Insertion reactions of heterocumulenes into Zn-C bonds: Synthesis and structural characterization of multinuclear zinc amidate complexes

Article abstract of DOI:10.1021/om101107e

Reactions of ZnMe₂ with isocyanates RNCO proceeded with insertion of the isocyanate into the Zn-Me bond, giving the corresponding heteroleptic amidate complexes [MeZnOC(Me)NR]_x (R = i-Pr (1), t-Bu (2)) and [{MeZn}₄Zn{OC(Me)NC₆F₅}₆] (3) in high yields. In contrast, ZnCp*₂ reacts with isocyanates and isothiocyanates with formation of homoleptic complexes of the type [Zn{OC(Cp*)NR}₂]₂ (R = Et (4), i-Pr (5)) and [Zn{SC(Cp*)N-i-Pr}₂]₂ (6). 1-6 were characterized by elemental analyses, multinuclear NMR (¹H, ¹³C, ¹⁹F) and IR spectroscopy, and single-crystal X-ray diffraction (1, 2, 5).

Full text of DOI:10.1021/om101107e

Organometallics 2011, 30, 1073–1078 1073
DOI: 10.1021/om101107e
Insertion Reactions of Heterocumulenes into Zn-C Bonds: Synthesis and
Structural Characterization of Multinuclear Zinc Amidate Complexes
€
Sarah Schmidt, Raphaela Schaper, Stephan Schulz,* Dieter Blaser, and Christoph Wolper
€
€
Institute of Inorganic Chemistry, University of Duisburg-Essen, 45117 Essen, Germany
Received November 25, 2010
Reactions of ZnMe2 with isocyanates RNCO proceeded with insertion of the isocyanate into the
Zn-Me bond, giving the corresponding heteroleptic amidate complexes [MeZnOC(Me)NR]x (R=
i-Pr (1), t-Bu (2)) and [{MeZn}4Zn{OC(Me)NC6F5}6] (3) in high yields. In contrast, ZnCp*2 reacts
with isocyanates and isothiocyanates with formation of homoleptic complexes of the type
[Zn{OC(Cp*)NR}2]2 (R=Et (4), i-Pr (5)) and [Zn{SC(Cp*)N-i-Pr}2]2 (6). 1-6 were characterized
by elemental analyses, multinuclear NMR (1H, 13C, 19F) and IR spectroscopy, and single-crystal
X-ray diffraction (1, 2, 5).
Introduction
C6H3, t-Bu, and SiMe3, respectively.5b In order to investigate
if the unexpected C-H activation reaction is restricted to
reactions of carbodiimides with ZnMe2, we reinvestigated
reactions of C(N-i-Pr)2 with different main-group-metal
alkyls such as AlMe3, GaMe3, MgMe2, and MeLi at tem-
peratures up to 120 °C and reaction times up to 10 days, but
no indication for a C-H activation reaction was found.6
We therefore became interested in reactions of ZnMe2
with isoelectronic heterocumulenes of the type YdCdX in
order to clarify if the C-H activation reaction also occurs
with these organic substrates. Insertion reactions of isocya-
nates RNCO into metal-carbon as well as metal-
hydrogen, metal-nitrogen, and metal-oxygen bonds of
main-group metals,7 transition metals,8 and lanthanides9
have been intensely studied in the past, and a large number
of complexes have been structurally characterized.10 In contrast,
Metal alkyl complexes of the type LnMR typically react with
carbodiimides C(NR0)2 with insertion of the carbodi-
imide into the metal-carbon bond and subsequent formation
of metal amidinate complexes of the general type RC-
(NR0)2MLn.1 Numerous complexes, including main-group me-
tals, transition metals, and lanthanide metals, have been prepared
and their potential capability to serve as precursors in catalysis2
and material sciences3 was demonstrated. We started only re-
cently to investigate reactions of zinc dialkyls with carbodiimides,
which surprisingly had not been investigated before, in more
detail. In remarkable contrast to the reaction of ZnEt2 with C(N-
i-Pr)2, which occurred with insertion of the carbodiimide into the
Zn-Et bond and subsequent formation of the expected amidi-
nate complex [{EtC(N-i-Pr)2}ZnEt]2,4 we found that ZnMe2
reacts with carbodiimides such as C(N-i-Pr)2 and C(NCy)2 with
C-H activation of the initially formed C-Me group and
formation of multinuclear amidinate complexes (Scheme 1).5
In contrast, no reaction occurred with carbodiimides contain-
ing sterically more demanding substituents such as 2,6-i-Pr2-
(6) Gutschank, B.; Schmidt, S.; Schulz, S. Unpublished results.
(7) (a) Chang, C.-C.; Chen, J.-H.; Srinivas, B.; Chiang, M. Y.; Lee,
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*To whom correspondence should be addressed. Tel: þ49 0201-
1834635. Fax: þ 49 0201-1833830. E-mail: stephan.schulz@uni-due.de.
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r
2011 American Chemical Society
Published on Web 02/08/2011 pubs.acs.org/Organometallics

1074 Organometallics, Vol. 30, No. 5, 2011
Schmidt et al.
Scheme 1. Different Reaction Pathways As Observed for the
Reactions of ZnR2 with Isopropylcarbodiimide
Scheme 2. Synthesis of 1-3
Figure 1. Solid-state structure of 1 (thermal ellipsoids are
shown at the 50% probability level; H atoms are omitted for
clarity).
insertion reactions of isocyanates into zinc-carbon bonds
have been investigated to a far lesser extent,11 whereas those
into zinc-hydrogen, zinc-amide, and zinc-alkoxide com-
plexes are more common.12 To date, only a very few zinc
amidate complexes, which were mostly prepared by alkane
elimination reactions of ZnR2 with carboxylic amides,13
have been structurally characterized. These complexes,
which are often tetrameric in the solid state as was already
suggested by Coates and Ridley,11 typically show the ami-
date moieties in a N,O-bridging coordination mode, with the
O atoms coordinating to adjacent Zn atoms.
Herein we report on reactions of ZnMe2 and ZnCp*2 with
several isocyanates RNCO (R = Et, i-Pr, t-Bu, C6F5) and
isothiocyanates RNCS containing organic substituents of
different steric bulk and electronic properties. The resulting
complexes 1-6 were characterized by multinuclear NMR
and IR spectroscopy, elemental analyses and single-crystal
X-ray diffraction (1, 2, 5).
prolonged reaction times (10 days) and high reaction tem-
peratures (up to 130 °C).15 In contrast, the reaction with
C6F5NCO yielded the unexpected complex [{MeZn}4Zn-
{OC(Me)N(C6F5)}6] (3).
1H and 13C NMR spectra of 1 and 2 showed the expected
resonances of the heteroleptic complexes due to the amidate
ligand and the Zn-Me group in the expected 1:1 molar ratio.
The characteristic NCO absorption bands as observed for
the isocyanates at 2245 cm-1 (t-BuNCO), 2251 cm-1
(i-PrNCO), and 2255 cm-1 ((C6F5)NCO) are shifted to 1572
cm-1 (1), 1577 cm-1 (2), and 1504 cm-1 (3), respectively.
Single crystals of 1 and 2 were obtained from solutions in
toluene upon storage at -30 °C.
1 and 2 crystallize in the triclinic space group P1. The
degree of oligomerization and the specific coordination
mode of the amidate ligand within the resulting complexes
is largely influenced by the steric demand of the isocyanate
substituent. The larger t-Bu group favors the formation of
the trimeric complex 2, whereas the sterically less demanding
i-Pr groups lead to the formation of the tetrameric complex
1. Moreover, the coordination modes of the amidate moi-
eties as observed in 1 and 2 differ significantly. 1 consists of
two eight-membered rings (top and bottom in Figure 1), in
which the amidate groups serve as N,O-bridging monoden-
tate (μ,η1:η1) donor ligands. The Zn-N bond lengths (mean
Results and Discussion
Equimolar amounts of ZnMe2 and RNCO react at 80 °C
with insertion of the isocyanate into one Zn-Me bond and
subsequent formation of the corresponding heteroleptic
amidate complexes [MeZnOC(Me)NR]x (R=i-Pr (1), t-Bu
(2)) in almost quantitative yields (Scheme 2). Comparable
insertion products were obtained from reactions of a
β-diketiminato zinc hydride complex with carbodiimides
and isocyanates, respectively.14 Homoleptic complexes
[Zn{OC(Me)NR}2] were not formed, even in the presence
of a 3-fold excess of the isocyanate and at higher reaction
temperatures (120 °C). Moreover, no indication for a C-H
activation reaction of the methyl group bound to the iso-
cyanate carbon atom, as was previously observed in reac-
tions of ZnMe2 with carbodiimides, was found, even after
˚
Zn-N=2.027(3) A) within these rings are shorter than the
˚
Zn-O bonds (mean Zn-O=2.080(7) A), as was observed
for comparable zinc amidate complexes.13b These two boat-
type eight-membered rings are fused by four additional
Zn-O bonds. The Zn-O bond lengths between the two
˚
rings (mean Zn-O = 2.056(3) A) are slightly shorter com-
pared to the Zn-O bond lengths within the eight-membered
rings, as was previously reported for tetrameric complexes of
the desired type.13b In contrast, the coordination mode of the
amidate ligands in 2 can be best described as being between
an N,O-chelating (η2) and N,O-bridging monodentate
(μ,η1:η1) fashion (Figure 2). The Zn-N (mean Zn-N =
(11) Coates, G. E.; Ridley, D. J. Chem. Soc. A 1966, 1064.
(12) See the following and references cited therein: (a) Han, R.;
Gorrell, I. B.; Looney, A. G.; Parkin, G. J. Chem. Soc. Chem. Commun.
1991, 717. (b) Rombach, M.; Brombacher, H.; Vahrenkamp, H. Eur. J.
€
Inorg. Chem. 2002, 153. (c) Schenk, S.; Notni, J.; Kohn, U.; Wermann,
K.; Anders, E. J. Chem. Soc., Dalton Trans. 2006, 4191.
(13) (a) Noltes, J. G.; Boersma, J. J. Organomet. Chem. 1969, 16, 345.
(b) Boss, S. R.; Haigh, R.; Linton, D. J.; Schooler, P.; Shields, G. P.;
Wheatley, A. E. H. J. Chem. Soc., Dalton Trans. 2003, 1001.
˚
2.031(7) A) and Zn-O bond lengths (mean Zn-O=2.011(6)
˚
A) within the puckered 12-membered ring are almost iden-
tical. As was observed for 1, each O atom adopts a trigonal-
planar coordination sphere due to the coordination to an
adjacent Zn atom. Even though these Zn-O bond lengths
€
(14) Schulz, S.; Eisenmann, T.; Schmidt, S.; Blaser, D.; Westphal, U.;
Boese, R. J. Chem. Soc., Chem. Commun. 2010, 46, 7226.
(15) Higher reaction temperatures resulted in the complete decom-
position of ZnMe2 and formation of elemental zinc.
˚
(mean Zn-O = 2.233(3) A) are significantly elongated
compared to those within the 12-membered ring, they clearly

Article
Organometallics, Vol. 30, No. 5, 2011 1075
Scheme 3. Synthesis of 4 - 6
different solutions were of rather poor quality and the
resulting structure model did not allow a detailed discussion
of the structural parameters. However, the connectivity of
the compound was determined without ambiguity. 3 consists
of five Zn atoms and six amidate ligands. The structure can
be best described as a 12-membered [MeZnOC(Me)NC6F5]3
ring with 3 N,O-chelating amidate moieties, in which the 3 O
atoms bind to an additional Zn atom. This central Zn atom
coordinates to three additional O atoms of a MeZn[OC-
(Me)NC6F5]3 moiety, hence adopting a distorted-octahedral
coordination sphere. Obviously, the formation of 3 occurred
through single-insertion reactions of four isocyanates into
four ZnMe2 molecules, whereas the fifth ZnMe2 molecule
underwent a double-insertion reaction with two isocyanates.
In order to investigate the isocyanate reaction in more
detail and to verify the role of the organozinc complex, we
reacted isocyanates and isothiocyanates with ZnCp*2 both
in equimolar amounts and with a 2-fold excess of the
isocyanates. Homoleptic complexes of the general type
[Zn{OC(Cp*)NR}2]2 (R=Et (4), i-Pr (5)) and [Zn{SC(Cp*)-
N-i-Pr}2]2 (6) were obtained in both reactions at relatively
low temperature (60 °C), demonstrating the double-insertion
reaction of isocyanates and isothiocyanates into the Zn-
Cp* group to be strongly favored (Scheme 3).17
Figure 2. Solid-state structure of 2 (thermal ellipsoids are
shown at the 50% probability level; H atoms are omitted for
clarity).
1H and 13C NMR spectra of 4-6 only showed a single set
of resonances due to the amidate and thioamidate ligands.
No indication for the presence of differently coordinated
amidates (η2-chelating and bridging μ,η1:η1 moieties) was
found in these spectra. Low-temperature 1H NMR spectra at
-60 °C also did not give two sets of resonances. IR spectra of
the free ligands show strong absorption bands at 2253 cm-1
(EtNCO), 2251 cm-1 (i-PrNCO), and 2148 cm-1 (i-PrNCS)
due to the antisymmetric NCO and NCS valence vibrations.
In complexes 4-6 these absorption bands are shifted to 1552
cm-1 (4), 1542 cm-1 (5), and 1518 cm-1 (6), respectively, as
was observed for the Zn amidate complexes 1-3.
Figure 3. Solid-state structure of 3 (H atoms are omitted, and
C6F5 groups and Me amidate groups are presented in a dimin-
ished fashion for clarity).
indicate an attractive Zn-O interaction. Therefore, 2 repre-
sents the first structurally characterized zinc complex exhi-
biting an N,O-chelating amidate ligand. A comparable
structural motif was previously observed in zinc pyridonate
and 9-isobutylguanidinate complexes.16 The Zn atoms in 1
and 2 adopt tetrahedral coordination spheres, and the Zn-C
Single crystals of 5 were obtained from a solution in
diisopropylbenzene upon storage at 0 °C. 5 crystallizes in
the triclinic space group P1 (Figure 4). The central structural
motif in 5 is the eight-membered Zn2(NCO)2 ring with two
N,O-bridging monodentate (μ,η1:η1) amidate groups. Both
Zn atoms in 5 are additionally coordinated by a second
amidate group, which adopts a chelating (η2) binding mode.
The eight-membered ring adopts a boat-type conformation
due to the presence of rather weak transannular Zn-O
˚
bond lengths as observed in 1 (mean value 1.974 A) and 2
˚
(mean value 1.957 A) are comparable and are in the typical
range reported for Zn-Me groups. The O, C, and N atoms of
the amidate moieties in 1 and 2 adopt almost ideal trigonal-
planar coordination spheres and the C-O (mean values: 1,
˚
˚
interactions (Zn1-O1 = 2.665 A; Zn2-O2 = 2.677 A), as
was observed in the amidinate complex {[EtC(N-i-Pr)2]-
˚
˚
1.302 A; 2, 1.310 A) and C-N bond lengths (mean values: 1,
4
ZnEt}2 (2.669(1), 2.653(1) A). In contrast, the heteroleptic
˚
˚
˚
1.295(2) A; 2, 1.289(2) A) within the amidate groups indicate
an almost perfect delocalization of the π electrons within the
NCO moieties.
amidinate complexes {[t-BuC(N-i-Pr)2]ZnX}2 (X = Me, I)
showed significantly stronger transannular Zn-N interac-
18
˚
Complex 3 adopts a rather unexpected structure in the
solid state (Figure 3). Single crystals of 3 were obtained
from solutions in dichloromethane upon storage at -30 °C.
Unfortunately, crystals of 3 which were obtained from
tions (2.1952(11), 2.136(3) A). The Zn-N bond lengths
within the eight-membered (mean value 1.9646(20) A) and
˚
˚
four-membered rings (mean value 1.9848(37) A) are compar-
(17) In the eqiuimolar reaction unreacted ZnCp*2 was also detected
(16) (a) Mowat, C. G.; Parsons, S.; Solan, G. A.; Winpenny, R. E. P.
Acta Crystallogr. 1997, C53, 282. (b) Badura, D.; Vahrenkamp, H. Eur.
J. Inorg. Chem. 2003, 3723.
by 1H NMR.
(18) Schmidt, S.; Schulz, S.; Bolte, M. Z. Anorg. Allg. Chem. 2009,
635, 2210.

1076 Organometallics, Vol. 30, No. 5, 2011
Schmidt et al.
comparable zinc complexes using 1,2-double-donor systems
such as peroxides, and hydrazides as well as hydroxyla-
mides.22 In addition, reactions of zinc alkyls with amino
alcohols proceeded with formation of a large variety of
complexes, including trimeric derivatives.23
Conclusion
ZnMe2 reacts with isocyanates with insertion into one
Zn-Me bond and subsequent formation of the heteroleptic
amidate zinc complexes [MeZnOC(Me)NR]x. The degree of
oligomerization strongly depends on the steric bulk of the
organic ligand bound to the nitrogen atom. No indication for
C-H activation reactions, as were observed for reactions of
ZnMe2 with carbodiimides, was found. In contrast, zinco-
cene Cp*2Zn reacts with isocyanates and isothiocyanates
with subsequent formation of homoleptic complexes of the
type [Zn{XC(Cp*)NR}2]2 (X=O, S).
Experimental Details
Figure 4. Solid-state structure of 5 (thermal ellipsoids are
shown at the 50% probability level; H atoms are omitted for
clarity).
All manipulations were performed in a Glovebox (MBraun)
under an Ar atmosphere or with standard Schlenk techniques.
Dry solvents were obtained from a solvent purification system
(MBraun) and degassed prior to use. ZnCp*2 was prepared
according to literature methods.24 A 1.2 M solution of ZnMe2
was obtained from Acros and used as received, whereas iso-
cyanates RNCO and i-PrNCS were distilled and carefully dried
over activated molecular sieves prior to use. A Bruker DMX 300
instrument was used for NMR spectroscopy. 1H, 13C{1H}, and
19F{1H} NMR spectra were referenced to internal C6D5H (1H, δ
7.154; 13C, δ 128.0) and THF-d8 (1H, δ 3.580, 1.730; 13C, δ 25.2,
67.4). IR spectra were recorded on a Bruker ALPHA-T FT-IR
spectrometer equipped with a single-reflection ATR sampling
module. Melting points were measured in sealed capillaries
and were not corrected. Elemental analyses were performed
at the Elementaranalyse Labor of the University of Duisburg-
Essen.
able, whereas the Zn-O bond lengths within the eight-
membered ring (mean value 1.9529(19) A) are significantly
˚
shorter than those within the four-membered rings (mean
˚
value 2.1560(61) A). As a consequence, the π electrons within
the η2-chelating amidate units rings (mean values C-O =
˚
˚
1.281(2) A and C-N=1.311(2) A) are rather localized. In
contrast, the π electrons within the bridging μ,η1:η1 amidate
moiety (mean values C-O=1.294(2) A and C-N=1.296(2)
A) are fully delocalized, as is indicated by the almost identical
˚
˚
C-O and C-N bond lengths. These findings most likely can
be explained by repulsive interactions between the sterically
demanding organic substituents.
Even though complexes 1-6 represent rare examples of
structurally characterized dimeric, trimeric, and tetrameric
zinc amidate complexes, comparable cage-type organozinc
complexes have been previously synthesized with different
organic ligands. Zinc alkoxides, for instance, have long been
known to adopt dimeric and tetrameric structures in the solid
state,19 whereas trimeric derivatives have only very recently
been reported.20 The same is true for zinc carboxylates and
carbamates, which have also been structurally characterized
General Experimental Procedure for the Synthesis of 1-3.
ZnMe2 (4.2 mL, 5 mmol) was added to a solution of the
isocyanate (5 mmol) in 20 mL of toluene and heated to 80 °C
for 3 days. The resulting solution was concentrated under
vacuum and stored at -30 °C. Colorless crystals of 1-3 were
formed within 12 h.
[MeZnOC(Me)N-i-Pr]4 (1). Yield: 3.43 g (95%). Melting
point: 184 °C. Anal. Found (calcd) for C24H52N4O4Zn4
(722.18 g/mol): H, 7.3 (7.3); C, 39.9 (39.9); N, 7.8 (7.8). 1H
NMR (300 MHz, C6D6, 25 °C): δ -0.36 (s, 3H, ZnCH3), 1.51 (d,
to some extent.21 Moreover, Mitzel, Redshaw, Lewinski, and
3
ꢀ
others have reported in the past decade on the synthesis of
6H, CH(CH3)2), 1.71 (s, 3H, CH3), 3.18 (sept, JHH =6.4 Hz,
ꢀ
(22) (a) Lewinski, J.; Suwala, K.; Kubisiak, M.; Ochal, Z.; Justyniak,
(19) See the following and references cited therein: (a) Enthaler, S.;
Eckhardt, B.; Inoue, S.; Irran, E.; Driess, M. Chem. Asian J. 2010, 5,
I.; Lipkowski, J. Angew. Chem. 2008, 120, 8006; Angew. Chem., Int. Ed.
2008, 47, 7888. (b) Lewinski, J.; Suwala, K.; Kaczorowski, T.; Gale-
zowski, M.; Gryko, D. T.; Justyniak, I.; Lipkowski, J. J. Chem. Soc.,
ꢀ
€
2017. (b) Jana, S.; Berger, R. J. F.; Frohlich, R.; Pape, T.; Mitzel, N. W.
€
Inorg. Chem. 2007, 46, 4293. (c) Polarz, S.; Strunk, J.; Ischenko, V.; van
den Berg, M. W. E.; Hinrichsen, O.; Muhler, M.; Driess, M. Angew.
Chem. 2006, 118, 3031; Angew. Chem., Int. Ed. 2006, 45, 2965.
Chem. Commun. 2009, 215. (c) Jana, S.; Frohlich, R.; Mitzel, N. W. Z.
Anorg. Allg. Chem. 2008, 634, 1477. (d) Elsegood, M. R. J.; Redshaw, C.
Chem.;Eur. J. 2008, 14, 3530. (e) Redshaw, C.; Elsegood, M. R. J.
€
J. Chem. Soc., Chem. Commun. 2006, 523. (f) Jana, S.; Frohlich, R.;
Berger, R. J. F.; Mitzel, N. W. J. Chem. Soc., Chem. Commun. 2006,
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838. (h) Jana, S.; Frohlich, R.; Mitzel, N. W. Eur. J. Inorg. Chem. 2006,
€
3936. (i) Jana, S.; Frohlich, R.; Mitzel, N. W. Chem.- Eur. J. 2006, 12,
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N. W. Eur. J. Inorg. Chem. 2006, 4219. (k) Lewinski, J.; Ochal, Z.;
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Article
Organometallics, Vol. 30, No. 5, 2011 1077
Table 1. Crystallographic Details for Complexes 1, 2, and 5
1
2
5
empirical formula
mol wt
cryst syst
C24H52N4O4Zn4
722.18
triclinic
P1
100(1)
11.3409(5)
11.8633(5)
13.2487(5)
74.605(2)
82.448(2)
76.447(2)
1666.11(12)
2
C21H45N3O3Zn3
583.71
triclinic
P1
203(1)
9.0753(4)
12.3820(5)
14.3193(6)
75.062(2)
76.264(2)
71.623(2)
1453.84(11)
2
C56H88N4O4Zn2 x 0.5 C12H18
1093.18
triclinic
P1
space group
T (K)
193(1)
˚
a (A)
13.2153(7)
13.5886(8)
18.7837(11)
79.754(3)
86.258(3)
72.867(3)
3171.7(3)
2
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
μ (mm-1
)
2.876
1.440
2.477
1.333
0.801
1.145
Dcalcd (g cm-3
)
cryst dimens (mm)
no. of rflns
no. of unique rflns
Rmerg
0.36 ꢀ 0.32 ꢀ 0.25
0.36 ꢀ 0.32 ꢀ 0.26
0.28 ꢀ 0.24 ꢀ 0.17
22 481
8223
17 582
5350
29 180
14 253
0.0225
325/0
0.0197
0.0515
1.085
0.484/-0.454
P
0.0190
271/0
0.0283
0.0767
1.059
0.510/-0.258
P
0.0175
631/0
0.0375
0.1068
1.016
0.632/-0.498
P
no. of params refined/restraints
R1a
wR2b
goodness of fitc
-3
˚
final max/min ΔF (e A
)
P
P
a R1 = (||Fo| - |Fc||)/ |Fo| (for I > 2σ(I)). - b wR2 = { [w(Fo - Fc2)2]/ [w(Fo2)2]}1/2 (for all data). c Goodness of fit = { [w(|Fo2| -
2
|Fc2|)2]/(Nobservns - Nparams)}1/2
.
˚
Table 2. Selected Bond Lengths (A) and Angles (deg) of 1 and 2
Complex 1
Zn(1)-N(31)
Zn(2)-N(11)
Zn(3)-N(21)
Zn(4)-N(1)
Zn(1)-O(21)
Zn(2)-O(1)
2.0198(12)
Zn(1)-C(6)
Zn(2)-C(16)
Zn(3)-C(26)
Zn(4)-C(36)
N(1)-C(1)
1.9778(15)
1.9709(16)
1.9687(14)
1.9775(14)
1.2958(18)
1.2956(18)
Zn(3)-O(31)
Zn(4)-O(11)
Zn(1)-O(1)
Zn(2)-O(31)
Zn(3)-O(11)
Zn(4)-O(21)
2.0720(10)
2.0652(9)
2.0551(10)
2.0485(10)
2.0541(9)
2.0658(10)
N(21)-C(21)
N(31)-C(31)
O(1)-C(1)
O(11)-C(11)
O(21)-C(21)
O(31)-C(31)
1.2950(17)
1.2940(18)
1.2989(17)
1.3046(16)
1.3011(16)
1.3044(17)
2.0224(12)
2.0308(11)
2.0357(12)
2.0815(9)
2.1007(10)
N(11)-C(11)
N(31)-Zn(1)-O(21) 100.35(4) C(11)-O(11)-Zn(4)
125.42(8)
C(1)-N(1)-Zn(4)
119.08(10) N(21)-C(21)-O(21) 120.38(12)
N(11)-Zn(2)-O(1)
N(21)-Zn(3)-O(31)
N(1)-Zn(4)-O(11)
98.17(4) N(11)-C(11)-O(11) 119.64(12) C(1)-O(1)-Zn(2)
127.08(9)
C(31)-N(31)-Zn(1)
119.84(10)
131.14(8)
97.90(4) C(21)-N(21)-Zn(3)
98.44(4) C(21)-O(21)-Zn(1)
119.79(9)
124.25(8)
N(1)-C(1)-O(1)
C(11)-N(11)-Zn(2) 119.60(9)
120.35(12) C(31)-O(31)-Zn(3)
N(31)-C(31)-O(31) 119.48(12)
2
Zn(1)-N(1)
2.031(2)
Zn(1)-C(7)
Zn(2)-C(17)
1.958(3)
1.954(3)
1.959(3)
1.315(3)
1.309(3)
133.87(9)
134.58(9)
119.37(8)
Zn(3)-O(3)
Zn(1)-O(2)
Zn(2)-O(3)
Zn(3)-O(3)
2.3032(18)
2.0078(18)
2.0237(18)
2.0008(18)
O(3)-C(21)
N(1)-C(1)
N(2)-C(11)
N(3)-C(21)
1.307(3)
1.285(3)
1.290(4)
1.292(3)
Zn(2)-N(2)
2.048(2)
2.015(2)
2.1953(18)
2.2017(18)
61.94(8)
61.63(8)
60.70(7)
Zn(3)-N(3)
Zn(3)-C(27)
Zn(1)-O(1)
O(1)-C(1)
O(2)-C(11)
Zn(3)-O(1)-Zn(1)
Zn(1)-O(2)-Zn(2)
Zn(2)-O(3)-Zn(3)
Zn(2)-O(2)
N(1)-Zn(1)-O(1)
N(2)-Zn(2)-O(2)
N(3)-Zn(3)-O(3)
O(2)-Zn(1)-O(1)
O(3)-Zn(2)-O(2)
O(1)-Zn(3)-O(3)
89.13(7)
92.75(7)
95.46(7)
N(1)-C(1)-O(1)
N(2)-C(11)-O(2)
N(3)-C(21)-O(3)
113.9(2)
114.1(2)
115.3(2)
1H, CH(CH3)2). 13C NMR (125 MHz, C6D6, 25 °C): δ -12.3
(ZnCH3), 20.0 (CH(CH3)2), 24.0 (CH3), 50.0 (CH(CH3)2), 175.2
(NCO). IR: ν 2968, 2929, 2894, 2871, 2825, 1577, 1452, 1423,
1381, 1365, 1334, 1172, 1126, 1034, 999, 829, 645, 616, 575, 556,
in CH2Cl2 at -30 °C. Colorless crystals of 3 were formed within
24 h.
Yield: 4.9 g (70%). Melting point: >220 °C. Anal. Found
(calcd) for C53H33N6F30O6Zn5 (1746.69 g/mol): H, 2.0 (1.9); C,
36.4 (36.4); N, 4.9 (4.8). 1H NMR (300 MHz, THF-d8, 25 °C): δ
-0.94 (s, 12H, ZnCH3), 1.81 (s, 6H, CH3), 2.11 (s, 12H, CH3).
13C NMR (125 MHz, C6D6, 25 °C): δ 1.4 (ZnCH3), 21.0 (CH3),
137.1 (Ar C), 140.5 (Ar C), 141.9 (Ar C), 145.2 (Ar C), 182.3
(NCO). 19F NMR (300 MHz, C6D6, 25 °C): -147.1, -149.0,
-162.8, -164.3, -165.6. IR: ν 2963, 1573, 1504, 1410, 1259,
515 cm-1
.
[MeZnOC(Me)N-t-Bu]3 (2). Yield: 2.66 g (91%). Melting
point: 188 °C. Anal. Found (calcd) for C21H45N3O3Zn3
(583.71 g/mol): H, 7.8 (7.8); C, 43.1 (43.2); N, 7.1 (7.2). 1H
NMR (300 MHz, C6D6, 25 °C): δ -0.26 (s, 3H, ZnCH3), 1.08 (s,
9H, C(CH3)3), 1.89 (s, 3H, CH3). 13C NMR (125 MHz, C6D6,
25 °C): δ -14.3 (ZnCH3), 20.5 (CH3), 30.9 (C(CH3)3), 50.6
(C(CH3)3), 173.6 (NCO). IR: ν 2974, 2901, 2832, 1572, 1466,
1381, 1363, 1339, 1214, 1162, 1154, 1064, 1033, 999, 846, 788,
1085, 1020, 989, 88, 792, 712, 656, 539, 505, 399 cm-1
.
General Experimental Procedure for the Synthesis of 4-6. A
solution of the isocyanate RNCO (2 mmol) or the isothiocya-
nate i-PrNCS (2 mmol) in 5 mL of toluene was added to a
solution of ZnCp*2 (0.34 g, 1 mmol) in 20 mL of toluene and
heated to 60 °C for 3 h. The resulting solution was concentrated
under vacuum and stored at 0 °C. Colorless crystalline solids of
4-6 were formed within 12 h.
667, 615, 594, 573, 530, 489, 407 cm-1
.
[{MeZn}4Zn{OC(Me)NC6F5}6] (3). ZnMe2 (4.2 mL, 5 mmol)
was added to a solution of the isocyanate (5 mmol) in 20 mL of
toluene and heated to 80 °C for 3 days. The suspension was
filtered, and the resulting solid was recrystallized from a solution

1078 Organometallics, Vol. 30, No. 5, 2011
Schmidt et al.
Table 3. Selected Bond Lengths (A) and Angles (deg) of 5
˚
[Zn{OC(Cp*)NEt}2]2 (4). Yield: 0.43 g (89%). Melting point:
257 °C. Anal. Found (calcd) for C52H80N4O4Zn2 (955.98
g/mol): H, 8.4 (8.4); C, 64.4 (65.3); N, 5.4 (5.9). 1H NMR (300
MHz, C6D6, 25 °C): δ 1.15 (t, 3JHH=7.2 Hz, 3H, CH2CH3), 1.58
(s, 3H, C5Me5), 1.68 (s, 6H, C5Me5), 1.96 (s, 6H, C5Me5), 2.95 (q,
3JHH = 7.2 Hz, 2H, CH2CH3). 13C NMR (125 MHz, C6D6,
25 °C): δ 10.3 (C5Me5), 11.2 (C5Me5), 18.2 (C5Me5), 23.2 (CH3),
34.2 (CH2), 65.6 (C5Me5), 136.3 (C5Me5), 140.1 (C5Me5), 171.0
(NCO). IR: ν 2966, 2913, 2853, 1552, 1520, 1442, 1395, 1333,
1281, 1261, 1174, 1086, 1064, 952, 894, 806, 723, 668, 639, 577,
Zn(1)-N(1)
Zn(1)-N(3)
Zn(2)-N(2)
Zn(2)-N(4)
Zn(1)-O(2)
Zn(1)-O(3)
Zn(2)-O(1)
Zn(2)-O(4)
Zn(1)-C(3)
1.9622(16)
1.9798(16)
1.9670(15)
1.9898(16)
1.9552(11)
2.1685(14)
1.9506(13)
2.1514(14)
2.4515(19)
Zn(2)-C(4)
N(1)-C(1)
O(1)-C(1)
N(2)-C(2)
O(2)-C(2)
N(3)-C(3)
O(3)-C(3)
N(4)-C(4)
O(4)-C(4)
2.4436(19)
1.293(2)
1.292(2)
1.298(2)
1.296(2)
1.312(3)
1.282(2)
1.309(3)
1.280(2)
511, 446 cm-1
.
N(1)-Zn(1)-O(2)
N(1)-Zn(1)-N(3)
N(3)-Zn(1)-O(2)
O(2)-Zn(1)-O(3)
N(1)-Zn(1)-O(3)
N(3)-Zn(1)-O(3)
N(2)-Zn(2)-O(1)
N(2)-Zn(2)-N(4)
118.84(6)
124.84(7)
112.86(6)
103.93(6)
117.64(6)
63.64(6)
N(4)-Zn(2)-O(1)
O(1)-Zn(2)-O(4)
N(2)-Zn(2)-O(4)
N(4)-Zn(2)-O(4)
N(1)-C(1)-O(1)
N(2)-C(2)-O(2)
N(3)-C(3)-O(3)
N(4)-C(4)-O(4)
117.49(6)
104.18(5)
119.92(6)
63.83(6)
117.61(16)
117.80(17)
115.40(17)
115.85(17)
[Zn{OC(Cp*)N-i-Pr}2]2 (5). Yield: 0.48 g (94%). Melting
point: >300 °C. Anal. Found (calcd) for C56H88N4O4Zn2
(1012.08 g/mol): H, 8.7 (8.8); C, 64.7 (66.5); N, 4.4 (5.5). H
1
NMR (300 MHz, C6D6, 25 °C): δ 1.18 (d, 3JHH =6.2 Hz, 6H,
CH(CH3)2), 1.60 (s, 3H, C5Me5), 1.69 (s, 6H, C5Me5), 1.99 (s,
116.16(6)
122.40(7)
3
6H, C5Me5), 3.41 (sept, JHH = 6.0 Hz, 1H, CH(CH3)2). 13C
NMR (125 MHz, C6D6, 25 °C): δ 10.2 (C5Me5), 11.0 (C5Me5),
23.8 (C5Me5), 26.4 (CH3), 49.9 (CH), 66.1 (C5Me5), 135.3
(C5Me5), 140.1 (C5Me5), 175.4 (NCO). IR: ν 2962, 2914, 2856,
1542, 1516, 1462, 1441, 1408, 1395, 1377, 1360, 1325, 1260,
1172, 1089, 1056, 1012, 872, 799, 730, 695, 682, 634, 575, 512,
corrections were performed semiempirically from equivalent
reflections on the basis of multiscans (Buker AXS APEX2).
Hydrogen atoms were refined using a riding model or rigid
methyl groups. The poor quality of the crystal of 3 (θmax=23°)
prevented a proper refinement of the structure model (R1 above
0.15, no anisotropic refinement possible). However, the con-
nectivity and atom types were determined without doubt. 5
crystallizes with one molecule of diisopropylbenzene disordered
over a center of inversion. The corrosponding carbon atoms
were refined isotropically, and the phenyl ring was constrained
to be a regular hexagon (AFIX 66).
The crystallographic data of the structures (excluding struc-
ture factors) have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication nos.
CCDC-794411 (1), CCDC-794410 (2), and CCDC-802042
(5). Copies of the data can be obtained free of charge on
application to The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, U.K. (fax, int.code_(1223)336-033; e-mail for
inquiry, fileserv@ccdc.cam.ac.uk; e-mail for deposition,
deposit@ccdc.cam.ac.uk).
463, 428 cm-1
.
[Zn{SC(Cp*)N-i-Pr}2]2 (6). Yield: 0.34 g (63%). Melting
point: 189 °C. Anal. Found (calcd) for C56H88N4S4Zn2
(1076.33 g/mol): H, 8.1 (8.2); C, 60.2 (62.5); N, 4.8 (5.2); S
10.4 (11.9). 1H NMR (300 MHz, CDCl3, 25 °C): δ 0.85 (d,
3JHH=6.1 Hz, 6H, CH(CH3)2), 1.36 (s, 3H, C5Me5), 1.74 (s, 6H,
3
C5Me5), 1.82 (s, 6H, C5Me5), 3.21 (sept, JHH = 6.1 Hz, 1H,
CH(CH3)2). 13C NMR (125 MHz, CDCl3, 25 °C): δ 10.6
(C5Me5), 11.1 (C5Me5), 24.1 (C5Me5), 26.9 (CH3), 50.1 (CH),
66.2 (C5Me5), 135.6 (C5Me5), 140.8 (C5Me5), 197.5 (NCO). IR:
ν 2969, 2904, 2851, 1658, 1518, 1438, 1381, 1360, 1260, 1242,
1174, 1161, 1095, 1013, 996, 934, 873, 798, 749, 630, 596, 497,
456, 442 cm-1
.
Single-Crystal X-ray Analyses. Crystallographic data for 1, 2,
and 5, which were collected on a Bruker AXS D8 Kappa
˚
diffractometer (Mo KR radiation, λ=0.710 73 A), are summar-
ized in Table 1; selected bond lengths and angles are given in
Tables 2 (1, 2) and 3 (5), respectively. 1 was measured at 100(1)
K, 2 at 203(1) K, and 5 at 193(1) K. The structures were solved
by direct methods (SHELXS-97)25 and refined anisotropically
by full-matrix least squares on F2 (SHELXL-97).26 Absorption
Acknowledgment. S.S. thanks the German Science
Foundation (DFG) for financial support (Grant No.
SCHU 1069/10-1).
Supporting Information Available: CIF files giving crystal-
lographic data for complexes 1, 2, and 5. This material is
available free of charge via the Internet at http://pubs.acs.org.
(25) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(26) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
€
€
€
Refinement; Universitat Gottingen, Gottingen, Germany, 1997.