Ni→ B interactions in nickel phosphino-alkynyl-borane complexes

Article abstract of DOI:10.1002/chem.200902888

Boron bends over for nickel : The Ni complexes [{t Bu₂PC≡ CB(QF_s)₂]Ni(cod)] (1) and [({tBu₂PC≡ CB(C₆F₅)₂}Ni(NCMc))] (2) derived from the reaction between the phosphinoalkynyl-borane tBu₂PC≡CB(C ₆F₅)₂ and [Ni(cod)₂] exhibit an unprecedented metal-alkyne interaction in which the borane substituent bends towards the metal affording a Ni→B dative interaction. (Chemical Equation Representation). (Chemical Equation Representation).

Full text of DOI:10.1002/chem.200902888

DOI: 10.1002/chem.200902888
Ni!B Interactions in Nickel Phos
ACHTUNGTRNEpNUNG hino-Alkynyl-Borane Complexes
Xiaoxi Zhao, Edwin Otten, Datong Song, and Douglas W. Stephan*[a]
The classical acid–base theory described by Lewis,[1] ac-
counts for much of the chemistry of the main group ele-
ments. In addition the interactions of Lewis bases with for-
mally Lewis acidic transition metals is a concept critical to
coordination chemistry. However it is the inverse situation,
that is the ability of transition metals to act as Lewis bases
and form Lewis acid–base adducts with Lewis acidic species
that has garnered much interest in the last 10 years.[2] De-
spite the recent flurry of activity in this area, it was indeed
some 30 years ago that Hughes and co-workers[3] first de-
nity to examine unusual M!B interactions. To that end, we
targeted the synthesis of a strongly polarized phosphino-al-
kynyl-borane. It is well documented that metal complexa-
tion of alkynes results in the “bend-back” of the substitu-
ents, consistent with a p-backbonding model involving dona-
tion of metal electron density to the p* orbital of the alkyne
[16]
ꢀ
and reduction of the C C bond. Herein, we report that
Ni complexation of a phosphino-alkynyl-borane results in
the unusual situation in which the boron substituent “bends
forward” toward the metal, accommodating a dative Ni!B
scribed the species [CpFe(CO)2AlPh3]
N
interaction.
[17]
ꢀ
Fe!Al dative bond. More recent work on such interactions
began in 1999 with the report by Hill et al.[4] of a Ru com-
plex of tris-thioimidazolylborane. The chelating nature of
the ligand in this ruthenaboratrane provided the B in close
proximity to Ru, affording a Ru!B dative bond. Since then
boryl-bridged heterobimetallic complexes[5] have also been
shown to incorporate M!B dative interactions. In addition,
Piers and co-workers have proposed possible contributions
from M!B dative interactions in their metal–borataalkene
complexes.[6] The groups of Hill,[4,7] Bourissou,[8] Parkin,[9]
and Emslie[10] among others[11] have employed ambiphilic li-
gands to probe the nature and impact of these unconven-
tional donor–acceptor interactions. Using such ligands, an
intramolecular M!B dative interaction can occur thermo-
dynamically facilitated by the chelate effect and without
ligand strain or distortion.[12]
The phosphino-alkyne tBu2PC CH
was prepared and
[18]
allowed to react with ClB
(C6F5)2 at ꢁ358C to give an off-
white product 1 in 72% isolated yield. Compound 1 exhibits
1
ꢁ
a H NMR doublet resonance at d=5.80 ppm with a P H
coupling of 469 Hz, indicative of the presence of a PH frag-
ment (31P: d=25.5 ppm). It also shows a 11B{1H} signal at
d=ꢁ12.8 ppm and three 19F resonances at d=ꢁ133.1,
ꢁ160.5, and 166.1 ppm, consistent with the presence of a
four-coordinate borate unit. These data confirm the formu-
lation of 1 as the alkynyl-linked zwitterionic phosphonium
ꢀ
borate tBu2PHC CBClACTHUNTRGNE(GNU C6F5)2 (Scheme 1). Treatment of 1
with excess Me2SiHCl results in the exchange of the B-
ꢀ
bound chloride for hydride, affording tBu2PHC CBH
(2) as colorless crystals in 79% yield (Scheme 1). A 1:1:1:1
G
quartet at d=3.25 ppm in the 1H NMR spectrum (1JBH
91 Hz) confirms the presence of a BH moiety. The acetylen-
In our own work, we have been probing the chemistry of
systems incorporating highly electrophilic B centers with
basic phosphine fragments in which steric demands preclude
P!B dative interactions.[13] Such systems, termed “frustrat-
ed Lewis pairs”,[14] afford unique reactivity on their own
right.[13b,c,15] In addition, they also provide a unique opportu-
ic carbon atom alpha to P is observed in the 13C NMR spec-
1
trum at d=64.4 ppm with a JCP of 158 Hz. The resonance
for the B-bound acetylenic carbon was not observed, pre-
sumably due to quadrupolar broadening. The proposed con-
[a] X. Zhao, Dr. E. Otten, Prof. Dr. D. Song, Prof. Dr. D. W. Stephan
Department of Chemistry, University of Toronto
80 St. George Street, Toronto Ontario (Canada)
E-mail: dstephan@chem.utoronto.ca
Homepage: http://www.chem.utoronto.ca/staff/DSTEPHAN
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200902888.
Scheme 1. Synthesis of 1–3.
2040
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2040 – 2044

COMMUNICATION
ꢀ
nectivity in 2 was confirmed by X-ray crystallography
(Figure 1).[19] Interestingly, viewing the molecule along the
BCCP vector in the solid state, it is noted that the substitu-
ents on B and P are eclipsed, with the BH and PH occupy-
ing the same plane.
formulation of 4 as (tBu2PC CB
G
(cod). Crystallo-
graphic data on the structure of 4 (Figure 2)[19] confirmed
that Ni adopts a pseudo-square-planar coordination geome-
Figure 2. POV-ray drawing of 4. All hydrogen atoms H are omitted for
o
ꢁ
ꢁ
clarity. Selected bond lengths [ꢁ] and angles [ ]: Ni C1 2.005(3), Ni C2
ꢁ
ꢁ
ꢁ
ꢁ
1.987(3), Ni B 2.358(3), P C1 1.792(3), C2 B 1.486(4), C1 C2 1.254(4),
C2-C1-P 155.5(3), C1-C2-B 156.3(3).
Figure 1. POV-ray drawing of 2. All hydrogen atoms except PH and BH
are omitted for clarity. Selected bond lengths [ꢁ] and angles [o] in the
ꢁ
ꢁ
ꢁ
PCCB fragment: P C 1.716(3), B C 1.598(4), C C 1.208(4); C-C-P
175.7(3), C-C-B 177.9(3).
try comprising a bidentate cod ligand, an alkynyl fragment,
ꢁ
and a coordinated B center. The elongated alkynyl C C
bond length of 1.254(4) ꢁ is consistent with a weakened
ꢀ
The synthetic strategy for the formation of 1 is related to
triple bond. This is also evident from the decrease in C C
the recently demonstrated reactivity of PhC CH with the
stretching frequency from 2125 cmꢁ1 in 2 to 1881 cmꢁ1 in 4.
ꢀ
ꢁ
frustrated Lewis pair, B
N
The salient structural feature in 4 is the short Ni B dis-
tance of 2.358(3) ꢁ and concomitant unusual trans disposi-
tion of the P and B groups on the (partially reduced) alkyn-
yl unit. The Ni B distance is somewhat longer than those
salt [HPtBu3]
[PhC CB
(C6F5)3].[15b] Bestmann and co-work-
ꢀ
ers[20] have previously reported a related species Ph2MePC
ꢀ
ꢁ
CBR3 (R=Ph, CH2Ph) prepared in a more conventional
ꢀ
fashion via generation of Ph2PC CLi, reaction with borane
and methylation with MeI.
previously
reported
for
Ni(triphosphine-borane)
(2.1677(16) ꢁ)[8f] and NiX(tris-thioimidazolylborane) (X=
Cl, N3, NCS, OAc) (2.079(13)–2.112(3) ꢁ).[9c] This may
result from the constraints imposed by the metal–alkyne in-
teraction and the required bending of the B toward Ni (C-
C-B angle: 156.3(3)8), as is observed in Emslieꢂs M(h3-
ꢁ
Treatment of 2 with tBu3P and B
neutral phosphino-alkynyl-borane tBu2PC CB
and the known salt [tBu3PH][HB
(C6F5)3].[13b] This reaction
results from the greater basicity and acidity of tBu3P and B-
(C6F5)3, respectively. The formation of 3 was confirmed by
ACHTNUGTNER(UNGN C6F5)3 generates the
ꢀ
AHCTNURTGEG(NNUN C6F5)2 (3)
AHCTUNGTRENNUNG
G
(BCC)-triarylborane) complexes (2.294(4) ꢁ).[10a] The Ni
ACHTUNGTRENNUNG
ꢁ
NMR analysis of the reaction mixture. Although no assigna-
ble 11B signal was observed, broad 19F resonances at d=
129.0, ꢁ147.9, and ꢁ162.3 ppm suggest a neutral three-coor-
dinate borane unit, while a singlet 31P signal at d=17.6 ppm
indicates a neutral phosphine moiety. Hence, 3 is believed to
exist in the monomeric form in solution despite the highly
Ccod bonds trans to B are significantly longer (Ni Cav
ꢁ
2.138(3) ꢁ) than those trans to the alkynyl fragment (Ni Cav
2.088(3) ꢁ), consistent with a dative Ni!B interaction that
is known to exert a strong trans influence.[22] Despite this in-
teraction, the sum of the C-B-C angles about B is 357.68.
Thus, the dative Ni to B interaction does not lead to signifi-
ꢀ
acidic B and basic P centers. A related compound, Ph2PC
cant pyramidalization at boron, consistent with the M to B
[5]
ꢁ
CBMes2 (Mes=2,4,6-trimethylphenyl), was reported by
interaction seen in Rh boryl compounds. It is also note-
Marder and co-workers.[21]
worthy that the B C(2) bond length of 1.486(4) ꢁ in 4 is
ꢁ
Although attempts to isolate the neutral species 3 from
solution resulted in unidentified decomposition products, re-
action of 3 generated in situ with [NiACTHNUTRGNENUG(cod)2] (cod=1,5-cyclo-
octadiene) in the presence of excess cod led to the forma-
tion of a new species 4. The broad 11B signal observed at d=
7.0 ppm along with the 19F signals at d=ꢁ129.3, ꢁ154.9, and
ꢁ163.1 ppm indicate the presence of a B center that is not
three-coordinate. A signal in the 13C NMR spectrum at d=
significantly shorter than in 2 and somewhat shorter than in
those alkynylboranes that have been structurally character-
ized (1.504(6)–1.529(6) ꢁ).[21,23] This suggests some degree
of “borato-allene” character in the BCC fragment as in its
all-carbon analogues that adopt the h3-propargyl/allenyl co-
ordination mode.[24]
The species 4 was also generated in the reaction of 2 with
[NiACTHUNTRGNENG(U cod)2]. Monitoring the reaction by NMR spectroscopy
120.7 ppm exhibiting a C P coupling of 57 Hz was attribut-
ed to the alkynyl carbon atom alpha to P. H NMR data re-
vealed a COD:PCCB-fragment ratio of 1:1, prompting the
revealed the initial formation of a species exhibiting 31P and
ꢁ
1
11B NMR signals at d=28.2 and ꢁ24.7 ppm, both of which
1
1
are doublets with diagnostic JPH and JBH, respectively. Over
Chem. Eur. J. 2010, 16, 2040 – 2044
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2041

D. W. Stephan et al.
with Ni is retained. In addition,
the formally pendant P is coor-
dinated to a second Ni center.
The coordination spheres of the
two Ni centers are completed
by coordination of NCMe. The
ꢁ
Ni Calkyne bonds were found to
be 1.9536(12) and 1.9714(13) ꢁ,
ꢁ
while the Ni B approach is
2.3243(15) ꢁ, slightly shorter
than that seen in 4, presumably
as a result of a more electron-
rich Ni donor. The six-mem-
bered ring formed by the
Ni2P2C2 core of the dimer is ap-
proximately planar with a maxi-
mum deviation from the least-
Scheme 2. Synthesis of 4 and 5.
the course of one day these signals are replaced by those at-
tributable to 4. The observed intermediate is proposed to be
a more classical metal–alkyne complex (Scheme 2). The fate
of the proton and hydride on P and B is not entirely clear.
Evidence of cyclooctene is observed in the reaction mixture
although it does not seem to be the only by-product from
H2 transfer. Regardless of the mechanism of loss of H2, it
appears that the Lewis acidity of the resulting free borane
drives the rearrangement of the metal-bound fragment to
permit the Ni!B dative interaction.
squares plane of 0.0805 ꢁ.
To probe the nature of the Ni!B interaction, DFT calcu-
lations[25] were undertaken. The geometry of 4 was opti-
mized by using the B3PW91 functional and 6-311G** basis
set affording 4calc, which was found to be very similar to the
crystallographically determined structure. The calculated
Ni!B separation was longer than the experimental value
by 0.06 ꢁ, while all other pertinent bond lengths differed by
less than 0.03 ꢁ. Importantly, 4calc showed B bending to-
ꢀ
wards Ni with an approximately coplanar NiACTHNURGTNE(NUG BC CP) frag-
ꢁ ꢀ
Treatment of 4 with MeCN results in the formation and
precipitation of a new product 5. NMR spectra obtained in
[D8]THF showed a 31P resonance at d=53.2 ppm, notably
shifted downfield from that of 4. Unfortunately, the
1H NMR spectrum is broad and uninformative, perhaps a
result of acetonitrile exchange; however, this could not be
confirmed due to the poor solubility at low temperature. Al-
though for 5 no 11B signal was observed, the resemblance of
its 19F NMR spectrum to that of 4 suggests a similar B envi-
ment and a B C C angle of 156.58, almost identical to the
experimentally determined value. The HOMO of 4calc not
only involves the interaction between the filled Ni dxy orbital
and vacant B px orbital, but also demonstrates significant
contributions from the interaction of Ni with the acetylenic
ꢀ
carbon on P (C(P)), as well as p-delocalization over the BC
C fragment (Figure 4a). The HOMO-1 of 4calc also shows
some contribution to the Ni BC C interaction, while the
HOMO-2, HOMO-13, and HOMO-20 exhibit classical
ꢁ
ꢀ
ꢁ
ronment. The IR spectrum of 5 in the solid state exhibited a
metal alkyne p-antibonding, p-donating, and s-donating
ꢁ1
ꢀ
ꢀ
coordinated C N stretch at 2269 cm and a C C stretch at
1838 cmꢁ1, suggesting a more reduced alkynyl group than in
4. The X-ray structure of 5 (Figure 3)[19] reveals its centro-
symmetric dimeric nature in which the B-C-C interaction
MOs, respectively. Interestingly, a NBO analysis found a
natural bond orbital corresponding to the Ni!B interaction
(Figure 4b). This NBO, with an occupancy of 1.63, is highly
polarized towards Ni with approximately 80.2% contribu-
tion from the Ni d orbital, signifying the dative nature of
the bond. The NPA atomic charge on B shows a rather mod-
erate decrease from 0.66 in the free ligand 3calc to 0.36 in the
complex 4calc, while that on C(P) also drop by 0.25 from 3calc
ꢁ
to 4calc. The NAO Wiberg bond index for 4calc suggests Ni
ꢁ
ꢁ
C
(P), Ni C(B) and Ni B bond orders of 0.40, 0.17, and 0.31,
respectively. These data support the notion that there is a
moderate degree of Ni!B dative interaction as the electron
ꢀ
density is delocalized over the BC C moiety affording a hy-
perconjugation-like stabilization. This is also evidenced by
significant delocalization energies provided by second-order
ꢁ
ꢀ
NBO interactions between Ni B s-orbitals and C C p-orbi-
tals (64 kcalmolꢁ1 for s!p*; 33 kcalmolꢁ1 for p!s*). Such
delocalization is believed to be responsible for the shorten-
ꢁ
Figure 3. POV-ray drawing of 5. All hydrogen atoms H are omitted for
o
ꢁ
ꢁ
clarity. Selected bond lengths [ꢁ] and angles [ ]: Ni C1 1.9536(12), Ni
ꢁ
ꢁ
ꢁ
ꢁ
C2 1.9714(13), Ni B 2.3243(15), Ni P 2.1982(4), Ni N 1.8674(11), P’
ing of the B CACTHNUTRGNE(UNG alkyne) distance in 4calc in comparison to
that in 3calc, and the retained planarity at the B center of 4.
ꢁ
ꢁ
C(1) 1.7877(13), C2 B1 1.486(2), C1 C2 1.2681(18); C2-C1-P’
145.44(11), C1-C2-B 153.50(13).
2042
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ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2040 – 2044

Nickel Phosphino-Alkynyl-Borane Complexes
COMMUNICATION
4F, o-C6F5), ꢁ154.85 (t, 2F, 3JFF =21 Hz, p-C6F5), 163.13 ppm (m, 4F, m-
C6F5); 31P{1H} NMR (C6D6): d=6.86 ppm (s); IR (thin film from
CH2Cl2): n˜ =1881 cmꢁ1 (u
(C C)); elemental analysis calcd (%) for
ꢀ
C30H30BF10PNi.C3.5H4: C 55.34, H 4.71; found: C 55.35, H 5.00.
Acknowledgements
D.W.S. and D.S. gratefully acknowledge financial support of NSERC of
Canada. D.W.S. is grateful for the support of a Canada Research Chair
and a Killam Research Fellow ship from the Killam Foundation. X.Z.
thanks the Province of Ontario and Digital Specialty Chemicals for an
Ontario Graduate Scholarship (OGSST). E.O. is grateful for the support
of a Rubicon postdoctoral fellowship from the Netherlands Organisation
for Scientific Research (NWO).
Keywords: alkyne complexes · boranes · dative metal–boron
bonding · nickel · nickel–borane interactions
[1] G. N. Lewis, Valence and the Structure of Atoms and Molecules,
Chemical Catalogue Company, New York, 1923.
[2] H. Braunschweig, C. Kollann, D. Rais, Angew. Chem. 2006, 118,
5380–5400; Angew. Chem. Int. Ed. 2006, 45, 5254–5274.
[3] J. M. Burlitch, M. E. Leonowicz, R. B. Petersen, R. E. Hughes,
Inorg. Chem. 1979, 18, 1097–1105.
Figure 4. a) Gaussview depiction of the HOMO of
4 (cutoff: 0.04).
[4] A. F. Hill, G. R. Owen, A. J. P. White, D. J. Williams, Angew. Chem.
1999, 111, 2920–2923; Angew. Chem. Int. Ed. 1999, 38, 2759–2761.
[5] a) D. Curtis, M. J. G. Lesley, N. C. Norman, A. G. Orpen, J. Star-
buck, J. Chem. Soc. Dalton Trans. 1999, 1687–1694; b) S. A. West-
cott, T. B. Marder, R. T. Baker, R. L. Harlow, J. C. Calabrese, K. C.
Lam, Z. Lin, Polyhedron 2004, 23, 2665–2677; c) H. Braunschweig,
K. Radacki, D. Rais, G. R. Whittell, Angew. Chem. 2005, 117, 1217–
1219; Angew. Chem. Int. Ed. 2005, 44, 1192–1193.
[6] a) K. S. Cook, W. E. Piers, R. McDonald, J. Am. Chem. Soc. 2002,
124, 5411–5418; b) K. S. Cook, W. E. Piers, S. J. Rettig, Organome-
tallics 1999, 18, 1575–1577; c) K. S. Cook, W. E. Piers, T. K. Woo, R.
McDonald, Organometallics 2001, 20, 3927–3937.
[7] a) M. R. S.-J. Foreman, A. F. Hill, G. R. Owen, A. J. P. White, D. J.
Williams, Organometallics 2003, 22, 4446–4450; b) M. R. S.-J. Fore-
man, A. F. Hill, A. J. P. White, D. J. Williams, Organometallics 2004,
23, 913–916; c) I. R. Crossley, A. F. Hill, Organometallics 2004, 23,
5656–5658; d) D. J. Mihalcik, J. L. White, J. M. Tanski, L. N. Zakhar-
ov, G. P. A. Yap, C. D. Incarvito, A. L. Rheingold, D. Rabinovitch,
Dalton Trans. 2004, 1626–1634; e) I. R. Crossley, M. R. S.-J. Fore-
man, A. F. Hill, A. J. P. White, D. J. Williams, Chem. Commun. 2005,
221–223; f) I. R. Crossley, A. F. Hill, A. C. Willis, Organometallics
2005, 24, 1062–1064; g) I. R. Crossley, A. F. Hill, E. R. Humphrey,
A. C. Willis, Organometallics 2005, 24, 4083–4086.
b) Molekel depiction of the NBO for the Ni!B interaction in 4 (cutoff:
0.05).
In summary, the crystallographic and computational data
herein illustrate that complexes 4 and 5 contain a dative
Ni!B interaction, which prompts an unconventional trans
metal–alkyne binding mode. The impact of such interactions
and the chemistry of highly polarized phosphino-alkynyl-
boranes continue to be subjects of investigation in our labo-
ratories.
Experimental Section
For full experimental and spectroscopic details for all compounds, see the
Supporting Information.
Synthesis of [(tBu2PC CBACHTGNUERTN(NGUN C6F5)2)NiACHTUNEGTRNNGNU CAHTNUGTRENUN(NG C6F5)3 (99 mg,
(cod)].0.5C7H8 (4): B
ꢀ
0.19 mmol) and PtBu3 (39 mg, 0.19 mmol) were added to 2 in toluene.
After the mixture had been stirred for 1 h, hexane was added and the
[8] a) S. Bontemps, G. Bouhadir, W. Gu, M. Mercy, C.-H. Chen, B. M.
Foxman, L. Maron, O. V. Ozerov, D. Bourissou, Angew. Chem. 2008,
120, 1503–1506; Angew. Chem. Int. Ed. 2008, 47, 1481–1484; b) S.
Bontemps, G. Bouhadir, K. Miqueu, D. Bourissou, J. Am. Chem.
Soc. 2006, 128, 12056–12057; c) S. Bontemps, H. Gornitzka, G. Bou-
hadir, K. Miqueu, D. Bourissou, Angew. Chem. 2006, 118, 1641–
1644; Angew. Chem. Int. Ed. 2006, 45, 1611–1614; d) S. Bontemps,
M. Sircoglou, G. Bouhadir, H. Puschmann, J. A. K. Howard, P. W.
Dyer, K. Miqueu, D. Bourissou, Chem. Eur. J. 2008, 14, 731–740;
e) M. Sircoglou, S. Bontemps, M. Mercy, N. Saffon, M. Takahashi,
G. Bouhadir, L. Maron, D. Bourissou, Angew. Chem. 2007, 119,
8737–8740; Angew. Chem. Int. Ed. 2007, 46, 8583–8586; f) M. Sirco-
glou, S. Bontemps, G. Bouhadir, N. Saffon, K. Miqueu, W. Gu, M.
Mercy, C.-H. Chen, B. M. Foxman, L. Maron, O. V. Ozerov, D. Bour-
issou, J. Am. Chem. Soc. 2008, 130, 16729–16738.
was mixture cooled at ꢁ358C for 3 h. Follwing filteration, [Ni
ACHTUNGERTN(NUNG cod)2]
(50 mg, 0.18 mmol) and 1,5-cyclooctadiene (190 mg, 1.8 mmol) were
added to the filtrate. Upon stirring for 6 h, the mixture was filtered and
the orange-red product precipitated from the concentrated solution at
ꢁ358C. Yield: 86 mg, 65%. 1H NMR (C6D6): d=7.13 (m, 1.5H, o/p-Ph,
toluene), 7.02 (m, 1H, m-Ph, toluene), 5.50 (br, 2H, =CH, cod), 4.88 (br,
2H, =CH, cod), 2.11 (s, 1.5H, CH3, toluene), 1.90 (m, 4H, CH2, cod),
1.67 (m, 4H, CH2, cod), 1.22 ppm (d, 18H, 3JHP =12.3 Hz, tBu); 11B{1H}
NMR (C6D6): d=6.98 ppm (br); 13C{1H} NMR (C6D6): d=147.89 (dm,
1JCF =241 Hz, o-C6F5), 140.49 (dm, 1JCF =247 Hz, p-C6F5), 137.96 (dm,
1JCF =250 Hz, m-C6F5), 137.90 (s, i-Ph, toluene), 129.34 (s, o-Ph, toluene),
1
128.69 (s, m-Ph, toluene), 125.68 (s, p-Ph, toluene), 120.70 (d, JCP
=
57 Hz, C CP), 108.62 (d, 3JCP =11.2 Hz, =CH, cod), 98.70 (s, =CH, cod),
ꢀ
2
33.03 (d, 1JCP =25 Hz, quat-tBu), 31.03 (s, CH2, cod), 29.60 (d, JCP
=
ꢀ
14 Hz, tBu), 28.31 (s, CH2, cod), 21.42 ppm (s, CH3, toluene). C CB and
[9] a) V. K. Landry, J. G. Melnick, D. Buccella, K. Pang, J. C. Ulichny,
G. Parkin, Inorg. Chem. 2006, 45, 2588–2597; b) K. Pang, S. M.
quat-C6F5 carbons were not observed. 19F NMR (C6D6): d=ꢁ129.32 (m,
Chem. Eur. J. 2010, 16, 2040 – 2044
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2043

D. W. Stephan et al.
Quan, G. Parkin, Chem. Commun. 2006, 5015–5017; c) K. Pang,
J. M. Tanshi, G. Parkin, Chem. Commun. 2008, 1008–1010.
[17] A. Kondoh, H. Yorimitsu, K. Oshima, J. Am. Chem. Soc. 2007, 129,
4099–4104.
[10] a) D. J. H. Emslie, L. E. Harrington, H. A. Jenkins, C. M. Robertson,
J. F. Britten, Organometallics 2008, 27, 5317–5325; b) S. R. Oakley,
K. D. Parker, D. J. H. Emslie, I. Vargas-Baca, C. M. Robertson, L. E.
Harrington, J. F. Britten, Organometallics 2006, 25, 5835–5838.
[11] a) S. Senda, Y. Ohki, T. Hirayama, D. Toda, J.-L. Chen, T. Matsumo-
to, H. Kawaguchi, K. Tatsumi, Inorg. Chem. 2006, 45, 9914–9925;
b) F. Jiang, P. J. Shapiro, F. Fahs, B. Twamley, Angew. Chem. 2003,
115, 2755–2757; Angew. Chem. Int. Ed. 2003, 42, 2651–2653; c) R. J.
Blagg, J. P. H. Charmant, N. G. Connelly, M. F. Haddow, A. G.
Orpen, Chem. Commun. 2006, 2350–2352.
[18] D. J. Parks, W. E. Piers, G. P. A. Yap, Organometallics 1998, 17,
5492–5503.
[19] CCDC-761563 (2), CCDC-761564 (4), and CCDC-761565 (5) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif
[20] H. J. Bestmann, H. Behl, M. Bremer, Angew. Chem. 1989, 101,
1303–1304; Angew. Chem. Int. Ed. 1989, 28, 1219–1221.
[21] Z. Yuan, N. J. Taylor, Y. Sun, T. B. Marder, I. D. Williams, C. Lap-
Tak, J. Organomet. Chem. 1993, 449, 27–37.
[12] G. Parkin, Organometallics 2006, 25, 4744–4747.
[22] F.-G. Fontaine, J. Boudreau, M.-H. Thibault, Eur. J. Inorg. Chem.
2008, 5439–5454.
[13] a) G. C. Welch, R. R. S. Juan, J. D. Masuda, D. W. Stephan, Science
2006, 314, 1124–1126; b) G. C. Welch, D. W. Stephan, J. Am. Chem.
Soc. 2007, 129, 1880–1881; c) S. J. Geier, T. M. Gilbert, D. W. Ste-
phan, J. Am. Chem. Soc. 2008, 130, 12632–12633.
[14] a) J. S. J. McCahill, G. C. Welch, D. W. Stephan, Angew. Chem. 2007,
119, 5056–5059; Angew. Chem. Int. Ed. 2007, 46, 4968–4971;
b) D. W. Stephan, Dalton Trans. 2009, 3129–3136; c) D. W. Stephan,
G. Erker, Angew. Chem. 2010, 122, 50–81; Angew. Chem. Int. Ed.
2010, 49, 46–76; d) D. W. Stephan, Org. Biomol. Chem. 2008, 6,
1535–1539.
[23] a) Z. Yuan, C. D. Entwistle, J. C. Collings, D. Albesa-Jovꢃ, A. S. Bat-
sanov, J. A. K. Howard, N. J. Taylor, H. M. Kaiser, D. E. Kaufmann,
S.-Y. Poon, W.-Y. Wong, C. Jardin, S. Fathallah, A. Boucekkine, J.-F.
Halet, T. B. Marder, Chem. Eur. J. 2006, 12, 2758–2771; b) J. J.
Eisch, B. Shafii, J. D. Odom, A. L. Rheingold, J. Am. Chem. Soc.
1990, 112, 1847–1853; c) M. J. Bayer, H. Pritzkow, W. Siebert, Eur.
J. Inorg. Chem. 2002, 2069–2072.
[24] a) K. Tsutsumi, S. Ogoshi, S. Nishiguchi, H. Kurosawa, J. Am.
Chem. Soc. 1998, 120, 1938–1939; b) M. W. Baize, P. W. Blosser, V.
Plantevin, D. G. Schimpff, J. C. Gallucci, A. Wojcicki, Organometal-
lics 1996, 15, 164–173; c) P. W. Blosser, J. C. Gallucci, A. Wojcicki,
J. Am. Chem. Soc. 1993, 115, 2994–2995; d) V. F. Quiroga Noram-
buena, A. Heeres, H. J. Heeres, A. Meetsma, J. H. Teuben, B.
Hessen, Organometallics 2008, 27, 5672–5683.
[25] Gaussian 03, Revision E.01, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, S. G. E., M. A. Robb, J. R. Cheeseman, J. J. A. Montgomery, Jr.,
T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyoto, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg,
V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Fores-
man, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Lahan, C. Y. Peng, A. Na-
nayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wallingford,
CT, 2004.
[15] a) P. A. Chase, G. C. Welch, T. Jurca, D. W. Stephan, Angew. Chem.
2007, 119, 8196–8199; Angew. Chem. Int. Ed. 2007, 46, 8050–8053;
b) M. A. Dureen, D. W. Stephan, J. Am. Chem. Soc. 2009, 131,
8396–8397; c) S. J. Geier, D. W. Stephan, J. Am. Chem. Soc. 2009,
131, 3476–3477; d) C. M. Mçmming, E. Otten, G. Kehr, R. Frçhlich,
S. Grimme, D. W. Stephan, G. Erker, Angew. Chem. 2009, 121,
6770–6773; Angew. Chem. Int. Ed. 2009, 48, 6643–6646; e) E.
Otten, R. C. Neu, D. W. Stephan, J. Am. Chem. Soc. 2009, 131,
9918–9919; f) M. Ullrich, A. J. Lough, D. W. Stephan, J. Am. Chem.
Soc. 2009, 131, 52–53; g) M. Ullrich, K. S.-H. Seto, A. J. Lough,
D. W. Stephan, Chem. Commun. 2009, 2335–2337; h) P. Spies, G.
Kehr, K. Bergander, B. Wibbeling, R. Frçhlich, G. Erker, Dalton
Trans. 2009, 1534–1541; i) P. Spies, G. Erker, G. Kehr, K. Bergander,
R. Frçhlich, S. Grimme, D. W. Stephan, Chem. Commun. 2007,
5072–5074; j) V. Sumerin, F. Schulz, M. Nieger, M. Leskela, T.
Repo, B. Rieger, Angew. Chem. 2008, 120, 6090–6092; Angew.
Chem. Int. Ed. 2008, 47, 6001–6003.
[16] a) M. A. Bennett, J. Castro, A. J. Edwards, M. R. Kopp, E. Wenger,
A. C. Willis, Organometallics 2001, 20, 980–989; b) B. L. Edelbach,
R. J. Lachicotte, W. D. Jones, Organometallics 1999, 18, 4660–4668;
c) R. Goddard, B. Apotecher, H. Hoberg, Acta Crystallogr. Sect. C
1987, 43, 1290–1293; d) U. Rosenthal, W. Schulz, J. Organomet.
Chem. 1987, 321, 103–117; e) D. Walther, A. Schmidt, T. Klettke, W.
Imhof, H. Gçrls, Angew. Chem. 1994, 106, 1421–1424; Angew.
Chem. Angew. Chem. Int. Ed. Engl. 1994, 33, 1373–1376.
Received: October 20, 2009
Published online: January 20, 2010
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