Access to new Janus head ligands: Linking sulfur diimides and phosphanes for hemilabile tripodal scorpionates

Article abstract of DOI:10.1039/c0dt00665c

Reactions of lithium dialkyl/phenyl phosphanylmethylides, RR′PCH(X)Li (R, R′ = Me, Et, Ph and R = Me, R′ = Ph; X = H or Me), with sulfur diimides S(NR′′)₂ (R′′ = ^tBu or SiMe₃) in an equimolar ratio yielded Janus head compl

Full text of DOI:10.1039/c0dt00665c

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An international journal of inorganic chemistry
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Volume 40 | Number 8 | 28 February 2011 | Pages 1621–1824
ISSN 1477-9226
COVER ARTICLE
Stalke et al.
Access to new Janus head ligands:
linking sulfur diimides and phosphanes
for hemilabile tripodal scorpionates
1477-9226(2011)40:8;1-G

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Cite this: Dalton Trans., 2011, 40, 1662
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PAPER
Access to new Janus head ligands: linking sulfur diimides and phosphanes for
hemilabile tripodal scorpionates†
Margret M. Meinholz,a Sushil K. Pandey,b Stephan M. Deuerleina and Dietmar Stalke*a
Received 15th June 2010, Accepted 24th November 2010
DOI: 10.1039/c0dt00665c
Reactions of lithium dialkyl/phenyl phosphanylmethylides, RR¢PCH(X)Li (R, R¢ = Me, Et, Ph and R =
t
Me, R¢ = Ph; X = H or Me), with sulfur diimides S(NR¢¢)2 (R¢¢ = Bu or SiMe3) in an equimolar ratio
t
yielded Janus head complexes with the structural motif [Li{RR¢PCH(X)S(NR¢¢)2}]2 (R¢¢ = Bu, SiMe3).
The basic core of these dimeric complexes is composed of a (LiN)2 four-membered ring containing two
four-coordinated lithium atoms. A lithium complex of the new Janus head ligand with another
structural motif [TMEDA·Li{Ph2PCH2S(NSiMe3)2}] (6) could be isolated from the reaction of
[Ph2PCH2Li·TMEDA] with S(NSiMe3)2. Two monomeric complexes [Mg{Me2PCH2S(NR¢¢)2}2] (7, 8)
were synthesised by a straightforward reaction of [Li{Me2PCH2S(NR¢¢)2}2] with MgCl2 in pentane. The
magnesium atom is chelated by one phosphorus atom and two nitrogen atoms of each unit of the
hemilabile ligand in a tripodal manner, leading to octahedral geometry around the magnesium cation.
A complete analysis of [Ph2PCH2(SNSiMe3)(HNSiMe3)] (9) is also described in which one nitrogen
atom of the imido moiety is protonated.
A literature survey shows that several tripodal ligand systems with
Introduction
group 15 elements as bridgehead atoms are known.4–15
Over the past few years our group has concentrated on
However, in most of these cases the metal is coordinated by
heteroatomic-substituted multidentate ligand systems featuring
the ancillary donors. Anionic ligands consisting of carbanions
two pendent arms and a second coordination site, which can also
and heavier group 14 elements are another possibility for creating
be referred to as “claw” ligands1 or scorpionates.2 Our principal
strategy is to develop these ligands which bear coordination sites
for both hard and soft metal centres in terms of the HSAB
concept.3,4 If both coordination sites of the ligand point in opposite
directions we call that a Janus head ligand. The functionalization
of organodiimidosulfinates may be expanded by the introduction
of an additional donor site in the backbone of the carbon
substituent at the central sulfur atom. Ideally, this donor should be
soft. By these means, simultaneous coordination of hard and soft
metals in heterobimetallic complexes would be feasible, promoting
their catalytic versatility.
Janus head systems (Fig. 1).16
Fig. 1 Some tripodal ligand systems.
If the length of the connecting clamp is large enough, both the
apical and ancillary donors of the ambidentate ligands will be able
to coordinate the same metal. In addition, such ambidentate sys-
tems will provide rigid and well defined coordination geometries
leading to interesting chemical properties and reactivity patterns.
It is apparent from recent breakthroughs in this area that such
ligands are about to be further developed and promising results are
likely to occur.17 Multifunctional ligands with podand topology
provide intrinsically well defined coordination geometries with
interesting bonding aspects and reactivity patterns. There is grow-
ing interest in multidentate hemilabile ligand systems featuring
dual functionality. The modification of classical chelating ligands
to produce novel and fluxional multidentate systems has opened
up an exciting area of research in the last few years.18 Janus
head complexes are finding ever increasing applications in areas
like heterolytic H2-splitting,19 NLO (non linear optic) materials,20
organic transformation,21 asymmetric catalysis,22 cross coupling,11
microbial agents23 or light emitting diodes (LEDs).24
aInstitut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tam-
mannstraße 4, 37077, Go¨ttingen, Germany. E-mail: dstalke@chemie.uni-
goettingen.de; Fax: +49-551-39-3459; Tel: +49-551-39-3000
bDepartment of Chemistry, University of Jammu, Jammu, 180 006, India
† Electronic supplementary information (ESI) available: Experimental
and crystallographic data, including the coordinates of all the species.
CCDC reference numbers 779986–779988 and 779990–779995. For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/c0dt00665c
1662 | Dalton Trans., 2011, 40, 1662–1671
This journal is
The Royal Society of Chemistry 2011
©

The complexes of magnesium metal with a ligand contain-
ing sulfur, nitrogen and phosphorus atoms may be promising
precursors for semiconducting materials in the sol–gel or CVD
process.25 Recently, the construction of (hetero)bimetallic or even
multimetallic complexes using Janus head ligands became an in-
teresting field of research since such complexes may serve as model
compounds for one-dimensionally conducting polymers.16,25,26
We have already targeted group 15 element centred ligands,1a,b
which are able to employ their substituent periphery in metal
coordination, and reported on lithium sulfur ylides.27,28
Results and discussion
The linkage of sulfurdiimide and phosphane in order to gain
access to a new type of Janus head ligand is achieved by
an equimolar reaction of lithium dialkyl/phenyl phosphanyl-
methanide, RR¢PCH(X)Li (RR¢ = Me, X = H (1, 2); RR¢ =
Ph, X = H (3); R = Et, X = Me (4); R = Me, R¢ = Ph, X = H
(5)) with bis(trimethylsilyl)sulfur diimide, S(NSiMe3)2, or bis(tert-
butyl)sulfur diimide, S(NtBu)2, in n-pentane under anhydrous and
inert gas conditions (Scheme 1).
t
The complex [(H5C3)Ni{ Bu2PCH2S(NSiMe3)2}], has been re-
ported in a patent as an active catalyst for the co-polymerization
of ethylene with polar co-monomers without further study.29
Therefore we have inserted bis(tert-butyl)sulfur diimide into the
Li–C bond of organolithium species to link a sulfur diimide with
a phosphanyl moiety to study the coordination geometry of the
resulting ligand.
Scheme 1
We report herein the synthesis, characterization and single
crystal X-ray structure elucidation of [Li{RR¢PCH(X)S(NR¢¢)2}]2
(R¢¢ = tBu, X = H, RR¢ = Me (1)/Ph (3), R = Me, R¢ =
Ph (5); R¢¢ = SiMe3, X = H, RR¢ = Me (2); R¢¢ = SiMe3,
X = Me, RR¢ = Et (4), [TMEDA·Li{Ph2PCH2S(NSiMe3)2}] (6),
[Mg{Me2PCH2S(NtBu)2}2] (7), [Mg{Me2PCH2S(NSiMe3)2}2] (8)
and [Ph2PCH2(SNSiMe3)(HNSiMe3)] (9).‡
Compounds 1–5 were obtained as white solids. The elemental
analyses were found to be consistent with the molecular formulae.
Compound 1 crystallizes from n-pentane as colourless plates
¯
in the triclinic space group P1. A dimer is formed owing to
the inadequate bite of the ligand to the small lithium cation
(Fig. 2). The Me2P-sidearm is not coordinating to the already
SN2-complexed lithium atom but to that of the second molecule.
The main core of the system is a (LiN)2 four-membered ring with
both the lithium atoms forming three N- and one P-contact each.
One nitrogen atom of each ligand unit is coordinated to both
lithium atoms while the second coordinates just the lithium atom
of one half of the dimer (Li1–N1/Li2–N4). The phosphorus
coordination to that lithium atom (Li1–P2/Li2–P1) provides
additional stability to the complex (Fig. 3). Both halves of the
dimer show almost no differences in bond lengths and angles. All
‡ Single-crystal structural analysis: The X-ray data sets were collected at
100(2) K on a Bruker TXS Mo rotating anode (1, 3, 4, 7 (T = 250 K), 8, 9) or
an INCOATEC Mo micro source39 (2, 5, 6) with mirror-monochromated
˚
Mo-Ka radiation (l = 0.71073 A). The single crystals were mounted in
inert oil under argon atmosphere by applying special cryo application
techniques.40 Structures were solved by direct methods with SHELXS and
refined by full-matrix least squares on F2 for all data with SHELXL.41,42
Non-hydrogen atoms were refined with anisotropic displacement parame-
ters. All H atoms were placed in calculated positions and refined using
a “riding-model”.[Li{Me2PCH2S(NtBu)2}]2(1): C22H52N4P2S2Li2, M =
¯
˚
˚
˚
512.62, triclini◦c, P1, a = 9.4916◦(4) A, b = 9.6726(4) A, c = 18.7808(8) A,
˚
S–N distances (1.6144(9)–1.6351(9) A) are slightly shorter than an
◦
3
˚
a = 98.772(1) , b = 92.004(1) , g = 114.778(1) , V = 1537.76(11) A ,
Z = 2, 27 095 reflections measured, 7923 independent reflections (Rint
=
0.0191), 305 parameters, R1 (all data) = 0.0341, R1[I > 2s(I)] = 0.0266,
wR2 (all data) = 0.0693, wR2[I > 2s(I)] = 0.0657, GoF = 1.054, largest
˚
(6): C27.5H52N4Si2PSLi, M = 564.89, monoclinic,◦C2/c, a = 33.944(5) A,
◦
˚
˚
b = 9.5352(13) A, c = 21.921(3) A, a = g = 90 , b = 101.895(3) , V =
-3
˚
diff. peak and hole 0.433 and -0.304 eA .[Li{Me2PCH2S(NSiMe3)2}]2(2):
3
˚
6942.4(17) A , Z = 8, 48 696 reflections measured, 6847 independent
¯
˚
C18H52N4Si4P2S2Li2, M = 576.94, triclinic, P1, a◦= 10.2715(11) A, b =
reflections (Rint = 0.0632), 441 parameters, 16 restraints, R1 (all data) =
0.0505, R1 [I > 2s(I)] = 0.0368, wR2 (all data) = 0.0942, wR2 [I
> 2s(I)] = 0.0871, GoF = 1.041, largest diff. peak and hole 0.348
◦
˚
˚
10.356(11) A, c = 10.4832(11) A, a = 68.636(1) , b = 65.728(1) , g =
◦
3
˚
60.990(1) , V = 869.77(16) A , Z = 1, 21 105 reflections measured, 3546
-3
t
independent reflections (Rint = 0.0145), 153 parameters, R1 (all data) =
0.0236, R1 [I > 2s(I)] = 0.0216, wR2 (all data) = 0.0619, wR2 [I >
2s(I)] = 0.0607, GoF = 0.861, largest diff. peak and hole 0.314 and
˚
and -0.245 eA .[Mg{Me2PCH2S(N Bu)2}2] (7): C22H52N4P2S2Mg, M =
˚
˚
523.07, orthorhombic, Fdd2, a = 37.169(8) A, b = 10.175(2) A, c =
3
˚
˚
16.851(4) A, V = 6373(2) A , Z = 8, 21 122 reflections measured, 3270
independent reflections, Rint = 0.0407, 180 parameters, R1 (all data) =
0.0467, R1[I > 2s(I)] = 0.0444, wR2 (all data) = 0.1147, wR2[I >
2s(I)] = 0.1137, GoF = 1.183, largest diff. peak and hole 0.228 and
-3
t
˚
-0.223 eA .[Li{Ph2PCH2S(N Bu)2}]2(3): C42H60N4P2S2Li2, M = 760.91,
¯
˚
˚
˚
triclinic, P1, a = 9.6236(11) A, b = 10.1512(12) A, c = 11.3253(13) A,
◦
◦
◦
3
˚
a = 73.936(2) , b = 84.728(2) , g = 88.960(2) , V = 1058.7(2) A , Z = 1,
25 994 reflections measured, 5259 independent reflections (Rint = 0.0399),
241 parameters, R1 (all data) = 0.0564, R1[I > 2s(I)] = 0.0391, wR2
(all data) = 0.1026, wR2[I > 2s(I)] = 0.0976, GoF = 1.054, largest diff.
-3
˚
-0.212 eA .[Mg{Me2PCH2S(NSiMe3)2}2] (8): C18H52N4Si4P2S2Mg, M =
˚
˚
587.37, monoclinic, P21/n, a = 10.2563(5◦) A, b = 17.8142(8) A, c =
◦
3
˚
˚
19.2917(9) A, a = g = 90 , b = 99.273(1) , V = 3478.7(3) A , Z = 4,
156 125 reflections measured, 9326 independent reflections (Rint = 0.0192),
296 parameters, R1 (all data) = 0.0238, R1 [I > 2s(I)] = 0.0213, wR2
(all data) = 0.0630, wR2 [I > 2s(I)] = 0.0612, GoF = 1.019, largest diff.
-3
˚
peak and hole 0.391 and -0.381 eA .[Li{Et2PCH(Me)S(NSiMe3)2}]2(4):
¯
˚
C24H64N4Si4P2S2Li2, M = 661.09, triclinic, P1, ◦a = 10.6002(6) A, b =
◦
˚
˚
10.635(1) A, c = 10.7744(6) A, a = 100.785(1) , b = 117.366(1) , g =
◦
3
-3
˚
˚
103.446(1) , V = 986.48(12) A , Z = 1, 39 887 reflections measured,
peak and hole 0.286 and -0.263 eA .Ph2PCH2(SNSiMe3)(HNSiMe3) (9):
˚
4676 independent reflections (Rint = 0.0146), 181 parameters, R1 (all
data) = 0.0299, R1 [I > 2s(I)] = 0.0277, wR2 (all data) = 0.0768, wR2
[I > 2s(I)] = 0.0747, GoF = 1.068, largest diff. peak and hole 0.686
C19H31N2Si2PS, M = 406.67, monoclinic, P21/n, a =◦12.9937(7) A, b =
◦
3
˚
˚
˚
9.9367(6) A, c = 18.1145(1) A, a = g = 90 , b = 99.843(1) , V = 2304.4(2) A ,
Z = 4, 43 786 reflections measured, 5491 independent reflections (Rint
=
-3
t
˚
and -0.453 eA .[Li{Ph(Me)PCH2S(N Bu)2}]2(5): C32H56N4P2S2Li2, M =
0.016), 235 parameters, R1 (all data) = 0.0289, R1 [I > 2s(I)] = 0.0278, wR2
(all data) = 0.0767, wR2 [I > 2s(I)] = 0.0757, GoF = 1.052, largest diff. peak
˚
˚
636.75, monoclinic, P21/c, a = 10.5006(1◦4) A, b = 20.753(3) A, c =
◦
3
-3
˚
˚
˚
8.5699(11) A, a = g = 90 , b = 97.279(2) , V = 1852.5(4) A , Z = 2,
39 157 reflections measured, 3784 independent reflections (Rint = 0.0274),
197 parameters, R1 (all data) = 0.0325, R1 [I > 2s(I)] = 0.0305, wR2
(all data) = 0.0788, wR2 [I>2s(I)] = 0.0778, GoF = 1.050, largest diff.
and hole 0.596 and -0.340 eA .Crystallographic data (excluding structure
factors) for the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC 779986 (1), 779990 (2), 779987 (3), 779991 (4),
779992 (5), 779993 (6), 779988 (7), 779994 (8) and 779995 (9).
∑
-3
˚
peak and hole 0.409 and -0.247 eA .[TMEDA Li{Ph2PCH2S(NSiMe3)2}]
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1662–1671 | 1663
©

Fig. 2 Molecular structure of [Li{Me2PCH2S(NtBu)2}]2 (1) in the crystal.
Anisotropic displacement parameters are depicted at the 50% probability
˚
level, hydrogen atoms are omitted for clarity. Selected bond lengths [A]
Fig. 4 Molecular structure of [Li{Me2PCH2S(NSiMe3)2}]2 (2) in the
crystal. Anisotropic displacement parameters are depicted at the 50%
probability level, hydrogen atoms are omitted for clarity. Atoms labeled
with prime (¢) are symmetry equivalents genera◦ted by 1 - x, 2 - y,
and angles [◦]: S1–N1 1.6144(9), S1–N2 1.6351(9), S1–C9 1.8406(11),
P1–C9 1.8403(11), Li1–N1 1.939(2), Li1–N2 2.398(2), Li2–P1 2.6425(19);
N1–S1–N2 104.74(5), N1–S1–C9 106.38(5), N2–S1–C9 100.60(5),
Li1–N2–Li2 69.23(7), N1–Li1–N2 71.93(7), N2–Li2–P1 76.79(6).
˚
1 - z. Selected bond lengths [A] and angles [ ]: S1–N1 1.6031(10),
S1–N2 1.6221(10), S1–C1 1.8286(12), P1–C1 1.8406(13), Li1–N1 1.989(2),
Li1–N2 2.315(2), Li1–P1¢ 2.655(2); N1–S1–N2 105.89(5), N1–S1–C1
102.66(6), N2–S1–C1 101.53(5), Li1–N2–Li1¢ 80.96(9), N1–Li1–N2
73.00(8), N2–Li1¢–P1 79.63(7).
Inspection of the molecular structures of 1 and 2 reveals that
the N2SCP ligand is indeed tridentate. Although the bite of the
ligand system is not optimized for lithium cations, the complexes
formed are surprisingly stable.
Fig. 3 Generic line drawing of complexes 1–5 (for R, R¢, R¢¢ and X see
Scheme 1).
The complex [Li{Ph2PCH2S(NtBu)2}]2 (3) was synthesized
by equimolar reaction of lithio(diphenylphosphino)methane-
tetramethylethylenediamine,
[Ph2PCH2Li·TMEDA],
with
˚
average sulfur–nitrogen single bond (1.69 A) and are in the range
S(NtBu)2 in n-pentane to modify the substituents at the
30
˚
of other alkyl diimidosulfinates (1.598–1.657 A).
The S–C bond lengths match with standard S–Csp3 single bonds
(1.83 A). Hence, S1 is surrounded by single bonds only and
adopts the tetrahedral environment akin to an sp3-hybridized
atom. The N1–S1–N2 (104.74(5)◦), N1–S1–C9 (106.38(5)◦) and
N2–S1–C9 (100.60(5)◦) angles are reduced with respect to the
ideal tetrahedral angle. This is according to the VSEPR theory,
because the stereochemically active lone pair at S1 takes up most
phosphorus atom. It was crystallized from toluene, yielding
colourless crystals in the space group P1with half a molecule in
the asymmetric unit.
The main core of the system also consists of a (LiN)2 four-
membered heteroatomic ring (Fig. 5). The structural character-
istics of 3 are thus akin to complexes 1 and 2. Nevertheless the
molecule has a centre of inversion. The bond lengths and angles
of 3 fall within the expected ranges.
¯
30
˚
space. Li1–N1 and Li2–N2 are in the typical range of Li–N bonds
30
˚
˚
(1.905–2.202 A). The Li2–P1 distance of 2.6425(19) A is slightly
longer than the average Li–P distances in Li(P–C–C N) systems
(2.520 A).18 The acute N2–Li2–P1 angle of 76.79(6) is typical for
such systems (73.10–87.35◦).28
◦
˚
It is easily possible to modify the ligand structure
by introducing different substituents at the sulfur atom.
[Li{Me2PCH2S(NSiMe3)2}]2 (2) crystallizes from n-pentane as
¯
colourless blocks in the triclinic space group P1 (Fig. 4). The
main core of the system consists of a (LiN)2 heteroatomic ring
just like in complex 1. All S–N bond distances (1.6031(10)–
˚
1.621(10) A) are slightly shorter than an average sulfur–nitrogen
single bond (1.69 A). Probably there is the presence of S+–N-
30
˚
Fig. 5 Molecular structure of [Li{Ph2PCH2S(NtBu)2}]2 (3) in the crystal.
Anisotropic displacement parameters are depicted at the 50% probabil-
ity level, hydrogen atoms are omitted for clarity. Atoms labeled with
prime (¢) are symmetry equivalents gen◦erated by 1 - x, 1 - y, -z.
electrostatic bond shortening as described for many S–N systems
from experimental and theoretical charge density investigations.31
The N1–S1–N2 (105.89(5)◦), N1–S1–C1 (102.66(6)◦) and N2–S1–
C1 (101.53(5)◦) bond angles are similar to 1. The shared lithium
coordination of N2 leads to longer Li–N distances (Li1–N2
˚
Selected bond lengths [A] and angles [ ]: S1–N1 1.6120(14), S1–N2
1.6925(14), S1–C13 1.8412(17), P1–C13 1.8404(17), Li1–N1 1.959(3),
Li1–N2 2.318(3), Li1–P1 2.657(3); N1–S1–N2 104.15(7), N1–S1–C13
106.45(8), N2–S1–C13 101.29(7), Li1–N2–S1 84.68(9), N1–Li1–N2
72.88(10), N1–Li1–P1 147.48(14), N2–Li1–P1 117.31(12).
˚
˚
2.315(2) and Li1¢–N2 2.029 A) compared to Li1–N1 (1.989(2) A).
Li1–N1 and Li1¢–N2 are in the typical range of Li–N bonds
(1.905–2.202 A),30 but Li1 seems to be weakly coordinated to N2.
˚
1664 | Dalton Trans., 2011, 40, 1662–1671
This journal is
The Royal Society of Chemistry 2011
©

In order to obtain more insight into the coordinative behavior of
the new N2SCP system, further modifications at the P,S bridging
carbon atom were introduced. The compound [Li{Et2PCH-
(Me)S(NSiMe3)2}]2 (4) is isostructural to 2 (Fig. 6). It is also
obtained as a dimer and the main core of the system is a (LiN)2
four-membered ring with both the lithium atoms displaying four
contacts to the donor atoms of each ligand (Fig. 5). Different to
2, in 4 chirality is introduced at the P,S bridging methylene carbon
atom C7. Due to the center of inversion in the middle of the (LiN)2
four-membered ring 4 crystallizes as a racemate. The S–N bond
(Fig. 7). Similar dynamic behaviour has already been observed in
other systems.32
˚
distances are almost equal to 2 and are 1.5906(10) A for S1–N1
˚
and 1.6235(10) A for S1–N2, respectively. The two (SN2) units
are inclined by 116.9◦ with respect to the (LiN)2 ring and the
ethyl phosphane moieties reside on opposite sides of the (SN2)
planes. Thus, the steric strain between the trimethylsilyl groups is
Fig. 7 Dynamic behaviour of complexes 1–5 in solution.
This hypothesis can be proven by the Li–P coupling constants
1
of approximately 19 Hz and the 13C{ H} NMR spectra of 3. The
˚
minimized. The S–C bond length of 1.8300(12) A exactly matches
phenyl carbon atoms show various multiplets, whose structure
can only be explained if both phosphorus atoms are coupled to
each other and thus influence the carbon atoms in the rings. With
phosphorus decoupling, however, those multiplets change into
singlets.
the value reported for the presence of a standard S–Csp3 single
bond.30 So, a tetrahedral environment around the sulfur atom
is assumed. The N1–S1–N2 (104.22(5)◦), N1–S1–C7 (102.57(6)◦)
and N2–S1–C7 (102.80(6)◦) angles are similar to 2. It is noteworthy
that the Li–N bond distances in 4 differ less from each other than
The NMR spectra of 4 show a signal doubling which is due to
the two diastereomers that are present in solution since C7 and
˚
in 2. The bond distance for Li1–N2 (2.219(2) A) is larger compared
˚
to Li1–N1 (2.028(2) A) since N2 is coordinated to both the lithium
1
C7¢ are stereocentres. The 31P{ H} spectrum for example shows
atoms. However, the Li1–N1 and Li1–N2 bond distances are in
the typical range of Li–N bonds as described for compound 2.
The N2–Li1¢–P1 angle of 83.25(7)◦ is less acute in 4 compared to
2, due to the bulkier groups on the phosphorus atom.
two septets at -30.74 and -27.34 ppm. Consequently, the 1H and
1
13C{ H} spectra are even more complicated, as the alkyl signals lie
very close to each other and are therefore overlaid.
Another possibility to generate a stereocentre in the ligand is
to introduce a phosphorus side-arm with two different P-bound
substituents. [Li{Ph(Me)PCH2S(NtBu)2}]2 (5) crystallizes from n-
pentane in the monoclinic space group P21/c. Compound 5 is also
obtained as a dimer and the main core of the system is the known
(LiN)2 four-membered ring. Most of the overall structural features
are similar to those in 1–4. Due to the centre of inversion in the
middle of the (LiN)2 heteroatomic ring, 5 as well as 4 crystallizes
as a racemate. The solid state structure is shown in Fig. 8.
Fig. 6 Molecular structure of [Li{Et2PCH(Me)S(NSiMe3)2}]2 (4) in the
crystal. Anisotropic displacement parameters are depicted at the 50%
probability level, hydrogen atoms are omitted for clarity. Atoms labeled
with prime (¢) are symmetry equivalents genera◦ted by 1 - x, 2 - y,
˚
1 - z. Selected bond lengths [A] and angles [ ]: S1–N1 1.5906(10),
Fig. 8 Molecular structure of [Li{Ph(Me)PCH2S(NtBu)2}]2 (5) in the
crystal. Anisotropic displacement parameters are depicted at the 50% prob-
ability level, hydrogen atoms are omitted for clarity. Atoms labeled with
prime (¢) are symmetry equivale◦nts generated by 2 - x, 2 - y, 2 - z. Selected
S1–N2 1.6235(10), S1–C7 1.8300(12), P1–C7 1.8682(13), Li1–N1 2.028(2),
Li1–N2 2.219(2), Li1¢–P1 2.622(2); N1–S1–N2 104.22(5), N1–S1–C7
106.57(6), N2–S1–C7 102.80(6), Li1¢–N2–Li1 69.46(10), N1–Li1–N2
73.19(8), N2–Li1¢–P1 83.25(7).
˚
bond lengths [A] and angles [ ]: S1–N1 1.6107(11), S1–N2 1.6278(11),
S1–C8 1.8398(13), P1–C8 1.8463(14), Li1–N1 1.957(3), Li1–N2 2.506(3),
Li1¢–P1 2.644(2); N1–S1–N2 105.68(6), N1–S1–C8 104.97(6), N2–S1–C8
98.81(6), Li1¢–N2–Li1 69.23(7), N1–Li1–N2 76.86(11), N2–Li1¢–P1
76.66(7).
From the NMR spectra of 1–4 in solution it is obvious that the
complexes show a dynamic behaviour different to the solid state.
7
1
1
Both the Li{ H} and 31P{ H} NMR spectra reveal a coupling
between two lithium atoms and one phosphorus atom and vice
versa (septet in 31P and a triplet in the 7Li NMR). This can only be
rationalized with a flipping Li–P-bond and on average the contact
of a single phosphorus atom to two lithium atoms in solution
The S–N bond distances are almost equal and lie in the range o◦f
˚
1.6107(11)–1.6278(11) A. The two (SN2) units are tilted by 134.4
with respect to the (LiN)2 ring with the phosphane moiety residing
on opposite sides of the (SN2) planes, which is due to the different
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1662–1671 | 1665
©

steric situation in 5 compared to 4. The N1–S1–N2 (105.68(6)◦)
and N1–S1–C8 (104.97(6)◦) angles are almost in the same range as
for compounds 2 and 4. However, the N2–S1–C8 angle of 98.81(6)◦
is slightly more acute than in 2 and 4. The acute N2–◦Li1–P1 angle
of 76.66(7)◦ is known for such systems (73.10–87.35 ),28 however,
this angle is the most acute among compounds 1–4.
The NMR spectra show a signal doubling that is due to
two diastereomers which are present in solution, according to
compound 4. In solution the phenyl rings can be arranged like
in the solid state (‘trans’) or the phosphorus side-arm can rotate
about the S–C bond. As a result both phenyl rings are on the same
side of the molecule (‘cis’). Both diastereomers have very similar
chemical shifts and their NMR signals are therefore overlaid. Thus
it is impossible to assign specific shifts to one specific diastereomer,
although it can be assumed that the trans isomer prevails as it
reduces steric strain in the ligand. Integration of the PCH3 signals
shows a ratio of 1 to 0.75 for trans to cis. As in all compounds
Fig. 9 Molecular structure of [TMEDA·Li{Ph2PCH2(SNSiMe3)2}] (6) in
the crystal. Anisotropic displacement parameters are depicted at the 50%
probability level, hydrogen atoms are omitted for clarity. Selected bond
1
of this type, the P–Li–P system is also obvious from the 13C{ H}
◦
˚
lengths [A] and angles [ ]: C13–P1 1.8557(18), C13–S1 1.8338(18), N1–S1
1.6070(15), N2–S1 1.6032(16), N1–Si1 1.7150(16), N2–Si2 1.7114(16);
N1–S1–N2 103.72(8), S1–C13–P1 108.79(9), S1–N1–Si1 117.55(9),
N1–Li1–N2 75.80(12), N3–Li1–N4 83.7(3).
spectra. The 13C nuclei are coupled to both phosphorus atoms over
the Li-bridge. Thus the resulting multiplets can be explained. In
31P decoupled spectra the couplings disappear.
Discussions of the crystal structures of [Li{Me2P-
CH2S(NtBu)2}]2 (1), [Li{Me2PCH2S(NSiMe3)2}]2 (2), [Li{Ph2-
PCH2S(NtBu)2}]2 (3), [Li{Et2PCH(Me)S(NSiMe3)2}]2 (4) and
[Li{Ph(Me)PCH2S(NtBu)2}]2 (5) reveal that the N2SCP ligands
are indeed tridentate, containing hard nitrogen and soft
phosphorus donor sites. Although the bite of the ligand system
is not optimized for lithium cations, the complexes formed are
quite stable. Even the softer phosphorus site coordinates the hard
longer than the bonds from the diimido anion. As the phosphorus
side-arm is not donating to the Li cation it is free for binding to
any other soft metal thus providing the opportunity to generate
heterobimetallic complexes.
The complexation potential of these Janus head scorpionates
is also evident from the facile formation of a stable monomeric
complex with magnesium (7) (Scheme 2).
-
lithium cation, yet in solution. It seems that the R2PCH2S(NR¢)2
anions are indeed the ligands which are complexing in the desired
way. Furthermore, the formation of dimers seems to be favored as
it helps to balance the electron deficiency of the metal cations.
The reaction of [Ph2PCH2Li·TMEDA] with S(NtBu)2 yielded
diphenylphosphinomethane-sulfurdiimide as lithium-dimer (3)
but when the tertiary butyl groups of the imido moiety were
replaced by trimethylsilyl groups the compound obtained was
[TMEDA·Li{Ph2PCH2S(NSiMe3)2}] (6) (Fig. 9). These results
were unexpected as per our strategy and are probably due
to the different electronic situation in the S(NSiMe3)2 moiety.
Compound 6 crystallizes from n-pentane as a monomer in the
monoclinic space group C2/c with half a pentane molecule in the
asymmetric unit.
Scheme 2
The reaction of 1 with MgCl2 in a 1 : 1 molar ratio afforded the
spirocyclic species [Mg{Me2PCH2S(NtBu)2}2] (7). The formation
of this magnesium complex demonstrates that the new Janus
head ligands are valuable multidentate chelating ligands due to
the intramolecular phosphane donor site held in close spacial
proximity to the functional imido groups. Complex 7 crystallizes
from n-pentane as colourless plates in the orthorhombic space
group Fdd2 (Fig. 10) with half a molecule in the asymmetric unit.
As the compound undergoes a phase transition at about 220 K the
X-ray diffraction data set had to be collected at -23 ◦C (see ESI†).
The monomeric structure shows a distorted octahedral ge-
ometry at the central magnesium dication. The molecule has
crystallographically imposed two-fold symmetry with the mag-
nesium atom situated on the two-fold axis. The magnesium is
bound by two nitrogen atoms and one phosphorus atom of
each phosphanyl side-arm as a five-membered chelating ring with
bite angles of 74.24(8)◦ (N1–Mg1–P1) to 70.82(8)◦ (N2–Mg1–
P1). This means that the N2SCP ligand behaves in a tridentate
manner thus demonstrating tripodal donation by means of two
terminal nitrogen atoms and side-arm donation by the phosphorus
atom. This side-arm donation brings these ligands into focus as
multidentate systems for metal complexation.
The coordination mode in this compound is new compared
to complexes 1–5. The lithium cation is four-fold N-coordinated.
The phosphorus atom is not taking part in the coordination as the
33
˚
Li ◊ ◊ ◊ P distance of 3.23 A is to long to be regarded a bond.
Nevertheless, an orientation towards the lithium ion can be
observed which is due to electrostatic attractions. Furthermore,
the S1–C13–P1 angle of 108.79(9)◦ indicates the inclination of the
phosphorus atom towards the lithium cation. Both phenyl rings
are twisted by 90◦ with respect to each other, facilitating close
packing of the molecules in the crystal. The central (SN2Li) ring is
almost perfectly planar with the phosphorus atom residing above
this plane. It is aligned with C13, S1, Li1 and both nitrogen atoms
of the TMEDA molecule. The N1–S1–N2 angle of 103.72(8)◦ is
slightly more acute than in the lithium complexes 1–5. The Li–N
˚
˚
distances range from 2.039(4) A (Li1–N2) to 2.167(10) A (Li1–
N3) with the bonds from the TMEDA molecule being marginally
Coordination of the magnesium atom shows Mg–N distances
in the range of 2.102(2) to 2.138(2) A. These values are
˚
1666 | Dalton Trans., 2011, 40, 1662–1671
This journal is The Royal Society of Chemistry 2011
©

Fig. 10 Molecular structure of [Mg{Me2PCH2S(NtBu)2}2] (7) in the
crystal. Anisotropic displacement parameters are depicted at the 30%
probability level, hydrogen atoms are omitted for clarity. Selected bond
Fig. 11 Molecular structure of [Mg{Me2PCH2S(NSiMe3)2}2] (8) in the
crystal. Anisotropic displacement parameters are depicted at the 50% prob-
ability level, hydrogen atoms are omitted for clarity. Selected bond lengths
◦
˚
lengths [A] and angles [ ]: S1–N1 1.617(2), S1–N2 1.622(2), S1–C9
1.838(4), Mg1–N1 2.102(2), Mg1–N2 2.138(2), Mg1–P1 2.9855(13);
S1–N1–Mg1 95.69(12), S1–N2–Mg1 94.14(11), N1–Mg1–N2 70.07(9)
N1–S1–N2 97.43(12).
◦
˚
[A] and angles [ ]: S1–N1 1.6123(8), S1–N2 1.6111(8), Mg1–N1 2.1481(8),
Mg1–N2 2.1276(8), Mg1–P1 2.8570(4); N1–S1–N2 100.44(4), N1–S1–C7
101.86(4), S1–C7–P1 107.75(5), S1–N1–Mg1 92.37(3), S1–N2–Mg1
93.15(4), N1–Mg1–N2 70.81(3), N1–Mg1–P1 72.54(2).
similar to those reported for compounds containing a sulfur-
30
˚
bonded imido nitrogen donor (2.035–2.295 A). However, there
tion of the ligand occurred, resulting in the formation of
[Ph2PCH2(SNSiMe3)(HNSiMe3)] (9). At the moment it is sup-
posed that this happened according to the C–H bond activation
reaction described in Scheme 3. Thus, a toluene molecule is
deprotonated, resulting in the formation of 9 and benzyl lithium.
˚
is a significant difference between the Mg1–N1 (2.102(2) A)
˚
and Mg1–N2 (2.138(2) A) bonds. The Mg–N bond distances
are marginally longer than in [Mg{(NSiMe3)2SN(SiMe3)2}2]
25
˚
(2.0592(6) A). The Mg–P bond length is not consistent
˚
with the predicted covalent value (2.65 A). The distance
˚
of 2.9855(13) A is enlongated in comparison to Mg–P dis-
tances in other mononuclear and dinuclear magnesium phos-
phanides e.g. [BuMg{P(CH(SiMe3)2)(C6H4-2-OMe)}]2 (2.5760(8)
˚
and 2.5978(8) A), Mg[P{CH(SiMe3)2}{C6H4-2-CH2NMe2}]2
Scheme 3
˚
˚
(2.556(1) A) and [Mg{[O,O¢-(Me2PCH2)2C6H3]2}2] 2.761(1) and
34
2.770(1) A). This elongation of the Mg–P bond distance is
Compound 9 crystallizes from toluene layered with n-pentane
in the monoclinic space group P21/n as a monomer. The solid
state structure is shown in Fig. 12.
attributed to the side-arm donation of a phosphanyl rather than
coordination of a phosphanide. It suggests a possible application
of this ligand in catalytic processes. With a different central metal,
it would be feasible to reversibly cleave the metal–phosphorus
bond to generate a pendent donor site for substrates or other
softer metal cations. The N–S–N bond angle (97.43(12)◦) is more
acute than in 1 and those in alkali metal derivatives (104.2–110.7◦),
but spans almost the same range as in comparable compounds
with Mg2+ or other dicationic metals (97.6–98.9◦).25 This can be
attributed to the higher charge on the magnesium dication, leading
to a stronger repulsion between the positively charged sulfur atom
and the metal ion.
The magnesium complex [Mg{Me2PCH2S(NSiMe3)2}2] (8) was
equally isolated by a transmetallation reaction of 2 with MgCl2 in
an equimolar ratio. Unlike compound 7, which crystallizes in the
orthorhombic space group Fdd2 and undergoes a phase transition
at about 220 K, this phenomenon could not be observed in 8. The
complex crystallizes from n-pentane as colourless blocks in the
monoclinic space group P21/n and is monomeric. The phosphanyl
diimido moiety is attached to the magnesium atom in the same
tripodal fashion involving donation from two terminal nitrogen
atoms and the side-arm donation from the phosphorus atom
leading to an approximately octahedral coordination polyhedron
(Fig. 11). The structural motif is the same as in the magnesium
compound 7.
Fig. 12 Molecular structure of [Ph2PCH2(SNSiMe3)(HNSiMe3)] (9) in
the crystal. Anisotropic displacement parameters are depicted at the 50%
probability level, hydrogen atoms except H1, which was freel◦y refined,
˚
are omitted for clarity. Selected bond lengths [A] and angles [ ]: C1–P1
1.8404(13), C13–P1 1.8526(11), C13–S1 1.8092(12), N1–S1 1.6520(9),
N2–S1 1.5698(10), N1–Si1 1.7421(10), N2–Si2 1.7184(10); N1–S1–N2
109.26(5), N2–S1–C13 102.99(5), N1–S1–C13 98.36(5), S1–N1–Si1
123.18(6), S1–N2–Si2 122.50(6), C7–P1–C13 102.17(7).
˚
When the reaction of [Ph2PCH2Li·TMEDA] and S(NSiMe3)2
The bond distances for P1–C1 (1.8404(13) A) and P1–C13
˚
was carried out in toluene instead of pentane, protona-
(1.8526(11) A) are similar to those of 1–5. The S1–C13 bond
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1662–1671 | 1667
©

distance is also slightly shorter than in complexes 1–5. The N1–
S1–N2 (109.26(5)◦) as well as the S1–C13–P1 angle (113.54(6)◦)
are widened compared to the lithiated species. The S–N bond
these new ligands also opens up the route to create multimetallic
complexes, which is becoming a rather important field nowadays
and further developments are anticipated. In essence we succeeded
in synthesizing new types of promising Janus head ligands that
show interesting hemilabile complexation properties both in the
solid state and in solution. Further investigations are under way
and open questions are to be addressed to fully understand the
stereochemistry of compounds 1–5 in solution and the protonation
of the anions by toluene. This will be achieved e.g. by variable
temperature NMR labeling studies.
˚
distances of 1.6520(9) (S1–N1) and 1.5698(10) A (S1–N2) are
very close to the predicted values for a single and double
bond.30 They also match the bond lengths of methyl(diimido)
sulfinic acid H(NtBu)2SMe and methylene-bis(triimido)sulfonic
acid H2C{S(NtBu)2(NHtBu)}2, which have S–N bond distances of
1.52 and 1.68 A.31,35 Looking at the packing of the molecules in the
˚
crystal, it is apparent that H1 is interacting with the p-system of
the phenyl ring of the next adjacent molecule (C7–C12). Both six-
membered rings are inclined by 99.1◦ with respect to each other.
This is due to the interaction of H14 with the p-system of the
second ring (C1–C6).
Experimental
General
Interestingly, after stirring the reaction mixture for 20 h, there
was evidence of a compound which gave a very broad signal at
All manipulations were performed either in an inert gas atmo-
sphere of purified dry nitrogen or argon with standard Schlenk
techniques or in an argon glove box. The glassware was dried at
130 ◦C, assembled hot and cooled under vacuum. All solvents were
dried over appropriate alkali metals, distilled and degassed prior
to use. The reactants were synthesized according to the literature
reports: S(NSiMe3)2,36 (S(NtBu)2)37 and [Ph2PCH2Li·TMEDA].38
1
-39 ppm in the 31P{ H} NMR spectrum. From this intermediate
compound the reaction to the final product (d31P = -28.8 ppm)
then proceeded very slowly at -25 ◦C. From the NMR spectrum
it was concluded that the intermediate compound is some kind of
lithium complex. When the same reaction (according to Scheme 3)
was carried out in pentane instead of toluene it was possible to
n
tBuLi and BuLi were supplied by Chemetall GmbH. All NMR
1
crystallize the lithium complex 6 (Fig. 9). The 31P{ H} NMR
spectra were either recorded on a Bruker Avance DPX 300 MHz
or Bruker Avance DRX 500 MHz spectrometer using TMS (1H,
13C and 29Si), H3PO4 (85%) (31P) and LiCl (7Li) as the external
reference and the protons of the deuterated solvents as the internal
standard. Elemental analyses (C, H, N and S) were carried out at
the Mikroanalytisches Labor, Institut fu¨r Anorganische Chemie,
Universita¨t Go¨ttingen.
spectrum of the crystals shows a very broad signal at -39 ppm. This
undoubtedly proves 6 to be the intermediate in the accruement of
9. With the free ligand at hand it should now be much easier
to obtain a great variety of mono- and bimetallic complexes
directly rather than following the metathesis or salt elimination
route. The reaction of 9 with metal amides or metal hydrides will
hopefully give new metal complexes. Compound 9 will prove to
be an excellent starting material for such reactions as it can be
prepared in nearly quantitative yield and great purity.
General preparation of lithiated phosphanes
tBuLi (1.38 M) was reduced to half of its volume and the
corresponding phosphane (PMe3, PEt3, Me2PPh) was added very
slowly at room temperature. After stirring for 14 h and refluxing
for 2 h in the case of PEt3, the white to light yellow precipitates
were filtered, washed with n-pentane (3 ¥ 5 mL) and dried in vacuo.
Conclusion
With this work we have widened the area of multifunctional
ligands and the scope of the Janus head ligands as well. The
multifunctionality could easily be achieved just by linking the
reactivity of sulfurdiimides and phosphane species. Modification
in the ligands is feasible by using different substituents on the
phosphane, diimido and C-bridgehead moieties. Compounds 1–5
are dimeric and the main core of the system consists of a (LiN)2
ring in which both the lithium atoms are four-coordinated by the
[Li{Me2PCH2S(NtBu)2}]2 (1). 1.67 g (9.60 mmol, 2.0 eq.)
S(NtBu)2 were slowly added to a slurry of 0.79 g (9.60 mmol,
2.0 eq.) Me2PCH2Li in 60 mL n-pentane at -78 ◦C. The mixture
was yellow at first and became light orange after stirring overnight
at room temperature. The clear solution was reduced to half
of its volume in vacuo. Storage at -25 ◦C for 5 days yielded
colorless crystals. Yield: 1.65 g (3.20 mmol) 67%; mp 143 ◦C
(from pentane, decomposition); Found: C, 51.6; H, 10.9; N, 10.8;
S, 12.3. C22H52N4P2S2Li2 requires C, 51.6; H, 10.2; N, 10.9; S
-
donor atoms of each ligand. It seems that the R2PCH(X)S(NR¢)2
anions are indeed tridentate ligands containing hard nitrogen
and soft phosphorus donor sites. The synthesis of complexes 7
and 8 provided evidence of the coordination versatility of these
newly synthesized ligands. This also indicates that the ligands with
podand topology are endowed with intrinsically distinct coordi-
nation geometries leading to fascinating bonding and reactivity
patterns. Transmetallation of 1–5 as well as protonation (9) and
metal coordination (6) opens a wide synthetic route to introduce
a variety of different metals and organometallic residues to the
tripodal Janus head ligand. The intrinsic topology of intramolec-
ularly coordinated tridentate ligands may introduce interesting
reactivity and electronic properties to the metal complexes. These
results are even more significant if we take into account that these
were obtained by a simple reaction between the sulfurdiimide and
corresponding lithiated phosphane. In addition, the formation of
1
12.5%; d H (500.13 MHz; C6D6): 0.896 (6 H, d, 2JP–H = 0.55 Hz,
P(CH3)2), 0.898 (6 H, d, 2JP–H = 0.55 Hz, P(CH3)2), 1.44 (36 H, s,
2
C(CH3)3), 2.676 (2 H, d, JP–H = 0.92 Hz, PCH2S), 2.678 (2 H,
d, 2JP–H = 0.92 Hz, PCH2S); d 13C (125.76 MHz; C6D6): 13.70 (d,
1JP–C = 1.65 Hz, PCH3), 13.73 (d, 1JP–C = 1.65 Hz, PCH3), 33.76 (s,
C(CH3)3), 54.02 (s, C(CH3)3), 64.83 (d, 1JP–C = 2.99 Hz, PCH2S),
1
64.92 (d, JP–C = 2.99 Hz, PCH2S); d 31P (202.46 MHz; C6D6):
1
7
-67.0 (sept, JP–Li = 18.5 Hz, LiPLi); d
(194.37 MHz; C6D6):
Li
2.22 ppm (t, 1JP–Li = 18.5 Hz, PLiP).
[Li{Me2PCH2S(NSiMe3)2}]2 (2). To
a
suspension of
Me2PCH2Li (0.60 g, 7.32 mmol, 2.0 eq) in n-pentane (40 mL)
S(NSiMe3)2 (1.51 g, 7.32 mmol, 2.0 eq) was added very slowly
1668 | Dalton Trans., 2011, 40, 1662–1671
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The Royal Society of Chemistry 2011
©

at -78 ◦C. The suspension was allowed to warm to room
temperature after 20 min and stirred for 24 h. The green-yellow
solution was filtered, reduced to half of its volume and stored
at -25 ◦C. Colourless crystals, suitable for structural analysis
were obta◦ined after two days. Yield: 1.64 g, 2.85 mmol, 78%;
mp 147.3 C (from pentane, decomp.); Found C, 37.21; H, 9.00;
N, 9.92; S, 11.14. C18H52N4Si4P2S2Li2 requires C, 37.21; H, 9.08;
N, 9.71; S, 11.12%; d 1H (500.13 MHz, C6D6): 0.32 (36 H, s,
S(NtBu)2 (1.98 g, 11.4 mmol, 2.0 eq.) was added very slowly at
-78 ◦C. After 20 min the suspension was allowed to warm to room
temperature and stirred for 24 h. The yellow-orange solution
was reduced to 2/3 of its volume and stored at -25 ◦C. After
three days, colourless crystals suitable for structural analysis,
were obtained. Yield: 2.65 g, 4.16 mmol, 73%; mp 125.5 ◦C (from
pentane, decomp.); Found: C, 59.33; H, 8.75; N, 8.79; S, 10.26.
C32H56N4P2S2Li2 requires C, 60.36; H, 8.86; N, 8.80; S, 10.07%;
Si(CH3)3), 0.83 (12 H, s, P(CH3)2), 2.65 (4 H, s, PCH2S); d 13C
d
1H (500.13 MHz, C6D6): 1.20 (3 H, s, PCH3), 1.32 (3 H, s,
1
(125.77 MHz, C6D6): 2.92 (Si(CH3)3), 12.92 (d, P(CH3)2, JP–C
=
PCH3), 1.37 (9 H, s, C(CH3)3), 1.38 (9 H, s, C(CH3)3), 1.43 (9 H, s,
C(CH3)3), 1.45 (9 H, s, C(CH3)3), 2.96–3.12 (4 H, m, PCH2S),
7.02–7.05 (2 H, m, p-H), 7.08–7.12 (4 H, m, m-H), 7.47–7.51 (4
H, m, o-H); d 13C (125.76 MHz, C6D6): 13.43 (dd, 1JP–C = 4.73 Hz,
31
3.31 Hz), 66.51 (d, PCH2S, 1JP–C = 10.94 Hz); d
(202.46 MHz,
P
1
7
C6D6): -67.87 (hept, JP–Li = 20.84 Hz); d Li (194.37 Hz, C6D6):
2.19 (t, JP–Li = 20.84 Hz); d 29Si (99.36 MHz, C6D6): -2.71 (s,
1
1JN–Si = 27.55 Hz).
3JP–C = 3.01 Hz, PLiPCH3), 13.60 (dd, JP–C = 5.02 Hz, JP–C
=
1
3
2.44 Hz, PLiPCH3), 33.51–33.67 (m, C(CH3)3), 53.94–54.40 (m,
[Li{Ph2PCH2S(NtBu)2}]2 (3). 1.74 g (10.0 mmol, 2.0 eq.)
S(NtBu)2 were slowly added to a slurry of 2.06 g (10.0 mmol,
2.0 eq.) [Li(H2CPPh2)· TMEDA] in 60 mL n-pentane at -78 ◦C. Af-
ter stirring overnight at room temperature, the white precipitate
was filtered, washed with pentane and dissolved in toluene. The
C(CH3)3), 64.10–64.27 (m, PCH2S), 128.56–128.70 (m, o-C),
3
5
131.89–132.27 (m, p-C), 139.65 (dd, JP–C = 3.49 Hz, JP–C
=
1.99 Hz, m-C), 139.97 (dd, 1JP–C = 3.16 Hz, 3JP–C = 2.24 Hz, i-C);
d
31P = (202.46 MHz, C6D6): -(51.98–51.51) (m, LiPLi); d 7Li
(194.37 Hz, C6D6): 2.41 (t, 1JP–Li = 13.43 Hz, PLiP).
◦
light yellow solution was kept at -25 C for three days, yielding
colourless crystals. Yield: 2.05 g (2.88 mmol) 78%; mp 123 ◦C
(from toluene, decomp.); Found: C, 64.6; H, 7.7; N, 6.5; S, 8.1.
[TMEDA·Li{Ph2PCH2S(NSiMe3)2}] (6). To
a slurry of
Ph2PCH2Li·TMEDA (3.01 g, 9.30 mmol, 1.0 eq.) in n-pentane
(50 mL) S(NSiMe3)2 (1.92 g, 9.30 mmol, 1.0 eq.) was slowly
added at -78 ◦C. After stirring at room temperature overnight,
the solution was filtered over celite, reduced in volume and stored
at -25 ◦C, yielding colourless crystals after 2 days.
1
C42H60N4P2S2Li2 requires C, 66.3; H, 8.0; N, 7.4; S, 8.4%; d H
(500.13 MHz; C6D6): 1.37 (36 H, s, C(CH3)3), 3.64 (4 H, s, PCH2S),
6.98–7.01 (4 H, m, p-H), 7.04–7.07 (8 H, m, m-H), 7.56–7.59 (8
H, m, o-H); d 13C (125.76 MHz; C6D6): 33.60 (s, C(CH3)3), 54.31
1
(s, C(CH3)3), 62.26 (d, JP–C = 17.49 Hz, PCH2S), 128.63–128.76
Yield: 4.44 g, 8.40 mmol, 90%; Found: C, 56.08; H, 8.48; N,
2
(m, i-C), 128.92 (s, p-C), 133.45–133.63 (m, JP–C = 18.30 Hz, o-
10.37; S, 6.28. C25H46N4Si2PSLi requires C, 56.78; H, 8.77; N,
1
C), 137.79–137.82 (m, 3JP–C = 3.76 Hz, m-C); d 31P (202.46 MHz;
10.59; S, 6.06%; d H (300.13 MHz, C6D6): 0.28 (18 H, s, Si(CH3)3),
7
C6D6): -32.57 (br s, LiPLi); d Li (194.37 MHz; C6D6): 2.63 ppm
1.77 (4 H, s br, N(CH2)2N), 2.07 (12 H, s, (CH3)2N), 3.47 (2 H, s
br, SCH2P), 6.99–7.12 (6 H, m, o-H, p-H), 7.59–7.70 (4 H, m, m-
H); d 13C (125.76 MHz, C6D6): 3.19 (Si(CH3)3), 45.82 ((CH3)2N),
(t, 1JP–Li = 12.8 Hz, PLiP).
[Li{Et2PCH(Me)S(NSiMe3)2}]2 (4). To
a suspension of
1
56.66 (N(CH2)2), 70.84 (d, JP–C = 23.99 Hz, PCH2S), 128.46 (d,
Et2PCH(Me)Li (0.13 g, 0.81 mmol, 2.0 eq.) in n-pentane (10 mL)
S(NSiMe3)2 (0.17 g, 0.81 mmol, 2.0 eq.) was added very slowly
at -78 ◦C. After 20 min the suspension was allowed to warm
to room temperature and stirred for 24 h. The yellow solution
was reduced to 1/2 of its volume and stored at -25 ◦C. After
one week, colourless crystals, suitable for structural analysis, were
obtained. Yield: 0.21 g, 0.32 mmol, 80%; mp 138.9 ◦C (from
pentane, decomp.); Found: C, 42.96; H, 9.58; N, 8.70; S, 9.83.
C24H64N4Si4P2S2Li2 requires C, 43.60; H, 9.76; N, 8.47; S, 9.70%; d
1H (500.13 MHz, C6D6): 0.36–0.37 (72 H, m, 2 ¥ Si(CH3)3), 0.92–
1.02 (24 H, m, 2 ¥ PCH2CH3), 1.17–1.22 (24 H, m, 2 ¥ PCH2CH3,
1/3 ¥ PCH(CH3)S), 1.43–1.54 (4 H, m, 2/3 ¥ PCH(CH3)S), 2.59–
2.68 (4 H, m, 2 ¥ PCH(CH3)S); d 13C (125.77 MHz, C6D6): 3.09–
3.42 (m, Si(CH3)3, 10.46–11.21 (m, PCH2CH3, PCH2CH3), 14.10
3JP–C = 6.02 Hz, m-C), 132.48 (d, 4JP–C = 18.74 Hz, p-C), 133.90 (d,
2JP–C = 19.50 Hz, o-C), 142.04 (d, 1JP–C = 14.98 Hz, ipso-C); d 31P
7
(121.49 MHz, C6D6): -38.78 (s br, PCH2S); d Li (194.37 MHz,
C6D6): 1.00(s); d 29Si (99.36 MHz, C6D6): -8.29(s).
[Mg{Me2PCH2S(NtBu)2}2] (7). 0.50 g (0.98 mmol, 1.0 eq.)
1 and 0.90 g (0.98 mmol, 1.0 eq.) MgCl2 were combined in an
argon drybox and dissolved in 40 mL n-pentane/thf at room
temperature. After stirring overnight, the solvent was removed
in vacuo and the resulting yellow powder suspended in 20 mL n-
pentane. The suspension was filtered over celite and the volume of
the filtrate was reduced. Colourless crystals were obtained after
storing the yellow solution for 3 days at 4 ◦C. Yield: 0.33 g
(0.63 mmol) 64%; mp 165.5 ◦C (from pentane, decomp.); Found:
C, 49.9; H, 10.0; N, 11.0; S, 12.2. C22H52N4P2S2Mg requires C,
2
4
(dd, JP–C = 111.5 Hz, JP–C = 8.81 Hz, PCH(CH3)S), 17.24 (dd,
2JP–C = 72.57 Hz, 4JP–C = 6.60 Hz, PCH(CH3)S), 63.34 (d, 1JP–C
13.48 Hz, PCH(CH3)S), 64.87 (d, 1JP–C = 14.34 Hz, PCH(CH3)S);
31P (202.46 MHz, C6D6): -30.74 (hept, 1JP–Li = 18.81 Hz, LiPLi),
1
=
50.5; H, 10.0; N, 10.7; S, 12.3; d H (500.13 MHz; C6D6): 0.98 (12
2
H, t, JP–H = 1.15 Hz, P(CH3)2), 1.39 (36 H, s, C(CH3)3), 2.21 (4
2
d
H, t, JP–H = 1.65 Hz, PCH2S); d 13C (125.76 MHz; C6D6): 14.67
1
7
-27.34 (hept, JP–Li = 19.16 Hz, LiPLi); d
(194.37 Hz, C6D6):
(d, 1JP–C = 4.06 Hz, P(CH3)2), 14.71 (d, 1JP–C = 4.06 Hz, P(CH3)2),
Li
1
2.27 (t, 1JP–Li = 18.81 Hz, PLiP), 2.37 (t, 1JP–Li = 19.16 Hz, PLiP);
33.67 (s, C(CH3)3), 53.08 (s, C(CH3)3), 65.92 (d, JP–C = 1.92 Hz,
1
d
29Si (99.36 MHz, C6D6): -4.19 (s, 1JN–Si = 26.61 Hz, NSi(CH3)3),
PCH2S), 65.94 (d, JP–C = 1.92 Hz, PCH2S); d 31P (202.46 MHz;
-3.65 (s, 1JN–Si = 27.16 Hz, NSi(CH3)3), -1.05 (s, 1JN–Si = 27.61 Hz,
NSi(CH3)3), -0.55 (s, 1JN–Si = 27.61 Hz, NSi(CH3)3).
C6D6): -82.69 ppm (s br, P(CH3)2).
[Mg{Me2PCH2S(NSiMe3)2}2] (8). 2 (0.54 g, 0.94 mmol,
1.0 eq.) and MgCl2 (0.13 g, 1.4 mmol, 1.5 eq.) were combined
in an argon drybox and dissolved in thf (10 mL). After stirring for
[Li{Me(Ph)PCH2S(NtBu)2}]2 (5). To
a
suspension of
Me(Ph)PCH2Li (1.50 g, 11.4 mmol, 2.0 eq.) in n-pentane (30 mL)
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1662–1671 | 1669
©

24 h at room temperature, the solvent was evaporated in vacuo
and the resulting powder was suspended in pentane (10 mL).
The suspension was filtered and reduced in volume. After storing
the colourless solution at 4 ◦C for four days, crystals suitable for
structural analysis were obtained. Yield: 0.53 g, 0.90 mmol, 96%;
mp 206.5 ◦C (from pentane, decomp.); Found C, 36.92; H, 9.27; N,
9.75; S, 11.11. C18H52N4Si4P2S2Mg requires C, 36.81; H, 8.92; N,
7 (a) J. Campora, I. Matas, B. Classen, P. Palma and E. Alvarez, Inorg.
Chim. Acta, 2006, 359, 3191; (b) A. M. Bond, R. Colten, F. Marken
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922.
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10 H. W. Roesky, Th. Gries, K. S. Dhathathreyan and H. Lueken, Z. Anorg.
1
9.54; S, 10.92%; d H (500.13 MHz, C6D6): 0.29 (36 H, s, Si(CH3)3),
Allg. Chem., 1987, 547, 199.
2
11 W.-H. Leung, Q.-F. Zhang and X.-Y. Yi, Coord. Chem. Rev., 2007, 251,
2266.
0.91 (12 H, s, P(CH3)2), 2.398 (2 H, d, JP–H = 1.93 Hz, PCH2S),
2.402 (2 H, d, 2JP–H = 1.93 Hz, PCH2S); d 13C (125.77 MHz, C6D6):
12 M. P. Batten, A. J. Canty, K. J. Cavell, T. Ru¨ther, B. W. Skelton and
A. H. White, Acta Crystallgr., Sect. C, 2004, 60, m311.
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Commun., 1995, 235; (b) T. N. Sorrell, W. E. Allen and P. S. White,
Inorg. Chem., 1995, 34, 952; (c) C. Kimblin, B. N. Bridgewater, D. G.
Churchill and G. Perkin, J. Chem. Soc. Dalton Trans., 2000, 2191; (d) W.
Klaeui, C. Piefer, G. Rheinwald and H. Lang, Eur. J. Inorg. Chem., 2000,
1549; (e) C. Kimblin, V. J. Murphy, T. Hascall, B. M. Bridgewater, J. B.
Bonanno and G. Parkin, Inorg. Chem., 2000, 39, 967; (f) P. C. Kunj,
G. J. Re i s s, W. Fr a n k a n d W. K l a¨ui, Chem. Eur. J., 2003, 3945; (g) A.
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1
2.75 (s, Si(CH3)3), 13.77 (d, JP–C = 2.30 Hz, P(CH3)2), 13.79 (d,
1JP–C = 2.30 Hz, P(CH3)2), 67.57 (s, PCH2S); d 29Si (99.36 MHz,
C6D6): -4.05 (s, 1JN–Si = 27.91 Hz, Si(CH3)3); d 31P (202.46 MHz,
C6D6): -84.63 (s, PCH2S).
[Ph2PCH2(SNSiMe3)(HNSiMe3)] (9). To
a
slurry of
Ph2PCH2Li·TMEDA (0.88 g, 2.72 mmol, 1.0 eq.) in pentane
(30 mL) S(NSiMe3)2 (0.56 g, 2.72 mmol, 1.0 eq.) was slowly
added at -78 ◦C. After stirring at room temperature overnight,
the solution was filtered over celite and the solvent evaporated
in vacuo. The precipitate was dissolved in toluene, reduced in
volume, layered with pentane and stored at -25 ◦C. After 2 months,
crystals suitable for structural analysis were obtained. Yield:
14 F. Eymery, P. Burattin, F. Mathey and P. Savignac, Eur. J. Org. Chem.,
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18 F. Armbruster, I. Fernandez and F. Breher, Dalton Trans., 2009,
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◦
1.07 g, 2.63 mmol, 97%; mp 138.3 C (from pentane, decomp.);
Found: C, 55.94; H, 7.66; N, 7.00; S, 8.00. C19H31Si2N2PS requires
1
C, 56.11; H, 7.68; N, 6.89; S, 7.88%; d H (500.13 MHz, C6D6):
2
0.22 (18 H, s, Si(CH3)3), 4.09 (2 H, d, JP–H = 0.80 Hz, PCH2S),
7.00–7.04 (2 H, m, p-H), 7.06–7.10 (4 H, m, m-H), 7.49–7.52 (2
H, m, o-H); d 13C (125.76 MHz, C6D6): 1.89 (Si(CH3)3), 63.59
1
3
(d, JP–C = 24.61 Hz, PCH2S), 128.76 (d, JP–C = 6.65 Hz, m-C),
129.00 (p-C), 133.34 (d, 2JP–C = 19.71 Hz, o-C), 138.43 (d, 1JP–C
=
14.76 Hz, ipso-C); d 31P (202.46 MHz, C6D6): -28.81 (s, PCH2S); d
Si (99.36 MHz, C6D6): 2.59 (s, 1JN–Si = 28.35 Hz); EI-MS m/z: 406
29
(M+, 17%), 318 (14, M - HNSiMe3), 286 (19, Ph2PCH2SNSiMe3),
272 (19, Ph2PCH2SiMe3), 207 (15, M - Ph2PCH2), 199 (100,
Ph2PCH2), 121 (44, SN(HSiMe3) + H), 73 (20, SiMe3).
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Acknowledgements
We kindly acknowledge funding from the DFG Priority Program
1178 and the Center of Materials Crystallography. We are grateful
for the continuous support from CHEMETALL GmbH, Frank-
furt and Langelsheim. S.K.P. and D.S. thank the DFG and INSA
for supplying the Indo-German exchange grant.
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©