Ligand functionalization, reactivity, and transformation at the selenide centers of [Pt2(μ-Se)2(PPh3)4] with organic halides

Article abstract of DOI:10.1021/om020114e

The selenium centers of [Pt₂(μ-Se)₂(PPh₃)₄] are subject to electrophilic attack from various organic halides. Reactions with Mel, n-BuCl, α,α′-dichloro-p-xylene, and α,α′-dichloro-o-xylene give [Pt₂(μ-Se)(μ-SeMe)(PPh₃)₄]⁺, [Pt₂(μ-Se)(μ-SeBu)(PPh₃)₄]⁺, [Pt₂(μ-Se)(μ-SeCH₂C₆H₄CH₂ Cl)(PPh₃)₄]⁺, and [Pt₂(μ-SeCH₂C₆H₄CH₂Se) (PPh₃)₄]²⁺, respectively, preserving the dinuclear core and giving rise to new selenium-derivatized ligand complexes. Reaction with oxalyl chloride gives [Pt(η²-Se₂C₂O₂-Se,Se′)(PPh ₃)₂], leading to the disintegration of the core to a mononuclear complex supported by a new chelating selenium donor ligand. Reactions with malonyl chloride and succinyl chloride give [(COCH₂COCl)Se]₂ and [(COCH₂CH₂COCl)Se]₂ respectively, leading to complex disintegration and liberation of new selenium materials. The crystal structures of the aggregates [Pt₂(μ-Se)(μ-SeMe)(PPh₃)₄][PF₆ ], [Pt₂(μ₃-Se)₂(PPh₃)₄(CH ₂C₆H₄CH₂)][PF₆]_1.25 [Cl]_0.75, and [Pt(η²-Se₂C₂O₂-Se,Se′)(PPh ₃)₂] are described. The potential of using [Pt₂(μ-Se)₂(PPh₃)₄] as a source for metal-assisted synthesis of new and unusual organoselenium compounds is discussed.

Full text of DOI:10.1021/om020114e

2944
Organometallics 2002, 21, 2944-2949
Liga n d F u n ction a liza tion , Rea ctivity, a n d
Tr a n sfor m a tion a t th e Selen id e Cen ter s of
[P t2(µ-Se)2(P P h 3)4] w ith Or ga n ic Ha lid es
J eremy S. L. Yeo,† J agadese J . Vittal,† William Henderson,‡ and
T. S. Andy Hor*,†
Departments of Chemistry, National University of Singapore, 3 Science Drive 3,
Singapore 117543, and University of Waikato, Private Bag 3105, Hamilton, New Zealand
Received February 13, 2002
The selenium centers of [Pt2(µ-Se)2(PPh3)4] are subject to electrophilic attack from various
organic halides. Reactions with MeI, n-BuCl, R,R′-dichloro-p-xylene, and R,R′-dichloro-o-xylene
give [Pt2(µ-Se)(µ-SeMe)(PPh3)4]+, [Pt2(µ-Se)(µ-SeBu)(PPh3)4]+, [Pt2(µ-Se)(µ-SeCH2C6H4CH2-
Cl)(PPh3)4]+, and [Pt2(µ-SeCH2C6H4CH2Se)(PPh3)4]2+, respectively, preserving the dinuclear
core and giving rise to new selenium-derivatized ligand complexes. Reaction with oxalyl
chloride gives [Pt(η2-Se2C2O2-Se,Se′)(PPh3)2], leading to the disintegration of the core to a
mononuclear complex supported by a new chelating selenium donor ligand. Reactions with
malonyl chloride and succinyl chloride give [(COCH2COCl)Se]2 and [(COCH2CH2COCl)Se]2
respectively, leading to complex disintegration and liberation of new selenium materials.
The crystal structures of the aggregates [Pt2(µ-Se)(µ-SeMe)(PPh3)4][PF6], [Pt2(µ3-Se)2(PPh3)4-
(CH2C6H4CH2)][PF6]1.25[Cl]0.75, and [Pt(η2-Se2C2O2-Se,Se′)(PPh3)2] are described. The potential
of using [Pt2(µ-Se)2(PPh3)4] as a source for metal-assisted synthesis of new and unusual
organoselenium compounds is discussed.
In tr od u ction
Organoselenide chemistry has attracted considerable
attention, primarily because of the biomedicinal,1 cata-
lytic,2 and conducting3 properties of the compounds.
These applications provide a platform for the syntheses
of various organoselenium and inorganic selenide sub-
stances. Relatively little, however, is known about the
behavior of coordinated selenide. This is hardly surpris-
ing, since most of the selenides are in a µ3 capping state,
which is not particularly nucleophilic or electrophilic,
acidic or basic, or oxidizing or reducing; hence, they are
stable and inert. Although ligand functionalization and
transformation remains a fascinating prospect for co-
ordinated selenides, in terms of understanding their
chemical and electronic behavior as well as a potentially
new source of organoselenides, there is a serious lack
of suitable models for such study. This work attempts
to address this problem. Using [Pt2(µ-Se)2(PPh3)4]4 (1)
as a model substrate, and taking advantage of the
nucleophilic and basic nature of a µ2 bridging selenide,
we hereby demonstrate a number of possibilities to
activate selenide using common organic halides. In
doing so, we assembled a range of new organoselenide
ligands that could have a significant bearing on our
ultimate goal of metal-assisted syntheses of new orga-
noselenium materials.5
Resu lts a n d Discu ssion
(I) Rea ctivity of [P t2(µ-Se)2(P P h 3)4] w ith Or ga -
n oh a lid es. We, together with other groups, have dis-
cussed the complicated nature of a seemingly straight-
forward alkylation of the sulfide analogue of 1: viz.,
[Pt2(µ-S)2(PPh3)4].6 Notably, alkylation by CH3I, giving
[Pt2(µ-S)(µ-SMe)(PPh3)4]I,7 was initially misidentified
as the doubly alkylated, dicationic [Pt2(µ-SMe)2(PPh3)4]-
I2.8 The latter complex thus far has eluded isolation,
although it remains the most likely intermediate en
* To whom correspondence should be addressed. Tel:
(65) 6874 2658/9; Fax: (65) 6779 1691. E-mail: andyhor@nus.edu.sg.
† National University of Singapore.
‡ University of Waikato.
(1) Scott, M. L.; Martin, J . L.; Shapiro, J . R.; Klayman, D. L.; Shrift,
A. Organic Selenium Compounds: Their Chemistry and Biology; Wiley-
Interscience: New York, 1973; Chapter 13, p 629. Lim, B. S.; Willer,
M. W.; Miao, M.; Holm, R. H. J . Am. Chem. Soc. 2001, 123, 8343. Sung,
K.-M.; Holm, R. H. Inorg. Chem. 2001, 40, 4518. Bray, R. C.; Adams,
B.; Smith, A. T.; Bennett, B.; Bailey, S. Biochemistry 2000, 39, 11258.
(2) Wang, K.; Stiefel, E. I. Science 2001, 291, 106. Kunkely, H.;
Vogler, A. Inorg. Chim. Acta 2001, 319, 183.
(4) Bencini, A.; Vaira, M. D.; Morassi, R.; Stoppioni, P. Polyhedron
1996, 15, 2079.
(5) Yeo, J . S. L.; Vittal, J . J .; Hor, T. S. A. Chem. Commun.,
submitted for publication.
(6) Fong, S.-W. A.; Hor, T. S. A. J . Chem. Soc., Dalton Trans. 1999,
639.
(3) Kobayashi, N.; Naito, T.; Inabe, T. Synth. Met. 2001, 120, 1055.
Kato, R.; Fujiwara, M.; Kashimura, Y.; Yamaura, J . Synth. Met. 2001,
120, 675. Batsanov, A. S.; Bryce, M. R.; Dhindsa, A. S.; Howard, J . A.
K.; Underhill, A. E. Polyhedron 2001, 20, 537.
(7) Briant, C. E.; Gardner, C. J .; Hor, T. S. A.; Howells, N. D.;
Mingos, D. M. P. J . Chem. Soc., Dalton Trans. 1984, 2645.
(8) Ugo, R.; La Monica, G.; Cenini, S.; Segre, A.; Conti, F. J . Chem.
Soc. A 1971, 522.
10.1021/om020114e CCC: $22.00 © 2002 American Chemical Society
Publication on Web 06/01/2002

Reactions of [Pt2(µ-Se)2(PPh3)4] with Organic Halides
Organometallics, Vol. 21, No. 14, 2002 2945
monocationic products [Pt2(µ-Se)(µ-SeBu)(PPh3)4][PF6]
(3) and [Pt2(µ-Se)(µ-SeCH2C6H4CH2Cl)(PPh3)4][PF6] (4),
whose NMR spectral features are similar.
F igu r e 1. ORTEP plot of the cation of the molecular
structure of [Pt2(µ-Se)(µ-SeMe)(PPh3)4][PF6] (2) with 50%
probability thermal ellipsoids. The phenyl rings are omitted
for clarity.
route to other thiolato-type decomposition products.
Similar decomposition in CH2Cl2 has been reported for
1, giving [Pt(η2-Se2CH2)(PPh3)2] and [PtCl2(PPh3)2].9 To
date, almost all double-alkylated derivatives of both
sulfide and selenide products have eluded isolation. The
reason for their instability remains a mystery. We
therefore decided to use organic dihalides to function-
alize the two selenide centers and, in doing so, stabilize
the dication product. We also continue our use of
ESMS10 to study species formed in situ in solution.
Excess MeI on 1 in Et2O gave a yellow precipitate that
can be metathesized with NH4PF6. Positive ion ESMS
analysis of the isolated product in CH2Cl2/MeOH showed
a peak at m/z 1612 corresponding to the expected [Pt2-
(µ-Se)(µ-SeMe)(PPh3)4][PF6] (2). Its 31P{1H} NMR spec-
Interestingly, when the reaction between 1 and MeI
was carried out in MeOH, it gave rise to a yellow
solution from which a yellow precipitate could be
isolated upon metathesis with NH4PF6. ESMS analysis
of this product in CH2Cl2/MeOH showed a peak at m/z
814 corresponding to [Pt2(µ-SeMe)2(PPh3)4]2+, along with
a few unidentified peaks. This was the first evidence
for dialkylation of this series of compounds. Its 31P{1H}
NMR spectrum gives a singlet at 18.4 ppm with the
associated satellites (1J (P-Pt) ) 2979 Hz), consistent
with the equivalent phosphines expected in [Pt2(µ-
SeMe)2(PPh3)4][PF6]2, and a few other signals similar
to those of the decomposition products of [Pt2(µ-Se)2-
(PPh3)4] in CDCl3. There is, however, no evidence for 2.
Attempts to obtain suitable crystals of the salts of [Pt2-
(µ-SeMe)2(PPh3)4]2+ for structural analysis were unsuc-
cessful due to rapid loss of solvate.
In an attempt to alkylate both selenido centers of 1
and to give stable/isolable products, we use a substrate
that is structurally conducive to crossing both selenium
atoms: viz., R,R′-dichloro-o-xylene. Single-crystal X-ray
analysis of the product confirmed the overhead-bridged
diplatinum selenolato dication [Pt2(µ-SeCH2C6H4CH2-
Se)(PPh3)4]2+ (5) (Figure 2), with 1.25 PF6- and 0.75 Cl-
trum is in agreement with AA′BB′X and AA′BB′XX′ spin
systems that can be approximated to an ABX first-order
pattern, because the long-range Pt-P and P-P coupling
constants are similar to the line widths of the main
resonances. The derivation of such spectra has been
described.7,11 A single-crystal X-ray structural analysis
of 2 revealed a diplatinum structure bridged by selenido
and methylselenato ligands (Figure 1, Tables 1 and 2).
The {Pt2Se2} core is slightly bent with a dihedral angle
(133.6°) significantly larger than that in [Pt2(µ-SeH)2-
(PPh3)4][PF6]2 (71.9°).12 These are in contrast with the
planar structure found in [Pt2Cl2(µ-SeEt)2(PEt3)2].13
The use of bulkier or difunctional halides, viz. 1-chlo-
robutane and R,R′-dichloro-p-xylene, also afforded the
(9) Khanna, P. K.; Morley, C. P.; Hursthouse, M. B.; Malik, K. M.
A.; Howarth, O. W. Heteroat. Chem. 1995, 6, 519.
(10) Fong, S.-W. A.; Vittal, J . J .; Henderson, W.; Hor, T. S. A.; Oliver,
A. G.; Rickard, C. E. F. Chem. Commun. 2001, 421.
(11) Hor, T. S. A. D. Philos. Thesis, University of Oxford, 1983. Yeo,
J . S. L. D. Philos. Thesis, National University of Singapore, 2001.
(12) Yeo, J . S. L.; Vittal, J . J .; Henderson, W.; Hor, T. S. A. J . Chem.
Soc., Dalton Trans. 2002, 328.
counteranions resulting from incomplete metathesis. As
a result, the two selenide ligands have been transformed
into a new R,R′-diselenato-o-xylene. This is the first
structural representation of a [Pt2(SeR)2P4] framework
in this series. It also marks a potentially simple metal-
assisted process to synthesize (HSeCH2)2C6H4, thus
(13) J ain, V. K.; Kannan, S.; Butcher, R. J .; J asinski, J . P.
Polyhedron 1995, 14, 3641.

2946 Organometallics, Vol. 21, No. 14, 2002
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p ou n d s 2, 5, a n d 6
Yeo et al.
2
5‚2H2O
6
formula
fw
cryst size (mm)
cryst syst
space group
a/Å
C
73H63F6Se2P5Pt2
C80H72Cl0.75F7.5O2Se2P5.25Pt2
C38H30O2Se2P2Pt
933.57
1757.18
0.34 × 0.22 × 0.04
monoclinic
P2/n
1945.31
0.20 × 0.18 × 0.14
monoclinic
C2/m
26.45(8)
23.71(6)
16.78(4)
90
127.86(7)
90
8304(38)
4
4.429
223(2)
1.30-25.00
-31 < h < 31
-28 < k < 28
-19 < l < 19
34 436
5438
7512
0.0515
0.1388
0.20 × 0.16 × 0.06
triclinic
P1h
18.1509(17)
10.3548(10)
18.3932(16)
90
107.029(2)
90
3305.4(5)
2
5.510
223(2)
1.97-30.01
-25 < h < 24
-14 < k < 14
-13 < l < 24
25 772
5769
9255
10.1941(6)
11.6717(6)
15.6797(8)
69.693(1)
85.515(1)
74.588(1)
1686.53(16)
2
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
µ/mm-1
T/K
6.446
223(2)
1.95-30.01
-14 < h < 14
-16 < k < 16
-22 < l < 22
26 263
8400
9793
0.0348
0.0631
θ range (deg)
index ranges
no. of rflns collected
no. of unique rflns
no. of obsd rflns (I > 2σ(I))
R1 (I > 2σ(I))
0.0499
0.0803
wR2 (all data)
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d s 2, 5, a n d 6
This form of ligand modification through dialkylation
of 1 by an organic dihalide can be extended to other
systems. For example, ESMS analysis of the reaction
2
5‚2H2O
6
Pt(1)-P(1)
Pt(1)-P(2)
Pt(1)-Se(1)
Pt(1)-Se(1A)
Pt(1A)-Se(1)
Pt(1A)-Se(1A)
Se(1)-C(1)
Se(1A)-C(2)
O(1)-C(1)
2.3011(18)
2.2890(17)
2.4623(7)
2.4827(7)
2.4827(7)
2.4623(7)
2.033(14)
2.291(6)
2.307(7)
2.465(6)
2.473(6)
2.473(6)
2.2877(8)
2.3030(9)
2.4458(4)
2.4611(4)
2.012(13)
1.905(4)
1.865(4)
1.214(4)
1.214(4)
1.535(5)
O(2)-C(2)
C(1)-C(2)
Pt(1)-Se(1)-Pt(1A)
Se(1)-Pt(1)-Se(1A)
P(1)-Pt(1)-P(2)
P(1)-Pt(1)-Se(1)
P(1)-Pt(1)-Se(1A)
P(2)-Pt(1)-Se(1)
P(2)-Pt(1)-Se(1A)
C(1)-Se(1)-Pt(1)
C(1)-Se(1)-Pt(1A)
88.26(2)
81.47(3)
97.42(6)
169.51(5)
88.06(3)
93.02(5)
174.31(5)
100.3(5)
100.1(4)
91.30(19)
81.2(2)
99.87(19)
91.5(2)
172.60(6)
167.53(7)
87.53(17)
104.3(4)
100.7(3)
88.329(13)
97.24(3)
91.66(2)
174.06(2)
170.78(2)
83.06(2)
105.10(12)
avoiding a process involving the noxious H2Se and
(ClCH2)2C6H4 in a cumbersome multistep synthesis. The
structure of 5 shows an interesting disorder of the xylyl
ring at the methylene groups across the {Se2C2} plane
(Figure 2b, Tables 1 and 2). This generates a 2-fold
symmetry with the C6 ring flipping from one end of the
molecule to the other divided by the {Se2C2} plane.
Accordingly, the 31P{1H} NMR spectrum also shows two
discrete resonances, corresponding to the phosphines at
the proximal and distal ends of the C6 ring. A low-
temperature study in CD2Cl2 (Figure 3) gave peak
broadening, beginning at ca. 253 K and resulting in a
featureless spectrum at 193 K. It possibly points to a
low-energy rocking process of the {Pt1 (or Pt1A)-Se1-
Se1A-C1-C1G-C2-C7} bicyclic ring. Apart from dif-
ferentiating the two proximal phosphines (P1A and
P2A) from the distal phosphines (P1 and P2), the slow
rocking motion would destroy the σ symmetry along the
Pt1Pt1A axis. These motions would collectively generate
four inequivalent phosphorus nuclei. This static state,
however, is not reached at the limit of the experiments
(193 K).
F igu r e 2. (a, top) ORTEP plot of the cation of the
molecular structure of [Pt2(µ3-Se)2(PPh3)4(CH2C6H4CH2)]-
[PF6]1.25[Cl]0.75 (5) with 50% probability thermal ellipsoids
Phenyl rings are omitted for clarity. (b, bottom) Structure
of compound 5, showing the disorder in the ring attached
to the {Pt2Se2} framework.

Reactions of [Pt2(µ-Se)2(PPh3)4] with Organic Halides
Organometallics, Vol. 21, No. 14, 2002 2947
F igu r e 3. VT 31P{1H} NMR spectra of compound 5 in CD2-
Cl2.
F igu r e 4. ORTEP plot of the molecular structure of [Pt-
(η2-Se2C2O2-Se,Se′)(PPh3)2] (6) with 50% probability ther-
mal ellipsoids.
mixtures of 1 and 1,3-dichloroacetone or 1,8-bis(bro-
momethyl)naphthalene also gave the analogous di-
cationic products. We have described earlier that this
use of ESMS can help us screen for positive reactions
and products and that, in many cases, successful hits
can be synthesized and isolated.14 We chose not to
pursue these substrates further, since the derivatives
are expected to behave similarly.
Sch em e 1. F or m a tion of
[P t(η2-Se2C2O2-Se,Se′)(P P h 3)2] (6) fr om 1 a n d Oxa lyl
Ch lor id e P ossibly th r ou gh a Dou ble-Alk yla tion
P r ocess
(II) Rea ctivity of [P t2(µ-Se)2(P P h 3)4] w ith Acid
Ch lor id es. We were interested in testing the reactivity
of selenide toward an sp2 carbon source. The use of a
non-hydrocarbon substrate was appealing, as we could
develop a new entry to other inorganic selenide materi-
als. Addition of oxalyl chloride to 1 in dry CH3CN
resulted in an instantaneous formation of an orange
suspension, which subsequently led to the isolation of
the new complex [Pt(η2-Se2C2O2-Se,Se′)(PPh3)2] (6). A
diselenooxalate.17 The proposed intermediate X could
not be detected or trapped, but liberation of PtCl2(PPh3)2
was easily verified by spectroscopic or chemical means.
Formation of 6 from 1 is driven by Se-C bond forma-
tion, which is related to S-C bond formation as in the
formation of Pt[S2(CR)2](PPh3)2 from PtS4(PPh3)2 and
RCCR.18 These are in contrast to the literature approach
to related [OC(R)dC(R′)Se]2- complexes through Se-C
bond cleavage, for example, of acyl-substituted di-
selenetanes.19 The other method that can be used is a
metal exchange, for example, between titanium maleate
and PtCl2(PPh3)2.20
We also examined other acid chloride substrates to
determine if the dinuclear disintegration and ligand
functionalization process can lead to any isolable orga-
noselenium residues. Reactions of 1 with malonyl or
succinyl chloride did not give the expected products [Pt-
(η2-Se2C2O2(CH2)n-Se,Se′)(PPh3)2], where n ) 1 (I), 2 (II).
Instead, they gave rise to an almost instantaneous
single-crystal X-ray crystallographic study revealed a
mononuclear square-planar Pt(II) complex with another
new ligandsdiselenooxalate serving as a chelate through
the selenium centers (Figure 4, Tables 1 and 2). This
breakup of the dinuclear structure (from 1 to 6) (Scheme
1) epitomizes the difficulty of dialkylation of [Pt2(µ-S)2-
(PPh3)4] without destroying the {Pt2S2} core, as de-
scribed earlier. It, however, turns a destructive process
to one that is potentially usefulsligand transformation
and metal-assisted assembly of a new selenium mate-
rial. This represents a facile entry to the rare 1,2-
diselenooxalate complexes,15 as compared to the rela-
tively common dithiooxalate complexes.16 To the best
of our knowledge, this is also the only entry through
ligand modification from selenide. This is significant,
since it avoids the laborious synthesis of potassium
(17) Matz, C.; Mattes, R. Z. Naturforsch., B 1978, 33, 461.
(18) Bolinger, C. M.; Rauchfuss, T. B. Inorg. Chem. 1982, 21, 3947.
(19) Yamazaki, S.; Deeming, A. J . Polyhedron 1996, 15, 1847.
Yamazaki, S. Chem. Lett. 1991, 1299. Yamazaki, S.; Ueno, T.; Hojo,
M. Bull. Chem. Soc. J pn. 1991, 64, 1404. Yamazaki, S.; Ama, T.; Hojo,
M.; Ueno, T. Bull. Chem. Soc. J pn. 1989, 62, 4036.
(14) Yeo, J . S. L.; Vittal, J . J .; Henderson, W.; Hor, T. S. A. J . Chem.
Soc., Dalton Trans. 2001, 315.
(15) Strauch, P.; Abram, S.; Drutkowski, U. Inorg. Chim. Acta 1998,
278, 118.
(16) Dietzsch, W.; Strauch, P.; Hoyer, E. Coord. Chem. Rev. 1992,
121, 43 and references within.
(20) Dudis, D. S.; King, C.; Fackler, J . P., J r. Inorg. Chim. Acta 1991,
181, 99.

2948 Organometallics, Vol. 21, No. 14, 2002
Yeo et al.
distribution patterns that were simulated using the ISOTOPE
program.22 The m/z values given are for the most intense peak
1
in the envelope in each case. H NMR and 13C NMR spectra
were recorded at 25 °C on a Bruker ACF 300 spectrometer (at
300 and 75.47 MHz, respectively) with Me4Si as internal
standard. The 31P NMR spectra were recorded at 121.39 MHz
with 85% H3PO4 as external reference. Infrared spectra were
recorded in the range 4000-400 cm-1, on a Perkin-Elmer FTIR
spectrometer. Elemental analyses were performed by the
microanalytical laboratory of the Department of Chemistry at
the National University of Singapore.
formation (at room temperature or -78 °C) of an orange-
brown solution in CH3CN. ESMS analysis of the malo-
nyl solution gave the dication {[(COCH2COCl)Se]2+-
2Na}2+ (m/z 207). The most likely source of Na+ is from
the solvent, as traces are often present in even HPLC-
grade solvents.21 The parent diselenium ligand, [(COCH2-
COCl)Se]2 (7), could be isolated in analytically pure
Ma ter ia ls. All substrates used for analysis were com-
mercially available from Aldrich. We have followed a modified
preparation of Pt2(µ-Se)2(PPh3)4 (1), which has been repeated.14
All reactions were performed under a positive pressure of
purified Ar, unless otherwise stated. Solvents were distilled
and degassed before use.
Syn th eses. [P t2(µ-Se)(µ-SeMe)(P P h 3)4][P F 6] (2). An ex-
cess of MeI (9.3 mg, 4.10 µL, 0.0656 mmol) was added to a
brown suspension of 1 (53.5 mg, 0.0335 mmol) in diethyl ether
(20 mL), and the mixture was stirred for 3 h. The resultant
yellow precipitate was filtered and redissolved in MeOH (15
mL). Excess NH4PF6 (10.0 mg, 0.0614 mol) was added. After
this mixture was stirred for 1 h, deionized water (50 mL) was
added to induce precipitation. The suspension was filtered and
the solid washed successively with 100 mL portions of deion-
ized water and Et2O and dried under vacuum, yielding a yellow
powder of 2 (0.0270 g, 46%). Anal. Found: C, 49.0; H, 3.4; P,
8.1. Calcd for C73H63F6Se2P5Pt2: C, 49.9; H, 3.6; P, 8.8. 31P-
{1H} NMR (CDCl3): δp 20.9 (m, 1J (P-Pt) ) 2686 Hz), 23.1
form. Similarly, the succinyl ion {[(COCH2CH2COCl)-
Se]2+Na}+ (m/z 419) was detected, which led to the
isolation of analytically and spectroscopically pure
[(COCH2CH2COCl)Se]2 (8). To our best of our knowl-
edge, these are hitherto unknown organoselenium ma-
terials.
1
1
ppm (m, J (P-Pt) ) 3241 Hz). H NMR (CDCl3): δH 1.21 (t,
3H, SeCH3), 6.92-7.41 ppm (m, 60H, 12C6H5). ESMS (MeCN-
H2O): m/z 1612 [M]+.
[P t2(µ-Se)(µ-SeBu )(P P h 3)4][P F 6] (3). Excess n-BuCl (7.1
mg, 9.0 µL, 0.0573 mmol) was added to a brown suspension of
1 (44.1 mg, 0.0276 mmol) in MeOH (20 mL). The resulting
yellow solution was stirred for 3 h, after which excess NH4-
PF6 (10.0 mg, 0.0614 mol) was added to give a yellow
suspension. After this mixture was stirred for 1 h, deionized
water (50 mL) was added to induce precipitation. The suspen-
sion was filtered and the solid washed successively with 100
mL portions of deionized water and Et2O and dried under
vacuum, yielding a yellow powder of 3 (0.0323 g, 65%). Anal.
Found: C, 50.0; H, 3.7; P, 8.1. Calcd for C76H69F6Se2P5Pt2: C,
Con clu sion
The high nucleophilicity of bridging selenide toward
various organic halides makes 1 a rare and valuable
precursor for complexes with unusual selenium-contain-
ing ligands and a potentially rich source of organose-
lenium substrates. There is virtually no limit on the
number of new materials that we can produce, since 1
is reactive essentially with all forms of haloorganics. The
question is the delicate control of the disintegration of
the dinuclear core, the stabilization of the mononuclear
complex, and its subsequent breakdown to liberate the
organoselenium residue. Our next target is to under-
stand the subtle balance of these sequential yet compet-
ing processes. Such an understanding is a prerequisite
for us to harness a complex disintegration process
whereby we can develop synthetically viable methods
for laboratory-scale preparation of materials that are
otherwise difficult to obtain.
1
50.7; H, 3.9; P, 8.6. 31P{1H} NMR (CDCl3): δp 20.0 (m, J (P-
1
1
Pt) ) 2699 Hz), 22.4 ppm (m, J (P-Pt) ) 3277 Hz). H NMR
(CDCl3): δH 0.67 (t, 3H, CH3), 0.84-0.89 (m, 4H, 2CH2), 1.20
(t, 2H, CH2), 7.08-7.41 ppm (m, 60H, 12C6H5). ESMS (MeCN-
H2O): m/z 1654 [M]+.
[P t2(µ-Se)(µ-SeCH2C6H4CH2Cl)(P P h 3)4][P F 6] (4). By a
procedure similar to that described for 3, R,R′-dichloro-p-xylene
(5.0 mg, 0.0286 mmol) and 1 (45.7 mg, 0.0286 mmol) gave a
yellow powder of 4 (0.0306 g, 57%). Anal. Found: C, 51.0; H,
3.5; P, 8.0. Calcd for C80H68F6ClSe2P5Pt2: C, 51.1; H, 3.6; P,
1
8.2. 31P{1H} NMR (CDCl3): δp 19.3 (m, J (P-Pt) ) 2663 Hz),
22.1 ppm (m, 1J (P-Pt) ) 3254 Hz). 1H NMR (CDCl3): δH 4.57
(m, 4H, 2CH2), 6.67-7.11 (m, 4H, C6H4), 7.31-7.77 (m, 60H,
12C6H5). ESMS (MeCN-H2O): m/z 1737 [M]+.
Exp er im en ta l Section
In str u m en ta tion . Samples for ESMS analysis were pre-
pared in 1 mL MeCN solutions of the analytes. Electrospray
mass spectra were obtained with a Finnigan/MAT TSQ 7000
mass spectrometer with the MeCN-H2O (50:50) mobile phase
driven at 0.03 mL min-1 using a Thermo Separation Products
SpectraSystem TSP4000 LC pump. Samples were injected via
a Rheodyne valve fitted with a 5 µL sample loop. The source
temperature was 200 °C. The capillary potential tip was 4500
V, with nitrogen used as both a drying and a nebulizing gas.
Peaks were assigned from the m/z values and from the isotope
[P t2(µ-SeCH2C6H4CH2Se)(P P h 3)4][P F 6]1.25[Cl]0.75 (5). By
a procedure similar to that described for 3, R,R′-dichloro-o-
xylene (17.9 mg, 0.1023 mmol) and 1 (161.4 mg, 0.1010 mmol)
gave an orange powder of 5 (0.1731 g, 90%). Anal. Found: C,
50.0; H, 3.6; P, 8.3. Calcd for C80H68Cl0.75F7.5Se2P5.25Pt2: C, 50.3;
1
H, 3.6; P, 8.5. 31P{1H} NMR (CDCl3): δp 15.1 (dt, J (P-Pt) )
3056, 2J (P-P) ) 19 Hz), 16.4 ppm (dt, 1J (P-Pt) ) 3016, 2J (P-
1
P) ) 15 Hz). H NMR (CDCl3): δH 4.11 (m, 4H, 2CH2), 6.70-
7.03 (m, 4H, C6H4), 7.18-7.53 (m, 60H, 12C6H5). ESMS
(MeCN-H2O): m/z 851 [M]2+
.
(21) Henderson, W.; Nicholson, B. K.; McCaffrey, L. J . Polyhedron
1998, 17, 4291.
(22) Arnold, L. J . J . Chem. Educ. 1992, 69, 811.

Reactions of [Pt2(µ-Se)2(PPh3)4] with Organic Halides
Organometallics, Vol. 21, No. 14, 2002 2949
[P t(η2-Se2C2O2-Se,Se′)(P P h 3)2] (6). An excess of oxalyl
chloride (34.4 mg, 50.00 µL, 0.2707 mmol) was added to a
brown suspension of 1 (321.5 mg, 0.2013 mmol) in MeCN (40
mL), which resulted an instantaneous formation of an orange
suspension. The mixture was filtered and the orange solid
collected and redissolved in CH2Cl2 (15 mL). n-Hexane (40 mL)
was added to induce precipitation. The suspension was filtered
and the solid washed successively with 100 mL of Et2O and
dried under vacuum, yielding an orange powder of 6 (0.1743
g, 93%). Anal. Found: C, 48.7; H, 3.2; P, 6.3. Calcd for
diffractometer, equipped with a CCD area detector using Mo
KR radiation (λ ) 0.710 73 Å). The software SMART23 was
used for collecting frames of data, indexing reflections, and
determining lattice parameters, SAINT23 for integration of
intensity of reflections and scaling, SADABS24 for empirical
absorption correction, and SHELXTL25 for space group and
structure determination, refinements, graphics, and structure
reporting. Hydrogen atoms were not located. The structures
were refined by full-matrix least squares on F2 with anisotropic
thermal parameters for non-hydrogen atoms, unless otherwise
2
C
38H30O2Se2P2Pt: C, 48.9; H, 3.2; P, 6.6%. 31P{1H} NMR
indicated (R1 ) ∑||Fo| - |Fc||/∑|Fo|, and wR2 ) {∑[w(Fo
-
(CDCl3): δp 16.1 ppm (s, 1J (P-Pt) ) 3109 Hz). 1H NMR
(CDCl3): δH 6.91-7.42 ppm (m, 30H, 6C6H5). ESMS (MeCN-
Fc2)2]/∑[w(Fo2)2]}1/2 (where w-1 ) σ2(Fo2) + (aP)2 + bP)). A
summary of parameters for the data collections and refine-
ments is given in Table 1.
H2O): m/z 957 [M+Na]+. IR (ν(CO), in CH2Cl2): 1632 cm-1
.
Suitable single crystals of [Pt2(µ-Se)(µ-SeMe)(PPh3)4][PF6]
(2), [Pt2(µ-SeCH2C6H4CH2Se)(PPh3)4][PF6]1.25[Cl]0.75 (5), and
[Pt(η2-Se2C2O2-Se,Se′)(PPh3)2] (6) for structure determination
were obtained by layering a CH2Cl2 solution of each compound
with hexane. For compound 5, the xylene ring attached to 1
is disordered. Only isotropic thermal parameters were refined
for the C atoms of phenyl ring D. The positions of Cl and O of
water were very severely disordered (Cl in four places and O
in seven places). The C atoms of phenyl rings show highly
anisotropic thermal parameters in general.
[(COCH2COCl)Se]2 (7). An excess of malonyl chloride (11.4
mg, 55.78 µL, 0.0809 mmol) was added to a brown suspension
of 1 (90.5 mg, 0.0567 mmol) in MeCN (40 mL). The resulting
orange-brown solution was filtered and the filtrate reduced
to dryness under vacuum. The orange oil obtained was
extracted with benzene, and subsequent careful solvent re-
moval of the extract under vacuum afforded a white solid. The
solid was dried under vacuum, yielding a white powder of 7
(0.0069 g, 33%). 1H NMR (CDCl3): δH 2.07 ppm (s, 4H, 2CH2).
13C NMR (CDCl3): δC 62.8 (2C, 2CH2), 173.8 ppm (4C, 4CO).
ESMS (MeCN-H2O): m/z 207 [M + 2Na]2+. IR (ν(CO), in CH2-
Cl2): 1601 cm-1
.
Ack n ow led gm en t. We acknowledge the National
University of Singapore (NUS) for support, and J .S.L.Y.
thanks the NUS for a research scholarship and for
attachment to the University of Waikato. W.H. thanks
the University of Waikato and the New Zealand Lottery
Grants Board for financial assistance and J ohnson
Matthey plc for a generous loan of platinum. We thank
G. K. Tan for her assistance in X-ray analysis.
[(COCH2CH2COCl)Se]2 (8). Following a procedure similar
to that described for 7, succinyl chloride (7.2 mg, 33.02 µL,
0.0465 mmol) and 1 (46.6 mg, 0.0292 mmol) gave a white
1
powder of 8 (0.0069 g, 60%). H NMR (CDCl3): δH 1.93 ppm
(s, 8H, 4CH2). 13C NMR (CDCl3): δC 40.5 (4C, 4CH2), 173.5
ppm (4C, 4CO). ESMS (MeCN-H2O): m/z 419 [M + Na]+. IR
(ν(CO), in CH2Cl2): 1605 cm-1
.
Cr ysta l Str u ctu r e Deter m in a tion a n d Refin em en t. The
data collection was performed on a Bruker AXS SMART
Su p p or tin g In for m a tion Ava ila ble: Data in CIF format,
showing details of the crystal structure determinations, atom
coordinates, equivalent isotropic displacement factors, bond
lengths and angles, and hydrogen coordinates for compounds
2, 5, and 6. This material is available free of charge via the
Internet at http://pubs.acs.org.
(23) SMART & SAINT Software Reference Manuals, version 4.0;
Siemens Energy & Automation, Inc., Analytical Instrumentation:
Madison, WI, 1996.
(24) Sheldrick, G. M. SADABS, Software for Empirical Absorption
Correction; University of Go¨ttingen, Go¨ttingen, Germany, 1993.
(25) Sheldrick, G. M. SHELXTL, version 5.03; Siemens Energy &
Automation, Inc., Analytical Instrumentation, Madison, WI, 1996.
OM020114E