A comparison of the coordination chemistry of Ph2SNH and Ph2SNCH2CH2CN.

Article abstract of DOI:10.1016/S0022-328X(00)00831-7

Reaction of excess Ph₂SNH (1) with [PPh₄]₂[Pd₂Br₆] results in the formation of homoleptic [Pd(Ph₂SNH)₄]Br₂. In contrast the analogous reaction of the N-substituted sulfimide Ph₂SN-CH₂CH₂CN (2) with [PPh₄]₂[Pd₂Br₆] only results in the formation of trans-[PdBr₂(Ph₂SNCH₂CH₂CN)₂] (3) even if the ligand is present in large excess. Lowering the reaction ratio to 2:1 (ligand: dimer) allows isolation of [PPh₄][PdBr₃(Ph₂SNCH₂CH₂CN)] (4). Compounds 3 and 4 constitute the first examples of fully characterised complexes of N-substituted sulfimides and X-ray crystallography confirm the ligands to be bound to the metal through nitrogen; although the nitrile end groups of the substituents have the potential to bind to metals, no evidence for this is seen in these particular systems.

Full text of DOI:10.1016/S0022-328X(00)00831-7

Journal of Organometallic Chemistry 623 (2001) 120–123
www.elsevier.nl/locate/jorganchem
A comparison of the coordination chemistry of Ph2SNH and
Ph2SNCH2CH2CN; the preparation and X-ray crystal structures of
[PPh4][PdBr3(Ph2SNCH2CH2CN)] and
trans-[PdBr2(Ph2SNCH2CH2CN)2], the first fully characterised
complexes of a N-substituted sulfimide
Paul F. Kelly a,*, Kevin G. Parker a, Miguel A. Rodiel a, Alexandra M.Z. Slawin b
a Department of Chemistry, Loughborough Uni6ersity, Loughborough, Leicestershire, LE11 3TU, UK
b Department of Chemistry, Uni6ersity of St Andrews, St Andrews, KY16 9ST, UK
Received 17 July 2000; accepted 17 October 2000
Abstract
Reaction of excess Ph2SNH (1) with [PPh4]2[Pd2Br6] results in the formation of homoleptic [Pd(Ph2SNH)4]Br2. In contrast the
analogous reaction of the N-substituted sulfimide Ph2SNꢀCH2CH2CN (2) with [PPh4]2[Pd2Br6] only results in the formation of
trans-[PdBr2(Ph2SNCH2CH2CN)2] (3) even if the ligand is present in large excess. Lowering the reaction ratio to 2:1 (ligand:
dimer) allows isolation of [PPh4][PdBr3(Ph2SNCH2CH2CN)] (4). Compounds 3 and 4 constitute the first examples of fully
characterised complexes of N-substituted sulfimides and X-ray crystallography confirm the ligands to be bound to the metal
through nitrogen; although the nitrile end groups of the substituents have the potential to bind to metals, no evidence for this is
seen in these particular systems. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Complexes; Palladium; Sulfimides; Nitriles
1. Introduction
ides suggesting that the versatile coordination chemistry
of the latter [4] should be amenable to the former. The
potential of the sulfimides goes further than this, how-
ever, thanks to the fact that unlike the sulfoxides they
can be derivatised on the nitrogen atom. The contrast
of the R2SNR% unit with that of R2SO allows the
introduction of R% groups with a range of properties.
They could, for example, provide steric control over the
resulting complex by placing bulky units close to the
nitrogen. They could also be chosen to provide an extra
coordination site for the ligand by the introduction of
an appropriate end group.
The starting point for the development of the latter
idea is clearly an assessment of the general coordination
chemistry of substituted derivatives of 1. In this study
we have, therefore, chosen to contrast the affinity of 1
towards simple palladium centres with that of
Ph2SNCH2CH2CN (2), a derivative chosen for its ease
of preparation from 1 and for the fact that it possesses
potentially coordinating cyano end groups.
Our recent reports on the reactivity of S,S-diphenyl-
sulfimide, Ph2SNH (1), towards a number of metal
centres have revealed an unexpectedly rich chemical
diversity. Thus we have seen unique product isomerism
(with the first examples of square-planar/pseudo-tetra-
hedral allogonism in a neutral Cu(II) complex [1]),
unexpected hydrogen-bonding features (e.g. between
cation and anion in [Co(Ph2SNH)6]Cl2 [2]) and metal-
mediated nitrile activation (with 1 adding to platinum-
bound acetonitrile [3]). All such observations serve to
confirm the obvious potential of sulfimides as a ver-
satile class of ligand whose chemistry has been essen-
tially ignored until now. This potential is further
enhanced by the close structural and electronic relation-
ship they share with sulfoxides. The R2SNR% unit of the
sulfimides is isoelectronic with the R2SO of the sulfox-
* Corresponding author.
E-mail address: p.f.kelly@lboro.ac.uk (P.F. Kelly).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00831-7

P.F. Kelly et al. / Journal of Organometallic Chemistry 623 (2001) 120–123
121
2. Results and discussion
crystallography (though as chloride salts in both cases).
Thus a very strong, broad NꢀH stretch is seen at 3114
cm−1 (compared to 3081, 3126 and 3056 cm−1 for
[Cu(Ph2-
The reaction of an excess of 1 with [PPh4]2[Pd2Br6]
mirrors that with [PPh4]2[PtCl4] [5] insofar as the ho-
moleptic cation [Pd(Ph2SNH)4]2+ results (Fig. 1). Thus
stirring a mixture of the two in CH2Cl2 overnight
results in gradual deposition of the bright yellow–or-
ange crystalline product. It can be characterised by its
distinctive IR spectrum. The latter is very similar to
that of its platinum and copper analogues, both of
which have had their structure confirmed by X-ray
SNH)4]Cl2, [Cu(Ph2SNH)4]Br2 and [Pt(Ph2SNH)4]Cl2,
respectively). The strength and width of this band is
distinctive to ionic complexes of 1 (thanks to the strong
degree of H-bonding between cation and anion); the
SꢀN stretch in this case (955 cm−1) is also in a similar
position to the aforementioned species (940, 936 and
934 cm−1, respectively). When allied to the microanaly-
sis results for this product there can be no doubt that
[Pd(Ph2SNH)4]Br2 has formed. Thus 1 appears capable
of complete substitution of all of the bromides in
[Pd2Br6]2−
.
If we move on to the propionitrile derivative of 1,
Ph2SNCH2CH2CN (2), we find a subtle difference in its
reactivity towards [Pd2Br6]2−. In this case reaction of
an excess of 2 proceeds quickly but with no production
of insoluble material even after stirring for a number of
days. Crystallisation of such mixtures only results in the
isolation of the orange coloured disubstituted species
[PdBr2(Ph2SNCH2CH2CN)2] (3). X-ray crystallography
confirms that, as in complexes of 1, both the sulfimide
ligands are N-bound; it also indicates a trans geometry
(Fig. 2). The ligands arrange themselves with the
CH2CH2CN units pointing away from, and on opposite
faces of, the PdBr2N2 coordination plane. Although
such an arrangement would leave the cyano groups
capable of interactions with neighbouring molecules
there are no significant close approaches to be seen.
Within the ligand the two most pertinent features for
contrast with previously characterised complexes of the
free sulfimide 1 are the SꢀN bond length and the angle
at the nitrogen (Table 1). In this case these values are
Fig. 1. The structures of 1 and 2.
Table 1
,
Selected bond distances (A) and angles (°) in complex 3
Bond distances
PdꢀN(1)
N(1)ꢀS(1)
2.038(4)
1.604(5)
PdꢀBr(1)
C(3)ꢀN(3)
2.4479(6)
1.159(10)
Bond angles
N(1)ꢀPdꢀBr(1)
PdꢀN(1)ꢀS(1)
92.20(11)
110.3(2)
N(1)ꢀPdꢀBr(1A)
C(10)ꢀS(1)ꢀC(4)
87.80(11)
101.8(3)
Table 2
,
Selected bond distances (A) and angles (°) in complex 4
Bond distances
PdꢀBr(1)
PdꢀBr(3)
N(1)ꢀS(1)
2.425)(1)
2.430(1)
1.581(7)
PdꢀBr(2)
PdꢀN(1) 2.026(7)
C(3)ꢀN(3)
2.423(2)
1.10(1)
,
1.60 A and 110.3°; although the former compares well
to values note for 1 as ligand, the angle is some 12° less
than in any complex of 1. This clearly reflects the extra
steric effect of the CH2 unit bound to the N compared
to a simple proton.
Bond angles
Br(1)ꢀPdꢀN(1)
PdꢀN(1)ꢀS(1)
88.1(2)
117.4(4)
Br(3)ꢀPdꢀN(1)
C(4)ꢀS(1)ꢀC(10)
88.8(2)
101.8(5)
Thus 2 appears to be unable to substitute all of the
bromide ions in [Pd2Br6]2−, providing an obvious con-
trast with 1. If the molar ratio of the reaction is lowered
a salt of the monosubstituted species [PdBr3(Ph2-
SNCH2CH2CN)]− (4) may be isolated. Interestingly it
appears to be easier to isolate the latter in good yield
than it is to generate the corresponding free sulfimide
analogue, [PPh4][PdBr3(Ph2SNH)]. In the latter case it
is likely that the product is contaminated with signifi-
cant amounts of more highly substituted products; 4
though may be readily isolated and crystallised (Table
2). X-ray crystallography (Fig. 3) confirms the presence
of the single sulfimide unit. Within this the SꢀN bond
,
length is marginally shorter than in 3 (1.58 A); in
contrast the angle at the N is significantly wider at
117.4°, though still far less than in any complex of 1 we
have thus far seen.
Fig. 2. The molecular structure of 3.

122
P.F. Kelly et al. / Journal of Organometallic Chemistry 623 (2001) 120–123
To conclude, we have demonstrated that N-substi-
tuted sulfimides can coordinate to metals in a similar
manner to the free sulfimide 1 (before this study no
fully characterised examples of such complexes have
been reported [6]). Although 2 is a less powerful ligand
than 1 insofar as it cannot (under these mild conditions
at least) fully substitute the bromides within [Pd2Br6]2−
, one or two ligands can be added to the palladium in
good yield. This result paves the way for the formation
of complexes of sulfimides with a range of substituents
and suggests that they also have the potential to act as
bridging ligands (though in the case of 2 the cyano end
groups are not strongly coordinating). Analogy with
sulfoxide coordination chemistry suggests there is much
worthwhile work to be done in this area.
Fig. 3. The molecular structure of the anion in 4.
3. Experimental
Table 3
X-ray data for 3 and 4
[PPh4]2[Pd2Br6] was prepared as noted previously
from PdCl2 [7]; 1 was prepared by our recently reported
modification of the literature method (the latter, and
indeed other published methods, proving to be unreli-
able in our hands) [8]. Compound 2 was generated by
the reaction of acrylonitrile with 1 using a slight (but, in
our experience, important) amendment to the literature
method [9] whereby the crude product was extracted
into cold Et2O to separate it from unreacted 1; removal
of the solvent yielded 2 as a pure oil (1H-NMR).
Compound
3
4
Colour, habit
Size (mm)
Formula
Orange block
0.19×0.11×0.1
C30H28Br2PdN4S2·0.5
Yellow plate
0.1×0.30×0.30
C39H34Br3PdN2S
C4H10
O
M
811.96
939.86
Triclinic
Crystal system
Space group
Unit cell dimensions
Triclinic
(
(
P1
P1
,
a (A)
10.4735(2)
11.7597(2)
14.8369(1)
87.391(1)
80.995(1)
81.437(1)
1784.29(5)
2
12.860(5)
13.33(1)
11.883(6)
109.10(6)
98.79(4)
89.92(6)
1899(2)
,
b (A)
3.1. trans-[PdBr2(Ph2SNCH2CH2CN)2] (3)
,
c (A)
h (°)
i (°)
k (°)
V (A )
A solution of [PPh4]2[Pd2Br6] (0.19 g, 0.11 mmol) in
CH2Cl2 (20 ml) was treated with a solution of 2 (0.25 g,
1 mmol) in the same solvent (10 ml) and the resulting
mixture stirred. There was an almost instantaneous
lightening of the colour to a bright orange; after stirring
for 1 day the volume of the solution was reduced to 3
ml and ether layered upon it. Slow diffusion of the
ether yielded a mixture of orange crystals and a dark
red oil. This oil–crystal mixture was separated and
quickly washed with cold acetone (3×3 ml) in order to
remove most of the oil. The solid was then redissolved
in CH2Cl2 and recrystallised by ether diffusion to yield
a crop of well-formed orange crystals.
3
,
Z
2
Difractometer
Bruker SMART
0.71073
10251
5104 [Rint 0.0229]
2.904
Rigaku AFC7S
0.71073
7010
6686 [Rint 0.049]
3.73
,
u (A)
Collected
Used
v (Mo–Ka)
(mm−1
)
Refined against
F2
F
R1
0.0651; wR2 0.1661
[I\2|(I)]
0.030; wR2 0.038
[I\3|(I)]
Yield 60 mg (35%); IR 2248 (mw) [w CꢀN], 924 cm−1
(m) [w SꢀN]; 1H-NMR (CDCl3) Phenyl multiplets plus l
3.12 (t, 8Hz, CH2), l 2.69 ppm (t, 8Hz, CH2). Anal.
Found: C, 46.9; H, 4.2; N, 6.6; Calc. for
C30H28Br2PdN4S2·0.5 C4H10O (i.e. half a molecule of
ether solvate per molecule — see Table 3): C, 47.3; H,
4.1; N, 6.6%.
A key observation in the above reaction comes when
less than the correct molar ratio of 2 is used in the
reaction. Crystallisation of the products yields 4 to-
gether with unreacted [PPh4]2[Pd2Br6]; in other words
there is no evidence that the cyano end groups within 4
can themselves coordinate to Pd (note that the starting
dimer is susceptible to attack by nitriles and thus reacts
with MeCN as solvent, for example). This of course
does not absolutely rule out coordination through the
cyano groups in the right circumstances, but it does
suggest that the latter’s nitrogen is a far poorer donor
than the sulfimide nitrogen.
3.2. [PPh4][PdBr3(Ph2SNCH2CH2CN)] (4)
A solution of [PPh4]2[Pd2Br6] (0.19 g,0.14 mmol) in
CH2Cl2 (20 ml) was treated with a solution of 2 (73 mg,

P.F. Kelly et al. / Journal of Organometallic Chemistry 623 (2001) 120–123
123
0.29 mmol) in the same solvent (10 ml) added dropwise
over the course of a minute with stirring. After stirring
for a further 1 h the volume of the solvent was reduced
to 2 ml in vacuo and the product precipitated with
Et2O (50 ml); a dark maroon coloured micro-crystalline
product was obtained by recrystallisation from
CH2Cl2–toluene while X-ray quality crystals were
grown by slow diffusion of ether into a CH2Cl2
solution.
technique to a maximum 2q value of 50.1°. Of 7010
measured reflections 6686 were unique. Data were cor-
rected for Lorentz and polarisation effects and an
empirical absorption correction was applied resulting in
transmission factors ranging from 0.601 to 1.00. Non-
hydrogen atoms were refined anisotropically; hydrogen
atoms were included but not refined. The structure was
solved by direct methods and refined by full-matrix
least-squares against F leading to R=0.030 [R=
S(ꢀFoꢀ−ꢀFcꢀ)/SꢀFoꢀ], Rw=0.038. The maximum/mini-
mum residual electron densities in the final DF map
Yield of recrystallised material 120 mg (46%). IR
1
2224 (mw) [w CꢀN], 913 cm−1 (m) [w SꢀN]. H-NMR
were 0.38 and −0.35 e A−3; calculations were per-
,
(CDCl3) Phenyl multiplets plus l 3.10 (t, 8Hz, CH2), l
2.86 ppm (t, 8Hz, CH2). Anal. Found: C, 49.0; H, 3.4;
N, 2.4; Calc. for C39H34Br3PdN2S: C, 49.8; H, 3.6; N,
3.0%.
formed using the TEXSAN crystallographic software
package of Molecular Structure Corporation [11].
3.3. [Pd(Ph2SNH)4]Br2
4. Supplementary material
A solution of [PPh4]2[Pd2Br6] (78 mg, 0.06 mmol) in
CH2Cl2 (20 ml) was treated with solid 1 (0.1 g, 0.5
mmol) and the mixture stirred. After all the solid had
dissolved the colour of the mixture lightened to yellow–
orange; it was allowed to stand overnight during which
time an orange crystalline material was deposited. This
was filtered, washed with CH2Cl2 and dried in vacuo.
Yield 72 mg (61%). IR 3114 (s, br) [w NꢀH], 955
cm−1 (s) [w SꢀN]. Anal. Found: C, 53.9; H, 4.0; N, 5.0;
Calc. for C48H44Br2PdN4S4: C, 53.8; H, 4.1; N, 5.2%.
Supplementary data have been deposited with the
Cambridge Crystallographic Data Centre, CCDC no.
146754 (3) and CCDC no. 146755 (4). Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1233-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
3.4. X-ray crystal structure of 3
The authors acknowledge Johnson Matthey for loans
of precious metals.
Crystals of 3 were grown by slow diffusion of ether
into a dichloromethane solution. Data were collected
(using a Bruker SMART diffractometer with graphite
monochromated Mo–Ka radiation) using small slices:
10 251 data collected, 5104 data used (Rint=0.0229).
Data were corrected for Lorentz and polarisation ef-
fects and an empirical absorption correction was ap-
plied resulting in transmission factors ranging from
0.496 to 0.693. The structures were solved (with one
unit of Et2O of crystallisation for every pair of
molecules of 3) by direct methods and refined by full-
matrix least-squares against F2 leading to R1=0.0651,
wR2=0.1661 with I\2|(I). The maximum/minimum
residual electron densities in the final DF map were
References
[1] P.F. Kelly, A.M.Z. Slawin, K.W. Waring, J. Chem. Soc. Dalton
Trans. (1997) 2853.
[2] P.F. Kelly, A.M.Z. Slawin, K.W. Waring, Inorg. Chem. Com-
mun 1 (1998) 249.
[3] P.F. Kelly, A.M.Z. Slawin, J. Chem. Soc. Chem.Commun.
(1999) 1081.
[4] For example: M. Otto, J. Parr, A.M.Z. Slawin, Organometallics
17 (1998) 4527 and references therein.
[5] P.F. Kelly, A.C. Macklin, A.M.Z. Slawin, K.W. Waring, Poly-
hedron 19 (2000) 2077
[6] Some examples of such complexes have been noted but not fully
characterised, for example: M. Toriuchi, G. Matsubayashi, H.
Koezuka, T. Tanaka, Inorg. Chim. Acta 17 (1976) 253.
[7] P.F. Kelly, A.M.Z. Slawin A. Soriano-Rama, J. Chem. Soc.
Dalton Trans. (1996) 53.
1.365 and −1.034 e A−3; calculations were performed
,
using SHELXTL [10].
3.5. X-ray crystal structure of 4
[8] P.F. Kelly, S.-M. Man, A.M.Z. Slawin, K.W. Waring, Polyhe-
dron 18 (1999) 3173.
[9] N. Furukawa, S. Oae, T. Yoshimura, Synthesis (1976) 30.
[10] Siemens SHELXTL, Revision 5.03, Siemens Analytical X-ray,
Madison, WI, USA, 1995.
[11] TEXSAN: Crystal Structure Analysis Package, Molecular Struc-
ture Corporation (1985 &1992).
Crystals of 4 were grown by slow diffusion of ether
into a dichloromethane solution. Data were collected
(using a Rigaku AFC7S diffractometer with graphite
monochromated Mo–Ka radiation) by the ꢀ–2q scan