Regioselectivities of the insertion reactions of unsymmetrical alkynes with the nickelacycles [NiBr(C6H4CH2PPh2-2)(L)] (L = tertiary phosphine)

Article abstract of DOI:10.1021/om0101083

The regioselectivities of the insertions of various alkynes into the Ni-Ph bond of the five-membered nickelacycles [NiBr(C₆H₄CH₂PPh₂)(PR₃)] (PR₃ = PEt₃ (2a), PPhBz₂ (2

Full text of DOI:10.1021/om0101083

2864
Organometallics 2001, 20, 2864-2877
Regioselectivities of th e In ser tion Rea ction s of
Un sym m etr ica l Alk yn es w ith th e Nick ela cycles
[NiBr (C6H4CH2P P h 2-2)(L)] (L ) Ter tia r y P h osp h in e)
Alison J . Edwards,†,‡ Stuart A. Macgregor,§ A. David Rae,†,‡ Eric Wenger,*,† and
Anthony C. Willis†,‡
Research School of Chemistry, Australian National University, Canberra,
A.C.T. 0200, Australia, and Department of Chemistry, Heriot-Watt University,
Riccarton, Edinburgh EH14 4AS, U.K.
Received February 12, 2001
The regioselectivities of the insertions of various alkynes into the Ni-Ph bond of the five-
membered nickelacycles [NiBr(C6H4CH2PPh2)(PR3)] (PR3 ) PEt3 (2a ), PPhBz2 (2b)) have
been determined by multinuclear NMR spectroscopic studies of the products. In some cases,
the resulting seven-membered nickelacycles have also been structurally characterized by
X-ray analyses. The results show that electronic factors are very important in controlling
the regioselectivity of these insertion reactions. For example, insertion of MeCtCCO2Me
into 2b forms mainly [NiBr{o-C(Me)dC(CO2Me)C6H4CH2PPh2}(PPhBz2)] (4b), whereas
CF3CtCCO2Et gives exclusively the alternative regioisomer (10b). On the basis of these
observations, a model based on frontier orbital interactions is proposed. The alkynylphos-
phines RCtCPPh2 insert regiospecifically into the Ni-C bonds of 2a ,b to give initially
complexes that contain three-membered phosphanickelacycles formed by coordination of the
PPh2 group to the adjacent metal. These species are unstable and subsequently dimerize
(R ) CO2Me) or undergo rearrangement (R ) Me, Ph) to give a bicyclic nickelacycle in which
the metal is part of both a six- and a four-membered ring.
In tr od u ction
reported.15-20 Surprisingly, no detailed investigations
into the factors governing the regioselectivity of these
reactions have been published. Both electronic and
steric arguments have been used to explain the substi-
tution patterns of the products, but neither could be
applied satisfactorily in all cases. For example, two
investigations of the insertions of tBuCtCMe into Ni-C
and Pd-C bonds have concluded that these reactions
were under steric control,17,21 whereas the regioselec-
tivities of the reactions of ester-activated alkynes with
nickelaindenes are better accounted for by invoking
electronic factors.22 Our interest in the reactions of
The insertions of alkynes and alkenes into metal-
carbon bonds are very important reactions in organo-
metallic chemistry and organic synthesis, and good
regioselectivity or even complete regiocontrol in these
reactions is essential. Complexes of group 10 metals are
of particular importance in this context.1-3 In particular,
the reactions of nickelacycles and palladacycles give
entries into synthetically important poly- or heterocyclic
molecules.4-14 Several mechanistic studies of the inser-
tions of alkynes into Ni-C and Pd-C bonds have been
* To whom correspondence should be addressed. E-mail: wenger@
rsc.anu.edu.au.
(10) Buchwald, S. L.; Broene, R. D. In Comprehensive Organome-
tallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Hegedus,
L. S., Eds.; Pergamon: Oxford, U.K., 1995; Vol. 12, p 771.
(11) Bennett, M. A.; Wenger, E. Chem. Ber./ Recl. 1997, 130, 1029.
(12) Spencer, J .; Pfeffer, M. In Advances in Metal-Organic Chem-
istry; Liebeskind, L. S., Ed.; J AI: Stamford, CT, 1998; Vol. 6, p 104.
(13) J ones, W. M.; Klosin, J . Adv. Organomet. Chem. 1998, 42, 147.
(14) Ca´mpora, J .; Palma, P.; Carmona, E. Coord. Chem. Rev. 1999,
193-195, 207.
(15) Martinez, M.; Muller, G.; Panyella, D.; Rocamora, M.; Solans,
X.; Font-Bard´ıa, M. Organometallics 1995, 14, 5552.
(16) Samsel, E. G.; Norton, J . R. J . Am. Chem. Soc. 1984, 106, 5505.
(17) Huggins, J . M.; Bergman, R. G. J . Am. Chem. Soc. 1981, 103,
3002.
† Australian National University.
‡ Single-Crystal X-ray Diffraction Unit.
§ Heriot-Watt University.
(1) Smith, A. K. In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Puddephatt, R. J ., Eds.;
Elsevier: Oxford, U.K., 1995; Vol. 9, p 29.
(2) Canty, A. J . In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A, Wilkinson, G., Puddephatt, R. J ., Eds.;
Elsevier: Oxford, U.K., 1995; Vol. 9, p 225.
(3) Anderson, G. K. In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Puddephatt, R. J ., Eds.;
Elsevier: Oxford, U.K., 1995; Vol. 9, p 431.
(4) J olly, P. W. In Comprehensive Organometallic Chemistry; Wilkin-
son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, U.K.,
1982; Vol. 8, p 649.
(18) de Vaal, P.; Dedieu, A. J . Organomet. Chem. 1994, 478, 121.
(19) Ryabov, A. D.; van Eldik, R.; Le Borgne, G.; Pfeffer, M.
Organometallics 1993, 12, 1386.
(5) Ryabov, A. D. Synthesis 1985, 233.
(6) Lindner, E. Adv. Heterocycl. Chem. 1986, 39, 237.
(7) Bennett, M. A. Pure Appl. Chem. 1989, 61, 1695.
(8) Pfeffer, M. Recl. Trav. Chim. Pays-Bas 1990, 109, 567.
(9) Ca´mpora, J .; Paneque, M.; Poveda, M. L.; Carmona, E. Synlett
1994, 465.
(20) Ferstl, W.; Sakodinskaya, I. K.; Beydoun-Sutter, N.; Le Borgne,
G.; Pfeffer, M.; Ryabov, A. D. Organometallics 1997, 16, 411.
(21) Spencer, J .; Pfeffer, M.; Kyritsakas, N.; Fischer, J . Organome-
tallics 1995, 14, 2214.
(22) Bennett, M. A.; Wenger, E. Organometallics 1995, 14, 1267.
10.1021/om0101083 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 06/01/2001

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2865
Sch em e 1
Sch em e 2
alkynes with five-membered nickelacycles started with
the discovery that benzyne-nickel complexes can insert
2 equiv of alkynes to give substituted naphthalenes with
various regiospecificities. For example, tert-butylacet-
ylene leads to a 1,3-disubstituted species, whereas
methyl 2-butynoate gives a symmetrical species with
the carboxylate groups in the 2,3-positions.22-24 These
reactions are believed to take place via initial formation
of a five-membered nickelacyclopentene complex. Sub-
sequent insertion into either the Ni-vinyl or -aryl bond
is assumed to yield a seven-membered species, which
cannot be identified because of fast reductive elimina-
tion to the naphthalene product. Therefore, nickela-
cycles more suited to a systematic study of their
reactions with alkynes were required.
Five-membered phosphanickelacycles [NiCl(o-C6H4-
CH2PPh2)(PR3)] (PR3 ) PMe2Ph, PEt3, PBz3; Bz )
benzyl, CH2Ph) have been reported to react with alkynes,
leading to stable seven-membered metallacycles by
insertions into the Ni-aryl bond (Scheme 1).25 One
reaction with an unsymmetrical alkyne, PhCtCCO2Et,
was carried out, leading to the product 1, in which the
phenyl substituent is located next to the metal; the
structure of 1 was confirmed by X-ray analysis.
Therefore, we have chosen to carry out a systematic
study of the insertion reactions of a large variety of
alkynes using the analogous five-membered nickela-
nickelacycle in the region δH 3.0-4.0. In the case of the
reactions carried out with 2b, four additional multiplets
for the inequivalent benzylic protons of the auxiliary bis-
(benzyl)phenylphosphine ligand (PBz2Ph) are also present
in the same region. The triethylphosphine CH2 groups
for the products arising from 2a are also inequivalent
and form two A3BCX multiplets in the region δH 1.60-
1.80.
cycles [NiBr(C6H4CH2PPh2-2)(PR3)] (PR3 ) PEt3 (2a ),
PPhBz2 (2b)), and the results are presented here. This
investigation has been carried out primarily by use of
multinuclear NMR spectroscopy to identify the different
regioisomers. Several key products have been isolated
and their structures confirmed by X-ray analyses. The
observed regioselectivities will be discussed.
The seven-membered nickelacycles resulting from the
reactions of 2b are generally more stable than their PEt3
analogues, but even so, only products bearing carbox-
ylate substituents could be isolated as solids. The more
electron-rich products arising from insertions of alkyl-
or aryl-substituted alkynes or bearing PEt3 as the
auxiliary ligand are very labile and decompose readily.
Hence, multinuclear NMR spectroscopy proved to be the
most convenient technique to investigate these reac-
tions.
Exp er im en ta l Resu lts
The nickelacycles 2a and 2b were obtained as stable
yellow solids after oxidative addition of o-BrC6H4CH2-
PPh2 with [Ni(cod)2] in the presence of 1 equiv of the
corresponding tertiary phosphine, as described by
Muller.25 These complexes are planar and show only one
signal for the benzylic CH2 group of the metallacycle in
1
the H NMR spectrum. Treatment of these complexes
with various unsymmetrical alkynes resulted in the
formation of seven-membered nickelacycles, the geom-
etries of which were determined spectroscopically. The
results are summarized in Scheme 2. The metallacycles
are nonplanar and show two complicated 1H NMR
signals for the inequivalent benzylic protons of the
(a ) In ser tion s of Ester -Activa ted Alk yn es. To
assess the validity of the NMR techniques we planned
to use, the insertion of ethyl phenylpropynoate was
carried out with the five-membered phosphanickelacycle
[NiBr(o-C6H4CH2PPh2}(PEt3)] (2a ). The reaction was
clean and formed only the product [NiBr{o-C(Ph)d
(23) Bennett, M. A.; Wenger, E. Organometallics 1996, 15, 5536.
(24) Bennett, M. A.; Cobley, C. J .; Rae, A. D.; Wenger, E.; Willis, A.
C. Organometallics 2000, 19, 1522.
(25) Muller, G.; Panyella, D.; Rocamora, M.; Sales, J .; Font-Bardia,
M.; Solans, X. J . Chem. Soc., Dalton Trans. 1993, 2959.
C(CO2Me)C6H4CH2PPh2}(PEt3)] (3a), in which the phen-
yl group on the vinyl moiety is adjacent to the metal,
as expected from the earlier study described above.25

2866 Organometallics, Vol. 20, No. 13, 2001
Edwards et al.
clean magnetization transfer to the methyl substituent
when the CH3 group of PEt3 (δH 1.03) is irradiated.
Reaction of methyl 2-butynoate with the analogous
complex 2b, bearing the more bulky tertiary phosphine
PBz2Ph, gives predominantly the same regioisomer (4b),
but minor amounts of a second product (5b) are also
observed. The ratio of 4b/5b is solvent-dependent and
varies from 7:1 for a reaction carried out in thf/C6D6 to
3.2:1 in CD2Cl2. The NMR data for 4b are similar to
those of 4a , and in this case, the structure assigned to
this compound from the NMR data was confirmed by
X-ray analysis (see below). The minor compound (5b)
2
has similar 31P NMR data but shows a J (PP) value for
the coupling between the trans phosphine ligands ca.
50 Hz larger than that in 4b (334 and 282 Hz, respec-
tively). These data are comparable with those for the
main insertion product obtained with HCtCCO2Me (see
below); hence, 5b is assumed to be the second insertion
isomer in which the carboxylate is adjacent to nickel,
F igu r e 1. Principal magnetization transfers observed
during the GOESY experiments with 3a .
The 31P NMR spectrum consists of two doublets, one at
δP 6.9 for the PEt3 ligand and one at δP 27.5 for the
PPh2 group, with a coupling constant of 301.7 Hz that
2
is characteristic of a trans J (PP) coupling. The 20 ppm
viz. [NiBr{o-C(CO2Me)dC(Me)C6H4CH2PPh2}(PPhBz2)].
In the case of HCtCCO2Me, the insertion reactions
with both 2a and 2b give the two possible regioisomers,
but the more abundant products always have the larger
2J (PP) values. The reaction of methyl propynoate with
2a is almost regiospecific, while the reaction with 2b
gives a 9:1 ratio of the two regioisomers. The 13C NMR
spectra of the main insertion products (6a and 6b,
respectively) show the vinyl carbon atoms bonded to
nickel, easily identified by their characteristic two-bond
coupling constants with the phosphorus atoms of ca. 39
and 30 Hz, at δC 149.05 and 149.25, these carbon atoms
being much more shielded than those of 3a , 4a , or 4b.
These R-carbon atoms are quaternary, as shown by APT
experiments; hence, they bear the carboxylate groups.
The two vinylic CH carbon atoms are also readily
upfield shift observed for the cyclometalated PPh2
group, when compared to that of 2a (δP 44.5), is
characteristic of an increase of the metallacycle from
five- to seven-membered as a result of the insertion of
the alkyne into the Ni-C bond.26 The regioselectivity
of the insertion can be deduced from the 13C NMR data
of the product, especially those of the carbon atoms of
the vinyl group resulting from the insertion of the
alkyne. The marked deshielding of the R-vinyl carbon
that is bonded to nickel (δC 173.91) can best be explained
by delocalization of the double bond on to an ester group
in the â position. Furthermore, the larger C-P coupling
constants observed for the quaternary carbon of the
phenyl substituent (13 and 6.6 Hz) when compared with
those of the carboxylate group (5.2 and 2.5 Hz) are a
good indication that the former is closer to the phos-
phine ligands and, hence, to the metal. The structure
assigned to 3a could be confirmed by use of the GOESY
pulse sequence, which clearly showed that the PEt3
ligand is in close contact with the phenyl group. Irradia-
tion of the CH2 group of PEt3 (δH 1.50-1.75) shows
magnetization transfer to the adjacent CH3 groups (δH
0.70) and to the ortho protons of the phenyl substituents
at δH 7.63. Some transfer is also observed to the proton
H6 (δH 7.87) (Figure 1), due to the boat-shaped confor-
mation of the seven-membered ring as shown for
structurally characterized examples below. These NMR
experiments have been successful in assigning the
structure of 3a ; hence, they have been applied to
determine the geometries of the insertion products for
all the alkynes discussed below.
3
located at ca. δC 142 with J (CP) values of 6.3 and 5.8
Hz, respectively. The proximity of the ester groups to
the auxiliary phosphine ligands was also confirmed by
GOESY experiments. Therefore, the major isomers in
this series of reactions can be formulated as [NiBr{o-
C(CO2Me)dC(H)C6H4CH2PPh2}(PR3)] (PR3 ) PEt3 (6a ),
PPhBz2 (6b)) (Scheme 2), and the structure of 6b has
been confirmed by X-ray structure analysis (see below).
The minor products are likely to be the alternative
regioisomers [NiBr{o-C(H)dC(CO2Me)C6H4CH2PPh2}-
(PPhBz2
)] (PR3 ) PEt3 (7a ), PPhBz2 (7b)).
t
Similar reaction of HCtCCO2 Bu with 2a gives a
mixture of products with NMR data almost identical
with those of 6a and 7a . The main difference between
this reaction and the regiospecific one of HCtCCO2Me
is the increased proportion of the isomer having the
vinylic carboxylate in the â-position (9a ); thus, the ratio
The reaction of methyl 2-butynoate with 2a is regio-
specific and occurs in the same sense as that discussed
above, hence the insertion product is formulated as
t
[NiBr{o-C(Me)dC(CO2Me)C6H4CH2PPh2}(PEt3)] (4a ).
The 13C NMR spectrum of 4a shows a coupling of 7.6
Hz between one of the phosphorus atoms and the carbon
of the vinylic methyl group, characteristic of a 3J (CP)
coupling, and the quaternary carbon bonded to nickel
is even more deshielded than in 3a (δC 197.00). GOESY
experiments confirm that the methyl substituent in 4a
is indeed close to the PEt3 ligand, as shown by the very
between [NiBr{o-C(CO2 Bu)dC(H)C6H4CH2PPh2}(PEt3)]
t
(8a) and [NiBr{o-C(H)dC(CO2 Bu)C6H4CH2PPh2}(PEt3)]
(9a ) is 5:1, as measured by 31P NMR spectroscopy.
The insertion reaction of CF3CtCCO2Et with 2b gives
only one regioisomer. The 31P NMR spectrum shows two
doublets of quartets at δP 9.2 for PBz2Ph and δP 32.2
2
for PPh2 with a large value of J (PP) (318.6 Hz) but a
rather small P-F coupling constant between the re-
spective phosphorus atoms and the CF3 group (4.7 and
(26) Garrou, P. E. Chem. Rev. 1981, 81, 229.

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2867
5.2 Hz). The 13C NMR resonance of the quaternary
carbon atom adjacent to nickel also shows a small
coupling with the fluorine atoms of CF3 (2.5 Hz). This
value is characteristic of a three-bond C-F coupling;27,28
hence, this carbon does not bear the CF3 group. There-
Sch em e 3
fore, the proposed structure for this product is [NiBr-
{o-C(CO2Et)dC(CF3)C6H4CH2PPh2}(PPhBz2)] (10b ).
Crystallization led to partial decomposition, and crystals
of only mediocre quality were obtained, but the geom-
etry of 10b could nevertheless be confirmed by X-ray
diffraction analysis.
(b ) In ser t ion s of Alk yl- or Ar yl-Su b st it u t ed
Alk yn es. The reactions of 2a and 2b with alkyl- and
aryl-substituted alkynes were carried out exclusively in
situ, as the resulting seven-membered nickelacycles
decompose readily in solution. The insertion of HCt
CtBu into the Ni-C bond of 2a gave only one regio-
isomer, having doublets in the 31P NMR spectrum at
δP 0.7 and 19.8. These signals are more shielded than
those of the insertion products described above, but
surprisingly the vinylic R-carbon is highly deshielded
and its 13C NMR signal is found at δC 173.88. This
carbon is quaternary, which allows the insertion product
to be tentatively formulated as [NiBr{o-C(tBu)dC(H)-
C6H4CH2PPh2}(PEt3)] (11a ) (Scheme 2). A similar reac-
tion carried out with HCtCSiMe3 led mainly to decom-
position, but traces of an insertion compound (13a ) could
be observed by 31P NMR spectroscopy. The data, espe-
cially the 2J (PP) value, are similar to those of 11a ;
hence, 13a is believed to be an insertion product having
the same geometry as 11a .
Reaction of HCtCPh with 2a gave only one major
insertion product (12a ) that decomposed readily. The
product of the analogous reaction carried out with 2b
was slightly less labile, and its 13C NMR spectrum could
be recorded. The main feature of the spectrum of this
product (12b) is a resonance located at δC 160.40, which
belongs to a quaternary vinylic R-carbon atom. As the
31P NMR data for 12a and 12b are very similar, the
structure proposed for the products of both insertions
of the cyclometalated PPh2 group, as demonstrated by
the irradiation of the ortho hydrogens of the latter group
at δH 8.16 (see Experimental Section). These NMR
experiments allow the unambiguous characterization of
14b as being [NiBr{o-C(Ph)dC(Et)C6H4CH2PPh2}-
(PPhBz2)], the minor product 15b being tentatively
assigned to the alternative regioisomer [NiBr{o-C(Et)d
C(Ph)C6H4CH2PPh2}(PPhBz2)].
(c) In ser tion s of Alk yn ylp h osp h in es. The results
of these experiments are summarized in Scheme 3.
Reaction of MeO2CCtCPPh2 with 2a gave one major
insertion product (>90% by 31P NMR spectroscopy)
having three sets of 31P NMR signals: two doublets of
doublets at δP 13.8 and 28.6 due to PEt3 and the
cyclometalated PPh2 groups, respectively, and a doublet
of doublets at δP -101.5. The latter phosphine is trans
is [NiBr{o-C(Ph)dC(H)C6H4CH2PPh2}(PR3)] (PR3 ) PEt3
(12a ), PBz2Ph (12b)).
The insertion reaction of EtCtCPh with 2b gave a
11:1 mixture of two labile regioisomers. The phosphorus
atoms of the major isomer (14b) are more shielded and
have a 2J (PP) value larger than those of the minor
isomer (15b). The 13C NMR signal for the quaternary
R-carbon of 14b is found at δC 148.75, but it is not
possible to tell whether it bears the phenyl or the ethyl
group. Investigation of 14b by GOESY NMR experi-
ments shows a large number of magnetization transfers,
which suggest that this complex is very crowded. For
example, irradiation of the signal at δH 2.87 correspond-
ing to a benzylic proton of the PBz2Ph ligand shows
magnetization transfer to several protons (aromatic and
benzylic) in the phosphine ligand, but also to the two
ortho protons of the vinylic phenyl group (δH 6.92). This
group is also in close contact with the axial phenyl ring
2
to the CH2PPh2 group, as shown by the J (PP) value of
239 Hz. This very shielded signal can be assigned to a
three-membered phosphanickelacycle with the carbon
atom being sp2-hybridized. Five-coordinate nickel com-
plexes possessing such fragments have recently been
obtained by protonation of η2-coordinated alkynylphos-
phines,29 and their 31P NMR spectra show similarly
shielded signals. An insertion product with such a
geometry can only be formed if the PPh2 group of the
incoming alkynylphosphine is located next to the metal.
The presence of the carboxylate group on the â-carbon
atom of the vinyl group, with respect to the nickel, is
also suggested by the strongly deshielded quaternary
carbon atom bonded to the metal (multiplet at δC
(27) Be´gue´, J .-P.; Bonnet-Delpon, D.; Mesureur, D.; Oure´vitch, M.
Magn. Reson. Chem. 1991, 29, 675.
(28) Matsubara, K.; Oba, A.; Usui, Y. Magn. Reson. Chem. 1998,
36, 761.
(29) Bennett, M. A.; Castro, J .; Edwards, A. J .; Kopp, M. R.; Wenger,
E.; Willis, A. C. Organometallics 2001, 20, 980.

2868 Organometallics, Vol. 20, No. 13, 2001
Edwards et al.
170.00-171.10). Therefore, the structure proposed for
this product is the five-coordinated nickelacycle [NiBr{o-
C(PPh2)dC(CO2Me)C6H4CH2PPh2}(PEt3)] (16) (Scheme
3). Over time, complex 16 loses PEt3 to give the dimeric
species [NiBr{µ-o-C(PPh2)dC(CO2Me)C6H4CH2PPh2}]2
(17). The latter complex has been identified by X-ray
analysis, confirming the assignment of the vinylic
substituents of the unstable species 16 (see below).
Treatment of 2a or 2b with MeCtCPPh2 very slowly
forms species similar to 16, viz. [NiBr{o-C(PPh2)dC-
(Me)C6H4CH2PPh2}(PR3)] (PR3 ) PEt3 (18a ), PBz2Ph
(18b)), with the characteristic 31P NMR signals of the
three-membered nickelacycles at δP -112.9 and -106.8,
respectively. However, the products are unstable; the
former decomposes readily, while the latter rearranges
with loss of PBz2Ph to give a new species having a 31P
NMR signal at δP -71.0 (19). The latter chemical shift
is indicative of a four-membered nickelacycle,26 but
further identification proved impossible due to decom-
position of the reaction mixture.
F igu r e 2. Molecular structure of 4b with selected atom
labeling. Thermal ellipsoids show 30% probability levels;
hydrogen atoms have been omitted for clarity.
Similar reaction of 2b with PhCtCPPh2 gives very
broad 31P NMR signals. After 48 h at 30 °C, the
complicated spectrum shows the mixture to contain
[NiBr{o-C(PPh2)dC(Ph)C6H4CH2PPh2}(PPhBz2)] (20)
(doublet at δP -101.0), a second species with a doublet
at δP -68.0 (21), and free PBz2Ph. The latter complex,
however, is more stable than its analogue 19 and could
be purified by passing the solution through a silica gel
column. Crystallization gave single crystals that were
suitable for X-ray analysis, and complex 21 could be
identified as being the bicyclic complex [NiBr{o-(PPh2)-
(Ph)CdCC6H4CH2PPh2}] (see below). This compound
contains a four-membered phosphanickelacycle, hence
the chemical shift at δP -68.0, whose formation can be
explained by elimination of PBz2Ph and cleavage of the
Ni-C bond, followed by a 1,2-shift of the phenyl sub-
stituent to the positively charged R-carbon atom of the
resulting zwitterionic intermediate (Scheme 3). By
analogy, the unstable compound 19 derived from MeCt
F igu r e 3. Molecular structure of 6b with selected atom
labeling. Thermal ellipsoids show 50% probability levels;
hydrogen atoms have been omitted for clarity, and carbon
atoms of the PBz2Ph and PPh2 groups have been drawn
as circles with small radii.
are shown, together with the atom labelings, in Figures
2-6, respectively; corresponding selected interatomic
distances and angles are listed in Tables 1-5.
CPPh2 is tentatively assigned as [NiBr{o-(PPh2)(Me)Cd
CC6H4CH2PPh2}]. As the formation of these rearrange-
The nickel atom in complex 4b is in a distorted-
square-planar environment, with atom C(8) being 0.8
Å from the best-fit plane defined by Ni-Br-P(1)-P(2).
The seven-membered ring is in a boat-shaped configu-
ration, with the plane of the aromatic ring C(1)-C(6)
being at right angles (95°) to the coordination plane of
the nickel. This geometry renders the two phenyl rings
of the cyclometalated PPh2 group and the two benzyl
groups of the auxiliary phosphine separately inequiva-
lent. This is in agreement with the four inequivalent
benzylic protons present in the 1H NMR spectrum of
4b and with the GOESY experiments which show close
contact between the aromatic proton bonded to C(6) and
the auxiliary phosphine ligand. Similar geometries have
been observed for other seven-membered nickelacycles
ment products was beyond the scope of the present
work, these reactions were not studied further.
(d ) Molecu la r Str u ctu r es of [NiBr {o-C(Me)dC-
(CO2Me)C6H4CH2P P h 2}(P P h Bz2)] (4b), [NiBr {o-C-
(CO2Me)dC(H)C6H4CH2P P h 2}(P P h Bz2)] (6b), [NiBr -
{o-C(CO2Me)dC(CF3)C6H4CH2P P h 2}(P P h Bz2)] (10b),
[NiBr {µ-o-C(P P h 2)dC(CO2Me)C6H4CH2P P h 2}]2 (17),
a n d [NiBr {o-(P P h 2)(P h )CdCC6H4CH 2P P h 2}] (21).
The molecular geometries of 4b, 6b, 10b, 17, and 21

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2869
F igu r e 4. Molecular structure of 10b with selected atom
labeling. Thermal ellipsoids show 50% probability levels;
hydrogen atoms have been omitted for clarity, and carbon
atoms of the PBz2Ph and PPh2 groups have been drawn
as circles with small radii.
F igu r e 6. Molecular structure of 21 with selected atom
labeling. Thermal ellipsoids show 30% probability levels;
hydrogen atoms have been drawn as circles with small
radii.
Ta ble 1. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 4b
Ni(1)-Br(1)
Ni(1)-P(2)
C(7)-C(8)
2.3670(6)
2.2300(9)
1.349(5)
Ni(1)-P(1)
Ni(1)-C(8)
C(8)-C(10)
2.1834(9)
1.880(3)
1.507(4)
P(1)-Ni(1)-P(2)
Ni(1)-C(8)-C(7)
C(7)-C(8)-C(10)
165.65(4)
128.1(2)
124.8(3)
Br(1)-Ni(1)-P(1)
Ni(1)-P(1)-C(9)
P(2)-Ni(1)-C(8)
95.59(3)
112.6(1)
91.2(1)
Ta ble 2. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 6b
Ni(1)-Br(1)
Ni(1)-P(2)
C(7)-C(8)
2.3544(3)
2.2167(5)
1.337(3)
Ni(1)-P(1)
Ni(1)-C(8)
C(8)-C(10)
2.1799(5)
1.9049(18)
1.495(3)
F igu r e 5. Molecular structure of 17 with selected atom
labeling. Asterisks indicate atoms generated by the crystal-
lographic 2-fold summetry. Thermal ellipsoids show 30%
probability levels; phenyl carbon atoms of the PPh2 groups,
except those directly attached to phosphorus (C(1), C(7),
C(24) and C(30)), and all hydrogen atoms have been
omitted for clarity.
P(1)-Ni(1)-P(2) 167.979(19) Br(1)-Ni(1)-P(1)
91.017(14)
Ni(1)-P(1)-C(9) 114.94(6)
Ni(1)-C(8)-C(7) 128.79(14)
C(7)-C(8)-C(10) 114.16(16)
P(2)-Ni(1)-C(8) 92.08(5)
Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 10b
Ni(1)-Br(1)
Ni(1)-P(2)
C(7)-C(8)
C(7)-C(13)
2.3505(15)
2.246(3)
1.340(13)
1.512(14)
Ni(1)-P(1)
Ni(1)-C(8)
C(8)-C(10)
2.201(3)
1.870(9)
1.483(14)
such as complex 1,25 [NiBr{C(CO2Me)dC(CO2Me)C10H6-
CF2CF2}(dcpe)] (22), produced by insertion of DMAD
P(1)-Ni(1)-P(2)
Ni(1)-C(8)-C(7)
166.64(11) Br(1)-Ni(1)-P(1)
93.82(8)
112.3(4)
91.2(3)
132.1(7)
Ni(1)-P(1)-C(9)
P(2)-Ni(1)-C(8)
into the Ni-naphthyl bond of [Ni(3-C10H6CF2CF2-2}-
(dcpe)],30 and the carboxylato complex resulting from
insertion of CO2 into the Ni-phenyl bond of the nick-
elacycle [Ni(o-C6H4CMe2CH2}(PMe3)2].31,32 The Ni-C(8)
distance (1.88 Å) is similar to those of other Ni-vinyl
bonds in such systems (1.92 Å in 22 or 1.90 Å in 1). The
distance C(7)-C(8) (1.35 Å) is typical of a CdC bond,
C(7)-C(8)-C(10) 121.0(8)
and its substitution pattern is identical with that
predicted by multinuclear spectroscopy: viz., the methyl
C(10) bonded to C(8) and the carboxylate carbon C(11)
bonded to C(7).
The structure of complex 6b is similar to that de-
scribed above and differs mainly in the position occupied
by the carboxylate, which is now bonded to C(8). The
nickel atom is in a distorted-square-planar environment,
with atoms C(8) and P(1) being -0.16 and 0.45 Å,
respectively, from the plane defined by Ni-Br-P(2).
The plane of the aromatic ring C(1)-C(6) has a dihedral
angle of 84° with the coordination plane of the nickel.
(30) Bennett, M. A.; Hockless, D. C. R.; Wenger, E. Organometallics
1995, 14, 2091.
(31) Carmona, E.; Palma, P.; Paneque, M.; Poveda, M. L.; Gutie´rrez-
Puebla, E.; Monge, A. J . Am. Chem. Soc. 1986, 108, 6424.
(32) Carmona, E.; Gutie´rrez-Puebla, E.; Mar´ın, J . M.; Monge, A.;
Paneque, M.; Poveda, M. L.; Ruiz, C. J . Am. Chem. Soc. 1989, 111,
2883.

2870 Organometallics, Vol. 20, No. 13, 2001
Edwards et al.
Ta ble 4. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 17
Ni(1)-P(1)
Ni(1)-Br(1)
C(20)-C(23)
2.232(5)
2.350(4)
1.354(23)
Ni(1)-P(2*)
Ni(1)-C(23)
P(2)-C(23)
2.238(5)
1.934(18)
1.796(18)
P(1)-Ni(1)-P(2*)
Br(1)-Ni(1)-P(2*)
Ni(1)-C(23)-P(2)
172.4(6)
89.1(2)
101.7(8)
Br(1)-Ni(1)-P(1)
88.9(2)
Br(1)-Ni(1)-C(23) 172.4(6)
Ni(1)-C(23)-C(20) 130.6(15)
C(19)-C(20)-C(23) 124.0(17) Ni(1*)-P(2)-C(23) 116.7(6)
Ta ble 5. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 21
Ni(1)-P(1)
Ni(1)-C(8)
C(2)-C(8)
C(9)-P(2)
2.186(2)
1.923(7)
1.475(9)
1.799(7)
Ni(1)-P(2)
Ni(1)-Br(1)
C(8)-C(9)
C(7)-P(1)
2.175(2)
2.356(2)
1.355(9)
1.836(8)
F igu r e 7. Graph of δ(CR) vs 2J (PP) for seven-membered
P(1)-Ni(1)-P(2)
P(1)-Ni(1)-C(8)
Ni(1)-C(8)-C(9)
C(8)-C(9)-C(10)
Ni(1)-C(8)-C(2)
150.4(1)
92.7(2)
108.6(6)
130.8(7)
124.1(5)
Br(1)-Ni(1)-C(8)
C(8)-Ni(1)-P(2)
C(8)-C(9)-P(2)
Ni(1)-P(2)-C(9)
Ni(1)-P(1)-C(7)
168.0(2)
70.1(2)
96.0(5)
84.4(3)
111.7(3)
nickelacycles [NiBr{o-CR(R1)dC(R2)C6H4CH2PPh2}(L)]. The
linear regressions gave y ) -1.019x + 483.6 for L ) PEt3
(complex 11a excluded) and y ) -0.970x + 464.3 for L )
PBz2Ph.
Ta ble 6. 13C NMR Ch em ica l Sh ifts (p p m ) of Ni-Cr
a n d Tr a n s 2J (P P ) Va lu es (Hz) for Seven -Mem ber ed
Nick ela cycles.
The molecular structure of 10b is of poorer quality
but shows clearly that the carboxylate group is attached
to C(8), whereas the CF3 group is bonded to C(7). The
nickel atom is in a slightly more distorted square planar
environment than that of 6b, the atoms C(8) and P(1)
being -0.55 and 0.55 Å, respectively, from the plane
defined by Ni-Br-P(2). The boat-shaped conformation
is similar to that of 4b and 6b, as shown by the dihedral
angle of 96° between the plane of the aromatic ring
C(1)-C(6) and the coordination plane of the nickel.
The molecular structure of the dimeric complex 17
shows a distorted-square-planar arrangement around
the nickel. Each metal is part of a bicyclic system. The
first cycle is the seven-membered ring resulting from
insertion of the alkynylphosphine MeO2CCtCPPh2 into
the Ni-C bond of 2a , in which the PPh2 group is
adjacent to nickel. The second cycle is a boat-shaped six-
membered ring connecting two nickelacycle units via
coordination of the PPh2 group of one metallacycle,
located on the vinyl carbons C(23) or C(23*), to the
nickel atom of the second one. The Ni-C distance (1.93
Å) is slightly longer than the ones in 4b, 6b, and 10b,
but all the other distances are unexceptional.
In the bicyclic complex 21, the coordination geometry
around the nickel is quite distorted from planarity, due
to the steric constraints imposed by the metal atom’s
being part of both a four- and a six-membered ring. The
four-membered nickelacycle Ni-P(2)-C(8)-C(9) is pla-
nar, but the phosphorus atom P(1) lies 0.85 Å above this
plane, while the bromine atom lies 0.17 Å below the
plane. The Ni-C(8) bond length (1.92 Å) is similar to
the values discussed above, while the Ni-P(2) distance
is in the normal range for a Ni-P bond. The double bond
between C(8) and C(9) is only slightly elongated (1.36
Å) when compared to a standard CdC bond and, as a
result, none of the angles in the four-membered ring is
close to 90°. The carbon atom C(9) is substituted by both
a phenyl group and a PPh2 group. The six-membered
nickelacycle has a strained boat-shaped conformation,
but all the bond lengths are in the usual ranges.
Ni-CR(R1)dCâ(R2)
entry
complex
R1
R2
δC(CR)
2J PP
1
2
3
4
5
6
7
8
9
3a
4a
6a
8a
11a
4b
10b
6b
12b
14b
Ph
Me
CO2Me
CO2 Bu
tBu
Me
CO2Et
CO2Me
Ph
CO2Et
CO2Me
H
H
173.91
197.00
149.05
150.80
173.88
195.77
165.24
149.25
160.40
148.75
301.7
274.6
321.8
324.8
319.4
282.1
318.6
328.6
318.6
321.2
t
H
CO2Me
CF3
H
H
Et
10
Ph
The clean regioselectivities and the relative stabilities
of the resulting seven-membered metallacycles in solu-
tion allowed the products to be identified by the use of
multinuclear NMR techniques, even though they often
could not be isolated. The magnetization transfers
observed during the GOESY experiments enable the
substitution patterns of the insertion products to be
determined, and the 13C NMR data of the vinylic carbon
atoms bonded to nickel give invaluable information
about the attached groups and about the electron
density of the vinyl moiety. For example, when an
electron-withdrawing substituent is located in the â-po-
sition with respect to the nickel atom, the R-carbon is
highly deshielded (see Table 6, entries 1, 2, and 6). The
only exception is complex 11a (entry 5), in which CR is
very deshielded even though this carbon is substituted
with a tert-butyl group and no electron-withdrawing
group is present. Possibly, this low-field chemical shift
arises from a distortion of the sp2 geometry of the
R-carbon caused by the steric interaction of the sub-
stituent with the auxiliary PEt3 ligand.
Analysis of the NMR data also showed that a linear
correlation exists between the 13C NMR chemical shift
of CR, i.e., its electron density, and the corresponding
2J (PP) value in the complex, as illustrated in Figure 7;
the more electron-deficient the R-carbon, the smaller the
coupling constant. The reasons for the influence of a
vinylic cis substituent on a trans coupling between two
phosphine groups are unclear. The lines obtained for
Discu ssion
Five-membered nickelacycles proved to be very useful
for the study of the insertions of unsymmetrical alkynes.

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2871
Sch em e 4
the PEt3 and PBz2Ph complexes are almost parallel,
with a horizontal shift of ca. 10 Hz between the two
slopes.
The regioselectivities for the alkyne insertions into
the Ni-C bonds of 2a and 2b are only slightly affected
by changing the auxiliary ligands from PEt3 to PBz2Ph
and are determined primarily by the nature of the
alkyne substituents.
The insertions of tert-butylacetylene, phenylacetylene,
and 1-phenyl-1-butyne formed unstable nickelacycles
having the tert-butyl or phenyl groups adjacent to nickel.
Such regioselectivities have precedents. These alkynes
have been shown to insert similarly into Ni-Me bonds,
and the proposed mechanism involves attack of the
methyl group onto the less-hindered carbon atom of the
alkyne.17,33
these insertion reactions are sensitive to both the size
of the carboxylate group and the size of the auxiliary
phosphine ligand is a good indication that both are
present in the coordination sphere of the metal during
the transition state, hence suggesting that the reaction
proceeds via a five-coordinate associative mechanism.
This observation is in agreement with kinetic studies
carried out with analogous phosphanickelacycles.15
The reaction of 2b with ethyl perfluoro-2-butynoate
gives exclusively the regioisomer in which the carbox-
ylate group is adjacent to the metal (10b). This is a
complete reversal of regioselectivity in comparison to
the insertions of the analogous nonfluorinated alkyne
leading to 4a and 4b. This observation again suggests
that electronic factors contribute greatly to the regio-
chemistry of alkyne insertions.
The regioselectivity determined in solution for the
insertion of ethyl phenylpropynoate with 2a is in
agreement with the solid-state structure of the product
reported for the analogous reaction with [NiCl(o-C6H4-
CH2PPh2)(PBz3)]:25 i.e., the phenyl group is adjacent to
the metal. In the case of the reactions of methyl
2-butynoate with 2a and 2b, the same substitution
pattern is preferred, as shown by both NMR techniques
and X-ray crystallography; replacement of the phenyl
group by a methyl group does not alter the regiochem-
istry of the reaction. Similar regioselectivities have been
observed with related benzyldimethylamine and ben-
zylthioether cyclopalladated dimers [PdCl{o-C6H4CH2-
One example of a possible electronic control has been
reported for the regioselective silastannation of alkynes
such as propyne and methoxyacetylene, catalyzed by a
palladium complex.39 This theoretical study showed that
the reaction takes place via insertion of the alkyne into
a Pd-Sn bond (Scheme 4) and that the main interaction
responsible for the reactivity is electron donation from
the HOMO of the palladium moiety (predominantly the
Pd d orbital in bonding combination with a Sn p orbital).
On the other hand, the regiochemistry, i.e., the orienta-
tion of the alkyne, is mainly dictated by an interaction
of the alkyne HOMO, polarized by the substituent, with
the LUMO of the palladium fragment, primarily located
on the Sn atom bonded to palladium.
Although our system differs in several respects from
that in Scheme 4, it nevertheless seemed of interest to
calculate the p-orbital contribution of each of the two
alkyne carbons to the occupied frontier π-orbital (the
one delocalized with the substituents). These HOMO
contributions were obtained by DFT calculations for
models of most alkynes used in this study. Very similar
p-orbital contributions were calculated when the geom-
etries of the alkynes were altered to mimic that likely
to be found in the transition state for insertion, i.e., with
an angle of 145° between the substituents and the C2
fragment instead of 180°.39,40 The results, listed in Table
7, suggest that all the experimental regioselectivities
can be accounted for by such a simple model. The major
contributions for PhCtCCO2H and MeCtCCO2H are
located on the carbon atom bearing the carboxylate
group (entries 5 and 6); hence, interaction with an
X)]2) (X ) NMe2, SR),34-37 but unfortunately, direct
comparison with phosphapalladacycles is not possible,
as the latter have been shown to be inert toward
insertions of alkynes under normal conditions.38 To
explain the regiochemistry observed for the reactions
of ethyl phenylpropynoate with these palladacycles,
possible hydrogen bonding between the carboxylate and
proton H6 of the metallacyclic phenyl group before
insertion into the Pd-C bond has been suggested.
The reactions of both methyl and tert-butyl propyno-
ates with 2a and 2b give preferentially the opposite
regioisomer; i.e., the major products bear the carboxyl-
ate groups adjacent to the metal and its bulky auxiliary
phosphine ligand, clearly a manifestation of electronic
control. However, as a minor effect, the steric interaction
between those two groups can influence the ratio
between the isomers. The reaction of methyl propynoate
with 2a , having PEt3 as auxiliary ligand, gives almost
regiospecifically 6a , whereas the same reaction carried
out with the PBz2Ph analogue 2b forms some of the
isomer having the carboxylate group adjacent to phenyl
(7b). Also, when the size of the ester group is increased,
e.g. by use of tert-butyl propynoate, the amount of the
second isomer increases correspondingly. The fact that
(33) Klein, H.-F.; Reitzel, L. Chem. Ber. 1988, 121, 1115.
(34) Maassarani, F.; Pfeffer, M.; Le Borgne, G. Organometallics
1987, 6, 2029.
(35) Maassarani, F.; Pfeffer, M.; Le Borgne, G. Organometallics
1987, 6, 2043.
(36) Maassarani, F.; Pfeffer, M.; Le Borgne, G. J . Chem. Soc., Chem.
Commun. 1987, 565.
(37) Spencer, J .; Pfeffer, M.; DeCian, A.; Fischer, J . J . Org. Chem.
1995, 60, 1005.
(38) (a) Lohner, P.; Pfeffer, M.; de Cian, A.; Fischer, J . C. R. Acad.
Sci. Paris, Ser. IIc 1998, 615. (b) Pfeffer, M. Personal communication.
(39) Hada, M.; Tanaka, Y.; Ito, M.; Murakami, M.; Amii, H.; Ito, Y.;
Nakatsuji, H. J . Am. Chem. Soc. 1994, 116, 8754.
(40) Macgregor, S. A.; Wenger, E. Manuscript in preparation.

2872 Organometallics, Vol. 20, No. 13, 2001
Edwards et al.
bromide in 2a ,b. More detailed DFT computational
studies investigating all these issues are underway.40
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments, unless otherwise
specified, were carried out under argon using standard Schlenk
techniques. All solvents were dried and degassed prior to use.
NMR spectra were recorded on a Varian XL-200E (1H at 200
MHz, 13C at 50.3 MHz, 31P at 81.0 MHz), a Varian Gemini
300BB or Varian Mercury 300 (1H at 300 MHz, 13C at 75.4
MHz, 31P at 121.4 MHz), or a Varian Inova-500 instrument
(1H at 500 MHz, 13C at 125.7 MHz). The chemical shifts (δ)
for 1H and 13C are given in ppm relative to residual signals of
the solvent and to external 85% H3PO4 for 31P. The spectra of
all nuclei (except 1H) were 1H-decoupled. The coupling con-
stants (J ) are given in Hz. The regioselectivities were inves-
tigated by use of the GOESY pulse sequence on the Inova-500
spectrometer. Infrared spectra were measured on a Perkin-
Elmer Spectrum One instrument. Mass spectra of the com-
plexes were obtained on a ZAB-SEQ4F spectrometer by the
fast-atom bombardment (FAB) technique or on a Micromass
Tof Spec 2E instrument by the MALDI/TOF technique.
The products of the insertion reactions (3-15) were gener-
ally unstable and have been studied primarily in situ by
multinuclear NMR spectroscopy (typically ca. 30-40 mg of
complex 2a or 2b in 0.5 mL of C6D6 or CD2Cl2). However, the
nickelacycles 4b, 6b, and 10b, having PBz2Ph as the auxiliary
ligand, could be crystallized and microanalytical data were
obtained in house. Single crystals for the rearrangement
products 17 and 21 were also isolated from NMR scale
reactions, but in these cases, not enough material could be
isolated to obtain microanalyses.
F igu r e 8.
Ta ble 7. Com p u ted Alk yn e Ca r bon p -Or bita l
Con tr ibu tion s (%) to th e Deloca lized Occu p ied
F r on tier Or bita ls of R1C1tC2R2
entry
R1
R2
C1
C2
1
2
3
4
5
6
7
8
H
H
H
Me
Ph
SiH3
Ph
48.0
29.1
43.4
27.5
25.9
41.1
29.5
38.2
40.3
12.6
41.0
16.5
8.5
32.9
32.5
38.6
Me
CO2H
CO2H
CO2H
CO2H
Ph
Me
CF3
H
empty orbital located on the carbon atom bonded to
nickel will lead to seven-membered complexes with the
carboxylate groups adjacent to the phenyl ring. An
illustration of such an interaction is given in Figure 8.
For CF3CtCCO2H a reversal of polarity in the alkyne
orbital is computed, consistent with the change in
regioselectivity observed experimentally. The regiose-
lectivities observed for the insertions of PhCtCH and
PhCtCMe can also be explained by similar electronic
arguments. The large p-orbital contributions for these
two alkynes are located on tCH and tCMe, respectively
(entries 2 and 4 of Table 7), hence leading to products
that have the phenyl groups adjacent to the metal.
In the case of the alkynylphosphines, the regioselec-
tivity can be best rationalized by coordination of the
phosphine group to the metal during the insertion step,
leading to formation of the bicyclic species 16, 18a ,b,
and 20 (Scheme 3). Because of the strain of the three-
membered nickelacycles, these complexes tend to rear-
range rapidly, either by internal migration of a substit-
uent as for 18b and 20 or by reaction with a neighboring
complex to form a dimer such as 17. As the primary
objective of this work was to determine the regioselec-
tivities of the insertion reactions, the mechanisms of
these subsequent rearrangements have not been inves-
tigated further.
Sta r tin g Ma ter ia ls. The (alkynyl)diphenylphosphines Ph2-
PCtCR (R ) Me, Ph, CO2Me)41-43 and the fluoro alkyne
CF3CtCCO2Et44 were prepared by following published proce-
dures. The complexes [NiBr(C6H4CH2PPh2)(PR3)] (PR3 ) PEt3
(2a ), PPhBz2 (2b)) were prepared by reaction of [Ni(cod)2]45
46
with o-BrC6H4CH2PPh2 in the presence of 1 equiv of the
corresponding tertiary phosphine, as described by Muller.25
2a . 1H NMR (300 MHz, CD2Cl2): δ 1.20 ([A3BCX] m, 9H,
J ) 5, CH3PEt), 1.79 ([A3BCX] m, 6H, J ) 5, CH2PEt), 3.86 (dd,
2
4
2H, J HP ) 6.0, J HP ) 1.3, CH2PPh2), 6.75 (t, 1H, J ) 4.7,
HPh), 6.82 (t, 1H, J ) 4.7, HPh), 6.97 (d, 1H, J ) 4.7, HPh), 7.15
(d, 1H, J ) 4.7, HPh), 7.35-7.60 (m, 6H, PPh2), 7.78 (t, 4H,
J ) 5.5, PPh2). 13C{1H} NMR (75.4 MHz, CD2Cl2): δ 8.42
(CH3), 16.19 (d, J CP ) 22.0, CH2), 43.35 (d, J CP ) 32.9, CH2),
123.59, 123.79, 124.20, 124.39 (CHPh), 128.35 (d, J CP ) 9.9,
CHPPh), 130.49 (CHPPh), 133.04 (d, J CP ) 9.9, CHPPh), 139.22
(d, J CP ) 14.3, CPPh), 147.60 (d, J CP ) 21.9, C2), 152.77 (app t,
J CP ) 24.1, C1-Ni). 31P{1H} NMR (81.0 MHz, C6D6): δ 11.8
Con clu sion
2
The insertions of alkynes into the Ni-C bonds of the
nickelacycles 2a and 2b seem to be governed mainly by
electronic factors, possibly a frontier orbital interaction
between the alkyne and the Ni-C bond. It is possible
to rationalize the observed regioselectivities on the basis
of a simple model in which the HOMO of the alkyne
overlaps with a LUMO located on the carbon atom of
the Ni-C bond. However, this model is purely empirical
and does not provide a precise description of the
interaction of the coordinated alkyne with the Ni-C
bond that would account for both reactivity and regio-
selectivity. Moreover, the regioselectivities established
for 2a ,b cannot be simply carried over to the benzyne-
nickel chemistry that prompted this work (see Introduc-
tion), as in the latter system methyl propynoate and
methyl 2-butynoate do not give products with opposite
regiochemistry.22-24 The reason for this difference may
be due to the presence of the electron-withdrawing
(d), 44.5 (d, J PP ) 343.2).
2b. 1H NMR (200 MHz, CD2Cl2): δ 3.32 (br t, 2H, J HP
)
11.5, CH2PPh2), 3.68 (br d, 4H, J HP ) 8.6, CH2Ph), 6.02 (d,
1H, J ) 7.5, HPh), 6.17 (t, 1H, J ) 7.5, HPh), 6.60 (t, 1H, J )
7.5, HPh), 6.82 (d, 1H, J ) 7.5, HPh), 7.15-7.60 (m, 6H, PPh2),
7.79 (t, 4H, J ) 8.3, PPh2). 13C{1H} NMR (75.4 MHz, CD2Cl2):
δ 32.16 (d, J CP ) 18.4, CH2Ph), 43.22 (d, J CP ) 32.5, CH2PPh2),
123.54, 123.76, 124.28, 124.35 (CHPh), 126.77 (CHPPh), 128.19
(d, J CP ) 9.1, CHPPh), 128.41 (CHPPh), 128.64 (d, J CP ) 9.5,
CHPPh), 130.17 (CHPPh), 130.47 (d, J CP ) 5.1, CHPPh), 130.80
(CHPPh), 132.36 (dd, J CP ) 36.4, 4.0, CPPh), 133.36 (d, J CP
)
(41) Charrier, C.; Chodkiewicz, W.; Cadiot, P. Bull. Soc. Chim. Fr.
1966, 1002.
(42) Carty, A. J .; Hota, N. K.; Ng, T. W.; Patel, H. A.; O’Connor, T.
J . Can. J . Chem. 1971, 49, 2706.
(43) Montlo, D.; Suades, J .; Dahan, F.; Mathieu, R. Organometallics
1990, 9, 2933.
(44) Hamper, B. C. Org. Synth. 1992, 70, 246.
(45) Schunn, R. A. Inorg. Synth. 1974, 15, 5.
(46) Abicht, H.-P.; Issleib, K. Z. Anorg. Allg. Chem. 1976, 422, 237.

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2873
9.4, CHPPh), 133.69 (d, J CP ) 10.0, CHPPh), 135.42 (d, J CP
)
merization products.47 Attempted purification by crystalliza-
tion led to decomposition.
3.1, CPBz), 140.47 (d, J CP ) 12.6, CPPh2), 147.46 (d, J CP ) 21.5,
C2), 151.80 (m, C1-Ni). 31P{1H} NMR (81.0 MHz, CD2Cl2): δ
6a . 1H NMR (300 MHz, CD2Cl2): δ 1.04 ([A3BCX] m, 9H,
2
J ) 7.5, CH3PEt), 1.63 ([A3BCX] m, 3H, J ) 7.5, CH2PEt), 1.75
17.1 (d), 47.6 (d, J PP ) 336.1). FAB-MS (nitrophenyl octyl
ether, C39H35BrNiP2): m/z 705 (42, MH+), 624 (100, MH+
-
2
([A3BCX] m, 3H, J ) 7.5, CH2PEt), 3.09 (app dt, 1H, J HH
)
4
2
2J HP ) 12.0, J HP ) 2.0, CH2PPh2), 3.51 (dd, 1H, J HH ) 12.0,
2J HP ) 10.0, CH2PPh2), 3.60 (s, 3H, OMe), 6.69 (br t, J ) 7,
Hvinyl), 6.86 (d, 1H, J ) 7.5, H3), 6.90-7.84 (m, 14H, Harom),
8.15-8.24 (m, 2H, HPPh). GOESY (500 MHz, CD2Cl2): irradia-
tion at δ 1.00-1.30 gave responses from δ 1.65, 1.77, 3.64, and
7.33. 13C{1H} NMR (50.2 MHz, C6D6): δ 7.97 (CH3), 14.98 (d,
J CP ) 23.1, CH2), 27.96 (CH3Bu), 33.44 (d, J CP ) 29.8, CH2),
80.25 (CBu), 126.07 (br s, CH), 126.80 (d, J CP ) 3, CH), 127.34
(d, J CP ) 9.4, CHPPh), 128.25-132.60 (m, CH + C), 133.25 (d,
J CP ) 8.8, CHPPh), 136.32 (d, J CP ) 37.1, CPPh), 141.64 (C),
141.97 (t, J CP ) 6.3, CHvinyl), 149.05 (dd, J CP ) 38.7, 30.7, Ni-
C), 167.53 (C), 170.46 (br s, CO). 31P{1H} NMR (81.0 MHz,
Br).
Rea ction of 2a w ith P h CtCCO2Et. In a typical experi-
ment, an NMR solution of 2a (36 mg, 0.068 mmol) in C6D6
(0.6 mL) was prepared under N2 at 5 °C, and ethyl phenyl-
propynoate (0.013 mL, 0.08 mmol) was added. 31P NMR
monitoring showed the reaction to be quantitative after 10 min
at room temperature, forming only one insertion product (3a ).
1H NMR (500 MHz, C6D6): δ 0.66 (t, 3H, J HH ) 7.0, CH3), 0.70
([A3BCX] m, 9H, J ) 7.5, CH3PEt), 1.62 ([A3BCX] m, 3H, J )
7.5, CH2PEt), 1.70 ([A3BCX] m, 3H, J ) 7.5, CH2PEt), 2.79 (app
2
2
4
dt, 1H, J HH ) J HP ) 12.0, J HP ) 2.0, CH2PPh2), 3.74-3.88
2
2
(m, 2H, OCH2), 4.02 (dd, 1H, J HH ) 12.0, J HP ) 9.0, CH2-
PPh2), 6.41 (d, 1H, J HH ) 7, H3), 6.73-7.10 (m, 10H), 7.18 (t,
1H, J HH ) 7, H4or5), 7.61 (dt, 2H, J ) 2, 10, HPPh), 7.63 (dd,
2H, J ) 8, 1.7, HPh), 7.87 (d, 1H, J HH ) 7, H6), 8.08 (t, 2H,
J ) 8, HPPh). GOESY (500 MHz, C6D6): irradiation at δ 3.74-
3.88 gave responses from δ 0.66 and 7.63; irradiation at δ 0.70
gave responses from δ 1.62, 1.70, 3.55, 7.61, 7.63, and 7.87;
irradiation at δ 1.50-1.75 gave responses from δ 0.70, 7.63,
and 7.87. 13C{1H} NMR (75.4 MHz, C6D6): δ 7.56 (CH3), 13.87
(CH3), 14.60 (d, J CP ) 23, CH2), 32.96 (d, J CP ) 26.3, CH2),
2
CD2Cl2): δ 9.3 (d), 30.9 (d, J PP ) 321.8).
7a . 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 13.9 (d), 33.8 (d,
2J PP ) 294.0).
Rea ction of 2a w ith HCtCCO2tBu . A solution of 2a (33
mg, 0.062 mmol) in CD2Cl2 (0.5 mL) was treated with HCt
CCO2 Bu (1 equiv). After 2 days, 31P NMR monitoring showed
t
a 5:1 mixture of the two insertion isomers 8a and 9a (>90%
total yield).
8a . 1H NMR (500 MHz, CD2Cl2): δ 0.90-1.80 (m, 15H,
t
t
4
60.15 (OCH2), 126.57, 126.79, 126.95, (CH), 127.18 (d, J CP
)
PEt3), 1.32 (s, 6H, Bu), 1.40 (s, 3H, Bu), 2.93 (dt, 1H, J HP
)
3.3, CH), 127.27 (br s, Cvinyl), 127.53 (d, J CP ) 7.7, CH), 128.80
(d, J CP ) 8.8, CHPPh), 129.87 (d, J CP ) 2.2, CHPPh), 130.04 (CH),
130.31 (d, J CP ) 2.2, CHPPh), 130.86 (d, J CP ) 4.4, CHPPh),
131.90 (dd, J CP ) 28.5, 4.4, CPPh), 132.73 (dd, J CP ) 13.0, 6.6,
CPh), 132.98 (d, J CP ) 7.7, CHPPh), 134.97 (d, J CP ) 9.9, CHPPh),
135.44 (d, J CP ) 42.6, CPPh), 142.23 (C1), 143.39 (d, J CP ) 3.3,
C2), 166.17 (dd, J CP ) 5.2, 2.5, CO), 173.91 (dd, J CP ) 30.7,
25.2, C-Ni). 31P{1H} NMR (81.0 MHz, C6D6): δ 6.9 (d), 27.5
2.0, J HH ) 2J HP ) 12.0, CH2PPh2), 3.54 (dd, 1H, J HH ) 12.0,
2J HP ) 9.2, CH2PPh2), 4.22-4.35 (m, 1H, Hvinyl), 6.62 (d, 1H,
J ) 7.3, H3), 7.08 (t, 1H, J ) 7.5, H4or5), 7.20-7.70 (m, 9H,
Harom), 8.05-8.20 (m, 3H, Harom). 13C{1H} NMR (50.2 MHz,
C6D6): δ 7.91 (CH3), 14.75 (d, J CP ) 24.2, CH2), 33.85 (d,
J CP ) 29.7, CH2), 51.20 (OMe), 126.50 (CH), 127.16 (br s, CH),
127.65 (d, J CP ) 8.8, CHPPh), 128.25-132.60 (m, CH + C),
132.99 (d, J CP ) 8.8, CHPPh), 134.19 (d, J CP ) 9.9, CHPPh),
136.00 (dd, J CP ) 36.5, 1.6, CPPh), 140.86 (t, J CP ) 6.3, CHvinyl),
141.50 (C), 150.80 (dd, J CP ) 38.3, 31.4, C-Ni), 167.53 (C),
168.69 (dd, J CP ) 4.4, 2, CO). 31P{1H} NMR (81.0 MHz, CD2-
2
2
2
(d, J PP ) 301.7).
Rea ction of 2a w ith MeCtCCO2Me. A suspension of 2a
(58 mg, 0.11 mmol) in ether (5 mL) was treated with methyl
2-butynoate (0.014 mL, 0.13 mmol) at 0 °C. After 1 h at room
temperature, the solvent was evaporated and the 31P NMR
spectrum of the yellow solid showed the reaction to be
quantitative, as only one phosphorus-containing compound
(4a ) was present. 1H NMR (500 MHz, CD2Cl2): δ 1.03 ([A3-
BCX] m, 9H, J ) 7.5, CH3PEt), 1.62 ([A3BCX] m, 3H, J ) 7.5,
2
Cl2): δ 7.7 (d), 29.4 (d, J PP ) 324.8).
9a . 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 13.9 (d), 34.0 (d,
2J PP ) 297.1).
Rea ction of 2a w ith HCtCP h . Treatment of a NMR
solution of 2a (29 mg, 0.054 mmol) in C6D6 (0.5 mL) with HCt
CPh (7.2 µL, 1.1 equiv) gave a dark red solution with only one
major insertion product (12a ), as shown by 31P NMR monitor-
ing. The reaction however was not very clean, and any
attempts to purify 12a led to decomposition.
CH2PEt), 1.80 ([A3BCX] m, 3H, J ) 7.5, CH2PEt), 2.44 (dd, 3H,
2
J HP ) 2.0, 1.5, CH3), 3.02 (app dt, 1H, J HH
)
2J HP ) 12.0,
4J HP ) 2.0, CH2PPh2), 3.48 (dd, 1H, J HH ) 12.0, J HP ) 9.0,
CH2PPh2), 3.55 (s, 3H, OMe), 6.73 (d, 1H, J ) 7.5, H3), 7.16 (t,
1H, J ) 7.5, H4or5), 7.26-7.31 (m, 6H, HPPh), 7.34 (t, 1H, J )
7.5, H5or4), 7.57-7.62 (m, 3H, H6+PPh), 8.11-8.15 (m, 2H, HPPh).
GOESY (500 MHz, CD2Cl2): irradiation at δ 1.03 gave
responses from δ 1.62, 1.80, 2.44, and 7.30; irradiation at δ
2.44 gave responses from δ 1.03, 1.62, 1.80, 3.55, and 8.13.
2
2
12a . 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 6.3 (d), 26.1 (d,
2J PP ) 308.5).
Rea ction of 2a w ith HCtCtBu . tert-Butylacetylene (11
µL, 0.09 mmol) was added to a solution of 2a (48 mg, 0.09
mmol) in CD2Cl2 (0.6 mL) at -78 °C. After 10 min at room
temperature, 31P NMR monitoring showed that 2a had com-
pletely reacted and that only one insertion product (11a ) was
present, together with traces of decomposition. Attempts to
isolate and purify the complex led to further decomposition.
13C{1H} NMR (75.4 MHz, C6D6): δ 8.11 (CH3), 14.83 (d, J CP
)
28.8, CH2), 24.80 (d, J CP ) 7.6, CH3), 33.18 (d, J CP ) 29.6, CH2),
50.41 (OMe), 126.15 (d, J CP ) 2.2, CH), 126.63 (br s, Cvinyl),
127.03 (d, J CP ) 3.3, CH), 127.62 (d, J CP ) 8.8, CHPPh), 128.99
(d, J CP ) 8.8, CHPPh), 129.79 (CH), 130.49 (CH), 130.59 (d,
J CP ) 2.2, CHPPh), 130.76 (d, J CP ) 4.4, CHPPh), 131.09 (dd,
J CP ) 31.0, 3.6, CPPh), 133.07 (d, J CP ) 9.9, CHPPh), 133.79 (C1),
134.05 (d, J CP ) 9.9, CHPPh), 135.60 (dd, J CP ) 37.3, 1.4, CPPh),
143.66 (d, J CP ) 1.9, C2), 162.22 (dd, J CP ) 5.2, 2.2, CO), 197.00
(dd, J CP ) 31.9, 25.2, C-Ni). 31P{1H} NMR (81.0 MHz, CD2-
Cl2): δ 9.4 (d), 29.0 (d, 2J PP ) 274.6). EI-MS (C30H37BrNiO2P2)
m/z 629 (1, M+ - H), 549 (3, M+ - Br), 471 (3), 373 (100,
C6H4(PPh2)(C(CO2Me)dCMe)).
Rea ction of 2a w ith HCtCCO2Me. Treatment of 2a (42
mg, 0.079 mmol) with 1.1 equiv of HCtCCO2Me at -78 °C in
CD2Cl2 (0.5 mL), followed by warming to room temperature,
gave 6a as the major insertion product, containing only a trace
(<8%) of the second isomer 7a , together with some cyclotri-
11a . 13C{1H} NMR (75.4 MHz, CD2Cl2): δ 8.34 (d, J CP
)
3.3, CH3), 15.96 (d, J CP ) 22.0, CH2), 30.09, 30.30, 32.26
(CH3tBu), 33.97 (d, J CP ) 31.8, CH2), 42.08 (CtBu), 51.20 (OMe),
123.70-132.80 (m, CH + C), 133.18 (t, J CP ) 7.7, CH), 133.76
(d, J CP ) 8.8, CHPPh), 136.79 (d, J CP ) 36.2, CPPh), 137.22 (d,
J CP ) 8.8, C), 138.72 (d, J CP ) 4.4, C), 143.44 (C), 170.75 (d,
J CP ) 26.4, C), 173.88 (dd, J CP ) 36.2, 24.1, C-Ni). 31P{1H}
2
NMR (81.0 MHz, CD2Cl2): δ 0.7 (d), 19.8 (d, J PP ) 319.4).
Rea ction of 2a w ith HCtCSiMe3. An NMR-scale reaction
of 2a (42 mg, 0.079 mmol) with 1 equiv of HCtCSiMe3 in CD2-
Cl2 (0.6 mL) gave only traces of an insertion product (13a ),
together with starting material and some decomposition.
Addition of an excess of alkyne led to complete decomposition.
(47) Diercks, R.; tom Dieck, H. Z. Naturforsch. 1984, B39, 180.

2874 Organometallics, Vol. 20, No. 13, 2001
Edwards et al.
13a . 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 4.5 (d), 26.1 (d,
2J PP ) 312).
5b. 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 9.5 (d), 32.4 (d,
2J PP ) 333.7).
Rea ction of 2b w ith F 3CCtCCO2Et. A suspension of 2b
(126 mg, 0.18 mmol) in ether (15 mL) was treated with F3-
CCtCCO2Et (26 µL, 0.18 mmol) at -78 °C. After the mixture
was warmed to room temperature, monitoring of the orange
solution by 31P NMR spectroscopy showed the reaction to be
quantitative. After filtration through Celite, the solvant was
removed in vacuo. Crystallization from chlorobenzene/pentane
was accompanied by decomposition and gave orange-red single
crystals of 10b (28 mg, 18%) of mediocre quality.
Rea ction of 2a w ith MeO2CCtCP P h 2. As described
above, a solution of 2a (34 mg, 0.064 mmol) in C6D6 (0.6 mL)
was treated with 1.2 equiv of MeO2CCtCPPh2. Monitoring by
31P NMR spectroscopy showed formation of one major com-
pound (16; >90%). Crystallization from CH2Cl2/pentane yielded
orange crystals of the rearrangement product 17, whose
dimeric structure was confirmed by X-ray analysis.
16. 1H NMR (300 MHz, CD2Cl2): δ 0.69 ([A3BCX] m, 9H,
J ) 7.5, CH3PEt), 1.37 ([A3BCX] m, 6H, J ) 7.5, CH2PEt), 3.35
(s, 3H, OMe), 3.41 (br d, 1H, J ) 8.5, CH2PPh2), 4.22-4.35
10b. IR (KBr): 3056 (m), 2996 (w), 1697 (s, νCO), 1597 (m),
1433 (s), 1301 (s, νCF), 1185 (vs), 1088 (vs), 696 (s), 523 (m),
4
(m, 1H, CH2PPh2), 6.17 (d, 1H, J ) 8, H3), 7.16 (dt, 1H, J )
1
510 (m), 492 (m), 477 (m) cm-1. H NMR (300 MHz, CD2Cl2):
1, 3J ) 8, H4or5), 7.00-7.90 (m, 22H, Harom). 13C{1H} NMR (75.4
MHz, C6D6): δ 8.31 (d, J CP ) 3.3, CH3), 17.90 (dd, J CP ) 19.8,
1.8, CH2), 39.38 (dd, J CP ) 22, 5.5, CH2), 51.41 (OMe),125.95,
126.29 (CH),128.1-130.4 (m, CH + C), 130.84 (CH), 131.17
(m, C), 1303.91 (d, J CP ) 12.1, CHPPh), 138.29 (dd, J CP ) 10,
4.3, C), 162.90 (dd, J CP ) 13.2, 3.3, CO), 170.0-171.10 (m,
C-Ni). 31P{1H} NMR (121.4 MHz, CD2Cl2): δ -101.5 (dd,
δ 0.83 (t, 3H, J ) 7.2, CH3), 3.04 (dt, 1H, J ) 13, 3, CH2P),
3.32 (dt, 1H, J ) 15.5, 3, CH2P), 3.48 (dd, 1H, J ) 15.5, 8,
CH2P), 3.66 (m, 1H, OCH2), 3.76 (dd, 1H, J ) 12, 8.8, CH2P),
3.81 (dd, 1H, J ) 15, 6, CH2P), 3.83 (m, 1H, OCH2), 3.86 (app
t, J ) 11.8, CH2P), 6.58 (d, 1H, J ) 7.8, HPh), 6.89 (d, 2H, J )
7.5, HPh), 7.03-7.67 (m, 24H, HPh), 8.18 (ddd, 2H, J ) 9.9, 8.4,
2.1, HPh). 13C{1H} NMR (75.4 MHz, CD2Cl2): δ 13.83 (CH3),
27.14 (d, J CP ) 23.7, CH2), 31.56 (d, J CP ) 18.1, CH2), 32.47
2
2J PP ) 239.0, 42.6, PPh2), 13.8 (dd, J PP ) 42.8, 27.9, PEt3),
2
28.6 (dd, J PP ) 239, 27.9, CH2PPh2).
(d, J CP ) 29.9, CH2PPh2), 60.73 (OCH2), 120.44 (qdd, J CF
)
17. 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 29.6 (br s), 19.3
277.2, J CP ) 5.1, 3.2, CF3), 126.60-134.90 (m, CH + C), 137.57
(C), 140.33 (br, C), 165.24 (ddq, J CP ) 32.5, 28.2, J CF ) 2.5,
C-Ni), 169.81 (d, J CP ) 3.8, CO). 31P{1H} NMR (81.0 MHz,
(br s).
Rea ction of 2a w ith MeCtCP P h 2. A solution of 2a (26
mg, 0.049 mmol) in CD2Cl2 (0.5 mL) was treated with 1.2 equiv
of MeCtCPPh2. After 16 h at room temperature, 31P NMR
2
4
2
C6D6): δ 9.2 (dq, J PP ) 318.6, J PF ) 4.7), 32.2 (dq, J PP
)
-
4
318.6, J PF ) 5.2). FAB-MS (nitrophenyl octyl ether, C45H40
BrF3NiO2P2) m/z 790 (18, MH+ - Br), 441 (100, C6H4(CH2-
PPh2){C(CF3)dC(CO2Et)}+). Anal. Calcd for C45H40BrF3NiO2-
P2: C, 62.10; H, 4.63. Found: C, 61.19; H, 4.72.
monitoring showed the main compound to be [NiBr{o-
C(PPh2)dC(Me)C6H4CH2PPh2}(PEt3)] (18a ). Attempted isola-
Rea ction of 2b w ith HCtCCO2Me. Methyl propynoate
(30 µL, 0.34 mmol) was added to a solution of 2b (239 mg,
0.34 mmol) in CH2Cl2 at -78 °C. The solution was warmed to
room temperature over 1 h. 31P NMR monitoring of the dark
red solution showed the reaction to be quantitative and that
the two isomers 6b and 7b were present in a 9:1 ratio. The
solvent was removed in vacuo. Crystallization from toluene/
pentane was accompanied by decomposition but afforded 31
mg (12%) of orange crystals of 6b suitable for X-ray analysis.
tion led to decomposition.
18a . 31P{1H} NMR (81.0 MHz, CD2Cl2): δ -112.9 (dd,
2J PP ) 238.0, 40.0, PPh2), 13.9 (dd, J PP ) 40.3, 20.5, PEt3),
2
2
29.7 (br d, J PP ) 234.1, CH2PPh2).
Rea ction of 2b w ith MeCtCCO2Me. A solution of 2b (30
mg) in CD2Cl2 (0.5 mL) was treated with 1.2 equiv of MeCt
CCO2Me at -78 °C. Monitoring by 31P NMR spectroscopy
showed the reaction to be quantitative after 5 min at room
temperature, giving a mixture of the two regioisomers 4b and
5b in a 3.2:1 ratio.
6b. IR (CH2Cl2): 3032 (m), 1688 (s, νCO), 1601 (m), 1495 (s),
1
1203 (vs), 828 (m), 499 (s), 470 (s) cm-1. H NMR (500 MHz,
CD2Cl2) δ 3.08-3.18 (m, 2H, PCH2), 3.28-3.42 (m, 2H, PCH2),
3.32 (s, 3H, OMe), 3.63 (br t, 1H, J ) 11, PCH2), 3.83 (dd, 1H,
J ) 13.7, 8, PCH2), 6.82 (d, 1H, J ) 7, HPh), 6.87 (d, 2H, J )
6.5, HPh), 7.11 (t, 2H, J ) 6.8, HPh), 7.12-7.66 (m, 23H), 8.24
(br t, 2H, J ) 7.2, HPh). 13C{1H} NMR (50.3 MHz, CD2Cl2): δ
27.57 (d, J CP ) 21.4, CH2), 30.75 (d, J CP ) 17.8, CH2), 34.53
(d, J CP ) 30.6, CH2PPh2), 51.34 (OMe), 126.58 (d, J CP ) 2, CH),
126.76 (d, J CP ) 2.3, CH), 126.88 (d, J CP ) 2, CH), 127.60-
132.00 (m, CH + C), 132.90 (d, J CP ) 9.5, CHPPh), 133.38 (d,
J CP ) 10.1, CHPPh), 134.11 (dd, J CP ) 9.6, 1.4, CHPPh), 134.60
(d, J CP ) 1.9, C), 134.84 (dd, 7.8, 1.6, C), 135.58 (d, J CP ) 1.5,
C), 135.90 (d, J CP ) 10.1, CPPh), 141.15 (br, C), 141.94 (t,
J CP ) 5.8, CHvinyl), 149.25 (dd, J CP ) 39.5, 29.5, C-Ni), 170.69
In another experiment in thf (0.5 mL)/C6D6 (0.1 mL), the
quantitative insertion gave a 7:1 mixture of 4b and 5b. Cooling
of the solution gave yellow X-ray-quality single crystals of 4b.
4b. IR (KBr): 3010 (w), 2922 (m), 1695 (vs, νCO), 1597 (m),
1536 (m), 1432 (s), 1268 (s), 1218 (vs), 1099 (s), 1030 (s), 779
(s), 739 (s), 693 (vs),509 (m), 493 (m) cm-1. 1H NMR (300 MHz,
CD2Cl2): δ 1.77 (br s, 3H, CH3), 2.99 (dd, 1H, J ) 15, 5.2,
CH2PBz), 3.02 (dt, 1H, J ) 1, 12.2, CH2P), 3.12 (ddd, 1H, J )
15.5, 13.1, 4.3, CH2PBz), 3.33 (dd, 1H, J ) 14.3, 5.5, CH2PBz),
3.47 (s, 3H, OMe), 3.55 (dd, 1H, J ) 12.1, 9.2, CH2P), 3.98
(dd, 1H, J ) 12.8, 9.2, CH2PBz), 6.71 (d, 2H, J ) 7, HPh), 6.81
(d, 1H, J ) 7.6, H3), 6.99 (t, 2H, J ) 8, HPh), 7.06-7.48 (m,
17H, HPh), 7.58-7.64 (m, 3H, H6+PPh), 7.94 (d, 2H, J ) 7.4,
HPh), 8.07-8.15 (m, 2H, HPPh). GOESY (500 MHz, CD2Cl2):
irradiation at δ 2.92-2.97 gave responses from δ 1.82 (s), 3.37
(dd), 6.76 (d), and 7.98 (d); irradiation at δ 1.80 gave responses
from δ 2.96 (dd), 7.99 (d), and 8.16 (m). 13C{1H} NMR (75.4
MHz, C6D6): δ 23.98 (d, J CP ) 6.5, CH3), 25.80 (d, J CP ) 22,
CH2), 29.61 (d, J CP ) 15.3, CH2), 33.35 (d, J CP ) 30.7, CH2-
PPh2), 50.92 (OMe), 126.64 (br s, CH), 127.29 (br s, CH),
127.60-131.50 (m, CH + C), 132.73 (C), 132.96 (d, J CP ) 9.9,
CHPPh), 133.30 (d, J CP ) 9.9, CHPPh), 133.69 (d, J CP ) 9.9,
CHPPh), 133.93-134.81 (m, C), 135.60 (dd, J CP ) 37.3, 1.4,
CPPh), 143.43 (dd, J CP ) 2.8, 1.6, C), 162.22 (dd, J CP ) 5.5, 2.3,
CO), 195.77 (dd, J CP ) 31.3, 24.5, C-Ni). 31P{1H} NMR (81.0
(dd, J CP ) 5.5, 3.0, CO). 31P{1H} NMR (81.0 MHz, CD2Cl2): δ
2
5.4 (d), 31.8 (d, J PP ) 328.6). Anal. Calcd for C43H39
-
BrNiO2P2: C, 65.51; H, 4.99; P, 7.86. Found: C, 65.50; H, 5.02;
P, 7.70.
7b. 31P{1H} NMR (81.0 MHz, CD2Cl2): δ 10.3 (d), 36.6 (d,
2J PP ) 300.3).
Rea ction of 2b w ith HCtCP h . Treatment of 2b (56 mg,
0.08 mmol) with HCtCPh (9 µL, 0.08 mmol) in CD2Cl2 (0.6
mL) led to the formation of one insertion product (12b), as
shown by 31P NMR spectroscopy. This very sensitive complex
decomposed overnight.
12b. 1H NMR (300, CD2Cl2): δ 2.85-3.05 (m, 2H, CH2),
3.10-3.20 (m, 1H, CH2), 3.30-3.45 (m, 2H, CH2), 3.85-3.405
(m, 1H, CH2), 6.53 (br, 1H, Harom), 6.84 (br, 2H, Harom), 6.90-
7.70 (m, 28H, Harom), 7.76 (br, 2H, Harom), 8.10 (br, 2H, PPh2).
2
MHz, CD2Cl2): δ 10.6 (d), 31.7 (d, J PP ) 282.1). Anal. Calcd
for C44H41BrNiO2P2‚1/2CH2Cl2: C, 63.27; H, 5.01. Found: C,
63.47; H, 5.30.

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2875
13C{1H} NMR (125.7 MHz, CD2Cl2): δ 26.22 (d, J CP ) 19.7,
CH2), 28.85 (d, J CP ) 16.9, CH2), 34.21 (d, J CP ) 30.3, CH2-
PPh2), 125.90-127.60 (m, CH), 127.94 (d, J CP ) 23, CPPh),
128.2-130.90 (m, CH), 131.05 (t, J CP ) 5.5, CHvinyl), 131.30
(d, J CP ) 4.6, CH), 131.69 (d, J CP ) 21.5, CPPh) 131.93 (m, C),
132.43 (d, J CP ) 9.2, CHPPh), 133.84 (t, J CP ) 20, C), 134.66 (d,
J CP ) 10.5, CH), 134.86 (d, J CP ) 8.6, C), 142.79 (C), 145.79
(C), 160.40 (dd, J CP ) 35.7, 25.2, C-Ni). 31P{1H} NMR (81.0
having a doublet at δP -101.0 (2J PP ) 220 ( 1 Hz), [NiBr{o-
(PPh2)(Ph)CdCC6H4CH2PPh2}] (21), with a doublet at δP
-68.0, and 2b. After 48 h at 30 °C, 2b had completely reacted
to give mainly 21 and free PBz2Ph. After filtration through
SiO2 (ether), orange crystals of 21 suitable for X-ray analysis
were obtained.
2
21. 1H NMR (300 MHz, CD2Cl2): δ 3.53 (dd, 2H, J ) 9.1,
2.2, CH2P), 6.85 (br t, 1H, J ) 7, HPh), 6.95-7.25 (m, 8H, Harom),
7.35-7.55 (m, 12H, Harom), 7.80-7.88 (m, 4H, HPPh), 7.92-8.00
(m, 4H, HPPh). 13C{1H} NMR (75.4 MHz, C6D6): δ 32.09 (d,
J CP ) 24.7, CH2PPh2), 126.80-134.00 (m, CH + C), 135.29 (m,
C), 136.67 (C), 138.15 (d, J CP ) 14.2, C), 142.30 (d, J CP ) 41.7,
MHz, CD2Cl2): δ 2.3 (d), 28.7 (d, J PP ) 318.6).
Rea ction of 2b w ith EtCtCP h . A solution of 2b (60 mg,
0.085 mmol) in CD2Cl2 (0.7 mL) was treated with EtCtCPh
(13 µL, 1.1 equiv) to give two insertion products, [NiBr{o-
C(Ph)dC(Et)C6H4CH2PPh2}(PPhBz2)] (14b ) and [NiBr{o-
C), 148.23 (dd, J CP ) 44, 5, C). 31P{1H} NMR (81.0 MHz, CD2-
C(Et)dC(Ph)C6H4CH2PPh2}(PPhBz2)] (15b), in a 11:1 ratio, as
shown by 31P NMR spectroscopy (estimated yield >80%). This
sensitive mixture of complexes decomposed within 24 h at
room temperature.
2
Cl2): δ -67.7 (d), 32.0 (d, J PP ) 308.7). EI-MS (C39H31
-
BrNiP2): m/z 619 (6, M+ - Br), 439 (17), 307 (33), 286 (100),
261 (28).
X-r a y Cr ysta llogr a p h y. Crystal data and details of data
collection, data processing, structure analysis, and structure
refinement are given in Table 8. All crystals were mounted
on a quartz fiber, the data for 4b‚0.5C6H6 being recorded at
-80 °C, those for 6b and 10b at -73 °C, and those for the
other two (17‚CH2Cl2 and 21) at 23 °C. The structures of 4b‚
0.5C6H6, 6b, and 21 were solved by direct methods (SIR92)48
and those of 17‚CH2Cl2 and 10b by Patterson methods
(PATTY);49 all were expanded with use of Fourier techniques
(DIRDIF94).50 The diffractions of 6b and 10b were measured
by a 95 mm CCD camera, and the intensities of the reflections
were processed by use of the computer programs Denzo and
Scalepak.51 Besides the molecular species 4b, the crystal-
lographic asymmetric unit also contained 0.5 molecule of
benzene. The non-hydrogen atoms were refined anisotropically
by full-matrix least squares. Hydrogen atoms were included
at geometrically determined positions (C-H ) 0.95 Å) and
periodically recalculated, but they were not refined. The
maximum and minimum peaks in the final difference Fourier
map were 0.95 and -0.79 e/Å3, respectively.
The crystal of 6b was of very good quality, and all non-
hydrogen atoms were refined anisotropically by full-matrix
least squares, whereas the hydrogen atoms were refined
isotropically. The maximum and minimum peaks in the final
difference Fourier map were 0.36 and -0.72 e/Å3, respectively.
The crystal of 10b was of poor quality and diffracted weakly.
However, a highly restrained refinement yielded a clearly
defined molecular structure. The geometries of the phenyl
rings such as bond lengths and angles and planarity were
imposed. All non-hydrogen atoms were refined anisotropically
by full-matrix least squares. Hydrogen atoms were included
at calculated positions (C-H ) 1.00 Å) and left riding with
their carbon of attachment. The maximum and minimum
peaks in the final difference Fourier map were 1.46 and -0.95
e/Å3, respectively.
1
14b. H NMR (500 MHz, CD2Cl2): δ 0.70 (t, J ) 7.3, CH3),
2.36 (app sept, 1H, J ) 7.3, CH2Et), 2.65 (app sept, 1H, J )
7.3, CH2Et), 2.87 (dt, 1H, J ) 14.8, 5.5, CH2PBz), 3.08 (t, 1H,
J ) 12.3, CH2P), 3.13 (dd, 1H, J ) 15, 4.5, CH2PBz), 3.66 (dd,
1H, J ) 15, 6.5, CH2PBz), 3.86 (dd, 1H, J ) 12, 9, CH2P), 4.18
(dd, 1H, J ) 13, 7.5, CH2PBz), 6.61 (d, 1H, J ) 7.5, H6), 6.85 (d,
2H, J ) 7, HPPh), 6.92 (d, 2H, J ) 9, HPh), 7.00 (t, 2H, J ) 8,
HPBz), 7.02 (t, 2H, J ) 7, HPBz), 7.07-7.25 (m, 11H, Harom), 7.28
(d, 2H, J ) 5.5, HPBz), 7.31-7.50 (m, 5H, Harom), 7.55 (d, 2H,
J ) 4, HPBz), 7.59 (t, 2H, J ) 7, HPPh ), 7.65 (t, 1H, J ) 7, H4or5),
2
8.16 (t, 2H, J ) 8.2, HPPh ). GOESY (500 MHz, CD2Cl2):
2
irradiation at δ 2.87 gave responses from δ 4.18, 6.84, 6.92,
7.00, and 7.28; irradiation at δ 3.13 gave responses from δ 6.84,
6.92, 7.00, and 7.55; irradiation at δ 8.16 gave responses from
δ 3.08, 3.86, 6.92, 7.08, and 7.59. 13C{1H} NMR (125.7 MHz,
CD2Cl2): δ 13.43 (CH3), 25.59 (dd, J CP ) 18.1, 2.8, CH2), 29.19
(dd, J CP ) 12.1, 1.7, CH2), 29.27 (d, J CP ) 2.5, CH2Et), 33.43
(d, J CP ) 29.7, CH2PPh2), 125.99-131.50 (m, CH), 132.14 (dd,
J CP ) 27.5, 6.6, CPPh), 132.56 (d, J CP ) 9.9, CHPPh), 132.80 (CH),
132.89 (d, J CP ) 2.2, CH), 132.95 (C), 133.64 (C), 134.08 (C),
134.36 (d, J CP ) 10.4, CHPPh), 134.59 (C), 135.03 (dd, J CP
)
10.4, 2.2, CPPh), 140.14 (br d, J CP ) 5, C), 140.26 (d, J CP ) 3.8,
C), 145.62 (C), 148.75 (dd, J CP ) 33, 21.7, C-Ni). 31P{1H} NMR
2
(81.0 MHz, CD2Cl2): δ 3.4 (d), 26.3 (d, J PP ) 321.2). MALDI/
TOF MS (C49H45BrNiP2): m/z 754 (M+ - Br).
15b. 31P{1H} NMR (81.0 MHz, CD2Cl2): (9.8 (d), 29.1 (d,
2J PP ) 308.6).
Rea ction of 2b w ith MeCtCP P h 2. A solution of 2b (28
mg, 0.04 mmol) in C6D6 (0.6 mL) was treated with 1.2 equiv.
MeCtCPPh2. After 1 h at room temperature, 31P NMR
monitoring showed mainly broad signals of starting material
and two doublets: a sharp one at δP 29.1 and a broad one at
δP -106.8 (J PP ) 225 ( 1 Hz) due to formation of [NiBr{o-
C(PPh2)dC(Me)C6H4CH2PPh2}(PPhBz2)] (18b). After 60 h at
In the crystal structure of 17‚CH2Cl2, the molecular species
was a dimer containing a 2-fold rotation axis coincident with
a crystallographic 2-fold axis. A molecule of CH2Cl2 was also
30 °C, no 2b remained. The spectrum showed broad signals
for 18b and for free PBz2Ph (δP -12.0) and appearance of a
(48) Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(49) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
PATTY and DIRDIF Program System; Technical Report of the Crystal-
lographic Laboratory; University of Nijmegen, Nijmegen, The Neth-
erlands, 1992.
broad doublet at δP -71 ( 1 due to [NiBr{o-(PPh2)(Me)Cd
CC6H4CH2PPh2}] (19) (2J PP ) 331 ( 1 Hz). Heating at 80 °C
for 18 h led to a ca. 1:1 mixture of 18b and 19, while further
heating led to decomposition.
(50) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J . M. M. The DIRDIF-94 Program
System; Technical Report of the Crystallographic Laboratory; Univer-
sity of Nijmegen, Nijmegen, The Netherlands, 1994.
(51) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter,
C. W., J r.; Sweet, R. M., Ed.; Academic Press: New York, 1997; Vol.
276, p 307.
Rea ction of 2b w ith P h CtCP P h 2. Reaction of 2b (62 mg,
0.088 mmol) with 1 equiv of PhCtCPPh2 in CD2Cl2 (0.5 mL)
gave very broad 31P NMR signals. After 1 h at room temper-
ature, the complicated spectrum showed at least three com-
pounds: [NiBr{o-C(PPh2)dC(Ph)C6H4CH2PPh2}(PPhBz2)] (20),

2876 Organometallics, Vol. 20, No. 13, 2001
Edwards et al.
Ta ble 8. Cr ysta l a n d Str u ctu r e Refin em en t Da ta for Com p ou n d s 4b, 6b, 10b, 17, a n d 21
4b
6b
10b
17
21
(a) Crystal Data
chem formula
C
47H44BrNiO2P2‚
0.5C6H6
C43H39BrNiO2P2
C45H40BrF3NiO2P2
(C35H29BrNiO2P2)2‚
CH2Cl2
C39H31BrNiP2
fw
841.41
788.35
870.37
1449.26
700.23
cryst syst
unit cell dimens
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
triclinic
monoclinic
monoclinic
monoclinic
monoclinic
9.776(3)
14.482(4)
15.326(4)
76.36(2)
75.75(2)
77.03(2)
2012(1)
P1h (No. 2)
1.389
2
17.6495(2)
10.56920(10)
20.3919(2)
27.914(2)
15.4458(10)
18.9929(12)
18.610(4)
15.700(2)
22.175(3)
10.870(3)
22.707(4)
13.162(3)
99.0906(5)
99.506(4)
105.55(1)
96.32(2)
3756.15(7)
P21/a (No. 14)
1.394
8076.4(8)
C2/c (No. 15)
1.432
6242(2)
C2/c (No. 15)
1.542
3229(1)
P21/n (No. 14)
1.440
space group
Dc (g cm-3
Z
)
4
8
4
4
F(000)
870
1624
3567
2952
1432
color, habit
yellow, block
0.34 × 0.19 × 0.12
29.03 (Cu KR)
orange, prism
0.15 × 0.18 × 0.08
1.70 (Mo KR)
orange-red, block
0.19 × 0.20 × 0.17
1.60 (Mo KR)
orange, needle
0.30 × 0.03 × 0.01
44.08 (Cu KR)
orange, wedge
0.30 × 0.15 × 0.10
34.67 (Cu KR)
cryst dimens (mm)
µ(cm-1
)
(b) Data Collection and Processing
diffractometer
X-radiation
Rigaku AFC6R
Cu KR (graphite
monochrom)
120.0
(-10,-15,0) to
(10,16,17)
Nonius KappaCCD
Mo KR (graphite
monochrom)
54.96
(-22,-13,-26) to
(22,13,26)
Nonius KappaCCD
Mo KR (graphite
monochrom)
46.9
(-31,-17,-21) to
(31,17,19)
Rigaku AFC6R
Cu KR (graphite
monochrom)
120.0
(0,0,-24) to
(20,17,24)
Rigaku AFC6R
Cu KR (graphite
monochrom)
120.2
(-12,0,0)
(12,25,14)
2θmax (deg)
data collected (h,k,l)
no. of rflns
total
6219
83 662
17 820
5022
5193
unique (Rint (%))
obsd
abs cor (transmissn
factors)
5960 (5.1)
5330 (I > 2σ(I))
analytical
(0.5322-0.7155)
none
8598 (5.0)
7062 (I > 3σ(I))
integration
(0.774-0.877)
none
5779 (8.5)
4643 (I > 3σ(I))
integration
(0.724-0.814)
none
4813 (21.0 for 0kl)
1706 (I > 3σ(I))
azimuthal scans
(0.81-0.96)
1.8
4801 (12.1)
2527 (I > 2σ(I))
analytical
(0.60-0.78)
1.59
decay (%)
(c) Structure Analysis and Refinement
structure soln
direct methods
(SIR92)
direct methods
(SIR92)
Patterson methods
(PATTY)
Patterson methods
(PATTY)
direct methods
(SIR92)
refinement
full-matrix least squares
no. of params
R(obsd data) (%)
Rw(obsd data) (%)
478
4.5
6.2
481
4.3
3.7
488
12.4
9.8
166
9.4
11.8
388
4.9
5.4
present but was 4-fold disordered. The crystal data, obtained
from a very thin needle, were of limited quality, and only 1706
out of 4813 independent measured reflections were considered
reliable. As a consequence, the comprehensive constrained
least-squares refinement software RAELS9652 was used, and
the use of constraints53-55 enabled 166 variables to adequately
describe the refinement of the 47 non-H atom sites. The Ni
and Br atoms were refined as anisotropic atoms, but refinable
rigid-body thermal parametrizations were used for all the
other atoms.53 Hydrogen atoms were included at calculated
positions (C-H ) 0.96 Å) after each refinement cycle. The
maximum and minimum peaks in the final difference Fourier
map were 1.39 and -0.97 e/Å3, respectively, located close to
the Ni or Br atoms.
The neutral atom scattering factors were taken from ref 59
for structure 17 and from ref 60 for all other structures. ∆f ′
and ∆f ′′ values and mass attenuation coefficients were taken
from ref 55 for 17 and from ref 61 for all other structures.
Com p u ta tion a l Deta ils. Density functional calculations
used the Amsterdam Density Functional program ADF1999.62
All atoms were described by a double-ú plus polarization STO
basis set with the frozen-core approximation being employed
for the 1s electrons of C, N, O, and F atoms and up to the 2p
electrons of Si and P. Geometry optimizations included the
gradient corrections of Becke63 and Perdew64 as well as the
(56) TEXSAN: Single-Crystal Structure Analysis Software, Version
1.8; Molecular Structure Corp., 3200 Research Forest Drive, The
Woodlands, TX 77381, 1997.
The non-hydrogen atoms of complex 21 were refined aniso-
tropically by full-matrix least squares. Hydrogen atoms were
included at geometrically determined positions (C-H ) 0.95
Å) and periodically recalculated, but they were not refined.
The maximum and minimum peaks in the final difference
Fourier map were 0.48 and -0.38 e/Å3, respectively.
The calculations were performed with use of the crystal-
lographic software packages teXsan,56 RAELS96,52 maXus,57
and CRYSTALS.58
(57) Mackay, S.; Gilmore, C. J .; Edwards, C.; Stewart, N.; Shank-
land, K. maXus Computer Program for the Solution and Refinement
of Crystal Structures; Nonius, MacScience, and The University of
Glasgow, 1999.
(58) Watkin, D. J .; Prout, C. K.; Carruthers, J . R.; Betteridge, P.
W. CRYSTALS Issue 10; Chemical Crystallography Laboratory, Ox-
ford, U.K., 1996.
(59) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic: Dordrecht, The Netherlands, 1995; Vol. C.
(60) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV.
(61) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C.
(62) (a) Baerends, E. J .; Ellis, D. E.; Ros, P. Chem. Phys. 1973, 2,
41. (b) te Velde, G.; Baerends, E. J . J . Comput. Phys. 1992, 99, 84. (c)
Fonseca Guerra, C.; Snijders, J . G.; te Velde, G.; Baerends, E. J . Theor.
Chem. Acc. 1998, 99, 391.
(52) Rae, A. D. RAELS96: A Comprehensive Constrained Least-
Square Refinement Program; Australian National University, Can-
berra, ACT, Australia, 1996.
(53) Rae, A. D. Acta Crystallogr. 1975, A31, 560, 570.
(54) Rae, A. D. Acta Crystallogr. 1984, A40 (Supplement), C428.
(55) Haller, K. J .; Rae, A. D.; Heerdegen, A. P.; Hockless, D. C. R.;
Welberry, T. R. Acta Crystallogr. 1995, B51, 187.
(63) Becke, A. D. Phys. Rev. A 1988, 38, 3098.
(64) Perdew, J . P. Phys. Rev. B 1986, 33, 8822.

Reactions of Alkynes with Nickelacycles
Organometallics, Vol. 20, No. 13, 2001 2877
quasi-relativistic corrections of Snijders and co-workers.65 The
optimization procedure developed by Versluis and Ziegler was
employed.66 Alkyne structures were optimized in C3v or Cs
symmetry as appropriate.
Ack n ow led gm en t. E.W. is grateful to the Austra-
lian Research Council for the award of a QEII Research
Fellowship. S.A.M. thanks the EPSRC for funding.
Su p p or tin g In for m a tion Ava ila ble: Tables giving full
crystallographic data for 4b‚0.5C6H6, 6b, 10b, 17‚CH2Cl2, and
21. This material is available free of charge via the Internet
at http://pubs.acs.org.
(65) (a) Snijders, J . G.; Baerends, E. J .; Ros, P. Mol. Phys. 1979, 38,
1909. (b) Ziegler, T.; Tschinke, V.; Baerends, E. J .; Snijders, J . G.;
Ravenek, W. J . Phys. Chem. 1989, 93, 3050. (c) van Lenthe, E.;
Baerends, E. J .; Snijders, J . G. J . Chem. Phys. 1993, 99, 4597.
(66) (a) Versluis, L.; Ziegler, T. J . Chem. Phys. 1988, 88, 322. (b)
Fan, L.; Ziegler, T. J . Am. Chem. Soc. 1992, 114, 10890.
OM0101083