Use of Se4N4 and Se(NSO)2 in the preparation of palladium adducts of diselenium dinitridc, Se2N2; crystal structure of [PPh4]2[Pd2Br6(Se2N 2)]

Article abstract of DOI:10.1039/a606311j

Reaction of Se₄N₄ with [NBuⁿ₄]₂[Pd₂Br₆] at 100°C in CH₂Cl₂ resulted in [NBuⁿ₄]₂[Pd₂Br₆(Se ₂N₂)] 1a in high yield (67%). In contrast to the reaction of [PPh₄]₂[Pd₂Br₆] with S₄N₄, which generates a number of products, the tetrabutylammonium salt generated only [NBuⁿ₄]₂[Pd₂Br₆(S ₂N₂)] 1b; comparison of the IR spectra of 1a and 1b allows unambiguous identification of the two bands due to E₂N₂ vibrations. While reaction of S(NSO)₂ with [Pt(PPh₃)₃] leads to a mixture of [Pt(S₂N₂)(PPh₃)₂] and [Pt(NSO)₂(PPh₃)₂], only the latter species forms in the analogous reaction of Se(NSO)₂. Two different results were also found in reactions with [PPh₄]₂[Pd₂Br₆]; while S(NSO)₂ appears surprisingly inert to this reagent, Se(NSO)₂ reacts, when present in excess, to give the unexpected product [PPh₄]₂[Pd₂Br₆(Se₂N ₂)] 1c. The crystal structure of the latter confirms the presence of the adducted diselenium dinitride unit.

Full text of DOI:10.1039/a606311j

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Use of Se4N4 and Se(NSO)2 in the preparation of palladium adducts
of diselenium dinitride, Se2N2; crystal structure of
[PPh4]2[Pd2Br6(Se2N2)]†
Paul F. Kelly,* Alexandra M. Z. Slawin and Antonio Soriano-Rama
Department of Chemistry, Loughborough University, Loughborough, Leics. LE11 3TU, UK
Reaction of Se4N4 with [NBun ]2[Pd2Br6] at 100 ЊC in CH2Cl2 resulted in [NBun ]2[Pd2Br6(Se2N2)] 1a in high yield
4
4
(67%). In contrast to the reaction of [PPh4]2[Pd2Br6] with S4N4, which generates a number of products, the
tetrabutylammonium salt generated only [NBun ]2[Pd2Br6(S2N2)] 1b; comparison of the IR spectra of 1a and 1b
4
allows unambiguous identification of the two bands due to E2N2 vibrations. While reaction of S(NSO)2 with
[Pt(PPh3)3] leads to a mixture of [Pt(S2N2)(PPh3)2] and [Pt(NSO)2(PPh3)2], only the latter species forms in the
analogous reaction of Se(NSO)2. Two different results were also found in reactions with [PPh4]2[Pd2Br6]; while
S(NSO)2 appears surprisingly inert to this reagent, Se(NSO)2 reacts, when present in excess, to give the unexpected
product [PPh4]2[Pd2Br6(Se2N2)] 1c. The crystal structure of the latter confirms the presence of the adducted
diselenium dinitride unit.
A number of significant inroads into the co-ordination chem-
istry of selenium–nitrogen and mixed selenium–sulfur–nitrogen
ligands have been reported in recent years.1 The nature of these
advances suggests that, ultimately, the range and structural
diversity of such complexes will rival that of their sulfur–
nitrogen congeners. By way of example, one of the best known
and most studied S᎐N ligands is [S2N2]2Ϫ, which occurs in com-
plexes such as [Pt(S2N2)(PR3)2] [Scheme 1(i)]. Recent work has
demonstrated the stability of complexes of the selenium ana-
logue, [Se2N2]2Ϫ [as in Scheme 1(iv)], and of the mixed ligand
[SeSN2]2Ϫ (ref. 2) [it is noteworthy that in the latter case only the
isomer illustrated in Scheme 1(ii) has been observed]. The
recent report of the preparation of the first examples of
adducts of neutral diselenium dinitride, Se2N2, added weight to
this conclusion.3 The adducts in question, salts of
[Pd2Cl6(Se2N2)]2Ϫ, form in the high-temperature reaction of
Se4N4 with simple halide-bridged palladium salts, and appear
to be stable both to air and friction (in marked contrast to
Se4N4 which is a particularly pernicious explosive).
Scheme
1
Metallocycles containing the [S2N2 ]2Ϫ [Se2N2 ]2Ϫ and
,
[SSeN2 ]2Ϫ ligands; note that isomer (iii) is as yet unknown
action of ammonia upon diethyl selenite,5 compounds S(NSO)2
and Se(NSO)2 by the literature routes. Infrared spectra were
recorded using a PE 2000 FT spectrometer.
CAUTION: Se4N4 is a severely explosive material; the risk of
detonation is exacerbated during reaction at high temperatures.
6
4
Here we report on the preparation of the bromide analogues
Preparation
of these adducts, i.e. salts of [Pd2Br6(Se2N2)]2Ϫ with either
[PPh4]+ or [NBun ]+ as cations. The advantage of the latter
[NBun ]2[Pd2Br6(Se2N2)] 1a. A mixture of Se4N4 (61 mg, 0.16
4
4
mmol) and [NBun ]2[Pd2Br6] (193 mg, 0.16 mmol) in CH2Cl2
cation is its markedly less complicated IR spectrum and this, in
conjuction with the presence of bromine in the system, allows a
more complete analysis of the spectrum than was previously
possible. In addition, we present the results of investigations
4
(50 cm3) was sealed in a thick-walled tube fitted with a Young’s
joint and heated to 100 ЊC using an oil-bath. After thorough
stirring at this temperature for 1.5 h the resulting dark mixture
was cooled, filtered through Celite (in air) and the volume of
the solvent reduced to ca. 5–10 cm3 in vacuo. At this point the
mixture was briefly heated to redissolve any solid and then
cooled overnight in a freezer. This resulted in a crop of well
formed claret coloured crystals which were isolated by decant-
ing the mother-liquor. The latter was allowed to evaporate
slowly in air, yielding a mixture of crystalline material and an
oily residue. Washing this mixture with cold CH2Cl2 (3 × 5 cm3)
yielded the pure crystals which were combined with the original
crop. Total yield 150 mg (67% based on palladium) {Found: C,
into the chemistry of
a potentially important synthon:
Se(NSO)2. First prepared by Haas et al.4 in 1991, this air-
sensitive material has been shown to react with TiCl4 to gener-
ate an adduct of (SSeN2). Here we report on investigations into
its reactivity towards simple platinum and palladium complexes
and contrast the results with those obtained for the sulfur ana-
logue, S(NSO)2.
Experimental
28.1; H, 5.1; N, 4.3. Calc. for [NBun ]2[Pd2Br6(Se2N2)]: C, 28.2;
Unless otherwise stated all reactions were performed under an
inert atmosphere. The 31P NMR measurements were performed
on a JEOL FX90Q spectrometer operating at 36.21 MHz and
run in CDCl3. The tetrabutylammonium and tetraphenylphos-
phonium salts of [Pd2Br6]2Ϫ were prepared from PdBr2 by the
action of KBr in water followed by addition of either [PPh4]Br
4
H, 5.3; N, 4.1%}. IR: 2964s, 2929s, 2873s, 1471s, 1382m,
1182mw, 1168m, 1110mw, 1065mw, 1032mw, 895m, 882m,
753ms, 740ms and 323m cmϪ1
.
[NBun ]2[Pd2Br6(S2N2)] 1b. A mixture of [NBun ]2[Pd2Br6]
4
4
or [NBun ]Br. Tetraselenium tetranitride was prepared from the
(160 mg, 0.14 mmol) and S4N4 (50 mg, 0.27 mmol) in CH2Cl2
(50 cm3) was stirred overnight and the resulting dark red solu-
tion reduced in volume to 5 cm3. Slow diffusion of diethyl ether
4
† E-Mail: p.f.kelly@lboro.ac.uk
J. Chem. Soc., Dalton Trans., 1997, Pages 559–562
559

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into this solution resulted in the formation of dark red crystals
made on a Rigaku AFC7S diffractometer with graphite-
of [NBun ]2[Pd2Br6(S2N2)] (115 mg, 66% based on palladium)
monochromated Cu-Kα radiation using the ω–2θ scan tech-
nique to a maximum 2θ value of 120.1Њ. Of 4231 measured
reflections 1456 were unique [I > 3σ(I )]. Data were corrected for
Lorentz-polarisation effects and an empirical absorption cor-
rection was applied resulting in transmission factors ranging
from 0.62 to 1.00.
4
(Found: C, 30.1; H, 5.5; N, 4.7. Calc.: C, 30.3; H, 5.7; N, 4.4%).
IR: 2961s, 2931ms, 2873ms, 1470s, 1381m, 1169m, 1109mw,
1064mw, 1033mw, 895m (sh), 882m, 855ms, 739m and
441mw cmϪ1
.
The mother-liquor from this crystallisation was reduced to
dryness and infrared spectroscopy used to compare this crude
material with the crystalline compound (see text).
Structure analysis and refinement. The structure was solved
by, and expanded, using Fourier techniques. Some non-
hydrogen atoms were refined anisotropically, while the rest were
refined isotropically; hydrogen atoms were included but not
refined. Refinement was by full-matrix least squares to
R = 0.046 [Σ(|Fo | Ϫ |Fc|)/Σ|Fo |], RЈ = 0.039. The maximum and
minimum residual electron densities in the final ∆F map were
0.86 and Ϫ0.78 e ÅϪ3 while the largest parameter shift in the final
refinement cycle was 0.05 times its e.s.d. All calculations were
performed using the TEXSAN crystallographic package.9
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature
citation and the reference number 186/355.
[PPh4]2[Pd2Br6(Se2N2)] 1c. Solid Se4N4 (150 mg, 0.4 mmol)
was added to a solution of [PPh4]2[Pd2Br6] (272 mg, 0.2 mmol)
in CH2Cl2 (50 cm3) in a thick-walled reaction tube fitted with a
Young’s greaseless joint. The mixture was stirred at room tem-
perature under a nitrogen atmosphere; more CH2Cl2 was added
to just below the seal of the joint which was then closed and the
tube immersed in a pre-heated oil-bath at 100 ЊC. After ca. 1 h
with continuous stirring the mixture consisted of a dark solu-
tion with dark coloured suspension. After cooling the solution
was filtered through Celite in air and reduced in volume to 2
cm3; layering with ether followed by slow diffusion yielded a
crop of well formed dark red-orange crystals of compound 1c.
Yield 65 mg (21% based upon Pd) {Found: C, 37.2; H, 2.3; N,
1.8. Calc. for [PPh4]2[Pd2Br6(Se2N2)]: C, 37.0; H, 2.6; N, 1.8%}.
Reaction of [Pt(PPh3)3] with S(NSO)2. Solid S(NSO)2 (14 mg,
0.09 mmol) was added, with stirring, to a solution of
[Pt(PPh3)3] (90 mg, 0.09 mmol) in toluene (60 cm3) and the
mixture stirred overnight. The solvent was removed in vacuo to
give a yellow solid. Phosphorus-31 NMR measurements
revealed the presence of cis-[Pt(NSO)2(PPh3)2]7 [δ 8.8,
1J(195Pt᎐31P) 3190], [Pt(S2N2)(PPh3)2]8 [δA 11.5, δx 24.1;
1JA(195Pt᎐31PA) 2995, 1Jx(195Pt᎐31Px) 2825 Hz] together with
P(S)Ph3 and PPh3.
Results and Discussion
Reactions of Se4N4
The last few years have seen an increase in interest in the chem-
istry of selenium–nitrogen systems,1 fuelled, in part, by the real-
isation that the chemistry of the main parent compound, Se4N4,
is far more diverse that had been previously thought. A good
example of the increased range of chemistry associated with
this material came with the isolation of the first adducts of
diselenium dinitride, a compound which, unlike its sulfur ana-
logue, has yet to be prepared in the free state.3 Thus, the high-
temperature reaction of Se4N4 with salts of [Pd2Cl6]2Ϫ results in
adducts of the type [Pd2Cl6(Se2N2)]2Ϫ, with the [PPh4]+ salt of
the latter characterised by X-ray crystallography.
Reaction of [Pt(PPh3)3] with Se(NSO)2. Solid Se(NSO)2
(15 mg, 0.07 mmol) was added, with stirring, to a solution of
[Pt(PPh3)3] (72 mg, 0.07 mmol) in toluene (60 cm3) to give a
suspension which was stirred overnight. The solvent was
removed from the reaction mixture in vacuo to give a yellow
solid. Phosphorus-31 NMR spectroscopy revealed the presence
of cis-[Pt(NSO)2(PPh3)2] [δ 8.8, 1J(195Pt᎐31P) 3190], and
P(Se)Ph3 [δ 35.38, 1J(77Se᎐31P) 730 Hz].
Reaction of Se(NSO)2 with [PPh4]2[Pd2Br6]. Solid Se(NSO)2
(35 mg, 0.17 mmol) was added to a solution of [PPh4]2[Pd2Br6]
(36 mg, 0.02 mmol) in CH2Cl2 (50 cm3) and the mixture
stirred overnight. At this point the solution was reduced in vol-
ume to 2 cm3 and layered with Et2O. After 48 h of slow diffu-
sion a mixture of red crystals and a non-crystalline solid (15
mg) was generated. X-Ray crystallography and microanalysis
revealed the red crystals to be [PPh4]2[Pd2Br6(Se2N2)] 1c
(Found: C, 36.6; H, 2.2; N, 1.75; S, 0.0%). The non-crystalline
solid was also shown to be predominantly [PPh4]2[Pd2Br6-
(Se2N2)] by microanalysis and IR spectroscopy (the latter iden-
tical to those for samples prepared from Se4N4 as above). Total
yield 15 mg, 37% based upon Pd.
We have now extended this reaction to salts of the bromo
species [Pd2Br6]2Ϫ. The tetraphenylphosphonium salt of the lat-
ter reacts to give [PPh4]2[Pd2Br6(Se2N2)] in much the same yield
as the chloro analogue; we have also characterised this species
by X-ray techniques after its unexpected formation from reac-
tions involving Se(NSO)2 (see below). The corresponding
tetrabutylammonium salt, [NBun ]2[Pd2Br6(Se2N2)] 1a, may
4
also be prepared by the reaction of [NBun ]2[Pd2Br6] with Se4N4
4
(Scheme 2). Two features make this the most interesting of the
palladium species so far isolated. First, the yield is high; a typ-
ical reaction generates the high-purity crystalline material in
some 67% yield (based on palladium), around three times that
of its [PPh4]+ analogue. This is an important consideration,
bearing in mind that the safety aspects of the use of Se4N4
(especially at such elevated temperatures) dictate that quantities
of <150 mg should be used. With this kind of yield, however,
such amounts of Se4N4 still allow the ready isolation of >100
mg of product, thus facilitating the investigation of its chemical
properties.
The other key feature of compound 1a is its infrared spec-
trum. By analogy with the spectra of salts of [Pd2X6(S2N2)]2Ϫ
we should expect to see two vibrational peaks associated with
the Se2N2 moiety.10 These are not apparent with, for example,
[PPh4]2[Pd2Cl6(Se2N2)] due to the presence of the strong cation
bands. We have previously shown that one of the desired bands
When the reaction was performed in a 1:1 or 2:1 ratio
of Se(NSO)2 :[PPh4]2[Pd2Br6] most of the [PPh4]2[Pd2Br6]
remained unchanged (as shown by microanalysis and IR
spectroscopy).
X-Ray crystallography
Crystal data for compound 1c. C48H40Br6N2P2Pd2Se2, M =
1556.95; orthorhombic, space group Pbca (no. 61), a =
18.200(7), b = 20.653(8), c = 13.496(10) Å, U = 5072(3) Å3,
Z = 4, Dc = 2.04 g cmϪ3. Red block of dimensions 0.10 ×
0.10 × 0.10 mm, µ(Cu-Kα) = 137.7 cmϪ1
F(000) = 2968.
, λ = 1.541 78 Å,
Data collection and processing. All measurements were
560
J. Chem. Soc., Dalton Trans., 1997, Pages 559–562

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Scheme
3
The reactivity of [Pt(PPh3 )3 ] towards S(NSO)2 and
Se(NSO)2
spectrum wherein the spectrum of 1a is subtracted from that of
its sulfur analogue, [NBun ]2[Pd2Br6(S2N2)] 1b (prepared by the
4
reaction of S4N4 with [NBun ]2[Pd2Br6], see below). Owing to
4
excellent correlation of the cation bands in each, only the two
chalcogen–nitrogen bands are left. As expected there is a shift to
low frequency on introducing the heavier chalcogen; thus the
bands at 855 and 441 cmϪ1 of 1b shift to 753 and 323 cmϪ1 for
1a.
Scheme 2 The reactivity of salts of [Pd2Br6 ]2Ϫ towards S4N4 and Se4N4
The formation of compound 1b in the reaction of [NBun ]2-
4
[Pd2Br6] with S4N4 is not a surprising result per se; what is
unexpected, however, is the fact that this appears to be the only
isolable product. By analogy with the reaction of [PPh4]2-
[Pd2Br6] with S4N4, the generation of salts of [Pd2Br4(S3N2)]2Ϫ
and [PdBr2(S2N2H)]Ϫ would also be expected to occur.10
Neither of these species crystallises from the crude product nor
are any of the characteristic IR bands associated with them
present for this material {for example, the medium-strength
band at 642 cmϪ1 indicative of [Pd2Br4(S3N2)]2Ϫ}. Quite why the
change in cation should have such a drastic effect upon reaction
products is not obvious. It is unlikely that either cation can
affect the course of reaction by direct chemical means, indeed
when the reaction of [PPh4]2[Pd2Br6] with S4N4 is monitored by
31P NMR spectroscopy then only the signal due to unchanged
[PPh4]+ is observed in the reaction mixture. It is possible that
small amounts of monomeric [PdBr4]2Ϫ are present in either
case and that this can influence the course of the reactions,
though we have yet to prove this.
Reactions of Se(NSO)2
Both S(NSO)2 and Se(NSO)2 are very reactive towards the plat-
inum(0) species [Pt(PPh3)3]. The course of such reactions may
be conveniently monitored by 31P NMR spectroscopy which
reveals a clear difference in the complexity of the two spectra,
with more signals being present in the reaction involving
S(NSO)2. In the latter case the products appear to mirror those
reported by Chivers et al.11 for the reaction with [Pt(PPh3)2-
(C2H4)], i.e. the most abundant species present is the metal-
locyclic [Pt(S2N2)(PPh3)2] 2 (Scheme 3).11 The only other identi-
fiable metal species present in any significant amount is the
[NSO]Ϫ complex [Pt(NSO)2(PPh3)2] 3, which is seen as a singlet
(with appropriate 195Pt satellites) at δ 8.8 and is about half as
abundant as 2. The other main components of the spectrum
are PPh3 and P(S)Ph3 which are present in the approximate
ratio 2:3.
Fig. 1 Difference IR spectrum in which the spectrum of compound 1a
has been substracted from that of 1b, revealing the two bands due to the
(E2N2 ) vibrations
may be revealed by substituting [NBun ]+ for [PPh4]+ but postu-
4
lated that the other was obscured by the Pd᎐Cl vibration. This
is confirmed by the spectrum of 1a; now the lack of intrusive
cation vibrations and the shift of the metal–halogen stretch to
lower frequency allow both bands to be resolved. As Fig. 1
shows, they are conveniently displayed by means of a difference
In the light of the above observations it was hoped that reac-
tion of Se(NSO)2 with [Pt(PPh3)3] would proceed in a similar
manner and generate a metallocycle. In view of the likelihood
(albeit difficult to prove absolutely) that the order of S and N
J. Chem. Soc., Dalton Trans., 1997, Pages 559–562
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Table 1 Selected bond distances (Å) and angles (Њ) in complex 1c
Pd(1)᎐Br(1)
Pd(1)᎐Br(2)
Pd(1)᎐Br(3)
2.424(2) Pd(1)᎐N(1)
2.294(2) N(1)᎐Se(1)
2.428(2) N(1)᎐Se(1*)
1.875(9)
1.809(10)
1.920(9)
N(1)᎐Pd(1)᎐Br(1)
N(1)᎐Pd(1)᎐Br(3)
88.0(1) Pd(1)᎐N(1)᎐Se(1*) 136.9(5)
84.0(3) Se(1*)᎐N(1)᎐Se(1) 94.2(4)
Pd(1)᎐N(1)᎐Se(1) 128.5(5) N(1)᎐Se(1)᎐N(1*) 85.8(4)
Fig. 2 Crystal structure of compound 1c
The structure of compound 1c is very much analogous to
that of [PPh4]2[Pd2Cl6(Se2N2)], with one intriguing difference.
In the latter case an asymmetry within the anions was noted
and ascribed to the presence of long-range intermolecular
interactions. Though an even more pronounced asymmetry
appears in 1c (witness the two Se᎐N bond lengths of 1.81 and
1.92 Å, Table 1) there is no concomitant intermolecular inter-
action. It appears that in this case the asymmetry is inherent to
the anions and is not the result of the crystal packing. Both
these bond lengths are significantly larger than those in the
chloro analogue (average length 1.79 Å) and in Se4N4. It is not
clear why the asymmetry exists, though it is perhaps noteworthy
that in [(AlBr3)2(Se2N2)], the only other adduct of Se2N2 so far
characterised by X-ray techniques, there is substantially less
asymmetry in the bond lengths.13
atoms in 3 mirrors that in the starting material it might be
hoped that the hitherto unseen isomer shown in Scheme
1(iii) would result. In fact, this is not the case. The reaction
is far simpler than that involving S(NSO)2; complex 3 results
in very high yield alongside triphenylphosphine selenide
(Scheme 3). No free PPh3 is left; neither is there any evidence for
the production of any metallocycle of the type shown in
Scheme 1.
It is possible to speculate that the difference in the two
reactions outlined above hinges on the relative strengths of the
chalcogen–nitrogen bonds in the starting materials. If we
assume that the reaction progresses via co-ordination/
reduction of the E(NSO)2 then a transitory complex of the type
[Pt{E(NSO)2}(PPh3)2], containing the [E(NSO)2]2Ϫ ligand,
might be envisaged. If the latter were bidentate through the two
nitrogens then the final rearrangement could proceed either
through loss of ‘E’ to give 3 and P(E)Ph3 (by reaction with free
PPh3) or through loss of sulfur and oxygen (presumably as SO2)
and formation of the metallocycle. The strength of the E᎐N
bond would, of course, be a key factor in determining which of
these two courses occurs; presumably in the case of Se(NSO)2
the weakness of the Se᎐N bond, and the inherent stability of
the NSO unit, conspire to generate the observed products. This
casts some doubt on the efficacy of Se(NSO)2 as a reagent for
the preparation of new species under conditions involving oxi-
dative addition.
The main conclusion to be drawn from this work is that
the efficiency of formation of Se2N2 adducts by reaction of
Se4N4 with palladium complexes is dependent upon both the
cations and the halide ligands present in the starting material.
The Se4N4–[NBun ]2[Pd2Br6] system appears to be the most
4
efficient; this is also the most useful in assigning the IR stretches
of the product. In addition, while it is clear that Se(NSO)2
has great promise as a new synthon, its chemistry does not
mirror that of its sulfur analogue and the isolation of the Se2N2
adduct 1c highlights its ability to exhibit unexpected reaction
pathways.
Given that, as we have already seen, S2N2 and Se2N2 adducts
readily form from [Pd6Br6]2Ϫ, and given that both S(NSO)2 and
Se(NSO)2 have been shown to react with TiCl4 to generate
Acknowledgements
We are grateful to Johnson Matthey for loans of precious
metal.
12
4
adducts of S2N2 and SSeN2 respectively, it would seem
reasonable to expect similar products to predominate when
[PPh4]2[Pd2Br6] is treated with E(NSO)2 (E = S or Se). In fact, in
both cases unexpected results are observed. In the case of E = S
there appears to be no reaction with [PPh4]2[Pd2Br6], even when
the former is present in excess and the reagents are allowed to
stir in solution overnight. In contrast, Se(NSO)2 reacts in an
equimolar ratio to give a crude mixture from which two species
may be crystallised by slow diffusion of ether into the dichlo-
romethane solutions. One of these is simply the starting
material, [PPh4]2[Pd2Br6]. Rather than the SeSN2 adduct one
might expect (cf. the TiCl4 products, see above), the other com-
pound actually proves to be [PPh4]2[Pd2Br6(Se2N2)] 1c i.e. the
diselenium dinitride adduct.
The identity of compound 1c has been confirmed by a num-
ber of techniques. X-Ray crystallography reveals the structure
shown in Fig. 2, consistent with the presence of two selenium
atoms in the central ring. In addition, microanalysis results in a
zero sulfur content, while infrared spectroscopy reveals a spec-
trum identical to that of a sample of [PPh4]2[Pd2Br6(Se2N2)]
prepared by the reaction of Se4N4 with [PPh4]2[Pd2Br6]. When
an eight-fold excess of Se(NSO)2 is used then 1c is the only
isolable palladium species. From a mechanistic point of view it
is very difficult to suggest how such a reaction is proceeding;
suffice it to say that the palladium species must catalyse sub-
stantial decomposition (and subsequent rearrangement) of
Se(NSO)2. The ultimate fate of the sulfur atoms in the reaction
is unknown.
References
1 T. M. Klapötke, in The Chemistry of Inorganic Ring Systems;
Studies in Inorganic Chemistry, ed. R. Steudel, Elsevier, Amsterdam,
1992, vol. 14, p. 409; T. Chivers, Main Group Chem. News, 1993, 1, 6.
2 P. K. Kelly, A. M. Z. Slawin, D. J. Williams and J. D. Woollins,
Chem. Soc. Rev., 1992, 245.
3 P. F. Kelly and A. M. Z. Slawin, Angew. Chem., Int. Ed. Engl., 1995,
34, 1758.
4 A. Haas, J. Kasprowski, K. Angermund, P. Betz, C. Kruger, Y. Tsay
and S. Werner, Chem. Ber., 1991, 124, 1895.
5 J. Adel, C. Ergezinger, R. Figge and K. Dehnicke, Z. Naturforsch.,
Teil B, 1988, 43, 639.
6 D. A. Armitage and A. W. Sinden, Inorg. Chem., 1972, 11, 1151.
7 I. P. Parkin, A. M. Z. Slawin, D. J. Williams and J. D. Woollins,
Polyhedron, 1989, 8, 835.
8 R. Jones, P. F. Kelly, D. J. Williams and J. D. Woollins, Polyhedron,
1985, 4, 1947.
9 TEXSAN, Crystal Structure Analysis Package, Molecular Structure
Corporation, Houston, TX, 1985 and 1992.
10 V. C. Ginn, P. F. Kelly, A. M. Z. Slawin, D. J. Williams and J. D.
Woollins, J. Chem. Soc., Dalton Trans., 1992, 963.
11 T. Chivers, F. Edelmann, U. Behrens and R. Drews, Inorg. Chim.
Acta, 1986, 116, 145.
12 H. W. Roesky, J. Anhaus and W. S. Sheldrick, Inorg. Chem., 1984,
23, 75.
13 P. F. Kelly and A. M. Z. Slawin, J. Chem. Soc., Dalton Trans., 1996,
4029.
Received 13th September 1996; Paper 6/06311J
562
J. Chem. Soc., Dalton Trans., 1997, Pages 559–562