New amino-dithiaphospholanes and phosphoramidodithioites and their rhodium and iridium complexes

Article abstract of DOI:10.1016/j.ica.2010.11.006

New sulfur derivatives of phosphoramidite ligands were synthesized and the impact of the sulfur unit on the spectroscopic properties of their rhodium and iridium complexes was investigated. The new ligands Bn₂NPSCH ₂CH₂S^a(P-S^a) (Bn = benzyl, 4), Bn₂NPSCHCHS^a(CH₂)₃C ^aH₂(P-S^a)(C^a-S^a) (6) and Bn₂NP(4-XC₆H₄OMe)₂ (X = S, 7a; X = O, 7b) were converted to the rhodium and iridium complexes trans-[Rh(CO)Cl(L) ₂] (L = 4, 6, 7), [RhCl(COD)(L)] (L = 4, 6, 7), [IrCl(COD)(7a)] and [IrCl₂Cp(6)]. For comparison, some phosphoramidite complexes of these formulations also were synthesized. The new metal complexes were spectroscopically analyzed. For the carbonyl complexes, the ν _CO IR stretching frequencies were lower than for the corresponding phosphite and phosphoramidite ligands. The ¹J _PRh coupling constants for the rhodium complexes with the new ligands were also smaller than for the respective phosphoramidite and phosphite complexes. Finally, the ¹J_PSe coupling constants of the selenides of the new ligands were lower than those of the phosphoramidite ligands but higher than for PPh₃. The spectroscopic data reveal that the new thio ligands 4, 6 and 7a are more electron donating than phosphites and phosphoramidites but less electron donating than PPh₃.

Full text of DOI:10.1016/j.ica.2010.11.006

Inorganica Chimica Acta 366 (2011) 209–218
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Inorganica Chimica Acta
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New amino-dithiaphospholanes and phosphoramidodithioites and their
rhodium and iridium complexes
⇑
Pushkar Shejwalkar, Sergey L. Sedinkin, Eike B. Bauer
University of Missouri – St. Louis, Department of Chemistry and Biochemistry, One University Boulevard, St. Louis, MO 63121, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 August 2010
Received in revised form 21 October 2010
Accepted 3 November 2010
Available online 13 November 2010
New sulfur derivatives of phosphoramidite ligands were synthesized and the impact of the sulfur unit on
the spectroscopic properties of their rhodium and iridium complexes was investigated. The new ligands
Bn2NPSCH2CH2Sa(P-Sa) (Bn = benzyl, 4), Bn2NPSCHCHSa(CH2)3CaH2(P-Sa)(Ca-Sa) (6) and Bn2NP(4-XC6H4-
OMe)2 (X = S, 7a; X = O, 7b) were converted to the rhodium and iridium complexes trans-[Rh(CO)Cl(L)2]
*
(L = 4, 6, 7), [RhCl(COD)(L)] (L = 4, 6, 7), [IrCl(COD)(7a)] and [IrCl2Cp (6)]. For comparison, some phos-
phoramidite complexes of these formulations also were synthesized. The new metal complexes were
Keywords:
spectroscopically analyzed. For the carbonyl complexes, the mC„O IR stretching frequencies were lower
Amino-dithiaphospholanes
Phosphoramidites
Ligand design
1
than for the corresponding phosphite and phosphoramidite ligands. The JPRh coupling constants for
the rhodium complexes with the new ligands were also smaller than for the respective phosphoramidite
1
and phosphite complexes. Finally, the JPSe coupling constants of the selenides of the new ligands were
P ligands
lower than those of the phosphoramidite ligands but higher than for PPh3. The spectroscopic data reveal
that the new thio ligands 4, 6 and 7a are more electron donating than phosphites and phosphoramidites
but less electron donating than PPh3.
Organometallic syntheses
Spectroscopy
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
We have recently reported that phosphoramidite complexes of
the formula [RuCl2(p-cymene)(1a–d)] are catalytically active in the
Phosphoramidites (1a–d, Fig. 1) are a monodentate, P-coordi-
nating ligand class originally utilized in catalysis by Feringa [1].
They are easy to synthesize, relatively air-stable and their architec-
ture can be modified at several position in their framework.
Phosphoramidites have been applied as ligands in a number of tran-
sition metal catalyzed organic transformations, such as enantiose-
lective conjugate enone addition reactions [2], hydrogenations
[3], allylic substitutions [4], allylic aminations [5], hydrosilylations
[6], hydrovinylations [7], cycloadditions [8], cyclopropanations [9],
hydroacylations [10], Diels–Alder [11] and Heck reactions [12]. It
has been reported that changes at the phosphoramidite skeleton
have a profound impact on yields and enantioselectivities in cata-
lytic applications of those ligands [13]. The phosphoramidite metal
complexes employed in catalysis are typically formed in situ and
the exact nature of the catalytically active species is not always
known [14]. Compared to many bidentate ligands, phosphorami-
dites are a flexible ligand class. Mezzetti pointed out that due to
secondary interactions of the aromatic backbone with the metal
center, they can serve as two-, four-, six-, or eight-electron donors
[15].
formation of b-oxo esters from propargylic alcohols and carboxylic
acids [16a]; complexes of the formulation [RuCl(Cp)(1c)(PPh)3]
exhibited catalytic activity in the Mukaiyama aldol reaction
[16b]; structurally related iron complexes showed catalytic
activity in the oxidation of methylene groups with peroxide
[16c]. During our investigations we found that steric tuning of
the phosphoramidite ligands has an influence on the catalytic
activity of their respective ruthenium complexes but we observed
no influence of electronic tuning efforts on the performance
of the respective ruthenium complexes. The ligand 1d bearing a
bromo substituent in the BINOL backbone exhibited catalytic
activity in b-oxo ester formation similar to its non-brominated
analog 1a (Fig. 1). We hypothesize that the bromo substituent is
too far away from the coordinating phosphorus atom, and thus
has no impact on the properties of the respective ruthenium
complex.
We speculated that electronic tuning must take place much clo-
ser to or directly at the coordinating phosphorus atom to signifi-
cantly impact the properties of the ligand and its respective
metal complexes. Replacing the two oxygen atoms connected to
the phosphorus by soft sulfur atoms seemed to hold the greatest
promise. Sulfur analogs of phosphoramidites are known in the
literature (such as 2 in Scheme 1) [17]. The cases where the
phosphorus and sulfur atoms are incorporated in a saturated,
⇑
Corresponding author. Tel.: +1 314 516 5311; fax: +1 314 516 5342.
E-mail address: bauere@umsl.edu (E.B. Bauer).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.11.006

210
P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
Ph
Ph
Ph
R'
R'
PCl3, NEt3
HN
Cl2P N
R
CH2Cl2, 0°C,
1 h
X
X
Ph
P N
3
R
SH
SH
SH
1
0.5 h
rt
SH
R = Me, R' = H, X=O, a
R = i-Pr, R' = H, X=O,
R = CH2Ph, R' = H, X=O,
R = Me, R' = Br, X=O, d
R = CH2Ph, R' = H, X=S,
b
(rac)-5
c
S
S
S
Ph
Ph
Ph
Ph
e
P
N
P N
S
Fig. 1. Phosphoramidite ligands and a thio derivative thereof.
4
6
(rac)- , 85%
82%
Scheme 2. Two step one plot synthesis of amino-dithiaphospholanes 4 and (rac)-6.
five-membered ring system, are referred to as amino-dithiaphos-
pholanes [17a], and have been utilized in the phosphorylation of
alcohols, as outlined in Scheme 1 [17a,18].
However, to the best of our knowledge, the sulfur analogs of
phosphoramidites have never been applied as ligands in transition
metal complexes. We thus were interested in investigating their
coordination chemistry, and what impact the replacement of oxy-
gen by sulfur would have on the properties of the resulting ligands
and metal complexes. Herein, we describe the synthesis of new
amino-dithiaphospholanes and phosphoramidodithioites, and
their coordination chemistry with rhodium and iridium, which is
unknown thus far. The impact of the sulfur on the properties of
the respective metal complexes was probed through analysis of
31P NMR shifts and coupling constants and also from IR mC„O
stretching frequencies. A portion of the work has been communi-
cated [19].
MeO
MeO
X
Ph
S
P N
Ph
P N
X
S
MeO
MeO
7 X=S, a (85%)
X=O, b (61%)
8 (50%)
Fig. 2. Novel phosphoramidodithioites.
2. Results and discussion
In a similar procedure, the known [21] racemic trans-cyclohex-
ane-1,2-dithiol ((rac)-5) was converted to the corresponding ami-
no-dithiaphospholane (rac)-6 which was obtained as a white
powder in 85% isolated yield (Scheme 2). We speculated that alco-
holysis of the dithiaphospholanes according to Scheme 1 might be
more difficult if an electron-donating group was placed in the
backbone of the sulfur portion of the ligands. Such a substitution
would increase the electron density at the phosphorus atom and
thus impede nucleophilic attack. Accordingly, 4-methoxythiophe-
nol was converted to the corresponding phosphoramidodithioite
7a employing the standard procedure described above for the
other ligands (Fig. 2). Ligand 7a was obtained as a colorless oil in
85% yield. For additional comparison, the oxygen analog of ligand
7a also was prepared. Following the standard procedure, phospho-
ramidite 7b was obtained as a white powder in 61% yield. Finally,
we speculated that steric protection of the P–N bond also might
have impact on the stability of the corresponding ligands. Accord-
ingly, we employed 2,2,6,6-tetramethylpiperidine and 4-methoxy-
thiophenol to obtain ligand 8 as colorless oil in 50% yield.
2.1. Ligand syntheses
We initially started our investigations with the sulfur analog 1e
(Fig. 1) [19]. Due to the lengthy three-step synthesis of the binaph-
thyl dithiol required for the synthesis of 1e, we sought simpler
dithiols for ligand synthesis. We thus employed commercial 1,2-
benzene-dithiol into the synthesis of corresponding ligands and
metal complexes [19]; but 1,2-benzene-dithiol is relatively expen-
sive, and prompted the search for cheaper alternatives. As amino-
dithiaphospholanes can be hydrolyzed by alcohols and water
(Scheme 1), we also looked for alternatives that were more
resistant towards hydrolysis. Based on these considerations, we
synthesized a set of electronically and sterically tuned amino-
dithiaphospholanes and phosphoramidodithioites, as shown in
Scheme 2 and Fig. 2.
Following synthetic pathways previously described in the liter-
ature for phosphoramidites by us [16a] and others [20], we first
converted commercial 1,2-ethanedithiol to the corresponding ami-
no-dithiaphospholane 4 as shown in Scheme 2. In a two step one
pot procedure, PCl3 was first converted to PCl2N(CH2Ph)2 (3) which
was subsequently reacted with 1,2-ethanedithiol to obtain the
amino-dithiaphospholane 4 as white crystals in 82% overall yield.
The new ligands were characterized by NMR (1H, 13C, 31P), IR,
MS and elemental analysis for all but one example. The spectro-
scopic data are consistent with the proposed structures. The 31P
NMR signals for the new compounds range from 102.0 to
133.2 ppm and thus show some dependency on the structure.
The new thio compounds showed a range of stabilities towards
hydrolysis by water or alcohols. Compound 7a is the most stable of
the examples; it is stable during purification by chromatography
and does not decompose in solution for several days, as deter-
mined by 1H and 31P NMR spectroscopy. The other new thio com-
pounds are less stable and show significant decomposition in
solution after several hours. Ligand 8 can be flash chromato-
graphed, while the other two ligands 4 and (rac)-6 decompose
S
S
S
S
ROH
P N
P OR
HN
+
2
Scheme 1. Phosphorylation utilizing amino-dithiaphospholane 2.

P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
211
during chromatography. It is not surprising that the ligands show
moderate hydrolysis sensitivity towards water and alcohols, as
the structurally related amino-dithiaphospholane 2 is known to
phosphorylate alcohols with concomitant P–N bond cleavage, as
shown in Scheme 1.
yellow powders in 40–89% isolated yields (Scheme 3). For compar-
ison, the complexes trans-[Rh(CO)Cl(L)2] (L = 7b, 11b; L = 1a, 12a,
L = 1c, 12b) were also synthesized in 49–73% yield.
Similarly, the complexes [RhCl(COD)(L)] (L = 4, 16; L = (rac)-6,
(rac)-13; L = 7a, 14a) and [IrCl(COD)(7a)] (15) were obtained as
yellow powders in 22–93% isolated yields (Scheme 4). For compar-
ison, the complex [RhCl(COD)(7b)] (14b) was also synthesized in
51% yield.
2.2. Metal complex syntheses
*
Finally, the complexes [IrCl2Cp (L)] (L = (rac)-6, (rac)-18; L = 7b,
Next, conversion of the new ligands to iridium and rhodium
complexes was explored. It is known that the commercial rhodium
precursor [Rh(CO)2Cl]2 forms square planar Rh(I) complexes with
the general formula trans-[Rh(CO)Cl(L)2] when treated with mono-
dentate phosphanes L [22]. In a similar bridge-splitting reaction,
[MCl(COD)]2 forms square planar complexes of composition
[MCl(COD)(L)] (M = Rh, Ir; COD = 1,5-cyclooctadiene) [23]. Finally,
in a related reaction, octahedral Ir(III) complexes of the general for-
17b) were obtained in 64% and 96% isolated yields as orange pow-
ders (Scheme 5). The tetramethylpiperidine derivative 8 failed to
be converted to any of the aforementioned metal complexes. No
reaction of this ligand with the dimeric metal complex precursors
took place under different conditions, and only ligand decomposi-
tion products were detected. We hypothesized that the four
methyl substituents at the piperidine create too much steric con-
gestion close to the coordinating phosphorus atom, and thus inhib-
iting metal phosphorus bond formation.
*
*
mula [IrCl2Cp (L)] (Cp = pentamethylcyclopentadienyl) can be ob-
tained from the known [24] dimeric precursor [IrCl2Cp*]2 and
monodentate ligands L [25].
The new metal complexes were analyzed by NMR (1H, 13C, 31P),
IR, mass spectrometry (including HRMS) and elemental analysis.
The FAB mass spectra showed a molecular ion peak for the metal
complexes. In addition, a diagnostic fragmentation pattern due to
loss of Cl and/or CO ligands was observed [26].
The coordination of the amino-dithiaphospholanes to the rho-
dium center was best observed by a shift of the 31P NMR signals
to lower fields in the spectra of the corresponding metal com-
plexes. The free amino-dithiaphospholanes 4, (rac)-6 and 7a and
Accordingly, the new ligands were converted to the correspond-
ing complexes as shown in Schemes 3–5. The bridge-splitting
reactions of the dimeric precursors with the ligands proceeded
smoothly in CH2Cl2, THF or toluene at room temperature, and were
complete after 1 h or less. Column chromatography resulted in
decomposition of the new complexes, but they could be purified
by washing and recrystallization. The complexes trans-[Rh(CO)-
Cl(L)2] (L = 4, 9; L = (rac)-6, (rac)-10; L = 7a, 11a) were isolated as
Ph
Ph
Ph
Ph
N
N
S
S
6
(rac)-
P
CO
P
P
X
Rh
toluene
1 h, rt
OC
S
S
Cl
Ph
Ph
OMe
7, touene
1 h, rt
Rh
MeO
N
Cl
[Rh(CO)2Cl]2
X
2
P
N
(rac)-10
11, X=S, a, 49%
2
Ph
88%
X=O, b, 73%
Ph
Ph
Ph
4
1a or 1c,
toluene,
rt, 1 h
toluene
1 h, rt
N
S
P
CO
P
S
R
O
Rh
S
S
N
Cl
Ph
Ph
O
Rh
P
OC
N
R
O
9, 89%
Cl
P
N
O
12
a
, R=Me, , 40%
R=CH2Ph, , 73%
R
R
b
Scheme 3. Syntheses of the complexes trans-[Rh(CO)Cl(L)2].
Ph
Ph
N
(rac)-6
CH2Cl2
1 h, rt
S
S
P
Rh
Cl
(rac)-13, 22%
2
OMe
7, CH2Cl2
[MCl(COD)] 2
1 h, rt
Ph
Ph
Ph
X
N
P
Ph
N
S
S
M
4
P
Cl
CH2Cl2
1 h, rt
Rh
16, 93%
14,
a
M = Rh, X=S, , 84%
Cl
b
M = Rh, X=O, , 51%
15, M = Ir, X=S, 58%
Scheme 4. Syntheses of the complexes [RhCl(COD)L].

212
P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
Ph
Ph
S
Ir
Cl
Ph
Ph
N
Ir
Cl
(rac)-6
7b,
CH2Cl2
Cl
P
N
P
S
Cl
[IrCl2Cp*]2
O
CH2Cl2
2
(rac)-18, 96%
17b, 64%
MeO
*
Scheme 5. Syntheses of the complexes [IrCl2Cp L].
8 showed 31P NMR signals between 102.0 and 133.2 ppm. The
rhodium complexes in Scheme 3 and 4 exhibited 31P NMR signals
between 127.3 and 142.1 ppm. In addition, the rhodium complexes
exhibited rhodium–phosphorus coupling (1JPRh = 161–199 Hz),
which were diagnostic of square planar complexes of the composi-
tion trans-[Rh(CO)Cl(L)2] [22a] or [RhCl(COD)(L)] [23]. In contrast
to the rhodium complexes, the 31P NMR signals for the Ir(III) com-
plexes 17b and 18 in Scheme 5 are shifted to higher field (79.5 and
90.7 ppm). Resonances between 95.0–93.3 and 9.5–9.1 ppm in the
13C NMR indicated coordinated Cp* for these complexes. The
bidentate coordination of the COD ligand in the complexes 13–16
was also confirmed by the NMR spectra. The 1H NMR spectra of
the complexes exhibited resonances between 5.59 and 5.52 and
between 3.92 and 3.75 ppm for the vinylic = CH protons. In the
13C NMR spectra, signals between 111.3 and 106.9 ppm and be-
tween 74.5 and 71.6 ppm for the vinylic carbon atoms were ob-
served, which are diagnostic for structurally related rhodium
complexes of the formula [RhCl(COD)(L)] [23].
The presence of single, strong mC„O signals between 1983 and
2010 cmꢀ1 in the IR spectra of the rhodium carbonyl complexes
9–12 also supported the proposed structures. These values are typ-
ical for structurally related rhodium monocarbonyl complexes
[27]. No IR signals for the dimeric [Rh(CO)2Cl]2 starting material,
which shows multiple mC„O absorptions were observed in the
new isolated complexes.
All NMR spectra for the metal complexes showed baseline pur-
ity and representative spectra are given in the Supplementary
material. However, the new complexes are sensitive to hydrolysis
as are the free ligands. When NMR samples of the complexes 9,
13 and 16 were treated with small amounts of water or methanol,
immediate decomposition occurred which was complete after
1 day; new peaks for dibenzylamine were observed, suggesting
cleavage of the P–N bond, following the reaction pathway shown
in Scheme 1. Extensive attempts to obtain X-ray quality crystals
of the complexes also resulted in ongoing decomposition. In most
cases, a crystalline precipitate formed, which turned out to be
dibenzylammonium chloride (as shown by X-ray and NMR). The
Ir(III) complexes exhibit direct evidence for both P–N bond and
P–S bond cleavage. Ligand 7a reacts with [IrCl2Cp*]2 to give a mix-
Decreasing νCO IR
Ph
stretching frequencies
with increasing electron
density at the metal.
Ph
R
R
N
X
X
P
CO
Rh
R
R
Decreasing 1JPRh
coupling constants with
increasing basicity of the
ligand.
X
X
Cl
Ph
P
N
S
X=O, S
Ph
Se
1
Increasing JPSe coupling
constants with decreasing
basicity of the ligand.
R'
R'
N
P
S
R
R
21
Fig. 4. Spectroscopic probes to asses the electronic properties of the new ligands.
ture of compounds, and one of them is a thiolate-bridged dimer 19
(Fig. 3) which was observed in the mass spectrum. When complex
14a was stored in the FAB matrix (4-nitrobenzyl alcohol) for one
hour, the molecular ion peak for 14a disappeared and new peaks
appeared in the mass spectrum, one of which was assigned to
the thiolate-bridged dimer 20 (Fig. 3). Accordingly, some of the ele-
mental analyses of the complexes were low on carbon, which we
tentatively ascribe to decomposition due to atmospheric moisture
[28]. While the complexes showed decomposition in protic sol-
vents such as water or methanol, all complexes appeared to be sta-
ble in the solid state for several months under ambient conditions.
NMR-tube experiments showed that (rac)-13 in CDCl3 and 14a at
elevated temperatures in deuterated toluene have lifetimes of at
least 1 day. In turn, the metal complexes of the phosphoramidite
ligands 1a and 1c appeared to be more stable and showed no signs
of hydrolysis.
2.3. Spectroscopic properties of the ligands and metal complexes
OMe
OMe
The exchange of the two oxygen atoms in phosphoramidite li-
gands by sulfur has a profound impact on the spectroscopic prop-
erties of the new ligands and the respective metal complexes
(Fig. 4).
Cl
S
Ir
Ir
The exchange of oxygen by sulfur results in a shift of the 31P
NMR signals of the corresponding thio ligands to higher field.
The phosphoramidite ligands 1a–d resonate between 145.2 and
152.3 ppm [2a], whereas the thio analogs 4, (rac)-6, 7a and 8
resonate between 102.0 and 133.8 ppm. A direct comparison of
the 31P NMR resonances is possible for the structurally related li-
gands 7a and 7b; the phosphorus signal of the sulfur analog 7a
(133.2 ppm) is shifted 6.6 ppm to higher fields compared to the
S
S
S
Rh
Rh
Cl
OMe
OMe
19
20
Fig. 3. Ligand decomposition products detected by mass spectrometry.

P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
213
Table 2
phosphoramidite ligand 7b (139.8 ppm). This trend is to be ex-
pected when the oxygen in phosphoramidite ligands as in 1a–d
is replaced by a softer sulfur atom, which increases the electron
density at the phosphorus. Sulfur is less electronegative than oxy-
gen, and it has been reported that more electronegative substitu-
ents on a phosphorus atom cause a downfield shift in the 31P
NMR spectra of their respective compounds [29].
1
31P NMR chemical shifts and JPSe coupling constants for different ligands.
Entry
Ligand
d (31P) ppm free ligand
1JPSe (Hz) Selenide
1
2
3
4
5
6
7
8
P(OPh)3
1a
P(OMe)3
7a
127.5 [33b]
149.4
139.8 [33b]
133.2
1025 [33b]
971.0 [34g]
954 [34b]
858
4
108.8
841
Furthermore, the new thio ligands also have an impact on the
spectroscopic properties of their respective rhodium and iridium
(rac)-6
8
102.0
133.2
835
832
1
complexes. For the rhodium complexes, the JPRh coupling con-
PPh3
ꢀ7.4 [33b]
735.4 [34a]
stants in the 31P NMR and the mC„O stretching frequencies in the
IR are particularly diagnostic. The values for each of these param-
eters are compiled in Table 1.
phos]+, the JPPt coupling constants decrease with increasing
electron-donating character of the pyridine ligand py-X (X =
electronically tunable substituent in the 4 position) [33c]. Accord-
1
It is known that the mC„O IR stretching frequencies of carbonyl
complexes are a sensitive probe of the electron density at the metal
center. Electron rich metal centers lower the mC„O stretching fre-
quencies in their respective IR spectra [30]. The mC„O absorptions
for the phosphoramidite complexes 12a and 12b are 2010 and
2017 cmꢀ1, respectively (Table 1, entries 9 and 10). In turn, the
1
ingly, the JPRh coupling constants for all complexes bearing the
thio ligands are about 29–46 Hz lower than those of the corre-
sponding phosphoramidites. The direct impact of the exchange of
oxygen by sulfur is best seen for the complexes 11b and 14b. Com-
plex 14a with the thio ligand 7a exhibited a 1JPRh coupling constant
of 197 Hz (Table 1, entry 3) which is 46 Hz lower than the coupling
constant for complex 14b bearing the phosphoramidite ligand 7b
(243 Hz, entry 4). The same trend is observed for the carbonyl com-
m
C„O stretches for the thio complexes 9, 10 and 11b were observed
between 1980 and 1983 cmꢀ1 (entries 5, 6 and 8). A direct compar-
ison is again possible with the complexes 11a (phosphoramidodi-
thioite ligand) and 11b (phosphoramidite ligand). The mC„O IR
frequency for 11a (1972 cmꢀ1) is 11 cmꢀ1 lower than that for
11b (1983 cmꢀ1, entries 7 and 8).
1
plex 11a bearing the thio ligand 7a. Its JPRh coupling constant
(166 Hz, entry 7) is about 29 Hz lower than that of complex 11b
bearing the phosphoramidite ligand 7b (194 Hz, entry 8). These
trends establish that the thio ligands are more electron donating
than the phosphoramidites.
Thus, the thio analogs of the phosphoramidite ligands create a
higher electron density at the metal, which can be ascribed to
the lower electronegativity and higher polarizability of the sulfur
atom compared to the oxygen atom. Accordingly, the complex
trans-[Rh(CO)Cl{P(OPh)3}2] with three oxygen substituents on
Finally, it is known from the literature that 31P-77Se coupling
constants also give insight into the electronic properties of the cor-
responding phosphorus compounds. It has been reported that
decreasing basicity of the phosphorus compound causes an in-
the phosphorus exhibits
a higher mC„O stretching frequency
(1998 cmꢀ1, entry 11) than complex 11b (two oxygen and one
nitrogen substituent, 1983 cmꢀ1, entry 12) and complex 11a (two
sulfur substituents and one nitrogen substituent, 1972 cmꢀ1, entry
7).
1
crease in the JPSe coupling constant of its respective selenide
[34]. In NMR tube experiments, the ligands 4, (rac)-6, 7a and 8
were converted to their corresponding selenides (21 in Fig. 4) by
treatment with selenium powder in CDCl3 for 1 h at 40 °C (see Sec-
tion 4). The formation of the selenides was confirmed by mass
spectrometry. The 1JPSe coupling constants together with reference
values of related compounds are compiled in Table 2.
In this series, PPh3 appears to be the most basic ligand with a
1JPSe coupling constant of 735.4 Hz (entry 8) whereas the phos-
phites P(OMe)3 and P(OPh)3 and the standard phosphoramidite
1a (Fig. 1) are the least basic ones (954–1025 Hz, entries 3 and
1). The thio ligands 4 (841 Hz), (rac)-6 (835 Hz), 7a (858 Hz) and
8 (832 Hz) are intermediate in their basicity (entries 4–7), being
less basic than PPh3 and more basic than phosphoramidites and
phosphites. This finding is in line with the other spectroscopic data
discussed above, establishing a higher electron-donating character
of the thio ligands compared to phosphoramidites. Among the new
ligands described herein, 7a is the least basic one.
There is also an impact of the oxygen/sulfur exchange on the
1JPRh coupling constants of the respective rhodium complexes (Ta-
ble 1). The 1JPRh coupling constants depend on steric and electronic
factors [32], making it difficult to establish clear trends. It has been
1
reported that the JPRh coupling constant in complexes of the for-
mula trans-[Rh(CO)Cl(PAr3)2] decreases with more electron-donat-
1
ing ligands PAr3 [33a]. Similarly, it has been shown that the JAgP
coupling constants in silver complexes of the formula [Ag(PX3)3]+
depend on the electronegativity of the atom directly bonded to
the phosphorus; an increase with increasing electronegativity
was observed, following the trend PR3 < P(NMe2)3 < P(OR)3 [33b].
Finally, in platinum complexes of the formula [Pt(CH3)(py-X)di-
Table 1
1JPRh coupling constants and mC„O stretching frequencies.
Entry
Complex
1JPRh (Hz)
mC„O (neat, cmꢀ1
)
3. Conclusion
1
2
3
4
5
6
7
8
[RhCl(COD)(4)] (16)
194
194
197
243
161
164
166
194
[RhCl(COD){(rac)-6}] (13)
[RhCl(COD)(7a)] (14a)
[RhCl(COD)(7b)] (14b)
[Rh(CO)Cl(4)2] (9)
[Rh(CO)Cl{(rac)-6}2] (10)
[Rh(CO)Cl(7a)2] (11a)
[Rh(CO)Cl(7b)2] (11b)
In conclusion, the present study shows together with the previ-
ously communicated data [19] for the first time the coordination
chemistry of amino-dithiaphospholanes and phosphoramidodi-
thioites with transition metals. A number of these ligands were
synthesized, where the coordinating phosphorus atom is bonded
to one nitrogen and two sulfur substituents and which showed a
range of stabilities towards hydrolysis. The ligands subsequently
were converted to rhodium and iridium complexes. The spectro-
scopic data clearly show that the exchange of the oxygen atoms
in phosphoramidites by sulfur has a profound impact on the spec-
troscopic properties of the ligands and their respective metal com-
plexes. As assessed by the IR data, the 1JPRh coupling constants and
1980
1983
1972
1983
2003 (CH2Cl2)
2010
2017
2011 (CH2Cl2)
1998 (KBr) [31b]
2016 (CH2Cl2) [31a]
1960 (KBr) [31b]
9
10
[Rh(CO)Cl(1a)2] (12a)
[Rh(CO)Cl(1c)2] (12b)
196
199
11
12
[Rh(CO)Cl{P(OPh)3}2]
[Rh(CO)Cl(PPh3)2]
210 [31a]
129 [33a]
1980 (CH2Cl2) [33a]

214
P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
1
the JPSe coupling constants, the thio containing ligands are more
electron donating than the phosphoramidite analogs. Thus, incor-
poration of sulfur is another efficient alternative for electronic tun-
ing of phosphorus-based ligand systems. Further investigation of
the coordination chemistry of amino-dithiaphospholanes and the
potential application as catalysts under non-protic conditions in
organic transformations is currently underway.
HRMS calcd for C20H24NPS2 373.1088, found 373.1093. IR (cmꢀ1
neat solid) 3019(w), 2931(w), 1490(m).
,
1H NMR (CDCl3): d = 7.36–7.16 (m, 10H, Ph), 4.26–4.10 (m, 2H,
0
NCH2), 4.08–3.91 (m, 2H, NCH2 ), 3.25–3.11 (m, 1H, CHS), 3.05–2.90
(m, 1H, CHS0), 2.37–2.22 (m, 2H, Cy), 1.94–1.75 (m, 2H, CH2), 1.72–
1.52 (m, 2H, CH2), 1.48–1.17 (m, 2H, CH2); 13C{1H} NMR (CDCl3):
d = 137.7 (s, Ph), 128.3 (d, J = 1.1 Hz, Ph), 128.2 (s, Ph), 127.1 (s,
Ph), 62.8 (d, J = 2.7 Hz, CHS), 57.6 (s, CHS), 51.8 (d, J = 17.6 Hz,
NCH2), 31.8 (s, CH2), 31.7 (s, CH2), 25.7 (s, CH2), 25.3 (s, CH2);
31P{1H} NMR (CDCl3): d = 102.0 (s).
4. Experimental section
4.1. General
4.2.3. bis(4-Methoxyphenyl)-dibenzylphosphoramidodithioite (7a)
4-Methoxythiophenol (1.5 mL, 1.7 g, 12 mmol) was converted
to 7a as described above for 4. The crude product was purified
by flash column chromatography on SiO2 (2 ꢁ 20 cm column;
eluted with 1:0 v/v hexanes/EtOAc ? 9:1 v/v hexanes/EtOAc) to
obtain the product 7a (2.15 g, 4.87 mmol, 85%) as a colorless oil.
Anal. Calc. for C28H28NO2PS2: C, 66.51; H, 5.58. Found: C, 66.80;
Chemicals were treated as follows: CH2Cl2, pentanes, distilled
from CaH2; THF, toluene, diethyl ether (Et2O), distilled from Na/
benzophenone. Phosphorus trichloride, triethyl amine, dibenzyl
amine, 1,2-ethanedithiol, cyclohexane-1,2-dithiol, 4-methoxy
thiophenol, 2,2,6,6-tetramethyl piperidine, 4-methoxyphenol (all
Aldrich) were used as received. The metal complexes [Rh(CO)2Cl]2
and [MCl(COD)]2 (M = Ir, Rh; Strem) were used as received. The li-
gands 1a [35] and 1c [13] as well as [IrCl2Cp*]2 [24] were synthe-
sized according to the literature.
NMR spectra were obtained at room temperature on a Bruker
Avance or a Varian Unity Plus instrument (1H: 300.13 MHz; 13C:
75.5 MHz; 31P: 121.5 MHz) and referenced to a residual solvent
signal; all assignments are tentative. Exact masses were obtained
on a JEOL MStation [JMS-700] Mass Spectrometer. Melting points
are uncorrected and were taken on an Electrothermal 9100 instru-
ment. IR spectra were recorded on a Thermo Nicolet 360 FT-IR
spectrometer. Elemental Analyses were performed by Atlantic
Microlab Inc., Norcross, GA, USA.
H, 5.59%. HRMS calcd for
C20H28NNaO2PS2 528.1197, found
528.1200. IR (cmꢀ1
,
neat solid) 3027(w), 2937(w), 2931(w),
2831(w), 1590(m), 1490(s).
1H NMR (CDCl3): d = 7.48–7.38 (m, 4H, aromatic), 7.25–7.10 (m,
6H, aromatic), 6.99–6.89 (m, 4H, aromatic), 6.87–6.79 (m, 4H, aro-
3
matic), 4.13 (d, JPH = 9.0 Hz, 4H, 2NCH2), 3.79 (s, 6H, 2CH3);
5
13C{1H} NMR (CDCl3): d = 159.5 (d, JCP = 2.2 Hz, 2CH3OC), 137.3
(d, JCP = 2.7 Hz), 135.4 (d, JCP = 4.4 Hz), 128.8 (s), 128.1 (s), 127.1
(s), 124.3 (d, JCP = 12.6 Hz), 114.7 (s, aromatic), 55.3 (s, 2CH3),
2
52.1 (d, JCP = 17.0 Hz, 2NCH2); 31P{1H} NMR (CDCl3): d = 133.2 (s).
4.2.4. bis(4-Methoxyphenyl)-2,2,6,6-tetramethylpiperidin-
1-ylphosphonodithioite (8)
2,2,6,6-Tetramethylpiperidine (0.96 mL, 0.81 g, 5.7 mmol) was
converted to 8 as described above for 4. The crude product was
purified by flash column chromatography on SiO2 (1.5 ꢁ 15 cm col-
umn; eluted with 1:0 v/v hexanes/EtOAc ? 9:1 v/v hexanes/EtOAc)
to obtain the product 4 (1.28 g, 50%) as a colorless oil. Anal. Calc. for
4.2. Syntheses
4.2.1. 1,2-Ethanedithio-N,N-dibenzyl-phosphoramidite (4)
To a Schlenk flask containing triethyl amine (4.8 mL, 34 mmol)
and phosphorus trichloride (0.5 mL, 5.7 mmol), CH2Cl2 (20 mL) was
added followed by dibenzylamine (1.1 mL, 5.7 mmol), which upon
addition, yielded a white smoke. The white slurry was stirred at
0 °C for 30 min upon which the color changed to yellow. 1,2-Eth-
anedithiol (0.58 mL, 0.65 g, 6.9 mmol) was then added. After
warming up to room temperature, the slurry stirred at room tem-
perature for 1 h. The slurry was diluted with CH2Cl2 (50 mL). The
organic layer was washed with H2O (50 mL), 0.2 M solution of
aqueous NaHSO4, H2O, with a saturated aqueous solution of NaH-
CO3 and H2O. The combined organic layers were dried over MgSO4
and concentrated in vacuo. The crude product was purified by pre-
cipitation from an EtOAc solution by addition of hexanes yielding 4
as a white solid (1.5 g, 4.7 mmol, 82%). Anal.Calc. for C16H18NPS2: C,
60.16; H, 5.68. Found: C, 60.66; H, 5.89%. HRMS calcd for
C23H32NO2PS2: C, 61.44; H, 7.17. Found: C, 61.45; H, 7.13%. HRMS
calcd for C23H32NNaO2PS2 472.1510, found 472.1516.
3
1H NMR (CDCl3): d = 7.35 (d, JHH = 7.5 Hz, 4H, aromatic), 6.77
3
(d, JHH = 8.7 Hz, 4H, aromatic), 3.72 (s, 6H, 2OCH3), 1.68 (broad s,
6H, 2CH3), 1.62–1.34 (m, 6H, 3CH2), 1.10 (broad s, 6H, 2CH3);
5
13C{1H} NMR (CDCl3): d = 159.2 (d, JCP = 2.8 Hz, 2CH3OC), 135.8
(d, JCP = 4.9 Hz), 126.1 (d, JCP = 20.3 Hz), 114.3 (d, JCP = 1.1 Hz),
2
2
0
60.2 (d, JCP = 9.3 Hz, NCH2), 58.1 (d, JCP = 31.8 Hz, NCH2 ), 55.2
0
(s, 2CH3O), 42.1 (broad s, CCH2), 40.6 (broad s, CCH2 ), 33.1 (d,
3
0
JCP = 24.2 Hz, 2CH3), 31.3 (broad s, 2CH3 ), 16.9 (s, CH2CH2CH2);
31P{1H} NMR (CDCl3): d = 133.2 (s).
4.2.5. bis(4-Methoxyphenyl)dibenzylphosphoramidite (7b)
A schlenk flask was charged with CH2Cl2 (8 mL) followed by tri-
ethylamine (1.2 mL, 2.9 mmol). The solution was cooled in ice bath
and PCl3 (0.25 mL, 2.9 mmol) was added dropwise, followed by
dibenzylamine (0.56 mL, 2.9 mmol). The solution was stirred at
room temperature for 1.5 h. In another schlenk flask 4-methoxy-
phenol (0.710 g, 5.72 mmol) was dissolved in CH2Cl2 (5 mL). The
reaction mixture was cooled in an ice bath and the solution of 4-
methoxyphenol was added dropwise. It was then stirred at rt over-
night. The reaction mixture was heated at 45 °C for one h. It was
then cooled and the solvent was concentrated to about 5 mL.
Diethyl ether (30 mL) was added to obtain a white solid. The sus-
pension was filtered, and the solvent was removed from the liquid
phase to get a white solid. The solid was then purified by column
on silica gel using CH2Cl2:hexane (60:40 v/v) to obtain 7b as white
solid (0.825 g, 1.74 mmol, 61%). Calcd for C28H28 NPO4: C, 71.02; H,
5.96. Found: C, 70.74; H, 5.83. HRMS calcd for C28H28 NPO4Na,
C
16H18NPS2 319.0618, found 319.0627. IR (cmꢀ1
, neat solid)
3023(w), 2894(w), 1492(m), 1452(m).
1H NMR (CDCl3): d = 7.39–7.12 (m, 10H, 2Ph), 4.03 (d,
3JPH = 10.9 Hz, 4H, 2NCH2), 3.56–3.41 (m, 2H, CHH0CHH0), 3.25–
3.10 (m, 2H, CHH0CHH0); 13C{1H} NMR (CDCl3): d = 137.6 (d,
3JCP = 1.65 Hz, 2NCH2C), 128.34 (s, Ph), 128.31 (d, JCP = 3.3 Hz, Ph),
2
127.2 (s, Ph), 52.0 (d, JCP = 17.0 Hz, 2NCH2), 41.3 (s, 2CH2);
31P{1H} NMR (CDCl3): d = 108.8 (s).
4.2.2. (rac)-N,N-2-Dibenzylamino-hexahydrobenzo[d][1,3,2]-
dithiaphospholane, (rac)-6
Cyclohexane-1,2-dithiol (rac)-5 (2.00 g, 13.5 mmol) was con-
verted to (rac)-6 as described above for 4. The crude product was
purified by precipitation from a CH2Cl2 solution by addition of hex-
anes yielding (rac)-6 as a white solid (4.28 g, 11.5 mmol, 85%).

P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
215
496.1653; found, 496.1663 (FAB+). MS (FAB, peg 600, NaI, m/z) [36]
496 ([7b+Na]+, 100%), 474 ([7b+H]+, 5%).
1H NMR (CDCl3): d = 7.49 (d, JHH = 8.6 Hz, 8H, aromatic), 7.39–
7.33 (m, 20H, aromatic), 6.61 (d, JHH = 8.8 Hz, 8H, aromatic),
4.16–4.12 (m, 8H, 4NCH2), 3.52 (s, 12H, 4CH3); 13C{1H} NMR
(CDCl3): d = 160.7 (s), 137.9 (s), 137.1 (s), 129.6 (s), 128.6 (s),
127.8 (s), 120.2 (s), 114.7 (s), 55.3, 53.6 (2s, 4CH3 + 4NCH2);
1H NMR (CDCl3): d = 7.70–7.63 (m, 10H, aromatic), 7.49–7.46
(m, 4H, aromatic), 7.27–7.24 (m, 4H, aromatic), 4.67–4.64 (m, 4H,
2NCH2), 4.14 (s, 6H, 2CH3); 13C{1H} NMR (CDCl3): d = 155.7 (s),
147.4 (d, JCP = 6.9 Hz), 137.9 (s), 128.9 (s), 128.4 (s), 127.2 (s),
121.4 (d, JCP = 7.5 Hz), 114.8 (s), 55.6 (s), 47.6 (d, JCP = 20.7 Hz);
31P{1H} NMR (CDCl3): d = 139.8 (s).
1
31P{1H} NMR (CDCl3): d = 132.0 (d, JPRh = 166 Hz).
4.2.9. trans-[Rh(CO)Cl(7b)2], (11b)
In a Schlenk flask [Rh(CO)2Cl]2 (0.010 g, 0.026 mmol) was dis-
solved in CH2Cl2 (2 mL). A solution of the phosphoramidite 7b
(0.050 g, 0.106 mmol) in CH2Cl2 (3 mL) was added to the solution
of metal precursor with stirring and the solution was stirred for
1 h. The solution was concentrated to nearly 1 mL and pentanes
(10 mL) were added. A precipitate formed. The suspension was
cooled in an ice bath. The pentane layer was decanted. The solid
was dried under high vacuum for 2 days at 40 °C to give the com-
plex 11b as a light yellow solid (0.112 g, 0.094 mmol, 73%). Calcd
for C57H56ClN2P2O9Rh: C, 61.49; H, 5.07. Found: C, 61.40; H, 5.05.
HRMS calcd for C56H5437ClN2P2O8Rh, 1084.2256; found,
1084.2057 (FAB+, [RhCl(7b)2]). MS (FAB, 4-NBA, m/z) [36] 1113
([11b+H]+, 2%), 1084 ([11bꢀCO]+, 10%), 1049 ([11bꢀCOꢀCl]+,
30%), 611 ([11bꢀCOꢀ7b]+, 100%), 604 ([11bꢀClꢀ7b]+, 95%), 575
([11bꢀCOꢀClꢀ7bꢀH]+, 35%); IR (cmꢀ1, neat solid) 1983(s, CO),
1500(s). IR (cmꢀ1, CH2Cl2) 3054(s), 2987(s), 2003(s, CO), 1503(s),
1265(s).
4.2.6. trans-[Rh(CO)Cl(4)2] (9)
In a Schlenk flask [Rh(CO)2Cl]2 (0.050 g, 0.129 mmol) was dis-
solved in toluene (3 mL). A solution of the ligand 4 (0.165 g,
0.515 mmol) in toluene (5 mL) was added to the solution of
[Rh(CO)2Cl]2 with stirring and the solution was stirred for 1 h. A so-
lid precipitated. The toluene layer was decanted. The solid was
washed with pentane (5 mL) and dried under high vacuum for
2 days at 40 °C to give the complex 9 as a yellow solid (0.184 g,
0.229 mmol, 89%) [37]. Calcd for C33H36ClN2P2ORhS4: C, 49.22; H,
4.51. Found: C, 46.41; H, 4.34. HRMS calcd for C32H36N2P2S4Rh,
741.0292; found, 741.0247 (FAB+). MS (FAB, 4-NBA, m/z) [36]
776 ([9ꢀCO]+, 5%), 741 ([9ꢀClꢀCO]+, 45%), 457 ([9 + HꢀCOꢀ4]+,
55%), 423 ([9 + HꢀClꢀCOꢀ4]+, 100%); IR (cmꢀ1
, neat solid)
1980(s, CO), 1494(s), 1452(s).
1H NMR [37] (CDCl3): d = 1H 7.31–7.09 (m, 20H, aromatic),
4.44–4.40 (m, 8H, 4NCH2), 3.44–3.41 (m, 4H, 4SCHH0), 3.30–3.26
(m, 4H, 4SCHH0); 13C{1H} NMR (CDCl3): d = 137.2 (s), 130.6 (s),
129.5 (s), 129.3 (s), 128.9 (s), 128.7 (s), 128.4 (s), 127.5 (s), 52.7
(s), 48.9 (s), 41.2 (s); 31P{1H} NMR (CDCl3): d = 132.5 (d,
1JPRh = 161 Hz).
1H NMR (CDCl3): d = 7.44–7.29 (m, 20H, aromatic), 7.13–7.02
(m, 8H, aromatic), 6.68–6.60 (m, 8H, aromatic), 4.28–4.24 (m, 8H,
4NCH2), 3.59 (s, 12H, 4CH3); 13C{1H} NMR (CDCl3): d = 156.4 (s),
146.2 (s), 137.6 (s), 129.2 (s), 128.7 (s), 127.6 (s), 122.3 (s), 114.6
(s), 55.6 (s), 50.0–49.9 (m); 31P{1H} NMR (CDCl3): d = 122.3 (d,
1JPRh = 194 Hz).
4.2.7. trans-[Rh(CO)Cl{(rac)-6}2], (rac)-10 [38]
To a Schlenk flask containing amino-dithiaphospholane (rac)-6
(0.138 g, 0.370 mmol) and [Rh(CO)2Cl]2 (0.036 g, 0.093 mmol), tol-
uene was added with stirring to obtain a dark red solution. Gas
evolution was observed. After 30 min at room temperature, the
solvent was removed by high vacuum and the residue was washed
with pentane (2 ꢁ 1 mL) and dried under vacuum to obtain (rac)-
10 as a light tan powder (0.149 g, 0.163 mmol, 88%), m.p. 165–
170 °C dec. (capillary). HRMS calcd for C40H49N2P2S4Rh 850.1309,
found 850.1302 (corresponds to [Rh{(rac)-6}2]+); MS (FAB, 4-NBA,
m/z) [36] 849 ([10ꢀ(CO)ꢀCl]+, 50%), 511 ([10ꢀ(CO)ꢀ(rac)-6]+,
100%), 476 ([10ꢀ(rac)-6ꢀClꢀ(CO)]+, 80%). IR (cmꢀ1, neat solid)
1983(s, CO), 3050(w), 2931(s), 2854(m).
4.2.10. trans-[Rh(CO)Cl(1a)2], (12a)
Complex 12a was synthesized from [Rh(CO)2Cl]2 (0.025 g,
0.064 mmol) and phosphoramidite 1a (0.093 g, 0.257 mmol) as de-
scribed above for 9. Yellow solid, (0.045 g, 0.051 mmol, 40%). HRMS
calcd for C44H3635ClN2O4P2Rh, 856.0894; found, 856.0910 (FAB+,
corresponds to [RhCl(1a)2]). MS (FAB, 4-NBA, m/z) [36] 885
([12a+H]+, 65%), 856 ([12aꢀCO]+, 25%), 821 ([12aꢀCOꢀCl]+, 25%);
IR (cmꢀ1, neat solid) 2010(s, CO).
1H NMR (CDCl3): d = 7.94–7.87 (m, 10H, aromatic), 7.44–7.40
(m, 6H, aromatic), 7.37–7.13 (m, 8H, aromatic), 2.74 (virtual t,
J = 5.4 Hz, 12H, 4NCH3); 13C{1H} NMR (CDCl3): d = 149.7 (s), 148.9
(s), 138.3 (s), 132.9 (s), 132.1 (s), 131.6 (s), 130.8 (s), 130.5 (s),
129.5 (s), 128.9 (s), 128.8 (s), 128.7 (s), 127.6 (s), 126.9 (s), 126.6
(s), 125.7 (s), 123.8 (s), 123.6 (s), 123.0 (s), 123.4 (s), 121.8 (s, aro-
1H NMR (CDCl3): d = 7.47–7.08 (m, 20H, 4Ph), 4.63–4.53 (br, 8H,
4NCH2), 3.42–3.34 (br, 4H, 4SCH), 2.11 (d, JHH = 12.0 Hz, 4H, 2CH2),
1.74 (d, JHH = 7.8 Hz, 4H, 2CH2), 1.59–1.14 (m, 8H, 4CH2); 13C{1H}
NMR (CDCl3): d = 137.5 (s, Ph), 130.7 (s, Ph), 129.3 (d, J = 2.0 Hz,
Ph), 128.7 (s, Ph), 128.6 (s, Ph), 127.5 (s, Ph), 62.1 (s, SCH), 59.4
(s, SCH0), 52.7 (s, NCH2), 31.5 (s, CH2), 26.0 (s, CH2), 25.7 (s, CH2);
matic), 38.6 (s, CH3), 38.5 (s, CH3 ); 31P{1H} NMR (CDCl3): d = 144.5
0
1
(d, JPRh = 196 Hz).
1
31P{1H} [38] NMR (CDCl3): d = 121.6 (d, JPRh = 161 Hz), 121.3 (d,
4.2.11. trans-[Rh(CO)Cl(1c)2], (12b)
1JPRh = 164 Hz).
Complex 12b was synthesized from [Rh(CO)2Cl]2 (0.018 g,
0.046 mmol) and phosphoramidite 1c (0.100 g, 0.198 mmol) as de-
scribed above for 9 (washings were performed with diethyl ether.
4.2.8. trans-[Rh(CO)Cl(7a)2], (11a)
Complex 11a was synthesized from [Rh(CO)2Cl]2 (0.018 g,
0.046 mmol) and ligand 7a (0.100 g, 0.198 mmol) as described
above for 9 (washing was performed with diethyl ether). Complex
11a was obtained as a yellow solid (0.057 g, 0.229 mmol, 49%).
Calcd for C57H56ClN2P2O5RhS4: C, 58.13; H, 4.79. Found: C, 57.92;
H, 4.79. LRMS calcd for C57H56N2 O5P2S4Rh, 1141.1602; found,
1141.1564 (FAB+, corresponds to [Rh(CO)(7a)2]+). MS (FAB, PEG
900 with NaI); calcd for C56H56N2 O4P2S4Rh, 1113.1653; found,
1113.1633 (FAB+, corresponds to [Rh(7a)2]+). MS (FAB, Peg 900,
NaI, m/z) [36] 1141 ([11aꢀCl]+), 1113 ([11aꢀClꢀCO]+), 1009
([11aꢀCOꢀSC6H4OCH3]+), 973 ([11aꢀClꢀCOꢀSC6H4OCH3]+), 608
Complex 12b was isolated as a light yellow solid (0.112 g,
0.094 mmol, 73%). Calcd for C69H52ClN2P2O5Rh: C, 69.67; H, 4.41.
Found: C, 68.98; H, 4.34. HRMS calcd for C68H5235ClN2P2O4Rh,
1160.2147; found, 1160.2134 (FAB+, corresponds to [RhCl(1c)2]).
MS (FAB, 4-NBA, m/z) [36] 1160 ([12bꢀCO]+, 45%), 1125
([12bꢀClꢀCO]+, 95%), 929 ([12bꢀCOꢀClꢀNBn2]+, 10%), 649
([12bꢀCOꢀ1c]+, 100%), 642 ([12bꢀClꢀ1c]+, 45%), 614
([12bꢀCOꢀClꢀ1c]+, 45%). IR (cmꢀ1, neat solid) 3058(w), 3028(w),
2017(s, CO), 1588(m); IR (cmꢀ1
2011(w, CO).
, CH2Cl2) 3054(w), 2987(w),
1H NMR (CDCl3): d = 7.94ꢀ7.91 (m, 2H, aromatic), 7.86ꢀ7.78
(m, 4H, aromatic), 7.66ꢀ7.63 (m, 2H, aromatic), 7.51ꢀ7.49 (m,
2H, aromatic), 7.44ꢀ7.30 (m, 28H, aromatic), 7.25ꢀ7.24 (m, 4H,
([11aꢀCl–ꢀOꢀ7a]+, 15%); IR (cmꢀ1
, neat solid) 1972(s, CO),
1588(s), 1489(s), 1244(s).

216
P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
aromatic), 7.05ꢀ7.03 (m, 2H, aromatic), 4.87ꢀ4.83 (m, 4H, 2NCH2),
3.70ꢀ3.60 (m, 4H, 2NCH2); 13C{1H} NMR (CDCl3): d = 149.3 (s),
148.3 (s), 137.3 (s), 137.1 (s), 132.6 (s), 131.9 (s), 131.4 (s), 130.7
(s), 130.5 (s), 129.0 (s), 128.8 (s), 128.5 (s), 127.7 (s), 127.4 (s),
127.2 (s), 126.7 (s), 126.3 (s), 125.5 (s), 125.3 (s), 123.4 (s), 123.3
(s), 122.9 (s), 120.9 (s, aromatic), 50.0 (s, CH2); 31P{1H} NMR
1H NMR (CDCl3): d = 7.37ꢀ7.19 (m, 10H, aromatic), 7.04–7.03
(m, 4H, aromatic), 6.70ꢀ6.67 (m, 4H, aromatic), 5.54 (broad s,
2H, 2 = CH), 4.30–4.26 (m, 4H, 2NCH2), 3.92 (broad s, 2H, 2 = CH),
3.68 (s, 6H, 2CH3), 2.28–2.17 (m, 4H, 2CH2), 2.05ꢀ2.02 (m, 4H,
2CH2); 13C{1H} NMR (CDCl3): d = 156.4 (s), 146.4 (d, J = 8.6 Hz),
137.9 (s), 129.2 (s), 128.6 (s), 127.5 (s), 122.2 (d, J = 4.8 Hz), 114.6
(s), 111.3 (dd, J = 5.8, J = 15.4 Hz, @CH), 71.6 (dd, J = 1.1,
J = 13.3 Hz, @CH), 55.8 (s), 50.8 (d, J = 11.6 Hz), 33.2 (s), 28.7 (s);
1
(CDCl3): d = 142.1 (d, JPRh = 199 Hz).
1
4.2.12. [RhCl(COD){rac-(6)}], (rac)-13
31P{1H} NMR (CDCl3): d = 112.9 (d, JPRh = 243 Hz).
In a Schlenk flask [RhCl(COD)]2 (0.060 g, 0.122 mmol) was dis-
solved in CH2Cl2 (2 mL). A solution of (rac)-6 (0.091 g, 0.244 mmol)
in CH2Cl2 (3 mL) was added to the solution of the metal precursor
with stirring and the solution was stirred for 1 h. The solution was
concentrated to about 1 mL. Pentane (5 mL) was added to the solu-
tion to precipitate the complex. The suspension was stirred for
10ꢀ15 min at 0 °C, the mother liquor was decanted and the resid-
ual solid was washed with pentane (5 mL). The solid was dried un-
der high vacuum for 2 days at 40 °C to give the complex (rac)-13 as
4.2.15. [IrCl(COD)(7a)], (15)
In a Schlenk flask [IrCl(COD)]2 (0.037 g, 0.055 mmol) was dis-
solved in THF (2 mL) and the ligand 7a (0.062 g, 0.122 mmol)
was added with stirring. The orange solution was stirred for 18 h.
The solvent was removed, and the residue washed with pentane
(2 ꢁ 3 mL). The solid was taken up in THF (2 mL), layered with pen-
tane and stored at ꢀ18 °C overnight. The solvent was decanted and
the solid was dried under high vacuum for 1 day to give the com-
plex 15 as a orange solid (0.060 g, 0.071 mmol, 58%). HRMS calcd
for C36H40NO2PS2193Ir, 806.1867; found, 806.1865 (FAB+, corre-
sponds to [Ir(COD)(7a)]). MS (FAB, 4-NBA, m/z) [36] 841 ([15]+,
5%), 806 ([15ꢀCl]+, 20%), 702 ([15ꢀSC6H4OCH3]+, 20%), 366
a
yellow solid (0.033 g, 0.053 mmol, 22%). Calcd for
C28H36ClNPRhS2: C, 54.24; H, 5.85. Found: C, 51.63; H, 5.67 [28].
HRMS calcd for C28H36NPRhS2, 584.1082; found, 584.1098 (FAB+,
corresponds to [Rh(COD){rac-(6b)}). MS (FAB, 4-NBA, m/z) [36]
619 ([13]+, 3%), 584 ([13ꢀCl]+, 100%), 511 ([13ꢀCOD]+, 80%), 476
([13ꢀClꢀCOD]+, 45%); IR (cmꢀ1, neat solid) 1978(s), 1494(s),
1450(s).
([7aꢀSC6H4OCH3]+, 100%); IR (cmꢀ1
,
neat solid) 3056(w),
2997(w), 2939(w), 2879(w), 2823(w), 1586(s), 1488(s), 1244(s).
1H NMR (CDCl3): d = 7.48ꢀ7.45 (d, JHH = 8.7 Hz, 4H, aromatic),
7.31–7.22 (m, 10H, aromatic), 6.73 (d, JHH = 8.4 Hz, 4H, aromatic),
5.23 (broad s, 2H, @CH), 4.09 (d, J = 12.5 Hz, 4H, 2NCH2), 3.77 (s,
6H, 2CH3), 3.36 (broad s, 2H, 2 = CH), 2.04–2.00 (m, 4H, 2CH2),
1.77–1.61 (m, 4H, 2CH2); 13C{1H} NMR (CDCl3): d = 160.6 (d,
JCP = 2.4 Hz), 138.5 (d, JCP = 3.2 Hz), 137.1 (d, JCP = 2.0 Hz), 129.1
(s), 128.3 (s), 127.4 (s), 118.7 (s), 114.4 (d, JCP = 1.4 Hz, aromatic),
97.6 (d, JCP = 16.5 Hz, @CH), 55.7 (d, JCP = 5.3 Hz), 53.1 (d,
JCP = 6.2 Hz), 33.3 (d, JCP = 3.5 Hz, CH2), 29.1 (d, JCP = 2.6 Hz, CH2);
31P{1H} NMR (CDCl3): d = 108.5 (s).
1H NMR (CDCl3): d = 7.53ꢀ7.24 (m, 10H, 2Ph), 5.52 (broad s, 2H,
2 = CH), 5.06ꢀ4.97 (m, 2H, NCH2), 4.48ꢀ4.38 (m, 2H, NCH2), 3.82 (s,
1H, @CH), 3.72 (s, 1H, @CH), 3.41ꢀ3.33 (m, 1H, CHS), 3.25ꢀ3.17 (m,
1H, CHS0), 2.45ꢀ2.39 (m, 2H, CH2), 2.27ꢀ2.02 (m, 8H, 4CH2),
1.88ꢀ1.19 (m, 6H, 3CH2); 13C{1H} NMR (CDCl3): d = 137.7 (d,
J = 2.3 Hz), 129.2 (s), 128.9 (s), 128.7 (s), 128.4 (s), 128.1 (s),
127.3 (s, aromatic), 107.2 (dd, J = 13.6 Hz, J = 7.1 Hz, @CH), 106.6
(dd, J = 15.0 Hz, J = 6.2 Hz, @CH), 75.4 (d, J = 14.0 Hz, @CH), 71.8
(d, J = 13.0 Hz, @CH), 61.7 (d, J = 3.4 Hz), 59.6 (d, J = 2.7 Hz), 53.2
(d, J = 9.5 Hz), 33.3 (d, J = 3.2 Hz), 32.6 (d, J = 3.3 Hz), 29.0 (s), 28.2
(s), 25.8 (d, J = 15.4 Hz); 31P{1H} NMR (CDCl3): d = 127.3 (d,
1JPRh = 194 Hz).
4.2.16. [RhCl(COD)(4)], (16)
Complex 16 was synthesized from [RhCl(COD)]2 (0.050 g,
0.101 mmol) and the ligand 4 (0.064 g, 0.202 mmol) as described
above for rac-13. Complex 16 was isolated as a yellow brown solid
(0.107 g, 0.189 mmol, 93%). Calcd for C24H30ClNPRhS2: C, 50.93; H,
5.34. Found: C, 49.61; H, 5.20 [28]. HRMS calcd for C24H30NPRhS2,
530.0612; found, 530.0605 (FAB+, corresponds to [Rh(COD)(4)]).
MS (FAB, 4-NBA, m/z) [36] 565 ([16]+, 5%), 530 ([16ꢀCl]+, 55%),
457 ([16ꢀCOD]+, 40%), 422 ([16ꢀClꢀCOD]+, 18%).
4.2.13. [RhCl(COD)(7a)], (14a)
Complex 14a was synthesized from [RhCl(COD)]2 (0.050 g,
0.101 mmol) and ligand 7a (0.103 g, 0.204 mmol) as described
above for rac-13. Complex 14a was isolated as a yellow solid
(0.128 g, 0.171 mmol, 84%). Calcd for
C36H40ClNO2PRhS2: C,
57.48; H, 5.36. Found: C, 57.37; H, 5.33. HRMS calcd for
C
36H40NO2PRhS2, 716.1293; found, 716.1272 (FAB+, corresponds
1H NMR (CDCl3): d = 7.37ꢀ7.24 (m, 10H, aromatic), 5.53 (broad
s, 2H, 2 = CH), 4.69 (d, J = 12.1 Hz, 4H, 2NCH2), 3.81 (broad s, 2H,
2 = CH), 3.55–3.46 (m, 2H, 2SCHH0), 3.32–3.25 (m, 2H, 2SCHH0),
2.39–2.25 (m, 4H, 2CH2), 2.11–2.05 (m, 4H, 2CH2); 13C{1H} NMR
(CDCl3): d = 137.8 (d, J = 2.5 Hz), 129.1 (s), 128.9 (s), 128.2 (s),
127.6 (s, aromatic), 107.2 (dd, J = 6.8 Hz, J = 14.9 Hz, @CH), 73.8
(d, J = 13.4 Hz, @CH), 53.4 (d, J = 9.3 Hz), 41.3 (d, J = 3.3 Hz), 34.5
(s), 33.2 (d, J = 2.8 Hz), 29.2 (s), 28.4 (s), 22.8 (s); 31P{1H} NMR
to [Rh(COD)(7a)]). MS (FAB, 4-NBA, m/z) [36] 716 ([14aꢀCl]+,
20%), 612 ([14aꢀClꢀSC6H4OCH3]+, 15%).
1H NMR (CDCl3): d = 7.63 (d, JHH = 8.0 Hz, 4H, aromatic),
7.43ꢀ7.21 (m, 10H, aromatic), 6.88 (d, JHH = 8.7 Hz, 4H, aromatic),
5.59 (broad s, 2H, @CH), 4.29–4.25 (m, 4H, 2NCH2), 3.91–3.89 (m,
2H, 2 = CH), 3.84 (s, 6H, 2CH3), 2.26 (m, 4H, 2CH2), 1.99 (m, 4H,
2CH2); 13C{1H} NMR (CDCl3): d = 160.9 (s), 138.7 (s), 137.4 (s),
129.4 (s), 128.6 (s), 127.7 (s), 119.5 (s), 115.0 (s), 114.7 (s),
107.5ꢀ107.2 (m, @CH), 72.6–72.5 (m, @CH), 55.7 (s), 53.9–53.8
(m), 33.1 (s), 28.8 (s); 31P{1H} NMR (CDCl3): d = 133.1 (d,
1JPRh = 197 Hz).
1
(CDCl3): d = 139.1 (d, JPRh = 194 Hz).
*
4.2.17. [IrCl2Cp (7b)], (17b)
In a Schlenk flask [IrCl2Cp*]2 (0.050 g, 0.063 mmol) was dis-
solved in CH2Cl2 (2 mL). A solution of the phosphoramidite 7b
(0.060 g, 0.126 mmol) in CH2Cl2 (3 mL) was added to the solution
of the metal precursor with stirring and the solution was stirred
for 1 h. The solution was concentrated to nearly 1 mL and pentane
(10 mL) was added. A precipitate formed. The mixture was cooled
in an ice bath and the pentane layer was decanted. The solid was
dried under high vacuum for 2 days at 40 °C to give the complex
17b as a yellow solid (0.070 g, 0.080 mmol, 64%). Calcd for
4.2.14. [RhCl(COD)(7b)], (14b)
Complex 14b was synthesized from [RhCl(COD)]2 (0.026 g,
0.053 mmol) and phosphoramidite 7b (0.050 g, 0.106 mmol) as de-
scribed above for rac-13. Complex 14b was isolated as a yellow solid
(0.039 g, 0.054 mmol, 51%). Calcd for C36H40ClNPO4Rh: C, 60.05; H,
5.60. Found: C, 59.79; H, 5.51. HRMS calcd for C36H40 NPO4Rh,
684.1750; found, 684.1757 (FAB+, corresponds to [RhCl(COD)(7b)]).
MS (FAB, Peg 600/900, NaI, m/z) [36] 684 ([14bꢀCl]+, 25%), 611
([14bꢀCOD]+, 100%), 575 ([14bꢀCODꢀCl]+, 45%).
C
38H43Cl2IrNO4P: C, 52.35; H, 4.97. Found: C, 50.39; H, 4.82 [28].
HRMS calcd for C38H4335Cl193IrNO4P, 836.2247; found, 836.2254

P. Shejwalkar et al. / Inorganica Chimica Acta 366 (2011) 209–218
217
Asymmetr. 20 (2009) 2167;
*
(FAB+, corresponds to [IrClCp (7b)]). MS (FAB, 4-NBA, m/z) [36]
871 ([17b]+, 5%), 836 ([17bꢀCl]+, 10%), 800 ([17bꢀ2Cl]+, 65%),
676 ([17bꢀN(CH2Ph)2]+, 10%), 640 ([17bꢀClꢀN(CH2Ph)2]+, 30%),
603 ([17bꢀ2ClꢀN(CH2Ph)2]+, 20%).
(c) W. Zhang, C.-J. Wang, W. Gao, X. Zhang, Tetrahedron Lett. 46 (2005) 6087;
(d) T. Pfretzschner, L. Kleemann, B. Janza, K. Harms, T. Schrader, Chem. Eur. J.
10 (2004) 6048;
(e) L.A. Arnold, R. Imbos, A. Mandoli, A.H.M. de Vries, R. Naasz, B.L. Feringa,
Tetrahedron 56 (2000) 2865.
1H NMR (CDCl3): d = 7.49ꢀ7.46 (m, 4H, aromatic), 7.26–7.17 (m,
10H, aromatic), 6.83–6.77 (m, 4H, aromatic), 4.24 (d, J = 9.0 Hz, 4H,
2NCH2), 3.78 (s, 6H, 2OCH3), 1.60 (d, J = 3.2 Hz, 15H, CH3); 13C{1H}
NMR (CDCl3): d = 156.2 (s), 146.3 (s), 146.2 (s), 136.7 (s), 136.6 (s),
129.8 (s), 128.1 (s), 127.5 (s), 122.4 (s), 122.4 (s), 114.5 (s), 95.4 (s,
CCH3, Cp*), 55.8 (s), 49.3 (d, JCP = 7.6 Hz, NCH2), 9.1 (s, CCH3, Cp*);
31P{1H} NMR (CDCl3): d = 79.5 (s).
´
[3] (a) N. Mršic, T. Jerphagon, A.J. Minnaard, B.L. Feringa, J.G. de Vries, Tetrahedron
Asymmetr. 21 (2010) 7;
(b) G. Erre, S. Enthaler, K. Junge, D. Addis, M. Beller, Adv. Synth. Catal. 351
(2009) 1437;
(c) N. Mršic´, A.J. Minnaard, B.L. Feringa, J.G. de Vries, J. Am. Chem. Soc. 131
(2009) 8358;
(d) I.D. Kostas, K.A. Vallianatou, J. Holz, A. Börner, Tetrahedron Lett. 49 (2008)
331;
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Adv. Synth. Catal. 350 (2008) 1081;
4.2.18. [IrCl2Cp*{(rac)-6}], (rac)-18
(f) W. Zhang, X. Zhang, J. Org. Chem. 72 (2007) 1020;
(g) B. Zhao, Z. Wang, K. Ding, Adv. Synth. Catal. 348 (2006) 1049;
(h) M. van den Berg, A.J. Minnaard, R.M. Haak, M. Leeman, E.P. Schudde, A.
Meetsma, B.L. Feringa, A.H.M. de Vries, C.E.P. Maljaars, C.E. Willans, D. Hyett,
J.A.F. Boogers, H.J.W. Henderickx, J.G. de Vries, Adv. Synth. Catal. 345 (2003) 308.
[4] (a) J.A. Raskatov, S. Spiess, C. Gnamm, K. Brödner, F. Rominger, G. Helmchen,
Chem. Eur. J. 16 (2010) 6601;
*
To a Schlenk flask containing [IrCl2Cp ]2 (0.081 g, 0.102 mmol),
amino-dithiaphospholane (rac)-6 (0.076 g, 0.204 mmol) was added
followed by CH2Cl2 (5 mL) to obtain an orange solution. The mix-
ture was allowed to stir under nitrogen atmosphere at room tem-
perature for 0.5 h. The solvent was removed by high vacuum, the
residue washed with diethyl ether (2 ꢁ 2 mL) and dried under vac-
uum to obtain (rac)-18 as an orange solid (0.148 g, 0.192 mmol,
96%), m.p. 195–200 °C dec. (capillary). Anal. Calc. for
(b) Q.-L. Xu, W.-B. Liu, L.-X. Dai, S.-L. You, J. Org. Chem. 75 (2010) 4615;
(c) S. Spiess, J.A. Raskatov, C. Gnamm, K. Brödner, G. Helmchen, Chem. Eur. J. 15
(2009) 11087;
(d) C.A. Falciola, A. Alexakis, Chem. Eur. J. 14 (2008) 10615;
(e) S. Shekar, B. Trantow, A. Leitner, J.F. Hartwig, J. Am. Chem. Soc. 128 (2006)
11770;
C
30H39Cl2IrNPS2: C, 46.68; H, 5.09. Found: C, 44.58; H, 4.98% [28].
HRMS calcd for C30H3937Cl191IrNPS2 736.1579, found 736.1556
(f) A. Alexakis, V. Albrow, K. Biswas, M. d’Augustin, O. Prietob, S. Woodward,
Chem. Commun. (2005) 2843.
*
(FAB+, corresponds to [IrClCp {(rac)-6}]). MS (FAB, 4-NBA, m/z)
[5] (a) L.M. Stanley, J.F. Hartwig, J. Am. Chem. Soc. 131 (2009) 8971;
(b) S. Spiess, C. Welter, G. Franck, J.-P. Taquet, G. Helmchen, Angew. Chem., Int.
Ed. 47 (2008) 7652.
[6] (a) F. Zhang, Q.-H. Fan, Org. Biomol. Chem. 7 (2009) 4470;
(b) X.-X. Guo, J.-H. Xie, G.-H. Hou, W.-J. Shi, L.-X. Wang, Q.-L. Zhou, Tetrahedron
Asymmetr. 15 (2004) 2231.
[7] H. Park, R. Kumareswaran, T.V. RajanBabu, Tetrahedron 61 (2005) 6352.
[8] (a) B.M. Trost, S.M. Silverman, J. Am. Chem. Soc. 132 (2010) 8238;
(b) R.T. Yu, E.E. Lee, G. Malik, T. Rovis, Angew. Chem., Int. Ed. 48 (2009) 2379;
(c) C. Nájera, M. de Gracia Retamosa, M. Martín-Rodríguez, J.M. Sansano, A. de
Cózar, F.P. Cossío, Eur. J. Org. Chem. (2009) 5622;
[36] 771 ([18]+, 5%), 736 ([18ꢀCl]+, 100%).
1H NMR (CDCl3): d = 7.36ꢀ7.20 (m, 10H, aromatic), 4.56 (t,
0
J = 13.1 Hz, 2H, NCH2), 3.98–3.86 (m, 2H, NCH2 ), 3.58ꢀ3.43 (m,
2H, CHS), 2.21 (t, J = 13.1 Hz, 2H, CH2), 1.86–1.74 (m, 2H, CH2),
1.70 (d, J = 3.2 Hz, 15H, 5CH3), 1.58ꢀ1.45 (m, 2H, CH2), 1.38 (d,
J = 12.6 Hz, 2H, CH2); 13C{1H} NMR (CDCl3): d = 136.6 (d,
J = 3.8 Hz), 129.6 (s), 128.2 (s), 127.5 (s, aromatic), 93.3 (d,
*
J = 3.3 Hz, CCH3, Cp ), 64.4 (d, J = 3.3 Hz, CHS), 61.4 (d, J = 2.2 Hz,
CHS0), 51.3 (d, J = 4.4 Hz, NCH2), 31.2 (d, J = 5.5 Hz, CH2), 31.0 (d,
J = 8.8 Hz, CH2), 25.9 (s, CH2), 25.3 (s, CH2), 9.1 (s, CCH3, Cp*);
31P{1H} NMR (CDCl3): d = 90.7 (s).
(d) C. Najera, M. de Garcia Retamosa, J.M. Sansano, Angew. Chem., Int. Ed. 47
(2008) 6055;
(e) N. Toselli, D. Martin, M. Achard, A. Tenaglia, T. Burgi, G. Buono, Adv. Synth.
Catal. 350 (2008) 280.
[9] D. Huber, A. Mezzetti, Tetrahedron Asymmetr. 15 (2004) 2193.
[10] R.T. Stemmler, C. Bolm, Adv. Synth. Catal. 349 (2007) 1185.
[11] J.W. Faller, P.P. Fontaine, Organometallics 24 (2005) 4132.
[12] (a) G. Rothenberg, S.C. Cruz, G.P.F. Van Strijdonck, H.J.C. Hoefsloot, Adv. Synth.
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(b) R. Imbos, A.J. Minnaard, B.L. Feringa, Dalton Trans. 10 (2003) 2017.
[13] A. Duursma, J.-G. Boiteau, L. Lefort, J.A.F. Boogers, A.H.M. de Vries, J.G. de Vries,
A.J. Minnaard, B.L. Feringa, J. Org. Chem. 69 (2004) 8045.
[14] (a) K. Schober, H. Zhang, R.M. Gschwind, J. Am. Chem. Soc. 130 (2008) 12310;
(b) H. Zhang, R.M. Gschwind, Angew. Chem., Int. Ed. 45 (2006) 6391.
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363 (2010) 474;
4.2.19. Typical NMR tube experiment to determine 31P-77Se coupling
constants
To a solution of 0.050 g of 7a (0.11 mmol) in 0.5 ml of CDCl3, Se8
(0.017 g, 0.026 mmol) was added. The reaction mixture was kept in
an NMR tube at 40 °C for 1 h. At that time, a 31P NMR spectrum was
1
recorded. 31P{1H} 95.1 (s, JPSe = 857.5 Hz) [39]; MS (FAB, 4-NBA,
m/z) [36] 586 ([7a+H]+, 13%), 446 ([7aꢀSC6H4OCH3]+, 25%), 306
([7aꢀ2SC6H4OCH3]+, 21%).
(c) I.S. Mikhel, H. Rüegger, P. Butti, F. Camponovo, D. Huber, A. Mezzetti,
Organometallics 27 (2008) 2937.
Acknowledgement
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(b) S. Costin, N.P. Rath, E.B. Bauer, Inorg. Chim. Acta 362 (2009) 1935;
(c) P. Shejwalkar, N.P. Rath, E.B. Bauer, Molecules 15 (2010) 2631.
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(c) A. Okruszeck, A. Sierzchała, M. Sochacki, W.J. Stec, Tetrahedron Lett. 33
(1992) 7585;
Funding from the National Science Foundation for the purchase
of the NMR spectrometer (CHE-9974801) and the purchase of the
mass spectrometer (CHE-9708640) is acknowledged.
Appendix A. Supplementary material
(d) N. Farschtschi, D.G. Gorenstein, Tetrahedron Lett. 29 (1988) 6843;
(e) K. Jurkschat, C. Mügge, A. Tzschach, W. Uhlig, A. Zschunke, Tetrahedron Lett.
23 (1982) 1345.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.11.006.
´
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