Chemistry of iridium(I) cyclooctadiene compounds with thiapentadienyl, sulfinylpentadienyl, and butadienesulfonyl ligands

Article abstract of DOI:10.1021/om2007166

The metathesis reaction of [(ν⁴-COD)Ir(μ-Cl)]₂ (4) with two equivalents of the sodium thiapentadienide (1Na) or potassium sulfinylpentadienide salt (2K) led to the formation of the corresponding dimers [(ν⁴-COD)Ir(μ₂-1-2,5-ν-CH₂CHCHCHS)] ₂ (5) and [(ν⁴-COD)Ir(μ₂-1-2,5-ν- CH₂CHCHCHSO)]₂ (9). The single-crystal analysis of 5 and 9 reveals the presence of the thiapentadienyl or sulfinylpentadienyl ligands bridging through the sulfur atoms and the terminal double bonds to both iridium centers. Treatment of 5 with two equivalents of PMe₃ produces [(ν⁴-COD)Ir(1-2,5-ν- CH₂CHCHCHS)PMe₃] (6), while compound Ir(1-2,5-ν-CH₂CHCHCHS)(CO)(PPh ₃)₂ (8) is obtained from reaction of Ir(CO)(Cl)(PPh ₃)₂ (7) with potassium thiapentadienide (1K). The 1H and ¹³C NMR support the preferred U conformation and the same ν^2,1-bonding mode of the thiapentadienyl ligand in each case. The reaction of 4 with butadienesulfinate salts M[CH2CHCHCHSO₂] (3M) (M = Li, K) affords the ion-pair complexes [(ν⁴-COD)IrCl(1-2,5-ν- CH₂CHCHCHS(O₂^-M⁺)] (M = Li, 10; M = K, 11). Compound (ν⁴-COD)Ir(μ-Cl)(1-2-ν-S,O-μ- OSOCHCHCHCH₂)Ir(ν⁴-COD) (12) can be isolated if the reaction of 4 with 3K is carried out at low temperature and after a short period of time in solution. The crystal structure of 12 shows a dinuclear compound where the butadienesulfonyl is bridging through the S and one of the O atoms to the iridium center. In solution, 12 dissociates in the presence of coordinating solvents, such as DMSO-d₆ or THF-d₈, while the dinuclear asymmetric structure of 12 remains in CDCl₃. The series of pentacoordinated Ir(I) complexes of general formula [(ν⁴-COD)Ir(1- 2,5-ν-CH₂CHCHCHSO₂)L] (L = PMe₃, 14; PMe₂Ph, 15; PMePh₂, 16; PPh₃, 17; DMSO, 18; and CO, 19) can be obtained, under mild conditions, from 11 and the corresponding ligand L, which shows different σ or π donor-acceptor properties. The disubstituted phosphine derivative [(ν⁴-COD)Ir(5-ν-CH ₂CHCHCHSO₂)(PMe₃)₂] (20) can be prepared directly from 14 and an excess of PMe₃. A comparative study of these derivatives was carried out through the analysis of the IR, mass spectrometry, and ¹H, ¹³C, and ³¹P NMR spectroscopy, as well as through the crystalline structures of 12, 14, 15, and 17-20, and allowed establishing trends among them. The presence of the butadienesulfonyl ligand in complexes 14-19 induces a total asymmetry that is reflected through the ¹H and ¹³C NMR. The preferred coordination mode (1-2,5-ν-) in the butadienesulfonyl ligand for complexes 14-19 was confirmed. A better synthetic procedure for 14 is described if [(ν⁴-COD)IrClPMe₃] (21) reacts with 3K. In contrast, no synthetic advantage was found in the formation of 17 or 20 when [(ν⁴-COD)IrClPPh₃] (22) or [(ν⁴-COD) IrCl(PMe₃)₂] (23) is used as a precursor. Monitoring reactions through ¹H and ³¹P NMR of 11, 12, and 14 in the presence of PMe₃ and 23 with 3K afforded mixtures of compounds, from which an equilibrium in the reaction mixture is proposed.

Full text of DOI:10.1021/om2007166

Article
pubs.acs.org/Organometallics
Chemistry of Iridium(I) Cyclooctadiene Compounds with
Thiapentadienyl, Sulfinylpentadienyl, and Butadienesulfonyl Ligands
Procoro Gamero-Melo,† Patricia Andrea Melo-Trejo, Marisol Cervantes-Vasquez,
Nelly Paola Mendizabal-Navarro, Brenda Paz-Michel, Tere Isabel Villar-Masetto,
Miguel Angel Gonzalez-Fuentes, and M. Angeles Paz-Sandoval*
Departamento de Química, Centro de Investigacion
Mexico 07360, D.F., Mexico
†Centro de Investigacion
y de Estudios Avanzados del IPN, Unidad Saltillo, Carretera Saltillo-Monterrey Km 13.5, C.P. 25900, Ramos
́
y de Estudios Avanzados del IPN, Avenida IPN # 2508, San Pedro Zacatenco,
́
́
́
Arizpe, Coahuila, Mexico
S
* Supporting Information
ABSTRACT: The metathesis reaction of [(η4-COD)Ir(μ-Cl)]2
(4) with two equivalents of the sodium thiapentadienide (1Na)
or potassium sulfinylpentadienide salt (2K) led to the formation
of the corresponding dimers [(η4-COD)Ir(μ2-1-2,5-η-
CH2CHCHCHS)]2 (5) and [(η4-COD)Ir(μ2-1-2,5-η-
CH2CHCHCHSO)]2 (9). The single-crystal analysis of 5 and
9 reveals the presence of the thiapentadienyl or sulfinylpenta-
dienyl ligands bridging through the sulfur atoms and the terminal
double bonds to both iridium centers. Treatment of 5 with two
equivalents of PMe3 produces [(η4-COD)Ir(1-2,5-η-
CH2CHCHCHS)PMe3] (6), while compound Ir(1-2,5-η-
CH2CHCHCHS)(CO)(PPh3)2 (8) is obtained from reaction
of Ir(CO)(Cl)(PPh3)2 (7) with potassium thiapentadienide
1
(1K). The H and 13C NMR support the preferred U conformation and the same η2,1-bonding mode of the thiapentadienyl
ligand in each case. The reaction of 4 with butadienesulfinate salts M[CH2CHCHCHSO2] (3M) (M = Li, K) affords the ion-pair
complexes [(η4-COD)IrCl(1-2,5-η-CH2CHCHCHS(O2−M+)] (M = Li, 10; M = K, 11). Compound (η4-COD)Ir(μ-Cl)(1-2-η-
S,O-μ-OSOCHCHCHCH2)Ir(η4-COD) (12) can be isolated if the reaction of 4 with 3K is carried out at low temperature and
after a short period of time in solution. The crystal structure of 12 shows a dinuclear compound where the butadienesulfonyl is
bridging through the S and one of the O atoms to the iridium center. In solution, 12 dissociates in the presence of coordinating
solvents, such as DMSO-d6 or THF-d8, while the dinuclear asymmetric structure of 12 remains in CDCl3. The series of
pentacoordinated Ir(I) complexes of general formula [(η4-COD)Ir(1-2,5-η-CH2CHCHCHSO2)L] (L = PMe3, 14; PMe2Ph, 15;
PMePh2, 16; PPh3, 17; DMSO, 18; and CO, 19) can be obtained, under mild conditions, from 11 and the corresponding ligand
L, which shows different σ or π donor−acceptor properties. The disubstituted phosphine derivative [(η4-COD)Ir(5-η-
CH2CHCHCHSO2)(PMe3)2] (20) can be prepared directly from 14 and an excess of PMe3. A comparative study of these
derivatives was carried out through the analysis of the IR, mass spectrometry, and 1H, 13C, and 31P NMR spectroscopy, as well as
through the crystalline structures of 12, 14, 15, and 17−20, and allowed establishing trends among them. The presence of the
1
butadienesulfonyl ligand in complexes 14−19 induces a total asymmetry that is reflected through the H and 13C NMR. The
preferred coordination mode (1-2,5-η-) in the butadienesulfonyl ligand for complexes 14−19 was confirmed. A better synthetic
procedure for 14 is described if [(η4-COD)IrClPMe3] (21) reacts with 3K. In contrast, no synthetic advantage was found in the
formation of 17 or 20 when [(η4-COD)IrClPPh3] (22) or [(η4-COD)IrCl(PMe3)2] (23) is used as a precursor. Monitoring
reactions through 1H and 31P NMR of 11, 12, and 14 in the presence of PMe3 and 23 with 3K afforded mixtures of compounds,
from which an equilibrium in the reaction mixture is proposed.
coordination modes that are adopted by this ligand and the
possibility of rearrangements observed. The electron-rich
complexes IrCl(PR3)3 (R = Me, Et)2 is an example of this
versatility; its reactivity, with the thiapentadienide, is quite
INTRODUCTION
■
The presence of the sulfur atom in heterodienyl ligands has
shown an interesting and versatile chemistry, as can be
appreciated comparatively from the results obtained with
previous analogous pentadienyl complexes.1 Since 1992, there
has been an interest in the reactions between iridium and
acyclic thiapentadienyl ligands because of the range of
Received: August 2, 2011
Published: December 27, 2011
© 2011 American Chemical Society
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Chart 1
different depending on the substituent R, which affords
interesting molecules derived from intramolecular C−H bond
activation. These reactions generate iridathiacyclohexadiene2−4
and iridathiacyclopentene,2−5 where the former six-membered-
ring compound can gradually convert to the corresponding
iridathiacycle with an exocyclic double bond, such as examples
A and B in Chart 1. Also, iridathiabenzene molecules have been
obtained using acyclic thiapentadienide salts as precursors.3,6
The chemistry of the thiapentadienyl compounds with
transition metals has also been developed, since 1987, based
on thiophenes, which, once coordinated with transition metals,
result in the activation of the heterocycle due to nucleophilic
attack by a variety of anions, including hydride donors,7−9 or
from electrophilic addition.10
These interactions between metals and thiophenes have been
the subject of much study because of their relevance to the
understanding of the chemistry of hydrodesulfurization. In
particular, this ring-opening reaction of thiophene with iridium
has been observed when Ir(H)2(triphos)(Et) produces, by
reductive elimination of ethane, the reactive 16-electron
fragment (triphos)IrH [triphos = MeC(CH2PPh2)3], which
affords the thiapentadienyl ligand coordinated through the
terminal double bond and the sulfur to iridium in Ir(1-2,5-η-
CH2CHCHCHS)(triphos) (C).11
Reactions of aqueous base with the dicationic iridium
thiophene complex [Cp*Ir(2,5-dimethyl-η5-thiophene)][X]2
(X = BF4, OTf) afford a mixture of mono-, di-, and tetranuclear
compounds [Cp*Ir(η4-SC(Me)CHCHC(O)Me)] (D),
[(Cp*Ir)2(μ2,η4-SC(Me)CHCHC(O)Me)](BF4) (E), [Cp*Ir-
(μ2,η3-SC(Me)CHCH2C(O)Me)]2(BF4)2 (F), and (Cp*Ir)-
[Cp*Ir(η4-SC(Me)CHCHC(O)Me)]3(BF4)2 (G).12 The
mononuclear acylthiolate complex [Cp*Ir(η4-SC(Me)-
CHCHC(O)Me)] (D) was also reported from the reaction
of [Cp*Ir(2,5-dimethyl-η5-thiophene)][BF4]2 with PhLi in
THF or (n-Bu)4N+OH− in MeCN,13 and the dicationic
thiophene complex readily adds secondary amines to afford
[Cp*Ir(η4-SC(Me)CHCHC(Me)(N(CH2)n)](BF4) (n = 4, 5)
(H).14
pentadienyl or butadienesulfonyl, have been developed in the
past decade, and, consequently, their capability as ligands in
organometallic transition compounds is still unknown.
Particularly, only a couple of examples in iridium chemistry
have been reported related with the metathesis reaction of
[Cp*IrCl2]2 with butadienesulfinate salts. Previous studies
show that [Cp*IrCl2]2, according to the size of the cation in
M[CH2CHCHCHSO2] (M = Li, 3Li; M = K, 3K), yields
dinuclear [Cp*Ir(Cl)2{(5-η-CH2CHCHCHSO2)}(Li)(THF)]2
or mononuclear [Cp*IrCl(1-2,5-η-CH2CHCHCHSO2)] com-
pounds, respectively.15 A strong dependence of reaction
efficiency on the nature of the phosphine has been observed
in Cp*IrCl(5-η-CH2CHCHCHSO2)PR3, (R = Me, Ph) from
addition reaction of Cp*IrCl[1-2,5-η-CH2CHCHCHSO2] with
PR3 (R = Me, Ph) or through the metathesis reaction of
Cp*Ir(Cl)2PR3 with the potassium butadienesulfinate.16
The butadienesulfonyl ligand has shown different coordina-
tion modes, chemical versatility, and stability, as observed by its
isomerization16−18 and inter- and intramolecular hydrogen
interactions.18,19
The chemistry of iridium with the cyclooctadiene ligand is
now explored; the first examples of dimeric structures [(η4-
17,20
COD)Ir(μ2-1-2,5-η-CH2CHCHCHE)]2
(E = S, SO),
which include bridging thia- and sulfinyl-pentadienyl ligands,19
were obtained after treatment of [(η4-COD)Ir(μ-Cl)]2 with
sodium thiapentadienide and potassium sulfinyl-pentadienide.
The reaction of lithium and potassium butadienesulfinates with
[(η4-COD)Ir(μ-Cl)]2 produced the corresponding ion-pair
complexes (η4-COD)IrCl(dioxo-thiapentadienide). Represen-
tative examples of the (η4-COD)Ir(dioxo-thiapentadienyl)L
compounds with two-electron-donor ligands L were synthe-
sized, including derivatives with a σ-donor (DMSO), a π-
acceptor (CO), and also different phosphines, which smoothly
change their steric and electronic properties, and a correspond-
ing comparative study was established. The interesting
chemistry displayed by these oxygen-containing thiapentadienyl
molecules, and especially their major differences relative to the
simple thiapentadienyl complexes, suggests that the sulfinyl-
pentadienyl and dioxo-thiapentadienyl ligands should also
prove interesting to study.
Alternative methods for the synthesis of the corresponding
oxidative derivatives of the thiapentadienyl ligand, such as the
5-oxothiapentadienyl or sulfinylpentadienyl, and 5,5-dioxothia-
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Scheme 1
Table 1. Crystal Data of Compounds 5 and 9
RESULTS AND DISCUSSION
■
A. Thiapentadienyl Chemistry. Reaction of [(η4-COD)-
Ir(μ-Cl)]2 (4) with two equivalents of sodium thiapentadienide
(1Na), prepared in situ in DMSO-d6, led to the formation of
the dimer [(η4-COD)Ir(μ2-1-2,5-η-CH2CHCHCHS)]2 (5)17,20
in 47% yield (Scheme 1).
5
9
molecular formula
mol wt
C24H38Ir2S2
775.06
C24H34Ir2O2S2
401.52
space group
a (Å)
P1
P21/n
̅
6.9771(2)
7.6804(2)
10.9819(3)
108.7530(1)
97.8670(10)
94.9330(10)
546.67(3)
1
7.9245(3)
12.1003(5)
12.4320(5)
90.00
The X-ray crystal structure contains two iridium atoms, two
thiapentadienyl ligands, and two cyclooctadiene ligands, Figure
1. Crystal data and selected bonds and angles are reported in
Tables 1 and 2, respectively.
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
103.6520(1)
90.00
V (Å3)
1158.41(8)
2
Z
cryst size(mm)
Dcalc (g cm−3)
limit θ
0.17 × 0.15 × 0.08
2.342
0.125 × 0.100 × 0.075
2.302
7.62−55.04
−9 ≤ h ≤ 8
−9 ≤ k ≤ 9
−14 ≤ l ≤ 14
7310
6.92−54.86
−10 ≤ h ≤ 10
−15 ≤ k ≤ 14
−16 ≤ l ≤ 16
4934
ranges
h, k, l
total no. of data
total no. of unique data
2470
2625
(Rint = 0.0850)
0.0418
(Rint = 0.0751)
0.0438
final R1
final wR2
GOF
0.1002
0.0865
Figure 1. Molecular structure of [(η4-COD)Ir(μ2-1-2,5-
CH2CHCHCHS)]2 (5).
1.034
0.971
ligand: C5−C6 [1.453(11) Å] and C9−C10 [1.405(11) Å].
The bond lengths of Ir−S are 2.3788(18) and 2.4900(17) Å.
The C1−C2, C3−C4, C4−S, and Ir1−S1 bond lengths of the
mononuclear compound [Ir(1-2,5-η-CH2CHCHCHS)-
(PMe3)3] show for the thiapentadienyl ligand similar data
[C1−C2, 1.441(15); C3−C4, 1.316(18); C4−S, 1.758(11);
Ir−S, 2.417(2) Å],4 where the Ir−S bond length shows an
intermediate value compared to the corresponding values of 5.
The more symmetric octahedral complex [Cp*Ir(μ2-SH)SH]2
shows shorter and more symmetric Ir−S bonds [2.380(4) and
2.386(4) Å].21
The dimer sits on a crystallographic inversion center located
at the midpoint of the C3−C4−C3a−C4a rhombus; thus only
half of the molecule is symmetrically independent. Each iridium
atom is (1-2,5-η) coordinated to one thiapentadienyl ligand
through the C1−C2 and S1 and η4-coordinated to one
cyclooctadiene ligand. The structure is held together by the
two thiapentadienyl ligands, which bridge through the sulfur
atoms both iridium centers. According to the bond angles, the
geometry of 5 is distorted trigonal-bipyramidal [C1−Ir1−S1,
93.8(2)°; C5−Ir1−S1a, 136.9(2)°]. The angle C1−Ir−C6
[175.3(3)°] shows the axial position of the coordinated double
bond of thiapentadienyl and cyclooctadiene ligands. In
addition, the terminal double bond C1−C2 [1.426(11) Å] of
the thiapentadienyl ligand coordinates to Ir1, while the internal
double bond C3−C4 [1.327(14) Å] remains uncoordinated.
The bond length of C4−S is 1.762(8) Å. The iridium atom
coordinates the nonconjugated double bonds of the COD
In the solid state compound 5 is in the anti configuration,
1
thereby minimizing steric crowding, while in solution the H
NMR spectrum of crystals of 5 shows, in CDCl3, a mixture of
isomers [(η4-COD)Ir(μ2-1-2,5-CH2CHCHCHS)]2 (5 and 5′)
in a 1:5 ratio, Scheme 2.
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Table 2. Selected Bond Lengths and Angles of Compounds 5 and 9
bond length (Å)
5
9
bond angles (deg)
5
9
C(1)−C(2)
C(2)−C(3)
C(3)−C(4)
C(4)−S(1)
C(1)−Ir(1)
C(2)−Ir(1)
Ir(1)-S(1A)
Ir(1)−S(1)
C(5)−Ir(1)
C(6)−Ir(1)
C(9)−Ir(1)
C(10)−Ir(1)
C(5)−C(6)
C(6)−C(7)
C(7)−C(8)
C(8)−C(9)
C(9)−C(10)
C(10)−C(11)
C(11)−C(12)
C(12)−C(5)
S(1)−O(1)
1.426(11)
1.472(13)
1.327(14)
1.762(8)
1.440(13)
1.469(13)
1.325(14)
1.777(9)
2.168(10)
2.178(9)
2.444(3)
2.329(2)
2.151(10)
2.109(9)
2.210(8)
2.230(8)
1.413(14)
1.520(14)
1.521(15)
1.504(15)
1.411(14)
1.510(14)
1.512(14)
1.517(14)
1.505(7)
C(1)−C(2)−C(3)
C(2)−C(3)−C(4)
C(3)−C(4)−S(1)
C(4)−S(1)−Ir(1)
C(1)−Ir(1)−S(1)
C(2)−Ir(1)−S(1)
C(5)−Ir(1)−S(1)
C(6)−Ir(1)−S(1)
C(9)−Ir(1)−S(1)
C(10)−Ir(1)−S(1)
C(1)−Ir(1)−C(2)
C(1)−Ir(1)−C(5)
C(1)−Ir(1)−C(6)
C(1)−Ir(1)−C(9)
C(1)−Ir(1)−C(10)
C(2)−Ir(1)−C(5)
C(2)−Ir(1)−C(6)
C(2)−Ir(1)−C(9)
C(2)−Ir(1)−C(10)
C(1)−Ir(1)−S(1A)
C(5)−Ir(1)−S(1A)
Ir(1)−S(1)−Ir(1A)
Ir(1)−S(1)−O(1)
118.5(7)
122.6(7)
119.8(6)
99.8(3)
93.8(2)
83.1(2)
87.0(2)
90.6(2)
162.8(2)
158.4(2)
38.5(3)
139.1(3)
175.3(3)
95.0(3)
86.7(3)
101.4(3)
140.9(3)
112.7(3)
83.9(3)
82.8(2)
136.9(2)
100.99(6)
115.7(9)
124.4(9)
117.5(7)
101.2(3)
94.6(3)
2.142(7)
2.178(7)
83.8(3)
2.4900(17)
2.3788(18)
2.144(6)
88.3(3)
93.8(3)
163.4(3)
158.7(3)
38.7(4)
2.154(7)
2.181(7)
2.205(7)
138.6(4)
171.1(4)
93.0(4)
1.453(11)
1.517(11)
1.529(12)
1.524(12)
1.405(11)
1.500(11)
1.505(12)
1.499(11)
84.9(4)
101.1(4)
139.8(4)
111.1(4)
82.6(4)
85.5(3)
135.1(3)
102.12(8)
116.8(3)
Scheme 2. Mixture of anti and syn Isomers 5 and 5′
143.73, 139.57 and 123.01, 121.93; see the Supporting
Information. The mass spectrum shows the molecular ion of
5 at 772, along with several fragmentations of the dimer, where
the base peak at m/z 384 corresponds to the molecular weight
of half of the dimeric complex.
Treatment of 5 with two equivalents of PMe3 produced [(η4-
COD)Ir(1-2,5-η-CH2CHCHCHS)PMe3] (6) in 53% yield,
Scheme 1. The yellow solid melts at 78−79 °C and is soluble in
hexane. The 1H and 13C NMR (Tables 3 and 4) supported the
preferred U conformation, the same η2,1-bonding mode of the
thiapentadienyl ligand, and the coordination of the PMe3,
which in the 31P NMR showed a singlet at −54.5 ppm, quite
close to that of free phosphine. The mass spectrum
corroborates the molecular ion of the 18-electron derivative 6
at m/z 462.
Scheme 3
The synthesis of Ir(1-2,5-CH2CHCHCHS)(CO)(PPh3)2 (8)
is described in Scheme 1. The cream solid was isolated from
reaction of Ir(CO)(Cl)(PPh3)2 (7) with potassium thiapenta-
dienide in THF in 82% yield. 1H and 13C NMR spectra (Tables
3, 4) exhibit the pattern of resonances that is characteristic of
the 1-2,5-η-thiapentadienyl bonding mode, which is the
preferred coordination mode in the chemistry of thiapenta-
dienyl-iridium2,4,11,15,23−27 -or rhodium28−30 compounds. The
31P NMR (Table 4) shows two doublets from magnetically
nonequivalent phosphines at −7.76 (d, J = 37.2 Hz) and −1.41
(d, 37.2 Hz). The presence of coordinated CO was confirmed
by IR, where a strong peak at 1982 cm−1 suggests that the
thiapentadienyl ligand reduced the capability of back-bonding
of the CO compared to the CO in the Vaska catalyst 7 (1954
cm−1). The mass spectrum, through the FAB technique, affords
a molecular ion at 830 m/z for 8.
The same 1H NMR spectrum was observed independently of
the temperature (room temperature or 50 °C), which may
suggest the presence of two dimer isomers 5 and 5′ involving an
anti−syn isomerization associated with the sulfur bridging
groups, which has already been documented for thiolato- and
hydrosulfide-bridged complexes.22 Full assignment could be
done for 5′, while 5 showed overlapped signals for H1, H2, and
most of the COD hydrogens, Table 3. The 13C{1H} NMR
spectroscopy, in Table 4, clearly shows the presence of 5 and 5′.
The iridium-coordinated carbons C1 and C2 resonate at δ
41.00, 41.19 and 63.56, 63.49 for 5 and 5′, respectively, while
the uncoordinated carbons C3 and C4 appear downfield at δ
Contrastingly, reaction of 7 with potassium pentadienide
produces exclusively Ir(1-3-η-pentadienyl)(CO)(PPh3)2, and
the 1-2,5-η-coordination mode is observed only when
potassium 2,4-dimethylpentadienide is used. The last one
affords an equilibrium mixture of [Ir(1-2,5-η-2,4-
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dimethylpentadienyl)(CO)(PPh3)2] and [Ir(1-3-η-2,4-
dimethylpentadienyl)(CO)(PPh3)2] in which, in methylene
chloride at 20 °C, the 1-3-η-pentadienyl complex predominates
slightly (1.5:1.0).31
A preliminary 1H and 31P NMR study of 8 in CDCl3, at room
temperature and after 22 days, showed the transformation of
the thiapentadienyl ligand from 1- to 2,5-η- into 5-η-.32 In the
latter, an S conformation was observed in solution and a singlet
at 31P δ 2.33; see Scheme 3 and Supporting Information.
B. Sulfinylpentadienyl Chemistry. The corresponding
sulfinylpentadienyl complex [(η4-COD)Ir(μ2-1-2,5-η-
CH2CHCHCHSO)]2 (9) can be prepared using a similar
procedure to that described for the thiapentadienyl analogue 5
(Scheme 1). However, manipulating the sulfinylpentadienide
salt 2M (M = Li, Na, K) is much more complicated, because it
easily suffers a dismutation to butadienesulfinate and
thiapentadienide, depending on the stability of the sulfinylpen-
tadienyl, which decreases in the following order: 2K > 2Na >
2Li.19 Considering the longer time observed for the
dismutation of 2K, the synthesis of 9 was carried out, forming
in situ 2K from 2,5-dihydrothiophene-1-oxide and KH in the
presence of 4. After 30 min, the mixture was filtered,
evaporated, and recrystallized from methylene chloride/diethyl
ether, which gave yellow crystals of 9 in very low yield (≅5
1
mg). The H NMR of the sulfinylpentadienyl ligand confirms
the coordination of H1 and H2 (2.17 and 3.12 ppm) and
noncoordination of H3 and H4 (5.99 and 6.84 ppm); the COD
signals are overlapped and were not assigned. The crystal
structure of 9 (Tables 1 and 2, Figure 2) was established,
showing a dimeric structure, analogous to 5.
Figure 2. Molecular structure of [(η4-COD)Ir(μ2-1-2,5-
CH2CHCHCHSO)]2 (9).
The Ir−S bond lengths [2.329(2) and 2.444(3) Å] are
shorter than those of 5 [2.3788(18) and 2.4900(17) Å], where
the corresponding longer bond lengths of 9 and 5 are attributed
to the coordination bond from the nonbonding lone pair of the
sulfur that interacts with the iridium atom to give a dimer.
Comparison between 9 and DMSO complexes, M = Ru(II),
Os(II), Pd(II), Pt(II), Pt(IV) [2.217(2)−2.343(3) Å],33 shows
that Ir(I) is in the highest value range. The bond length SO
is 1.505(7) Å, which is similar to the average value of
noncoordinated sulfoxides and among the highest top values of
reported bond lengths of SO bonds in DMSO complexes,
where coordination is through the sulfur atom (1.42−1.512
Å).33 The bond angle in 9 suggests a distorted trigonal-
bipyramidal geometry, where C1−C2 and C5−C6 are in axial
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positions [C1−Ir1−C6, 171.1(4)°] and the sulfur atom [C1−
Ir1−S1, 94.6(3)°] is almost perpendicular to C1−C2. Due to
the presence of the oxygen atom on the sulfur, the bond angles
of the sulfinylpentadienyl ligand in 9 [C1−C2−C3, 115.7(9)°;
C2−C3−C4, 124.4(9)°; C3−C4−S1, 117.5(7)°] show the
greatest deviation compared to the thiapentadienyl analogue 5
[C1−C2−C3, 118.5(7)°; C2−C3−C4, 122.6(7)°; C3−C4−S1,
119.8(6)°] and the typical free diene (120°).
and 11 (0.5−75.0 and 80−6000 nm). The tendency to favor
polydisperse aggregates was higher in the lithium derivative
(predominates between 70 and 6000 nm) compared to that
shown by the potassium (predominates at 0.5−75.0 nm), which
suggests that some kinds of oligomers, with the same empirical
formula, cannot be discriminated in the case of 10 and 11; see
the Supporting Information.
The IR spectra showed strong bands for OSO
vibrations of 10 (νas 1133, 1108 and νs 1029 cm−1) and 11
(νas 1146, 1108 and νs 1041 cm−1); those for 10 were at lower
wavenumber than those of 11. Both ion-pair complexes 10 and
11 were at lower frequencies compared to those of non-ion-pair
derivatives, such as [(η4-COD)Ir(1-2,5-η-CH2CHCHCHSO2)-
L] (L = DMSO, 18: 1166, 1100, 1051 cm−1; L = CO, 19: 1171,
1052 cm−1, vide infra). This can be attributed to the alkaline
metal interaction with the OSO fragment in 10 and 11,
vide infra. The analogy between NMR spectroscopic data for
3M (M = Li, Na, K) has been proposed as indicative that the
metal is interacting exclusively with the sulfonyl group, in which
the charge is delocalized along with the oxygen−sulfur−oxygen
atoms.19 The same trend is also observed here for compounds
10 and 11. The (1-2,5-η-) bonding mode of the butadiene-
sulfonyl ligand in 10 and 11 was evident from 1H and 13C{1H}
C. Butadienesulfonyl Chemistry. [(η4-COD)IrCl(1-2,5-
η-CH2CHCHCHS(O2−M+)]. The synthesis of compounds [(η4-
COD)IrCl(1-2,5-η-CH2CHCHCHS(O2−M+)] (M = Li, 10; M
= K, 11) was carried out by mixing compound 4 and two
equivalents of the salts 3M (M = Li, K) suspended in THF at
room temperature, Scheme 4.
Scheme 4
1
NMR spectroscopy, as described in Tables 3 and 4. In the H
NMR spectra, H4 and H3 resonate at a typical olefinic value of
δ 5.83 and 6.12, while H1, H1′, and H2 are shifted substantially
upfield to δ 2.08−2.09, 2.85−2.86, and 4.61, respectively.
Similarly, in the 13C{1H} NMR the metal-coordinated carbons
C1 and C2 resonate at around δ 41 and 62, respectively, while
the uncoordinated carbons C3 and C4 appear downfield at
around δ 139 and 141, respectively. The 7Li NMR in DMSO-d6
shows a singlet at 4.2 ppm for 10.
The microanalysis showed one lithium and chloro, or the
corresponding potassium and chloro, per each molecule of (η4-
COD)Ir(1-2,5-η-CH2CHCHCHSO2) in 10 and 11, respec-
tively. The isolated product 11, upon dissolution in CDCl3,
showed a precipitate identified as KCl. The evidence of KCl
was unequivocally established in solution by electrochemical
detection of Cl−, as well as the isolation and powder diffraction
of the solid, which was filtered from the synthetic reaction of
compound 16 (vide infra).
Cyclic voltammetry confirmed the formation of the ion-pair
[(η4-COD)IrCl(1-2,5-η-CH2CHCHCHS(O2−K+)] (11), and
an electrochemical experiment was also carried out in order
to demonstrate the presence of the potassium cation in 11; it
was possible to trap the cation with 18-crown-6 ether, which
shows that there is a proportional response between the current
intensity and the concentration of the crown-ether. This
suggests that the K+ cation was trapped by the ether and
released higher concentrations of free 11−; see the Supporting
Information.
The higher stability of 3K, as well as the easier removal of
KCl compared to LiCl from 11 and 10 in the presence of donor
molecules, determined the use of 11 in the development of the
iridium-cyclooctadiene chemistry.
As already mentioned, the reaction of 4 in THF with 3K,
after stirring for 1 h at room temperature, gave a cream powder
of 11 in 66% yield. If shorter reaction times (10 min) are used
at low temperature (−110 °C) and after evaporating of THF,
an intermediate mustard-yellow solid, (η4-COD)Ir(μ-Cl)(1-2-
η-S,O-μ-OSOCHCHCHCH2)Ir(η4-COD) (12), is isolated in
60% yield, Scheme 4. Compound 12 showed the butadiene-
sulfonyl ligand bonding in an intermolecular fashion, as a
In each case, the product or reaction showed a transparent
amber solution, from which product 10 or 11 could be isolated
in 69% and 66% yield, respectively. The formation of a dimeric
structure, such as [(η4-COD)Ir(Cl)(5-η-CH2CHCHCHSO2)-
(Li)]2, analogous to the Cp*Ir derivatives15 described in the
Introduction, or the mononuclear ion-pair complex [(η4-
COD)IrCl(1-2,5-η-CH2CHCHCHS(O2−Li+)] (10) such as
those found in Cp*Ru34 and Cp*Rh35 chemistry could be
expected. On the basis of the mass spectra and without
crystallographic evidence, we describe the structure as
mononuclear ion-pair 10.
The mass spectrum of 10 shows a molecular ion at 460 m/z
assigned to [10]+, along with fragments at 425, 418, 352, and
316 m/z as a consequence of losing Cl, LiCl, and COD (Cl and
COD), respectively. This detailed pattern differs from that
found in previous dinuclear compounds prepared with the
Cp*Ir fragments (M = Rh, Ir), which are quite fragile in the
mass spectrometry experimental conditions. However, prelimi-
nary experiments via dynamic laser-light scattering of 10, 11,
and (η4-COD)Ir(1-2,5-η-CH2CHCHCHSO2)PPh3 (17) (vide
infra) showed a monodisperse mixture for 17 (250−550 nm)
and polydisperse mixtures for 10 (0.5−10.0 and 70−6000 nm)
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Table 5. Crystal Data for Iridium Compounds 12, 14, 15, and 17−20
12
14
15
17
18
19
20
formula
mol wt
space group
a (Å)
C20H29ClIr2O2S
753.34
C15H26IrO2PS
493.59
C20H28IrO2PS
555.65
C30H32IrO2PS·CHCl3
799.15
C14H23IrO3S2·2CH2Cl2 C13H17IrO3S
C18H35IrO2P2S
569.66
665.50
445.53
P21/n
P21/n
P212121
8.9049(2)
14.1185(3)
15.1554(3)
90.00
P212121
P1
̅
P21/n
P21/c
6.89680(10)
15.7763(3)
19.2556(4)
90.00
11.4365(6)
12.6545(6)
12.5745(7)
90.00
10.1020(2)
14.2439(3)
20.7100(4)
90.00
9.3620(3)
10.5183(4)
13.1777(6)
96.051(2)
108.552(2)
108.589(2)
1134.71(8)
2
8.26540(10)
24.3232(4)
13.0908(3)
90.00
9.5092(2)
14.5052(3)
16.0327(3)
90.00
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
100.3440(1)
90.00
111.603(3)
90.00
90.00
90.00
100.5710(1)
90.00
99.7080(10)
90.00
90.00
90.00
2061.07(7)
4
1691.99(15)
4
1905.40(7)
4
2980.00(10)
4
2587.12(8)
8
2179.77(8)
4
cryst size (mm) 0.25 × 0.10 ×
0.15 × 0.10 ×
0.10
0.35 × 0.15 ×
0.15
0.15 × 0.15 × 0.15
0.38 × 0.25 × 0.13
0.40 × 0.30 × 0.45 × 0.25 ×
0.08
0.20
0.20
Dcalc (g cm−3)
limit θ
2.428
1.938
1.937
1.781
1.948
2.288
1.736
7.20−54.94
−8 ≤ h ≤ 8
−20 ≤ k ≤ 18
−22 ≤ l ≤ 24
4.74−54.98
−14 ≤ h ≤ 14 −11 ≤ h ≤ 11
−15 ≤ k ≤ 16 −18 ≤ k ≤ 15
−16 ≤ l ≤ 15
16 094
7.06−54.94
6.94−54.96
−12 ≤ h ≤ 13
−18 ≤ k ≤ 15
−23 ≤ l ≤ 26
18 417
6.62−55.06
−12 ≤ h ≤ 11
−13 ≤ k ≤ 13
−17 ≤ l ≤ 16
10 319
5.94−54.96
5.88−54.98
ranges
−10 ≤ h ≤ 10 −11 ≤ h ≤ 12
−31 ≤ k ≤ 29 −18 ≤ k ≤18
−16 ≤ l ≤ 16 −19 ≤ l ≤20
h, k, l
−19 ≤ l ≤ 19
12 459
total no. of data 18 078
23 128
26 713
total no. of
unique data
4525
3815
4240
6708
5128
5833
4992
Rint = 0.0483
0.0460
Rint = 0.0845
0.0431
Rint = 0.0302
0.0197
Rint = 0.0699
0.0390
Rint = 0.0573
0.0480
Rint = 0.0732
0.0372
Rint = 0.0819
0.0370
final R1
final wR2
GOF
0.0569
0.0879
0.0409
0.0691
0.1122
0.0740
0.0839
1.137
1.054
0.972
1.027
1.030
1.025
1.060
sulfinato-O,S complex,36 which was fully characterized,
including the crystal structure, Table 5 and Figure 3.
It is also interesting to mention that, in solution, dinuclear
compound 12 dissociates in the presence of coordinating
solvents, such as DMSO-d6 or THF-d8, while the dinuclear
asymmetric structure remains in CDCl3; see the Supporting
Information. IR of 12 shows the corresponding SO2 vibration
bands at 1151 (vs, br), 1107 (s, sh), 1034 (vs), and 1004 (s,
sh).
When a suspension of 3K in THF is added to 12, there is
evidence of formation of 11 along with traces of another
complex, tentatively assigned as (η4-COD)Ir(1-2,5-η-
CH2CHCHCHSO2)(5-η-S(O2−K+)CHCHCHCH2) (13), ac-
cording to the 1H NMR, which gives evidence of two
butadienesulfonyl ligands coordinated to the Ir(COD) frag-
ment in different (1-2,5-η-) and (5-η-) bonding modes. This
reaction was nonselective, showing a mixture of 13, 3K, and 11,
from which we could remove 3K, but were unable to isolate 13
as a pure compound.
[(η4-COD)IrCl(1-2,5-η-CH2CHCHCHSO2)L]. The series of
pentacoordinated Ir(I) complexes of general formula [(η4-
COD)Ir(1-2,5-η-CH2CHCHCHSO2)L] (L = PMe3, 14;
PMe2Ph, 15; PMePh2, 16; PPh3, 17; DMSO, 18; and CO,
19) were prepared, under mild conditions, from 11 and the
corresponding ligand L, which shows different σ or π donor−
acceptor properties. Compounds 15−17, which are derivatives
with aromatic groups in the phosphine ligands, gave the highest
yields (44−97%); the lowest yield, 14, was obtained for the
most basic PMe3 (32%). The σ-donor DMSO affords complex
18 in 55% yield, while the best π-acceptor ligand, CO in
complex 19, required double chromatography, and it was
obtained in 60% yield. Compounds 14−19 are readily soluble
in THF and CHCl3, Scheme 5.
Figure 3. Molecular structure of [(η4-COD)Ir(μ-Cl)(1-2-η-S,O-μ-
OSOCHCHCHCH2)-Ir(η4-COD)] (12).
Compound 12 is formed by a half-molecule of the dimer 4,
which bridges, through the chloro atom, to a (η4-COD)Ir(1-
2,5-η-CH2CHCHCHSO2); one oxygen of the butadienesul-
fonyl ligand also bridges the corresponding (η4-COD)IrCl
fragment. The bond length of S1−Ir1 is particularly short
[2.2738(14) Å] compared to that in 14, 15, 17−20 [average
2.31 Å, Table 6] and Cp*IrCl(1-2,5-η-CH2CHCHCHSO2)
[2.3091(18) Å]12 and is even shorter than that in the dimeric
structures [Cp*Ir(Cl)2{(5-η-CHRCHCRCHSO2)}(Li)-
(THF)]2 [average 2.2948 Å]. As expected, S1−O2 [1.507(5)
Å] is significantly longer, due to the O2 to Ir2 bridging bond.
The bond lengths Ir1−Cl2 [2.5392(14) Å] and Ir2−Cl2
[2.3662(14) Å] are longer and shorter, respectively, than those
in 4, where a range of 2.397−2.407 Å is observed.37
The disubstituted trimethylphosphine complex [(η4-COD)-
Ir(5-η-SO2CHCHCHCH2)(PMe3)2] (20) was obtained by
addition of six equivalents of phosphine to compound 14,
Scheme 5. All derivatives 14−19 are fairly stable kinetically in
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Scheme 5
Scheme 7
the solid state, slightly air-sensitive in solution, and thermally
stable, while 20 easily dissociates PMe3, affording an equilibria
with 14 and 20′ (vide infra). The phosphine derivatives 14−17
and 20 melt sharply, without decomposition, while 18 and 19
melt with decomposition.
Compounds 14, 15, 18, and 19 were prepared in situ, using
stoichiometric amounts of dimer 4 with 3Na, 3Li, or 3K in the
presence of two equivalents of the PMe3 or PMe2Ph and excess
DMSO or CO. However, better yields can be obtained from
the former reaction in which 11 was previously isolated. Also,
lower yields were obtained when 10 was used, and because of
that, all reactions described here, as already mentioned, will be
related to the addition reactions exclusively to compound 11,
except for [(η4-COD)Ir(1-2,5-η-SO2CHC(Me)CHCH(Me))-
PMe3] (14Me), which was obtained only from reaction of 4
and two equivalents of Li[SO2CHC(Me)CHCHMe] and
PMe3, Scheme 6.
advantage was found in the formation of 17, which was isolated
in 53.0% yield compared to the 82.0% yield obtained from the
addition reaction of PPh3 to 11, Scheme 5.
Interestingly, compound [(η4-COD)IrCl(PMe3)2] (23) in
1
the presence of 3K showed, through the H NMR, that it was
not a useful precursor of 20 due to its competition in the
formation of 14 and an intermediate species, tentatively
proposed as [(η4-COD)Ir(5-η-SO2CHCHCHCH2)(PMe3)]2
(20′),38 which will be discussed below. The reaction between
[(η4-COD)Ir(PMe3)3]Cl (24) and one equivalent of 3K in
THF did not show formation of 20 or 20′, while OPMe3, 14,
and an unidentified compound (31P NMR δ −33.0) were
detected in 0.14:0.64:0.22 ratio, respectively. According to
these results, several monitoring reactions were carried out in
order to understand the competition among species present in
solution: (a) Reaction between 23 and different stoichiometries
of 3K in THF showed that under low concentration of 3K, 14
and small amounts of 20′ were formed, whereas in a 10-fold
excess of 3K, compound 20 was also observed, along with 14,
20′, 23, and OPMe3. Independently of the concentration of 3K,
all reactions favored the formation of 14.
Scheme 6
(b) The reaction between 11 and PMe3 in THF-d8, at room
temperature, showed basically formation of 14. A second and
third equivalent of PMe3 showed 20′, 20, and 14 in relative
0.43:0.32:0.19 and 0.18:0.58:0.10 ratios, respectively. Even
under the presence of free PMe3 compounds 20′ and 14
remained with 20 in the reaction mixture, which suggests that
there is an equilibrium among them (Scheme 7a), as it was also
concluded from monitoring the reaction between 12 and PMe3
(Scheme 7b, vide infra).
(c) Compound 12, in the presence of one equivalent of
PMe3, in THF-d8, showed easy coordination and dissociation of
the phosphine, which afforded a mixture of 14, 21, and 23,
Scheme 7b. First, 23 was predominating, and with time one
Compound 19 in the presence of THF and 1.5 equivalents of
PMe3 shows total conversion to a mixture of 14 and 20, which
confirms the lability of the CO−Ir bond, the stronger Ir−PMe3
bond to give 14, and the labile coordination of the terminal
double bond to afford 20 with two PMe3's coordinated to Ir.
The mixture of reaction of 14 and 20 was impossible to
purify due to the presence of an equilibria; see Scheme 7a. The
low yield obtained for 14 (32%) motivated us to find a better
synthetic precursor that did not require the addition of PMe3.
The complex [(η4-COD)IrClPMe3] (21) was prepared in 73%
yield, which after the metathesis reaction with 3K afforded the
corresponding 14, in 79% yield. Contrasting this result, when
[(η4-COD)IrClPPh3] (22) reacted with 3K, no synthetic
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PMe3 was dissociated and 21 and 14 were observed as major
compounds in an almost 1:1 ratio. Addition of a second and
third equivalent of PMe3 showed the same trend. As expected,
after consecutive addition of two equivalents of 3K, compound
14 was predominating, and finally, the addition of three more
equivalents of PMe3 gave spectroscopic evidence of 20′ and, in
higher amount, compound 20,39 but always with 14 and free
PMe3.
11 > 10. Considering the stretching frequencies of other
complexes with the butadienesulfonyl ligand, such as the ion-
pair complexes Cp*RhCl(5-η-SO2CHCHCHCH2)(5-η-S-
(O2−K+)CHCHCHCH2) (1175, 1111, and 1050 cm−1)35 and
Cp*Ru(1-2,5-η-SO2 CHCHCHCH2 )(5-η-S(O2− K+ )-
CHCHCHCH2) (1136, 1108, and 1024 cm−1),34 those could
be included in the previous trend, along with complexes 14−19
and 10, respectively, showing better delocalization of the
ruthenium complex compared to the isoelectronic rhodium
analogue.
(d) The reaction of 14 with 1 equiv of PMe3 in C6D6 at
room temperature showed immediate transformation into 20
and 20′, along with 14 and free PMe3 (Scheme 7a). The
addition of two more equivalents of PMe3 showed the highest
amount of 20 formed, along with reduction of the amount of
20′, 14, and PMe3 in a 0.46:0.20:0.04:0.30 ratio, respectively.
After 3 days, 20 dissociated with the corresponding increase of
20′, 14, and PMe3 (0.26:0.34:0.07:0.33). From this result, it was
also evident that 20 dissociates PMe3 and the dimer 20′ plays a
role in the equilibrium among 14 and 20. From monitoring
reactions b, c, and d, it can be concluded that the excess of
PMe3 favors the formation of 20, which easily dissociates PMe3
to afford the coordinatively unsaturated complex (η4-COD)Ir-
(5-η-SO2CHCHCHCH2)(PMe3) (14′), which can dimerize to
20′ or go back, in the presence of PMe3, to the formation of 20.
Compound 20′ can also go back to 14, by dissociation of the
dimer and the consequent coordination of the terminal double
bond; the presence of this equilibrium avoided a selective
reaction for 20. An even greater lack of selectivity for 20 was
observed when iridium chloro complexes, such as 23 or 24,
were used as precursors. According to the reactivity of 21, 20,
or 23, it is evident that one Ir−PMe3 bond bonds strongly,
while the second one, in 20 and 23, is labile.
The carbonyl stretching frequency in compound 19 shows a
strong band at 2049 cm−1, which reflects the lowest
retrodonation compared to the thiapentadienyl complex Ir(1-
2,5-η-CH2CHCHCHS)(CO)(PPh3)2 (8) (νCO, 1982 cm−1),
IrCl(CO)(PPh3)2 (νCO, 1954 cm−1), and IrCl(CO)-
(PPh3)2SO2 [(νCO, 2013 cm−1; νSO2, 1197, 1049 cm−1)43
and (νCO, 2020 cm−1; νSO2, 1198, 1185, 1048, 559 cm−1)44].
The carbonyl retrodonation decreases strongly in the
presence of the thiapentadienyl ligand, and even more if the
sulfonyl or butadienesulfonyl ligand is present, which reflects
the π-bonding of SO2 and consequent lability of CO in the
presence of coordinated sulfonyl groups. The fragile bond Ir−
CO was also confirmed when 19, under very mild conditions,
afforded a mixture of compounds 14 and 20 (vide supra).
NMR Spectra. The presence of the butadienesulfonyl ligand
in the complexes 14−19 induced a total asymmetry, which was
reflected in complex spectra, from which full assignment was
done based on two-dimensional HETCOR (1H, 13C) and
COSY (1H, 1H) experiments, which aided in assigning some of
1
the H and 13C signals in Tables 3 and 4, respectively.
There was a preferred coordination mode in the chemistry of
the adducts 14−19, where the butadienesulfonyl ligand was
coordinated through the sulfur atom η1 and η2 with the
terminal double bond (C1−C2) to the iridium atom. This type
of bonding has been previously observed for several
butadienesulfonyl iridium15,16 and rhodium16,35 compounds,
as well as for thiapentadienyl and sulfinylpentadienyl
compounds, vide supra.
1
Considering that the H and 13C NMR showed signals for
20′ corresponding to η4-COD, 5-η-SO2CHCHCHCH2, and
PMe3, and in order to explain the general trends observed
through the monitoring reactions described above, it is being
proposed that 20′ is dimeric. It was noted that 20′ was not
immediately consumed after being formed, even in excess
PMe3. This fact should discriminate a coordinatively unsatu-
rated complex 14′, therefore suggesting the tentative formation
of a dimeric structure that could be interacting though the S
and O atoms of the butadienesulfonyl ligands with the two
iridium centers. The S, O-bonded sulfinato complex 20′ is
proposed as the kinetic product, while the thermodynamic 20
or 14 is exclusively an S-bound sulfinate, as expected for a soft
metal.
In the 13C NMR there was a clear trend of increasing π-
retrodonation at C1−C2 going from [(η4-COD)Ir(1-2,5-η-
SO2CHCHCHCH2)(PR3)], where PR3 increased methyl
substitution from PPh3 until PMe3, which was also reflected
1
in H1, H1′, and H2 through the H NMR.
The cyclooctadiene bound to iridium in 14−19 showed eight
different carbon atoms, where significant lower frequency
chemical shifts were observed for C5 and C6, compared to
those of C9 and C10 (Δδ ≅ 20−30), where C9 and C10
showed a significant reduced capability of retrodonation. The
coordinated olefins C5−C6 with the strongest and lowest
retrodonation were those corresponding to the PMe3 [C5 (δ
66.38) and C6 (δ 68.16)] and CO [C5 (δ 75.69) and C6 (δ
76.49)] derivatives, respectively.
Infrared Spectra. The infrared data of the complexes 14−
19 show several characteristic items connected basically with
the sulfoxide group. Strong intensity signals are observed for
the antisymmetric and symmetric vibration SO in the region
(1174−1166 and 1110−1098 cm−1) and (1052−1019 cm−1),
respectively. Similar stretching frequencies at 1198 (νas), 1185
40
(νas), and 1048 (νs) cm−1
are reported for IrCl(CO)-
1
(PPh3)2SO2, where the corresponding bands are at slightly high
frequency, which reflects the influence of the butadiene
fragment bonded to SO2, in the case of 14−19. The free SO2
shows two bands at higher frequencies [1340 (νas) and 1150
(νs) cm−1],40 and theoretical and experimental studies related
to the vibration of the SO group,41 as well as the influence of
different solvents in the IR of DMSO and DMSO-d6, have been
reported in the region of 1250−1100 cm−1 for νas and 1100−
1000 cm−1 for νs.42 According to the above, qualitatively, the
relative bond order in the SO bond decreases in the
following order: SO2 > IrCl(CO)(PPh3)2SO2 > 14−19 > 12 ∼
The H NMR spectra of the COD-coordinated ligand for
compounds 14−18, except in a few cases of overlapping,
showed nonequivalent hydrogens for the CH and CH2 signals,
which gave evidence for the lack of symmetry of this
nonconjugated unsaturated ligand. Full inequivalence of 12
hydrogens of the COD ligand was found in compound 19, as
described in the Supporting Information.
There was significant similarity in the 13C chemical shifts of
18 (CDCl3), 12, 10, and 11 (DMSO-d6), which suggests the
stronger σ-donor character of DMSO compared to phosphines
1
and CO. The H and 13C NMR of compound 18 showed two
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magnetically nonequivalent methyl groups for the DMSO
ligand (1H δ: 3.34 and 3.46; 13C δ: 45.49 and 47.10,
respectively), which gave evidence of the rigidity and chirality
of 18. Different methyl environments in coordinated DMSO
have also been proved as indicative of a lack of any symmetry
element in complex [RuCl(DMSO)2{HB(methimazolyl)3];45
diastereotopic methyl groups of two equivalent DMSOs trans
46
to Cl in [cis,fac-RuCl2(DMSO-O)3(NO)]BF4 have been
reported as well as chiral iridium compounds, such as
cyclometalated derivatives of Cp*IrCl2(DMSO) with crotonic
acids47 or complexes [Cp*IrMe(DMSO)(X)] (X = Cl, Br, I)48
or [Cp*IrMe(DMSO)(L)]PF6 (L = MeCN, O2CCF3).48
1
The H and 13C NMR of 20 are diagnostic and showed that
both double bonds of the butadienesulfonyl ligand were not
coordinated to the metal. At room temperature, the 31P NMR
spectrum of 20 exhibited a singlet at −52.4 ppm. A dynamic
process was evident by 1H and 13C NMR where only one set of
CH [3.20 (s); 68.60 (d, 5.3 Hz)], two sets of CH2 [2.23 (m),
2.40 (m)], and one set of CH2 [34.18 (s, br)] were observed
for the COD-coordinated ligand. There was a typical second-
order coupling for the methyl groups of the phosphine ligands
Figure 4. Molecular structure of (η4-COD)Ir(1-2,5-η-
CH2CHCHCHSO2)PMe3 (14).
1
in the H NMR (1.62 ppm) and a complex coupling at 20.02
ppm that was observed by 13C NMR. As the 31P NMR of
compound 20 (δ −52.4) was identical to 23 or 24 (in CDCl3,
there was no evidence of dissociation of PMe3 for 24), it was
1
only possible to identify 20 by H and 13C NMR. The full
spectroscopic NMR data of 22 and 23 are included in Tables 3
and 4 because they have been only partially reported. In 21 and
22 the cyclooctadiene is bound to the square-planar iridium
center, showing inequivalent alkene resonances because of the
1
distinct trans ligands, as shown by two H NMR signals at
lowest field at δ 2.87, 5.33 and δ 2.73, 5.19, for hydrogens of
the CH carbons at C5,6 and C9,10, respectively. Those
hydrogen signals correlated in the HETCOR (1H, 13C) spectra
with carbon singlets at δ 51.37 and 54.03 and two doublets at δ
93.38 and 94.44 with JCP coupling constant of 14.6 and 14.3 Hz,
respectively. The latter coupling reflects the coordination of the
corresponding phosphine trans to the C9−C10. The trend
observed by Crabtree and Morris,49 concerning the electronic
effects of the trans ligands in the COD vinyl protons of [(η4-
COD)IrClL] complexes, was still confirmed for compound 21.
Two pair of carbon signals at δ 33.95, 29.20 and δ 33.90, 29.97
were observed for the methylene carbons in 21 and 22, from
which selective irradiations in 22 and correlation experiments
allowed us to assign the corresponding hydrogens C7, C12 and
C8, C11 at low and high frequency, respectively.
Figure 5. Molecular structure of (η4-COD)Ir(1-2,5-η-
CH2CHCHCHSO2)PMe2Ph (15). Some hydrogens atoms are
omitted for clarity.
Crystal Structures. The solid-state structures of com-
pounds 14, 15, and 17−20 are presented in Figures 4, 5, and
6−9, respectively. The crystal data and selected bond lengths
and angles are provided in Tables 5, 6, and 7, respectively. The
crystal structure determination of compound 19 revealed the
presence of two independent molecules in the unit cell. These
molecules are structurally identical, and for clarity, the crystal
data and structure of only one is shown in Tables 5−7 and
Figure 8. One and two molecules of chloroform and
dichloromethane cocrystallized with compounds 17 and 18,
respectively. Distorted trigonal-bipyramidal (tbpy) geometries
were established for all crystalline structures. In general, the
structural parameters for complexes 14, 15, and 17−19
correspond fairly closely to each other. The equatorial plane
of the tbpy contains the coordinated double bonds C5−C6 of
the COD and C1−C2 of the butadienesulfonyl ligands, as well
as the P, S, or C atom corresponding to ligand L (L =
phosphine, DMSO, or CO), while the sulfur of the
butadienesulfonyl ligand and the double bond C9−C10 of
the COD are in axial positions.
The bonding parameters within the butadienesulfonyl ligands
are quite similar, except for 20, which is coordinated exclusively
through the sulfur atom. The terminal double bond of the
butadienesulfonyl ligands in 14, 15, and 17−19 is coordinated
to the iridium center, which is clearly demonstrated by the
enlargement of the bond lengths due to the retrodonation of
C1−C2, which are in the range 1.415−1.434 Å. In contrast, the
internal double bonds, which are not coordinated, show the
typical sp2 C3−C4 bond length between 1.293 and 1.340 Å,
respectively. The C1−C2−C3−C4 and C2−C3−C4−S1
torsional angles for the (1-2,5-η)-butadienesulfonyl complexes
[63.32(1.16)°, 2.43(1.26)° 14; 63.06(0.69)°, 1.44(0.74)° 15;
63.49(0.95)°, 5.27(0.97)° 17; 67.53(1.17)°, 3.63(1.26)° 18;
61.56(1.03)°, 5.39(1.08)° 19] imply that the ligand can be
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Figure 6. Molecular structure of (η4-COD)Ir(1-2,5-η-
CH2CHCHCHSO2)PPh3 (17).
Figure 8. Molecular structure of (η4-COD)Ir(1-2,5-η-
CH2CHCHCHSO2)(CO) (19).
Figure 7. Molecular structure of (η4-COD)Ir(1-2,5-η-
CH2CHCHCHSO2)(DMSO) (18).
described more accurately as a U conformer than an S one. In
contrast, compound 20 shows a torsional angle of 178.55(0.82)
°, −3.55(1.20)°, which gives evidence of the butadienesulfonyl
ligand being S shaped, and where the double bonds are not
coordinated to the iridium atom, according to C1−C2
[1.335(11) Å] and C3−C4 [1.330(9) Å] bond lenghts. The
C4−S bond length in all crystalline structures reported here
showed a carbon bond length that lies between normal C−S
single bond (1.82 Å) and double bond (1.60 Å).50 Compound
20 [1.790(7) Å] showed the longest C4−S bond lengths, where
the coordination of the butadienesulfonyl ligand is through an
η1-bonding mode. The longer bond distance C4−S observed in
17 [1.788(7) Å] is attributed to the bulky PPh3 coordinated
also to the iridium center.
Figure 9. Molecular structure of (η4 -COD)Ir(5-η-
CH2CHCHCHSO2)(PMe3)2 (20).
The S1−O1 and S1−O2 (average value 1.46 Å) reflect
typical values for sulfonyl groups (1.457 Å).51 The Ir−S bond
lengths decreased according to the number of oxygen atoms
bonded to sulfur, as observed in 5 [2.3788(18), 2.4900(17) Å],
9 [2.329(2), 2.444(3) Å], and the average value of 2.31 Å found
in butadienesulfonyl derivatives 14, 15, and 16−19. The Ir−P
bond lengths showed, as expected, the longest value for the
bulky triphenylphosphine complex 17 [2.4563(16) Å], and 20
showed different Ir−P bond lengths [Ir1−P1, 2.3731(14) and
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Ir1−P2, 2.3334(13) Å], where the shortest is reflecting a higher
trans effect of the COD ligand on P2.
[2.317(3) Å] and Ir−S [2.334(3) Å], respectively, than those
observed in 14 [Ir−P, 2.398(2) Å; Ir−S, 2.3076(19) Å].
A comparison with pentadienyl complexes, such as Ir(2,4-
The iridium−COD bonding in 14, 15, and 17−19 showed,
as expected for d8 tbpy geometry,52 shorter Ir−C bond lengths
for the equatorial Ir−C5 [range: 2.169−2.203 Å] and Ir−C6
[range: 2.170−2.198 Å] compared to the axially coordinated
Ir−C9 [range: 2.280−2.329 Å] and Ir−C10 [range: 2.249−
2.287 Å], which confirms the strongest binding of an olefin to a
d8 metal center in a trigonal plane. This stronger iridium−olefin
interaction is also reflected in the longer bond length between
C5−C6 [range: 1.401−1.434 Å], which gives evidence of a
more efficient retrodonation compared to that of C9−C10
[range: 1.372−1.390 Å].
Compound 20 showed a similar trend; however, the
differences between Ir−C of the corresponding C5 [2.190(6)
Å], C6 [2.168(5) Å] and C9 [2.200(6) Å], C10 [2.229(5) Å]
were shorter. The bond lengths C5−C6 [1.437(9) Å] and C9−
C10 [1.412(9)] were slightly different from those described
before; this seems to be the result of the presence a second
phosphine P2, C6−Ir−P2 [167.21(18)°], where a trans
influence was also present. A more symmetric coordination of
the cyclooctadiene ligand was also observed through NMR
spectroscopy in solution for 20.
Comparison of the bond lengths of C1−C2 of the phosphine
derivatives 14 [1.426(12) Å], 15 [1.434(6) Å], and 17
[1.429(10) Å] with the corresponding Ir(2,4-dimethyl-1,4-5-
η-pentadienyl)(PMe3)3 [1.469(13) Å]31 shows a lower
retrodonation in the butadienesulfonyl derivatives, as expected
for less electron-rich complexes. A higher retrodonation of the
cyclooctadiene ligand in the thiapentadienyl 5 related to 1-2,5-
η-butadienesulfonyl derivatives 14−19 (independently of the
substituted L) was observed, according to longer carbon−
carbon double bond lengths [C5−C6, 1.446(12) Å and C9−
C10, 1.403(12) Å] and shorter carbon−iridium bond lengths
[C5−Ir, 2.135(7) Å; C6−Ir, 2.155(8) Å; C9−Ir, 2.182(8) Å;
C10−Ir, 2.201(8) Å] compared to those of 1-2,5-η-
butadienesulfonyl derivatives [C5−C6, range: 1.401−1.426 Å,
except for 17 (1.434(10) Å); C9−C10, range: 1.372−1.390 Å;
C5−Ir, range: 2.169−2.203 Å; C6−Ir, range: 2.170−2.198 Å;
C9−Ir, range: 2.243−2.329 Å; C10−Ir, range: 2.249−2.287 Å].
A similar trend was observed for 22 and 17, in which 22
showed a better retrodonation, in a more symmetric cyclo-
octadiene−iridium interaction, according to carbon−carbon
and carbon−iridium bond lengths.53 The Ir−P bond length is
strongly affected by the presence of the sulfonyl group in the
heterodienyl ligand, as observed from 14 [2.398(2) Å] and 20
[2.3731(14) Å], which show significantly longer Ir−P bond
lengths compared to those of thiapentadienyl and pentadienyl
derivatives: Ir(1-2,5-η-thiapentadienyl)(PMe3)3 [2.261(3),
2.293(3), and 2.323(2) Å]4 and Ir(2,4-dimethyl-1,4-5-η-
pentadienyl)(PMe3)3 [2.291(3), 2.288(2), and 2.323(3) Å].31
Similarly long bond values were found for butadienesulfonyl
derivatives with PMe2Ph [2.3896(10) Å, 15] and PPh3
[2.4563(16) Å, 17]. Also, the Ir−S, Ir−C1, and Ir−C2 showed
clearly the influence of the sulfonyl group. The Ir−S bond
lengths in compounds 14, 15, 17, 18, 19, and 20 are shorter
(range: 2.3011−2.3168 Å) compared to those of the
thiapentadienyl complex Ir(1-2,5-η-thiapentadienyl)(PMe3)3
[2.417(3) Å],4 while Ir−C1 (range: 2.140−2.177 Å) and Ir−
C2 (range: 2.163−2.191 Å) are longer compared to those of
the thiapentadienyl complex [2.110(9) and 2.139(9) Å],4
respectively. Comparison of [Cp*Ir(PMe3)(SO2Me)(MeCN)]-
[OTf]54 shows shorter and longer bond lengths for Ir−P
31
dimethyl-1,4-5-η-pentadienyl)(CO)(PPh3)2 and Ir(syn-1-3-η-
pentadienyl)(CO)(PPh3)2,31 was carried out due to the lack of
crystalline structures of iridium complexes that contain
thiapentadienyl, along with CO and/or PPh3 ligands. The Ir−
P is significantly longer for 17 [2.4563(16) Å] compared to
Ir(2,4-dimethyl-1,4-5-η-pentadienyl)(CO)(PPh3)2 [2.336(2)
Å] and Ir(syn-1-3-η-pentadienyl)(CO)(PPh3)2 [2.296(3) Å],
while bond angles P1−Ir1−C1 are very close to 90° in all cases.
The Ir−CO bond length is significantly longer in 19 [1.950(7)
Å] compared to pentadienyl complexes described above: 2,4-
dimethyl derivative [1.886(7) Å] and syn-1-3-η-pentadienyl
[1.872(12) Å]. The same trend was reflected through the IR
spectra, vide supra.
CONCLUSIONS
■
This study demonstrates that the thiapentadienyl, sulfinylpen-
tadienyl, and butadienesulfonyl in cyclooctadiene iridium
complexes can act as sulfur and oxygen bridging ligands.
Compounds 5, 6, and 10−19 show totally asymmetric
cyclooctadiene ligands. The presence of the SO2 in the
heterodienyl ligand modifies significantly the structural and
electronic properties of the corresponding metallic derivatives,
compared to those previously obtained with the oxo, aza, and
thiapentadienyl ligands. The research in the field of
butadienesulfonyl ligands will continue in order to explore
and learn, in more detail, about their synthetic potential; this
will afford novel properties, such as bonding mode, polarity,
chirality, and peculiar reactivity.
EXPERIMENTAL SECTION
■
All experiments were carried out under a nitrogen atmosphere by
using standard Schlenk-type equipment, and the hydrides and lithium
and potassium salts were weighed in a glovebox. The solvents were
dried by standard methods (diethyl ether and THF with Na/
benzophenone) and distilled under nitrogen prior to use. Deuterated
solvents were degassed, and DMSO-d6 (Cambridge Isotopes
Laboratory Inc.) was dried with Na before use. The preparation of
sodium and potassium thiapentadienyl salts17,19 1Na, 1K, and
sulfinylpentadienyl 2K19 and lithium and potassium butadienesulfonyls
3Li, 3K, and Li[MeCHCHC(Me)CHSO2],19 as well as complexes
[Ir(η4-COD)(μ-Cl)]2 (4),55 trans-Ir(CO)Cl(PPh3)2 (7),56,57 Ir(η4-
COD)(Cl)PPh3 (22),49,53,58 Ir(η4-COD)(Cl)(PMe3)2 (23),57 and
[Ir(η4-COD)(PMe3)3]Cl (24)59 has already been published. All other
chemicals were used as purchased from Pressure Chemicals, Sigma-
Aldrich, Strem Chemicals, Merck, and J. T. Baker, Co. (industrial
grade).
7
The 1H, 13C, 31P, Li, and 11B NMR spectra were recorded on
Bruker 300, Jeol GSX-270, and JEOL Eclipse 400 MHz instruments
and referenced internally using the residual protio and carbon solvent
resonances relative to tetramethylsilane. External standards for 31P and
7Li NMR were H3PO4 and LiCl. Mass spectra were recorded on a
Hewlett-Packard 5890-MS-Engine. High-resolution mass spectra were
obtained by LC/MSD TOF on an Agilent Technologies instrument
with APCI as ionization source and FAB or ESI at the University of
Washington, St. Louis, MO, USA. Elemental analyses were performed
in a Thermo-Finnigan model Flash 1112 at the Chemistry Department
at Cinvestav and Desert Analytics, Tucson, AZ, USA. Infrared spectra
were recorded on a FT-IR Perkin-Elmer 1600 spectrometer using KBr
pellets (4000−400 cm−1) and Nujol in PTFE (4000−200 cm−1).
Melting points were determined in a Melt-Temp Gallenkamp (digital)
and are uncorrected.
Dynamic Laser-Light Scattering (DLS) Instrumentation and
Measurements. For dynamic DLS measurements of compounds 10,
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11, and 17, the samples were prepared in THF at highly diluted
concentrations, and then they were filtered through a Millipore 0.5 μm
LCR filter for dust removal and poured in a quartz cell. A commercial
DLS spectrometer (Malvern Zetasizer Nano 90) equipped with a fast
correlator card (minimum sample time is 12.5 ns) and temperature
control from 2 to 90 °C was used for measurements. A He−Ne laser
operated at 633 nm and 4.0 mW was used as the light source using a
multiple narrow method. The primary beam was vertically polarized.
Scattered intensity was taken at 90° to the incident beam. For the
calculation of the hydrodynamic radius Rh in THF values of 0.4549
and 1.409 were used for the viscosity η and the refractive index RI,
respectively. A value of 1.4 was used as the refractive index of
complexes 10, 11, and 17.
Crystal Structure Determination. X-ray diffraction measure-
ments were made at 169(2) K (17, 19, 20); 198(2) K (15); 203(2) K
(14); and 293(2) K (9, 12, 18) on an Enraf Nonius-Kappa CCD or at
298(2) K on a CAD4 (5) diffractometer, using graphite-monochro-
mated Mo Kα radiation (λ = 0.71073 Å). A summary of crystal data
collection and refinement (SHELX-97) parameters for compounds is
given in Tables 1, 2, and 5−7. The ellipsoids were drawn at 45%
probability for all crystalline structures.
brown solid was removed. Evaporation of the solvent and drying under
vacuum afforded 24.0 mg of yellow solid, which after recrystallization
in CH2Cl2/Et2O afforded yellow crystals (5 mg), which did not melt
below 260 °C.
Synthesis of [(η4-COD)IrCl(1-2,5-η-(SO2Li)CHCHCHCH2)]
(10). A suspension of 3Li (37.0 mg, 0.30 mmol) in THF (5 mL) was
stirred and added dropwise, at −110 °C (liquid N2/EtOH), to a
suspension of 4 (100 mg, 0.15 mmol) in 5 mL of THF. The reaction
mixture was allowed to reach room temperature (≅40 min) and was
stirred for an additional 1 h. The amber solution was filtered, and the
volume of THF was reduced to ≅2 mL. Addition of diethyl ether (≅12
mL) gave a precipitate, which, after filtration, washing three times with
diethyl ether (4 mL), and subsequent drying, afforded a cream powder
of 10 (95.0 mg, 0.021 mmol) in 69.0% yield, which did not melt below
250 °C. IR (KBr, cm −1): 1638 (s, br), 1612 (s, br), 1473 (w), 1446
(m), 1429 (sh), 1358 (vw), 1333 (m), 1305 (s), 1248 (w), 1218 (w),
1133 (vs, br), 1108 (vs, sh), 1029 (vs, br), 875 (m), 828 (vs), 784 (w),
733 (s), 669 (s), 571 (s), 448 (s, br). LR FAB-MS (matrix: 3-NBA-Li):
m/z 460 [M+], 425, 417, 353, 313, 307, 289. HR FAB-MS: m/z
425.0734 (−1.1 ppm). Anal. Calcd for C12H17ClLiO2SIr: C, 31.34; H,
3.73. Found: C, 31.42; H, 4.18.
Synthesis of [(η4-COD)IrCl(1-2,5-η-(SO2K)CHCHCHCH2)]
(11). A suspension of 3K (139.5 mg, 0.90 mmol) in THF (10 mL) was
stirred and added, dropwise at −110 °C (liquid N2/EtOH), to a
suspension of 4 (300.0 mg, 0.45 mmol) in 20 mL of THF. The
reaction mixture was allowed to reach room temperature (≅40 min)
and was stirred for an additional hour. The solution was filtered three
times, and the volume of THF was reduced to 5 mL. Addition of
pentane (70 mL) allowed the precipitation of a cream powder, which
after drying under vacuum, afforded compound 11 in 66.0% yield
(270.0 mg, 0.55 mmol). It did not melt up to 250 °C. The THF/
pentane solution was evaporated under vacuum to afford 12 in 9.0%
yield (30.0 mg, 0.04 mmol). Compound 11: IR (KBr, cm −1): 1639 (s,
sh), 1611 (s), 1474 (m), 1446 (s), 1358 (w), 1332 (s, sh), 1306 (s),
1217 (w), 1146 (vs, br), 1108 (vs, sh) 1041 (vs, br), 949 (w), 874 (w),
824 (s), 786 (w), 731 (s), 666 (s), 569 (s), 523 (w) 445 (s). IR
(Nujol, cm−1): 251 (s), 234 (m). ESI+ TOF: (C12H17O2SKIr) m/z
457.0210; error ppm: −0.0614; DBE: 5.0. Anal. Calcd for
C12H17ClKO2SIr: C, 29.29; H, 3.48; S, 6.52. Found: C, 29.17; H,
3.88; S, 6.81.
Synthesis of [(η4-COD)Ir(1-2,5-η-(μ2-S)CHCHCHCH2)]2
(5). Into a Schlenk flask equipped with a stir bar were placed NaH
(12.0 mg, 0.49 mmol), 0.8 mL of DMSO-d6, and 2,5-dihydrothiophene
(36.3 μL, 39.0 mg, 0.45 mmol). After the mixture was stirred in an
ultrasonic bath for 9 h (25−35 °C), an amber solution was observed,
and 4 (150.0 mg, 0.22 mmol) was added; a brown solid in a dark red
solution was obtained immediately. Addition of hexane afforded more
brown solid, which was filtered and washed with hexane. The volume
of the dark red solution was reduced, and more precipitate was
obtained after addition of acetone. The solid was recrystallized from
CH2Cl2/Et2O at 0 °C as a yellow, crystalline solid in 47.1% yield (81.0
mg, 0.105 mmol). Mp: 181−184 °C. EI-MS (70 eV): m/z 772 [M]+,
662, 577, 554, 384, 301, 277, 245. Anal. Calcd for C24H34S2Ir2: C
37.39, H 4.44. Found: C 37.70, H 4.47.
Synthesis of [(η4-COD)Ir(1-2,5-η-SCHCHCHCH2)PMe3]
(6). Compound 5 (58.0 mg, 0.075 mmol) was placed in a Schlenk
flask with a stir bar and was dissolved in 10 mL of CH2Cl2. The
solution was cooled at −78 °C, and PMe3 (0.018 mL, 0.17 mmol) was
added. The reaction mixture was allowed to reach room temperature
and was stirred 2 h; the yellow color of the solution faded. The solvent
was removed under vacuum, and 6 was extracted from the residue with
hexane, affording a yellow solid in 53.2% yield (37.0 mg, 0.08 mmol).
Mp: 78−79 °C. EI-MS (70 eV): m/z 462 [M]+, 407, 385, 376, 303,
268, 108, 85, 76, 61, 53.
Synthesis of [Ir(1-2,5-η-SCHCHCHCH2)(CO)(PPh3)2] (8).
Compound 7 (300.0 mg, 0.384 mmol) was placed in a Schlenk flask
with a stir bar and was dissolved in 15 mL of THF. Slow addition of
0.4 mL of 1K in DMSO (0.24 g/mL, 95.0 mg, 0.77 mmol), at room
temperature, afforded an amber solution, which was stirred for 2 h.
Removal of the solvent under vacuum gave an oily solid, which was
washed with deoxygenated water (4 × 5 mL) and dried in an oil bath
(55 °C) under vacuum for 9 h. A cream solid was isolated in 81.8%
yield (261.0 mg, 0.32 mmol). Mp: 140−143 °C. IR (KBr): 3055 (m),
2336 (w), 1982 (vs), 1572 (m), 1481 (m), 1434 (s), 1307 (w), 1186
(m), 1092 (m), 1028 (w), 999 (w), 988 (w), 848 (w), 746 (m), 696
(s), 515 (s), 453 (w), 418 (w). LR FAB-MS: m/z 830 [M]+, 745, 715,
636, 568, 540, 453, 375. Anal. Calcd for C41H35OP2SIr·H2O: C 58.08,
H 4.16. Found: C 58.06, H 4.29.
Synthesis of [(η4-COD)Ir(μ-Cl)(1-2-η-S,O-μ-OSOCHCHCH
CH2)Ir(η4-COD)] (12). A suspension of 3K (139.5 mg, 0.90 mmol) in
THF (10 mL) was stirred and added dropwise at −110 °C (liquid N2/
EtOH) to a suspension of 4 (300.0 mg, 0.45 mmol) in 20 mL of THF.
The reaction mixture was allowed to reach −70 °C. The solution was
immediately filtered three times at this temperature; the solution was
kept in a cold bath, and the volume of THF was reduced to 5 mL.
Addition of pentane (70 mL) allowed the precipitation of a cream
solid, which, after filtration and drying, afforded compound 11 (76 mg,
0.15 mmol) in 19.0% yield. The cold solution was evaporated under
vacuum to afford a crystalline yellow solid in 60.0% yield (200.0 mg,
0.26 mmol). Compound 12 decomposes at 150 °C without melting.
Single crystals were obtained from recrystallization of THF/pentane.
IR (KBr, cm −1): 1639 (s, br), 1609 (s, br), 1472 (s, sh), 1447 (s),
1380 (w), 1331 (m), 1305 (s), 1266 (vw), 1220 (vw), 1151 (vs, br),
1107 (s, sh), 1034 (vs), 1004 (s, sh), 952 (vs), 915 (w), 872 (w), 828
(s), 785 (w, sh), 726 (s), 664 (s), 592 (w), 568 (w) 522 (vw), 445
(m). IR (Nujol, cm−1): 251 (s). ESI+ TOF: m/z 719.1216 [M+ − Cl].
Anal. Calcd for C20H29ClO2SIr2: C, 31.89; H, 3.88; S, 4.26. Found: C,
32.04; H, 3.94; S, 3.87.
Synthesis of [(η4-COD)Ir(1-2,5-η-(μ-SO)CHCHCHCH2)]2
(9). KH (7.0 mg, 0.18 mmol) and 0.8 mL of DMSO-d6 were placed
into a Schlenk flask equipped with a stir bar, and the mixture was
cooled at 0 °C. A mixture of 0.025 mL of 2,3- and 2,5-
dihydrothiophene-1-oxide in 37.5% and 62.5% yield (11 mg, 0.11
mmol and 18.6 mg, 0.18 mmol, respectively) was added. The reaction
mixture reached room temperature, and after 30 min of stirring, a
green solution was obtained. Addition of 4 (50.0 mg, 0.074 mmol)
afforded an amber solution and a green-yellow solid suspension. After
30 min the reaction mixture was filtered and the solid was washed with
Et2O. The solid was treated with CH2Cl2, and a small amount of a
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHCHCHCH2)PMe3]
(14). (a) PMe3 (15.0 mg, 21.0 μL, 0.20 mmol) was added to a yellow
solution of 11 (100.0 mg, 0.20 mmol) in THF (20 mL) at −110 °C
(liquid N2/EtOH). After 10 min, the reaction mixture was allowed to
reach room temperature and was stirred for an additional hour. The
solution was filtered three times, and the volume of THF was reduced
to 5 mL. Addition of pentane (60.0 mL) allowed the precipitation of a
light yellow powder, which, after drying under vacuum, afforded
compound 14 in 32.0% yield (32.0 mg, 0.065 mmol), with mp 199−
201 °C. Single crystals were obtained from a CHCl3 solution at −40
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°C. IR (CDCl3, cm −1): 2964 (w), 2845 (w), 2241 (w), 1613 (w),
1415 (w, br), 1261 (s), 1167 (vw), 1098 (s), 1047 (s), 1016 (s), 960
(vw), 919 (vs, sh), 900 (vs), 867 (vw), 808 (s), 754 (s), 716 (s), 651
(s), 561 (vw), 525 (vw). IR (KBr, cm−1): 1638 (w, sh), 1614 (s), 1474
(w), 1455 (w), 1424 (s), 1385 (w), 1359 (w), 1336 (w), 1304 (s),
1281 (s, sh), 1215 (w), 1170 (vs, br), 1098 (s), 1048 (vs, br), 951 (vs,
br), 902 (w, sh), 848 (m), 816 (s), 731 (m), 710 (s), 658 (m), 557
(m), 522 (m), 440 (s). EI-MS (20 eV): m/z 494 (2) [M+], 430, 374,
295, 109. Anal. Calcd for C15H26O2PSIr: C, 36.50; H, 5.31. Found: C,
36.65; H, 5.33.
(b) Compound 21 (132.0 mg, 0.32 mmol) was dissolved in THF
(15 mL) to give an orange solution, which was cooled at −110 °C
(liquid N2/EtOH); then, 3K (60.0 mg, 0.38 mmol), previously
suspended in THF, was added. The reaction mixture was allowed to
reach room temperature and was stirred 1.5 h, and a slightly yellow
suspension was obtained. The volume of the solution was reduced to
∼3 mL under vacuum, and cold hexane (60 mL) was added. A cream
solid precipitated, which was filtered and dried to afford 125.0 mg
(79.0%, 0.25 mmol).
Calcd for C30H32O2PSIr·CHCl3: C, 46.59; H, 4.16. Found: C, 46.89;
H, 4.57.
(b) Compound 22 (100.0 mg, 0.17 mmol) was dissolved in 15 mL
of THF to form an orange solution, which was cooled at −110 °C
(liquid N2/EtOH), and then 3K (26.1 mg, 0.17 mmol), previously
suspended in THF, was added. After addition, the reaction mixture
was allowed to reach room temperature and was stirred for 1 h; it gave
a yellow solution. The volume of solution was reduced to ∼3 mL
under vacuum; then cold hexane was added to precipitate a cream
solid, which was filtered and dried under vacuum; this afforded 60.0
mg (53.0%, 0.09 mmol) of 17.
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHCHCHCH2)-
DMSO] (18). (a) A Schlenk was charged with 3K (47.0 mg, 0.30
mmol) and DMSO (2 mL). After addition of compound 4 (100.0 mg,
0.15 mmol) at room temperature, the reaction mixture was stirred for
1 h; then it was filtered, and the solvent was removed under vacuum
using an oil bath at 65−75 °C. An oily residue, along with a pale cream
solid, was treated with CH2Cl2. The solution was filtered and
evaporated under vacuum, and the powder was washed with hexane.
After drying, compound 18 (73.0 mg, 0.15 mmol) was obtained as a
pale cream solid in 49.0% yield. Single crystals were obtained from a
CHCl3 solution at room temperature. IR (CHCl3, cm−1): 1223 (vs),
1166 (w), 1100 (m), 1051 (vs), 819 (m, br), 781 (m, br), 730 (m, br),
713 (m, br), 661 (m), 563 (w), 446 (m), 416 (s). EI-MS (m/z, %,
assignment): 418 [M+ − L]. Anal. Calcd for C14H23O3S2Ir: C, 33.49;
H, 5.09. Found: C, 33.33; H, 5.00.
(b) Compound 11 (100.0 mg, 0.20 mmol) was dissolved in DMSO
(3 mL) and stirred, at room temperature, for 1 h. The DMSO was
evaporated to dryness under vacuum and an oil bath (65−75 °C,
decomposition of 18 due to the loss of COD was spectroscopically
observed at higher temperatures). Extraction with CH2Cl2 (30 mL)
gave a pale yellow solution, which was filtered, and the volume was
reduced to ∼1 mL; after addition of pentane (20 mL), a pale cream
precipitate was obtained. Filtration and drying under vacuum afforded
compound 18 in 55.0% yield (55.0 mg, 0.11 mmol). Mp: 152−153 °C
(dec).
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHC(Me)CHCHMe)-
PMe3] (14Me). A suspension of Li[SO2CHC(Me)CHCHMe] (23.0
mg, 0.15 mmol) in THF (14 mL) was stirred and added dropwise at
−110 °C (liquid N2/EtOH) to a suspension of 4 (50.0 mg, 0.074
mmol) in 4 mL of THF. The reaction mixture was allowed to reach
room temperature (≅40 min) and was stirred for an additional 75 min.
The amber solution was cooled again to −110 °C, and PMe3 (11.4 mg,
16.0 μL, 0.15 mmol) was added. The solution reached room
temperature and was stirred for 90 min. The yellow solution was
filtered, and the volume of THF was reduced to ≅2 mL. Addition of
diethyl ether gave a precipitate, which, after filtration, washing with
hexane, and subsequent drying, afforded a yellow-cream solid of 14Me
(44.0 mg, 0.084 mmol) in 56.7% yield. IR (CDCl3, cm−1): 1603(vw),
1430 (w, br), 1261 (m), 1156 (w), 1098 (m, br), 1042 (s), 1022 (m,
sh), 957 (w), 916 (vs, sh), 900 (vs), 866 (vw), 807 (m, br), 754 (vs,
br), 722 (vs, br), 651 (s), 613 (vw), 557 (w), 515(w).
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHCHCHCH2)-
PMe2Ph] (15). This reaction was conducted analogously to method
(a) for 14, using compound 11 (100.0 mg, 0.20 mmol) in 10 mL of
THF and PMe2Ph (28.0 mg, 29.0 μL, 0.20 mmol). Workup was
conducted similarly. A pale cream powder of 15 was obtained in 97.0%
yield (110.0 mg, 0.20 mmol), with mp 219−220 °C (dec).
Recrystallization (CH2Cl2/Et2O, 1:2) at −40 C gave colorless crystals
for the X-ray diffraction study. IR (CHCl3): 1610 (w), 1480 (w), 1439
(m), 1411 (sh), 1384 (w), 1334 (w), 1302 (w), 1262 (vs), 1189 (m),
1169 (m), 1110 (vs), 1019 (vs), 958 (m), 918 (s), 872 (w), 800 (vs),
699 (m, br), 655 (w), 556 (m), 521 (w), 493 (m), 442 (m), 415 (w).
EI-MS: m/z 556 [M+], 492, 435, 330, 138. Anal. Calcd for
C20H28O2PSIr: C, 43.23; H, 5.08. Found: C, 43.53; H, 5.30.
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHCHCHCH2)CO]
(19). A solution of 11 (100.0 mg, 0.20 mmol) in 15 mL of THF
was filtered, at room temperature, to a glass reactor, and CO was
introduced at one atmosphere. After stirring 6 min, a precipitate was
observed; it was filtered, and column chromatography under silica gel
(10 × 2 cm) with a mixture of solvents THF/Et2O (2:1) was carried
out. The light brown solution was evaporated until dryness, and a
second chromatography (6 × 2 cm) was carried out with the same
mixture of solvents. The light amber solution was evaporated, and 54.0
mg (0.12 mmol) of crystalline, pale amber product 19 was obtained in
60.0% yield, with mp 194−197 °C (dec). IR (CHCl3, νCO, cm−1):
2058 (vs). IR (KBr): 2054 (vs), 1609 (m, br), 1442 (m, br), 1171 (s,
br), 1103 (m, br), 1052 (vs, br), 820 (s), 727 (w, br), 697 (w, br), 661
(m, br), 651 (w, br), 528 (m, br), 485 (m, br). Anal. Calcd for
C13H17O3SIr: C, 35.03; H, 3.85. Found: C, 35.32; H, 4.00.
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHCHCHCH2)-
PMePh2] (16). This reaction was conducted analogously to method
(a) for 14, using compound 11 (218.5 mg, 0.44 mmol) in 40 mL of
THF and PMePh2 (89.0 mg, 83.0 μL, 0.44 mmol). Workup was
conducted similarly. A cream powder of 16 was obtained in 44.0%
yield (120.0 mg, 0.19 mmol) with mp 132−134 °C. IR (KBr): 1613 (s,
br), 1587 (w, sh), 1481 (s), 1435 (vs), 1365 (w), 1305 (vs), 1255 (w,
sh), 1174 (vs, br), 1110 (s, br), 1050 (vs, br), 899 (vs, br), 848 (w),
814 (vs), 744 (vs, br), 698 (vs), 658 (s), 560 (s), 511 (s), 488 (s, sh),
442 (vs). EI-MS (70 eV): m/z, 619 [M+], 418, 313, 256. Anal. Calcd
for C25H30O2PSIr: C, 48.61; H, 4.89. Found: C, 48.61; H, 5.53.
Synthesis of [(η4-COD)Ir(1-2,5-η-SO2CHCHCHCH2)PPh3]
(17). (a) This reaction was conducted analogously to that for 14 (a)
using compound 11 (100.0 mg, 0.20 mmol) in 10 mL of THF and
PPh3 (53.0 mg, 0.20 mmol). Workup was conducted similarly. A pale
cream powder of 17 was obtained in 82.0% yield (113.2 mg, 0.17
mmol), with mp 191−192 °C. Single, yellow-orange crystals were
obtained from a CHCl3 solution at −40 °C. IR (KBr, cm −1): 1617
(w), 1482 (m), 1435 (s), 1307 (m, br), 1188 (vs, sh), 1173 (vs), 1106
(m), 1047 (vs), 816 (s), 754 (m), 733 (w), 659 (m), 618 (w), 558
(m), 525 (s), 466 (w), 442 (m). EI-MS: m/z, 418 [M+ − L]. Anal.
Synthesis of [(η4-COD)Ir(5-η-SO2CHCHCHCH2)(PMe3)2]
(20). A solution of 14 (100.0 mg, 0.20 mmol) in 3 mL of benzene
was stirred, and PMe3 (0.13 mL, 1.20 mmol) was added; the mixture
was stirred for 1 h at room temperature. The cream powder that
precipitated in the reaction mixture was filtered and washed with 3 mL
of benzene and dried under vacuum. The very pale cream product 20
was obtained (80.0 mg, 0.14 mmol) in 69.0% yield, with mp 99−101
°C. Single crystals were obtained from slow diffusion of THF/hexane
at −50 °C. IR (KBr, cm−1): 1647 (s), 1575 (w, sh), 1477 (w, sh), 1430
(s), 1292 (s), 1163 (vw), 1019 (s, br), 949 (vs, br), 864 (m), 777 (m),
724 (s), 672 (m), 646 (w), 592 (w, br), 465 (w, br). FAB-MS (3-
NBA): m/z 569 [M+].
Synthesis of [(η4-COD)Ir(Cl)(PMe3)] (21). Compound [(η4-
COD)Ir(μ-Cl)]2 (4) (200.0 mg, 0.30 mmol) was dissolved in THF
(10 mL), giving a red-orange solution, which was treated with PMe3
(62.0 μL, 0.6 mmol) at −110 °C (N2 liquid/EtOH). The solution
turned yellow, the cold bath was removed, and the reaction mixture
was allowed to reach room temperature. The solution was filtered, the
solvent was removed in vacuo, and the residue was washed with
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Article
pentane (2 × 10 mL) and dried in vacuo. The orange solid (178 mg,
0.43 mmol) was obtained in 73.0% yield and was stored in a
refrigerator to avoid decomposition. Mp: 94−96 °C. EI-MS (20 eV):
m/z 412 [M+], 374, 346, 322, 294, 268, 210, 192, 57. IR (KBr, cm −1):
1956 (w, br), 1741 (w, br), 1607 (w, br), 1497 (w), 1469 (m, sh),
1441 (s, sh), 1419 (s), 1326 (m), 1280 (s), 1262 (s), 1159 (w), 1095
(s, br), 1023 (s, br), 954 (vs, br), 880 (s, br), 801 (vs, br), 736 (s), 675
(s), 516 (m), 466 (m). Anal. Calcd for C11H21ClPIr: C, 32.07; H, 5.13.
Found: C, 32.60; H, 5.28.
equivalents of PMe3 (3 × 13.0 μL, 3 × 0.12 mmol), at room
temperature, afforded a mixture of compounds 14, 20, and 20′.
ASSOCIATED CONTENT
* Supporting Information
■
S
Tables of crystallographic data, including atomic coordinates,
bond lengths and angles, anisotropic thermal parameters, and
least-squares planes for compounds 5, 9, 12, 14, 15, 17−20
(CCDC 840745−840753) and 22. IR spectra of compound 11,
1H and 13C NMR of compounds 5, 12, and 19, as well as 31P
NMR spectra of monitoring reactions of 11 with PMe3 and 12
with PMe3 and 3K. Spectroscopic evidence of the trans-
formation of 8 in CDCl3 and voltamograms of the electro-
chemistry experiments of 11 and 18; experimental evidence in
solution and in the solid state of KCl, as well as DLS size
distribution of 10, 11, and 17 and TGA of compound 11. This
material is available free of charge via the Internet at http://
pubs.acs.org.
Synthesis of [(η4-COD)Ir(Cl)(PPh3)] (22). The synthesis was
carried out as described in the literature.49,58a 31P NMR and mass
spectrometry data are included, because they have not been reported.
Crystals were obtained from recrystallization of CH3Cl/hexane at −5
°C. Yield: 86%. Mp: 176−177 °C. EI-MS: m/z 598 [M+], 560 [M −
Cl]+, 452 [M − Cl − COD]+, 262 [PPh3]+. IR (KBr, cm−1): 1964 (w,
br), 1892 (w, br), 1813 (w, br), 1587 (w, br), 1480 (s), 1433 (vs),
1327 (m), 1221 (m), 1183 (m), 1158 (w), 1094 (vs), 1028 (w), 1000
(m), 971 (w), 891 (w), 818 (w), 751 (vs), 697 (vs), 536 (vs), 514
(vs), 493 (vs), 448 (m).
Synthesis of [(η4-COD)Ir(Cl)(PMe3)2] (23). The synthesis was
carried out as described in the literature.57 13C and 31P NMR, IR
spectroscopy, and mass spectrometry data are included because they
have not been published. Mp: 112−114 °C (dec). ESI+ TOF: m/z
453.1446; error ppm: 0.5044; DBE: 2.0. IR (KBr, cm−1): 1960 (w, br),
1656 (w, sh), 1623 (m), 1479 (w, sh), 1432 (s), 1293 (s), 1257 (w),
1211 (w), 1187 (w), 1164 (w), 1045 (w), 973 (vs, sh), 953 (vs, br),
868 (s), 725 (s), 673 (s), 466 (w).
AUTHOR INFORMATION
Corresponding Author
*E-mail: mpaz@cinvestav.mx.
■
ACKNOWLEDGMENTS
■
Synthesis of [(η4-COD)Ir(PMe3)3]Cl (24). The synthesis was
carried out as described in the literature.59 13C and 31P NMR, IR
spectroscopy, and mass spectrometry data and chemical analysis are
included. Mp: 140−141 °C (dec). ESI+ TOF: m/z 529.1891; error
ppm: 0.4531; DBE: 1.0. IR (KBr, cm−1): 1623 (m), 1479 (vw, sh),
1432 (s), 1325 (vw, sh), 1293 (s), 1244 (w), 1210 (w), 1187 (w),
1164 (w), 1044 (w), 976 (vs, sh), 953 (vs, br), 902 (s, sh) 868 (s), 793
(vw), 725 (s), 673 (s), 466 (w). 1H NMR (CDCl3, 300 MHz): δ 1.63
(m 3H), 2.24 (m, 4H), 2.38 (m, 4H), 3.22 (m, 4H). 13C{1H} NMR
(CDCl3, 75.5 MHz): δ 20.0 (m, PMe3), 34.1 (s, CH2,COD), 68.5 (m,
J = 4.8 Hz, CH, COD). 31P NMR (CDCl3, 121.5 MHz): −52.35 (s).
Anal. Calcd for C17H39ClP3Ir: C, 36.20; H, 6.97. Found: C, 36.22; H,
6.87.
Financial support for this work was provided by Conacyt,
Mexico (46556-E). P.G.M., B.P.M., and N.P.M.N. thank
Conacyt for graduate and undergraduated scholarships. We
́ ́
thank P. Juarez-Saavedra, V. M. Gonzalez Diaz, G. Cuellar
Rivera, M. A. Leyva Ramirez, and M. Campos for assistance
with some of the IR and microanalysis, NMR, mass spectra, X-
ray diffraction studies, and TGA analysis, respectively. The
authors would also like to thank an anonymous reviewer for
insightful suggestions.
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(38) Although unambiguous characterization of 20′ was not possible,
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consecutive addition of PMe3 in C6D6; see text. The tentative
assignment of [(η4-COD)Ir(5-η-SO2CHCHCHCH2)(PMe3)]2 (20′):
1H NMR (C6D6): δ 5.10 (d, 6.6, H1), 5.13 (d, 10.8, 17.4, H1′), 8.51
(dt, 6.5, 17.2, H2), 5.79 (t, 10.8, H3), 6.55 (d, 11.1, H4), 1.33 (d, 7.9,
PMe3), 3.26 (s, br, CH, COD), 1.88−2.30 (m, CH2, COD). 13C{1H}
NMR (C6D6): δ 120.2 (C1), 133.3 (C2), 127.8 (C3), 145.4 (t, 3.1,
C4), 67.6 (t, 4.6, 5.4, CH2, COD), 33.9 (CH2, COD), 18.3 (m, 3.8,
33.1, PMe3). 31P NMR (C6D6): δ −46.22 (s).
(39) Compounds 23 and 24 could not be excluded from the reaction
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and 31P NMR data. See Tables 3 and 4. Compound 20 can only be
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chemical shifts of the butadienesulfonyl ligand.
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190
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