Rigid-rod polymers, oligomers, and model complexes with Pt-Pt bonds in the backbone

Article abstract of DOI:10.1021/om960420q

Reaction of [Pt₂Cl₂(μ-dppm)₂], dppm = Ph₂PCH₂PPh₂, with PhC≡CH in methanol gives [Pt₂Cl₂(μ-dppm)₂(μ-PhCCH)], 1, or, in the presence of base, [Pt₂(C≡CPh)₂(μ-dppm)₂], 2, or [Pt₂(C≡CPh)₂(μ-dppm)₂(μ-PhCCH)], 4. Complex 2 reacts with chlorinated solvents to reform [Pt₂Cl₂(μ-dppm)₂], but in the presence of base, [Pt₂(C≡CPh)₂(μ-dppm) ₂(μ-OH?Cl)], 3, may be formed. Complexes 1 and 3 have been characterized by X-ray structure determinations, and the conditions for formation of 2 have been optimized as a model reaction for polymer formation by using diacetylenes. Reaction of [Pt₂Cl₂(μ-dppm)₂] with HC≡CArC≡CH in methanol in the presence of base gives insoluble oligomers characterized as Cl-[Pt₂(μ-C≡CArC≡C)₂(μ-dppm) ₂]_x[Pt₂Cl(μ-dppm)₂], 5, that is as a diacetylide bridged oligomer with chloride end groups; depending on the diacetylide used x varies from ca. 3-12. Cationic polymers [Pt₂(μ-dppm)₂(μ-L-L)]_x(BF ₄)_2x, 6 or 7, are formed by reaction of [Pt₂Cl₂(μ-dppm)₂] with diisocyanide ligands C≡NArN≡C or with the diphosphine ligand Ph₂PC₆H₄PPh₂, respectively. In contrast, the diphosphine ligand i-Pr₂PC₆H₄C₆H₄P-i-Pr ₂, having a longer spacer group, gives the cyclic complex [Pt₂(μ-dppm)₂(μ-i-Pr₂PC₆H ₄C₆H₄P-i-Pr₂)]₂(BF ₄)₄. The polymeric complexes 5-7 are insoluble or sparingly soluble in common organic solvents. They represent rare examples of conjugated, rigid-rod oligomers or polymers with metal-metal bonds in the backbone.

Full text of DOI:10.1021/om960420q

Organometallics 1996, 15, 5321-5329
5321
Rigid -Rod P olym er s, Oligom er s, a n d Mod el Com p lexes
w ith P t-P t Bon d s in th e Ba ck bon e
Michael J . Irwin, Guochen J ia, J agadese J . Vittal, and Richard J . Puddephatt*
Department of Chemistry, University of Western Ontario, London, Canada N6A 5B7
Received May 29, 1996X
Reaction of [Pt2Cl2(µ-dppm)2], dppm ) Ph2PCH2PPh2, with PhCtCH in methanol gives
[Pt2Cl2(µ-dppm)2(µ-PhCCH)], 1, or, in the presence of base, [Pt2(CtCPh)2(µ-dppm)2], 2, or
[Pt2(CtCPh)2(µ-dppm)2(µ-PhCCH)], 4. Complex 2 reacts with chlorinated solvents to re-
form [Pt2Cl2(µ-dppm)2], but in the presence of base, [Pt2(CtCPh)2(µ-dppm)2(µ-OH‚‚‚Cl)], 3,
may be formed. Complexes 1 and 3 have been characterized by X-ray structure determina-
tions, and the conditions for formation of 2 have been optimized as a model reaction for
polymer formation by using diacetylenes. Reaction of [Pt2Cl2(µ-dppm)2] with HCtCArCtCH
in methanol in the presence of base gives insoluble oligomers characterized as Cl-[Pt2(µ-
CtCArCtC)2(µ-dppm)2]x[Pt2Cl(µ-dppm)2], 5, that is as a diacetylide bridged oligomer with
chloride end groups; depending on the diacetylide used x varies from ca. 3-12. Cationic
polymers [Pt2(µ-dppm)2(µ-L-L)]x(BF4)2x, 6 or 7, are formed by reaction of [Pt2Cl2(µ-dppm)2]
with diisocyanide ligands CtNArNtC or with the diphosphine ligand Ph2PC6H4PPh2,
respectively. In contrast, the diphosphine ligand i-Pr2PC6H4C6H4P-i-Pr2, having a longer
spacer group, gives the cyclic complex [Pt2(µ-dppm)2(µ-i-Pr2PC6H4C6H4P-i-Pr2)]2(BF4)4. The
polymeric complexes 5-7 are insoluble or sparingly soluble in common organic solvents.
They represent rare examples of conjugated, rigid-rod oligomers or polymers with metal-
metal bonds in the backbone.
In tr od u ction
This paper describes the synthesis and characteriza-
tion of some linear-chain polymers containing Pt-Pt
bonds bridged by the conjugated ligands, including
diacetylides -CtCArCtC-, diisocyanides CtNArNtC,
and diphosphines PR2ArPR2, where Ar is an aromatic
spacer group, and of some model complexes. The
ligands used in this research have previously been
employed in the synthesis of rigid rod polymers of
platinum(II) or gold(I).2,5
There are several known types of linear-chain poly-
nuclear complexes containing platinum, many of which
have unusual properties. These include the stacked,
one-dimensional conductors, such as K2Pt(CN)4Br0.30
‚
3H2O,1 and the rigid rod polymers, such as [Pt(PR3)2-
(µ-CtCRCtC-]n, which may exhibit liquid-crystalline,
optical nonlinear or electrical conducting properties.2
Recently, it was shown that halogen bridged, linear-
chain complexes such as the mixed-valence Pt(II)/
Pt(IV) complex [Pt(NH2Et)4][PtCl2(NH2Et)4]Cl4‚4H2O
and the barrel-shaped complex ion K4[Pt2(P2O5-
H2)4X]‚nH2O (X ) Cl, Br, I), which contain no metal-
metal bonds, are semiconductors.3 There are relatively
few reports of polymeric arrays containing metal-metal
bonds in the backbone,4 and with this in mind, it was
of interest to synthesize polynuclear complexes contain-
ing Pt-Pt bonds linked by conjugated organic ligands.
The properties could then be compared to those of the
related compounds without metal-metal bonds.2
Exp er im en ta l Section
The complexes [Pt2Cl2(µ-dppm)2],6 [Pt2(PPh3)2(µ-dppm)2]-
(BF4)2,7 and [Pt2(CtNXy)2(µ-dppm)2](BF4)2,8 where Xy ) 2,6-
Me2C6H3, 1,4-bis(diphenylphosphino)benzene,9 4,4′-(i-Pr)2-
PC6H4C6H4P(i-Pr)2,10 diisocyanoarenes,11 and dialkynylarenes,10
were prepared by literature methods.
NMR spectra were recorded by using a Gemini 300 spec-
trometer. 1H NMR chemical shifts were measured relative to
partially deuterated solvent peaks but are reported relative
(5) (a) Feinstein-J affe, I.; Barash, C. Inorg. Chim. Acta 1991, 185.
(b) Feinstein-J affe, I.; Brain, I.; Mahalu, D.; Cohen, S.; Lawrence, S.
A. Inorg. Chim. Acta 1988, 154, 128. (c) Feinstein-J affe, I.; Frolow, F.;
Wacherle, L.; Goldman, A.; Efraty, A. J . Chem. Soc., Dalton Trans.
1988, 469. (d) Keppler, U.; Hanack, M. Chem. Ber. 1986, 119, 3363.
(e) Deger, S.; Hanack, M. Synth. Met. 1986, 13, 319. (f) Keppler, U.;
Schneider, O.; Stoffler, W.; Hanack, M. Tetrahedron Lett. 1984, 25,
3679. (g) Bradford, A. M.; Kristof, E.; Rashidi, M.; Yang, D. S.; Payne,
N. C.; Puddephatt, R. J . Inorg. Chem. 1994, 33, 2355. (h) J ia, G.;
Puddephatt, R. J .; Vittal, J . J .; Payne, N. C. Organometallics 1993,
12, 263. (i) Stang, P. J .; Cao, D. H.; Saito, S.; Arif, A. M. J . Am. Chem.
Soc. 1995, 117, 6273.
(6) Brown, M. P.; Puddephatt, R. J .; Rashidi, M.; Seddon, K. R. J .
Chem. Soc., Dalton Trans. 1977, 951.
(7) Brown, M. P.; Franklin, S. J .; Puddephatt, R. J .; Thomson, M.
A.; Seddon, K. R. J . Organomet. Chem. 1979, 178, 281.
(8) Grundy, K. R.; Robertson, K. N. Organometallics 1983, 2, 1736.
(9) Baldwin, R. A.; Washburn, R. M. J . Org. Chem. 1965, 30, 3860.
(10) J ia, G.; Puddephatt, R. J .; Scott, J . D.; Vittal, J . J . Organome-
tallics 1993, 12, 3565.
(11) Hoffmann, P. T.; Gokel, G.; Marquerding D.; Ugi, I. In Isonitrile
Chemistry; Ugi, I., Ed.; Academic Press: New York, 1971.
X Abstract published in Advance ACS Abstracts, November 15, 1996.
(1) Ferraro, J . R.; Williams, J . M. in Introduction to Synthetic
Electrical Conductors. Academic Press Inc.: New York, 1987; p 139.
(2) (a) Porter, P. L.; Guha, S.; Kang, K.; Frazier, C. C. Polymer 1991,
32, 1756 and references therein. (b) Lewis, J .; Khan, M. S.; Kakkar,
A. K.; J ohnson, B. F. G.; Marder, T. D.; Fyfe, H. B.; Wittman, F.; Friend,
R. H.; Dray, A. E. J . Organomet. Chem. 1992, 425, 165 and references
therein. (c) Abe, A.; Kimura, N.; Tabata, S. Macromolecules 1991, 24,
6238. (d) Davies, S. J .; J ohnson, B. F. G.; Khan, M. S.; Lewis, J . J .
Chem. Soc., Chem. Commun. 1991, 187. (e) Faust, R.; Diederich, F.;
Gramlich, V.; Seiler, P. Angew. Chem., Int. Ed. Engl. 1995, 111. (f)
Frapper, G.; Kertesz, M. Inorg. Chem. 1993, 32, 732.
(3) (a) Clark, R. J . H. in Lower-Demensional Systems and Molecular
Electronics; Metzger, R. M., Day, P., Papavassilion, G. C., Eds.; Plenum
Press: New York, 1991; p 263. (b) Butler, L. G.; Zietlow, M. H.; Che,
C. M.; Schaeffer, W. P.; Sridhar, S.; Grunthaner, P. J .; Swanson, B. I.;
Clark, R. J . H.; Gray, H. B. J . Am. Chem. Soc. 1988, 110, 1155.
(4) Cayton, R. H.; Chisholm, M. H.; Huffman, J . C.; Lobkovsky, E.
B. J . Am. Chem. Soc. 1991, 113, 8709.
S0276-7333(96)00420-7 CCC: $12.00 © 1996 American Chemical Society

5322 Organometallics, Vol. 15, No. 25, 1996
Irwin et al.
to tetramethylsilane. Phosphorus chemical shifts were deter-
mined relative to 85% H3PO4 as an external standard. IR
spectra were recorded as Nujol mulls on a Perkin-Elmer FTIR
spectrometer. Thermal analyses (DSC and TGA) were carried
out by using a Perkin-Elmer DSC 7 and TAC7/DX differential
scanning calorimeter and thermogravimetric analyzer, respec-
tively. Molecular weight measurements were determined
using a Waters 600 GPC equipped with a Waters 410 dif-
ferential refractor as a detector. Molecular modeling was
carried out using the Cache 3.8 molecular modeling program.
[P t2Cl2(µ-d p p m )2(µ-HCdCP h )], 1. A mixture of [Pt2Cl2-
(µ-dppm)2] (0.10 g, 0.081 mmol) and PhCtCH (0.10 g, 0.98
mmol) in MeOH (30 mL) was stirred at room temperature
overnight. The reaction mixture initially became clear, and
then a yellow precipitate formed. The precipitate was collected
by filtration, washed with MeOH, and dried. Yield: 78 mg,
72%. NMR in C6D6: δ(31P) ) 3.18 [m, 1J (PtP) ) 3280 Hz,
mmol), HCtCC6H2Me2CtCH (17 mg, 0.080 mmol), and NaOMe
(50 mg, 0.92 mmol) in a mixed solvent of MeOH (20 mL)/THF
(10 mL) was stirred at room temperature overnight to give a
yellow precipitate. The precipitate was collected by filtration,
washed with MeOH, H2O, and MeOH, and dried. Yield: 93
mg, 82%. The compound is insoluble in common organic
solvents. IR: ν(CtC) ) 2084 cm-1. FAB-MS: 1311 [Pt2(CCC6-
H2Me2CC)(dppm)2+]; 1194 [trace, Pt2(dppm)2Cl+]; 1159
[Pt2(dppm)2Cl+]. Anal. Calcd for (C62H52P4Pt2)12(C50H44Cl2-
P4Pt2): C, 56.2; H, 4.0. Found: C, 56.2; H, 3.9. Note that the
analytical data are also reasonably close to the expected value
for the polymer (C62H52P4Pt2)x. Anal. Calcd C, 56.8; H, 4.0.
C l[P t 2 (µ-C tC C 6 H 4 C 6 H 4 C tC )(µ-d p p m )2 ]x [P t 2 C l(µ-
d p p m )2], 5c. A mixture of [Pt2Cl2(µ-dppm)2] (0.10 g, 0.081
mmol), HCCC6H4C6H4CCH (16 mg, 0.079 mmol), and NaOMe
(50 mg, 0.92 mmol) in a mixed solvent of MeOH (20 mL)/THF
(10 mL) was stirred at room temperature overnight to give a
yellow precipitate, which was collected by filtration, washed
with MeOH, H2O, and MeOH and dried. Yield: 89 mg, 80%.
The compound is insoluble in common organic solvents. IR:
ν(CtC) ) 2087 cm-1. FAB-MS: m/z ) 1394 [Pt2(CCC6H4C6H4-
CC)(dppm)2Cl+]; 1359 [Pt2(CCC6H4C6H4CC)(dppm)2+]; 1194
[Pt2(dppm)2Cl+]; 1159 [Pt2(dppm)2+]. Anal. Calcd for (C66H52P4-
Pt2)3(C50H44Cl2P4Pt2): C, 56.1; H, 3.9. Found: C, 55.8; H, 3.8.
[P t2(µ-d p p m )2(CNC6H4NC)]x(BF 4)2x, 6a . To a mixture of
[Pt2Cl2(µ-dppm)2] (50 mg, 0.041 mmol) and NaBF4 (0.10 g, 0.90
mmol) in MeOH (30 mL) was added CNC6H4NC (5.3 mg, 0.041
mmol). The resulting mixture was stirred overnight to give
an orange solid. The solid was collected by filtration, washed
with MeOH, H2O, MeOH, and ether, and dried. Yield: 40 mg,
67%. The compound is insoluble in common organic solvents.
IR: ν(NtC) ) 2159 cm-1. Anal. Calcd for C58H48B2F8N2P4-
Pt2‚2H2O: C, 46.6; H, 3.5. Found: C, 46.6; H, 3.7.
2
1
2J (PtP) ) 170 Hz, J (PP) ) 14 Hz], 5.44 [m, J (PtP) ) 3360
Hz, 2J (PtP) ) 125 Hz, 2J (PP) ) 14 Hz]. NMR in CD2Cl2:
δ(1H) ) 2.8-3.2 [br m, 2H, CH2]; 3.6-3.8 [m, 2H, CH2], 6.5-
8.0 [m, 45H, Ph]. Anal. Calcd for C58H50Cl2P4Pt2: C, 52.3;
H, 3.8. Found: C, 52.1; H, 3.8.
[P t 2(CtCP h )2(µ-d p p m )2], 2. A mixture of [Pt2Cl2(µ-
dppm)2] (0.10 g, 0.081 mmol), PhCtCH (0.10 g, 0.98 mmol),
and NaOMe (50 mg, 0.92 mmol) in MeOH (40 mL) was stirred
at room temperature for 3 h to give a yellow precipitate. The
solvent was then evaporated under vacuum, and the residue
was extracted with benzene. The benzene was evaporated and
the residue was washed with MeOH, to give a yellow precipi-
tate, which was collected by filtration, washed with MeOH and
dried. Yield: 88 mg, 80%. NMR in C6D6: δ(31P) ) 2.07 [s,
2
1J (PtP) ) 2930 Hz, J (PtP) ) -70 Hz]; δ(1H) ) 4.86-5.15 [br
m, 4H, CH2]; 6.16-7.90 [m, 50H, Ph]. IR: ν(CtC) ) 2095
cm-1. FAB-MS: m/z ) 1362 {26%, [HPt2(CCPh)2(µ-dppm)2]+};
1260 {100%, [Pt2(CCPh)(µ-dppm)2]+}; 1159 {75%, [Pt2(µ-
dppm)2]+}. Anal. Calcd for C66H54P4Pt2: C, 58.2; H, 4.0.
Found: C, 58.4; H, 3.9.
[P t2(µ-d p p m )2(CNC6H3MeNC)]x(BF 4)2x, 6b. This was
prepared in a similar way from [Pt2Cl2(µ-dppm)2] (50 mg, 0.041
mmol) and NaBF4 (0.10 g, 0.90 mmol) in MeOH (30 mL) with
CNC6H3MeNC (5.8 mg, 0.041 mmol). Yield: 42 mg, 70%. The
compound is insoluble in common organic solvents. IR:
ν(NtC) ) 2160 cm-1. Anal. Calcd for C59H50B2F8N2P4Pt2: C,
48.0; H, 3.4. Found: C, 47.8; H, 3.7.
[P t2(CtCP h )2(µ-d p p m )2(µ-OH‚‚‚Cl)], 3. Over
a 12 h
period, pentane was allowed to diffuse into a saturated solution
of crude 2 in 1,2-dichloroethane. Two large crystals were
removed, and an X-ray diffraction study confirmed the struc-
ture of 3 (see below). After a further day, several smaller
crystals had formed which were found to be [Pt2Cl2(µ-dppm)2]
by the 31P NMR spectrum.
[P t2(µ-d p p m )2(CNC6Me4NC)]x(BF 4)2x, 6c. This was pre-
pared in a similar way from [Pt2Cl2(µ-dppm)2] (50 mg, 0.041
mmol) and NaBF4 (0.10 g, 0.90 mmol) in MeOH (30 mL) with
CNC6Me4NC (7.5 mg, 0.041 mmol). Yield: 48 mg, 77%. The
compound is insoluble in common organic solvents. IR:
[P t2(CtCP h )2(µ-d p p m )2(µ-HCdCP h )], 4. To a suspen-
sion of [Pt2Cl2(µ-dppm)2] (0.10 g, 0.081 mmol) and NaOMe (50
mg, 0.90 mmol) in MeOH (40 mL) was added PhCtCH (0.10
g, 0.98 mmol). The resulting mixture was stirred at room
temperature for 2 days to give a yellow precipitate. The
precipitate was collected by filtration, washed with MeOH, and
dried. Yield: 70 mg, 59%. NMR in C6D6: δ(31P) ) 1.69 [m,
ν(NtC) ) 2157 cm-1
. Anal. Calcd for C62H56B2F8N2P4Pt2‚-
2H20 C, 47.9; H, 3.9. Found: C, 46.7; H, 3.6.
[P t2(µ-d p p m )2(CNC6H2tBu 2NC)]x(BF 4)2x, 6d . This was
prepared in a similar way from [Pt2Cl2(µ-dppm)2] (50 mg, 0.041
mmol) and NaBF4 (0.10 g, 0.90 mmol) in MeOH (30 mL) with
CNC6H2tBu2NC (8.8 mg, 0.042 mmol). Yield: 46 mg, 73%. The
compound is insoluble in common organic solvents. IR:
2
1
1J (PtP) ) 3180 Hz, J (PP) ) 16 Hz]; 2.78 [m, J (PtP) ) 3230
Hz, J (PP) ) 16 Hz]; δ(1H) ) 2.7-3.2 (br m, 2H, CH2], 3.7-
2
ν(NtC) ) 2160 cm-1
. Anal. Calcd for C66H64B2F8N2P4Pt2‚
3.9 [m, 2H, CH2], 6.3-8.1 [m, 55H, Ph]. IR: ν(CtC) ) 2089
cm-1. FAB-MS: m/z ) 1463 {100%, [Pt2(CCPh)2(µ-dppm)2]-
(HCCPh)]+}; 1260 {6%, [Pt2(CCPh)(µ-dppm)2]+}; 1159 {33%,
[Pt2(µ-dppm)2]+}. Anal. Calcd for C74H60P4Pt2: C, 60.7; H, 4.1.
Found: C, 60.4; H, 4.4.
2H2O C, 48.7; H, 4.0. Found: C, 49.0; H, 4.0.
[P t2(µ-d p p m )2(P P h 2C6H4P P h 2)]x(BF 4)2x, 7a . A mixture
of [Pt2Cl2(µ-dppm)2] (0.10 g, 0.081 mmol) and PPh2C6H4PPh2
(3.6 mg, 0.081 mmol) in MeOH (30 mL) was stirred at room
temperature for 4 h to give a clear yellow solution. To the
reaction mixture was then added NaBF4 (0.20 g, 1.8 mmol),
and the resulting mixture was stirred overnight to give a
yellow precipitate. The MeOH was then removed completely,
and the residue was washed with H2O to give a yellow powder,
which was collected by filtration, washed with H2O, MeOH,
benzene, and ether, and dried. Yield: 115 mg, 80%. NMR in
acetone-d6: δ(31P) ) -13 to +18 [br, m, Ph2P]; δ(1H) ) 4.3-
Cl[P t2(µ-CtCC6H4CtC)(µ-dppm )2]x[P t2Cl(µ-dppm )2], 5a.
mixture of [Pt2Cl2(µ-dppm)2] (0.10 g, 0.081 mmol),
A
HCtCC6H4CtCH (17 mg, 0.081 mmol) and NaOMe (50 mg,
0.92 mmol), in a mixed solvent of MeOH (20 mL)/THF (10 mL)
was stirred at room temperature overnight to give a yellow
precipitate, which was collected by filtration, washed with
MeOH, H2O, and MeOH, and dried. Yield: 90 mg, 81%. The
compound has low solubility in common organic solvents. IR:
ν(CtC) ) 2089 cm-1. FAB-MS: m/z ) 1318 [Pt2(CCC6H4CC)-
(dppm)2Cl+]; 1283 [Pt2(CCC6H4CC)(dppm)2+]; 1194 [Pt2(dppm)2-
8.7 [br m, CH2 and Ph], 2.7 [s, H2O]. Anal. Calcd for C80H86
-
B2F8N2P6Pt2‚2H2O: C, 52.9; H, 4.0. Found: C, 52.8; H, 4.2.
[P t2(µ-dppm )2((i-P r )2P C6H4C6H4P (i-P r )2)]2(BF4)4, 8. This
was prepared in a similar way from [Pt2Cl2(µ-dppm)2] (0.10 g,
0.081 mmol) and P(i-Pr)2C6H4C6H4P(i-Pr)2 (3.2 mg, 0.081
mmol) in MeOH (30 mL) with NaBF4 (0.20 g, 1.8 mmol).
Yield: 120 mg, 86%. NMR in acetone-d6: δ(31P) ) -2.50 [s,
Cl+]; 1159 [Pt2(dppm)2+]. Anal. Calcd for (C66H52P4Pt2)5(C50
44Cl2P4Pt2): C, 55.0; H, 3.7. Found: C, 54.9; H, 3.8.
C l[P t 2 (µ-C tC C 6 H 2 M e 2 C tC )(µ-d p p m )2 ]x [P t 2 C l(µ-
d p p m )2], 5b. A mixture of [Pt2Cl2(µ-dppm)2] (0.10 g, 0.081
-
H

Model Complexes with Pt-Pt Bonds
Organometallics, Vol. 15, No. 25, 1996 5323
J (PtP) ) 2900 Hz, dppm]; 21.12 [s, 1J (PPt) ) 2540 Hz, 2J (PtP)
) 1660 Hz, Pr2P]; δ(1H) ) 4.4-5.5 [br m, CH2]; 6.7-8.6 [br m,
Ph]; 2.8 [s, H2O]. Anal. Calcd for C74H80B2F8N2P6Pt2‚2H2O:
C, 50.6; H, 4.6. Found: C, 50.1; H, 4.6.
Ta ble 1. Cr ysta l Da ta a n d Exp er im en ta l Deta ils
for 1‚0.5EtOH a n d 3‚H2O‚2MeOH‚0.5C5H12
complex
1‚0.5C2H5OH
3‚H2O‚2CH3OH‚0.5C5H12
X-r a y Str u ctu r e Deter m in a tion s. Yellow, cubic crystals
of [Pt2Cl2(µ-dppm)2(µ-HCdCPh)], 1, were grown from a mix-
ture of CH2Cl2 and n-pentane at room temperature; a crystal
with dimensions of 0.26 × 0.26 × 0.20 mm was used. A large
yellow, cubic crystal of [Pt2(CCPh)2(µ-dppm)2(µ-OH)]Cl, 3, was
grown from a mixture of C2H4Cl2 and n-pentane at room
temperature and was cut to give a fragment of dimensions 0.37
× 0.35 × 0.25 mm. In each case, the crystal was wedged inside
a Lindemann capillary tube, flame sealed, and used for the
X-ray analysis. The diffraction experiments were carried out
using a Siemens P4 diffractometer with XSCANS software
package12 using graphite-monochromated Mo KR radiation at
25 °C.
For 1, the cell constants were obtained by centering 38 high-
angle reflections (16.7 e 2θ e 25.0°). The Laue symmetry 4/m
was determined by merging symmetry-equivalent reflections.
A total of 6179 reflections were collected in the θ range 1.9-
23.0° (-1 e h e 23, -1 e k e 23, -1 e l e 15) in θ-2θ scan
mode at variable scan speeds (1-10 deg/min). Background
measurements were made at the ends of the scan range. Four
standard reflections were monitored at the end of every 297
reflections collected. At the end of the data collection, the faces
of the data crystal were indexed and the distances between
them were measured. A Guassian absorption correction was
applied to the data (µ ) 4.498 mm-1). The maximum and
minimum transmission factors are 0.508 and 0.429, respec-
tively. In the primitive system with Laue symmetry 4/m, the
systematic absences (00l, l ) 4n + 1) indicated that the space
group is either P41 (No. 76) or P43 (No. 78). The choice of the
space group P41 was confirmed by refining the Flack param-
eter.13
For 3, the cell constants were obtained by centering 25 high-
angle reflections (24.8 e 2θ e 25.0°). The Laue symmetry 2/m
was determined by merging symmetry-equivalent reflections.
A total of 9414 reflections were collected in the θ range 1.9-
22.5o (-1 e h e 19, 1 e k e 19, 1 e l e 19) in θ-2θ scan mode
at variable scan speeds (1-10 deg/min). Background mea-
surements were made at the ends of the scan range. An
empirical absorption correction was applied to the data on the
basis of ψ scan reflections. The systematic absences indicated
the space group P21/c.
The data processing, solution, and the initial refinements
were done using SHELXTL-PC14 programs. The final refine-
ments were performed using SHELXL-9315 software programs.
For 1, anisotropic thermal parameters were refined for all the
Pt, Cl, P, and carbon atoms C(1), C(2), C(9), and C(10). Half
a molecule of ethanol solvate was located in the difference
Fourier. The C-O and C-C distances were fixed and not
refined. A common isotropic thermal parameter was refined
for the solvent atoms. The hydrogen atoms were included in
the calculated positions for the purpose of structure factor
calculations only. All the phenyl rings in the dppm ligands
were treated as regular hexagons with C-C ) 1.395 Å. The
isotropic thermal parameters of the phenyl carbon atoms
(C(3)-C(8)) attached to the C(2) atom were somewhat large.
A satisfactory disorder model could not be formulated from
the difference Fourier map. Refinement of the anisotropic
thermal parameters for these carbon atoms did not yield a
satisfactory result. A 2-fold symmetry was applied to this ring
using soft constraints. In the final least-squares refinement
cycles of F2, the model converged at R1 ) 0.0532, wR2 )
formula
fw
T, K
λ, Å
space group
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
C59H53Cl2O0.5P2Pt2
1354.97
298
0.710 73
P41
21.273(2)
21.273(2)
14.408(3)
C70.5H71Cl1O4P4Pt2
1531.78
298
0.710 73
P21/c
18.206(2)
13.455(1)
26.303(2)
108.03(1)
6126.8(9)
4
1.661
4.76
3036
5902
0.0507
0.1092
1.018
6520(2)
4
1.38
4.498
2644
4201
0.0532
0.1263
1.039
F
calcd, g cm-3
µ, mm-1
F(000)
NOa
R1b
wR2c
Sd
a
b
NO ) number of observed reflections with Fo > 4σ(Fo). R1
) ∑(||Fo| - |Fc||)/∑|Fo|. c wR2 ) [∑w(Fo - Fc2)2/∑wFo
]
.
S )
2
4 1/2 d
goodness of fit ) [∑w(Fo2 - Fc2)2/(n - p)]1/2, where n is the number
of reflections and p is the number of parameters refined.
0.1263, and Goof ) 1.039 for 4201 observations with Fo g 4σ-
(Fo) and 239 parameters, and R1 ) 0.0759 and wR2 ) 0.1439
for all 5169 data. In the final difference Fourier synthesis the
electron density fluctuates in the range 0.776 to -0.624 e Å-3
,
of which the top peak was associated with the atom C(25) at
a distance of 1.27 Å. The mean and maximum shift/esd values
in the final cycles are 0.002 and 0.042, respectively. The
absolute structure parameter was refined to -0.01(2). For 3,
anisotropic thermal parameters were refined for all the Pt,
Cl, P, O(1), and the carbon atoms C(1)-C(4). One molecule
of water in two positions (occupancies 0.5/0.5), two molecules
of methanol solvate (disordered in three positions), and half a
molecule of pentane were located in the difference Fourier
map. Anisotropic thermal parameters were refined for the
oxygen atoms O(2) and O(3) of the water molecules. The C-C
distance and the C-C-C angles were fixed for the pentane
molecule and not refined. Similarly the C-O distances were
fixed at 1.385 Å for all the methanol molecules. A common
isotropic thermal parameter was refined for each group of
solvate molecules. The hydrogen atoms of the cation were
included in the calculated positions for the purpose of structure
factor calculations only. All the phenyl rings were restrained
to have the symmetry C2v. In the final least-squares refine-
ment cycles on F2, the model converged at R1 ) 0.0507, wR2
) 0.1092, and Goof ) 1.018 for 5902 observations with Fo
g
4σ(Fo) and 414 parameters, and R1 ) 0.0809 and wR2 )
0.1286 for all 7956 data. In the final difference Fourier
synthesis the electron density fluctuates in the range 0.832
to -0.948 e Å-3, of which the top peak was associated with
Pt(1) at a distance of 1.04 Å. The mean and maximum shift/
esd values in the final cycles are 0.001 and 0.008, respectively.
The experimental details and crystal data are in Table 1, while
complete positional and thermal parameters, bond distances
and angles, and anisotropic thermal parameters have been
included in the Supporting Information.
Resu lts a n d Discu ssion
Mod el Com p ou n d s a n d th e Rea ction s of [P t2Cl2-
(µ-d p p m )2] w ith P h CtCH. When this work began,
several cationic, diplatinum(I) complexes of the type
[Pt2(µ-dppm)2L2][X]2 had been prepared by the reaction
of [Pt2Cl2(µ-dppm)2] with the ligands L (L ) monoden-
tate phosphine or isocyanide) in the presence of anions
X- ) [BF4]-, [PF6]-, and [ClO4]- (eq 1).7,8 Thus it could
(12) XSCANS; Siemens Analytical X-ray Instruments Inc.: Madison,
WI, 1990.
(13) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(14) Sheldrick, G. M. SHELXTL-PC; Siemens Analytical X-Ray
Instruments Inc.: Madison, WI, 1990.
(15) Sheldrick, G. M. SHELXL-93; Department fuer Anorg. Chemie,
University of Goettingen: Goettingen, Germany, 1993.

5324 Organometallics, Vol. 15, No. 25, 1996
Irwin et al.
Sch em e 1
reasonably be expected that polymeric compounds could
be synthesized by the similar reactions of [Pt2Cl2(µ-
dppm)2] with diphosphine or diisocyanide ligands
(eq 2).
However, the model compounds for neutral diacetyl-
ide-bridged polymers are [Pt2(µ-dppm)2(CtCR)2] and
the reported synthetic route is not suitable for the
synthesis of polymers.16a Therefore the reactions of [Pt2-
Cl2(µ-dppm)2] with the alkyne PhCCH have been stud-
ied under various conditions in order to determine if it
is possible to prepare [Pt2(µ-dppm)2(CtCPh)2] in good
yield and hence to test the feasibility of the synthesis
of the related polymers.
alkynes having electron-withdrawing substituents (e.g.
RCtCR with R ) CO2Me or CF3) with the complexes
[Pt2X2(µ-dppm)2], X ) Cl or CCPh,16,17 [Pt2H(µ-H)Me-
(µ-dppm)2]SbF6,18 and [Pt2Me2(µ-H)(µ-dppm)2]PF618 are
known to give complexes with structures analogous to
1, but phenylacetylene could well behave differently
since it does not contain electronegative substituents.
Vinylidene-bridged diplatinum complexes such as [Pt2-
(µ-CdCHPh)(CtCPh)(PEt3)4]BF4, [Pt2(µ-CdCHPh)-
(CtCPh)(PEt3)3X] (X ) Cl, Br, I, NCS, SPh), and [Pt2(µ-
CdCHPh)(PEt3)3X2] (X ) Cl, Br, I, NCS, SPh) are
known to contain the Pt2(µ-CdCHPh) group.19 Since
the NMR and IR data do not distinguish between the
two likely bonding modes, the structure of 1 was
determined crystallographically.
The molecular structure of 1 is shown in Figure 1,
and selected bond lengths and angles are presented in
Table 2. The expected presence of a trans,trans-Pt2(µ-
dppm)2 unit in 1 is confirmed. More importantly, it is
shown that the phenylacetylene is present in the di-σ-
bonded, parallel bonding mode, Pt2(µ-PhCdCH), and
has not isomerized to the phenylvinylidene isomeric
form. Overall then, each platinum has the square-
planar trans-PtP2ClC donor set expected for a d8 plati-
num(II) center. Clearly, the complex can be described
as having a type of A-frame structure. This is analogous
to the structure of [Pd2Cl2(µ-CF3CdCCF3)(µ-dppm)2],16c
but although similar platinum complexes have been
prepared, none has been characterized by an X-ray
Phenylacetylene reacted at room temperature with
[Pt2Cl2(µ-dppm)2] in methanol to give the pale yellow
compound [Pt2Cl2(µ-PhCCH)(µ-dppm)2], 1 (Scheme 1).
Normally, electronegative substituents on the alkyne
are required for such reactions to be successful16 but it
has been shown that simple alkynes will add to [Pd2-
Cl2(µ-dppm)2] in the presence of acid.16a In the present
case, the solvent methanol may serve as a weak acid to
reversibly protonate the metal-metal bond of [Pt2Cl2-
(µ-dppm)2] and hence catalyze the addition of phenyl-
acetylene. The 31P NMR spectrum of 1 in benzene
displays two signals at δ ) 3.18 [1J (PtP) ) 3280 Hz,
2J (PtP) ) 170 Hz, 2J (PP) ) 14 Hz] and at δ ) 5.44
[1J (PtP) ) 3360 Hz, 2J (PtP) ) 125 Hz, 2J (PP) ) 14 Hz],
consistent with an unsymmetrical A-frame structure.
The 1H NMR spectrum gave two resonances for the
protons CHaHb of the dppm ligands as expected for an
A-frame structure. Unfortunately, the PhCCH proton
resonance was not resolved, presumably because it is
obscured by the phenyl group resonances. On the basis
of the analytical and NMR data, it was not possible to
distinguish between the proposed structure 1, with a
µ-PhCdCH group, and the isomeric vinylidene struc-
ture, with a µ-CdCHPh group. There are precedents
for both types of complex.16-19 Thus, reactions of
(16) (a) Langrick, C. R.; Pringle, P. G.; Shaw, B. L. J . Chem. Soc.,
Dalton Trans. 1985, 1015. (b) Balch, A. L.; Hunt, C. T.; Lee, C.-L.;
Olmstead, M. M.; Farr, J . P. J . Am. Chem. Soc. 1981, 103, 3764. (c)
Lee, C.-L.; Hunt, C. T.; Balch, A. L. Inorg. Chem. 1981, 20, 2498. (d)
Higgins, S. J .; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1988, 457. (e)
Pringle, P. G.; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1983, 889. (f)
Uson, R.; Fornies, J .; Martinez, F.; Navarro, R.; Frias, M. C. Inorg.
Chim. Acta 1987, 132, 217. (g) Davies, J . A.; Kirschbaum, K.; Kluwe,
C. Organometallics 1994, 13, 3664. (h) Davies, J . A.; Kluwe, C.
Organometallics 1995, 14, 4257.
(17) (a) Puddephatt, R. J .; Thomson, M. A. Inorg. Chim. Acta 1980,
45, L281. (b) Puddephatt, R. J .; Thomson, M. A. Inorg. Chem. 1982,
21, 725.
(18) Azam, K. A.; Puddephatt, R. J . Organometallics 1983, 2, 1396.
(19) Baralt, E.; Boudreaux, E. A.; Demas, J . N.; Lenhert, P. G.;
Lukehart, C. M.; McPhail, A. T.; McPhail, D. R.; Meyers, J . B., J r.;
Sacksteder, L.; True, W. R. Organometallics 1989, 8, 2417.

Model Complexes with Pt-Pt Bonds
Organometallics, Vol. 15, No. 25, 1996 5325
of Pt-Cl distances in square-planar Pt(II) complexes,
due to the high trans influence of the σ-carbon donor.21
The Pt-P bond lengths in 1 [2.286(4) and 2.290(4) Å]
are comparable with those in the A-frame complex [Pt2-
Cl2(µ-dppm)2(µ-CH2)], and in addition, the PPtP angles
are similarly distorted from linearity at 169.7(2) and
170.0(2)°.22 In [Pt2Cl2(µ-dppm)2(µ-CH2)], the C-Pt-Cl
angles are close to linear, but in 1 they are much more
distorted at 162.8(5) and 165.6(3)°, although the Pt-C
bond lengths in 1 are not unusual at 2.00(2) and 2.02-
(1) Å. Finally, each Pt2P2C unit adopts an envelope
conformation with the CH2 flap toward the HCdCPh
ligand, presumably to reduce steric interactions by
directing the axial phenyl groups of the dppm ligands
away from the apex ligand, in this case the µ-PhCCH
group.22
It is clear from the above that alkynylplatinum com-
plexes cannot be prepared simply by reaction of [Pt2-
Cl2(µ-dppm)2] with an alkyne but that a base must be
present to deprotonate the alkyne. Reaction products
of phenylacetylene with [Pt2Cl2(µ-dppm)2] in the pres-
ence of base varied depending on reaction conditions.
The reaction with PhCCH and NaOMe in methanol at
room temperature for 2 h gave a yellow compound
identified as [Pt2(CtCPh)2(µ-dppm)2], 2, in good yield
(Scheme 1).16a The spectroscopic data are in good
agreement with the literature16a and prove that a linear,
symmetric structure containing a Pt-Pt bond is
present.23 In particular, the 31P NMR spectrum con-
F igu r e 1. View of the structure of [Pt2Cl2(µ-PhCCH)(µ-
dppm)2].
Ta ble 2. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 1
Pt(1)-C(1)
Pt(1)-P(1)
Pt(2)-C(2)
Pt(2)-P(4)
P(1)-C(10)
P(1)-C(21)
P(2)-C(31)
P(3)C(51)
2.00(2)
2.290(4)
2.02(1)
2.288(4)
1.83(2)
1.83(1)
1.85(1)
1.80(1)
1.84(2)
1.81(1)
1.31(2)
Pt(1)-P(2)
Pt(1)-Cl(1)
Pt(2)P(3)
2.286(4)
2.395(5)
2.284(5)
2.409(5)
1.83(1)
1.81(1)
1.85(2)
1.83(1)
1.79(1)
1.82(1)
1.543(5)
Pt(2)-Cl(2)
P(1)-C(11)
P(2)-C(41)
P(2)-C(9)
P(3)-C(61)
P(4)-C(10)
P(4)-C(71)
C(2)C(3)
P(3)-C(9)
P(4)-C(81)
C(1)-C(2)
1
tains a singlet at δ ) 2.07, with J (PtP) ) 2930 Hz and
2J (PtP) ) -70 Hz, and the large negative value observed
for 2J (PtP) is indicative of a metal-metal-bonded di-
platinum(I) complex.16,23
C(1)-Pt(1)-P(2)
P(2)-Pt(1)-P(1)
P(2)-Pt(1)-Cl(1)
C(2)-Pt(2)-P(3)
P(3)-Pt(2)-P(4)
P(3)-Pt(2)-Cl(2)
C(10)-P(1)-C(11)
C(11)-P(1)-C(21)
C(11)-P(1)-Pt(1)
C(41)-P(2)-C(31)
C(31)-P(2)-C(9)
C(31)-P(2)-Pt(1)
C(51)-P(3)-C(61)
C(61)-P(3)-C(9)
C(61)-P(3)-Pt(2)
C(10)-P(4)-C(81)
C(81)-P(4)-C(71)
C(81)-P(4)-Pt(2)
C(2)-C(1)-Pt(1)
C(1)-C(2)-Pt(2)
P(3)-C(9)-P(2)
83.0(5)
170.0(2)
97.0(2)
87.8(4)
169.7(2)
92.1(2)
103.0(6)
104.2(6)
116.8(4)
103.5(5)
102.2(7)
110.3(4)
102.4(6)
101.9(7)
116.8(4)
101.0(7)
105.1(5)
119.9(4)
121(1)
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-Cl(1)
P(1)Pt(1)Cl(1)
88.4(5)
162.8(5)
92.7(2)
84.7(4)
165.6(3)
96.9(2)
105.3(7)
115.6(5)
110.7(5)
103.2(7)
120.1(4)
115.5(5)
102.3(7)
113.9(4)
117.4(6)
103.5(6)
114.1(5)
111.6(4)
115(1)
Several related binuclear alkynylplatinum complexes
have been reported. The Pt(II) complexes [Pt2(CtCR)4-
(µ-L-L)2] (R ) Ph, Me, CF3, p-tolyl; L-L ) dppm, depm,
dmpm, dippm) have been prepared by the reactions of
PtCl2(L-L) with RCtCLi24,25 or with RCtCH in the
presence of alkoxides.26,27 The Pt2Au cluster complexes
[Pt2(CtC-t-Bu)2(µ-AuX)(µ-dppm)2 (X ) Cl, I) were ob-
tained from [Pt2(CtC-t-Bu)2(µ-AuCtC-t-Bu)(µ-dppm)2],
which was synthesized by reaction of [Pt2(µ-dppm)3]
with AuCtC-t-Bu.28
The complex [Pt2(CtCPh)2(µ-dppm)2], 2, models the
related polymers linked by diacetylides, and so several
attempts were made to grow crystals suitable for X-ray
diffraction. Unfortunately, crystals grown from benzene
or THF solutions were not of suitable size, while, in
chloroform or methylene chloride, 2 reacts to give [Pt2-
Cl2(µ-dppm)2]. Crystals of 2 can be obtained from 1,2-
dichloroethane but are usually unsuitable for Xray
structure determination. In one case, two crystals
C(2)-Pt(2)-P(4)
C(2)-Pt(2)-Cl(2)
P(4)-Pt(2)-Cl(2)
C(10)-P(1)-C(21)
C(10)-P(1)-Pt(1)
C(21)-P(1)-Pt(1)
C(41)-P(2)-C(9)
C(41)-P(2)-Pt(1)
C(9)-P(2)-Pt(1)
C(51)-P(3)-C(9)
C(51)-P(3)-Pt(2)
C(9)-(3)-Pt(2)
C(10)-P(4)-C(71)
C(10)-P(4)-Pt(2)
C(71)-P(4)-Pt(2)
C(1)-C(2)-C(3)
C(3)-C(2)-Pt(2)
P(4)-C(10)-P(1)
124(1)
114.9(9)
120(1)
119.4(8)
structure determination.16,17 This also appears to be the
first structure of a complex of this type in which the
alkyne does not have electronegative substituents.
The Pt‚‚‚Pt separation of 3.480(4) Å in 1 falls well
outside the range considered typical of Pt-Pt single
bonds [ca. 2.53-2.89 Å].20 In addition, the angles C(2)-
C(1)Pt(1) and C(1)C(2)Pt(2) of 121(1) and 124(1)°, re-
spectively, are close to those expected for sp2 hybridiza-
tion at C(1) and C(2). Thus the bonding in the Pt2(µ-
PhCCH) group is best considered in terms of a diplati-
nated alkene with no metal-metal bonding.16,17 Most
other features of the coordination sphere about the Pt
centers are as expected. The Pt-Cl distances of 2.395-
(5) and 2.409(5) Å are near the upper end of the range
(21) Cardin, C. J .; Cardin, D. J .; Lappert, M. F.; Muir, K. W. J .
Chem. Soc., Dalton Trans. 1974, 46. Manojlovic-Muir, Lj.; Muir, K.
W. Inorg. Chim. Acta 1974, 10, 47.
(22) Manojlovic-Muir, Lj.; Muir, K. W.; Azam, K. A.; Frew, A. A.;
Lloyd, B. R.; Puddephatt, R. J . Organometallics 1985, 4, 1400.
(23) 31P NMR of these types of compounds has been extensively
treated earlier.6
(24) Puddephatt, R. J .; Thomson, M. A. J . Organomet. Chem. 1982,
238, 231.
(25) Pringle, P. G.; Shaw, B. L. J . Chem. Soc., Chem. Commun. 1982,
581.
(26) McLennan, A. J .; Puddephatt, R. J . Organometallics 1985, 4,
485.
(27) Anderson, G. K.; Lumetta, G. J . J . Organomet. Chem. 1985,
295, 257.
(20) Manojlovic-Muir, Lj.; Muir, K. W. J . Organomet. Chem. 1981,
219, 129 and references therein.
(28) Manojlovic-Muir, L.; Muir, K. W.; Treurnicht, I.; Puddephatt,
R. J . Inorg. Chem. 1987, 26, 2418.

5326 Organometallics, Vol. 15, No. 25, 1996
Irwin et al.
conformation of the Pt2(µ-dppm) groups is similar to that
in complex 1, with the methylene group in each dppm
unit directed toward the µ-OH‚‚‚Cl bridge, presumably
to minimize steric repulsions.22 The bond parameters
associated with the PtCtCPh and Pt2(µ-dppm) groups
are unexceptional (Table 3).28,29 The µ-OH group is
positioned symmetrically relative to the two Pt centers
with Pt-O ) 2.074(7) and 2.098(7) Å. The hydrogen
atom of the µ-OH‚‚‚Cl group was not located in the
structure determination, but it is presumed to be
hydrogen bonded to the chloride ion. Thus, the distance
O‚‚‚Cl of 3.172 Å is shorter than the van der Waals
distance of ca. 3.3 Å. When the hydrogen atom is placed
in the idealized position in the Pt2(µ-OH) unit with d(O-
H) ) 0.97 Å, the distance H‚‚‚Cl and angle O-H‚‚‚Cl
are calculated to be 2.24 Å and 159.4°, respectively,
again supporting a strong hydrogen bond H‚‚‚Cl. The
structure is very similar to that found for [Ir2(CO)2(µ-
OH‚‚‚Cl)(µ-dppm)2], which has terminal IrCO units in
place of the PtCCPh units of 3 and which has d(O‚‚‚Cl)
) 3.10(2) Å, d(H‚‚‚Cl) ) 2.13 Å, and angle O-H‚‚‚Cl )
163°. For this complex, the H atom was located in the
X-ray structure determination but was not refined.30
Interestingly, most other hydroxoplatinum complexes
containing the ligand dppm have chelating rather than
bridging dppm ligands.31
F igu r e 2. View of the structure of [Pt2(CCPh)2(µ-OH‚‚‚
Cl)(µ-dppm)2].
Ta ble 3. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) in 3
Pt(1)-Pt(2)
Pt(1)-O(1)
Pt(1)-P(2)
Pt(2)-O(1)
Pt(2)-P(3)
P(1)-C(10)
P(2)-C(1d)
P(2)-C(20)
P(3)-C(20)
P(4)-C(1h)
P(4)-C(10)
C(2)-C(11)
C(4)-C(21)
3.1431(7)
2.098(7)
2.309(3)
2.074(7)
2.303(3)
1.83(1)
1.82(1)
1.84(1)
1.83(1)
1.81(1)
1.83(1)
1.45(2)
1.43(2)
Pt(1)-C(1)
Pt(1)-P(1)
Pt(2)-C(3)
Pt(2)-P(4)
P(1)-C(1a)
P(1)-C(1b)
P(2)-C(1c)
P(3)-C(1f)
P(3)-C(1e)
P(4)-C(1g)
C(1)-C(2)
C(3)-C(4)
1.93(1)
2.307(3)
1.95(1)
2.302(3)
1.81(1)
1.85(1)
1.83(1)
1.82(2)
1.83(1)
1.82(1)
1.19(2)
1.22(2)
The final product isolated from this reaction system
is a bright yellow solid characterized as [Pt2(CtCPh)2-
(µ-dppm)2(µ-HCdCPh)], 4. This was isolated when a
mixture of [Pt2Cl2(µ-dppm)2], NaOMe, and PhCtCH in
MeOH was stirred at room temperature for 2 days
(Scheme 1). If the reaction time was less than 15 h,
the isolated product was contaminated by [Pt2(CtCPh)2-
(µ-dppm)2], 2. Hence it appears that 4 is formed by
addition of phenylacetylene to the Pt-Pt bond of 2. A
related complex is [Pt2(CtCPh)2(µ-CtCPh)(µ-dppm)2]+,
which is formed by reaction of [Pt(dppm)2]2+ with Hg-
(CtCPh)2.32 Formally this is related to 4 by addition
or loss of H-. The spectroscopic data for 4 are consistent
with a structure containing two phenylacetylide units
and a coordinated PhCdCH or CdCHPh ligand. The
FAB-MS gave a parent ion due to [Pt2(CCPh)2(µ-dppm)2]-
(HCCPh)]+. The 31P NMR spectrum of 4 in benzene
C(1)-Pt(1)-O(1)
O(1)-Pt(1)-P(1)
O(1)-Pt(1)-P(2)
C(1)-Pt(1)-Pt(2)
P(1)-Pt(1)-Pt(2)
C(3)-Pt(2)-O(1)
O(1)-Pt(2)-P(4)
O(1)-Pt(2)-P(3)
C(3)-Pt(2)-Pt(1)
P(4)-Pt(2)-Pt(1)
Pt(2)-O(1)-Pt(1)
P(3)-C(20)-P(2)
C(1)-C(2)-C(11)
C(3)-C(4)-C(21)
177.3(4)
92.7(2)
86.0(2)
140.3(4)
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-P(2)
P(1)-Pt(1)-P(2)
O(1)-Pt(1)-Pt(2)
89.9(4)
91.5(4)
178.6(1)
40.8(2)
89.02(8)
90.2(4)
92.6(4)
176.5(1)
41.4(2)
89.88(8)
115.4(7)
176(1)
89.76(8) P(2)-Pt(1)-Pt(2)
175.8(4)
92.5(2)
84.5(2)
141.9(4)
C(3)-Pt(2)-P(4)
C(3)-Pt(2)-P(3)
P(4)-Pt(2)-P(3)
O(1)-Pt(2)-Pt(1)
89.10(8) P(3)-Pt(2)-Pt(1)
97.8(3)
115.4(6)
177(1)
P(4)-C(10)-P(1)
C(2)-C(1)-Pt(1)
C(4)-C(3)-Pt(2)
173(1)
1
177(1)
contained two resonances at δ ) -1.69 with J (PtP) )
1
3180 Hz and at 2.78 ppm with J (PtP) ) 3230 Hz. The
31P NMR parameters are similar to those reported for
1 and for [Pt2Cl2(µ-HCdCCF3)(µ-dppm)2].17 Thus, al-
though the vinylidene structure is not eliminated as a
possibility, all the evidence is consistent with the
presence of a µ-PhCCH group in 4.
grown from a highly concentrated solution of crude 2
in C2H4Cl2 did prove suitable, but reaction with solvent
and base had occurred and the crystals proved to be [Pt2-
(CtCPh)2(µ-dppm)2(µ-OH‚‚‚Cl)], 3 (Scheme 1). Complex
3 is formed only in low yield, and the mechanism of
formation is not clear. It is likely that the primary
reaction is with the chlorinated solvent to give [Pt2-
(CtCPh)2(µ-dppm)2(µ-Cl)]Cl and ethylene, and this
intermediate then reacts further to give [Pt2Cl2(µ-
dppm)2] or reacts with base to give 3. The molecular
structure of 3 is shown in Figure 2 and is characterized
by the bond lengths and angles listed in Table 3.
The structure of 3 is that of a typical “A-frame”
with a trans,trans-Pt2(µ-dppm)2 bridged by a µ-OH‚‚‚
Cl group and with a terminal phenylacetylide ligand
bound to each platinum atom. The Pt‚‚‚Pt separation
of 3.143(1) Å, as was the case for 1, falls well outside
the range of Pt-Pt σ-bond lengths.20 The platinum
centers have square-planar stereochemistry. Thus the
angles C-Pt-O ) 175.8(4) and 177.3(4)° and P-Pt-P
) 176.5(1) and 178.6(1)° are all close to linear. The
From the above studies, the optimum conditions for
formation of [Pt2(CtCPh)2(µ-dppm)2], 2, were deter-
mined, and these same conditions were then used in the
synthesis of diacetylide-bridged polymers, as outlined
below.
F or m a t ion of Oligom er s w it h Dia cet ylid e
Br id ges. Reaction of [Pt2Cl2(µ-dppm)2] with 1 equiv of
the appropriate diacetylene HCtCArCtCH in the pres-
ence of NaOMe gave insoluble, yellow, oligomeric di-
acetylide bridged complexes, characterized as Cl[-Pt2-
(CtCArCtC)(µ-dppm)2]x[Pt2(µ-dppm)2]Cl, 5 (eq 3). Ana-
(29) Sutherland, B. R.; Cowie, M. Organometallics 1985, 4, 1637.
(30) Li, J . J .; Sharp, P. R. Inorg. Chem. 1994, 33, 183.
(31) Yam, V. W. W.; Chan, L. P.; Lai, T. F. Organometallics 1993,
12, 2197.
(32) Sarapu, A. C.; Fenske, R. F. Inorg. Chem. 1975, 14, 247.

Model Complexes with Pt-Pt Bonds
Organometallics, Vol. 15, No. 25, 1996 5327
Ta ble 4. P la tin u m 4f7/2 Bin d in g En er gies (BE’s)
fr om XP S of Selected Dip la tin u m (I) Mod el
Com p lexes, Oligom er s a n d P olym er s
complex
Pt 4f7/2 BE (eV)
[Pt2Cl2(µ-dppm)2]
72.3
72.8
72.2
72.4
73.3
73.2
73.2
73.2
72.8
73.2
2
5b
5c
[Pt2(CNXy)2(µ-dppm)2][BF4]2
6a
6c
6d
[Pt2(PPh3)2(µ-dppm)2][BF4]2
8
characterized by their analytical data and by compari-
son of their IR spectra with that of the known model
complex [Pt2(µ-dppm)2(CtN-4-tolyl)2]2+, which is formed
from the similar reaction of [Pt2Cl2(µ-dppm)2] with 2
equiv of 4-MeC6H4NtC.8 Thus, the IR spectra of 6
display strong bands due to ν(NtC) in the range 2157-
2160 cm-1, similar in intensity and frequency to the
corresponding band in the spectrum of [Pt2(µ-dppm)2-
(CtN-4-tolyl)2]2(ClO4)2 [ν(NtC) ) 2168 cm-1).8 For
comparison, the CN stretching frequencies for the free
lytical data indicate that the average value of x is ca. 3
when Ar ) 4,4′-C6H4-C6H4, 5 when Ar ) 1,4-C6H4, and
12 when Ar ) 1,4-C6H2-2,5-Me2. Since the complexes
are insoluble, it is not possible to determine molecular
weights in solution. The IR spectra of 5 are similar to
that of [Pt2(CtCPh)2(µ-dppm)2], having a medium-
intensity band near 2087 cm-1 due to ν(CtC) but no
band near 3300 cm-1 assignable to ν(CC-H), thus
supporting the presence of chloride rather than acety-
lene end groups. The presence of chloride end groups
is strongly supported by FAB mass spectral data. The
major peak in each oligomer 5 is due to the ion [Pt2-
(dppm)2(CCArCC)]+, but 5a ,c also give minor peaks due
to the ions [Pt2(dppm)2(CCArCC)Cl]+ and [Pt2(dppm)2-
Cl]+. Oligomer 5b, for which the analytical data in-
dicate the longest chain length, gives no peak corre-
sponding to [Pt2(dppm)2(CCArCC)Cl]+ and only a barely
detectable peak due to [Pt2(dppm)2Cl]+. It is clear that
the chain growth steps in the formation of 5 are not
efficient, thus leading to oligomers only. A likely cause
is the very low solubility of the oligomers 5, which
results in precipitation from solution before extensive
chain growth can occur. This is consistent with the
observation that the derivative with Ar ) C6H2Me2, in
which the methyl substituents give increased solubility,
gives the highest value of the degree of polymerization
x. The XPS spectra of the oligomers 5 give very similar
Pt 4f7/2 binding energies as in the model compound 2
(Table 4).
diisocyanides range from 2100 to 2115 cm-1
. The
increase (ca. 45 cm-1) in the CN stretching frequency
of the isocyanide on coordination is well documented.33
If the end group was a monodentate diisocyanide, a
band due to free isocyanide might be expected but was
not resolved. We suggest that the chain length is great
enough that the end-group band is too weak to observe
but cannot rule out the possibility that there is a
different end group. The XPS spectra of the oligomers
6 give very similar Pt 4f7/2 binding energies as in the
model compound [Pt2(CtNXy)2(µ-dppm)2]2+ (Table 4).
A Ch a in a n d a Rin g w ith Dip h osp h in e Br id ges.
The reaction of [Pt2Cl2(µ-dppm)2] with 1 equiv of Ph2-
PC6H4PPh2 in methanol in the presence of excess NaBF4
yielded a yellow solid, characterized as [Pt2(µ-dppm)2(µ-
PPh2C6H4PPh2)]x(BF4)2x, 7 (eq 5). The compound is
F or m a t ion of P olym er s w it h Diisocya n id e
Br id ges. Reaction of [Pt2Cl2(µ-dppm)2] with 1 equiv of
a diisocyanide CtNArNtC (Ar ) C6H4, C6H3Me, C6-
Me4, C6H2t-Bu2) in methanol in the presence of excess
NaBF4 gave the pale-yellow (Ar ) C6Me4) or pale orange
(Ar ) C6H4, C6H3Me, C6H2tBu2) polymeric complexes
[Pt2(µ-dppm)2(CtNArNtC)]x(BF4)2x, 6 (eq 4). The solids
soluble in acetone and slightly soluble in halogenated
solvents such as dichloromethane and chloroform but
insoluble in benzene, hexane, and ether. The 31P NMR
spectrum of 7 contains a series of complicated broad
multiplets in the region δ ) -13 to +18, and the
resonances in the 1H NMR spectrum are also broad,
suggesting that 7 is polymeric. The molecular weight
determination by GPC was not possible, since the
solubility of 7 in tetrahydrofuran was poor.
The analogous reaction of [Pt2Cl2(µ-dppm)2] with 1
equiv of i-Pr2PC6H4C6H4Pi-Pr2 also gave a yellow solid
(33) Achar, S.; Scott, J . D.; Puddephatt, R. J . Organometallics 1992,
11, 2325.
are insoluble in common organic solvents and so were

5328 Organometallics, Vol. 15, No. 25, 1996
Irwin et al.
F igu r e 3. 31P NMR spectrum (121.5 MHz) of complex 8.
The peaks marked with a closed circle are due to dppm,
and those marked with a diamond are due to the i-Pr2P
phosphorus atoms. Note the two sets of 195Pt satellite peaks
2
due to 1J (PtP) and J (PtPtP) for the i-Pr2P resonance. The
F igu r e 4. Structure of complex 8 as predicted by molec-
ular mechanics calculations. Only four phenyl substituents
of the dppm ligands are shown for clarity, but it can be
seen that the biphenyl spacer is long enough so that steric
effects between phenyl groups are not severe.
cis coupling 2J (PPtP) between i-Pr2P and Ph2P phosphorus
atoms of 14 Hz is barely resolved in this spectrum.
but with very different NMR properties, and the product
is characterized as the ring compound [Pt2(µ-dppm)2(µ-
i-Pr2PC6H4C6H4Pi-Pr2)]2(BF4)4, 8 (eq 6). The 31P NMR
F igu r e 5. Differential scanning calorimetry (DSC) traces
for the polymeric complex 7 and the cyclic complex 8 (the
scales are shown by the solid bars). Note the sharp melting
transition for 8 but not for 7. These are traces obtained
after heating the samples to 150 °C, followed by cooling to
room temperature, and then reheating.
spectrum of 8 (Figure 3) is sharp and well resolved and
contains single resonances for the phosphorus atoms of
1
dppm at δ ) -2.50, with J (PtP) ) 2900 Hz, and of i-Pr2-
1
PC6H4C6H4Pi-Pr2 at δ ) 21.12, with J (PPt) ) 2540 Hz
ring. Very large angle distortions at platinum are
necessary in order to decrease these interactions, and
the ring structure has very high energy (it is calculated
to be ca. 130 kJ mol-1 higher in energy than 8); hence
the chain structure is preferred.
2
2
and J (PtP) ) 1660 Hz. The large value of J (PtP) is
characteristic of a linear Pt-Pt-P linkage.7 This
spectrum and the much higher solubility compared to
7 appeared to be inconsistent with a polymeric structure
for 8. The molecular size was investigated by GPC
analysis of 8 in comparison to the known complex [Pt2-
(dppm)2(PPh3)2]2+ in tetrahydrofuran solution, employ-
ing linear polystyrene standards. Of course, absolute
molecular weights cannot be determined in this way,
but relative molecular weights may be expected. The
apparent molecular weight was 693 for the complex [Pt2-
(dppm)2(PPh3)2]2+ and 1638 for 8, which is fully consis-
tent with a 2-fold increase in molecular size. Both the
model compound and 8 gave single sharp peaks in the
GPC, indicating that a molecular compound was present
rather than a polymer with a distribution of molecular
weights. Hence the cyclic structure 8 is supported by
this measurement.
Th er m a l P r op er ties of th e P olym er s. The ther-
mal properties of the oligomers or polymers 5-7 were
carried out using thermogravimetric analysis (TGA) and
differential scanning calorimetry (DSC). Each complex
underwent major weight loss in the temperature range
330-480 °C, but further slow weight loss occurred at
higher temperatures so that the weight loss associated
with a residue of pure platinum was not obtained at the
maximum temperatures studied.
DSC studies show that the compounds 5-7 exhibit
broad endothermic transitions over the temperature
range ca. 30-200 °C. In contrast, complex 8 gave a
melting endotherm beginning at 228 °C, again indicat-
ing that it is not a polymer (Figure 5). When samples
of 5-7 were heated to 150 °C for 30 min and then cooled
and reheated, the broad endotherm in the region 25-
125 °C was not observed. Similar observations were
made during the study of polymers prepared by the
oxidative addition of 2-bromoethyl methacrylate to
[PtMe2(bu2bipy)], followed by free radical polymeriza-
tion. In this case, it was argued that the polymers
Why do the two diphosphines give different product
types? Molecular modeling studies show that the 4,4′-
biphenyl spacer group in i-Pr2PC6H4C6H4P-i-Pr2 is long
enough to bridge two diplatinum(I) units without undue
steric effects (Figure 4) but that the single benzene
spacer in PPh2C6H4PPh2 is not. The major problems
in the latter case arise from strong steric effects between
the phenyl substituents of the dppm ligands across the

Model Complexes with Pt-Pt Bonds
Organometallics, Vol. 15, No. 25, 1996 5329
precipitated in a strained conformation and on heating
relaxed to a less strained form.32 A similar effect may
be occurring here.
rings can be formed if the spacer group between the
phosphorus donors is long enough to allow this.
Ack n ow led gm en t. We thank the NSERC (Canada)
and the OCMR, for financial support and for scholar-
ships to M.J .I., and M. Biesinger for assistance with the
XPS spectra.
Con clu sion s
It is clear from this work that rigid-rod oligomers and
polymers with Pt-Pt bonds in the backbone, analogous
to those already known without the metal-metal bonds,2
can be prepared. The oligomers can be neutral if the
bridging ligands are diacetylides or cationic if the
bridging ligands are diisocyanides. The case in which
the bridging ligands are diphosphines is more complex,
due to the angular coordination at phosphorus, and
Su p p or tin g In for m a tion Ava ila ble: Tables of complete
atomic coordinates and thermal parameters, bond distances
and angles, and anisotropic parameters for complexes 1 and
3 (16 pages). Ordering information is given on any current
masthead page.
OM960420Q