Synthesis of neutral tetranuclear and octanuclear macrocyclic platinum- butadiyne heterocyclynes [13]

Full text of DOI:10.1021/ja981040u

J. Am. Chem. Soc. 1998, 120, 12149-12150
12149
Scheme 1. The Synthesis of the Platinum Butadiyne
Heterocyclyne 4
Synthesis of Neutral Tetranuclear and Octanuclear
Macrocyclic Platinum-Butadiyne Heterocyclynes
Samia M. ALQaisi, Kevin J. Galat, Minghui Chai,
Dale G. Ray, III, Peter L. Rinaldi, Claire A. Tessier,* and
Wiley J. Youngs*
Department of Chemistry, The UniVersity of Akron
Akron, Ohio 44325-3601
ReceiVed March 27, 1998
We have been studying the coordination chemistry of cyclic
trialkyne ligands which we refer to as cyclynes and heterocy-
clynes. In these ligands the alkynes are arranged in a plane to
produce a triangular cavity. In many instances a single metal
atom can coordinate in the cavity to the three alkynes.1 In the
case of heterocyclynes, this coordination chemistry is somewhat
reminiscent of that of acetylide tweezer complexes,2 although the
cyclic nature of the heterocyclyne ligand can give additional
stabilization to the complex.1j
If the cavity of the heterocyclyne were larger, it could serve
to coordinate multiatom species in the cavity. In regards to
catenane and rotaxane3 synthesis, interesting species to thread
through a larger cavity include metal-acetylide polymers and
carbon nanotubules. A larger cavity could be obtained by
enlarging the ring to include more alkynes4 and/or to include
transition metals. Heterocyclynes with platinum atoms as the
heteroatoms within the ring have been synthesized.2q,5 Others
have reported that charged6 and neutral7 macrocyclic tetrametallic
planar squares can be assembled by strategies which involve
(1) (a) Ferrara, J. D., Tessier-Youngs, C., Youngs, W. J. J. Am. Chem.
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Organometallics 1987, 6, 676. (c) Ferrara, J. D.; Tessier-Youngs, C.; Youngs,
W. J. J. Am. Chem. Soc. 1988, 110, 3326. (d) Djebli, A.; Ferrara, J. D.; Tessier-
Youngs, C.; Youngs, W. J. J. Chem. Soc., Chem. Commun. 1988, 548. (e)
Ferrara, J. D.; Tanaka, A. A.; Fierro, C.; Tessier-Youngs, C. A.; Youngs W.
J. Organometallics 1989, 8, 2089. (f) Kinder, J. D.; Tessier, C. A.; Youngs,
W. J. Synlett 1993, 149. (g) Youngs, W. J.; Kinder, J. D.; Bradshaw, J. D.;
Tessier, C. A. Organometallics 1993, 12, 2406. (h) Guo, L.; Bradshaw, J. D.;
Tessier, C. A.; Youngs, W. J. Organometallics 1995, 14, 586. (i) Guo, L.;
Bradshaw, J. D.; McConville, D. B.; Tessier, C. A.; Youngs, W. J.
Organometallics 1997, 16, 1685. (j) Zhang, D.; McConville, D. B.; Hrabusa,
J. M.; Tessier, C. A.; Youngs, W. J. J. Am. Chem. Soc. 1998, 120, 3506.
(2) (a) Yasufuku, K.; Yamazaki, H. Bull. Chem. Soc. Jpn. 1972, 45, 2664.
(b) Lang, H.; Zsolnai, L. J. Organomet. Chem. 1991, 406, C5. (c) Lang, H.;
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Lang, H.; Imhof, W. Chem. Ber. 1992, 125, 1307. (e) Lang, H.; Herres, M.;
Zsolnai, L. Organometallics 1993, 12, 5008. (f) Lang, H.; Herres, M.; Zsolnai,
L. Bull. Chem. Soc. Jpn. 1993, 66, 429. (g) Lang, H.; Herres, M.; Imhof, W.
J. Organomet. Chem. 1994, 465, 283. (h) Lang, H.; Weber, C. Organometallics
1995, 14, 4415. (i) Janssen, M. D.; Herres, M.; Spek, A. L.; Grove, D. M.;
Lang, H.; van Koten, G. J. Chem. Soc., Chem. Commun. 1995, 925. (j) Pulst,
S.; Arndt, P.; Baumann, W.; Tillack, A.; Kempe, R.; Rosenthal, U. J. Chem.
Soc., Chem. Commun. 1995, 1753. (k) Lang, H.; Blau, S.; Nuber, B.; Zsolnai,
L. Organometallics 1995, 14, 3216. (l) Janssen, M. D.; Herres, M.; Zsolnai,
L.; Spek, A. L.; Grove, D. M.; Lang, H.; van Koten, G. Inorg. Chem. 1996,
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Zhang, D.; McConville, D. B.; Tessier, C. A.; Youngs, W. J. Organometallics
1997, 16, 824. (r) Ciriano, M.; Howard, J. A. K.; Spencer, J. L.; Stone, F. G.
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knowledge of the coordination chemistry of the metal. These
previously reported squares have edges composed of relatively
bulky groups such as pyridine, 4,4′-bipyridine, 4,4′-dicyanobi-
phenyl, diazaperylene, and porphyrins. Herein we report the high-
yield, gram-scale synthesis of tetraplatinum and octaplatinum
square heterocyclynes which have large cavities and in which
the rings are composed of only platinum and butadiyne fragments.
These are the first reported examples of macrocycles where the
ring is composed of only transition metals and alkynes. It should
be noted that the relatively bulky groups on the edges of the
previously reported platinum squares6,7 increase the steric hin-
drance at the center relative to the squares reported here where
the edges are composed of butadiynes. This makes their cavities
more crowded and less likely to be good candidates for the
formation of catenanes and rotaxanes threaded with metal-
acetylide polymers and tubule derivatives.
The synthesis of the square [Pt(P2C2H4(C6H11)4)C4]4 4 is
outlined in Scheme 1. Chelating phosphines were used in order
to enforce the required cis geometry at the platinum atom. The
precursor 1,2-bis(dicyclohexylphosphino)ethane platinum di-
butadiyne 3 was prepared by two different methods with both
methods using the CuI-catalyzed8 coupling of platinum with acet-
ylides. Bubbling butadiyne9 into a suspension of [(C6H11)2P)2C2H4]-
PtCl2 1, diethylamine, diethyl ether, and a catalytic amount of
(6) (a) Fujita, M.; Yazaki, J.; Ogura, K. J. Am. Chem. Soc. 1990, 112,
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Fujita, M.; Yazaki, J.; Ogura, K. Tetrahedron Lett. 1991, 32, 5589. (d) Stang,
P. J.; Olenyuk, B. Acc. Chem. Res. 1997, 30, 502. (e) Manna, J.; Kuehl, C. J.;
Whiteford, J. A.; Stang, P. J.; Muddiman, D. C.; Hofstadler, S. A.; Smith, R.
D. J. Am. Chem. Soc. 1997, 119, 11611. (f) Whiteford, J. A.; Lu, C. V.; Stang,
P. J. J. Am. Chem. Soc. 1997, 119, 2524. (g) Stang, P. J.; Chen, K.; Arif, A.
M. J. Am. Chem. Soc. 1995, 117, 8793. (h) Stang, P. J.; Cao, D. H.; Saito, S.;
Arif, A. M.. J. Am. Chem. Soc. 1995, 117,6273. (i) Stang, P. J.; Chen, K. J.
Am. Chem. Soc. 1995, 117, 1667.
(4) Modern Acetylene Chemistry; Stang, P. J., Diederich, F., Ed.; VCH:
New York, 1995; Chapters 8, 9, 12, and 13.
(5) (a) Bradshaw, J. D.; Guo, L.; Tessier, C. A.; Youngs, W. J.;
Organometallics 1996, 15, 2582. (b) Pak, J. J.; Weakley, T. J. R.; Haley, M.
M. Organometallics 1997, 16, 4505.
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10.1021/ja981040u CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/06/1998

12150 J. Am. Chem. Soc., Vol. 120, No. 46, 1998
Communications to the Editor
CuI at -20 °C for 1 h, followed by stirring at room temperature
for 20 min gave 3 as a yellow powder in 95% yield. In the second
method 1,2-bis(dicyclohexylphosphino)ethane platinum bis(tri-
methylsilylbutadiyne) 2 was synthesized by reacting HCtCCt
Scheme 2. The Synthesis of the Octaplatinum Butadiyne
Heterocyclyne 6
9
CSiMe3 with 1 in diethylamine in the presence of CuI at room
temperature for 4 days. Workup and purification by flash
chromatography on alumina eluting with 1:2 CH2Cl2/hexane gave
2 as a white solid. Reaction of 2 with KF and H2O in DMF at
room temperature for 24 h afforded 3 as a pale yellow powder in
65% yield. Compound 3 was characterized via 1H, 31P{1H}, 13C-
{1H} NMR, IR, mass spectroscopy, elemental analysis, and X-ray
crystallography.10,11 A FAB-MS spectrum obtained from a
methanol solution of 3 in a nitrobenzyl alcohol matrix showed
M+ of 12C34H50P2195Pt at m/z 715.27 (calculated 715.30). Catalytic
CuI coupling8 of 1 with 3 in a mixture of 1:1 diethylamine/diethyl
ether at room temperature for 5 days gave 4 in 98% yield (Scheme
1). Syntheses of 4 in large scale required longer reaction times
for the reaction to go to completion. Compound 4 was character-
ized via 1H, 31P{1H}, 13C{1H}, 195Pt NMR, IR, melting point, mass
spectroscopy, and elemental analysis. A FAB-MS spectrum of
a methanol solution of 4 in a nitrobenzyl alcohol matrix gave an
M+ of 12C120H192195Pt4P8 at m/z 2661.05 (calculated 2661.15). The
195Pt NMR for 4 showed a triplet at 1361 ppm (JPt-P ) 2287
Hz). The 31P{1H}NMR for 4 at 61.8 ppm (JPt-P ) 2293 Hz)
showed a shift upfield by nearly one ppm and a slight increase
in the phosphorus-platinum coupling constant as compared to
precursor 3 at 62.8 ppm (JPt-P ) 2285 Hz). The 13C{1H} NMR
(CDCl3) showed a flip in the relative shifts of the R and â
butadiyne carbons; in 3 the R carbons appeared at 99.9 ppm
6 as a yellow powder in 80% yield. The 195Pt NMR for 6 showed
two triplets at 1369.4 ppm (JPt-P ) 2156 Hz) and the other at
1529 ppm (JPt-P ) 2473 Hz). The 31P{1H} NMR (C6D6) exhibits
two sharp singlets with one at 5.7 ppm (JPt-P ) 2369 Hz) and
the other at 61.9 ppm (JPt-P ) 2242 Hz). In CDCl3 these peaks
occur at 5.2 ppm (JPt-P ) 2403 Hz) and 61.9 ppm (JPt-P ) 2261
Hz). These are near the positions for the central peaks for 5 (5.5
ppm JPt-P ) 2288 Hz) and 3 (62.8 ppm JPt-P ) 2285 Hz) in
CDCl3 but shifted slightly and with a small difference in the P-Pt
coupling constants. A FAB-MS spectrum obtained from a
benzene solution of 6 in a nitrobenzyl alcohol matrix gave a broad
molecular ion M+ with a maximum at 5251.0 compared with a
12
calculated value of 5250.49 for
C
H408195Pt8P16. Compound
232
2
(2Jtrans P-C ) 135 Hz, Jcis P-C ) 15 Hz, JPt-C ) 1090 Hz), and
6 is stable in nonhalogenated solvents. It is soluble in toluene,
benzene, chloroform, methylene chloride, and acetone. Com-
pound 6 reacts with chloroform to form a mixture of 1, 3, 5,
and bis(tri-n-butylphosphine)platinumdichloride within a few
hours.
The combination of 4 with 1.5 equiv of AgOTf or AgBF4 gave
a mixture of products having 4 to Ag+ ratios of 1:1 to 1:4 with
the silver salts associated with the acetylide fragments of 4 in
what we assume to be a tweezer2 fashion. The principal product
with AgOTf showed an absorption peak in the 31P{1H} NMR at
the â carbons at 93.3 ppm (3Jtrans P-C ) 32 Hz, 3Jcis P-C < 0.1 Hz,
2JPt-C ) 308 Hz), whereas in 4 the R carbons appeared at 94.7
2
ppm (2Jtrans P-C ) 139 Hz, Jcis P-C ) 12 Hz, JPt-C ) 1084 Hz),
and the â carbons at 98.9 ppm (3Jtrans P-C ) 32 Hz, 3Jcis P-C < 0.1
2
Hz, JPt-C ) 313 Hz), respectively. The R and â carbons in 3
and 4 were unambiguously assigned by their coupling constants
to the phosphorus and platinum atoms. The IR spectrum of 3
exhibited two strong CtC stretches at 2082 cm-1 (s) and 2146
cm-1 (s), and a tC-H stretch at 3307 cm-1, whereas that of 4
showed CtC stretches at 2075 cm-1 (w) and 2142 cm-1 (s).
Under nitrogen, compound 3 decomposed at 165-168 °C, where-
as 4 decomposed at 187-195 °C. Compound 4 is air stable in
the solid state, but decomposes slowly in CH2Cl2, CHCl3, C6H5Cl,
and o-C6H4Cl2 to form 1. Compound 4 is soluble in the above
halogenated solvents, DMSO, DMF, and MeOH and is slightly
soluble in THF and acetone.
62.1 ppm (JPt-C ) 2423 Hz) compared to 4 at 61.8 ppm (JPt-P
)
2293 Hz) with several peaks a fraction of a ppm downfield from
the major peak. The FAB mass spectrum gave a broad M+ peak
12
with a maximum at 3170.0 (cal 3172.77 for
(
C
H192195Pt4P8
120
108AgSO3CF3)2. The MALDI mass spectrum gave a broad M+
peak with a maximum at 2918 (cal 2916.96 for 12C120H192195Pt4P8
108AgSO3CF3). Only one CtC stretch (at 2102 cm-1) was
observed compared to two for 4 (see above). The FAB mass
spectrum of the product of 4 with AgBF4 gave a broad M+ peak
with maximum at 3434.4 which is consistent with compound 4
complexed with 4AgBF4 units with a calculated M+ of 3436.78
(12C120H192195Pt4P8 (108AgBF4)4). The MALDI mass spectrum gave
a broad M+ of 2772.49 (cal. 2768.06 for 12C120H192195Pt4P8108Ag+).
We are currently synthesizing a variety of heterocyclyne alkyne
squares of different sizes, and are examining the reaction
chemistry of these carbon and platinum rich compounds. We
are particularly interested in the threading of polyynes through 4
and the threading of nanotubules through 6.
The octaplatinum heterocyclyne butadiyne square [Pt(P2C2H4-
(C6H11)4)C4Pt(P(nBu)3)2C4]4 6 was assembled from components
which had the required cis and trans geometries at platinum, as
shown in Scheme 2. The synthesis of bis(tri-n-butylphosphine)
platinum dibutadiyne 5 was based on a method similar to that
reported by Hagihara et al.8,11a,12 Combining 1 with 5 in diethyl-
amine in the presence of CuI at room temperature for 36 h gave
(8) (a) Takahashi, S.; Kariya, M.; Yatake, T.; Sonogashira, K.; Hagihara,
N. Macromolecules 1978, 11, 1063. (b) Sonogashira, K.; Kataoka, S.;
Takahashi, S.; Hagihara, N. J. Organomet. Chem. 1978, 160, 319. (c)
Sonogashira, K.; Ohga, K.; Takahashi, S.; Hagihara, N. J. Organomet. Chem.
1980, 188, 237.
(9) Brandsma, L. PreparatiVe Acetylenic Chemistry, 2nd ed.; Elsevier: New
York, 1988.
(10) Crystal data for C34H50P2Pt‚1/2CH2Cl2: Mr ) 758.23, monoclinic, space
group Cc, a ) 20.707(7) Å, b ) 13.314(4) Å, c ) 13.038(4) Å, â ) 97.05-
(3)°, V ) 3567(2) Å3, Z ) 4, Dc ) 1.412 g cm-3, µ ) 4.118 mm-1, F(000)
) 1532, T ) 178 K. Difabs absorption correction. Refinement for data with
I > 2σ(I)(2558 reflections) gave R1(F) ) 0.0511 and wR2(F2) ) 0.1130 for
all data.
Acknowledgment. We thank the National Science Foundation for
financial support. Dr. Douglas Gage of MSU-NIH Mass Spectrometry
Facility for providing mass spectral data, and Chrys Wesdemiotis and
James Tour for useful discussions.
(11) (a) SHELXTL Version 5.0γ Siemens Analytical Instruments, Inc., Mad-
ison, WI, 1994. (b) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(12) Crystal data for C32H56P2Pt: Mr ) 697.80, triclinic, space group P-1,
a ) 9.6419(11) Å, b ) 9.9869(11) Å, c ) 18.376(2) Å, R ) 102.120(9)°, â
Supporting Information Available: Experimental procedures and
spectral data of products, tables of crystal data and structure refinement
details, and bond distances and angles (24 pages, print/PDF). See any
current masthead page for ordering information and Web access
instructions.
) 95.799(9)°, γ ) 91.203(9)°, V ) 1719.5(3) Å3, Z ) 2, Dc ) 1.348 g cm-3
,
µ ) 4.190 mm-1, F(000) ) 712, T ) 178 K. Semiempirical absorption
correction. Refinement for data with I > 2σ(I)(5428 reflections) gave R1(F)
) 0.0212 and wR2(F2) ) 0.0499 for all data.
JA981040U