Rings and linear polymers formed by addition of silver perchlorate to trans-[Pt(C≡CR)2(PMe2Ph)2] (R = But, H)

Article abstract of DOI:10.1039/a607358a

Addition of AgClO₄ to trans-[Pt(C≡CR)₂(PMe₂Ph)₂] (R = Bu^t, H) gives 1:1 adducts of the general formula trans-[PtAg(ClO₄)(μ-C≡CR)₂(PMe ₂Ph)₂] which are cycli

Full text of DOI:10.1039/a607358a

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Rings and linear polymers formed by addition of silver perchlorate to
trans-[Pt(C·CR)2(PMe2Ph)2] (R = But, H)
Shinsaku Yamazaki,*a Antony J. Deeming,*b Despo M. Speel,b David E. Hibbs,c Michael B. Hursthousec and
K. M. Abdul Malikc
a Chemistry Laboratory, Kochi Gakuen College, 292 Asahi Tenjin-Cho, Kochi 780, Japan
b Department of Chemistry, University College London, 20 Gordon Street, London, UK WC1H 0AJ
c School of Chemistry and Applied Chemistry, University of Wales, PO Box 912, Cardiff, UK CF1 3TB
Addition of AgClO4 to trans-[Pt(C·CR)2(PMe2Ph)2]
(R = But, H) gives 1:1 adducts of the general formula trans-
[PtAg(ClO4)(m-C·CR)2(PMe2Ph)2] which are cyclic dimers
crystal X-ray diffraction.2 In 3 one silver ion coordinates to each
of the two alkynyl ligands and polymerisation is prevented.
However, with restricted addition of AgClO4 (1 mol/mol Pt
complex) to trans-[Pt(C·CBut)2(PMe2Ph)2] 1a, a complex is
formed which crystallised from benzene as trans-[Pt2Ag2(m-
C·CBut)4(PMe2Ph)4][ClO4]2·2C6H6 4·2C6H6.† The stoichio-
metry fits a linear polymer but in this case an alternative cyclic
dimer is formed. The X-ray structure was determined at 150(2)
K because of crystal degradation at 293 K (see Fig. 1).‡ In
contrast to compound 3, the silver atoms in 4 coordinate on the
same face of the Pt coordination plane allowing two square-
planar Pt complexes to be glued parallel to each other by two
2
when R = But (ClO4 not coordinated) or linear polymers
when R = H (ClO42 coordinated to silver).
cis-Dialkynyl complexes of platinum behave as chelating
bidentate ligands at copper(i) and silver(i). cis-[Pt(CuCl)(C·
CBut)2(PMe2Ph)2] 1 contains Cu coordinated to two alkynes
and
a
chloride
ligand
and
=
the
complexes
[Pt2M(C·CPh)4(dppe)2][BF4] (M
Cu1, Ag2) and cis-
[Pt2Ag(C·CPh)4(PPh3)4][ClO4]3 contain Ag or Cu atoms
coordinated tetrahedrally to four alkyne groups. Some recent
examples of coordination of Pt alkynyl complexes to silver(i)1–4
and a review by Fornie´s and Lalinde have appeared.5
L2
Pt
ButC
C
C
CBut
Attempting to form linear polymers containing M(m-
C·CR)MA components, we coupled CuCl with trans-
[Pt(C·CBut)2(PMe2Ph)2]. Since the alkynyl ligands are trans at
platinum, chelation is not possible and the linear polymer
[{PtCu2Cl2(C·CBut)2(PMe2Ph)2}n] with the polymer backbone
···Pt[(m-C·CR)CuCl2Cu(m-RC·C)Pt]n(m-C·CR)··· was ob-
tained.6 This paper describes our preparation of halide-free
polymers with the backbone ···Pt(m-C·CR)[Ag(m-RC·C)Pt(m-
C·CR)]nAg··· composed only of metal and bridging alkynyl
ligands.
Ag
Ag
[ClO4]2
ButC
C
Pt
L2
C
CBut
4 (L = PMe2Ph)
The complex trans-[Pt(C·CBut)2(PMe2Ph)2] 1a reacts with
AgClO4 (2 mol/mol Pt) in acetonitrile to give trans-[PtAg2
(MeCN)x(m-C·CBut)2(PMe2Ph)2][ClO4]2 2 (x is probably 4)
and we have determined the X-ray structure of the correspond-
ing copper complex with x = 4.2 Treatment of 2 with pyridine
gave the neutral derivative trans-[PtAg2(ClO4)2(py)2(m-
C·CBut)2(PMe2Ph)2] 3 which was characterised by single-
P(1)
P(2)
C(5)
C(6)
R
C
C(18)
C(17)
PhMe2P
C
C
Pt(1)
Pt
PMe2Ph
C
R
Ag(1)
Ag(2)
1a R = But
b R = H
Pt(2)
C(12)
C(11)
P(3)
C(24)
C(23)
P(4)
N
OClO3
Ag
But
C
PhMe2P
C
Pt
C
PMe2Ph
C
But
Ag
O3ClO
N
Fig. 1 Structure of the square dicationic complex in trans-[Pt2Ag2(m-
C·CBut)4(PMe2Ph)4][ClO4]2·2C6H6 4·2C6H6. The non-coordinated per-
chlorate ions and the benzene molecule are not shown.
3
Chem. Commun., 1997
177

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Ag+ ions. The perchlorate ions are not coordinated. The Pt2Ag2
set of atoms is closely planar and approximately square [Pt–Ag
distances 3.1960(10), 3.2161(9), 3.2080(9), 3.2683(10) Å; Pt–
Ag–Pt angles 86.51(2), 85.44(2)°; Ag–Pt–Ag angles 93.26(2),
94.79(2)°; Pt···Pt 4.3938(9) Å and Ag···Ag 4.7138(9) Å]. The
Ag atoms appear to be pulled in towards the centre of the square
resulting in shorter contacts with the a than the b alkynyl carbon
atoms [av. Ag–Ca 2.236 Å, av. Ag–Cb 2.448 Å] (Fig. 2). Pt···Ag
distances up to 2.95 Å have been considered to indicate donor
interactions from Pt to Ag but in this case the average Pt···Ag
distance of 3.22 Å shows that such interactions must be
extremely weak.7
plane (as in 4 but not 3) forming a zigzag chain with a
perchlorate ion in each cavity along the chain. In addition to the
short coordinated Ag–O distance [Ag(1)–O(1) 2.65(1) Å], there
are number of ClO42-to-chain contacts which might help to
stabilize this arrangement. The shortest C·CH···O contact is too
long to be considered a hydrogen bond. [Cb···O 3.56 Å]. Fig. 2
shows the differences in the geometries of Ag+ coordination in
compounds 4 and 5. The Ag+ ion is more closely coordinated to
Ca than Cb in 5, the reverse of the situation in 4, and Pt···Ag
distance are much longer in 5 than in 4.
We have tried to synthesise analogues of 5 with other counter
2
ions such as BPh4 which are too big to fit the cavities or
The But groups in 4 are bent away from each other [av.
CaCbC(But) 169.1°], as are the tertiary phosphines [P–Pt–P
160.06(8), 163.95(8)°], suggesting that replacement of the But
groups by smaller substituents would allow the cyclic molecules
to relax into a tighter configuration. However, addition of
AgClO4 (1 mol/mol Pt) to trans-[Pt(C·CH)2(PMe2Ph)2] gives
crystals of trans-[PtAg(ClO4)(m-C·CH)2(PMe2Ph)2] 5† which,
rather than forming a cyclic dimer, gives a linear polymer (X-
ray structure, Fig. 3).‡ Relaxation of crowding around Ag has
allowed the perchlorate to coordinate to it and the trans PMe2Ph
ligands to become closely linear [P–Pt–P 177.2(1)°]. The Ag+
ions still coordinate on the same face of each Pt coordination
unlikely to coordinate but no crystalline products could be
obtained. We have still to assess properly the factors that control
the mode of aggregation of [PtAg(ClO4)(C·CR)2(PMe2Ph)2]
units in complexes of this type.
We thank the Royal Society and the Japan Promotion of
Sciences (S. Y.) for support for this collaboration.
Footnotes
† Synthesis and spectra of Ag–Pt complexes. Compound 4: a solution of 1a
(0.223 g) in acetonitrile was treated with AgClO4 (0.081 g). Addition of
benzene and slow evaporation at room temp. gave pale yellow crystals of
4·2C6H6 (0.240 g, 98%); n(C·C) (Nujol), 2031w cm21; 1H NMR (CD3CN):
d 1.17 (s, But), 2.02 [t, J(PH) 7.4, J(PtH) 30.8 Hz, PMe2Ph], 7.37 (s, C6H6),
7.4–8.0 (PMe2Ph); 13C{1H} NMR (CDCl3) d 15.08 [t, J(PC) 39.1 Hz,
PMe2Ph], 30.82 (CMe3), 32.55 (CMe3); 31P{1H} NMR (CDCl3) d 214.79
[J(PtP) 2109 Hz].
But
But
2.007(3)Pt2.022(3)
C
C
C
C
Compound 5: a solution of 1b {prepared from cis-[PtCl2(PMe2Ph)2] and
NaC2H in liquid NH3} (0.20 g) in acetonitrile was treated with AgClO4
(0.088 g). Addition of benzene led to the gradual crystallization of pale
yellow crystals (0.11 g, 40%), n(C·C) (Nujol), 1914 cm21; 1H NMR spectra
Ag
Ag
(CD3CN) show
a
mixture, FABMS (NOBA matrix) showed
[Pt2Ag(C2H)4(PMe2Ph)4]+ and [PtAg(C2H)2(PMe2Ph)2]+ as the highest
mass ions.
‡ Crystal data. Compound 4·2C6H6: C68H92Ag2Cl2O8P4Pt2, pale yellow
C
C
C
Pt
C
C
But
H
But
2.009(3) 2.014(3)
(a)
crystals from benzene, 0.40 3 0.20 3 0.15 mm, M = 1838.12, triclinic,
–
space group P1, a
= 14.608(2), b = 16.338(2), c = 16.356(3) Å,
1.983(9) 1.999(10)
a = 87.28(1), b = 75.02(1), g = 76.43(1)°, U = 3665.3(13) Å3, Z = 2,
Dc = 1.66 g cm23, 9854 unique data, 9854 used, 723 parameters, R1
= 0.0522, wR2 = 0.0916. Compound 5: C20H24AgClO4P2Pt, pale yellow
crystals from acetonitrile–benzene, 0.09 3 0.22 3 0.40 mm, M = 728.29,
Pt
H
C
C
C
Ag
Ag
monoclinic, space group P21/c,
a = 10.481(2), b = 12.236(2),
OClO3
H
OClO3
c = 18.868(3) Å, b = 101.53(1)°, U = 2371.3(6) Å3, Z = 4, Dc = 2.04
g cm23, 4173 unique data, 3163 used [Io > 3s(Io)], 262 parameters,
R = 0.0387, Rw = 0.0428.
Pt
C
C
C
C
Atomic coordinates, bond lengths and angles, and thermal parameters
have been deposited at the Cambridge Crystallographic Data Centre
(CCDC). See Information for Authors, Issue No. 1. Any request to the
CCDC for this material should quote the full literature citation and the
reference number 182/324.
Pt
H
(b)
Fig. 2 Details of the Ag/Pt/alkynyl ligand geometries in 4·2C6H6 (a) and in
5 (b); distances in Å
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Fig. 3 Structure of the linear polymer [{PtAg(ClO4)(C·CH)2(PMe2Ph)2}n]
5; in this case the coordinated perchlorate ions are shown
Received, 29th October 1996; Com. 6/07358A
178
Chem. Commun., 1997