Formation of phenylene oligomers using platinum-phosphine complexes

Article abstract of DOI:10.1021/om010111m

The reaction of biphenylene with a series of platinum bis-phosphine precursors [PtL₂] leads to a variety of C-H and C-C bond activation reactions. With L = triethylphosphine, cleavage of the carbon-carbon bond of biphenylene has been shown to c

Full text of DOI:10.1021/om010111m

Organometallics 2001, 20, 2759-2766
2759
F or m a tion of P h en ylen e Oligom er s Usin g
P la tin u m -P h osp h in e Com p lexes
Nira Simhai, Carl N. Iverson, Brian L. Edelbach, and William D. J ones*
Department of Chemistry, University of Rochester, Rochester, New York 14627
Received February 12, 2001
The reaction of biphenylene with a series of platinum bis-phosphine precursors [PtL2]
leads to a variety of C-H and C-C bond activation reactions. With L ) triethylphosphine,
cleavage of the carbon-carbon bond of biphenylene has been shown to catalytically form
tetraphenylene. With L2 ) But PCH2PBut , the simple C-C cleavage of biphenylene is
2
2
observed. With L ) PPh2But, ortho metalation of the phosphine occurs to give a C-H
activation product. Mechanistic details of these reactions are discussed. With L ) tri-
phenylphosphine, however, biphenylene is not cleaved by the [L2Pt] fragment, but the
independently prepared C-C insertion adduct does react with biphenylene to give five
different products, including triphenylene, tetraphenylene, phenyltriphenylene, and hexa-
phenylene isomers.
In tr od u ction
senting C-H activation at the R-carbon, but the ther-
modynamic product is (C5Me5)Rh(PMe3)(2,2′-biphenyl),
which results from C-C activation of one aryl-aryl
bond (eq 1).5 These types of C-C insertion products are
The activation of carbon-carbon bonds by homoge-
neous metal catalysts is an area of active research in
organometallic chemistry.1 Much of this interest is
sparked by the fact that the ability to break C-C bonds
is of vital importance to the petroleum industry. Selec-
tive activation of C-C bonds is crucial for petroleum
refining and transformation. Unfortunately, C-C bonds
are among the least reactive of all bonds, which is why
this area continues to present a fundamental challenge
to organometallic chemists.
Many known examples of C-C bond activation have
relied on the attainment of aromaticity or relief of ring
strain in order to promote C-C bond breakage.2 Ex-
amples have also been found where an alkyl group
forced into proximity with the metal leads to oxidative
addition of the C-C bond.3 One substrate that is
particularly reactive is biphenylene, a molecule that
contains a strained four-membered ring which can be
cleaved by a variety of metal complexes.4 In addition,
such a reaction is thermodynamically favored due to the
formation of two strong metal-aryl bonds. This is
demonstrated by the reaction of biphenylene with
(C5Me5)Rh(PMe3)(Ph)H. The kinetic product of this
reaction is (C5Me5)Rh(PMe3)(biphenylenyl)(H), repre-
also produced in reactions that model the hydrodesulfur-
ization of dibenzothiophene.6
Rhodium and cobalt complexes of the form (C5Me5)-
M(C2H4)2 have also been shown to react with biphen-
ylene to form the bimetallic species (C5Me5)2M2(2,2′-
biphenyl).7 A number of studies of reactions with Ni,
Pd, and Pt complexes have also been conducted. Com-
pounds containing these metals react catalytically with
biphenylene in a variety of ways. One such interesting
reaction involves the catalytic transformation of bi-
phenylene to tetraphenylene using a platinum phos-
phine catalyst (eq 2),8 and Ni(COD)(PMe3)2 has also
(1) Topics in Organometallic Chemistry: Activation of Unreactive
Bonds and Organic Synthesis; Murai, S., Ed.; Springer-Verlag: Berlin,
1999.
(2) (a) Kang, J . W.; Moseley, K.; Maitlis, P. M. J . Am. Chem. Soc.
1969, 91, 5970. Crabtree, R. H.; Dion, R. P.; Gibboni, D. J .; McGrath,
D. V.; Holt, E. M. J . Am. Chem. Soc. 1986, 108, 7222. (b) Periana, R.
A.; Bergman, R. G. J . Am. Chem. Soc. 1986, 108, 7346. Cassar, L.;
Eaton, P. E.; Halpern, J . J . Am. Chem. Soc. 1970, 92, 3515. Ros, R.;
Lenarda, M.; Pahor, N. B.; Calligaris, M.; Delisa, P.; Randaccio, L.;
Graziani, M. J . Chem. Soc., Dalton 1976, 1937.
(3) Suggs, J . W.; J un, C.-H. J . Chem. Soc., Chem. Commun. 1985,
92-93. van der Boom, M. E.; Liou, S.-Y.; Ben-David, Y.; Gozin, M.;
Milstein, D. J . Am. Chem. Soc. 1998, 120, 13415.
(4) (a) Eisch, J . J .; Piotrowski, A. M.; Han, K. I.; Kruger, C.; Tsay,
Y. H. Organometallics 1985, 4, 224. (b) Lu, Z.; J un, C.; De Gala, S. R.;
Sigalas, M.; Eisenstein, O.; Crabtree, R. H. J . Chem. Soc., Chem.
Commun. 1993, 1877. (c) Atkinson, E. R.; Levins, P. L.; Dickelman, T.
E. Chem. Ind. (London) 1964, 934.
(5) Perthuisot, C.; J ones, W. D. J . Am. Chem. Soc. 1994, 116, 3647.
(6) Vicic, D. A.; J ones, W. D. J . Am. Chem. Soc. 1997, 119, 10855.
Vicic, D. A.; J ones, W. D. J . Am. Chem. Soc. 1999, 121, 7606.
(7) Perthuisot, C.; Edelbach, B. L.; Zubris, D. E.; J ones, W. D.
Organometallics 1997, 16, 2016.
(8) (a) Edelbach, B. L.; Vicic, D. A.; Lachicotte, R. J .; J ones, W. D.
Organometallics 1998, 17, 4784. (b) Edelbach, B. L.; Lachicotte, R. J .;
J ones, W. D. Organometallics 1999, 18, 4040.
10.1021/om010111m CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/11/2001

2760 Organometallics, Vol. 20, No. 13, 2001
Simhai et al.
Sch em e 1
F igu r e 1. Thermal ellipsoid plot of (dtbpm)Pt(2,2′-bi-
phenyl) (4). Ellipsoids are shown at the 30% level. There
is a rotational disorder in the tert-butyl groups (not shown).
Sch em e 2
been used to catalyze this reaction.9 Another reaction
uses nickel to catalytically produce fluorenone (eq 3).8
each case, a different reactivity was observed, as
presented below.
The catalytic mechanism of the tetraphenylene form-
ing reaction is outlined in Scheme 1. The first step
involves the dissociation of a phosphine ligand and
insertion of biphenylene to give the intermediate 1.
Reversible loss of phosphine from 1 followed by C-C
bond activation of another biphenylene and rapid re-
coordination of phosphine gives the Pt(IV) intermediate.
This step is inhibited by excess phosphine, as recoor-
dination of phosphine to species I occurs at a much
faster rate than C-C bond cleavage. Reductive C-C
coupling of adjacent aryl groups in the Pt(IV) species
gives complex 2. Tetraphenylene is then reductively
eliminated, and rapid insertion of another biphenylene
continues the cycle.10 This mechanism was proposed on
the basis of kinetic analysis and the identification of
complexes 1, I, and 2 as intermediates in the cycle. 1
was independently synthesized from (PEt3)3PtCl2 and
2,2′-dilithiobiphenyl. Heating this complex at 120 °C in
the presence of excess biphenylene resulted in a more
rapid formation of tetraphenylene than when Pt(PEt3)3
was used as the catalyst.
Resu lts a n d Discu ssion
Rea ctivity of [P t(d tbp m )]. The reactive intermedi-
ate [Pt(dtbpm)] has been described by Hofmann and can
be generated readily from the thermal elimination of
neopentane from (dtbpm)Pt(neopentyl)H (3).11 The reac-
tion of 3 with biphenylene in THF-d8 solution can be
monitored easily by 31P NMR spectroscopy. The two
resonances for 3 each appear as doublets with 195Pt
satellites (δ 7.3, J P-P ) 14 Hz, J Pt-P ) 1361 Hz; δ -8.0,
d, J P-P ) 14 Hz, J Pt-P ) 1345 Hz) and are seen to
diminish as a single new singlet resonance for a product
is observed at δ 4.7 (J Pt-P ) 1453 Hz). The 1H NMR
spectrum shows resonances in the aromatic region (two
triplets plus two doublets), consistent with the formation
of the simple C-C insertion product (dtbpm)Pt(2,2′-
biphenyl) (4; Scheme 2). The structure of 4 was con-
firmed by X-ray diffraction (Figure 1) and is typical of
other square-planar 2,2′-biphenyl complexes, although
the P-Pt-P bond angle is fairly acute (74°). 4 can also
be independently synthesized by the reaction of (dtbpm)-
PtCl2 with 2,2′-dilithiobiphenyl.
Altering the substituents of the phosphine ligands of
1 has a pronounced effect on its reactivity and is the
subject of the present study. Four different bis-phos-
phine platinum complexes have been investigated:
[Pt(dtbpm)], [Pt(dippm)], [Pt(PPh2But)2], and [Pt(PPh3)2]
(dtbpm ) But PCH2PBut , dippm ) Pri PCH2PPri ). In
Unlike the PEt3 analogue 1, 4 does not react further
with biphenylene to give a species similar to 2 or
tetraphenylene. 4 does not react with CO to generate
fluorenone, even at elevated temperatures (125 °C). The
lack of reactivity with CO is somewhat surprising, but
2
2
2
2
(9) Schwager, H.; Spyroudis, S.; Vollhardt, K. P. C. J . Organomet.
Chem. 1990, 382, 191-200.
(10) Edelbach, B. L.; Lachicotte, R. J .; J ones, W. D. J . Am. Chem.
Soc. 1998, 120, 2843.
(11) (a) Hofmann, P.; Heiss, H.; Mu¨ller, G. Z. Naturforsch. 1987,
42b, 395. (b) Hofmann, P.; Heiss, H.; Neiteler, P.; Mu¨ller, G.; Lach-
mann, J . Angew. Chem., Int. Ed. Engl. 1990, 29, 880. (c) Hofmann, P.;
Unfried, G. Chem. Ber. 1992, 125, 659.

Formation of Phenylene Oligomers Using Pt-Phosphine Complexes
Organometallics, Vol. 20, No. 13, 2001 2761
Ta ble 1. Selected Dista n ces (Å) a n d An gles (d eg)
for P t2(µ-d tbp m )2 (5)
molecule
A
B
C
D
Bond Distances
2.7948(11) 2.8078(12) 2.802(7) 2.798(5)
Pt(1)-Pt(2)
Pt(1)-P(1)
Pt(1)-P(3)
Pt(2)-P(2)
Pt(2)-P(4)
2.245(5)
2.237(5)
2.246(5)
2.238(6)
2.250(5)
2.249(5)
2.232(6)
2.242(6)
2.244(16) 2.228(15)
2.248(16) 2.229(15)
2.230(16) 2.250(15)
2.245(16) 2.238(16)
Bond Angles
P(3)-Pt(1)-P(1) 172.9(2) 173.7(2)
175.0(9) 172.5(8)
P(3)-Pt(1)-Pt(2) 93.16(15) 92.53(16) 92.6(7)
P(1)-Pt(1)-Pt(2) 93.97(14) 93.49(15) 92.4(6)
93.1(6)
94.4(6)
170.9(10) 173.1(8)
P(4)-Pt(2)-P(2) 172.5(2)
171.9(2)
P(4)-Pt(2)-Pt(1) 93.78(15) 94.06(16) 93.3(7)
94.1(6)
92.7(5)
F igu r e 2. Thermal ellipsoid plot of Pt2(µ-dtbpm)2, (5). Only
one of two disorder components is shown. Ellipsoids are
shown at the 30% level.
P(2)-Pt(2)-Pt(1) 93.21(15) 93.43(17) 94.6(7)
P(1)-C(17)-P(2) 114.9(9)
113.2(11) 112.9(18) 115.3(16)
P(3)-C(34)-P(4) 115.3(16) 118.7(11) 118.9(18) 115.3(17)
earlier studies showed that 1 was also unreactive
toward CO. 4 also does not react with diphenylacetylene
or dihydrogen, unlike 1. It is possible that the chelating
nature of the phosphine in 4 prevents the dissociation
of one phosphorus, as was shown to be required in the
mechanism for tetraphenylene formation (Scheme 1).
However, reaction with tert-butyl isocyanide at 55 °C
leads to phosphine displacement to give Pt(CN-t-Bu)2-
(2,2′-biphenyl) and free dtbpm. This product can be
synthesized independently from (COD)Pt(2,2′-biphenyl)
and CNBut. Also, in the absence of substrate thermoly-
sis of 3 gives the unreactive dimer [Pt(µ-dtbpm)]2 (5),
in which the phosphine bridges the two metal centers.12
1
The H NMR spectrum for 5 shows a single tert-butyl
F igu r e 3. Thermal ellipsoid plot of Pt(PPh2But)2(2,2′-
biphenyl) (6). Ellipsoids are shown at the 30% level.
environment (δ 1.47, m) and a triplet for the methylene
group (J P-H ) 3.7 Hz), indicating a highly symmetric
structure. The 31P NMR spectrum displays a singlet
with Pt satellites (J Pt-P ) 4479 Hz) at δ 84.3.
of two formally d10 metal centers, has been described
previously in other d10-d10 dimers and involves mixing
of the empty p orbitals with the filled d orbitals to give
bonding character between the metals.12,15,16 Hofmann
has reported the structure of the related compound
[Cu2(µ-dtbpm)2]2+, which shows similar features,17 and
the palladium dimer [Pd(dcpe)]2 has also been found to
have a significant Pd0-Pd0 interaction.18 Second, the
Pt2P4 unit is not planar but is twisted about the Pt-Pt
bond by 20°, giving the molecule a D2 or “propeller”
symmetry. The P-Pt-P bond angles are nearly linear
(173°). In the overlapping of the disordered molecules
(A/C or B/D), the right-handed propeller A overlaps with
the left-handed propeller C, and vice versa for B and
D. The tert-butyl groups of each molecule occupy roughly
the same region of space, which accounts for the
remarkable crystallization disorder that is observed.
Rea ctivity of (d ip p m )P t(2,2′-bip h en yl). The com-
plex related to 3 but with isopropyl groups in place of
tert-butyl groups has also been synthesized by reaction
of (COD)Pt(neopentyl)Cl with dippm and NaHB(OMe)3.
Single crystals of 5 were grown from THF solution at
-20 °C, and a small crystal was used to determine the
structure. The molecule crystallizes in triclinic space
group P1h, with 2 molecules per asymmetric unit. The
initial solution showed the basic skeletal framework for
the two independent molecules (A and B), but a second
orientation of the compound could be seen overlapping
the primary orientation at a 90° angle (C and D). A
successful refinement of this disorder was carried out
by including the secondary orientation (molecules C and
D) with a geometry constrained to be the same as that
of the primary orientation (molecules A and B). The
populations of the disorder partners were allowed to
vary independently (15.5(2)% C, 19.7(2)% D), with each
site containing one molecule total. Only the platinum
and phosphorus atoms were refined anisotropically,
with the carbon atoms restrained to similar (U ( 0.04)
isotropic values. The resulting structure is shown in
Figure 2. Table 1 gives selected distances and angles.
Several features of the structure are worth noting.
First, the platinum-platinum distance is 2.80 Å and is
slightly longer than the Pt-Pt single bond in molecules
containing Pt(I)-Pt(I) centers such as [Pt2(dppm)2-
(CO)2]+2 (2.642 Å)13 or Pt2(dppm)2Cl2 (2.651 Å).14 The
presence of a metal-metal bond, despite the presence
(13) Fisher, J . R.; Mills, A. J .; Sumner, S.; Brown, M. P.; Thomson,
M. A.; Puddephatt, R. J .; Frew, A. A.; Manojlovic-Muir, L.; Muir, K.
W. Organometallics 1982, 1, 1421.
(14) Manojlovic- Muir, L.; Muir, K. W.; Solomun, T. Acta Crystallogr.
1979, B35, 1237.
(15) Pyykko¨, P. Chem. Rev. 1997, 97, 597.
(16) Dedieu, A.; Hoffmann, R. J . Am. Chem. Soc. 1978, 100, 2074.
(17) Straub, B. F.; Rominger, F.; Hofmann, P. Inorg. Chem. 2000,
39, 2113.
(18) Pan, Y.; Mague, J . T.; Fink, M. J . J . Am. Chem. Soc. 1993, 115,
3842.
(12) This dimer was observed by Hofmann and proposed to have
the structure shown in Scheme 2, but without a Pt-Pt bond.9b Recent
results with the cyclohexylphosphine derivative give X-ray-quality
crystals (Hofmann, P. Private communication).

2762 Organometallics, Vol. 20, No. 13, 2001
Simhai et al.
This compound loses neopentane more slowly than 3 (85
°C, 13 h) but does not give the C-C insertion product
analogous to 4. Rather, a dimer is formed exclusively,
analogous to 5. The 31P NMR spectrum of the dimer
appears as a singlet at δ 62.3 (with platinum satellites).
No reaction of 3 with biphenylene occurs at 22 °C.
Rea ctivity of [P t(P P h 2Bu t)2]. The synthesis of the
PPh2But analogue of 1 proved not to be straightforward.
Reaction of (COD)Pt(2,2′-biphenyl) with PPh2But failed
to give the substitution product. Rather, the complex
was formed by way of the diethyl sulfide complex as
shown in eq 4. A single-crystal X-ray structure of 6
F igu r e 4. Thermal ellipsoid plot of Pt(PPh3)2(2,2′-bi-
phenyl) (8). Ellipsoids are shown at the 30% level.
(Figure 3) shows square-planar coordination just as in
1 and 4. The 31P NMR spectrum of 6 shows the expected
singlet (with 195Pt satellites, J Pt-P ) 2000 Hz) at δ 43.64.
When a C6D6 solution of 6 is heated to 80 °C for 1 h,
two new products are observed, each with two distinct
types of phosphorus atoms, in the 31P NMR spectrum
(isomer A δ 32.34, d, J P-P ) 14 Hz, J Pt-P ) 2054 Hz, δ
-4.10, d, J P-P ) 14 Hz, J Pt-P ) 1028 Hz; isomer B, δ
31.19, d, J P-P ) 14 Hz, J Pt-P ) 2050 Hz, δ -3.87, d,
J P-P ) 14 Hz, J Pt-P ) 986 Hz). The 31P-195Pt coupling
constants for all resonances are in the range commonly
observed for phosphorus trans to an aryl ring. The prod-
ucts are assigned as rotamers of the ortho-metalation
derivative 7 as shown in eq 5. Formation of 7 most likely
F igu r e 5. Thermal ellipsoid plot of phenylterphenylene
(C). Ellipsoids are shown at the 30% level.
Sch em e 3
occurs by way of oxidative addition of a C-H bond in 6
to give a Pt(IV) intermediate followed by reductive
elimination of a 2,2′-biphenyl C-H bond. This reaction
is apparently reversible, as heating 7 to 130 °C in the
presence of biphenylene leads to the slow catalytic
formation of tetraphenylene (∼1 turnover/week).
Rea ctivity of [P t(P P h 3)2]. The reaction of Pt(PPh3)3
with biphenylene does not lead to the formation of a
C-C insertion product. Either the fragment [Pt(PPh3)2]
is kinetically unable to insert into the bond or the
insertion product is thermodynamically unstable. The
latter possibility can be disregarded, however, as the
complex Pt(PPh3)2(2,2′-biphenyl) (8) can be prepared
independently by reaction of Pt(PPh3)2Cl2 with 2,2′-
dilithiobiphenyl. The adduct shows a singlet in the 31P
NMR spectrum at δ 30.75 (J Pt-P ) 2009 Hz). A single-
crystal X-ray structure of 8 is shown in Figure 4 and
shows a square-planar structure similar to that of 4 and
6.
formation of three major and two minor organic prod-
ucts (Scheme 3).
Analysis by GCMS showed the five products A-E in
a 16:17:60:4:3 ratio, in order of retention time. The first
product to elute (A; 16%) was identified as tetraphen-
ylene, with mass 304, by comparison with an authentic
sample. The next product had a mass of 228, corre-
sponding to triphenylene (B; 17%), also by comparison
with an authentic sample. The similar retention times
of A and B (see the Supporting Information) appears
to be attributable to the nonplanar and highly sym-
metrical (D2d) structure of tetraphenylene. The third
compound C was the most abundant (60%) and was
identified as phenylterphenylene by comparison with an
authentic sample. C was also identified by single-crystal
X-ray diffraction (Figure 5). The two minor products D
(4%) and E (3%) had long retention times and each
displayed m/z 456. None of the five compounds showed
significant fragmentation at 70 eV ionization energy,
consistent with their formation as fused ring systems
of the type (C6H4)n, where n ) 3, 4, or 6.
Curiously, while the 14-electron L2Pt0 fragment does
not insert into C-C bonds of biphenylene, the PtII metal
center in 8 appears to insert. Reaction of 8 with
biphenylene at 100 °C leads to the stoichiometric
The three major products (A-C) were isolated by
preparative TLC, but insufficient quantities of the long-

Formation of Phenylene Oligomers Using Pt-Phosphine Complexes
Organometallics, Vol. 20, No. 13, 2001 2763
retention-time products (D, E) were isolated to permit
complete characterization. 1H NMR spectra of A-C
were consistent with their identification as triphen-
ylene, tetraphenylene, and phenylterphenylene. Prod-
ucts D and E can be tentatively identified by their
masses and by making a basic assumption. In the
catalytic transformation of biphenylene to tetraphen-
ylene, aryl-aryl C-C single bonds were made and
broken. Consequently, one might expect products of the
type (C12H8)n by a series of ring-opening/ring-forming
metatheses. The masses of the unknown products are
consistent with even-numbered combinations of phen-
ylene rings, (C6H4)6. Compounds D and E with m/z 456
can therefore be assigned as two isomers of hexa-
phenylene, which are known compounds produced in the
decomposition of M(2,2′-biphenyl)3 compounds in the
literature.19 They do not interconvert even at elevated
temperatures (eq 6). No independent samples of hexa-
reaction chemistry. Reaction of Pt(PPh2But)2(2,2′-bi-
phenyl) with biphenylene leads to the formation of a
phosphine ortho-metalated product, which can also
participate in the catalytic dimerization of biphenylene
to give tetraphenylene. Reaction of biphenylene with
(PPh3)2Pt(2,2′-biphenyl) leads to the major product
phenyltriphenylene, followed by tetraphenylene and
then triphenylene. The presence of triphenylene is
shown to occur via P-C activation of the phosphine
ligand phenyl groups. Two unique isomers of hexa-
phenylene were also observed in the product mixture.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were per-
formed under an N2 atmosphere, either on a high-vacuum line
using modified Schlenk techniques or in a Vacuum Atmo-
spheres Corp. glovebox. Tetrahydrofuran, toluene, and diethyl
ether were distilled from dark purple solutions of benzo-
phenone ketyl. Alkane solvents were made olefin-free by
stirring over H2SO4, washing with aqueous KMnO4 and water,
and distilling from dark purple solutions of tetraglyme/
benzophenone ketyl. Tetrahydrofuran-d8, benzene-d6, and
CD2Cl2 were purchased from Cambridge Isotope Lab. The
liquids were distilled under vacuum from dark purple solutions
of benzophenone ketyl or dried over 4 Å molecular sieves and
stored in ampules with Teflon-sealed vacuum-line adaptors.
PPh2Cl was purchased from Strem Chemical Co. The prepara-
tions of Pt(PPh3)2Cl2,21 [(2,2′-biphenyl)Pt(µ-SEt2)]2,22 (dtbpm)-
PtCl2,23 (dtbpm)Pt(neopentyl)H,11 (COD)Pt(neopentyl)Cl,24
(COD)Pt(2,2′-biphenyl),25 (tBuNC)2Pt(2,2′-biphenyl),25 (LiT-
MEDA)2(2,2′-biphenyl),26 Me2Sn(2,2′-biphenyl),26 bis(diiso-
propylphosphino)methane,27 and biphenylene28 were all pre-
pared according to literature procedures.
phenylene were available to confirm this assignment.
Deter m in a tion of th e Or igin of Tr ip h en ylen e.
Triphenylene presents an anomaly because it has an
odd number of phenylene rings, unlike the other prod-
ucts. Since the biphenylene substrate consisted of an
even number of rings, the presence of triphenylene may
have indicated more complex C-C bond cleavage. That
is, this product may have resulted from breaking both
aryl-aryl bonds in biphenylene. Alternatively, tri-
phenylene may have come from activation of one of the
triphenylphosphine ligands on the catalyst, which un-
derwent P-C bond cleavage20 over the reaction.
To probe these two possibilities, the reaction was
repeated with a modified catalyst. The perdeutero
derivative [P(C6D5)3]2Pt(2,2′-biphenyl) was synthesized,
and the reaction with biphenylene was performed as
before. Examination of the product by GCMS showed a
peak for triphenylene with a mass of 232 was observed,
indicating that one of the phenylene rings has arisen
from the phosphine ligand (eq 7). It was therefore
All NMR spectra were recorded on a Bruker AMX400 (1H,
1
31P) spectrometer. All H and 31P chemical shifts are reported
in ppm (δ) relative to residual solvent resonances or 85%
phosphoric acid. Analyses were obtained from Desert Analyt-
ics. A Siemens SMART system with a CCD area detector was
used for X-ray structure determination. Gas chromatography-
mass spectrometry was performed on a 5890 Series II gas
chromatograph fitted with an HP 5970 Series mass selective
detector.
Rea ction of (d tbp m )P t(n eop en tyl)H (3) w ith Bip h en -
ylen e. 3 (10 mg, 0.017 mmol) and biphenylene (13.3 mg, 0.087
mmol) were placed in a resealable NMR tube and dissolved in
0.6 mL of THF. The reaction mixture was heated to 55 °C and
was judged complete after 1.5 h, on the basis of changes in
the 31P NMR spectrum (see text). The major product (>90%)
was 4, although a small amount of the dimer Pt2(µ-dtbpm)2
(5, ∼5%) and other uncharacterized products (∼5%) were
observed. The volatile materials were removed under vacuum,
the excess biphenylene was removed by sublimation, and the
1
residue was redissolved in CDCl3. H and 31P NMR spectra of
the major product were consistent with the C-C-activated
Pt(II) complex 4.
determined that the third phenylene ring in tri-
phenylene does indeed come from the metal ligands and
not from biphenylene cleavage.
(21) Bailar, J . C.; Itatani, H. Inorg. Chem. 1965, 4, 1618.
(22) Zelewsky, A.; Cornioley-Bevschel, C. Inorg. Chem. 1987, 26,
3334.
(23) Hofmann, P.; Heiss, H.; Muller, G. Z. Naturforsch. 1987, 42B,
395.
Con clu sion s
(24) Brainard, R. L.; Miller, T. M.; Whitesides, G. M. Organometal-
lics 1986, 5, 1481.
(25) Uson, R.; Vicente, J .; Cirac, J . A.; Chicote, M. T. J . Organomet.
Chem. 1980, 198, 105.
Reaction of biphenylene with Pt(dtbpm)(neopentyl)H
gives the expected C-C insertion adduct, but no further
(19) Wittig, G.; Ru¨mpler, K.-D. Liebigs Ann. Chem. 1971, 1.
Irngartinger, H. Isr. J . Chem. 1972, 10, 635. Ernst, L.; Mannschreck,
A.; Ru¨mpler, K.-D. Org. Magn. Reson. 1973, 5, 125. Irngartinger, H.
Acta Crystallogr. 1973, B29, 894. Hirschler, M. M.; Taylor, R. J . Chem.
Soc., Chem. Commun. 1980, 967.
(26) Neugebauer, W.; Kos, A. J .; Schleyer, P. v. R. J . Organomet.
Chem. 1982, 228, 107.
(27) Novikova, Z. S.; Prischenko, A. A.; Lutsenko, I. F. Zh. Obshch.
Khim. 1977, 47, 775.
(28) Logullo, F. M.; Seitz, A. H.; Friedman, L. In Organic Syntheses;
Yates, P., Ed.; Wiley: New York, 1968; Vol. 48, pp 54-59.
(20) Garrou, P. E. Chem. Rev. 1985, 85, 171.

2764 Organometallics, Vol. 20, No. 13, 2001
Simhai et al.
P r ep a r a t ion of (d t b p m )P t (2,2′-b ip h en yl) (4). 2,2′-Di-
lithiobiphenyl, used in situ from BunLi (0.81 mmol, 0.3 mL of
2.6 M hexanes solution) and 2,2′-dibromobiphenyl (120 mg,
0.39 mmol) in 6 mL of Et2O at 0 °C, was added dropwise to a
solution of (dtbpm)PtCl2 (200 mg, 0.35 mmol) in 10 mL of
toluene. The yellow reaction mixture was quenched with 10
mL of H2O after stirring at room temperature for 42 h. The
mixture was extracted with 50 mL each of toluene and THF.
The organic portion was dried with MgSO4, and the solvents
were removed in vacuo. Recrystallization from CH2Cl2 and
Et2O at -15 °C yielded yellow crystals (103 mg, 45%). 1H NMR
(CDCl3): δ 7.67 (br t, J Pt-H ) 62 Hz, 2 H, Hortho-Pt), 7.31 (d, J
) 8.8 Hz, 2 H), 6.92 (t, J ) 7.0 Hz, 2 H), 6.76 (t, J ) 7.2 Hz,
2 H), 3.52 (t, J P-H ) 7.6 Hz, 2 H, PCH2P), 1.49 (d, J P-H ) 12.8
Hz, 36 H, (CH3)3CP). 31P NMR (CDCl3); δ 4.7 (t, J Pt-P ) 1445
Hz). Mp: did not melt or decompose under 255 °C. Anal. Calcd
(found): C, 53.44 (53.38); H, 7.12 (7.16).
Rea ction of (d tbp m )P t(2,2′-bip h en yl) w ith H 2. 4 (8 mg,
0.012 mmol) was placed in a resealable NMR tube with a gas
bulb attached and placed under vacuum. A 0.60 mL portion
of THF-d8 was added to the tube by vacuum transfer, and the
headspace (approximately 5 mL) was filled with 1 atm of H2.
No change was observed in the reaction mixture following 4.5
days of thermolysis at 120 °C. Extended heating at 150 °C
resulted in no change in the NMR spectrum.
Rea ction of (d tbp m )P t(2,2′-bip h en yl) w ith P h CtCP h .
4 (8.1 mg, 0.012 mmol) and diphenylacetylene (10.9 mg, 0.61
mmol) were placed in a NMR tube and dissolved in 0.60 mL
of THF-d8. The mixture was frozen in liquid N2 and quickly
flame-sealed. No change was observed in the reaction mixture
following 4.5 days of thermolysis at 120 °C. Extended heating
at 150 °C resulted in no change in the NMR spectrum.
Rea ction of (d tbp m )P t(2,2′-bip h en yl) w ith CO. 4 (8 mg,
0.012 mmol) was placed in a resealable NMR tube and placed
under vacuum. A 0.60 mL portion of THF-d8 was added to the
tube by vacuum transfer, and the headspace was filled with 1
atm of CO. No change was observed in the reaction mixture
following 4 days of thermolysis at 85 °C. Extended heating at
150 °C resulted in no change in the NMR spectrum.
R ea ct ion of (d t b p m )P t (2,2′-b ip h en yl) w it h Bu t NC. 4
(8.1 mg, 0.012 mmol) was placed in a resealable NMR tube
and dissolved in 0.60 mL of C6D6. ButNC (14 µL, 0.12 mmol)
was added to the solution via syringe. The mixture was allowed
to react overnight at room temperature. 1H and 31P NMR
indicated complete conversion to (tBuNC)2Pt(2,2′-biphenyl) and
free dtbpm.
a solution of (dippm)Pt(neopentyl)Cl (101 mg, 0.18 mmol) in
1 mL of THF. The reaction was stirred at room temperature
for 2 h and then quenched with 8 mL of cold H2O at 0 °C. The
mixture was extracted with 4 × 10 mL of Et2O. The organic
portion was then washed with 3 × 10 mL of H2O, dried with
MgSO4, and evaporated under vacuum to yield a waxy solid.
Recrystallization from toluene and hexanes at -15 °C yielded
1
tan crystals (27 mg, 28%). H NMR (THF-d8): δ 3.11 (t, J P-H
i
i
) 8.4 Hz, 2 H, PCH2P), 2.27 (m, 2 H, Pr H), 2.03 (m, 2 H, Pr
H), 2.00 (dd, J P-H ) 9.2 Hz, J P-H ) 6.8 Hz, J Pt-H ) 85 Hz, 2
i
H, CH2C(CH3)3), 1.3-1.1 (m, 24 H, Pr methyls), 0.97 (s, 9 H,
CH2C(CH3)3), -3.68 (dd, J P(trans)-H ) 212 Hz, J P(cis)-H ) 12 Hz,
J Pt-H ) 1304 Hz, 1 H, Pt-H). 31P NMR (THF-d8): δ -1.8 (d,
J Pt-P ) 1369 Hz, J P-P ) 22 Hz), -12.4 (d, J Pt-P ) 1377 Hz,
J P-P ) 22 Hz).
Th er m olysis of (d ip p m )P t(n eop en tyl)H. (dippm)Pt(neo-
pentyl)H (7.8 mg, 0.015 mmol) was placed in a resealable NMR
tube and dissolved in 0.6 mL of THF-d8. Formation of the
dimer, Pt2(µ-dippm)2, was complete after heating for 13 h at
1
85 °C. H NMR (THF-d8): δ 2.08 (broad septet, 8 H, J H-H
)
i
6.8 Hz, Pr H), 1.79 (t, 4 H, J P-H ) 3.6 Hz, J Pt-H ) 42 Hz,
PCH2P), 1.29 (m, 24 H, iPr methyls), 1.22 (m, 24 H, iPr
methyls). 31P NMR (THF-d8): δ 62.3 (m, J Pt-P ) 4312 Hz, J Pt-P
) 89 Hz).
P r ep a r a tion of P P h 2Bu t. A 6.145 g (0.0278 mmol) portion
of PPh2Cl was dissolved in 45 mL of Et2O, and 18.2 mL of
ButLi (1.7 M in pentane, 0.031 mmol) was added slowly with
cooling in an ice bath. The solution was warmed to room
temperature and then refluxed overnight. The dark brown
solution was separated from the LiCl precipitate and the
solvent removed under vacuum (0.1 Torr). The product was
1
isolated by vacuum distillation (∼55 °C). H NMR (THF-d8):
δ 1.47 (d, J P-H ) 12.2 Hz, 9 H), 7.3 (m, 6 H), 7.55 (m, 4 H). 31
NMR (THF-d8): δ 20.24 (s).
P
P r ep a r a tion of (P P h 2Bu t)2P t(2,2′-bip h en yl) (6). A slurry
of 89.6 mg (0.102 mmol) of [(2,2′-biphenyl)Pt(µ-SEt2)]2 in 15
mL of THF was treated with 0.6 mmol of PPh2But (0.37 mL of
1.63 M solution). After 75 min, all of the solid had dissolved
to give a clear yellow solution. The THF was removed under
vacuum and the residue washed with benzene to remove excess
phosphine. The product remained as pale yellow air-stable
crystals and was recrystallized from CH2Cl2. Data for 6 are
1
as follows. H NMR (THF-d8): δ 8.151 (br s, 4 H), 7.600 (br s,
8 H), 7.426 (t, J ) 7.3 Hz (Pt satellites), 2 H), 7.288 (d, J , 7.3
Hz, 2 H), 6.876 (br s, 2 H), 6.789 (t, J ) 7.3 Hz, 2 H), 6.609 (br
s, 6 H), 6.377 (t, J ) 7.3 Hz, 2 H), 1.197 (d, J ) 13.3 Hz, 18
H). 31P NMR (THF-d8): δ 43.64 (s, J Pt-P ) 2000 Hz). Anal.
Calcd (found) for 6‚2CH2Cl2: C, 55.15 (54.59); H, 5.03 (5.16).
Th er m olysis of (d tbp m )P t(n eop en tyl)H (3). 3 (8.0 mg,
0.014 mmol) was placed in a resealable NMR tube and
dissolved in 0.6 mL of THF-d8. The tube was frozen in liquid
N2 and flame-sealed. Formation of the dimer Pt2(µ-dtbpm)2 (5)
Th er m olysis of (P P h 2Bu t)2P t(2,2′-bip h en yl) (6). A 10 mg
portion of 6 was dissolved in 0.6 mL of THF-d8 and placed in
a resealable NMR tube. The sample was heated to 80 °C, and
after 1 h the starting material had been replaced by a new
product, identified spectroscopically as rotamers of the ortho-
metalation product 7. Data for 7 are as follows. 1H NMR (THF-
d8): isomer A, δ 7.86 (t, J ) 8 Hz, 2 H), 7.63 (d, J ) 8 Hz, 2
H), 7.33 (m, 2 H), 7.20-7.00 (m, 20 H), 6.93 (m, 2 H), 0.770,
1.146 (d, J ) 10.2 Hz, 9 H), 0.735 (d, J ) 9.8 Hz, 9 H); isomer
B, δ 0.818 (d, J ) 14.0 Hz, 9 H), 0.696, d, J ) 13.8 Hz, 9 H),
other resonances obscured. 31P NMR (THF-d8): isomer A, δ
32.34 (d, J P-P ) 14 Hz, J Pt-P ) 2054 Hz), -4.10 (d, J P-P ) 14
Hz, J Pt-P ) 1028 Hz); isomer B, δ 31.19 (d, J P-P ) 14 Hz, J Pt-P
) 2050 Hz), -3.87 (d, J P-P ) 14 Hz, J Pt-P ) 986 Hz).
Rea ction of (P P h 2Bu t)2P t(2,2′-bip h en yl) w ith Bip h en -
ylen e. A sample of 9 mg of 6 (0.0108 mmol) and 8.2 mg (0.054
mmol) of biphenylene was dissolved in 0.6 mL of THF-d8 and
placed in a resealable NMR tube. The sample was heated to
130 °C and the reaction monitored by periodic recording of 1H
NMR spectra. Over a period of 40 days, the biphenylene was
seen to be converted catalytically into tetraphenylene (∼1
turnover/week).
1
was complete after heating for 1.5 h at 55 °C. H NMR (THF-
d8): δ 1.94 (t, J P-H ) 3.7 Hz, J Pt-H ) 34 Hz, 4 H, PCH2P),
t
1.47 (m, 72 H, Bu methyls). 31P NMR (THF-d8): δ 84.3 (m,
J Pt-P ) 4479 Hz, J Pt-P ) 41 Hz).
P r ep a r a tion of (d ip p m )P t(n eop en tyl)Cl. Bis(diisopro-
pylphosphino)methane (87 mg, 0.35 mmol) in 1.5 mL of CH2Cl2
was added dropwise to (COD)Pt(neopentyl)Cl (120 mg, 0.29
mmol) in 2 mL of CH2Cl2. The reaction mixture was stirred at
room temperature for 1 h, and then the volatile materials were
removed by vacuum. A total of 103 mg (63%) of white
(dippm)Pt(neopentyl)Cl was isolated by column chromatogra-
phy (CH2Cl2, SiO2, 14 × 2.5 cm). 1H NMR (CDCl3): δ 2.70 (dd,
J P-H ) 9.6 Hz, J P-H ) 7.6 Hz, J Pt-H ) 39 Hz, 2 H, PCH2P),
i
i
2.41 (m, 2 H, Pr H), 2.29 (m, 2 H, Pr H), 1.62 (dd, J P-H ) 7.6
Hz, J P-H ) 3.6 Hz, J Pt-H ) 63 Hz, 2 H, CH2C(CH3)3), 1.4-1.2
(m, 24 H, Pr methyls), 1.04 (s, 9 H, CH2C(CH3)3). 31P NMR
i
(CDCl3); δ -12.4 (d, J Pt-P ) 1152 Hz, J P-P ) 42 Hz, trans
neopentyl), -15.4 (d, J Pt-P ) 4019 Hz, J P-P ) 42 Hz, trans
Cl).
P r ep a r a tion of (d ip p m )P t(n eop en tyl)H. NaHB(OMe)3
(59 mg, 0.46 mmol) in 1.5 mL of THF was added dropwise to

Formation of Phenylene Oligomers Using Pt-Phosphine Complexes
Organometallics, Vol. 20, No. 13, 2001 2765
Ta ble 2. Su m m a r y of Cr ysta llogr a p h ic Da ta for 4, 5, 6, 8, a n d C
4
5
6
8
C
Crystal Parameters
chem formula
fw
PtP2C29H46
651.69
Pt2P4C34H76
999.01
PtP2C44H46
831.84
PtP2C48H38‚CH2Cl2‚2H2O C24H32
992.77
320.50
cryst syst
space group (No.)
Z
orthorhombic
Pnma
4
triclinic
P1h
4
monoclinic
C2/c
4
monoclinic
P21/n
4
monoclinic
P21/c
8
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
16.28370(10)
19.9282(2)
8.47700(10)
90
90
90
11.9290(12)
17.0879(17)
22.465(2)
72.623(2)
83.087(2)
71.827(2)
4150.4(7)
1.599
15.3446(4)
12.6371(3)
18.6507(5)
90
92.6390(10)
90
16.7917(2)
13.4726(2)
20.30490(10)
90
107.6270(10)
90
19.1209(11)
5.7541(3)
29.742(2)
90
108.057(2)
90
2750.83(5)
1.574
3612.7(2)
1.529
4377.86(9)
1.506
3111.2(3)
1.368
F
calcd, g cm-3
cryst dimens, mm3
temp, °C
0.22 × 0.22 × 0.36 0.04 × 0.10 × 0.24 0.16 × 0.18 × 0.24 0.24 × 0.26 × 0.38
0.12 × 0.16 × 0.24
-80
-80
-80
-80
-80
radiation (λ, Å)
Mo (0.710 73)
0.3/30
4.1-56.8
16 337
Mo (0.710 73)
0.3/5
3.6-56.6
26 434
Mo (0.710 73)
0.3/30
2.9-46.5
10 983
frame range, deg/time, s
2θ range, deg
no. of data collected
no. of unique data
3430
10 185
4260
no. of obsd data (I > 2σ(I)) 3083
agreement between 0.0264
equiv data (Rint
3779
0.0295
2717
0.0601
0.0712
0.0211
)
no. of params varied
196
5.232
SADABS
763
6.908
SADABS
0.593-0.928
0.0753, 0.1665
0.1395, 0.1977
0.934
213
4.003
SADABS
0.678-0.928
0.0282, 0.0509
0.0361, 0.0531
1.073
488
3.438
SADABS
0.927-0.733
0.0410, 0.1441
0.0488, 0.1493
1.209
433
0.076
SADABS
0.566-0.862
0.0839, 0.1467
0.1413, 0.1682
1.118
µ, mm-1
abs cor
range of transmissn factors 0.616-0.928
R1(Fo), wR2(Fo2) (I > 2σ)
0.0196, 0.0452
R1(Fo), wR2(Fo2) (all data) 0.0244, 0.0467
goodness of fit 1.079
P r ep a r a tion of (P P h 3)2P t(2,2′-bip h en yl) (8). A 1.185 g
(1.50 mmol) portion of Pt(PPh3)2Cl2 was dissolved in 50 mL of
Et2O and a solution of 2,2′-dilithiobiphenyl (1.32 mL, 2.4 M
in hexanes, 3.18 mmol) added dropwise via syringe. The
solution turned yellow-green over a few hours, after which 10
mL of water was added. The organic layer was separated, dried
with MgSO4, and evaporated to give yellow crystals of the
product (0.75 g, 73%). Data for 8 are as follows. 1H NMR (THF-
d8): δ 7.491 (t, J ) 8.4 Hz, 12 H); 7.252 (dm, J ) 7.4 Hz, 2 H);
7.206 (td, J ) 7.5, 1.3 Hz, 6 H); 7.081 (td, J ) 6.9, 1.3 Hz, 12
H); 6.837 (td, J ) 6.7, 2.7 Hz, 2 H); 6.660 (t, J ) 7.5 Hz, 2 H);
6.093 (tm, J ) 7.4 Hz, 2 H). 31P NMR (THF-d8): δ 30.75 (s,
J Pt-P ) 2009 Hz). Anal. Calcd (found) for 8: C, 66.13 (66.08);
H, 4.39 (4.68).
bright yellow mixture was stirred at 0 °C for 30 min and then
warmed to room temperature and stirred for 1 h. The flask
was cooled in a -20 °C freezer overnight, and 0.82 g of yellow
crystals was isolated (41% yield).
Syn th esis of (P P h 3-d 15)2P t(2,2′-bip h en yl). A 124 mg
(0.151 mmol) portion of (PPh3-d15)2PtCl2 was combined with
95 mg of the dilithio-biphenyl-TMEDA complex and dis-
solved in 15 mL of THF. This mixture was stirred for
approximately 20 min, during which time the solution became
clear. The solvent was removed in vacuo, and ∼20 mL of
toluene was added. The white precipitate (LiCl) was removed
by filtration and the solvent removed by vacuum. A total of
79 mg (0.087 mmol) of the yellow product was isolated (58%
yield).
Reaction (P P h 3)2P t(2,2′-biph en yl) of with Biph en ylen e.
A 144.5 mg (0.85 mmol) portion of biphenylene was dissolved
in ∼1.3 mL of THF, and 871 mg (0.188 mmol) of (PPh3)2Pt-
(2,2′-biphenyl) was added. The mixture was heated to 100 °C
and refluxed for 2 h. The solvent and excess biphenylene were
removed by sublimation (60 °C, 0.04 Torr). The products were
isolated by preparative TLC, using hexane as the eluent, on
SiO2. Characterization was accomplished by GC/MS and 1H
NMR spectroscopy and comparison with authentic samples.
Yields of each product were determined from the areas of the
GC trace and are as follows: phenyltriphenylene, 60%; tetra-
phenylene, 16%; triphenylene, 17%; centrosymmetrical hexa-
phenylene, 4%; helical hexaphenylene, 3%.
Syn t h esis of (P P h 3-d 15)2P t Cl2. An 81 mg (0.168 mmol)
portion of (COD)PtCl2 was dissolved in ∼3 mL of CH2Cl2. A
103 mg (0.37 mmol) amount of PPh3-d15 was added, and the
solution turned yellow. The reaction mixture was stirred at
room temperature for 20 min, after which it was layered with
ether and cooled to -20 °C. A total of 82.9 mg (0.101 mmol) of
white crystals was recovered by filtration, a 74% yield.
Syn th esis of (LiTMEDA)2(2,2′-bip h en yl). A 1.57 g (5.0
mmol) portion of 2,2′-dibromobiphenyl was dissolved in 50 mL
of diethyl ether. The solution was cooled to 0 °C, after which
1.46 g (12.5 mmol) of tetramethylethylenediamine and 6.6 mL
of a 1.6 M solution (10.5 mmol) of n-BuLi were added. The
X-r a y Str u ctu r e Deter m in a tion s of 4, 5, 6, 8, a n d C.
Single crystals of 4, 5, 6, 8, and C were mounted under
Paratone-8277 on glass fibers and immediately placed under
a cold nitrogen stream at -80 °C on the X-ray diffractometer.
The X-ray intensity data were collected on a standard Siemens
SMART CCD area detector system equipped with a normal-
focus molybdenum-target X-ray tube operated at 2.0 kW (50
kV, 40 mA). A total of 1321 frames of data (1.3 hemispheres)
were collected using a narrow frame method with scan widths
of 0.3° in ω and exposure times of 5-30 s/frame using a
detector-to-crystal distance of 5.09 cm (maximum 2θ angle of
56.54°) for all of the crystals. The total data collection time
was 4-12 h. Frames were integrated with the Siemens SAINT
program for all of the data sets. The unit cell parameters for
all of the crystals were based upon the least-squares refine-
ment of three-dimensional centroids of >5000 reflections.29
Data were corrected for absorption using the program
SADABS.30 Space group assignments were made on the basis
of systematic absences and intensity statistics by using the
(29) It has been noted that the integration program SAINT produces
cell constant errors that are unreasonably small, since systematic error
is not included. More reasonable errors might be estimated at 10×
the listed value.
(30) The SADABS program is based on the method of Blessing;
see: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.

2766 Organometallics, Vol. 20, No. 13, 2001
Simhai et al.
XPREP program (Siemens, SHELXTL 5.04). The structures
were solved by using direct methods and refined by full-matrix
least-squares on F2.31 For all of the structures, the non-
hydrogen atoms were refined with anisotropic thermal pa-
rameters, and hydrogens were included in idealized positions.
4 was found to have a rotational disorder in the tert-butyl
groups. It was modeled by including two tert-butyl groups at
50% occupancy, with the tert-butyl groups restrained to have
similar geometries by keeping C-C nearest-neighbor dis-
tances, C-C next-nearest-neighbor distances, and P-C dis-
tances similar. 6 lies on a 2-fold axis. 8 also contained one
CH2Cl2 and two water molecules in the asymmetric unit. 5
and C have two independent molecules within the asymmetric
unit. In addition, 5 showed a disorder in which a fraction of
the molecules of 5 were rotated by 90°. The disorder model
described in the text was employed with molecule C being
constrained to the same geometry as molecule B and molecule
D constrained to the same geometry as molecule A. The
populations of A and B were allowed to vary independently.
The phosphorus and platinum atoms were refined with aniso-
tropic thermal parameters, carbon atoms were refined isotro-
pically, and hydrogens were included in idealized positions.
Table 2 gives a summary of relevant crystallographic data.
Positional parameters for all atoms, anisotropic thermal
parameters, all bond lengths and angles, and fixed hydrogen
positional parameters are given in the Supporting Information
for all structures.
Ack n ow led gm en t is made to the U.S. Department
of Energy (Grant No. FG02-86ER113596) for their
support of this work. We also thank Prof. Peter Hof-
mann for valuable discussions concerning his studies
of the dimer 5 and related species.
Su ppor tin g In for m ation Available: Figures giving GCMS
traces for the reaction of 8 with biphenylene and tables of
crystallographic data for 4, 5, 6, 8, and C. This material is
available free of charge via the Internet at http://pubs.acs.org.
(31) Using the SHELX95 package, R1 ) (∑||Fo| - |Fc||)/∑|Fo| and
wR2 ) {[∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]}1/2, where w ) 1/[σ2(Fo2) + (aP)2 +
bP] and P ) [f 0(Max 0, Fo2) + (1 - f)Fc2].
OM010111M