Catalytic carbon-carbon bond activation and functionalization by nickel complexes

Article abstract of DOI:10.1021/om990387i

The nickel alkyne complexes (dippe)Ni(PhC≡CPh), 1, (dippe)Ni(MeC≡CMe), 2, (dippe)-Ni(MeO₂CC≡CCO₂Me), 3, (dippe)Ni(CH₃OCH₂C≡CCH₂OCH₃), 4, and (dippe)Ni(CF₃C≡CCF₃), 5, were synthesized (dippe = bis(diisopropylphosphino)ethane) and characterized by ¹H, ³¹P, and ¹³C{¹H} NMR spectroscopy. Complexes 1, 2, and 3 were characterized by X-ray crystallography. The thermolysis of complex 1 or 2 (120°C) in the presence of excess biphenylene and excess alkyne results in very slow catalytic formation of the corresponding 9,10-disubstituted phenanthrene. However, addition of ～6 mol % O₂ (based on the metal complex) to the reaction mixture results in an acceleration in catalysis at lower temperatures (～70-80°C). The thermolysis of complexes 3 or 4 with excess biphenylene and excess alkyne leads to the alkyne cyclotrimerization product as the major organic species formed in the reaction. Fluorenone was catalytically produced by heating (dippe)Ni(CO)₂, biphenylene, and CO. Catalytic insertion of 2,6-xylylisocyanide into the strained C-C bond of biphenylene was also achieved by heating (dippe)Ni(2,6-xylylisocyanide)₂, excess biphenylene, and 2,6-xylylisocyanide. Mechanistic schemes are proposed for these reactions.

Full text of DOI:10.1021/om990387i

4040
Organometallics 1999, 18, 4040-4049
Ca ta lytic Ca r bon -Ca r bon Bon d Activa tion a n d
F u n ction a liza tion by Nick el Com p lexes
Brian L. Edelbach, Rene J . Lachicotte, and William D. J ones*
Department of Chemistry, University of Rochester, Rochester, New York 14627
Received May 24, 1999
The nickel alkyne complexes (dippe)Ni(PhCtCPh), 1, (dippe)Ni(MeCtCMe), 2, (dippe)-
Ni(MeO2CCtCCO2Me), 3, (dippe)Ni(CH3OCH2CtCCH2OCH3), 4, and (dippe)Ni(CF3CtCCF3),
5, were synthesized (dippe ) bis(diisopropylphosphino)ethane) and characterized by 1H, 31P,
and 13C{1H} NMR spectroscopy. Complexes 1, 2, and 3 were characterized by X-ray
crystallography. The thermolysis of complex 1 or 2 (120 °C) in the presence of excess
biphenylene and excess alkyne results in very slow catalytic formation of the corresponding
9,10-disubstituted phenanthrene. However, addition of ∼6 mol % O2 (based on the metal
complex) to the reaction mixture results in an acceleration in catalysis at lower temperatures
(∼70-80 °C). The thermolysis of complexes 3 or 4 with excess biphenylene and excess alkyne
leads to the alkyne cyclotrimerization product as the major organic species formed in the
reaction. Fluorenone was catalytically produced by heating (dippe)Ni(CO)2, biphenylene, and
CO. Catalytic insertion of 2,6-xylylisocyanide into the strained C-C bond of biphenylene
was also achieved by heating (dippe)Ni(2,6-xylylisocyanide)2, excess biphenylene, and 2,6-
xylylisocyanide. Mechanistic schemes are proposed for these reactions.
In tr od u ction
ylene to biphenyl has been reported using (C5Me5)Rh-
(PMe3)H25e and several platinum, palladium, and nickel
phosphine complexes.5i Recently, we reported that tet-
raphenylene can be formed catalytically from biphen-
ylene via catalytic carbon-carbon bond activation and
formation by platinum and palladium phosphine com-
plexes.5g Ito et al. were able to catalytically cleave two
C-C bonds of strained spiro cyclobutanones using a
rhodium(I) species.5j Liebeskind has also used Ni(COD)2
to catalyze the insertion of acetylenes into the C-C
bonds of cyclobutenones to give phenols.5l
Homogeneous C-C bond cleavage and functionaliza-
tion by transition metal complexes is currently an active
area of research in organometallic chemistry. Stoichio-
metric C-C bond activation by several metal complexes
has been reported.1 Most of these examples rely on relief
of ring strain,2 attainment of aromaticity,3 or intramo-
lecular addition in which the C-C bond is forced into
close proximity to the metal.4
Catalytic C-C bond activation is less common,2k,4a,5
and most of these examples also rely on relief of ring
strain. For example catalytic hydrogenolysis of biphen-
Catalytic cleavage of strong C-C bonds by homoge-
neous metal complexes is a very recent development.
Milstein and co-workers reported the catalytic hydro-
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10.1021/om990387i CCC: $15.00 © 1999 American Chemical Society
Publication on Web 08/17/1999

Catalytic C-C Bond Activation
Organometallics, Vol. 18, No. 20, 1999 4041
F igu r e 1. ORTEP drawing of (dippe)Ni(PhCtCPh), 1.
Selected distances (Å): Ni(1)-C(16), 1.877(2); Ni(1)-C(15),
1.881(2); Ni(1)-P(1), 2.1468(6); Ni(1)-P(2), 2.1509(6); C(15)-
C(16), 1.285(3).
F igu r e 2. ORTEP drawing of (dippe)Ni(MeCtCMe), 2.
Selected distances (Å): Ni(1)-C(2), 1.877(2); Ni(1)-C(3),
1.888(2); Ni(1)-P(1), 2.1370(5); Ni(1)-P(2), 2.1433(5); C(2)-
C(3), 1.279(3).
genolysis and hydrosilation of a strong C-C bond using
a rhodium complex.5h The cleavage was aided by “forc-
ing” the C-C bond into the proximity of the metal
center. J un and Lee reported homogeneous catalytic
C-C bond cleavage of unstrained ketones.5k In this case,
the cleavage was facilitated by chelation assistance of
2-amino-3-picoline to a rhodium(I) complex.
nickel(0) alkyne complexes with electron-donating chelat-
ing phosphines.7
Ca t a lyt ic F or m a t ion of 9,10-(d isu b st it u t ed )-
P h en a n th r en es. In 1985 Eisch et al. formed 9,10-
diphenylphenanthrene in greater than 50% yield by
heating (PEt3)2Ni(2,2′-biphenyl) at 70 °C in the presence
of diphenylacetylene.8 Wakatsuki et al. also formed 9,10-
diphenylphenanthrene in 45% yield by heating diphen-
ylacetylene and CpCo(PPh3)(2,2′-biphenyl) at 95 °C for
3 days.9 We obtained a similar result by heating a
mixture of diphenylacetylene (2 equiv) and (dippe)Ni-
(2,2′-biphenyl) at 70 °C. This procedure leads to the
quantitative formation of 9,10-diphenylphenanthrene
and complex 1 (eq 1).
In this work we demonstrate that nickel complexes
can catalytically functionalize biphenylene with alkynes,
CO, and isocyanides to give 9,10-disubstituted phenan-
threnes, fluorenone, and fluorene imines, respectively.
Catalytic cycles are proposed for the various systems
that were evaluated.
Resu lts a n d Discu ssion
P r ep a r a tion a n d Ch a r a cter iza tion of Nick el
Alk yn e P h osp h in e Com p lexes. Several different
methodologies were used to prepare the acetylene
nickel(0) phosphine complexes employed in this study.
The first method involved the addition of the alkyne to
(dippe)Ni(COD). In the second method the alkyne was
added to [(dippe)Ni(H)]2. In a third method, (dippe)NiCl2
was reduced to nickel(0) with Na(Hg) amalgam in the
presence of the alkyne. While the latter method often-
times gave the highest yield, the ease of workup in the
first method made it the preferred procedure in most
cases. The following new compounds were synthe-
sized via method 1: (dippe)Ni(PhCtCPh), 1, (dippe)-
Ni(MeCtCMe), 2, (dippe)Ni(MeO2CCtCCO2Me), 3,
(dippe)Ni(CH3OCH2CtCCH2OCH3), 4, and (dippe)Ni-
(CF3CtCCF3), 5. These compounds were characterized
To test whether the formation of 9,10-diphenylphenan-
threne could be made catalytic, a mixture of complex 1
(0.028 M), biphenylene (8 equiv), and diphenylacetylene
(8 equiv) was heated in toluene-d8 at 110 °C in a
resealable NMR tube for 40 h. Only a small amount of
9,10-diphenylphenanthrene had formed after this time
(∼0.2 turnovers). The only metal-containing compound
observed by 1H and 31P NMR spectroscopy was complex
1. However, if oxygen (∼6 mol % based on complex 1) is
introduced to the NMR tube (via the addition of air),
the turnover rate for the formation of 9,10-diphenyl-
phenanthrene increases dramatically (∼3 turnovers/h
1
by H, 31P, and 13C{1H} NMR spectroscopy. Compound
5 was also characterized by 19F NMR spectroscopy. The
13C{1H} resonances of the alkyne carbons are similar
to those reported for other bis(phosphine)nickel(0) acety-
lene complexes.6 Compounds 1, 2, and 3 were also
characterized by X-ray crystallography (Figures 1-3).
These compounds are distorted square-planar complexes
(the alkyne is in the plane) with carbon-carbon triple-
bond distances similar to those reported for other
1
at 70 °C). The only metal complex identified by H and
31P{1H} NMR spectroscopy is compound 1. A small
(7) (a) Bonrath, W. Ph.D. Dissertation, University of Bochum, 1988.
(b) Porschke, K. R.; Mynott, R.; Angermund, K.; Kruger, C. Z.
Naturforsch. B: Anorg. Chem., Org. Chem. 1985, 40, 199. (c) Porschke,
K. R. Angew. Chem., Int. Ed. Engl. 1987, 26, 1288. (d) Bonrath, W.;
Porschke, K. R.; Wilke, G.; Angermund, K.; Kruger, C. Angew. Chem.,
Int. Ed. Engl. 1988, 27, 833.
(8) Eisch, J . J .; Piotrowski, A. M.; Han, K. I.; Kru¨ger, C.; Tsay, Y.
H. Organometallics 1985, 4, 224.
(9) Wakatsuki, Y.; Nomura, O.; Tone, H.; Yamazaki, H. J . Chem.
Soc., Perkin Trans. 2 1980, 1344.
(6) Bartik, T.; Happ, B.; Iglewsky, M.; Bandmann, H.; Boese, R.;
Heimbach, P.; Hoffmann, T.; Wenschuh, E. Organometallics 1992, 11,
1235.

4042 Organometallics, Vol. 18, No. 20, 1999
Edelbach et al.
The reaction of 4 with 1,4-dimethoxy-2-butyne and
biphenylene in toluene at 70 °C resulted in the forma-
tion of the cyclotrimerization product hexakis(methoxy-
methyl)benzene and 9,10-bis(methoxymethyl)phenan-
1
threne in a 7:1 ratio (based on H NMR spectroscopy).
Heating a THF mixture of complex 3 with dimethyl
acetylenedicarboxylate and biphenylene at 85 °C results
in exclusive formation of the cyclotrimerization product
benzenehexacarboxylic acid hexamethyl ester. Perhaps
the alkyne with the most electron-withdrawing substit-
uents is hexafluoro-2-butyne. Hexafluoro-2-butyne was
reacted with complex 5 and biphenylene at 85 °C in
THF-d8 in a resealable NMR tube. An orange solid
formed when the reaction mixture was cooled to room
temperature, assigned as the polymer of hexafluoro-2-
butyne.12 Neither the cyclotrimerization product nor the
phenanthrene product was observed by high tempera-
F igu r e 3. ORTEP drawing of (dippe)Ni(MeO2CCtCCO2-
Me), 3. Selected distances (Å): Ni(1)-C(1), 1.871(2); Ni(1)-
C(2), 1.871(2); Ni(1)-P(1), 2.1491(5); Ni(1)-P(2), 2.1499(5);
C(1)-C(2), 1.290(3).
1
ture (65 °C) H or 19F NMR spectroscopy.
Mech a n ism of P h en a n th r en e F or m a tion . Several
observations offer suggestions as to the possible mech-
anism of these reactions. As mentioned earlier the
formation of 9,10-(diphenyl)phenanthrene is extremely
slow without prior addition of O2 to the reaction
mixture, even at elevated temperatures (120 °C). How-
ever, heating a mixture of (dippe)Ni(PhCtCPh), di-
phenylacetylene, and biphenylene at 70 °C following the
addition of ∼6 mol % O2 results in the rapid formation
of 9,10-(diphenyl)phenanthrene as well as a small
amount of bis(diisopropylphosphino)ethane dioxide. The
amount of bis(diisopropylphosphino)ethane dioxide (δ,
52.0), bis(diisopropylphosphino)ethane monoxide (δ 51.2,
J ) 35 Hz and 9.8, J ) 35 Hz, THF-d8), and a pair of
resonances with an AB pattern at δ 52.5 and 45.5 could
also be detected in the 31P{1H} spectrum of the reaction
mixture. Furthermore, the resonances in both the 31P
1
and H NMR spectra were considerably broadened. A
small amount of hexaphenylbenzene was observed by
1H NMR spectroscopy as well as by GC/MS. Presum-
ably, hexaphenylbenzene arises as a result of the
catalytic cyclotrimerization of diphenylacetylene by a
nickel species in the reaction mixture.10 If complex 1
and diphenylacetylene are heated at 70 °C in the
absence of biphenylene or added O2, hexaphenylbenzene
is formed catalytically.
1
resonances in the H NMR spectrum of the sample are
broad under these conditions, but the resonances in the
1H NMR spectrum sharpen if this solution is degassed
and filtered to remove any suspended particles. Con-
tinued heating of the mixture results in the catalytic
formation of 9,10-diphenylphenanthrene at approxi-
mately the same turnover rate as before filtering and
O2 removal. If a small amount of dippe is added to the
reaction mixture at this point, catalysis stops. If a
sufficient amount of O2 is admitted to oxidize the excess
phosphine as well as a small amount of (dippe)Ni-
(PhCtCPh), the catalytic formation of 9,10-diphenyl-
phenanthrene continues. Addition of 1 equiv of O2
(relative to the metal complex) to a reaction mixture
containing (dippe)Ni(PhCtCPh), diphenylacetylene, and
biphenylene results in the formation of bis(diisopropyl-
phosphino)ethane dioxide, free acetylene, and “Ni metal”.
Heating this reaction mixture does not give 9,10-
diphenylphenanthrene. If an aliquot of a spent catalytic
reaction is added to an NMR tube containing (dippe)-
Ni(PhCtCPh), diphenylacetylene, and biphenylene and
the mixture is then heated at 85 °C without added O2,
9,10-diphenylphenanthrene is formed catalytically, al-
beit at a somewhat slower rate.
Other alkynes were tested as potential organic pre-
cursors for the catalytic formation of 9,10-(disubstitut-
ed)phenanthrenes. In each case (dippe)Ni(alkyne), bi-
phenylene, and the appropriate alkyne were combined
in a resealable NMR tube. Oxygen (∼6 mol % based on
the nickel complex) was introduced via the addition of
air. The mixture was then heated, and the reaction was
1
monitored by 31P{1H} and H NMR spectroscopy. The
results are summarized in Scheme 1.
The reaction of complex 2 with dimethylacetylene,
biphenylene, and O2 produced 9,10-dimethylphenan-
threne catalytically (∼1 TO/h at 70 °C in toluene-d8).
No hexamethylbenzene was observed by 1H NMR
spectroscopy or GC/MS. The reaction of (dippe)Ni-
(HCtCH) with acetylene, biphenylene, and O2 in THF-
d8 at 85 °C produced a black intractable solid, presum-
ably polyacetylene,11 as the major product. The polymer-
ization of acetylene by several metal catalysts has been
reported.11b Traces of benzene and phenanthrene were
1
Other related complexes were examined for the
similar catalytic formation of phenanthrene. An NMR
tube containing (bipy)Ni(PhCtCPh) (bipy ) bipyridine),
diphenylacetylene, and biphenylene was heated at 85
°C in THF-d8. 9,10-(Diphenyl)phenanthrene was formed
catalytically, but the turnover rate was slower (∼1.2 TO/
h) than that observed with the (dippe)Ni(PhCtCPh) and
added O2. Addition of ∼6 mol % O2 (via addition of air)
to the reaction mixture had no effect on the turnover
observed in the H NMR spectrum and by GC/MS.
The use of acetylenes with electron-withdrawing
substituents led to the formation of more cyclotrimer-
ization product relative to the phenanthrene product.
(10) The cyclotrimerization of substituted acetylenes by nickel
complexes is well-known. For example see: Reppe, W.; von Kutepow,
N.; Magin, A. Angew. Chem., Int. Ed. Engl. 1969, 8, 7. J olly, P. W.;
Wilke, G. The Organic Chemistry of Nickel; Academic Press: New York,
1975; Vol. 2. Takahashi, T.; Xi, Z.; Yamazaki, A.; Liu, Y.; Nakajima,
K.; Kotora, M. J . Am. Chem. Soc. 1998, 120, 1672, ref 3.
(11) (a) Daniels, W. E. J . Org. Chem. 1964, 29, 2936. (b) Shirakawa,
H. Synth. Met. 1995, 69, 3. (c) Shirakawa, H. Mol. Cryst. Liq. Cryst.
1989, 171, 235.
(12) Nishimura. S.; Nagai, A.; Takahashi, A.; Narita, T.; Hagiwara,
T.; Hamana, H. Macromolecules 1992, 25, 1648.

Catalytic C-C Bond Activation
Organometallics, Vol. 18, No. 20, 1999 4043
Sch em e 1
rate. Except for slight broadening of the resonances in
the H NMR spectrum, no other changes were observed
upon addition of O2.
Ni(acac)(L)CH3 (where L ) phosphine) the alkyne must
enter a square-planar coordination site prior to inser-
tion. They noted that insertion of alkynes into the metal
alkyl bond is preceded by loss of phosphine.15 Samsel
and Norton arrived at similar conclusions for intramo-
lecular acetylene insertion into Pd-carbon bonds.16 In
the present case the chelating dippe ligand disfavors
phosphine dissociation, thereby decreasing the likeli-
hood of forming a square-planar intermediate with the
alkyne in that plane.
The addition of O2 might facilitate the loss of coordi-
nated alkyne by oxidizing (dippe)Ni(PhCtCPh) to give
the cationic nickel species [(dippe)Ni(PhCtCPh)]+. If
loss of alkyne and subsequent cleavage of biphenylene
is more rapid from [(dippe)Ni(PhCtCPh)]+ than from
the neutral species, the rate of catalysis might increase,
providing that insertion into the Ni-aryl bond is ac-
cessible in this case. To test this hypothesis, two
oxidizing agents more potent than O2 were tested: 1,1′-
diacetylferrocene silver tetrafluoroborate (+0.49 V vs
Fc) and Fe(bipy)3(PF6)2 (+0.66 V vs Fc).17 A THF
solution of (dippe)Ni(PhCtCPh), diphenylacetylene,
biphenylene, and 6 mol % (based on 1) 1,1′-diacetyl-
ferrocene silver tetrafluoroborate was heated at 85 °C.
No 9,10-diphenylphenanthrene was observed after 12
h. Addition of ∼10 mol % O2 and continued heating
resulted in catalytic formation of 9,10-diphenylphenan-
threne. A similar reaction using Fe(bipy)3(PF6)2 as the
oxidizing agent did not lead to the production of 9,10-
diphenylphenanthrene under similar conditions. These
observations argue against oxidation of the metal
acetylene complex by O2.
1
The phosphine-free complex Ni2(COD)2(PhCtCPh)13
was added to a THF solution of diphenylacetylene and
biphenylene. The 1H NMR spectrum reveals an equi-
librium between the dimer Ni2(COD)2(PhCtCPh) and
the monomer (COD)Ni(PhCtCPh). Heating the mixture
at 85 °C initially leads to the formation of hexaphenyl-
benzene, COD, and a small amount of 9,10-diphenyl-
phenanthrene. However, with continued heating more
COD is released and the rate of formation of 9,10-
diphenylphenanthrene exceeds that of hexaphenylben-
zene. No change in the rate of formation of phenan-
threne is observed when a 2:1 mixture of complex 1 and
Ni2(COD)2(PhCtCPh) is heated at 85 °C with di-
phenylacetylene and biphenylene. The concentration of
complex 1 is unchanged over the course of the reaction.
The complex (PPh3)2Ni(PhCtCPh)14 was found to also
be an excellent catalyst for the insertion of diphenyl-
acetylene into biphenylene in the presence of O2. A
solution containing Ni(PPh3)2(PhCtCPh) (0.024 M) and
equimolar substrates (0.25 M each) gave about a 20%
yield of diphenylphenanthrene upon standing for 24 h
following addition of 8% O2. A small quantity of OdPPh3
was seen by 31P NMR spectroscopy (δ 26.03, ∼3%).
Heating the THF solution to 60 °C resulted in the
complete conversion to product in 15-20 min.
One possible mechanism for the catalytic formation
of these phenanthrenes may involve reversible loss of
the coordinated alkyne to give [(dippe)Ni(0)]. The C-C
bond of biphenylene is then cleaved by [(dippe)Ni(0)],
resulting in the formation of (dippe)Ni(2,2-biphenyl).
Alkyne coordination to give a five-coordinate complex
followed by insertion of alkyne into the Ni-aryl bond
and reductive elimination of phenanthrene regenerates
(dippe)Ni(0). In the absence of added O2 this mechanism
may well be operating, albeit slowly. Huggins and
Bergman established that for complexes of the type
The rate of catalysis was monitored as a function of
O2 concentration. Six NMR tubes were prepared, each
containing 1, biphenylene (10 equiv), and diphenylphen-
anthrene (10 equiv) in THF-d8. Various amounts of
oxygen (6, 13, 20.5, 28, 40, and 52 mol % based on 1)
were admitted (via air) to the NMR tubes. A 31P{1H}
NMR spectrum of the mixtures after addition of O2
revealed a small amount of bis(diisopropylphosphino)-
(13) Muetterties, E. L.; Pretzer, W. R.; Thomas, M. G.; Beier, B. F.;
Thorn, D. L.; Day, V. W.; Anderson, A. B. J . Am. Chem. Soc. 1978,
100, 2090.
(14) Rosenthal, U. Z. Anorg. Allg. Chem. 1981, 482, 179. Greaves,
E. O.; Lock, C. J . L.; Maitlis, P. M. Can. J . Chem. 1968, 46, 3879.
(15) Huggins, J . M.; Bergman, R. G. J . Am. Chem. Soc. 1981, 103,
3002.
(16) Samsel, E. G.; Norton, J . R. J . Am. Chem. Soc. 1984, 106, 5505.
(17) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877.

4044 Organometallics, Vol. 18, No. 20, 1999
Edelbach et al.
Sch em e 2
Figu r e 4. Initial rate of formation of 9,10-diphenylphenan-
threne vs mol % O2 for the reaction of 1 (0.030 M) with
diphenylacetylene (0.30 M) and biphenylene (0.30 M) at
60 °C. The initial rate (M-1 s-1) was calculated from the
slope of concentration of 9,10-diphenylphenanthrene vs
time during the first 10 min of reaction.
ethane dioxide and bis(diisopropylphosphino)ethane
monoxide and the two doublet of doublets resonances
at δ 52.5 and 45.6. The latter resonances are consistent
with the formation of a Ni complex coordinated to one
bis(isopropyl) phosphine, while the other bis(isopropyl)
phosphine is oxidized and no longer coordinated to the
metal center. The concentration of all these species
increased relative to 1 as more O2 was admitted. The
NMR tubes were heated at 60 °C, and the initial rate
of catalysis was monitored via 1H NMR spectroscopy.
The results are displayed in Figure 4. Increasing the
concentration of O2 increases the initial rate of catalysis
moderately up to ∼30-40 mol % O2, after which point
additional O2 leads to a decrease in the rate of catalysis.
All of the reactions went to completion with the excep-
tion of the 6 mol % O2 reaction, which stopped with ∼2
equiv of biphenylene and diphenylphenanthrene re-
maining. A 31P{1H} NMR spectrum of the mixtures after
consumption of biphenylene and phenanthrene revealed
no changes in the relative amounts of the phosphine-
containing species.
Sch em e 3
Given the observations discussed above, the following
conclusions can be drawn. First, O2 can be ruled out as
a one-electron oxidizing agent in these reactions since
oxidants stronger than O2 had no effect on the rate of
catalysis. Second, oxygen is not required once catalysis
begins, as it can be removed and catalysis continues.
Third, coordinated phosphine is not required for the
catalysis since Ni2(COD)2(PhCtCPh) and (bipy)Ni-
(PhCtCPh) work. These observations imply that the
role of oxygen might simply be to remove the phosphine
ligand from the metal center (as phosphine oxide),
thereby forming a more active catalyst.
Since we were unable to observe the active catalyst
spectroscopically, we can only speculate as to its struc-
ture. The catalytic cycle depicted in Scheme 2 represents
a plausible mechanistic pathway for the formation of
9,10-disubstituted phenanthrenes. The addition of O2
leads to release of the phosphine in its oxidized form.
Subsequent cleavage of the strained C-C bond in
biphenylene by the putative Ni(0) species results in the
formation of intermediate A (Scheme 2). This complex
coordinates a second acetylene molecule to generate B.
While the structure of B is unlikely to be a square-
planar complex, if one of the alkynes is coordinated in
the plane of the biphenyl group, rapid insertion into the
Ni-C bond can occur, generating compound C. Complex
C can reductively eliminate the phenanthrene and
regenerate A. Intermediates A, B, and C would all
display only aromatic resonances in the 1H NMR
spectrum and would be difficult to identify under the
reaction conditions.
This catalytic cycle is similar to the commonly ac-
cepted mechanism for the cyclotrimerization of alkynes
outlined in Scheme 3.18 In the present case, after the
reductive elimination of the organic product, C-C
cleavage of biphenylene gives the boxed species A rather
than the bis(η2-coordinated)alkyne complex depicted in
Scheme 3. It has been established that the nickel(0)-
alkyne bond strength is greatest for compounds contain-
ing donor ligands and/or acetylenes with electron-
(18) Schore, N. E. Chem. Rev. 1988, 88, 1081.

Catalytic C-C Bond Activation
Organometallics, Vol. 18, No. 20, 1999 4045
(dippe)Ni(CO). Coordination of CO to (dippe)Ni(CO) to
form (dippe)Ni(CO)2 is probably more rapid than cleav-
age of biphenylene, which is consistent with the obser-
vation that the resting state species is (dippe)Ni(CO)2.
There is spectroscopic evidence for the formation of
compound X under certain conditions. If the reaction is
performed in an NMR tube with thorough mixing, an
orange solution results and the only nickel species
F igu r e 5. Possible structure of oxidized intermediate.
1
observed in the H and 31P NMR spectra is (dippe)Ni-
withdrawing groups. Furthermore, the degree of com-
plexation is directly proportional to the rate of cyclo-
trimerization of alkynes.19 This may account for the
relative increase in cyclotrimerization to phenanthrene
formation when alkynes with acceptor groups are
employed.
(CO)2. However, if CO mixing is inefficient, as in an
1
unshaken NMR tube, the solution is red. A H NMR
spectrum of the red sample displays four isopropyl
methyl resonances at δ 1.450 (J P-H ) 15.2, 7.1 Hz),
1.364 (J P-H ) 13.4, 7.1 Hz), 0.662 (J P-H ) 13.4, 7.0 Hz),
and 0.316 (J P-H ) 15.3, 7.1 Hz) as well as new aromatic
resonances (some are obscured by fluorenone). The 31P
NMR spectrum displays two new doublets at δ 77.52
(J P-P ) 55.2 Hz) and 69.16 (J P-P ) 56.4 Hz), consistent
with a nickel species containing inequivalent phos-
phines. Compound X has inequivalent phosphines by
virtue of CO insertion into the Ni-C bond, and the
isopropyl methyl groups on each phosphorus are dia-
stereotopic. The fact that this compound is only observed
under CO-deficient conditions is consistent with the CO-
facilitated reductive elimination of fluorenone from X.
Ca ta lytic P r od u ction of F lu or en e Im in es. The
migratory insertion of isocyanides, CNR, into metal-
carbons bonds is a well-known reaction in organo-
metallic chemistry. Insertion of isocyanides into Ni-
aryl bonds has been established.20 Insertion of iso-
cyanide into a Co-aryl bond was accomplished by
heating a mixture of 2,6-xylyl isocyanide and CpCo-
(PPh3)(2,2′-biphenyl) at 110 °C for 9 h, resulting in the
formation of (2,6-xylyl)-fluoren-9-ylideneamine, 6, in
44% yield.9 In this study, compound 6 and (dippe)Ni-
(CN-2,6-xylyl)2, 7, were formed in a 1:1 ratio in quan-
titative yield at room temperature by mixing (dippe)-
Ni(2,2′-biphenyl) and 2,6-xylyl isocyanide (eq 2).
Another possible intermediate in the formation of the
phenanthrenes may be the dimer shown in Figure 5.
In this case one arm of the bis(phosphine) is oxidized
and coordinated to one metal center, while the other
phosphine is coordinated to a different metal center. As
discussed above, the 31P{1H} spectrum displayed reso-
nances for a species with an A2B2 pattern. A simulated
fit of these NMR resonances is consistent with the
structure depicted in Figure 5 (see Supporting Informa-
tion). Release of the oxygenated phosphine from a nickel
would result in a 14-electron Ni(0) complex capable of
cleaving the C-C bond of biphenylene. Subsequent
insertion of acetylene and reductive elimination of the
phenanthrene regenerates a Ni(0) species. The rate of
catalysis should increase as the concentration of this
complex increases if such a species is an intermediate
in the catalytic formation of phenanthrenes. While the
concentration of this compound was largest upon addi-
tion of 52 mol % O2 (based on 1), the initial rate of
catalysis was decreased relative to addition of 40 mol
% O2. This observation is inconsistent with a monooxi-
dized phosphine Ni complex being an intermediate in
the major pathway to phenanthrene formation. However
the intermediate shown in Figure 5 cannot be ruled out
as part of an alternative pathway for the formation of
phenanthrenes.
Ca ta lytic Ca r bon yla tion of Bip h en ylen e. Previ-
ously we have demonstrated that (C5Me5)Rh(CO)2 reacts
with biphenylene in the presence of CO to give fluo-
renone catalytically.2k In the present study we found
that (dippe)Ni(2,2′-biphenyl) reacted with biphenylene
under a CO atmosphere at room temperature to give
fluorenone and (dippe)Ni(CO)2 in a 1:1 ratio (based on
1H NMR spectroscopy). Eisch et al. obtained similar
results when they treated (PEt3)2Ni(2,2′-biphenyl) with
CO at -78 °C.8 Fluorenone was also formed in 43% yield
by mixing CpCo(PPh3)(2,2′-biphenyl) and CO at room
temperature.9
Heating a THF-d8 mixture of (dippe)Ni(CO)2 at 95 °C
with 5 equiv of biphenylene under an atmosphere of CO
resulted in the catalytic formation of fluorenone (∼2 TO/
day). The resting state species is (dippe)Ni(CO)2. Scheme
4 shows the proposed mechanism for the formation of
fluorenone. The first step is reversible loss of CO from
the resting state species (dippe)Ni(CO)2 to give the
putative 14-electron complex (dippe)Ni(CO). This is
followed by carbon-carbon bond cleavage of biphenylene
and CO insertion into the Ni-C bond of the coordinated
biphenyl. Displacement of fluorenone by CO regenerates
Heating compound 7 at 107 °C with 2 equiv of
biphenylene results in the formation of compound 6, a
small amount of tetraphenylene, and a new nickel
complex, Z. The new nickel compound displays four
broad isopropyl methyl resonances centered at δ 1.40,
1.19, 0.779, and 0.208 as well as new aromatic reso-
nances (some are obscured by compound 6). The 31P
NMR spectrum displays two new doublets with an AB
pattern at δ 62.23 (J P-P ) 54.2 Hz) and 61.83 (J P-P
)
51.7 Hz) and a small amount of (dippe)Ni(2,2′-biphenyl).
These results are consistent with a nickel species
containing inequivalent phosphines. Compound Z has
inequivalent phosphines by virtue of isocyanide inser-
(20) (a) Ca´mpora, J .; Gutie´rrez, E.; Monge, A.; Poveda, M. L.;
Carmona, E. Organometallics 1992, 11, 2644. (b) Ca´mpora, J .; Guti-
e´rrez, E.; Monge, A.; Poveda, M. L.; Ruiz, C.; Carmona, E. Organo-
metallics 1993, 12, 4025.
(19) Rosenthal, U.; Schulz, W. J . Organomet. Chem. 1987, 321, 103.

4046 Organometallics, Vol. 18, No. 20, 1999
Edelbach et al.
Sch em e 4
phosphorus-containing Ni species which can be gener-
ated by addition of O2 to (dippe)Ni(RCtCR). Experi-
mental evidence suggests that the role of oxygen is to
remove the dippe ligand by oxidation, thereby generat-
ing the active catalyst. Catalytic carbonylation of bi-
phenylene to generate fluorenone was also achieved
with (dippe)Ni(CO)2 as the catalyst precursor. Finally,
it was demonstrated that isocyanides can insert into the
C-C bond of biphenylene to generate fluorene imines.
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 Corporation glovebox. Tetrahydrofuran and toluene
were distilled from dark purple solutions of benzophenone
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 and toluene-d8 were purchased from Cam-
bridge Isotope Labs, distilled under vacuum from dark purple
solutions of benzophenone ketyl, and stored in ampules with
Teflon-sealed vacuum line adapters. The preparations of 1,1′-
diacetylferrocene silver tetrafluoroborate,21 biphenylene,22 neo-
pentylisocyanide,23 dippe,24 (bipy)Ni(PhCtCPh),25 Ni2(COD)2-
(PhCtCPh),13 (dippe)Ni(COD),26 [(dippe)NiH]2,5i (dippe)Ni(2,2′-
biphenyl),27 2,2′-dilithiobiphenyl,28 (dippe)Ni(HCtCH),7a (dippe)-
Ni(CO)2,7a and (PPh3)2Ni(PhtCPh)14 have been previously
reported. Ni(COD)2, Fe(bipy)3(PF6)2, and all of the alkynes with
the exception of 1,4-dimethoxy-2-butyne were purchased from
Aldrich Chemical Co. The alkyne 1,4-dimethoxy-2-butyne was
purchased from Lancaster. 2,6-Xylyl isocyanide was purchased
from Fluka, 2,2′-dibromobiphenyl was purchased from Alfa
Aesar (Avocado), and dppe was purchased from Strem. The
liquids were stirred over sieves, freeze-pump-thaw degassed
three times, and vacuum distilled prior to use.
Sch em e 5
All NMR spectra were recorded on a Bruker AMX400 (1H,
1
31P, 13C) or Avance400 (1H, 31P, 13C, 19F) spectrometer. All H
chemical shifts are reported in ppm (δ) relative to tetrameth-
ylsilane and referenced using chemical shifts of residual
solvent resonances (THF-d8, δ 1.73, toluene-d8, δ 2.09). 31P
NMR spectra were referenced to external 30% H3PO4 (δ 0.0).
19F NMR spectra were referenced to external C6F5CF3. CFCl3
appears at δ +62.54 relative to internal C6H5CF3 in THF-d8
solvent. GC-MS was conducted on a 5890 Series II gas
chromatograph fitted with an HP 5970 series mass selective
detector. Analyses were obtained from Desert Analytics. A
Siemens SMART system with a CCD area detector was used
for X-ray structure determination.
P r ep a r a tion of (d ip p e)Ni(P h CtCP h ), 1. (dippe)Ni(COD)
(186 mg, 0.43 mmol) and diphenylacetylene (93 mg, 0.52 mmol)
were dissolved in 8 mL of benzene in an ampule. The solution
was heated at 65 °C for 36 h. The solvent was removed under
vacuum, and the orange solid was dissolved in a minimum of
tion into the Ni-C bond. Addition of excess 2,6-xylyl
isocyanide to compound Z gives 6 and 7. These results
are consistent with compound Z being the isocyanide
insertion product depicted in Scheme 5.
Interestingly, heating a mixture of 7, biphenylene,
and 2,6-dimethylphenyl isocyanide does not lead to
immediate formation of 6. An induction period is
observed; however, once catalysis begins, the turnover
rate is greater than 10/day at 107 °C. Similar behavior
is observed with (dppe)Ni(2,6-xylyl isocyanide)2, 8 (no
significant rate acceleration was observed). In light of
the similarities between the CO and isocyanide reac-
tions, an analogous catalytic cycle for the formation of
6 is depicted in Scheme 5.
(21) Carty, P.; Dove, M. F. A. J . Organomet. Chem. 1971, 28, 125.
(22) Yates, P. Organic Synthesis; Wiley: New York, 1968; Collect.
Vol. 48, p 12.
(23) Schuster, R. E. Organic Synthesis; Wiley: New York, 1973;
Collect. Vol. 5, p 772.
(24) Cloke, F. G. N.; Gibson, V. C. Green, M. L. H.; Mtetwa, V. S.
B.; Prout, K. J . Chem. Soc., Dalton Trans. 1988, 2227.
(25) Rosenthal, U.; Nauck, C.; Arndt, P.; Pulst, S.; Baumann, W.;
Burlakov, V. V.; Go¨rls, H. J . Organomet. Chem. 1994, 484, 81.
(26) Bonrath, W.; Po¨rschke, K. R.; Wilke, G.; Angermund, K.;
Kru¨ger, K. Angew. Chem., Int. Ed. Engl. 1988, 27, 833. Werner
Bonrath, Ph.D. Thesis, Max-Planck-Institute fu¨r Kohlenforschung,
1988.
Con clu sion s
The catalytic functionalization of biphenylene with
disubstituted alkynes to give 9,10-disubstituted phenan-
threnes has been demonstrated using (dippe)Ni(RCtCR)
complexes as catalyst precursors. Alkynes containing
electron-donating or mildly electron-withdrawing groups
R to the alkyne carbon favor phenanthrene formation
vs cyclotrimerization product. However, cyclotrimeriza-
tion products increase relative to phenanthrene forma-
tion as the substituents on the R carbon become more
electron withdrawing. Terminal alkynes favor polymer
formation. The active catalyst appears to be a non-
(27) Edelbach, B. E.; Vicic, D. A.; Lachicotte, R. J .; J ones, W. D.
Organometallics 1998, 17, 4784.
(28) Gardner, S. A.; Gordon, H. B.; Rausch, M. D. J . Organomet.
Chem. 1973, 60, 179.

Catalytic C-C Bond Activation
Organometallics, Vol. 18, No. 20, 1999 4047
THF, layered with hexanes, and cooled to -30 °C overnight.
Orange crystals were isolated by filtration (yield: 165 mg of
orange X-ray quality crystals, 77%). NMR data for 1: 1H NMR
bottom flask with 20 mL of THF. Hexafluoro-2-butyne (1 atm)
was added to the flask. The solution immediately turned
orange. The solvent, excess COD, and alkyne were removed
under vacuum. The orange/brown solid was dissolved in a
minimum of hexanes and cooled to -30 °C. The orange crystals
were washed with cold MeOH (yield: 172 mg, 61%). NMR data
for 5: 1H NMR (THF-d8): δ 2.146 (sept, CHMe2, J H-H ) 7.5
Hz, 4 H), 1.791 (d, PCH2CH2P, J H-P ) 8.5 Hz, 4 H), 1.133
(overlapping quartet, CHMe2, 24 H). 31P{1H} NMR (THF-d8):
δ 85.74 (s). 19F NMR (THF-d8): δ 11.12 (d, J F-P ) 7.6 Hz).
13C{1H} NMR (THF-d8): δ 125.9 (t, J P-C ) 10.4 Hz), 123.3 (t,
J P-C ) 10.4 Hz), 26.0 (d, J P-C ) 24.0 Hz), 22.1 (t, J P-C ) 19.3
Hz), 19.9 (t, J ) 3.0 Hz), 19.0 (s). Anal. Calcd for C18H32P2F6-
Ni: C, 44.78; H, 6.68. Found: C, 44.54; H, 7.09.
P r ep a r a tion of (d ip p e)Ni(CN-2,6-xylyl)2, 7. (dippe)Ni-
(COD) (430 mg, 1.0 mmol) was dissolved in 15 mL of THF. To
this solution was added 2,6-dimethylbenzene isocyanide (340
mg, 2.58 mmol) dropwise at room temperature. The mixture
was stirred for 2 h, during which time it became orange in
color. The solvent and excess COD were removed under
vacuum, leaving an orange oil behind (yield: 459 mg, 79%).
NMR data for 8: 1H NMR (THF-d8): δ 7.0-6.9 (m, 6 H), 2.369
(s, 6 H), 2.020 (sept, CHMe2, J H-H ) 6.8 Hz, 4 H), 1.527 (d,
PCH2CH2P, J H-P ) 8.4 Hz, 4 H), 1.206 (q, CHMe2, J H-H ) J P-H
) 7.0 Hz, 12 H), 1.037 (q, CHMe2, J H-H ) 7.1 Hz, 12 H).
31P{1H} NMR (THF-d8): δ 76.59 (s).
P r ep a r a tion of (d p p e)Ni(CN-2,6-xylyl)2, 8. (dppe)Ni-
(COD) (150 mg, 0.265 mmol) was dissolved in 5 mL of THF.
To this solution was added 2,6-dimethylbenzene isocyanide (70
mg, 0.533 mmol) dropwise at room temperature. The mixture
was stirred for 2 h, during which time it became orange in
color. The solvent and excess COD were removed under
vacuum. The solid was extracted with a minimum of hexanes,
filtered through a glass plug, and cooled to -30 °C, giving
orange crystals (yield: 130 mg, 68%). NMR data for 8: 1H
NMR (THF-d8): δ 7.79-7.72 (m, 8 H), 7.27-7.17 (m, 12 H),
6.94 (s, 6 H), 2.25 (d, PCH2CH2P, J H-P ) 15.3 Hz, 4 H), 2.16
(s, 12 H). 31P{1H} NMR (THF-d8): δ 46.32 (s). Anal. Calcd for
(THF-d8): δ 7.349 (d, J H-H ) 7.4 Hz, 4 H), 7.152 (t, J H-H
)
7.4 Hz, 4 H), 6.987 (t, J H-H ) 7.3 Hz, 2 H), 2.127 (sept, CHMe2,
J H-H ) 7.2 Hz, 4 H), 1.657 (d, PCH2CH2P, J H-P ) 9.2 Hz, 4
H), 1.078 (quintet, CHMe2, J H-H ) 7.2, J P-H ) 7.2 Hz, 24 H).
31P{1H} NMR (THF-d8): δ 79.35 (s). 13C{1H} NMR (THF-d8):
δ 141.3 (t, tC-Ph, J P-C ) 7.1 Hz), 132.3 (s), 128.3 (d, J P-C
)
8.6 Hz), 127.3 (s), 124.9 (s), 26.7 (t, J P-C ) 10.4 Hz), 22.2 (t,
J P-C ) 19.1 Hz), 20.4 (t, J P-C ) 4.0 Hz), 19.1 (s). Anal. Calcd
for C28H42P2Ni: C, 67.35; H, 8.48. Found: C, 67.49; H, 8.55.
P r ep a r a t ion of (d ip p e)Ni(MeCtCMe), 2. (dippe)Ni-
(COD) (150 mg, 0.35 mmol) was dissolved in a round-bottom
flask with 10 mL of benzene. Dimethylacetylene (55 µL, 0.70
mmol) was dissolved in 5 mL of benzene and added dropwise
to the (dippe)Ni(COD) solution. The mixture was stirred at
room temperature for 3 days, during which time the solution
slowly turned orange, then dark orange. The solvent was
removed under vacuum, and the orange solid was washed with
cold methanol to remove excess COD. The solid was dissolved
in a minimum of acetone and cooled to -30 °C overnight
(yield: 86 mg of yellow X-ray quality crystals, 66%). NMR data
for 2: 1H NMR (THF-d8): δ 2.400 (d, J H-H ) 5.2, 2.9 Hz, 6 H),
2.024 (sept, CHMe2, J H-H ) 6.9 Hz, 4 H), 1.532 (d, PCH2CH2P,
J H-P ) 8.6 Hz, 4 H), 1.124 (q, CHMe2, J H-H ) J P-H ) 8.0 Hz,
12 H), 1.037 (q, CHMe2, J H-H ) J P-H ) 5.8 Hz, 12 H). 31P{1H}
NMR (THF-d8): δ 80.16 (s). 13C{1H} NMR (THF-d8): δ 124.3
(t, tC-Me, J P-C ) 19.7 Hz), 26.0 (t, J P-C ) 10.0 Hz), 22.9 (t,
J P-C ) 19.5 Hz), 20.2 (t, J P-C ) 4.4 Hz), 19.3 (s), 15.4 (t, J P-C
) 11.1 Hz). Anal. Calcd for C18H38P2Ni: C, 57.63; H, 10.21.
Found: C, 57.43; H, 10.47.
P r epar ation of (dippe)Ni(MeO2CCtCCO2Me), 3. (dippe)-
Ni(COD) (100 mg, 0.233 mmol) was dissolved in a round-
bottom flask with 15 mL of THF. Dimethyl acetylenedicar-
boxylate (21 µL, 0.17 mmol) was dissolved in 5 mL of THF
and added dropwise to the (dippe)Ni(COD) solution. The
solution immediately turned orange/brown. The mixture was
stirred for 12 h, the solvent and excess COD were removed
under vacuum, and the orange solid was redissolved in 25 mL
of THF. An additional 31 µL of dimethylacetylenedicarboxylate
dissolved in 5 mL of THF was added dropwise to the mixture,
the mixtire was stirred for 12 h at room temperature, and the
solvent and excess COD were removed under vacuum. The
solid was dissolved in a minimum of THF and layered with
hexanes. After 12 h, the mother liquor was removed from the
clear crystals (benzenehexacarboxylic acid hexamethyl ester)
and cooled to -30 °C. After 2 days, 30 mg of orange, X-ray
quality crystals of 3 were isolated (yield: 28%). NMR data for
3: 1H NMR (THF-d8): δ 3.625(s, 6 H), 2.106 (sept, CHMe2,
J H-H ) 7.8 Hz, 4 H), 1.703 (d, PCH2CH2P, J H-P ) 9.5 Hz, 4
H), 1.109 (overlapping quartets, CHMe2, J H-H ) J P-H ) 6.9
Hz, 24 H). 31P{1H} NMR (THF-d8): δ 71.24 (s). Anal. Calcd
for C20H38O4P2Ni: C, 51.87; H, 8.27. Found: C, 51.89; H, 8.20.
P r ep a r a tion of (d ip p e)Ni(CH3OCH2CtCCH2OCH3), 4.
(dippe)Ni(COD) (200 mg, 0.47 mmol) was dissolved in a round-
bottom flask with 20 mL of THF. 1,4-Dimethoxy-2-butyne (80
mg, 100 µL, 0.70 mmol) was added, and the mixture was
heated to 70 °C for 2 h. The solvent, COD, and excess 1,4-
dimethoxy-2-butyne were removed under vacuum, giving a
dark oil (125 mg, 62%). NMR data for 4: 1H NMR (THF-d8):
C
44H42P2N2Ni: C, 73.46; H, 5.88. Found: C, 73.26; H, 5.78.
Gen er al P r ocedu r e for Catalytic For m ation of P h en an -
th r en es. A solution containing the metal complex (0.033 M),
biphenylene (0.33 M), and the appropriate acetylene (0.36 M)
was prepared in 0.6 mL of toluene-d8 or THF-d8 and added to
a resealable NMR tube. The NMR tube was degassed and filled
with 700 mm N2. The NMR tube was then momentarily opened
to air, which introduced an additional 60 mm air into the tube,
resulting in ∼6 mol % O2 vs the metal complex (total P ) 760
mm ) 748 mm N2 + 12 mm O2; Vtube ) 2.0 mL; T ) 300 K;
mmol O2 ) PV/RT ) (12/760 atm)(0.002 L)/[(0.082 L‚atm/mol‚
K)(300 K)] × 1000 ) 0.0013 mmol O2 ) 6.5% based on Ni).
The NMR tube was heated at the appropriate temperature (see
Scheme 1) in a constant-temperature oil bath thermostatically
controlled ((0.5 °C). The NMR tube was removed at various
intervals and cooled to room temperature, and a 1H NMR
spectrum was recorded. The catalytic turnover number was
calculated from the ratio of phenanthrene product to metal
species. Initial rates were used to calculate the turnover rate.
Toluene-d8 and THF-d8 work equally well with virtually no
difference in turnover rate.
P h en a n t h r en e Ca t a lyt ic R a t e a s a F u n ct ion of O2
Con cen tr a tion . Six resealable NMR tubes containing (dippe)-
Ni(PhCtCPh) (0.030 M), biphenylene (0.30 M), and diphenyl-
acetylene (0.30 M) were prepared with dioxane as an internal
standard in THF-d8. Each tube was charged with O2 (via air)
as described above: 6, 13, 20.5, 28 40, and 52 mol % based on
1. The tubes were thoroughly mixed for several minutes and
filtered through a glass plug. A 31P{1H} spectrum of each
sample displayed 1, bis(diisopropylphosphino)ethane dioxide
(δ, 52.0), bis(diisopropylphosphino)ethane monoxide (δ 51.2,
δ 4.661, (s, 4 H), 3.289, (s, 6 H), 2.093 (sept, CHMe2, J H-H
)
7.1 Hz, 4 H), 1.582 (d, PCH2CH2P, J H-P ) 8.6 Hz, 4 H), 1.117
(1:22:1 quartet, CHMe2, J H-H ) J P-H ) 7.1 Hz, 12 H), 1.036
(q, CHMe2, J H-H ) J P-H ) 7.1 Hz, 12 H). 31P{1H} NMR (THF-
d8): δ 82.32 (s). 13C{1H} NMR (THF-d8): δ 129.9 (t, tC-CH2,
J P-C ) 19.5 Hz), 72.2 (t, J P-C ) 9.7 Hz), 57.2 (s), 26.2 (t, J P-C
) 10.4 Hz), 22.7 (t, J P-C ) 19.3 Hz), 20.3 (t, J P-C ) 4.1 Hz),
19.2 (s).
P r ep a r a tion of (d ip p e)Ni(CF 3CtCCF 3), 5. (dippe)Ni-
(COD) (250 mg, 0.58 mmol) was dissolved in a 50 mL round-
J
) 35 Hz and 9.8, J ) 35 Hz, THF-d8), and a pair of
resonances with A2B2 patterns at δ 52.5 and 45.5. A simulation

4048 Organometallics, Vol. 18, No. 20, 1999
Edelbach et al.
Ta ble 1. Selected X-r a y Da ta for 1, 2, a n d 3
of the resonances of the latter compound is consistent with
the dimer depicted in Figure 5 (see Supporting Information).
Each tube was then heated in an NMR probe at 60 °C. The
crystal
parameters
1
2
3
1
reactions were monitored by H NMR spectroscopy. A plot of
chemical formula
fw
cryst syst
space group, Z
a, Å
C28H42P2Ni C18H38P2Ni C20H38P2O4Ni
concentration of 9,10-diphenylphenanthrene vs time was
generated using only initial reaction times (10-12 min). The
slope was calculated for each reaction. The results are depicted
in Figure 4.
499.27
monoclinic
P21/n
375.13
monoclinic
P21
463.15
monoclinic
P21/n
9.15130(10) 7.83800(10) 10.7338(2)
27.18890(10) 13.6572(3) 9.62210(10)
11.11780(10) 10.24810(10) 23.1508(2)
b, Å
c, Å
Gen er a l P r oced u r e for Ca ta lytic F or m a tion of F lu o-
r en on e. A solution containing (dippe)Ni(CO)2 (0.056 M) and
biphenylene (0.28 M) was prepared in THF-d8 and added to a
resealable NMR tube. The NMR tube was charged with 1 atm
of CO. The NMR tube was heated at 100 °C in a constant-
temperature oil bath thermostatically controlled ((0.5 °C). The
NMR tube was removed at various intervals and cooled to
â, deg
104.8630(10) 104.78
94.8240(10)
2382.58(5)
-80
vol, Å3
2673.71(4)
-80
1.240
1060.73(3)
-80
1.175
6673
4230
4072
200
temp, °C
F
calc, g cm-3
1.291
no. of data collected 16186
no. of unique data 6280
no. of observed data 5392
14048
5545
4484
1
room temperature, and a H NMR spectrum was recorded. The
no. of params varied 280
254
catalytic turnover number was calculated from the ratio of
fluorenone product to metal species with hexamethylbenzene
as internal standard. Initial rates were used to calculate the
turnover rate.
2
R1(Fo), wR2(Fo
(I > 2σ(I))
)
0.0442,
0.0787
0.0559,
0.0827
1.160
0.0243,
0.0328,
0.0718
0.0477,
0.0768
1.039
0.0585
0.0259,
0.0594
1.038
R1(Fo), wR2(Fo2),
all data
Gen er a l P r oced u r e for Ca ta lytic F or m a tion of F lu o-
r en e Im in e. A solution containing (dippe)Ni(CN-2,6-xylyl)2
(0.038 M), biphenylene (0.22 M), and 2,6-xylylisocyanide was
prepared in THF-d8 and added to a resealable NMR tube. The
NMR tube was heated at 107 °C in a constant-temperature
oil bath thermostatically controlled ((0.5 °C). The NMR tube
was removed at various intervals and cooled to room temper-
ature, and a 1H NMR spectrum was recorded. The catalytic
turnover number was calculated from the ratio of product to
metal species. Initial rates were used to calculate the turnover
rate.
goodness of fit
als34 of R1 ) 4.42% (I > 2σ(I)), wR2 ) 7.87% (I > 2σ(I)). Table
1 gives selected data collection parameters. In ORTEP dia-
grams, ellipsoids are shown at the 30% level and hydrogen
atoms have been omitted for clarity.
X-r a y Str u ctu r a l Deter m in a tion of 2. A pale yellow
crystal of approximate dimensions 0.38 × 0.26 × 0.22 mm3
was cut from a cluster, mounted under Paratone-8277, and
immediately placed in a cold nitrogen stream at -80 °C on
the X-ray diffractometer. The X-ray intensity data were
collected as for 1 above. Frames were integrated with the
Siemens SAINT program to yield a total of 6673 reflections,
of which 4230 were independent (Rint ) 1.47%, Rsig ) 2.84%)
and 4072 were above 2σ(I). Laue symmetry revealed a mono-
clinic crystal system, and the final unit cell parameters (at
-80 °C) were determined from the least-squares refinement
of three-dimensional centroids of 5901 reflections. Data were
corrected for absorption with the SADABS program. The space
group was assigned as P21 and the structure was solved by
using direct methods and refined employing full-matrix least-
squares on F2 (Siemens, SHELXTL, version 5.04). For a Z
value of 2, there is one molecule in the asymmetric unit. All
of the non-H atoms were refined anisotropically, and the
hydrogen atoms were included in idealized positions giving a
data:parameter ratio of approximately 20:1. The structure
refined to a goodness of fit (GOF) of 1.038 and final residuals
of R1 ) 2.43% (I > 2σ(I)), wR2 ) 5.85% (I > 2σ(I)). Table 1
gives selected data collection parameters.
X-r a y Str u ctu r a l Deter m in a tion of 3. A yellow fragment
of approximate dimensions 0.24 × 0.28 × 0.40 mm3 was cut
from a large cluster of crystals, mounted under Paratone-8277
on a glass fiber, and immediately placed in a cold nitrogen
stream at -80 °C on the X-ray diffractometer. The X-ray
intensity data were collected as for 1 above. Frames were
integrated to a maximum 2θ angle of 56.6° with the Siemens
SAINT program to yield a total of 14048 reflections, of which
5545 were independent (Rint ) 2.94%, Rsig ) 4.03%) and 4484
were above 2σ(I). Laue symmetry revealed a monoclinic crystal
system, and the final unit cell parameters (at -80 °C) were
determined from the least-squares refinement of three-
dimensional centroids of 8192 reflections. Data were corrected
for absorption with the SADABS program. The space group
was assigned as P21/n, and the structure was solved by using
direct methods and refined employing full-matrix least-squares
on F2 (Siemens, SHELXTL, version 5.04). For a Z value of 4,
there is one molecule in the asymmetric unit. All of the atoms
were refined anisotropically, and hydrogen atoms were in-
X-r a y Str u ctu r a l Deter m in a tion of 1. A colorless needle
of approximate dimensions 0.28 × 0.22 × 0.18 mm3 was cut
from a large cluster of crystals and mounted under Paratone-
8277 on a glass fiber and immediately placed in 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 30 s/frame using a detector-
to-crystal distance of 5.09 cm (maximum 2θ angle of 56.6°).
The total data collection time was approximately 12 h. Frames
were integrated to a maximum 2θ angle of 56.6° with the
Siemens SAINT program to yield a total of 16186 reflections,
of which 6280 were independent (Rint ) 2.72%, Rsig ) 3.74%)29
and 5392 were above 2σ(I). Laue symmetry revealed a mono-
clinic crystal system, and the final unit cell parameters (at
-80 °C) were determined from the least-squares refinement
of three-dimensional centroids of 8192 reflections.30 Data were
corrected for absorption with the SADABS31 program. The
space group was assigned as P21/n, and the structure was
solved by using direct methods and refined employing full-
matrix least-squares on F2 (Siemens, SHELXTL,32 version
5.04). For a Z value of 4, there is one molecule in the
asymmetric unit. All of the atoms were refined anisotropically,
and hydrogen atoms were included in idealized positions giving
a data:parameter ratio of approximately 20:1. The structure
refined to a goodness of fit (GOF)33 of 1.160 and final residu-
2
(29) Rint ) ∑|Fo - Fo2(mean)|/∑[Fo2]; Rsigma ) ∑[σ(Fo2)]/∑[Fo2].
(30) 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.
(31) The SADABS program is based on the method of Blessing;
see: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.
(32) SHELXTL: Structure Analysis Program, version 5.04; Siemens
Industrial Automation Inc.: Madison, WI, 1995.
(33) GOF ) [∑[w(Fo - Fc2)2]/(n - p)]1/2, where n and p denote the
(34) R1 ) (∑||Fo | - |Fc||)/∑|Fo|; wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]1/2
,
2
2
number of data and parameters.
where w ) 1/[σ2(Fo2) + (aP)2 + bP] and P ) [(max;0,Fo2) + 2Fc2]/3.

Catalytic C-C Bond Activation
Organometallics, Vol. 18, No. 20, 1999 4049
cluded in idealized positions giving a data:parameter ratio of
approximately >15:1. The structure refined to a goodness of
fit (GOF) of 1.039 and final residuals of R1 ) 3.28% (I > 2σ(I)),
wR2 ) 7.18% (I > 2σ(I)).
Su p p or tin g Ma ter ia l Ava ila ble includes a simulation of
the 31P NMR spectrum for the intermediate shown in Figure
5 and tables of crystallographic data including atomic coordi-
nates, thermal parameters, and bond distances and angles.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Ack n ow led gm en t is made to the U.S. Department
of Energy (Grant FG02-86ER13569) for their support
of this work.
OM990387I