Employing a neutral “PN3P” pincer to access mer-Re(I) tricarbonyl complexes: Autoionization of a halo ligand and the role of an N-R (R = H, Me) substituent

Article abstract of DOI:10.1016/j.poly.2017.08.020

A series of monovalent Re complexes, mer-[Re{κ³-2,6-(Ph₂PNH)₂NC₅H₃}(CO)₃]⁺, cis-[Re{κ³-2,6-(Ph₂PNMe)₂NC₅H₃}(CO)₂Cl], and mer-[Re{κ³-2,6-(Ph₂PNMe)₂NC₅H₃}(CO)₃]⁺ supported by neutral “PN₃P” ligands have been synthesized by addition of pincer ligand to Re(CO)₅X (X = Cl, Br). The products were characterized by multinuclear NMR and single crystal X-ray diffraction studies and showed a dependence on the identity of the halo ligand in starting material and on the substitution pattern of the pincer ligand. The formation of the mer-Re(CO)₃ core geometry and the autoionization of halide ligand in the majority of these species is in marked contrast to the bulk of the literature on the substitution chemistry of Re(I) carbonyl halides.

Full text of DOI:10.1016/j.poly.2017.08.020

Polyhedron xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Employing a neutral ‘‘PN P” pincer to access mer-Re(I) tricarbonyl
3
complexes: Autoionization of a halo ligand and the role of an
N-R (R = H, Me) substituent
⇑
Gyandshwar Kumar Rao, Ilia Korobkov, Bulat Gabidullin, Darrin Richeson
Department of Chemistry and Biomolecular Sciences and the Center for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
a r t i c l e i n f o
a b s t r a c t
3
+
3-2,6-
supported by neutral
X (X = Cl, Br). The products
Article history:
A
series of monovalent Re complexes, mer-[Re{
j
-2,6-(Ph PNH) NC H }(CO) ] , cis-[Re{
j
2
2
5
3
3
Received 29 June 2017
Accepted 18 August 2017
Available online xxxx
3
+
(Ph
2
PNMe)
2
NC
5
H
3
}(CO)
2
Cl], and mer-[Re{
j
-2,6-(Ph
2
PNMe)
2
NC
H
5 3
3
}(CO) ]
‘‘PN
3
P” ligands have been synthesized by addition of pincer ligand to Re(CO)
were characterized by multinuclear NMR and single crystal X-ray diffraction studies and showed a
dependence on the identity of the halo ligand in starting material and on the substitution pattern of
the pincer ligand. The formation of the mer-Re(CO) core geometry and the autoionization of halide
3
ligand in the majority of these species is in marked contrast to the bulk of the literature on the substitu-
tion chemistry of Re(I) carbonyl halides.
5
Keywords:
Rhenium
Pincer
Meridional
PNP
Ó 2017 Elsevier Ltd. All rights reserved.
Autoionization
0
1
. Introduction
The versatile tridentate architectures provided by pincer
ligands derived from the N,N -bis(diphenylphosphino)-2,6-
diaminopyridine (L1) architecture and their application as pincer
ligands [23,24]. We use the notation ‘‘PN
3
P” in order to differenti-
ligands have been recognized as an effective means to modify
and control the properties of metal complexes from across the
periodic table. A common structural motif for this scaffold is orga-
nized around a central aromatic backbone with two Lewis base
donor groups which are linked to the core with different spacers.
Monoanionic versions, with a deprotonated central linker, are
one of the most developed class of pincer ligands. There are also
a variety of neutral arrangements, often built around central pyri-
ate these ligand scaffolds from, for example, di(phosphinomethyl)
pyridine, 2,6-{R
2
PCH
2
}
2
(NC
5
H
3
) (‘‘PNP”), ligands.
0
N,N -bis(diphenylphosphino)-2,6-diaminopyridine (L1) was
first introduced in 1987 with the characterization of neutral car-
bonyl compounds of group 6 and as complexes of divalent MCl
(M = Ni, Pd, Pt) species [25,26]. These researchers also reported
an In(III) compound, [2,6-{Ph PNH} (NC )]InCl displaying a
2
2
2
H
5 3
3
ligand with meridional coordination to yield a pseudooctahedral
complex [27]. The Kirchner group has made major contributions
to this ligand scaffold with variation to both the P-Ph groups and
the N-H moieties [28–34]. In particular, we were interested in
exploring the application of the N–Me ligand L2 as this modifica-
tion would remove a reactive site for deprotonation, introduce a
steric load to the ligand and may provide stronger electron dona-
tion to a coordinated metal center [28–30,35,36]. The literature
3
dine frameworks and providing ‘‘NNN”, ‘‘PNN”, ‘‘PNP” and ‘‘PN P”
donor arrays. The design features and applications of the metal
complexes of these ligands have been reviewed in relation to their
synthesis, their reactivity with small molecule, and catalysis
[
1–13].
Our initial interest in pincer ligands originated with the applica-
tion of bis(imino)pyridine scaffolds (a neutral ‘‘NNN” framework)
to investigate fundamental metal/ligand bonding issues and their
ability to provide the appropriate ligand field and coordination
geometry to prepare monometallic single molecule magnets
3
for this PN P ligand family has been reviewed [5].
[
14–22]. With the idea of extending this chemistry and developing
new directions we initiated a program to include the neutral
⇑
Corresponding author.
E-mail address: darrin@uottawa.ca (D. Richeson).
http://dx.doi.org/10.1016/j.poly.2017.08.020
277-5387/Ó 2017 Elsevier Ltd. All rights reserved.
0
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

2
G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
The chemistry of rhenium(I) carbonyl complexes is dominated
by complexes derived from mono- and disubstitution of Re
CO) X (X = halo ligand). It has been known for nearly 50 years that
the common substitution pattern with Re(CO) X is sequential
replacement of up to two CO groups cis to the halo group thus lead-
ing to compounds with a fac-tri(carbonyl)Re core [37–40]. It is
both interesting and significant that even when potentially triden-
tate ligands were employed, the formation of bidentate coordina-
tion to facial tricarbonyl isomers are the only reported products
of X = Cl, this reaction led to the formation of compound 1 in 75%
yield. Consistent with this formulation as a mer-tricarbonyl species
was the appearance of three CO stretching bands at 1911, 1961,
(
5
ꢀ1
5
2065 cm in the infrared spectrum of the isolated product. The
3
1
1
P{ H} NMR spectrum of 1 exhibited a characteristic singlet at
68.8 ppm indicating equivalent P centers within 1 and this chemi-
cal shift was reminiscent of that observed for the PNP complex of
3
2,6-bis(di-tert-butylphosphinomethyl)-pyridine,
cis-[Re(
j
-2,6-
t
13
1
2 2 2 5 3 2
{ Bu PCH } NC H )(CO) Cl] [51]. The C{ H}NMR of 1 displayed
[
41–43]. One of these reports provides tantalizing spectroscopic
the anticipated two CO signals at d 190.7 and 198.5 ppm. Finally,
2
evidence of the conversion of the bidentate fac-[Re(
(
heating at to 270 °C in the solid state [43]. There is a unique report
for the facial tridentate coordination of 2,6-bis(pyrazolylmethyl)
pyridine (‘‘BPz”, Fig. S1) to yield the ionic species fac-[Re(
(
BPz)X(CO)
The recent reports of structurally and spectroscopically charac-
terized complexes of tridentate ‘‘NNN” ligand frames, such as ter-
pyridine and bis(imino)pyridine, have stimulated an increasing
interest in targeting pincer supported Re(I) carbonyl complexes
j
-terpy)Br
the proton NMR spectra showed a characteristic triplet for the
3
3
CO)
3
] complex into the cis-[Re(
j
-terpy)Br(CO)
2
] with CO loss by
para-CH for the pyridine at d 6.85 ppm ( JHH=8.4 Hz). This spectro-
3
scopic data pointed to the formation of the complex, mer-[Re(
j
-
+
ꢀ
2 2 5 3 3
2,6-{Ph PNH} NC H )(CO) ] Cl (1) formed by loss of two carbonyl
3
j
-BPz)
ligands and autoionization to liberate the chloro ligand.
+
ꢀ
2
CO)
3
] X starting from the more typical bidentate fac-[Re(
j
-
Fortunately, X-ray quality crystals of 1 could be reproducibly
obtained and used to confirm the proposed identity and structural
features for 1 and these results are summarized in the structural
3
] (X = Cl, Br, I) complex [44].
diagram presented in Fig. 1 (Tables S1, S2 and Fig. S2). The struc-
3
ture of 1 confirmed our proposition for the cation as mer-[Re(
j
-
+
2,6-{Ph
pseudo-octahedral Re(I) cationic species supported by the triden-
tate PN P pincer ligand and with the coordination environment
2
PNH}
2
NC
5
H )(CO)
3
3
]
and revealed
a
six-coordinate
[
45–50]. A common feature of these reports is these syntheses
required high temperature reactions in order to get tridentate
coordination.
The applications of pyridine-based ‘‘PNP” pincer ligands with Re
are particularly rare and only recently has the Re(I) chemistry been
3
completed by three meridional CO ligands. There are two different
environments for the CO ligands with one of them laying in the
pseudo-equatorial site of the ligand plane (C(31)–O(2)) and the
other two residing in axial sites and trans to each other. The chlo-
ride counterion, that originated from the Re starting material, was
well-separated from the Re-centered cation.
investigated. Given the strong historical precedent for bidentate
t
ligand coordination, the reaction of Re(CO)
butylphosphinomethyl)pyridine to yield cis-[Re(
PCH NC )(CO) Cl] under rather mild conditions (80 °C/THF)
is noteworthy [51]. The non-innocent nature of this ligand frame
was exploited for reactions with CO [52]. In that case, the dearo-
matized ligand, generated by deprotonation of a CH group, was
able to participate in reversible CO binding and hydrogenation
chemistry. Only three reports for higher oxidation state Re com-
plexes with ‘‘PNP” ligands have appeared. A Re(III) complex of this
ligand family, mer-[Re(
structurally characterized [53] as have three mixed valent, multi-
5
Cl with 2,6-bis(di- -
3
t
j
2
-2,6-{ Bu -
2
}
2
H
5 3
2
Similar reactivity was observed when the bromo analog, Re
(CO)
5
Br, was employed in the analogous reaction scheme with L1
3
2
as shown in Scheme 1 to yield the ionic compound 2, [Re(
2 2 5 3 3
{Ph PNH} NC H )(CO) ] Br . Not surprisingly, compound 2 yielded
j
-2,6-
+
ꢀ
2
2
NMR and IR spectroscopic signatures very similar to 1 which sup-
ported our initial formulation. Again, we obtained crystals of 2
which were analyzed by single crystal X-ray analysis and which
gave definitive confirmation of a nearly identical connectivity of
the cationic Re complex with the non-coordinated anion replace
by bromide (Tables S1, S2 and Fig. S3). Complexes 1 and 2 not only
3
j
2
-2,6-{Cy PCH
2
}
2
NC
5
H )Cl
3 3
]
has been
5+
ple bonded dirhenium complexes in which the [Re
2
]
core has
NC
ligand [54]. Finally, some rhenium(V) oxo complexes bearing
3
one of the Re centers coordinated to a
j
-2,6-{Ph
2
PCH
2
}
2
5
H
3
3
represent the first complexes of the ‘‘PN P” ligand family, they also
provide structures that significantly contrast with reported pincer
t
different bis(R
2
phosphinomethyl)pyridine (R = Cy, Bu, Ph) ligands
species. In particular, the autoionization of the Re-halo group and
+
have been reported and the non-innocent behavior of the ‘‘PNP”
ligands discussed [55].
more specifically the formation of the mer-Re(CO)
3
core.
In terms of ligand variation, we anticipated that the change of
the N-H of the ligand to an N-Me moiety to give L2 would intro-
duce a steric load to the ligand, may provide stronger electron
donation to a coordinated metal center and remove the potentially
reactive NH group [28–30,35,36]. Under the same conditions
Replacement of one of the PR
NEt gives ‘‘PNN” ligand, 2-[(diethylamino)methyl]-6-
(diphenylphosphino)methyl]pyridine. This ligand reacted
smoothly with Re(CO) X at 110 °C in toluene to yield the Re(I) pin-
2
arms of the ‘‘PNP” frame with
2
a
[
5
cer complexes cis-[Re(PNN)(CO)
2
X] (X = Cl, Br) analogs of the ‘‘PNP”
employed for the reaction with L1, the reaction of Re(CO)
5
Cl was
complex [56].
carried out with L2 to yield complex 3 as shown in Scheme 2.
0
31
1
Herein, we report the first Re complexes of N,N -bis
The single P{ H} resonance d = 87.1 ppm suggested a symmetri-
cal coordination environment. The IR spectrum of 3 displayed only
0
(
(
diphenylphosphino)-2,6-aminopyridine
(L1)
and
N,N -bis
ꢀ1
diphenylphosphino)-2,6-(methylamino)pyridine (L2). Of particu-
P frameworks yielded tridentate complexes
under rather mild conditions compared to the recently reported
‘NNN” frameworks. The formation of meridional-tricarbonyl com-
two mCO at 1834 and 1954 cm . These carbonyl carbons appeared
1
3
1
lar note is that the PN
3
in the C{ H} NMR at d 187.8 and 194.5 ppm.
The spectroscopic divergence between 3 and 1 suggested a
structural difference for 3. Colorless crystals of 3 were readily
obtained from dichloromethane and the results of a single crystal
X-ray analysis are displayed in Fig. 2 (Tables S3, S4 and Fig. S4).
The distorted pseudo-octahedral Re coordination environment is
constructed from the meridionally coordinated pincer ligand, two
cis-oriented carbonyl ligands, and a chloro ligand. The chloro group
‘
plexes was dominant and the products of these reactions showed
a dependence on the identity of the ligand N-R group as well as
the halo group bonded to Re starting material.
2
. Results and discussion
3
is cis to the Npy and perpendicular to the PN P coordination plane.
The two CO ligands reside in different environments with one
(C(33)–O(2)) being along the same axis and trans to the chloro
ligand and the other (C(32)–O(1)) residing in an equatorial site.
Complex 3 displays a coordination environment reminiscent of
0
Reaction of soluble N,N -bis(diphenylphosphino)-2,6-aminopy-
ridine ligand (L1) with the Re(I) starting material, Re(CO)
X = Cl, Br), followed the routes outlined in Scheme 1. In the case
5
X
(
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
3
Scheme 1.
indicated some structural similarity for the PN
3
P ligand environ-
ment of 4 with 3. However, from the infrared spectrum for 4, which
displayed four carbonyl stretches at 1854, 1931, 1967, and
ꢀ
1
2
1
063 cm , and from the appearance of four signals at d 185.3,
1
3
86.4, 187.3, and 193.6 ppm in the C NMR, it was clear that 4
was structurally different than 3.
Crystals of 4 were readily obtained from dichloromethane solu-
tions and single crystal X-ray analysis clarified the constitution of
3
this product as the cation/anion pair mer-[Re(
j
-2,6-{Ph
2
PNMe}
2
-
+
ꢀ
NC H )(CO) ] [Re(CO) Br ] as shown in Fig. 3 (Tables S5, S6 and
5 3 3 4 2
Fig. S5). The cation component of 4 was completely analogous to
that observed in 1 and 2 with the replacement of the L1 ligand
I
on the mer-Re (CO)
3
unit with ligand L2. In 4 the PN
3
P ligand is
coordinated in a tridentate mode with a meridional arrangement
of the three carbonyl groups which can be assigned as one equato-
rial site, and two axial carbonyl ligands. The anion was an unantic-
ipated part of the product and consists of a pseudo-octahedral ReI
center with cis-oriented bromo groups and four CO ligands. This
2 2 5 3 3
j PNH} NC H )(CO) ] Cl ,
3-2,6-{Ph
+
ꢀ
Fig. 1. Molecular structure of the cation of [Re(
. For clarity, the ligand carbon atoms are rendered in wire frame and hydrogen
1
anion, which can be independently prepared by reaction of Re
atoms, other than N-H atoms, have been omitted. Selected bond distances (Å) and
angles (°): Re(1)–C(31) 1.921(3), Re(1)–C(32) 1.982(3), Re(1)–C(30) 1.987(3), Re(1)–
N(1) 2.174(2), Re(1)–P(1) 2.3659(8), Re(1)–P(2) 2.3706(8), P(1)–Re(1)–P(2) 157.81
ꢀ
(
CO)
5
Br and Br anion, is well-known in the literature and has been
structurally characterized [57–59]. These structural features and
ꢀ
the Re(CO)
4
Br
2
anion in particular, explain the additional spectro-
(
3), C(31)–Re(1)–N(1) 179.33(12).
scopic features associated with the carbonyl groups.
The yield of this reaction is limited due to the fact that the reac-
the ‘‘PNP” complex cis-[Re(PNP)(CO)
cies cis-[Re(PNN)(CO) X] [56].
Attempts to employ L2 in reaction with Re(CO)
2
Cl] [51] and the ‘‘PNN” spe-
tion stoichiometry was deficient in Re(CO) Br. Attempts were
5
2
made to improve the yield by adjusting the reaction stoichiometry
5
Br did not fol-
to a Re(CO) Br:L2 ratio of 2:1. Unfortunately, this reaction resulted
5
low the route observed with the chloro starting material, rather
these reactions followed the pathways shown in Scheme 3. Reac-
in isolation of a different product, compound 5, which was interro-
gated with NMR and IR spectroscopy. While the ligand-centered
1
31
tion of equal molar ratio of L2 and Re(CO)
5
Br yielded a colorless
spectroscopy of 5 (e.g. H and P NMR) was nearly identical to that
product, compound 4. The 1H and P NMR spectroscopy for 4
looked similar to that obtained for 3. In particular, the appearance
of the NMe signal at d 3.21 ppm as well as the pattern for the aro-
matic signals and the single 31P{ H} NMR resonance at d 87.9 ppm
31
13
of 4, the carbonyl signatures obtained by C NMR and IR spec-
troscopy showed additional signals. In particular, 5 displayed three
1
3
C resonances at 185.8, 187.4, and 193.7 ppm and five mCO peaks in
1
ꢀ1
the IR at 1843, 1921, 1965, 1993, 2063 cm . On the basis of these
Scheme 2.
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

4
G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
2 2 5 3 3
the formulae mer-[Re(j PNR} NC H )(CO)
3-2,6-{Ph ]+ (R = H or
Me). Furthermore, these four products are logically derived from
autoionization of the Re-X function to release halide anions which
either functioned as counterions, in the case of 1 and 2, or appar-
ently reacted further with starting material to yield halide substi-
ꢀ
tuted rhenium carbonyl anions of 4 (e.g. Re(CO)
4
Br
2
) and 5 (e.g.
ꢀ
Re
2
6
(CO) (l-Br)
3
). In these four cases, the reaction proceeds along
a unique path to yield pincer-supported mer-(tricarbonyl)Re(I)
complexes unprecedented in the literature. In contrast to these
reactions, the reaction of L2 and Re(CO)
different and more conventional pathway to yield cis-[Re(
Ph PNMe} NC )(CO) Cl], 3. This complex is the ‘‘PN P” analog
of [Re( -PNP)Cl(CO) ] [51] and [Re( ] [56]. These
5
Cl apparently followed a
3
j
-2,6-
{
2
2
H
5 3
2
3
3
3
j
2
j -PNN)X(CO)
2
three species would appear to have followed a reaction pathway
that is consistent with the large body of literature for substitution
5
reactions of Re(CO) X. Namely, the initial formation of a bidentate
‘
‘fac-LRe(CO) X” via the substitution reactions of two CO ligands cis
3
Fig. 2. Molecular structure of cis-[Re{
clarity, the ligand carbon atoms are rendered in wire frame and hydrogen atoms
have been omitted. Selected bond distances (Å) and angles (°): Re(1)–C(32) 1.932
j
3-2,6-(Ph
2
PNMe)
2
NC
5
H
3
}(CO)
2
Cl], 3. For
to the Br group [37–40]. The third pincer arm would then coordi-
nate through substitution of a third CO that is also cis to the Br
ligand with the resulting complexes exhibiting analogous coordi-
nation environments.
(
2
(
14), Re(1)–C(33) 1.984(18), Re(1)–N(1) 2.166(12), Re(1)–P(1) 2.332(4), Re(1)–P(2)
.365(4), Re(1)–Cl(1) 2.505(4), P(1)–Re(1)–P(2) 159.09(13), C(32)–Re(1)–N(1) 177.0
5).
With the goal of gaining an understanding of the origin of the
different observations for the reactions of Re(CO)
CO)
and the cationic complex mer-Re(
using the B3LYP functional and a mixed basis set of LANL2DZ for
Re, DZVP for Br and TZVP for the remaining atoms. The optimized
structures were an excellent match to the experimental structures
indicating that they represent good models for this chemistry
5
Cl versus Re
(
5
Br with L2, we performed a DFT optimization on complex 3
observations, we anticipated that 5 may be constituted of a cation/
anion pair with an anion possessing Re-carbonyl groups.
We were pleased to obtain crystals of compound 5 that were
successfully analyzed by X-ray crystallography and provided the
structure for the cationic component displayed in Fig. 4 (Tables
3
)(CO)+
3
j
-2,6-{Ph
2
PNMe}
2
NC
5
H
3
S5, S6 and Fig. S6). The cation of 5 displayed the same structural
(
Tables S7–S9). In order to make a thermodynamic comparison
3
constituents,
j
3
-PN P ligation and a meridional orientation for
3
+
ꢀ
2
between mer-[Re(
(
j
-2,6-{Ph
2
PNMe}
2
NC
5
H
3
)(CO)
3
] [Re(CO)
4
X ]
the three carbonyl groups, as observed for 4. This environment pro-
3
X = Cl, Br) and cis-[Re(
j
-2,6-{Ph PNMe}
2
2
NC
5 3
H )(CO)
2
Cl], we opti-
vided a rationalization for three of the m
CO and two of the 1 C sig-
3
mized and carried out frequency calculations on all of the com-
plexes in the following set of balanced equations:
nals arising from the mer-tricarbonyl structure. The unexpected
ꢀ
Re
2
(CO)
6
(
l
-Br)
3
anion provided the source for two of the addi-
m
1
cis-½Reðj3-2; 6-fPh
tional observed
CO and a third 13C{ H} NMR resonance. Once
2
PNMeg
2
NC
5
H
3
ÞðCOÞ
2
Clꢁ þ ReðCOÞ
3
5
Cl !
ð1Þ
3
þ
ꢀ
again, although not expected from this reaction, this anion is
mer-Ref
j
-2; 6-ðPh PNMeÞ NC H gðCOÞ þ ReðCOÞ Cl2
2
2
5
3
4
reported in the literature and has been structurally characterized
ꢀ
[
60,61]. Interestingly, the initial report for the Re
2
6
(CO) (l
-Br)
3
cis-½Reðj3-2; 6-Ph
2
PNMe
2
NC
5
H
3
ÞðCOÞ Brꢁ þ ReðCOÞ Br !
2
5
anion involved the reaction of Re(CO)
5
Br and toluene to yield an
þ
ꢀ
ð2Þ
mer-Rej3-2; 6-ðPh
PNMeÞ
NC
H
3
ðCOÞ
þ ReðCOÞ
Br
6
+
ꢀ
2
2
5
3
4
2
ionic species, [(
g
-(toluene)Re(CO)
3
] Re
2
(CO)
6
(l-Br)
3
.
Considering the five different pincer products obtained from the
reactions of Re(CO) X (X = Cl, Br) and L1 or L2, it seems that the
common route for this reaction is represented by compounds 1,
, 4, and 5. The four cations obtained in these reactions displayed
These DFT optimizations were carried out using the B3LYP func-
tional and the same mixed basis set (LANL2DZ, DZVP and TZVP). In
addition, we employed the PCM formalism within Gaussian 09
using tetrahydrofuran as the solvent. The goal here was to try to
5
2
Scheme 3.
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
5
In conclusion, we have successfully applied two ‘‘PN
3
P” ligands
to support five new Re(I) carbonyl species thus providing the first
application of this ligand family in Re chemistry. The dominant
3
products of this chemistry are pincer ligated cations, mer-Re(
2
j
-
+
2 2 5 3 3
,6-{Ph PNR} NC H }(CO) , that result from an autoionization of
the Re-X (X = Cl, Br) of the starting material. The reaction pathway
remains a part of our ongoing investigations; however, it seems
clear that this substitution does not follow the conventional route
of preferential substitution of ligands cis to the Re-X group that is
dominant in the literature. The influence of both the identity of the
5
halo ligand in the Re(CO X (X = Cl, Br) starting material and the NR
substituent is part of our continuing examination of this chemistry.
3
. Experimental
3.1. General procedures
3-2,6-{Ph
2
-
Reagents were purchased from Strem Chemicals and used as
received. Analytical grade solvents were purchased from Aldrich
and used as received.
Fig. 3. One of the two cations of the molecular structure for mer-[Re(
j
PNMe} NC )(CO) ][Re(CO) Br ] (4). For clarity, the ligand carbon atoms are
rendered in wire frame and the anion and hydrogen atoms have been omitted.
Selected bond distances (Å) and angles (°): Re(2)–C(67) 1.925(8), Re(2)–C(66) 1.991
2
5
H
3
3
4
2
(
10), Re(2)–C(68) 1.997(9), Re(2)–N(4) 2.169(6), Re(2)–P(4) 2.3396(17), Re(2)–P(3)
2
.3608(18), C(67)–Re(2)–N(4) 176.5(3), P(4)–Re(2)–P(3) 158.99(7).
3.2. X-ray crystallography
Data collection results for compounds 1–5 represent the best
data sets obtained in several trials for each sample. The crystals
were mounted on thin glass fibers using paraffin oil. Prior to data
collection crystals were cooled to 200(2) °K. Data were collected
on a Bruker AXS SMART single crystal diffractometer equipped
with a sealed Mo tube source (wavelength 0.71073 Å) APEX II
CCD detector. Raw data collection and processing were performed
with APEX II software package from BRUKER AXS [63].
Diffraction data for samples 1, 3, and 5 were collected with a
sequence of 0.3°
x scans at 0, 120, and 240° in u. Due to lower unit
cell symmetry in order to ensure adequate data redundancy,
diffraction data for 2 and 4 were collected with a sequence of
0
.3°
x
scans at 0, 90, 180 and 270° in u. Initial unit cell parameters
scan each col-
were determined from 60 data frames with 0.3°
x
lected at the different sections of the Ewald sphere. Semi-empirical
absorption corrections based on equivalent reflections were
applied [64]. Systematic absences in the diffraction data-set and
unit-cell parameters were consistent with triclinic P-1 (№2) for
2 2 5 3 3
j PNMe} NC H )(CO) ]
3-2,6-{Ph
Fig. 4. Structure of the cation portion of mer-[Re(
Re (CO) -Br) ] (5). For clarity the ligand carbon atoms are rendered in wire
frame representation and anion and hydrogen atoms are omitted. Selected bond
[
2
6
(l
3
compounds 2 and 4, monoclinic P2
and 5, monoclinic P2 /n (№14, alternative settings) for compound
. Solutions in the centrosymmetric space groups for all com-
1
/c (№14) for compounds 3
1
distances (Å) and angles (°): Re(1)–C(33) 1.928(6), Re(1)–C(34) 1.979(6), Re(1)–C
1
(
32) 1.990(7), Re(1)–N(1) 2.171(4), Re(1)–P(2) 2.3511(15), Re(1)–P(1) 2.3677(16), C
pounds yielded chemically reasonable and computationally stable
results of refinement. The structures were solved by direct meth-
ods, completed with difference Fourier synthesis, and refined with
(
33)–Re(1)–N(1) 178.0(2), P(2)–Re(1)–P(1) 157.44(6).
2
understand a potential thermodynamic origin for the observation
of divergent reactions of L2 with Re(CO) X (X = Cl, Br). It is impor-
tant to realize that like the two bromo anions observed with 4 (e.g.
Re(CO)
Re (CO)
full-matrix least-squares procedures based on F .
Structural model for 2 contains one molecule of positively
charged Re complex, one bromine counter-anion and one crystal-
lization water molecule. All fragments are located in the general
positions.
5
ꢀ
ꢀ
ꢀ
2
4
Br
2
) and 5 (e.g. Re
2
(CO)
6
(l
-Br)
3
), both Re(CO)
4
Cl
[58] and
ꢀ
2
6
(
l-Cl)
3
[60,62] are known in the literature and the dirhe-
nium anion has been structurally characterized. Table 1 provides
the computed free energies for the compounds in Eqs. (1) and (2).
Structure of 4 reveals two Re containing target molecules and
0
0
two ‘‘ReBr counter-anions per unit cell. Large residual electron
2
Both Eqs. (1) and (2) gave small negative
D
G values of
density peaks were refined as partially occupied (37%) methanol
molecule and three water solvent molecules (54%, 35%, 46%) based
on the synthesis information. Occupancy of the solvent molecules
were allowed to refine on the initial stages of the refinement but
were fixed for the final refinement cycles to obtain constant unit
cell atomic content.
ꢀ
0.00195 Hartree (i.e. ꢀ1.22176 kcal/mol) for Eq. (1) and
ꢀ
0.00587 Hartree (i.e. ꢀ3.68348 kcal/mol) for Eq. (2). It would thus
appear that formation of the cation/anion pair, as was observed in
the case of formation of compound 4, are slightly favored thermo-
dynamically for both the chloro and bromo species. Since these
computed values for
D
G are quite small, it is possible that the
For compound 5 the structure consisted of one Re target com-
products are in fact not favored for the chloro complex or that
kinetic factors have played a role in the observed products. Inter-
2 3
pound molecule and one ‘‘Re Br ” counter anion. Both structural
fragments are located in the general positions of the unit cell.
The sample for 3 was contaminated by considerable amount of
microcrystalline material. Structural data set was showing visible
estingly, although reported, there are no reported structurally
ꢀ
characterized Re(CO)
4
Cl
2
compounds.
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

6
G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
Table 1
Tabulated values for the sum of electronic and thermal free energies (Hartree) for the compounds in Eqs. (1) and (2). Optimizations were carried out using the default THF solvent
parameters with the PCM model in Gaussian 09.
P)(CO)+
Re(CO)
X
ꢀ
Compound
Re(PN
3
P)(CO)
2
X
Re(CO)
5
X
Re(PN
3
3
4
X = Cl
X = Br
ꢀ2812.026646
ꢀ4925.495978
ꢀ1106.371209
ꢀ3219.845417
ꢀ2464.985970
ꢀ2464.985970
ꢀ1453.413902
ꢀ5680.361295
amount of the diffraction intensities that could not be attributed to
the proposed space group. The data set was tried for non-merohe-
dral and pseudo-merohedral twinning. However no reasonable
transformation matrixes were discovered. The obtained data set
was integrated using only one unit cell and the structure was
solved for non-twinning model. Due to unaccounted reflections
intensities it was necessary to apply thermal constrains (SIMU,
RIGU) of the anisotropic refinement stages to ensure acceptable
values of thermal motion parameters for non-hydrogen atoms.
Structural model for 3 consists of one molecule of Re compound
located in the general position of the unit cell.
Structural solution for 1 compound reveals one molecule of Re
target species and one chlorine counter-anion. Both fragments
are located in the general positions of the unit cell. It was
attempted to interpret residual electron density peaks with the
values of 0.99 e as a possible crystallization solvent. However, such
attempts were unsuccessful without considerable amount of geo-
metrical restrains, therefore the solvent fragments were omitted
from the final refinement of the structural model.
J = 16.0 Hz), 128.5 (t, J = 6.6 Hz), 121.1, 131.3 (d, J = 21 Hz), 139.3,
139.8, 157.5 (dd, J = 2 & 21.0 Hz). P{ H} (121 MHz, CDCl , 25 °C,
3
3
1
1
3
H PO
3
): d (ppm): 25.9.
0
4
.2. Synthesis of N,N -dimethyl-2,6-diaminopyridine
2
,6-Dibromopyridine (10.0 g, 42.2 mmol) was stirred with
4
0 mL methylamine (40% solution in water) at 200 °C for 20 h in
a sealed tube. The solution was cooled and mixed with 100 mL
water. The aqueous layer was then extracted with chloroform
twice. The chloroform layer was dried over sodium sulphate. The
solvent was evaporated off under reduced pressure on a rotary
evaporator to get dark red colored compound which was further
purified by column chromatography using a mixture of ethylac-
etate and hexane followed by dichloromethane. Yellow solid.
1
Yield: 4.91 g (85%). NMR: H (400 MHz, CDCl
3
, 25 °C, TMS): d
(
ppm): 2.85 (d, 6H, Me, J = 5.2 Hz), 4.40 (bs, 2H, NH), 5.74 (d, 2H,
J = 7.9 Hz), 7.29 (t, 1H, J = 7.9 Hz) [67].
All non-hydrogen atoms in structural models of all compounds
were refined with the full set of anisotropic thermal motion
parameters. For all the compounds hydrogen atoms positions were
initially assigned based on geometry of bearing non-hydrogen
atoms. After initial placement all hydrogen atoms were treated
as idealized contributions during the refinement. All scattering fac-
tors are contained in several versions of the SHELXTL program library,
with the latest version used being v.6.12 [65].
0
0
4
.3. Synthesis of N,N -bis(diphenylphosphino)-N,N -methyl-2,6-
diaminopyridine (L2)
The ligand was synthesized by the slight modification of known
procedure [28]. Butyllithium (2.5 M in hexane, 8.0 mmol, 3.2 mL)
was dropwise added to a toluene (100 mL) solution of N,N -
dimethyl-2,6-diaminopyridine (1.0 g, 7.3 mmol) cooled on ice-salt
bath. The mixture was stirred at room temperature for 2 h. It was
then cooled to ꢀ78 °C using dry ice-acetone bath and 1.3 mL
(7.3 mmol) of chlorodiphenylphosphine was added. The resulting
reaction mixture was stirred for 2 h at room temperature and
refluxed for 18 h. The solution was cool to room temperature and
0
4
. Computational details
Density functional theory (DFT) calculations have been per-
formed using the Gaussian 09 package [66]. The structures of all
species were optimized using the B3LYP exchange–correlation
functional with the LanL2DZ basis set for Re, the DZVP basis set
for Br and the all-electron TZVP basis set for C H N P Cl. Computa-
tions were performed on complexes solvated with THF using the
integral equation formalism variant of PCM, with the default
parameters for tetrahydrofuran.
2
filtered twice with a frit containing Celite under N atmosphere.
The above procedure was repeated with the yellow solution. The
resulting reaction mixture was filtered and solvent was removed
under vacuum yielding yellow oil. This oil was refluxed in acetoni-
trile for 10 min which on cooling at room temperature results in
the white precipitate. Acetonitrile was decant and compound
1
was dried under vacuum. Yield: 1.70 g (46%). NMR: H (300 MHz,
CDCl
J = 7.9 Hz), 7.32–7.42 (m, 21H). P{ H} (121 MHz, CDCl
PO ): d (ppm): 49.5.
3
, 25 °C, TMS): d (ppm): 2.85–2.86 (m, 6H, CH
3
), 6.82 (d, 2H,
3
1
1
3
, 25 °C,
0
4
.1. Synthesis of N,N -bis(diphenylphosphino)-2,6-diaminopyridine
H
3
3
(L1)
+
ꢀ
ꢀ
4
.4. [Re{2,6-(Ph
2
PNH)
2 5 3 3
NC H }(CO) ] Br /Cl 1 and 2
The ligand was synthesized by the slight modification of known
procedure [25,26]. 2,6-Diaminopyridine (2.18 g, 20 mmol), dis-
solved in 40 mL dry THF, was cooled on ice-salt bath under N
atmosphere. A solution of chlorodiphenylphosphine (9.24 mL,
Ligand
(0.187 g,
0.393 mmol),
Re(CO)
5
Br
(0.159 mg,
2
0
.393 mmol)/Re(CO) Cl (0.141 mg, 0.393 mmol) and a stir bar were
added in a 100 mL round bottom flask containing 20 mL dry THF in
glove box. The solution was taken out and refluxed for 4 h under N
5
4
4
2 mmol) in 10 mL THF was added. Triethylamine (44 mmol,
.5 g) was dropwise added to the reaction mixture. The resulting
2
atmosphere. Solvent was concentrated to 5 mL and 50 mL hexane
was added to precipitate a solid which was filtered and dried under
vacuum give complexes. Crystallization was carried out in dichlor-
omethane/hexane mixtures.
reaction mixture was stirred for 2 h at room temperature and
refluxed for 16 h. The solution was cooled to room temperature
and filtered twice with a frit containing Celite under N atmo-
2
sphere. The solvent of resulting reaction mixture was removed
under vacuum which was further washed with dry hexane
1
(
3 ꢂ 50 mL) yielding colorless solid. Yield: 7.25 g (76%). NMR:
H
4.5. [Re{2,6-(Ph
2 2 5 3 3
PNH) NC H }(CO) ]Cl (1)
(
300 MHz, CDCl 25 °C, TMS):
3
,
d
(ppm): 5.02 (d, 2H, NH,
J = 8.3 Hz), 6.50 (d, 2H, J = 8.3 Hz), 7.33–7.38 (m, 12H), 7.45–7.49
Yield (0.218 g, 75.4%); 1H NMR (400 MHz, CD
(t, 1H, J = 8.4 Hz), 7.25–7.38 (m, 14H), 7.86–7.98 (m, 8H), 11.4
2
Cl
2
, 25 °C): 6.85
1
3
1
(
m, 9H).
3
C{ H} NMR (75 MHz, CDCl , 25 °C): d = 99.0 (t,
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
7
1
5; Yield 0.140 g (45%); 1H NMR (400 MHz, CDCl
d = 3.19 (t, J = 2.8 Hz, 6H, CH
(m, 20H), 8.13 (t, J = 8.3 Hz, 1H). C{ H} NMR (100 MHz, CDCl
25 °C): d = 37.8 (s, CH ), 103.0 (t, J = 3.3 Hz), 129.6 (t, J = 5.5 Hz),
130.5 (t, J = 6.7 Hz), 132.1 (t, J = 28.5 Hz), 132.1, 143.5, 161.6 (t,
(
(
s, 2H). 13C{ H} NMR (100 MHz, DMSO, 25 °C): 103.8, 131.7, 133.5
3
, 25 °C):
), 6.93 (d, J = 8.0 Hz, 2H), 7.51–7.55
t, J = 6.3 Hz), 134.3, 139.4 (t, J = 29.6 Hz), 143.7, 164.6 (t,
3
31
1
13
1
J = 7.5 Hz), 190.7, 198.5. P{ H} NMR (161 MHz, CD
8.8. HR-MS (CH
CN): [MꢀCl] m/z 746.0909; calcd value for C32
Re 746.0901 (d 1.1). Infrared data (cm ): 589, 609,
33, 690, 701, 740, 798, 853, 895, 998, 1051, 1102, 1171, 1187,
219, 1305, 1335, 1397, 1469, 1575, 1613, 1911, 1961, 2065,
725, 2766, 2813, 2988.
2
Cl
2
, 25 °C):
3
,
6
3
-
3
ꢀ1
25 3 3 2
H N O P
31
1
6
1
2
J = 9.3 Hz), 185.8, 187.4 (t, J = 8.9 Hz), 193.7.
(162 MHz, CDCl , 25 °C): d = 88.6. HR-MS (CH CN): [MꢀRe(CO)
Br ] m/z 774.1171; calcd value for C34 Re 774.1214 (d
5.5). Infrared data (cm ): 586, 612, 637, 650, 693, 741, 778,
P{ H} NMR
3
3
6
-
3
29 3 3 2
H N O P
ꢀ1
ꢀ
8
1
67, 951, 996, 1050, 1098, 1142, 1181, 1252, 1292, 1350, 1397,
422, 1434, 1459, 1575, 1601, 1843, 1921, 1965, 1993, 2063, 3052.
4
2 2 5 3 3
.6. [Re{2,6-(Ph PNH) NC H }(CO) ]Br (2)
White powder. Yield 0.194 g (66.9%); 1H NMR (400 MHz, CD
2
, 25 °C): 6.92 (t, 1H, J = 7.8 Hz), 7.30–7.40 (m, 12H), 7.41 (d,
-
2
Acknowledgement
Cl
2
(
13
1
H, J = 7.88 Hz), 7.89–7.93 (m, 8H), 10.6 (s, 2H, NH). C{ H} NMR
100 MHz, DMSO, 25 °C): d = 101.3, 128.8 (t, J = 23.3Hz), 130.8 (t,
J = 29.6Hz), 131.6, 136.3 (t, J = 29.9 Hz), 140.1, 161.7 (t, J = 9.5 Hz),
We thank the Natural Sciences and Engineering Research Coun-
cil of Canada (NSERC) for funding.
3
1
1
1
87.9, 195.2. P{ H} NMR (161 MHz, CD
MS (CH
CN): [MꢀBr] m/z 746.0934; calcd value for C32
Re 746.0901 (d 4.4). Infrared data (cm ): 589, 609, 633, 690, 701,
2 2
Cl , 25 °C): d = 68.0. HR-
H
25
N
3
O P
3 2
-
Appendix A. Supplementary data
3
ꢀ1
7
1
40, 798, 853, 895, 998, 1051, 1102, 1171, 1187, 1219, 1305, 1335,
397, 1436, 1469, 1575, 1613, 1912, 1961, 2065, 2718, 2889, 2994.
CCDC 1558915-1558919 contains the supplementary crystallo-
graphic data for 1–5. These data can be obtained free of charge via
http://dx.doi.org/10.1016/j.poly.2017.08.020, or from the Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk. Supplementary data associated with this article
can be found, in the online version, at http://dx.doi.org/10.1016/j.
poly.2017.08.020.
2 2 5 3 2
4.7. Synthesis of [Re{2,6-(Ph PNMe) NC H }(CO) Cl] (3)
A solution of ligand L2 (0.101 g, 0.2 mmol) was made in 15 mL
of tetrahydrofuran. Re(CO) Cl (0.072 g, 0.2 mmol) was added via
5
stirring to the THF solution of ligand in glove box. The mixture
was further stirred for 2 h at 100 °C. The colorless solution was
cooled and the volume was reduced to ꢃ5 mL under vacuum. Addi-
tion of excess hexane resulted in the formation of a colorless pow-
der. Single crystals of 3 were grown from a dichloromethane/
References
[
1] H.A. Younus, W. Su, N. Ahmad, S. Chen, F. Verpoort, Adv. Synth. Catal. 357
(2015) 283.
[
2] D. Milstein, Philos. Trans. R. Soc. A 373 (2015) 20140189.
hexane solution.
1
[3] C. Gunanathan, D. Milstein, Chem. Rev. 114 (2014) 12024.
4] D.M. Roddick, D. Zargarian, Inorg. Chim. Acta 422 (2014) 251.
3
; Yield 0.101 g (65%); H NMR (300 MHz, DMSO, 25 °C):
[
d = 3.14 (s, 6H, CH
8
d = 37.3 (s, CH ), 102.5, 129.5 (t, J = 5.4 Hz), 130.5 (t, J = 6.7 Hz),
3
3
), 6.87 (d, J = 8.4 Hz, 2 H), 7.61–7.70 (m, 20H),
.09 (t, J = 8.4 Hz, 1H). C{ H} NMR (75 MHz, DMSO, 25 °C):
[5] H. Li, B. Zheng, K.-W. Huang, Coord. Chem. Rev. 293–294 (2015) 116.
[6] C. Gunanathan, D. Milstein, Science 341 (2013) 1229712.
13
1
[
7] J. Choi, A.H.R. MacArthur, M. Brookhart, A.S. Goldman, Chem. Rev. 111 (2011)
761.
8] N. Selander, K.J. Szabó, Chem. Rev. 111 (2011) 2048.
1
1
32, 132.1 (t, J = 28.6 Hz), 142.2, 164.5 (t, J = 9.4 Hz), 187.8, (t,
[
3
1
1
J = 10.6 Hz), 194.5.
P{ H} NMR (121 MHz, DMSO, 25 °C):
CN): [MꢀCl + CH CN] m/z 787.1495; calcd
Re 787.1530 (d ꢀ4.5). Infrared data
cm ): 573, 598, 611, 658, 692, 714, 738, 787, 866, 950, 999,
[9] S. Schneider, J. Meiners, B. Askevold, Eur. J. Inorg. Chem. (2012) 412.
10] J.I. Van Der Vlugt, J.N.H. Reek, Angew. Chem., Int. Ed. 48 (2009) 8832.
11] L.C. Liang, Coord. Chem. Rev. 250 (2006) 1152.
[
[
[
d = 87.1. HR-MS (CH
value for
(
3
3
35 32 4 2 2
C H N O P
12] M.E. van der Boom, D. Milstein, Chem. Rev. 103 (2003) 1759.
ꢀ1
[13] M. Albrecht, M.M. Lindner, Dalton Trans. 40 (2011) 8733.
[
14] T. Jurca, L.K. Hiscock, I. Korobkov, C.N. Rowley, D.S. Richeson, Dalton Trans. 43
2014) 690.
1
1
074, 1103, 1141, 1177, 1249, 1295, 1350, 1427, 1459, 1474,
565, 1593, 1834, 1954, 3089.
(
[
[
15] T. Jurca, I. Korobkov, S.I. Gorelsky, D.S. Richeson, Inorg. Chem. 52 (2013) 5749.
16] T. Jurca, J. Lummiss, T.J. Burchell, S.I. Gorelsky, D.S. Richeson, J. Am. Chem. Soc.
1
31 (2009) 4608.
17] T. Jurca, S. Ouanounou, S.I. Gorelsky, I. Korobkov, D.S. Richeson, Dalton Trans.
1 (2012) 4765.
18] T. Jurca, I. Korobkov, G.P.A. Yap, S.I. Gorelsky, D.S. Richeson, Inorg. Chem. 49
2010) 10635.
19] T. Jurca, S.I. Gorelsky, I. Korobkov, D.S. Richeson, Dalton Trans. 40 (2011) 4394.
4
.8. [RePNP(CO)
3
]ꢄRe(CO)
4
Br
2
(4), [RePNP(CO)
3
]ꢄRe
2 6 3
(CO) Br (5)
[
[
[
4
A solution of ligand L2 (0.101 g, 0.2 mmol) was made in 15 mL
(
of tetrahydrofuran Re(CO) Br (0.0.081 g, 0.2 mmol in case of
/0.162 g, 0.4 mmol in case of 5) was added via stirring to the
5
4
[20] T. Jurca, A. Farghal, P. Lin, I. Korobkov, M. Murugesu, D.S. Richeson, J. Am.
Chem. Soc. 133 (2011) 15814.
THF solution of ligand in glove box. The mixture was further stirred
for 2 h at 100 °C. The colorless solution was cooled and the volume
was reduced to ꢃ5 mL under vacuum. Addition of excess hexane
led to formation of colorless powders. Single crystals of 4 and 5
[
21] T. Jurca, O. Ramadan, I. Korobkov, D.S. Richeson, J. Organomet. Chem. 802
2016) 27.
(
[22] T. Jurca, S. Ouanounou, W. Shih, T. Ong, G.P.A. Yap, I. Korobkov, S. Gorelsky, D.
Richeson, Dalton Trans. 45 (2016) 14327.
23] G.K. Rao, W. Pell, I. Korobkov, D. Richeson, Chem. Commun. 52 (2016) 8010.
24] G.K. Rao, S.I. Gorelsky, I. Korobkov, D. Richeson, Dalton Trans. 44 (2015) 19153.
[25] W. Schirmer, U. Florke, H.-J. Haupt, Z. Anorg. Allg. Chem. 545 (1987) 83.
26] W. Schirmer, U. Florke, H.-J. Haupt, Z. Anorg. Allg. Chem. 574 (1989) 239.
[27] U. Florke, H.-J. Haupt, Zeitschrift fur Crystallogr. 196 (1991) 299.
28] S.R.M.M. De Aguiar, B. Stöger, E. Pittenauer, M. Puchberger, G. Allmaier, L.F.
Veiros, K. Kirchner, J. Organomet. Chem. 760 (2014) 74.
[29] B. Bichler, C. Holzhacker, B. Stöger, M. Puchberger, L.F. Veiros, K. Kirchner,
Organometallics 32 (2013) 4114.
30] Ö. Öztopcu, C. Holzhacker, M. Puchberger, M. Weil, K. Mereiter, L.F. Veiros, K.
Kirchner, Organometallics 32 (2013) 3042.
[31] D. Benito-Garagorri, L.G. Alves, L.F. Veiros, C.M. Standfest-Hauser, S. Tanaka, K.
Mereiter, K. Kirchner, Organometallics 29 (2010) 4932.
32] D. Benito-Garagorri, L.G. Alves, M. Puchberger, K. Mereiter, L.F. Veiros, M.J.
Calhorda, M.D. Carvalho, L.P. Ferreira, M. Godinho, K. Kirchner,
Organometallics 28 (2009) 6902.
[
[
were grown from dichloromethane/hexane solutions.
1
4; Yield 0.098 g (40%); H NMR (400 MHz, CDCl
3
, 25 °C):
[
d = 3.21 (t, J = 2.6 Hz, 6 H, CH
3
m, 20H), 8.13 (t, J = 8.3 Hz, 1H). C{ H} NMR (100 MHz, CDCl ,
3
), 6.86 (d, J = 8.4 Hz, 2H), 7.58–7.60
13
1
(
2
1
[
5 °C): d = 37.7 (s, CH
30.5 (t, J = 6.6 Hz), 132.0 (t, J = 28.5 Hz), 132.1, 143.2, 161.6 (t,
3
), 102.7 (t, J = 3.3 Hz), 129.6 (t, J = 5.5 Hz),
31
1
J = 9.3 Hz), 185.3, 186.4, 187.3 (t, J = 9.1 Hz), 193.6. P{ H} NMR
162 MHz, CDCl , 25 °C): d = 87.9. HR-MS (CH CN): [MꢀRe(CO)
Br ] m/z 774.1222; calcd value for C34 Re 774.1214 (d
[
(
3
3
4
-
2
H
29
N
3
O
3
P
2
ꢀ1
1
9
1
.0). Infrared data (cm ): 583, 611, 638, 693, 739, 779, 866, 950,
97, 1050, 1073, 1097, 1141, 1178, 1252, 1297, 1355, 1397,
434, 1463, 1575, 1596, 1854, 1931, 1967, 2063, 2972.
[
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020

8
G.K. Rao et al. / Polyhedron xxx (2017) xxx–xxx
[
[
[
[
33] D. Benito-Garagorri, J. Wiedermann, M. Pollak, K. Mereiter, K. Kirchner, [50] P. Bulsink, A. Alghamdi, P. Joshi, I. Korobkov, T. Woo, D. Richeson, Dalton Trans.
Organometallics 26 (2007) 217.
2 (2016) 8885.
34] D. Benito-Garagorri, E. Becker, J. Wiedermann, W. Lackner, M. Pollak, K.
Mereiter, J. Kisala, K. Kirchner, Organometallics 25 (2006) 1900.
35] S. Qu, Y. Dang, C. Song, M. Wen, K.W. Huang, Z.X. Wang, J. Am. Chem. Soc. 136
[51] M. Vogt, A. Nerush, M.A. Iron, G. Leitus, Y. Diskin-Posner, L.J.W. Shimon, Y. Ben-
David, D. Milstein, J. Am. Chem. Soc. 135 (2013) 17004.
[52] M. Vogt, A. Nerush, Y. Diskin-Posner, Y. Ben-David, D. Milstein, Chem. Sci. 5
(2014) 2043.
[53] H.F. Lang, P.E. Fanwick, R.A. Walton, Inorg. Chim. Acta 329 (2002) 1.
[54] S.-M. Kuang, P.E. Fanwick, R.A. Walton, Inorg. Chem. 41 (2002) 405.
[55] T.J. Korstanje, M. Lutz, J.T.B.H. Jastrzebski, R.J.M. Klein Gebbink,
Organometallics 33 (2014) 2201.
(
2014) 4974.
36] L.P. He, T. Chen, D.X. Xue, M. Eddaoudi, K.W. Huang, J. Organomet. Chem. 700
2012) 202.
(
[37] M.S. Wrighton, D.L. Morse, L. Pdungsap, J. Am. Chem. Soc. 97 (1975) 2073.
[38] F. Zingales, U. Sartorelli, F. Canziani, M. Raveglia, Inorg. Chem. 6 (1967) 154.
[39] F. Zingales, U. Sartorelli, A. Trovati, Inorg. Chem. 6 (1967) 1246.
[40] J.D. Atwood, T.L. Brown, J. Am. Chem. Soc. 98 (1976) 3160.
[
[56] K.R. Pichaandi, M.G. Mazzotta, J.S. Harwood, P.E. Fanwick, M.M. Abu-Omar,
Organometallics 33 (2014) 1672.
41] K.G. Orrell, A.G. Osborne, V. Sik, M.W. da Silva, M.B. Hursthouse, D.E. Hibbs, K.
M.A. Malik, N.G. Vassilev, J. Organomet. Chem. 538 (1997) 171.
[57] E.W. Abel, I.S. Butler, M.C. Ganorkar, C.R. Jenkins, M.H.B. Stiddard, Inorg. Chem.
5 (1966) 25.
[
[
[
[
42] J. Granifo, S.J. Bird, K.G. Orrell, A.G. Osborne, V. Šik, Inorg. Chim. Acta 295
[58] I. Ahmed, A.M. Bond, R. Colton, M. Jurcevic, J.C. Traeger, J.N. Walter, J.
Organomet. Chem. 447 (1993) 59.
(
1999) 56.
43] E.W. Abel, V.S. Dimitrov, N.J. Long, K.G. Orrell, A.G. Osborne, M.P.M.B.
Hursthousec, M.A. Mazid, J. Chem. Soc. Dalton. Trans. (1993) 597–603.
44] K.G. Orrell, A.G. Osborne, M.W. da Silva, M.B. Hursthouse, S.J. Coles, Polyhedron
[59] M. Hojjatief, S. Muralidharan, H. Freiser, Tetrahedron 45 (1989) 1611.
[60] R.L. Davis, N.C. Baenziger, Inorg. Nucl. Chem. Lett. 13 (1977) 475.
[61] B.J. Brisdon, D.A. Edwards, J.W. White, J. Organomet. Chem. 161 (1978) 233.
[62] C.P. Hrung, M. Tsutsui, D.L. Cullen, E.F. Meyer Jr., C.N. Morimoto, J. Am. Chem.
Soc. 100 (1978) 6068.
[63] APEX Software Suite v. 2012; Bruker AXS: Madison, WI, 2005.
[64] R.H. Blessing, Acta Crystallogr., Sect. A (1995) 33.
[65] G.M. Sheldrick, Acta Crystallogr., Sect. A (2008) 112.
[66] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, G.A. Petersson, H. Nakatsuji, et al., Gaussian 09,
Revision A.02. Gaussian Inc.: Wallingford, CT 2016.
1
6 (1997) 3003.
45] B. Laramée-Milette, N. Zaccheroni, F. Palomba, G.S. Hanan, Chem. Eur. J. (2017)
370.
6
[
[
[
46] B. Laramée-Milette, C. Lachance-Brais, G.S. Hanan, Dalton Trans. 44 (2015) 41.
47] D.R. Black, S.E. Hightower, Inorg. Chem. Commun. 24 (2012) 16.
48] B.A. Frenzel, J.E. Schumaker, D.R. Black, S.E. Hightower, Dalton Trans. 42 (2013)
1
2440.
[
49] T. Jurca, W.-C. Chen, S. Michel, I. Korobkov, T.-G. Ong, D.S. Richeson, Chem. Eur.
J. 19 (2013) 4278.
[67] I. Okamoto, M. Terashima, H. Masu, M. Nabeta, K. Ono, N. Morita, K. Katagiri, I.
Azumaya, O. Tamura, Tetrahedron 67 (2011) 8536.
Please cite this article in press as: G.K. Rao et al., Polyhedron (2017), http://dx.doi.org/10.1016/j.poly.2017.08.020