Synthesis of various (arylimido)vanadium(V)-methyl complexes containing ketimide ligands and reactions with alcohols, thiols, and borates: Implications for unique reactivity toward alcohols

Article abstract of DOI:10.1021/om061121w

The reactions of (ArN)VMe(N=C^tBu₂)₂ (1, Ar = 2,6-Me₂C₆H₃) with various alcohols, thiols, and borates (Broensted and/or Lewis acids) were investigated. Treatment of complex 1 with 1.0 equiv of various alcohols cleanly afforded other methyl complexes of the type (ArN)VMe(N=C^tBu₂)(OR) [OR = O-2,6-Me₂C₆H₃ (2a), O-4-^tBu-2,6- ⁱPr₂C₆H₂ (2b), OPh (2c), OC ₆F₆ (2d), OⁱPr (2e), OCH₂CH ₂-CH=CH₂ (2f), OCH₂(CH₂) ₃CH=CH₂ (2g)], and a reaction with the methyl group did not occur in all cases. In contrast, protonolysis of the methyl group took place in the reaction of 1 with 2,6-Me₂C₆H₃SH or 1-hexanethiol. The reaction of 1 with [PhN(H)Me₂][B(C ₆F₅)₄] and [Ph₃C][B(C ₆F₅)₄] in THF gave the cationic complex [(ArN)V(N=C^tBu₂)₂(THF)₂][B(C ₆F₅)₄] (4a), exclusively through abstraction or protonolysis of the methyl group. The reaction of 2a (or 2b) with 2,6-Me ₂C₆H₃OH (or 4-^tBu-2,6- ⁱPr₂C₆H₂OH) gave the bis(aryloxo) complex (ArN)VMe(OAr′)₂ [Ar′ = O-2,6-Me₂C ₆H₃ (5a), O-4-^tBu-2,6-ⁱPr ₂C₆H₂ (5b)], and the reaction with a methyl group did not occur even in the presence of an additional equivalent of phenol. The reaction of 2a with 4-^tBu-2,6-ⁱPr₂C ₆H₂OH at 25 °C afforded the aryloxo scrambled mixture of 2a and 2b and then gave three bis(aryloxo) analogues upon heating to 60 °C for 12 h. The results clearly indicate that the reactions with phenols proceed via pentacoordinated trigonal bipyramidal intermediates formed by coordination of the oxygen atom in the phenol trans to the methyl group.

Full text of DOI:10.1021/om061121w

Organometallics 2007, 26, 2579-2588
2579
Synthesis of Various (Arylimido)vanadium(V)-Methyl Complexes
Containing Ketimide Ligands and Reactions with Alcohols, Thiols,
and Borates: Implications for Unique Reactivity toward Alcohols
Junji Yamada, Michiya Fujiki, and Kotohiro Nomura*
Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama,
Ikoma, Nara 630-0101, Japan
ReceiVed December 11, 2006
The reactions of (ArN)VMe(NdCtBu2)2 (1, Ar ) 2,6-Me2C6H3) with various alcohols, thiols,
and borates (Bro¨nsted and/or Lewis acids) were investigated. Treatment of complex 1 with 1.0 equiv of
various alcohols cleanly afforded other methyl complexes of the type (ArN)VMe(NdCtBu2)(OR)
[OR ) O-2,6-Me2C6H3 (2a), O-4-tBu-2,6-iPr2C6H2 (2b), OPh (2c), OC6F6 (2d), OiPr (2e), OCH2CH2-
CHdCH2 (2f), OCH2(CH2)3CHdCH2 (2g)], and a reaction with the methyl group did not occur
in all cases. In contrast, protonolysis of the methyl group took place in the reaction of 1 with 2,6-
Me2C6H3SH or 1-hexanethiol. The reaction of 1 with [PhN(H)Me2][B(C6F5)4] and [Ph3C][B(C6F5)4] in
THF gave the cationic complex [(ArN)V(NdCtBu2)2(THF)2][B(C6F5)4] (4a), exclusively through
abstraction or protonolysis of the methyl group. The reaction of 2a (or 2b) with 2,6-Me2C6H3OH (or
4-tBu-2,6-iPr2C6H2OH) gave the bis(aryloxo) complex (ArN)VMe(OAr′)2 [Ar′ ) O-2,6-Me2C6H3 (5a),
O-4-tBu-2,6-iPr2C6H2 (5b)], and the reaction with a methyl group did not occur even in the presence of
an additional equivalent of phenol. The reaction of 2a with 4-tBu-2,6-iPr2C6H2OH at 25 °C afforded the
aryloxo scrambled mixture of 2a and 2b and then gave three bis(aryloxo) analogues upon heating to 60
°C for 12 h. The results clearly indicate that the reactions with phenols proceed via pentacoordinated
trigonal bipyramidal intermediates formed by coordination of the oxygen atom in the phenol trans to the
methyl group.
organic reactions, especially with regard to catalytic cycles or
reaction pathways. Some classical Ziegler-type vanadium
catalysts are known to exhibit unique characteristics, such as
the synthesis of ultrahigh molecular weight polymer with a
relatively narrow polydispersity through rapid propagation in
olefin coordination/insertion polymerization and the synthesis
of propylene-methyl methacrylate diblock copolymers by living
polymerization.2e,3,4 Therefore, the synthesis and reaction chem-
istry of vanadium complexes, especially (cationic) alkyl com-
plexes, have attracted considerable attention.5-8 Some reactions
Introduction
Transition metal-alkyl complexes are some of the most
important reagents or intermediates in stoichiometric/catalytic
organic reactions, as well as in olefin polymerization.1,2 The
synthesis and reaction chemistry of transition metal-alkyl
complexes have thus been important in the design of efficient
catalysts as well as for obtaining a better understanding of the
* Corresponding author. Tel: +81-743-72-6041. Fax: +81-743-72-6049.
E-mail: nomurak@ms.naist.jp.
(1) For example (general text of metal-alkyl chemistry): (a) In The
Organometallic Chemistry of the Transition Metals, 4th ed.; Crabtree, R.
H., Ed.; John Wiley & Sons, Inc.: Hoboken, NJ, 2005; p 53. (b) In Synthesis
of Organometallic Compounds: A Practical Guide; Komiya, S., Ed.; John
Wiley & Sons Ltd.: West Sussex, England, 1997.
(2) Related reviews for olefin polymerization catalysts (including
vanadium complexes): (a) Gambarotta, S. Coord. Chem. ReV. 2003, 237,
229. (b) Hagen, H.; Boersma, J.; van Koten, G. Chem. Soc. ReV. 2002, 31,
357. (c) Bolton, P. D.; Mountford, P. AdV. Synth. Catal. 2005, 347, 355.
(d) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003, 103, 283. (e)
Nomura, K. In New DeVelopments in Catalysis Research; Bevy L. P., Ed.;
Nova Science Publishers, Inc.: New York, 2005; p 199.
(3) Pioneering 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)
Junghanns, V. E.; Gumboldt, A.; Bier, G. Makromol. Chem. 1962, 58, 18.
(d) Carrick, W. L.; Reichle, W. T.; Pennella, F.; Smith. J. J. J. Am. Chem.
Soc. 1960, 82, 3887. (e) Natta, G.; Mazzanti, G.; Valvassori, A.; Sartori,
G.; Fiumani, D. J. Polym. Sci. 1961, 51, 411. (f) Gumboldt, V. A.; Helberg,
J.; Schleitzer, G. Makromol. Chem. 1967, 101, 229. (g) Lehr, M. H.
Macromolecules 1968, 1, 178. (h) Christman, D. L.; Keim, G. I. Macro-
molecules 1968, 1, 358. (i) Christman, D. L. J. Polym. Sci., Polym. Chem.
Ed. 1972, 10, 471.
(5) Some structural characterizations and reaction chemistry of V(III),-
(IV) methyl complexes: (a) Hessen, B.; Teuben, J. H.; Lemmen, T. H.;
Huffman, J. C.; Caulton, K. G. Organometallics 1985, 4, 946. (b) Hessen,
B.; Lemmen, T. H.; Luttikhedde, H. J. G.; Teuben, J. H.; Petersen, J. L.;
Jagner, S.; Huffman, J. C.; Caulton, K. G. Organometallics 1987, 6, 2354.
(c) Hessen, B.; Meetama, A; Teuben, J. H. J. Am. Chem. Soc. 1989, 111,
5977. (d) Gerlach, C. P.; Arnold, J. Organometallics 1996, 15, 5260. (e)
Aharonian, G.; Feghali, K.; Gambarotta, S.; Yap, G. P. A. Organometallics
2001, 20, 2616. (f) Feghali, K.; Harding, D. J.; Reardon, D.; Gambarotta,
S.; Yap, G.; Wang. Q. Organometallics 2002, 21, 968. (g) Choukroun, R.;
Lorber, C.; Donnadieu, B. Organometallics 2002, 21, 1124. (h) Liu, G.;
Beetstra, D. J.; Meetsma, A.; Hessen, B. Organometallics 2004, 23, 3914.
(6) Examples for structurally characterized V(V) alkyls: (a) de With,
J.; Horton, A. D.; Orpen, A. G. Organometallics 1990, 9, 2207. (b) Murphy,
V. J.; Turner, H. Organometallics 1997, 16, 2495.
(7) Examples: (a) Preuss, F.; Ogger, L. Z. Naturforsch. 1982, 37B, 957.
(b) Devore, D. D.; Lichtenhan, J. D.; Takusagawa, F.; Maatta, E. J. Am.
Chem. Soc. 1987, 109, 7408. (c) Preuss, F.; Becker, H.; Kraub, J.; Sheldrick,
W. J. Z. Naturforsch. 1988, 43B, 1195. (d) Preuss, F.; Becker, H.; Wieland,
T. Z. Naturforsch. 1990, 45B, 191. (e) Solan, G. A.; Cozzi, P. G.; Floriani,
C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1994, 13, 2572. (f) Chan,
M. C. W.; Cole, J. M.; Gibson, V. C.; Howard, J. A. K. Chem. Commun.
1997, 2345.
(4) Pioneering examples for synthesis of block copolymers by living
polymerization using vanadium catalysts: (a) Doi, Y.; Ueki, S.; Soga, K.
Macromolecules 1979, 12, 814. (b) Doi, Y.; Hizal, G.; Soga, K. Makromol.
Chem. 1987, 188, 1273.
(8) Our previous examples: (a) Yamada, J.; Fujiki, M.; Nomura, K.
Organometallics 2005, 24, 2248. (b) Yamada, J. and Nomura, K. Orga-
nometallics 2005, 24, 3621.
10.1021/om061121w CCC: $37.00 © 2007 American Chemical Society
Publication on Web 04/07/2007

2580 Organometallics, Vol. 26, No. 10, 2007
Yamada et al.
Scheme 1
Scheme 2
concerning (cationic) vanadium-alkyl complexes that contain
one or two cyclopentadienyl (Cp′) ligands have been described
in the literature5a-c with regard to titanocene (zirconocene) or
half-titanocene.9 However, there are still few examples of the
synthesis of vanadium-alkyls that do not include the Cp′ ligand.
This may be due to the fact that these vanadium-alkyls tend
to be reactive and/or thermally labile, and reductions to lower
oxidation states were often observed in reactions with organo-
metallic reagents.7
In general, metal-alkyl bonds, especially those with early
transition metals, are more nucleophilic than those with late
transition metals and are thus highly reactive toward Bro¨nsted/
Lewis acids.1,9,10 For instance, cationic alkyl complexes, which
have been proposed to be the catalytically active species for
olefin coordination polymerization, are generated from their
dialkyl analogues by reacting them with cocatalysts via facile
protonolysis or alkyl abstraction.9 Some organometallic com-
plexes can thus be grafted onto a silica surface through the
reaction of alkyl compounds with the silanol groups on the
surface.9c,11,12
We recently communicated the synthesis and structural
characterization of a vanadium-methyl complex of the type
(ArN)V(Me)(NdCtBu2)2 (1, Ar ) 2,6-Me2C6H3).8b Complex 1
showed unique reactivity toward alcohols (phenols) to exclu-
sively give various methyl complexes by ligand exchange
between the ketimide and alkoxy (aryloxo) groups without
accompanying protonolysis of the methyl group with the
alcohols (phenols). The results clearly indicated that the methyl
group in 1 is not reactive toward alcohol under these conditions,8b
although ordinary metal-alkyl bonds (especially in early
transition metals) readily react with alcohol to give alkoxide
(aryloxide).10-12 Therefore, we conducted some reactions of 1
with various alcohols, thiols, and borates, including the isolation
of cationic vanadium(V) complexes, to examine why 1 did not
react with alcohol.
Scheme 3
prepared by treating (ArN)VCl(NdCtBu2)2 with 1.0 equiv of
MeMgBr in Et2O (yield 85%), as described previously (Scheme
1).8b Alternatively, 1 could also be prepared directly from (ArN)-
VCl3 without isolation of (ArN)VCl(NdCtBu2)2 (yield 58%).
The crystal structure8b showed that 1 has a distorted tetrahedral
geometry around the vanadium, and the V-N(CtBu2) distances
(1.825-1.827 Å) are slightly longer than those in the chloride
complex (1.803-1.805 Å).8b The V-Me distance (2.064 Å) is
within the range of V(V)-C bond lengths in (arylimido)-
vanadium(V)-dibenzyl analogues (2.026-2.103 Å)6b and is
close to that in Li[(tBu3SiN)2VMe2] (2.043, 2.050 Å);6a the
distance is shorter than those in some V(II-IV)-Me complexes
(2.118,6f 2.206-2.222 Å5a,b,g,h).
Reactions of 1 with 1.0 equiv of phenols exclusively gave
another vanadium(V)-methyl complex of the type (ArN)VMe-
(NdCtBu2)(OAr′) [Ar′ ) 2,6-Me2C6H3 (a), 4-tBu-2,6-iPr2C6H2
(b), Ph (c), OC6F5 (d)], by replacement with the ketimide ligand
(Scheme 2).8b The reaction with the methyl group did not
proceed under these conditions, although 1 is a rather electron-
deficient vanadium(V)-alkyl complex, and no significant
differences were observed in the corresponding resonances (in
1H and 13C NMR spectra) as well as in the V-Me bond distance
(2.064 Å) from those of reported vanadium-methyl complexes.5
The selectivity in the reaction was not dependent upon the kind
of phenol employed, and the exchange reaction of 1 took place
Results and Discussions
1. Synthesis of (ArN)VMe(NdCtBu2)2 (1) and Reactions
of Alcohols and Thiols. The vanadium(V)-methyl complex,
of the type (ArN)VMe(NdCtBu2)2 (1, Ar ) 2,6-Me2C6H3), was
(9) For example (reviews): (a) Jordan, R. F. AdV. Organomet. Chem.
1991, 32, 325. (b) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger,
B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (c)
Chen, E. Y-. X.; Marks, T. J. Chem. ReV. 2000, 100, 1391.
(10) For example: In ComprehensiVe Organometallic Chemistry II; Abel,
F. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press: Oxford, 1995;
Vol. 4.
(11) Related review article: (a) Cope´ret, C.; Chavanas, M.; Saint-
Arroman, R. P.; Basset, J. M. Angew. Chem., Int. Ed. 2003, 42, 156. (b)
Thomas, J. M.; Raja, R.; Lewis, D. W. Angew. Chem., Int. Ed. 2005, 44,
6456.
(12) Recent examples: (a) Rhers, B.; Salameh, A.; Baudouin, A.;
Quadrelli, E. A.; Taoufik, M.; Cope´ret, C.; Lefebvre, F.; Basset, J. -M.;
Solans-Monfort, X.; Eisenstein, O.; Lukens, W. W.; Lopez, L. P. H.; Sinha,
A.; Schrock, R. R. Organometallics 2006, 25, 3554. (b) Nicholas, P.; Ahn,
H. S.; Marks, T. J. J. Am. Chem. Soc. 2003, 125, 4325. (c) McKittrick, M.
W.; Jones, C. W. J. Am. Chem. Soc. 2004, 126, 3052.

Reaction of (ArN)VMe(X)2 with Alcohols, Thiols, and Borates
Organometallics, Vol. 26, No. 10, 2007 2581
Table 2. Selected Bond Distances (Å) and Angles (deg) for
[V(N-2,6-Me2C6H3)(NdCtBu2)2(THF)2][B(C6F5)4] (4a)
Bond Distances
V(1)-O(1)
V(1)-N(1)
V(1)-N(3)
N(2)-C(9)
2.007 (2)
1.655 (2)
1.808 (2)
1.264 (4)
V(1)-N(2)
N(1)-C(1)
N(3)-C(18)
1.808 (2)
1.385 (4)
1.260 (4)
Bond Angles
O(1)-V(1)-N(1)
O(1)-V(1)-N(3)
N(1)-V(1)-N(3)
N(2)-V(1)-N(3)
V(1)-N(2)-C(9)
100.40 (12)
109.02 (12)
107.65 (13)
122.22 (13)
171.6 (2)
O(1)-V(1)-N(2)
107.27 (10)
N(1)-V(1)-N(2)
V(1)-N(1)-C(1)
V(1)-N(3)-C(18)
108.11 (13)
174.6 (2)
178.9 (3)
Table 3. Crystal Data and Collection Parameters of
Complexes 3a and 4aa
3a
4a
formula
fw
C34H54N3SV
587.82
C54H53BF20N3OV
1201.75
cryst color, habit
cryst size (mm)
cryst syst
space group
a (Å)
brown, prism
0.80 × 0.60 × 0.20
monoclinic
P21/c (#14)
12.086(3)
16.246(4)
17.986(7)
84.449(14)
3515.1(18)
4
red, block
0.80 × 0.80 × 0.44
monoclinic
P21/c (#14)
15.606(5)
15.262(4)
24.342(6)
93.897(13)
5784.3(27)
4
b (Å)
c (Å)
Figure 1. ORTEP drawing (30% probability ellipsoids) of 3a. All
hydrogen atoms are omitted for clarity.
â (deg)
V (Å3)
Z value
D
calcd (g/cm3)
1.111
1.380
F000
1272.00
2456.0
temp (K)
243
3.658
6.05-54.97
33 359
243
2.752
6.01-54.97
53 601
µ(Mo KR) (cm-1
2θ range (deg)
)
no. of reflns measd
no. of observations
(I > 2.00σ(I))
no. of variables
R1
11 424
7733
406
802
0.0627
0.1220
1.002
0.0565
0.1632
1.004
wR2
goodness of fit
a Diffractometer: Rigaku RAXIS-RAPID imaging plate. Structure solu-
tion: direct methods. Refinement: full-matrix least-squares. Function
minimized: ∑w(|Fo| - |Fc|)2 (w ) least-squares weights). Standard
deviation of an observation of unit weight: [∑w(|Fo| - |Fc|)2/(No - Nv)]1/2
(No ) number of observations, Nv ) number of variables).
of the ketimide with alkoxide was also observed in the reaction
of 1 with 3-buten-1-ol or 5-hexen-1-ol in n-hexane to give the
corresponding (ArN)VMe(NdCtBu2)[OCH2(CH2)nCHdCH2] [n
) 1 (2f), 3 (2g)] exclusively (86% for 2f, 66% for 2g,
respectively, Scheme 2).13-15 Both 2f and 2g gave two
resonances in the 51V NMR spectra, and the ratios were highly
dependent upon the temperature measured.13 The species in the
higher field was observed exclusively at 60 °C and was
identified as olefin dissociated species (2fdis and 2gdis) based
on 1H NMR spectra, not only because the resonances observed
at 4.5-6.0 ppm were identical to those in our previous example
with Ti,15 but also because the reaction of 1 with n-hexanol
Figure 2. ORTEP drawing (30% probability ellipsoids) of 4a.
B(C6F5)4 and all hydrogen atoms are omitted for clarity.
Table 1. Selected Bond Distances (Å) and Angles (deg) for
V(N-2,6-Me2C6H3)(NdCtBu2)2(S-2,6-Me2C6H3) (3a)
Bond Distances
V(1)-S(1)
V(1)-N (1)
V(1)-N (3)
N(2)-C (9)
2.300 (4)
1.661 (4)
1.819 (2)
1.267 (2)
S(1)-C(27)
V(1)-N(2)
N(1)-C(1)
N(3)-C(18)
1.775 (2)
1.808 (3)
1.389 (2)
1.267 (2)
(13) For more details, see the Supporting Information.
(14) Selected related examples for synthesis of Ti(IV) or Zr(IV)
alkoxide-alkene complexes: (a) Wu, Z.; Jordan, R. F.; Petersen, J. L.
J. Am. Chem. Soc. 1995, 117, 5867. (b) Carpentier, J. F.; Wu, Z.; Lee,
C. W.; Stro¨mberg, S.; Christopher, J. N.; Jordan, R. F. J. Am. Chem. Soc.
2000, 122, 7750. (c) Carpentier, J.-F.; Maryin, V. P.; Luci, J.; Jordan,
R. F. J. Am. Chem. Soc. 2001, 123, 898. (d) Stoebenau, E. J., III;
Jordan, R. F. J. Am. Chem. Soc. 2003, 125, 3222. (e) Stoebenau, E. J., III;
Jordan, R. F. J. Am. Chem. Soc. 2004, 126, 11170. (f) Stoebenau, E. J., III;
Jordan, R. F. J. Am. Chem. Soc. 2006, 128, 8162.
Bond Angles
N(1)-V(1)-S(1)
N(3)-V(1)-S(1)
N(3)-V(1)-N(1)
V(1)-N(1)-C(1)
V(1)-N(3)-C(18)
100.77 (7)
112.21 (6)
112.09 (8)
166.55 (2)
166.84 (2)
N(2)-V(1)-S(1)
N(2)-V(1)-N(1)
N(3)-V(1)-N(2)
V(1)-N(2)-C(9)
V(1)-S(1)-C(27)
116.22 (7)
107.95 (9)
107.49 (8)
172.8 (2)
108.14 (8)
(15) Synthesis and structural determination of Cp*TiMe[OCH2(CH2)n-
CHdCH2](O-2,6-iPr2C6H3) (n ) 1, 3) and Cp*Ti(CF3SO3)[OCH2(CH2)n-
CHdCH2](O-2,6-iPr2C6H3): Nomura, K.; Hatanaka, Y. Inorg. Chem.
Commun. 2003, 6, 517.
exclusively even with C6F5OH (to give 2d). Treatment of 1 with
iPrOH afforded (ArN)VMe(NdCtBu2)(OiPr) (2e), and the
reaction with the methyl group did not take place.8b The reaction

2582 Organometallics, Vol. 26, No. 10, 2007
Yamada et al.
Scheme 4
afforded a species observed at -238 ppm in the 51V NMR
spectrum that was accompanied by the formation of HNdCt-
Bu2, as reported previously.8b In contrast, the species observed
in the lower field became dominant below -40 °C, and we
assume that this would be the olefin-coordinated species (2fco
and 2gco).16 The insertion did not take place under these
conditions. ∆G values of 8.5 kcal/mol for 2f and 8.6 kcal/mol
for 2g were thus assumed from the 51V NMR spectra measured
at various temperatures (-60 to 60 °C).13 There was no
significant difference in the effect of the methylene length in
alkene-1-ol (3-buten-1-ol vs 5-hexen-1-ol) on the integration
ratios (equilibrium) between the coordinated and dissociated
species, and these findings were somewhat different from
those in our previous report with titanium, Cp*Ti(CF3SO3)-
[OCH2(CH2)nCHdCH2](O-2,6-iPr2C6H3) (n ) 1, 3), whereas
olefin did not coordinate with titanium.15
Scheme 5
reaction with various alcohols. It is well known that cationic
alkyl complexes, which have been proposed to be the catalyti-
cally active species for olefin coordination polymerization, are
generated from its dialkyl analogues by reacting with borates.9
To examine the detailed reactivity of the V-Me bond in 1,
reactions with borates (strong Brønsted acid) were conducted
in this study.
The reaction of 1 with 1.0 equiv of [PhN(H)Me2][B
(C6F5)4] in THF afforded cationic [(ArN)V(NdCtBu)2(THF)2]-
[B(C6F5)4] (4a) via protonolysis of the V-Me bond and free
PhNMe2. The exclusive formation of these compounds was
confirmed by NMR spectroscopy (Scheme 4). The same
compound (4a) could be isolated by the reaction of 1 with 1.0
equiv of [Ph3C][B(C6F5)4], a strong alkyl abstracting reagent,
To examine why the methyl group in 1 did not react with
alcohol, we planned the reaction of 1 with thiols. The reaction
of 1 with 1.0 equiv of 2,6-Me2C6H3SH afforded (ArN)V(Nd
CtBu2)2(S-2,6-Me2C6H3) (3a) via cleavage of the V-Me bond
by facile protonolysis (75% yield, Scheme 3). The product was
1
identified by H, 13C, and 51V NMR spectra, and the structure
was determined by X-ray crystallography, as shown in Figure
1. Selected bond distances and angles are also summarized in
Table 1. The crystal structure showed that 3a has a distorted
tetrahedral geometry around the vanadium metal center, and
the V-N(CtBu2) distances (1.808-1.819 Å) were intermediate
between those in the chloride analogue (ArN)VCl(NdCtBu2)2
(1.803-1.805 Å)8b and the methyl analogue (1, 1.825-1.827).
The V-S distance (2.300 Å) is slightly longer than those in
V(NC6H4Cl-4)[N(CH2CH2S)3] (2.251 Å)17b and [V(CH3CN)6]-
[VCl2{O(CH2CH2S)2}]2,17c is close to that in the penta-
coordinated vanadium(III) thiolate complex V[P(C6H4-2-S)3]
(1-methylimidazole) (average 2.302 Å)18 and V(O-2,6-i-
Pr2C6H3){O(CH2CH2S)2}(pyridine) (average 2.298 Å),17a
and is within the range expected for V-S single bonds
and comparable to those in other vanadium(III) thiolate com-
plexes.19
(16) A reviewer pointed out a possibility of formation of the [2+2]
adduct with the arylimido complex as proposed by Odom et al. for
synthesis of amines by titanium-mediated transfer of alkenyl groups from
alcohol (Ramanathan, B.; Odom, A. L. J. Am. Chem. Soc. 2006, 128, 9344.
Related report for hydroamination of alkynes by (arylimido)
vanadium complexes: Lorber, C.; Choukroun, R.; Vendier, L. Organome-
tallics 2004, 23, 1845). However, no significant differences in the resonances
ascribed to aromatic and methyl protons in the arylimido ligand
were observed between the dissociated and (proposed) coordinated species
in the 1H NMR spectra, and the observed equilibrium is reversible. In
addition, no resonances ascribed to the carbene species were seen. On the
basis of these results, it is concluded that the formed species are simple
olefin-coordinated species, although we could not completely exclude a
possibility of formation of the metallacycle. For example (tungsten,
titanium): (a) Bennett, J.; Wolczanski, P. T. J. Am. Chem. Soc. 1997, 119,
10696. (b) Lokare, K. S.; Ciszewski, J. T.; Odom, A. L. Organometallics
2004, 23, 5386. K.N. expresses his thanks to a reviewer for pointing out
this issue.
(17) (a) Janas, Z.; Jerzykiewicz, L. B.; Richards, R. L.; Sobota, P. Chem.
Commun. 1999, 1105. (b) Davies, S. C.; Hughes, D. L.; Janas, Z.;
Jerzykiewicz, L. B.; Richards, R. L.; Sanders, J. R.; Silverston, J. E.; Sobota,
P. Inorg. Chem. 2000, 39, 3485. (c) Janas, Z.; Jerzykiewicz, L. B.;
Przybylak, S.; Richards, R. L.; Sobota, P. Organometallics 2000, 19, 4252.
(18) Hsu, H. F.; Chu, W. C.; Hung, C. H.; Liao, J. H. Inorg. Chem.
2003, 42, 7369.
(19) For other examples: (a) Randall, C. R.; Armstrong, W. H. J. Chem.
Soc., Chem. Commun. 1988, 986. (b) Davies, S. C.; Hughes, D. L.;
Janas, Z.; Jerzykiewicz, L. B.; R. L. Richards, R. L.; Sanders, J. R.;
Sobota, P. Chem. Commun. 1997, 1261. (c) Henkel, G.; Krebs, B.;
Schmidt, W. Angew. Chem., Int. Ed. Engl. 1992, 31, 1366. (d) Wiggins, R.
W.; Huffman, J. C.; Christou, G. J. Chem. Soc., Chem. Commun. 1983,
1313. (e) Szeymies, D.; Krebs B.; Henkel, G. Angew. Chem., Int. Ed. Engl.
1983, 22, 885. (f) Dorfman, J. R.; Holm, R. H. Inorg. Chem. 1983,
22, 3179.
The reaction of 1 with n-C6H13SH in n-hexane afforded
(ArN)V(NdCtBu2)2(S-n-C6H13) (3b) as the sole product, as
1
confirmed by both H and 13C NMR spectra, via cleavage of
the V-Me bond by facile protonolysis. These facts clearly
indicate that the reaction mechanism should differ between
alcohol and thiol, and the reaction with thiols favored proto-
nolysis with V-Me bonds as seen in ordinary metal akyl
complexes with early transition metals.1,9,10
2. Reactions of (ArN)VMe(NdCtBu2)2 (1) with Various
Borates. As described above, cleavage of the V-Me bond in
1 was favored in the reaction with thiols, whereas exclusive
ligand exchanges with the ketimide ligand were seen in the

Reaction of (ArN)VMe(X)2 with Alcohols, Thiols, and Borates
Organometallics, Vol. 26, No. 10, 2007 2583
Figure 3. 51V NMR spectra of the reaction of 2a with 4-tBu-2,6-iPr2C6H2OH (a-d) and 2b with 2,6-Me2C6H3OH (e-h) in CDCl3.
51V NMR spectra for (a) 2a, (b) reaction mixture of 2a with 4-tBu-2,6-iPr2C6H2OH (after 30 min at 25 °C), (c) reaction mixture of 2a with
4-tBu-2,6-iPr2C6H2OH (at 60 °C for additional 12 h after b), and (d) 5a. 51V NMR spectra for (e) 2b, (f) reaction mixture of 2b
with 2,6-Me2C6H2OH (after 30 min at 25 °C), (g) reaction mixture of 2b with 2,6-Me2C6H2OH (at 60 °C for additional 12 h after f), and
(h) 5b.
Scheme 6
and the quantitative formation of 4a and Ph3CCH3 was
clean 1H and 51V NMR spectra in addition to resonances
ascribed to the formation of MeB(C6F5)3 (0.48 ppm, B-Me),
which strongly suggested the exclusive formation of [(ArN)V-
(NdCtBu)2(THF)2][MeB(C6F5)3] (4b).
1
confirmed by H and 51V NMR spectra. Compound 4a could
1
be cleanly isolated (90%) and was identified by H, 13C, 19F,
and 51V NMR spectra and elemental analysis. On the basis of
the results of both the 1H NMR spectrum and elemental analysis,
two THF molecules per vanadium remained in the resultant red
microcrystals. The reaction of 1 with B(C6F5)3 also gave similar
1
Moreover, the H and 51V NMR spectra for the reaction
of 2a with 1.0 equiv of [PhN(H)Me2][B(C6F5)4] also suggested
the exclusive formation of the corresponding cationic species

2584 Organometallics, Vol. 26, No. 10, 2007
Yamada et al.
Scheme 7
4c via protonolysis of
a
V-Me group accompanied
3. Mechanistic Studies for Reaction of (2,6-Me2C6H3N)-
VMe(NdCtBu2)2 (1) with Alcohol. Exploration for Unique
Reactivity of the Vanadium-Methyl Bonds toward Alcohol.
As described above, the V-Me bond in 1 reacted with thiols
and borates, whereas the V-Me bond in 1 did not react with
alcohols. To explain this unique reactivity of 1, especially toward
alcohol, we explored the reaction chemistry in more detail.
by the liberation of free PhNMe2. These results clearly
indicated that cleavage of the V-Me bond was favored in all
cases.
Red block microcrystals of 4a suitable for X-ray crystal-
lographic study were obtained from a chilled (-30 °C) and
concentrated THF solution containing 4a layered by n-hexane
(Figure 2). Selected bond distances and angles for 4a are
summarized in Table 2. The crystallographic analysis of 4a
indicates that 4a has a pseudo-tetrahedral geometry around the
vanadium center with the coordination of one THF molecule.
The position of another THF molecule could not be defined/
determined probably because the THF molecule might be
located among crystal lattices. The V-N(CtBu2) distances
(1.802-1.808 Å) are comparable to those found in (ArN)VCl-
(NdCtBu2)2 and somewhat shorter than those in 1. The V-O
distance (2.007 Å) is similar to that found in four-coordinated
cationicvanadium(IV)alkylidenecomplex(2.000Å)[(Nacnac)Vd
CHtBu(THF)](BPh4) [Nacnac ) {ArNC(Me)CHC(Me)NAr}-,
Ar ) 2,6-iPr2C6H3]20 and somewhat shorter than that found in
THF-coordinated vanadium(III) complexes containing amine
tris(phenolate) and triamidoamine ligands (2.107-2.152 Å).21
When 1.0 equiv of 2,6-Me2C6H3OH was added to a Teflon-
sealed NMR tube containing a CDCl3 solution of 2a, the
formation of HNdCtBu2 (1.31 and 9.39 ppm) was observed in
1
the H NMR spectrum. In contrast, the generation of methane
was not observed even after 24 h. A new resonance at -64
ppm was observed in the 51V NMR spectrum in addition to 2a
(-185 ppm) in the above CDCl3 solution, and the conversion
of 2a reached 60% after 24 h (at 25 °C). This result is in unique
contrast to that in the reaction of 1 with 2,6-Me2C6H3OH, since
the reaction was complete within 30 min (starting at -30 to
25 °C). The quantitative conversion of 2a could be achieved if
2.0 equiv of 2,6-Me2C6H3OH was added to 2a after 24 h (at
25 °C). Note that the formation of methane was not observed
even if 2.0 equiv of 2,6-Me2C6H3OH was added to 2a. The 1H
NMR spectra for the resultant compound showed resonances
that could be assigned to the ketimide/aryloxo exchange reaction
product, (ArN)VMe(O-2,6-Me2C6H3)2 (5a), according to the
integration ratio of the aryloxo group and the arylimido group
in addition to a resonance at 2.11 ppm ascribed to the
vanadium-methyl bond as well as to the disappearance of the
(20) Basuli, F.; Kilgore, U. J.; Hu, X.; Meyer, K.; Pink, M.; Huffman,
J. C.; Mindiola, D. J. Angew. Chem., Int. Ed. 2004, 43, 3156.
(21) (a) Nomura, K.; Schrock, R. R.; Davis, W. M. Inorg. Chem. 1996,
35, 3695. (b) Groysman, S.; Goldberg, I.; Goldschmidt, Z.; Kol, M. Inorg.
Chem. 2005, 44, 5073. (c) Smythe, N. C.; Schrock, R. R.; Mu1ller, P.;
Weare, W. W. Inorg. Chem. 2006, 45, 9197.

Reaction of (ArN)VMe(X)2 with Alcohols, Thiols, and Borates
Organometallics, Vol. 26, No. 10, 2007 2585
ketimide ligand (Scheme 5). The formation of 5a could also be
confirmed by comparison of the resonances in 1H and 51V NMR
spectra for the bis(aryloxo)-chloro analogue, (ArN)VCl(O-2,6-
Me2C6H3)2 (6), and the tris(aryloxo) analogue, (ArN)V(O-2,6-
Me2C6H3)3 (7), which could be prepared and identified inde-
pendently by the reaction of (ArN)VCl3 with 2.0 or 3.0 equiv
of LiO-2,6-Me2C6H3 in Et2O according to an analogous method
for the preparation of (ArN)VCl2(O-2,6-Me2C6H3).22,23 It should
be noted that the vanadium-methyl bond in the bis(aryloxo)
analogue (5a) was stable even in the presence of an additional
1.0 equiv of 2,6-Me2C6H3OH, and no reaction took place upon
stirring for long hours (after 24 h at 25 °C). The formation of
(ArN)VMe(O-4-tBu-2,6-iPr2C6H2)2 (5b) was also confirmed by
the reaction of 2b with 4-tBu-2,6-iPr2C6H2OH under the similar
conditions (12 h).
favored.25 Thus, on the basis of Scheme 7, it is assumed that
proton migration to the aryloxide ligand occurred quickly,
whereas migration to the ketimide ligand was relatively slow
under these conditions.26
Conclusion
We have explored the reactions of (ArN)VMe(NdCtBu)2 (1)
with various alcohols, thiols, and borates. The reaction of the
V-Me bonds in 1 with thiols and borates took place exclusively
to give corresponding thiolates and cationic complexes, respec-
tively. In contrast, the V-Me in 1 did not react with alcohols
to afford other methyl complexes via ligand substitution between
the ketimide and the alkoxide/phenoxide. The reaction of (ArN)-
VMe(NdCtBu)(OAr′) (2, Ar′ ) 2,6-Me2C6H3, 4-tBu-2,6-iPr2C6H2)
with phenols gave other methyl complexes, (ArN)VMe(OAr′)2
(5), and the reaction with the Me group did not occur even in
the presence of 2.0 equiv of phenol. On the basis of our experi-
ments, we propose that the reaction with alcohols proceeded in
the following steps: (1) the alcohols initially approached the
electron-deficient metal center trans to the methyl group to give
a pentacoordinated trigonal bipyramidal species, and (2) proton
transfer to the aryloxide/ketimide occurred to give ketimine/
phenol dissociation. In contrast to the reaction with alcohols,
facile protonolysis took place in the reaction of 1 or 2 with
thiols or borates to give thiolate complexes or cationic com-
plexes, respectively. These results should be useful for the
preparation of various vanadium-alkyl complexes as well as
to achieve a better understanding of the basic reaction mech-
anism in vanadium-catalyzed organic synthesis.
In order to explore the unique reactivity of the Me groups in
both 2a and 5a toward phenol, we performed the reaction of
2a with 4-tBu-2,6-iPr2C6H2OH (and 2b with 2,6-Me2C6H3OH)
according to Scheme 6, and the results are shown in Figure 3.
Rapid scrambling of 2a and 2b was seen when 2a was treated
with 1.0 equiv of 4-tBu-2,6-iPr2C6H2OH in CDCl3 at 25 °C
(Figure 3b), and the resultant solution eventually gave a ca. 1:1
mixture of 2a and 2b, as confirmed by 1H and 51V NMR spectra
(within 30 min at 25 °C). The solution gave three species, as
confirmed by the 51V NMR spectrum (-64, -70, and -78 ppm)
in an approximately 1:2:1 ratio, respectively (Figure 3c), upon
heating at 60 °C for 12 h. The resonances observed at -64 and
-78 ppm could be assigned as 5a and 5b, respectively, and we
estimated that the species at -70 ppm could be assigned as the
mixed bis(aryloxo) complex (ArN)VMe(O-4-tBu-2,6-iPr2C6H2)-
1
(O-2,6-Me2C6H3) (5c) on the basis of the H NMR spectrum.
Similar results were observed if 2b was treated with 2,6-
Me2C6H3OH in CDCl3, as shown in Figure 3e-h. The reaction
with the Me group did not occur in either 2a,b or 5a,b even
after 12 h at 60 °C.
Experimental Section
General Procedures. All experiments were carried out under a
nitrogen atmosphere in a Vacuum Atmospheres drybox or using
standard Schlenk techniques. Anhydrous-grade benzene, diethyl
ether, n-hexane, and THF (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 the drybox under N2 and were passed
through an short alumina column under N2 stream before use. All
chemicals used were of reagent grade and were purified by the
standard purification procedures. Reagent-grade B(C6F5)3, [Ph3CB]-
[(C6F5)4], and [PhN(H)Me2][B(C6F5)4] (Asahi Glass Co. Ltd.) were
stored in the drybox and were used as received. Synthesis of LiNd
CtBu2 was also according to the reported procedure.27 Elemental
We believe that these results clearly explain the unique
reactivity of both 1 and 2a,b toward alcohol according to
Scheme 7. Both phenol-scrambling and the phenol/ketimide
exchange reaction should be preferred if the phenol approaches
the electrophilic vanadium metal center trans to the Me group
(NNN face in 1 or NNO face in 2a,b, and not the NNC faces
in 1 or 2a,b), to give pentacoordinated trigonal bipyramidal
intermediates (shown in brackets in Scheme 7). The reaction
with the Me group would not occur if the reaction takes place
via this proposed intermediate. A similar assumption was also
proposed by Schrock et al.24 in the alkoxide exchange reaction
(25) The result for simple energy evaluations [coordination energies
defined as ∆Ecoord ) E(complex 1) + E(2,6-Me2C6H3OH) - E(proposed intermediate)
(complex 1), E(2,6-Me2C6H3OH), E(proposed intermediate) are heat of formation for
of Mo(NAr)(CHtBu)(CH2 Bu)(OAr) with ROH (OR ) OCMe3,
t
;
E
OAd, OC6F5; Ad ) adamantyl) and assumed a similar inter-
mediate. Simple PM3 estimation also suggests that the proposed
intermediate would be more stable than the other probable
intermediate.25 The same estimation suggests that the formation
of a similar intermediate caused destabilization in the reaction
with thiol, which suggests that simple protonation should be
complex 1, 2,6-Me2C6H3OH, and the proposed intermediates, respectively]
for three proposed intermediates in the reaction [equilibrium geometry at
ground state with semiempirical PM3, geometry optimization, RHF/PM3D
Spartan ’04 for Windows (Wavefunction Inc.)] suggested that co-
ordination of phenol trans to the methyl group seemed more stable (∆Ecoord
) 3.31 kcal/mol) than the others [∆Ecoord ) -1.97 and -24.88 kcal/mol
for the proposed intermediates when the phenol coordinates trans to
arylimido and ketimide, respectively]. In contrast, the coordination of 2,6-
Me2C6H3SH to the vanadium in 1 caused destabilization in all cases (∆Ecoord
) -5.21, -12.35, and -20.88 kcal/mol; 2,6-Me2C6H3SH trans to arylimido,
ketimide, and Me, respectively). These results may also suggest the
formation of five-coordinated trigonal bipyramidal species by coordination
of the phenol to 1, although more precise geometry optimizations are
necessary for a more precise evaluation.
(26) A reviewer commented that we do not mention the possibility of
the arylimido ligand acting as a proton shuttle. As described in ref 25 and
our experimental results, the reaction of 1 with thiols may occur by simple
protonolysis not by coordination of thiols, although we do not have clear
evidence for the mechanism.
(27) (a) Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J. Am. Chem. Soc.
2000, 122, 5499. (b) Zhang, S.; Piers, W. E. Organometallics 2001, 20,
2088.
(22) Nomura, K.; Sagara, A.; Imanishi, Y. Macromolecules 2002, 35,
1583.
(23) Although the exclusive formation of 5a could be confirmed by both
1H and 51V NMR spectra, an attempt to isolate 5a as microcrystals was
unsuccessful probably due to the improved solubility in organic solvent
and/or contamination of residual phenol in trace amounts. The identification
of 5a was thus made by comparison of both 1H and 51V NMR spectra with
the chloro-bis(aryloxo) analogue, (ArN)VCl(O-2,6-Me2C6H3)2 (6), and the
tris(aryloxo) analogue, (ArN)V(O-2,6-Me2C6H3)3 (7), which could be
prepared and identified independently by the reaction of (ArN)VCl3 with
2.0 or 3.0 equiv of LiO-2,6-Me2C6H3 in Et2O according to the analogous
method for the preparation of (ArN)VCl2(O-2,6-Me2C6H3).22
(24) Sinha, A.; Lopez, L. P. H.; Schrock, R. R.; Hock, A. S.; Mu¨ller, P.
Organometallics 2006, 25, 1412.

2586 Organometallics, Vol. 26, No. 10, 2007
Yamada et al.
analyses were performed by using a PE2400II Series (Perkin-Elmer
Co.). Some analytical runs were performed twice to confirm the
reproducibility in the independent analysis/synthesis runs.
127.0, 128.8, 135.8, 162.3, 165.3, 198.8. 51V NMR (CDCl3): δ
-153 (∆ν1/2 ) 1817 Hz). Anal. Calcd for C24H35N2OV: C, 68.88;
H, 8.43; N, 6.69. Found: C, 68.62; H, 8.36; N, 6.44.
Synthesis of VMe(N-2,6-Me2C6H3)(NCtBu2)(OC6F5) (2d). Syn-
thesis of 2d was carried out according to the same procedure as
that in 2a except that C6F5OH (92 mg, 0.50 mmol) was used in
place of 2,6-Me2C6H2OH. Yield: 202 mg (79%). 1H NMR
(CDCl3): δ 1.31 (s, 18H, (CH3)3C-), 1.49 (3H, V-CH3), 2.42 (s,
6H, CH3), 6.79 (t, 1H), 6.90 (d, 3H). 13C NMR (CDCl3): δ 18.7,
30.3, 43.1 (br, V-Me), 45.6, 125.1, 127.1, 133.4, 135.8, 136.6, 138.5,
139.1, 139.9, 140.9, 163.7, 203.9. 19F NMR (CDCl3): δ -171.64,
-167.13, -160.94. 51V NMR (CDCl3): δ -98 (∆ν1/2 ) 295 Hz).
1
All H, 13C, and 51V NMR spectra were recorded on a JEOL
1
JNM-LA400 spectrometer (399.65 MHz for H, 100.40 MHz for
13C, and 105.31 MHz for 51V), and 19F NMR spectra were recorded
on a JEOL JNM-ECP600NK spectrometer (564.69 MHz for 19F).
All spectra were obtained in the solvent indicated at 25 °C unless
otherwise noted. Chemical shifts are given in ppm and are
1
referenced to SiMe4 (δ 0.00, H, 13C), CF3C6H5 (δ -64.0, 19F),
H3PO4 (δ 0.00, 31P), and VOCl3 (δ 0.00, 51V). Coupling constants
and half-width values, ∆ν1/2, are given in Hz.
Synthesis of VMe(N-2,6-Me2C6H3)(NCtBu2)(OiPr) (2e). Syn-
thesis of 2e was carried out by the same procedure as that in 2a
except that iPrOH (48 mg, 0.80 mmol) was used in place of phenol.
One-Pot Synthesis of VMe(N-2,6-Me2C6H3)(NdCtBu2)2 (1).
To an Et2O solution (60 mL) containing VCl3(N-2,6-Me2C6H3)
(1.38 g, 5.0 mmol) was added LiNdCtBu2 (1.55 g, 10.5 mmol) at
-30 °C. The reaction mixture was warmed slowly to room
temperature (25 °C), and the mixture was stirred for an additional
6 h. MeMgBr (3.0 M in Et2O, 1.83 mL) was then added dropwise
to the reaction mixture that had been at -30 °C. The mixture was
then warmed slowly to room temperature and was stirred for an
additional 4 h. The solution was then placed in a rotary evaporator
in Vacuo to remove solvent (hexane, Et2O), and the resultant residue
was extracted with hot n-hexane (ca. 100 mL). The n-hexane extract
was then placed in Vacuo, and the resultant residue was layered by
n-hexane (ca. 10 mL) at -30 °C. The chilled solution was placed
1
Yield: 286 mg (93%). H NMR (CDCl3): δ 1.03 (3H, V-CH3),
1.28 (s, 18H, (CH3)3C-), 1.28 (d, 6H, (CH3)2CH-), 2.52 (s, 6H,
CH3), 4.87 (hept, 1H, (CH3)2CH-), 6.70 (t, 1H), 6.92 (d, 2H). 13
C
NMR (CDCl3): δ 19.3, 26.9, 30.5, 35.0 (br V-Me), 44.8, 77.6,
123.0, 127.0, 134.2, 161.8, 198.8. 51V NMR (CDCl3): δ -244
(∆ν1/2 ) 311 Hz).
Synthesis of VMe(N-2,6-Me2C6H3)(NCtBu2)(OCH2CH2CHd
CH2) (2f). Synthesis of 2f was carried out according to the same
procedure as that in 2a except that 3-butene-1-ol (30 mg, 0.42
mmol) was used in place of 4-tBu-2,6-iPr2C6H2OH. Yield: 137 mg
(86%). 1H NMR (CDCl3): δ 1.15 (s, br, 3H, V-CH3), 1.27 (s, 18H,
(CH3)3C-), 2.62 (2H, OCH2CH2), 2.62 [s, 6H, (CH3)2], 4.55 (2H),
4.75-4.86 (2H), 5.56 (1H), 6.76 (t, 1H), 6.93 (d, 2H). 13C NMR
(CDCl3): δ 14.2, 19.4, 22.6, 30.6, 31.6, 39.3, 42.6, 45.0, 45.6, 75.2,
116.4, 123.5, 127.3, 134.7, 137.3, 158.1, 185.8. 51V NMR
(CDCl3): δ -103 (∆ν1/2 ) 1632 Hz), -231 (∆ν1/2 ) 579 Hz).
Anal. Calcd for C22H37N2OV: C, 66.64; H, 9.41; N, 7.07. Found:
C, 66.95; H, 9.70; N, 6.76.
1
in the freezer to give red microcrystals. Yield: 1.35 g (58%). H
NMR (CDCl3): δ 0.88 (br, 3H, V-CH3), 1.31 (s, 18H, (CH3)3C-
), 2.44 (s, 6H, CH3), 6.67 (t, 1H), 6.86 (d, 2H). 13C NMR (CDCl3):
δ 19.4, 30.8, 36.7, 45.6, 122.2, 126.8, 134.1, 162.7, 199.4. 51V NMR
(CDCl3):
δ -138.8 (∆ν1/2 ) 324 Hz). Anal. Calcd for
C27H48N3V: C, 69.64; H, 10.39; N, 9.03. Found: C, 69.16; H,
10.14; N, 9.09.
Synthesis of VMe(N-2,6-Me2C6H3)(NCtBu2)(O-2,6-Me2C6H3)
(2a). To a n-hexane solution (10 mL) containing 1 (372 mg, 0.80
mmol) was added 2,6-Me2C6H2OH (98 mg, 0.80 mmol) at
-30 °C. The reaction mixture was warmed slowly to room
temperature and was stirred for an additional 3 h. The solution was
concentrated in Vacuo, and the chilled solution (-30 °C) yielded
t
SynthesisofVMe(N-2,6-Me2C6H3)(NCBu2)(OCH2CH2CH2CH2CHd
CH2) (2g). Synthesis of 2g was carried out by the same procedure
as that in 2a except that 5-hexene-1-ol (20 mg, 0.20 mmol) was
used. Yield: 56 mg (66%). 1H NMR (CDCl3 at 20 °C): δ 1.07 (s,
br, 3H, V-CH3), 1.25 (s, 18H, (CH3)3C-), 1.41 (2H), 1.71 (2H),
1.97 (2H), 2.53 (s, 6H, CH3), 4.52 (2H), 4.89-4.94 (2H), 5.71 (1H),
6.74 (t, 1H), 6.91 (d, 2H). 13C NMR (CDCl3 at 20 °C): δ 14.1,
19.4, 22.6, 25.0, 30.5, 31.6, 33.6, 34.2, 42.2, 44.9, 76.3, 114.2,
123.4, 127.2, 134.6-137.2, 138.9, 159.7, 185.4, 198.8. 51V NMR
(CDCl3 at 20 °C): δ -105 (∆ν1/2 ) 1685 Hz), -237 (∆ν1/2 ) 527
Hz). Anal. Calcd for C24H41N2OV: C, 67.90; H, 9.73; N, 6.60.
Found: C, 67.97; H, 9.88; N, 6.62.
1
335 mg (94%) of 2a as red microcrystals. H NMR (CDCl3): δ
1.34 (3H, V-CH3), 1.41 (s, 18H, (CH3)3C-), 2.33 (s, 6H, CH3),
2.47 (s, 6H, CH3), 6.81 (m, 2H), 6.96 (d, 2H), 7.03 (d, 2H). 13C
NMR (CDCl3): δ 17.6, 18.9, 30.5, 38.5 (br, V-Me), 45.4, 120.4,
123.9, 126.8, 127.1, 128.0, 162.8, 163.87, 201.3. 51V NMR
(CDCl3): δ -185 (∆ν1/2 ) 253 Hz). Anal. Calcd for C26H39N2-
OV: C, 69.93; H, 8.80; N, 6.27. Found: C, 70.02; H, 8.98; N, 6.20.
Synthesis of VMe(N-2,6-Me2C6H3)(NCtBu2)(O-4-tBu-2,6-
iPr2C6H2) (2b). Synthesis of 2b was carried out according to the
same procedure as that in 2a except that 4-tBu-2,6-iPr2C6H2OH
(47 mg, 0.20 mmol) was used in place of 2,6-Me2C6H2OH. Yield:
Reaction of 1 with n-Hexanol: Synthesis of V(N-2,6-Me2C6H3)-
(NCtBu2)[OCH2(CH2)4CH3]. The synthesis was carried out by the
same procedure as that in 2a except that n-hexanol (42 mg, 0.41
mmol) was used. 1H NMR (CDCl3): δ 0.82 (3H), 1.04 (s, br, 3H,
V-CH3), 1.23 (s, 18H, (CH3)3C-), 1.25-1.28 (m, 6H), 1.66 (2H),
2.51 (s, 6H, CH3), 4.50 (2H), 6.73 (t, 1H), 6.90 (d, 2H). 51V NMR
(CDCl3): δ -238 (∆ν1/2 ) 419 Hz).
1
104 mg (93%). H NMR (CDCl3): δ 1.18 (d, 12H, Me2CH-),
1.34 (s, 9H, para-(CH3)3C), 1.37 (s, 18H, (CH3)3C), 2.52 (s, 6H,
CH3), 3.56 (hept, 2H, Me2CH-), 6.79 (t, 1H), 6.94 (d, 2H), 7.08
(s, 2H). The V-Me signal was not found due to a peak over-
V(N-2,6-Me2C6H3)(NdCtBu2)(S-2,6-Me2C6H3) (3a). To an n-
hexane solution (10 mL) containing 1 (186 mg, 0.40 mmol) was
added 2,6-Me2C6H3SH (57 mg, 0.41 mmol) at -30 °C. The reaction
mixture was warmed slowly to room temperature (25 °C) and was
stirred for an additional 3 h. The solution was concentrated in Vacuo,
and the chilled solution (-30 °C) yielded 176 mg (75%) of 3a as
lapping with tBu groups in both aryloxo and ketimide ligands. 13
C
NMR (CDCl3): δ 19.1, 23.2, 23.4, 26.8, 30.5, 31.7, 34.6, 38.3
(br, V-Me), 45.2, 119.5, 123.6, 127.0, 134.5, 136.5, 143.3, 158.1,
162.5, 200.7. 51V NMR (CDCl3): δ -197 (∆ν1/2 ) 284 Hz).
Anal. Calcd for C34H55N2OV: C, 73.08; H, 9.92; N, 5.01. Found
(1): C, 72.98; H, 10.14; N, 4.99. Found (2): C, 73.14; H, 9.72;
N, 5.11.
1
brown crystals. H NMR (CDCl3): δ 1.22 (s, 36H, (CH3)3C-),
2.39 (s, 6H, CH3), 2.51 (s, 6H, CH3), 6.73 (t, 1H), 6.83 (t, 1H),
6.88 (d, 2H), 6.92 (d, 2H). 13C NMR (CDCl3): δ 19.1, 23.9, 30.4,
45.2, 123.6, 124.4, 126.8, 126.9, 134.4, 139.5, 144.6, 163.3, 198.5.
51V NMR (CDCl3): δ -132 (∆ν1/2 ) 341 Hz).
Synthesis of VMe(N-2,6-Me2C6H3)(NCtBu2)(OPh) (2c). Syn-
thesis of 2c was carried out according to the same procedure as
that in 2a except that PhOH (39 mg, 0.41 mmol) was used in place
1
of 2,6-Me2C6H2OH. Yield: 154 mg (92%). H NMR (CDCl3): δ
Reaction of 1 with n-C6H13SH (3b). To a NMR tube equipped
with a Teflon (Young) valve containing a C6D6 solution
(0.5 mL) of 1 (47 mg, 0.1 mmol) was added n-C6H13SH (12 mg,
0.1 mmol) at room temperature (25 °C). Three sets of resonances
1.30 (s, 18H, (CH3)3C-), 1.43 (3H, V-CH3), 2.45 (s, 6H, CH3),
6.77 (t, 1H), 6.89 (d, 3H), 7.04 (d, 2H), 7.19 (t, 2H). 13C NMR
(CDCl3): δ 19.1, 30.4, 39.7 (br, V-Me), 45.0, 119.3, 121.0, 124.0,

Reaction of (ArN)VMe(X)2 with Alcohols, Thiols, and Borates
Organometallics, Vol. 26, No. 10, 2007 2587
ascribed to the product (3b), methane (0.15 ppm), and the
starting material (1) (conversion 72%) were observed in the H
in aryloxo. 13C NMR (CDCl3): δ 17.3, 18.0, 53.5 (br, V-Me), 122.0,
125.7, 126.1, 127.1, 128.1, 135.9, 164.1. 51V NMR (CDCl3): δ
-64 (∆ν1/2 ) 348 Hz).
1
NMR spectrum, and two resonances ascribed to 1 and 3b were
1
observed in the 51V NMR spectrum. H NMR (C6D6): δ 0.82,
Formation of VMe(N-2,6-Me2C6H3)(O-4-tBu-2,6-iPr2C6H3)2
(5b). To a CDCl3 (ca. 0.5 mL) solution containing 2b (33 mg, 0.059
mmol) was added 4-tBu-2,6-iPr2C6H2OH (14 mg, 0.059 mmol) at
room temperature. NMR measurements were conducted after 1 and
12 h. The quantitative conversion was achieved after 12 h. 1H NMR
0.94, 1.15-1.45, 1.28, 1.33, 1.88, 2.68 (s, 6H, CH3), 2.93, 3.67,
6.72 (t, 1H), 6.91 (d, 2H). 51V NMR (C6D6): δ -153.6 (∆ν1/2
316 Hz).
)
Synthesis of [V(N-2,6-Me2C6H3)(NdCtBu2)2(THF)2][B(C6F5)4]
(4a). To a THF solution (4 mL) containing 1 (186 mg, 0.40 mmol)
was added [Ph3C][B(C6F5)4] (369 mg, 0.40 mmol) at -30 °C. The
reaction mixture was allowed to warm to room temperature (25
°C) and was stirred for 1 h. Removal of solvent from the mixture
i
t
(CDCl3): δ 1.15 (dd, 24H, Pr-CH3), 1.28 (s, 18H, Bu), 2.15 (br,
i
3H, V-Me), 2.17 (s, 6H, CH3 on arylimido), 3.47 (hept, 4H, Pr-
CH), 6.74 (1H), 6.81 (4H), 7.07, (s, 4H). 13C NMR (CDCl3): δ
18.3, 23.1, 23.5, 27.0, 31.6, 34.6, 52.8 (br, V-Me), 119.6, 125.2,
127.0, 135.1, 135.9, 144.9, 160.2, 163.5. 51V NMR (CDCl3): δ
-78 (∆ν1/2 ) 458 Hz).
in Vacuo gave
a mixture of 4a and Ph3CCH3 quantita-
tively. Recrystallization from THF/n-hexane afforded red block
1
Synthesis of VCl(N-2,6-Me2C6H3)(O-2,6-Me2C6H3)2 (6). To an
Et2O solution (10 mL) containing VCl2(N-2,6-Me2C6H3)(O-2,6-
Me2C6H3) (724 mg, 2.0 mmol) was added LiO-2,6-Me2C6H3 (256
mg, 2.0 mmol) at -30 °C. The reaction mixture was warmed slowly
to room temperature, and the mixture was stirred for an additional
3 h. The solution was then removed in Vacuo, and the resultant
residue was extracted with hexane (ca. 30 mL). The hexane extract
was concentrated in Vacuo, and the chilled solution (-30 °C)
microcrystals. Yield: 460 mg (90%). H NMR (CDCl3): δ 1.34
(s, 36H, (CH3)3C-), 1.85 (br, 8H, thf), 2.58 (s, 6H, CH3), 3.73 (br,
8H, thf), 6.89 (t, 1H), 6.95 (d, 2H). 13C NMR (CDCl3): δ 18.9,
25.5, 30.3, 45.8, 68.6, 123.8, 127.7, 135.0, 135.7, 136.9, 137.4,
139.3, 147.0, 149.4, 167.0, 207.2. 19F NMR (CDCl3): δ -134.4,
-164.5, -168.3. 51V NMR (CDCl3): δ -92 (∆ν1/2 ) 714 Hz).
Anal. Calcd for C58H61BF20N3O2V: C, 54.69; H, 4.79; N, 3.30.
Found (1): C, 54.37; H, 4.79; N, 3.12. Found (2): C, 54.71; H,
4.82; N, 3.15.
1
yielded 744 mg (83%) of the desired product. H NMR (CDCl3):
δ 2.07 (s, 6H, Me2), 2.36 (s, 12H, aryloxo-Me2), 6.74 (s, 3H), 6.88
(t, 2H), 7.02 (d, 2H). 13C NMR (CDCl3): δ17.4, 17.7, 123.9, 126.1,
127.2, 128.0, 128.3, 137.6, 167.0. 51V NMR (CDCl3): δ -207
(∆ν1/2 ) 411 Hz). Anal. Calcd for C24H27ClN3O2V: C, 64.36; H,
6.08; N, 3.13. Found (1): C, 64.51; H, 6.12; N, 3.07. Found (2):
C, 64.95; H, 6.07; N, 3.08.
Synthesis of [V(N-2,6-Me2C6H3)(NdCtBu2)2(THF)2][B(C6F5)4]
(4a) from
1 by Reaction with [PhN(H)Me2][B(C6F5)4].
One equivalent of [PhN(H)Me2][B(C6F5)4] (160 mg, 0.20 mmol)
was added to a solution of 1 (93 mg, 0.20 mmol) in THF at
-30 °C, and the resulting mixture was warmed gradually under
continuous stirring for 1 h at room temperature. Removal of
solvent from the reaction mixture in Vacuo gave a mixture of
the product (4a) and PhNMe2: the 1H NMR spectrum of the mixture
was identical to that of the isolated 4a except for the signals
of PhNMe2. 1H NMR (CDCl3): δ 1.35 (s, 36H, (CH3)3C-),
1.89 (br, 8H, thf), 2.58 (s, 6H, CH3), 3.98 (br, 8H, thf), 6.89
(t, 1H), 6.95 (d, 2H). 51V NMR (CDCl3): δ -92 (∆ν1/2 ) 704
Hz).
Synthesis of V(N-2,6-Me2C6H3)(O-2,6-Me2C6H3)3 (7). Treat-
ment of V(N-2,6-Me2C6H3)Cl3 (138 mg, 0.5 mmol) with 3.0 equiv
of LiO-2,6-Me2C6H3 in Et2O caused the precipitation of LiCl,
and color of the solution changed from dark green to dark red.
After 12 h, all volatiles were removed under reduced pressure and
the product was extracted with hot n-hexane. Concentrating
and cooling of the mixture to room temperature afforded 241 mg
1
(90% yield) of 7 as dark red microcrystals. H NMR (CDCl3): δ
Synthesis of [V(N-2,6-Me2C6H3)(NdCtBu2)2(THF)2][MeB
(C6F5)3] (4b) from 1 by Reaction with [B(C6F5)3]. To a THF
solution (5.0 mL) containing 1 (186 mg, 0.40 mmol) was added
B(C6F5)3 (204 mg, 0.40 mmol) at -30 °C. The reaction mixture
was warmed slowly to room temperature (25 °C) and was stirred
for 1 h. Solvent in the mixture was then removed in Vacuo to give
analytically pure product (447 mg, quantitative) that was considered
1.89 (s, 6H, CH3), 2.33 (s, 18H, CH3), 6.72 (s, 3H, NAr), 6.82 (t,
3H, p-OAr), 7.00 (d, 6H, m-OAr). 13C NMR (CDCl3): δ 17.4, 17.5,
122.4, 126.6, 126.8, 127.1, 128.2, 136.2, 166.2. 51V NMR
(CDCl3): δ -373 (∆ν1/2 ) 395 Hz). Anal. Calcd for C32H36-
NO3V: C, 72.03; H, 6.80; N, 2.63. Found: C, 72.13; H, 6.89; N,
2.58.
Typical Reaction of 2a with 4-tBu-2,6-iPr2C6H2OH in CDCl3.
To a Teflon-sealed NMR tube containing CDCl3 (ca. 0.5 mL) and
2a (45 mg, 0.10 mmol) was added 4-tBu-2,6-iPr2C6H2OH (23 mg,
0.10 mmol) in one portion, and the resultant solution was monitored
by both 1H NMR and 51V NMR (shown in Figure 3b). The solution
was then heated to 60 °C and was stirred for an additional 12 h
(the spectrum shown in Figure 3c).
Crystallographic Analysis. All measurements were made on a
Rigaku RAXIS-RAPID imaging plate diffractometer with graphite-
monochromated Mo KR radiation. The selected crystal collection
parameters are listed below (Table 1), and the detailed results are
described in the attached reports. All structures were solved by
direct methods and expanded using Fourier techniques,28 and the
non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were included but not refined. All calculations for complexes 3a
and 4a were performed using the CrystalStructure29,30 crystal-
lographic software package.
1
to be 4b. H NMR (CDCl3): δ 0.48 (s, 3H, BMe), 1.34 (s, 36H,
(CH3)3C-), 1.91 (br, 8H, thf), 2.57 (s, 6H, CH3), 3.82 (br, 8H,
thf), 6.88 (t, 1H), 6.97 (d, 2H). 51V NMR (CDCl3): δ -94 (∆ν1/2
) 816 Hz).
Synthesis of [V(N-2,6-Me2C6H3)(NdCtBu2)(O-2,6-Me2C6H3)-
(THF)2][B(C6F5)4] (4c) from 2a by Reaction with [PhN(H)Me2]-
[B(C6F5)4]. One equivalent of [PhN(H)Me2][B(C6F5)4] (320 mg,
0.40 mmol) was added to a solution of 2a (179 mg, 0.20 mmol) in
THF at -30 °C. The resulting mixture was stirred for 1 h at room
temperature (25 °C). The removal of THF from the solution gave
a mixture of the product (4c) and free PhNMe2. The exclusive
formation of 4c was confirmed by 1H and 51V NMR spectroscopy.
1H NMR (CDCl3): δ 1.34 (s, 18H, (CH3)3C-), 1.97 (br, 8H, thf),
2.25 (s, 6H, CH3 on aryloxo), 2.50 (s, 6H, CH3 on arylimido), 4.00
(br, 8H, thf), 6.92 (t, 1H), 6.98 (s, 3H), 7.05 (d, 2H). 51V NMR
(CDCl3): δ -77 (∆ν1/2 ) 790 Hz).
Formation of VMe(N-2,6-Me2C6H3)(O-2,6-Me2C6H3)2 (5a). To
a CDCl3 (ca. 0.5 mL) solution containing 2a (45 mg, 0.10 mmol)
was added 2,6-Me2C6H3OH (24 mg, 0.20 mmol) at room temper-
ature. NMR measurements were conducted after 0.5, 5.0, and 24
(28) 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.
(29) CrystalStructure 3.6.0, Crystal Structure Analysis Package; Rigaku
and Rigaku/MSC: The Woodlands, TX, 2000-2004.
(30) Watkin, D. J., Prout, C. K., Carruthers, J. R., Betteridge, P. W.
CRYSTALS Issue 10; Chemical Crystallography Laboratory: Oxford, UK,
1996.
1
h. The quantitative conversion was achieved after 24 h. H NMR
(CDCl3): δ 2.11 (s, 6H, CH3), 2.29 (s, 12H, CH3), 6.75-6.84 (m,
5H), 6.97-7.01 (m, 4H). The V-Me signal was not found (observed
as a shoulder at ca. 2.23 ppm) due to overlapping by the Me group

2588 Organometallics, Vol. 26, No. 10, 2007
Yamada et al.
Supporting Information Available: Figures giving fits
Acknowledgment. We are grateful to Mr. Shohei Katao
(NAIST) for his assistance in the crystallographic analysis. J.Y.
expresses his thanks to the JSPS for a predoctoral fellowship
(No. 5042) and Prof. Bart Hessen (University of Groningen,
The Netherlands) for helpful discussions. K.N. also acknowl-
edges Prof. M. Hirano and Prof. S. Komiya (Toyko Univ. A&T)
for helpful comments. This research was supported partly by
the Tokuyama Science Foundation.
1
used to determine ∆G values for reaction intermediates, H and
51V NMR spectra for 2f,g; crystal structure determination reports
for 3a and 4a. Crystallographic data are also given as CIF files.
These materials are available free of charge via the Internet at
http://pubs.acs.org.
OM061121W