The preparation and structure of [Pt(S2N2){P(OR) nR′3-n}2] and [Pt(SeSN 2){P(OMe)nPh3-n] (n = 0-3)

Article abstract of DOI:10.1002/ejic.201000329

Dissolution of [S₄N₃]Cl in liquid ammonia produces a reactive solution which on treatment with cis [PtCl₂(PR ₃)₂] gives [S₂N₂]^2- complexes in 32-76% yields. Similarly, SeCl₄ and [S₄N ₃]Cl in a ratio of 5:1 react cleanly with cis-[PtCl ₂{P(OMe)_n-Ph_3-n}] to give the desired selenosulfur dinitrido, [SeSN₂]^2- complexes with no phosphorus containing starting material evident: by ³¹P NMR spectroscopy. The new complexes were characterised by IR, ³¹P NMR, microanalysis and X-ray crys tallography with nine crystal structures being reported. In ³¹P nmr the ¹J PtP coupling constants are influenced by the oxygen content of their phosphorus ligands. In the mixed chalcogen complexes the Pt-N bond lengths appear to follow a simple trend as a consequence of the electronic properties of the phosphorus ligand and these trends can be interpreted empirically by examination of the LUMO but are not well supported by DFT calculations.

Full text of DOI:10.1002/ejic.201000329

FULL PAPER
DOI: 10.1002/ejic.201000329
The Preparation and Structure of [Pt(S2N2){P(OR)nRЈ3–n}2] and
[Pt(SeSN2){P(OMe)nPh3–n}2] (n = 0–3)
Paul G. Waddell,[a] Alexandra M. Z. Slawin,[a] Nicolas Sieffert,[a] Michael Bühl,[a] and
J. Derek Woollins*[a]
Keywords: Sulfur / Selenium / Platinum / DFT calculations
Dissolution of [S4N3]Cl in liquid ammonia produces a reac-
tive solution which on treatment with cis [PtCl2(PR3)2] gives
[S2N2]2– complexes in 32–76% yields. Similarly, SeCl4 and
[S4N3]Cl in a ratio of 5:1 react cleanly with cis-[PtCl2{P(OMe)n-
Ph3–n}] to give the desired selenosulfur dinitrido, [SeSN2]2–
complexes with no phosphorus containing starting material
evident by 31P NMR spectroscopy. The new complexes were
characterised by IR, 31P NMR, microanalysis and X-ray crys-
tallography with nine crystal structures being reported. In 31
P
nmr the 1J PtP coupling constants are influenced by the oxy-
gen content of their phosphorus ligands. In the mixed chal-
cogen complexes the Pt–N bond lengths appear to follow a
simple trend as a consequence of the electronic properties of
the phosphorus ligand and these trends can be interpreted
empirically by examination of the LUMO but are not well
supported by DFT calculations.
using [Me2SnS2N2]2 or [nBu2SnS2N2]2. We have also shown
the value of the use of [S4N3]Cl in liquid ammonia as a
Introduction
The discovery of the unusual electrical properties of solvent in these reaction but have not established it for the
(SN)x polymer in 1973 led to sustained interest in this area synthesis of M(S2N2) systems.[10,11]
though M-S-N chemistry has been of interest since the
Surprisingly there is some ambiguity about the bond
1950s[1] and examples are shown in Figure 1. The disulfur length pattern in some [Pt(S2N2)(PR3)2] complexes[14] and
dinitride dianion is not known in simple salts but can be there is only one example of a [Pt(S2N2){P(OR)3}2] com-
isolated in metal complexes and as fragments in hetero- plex whose formulation was proposed using only IR spec-
cycles.[2–7] These complexes may be protonated at the metal- troscopy and microanalysis data.[15] The formulation of this
coordinated nitrogen and we have previously commented complex remains doubtful.
on the structural consequences of this protonation.[8,9] M-
In addition to [S2N2]2– complexes, some selenium-substi-
S-N complexes may be prepared by a variety of routes, e.g. tuted analogues have been investigated.[16–21] As yet only
oxidative addition of S4N4 or S4N4H4 with [Pt(PPh)4], reac- one [SeSN2]2– containing complex [Pt(SeSN2)(PMe2Ph)2]
tion of Na[S3N3] with [PtCl2(PR3)2] or transmetallation has been analysed using X-ray crystallography and this ex-
Figure 1. Examples of fully characterised M-S-N species.[12,13]
ample was found to exhibit a twofold disorder about the
[a] School of Chemistry, University of St Andrews,
ring. Given the need to develop routes in liquid ammonia,
St Andrews, Scotland, KY16 9ST
E-mail: jdw3@st-and.ac.uk
the lack of crystal data for selenium-substituted analogues
Eur. J. Inorg. Chem. 2010, 3185–3194
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J. D. Woollins et al.
FULL PAPER
Mixed-chalcogen compounds containing the [SeSN2]2–
fragment have been synthesised using [Se2SN2]2Cl2 or a
combination of SeCl4 and [S4N3]Cl in liquid ammonia. The
nature of the species in the liquid ammonia solution has
not been determined. As dissolution of [S4N3]Cl in liquid
ammonia results in formation of [S3N3]– it is possible that
this species is in equilibrium with a range of change SN
anions which can undergo chalcogen exchange to give
mixed SeSN anions. The formation of the PtSeSN2 rings
with selenium always platinum-bound may suggest that the
SeSN anions have terminal selenium atoms. Certainly we
would expect that SeNSN would be a more stable isomer
than SNSeN. Furthermore SeNSN could be readily formed
by chain lengthening of the well know [NSN]2– dianion.[25]
After a number of trials we employed SeCl4 and [S4N3]Cl
of these complexes, bond length ambiguity mentioned
above and the poor understanding of the bonding in these
types of molecules we have studied the synthesis, structure
and spectroscopic properties of simple [Pt(S2N2){P(OR)n-
RЈ3–n}2] and [Pt(SeSN2){P(OMe)nPh3–n}2] complexes. Here
we report the synthesis of several of these [Pt(S2N2){P(OR)n-
RЈ3–n}2] and [Pt(SeSN2){P(OMe)nPh3–n}2] complexes which
have been characterised by IR spectroscopy, 31P NMR
spectroscopy, elemental analysis and X-ray crystallography.
Results and Discussion
There are
a
number of possible routes to
[Pt(S2N2){P(OR)3}2] complexes. Use of S4N4 or [S3N3]–
salts are best avoided because of explosion hazard. We
chose to generate the appropriate anion in situ using [S4N3]-
Cl in liquid ammonia which reacted cleanly with cis-
[PtCl2(PR3)] to give the desired disulfur dinitrido complexes
with no phosphorus containing starting material evident by
31P NMR spectroscopy. Though the mechanism and its
stoichiometry are complex and are not completely under-
stood to date, the stoichiometry of 14 equiv. of [S4N3]Cl
to 9 equiv. of cis-[PtCl2(PR3)] is in accord with previously
suggested equilibria; see Equations (1)–(3).[23,24]
in
a ratio of 5:1 which reacted cleanly with cis-
[PtCl2(P(OMe)nPh3–n)] to give the desired selenosulfur dini-
trido complexes with no phosphorus containing starting
material evident by 31P NMR spectroscopy however trace
amounts of the disulfur analogue were observed.
The new complexes [Pt(SeSN2){P(OMe)nPh3–n}2] (7, n =
3, 8, n = 2, 9, n = 1) were characterised by 31P NMR, IR,
microanalysis (Table 1, 2) and X-ray crystallography. The
X-ray of the previously reported complex 10 (n = 0) was
also determined. In their IR spectra the vibrations due
characteristic of the [SeSN2]2– fragment were assigned by
analogy with previously reported [Pt(SeSN2)(PR3)2] com-
plexes.[21] In the case of 9 the νSN vibration typically ob-
served at ca. 1070 cm–1 was slightly lower than expected
(1059 cm–1). The corresponding stretch observed in
[S2N2]2– complexes is observed at ca. 1045 cm–1. Vibrations
indicative of νPtSe were not observed and are likely to be
very low in frequency compared to the νPtS stretch in
[S2N2]2– complexes (ca. 350 cm–1) due to the larger mass of
selenium compared to sulfur. The intensity of the
ν(P–O–alkyl) vibration (1050–1030 cm–1) increases with the
oxygen content as would be expected. Distinct vibrations
due to the P-Ph group (approx. 1440 cm–1) were also ob-
served for 8 and 9.
7S4N3 + 6NH3 h 9S3N3 + H2S + 16H+
(1)
(2)
(3)
=
+
–
–
2–
2S3N3 i S4N4 + S2N2
2–
[PtCl2(PR3)2] + S2N2 i [Pt(S2N2)(PR3)2] + 2Cl–
The new complexes {1, PR3 = P(OEt)3; 2, PR3
P(OnBu)3; 3, PR3 = P(OPh)3; 4, PR3 = P(OMe)3; 5, PR3 =
P(OMe)2Ph; 6, PR3 = P(OMe)2Ph} were characterised by
31P NMR (Table 1), IR, microanalysis (Table 2) and X-ray
crystallography. In their IR spectra the important νSN vi-
brations were assigned by analogy with previously reported
[Pt(S2N2)(PR3)2] complexes.[2] However, the presence of the
ν(P–O–alkyl) vibration (1050–1030 cm–1) obscures one of the
νSN vibrations, which is normally observed around
1050 cm–1 for 1 and 4 though the band at around 680 cm–1
is not obscured. The intensity of the ν(P–O–alkyl) vibration
(1050–1030 cm–1) increases with the oxygen content as
would be expected. Distinct vibrations due to the P-Ph
group (approx. 1440 cm–1) were also observed for 5 and 6.
The 31P NMR of 1–10 exhibit AX doublets (Table 1, see
Figure 2 for labelling and Figure 3 for a typical spectrum)
2
1
with JP,P couplings together with satellites due to JPt-P
couplings. 7–10 also exhibit JP-Se(trans) couplings[26] though
2
2JP-Se(cis) couplings were not observed. These couplings en-
Table 1. 31P NMR chemical shifts (ppm) and coupling constants (Hz) for 1–10 and [Pt(S2N2)(PPh3)2].
δA
δX
1JA
1JX
2JP-P
2JP-Se(trans)
[Pt(S2N2){P(OEt)3}2] (1)
[Pt(S2N2){P(OnBu)3}2] (2)
[Pt(S2N2){P(OPh)3}2] (3)
[Pt(S2N2){P(OMe)3}2] (4)
[Pt(S2N2){P(OMe)2Ph}2] (5)
[Pt(S2N2){P(OMe)Ph2}2] (6)
[Pt(S2N2)(PPh3)2]
[Pt(SeSN2){P(OMe)3}2] (7)
[Pt(SeSN2){P(OMe)2Ph}2] (8)
[Pt(SeSN2){P(OMe)Ph2}2] (9)
[Pt(SeSN2){(PPh)3}2] (10)
98.5
102.8
89.6
105.3
120.4
91.8
105.5
109.0
96.7
110.9
126.2
104.1
23.6
108.1
124.8
103.1
22.6
4498
4470
4634
4502
3864
3287
2994
4530
3868
3309
2995
4415
4334
4503
4395
3761
3249
2827
4571
3900
3391
2956
49.3
49.3
54.0
51.0
37.6
28.2
22
49
33
26
21
11.4
106.0
122.9
89.3
94
75
66
54
7.2
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M-S-N Complexes
Table 2. Microanalyses, yields, melting points and selected IR absorptions with tentative assignments [cm–1] for 1 and 3–9.[a]
ν
νSN/SeN
νPtN
δSN
νPtS
% C
% H
Yield
M.p.
(°C)
˜
SN
(calcd.) (calcd.) (%)
[Pt(S2N2){P(OEt)3}2] (1)
686 s[b]
618 m
618 m
614 w
469 m
491 s
370 m
380 w
372 m
354 m
357 w
354 w
23.25
(23.26)
45.90
(46.13)
13.23
(13.46)
4.78
(4.88)
3.12
(3.28)
3.08
(3.39)
47
32
58
138–
142
117–
120
123–
125
[Pt(S2N2){P(OPh)3}2]·0.5CH2Cl2 687 s[b]
(3)
[Pt(S2N2){P(OMe)3}2] (4)
682 s[b]
467 w
1094(17)
727(10)
648(3)[c] 492(2)[d] 366(2)[e] 362(1)
[Pt(S2N2){P(OMe)2Ph}2]
·0.5CH2Cl2 (5)
1047 s 684 m
1042 s 680 m
1068s 633m
613 m
615 w
541 m
467 m
462 m
401 w
371 m
360 w
357 w
355 m
349 w
29.74
(29.58)
43.22
(43.39)
12.76
(12.37)
3.38
(3.46)
3.79
(3.64)
2.70
(3.12)
62
60
76
139–
142
160–
163
132–
134
[Pt(S2N2){P(OMe)Ph2}2] (6)
[Pt(SeSN2){P(OMe)3}2] (7)
1110(10)
659(7)[f]
580(3)[g] 428(1) 360(2) 246(1)[g]
[d]
[e]
[Pt(SeSN2){P(OMe)2Ph}2]
·0.5CH2Cl2 (8)
[Pt(SeSN2){P(OMe)Ph2}2]
·0.5CH2Cl2 (9)
1071 s 634 m
556 s
542 s
402 m
357 m
27.38
(27.64)
39.42
2.82
(3.23)
2.96
51
63
184–
187
146–
149
1059 s 634 m
402 w
355 w
(39.34)
(3.36)
[a] Printed in italics: PBE0/ECP1 computed harmonic frequencies (in parentheses: intensities in 104 M/mol; maximum absorption around
60.104 M/mol). [b] Band obscured by P–O–alkyl absorption. [c] Combination with δNSN and δPtNS. [d] Combination with δSNS. [e]
SN2 out-of-plane. [f] Combination of νsym,PtN/SeN and δNSN. [g] νasym,PtN/SeN. hν,PtSe.
abled assignment of the individual phosphorus resonances. cation as to the trans-influence[27,28] of the chalcogen–nitro-
By analogy with phosphane complexes, the largest 1J(195Pt- gen fragments. From the coupling constants we can see that
31P) coupling constant in [S2N2]2– complexes is assigned to the trans influence of the [S2N2]2– fragment is greater than
the phosphorus trans to the nitrogen (δA) as this platinum– that of the chlorine atoms as the coupling constants are
phosphorus bond is generally the shorter of the two and the seen to decrease by over 20% for both PA and PX indicating
shorter distance can be associated with the larger coupling weaker Pt–P bonds in both cases. When compared with
1
constant. The smaller of the two 1JPt,P values is assigned to [SeSN2]2– complexes, the JA values are observed to be of a
the phosphorus trans to sulfur (δA). In [SeSN2]2– complexes similar magnitude and 1JA is seen to be ca. 100–200 Hz
1
similar JA values are observed to those in [S2N2]2– com- greater than that observed in [S2N2]2– complexes. The trans
plexes however in the case the 1JX (the phosphorus trans to influence of selenium in the [SeSN2]2– fragment can hence
selenium is the larger value).
be said to be less than that of the sulfur in the [S2N2]2–
fragment.
The co-ordination shifts of the [Pt(S2N2)(PR3)] (R =
alkyl, aryl) relative to their [PtCl2(PR3)2] starting materials
are about –8 ppm for δA and about +7 ppm for δX2. For
the phosphite-containing complexes the chemical shifts also
exhibit a relatively constant co-ordination shift compared
to their starting materials: δA is shifted by ca. +31 ppm and
δX by ca. +37 ppm for all the phosphite systems. The chemi-
cal shifts for 7–10 were found to be similar to their
[S2N2]2– analogues.
Figure 2. Labelling of the phosphorus atoms (E = S or Se).
As expected the coupling constants for 1 to 10 are in-
fluenced by the phosphorus ligands. The effect of replacing
phenyl groups of the phosphanes with methyl groups in
2
[S2N2]2– complexes has been previously reported,[2] with J
1
The JP,P coupling constants increase in the order PPh3
Ͻ P(OMe)Ph2 Ͻ P(OMe)2Ph Ͻ P(OMe)2 from ca. 22 Hz
to ca. 49 Hz presumably reflecting the relative Pt–P bond
strengths in this series. Similarly JP-Se(trans) for 7–10 de-
being observed to decrease in the order PPh3
Ͼ
Pt–P
PMePh2 Ͼ PMe2Ph Ͼ PMe3. The effect of replacing phenyl
groups in the phosphorus ligand with methoxy groups has
the opposite effect in both [S2N2]2– and [SeSN2]2– com-
plexes with the coupling constants increasing in the order
PPh3 Ͻ P(OMe)Ph2 Ͻ P(OMe)2Ph Ͻ P(OMe)3 (Table 1,
2
creases from 94 to 60 Hz. No cis-selenium satellites were
observed and given the small magnitudes of previously re-
ported JP-Se(cis) values this is understandable.[26]
2
Figures 4 and 5).
The structures of the [S2N2]2– complexes 1 and 3–6
Comparing JPt,P values observed for [S2N2]2– and (Table 3, Figures 6 and 7) exhibit square-planar geometry
[SeSN2]2– complexes with the same phosphorus ligand with about platinum. The Pt–P distances (Table 3, Figure 8) lie
those of their dichloride starting materials gives some indi- in the range 2.217(3) Å and 2.256(2) Å. One might antici-
1
Eur. J. Inorg. Chem. 2010, 3185–3194
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J. D. Woollins et al.
FULL PAPER
Figure 3. 31P{1H} NMR spectrum (109 MHz, CH2Cl2 solution) of 4.
Figure 4. Variation of 1JA and 1JX in [Pt(S2N2){P(OMe)nPh3–n}2]
complexes.
1
1
Figure 5. Variation of JA and JX in [Pt(SeSN2){P(OMe)nPh3–n}2]
complexes.
pate a difference in Pt–P bond length trans to sulfur versus measurable crystallographically. The bond lengths and
trans to nitrogen and there does appear to be a trend sug- angles are comparable to equivalent complexes with phos-
gesting that Pt–P(2) (trans to nitrogen) is usually shorter phane ligands with two short sulfur–nitrogen bonds, which
[i.e. for those where there is a structurally relevant differ- are slightly longer than a typical sulfur–nitrogen double
ence, Pt–P(2) is shorter than Pt–P(1)]. In general all of the bond (1.45 Å) ranging from 1.515(8)–1.590(9) Å and one
Pt–P distances observed for 1 and 3–6 are longer than for long sulfur–nitrogen bond, which corresponds to the length
the chloride complexes. The Pt–N bond lengths are in the of a typical sulfur–nitrogen single bond (1.69 Å) ranging
range 2.016(4)–2.070(7) Å and the Pt–S bond lengths are in from 1.673(9)–1.709(11) Å. There is a small departure from
the range 2.289(2)–2.295(3) Å. The Pt–N distance appears this trend in the case of 6 for which there is one short, one
more sensitive to the nature of the phosphane/phosphite long and one medium intermediate length bond indicating
though we cannot see any direct trends.
some degree of electron delocalisation. If the S–N bond
As changing the phosphorus ligands gave rise to trends lengths in 1 are discounted (since this structure contains
in coupling constants in 31P NMR we wondered if we might significant disorder) then the average bond lengths for the
see an effect on the geometry of the metal sulfur-nitrogen remaining structures are N(1)–S(1) 1.54(2), S(1)–N(2)
ring complexes. On the whole however this effect was not 1.58(2) and S(2)–N(2) 1.69(2) Å. Bond angles within the
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M-S-N Complexes
Table 3. Selected bond lengths [Å] and angles [°] for 1, 3–6 and [Pt(S2N2)(PPh3)2]. Values printed in italics are DFT-calculated parameters
(asterisks * denote two-fold disorder).
[7]
[4]
1
3
4
5
6
[Pt(S2N2)(PPh3)2]·4CH2Cl2
[Pt(S2N2)(PPh3)2]·C7H8
Pt–N(1)
2.050(17)
2.057(11)
2.064(8)
2.019
2.016(4)
2.070(7)
2.018(4)
2.017
2.093(13)
2.017
Pt–S(2)
2.293(9)
2.237(2)
2.239(2)
1.69(2)*
1.46(2)*
1.763(17)*
93.57(7)
2.291(3)
2.234(3)
2.221(3)
1.541(11)
1.589(13)
1.689(12)
96.18(11)
2.295(3)
2.315
2.246(3)
2.257
2.217(3)
2.244
1.544(13)
1.567
1.554(13)
1.570
1.709(11)
1.682
93.89(15)
96.2
2.2923(15)
2.2407(15)
2.2175(15)
1.572(5)
2.289(2)
2.256(2)
2.250(2)
1.515(8)
1.590(9)
1.673(9)
96.14(7)
2.288(5)
2.308
2.317(4)
2.334
2.263(4)
2.299
1.546(16)
1.563
1.567(19)
1.571
1.682(16)
1.687
98.4(1)
100.2
2.294(6)
2.308
2.308(5)
2.334
2.259(3)
2.299
1.499(16)
1.563
1.702(15)
1.571
1.548(12)
1.687
97.8(1)
100.2
Pt–P(1)
Pt–P(2)
N(1)–S(1)
S(1)–N(2)
N(2)–S(2)
P(1)–Pt–P(2)
1.568(5)
1.702(5)
95.12(6)
N(1)–Pt–S(2)
Pt–N(1)–S(1)
N(1)–S(1)–N(2) 120.6(12)
S(1)–N(2)–S(2) 115.2(14)
90.5(5)
109.5(10)
88.5(3)
87.8(4)
115.0(7)
117.2(6)
116.6(7)
103.4(4)
88.78(15)
115.1(3)
116.7(3)
115.8(3)
103.60(18)
87.0(2)
87.6(5)
116.2(9)
116.0(9)
116.1(11)
104.0(7)
86.8(4)
113.5(7)
117.5(7)
113.7(8)
108.4(7)
114.6(6)
116.9(6)
116.3(6)
103.6(4)
115.6(4)
117.0(4)
115.6(5)
104.9(3)
N(2)–S(2)–Pt
103.3(9)
Figure 7. X-ray crystal structure of 1 showing twofold disorder
Figure 6. X-ray crystal structure of 6. The structures of 3–5 are not
illustrated as they are similar.
about the [S2N2]2– fragment.
ring were fairly consistent throughout and were comparable bond length decreases from 1.532(9)–1.480(7) Å with the
to previously reported examples. When compared to the PPh3 complex having the shortest N(1)–S(1) distance. Inter-
starting materials the bond angle P(1)–Pt–P(2) was ob- estingly, and perhaps counter-intuitively, the Pt–P distances
served to be smaller with a range of 96.18(11)–93.57(7) Å.
in 7–10 [in the range 2.214(2) Å and 2.3069(17) Å] also in-
The structures of the [SeSN2]2– complexes 7–10 (Table 4, crease as OMe is replaced by Ph for both Pt–P(1) and Pt–
Figure 9) also exhibit square-planar geometry about plati- P(2) (Figure 10).
num. Unlike the previously reported structure, none of the
In order to understand these apparent trends in bond
structures exhibit detectable disorder. Only 9 was observed lengths we performed DFT calculations on a range of com-
to be isomorphous (ie similar unit cell and crystal system) plexes. For compounds 4 and 7, the DFT-computed IR
to its [S2N2]2– analogue. Of the bonds within the ring those data are included in Table 2 for comparison. The computed
involving N(1) are most sensitive to the nature of the phos- harmonic frequencies are systematically larger than the ob-
phorus ligand. The Pt–N(1) bond lengths increases from served fundamentals (by typically 30–40 cm–1), but overall
2.041(9)–2.095(4) Å as the OMe groups are successively re- the observed patterns assigned to the metallacycle are rea-
placed by Ph groups ie the phosphane complex has the sonably well reproduced computationally. Since the
longest Pt–N(1) bond length. Concurrently, the N(1)–S(1) [S2N2]2– ligand often appears to be disordered we included
Eur. J. Inorg. Chem. 2010, 3185–3194
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J. D. Woollins et al.
FULL PAPER
Figure 10. Variation of Pt–P(A) and Pt–P(X) bond lengths in
[Pt(SeSN2){P(OMe)nPh3–n}2] complexes.
Figure 8. Variation of Pt–P(A) and Pt–P(X) bond lengths in
[Pt(S2N2){P(OMe)nPh3–n}2] complexes.
an example of the protonated system which appears more
well-behaved crystallographically. The results of the DFT
calculations are shown in Tables 3 and 4. It is striking that
these calculations, whilst fitting the protonated structures
well, do not mirror the observed trends in Pt–N and S–N
bond lengths. The DFT calculations suggest that the Pt–N
bond length is not significantly influenced by the nature
of the trans ligand in the compounds studied here. Quite
unusually, the DFT-optimised Pt–N distances are notice-
ably shorter than most of the X-ray data. For the model
system [Pt(S2N2)(PH3)2], PBE0-optimised distances agree
well with those obtained at the CCST(T) level, the “gold
standard” of ab initio quantum chemistry. There is thus no
evidence for a particular DFT problem with this kind of
bond.[29]
Figure 9. X-ray crystal structure of 9. The structures of 7, 8 and 10
are not illustrated as they are similar.
Table 4. Selected bond lengths [Å] and angles [°] for 7–10. Values printed in italics are DFT-calculated parameters.
7
8
9
10
Pt–N(1)
2.041(9)
2.025
2.065(4)
2.074(13)
2.095(4)
2.022
Pt–Se(1)
2.3874(11)
2.423
2.214(2)
2.240
2.243(2)
2.263
1.532(9)
1.562
1.571(7)
1.564
1.826(9)
1.838
94.83(9)
96.9
2.4099(5)
2.2266(13)
2.2480(14)
1.523(4)
2.3987(16)
2.2517(18)
2.2609(16)
1.496(15)
1.547(16)
1.858(15)
96.29(14)
2.3818(9)
2.421
2.2664(12)
2.295
2.3069(17)
2.338
1.480(7)
1.557
1.572(6)
1.565
1.819(5)
1.843
97.84(5)
100.5
Pt–P(1)
Pt–P(2)
N(1)–S(1)
S(1)–N(2)
N(2)–Se(1)
P(1)–Pt–P(2)
1.564(5)
1.858(4)
94.94(5)
P(2)–Pt–Se(1)
P(1)–Pt–N(1)
N(1)–Pt–Se(1)
Pt–N(1)–S(1)
N(1)–S(1)–N(2)
S(1)–N(2)–Se(1)
N(2)–Se(1)–Pt
174.37(3)
179.4(2)
88.0(2)
117.9(4)
118.4(4)
115.0(5)
100.7(2)
173.45(7)
173.80(11)
87.87(12)
117.8(2)
119.5(2)
114.8(2)
172.49(4)
175.32(16)
86.7(3)
119.1(7)
118.8(7)
115.1(8)
100.2(4)
170.74(3)
176.85(18)
86.31(18)
118.5(2)
118.9(2)
114.8(4)
101.5(2)
100.01(15)
3190
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 3185–3194

M-S-N Complexes
We considered that even a small component of disorder phosphorus ligand with a range of 94.83(9)° to 97.84(5)°
in eg the [SeSN2]2– could cause apparent lengthening of the increasing in the order 7 Ͻ 8 Ͻ 9 Ͻ 10. Similarly the N(1)–
Pt–N bond length and re-examined our crystal structures Pt–Se angles [which are comparable to the N(1)–Pt–S(2)
carefully for residual electron density peaks as well as look- angles of [Pt(S2N2){P(OMe)nPh3–n}2] complexes with a
ing carefully at the thermal parameters. We do not see any range of 86.31(18)° to 88.0(2)°] increase as the P(1)–Pt–P(2)
evidence of disorder.
bond angle decreases, again reflecting the increasing steric
The HOMO and LUMO of the Pt(SSeN2) fragment were bulk of the phosphorus ligands. At the PBE0 level, P–Pt–P
examined (Figures 11 and 12). On going from phosphane bond angles tend to be overestimated by up to ca. 2°, which
to phosphite ligands, the weaker σ-donor capability should for [Pt(S2N2)(PPh3)2] is remedied at the dispersion-cor-
result in shorter Pt–N and longer N(1)–S(1) bonds (as less rected B97-D level, where a P–Pt–P angle of 97.5° is ob-
electron density is donated into this LUMO). On the other tained, in excellent agreement with experiment.
hand, the HOMO has antibonding character for both
bonds. The stronger π-acceptor capability of phosphites
over phosphanes should thus produce shorter bonds (as
Conclusions
more electron density is removed from the HOMO).[30]
We have synthesised the series of complexes
[Pt(S2N2){P(OR)nRЈ3–n}2] and [Pt(SeSN2){P(OMe)n-
While no clear trend can be predicted for the N(1)–S(1)
distance on these grounds, the Pt–N bond should contract
with an increasing number of phosphites, in good apparent
agreement with the observed trend. So overall we can see
that the trends in bond lengths are not well supported by
the DFT calculations though empirical arguments based on
the LUMO may be used to rationalise the trends. We can-
not judge if the difficulties here are a consequence of experi-
mental or computational difficulties.
Ph3–n}2] (n = 0–3) by straightforward and relatively low-
hazard routes in liquid ammonia. In common with other
S/Se-N systems the bonding in these complexes proves to
be difficult to rationalise in detail. Whilst there appear to
be structural trends, particularly in the selenium containing
systems, these are not well modelled by the DFT calcula-
tions and further detailed work may be needed to under-
stand the differences between experiment and calculations
in these systems.
Experimental Section
General: Unless otherwise stated all manipulations were performed
under an oxygen-free nitrogen atmosphere, using standard Schlenk
techniques and glassware. Solvents were dried and stored according
to common procedures. Reagents were obtained from Aldrich and
used without further purification, Solution state NMR spectra
were recorded using a JEOL GSX Delta 270. Microanalyses were
performed by the University of St. Andrews microanalysis service.
The compound [S4N3]Cl was prepared by standard methods.[31] cis-
Figure 11. Backbonding from Pt to the π* orbital on N in the
metallacycles studied here.
[PtCl2{P(OR)nRЈ3–n}2] {(P(OR)nRЈ3–n 2 = P(OPh)3, P(OnBu)3,
)
P(OEt)3, P(OMe)3, P(OMe)2Ph or P(OMe)Ph2} were prepared
from [PtCl2(cyclo-octa-1,5-diene)][32] and two equivalents of the
phosphite, phosphonite or phosphinite in dichloromethane. cis-
[PtCl2(PPh3)2] was prepared via reaction of K2[PtCl4] in water and
with PPh3 in ethanol.[33] All compounds were characterised using
31P NMR spectroscopy. Low solubility and sample size prevented
measurement of 77Se NMR spectroscopy.
Figure 12. Frontier molecular orbitals of the Pt(S2N2) fragment (in
the geometry of the PMe3 complex, PBE0/ECP1 level).
CAUTION: Reactions involving S-N compounds may generate ex-
plosive S4N4. S4N4 explodes upon mechanical or heat shock. Its
explosiveness increases with the purity of the substance. Kevlar
gloves and visor should be used when manipulating S4N4. Residues
of S4N4 were disposed of by decomposition with aqueous NaOH.
The variation in Pt–P bond length can be correlated with
1
the decreasing magnitude of JPt,P, which is itself a crude
measure of bond strength. The remaining three bonds in
the metallacycle appear less sensitive to the phosphorus li-
gand and do not exhibit any distinguishable trend [S(1)–
N(2) range 1.547(16)–1.572(6) Å and N(2)–Se(1) range
1.819(5)–1.858(15) Å]. The Pt–Se bond lengths are in the
range 2.3818(9)–2.4099(5) Å.
Preparation of Disulfur Dinitrido Complexes [Pt(S2N2){P(OR)n-
RЈ3–n}2] {PR3 = P(OMe)3, P(OMe)2Ph, P(OMe)Ph2, P(OPh)3,
P(OnBu)3 or P(OEt)3}: In a typical reaction, liquid ammonia
(30 mL) was condensed using a condenser filled with dry ice and
acetone into a Schlenk tube in a dry ice/acetone bath. To this [S4N3]
Cl (0.78 mmol) was added to produce a dark red solution. After
stirring for 30 min [PtCl2{P(OR)nRЈ3–n}2] (0.5 mmol) was added.
Over the course of one hour the solution lightened to a pale orange
When compared to the [S2N2]2– analogues the P(1)–Pt–
P(2) bond angles in the mixed-chalcogen complexes are ob-
served to be similar and influenced by the steric bulk of the colour. After stirring the reaction mixture at –78 °C for 3 h the
Eur. J. Inorg. Chem. 2010, 3185–3194
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3191

J. D. Woollins et al.
FULL PAPER
solution was warmed to room temp. and the ammonia was evapo-
rated under a stream of nitrogen. The resulting pale orange residue
was dried in vacuo then dissolved in dichloromethane (10 mL) and
filtered through celite. The product was precipitated via slow ad-
dition of hexane. Isolated yields were 30–65%. Attempts to isolate
[Pt(S2N2) {P(OnBu)3}2] gave only oils. Crystals suitable for X-ray
crystallography were grown by slow diffusion of hexane into a solu-
tion of the complex in dichloromethane.
residue was dried in vacuo then dissolved in dichloromethane
(10 mL) and filtered through celite. The product was precipitated
via slow addition of hexane; isolated yields were 50–75%.
Crystals suitable for X-ray crystallography were grown by slow dif-
fusion of hexane into a solution of the complex in dichlorometh-
ane.
Crystallography
Crystal structure data were collected for 1, 4, 5 and 6 at 93 K on
a Rigaku MM007 confocal optics/Saturn CCD diffractometer
using Mo-Kα radiation (λ = 0.71073 Å), for 3, 7, 8, 9 and 10 at
125 K using a Rigaku SCX-Mini. All data was corrected for ab-
sorption. The structures were solved by direct methods and refined
by full-matrix least-squares methods on F2 values of all data.[34]
Refinements were performed using SHELXL.[35]
Preparation of Monoselenium Monosulfur Dinitrido Complexes
[Pt(SeSN2){P(OMe)nPh3–n}2] (n = 0–3): In a typical reaction liquid
ammonia (30 mL) was condensed using a condenser filled with dry
ice and acetone into a Schlenk tube in a dry ice/acetone bath. To
this [S4N3]Cl (0.78 mmol) and SeCl4 (3.9 mmol) were added to pro-
duce a dark red solution. Over the course of 30 min the solution
became pale orange in colour. [PtCl2{P(OMe)nPh3–n}2] (0.5 mmol)
was then added. After stirring the reaction mixture at –78 °C for
3 h the solution was warmed to room temp. and the ammonia was
evaporated under a stream of nitrogen. The resulting dark brown
CCDC-755579(for 1), -755580 (for 3), -755581 (for 4), -755582 (for
5), -755583 (for 6, Table 5), -766913 (for 7), -766914 (for 8), -766915
(for 9), -766916 (for 10, Table 6) contain the supplementary crystal-
Table 5. Experimental and refinement details for the X-ray structures of 1 and 3–6.
1
3
4
5
6
Fw
M
[C12H18N2O6P2PtS2] [C36H30N2O6P2PtS2] [C6H18N2O6P2PtS2] [C16H22N2O4P2PtS2] [C26H26N2O2P2PtS2]
619.54
907.77
125
535.37
93
627.51
93
719.64
93
Temperature /K
93
Crystal system
Space group
a /Å
b /Å
c /Å
α /°
β /°
monoclinic
P21/c
8.900(4)
13.719(10)
18.519(13)
90
101.345(11)
90
2217(3)
4
triclinic
P1
monoclinic
P2(1)
8.299(4)
6.783(3)
14.587(6)
90
101.864
90
803.7(6)
2
monoclinic
P21/c
19.622(2)
13.4726(11)
18.8268
90
117.33(3)
90
4421.6(14)
8
orthorhombic
P2(1)2(1)2(1)
10.2231(11)
14.6259(16)
17.7113(19)
90
90
90
2648.2(5)
4
5.604
¯
10.8476(13)
13.2659(15)
13.4783(16)
78.290(3)
78.106(3)
67.963(3)
1742.3(4)
2
γ /°
V /Å3
Z
µ(Mo-Kα) /mm–1
6.689
1.856
4.288
1.730
9.207
2.212
6.704
1.885
Dc /Mgm–3
1.805
Independent reflections (Rint
Max. and min. transmission
Final R,RЈ
)
4006 (0.1219)
0.792, 1.000
0.0449, 0.1024
6341 (0.1000)
0.414, 1.000
0.0783, 0.1748
3.091/–2.635
2882 (0.0490)
0.740, 1.000
0.0418, 0.0997
2.049/–1.099
8052 (0.0455)
0.696, 1.000
0.0353, 0.0842
3.854/–1.439
4803 (0.1261)
0.971, 1.000
0.0442, 0.1105
1.394/–1.725
Largest difference peak/hole /eÅ–3 2.591/–1.418
Table 6. Experimental and refinement details for the X-ray structures of 7–10.
7
8
9
10·2H2O
Fw
M
[C6H18N2O6P2SSePt]
582.28
125
[C16H22N2O4P2SSePt]
674.42
125
[C26H26N2O2P2SSePt]
766.56
125
[C36H32N2O2P2SSePt]
894.73
125
Temperature /K
Crystal system
Space group
a /Å
b /Å
c /Å
α /°
β /°
monoclinic
P21/c
15.1888(8)
6.8320(4)
16.4967(9)
90
109.6816(13)
90
1611.85(15)
4
monoclinic
P21/n
9.0315(3)
17.8064(5)
13.5320(4)
90
102.6458(9)
90
2123.41(11)
4
orthorhombic
P2(1)2(1)2(1)
10.1701(4)
14.7525(5)
18.0251(6)
90
triclinic
P1
¯
11.3630(4)
12.1702(5)
16.5588(7)
93.4760(10)
108.3000(10)
113.4650(10)
1948.47(13)
2
90
90
γ /°
V /Å3
2704.39(17)
4
6.736
Z
µ(Mo-Kα) /mm–1
11.276
2.399
8.569
2.109
4.687
1.525
Dc /Mgm–3
1.883
Independent reflections (Rint
Max. and min. transmission
Final R,RЈ
)
13159 (0.102)
0.2353, 0.0930
0.0416, 0.1062
22112 (0.063)
0.4253, 0.1895
0.0326, 0.0619
1.51/–1.24
23268 (0.064)
0.3451, 0.1636
0.0311, 0.0648
1.50/–0.74
16900 (0.043)
0.4111, 0.2066
0.0502, 0.1545
2.76/–1.27
Largest difference peak/hole /eÅ–3 3.32/–2.19
3192
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 3185–3194

M-S-N Complexes
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lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Computational Details
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Geometries were fully optimised at the PBE0/ECP1 level, i.e. em-
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Dresden relativistic effective core potential (SDD ECP) along with
its [6s5p3d] valence basis on Pt,[37] Binning and Curtiss’ 962(d) ba-
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tion of bond lengths between third-row transition metals and their
ligands.[40] For [Pt(S2N2)(PMe3)2], reoptimisation with the larger
TZVP basis[41] (including the 6s4p3d1f valence basis[42] for the
SDD ECP) afforded only minor changes in the Pt ligand and S–
N bond lengths (typically less than 1 pm). [Pt(S2N2)(PH3)2] was
reoptimised at the CCSD(T)/TZVP level, imposing Cs symmetry
(the minimum character of which had been confirmed by a fre-
quency calculation at the PBE0/ECP1 level). Finally, some explor-
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had been shown to be beneficial for the description of metal-phos-
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Eur. J. Inorg. Chem. 2010, 3185–3194