Structural characterization and self-association of (arylimido)vanadium(V) triisopropoxides

Article abstract of DOI:10.1021/ic800528m

(Arylimido)vanadium(V) triisopropoxides, [(p-RC₆H ₄N)V(OⁱPr)₃] (R = NMe₂, OMe, H, CN, NO₂, Br), were prepared by the reaction of VO(OⁱPr) ₃ with the aryl isocyanates without solvent. The structures of the (arylimido)vanadium(V) triisopropoxides were characterized by single-crystal X-ray structure determination to elucidate the substituent effect on the self-association properties. Controlled association of the (arylimido) vanadium(V) triisopropoxides to the μ-oxo-bridged dimer complexes or the μ-imido-bridged dinuclear complex was achieved by changing the p-substituent on the benzene rings, which regulates the nature of the imido bonds. Furthermore, the one-dimensional linear polymer complex or the one-dimensional zigzag one through μ-oxo-bridging was formed in a solid state with the bimetallic (arylimido)vanadium(V) complex, [(ⁱPrO) ₃V(N-P-C₆H₄N)V(OⁱPr)₃] or [(ⁱPrO)₃V(N-m-C₆H₄N)V(O ⁱPr)₃], respectively.

Full text of DOI:10.1021/ic800528m

Inorg. Chem. 2008, 47, 7638-7643
Structural Characterization and Self-Association of
(Arylimido)vanadium(V) Triisopropoxides
Toshiyuki Moriuchi,* Kenta Ishino, Tomohiko Beppu, Masafumi Nishina, and Toshikazu Hirao*
Department of Applied Chemistry, Graduate School of Engineering, Osaka UniVersity,
Yamada-oka, Suita, Osaka 565-0871, Japan
Received March 24, 2008
(Arylimido)vanadium(V) triisopropoxides, [(p-RC6H4N)V(OiPr)3] (R ) NMe2, OMe, H, CN, NO2, Br), were prepared
by the reaction of VO(OiPr)3 with the aryl isocyanates without solvent. The structures of the (arylimido)vanadium(V)
triisopropoxides were characterized by single-crystal X-ray structure determination to elucidate the substituent effect
on the self-association properties. Controlled association of the (arylimido)vanadium(V) triisopropoxides to the µ-oxo-
bridged dimer complexes or the µ-imido-bridged dinuclear complex was achieved by changing the p-substituent on
the benzene rings, which regulates the nature of the imido bonds. Furthermore, the one-dimensional linear polymer
complex or the one-dimensional zigzag one through µ-oxo-bridging was formed in a solid state with the bimetallic
(arylimido)vanadium(V) complex, [(iPrO)3V(N-p-C6H4N)V(OiPr)3] or [(iPrO)3V(N-m-C6H4N)V(OiPr)3], respectively.
Introduction
On the other hand, only few examples for the preparation
of µ-imido-brigded vanadium(IV) complexes, cyclodivana-
dazenes, from (imido)vanadium(V) complexes have been
reported4a,d-f although the imido nitrogen is considered to
participate in the coordination to another metal center. A
substituent of the imido ligand is expected to influence the
properties of the imido bond sterically and electronically.
We herein report the structural characterization and self-
association of (arylimido)vanadium(V) triisopropoxides de-
pending on the p-substituents of the benzene rings.
Architectural control of transition metal-directed assembly
is one of the current research areas to create organized
nanostructures for advanced materials.1 Imido ligands are
recognized as a particularly suitable ligand for stabilization
of transition metal complexes in high oxidation states through
extensive ligand-to-metal π donation.2 (Imido)vanadium(V)
complexes have attracted much attention3,4 because of their
potential applications as catalysts for olefin polymerization,5
C-H activation,6 and other related reactions.7 (Imido)vana-
dium(V) complexes with alkoxide ligands are known to
dimerize through µ-oxo-bridging in the crystal structures.3e,m
(3) (a) Preuss, F.; Towae, W. Z. Naturforsch., B 1981, 36, 1130–1135. (b)
Preuss, F.; Towae, W.; Kruppa, V.; Fuchslocher, E. Z. Naturforsch., B
1984, 39, 1510–1517. (c) Maatta, E. A. Inorg. Chem. 1984, 23, 2560–
2561. (d) Preuss, F.; Becker, H.; Ha¨usler, H.-J. Z. Naturforsch., B 1987,
42, 881–888. (e) Devore, D. D.; Lichtenhan, J. D.; Takusagawa, F.;
Maatta, E. A. J. Am. Chem. Soc. 1987, 109, 7408–7416. (f) Carofiglio,
T.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Inorg. Chem. 1989, 28,
4417–4419. (g) Plass, W.; Verkade, J. G. Inorg. Chem. 1993, 32, 3762–
3765. (h) Hill, P. L.; Yap, G. P. A.; Rheingold, A. L.; Maatta, E. A.
J. Chem. Soc., Chem. Commun. 1995, 737–738. (i) Fickes, M. G.; Davis,
W. M.; Cummins, C. C. J. Am. Chem. Soc. 1995, 117, 6384–6385. (j)
Duan, Z.; Schmidt, M.; Young, V. G., Jr.; Xie, X.; McCarley, R. E.;
Verkade, J. G. J. Am. Chem. Soc. 1996, 118, 5302–5303. (k) Murphy,
V. J.; Turner, H. Organometallics 1997, 16, 2495–2497. (l) Witte, P. T.;
Meetsma, A.; Hessen, B. J. Am. Chem. Soc. 1997, 119, 10561–10562.
(m) Lutz, M.; Hagen, H.; Schreurs, A. M. M.; Spek, A. L.; van Koten,
G. Acta Crystallogr. 1999, C55, 1636–1639. (n) Montilla, F.; Pastor,
A.; Monge, A.; Gutie´rrez-Puebla, E.; Galindo, A. J. Chem. Soc., Dalton
Trans. 1999, 2893–2896. (o) Billen, M.; Hornung, G.; Preuss, F. Z.
Naturforsch., B 2003, 58, 975–989. (p) Yamada, J.; Nomura, K.
Organometallics 2005, 24, 3621–3623. (q) Du¨rr, S.; Bechlars, B.;
Radius, U. Inorg. Chim. Acta 2006, 359, 4215–4226.
* To whom correspondence should be addressed. E-mail: moriuchi@
chem.eng.osaka-u.ac.jp (T.M.), hirao@chem.eng.osaka-u.ac.jp (T.H.). Tel:
+81-6-6879-7413. Fax: +81-6-6879-7415.
(1) For reviews on this subject after 2000, see (a) Leininger, S.; Olenyuk,
B.; Stang, P. J. Chem. ReV. 2000, 100, 853–908. (b) Ziessel, R. Coord.
Chem. ReV. 2001, 216-217, 195–223. (c) Sun, S.-S.; Lees, A. J. Coord.
Chem. ReV. 2002, 230, 171–192. (d) Sun, W.-Y.; Yoshizawa, M.;
Kusukawa, T.; Fujita, M. Curr. Opin. Chem. Biol. 2002, 6, 757–764.
(e) Bu¨nzli, J.-C. G.; Piguet, C. Chem. ReV. 2002, 102, 1897–1928. (f)
Wu¨rthner, F.; You, C.-C.; Saha-Mo¨ller, C. R. Chem. Soc. ReV. 2004,
33, 133–146. (g) Kobuke, Y. Eur. J. Inorg. Chem. 2006, 233, 3–2351.
(h) Tanase, S.; Reedijk, J. Coord. Chem. ReV. 2006, 250, 2501–2510.
(i) Kleij, A. W.; Reek, J. N. H. Chem. Eur. J. 2006, 12, 4218–4227. (j)
Pitt, M. A.; Johnson, D. W. Chem. Soc. ReV. 2007, 36, 1441–1453. (k)
Cookson, J.; Beer, P. D. Dalton Trans. 2007, 1459–1472.
(2) (a) Wigley, D. E. In Prog. Inorg. Chem.; Karlin, K. D., Ed.; Wiley-
Interscience: New York, 1994; Vol. 42, pp 239-482. (b) Nugent, W. A.;
Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley-Interscience: New
York, 1998.
7638 Inorganic Chemistry, Vol. 47, No. 17, 2008
10.1021/ic800528m CCC: $40.75  2008 American Chemical Society
Published on Web 08/06/2008

(Arylimido)Wanadium(V) Triisopropoxides
Results and Discussion
The (arylimido)vanadium(V) triisopropoxides bearing the
electron-withdrawing para-substituents are not always ob-
tained in good yields by general methods using a solvent.
To overcome this problem, a synthetic approach to (arylimi-
do)vanadium complexes was modified. The reaction of
VO(OiPr)3 with various para-substituted aryl isocyanates
without solvent at 140 °C was performed to afford the
corresponding (arylimido)vanadium(V) triisopropoxides, [(p-
RC6H4N)V(OiPr)3] (1: R ) NMe2, 88%; 2: R ) OMe, 87%;
3: R ) H, 72%; 4: R ) CN, 87%; 5: R ) NO2, 61%). By
using this synthetic approach, (arylimido)vanadium(V) tri-
isopropoxides were found to be obtained with ease in good
yields. In the 1H NMR spectra of the (arylimido)vanadium(V)
triisopropoxides, the aryl protons exhibited downfield shift
as compared with the corresponding anulines, probably
because of the electron-withdrawing nature of the imido bond
(1: 7.12 and 6.47 ppm, N,N-dimethyl-p-phenylenediamine:
6.66-6.59 ppm; 2: 7.15 and 6.72 ppm, p-anisidine: 6.71 and
6.62 ppm; 3: 7.24, 7.17, and 7.05 ppm, aniline: 7.13, 6.73
and 6.67 ppm; 4: 7.55 and 7.18 ppm, p-cyanoaniline: 7.42
and 6.66 ppm; 5: 8.12 and 7.21 ppm, p-nitroaniline: 8.04
and 6.65 ppm;).
The structural elucidation of the (arylimido)vanadium(V)
triisopropoxides was performed by the single-crystal X-ray
structure determination (Figure 1 and Table 1). The selected
bond lengths and angles are listed in Tables 2 and 3,
respectively. The solid state imido structure of 2 bearing the
electron-donating methoxy group was characterized by the
V(1)-N(1) distance of 1.677(2) Å and the nearly linear
V(1)-N(1)-C(1) angle of 177.3(2)°, suggesting the greater
participation of an sp-hybridized character in the nitrogen
of the imido bond. Furthermore, a dimeric structure, in which
each vanadium atom is coordinated in a trigonal-bipyramidal
geometry (τ ) 0.96)8 with the imido and bridging isopro-
poxide ligands in the apical positions, was observed in the
crystal packing (Figure 1b and Table 4). The V(1)-V(1*)
internuclear distance of 3.30 Å indicates the absence of any
bonding interaction between the vanadiums. The axial
V(1)-O(1*) bond is 0.40 Å longer than the equatorial
V(1)-O(1) bond in the bridging isopropoxy group. The long
axial V-O distance trans to the imido ligand suggests the
weaker coordination.
The dimer complexes were also formed in the case of 1
bearing the electron-donating dimethylamino group and the
nonsubstituted complex 3 in the crystals (Figure 1a and 1c,
respectively). Linearity of the imido angles slightly decreased
(1: V(1)-N(1)-C(1), 174.3(3)°; 3: V(1)-N(1)-C(1), 175.1(1)
and 175.6(1)°) although the V(1)-N(1) distance (1.678(3)
Å for 1, 1.673(1) and 1.674(1) Å for 3) equals the one
observed with 2. In these (arylimido)vanadium(V) triisopro-
poxides, the greater participation of an sp-hybridized char-
acter in the nitrogen of the imido bond is suggested, resulting
in the formation of the µ-oxo-bridged dimer complexes. The
molecular structure of 4 bearing the electron-withdrawing
cyano group was also characterized by the dimeric structure
with the V(1)-N(1) distance of 1.674(2) Å and the nearly
linear V(1)-N(1)-C(1) angle of 178.6(2)° (Figure 1d).
(4) (a) Preuss, F.; Becker, H.; Kaub, J.; Sheldrick, W. S. Z. Naturforsch.,
B 1988, 43, 1195–1200. (b) Ruiz, J.; Vivanco, M.; Floriani, C.; Chiesi-
Villa, A.; Guastini, C. J. Chem. Soc., Chem. Commun. 1991, 214–215.
(c) Leung, W.-H.; Danopoulos, A. A.; Wilkinson, G.; Hussain-Bates,
B.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1991, 2051–2061.
(d) Preuss, F.; Overhoff, G.; Becker, H.; Ha¨usler, H.-J.; Frank, W.;
Reiss, G. Z. Anorg. Allg. Chem. 1993, 619, 1827–1833. (e) Solan, G. A.;
Cozzi, P. G.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics
1994, 13, 2572–2574. (f) Buijink, J.-K. F.; Meetsma, A.; Teuben, J. H.;
Kooijman, H.; Spek, A. L. J. Organomet. Chem. 1995, 497, 161–170.
(g) Wheeler, D. E.; Wu, J.-F.; Maatta, E. A. Polyhedron 1998, 17, 969–
976. (h) Preuss, F.; Tabellion, F.; Overhoff, G.; Reiss, G. Z. Anorg.
Allg. Chem. 2000, 626, 1665–1675. (i) Lorber, C.; Choukroun, R.;
Donnadieu, B. Inorg. Chem. 2002, 41, 4217–4226. (j) Lorber, C.;
Choukroun, R.; Vendier, L. Inorg. Chem. 2007, 46, 3192–3202.
(5) (a) Scheuer, S.; Fischer, J.; Kress, J. Organometallics 1995, 14, 2627–
2629. (b) Chan, M. C. W.; Cole, J. M.; Gibson, V. C.; Howard, J. A. K.
Chem. Commun. 1997, 2345–2346. (c) Chan, M. C. W.; Chew, K. C.;
Dalby, C. I.; Gibson, V. C.; Kohlmann, A.; Little, I. R.; Reed, W. Chem.
Commun. 1998, 1673–1674. (d) Coles, M. P.; Dalby, C. I.; Gibson,
V. C.; Little, I. R.; Marshall, E. L.; Ribeiro da Costa, M. H.; Mastroianni,
S. J. Organomet. Chem. 1999, 591, 78–87. (e) Hagen, H.; Bezemer,
C.; Boersma, J.; Kooijman, H.; Lutz, M.; Spek, A. L.; van Koten, G.
Inorg. Chem. 2000, 39, 3970–3977. (f) Nomura, K.; Sagara, A.;
Imanishi, Y. Chem. Lett. 2001, 36–37. (g) Yamada, J.; Fujiki, M.;
Nomura, K. Organometallics 2005, 24, 2248–2250. (h) Sato, Y.;
Nakayama, Y.; Yasuda, H. J. Appl. Polym. Sci. 2005, 97, 1008–1015.
(i) Bigmore, H. R.; Zuideveld, M. A.; Kowalczyk, R. M.; Cowley, A. R.;
Kranenburg, M.; Mclnnes, E. J. L.; Mountford, P. Inorg. Chem. 2006,
45, 6411–6423.
(6) (a) de With, J.; Horton, A. D.; Orpen, A. G. Organometallics 1990, 9,
2207–2209. (b) de With, J.; Horton, A. D. Angew. Chem., Int. Ed. Engl.
1993, 32, 903–905. (c) de With, J.; Horton, A. D.; Orpen, A. G.
Organometallics 1993, 12, 1493–1496. (d) Cundari, T. R. Organome-
tallics 1994, 13, 2987–2994.
(7) (a) Birdwhistell, K. R.; Boucher, T.; Ensminger, M.; Harris, S.; Johnson,
M.; Toporek, S. Organometallics 1993, 12, 1023–1025. (b) Tabellion,
F.; Nachbauer, A.; Leininger, S.; Peters, C.; Preuss, F.; Regitz, M.
Angew. Chem., Int. Ed. 1998, 37, 1233–1235. (c) Birdwhistell, K. R.;
Lanza, J.; Pasos, J. J. Organomet. Chem. 1999, 584, 200–205. (d) Peters,
C.; Tabellion, F.; Schro¨der, M.; Bergstra¨sser, U.; Preuss, F.; Regitz,
M. Synthesis 2000, 417–428. (e) Montilla, F.; Pastor, A.; Galindo, A.
J. Organomet. Chem. 2004, 689, 993–996. (f) Lorber, C.; Choukroun,
R.; Vendier, L. Organometallics 2004, 23, 1845–1850. (g) Montilla,
F.; del R´ıo, D.; Pastor, A.; Galindo, A. Organometallics 2006, 25, 4996–
5002.
(8) The structural parameter τ ) (ꢀ - R)/60 for the coordination geometry
of the five-coordinated complex proposed byAddison and Reedijik
shows τ ) 0.96 for 2, where R and ꢀ represent two basal angles (ꢀ >
R). The parameters for an ideal square pyramidal and trigonal
bipyramidal geometries are τ ) 0 (R ) ꢀ ) 180°) and τ ) 1 (R )
120° and ꢀ ) 180°), respectively. The τ value of 2 indicates that the
coordination geometry around the vanadium atom is a trigonal bipyra-
mid. (a) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor,
G. C. J. Chem. Soc., Dalton Trans. 1984, 134, 9–1356.
Inorganic Chemistry, Vol. 47, No. 17, 2008 7639

Moriuchi et al.
Figure 1. Molecular structures of (a) 1, (b) 2, (c) 3, (d) 4, and (e) 5 for the oxo-bridged dimer, and (f) 6b for the imido-bridged dimer.
Table 1. Crystallographic Data for 1-5, 6b, and 7-8
1
2
3
4
5
6b
7
8
empirical formula C17H31N2O3V1 C16H28N1O4V1 C15H26N1O3V1 C16H25N2O3V1 C15H25N2O5V1 C24H36N2O4Br2V2 C24H46N2O6V2 C24H46N2O6V2
formula weight
crystal system
space group
a, Å
b, Å
c, Å
362.39
349.34
319.32
monoclinic
344.33
monoclinic
364.31
monoclinic
678.25
triclinic
j
560.52
monoclinic
P21/n (No. 14) P21/c (No. 14)
11.6041(6)
10.1850(5)
13.9926(7)
560.52
monoclinic
triclinic
triclinic
j
j
P1 (No. 2)
P1 (No. 2)
P21/n (No. 14) P21/c (No. 14) P21/c (No. 14) P1 (No. 2)
9.8688(8)
10.6487(8)
11.823(1)
77.008(2)
68.593(2)
68.278(2)
1068.8(2)
2
9.646(1)
10.340(1)
11.547(2)
83.156(3)
71.755(5)
63.172(5)
975.8(2)
2
1.189
5.23
4
0.71069
0.065
0.188
13.9263(6)
13.2611(6)
19.1670(9)
9.3345(4)
12.8258(7)
16.0171(9)
9.4051(2)
10.7161(2)
19.2289(5)
9.1967(2)
9.2848(8)
18.4382(8)
91.797(3)
93.680(4)
94.664(5)
1564.9(2)
2
1.439
31.86
2
0.71069
0.071
0.200
9.9672(3)
33.138(1)
19.6333(5)
R, deg
ꢀ, deg
90.803(1)
92.1714(9)
93.7582(9)
107.412(2)
93.2869(8)
γ, deg
V, Å3
3539.4(3)
8
1.198
5.66
4
0.71075
0.039
0.145
2
1916.2(2)
4
1.193
5.29
1933.84(8)
4
1.251
5.35
1578.0(1)
2
1.180
6.26
6474.0(3)
8
1.150
6.10
Z
Dcalcd, g cm-3
1.126
µ(Mo KR), cm-1 4.77
T, °C
4
23
23
4
4
λ(Mo KR), Å
0.71075
0.057
0.224
0.71069
0.064
0.166
0.71069
0.049
0.146
0.71069
0.039
0.144
0.71069
0.078
0.199
R1a
wR2b
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2)[∑w(Fo - Fc )2/∑w(Fo )2]1/2
.
2
2
Linearity of the imido angle increased as compared with 2,
probably because of the contribution of π-conjugation. The
slightly decreased imido angle (V(1)-N(1)-C(1), 172.8(1)°)
with the V(1)-N(1) distance of 1.670(2) Å was observed in
the case of 5 bearing the electron-withdrawing nitro group
(Figure 1e). The para-substituent of the aryl moiety was
found to affect the hybridized properties and structures of
the(arylimido)vanadium(V)compoundsthroughπ-conjugation.
The imido structure is considered to be an important factor
to control the assembly. The imido nitrogen with the larger
contribution of an sp2-hybridized character could coordinate
to another metal center by using a lone pair although such
7640 Inorganic Chemistry, Vol. 47, No. 17, 2008

(Arylimido)Wanadium(V) Triisopropoxides
Table 2. Selected Bond Lengths (Å) for 1-5, 6b, and 7-8
1
2
3a
4
5
6ba
7b
8a
V1-N1 1.678(3) 1.677(2) 1.673(1) 1.674(1) 1.674(2) 1.670(2) 1.853(6) 1.844(6) 1.678(2) 1.674(4) 1.664(4) 1.673(4) 1.668(4)
V1-N1*
V1-V1*
1.856(6) 1.850(6)
2.524(3) 2.526(3)
V1-O1 1.850(3) 1.843(2) 1.844(1) 1.846(1) 1.835(2) 1.842(1) 1.742(6) 1.763(5) 1.865(2) 1.845(4) 1.857(4) 1.844(3) 1.849(4)
V1-O2 1.798(3) 1.794(2) 1.794(1) 1.787(1) 1.785(2) 1.781(2) 1.741(7) 1.742(6) 1.788(2) 1.782(4) 1.792(4) 1.781(4) 1.783(4)
V1-O3 1.789(4) 1.792(3) 1.789(1) 1.797(1) 1.781(2) 1.786(2)
V1-O1* 2.226(2) 2.245(1) 2.240(1) 2.233(1) 2.242(2) 2.239(1)
1.795(1) 1.789(4) 1.792(5) 1.790(4) 1.782(4)
2.198(1) 2.245(4) 2.224(4) 2.216(4) 2.274(4)
1.375(4) 1.368(2) 1.378(2) 1.376(2) 1.375(4) 1.380(3) 1.41(1) 1.404(10) 1.372(2) 1.389(6) 1.399(7) 1.385(7) 1.383(7)
C1-N1
a Two independent molecules exist in an asymmetric unit. b The molecule sits on an inversion center.
Table 3. Selected Bond Angles (deg) for 1-5, 6b, and 7-8
1
2
3a
4
5
6ba
7b
8a
C1-N1-V1 174.3(3) 177.3(2)
C1-N1-V1*
175.1(1) 175.6(1) 178.6(2)
172.8(1) 138.0(5) 135.7(5) 177.8(1) 171.9(4) 179.8(4) 177.0(4) 177.9(4)
136.2(5) 138.0(5)
85.8(3) 86.3(3)
V1-N1-V1*
V1-O1-V1* 106.6(1) 107.03(7) 107.49(5) 107.17(5) 107.61(10) 108.12(6)
107.74(6) 107.7(2) 108.0(2) 105.9(2) 108.1(2)
N1-V1-O1 101.9(1) 101.92(9) 101.82(6) 101.74(6) 101.3(1)
N1-V1-O2 100.0(1) 101.85(9) 100.01(6) 102.56(6) 102.5(1)
103.75(7) 113.5(3) 111.9(3) 100.90(7) 103.1(2) 101.4(2) 101.0(2) 101.0(2)
100.06(8) 112.4(3) 111.4(3) 100.64(7) 102.2(2) 101.0(2) 101.9(2) 101.1(2)
N1-V1-O3 101.9(2) 101.0(1)
102.61(6) 99.88(6) 100.8(1)
100.31(8)
175.59(7)
100.40(8) 99.6(2) 101.8(2) 100.5(2) 101.8(2)
173.15(7) 174.9(2) 173.4(2) 174.6(2) 173.1(2)
N1-V1-O1* 175.0(2) 174.88(9) 173.87(5) 174.22(5) 173.6(1)
N1*-V1-O1
N1*-V1-O2
N1-V1-N1*
N1-V1-V1*
112.4(3) 112.8(3)
111.5(3) 112.9(3)
94.2(3) 93.7(3)
47.2(2) 46.9(2)
O1-V1-O2 118.0(2) 116.93(10) 118.65(5) 116.67(5) 115.75(10) 118.42(7) 111.6(3) 112.8(3) 118.75(7) 115.3(2) 117.2(2) 118.2(2) 118.0(2)
O1-V1-O3 116.9(1) 117.45(9) 116.54(5) 118.23(5) 118.5(1)
O1-V1-O1* 73.4(1) 72.97(7) 72.57(4) 72.69(4) 72.39(10) 71.88(6)
O2-V1-O3 113.9(1) 113.78(10) 113.22(5) 113.68(6) 114.1(1)
O2-V1-O1* 80.98(10) 81.13(6)
O3-V1-O1* 82.0(1) 81.35(8)
a Two independent molecules exist in an asymmetric unit. b The molecule sits on an inversion center.
117.04(7)
119.65(7) 118.9(2) 118.8(2) 117.0(2) 117.6(2)
72.26(6) 72.3(2) 72.0(2) 73.6(1) 72.1(1)
111.55(7) 114.0(2) 112.5(2) 113.9(2) 113.2(2)
82.68(6) 82.0(2) 82.2(1) 81.1(2) 82.0(2)
83.76(6) 81.1(2) 82.1(2) 82.3(2) 82.5(2)
113.08(7)
81.89(6)
82.44(6)
80.99(5) 81.66(5) 81.73(9)
82.40(5) 81.79(5) 81.61(8)
Table 4. Structural Parameter τ of 1-5 and 7-8
3a 7b
A bimetallic complex containing the bridging isopropoxide
ligands is envisioned to expand self-association through
µ-oxo-bridging in a crystal state. The complex 7, [(OiPr)3V(N-
p-C6H4N)V(OiPr)3], was produced by the treatment of
VO(OiPr)3 with 1,4-phenylenediisocyanate in 80% yield. The
structure of 7 was confirmed by X-ray crystallographic
analysis. Because of the conjugation, the V-N-Ph-N-V
core is almost linear with the V(1)-N(1) distance of 1.678(2)
Å and the V(1)-N(1)-C(1) angle of 177.8(1)°. As expected,
the one-dimensional linear polymer complex was formed
through µ-oxo-bridging in the crystal packing as shown in
Figure 2a. The bimetallic complex 8, [(OiPr)3V(N-m-
C6H4N)V(OiPr)3], which was prepared from 1,3-phenylene-
diisocyanate in 60% yield, afforded the one-dimensional
zigzag polymer complex through µ-oxo-bridging as depicted
in Figure 2b.
1
2
4
5
8a
τ
0.95 0.96 0.92 0.93 0.92 0.95 0.89 0.93 0.91 0.94 0.92
a Two independent molecules exist in an asymmetric unit. b The molecule
sits on an inversion center.
coordination is not possible with the greater participation of
an sp-hybridized character. The self-association was found
to be controlled by the characteristics of the V-N imido
bond, which depends on the difference in π-conjugation of
the p-substituent on the benzene ring. It should be noted that
the µ-imido-brigded dinuclear vanadium(IV) complex 6b,
[V(µ-N-p-C6H4Br)(OiPr)2]2, was obtained in 83% yield by
recrystallization of the (arylimido)vanadium(V) complex 6a,
[(p-BrC6H4N)V(OiPr)3], which was initially formed by the
reaction with 4-bromophenylisocyanate in 84% yield. The
lone pair on the nitrogen atom coordinates to the vanadium
center to afford the cyclodivanadazene 6b. The single-crystal
X-ray structure determination of the complex 6b, wherein
two independent molecules exist in an asymmetric unit,
revealed a dinuclear structure with two imido ligands
bridging two V(OiPr)2 moieties. Each vanadium atom is
coordinated in a distorted tetrahedral geometry as shown in
Figure 1f. The torsion angles V(1)-N(1)-V(1*)-N(1*) (0.0
and 0.0000(1)°) indicate that the V2N2 core is almost planar.
The V(1)-V(1*) distances of 2.524(3) and 2.526(3) Å are
close to those found in the cyclodivanadazenes so far
reported.4a,b,d-f,h-j,7f The V-N distances (V(1)-N(1) )
1.853(6) and 1.844(6)Å, V(1)-N(1*) ) 1.856(6) and
1.850(6)Å) are about 0.17 Å longer than that of 2. The
V(1)-N(1)-V(1*) angles of the V2N2 core are 85.8(3) and
86.3(3)°, indicating no hybridization on the nitrogen atom.
In the 51V NMR spectra of d0 diamagnetic vanadium
complexes, the vanadium nuclei become increasingly shielded
as the electronegativity of the ligand attached to the
coordination center increases.3e 51V NMR was measured to
clarify the electronic environment of the vanadium atom. The
51V chemical shift of the nonsubstituted (phenylimido)va-
nadium(V) complex 3 was detected at -628 ppm. In the
51V NMR spectra of the (arylimido)vanadium(V) triisopro-
poxides, 51V chemical shifts were observed at a lower field
with increase of the electron-donating capability of the para-
substituent (1: -549 ppm, 2: -602 ppm). On the contrary,
the electron-withdrawing substituent, in which the imido
nitrogen atom becomes more electronegative to increase 51
V
nuclear shielding, caused the higher field shift (4: -640 ppm,
5: -642 ppm). These results are consistent with those of
Inorganic Chemistry, Vol. 47, No. 17, 2008 7641

Moriuchi et al.
Figure 2. A portion of a layer containing the one-dimensional linear molecular assembly through oxo-bridging in the crystal packing of (a) 7 and (b) 8.
the (arylimido)vanadium(V) trichlorides reported by Maatta
and co-workers.3e It should be noted that the imido-brigded
dinuclear vanadium(IV) complex 6b exhibited the 51V
chemical shift at 226 ppm despite of the d1 vanadium(IV)
species. The formation of the V-V single bond, in which
each vanadium serves as a σ donor, is considered to cause
the deshielding of the 51V nuclei in the imido-bridged
dimer.4f,j The conjugated bimetallic complex 7 showed the
51V chemical shift at -602 ppm, indicating that the electronic
environment of the vanadium atom of 7 is likely to be almost
the same as that of 2 bearing the electron-donating methoxy
group. On the other hand, the 51V chemical shift of the meta-
substituted bimetallic complex 8 was observed at -637 ppm,
which is close to that of 4 bearing the electron-withdrawing
cyano group. These results indicate that the electronic
environment of the vanadium atom appears to be controlled
by the π conjugated substituent.
vanadium center by the π conjugation. Regulation of the
redox properties of the vanadium center is considered to be
one of the key factors to develop of an efficient vanadium
catalytic system.9 The application of (arylimido)vanadium(V)
complexes for catalysis is now in progress.
Experimental Section
General Methods. All manipulations were carried out under an
atmosphere of nitrogen in a Vacuum Atmospheres drybox or using
standard Schlenk techniques. All reagents and solvents were
purchased from commercial sources and were further purified by
the standard methods, if necessary. Solvents were dried by refluxing
in the presence of appropriate drying reagents, distilled under an
1
atmosphere of nitrogen, and were stored in the drybox. H NMR
spectra were recorded on a JEOL JNM-ECP 400 (400 MHz) or
Varian MERCURY 300 (300 MHz) spectrometer. The chemical
shifts were referenced to the residual resonances of deuterated
solvents. 51V NMR spectra were obtained with a JEOL JNM-ECP
400 (105 MHz) spectrometer with VOCl3 as an external standard.
Conclusions
The (arylimido)vanadium(V) and the corresponding bi-
metallic triisopropoxides were prepared by the reaction of
VO(OiPr)3 with the aryl isocyanates and diisocyanates,
respectively, without solvent. Structural characterization by
the single-crystal X-ray structure determination indicates the
substituent effect on the self-association properties. The para-
substituent of the aryl moiety controls the assembly of the
(arylimido)vanadium(V) triisopropoxides to give the µ-oxo-
bridged dimer complexes or the µ-imido-bridged dinuclear
complex. The present architectural control of the dimensional
structures is considered to be a useful approach to artificial
organized metallic systems. Furthermore, the para-substituent
was demonstrated to affect the electronic properties of the
General Procedure for the Preparation of (Arylimido)vana-
dium(V) Triisopropoxide by Using para-Substituted Aryl Iso-
cyanate. A mixture of vanadium(V) oxytriisoproxide (495 µL, 2.1
mmol) and the corresponding para-substituted aryl isocyanate (2.0
mmol) was stirred in no solvent under an atmosphere of nitrogen
at 140 °C for 3 h. The resulting mixture was then allowed to be
cooled to room temperature, and then 20 mL of dichloromethane
was added. The resulting solution was filtered off, and the filtrate
was evaporated under reduced pressure. The resultant residue was
recrystallized from hexane or dichloromethane at -30 °C, giving
the desired (arylimido)vanadium(V) triisoproxide.
1
1: Isolated yield 88%; H NMR (400 MHz, CD2Cl2) δ 7.12 (d,
J ) 9.1 Hz, 2H), 6.47 (d, J ) 9.1 Hz, 2H), 5.13 (sept, J ) 6.0 Hz,
7642 Inorganic Chemistry, Vol. 47, No. 17, 2008

(Arylimido)Wanadium(V) Triisopropoxides
3H), 2.97 (s, 6H), 1.34 (d, J ) 6.0 Hz, 18H); 51V NMR (105 MHz,
Preparation of the µ-Imido-Brigded Dinuclear Vanadium(IV)
Complex 6b. The recrystallization of the (arylimido)vanadium(V)
complex 6a (2.0 mg, 0.005 mmol) from 1.5 mL of hexane and 0.5
mL of dichloromethane at room temperature afforded the µ-imido-
brigded dinuclear vanadium(IV) complex 6b in 83% yield.
6b: Isolated yield 83%; 1H NMR (300 MHz, CD2Cl2) δ 7.54 (d,
J ) 8.7 Hz, 4H), 7.36 (d, J ) 8.7 Hz, 4H), 4.13 (sept, J ) 6.0 Hz,
4H), 0.91 (d, J ) 6.0 Hz, 24H); 51V NMR (105 MHz, CD2Cl2)
226 ppm (br s, the line width at half-height is 390 Hz).
X-ray Structure Analysis. All measurements for 1-5, 6b, and
7-8 were made on a Rigaku RAXIS-RAPID Imaging Plate
diffractometer with graphite monochromated Mo KR radiation. The
structures of 2-5, and 7-8 were solved by direct methods and
expanded using Fourier techniques. The structures of 1 and 6b were
solved by heavy-atom Patterson methods and expanded using
Fourier techniques. The non-hydrogen atoms were refined aniso-
tropically. The H atoms were placed in idealized positions and
allowed to ride with the C atoms to which each was bonded. The
rather high R1 and wR2 for 6b and 8 are probably due to the data
quality. Crystallographic details are summarized in Table 1. Selected
bond lengths and bond angles are listed in Table 2 and Table 3,
respectively. Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre (CCDC) as supplementary
publication no. CCDC-668956 for 1, CCDC-656899 for 2, CCDC-
668957 for 3, CCDC-656902 for 4, CCDC-668958 for 5, CCDC-
656901 for 6b, CCDC-656900 for 7, and CCDC-668959 for 8.
Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: (internat.)
+44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
1
CD2Cl2) -549 ppm (t, J51V/14N ) 114 Hz).
1
2: Isolated yield 87%; H NMR (400 MHz, CD2Cl2) δ 7.15 (d,
J ) 9.0 Hz, 2H), 6.72 (d, J ) 9.0 Hz, 2H), 5.12 (sept, J ) 6.1 Hz,
3H), 3.78 (s, 3H), 1.34 (d, J ) 6.1 Hz, 18H); 51V NMR (105 MHz,
1
CD2Cl2) -602 ppm (t, J51V/14N ) 114 Hz).
3: Isolated yield 72%; 1H NMR (400 MHz, CD2Cl2) δ 7.24 (dd,
J ) 8.4, 7.3 Hz, 2H), 7.17 (d, J ) 8.4 Hz, 2H), 7.05 (t, J ) 7.3
Hz, 1H), 5.14 (sept, J ) 6.2 Hz, 3H), 3.78 (s, 3H), 1.35 (d, J )
1
6.2 Hz, 18H); 51V NMR (105 MHz, CD2Cl2) -628 ppm (t, J51V/
14N ) 114 Hz).
1
4: Isolated yield 87%; H NMR (400 MHz, CD2Cl2) δ 7.55 (d,
J ) 8.1 Hz, 2H), 7.18 (d, J ) 8.1 Hz, 2H), 5.11 (sept, J ) 6.0 Hz,
3H), 1.34 (d, J ) 6.0 Hz, 18H); 51V NMR (105 MHz, CD2Cl2)
1
-640 ppm (t, J51V/14N ) 116 Hz).
1
5: Isolated yield 61%; H NMR (400 MHz, CD2Cl2) δ 8.12 (d,
J ) 9.0 Hz, 2H), 7.21 (d, J ) 9.0 Hz, 2H), 5.13 (sept, J ) 6.0 Hz,
3H), 3.78 (s, 3H), 1.35 (d, J ) 6.0 Hz, 18H); 51V NMR (105 MHz,
1
CD2Cl2) -642 ppm (t, J51V/14N ) 114 Hz).
6a: Isolated yield 84%; 1H NMR (300 MHz, CD2Cl2) δ 7.36 (d,
J ) 8.7 Hz, 2H), 7.04 (d, J ) 8.7 Hz, 2H), 5.11 (sept, J ) 6.3 Hz,
3H), 1.34 (d, J ) 6.3 Hz, 18H); 51V NMR (105 MHz, CD2Cl2)
1
-629 ppm (t, J51V/14N ) 116 Hz).
1
7: Isolated yield 80%; H NMR (400 MHz, CD2Cl2) δ 7.02 (s,
4H), 5.11 (sept, J ) 6.1 Hz, 6H), 1.33 (d, J ) 6.1 Hz, 36H); 51V
1
NMR (105 MHz, CD2Cl2) -602 ppm (t, J51V/14N ) 114 Hz).
1
8: Isolated yield 60%; H NMR (400 MHz, CD2Cl2) δ 7.10 (t,
J ) 8.0 Hz, 1H), 6.96 (s, 1H), 6.86 (d, J ) 8.0 Hz, 2H), 5.11
(sept, J ) 6.2 Hz, 6H), 1.34 (d, J ) 6.2 Hz, 36H); 51V NMR (105
Acknowledgment. Thanks are due to the Analytical
Center, Graduate School of Engineering, Osaka University,
for the use of the NMR instruments.
1
MHz, CD2Cl2) -637 ppm (t, J51V/14N ) 115 Hz).
(9) Hirao, T. Chem. ReV. 1997, 97, 2707–2724.
IC800528M
Inorganic Chemistry, Vol. 47, No. 17, 2008 7643