sp carbon chains surrounded by sp3 carbon double helices: Directed syntheses of wirelike Pt(C≡C)nPt moieties that are spanned by two P(CH2)mP linkages via alkene metathesis

Article abstract of DOI:10.1021/ja071612n

Reactions of trans-(C₆F₅)(Ph₂P(CH ₂)_m′CH=CH₂)₂PtCl (1; m′ = a, 6; b, 7; c, 8; d, 9; e, 10) and H(C≡C)₂H (HNEt ₂, cat. Oil) give trans-(C₆F_5<

Full text of DOI:10.1021/ja071612n

Published on Web 06/13/2007
sp Carbon Chains Surrounded by sp3 Carbon Double
Helices: Directed Syntheses of Wirelike Pt(CtC)nPt Moieties
That Are Spanned by Two P(CH2)mP Linkages via Alkene
Metathesis
Laura de Quadras,† Eike B. Bauer,† Wolfgang Mohr,† James C. Bohling,‡
Thomas B. Peters,‡ Jose´ Miguel Mart´ın-Alvarez,‡ Frank Hampel,† and
John A. Gladysz*,†
Contribution from the Institut fu¨r Organische Chemie and Interdisciplinary Center for Molecular
Materials, Friedrich-Alexander-UniVersita¨t Erlangen-Nu¨rnberg, Henkestraâe 42,
91054 Erlangen, Germany, and Department of Chemistry, UniVersity of Utah,
Salt Lake City, Utah 84112
Received March 13, 2007; E-mail: gladysz@chemie.uni-erlangen.de
Abstract: Reactions of trans-(C6F5)(Ph2P(CH2)m′CHdCH2)2PtCl (1; m′ ) a, 6; b, 7; c, 8; d, 9; e, 10) and
H(CtC)2H (HNEt2, cat. CuI) give trans-(C6F5)(Ph2P(CH2)m′CHdCH2)2Pt(CtC)2H (3a-e, 80-95%). Oxidative
homocouplings of 3a-d under Hay conditions (O2, cat. CuCl/TMEDA, acetone) yield trans,trans-(C6F5)-
(Ph2P(CH2)m′CHdCH2)2Pt(CtC)4Pt(Ph2P(CH2)m′CHdCH2)2(C6F5) (4a-d, 64-84%). Treatment of 3c-e with
excess HCtCSiEt3 under Hay conditions gives trans-(C6F5)(Ph2P(CH2)m′CHdCH2)2Pt(CtC)3SiEt3 (56-
73%). Homocouplings (n-Bu4N+ F-, Me3SiCl, Hay conditions) afford trans,trans-(C6F5)(Ph2P(CH2)m′CHdCH2)2-
Pt(CtC)6Pt(Ph2P(CH2)m′CHdCH2)2(C6F5) (13c-e, 59-64%). Reactions of 4a-d and 13c-e with Grubbs’
catalyst, followed by hydrogenation, give mixtures of trans,trans-(C6F5)(Ph2P(CH2)mPPh2)Pt(CtC)nPt-
(Ph2P(CH2)mPPh2)(C6F5) with termini-spanning diphosphines and trans,trans-(C6F5)(Ph2P(CH2)mPPh2)Pt-
(CtC)nPt(Ph2P(CH2)mPPh2)(C6F5) with trans-spanning diphosphines (m ) 2m′ + 2; n ) 4, 6). The latter (n
) 4) are independently synthesized by similar metatheses/hydrogenations of 1a-d to give trans-(C6F5)-
(Ph2P(CH2)mPPh2)PtCl (49-59%), followed by analogous introductions of (CtC)4 chains (66-77%). Crystal
structures of complexes with termini-spanning diphosphines show sp3 chains with both double-helical (m/n
) 20/4) and nonhelical (m/n ) 20/6) conformations, and highly shielded sp chains. The sp3 chains of
complexes with trans-spanning diphosphines exhibit double half-clamshell conformations. The dynamic
properties of both classes of molecules are analyzed in detail.
Introduction
redox states are very labile and appear to decompose via
bimolecular reactions involving the carbon chain.4b Hence, we
have sought to sterically protect such species, hoping to expand
the range of longer-lived redox states.8
In the preceding paper,9 we described unprecedented coor-
dination-driven self-assembly processes involving the penta-
fluorophenyl-substituted diplatinum polyynediyl complexes
trans,trans-(C6F5)(p-tol3P)2Pt(CtC)nPt(Pp-tol3)2(C6F5) (n ) 4,
Complexes in which wirelike sp carbon chains span two
metals, LyMCxMLy, are of intense current interest.1-3 They
contain what can be regarded as the most fundamental type of
unsaturated bridging ligand, which unlike nearly all others can
never be twisted out of conjugation. Such species have a rich
redox chemistry,2,4,5 and the carbon chains can mediate a variety
of charge- and electron-transfer processes.6,7 However, some
† Universita¨t Erlangen-Nu¨rnberg.
(5) Lead papers from other research groups: (a) Bruce, M. I.; Low, P. J.;
Costuas, K.; Halet, J.-F.; Best, S. P.; Heath, G. A. J. Am. Chem. Soc. 2000,
122, 1949. (b) Coat, F.; Paul, F.; Lapinte, C.; Toupet, L.; Costuas, K.;
Halet, J.-F. J. Organomet. Chem. 2003, 683, 368. (c) Venkatesan, K.; Fox,
T.; Schmalle, H. W.; Berke, H. Organometallics 2005, 24, 2834.
(6) Long, N. J.; Williams, C. K. Angew. Chem., Int. Ed. 2003, 42, 2586; Angew.
Chem. 2003, 115, 2690.
‡ University of Utah.
(1) Bruce, M. I.; Low, P. J. AdV. Organomet. Chem. 2004, 50, 179.
(2) Paul, F.; Lapinte, C. In Unusual Structures and Physical Properties in
Organometallic Chemistry; Gielen, M.; Willem, R.; Wrackmeyer, B., Eds.;
Wiley: New York 2002; pp 220-291.
(3) Szafert, S.; Gladysz, J. A. Chem. ReV. 2003, 103, 4175; 2006, 106, PR1-
PR33.
(7) Low, P. J. Dalton Trans. 2005, 2821.
(4) (a) Brady, M.; Weng, W.; Zhou, Y.; Seyler, J. W.; Amoroso, A. J.; Arif,
A. M.; Bo¨hme, M.; Frenking, G.; Gladysz, J. A. J. Am. Chem. Soc. 1997,
119, 775. (b) Dembinski, R.; Bartik, T.; Bartik, B.; Jaeger, M.; Gladysz, J.
A. J. Am. Chem. Soc. 2000, 122, 810. (c) Paul, F.; Meyer, W. E.; Toupet,
L.; Jiao, H.; Gladysz, J. A.; Lapinte, C. J. Am. Chem. Soc. 2000, 122,
9405.
(8) (a) Meyer, W. E.; Amoroso, A. J.; Horn, C. R.; Jaeger, M.; Gladysz, J. A.
Organometallics 2001, 20, 1115. (b) Horn, C. R.; Gladysz, J. A. Eur. J.
Inorg. Chem. 2003, 9, 2211.
(9) Stahl, J.; Mohr, W.; de Quadras, L.; Peters, T. B.; Bohling, J. C.; Mart´ın-
Alvarez, J. M.; Owen, G. R.; Hampel, F.; Gladysz, J. A. J. Am. Chem.
Soc. 2007, 129, 8282.
9
8296
J. AM. CHEM. SOC. 2007, 129, 8296-8309
10.1021/ja071612n CCC: $37.00 © 2007 American Chemical Society

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
Scheme 1. Limiting Structures for Complexes Derived from
C6F5Pt(CtC)nPtC6F5 Units and Diphosphines Ar2P(CH2)mPAr2
(A-C), and Synthetic Approach (D, E)
the P(CH2)m′X moieties would be joined by coupling reactions.
This avoids phosphine substitution steps at all stages of the
sequence and reduces the number of possibilities for oligomer
formation. However, isomeric products C with trans-spanning
diphosphine ligands might also be generated. Since the sp carbon
chains in such complexes would also to some degree be
sterically shielded, independent syntheses were incorporated into
this study.
Following a democratic vote by the subset of authors who
initiated this project a decade ago, a speculative coupling
sequence involving alkene metathesis (E with X ) CHdCH2,
Scheme 1) and CdC hydrogenation was selected. As detailed
in the narrative below, this high-risk undertaking proved to be
remarkably successful, significantly advancing the art of orga-
nometallic chemistry with respect to rational, directed syntheses
of new metal-containing materials. Although the overall yields
are moderate, the route is general and does not require “magic
numbers” of sp and sp3 carbon atoms. A portion of this work
has been communicated,11 and additional details12 and further
extensions13 are supplied elsewhere.
Results
1. Pt(CtC)4Pt Complexes with Alkene-Containing Phos-
phine Ligands. Platinum chloride complexes of the formula
trans-(Ar′)(Ar3P)2PtCl are easily converted to platinum alkynyl
species via Sonogashira-like reactions.14 Accordingly, the
chloride complexes trans-(C6F5)(Ph2P(CH2)m′CHdCH2)2PtCl (1;
m′ ) a, 6; b, 7; c, 8; d, 9; e, 10) were prepared from the
substitution-labile tetrahydrothiophene complex [Pt(µ-Cl)(C6F5)-
(tht)]215 and the corresponding alkene-containing diphenylphos-
phines Ph2P(CH2)m′CHdCH2 (2) as described earlier.16,17
As shown in Scheme 2, 1a-e were combined with H(Ct
C)2H under standard conditions (HNEt2, cat. CuI). Workups
gave the butadiynyl complexes 3a-e as yellow or yellow-tan
oils in 80-95% yields. Complexes 3a-e, and all other new
compounds below, were characterized by IR and NMR (1H,
13C, 31P) spectroscopy and mass spectrometry, as summarized
in the Experimental Section. In most cases, satisfactory mi-
croanalyses were also obtained. The IR and NMR properties
of 3a-e were similar to those of closely related platinum
6) and bis(R,ω-diarylphosphino)alkanes Ar2P(CH2)mPAr2 (m )
10-12, 14, 18). These afford adducts with sterically shielded
sp carbon chains, as illustrated by A and B in Scheme 1. When
the polymethylene or sp3 chains are sufficiently long, chiral
double-helical conformations A are possible. These are found
crystallographically for n/m ) 4/14 and 6/18 and as reported
elsewhere for 3/14.10 However, in solution they are in rapid
equilibrium with achiral nonhelical conformations, such as B.
The complexes with n/m ) 4/14 gave radical cations with
stabilities significantly greater than analogues lacking sp3 carbon
chains. However, with certain n/m combinations (4/16, 4/18,
4/32, 6/19, 6/20, 6/22, 6/24, 6/28, 8/28), only oligomeric
products could be isolated. We wanted to expand the number
of available complexes, so that the following types of questions
could be addressed: (a) What is the maximum degree of helicity
(sp3 chain twisting) possible for a given sp chain length? (b)
Do more tightly twisted systems afford still longer lived radical
cations and/or higher barriers for equilibration with B? (c) Are
such barriers affected by the sp chain length?
butadiynyl complexes.14 The 31P NMR spectra exhibited 1J(31P,195
-
Pt) couplings of approximately 2500 Hz, which is typical for
trans platinum(II) bis(phosphine) complexes.18
We did not anticipate that the introduction of the butadiynyl
ligand would be compromised by the vinyl groups in the
phosphine ligands. However, we were not so sanguine with
(11) (a) Stahl, J.; Bohling, J. C.; Bauer, E. B.; Peters, T. B.; Mohr, W.; Mart´ın-
Alvarez, J. M.; Hampel, F.; Gladysz, J. A. Angew. Chem., Int. Ed. 2002,
41, 1871; Angew. Chem. 2002, 114, 1951. (b) de Quadras, L.; Hampel, F.;
Gladysz, J. A. Dalton Trans. 2006, 2929.
(12) (a) Mohr, W. Doctoral Dissertation, Universita¨t Erlangen-Nu¨rnberg, 2002.
(b) Bauer, E. B. Doctoral Dissertation, Universita¨t Erlangen-Nu¨rnberg, 2003.
(c) de Quadras, L. Doctoral Dissertation, Universita¨t Erlangen-Nu¨rnberg,
2006.
(13) de Quadras, L.; Bauer, E. B.; Stahl, J.; Zhuravlev, F.; Hampel, F.; Gladysz,
J. A. New J. Chem. 2007. Manuscript submitted for publication.
(14) (a) Mohr, W.; Stahl, J.; Hampel, F.; Gladysz, J. A. Chem.sEur. J. 2003,
9, 3324. (b) Zheng, Q.; Gladysz, J. A. J. Am. Chem. Soc. 2005, 127, 10508.
(c) Zheng, Q.; Bohling, J. C.; Peters, T. B.; Frisch, A. C.; Hampel, F.;
Gladysz, J. A. Chem.sEur. J. 2006, 12, 6486.
Thus, an alternative synthetic strategy was investigated. This
involved the binding of functionalized monophosphines with
P(CH2)m′X linkages to platinum prior to attaching an sp carbon
chain (D, Scheme 1). After generation of the polyynediyl bridge,
(15) Uso´n, R.; Fornie´s, J.; Espinet, P.; Alfranca, G. Synth. React. Inorg. Met.-
Org. Chem. 1980, 10, 579.
(16) Bauer, E. B.; Hampel, F.; Gladysz, J. A. Organometallics 2003, 22, 5567.
(17) (a) Lewanzik, N.; Oeser, T.; Blu¨mel, J.; Gladysz, J. A. J. Mol. Catal. A:
Chem. 2006, 254, 20. (b) de Quadras, L.; Stahl, J.; Zhuravlev, F.; Gladysz,
J. A. J. Organomet. Chem. 2007, 692, 1859.
(10) Owen, G. R.; Stahl, J.; Hampel, F.; Gladysz, J. A. Organometallics 2004,
23, 5889.
(18) Grim, S. O.; Keiter, R. L.; McFarlane, W. Inorg. Chem. 1967, 6, 1133.
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8297

A R T I C L E S
de Quadras et al.
Scheme 2. Syntheses of Diplatinum Octatetraynediyl Complexes
Scheme 3. Syntheses of Diplatinum Octatetraynediyl Complexes
with Alkene-Containing Phosphine Ligandsa
with trans-Spanning Diphosphine Ligandsa
a Conditions: (a) H(CtC)2H, HNEt2, cat. CuI; (b) O2, acetone, cat. CuCl/
TMEDA.
respect to subsequent oxidative homocouplings of 3. Nonethe-
less, as shown in Scheme 2, when 3a-d were reacted under
Hay conditions (O2, cat. CuCl/TMEDA, acetone), workups gave
the octatetraynediyl or Pt(CtC)4Pt complexes 4a-d as yellow
or tan oils in 64-84% yields. Again, the IR and NMR properties
closely resembled those of related complexes.14
2. Pt(CtC)4Pt Complexes with trans-Spanning Diphos-
phine Ligands. In order to better analyze alkene metathesis
reactions of 4a-d, authentic samples of the possible byproducts
C (Scheme 1) were first prepared. As shown in Scheme 3, the
chloride complexes 1a-d were converted by a sequence
involving alkene metathesis (Grubbs’ first generation catalyst)
and hydrogenation (10% Pd/C) to the 17-, 19-, 21-, and 23-
membered macrocycles 5a-d in 49-59% overall yields. The
syntheses of 5a,c,d have been reported previously.16
A reaction of 5a and H(CtC)2H analogous to those of 1a-e
in Scheme 2 afforded the butadiynyl complex 6a in 86% yield.
However, similar protocols were less effective with 5b-d. Thus,
5b-d were treated with the readily available bifunctional silyl/
stannyl diyne Me3Sn(CtC)2SiMe3,19 followed by CuI (0.2
equiv) and KPF6 (1.1 equiv). Workups gave the trimethylsi-
lylbutadiynyl complexes 7b-d as white powders in 79-80%
yields. Complex 6a could be oxidized to the Pt(CtC)4Pt
complex 8a in 84% yield under Hay conditions identical to those
in Scheme 2. Complexes 7b-d were first treated with wet
n-Bu4N+ F-, which effects protodesilylation to butadiynyl
complexes. Then Me3SiCl was added,20 and the crude mixtures
were similarly oxidized. Workups afforded 8b-d as yellow
powders in 84-90% yields.
The preceding complexes exhibited several distinctive proper-
ties. First, the mass spectra of 8a-d showed molecular ions,
but they were always less intense than monoplatinum fragment
ions. In contrast, the mass spectra of the title complexes, which
feature three bridging ligands linking the platinum atoms, always
showed molecular ions that were much more intense than
monoplatinum fragment ions.9
a Conditions: (a) 5-7 mol % Grubbs’ Catalyst; (b) 10% Pd/C, 1 atm of
H2; (c) H(CtC)2H, HNEt2, cat. CuI; (d) Me3Sn(CtC)2SiMe3, KPF6, cat.
CuI; (e) O2, acetone, cat. CuCl/TMEDA; (f) wet n-Bu4N+ F-; (g) Me3SiCl.
Second, the PPh2 groups and methylene protons in 5-8 are
diastereotopic and can, in principle, give separate NMR signals.
However, as analyzed in detail elsewhere,16,21 net exchange
occurs when one of the platinum ligands is small enough to
pass through the macrocycle by rotation about the P-Pt-P axis.
This is facile for the chloride ligand in 5a16,21 and by extension
the higher homologues 5b-d. With the 17- and 19-membered
macrocycles 6a, 7b, and 8a-b, two sets of PPh2 13C NMR
signals as well as PCH2 and PCH2CH2 1H NMR signals are
observed at room temperature (Figures s1-s3, Supporting
Information). Hence, passage of the pentafluorophenyl and
polyynyl ligands through the macrocycles is slow on the NMR
time scale.22
In contrast, the 21- and 23-membered macrocycles 7c,d and
8c,d exhibit only a single set of NMR signals. Thus, passage
(21) Skopek, K.; Hershberger, M.; Gladysz, J. A. Coord. Chem. ReV. 2007, in
press (DOI: 10.1016/j.ccr.2006.12.015).
(22) There are additional subtleties associated with these processes, as dia-
grammed elsewhere.12b,c For example, for net exchange of diastereotopic
groups in 8a-d, both pentafluorophenyl ligands must pass through their
respective macrocycles.
(19) (a) Bunz, U. H. F.; Enkelmann, V. Organometallics 1994, 13, 3823 (see
footnote 14). (b) Zheng, Q.; Hampel, F.; Gladysz, J. A. Organometallics
2004, 23, 5896.
(20) This reagent, which is necessary for the success of the couplings,14 is
believed to serve as a F- ion scavenger.
9
8298 J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
Table 1. Key Crystallographic Distances [Å] and Angles [deg]
7b
7b
a
complex
(molecule 1)
(molecule 2)
8a
‚
EtOHa
8c‚
(C6H12
)
8da
11d
14da
Pt ‚ ‚ ‚ Pt(Si)
7.627
7.633
7.558
7.633
12.935
12.952
12.901
12.922
12.780
12.891
12.781(3)
12.899
18.0247(5)
18.056
sum of bond lengths,
Pt1 to Pt2(Si)
Pt1-C1
2.007(4)
1.204(6)
1.373(6)
1.212(6)
1.834(5)
-
-
-
2.004(4)
1.214(6)
1.367(6)
1.218(6)
1.830(5)
-
-
-
1.985(5)
1.221(8)
1.368(8)
1.217(8)
1.370(2)
-
-
-
1.989(3)
1.217(5)
1.365(5)
1.211(5)
1.358(7)
-
-
-
1.976(3)
1.218(4)
1.367(5)
1.209(5)
1.351(7)
-
-
-
1.978(5)
1.222(7)
1.366(7)
1.193(7)
1.371(8)
1.203(8)
1.358(7)
1.216(7)
1.992(6)
174.4(5)
176.4(6)
176.3(7)
176.0(7)
176.0(7)
178.9(7)
179.5(7)
175.0(5)
174.7
1.984(6)
1.227(8)
1.370(9)
1.205(8)
1.347(9)
1.214(9)
1.362(13)
-
C1-C2
C2-C3
C3-C4
C4-C5(Si)
C5-C6
C6-C7(C6′)
C7-C8
C8-Pt2
-
-
-
-
-
-
Pt1-C1-C2
C1-C2-C3
177.9(4)
177.7(5)
178.6(6)
178.6(5)
-
-
-
-
177.9
178.1
-
3.842
7.345, 7.804
179.1(4)
173.9(5)
176.5(5)
169.3(4)
-
-
-
-
179.1
173.2
-
3.766
8.197, 8.728
175.9(6)
178.3(8)
177.8(8)
179.0(11)
-
-
-
-
175.9
178.4
4.118
3.680
7.191, 7.662
177.5(3)
175.7(4)
177.9(4)
177.7(6)
-
-
-
-
177.5
177.1
4.202
3.744
169.6(3)
175.2(4)
176.8(4)
179.3(5)
-
-
-
-
169.6
177.1
4.214
3.815
174.9(5)
177.8(7)
178.5(8)
178.4(8)
178.8(9)
179.1(12)
-
C2-C3-C4
C3-C4-C5(Si)
C4-C5-C6
C5-C6-C7(C6′)
C6-C7-C8
C7-C8-Pt2
av Pt-Csp-Csp
av Csp-Csp-Csp
av sp/sp3 distanceb
av π stackingd
distance Pt to distal
carbonse
-
174.9
178.5
3.999
3.705
177.2
4.133c
3.810
-
8.799, 9.594
10.561, 10.594
-
minus van der Waals radius
of carbon (Å)f,g
P-Pt-P/Pt angleh
Pt+P+P+Ci+C1 angleh
6.104
7.028
5.962
7.894
8.861
-
-
-
-
-
-
0
0
0
0
0
0
294.8
297.5
0
0
a This molecule exhibits an inversion center. b Average distance from every CH2 group to the Pt-Pt vector. c Helix pitch, 15.61; degree of helicity,
81.9%. d Distance between midpoints of the C6F5 and C6H5 rings. e The two carbon atoms in the middle of the methylene chain. f With respect to previous
table entry. g The shortest platinum-carbon distance is used. h Angle between planes defined by these atoms on each endgroup.
of the pentafluorophenyl ligand through these larger rings is
rapid on the NMR time scale (crystal structures below show
that the polyynyl ligands are too long). In order to further
characterize these processes, variable temperature spectra of
representative complexes were recorded. As illustrated in the
Supporting Information, the PCHH′ and PCHH′CHH′ 1H NMR
signals of 8b did not decoalesce at 120 °C in toluene-d8.
Application of the coalescence formula (∆υ 103.9 Hz, PCHH′)23
established a lower limit of 18.9 kcal/mol (∆G‡, 120 °C) for
the exchange barrier. When 1H and 13C NMR spectra of 8c were
recorded at -115 °C in CDFCl2, no decoalescence or significant
line broadening was observed.
Complexes 8a,c-d or solvates thereof could be crystallized.
The crystal structures were solved as summarized in the
Supporting Information. Key metrical parameters are given in
Table 1.
As shown in Figure 1, the macrocycles exhibit double half-
clamshell conformations of idealized C2h symmetry that con-
siderably shield the sp carbon chains. The crystal structure of
the trimethylsilylbutadiynyl complex 7b was also determined.
As shown in Figure 2, two independent molecules were found
in the unit cell. In one, the trimethylsilyl group was disordered;
in the other, two sp3 carbon atoms were disordered. Only the
major conformations are depicted. Other data for 7b are
incorporated into Table 1.
der Waals radius of fluorine is added (1.47 Å),24 the effective
radius of the PtC6F5 moiety is obtained (7.68-7.72 Å). This
can be compared to the distances from platinum to distal carbons
of the macrocycle, i.e., the two in the middle of the methylene
chain (Table 1). When the van der Waals radius of carbon (1.70
Å) is subtracted from the lower value, a “bridge height” is
obtained. In the case of 8c and 8d, there is sufficient “clearance”
for the PtC6F5 moiety to pass under the bridge (7.89 Å and
8.61 Å vs 7.68-7.72 Å). However, with 7b and 8a the values
are too small (6.10-7.03 Å and 5.96 Å), in accord with the
NMR properties. A similar analysis for the PtCtCCtCSiMe3
moiety of 7b gives a much greater radius (10.59 Å using a
hydrogen atom of a methyl group).
3. Double-Helical Pt(CtC)4Pt Complexes. With the above
compounds in hand, the stage was set for the title sequence in
Scheme 4. On paper, alkene metatheses of 4a-d are fraught
with potential complications. In addition to undesired intermo-
lecular condensations, the intermediate catalyst-bound alkylidene
(RCHdM) might add to a CtC bond, per the key step in enyne
metathesis.25 Nonetheless, the reaction of 4a (ca. 0.001 M in
CH2Cl2) and Grubbs’ catalyst (7 mol %) smoothly gave a
mixture of metathesis products in 96% yield after workup. The
C/H microanalysis was in agreement with the isomeric com-
plexes 9a, with termini-spanning diphosphine ligands, and 10a,
with trans-spanning diphosphine ligands. The most intense peak
in the mass spectrum was a monoplatinum ion, followed by
The distances from the platinum atoms to the p-fluorine atoms
in 7b and 8a,c-d range from 6.21 to 6.25 Å. When the van
(23) Ohki, M. Applications of Dynamic NMR Spectroscopy to Organic Chemistry;
(24) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(25) Diver, S. T.; Giessert, A. J. Chem. ReV. 2004, 104, 1317.
VCH: 1985.
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8299

A R T I C L E S
de Quadras et al.
Figure 1. Thermal ellipsoid plots (50% probability level) of 8a‚EtOH (F), 8c‚(C6H12) (G; dominant conformation), and 8d (H) with hydrogen and solvate
molecules omitted, and views parallel (I, J, K) and perpendicular (L, M, N) to the C6F5 planes with atoms at van der Waals radii.
apparent (δ 5.35-5.37). A 31P NMR spectrum exhibited six
peaks with a 12:30:24:22:7:6 area ratio. Although six E/Z
isomers of 9a and 10a are possible, oligomers might also
1
account for some signals. With four peaks, J(31P,195Pt) cou-
plings of ca. 2500 Hz were apparent, characteristic of trans
platinum(II) bis(phosphine) complexes.18
To simplify analysis, we sought to reduce the CdC bonds
of 9a/10a without affecting the CtC bonds. We were
unaware of any precedent for such chemoselectivity with
organic compounds. However, as shown in Scheme 4, pal-
ladium-catalyzed hydrogenation proved successful. In order
to avoid over-reductions, and to work up incomplete reactions,
low H2 pressures and extended reaction periods (7-14 d) were
employed. Alumina filtrations gave the crude product mixtures
in 73-93% yields. These were expected to consist mainly of
11a and 8a, which were independently synthesized in the
preceding paper9 and Scheme 3, respectively.
1
The H NMR spectra of the mixtures showed that all of the
CHdCH linkages had been reduced. The mass spectra exhibited
strong molecular ions. However, a 31P NMR spectrum of a
typical mixture showed five signals in a 40:35:16:5:4 ratio,
corresponding to 11a, 8a, and three byproducts. Since the
byproducts were not evident in the mass spectra, they were
presumed to be oligomeric. Column chromatography of one
sample afforded a 11a/8a mixture in 33% yield. Preparative
thin layer chromatography of another afforded 11a as a yellow
powder in 32% yield.
Figure 2. Thermal ellipsoid plots (50% probability level) of the dominant
As summarized in Scheme 4, analogous sequences were
conducted with 4b-d, which feature longer sp3 carbon seg-
ments. The crude metathesis products (96-97%) were not
analyzed but rather directly hydrogenated. Chromatography gave
the target molecules 11b-d, with termini-spanning diphosphine
ligands, in 15-48% yields. In the last two reactions, 8c,d, with
conformations of the two independent molecules in crystalline 7b with
hydrogen atoms omitted.
the molecular ion (60%). No triplatinum or tetraplatinum ions
were detected.
The 1H NMR spectrum showed no vinyl residues, indicating
metathesis to be g98% complete. New CHdCH signals were
9
8300 J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
Scheme 4. Syntheses of Diplatinum Octatetraynediyl Complexes
was disordered over multiple positions, and the best solution
with all hydrogen atoms is depicted.
with Termini-Spanning Diphosphine Ligandsa
The angle defined by the P-Pt-P/P planes of 11d, 294.8°
(81.9% helicity), corresponds to more than three-quarters of a
twist. This is significantly greater than that of the lower
homologue 11a in the preceding paper, which features sp3 chains
containing 14 carbon atoms (196.5°-196.6° or 54.6% helicity).9
As illustrated by the space-filling representations P and Q
(Figure 3), the sp chain is nearly completely shielded.
The average distance of the sp3 carbon atoms from the
platinum-platinum vector in 11d approximates the radius of
the double helix. This value, 4.13 Å, is greater than those of
the four homologues with diphosphines of the formula
Ar2P(CH2)14PAr2 in the preceding paper (3.76-3.90 Å),9
indicative of a “looser” helix. Interestingly, 11d is the first
diplatinum polyynediyl species trans,trans-(X)(R3P)2Pt(Ct
C)nPt(PR3)2(X) (n g 3; R ) alkyl, Ar) among more than 16
examples3,9,10,14,19b,26 to crystallize without nearly coplanar
endgroups.
4. Pt(CtC)6Pt Complexes. Dodecahexaynediyl complexes
with sp3 chains of greater than 18 carbon atoms could not be
accessed by the route in the preceding paper.9 Thus, as shown
in Scheme 5, the butadiynyl complexes 3c-e were treated with
excess HCtCSiEt3 under Hay cross-coupling conditions. In
accord with much precedent,14 workups gave the triethylsilyl-
hexatriynyl complexes 12c-e as yellow oils in 56-73% yields.
In all cases, minor amounts of the homocoupling products 4c-e
(9-19%) were also isolated.
Complexes 12c-e were treated with wet n-Bu4N+ F- to
generate the corresponding hexatriynyl complexes, which are
known for related systems to be quite labile. After addition of
Me3SiCl,20 Hay homocoupling conditions afforded the Pt(Ct
C)6Pt complexes 13c-e as yellow oils or solids in 59-64%
yields. The properties of 12c-e and 13c-e were similar to those
of related complexes with other phosphine ligands.14
Complexes 13c-e were subjected to metathesis/hydrogena-
tion sequences analogous to those in Scheme 4. In all cases,
mixtures of products with termini-spanning diphosphine ligands
(14c-e) and trans-spanning diphosphine ligands (15c-e) were
obtained. Chromatography gave pure 14c and 14d, which feature
sp3 chains with 18 and 20 carbon atoms, as yellow powders in
15-18% overall yields. The former complex was described in
the preceding paper.9 Analyses of other fractions by mass
spectrometry showed the formation of 15c,d, as inferred by
fragmentation patterns analogous to those of 8a-d. However,
14e could not be separated from 15e (combined overall yield
38%). Complexes 14c-e showed no tendency to convert to
insoluble oligomers.
a Conditions: (a) 5-7 mol % Grubbs’ catalyst (b) 10% Pd/C, 1 atm of
H2.
trans-spanning diphosphine ligands, were also isolated in 10%
and 16% yields. Intermediate fractions afforded 2:1 11c/8c and
11d/8d mixtures (14% and 32% yields). The formation of some
8b could be verified by the characteristic mass spectral
fragmentation pattern.
Importantly, 11b-d could not be accessed by the route
described in the preceding paper.9 None of these complexes
showed any tendency to oligomerize. Crystals of 11d, in which
the sp3 chains contain 20 carbon atoms, were obtained. The
structure was determined analogously to those above. Key
metrical parameters are summarized in Table 1. As shown in
Figure 3 (top), a chiral double-helical conformation was found,
with both enantiomers in the unit cell. As detailed in the
Experimental Section, a nine-atom segment of one sp3 chain
Crystals of 14d were obtained, and the structure was
determined analogously to those above. Metrical parameters are
summarized in Table 1. As shown in Figure 3 (bottom), a
nonhelical conformation was found. This was a moderate
surprise, as the lower homologue 14c features both helical and
nonhelical molecules in the unit cell,9 and the two additional
sp3 carbon atoms in each chain of 14d should have facilitated
the necessary twisting. Thus, for Pt(CtC)6Pt systems, sp3 chains
(26) (a) Wong, W.-Y.; Wong, C.-K.; Lu, G. L.; Cheah, K.-W.; Shi, J.-X.; Lin,
Z. J. Chem. Soc., Dalton Trans. 2002, 4587. (b) See also: Yam, V. W.-
W.; Wong, K. M.-C.; Zhu, N. Angew. Chem., Int. Ed. 2003, 42, 1400;
Angew. Chem. 2003, 115, 1438.
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8301

A R T I C L E S
de Quadras et al.
Figure 3. Thermal ellipsoid plots (50% probability level) of 11d (O; dominant conformation) and 14d (R) with hydrogen atoms omitted, and views parallel
(P, S) and perpendicular (Q, T) to the C6F5 planes with atoms at van der Waals radii.
with 18-20 carbon atoms apparently constitute the transition
regime between nonhelical and helical structures.
conditions. After 3 d, workup gave ca. 97% of the original
sample mass. The 31P NMR spectrum showed two peaks (90:
10), with the major signal corresponding to educt. The 1H NMR
spectrum exhibited only trace signals in the methylene region
(relative integral 2.1:36 vs the methyl groups).
Starting from either of the phosphorus atoms of 14d in the
top portion of view R or S (Figure 3), the sp3 chain initially
descends. However, rather than connecting to an anti phosphorus
atom in the bottom portion, the sp3 chain turns parallel to the
sp chain and eventually ascends to the opposite syn phosphorus
atom in the top portion. The net result is a two-dimensional
steric insulation, which leaves the sp chain distinctly exposed
on two sides, as illustrated in T. The average distance of the
sp3 carbon atoms from the platinum-platinum vector (4.00 Å)
is slightly greater than those in the helical and nonhelical forms
of 14c (3.91 and 3.98 Å).
5. Additional Experiments. In order to compare the redox
properties of the above complexes to those in the preceding
paper, cyclic voltammograms were recorded under identical
conditions. Data are summarized in Table 2, and representative
traces are given in the Supporting Information. Oxidations were
observed, presumably to mixed valent platinum(II)/platinum-
(III) species. The reversibilities were fair to moderate, and the
principal trends are analyzed below.
The reaction was repeated under 30 atm of H2. After 16 h,
workup gave ca. 92% of the original sample mass. The 31P NMR
spectrum showed three peaks (81:16:3), with the major signal
corresponding to the educt trans,trans-(C6F5)(p-tol3P)2Pt(Ct
1
C)4Pt(Pp-tol3)2(C6F5). The H NMR spectrum again exhibited
trace signals in the methylene region (relative integral 2.6:36).
Hence, we conclude that the CtC linkages in the diplatinum
octatetraynediyl complexes are intrinsically less reactive than
disubstituted alkenes under the hydrogenation conditions uti-
lized.
When 11 and 8 were heated in capillaries, there was no sign
of decomposition below 150 °C or melting at much higher
temperatures. TGA measurements showed no mass loss below
243 °C. DSC measurements with 11a,9 11b, and 8a established
particularly high stabilities (Te ) 244.0 (endotherm), 249.6
(exotherm), 210.1 (endotherm) °C). However, 11d, 8c, and
8d exhibited exotherms at much lower temperatures (Te )
113.2, 100.7, 154.7 °C), in some cases followed by endotherms.
With 8b, three endotherms were observed (Te ) 126.5, 182.9,
217.4 °C). These phenomena raise the possibility of solid state
isomerizations or oligomerizations (exotherms) and/or phase
transitions (endotherms). However, further investigations of
Another redox issue involves the chemoselectivities of the
hydrogenations in Schemes 4 and 5. We wondered whether the
P(CH2)m′CHdCH(CH2)m′P segments might shield the sp carbon
chain from the catalyst, favoring CdC hydrogenation. Hence,
the unshielded octatetraynediyl complex trans,trans-(C6F5)(p-
tol3P)2Pt(CtC)4Pt(Pp-tol3)2(C6F5)14 was subjected to similar
9
8302 J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
Scheme 5. Syntheses of Diplatinum Dodecahexaynediyl
Complexes with Termini- or trans-Spanning Diphosphinesa
Figure 4. Other approaches to shielded polyynes involving alkene
metathesis.
Discussion
1. Syntheses. Schemes 4 and 5 establish a new strategy for
sterically shielding unsaturated assemblies that connect two
electroactive groups,27-30 complementing that in the preceding
paper.9 Related efforts in other laboratories have featured
cyclophane27a-d,29 and cyclodextrin27e derived rotaxanes, and
dendrimers.28 However, prior to this work, no approaches
involving alkene metathesis had been attempted. The success
of Schemes 4 and 5 hinges upon three factors that could not be
taken for granted in advance: (1) the ability to oxidatively
couple Pt(CtC)n/2H species in the presence of pendant vinyl
groups; (2) the ability of Grubbs’ catalyst to metathesize terminal
alkene moieties in the presence of Pt(CtC)nPt linkages and 16-
valence-electron metal centers; (3) the ability to hydrogenate
disubstituted alkenes in the presence of Pt(CtC)nPt linkages.
Recently, a conceptually related approach to sterically shield-
ing polyynes was investigated, using the silicon-substituted diyne
16 shown in Figure 4.31 Each silicon features an aryl group with
two meta-disposed (CH2)2CHdCH2 substituents. In principle,
a twofold intramolecular alkene metathesis could “sandwich”
the diyne segment between the aryl groups (arrows). However,
an alternative SisC(X)dC conformer proved more reactive, and
only 17, in which one side of the diyne is shielded, was isolated.
Figure 4 leads into an obvious question regarding the ring
closure selectivities in Schemes 4 and 5. First, products with
termini-spanning diphosphine ligands dominate over those with
trans-spanning diphosphine ligands (11 vs 8 and 14 vs 15).
However, given the oligomeric byproducts and presence of E/Z
CdC isomers prior to hydrogenation, more exact in situ analyses
a Conditions: (a) HCtCSiEt3, O2, acetone, cat. CuCl/TMEDA; (b) wet
n-Bu4N+ F-; (c) Me3SiCl; (d) O2, acetone, cat. CuCl/TMEDA; (e) 5-7
mol % Grubbs’ catalyst; (f) 10% Pd/C, 1 atm of H2.
Table 2. Cyclic Voltammetry Dataa
complex
Ep/a
[V]
Ep/c
[V]
E°
[V]
∆E
[mV]
76
75
77
63
105
97
82
76
ic/a
4b
4c
8a
8b
8c
8d
11a
11b
11c
11d
14c
14d
1.306
1.314
1.298
1.314
1.319
1.305
1.306
1.298
1.318
1.300
1.465
1.444
1.237
1.245
1.221
1.251
1.214
1.208
1.224
1.222
1.261
1.236
1.372
1.357
1.271
1.279
1.260
1.283
1.272
1.256
1.265
1.260
1.289
1.268
1.418
1.400
0.54
0.54
0.65
0.55
0.43
0.53
0.78
0.80
0.73
0.82
0.35
0.37
(27) (a) Anderson, S.; Aplin, R. T.; Claridge, T. D. W.; Goodson T., III; Maciel,
A. C.; Rumbles, G.; Ryan, J. F.; Anderson, H. L. J. Chem. Soc., Perkin
Trans. 1 1998, 2383. (b) Taylor, P. N.; O’Connell, M. J.; McNeill, L. A.;
Hall, M. J.; Aplin, R. T.; Anderson, H. L. Angew. Chem., Int. Ed. 2000,
39, 3456; Angew. Chem. 2000, 112, 3598. (c) Buston, J. E. H.; Marken,
F.; Anderson, H. L. J. Chem. Soc., Chem. Commun. 2001, 1046. (d) Taylor,
P. N.; Hagan, A. J.; Anderson, H. L. Org. Biomol. Chem. 2003, 1, 3851.
(e) Michels, J. J.; O’Connell, M. J.; Taylor, P. N.; Wilson, J. S.; Cacialli,
F.; Anderson, H. L. Chem.sEur. J. 2003, 9, 6167. (f) Terao, J.; Tang, A.;
Michels, J. J.; Krivokapic, A.; Anderson, H. L. Chem. Commun. 2004, 56.
(g) Klotz, E. J. F.; Claridge, T. D. W.; Anderson, H. L. J. Am. Chem. Soc.
2006, 128, 15374.
77
63
93
88
a Conditions: (7-9) × 10-4 M, n-Bu4N+ BF4-/CH2Cl2 at 22.5 ( 1 °C;
Pt working and counter electrodes, potential vs Ag wire pseudoreference;
scan rate 100 mV s-1; ferrocene ) 0.46 V.
(28) Schenning, A. P. H. J.; Arndt, J.-D.; Ito, M.; Stoddart, A.; Schreiber, M.;
Siemsen, P.; Martin, R. E.; Boudon, C.; Gisselbrecht, J.-P.; Gross, M.;
Gramlich, V.; Diederich, F. HelV. Chim. Acta 2001, 84, 296.
(29) (a) Lee, D.; Swager, T. M. Synlett 2004, 149. (b) Kwan, P. H.; Swager, T.
M. Chem. Commun. 2005, 5211.
these higher-temperature processes are beyond the scope of the
present study.
Finally, low temperature 1H and 13C NMR spectra of 11b-d
and 14d were recorded in CD2Cl2 and CDFCl2 under conditions
similar to those used for related compounds in the preceding
paper.9 No decoalescence phenomena were observed.
(30) Li, C.; Numata, M.; Bae, A.-H.; Sakurai, K.; Shinkai, S. J. Am. Chem.
Soc. 2005, 127, 4548.
(31) Simpkins, S. M. E.; Kariuki, B. M.; Cox, L. R. J. Organomet. Chem. 2006,
691, 5517.
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8303

A R T I C L E S
de Quadras et al.
are not feasible. The combination of 8 and 16 sp and sp3 carbon
atoms (11b) appears particularly favorable for termini-spanning
diphosphine ligands. Complexes with oxygen-containing
P(CH2)2O(CH2)2CHdCH2linkagesgiveanalogousselectivities.11b,13
However, analogues with geminal dimethyl groups can exhibit
opposite selectivities.12b,13
The good yields of monoplatinum complexes with trans-
spanning diphosphine ligands in Scheme 3 (5a,b) underscore
the viability of this ring-closure mode. We have conducted many
other types of ring closing alkene metatheses in the coordination
spheres of platinum(II) complexes16,17a,32,33 and, in most cases,
believe that the product distributions are kinetic or, at a
minimum, that not all possible products have been thermody-
namically sampled. Only in a few cases, involving smaller rings
and Grubbs’ second generation catalyst, has it been possible to
equilibrate monomers and oligomers.32,34 Hence, there remains
the possibility that catalytic conditions that promote higher
turnover numbers may give altered selectivities.
The stabilities of the title complexes with respect to oligo-
merization has implications for the reactions of trans,trans-
(C6F5)(p-tol3P)2Pt(CtC)nPt(Pp-tol3)2(C6F5) and Ar2P(CH2)m-
PAr2 in the preceding paper. In some of the cases where
oligomers are isolated (n/m ) 4/g16, 6/g19), NMR signals
corresponding to the target molecules can be detected prior to
concentration of the reaction mixture. This suggests that
oligomerization is promoted by some species present. In our
opinion, likely candidates would include the displaced phosphine
Pp-tol3 as well as any excess Ar2P(CH2)mPAr2. However,
mechanistic investigations are beyond the scope of our present
work.
2. Crystal Structures. Of the new structures in Figures 1-3,
four contain trans-spanning diphosphine ligands. We have
previously reported the syntheses and structures of a variety of
such monoplatinum complexes with C6F5PtCl moieties (e.g.,
5a,c,d).16,17a,21 Complex 7b (Figure 2) represents an analogue
that features both a new ligand (trimethylsilylbutadienyl) and
macrocycle size (19). It exhibits the usual aryl/C6F5/aryl stacking
motif.
The average distance of the sp3 carbon atoms from the
platinum-platinum vector is also considerably greater (4.12 vs
4.05-3.98 Å). The crystal structure of 8d can similarly be
compared to that of the helical isomer 11d (Figure 3, top).
Again, the steric shielding is not as extensive, and the sp3 carbon
atoms are further removed from the sp chain (4.21 vs 4.13 Å).
The crystal structure of 11d is remarkable for the extensive
degree of twisting between the endgroups (294.8°). This is
significantly greater than that in four lower homologues with
diphosphines of the formula Ar2P(CH2)14PAr2 in the preceding
paper (189.9°-196.6°). Hence, increasing the length of the sp3
carbon chain can markedly increase helicity. However, the
increased average distance of the sp3 carbon atoms from the
platinum-platinum vector in 11d (4.13 vs 3.76-3.90 Å) hints
at a possible limit. As the sp3 chains become longer, the contact
surface of the sp chain will eventually be saturated, requiring
helices of greater radii or alternative conformations.35
The sp3 chains in both 11d and 14d contain 20 carbon atoms.
However, the crystal structure of the latter (Figure 3, bottom)
exhibits a nonhelical conformation. Although this can be
rationalized from the increased sp chain length (12 vs 8 carbon
atoms), the structural data for the lower homologue 14c, which
exhibits both helical and nonhelical molecules in the unit cell,
had led us to anticipate a helical structure. Unfortunately, crystals
of the higher homologue 14e could not be obtained. Nonetheless,
we view analogues with sp3 chains of 24 to 36 carbon atoms as
particularly promising for highly coiled double-helical structures,
and synthetic efforts remain underway.
3. Spectroscopic, Redox, and Dynamic Properties. In
principle, the new complexes 11b-d and 14d,e allow the effect
of longer sp3 carbon chains upon the spectroscopic properties
of the title molecules to be defined. In practice, and as with the
shorter sp3 chains, all data are very similar to those of Pt(Ct
C)nPt complexes that lack termini-spanning diphosphine ligands.
The uncyclized monophosphine complexes 4a-d and 13c-e
also constitute useful reference compounds. Tables that compare
IR and NMR data are supplied in the Supporting Information.
The most pronounced trend is a slight downfield shift of the
PtCt 13C NMR signal in the series 11a-c (98.6, 99.3, 101.0
ppm).
A related question involves the relative spectroscopic proper-
ties of complexes with termini- and trans-spanning diphosphine
ligands, such as 11 vs 8. As noted above, the mass spectra
exhibit significant differences. However, the IR and UV-visible
spectra are identical, as tabulated in the Supporting Information.
The PtCtCCtC and PCH2CH2CH2 13C NMR chemical shifts
all fall into narrow ranges. Of the latter group, the PCH2CH2CH2
(31.7-30.6 ppm) and PCH2 (28.5-27.9 ppm) signals are the
furthest downfield (PCH2CH2, 26.6-25.6 ppm). Interestingly,
11a-d always exhibit more CH2 signals with chemical shifts
As noted above, the diplatinum complexes 8a,c,d crystallize
in “double half-clamshell” conformations (Figure 1). The
periphery of the clamshell is best viewed from a plane
perpendicular to that of the C6F5 ligand, as shown in I, J, and
K. As the number of sp3 carbon atoms increases from 14 to 18
to 20, the periphery extends further from the platinum atom,
shifting the line-of-sight to the sp chain. The average distances
of the sp3 carbon atoms from the platinum-platinum vector
also increase slightly (4.12, 4.20, 4.21 Å). At the same time,
the methylene groups occupy increasing amounts of space above
and below the planes of the C6F5 ligands, until saturation is
achieved with 8d (compare L, M, N). The net result is a marked
increase in the steric shielding of the sp chain.
(35) As tabulated in the Supporting Information, there are seven gauche segments
in the one non-disordered sp3 chain of 11d, as opposed to three to four in
each sp3 chain of the four Ar2P(CH2)14PAr2 homologues. However, near
one terminus, two are of the opposite sign. We intuit this situation as
follows. If the endgroup planes were twisted to the maximum degree
allowed by the sp3 chain lengths, all gauche segments should have the same
helical chirality. Short of this limit, there is “play” in the sp3 chains, as
reflected by a greater average sp3/sp chain distance. Thus, the gauche
segments can “overshoot” the plane of the endgroup and, by necessity,
must “double back”, resulting in two chirality domains. This feature is also
The crystal structure of 8a‚EtOH can be compared with those
of two solvates of the double-helical isomer 11a in the preceding
paper.9 When viewed from perspectives such as I and L, the
steric shielding of the sp carbon chain is much less extensive.
(32) Shima, T.; Bauer, E. B.; Hampel, F.; Gladysz, J. A. Dalton Trans. 2004,
1012.
(33) Nawara, A. J.; Shima, T.; Hampel, F.; Gladysz, J. A. J. Am. Chem. Soc.
2006, 128, 4962.
found in one sp3 chain of one of the four Ar2P(CH2)14PAr2 homologues,
9
11a‚(benzene)1.5
.
The average sp3/sp distance is greater than that of the
(34) Shima, T.; Hampel, F.; Gladysz, J. A. Angew. Chem., Int. Ed. 2004, 43,
5537; Angew. Chem. 2004, 116, 5653.
pseudopolymorph 11a‚(toluene)1.5 (4.05 vs. 3.98 Å), in which the gauche
torsion angles have the same sign.
9
8304 J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
between those of the PCH2CH2CH2 and PCH2 signals than 8a-
d. This suggests, in accord with established shielding trends,36
a small but detectable downfield shift of the sp3 carbon atoms
that run along the sp chain.
future papers will detail efforts directed at analogous compounds
with functional modifications of the sp3 chain that have the
potential to raise these barriers.13
Experimental Section38
As analyzed in the preceding paper, the ic/a and ∆E values
obtained by cyclic voltammetry (Table 2) are presumed to reflect
the relative stabilities of the corresponding radical cations.9
Complexes 4b,c, which contain monophosphine ligands with
potentially reactive vinyl groups and sp carbon chains that are
quite exposed, exhibit relatively low ic/a values (0.54). The
complexes 8a-d, with trans-spanning diphosphine ligands, are
on the average similar (0.43-0.65). However, the double-helical
complexes 11a-d give significantly higher values (0.73-0.82),
consistent with enhanced radical cation stabilities. The oxidation
of the most highly coiled 11d exhibits the highest degree of
reversibility (∆E 63 mV; ic/a 0.82).
Although oxidations of the dodecahexaynediyl complexes
14c,d are poorly reversible (ic/a 0.35-0.37), this represents an
improvement over nonshielded analogues.14a The more positive
E° values for 14c,d indicate thermodynamically more difficult
oxidations. This chain length effect is general for all polyynediyl
complexes, and the origin has been defined by computational
studies.37
Unfortunately, low-temperature NMR spectra of 11b-d and
14d did not show any decoalescence phenomena. A chiral
double-helical structure (A, Scheme 1) should give separate
signals for various diastereotopic groups, providing that inter-
conversion with the enantiomer is slow on the NMR time scale.
Thus, despite the many helical crystal structures, other pos-
sibilities cannot be excluded for the dominant conformation of
the title molecules in solution. Nonetheless, we remain optimistic
that barriers should increase into a measurable regime with
longer sp and sp3 carbon chains. Hence, higher homologues of
14c-e with additional methylene groups remain under active
pursuit.
Additional approaches to increasing the barrier for enantiomer
interconversion are readily identified. Possibilities include
introducing (a) functional groups into the sp3 chain that might
have attractive interactions with the sp chains or (b) groups that
could raise barriers to the sp3-sp3 carbon-carbon bond rotations
necessary to convert gauche conformational segments into their
enantiomers. Our initial efforts with the former have been
communicated,11b and both will be detailed in subsequent full
papers.13
trans-(C6F5)(Ph2P(CH2)6CHdCH2)2Pt(CtC)2H (3a). A Schlenk
flask was charged with trans-(C6F5)(Ph2P(CH2)6CHdCH2)2PtCl (1a;16
0.830 g, 0.838 mmol), CuI (0.033 g, 0.18 mmol), CH2Cl2 (5.4 mL),
and HNEt2 (54 mL) with stirring and cooled to -45 °C. Then H(Ct
C)2H (15.8 mL, 13.4 mmol, ca. 2.4 M in THF)39 was added, and the
mixture turned light yellow. The cold bath was allowed to warm to 10
°C over the course of 3 h and was then removed. After an additional
2.5 h (orange supernatant/white precipitate), the solvent was removed
by oil pump vacuum. The tan residue was extracted with toluene (3 ×
3 mL). The combined extracts were filtered through an alumina column
(4 cm × 2.5 cm), which was eluted with toluene. The solvent was
removed from the filtrate/washings by oil pump vacuum to give 3a as
a yellow-tan oil (0.746 g, 0.743 mmol, 89%). Calcd for C50H51F5P2Pt:
C: 59.82; H: 5.12. Found: C: 59.77; H: 5.11.
1
NMR (δ, CDCl3) H 7.41 (m, 8H of 4 Ph), 7.27 (m, 4H of 4 Ph),
7.20 (m, 8H of 4 Ph), 5.81-5.73 (m, 2H, CHd), 4.99-4.88 (m, 4H,
dCH2), 2.52 (m, 4H, PCH2), 1.97 (m, 4H, CH2CHd), 1.72 (m, 4H,
PCH2CH2), 1.38-1.26 (m, 12H, remaining CH2); 13C{1H}40,41 146.5
1
1
(d, JCF ) 235 Hz, o to Pt), 139.2 (s, CHd), 136.5 (dm, JCF ) 240
2
Hz, m/p to Pt), 133.2 (virtual t, JCP ) 5.5 Hz, o to P), 131.9 (virtual
t, 1JCP ) 26.7 Hz, i to P), 130.4 (s, p to P), 128.1 (virtual t, 3JCP ) 5.5
Hz, m to P), 114.4 (s, dCH2), 92.4 (s, PtCtC), 72.4 (s, PtCtCC),
3
59.8 (s, PtCtCCtC), 33.8 (s, CH2CHd), 31.2 (virtual t, JCP ) 7.5
1
Hz, PCH2CH2CH2), 28.8 (s, CH2), 28.6 (s, CH2), 28.2 (virtual t, JCP
) 17.5 Hz, PCH2), 25.5 (s, PCH2CH2); 31P{1H} 15.5 (s, JPPt ) 2568
1
Hz).42
IR (cm-1, oil film) νtCH 3308 (w), νCtC 2150 (m). MS:43 1005 (3a+,
3%), 954 ([3asC4H]+, 10%), 785 ([3asC4HsC6F5]+, 8%), 489 ([Pt-
(Ph2P(CH2)6CHdCH2)]+, 60%), 297 ([Ph2P(CH2)6CHdCH2]+, 100%).
trans,trans-(C6F5)(Ph2P(CH2)6CHdCH2)2Pt(CtC)4Pt(Ph2P-
(CH2)6CHdCH2)2(C6F5) (4a). A three-necked flask was charged with
3a (0.400 g, 0.398 mmol) and acetone (10 mL) and fitted with a gas
inlet needle and a condenser chilled via circulating -18 °C ethanol.44
A Schlenk flask was charged with CuCl (0.050 g, 0.51 mmol) and
acetone (15 mL), and TMEDA (0.020 mL, 0.13 mmol) was added with
stirring. After 0.5 h, stirring was halted (blue supernatant/yellow-green
solid). Then O2 was bubbled through the three-necked flask with stirring,
and the solution heated to 65 °C. The blue supernatant was added in
portions over 1.5 h. After an additional 0.5 h, the solvent was removed
by rotary evaporation and oil pump vacuum. Toluene was added (2 ×
3 mL), and the mixture was transferred to an alumina column (4 cm ×
2.5 cm), which was rinsed with toluene until UV monitoring (fluores-
cence of spotted TLC plate) showed no absorbing material (ca. 30 mL).
Conclusion
(38) A representative procedure for each type of transformation and all
metathesis/hydrogenation sequences involving diplatinum complexes that
afford a pure product are described in the text. All other syntheses are
detailed in the Supporting Information.
This paper has established the viability of alkene metatheses
in platinum coordination spheres, together with other reactions
with little if any precedent, for the construction of novel
sterically shielded polyynediyl complexes of the types A-C
(Scheme 1). These sequences significantly advance the art of
organometallic chemistry with respect to rational, directed
syntheses of new metal-containing materials. With a single
exception, all complexes of the types A/B with sufficiently long
methylene chains crystallize in double-helical conformations.
Similar conformations are thought to dominate in solution, but
conclusive data have proved elusive, presumably due to low
barriers for interconversion of the enantiomers. Accordingly,
(39) Verkruijsse, H. D.; Brandsma, L. Synth. Commun. 1991, 25, 657. The H(Ct
C)2H concentration is calculated from the mass increase of the THF solution.
CAUTION: this compound is explosive and literature precautions should
be followed.
(40) (a) In some 13C NMR spectra, the PtCt signal or certain C6F5 signals
were not observed. (b) For virtual triplets (Hersh, W. H. J. Chem. Educ.
1997, 74, 1485), the J values represent the apparent couplings between
adjacent peaks. (c) The PtCtCCtC signals were assigned according to
trends established earlier.14
(41) Complexes with PtPCH2CH2CH2 linkages exhibit a characteristic pattern
of 13C signals. The signals were assigned by analogy to related platinum
complexes as described in the previous9 and following13 full papers in this
series.
(42) This coupling represents a satellite (d; 195Pt ) 33.8%) and is not reflected
in the peak multiplicity given.
(43) FAB (3-nitrobenzyl alcohol matrix); m/z for the most intense peak of the
isotope envelope; relative intensities are for the specified mass range.
(44) Without a chilled condenser, aspirated acetone must be replenished during
the reaction.
(36) Wannere, C. S.; Schleyer, P. v. R. Org. Lett. 2003, 5, 605.
(37) Zhuravlev, F.; Gladysz, J. A. Chem.sEur. J. 2004, 10, 6510.
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8305

A R T I C L E S
de Quadras et al.
The solvent was removed by rotary evaporation and oil pump vacuum
to give 4a as a tan oil (0.335 g, 0.167 mmol, 84%). Calcd for
2.66-2.56 (m, 4H, PCHH′), 2.18-2.15 (m, 4H, PCH2CHH′), 1.86 (m,
4H, PCH2CHH′), 1.52-1.11 (m, 40H, remaining CH2); 13C{1H}40,41
145.5 (dm, JCF ) 233 Hz, o to P), 136.3 (dm, JCF ) 258 Hz, m/p to
1
1
C
100H100F10Pt2P4: C, 59.88; H, 5.02. Found: C, 59.85; H, 5.39.
NMR (δ, CDCl3) H 7.45 (m, 16H of 8 Ph), 7.31 (m, 8H of 8 Ph),
2
1
1
Pt), 134.7 (virtual t, JCP ) 6.5 Hz, o to P), 132.2 (virtual t, JCP
)
27.4 Hz, i to P), 131.4 (virtual t, 1JCP ) 28.5 Hz, i to P), 131.0 (virtual
7.24 (m, 16H of 8 Ph), 5.83-5.72 (m, 4H, CHd), 4.99-4.87 (m, 8H,
dCH2), 2.55 (m, 8H, PCH2), 2.01 (m, 8H, CH2CHd), 1.75 (m, 8H,
PCH2CH2), 1.42-1.26 (m, 24H, remaining CH2); 13C{1H}40,41 146.1
(dm, 1JCF ) 230 Hz, o to Pt), 139.1 (s, CHd), 136.5 (dm, 1JCF ) 245
2
t, JCP ) 5.4 Hz, o to P), 130.95 (s, p to P), 129.5 (s, p to P), 128.3
(virtual t, 3JCP ) 5.3 Hz, m to P), 127.5 (virtual t, 3JCP ) 4.6 Hz, m to
P), 94.2 (s, PtCtC), 63.8 (s, PtCtCC), 58.4 (s, PtCtCCtC), 30.9
3
1
2
(virtual t, JCP ) 8.1 Hz, PCH2CH2CH2), 28.6 (virtual t, JCP ) 17.9
Hz, m/p to Pt), 133.0 (virtual t, JCP ) 5.8 Hz, o to P), 131.5 (virtual
t, 1JCP ) 28.0 Hz, i to P), 130.3 (s, p to P), 127.9 (virtual t, 3JCP ) 5.2
Hz, m to P), 114.4 (s, dCH2), 94.2 (s, PtCtC), 63.7 (s, PtCtCC),
Hz, PCH2), 27.6 (s, CH2), 27.5 (s, CH2), 27.2 (s, CH2), 26.3 (s, CH2),
1
25.8 (s, PCH2CH2); 31P{1H} 14.7 (s, JPPt ) 2576 Hz).42
3
IR (cm-1, powder film) νCtC 2142 (m), 1998 (w). MS:43 1954 (8a+,
26%), 1786 ([8a-C6F5]+, <2%), 928 ([(C6F5)Pt(PPh2(CH2)14PPh2)]+,
100%), 759 ([Pt(PPh2(CH2)14PPh2)]+, 40%)
58.0 (s, PtCtCCtC), 33.8 (s, CH2CHd), 31.2 (virtual t, JCP ) 7.7
1
Hz, PCH2CH2CH2), 28.8 (s, CH2), 28.6 (s, CH2), 28.2 (virtual t, JCP
1
) 17.9 Hz, PCH2), 25.4 (s, PCH2CH2); 31P{1H} 14.2 (s, JPPt ) 2565
Hz).42
IR (cm-1, oil film) νCtC 2150 (m), 2003 (w). UV-vis:45 291
(66 400), 320 (81 600), 355 (7200), 381 (4000), 411 (2400). MS:43 2005
(4a+, 20%), 954 ([(C6F5)Pt(Ph2P(CH2)6CHdCH2)2]+, 100%).
trans,trans-(C6F5)(Ph2P(CH2)16PPh2)Pt(CtC)4Pt(Ph2P(CH2)16PPh2)-
(C6F5) (8b). A three-necked flask was charged with 7b (0.209 g, 0.194
mmol) and acetone (10 mL) and fitted with a gas inlet needle and a
condenser chilled via circulating -18 °C ethanol.44 A Schlenk flask
was charged with CuCl (0.100 g, 1.01 mmol) and acetone (15 mL),
and TMEDA (0.200 mL, 1.20 mmol) was added with stirring. After
0.5 h, stirring was halted (blue supernatant/yellow-green solid). Then
n-Bu4N+ F- (0.039 mL, 0.039 mmol, 1 M in THF/5 wt % H2O) was
added to the solution of 7b with stirring. After 20 min, Me3SiCl (0.024
mL, 0.19 mmol) was added. Then O2 was bubbled through the three-
necked flask with stirring, and the solution heated to 65 °C. The blue
supernatant was added in portions over 4 h. After an additional 0.5 h,
the solvent was removed by oil pump vacuum. The residue was
extracted with hexanes (2 × 5 mL) and then toluene (3 × 5 mL). The
extracts were filtered in sequence through an alumina column (4 cm
× 2 cm), which was rinsed with toluene. The solvent was removed
from the toluene fractions by rotary evaporation and oil pump vacuum.
The residue was chromatographed on a silica gel column (10 cm × 1
cm, 70:30 v/v hexanes/CH2Cl2). The solvent was removed from the
product-containing fractions by oil pump vacuum to give 8b as a yellow
powder (0.176 g, 0.0878 mmol, 90%), dec pt. > 207 °C (gradual
darkening without melting). Calcd for C100H104F10P4Pt2: C, 59.76; H,
5.22. Found: C, 58.94; H, 5.22. DSC:46 endotherm with Ti, 112.5 °C;
Te, 126.5 °C; Tc, 131.9 °C; Tf, 154.3 °C; endotherm with Ti, 174.4 °C;
Te, 182.9 °C; Tc, 186.4 °C; Tf, 188.7 °C; endotherm with Ti, 200.6 °C;
Te, 217.4 °C; Tc, 219.7 °C; Tf, 230.2 °C. TGA: weight loss 33%, 243-
414 °C.
trans-(C6F5)(Ph2P(CH2)16Ph2P)Pt(CtC)2SiMe3 (7b). A Schlenk
flask was charged with 5b (0.223 g, 0.225 mmol), Me3Sn(CtC)2SiMe3
(0.077 g, 0.27 mmol),19 CuI (0.0086 g, 0.0045 mmol), KPF6 (0.049 g,
0.27 mmol), CH2Cl2 (4 mL), and methanol (4 mL) with stirring. After
16 h, the solvent was removed by oil pump vacuum. The residue was
chromatographed on an alumina column (7 cm × 2 cm, 90:10 v/v
hexanes/CH2Cl2). The solvent was removed from the product-containing
fractions by oil pump vacuum to give 7b as a white powder (0.191 g,
0.177 mmol, 79%), mp 171 °C. Calcd for C53H61F5P2PtSi: C, 59.04;
H, 5.70. Found: C, 58.75; H, 5.70. DSC:46 endotherm with Ti, 45.2
°C; Te, 51.9 °C; Tp, 55.6 °C; Tc, 58.1 °C; Tf, 62.9 °C; exotherm with
Ti, 66.3 °C; Te, 78.2 °C; Tp, 86.5 °C; Tc, 90.8 °C; Tf, 106.4 °C;
endotherm with Ti, 153.3 °C; Te, 174.9 °C; Tp, 176.5 °C; Tc, 177.9 °C;
Tf, 199.7 °C. TGA: weight loss 36%, 230-396 °C.
1
NMR (δ, CDCl3) H 7.79-7.77 (m, 4H of 4 Ph), 7.45-7.39 (m,
6H of 4 Ph), 7.17-7.10 (m, 2H of 4 Ph), 7.08-7.05 (m, 8H of 4 Ph),
2.81-2.77 (m, 2H, PCHH′), 2.63-2.59 (m, 2H, PCHH′), 2.18-2.16
(m, 2H, PCH2CHH′), 1.86-1.84 (m, 2H, PCH2CHH′), 1.55-1.32 (m,
24H, remaining CH2), 0.09 (s, 9H, SiCH3); 13C{1H}40,41 146.5 (dm,
1
1JCF ) 221 Hz, o to Pt), 136.3 (dm, JCF ) 235 Hz, m/p to Pt), 134.4
(virtual t, 2JCP ) 6.3 Hz, o to P), 132.0 (virtual t, 1JCP ) 26.8 Hz, i to
P), 131.7 (virtual t, 2JCP ) 5.2 Hz, o to P), 131.4 (virtual t, 1JCP ) 28.3
Hz, i to P), 130.0 (s, p to P), 129.0 (s, p to P), 128.2 (virtual t, 3JCP
)
5.4 Hz, m to P), 128.0 (virtual t, 3JCP ) 5.9 Hz, m to P), 99.1 (s, PtCt),
1
NMR (δ, CDCl3) H 7.80-7.76 (m, 8H of 8 Ph), 7.44-7.37 (m,
93.8, 92.4, 76.8 (3 s, PtCtCCtC), 30.8 (virtual t, 3JCP ) 7.7 Hz, PCH2-
12H of 8 Ph), 7.15-7.14 (m, 4H of 8 Ph), 7.06-7.03 (m, 16H of 8
Ph), 2.69-2.57 (m, 8H, PCH2), 2.10-2.06 (m, 4H, PCH2CHH′), 1.86-
1.84 (m, 4H, PCH2CHH′), 1.55-1.29 (m, 48H, remaining CH2); 13C-
1
CH2CH2), 28.3 (virtual t, JCP ) 18.2 Hz, PCH2), 28.1 (s, CH2), 27.9
(s, 2 CH2), 27.6 (s, CH2), 27.4 (s, CH2), 25.4 (s, PCH2CH2), 0.9 (s,
1
SiCH3); 31P{1H} 14.3 (s, JPPt ) 2586 Hz).42
1
1
{1H}40,41 145.8 (dm, JCF ) 248 Hz, o to Pt), 136.3 (dm, JCF ) 260
IR (cm-1, powder film) νCtC 2181 (w), 2131 (m). MS:43 1079 (7b+,
100%), 956 ([7b-C2SiMe3]+, 40%), 787 ([7b-C2SiMe3-C6F5]+, 90%).
2
Hz, m/p to Pt), 134.5 (virtual t, JCP ) 6.3 Hz, o to P), 132.0 (virtual
t, 1JCP ) 26.8 Hz, i to P), 131.3 (virtual t, 2JCP ) 5.3 Hz, o to P), 131.1
1
(virtual t, JCP ) 28.2 Hz, i to P), 130.8 (s, p to P), 129.5 (s, p to P),
trans,trans-(C6F5)(Ph2P(CH2)14PPh2)Pt(CtC)4Pt(PPh2(CH2)14PPh2)-
(C6F5) (8a). Complex 6a (0.060 g, 0.062 mmol), acetone (5 mL), CuCl
(0.050 g, 0.51 mmol), acetone (15 mL), TMEDA (0.020 mL, 0.13
mmol), and O2 were combined in a procedure analogous to that for
4a. An identical workup gave 8a as a yellow powder (0.050 g, 0.076
mmol, 84%), dec pt. > 208 °C (gradual darkening without melting).
Calcd for C96H96F10P4Pt2: C, 59.02; H, 4.95. Found: C, 59.44; H, 5.46.
DSC:46 endotherm with Ti, 183.2 °C; Te, 210.1 °C; Tp, 215.3 °C; Tc,
224.0 °C; Tf, 230.2 °C. TGA: onset of mass loss, 264.1 °C (Te).
128.2 (virtual t, 3JCP ) 5.4 Hz, m to P), 127.5 (virtual t, 3JCP ) 4.7 Hz,
m to P), 99.4 (s, PtCt), 92.3 (s, PtCtC), 63.7 (s, PtCtCC), 58.4 (s,
3
PtCtCCtC), 31.1 (virtual t, JCP ) 7.7 Hz, PCH2CH2CH2), 28.4
(virtual t, 1JCP ) 18.2 Hz, PCH2), 28.4 (s, CH2), 28.2 (s, CH2), 28.1 (s,
CH2), 27.4 (s, CH2), 27.1 (s, CH2), 25.8 (s, PCH2CH2); 31P{1H} 14.4
(s, JPPt ) 2576 Hz).42
1
IR (cm-1, powder film) νCtC 2146 (m), 2003 (w). UV-vis:45 263
(88 000), 291 (105 000), 321 (130 000), 353 (6200), 379 (5000), 410
(2700). MS:43 2009 (8b+, 45%), 956 ([(C6F5)Pt(Ph2P(CH2)16PPh2)]+,
100%), 785 ([Pt(Ph2P(CH2)16PPh2)]+, 70%).
1
NMR (δ, CDCl3) H 7.85-7.83 (m, 8H of 8 Ph), 7.46-7.40 (m,
12H of 8 Ph), 7.12-6.96 (m, 20H of 8 Ph), 2.73-2.66 (m, 4H, PCHH′),
Alkene Metathesis of 4a. A two-necked flask was charged with
Grubbs’ catalyst (ca. half of 0.008 g, 0.01 mmol), 4a (0.299 g, 0.149
mmol), and CH2Cl2 (140 mL) with stirring and fitted with a condenser.
The solution was refluxed. After 2 h, the remaining catalyst was added.
After 3 h, the solvent was removed by rotary evaporation and oil pump
vacuum to give a tan solid. Then CH2Cl2 was added (2 × 3 mL), and
(45) UV-visible spectra were recorded in CH2Cl2 (1.25 × 10-5 M unless noted).
(46) (a) DSC and TGA data were treated as recommended by: Cammenga, H.
K.; Epple, M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1171; Angew. Chem.
1995, 107, 1284. The Te values best represent the temperature of the phase
transition or exotherm. (b) Except in cases of desolvation, DSC measure-
ments were not continued beyond the onset of mass loss (TGA).
Absorptions are in nm (ꢀ, M-1 cm-1).
9
8306 J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
the sample was transferred to an alumina column (4 cm × 2.5 cm).
The column was eluted with CH2Cl2 until UV monitoring showed no
absorbing material (ca. 30 mL). The solvent was removed by rotary
evaporation and oil pump vacuum to give a mixture of cyclized products
as a tan solid (0.280 g, 0.144 mmol, 96%). Calcd for C96H92F10P4Pt2:
C, 59.14; H, 4.76. Found: C, 58.99; H, 4.86.
Found: C, 58.56; H, 5.22. DSC:46 exotherm with Ti, 215.7 °C; Te, 249.6
°C; Tc, 253.5 °C; Tf, 269.5 °C. TGA: weight loss 32%, 276-414 °C.
NMR (δ, CDCl3) H 7.45-7.42 (m, 16H of 8 Ph), 7.31-7.27 (m,
1
8H of 8 Ph), 7.23-7.19 (m, 16H of 8 Ph), 2.72-2.71 (m, 8H, PCH2),
2.07-2.06 (m, 8H, PCH2CH2), 1.57-1.52 (m, 8H PCH2CH2CH2),
1
1.42-1.29 (m, 40H, remaining CH2); 13C{1H}40,41 145.6 (dm, JCF
)
221 Hz, o to Pt), 136.3 (dm, 1JCF ) 250 Hz, m/p to Pt), 132.8 (virtual
t, 2JCP ) 5.7 Hz, o to P), 131.6 (virtual t, 1JCP ) 27.8 Hz, i to P), 130.2
(s, p to P), 127.8 (virtual t, JCP ) 5.0 Hz, m to P), 99.3 (s, PtCt),
1
NMR (δ, CDCl3) H 7.90 (m, 6H of 8 Ph), 7.48-6.89 (m, 34H of
8 Ph), 5.37-5.35 (m, 4H, CHdCH), 2.73-2.62 (m, 8H, PCH2), 2.35-
2.32 (m, 4H, PCH2CHH′), 2.04 (m, 12H, PCH2CHH′, CH2CHdCH),
3
1
1.42-1.26 (m, 24H, remaining CH2); 31P{1H} 15.9 (s, JPPt ) 2594
94.0 (s, PtCtC), 63.7 (s, PtCtCC), 57.8 (s, PtCtCCtC), 30.9 (virtual
t, 3JCP ) 7.7 Hz, PCH2CH2CH2), 29.3 (s, CH2), 29.0 (s, CH2), 28.9 (s,
Hz,42 12%), 15.8 (s, 1JPPt ) 2585 Hz,42 30%), 15.2 (s, 1JPPt ) ca. 2579
Hz,42 24%), 15.1 (1JPPt ) ca. 2579 Hz,42 22%), 15.0 (s, 7%), 14.8 (s,
6%). IR (cm-1, powder film) νCtC 2150 (m). MS:43 1949 (M+
(intramolecular metathesis), 100%), no other significant peaks > 1200.
1
CH2), 28.7 (s, CH2), 28.5 (s, CH2), 28.2 (virtual t, JCP ) 18.2 Hz,
1
PCH2), 25.9 (s, PCH2CH2); 31P{1H} 14.7 (s, JPPt ) 2575 Hz).42
IR (cm-1, powder film) νCtC 2142 (m), 2001 (w). UV-vis:45 263
(84 000), 290 (105 000), 318 (130 000), 352 (6400), 379 (5500), 410
(2900). MS:43 2009 (11b+, 100%).
trans,trans-(C6F5)(Ph2P(CH2)14PPh2)Pt(CtC)4Pt(Ph2P(CH2)14PPh2)-
Alkene Metathesis of 4c. Grubbs’ catalyst (0.007 g, 0.008 mmol),
4c (0.277 g, 0.131 mmol), and CH2Cl2 (220 mL) were combined in a
procedure analogous to that for 4b. An identical workup gave a mixture
of cyclized products as a yellow oil (0.262 g, 0.127 mmol, 97%).
NMR (δ, CDCl3) H 7.46-7.40 (m, 16H of 8 Ph), 7.31-7.27 (m,
8H of 8 Ph), 7.24-7.21 (m, 16H of 8 Ph), 5.41-5.28 (m, 4H, CHd
(C6F5) (11a). A Schlenk flask was charged with metathesized 4a (0.350
g, 0.180 mmol), 10% Pd/C (0.035 g, 0.018 mmol), ClCH2CH2Cl (10
mL), and ethanol (20 mL), flushed with H2, and fitted with a balloon
filled with H2. The mixture was stirred for 7 d. The solvent was removed
by rotary evaporation. Then CH2Cl2 was added to the residue. The
mixture was filtered through an alumina column (7 cm × 1.5 cm),
which was rinsed with additional CH2Cl2. The solvent was removed
from the filtrate by rotary evaporation (0.255 g, 0.130 mmol, 73%).
The crude 11a/8a was purified by preparative thin layer chromatography
(silica gel, 60:40 v/v hexanes/CH2Cl2). The main (middle) band was
extracted to give 11a as a yellow powder (0.110 g, 0.058 mmol, 32%).47
1
CH), 2.69-2.64 (m, 8H, PCH2), 2.09-1.98 (m, 16H, PCH2CH2, CH2-
1
CHd), 1.50-1.18 (m, 40H, remaining CH2); 31P{1H} 15.1 (s, JPPt
)
2583 Hz),42 14.6 (s, major, JPPt ) 2583 Hz),42 14.4 (s), 14.2 (s).
1
trans,trans-(C6F5)(Ph2P(CH2)18PPh2)Pt(CtC)4Pt(Ph2P(CH2)18PPh2)-
(C6F5) (11c). Metathesized 4c (0.262 g, 0.127 mmol), 10% Pd/C (0.014
g, 0.013 mmol), ClCH2CH2Cl (10 mL), ethanol (8 mL), and H2 were
combined in a procedure analogous to that for 11b. A similar workup
gave (from fractions of the silica gel column) 11c (0.0380 g, 0.0183
mmol, 15%), an 11c/8c mixture (0.0362 g, 0.175 mmol, 14%; 2:1 by
31P NMR), and 8c (0.0258 g, 0.0125 mmol, 10%) as yellow powders.
Data for 11c:48 dec pt. > 200 °C (gradual darkening without melting).
1
NMR (δ, CDCl3) H 7.43-7.17 (m, 40H of 8 Ph), 2.68 (m, 8H,
PCH2), 2.12 (m, 8H, PCH2CH2), 1.57 (m, 8H, PCH2CH2CH2), 1.50-
1.26 (m, 32H, remaining CH2); 13C{1H}40,41 145.7 (dm, JCF ) 220
1
1
Hz, o to Pt), 136.2 (dm, JCF ) 240 Hz, m/p to Pt), 132.8 (virtual t,
2JCP ) 5.7 Hz, o to P), 131.9 (virtual t, JCP ) 27.6 Hz, i to P), 130.1
1
3
(s, p to P), 127.8 (virtual t, JCP ) 5.0 Hz, m to P), 98.5 (s, PtCt),
94.2 (s, PtCtC), 63.4 (s, PtCtCC), 57.8 (s, PtCtCCtC), 30.6 (virtual
1
NMR (δ, CDCl3) H 7.42-7.38 (m, 16H of 8 Ph), 7.29-7.26 (m,
8H of 8 Ph), 7.22-6.99 (m, 16H of 8 Ph), 2.68-2.65 (m, 8H, PCH2),
t, 3JCP ) 7.8 Hz, PCH2CH2CH2), 30.0 (s, CH2), 29.6 (s, CH2), 29.3 (s,
1
CH2), 28.1 (virtual t, JCP ) 18.5 Hz, PCH2), 28.0 (s, CH2), 25.6 (s,
1.96-1.95 (m, 8H, PCH2CH2), 1.54-1.49 (m, 8H, PCH2CH2CH2),
PCH2CH2); 31P{1H} 15.0 (s, JPPt ) 2582 Hz).42
1
1
1.35-1.27 (m, 56H, remaining CH2); 13C{1H}40,41 146.2 (dm, JCF
)
Alkene Metathesis of 4b. Grubbs’ catalyst (0.008 g, 0.01 mmol),
4b (0.351 g, 0.170 mmol), and CH2Cl2 (190 mL) were combined in a
procedure analogous to that for 4a. A similar workup (3 cm × 2 cm
alumina column) gave a mixture of cyclized products as a yellow oil
(0.327 g, 0.162 mmol, 96%).
245 Hz, o to Pt), 136.8 (dm, 1JCF ) 247 Hz, m/p to Pt), 133.2 (virtual
t, 2JCP ) 5.7 Hz, o to P), 131.9 (virtual t, 1JCP ) 27.8 Hz, i to P), 130.7
3
(s, p to P), 128.2 (virtual t, JCP ) 5.0 Hz, m to P), 101.0 (s, PtCt),
94.0 (s, PtCtC), 63.8 (s, PtCtCC), 58.1 (s, PtCtCCtC, 31.7 (virtual
t, 3JCP ) 7.5 Hz, PCH2CH2CH2), 29.5 (s, triple intensity, 3 CH2), 29.4
1
NMR (δ, CDCl3) H 7.45-7.43 (m, 16H of 8 Ph), 7.34-7.30 (m,
1
(s, CH2), 29.3 (s, CH2), 29.1 (s, CH2), 28.5 (virtual t, JCP ) 17.9 Hz,
8H of 8 Ph), 7.25-7.22 (m, 16H of 8 Ph), 5.42-5.32 (m, 4H, CHd
CH), 2.70-2.62 (m, 8H, PCH2), 2.03-1.99 (m, 16H, PCH2CH2, CH2-
CHd), 1.51-1.29 (m, 40H, remaining CH2); 31P{1H} 14.5 (s), 14.4
1
PCH2), 26.6 (s, PCH2CH2); 31P{1H} 14.5 (s, JPPt ) 2570 Hz).42
IR (cm-1, powder film) νCtC 2146 (m), 2001 (w). UV-vis:45 263
(88 000), 290 (112 000), 319 (138 000), 352 (6300), 379 (5400), 410
(2900). MS:43 2066 (11c+, 100%).
(major, s, JPPt ) 2571 Hz),42 14.3 (s), 14.2 (s). MS:43 2005 (M+
1
(intramolecular metathesis), 100%), 1837 ([M - C6F5]+, 20%).
trans,trans-(C6F5)(Ph2P(CH2)16PPh2)Pt(CtC)4Pt(Ph2P(CH2)16PPh2)-
Alkene Metathesis of 4d. Grubbs’ catalyst (ca. half of 0.009 g, 0.01
mmol), 4d (0.327 g, 0.150 mmol), and CH2Cl2 (250 mL) were combined
in a procedure analogous to that for 4b. An identical workup gave a
mixture of cyclized products as a yellow oil (0.305 g, 0.144 mmol,
96%).
(C6F5) (11b). A Schlenk flask was charged with metathesized 4b (0.327
g, 0.162 mmol), 10% Pd/C (0.018 g, 0.017 mmol), ClCH2CH2Cl (15
mL), and ethanol (15 mL), flushed with H2, and fitted with a balloon
filled with H2. The mixture was stirred for 14 d. The solvent was
removed by oil pump vacuum. The residue was extracted with CH2-
Cl2. The extract was filtered through an alumina column (2 cm × 2
cm), which was rinsed with CH2Cl2 until UV monitoring showed no
absorbing material (ca. 40 mL). The solvent was removed from the
filtrate by oil pump vacuum to give crude 11b/8b, which was
chromatographed on a silica gel column (30 cm × 1.5 cm, 80:20 v/v
hexanes/CH2Cl2). The solvent was removed from the first product-
containing fraction by oil pump vacuum to give 11b as a yellow solid
(0.165 g, 0.0778 mmol, 48%), dec pt. >200 °C (gradual darkening
without melting). Calcd for C100H104F10P4Pt2: C, 59.76; H, 5.22.
1
NMR (δ, CDCl3) H 7.45-7.43 (m, 16H of 8 Ph), 7.33-7.30 (m,
8H of 8 Ph), 7.26-7.22 (m, 16H of 8 Ph), 5.43-5.30 (m, 4H, CHd
CH), 2.70-2.63 (m, 8H, PCH2), 2.03-1.99 (m, 16H, PCH2CH2, CH2-
CHd), 1.51-1.29 (m, 48H, remaining CH2); 31P{1H} 14.5 (s, major,
1JPPt ) 2567 Hz),42 14.4 (s), 14.2 (s). MS:43 2118 (M+ (intramolecular
metathesis), 100%).
trans,trans-(C6F5)(Ph2P(CH2)20PPh2)Pt(CtC)4Pt(Ph2P(CH2)20PPh2)-
(C6F5) (11d). Metathesized 4d (0.305 g, 0.144 mmol), 10% Pd/C (0.015
g, 0.014 mmol), ClCH2CH2Cl (8 mL), ethanol (5 mL), and H2 were
combined in a procedure analogous to that for 11c. An identical workup
gave 11d (0.0551 g, 0.0259 mmol, 18%), an 11d/8d mixture (0.0982
(47) A complementary sequence is given in the Supporting Information.
(48) A satisfactory microanalysis was not obtained for this compound.
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8307

A R T I C L E S
de Quadras et al.
g, 0.0463 mmol, 32%; 2:1 by 31P NMR), and 8d (0.0488 g, 0.0230
mmol, 16%) as yellow powders. Data for 11d: dec pt. >190 °C (gradual
darkening without melting). Calcd for C108H120F10P4Pt2: C, 61.12; H,
5.70. Found: C, 60.82; H, 5.71. DSC:46 exotherm with Ti, 102.1 °C;
Te, 113.2 °C; Tp, 121.7 °C; Tc, 126.6 °C; Tf, 137.7 °C; endotherm with
Ti, 197.7 °C; Te, 218.7 °C; Tp, 225.2 °C; Tc, 226.9 °C; Tf, 230.5 °C.
TGA: weight loss 29%, 272-402 °C.
cm alumina column; 20 cm × 2 cm silica gel column, 90:10 v/v
hexanes/CH2Cl2) gave 13c as a yellow oil that solidified over the
course of several days (0.170 g, 0.0785 mmol, 64%). Calcd for
C
112H116F10P4Pt2: C, 62.10; H, 5.40. Found: C, 61.31; H, 5.65.
DSC:46 endotherm with Ti, 100.3 °C; Te, 123.2 °C; Tp, 124.9 °C; Tc,
126.9 °C; Tf, 149.8 °C. TGA: weight loss 38%, 225-414 °C.
1
NMR (δ, CDCl3) H 7.47-7.43 (m, 16H of 8 Ph), 7.36-7.32 (m,
1
3
NMR (δ, CDCl3) H 7.42-7.38 (m, 16H of 8 Ph), 7.30-7.26 (m,
8H of 8 Ph), 7.28-7.24 (m, 16H of 8 Ph), 5.80 (ddt, 4H, JHHtrans
)
3
3
8H of 8 Ph), 7.24-7.19 (m, 16H of 8 Ph), 2.63-2.62 (m, 8H, PCH2),
1.92 (m, 8H, PCH2CH2), 1.52 (m, 8H, PCH2CH2CH2), 1.23-1.13 (m,
60H, remaining CH2); 13C{1H}40,41 132.7 (virtual t, 2JCP ) 5.8 Hz, o to
17.0 Hz, JHHcis ) 10.2 Hz, JHH ) 6.7 Hz, CHd), 4.98 (br d, 4H,
3JHHtrans ) 17.1 Hz, dCHEHZ), 4.91 (br d, 4H, JHHcis ) 10.2 Hz, d
3
CHEHZ), 2.55-2.51 (m, 8H, PCH2), 2.05-1.99 (m, 8H, CH2CHd),
1.75-1.73 (m, 8H, PCH2CH2), 1.36-1.26 (m, 40H, remaining CH2);
1
P), 131.3 (virtual t, JCP ) 27.9 Hz, i to P), 130.1 (s, p to P), 127.7
(virtual t, 3JCP ) 5.0 Hz, m to P), 93.4 (s, PtCtC), 68.2 (s, PtCtCC),
13C{1H}40,41 139.2 (s, CHd), 136.6 (dm, JCF ) 251 Hz, m/p to Pt),
1
3
2
1
57.5 (s, PtCtCCtC), 31.1 (virtual t, JCP ) 7.7 Hz, PCH2CH2CH2),
132.9 (virtual t, JCP ) 5.7 Hz, o to P), 131.0 (virtual t, JCP ) 28.0
3
29.0 (s, CH2), 28.94 (s, CH2), 28.93 (s, CH2), 28.87 (s, CH2), 28.7 (s,
Hz, i to P), 130.4 (s, p to P), 128.0 (virtual t, JCP ) 5.1 Hz, m to P),
1
CH2), 28.6 (s, CH2), 27.9 (virtual t, JCP ) 18.1 Hz, PCH2), 25.5 (s,
114.1 (s, dCH2), 105.4 (s, PtCt), 93.4 (s, PtCtC), 65.5, 63.0, 61.0,
1
3
PCH2CH2); 31P{1H} 14.6 (s, JPPt ) 2569 Hz).42
57.1 (4 s, PtCtCCtCCtC), 33.8 (s, CH2CHd), 31.2 (virtual t, JCP
IR (cm-1, powder film) νCtC 2144 (m), 2001 (w). UV-vis:45 263
(87 500), 290 (111 000), 318 (136 000), 352 (6400), 379 (5500), 410
(3000). MS:43 2121 (11d+, 100%), 1953 ([11d - C6F5]+, 10%).
trans-(C6F5)(Ph2P(CH2)8CHdCH2)2Pt(CtC)3SiEt3 (12c). A three-
necked flask was charged with 3c (0.640 g, 0.604 mmol), acetone (20
mL), and HCtCSiEt3 (1.20 mL, 12.7 mmol) and fitted with a gas inlet
) 7.5 Hz, PCH2CH2CH2), 29.2 (s, CH2), 29.09 (s, CH2), 29.06 (s, CH2),
28.9 (s, CH2), 28.2 (virtual t, 1JCP ) 17.5 Hz, PCH2), 25.4 (s, PCH2CH2);
1
31P{1H} 13.9 (s, JPPt ) 2544 Hz).42
IR (cm-1, oil film) νCtC 2132 (m), 2094 (m), 1997 (w). UV-vis
(1.25 × 10-6 M):45 311 (75 500), 332 (201 000), 354 (315 000). MS:43
2166 (13c+, 20%), 1010 ([(C6F5)Pt(Ph2P(CH2)8CHdCH2)2]+, 100%).
Alkene Metathesis of 13c. A two-necked flask was charged with
Grubbs’ catalyst (ca. half of 0.014 g, 0.017 mmol) and CH2Cl2 (300
mL) and fitted with a condenser and a dropping funnel. The solution
was refluxed. The dropping funnel was charged with a solution of 13c
(0.548 g, 0.251 mmol) in CH2Cl2 (50 mL). One-half of the solution
was added over 0.5 h. After 2 h, the remaining catalyst was added,
followed by the remaining 13c. After an additional 2 h, the solvent
was removed by oil pump vacuum, and CH2Cl2 (2 × 3 mL) was added.
The sample was transferred in two portions to an alumina column (3
cm × 2.5 cm), which was rinsed with CH2Cl2 until UV monitoring
showed no absorbing material (ca. 50 mL). The solvent was removed
by oil pump vacuum to give a mixture of cyclized products as a yellow
oil (0.402 g, 0.187 mmol, 75%).
needle and a condenser chilled via circulating -18 °C ethanol.44
A
Schlenk flask was charged with CuCl (0.200 g, 2.02 mmol) and acetone
(30 mL), and TMEDA (0.400 mL, 2.40 mmol) was added with stirring.
After 0.5 h, stirring was halted (blue supernatant/yellow-green solid).
Then O2 was bubbled through the three-necked flask with stirring, and
the solution was heated to 65 °C. The blue supernatant was added in
portions over 2 h. After an additional 0.5 h, the solvent was removed
by rotary evaporation and oil pump vacuum. The residue was extracted
with hexanes (2 × 5 mL) and then toluene (3 × 5 mL). The extracts
were passed in sequence through an alumina column (6 cm × 2 cm),
which was rinsed with toluene. The solvent was removed from the
toluene fractions by rotary evaporation. The residue was chromato-
graphed on a silica gel column (20 cm × 2.5 cm, 90:10 v/v hexanes/
CH2Cl2). The solvent was removed from the product-containing
fractions by oil pump vacuum to give 12c as a yellow oil (0.525 g,
0.438 mmol, 73%). Elution with 70:30 v/v hexanes/CH2Cl2 gave 4c
(0.122 g, 0.058 mmol, 19%). Data for 12c: Calcd for C62H73F5P2PtSi:
C, 62.14; H, 6.32. Found: C, 61.83; H, 6.32.
NMR (δ, CDCl3) 31P{1H} 14.9 (s, 1JPPt ) 2564 Hz),42 14.4 (s), 14.2
1
1
(s, JPPt ) 2652 Hz),42 14.1 (s, major, JPPt ) 2556 Hz),42 13.9 (s).
MS:43 2110 (M+ (intramolecular metathesis), 100%), 982 ([(C6F5)Pt-
(Ph2P(CH2)8CHdCH(CH2)8PPh2)]+, 60%), 815 ([Pt(Ph2P(CH2)8CHd
CH(CH2)8PPh2)]+, 50%).
NMR (δ, CDCl3): 1H 7.52-7.47 (m, 8H of 4 Ph), 7.37-7.33 (m,
trans,trans-(C6F5)(Ph2P(CH2)18PPh2)Pt(CtC)6Pt(Ph2P(CH2)18PPh2)-
3
4H of 4 Ph), 7.30-7.26 (m, 8H of 4 Ph), 5.83 (ddt, 2H, JHHtrans
)
3
3
(C6F5) (14c). Metathesized 13c (0.402 g, 0.187 mmol), 10% Pd/C (0.026
g, 0.025 mmol), ClCH2CH2Cl (15 mL), ethanol (15 mL), and H2 were
combined in a procedure analogous to that for 11b. An identical workup
gave 14c as a yellow powder (0.080 g, 0.038 mmol, 20%), dec pt. >
230 °C.
17.0 Hz, JHHcis ) 10.2 Hz, JHH ) 6.7 Hz, CHd), 5.02 (br d, 2H,
3JHHtrans ) 17.0 Hz, dCHEHZ), 4.95 (br d, 2H, JHHcis ) 10.2 Hz, d
3
CHEHZ), 2.61-2.58 (m, 4H, PCH2), 2.09-2.04 (m, 4H, CH2CHd),
1.84-1.82 (m, 4H, PCH2CH2), 1.43-1.32 (m, 20H, remaining CH2),
0.97 (t, 9H, 3JHH ) 7.9 Hz, CH3), 0.57 (q, 6H, 3JHH ) 7.9 Hz, SiCH2);
13C{1H}40,41 145.9 (dm, 1JCF ) 237 Hz, o to Pt), 139.1 (s, CHd), 136.6
(dm, 1JCF ) 235 Hz, m/p to Pt), 132.9 (virtual t, 2JCP ) 5.8 Hz, o to P),
131.2 (virtual t, 1JCP ) 28.0 Hz, i to P), 130.4 (s, p to P), 127.9 (virtual
1
NMR (δ, CDCl3) H 7.40-7.38 (m, 16H of 8 Ph), 7.30-7.28 (m,
8H of 8 Ph), 7.22-7.20 (m, 16H of 8 Ph), 2.71-2.68 (m, 8H, PCH2),
2.10-2.06 (m, 8H, PCH2CH2), 1.54-1.50 (m, 8H, PCH2CH2CH2),
1.40-1.36 (m, 8H, PCH2CH2CH2CH2), 1.25-1.18 (m, 40H, remaining
3
t, JCP ) 5.1 Hz, m to P), 114.1 (s, dCH2), 102.7 (s, PtCt), 93.1 (s,
1
2
PtCtC), 91.0 (s, CtCSi), 80.6 (s, tCSi), 65.7 (s, PtCtCC), 55.9 (s,
PtCtCCtC), 33.8 (s, CH2CHd), 31.2 (virtual t, 3JCP ) 7.6 Hz, PCH2-
CH2CH2), 29.3 (s, CH2), 29.0 (s, double intensity, 2 CH2), 28.9 (s,
CH2); 13C{1H}40,41 143.8 (dd, JCF ) 225 Hz, JCF ) 30 Hz, o to Pt),
136.5 (dm, 1JCF ) 242 Hz, m/p to Pt), 132.8 (virtual t, 2JCP ) 6.0 Hz,
o to P), 131.0 (virtual t, 1JCP ) 27.9 Hz, i to P), 130.4 (s, p to P), 127.9
1
3
CH2), 28.2 (virtual t, JCP ) 18.1 Hz, PCH2), 25.5 (s, PCH2CH2), 7.3
(virtual t, JCP ) 5.0 Hz, m to P), 103.8 (s, PtCt), 93.6 (s, PtCtC),
1
3
(s, CH3), 4.3 (s, SiCH2); 31P{1H} 14.2 (s, JPPt ) 2558 Hz).42
65.0, 62.7, 61.0, 57.3 (4 s, PtCtCCtCCtC), 30.9 (virtual t, JCP
)
IR (cm-1, oil film) νCtC 2150 (m), 2018 (m). MS:43 1198 (12c+,
40%), 1011 ([12c - C6SiEt3]+, 100%), 842 ([12c - C6SiEt3 - C6F5]+,
40%).
7.9 Hz, PCH2CH2CH2), 30.2 (s, CH2), 30.1 (s, CH2), 30.03 (s, CH2),
1
29.97 (s, CH2), 28.4 (virtual t, JCP ) 18.2 Hz, PCH2), 25.7 (s,
1
PCH2CH2); 31P{1H} 14.5 (s, JPPt ) 2554 Hz).42
IR (cm-1, powder film) νCtC 2131 (m), 2092 (s), 1996 (m); UV-
vis (1.25 × 10-6 M):45 312 (79 200), 331 (234 000), 354 (361 000).
MS:43 2113 (14c+, 100%), 1945 ([14c - C6F5]+, 8%).
trans,trans-(C6F5)(Ph2P(CH2)8CHdCH2)2Pt(CtC)6Pt(Ph2P-
(CH2)8CHdCH2)2(C6F5) (13c). Complex 12c (0.287 g, 0.244 mmol),
acetone (15 mL), CuCl (0.260 g, 2.63 mmol), acetone (15 mL), TMEDA
(0.520 mL, 3.12 mmol), n-Bu4N+ F- (0.050 mL, 0.050, 1 M in THF/5
wt % H2O), Me3SiCl (0.040 mL, 0.32 mmol), and O2 were combined
in a procedure analogous to that for 8b. A similar workup (3 cm × 2
Alkene Metathesis of 13d. Grubbs’ catalyst (0.010 g, 0.013 mmol),
CH2Cl2 (150 mL), 13d (0.396 g, 0.178 mmol), and CH2Cl2 (50 mL)
were combined in a procedure analogous to that for 13c. An identical
9
8308 J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007

sp Carbon Chains within sp3 Carbon Double Helices
A R T I C L E S
workup gave a mixture of cyclized products as a yellow powder (0.292
g, 0.135 mmol, 76%).
IR (cm-1, powder film) νCtC 2131 (m), 2092 (s), 1996 (m); UV-
vis (1.25 × 10-6 M):45 312 (67 200), 333 (181 000), 354 (306 000).
MS:43 2170 (14d+, 100%).
NMR (δ, CDCl3) 31P{1H} 16.6 (s), 13.9 (s), 13.6 (s), 13.3 (s, major),
13.2 (s), 13.1 (s, major), 11.8 (s), 11.7 (s). MS:43 2165 (M+ (intramo-
lecular metathesis), 100%).
Acknowledgment. We thank the Deutsche Forschungsge-
meinschaft (SFB 583), the US NSF (CHE-9732605), Johnson
Matthey (platinum loan), the Ministerio de Educacio´n y Ciencia,
and the Fulbright Commission (Fellowships, J.M.M.-A.) for
support, Dr. Qinglin Zheng for the sample of Me3Sn(Ct
C)2SiMe3, and Ms. Helene Kuhn for technical assistance.
trans,trans-(C6F5)(Ph2P(CH2)20PPh2)Pt(CtC)6Pt(Ph2P(CH2)20PPh2)-
(C6F5) (14d). Metathesized 13d (0.292 g, 0.135 mmol), 10% Pd/C
(0.026 g, 0.025 mmol), ClCH2CH2Cl (15 mL), ethanol (15 mL), and
H2 were combined in a procedure analogous to that for 11b. An identical
workup gave 14d as a yellow powder (0.089 g, 0.032 mmol, 24%),
dec pt. > 220 °C. Calcd for C112H120F10P4Pt2: C, 61.99; H, 5.57.
Found: C, 60.77; H, 5.58.
Supporting Information Available: Continuation of the
Experimental Section, including general methods, syntheses and
characterization of higher homologues,38 figures of NMR spectra
and cyclic voltammetry traces, details of crystallographic data
collection and refinement,49 and tables of spectroscopic and
crystallographic data. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
NMR (δ, CDCl3) H 7.42-7.39 (m, 16H of 8 Ph), 7.31-7.28 (m,
8H of 8 Ph), 7.25-7.22 (m, 16H of 8 Ph), 2.73-2.68 (m, 8H, PCH2),
2.10-2.07 (m, 8H, PCH2CH2), 1.54-1.50 (m, 8H, PCH2CH2CH2),
1.38-1.35 (m, 8H, PCH2CH2CH2CH2), 1.32-1.24 (m, 68H, remaining
CH2); 13C{1H}40,41 145.6 (dm, 1JCF ) 239 Hz, o to Pt), 132.8 (dm, 1JCF
2
) 253 Hz, m/p to Pt), 132.8 (virtual t, JCP ) 6.0 Hz, o to P), 131.5
1
(virtual t, JCP ) 27.8 Hz, i to P), 130.4 (s, p to P), 128.0 (virtual t,
3JCP ) 5.1 Hz, m to P), 93.6 (s, PtCtC), 62.8, 61.0, 57.1, 53.4 (4 s,
PtCtCCtCCtC), 30.9 (virtual t, 3JCP ) 7.9 Hz, PCH2CH2CH2), 29.9
(s, CH2), 29.8 (s, CH2), 29.9-28.6 (several signals, remaining CH2),
JA071612N
(49) Additional data are available from the Cambridge Crystallographic data
Centre via the following CCDC numbers: 624437 (7b), 624434 (8a‚EtOH),
624436 (8c‚C6H12), 295840 (8d), 295839 (11d), 624435 (14d).
1
28.4 (virtual t, JCP ) 18.2 Hz, PCH2), 25.7 (s, PCH2CH2). 31P{1H}
1
14.5 (s, JPPt ) 2576 Hz).42
9
J. AM. CHEM. SOC. VOL. 129, NO. 26, 2007 8309