Oxidative addition of phenylselenyl halides to platinum(0) complexes: Characterisation and reactivity of the products [PtX(SePh)-(N,N-chelate)(olefin) ] (X = Cl, Br, I)

Article abstract of DOI:10.1002/ejic.200400536

The oxidative addition of PhSeX (X = Cl, Br, I) to Pt⁰ complexes of formula [Pt(N,N-chelate)(olefin)] is described, The reaction quantitatively affords the trigonal-bipyramidal products [PtX(SePh)(N,N-chelate)(olefin)] with the X and SePh fragm

Full text of DOI:10.1002/ejic.200400536

FULL PAPER
Oxidative Addition of Phenylselenyl Halides to Platinum(0) Complexes:
Characterisation and Reactivity of the Products [PtX(SePh)-
(N,N-chelate)(olefin)] (X ؍ Cl, Br, I)
Vincenzo G. Albano,*[a] Vincenzo De Felice,[b] Magda Monari,[a] Giuseppina Roviello,[c] and
Francesco Ruffo*[c]
Keywords: Isomers / Oxidative addition / Platinum / Selenium
The oxidative addition of PhSeX (X = Cl, Br, I) to Pt0 com-
plexes of formula [Pt(N,N-chelate)(olefin)] is described. The
ism of some of these complexes. The reactivity of the axial
ligands towards electrophilic reagents is also investigated,
reaction quantitatively affords the trigonal-bipyramidal prod- and the molecular structures of [PtX(SePh)(dmphen)(dime-
ucts [PtX(SePh)(N,N-chelate)(olefin)] with the X and SePh
fragments in the axial positions. NMR spectroscopic data
have allowed us to gain insights into the geometrical isomer-
thyl fumarate)] (X = Br, I) are compared.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Introduction
Five-coordinate [M(X)(Y)(N,N-chelate)(olefin)] (1; M ϭ
Pd or Pt) complexes have proved to be particularly suitable
for studying the coordination properties of several ions and
molecules (Figure 1).[1] Due to their stability and inertness,
metal adducts of a series of ligand fragments have been iso-
lated,[1,2] including some containing ligands with poor sta-
bility in the ‘‘free’’ state.[3] For example, a variety of or-
ganometallic fragments can sturdily occupy an axial posi-
tion in a series of compounds containing the same
{MX(N,N-chelate)(olefin)} moiety, thus offering the pos-
sibility to assess trends.[2] Alternatively, unstable vinyl al-
cohol can be coordinated and its fairly rich chemical behav-
iour at the metal centre can be compared with that of a
variety of olefins in the same environment.[3]
Figure 1. General formula for complexes 1; M ϭ Pd, Pt; X ϭ Cl,
Br, I, OR, SeR, TeR; Y ϭ H, R, Ar, GeRnCl3Ϫn, SnRnCl3Ϫn
,
PbRnCl3Ϫn, HgR, SeR, TeR
with chalcogenide ligands were not known[5] and very lim-
ited information on the reactivity of these coordinated frag-
ments was available.[6]
Our previous work[4a,4b] dealt with the characterisation
of complexes of type 1 (M ϭ Pt)[7] containing two organo-
chalcogenide ligands obtained by oxidative addition of
REϪER molecules to suitable Pt0 precursors 2 [Reaction
(1) in Scheme 1]. During these studies we also found that,
when E ϭ Se, the reaction is a rare example of an equilib-
rium. This offered the uncommon opportunity to analyse
the subtle effects of the ligand properties on the equilib-
rium.
Recently,[4] we have focused our attention on five-coordi-
nate complexes bearing organochalcogenide ligands ER
(E ϭ O, S, Se, Te) in the axial position. This study was
started because coordinatively saturated PtII compounds
[a]
`
Dipartimento di Chimica ‘‘G. Ciamician’’ Universita di
Bologna,
Via Selmi 2, 40126 Bologna, Italy
Fax: ϩ 39-051-209-9456
E-mail: vincenzo.albano@unibo.it
Dipartimento STAT,
In this paper we report on the addition of phenylselenyl
halides to the same Pt0 precursors [Reaction (2) in
Scheme 1]. This has led to new five-coordinate compounds
containing SePh and X in the apical sites. Analysis of the
NMR spectroscopic and structural data of the new species
revealed new information on the coordination properties of
both organochalcogenides and halides. Furthermore, rel-
evant aspects of the reactivity of the new compounds have
been examined.
[b]
[c]
Via Mazzini 8, 86170 Isernia, Italy
`
Dipartimento di Chimica, Universita di Napoli ‘‘Federico II’’,
Complesso Universitario di Monte S. Angelo,
Via Cintia, 80126 Napoli, Italy
Fax: ϩ 39-081-674-090
E-mail: ruffo@unina.it
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
416
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400536
Eur. J. Inorg. Chem. 2005, 416Ϫ422

Oxidative Addition of Phenylselenyl Halides to Platinum(0) Complexes
FULL PAPER
Characterisation of the Products
The characterisation of the products was carried out by
1H and 13C NMR spectroscopy (Table 1) and elemental
analysis. In two cases, namely [1d(Br)(SePh)] and [1d(I)-
(SePh)], the X-ray molecular structure was also determined.
1
Analysis of the H NMR spectra confirmed that the ad-
ditions proceed by activation of the seleniumϪhalogen
bond and unequivocally confirmed the trigonal bipyrami-
dal geometry of the products. The most relevant features
are the high-field shift of the olefin protons signals by at
least 2 ppm with respect to the free alkene, as typically
found in complexes of type 1,[1] and the significant high-
field shift of the PhSe- protons, which is attributable to the
presence of a specific interaction between the phenyl ring
of the selenide ligand and the rings of dmphen. This inter-
action is also present in the solid state, and has already been
discussed for [1(EPh)2] complexes.[4a]
As for the stereochemical aspects, the number of possible
isomers depends on the symmetry of the alkene. Of course,
ethylene (D2h) affords only one isomer and the alkene pro-
tons resonate as an AB quadruplet. In the presence of di-
methyl maleate (C2v), two isomers[8] may exist according to
the orientation of the olefin substituents. The NMR spectra
of freshly dissolved [1c(Cl)(SePh)] and [1c(Br)(SePh)] sug-
gest the presence of only one rotamer whose olefin protons
resonate at δ ϭ 4.31 and δ ϭ 4.28 ppm, respectively. In both
cases, on standing in solution, slow conversion (days to
completion) to the thermodynamically stable isomers was
observed. The chemical shifts of the olefin protons for the
latter species are δ ϭ 4.60 and δ ϭ 4.74, respectively.
The correct geometry of the two isomers can be reason-
ably assigned by considering the NMR spectroscopic data
of the known complexes [Pt(SePh)2(dmphen)(dimethyl ma-
leate)][4b] and [PtCl2(dmphen)(dimethyl maleate)].[9] In the
former species the olefin protons are necessarily oriented
towards the SePh ligand, and resonate at δ ϭ 4.34 ppm.
This value is very close to that found for the first, kinetically
formed isomer of [1c(Cl)(SePh)]. In the dichloro species the
maleate protons face the halide and their signal appears at
δ ϭ 4.79 ppm, a value close to that found for the thermo-
dynamically stable rotamer of [1c(Cl)(SePh)]. Hence, it is
inferred that the olefin protons are likely to face the selenide
ligand in the initially formed isomer, while they are oriented
towards the chloride in the thermodynamically stable rot-
amer. This correlation can be reasonably extended to the
bromo species [1c(Br)(SePh)]. It should be noted that an
analogous relationship holds true for complexes of 1 bear-
ing a halide and a hydrocarbyl group[7] in the axial posi-
tions. In all cases, the chemical shift of the maleate protons
is higher in the isomer in which these nuclei are oriented
towards the halogen.
Scheme 1
Results and Discussion
Synthesis of the Complexes
Oxidative addition of the phenylselenyl halides was car-
ried out with the three-coordinate precursors 2 shown in
Scheme 1. The chelating ligand 2,9-dimethyl-1,10-phen-
anthroline (dmphen) was used due to its well-known ability
to stabilise trigonal bipyramidal complexes of d8 ions.[1]
Olefins with increasing electron-acceptor properties were
used: ethylene (a), methyl acrylate (b), dimethyl maleate (c),
dimethyl fumarate (d), diphenyl fumarate (e) and fumarodi-
nitrile (f). As a consequence the metalϪolefin bond in the
Pt0 complexes containing c, d, e or f is characterised by a
substantial π-backdonation contribution, thus enhancing
the stability of the five-coordinate complexes by removing
electronic density from the metal. These compounds are
stable in solution and can be stored at room temperature
for several days without appreciable decomposition. The
ethylene or methylacrylate precursors are more sensitive to
moisture, oxidising agents or heat, and were therefore
freshly prepared before use.
All the additions were performed in chloroform, in which
the complexes generally display reasonable solubility. The
reactions were complete within a few seconds, as revealed
by the change of the solution colour from yellow (red for
ethylene derivative) to pink. The products were crystallised
in high yield by dropwise addition of diethyl ether to the
reaction mixture. The ethylene complex could be isolated in
pure form only with Cl-SePh, while in the case of the other
haloselenides it was always accompanied by significant im-
Coordination of dimethyl fumarate or fumarodinitrile
purities, which could not be removed even by careful crys- (C2h) results in the formation of an enantiomeric couple,
tallisation. The compounds are soluble in chloroform or di- which, of course, is not distinguishable by NMR spec-
chloromethane with the exception of [1f(Br)(SePh)] (M ϭ troscopy in the absence of a shift reagent. The olefin pro-
Pt), which displays a fair solubility only in tetrachloro- tons here are not equivalent, and resonate as doublets. It is
ethane.
interesting to note that the chemical-shift difference (∆δ)
Eur. J. Inorg. Chem. 2005, 416Ϫ422
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
417

V. G. Albano, V. De Felice, M. Monari, G. Roviello, F. Ruffo
FULL PAPER
1
Table 1. Selected Ha and 13Cb NMR spectroscopic data for complexes [Pt(X)(SePh)(dmphen)(olefin)]
Compound
Olefin[c]
Me(dmphen)
3.36 (s, 6 H)
Other selected signals
X ϭ Cl, olefin ϭ ethylene
3.36 (app d, 2 H)
6.68 (t, 1 H), 6.46 (d, 2 H), 6.30 (t, 2 H)
1a(Cl)(SePh)
3.16 [app d, 2 H (70)]
[32.8 (325)]
X ϭ Cl, olefin ϭ methyl acrylate
1b(Cl)(SePh)
Diast.:[d] 4.43 (dd, 1 H)
3.90 (d, 1 H), 3.17 (d, 1 H)
Diast.:[e] 4.60 (dd, 1 H),
3.65 (d, 1 H), 3.41 (d, 1 H)
4.31 [s, 2 H (75)][d]
4.60 [s, 2 H (79)][e]
[32.6 (376)][e]
Diast.[d]: 3.49 (s, 3 H)
3.28 (s, 3 H)
Diast.[d]: 6.74 (t, 1 H), 6.49 (d, 2 H)
6.35 (t, 2 H), 3.75 (s, 3 H, OMe)
Diast.[e]: 6.49 (t, 1 H), 6.26 (d, 2 H)
6.03 (t, 3 H), 3.82 (s, 3 H, OMe)
Diast.[d]: 6.74 (t, 1 H), 6.49 (d, 2 H)
6.33 (t, 2 H), 3.78 (s, 6 H, OMe)
Diast.[e]: 6.58 (t, 1 H), 6.33 (d, 2 H)
6.13 (t, 2 H), 3.83 (s, 6 H, OMe)
6.47 (t, 1 H), 6.27 (d, 2 H), 6.03 (t, 2 H)
3.82 (s, 3 H, OMe), 3.72 (s, 3 H, OMe)
Diast.[e]: 3.60 (s, 3 H)
3.46 (s, 3 H)
X ϭ Cl, olefin ϭ dimethyl maleate
1c(Cl)(SePh)
3.42 (s, 6 H)[d]
3.50 (s, 6 H)[e]
X ϭ Cl, olefin ϭ dimethyl fumarate
1d(Cl)(SePh)
5.16 [d, 1 H (82)]
4.98 [d, 1 H (76)]
3.70 (s, 3 H)
3.62 (s, 3 H)
[32.7 (332), 31.4 (346)]
5.54 [d, 1 H (82)]
5.29 [d, 1 H (77)]
X ϭ Cl, olefin ϭ diphenyl fumarate
1e(Cl)(SePh)
3.74 (s, 3 H)
3.72 (s, 3 H)
7.45Ϫ7.10 (m, 10 H), 6.51 (t, 1 H)
6.32 (d, 2 H), 6.08 (t, 2 H)
[33.3 (340), 32.0 (341)]
4.25 [d, 1 H (75)]
4.03 [d, 1 H (63)]
X ϭ Cl, olefin ϭ fumarodinitrile
1f(Cl)(SePh)
3.40 (s, 3 H)
3.26 (s, 3 H)
6.82 (t,1 H), 6.49 (d,2 H), 6.35 (t, 2 H)
[14.4 (374), 13.5 (354)][f]
Diast.[d]: 4.52 (dd, 1 H)
4.12 (d, 1 H), 3.28 (d, 1 H)
Diast.[e]: 4.85 (dd, 1 H),
3.88 (d, 1 H), 3.61 (d, 1 H)
4.28 [s, 2 H (75)][d]
4.74 [s, 2 H (83)][e]
[34.2 (364)][e]
X ϭ Br, olefin ϭ methyl acrylate
1b(Br)(SePh)
Diast.[d]: 3.58 (s, 3 H)
3.38 (s, 3 H)
Diast.[d]: 6.74 (t, 1 H), 6.46 (d, 2 H)
6.34 (t, 2 H), 3.86 (s, 3 H, OMe)
Diast.[e]: 6.46 (t, 1 H), 6.23 (d, 2 H)
6.02 (t, 2 H), 3.92 (s, 3 H, OMe)
Diast.[d]: 6.73 (t, 1 H), 6.48 (d, 2 H)
6.33 (t, 2 H), 3.80 (s, 6 H, OMe)
Diast.[e]: 6.62 (t, 1 H), 6.34 (d, 2 H)
6.18 (t, 2 H), 3.83 (s, 6 H, OMe)
6.50 (t, 1 H), 6.25 (d, 2 H)
6.06 (t, 2 H), 3.82 (s, 3 H, OMe)
3.72 (s, 3 H, OMe)
7.40Ϫ7.20 (m, 10 H), 6.64 (br, 1 H)
6.36 (br, 2 H), 6.20 (br, 2 H)
Diast.[e]: 3.68 (s, 3 H)
3.54 (s, 3 H)
X ϭ Br, olefin ϭ dimethyl maleate
1c(Br)(SePh)
3.38 (s, 6 H)[d]
3.48 (s, 6 H)[e]
X ϭ Br, olefin ϭ dimethyl fumarate
1d(Br)(SePh)
5.24 [d, 1 H (84)]
4.93 [d, 1 H (78)]
[32.6 (322), 32.0 (353)]
5.65 [d, 1 H (74)]
5.33 [d, 1 H (83)]
3.68 (s, 3 H)
3.61 (s, 3 H)
X ϭ Br, olefin ϭ diphenyl fumarate
1e(Br)(SePh)
3.68 (s, 3 H)
3.63 (s, 3 H)
X ϭ Br, olefin ϭ fumarodinitrile
1f(Br)(SePh)
4.38 [d, 1 H (76)]
4.02 [d, 1 H (67)]
[12.1 (388), 11.8 (362)][f]
5.34 [d, 1 H (83)]
4.84 [d, 1 H (76)]
[31.0 (356), 30.7 (346)]
3.62 (app d, 2 H)
3.41 (app d, 2 H)
3.41 (s, 3 H)
3.26 (s, 3 H)
6.83 (t, 1 H), 6.48 (d, 2 H), 6.40 (t, 2 H)
X ϭ I, olefin ϭ dimethyl fumarate
1d(I)(SePh)
3.62 (s, 3 H)
3.59 (s, 3 H)
6.55 (t, 1 H), 6.22 (d, 2 H), 6.06 (t, 2 H)
3.80 (s, 3 H, OMe), 3.75 (s, 3 H, OMe)
[PtCl(dmphen){Se(Ph)Me}(ethylene)]BF4
1a(Cl)(SePhMe)
3.46 (s, 3 H)
3.24 (s, 3 H)
7.17 (t, 1 H), 6.84 (t, 2 H), 6.51 (d, 2 H)
3
2
2.35 (s, 3 H, SeMe, JPt,H ϭ 35, JSe,H ϭ 9 Hz)
[PtCl(dmphen){Se(Ph)Me}-
(dimethyl maleate)]BF4
1c(Cl)(SePhMe)
Diast.[d]: 4.56 [ABq, 2 H (71)]
Diast.[e]: 4.99 [d, 1 H (77)],
4.62 [d, 1 H (76)]
Diast.[d]: 3.58 (s, 3 H)
3.36 (s, 3 H)
Diast.[d]: 3.78 (s, 6 H, OMe)
3
2
2.51 (s, 3 H, SeMe, JPt,H ϭ 33, JSe,H ϭ 6 Hz)
Diast.[e]: 3.42 (s, 3 H)
3.21 (s, 3 H)
Diast.[e]: 3.88 (s, 3 H, OMe), 3.86 (s, 3 H, OMe)
3
2
1.84 (s, 3 H, SeMe, JPt,H ϭ 36, JSe,H ϭ 6 Hz)
6.81 (t, 1 H), 6.49 (t, 2 H), 6.28 (d, 2 H)
3.98 (s, 3 H, OMe), 3.78 (s, 3 H, OMe)
[PtCl(dmphen){Se(Ph)Me}-
(dimethyl fumarate)]BF4
1d(Cl)(SePhMe)
5.00 [ABq, 2 H (72)][g]
3.69 (s, 3 H)
3.42 (s, 3 H)
3
2
3.01 (s, 3 H, SeMe, JPt,H ϭ 30, JSe,H ϭ 7 Hz)
[Pt(SePh)(dmphen)(MeCN)(ethylene)]BF4
1a(SePh)(MeCN)
3.78 (app d, 2 H, 69)
3.41 (app d, 2 H, 61)
3.18 (s, 6 H)
6.99 (m, 1 H), 6.57 (m, 4 H)
[a]
[b]
[c]
1
At 200 or 300 MHz and 298 K.
At 50.2 or 75.4 MHz and 298 K; values given in square brackets.
2JPt,H and JPt,C [Hz] in
[d]
[e]
[f]
parentheses (when measurable).
Kinetically formed isomer.
Thermodynamically stable isomer.
Spectra recorded in C2D2Cl4
(13C2D2Cl4: δ ϭ 74.15 ppm as internal standard). More abundant isomer.
[g]
between the CHϭ signals in the dimethyl fumarate com-
Finally, two enantiomeric couples are formed with methyl
plexes is close to that for the corresponding maleate rota- acrylate. Actually, two patterns are present in the NMR
mers. This is in agreement with the fact that one fumarate spectra of both [1b(Cl)(SePh)] and [1b(Br)(SePh)]. The
proton is oriented towards the halide, while the other faces spectrum of a freshly prepared solution of the latter com-
the selenide ligand.
pound shows the two isomers in a 2:1 ratio. After three
418
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 416Ϫ422

Oxidative Addition of Phenylselenyl Halides to Platinum(0) Complexes
FULL PAPER
˚
hours the species are present in equimolar amounts, and
within six days the conversion to the stable isomer is com-
plete. In a similar fashion the isomeric ratio for the chloro
derivative is initially 1:1 and after five days one isomer be-
comes by far the more abundant. The correlation men-
tioned above for the dimethyl maleate complexes (see
Table 1) indicates that the carboxymethyl groups are ori-
ented towards the halide in the thermodynamically stable
isomer.
Table 2. Selected bond lengths [A] and angles [°] for [1d(Br)(SePh)]
and [1d(I)(SePh)]
[1d(Br)(SePh)]
[1d(I)(SePh)]
PtϪBr
PtϪI
PtϪSe
2.5195(9)
Ϫ
2.6855(9)
2.472(1)
2.190(8)
2.180(9)
2.09(1)
2.11(1)
1.43(2)
1.922(6)
75.9(3)
Ϫ
176.81(4)
104.0(2)
91.9(3)
91.0(3)
87.0(2)
86.1(2)
Ϫ
2.4537(9)
2.160(7)
2.201(7)
2.087(9)
2.101(8)
1.44(1)
1.930(5)
76.2(3)
177.12(3)
Ϫ
PtϪN(1)
PtϪN(2)
PtϪC(1)
PtϪC(2)
C(1)ϪC(2)
SeϪC(21)
N(1)ϪPtϪN(2)
SeϪPtϪBr
SeϪPtϪI
The X-ray Molecular Structures of [1d(Br)(SePh)] and
[1d(I)(SePh)]
The crystals of the title species are isomorphous (see Exp.
Sect.), therefore the molecules are strictly isostructural in
the solid state and experience equal force fields. This situ- PtϪSeϪC(21)
103.6(2)
Ϫ
IϪPtϪC(1)
ation allows close comparisons of the bond values so that
IϪPtϪC(2)
even minor differences can be discussed. Figure 2 shows a
IϪPtϪN(1)
Ϫ
Ϫ
Ϫ
perspective drawing of the molecules; an axial view is
IϪPtϪN(2)
shown in Figure 3. Table 2 contains a comparison of the
most significant bond parameters of the two species.
BrϪPtϪC(1)
BrϪPtϪC(2)
BrϪPtϪN(1)
BrϪPtϪN(2)
91.7(3)
90.6(3)
87.5(2)
85.7(2)
Ϫ
Ϫ
Ϫ
asymmetric configuration because the C2 symmetry of di-
methyl fumarate does not match the idealised Cs symmetry
of the remaining moiety. It should be noted that the phenyl
ring of the SePh ligand is approximately placed above the
central ring of the phenanthroline (Figure 2), while in the
bis(phenylselenide) derivative [Pt(SePh)2(dimethyl fumara-
te)(dmphen)] the phenyl rings match both pyridine rings
from opposite sides.[4a] In that case we assumed the presence
of preferential interactions between the ring dipoles. It is
likely that the Cs geometry found in the present case allows
an efficient crystal packing rather than a conformation that
would optimise the intramolecular interactions. The non-
equivalence of the axial ligands causes a tilting of the phen-
anthroline on the side of the less bulky halide ligand [angle
between coordination and phenanthroline planes of
10.6(3)° and 10.5(4)° for bromide and iodide, respectively].
Significant variations are observed for the bonding inter-
actions of the axial ligands. The difference in the
PtϪhalogen distances [PtϪBr 2.520(1) and PtϪI 2.685(1)
Figure 2. ORTEP drawing (30% probability thermal ellipsoids) of
[PtX(SePh)(dmphen)(dimethyl fumarate)] [1d(X)(SePh)] (Xϭ Br,
I); only the olefinic hydrogens are shown for the sake of clarity
˚
A] is consistent with the difference between their covalent
˚
˚
radii (0.19 A). The PtϪSe interaction is 0.02 A shorter in
˚
the bromide derivative [2.453(1) and 2.472(1) A, respec-
tively]. This effect, if compared with the even longer value
found in the bis(selenide) derivative [Pt(SePh)2(dimethyl fu-
[4a]
˚
marate)(dmphen)] [average value 2.517(1) A],
suggests a
correlation of the PtϪSe distance with the electronegativity
difference between the apical donor atoms. In other words,
as the bonds in the linear SeϪPtϪX unit (X ϭ Br, I, Se)
result from interactions with the same metal-atom orbitals,
Figure 3. View down the XϪSeϪPt axis (X
ϭ Br, I) of
[PtX(SePh)(dmphen)(dimethyl fumarate)] [1d(X)(SePh)]; hydrogen
atoms are omitted for clarity
The molecular geometry is as expected. The phenanthro- the ligand-to-metal donation is balanced between the com-
line nitrogen atoms and fumarate double bond define the petitors according to their donor properties, and the PtϪSe
equatorial coordination plane, and the halide and selenide bond becomes stronger in the bromide and weaker in the
atoms occupy the axial positions. The molecules exhibit an bis(selenide) derivative.
Eur. J. Inorg. Chem. 2005, 416Ϫ422
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
419

V. G. Albano, V. De Felice, M. Monari, G. Roviello, F. Ruffo
FULL PAPER
The equatorial PtϪN and PtϪC interactions are affected
much less by the changes in the axial ligands, and the differ-
ences are barely significant in terms of experimental errors.
However, we note that, in agreement with the situation dis-
cussed for the axial ligands, the bonds in the bromide de-
rivative are slightly, but systematically, shorter than in the
iodide. The average values are as follows: PtϪN 2.180(7),
˚
2.185(8) and PtϪC 2.086(8), 2.097(9) A, respectively. Corre-
spondingly, the olefin CϭC distance is slightly longer in the
˚
bromide derivative [1.437(12) against 1.425(15) A], and the
CϪCϭCϪC torsion angle is slightly higher in the bromide
[46.1(9) against 44.5(9)°], indicating slightly more sp3 rehy-
bridisation where more donation is allowed.
Scheme 2
Reactivity
In no case was the oxidative addition of phenylselenyl
halides to the platinum(0) precursors found to be an equi-
librium. The reaction was quantitative even with fumarodi-
nitrile, which stabilises the low oxidation state of the metal
through a very effective π-backdonation. These results par-
allel those obtained when PhSe-SePh[4b] is allowed to react
with the same complexes, while with MeSe-SeMe[4a] the re-
actions were found to be an equilibrium. However, these
findings are not surprising since the PtϪX bond
strengths[10] are relatively high compared to those of the
other bonds that form or break in the reaction. Thus, the
addition of the selenenyl halides is enthalpically driven
towards the products. Furthermore, the above-mentioned
intramolecular interaction between aromatic rings helps to
stabilise the five-coordinate complexes.
Some relevant aspects of the reactivity of the new com-
plexes have been explored. The ability of the coordinated
SeR ligands to undergo electrophilic attack was confirmed
by reacting [1a(Cl)(SePh)], [1c(Cl)(SePh)] (kinetic isomer)
and [1d(Cl)(SePh)] with trimethyloxonium tetrafluorobo-
rate (reaction 1 of Scheme 2). The corresponding products
are formally monopositive cationic complexes bearing Se-
(Me)Ph as the axial ligand. Accordingly, the compounds are
fairly soluble only in nitromethane. The presence of Me on
selenium was confirmed by the presence of a singlet coupled
to both 77Se and 195Pt in the 1H NMR spectrum. Of course,
upon addition of the methyl group, the selenium atom be-
comes stereogenic. In the presence of a prochiral olefin such
as dimethyl fumarate, two diastereomeric couples form, and
these were observed in solution for [1d(Cl)(SePhMe)] in an
8:3 ratio.
ment with a silver salt (reaction 2 of Scheme 2). The reac-
tion was performed with the ethylene compound
[1a(Cl)(SePh)] and affords the corresponding monopositive
cation of [1a(SePh)(MeCN)], which, again, is fairly soluble
only in nitromethane.
Conclusions
The chemistry described in this paper confirms the pecul-
iar aptitude of trigonal bipyramidal complexes of plati-
num(ii), such as 1, to function as effective models for com-
paring the behaviour of ligands. Thus, new five-coordinate
PtII complexes with a halide and the SePh ligand in axial
positions have been isolated and relevant aspects of their
reactivity elucidated. The availability of the new com-
pounds has allowed a comparison of the coordination and
spectral properties of halides and organochalcogenides in
identical environments. NMR spectroscopy has also been
employed for this homogeneous class of compounds to ana-
lyse the geometrical isomerism displayed by some of the
compounds.
Experimental Section
General: 1H and 13C NMR spectra were recorded with Varian XL-
200 or Varian Gemini spectrometers. The NMR spectroscopic data
1
are reported in Table 1. H and 13C NMR chemical shifts are re-
ported in δ units (ppm) relative to the solvent (CHCl3: δ ϭ 7.26
ppm; CHD2NO2: δ ϭ 4.33 ppm; 13CDCl3: δ ϭ 77.0 ppm;
13C2D2Cl4: δ ϭ 74.15 ppm). Phenylselenyl chloride, phenylselenyl
bromide, the diphenyl diselenide compound with iodine (1:1) and
the trimethyloxonium salt were commercially available. Platinum(0)
precursors were obtained according to a described method.[11] Sol-
vents and reagents were of AnalaR grade and used without
further purification.
In the spectrum of [1c(Cl)(SePhMe)], which is obtained
upon addition of trimethyloxonium tetrafluoroborate to the
kinetic isomer of [1c(Cl)(SePh)], the CHϭ protons resonate
as two doublets, while the methoxy groups are still equiva-
lent. The lack of sensitivity of the methoxy protons towards
the transformation of the selenide ligand suggests that the
coordination stereochemistry of the olefin is retained. In
solution, the compound slowly isomerises into the most
stable isomer, as is the case for the parent compound.
Another aspect of this study has dealt with the reactivity
of the other axial ligand — the halide. This can be replaced
Synthesis of Complexes 1 of Formula [PtX(SePh)(dmphen)(olefin)]
(X؍ Cl, Br): A solution of the appropriate selenyl compound
PhSeX (0.15 mmol) in a minimum amount of chloroform (0.5 mL)
was added to a suspension of the three-coordinate compound 2aϪf
(0.15 mmol) in chloroform (0.5 mL). After stirring at room tem-
by a neutral ligand, for example acetonitrile, upon treat- perature for 5 min, addition of diethyl ether afforded the deep rose-
420 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjic.org
Eur. J. Inorg. Chem. 2005, 416Ϫ422

Oxidative Addition of Phenylselenyl Halides to Platinum(0) Complexes
FULL PAPER
violet product, which was washed with diethyl ether and dried.
(0.13 mmol) was added to a solution of five-coordinate product
[1a(Cl)(SePh)]: Yield: 75 mg (80%). C22H21ClN2PtSe (622.8) calcd.
[1a(Cl)(SePh)] (0.13 mmol) in nitromethane under nitrogen at
C 42.43, H 3.40, N 4.50; found C 42.12, H 3.22, N 4.37. 273 K. After stirring for 30 min, the residual solid was filtered
[1b(Cl)(SePh)]: Yield: 85 mg (83%). [1c(Cl)(SePh)]: Yield: 100 mg through a small Celite pad. The addition of diethyl ether to the
(90%). C26H25ClN2O4PtSe (738.8) calcd. C 42.27, H 3.41, N 3.79;
resulting solution afforded the light-yellow product, which was
found C 42.03, H 3.54, N 3.63. [1d(Cl)(SePh)]: Yield: 98 mg (88%). washed with diethyl ether and dried. Yield: 74 mg (80%).
[1e(Cl)(SePh)]: Yield: 110 mg (85%). [1f(Cl)(SePh)]: Yield: 91 mg
(90%). [1b(Br)(SePh)]: Yield: 87 mg (80%). [1c(Br)(SePh)]: Yield:
X-ray Crystallography: Crystals of suitable quality were grown
from a 1:1 mixture of chloroform and diethyl ether. The X-ray
intensity data for [1d(Br)(SePh)] and [1d(I)(SePh)] were measured
with a Bruker AXS SMART 2000 diffractometer, equipped with a
CCD detector. Cell dimensions and the orientation matrix were
initially determined from a least-squares refinement on reflections
measured in three sets of 20 exposures, collected in three different
ω regions, and eventually refined against all data. For all crystals,
a full sphere of reciprocal space was scanned by 0.3° ω steps, with
the detector kept at a distance of 5.0 cm from the sample. The
software SMART[12] was used for collecting frames of data, in-
dexing the reflections and determining the lattice parameters. The
collected frames were then processed for integration by the SAINT
program,[12] and an empirical absorption correction was applied
using SADABS.[13] The structures were solved by direct methods
(SIR 97)[14] and subsequent Fourier syntheses and refined by full-
matrix least-squares on F2 (SHELXTL),[15] using anisotropic ther-
mal parameters for all non-hydrogen atoms. All hydrogen atoms
except the olefinic hydrogen atoms, which were located in the Four-
ier map and refined isotropically, were added in calculated posi-
tions, included in the final stage of refinement with isotropic ther-
mal parameters, U(H), of 1.2 Ueq(C) [U(H) ϭ 1.5 Ueq(C-Me)], and
allowed to ride on their carrier carbon atoms. Crystal data and
details of the data collection for all structures are reported in
Table 3. CCDC-237837 and -237838 for [1d(Br)(SePh)] and
[1d(I)(SePh)], respectively, contain the supplementary crystallo-
102 mg
(87%).
[1d(Br)(SePh)]:
Yield:
96 mg
(82%).
C26H25BrN2O4PtSe (783.3) calcd. C 39.87, H 3.22, N 3.58; found
C 40.02, H 3.18, N 3.69. [1e(Br)(SePh)]: Yield: 112 mg (82%).
[1f(Br)(SePh)]: Yield: 92 mg (86%). C24H19BrN4PtSe (717.2) calcd.
C 40.19, H 2.67, N 7.81; found C 40.35, H 2.81, N 7.60.
Synthesis of [PtI(SePh)(dmphen)(dimethylfumarate)] [1d(I)(SePh)]:
The 1:1 diphenyl diselenide compound with iodine (0.11 mmol) was
added to
a magnetically stirred suspension of 2d (0.12 g,
0.22 mmol) in chloroform (1 mL). The dark-red solution was
stirred at room temperature for 5 min. Subsequent addition of di-
ethyl ether afforded the product, which was washed with diethyl
ether and dried. Yield: 100 mg (80%).
Synthesis of Complexes 1 of Formula [PtCl(dmphen){Se(Ph)Me}-
(olefin)]BF4: A solution of trimethyloxonium tetrafluoborate salt
(0.019 g, 0.13 mmol) in nitromethane (0.5 mL) was added to the
appropriate coordinatively saturated compound [1a(Cl)(SePhMe)],
[1c(Cl)(SePhMe)] or [1d(Cl)(SePhMe)] (0.13 mmol). After stirring
at room temperature for 5 min, slow addition of diethyl ether to
the resulting solution afforded the yellow product, which was
washed with diethyl ether and dried. [1a(Cl)(SePhMe)]: Yield:
70 mg
(74%).[1c(Cl)(SePhMe)]:
Yield:
77 mg
(70%).
C27H28BClF4N2O4PtSe (840.7) calcd. C 38.58, H 3.36, N 3.33;
found C 39.01, H 3.35, N 3.40. [1d(Cl)(SePhMe)]: Yield: 74 mg
(68%).
Synthesis of [Pt(SePh)(dmphen)(MeCN)(ethylene)]BF4 [1a(SePh)- graphic data for this paper. These data can be obtained free of charge
(MeCN)]: A solution of silver tetrafluoroborate in acetonitrile at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Table 3. Crystal data and experimental details for [1d(Br)(SePh)] and [1d(I)(SePh)]
[1d(Br)(SePh)]
[1d(I)(SePh)]
Empirical formula
Formula mass
T [K]
C26H25BrN2O4PtSe
783.44
298(2)
C26H25IN2O4PtSe
830.43
298(2)
˚
λ [A]
0.71073
0.71073
Crystal symmetry
Space group
monoclinic
P21/c
11.3454(4)
16.1178(7)
14.0108(6)
93.367(1)
monoclinic
P21/c
11.4073(5)
16.1014(7)
14.1829(6)
93.194(1)
˚
a [A]
˚
b [A]
˚
c [A]
β [°]
3
˚
Cell volume [A ]
2557.6(2)
2601.0(2)
Z
4
4
Dc [Mg·mϪ3
]
2.035
8.507
1496
2.121
8.016
1568
µ(Mo-Kα) [mmϪ1
F(000)
]
Crystal size [mm]
θ limits [°]
0.14 ϫ 0.16 ϫ 0.25
2.53Ϫ24.99
20312 (Ϯh, Ϯk, Ϯl)
4355 [R(int) ϭ 0.055]
0.12 ϫ 0.15 ϫ 0.15
2.53Ϫ29.99
21966 (Ϯh, Ϯk, Ϯl)
7523 [R(int) ϭ 0.079]
Reflections collected
Unique observed reflections
[Fo Ͼ 4σ(Fo)]
Goodness-of-fit-on F2
R1 (F)[a] wR2 (F2)[b]
Largest diff. peak and hole [e·A
1.069
0.0430, 0.0979
1.95 and Ϫ1.48
0.989
0.0542, 0.1375
1.68 and Ϫ2.56
Ϫ3
˚
]
[a]
[b]
2
2 2
2 2 1/2
2
2
2
R1 ϭ Σ||Fo| Ϫ |Fc||/Σ|Fo|. wR2 ϭ [Σw(Fo Ϫ Fc ) /Σw(Fo ) ] where w ϭ 1/[σ2(Fo ) ϩ (aP)2 ϩ bP] and P ϭ (Fo ϩ 2Fc )/3.
Eur. J. Inorg. Chem. 2005, 416Ϫ422
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
421

V. G. Albano, V. De Felice, M. Monari, G. Roviello, F. Ruffo
FULL PAPER
Crystallographic Data, 12 Union Road, Cambridge, CB2 1EZ, UK;
[5k]
ton Trans. 2001, 3430Ϫ3434.
R. Song, K. M. Kim, S. S.
[5l]
Lee, J. S. Sohn, Inorg. Chem. 2000, 39, 3567Ϫ3571.
A. J.
Fax: ϩ 44-1223-336-033; E-mail: deposit@ccdc.cam.ac.uk].
[5m]
Canty, H. Jin, J. Organomet. Chem. 1998, 565, 135Ϫ140.
A. J. Canty, H. Jin, B. W. Skelton, A. H. White, Inorg. Chem.
Acknowledgments
1998, 37, 3975Ϫ3981. [5n] K. M. Kim, Y. S. Sohn, Inorg. Chem.
[5o]
1998, 37, 6109Ϫ6112.
M. S. Davies, T. W. Hambley, Inorg.
The authors thank the MIUR (Programmi di Ricerca Scientifica
di Rilevante Interesse Nazionale, Cofinanziamento 2001Ϫ2002)
and the Universita’ di Bologna and Napoli for financial support
and the Centro Interdipartimentale di Metodologie Chimico-Fis-
Chem. 1998, 37, 5408Ϫ5409. [5p] A. J. Canty, S. D. Fritsche, H.
Jin, J. Patel, B. W. Skelton, A. H. White, Organometallics 1997,
16, 2175Ϫ2182. [5q] U. Bierbach, T. W. Hambley, J. D. Roberts,
N. Farrell, Inorg. Chem. 1996, 35, 4865Ϫ4872. [5r] K. T. Aye, J.
J. Vittal, R. J. Puddephatt, J. Chem. Soc., Dalton Trans. 1993,
1835Ϫ1839.
`
iche, Universita di Napoli ‘‘Federico II’’ for NMR facilities.
[6a] R. E. Barrientos-Astigarraga, P. Castellani, J. V. Comasseto,
[6]
[1]
V. G. Albano, G. Natile, A. Panunzi, Coord. Chem. Rev. 1994,
H. B. Formiga, N. C. da Silva, C. Y. Sumida, M. L. Vieira, J.
133, 67Ϫ114.
[6b]
[2] [2a]
Organomet. Chem. 2001, 623, 43Ϫ47.
A. Ogawa, J. Or-
M. E. Cucciolito, F. Giordano, A. Panunzi, F. Ruffo, V. De
ganomet. Chem. 2000, 611, 463Ϫ474. [6c] S.-K. Kang, S.-W. Lee,
[2b]
Felice, J. Chem. Soc., Dalton Trans. 1993, 3421Ϫ3426.
G. Albano, C. Castellari, M. Monari, V. De Felice, M. L. Fer-
rara, F. Ruffo, Organometallics 1995, 14, 4213Ϫ4221.
V.
H.-C. Ryu, Chem. Commun. 1999, 2117Ϫ2118. [6d] J. C. Bayon,
`
[2c]
`
C. Claver, A. M. Masdeu-Bulto, Coord. Chem. Rev. 1999,
V. G.
[6e]
193Ϫ195, 73Ϫ145.
Soc. 1998, 120, 8249Ϫ8250.
L.-B. Han, M. Tanaka, J. Am. Chem.
Albano, M. L. Ferrara, M. Monari, A. Panunzi, F. Ruffo, In-
org. Chim. Acta 1999, 285, 70Ϫ75.
[6f]
H. Kuniyasu, K. Sugoh, M.
Song Su, H. Kurosawa, J. Am. Chem. Soc. 1997, 119,
[3]
[4]
F. Giordano, F. Ruffo, A. Saporito, A. Panunzi, Inorg. Chim.
Acta 1997, 264, 231Ϫ237.
4669Ϫ4677.
[7]
[4a] V. G. Albano, M. Monari, I. Orabona, A. Panunzi, F. Ruffo,
J. Am. Chem. Soc. 2001, 123, 4352Ϫ4353. [4b] V. G. Albano, M.
Throughout this paper the labels of compounds 1 and 2 con-
tain a letter, which identifies the alkene (see Scheme 1), fol-
lowed by the axial ligands (only for 1).
Monari, I. Orabona, A. Panunzi, G. Roviello, F. Ruffo, Or-
[8] [8a]
[4c]
M. L. Ferrara, I. Orabona, F. Ruffo, V. De Felice, J. Or-
ganometallics 2003, 22, 1223Ϫ1230.
A. Panunzi, G. Rovi-
[8b]
[4d]
ganomet. Chem. 1996, 519, 75Ϫ82.
S. Bartolucci, P. Carpi-
ello, F. Ruffo, Organometallics 2002, 21, 3503Ϫ3505.
A.
nelli, V. De Felice, B. Giovannitti, A. De Renzi, Inorg. Chim.
Acta 1992, 197, 51Ϫ57.
V. G. Albano, C. Castellari, M. L. Ferrara, A. Panunzi, F.
Ruffo, J. Organomet. Chem. 1994, 469, 237Ϫ244.
F. R. Hartley, Nature, Phys. Sci. 1972, 236, 75Ϫ77.
A. De Renzi, A. Panunzi, F. Ruffo, Inorg. Synth. 1998, 32,
158Ϫ162.
SMART & SAINT Software Reference Manuals, version 5.051
(Windows NT Version), Bruker Analytical X-ray Instruments
Inc., Madison, WI, 1998.
G. M. Sheldrick, SADABS, program for empirical absorption
correction, University of Göttingen, Germany, 1996.
A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, A.
G. G. Moliterni, M. C. Burla, G. Polidori, M. Camalli, D. Si-
liqi, Acta Crystallogr., Sect. A 1996, 52, C79.
G. M. Sheldrick, SHELXTLplus (Windows NT Version) Struc-
ture Determination Package, Version 5.1., Bruker Analytical X-
ray Instruments Inc., Madison, WI, USA, 1998.
Received June 18, 2004
Panunzi, G. Roviello, F. Ruffo, Inorg. Chem. Commun. 2003,
6, 1282Ϫ1286.
[9]
[5]
The only known species containing chalcogenide ligands σ-
bonded to platinum are square-planar complexes of PtII and
[10]
[11]
octahedral PtIV derivatives. For recent examples of PtII species,
[5a]
´
R. Oilunkaniemi, R. S. Laitinen, M. Ahlgren, J. Or-
see:
[5b]
ganomet. Chem. 2001, 623, 168Ϫ175.
S. Ford, M. R.
[12]
Lewtas, C. P. Morley, M. Di Vaira, Eur. J. Inorg. Chem. 2000,
933Ϫ938. [5c] A. K. Singh, S. Sharma, Coord. Chem. Rev. 2000,
[5d]
209, 49Ϫ98 and references cited therein.
R. Oilunkaniemi,
[13]
[14]
´
R. S. Laitinen, M. Ahlgren, J. Organomet. Chem. 1999, 587,
[5e]
200Ϫ206.
Soc. 1997, 119, 1795Ϫ1796.
Tanaka, J. Am. Chem. Soc. 1997, 119, 8133Ϫ8134. For recent
L.-B. Han, N. Choi, M. Tanaka, J. Am. Chem.
[5f]
L.-B. Han, S. Shimada, M.
examples related to PtIV or PdIV species, see:
A. J. Canty,
[5g]
[15]
M. C. Denney, J. Patel, H. Sun, B. W. Skelton, A. H. White, J.
Organomet. Chem. 2004, 689, 672Ϫ677.
C. Jennings, R. J. Puddephatt, Inorg. Chem. 2003, 42,
4553Ϫ4558. [5i] V. V. Rostovtsev, L. M. Henling, J. A. Labinger,
J. E. Bercaw, Inorg. Chem. 2002, 41, 3608Ϫ3619. [5j] M. Rashidi,
M. Nabavizadeh, R. Hakimelahi, S. Jamali, J. Chem. Soc., Dal-
[5h]
M. C. Janzen, M.
Early View Article
Published Online November 24, 2004
422
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 416Ϫ422