OCO and NCO chelated derivatives of heavier group 15 elements. Study on possibility of cyclization reaction via intramolecular ether bond cleavage

Article abstract of DOI:10.1039/c1dt10234f

A set of four pincer ligands, either the OCO type ligands L^1-3 [2,6-(ROCH₂)₂C₆H₃]^-, where R = Me (L¹), mesityl (L²), t-Bu (L³) or novel NCO ligand [2-(Me

Full text of DOI:10.1039/c1dt10234f

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Pincers and other hemilabile ligands
Guest Editors Dr Bert Klein Gebbink and Gerard van Koten
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PAPER
OCO and NCO chelated derivatives of heavier group 15 elements. Study on
possibility of cyclization reaction via intramolecular ether bond cleavage†
Libor Dosta´l,*a Roman Jambor,a Alesˇ Ru˚zˇicˇka,a Robert Jira´sko,b Jaroslav Holecˇeka and Frank De Proftc
Received 11th February 2011, Accepted 10th March 2011
DOI: 10.1039/c1dt10234f
A set of four pincer ligands, either the OCO type ligands L1–3 [2,6-(ROCH2)2C6H3]-, where R = Me (L1),
mesityl (L2), t-Bu (L3) or novel NCO ligand [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]- was studied. The
reaction of L4Li with PCl3 resulted in isolation of [2-(OCH2)-6-(Me2NCH2)C6H3]PCl (1) as a result of
intramolecular ether bond cleavage and elimination of t-BuCl. The conversion between the
organolithium compounds L1,2,4Li and AsCl3 led to the desired chlorides, i.e. (L1)2AsCl (2), L2AsCl2
(3), L4AsCl2 (5), but an analogous reaction using the L3Li compound gave [2-(OCH2)-6-
(t-BuOCH2)C6H3]AsCl (4) as a result of intramolecular cyclization. The organoantimony
chloride L3SbCl2 was shown to undergo very slow cyclization in CDCl3 again via elimination of t-BuCl
giving [2-(OCH2)-6-(t-BuOCH2)C6H3]SbCl (6) and it was demonstrated that this reaction may be
accelerated by preparation of L3Sb(Cl)(OTf) (7) with more Lewis acidic central atom. On the contrary,
both antimony derivatives of the NCO ligand L4, not only the chloride L4SbCl2 (8) but also the ionic
pair containing highly Lewis acidic cation [L4SbCl]+[CB11H12]- (9), are stable without any indication for
etheral bond cleavage. The situation is rather similar in the case of organobismuth derivatives of L4,
which allowed isolation of compounds L4BiCl2 (10), L4Bi(Cl)(OTf) (11) and [L4BiCl]+[CB11H12]- (12).
All studied compounds were characterized by the help of 1H and 13C NMR spectroscopy, ESI mass
spectrometry, elemental analysis and (except 1) by single-crystal X-ray diffraction.
Introduction
The chemistry of potentially terdentate, so-called pincer1 type, lig-
ands has developed into a well established branch of organometal-
lic chemistry during the last four decades, which has been contin-
uously reviewed.2 The majority of ligands contained nitrogen3 or
phosphorus4 atoms as inbuilt donor centers, but ligands using
other donor atoms such as S, As, Se, or even carbenes emerged.5
Scheme 1
On the contrary, ligands based on an oxygen donor were not
used. In 1998,6 Jurkschat et al. enriched the pincer family by the
-
introduction of the OCO ligand, {4-t-Bu-2,6-[P(O)(OR)2]2C6H2}
resulted to closure of five-membered cycles, in which the central
(R = Et or i-Pr). The chemistry of this ligand has been extended
atoms are connected to oxygen atoms by a single covalent bond
to Li, Si, Sn and Pb up to now.7 The intramolecular cyclization
instead of a M←O dative interaction. This cyclization suggested,
reaction8 is one of the most interesting results, which has been
although other possibilities are also available, generation of
obtained in the course of the investigation of OCO chelated main
organometallic cations as strong Lewis acids. From these studies,
group element compounds (Scheme 1). This type of reaction
one may conclude that the central atom has to possess sufficient
Lewis acidity to undergo such cyclization.
aDepartment of General and Inorganic Chemistry, Faculty of Chemical
Of note, Veige et al. have reported on utilization of an interesting
Technology, University of Pardubice, Studentska´ 573, CZ - 532 10, Pardu-
trianionic OCO pincer ligand recently, where two metallacycles
bice, Czech Republic. E-mail: libor.dostal@upce.cz; Fax: +420466037068;
are formed with the central atom.9 Vicente et al. also described
Tel: +420466037163
utilization of a 2,6-dinitroaryl ligand as a OCO pincer.10
Non-symmetrically substituted pincer type ligands containing
two different coordinating ligand arms (especially NCP, OCS and
OCP types) were described as well.11 The unique coordination en-
vironment provided by these unsymmetric pincer ligands enabled
new modes of reactivity.2d,12
bDepartment of Analytical Chemistry, Faculty of Chemical Technology,
University of Pardubice, Studentska´ 573, CZ - 532 10, Pardubice, Czech
Republic
cEenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB),
Pleinlaan 2, B-1050, Brussels, Belgium
† CCDC reference numbers 801796–801806. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt10234f
8922 | Dalton Trans., 2011, 40, 8922–8934
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©

We reported on OCO pincer type ligands based on ether donor
groups in 200213 (Fig. 1A) and developed their chemistry to other
main group elements.14 However, significant problems were met
during reactions of lithium precursors with strong Lewis acids e.g.
AlCl3, SiCl4 or SnCl4, and desired products were not isolated,
or adducts such as AlCl3·Et3N had to be used for successful
syntheses.15 On the contrary, we have demonstrated that OCO
chelating ligands L1–3 (Fig. 1A) may be used for stabilization of
organoantimony halides of the type L1–3SbX2 (X = F, Cl, or I).14a,f
Significant differences in behaviour of L1 and L3 were obtained,
when the Lewis acidity of the antimony atom was increased.
While the L1 ligand is able to stabilize organoantimony cations or
triflates [L1SbCl]+[X]- (X = OTf or CB11H12) (Fig. 2A),16 significant
problems were met in similar reactions with the ligand L3. Thus,
use of the ligand L3 resulted in mixtures of products, probably
due to an intramolecular ether bond cleavage since the t-Bu group
in L3 should be a significantly better leaving group than methyl in
the case of the ligand L1.16
and closure of a five-membered oxastibol ring.18 This finding
proved the possibility of intramolecular bond disruption and
cyclization in the case of organometallic compounds containing
OCO pincer type ligands (Fig. 1A) and prompted us to study this
phenomenon in more detail.
As a part of these studies, we report here on experimental
investigation dealing with possible cyclization reactions in the
series of group 15 element (P to Bi) compounds containing
ligands L1–4 (Fig. 1A, B). The utilization of these four ligands
enables us to follow two basic trends: (i) varying substituents
on the etheral oxygen atoms in the ligands L1–3; (ii) influence
of the presence of the nitrogen donor atom in the ligand L4.
This ligand is purposely substituted by the t-Bu group on the
etheral oxygen atom, since the t-Bu group is believed to be
the best leaving group in the cyclization reaction. All studied
compounds 1–12 (Schemes 2–5) were characterized by the help
of multinuclear NMR spectroscopy, ESI mass spectrometry, and
except the compound 1 (oil), by X-ray diffraction.
Scheme 2
Fig. 1
Fig. 2
These conclusions were often supported by results obtained
by electrospray ionization (ESI) mass spectra of OCO chelated
organometallic compounds. Especially, the tandem mass spectra
of the ions containing OCO ligands showed further fragmentation
of the CH2OR pendant arms of the ligands, thus in most cases
alkene losses for tert-butyl and isopropyl substituted ligands
were detected, whereas alcohol or aldehyde losses were preferred
for methyl and ethyl substitution of a pincer ligand. It is also
noteworthy, that the neutral loss of butene is even observed in
full scan mass spectra for most of organometallic compounds that
contain OCO ligands with t-Bu groups (L3) (Fig. 1A).17
It has been shown recently that the reaction of organoantimony
sulfide [L3SbS]2 with iodine gave an oxastibol (Fig. 2B) as a side
product. In this compound, one of the t-Bu groups was eliminated
from the molecule under formation of a new Sb–O covalent bond
Scheme 3
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Dalton Trans., 2011, 40, 8922–8934 | 8923
©

elimination of t-BuCl in the course of the reaction (Scheme 2). This
fact points to the same behaviour of the NCO chelated compound
in comparison with OCO ones. The P←N coordination most
probably does not saturate the Lewis acidic phosphorus atom
enough, so leading to cyclization, and this finding also establishes
that the t-Bu moiety is a good leaving group in this cyclization.
Organoarsenic compounds
Albeit OCO chelated organophosphorus compounds were studied
in detail in the past, similar organoarsenic compounds are
unknown. Thus, reactions of L1–4Li with AsCl3 were studied to
obtain OCO chelated organoarsenic chlorides (Scheme 3). The
reaction between L1Li and AsCl3 gave diorganoarsenic compound
(L1)2AsCl (2) as the only isolable product regardless on the
molar L1 : As ratio used (1 : 1 or 2 : 1), the second variant, however,
1
giving better yields of 2. The H NMR spectra of 2 contains an
AB pattern (4.48 ppm) for OCH2 groups and a signal at 3.21 ppm
for CH3O moieties, indicating fluxional behaviour of 2 in solution.
The reaction of L2Li and AsCl3 gave desired L2AsCl2 (3) in good
yield, as demonstrated by 1H and 13C NMR spectra. The 1H NMR
spectrum contains only one sharp signal for the OCH2 moiety
(5.35 ppm) indicating most probably again fluxional behaviour in
solution (coordination/de-coordination of ligands arms), because
only one of the ligand’s arms is coordinated to the central arsenic
atom in the solid state (vide infra). Of note, treatment of L3Li
with one molar equivalent of AsCl3 led to the elimination of
t-BuCl and isolation of the cyclized product [2-(OCH2)-6-(t-
BuOCH2)C6H3]AsCl (4). This fact was clearly demonstrated by
the 1H NMR spectrum of 4, which contains two signals for
OCH2 moieties (4.76 and 5.56 ppm in 2 : 2 integral ratio) and only
one signal for t-BuO group (integral intensity 9). Three signals
(1 : 1 : 1 ratio) are observed in the aromatic region of the 1H NMR
spectrum of 4. These findings well correspond to those observed
in the case of OCO coordinated organophosphorus compounds.
Finally, using ligand L4, bearing a nitrogen donor centre, allowed
synthesis of the dichloride L4AsCl2 (5) and the t-BuO group
remains intact in this compound, as revealed by 1H and 13C NMR
spectra. This finding is notable and suggests that the presence of
the nitrogen donor atom restrains the propensity of the t-BuO
group to undergo cyclization in the case of 5, in comparison to
a smooth cyclization of one of the ligand’s arms in compound 4,
where the OCO ligand L3 was used.
Scheme 4
Scheme 5
Results and discussion
The discussion is arranged consecutively according to the central
atom used. New compounds are numbered and their syntheses are
described in detail in the Experimental section. Compounds that
have been already published, are not numbered, but are described
by their formulas and cited in references.
Organophosphorus compounds
The cyclization among similar OCO and CO chelated organophos-
phorus compounds has recently been studied in detail by
Yoshifuji.19 These studies showed that the organophosphorus
dichlorides smoothly undergo intramolecular cyclization with
concomitant elimination of an alkyl chloride yielding compounds
with a covalent P–O bond (Fig. 2C). However, when an aryl was
used as the substituent on the etheral oxygen atom no cleavage
of the ether bond is observed. This difference was ascribed to a
change of the hybridization of the carbon atom from sp3 (alkyl) to
sp2 (aryl). These results well coincide with our findings on OCO
ligands L2 and L3, thus the compound L3PCl2 is not isolable and
readily eliminates t-BuCl to give a five-membered C3PO ring, while
compound L2PCl2 is stable.20
Similarly, the reaction of L4Li with PCl3 led to the cyclized
product 1 in good yield (Scheme 2). The 31P NMR spectrum of 1
revealed one signal at 165.9 ppm and this value well corresponds
to that at 172.6 ppm for an OCO-cyclized analogue.20 The signal
of the t-Bu moiety is absent in the 1H NMR spectra also proving
The molecular structures of 2–5 were determined by single-
crystal X-ray diffraction and are depicted in Fig. 3–6, relevant
geometric parameters are given in the figures captions and the
crystallographic data are summarized in the Experimental section.
Only one of four oxygen atoms of ligands L1 (Fig. 3) is
coordinated to the arsenic atom in 2 as demonstrated by the
˚
bond length As(1)–O(1) 2.610(6) A (dvdW(As,O) = 3.37, dcov(As,O) =
˚
1.89 A). The coordination polyhedron of the arsenic atom As(1)
in 2 can be described as a distorted vacant trigonal bipyramid as a
result of this intramolecular As–O contact. The oxygen atom O(1)
and the chlorine atom Cl(1) are located in the axial positions with
the angle Cl(1)–As(1)–O(1) 162.6(2)◦. The equatorial positions are
occupied by two ipso carbon atoms C(1) and C(11) and the third
position is most probably filled by the arsenic lone pair leading to
the narrowing of the bonding angle C(1)–As(1)–C(11) to 104.3(3)◦
from an ideal value 120◦ for a trigonal-pyramidal environment.
8924 | Dalton Trans., 2011, 40, 8922–8934
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©

Fig. 3 Molecular structure of 2 (ORTEP drawing with 30% prob-
ability ellipsoids) with the labelling scheme. Hydrogen atoms have
˚
been omitted for clarity. Selected bond lengths (A) and angles
(◦): As(1)–C(1) 1.971(7), As(1)–C(11) 1.993(7), As(1)–O(1) 2.610(6),
As(1)–O(3) 3.322(8), As(1)–Cl(1) 2.259(2); C(1)–As(1)–C(11) 104.3(3),
Cl(1)–As(1)–O(1) 162.6(2), C(1)–As(1)–Cl(1) 99.1(2), C(11)–As(1)–Cl(1)
91.1(2), C(1)–As(1)–O(1) 74.0(2), C(11)–As(1)–O(1) 75.6(3).
Fig. 5 Molecular structure of 4 (ORTEP drawing with 30% prob-
ability ellipsoids) with the labelling scheme. Hydrogen atoms have
˚
been omitted for clarity. Selected bond lengths (A) and angles
(◦): As(1)–C(1) 1.903(5), As(1)–O(1) 1.786(4), As(1)–O(2) 2.627(3),
As(1)–Cl(1) 2.262(2); C(1)–As(1)–Cl(1) 94.86(17), O(1)–As(1)–O(2)
157.13(18), Cl(1)–As(1)–O(1) 98.95(15), Cl(1)–As(1)–O(2) 92.02(10),
C(1)–As(1)–O(1) 88.5(2), C(1)–As(1)–O(2) 70.53(18).
Fig. 4 Molecular structure of 3 (ORTEP drawing with 30% probability
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitted
Fig. 6 Molecular structure of 5 (ORTEP drawing with 30% probability
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): As(1)–C(1) 1.958(2),
As(1)–O(2) 2.5907(18), As(1)–Cl(1) 2.2259(7), As(1)–Cl(2) 2.2034(7);
C(1)–As(1)–Cl(1) 97.62(7), C(1)–As(1)–Cl(2) 100.18(7), C(1)–As(1)–O(2)
74.73(8), Cl(1)–As(1)–O(2) 166.83(4), Cl(2)–As(1)–O(2) 93.20(5).
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): As(1)–C(1) 1.928(3),
As(1)–N(1) 2.131(3), As(1)–O(1) 2.487(2), As(1)–Cl(1) 2.5143(11),
As(1)–Cl(2) 2.4470(10); N(1)–As(1)–O(1) 155.73(11), Cl(1)–As(1)–Cl(2)
175.88(2), C(1)–As(1)–N(1) 82.75(13), C(1)–As(1)–O(1) 73.06(12),
C(1)–As(1)–Cl(1) 89.28(10), C(1)–As(1)–Cl(2) 89.18(10).
The coordination polyhedron of the central atom in 3 (Fig. 4)
resembles that found in compound 2, i.e. a distorted vacant
trigonal bipyramid, but the molecular structure of 3 contains two
chlorine atoms instead of two ligands in comparison to 2. Again
only one of the oxygen atoms, O(2), is coordinated to As(1) with
axial positions (bonding angle Cl(1)–As(1)–O(2) 166.83(4)◦) and
the equatorial plane is formed by the C(1), Cl(2) atoms (angle
C(1)–As(1)–Cl(2) 100.18(7)◦) and the lone pair of the arsenic atom.
Determination of the molecular structure of 4 (Fig. 5) proved
the proposed structure, in which one of the ligand arms of L3 is
broken under elimination of t-BuCl leading to formation of a new
˚
a bond length As(1)–O(2) 2.5907(18) A. This distance is slightly
˚
shorter than that in 2 (2.610(6) A) reflecting higher Lewis acidity
of the central atom. The donor atoms O(2) and Cl(1) atom occupy
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Dalton Trans., 2011, 40, 8922–8934 | 8925
©

As–O bond and closure of a five-membered oxa-arsa ring system.
Using ligand L4 (Scheme 5) allowed isolation of the chlo-
ride L4SbCl2 (8), that showed no propensity to cyclization, and
an even more stable ionic compound [L4SbCl]+[CB11H12]- (9)
was prepared, that is stable in solution for several weeks. The
stability of both compounds in comparison to OCO chelated
analogues L3SbCl2 and 7 is most probably again the result of the
amino pendant arm, which more effectively saturates the antimony
centre in comparison to two ethereal donor centers in the case of
the ligand L3.
The molecular structures of 6–9 are shown in Fig. 7–10 together
with relevant structural parameters. In contrast to the monomeric
structure of the arsenic analogue 4, compound 6 forms a relatively
tightly bonded cyclic tetramer, due to significant intermolecular
Sb–O contacts. It is evident that one of the ligand arms on each
ligand was cleaved under formation of a new Sb–O covalent
bond. The bond distances are Sb(1)–O(2) 2.045(4), Sb(2)–O(4)
˚
The bond length As(1)–O(1) is 1.786(4) A and corresponds well
˚
to the value for a As–O covalent bond (dcov(As,O) = 1.89 A).
The second arm of the ligand remains intact and is coordinated
˚
to the central atom with bond distance As(1)–O(2) 2.627(3) A
and this value resembles those found in 2 and 3. The value of
the bonding angle O(1)–As(1)–O(2), although the oxygen atoms
are coordinated formally in the apical positions of a distorted
vacant trigonal bipyramid, is highly acute 157.13(18)◦ and this
must be ascribed to the ring strain of the oxa-arsa ring. The
molecular structure of 4 remains essentially monomeric without
any significant intermolecular contact, which is in a sharp contrast
to antimony analogues (Fig. 2B)18 and 6 with the tetrameric
structure vide infra.
Both donor atoms, the oxygen atom O(1) as well as nitrogen
atom N(1), are coordinated to the central arsenic atom As(1) with
˚
˚
bond distances As(1)–O(1) 2.487(2) and As(1)–N(1) 2.131(3) A in
2.050(5), Sb(3)–O(6) 2.045(4) and Sb(4)–O(8) 2.037(5) A and
˚
the molecular structure of 5 (Fig. 6). These dative coordinations
lead to a distorted tetragonal pyramidal shape of the coordination
polyhedron of the central As(1) atom. The basal plane is formed by
the donor atoms (N(1) and O(1)) and both chlorine atoms, which
are both coordinated mutually in a pseudo-trans fashion with
bonding angles N(1)–As(1)–O(1) 155.73(11) and Cl(1)–As(1)–
Cl(2) 175.88(2)◦. The apex is occupied by the ipso carbon atom
C(1). This type of environment is very typical for dihalogeno-OCO
and -NCN pincer type antimony and bismuth compounds.14a,21
well correspond to dcov(Sb,O) = 2.02 A. The second arm of each
ligand (oxygen atoms O(1), O(3), O(5) and O(7)) remains intact
but still show significant contact with central antimony atoms
(range of bond distances 2.605(5)–2.593(7) A). The coordination
˚
Organoantimony compounds
As mentioned in the introduction, different behaviour of ligands L1
and L3 was observed in organoantimony cations16 and this
fact made us study organoantimony compounds containing the
ligand L3 in more detail. The chloride L3SbCl2 is stable in the
solid state for several months and in CDCl3 solution for a period
of several weeks.14a Nevertheless, very slow cyclization of L3SbCl2
with concomitant elimination of t-BuCl, yielding compound [2-
(OCH2)-6-(t-BuOCH2)C6H3]SbCl (6), was observed in CDCl3
solution and was monitored by 1H NMR spectroscopy (Scheme 4).
The 1H NMR spectrum of L3SbCl2 contains one signal for OCH2
moieties at 5.03 ppm, but upon standing in CDCl3 solution at
ambient temperature two additional singlets for OCH2 groups
(4.77 and 5.63 ppm, 2 : 2 integral ratio) and one singlet for t-
BuO group (1.47 ppm, integral intensity 9) emerged, pointing to
formation of 6. These signals increased in their intensity giving
ca. 60% conversion after 6 months. Attempts to accelerate this
reaction by heating were hampered in part by decomposition
and hydrolysis leading to a mixture of decomposition products.
According with the idea that the cyclization is caused by Lewis
acidity of the central antimony atom, one of the chlorine atoms
in L3SbCl2 was substituted by a triflate group by reaction with
Fig. 7 Molecular structure of 6 (ORTEP drawing with 30% probability
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Sb(1)–C(1) 2.109(8),
Sb(1)–Cl(1) 2.457(3), Sb(1)–O(1) 2.600(5), Sb(1)–O(2) 2.045(4), Sb(2)–
C(13) 2.117(6), Sb(2)–Cl(2) 2.476(2), Sb(2)–O(3) 2.605(5), Sb(2)–O(4)
2.050(5), Sb(3)–C(25) 2.103(9), Sb(3)–Cl(3) 2.441(3), Sb(3)–O(5)
2.593(7), Sb(3)–O(6) 2.045(4), Sb(4)–C(37) 2.093(6), Sb(4)–Cl(4)
2.464(3), Sb(4)–O(7) 2.599(6), Sb(4)–O(8) 2.037(5), Sb(1)–O(4) 2.444(6),
Sb(2)–O(6) 2.432(5), Sb(3)–O(8) 2.477(6), Sb(4)–O(2) 2.485(5);
O(1)–Sb(1)–O(2) 148.51(18), Cl(1)–Sb(1)–O(4) 170.38(13), O(3)–
Sb(2)–O(4) 148.61(14), Cl(2)–Sb(2)–O(6) 170.24(12), O(5)–Sb(3)–O(6)
148.4(2), Cl(3)–Sb(3)–O(8) 168.31(14), O(7)–Sb(4)–O(8) 149.23(17),
1
silver triflate to give L3SbCl(OTf) (7). The H NMR spectrum
of 7 contains sharp signals for both OCH2 and CH3O groups
(5.17 and 1.70 ppm, respectively). The presence of the OTf group
was established also by observation of a quartet in the 13C NMR
spectrum at 119.7 ppm (1J(13C,19F) = 318 Hz). The increased Lewis
acidity of the antimony atom in 7 accelerates the cyclization
process and full conversion to compound 6 can be observed
typically in only 6–7 days in CDCl3 solution (Scheme 4).
Cl(4)–Sb(4)–O(2)
168.60(12),
O(2)–Sb(1)–O(4)
89.36(19),
Sb(1)–O(4)–Sb(2) 130.68(18), O(4)–Sb(2)–O(6) 90.60(19), Sb(2)–O(6)–
Sb(3) 130.93(19), O(6)–Sb(3)–O(8) 90.39(19), Sb(3)–O(8)–Sb(4)
130.06(18), O(8)–Sb(4)–O(2) 89.12(19), Sb(4)–O(2)–Sb(1) 128.8(2).
8926 | Dalton Trans., 2011, 40, 8922–8934
This journal is
The Royal Society of Chemistry 2011
©

Fig. 9 Molecular structure of 8 (ORTEP drawing with 30% probability
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Sb(1)–C(1) 2.104(3),
Sb(1)–N(1) 2.336(3), Sb(1)–O(1) 2.485(2), Sb(1)–Cl(1) 2.5846(14),
Sb(1)–Cl(2) 2.6174(14); C(1)–Sb(1)–N(1) 77.36(12), C(1)–Sb(1)–O(1)
70.86(12), C(1)–Sb(1)–Cl(1) 87.44(9), C(1)–Sb(1)–Cl(2) 86.94(9),
N(1)–Sb(1)–O(1) 148.22(11), Cl(1)–Sb(1)–Cl(2) 174.38(4).
Fig.
8
Molecular structure of 7 (ORTEP drawing with 30%
probability ellipsoids) with the labelling scheme. Hydrogen atoms
have been omitted for clarity. Selected bond lengths (A) and an-
˚
gles (◦): Sb(1)–C(1) 2.093(3), Sb(1)–Cl(1) 2.3950(10), Sb(1)–O(1)
2.312(2), Sb(1)–O(2) 2.275(2), Sb(1)–O(3) 2.971(3), Sb(1)–O(5) 2.998(3);
C(1)–Sb(1)–O(1) 74.37(11), C(1)–Sb(1)–O(2) 75.31(11), C(1)–Sb(1)–O(3)
85.01(11), C(1)–Sb(1)–O(5) 85.29(11), C(1)–Sb(1)–Cl(1) 95.56(9),
Cl(1)–Sb(1)–O(1) 86.72(6), O(1)–Sb(1)–O(5) 72.49(9), O(5)–Sb(1)–O(3)
46.11(10), O(3)–Sb(1)–O(2) 68.49(9), O(2)–Sb(1)–Cl(1) 68.49(9).
polyhedron at each antimony atom Sb(1–4) may be best described
as a strongly distorted tetragonal pyramid, with the ipso carbon
atoms in the axial position, as a result of a additional intermolecu-
lar contact with the oxygen atoms of the neighboring molecule, e.g.
the Sb(1)–O(4) contact. These intermolecular contacts fall within
˚
a narrow interval 2.432(5)–2.485(5) A. Interestingly, these contacts
are stronger than those found in the iodine analogue Fig. 2B. The
resulting central Sb4O4 ring is strongly puckered as demonstrated
by the selected bond angles, see figure caption.
The molecular structure of compound 7 (Fig. 8) is of particular
interest in this study, because its structure may shed some light on
the reason why this compound undergoes the cyclization reaction
to 6 so smoothly, in comparison with the chloride L3SbCl2. The
coordination number of the central atom Sb(1) is six and the
coordination polyhedron may be best described as a strongly
distorted pentagonal pyramid. This is a result of the rigid
tridentate coordination of the pincer ligand (atoms C(1), O(1)
and O(2)), bidentate coordination of the triflate moiety (O(3) and
O(5)) and the sixth coordination place is occupied by the chlorine
atom Cl(1). The heteroatoms form the basal plane and the carbon
atom C(1) is located in the apical position. The triflate group is
coordinated to the central atom very weakly as demonstrated by
Fig. 10 Molecular structure of 9 (ORTEP drawing with 30% probability
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Sb(1)–C(1) 2.101(2),
Sb(1)–N(1) 2.2881(17), Sb(1)–O(1) 2.4706(15), Sb(1)–Cl(1) 2.3668(6);
C(1)–Sb(1)–N(1) 77.27(7), C(1)–Sb(1)–O(1) 71.50(7), C(1)–Sb(1)–Cl(1)
95.08(7), N(1)–Sb(1)–O(1) 148.68(6), N(1)–Sb(1)–Cl(1) 90.40(5),
O(1)–Sb(1)–Cl(1) 94.57(4).
˚
the bond distances Sb(1)–O(3) 2.971(3), Sb(1)–O(5) 2.998(3) A,
3
14a
˚
˚
which are significantly longer than dcov(Sb,O) = 2.02 A, but still
compound L SbCl2 are 2.6911(13) and 2.6294(14) A. Provided
that we accept strong intramolecular interactions as a starting
point for the cyclization process, the comparison of these Sb–O
interactions clearly explains the relative ease of cyclization for
compound 7 in comparison to the chloride L3SbCl2 (vide supra).
˚
below the dvdW(Sb,O) = 3.52 A. In contrast, the intramolecular
Sb–O(pincer) dative interactions (Sb(1)–O(1) 2.312(2), Sb(1)–O(2)
˚
2.275(2) A) are the strongest observed by us so far among all
organoantimony derivatives of L3; the corresponding values in
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Dalton Trans., 2011, 40, 8922–8934 | 8927
©

This conclusion seems to be even more valid in solution, where
the triflate group may easily de-coordinate from the central atom
and in such a way further increase the Lewis acidity of the central
atom in 7. Strengthening of the Sb–O interaction is expected which
will promote the cyclization.
Organobismuth compounds
The situation in the case of organobismuth derivatives is not so
complicated in comparison with the antimony analogues. The
OCO chelated organobismuth cation was shown to be stable in
the compound [L3BiCl]+[CB11H12]-.16 Analogously, the bismuth
compound L4BiCl2 (10) can be prepared as a stable solid and
was characterized by 1H and 13C NMR spectra, where only
one sharp signal is obtained for both OCH2 and NCH2 groups
(4.78 and 5.08 ppm). Conversion of 10 with silver salts of polar
groups gave compounds L4BiCl(OTf) (11) and [L4BiCl]+[CB11H12]-
(12) (Scheme 5). Both compounds are stable in solution for
extended times without any indication for a cyclization process.
Molecular structures of 10–12 are illustrated in Fig. 11–13
with selected structural parameters given in the figure captions.
The structure of the NCO chelated organobismuth chloride 10 is
depicted in Fig. 11. The coordination polyhedron is rather similar
to the arsenic (5) and antimony (8) analogues, i.e. a strongly
distorted tetragonal pyramid as a consequence of meridional
coordination of the pincer ligand L4. Of note, there is an additional
Other aspects are also relevant in this discussion. The closest
values of Sb–O intramolecular interactions to those in 7 were
3
14a
˚
observed in the compound L SbI2 (2.302(2) and 2.343(2) A),
a formal precursor of the only cyclized product (Fig. 2B)
reported to date, thus confirming our idea. Moreover, in the
cation of ionic pairs containing the ligand L1 (Fig. 1A), such
as [L1SbCl]+[CB11H12]-, and the corresponding triflates16 the Sb–O
˚
interactions are in the range 2.226(7)–2.324(4) A, thus comparable
to the values in 7. Nevertheless, the methyl groups on the ligand
arms in the ligand L1 remained intact proving that the propensity
of t-Bu group (L3) elimination is easier than elimination of the
methyl groups in L1. Finally, in the case of t-Bu substituted NCO
ligand L4 the oxygen containing ligand arm is not cleaved even
in the ionic pair [L4SbCl]+[CB11H12]- 9 (for description of its
molecular structure see below). Also the Sb–O bond distance is
˚
intermolecular contact of 3.618(2) A between the central atom
Bi(1) and the chlorine tom Cl(1a) from the adjacent molecule
Bi(1)–Cl(1a) (dvdW(Bi,Cl) = 4.09 A) leading to a very weakly
coordinated dimeric unit in the solid state. This finding reflects
the preference of the bismuth atom to adopt higher coordination
numbers in comparison to lighter group 15 analogues as reported
for similar compounds previously.14a
˚
quite long 2.4706(15) A in 9 most probably as a result of an effective
saturation of the central antimony atom by the N-donor ligand
arm. This fact may point to the conclusion that the cleavage of
the etheral bond will be more feasible in the case of OCO than in
NCO ligands.
The molecular structure of compound 8 is shown in Fig. 9.
In fact, this structure is closely related to the arsenic ana-
logue L4AsCl2 5. Thus the coordination polyhedron of the central
antimony atom may be defined as a strongly distorted tetragonal
pyramid, where the basal plane is formed by two chlorine atoms in
a trans orientation, Cl(1)–Sb(1)–Cl(2) 174.38(4)◦, and the donor
atoms N(1) and O(1) (angle N(1)–Sb(1)–O(1) 148.22(11)◦). The
apex is occupied by the ipso carbon atom C(1). Concerning
the Sb–O interaction as the main important structural feature
˚
˚
(Sb(1)–O(1) 2.485(2) A), the coordination is stronger than found
in L3SbCl2. This result seems to contradict the fact that nitrogen
atoms saturate the central metal more efficiently and so weaker
Sb–O interaction in 8 might be expected in comparison to the
OCO chelated L3SbCl2. However, the strengthening of the Sb–
O interaction in 8 can be ascribed to a change in the ligand
coordination geometry from pseudo-facial in L3SbCl2 (O–Sb–O
angle 116.◦73(4)◦) to pseudo-meridional in 8 (N(1)–Sb(1)–O(1)
148.22(11) ).21a
Compound 9 forms a well separated ionic pair (Fig. 10).
The structure of the cationic part of 9 is best described as
a vacant trigonal bipyramid, where the apical positions are
occupied by the donor atoms N(1) and O(1) (angle N(1)–Sb(1)–
O(1) 148.68(6)◦). The intramolecular Sb(1)–N(1) interaction
Fig. 11 Molecular structure of 10 (ORTEP drawing with 30% probability
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitt◦ed
˚
for clarity. a = 1 - x, 1 - y, -z. Selected bond lengths (A) and angles ( ):
Bi(1)–C(1) 2.207(6), Bi(1)–N(1) 2.429(8), Bi(1)–O(1) 2.556(6), Bi(1)–Cl(1)
2.733(3), Bi(1)–Cl(2) 2.644(3), Bi(1)–Cl(1a) 3.618(2); N(1)–Bi(1)–O(1)
143.5(2), Cl(1)–Bi(1)–Cl(2) 177.06(8), C(1)–Bi(1)–Cl(1a) 156.85(19).
˚
2.2881(17) A is, interestingly, slightly shorter in comparison to
The formally dimeric structure is retained also in the case of the
compound 11 (Fig. 12), but now the bridges are formed by triflate
groups. The triflate moieties are coordinated only very weakly
as demostrated by bond distances Bi(1)–O(2) 2.665(10), Bi(1)–
the analogous purely NCN chelated organoantimony cation (Sb–
N bond distances 2.379(5) and 2.442(4) A). This fact again
22
˚
points to the conclusion that due to the very strong Sb–N
intramolecular interaction in the NCO (ligand L4) derivatives,
the nitrogen donor atom provides a high level of saturation of the
Lewis acidic central antimony atom leaving the Sb–O coordination
as not so crucial for the stabilization of the cation (cf. Sb(1)–
O(1) 2.4706(15) A distance in 9 is apparently weaker than in
analogous OCO chelated compounds such as in 7, 2.312(2) and
2.275(2) A).
˚
˚
O(3b) 3.009(9), Bi(1)–O(4b) 3.372(10) A (dcov(Bi,O) = 2.10 A,
d
˚
vdW(Bi,O) = 3.52 A) similarly to the OCO chelated analogue 7.
This bonding situation may be thus described also as contact ion
pairs, where two triflate anions are caught between two bismuth
cations. The pincer ligands are coordinated in tridentate fashion
˚
˚
with bond distances Bi(1)–N(1) 2.431(11), Bi(1)–O(1) 2.558(9) A
˚
in a pseudo-meridional fashion. The coordination number of the
8928 | Dalton Trans., 2011, 40, 8922–8934
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The Royal Society of Chemistry 2011
©

Mass spectrometry
Tandem mass spectra of studied ions containing ligands L1–4
showed the neutral loss of Dm/z 32 CH3OH for 2, Dm/z 136
C9H11OH for 3 and Dm/z 56 C4H8 ((CH3)2C CH2). Major frag-
mentation mechanisms for other studied compounds containing
ligands L3 or L4 were related to fragmentation of ligand arm with
the t-Bu substituent on the oxygen atom. These finding proved
the propensity of the oxygen containing ligand arm to be cleaved
under the measurement conditions.
Theoretical considerations
Better insight into the cyclization behaviour of selected com-
pounds can be obtained from theoretical calculations. Starting
from the molecular structures, the compounds containing OCO
and NCO ligands i.e. L3MCl2 and L4MCl2 (M = Sb and Bi) were
fully optimized at the B3LYP24/cc-pVDZ25 level (on Sb and Bi,
the cc-pVDZ-PP basis set26 was used) using the Gaussian 09
program.27 Subsequent NBO analysis28 reveals that in case of
the L4 ligand (NCO), an important interaction exists between
the lone pairs on both oxygens and nitrogen and the formal
empty p orbital on Sb and Bi, which coincides with strong
Fig. 12 Molecular structure of 11 (ORTEP drawing with 30% probability
ellipsoids) with the labelling scheme. Hydrogen atoms have been omitted
˚
for clarity. a, b = 1 - x, -y, 1 - z. Selected bond lengths (A) and
angles (◦): Bi(1)–C(1) 2.207(11), Bi(1)–N(1) 2.431(11), Bi(1)–O(1) 2.558(9),
Bi(1)–Cl(1) 2.431(11), Bi(1)–O(2) 2.665(10), Bi(1)–O(3b) 3.009(9),
Bi(1)–O(4b) 3.372(10); C(1)–Bi(1)–O(1) 69.4(5), C(1)–Bi(1)–N(1) 74.0(4),
C(1)–Bi(1)–Cl(1) 91.9(3), C(1)–Bi(1)–O(2) 80.0(3), C(1)–Bi(1)–O(3b)
140.2(3), C(1)–Bi(1)–O(4b) 169.5(3).
intramolecular donor atom–metal interactions. Both structures
can be approximately described by the formal formula L4M2+Cl2
.
2-
In the case of OCO chelated L3BiCl2, there is a comparable
interaction between the lone pairs on both oxygens with the formal
empty p orbital on Bi and this compound can also be described
as L3Bi2+Cl22-. None of these three compounds is found to undergo
cyclization. In the case of Sb congener L3SbCl2 however, this
interaction is absent and an interaction exists between the oxygen
lone pairs and the antibonding orbital of the Sb–Cl bonds. NBO
analysis in this case clearly identifies two Sb–Cl bonds. This fact
suggests that the cyclization process may be related to the nature of
the metal–donor atom interaction. Thus interaction must not just
be only between the lone pairs of donor atoms and empty orbitals
of the central metal forming a Lewis pair. Electron density of the
donor atoms can be, as shown by for example L3SbCl2, donated
to antibonding orbitals of the compound backbone and such an
interaction may be a impetus for cyclization.
Fig. 13 Molecular structure of 12 (ORTEP drawing with 30% prob-
ability ellipsoids) with the labelling scheme. Hydrogen atoms have
Conclusions
been omitted for clarity.
a = 1 - x, -y, 1 - z. Selected bond
◦
˚
The set of group 15 pincer compounds with one (L4) or two (L1–3
)
lengths (A) and angles ( ): Bi(1)–C(1) 2.180(9), Bi(1)–N(1) 2.420(5),
Bi(1)–O(1) 2.534(3), Bi(1)–Cl(1) 2.4819(12); C(1)–Bi(1)–N(1) 74.68(14),
C(1)–Bi(1)–O(1) 69.54(14), C(1)–Bi(1)–Cl(1) 93.21(13), N(1)–Bi(1)–O(1)
144.21(11).
pendant CH2OR groups was prepared, with the aim to follow the
ability of this ligand arm to undergo intramolecular cyclization
via ether bond disruption. Although, this set of compounds is
still quite limited, the knowledge obtained in the course of this
study enable us to make some preliminary conclusions for group
15 derivatives. (i) It is evident that the propensity to cyclization
decreases from P to Bi, and no cyclization process was detected in
the latter case. (ii) Regarding the structure of the oxygen ligand arm
i.e. R group in CH2OR, it seems that only the alkyl (sp3 hybridized)
substituents are prone to cyclization, especially the t-Bu group,
because changing to aryl (mesityl, sp2 hybridized) group gave
stable products even with phosphorus as the central atom. (iii) The
presence of the nitrogen pendant arm CH2NMe2 helps to prevent
cyclization of CH2Ot-Bu, thus for example the smooth cyclization
reaction with arsenic chloride in the case of OCO ligand L3 was not
central bismuth atom is seven taking all the Bi–O(triflate) contacts
into account.
Compound 12 forms an ionic pair (Fig. 13) similarly to the
antimony analogue 9. The vacant trigonal-bipyramidal array of
the cation of 12 is built up by the pincer ligand (pseudo-meridional
coordination with N(1)–Bi(1)–O(1) 144.21(11)◦) and the chlorine
atom Cl(1) occupying one of the equatorial positions. The values
of the intramolecular interactions Bi(1)–N(1) 2.420(5), Bi(1)–O(1)
˚
2.534(3) A resemble those of analogous OCO and NCN chelated
ionic pairs.16,23
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©

observed in the case of NCO ligand L4. Similarly, the cyclization
may proceed in the case of OCO antimony compounds, but not
for NCO ones. (iv) The cyclization itself requires formation of a
higly Lewis acidic central fragment, which in turn leads to strong
intramolecular interaction, so promoting the cyclization process.
2 as colorless crystals (0.77 g, 55%), mp: 95–98 ◦C. Anal. Calc.
for C20H26ClAsO4 (MW 440.80): C, 54.5; H, 6.0. Found: C, 54.7;
1
H, 6.2%. H NMR (500 MHz, CDCl3): d 3.21 (6H, s, CH3O),
4.48 (4H, AB pattern, OCH2), 7.33 (3H, m, Ar-H3,4,5). 13C NMR
(125.76 MHz, CDCl3): d 58.0 (s, CH3O), 74.4 (s, OCH2), 128.2
(s, Ar-C3,5), 129.2 (s, Ar-C4), 142.0 (Ar-C1), 143.0 (s, Ar-C2,6).
Positive-ion MS: m/z 405 [M - Cl]+ (100%).
Experimental
Synthesis of [2,6-(2¢,4¢,6¢-Me3C6H2OCH2)2C6H3]AsCl2 (3).
A
General procedures
hexane solution of n-BuLi (2.2 mL, 3.47 mmol, 1.6 M solution)
was added to solution of L2H (1.3 g, 3.47 mmol) in hexane (30 mL)
and stirred for 12 h. The resulting suspension of L2Li was added
to a pre-cooled solution (-30 ◦C) of AsCl3 (0.63 g, 0.29 mL,
3.47 mmol) in hexane (20 mL). The reaction mixture was stirred
for 4 h then hexane (10 mL) was added. The suspension was
filtered and the solid was extracted with CHCl3 (20 mL). The
extract was evaporated and washed with hexane (10 mL) to give
3 as a cream solid (0.81 g, 45%), mp 164–166 ◦C. Anal. Calc. for
C26H29Cl2AsO2 (MW 519.35): C, 60.1; H, 5.6. Found: C, 60.2; H,
5.7%. 1H NMR (500 MHz, CDCl3): d 2.26 (12H, s, 2,6-(CH3) of
mesityl), 2.28 (6H, s, 4-(CH3) of mesityl), 5.35 (4H, s, OCH2), 6.87
(4H, s, Ar-mesityl), 7.58 (1H, t, Ar-H4), 7.75 (2H, d, Ar-H3,5).
13C NMR (125.76 MHz, CDCl3): d 17.1 (s, 2,6-(CH3) of mesityl),
20.9 (s, 4-(CH3) of mesityl), 72.5 (s, OCH2), 128.4 (s, Ar-C3,5),
129.7 (s, mesityl-C3,5), 130.8 (s, mesityl-C2,6), 132.2 (s, Ar-C4),
134.0 (s, mesityl-C4), 141.8 (Ar-C1), 143.2 (s, Ar-C2,6), 153.9 (s,
mesityl-C1). Positive-ion MS: m/z 521 [L2As(OH)2 + K]+ (6%);
m/z 505 [L2As(OH)2 + Na]+ (27%); m/z 483 [M - Cl]+ (9%);
m/z 465 [L2As(OH)]+ (100%); m/z 329 [L2As(OH) - C9H11OH]+
(4%). Negative-ion MS: m/z 535 [L2AsCl(OH) + Cl]- (100%)
All air- and moisture-sensitive manipulations were carried out un-
der an argon atmosphere using standard Schlenk tube techniques.
All solvents were dried by standard procedures and distilled
prior to use. 1H, 13C NMR spectra were recorded on Bruker
500 Avance or Bruker 400 MHz spectrometers, using a 5 mm
tuneable broadband probe. Appropriate chemical shifts in 1H
and 13C NMR spectra were related to the residual signals of
the solvent (CDCl3: d(1H) = 7.27 ppm and d(13C) = 77.23 ppm,
C6D6: d(1H) = 7.16 ppm). 31P NMR spectra were relative to
external H3PO4 (d(31P) = 0.00 ppm) The positive- and negative-
ion electrospray ionization (ESI) mass spectra were measured on
an ion trap analyzer Esquire 3000 (Bruker Daltonics, Bremen,
Germany) in the range m/z 50–1000. The samples were dissolved
in acetonitrile and analyzed by direct infusion at a flow rate
of 3 mL min-1. The ion source temperature was 300 ◦C, the
tuning parameter compound stability was 100%, the flow rate and
the pressure of nitrogen were 4 l min-1 and 10 psi, respectively.
The starting compounds: AgO3SCF3 (99%), PCl3 (99.999%),
AsCl3 (99.99%), SbCl3 (99.999%) and BiCl3 (99.999%), were
obtained from commercial suppliers and used as delivered. The
ligands L1–4 were prepared according to published works or by
analogous procedures.13,18,21a AgCB11H12 was prepared according
to the method of Reed.29
Synthesis of [2-(OCH2)-6-(t-BuOCH2)C6H3]AsCl (4). A solu-
tion of L3Li30 (1.19 g, 4.64 mmol) in Et2O (20 mL) was added
to a solution of AsCl3 (0.84 g, 0.39 mL, 4.64 mmol) in Et2O
(30 mL) at -70 ◦C. The reaction mixture was stirred for 12 h at r.t.
and filtered. The filtrate was evaporated and crystallization of the
Syntheses
◦
residue from hexane at 0 C gave 4 as colorless crystals (0.87 g,
Synthesis of [2-(OCH2)-6-(Me2NCH2)C6H3]PCl (1). A hexane
solution of n-BuLi (1.6 mL, 2.49 mmol, 1.6 M solution) was added
to a solution of L4H (0.55 g, 2.49 mmol) in hexane (30 mL) and
stirred for 3 h. The resulting orange solution of L4Li was added to a
pre-cooled solution (-80 ◦C) of PCl3 (0.34 g, 0.22 mL, 2.49 mmol)
in toluene (20 mL). The reaction mixture was stirred for 12 h at
r.t. and the reaction mixture was filtered and the residual solid
was washed with hexane (10 mL). The filtrate was evaporated
in vacuo and the resulting yellowish oil was characterized as 1.
Yield: 0.43 g (75%). Anal. Calc. for C12H16ClPO2 (MW 258.69):
62%), mp 69 ◦C. Anal. Calc. for C12H16ClAsO2 (MW 302.63):
1
C, 47.6; H, 5.3. Found: C, 47.7; H, 5.5%. H NMR (500 MHz,
CDCl3): d 1.43 (9H, s, (CH3)3CO), 4.76 (2H, s, (CH3)3COCH2),
5.56 (2H, s (br), AsOCH2), 7.20 (1H, d, Ar-H), 7.35 (1H, d, Ar-H),
7.45 (1H, dd, Ar-H). 13C NMR (125.76 MHz, CDCl3): d 27.7 (s,
(CH3)3CO), 62.1 (s, (CH3)3COCH2), 76.2 (s, (CH3)3COCH2), 77.1
(s, AsOCH2), 119.9, 123.7, 130.6, 141.6, 143.1, 148.0 (s, Ar-C).
Positive-ion MS: m/z 591 [L2As2O + H2O + Na]+ (42%); m/z 573
[L2As2O + Na]+ (9%); m/z 551 [L2As2O + H]+ (13%); m/z 323
[LAs(OH) + K]+ (10%); m/z 307 [LAs(OH) + Na]+ (100%).
1
C, 55.7; H, 6.2. Found: C, 55.5; H, 6.4%. H NMR (500 MHz,
C6D6): d 2.07 (6H, s, (CH3)2N), 3.23 (2H, s (br), NCH2), 5.10
Synthesis of [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]AsCl2 (5).
A
(2H, s (br), POCH2), 6.78 (2H, m, Ar-H), 7.04 (1H, br, Ar-H). 31
P
hexane solution of n-BuLi (1.7 mL, 2.71 mmol, 1.6 M solution)
was added to solution of L4H (0.6 g, 2.71 mmol) in hexane
(30 mL) and stirred for 3 h. The resulting orange solution of L4Li
was added to a pre-cooled solution (-60 ◦C) of AsCl3 (0.49 g,
0.23 mL, 2.71 mmol) in hexane (20 mL). The reaction mixture
was stirred for 12 h at r.t. and the reaction mixture was filtered.
The remaining solid was washed with hexane and extracted with
CH2Cl2 (20 mL). The extract was evaporated and the crude solid
was crystallized from a minimum amount of CH2Cl2 to give 5
as colorless crystals (0.43 g, 43%), mp 166 ◦C (decomp.). Anal.
Calc. for C14H22Cl2AsON (MW 366.17): C, 45.9; H, 6.1. Found:
NMR (161.98 MHz, C6D6): d 165.9.
Synthesis of [2,6-(MeOCH2)2C6H3]2AsCl (2). A hexane solu-
tion of n-BuLi (4.1 mL, 6.44 ◦mmol, 1.6 M solution) was added
to a pre-cooled solution (-70 C) of L1Br (1.58 g, 6.44 mmol) in
Et2O (30 mL) and stirred for 2 h at this temperature. The resulting
orange solution of L1Li was added to a solution of AsCl3 (0.59 g,
0.27 mL, 3.22 mmol) in Et2O (20 mL) at -70 ◦C. The reaction
mixture was stirred for 24 h at r.t. and evaporated in vacuo. The
residue was extracted with toluene (30 mL) and evaporated to
dryness. The crude product was crystallized from hexane to give
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©

1
C, 45.7; H, 6.0%. H NMR (500 MHz, CDCl3): d 1.52 (9H, s,
(30 mL) and stirred for 5 h. The resulting orange solution of L4Li
was added to a pre-cooled solution (-60 ◦C) of SbCl3 (0.74 g,
3.3 mmol) in Et2O (30 mL). The reaction mixture was stirred
for 12 h. The volume of reaction mixture was reduced to ca one
half and hexane (10 mL) was added. The insoluble material was
collected by filtration and extracted with CH2Cl2 (30 mL). The
extract was evaporated to dryness, washed with hexane (10 mL)
and dried in vacuo to give 8 as a cream solid (0.83 g, 61%), mp
186 ◦C (decomp.). Anal. Calc. for C14H22Cl2SbON (MW 412.99):
(CH3)3CO), 3.16 (6H, s, (CH3)2N), 4.49 (2H, s, NCH2), 4.84 (2H, s,
OCH2), 7.17 (2H, m, Ar-H), 7.31 (1H, dd, Ar-H). 13C NMR
(125.76 MHz, CDCl3): d 28.1 (s, (CH3)3CO), 50.4 (s, (CH3)2N),
62.7 (s, NCH2), 67.1 (s, OCH2), 80.2 (s, (CH3)3CO), 123.3, 125.0,
130.5, 140.5, 141.6, 147.2 (s, Ar-C). Positive-ion MS: m/z 623
[(L4)2As2O2 + H]+ (15%); m/z 352 [L4As(OH)2 + Na]+ (10%); m/z
312 [L4As(OH)]+ (100%); m/z 296 [L4As(OH)2 + Na - C4H8]+
(2%); m/z 256 [L4As(OH) - C4H8]+ (16%).
1
C, 40.7; H, 5.4. Found: C, 40.9; H, 5.5%. H NMR (500 MHz,
Synthesis of [2-(OCH2)-6-(t-BuOCH2)C6H3]SbCl (6).
CDCl3): d 1.60 (9H, s, (CH3)3CO), 3.02 (6H, s, (CH3)2N), 4.39
(2H, s, NCH2), 4.95 (2H, s, OCH2), 7.22 (2H, m, Ar-H), 7.34
(1H, dd, Ar-H). 13C NMR (125.76 MHz, CDCl3): d 28.6 (s,
(CH3)3CO), 49.2 (s, (CH3)2N), 64.3 (s, NCH2), 67.2 (s, OCH2),
81.6 (s, (CH3)3CO), 124.6, 124.7, 129.9, 143.0, 154.9 (s, Ar-C), (Ar-
C1) not observed. Positive-ion MS: m/z 398 [L4Sb(OH)2 + Na]+
(100%); m/z 376 [M - Cl]+ (31%); m/z 358 [L4SbOH]+ (12%); m/z
342 [L4Sb(OH)2 + Na - C4H8]+ (7%); m/z 320 [M - Cl - C4H8]+
(10%). Negative-ion MS: m/z 446 [M + Cl]- (100%).
Method A. Compound L3SbCl2 (50 mg, 0.11 mmol) was
dissolved in dried (distilled from LiAlH4) CDCl3 (2 mL) and the
resulting mixture was stirred in a NMR tube. The progress of the
1
reaction was monitored by H NMR spectroscopy. The reaction
was stopped after 6 months, with the conversion of the starting
compound to compound 6 in ca. 60%. The solvent was evaporated
in vacuo. Compound 6 was obtained after recrystallization of the
solid residue from a CH2Cl2–hexane mixture to give 6 (19 mg, 48%)
mp 123 ◦C (decomp.). Anal. Calc. for C12H16ClSbO2 (MW 349.46):
1
Synthesis of [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]SbCl(CB11H12)
(9). AgCB11H12 (90 mg, 0.36 mmol) was added as a solid to
a solution of 8 (150 mg, 0.36 mmol) in CH2Cl2 (10 mL) and
stirred for 2 h. Than the insoluble material was filtered off and
the filtrate was evaporated in vacuo and washed with hexane.
The crude product was recrystallized from a CH2Cl2–hexane
mixture (142 mg, 75%), mp 186 ◦C (decomp.). Anal. Calc. for
C15H34B11ClSbON (MW 520.57): C, 34.6; H, 6.6. Found: C, 34.7;
H, 6.8%. 1H NMR (500 MHz, CDCl3): d 1.61 (9H, s, (CH3)3CO),
2.97 (6H, s, (CH3)2N), 4.37 (2H, s, NCH2), 5.04 (2H, s, OCH2),
7.39 (1H, d, Ar-H), 7.43 (1H, d, Ar-H), 7.57 (1H, dd, Ar-H).
13C NMR (125.76 MHz, CDCl3): d 28.7 (s, (CH3)3CO), 47.1 (s,
(CH3)2N), 52.1 (s (br), C-cage), 65.6 (s, NCH2), 66.4 (s, OCH2),
84.5 (s, (CH3)3CO), 125.2, 125.6, 133.1, 144.8, 144.6, 145.3 (s,
Ar-C). Positive-ion MS: m/z 398 [L4Sb(OH)2 + Na]+ (33%);
m/z 376 [L4SbCl]+ (17%); m/z 358 [L4SbOH]+ (100%); m/z 342
[L4Sb(OH)2 + Na - C4H8]+ (5%); m/z 320 [L4SbCl - C4H8]+ (8%)
m/z 302 [L4SbOH - C4H8]+ (18%). Negative-ion MS: m/z 145
[CB11H12]- (100%).
C, 41.2; H, 4.6. Found: C, 41.4; H, 4.5%. H NMR (500 MHz,
CDCl3): d 1.47 (9H, s, (CH3)3CO), 4.77 (2H, s, (CH3)3COCH2),
5.63 (2H, s (br), SbOCH2), 7.16 (1H, d, Ar-H), 7.30 (1H, d, Ar-
H), 7.41 (1H, dd, Ar-H). 13C NMR (125.76 MHz, CDCl3): d 28.4
(s, (CH3)3CO), 63.0 (s, (CH3)3COCH2), 75.3 (s, (CH3)3COCH2),
78.1 (s, SbOCH2), 120.9, 123.3, 130.2, 143.8, 150.1, 151.5 (s, Ar-
C). Positive-ion MS: m/z 661 [L2Sb2O2H2 + H]+ (100%); m/z 349
[M + H]+ (10%); m/z 293 [M + H - C4H8]+ (65%). Negative-ion
MS: m/z 383 [M + Cl]- (77%); m/z 291 [M - H - C4H8]- (100%).
Method B. Compound 7 (30 mg, 0.05 mmol) was put into
a NMR tube and dried (distilled from LiAlH4) CDCl3 (2 mL)
was added and the resulting mixture was stirred. The progress of
the reaction was monitored by H NMR spectroscopy, showing
the full conversion of 7 to 6 typically in 6 days. The H and 13C
1
1
NMR data were consistent with those obtained by method A. The
product was not isolated.
Synthesis of [2,6-(t-BuOCH2)C6H3]SbCl(CF3SO3) (7). A mix-
ture of L3SbCl2 (0.25 g, 0.56 mmol) and AgOTf (0.14 g, 0.56 mmol)
in CH2Cl2 was stirred for 10 min. The precipitated AgCl was
filtered of and the mixture was evaporated in vacuo. The remaining
solid was washed with hexane (10 mL) and dried in vacuo to give
Synthesis of [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]BiCl2 (10).
A
hexane solution of n-BuLi (4.2 mL, 6.7 mmol, 1.6 M solution) was
added to solution of L4H (1.48 g, 6.7 mmol) in hexane (30 mL) and
stirred for 5 h. The resulting orange solution of L4Li was added to
a pre-cooled solution (-60 ◦C) of BiCl3 (2.11 g, 6.7 mmol) in Et2O
(60 mL). The reaction mixture was stirred for 12 h. The volume of
reaction mixture was reduced to ca. one half and hexane (10 mL)
was added. The insoluble material was collected by filtration and
extracted with CH2Cl2 (30 mL). The extract was evaporated to
dryness, washed with hexane (10 mL) and dried in vacuo to give 10
as a cream solid. (1.57 g, 47%), mp 228 ◦C (decomp.). Anal. Calc.
for C14H22Cl2BiON (MW 500.22): C, 33.6; H, 4.4. Found: C, 33.9;
H, 4.5%. 1H NMR (500 MHz, CDCl3): d 1.54 (9H, s, (CH3)3CO),
3.13 (6H, s, (CH3)2N), 4.78 (2H, s, NCH2), 5.08 (2H, s, OCH2), 7.47
(1H, dd, Ar-H), 7.73 (1H, d, Ar-H), 7.80 (1H, d, Ar-H). 13C NMR
(125.76 MHz, CDCl3): d 28.7 (s, (CH3)3CO), 48.9 (s, (CH3)2N),
68.4 (s, NCH2), 71.4 (s, OCH2), 81.0 (s, (CH3)3CO), 127.2, 128.2,
129.2, 150.0, 152.4 (s, Ar-C), (Ar-C1) not observed. Positive-ion
MS: m/z 464 [M - Cl]+ (100%); m/z 408 [M - Cl - C4H8]+ (10%).
Negative-ion MS: m/z 534 [M + Cl]- (100%).
◦
7 as a white powder (0.28 g, 88%), mp 115 C (decomp.). Anal.
Calc. for C17H25ClSbSO5F3 (MW 555.65): C, 36.8; H, 4.5. Found:
1
C, 36.9; H, 4.7%. H NMR (500 MHz, CDCl3): d 1.70 (18H, s,
(CH3)3CO), 5.17 (4H, s, OCH2), 7.28 (2H, d, Ar-H3,5), 7.46 (1H,
t, Ar-H4). 13C NMR (125.76 MHz, CDCl3): d 28.7 (s, (CH3)3CO),
68.0 (s, OCH2), 87.4 (s, (CH3)3CO), 119.7 (q, CF3, J(13C,19F) =
1
318 Hz), 123.0 (s, Ar-C3,5), 131.1 (s, Ar-C4), 142.9 (s, Ar-C2,6),
147.7 (Ar-C1). Positive-ion MS: m/z 791 [(L3)2Sb2O2 + H2O +
H]+ (24%); m/z 773 [(L3)2Sb2O2 + H]+ (17%); m/z 405 [L3SbCl]+
(20%); m/z 387 [L3SbOH]+ (100%); m/z 349 [L3SbCl - C4H8]+
(11%); m/z 331 [L3SbOH - C4H8]+ (58%); m/z 313 [L3SbOH -
C4H8 - H2O]+ (23%); m/z 293 [L3SbCl - 2C4H8]+ (21%); m/z 257
[L3SbOH - 2C4H8 - H2O]+ (21%). Negative-ion MS: m/z 149
[CF3SO3]- (100%).
Synthesis of [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]SbCl2 (8).
A
hexane solution of n-BuLi (2.1 mL, 3.3 mmol, 1.6 M solution)
was added to a solution of L4H (0.73 g, 3.3 mmol) in hexane
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8922–8934 | 8931
©

Synthesis of [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]BiCl(CF3SO3)
(11). Analogously to the procedure described for 9. AgOTf
(119 mg, 0.46 mmol) and 10 (230 mg, 0.46 mmol). (11, 166 mg,
group within the carborane cage in the structure of 9 was placed
by the help of C–B and B–B interatomic distances comparison.
There are large electron density maxima in close proximity of the
Bi atom in 10, 11 and 12. This is probably due to the application
of an improper absorption correction method. We tried different
possible methods but the best result obtained for this parameter is
still unsatisfactorily high. In the case of bismuth compounds the
location of the maxima, which have no chemical significance, we
think is not a serious problem.
◦
59%), mp 171–174 C. Anal. Calc. for C15H22ClF3BiO4NS (MW
613.84): C, 29.4; H, 3.6. Found: C, 29.6; H, 3.7%. 1H NMR
(500 MHz, CDCl3): d 1.61 (9H, s, (CH3)3CO), 3.11 (6H, s,
(CH3)2N), 4.77 (2H, s, NCH2), 5.16 (2H, s, OCH2), 7.59 (1H,
dd, Ar-H), 7.84 (1H, d, Ar-H), 7.92 (1H, d, Ar-H). 13C NMR
(125.76 MHz, CDCl3): d 28.5 (s, (CH3)3CO), 48.4 (s (br),
(CH3)2N), 69.0 (s, NCH2), 71.1 (s, OCH2), 82.1 (s, (CH3)3CO),
Crystallographic data for 2. 2(C20H26AsClO4), M = 881.56, or-
1
119.3 (q, CF3, J(13C,19F) = 320 Hz), 127.3, 128.4, 130.4, 151.2,
˚
thorhombic, Pna21, a = 17.0370(5), b = 7.618(2), c = 31.5390(14) A,
153.4 (s, Ar-C), (Ar-C1) not observed. Positive-ion MS: m/z 464
[L4BiCl]+ (100%); m/z 408 [L4BiCl - C4H8]+ (69%). Negative-ion
MS: m/z 149 [CF3SO3]- (100%).
3
˚
V = 4093.4(13) A , Z = 4, T = 150(1) K, 17720 total reflections,
8315 independent (Rint = 0.051, R1 (obs. data) = 0.062, wR2 (all
data) 0.125).
Synthesis of [2-(Me2NCH2)-6-(t-BuOCH2)C6H3]BiCl(CB11H12)
(12). Analogously to the procedure described for 9. AgCB11H12
(88 mg, 0.35 mmol) and 10 (175 mg, 0.35 mmol). (12, 115 mg,
63%), mp 205 ◦C (decomp.). Anal. Calc. for C15H34ClB11BiON
(MW 520.57): C, 34.6; H, 6.6. Found: C, 34.7; H, 6.8%. 1H
NMR (500 MHz, CDCl3): d 1.59 (9H, s, (CH3)3CO), 3.11 (6H, s,
(CH3)2N), 4.84 (2H, s, NCH2), 5.17 (2H, s, OCH2), 7.68 (1H,
dd, Ar-H), 7.91 (1H, d, Ar-H), 8.04 (1H, d, Ar-H). 13C NMR
(125.76 MHz, CDCl3): d 28.6 (s, (CH3)3CO), 47.9 (s, (CH3)2N),
53.1 (s (br), C-cage), 69.3 (s, NCH2), 71.5 (s, OCH2), 83.1 (s,
(CH3)3CO), 127.7, 129.0, 131.3, 151.4, 153.9 (s, Ar-C), (Ar-C1)
not observed. Positive-ion MS: m/z 464 [L4BiCl]+ (100%); m/z
408 [L4BiCl - C4H8]+ (94%). Negative-ion MS: m/z 145 [CB11H12]-
(100%).
Crystallographic data for 3. C26H29AsCl2O2), M = 519.31,
¯
˚
triclinic, P1, a = 8.0719(6), b = 11.9821(9), c = 13.1989(6) A, a =
◦
3
˚
80.579(5), b = 79.169(4), g = 79.737(7) , V = 1222.53(14) A , Z =
2, T = 150(1) K, 22718 total reflections, 5590 independent (Rint
0.036, R1 (obs. data) = 0.036, wR2 (all data) 0.075).
=
Crystallographic data for 4. C12H16AsClO2, M = 302.62,
˚
monoclinic, C2/c, a = 25.3962(7), b = 8.1221(9), c = 14.6069(12) A,
3
˚
b = 116.012(7), V = 2707.7(4) A , Z = 8, T = 150(1) K, 10758 total
reflections, 3091 independent (Rint = 0.134, R1 (obs. data) = 0.067,
wR2 (all data) 0.087).
Crystallographic data for 5. C14H22AsCl2ON, M = 366.15,
monoclinic, P21/c,
a
=
11.2757(8),
b
=
10.3700(4),
˚
c
=
3
˚
16.1121(16) A, b = 121.939(6), V = 1598.8(2) A , Z = 4, T =
150(1) K, 14207 total reflections, 3642 independent (Rint = 0.043,
R1 (obs. data) = 0.041, wR2 (all data) 0.085).
X-Ray crystallography
Suitable single crystals were mounted on glass fibre with oil
and measured on four-circle diffractometer KappaCCD with
Crystallographic data for 6. C48H64Sb4Cl4O8·4.5CH2Cl2 M =
1779.96, monoclinic, P21/c, a = 18.544(2), b = 19.350(2), c =
3
CCD area detector by monochromatized Mo-Ka radiation (l =
˚
˚
26.135(3) A, b = 134.565(12), V = 6681.3(14) A , Z = 4, T =
150(1) K, 81089 total reflections, 13081 independent (Rint = 0.059,
R1 (obs. data) = 0.053, wR2 (all data) 0.105).
31
˚
0.71073 A) at 150(1) K. Numerical absorption corrections from
crystal shape were applied for all crystals. The structures were
solved by the direct method (SIR92)32 and refined by a full-matrix
least-squares procedure based on F2 (SHELXL97)33 Hydrogen
atoms were fixed into idealized positions (riding model) and
assigned temperature factors Uiso(H) = 1.2Ueq (pivot atom) or
of 1.5Ueq for the methyl moiety with C–H = 0.96, 0.97 and
Crystallographic data for 7. C16H25SbClO2·CF3SO3, M =
555.63, monoclinic, P21/c, a = 9.3050(10), b = 12.4460(12), c =
3
˚
˚
19.4031(14) A, b = 104.615(6), V = 2174.4(4) A , Z = 4, T = 150(1)
K, 17557 total reflections, 4950 independent (Rint = 0.045, R1 (obs.
data) = 0.036, wR2 (all data) 0.069).
˚
0.93 A for methyl, methylene and hydrogen atoms in aromatic
ring, respectively. The final difference maps displayed no peaks
of chemical significance, as the highest peaks and holes are
Crystallographic data for 8. C14H22SbCl2ON, M = 412.98,
˚
monoclinic, P21/c, a = 11.525(4), b = 10.5691(13), c = 16.038(3) A,
3
˚
˚
in close vicinity (~ 1 A) of the heavy atoms, in the case of
b = 122.680(18), V = 1644.3(7) A , Z = 4, T = 150(1) K, 12117
compounds 3–5, 7 and 8. Two independent molecules were
observed in the asymmetric unit cell of 2. One of the coordinating
arms of one of the molecules is strongly disordered. It was not
possible to model this disordered group with a satisfactory result,
nevertheless the second molecule was well modeled. There is
disordered solvent (dichloromethane) in the small, porous and
weakly diffracting crystal of 6. Attempts were made to model this
disorder or split it into two positions but this was unsuccessful.
PLATON/SQUEEZE34 was used to correct the data for the
presence of disordered solvent. A potential solvent volume of
total reflections, 3748 independent (Rint = 0.034, R1 (obs. data) =
0.033, wR2 (all data) 0.075).
Crystallographic data for 9. C14H22SbClON·CB11H12·CH2Cl2
¯
M = 605.47, triclinic, P1, a = 9.5870(3), b = 12.0591(6), c =
◦
˚
13.2669(6) A, a = 65.008(5), b = 88.935(4), g = 84.972(3) , V =
1384.54(12) A , Z = 2, T = 150(1) K, 29624 total reflections, 6648
3
˚
independent (Rint = 0.020, R1 (obs. data) = 0.023, wR2 (all data)
0.059).
Crystallographic data for 10. C14H22BiCl2ON, M = 500.21,
3
˚
852 A was found. 433 electrons per unit cell worth of scattering
monoclinic, P21/c,
a
=
9.21985(4),
b
=
11.7940(7),
˚
c
=
3
˚
were located in the void. The calculated stoichiometry of solvent
was calculated to be ten additional molecules of dichloromethane
per unit cell which results in 420 electrons per unit cell. The C–H
17.0903(11) A, b = 112.714(4), V = 1714.25(16) A , Z = 4, T =
150(1) K, 12032 total reflections, 3853 independent (Rint = 0.042,
R1 (obs. data) = 0.042, wR2 (all data) 0.093).
8932 | Dalton Trans., 2011, 40, 8922–8934
This journal is
The Royal Society of Chemistry 2011
©

Crystallographic data for 11. C14H22BiClON·CF3SO3, M =
Ludwig and K. Jurkschat, Organometallics, 2001, 20, 4654; (d) M.
Mehring, C. Low, M. Schu¨rmann and K. Jurkschat, Eur. J. Inorg.
Chem., 1999, 887.
9 (a) S. Sarkar, A. R. Carlson, M. K. Veige, J. M. Falkowski, K. A.
Abboud and A. S. Veige, J. Am. Chem. Soc., 2008, 130, 1116; (b) S.
Kuppuswamy, A. J. Peloquin, I. Ghiviriea, K. A. Abboud and A. S.
Veige, Organometallics, 2010, 29, 4227.
¯
˚
613.83, triclinic, P1, a = 7.7441(5), b = 11.0320(8), c = 12.5790(8) A,
◦
3
˚
a = 74.564(5), b = 85.146(5), g = 74.351(5) , V = 997.39(12) A ,
Z = 2, T = 150(1) K, 18498 total reflections, 4494 independent
(Rint = 0.087, R1 (obs. data) = 0.079, wR2 (all data) 0.192).
Crystallographic data for 12. C14H22BiClON·CB11H12·
10 J. Vicente, A. Arcas and M. D. Ga´lvez-Lo´pez, Organometallics, 2004,
23, 3521.
¯
2CH2Cl2, M = 777.62, triclinic, P1, a = 9.1429(7), b = 11.9780(4◦),
11 (a) M. Gandelman, A. Vigalok, L. J. W. Shimon and D. Milstein,
Organometallics, 1997, 16, 3981; (b) M. Gandelman, L. Konstanti-
novski, H. Rozenberg and D. Milstein, Chem.–Eur. J., 2003, 9,
2595; (c) M. Gandelman, B. Rybtchinski, N. Ashkenazi, R. M.
Gauvin and D. Milstein, J. Am. Chem. Soc., 2001, 123, 5372; (d) B.
Rybtchinski, S. Oevers, M. Montag, A. Vigalok, H. Rozenberg, J. M. L.
Martin and D. Milstein, J. Am. Chem. Soc., 2001, 123, 9064; (e) J.
Fischer, M. Schu¨rmann, M. Mehring, V. Zachwieja and K. Jurkschat,
Organometallics, 2006, 25, 2886.
˚
c = 15.2951(9) A, a = 71.583(6), b = 81.044(6), g = 87.254(7) ,
3
˚
V = 1569.86(17) A , Z = 2, T = 150(1) K, 27420 total reflections,
7142 independent (Rint = 0.031, R1 (obs. data) = 0.030, wR2 (all
data) 0.070).
Acknowledgements
12 (a) V. A. Kozlov, D. V. Aleksanyan, Y. V. Nelyubina, K. A. Lyssenko,
A. A. Vasil’ev, P. V. Petrovskii and I. L. Odinest, Organometallics,
2010, 29, 2054; (b) A. Choualeb, A. J. Lough and D. G. Gusev,
Organometallics, 2007, 26, 5224; (c) V. Gomez-Benitez, R. A. Toscano
and D. Morales-Morales, Inorg. Chem. Commun., 2007, 10, 1; (d) E.
Poverenov, M. Gandelman, L. J. W. Shimon, H. Rozenberg, Y. Ben-
David and D. Milstein, Organometallics, 2005, 24, 1082; (e) G. R.
Fulmer, W. Kaminski, R. A. Kemp and K. I. Goldberg,
Organometallics, 2011, 30, 1627.
The authors thank the Grant agency of the Czech Republic
project no. P207/10/0215 and the Ministry of Education of
the Czech Republic (projects MSM0021627501) for financial
support. R. Jira´sko acknowledges the support of grant project No.
MSM0021627502 sponsored by The Ministry of Education, Youth
and Sports of the Czech Republic. F. D. P. wishes to acknowledge
the Research Foundation Flanders (FWO) and the Free University
of Brussels (VUB) for continuous support to his research group.
13 R. Jambor, L. Dosta´l, A. Ru˚,zˇicˇka, I. C´ısarˇova´, J. Brus and J. Holecˇek,
Organometallics, 2002, 21, 3996.
14 For example, see: (a) L. Dosta´l, I. C´ısarˇova´, R. Jambor, A. Ru˚zˇicˇka, R.
Jira´sko and J. Holecˇek, Organometallics, 2006, 25, 4366; (b) L. Dosta´l,
R. Jambor, A. Ru˚zˇicˇka, I. C´ısarˇova´ and J. Holecˇek, Appl. Organomet.
Chem., 2005, 19, 797; (c) B. Kasˇna´, R. Jambor, L. Dosta´l, I. C´ısarˇova´, J.
Notes and references
1 G. van Koten, Pure Appl. Chem., 1989, 61, 1681.
ˇ
2 For several examples, see: (a) M. Albrecht and G. van Koten, Angew.
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Chem. Rev., 2003, 103, 1759; (c) The Chemistry of Pincer Compounds,
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915.
Holecˇek and B. St´ıbr, Organometallics, 2006, 25, 5139; (d) L. Dosta´l, R.
Jambor, A. Ru˚zˇicˇka, A. Lycˇka, J. Brus and F. de Proft, Organometallics,
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Locharˇ, L. Benesˇ and F. de Proft, Inorg. Chem., 2009, 48, 10495; (f) L.
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