Diorganodiselenides and zinc(ii) organoselenolates containing (imino)aryl groups of type 2-(RNCH)C6H4

Article abstract of DOI:10.1039/c2dt30098b

Several new diorganodiselenides containing (imino)aryl groups, [2-(RNCH)C₆H₄]₂Se₂ [R = Me ₂NCH₂CH₂ (4), O(CH₂CH ₂)₂NCH₂CH₂ (5), PhCH₂ (6), 2′,6′-ⁱPr₂C₆H₃ (7)] were obtained by reacting [2-{(O)CH}C₆H₄] ₂Se₂ (3) with RNH₂. Treatment of the diselenides 6 and 7 with stoichiometric amounts of K-selectride or Na resulted in isolation of the selenolates K[SeC₆H₄(CHNCH ₂Ph)-2] (9) and Na[SeC₆H₄(CHNC ₆H₃ⁱPr₂-2′,6′)-2] (10), respectively. The reaction of potassium selenolates with anhydrous ZnCl ₂ (2:1 molar ratio) gave Zn[SeC₆H₄(CHNCH ₂Ph)-2]₂ (11) and Zn[SeC₆H ₄(CHNC₆H₃ⁱPr₂-2′, 6′)-2]₂ (12). When the dark green solution obtained from diselenide 7 and an excess of Na (after removal of the unreacted metal) was reacted with anhydrous ZnCl₂ a carbon-carbon coupling reaction occurred and the 9,10-(2′,6′-ⁱPr₂C ₆H₃NH)₂C₁₄H₁₀ (8) species was obtained. The compounds were investigated in solution by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, including 2D and variable temperature experiments) and by mass spectrometry. The molecular structures of 6, 8, 11 and 12 were established by single-crystal X-ray diffraction. All compounds are monomeric in the solid state. In the diselenide 6 the (imino)aryl group acts as a (C,N)-ligand resulting in a distorted T-shaped coordination geometry of type (C,N)SeX (X = Se). For the zinc complexes 11 and 12 the (Se,N) chelate pattern of the selenolato ligands results in tetrahedral Zn(Se,N) ₂ cores. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt30098b

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PAPER
Diorganodiselenides and zinc(II) organoselenolates containing (imino)aryl
groups of type 2-(RNvCH)C6H4†‡
Alpar Pöllnitz,a Cristian Silvestru,a Jean-François Carpentierb and Anca Silvestru*a
Received 13th January 2012, Accepted 10th February 2012
DOI: 10.1039/c2dt30098b
Several new diorganodiselenides containing (imino)aryl groups, [2-(RNvCH)C6H4]2Se2
[R = Me2NCH2CH2 (4), O(CH2CH2)2NCH2CH2 (5), PhCH2 (6), 2′,6′-iPr2C6H3 (7)] were obtained by
reacting [2-{(O)CH}C6H4]2Se2 (3) with RNH2. Treatment of the diselenides 6 and 7 with stoichiometric
amounts of K-selectride or Na resulted in isolation of the selenolates K[SeC6H4(CHvNCH2Ph)-2] (9)
i
and Na[SeC6H4(CHvNC6H3 Pr2-2′,6′)-2] (10), respectively. The reaction of potassium selenolates with
anhydrous ZnCl2 (2 : 1 molar ratio) gave Zn[SeC6H4(CHvNCH2Ph)-2]2 (11) and
i
Zn[SeC6H4(CHvNC6H3 Pr2-2′,6′)-2]2 (12). When the dark green solution obtained from diselenide 7
and an excess of Na (after removal of the unreacted metal) was reacted with anhydrous ZnCl2 a
carbon–carbon coupling reaction occurred and the 9,10-(2′,6′-iPr2C6H3NH)2C14H10 (8) species was
obtained. The compounds were investigated in solution by multinuclear NMR (1H, 13C, 77Se, including
2D and variable temperature experiments) and by mass spectrometry. The molecular structures of 6, 8, 11
and 12 were established by single-crystal X-ray diffraction. All compounds are monomeric in the solid
state. In the diselenide 6 the (imino)aryl group acts as a (C,N)-ligand resulting in a distorted T-shaped
coordination geometry of type (C,N)SeX (X = Se). For the zinc complexes 11 and 12 the (Se,N) chelate
pattern of the selenolato ligands results in tetrahedral Zn(Se,N)2 cores.
reduce the degree of oligomerization for Group 12 metal seleno-
Introduction
lates, i.e. (i) the use of organoselenolato ligands with bulky sub-
stituents,31 (ii) the increase of the coordination number to the
Organoselenium compounds containing an intramolecular
metal centre by additional neutral ligands,31d,32 or (iii) a combi-
N→Se interaction have attracted much interest in recent years
mainly due to their increased stability as monomeric species and
their applications in biology, asymmetric synthesis, catalysis or
microelectronics.1–19 The presence of an organic group contain-
ing donor atoms available for intramolecular coordination pro-
vides increased stability of the monomeric Main Group metal
selenolates.20–29 The Group 12 metal selenolates have raised
considerable interest as single-source precursors for CVD pro-
cesses.30 Different strategies have been used in order to avoid
polymerization, to stabilize monomeric species or, at least, to
nation of the advantages of both the above approaches by using
organic groups containing donor atoms capable of intramolecular
coordination.29,30d,e,33
As part of our interest in hypervalent organoselenium com-
pounds containing organic groups with pendant arms19 and their
use as precursors for the preparation of metal selenolates, we
have reported recently on the synthesis, solution behaviour and
molecular structures of some new Group 12 metal complexes of
M[SeC6H4(CH2NR2)-2]2 (R = Me, Et; M = Zn, Cd).34 As a con-
tinuation of these previous studies we report herein the synthesis
and spectroscopic characterization of several new diorganodise-
lenides containing (imino)aryl groups, [2-(RNvCH)C6H4]2Se2
[R = Me2NCH2CH2 (4), O(CH2CH2)2NCH2CH2 (5), PhCH2 (6),
2′,6′-iPr2C6H3 (7)], as well as the alkali metal,
M[SeC6H4(CHvNR)-2] [M = K, R = PhCH2 (9); M = Na,
aDepartamentul de Chimie Anorganica, Facultatea de Chimie si
Inginerie Chimica, Universitatea Babes-Bolyai, RO-400028 Cluj-
Napoca, Romania. E-mail: ancas@chem.ubbcluj.ro; Fax: (+40) 264-
590818; Tel: (+40) 264-593833
bCatalysis and Organometallics, UMR CNRS 6226-Université de
Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
†Electronic supplementary information (ESI) available: X-ray crystallo-
graphic data in CIF format for 6, 8, 11 and 12; numbering schemes for
NMR resonance assignments; selected molecular parameters for 8;
figures representing the optical isomers in the crystals of compounds 11
and 12; figures representing the supramolecular architectures in the crys-
tals of 6, 8, 11 and 12; variable temperature NMR spectra for 12. CCDC
reference numbers 811932 (6), 811929 (8), 811930 (11) and 811931
(12). For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c2dt30098b
R
=
2′,6′-iPr2C6H3 (10)], and the zinc(II) selenolates,
Zn[SeC6H4(CHvNR)-2]2 [R = PhCH2 (11), 2′,6′-iPr2C6H3
(12)]. A serendipitous product, 9,10-(2′,6′-iPr2C6H3NH)2C14H10
(8), is also described. It was isolated following a carbon–carbon
coupling process which occurred when the reaction of the dark
green solution obtained from diselenide 7 and excess of Na
(after removal of the unreacted metal) was reacted with anhy-
drous ZnCl2. It should be noted here that C–C coupling reactions
were previously described to occur when the reduction of
‡Dedicated to Professor Ionel Haiduc on the occasion of his 75th
birthday.
5060 | Dalton Trans., 2012, 41, 5060–5070
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transition metal complexes supported by Schiff-base ligands was
carried out with elemental sodium.35
thus suggesting the equivalence of the organic groups in the
molecule of the unique species, i.e. the diselenide, present in sol-
1
ution. The H NMR spectra clearly show the formation of the
–CHvN– double bond due to the upfield shift observed for the
CH proton from δ 10.16 ppm for the starting material 3 (alde-
hyde derivative) to δ 8.57 (4), 8.53 (5), 8.67 (6) and 8.52 (7)
ppm (imine derivatives). Therefore 1H NMR spectroscopy is
very useful to monitor the condensation reactions to yield dior-
ganodiselenides supported by Schiff-base ligands (for details,
see ESI†).
Results and discussion
Synthesis and characterization of diselenides [2-(RNvCH)
C6H4]2Se2 [R = Me2NCH2CH2 (4), O(CH2CH2)2NCH2CH2 (5),
PhCH2 (6), 2′,6′-iPr2C6H3 (7)]
The diselenide 3, already described in the literature,10c,11h,36 is a
useful starting material for the synthesis of diorgano diselenium
(I) compounds supported by Schiff-base ligands11h and it was
obtained using an original, efficient procedure to deprotect the
corresponding acetal 2 using aqueous HCl. The diselenides 4–7
were prepared by simple condensation between 3 and the corre-
sponding amines (Scheme 1). When the reaction was carried out
in CH2Cl2 in the presence of anhydrous Na2SO4 or in refluxing
toluene with a Dean–Stark trap, with or without acid catalyst, no
condensation product was observed and the unreacted starting
materials were quantitatively recovered. The desired conden-
sations were achieved in refluxing acetonitrile, in the absence of
TosOH or anhydrous Na2SO4. It should also be noted that the
attempts to prepare compound 7 using the treatment of the
Grignard reagent with elemental selenium, followed by hydroly-
sis/oxidation, have failed. Similar condensation reactions were
used to prepare mercury(II)37 and antimony(III)38 complexes sup-
ported by (imino)aryl ligands of the same type.
77Se NMR spectroscopy is a useful tool for the characteriz-
ation of organoselenium compounds due to the high sensitivity
of this nucleus. The 77Se chemical shifts of the diselenides 4–7
range from δ 467.9 to 471.1 ppm. The observed values are in
good agreement with that found for the related [2-
(PhMeCHvNCH)C6H4]2Se2 (δ 478 ppm).11h The downfield
shift for compounds 4–7 compared to the related diselenides [2-
{E(CH2CH2)2NCH2}C6H4]2Se2 (E = O, δ 424.0 ppm; E = MeN,
δ
425.4 ppm),19b [2-(R2NCH2)C6H4]2Se2 (R
= Me, δ
430 ppm;11a R = Et, δ 427.4 ppm34) or [2-(CyMeNCH2)
C6H4]2Se2 (δ 431.9 ppm),10a might indicate that the sp2 nitrogen
atom is involved in
interaction.11h
a
stronger intramolecular N→Se
In the IR spectra of compounds containing Schiff-base ligands
the stretching vibration of the carbon–nitrogen double bond is
expected to be found in the 1650–1550 cm−1 region. Broad
bands of medium intensity, shifted to lower wave numbers,
would be expected for the title compounds if intramolecular
N→Se coordination is present and consequent delocalization of
the π electrons in the –CvN– bond over the formed C3NSe ring
occurs. The νCvN stretching vibration was observed at 1642 and
1634 cm−1 for compounds 6 and 7, respectively. The sharp
pattern of the bands is consistent with a considerable weakness
of the intramolecular N→Se coordination, if present.
The solid state molecular structure of 6 was established by
single-crystal X-ray diffraction and it is depicted in Fig. 1.
Selected interatomic distances and angles are listed in Table 1.
The crystal contains discrete molecules of diastereoisomer E
regarding both –CvN– double bonds. The conformation of the
The new diselenides were obtained in good or moderate yields
as orange oils (4 and 5) or pale yellow solids (6 and 7). They are
soluble in common organic solvents, such as acetonitrile (hot,
for 6 and 7) or chloroform. NMR data of 4–7 as well as elemen-
tal analytical data are consistent with the anticipated formulas.
The NMR spectra of the new compounds 4–7 were recorded
in CDCl3 solution, at room temperature. The assignment of res-
1
onances in the H and 13C NMR spectra was made on the basis
of 2D NMR (HSQC, HMBC and COSY) correlation spectra (for
the numbering schemes, see ESI†). The room temperature NMR
(1H, 13C) spectra for compounds 4–7 provided no evidence for
the presence of N→Se intramolecular interactions in solution.
For all compounds only one set of resonances was observed,
Fig. 1 ORTEP representation at 30% probability and atom numbering
scheme for 6.
Scheme 1 Preparation of diselenides 4–7.
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Table 1 Selected bond distances (Å) and angles (°) for compound 6
Se(1)–Se(2)
Se(1)–C(1)
Se(1)–N(1)
2.3585(4)
1.935(3)
2.795(2)
Se(2)–C(15)
Se(2)–N(2)
1.932(3)
2.650(2)
N(1)–C(7)
N(1)–C(8)
1.254(3)
1.455(3)
N(2)–C(21)
N(2)–C(22)
1.249(3)
1.459(3)
C(1)–Se(1)–Se(2)
C(1)–Se(1)–N(1)
N(1)–Se(1)–Se(2)
102.34(8)
74.31(9)
166.21(5)
C(15)–Se(2)–Se(1)
C(15)–Se(2)–N(2)
N(2)–Se(2)–Se(1)
103.01(8)
75.51(9)
176.49(5)
Scheme 2 Preparation of compound 8.
C(7)–N(1)–C(8)
C(7)–N(1)–Se(1)
C(8)–N(1)–Se(1)
118.5(2)
98.0(2)
143.5(2)
C(21)–N(2)–C(22)
C(21)–N(2)–Se(2)
C(22)–N(2)–Se(2)
119.2(3)
101.5(2)
138.9(2)
C–Se–Se–C skeleton can be discussed in terms of “cisoid”
(C–Se–Se–C torsion angle smaller than 90°) and “transoid”
(C–Se–Se–C torsion angle larger than 90°) conformations. The
torsion angle found for the C(1)–Se(1)–Se(2)–C(15) core in
the molecule of 6 [77.8(1)°] is consistent with a “cisoid”
conformation.
The intramolecular selenium–nitrogen interactions established
in the diselenide 6 are not equivalent [Se(1)–N(1) 2.795(2) Å;
Se(2)–N(2) 2.650(2) Å; cf. the sum of the corresponding van der
Waals radii, ∑rvdW(Se,N) = 3.54 Å39]. They are significantly
shorter than in the related [2-(R2NCH2)C6H4]2Se2 [R = Me,
2.856(3)/2.863(4) Å;11a R = Et, 2.713(5)/3.068(6) Å34] or [2-{E
(CH2CH2)2NCH2}C6H4]2Se2 [E = O, 2.813(2)/2.825(3) Å; E =
MeN, 3.135(3)/2.7393(3) Å],19b a behaviour consistent with the
sp2 nature of the donor nitrogen atoms. Consequently, the sum of
the angles around each nitrogen atom [360.0(2)° for N(1) and
359.6(2)° for N(2)] is consistent with a trigonal planar geometry.
Due to the intramolecular N→Se interactions a distorted T-
shaped geometry is achieved around each selenium atom (hyper-
valent 10-Se-3 species).40 The five-membered chelate rings thus
formed are basically planar, with a deviation of 0.101(2) Å of N
(1) and 0.061(2) Å of N(2) from the best residual Se(1)C3 and
Se(2)C3 planes, respectively.
A closer check of the crystal packing of the diselenide 6
revealed C–Haryl⋯π (Phcentroid) distances which suggest some π
interaction between a hydrogen atom and an aromatic ring (i.e.
H⋯Phcentroid contacts shorter than 3.1 Å, with an angle γ
between the normal to the phenyl ring and the line defined by
the H atom and Phcentroid smaller than 30°). These result in the
formation of polymeric chains along the b axis [C(21)–H(21)
⋯Phcentroid{C(9a)–C(14a)} 2.96 Å, γ = 10.7°] (for details, see
ESI†).
Fig. 2 ORTEP representation at 30% probability and atom numbering
scheme for 8. Hydrogen atoms [except those attached to C(13), C(14)
and nitrogen atoms] are omitted for clarity.
spectrum we presumed that this product does not contain sel-
enium. The MS studies were also consistent with the absence of
selenium and any metal. Detailed NMR studies were used to elu-
cidate the structure of this compound. The presence of a doublet
1H resonance in the aliphatic region (δ 4.14 ppm) uncorrelated to
a carbon atom in the HSQC spectrum suggests a reduction of the
imino group to an amino group, i.e. from –NvCH– to –NH–
CH– (also supported by the doublet resonance at δ 4.99 ppm
assigned to the –CH– group). The formation of the serendipitous
coupling product 8 (Scheme 2) was also supported by the ESI+
mass spectrum which contains peaks corresponding to the
pseudo-molecular ion [M + H+] with the expected isotopic
distribution.
Single crystals of 8 were obtained by slow evaporation of an
acetonitrile solution and an X-ray diffraction study has confirmed
the proposed molecular structure. A molecule of 8 is depicted in
Fig. 2 and reveals the presence of the –NH–CH– system as result
of the imino group reduction and the C–C coupling reaction (the
molecular parameters for 8 are available in the ESI†).
In the crystal of 8 dimer associations are formed through
C–Haryl⋯π (Phcentroid) interactions [C(4)–H(4)⋯Phcentroid{C(27)–
C(32)} 2.86 Å, γ = 12.6°]. Two intramolecular C–Halkyl⋯π
(Phcentroid) interactions [C(23)–H(23B)⋯Phcentroid{C(7)–C(12)}
2.86 Å, γ = 2.5°; C(36)–H(36)⋯Phcentroid{C(27)–C(32)} 3.00 Å,
γ = 28.3°] are also present. Such dimers are further associated
through C–Hmethyl⋯π (Phcentroid) interactions [C(35)–H(35A)
⋯Phcentroid{C(15a)–C(20a)} 2.84 Å, γ = 11.5°] into ribbon-like
chain polymers. Layers are built subsequently from parallel
chains linked by C–Hmethyl⋯π (Phcentroid) interactions [C(34)–H
(34A)⋯Phcentroid{C(27)–C(32)} 2.84 Å, γ = 14.9°] (for details,
see ESI†).
Synthesis and characterization of the serendipitous product,
9,10-(2′,6′-iPr2C6H3NH)2C14H10 (8), and of the metal
organoselenolates, M[SeC6H4(CHvNR)-2] [M = K, R = PhCH2
(9); M = Na, R = 2′,6′-iPr2C6H3 (10)], and Zn
[SeC6H4(CHvNR)-2]2 [R = PhCH2 (11), 2′,6′-iPr2C6H3 (12)]
In an attempt to prepare a zinc(II) selenolate the dark green THF
solution resulting from reducing the diorganodiselenide 7 with a
large excess of sodium mirror was added to ZnCl2, under argon.
After working-up the reaction mixture, yellow crystals of 8 were
isolated. Since no resonance was observed in the 77Se NMR
5062 | Dalton Trans., 2012, 41, 5060–5070
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Scheme 4 Preparation of compounds 11 and 12.
achieved using sodium sand (a stoichiometric amount of Na was
used to avoid over-reduction) to yield the sodium selenolate 10.
The diselenides 4 and 5 were not used in this work to prepare
new alkali metal selenolates or the corresponding zinc(II) com-
1
plexes. The H NMR spectra for the selenolates 9 and 10 were
recorded in THF-d8. A downfield shift of the resonance for the
imine proton was observed for the potassium selenolate 9 (δ
9.58 ppm) compared to the corresponding diselenide 6 (δ
8.67 ppm). The reaction of 7 with sodium sand, in THF-d8, was
monitored for 15 days in an NMR tube. The resonance corre-
sponding to the proton of the –CHvN– group was also signifi-
cantly shifted downfield for the selenolate 10 (δ 9.15 ppm) with
respect to the starting diselenide 7 (δ 8.52 ppm).
Zinc(II) selenolates 11 and 12 were prepared by salt metathesis
reactions between anhydrous ZnCl2 and two equivalents of the
corresponding potassium selenolates (Scheme 4). The resulting
greenish-yellow solids are moderately air-sensitive and they
decompose to the corresponding diselenides in a few days. Spec-
troscopic studies, as well as elemental analytical data, are con-
sistent with the anticipated formulas. Atmospheric pressure
chemical ionization (APCI+) mass spectra showed for both zinc
complexes significant peaks corresponding to the pseudo-mol-
ecular ion [M + H+].
The IR spectra indicated the presence of the –CvN– double
bond for these Zn(II) complexes supported by Schiff-base
ligands. The νCvN stretching vibration was observed at
1617 cm−1 and 1604 cm−1 for 11 and 12, respectively, shifted to
lower wavenumbers when compared to the corresponding disele-
nides (νCvN 1642 and 1634 cm−1 for 6 and 7, respectively).
This is consistent with a strong intramolecular N→Zn coordi-
nation and consequent partial electron delocalization within
the six-membered ZnSeC3N ring, assuming a solid state
structure similar to that established for the related Zn-
[SeC6H4(CH2NMe2)-2]2.34
Scheme 3 The proposed mechanism for the formation of 8 (R =
2′,6′-iPr2C6H3).
A mechanism for the formation of 8 (Scheme 3) can be specu-
lated based on (i) the deep green colour of the THF solution
obtained from the diselenide 7 and a large excess of sodium, and
(ii) the cis-9,10-bis(arylamino)-9,10-dihydroanthracene core of
the finally isolated organic species 8. In a first step a radical
intermediate (A) is considered to be formed through a THF-
assisted process, followed by its conversion to an organosodium
species (B) in the presence of excess Na. Treatment with ZnCl2
results in an organozinc(II) species which undergoes a rearrange-
ment with C–C bond formation. The formation of the intermedi-
ate complex (D) might be decisive for the isolation of the cis-8
isomer. It should be mentioned here the recent report of the reac-
tion of 2-(2′,6′-iPr2C6H3NvCH)C6H4Li with TiCl4 (2 : 1 molar
ratio) which resulted in isolation of the unexpected [cis-9,10-
PhenH2(NR)2TiCl2] species (PhenH2 = 9,10-dihydrophenan-
threne; R = 2′,6′-iPr2C6H3), which contains a related organic
ligand obtained by sequential intramolecular C–C bond-forming
reductive elimination and oxidative coupling reactions.41
The NMR spectra of complexes 11 and 12 were recorded in
CDCl3 solution. The assignment of resonances in the 1H and 13
C
NMR spectra was based on 2D NMR (HSQC, HMBC and
COSY) correlation spectra (for the numbering schemes see
ESI†). The room-temperature H NMR spectrum of 11 displays
an AB spin system in the aliphatic region for the methylene
protons of the benzyl moiety attached to nitrogen. In the
Alkali metal selenolates are useful reagents for the preparation
of other metal selenolates by metathesis reactions. Potassium
selenolate 9 was prepared by reductive cleavage of the Se–Se
bond in the diselenide 6 using potassium tri-sec-butyl hydrobo-
rate (K-selectride). Successful reduction of diselenide 7 was
1
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Fig. 3 1H NMR spectra (CDCl3, 300 MHz) of compound 12 at (a) −40 °C, and (b) +50 °C.
aromatic region the singlet resonance for the imine proton (δ
7.99 ppm) is shifted significantly upfield with respect to the
related diselenide 6 (δ 8.67 ppm).
1
The H NMR spectrum recorded at room temperature for 12
shows evidence of a dynamic process in solution which makes
interpretation of the spectrum difficult (see ESI, Fig. S8b†).
Therefore, variable temperature NMR experiments were carried
out for this compound. The assignments of the chemical shifts in
the spectra recorded at +50 °C and −40 °C were made according
to the numbering schemes shown in Scheme 5 [(a) and (b) for
+50 °C and −40 °C, respectively], and are based on 2D NMR
experiments.
Scheme 5 Numbering scheme for NMR assignments for compound
12.
The two selenolato ligands in the molecular unit of 12 are
equivalent since only one singlet resonance was observed in the
aromatic region for the imine proton in the considered tempera-
ture range (+50 °C to −40 °C), e.g. δ 8.19 ppm at +50 °C, δ
8.20 ppm at +20 °C, and δ 8.24 ppm at −40 °C. In the 1H
(Fig. 3b) and 13C NMR (see ESI, Fig. S9a†) spectra recorded at
+50 °C all isopropyl groups appear equivalent, thus suggesting a
fast dynamic process in solution. However, the intramolecular
N→Zn coordination induces restriction in the free rotation of the
bulky 2,6-iPr2C6H3 groups and therefore non-equivalence of the
two halves of this aromatic moiety. This behaviour was clearly
−40 °C. The significant upfield shift of the 77Se resonance of
complex 12 compared to that of the diselenide 7 is due to the
filled d orbitals (d10) of the metal, which thus cannot accept elec-
tron density from the selenolato RSe− ligand.33a At lower temp-
erature (−40 °C) the molecular structure is frozen closer to that
observed in the solid state (see subsequent discussion) and the
stronger N→Zn intramolecular interaction results in more polar
metal–selenium bond and, consequently, in a further increased
upfield shift of the 77Se resonance of complex 12.
Single crystals of 11 and 12 were obtained from a CH2Cl2–n-
hexane mixture (1 : 5, v/v), in inert atmosphere. The solid state
molecular structures of both compounds were established by X-
ray diffraction and are depicted in Fig. 4 and 5. Selected intera-
tomic distances and angles are listed in Table 2.
The crystals of the zinc(II) complexes 11 and 12 consist of dis-
crete molecules separated by normal van der Waals distances
between heavy atoms. In both cases the organoselenolato groups
behave as monometallic biconnective moieties, being attached to
the metal centre covalently by selenium and secondarily by the
iminic nitrogen of the pendant arms. The length of the zinc–sel-
enium bonds [Zn(1)–Se(1) 2.3523(11)/Zn(1)–Se(2) 2.3659(12)
1
revealed in the H (Fig. 3a) and 13C NMR (see ESI, Fig. S9c†)
spectra recorded at −40 °C, when the dynamic process was
frozen and two sets of resonances were clearly observed for the
two halves of a 2,6-iPr2C6H3 group, including two doublet res-
onances in the aromatic region [δ 6.83 ppm (3JHH 7.6 Hz), and
7.33 ppm (3JHH 7.7 Hz)] observed for the H-3′a and H-3′b
protons (Scheme 5b).
The 77Se NMR spectra also indicated an increase in the
strength of the N→Zn intramolecular coordination as the
observed resonance was shifted from δ −2.5 ppm to δ
−22.1 ppm when decreasing the temperature from +50 °C to
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Table 2 Selected bond distances (Å) and angles (°) for compounds 11
and 12
11
12a
Zn(1)–Se(1)
Zn(1)–Se(2)
Zn(1)–N(1)
Zn(1)–N(2)
2.3523(11)
2.3659(12)
2.018(5)
Zn(1)–Se(1)
Zn(1)–N(1)
2.3562(7)
2.078(4)
2.063(5)
Se(1)–C(1)
N(1)–C(7)
N(1)–C(8)
1.910(6)
1.284(7)
1.472(7)
Se(1)–C(1)
N(1)–C(7)
N(1)–C(8)
1.894(6)
1.277(6)
1.451(6)
Se(2)–C(15)
N(2)–C(21)
N(2)–C(22)
1.908(6)
1.271(7)
1.485(7)
Se(1)–Zn(1)–Se(2)
Se(1)–Zn(1)–N(1)
Se(2)–Zn(1)–N(2)
Se(1)–Zn(1)–N(2)
Se(2)–Zn(1)–N(1)
N(1)–Zn(1)–N(2)
118.92(4)
102.36(12)
98.18(12)
118.66(14)
116.21(12)
101.98(18)
Se(1)–Zn(1)–Se(1a)
Se(1)–Zn(1)–N(1)
125.22(5)
97.93(12)
Fig. 4 ORTEP representation at 30% probability and atom numbering
scheme for the ΔZn-(SZn(N1),SZn(N2))-11 isomer. Hydrogen atoms have
been omitted for clarity.
Se(1)–Zn(1)–N(1a)
N(1)–Zn(1)–N(1a)
C(1)–Se(1)–Zn(1)
110.06(12)
117.0(2)
C(1)–Se(1)–Zn(1)
C(15)–Se(2)–Zn(1)
101.95(18)
100.38(18)
99.26(17)
C(7)–N(1)–Zn(1)
C(8)–N(1)–Zn(1)
C(7)–N(1)–C(8)
126.7(4)
115.6(3)
117.3(5)
C(7)–N(1)–Zn(1)
C(8)–N(1)–Zn(1)
C(7)–N(1)–C(8)
125.0(4)
117.5(3)
116.1(4)
C(21)–N(2)–Zn(1)
C(22)–N(2)–Zn(1)
C(21)–N(1)–C(22)
126.8(4)
117.3(4)
115.9(5)
a Symmetry equivalent atoms (−x, y, 0.5 − z) are given by “a”.
N⋯N edge. Zinc complexes containing a Schiff base ligand43 or
a reduced Schiff base ligand44 were previously reported to crys-
tallize as ΛZn and ΔZn isomers, respectively.
The ZnSeC3N metallacycles exhibit different conformations.
In the molecule of 11 one six-membered chelate ring is almost
planar [deviations from the best SeC3: Zn(1) 0.162 Å, N(1)
−0.007 Å], while the other one exhibits a boat conformation
with selenium and Cimine atoms at the apices. By contrast, for 12
both six-membered chelate rings have a boat conformation with
selenium and Cimine atoms at the apices.
Fig. 5 ORTEP representation at 30% probability and atom numbering
scheme for the ΔZn-(SZn(N1),SZn(N1a))-12 isomer. Hydrogen atoms have
been omitted for clarity.
The intramolecular N→Zn coordination resulting in non-
planar chelate rings induces planar chirality (with the aromatic
ring and the metal atom as chiral plane and pilot atom, respect-
ively; isomers are given as SZn(N) and RZn(N)).45 Therefore both
compounds crystallize as a 1 : 1 mixture of ΔZn-(SZn(N),SZn(N))/
ΛZn-(RZn(N),RZn(N)) isomers (with respect to the metal centre and
the two chelate rings per molecular unit, respectively).
Å in 11; Zn(1)–Se(1) 2.3562(7) Å in 12] is similar to that
observed in the related Zn[SeC6H4(CH2NMe2)-2]2 [Zn(1)–Se(1)
2.390(2) Å].34 Consistent with the sp2 nature of the donor nitro-
gen atoms, the intramolecular metal–nitrogen interactions
in 11 [Zn(1)–N(1) 2.018(5)/Zn(1)–N(2) 2.063(5) Å] and 12
[Zn(1)–N(1) 2.078(4) Å] are slightly stronger [cf. the sum of the
corresponding van der Waals radii, ∑rvdW(Zn,N) = 2.94 Å39]
than in Zn[SeC6H4(CH2NMe2)-2]2 [Zn(1)–N(1) 2.124(5) Å].34
The tetrahedral geometry achieved around the zinc centre is
distorted, with dihedral angle of 83.4° (for 11) and 81.6° (for
12) between the two ZnSeN planes. A distorted tetrahedral
complex with unsymmetrical chelate ligands has a C2-symmetry
and its molecule is helical. The corresponding enantiomeric
configurations at the metal can be given as ΔM (or PM) and ΛM
(or MM) with respect to the right-handed or left-handed helicity
of the two chelate rings along the C2-axis42 passing through the
centre of the Se⋯Se edge, the metal ion and the centre of the
In contrast to the Zn[SeC6H4(CH2NMe2)-2]2 analogue,34 in
11 and 12 the two C6H4 rings of the molecular unit are placed
on opposite sides of the best plane described by the nitrogen and
the imino carbon atoms with respect to the selenium and the zinc
atoms. In the case of the centrosymmetric molecule of 12 this
brings the aromatic C6H4 rings closer to the methyl groups of
the 2,6-iPr2C6H3 moieties and weak C–Hmethyl⋯π (Phcentroid
)
interactions [C(19)–H(19C)⋯Phcentroid{C(1a)–C(6a)} 2.93 Å,
γ = 8.0°] are established.
A closer inspection of the crystal structure of the zinc(II)
selenolates revealed supramolecular associations built through
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C–H⋯π (Phcentroid) interactions. Thus, in the crystal of 11 inter-
molecular C–Haryl⋯π (Phcentroid) interactions [C(5)–H(5)⋯Phcen-
troid{C(23b)–C(28b)} 2.73 Å, γ = 0.8°] are established between
neighbouring molecules resulting in zig-zag chain polymers of
either ΛZn-(RZn(N1),RZn(N2)) or ΔZn-(SZn(N1),SZn(N2)) isomers, res-
pectively. By contrast, the crystal of 12 contains chain polymers
performed on a VarioEL analyser. For the alkali metal organose-
lenolates 9 and 10 elemental analyses were not performed due to
their high sensitivity to hydrolysis. All manipulations were
carried out under an inert atmosphere of argon using Schlenk
techniques. Solvents were dried and freshly distilled under argon
prior to use. The acetal 2-[(CH2O)2CH]C6H4Br48 was obtained
according to a reported literature method. All other reagents
were obtained from Aldrich or Merck, and were used as
received.
of alternating ΛZn-(RZn(N1),RZn(N1a)) and ΔZn-(SZn(N1),SZn(N1a)
)
isomers doubly bridged through C–Hmethyl⋯π (Phcentroid) inter-
actions [C(15)–H(15C)⋯Phcentroid{C(8a)–C(13a)} 2.92 Å, γ =
4.0°] (for details, see ESI†). Apparently, in both cases no contacts
are established between parallel polymeric chains.
Synthesis of [2-{(CH2O)2CH}C6H4]Li (1). The compound was
prepared according to a reported method11e from a solution of
n-BuLi in hexane (13.0 mL, 1.6 M, 20.8 mmol) and 2-bromo-
benzaldehyde acetal (4.696 g, 20.5 mmol) in diethyl ether
(100 mL). The resulting white precipitate was left to deposit,
washed with diethyl ether (2 × 50 mL) and dried in vacuum to
give 1.952 g (61%) of compound 1.
Conclusions
New diorganodiselenides supported by Schiff-base ligands,
[2-(RNvCH)C6H4]2Se2 [R = Me2NCH2CH2 (4), O(CH2CH2)2-
NCH2CH2 (5), PhCH2 (6), 2′,6′-iPr2C6H3 (7)] were prepared and
characterized in solution and in the solid state. When anhydrous
ZnCl2 was treated with the dark green solution obtained
from diselenide 7 and an excess of Na (after removal of the
unreacted metal) a C–C coupling reaction occurred and the 9,10-
(2′,6′-iPr2C6H3NH)2C14H10 (8) species was obtained. Treatment
of anhydrous ZnCl2 with potassium selenolates gave Zn
[SeC6H4(CHvNCH2Ph)-2]2 (11) and Zn[SeC6H4(CHvNC6H3-
iPr2-2′,6′)-2]2 (12). For 12 a dynamic behaviour in solution was
evidenced by variable temperature NMR studies. The solid-state
monomeric structure of both complexes is stabilized by intramo-
lecular N→Zn interactions. The unsymmetrical (Se,N) chelate
pattern of the selenolato ligands resulted in distorted tetrahedral
Zn(Se,N)2 cores with non-planar ZnSeC3N metallacycles. This
induces both helical chirality at the metal centre and planar chir-
ality and therefore the complexes were found to crystallize as a
1 : 1 mixture of ΔZn-(SZn(N),SZn(N))/ΛZn-(RZn(N),RZn(N)) isomers.
Synthesis of [2-{(CH2O)2CH}C6H4]2Se2 (2). The diselenide
was obtained according to a slightly modified published proce-
dure.11e Selenium powder (0.987 g, 12.50 mmol) was added
under argon to a solution of 1 (1.951 g, 12.50 mmol) in dry
THF (100 mL). The reaction mixture was stirred for 2 h and then
it was poured into water (100 mL). Stirring was continued for
one hour, then the resulting mixture was filtered to remove
unreacted selenium powder and extracted with diethyl ether and
CH2Cl2. The combined organic extracts were dried over anhy-
drous Na2SO4, concentrated to ca. 10 mL and hexane (50 mL)
was added. The resulting precipitate was collected by filtration
and dried in vacuum to afford 2 as a yellowish solid (1.539 g,
54%). 1H NMR (300 MHz, CDCl3): δ 4.13 (8 H, m, H-8,
C2H4O2), 6.04 (2 H, s, H-7, O2CH), 7.27 (4 H, m, H-4,5, C6H4),
7.50 (2 H, m, H-3 or H-6, C6H4), 7.81 (2 H, m, H-3 or H-6,
C6H4). 77Se NMR (57.3 MHz, CDCl3): δ 411.6.
Supramolecular associations built through C–H⋯π (Phcentroid
)
interactions were found in the crystals of the diselenide 6, and
species 8 resulting from a C–C coupling reaction, as well as the
zinc(II) organoselenolates 11 and 12.
Synthesis of [2-{(O)CH}C6H4]2Se2 (3). A solution of HCl
(3.5 mL, 1 M) was added to a stirred solution of 2 (0.808 g,
1.77 mmol) in acetone (30 mL). The reaction mixture was
refluxed for 1 h and then it was concentrated until precipitation
started. Water (10 mL) was added and the solid product was
filtered, washed with water and dried in vacuum to give com-
Experimental section
1
pound 3 as a yellow solid (0.620 g, 95%). H NMR (300 MHz,
General procedures
CDCl3): δ 7.41 (4 H, m, H-4,5, C6H4), 7.83 (4 H, m, H-3,6,
C6H4), 10.16 (2 H, s, H-7, CHvO). 77Se NMR (57.3 MHz,
CDCl3): δ 457.4.
Multinuclear NMR spectra were recorded at room temperature
on BRUKER 200, 300, 400 and 500 instruments. Variable temp-
erature studies were recorded on BRUKER 500 (for 11) and 300
(for 12) instruments. The 1H and 13C chemical shifts are
reported in δ units (ppm) relative to the residual peak of the
deuterated solvent (ref. CHCl3: 1H 7.26, 13C 77.0 ppm; THF: 1H
3.58, 1.73 ppm). 1H and 13C resonances were assigned generally
using 2D NMR experiments (COSY, HMQC and HMBC). The
77Se spectra were obtained using diphenyl diselenide as an exter-
nal standard. Chemical shifts are reported relative to dimethyl
selenide (δ 0 ppm) by assuming that the resonance of the stan-
dard is at δ 461 ppm.46 The NMR spectra were processed using
the MestReC and MestReNova software.47 Mass spectra (ESI and
APCI) were recorded on an Agilent 6320 Ion Trap instrument.
Infrared spectra were recorded on a Jasco FTIR 615 machine, as
KBr pellets. Melting points were measured on an Electrothermal
9200 apparatus and are not corrected. Elemental analyses were
Synthesis of [2-(Me2NCH2CH2NvCH)C6H4]2Se2 (4). 2-
(Dimetilamino)ethylamine (0.100 g, 1.13 mmol) was added to a
stirred solution of 3 (0.208 g, 0.54 mmol) in acetonitrile
(30 mL), at reflux temperature. The reaction mixture was
refluxed for one hour after which the solvent was removed. The
remaining residue was extracted with hexane (2 × 20 mL) and
the evaporation of the solvent yielded 4 as an orange oil
(0.184 g, 67%). Anal. Calcd for C22H30N4Se2 (508.43): C,
51.97; H, 5.95; N 11.02; Found: C, 51.68; H, 5.76; N 10.86%.
1H NMR (300 MHz, CDCl3): δ 2.33 (12 H, s, H-10, N(CH3)2),
2.74 (4 H, t, H-9, CH2, 3JHH 7.0 Hz), 3.86 (4 H, t, H-8,vNCH2,
3JHH 6.9 Hz), 7.21 (4 H, m, H-4,5, C6H4), 7.53 (2 H, dd, H-3,
C6H4, 3JHH 7.1, 4JHH 1.5 Hz), 7.85 (2 H, d, H-6, C6H4, 3JHH 7.4
Hz), 8.57 (2 H, s, H-7, CHvN). 13C NMR (75.5 MHz, CDCl3):
5066 | Dalton Trans., 2012, 41, 5060–5070
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δ 45.90 [s, C-10, N(CH3)2], 58.69 (s, C-8,vNCH2), 60.31 (s,
C-9, CH2), 125.65 (s, C-5), 130.26 (s, C-4), 131.31 (s, C-3 or
C-6), 131.36 (s, C-3 or C-6), 133.39 (s, C-2), 134.75 (s, C-1),
161.63 (s, C-7, CHvN). 77Se NMR (57.3 MHz, CDCl3): δ
467.9.
C-3′), 124.62 (s, C-4′), 125.80 (s, C-5), 131.15 (s, C-4), 131.66
(s, C-6), 132.57 (s, C-3), 134.39 (s, C-1 or C-2), 134.61 (s, C-1
or C-2), 137.92 (s, C-2′), 147.33 (s, C-1′), 162.34 (s, C-7,
CHvN). 77Se NMR (57.3 MHz, CDCl3): δ 471.1. IR (KBr):
ν(–CHvN–) 1634(s) cm−1
.
Synthesis of 9,10-(2′,6′-iPr2C6H3NH)2C14H10 (8). A solution
of 7 (0.40 g, 0.58 mmol) in anhydrous THF (50 mL) was added
to a sodium mirror (large excess), under argon atmosphere. The
reaction mixture was stirred overnight, then filtered to remove
unreacted Na. The resulting dark green solution was added via
canula to ZnCl2 (0.079 g, 0.58 mmol) in anhydrous THF
(10 mL). The reaction was left overnight to complete, then the
THF was removed under vacuum and the remaining crude
product was treated with acetonitrile in open atmosphere. The
insoluble solid was filtered off and slow evaporation of the
solvent from the clear solution yielded 8 as yellow, needle-
shaped, crystals (0.121 g, 38%), mp 187–188 °C. Anal. Calcd
for C38H46N2 (530.77): C, 85.99; H, 8.74; N 5.28; Found: C,
Synthesis of [2-{O(CH2CH2)2NCH2CH2NvCH}C6H4]2Se2
(5). 4′-(2-Aminoethyl)morfoline (0.141 g, 1.08 mmol) was
added to a stirred solution of 3 (0.199 g, 0.54 mmol) in aceto-
nitrile (30 mL), at reflux temperature. The reaction mixture was
refluxed for one hour and then the solvent was removed. The
remaining residue was extracted with hexane (2 × 20 mL) and
the evaporation of the solvent yielded 5 as an orange oil
(0.240 g, 75%). Anal. Calcd for C26H34N4O2Se2 (592.50): C,
1
52.71; H, 5.78; N 9.46; Found: C, 52.46; H, 5.86; N 9.33%. H
NMR (300 MHz, CDCl3): δ 2.54 (8 H, t, H-10, NCH2, 3JHH 4.5
3
Hz), 2.76 (4 H, t, H-9, CH2N, JHH 6.9 Hz), 3.69 (8 H, t, H-11,
3
3
CH2O, JHH 4.6 Hz), 3.85 (4 H, t, H-8,vNCH2, JHH 6.7 Hz),
7.19 (4 H, m, H-4,5, C6H4), 7.50 (2 H, dd, H-3, C6H4, 3JHH 7.3,
4JHH 1.6 Hz), 7.83 (2 H, d, H-6, C6H4, 3JHH 7.5 Hz), 8.53 (2 H,
s, H-7, CHvN). 13C NMR (75.5 MHz, CDCl3): δ 53.77 (s,
C-10, NCH2), 57.55 (s, C-8,vNCH2), 59.25 (s, C-9, CH2N),
66.78 (s, C-11, CH2O), 125.59 (s, C-5), 130.18 (s, C-4), 131.16
(s, C-3 or C-6), 131.23 (s, C-3 or C-6), 133.19 (s, C-2), 134.55
(s, C-1), 161.66 (s, C-7, CHvN). 77Se NMR (57.3 MHz,
CDCl3): δ 467.9.
1
85.77; H, 8.62; N 5.26%. H NMR (300 MHz, CDCl3): δ 1.12
3
(24 H, d, H-8′, CH3, JHH 6.8 Hz), 3.36 (4 H, hept, H-7′, CH,
3JHH 6.8 Hz), 4.14 (2 H, d, NH, 3JHH 6.5 Hz), 4.99 (2 H, d, H-9,
3
CH, JHH 6.5 Hz), 7.19 (14 H, m, H-3′,4′, C6H3 + H-1,2). 13C
NMR (75.5 MHz, CDCl3): δ 23.98 (s, C-8′, CH3), 27.99 (s,
C-7′, CH), 64.23 (s, C-9, NHCH), 123.40 (s, C-3′), 124.75 (s,
C-4′), 127.35 (s, C-2), 128.53 (s, C-1), 139.22 (s, C-1a), 141.34
(s C-1′), 144.81 (s, C-2′). MS (ESI+), m/z (%): 531 (100)
[M + H+].
Synthesis of [2-(PhCH2NvCH)C6H4]2Se2 (6). Benzyl amine
(0.231 g, 2.16 mmol) was added to a stirred solution of 3
(0.398 g, 1.08 mmol) in acetonitrile (100 mL), at reflux tempera-
ture. The reaction mixture was refluxed for one hour. Cooling of
the reaction mixture yielded compound 6 as a pale yellow solid
(0.555 g, 94%) which was filtered off and dried in vacuum, mp
134–135 °C. Anal. Calcd for C28H24N2Se2 (546.41): C, 61.55;
Synthesis of K[SeC6H4(CHvNCH2Ph)-2] (9). KB[CH(CH3)
C2H5]3H (K-selectride) (1 mL of 1 M solution in THF) was
added dropwise to a stirred solution of 6 (0.27 g, 0.5 mmol) in
anhydrous THF (30 mL) at −78 °C, under argon atmosphere.
Stirring was continued until the reaction mixture warmed up to
room temperature. The solvent was removed under vacuum and
the crude product was washed with anhydrous toluene and
1
H, 4.43; N 5.13; Found: C, 61.26; H, 4.56; N 5.26%. H NMR
(300 MHz, CDCl3): δ 5.01 (4 H, s, H-8, NCH2), 7.28 (6 H, m,
3
1
H-4,5, C6H4 + H-4′, C6H5), 7.42 (4 H, t, H-3′, C6H5, JHH 7.5
pentane to yield an orange solid. H NMR (200 MHz, THF-d8):
3
Hz), 7.52 (4 H, d, H-2′, C6H5, JHH 7.5 Hz), 7.60 (2 H, d, H-3,
δ 4.72 (2 H, s, H-8, NCH2), 6.66 (2 H, m, aryl), 7.25 (5 H, m,
aryl), 7.71 (2 H, m, aryl), 9.58 (1 H, s, H-7, CHvN).
C6H4, 3JHH 7.1 Hz), 7.95 (2 H, d, H-6, C6H4, 3JHH 7.7 Hz), 8.67
(2 H, s, H-7, CHvN). 13C NMR (75.5 MHz, CDCl3): δ 63.97
(s, C-8,vNCH2), 125.68 (s, C-4 or C-5), 126.94 (s, C-4′),
127.92 (s, C-2′), 128.46 (s, C-3′), 130.43 (s, C-4 or C-5), 131.44
(s, C-6), 131.74 (s, C-3), 133.45 (s, C-1), 134.63 (s, C-2),
138.92 (s, C-1′), 161.94 (s, C-7, CHvN). 77Se NMR
(57.3 MHz, CDCl3): δ 470.3. IR (KBr): ν(–CHvN–) 1642(s)
i
Synthesis of Na[SeC6H4(CHvNC6H3 Pr2-2′,6′)-2] (10).
Sodium (6 mg, 0.26 mmol) was mixed with 7 (89.4 mg,
0.13 mmol) in an NMR tube with a Young tap and THF-d8 (ca.
0.6 mL) was condensed over the mixture. The yellow reaction
mixture was monitored for several days until the NMR spectrum
1
cm−1
.
of the mixture remained unchanged. H NMR (200 MHz, THF-
3
d8): δ 1.18 (12 H, d, H-8′, CH3, JHH 6.6 Hz), 3.13 (2 H, hept,
Synthesis of [2-(2′,6′-iPr2C6H3NvCH)C6H4]2Se2 (7). 2,6-Dii-
sopropylaniline (0.365 g, 2.06 mmol) was added to a stirred sol-
ution of 3 (0.379 g, 1.03 mmol) in acetonitrile (30 mL), at reflux
temperature. The reaction mixture was refluxed for one hour to
give compound 7 as a pale yellow solid (0.403 g, 57%) which
was filtered off and dried in vacuum, mp 148–149 °C. Anal.
Calcd for C38H44N2Se2 (686.70): C, 66.47; H, 6.46; N 4.08;
Found: C, 66.23; H, 6.25; N 4.26%. 1H NMR (300 MHz,
3
H-7′, CH, JHH 6.8 Hz), 6.96 (5 H, m, H-3′,4′, C6H3 + H-4,5,
C6H4), 7.86 (2 H, m, H-3,6, C6H4), 9.15 (1 H, s, H-7, CHvN).
Synthesis of Zn[SeC6H4(CHvNCH2Ph)-2]2 (11). A solution
of 10 [prepared as above from K-selectride (1 mL of 1 M sol-
ution in THF) and 6 (0.273 g, 0.50 mmol) in anhydrous THF
(30 mL)] was added via canula to ZnCl2 (0.068 g, 0.50 mmol)
in anhydrous THF (10 mL). The reaction was left overnight to
complete. The THF was removed in vacuum, the crude product
was treated with anhydrous CH2Cl2 and the KCl was filtered off.
The solvent was evaporated from the clear solution, the remain-
ing solid was washed several times with anhydrous diethyl ether
and then dried in vacuum to give 11 as a greenish-yellow solid
3
CDCl3): δ 1.23 (24 H, d, H-8′, CH3, JHH 6.9 Hz), 3.11 (4 H,
hept, H-7′, CH, 3JHH 6.8 Hz), 7.19 (6 H, m, H-3′,4′, C6H3), 7.35
(4 H, m, H-4,5, C6H4), 7.70 (2 H, m, H-3, C6H4), 8.05 (2 H, m,
H-6, C6H4), 8.52 (2 H, s, H-7, CHvN). 13C NMR (75.5 MHz,
CDCl3): δ 23.79 (s, C-8′, CH3), 28.06 (s, C-7′, CH), 123.01 (s,
This journal is © The Royal Society of Chemistry 2012
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View Article Online
Table 3 Crystallographic data for compounds 6, 8, 11 and 12
6
8
11
12
Empirical formula
M
C28H24N2Se2
546.41
C38H46N2
530.77
C28H24N2Se2Zn
611.78
C38H44N2Se2Zn
752.04
T
297(2)
Monoclinic
P21/c
297(2)
297(2)
Monoclinic
P21/n
297(2)
Monoclinic
C2/c
Crystal system
Space group
Triclinic
ˉ
P1
a (Å)
b (Å)
c (Å)
α (°)
10.8520(8)
22.7903(18)
9.6203(7)
90.00
90.1520(10)
90.00
10.6487(10)
11.7585(11)
13.4318(12)
90.607(2)
93.675(2)
106.769(2)
1606.3(3)
2
13.398(5)
14.424(6)
13.532(5)
90.00
110.608(7)
90.00
15.0512(16)
13.1067(14)
18.4747(19)
90.00
101.281(2)
90.00
β (°)
γ (°)
V (Å3)
2379.3(3)
4
2447.7(17)
4
3574.1(7)
4
Z
No. of reflections collected
No. of independent reflections
Absorption correction
22 703
15 517
11 492
12 649
4190 (Rint = 0.0476)
Multi-scan50
3.126
0.0291
0.0681
5617 (Rint = 0.0557)
Multi-scan50
0.063
0.0799
0.1532
4214 (Rint = 0.0953)
Multi-scan50
3.997
0.0584
0.1490
3143 (Rint = 0.0582)
Multi-scan50
2.751
0.0660
0.1187
μ(Mo-Kα) (mm−1
R1 [I > 2σ(I)]
wR2
)
GOF on F2
1.053
1.196
0.978
1.211
3
(0.142 g, 46%), mp 215–216 °C. Anal. Calcd for
(2 H, d, H-3′b, C6H3, JHH 7.7 Hz), 7.50 (2 H, d, H-6, C6H4,
1
C28H24N2Se2Zn (611.78): C, 54.97; H, 3.95; N 4.58; Found: C,
3JHH 7.8 Hz), 8.24 (2 H, s, H-7, CHvN). H NMR (300 MHz,
CDCl3, +50 °C): δ 1.02 (24 H, s, br, H-8, CH3), 3.03 (4 H, s, br,
H-7, CH), 6.92 (2 H, t, H-5, C6H4, JHH 7.5 Hz), 7.06 (8 H, m,
H-3′, C6H3 + H-3,4, C6H4), 7.18 (2 H, t, H-4′, C6H3, JHH 7.6
1
54.76; H, 3.85; N 4.36%. H NMR (500 MHz, CDCl3): δ AB
3
spin system with A at 4.63 and B at 4.74 ppm (4 H, H-8, NCH2,
3
3
2JHH 13.8 Hz), 6.89 (4 H, d, H-2′, C6H5, JHH = 7.5 Hz), 7.12
3
(12 H, m, H-3,4,5, C6H4 + H-3′,4′, C6H5), 7.95 (2 H, d, H-6,
Hz), 7.53 (2 H, d, H-6, C6H4, JHH 7.8 Hz), 8.19 (2 H, s, H-7,
C6H4, JHH 7.4 Hz), 7.99 (2 H, s, H-7, CHvN). 13C NMR
CHvN). 13C NMR (75.5 MHz, CDCl3, −40 °C): δ 20.69 (s,
C-8′a1, CH3), 23.56 (s, C-8′b2, CH3), 25.22 (s, C-8′a2, CH3),
25.71 (s, C-8′b1, CH3), 28.52 (s, C-7′b, CH), 29.37 (s, C-7′a,
CH), 122.28 (s, C-3′a), 123.72 (s, C-4), 124.07 (s, C-3′b), 126.71
(s, C-4′), 131.38 (s, C-5), 131.84 (s, C-2), 137.20 (s, C-3),
137.77 (s, C-1), 138.58 (s, C-2′a), 138.64 (s, C-6), 141.30 (s,
C-2′b), 146.63 (s, C-1′), 173.37 (s, C-7, CHvN). 13C NMR
(75.5 MHz, CDCl3, +50 °C): δ 23.94 (s, br, C-8′, CH3), 29.12
(s, C-7′, CH), 123.47 (s, C-3′, C-4), 126.90 (s, C-4′), 131.06 (s,
C-5), 132.48 (s, C-2), 137.04 (s, C-3), 139.21 (s, C-6), 139.46
(s, C-1), 140.55 (s, C-2′), 147.02 (s, C-1′), 173.92 (s, C-7,
CHvN). 77Se NMR (76.3 MHz, CDCl3, −40 °C): δ −22.1. 77Se
NMR (76.3 MHz, CDCl3, +20 °C): δ −9.4. 77Se NMR
(76.3 MHz, CDCl3, +50 °C): δ −2.5. MS (APCI+), m/z (%): 753
3
(125.8 MHz, CDCl3): δ 64.34 (s, C-8,vNCH2), 123.31 (s, C-4),
127.76 (s, C-4′), 128.44 (s, C-3′), 128.86 (s, C-2′), 130.88 (s,
C-5), 131.54 (s, C-1), 135.33 (s, C-1′), 138.70 (s, C-3), 139.10
(s, C-6), 139.33 (s, C-2), 172.00 (s, C-7, CHvN). 77Se NMR
(76.3 MHz, CDCl3): δ 20.2. MS (APCI+), m/z (%): 654 (15) [M
+ CH3CN + H+]. 613 (100) [M + H+]. IR (KBr): ν(–CHvN–)
1617(s) cm−1
.
i
Synthesis of Zn[SeC6H4(CHvNC6H3 Pr2-2′,6′)-2]2 (12). KB
[CH(CH3)C2H5]3H (K-selectride) (1 mL of 1 M solution in
THF) was added dropwise to a stirred solution of 7 (0.343 g,
0.50 mmol) in anhydrous THF (30 mL) at −78 °C, under argon
atmosphere. Stirring was continued until the reaction mixture
warmed up to room temperature. The resulting solution was
added via canula to ZnCl2 (0.068 g, 0.50 mmol) in anhydrous
THF (10 mL). The reaction was left overnight to complete. The
THF was removed in vacuum, the crude product was treated
with anhydrous CH2Cl2 and the KCl was filtered off. The
solvent was evaporated from the clear solution, the remaining
solid was washed with anhydrous diethyl ether (20 mL) and then
dried in vacuum to give 12 as a greenish-yellow solid (0.213 g,
56%), mp 236–237 °C. Anal. Calcd for C38H44N2Se2Zn
(752.04): C, 60.69; H, 5.90; N 3.72; Found: C, 60.36; H, 5.85;
(100) [M + H+]. IR (KBr): ν(–CHvN–) 1604 (s) cm−1
.
Crystal structures
Yellow crystals of 6 were obtained by slow diffusion, using a
CH2Cl2–CH3CN system (1 : 4 by volume). Colourless crystals of
8 were grown by slow evaporation of an acetonitrile solution.
Yellow crystals of 11 (at room temperature) and 12 (at −20 °C)
were grown by slow diffusion using a CH2Cl2-n-hexane system
(1 : 4 by volume), under argon. The details of the crystal struc-
ture determination and refinement are given in Table 3. The crys-
tals were mounted with epoxy glue on cryoloops and the data
were collected at room temperature on a Bruker SMART APEX
diffractometer, using graphite-monochromated Mo-Kα radiation
(λ = 0.71073 Å). The structures were refined with anisotropic
thermal parameters. The hydrogen atoms attached to nitrogens in
8 were located from the difference map. The other hydrogen
1
N 3.58%. H NMR (300 MHz, CDCl3, −40 °C): δ 0.41 (6 H, d,
3
3
H-8′a1, CH3, JHH 6.1 Hz), 0.98 (6 H, d, H-8′a2, CH3, JHH 6.3
3
Hz), 1.05 (6 H, d, H-8′b1, CH3, JHH 6.6 Hz), 1.39 (6 H, d,
3
3
H-8′b2, CH3, JHH 6.5 Hz), 2.54 (2 H, hept, H-7′a, CH, JHH 6.2
3
Hz), 3.24 (2 H, hept, H-7′b, CH, JHH 6.5 Hz), 6.83 (2 H, d,
3
3
H-3′a, C6H3, JHH 7.6 Hz), 6.99 (2 H, t, H-5, C6H4, JHH 7.3
3
Hz), 7.08 (2 H, t, H-4, C6H4, JHH 7.3 Hz), 7.16 (2 H, d, H-3,
C6H4, 3JHH 7.6 Hz), 7.22 (2 H, t, H-4′, C6H3, 3JHH 7.7 Hz), 7.33
5068 | Dalton Trans., 2012, 41, 5060–5070
This journal is © The Royal Society of Chemistry 2012

View Article Online
19 (a) M. Kulcsar, A. Silvestru, C. Silvestru, J. E. Drake,
C. L. B. MacDonald, M. E. Hursthouse and M. E. Light, J. Organomet.
Chem., 2005, 690, 3217; (b) M. Kulcsar, A. Beleaga, C. Silvestru,
A. Nicolescu, C. Deleanu, C. Todasca and A. Silvestru, Dalton Trans.,
2007, 2187; (c) A. Beleaga, M. Kulcsar, C. Deleanu, A. Nicolescu,
C. Silvestru and A. Silvestru, J. Organomet. Chem., 2009, 694, 1308;
(d) A. Pöllnitz, V. Lippolis, M. Arca and A. Silvestru, J. Organomet.
Chem., 2011, 696, 2837; (e) E. Duhamel, A. Pöllnitz, A. Stegarescu and
A. Silvestru, Z. Anorg. Allg. Chem., 2011, 637, 1355.
atoms were refined with a riding model and a mutual isotropic
thermal parameter. For structure solving and refinement the
software package SHELX-97 was used.49 The drawings were
created with the Diamond program.51
Acknowledgements
20 (a) E. Labisbal, J. Romero, M. L. Duran, J. A. Garcia-Vazquez, A. Sousa,
U. Russo, R. Pritchard and M. Renson, J. Chem. Soc., Dalton Trans.,
1993, 755; (b) J. Romero, M. L. Duran, J. A. Garcia-Vazquez,
A. Castineiras, A. Sousa, L. Christiaens and J. Zubieta, Inorg. Chim.
Acta, 1997, 255, 307.
21 (a) L. Pech, Yu. Bankovsky, V. Belsky, A. Stash and J. Ashaks, Latv.
Khim. Z. (Latvian J. Chem.), 1996, 63; (b) E. Silina, S. Belyakov,
J. Ashaks, L. Pech and D. Zaruma, Acta Crystallogr., Sect. C: Cryst.
Struct. Commun., 2007, 63, m62; (c) E. Silina, J. Ashaks, S. Belyakov,
A. Tokmakov, L. Pech and D. Zaruma, Chem. Heterocycl. Compd., 2007,
43, 1582; (d) E. Silina, S. Belyakov, J. Ashaks, A. Tokmakov, L. Pech
and D. Zaruma, Chem. Heterocycl. Compd., 2009, 45, 860.
Financial support from National University Research Council
(CNCSIS, Romania; Research Project No. PNII-ID 2404/2008
and BD 151/2008) is greatly appreciated. A.P. is grateful for a
fellowship offered by the Hungarian Academy of Sciences. The
support provided by the NATIONAL CENTER FOR X-RAY
DIFFRACTION (Babes-Bolyai University, Cluj-Napoca,
Romania) for the solid state structure determinations is highly
acknowledged.
22 (a) Y. Cheng, T. J. Emge and J. G. Brennan, Inorg. Chem., 1996, 35, 342;
(b) Y. Cheng, T. J. Emge and J. G. Brennan, Inorg. Chem., 1996, 35, 7339.
23 N. Chopra, L. C. Damude, P. A. W. Dean and J. J. Vittal, Can. J. Chem.,
1996, 74, 2095.
24 G. Mugesh, H. B. Singh and R. J. Butcher, J. Chem. Res., 1999, 416,
1801.
25 J. Laube, S. Jager and C. Thone, Eur. J. Inorg. Chem., 2001, 1983.
26 R.-Y. Tan, H.-B. Song and L.-F. Tang, J. Organomet. Chem., 2006, 691,
5964.
27 C. R. Kowol, R. Eichinger, M. A. Jakupec, M. Galanski, V. B. Arion and
B. K. Keppler, J. Inorg. Biochem., 2007, 101, 1946.
References
1 G. Mugesh and H. B. Singh, Chem. Soc. Rev., 2000, 29, 347.
2 Organoselenium Chemistry: Modern Developments in Organic Synthesis,
Topics in Current Chemistry, ed. T. Wirth, Springer, Berlin, 2000, vol.
208.
3 N. Furukawa, K. Kobayashi and S. Sato, J. Organomet. Chem., 2000,
611, 116, and references therein.
4 G. Mugesh, W.-W. du Mont and H. Sies, Chem. Rev., 2001, 101, 2125,
and references therein.
5 G. Mugesh and H. B. Singh, Acc. Chem. Res., 2002, 35, 226.
6 A. J. Mukherjee, S. S. Zade, H. B. Singh and R. B. Sunoj, Chem. Rev.,
2010, 110, 4357, and references therein.
28 G. Kedarnath, L. B. Kumbhare, S. Dey, A. P. Wadawale, V. K. Jain and
G. K. Dey, Polyhedron, 2009, 28, 2749.
29 J. Konu and T. Chivers, Chem. Commun., 2010, 46, 1431.
30 (a) J. G. Brennan, T. Siegrist;, P. J. Carroll, S. M. Stuczynski, L. E. Brus
and M. L. Steigerwald, J. Am. Chem. Soc., 1989, 111, 4141; (b) J.
G. Brennan, T. Siegrist, P. J. Carroll, S. M. Stuczynski, P. Reynders, L.
E. Brus and M. L. Steigerwald, Chem. Mater., 1990, 2, 403;
(c) M. Bochmann and K. J. Webb, J. Chem. Soc., Dalton Trans., 1991,
2325; (d) Y. Cheng, T. J. Emge and J. G. Brennan, Inorg. Chem., 1994,
33, 3711; (e) R. Kaur, H. B. Singh, R. P. Patel and S. K. Kulshreshta, J.
Chem. Soc., Dalton Trans., 1996, 461; (f) M. Afzaal, M. A. Malik and
P. O ’Brien, J. Mater. Chem., 2010, 20, 4031, and references cited therein.
31 (a) M. Bochmann, K. J. Webb, M. B. Hursthouse and M. Mazid, J.
Chem. Soc., Dalton Trans., 1991, 2317; (b) M. Bochmann, A.
P. Coleman and A. K. Powell, Polyhedron, 1992, 11, 507;
(c) K. Ruhlandt-Senge and P. P. Power, Inorg. Chem., 1993, 32, 4505;
(d) J. J. Ellison, K. Ruhlandt-Senge, H. H. Hope and P. P. Power, Inorg.
Chem., 1995, 34, 49.
32 (a) A. P. Arnold, A. J. Canty, B. W. Skelton and A. H. White, J. Chem.
Soc., Dalton Trans., 1982, 607; (b) M. Bochmann, K. J. Webb,
M. Harman and M. B. Hursthouse, Angew. Chem., Int. Ed. Engl., 1990,
29, 638; (c) M. Bochmann, K. J. Webb, M. B. Hursthouse and M. Mazid,
Chem. Commun., 1991, 1735; (d) M. Bochmann, G. C. Bwembya and A.
K. Powell, Polyhedron, 1993, 12, 2929; (e) M. Bochmann, G.
C. Bwembya, R. Grinter, A. K. Powell, K. J. Webb, M. B. Hursthouse,
K.-M. Abdul-Malik and M. A. Majid, Inorg. Chem., 1994, 33, 2290;
(f) D. Labahn, F. M. Bohnen, R. Herbst-Irmer, E. Pohl, D. Stalke and H.
W. Roesky, Z. Anorg. Allg. Chem., 1994, 620, 41; (g) M. A. Beswick, P.
R. Raithby, A. Steiner, J. C. Vallet, K. L. Verhorevoort and D. S. Wright,
J. Chem. Soc., Dalton Trans., 1996, 2183; (h) R. Subramanian,
N. Govindaswamy, R.A. Santos, S. A. Koch and G. S. Harbison, Inorg.
Chem., 1998, 37, 4929; (i) M. A. Malik, M. Motevalli and P. O’Brien,
Polyhedron, 1999, 18, 1259; ( j) V. W.-W. Yam, Y.-L. Pui and K.-
K. Cheung, New J. Chem., 1999, 23, 1163; (k) Y.-w. Jun, J.-E. Koo and
J. Cheon, Chem. Commun., 2000, 1243; (l) E. S. Lang, M. M. Dias, S.
S. dos Santos, E. M. Vazquez-Lopez and U. Abram, Z. Anorg. Allg.
Chem., 2004, 630, 462; (m) M. Yosef, A. K. Schaper, M. Froba and
S. Schlecht, Inorg. Chem., 2005, 44, 5890; (n) E. S. Lang, R. Stieler and
G. M. de Oliveira, Polyhedron, 2010, 29, 1760.
7 V. P. Singh, H. B. Singh and R. J. Butcher, Eur. J. Inorg. Chem., 2010,
637, and references therein.
8 K. Selvakumar, H. B. Singh and R. J. Butcher, Chem.–Eur. J., 2010, 16,
10576, and references therein.
9 H. Fujihara, H. Mima and N. Furukawa, J. Am. Chem. Soc., 1995, 117,
10153.
10 (a) M. Iwaoka and S. Tomoda, J. Am. Chem. Soc., 1996, 118, 8077;
(b) K. Fujita, K. Murata, M. Iwaoka and S. Tomoda, Tetrahedron, 1997,
53, 2029; (c) M. Iwaoka, H. Komatsu, T. Katsuda and S. Tomoda, J. Am.
Chem. Soc., 2004, 126, 5309.
11 (a) R. Kaur, H. B. Singh and R. P. Patel, J. Chem. Soc., Dalton Trans.,
1996, 2719; (b) A. Panda, G. Mugesh, H. B. Singh and R. J. Butcher,
Organometallics, 1999, 18, 1986; (c) G. Mugesh, A. Panda, H. B. Singh
and R. J. Butcher, Chem.–Eur. J., 1999, 5, 1411; (d) G. Mugesh,
A. Panda, S. Kumar, S. D. Apte, H. B. Singh and R. J. Butcher, Organo-
metallics, 2002, 21, 884; (e) G. Mugesh, A. Panda, H. B. Singh, N.
S. Punekar and R. J. Butcher, J. Am. Chem. Soc., 2001, 123, 839;
(f) K. Kandasamy, S. Kumar, H. B. Singh, R. J. Butcher and K.
T. Holman, Eur. J. Inorg. Chem., 2004, 1014; (g) S. Kumar,
K. Kandasamy, H. B. Singh, G. Wolmershauser and R. J. Butcher, Orga-
nometallics, 2004, 23, 4199; (h) A. Panda, S. S. Zade, H. B. Singh and
G. Wolmershauser, J. Organomet. Chem., 2005, 690, 3142; (i) S. Kumar,
S. Panda, H. B. Singh, G. Wolmershauser and R. J. Butcher, Struct.
Chem., 2007, 18, 127.
12 (a) C. Santi and T. Wirth, Tetrahedron: Asymmetry, 1999, 10, 1019;
(b) T. Wirth, Angew. Chem., Int. Ed., 2000, 39, 3740.
13 K. Hiroi, Y. Suzuki and I. Abe, Tetrahedron: Asymmetry, 1999, 10, 1173.
14 (a) M. Tiecco, L. Testaferri, C. Santi, C. Tomassini, F. Marini, L. Bagnoli
and A. Temperini, Tetrahedron: Asymmetry, 2000, 11, 4645;
(b) M. Tiecco, L. Testaferri, C. Santi, C. Tomassini, F. Marini, L. Bagnoli
and A. Temperini, Angew. Chem., Int. Ed., 2003, 42, 3131.
15 (a) M. Uchiyama, S. Satoh and A. Ohta, Tetrahedron Lett., 2001, 42,
1559; (b) M. Uchiyama, M. Hirai, M. Nagata, R. Katoh, R. Ogawa and
A. Ohta, Tetrahedron Lett., 2001, 42, 4653.
16 L. A. Braga, S. J. N. Silva, D. S. Luedtke, R. L. Drekener, C. C. Silveira,
J. B. T. Rocha and L. A. Wessjohann, Tetrahedron Lett., 2002, 43, 7329.
17 Y. Miyake, Y. Nishibayashi and S. Uemura, Bull. Chem. Soc. Jpn., 2002,
75, 2233.
33 (a) G. Mugesh, H. B. Singh, R. P. Patel and R. J. Butcher, Inorg. Chem.,
1998, 37, 2663; (b) E. Silina, J. Ashaks, V. Belsky, A. Stash, L. Pech and
Yu. Bankovsky, Latv. Khim. Z. (Latvian J. Chem.), 2001, 419; (c) S. Dey,
V. K. Jain, S. Chaudhury, A. Knoedler and W. Kaim, Polyhedron, 2003,
18 T. M. Klapötke, B. Krumm and K. Polborn, J. Am. Chem. Soc., 2004,
126, 710.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 5060–5070 | 5069

View Article Online
22, 489; (d) S. D. Apte, S. S. Zade, H. B. Singh and R. J. Butcher, Orga-
nometallics, 2003, 22, 5473; (e) J. G. Melnick, A. Docrat and G. Parkin,
Chem. Commun., 2004, 2870; (f) K. Kandasamy, H. B. Singh and
G. Wolmershauser, Inorg. Chim. Acta, 2005, 358, 207; (g) M. Minoura,
V. K. Landry, J. G. Melnick, K. Pang, L. Marchio and G. Parkin, Chem.
Commun., 2006, 3990; (h) J. G. Melnick and G. Parkin, Dalton Trans.,
2006, 4207; (i) L. Pech, S. Belyakov, J. Ashaks, E. Silina and D. Zaruma,
Chem. Heterocycl. Compd., 2007, 43, 106; ( j) V. K. Landry, D. Buccella,
K. Pang and G. Parkin, Dalton Trans., 2007, 866; (k) D.-L. Ma, H.-
J. Zhang, Z. Shen and D.-Z. Niu, Z. Kristallogr.-New Cryst. Struct.,
2009, 224, 283; (l) J. G. Melnick, K. Yurkerwich and G. Parkin, J. Am.
Chem. Soc., 2010, 132, 647.
38 P. Sharma, D. Pérez, J. Vázquez, A. Toscano and R. Gutiérrez, Inorg.
Chem. Commun., 2007, 10, 389.
39 J. Emsley, Die Elemente, Walter de Gruyter, Berlin, 1994.
40 The N–X–L nomenclature system has been previously described: N
valence shell electrons about a central atom X with L ligands. C.
W. Perkins, J. C. Martin, A. J. Arduengo III, W. Lau, A. Alegria and
K. Kochi, J. Am. Chem. Soc., 1980, 102, 7753.
41 D. Zhao, W. Gao, Y. Mu and L. Ye, Chem.–Eur. J., 2010, 16, 4394.
42 R. E. Ernst, M. J. O’Connor and R. H. Holm, J. Am. Chem. Soc., 1967,
89, 6104.
43 C. Evans and D. Luneau, J. Chem. Soc., Dalton Trans., 2002, 83.
44 V. K. Muppidi, P. S. Zacharias and S. Pal, Inorg. Chem. Commun., 2005,
8, 543.
45 IUPAC Nomenclature of Organic Chemistry, Pergamon Press, Oxford,
1979.
46 P. N. Jayaram, G. Roy and G. Mugesh, J. Chem. Sci., 2008, 120, 143.
47 MestReC and MestReNova, Mestrelab Research S.L., A Coruña 15706,
Santiago de Compostela.
48 S. C. Menon, H. B. Singh, R. P. Patel, K. Das and R. J. Butcher, Organo-
metallics, 1997, 16, 563.
49 G. M. Sheldrik, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008, 64,
112.
50 G. M. Sheldrick, SADABS, Program for Area Detector Adsorption Cor-
rection, Institute for Inorganic Chemistry, University of Göttingen,
Germany, 1996.
34 A. Pölnitz, A. Rotar, A. Silvestru, C. Silvestru and M. Kulcsar, J. Orga-
nomet. Chem., 2010, 695, 2486.
35 (a) S. Gambarotta, C. Floriani, A. Chiesi-Villa and C. Guastini, J. Chem.
Soc., Chem. Commun., 1982, 756; (b) S. Gambarotta, F. Urso,
C. Floriani, A. Chiesi-Villa and C. Guastini, Inorg. Chem., 1983, 22,
3966; (c) S. Gambarotta, M. Mazzanti, C. Floriani and M. Zehnder, J.
Chem. Soc., Chem. Commun., 1984, 1116; (d) E. Gallo, E. Solari, S. De
Angelis, C. Floriani, N. Re, A. Chiesi-Villa and C. Rizzoli, J. Am. Chem.
Soc., 1993, 115, 9850; (e) S. De Angelis, E. Solari, E. Gallo, C. Floriani,
A. Chiesi-Villa and C. Rizzoli, Inorg. Chem., 1996, 35, 5995; (f) P.
G. Cozzi, Chem. Soc. Rev., 2004, 33, 410; (g) B.-Y. Li, Y.-M. Yao, Y.-
R. Wang, Y. Zhang and Q. Shen, Inorg. Chem. Commun., 2008, 11, 349.
36 L. Syper and J. Młochowski, Tetrahedron, 1988, 44, 6119.
37 K. R. Flower, V. J. Howard, S. Naguthney, R. G. Pritchard, J. E. Warren
and A. T. McGown, Inorg. Chem., 2002, 41, 1907.
51 DIAMOND-Visual Crystal Structure Information System; Crystal Impact:
Postfach 1251, D-53002 Bonn, Germany, 2001.
5070 | Dalton Trans., 2012, 41, 5060–5070
This journal is © The Royal Society of Chemistry 2012