C-H nickellation of phenol-derived phosphinites: Regioselectivity and structures of cyclonickellated complexes

Article abstract of DOI:10.1039/c7dt03403b

This report describes the results of a study on the ortho-C-H nickellation of the aryl phosphinites i-Pr₂P(OAr) derived from the following four groups of substituted phenols: 3-R-C₆H₄OH (R = F (b), Me (c), MeO (d), Cl (e)); 3,5-R₂-C₆H₃OH (R = F (f), Me (g), Cl (h), OMe (i)); 2-R-C₆H₄OH (R = Me (j), Ph(k)); and 2,6-R₂-C₆H₃OH (R = Me (l), Ph (m)). No nickellation was observed with the phosphinites derived from the 3,5-disubstituted phenols g and h, and the 2,6-disubstituted phenols l and m; in all other cases nickellation occurred at an ortho-C-H to generate either the Br-bridged dimers [{κ^P,κ^C-(i-Pr)₂POAr}Ni(μ-Br)]₂ (1b-1f, 1j, and 1k) or the monomeric acetonitrile adduct {κ^P,κ^C-ArOP(i-Pr)₂}Ni(Br)(NCMe) (1i-NCMe). Analysis of C-H nickellation regioselectivity with 3-R-C₆H₄OH pointed to the importance of substituent sterics, not electronics: nickellation occurred at the least hindered position either exclusively (for R = Me (c), MeO(d), and Cl (e)) or predominantly (for R = F (b); 6:1). This conclusion is also consistent with the observation that C-H nickellation is possible with the 3,5-disubstituted aryl phosphinites bearing F and OMe, but not with the more bulky substituents Me or Cl. For the 2-substituted aryl phosphinites, C-H nickellation occurs at the unsubstituted ortho-C-H and not on the R substituent, regardless of whether the alternative C-H moiety of the substituent is sp³ (R = Me (j)) or sp² (R = Ph (k)). The system thus reveals a strong preference for formation of 5-membered metallacycles. Consistent with this reactivity, no nickellation occurs with (2,6-R₂-C₆H₃O)P(i-Pr)₂. Tests with the parent dimer derived from i-Pr₂P(OPh) showed that conversion to the monomeric acetonitrile adduct is highly favored, going to completion with only a small excess of MeCN. All new cyclonickellated complexes reported in this study were fully characterized, including by single crystal X-ray diffraction studies. The solid state structures of the dimers 1b and 1d showed an unexpected feature: two halves of the dimers displayed non-coplanar conformations that place the two Ni(ii) centers at shortened distances from each other (2.94-3.16 ?). Geometry optimization studies using DFT have shown that such non-coplanar conformations stabilize the complex, implying that the "bending" observed in these complexes is not caused by packing forces. Indeed, it appears that the occurrence of coplanar conformations in the solid state structures of these dimers is a simple consequence of packing forces rather than an intrinsic property of the compound.

Full text of DOI:10.1039/c7dt03403b

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Efficient extraction of sulfate from water using
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C−H Nickellaꢀon of Phenol-Derived Phosphinites: Regioselectivity
and Structures of Cyclonickellated Complexes
Received 00th January 20xx,
Accepted 00th January 20xx
Loïc P. Mangin and Davit Zargarian*
Abstract. This report describes the results of a study on the ortho-C-H nickellation of the aryl phosphinites i-Pr2P(OAr)
derived from the following four groups of substituted phenols: 3-R-C6H4OH (R= F (b), Me (c), MeO (d), Cl (e)); 3,5-R2-
C6H3OH (R= F (f), Me (g), Cl (h), OMe (i)); 2-R-C6H4OH (R= Me (j), Ph(k)); and 2,6-R2-C6H3OH (R= Me (l), Ph (m)). No
nickellation was observed with the phosphinites derived from the 3,5-disubstituted phenols g and h, and the 2,6-
disubstituted phenols l and m; in all other cases nickellation occurred at an ortho-C-H to generate either the Br-bridged
dimers [{κP,κC-(i-Pr)2POAr}Ni(μ-Br)]2 (1b-1f, 1j, and 1k) or the monomeric acetonitrile adduct {κP,κC-ArOP(i-
Pr)2}Ni(Br)(NCMe) (1i-NCMe). Analysis of C-H nickellation regioselectivity with 3-R-C6H4OH pointed to the importance of
substituent sterics, not electronics: nickellation occurred at the least hindered position either exclusively (for R= Me (c),
MeO(d), and Cl (e)) or predominantly (for R= F (b); 6:1). This conclusion is also consistent with the observation that C-H
nickellation is possible with the 3,5-disubstituted aryl phosphinites bearing F and OMe, but not with the more bulky
substituents Me or Cl. For the 2-substituted aryl phosphinites, C-H nickellation occurs at the unsubstituted ortho-C-H and
not on the R substituent, regardless of whether the alternative C-H moiety of the substituent is sp3 (R= Me (j)) or sp2 (R= Ph
(k)). The system thus reveals a strong preference for formation of 5-membered metallacycles. Consistent with this
reactivity, no nickellation occurs with (2,6-R2-C6H3O)P(i-Pr)2. Tests with the parent dimer derived from i-Pr2P(OPh) showed
that conversion to the monomeric acetonitrile adduct is highly favored, going to completion with only a small excess of
MeCN. All new cyclonickellated complexes reported in this study were fully characterized, including by single crystal X-ray
diffraction studies. The solid state structures of the dimers 1b and 1d showed an unexpected feature: two halves of the
dimers displayed non-coplanar conformations that place the two Ni(II) centers at shortened distances from each other
(2.94─3.16 Å). Geometry optimization studies using DFT have shown that such non-coplanar conformations stabilize the
complex, implying that the “bending” observed in these complexes is not caused by packing forces. Indeed, it appears that
the occurrence of coplanar conformations in the solid state structures of these dimers is a simple consequence of packing
forces rather than an intrinsic property of the compound.
DOI: 10.1039/x0xx00000x
www.rsc.org/
manner, thus bypassing the isolation and manipulation of the
cyclometallated species that are thought to be intermediates in
these processes. On the other hand, intercepting such key
Introduction
Chelation-assisted C-H metallation and derivatization is an
attractive methodology for the sustainable synthesis of complex
organic molecules.1 This approach is generally considered to be
even more powerful when (i) simple salts or derivatives of the more
abundant 3d metals can serve as required metallic precursors, and
(ii) the directing functional group(s) required for chelation can be
installed and removed easily (“traceless functionalization”).2 From a
practical point of view, another desired feature of metallation-
functionalization protocols is that they proceed in a one-pot
intermediates of the catalytic cycle and probing their properties can
be potentially advantageous for rational design of new metallation-
functionalization processes and their optimization. For instance,
isolation of the cyclometallated species arising from the C-H
metallation can facilitate the modelling of this step and allow a
systematic study of the functionalization step as well.
The emergence over the past decade of an increasing number of
reports on nickel-catalyzed C-H functionalization reactions has
demonstrated that in this context Ni precursors can be viable
alternatives to their more widely-used Pd counterparts.3 These
developments and our longstanding interest in organonickel
chemistry,4 including the synthesis and reactivities of pincer-type
nickel complexes,5 led us to prepare nickellacyclic complexes via C-
H
nickellation and study their structures, stabilities, and
functionalization aptitudes. The preparation of the orthonickellated
phosphinite complexes [{κP,κC-(i-Pr)2POAr}Ni(μ-Br)]2 or trans-{κP,κC-
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Scheme 1. Alternative protocols for preparation of orthonickellated complexes from aryl phosphinites.
ArOP(i-Pr)2}NiBr{i-Pr2P(OAr)} derived from substituted phenols, R-
C6H4OH, was reported recently (Scheme 1).6,7
Results & Discussion
This first report outlined the impact of substituent R on relative
cyclonickellation rates for R-C6H4OP(i-Pr)2 (COOMe < Me < OMe),
indicating that the C-H nickellation step follows an electrophilic
mechanism; this finding was consistent with our postulates on how
POCOP-type pincer ligands undergo C-H nickellation.8 This report
also showed that the cyclonickellated complexes in question can be
benzylated at the nickellated carbon, thus providing a proof of
concept for the functionalization step.6 On the other hand, our
initial results did not provide much insight on the regioselectivity of
cyclonickellation, nor did they result in a broad scope for the
functionalization step. It was thus evident that much was left to do
to develop a better understanding of the factors that govern C-H
nickellation and the reactivities of the resulting species.
Revised procedure for cyclonickellation of arylphosphinites. Vabre
et al.6 have reported that extended heating of the Ni(II) precursor
{(i-PrCN)NiBr2}n in toluene with i-Pr2P(OPh), a, and NEt3 facilitates
direct ortho-C-H nickellation; this reaction generated both the Br-
bridged dinickel complex {κP,κC-C6H4OP(i-Pr)2}NiBr}2 (1a) and its
monomeric i-Pr2P(OPh) adduct bearing
a
non-cyclometallated
(1a-
phosphinite,
trans-{{κP,κC-C6H4OP(i-Pr)2}Ni{i-Pr2P(OPh)}Br
P(OPh)(i-Pr)2) (Scheme 1). Controlling the precise phosphinite: Ni-
precursor ratio in this protocol allowed the exclusive or
predominant formation of one or the other of the two products. For
example, using a 1.0 : 0.6 ratio gave the thermodynamically more
favored mononickel adduct exclusively, whereas a 1 : 2 ratio gave
the dinickel species.6
As a continuation of our initial studies, we have examined the
regioselectivity of C-H nickellation with aryl phosphinites RnC6H(5-
n)OP(i-Pr)2 derived from substituted phenols. The results presented
herein show that C-H nickellation of substrates derived from 3-R-
C6H4OH (R = Me, OMe, Cl) takes place selectively at the less
hindered ortho position, whereas nickellation of substrates derived
from 2-R-C6H4OH (R = Me, Ph) takes place at the unsubstituted
ortho C-H of the phenol ring, and not on the ring substituents. In
contrast to the reactivity of these mono-substituted substrates, no
nickellation takes place with disubstituted phosphinites derived
from 2,6-R2-C6H3OH (R = Me, Ph) or 3,5-R2-C6H3OH (R = Me, Cl),
whereas the less bulky analogues of the latter phosphinites (R = F,
OMe) did undergo nickellation. The observed nickellation reactions
led to the dimeric species [{κP,κC-(i-Pr)2POAr}Ni(μ-Br)]2 in every case
except with 3,5-(MeO)2-C6H3OP(i-Pr)2, which produced the
monomeric acetonitrile adduct trans-{κP,κC-3,5-(MeO)2-C6H3OP(i-
Pr)2}NiBr(NCMe). The present report discusses these results in
terms of the steric and electronic properties of the R-substituents,
and describes the solid state structures and NMR spectra of the
various cyclonickellated complexes obtained.
To improve the atom-efficiency of the orthonickellation reaction
under discussion, we probed the influence of various solvents with
a view to favoring the formation of the dimeric species 1a. Our tests
showed that using acetonitrile as solvent led to orthonickellation at
lower temperatures and over a shorter reaction time. This modified
protocol also required only a small excess of the Ni(II) precursor to
smoothly generate the monomeric MeCN adduct as a stable
intermediate species, from which we could obtain the target Br-
bridged dimer after work-up (Scheme 1). In contrast, conducting
the nickellation reactions in THF or ethyl acetate showed rates that
were intermediate between those observed in toluene and
acetonitrile, such that the nickellation was incomplete after 24 h.
We believe that the main advantages of using acetonitrile in this C-
H nickellation protocol, i.e., exclusive access to the dimeric species
over shorter reaction times, can be attributed to two factors. First,
acetonitrile reaction mixtures remain homogeneous throughout the
entire reaction span, thus providing
a
greater effective
concentration of Ni and maintaining a Ni : phosphinite ratio of ≈ 1 :
1. Second, formation of the undesired adduct 1a-P(OPh)(i-Pr)2
during the reaction is circumvented by the facile formation of the
analogous acetonitrile adduct, as illustrated in Scheme 1. This
assertion was confirmed by the 31P{1H} NMR spectra recorded for
2 | J. Name., 2012, 00, 1-3
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toluene solutions of the authenticated dimeric species 1a to which Regioselectivity of C-H nickellation with new aryl phosphinites
were added various amounts of acetonitrile (Figure 1). These
spectra show that portion-wise addition of acetonitrile to the
dimeric species (represented by the P singlet at ca. 196.7 ppm)
converts it into the monomeric acetonitrile adduct 1a-NCMe
(represented by a new singlet at ca. 193.5 ppm).
derived from 3-substituted phenols. Having optimized the protocol
for the synthesis of 1a, we set out to test our new, acetonitrile-
based synthetic protocol for the C-H nickellation of phosphinites
derived from substituted phenols. The first substrate we tested was
3-F-C6H4OP(i-Pr)2 (b) for which cyclonickellation via the toluene-
based protocol had given the two regioisomers of trans-{{κP,κC-F-
C6H4OP(i-Pr)2}Ni{i-Pr2P(OAr)}Br in a 5.6:1 ratio, the major isomer
arising from the metallation at the less hindered position (para to
the C-F moiety.6 Applying the new protocol to this phosphinite gave
the anticipated dimers with a comparable regioselectivity (Scheme
2).9
Keq > 103
O
O
NCMe
(eq. 1)
(i-Pr)2P
Ni
i-Pr2P
Ni
Br
NCMe
Br
2
1a
1a-NCMe
4.0 eq MeCN
2.0 eq MeCN
1.5 eq MeCN
1.0 eq MeCN
Scheme 2. Orthonickellation of 3-F-C6H4OH in acetonitrile.
0.5 eq MeCN
No MeCN
Next, we used the acetonitrile-based protocol to expand our
investigation of the nickellation regioselectivity beyond 3-F-C6H4OH.
As shown in Scheme 3, cyclonickellation of aryl phosphinites
derived from 3-Me-, 3-MeO-, and 3-Cl-C6H4OH occurs exclusively at
the ortho position farthest from the substituent. Analysis of the
reaction mixtures by 31P NMR spectroscopy helped signal complete
conversion of the starting materials to the nickellated species
(singlet at ca. 190─200 ppm), and established the regioselectivities
shown in Scheme 3. Work-up furnished the new cyclonickellated
Figure 1. 31P{1H} NMR (162 MHz, 25 mM in PhMe) spectra of 1a
upon portion-wise addition of MeCN
The identity of 1a-NCMe was confirmed by its direct synthesis,
which was done as follows. Addition of 10 equiv of MeCN to a
suspension of 1a in Et2O led to an immediate color change from
orange to yellow, and evaporation gave the adduct 1a-NCMe as a
yellow powder that could be isolated in 86 % yield. The 1H NMR
spectrum of this solid in CD3CN matched that of 1a in CD3CN, and
the structural assignment was confirmed by single crystal
diffraction studies (vide infra). That more than 2 equiv of MeCN are
required for a complete transformation of 1a to 1a-NCMe suggests
species 1c-1e as orange solids, which were completely
characterized by NMR spectroscopy and single crystal diffraction
studies; these results will be presented later, following the
discussion of the regioselectivity issues.
a dimerꢀ
monomer equilibrium (eq. 1). Integration of the 31P
signals for the two species (Figure 1) allowed us to estimate a large
equilibrium constant (Keq ≈ ca. 103-104), which implies a strong
preference for the monomeric adduct. A similar conclusion was
drawn from the UV-vis spectra recorded for a toluene solution of 1a
before and after addition of 10 equiv acetonitrile: the orange
solution of the dimer (λmax = 434 nm; ε[Ni] = 737 M-1.cm-1) turned
yellow (λmax = 403 nm, ε[Ni] = 1414 M-1.cm-1) as a result of the
formation of 1a-NCMe. (See Figure S1 for these spectra.) The
greater thermodynamic preference for the acetonitrile adduct also
explains why it proved difficult to isolate analytically pure samples
of the dimer from acetonitrile solutions; indeed, most samples
showed the presence of traces of nitrogen (<0.10 %) unless they
were subjected to multiple recrystallizations and extended
evaporation under vacuum.
Scheme 3. Cyclonickellation of 3-substituted and 3,5-disubstituted
aryl phosphinites
In light of the observation that the C-H nickellation reactions in
question are regioselective regardless of the electron-donating or
electron-withdrawing nature of the substituents, we conclude that
the main determinant of regioselectivity is sterics, not electronics.
This would explain why nickellation is regiospecific with substrates
c
and bearing substituents Me and Cl, respectively, which are of
e
opposite electronic properties but very similar van der Waals
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spherical volumes.10 Moreover, substrate
b bearing the smallest (derived from ortho-cresol) to test if nickellation at the Csp3-H of the
non-hydrogen substituent, F, is the only case where the nickellation 2-Me substituent might be competitive with the anticipated ortho-
regioselectivity is less than 100% (6:1). nickellation at the unsubstituted position. The results confirmed,
Cyclonickellation of aryl phosphinites derived from 3,5- however, exclusive reactivity at the unsubstituted ortho-C-H
disubstituted phenols. In order to establish whether the position. That the outcome of this reaction is not necessarily due to
regioselectivities observed with substrates b-e reflect a mere the intrinsically more favorable nickellation of sp2 vs sp3 C-H
preference for the least hindered C-H bond, or whether the moieties was inferred from the nickellation of phosphinite
k
sterically hindered C-H bond is simply inaccessible, we tested the (derived from 2-phenylphenol), which also occurred at the
cyclometallation of the disubstituted substrates 3,5-R2-C6H3OP(i- unsubstituted ortho-C-H position of the main aryl ring and not the
Pr)2 (R= F (
cyclonickellation occurs with the substrates bearing the smaller
substituents F and OMe ( in Scheme 3 and
in Scheme 4),10
whereas substrates and bearing the larger Me or Cl substituents
f), Me (g), Cl (h), MeO (i
)). These tests showed that sp2 C-H moiety of the substituent (Scheme 5).
f
i
g
h
did not metallate even after 5 days of heating (Scheme 3).
The above observations confirm the crucial importance of
substituent size on C-H nickellation in our system, and suggest that
Me and Cl substituents are beyond the steric limits of
cyclonickellation. Another noteworthy insight gained from these
tests concerns the rate of nickellation, which was quite rapid with
Scheme 5. Cyclonickellation of various mono- or di-ortho-
substituted aryl phosphinites.
the MeO-bearing substrate
substrate (16 vs. 60 h for >90% conversion). A similar trend was
evident in the nickellation rates of substrates and vs. substrate
i and much slower with the F-bearing
f
The above-discussed reactivity, i.e., exclusive nickellation at the
unsubstituted ortho-C-H position of the phenol ring as opposed to
the C-H moiety of the methyl or phenyl substituent, is presumably a
result of the more favorable energetics of the 5-membered
metallacycles that form at the transition state versus the alternative
6- or 7-membered metallacycles. Comparison of these results to
related literature reports reveals that the regioselectivity under
discussion is a function of the metal precursor; it also depends on
whether the substrate ArOH is derivatized or not. For instance,
c
d
e
(16 vs. 40 h, Scheme 3). These observations are consistent with the
presumed electrophilic nature of the C-H nickellation.8
Finally, tests conducted on substrate
i showed that steric bulk
influences not just regioselectivity of C-H nickellation but also the
structure of the resulting cyclonickellated product. As shown in
Scheme 4, nickellation of substrate i followed by the usual workup
failed to give the anticipated µ-Br dimeric species, giving instead the
monomeric MeCN adduct 1i-NCMe. This result raised the question
of whether the dimeric structure is altogether inaccessible for this
using
a
Rh(I) pre-catalyst along with ArOPR2 leads to
metallation/coupling with aryl halides at the ortho-C-H of both the
substrate, or is it merely less stable for substrate i in comparison to
main ring (5-membered metallacycle) and the Ph substituent at the
other less bulky substrates. To answer this question, we attempted
to drive off the coordinated acetonitrile from the monomeric
acetonitrile adduct and generate the putative dimer. However, 1i-
NCMe remained unchanged after heating a toluene solution of it to
60 °C and evaporation to dryness under reduced pressure (Scheme
4). This observation indicated that the steric hindrance engendered
ortho
position
(7-membered
metallacycle),11
whereas
metallation/coupling of underivatized 2-aryl phenols with
Pd(OAc)2/Cs2CO3 as pre-catalyst occurs only at the ortho-C-H of the
Ph substituent (6-membered metallacycle).12
Two other reactions were carried out with ligands bearing
substituents at both ortho positions to test if nickellation can be
by the two MeO substituents in substrate
dimerization of its cyclonickellated derivative, thus favoring the
formation of 1i-NCMe
i strongly disfavors
forced on a substituent C-H site. Thus, reactions with ligands
l
(derived from 2,4,6-Me3-C6H2OH)13 and
m
(derived from 2,6-Ph2-
.
C6H3OH) were examined, but neither showed any nickellation even
after 5 days of heating. To establish whether this lack of reactivity is
due to the inability of these phosphinites to coordinate to the Ni
center, we examined the reactivity of the Ni precursor with two
equivalents of ligand
m in the absence of added base. Similarly to
what had been observed with all other less hindered phosphinites,
no coordination was observed at r.t., but heating the reaction
mixture to 80 °C for one hour led to a brownish mixture that
showed a new 31P resonance at 134 ppm, which is in a region
characteristic of the bis-phosphinite complexes trans-(i-
Pr2POAr)2NiBr2. We conclude that sterically hindered phosphinites
can coordinate to Ni(II), at least in the absence of other
nucleophiles. This implies in turn that the observed failure to induce
Scheme 4. Formation of 1i-NCMe from cyclonickellation of i.
Cyclonickellation of 2-substituted aryl phosphinites. Our
investigation of nickellation regioselectivity continued with
phosphinites derived from 2-substituted phenols (Scheme 5). We
first examined the reaction of {(i-PrCN)NiBr2}n with phosphinite
j
4 | J. Name., 2012, 00, 1-3
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Table 1. Selected structural parameters for dimers and MeCN adducts.a
Ni-C
Ni-P
trans-Ni-Brb
cis-Ni-Lb
2.3641(7)
2.3781(7)
2.3815(5)
C-Ni-P
82
Br-Ni-L
88
Ni-Br-Ni
92
Ni---Ni
3.415
3.164
3.444
τ4
1a
1b
1c
1.914(4)
1.911(4)
1.920(3)
2.095(1)
2.106(1)
2.0963(7)
2.377
0.059
0.056
0.042
0.052;
2.3736(8)
2.390
84
87
83
82
88
92
1.914(2);
1.88(3);
1.95(3)
79;
83;
87
2.0985(5);
2.0972(5)
2.3803(3);
2.3851(3)
2.3857(3);
2.3875(3)
1dc
87
76
2.9406(3) 0.113;
0.116
1e
1f
1j
1.914(2)
2.0987(7)
2.1017(5)
2.0936(4)
2.382
2.3796(5)
2.386
82
88
86
87
92
94
93
3.436
3.485
3.444
0.036
0.102
0.059
1.931(2)
1.911(2)
2.3743(3)
2.3759(3)
82
83
2.392
1.894(10)─
1.926(10)
1.916(2)
2.098(3)─
2.105(3)
2.1018(6)
2.357(2)─
2.389(2)
2.387(2)─
2.398(2)
1.913(2)
3.458─
3.471
-
0.030─
0.084
0.074
1kd
81─83
86─87
93─94
1a-NCMe
1i-NCMe
2.3533(4)
83
83
91
91
-
-
1.932(2)
2.1000(6)
2.3613(4)
1.915(2)
-
0.204
a) The values for angles have been rounded up to the nearest degree. b) Designation of cis- and trans-Ni-Br bonds is with respect to the
Ni-C2 bond. c) In this nonsymmetrical structure, two different values are observed for all parameters except the Ni-C distance and C-Ni-
P angle for which three different values are observed due to the presence of disorder in one half of the dimer. d) These ranges
represent the bond distances and angles observed in the four molecules present in the asymmetric unit.
C-H nickellation in disubstituted ligands
l and m, even after neither the steric bulk nor the substituent position has any
extended heating, likely reflects the strong energetic preference for significant bearing on the overall coordination geometry of the
transition states leading to formation of 5-membered nickellacycles. dimeric complexes. To be sure, some degree of tetrahedral
distortion is evident in all dimeric complexes studied here, but
these are fairly insignificant as can be deduced from the small τ4
Solid state structures of the new complexes. Solid state structures
were determined for 9 new cyclonickellated complexes, of which
two are monomeric adducts and 7 dimers. The results of these values that define these distortions15 (0.03 to 0.12; Tables 1 and
analyses allowed us to unequivocally establish the identities of all
complexes. In the case of complex 1k, resolution of the structural
data was problematic due to the twinned crystals obtained;14
hence, structural discussion in this case will be limited to those
features that are established with confidence. The pertinent
structural parameters for all complexes are listed in Table 1 and
Tables S2─S3, the molecular drawings are shown in Figures 2─5 and
Figures S86─S90, and the main findings are discussed below.
S2─S3). It should also be noted here that the presence in 1f of an F
substituent vicinal to the nickellation site causes little distortion (τ4
= 0.102), whereas major structural distortions are evident in 1i-
NCMe due to the presence of MeO (vide supra). This difference is
likely a reflection of the smaller van der Waals volume of F
compared to that of MeO.
The nature of the substituents also has little or no impact on bond
distances found in the dimeric complexes: the values for Ni-P
(2.094─2.106 Å), Ni-C (1.911─1.931 Å), and Ni-Br (2.374─2.393 Å)
fall within the normal range for related Ni(II) complexes. Comparing
these values to the corresponding distances in the related
resorcinol-based pincer complexes (Rn-POCOPi-Pr)NiBr reveals that
the cyclonickellated compounds under discussion here feature
somewhat longer distances for Ni-C (1.91 vs 1.89 Å) and Ni-Br(2.36-
2.39 vs 2.323 Å), but slightly shorter P-Ni bond distances (2.10 vs
2.142/2.153 Å).16
Complex 1a-NCMe (Figure 2), the mononuclear acetonitrile adduct
obtained from cyclonickellation of unsubstituted phosphinite
a,
showed a fairly unremarkable solid state structure in which the
largest distortion is the smaller-than-ideal bite angle of the
metallated phosphinite moiety (ca. 83°). By comparison, relatively
major angular distortions were noted in the analogous monomeric
adduct 1i-NCMe obtained from nickellation of the phosphinite
derived from 3,5-methoxy-phenol (Figure 2). Thus, the two trans
angles are compressed to ca. 166° and 164°, and the C-Ni-N cis
angle is enlarged to 100°. These non-ideal angles translate into a
much more pronounced tetrahedral distortion in 1i-NCMe vs. 1a-
NCMe, as reflected in τ4 values of 0.20 and 0.07, respectively.15 We
One unexpected and fairly significant structural distortion that was
observed in some dimeric complexes regards the relative spatial
orientations of the two halves of these molecules. As expected,
dimers possessing an inversion center adopt a structure wherein
the two halves of the dimer are coplanar, whereas dimers that do
not crystallize on an inversion center display various degrees of
deviation from co-planarity. The extent of the “bending” of the two
halves of the dimers is conveniently quantified by the torsion angles
conclude, therefore, that the presence of
a non-hydrogen
substituent vicinal to the nickellation site distorts the solid state
structure of these complexes. In the crystal structures of the
dimeric species 1b-1f, 1j, and 1k (Figures 3─5 and S86─S90), both Ni
centers adopt nearly ideal square planar geometries, indicating that
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Figure 2. Top views of the molecular diagrams for complexes 1a-NCMe (left) and 1i-NCMe (middle), and side view for complex 1i-NCMe
(right). Thermal ellipsoids are shown at the 50% probability level. Hydrogens in all diagrams and Me groups in the side view of 1i-NCMe
have been omitted for clarity.
Of course, such shortened distances do not necessarily imply
bonding interactions as they are still longer than the sum of
covalent radii for two Ni(II) atoms (≈ 2.50 Å)18, but they are still
shorter than the sum of two van der Waals radii (≈ 3.26 Å).
Ni1-ꢀ-Br1-ꢀ-Br2-Ni2 atoms, which would be 180° in a coplanar
arrangement (no bending at all). The measured values of this
torsion angle ranged from ca. 170─172°17 in 1k to ca. 133° in 1b and
ca. 116° in 1d. One consequence of the “bending” represented by
the torsion angles for 1b and 1d is a shrinking of the Ni-Br-Ni angle,
Indeed, such interactions would be rather surprising given that the
filled dz² orbitals in these d8 centers are expected to favor a
conformation that would minimize any orbital interactions. On this
basis alone, a coplanar conformation (torsion angle = 180°) would
have been optimal in the absence of packing forces.
which is 83° in 1b and 76° in 1d, compared to angles of
≥ 92° in all
coplanar dimers. A potentially even more significant structural
consequence of the bending is that it brings the two Ni centers
closer to each other; thus, the Ni---Ni distances are 3.16 Å in 1b and
2.94 Å in 1d, compared to > 3.4 Å in coplanar dimers.
Figure 3. Top and side views of the molecular diagram for complex Figure 4. Top view of the molecular diagram for complex 1f and side
1d. Thermal ellipsoids are shown at the 50% probability level; view for a portion of the dimer. Thermal ellipsoids are shown at the
hydrogens in both views and the P-substituents in the side view 50% probability level; hydrogens are omitted for clarity. The side
have been omitted for clarity.
view shows the ligands around only one Ni atom.
6 | J. Name., 2012, 00, 1-3
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causes for this preference for bent conformations cannot be
identified at this point. Indeed, it is still unclear whether this
tendency is driven by stabilizing interactions between the two d8
centers, or whether the shortened Ni---Ni distances observed are
simply the consequence of the bending, as opposed to being its
cause. What seems clear at this point is that no simple correlation
exists between the degree of bending and Ni---Ni distances in
complexes studied, on the one hand, and the electron-withdrawing
or -releasing properties of their ring substituents (3-F, 3-MeO) on
the other. This phenomenon will be probed in future investigations.
Figure 5. Top view of the molecular diagram for complex 1k.
Thermal ellipsoids are shown at the 50% probability level;
hydrogens are omitted for clarity.
NMR characterization of the cyclonickellated dimers. All attempts
to record informative NMR spectra using CDCl3, CD2Cl2, or C6D6
solutions of the dimeric complexes resulted in poorly resolved
spectra featuring low signal-to-noise ratios. In contrast, CD3CN
solutions gave high-quality spectra that facilitated solution
characterization of these complexes. This difference in the spectral
quality as a function of solvent nucleophilicity is presumably due to
a relatively slow dynamic process occurring in non-nucleophilic
solvents (e.g., the flipping up and down of the dimer), whereas
complete dissociation of the dimers takes place in acetonitrile to
give monomeric acetonitrile adducts that do not experience this
fluxionality.19 To shed some light on this issue, we carried out a
computational study to estimate the energy barrier required for the
flipping motion of a simplified model (Me2P instead of i-Pr2) for the
bent dimer 1a. (See SI for technical details on this study.) The
We have probed this phenomenon using DFT calculations to
identify the optimal geometries for the dimeric complex 1d in
toluene. All optimizations were carried out using Gaussian 16 with
M06 functional method in implicit toluene solvent using the SMD
model. The experimentally obtained solid state structure for 1d was
used as the beginning point for the first geometry optimizations;
these led to a bent structure featuring Ni---Ni bond distances and
torsion angles very similar to those found in the solid state
structure (ca. 2.75 Å vs. 2.94 Å; 102° vs 116° respectively). The
geometry was then allowed to unfold to a structure displaying a
coplanar conformation around Ni1-Br1-Br2-Ni2. Optimization of this
coplanar geometry led to a local minimum, which was found to be
less stable than the bent structure: ΔG°bending = -6.5 kJ/mol.
energy barrier obtained for flipping 1a-PMe2 via
a coplanar
DFT optimizations were also applied to 1a, the parent dimer that
crystallizes on an inversion center and hence adopts a coplanar
structure in the solid state. In this case, too, the planar structure
obtained after initial optimizations appeared to be only a local
minimum, because optimizations carried out on starting structures
featuring non-coplanar Ni2Br2 cores led to a bent geometry that was
more stable relative to the coplanar structure: torsion angle of
104°; Ni---Ni bond distance of ca. 2.77 Å; ΔG°bending = -5.7 kJ/mol.
In order to avoid local minima resulting from the different possible
orientations of the i-Pr groups in the P(i-Pr)2 moieties, further
transition state was only 11.6 kJ/mol, which is easily accessible at
room temperature. This result implies that the relatively slow up
and down flipping of dimers in solution might well be the cause of
the poorly-resolved NMR spectra alluded to above.20 Regardless of
the precise reason(s) for these observations, it should be
emphasized that the well-resolved spectra discussed below are
those of the monomeric acetonitrile adducts
Pr)2}NiBr(NCCD3) derived from each dimer.
{ ,
κP κC-R-ArOP(i-
The 31P{1H} NMR spectra recorded for the CD3CN samples of all
dimers displayed singlet resonance at 190-198 ppm. The
a
optimizations were carried out on the PMe2 analogues of 1a and 1d
.
corresponding 1H NMR spectra were also consistent with the loss of
one aromatic proton as a result of nickellation, and featured the
characteristic signals for i-Pr protons (two dd for the diastereotopic
Me groups, and a pseudo-octuplet for the methyne C-H). For the
dimeric complex 1f, the assignments of the H-P and H-F couplings
were facilitated thanks to the selectively decoupled 1H{31P} and
1H{19F} spectra (See Figures 6 and S50─S52). Further evidence for
nickellation was also obtained from the 13C{1H} NMR spectra
featuring doublets at 105 – 130 ppm (2JCP = 30–40 Hz) and 160–168
ppm (2JCP = 11–15 Hz) for the nickellated carbon C2 and the O-
bearing carbon C1, respectively. In some cases, P-C coupling was
also visible for other aromatic carbons, but these showed generally
As a further measure for ensuring the reliability of our optimization
studies, the PMe2 analogue of 1d was allowed to adopt the three
possible conformations due to the two orientations of the MeO
substituents observed in the crystal structure of 1d. (See SI for
details of these structures.) In all four cases, optimizations
generated bent structures for these PMe2 analogues of 1a and 1d
,
with structural parameters very similar to those seen in the solid
state structure of the P(i-Pr)2 complexes: torsion angles ≈ 100─103°;
Ni---Ni distances ≈ 2.68−2.70 Å. As before, freezing the torsion
angles at 180° (coplanar structures) followed by optimization
yielded a local minimum for each structure, but these were always
less stable than the bent ones by 1.3−3.8 kJ/mol.
4
much smaller coupling constants (3JCP and JCP < 5 Hz). The NMR
Altogether, the results of our DFT studies imply that this family of
dimeric Ni(II) complexes must have an intrinsic preference for
adopting non-coplanar conformations. As a result, non-coplanar
conformations are found in the solid state unless there is a
crystallographic inversion center in the unit cell. The underlying
spectra of the CD3CN solutions of dimers 1b/1b’, 1f, and 1k showed
particularly intriguing coupling patterns and provided a wealth of
information about the various coupling interactions
.
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Very informative coupling patterns were also observed in the
spectra recorded for 1k/CD3CN, the complex derived from 2-
phenylphenol. For instance, a singlet was observed for C10 (the
para position on Ph substituent), whereas two doublets were found
for C8/12 and C9/11 (the ortho- and meta-C nuclei on the Ph
substituent) featuring unusually large couplings due to dipolar
coupling to the 31P nucleus (JCP = 107 and 140 Hz, respectively).
Assignments of C8/12 and C9/11 for the 2-Ph substituent were
confirmed by HSQC experiments. The signals for the quaternary
carbons C6 and C7 were not detected at all.
*
*
Conclusions
Figure 6. Aromatic region of the 1H, 1H{19F}, and 1H{31P} NMR
spectra of 1f, disclosing JHF, JHH and JHP couplings.
The following are the main findings of this study with respect to C-H
nickellation regioselectivity: (a) the aryl phosphinites i-Pr2POAr
undergo C-H nickellation when heated in acetonitrile solutions
containing the nickel precursor [(i-PrCN)NiBr2]n and NEt3, giving the
For example, the 19F NMR spectrum for the mixture of the two
acetonitrile adducts trans
-
{
κP
,
κC-ArOP(i-Pr)2}Ni(NCMe)Br that upon
regioisomers 1b and 1b’ displayed a pseudo-quartet at -118 ppm
for the major isomer with para-F (3JHF ≈ 4JHF ≈ 9 Hz) and a doublet of work-up yield the dimeric species {κP
,
κC-ArOP(i-Pr)2}2Ni2Br2 for
doublets at -95 ppm for the minor isomer with ortho-F (3JHF = 9 Hz, every substrate tested except that with Ar= 3,5-(OMe)2-C6H3 that
4JHF = 6 Hz). Correlating these chemical shifts with those of the two
{ ,
κP κC-3,5-(OMe)2-C6H3 OP(i-
gave the acetonitrile adduct
δ
-116.4 (q, 3JHF = 3JH’F = 4JFF = 9 Hz) and -93 Pr)2}NiBr(NCMe); (b) the C-H nickellation of all but one of the
19F resonances found at
3
(t, JHF
=
4JFF = 9 Hz) for dimer 1f allowed an unambiguous phosphinites derived from 3-R-C6H4OH occurs regioselectively at
identification of the two F nuclei.
the less hindered ortho position, the only exception being observed
with substrate (3-F-C6H4O)P(i-Pr)2 that gives a 6:1 mixture of
The 13C NMR spectrum of 1f/NCCD3 was also quite informative: two
13C doublets of doublets featuring large JFC coupling constants (ca. regioisomers (major one nickellated at the less hindered ortho
240 Hz) were readily attributed to the two F-bearing carbon nuclei position); (c) the C-H nickellation of both phosphinites derived from
C5 and C3 (see Figure S53 in SI). However, the doublets in question 2-R-CH4OH (R= Me, Ph) also occurs regioselectively at the only
did not display any JC-P coupling, which precluded their assignment available ortho C-H of the phenol ring, not at the substituent C-H
to the specific nuclei C3 and C5. On the other hand, the data moiety; (d) no C-H nickellation occurs with the disubstituted
1
allowed exact assignments for the remaining carbon nuclei of the phosphinites derived from 2,6-R2-C6H3OH (R= Me, Ph), whereas for
2
those derived from 3,5-R2-C6H3OH C-H nickellation was possible
aromatic ring in 1f. Thus, C2 and C6 showed (Figure 7) both JCP (39
3
2
Hz) and JCP (13 Hz) as well as JCF (ca. 36 and 24 Hz, respectively) with R= F or OMe but not Me or Cl.
4
and even JCF coupling constants (ca. 3 and 4 Hz, respectively). A The above results indicate that the reactivity with 3-substituted is
ddd 13C resonance at 168 ppm was attributed to C1 (3JCF = 25 Hz; highly sensitive to the steric size of the phenol substituent(s),
3JCF’ = 14 Hz; JCP = 11 Hz), while another ddd was observed for C4 nickellation occurring exclusively or preferentially at the less
2
2
and attributed to two different JCF couplings: 36 and 25 Hz. Finally, congested site, whereas C-H nickellation with the 3,5-disubstituted
it is noteworthy that we observe P-C6 coupling but no P-H6 substrates is altogether inaccessible with the substituents Me and
Cl. Another important factor is the size of the resulting
nickellacycles: the greater preference for 5-membered
coupling, whereas the opposite is the case for C4, i.e., we observe
P-H4 coupling but no P-C4 coupling.
a
nickellacycle precludes nickellation at the phenol substituent C-H
sites in 2-substituted and 2,6-disubstitued substrates.
Other interesting findings of this study include the confirmation of a
previously noted observation that C-H nickellation of these
substrates occurs more readily with electron-rich substrates (R =
Me, OMe), and also the observation that the dimers adopt more
stable bent conformations and they break apart into monomeric
adducts in the presence of even weakly nucleophilic reagents such
as acetonitrile. This latter reactivity should open the way to
potentially interesting functionalization pathways, which we intend
to explore. Our future studies will also focus on elucidating the
mechanism of C-H nickellation.
*
*
Figure 7. Selected regions in the 13C{1H} NMR of 1f displaying JCF and
JCP couplings.
8 | J. Name., 2012, 00, 1-3
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vacuum and the residues were extracted with toluene by filtration
through Celite®. The toluene was removed under vacuum and the
residues (deliquescent solids or dark orange pasty products) were
dissolved in a minimum of Et2O, precipitated with hexanes, filtered
off and the solids washed with a minimum of hexanes to complete
removal of impurities. The remaining solid was dried under vacuum
to yield a bright to dull orange powder. Single crystals were
obtained by slow evaporation of an Et2O solution kept under N2.
Conflicts of interest
The authors declare no conflicts of interest.
Acknowledgements
[{κP κC-(
, i-Pr)2PO-C6H4}Ni(μ-Br)]2 (1a). This compound has been
The authors gratefully acknowledge financial support provided by:
NSERC of Canada (Discovery grants to D.Z.); Centre in Green
Chemistry and Catalysis (CGCC/CCVC, summer research stipends
and travel awards); Université de Montréal (graduate scholarships
to L. P. M.). We also thank our colleagues, Dr. M. Simard (for help
with the resolution of the solid state structure for complex 1k),
Prof. F. Schaper (for valuable advice on the refinement of this
structure), and Mr. J.-P. Cloutier (for discussions with regards to the
DFT studies). Finally, Compute Canada-Calcul Canada is
acknowledged for access to Westgrid Computational Facilities.
synthesized previously via a different procedure.6 The revised
general procedure described above was applied on a 5.00 mmol
scale in MeCN over 16 h at 80 °C. Yield of the bright orange powder
obtained: 1.514 g (2.17 mmol, 87 %). The NMR spectroscopic data
in CD3CN confirmed the identity of the compound. 1H NMR (500
3
3
MHz, 20 °C, CD3CN): δ 1.31 (dd, 6H, CH(CH3)(CH3), JHH = 7.0, JHP
=
3
3
14.9), 1.46 (dd, 6H, CH(CH3)(CH3), JHH = 7.2, JHP = 17.5), 2.44 (oct,
2H, CH(CH3)2, 3JHH ≈ 2JHP = 7.1), 6.63 (dd, 1H, C6Ar-H, 3JHH = 7.9, 4JHH
=
3
4
5
1.3), 6.68 (tt, 1H, C4Ar-H, JHH = 7.4, JHH ≈ JHP = 1.1), 6.98 (tm, 1H,
3
4
3
4
C5Ar-H, JHH = 7.5, JHH = 1.4), 7.16 (dt, 1H, C3Ar-H, JHH = 7.6, JHH
≈
4JHP = 1.4). 13C{1H} NMR (125.7 MHz, 20 °C, CD3CN): δ 16.88 (d, 2C,
Experimental section
2
2
CH(CH3)(CH3), JCP = 1.9), 18.50 (d, 2C, CH(CH3)(CH3), JCP = 2.7),
General considerations. All manipulations were carried out under a
nitrogen atmosphere using standard Schlenk techniques and an
inert-atmosphere box. The solvents were dried by passage over a
column of activated alumina, collected under nitrogen, and stored
over 4 Å molecular sieves. Triethylamine was dried over CaH2.
Synthesis of the nickel precursor {(i-PrCN)NiBr2}n used throughout
this study has been described previously.21 3,5-dichlorophenol was
synthesized from demethylation of 3,5-dichloroanisole in refluxing
48 % aq. HBr. All other reagents were purchased from Sigma-Aldrich
and used without further purification.
1
3
29.07 (d, 2C, CH(CH3)(CH3), JCP = 29.0), 110.60 (d, 1C, C6Ar-H, JCP
13.2), 121.43 (d, 1C, C4Ar-H, 4JCP = 2.0), 127.56 (s, 1C, C5Ar-H), 133.78
=
2
3
(d, 1C, C2Ar-Ni, JCP = 33.9), 139.11 (d, 1C, C3Ar-H, JCP = 2.6), 167.66
(d, 1C, C1Ar-OP, 2JCP = 11.9). 31P{1H} NMR (202.4 MHz, 20 °C, CD3CN):
δ 196.21 (s, 1P).
[{κP
,
κC-(
i-Pr)2PO-(5-F-C6H3)}Ni(
μ , i-Pr)2PO-(3-
-Br)]2 (1b) and [(κP κC-(
F-C6H3)Ni(μ-Br)]2 (1b’). Applying the general procedure given above
(at 80 °C for 36 h) gave a bright orange powder. Yield: 382 mg
(0.522 mmol). This solid was shown by 31P{1H} and 19F NMR spectra
to contain the two isomers 1b (major, metallated para to F) and 1b’
(minor, metallated ortho to F) in a 6.5 : 1 ratio. Spectroscopic data
for 1b :1H NMR (500 MHz, 20 °C, CD3CN): δ 1.30 (dd, 6H,
CH(CH3)(CH3), 3JHH = 7.2, 3JHP = 15.1), 1.46 (dd, 6H, CH(CH3)(CH3), 3JHH
= 7.2, 3JHP = 17.6), 2.44 (oct, 2H, CH(CH3)2, 3JHH ≈ 2JHP = 7.2), 6.45 (dd,
Unless otherwise specified, all 1D NMR spectra were recorded at
500 MHz (1H), 125.72 MHz (13C), 202.4 MHz (31P) and 470.4 MHz
(
19F), whereas the HSQC experiments were recorded at 400 MHz
(1H) and 100.6 MHz (13C). Chemical shift values are reported in ppm
(δ) and referenced internally to the residual solvent signals (1H and
13C: 1.94 and 118.26 ppm for CHD2CN) or externally (31P, H3PO4 in
D2O, δ = 0; 19F, CFCl3, δ = 0). The values for J coupling are given in
Hz. The NMR data obtained for CD3CN solutions of the dimeric
complexes correspond to the corresponding monomeric NCCD3
adducts.
3
3
1H, C6Ar-H, JHF = 10.2, 4JHH = 2.6), 6.48 (tdd, 1H, C4Ar-H, JHH ≈ 3JHF
=
=
9.4, 4JHH = 2.7, 5JHP = 0.9), 7.11 (tm, 1H, C3Ar-H, 3JHH ≈ 4JHF = 7.3, 4JHP
0.8). 13C{1H} NMR (125.7 MHz, 20 °C, CD3CN): δ 18.04 (d, 2C,
2
2
CH(CH3)(CH3), JCP = 1.9), 18.65 (d, 2C, CH(CH3)(CH3), JCP = 2.7),
1
2
29.34 (d, 2C, CH(CH3)(CH3), JCP = 29.0), 98.89 (dd, 1C, C6Ar-H, JCF
=
3
2
4
24.7, JCP = 13.9), 108.01 (dd, 1C, C4Ar-H, JCF = 19.6, JCP = 1.7),
General procedure for the synthesis of cyclonickellated
phosphinite dimers. To a solution of ArOH (2.00 mmol) in 20 mL dry
THF was added Et3N (2.20 mmol, 307 μL, 1.10 equiv) and then ClP(i-
Pr)2 (2.10 mmol, 334 μL, 1.05 equiv) after which salt precipitation
started. The mixture was stirred at room temperature until the
reaction was complete (from 0.5 to 20 h, as monitored by 31P NMR).
The solvent was removed under vacuum, the residues extracted
with Et2O (3x15 mL), and evaporated to yield a colourless to pale
yellow oil. To the latter was added dry MeCN (20 mL), {(i-
PrCN)NiBr2}n (2.40 mmol, 691 mg, 1.2 equiv), and Et3N (2.40 mmol,
335 μL, 1.2 equiv). The resulting green to brownish-green
homogeneous mixture was stirred at 80 °C until the reaction was
complete (monitored by the disappearance of the starting material
31P signal at ca. 135 ppm). The solvent was then removed under
128.20 (d, 1C, C2Ar-Ni, 2JCP = 34.2), 139.60 (dd, 1C, C3Ar-H, JCF = 8.5,
3
3JCP = 3.1), 163.53 (d, 1C, C5Ar-F, JCF = 240.8), 167.84 (dd, 1C, C1Ar-
2
OP, 3JCF = 13.2, 2JCP = 11.2). 31P{1H} NMR (202.4 MHz, 20 °C, CD3CN):
δ 197.72 (s, 1P). 19F NMR (470.4 MHz, 20 °C, CD3CN): δ -118.39 (q,
1F, C5Ar-F, 3JHF ≈ 4JHF = 9.4). Spectroscopic data for 1b’ : 1H NMR (500
3
3
MHz, 20 °C, CD3CN): δ 1.30 (dd, 6H, CH(CH3)(CH3), JHH = 7.2, JHP
=
3
3
15.1), 1.47 (dd, 6H, CH(CH3)(CH3), JHH = 7.1, JHP = 17.7), 2.44 (oct,
2H, CH(CH3)2, 3JHH ≈ 2JHP = 7.2), 6.38 (1H, tm, C4Ar-H, 3JHH ≈ 3JHF= 8.5,
4JHH = 1.1), 6.51 (1H, dd, C6Ar-H, JHH = 7.9, 4JHH = 1.1), 6.98 (1H, qm,
C5Ar-H, 3JHH = 7.9, 4JHF = 6.2, 5JHP = 1.1). 13C{1H} NMR (125.7 MHz, 20
3
2
°C, CD3CN): δ 18.09 (d, 2C, CH(CH3)(CH3), JCP = 2.2), 18.78 (d, 2C,
2
1
CH(CH3)(CH3), JCP = 2.2), 29.75 (d, 2C, CH(CH3)(CH3), JCP = 30.0),
107.40 (dd, 1C, C6Ar-H, 3JCP = 12.2, 4JCF = 2.6), 109.24 (dd, 1C, C4Ar-H,
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4
3
3JCF = 29.7, JCP = 1.4), 128.91 (d, 1C, C5Ar-H, JCF = 10.2), 168.82 (m, powder. Yield: 475 mg (0.618 mmol, 62%). 1H NMR (500 MHz, 20 °C,
1
3
3
1C, C1Ar-OP), 171.68 (d, 1C, C3Ar-F, JCF = 238.8), C2Ar-Ni was not CD3CN): δ 1.31 (dd, 6H, CH(CH3)(CH3), JHH = 7.1, JHP = 15.4), 1.48
detected. 31P{1H} NMR (202.4 MHz, 20 °C, CD3CN): δ 192.04 (s, 1P). (dd, 6H, CH(CH3)(CH3), JHH = 7.1, JHP = 17.6), 2.45 (oct, 2H,
3
3
19F NMR (470.4 MHz, 20 °C, CD3CN): δ -95.55 (dd, 1F, C3Ar-F, JHF
=
CH(CH3)2, JHH ≈ =
2JHP = 7.1), 6.24 (tdd, 1H, C4Ar-H, JHF 3JHF’ = 9.9,
3
3
3
9.3, JHF = 6.2). Anal. Calc. for C24H34F2O2P2Ni2Br2: C, 39.40; H, 4.68. 4JHH = 2.5, 5JHP = 1.1), 6.35 (ddd, 1H, C6Ar-H, 3JHF = 9.6, 4JHH = 2.4, 5JHF
4
Found: C, 38.61; H, 4.86; N, 0.24.
[{κP κC-(
-Pr)2PO-(5-Me-C6H3)}Ni(μ-Br)]2 (1c). Applying the general
procedure given above (at 80 °C for 16 h) gave a dull orange
powder. Yield: 487 mg (0.673 mmol, 67%). 1H NMR (500 MHz, 20 °C,
= 1.1). 13C{1H} NMR (125.7 MHz, 20 °C, CD3CN): δ 16.82 (d, 2C,
2
2
CH(CH3)(CH3), JCP = 2.4), 18.52 (d, 2C, CH(CH3)(CH3), JCP = 2.2),
,
i
29.58 (d, 2C, CH(CH3)(CH3), 1JCP = 29.8), 95.64 (ddd, 1C, C6Ar-H, 2JCF
=
=
3
4
2
2
24.7, JCP = 13.0, JCF’ = 3.9), 97.16 (dd, 1C, C4Ar-H, JCF = 36.0, JCF’
2
2
4
3
3
25.0), 112.53 (ddd, 1C, C2Ar-Ni, JCP = 39.4, JCF = 36.2, JCF’ = 3.3),
163.13 (dd, 1C, C3Ar-F or C5Ar-F,1JCF =240.7, 3JCF = 15.6), 168.29 (ddd,
1C, C1Ar-OP, 3JCF = 25.3, 3JCF’ = 14.3, 2JCP = 10.9), 171.05 (dd, 1C, C3Ar-
F or C5Ar-F, 1JCF = 239.7, 3JCF = 14.2). 31P{1H} NMR (202.4 MHz, 20 °C,
CD3CN): δ 193.52 (s, 1P). 19F NMR (470.4 MHz, 20 °C, CD3CN): δ -
CD3CN): δ 1.29 (dd, 6H, CH(CH3)(CH3), JHH = 7.0, JHP = 14.9), 1.45
3
3
(dd, 6H, CH(CH3)(CH3), JHH = 7.2, JHP = 17.5), 2.19 (s, 3H, Ar-CH3),
3
2.42 (oct, 2H, CH(CH3)2, JHH
≈
2JHP = 7.2), 6.49 (s, 1H, C6Ar-H), 6.52
(d, 1H, C4Ar-H, JHH = 7.8), 7.01 (d, 1H, C3Ar-H, JHH = 7.8), 13C{1H}
3
3
NMR (125.7 MHz, 20 °C, CD3CN): δ 17.75 (d, 2C, CH(CH3)(CH3), 2JCP
=
3
3
4
3
2
116.38 (q, 1F, C5Ar-F, JHF ≈ JH’F ≈ JFF = 9.0), -92.62 (t, C3Ar-F, JHF
≈
1.8), 18.37 (d, 2C, CH(CH3)(CH3), JCP = 2.8), 20.46 (s, 1C, Ar-CH3),
4JFF = 9.0). Anal. Calc. for C24H32O2P2F4Ni2Br2: C, 37.55; H, 4.20.
1
3
28.87 (d, 2C, CH(CH3)(CH3), JCP = 29.0), 111.28 (d, 1C, C6Ar-H, JCP
=
4
2
Found: C, 37.75; H, 4.01; N, 0.07.
13.2), 122.24 (d, 1C, C4Ar-H, JCP = 1.8), 129.33 (d, 1C, C2Ar-Ni, JCP
=
34.4), 137.59 (s, 1C, C5Ar-Me), 138.64 (d, 1C, C3Ar-H, JCP = 2.7), {(κP κC-(
, i-Pr)2PO-(3,5-(MeO)2-C6H2)}NiBr(NCMe) (1i-NCMe). The
3
167.50 (d, 1C, C1Ar-OP), 2JCP = 12.3). 31P{1H} NMR (202.4 MHz, 20 °C, general procedure given above was applied at 70 °C for 16 h gave a
CD3CN): δ 195.79 (s, 1P). Anal. Calc. for C26H40O2P2Ni2Br2: C, 43.15; dull orange powder. It is important to emphasize that these
H, 5.57. Found: C, 42.88; H, 5.69; N, 0.03.
[{κP κC-(
-Pr)2PO-(5-MeO-C6H3)}Ni( -Br)]2 (1d). Applying the general
reaction mixtures were protected from ambient light with
aluminum foil during the reaction and during the extraction. Failure
to keep out ambient light at all moment, including during work-up,
hindered the cyclonickellation reaction. Yield: 480 mg (1.07 mmol,
,
i
μ
procedure given above (at 80 °C for 16 h) gave a dull orange
powder. Yield: 452 mg (0.598 mmol, 60%). 1H NMR (500 MHz, 20 °C,
53%). 1H NMR (500 MHz, 20 °C, CD3CN):
δ 1.27 (dd, 6H,
3
3
CD3CN): δ 1.30 (dd, 6H, CH(CH3)(CH3), JHH = 7.1, JHP = 14.9), 1.45
CH(CH3)(CH3), 3JHH = 7.1, 3JHP = 14.9), 1.47 (dd, 6H, CH(CH3)(CH3), 3JHH
3
3
(dd, 6H, CH(CH3)(CH3), JHH = 7.2, JHP = 17.5), 2.42 (oct, 2H,
CH(CH3)2, 3JHH ≈ 2JHP = 7.2), 3.69 (s, 3H, Ar-OCH3), 6.28 (d, 1H, C6Ar-H,
3
= 7.3, JHP = 17.4), 1.96 (s, 3H, free CH3CN), 2.38 (oct, 2H, CH(CH3)2,
2
3JHH ≈ JHP = 7.2), 3.67 (s, 1H, ArO-CH3), 3.69 (s, 1H, ArO-CH3), 5.90
3
4
5
4JHH = 2.6), 6.31 (ddd, 1H, C4Ar-H, JHH = 8.5, JHH = 2.6, JHP = 0.9),
7.00 (dd, 1H, C3Ar-H, 3JHH = 8.5, 4JHH = 1.0). 13C{1H} NMR (125.7 MHz,
20 °C, CD3CN): δ 16.85 (d, 2C, CH(CH3)(CH3), 2JCP = 2.0), 18.47 (d, 2C,
4
(m, 1H, C4Ar-H), 5.97 (d, 1H, C6Ar-H, JHH = 2.3 Hz). 13C{1H} NMR
2
(125.7 MHz, 20 °C, CD3CN): δ 16.60 (d, 2C, CH(CH3)(CH3), JCP = 2.2),
2
2
1
18.28 (d, 2C, CH(CH3)(CH3), JCP = 2.4), 29.00 (d, 2C, CH(CH3)(CH3),
CH(CH3)(CH3), JCP = 2.8), 28.98 (d, 2C, CH(CH3)(CH3), JCP = 28.8),
1JCP = 29.2), 55.14 (s, 1C, ArO-CH3), 55.49 (s, 1C, ArO-CH3), 90.17 (d,
3
55.45 (s, 1C, Ar-OCH3), 97.42 (d, 1C, C6Ar-H, JCP = 14.0), 107.28 (d,
4
2
1C, C6Ar-H, JCP = 13.3), 92.58 (s, 1C, C4Ar-H), 107.98 (d, 1C, C2Ar-Ni,
1C, C4Ar-H, JCP = 1.7), 122.96 (d, 1C, C2Ar-Ni, JCP = 35.5), 139.03 (d,
1C, C3Ar-H, 3JCP = 3.0), 160.59 (s, 1C, C5Ar-OCH3), 168.04 (d, 1C, C1Ar-
OP, 2JCP = 13.4). 31P{1H} NMR (202.4 MHz, 20 °C, CD3CN): δ 196.07 (s,
1P). Anal. Calc. for C26H40O4P2Ni2Br2: C, 41.32; H, 5.34. Found: C,
43.41; H, 5.89; N, 0.05.
2
2JCP = 38.4), 161.12 (s, 1C, C5Ar-OMe), 167.24 (d, 1C, C1Ar-OP, JCP
=
11.3), 168.22 (d, 1C, C3Ar-OMe, 3JCP = 2.0). 31P{1H} NMR (202.4 MHz,
20 °C, CD3CN): δ 189.97 (s, 1P). Anal. Calc. for C26H40O2P2Ni2Br2: C,
42.81; H, 5.61; N, 3.12. Found: C, 41.39; H, 5.55; N, 1.69. The lower
C- and N-contents of this sample indicate some contamination of
the title compound. We have used careful NMR analysis of various
samples to rule out the possibility of contamination by the
phosphinite adduct 1i-L or the anticipated dimer. On the other
hand, we have noted that this compound appears to be light-
sensitive, which might explain the presence of impurities;
unfortunately, we have not been able to identify the process of the
side-products it might generate.
[(κP κC-(
, i-Pr)2PO-(5-Cl-C6H3)Ni(μ-Br)]2 (1e). Applying the general
procedure given above (at 80 °C for 60 h) gave a dull orange
powder. Yield: 542 mg (0.709 mmol, 71%). 1H NMR (500 MHz, 20 °C,
3
3
CD3CN): δ 1.31 (dd, 6H, CH(CH3)(CH3), JHH = 7.0, JHP = 15.2), 1.46
3
3
(dd, 6H, CH(CH3)(CH3), JHH = 7.2, JHP = 17.6), 2.45 (oct, 2H,
3
2
CH(CH3)2, JHH ≈ JHP = 7.2), 6.69 (s, 1H, C6Ar-H), 6.70 (ddd, 1H, C3Ar-
3
4
5
H, JHH = 8.0, JHP = 2.1, , JHH = 1.0), 7.12 (dd, 1H, C4Ar-H, 3JHH = 8.0,
5JHP = 1.0). 13C{1H} NMR (125.7 MHz, 20 °C, CD3CN): δ 16.39 (d, 2C,
[{κP κC-(
, i-Pr)2PO-(6-Me-C6H3)}Ni(μ-Br)]2 (1j). Applying the general
2
2
CH(CH3)(CH3), JCP = 1.9), 18.00 (d, 2C, CH(CH3)(CH3), JCP = 2.7),
1
3
procedure given above (at 80 °C for 16 h) gave a dull yellowish-
orange powder. Yield: 465 mg (0.642 mmol, 64%). 1H NMR (500
28.73 (d, 2C, CH(CH3)(CH3), JCP = 28.8), 110.44 (d, 1C, C6Ar-H, JCP
=
3
13.5), 120.66 (d, 1C, C3Ar-H, JCP = 1.6), 131.74 (s, 1C, C5Ar-Cl),
3
3
2
4
MHz, 20 °C, CD3CN): δ 1.32 (dd, 6H, CH(CH3)(CH3), JHH = 7.0, JHP
=
132.09 (d, 1C, C2Ar-Ni, JCP = 34.2), 139.43 (d, 1C, C4Ar-H, JCP = 2.7),
167.35 (d, 1C, C1Ar-OP, 2JCP = 12.8). 31P{1H} NMR (202.4 MHz, 20 °C,
CD3CN): δ 198.12 (s, 1P). Anal. Calc. for C24H34O2P2Cl2Ni2Br2: C,
37.70; H, 4.48. Found: C, 37.38; H, 4.56, N, 0.18.
, i-Pr)2PO-(3,5-F2-C6H2)}Ni(μ-Br)]2 (1f). Applying the general
[{κP κC-(
procedure given above (at 80 °C for 80 h) gave a deep orange
14.6), 1.35 (dd, 6H, CH(CH3)(CH3), 3JHH = 7.2, 3JHP = 17.5), 2.14 (s, 3H,
Ar-CH3), 2.45 (oct, 2H, CH(CH3)2, 3JHH ≈ 2JHP = 7.1), 6.58 (t, 1H, C4Ar-H,
3JHH = 7.3), 6.82 (d, 1H, C5Ar-H, 3JHH = 7.3), 6.97 (d, 1H, C3Ar-H, 3JHH
=
7.6). 13C{1H} NMR (125.7 MHz, 20 °C, CD3CN): δ 16.05 (m, 2C,
CH(CH3)(CH3) + Ar-CH3), 17.79 (d, 2C, CH(CH3)(CH3), 2JCP = 2.7), 28.27
10 | J. Name., 2012, 00, 1-3
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1
4
(d, 2C, CH(CH3)(CH3), JCP = 29.2), 119.82 (d, 1C, C6Ar-Me, JCP
=
12.5), 120.82 (d, 1C, C4Ar-H, 4JCP = 2.1), 128.01 (s, 1C, C5Ar-H), 132.52
2
4
(d, 1C, C2Ar-Ni, JCP = 34.1), 135.80 (d, 1C, C3Ar-H, JCP = 2.5), 165.10
(d, 1C, C1Ar-OP, 3JCP = 12.1). 31P{1H} NMR (202.4 MHz, 20 °C, CD3CN):
δ 193.78 (s, 1P). Anal. Calc. for C26H40O2P2Ni2Br2: C, 43.15; H, 5.57.
Found: C, 42.75; H, 5.51; N, 0.06.
, i-Pr)2PO-(6-Ph-C6H3)}Ni(μ-Br)]2 (1k). Applying the general
[{κP κC-(
procedure given above (at 80 °C for 16 h) gave a dull yellowish-
orange powder. Yield: 625 mg (0.737 mmol, 74%). 1H NMR (500
3
3
MHz, 20 °C, CD3CN): δ 1.26 (dd, 6H, CH(CH3)(CH3), JHH = 7.3, JHP
=
3
3
15.0), 1.48 (dd, 6H, CH(CH3)(CH3), JHH = 7.3, JHP = 17.6), 2.41 (oct,
2H, CH(CH3)2, 3JHH ≈ 2JHP = 7.3), 6.77 (td, 1H, C4Ar-H, 3JHH = 7.6, 5JHP
=
0.9), 7.06 (dt, 1H, C3Ar-H, JHH = 7.6, 4JHH = 4JHP = 1.4), 7.17 (dm, 1H,
3
C5Ar-H, JHH = 7.7), 7.29 (tt, 1H, p-CAr-H (Ph), JHH = 7.3, 4JHH = 1.3),
3
3
7.38 (t, 2H, m-CAr-H (Ph), JHH = 7.4), 7.49 (dm, 2H, o-CAr-H (Ph), 3JHH
3
= 7.3). 13C{1H} NMR (125.7 MHz, 20 °C, CD3CN): δ 16.98 (d, 2C,
2
2
CH(CH3)(CH3), JCP = 1.9), 18.50 (d, 2C, CH(CH3)(CH3), JCP = 2.7),
1
4
29.14 (d, 2C, CH(CH3)(CH3), JCP = 29.4), 122.21 (d, 1C, C4Ar-H, JCP
=
3
1.9), 125.16 (d, 1C, C3Ar-H, JCP = 12.1), 127.99 (d, 2C, m-CAr-H (Ph),
JCP = 139.5), 129.12 (d, 2C, o-CAr-H (Ph), JCP = 106.8), 135.65 (d, 1C,
2
5
C2Ar-Ni, JCP = 33.0), 138.64 (d, 1C, C5Ar-H, JCP = 2.7), 139.78 (s, 1C,
2
p-CAr-H (Ph)), 163.78 (d, 1C, C1Ar-OP, JCP = 12.6), CqAr-Ar were not
detected. 31P{1H} NMR (202.4 MHz, 20 °C, CD3CN): δ 196.11 (s, 1P).
Anal. Calc. for C36H44O2P2Ni2Br2: C, 51.00; H, 5.23. Found: C, 50.67;
H, 5.44; N, 0.05.
, i-Pr)2PO-C6H4)}NiBr(NCMe) (1a-NCMe). 278 mg (400 µmol)
{(κP κC-(
of 1a was suspended in 10 mL Et2O, and 209 µL MeCN (4.00 mmol,
10 eq) was added. The solid readily dissolved to give a yellow
solution which was stirred at room temperature for 30 min.
Removal of the solvent under vacuum gave a yellow powder (267
mg, 687 µmol, 86 %). 1H NMR data in CD3CN matched the data
reported for the dimeric species 1a in CD3CN (+ 3H for free CH3CN),
and crystallization confirmed the identity of the MeCN adduct.
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Notes and references
van Koten and D. Milstein. DOI: 10.1007/978-3-642-31081-2_5.
Springer-Verlag, Berlin Heidelberg. (f) Vabre, B.; Canac, Y.;
Duhayon, C.; Chauvin, R.; Zargarian, D. Chem. Comm. 2012, 48,
10446 – 10448. (g) Spasyuk, D. M.; Gorelsky, S. I.; van der Est,
1
For representative reviews on the subject of C-H functionalization
see: (a) Kakiuchi, F.; Kochi, T. Synthesis 2008, 3013. (b)
Ackermann, L. Chem. Rev. 2011, 111, 1315. (c) Yamaguchi, J.;
Yamaguchi, A. D.; Itami, K. Angew. Chem. Int. Ed. 2012, 51,
8960. (d) Ackermann, L. Chem. Commun. 2010, 46, 4866. (e)
Chen, D. Y.-K.; Youn, S. W. Chem. Eur. J. 2012, 18, 9452. (f)
A.; Zargarian, D. Inorg. Chem. 2011
, 50, 2661-2674. (h)
Castonguay, A.; Beauchamp, A. L.; Zargarian, D. Inorg. Chem.
2009, 48, 3177-3184.
6
7
Vabre, B.; Deschamps, F.; Zargarian, D. Organometallics 2014, 33,
6623–6632.
Arockiam, P. B.; Bruneau, C.; Dixneuf, P. H. Chem. Rev. 2012
,
112, 5879. (g) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem.
Rev. 2010, 110, 624. (h) Rouquet, G.; Chatani, N. Angew. Chem.
Int. Ed. 2013, 52, 11726. (i) Lyons, T. W.; Sanford, M. S. Chem.
Rev. 2010, 110, 1147. (j) Xu, L.-M.; Li, B.-J.; Yang, Z.; Shi, Z.-J.
Chem. Soc. Rev. 2010, 39, 712. (k) Sehnal, P.; Taylor, R. J. K.;
Fairlamb, I. J. S. Chem. Rev. 2010, 110, 824.
The analogous Pd dimers have been reported by Bedford’s group:
Bedford, R. B.; Hazelwood (née Welch), S. L.; Horton, P. N.;
Hursthouse, M. B. Dalton Trans. 2003, 4164-4174.
A combined kinetic and DFT study on C-H nickellation of POCOP-
8
and PCP-type pincer ligands has established that the C-H
nickellation step proceeds via an electrophilic mechanism:
Vabre, B; Lambert, M. L.; Petit, A.; Ess, D. H.; Zargarian, D.
Organometallics 2012, 31, 6041−6053.
2
3
Gulevich, A. V.; Melkonyan, F. S.; Sarkar, D.; Gevorgyan, V. J. Am.
Chem. Soc. 2012, 134, 5528.
9
It should be noted that the regioselectivity of C-H metalation
observed in our system seems to be similar to that reported for
palladation of 2-(3-F-Ph)-pyridine (Kalyani, D.; Sanford, M. S.
Org. Lett. 2005, 7, 4149), but opposite of C-H activation reaction
by Ni(0) (Doster, M. E.; Hatnean, J. A.; Jeftic, T.; Modi, S.;
Johnson, S. A. J. Am. Chem. Soc. 2009, 132, 11923-11925).
Interestingly, sterics also seem to be important in the reaction
of fluorobenzenes with Rh(I) in that the kinetic products are
those involving less congested C-H moieties, whereas heating
the product mixture favors the products featuring Rh-C bonds
adjacent to fluoro-substituted sites: Evans, M. E.; Burke, C. L.;
Yaibuathes, S.; Clot, E.; Eisenstein, O.; Jones, W. D. J. Am. Chem.
Soc. 2009, 131, 13464-13473.
(a) Kanyiva, K. S.; Nakao, Y.; Hiyama, T. Angew. Chem. Int. Ed.
2007, 46, 8872. (b) Nakao, Y.; Kanyiva, K. S.; Hiyama, T. J. Am.
Chem. Soc. 2008, 130, 2448. (c) Tobisu, M.; Hyodo, I.; Chatani,
N. J. Am. Chem. Soc. 2009, 131, 12070. (d) Shacklady-McAtee,
D. M.; Dasgupta, S.; Watson, M. P. Org. Lett. 2011, 13, 3490. (e)
Ogata, K.; Atsuumi, Y.; Shimada, D.; Fukuzawa, S. Angew. Chem.
Int. Ed. 2011, 50, 5896. (f) Shiota, H.; Ano, Y.; Aihara, Y.;
Fukumoto, Y.; Chatani, N. J. Am. Chem. Soc. 2011, 133, 14952.
(g) Aihara, Y.; Chatani, N. J. Am. Chem. Soc. 2013, 135, 5308. (h)
Song, W.; Lackner, S.; Ackermann, L. Angew. Chem. Int. Ed.
2014, 53, 2477.
4
(a) Baho, N.; Zargarian, D. Inorg. Chem. 2007, 46, 299-308. (b)
Groux, L. F.; Zargarian, D. Organometallics 2003, 22, 4759-4769.
(c) Groux, L. F.; B.-Gariépy, F.; Zargarian, D.; Vollmerhaus, R.
The estimated vdW volumes (in cm3/mol) of these fragments
increase in the following order: F (5.0) < OH (8.0) < Cl (12.0) <
Me (13.7). (a) Bondi, A. J. Phys. Chem. 1964, 68, 441. (b) Pauling,
L. “Nature of the Chemical Bond and the Structure of Molecules
and Crystals: An Introduction to Modern Structural Chemistry”,
third edition, Cornel University Press, 1960, pp. 260-261.
10
Organometallics 2000
,
19, 1507. (d) Fontaine, F.-G.;
Kadkhodazadeh, T.; Zargarian, D. J. Chem. Soc., Chem. Commun.
1998, 1253-1254.
5
(a) Hao, J.; Mougang-Soumé, B; Vabre, B.; Zargarian, D. Angew.
Chem. Int. Ed. 2014, 53, 3218-3222. (b) Hao, J.; Vabre, B.;
Mougang-Soumé, B; Zargarian, D. Chem. Eur. J. 2014, 20, 12544-
12552. (c) Vabre, B.; Petiot, P.; Declercque, R.; Zargarian, D.
Organometallics 2014, 33, 5173-5184. (d) Vabre, B.; Lindeperg,
F.; Zargarian, D. Green Chem. 2013, 15, 3188. (e) Zargarian, D.;
Castonguay, A.; Spasyuk, D. M. “ECE-Type Pincer Complexes of
Nickel”, in Top. Organomet. Chem. 2013, 40, 131-174. Eds. G.
11 Bedford, R. B.; Limmert, M. E. J. Org. Chem. 2003, 68, 8669-8682.
12
Satoh, T.; Kawamura, Y.; Miura, M.; Nomura, M. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1740.
13
When electing to probe the reactivities of substrate l, we were
also mindful of the difficult but not impossible activation of a C-
Me bond in this substrate. See Milstein’s report for a precedent
12 | J. Name., 2012, 00, 1-3
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ARTICLE
on this type of reactivity with Ni(II): van der Boom, M. E.; Liou,
S.-Y.; Shimon, L. J. W.; Ben-David, Y.; Milstein, D. Inorg. Chim.
Acta 2004, 357, 4015–4023.
details.) Thus, the putative s-cis dimer seems feasible, but the
proposed conformational isomerization pathway passing
through a tetrahedral intermediate/ transition sate seems
thermally inaccessible at r.t. We also remain skeptical with
respect to an isomerization pathway involving a Ni-Br bond
scission, which would generate a 3-coordinate, 14-electron
intermediate. Attempts to estimate the energy of such an
intermediate by DFT were unsuccessful, implying that it is
thermally inaccessible
14
Complex 1k crystallized in P21 space group, but very close to
P21/a or orthorhombic due to pseudo-symmetry.
The non-
restrained refinement process yielded one non-positive definite
atom and several atoms featuring ellipsoids with high ratios of
atomic displacement parameters. A highly restrained RIGU
command was thus applied to all atoms to sort out these issues.
It should be noted that data collected at two different
temperatures (100 and 150 K) gave very similar results,
suggesting that the resolution problems mentioned above are
not due to a phase transition at or near the data collection
temperature.
21 Vabre, B.; Spasyuk, D. M.; Zargarian, D. Organometallics 2012, 31,
8561−8570.
15
These values were derived by applying the following equation τ4
= {360 – (α + β)]/141 wherein α and β are the greater bond
angles in the given structure. This approach generates values
ranging from 0 for an ideal square plane to 1 for an ideal
tetrahedron. For a discussion of this topic see the following
reports: (a) Yang, L.; Powell, D. R.; Houser, R. P. Dalton Trans.
2007, 955. (b) Okuniewski, A.; Rosiak, D.; Chojnacki, J.; Becker,
B. Polyhedron 2015 90, 47–57.
16
(a) Lefèvre, X.; Spasyuk, D. M.; Zargarian, D. J. Organomet. Chem.
2011, 696, 864. (b) Lefèvre, X.; Durieux, G.; Lesturgez, S.;
Zargarian, D. J. Mol. Catal. A 2011, 335, 1. (c) Lapointe, S.;
Vabre, B.; Zargarian, D. Organometallics 2015, 34, 3520–3531.
(d) Salah, A.; Corpet, M.; Khan, N. u-H.; Zargarian, D.; Spasyuk,
D. New J. Chem. 2015, 39, 6649–6658.
17
This value represents the range of torsion angles in the 4
independent molecules in the unit cell of this compound.
18 Cordero, B.; Gómez, V.; Platero-Prats, A. E.; Revés, M.; Echeverría,
J.; Cremades, E.; Barragán, F.; Alvarez, C. Dalton Trans. 2008
,
2832.
19
20
We recognize that monomeric acetonitrile adducts likely
exchange rapidly with CD3CN solvent, but we have not
attempted to confirm the occurrence of these processes.
A reviewer of our manuscript suggested that the exchange
process in question might occur via an s-trans-to-s-cis
isomerization process proceeding via one or the other of the
following alternative pathways, a conformational isomerization
(square-planarꢀtetrahedral) or a Ni-Br bond scission followed
by rotation around the remaining Ni-ꢀ-Br bond. We have
probed these scenarios briefly using DFT studies carried out on
the title dimeric complexes. These studies showed that the
isolated s-trans dimers are more stable than both the s-cis
isomer (by 10.0 kJ/mol) and the proposed tetrahedral
intermediate/transition-state (by 68.3 kJ/mol). (See SI for
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DOI: 10.1039/C7DT03403B
TOC text for
C−H Nickellation of PhenolꢀDerived Phosphinites:
Regioselectivity and Structures of Cyclonickellated
Complexes
Loïc P. Mangin and Davit Zargarian*
Département de chimie, Université de Montréal, Montréal (Québec), Canada H3C 3J7
zargarian.davit@umontreal.ca
Cyclonickellation of aryl phosphinites derived from substituted phenols is regioselective: high
sensitivity to sterics favors nickellation at the less hindered CꢀH.