Insertion reactions of phenyl isocyanate into hafnium nitrogen bonds: Synthesis and reactivity of hafnium complexes bearing substituted pyrrolyl ligands

Article abstract of DOI:10.1016/j.jorganchem.2004.07.046

A bis(diethylamido)hafnium compound [C₄(CH₂NMe ₂)-2]₂Hf(NEt₂)₂ (1) has been prepared in 79% yield by reacting Hf(NEt₂)₄ with 2 equiv. of [C₄H(CH₂NMe₂)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl isocyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium-NEt₂ bonds to generate [C₄(CH₂NMe₂)-2]₂Hf[PhNC (NEt₂)O]₂ (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week in toluene produces a mixture of 2 and [C₄(CH₂NMe ₂)-2]Hf[PhNC(NEt₂)O]₃ (3). For comparison, reacting Hf(NEt₂)₄ with 4 equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf-N bonds, and forms a tetrakis-ureato hafnium compound Hf[PhNC(NEt₂)O]₄ (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the ureato fragments of 2 are resonance delocalized between the C-O, C-NPh, and C-NEt₂ bonds, which are all partially doubly bonded.

Full text of DOI:10.1016/j.jorganchem.2004.07.046

Journal of Organometallic Chemistry 689 (2004) 3362–3369
www.elsevier.com/locate/jorganchem
Insertion reactions of phenyl isocyanate into hafnium nitrogen
bonds: synthesis and reactivity of hafnium complexes
bearing substituted pyrrolyl ligands
a
Kun-Chun Hsieh , Wen-Yi Lee , Chun-Liang Lai , Ching-Han Hu , Hon Man Lee ,
a
a
a
a
a,
b
b
Jui-Hsien Huang *, Shie-Ming Peng , Gene-Hsing Lee
a
Department of Chemistry, National Changhua University of Education, Changhua 500, Taiwan
b
Department of Chemistry, National Taiwan University, Taipei 100, Taiwan
Received 26 March 2004; accepted 27 July 2004
Available online 27 August 2004
Abstract
A bis(diethylamido)hafnium compound [C4H3N(CH2NMe2)-2]2Hf(NEt2)2 (1) has been prepared in 79% yield by reacting
Hf(NEt2)4 with 2 equiv. of [C4H3NH(CH2NMe2)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl iso-
cyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium–NEt2 bonds to generate
[C4H3N(CH2NMe2)-2]2Hf[PhNC(NEt2)O]2 (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week
in toluene produces a mixture of 2 and [C4H3N(CH2NMe2)-2]Hf[PhNC(NEt2)O]3 (3). For comparison, reacting Hf(NEt2)4 with 4
equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf–N bonds, and forms a tetrakis-
ureato hafnium compound Hf[PhNC(NEt2)O]4 (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the
ureato fragments of 2 are resonance delocalized between the C–O, C–NPh, and C–NEt2 bonds, which are all partially doubly
bonded.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Phenyl isocyanate; Insertion hafnium; Pyrrolyl
1. Introduction
and Nobel [8] described the transition-metal-mediated
reactions of organic isocyanates, which covered a broad
range of metal complexes. Insertion reactions of isocya-
nates into metal carbon or metal nitrogen bonds have
been known [9–12]; however, the insertion reactions of
isocyanates into early transition metal–nitrogen bonds
still remain undeveloped [13–19]. Examples showed by
Lappert and coworkers [20] were those M(NMe2)4
(M = Ti, Zr, Hf) react exothermically with excess of
phenyl isocyanates to give M[NPhC(O)NMe2]4. How-
ever, no crystal structures were presented.
Organic isocyanates are useful compounds in organic
synthesis because they are easily accessible and highly
active toward unsaturated substrates [1]. In addition,
isocyanate compounds are widely used in polymeriza-
tion chemistry for producing polyurethane [2]. Some
of the organic reactions of isocyanates are catalyzed
by transition metal complexes [3–7] and the reactions
of organic isocyanates with transition metals have been
studied extensively. An excellent review by Braunstein
To better understand the reactivity of isocyanates
toward early transition metal nitrogen bonds, here we
report the synthesis and characterization of hafnium
amide complexes and their reactivity toward isocyanates.
*
Corresponding author. Tel: +886 4 723 2105x3531; fax: +886 4
721 1190.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.07.046

K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
3363
2. Results and discussion
to its metal center in various modes, as shown in
Scheme 2. The broad signals can be resolved in higher
field NMR spectrometer. When a 600 MHz NMR spec-
trometer was used, the 1H NMR spectra of 2 exhibit two
peaks for the dimethylamino groups and multiple reso-
nances for the diethyl amino fragments. A comparison
2.1. Synthesis and characterization
A bis(diethylamido)hafnium compound [C4H3N(CH2
NMe2)-2]2Hf(NEt2)2 (1) has been prepared in 79% yield
by a deamination reaction between Hf(NEt2)4 and 2
equiv. of [C4H3NH(CH2NMe2)-2] in heptane (Scheme
1). Compound 1 is highly air- and moisture sensitive,
which readily decomposes upon exposure to the atmos-
phere. The 1H and 13C NMR spectra of 1 exhibit a sym-
metrical geometry with only one set of signals for the
substituted pyrrolyl and diethylamido ligands being
observed.
Reactions of compound 1 with CO2 and CS2 do not
result in isolable insertion products, but rather afford
the regeneration of substituted pyrrolyl ligands and
un-identified products. In contrast, reaction of 1 with
2 equiv. of phenyl isocyanate at room temperature in
diethyl ether for 30 min results in the PhNCO being in-
serted selectively into Hf–NEt2 bonds to generate
[C4H3N(CH2NMe2)-2]2Hf[PhNC(NEt2)O]2 (2) in 56%
yield. The 13C NMR spectrum of 2 revealed a resonance
at d 165.9, which is assignable to the quaternary carbons
of ureato PhNC(NEt2)O fragments. The 1H NMR spec-
trum of 2 obtained from a 300 MHz NMR spectrometer
contains sharp resonances at d 6.59 and 6.45 attributable
to the pyrrolyl fragments of the bidentate ligands. How-
ever, the dimethylamino fragments of the bidentate lig-
ands (d 2.18) as well as the diethylamino fragments (d
2.78 and 0.73) exhibit broad signals. The signal-broad-
ening can probably be attributed to the fluxionality of
the ureato PhNC(NEt2)O fragments of 2, which bind
1
of the H NMR spectra of 2 obtained from 300 and
600 MHz NMR spectrometers was shown in Fig. 1.
Prolong stirring of 1 with 2 equiv. of PhNCO in tol-
uene at room temperature for 6 days, a mixture of com-
pounds 2 and [C4H3N(CH2NMe2)-2]Hf[PhNC(NEt2)
O]3 (3) can be obtained according to the 1H NMR spec-
tra. Pure compound 3 can be obtained in 14% yield after
removing volatiles and repeating recrystallization of the
mixture from a diethyl ether solution. The 13C NMR
spectrum of 3 revealed two resonances at d 166.2 and
167.0, which are assignable to the quaternary carbons
of ureato PhNC(NEt2)O fragments. Again, the dimeth-
ylamino fragments of the bidentate ligands (d 2.67) as
well as the diethylamino fragments (d 2.27–2.73 and
0.73) exhibit broad signals due to the exchanging of
bonding modes as shown in Scheme 2. No reaction
was observed when monitoring a C6D6 solution of 2
for more than 80 h. Therefore, the formation of 3 was
proposed as the results of ligand redistribution, which
only occurs when excess of PhNCO is present. Indeed,
when small amount of PhNCO was added to the a solu-
tion of compound 2 in C6D6, 3 was formed together
with several un-identified compounds within 12 h at
50 °C, according to the 1H NMR spectra. However,
the real mechanism for the ligand redistribution is still
unclear. Attempts to increase the yield of compound 3
by reacting 1 with 3 equiv. of PhNCO in toluene result
NMe2
NEt2
O
N
N
O
N
Hf
Ph
N
NMe2
NEt2
Ph
Hf(NEt2)4
2
2
N
H
2 PhNCO
diethyl ether
NMe2
NMe2
NEt2
NMe2
NEt2
O
N
N
N
2 PhNCO
toluene
N
O
Hf
Ph
Hf
Ph
2
+
N
NEt2
6 days
O
NMe2
N
NEt2
Et2N
Ph
1
3
Scheme 1.

3364
K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
O
Ph
O
O
Et2N
Hf
NEt2
C
Hf
NEt2
C
NEt2
N
Hf
C
O
NEt2
N
N
4 PhNCO
N
O
N
Hf(NEt2)4
Hf
Ph
Ph
O
Ph
Ph
N
Ph
O
N
NEt2
Scheme 2.
Et2N
Ph
4
Scheme 3.
spectrum of 4 exhibited a singlet at d 166.6 for the qua-
ternary carbon of ureato PhNC(NEt2)O, which is simi-
lar to that of 2.
2.2. Molecular structures of compounds 1, 2, 3 and 4
Crystals of 1 suitable for crystallographic studies
were obtained from a toluene solution at ꢀ20 °C.
Molecular structure of 1 and selected bond distances
and angles are given in Fig. 2 and Table 1, respectively.
The geometry of 1 is best described as a distorted octa-
hedral with bond angles of the three axes N(1)–Hf(1)–
N(6), N(4)–Hf(1)–N(5), and N(2)–Hf(1)–N(3) of
153.54(9)°, 162.45(8)°, and 165.08(8)°, respectively.
The two substituted pyrrolyl ligands bond to the haf-
nium center with acute angles of 70.82(9)° and
71.22(8)°. The two diethylamido ligands bind to the Le-
wis acidic hafnium atom in an asymmetrical manner and
result in a short bond distance of Hf(1)–C(19) (2.845(3)
Fig. 1. The 1H NMR spectra for compound 2 ranged from d 0–3,
asterisk ( ) represent un-identified products (a) 300 MHz NMR
*
spectrometer (b) 600 MHz spectrometer.
˚
A) with small bond angle of Hf(1)–N(6)–C(19)
(106.20(19)°). However, the two diethylamido ligands
in a mixture of 2, 3, 4, and several un-identified prod-
ucts. Therefore, we conclude that when 2 equiv. of
PhNCO was added in a solution of 1, it can only insert
selectively into the Hf–amide bonds and only com-
pounds 2 and 3 can be isolated. However, addition of
PhNCO into hafnium–pyrrolyl bond may occur when
excess of PhNCO was presented in the reaction solution
1
(i.e., > 2 equiv.), according to H NMR spectra [21].
The reaction became complicate and several un-identi-
fied products besides 2 and 3 were found. All the at-
tempts to isolate new compounds are not successful.
For comparison, reacting Hf(NEt2)4 with 4 equiv. of
PhNCO in a toluene solution at room temperature re-
sults in the PhNCO inserted into Hf–N bonds forming
a tetrakis–ureato hafnium compound Hf[PhNC(NE-
t2)O]4 (4) in 88% yield (Scheme 3). A similar compound,
Hf[PhNC(NMe2)O]4, has been synthesized by Lappert
and coworkers [20]. The 1H NMR spectrum of 4 exhibits
only one set of quartet and triplet at d 2.89 and 0.71 for
the ethyl protons of diethylamino groups, indicating
that the four ureato PhNC(NEt2)O groups are equiva-
lent in solution at room temperature. The 13C NMR
Fig. 2. The molecular structure of 1. Thermal ellipsoids were drawn at
50% probability level.

K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
3365
Table 1
Selected bond distances and angles for compounds 1, 2, 3 and 4
1
Hf(1)–N(1)
Hf(1)–N(4)
2.207(3)
2.635(2)
Hf(1)–N(2)
Hf(1)–N(5)
2.495(2)
2.023(2)
Hf(1)–N(3)
Hf(1)–N(6)
2.174(2)
2.046(2)
N(1)–Hf(1)–N(2)
N(1)–Hf(1)–N(6)
N(4)–Hf(1)–N(5)
70.82(9)
153.54(9)
162.45(8)
N(3)–Hf(1)–N(4)
N(2)–Hf(1)–N(3)
71.22(8)
165.08(8)
2
Hf(1)–N(1)
Hf(1)–N(5)
Hf(1)–O(1)
Hf(1)–C(26)
C(8)–N(4)
C(26)–N(8)
2.202(8)
2.207(8)
2.188(7)
2.668(11)
1.338(12)
1.336(13)
Hf(1)–N(2)
Hf(1)–N(6)
Hf(1)–O(2)
N(3)–C(8)
N(7)–C(26)
2.563(9)
2.552(11)
2.189(7)
1.334(12)
1.327(12)
Hf(1)–N(3)
Hf(1)–N(7)
Hf(1)–C(8)
C(8)–O(1)
C(26)–O(2)
2.229(8)
2.253(9)
2.648(10)
1.287(11)
1.312(11)
N(1)–Hf(1)–N(2)
O(1)–Hf(1)–N(3)
N(2)–Hf(1)–C(26)
N(3)–C(8)–O(1)
67.1(3)
59.1(3)
161.7(3)
112.5(9)
N(5)–Hf(1)–N(6)
O(2)–Hf(1)–N(7)
N(6)–Hf(1)–C(8)
N(7)–C(26)–O(2)
66.6(3)
58.9(3)
165.1(3)
111.8(9)
3
Hf(1)–O(3)
Hf(1)–N(7)
Hf(1)–N(3)
Hf(1)–C(18)
O(1)–C(7)
O(3)–C(29)
2.181(6)
2.206(6)
2.260(6)
2.652(8)
1.286(9)
1.316(12)
Hf(1)–O(2)
Hf(1)–N(1)
Hf(1)–N(8)
Hf(1)–C(29)
O(2)–C(18)
N(5)–C(29)
2.189(5)
2.250(6)
2.468(6)
2.656(9)
1.295(9)
1.313(11)
Hf(1)–O(1)
Hf(1)–N(5)
Hf(1)–C(7)
N(1)–C(7)
N(3)–C(18)
2.191(6)
2.251(6)
2.636(8)
1.304(10)
1.38(11)
N(7)–Hf(1)–N(8)
O(2)–Hf(1)–N(3)
88.1(2)
58.9(2)
O(1)–Hf(1)–N(1)
O(3)–Hf(1)–N(5)
58.5(2)
59.1(2)
4
Hf(1)–N(1)
Hf(1)–N(7)
Hf(1)–O(3)
Hf(1)–C(12)
O(1)–C(1)
O(2)–C(12)
O(3)–C(23)
O(4)–C(34)
2.264(3)
2.252(6)
2.184(3)
2.647(4)
1.275(6)
1.289(4)
1.294(4)
1.294(4)
Hf(1)–N(3)
Hf(1)–O(1)
Hf(1)–O(4)
Hf(1)–C(23)
C(1)–N(2)
2.251(3)
2.208(4)
2.189(3)
2.653(4)
1.361(5)
1.349(5)
1.347(5)
1.346(5)
Hf(1)–N(5)
Hf(1)–O(2)
Hf(1)–C(1)
Hf(1)–C(34)
C(1)–N(1)
C(12)–N(3)
C(23)–N(5)
C(34)–N(7)
2.251(3)
2.185(3)
2.658(4)
2.655(4)
1.356(6)
1.355(5)
1.329(5)
1.340(7)
C(12)–N(4)
C(23)–N(6)
C(34)–N(8)
O(1)–Hf(1)–N(1)
O(3)–Hf(1)–N(5)
O(1)–C(1)–N(1)
O(3)–C(23)–N(5)
58.96(15)
59.04(10)
113.6(4)
112.8(3)
O(2)–Hf(1)–N(3)
O(4)–Hf(1)–N(7)
O(2)–C(12)–N(3)
O(4)–C(34)–N(7)
59.55(10)
59.23(16)
112.9(3)
112.9(4)
become equivalent in solution due to their low rotation
energy barriers.
than those of compound 1, presumably due to the larger
ureato ligands compressing the bond angles of the che-
lated substituted pyrrolyl ligands. The N–C (ranged
Crystals of 2 were obtained from a diethyl ether solu-
tion at ꢀ20 °C. The molecular structure and selected
bond distances and angles of 2 are shown in Fig. 3
and Table 1, respectively. Compound 2 can be viewed
as an eight coordinated hafnium compound with the
two ureato ligands are bonded to hafnium through
nitrogen and oxygen atoms. Compound 2 possesses
two planar ureato metallacycles, which contain obtuse
N–C–O angles of 112.5(9)° and 111.8(9)°, as well as
acute N–Hf–O angles of 59.1(3)° and 58.9(3)°. The
two substituted pyrrolyl ligands bond to the hafnium
center with acute angles of 67.1(3)° and 66.6(3)°, smaller
˚
from 1.327(12) to 1.338(13) A) and C–O (1.287(11) to
˚
1.312(11) A) bond distances of ureato fragments are
both in the range of partially double bond, indicating
that the p electrons of the ureato fragments are equally
delocalized in the NC(N)O core.
Crystals of 3 suitable for crystallographic studies
were obtained after repeating recrystallization of a mix-
ture of compounds 2 and 3 diethyl ether solution at
ꢀ20 °C. The molecular structure and selected bond dis-
tances and angles of 3 are shown in Fig. 4 and Table 1,
respectively. A disorder occurred at one of the methyl

3366
K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
Fig. 5. The molecular structure of 4. Thermal ellipsoids were drawn at
30% probability level.
Fig. 3. The molecular structure of 2. Thermal ellipsoids were drawn at
30% probability level.
carbon which was separated into C(33) and C(33)0 with
the occupancy ratio of 60/40. The bond distances and
angles of 3 were similar to those of 2.
O
O
O
0
O
0
N
0
0
N
O
N 0
Hf
Even though Hf[PhNC(NMe2)O]4, analogous to
compound 4, has been synthesized [20], no crystal struc-
ture of that has been obtained. Crystals of 4 suitable for
crystallographic studies were obtained from a toluene
solution at ꢀ20°C. The molecular structure and selected
bond distances and angles of 4 are shown in Fig. 5 and
Table 1, respectively. Compound 4 can also be viewed as
an eight coordinate MX8 geometry [22] where ureato
fragments bond to the hafnium atom through nitrogen
and oxygen atoms. A simplified geometry of 4 is shown
in Fig. 6 where the eight coordinated atoms are located
N
Hf
N
0N
0
N
O
N
O0
O
(a)
(b)
Fig. 6. Hf(g3-NCO)4 core inscribed within (a) two perpendicular
rectangles and (b) an idealized cube showing the eight coordinate
HfN4O4 unit.
on two perpendicular rectangles or in an idealized cube.
The four ureato fragments coordinate to the hafnium
atom forming four planar metallacycles. The bond dis-
tances and angles of 4 around the ureato metallacycles
are similar to that of 2, indicating that the p electrons
of ureato fragments are evenly distributed.
2.3. Theoretical calculation
All calculations were performed using the hybrid
B3LYP density functional theory [23,24]. For the basis
sets we chose 6-31 G* for H, C, N, O, and LANL2DZ
effective core potential plus basis functions for hafnium
[25,26]. The reaction of 1 with PhNCO, which yields 2,
was calculated as an exothermic reaction with ꢀ65.7
kcal/mol for the heat of emission. The calculated bond
distances and angles of 1 and 2 are close to the experi-
mental data (see supporting information). As suggested
in Scheme 2, the unpaired electrons of the ureato frag-
ments of 2 are resonance delocalized between the C–O,
C–NPh, and C–NEt2 bonds, which are all partially dou-
bly bonded.
Fig. 4. The molecular structure of 3. Thermal ellipsoids were drawn at
30% probability level. C(33) and C(33)0 are disorder sites with
occupancy ration of 60/40.

K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
3367
3. Experimental
CH), 7.27–6.95 (m, 10H, phenyl and pyrrolyl CH),
6.59 (m, 2H, pyrrolyl CH), 6.45 (m, 2H, pyrrolyl CH),
4.09 (d, JHH = 13.2 Hz, CHaHbNMe2), 3.14 (d,
JHH = 13.2 Hz, CHaHbNMe2), 2.78 (br, 8H, NCH2CH3),
2.18 (br, 12H, CH2NMe2), 0.79 (br, 6H, NCH2CH3),
0.60 (br, 6H, NCH2CH3). 13C NMR (C6D6): 165.9 (s,
NCO), 146.4 (s, phenyl Cipso), 136.3 (s, pyrrolyl Cipso),
129.9 (d, JCH = 181 Hz, pyrrolyl CH), 128.2 (d,
JCH = 158 Hz, phenyl CH), 127.9, 122.9 (d, JCH = 160
Hz, phenyl CH), 107.0 (d, JCH = 163 Hz, pyrrolyl
CH), 104.9 (d, JCH = 156 Hz, pyrrolyl CH), 61.2 (t,
JCH = 134 Hz, CH2NMe2), 49.5 (q, JCH = 137 Hz,
NMe2), 41.2 (t, JCH = 137 Hz, NCH2CH3), 13.2 (q,
JCH = 126 Hz, NCH2CH3). Anal. Calc. for
C36H52N8O2Hf: C, 53.56; H, 6.49; N, 13.88. Found: C,
52.73; H, 5.93; N, 13.99%.
3.1. General procedure
All reactions were performed under a dry nitrogen
atmosphere using standard Schlenk techniques or in a
glove box. Toluene, diethyl ether, and heptane were
dried by refluxing over sodium benzophenone ketyl.
CH2Cl2 was dried over P2O5. All solvents were distilled
and stored in solvent reservoirs which contained 4 A
molecular sieves and were purged with nitrogen. CDCl3
was degassed by freeze-and-thaw method and dried over
4 A molecular sieves. H and 13C NMR spectra were re-
˚
˚
1
corded on a Bruker AC 200 or an Avance 300 NMR
spectrometer at room temperature if not stated other-
wise. Chemical shifts for H and 13C spectra were re-
1
corded in ppm relative to the residual protons and 13C
of CDCl3 (d 7.24, 77.0) and C6D6 (d 7.16, 128.0). Ele-
mental analyses were performed on a Heraeus CHN-
OS Rapid Elemental Analyzer at the Instrument Center,
NCHU. (2-dimethylaminomethyl)pyrrole was synthe-
sized according to published literature [27,28]. HfCl4
was purchased from Aldrich Co. and used as received.
3.4. [C4H3N(CH2NMe2)-2]Hf[PhNC(NEt2)O]3 (3)
Similar procedure as for 2 has been used here. 1 (2.0
g, 3.5 mmol) and PhNCO (0.84 g, 7.1 mmol) were used
and stirred for 6 days. Repeating recrystallization of
resulting mixture from a diethyl ether solution yields
0.40 g of 3 in 14% yield. Small amount of 2 was found
in the final product. 1H NMR (C6D6): 7.58 (m, 1H, phe-
nyl CH), 6.90–7.38 (br, 15H, phenyl + pyrrolyl CH),
6.67 (m, 1H, pyrrolyl CH), 6.54 (m, 1H, pyrrolyl CH),
4.01 (m, 2H, CH2NMe2), 2.65–2.73 (br, 15H, N
CH2Me+NMe), 2.27 (br, 3H, NMe), 0.73 (br, 18H,
NCH2Me). 13C NMR (C6D6): 167.0 (s, NCO), 166.2
(s, NCO), 146.7 (s, br, phenyl, Cipso), 135.6 (s, pyrrolyl,
3.2. [C4H3N(CH2NMe2)-2]2Hf(NEt2)2 (1)
To a 100 mL Schlenk flask charged with 20 mL hep-
tane and Hf(NEt2)4 (3.0 g, 6.42 mmol) was added drop-
wise with a C4H4N(CH2NMe2) (1.59 g, 12.8 mmol)/
heptane (20 mL) solution at room temperature with stir-
ring for 12 h. Volatiles were removed under vacuum and
the resulting solids were recrystallized from a toluene
solution to generate 2.89 g of white solids in 79% yield.
1H NMR (C6D6): 7.18 (m, 2H, pyrrolyl CH), 6.56 (m,
2H, pyrrolyl CH), 6.32 (m, 2H, pyrrolyl CH), 3.48 (m,
12H, NCH2CH3 and CH2NMe2), 2.02 (s, 12H,
CH2NMe2), 0.84 (t, 12H, NCH2CH3). 13C NMR
(C6D6): 136.0 (s, pyrrolyl Cipso), 128.5 (d, JCH = 178
Hz, pyrrolyl CH), 109.4 (d, JCH = 165 Hz, pyrrolyl
CH), 104.9 (d, JCH = 164 Hz, pyrrolyl CH), 63.0 (t,
JCH = 137 Hz, CH2NMe2), 48.4 (q, JCH = 136 Hz,
NMe2), 40.8 (t, JCH = 131 Hz, NCH2CH3), 13.0 (q,
JCH = 125 Hz, NCH2CH3). Anal. Calc. for
C22H42N6Hf: C, 46.43; H, 7.44; N, 14.77. Found: C,
45.60; H, 7.79; N, 15.23%.
C
ipso), 128.8 (d, JCH = 183 Hz, pyrrolyl CH), 128.3 (d,
JCH = 159 Hz, phenyl CH), 124.7 (d, JCH = 156 Hz, phe-
nyl CH,), 124.3 (d, JCH = 156 Hz, phenyl CH), 122.2 (d,
JCH = 162 Hz, phenyl CH), 106.4 (d, JCH = 174 Hz, pyr-
rolyl CH,), 103.0 (d, JCH = 163 Hz, pyrrolyl CH), 62.5
and 62.6 (two t, JCH = 139 Hz, CH2NMe2), 48.6 (q,
JCH = 140 Hz, NMe), 41.4 (t, JCH = 134 Hz, NCH2Me),
37.2 (q, JCH = 138 Hz, NMe), 13.4 (q, JCH = 128 Hz,
NCH2Me). No elemental analysis was performed due
to small amount of compound 2 was presented.
3.5. Hf[PhNC(NEt2)O]4 (4)
To a 50 mL Schlenk flask charged with 20 mL toluene
and Hf(NEt2)4 (1.0 g, 2.14 mmol) was added PhNCO
(1.02 g, 8.56 mmol) via syringe at room temperature.
The color remained pale yellow after 1 h of stirring. Vol-
atiles were removed under vacuum and the resulting sol-
ids were recrystallized from a toluene solution at ꢀ20 °C
to generate 1.78 g of white solids in 88% yield. 1H NMR
(C6D6): 7.35–6.95 (m, 20H, phenyl CH), 2.89 (q, 16H,
NCH2CH3), 0.71 (t, 24H, NCH2CH3). 13C NMR
(C6D6): 166.6 (s, NCO), 147.9 (s, phenyl Cipso), 128.2
(d, JCH = 156 Hz, phenyl CH), 124.5 (d, JCH = 159
Hz, phenyl CH), 121.6 (d, JCH = 159 Hz, phenyl CH),
3.3. [C4H3N(CH2NMe2)-2]2Hf[PhNC(NEt2)O]2 (2)
To a 50 mL Schlenk flask charged with 20 mL diethyl
ether and 1 (2.0 g, 3.5 mmol) was added PhNCO (0.84 g,
7.1 mmol) via syringe at room temperature. The solu-
tion color changed from pale yellow to dark red. Vola-
tiles were removed under vacuum after 30 min stirring
and the resulting solids were recrystallized from a
diethyl ether solution to generate 1.59 g of white solids
1
in 56% yield. H NMR (C6D6): 7.67 (m, 2H, phenyl

3368
K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
Table 2
Crystallographic data and refinement for compounds 1, 2, 3 and 4
1
2
3
4
Formula
Fw
C22H42HfN6
569.11
293(2)
C36H52HfN8O2
807.35
150(2)
C40H56HfN8O3
875.42
150(1)
C44H60HfN8O4
943.49
150(2)
Temperature (K)
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
Cc
˚
a (A)
10.022(3)
16.370(4)
15.515(4)
104.020(4)
2469.4(11)
4
15.548(4)
10.867(3)
21.237(5)
94.427(4)
3577.5(14)
4
11.1338(1)
23.5981(3)
15.1340(2)
105.8891(5)
3824.33(8)
4
11.4627(15)
16.219(2)
23.993(3)
100.622(2)
4384.1(10)
4
˚
b (A)
˚
c (A)
b (°)
3
˚
V (A )
Z
Dcalc (g/cm3)
F(000)
1.531
1152
1.499
1648
1.520
1792
1.429
1936
h Range (°)
1.84–27.58
15560
1.31–27.55
24310
1.64–25.00
30498
1.73–27.53
21771
No. of reflections collected
No. of independent reflections (Rint
No. of parameters
Goodness of fit on F2ꢀ
Final R, wR2[I > 2r(I)]
R, wR2 (all data)
)
5657 (0.0374)
270
0.848
8142 (0.1254)
424
0.898
6728 (0.0619)
469
1.127
9677 (0.0317)
514
0.921
0.0221, 0.0388
0.0338, 0.0401
0.884, ꢀ1.271
0.0606, 0.1582
0.1205, 0.1834
2.847, ꢀ2.502
0.0543, 0.1414
0.0856, 0.1691
1.984, ꢀ1.263
0.0263, 0.0544
0.0307, 0.0544
1.392, ꢀ0.398
ꢀ3
˚
Dqmax,min (e A
)
41.4 (t, JCH = 137 Hz, NCH2CH3), 13.4 (q, JCH = 126
Hz, NCH2CH3). Anal. Calc. for C44H60N8O4Hf: C,
56.01; H, 6.41; N, 11.88. Found: C, 56.03; H, 6.07; N,
12.01.
Data Centre, CCDC nos. 234583–234585 and 243419.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1 EZ, UK (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.ca-
m.ac.uk). Data for theoretical calculation can be ob-
tained from the author by request via e-mail at
juihuang@cc.ncue.edu.tw. Supplementary data associ-
ated with this article can be found, in the online version,
at doi:10.1016/j.jorganchem.2004.07.046.
4. X-ray structure determination of compounds 1, 2, 3 and 4
The crystals 1, 2, and 4 were mounted in glass fi-
bers under nitrogen and transferred to a goniostat.
Data were collected on a Bruker SMART CCD dif-
fractometer with graphite-monochromated Mo Ka
radiation with the radiation wavelength of
References
˚
0.71073 A. Data for crystal 3 were collected on a
SADABS
[1] H. Ulrich, Acc. Chem. Res. 2 (1969) 186.
[2] J.H. Saunder, K.C. Frisch, Polyurethanes, Wiely-Interscience,
New York, 1962.
Nonius KappaCCD diffractometer.
A
absorption correction was made. All refinements were
carried out by full-matrix least squares using aniso-
tropic displacement parameters for all non-hydrogen
atoms. All the hydrogen atoms are calculated. The
crystal data are summarized in Table 2.
[3] F. LÕEplattenier, P. Matthys, F. Calderazzo, Inorg. Chem. 9
(1970) 342.
[4] A.F.M. Iqbal, J. Org. Chem. 37 (1972) 2791.
[5] J.A. Smieja, J.E. Gozum, W.L. Gladfelter, Organometallics 6
(1987) 1311.
[6] G.D. Williams, R.R. Whittle, G.L. Geoffroy, A.L. Rheingold, J.
Am. Chem. Soc. 109 (1987) 3936.
Acknowledgement
[7] S.R. Foley, Y. Zhou, G.P.A. Yap, D.S. Richeson, Inorg. Chem.
39 (2000) 924.
[8] P. Braunstein, D. Nobel, Chem. Rev. 89 (1989) 1927.
[9] P. Legzdins, S.J. Rettig, K.J. Ross, Organometallics 13 (1994)
569.
We thank the National Science Council of Taiwan for
the financial support and the National High Perform-
ance Computing Center of Taiwan for supporting data-
bank searching.
[10] B. Srinivas, C.C. Chang, C.H. Chen, M.Y. Chiang, I.T. Chen, Y.
Wang, G.H. Lee, J. Chem. Soc., Dalton Trans. (1997) 957.
[11] R.L. Cowan, W.C. Trogler, J. Am. Chem. Soc. 111 (1989) 4750.
[12] K. Weiss, U. Schubert, R.R. Schrock, Organometallics 5 (1986)
397.
Appendix A. Supplementary material
[13] W.J. Evans, K.J. Forrestal, J.W. Ziller, J. Am. Chem. Soc. 120
(1998) 9273.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
[14] Q. Shen, H. Li, C. Yao, Y. Yao, L. Zhang, K. Yu, Organome-
tallics 20 (2001) 3070.

K.-C. Hsieh et al. / Journal of Organometallic Chemistry 689 (2004) 3362–3369
3369
[15] X.G. Zhou, L.B. Zhang, M. Zhu, R.F. Cai, L.H. Weng, Z.X.
[24] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[25] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270.
Huang, Q.J. Wu, Organometallics 20 (2001) 5700.
[16] W.J. Evans, R.N.R. Broomhall-Dillard, J.W. Ziller, J. Organo-
met. Chem. 569 (1998) 89.
[26] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A.
Robb, J.R. Cheeseman, V.G. Zakrzewski, J.A. Montgomery Jr.,
R.E. Stratmann, J.C. Burant, S. Dapprich, J.M. Millam, A.D.
Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V.
Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C.
Adamo, S. Clifford, J. Ochterski, G.A. Petersson, P.Y. Ayala, Q.
Cui, K. Morokuma, D.K. Malick, A.D. Rabuck, K. Raghava-
chari, J.B. Foresman, J. Cioslowski, J.V. Ortiz, B.B. Stefanov, G.
Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A.
Nanayakkara, C. Gonzalez, M. Challacombe, P.M.W. Gill, B.
Johnson, W. Chen, M.W. Wong, J.L. Andres, C. Gonzalez, M.
Head-Gordon, E.S. Replogle, J.A. Pople, Revision A.12 ed.,
Gaussian Inc., Pittsburgh PA, 2001.
[17] L. Mao, Q. Shen, M. Xue, J. Sun, Organometallics 16 (1997)
3711.
[18] J.L. Thorman, I.A. Guzei, V.G. Young Jr., L.K. Woo, Inorg.
Chem. 38 (1999) 3814.
[19] S. Gambarotta, S. Strologo, C. Floriani, A. Chiesi-Villa, C.
Guastini, Inorg. Chem. 24 (1985) 654.
[20] G. Chandra, A.D. Jenkins, M.F. Lappert, R.C. Srivastava, J.
Chem. Soc. A (1970) 2550.
[21] A reaction product of PhNCO with 2-(diemthylaminomethylpyr-
role) see: C.F. Chia, H.J. Chen, J.C. Chang, C.H. Hung, C.C.
Lai, C.H. Hu, J.H. Huang, Inorg. Chem. 43 (2004) 2183.
[22] M.H. Chisholm, C.E. Hammond, D. Ho, J.C. Huffman, J. Am.
Chem. Soc. 108 (1986) 7860.
[27] W. Herz, K. Dittmer, J. Am. Chem. Soc. 69 (1947) 1698.
[28] I.T. Kim, R.L. Elsenbaumer, Tetrahedron Lett. 39 (1998) 1087.
[23] A.D.J. Becke, J. Chem. Phys. 98 (1993) 5648.