Platinum(II) complexes of 2-(dimethylamino)ethylselenolate - Donor-acceptor inter-ligand interactions as evident from experimental and TD-DFT computational analysis

Article abstract of DOI:10.1002/1099-0682(200111)2001:11<2965::AID-EJIC2965>3.0.CO;2-7

Several platinum(II) complexes of 2-(dimethylamino)ethaneselenolate with the formulae, [PtCl(SeCH₂CH₂NMe₂)(PR₃)] (1), [PtPh(SeCH₂CH₂NMe₂)(PnBu₃)] (2), [Pt₂Ph₂(Cl)(SeCH₂-CH₂NMe ₂)(PnBu₃)₂] (3), [Pt₂Cl₃(SeCH₂CH₂NMe ₂)(PR₃)₂] (4), [Pt (SeCH₂CH₂NMe₂)₂(P-P)] (5), [Pt₂(SeCH₂CH₂NMe₂)₂- (P-P)₂]⁺⁺ (6), and [Pt(SeCH₂CH₂NMe₂)(PPh₃)] _n[PF₆]_n (7) have been synthesized and characterized by elemental analysis, UV/Vis and NMR (¹H, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectroscopy. The stereochemistry of these complexes (1-7) has been deduced from NMR spectroscopic data. A weak absorption in the UV/Vis spectrum of 1 has been assigned to a ligand (Se)-to-ligand (PR3) charge transfer (LLCT), supported by TD-DFT calculations. The structures of [PtCl(SeCH₂CH₂NMe₂)(PPh₃)] and [Pt₂Ph₂(Cl)(SeCH₂CH₂NMe ₂)(PnBu₃)₂] have been established by single crystal X-ray diffraction analysis. Each platinum atom in the latter is coordinated to four different ligands and Me₂NCH₂CH₂Se behaves as μ₂-bridging and is also simultaneously chelated to one of the platinum atoms.

Full text of DOI:10.1002/1099-0682(200111)2001:11<2965::AID-EJIC2965>3.0.CO;2-7

FULL PAPER
Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate ؊
Donor؊Acceptor Inter-Ligand Interactions as Evident from Experimental and
TD-DFT Computational Analysis
Sandip Dey,[a] Vimal K. Jain,*[a] Axel Knoedler,[b] Wolfgang Kaim,[b] and Stanislav Zalis[c]
Keywords: Platinum / Selenium / NMR spectroscopy / Density functional calculations
Several platinum(II) complexes of 2-(dimethylamino)ethane- from NMR spectroscopic data. A weak absorption in the UV/
selenolate with the formulae, [PtCl(SeCH2CH2NMe2)(PR3)]
(1), [PtPh(SeCH2CH2NMe2)(PnBu3)] (2), [Pt2Ph2(Cl)(SeCH2-
CH2NMe2)(PnBu3)2] (3), [Pt2Cl3(SeCH2CH2NMe2)(PR3)2] (4),
[Pt(SeCH2CH2NMe2)2(P−P)] (5), [Pt2(SeCH2CH2NMe2)2-
(P−P)2]++ (6), and [Pt(SeCH2CH2NMe2)(PPh3)]n[PF6]n (7) have
Vis spectrum of 1 has been assigned to a ligand (Se)-to-li-
gand (PR3) charge transfer (LLCT), supported by TD-DFT
calculations. The structures of [PtCl(SeCH2CH2NMe2)(PPh3)]
and [Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)2] have been estab-
lished by single crystal X-ray diffraction analysis. Each plat-
been synthesized and characterized by elemental analysis, inum atom in the latter is coordinated to four different li-
UV/Vis and NMR (1H, 31P, 77Se, 195Pt) spectroscopy. The ste- gands and Me2NCH2CH2Se behaves as µ2-bridging and is
reochemistry of these complexes (1−7) has been deduced
also simultaneously chelated to one of the platinum atoms.
Introduction
Results and Discussion
Synthesis and Spectroscopy
Platinum group metal chalcogenolates have attracted
considerable attention during the last 15 years or so due to
their wide structural diversity[1] and relevance in
catalysis,[2Ϫ5] and as a result of being precursors for the
synthesis of metal chalcogenides[6Ϫ8] for electronic de-
vices.[9] The area of metal chalcogenolates has been domi-
nated by molecules containing the MϪSR linkage.[1] In
most cases these molecules have been isolated as non-volat-
ile, insoluble (or sparingly soluble) polymers, thus making
them inconvenient as precursors for the synthesis of metal
chalcogenides. Although several strategies have been ad-
opted to suppress polymerisation, the use of hybrid ligands
containing both soft chalcogen and hard N donor atoms
has been quite successful, such as pyridine-2-thiolate[10] or
aliphatic mercapto amines.[11Ϫ14] The continued current in-
terest in selenium containing inorganic materials[15] and in
pursuance of our program on the design and development
of molecular precursors, we explored some chemistry of in-
ternally functionalized selenolates, viz. pySe[16] and
Me2NCH2CH2SeϪ.[8] Herein we now report the synthesis,
spectroscopy, electrochemistry, structures, and DT-DFT
calculations of platinum complexes derived from the latter
ligand.
Treatment of [Pt2Cl2(µ-Cl)2(PR3)2] with two equivalents
of NaSeCH2CH2NMe2, prepared by the reductive cleavage
of the SeϪSe bond in (Me2NCH2CH2Se)2 with sodium
borohydride, afforded dimethylaminoethylselenolate com-
plexes of the type [PtCl(η2-SeCH2CH2NMe2)(PR3)] (1)
[PR3 ϭ PEt3 (1a), PnPr3 (1b), PnBu3 (1c), PMe2Ph (1d), or
PMePh2 (1e)] (Scheme 1). The analogous triphenylphos-
phane complex, [PtCl(SeCH2CH2NMe2)(PPh3)] (1f) can be
readily prepared by the reaction of PtCl2(PPh3)2 with one
equivalent of NaSeCH2CH2NMe2.
1
The H NMR spectra of 1 showed the expected integra-
tion and peak multiplicities. The selenolate proton reson-
ances, i.e., SeCH2, NMe2, NCH2 were flanked with plat-
inum satellites with 3J(Pt-H) being 24Ϫ27, 14Ϫ18, and
3
36Ϫ42 Hz, respectively. The observed magnitudes of J(Pt-
H) can be compared with platinum complexes containing
neutral RSeCH2CH2NMe2 ligands.[17,18] The 31P NMR
spectra of 1 exhibited single resonances flanked with 195Pt
1
satellites. The magnitude of J(Pt-P), (3434Ϫ3662 Hz) in-
dicates that the phosphane ligand is trans to the nitrogen
atom of the chelated [SeCH2CH2NMe2]Ϫ group.[16,19,20]
The 195Pt{1H} NMR spectra of these complexes displayed
a doublet due to coupling with a single 31P nucleus. The
doublet appeared in a narrow range of δ ϭ Ϫ4266 to
Ϫ4308. As is evident from Table 1, there is shielding of the
195Pt resonances as the phosphane ligand is changed from
PMe2Ph to PMePh2 through PPh3. A similar trend is evid-
ent for 77Se and 31P chemical shifts which, however, showed
deshielding. The 77Se NMR resonances for 1 appeared as a
triplet owing to the coupling with the 195Pt nucleus. The
resonance for 1f, however, appeared as a broad signal and
[a]
Novel Materials & Structural Chemistry Division, Bhabha
Atomic Research Center (B.A.R.C.),
Mumbai-400085, India
[b]
Institut für Anorganische Chemie, Universität Stuttgart,
Pfaffenwaldring 55, 70569 Stuttgart, Germany
[c]
J. Heyrovsky Institute of Physical Chemistry, Academy of
Sciences of the Czech Republic,
Dolejskova 3, 18223 Prague, Czech Republic
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/1111Ϫ2965 $ 17.50ϩ.50/0
2965

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. Zalis
FULL PAPER
Scheme 1
Table 1. 31P{1H}, 77Se{1H} and 195Pt{1H} NMR spectroscopic data (δ in ppm, J in Hz) for dimethylaminoethaneselenolate complexes
of platinum(II)
Complex
195Pt{1H}
77Se{1H}
31P{1H}
δ
1J(195Pt-31P)
δ
1J(195Pt-77Se)
1J(195Pt-31P)
[PtCl(SeCH2CH2NMe2)(PEt3)] (1a)
[PtCl(SeCH2CH2NMe2)(PnPr3)] (1b)
[PtCl(SeCH2CH2NMe2)(PnBu3)] (1c)
[PtCl(SeCH2CH2NMe2)(PMe2Ph)] (1d)
Ϫ4308(d)
Ϫ4283(d)
Ϫ4284(d)
Ϫ4266
3407
3400
3394
3439
140.1
138.5
137.8
164(d)
147
129
138
4.5
3434
3415
3416
3454
Ϫ4.7
Ϫ4.0
Ϫ21.8
123
2J(Se-P) ϭ 24
[PtCl(SeCH2CH2NMe2)(PMePh2)] (1e)
Ϫ4293(d)
3555
190.6(d)
104
Ϫ6.8
3571
2J(Se-P) ϭ 30
[PtCl(SeCH2CH2NMe2)(PPh3)] (1f)
[Pt(Ph)(SeCH2CH2NMe2)(PnBu3)] (2)
[Pt2(Ph)2Cl(SeCH2CH2NMe2)(PnBu3)2] (3)
Ϫ4305
Ϫ4245
Ϫ4295
Ϫ4073
Ϫ
3658
3845
3776
3761
Ϫ
218.6(br)
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
7.4
3662
3834
3783
3829
3203
3355
3581
3359
2412
2859
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ3.1
Ϫ1.0
Ϫ4.2
5.1
[Pt2Cl3(SeCH2CH2NMe2)(PEt3)2] (4a)
[Pt2Cl3(SeCH2CH2NMe2)(PMe2Ph)2] (4b)
3.5
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ21.0
Ϫ22.4
Ϫ52.9
46.7
[Pt(SeCH2CH2NMe2)2(dppm)] (5a)
[Pt(SeCH2CH2NMe2)2(dppe)] (5b)
Ϫ4251(t)
Ϫ4958(t)
2429
2884
78.0
29.3
294
264
J(Se-P) ϭ 11
[Pt(SeCH2CH2NMe2)2(dppp)] (5c)
Ϫ4913(t)
2783
2738
53.5
255.0
279
472
Ϫ1.8
Ϫ39.3(d)
2849
2286
[Pt2(SeCH2CH2NMe2)2(dppm)2][BPh4]2 (6a) Ϫ4065(d,d)
J(P-P) ϭ 65
2745
Ϫ44.8(d)
J(P-P) ϭ 65
2822
3158
[Pt2(SeCH2CH2NMe2)2(dppe)2][BPh4]2 (6b)
[Pt2(SeCH2CH2NMe2)2(dppp)2][BPh4]2 (6c)
Ϫ4680(d,d)
Ϫ4534(d,d)
2852
2706
276.6
309.8
385
316
47.3
36.9
Ϫ1.8(d)
2676
J(P-P) ϭ 31
3048
Ϫ13.7(d)
J(P-P) ϭ 31
3330
[Pt(SeCH2CH2NMe2)(PPh3)]n[PF6]n (7)
Ϫ4071(d)
(major)
Ϫ3854
3323
3337
49.8
17.9
Ϫ
Ϫ
5.3
(major)
3.1
3353
(minor)
(minor)
hence platinum coupling could not be resolved. The magni-
Reaction of [Pt2Ph2(µ-Cl)2(PnBu3)2] with two equivalents
tude of J(195Pt-77Se) is comparable to that of the values of NaSeCH2CH2NMe2, affords a mixture of products,
reported for mononuclear platinum selenolates.[16,21,22] The [PtPh(SeCH2CH2NMe2)(PnBu3)] (2) and [Pt2Ph2(Cl)-
appearance of a single resonance in 77Se NMR spectra sug- (SeCH2CH2NMe2)(PnBu3)2] (3). Compound 3 appears to
gests that the phosphane is cis to the selenium atom as the be an intermediate product in the reaction, which on fur-
2J(77Se-31P)cis couplings are usually small (Ͼ 10 Hz).[22,23] ther reaction with NaSeCH2CH2NMe2 yields 2. The calcu-
However, such couplings are slightly larger for 1d and 1e lated values of C, H, and N for the two are not significantly
(24 and 30 Hz, respectively) and could thus be resolved in different, hampering an unambiguous identification of 2
1
the 77Se NMR spectra.
and 3. The two can, however, be separated by repeated
2966
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate
FULL PAPER
recrystallization. The NMR spectroscopic data for 2 can be ited single resonances suggesting that two bridging selenol-
compared with 1 as described above. Although the magni- ate ligands are equivalent. The signals are deshielded with
1
tude of J(Pt-P) is greater (418 Hz) than that of 1c, it is in increased 1J(Pt-Se) in comparison to the corresponding res-
compliance with ArPtII complexes in which the phosphane onance for 5. However the 31P{1H} (Figure 1) and
is trans to nitrogen, e.g. [Pt2R2(µ-NϪN)2(PR3)2] (R ϭ Me 195Pt{1H} (Figure 2) spectra showed two sets of resonances,
or aryl, NϪN ϭ pyrazole).[24] The 31P and 195Pt NMR and doublet of doublets, respectively; a pattern indicative
spectra of 3 exhibited two separate resonances attributable of non-equivalence of phosphorus nuclei of the PϪP ligand.
to ‘‘PtPhCl(PnBu3)’’ and ‘‘PtPh(SeϪN)(PnBu3)’’ fragments. The spectra of 6a and 6c further showed phosphorus coup-
1
The magnitude of J(Pt-P) suggests that the phosphane li- ling, thus each signal appeared as a doublet (Figure 1). The
gand is trans to Cl in the former and trans to N in the X-ray structures of several mononuclear compounds
latter fragment.[25] This stereochemistry is unambiguously [M(ER)2(PϪP)] (E ϭ S or Se, M ϭ Pd or Pt) have been
established by X-ray structural analysis (see later).
reported.[13,23] The structures reveal that in thiolates the two
The chloro analogue of 3, [Pt2Cl3(SeCH2CH2NMe2)- MϪS distances are nearly identical,[13,23] but for selenolates
(PR3)2] (4) [PR3 ϭ PEt3 (4a), PMe2Ph (4b)] can be obtained the two MϪSe distances differ markedly[21,23,26] (e.g. Pt-
[26]
˚
readily by treatment of [Pt2Cl2(µ-Cl)2(PR3)2] with 1 in 1:2 (Sepy)2(dppe) PtϪSe ϭ 2.498, 2.433 A).
Similar differ-
molar ratio. The 31P NMR spectra of a freshly prepared ences in PtϪE distances in binuclear complexes [Pt2X2(µ-
solution exhibited two singlets each flanked with platinum ER)2(PR3)2] (ER ϭ SeEt, SeCH2Ph)[19,27] are reported. The
satellites. The signal of lower frequency may be attributed selenolato ligands form an asymmetric Pt2Se2 ring[19,27]
to the phosphane attached to the metal atom containing the whereas the thiolates give a symmetrical Pt2S2 fragment.[28]
chelating SeϪN ligand. The magnitude of 1J(Pt-P) coupling On chelation of M(ER)2(PϪP) with another metal centre,
associated with this signal is reduced (ഠ 90 Hz) relative to binuclear complexes such as [M2(ER)2(PϪP)2]ϩϩ
[11,13]
that of the corresponding mononuclear complex. The se- (M ϭ Pd or Pt) are formed when E ϭ S a symmetrical
cond resonance at higher frequency may be assigned to the M2E2 bridge forms as shown by the X-ray structure of
[13]
phosphane coordinated to the metal atom containing two [M2(µ-SC5H9NMe)2(dppe)2][BPh4]2
where MϪS dis-
chlorines and the selenium atom. Similar NMR spectro- tances are nearly equivalent. Accordingly all phosphorus
scopic data have been reported for [Pt2Cl3(µ- nuclei become chemically equivalent and display only one
Sepy)(PR3)2].[16] Although the spectra of 4b did not change 31P NMR resonance.[11,13,21,23] In case of binuclear cationic
with time, 4a slowly isomerised in solution to establish an selenolate complexes, as observed for [Pt2Cl2(µ-
equilibrium with another species 4aЈ. Thus, a CDCl3 solu- SeR)2(PR3)2],[19,27] the MϪSe bridge may be asymmetric (I)
tion of 4a, after 2 h, displayed four resonances (δ ϭ 5.1, due to different MϪSe distances consequently making the
3.4, 3.1, 2.4), each showing platinum satellites, the intensity
of which changed with time until an equilibrium is reached
after two days. No change occurs after a week. It is likely
that the ‘‘PtCl2(PR3)’’ fragment of 4a isomerises from cis-
‘‘PtCl2’’ to the trans-‘‘PtCl2’’ configuration, a structure ob-
served for palladium complex, [Pd2Cl3(Sepy)(PR3)2].[16]
1
Thus, the second set of resonances (δ ϭ 3.1, J(Pt-P) ϭ
1
3504 Hz; δ ϭ 2.4, J(Pt-P) 3218 Hz) may be attributed to
4aЈ in which ‘‘PtCl2’’ has a trans configuration.
Reaction of PtCl2(PϪP) with two equivalents of Na-
SeCH2CH2NMe2 yields, mononuclear [Pt(SeCH2CH2-
NMe2)2(PϪP)] (5) [PϪP ϭ dppm (5a), dppe (5b), dppp
(5c)] as yellow crystalline solids. The NMR spectra (31P,
77Se, 195Pt) (Table 1) are similar to several organochalcogen-
olates [Pt(ER)2(PϪP)] reported by us.[16,21,23,26] These com-
plexes have been assigned a cis configuration. Unlike 1, the
Me2NCH2CH2Se in 5 acts in monodentate fashion i.e.,
binding through selenium only. This mode of binding can
readily be identified from 1H NMR spectra. The NMe2 pro-
tons in 5 appear at δ ഠ 2.0 with the absence of 195Pt coup-
lings whereas in 1 they appear at δ ഠ 2.7 with 195Pt coup-
lings. When the reaction is carried out in 1:1 stoichiometry
in the presence of NaBPh4 (Scheme 1), a new series of bi-
Figure 1. 31P{1H} NMR spectrum of [Pt2(SeCH2CH2N-
Me2)2(dppp)2][BPh4]2 (6c) in CDCl3
nuclear
complexes,
[Pt2(SeCH2CH2NMe2)2(PϪP)2]-
[BPh4]2 (6) [PϪP ϭ dppm (6a), dppe (6b), dppp (6c)] could
be isolated. Complex 6 can also be prepared, as pale yellow
fibrous crystals, by the reaction of
5
with
Figure 2. 195Pt{1H} NMR spectrum of [Pt2(SeCH2CH2N-
[Pt(solvent)2(PϪP)][BPh4]2. The 77Se NMR spectra exhib- Me2)2(dppp)2][BPh4]2 (6c) in CDCl3
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973
2967

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. Zalis
FULL PAPER
phosphorus nuclei magnetically different. The two in-
equivalent phosphorus nuclei are coupled together to give
doublets in the 31P NMR spectra of 6a and 6c. The magni-
2
tude of J(P-P) couplings are in accordance with the litera-
2
ture values.[29] The absence of J(P-P) in 6b might be due
to different signs of 3J(P-P), 2J(P-P) coupling operating
through PϪCϪCϪP and PϪPtϪP routes, respectively.[30]
The intensity of two resonances (Figure 1) is significantly
different. This can be attributed to the difference in the
magnitude of T1 of two sites, as reported earlier.[30]
Figure 3. UV/Vis spectrum of [PtCl(SeCH2CH2NMe2)(PPh3)] (1f)
in CH2Cl2
Table 2. UV/Vis absorption data of some platinum complexes re-
corded in CH2Cl2
Treatment of 1f with AgPF6 affords [Pt(SeCH2-
CH2NMe2)(PPh3)]n[PF6]n (7). The 31P, 77Se, and 195Pt spec-
tra exhibited two separate resonances in approximately a
Complex
λmax (nm)
1
2:1 ratio. The J(Pt-P) in 31P and 195Pt NMR spectra are
[PtCl(SeCH2CH2NMe2)(PEt3)] (1a)
[PtCl(SeCH2CH2NMe2)(PMe2Ph)] (1d)
[PtCl(SeCH2CH2NMe2)(PMePh2)] (1e)
[PtCl(SeCH2CH2NMe2)(PPh3)] (1f)
284, 405
283, 405
266 sh, 273 sh, 293 sh, 418
268 sh, 275 sh, 300 sh, 430
comparable, indicating that both the species have similar
configuration. Recently we have reported the structure of
[{Pd(SeCH2CH2NMe2)Cl}n] which is a trimer (n ϭ 3) in
which the chelated SeϪN ligand bridges another palladium
atom through Se.[8] The observed two signals may be inter-
preted for dimeric (II) and trimeric (III) forms in which
each platinum is bonded to two Se atoms, one N and one
PPh3 in nearly similar environments.
According to cyclic voltammetry in CH2Cl2/0.1
mol·dmϪ3 Bu4NPF6 the PtII complexes 1 and 3 are oxidised
irreversibly. The peak potentials for 1 show little variation
(0.83Ϫ0.89 V vs. ferrocene/ferrocenium), confirming that it
is primarily the selenolate part (HOMO) which loses an
Ϫ
electron and not the PR3 ligating platinum centre. The
bridging selenolate in compound 3 is hard to oxidise as il-
lustrated by the anodic peak potential of 1.13 V for irrevers-
ible oxidation.
Electronic Structure Calculations on 1f
The ADF/BP calculated one-electron scheme of the
[PtCl(SeCH2CH2NMe2)(PPh3)] complex is schematically
given in Figure 4. The composition of important molecular
Absorption Spectra and Electrochemistry
The absorption spectra of the complexes [PtCl-
(SeCH2CH2NMe2)(PR3)] in CH2Cl2 solution are charac-
terised by a very weak band at 400Ϫ430 nm (Figure 3,
Table 2). The band is hypsochromically shifted on replacing
the phenyl substituents on the PR3 group by donating alkyl
groups. As will be confirmed by TD-DFT calculations (see
below) this absorption is due to a ligand (Se)-to-ligand
(PR3) charge transfer (LLCT) transition. The geometry ob-
viously allows only rather poor orbital overlap, resulting in
very weak yet well discernible bands (Figure 3). A similar
band with ε ϭ 80 molϪ1·dm3·cmϪ1 at 514 nm has been re-
ported for the palladium analogue [PdCl(SeCH2CH2N-
Me2)(PPh3)].[8] Allowed transitions occur only at higher en-
ergies with λmax Ͻ 300 nm, in agreement with theory. The
dinuclear species [Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)2]
does not allow a detectable Se-to-PnBu3 transition in the
visible or near UV region(Table 2).
Figure 4. ADF/BP calculated qualitative MO scheme of 1f
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973
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Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate
FULL PAPER
Me2)(PH3)] model with different DFT program configura-
tions. In agreement with the experiments, there is one very
weak transition (HOMOǞLUMO, oscillator strength
Ͻ 10Ϫ3) at low energy, set apart by more than 1 eV from
the following singlet transitions (Table 5). The calculated
excitation energies of about 2.4 eV (corresponding to ca.
500 nm) are in broad agreement with the 400Ϫ430 nm ob-
served for various substituted derivatives (Table 2). This
conspicuous absorption must be formulated mainly as li-
gand (Se)-to-ligand (PR3) charge transfer, as has been pro-
posed previously for palladium analogues.[8]
Table 3. ADF/BP calculated one-electron energies and percentage
composition of selected highest occupied and lowest unoccupied
molecular orbitals of [PtCl(SeCH2CH2NMe2)(PPh3)] (1f) expressed
in terms of composing fragments
MO
E [eV] Prevailing
Pt
PPh3 Se Cl N
Character
Unoccupied Ϫ
92a
91a
Ϫ1.87 PPh3
Ϫ2.06 PPh3
3 (d)
2 (d)
90
94
63
2
9
2
3
90a
Ϫ2.11 dPt ϩ PPh3 ϩ Se 13 (d)
3
Occupied
89a
88a
Ϫ4.05 Se ϩ dPt
Ϫ5.37 dPt
29 (d)
11 (s); 57(d) 1
Ϫ
58 10 Ϫ
7
23 Ϫ
Crystal Structures of 1f and 3
87a
86a
85a
84a
Ϫ5.45 dPt ϩ Cl
Ϫ5.70 Cl ϩ Se ϩ dPt
Ϫ6.16 Cl ϩ Se
Ϫ6.25 dPt
5 (s); 42(d)
1(p); 19 (d)
3(p); 4 (d)
78 (d)
3
43
25 50
46 34
3 2
10 3 2
An ORTEP plot of 1f with the crystallographic num-
bering scheme is shown in Figure 5, and Table 6
summarises essential data. The geometry around the pla-
tinum atom is essentially square planar with the atoms P,
Cl, Se, and N defining the coordination sphere. The phos-
phane ligand is trans to the nitrogen atom of the chelating
selenolate group as inferred from the NMR spectroscopic
data. The five-membered chelate ring (PtϪSeϪCϪCϪN)
exists in a puckered conformation with the carbon atoms
C(19) and C(20) lying on opposite sides of the mean plane.
The structure of 1f is isomorphous to its palladium ana-
logue, [PdCl(SeCH2CH2NMe2)(PPh3)][8] and various bond
lengths and angles in the two structures are comparable.
4
10
72
83a
Ϫ6.60 PPh3
6 (d)
orbitals is summarised in Table 3. The highest molecular
orbital 89a is formed mainly from a Se p orbital with some
additional metal contribution. Pt 5d and Cl 3p orbitals con-
tribute significantly to the next lower lying occupied MOs.
The set of the lowest lying unoccupied molecular orbitals,
90a, 91a, and 92a, is to a large extent located on the PPh3
fragment. The composition of the occupied MOs of the
[PtCl(SeCH2CH2NMe2)(PH3)] model (Table 4) corresponds
to those of the PPh3 complex. The lowest lying molecular
orbital is delocalised; PH3 localised unoccupied MOs lie at
a rather high energy. The excitation energies listed in
Table 5 were calculated for the [PtCl(SeCH2CH2N-
Table 4. ADF/BP calculated one-electron energies and percentage
composition of selected highest occupied and lowest unoccupied
molecular orbitals of model complex [PtCl(SeCH2CH2NMe2)
(PH3)] expressed in terms of composing fragments
MO
E [eV] Prevailing
Pt
PH3 Cl Se
Character
Unoccupied
49a
48a
47a LUMO Ϫ2.23 delocalized
Occupied
Ϫ
Ϫ0.77 PH3
Ϫ0.83 PH3
17(d)
7(d)
28 (d)
68
47
20
10
30
11 28
47a HOMO Ϫ4.30 Se ϩ dPt
28 (d)
18 (s); 71(d)
2 (s); 27(d)
2
9
4
62
7
5
46a
45a
44a
43a
42a
Ϫ5.58 dPt
Ϫ5.71 dPt ϩ Cl
Ϫ5.85 Cl ϩ Se ϩ dPt 1(p); 16 (d)
Ϫ6.10 Se ϩ Cl
Ϫ6.40 dPt
Ϫ
Ϫ
Ϫ
1
61
57 24
36 52
7 (d)
85 (d)
11
Ϫ
Ϫ
Figure 5. Molecular structure of [PtCl(SeCH2CH2NMe2)(PPh3)]
(1f) with crystallographic numbering scheme
Table 5. Selected calculated lowest TD DFT singlet excitation energies (eV) for [PtCl(SeCH2CH2NMe2)(PH3)]
ADF/BP
Transition energy [eV]
G98/B3LYP
State
Main character
Oscillator strength
Transition energy [eV]
Oscillator strength
1A1
1A1
1A1
1A1
1A1
HOMO Ǟ LUMO
2.24
3.55
3.58
3.67
4.71
0.0004
0.001
0.002
0.010
0.082
2.53
3.71
3.95
4.08
5.09
0.0006
0.002
0.005
0.012
0.190
HOMO Ǟ LUMO ϩ1
HOMO Ϫ 1 Ǟ LUMO
HOMO Ǟ LUMO ϩ 2
HOMO Ϫ4 Ǟ LUMO
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973
2969

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. Zalis
FULL PAPER
˚
˚
Table 6. Selected bond lengths [A] and bond angles [°] with esd’s
for [PtCl(SeCH2CH2NMe2)(PPh3)] (1f)
Table 7. Selected bond lengths [A] and bond angles [°] with esd’s
for [Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)] (3)
PtϪN
PtϪP
PtϪSe
PtϪCl
SeϪC(19)
NϪPtϪP
NϪPtϪSe
PϪPtϪSe
NϪPtϪCl
PϪPtϪCl
SeϪPtϪCl
PdϪSeϪC(19)
2.161 (5)
2.2292 (15)
2.3773(7)
2.3788 (15)
1.953 (6)
174.57 (14)
87.02 (14)
91.07 (4)
90.61 (15)
90.89 (6)
174.92 (4)
95.9 (2)
NϪC(20)
NϪC(21)
NϪC(22)
C(19)ϪC(20)
PϪC (av)
C(20)ϪNϪC(21)
C(20)ϪNϪC(22)
C(21)ϪNϪC(22)
PtϪNϪC(21)
PtϪNϪC(22)
PtϪNϪC(20)
NϪC(20)ϪC(19)
SeϪC(19)ϪC(20)
1.501 (8)
1.485 (8)
1.486 (8)
1.502 (9)
1.830
107.1 (5)
109.5 (5)
106.6 (5)
114.9 (4)
107.2 (4)
111.3 (4)
112.2 (5)
108.9 (4)
Pt(1)ϪSe
Pt(1)ϪP(1)
Pt(1)ϪCl
Pt(1)ϪC(11)
SeϪC(1)
2.4793(14) Pt(2)ϪSe
2.4562(12)
2.227(2)
2.177(9)
2.039(10)
1.542(18)
90.7(3)
2.235(3)
2.432(3)
2.010(10)
1.931(12)
Pt(2)ϪP(2)
Pt(2)ϪN
Pt(2)ϪC(5)
NϪC(2)
C(11)ϪPt(1)ϪP(1) 92.1(3)
C(5)ϪPt(2)ϪN
C(11)ϪPt(1)ϪCl
P(1)ϪPt(1)ϪCl
C(11)ϪPt(1)ϪSe
P(1)ϪPt(1)ϪSe
ClϪP(1)ϪSe
Pt(1)ϪSeϪPt(2)
Pt(1)ϪSeϪC(1)
178.4(3)
88.20(11)
85.1(3)
175.23(8)
94.69(8)
111.69(8)
101.7(4)
C(5)ϪPt(2)ϪP(2) 88.5(3)
P(2)ϪPt(2)ϪN
C(5)ϪPt(2)ϪSe
NϪPt(2)ϪSe
P(2)ϪPt(2)ϪSe
Pt(2)ϪNϪC(2)
SeϪC(1)ϪC(2)
Pt(2)ϪSeϪC(1)
178.9(2)
174.0(3)
87.2(2)
93.64(7)
109.2(7)
110.7(9)
95.3(4)
The molecular structure of [Pt2Ph2(Cl)(SeCH2CH2N-
Me2)(PnBu3)2] (3), established by the X-ray diffraction
method, is illustrated in Figure 6. Selected bond lengths and
bond angles are given in Table 7. The structure consists of
two distorted square planar platinum atoms which are held
together by a bridging selenolate centre. The two square
planes of the platinum atoms are inclined to each other
through a Pt(1)ϪSeϪPt(2) angle of 111.69 (5)°. Each pla-
tinum atom is coordinated to four different ligand atoms.
The Pt(1) centre is coordinated to Ph, Cl, PBu3, and the
selenium atom, the latter being mutually trans. The Pt(2)
atom is bound to the chelating Me2NCH2CH2Se ligand and
to the other PBu3 and Ph groups. The phosphane is trans
to the nitrogen atom whereas Se is trans to Ph. The PtϪSe
The comparable trans influence of PBu3 and Ph groups is
evident from the 1J(Pt-P) values from NMR spectra. Other
distances, PtϪP, PtϪCl, PtϪN, and PtϪC are well in agree-
ment with those reported in the literature.[16,21,23,26]
Experimental Section
All the reactions were carried out under a nitrogen atmosphere in
dry, distilled analytical grade solvents to prevent oxidation of the
oxygen sensitive selenolate ions. The complexes K2[PtCl4], cis-
[PtCl2(PPh3)2], cis-[PtCl2(PϪP)], trans-[Pt2Cl2(µ-Cl)2(PR3)2], and
the mixture of cis- and trans-[Pt2Ph2(µ-Cl)2(PnBu3)2] (PϪP ϭ
dppm, dppe, dppp; PR3 ϭ PEt3, PnPr3, PnBu3, PMe2Ph, PMePh2)
were prepared by the literature methods.[31,32,33] Melting points
were determined in capillary tubes and are uncorrected. Microana-
lyses were performed by the Analytical Chemistry Division of
B.A.R.C. 1H, 31P{1H}, 77Se{1H}, and 195Pt{1H} NMR spectra
were recorded on a Bruker DPX-300 NMR spectrometer operating
at 300, 121.49, 57.31, 64.52 MHz, respectively. Chemical shifts are
relative to internal chloroform peak (δ ϭ 7.26) for 1H, external
85% H3PO4 for 31P, Me2Se for 77Se, and Na2PtCl6 for 195Pt. UV/
Vis absorption spectra were recorded on a Bruins Instruments
Omega 10 spectrophotometer. Cyclic voltammetry was carried out
at 100 mV/s scan rate in dichloromethane/0.1  Bu4NPF6 using a
three electrode configuration (glassy carbon working electrode, Pt
counter electrode, Ag/AgCl reference) and a PAR 273 potentiostat
and function generator. The ferrocene/ferrocenium couple served
as internal reference.
˚
distances in 1f [2.3788(15) A] and 3 [2.4793(14) and
˚
2.4562(12) A] are significantly different, although these dis-
tances are in agreement with the standard values. The
longer PtϪSe distances in 3 compared with that of 1f reflect
greater trans influence of Ph and PBu3 than the chloride.
Ground state electronic structure calculations on [PtCl-
(SeCH2CH2NMe2)(PPh3)] have been done by density-functional
theory (DFT) methods using the ADF2000.01[34,35] and Gaussian
98[36] program packages. The lowest excited states were calculated
by the time dependent DFT (TD-DFT) method (both ADF and
G98 programs) for the model system [PtCl(SeCH2CH2N-
Me2)(PH3)]. Within the ADF program, Slater type orbital (STO)
basis sets of double-ζ quality with polarisation functions within the
phenyl rings and triple-ζ for the rest of the system were employed.
The inner shells were represented by the frozen core approximation
(1s for C, N 2p for Cl, 3p for Se, and 1sϪ4d for Pt were kept
frozen). The following density functionals were used within ADF:
The local density approximation (LDA) with VWN parameteris-
ation of electron gas data or the functional including Becke’s gradi-
ent correction[37] to the local exchange expression in conjunction
Figure 6. ORTEP plot of [Pt2Ph2Cl(SeCH2CH2NMe2)(PnBu3)2] (3)
with crystallographic numbering scheme
2970
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973

Platinum(II) Complexes of 2-(Dimethylamino)ethylselenolate
with Perdew’s gradient correction[38] to the LDA expression (ADF/
FULL PAPER
evaporated under reduced pressure and the residue was extracted
BP). The scalar relativistic (SR) zero order regular approximation with dichloromethane (3ϫ7 cm3), the solution was passed through
(ZORA) was used within the study. Within Gaussian-98 Dunning’s
polarized valence double-ζ basis sets[39] were used for C, N, Cl,
and H atoms; quasirelativistic effective core pseudopotentials and
a corresponding optimized set of basis functions was employed for
Pt[40] and Se.[41] Becke’s three parameter hybrid functional with the
Lee, Yang, and Parr correction functional (B3LYP)[42] was used in
Gaussian 98 calculations (G98/B3LYP). The calculation on the
model system [PtCl(SeCH2CH2NMe2)(PH3)] was done with the ex-
perimental geometry of the PPh3 complex with an optimized struc-
ture of the PH3 ligand.
a Florisil column and the solvent removed in vacuo. The residue
was recrystallised from hexane (yield 210 mg, 65%). All other
mononuclear complexes [PtCl(SeCH2CH2NMe2)(PR3)] (PR3
ϭ
PnPr3, PnBu3, PMe2Ph, PMePh2) were prepared in a similar man-
ner. Pertinent data are summarized in Table 8.
2. Preparation of [PtCl(SeCH2CH2NMe2)(PPh3)] (1f): Prepared
analogously as described in method 5 by using [PtCl2(PPh3)2]
(268.8 mg, 0.34 mmol) NaSeCH2CH2NMe2 [prepared from
(Me2NCH2CH2Se)2 (54.4 mg, 0.18 mmol) and NaBH4 (14.0 mg,
0.37 mmol)]. The residue was washed thoroughly with diethyl ether
to remove liberated triphenylphosphane and then recrystallised
from CH2Cl2/acetone mixture as yellow-orange crystals (yield
158 mg, 72%).
1. Preparation of [PtCl(SeCH2CH2NMe2)(PEt3)] (1a): To a freshly
prepared methanolic solution (5 cm3) of NaSeCH2CH2NMe2 [pre-
pared from (Me2NCH2CH2Se)2 (99.7 mg, 0.32 mmol) and NaBH4
(25.4 mg, 0.67 mmol)] was added a dichloromethane solution (20
cm3) of [Pt2Cl2(µ-Cl)2(PEt3)2] (247.7 mg, 0.32 mmol). The reaction 3. Preparation of [PtPh(SeCH2CH2NMe2)(PnBu3)] (2) and
mixture was stirred at room temperature for 4 h. The solvents were [Pt2Ph2Cl(SeCH2CH2NMe2) (PnBu3)2] (3): Prepared analogously
1
Table 8. Physical, analytical and H NMR spectroscopic data for dimethylaminoethaneselenolate complexes of platinum(II)
Complex
Recrystallisation M.p. Analysis:Found (calcd)
1H NMR spectroscopic data
solvent
(0C)
63
(%)
C
(% yield)
H
N
δ
[PtCl(SeCH2CH2NMe2)-
(PEt3)] (1a)
hexane (65)
23.6
(24.0)
5.3
(5.0)
2.6
(2.8)
1.40 [d,t, 7.6 Hz (t), 17 Hz (d) PCH2Me]; 1.86 [d,q, 7.6 Hz (q),
17 Hz (d) PCH2-]; 2.33 [t, 6.1 Hz, 3J(Pt-H) ϭ 27 Hz, SeCH2];
2.75 [d, 4J(P-H) ϭ 2.6 Hz, 3J(Pt-H) ϭ 17 Hz, NMe2]; 2.86
[d, t, 1.7 Hz (d) 4J(P-H), J(H-H) ϭ 7 Hz; 3J(Pt-H) ϭ 36 Hz, NCH2]
1.04 (t, 7.2 Hz, PCH2CH2Me); 1.52Ϫ1.67 (m, PCH2CH2-);
1.75Ϫ1.87 (m, PCH2-); 2.33 [t, 6.2 Hz, 3J(Pt-H) ϭ 27 Hz, SeCH2];
2.74 [d, 4J(P-H) ϭ 2.5 Hz, 3J(Pt-H) ϭ 15 Hz, NMe2];
2.85 [t, d, 4J(P-H) ϭ 1.5, 6 Hz (d), 3J(Pt-H) ϭ 37 Hz, NCH2-]
0.85 (t, 7.1 Hz, P CH2CH2CH2Me); 1.30Ϫ1.50
(m, PCH2CH2CH2-); 1.72Ϫ1.80 (m, PCH2-); 2.24 [t, 6.2 Hz,
3J(Pt-H) ϭ 27 Hz, SeCH2]; 2.67 [d, 4J(P-H) ϭ 2.6 Hz,
3J(Pt-H) ϭ 14 Hz, NMe2]; 2.78 [d, t, 4J(P-H) ϭ 1.5, 5 Hz (t),
3J(Pt-H) ϭ 36 Hz, NCH2-]
[PtCl(SeCH2CH2NMe2)-
(PnPr3)] (1b)
hexane
(72)
87
46
28.3
6.0
2.8
(28.8)
(5.8)
(2.6)
[PtCl(SeCH2CH2NMe2)-
(PnBu3)] (1c)
hexane
(80)
32.2
(32.9)
6.3
(6.4)
2.1
(2.4)
[PtCl(SeCH2CH2NMe2)-
(PMe2Ph)] (1d)
CH2Cl2/hexane
(69)
156
27.3
(27.7)
3.9
(4.1)
2.5
(2.7)
1.80, 1.81 [each d, 2J(P-H) ϭ 11.2 Hz, 3J(Pt-H) ϭ 40 Hz, PMe2];
2.23 (br, SeCH2); 2.70 [d, 3J(P-H) ϭ 2.2 Hz, NMe2]; 2.85
[br, 3J(Pt-H) ϭ 38 Hz, NCH2]; 7.34 (br), 7.67 (br) (Ph)
2.23 [d, J(P-H) ϭ 11.2, 3J(Pt-H) ϭ 32 Hz, PMe]; 2.21 (SeCH2,
merged with PMe resonance) 2.83 [d, 4J(P-H) ϭ 2.8 Hz,
3J(Pt-H) ϭ 18 Hz, NMe2]; 2.99 [d, t, 1.6 Hz (d) 4J(P-H),
J(H-H) ϭ 6.1 Hz; 3J(Pt-H) ϭ 38 Hz, NCH2]; 7.38Ϫ7.43 (m) (Ph)
2.21 [t, 6.2 Hz 3J(Pt-H) ϭ 24 Hz, SeCH2]; 2.88 [d, 4J(P-H) ϭ
2.8 Hz, 3J(Pt-H) ϭ 17 Hz, NMe2]; 3.08 [d, t, (d) 4J(P-H) ϭ
1.5 Hz, J(H-H) ϭ 6.2 Hz; 3J(Pt-H) ϭ 42 Hz, NCH2];
7.33Ϫ7.49 (m) 7.68Ϫ7.49 (m) (Ph)
0.89 (t, 7.2 Hz, PCH2CH2CH2Me); 1.34 (m, PCH2CH2CH2-);
1.50 (m, PCH2CH2-); 2.33 [d, 4J(P-H) ϭ 1.9 Hz, 3J(Pt-H) ϭ
27 Hz, NMe2]; 2.45 (t, 6 Hz, SeCH2); 2.99 [t, d, 4J(P-H) ϭ
2.2 Hz; J(H-H) ϭ 5.5 Hz, 3J(Pt-H) ϭ 38 Hz, NCH2-],
6.89Ϫ7.00 (m), 7.45Ϫ7.48 (m) (Ph)
[PtCl(SeCH2CH2NMe2)-
(PMePh2)] (1e)
CH2Cl2/hexane
(45)
199(d) 34.5
(35.1)
3.7
(4.0)
2.2
(2.4)
[PtCl(SeCH2CH2NMe2)-
(PPh3)] (1f)
CH2Cl2/acetone 235(d) 40.4
3.5
(3.9)
2.1
(2.2)
(72)
(41.0)
[PtPh(SeCH2CH2NMe2)-
(PnBu3)] (2)
hexane
(40)
147
41.6
(42.2)
6.7
(6.8)
1.1
(2.2)
[Pt2Ph2(Cl)(SeCH2CH2NMe2)-
(PnBu3)2] (3)
153
41.6
(42.3)
6.8
(6.6)
1.0
(1.2)
0.90 (m, PCH2CH2CH2Me); 1.26Ϫ1.88 (m, PCH2CH2CH2-);
2.01 (s, NMe2); 2.20 (br, SeCH2), 2.43 (br, NCH2),
7.38Ϫ7.57 (m, Ph)
[Pt2Cl3(SeCH2CH2NMe2)-
(PEt3)2] (4a)
[Pt2Cl3(SeCH2CH2NMe2)-
(PMe2Ph)2] (4b)
hexane
(80)
hexane
(87)
187
102
21.1
4.2
1.7
1.16 (m, PCH2Me); 1.82Ϫ2.16 (m; PCH2-); 2.63 (br, SeCH2);
2.79 (br, NMe2) 3.02 (br, NCH2).
(21.7)
25.7
(4.6)
3.5
(1.6)
1.3
1.64, 1.83, 1.88, 2.04 (each d, 11.5 Hz PMe2), 2.55 [d, 4J(P-H) ϭ
2.3 Hz], 3.00 [d, 4J(P-H) ϭ 2.8 Hz, NMe2 1:1], 3.58 (br., NCH2),
2.64 (br, SeCH2), 7.32Ϫ7.54(m), 7.76Ϫ7.83 (m) (Ph)
1.96 (s, NMe2); 2.42 (br, SeCH2); 2.59 (br, NCH2); 4.35
[t, 2J(P-H) ϭ 10.4 Hz; 3J(Pt-H) ϭ 44 Hz, PCH2-];
7.39Ϫ7.47 (m), 7.82Ϫ7.89 (m) (Ph)
(26.0)
(3.5)
(1.5)
[Pt(SeCH2CH2NMe2)2-
(dppm)] (5a)
acetone/hexane
(62)
154
44.2
(44.9)
4.8
(4.8)
3.0
(3.2)
[Pt(SeCH2CH2NMe2)2-
(dppe)] (5b)
[Pt(SeCH2CH2NMe2)2-
(dppp)] (5c)
[Pt2(SeCH2CH2NMe2)2-
(dppm)2][BPh4]2 (6a)
[Pt2(SeCH2CH2NMe2)2-
(dppe)2][BPh4]2 (6b)
acetone/hexane
(60)
184
162
84
44.8
4.9
3.0
2.03 (s, NMe2); 2.15Ϫ2.56 (m, NCH2, SeCH2, PCH2); 7.51 (br),
7.88Ϫ7.96 (m) (Ph)
1.88 (s, NMe2); 1.94Ϫ2.96 (overlapping resonance due to NCH2,
SeCH2, PCH2) 7.29Ϫ7.82 (m, Ph)
2.47 (br, NMe2); 2.74 (br, SeCH2); 2.82 (br, NCH2); 4.04
[t, 2J(P-H) ϭ 11 Hz PCH2-]; 6.75Ϫ6.93 (m), 7.23Ϫ7.62 (m) (Ph)
1.80Ϫ1.95 (br, PCH2); 2.34 (s, J(Pt-H) ϭ 16 Hz NMe2);
2.61 (br, SeCH2); 3.05 [br, 3J(Pt-H) ϭ 45 Hz NCH2];
6.77Ϫ6.91 (m), 7.18Ϫ7.31 (m), 7.37Ϫ7.69 (m) (Ph)
1.68 (br, PCH2); 2.17 (s, NMe2); 2.25 (br, CH2-CH2P), 2.49
(br, SeCH2); 3.07 [br, J(Pt-H) ϭ 46 Hz, NCH2];
(45.6)
44.7
(4.9)
4.8
(3.1)
2.0
acetone/hexane
(75)
(46.2)
60.6
(5.1)
5.0
(3.1)
1.1
CH2Cl2/hexane
(65)
acetone/hexane
(72)
(60.6)
60.3
(5.0)
5.2
(1.3)
1.4
126
(61.0)
(5.1)
(1.3)
[Pt2(SeCH2CH2NMe2)2-
(dppp)2][BPh4]2 (6c)
acetonehexane
(60)
195
60.5
(61.3)
5.1
(5.2)
1.1
(1.3)
6.87Ϫ7.06 (m); 7.42Ϫ7.64 (m) (Ph)
2.79 (s, NMe2 ϩ NCH2 base of the peak broadened);
2.30 (br, SeCH2); 7.34Ϫ7.70 (m) Ph.
[Pt(SeCH2CH2NMe2)-
(PPh3)]n[PF6]n (7)
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973
2971

S. Dey, V. K. Jain, A. Knoedler, W. Kaim, S. Zalis
as described in method 1 from [Pt2Ph2(µ-Cl)2(PnBu3)2] (99.5 mg, was added and the whole mixture was stirred for 3 h. Solvents were
FULL PAPER
0.10 mmol)
and
NaSeCH2CH2NMe2
[prepared
from
evaporated in vacuo and the residue was extracted with dichloro-
methane and passed through a Florisil column. The solvent was
(Me2NCH2CH2Se)2 (32 mg, 0.11 mmol) and NaBH4 (8.9 mg,
0.23 mmol)]. The 31P and 195Pt NMR spectra of this product exhib- evaporated in vacuo, the residue was washed with hexane and
ited three resonances. The product on recrystallization from hexane
recrystallised from a CH2Cl2/hexane mixture (yield 261 mg, 65%).
gave colourless crystals of [PtPh(SeCH2CH2NMe2)(PnBu3)] (yield Other cationic complexes [Pt2(SeCH2CH2NMe2)2(PϪP)2][BPh4]2
29 mg, 24%). The supernatant solution on repeated recrystalliza-
tion from hexane containing ഠ 5% benzene afforded
[Pt2Ph2(Cl)(SeCH2CH2NMe2)(PnBu3)2] (54 mg, 48%).
(PϪP ϭ dppe, dppp) were prepared in a similar way.
b) To a methanolic suspension (8 cm3) of [PtCl2(dppm)] (215.7 mg,
0.33 mmol) a methanolic solution (3 cm3) of NaBPh4 (114.2 mg,
0.33 mmol) was added and stirred for 1 h whereupon a pale yellow
solution formed. To this a freshly prepared methanolic solution of
NaSeCH2CH2NMe2 [prepared from (Me2NCH2CH2Se)2 (51.4 mg,
0.17 mmol), NaBH4 (13.2 mg, 0.35 mmol)] and 20 cm3 of dichloro-
methane was added and stirred. After 3 h the solvents were stripped
off under vacuum. The residue was extracted with dichloromethane
(3ϫ7 cm3) and passed through a Florisil column. The volume of
the solution was reduced to 5 cm3. Recrystallisation from CH2Cl2/
hexane mixture gave yellow solid (yield 216 mg, 62%).
4. Preparation of [Pt2Cl3(SeCH2CH2NMe2)(PEt3)2] (4a): Solid
[PtCl(SeCH2CH2NMe2)(PEt3)] (17.7 mg, 0.04 mmol) was mixed
with [Pt2Cl2(µ-Cl)2(PEt3)2] (13.5 mg, 0.02 mmol) in CDCl3 (0.5
cm3) in an NMR tube. After a few days the solution was dried in
vacuo, the pale yellow product was washed with hexane and dried
in vacuo (yield 25.0 mg, 80%).
5. Preparation of [Pt(SeCH2CH2NMe2)2(dppe)] (5b): To a stirred
methanolic solution (5 cm3) of NaSeCH2CH2NMe2 [prepared from
(Me2NCH2CH2Se)2 (92.8 mg, 0.31 mmol) and NaBH4 (23.8 mg,
0.63 mmol)] solid [PtCl2(dppe)] (201.5 mg, 0.30 mmol) was added.
To this mixture dry acetone (20 cm3) was added whereupon a yel-
low solution formed which was stirred for 3 h at room temperature.
The solvents were stripped off under vacuum and the residue was
extracted with acetone (3ϫ7 cm3) and filtered. The filtrate was re-
duced to a minimum volume (5 cm3), a few drops of hexane were
added to yield yellow crystals of the title complex (yield 163 mg,
60%).
7. Preparation of [Pt(SeCH2CH2NMe2)(PPh3)]n[PF6]n (7): An acet-
one solution (15 cm3) of AgPF6 (51 mg, 0.21 mmol) was added
to solid [PtCl(SeCH2CH2NMe2)(PPh3)] (116 mg, 0.20 mmol) with
stirring. Silver chloride immediately precipitated with concomitant
colour change from orange to pale yellow. The reactants were
stirred at room temperature for 4 h. Precipitated AgCl was filtered
through celite and the solvent was evaporated in vacuo. The yellow
residue was examined by NMR spectroscopy.
The complexes [Pt(SeCH2CH2NMe2)2(PϪP)] (PϪP ϭ dppm, dppe)
were prepared in an analogous manner.
Crystallography: X-ray data of an orange crystal of
[PtCl(SeCH2CH2NMe2)(PPh3)] (1f) (0.2ϫ0.2ϫ0.2 mm) and
a
6. Preparation of [Pt2(SeCH2CH2NMe2)2(dppm)2][BPh4]2 (6a): a) A
colourless crystal of [Pt2Ph2Cl(SeCH2CH2NMe2)-
dichloromethane suspension of (20 cm3) of [PtCl2(dppm)] (PnBu3)2] (3) (0.3ϫ0.3ϫ0.3 mm) were collected at 173(2) K on a
(248.9 mg, 0.38 mmol) was added to a stirred methanolic solution Siemens P3 diffractometer using graphite monochromated Mo-Kα
(5 cm3) of NaSeCH2CH2NMe2 [prepared from (Me2NCH2CH2Se)2 radiation (λ ϭ 0.71073 A), employing the ω-2θ scan technique. The
˚
(59.2 mg, 0.20 mmol) and NaBH4 (15.5 mg, 0.41 mmol)]. After 1 h
of stirring a methanolic solution of NaBPh4 (133.5 mg, 0.39 mmol)
unit cell parameters (Table 9) were determined from 25 reflections
each, measured by random search routine. The intensity data were
Table 9. Crystal data and structure refinement for [PtCl(SeCH2CH2NMe2)(PPh3)] (1f) and [Pt2Ph2Cl(SeCH2CH2NMe2)(PnBu3)2] (3)
1f
3
Empirical formula
Molecular mass
Crystal system,
Space group
C22H25ClNPSePt
643.90
Monoclinic,
P21/n
C43H68ClNP2SePt2
1165.55
Triclinic,
¯
P1
Unit cell dimensions:
˚
a [A]
9.4299(19)
19.972(4)
11.704(2)
9.3083(19)
15.859(3)
16.587(3)
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
108.96(3)
97.55(3)
93.32(3)
2282.5(8)
95.19(3)
3
˚
V [A ]
2175.6(8)
Z
4
4
Dc [Mg·mϪ3
]
1.966
8.326
1232
1.924
7.938
1300
Absorption coefficient µ [mmϪ1
F(000)
]
Range for data collection [°]
Refinement method
Reflections collected/unique
Data/restraints/parameters
Goodness of fit on F2
Final R indices
2.03 to 30.00
1.55 to 30.00
Full-matrix least-squares on F2Ͼ0
7797/6351
Full-matrix least-squares on F2Ͼ0
14091/13328
6351/0/244
0.937
R1 ϭ 0.0444, wR2 ϭ 0.1151
R1 ϭ 0.0574, wR2 ϭ 0.1263
2.000 and Ϫ5.602
13328/0/419
1.092
R1 ϭ 0.0357, wR2 ϭ 0.0838
R1 ϭ 0.0996, wR2 ϭ 0.1798
2.340 and Ϫ2.075
R indices (all data)
Largest diff. peak and hole [e·A
Ϫ3
˚
]
2972
Eur. J. Inorg. Chem. 2001, 2965Ϫ2973

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2973