (CH
C H BN O Rh: C, 45.96; H, 5.79; N, 13.40. Found: C, 46.07; H, 5.70;
3
), 32.0 (CMe
3
). B NMR (160 MHz, CDCl , 25 °C): -3.97
3
-
1
2
2
2
Cl ): ν(CO) 2053, 1986 cm . Anal. Calcd for
1
6
24
4 2
2
1021062 to X.-T.C.), and the U.S. National Science Foundation
N, 13.37.
Synthesis of 2a,b. Method 1. A solution of [H B(Im Bu) ]M
(
No. CHE-1012173 to Z.-L.X.).
t
2
2
(
CO)
mmol) and [FeCp
15 mL) was stirred at room temperature for 4 h. The unreacted
FeCp ][PF ] was removed by filtration, and the filtrate was subse-
2
(M = Ir (1a), 102 mg, 0.20 mmol; M = Rh (1b), 84 mg, 0.20
’
REFERENCES
(1) (a) Hahn, F. E.; Jahnke, M. C. Angew. Chem., Int. Ed. 2008,
2
][PF ] (135 mg, 0.41 mmol) in diethyl ether
6
(
[
47, 3122–3172. (b) Jahnke, M. C.; Hahn, F. E. Top. Organomet. Chem.
2010, 30, 95–129. (c) Bourissou, D.; Guerret, O.; Gabbaï, F. P.;
Bertrand, G. Chem. Rev. 2000, 100, 39–91. (d) N-Heterocyclic Carbenes
in Synthesis; Nolan, S. P., Ed.; Wiley-VCH: Weinheim, Germany, 2006.
(2) Arduengo, A. J.; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1991,
113, 361–363.
2
6
quently concentrated and purified by column chromatography. Elution
first with hexane removed ferrocene, and subsequent elution with
hexane/diethyl ether (4:1) afforded the desired product [F B
2
t
(Im Bu)
2
]M(CO)
2
(M = Ir (2a), M = Rh (2b)).
t
Method 2. A solution of [H
2
B(Im Bu)
2
]M(CO)
2
(M = Ir (1a), 102
(104 mg,
.41 mmol) in diethyl ether (15 mL) was stirred at room temperature for
h, leading to formation of an yellow solution and a gray precipitate. The
(
3) (a) Herrmann, W. A. Angew. Chem., Int. Ed. 2002,
mg, 0.20 mmol; M = Rh (1b), 84 mg, 0.20 mmol) and AgPF
0
4
solution was filtered through Celite and reduced to dryness to give a
yellow powder. Recrystallization from a mixture of diethyl ether and
hexane yielded yellow crystals of the products [F B(Im Bu) ]M(CO)
6
41, 1290–1309. (b) Díez-Gonz ꢀa lez, S.; Marion, N.; Nolan, S. P. Chem.
Rev. 2009, 109, 3612–3676. (c) Poyatos, M.; Mata, J. A.; Peris, E. Chem.
Rev. 2009, 109, 3677–3707. (d) Mata, J. A.; Poyatos, M.; Peris, E. Coord.
Chem. Rev. 2007, 251, 841–859.
(
4) (a) Sanz, S.; Benítez, M.; Peris, E. Organometallics 2010,
t
2
2
2
29, 275–277. (b) Leung, C. H.; Incarvito, C. D.; Crabtree, R. H.
Organometallics 2006, 25, 6099–6107. (c) Vogt, M.; Pons, V.; Heinekey,
D. M. Organometallics 2005, 24, 1832–1836. (d) Yang, C. H.; Beltran, J.;
Lemaur, V.; Cornil, J.; Hartmann, D.; Sarfert, W.; Fr €o hlich, R.; Bizzarri,
C.; De Cola, L. Inorg. Chem. 2010, 49, 9891–9901. (e) Sanz, S.; Azua, A.;
Peris, E. Dalton Trans. 2010, 39, 6339–6343. (f) Burling, S.; Field, L. D.;
Li, H. L.; Messerle, B. A.; Turner, P. Eur. J. Inorg. Chem.
(
M = Ir (2a), M = Rh (2b)).
1
2
a: yield 61 mg (56%). H NMR (500 MHz, CDCl , 25 °C): δ 7.30
3
t
t
(s, 2H, ring-CHdCHN- Bu), 7.12 (s, 2H, ring-CHdCHN- Bu), 1.76
1
3
(
1
s, 18H, CMe
3 3
t
). C NMR (125 MHz, CDCl , 25 °C): 182.4 (CO),
69.2 (carbene-C), 121.3 (ring-CHdCHN- Bu), 117.9 (ring-CHd
t
11
CHN- Bu), 57.4 (CMe
2
3
), 32.1 (CMe
3
). B NMR (160 MHz, CDCl
3
,
1
9
2
003, 3179–3184. (g) Meyer, D.; Ahrens, S.; Strassner, T. Organome-
5 °C): 4.93 (BH
2
). F NMR (470.5 MHz, CDCl , 25 °C): -135.0
3
2
1
a
2
tallics 2010, 29, 3392–3396.
(dq, J
F
a
-F
b
= 87.0 Hz, J
F
a
-B= 27.3 Hz, F ), -162.7 (dq, J
F
a
-F
= 83.5
b
1
b
-1
(5) (a) Gorrell, I. B.; Looney, A.; Parkin, G.; Rheingold, A. L. J. Am.
Chem. Soc. 1990, 112, 4068–4069. (b) Reger, D. L.; Knox, S. J.; Lebioda,
L. Organometallics 1990, 9, 2218–2222. (c) Reger, D. L.; Knox, S. J.;
Rheingold, A. L.; Haggerty, B. S. Organometallics 1990, 9, 2581–2587.
Hz, J
Anal. Calcd for C16
C, 35.80; H, 4.08; N, 10.31. MS (ESI ): m/z (%) 469.50 [M - 2CO -
F] (100%), 567.17 [M þ Na] (85%), 1108.83 [2M þ Na] (14%).
F 2 2
-B = 25.0 Hz, F ). FT-IR (CH Cl ): ν(CO) 2052, 1981 cm .
b
H
22BF
2
IrN
4
O
2
: C, 35.32; H, 4.08; N, 10.31. Found:
þ
þ
þ
þ
(d) Hill, A. F.; White, A. J. P.; Williams, D. J.; Wilton-Ely, J. D. E. T.
1
2
3
b: yield 45 mg (50%). H NMR (500 MHz, CDCl , 25 °C): δ 7.30
t
Organometallics 1998, 17, 4249–4258. (e) Diaz-Requejo, M. M.; Nica-
sio, M. C.; Perez, P. J. Organometallics 1998, 17, 3051–3057. (f)
Rodriguez, V.; Atheaux, I.; Donnadieu, B.; Sabo-Etienne, S.; Chaudret,
B. Organometallics 2000, 19, 2916–2926. (g) Yeston, J. S.; Bergman,
R. G. Organometallics 2000, 19, 2947–2949. (h) Yeston, J. S.; McNamara,
B. K.; Bergman, R. G.; Moore, C. B. Organometallics 2000, 19, 3442–3446.
t
(s, 2H, ring-CHdCHN- Bu), 7.04 (s, 2H, ring-CHdCHN Bu), 1.73 (s,
1
3
1
1
=
8H, CMe3). C NMR (125 MHz, benzene-d , 25 °C): 189.6 (d, J
6
Rh,C
1
58.3 Hz, CO), 171.5 (d, JRh,C = 42.5 Hz, carbene-C), 121.6 (ring-
t
t
CHdCHN- Bu), 117.4 (ring-CHdCHN- Bu), 56.9 (CMe
(
3
19
), 31.9
11
CMe3). B NMR (160 MHz, CDCl , 25 °C): 5.02 (BH ). F NMR
3
2
2
010
dx.doi.org/10.1021/om200036w |Organometallics 2011, 30, 2006–2011

Organometallics
i) Saly, M. J.; Winter, C. H. Organometallics 2010, 29, 5472–5480. (j)
ARTICLE
(
Trzeciak, A. M.; Borak, B.; Ciunik, Z.; Zi ꢀo zkowski, J. J.; Guedes da Silva,
M. F. C.; Pombeiro, A. J. L. Eur. J. Inorg. Chem. 2004, 1411–1419.
(6) (a) Pizzano, A.; Sanchez, L.; Gutierrez, E.; Monge, A.; Carmona,
E. Organometallics 1995, 14, 14–16. (b) Hill, A. F.; Malget, J. M. J. Chem.
Soc., Dalton Trans. 1997, 2003–2004. (c) Ghosh, P.; Parkin, G. J. Chem.
Soc., Dalton Trans. 1998, 2281–2284. (d) Chowdhury, S. K.; Samanta,
U.; Puranik, V. G.; Sarkar, A. Organometallics 1997, 16, 2618–2622. (e)
Looney, A.; Han, R.; Gorrell, I. B.; Cornebise, M.; Yoon, K.; Parkin, G.;
Rheingold, A. L. Organometallics 1995, 14, 274–288.
(
7) Page, M. J.; Messerle, B. A.; Wagler, J. Organometallics 2009,
8, 6145–6151.
8) Fr €a nkel, R.; Kniczek, J.; Ponikwar, W.; N €o th, H.; Polborn, K.;
Fehlhammer, W. P. Inorg. Chim. Acta 2001, 312, 23–39.
9) Shishkov, I. V.; Rominger, F.; Hofmann, P. Organometallics
009, 28, 3532–3536.
10) Arrowsmith, M.; Hill, M. S.; Kociok-K €o hn, G. Organometallics
009, 28, 1730–1738.
11) Nieto, I.; Bontchev, R. P.; Smith, J. M. Eur. J. Inorg. Chem.
008, 2476–2480.
12) (a) Cheng, Y.; Lu, X. Y.; Xu, H. J.; Li, Y. Z.; Chen, X. T.; Xue,
2
(
(
2
2
2
(
(
(
Z. L. Inorg. Chim. Acta 2010, 363, 430–437. (b) Sun, J. F.; Chen, F.;
Dougan, B. A.; Xu, H. J.; Cheng, Y.; Li, Y. Z.; Chen, X. T.; Xue, Z. L.
J. Organomet. Chem. 2009, 694, 2096–2105. (c) Lu, X. Y.; Chen, F.; Xu,
W. F.; Chen, X. T. Inorg. Chim. Acta 2009, 362, 5113–5116. (d) Cheng,
Y.; Xu, H. J.; Sun, J. F.; Li, Y. Z.; Chen, X. T.; Xue, Z. L. Dalton Trans.
2
009, 7132–7140. (e) Cheng, Y.; Sun, J. F.; Yang, H. L.; Xu, H. J.; Li,
Y. Z.; Chen, X. T.; Xue, Z. L. Organometallics 2009, 28, 819–823.
13) (a) Pugh, D.; Danopoulos, A. A. Coord. Chem. Rev. 2007,
51, 610–641. (b) Mas-Marz ꢀa , E.; Poyatos, M.; Sana ꢀu , M.; Peris, E. Inorg.
(
2
Chem. 2004, 43, 2213–2219. (c) Mas-Marz ꢀa , E.; Peris, E.; Castro-
Rodríguez, I.; Meyer, K. Organometallics 2005, 24, 3158–3162.
(14) (a) Abernethy, R. J.; Hill, A. F.; Smith, M. K.; Willis, A. C.
Organometallics 2009, 28, 6152–6159. (b) Burtscher, D.; Perner, B.;
Mereiter, K.; Slugovc, C. J. Organomet. Chem. 2006, 691, 5423–5430.
(15) (a) Viciano, M.; Poyatos, M.; Sana ꢀu , M.; Peris, E.; Rossin, A.;
Ujaque, G.; Lled ꢀo s, A. Organometallics 2006, 25, 1120–1134. (b)
Viciano, M.; Mas-Marz ꢀa , E.; Sana ꢀu , M.; Peris, E. Organometallics 2006,
2
5, 3063–3069.
16) Garcia, R.; Gano, L.; Maria, L.; Paulo, A.; Santos, L.; Spies, H.
J. Biol. Inorg. Chem. 2006, 11, 769–782.
17) (a) Díez-Gonz ꢀa lez, S.; Nolan, S. P. Coord. Chem. Rev. 2007,
(
(
2
4
51, 874–883. (b) Dr €o ge, T.; Glorius, F. Angew. Chem., Int. Ed. 2010,
9, 6940–6952. (c) Chianese, A. R.; Li, X.; Janzen, M. C.; Faller, J. W.;
Crabtree, R. H. Organometallics 2003, 22, 1663–1667. (d) Kelly, R. A.,
III; Clavier, H.; Giudice, S.; Scott, N. M.; Stevens, E. D.; Bordner, J.;
Samardjiev, I.; Hoff, C. D.; Cavallo, L.; Nolan, S. P. Organometallics
2
007, 27, 202–210. (e) Wolf, S.; Plenio, H. J. Organomet. Chem. 2009,
694, 1487–1492.
(
18) (a) Clark, H. C.; Goel, S. J. Organomet. Chem. 1979,
1
7
65, 383–389. (b) King, R. B.; Bond, A. J. Organomet. Chem. 1974,
3, 115–118. (c) Fernandez, M. J.; Rodriguez, M. J.; Oro, L. A.
Polyhedron 1991, 10, 1595–1598.
19) Liu, J. P.; Ren, Z. Y.; Zhao, Y. H.; Zhang, H. B. Chin. J. Org.
Chem. 2004, 24, 1091–1094.
20) Roberto, D.; Cariati, E.; Psaro, R.; Ugo, R. Organometallics
994, 13, 4227–4231.
21) Cao, W. L. W., H. B.; Gao, X. X.; Zhang, J. J.; Zhang, J. C. Chin.
J. Catal. 2004, 25, 556–560.
(
(
1
(
2
011
dx.doi.org/10.1021/om200036w |Organometallics 2011, 30, 2006–2011