Preparation and characterization of (R2N)2VCl2 [R=Cy, i-Pr] and its activity as olefin polymerization catalyst

Article abstract of DOI:10.1016/S0022-328X(98)00366-0

Reaction of VCl₃(THF)₃ with one equivalent of R₂NLi [R=i-Pr, Cy] formed the tetravalent (R₂N)₂VCl₂ [R=i-Pr (1a), Cy (1b)] which was isolated in crystalline form. The formation of these species is likely to be ascribed to a disproportionation reaction since a divalent vanadium complex, VCl₂(TMEDA)₂ complex was isolated upon treatment of the reaction mixtures with TMEDA. Complexes 1 can be alkylated with RLi to yield the corresponding (R₂N)₂VR₂ (2) derivatives in good yield. Preliminary data on ethylene-propylene (EP) co-polymerization obtained with compounds 1 in conjunction with various aluminum alkyl compounds are described.

Full text of DOI:10.1016/S0022-328X(98)00366-0

Journal of Organometallic Chemistry 562 (1998) 53–60
Preparation and characterization of (R2N)2VCl2 [R=Cy, i-Pr] and its
activity as olefin polymerization catalyst1
Natalie Desmangles a, Sandro Gambarotta a,*, Corinne Bensimon a, Stephen Davis b,
Hayder Zahalka b
a Department of Chemistry, Uni6ersity of Ottawa, Ottawa, Ontario K1N 6N5, Canada
b Department of Research and De6elopment, Bayer Incorporated, Sarnia, Ontario, Canada
Received 27 June 1997
Abstract
Reaction of VCl3(THF)3 with one equivalent of R2NLi [R=i-Pr, Cy] formed the tetravalent (R2N)2VCl2 [R=i-Pr (1a), Cy (1b)]
which was isolated in crystalline form. The formation of these species is likely to be ascribed to a disproportionation reaction since
a divalent vanadium complex, VCl2(TMEDA)2 complex was isolated upon treatment of the reaction mixtures with TMEDA.
Complexes 1 can be alkylated with RLi to yield the corresponding (R2N)2VR2 (2) derivatives in good yield. Preliminary data on
ethylene–propylene (EP) co-polymerization obtained with compounds 1 in conjunction with various aluminum alkyl compounds
are described. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Vanadium; Alkylamido; Alkyl; Ethylene–propylene co-polymerization
1. Introduction
though exhibiting lower catalytic activity than group 4
metal metallocene, display the advantage to perform
well in a variety of oxidation states by producing
polymers and copolymers with desirable physical prop-
erties and a high level of tacticity [4]. In contrast to this
great potential, vanadium was largely ignored by the
recent revival of interest for the new generation of
Ziegler–Natta catalysts since the focus of the current
polyolefins literature mainly remains on the employ-
ment of group 4 metals with a minor emphasis on
lanthanides. Conversely, developing new vanadium-
based Ziegler–Natta type catalysts may pose significant
synthetic challenges given that group 5 metallocene or
cyclopentadienyl derivatives do not show a particularly
strong inclination towards insertion reactions [5] (an
obvious prerequisite for Ziegler–Natta catalysis). Thus
in an attempt to take advantage of the potential of
vanadium as a Ziegler–Natta catalyst, we have recently
embarked on a project aimed to the development of
new vanadium complexes containing anionic organic
amides as ancillary ligands [6]. What is making this
The employment of group 4 metals and lanthanides
plays a primary role in the vast literature of Ziegler–
Natta catalysis [1]. This is mainly due to the distinct
versatility of the metallocenic derivatives of these
metals for which a wealth of synthetic methodologies
were developed [2]. By contrast, limited information is
available for the group 5 elements in spite of the fact
that a few medium and high valent vanadium com-
plexes [VCl4, VOCl3 and V(acac)3] display, in conjunc-
tion with organoaluminum co-catalyst, a remarkable
catalytic activity as Ziegler–Natta polymerization cata-
lysts [3]. These species are currently used for the com-
mercial production of ethylene–propylene–diene
elastomers [EP(D)M] ([3]s). Vanadium compounds, al-
* Corresponding author. Tel.: +1 613 5625199; fax: +1 613
5625170.
1 Dedicated to Prof. R. Bruce King on the occasion of his 60th
birthday.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00366-0

54
N. Desmangles et al. / Journal of Organometallic Chemistry 562 (1998) 53–60
Fig. 1. Thermal ellipsoid plot of 1b. Thermal ellipsoids are drawn at the 50% probability level.
data were consistent with the proposed formulation
while the magnetic moments, calculated on the basis of
this formula, were always in agreement for the d1
electronic configuration of tetravalent vanadium.
The molecular connectivity and the formula were
confirmed by a crystal structure obtained in the case of
the cyclohexyl derivative 1b. The complex is monomeric
and is formed by a vanadium atom surrounded by two
amide groups and two chlorine atoms which impose a
distorted tetrahedral coordination geometry to the
metal center [N1–V1–Cl1=105.0(2), N1–V1–N2=
family of ligands particularly attractive is the possibility
of fine tuning the electronic and steric features around
the metal center through a virtually unlimited choice of
the organic substituents attached to the nitrogen donor
atom.
We describe in this paper the preparation of novel
V(IV) amide complexes as well as a preliminary study
of their organometallic chemistry and utility for olefin
polymerization.
2. Results and discussion
106.8(2),
N1–V1–Cl2=113.6(2),
N2–V1–Cl2=
104.0(2), N2–V1–Cl1=114.2(2)°] (Fig. 1). The V–Cl
˚
We have recently described the reaction of
VCl3(THF)3 with anionic organic amides forming a
series of monomeric and dimeric bis-amide V(III)
(R2N)2VCl derivatives [7]. The fact that these com-
plexes can be prepared in a rather straightforward
manner via chlorine replacement reaction, implies that
a mononuclear ‘(amide)VCl2’ complex is formed as a
transient intermediate. In an attempt to isolate and
characterize this intermediate species we have reacted
VCl3(THF)3 with one equivalent of R2NLi [R=i-Pr,
Cy, Bz]. The reaction proceeds forming an intense red
color upon mixing. Dark orange crystals of (R2N)2VCl2
[R=i-Pr (1a), Cy (1b)] were isolated after suitable
work-up upon cooling their hexane solutions. The com-
plexes are paramagnetic, moderately air sensitive and
test positive for the presence of chlorine and negative
for lithium. X-ray fluorescence experiments yielded a
1:2 vanadium to chlorine ratio. Combustion analysis
distances [V1–Cl1=2.256(2), V1–Cl2=2.217(2) A]
and angles [Cl1–V1–Cl2=113.3(1)°] fall in the ex-
pected range. As usual, the coordination geometry
around the amide nitrogen is trigonal planar [V1–N1–
C1=124.8(4), V1–N1–C7=120.1(4)°] which, together
with the short V–N distances [V1–N1=1.808(5), V1–
˚
N2=1.834(5)A], suggests the presence of a significant
extent of VꢀN double bond.
The formation of a tetravalent vanadium from a
trivalent starting material is rather surprising given that
anionic organic amides are well known to act as reduc-
ing agents [8] and to be able to stabilize low-valent
states [9]. Therefore, the formation of these species has
to be explained with the occurrence of a disproportion-
ation, perhaps similar to that observed in the case of
dinuclear Zr(III) derivatives [10]. In this event, a V(II)
species [probably VCl2(THF)x] should be formed as
byproduct of the reaction. To probe this possibility, we

N. Desmangles et al. / Journal of Organometallic Chemistry 562 (1998) 53–60
55
Scheme 1. Reaction scheme depicting production of complexes 1 and 2.
have treated the reaction mixture with TMEDA. The
treatment produces a light blue crystalline solid in low
yet significant yield which was identified as
VCl2(TMEDA)2 by comparison of the spectroscopic
properties with those of an analytically pure sample.
The most simple manner to envision the process and
to account for these observations is through the reaction
sequence depicted in Scheme 1.
The reaction may be explained by assuming the
formation of an asymmetric and dinuclear intermediate
which undergoes slow and spontaneous cleavage to
originate the two V(IV) and V(II) moieties. The stability
of the two species is likely to be the thermodynamic
driving force for the cleavage of the dinuclear structure.
In agreement with this hypothesis, the reaction of both
[(R2N)2V(v-Cl)]2 and (R2N)2V(v-Cl)2Li(THF)2 with
VCl3 also gave similar yield of (R2N)2VCl2. As for
above, even in this case ‘VCl2’ was isolated and identified
as VCl2(TMEDA)2 after treating the reaction mixture
with TMEDA.
that both the chlorine atoms were replaced and satisfac-
tory combustion analysis data in agreement with the
proposed formulation were obtained for all the com-
pounds. The magnetic moments were in all cases in
agreement with the d1 electronic configuration expected
for a V(IV) species. Compounds 2 are only moderately
stable at room temperature (r.t.) and rapidly decompose
at about 60°C to form new species whose structure is
currently under investiga-tion.
In the case of the neopentyl derivative, the molecular
connectivity was elucidated by an X-ray crystal struc-
ture. The structure consists of a distorted tetrahedral
vanadium center [N1–V1–N2=117.5(1), N1–V1–
C25=110.1(1), N1–V1–C30=106.0(1), N2–V1–
C25=105.6(1), N2–V1–C30=111.3(1), C25–V1–
C30=105.8(1)°] surrounded by two nitrogen atoms of
the two amides and two alkyl groups (Fig. 2). The V–N
distances are normal [V1–N1=1.877(2), V1–N2=
˚
1.878(2) A] and compare well with those of the dich-
loro derivative 1b. The V–C distances are also in the
expected range [V1–C25=2.088(3), V1–C30=2.095(3)
Attempts to replace the chlorine atoms in 1 with alkyls
functions were carried out with a few alkyl lithium
reagents. The reactions of 1 and RLi proceeded rapidly
at −10°C in ether or hexane to produce the correspond-
ing dialkyl derivatives (R2N)2VR2 [R=Np (2a), Ph (2b),
Bz (2c)]. All these compounds were isolated in crystalline
form as dark brown air sensitive materials. All the
compounds tested negative for chlorine, thus confirming
˚
A]. The coordination geometry around the nitrogen
atom is trigonal planar as expected [V1–N1–C1=
127.1(2),
V1–N1–C7=115.9(2),
C1–N1–C7=
116.9(2)°].
Not surprisingly, complexes 2 did not display any
significant olefin polymerization activity under the usual
reaction conditions. Just
a violent reaction was

56
N. Desmangles et al. / Journal of Organometallic Chemistry 562 (1998) 53–60
dium atom was modified by the interaction with the
aluminium co-catalyst. Unfortunately, attempts to iso-
late and characterize the catalytically active species led
to highly pyrophoric microcrystalline catalysts in good
yield, whereas efforts to grow crystals of suitable size
for crystal structure determination were so far
unsuccessful.
By using the most effective catalyst/co-catalyst sys-
tem, the production of PE reached the amount of about
265 Kg of polymer mol−1 catalyst h−1 at 1 bar. After
the initial production of ethylene during the first 15–30
min, the reaction proceeded at low steady rate for
about 20 h when no significant production of PE was
observed anymore. This indicates that the catalyst was
probably deactivated. Addition of chlorinated hydro-
carbon (BzCl, ClCH2CH2Cl or CHCl3) to the reaction
mixture, followed by addition of the co-catalyst,
restarted the polymerization. The deactivation of vana-
dium Ziegler–Natta catalysts is commonly ascribed to
the reduction of the metal center (probably through
i-H elimination) towards formation of divalent species
[3]. However, homopolymerization of ethylene with
trivalent (R2N)2V(v-Cl)2Li(THF)2 or [(R2N)2V(v-Cl)]2
[7] did not give any appreciable polymerization reac-
tion, while treatment of these complexes with halo-
genated hydrocarbons formed the tetravalent
(R2N)2VCl2 catalyst. On the basis of these observations,
we tentatively suggest that the catalyst deactivation in
our system is probably caused by the reduction of
(R2N)2VCl2 to the corresponding trivalent species.
Complexes 1 were tested for ethylene–propylene (EP)
co-polymerization activity with a series of AlRxCl(3−x)
under 2 bar pressure. The results are shown in Table 1.
Under the conditions employed, activity was negligible
with Et3Al but increased with increasing chlorine con-
tent. The activity reached a maximum with Et2AlCl3
which makes this species a promising catalyst for the
production of elastomers. The FTIR spectrum (Fig. 3)
is typical of a random copolymer as evidenced by the
fingerprint region from 700 to 1200 cm−1. The ethylene
content, evaluated via IR spectroscopy by using the
ratio of peak heights of the two resonances at 1155 and
720 cm−1 after calibration with known standards ac-
Fig. 2. Thermal ellipsoid plot of 2a. Thermal ellipsoids are drawn at
the 50% probability level.
observed with butadiene leading to the formation of a
viscous polymer. Even attempts to improve reactivity
by treatment with Lewis acids such as VCl3 or (F5C6)3B
did not modify the inertness of this system toward
polymerization. Conversely, simple treatment of 2 with
anhydrous AlCl3 gave an active polymerization catalyst
(188 Kg of polyethylene (PE) mol−1 catalyst h−1 at a
maximum pressure of 1 bar). These results clearly show
that the concomitant presence of both vanadium and
aluminium is indeed necessary to produce catalytic
activity. Accordingly, complexes 1 act as ethylene poly-
merization catalysts at r.t. and under one atmosphere
of ethylene while in conjunction with a wide variety of
aluminum alkyl co-catalysts (Me3Al, Et3Al, EtAlCl2,
Et1.5AlCl1.5, i-BuAlCl2). We have observed that upon
mixing the catalyst with the co-catalyst an immediate
color change occurred in the hexane solution thus
suggesting that the coordination sphere of the vana-
Table 1
Ethylene–propylene co-polymerization activity of complex 1
Catalyst (R2N)2VCl2
Co-catalyst
Activity (kg EP mol−1 V h−1
)
Composition (wt% ethylene)
R=i-Pr
Et3Al
24
80
860
330
40
135
330
140
—
—
73
71
—
73
73
—
Et2AlCl
Et1.5AlCl1.5
EtAlCl2
Et3Al
Et2AlCl
Et1.5AlCl1.5
EtAlCl2
R=Cy

N. Desmangles et al. / Journal of Organometallic Chemistry 562 (1998) 53–60
57
Fig. 3. FTIR of the EP copolymer.
Elmer 2400 CHN analyzer. Ratios between heavy
atoms were determined by X-ray fluorescence by using
a Philips 2400 instrument.
cording to ASTM procedure D-3900, was typically in
the range 71–73%. In a typical experiment carried out
on (i-Pr2N)2VCl2 and aluminum sesquichloride as a
co-catalyst, the molecular weight was significantly high
(Mw=2293000, Mw/Mn=3.0).
Evaluation of the catalysts were carried out using
ethylene–propylene co-polymerization in hexane solu-
tion at 2 bar total pressure and 22°C. Polymerization
were carried out in 200 ml of hexane in magnetically
agitated glass reactors at 2 bar pressure using a contin-
uous flow of 1000 sccm of both ethylene and propylene.
After equilibration of the hexane with the EP feed at
22°C, 0.2 mmol of co-catalyst were added followed by
the addition of 5 mmol vanadium catalyst. These condi-
tions gave a final concentration of 25 mM [catalyst] and
40/l Al/V. Polymerization was carried out for 15 min
followed by addition of 2 ml ethanol and depressuriza-
tion. The EP rubber was recovered by solvent
evaporation.
3. Experimental section
All operations were performed under inert atmo-
sphere by using standard Schlenk techniques. Cy2NLi
[11] and (i-Pr)2NLi [12] were prepared according to
published procedures. Alkyl lithium derivatives were
prepared according to standard procedures. Ethylene,
propylene (Matheson) were dried over a column of
molecular sieves. Aluminum alkyls solutions in hexane
(Aldrich) were used as received. IR spectra were
recorded on a Mattson 9000 FTIR instrument from
Nujol mulls prepared in a dry-box. Samples for mag-
netic susceptibility measurements were weighed inside a
dry-box equipped with an analytical balance, and
sealed into calibrated tubes. Magnetic measurements
were carried out with a Gouy balance (Johnson
Matthey) at r.t. The magnetic moments were calculated
following standard methods [13] and corrections for
underlying diamagnetism were applied to data [14].
Elemental analyses were carried out with a Perkin
3.1. Synthesis of (i-Pr2N)2VCl2 (1a)
A suspension of VCl3(THF)3 (1.07 g, 2.8 mmol) in
THF (75 ml) was treated at r.t. with freshly prepared
i-Pr2NLi (0.33 g, 3.0 mmol). The color immediately
turned dark red. After stirring overnight at r.t., the
solvent was evaporated in vacuo. The residual oil was
redissolved in hexane (100 ml) and the resulting suspen-
sion filtered, concentrated to small volume and allowed

58
N. Desmangles et al. / Journal of Organometallic Chemistry 562 (1998) 53–60
to stand at −78°C. Dark red crystals of (i-Pr2N)2VCl2
(0.33 g, 1.0 mmol, 71% based on Liamide) separated.
IR (Nujol mull, cm−1) w: 2897(br), 2687(br), 1457(s),
1372(s), 1338(m), 1261(w), 1185(w), 1145(m), 1124(m),
1101(s), 970(w), 924(w), 859(w), 814(w), 780(w), 723(w).
Anal. Calc. (found) for C12H28N2Cl2V: C 44.73 (44.70),
H 8.76 (8.72), N 8.69 (9.10). veff=1.89 vB.
(75 ml) at r.t. The color turned dark red. After stirring
for 30 min, the addition of TMEDA (1.45 ml, 9.61
mmol) to the dark red solution did not cause any
significant color change. After evaporation of the sol-
vent to dryness, hexane (75ml) was added to the dark
residue. The addition of hexane caused the precipita-
tion of a light blue solid mixed with a light brown solid.
After filtration the mixed solid was recrystallized from
THF affording analytically pure light blue crystals of
VCl2(TMEDA)2 (35%) which were identified by com-
parison of the spectroscopic data with those of an
analytically pure sample.
3.2. Synthesis of (Cy2N)2VCl2 (1b)
3.2.1. Method A
Freshly prepared Cy2NLi (0.47 g, 2.83 mmol) was
added to a red suspension of VCl3(THF)3 (1.05 g, 2.81
mmol) in THF (75 ml) at r.t. The color immediately
turned dark red and the resulting solution was stirred
overnight at r.t. After evaporation of the solvent to
dryness, hexane (100 ml) was added to the oily residue.
The resulting suspension was filtered and the solution
was concentrated to small volume. Dark red crystals of
(Cy2N)2VCl2 (0.57 g, 1.2 mmol, 42%) were separated
after allowing the red solution to stand at −30°C for
two days. IR (Nujol mull, cm−1) w: 2907(br), 2690(w),
1455(s), 1376(s), 1342(m), 1258(w), 1145(vw), 1136(m),
1077(m), 1026(m), 954(m), 889(m), 842(m), 804(m),
784(w), 723(w). Anal. Calc. (found) for C24H44N2Cl2V:
C 59.75 (60.41), H 9.19 (9.50), N 5.81 (6.02). veff=2.00
vB.
3.3.2. Method B
Freshly distilled TMEDA (0.82 ml, 5.3 mmol) was
added to a red suspension of VCl3(THF)3 (1.00 g, 2.7
mmol) in THF (75 ml) at r.t. Addition of solid Cy2NLi
(0.51 g, 3.0 mmol) to the resulting violet solution
turned the color light brown. After evaporation of the
solvent in vacuo, the addition of diethyl ether (75 ml)
caused the precipitation of a light blue microcrystalline
VCl2(TMEDA)2 (0.71g, 2.0 mmol, 74%) which was
identified by comparison of the spectroscopic data with
those of an analytically pure sample.
3.4. Synthesis of (Cy2N)2VNp2 ·0.25hexane (2a)
Solid NpLi (0.33 g, 4.22 mmol) was added to a dark
red solution of (Cy2N)2VCl2 (0.98 g, 2.0 mmol) in
hexane (75 ml) at r.t. The color slightly turned dark
orange and the resulting solution was stirred overnight
at r.t. After filtration of LiCl, the solution was concen-
trated to 20–30 ml and allowed to cool down to
−30°C overnight. Dark crystals of (Cy2N)2VNp2 (0.23
g, 0.46 mmol, 23%) were separated. IR (Nujol mull,
cm−1) w: 2905(s), 2689(w), 1456(s), 1375(sh), 1230(w),
1093(m), 1026(m), 956(sh), 891(w), 843(m), 802(m),
3.2.2. Method B
Brown solid [(Cy2N)2VCl]2 (1.7 g, 1.9 mmol) was
added to a red suspension of VCl3(THF)3 (1.46 g, 3.9
mmol) in THF (100 ml) at r.t. The color turned instan-
taneously dark red. After evaporation of the solvent in
vacuo, the dark red oil was dissolved in hexane (75 ml).
Dark red crystals of 1b (1.7 g, 3.6 mmol, 90% based on
VCl3(THF)3) were obtained after allowing the red solu-
tion to stand at −30°C overnight.
722(sh).
Anal.
Calc.
(found)
for
C34H66N2V·0.25hexane: C 73.90 (73.56), H 12.23
(12.01), N 4.92 (4.66). veff=1.85 vB.
3.2.3. Method C
Solid Cy2NLi (4.45 g, 23.7 mmol) was added to a
suspension of VCl4(dme) (3.3 g, 11.8 mmol) in THF
(100 ml) at −78°C. The color gradually changed to the
purple brown and after 8 h stirring at r.t., the solvent
was removed in vacuo. The residue was extracted with
hexane and filtered to remove LiCl. The filtrate was
allowed to stand at −30°C overnight yielding dark
brown crystals of 1b (3.1 g, 6.4 mmol, 55%). The
compound was identified by comparison of the analyti-
cal and spectroscopic data of an analytically pure
sample.
3.5. Synthesis of (Cy2N)2VPh2 (2b)
Solid PhLi (0.29 g, 3.45 mmol) was added to a dark
red solution of (Cy2N)2VCl2 (0.66 g, 1.37 mmol) in
hexane (75 ml) at r.t. The color slightly turned dark
orange and the resulting solution was stirred overnight
at r.t. After filtration of LiCl, the solution was concen-
trated to about 25 ml and allowed to stand at −30°C
overnight. Dark microcrystalline solid of (Cy2N)2VPh2
(0.58 g, 1.0 mmol, 73%) were separated. IR (Nujol
mull, cm−1) w: 2907(br), 2692(w), 1457(s), 1447(vw),
1376(sh), 1366 (vw), 1260(m), 1100(vw), 1090(vw),
1080(vw), 1070(m), 1059(vw), 1038(m), 960(shw),
891(w), 813(vw), 803(m), 722(sh), 698(sh). Anal. Calc.
(found) for C36H54N2V: C 76.42 (76.11), H 9.62 (9.38),
N 4.95 (4.88). veff=1.80 vB.
3.3. Isolation of VCl2(TMEDA)2
3.3.1. Method A
Solid Cy2NLi (0.95 g, 5.7 mmol) was added to a red
suspension of VCl3(THF)3 (1.78 g, 4.76 mmol) in THF

N. Desmangles et al. / Journal of Organometallic Chemistry 562 (1998) 53–60
59
Table 3
3.6. Synthesis of (Cy2N)2VBz2 (2c)
˚
Selected bond distances (A) and angles (°)
A solution of BzMgCl (5.8 ml, 5.8 mmol, 1 M in
ether) was added to a dark red solution of (Cy2N)2VCl2
(1.4 g, 2.9 mmol) in hexane (75 ml) at r.t. The color
turned brownish orange and the resulting solution was
stirred overnight at r.t. After filtration of LiCl, the
solution was concentrated to 20–30 ml and allowed to
stand at −30°C overnight. Dark microcrystalline solid
of (Cy2N)2VBz2 (0.9 g, 1.5 mmol, 52%) were separated.
IR (Nujol mull, cm−1) w: Anal. Calc. (found) for
C38H58N2V: C 76.86 (76.66), H 9.85 (9.69), N 4.72
(4.61). veff=1.77 vB.
1b
2a
V1–Cl1
V1–Cl2
V1–N1
V1–N2
Cl1–V1–Cl2
Cl1–V1–N1
Cl1–V1–N2
Cl2–V1–N1
Cl2–V1–N2
V1–N1–C1
V1–N1–C7
V1–N1–C1
V1–N1–C7
2.226(2)
2.217(2)
1.808(5)
1.834(5)
V1–N1
V1–N2
V1–C25
V1–C30
C25–V1–C30
N1–V1–N2
N1–V1–C25
N1–V1–C30
N2–V1–C25
N2–V1–C30
C1–N1–C7
1.877(2)
1.878(2)
2.088(3)
2.095(3)
113.3(1)
105.8(1)
105.0(2)
114.2(2)
113.6(2)
104.0(2)
124.8(4)
120.1(4)
127.1(2)
115.8(2)
117.5(1)
110.0(1)
106.0(1)
105.5(1)
111.3(1)
116.9(2)
3.7. X-ray crystallography
Data were collected at −153°C for suitable air-sensi-
tive crystals mounted on a glass fiber inside a drybox
and transferred under the liquid nitrogen stream of the
cooling system of either Nonius CAD-4 or Siemens
CCD X-ray diffractometers. The ꢀ−2q scan technique
was used. Data were collected until 100° of 2q for 1b
(Cu radiation) and to 57.0° for 2a (Mo radiation). Cell
constants and orientation matrices were obtained from
the least-squares refinement of 25 centered reflections.
The intensities of three standard reflections, measured
after every 150 reflections, showed no statistically sig-
nificant decay over the duration of the data collections.
Data were corrected for Lorentz and polarization ef-
fects and for absorption (PSI scan). The structures were
solved by direct methods resulting in locating all the
non-hydrogen atoms. Their positions were refined an-
isotropically. Hydrogen atom positions were calculated
but not refined. Complex 1b contains two crystallo-
graphically-independent and nearly identical molecules
in the lattice while complex 2a has one disordered
molecule of hexane per unit cell. Attempts to model the
disorder did not improve the thermal parameters and
the quality of the refinement. The data were processed
using the NRCVAX software packages on a Silicon
Graphics workstation. Refinements were carried out by
using full-matrix least-squares techniques on F mini-
mizing the function Sw(ꢀF0ꢀ−ꢀFcꢀ)2, where w=4F02/
|2(F20) and F0 and Fc are the observed and calculated
structure factors, respectively. Atomic scattering factors
and anomalous dispersion terms were taken from the
usual sources (Cromer and Waber) [15]. Details on the
data collections and structure refinement are listed in
Table 2. The final atomic coordinates are given as
Supplementary Material (see below). Selected bond dis-
tances and angles are given in Table 3.
Table 2
4. Supplementary material available
Crystal data and structure analysis results
1b
2a
Listing of atomic coordinates, thermal parameters,
bond distances and angles for 1b and 2a.
Formula
C24H44N2VCl2
482.48
Pbna
15.669(4)
36.004(1)
18.871(4)
C34H66N2V·0.25C6H14
575.39
P21/a
17.7491(2)
10.6826(2)
20.8487(3)
Formula weight
Space group
˚
a (A)
Acknowledgements
˚
b (A)
˚
c (A)
This work was supported by the National Science
and Engineering Council of Canada (NSERC operating
grant) and by the generosity of Bayer (Sarnia, Ontario).
i (°)
V (A )
109.479(1)
33726.8(1)
4
–
3
˚
10 646(4)
8
1.54056
−153
1.205
50.4
Z
˚
Radiation (Kh A)
0.70930
−153
1.026
2.9
T (°C)
Dcalc (g cm−3
)
vcalc (cm−1
)
References
R
Rw
GOF
0.048
0.051
2.02
0.053
0.77
1.91
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