Electron-deficient vanadium(III) alkyl and allyl complexes with amidinate ancillary ligands

Article abstract of DOI:10.1021/om980431e

Vanadium(III) amidinate complexes (amidinate)₂VCl and (amidinate)VCl₂(THF)₂ were prepared for two different amidinate ligands, [PhC(NSiMe₃)₂]^- and [t-BuC(Ni-Pr)₂]^-. These served as precursors for amidinate V(III) alkyl and allyl derivatives. The allyl ligand in (amidinate)₂V(allyl) is η³-bound, indicating that the amidinates act as four-electron anionic ligands. The 12-electron alkyl complex [PhC(NSiMe₃)₂]₂VMe catalyzes the slow oligomerization of ethene to linear olefins at 80°C. The bis-allyl complex [t-BuC(Ni-Pr)₂]V(η³-allyl)₂ was prepared and structurally characterized, but its analogue with the [PhC(NSiMe₃)₂] ligand already decomposes around -30°C. This shows that the substituent pattern of the amidinate ancillary ligand can strongly affect the stability of organometallic derivatives.

Full text of DOI:10.1021/om980431e

4090
Organometallics 1998, 17, 4090-4095
Electr on -Deficien t Va n a d iu m (III) Alk yl a n d Allyl
Com p lexes w ith Am id in a te An cilla r y Liga n d s†
Edward A. C. Brussee, Auke Meetsma, Bart Hessen, and J an H. Teuben*
Center for Catalytic Olefin Polymerization, Department of Chemistry, University of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands
Received May 26, 1998
Vanadium(III) amidinate complexes (amidinate)2VCl and (amidinate)VCl2(THF)2 were
prepared for two different amidinate ligands, [PhC(NSiMe3)2]- and [t-BuC(Ni-Pr)2]-. These
served as precursors for amidinate V(III) alkyl and allyl derivatives. The allyl ligand in
(amidinate)2V(allyl) is η3-bound, indicating that the amidinates act as four-electron anionic
ligands. The 12-electron alkyl complex [PhC(NSiMe3)2]2VMe catalyzes the slow oligomer-
ization of ethene to linear olefins at 80 °C. The bis-allyl complex [t-BuC(Ni-Pr)2]V(η3-allyl)2
was prepared and structurally characterized, but its analogue with the [PhC(NSiMe3)2] ligand
already decomposes around -30 °C. This shows that the substituent pattern of the amidinate
ancillary ligand can strongly affect the stability of organometallic derivatives.
In tr od u ction
carbyl complex with amidinate ligands, [MesC-
(Nc-C6H11)2]2VMes (Mes ) 2,4,6-Me3C6H2) formed by
reaction of VMes3(THF) with dicyclohexyl carbodi-
imide,5 suggests that these ligands can be suitable to
prepare electron-deficient V(III) hydrocarbyls. In this
contribution we have used two different amidinate
ligands, the ubiquitous N,N′-bis(trimethylsilyl)benz-
amidinate [PhC(NSiMe3)2]- ([A]-)3a,b and the N,N′-bis-
(isopropyl)-tert-butylimidinate [t-BuC(Ni-Pr)2]- ([B]-)
recently employed by J ordan et al. in organoaluminum
chemistry,3f to prepare new electron-deficient vana-
dium(III) alkyl and allyl species. Indeed, the reactivity
of the V-C bond in the (amidinate)2V(alkyl) species is
enhanced relative to that in Cp2V(alkyl), and [A]2V-
(alkyl) was found to catalyze the oligomerization of
ethene to linear olefins.
The reactivity of the 16-electron vanadium(III) vana-
docene alkyls Cp2VR1 is strongly influenced by the
presence of two unpaired valence electrons (S ) 1 for
these d2 compounds). Interaction with Lewis-basic
substrates requires the pairing of these electrons (or an
η5- to η3-ring slippage of the Cp ligand) in order to free
a suitable metal-centered orbital. The unfavorability
of this is illustrated by the fact that the allyl ligand in
Cp2V(CH2CHdCH2) is η1-bonded,1b whereas in the d1
Ti(III) analogue this group is an η3-allyl.2 Thus reactiv-
ity of these V(III) species toward substrates of low
polarity (such as olefins) is essentially absent (even
(C5Me5)2VH does not react with ethene up to a pressure
of 17 bar1d). We sought to increase the reactivity of
neutral vanadium(III) alkyls toward olefins by using
amidinate ([RC(NR′)2]-) ancillary ligands instead of
cyclopentadienyls. Amidinates can readily be prepared
with a variety of substituents R and R′3 and can impart
substantial steric protection while formally contri-
buting less valence electrons to the bonding than Cp
ligands.4 The one example known of a V(III) hydro-
Resu lts a n d Discu ssion
Syn th esis of Am id in a te Va n a d iu m Ch lor id es.
Amidinate vanadium(III) chlorides that are suitable
precursors for amidinate vanadium(III) hydrocarbyl
species were found to be readily accessible from VCl3-
(THF)3 and the lithium amidinates. The syntheses
performed are summarized in Scheme 1.
The reaction of VCl3(THF)3 with 2 equiv of [A]Li(THF)
in THF yields [A]2VCl(THF) (1) as green crystals in 43%
isolated yield after pentane extraction. Heating solid
1 in vacuo at 120 °C for 4 h liberates the coordinated
THF to give the known compound [A]2VCl (2), described
previously by Gambarotta et al.6 For the amidinate [B]
the base-free [B]2VCl (3) is directly obtained in 69%
yield from the initial pentane extract, suggesting that
the metal center in 3 has considerably less affinity
toward THF than in 2.
* To whom correspondence should be addressed. E-mail: teuben@
chem.rug.nl.
† Netherlands Institute for Catalysis Research (NIOK) publication
no. RUG 98-4-02.
(1) (a) De Liefde Meijer, H. J .; J anssen, M. J .; Van der Kerk, G. J .
M. Recl. Trav. Chim. Pays-Bas 1961, 80, 831. (b) Siegert, F. W.; De
Liefde Meijer, H. J . J . Organomet. Chem. 1968, 15, 131. (c) Bouwman,
H.; Teuben, J . H. J . Organomet. Chem. 1976, 110, 327. (d) Curtis, C.
J .; Smart, J . C.; Robbins, J . L. Organometallics 1985, 4, 1283.
(2) (a) Martin, H. A.; J ellinek, F. J . Organomet. Chem. 1967, 8, 115.
(b) Helmholdt, R. B.; J ellinek, F.; Martin, H. A.; Vos, A. Recl. Trav.
Chim. Pays-Bas 1967, 86, 1263.
(3) (a) Sanger, A. R. Inorg. Nucl. Chem. Lett. 1973, 9, 351. (b) Boere´,
R. T.; Oakley, R. T.; Reed, R. W. J . Organomet. Chem. 1987, 331, 161.
(c) Scherer, O.; Hornig, P. Chem. Ber. 1968, 101, 2533. (d) Barker, J .;
Kilner, M.; Gould, R. O. J . Chem. Soc., Dalton Trans. 1987, 2687. (e)
Barker, J .; Cameron, N.; Kilner, M.; Mahoud, M. M.; Wallwork, S. C.
J . Chem. Soc., Dalton Trans. 1986, 1359. (f) Coles, M. P.; Swenson, D.
C.; J ordan, R. F.; Young, V. G., J r. Organometallics 1997, 16, 5183,
(4) See for example: Duchateau, R.; Van Wee, C. T.; Meetsma, A.;
Van Duijnen, P. Th.; Teuben, J . H. Organometallics 1996, 15, 2279.
(5) Vivanco, M.; Ruiz, J .; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.
Organometallics 1993, 12, 1794.
and references therein. For
a
review of the coordination of the
(6) (a) Hao, S.; Berno, P.; Minhas, R. K.; Gambarotta, S. J . Am.
Chem. Soc. 1994, 116, 7417. (b) Hao, S.; Berno, P.; Minhas, R. K.;
Gambarotta, S. Inorg. Chim. Acta 1996, 244, 37.
[PhC(NSiMe3)2]- ligand see: Edelmann, F. T. Coord. Chem. Rev. 1994,
137, 403.
S0276-7333(98)00431-2 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 08/13/1998

V(III) Alkyl and Allyl Complexes
Organometallics, Vol. 17, No. 18, 1998 4091
Sch em e 1
F igu r e 1. Structure of [t-BuC(Ni-Pr)2]VCl2(THF)2 (5).
Hydrogen atoms are omitted for clarity.
Ta ble 1. Selected Bon d Dista n ces a n d An gles for
[t-Bu C(Ni-P r )2]VCl2(THF )2 (5)
Bond Distances (Å)
V-Cl(1)
V-Cl(2)
V-O(1)
V-O(2)
2.395(2)
2.3796(18)
2.058(4)
2.056(4)
V-N(1)
2.032(5)
2.034(5)
1.323(8)
1.341(8)
V-N(2)
N(1)-C(4)
N(2)-C(4)
Bond Angles (deg)
N(1)-V-N(2)
Cl(1)-V-Cl(2)
O(1)-V-O(2)
Cl(1)-V-N(1)
Cl(2)-V-N(2)
O(1)-V-N(1)
63.46(19)
94.00(7)
176.7(2)
102.15(15)
100.46(14)
90.49(19)
O(2)-V-N(1)
Cl(1)-V-O(1)
Cl(1)-V-O(2)
V-N(1)-C(1)
V-N(2)-C(9)
N(1)-C(4)-N(2)
91.60(19)
89.59(15)
87.52(15)
134.5(4)
133.7(4)
106.7(5)
Reaction of VCl3(THF)3 with 1 equiv of [A]Li(THF)
in THF produces the green mono-benzamidinate deriva-
tive [A]VCl2(THF)2 (4), which was isolated in 58% yield
after extraction with diethyl ether. The corresponding
red-purple [B]VCl2(THF)2 (5) can be prepared in similar
fashion, but is rather difficult to obtain in pure form
from this reaction mixture. It is more conveniently
prepared (in 83% isolated yield) by a comproportionation
reaction between the bis-amidinate complex 3 and VCl3-
(THF)3 by refluxing in THF for 1 h. The compound was
characterized by single-crystal X-ray diffraction (Figure
1) but loses THF rather easily in the solid state. The
accuracy of the structure determination of 5 is dimin-
ished somewhat by the presence of disorder in the
coordinated THF ligands, but it is clearly shown that
the metal center is distorted octahedrally coordinated
by two chlorides, two THF molecules, and the two
nitrogens of the amidinate ligand. The THF molecules
are oriented trans to each other, with the two chlorides
in cis position. Pertinent bond lengths and angles are
given in Table 1.
The amidinate vanadium(III) chlorides 1-5 are para-
magnetic, which is expressed by their characteristically
broad 1H NMR spectra with line widths (∆ν1/2) up to
550 Hz. The spectra are still quite well resolved at
ambient temperature, and for example, for the benz-
amidinate ligand [A] the individual aromatic protons
can readily be identified in the region δ 11.5-7.0 ppm.
Syn th esis of Bis(a m id in a te) Va n a d iu m Hyd r o-
ca r byls. Both base-free bis-amidinate compounds 2
and 3 react readily with alkyl and allyl Grignard
F igu r e 2. Structure of [PhC(NSiMe3)2]2V(η3-allyl) (8,
major conformer). Hydrogen atoms are omitted for clarity.
reagents to give the corresponding hydrocarbyl com-
pounds [A]2VR (R ) Me, 6; Et, 7; allyl, 8) and [B]2VR
(R ) Me, 9; allyl, 10), which were isolated as red or
orange crystalline solids in typical yields of 60-70% by
crystallization from pentane. The compounds again
show broad resonances of the amidinate ligand protons
1
in their H NMR spectra, indicating their paramagnetic
nature. Resonances due to the metal-bound hydrocarbyl
groups could not be identified in the chemical shift range
of δ ( 250 ppm.
IR spectroscopic data suggest an η3-bonding mode for
the allyl ligands (νCCC ) 1518 cm-1 (8), 1499 cm-1 (10)),
which was corroborated by a crystal structure determi-
nation of 8 (Figure 2, bond distances and angles in Table
2). The η3-allyl ligand in 8 is disordered over two
orientations that could be refined separately (0.7:0.3

4092 Organometallics, Vol. 17, No. 18, 1998
Brussee et al.
Ta ble 2. Selected Bon d Dista n ces a n d An gles for
th e Ma jor Con for m er of [P h C(NSiMe3)2]2V(η3-C3H5)
(8)
Bond Distances (Å)
V-N(1)
V-N(2)
V-N(3)
V-N(4)
V-C(27)
V-C(28)
V-C(29)
2.051(1)
2.144(1)
2.164(1)
2.051(1)
2.280(17)
2.293(3)
2.334(7)
C(27)-C(28)
C(28)-C(29)
N(1)-C(4)
1.387(15)
1.375(8)
1.340(2)
1.320(2)
1.315(2)
1.341(2)
N(2)-C(4)
N(3)-C(17)
N(4)-C(17)
Bond Angles (deg)
F igu r e 3. Structure of [t-BuC(Ni-Pr)2]V(η3-allyl)2 (11).
N(1)-V-N(2)
N(3)-V-N(4)
C(27)-V-C(29)
64.82(5)
64.57(5)
64.0(4)
N(3)-V-C(28) 108.87(9)
N(4)-V-C(28) 128.34(10)
Hydrogen atoms are omitted for clarity.
N(1)-V-N(3)
N(1)-V-N(4)
106.26(5)
109.10(5)
164.97(5)
105.76(5)
C(27)-C(28)-C(29) 124.6(8)
Ta ble 3. Selected Bon d Dista n ces a n d An gles for
[t-Bu C(Ni-P r )2]V(η3-C3H5)2 (11)
N(1)-V-C(28)
N(2)-V-C(28)
121.07(10) N(2)-V-N(3)
86.14(9)
N(2)-V-N(4)
Bond Distances (Å)
V-N(1)
V-N(2)
V-C(12)
V-C(13)
V-C(14)
V-C(15)
V-C(16)
2.0981(19)
2.0124(17)
2.335(3)
2.255(3)
2.233(3)
2.191(3)
2.278(3)
V-C(17)
2.340(3)
1.320(3)
1.358(3)
1.377(4)
1.391(4)
1.378(5)
1.371(5)
populations) and that correspond roughly with a rota-
tion around the V-allyl “centroid” axis of nearly 180°.
For both orientations the allyl C-C and V-C distances
are consistent with a normal, undistorted trihapto-allyl
group.7 The contrast of the allyl binding mode in 8 and
10 with the (16-electron, S ) 1) bis-cyclopentadienyl
analogue Cp2V(allyl), which has an η1-allyl group,1b
illustrates the four-valence electron nature of the amid-
inate monoanionic ligand. The vanadium center in 8
can be described as a highly distorted octahedron,
coordinated by the four amidinate nitrogens and the two
allyl methylene carbons.
N(1)-C(4)
N(2)-C(4)
C(12)-C(13)
C(13)-C(14)
C(15)-C(16)
C(16)-C(17)
Bond Angles (deg)
64.32(7)
118.44(9)
136.70(11) N(1)-C(4)-N(2)
132.78(9)
123.42(9)
87.93(12)
N(1)-V-N(2)
N(1)-V-C(13)
N(1)-V-C(16)
N(2)-V-C(13)
N(2)-V-C(16)
C(13)-V-C(16)
V-N(1)-C(1)
V-N(2)-C(9)
137.75(14)
136.64(16)
109.66(18)
C(12)-C(13)-C(14) 122.6(3)
C(15)-C(16)-C(17) 123.5(3)
The bis(amidinate) vanadium hydrocarbyls 6-10 are
thermally quite robust, including the ethyl derivative
7, and can be kept at 75-100 °C in C6D6 solution in
sealed NMR tubes for days without noticeable decom-
position. The systems are electron deficient (the alkyl
derivatives are formally 12-electron compounds), though
not extremely Lewis acidic (e.g., THF adducts of 6 and
9 could not be isolated). The formal electron count of
(amidinate)2V(alkyl) and the observation that the allyl
ligand in (amidinate)2V(allyl) is η3-bound suggest that
a suitable orbital is available for interaction with
unsaturated substrates and that these species should
be more reactive toward olefins than the Cp2V(alkyl)
compounds.
Oligom er iza tion of Eth en e by (Am id in a te)2V-
(a lk yl). The methyl complex 6 slowly catalyzes the
oligomerization of ethene (in a closed NMR tube, C6D6
solvent) at 80 °C to give a Flory-Schultz distribution
of linear 1- and 2-alkenes with [Cn]/[Cn-2] ) 0.60. The
observed product ratio 1-alkene/Z-2-alkene/E-2-alkene
is 1:0.38:0.14. A quantitative analysis (using an inter-
nal cyclooctane standard) of the Codd olefins, formed by
initial insertion of ethene into the V-Me bond, suggests
that the majority of metal centers present are active in
the catalysis: on 10 µmol of 6 used in the experiment,
9.3(5) µmol of Codd olefin was observed. The observed
catalysis is slow (24 equiv of ethene are consumed over
a period close to 24 h, the conversion can conveniently
be followed by 1H NMR spectroscopy) but persistent, as
after full conversion of the ethene new portions of ethene
added are consumed at a similar rate. This corresponds
with the observed thermal robustness of the (amid-
inate)2V(n-alkyl) species (vide supra).
Syn th esis of (Am id in a te)V(a llyl)2. Reaction of the
mono-benzamidinate complex 4 with 2 equiv of allyl-
MgCl in THF at -80 °C initially produces an orange
solution that turns deep brown on warming above -40
°C. Workup at 0 °C did not allow isolation of vanadium
allyl species from this reaction. In contrast, a similar
reaction of [B]VCl2(THF)2 (5) afforded the paramagnetic
amidinate bis-allyl complex [B]V(allyl)2 (11) as red
crystals in 43% yield after extraction with pentane at 0
°C followed by concentration and cooling of the solution
to -80 °C. A crystal structure determination confirmed
the identification of the compound as [B]V(η3-allyl)2
(Figure 3, pertinent bond distances and angles in Table
3). The η3-bonding mode of the allyl ligands was also
confirmed by IR spectroscopy (νCCC ) 1514 cm-1).
The structure of 11 can be described as a strongly
distorted octahedron, with vanadium coordinated by
the N atoms and the allyl CH2 groups and with the
three large angles around V being N(1)-V-C(17) )
150.67(11)°, N(2)-V-C(12) ) 150.04(9)°, and C(14)-
V-C(15) ) 145.36(11)°. The V-C(14/15) distances are
about 0.1 Å longer than the V-C(12/17) distances, which
is possibly due to a larger trans-influence of the carbon
ligands. Thus the η3-bonding of the allyl ligands in 11
appears to be much more asymmetrical than, for
example, in CpM(η3-allyl)2 (M ) Cr, Mo),8 although this
is not reflected in an asymmetry of the C-C distances
within the allyl groups.
The 14-electron bis-allyl complex 11 is still thermally
quite labile and decomposes in C6D6 solution at 20 °C
with a half-life of about 6 h (1.5 h at 50 °C), releasing a
mixture of propene and 1,5-hexadiene. No well-defined
(7) The highly distorted allyl moiety observed in [A]2Ti(allyl) could
possibly be due to a similar type of disorder. Dick, D. G.; Duchateau,
R.; Edema, J . J . H.; Gambarotta, S. Inorg. Chem. 1993, 32, 1959.
(8) (a) J olly, P. W.; Kru¨ger, C.; Roma˜o, C. C.; Roma˜o, M. J .
Organometallics 1984, 3, 936. (b) Angermund, K.; Do¨hring, A.; J olly,
P. W.; Kru¨ger, C.; Roma˜o, C. C. Organometallics 1986, 5, 1268.

V(III) Alkyl and Allyl Complexes
Organometallics, Vol. 17, No. 18, 1998 4093
1601(w), 1507(m), 1404(m), 1348(s), 1246(s), 1167(w), 1074(w),
1030(w), 1009(w), 999(w), 974(s), 922(w), 841(s), 785(m), 766(s),
727(m), 704(m), 637(w), 615(w), 606(w), 536(m), 513(w), 444(w).
Anal. Calcd for C30H54N4Si4ClOV: C, 52.56; H, 7.94; N, 8.17;
V, 7.43; Cl, 5.17. Found: C, 52.24; H, 8.14; N, 7.73; V, 7.18;
Cl, 5.32.
Syn th esis of [P h C(NSiMe3)2]2VCl (2). Compound 1 (0.50
g, 0.73 mmol) was heated for 4 h in a vacuum (0.01 mbar) at
120 °C. The loss of the THF ligand was accompanied by a
color change from green to red. Recrystallization of the red
residue from toluene gave 2 as red crystals (0.34 g, 0.55 mmol,
75%). 1H NMR (C6D6, 200 MHz, 25 °C): δ 10.20 (∆ν1/2 ) 250
Hz, 4H, Ph), 9.44 (∆ν1/2 ) 49 Hz, 4H, Ph), 7.43 (∆ν1/2 ) 20 Hz,
2H, Ph), 1.29 (∆ν1/2 ) 285 Hz, 36H, SiMe3). IR (Nujol mull,
KBr, cm-1): 1628(w), 1601(w), 1576(w), 1507(s), 1447(s),
1404(m), 1348(s), 1246(s), 1167(m), 1093(w), 1074(w), 1030(w),
1009(m), 999(m), 974(s), 922(m), 841(s), 783(m), 766(s), 727(m),
704(s), 694(m), 637(w), 615(w), 606(w), 536(m), 515(w), 446(w).
The IR spectrum corresponds to the one described by Gam-
barotta et al.6b
Syn th esis of [t-Bu C(Ni-P r )2]2VCl (3). [t-BuC(Ni-Pr)2]Li
(4.10 g, 21.6 mmol) and VCl3(THF)3 (4.03 g, 10.8 mmol) in 50
mL of toluene were heated at 50 °C for 0.5 h. A color change
from purple to brown-orange was observed. After removal of
the solvent, the residue was extracted with pentane (30 mL).
Concentration of the solution and cooling to -20 °C yielded
2.92 g of 3. Concentration of the mother liquor afforded a
second crop of 0.43 g (3.35 g, 7.4 mmol, 69% in total). 1H NMR
(C6D6, 300 MHz, 25 °C): δ 5.08 (∆ν1/2 ) 135 Hz, 24H, CH-
(CH3)2), 3.53 (∆ν1/2 ) 540 Hz, 18H, C(CH3)3). IR (Nujol mull,
KBr, cm-1): 1491(m), 1400(m), 1323(s), 1304(s), 1227(w),
1179(s), 1159(m), 1121(m), 1018(m), 966(w), 921(w), 812(w),
721(m), 681(m), 671(m), 503(m). Anal. Calcd for C22H46N4-
ClV: C, 58.33; H, 10.24; N, 12.37. Found: C, 58.18; H, 10.23;
N, 12.18.
organovanadium compounds could be isolated from the
decomposition. Thus 11 is less stable than the 16-
electron complex CpV(allyl)2,9 but significantly more
stable than the [A]V(allyl)2 analogue that appears to
decompose below -30 °C in solution (vide supra). Like
CpV(allyl)2, 11 is able to catalyze the isomerization of
1-hexene to 2-hexenes, but conversion is limited due to
the thermolability of the system.
Con clu sion s
In conclusion, we have shown that amidinates are
suitable ancillary ligands for electron-deficient vana-
dium(III) hydrocarbyl species. The four-electron nature
of the amidinate ligand is evident from the η3-bonding
of the allyl in (amidinate)2V(allyl) and the ability of
(amidinate)2V(alkyl) compounds to catalyze the oligo-
merization of ethene (albeit slowly). The bis(amidinate)
vanadium hydrocarbyls are all thermally robust, but for
the 14-electron (amidinate)V(η3-allyl)2 species the sta-
bility crucially depends on the nature of the amidinate
ligand. Apart from the differences in steric shielding
of the metal center, it is likely that the electronic
differences between the two amidinate ligands used in
this study (as shown, for example, in the significantly
different colors of isostructural derivatives of the two
ligands) are of importance. This aspect, and its effects
on complex reactivity, will be a subject of further study.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All vanadium compounds de-
scribed here are highly air and moisture sensitive, and all
experiments were performed under nitrogen atmosphere using
standard glovebox, Schlenk, and vacuum-line techniques.
Deuterated solvents (Aldrich) were dried over Na/K alloy and
vacuum transferred before use. Other solvents were distilled
from Na/K alloy (diethyl ether, pentane, THF) or Na (toluene)
before use. [PhC(NSiMe3)2]Li(THF)3a,b and [t-Bu(Ni-Pr)2]Li3f
were prepared according to literature procedures. Ethene
(Union Carbide, 99.99%) was used as received. NMR spectra
were run on Varian Gemini 200 and VXR-300 spectrometers.
IR spectra were recorded from Nujol mulls between KBr disks
Syn th esis of [P h C(NSiMe3)2]VCl2(THF )2 (4). Addition
of [PhC(NSiMe3)2]Li(THF) (2.13 g, 6.2 mmol) to a solution of
VCl3(THF)3 (2.32 g, 6.2 mmol) in THF (50 mL) afforded a green
solution. The solution was stirred for 3 h, after which the
solvent was removed in vacuo. The remaining solid was
stripped by 20 mL of pentane and subsequently extracted with
40 mL of ether. Concentration and cooling to -20 °C yielded
1.90 g (3.6 mmol, 58%) of 4 as green crystals. 1H NMR (C6D6,
200 MHz, 25 °C): δ 11.30 (∆ν1/2 ) 27 Hz, 2H, Ph), 9.30 (∆ν1/2
) 410 Hz, 2H, Ph), 6.97 (∆ν1/2 ) 21 Hz, 1H, Ph), 3.55 (∆ν1/2
)
55 Hz, 8H, THF R-H), 1.47 (∆ν1/2 ) 41 Hz, 8H, THF â-H), -0.60
(∆ν1/2 ) 48 Hz, 18H, SiMe3). IR (Nujol mull, KBr, cm-1):
1674(w), 1643(w), 1589(w), 1568(w), 1499(w), 1443(s), 1393(s),
1343(w), 1246(m), 1181(w), 1076(w), 1037(w), 1020(m), 1003(w),
986(m), 918(w), 862(s), 843(s), 785(m), 762(m), 700(m), 685(w),
521(w), 451(w). Anal. Calcd for C21H39N2Si2Cl2O2V: C, 47.63;
H, 7.42; N, 5.29; V, 9.62. Found: C, 47.07; H, 7.49; N, 5.01;
V, 9.36.
Syn th esis of [t-Bu C(Ni-P r )2]VCl2(THF )2 (5). A mixture
of VCl3(THF)3 (0.78 g, 2.08 mmol) and [t-BuC(Ni-Pr)2]2VCl
(0.94 g, 2.08 mmol) in THF (30 mL) was refluxed for 1 h. The
red-purple solution was evaporated to dryness, resulting in
an intense purple solid, which was stripped three times with
pentane (15 mL) and subsequently washed with pentane (3 ×
5 mL). Crystallization by diffusion of pentane (25 mL) into a
THF (10 mL) solution yielded red-purple bar-shaped crystals
of 5 (0.78 g, 1.74 mmol, 83%). 1H NMR (C6D6, 300 MHz, 25
°C): δ 6.89 (∆ν1/2 ) 110 Hz, 12H, CH(CH3)2), 3.34 (∆ν1/2 ) 28
Hz, 8H, THF R-H), 1.52 (∆ν1/2 ) 24 Hz, 8H, THF â-H),1.10
(∆ν1/2 ) 345 Hz, 9H, C(CH3)3). IR (Nujol mull, KBr, cm-1):
1323(s), 1246(w), 1186(s), 1128(m), 1094(w), 1017(s), 957(w),
924(m), 856(w), 719(m), 681(m), 480(m), 459(m), 426(m).
Syn th esis of [P h C(NSiMe3)2]2VMe (6). [PhC(NSiMe3)2]2-
VCl(THF) (0.85 g, 1.24 mmol) was dissolved in THF (25 mL)
and cooled to -78 °C. To this intense green solution was added
MeMgCl (0.41 mL of a 3 M solution in THF, 1.24 mmol). On
on
a Mattson-4020 Galaxy FT-IR spectrometer. GC/MS
analyses were run on a Hewlett-Packard 6890 GC system with
HP-5NS cross-linked 5% PHME siloxane column and HP 5973
mass selective detector. The results were quantified using a
GC system equipped with FID detector and cyclooctane as
internal standard. Elemental analyses were carried out at the
Micro-Analytical Department of the University of Groningen.
Found values are the average of at least two independent
determinations.
Syn t h esis of [P h C(NSiMe3)2]2VCl(TH F ) (1). [PhC-
(NSiMe3)2]Li(THF) (4.90 g, 14.3 mmol) was added to a solution
of VCl3(THF)3 (2.67 g, 7.2 mmol) in THF (50 mL) at -78 °C.
Upon warming to room temperature a green color formed. The
volatiles were removed in vacuo after 3 h stirring at room
temperature. To remove residual THF, the residue was stirred
with 20 mL of ether, which was subsequently pumped off. After
extraction of the residue with 40 mL of ether, the resulting
solution was concentrated and cooled to -20 °C, affording 2.1
g (3.1 mmol, 43%) of 1 as green bar-shaped plates. 1H NMR
(C6D6, 200 MHz, 25 °C): δ 10.43 (∆ν1/2 ) 20 Hz, 4H, Ph), 8.84
(∆ν1/2 ) 110 Hz, 4H, Ph), 7.34 (∆ν1/2 ) 16 Hz, 2H, Ph), 2.20
(∆ν1/2 ) 19 Hz, 8H, THF R-H), 0.60 (∆ν1/2 ) 150 Hz, 36H, SiMe3
+ 8H, THF â-H). IR (Nujol mull, KBr, cm-1): 1667(w),
(9) Nieman, J .; Pattiasina, J . W.; Teuben, J . H. J . Organomet. Chem.
1984, 262, 157.

4094 Organometallics, Vol. 17, No. 18, 1998
Brussee et al.
warming to room temperature, the color changed to orange-
brown. The reaction mixture was stirred for 1 h at room
temperature before removing the solvent under reduced pres-
sure. The resulting orange solid was stripped twice with
pentane (10 mL) and subsequently extracted with 30 mL of
pentane. Concentration and cooling to -80 °C yielded 0.45 g
(0.76 mmol, 61%) of 6 as orange crystals. 1H NMR (C6D6, 200
pentane (30 mL). Concentration and cooling to -20 °C gave
0.17 g of 10 as red crystals. Concentration of the mother liquor
yielded an additional 0.1 g (0.27 g, 0.59 mmol, 72% in total).
1H NMR (C6D6, 200 MHz, 25 °C): δ 4.31 (∆ν1/2 ) 110 Hz 24H,
CH(CH3)2), 2.48 (∆ν1/2 ) 450 Hz, 18H, C(CH3)3). IR (Nujol
mull, KBr, cm-1): 3077(w), 1508(m), 1402(s), 1331(s), 1308(s),
1262(m), 1223(w), 1179(s), 1128(m), 1088(w), 1017(m), 974(w),
928(w), 891(w), 874(w), 801(m), 772(w), 746(m), 721(m), 665(w),
627(w), 550(w), 480(m), 442(w), 424(w). Anal. Calcd for
MHz, 25 °C): δ 10.62 (∆ν1/2 ) 145 Hz, 4H, Ph), 9.44 (∆ν1/2
)
31 Hz, 4H, Ph), 7.20 (∆ν1/2 ) 19 Hz, 2H, Ph), 1.86 (∆ν1/2 ) 205
Hz, 36H, SiMe3). IR (Nujol mull, KBr, cm-1): 1630(w),
1600(w), 1578(w), 1505(m), 1258(m), 1244(s), 1177(w), 1169(w),
1157(w), 1102(w), 1074(w), 1032(w), 1000(m), 978(s), 916(m),
843(s), 785(m), 758(s), 721(m), 700(m), 683(m), 635(w), 613(w),
604(w), 575(w), 532(m), 442(w). Anal. Calcd for C27H49N4-
Si4V: C, 54.69; H, 8.33; N, 9.45. Found: C, 54.55; H, 8.33; N,
9.23.
C
25H51N4V: C, 65.47; H, 11.21; N, 12.22. Found: C, 65.07; H,
11.23; N, 12.08.
Syn th esis of [t-Bu C(Ni-P r )2]V(η3-C3H5)2 (11). To a cold
solution of [t-BuC(Ni-Pr)2]VCl2(THF)2 (5) (1.26 g, 3,34 mmol)
in 20 mL of THF was added 7.5 mL of a 0.89 M allylMgCl
solution in THF. The reaction mixture was slowly warmed to
-20 °C, and the red-orange solution was stirred for half an
hour. After removing the volatiles in vacuo the residue was
stripped with pentane (15 mL) and subsequently extracted
with 30 mL of pentane. Concentration of the solution and
cooling to -80 °C yielded 11 as red bar-shaped crystals (0.45
g, 1.42 mmol, 43%). 1H NMR (C6D6, 200 MHz, 25 °C): δ 5.93
(∆ν1/2 ) 57 Hz, 12H, CH(CH3)2), 2.00 (∆ν1/2 ) 250 Hz, 9H,
C(CH3)3). IR (Nujol mull, KBr, cm-1): 3077(w), 3063(w),
1630(w), 1514(s), 1489(m), 1398(m), 1360(m), 1325(s), 1310(s),
1262(w), 1246(w), 1181(s), 1130(m), 1117(m), 1082(w), 1018(m),
920(w), 874(w), 828(s), 812(s), 775(m), 756(w), 723(m), 675(w),
662(w), 615(m), 552(w), 500(w), 465(m), 424(w). Anal. Calcd
for C17H33N2V: C, 64.53; H, 10.51; N, 8.85. Found: C, 64.00;
H, 10.60; N, 8.56.
Syn th esis of [P h C(NSiMe3)2]2VEt (7). A suspension of
1.30 g (2.12 mmol) of [PhC(NSiMe3)2]2VCl in 25 mL of ether
was cooled to -80 °C. Subsequently, EtMgBr (1.60 mL of a
1.34 M solution in ether, 2.14 mmol) was added. Upon
warming to room temperature, the orange reaction mixture
was stirred for 30 min, after which the solvent was evaporated.
The remaining solid was extracted with 25 mL of pentane.
Concentration and cooling of the solution at -80 °C yielded 7
as an orange microcrystalline powder (0.85 g, 1.40 mmol, 66%).
1H NMR (C6D6, 300 MHz, 25 °C): δ 10.50 (∆ν1/2 ) 170 Hz,
4H, Ph), 9.38 (∆ν1/2 ) 34 Hz, 4H, Ph), 7.50 (∆ν1/2 ) 17 Hz, 2H,
Ph), 0.79 (∆ν1/2 ) 340 Hz, 36H, SiMe3). IR (Nujol mull, KBr,
cm-1): 1499(m), 1258(m), 1246(s), 1167(w), 1121(w), 1072(w),
1030(w), 1001(m), 980(s), 922(w), 845(s), 785(m), 762(s),
745(m), 725(m), 702(m), 683(m), 615(w), 604(w), 527(m),
442(w).
Syn th esis of [P h C(NSiMe3)2]2V(η3-C3H5) (8). To a solu-
tion of [PhC(NSiMe3)2]2VCl (0.73 g, 1.19 mmol) in THF (25
mL) was added C3H5MgCl (1.7 mL of a 0.72 M solution in THF,
1.22 mmol) at -78 °C. The red solution was stirred for 1 h at
room temperature, after which the solvent was removed in
vacuo and the solid residue was stripped two times with 10
mL of pentane and subsequently extracted with 30 mL of
pentane. The filtrate was concentrated and cooled overnight
at -80 °C, yielding 0.50 g (0.81 mmol, 68%) of 8 as red-colored
block-shaped crystals. 1H NMR (C6D6, 200 MHz, 25 °C): δ
10.26 (∆ν1/2 ) 230 Hz, 4H, Ph), 9.17 (∆ν1/2 ) 34 Hz, 4H, Ph),
8.28 (∆ν1/2 ) 19 Hz, 2H, Ph), 1.14 (∆ν1/2 ) 191 Hz, 36H, SiMe3).
IR (Nujol mull, KBr, cm-1): 1664(w), 1630(w), 1518(w),
1499(m), 1310(w), 1260(m), 1242(s), 1169(w), 1163(w), 1099(w),
1072(w), 1028(w), 1003(m), 978(s), 918(w), 841(s), 783(m),
764(s), 725(m), 700(m), 690(m), 635(w), 613(w), 606(w), 515(m),
465(w), 442(w). Anal. Calcd for C29H51N4Si4V: C, 56.27; H,
8.30; N, 9.05. Found: C, 56.25; H, 8.32; N, 8.93.
Syn th esis of [t-Bu C(Ni-P r )2]2VMe (9). To a THF (15 mL)
solution of [t-BuC(Ni-Pr)2]2VCl (3) (0.40 g, 0.88 mmol) was
added MeMgCl (0.3 mL of a 3.0 M THF solution, 0.90 mmol)
at -80 °C. Upon warming up to room temperature, the color
of the solution changed to brown-yellow. The mixture was
stirred for 0.5 h. After evaporation of the volatiles the brown-
orange residue was stripped with pentane (2 × 10 mL) and
subsequently extracted with 25 mL of pentane. Concentration
and cooling of the solution at -80 °C afforded 9 as plate-shaped
orange crystals (0.13 g, 0.30 mmol, 34%). 1H NMR (C6D6, 200
MHz, 25 °C): δ 4.65 (∆ν1/2 ) 144 Hz, 24H, CH(CH3)2), 3.56
(∆ν1/2 ) 475 Hz, 18H, C(CH3)3). IR (Nujol mull, KBr, cm-1):
1491(s), 1402(s), 1358(s), 1327(s), 1306(s), 1225(w), 1181(s),
1159(m), 1128(m), 1119(m), 1017(m), 945(w), 926(w), 891(w),
874(w), 837(w), 814(w), 758(w), 719(m), 681(m), 669(m), 573(w),
552(w), 507(m), 425(w). Anal. Calcd for C23H49N4V: C, 63.86;
H, 11.42; N, 12.72. Found: C, 63.34; H, 11.35; N, 12.72.
Syn th esis of [t-Bu C(Ni-P r )2]2V(η3-C3H5) (10). AllylMgCl
(0.9 mL of a 0.89 M THF solution) was added to a solution of
[t-BuC(Ni-Pr)2]2VCl (3) (0.37 g, 0.82 mmol) in THF (20 mL)
After removal of the solvent the red residue was extracted with
Eth en e Oligom er iza tion by [P h C(NSiMe3)2]2VMe (6).
An NMR tube equipped with a Teflon stopcock (which can be
attached to a vacuum line) was charged with a solution of 6
mg (0.010 mmol) of [PhC(NSiMe3)2]2VMe in 0.4 mL of benzene-
d6. On a vacuum line, a portion of ethene (0.24 mmol, 24
equiv) was condensed into the NMR tube, after which the
stopcock was closed and the tube warmed to 80 °C (CAU-
TION: the initial pressure in the tube is calculated to be about
3 bar). This procedure was repeated four more times with
intervals of 24 h (monitoring the reaction by NMR spectroscopy
showed full consumption of one portion of the ethene in that
period). After full conversion of the last portion of ethene the
reaction mixture was quenched with a drop of methanol and
filtered over silica. The filtrate was analyzed by GC/MS and
quantified using an internal cyclooctane standard (4.1 mg,
0.036 mmol).
Cr ysta l Str u ctu r e Deter m in a tion s. Suitable crystals of
5, 8, and 11 were mounted on a glass needle in a drybox and
transferred under inert atmosphere into the cold nitrogen
stream on an Enraf-Nonius CAD4-F diffractometer (mono-
chromated Mo KR radiation, ∆ω ) 0.90 + 0.34 tan θ).
Accurate cell parameters and an orientation matrix were
determined from the setting angles (SET410) of 22 reflections
in the ranges 11.90° < θ < 18.42° (5), 17.69° < θ < 20.78° (8),
and 12.22° < θ < 18.21° (11). Reduced cell calculations did
not indicate any higher lattice symmetry.11 Crystal data and
details on data collection and refinement are presented in
Table 4. Intensity data were corrected for Lorentz and
polarization effects, but not for absorption. The structures
were solved by Patterson methods and subsequent difference
Fourier techniques (DIRDIF12). All calculations were per-
formed on a HP9000/735 computer with the program packages
SHELXL13 (least-squares refinements) and PLATON14 (cal-
(10) Boer, J . L. de; Duisenberg, A. J . M. Acta Crystallogr. 1984, A40,
C410.
(11) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
(12) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF-97 program system; Crystallography Laboratory; University
of Nijmegen: Nijmegen, The Netherlands 1997.
(13) Sheldrick, G. M. SHELX-97. Program for the Solution and
Refinement of Crystal Structures; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.

V(III) Alkyl and Allyl Complexes
Organometallics, Vol. 17, No. 18, 1998 4095
Ta ble 4. Cr ysta llogr a p h ic Da ta for 5, 8, a n d 11
5
8
11
formula
mol wt
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C
19H39Cl3N2O2V
C29H51N4Si4V
619.03
C17H33N2V
316.40
449.38
monoclinic
P21/n (No. 14)
12.593(1)
12.216(1)
14.945(1)
triclinic
P1h (No. 2)
10.900(1)
11.849(1)
15.208(1)
112.598(4)
99.134(5)
93.208(4)
1775.3(3)
2
monoclinic
C2/c (No. 15)
12.800(1)
16.380(1)
18.531(1)
92.85(1)
109.331(7)
2296.2(3)
4
1.300
3666.2(4)
8
1.146
Z
D
calc, g cm-3
1.158
F(000)
960
6.8
664
4.4
1376
5.4
0.12 × 0.20 × 0.44
µ(Mo KRj), cm-1
cryst size, mm
0.25 × 0.34 × 0.50
0.25 × 0.30 × 0.45
Data Collection
Mo KRj
radiation
λ(Mo KR), Å
T, K
Mo KRj
0.710 73
130
Mo KRj
0.710 73
130
0.710 73
130
θ range, deg
scan type
data set
horz, vert aperture, mm
ref reflns, rms dev in %
1.36, 27.0
ω/2θ
1.40, 27.0
ω/2θ
1.17, 26.0
ω/2θ
0:14, 0:14, -19:17
3.2 + tan θ; 4.0
222, 2.85
2-20, 1.43
2-22, 1.44
1.000-1.040
107.8
-13:13, -15:13, 0:19
3.2 + tan θ; 4.0
-1-14, 0.8
021, 1.0
400, 0.7
1.000-1.009
107.36
-15:0, 0:20, -21:22
3.2 + tan θ; 4.0
-2-20, 3.3
-3-1-2, 2.5
-2-21, 1.8
1.000-1.007
76.9
drift correction
X-ray exposure time, h
no. of total data
4516
7990
3894
no. of unique data
4091
7694
3587
no. of data with criterion: (Fo g 4.0σ(Fo))
2293
0.046
0.105
6601
0.010
0.018
2649
0.0302
0.0354
2
2
Rint ) ∑[|Fo - Fo2(mean)|]/∑[Fo
]
Rsig ) ∑σ(Fo2)/∑[Fo
]
2
Refinement
4091
243
0.2108
0.0977, 2.00
0.0803
2
no. of rflns (Fo g 0)
no. of refined params
wR(F2)a
7347
570
0.0797
0.0486, 0.519
0.0308
3587
313
0.0930
0.0530, 0.0
0.0401
weighting scheme:b a, b
R(F)
goodness of fit
1.047
-0.54, 1.13(12)
<0.001
1.032
-0.37, 0.40(5)
<0.001
0.995
-0.25, 0.56(5)
<0.001
min, max resid density, e/Å3
(∆/σ)max final cycle
wR(F2) ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]]1/2 for Fo > 0. w ) 1/[σ2(Fo2) + (aP)2 + bP] and P ) [max(Fo2,0) + 2Fc2]/3. c R(F) ) ∑(||Fo| -
a
2
2
b
|Fc||)/∑|Fo| for Fo > 4.0σ(Fo).
culation of geometric data and the ORTEP illustrations). For
5, the hydrogen atoms were included in the final refinement
riding on their carrier atoms with U ) cUequiv of their parent
atom, where c ) 1.2 for the aromatic/non-methyl hydrogen
atoms and c ) 1.5 for the methyl hydrogen atoms and where
values Uequiv are related to the atoms to which the H atoms
are bonded. The methyl groups were refined as rigid groups,
which were allowed to rotate free. Some atoms showed large
thermal displacement parameters, suggesting some degree of
disorder, which is in line with the weak scattering power of
the crystals investigated. For 8, refinement was complicated
by a specific disorder problem: from the solution it was clear
that the C(28) atom position (of the allyl ligand) was disordered
over two positions, indicating two disordered geometries for
the ligand. In the final refinement the minor component of
the disordered allyl ligand was restrained to the major
component. A subsequent difference Fourier synthesis re-
sulted in the location of all the hydrogen atoms, except those
belonging to the minor component of the allyl ligand. These
hydrogen atoms were included in the final refinement riding
on their carrier atoms with their positions calculated by using
hybridization at the C atom as appropriate with Uiso ) 1.2Uequiv
of their parent atom and at a multiplicity due to the disorder
of the minor fraction. The sof of the major component of the
disordered allyl ligand model refined to a value of 0.700(7).
For 11, the positional and anisotropic thermal displacement
parameters for the non-hydrogen atoms were refined.
A
subsequent difference Fourier synthesis resulted in the loca-
tion of all the hydrogen atoms, of which the coordinates and
isotropic thermal displacement parameters were refined.
Ack n ow led gm en t. This investigation was carried
out in connection with NIOK, The Netherlands Institute
for Catalysis Research, and supported by the Depart-
ment of Economic Affairs of The Netherlands.
Su p p or tin g In for m a tion Ava ila ble: Full details of the
structure determinations of 5, 8, and 11 including lists of
atomic coordinates, bond distances and angles, and thermal
parameters (18 pages). Ordering information is given on any
current masthead page.
(14) Spek, A. L. PLATON. Program for the Automated Analysis of
Molecular Geometry, Version October 1996; University of Utrecht:
Utrecht, The Netherlands.
OM980431E