P-N Bridged Dinuclear Rh-METAMORPhos Complexes: NMR and Computational Studies

Article abstract of DOI:10.1002/ejic.201800397

Sulfonamido-phosphoramidites are known to form six-membered ring Rh-P-N-Rh-P-N- dinuclear complexes. Apart from a single X-ray structure, little is known about their three dimensional structure in solution. This study proposes a ³¹P, ¹⁵

Full text of DOI:10.1002/ejic.201800397

A Journal of
Accepted Article
Title: P-N bridged dinuclear Rh-METAMORPhos complexes: NMR and
computational studies
Authors: Frederic William Patureau, Jessica Groß, Jan Meine Ernsting,
Christoph van Wüllen, and Joost Reek
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201800397
Link to VoR: http://dx.doi.org/10.1002/ejic.201800397

European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
P-N bridged dinuclear Rh-METAMORPhos complexes: NMR and
computational studies
[
a,b,c]
[b]
[a]
[b]
Frederic W. Patureau,
Jessica Groß, Jan Meine Ernsting, Christoph van Wüllen,* and Joost N.
[
a]
H. Reek*
Abstract: Sulfonamido-phosphoramidites are known to form 6-
membered ring Rh-P-N-Rh-P-N- dinuclear complexes. Apart from a
single X-ray structure, little is known about their three dimensional
attributions: JRhP = 261 Hz, JRhP’ = - 3 Hz, JPP’ = 29 Hz and JRhRh’
~ 0 Hz.
[
7]
31
15
103
structure in solution. This study proposes a P, N and Rh NMR
investigation of the question, as a well as a DFT study. The
15
AA’MM’XX’
6
spin system of the corresponding
N-enriched
dinuclear complex is notably described.
Introduction
[
1,2]
Since the ground-breaking 1865 proposition of Kekulé,
the
atomic 6-membered ring structure has been found to be one of
the most dominant cyclic arrangements in Nature. This arises
from the relative stability of the 6-membered ring versus other
ring sizes. In this study, we propose to prove: 1) that
[
3]
sulfonamido-phosphoramidite
(METAMORPhos)
ligands
promote a characteristic Rh-P-N-Rh-P-N- 6-membered ring
[
4]
organometallic dinulcear structure, 2) that a strong Rh-N bond
1
5
exists in solution, 3) that N enrichment of this characteristic
dinuclear complex leads to a rare AA’MM’XX’ 6-spin system
3
1
103
15
including P,
Rh, and N nuclei, in which we propose to
[
5]
solve the spin-spin couplings. Moreover, we propose to
investigate the 3D-geometries of those complexes through
computational studies, and thereby investigate the possibility of
several conformers/twistamers in solution.
Scheme 1. Preparation of Rh (nbd) (L)
2
2
2
2
3
In the case of L (R = CF ), which we will utilize as second
Joining anionic phosphoramidite METAMORPhos ligand
METAMORPhos ligand in this study, JRhP = 265 Hz, JRhP’ = - 3
1
I
(
HNEt
leads to dinuclear complex Rh
releasing one equivalent of (HNEt
norbornadiene) per Rh center. This dinuclear complex yields a
3
)(L ) together with cationic Rh precursor Rh(nbd)
2
BF
(Scheme 1, Figure 1),
) salt and one nbd
4
Hz, JPP’ = 21 Hz. These NMR coupling constants confirm the
1
1 or 2
2
(nbd)
2
(L )
)(BF
2
symmetrical dinuclear disposition of Rh (nbd) (L
2
2
)2, but say
3
4
little about the coordination mode of the dinuclear core in the
organometallic complex. In particular, at this point, neither NMR
nor HRMS distinguishes -P,N bridging (Structure I) versus P,O
bridging mode (Structure II). In 2009, early DFT calculations
indicated that the -P,N bridging mode should be favored by
(
3
1
characteristic AA’XX’ 4-spin system in the P NMR profile,
which we originally reported in 2009.
system can be easily solved with Günther’s equations. In the
[
4a]
The 4-spin coupling
[
6]
1
[4a]
case of L (R = para-n-butyl-phenyl), J = 261 Hz, J’ = - 3 Hz, J
29 Hz and J is negligible. Because JPP’ was expected to be
significantly superior to JRhRh’, we originally assigned A-spins to
A
approximatively 6 kcal/mol. This was confirmed in 2013 when
=
X
the racemic CF3- analogue of this complex based on
2
(HNEt )(±L ) was successfully crystallized and characterized by
3
3
1
103
P and X-spins to
Rh, thus yielding the following coupling
X-Ray, thus demonstrating the P,N character of the ligand in a
[
8]
cyclic six membered ring Rh-P-N-Rh-P-N- structure. This was
the first direct experimental evidence for the -P,N bridging
mode in the solid state. However, in other organometallic
complexes based on METAMORPhos ligands, including Rh
complexes, the P,O coordination mode was found to take place
[
[
[
a]
b]
c]
F. W. Patureau, J. M. Ernsting, J. N. H. Reek,
Van’t Hoff Institute for Molecular Sciences, University of Amsterdam,
Science Park 904 1098 XH Amsterdam (The Netherlands)
E-mail: j.n.h.reek@uva.nl
F. W. Patureau, J. Groß, C. van Wüllen,
FB Chemie, TU Kaiserslautern,
[
3b-c]
as well.
These dinuclear complexes are not always easy to
crystallize however, and in addition, solid and solutions states
could greatly differ in the assembly of dinuclear complexes.
Moreover, the diastereomeric effects arising from the C -chiral
2
binol backbones may have unexpected influence on the
dinuclear complexation mode (ie dinuclear structure I or II). We
therefore propose here an NMR method in order to characterize
Erwin Schrödinger Strasse 52, 67663 Kaiserslautern
E-Mail (DFT calculations): vanwullen@chemie.uni-kl.de
Parts of this work were developed in the doctoral thesis of FWP, 2
nd
December 2009, University of Amsterdam, Netherlands. Current
affiliation of FWP: TU Kaiserslautern.
NMR spectra, supporting information for this article is given via a
link at the end of the document.
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
103Rh.500.002.2rr.esp
those organometallic systems in solution, as well as
computational investigation.
a
4
46
48
50
52
54
56
58
60
62
64
66
68
70
472
74
76
78
80
82
84
4
4
4
4
4
1
03Rh.500.002.2rr.esp
9
6.5
96.0
95.5
95.0
4
Chemical Shift (ppm)
4
4
51
4
4
452
4
4
453
4
454
4
4
4.650
4.625
4.600
F2 Chemical Shift (ppm)
4
4
4
4
4.5
4.0
3.5
3.0
2.5
F2 Chemical Shift (ppm)
104.0
103.5
103.0
Chemical Shift (ppm)
3
1
1
Figure 1. Real and simulated
P{ H} NMR (CD
2 2
Cl , 202.3 MHz), of
1
Rh
RhRh’ ≈ 0 Hz, top, and of Rh
3
1 Hz; JRhRh’ ≈ 0 Hz, beneath, (the CF gives a singlet in F NMR: no
2 2 2
(nbd) (R-L ) , (AA’ part), JRhP = 261 Hz, JRhP’ = - 3 Hz, JPP’ = 29 Hz and
2
J
2
2 2
(nbd) (R-L )2, JPRh = 265 Hz; JPRh’ = -3.0 Hz; JPP’ =
19
significant interference with the AA’XX’ 4-spin system).
4
80
475
470
465
460
455
450
Chemical Shift (ppm)
1
103
1
Results and Discussion
2 2 2
Figure 2. H- Rh HMQC NMR experiment of Rh (nbd) (L ) (121.5 and 9.4
103
MHz respectively, top), and projection along Rh axis
1
2 2 2
When we first discovered the dinuclear complex Rh (nbd) (L )
[
4a]
in 2009,
we originally imagined it as a single most stable
Because part of the characterization difficulties in those systems
arise from the second order symmetry, we had originally decided
that a convenient solution could be to simplify the spin system
by performing a scrambling experiment. One of the aims was
to suppress the second ordered AA’XX’ 4-spin system. Thus,
regioisomer. The first X-ray structure of such a dinuclear system,
[
8]
published in 2013, comforted this idea. However, when we
1
03
started to look deeper into the
Rh NMR of those species in
[
4a]
solution, it became clear that this notion needed further
1
03
investigations. An initial Rh NMR study of dinuclear complex
1
2
1
[
HNEt
and Rh(nbd)
obtains an approximatively statistical mixture (~ 25:50:25) of
3
][(R)-L ] can be united with inequivalent [HNEt
3
][(R)-L ]
Rh
2 2 2
(nbd) (L ) was performed, in which we were hoping to find
3
1
BF in a 1:1:1 ratio. Under those conditions, one
4
the XX’ half spin system corresponding to the AA’ part of the
P
2
1
103
NMR (Figure 1). However, the H- Rh HMQC spectra of
1
1
homo1-, hetero-, and homo2- complexes: Rh
2 2 2 2 2
Rh (nbd) (L )(L ), and Rh (nbd) (L ) respectively. Therefore,
in the case of the combination of (R)-L and (R)-L , the statistical
2
[4a]
(nbd)
2
2
(L ) ,
Rh
2
(nbd)
2
(L )
2
revealed
a
more complex situation than
1
2
2
[
4a, 9]
anticipated (Figure 2).
In particular, it is unclear whether the
1
2
1
03
projection along the Rh axis belongs solely to a second order
XX’ half spin system (Figure 2), or if some additional lines are
present as well.
distribution indicates that no significant sorting occurs (Figure 3).
1
2
2 2
As expected, in the hetero combination: Rh (nbd) (L )(L ), the
second order has completely disappeared and each
phosphorous signal now displays a simple first order doublet of
1
3
doublet ( JP-Rh and
JP1-P2, Figure 3). This interpretation is
3
1
103
confirmed by a special P{ Rh} NMR experiment of this
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
3
mixture, in which the latter signals become simple doublets ( JP1-
P2), while previously second ordered homo1 and homo2
103Rh_2.006.001.2rr.esp
1
2
complexes Rh
expected, singlets. In this particular system,
2
(nbd)
2
(L )
2
and Rh
2
(nbd)
2
(L )
2
become, as
1
JP1or2-Rh1or2 = 268
420
1
3
Hz,
performed
Strikingly, the first order Rh
display as originally anticipated a single line per Rh atom along
J
P2or1-Rh2or1 = 258 Hz, and finally
J
P1-P2 = 25 Hz. We then
3
1
103
425
430
a
P- Rh HMQC experiment of the mixture.
1
2
2
2
(nbd) (L )(L ) complex does not
435
1
03
440
445
the
Rh axis (Figure 4). Indeed, each of the two inequivalent
1
2
Rh atoms in Rh
2
2
(nbd) (L )(L ) is in fact splitted in a least 6
4
50
individual lines, lacking any obvious symmetry. Moreover, the
most outer lines are distant by at least 119 Hz, which arguably
455
excludes any unexpected NMR coupling. This is supported by
460
465
470
475
3
the fact that large
models. Moreover, H- Rh NMR couplings arising from the
nbd unit are known not to exceed 4 Hz. This is in good
JRh-Rh couplings don’t fit in our simulation
[
7]
1
103
[
9]
1
accordance with the H NMR profiles of our Rh
2 2 2
(nbd) (L)
480
complexes, for which the largest vinylic signals don’t exceed 3 to
4
85
[
7]
4
Hz NMR couplings.
490
495
106
104
102
100
98
96
94
92
F2 Chemical Shift (ppm)
103Rh_2.006.001.2rr.esp
4
20
22
24
26
28
30
4
4
4
4
4
105.1, 432.25, 0.4
1
05.1, 433.64, 0.35
05.1, 435.23, 0.57
432
434
1
4
36
38
440
42
44
46
48
50
52
54
56
58
60
1
05.1, 438.01, 0.72
05.1, 441.72, 0.25
4
1
4
1
05.1, 444.9, 0.12
4
4
4
4
4
4
4
4
1
06
105
104
103
102
101
100
99
98
97
96
95
94
93
92
4
Chemical Shift (ppm)
106.5
106.0
105.5
105.0
104.5
104.0
103.5
103.0
102.5
102.0
101.5
101.0
F2 Chemical Shift (ppm)
31
103
Figure 4. Scrambling experiment, P- Rh HMQC NMR experiment (121.5
and 9.4 MHz respectively, top), and zoom in on the top left pattern (beneath)
3
1
1
1
2
It thus seems that the P{ H} NMR profile of Rh
2 2
(nbd) (L )(L ),
displaying one dd for each ligand, could be in fact an
3
1
103
average/overlap of several species. In contrast to P,
Rh
NMR benefits from a considerably larger span of chemical shifts,
and is thus more sensitive to minor geometry changes. Likewise,
Pt NMR has also been found in previous studies to be very
1
06
105
104
103
102
101
100
99
98
97
96
95
94
93
92
Chemical Shift (ppm)
195
31
1
Figure 3. Scrambling experiment (top), P{ H} NMR (CD
2
Cl
2
, 121.5 MHz,
sensitive to minor geometrical changes in the coordination
31
103
middle, see SI for the 202 MHz spectrum), and P{ Rh} NMR (CD
MHz, beneath)
2
Cl , 121.5
2
[10]
sphere of the metal center. In the present case, several chair,
boat and twist configurations may be envisaged, each potential
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
configuration further sub-divided in twistameric and
which the P-N lines are quasi parallel, and which differ “only” by
the arrangement of the binaphhol and sulfone units (B1 and B2).
A chair configuration (S) was also identified, as well as four
diastereomeric isomerism.
A
great number of those
configurations might thus potentially co-exist in solution at room
temperature. This intriguing possibility, which is reminiscent of
the various possible conformers of cyclohexane and its organic
twistamers (Twist a-d, Figure 5). Importantly, in all cases, Twist
2
b dominates all other conformers. For Rh
2
(nbd)
2
(L )
2
, Twist b
derivatives, called for a detailed DFT investigation. The full
dominates the next most stable conformer (Twist a) by 25
1
1
model minus the butyl chain of complexes Rh
2
(nbd)
2
(L )
2
,
kJ/mol. In Rh
2 2 2
(nbd) (L ) , the next most stable conformer is the
1
2
2
1
Rh
2
(nbd)
2
(L )(L ), and Rh
2
(nbd)
2
(L )
2
were thus respectively
boat B2, by 44 kJ/mol, and in the hetero complex Rh (nbd) (L )
2 2 2
considered, under all imaginable conformer possibility. Only
homo-chiral (R)-binaphthol derived dinuclear complexes were
investigated. The mixed chiral (R)/(S) case was not considered
because of the self-sorting effect (Scheme 1).
the next most stable conformers is the chair S by 49 kJ/mol. All
energies and structures are provided in the SI. Clearly, at room
temperature, the equilibrium co-existence of several regio-
isomers seems excluded by these gas-phase DFT calculations.
We then also quantified solvent effects by a series of COSMO
calculations (supporting Information, Tables S13-S15). While
there is some effect on relative conformer stability, the overall
picture remains unchanged, especially that Twist b is by far the
most stable conformer. Noteworthy to mention, in all three
All DFT calculations were originally performed in the gas-phase.
It was found that the 6-membered Rh-P-N-Rh-P-N- has at least
seven optimizable conformers of various energies for each
dinuclear complex. Two boat conformers were notably found, in
1
Figure 5. The seven conformers: Boat B1, B2, Chair S, Twistamers a, b, c, and d, all represented for Rh
2
(nbd)
2
(R-L )
2
, in the gas phase.
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
complexes, the most stable Twist b displays a similar Rh-Rh
was then united with Rh(nbd)
2
BF
4
to produce the characteristic
1
2
15
3
31
1
distance, of 3.34 Å for Rh
2
(nbd)
2
(L )
2
, 3.32 Å for Rh
2
1
(nbd)
2
(L )
(L )(L ). In the
, the Rh-Rh distance
2
,
2 2 2
dinuclear complex Rh (nbd) ( N-L ) . The resulting P{ H}
2
and of 3.31 Å for the mixed complex Rh
2
(nbd)
2
NMR profile is presented in Figure 7, together with its
corresponding simulation. By analogy with Rh (nbd) (L ) , which
2 2 2
2
1
solid state X-ray structure of Rh
2
(nbd)
2
(L )
2
is 3.1460(4) Å. Again, the apparent deviation may come from
comparing gas-phase (DFT) and solid state. In general,
surprisingly, the contrasting electronic and steric parameters of
is electronically and sterically most similar, the following NMR
coupling constants: JRhP = 261 Hz, JRhP’ = - 3 Hz, JPP’ = 29 Hz
and JRhRh’ = 0 Hz can be considered unchanged. Unfortunately,
1
2
1
31
1
L (NTs) versus L (NTf) do not seem to impact much the Rh-Rh
distance nor the relative energies and structures of the various
conformers (Figure 5). Likewise, the N-Rh bond, which is
strategic to maintain the 6-membered ring dinuclear structure of
the complex, is remarkably consistent in the most stable Twist b
the strategic J15N-Rh does not impact the P{ H} NMR simulation
1
5
3
of Rh
2 2 2
(nbd) ( N-L ) . Indeed, a small (2Hz) or large value (50
Hz) yields the same profile. In other words, one cannot utilize
3
1
1
1
the P{ H} simulation to iteratively determine
J15N-Rh. On the
1
31
1
other hand,
J15N-P could be approached by iterative P{ H}
1
2
2 2 2 2 2 2
isomer of Rh (nbd) (L ) (2.189 Å), of Rh (nbd) (L ) (2.206 Å),
simulations and found to be 88 Hz.
and the X-ray structure of the latter (2.185(3) Å). For a visual
comparison, we have reproduced the known X-Ray structure of
2
2
Rh
2
(nbd)
2
(R-L )
2
•Rh
2
(nbd)
2
(S-L )
2
and the computated most
2
stable Twist b conformer of Rh
2
(nbd) (R-L ) in Figure 6.
2 2
15
3
15
3
3 2 2 2
Scheme 2. Synthesis of (HNEt )( N-L ) and Rh (nbd) ( N-L ) .
1
31
In order to determine the strategic J15N-Rh coupling, another P-
1
03
15
3
Rh HMQC experiment was conducted on Rh
2 2 2
(nbd) ( N-L ) .
The resulting 2D profile is presented in Figure 7. Four large
103
doublets are clearly visible along the
Rh axis, each
corresponding to one of the four great line packages along the
3
1
103
P axis. Each
Rh-directed doublet displays the same large
1
coupling: J15N-Rh = 30 +/- 1 Hz. Importantly, the projection along
the Rh axis gives approximatively the same pattern which had
been observed for Rh (nbd) (L ) and Rh (nbd) (L )(L ), only
2 2 2 2 2
each line doubled by a 30 Hz coupling ( J15N-Rh). The full spin
1
03
1
1
2
1
Figure 6. ORTEP representation (30% probability) of the known
2
2
X-ray structure of Rh
Rh (nbd) (R-L )
2 2 2
2
(nbd)
part is represented (CCDC-931393, top), and
corresponding computed optimized geometry of Rh (nbd) (R-
in the most stable conformer Twist b (gas phase, bottom
picture).
2
(R-L )
2
•Rh
2
(nbd)
2
(S-L )
2
,
the
system is represented in Scheme 3.
2
[8]
2
2
2
L )
2
The reality and strength of the N-Rh bond in solution was then
1
5
15
looked at with N enrichment. In order to do so, a 99% N-
1
enriched METAMORPhos analogue of L was prepared in two
simple steps: (HNEt )( N-L ). The latter displays a characteristic
3
P-15N = 70 Hz (Scheme 2). It should be noted that while the JH-
5N NMR coupling in N-TsNH
coupling could be detected between the N of (HNEt
and the proton of the HNEt cation. This is in good agreement
with the ionic character of the phosphoramidite. (HNEt
1
5
3
1
1
J
15
1
2
is quite large, at 80 Hz, no NMR
1
5
15
3
3
)( N-L ),
3
1
5
3
31
15
103
3
)( N-L )
Scheme 3. AA’MM’XX’ 6 spin system based on P, N and Rh, all none
displayed NMR couplings are approximatively 0 Hz.
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
2
2
[8]
Rh
2 2 2 2 2 2
(nbd) (R-L ) •Rh (nbd) (S-L ) ), may account for a similar
3
1
1
effect. It should be noted that the P{ H} NMR simulation does
2
not accommodate a
J
15N-P larger than 1 Hz, above which the
simulated P{ H} profile becomes significantly more complex
more lines) than reality. In order to illustrate this point,
3
1
1
(
2
simulations at
J15N-P = 0, 1, 2, and 5 Hz are provided in
[
7]
2
supplementary information. Finally, it should be noted that JRh-
5N’ is probably small, certainly much smaller than the J15N-Rh =
0 +/- 1 Hz. However, its value does not affect the P{ H} NMR
simulation, rendering iterative estimation impossible. The
1
1
3
1
1
3
1
03
Rh
axis projections are moreover too broad for direct determination.
100.0
99.5
99.0
98.5
98.0
97.5
97.0
3
In contrast, we can however safely say that J15N-15N’ ~ 0 Hz, as
Chemical Shift (ppm)
31
1
any other value significantly alters the P{ H} NMR simulation
compared to reality.
Conclusions
In conclusion, we reported here the first AA’MM’XX’ 6-spin
3
1
15
103
system based on P, N and Rh. It is as far as we know also
the first such AA’MM’XX’ 6-spin system to involve a transition
1
5
metal. N-enrichment of METAMORPhos has allowed the NMR
characterization of the Rh-N bond in the 6-membered ring
1
Rh
2
(nbd)
2
(L)
2
complex, in solution. The J15N-Rh was found to be
3
0 Hz, which is as far as we know also one of the largest ever
1
5
103
[11]
reported NMR coupling between N and Rh. This relatively
high value suggests the existence of a strong N-Rh bond in the
dinuclear complex in solution. Moreover,
1
03
Rh NMR
characterization and computational studies revealed that several
conformers/twistamers are conceivable, even if Twistamer b
seems to have
a significant advantage over the other
conformers according to those DFT studies. The interpretation of
1
03
the multiple
Rh NMR lines observed for these complexes
remains therefore open. In general, the characteristic dinuclear
disposition of these complexes could have an impact on the
development of future cooperative catalysis applications, such
as asymmetric hydrogenation reactions. We hope that this study
will also inspire characterization and computational solutions for
other organometallic coordination problems, particularly those
based on cooperative dinuclear complexes.
Experimental Section
Synthetic procedures and selected characterization (for spectra, see SI).
All reactions were carried out in dry glassware under argon or nitrogen
atmosphere. Every solution addition or transfer was performed with
syringes. All solvents were dried and distilled with standard procedures.
Chromatographic purifications were performed by flash chromatography
on silica gel 60-200 μm, 60 Å. Nuclear Magnetic Resonance experiments
1
5
3
Figure 7. AA’ part of AA’MM’XX’ 6-spin system of Rh
2
(nbd)
202.3 MHz) and corresponding simulation (top),
P- Rh HMQC NMR experiment (121.5 and 9.4 MHz
2 2
( N-L ) in
31
1
2 2
P{ H} NMR (CD Cl ,
103
31
corresponding
respectively, middle down), and zoom in of the latter spectrum.
1
were performed either on a Varian Inova500 spectrometer ( H: 500 MHz,
3
1
13
1
P: 202.3 MHz, C: 125.7 MHz), Varian Mercury300 ( H: 300.1 MHz,
2
Conversely, it is mildly surprising that the J15N-P across the Rh
19
31
1
31
F: 282.4 MHz, P: 121.5 MHz), or Bruker DRX300 ( H: 300 MHz, P:
21.5 MHz, Rh: 9.4 MHz). All available spectra can be found in the SI.
atom was found to be very small, less than 1 Hz. It is well known
however that small coordination angles (cis coordination) can
dramatically decrease the NMR coupling between two
inequivalent P spins at a metal center. By extension, the rather
short N-Rh-P angle (93.22(7)° in the crystal structure of
103
1
1
[4a]
2 2 2
Rh (nbd) (R-L ) was partly described in a previous publication.
3
1
31
1
3
P{ H} NMR (202.3 MHz, CDCl , rt)  (ppm): 95.869 (AA’XX’ half spin
1 2 3 3
system,
JP-Rh = 260.7 Hz; JP-Rh’ = -2.6 Hz; JP-P’ = 28.7 Hz; JRh-Rh’ ≈ 0
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
+
+
Hz). MS (FAB ): m/z calcd. for C74
H
66
N
2
O
8
P
Rh S
2 2 2
([M] ): 1442.18;
Cl ):
suspension was stirred at r.t. for 1h. The solvent was evaporated. The
product was dissolved in THF, filtered and evaporated. Finally the
31
103
obsd.: 1442.2. P- Rh HMQC (121.5 and 9.4 MHz, CD
2
2
product was crystallized from CH
2
1
Cl
2
/ Hexanes (2:3). Isolated yield:
H NMR (500 MHz, CD Cl , 298 K) 
ppm): 7.823 (broad d ≈ small second order, J = 8 Hz, 2 aromatic H),
15
1
7.5 %, white crystals: Ts- NH
2
.
2
2
3
(
3
7
J
.375 (broad d ≈ small second order, J = 8 Hz, 2 aromatic H), 4.933 (d,
H-15N = 80 Hz, Ts- NH ), 2.469 (s, CH of Ts moiety). C{ H} NMR
2 3
1
15
13
1
458
460
462
464
466
468
470
(
125.7 MHz, CD
2
Cl
2
3
, 298 K):  (ppm): 144.301 (s, Cquat., CH -C), 139.885
2
15
2
(d, JC-15N = 4 Hz, Cquat., C-SO2- NH ), 130.262 (s, CH), 126.832 (s, CH),
15
2
1.798 (s, CH
dissolved in 12 mL THF and Et
+)-1,1’-Bi-2-naphthol-PCl (7.0 mmol, 1eq.) was added dropwise under
3
of Ts- NH
2
). 1.6 mmol of this compound was then
3
N (4 mmol). A 5 mL THF solution of R-
(
strong magnetic stirring, leading to a suspension, which was stirred at rt
overnight. The solution was then filtered and evaporated. The product
was submitted to 10 mL Et
2
O and subsequently evaporated. The process
O. The
was repeated twice. The product was then washed with 10 mL Et
2
product was obtained as a white powder with a close to quantitative yield.
3
1
1
P{ H} NMR (202.3 MHz, CD
2
Cl
2
, 298 K)  (ppm): +171.9 (very broad m).
98
97
F2 Chemical Shift (ppm)
96
31
1
P{ H} NMR (121.5 MHz, THF unlocked, rt) approx. 174 ppm (sharp d.,
2
[4a]
1
1
1
Rh
2
(nbd)
2
(R-L )
2
was partly described in a previous publication.
H
2 2
JP-15N = 70 Hz). H NMR (500 MHz, CD Cl , 298 K)  (ppm): 10.2 (broad.
3 2
31
1
NMR (500 MHz, CDCl
(ppm):103.487 (AA’XX’ half spin system: JP-Rh = 264.8 Hz; JP-Rh’ = -3.0
P-P’ = 21.2 Hz;
ppm): -75.969 (s, CF
3
, rt)  (ppm): P{ H} NMR (202.3 MHz, CD
2
Cl
2
, rt)
s, NH), 8.017-6.925 (aromatic area), 2.788 (dq, q: JHa-CH3 = 7 Hz, d: JHa-
1
2
a
a
b
b

Hz;
(
for
3 3
Hb = 14 Hz, H of CH -CH H -N), 2.498 (s, CH -Ar) 2.482 (broad m, H of
CH
3
3
19
a
b
3
a
b
13
1
J
J
Rh-Rh’ ≈ 0 Hz). F NMR (282.4 MHz, CD
2
Cl
2
, r.t.) 
3
-CH H -N), 0.827 (t, J = 7 Hz, CH
3
-CH H -N). C{ H} NMR (125.7
+
), -148.734 (s, Et
3
NHBF
4
). MS (FAB ): m/z calcd.
MHz, CD
2
Cl 298 K) (ppm): note: some lines are missing or
2
,

3
+
31 103
C H
56 40
F
6
N
2
O
P
8 2
Rh
S
2 2
([M] ): 1313.97; obsd.: 1313.9.
Cl ):
P- Rh
overlapped, main lines: 133.37 (Cquat), 131.89 (Cquat), 131.19 (Cquat),
130.58 (CH), 129.53 (2CH), 129.41 (CH), 129.23 (CH), 128.90 (CH),
HMQC (121.5 and 9.4 MHz, CD
2
2
1
1
28.69 (CH), 127.15 (CH), 126.75 (CH), 126.59 (CH), 126.47 (2CH),
25.20 (CH), 124.97 (CH), 124.57 (CH), 122.80 (CH), 45.52 (CH of
2
464
466
468
470
472
474
476
478
Et
3
NH+), 21.70 (CH
3
), 8.46 (CH
3
of Et
3
NH+).
15
3
15
3
Rh
with Rh(nbd)
resulting in a very dark blue solution. P NMR yield: quantitative.
2
(nbd)
2
(
N-L )
2
: ligand (HNEt
3
)( N-L ) (0.10 mmol, 1eq.) was united
2 4 2 2
BF (0.10 mmol, 1 eq.) and dissolved in 0.6 mL of CD Cl ,
31
31
P
+
NMR characterization: see scheme 3 and Figure 6. MS (FAB ): m/z calcd.
15
+
1
for C68
H
54
N O P
2 8 2
Rh
, 298 K)  (ppm): 8.22 (d, J = 8.8 Hz, 1H), 8.10 (d, J =
.3 Hz, 1H), 8.01 (d, J = 8.3 Hz, 1H), 7.96 (d, J = 8.8 Hz, 1H), 7.91 (d, J =
.5 Hz, 1H), 7.8-7.1 (aromatic area), 6.78 (broad s, ~ 4H, free nbd), 6.74
2 2
S : [M] ): 1360.08; obsd.: 1360.1007. H NMR
(
8
8
500 MHz, CD Cl
2 2
(
4
=
d, J = 8.1 Hz, 2H), 6.30 (~q, J ~ 3.7 Hz, 1H), 5.95 (~q, J ~ 3.7 Hz, 1H),
1
05
104
F2 Chemical Shift (ppm)
103
3
.66 (s, 1H), 4.02 (s, 1H), 3.61 (s, 2H, free nbd), 3.43 (s, 1H), 3.17 (dq, J
2
2
Rh
2
(nbd)
2
(R-L )
2
2
•Rh (nbd)
2
(S-L )
2
was described in
a
previous
3
+
7.4 Hz, J = 5.2 Hz, 6H, CH
3
-CH
2
-NH ), 2.58 (s, 1H), 2.20 (s, 3H, CH
3
-
[
8]
publication.
3
Ar), 2.00 (s, ~2H, ~free nbd), 1.50-1.30 (aliphatic area), 1.36 (t, J = 7.5
Hz, ~9H, CH -CH -NH ). C{ H} NMR (125.7 MHz, CD Cl , 298 K) 
3 2 2 2
+
13
1
1
2
[4a]
Rh
2
(nbd)
2
(R-L )(R-L ): was partly described in a previous publication.
NH][1] (0.013 mmol, 1eq.) and (R)-[Et
eq.) were united with Rh(nbd) BF (0.026 mmol, 2 eq.) and dissolved in
.6 mL of CD Cl , resulting in a very dark purple solution. P NMR yield:
(ppm): note: due to the large number of lines, NMR couplings were not
systematically solved, only the visible lines are given: 150.45 (Cquat),
150.33 (Cquat), 148.95 (Cquat), 142.46 (Cquat), 142.23 (Cquat), 132.87 (Cquat),
132.76 (Cquat), 132.34 (Cquat), 131.51 (Cquat), 130.79 (CH), 130.08 (CH),
129.70 (CH), 129.52 (CH), 129.11 (2CH), 128.74 (CH), 127.42 (2CH),
127.23 (CH), 126.68 (CH), 126.53 (CH), 126.13 (CH), 125.89 (CH),
125.47 (CH), 124.19 (CH), 123.85 (Cquat), 123.42 (CH), 121.83 (Cquat),
ligand (R)-[Et
3
3
NH][2] (0.013 mmol,
1
0
2
4
3
1
2
2
1
2
quantitative, as
a
statistical mixture: Rh
2
(nbd)
2
(R-L )(R-L )
/
1
2
31
1
Rh
2
(cod)
2
(R-L )
2
/ Rh
2
(nbd)
2 2
(R-L ) (50:25:25). P{ H} NMR (202.3
1
2
MHz, 107 mM in CD
P2-Rh2 = 268 Hz,
P1-P2 = 25 Hz, P of L ). P{ H, Rh} NMR (121.5 MHz, CD
ppm): Rh
P1 = 25 Hz), the following data had not been reported before: P- Rh
HMQC (121.5 and 9.4 MHz, CD
2
Cl
2
, rt)  (ppm): Rh (nbd) (R-L )(R-L ): 103.78 (dd,
2 2
2
1
3
2
1
1
1
J
J
J
P2-P1 = 25 Hz, P of L ); 93.65 (dd, JP1-Rh1 = 258 Hz,
97.44 (d,
65.36 (CH
J
13C-103Rh = 11.0 Hz, CH), 92.14 (d,
J
13C-103Rh = 14.8 Hz, CH),
1
3
1
1
31
1
103
1
2
Cl
2
, r.t.) 
2
, free nbd), 60.21 (d, J13C-103Rh = 9.3 Hz, CH), 57.65 (d, J13C-
1
2
3
3
+
(
2
(nbd)
2
(R-L )(R-L ): 103.78 (d,
J
P2-P1 = 25 Hz), 93.65 (d,
J
P1-
2 3
103Rh = 8.4 Hz, CH), 52.61 (CH), 52.35 (CH), 47.65 (CH of Et NH ), 46-8
(aliphatic area), including: 21.6 (CH
31
103
+
3 3
-Ar), 9.07 (CH of Et3NH ).
103
2
Cl
2
): main
Rh lines (9.4 MHz) of
1
2
Rh (nbd) (R-L )(R-L ): (ppm/(relative intensity)): 432.25 (0.4), 433.64
2 2
Quantum chemical calculations: All DFT calculations were performed
in the gas-phase using the B3LYP functional
basis for all atoms. The rhodium atom carries a quasirelativistic effective
core potential (def2-ecp)
(
(
(
0.35), 435.23 (0.57), 438.01 (0.72), 441.72 (0.25), 444.9 (0.12), 473.16
0.37), 474.36 (0.32), 476.18 (0.52), 478.99 (0.76), 482.71 (0.30), 485.59
0.14), see also Figure 4. MS (FAB ): m/z calcd. for
[12]
[13]
and the def2-TZVP
+
[14]
replacing 28 core electrons. The D3
was used to account for dispersion
+
C
65
H
53
F
3
N
2
O
8
P Rh S
2 2 2
([M] ): 1378.08; obsd.: 1378.1.
[15]
correction by Stefan Grimme
interaction. For the sake of completeness, the dispersion contribution to
relative conformer energies is documented in the supporting Information,
15
3
15
Ligand (HNEt
mmol) was exposed to 200 mL CH
Et N (23 mmol) was added to it under strong magnetic stirring. The
3
)( N-L ): commercially available NH
4
Cl (>98%, 9.2
[
16]
2
Cl together with Ts-Cl (9.2 mmol).
2
Tables S7-S9. All calculations were performed with TURBOMOLE. For
[
17]
3
geometry optimization steps the Berny algorithm
as implemented in
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
[
18]
1
103
Gaussian 09 was used, using the “external” interface of that program.
This means, all energies, gradients, and force constants are calculated
with TURBOMOLE, and the Gaussian program decides on which steps
to take on the potential energy surface. Except in a single case (see
supporting Information, Table S6), all minima were characterised by
frequency calculations having no negative Hessian eigenvalue. To asses
the importance of solvent effects on relative conformer energies,
geometry optimizations have also been performed with the COSMO
[9]
H- Rh HMQC NMR, selected references: a) J. M. Ernsting, S.
Gaemers, C. J. Elsevier, Magnetic Resonance in Chemistry 2004, 42,
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10, 4029; g) M. Buhl, W. Baumann, R. Kadyrov, A. Borner, Helvetica
Chimica Acta 1999, 82, 811.
[
19]
model
(see supporting Information, Tables S13-S15). While solvation
somewhat affects the relative stability, it does not change the overall
trend.
195
[
10] For Pt NMR, see: a) B. M. Still, P. G. A. Kumar, J. R. Aldrich-Wright,
W. S. Price, Chem. Soc. Rev. 2007, 36, 665; b) E. Gabano, E. Marengo,
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F. D. Rochon, Applied Spect. Rev. 2006, 41, 185.
Acknowledgements
The authors thank Han Peeters for the mass spectrometry
experiments, and NRSCC, BASF, and EZ for financial support.
This work was also supported in part (A.L.S.) by the Council for
the Chemical Sciences of The Netherlands Organization for
Scientific Research (CW-NWO). The authors affiliated to the TU
Kaiserslautern also acknowledge the DFG-funded transregional
collaborative research center SFB/TRR 88 ‘‘Cooperative effects
in homo and heterometallic complexes’’ (http://3MET.de).
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Magn. Reson. Chem. 1997, 35, 904.
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Keywords: METAMORPhos • Rh dinuclear complex •
1
03
cooperative catalysis • AA’MM’XX’ 6 spin system • Rh NMR
[
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[
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Patureau, C. Worch, M. A. Siegler, A. L. Spek, C. Bolm, J. N. H. Reek,
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[
[
7]
8]
See experimental section.
[
F. G. Terrade, M. Lutz, J. N. H. Reek, Chem. Eur J. 2013, 19, 10458,
2
2
the X-Ray structure of Rh
2 2 2 2 2 2
(nbd) (R-L ) •Rh (nbd) (S-L ) : CCDC-
931393.
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European Journal of Inorganic Chemistry
10.1002/ejic.201800397
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
Sulfonamido-phosphoramidites are
known to form 6-membered ring Rh-P-
N-Rh-P-N- dinuclear complexes. Apart
from a single X-ray structure, little is
known about their three dimensional
structure in solution. This study
Dinuclear Complexes*
F. W. Patureau, J. Groß, J. M. Ernsting,
C. van Wüllen,* J. N. H. Reek*
Page No. – Page No.
3
1
15
103
proposes a P, N and Rh NMR
investigation of the question, as a well
as a DFT study. The AA’MM’XX’ 6
P-N bridged dinuclear Rh-
METAMORPhos complexes: NMR and
computational studies
1
5
spin system of the corresponding N-
enriched dinuclear complex is notably
described.
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