Reactions of an (arylimido)vanadium(v)-alkylidene, V(CHSiMe 3)(N-2,6-Me2C6H3)(N=C tBu2)(PMe3), with nitriles, diphenylacetylene, and styrene

Article abstract of DOI:10.1021/om800479u

Reactions of a vanadium(V)-alkylidene, (ArN)V(CHSiMe₃)(N=C ^tBu₂)(PMe₃) (1, Ar = 2,6-Me₂C ₆H₃), with various nitriles, diphenylacetylene, and styrene have been explored. Treatment of 1 with RC≡N (R = Me, ^tBu, Ph) afforded a ring-opened bis(imido) complex, (ArN)V[NC(R)=CHSiMe₃](N=C^tBu₂)(PMe ₃) [R = Me (2), ^tBu (3), Ph (4)], and the structure of 4 by X-ray crystallography indicates that 4 has a distorted tetrahedral geometry around vanadium. Insertion of the nitrile into 2-4 did not occur upon further addition. The reaction of 1 with 1.0 equiv of PhC=CPh afforded the corresponding metallacyclobutene analogue, (ArN)V[C(Ph)=C(Ph)CHSiMe₃)](N=C ^tBu₂)(PMe₃) (5). The reaction of 1 with styrene afforded the metallacyclopropane analogue, (ArN)V(CH₂CHPh)(N=C ^tBu₂)(PMe3) (6), although the reaction with 1,1-diphenylethylene did not take place. The X-ray crystallographic analysis of 6 indicates that the vanadium atom in 6 is pentacoordinated with the arylimido ligands in the apical site of a distorted square pyramid.

Full text of DOI:10.1021/om800479u

Organometallics 2008, 27, 5353–5360
5353
Reactions of an (Arylimido)vanadium(V)-Alkylidene,
V(CHSiMe3)(N-2,6-Me2C6H3)(NdCtBu2)(PMe3), with Nitriles,
Diphenylacetylene, and Styrene
Wenjuan Zhang, Junji Yamada, and Kotohiro Nomura*
Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama,
Ikoma, Nara 630-0101, Japan
ReceiVed May 26, 2008
Reactions of a vanadium(V)-alkylidene, (ArN)V(CHSiMe3)(NdCtBu2)(PMe3) (1, Ar ) 2,6-Me2C6H3),
with various nitriles, diphenylacetylene, and styrene have been explored. Treatment of 1 with RCt N (R
) Me, tBu, Ph) afforded a ring-opened bis(imido) complex, (ArN)V[NC(R)dCHSiMe3](NdCtBu2)(PMe3)
t
[R ) Me (2), Bu (3), Ph (4)], and the structure of 4 by X-ray crystallography indicates that 4 has a
distorted tetrahedral geometry around vanadium. Insertion of the nitrile into 2-4 did not occur upon
further addition. The reaction of 1 with 1.0 equiv of PhCt CPh afforded the corresponding metallacyclo-
butene analogue, (ArN)V[C(Ph)dC(Ph)CHSiMe3)](NdCtBu2)(PMe3) (5). The reaction of 1 with styrene
afforded the metallacyclopropane analogue, (ArN)V(CH2CHPh)(NdCtBu2)(PMe3) (6), although the
reaction with 1,1-diphenylethylene did not take place. The X-ray crystallographic analysis of 6 indicates
that the vanadium atom in 6 is pentacoordinated with the arylimido ligands in the apical site of a distorted
square pyramid.
by molybdenum.1,2 Although classical Ziegler-type vanadium
catalysts displayed unique characteristics in olefin coordination
insertion polymerization (notable reactivity toward olefins),6,7
examples with vanadium-alkylidenes have been limited.4,8-10
Since no examples had been known until recently concerning
synthesis of “olefin metathesis active” vanadium-alkylidene,
the synthesis and its reaction chemistry are thus promising
subjects in terms of basic understanding in organometallic
chemistry as well as application as the catalyst.
Introduction
Transition metal-alkylidene complexes are important inter-
mediates in olefin metathesis [such as ring-opening metathesis
polymerization (ROMP), ring-closing metathesis (RCM), cross-
metathesis (CM) reactions, etc.], which introduces promising
possibilities for synthesis of both functional polymers and
valuable organic compounds,1 as demonstrated especially by
molybdenum2 and ruthenium.3 High-oxidation-state early transi-
tion metal alkylidene complexes attract considerable attention,2,4,5
because they play essential roles as catalysts in olefin metathesis
and Wittig-type or group transfer reactions,1,2,4 as demonstrated
We recently focused on the high-oxidation state (arylimido)-
vanadium(V) complexes containing anionic donor ligands
* Corresponding author. Tel: +81-743-72-6041. Fax: +81-743-72-6049.
E-mail: nomurak@ms.naist.jp.
(6) Examples:(a) Carrick, W. L. J. Am. Chem. Soc. 1958, 80, 6455. (b)
Carrick, W. L.; Kluiber, R. W.; Bonner, E. F.; Wartman, L. H.; Rugg, F. M.;
Smith, J. J. J. Am. Chem. Soc. 1960, 82, 3883. (c) Carrick, W. L.; Reichle,
W. T.; Pennella, F.; Smith, J. J. J. Am. Chem. Soc. 1960, 82, 3887. (d)
Lehr, M. H. Macromolecules 1968, 1, 178.
(7) For reviews, see: (a) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV.
2003, 103, 283. (b) Gambarotta, S. Coord. Chem. ReV. 2003, 237, 229. (c)
Hagen, H.; Boersma, J.; van Koten, G. Chem. Soc. ReV. 2002, 31, 357. (d)
Nomura, K. In New DeVelopments in Catalysis Research; Bevy, L. P., Ed.;
NOVA Science Publishers: New York, 2005; p 199.
(8) Examples of isolation of terminal vanadium(III),(IV) alkylidenes: (a)
Hessen, B.; Meetsma, A.; Teuben, J. H. J. Am. Chem. Soc. 1989, 111, 5977.
(b) Hessen, B.; Meetsma, A.; Van Bolhuis, F.; Teuben, J. H.; Helgesson,
G.; Jagner, S. Organometallics 1990, 9, 1925. (c) Hessen, B.; Buijink, J.-
K. F.; Meetsma, A; Teuben, J. H.; Helgesson, G.; Hakansson, M.; Jagner,
S; Spek, A. L. Organometallics 1993, 12, 2268. (d) Basuli, F.; Kilgore,
U. J.; Hu, X.; Meyer, K.; Pink, M.; Huffman, J. C.; Mindiola, D. J. Angew.
Chem., Int. Ed. 2004, 43, 3156–3159. (e) Basuli, F.; Bailey, B. C.; Brown,
D.; Tomaszewski, J.; Huffman, J. C.; Baik, M.-H.; Mindiola, D. J. J. Am.
Chem. Soc. 2004, 126, 10506.
(9) Examples of isolation of terminal vanadium(V)-alkylidenes: (a)
Buijink, J.-K. F.; Teuben, J. H.; Kooijman, H.; Spek, A. L. Organometallics
1994, 13, 2922 No reaction between CpV(CHPh)(NAr)(PMe3) and nor-
bornene or acetone was observed. (b) Yamada, J.; Fujiki, M.; Nomura, K.
Organometallics 2005, 24, 2248. (c) Kilgore, U. J.; Sengelaub, C. A.; Pink,
M.; Fout, A. R.; Mindiola, D. J. Angew. Chem., Int. Ed. 2008, 47, 3769.
(10) Examples of related complexes containing vanadium(V)-carbon
double bonds:(a) Hessen, B.; Meetsma, A.; van Bolhuis, F.; Teuben, J. H.
Organometallics 1990, 9, 1925. (b) Moore, M.; Gambarotta, S.; Yap, G.;
Liable-Sands, L. M.; Rheingold, A. L. Chem. Commun. 1997, 643.
(1) For examples, see: (a) Buchmeiser, M. R. Chem. ReV. 2000, 100,
1565. (b) Grubbs, R. H., Ed. Handbook of Metathesis; Wiley-VCH:
Weinheim, Germany, 2003; Vols. 1-3. (c) Khosravi, E., Szymanska-Buzar,
T., Eds. Ring-Opening Metathesis Polymerisation and Related Chemistry;
Kluwer: Dordrecht, The Netherlands, 2002. (d) Imamoglu, Y., Dragutan,
V., Eds. Metathesis Chemistry; Springer: Dordrecht, The Netherlands, 2007.
(2) For examples, see: (a) Schrock, R. R. Acc. Chem. Res. 1990, 23,
158. (b) Schrock, R. R. In Alkene Metathesis in Organic Synthesis; Fu¨rstner,
A.,Ed.; Springer: Berlin, Germany, 1998; p 1. (c) Schrock, R. R. In
Handbook of Metathesis; Grubbs, R. H., Ed.; Wiley-VCH: Weinheim,
Germany, 2003; Vol. 1, p 8.
(3) For examples, see: (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res.
2001, 34, 18–29. (b) Nguyen, S. T.; Trnka, T. M. In Handbook of
Metathesis; GrubbsR. H., Ed.; Wiley-VCH: Weinheim, 2003; Vol. 3, pp
61-85.
(4) For examples, see: (a) Schrock, R. R. Acc. Chem. Res. 1979, 12,
98. (b) Schrock, R. R. Chem. ReV. 2002, 102, 145. (c) Mindiola, D. Acc.
Chem. Res. 2006, 39, 813. (d) Mindiola, D.; Bailey, B.; Basuli, F. Eur.
J. Inorg. Chem. 2006, 16, 3135.
(5) For example (pioneering examples in titanium), see: (a) Gilliom,
L. R.; Grubbs, R. H. J. Am. Chem. Soc. 1986, 108, 733. (b) The role of the
“Tebbe complex” in olefin metathesis: Grubbs, R. H. In Handbook of
Metathesis; Grubbs, R. H., Ed.; Wiley-VCH: Weinheim, Germany, 2003;
Vol. 1, p 4. (c) Pioneering work concerning the so-called Tebbe reagent
(c-e): Tebbe, F. N.; Parshall, G. W.; Reddy, G. S. J. Am. Chem. Soc. 1978,
100, 3611. (d) Tebbe, F. N.; Parshall, G. W.; Ovenall, D. W. J. Am. Chem.
Soc. 1979, 101, 5074. (e) Tebbe, F. N.; Parshall, G. W.; Ovenall, D. W.
J. Am. Chem. Soc. 1980, 102, 6149.
10.1021/om800479u CCC: $40.75
2008 American Chemical Society
Publication on Web 09/18/2008

5354 Organometallics, Vol. 27, No. 20, 2008
Zhang et al.
alkylidene recently reported)12 or (ii) a mixture of isomers (syn/
antiisomers,asseeninthemolybdenum-alkylidenecomplexes),2,4b
are considered for the explanation.15 Although PMe3 coordinated
to the vanadium metal center in the aryloxo-alkylidene
V(CHSiMe3)(N-2,6-Me2C6H3)(O-2,6-iPr2C6H3), dissociates par-
tially in the solution,12 the possibility of the presence of two
(syn/anti) isomers is preferably considered in this case.14,15 This
is not only because the PMe3-coordinated species (1, should be
major) should have been observed in higher field than the
dissociated one by electron donation with PMe39b,12,15 but also
because addition of (2 or 5 equiv of) PMe3 into the C6D6 solution
containing 1 afforded formation of several species observed in
the 51V NMR spectra (probably formation of two PMe3-
coordinated species).15 This may also correspond to the observed
fact in the reactions with CH3CN and PhCt CPh, as described
below.
Scheme 1
including synthesis and some reactions of the alkyl11,12 and the
alkylidene9b,12 complexes. We demonstrated that the dichloro
complexes, (ArN)VCl2(X) (X ) aryloxo, ketimide, phenoxy-
imine), exhibited promising characteristics as catalyst precursors
for olefin coordination insertion polymerization in the presence
of Al cocatalysts.7d,11c,13 Moreover, we also demonstrated
recently that an isolated (arylimido)vanadium(V)-alkylidene,
(ArN)V(CHSiMe3)(NdCtBu2)(PMe3) (1, Ar ) 2,6-Me2C6H3),
exhibited notable catalytic activity for ring-opening metathesis
polymerization (ROMP) of norbornene as the first example with
vanadium, and the activity markedly increased at higher
temperature (80 °C).9b Since, as described above, examples of
the terminal vanadium(V)-alkylidenes are scarce,9,12 in this
paper, we thus explored some reactions of the isolated
(arylimido)vanadium(V)-alkylidene (1) with various nitriles,
diphenylacetylene, and certain olefins (styrene, 1,1-diphenyl-
ethylene).
Complex 1 exhibited remarkable catalytic activity for ring-
opening metathesis polymerization of norbornene without
cocatalyst (Table 1).9b The catalytic activity (turnover number,
TON) was low when the ROMP was conducted at 25 °C (runs
1, 2), whereas a standard Schrock-type initiator, Mo(CHCMe2Ph)-
(N-2,6-iPr2C6H3)(OtBu)2 (Mo), exhibited especially remarkable
catalytic activity under similar conditions (run 4).9b,16 The
activity of 1 increased at 50 °C, whereas the activity of Mo
was negligible due to the decomposition of the catalytically
active species (runs 5-8). The activities of 1 in benzene were
higher than those in toluene. Note that the activity markedly
increased at the higher temperature of 80 °C, and the observed
activity was higher than that by known Ru(CHPh)(Cl)2(PCy)2
(15) Two possibilities, (i) partial dissociation of PMe3 (as observed in
the alkylidene recently reported)12 and (ii) a mixture of isomers (syn/anti
isomers, as seen in the molybdenum-alkylidene complexes),2,4b have to
be considered for explanation for the two resonances in the 51V NMR spectra
of 1. PMe3 in the aryloxo-alkylidene V(CHSiMe3)(N-2,6-Me2C6H3)-
(O-iPr2C6H3)(PMe3) dissociated partially, confirmed by both the elemental
analysis and the NMR spectra,12 and the 1H NMR spectrum of 1 (in C6D6)
showed only one broad resonance ascribed to the alkylidene proton and
only one broad resonance ascribed to the alkylidene was observed in the
13C NMR spectrum (and one broad resonance was seen in the 31P NMR
spectrum).14 The latter possibility (the presence of isomers, shown below
in eq a) should be, however, positively considered, not only because the
PMe3-dissociated species (should be minor) should have been observed in
lower field than the coordinated one (1)9b,12 but also because addition of
PMe3 into the C6D6 solution containing 1 gave the other species (probably
formation of two PMe3-coordinated species). The fact that the reactions of
the alkylidene 1 with diphenylacetylene (or with CH3CN) gave a mixture
of two isomers would also support the latter possibility. Moreover, the fact
that the resultant polymers in the ring-opening metathesis polymerization
(ROMP) of norbornene possessed cis/trans olefinic double bonds9b may
also suggest the latter possibility. K.N. would like to thank a reviewer for
pointing out this issue. PMe3 in 1 would be in fact partially dissociated in
the solution, as seen in the aryloxo-alkylidene,12 and this fact might suggest
the former possibility, but the degree in 1 would probably be too low
(according to the elemental analysis). These issues including full explanation
of the observed facts should be solved in our future publications. NMR
spectra of 1 for the full identification and the spectra upon addition of PMe3
are shown in the Supporting Information.
Results and Discussion
An (arylimido)vanadium(V)-alkylidene complex, (ArN)V-
(CHSiMe3)(NdCtBu2)(PMe3) (1, Ar ) 2,6-Me2C6H3), was
prepared by R-H abstraction from (ArN)V(CH2SiMe3)2-
(NdCtBu2) upon heating in C6D6 in the presence of PMe3
(Scheme 1).9b This is the common method to prepare high-
oxidation-state metal alkylidenes by promoting R-hydrogen
abstraction reactions from metal alkyl complexes lacking
ꢀ-hydrogens, and addition of PMe3 was required to promote
the abstraction by steric crowding.4 The analytically pure
complex 1 was isolated by recrystallization from the chilled
n-hexane solution (-30 °C). A resonance ascribed to the
R-proton (VdCHSiMe3) was appeared at 14.5 ppm (broad),14
and the resonance ascribed to the R-carbon (VdCHSiMe3) was
observed at 302.0 ppm (broad).9b,14 These results thus indicate
that 1 is a nucleophilic carbene (alkylidene) of the general type.4
Two resonances were seen in the 51V NMR spectra,14
although only one resonance ascribed to the alkylidene proton/
carbon was observed in the 1H/13C NMR spectrum. Two
possibilities, (i) partial dissociation of PMe3 (as observed in the
(11) (a) Yamada, J.; Nomura, K. Organometallics 2005, 24, 3621. (b)
Yamada, J.; Fujiki, M.; Nomura, K. Organometallics 2007, 26, 2579. (c)
Onishi, Y.; Katao, S.; Fujiki, M.; Nomura, K. Organometallics 2008, 27,
2590.
(12) Nomura, K.; Onishi, Y.; Fujiki, M.; Yamada, J. Organometal-
lics 2008, 27, 3818. These results were partly presented at the XVIIth
International symposium on olefin metathesis (ISOMXVII), July2007,
Pasadena, CA.
(13) (a) Nomura, K.; Sagara, A.; Imanishi, Y. Macromolecules 2002,
35, 1583. (b) Wang, W.; Yamada, J.; Fujiki, M.; Nomura, K. Catal.
Commun. 2003, 4, 159. (c) Wang, W.; Nomura, K. Macromolecules 2005,
38, 5905. (d) Wang, W.; Nomura, K. AdV. Synth. Catal. 2006, 348, 743.
(14) The NMR spectra for 1 and the spectra monitoring the reaction
of 1 with RCN (and with styrene) are shown in the Supporting
Information.
(16) Nomura, K.; Atsumi, T.; Fujiki, M.; Yamada, J. J. Mol. Catal. A
2007, 275, 1.

Reaction of (Arylimido)Vanadium(V)-Alkylidene
Organometallics, Vol. 27, No. 20, 2008 5355
Table 1. Ring-Opening Metathesis Polymerization (ROMP) of Norbornene (NBE) by V(CHSiMe3)(N-2,6-Me2C6H3)(NdCtBu2)(PMe3) (1),
Ru(CHPh)Cl2(PCy3)2 (Ru, Cy ) cyclohexyl), and Mo(CHCMe2Ph)(N-2,6-iPr2C6H3)(OtBu)2 (Mo)a
d
d
run
complex (µmol)
solvent
NBE/mmol
NBE concb
temp/°C
time/min
TONc
Mw × 10-4
Mw/Mn
1e
2
1
1
(1.0)
(1.0)
benzene
toluene
toluene
toluene
benzene
toluene
toluene
toluene
benzene
benzene
benzene
toluene
toluene
toluene
2.12
1.06
2.12
2.12
2.12
2.12
2.12
2.12
2.12
2.12
2.12
2.12
2.12
2.12
0.22
0.44
0.22
0.44
0.22
0.22
0.22
0.44
0.22
0.22
0.22
0.22
0.22
0.22
25
25
25
25
50
50
50
50
80
80
80
80
80
80
360
360
60
267
82
1306
8550
1275
166
320
trace
967
1583
2071g
1244
1446
350
46
2.3
3e
4f
Ru (1.0)
Mo (0.20)
54
160
49
1.7
1.2
1.6
60
5e
6e
7
1
1
1
(1.0)
(1.0)
(1.0)
180
180
360
40
30
60
120
60
120
60
8f
Mo (0.20)
9e
10e
11e
12
13
14e
1
1
1
1
1
(1.0)
(1.0)
(1.0)
(1.0)
(1.0)
140
133
115
32
1.3
1.4
1.6
2.8
2.5
33
Ru (1.0)
a Conditions: catalyst 0.2 or 1.0 µmol, NBE 1.06 or 2.12 mmol, benzene or toluene 9.6 mL (run 2 2.4 mL, runs 4,8 4.8 mL). b Initial NBE conc. in
mmol/mL, c TON ) NBE consumed (mmol)/V (mmol). d GPC data vs polystyrene standards. e Cited from reference.9b f Cited from ref 16. g Yield 98%.
Scheme 2
under the same conditions due to the improved thermal stability
(runs 9-14).9b
assumed to proceed via formation of a putative azametallacy-
clobutene intermediate and the subsequent cross-metathesis. We
thus explored the reactivity of our vanadium(V)-alkylidene
(ArN)V(CHSiMe3)(NdCtBu2)(PMe3) (1), including isolation of
the reaction product with various nitriles.
1. Reactions of (ArN)V(CHSiMe3)(NdCtBu2)(PMe3) (1)
with RCN. It is known that CpV(CHCMe3)(dmpe) [dmpe )
t
1,2-bis(dimethylphosphino)ethane] slowly reacts with BuCN
Treatment of 1 with CH3CN, tBuCN, and PhCN in n-hexane
or in toluene-d8 cleanly afforded the corresponding vinylimido
complexes (ArN)V[NC(R)dCHSiMe3](NdCtBu2)(PMe3) [R )
at 60 °C to afford the vinylimido analogue CpV[NC-
(CMe3)dCHCMe3](dmpe) (65% conversion after 16 h).8c It is
also known that Ta(V)-alkylidenes, [TadCHR′] (R′ ) CMe3
or Ph), react with nitriles, RCN (R ) CH3, tBu, or Ph), to afford
the vinylimido complexes with a mixture of E- and Z-isomers
formed by insertion of RCN into the TadCHCR′ bond.2a,17
Moreover, the reactions of [TidCHR′] fragments (R′ ) H, tBu)
with tBuCN18a or (2,4,6-Me3C6H2)CH2CN18b afforded the
vinylimido complexes, and the subsequent reaction with an
additional tBuCN (or reaction with 2 equiv of PhCN) gave the
diazatitanacyclohexadiene complex.18a,c These reactions were
t
Me (2), Bu (3), Ph (4)], and the isolated complexes were
1
identified by H, 13C, and 51V NMR spectra and elemental
analysis (Scheme 2). The structure for 4 (including confirmation
that 4 is not the azametallacyclobutene but the vinylimido
analogue) was determined by X-ray crystallography (Figure 1).
t
The reaction of 1 with BuCN cleanly took place, and rapid,
exclusive formation of 3 was observed (by 1H NMR spectra in
C6D6) even by simply mixing at 25 °C.14 The analytically pure
3 was isolated from a chilled n-hexane solution (-30 °C).
The reaction of 1 with 1.0 equiv of PhCN also took place
similarly, affording the vinylimido analogue 4 exclusively as
monitored by 1H NMR spectrum, and further addition of PhCN
(2 equiv to V) did not give the diazavanadacyclohexadiene
complex,14 which was obtained in the reaction with the
(17) Selected examples for reaction with nitriles (Ta): (a) Schrock, R. R.;
Fellmann, J. D. J. Am. Chem. Soc. 1978, 100, 3359–3370. (b) Wood, C. D.;
McLain, S. J.; Schrock, R. R. J. Am. Chem. Soc. 1979, 101, 3210–3220.
(c) Mashima, K.; Yonekura, H.; Yamagata, T.; Tani, K. Organometallics
2003, 22, 3766–3772.
(18) Selected examples for reaction with nitriles (Ti): (a) Doxsee, K. M.;
Farahi, J. B.; Hope, H. J. Am. Chem. Soc. 1991, 113, 8889. (b) Basuli, F.;
Bailey, B. C.; Watson, L. A.; Tomaszewski, J.; Huffman, J. C.; Mindiola,
D. J. Organometallics 2005, 24, 1886. (c) van der Heiden, H.; Hessen, B.
Inorg. Chim. Acta 2003, 345, 27.
(19) Detailed analysis parameters including CIF files are shown in the
Supporting Information.

5356 Organometallics, Vol. 27, No. 20, 2008
Zhang et al.
Figure 1. ORTEP drawings of V(N-2,6-Me2C6H3)[NC(Ph)dCHSiMe3](NdCtBu2)(PMe3) (4). Thermal ellipsoids are drawn at the 50%
probability level, and H atoms are omitted for clarity.19
Table 2. Selected Bond Distances and Angles for
titanium-alkylidene.18a,c The vinylimido complex 4 was thus
V(N-2,6-Me2C6H3)[NC(Ph)dCHSiMe3](N)CtBu2)(PMe3) (4)a
isolated from the reaction mixture. The reaction took place
rapidly even if PMe3 (1 equiv to V) was added in the reaction
Bond Distances (Å)
V(1)-P(1)
V(1)-N(1)
V(1)-N(2)
V(1)-N(3)
2.4204(11) N(3)-C(21)
1.382(3)
1.356(5)
1.271(3)
1.390(3)
mixture before adding PhCN, and the reaction product 4 was
observed exclusively by adding PhCN (1 or 2 equiv to V) into
the NMR tube of a C6D6 solution containing 1 and PMe3.14
The results thus suggest that dissociation of PMe3 may not
be required for formation of the proposed azametallacyclobutene
intermediate (shown in Scheme 2), which means that we are
not sure whether the reaction proceeded via a dissociative
(dissociation of PMe3 and then coordination of PhCN) or an
associative (coordination of both PMe3 and PhCN) pathway.
The reaction of 1 with 2.0 equiv of CH3CN also afforded the
vinylimido complex 2 as the sole isolated product. Only one
resonance ascribed to the olefinic proton (dCHSiMe3) was seen
1.693(2)
1.844(2)
1.721(2)
C(21)-C(22)
N(2)-C(12)
N(1)-C(4)
Bond Angles (deg)
P(1)-V(1)-N(1)
P(1)-V(1)-N(2)
P(1)-V(1)-N(3)
N(1)-V(1)-N(2) 112.94(8)
N(1)-V(1)-N(3) 117.05(11)
V(1)-N(1)-C(4) 173.5(2)
91.03(9)
108.87(9)
103.97(8)
N(2)-V(1)-N(3)
V(1)-N(2)-C(12)
V(1)-N(3)-C(21)
N(3)-C(21)-C(26) 115.9(2)
N(3)-C(21)-C(22) 123.4(2)
Si(1)-C(22)-C(21) 126.1(2)
118.36(9)
169.2(2)
157.9(2)
a Detailed analysis conditions, see the Supporting Information.19
supine-2,3-dimethyl-1,3-butadiene)[1.824(3)Å].17cTheC(21)-C(22)
distance [olefinic double bond, 1.356(3) Å] is close to that in
CpV[NC(CMe3)dCHCMe3](dmpe) [1.353(4) Å].8c The V-P
bond distance [V(1)-P(1) 2.4204(11) Å] is shorter than those
in 1 [2.4331(7) Å] and in V(NAr)Cl2(NdCtBu2)(PMe3) [2.527(2)
Å],9b clearly suggesting that PMe3 strongly coordinates to V.
In contrast, the V-N(ketimide) distance [1.844(2) Å] is close
to those in 1 [1.847(2) Å] and (ArN)VCl2(NdCtBu2)(PMe3)
[1.839(4) Å].9b
1
(at 4.86 ppm in 3 and 5.09 ppm in 4) in the H NMR spectra
of 3 and 4, whereas two peaks were seen in that of 2, probably
because complex 2 is a mixture of E- and Z-isomers because
t
of the lesser steric bulk of CH3CN compared to BuCN and
PhCN.
Selected bond distances and angles for 4 are summarized in
Table 2. The X-ray crystallographic analysis of 4 shows that 4
has a distorted tetrahedral geometry around vanadium,19 and
the structure also indicates the Z stereochemistry of the CdC
bond. The V-N(vinylimido) bond distance [V(1)-N(3) 1.721(2)
Å] is somewhat longer than that in the V-N(arylimido)
[V(1)-N(1) 1.693(2) Å] but shorter than that in V-N(ketimide)
[V(1)-N(2) 1.844(2) Å]. The difference in the bond distances
between the vinylimido and the arylimido ligands is also
influenced by their bond angles [V(1)-N(1)-C(4) 173.5(2)°
vs V(1)-N(3)-C(21) 157.9(2)°]. The V-N(vinylimido) bond
distance [1.721(2) Å] is longer than that in CpV[NC-
(CMe3)dCHCMe3](dmpe) [1.707(2) Å],8c and the value is
apparently shorter than that in Cp*Ta[NC(tBu)dCHPh](η4-
2. Reactions of (ArN)V(CHSiMe3)(NdCtBu2)(PMe3) (1)
with Diphenylacetylene. It is known that CpTaCl2(CHCMe3)
reacts with PhCt CPh to afford another alkylidene, CpTaCl2-
[C(Ph)C(Ph)dCHCMe3],4a,17b and that Ta(CHCMe3)(O-2,6-
iPr2C6H3)3(THF) reacts with PhCt CPh to afford THF-free
metallacyclobutene, and the ring-opening reaction was induced
upon addition of pyridine to afford the vinylalkylidene com-
plex.20 Living polymerization of 1-butyne was thus initiated by
the vinylalkylidene complex in the presence of pyridine.20 It is
also known that [Cp2TidCH2] reacts with substituted acetylenes
to form titanacylobutenes.21 We thus explored reaction of the

Reaction of (Arylimido)Vanadium(V)-Alkylidene
Organometallics, Vol. 27, No. 20, 2008 5357
Scheme 3
Scheme 4
vanadium-alkylidene 1 with PhCt CPh including isolation of
the reaction product.
Treatment of 1 with 1 equiv of PhCt CPh in toluene-d8
afforded the corresponding vanadacylobutene (ArN)V[C(Ph)d
C(Ph)CHSiMe3)](NdCtBu2)(PMe3) (5, Scheme 3), and the
analytically pure 5 could be isolated by recrystallization from
a chilled n-hexane solution (-30 °C). The resultant complex
(5) was identified based on 1H, 13C, and 51V NMR spectra and
by elemental analysis. The 51V NMR spectrum showed two
resonances at -321.3 and -358.8 ppm, and the 1H NMR
spectrum also showed two resonances assigned to HR (3.35,
3.34, dCH-SiMe3), Ar-CH3 (2.63, 2.50), PMe3 (0.90, 0.64), and
SiMe3 (0.41, 0.21). A similar trend was observed in the 13C
NMR spectrum (188.8, 185.7, 144.6, 143.9, 89.5), and these
results are similar to those in Ta[C(Ph)C(Ph)CH(CMe3)](O-2,6-
iPr2C6H3)3.20 The possibility of formation of the vinylalkylidene
species [VdC(Ph)dC(Ph)CHSiMe3] is rejected because no
corresponding resonances ascribed to the alkylidene were
seen.17b The results thus suggest that the resultant complex 5 is
a mixture of two isomers (as shown in Scheme 3), probably
formed via insertion of PhCt CPh into syn or anti isomers (the
arylimido and the alkylidene).
3. Reactions with Styrene and 1,1-Diphenylethylene. The
vanadium(V)-alkylidene 1 readily reacted with 1 equiv of
styrene in d8-toluene (at -30 to 25 C, 2 h), and the 51V NMR
spectrum showed two resonances.14 The major product appeared
at 180.3 ppm and was isolated in a pure form by recrystallization
from a chilled n-hexane solution (-30 °C), and the complex
was identified as a metallacyclopropane complex, (ArN)V-
1
(CH2CHPh)(NdCtBu2) (6), based on H, 13C, and 51V NMR
spectra and elemental analysis. Three multiplet resonances at
4.14, 3.06, and 2.08 ppm were observed in the 1H NMR
spectrum, which can be ascribed to the three ring-protons of
the metallacyclopropane. The metallacycle structure of 6 was
eventually determined by X-ray crystallography (Figure 2), as
described below. However, reactions of 1 with 1,1-diphenyl-
ethylene recovered the alkylidene 1 in high yields under the
same conditions.14 The reaction did not take place, even if the
reaction continued overnight (24 h).14
Figure 2. ORTEP drawings of V(N-2,6-Me2C6H3)(CH2-
CHPh)(NdCtBu2)(PMe3) (6). Thermal ellipsoids are drawn at the
50% probability level, and H atoms are omitted for clarity.19
Selected bond lengths and angles for 6 are summarized in
Table 3.19 The X-ray crystallographic analysis of 6 shows that
the vanadium atom in 6 is pentacoordinated with the arylimido
ligands in the apical site of a distorted square pyramid,19 as
exemplified by N(2)-V(1)-P(1) [112.57(15)°], N(2)-V(1)-C(9)
[105.5(2)°],P(1)-V(1)-C(10)[88.14(17)°],andC(9)-V(1)-C(10)
[39.1(2)]bondangles(total345.31°).TheV-N(imido)-C(phenyl)
bond angle is 177.3(3)°, and the V-N(1) distance [1.670(5)
Å] is somewhat shorter than those in the vinylimido complex
[4, 1.693(2) Å] and the alkylidene [1, 1.679(2) Å], but is longer
than those in (ArN)VCl2(NdCtBu2) [1.660(2) Å] and
(ArN)VCl2(NdCtBu2)(PMe3) [1.652(3) Å].9b The V(1)-C(10)
bond distance [2.165(5) Å] is shorter than that in V(1)-C(9)
Table 3. Selected Bond Distances and Angles for
V(N-2,6-Me2C6H3)(CH2CHPh)(NdCtBu2)(PMe3) (6)a
Bond Distances (Å)
V(1)-P(1)
V(1)-N(1)
V(1)-N(2)
V(1)-C(9)
V(1)-C(10)
N(1)-C(1)
2.4483(19) C(9)-C(10)
1.422(8)
1.465(10)
1.403(9)
1.390(10)
1.262(7)
1.500(9)
1.670(5)
1.825(4)
2.070(5)
2.165(5)
1.376(8)
C(10)-C(11)
C(11)-C(12)
C(11)-C(16)
N(2)-C(17)
C(2)-C(7)
Bond Angles (deg)
91.93(15) N(1)-V(1)-C(9)
N(1)-V(1)-C(10) 111.2(9)
N(1)-V(1)-P(1)
N(1)-V(1)-N(2)
N(2)-V(1)-P(1)
N(2)-V(1)-C(10)
P(1)-V(1)-C(10)
V(1)-N(2)-C(17)
V(1)-C(9)-C(10)
104.9(2)
113.8(2)
112.57(15)
129.1(2)
88.14(17)
171.2(4)
74.1(3)
N(2)-V(1)-C(9)
P(1)-V(1)-C(9)
V(1)-N(1)-C(1)
C(9)-V(1)-C(10)
V(1)-C(10)-C(9)
105.5(2)
127.28(16)
177.3(3)
39.1(2)
(20) Wallace, K. C.; Liu, A. H.; Davis, W. M.; Schrock, R. R.
Organometallics 1989, 8, 644.
(21) (a) Lee, J. B.; Ott, K. C.; Grubbs, R. H. J. Am. Chem. Soc. 1982,
104, 7491. (b) Petasis, N. A.; Fu, D.-K. Organometallics 1993, 12, 3776.
66.8(2)
V(1)-C(10)-C(11) 107.8(3)
C(9)-C(10)-C(11) 121.2(5)
a Detailed analysis conditions, see the Supporting Information.19

5358 Organometallics, Vol. 27, No. 20, 2008
Zhang et al.
[2.070(5) Å], and the V(1)-C(10)-C(9) bond angle [66.8(2)°]
is smaller than that in V(1)-C(9)-C(10) [74.1(3)°]; this is
probably due to an influence by the phenyl substituent in 6.
These bond distances are somewhat longer than that of V-Me
in V(NAr)(Me)(NdCtBu)2 [2.064(2) Å].11a The V-P distance
[2.4483(19) Å] is longer than those in the vinylimido complex
[4, 2.4204(11) Å] and the alkylidene [1, 2.4331(7) Å] but shorter
than that in (ArN)VCl2(NdCtBu2)(PMe3) [2.527(2) Å].9b
It has been known that Cp2Ta(CH2)(CH3) decomposed via
bimolecular bridged methylidene intermediate [Cp2Ta(CH3)]2(µ2-
CH2)2 in the presence of PMe3 to afford a metallacyclopropane,
Cp2Ta(CH2CH2)(CH3), and Cp2Ta(CH3)(PMe3).4a,22 Another
metallacyclopropane complex, W(NPh)(CH2CH2)[o-(Me3SiN)2-
C6H4](PMe3)2, was also formed from the (arylimido)tungsten
dialkyl complex W(NPh)(CH2CH3)2[o-(Me3SiN)2C6H4] in the
presence of PMe3.23 These reactions were postulated to proceed
via dimeric intermediate such as [Cp2Ta(CH3)]2, which was
formed by loss of ethylene from the dimeric methylidene
intermediate [Cp2Ta(CH3)]2(µ2-CH2)2.22,23 Moreover, it is also
reported that (arylimido)tungsten dimer [W(NAr){OCMe2-
(CF3)}]2 inserted ethylene to give a [W(NAr){OCMe2-
(CF3)}]2(CH2CH2) that contains a slightly bent ditungstenacy-
clobutane ring.23 Although we have, however, no clear results
concerning mechanistic details at this moment, we thus assume
that the vanadacyclopropane 6 may be formed via a certain
dimeric intermediate (as a scheme generating 6 from 1 with 1
equiv of styrene).24 These decompositions (formation of the
dimeric species) should be dependent upon the nature of the
metal-alkylidene species including the electronic and steric
nature of ligands employed,25 and the results here are noteworthy
in terms of designing efficient catalysts with vanadium.
to be vanadium(V) (d0, two vanadium-carbon σ-bonds with
styrene) rather than vanadium(III) (d2, π-bonding, η2 fashion
with styrene). Although Mo(NAr′)(Biphen)(ethylene)(Et2O)
initiated ROMP without a cocatalyst,25a 6 did not show catalytic
activity under certain conditions.26
Concluding Remarks
Reactions of V(N-2,6-Me2C6H3)(CHSiMe3)(NdCtBu2)(PMe3)
(1) with nitriles (RCt N, R ) CH3, tBu, Ph), diphenylacetylene,
and styrene have been explored. The vinylimido complexes
(ArN)V[NC(R)dCHSiMe3](NdCtBu2)(PMe3) [R ) Me (2), tBu
(3), Ph (4)] were formed exclusively by treating 1 with RCt N,
and these reactions proceeded via an azametalacyclobutene
intermediate and subsequent cross-metathesis. However, inser-
tions of nitriles into 2-4 did not occur upon further addition.
The reaction of 1 with PhCt CPh afforded vanadacylobutene 5
exclusively as a mixture of isomers. A metallacyclopropane
analogue, V(N-2,6-Me2C6H3)(CH2CHPh)(NdCtBu2) (6), was
formed by reaction of 1 with styrene, and the structure was
determined by X-ray crystallography. However, the reaction of
1 with 1,1-diphenylethylene did not take place, and 6 did not
initiated ROMP of norbornene, as reported in
Mo(NAr′)(Biphen)(ethylene)(Et2O). The present vanadium(V)-
alkylidene 1 initiates ROMP of norbornene without cocatalyst
(as the first example with vanadium), and promising reactivities
toward unsaturated compounds were observed. Therefore, we
believe that the results presented here should be important
information for better understanding of the vanadium(V)-
alkylidene chemistry as well as for designing more efficient
vanadium catalysts for both olefin metathesis and the other
organic transformations through the vanadium-alkylidene.
Two vanadium carbon bond distances in the metallacyclo-
propane analogue 6 [V(1)-C(9), V(1)-C(10): 2.070(5), 2.165(5)
Å, respectively] are shorter than those in W(NPh)(CH2CH2)[o-
(Me3SiN)2C6H4](PMe3)2 [2.223(5), 2.234(5) Å]23 and are close
to or somewhat shorter than those in Mo(NAr′)(Biphen)-
(ethylene)(Et2O) [2.204(9), 2.128(9) Å] formed from Mo-
(NAr′)(CHCMe2Ph)(Biphen) by treating with 2 equiv of eth-
ylene via ꢀ-H elimination.24 The C(9)-C(10) bond distance
[1.422(8) Å] is shorter than that in W(NPh)(CH2CH2)[o-
(Me3SiN)2C6H4](PMe3)2 [1.434(6) Å],23 but longer than that in
Mo(NAr′)(Biphen)(ethylene)(Et2O) [1.400(13) Å]. These results
thus suggest that styrene coordinates to vanadium in a η2
fashion. Since the resultant complex is diamagnetic and the
vanadium atom in 6 is pentacoordinated with the arylimido
ligands in the apical site of a distorted square pyramid, confirmed
by X-ray crystallography, the oxidation state of 6 is considered
Experimental Section
General Procedures. All experiments were carried out under a
nitrogen atmosphere in a Vacuum Atmospheres drybox or using
standard Schlenk techniques. All chemicals used were of reagent
grade and were purified by standard purification procedures.
Anhydrous grade benzene, toluene, diethyl ether, and n-hexane
(Kanto Kagaku Co., Ltd.) were transferred into a bottle containing
molecular sieves (a mixture of 3A 1/16, 4A 1/8, and 13X 1/16) in
a drybox under N2 and were passed through a short alumina column
under N2 stream before use. The starting (arylimido)vanadium(V)-
alkylidene, V(CHSiMe3)(N-2,6-C6H3)(NdCtBu2)(PMe3) (1), was
prepared according to a published procedure, as described below.9b
Elemental analyses were performed by using a PE2400II Series
(Perkin-Elmer Co.), and some analytical runs were performed twice
to confirm the reproducibility in the independent analysis/synthesis
runs. All 1H, 13C, and 51V NMR spectra were recorded on a JEOL
(22) Bimolecular decomposition of Cp2Ta(CH2)(CH3) in the presence
of PMe3 afforded Cp2Ta(V)(CH2CH2)(CH3) and Cp2Ta(CH3)(PMe3): (a)
Schrock, R. R J. Am. Chem. Soc. 1975, 97, 6577. (b) Schrock, R. R.; Sharp,
P. R. J. Am. Chem. Soc. 1978, 100, 2389.
(23) Wang, S. S.; Vander-Lende, D. D.; Abboud, K. A.; Boncella, J. M.
Organometallics 1998, 17, 2628.
(24) Formation of Mo(NAr′)(Biphen)(ethylene) complex from
Mo(NAr′)(CHCMe2Ph)(Biphen) by reacting with 2 equiv of ethylene via
ꢀ-H elimination: (a) Tsang, W. C. P.; Jamieson, J. Y.; Aeilts, S. L.; Hultzsch,
K. C.; Schrock, R. R.; Hoveyda, A. H. Organometallics 2004, 23, 1997. In
our case, we would be able to eliminate this possibility [a route via formation
of vanadium(III) and subsequent addition of styrene], because the observed
reaction product by 51V NMR spectrum14 from the reaction of 1 with 1
equivofstyrenewas6exclusively.TherelatedreactioninCpTi(CHMe3)[PMe2-
CH2C(O)-CMe2-o-C6H4CMe2] (The titanium-alkylidene reacts with eth-
ylene, initially forming a metallacycle, while subsequent reactions produce
a stable ethylene complex). (b) van Doorn, J. A.; van der Heijden, H.
Organometallics 1995, 14, 1278.
1
JNM-LA400 spectrometer (399.65 MHz for H, 100.40 MHz for
13C, 105.31 MHz for 51V). All spectra were obtained in the solvent
indicated at 25 °C unless otherwise noted. Chemical shifts are given
1
in ppm and are referenced to SiMe4 (δ 0.00, H, 13C) and VOCl3
(δ 0.00, 51V). Coupling constants and half-width values, ∆ν1/2, are
given in Hz.
Synthesis of V(CHSiMe3)(N-2,6-Me2C6H3)(NCtBu2)(PMe3)
(1).9b A C6D6 solution (60 mL) containing (ArN)V(CH2SiMe3)2-
(NdCtBu2) (3.15 g, 6.50 mmol) and PMe3 (3.46 g, 45.5 mmol)
was allowed to warm at 80 °C. The mixture was stirred for 40 h,
and the solution was filtered through a Celite pad. The filtrate was
concentrated in Vacuo, and the resultant tan residue was dissolved
in a minimum amount of n-hexane. The concentrated solution was
(25) (a) Schrock, R. R.; Lopez, L. P. H.; Hafer, J.; Singh, R.; Sinha,
A.; Mu¨ller, P. Organometallics 2005, 24, 5211. (b) Lopez, L. P. H.; Schrock,
R. R.; Mu¨ller, P. Organometallics 2006, 25, 1978.
(26) Negligible amount of polymer was collected when a toluene solution
(5 mL) containing complex 6 (5 mg, 10 µmol) and norbornene 200 mg
(2.1 mmol) was heated at 80 °C for 1 h.

Reaction of (Arylimido)Vanadium(V)-Alkylidene
Organometallics, Vol. 27, No. 20, 2008 5359
Table 4. Crystal Data, Collection Parameters of
V(N-2,6-Me2C6H3)[NC(Ph)dCHSiMe3](NdCtBu2)(PMe3) (4) and
V(N-2,6-Me2C6H3)(CH2CHPh)(NdCtBu2)(PMe3) (6)a
placed in the freezer at -30 °C, yielding 1.05 g (2.22 mmol, 34%)
of red prism-shape microcrystals that were suitable for crystal
structure analysis. The reason for the low yield may be due to the
difficulty in isolating as the microcrystals (because of high solubility
in n-hexane), because the 1H NMR spectrum for the reaction
4
6
formula
fw
C31H51N3PSiV
575.76
C28H44N2PV
490.58
1
mixture showed formation of 1 exclusively. H NMR (C6D6): δ
cryst color, habit
cryst size (mm)
cryst syst
space group
a (Å)
red, block
brown, block
0.38 (s, 9H, CHSi(CH3)3), 0.93 (d, 9H, PMe3), 1.25 (s, 18H,
(CH3)3C-), 2.78 (s, 6H, (CH3)2), 6.82 (t, 1H), 7.09 (d, 2H), 14.52
(br, 1H, CHSi(CH3)3). 13C NMR (CDCl3): δ 2.8 (SiMe3), 17.4,
17.7, 20.2, 31.0, 42.4, 121.9, 127.6, 134.5, 161.7, 193.8, 302.0.
31P NMR (C6D6): δ -10-20 (broad). 51V NMR (C6D6): δ -27,
80. Anal. Calcd for C24H46N2PSiV: C, 60.99 (58.68 + VC,
vanadium carbide); H, 9.81; N, 5.93. Found: C, 58.68; H, 9.72; N,
5.73.
0.22 × 0.18 × 0.12 0.30 × 0.20 × 0.06
monoclinic
C2/c (#15)
23.8758(10)
15.1189(5))
21.5604(8)
118.5805(10)
6834.4(4))
8
monoclinic
P21/n (#14)
8.6734(6)
11.4636(9)
28.5749(19)
92.0450(17)
2839.4(4)
4
b (Å)
c (Å)
ꢀ (deg)
V (Å3)
Z value
Dcalcd (g/cm3)
F000
1.119
2480.00
193
3.940
1.148
1056.00
243
Preparation of V(N-2,6-Me2C6H3)[NC(Me)dCHSiMe3](Nd
CtBu2)(PMe3) (2). Into a toluene-d8 (3 mL) solution containing 1
(318 mg, 0.67 mmol) was added at -30 °C 2 equiv of CH3CN (55
mg, 1.34 mmol). The mixture was warmed slowly to room
temperature and was stirred for 24 h. The solution was then filtrated
through a Celite pad, and the filter cake was washed adequately
with n-hexane. The combined filtrate and the wash were placed in
a rotary evaporator to remove n-hexane and toluene in Vacuo. The
resultant solid was then dissolved in a minimum amount of n-hexane
and was placed in the freezer (-30 °C). Analytically pure 2 (100
mg, 0.19 mmol) was collected from the chilled solution as dark
brown microcrystals. Yield: 28.9% (mixture of isomers, E- and Z-).
1H NMR (C6D6): δ 7.07 (d, 2H, J ) 7.32, Ar-H), 6.79 (t, 1 H, J
) 6.60, Ar-H), 4.77 and 4.46 (s, 1H, VCHSiMe3), 2.74 and 2.70
(s, 6H, Ar-CH3), 2.40 and 2.15 (s, 3H, NCCH3), 1.30-1.24 (m,
18H, J ) 2.92, C(CH3)3), 0.96 (d, 9H, J ) 8.8, PMe3-H), 0.41 +
0.31 (s, 9H, Si(CH3)3). 51V NMR (C6D6): -484.9, -537.4. 13C
NMR (C6D6): 133.5, 125.1, 122.2, 122.0, 121.5, 103.2, 102.5, 42.1,
41.4, 31.2, 31.1, 30.9, 30.7, 24.3, 19.9, 19.6, 16.0, 15.8, 15.6, 1.4,
1.03, 0.96. The imido carbon, ketimide carbon, and dN-C(Me)d
resonances were not observed probably due to their low intensities.
Anal. Calcd for C26H49N3SiVP: C, 60.79; H, 9.61; N, 8.18. Found:
C, 60.93; H, 9.62; N, 7.86.
temp (K)
µ
(Mo KR) (cm-1
)
4.223
no. of reflns measd
total: 33 031,
unique: 7791
total: 22 575,
unique: 5169
1832
333
0.0478
no. of obsns (I > 2.00σ(I)) 4188
no. of variables
R1 (I > 2.00σ(I))
wR2 (I > 2.00σ(I))
goodness of fit
385
0.0412
0.0886
1.013
0.0802
1.011
a Detailed analysis conditions, see the Supporting Information.19
due to the low intensity. Anal. Calcd for C31H51N3PSiV: C, 64.67;
H, 8.93; N, 7.30. Found: C, 64.23; H, 9.19; N, 7.11.
Preparation of V(N-2,6-Me2C6H3)[C(Ph)dC(Ph)CHSiMe3)]-
(NdCtBu2)(PMe3) (5). Into a toluene-d8solution containing 1 (300
mg, 0.63 mmol) was added 1 equiv of diphenylacetylene (113 mg,
0.63 mmol) at -30 °C. The mixture was warmed slowly to room
temperature and was then stirred for 24 h. The solution was filtered
through a Celite pad, and the filter cake was adequately washed
with n-hexane. The combined filtrate and the wash were placed in
a rotary evaporator to remove the solvent in Vacuo. The resultant
solid was then dissolved in a minimum amount of n-hexane. The
chilled solution (-30 °C) gave brown microcrystals (118 mg, 0.18
Preparation of V(N-2,6-Me2C6H3)[NC(tBu)dCHSiMe3](Nd
1
mmol). Yield: 28.5%. H NMR (C6D6): δ 7.94 (d, J ) 7.32, 1H,
CtBu2)(PMe3) (3). Into a n-hexane solution (5 mL) containing 1
Ar-H), 7.71 (m, 3H, Ar-H and Ph-H), 7.52 (m, 1H, Ar-H),
7.11-6.79 (m, 8H, Ph-H), 3.35 and 3.34 (d, 1H, -CHSiMe3), 2.63
and 2.50 (s, 6H, Ar-CH3), 1.34-1.05 (m, 18H, C(CH3)3), 0.74 and
0.63 (s, 9H, P(CH3)3), 0.41 and 0.21 (s, 9H, Si(CH3)3). 51V NMR
(C6D6): δ -326.4, -366.0. 13C NMR (C6D6): δ 188.8, 185.7, 144.6,
143.9, 139.5, 138.6, 136.4, 134.9, 131.6, 130.8, 130.1, 129.6, 129.0,
127.0, 125.6, 125.3, 125.1, 123.6, 123.4, 123.2, 122.8, 92.8, 89.8,
62.0, 60.8, 60.0, 44.6, 42.6, 41.9, 41.4, 40.6, 31.2, 30.7, 30.3, 20.0,
19.4, 17.2, 17.0, 13.9, 13.7, 3.5, 2.9. Anal. Calcd for C38H56N2PSiV:
C, 70.12; H, 8.67; N, 4.30. Found: C, 70.58; H, 8.52; N, 4.42.
Preparation of V(N-2,6-Me2C6H3)(CH2CHPh)(NdCtBu2)-
(PMe3) (6). Into a toluene-d8 solution containing 1 (500 mg, 1.06
mmol) was added styrene (110 mg, 1.06 mmol) at -30 °C. The
mixture was warmed slowly to room temperature and was stirred
for 2 h. The solvent was then removed in Vacuo, and the residue
was dissolved in a minimum amount of n-hexane. The chilled
solution (-30 °C) afforded analytically pure 6 as brown microc-
t
(236 mg, 0.50 mmol) was added at room temperature BuCN (50
mg, 0.50 mmol). After the mixture was stirred for 6 h, the solution
was placed in the freezer (-30 °C). The brown microcrystals were
collected from the chilled solution. Yield: 224 mg (81%). 1H NMR
(C6D6): δ 7.07 (d, 2H, J ) 7.32, Ar-H), 6.80 (t, 1H, J ) 7.32,
Ar-H), 4.78 (s, 1H, dCHSi), 2.66 (s, 6H, Ar-CH3), 1.54 (s, 9H,
NC(C(CH3)3)), 1.33 (s, 9H, NC(C(CH3)3)), 1.30 (s, 9H, NC-
(C(CH3)3)), 1.06 (d, J ) 8.8, 9H, PMe3), 0.39 (s, 9H, Si(CH3)3).
13C NMR (C6D6): δ 189.5, 183.0, 160.0, 133.5, 127.7, 121.7, 101.1,
42.2, 41.8, 40.3, 31.2, 30.8, 20.6, 16.0, 1.6. 51V NMR (C6D6): δ
-466 (∆ν1/2 ) 1356 Hz). Anal. Calcd for C29H55N3PSiV: C, 62.67;
H, 9.97; N, 7.56. Found: C, 62.40; H, 10.22; N, 7.57.
Preparation of V(N-2,6-Me2C6H3)[NC(Ph)dCHSiMe3](Nd
CtBu2)(PMe3) (4). Into a n-hexane (5 mL) solution containing 1
(208 mg, 0.44 mmol) was added at -30 °C 2.0 equiv of PhCN (90
mg, 0.88 mmol). The mixture was warmed slowly to room
temperature and was stirred for 2 h. The solution was then
concentrated in Vacuo and was placed in the freezer (-30 °C). The
brown microcrystals (120 mg, 0.21 mmol) were collected from the
1
rystals (128 mg, 0.26 mmol). Yield: 24.5%. H NMR (C6D6): δ
7.09 (t, 1H, J ) 7.32, Ar-H), 6.95 (d, 2 H, J ) 7.32, Ar-H),
6.80-6.71 (m, 5H, Ph-H), 4.13 (m, 1H, cyclo-H), 3.05 (m, 1H,
cyclo-H), 2.46 (s, 6H, CH3), 2.08 (m, 1H, cyclo-H), 1.32 (s, 18 H,
tBu-H), 0.66 (d, 9H, J ) 7.32, PMe3). 51V NMR (C6D6): δ 183.5
(∆ν1/2 ) 1053.1 Hz). 13C NMR (C6D6): δ 204.5, 183.2, 157.9,
147.3, 134.2, 134.1, 129.0, 128.6, 122.2, 121.8, 72.6, 43.6, 31.2,
23.2, 19.3, 14.9, 14.7. Anal. Calcd for C28H44N2PV: C, 68.55; H,
9.04; N, 5.71. Found: C, 68.05; H, 9.28; N, 5.53.
1
chilled solution. Yield: 47.3%. H NMR (C6D6): δ 7.95 (d, J )
6.84, 2H, Ar-H), 7.04-7.09 (m, 5H, Ph-H), 6.79 (t, J ) 7.80, 1H,
Ar-H), 5.09 (s, 1H, VCHSi), 2.59 (s, 6H, Ar-CH3), 1.36 (s, 9H,
t
tBu-H), 1.22 (s, 9H, Bu-H), 0.82 (d, J ) 8.8, 9H, PMe3-H), 0.47
(s, 9H, Si(CH3)3). 51V NMR (C6D6): δ -485.3 (∆ν1/2 ) 1638 Hz).
13C NMR (C6D6): δ 190.9, 172.1, 145.9, 134.6, 127.5, 127.1, 122.2,
106.5, 42.3, 41.9, 31.2, 31.0, 23.0, 19.6, 15.5, 15.2, 1.3. The
ketimide carbon signal was not observed about 160 ppm probably
Crystallographic Analysis. All measurements were made on a
Rigaku RAXIS-RAPID imaging plate diffractometer with graphite-

5360 Organometallics, Vol. 27, No. 20, 2008
Zhang et al.
monochromated Mo KR radiation. The selected crystal collection
parameters are summarized in Table 4, and the detailed results are
described in the Supporting Information. All structures were solved
by direct methods and expanded using Fourier techniques,27 and
the non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included but not refined. All calculations for complexes
4 and 6 were performed using the Crystal Structure28 crystal-
lographic software package.
work was partly supported by a Grant-in-Aid for Scientific
Research on Priority Areas (No. 19028047, “Chemistry
of Concerto Catalysis”) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan. W.Z.
expresses her thanks to JSPS for a postdoctoral fellowship
(P06349).
Supporting Information Available: 1H, 13C, 31P, and 51V NMR
spectra (in C6D6 at 25 °C) for V(N-2,6-Me2C6H3)(CHSi-
Me3)(NdCtBu2)(PMe3) (1) (and the spectra upon addition of PMe3),
selected NMR spectra for reactions of 1 with nitriles, styrene, and 1,1-
diphenylethylene, and CIF files and structure reports for V(N-2,6-
Me2C6H3)[NC(Ph)dCHSiMe3](NdCtBu2)(PMe3) (4) and V(N-2,6-
Me2C6H3)(CH2CHPh)(NdCtBu2)(PMe3) (6). These materials are
available free of charge via the Internet at http://pubs.acs.
org.
Acknowledgment. We are grateful to Mr. Shohei Katao
(NAIST) for his assistance in the crystallographic analysis,
and Prof. Michiya Fujiki (NAIST) for discussions. This
(27) DIRDIF94: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman,
W. P.; de Delder, R.; Israel, R.; Smits, J. M. M. The DIRDIF94 program
system, Technical report of crystallography laboratory; University of
Nijmegen: The Netherlands, 1994.
(28) (a) Crystal Structure 3.6.0: Crystal Structure Analysis Package;
Rigaku and Rigaku/MSC: The Woodlands, TX, 2000-2004. (b) Watkin,
D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P. W. CRYSTALS Issue
10; Chemical Crystallography Laboratory: Oxford, UK., 1996.
OM800479U