Di(benzothiazol-2-yl)phosphanide as a janus-head ligand to caesium

Article abstract of DOI:10.1002/chem.200601221

Starting from tris(benzothiazol-2-yl)phosphane (1) an advanced Janus-head ligand, di(benzothiazol-2-yl)phosphane (2), was synthesised and structurally characterised. The heteroaryl substituents of this ligand provide both hard and soft donor sites. Surprisingly, the phosphorus atom in 2 is divalent and the hydrogen atom is directly bonded to one ring nitrogen atom and hydrogen bonded to the second. Compound 2 decomposes in any common solvent other than diethyl ether and a new preparation to improve the yields of 2 is presented. A coordination polymer, [{Cs(bth)₂P}₈] (3) (bth = benzothiazol-2-yl), was obtained when the sec-phosphane 2 was allowed to react with elemental caesium in a 1:1 ratio in diethyl ether at -78°C. In 3 each anion is coordinated to four caesium cations and vice versa. The central phosphorus atom is coordinated to two metal atoms above and below the mean plane of the anion in positions in which the two lone pairs of a four-electron donor are anticipated. Two additional cations μ-bridge both ring nitrogen atoms. Hence both faces of the Janus-head ligand are coordinated to the same number of metal cations but in a different way.

Full text of DOI:10.1002/chem.200601221

DOI: 10.1002/chem.200601221
Di(benzothiazol-2-yl)phosphanide as a Janus-Head Ligand to Caesium
Thomas Stey,[a] Matthias Pfeiffer,[a] Julian Henn,[a] Sushil K. Pandey,[b] and
Dietmar Stalke*[a]
Abstract: Starting from tris(benzothia-
zol-2-yl)phosphane (1) an advanced
Janus-head ligand, di(benzothiazol-2-
yl)phosphane (2), was synthesised and
structurally characterised. The hetero-
aryl substituents of this ligand provide
both hard and soft donor sites. Surpris-
ingly, the phosphorus atom in 2 is diva-
lent and the hydrogen atom is directly
bonded to one ring nitrogen atom and
hydrogen bonded to the second. Com-
pound 2 decomposes in any common
solvent other than diethyl ether and a
new preparation to improve the yields
of 2 is presented. A coordination poly-
is coordinated to four caesium cations
and vice versa. The central phosphorus
atom is coordinated to two metal
atoms above and below the mean
plane of the anion in positions in which
the two lone pairs of a four-electron
donor are anticipated. Two additional
cations m-bridge both ring nitrogen
atoms. Hence both faces of the Janus-
head ligand are coordinated to the
same number of metal cations but in a
different way.
mer, [{Cs(bth)2P}8] (3) (bth=benzo-
G
thiazol-2-yl), was obtained when the
sec-phosphane 2 was allowed to react
with elemental caesium in a 1:1 ratio in
diethyl ether at À788C. In 3 each anion
Keywords: alkali metals · caesium ·
N ligands · P ligands · phosphanes
Introduction
head” ligands. An advantage of these molecular staples is
the combination of soft and hard coordination sites in the
same molecule. In this sense we embarked on developing an
enhanced Janus-head ligand system to investigate its reactiv-
ity as well as its coordination ability. Di(benzothiazol-2-yl)-
phosphane was chosen as a target because the benzothiazol-
yl substituent (bth=C5H4SN) features a sulfur atom and a
nitrogen atom as potential donor centres. Thiazol is an elec-
tron-rich heteroaromatic ring in which the p electrons are
mainly located on the nitrogen atom. Equipped with these
substituents, a secondary phosphanide should provide rich
coordination-site selectivity to various metal fragments.
Various possible conformations of the system (trans–trans,
cis–cis and cis–trans (Scheme 1), not including the non-
planar modifications) make this ligand more compatible
Pincer ligands with an active coordinating periphery[1] have
attracted more and more attention during recent decades.[2]
Over the last few years our group has concentrated on het-
eroaromatic-substituted chelating ligands.[3] These ligands do
not only bear coordination sites for either hard or soft metal
centres in terms of the hard–soft acid–base (HSAB) concept
by Pearson,[4] but also for both. Depending on the metal
fragment offered, the ligands act as a N,N-, P,N-chelating, or
P-coordinating ligand.[5] Ligands of this type find many ap-
plications in alkane dehydrogenation,[6] cyclometalation,[7]
cross-coupling,[8] organic transformation,[9] catalyst recov-
ery,[10] antimicrobial agents,[11] light-emitting diodes (LEDs)
and other electrophosphorescent devices.[12] To obtain heter-
obimetallic complexes it is useful to implement additional
and qualitatively different coordination sites in the phos-
phane ligand periphery. This leads to the so-called “Janus-
[a] Dr. T. Stey, Dr. M. Pfeiffer, Dr. J. Henn, Prof. Dr. D. Stalke
Institut für Anorganische Chemie der Universität Gçttingen
Tammannstrasse 4, 37077 Gçttingen (Germany)
Fax : (+49)551-39-3459
E-mail: dstalke@chemie.uni-goettingen.de
[b] Dr. S. K. Pandey
Department of Chemistry, University of Jammu
Jammu 180006 (India)
Scheme 1. Various different conformations of the planar di(benzothiazol-
2-yl)phosphanide anion.
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FULL PAPER
than homoatomic pincers or hemilabile ligands. Only a few
benzothiazol-2-yl-substituted phosphanes have been struc-
turally characterised, namely, 1,2-bis{di(benzothiazol-2-yl)-
phosphanyl}ethane,[13] 1,1-bis{di(benzothiazol-2-yl)phospha-
nyl}methane[14] and tris(benzothiazol-2-yl)phosphane.[15] In
some cases, such as the latter, the reaction of the lithiated
benzothiazol-2-ide with phosphorus trichloride gives mainly
the coupling product.[16] In this paper, we report on the syn-
thesis, reactivity, X-ray structural and DFT computational
characterisation of the new di(benzothiazol-2-yl)phosphane
and the caesium phosphanide derivative.
Results and Discussion
Scheme 2. Syntheses of the tert-phosphane P
ACHTREUNG
HP(bth)2 (2) and the caesium phosphanide [{CsP
A
ACHTREUNG
Syntheses: Both the tris(benzothiazol-2-yl)phosphane, P-
A
N
(2), were prepared according to the method published by
Moore and Whitesides.[15] First, benzothiazol was silylated
(Scheme 2a) and reacted with phosphorus trichloride at
À788C to give 1 (Scheme 2b). Phosphane 2 was obtained by
reaction of 1 with elemental lithium in THF at room temper-
ature followed by its subsequent hydrolysis with degassed
water. As a major side product the substituent coupling
product bisbenzothiazol ((C7H4NS)2) was obtained
(Scheme 2c).[17] Reacting the sec-phosphane 2 with elemen-
tal caesium at À788C (dry ice) gave the caesium phospha-
nide 3 (Scheme 2d).
vative assembly was developed, which is based on the idea
of a Soxhlet extractor. The use of this apparatus resulted in
greatly improved yields of approximately 60%. The hydroli-
sation mixture was added to the extraction flask with the ex-
tractor in the centre adapter (Figure 1). Diethyl ether was
heated to reflux in the left flask and gaseous diethyl ether
passed through the riser and condensed at the cooling unit.
From there, the solvent dropped into the extractor, which is
porous in order to force the solvent to interact with the mix-
ture in the extraction flask. The diethyl ether containing the
phosphane rose up the extraction flask to the overflow and
ran back into the left flask after being dried over magnesi-
um sulfate. The phosphane stayed in the left flask while the
diethyl ether started the cycle again.
Owing to the originally very poor yields obtained for 2
(about 10% based on the employed benzothiazol), an inno-
Abstract in German: Ausgehend vom Tris(benzothiazol-2-
yl)phosphane, P
ein verbesserter Januskopfligand, das Di(benzothiazol-2-yl)-
phosphan, HP(bth)2 (2), synthetisiert und dessen Einkristall-
A
ACHTREUNG
struktur bestimmt. Die Heteroarylsubstituententen des Ligan-
den stellen zusätzlich jeweils sowohl harte als auch weiche
Koordinationsstellen zur Verfügung. Das Phosphoratom in 2
ist überraschenderweise nur zweibindig, da das Wasserstoff-
atom an ein Ringstickstoffatom gebunden ist und über eine
intramolekulare Wasserstoffbrückenbindung vom zweiten
Ring koordiniert wird. Da sich 2 in jedem anderen Lçsungs-
mittel als Diethylether zersetzt wird hier eine verbesserte Dar-
stellung mit hçheren Ausbeuten beschrieben. In der Reaktion
des sec. Phosphans 2 mit elementarem Cäsium im Molver-
hältnis 1:1 in Ether bei À788C wird [{Cs
A
ten. In diesem Koordinationspolymer ist jedes Phosphanid
von vier Cäsiumkationen vice versa koordiniert. Das Brück-
enkopfatom ist von zwei Metallatomen ober- und unterhalb
der Ligandebene in den Positionen der beiden freien Elektro-
nenpaare eines 4-Elektronen-Donors koordiniert. Die übri-
gen beiden Kationen verbrücken jeweils die beiden Ringstick-
stoffatome. Beide Gesichter des Januskopfliganden sind von
derselben Anzahl Metallatome koordiniert, jedoch in einer
unterschiedlichen Art und Weise.
Figure 1. Glass apparatus used to hydrolyse [LiP
from the reaction mixture.
A
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3637

D. Stalke et al.
Surprisingly, the NMR data from solutions of 2 already
show the phosphorus atom to be divalent because the hy-
drogen atom of the sec-phosphane is not located at the
phosphorus atom but is placed at a ring nitrogen atom.
+48C and red crystals suitable for single-crystal X-ray dif-
fraction analysis were yielded.
Crystal-structure determinations of 1 and 2: Tris(benzothia-
zol-2-yl)phosphane (1) crystallises in the rhombohedral
space group R3c with a third of the two molecules in each
asymmetric unit. The phosphorus atoms are located at the
threefold axis. The solid-state structure of one stereoisomer
of 1 is depicted in Figure 2. The two stereoisomers are dis-
Hence, the connectivity in 2 is different from that of pyridyl
[18]
(Py)-substituted Janus-head ligands like HPPy2
or
H2CPy2.[19] In the first, the hydrogen atom is bonded to the
phosphorus atom, as clearly shown by NMR and IR spectra
(31P NMR: 1J(P,H) =225 Hz; IR: n˜(P,H) =2312 cmÀ1). Phos-
phane 2 is reminiscent of diacylphosphanes, which show
keto–enol tautomerism in solution.[20] The N H tautomer is
À
stable in diethyl ether causing a signal in the 31P NMR spec-
3
trum at d=6.81 ppm with a JP, H coupling constant of 8 Hz.
If, for example, tetrahydrofuran is used as the solvent, a
second signal at d=À65.77 ppm starts growing, which can
1
À
be assigned to the P H tautomer. The JP, H coupling con-
stant is 226 Hz and therefore close to that of di(pyrid-2-yl)-
À
phosphane. Surprisingly, the P H tautomer is not stable and
a transformation to tris(benzothiazol-2-yl)phosphane and
the primary (benzothiazol-2-yl)phosphane occurs. The ab-
sence of any common organic solvent other than diethyl
ether seems to be of vital importance for the stability of 2.
In any other solvent tested so far (e.g., pentane, hexane, tol-
uene, THF, dioxane), ligand scrambling takes place as
shown in Scheme 3.
Figure 2. Structure of tris(benzothiazol-2-yl)phosphane (1). The aniso-
tropic displacement parameters are depicted at the 50% probability
À
level. Selected bond lengths [pm] and angles [8]: P(1) C(1) 182.0(2),
À
À
C(1) N(1) 129.3(2), C(1) S(1) 174.3(2); C(1)-P(1)-C(1A) 101.87(7).
tinguished by the rotation di-
rection of the propeller-like
molecules. The sequence of the
heteroatoms around the phos-
phorus atom as the hub is S–N–
S–N–S–N. In the lattice the
molecules are stacked with the
lone pair on each phosphorus
atom pointing in the same di-
rection but with a ring nitrogen
atom on top of a sulfur atom
À
and vice versa. The P C dis-
tance of 182.0(2) pm is in ac-
Scheme 3. Ligand scrambling of 2 in any solvent other than diethyl ether.
cordance with that in PPy3.[21]
The relatively acute C-P-C
Consequently, all reactions starting from di(benzothiazol-
2-yl)phosphane (2) have to be carried out in diethyl ether.
The solid parent phosphane 2 decomposes gradually, as indi-
cated by a colour change from bright yellow to orange. Si-
multaneously, the consistency changes from a powder to a
paste with reduced solubility and reactivity. Therefore, the
starting material needs to be stored in a sealed flask at
À388C under a dry, inert gas atmosphere.
angle of 101.87(7)8 is a result of the stereochemically active
lone pair at the phosphorus atom.
Di(benzothiazol-2-yl)phosphane (2) crystallises in the or-
thorhombic space group Pbca with the whole molecule in
the asymmetric unit. The solid-state structure of 2 is depict-
ed in Figure 3. The structure shows that the phosphorus
atom is divalent and that the hydrogen atom is located at
one of the ring nitrogen atoms. The position was taken from
a difference Fourier map and refined freely.
sec-Phosphane 2 was allowed to react with elemental cae-
sium in a 1:1 ratio in diethyl ether at À788C to obtain the
Interestingly, this protonation of one ring causes no struc-
tural differences of the bth rings. The hydrogen atom H2 is
additionally linked to the second nitrogen atom by a hydro-
gen bond. The bond length of 192(5) pm for the hydrogen
metal phosphanide [{CsP(bth)2}n] (3) (Scheme 2d). The reac-
A
tion mixture turned deep red while gas was evolved. After
four hours of being stirred at this temperature, the solution
was allowed to warm to ambient temperature. After reduc-
ing the amount of solvent the reaction mixture was stored at
bond N1···H2 is rather short.[22] The atoms N1···H2 N2 in-
À
clude an angle of 140(4)8. The sums of the angles around
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Janus-Head Ligand
FULL PAPER
atoms in positions where the two lone pairs are anticipated
(Figure 5c).
Theoretical studies of 2: The solid-state structure shows di(-
À
benzothiazol-2-yl)phosphane (2) to be the N H tautomer of
À
the P H form anticipated for sec-phosphanes. In particular,
À
in view of the decomposition channel via the P H tautomer,
Figure 3. Solid-state structure of di(benzothiazol-2-yl)phosphane (2). The
anisotropic displacement parameters are depicted at the 50% probability
it was of great interest to get information about the energy
differences of both forms. Theoretical calculations are an ex-
cellent tool to determine the relative energies of various
conformers. Geometries were optimised at the B3LYP/6-
311++G** level of theory and the total energies were calcu-
lated.[25] The X-ray structure was used as the starting geome-
À
À
level. Selected bond lengths [pm] and angles [8]: P1 C1 178.4(5), P1 C8
À
À
À
177.8(4), N1···H2 192(5), N2 H2 85(5), C1 N1 133.1(6), C8 N2 133.4(5),
N1···N2 262.3(5); C1-P1-C8 98.7(2), N2-H2···N1 140(4); C8-N2-H2
119(3), C14-N2-H2 124(3), C1-N1···H2 104(1), C7-N1···H2 143(1), planes
(bth)/(bth’) 169.48.
T
À
try. As reference geometries, the P H tautomer was calcu-
lated in trans–trans, cis–trans, and cis–cis arrangements
(Figure 4).
the nitrogen atoms N1 and N2 are close to 3608 and are in
2
À
accordance with sp hybridisation. The P C bond lengths of
178 pm on average are equal within their estimated standard
deviations but are considerably shorter than those in 1. Con-
sidering the mere distances, they are half-way between a
single and a double bond,[23] thus supporting the canonical
diagram A in Scheme 4. Clearly, further reduction of the C-
The optimised structure derived from the experimentally
determined geometry turned out to be the energetically
most favourable. Although bond lengths and angles in this
structure differ from those found in 2, the experimental ge-
À
ometry is almost reproduced. Whereas the P C bond
lengths in 2 are identical within
estimated standard deviations
À
À
(P1 C1
178.4(5),
P1 C8
177.8(4) pm), they differ more
significantly in the calculated
À
À
geometry (P1 C1 181.6, P1 C8
175.5 pm). All of the bond
lengths are between those for
Scheme 4. Lewis diagrams to rationalise the bonding in sec-phosphane 2.
À
P C double and single bonds.
The average bond length of
P-C angle to 98.7(2)8 relative to 1 is caused by reduced
steric crowding and by the intramolecular hydrogen bond.
However, there might be two lone pairs located at the cen-
tral phosphorus atom causing the acute angle. The Lewis di-
agram B in Scheme 4 might contribute considerably to ex-
plaining the bonding in the sec-phosphane 2.
This is substantiated by the fact that we recently deter-
mined by means of experimen-
178.6 pm matches that of the experimentally determined
À
structure very well. Similarly, the Cipso N bond lengths differ
À
more significantly in the calculated structure (C1 N1 131.2,
À
À
C8 N2 135.4 pm) than in the experimental structure (C1
N1 133.1(6), C8 N2 133.4(5) pm). Although the merge of
À
distances in both parts of the experimental structure might
suggest the superposition of protonated and deprotonated
tal charge-density determina-
tion two lone pairs to be pres-
ent in the metallaphosphane
[AlMe2P(m-Py)2] containing a
G
divalent PIII atom. In the sec-
phosphane PPy2(H), the hydro-
gen atom was found to be locat-
ed at the ring nitrogen atom as
well and can be employed in
unusual m-bridging to two
W(CO)5 moieties in an unsup-
ported
[{(OC)5W}2
mimicking
dinuclear
complex
A
a
four-electron
donor.[24] Moreover, the phos-
phorus atom in the caesium
Figure 4. Optimised geometries for the tautomeric forms of 2: a) optimised X-ray structure (0.0 kJmolÀ1);
phosphanide [{CsP(bth)2}n] (3)
C
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3639

D. Stalke et al.
In the coordination polymer (Figure 5a) each anion is co-
ordinated to four caesium cations and vice versa. The cen-
tral phosphorus atom is coordinated to two caesium cations
above and below the mean plane of the anion. Two addi-
tional metal atoms m-bridge the nitrogen ring atoms (Fig-
ure 5b). Conjugation in the anion is precluded because of
the butterfly arrangement of the substituents. Both bth
mean planes intersect at an angle of 147.58 (Figure 5c). The
coordination polyhedron of each caesium cation can be best
described as a trigonal prism. One of the rectangles is made
up of four nitrogen atoms. The two rectangles forming the
sides of the triangle are derived from the same anion. The
prism is completed by the edge opposite the N4 rectangle
occupied by the two phosphorus atoms (Figure 5d).
À
The P C bond length in the anionic ligand is slightly elon-
gated relative to 2 to 179.2(4) pm because the electron den-
sity at the phosphorus atom is occupied by two caesium cat-
ions and not coupled into the heteroaromatic rings. The
bond lengths match those in [{CsP(py)
2(pmdeta)}2][26]
G
(pmdeta=N,N,N’,N’,N’’-pentamethyldiethylenetriamine) al-
most perfectly, although the phospha-aza-allylic p-coordina-
À
tion in the latter is not observed in 3. The P Cs bond
lengths in 3 are 367.2(2) and 361.6(2) pm. Corresponding
bond lengths listed in the CSD span a wide range from
342 to 411 pm.[27] This is particularly emphasised in
[Cs([18]crown-6)P(H)tBu3C6H2] with two independent mole-
À
cules present in the asymmetric unit. The P Cs bond lengths
of 384.7(2) and 406.9(3) pm in two otherwise almost identi-
cal molecules vary by 20 pm.[28] The N Cs bond lengths are
À
321.4(4) and 318.6(3) pm. In polymeric [(Cs
2(m-thf){Ph-
Figure 5. Crystal structure of [{Cs(bth)2P}n] (3): a) the coordination poly-
A
(Me3SiN)P}2)n] a similar bonding situation with two m-bridg-
mer; b) the metal coordination of a single phosphanide; the anisotropic
displacement parameters are depicted at the 50% probability level;
c) the butterfly arrangement of the anion; d) the coordination poly-
hedron of the caesium cation. Selected bond lengths [pm] and angles [8]:
À
ing Cs cations across N···N is present and the N Cs bond
lengths range from 309.5(4) to 316.2(4) pm.[29] The N1···N1A
distance in 3 is 321.4(7) pm. This is the largest distance ob-
served for the bite distance in di(benzothiazol-2-yl)phospha-
nides so far. The benzothiazol-2-yl rings are rotated about
À
À
À
À
P1 C1 179.2(4), Cipso N 131.3(5), N1 Cs1 321.4(4), N1 Cs1B 318.6(3),
À
À
P1 Cs1C 367.2(2), P1 Cs1D 361.6(2), N1···N1A 321.4(7), C-P-C
103.3(3), Nbth-Cs1-Nbth’ 60.0(1), Nbth-Cs1B-Nbth’ 60.6(1), Cs1C-P-Cs1D
À
the P Cipso bonds in the same direction. The best planes de-
126.1(1), planes (bth)/(bth’) 147.58.
G
fined by the atoms of the heteroaromatic rings include an
angle of 147.58. The maximum in bite distance in this com-
pound is caused by the maximum rotation of the heteroaro-
rings or a double minimum for the hydrogen bond, the
structure shows no indication of two hydrogen sites of 0.5
occupation factor. The total energy of the optimised X-ray
À
matic rings about the P C bonds (Figure 5c). The butterfly
arrangement is a compromise between planarity required
for conjugation and the affinity of the cationic metals to the
maxima of electron density. The rotation of the heteroaro-
À
structure was defined to be zero. The energies for the P H
isomers span the range from 22.54 kJmolÀ1 for the cis–trans
arrangement to 28.65 kJmolÀ1 for the cis–cis conformation.
In all non-planar geometries the heteroaromatic rings are
À
matic rings about the P Cipso bonds facilitates close proximi-
ty of the caesium cations to the sulfur atoms. The S1···Cs1D
distance is 412.7(1) pm. This is at the long end of the pub-
lished range.[28] Only a few S···Cs distances are listed. Thiola-
to complexes show the shortest distances from approximate-
ly 330 to 360 pm.[30] Distances for dative bonds found in thi-
oethers or thioketones range from approximately 370 to
390 pm.[31] However, there is no doubt that the S···Cs inter-
actions enhance the formation of the butterfly arrangement.
À
rotated about the P C bonds. The angles included by the
ring systems range from 33.4 (cis–cis conformer) through
102.4 (trans–trans conformer) to 104.18 (cis–trans confor-
mer). The crystal structure of 2 displays an almost planar
molecule. The total energy of the system clearly decreases
À
through the formation of a strong N H···N hydrogen bond.
Crystal-structure determination of 3: [{CsP(bth)2}n] (3) crys-
A
tallises in the orthorhombic space group Cmc21 with the
asymmetric unit consisting of half the monomer. The di(ben-
zothiazol-2-yl)phosphanide is generated by a mirror plane.
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Janus-Head Ligand
FULL PAPER
Synthesis of [{Cs(bth)2P}n] (3): Elemental caesium (1.00 g, 7.52 mmol) in
A
Conclusion
diethyl ether (60 mL) was reacted with 2 (2.00 g, 6.66 mmol) in diethyl
ether (60 mL) at À788C. The reaction mixture turned deep red while
evolving gas. After the solution had been stirred for 4 h at this tempera-
ture it was allowed to warm up to ambient temperature. After the
amount of solvent was reduced, the reaction mixture was stored at 48C.
Red crystals (2.07 g, 73%) suitable for single-crystal X-ray diffraction
analysis were obtained. M.p. 2348C (decomp); 1H NMR (300.1 MHz,
In conclusion, di(benzothiazol-2-yl)phosphane is a rare ex-
ample of a phosphane containing a divalent phosphorus
atom in the centre and accommodating the hydrogen atom
in the ligand periphery. Computational investigations prove
this conformer to be about 22 kJmolÀ1 more stable than the
C6D6): d=6.92 (ddd, 3JH3,H4 =7.44 Hz, 3JH5,H4 =7.44 Hz, 4JH6,H4 =1.14 Hz,
À
best P H tautomer. However, owing to its decomposition in
4
2H; H4, H11), 7.12 (ddd, 3JH4,H5 =7.09 Hz, 3JH6,H5 =8.14 Hz, JH3,H5
=
any common solvent other than diethyl ether, this phos-
phane has to be prepared and handled with special care. An
individual Soxhlet extractor and low temperatures are re-
quired to ascertain reasonable yields. Both faces of the
Janus-head ligand in 3 are coordinated to the same number
of ceasium cations but in a different way. The central phos-
phorus atom in the coordination polymer is bound to two
metal atoms above and below the mean plane of the anion
in positions where the two lone pairs are anticipated, thus
mimicking a four-electron donor. Two additional cations m-
bridge both ring nitrogen atoms. Long-range Cs···S distances
help to establish the solid-state structure. Hence, the ligand
is a promising anionic staple in heterobimetallic complexes,
simultaneously suiting various coordination requirements
like radius, polarisability and haptisity of a variety of organo-
3
1.27 Hz, 2H; H5, H12), 7.53 (d, JH5,H6 =8.14 Hz, 2H; H6, H13), 7.60 ppm
(d, JH4,H3 =7.44 Hz, 2H; H3, H10); 13C NMR (75.5 MHz, C6D6): d=120.6
3
(s, 2C; C3, C10), 121.0 (s, 2C; C6, C13), 125.2 (s, 2C; C4, C11), 126.8 (s,
2C; C5, C12), 131.8 (s, 2C; C2, C9), 155.1 (s, 2C; C7, C14), 156.9 ppm (s,
2C; C1, C8); 31P NMR (121.5 MHz, H3PO4 (85%)): d=14.23 ppm (s, 1P;
P1); elemental analysis calcd (%) for 3: C 38.90, H 1.87, N 6.48, S 14.83;
found: C 41.89, H 3.97, N 3.97, S 9.06.
Theoretical studies: Zero-temperature vacuum DFT calculations were
performed by employing Beckeꢁs three-parameter exchange functional
and the correlation functional of Lee, Yang and Parr (B3LYP)[32,33] in
combination with a 6-311++G** Gaussian basis set included in the
Gaussian 98 program. No symmetry restrictions were imposed. Using the
crystal structure coordinates of 2 as a starting point for geometry optimi-
sations gave a planar configuration. The topological analyses were per-
formed with the AIM2000 program package[34] by using the converged
densities from the geometry optimisation.
Structure determination of 1–3: Crystallographic data for 1–3 are listed
in Table 1. All data were measured at low temperature[35] by using graph-
ite monochromated MoKa radiation (l=71.073 pm) on a Bruker D8 goni-
ometer platform, equipped with a Smart Apex CCD detector. Cell pa-
rameters were determined and refined by using the SMART software.[36]
Series of w scans were performed at several f settings. Raw frame data
were integrated by using the SAINT program.[37] The structures were
solved by using direct methods and refined by means of full-matrix least-
squares cycles on F2 by using SHELXTL.[38] Data of 2 and 3 were empiri-
cally absorption corrected with SADABS 2.[39] The position of the hydro-
gen atom H2 at N2 in 2 was taken from the difference Fourier map and
metallic residues.
Experimental Section
General procedures: All experiments were carried out in a dry nitrogen
or an argon atmosphere by using modified Schlenk techniques and a dry
box. Solvents were freshly distilled from a sodium–potassium alloy prior
to use. The reactants used were either procured commercially or synthes-
ised according to published procedures.
Table 1. Crystallographic data for compounds 1–3.
NMR spectra were recorded at room temperature on a Bruker DRX 300
spectrometer at 300.1 (1H), 75.5 (13C), or 121.5 MHz (31P). Chemical
shifts are in d relative to the solvent used for H and to H3PO4 (85%) for
1
2
3
1
formula
C21H12N3PS3
433.49
618731
C14H9N2PS2
300.32
618732
C14H8CsN2PS2
432.22
618734
Mr [gmolÀ1
CCDC no.
T [K]
]
31P. Elemental analyses were performed at the Mikroanalytisches Labor
des Instituts für Anorganische Chemie der Universität Würzburg. The
melting and decomposition points were determined by using differential
thermo analysis (DTA) on a Thermal Analyzer 9000 (Du Pont) instru-
ment and a Differential Scanning Calorimetry (DSC) cell. IR spectra
were recorded on a Bruker IFS 25 spectrometer.
173(2)
100(2)
173(2)
crystal system
space group
a [pm]
rhombohedral orthorhombic orthorhombic
R3c
Pbca
Cmc21
2579.61(15)
732.46(4)
806.45(5)
1.52376(15)
4
2009.6(3)
2009.6(3)
1552.4(3)
5.429(2)
12
1460.7(5)
727.2(3)
2447.8(8)
2.6001(16)
8
b [pm]
Synthesis of tris(benzothiazol-2-yl)phosphane (1): The compound was
synthesised and characterised by following the procedure published in
ref. [15].
c [pm]
V [nm3]
Z
Synthesis of di(benzothiazol-2-yl)phosphane (2): Tris(benzothiazol-2-yl)-
phosphane (12.00 g, 27.71 mmol) was dissolved in THF (60 mL) and al-
lowed to react with an excess of elemental lithium. The colourless solu-
tion turned red. After two hours of stirring the remaining metal was re-
moved and THF was replaced by diethyl ether. The solution was diluted
with diethyl ether and dried over magnesium sulfate. Storing the solution
at À408C yielded pale yellow needles (7.24 g, 87%) suitable for single-
crystal X-ray diffraction analysis. M.p. 1028C; 1H NMR (300.1 MHz,
C4D10O): d=6.78 (dd, 3JH3,H4 =7 Hz, 3JH5,H4 =8 Hz, 2H; H4, H11), 6.92
1calcd [MgmÀ3
]
1.591
1.534
1.884
m [mmÀ1
(000)
]
0.511
0.517
2.798
F
A
2664
1232
832
crystal size [mm]
q range [8]
reflections collected
0.5”0.3”0.3
3.35 to 25.01
11162
0.2”0.1”0.01 0.4”0.03”0.02
2.17 to 25.04
15966
2.89 to 26.37
6839
independent reflections 2240
2655
1719
absorption correction
max/min transmission
data/restraints/param.
–empirical
–1.000/0.581
2240/1/164
empirical
1.000/0.822
2292/0/175
0.0561
(dd, 3JH4,H5 =8 Hz, 3JH6,H5 =8 Hz, 2H; H5, H12), 7.22 (d, 3JH5,H6 =8 Hz,
1587/1/94
0.0262
2H; H6, H13), 7.28 (d, 3JH4,H3 =7 Hz, 2H; H3, H10) 8.05 ppm (d, JP, H
=
3
final R index [I>2s(I)] 0.0244
8 Hz, 1H; H2); 13C NMR (75.5 MHz, C4D10O): d=121.6 (s, 2C; C3,
C10), 123.3 (s, 2C; C6, C13), 124.2 (s, 2C; C4, C11), 126.4 (s, 2C; C5,
C12), 137.8 (s, 2C; C2, C9), 155.4 (s, 2C; C7, C14), 155.5 ppm (s, 2C; C1,
C8); 31P NMR: 6.81 ppm (s, 1P; P1); elemental analysis calcd (%) for 2:
C 55.99, H 3.02, N 9.33, S 21.35; found: C 56.25, H 3.31, N 9.20, S 20.77.
R index (all data)
0.0653
0.0926
0.0285
largest diff. peak/hole
299/À257
497/À335
758/À493
A
flack x parameter[40]
0.01(6)
–0.02(2)
Chem. Eur. J. 2007, 13, 3636 –3642
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3641

D. Stalke et al.
refined freely. All other hydrogen atom positions were refined by using a
riding model. The Uiso values for the hydrogen atoms of a CH3 group
were set to 150%, those of all other hydrogen atoms to 120% of the Ueq
values of the corresponding C atoms. All non-hydrogen atoms were re-
fined anisotropically. The absolute structures of 1 and 3 were refined suc-
cessfully by refining the Flack x parameter.[40] CCDC-618731, -618732
and -618734 (see Table 1) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
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Received: August 24, 2006
Published online: February 1, 2007
3642
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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 3636 –3642