Structure and reactivity of mono- and dinuclear diiminate zinc alkyl complexes

Article abstract of DOI:10.1016/S0022-328X(03)00544-8

The synthesis, structure and reactivity of several diiminate ligands are presented. The syntheses of five representative β-diiminate (BDI) zinc alkyl complexes and one β-oxo-δ-diiminate (BODDI) zinc alkyl are described. BDI ligands with varying backbone and N -aryl substituents display different solid state structures. [(BDI)ZnR] are synthesized by the reaction of (BDI)H with ZnR₂ in quantitative yield. Previously reported (BDI-1)ZnEt is a three-coordinate monomer in the solid state whereas [(BDI-3)ZnEt]_∞ [(BDI-3)=2-((2,6-diisopropylphenyl) amido)-3-cyano-4-((2,6-diisopropylphenyl)imino-2-pentene] and [(BDI-4) ZnEt]_∞ [(BDI-4)=2-((2,6-diethylphenyl)amido)-3-cyano-4- ((2,6-diethylphenyl)imino-2-pentene] form one dimensional coordination polymers. The bimetallic complex [(BODDI-1)(ZnEt)₂] [(BODDI-1)=2,6-bis((2,6-diisopropylphenyl)amido)-2,5-heptadien-4-one] is prepared through the reaction of (BODDI-1)H₂ with two equivalents ZnEt₂. Both [(BDI)ZnEt] and [(BODDI)ZnEt] complexes react with acetic acid to give the acetate complexes in moderate to high yields, offering a superior synthetic route to these complexes. [(BDI)ZnR] [BDI=(BDI-3) or 1,1,1-trifluoro-2- ((2,6-diisopropylphenyl) amido)-4-((2,6-diethylphenyl)imino-2-pentene), (BDI-5)] complexes react with MeOH to produce [{(BDI)Zn(μ-OMe)} ₂Zn(μ-OMe) ₂] in moderate yields. The molecular structures of [(BDI-3)ZnEt], [(BDI-4)ZnEt], [(BODDI-1)(ZnEt) ₂], [(BODDI-1) Zn₂(μ-OAc)₂], [{(BDI-3)Zn(μ-OMe)}₂ Zn(μ-OMe)₂] and [{(BDI-5)Zn(μ-OMe)}₂ Zn(μ-OMe)₂] have been determined by X-ray diffraction.

Full text of DOI:10.1016/S0022-328X(03)00544-8

Journal of Organometallic Chemistry 683 (2003) 137Á148
/
www.elsevier.com/locate/jorganchem
Structure and reactivity of mono- and dinuclear diiminate zinc alkyl
complexes
Scott D. Allen, David R. Moore, Emil B. Lobkovsky, Geoffrey W. Coates *
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14850-1301, USA
Received 3 May 2003; received in revised form 7 June 2003; accepted 7 June 2003
Abstract
The synthesis, structure and reactivity of several diiminate ligands are presented. The syntheses of five representative b-diiminate
(BDI) zinc alkyl complexes and one b-oxo-d-diiminate (BODDI) zinc alkyl are described. BDI ligands with varying backbone and
N-aryl substituents display different solid state structures. [(BDI)ZnR] are synthesized by the reaction of (BDI)H with ZnR2 in
quantitative yield. Previously reported (BDI-1)ZnEt is a three-coordinate monomer in the solid state whereas [(BDI-3)ZnEt]ꢀ
[(BDI-3)ꢀ
2-((2,6-diethylphenyl)amido)-3-cyano-4-((2,6-diethylphenyl)imino-2-pentene] form one dimensional coordination polymers. The
bimetallic complex [(BODDI-1)(ZnEt)2] [(BODDI-1)ꢀ2,6-bis((2,6-diisopropylphenyl)amido)-2,5-heptadien-4-one] is prepared
/
2-((2,6-diisopropylphenyl)amido)-3-cyano-4-((2,6-diisopropylphenyl)imino-2-pentene] and [(BDI-4)ZnEt]ꢀ [(BDI-4)ꢀ
/
/
through the reaction of (BODDI-1)H2 with two equivalents ZnEt2. Both [(BDI)ZnEt] and [(BODDI)ZnEt] complexes react with
acetic acid to give the acetate complexes in moderate to high yields, offering a superior synthetic route to these complexes.
[(BDI)ZnR] [BDIꢀ(BDI-3) or 1,1,1-trifluoro-2-((2,6-diisopropylphenyl)amido)-4-((2,6-diethylphenyl)imino-2-pentene), (BDI-5)]
/
complexes react with MeOH to produce [{(BDI)Zn(m-OMe)}2Zn(m-OMe)2] in moderate yields. The molecular structures of [(BDI-
3)ZnEt], [(BDI-4)ZnEt], [(BODDI-1)(ZnEt)2], [(BODDI-1)Zn2(m-OAc)2], [{(BDI-3)Zn(m-OMe)}2Zn(m-OMe)2] and [{(BDI-5)Zn(m-
OMe)}2Zn(m-OMe)2] have been determined by X-ray diffraction.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Zinc alkyl complexes; Diiminate ligands; Reactivity
1. Introduction
merizations are some of the recent accomplishments
using this ubiquitous ligand set [1].
b-Diiminate (BDI) ligands (Scheme 1) continue to
gain attention in coordination chemistry [1]. BDI
ligands are uninegative, chelating ligands that provide
a suitable steric environment to prevent bis-ligation to
metals. The appeal for using these ligands stems from
the ease of synthesis and the variety of steric and
electronic modifications available to the ligand frame-
work. These attributes have facilitated the synthesis of a
wide array of main group and transition metal com-
plexes. The synthesis and isolation of complexes con-
taining metals in unusual oxidation states, preparation
of structural models for protein active sites, and the
development of catalysts for a diverse range of poly-
Of particular interest to our group is the polymeriza-
tion of cyclic esters and the alternating copolymerization
of epoxides and carbon dioxide using well-defined,
single site catalysts. BDI ligands have been the scaffold
for a wide variety of (BDI)MX (Mꢀ
Xꢀ
N(TMS)2, OMe, OiPr, OAc) complexes and have
shown to be efficient initiators for the polymerization of
lactide [2Á4], b-butyrolactone [5], and the alternating
/
Zn, Mg, Ca, Sn;
/
/
copolymerization of epoxides and CO2 [6]. Even though
Zn alkyls [7] are poor initiators for these polymeriza-
tions, they are crucial intermediates in the synthesis of
the active initiators. [1]
Our interest in the chemistry of (BDI)ZnR complexes
is twofold. First, we look to exploit the ZnÁC function-
/
ality as a route to new initiating groups in this class of
polymerization catalysts. Second, we continue to probe
the chemistry of well-defined BDI metal alkyls as
* Corresponding author. Tel.: ꢁ
4137.
E-mail address: gc39@cornell.edu (G.W. Coates).
/
1-607-255-5447; fax: ꢁ1-607-255-
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00544-8

138
S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á148
/
on the backbone of one complex links to an open zinc
coordination site of another complex. Both [(BDI-
3)ZnEt]ꢀ (crystal containing two molecules of toluene
per unit cell) and [(BDI-4)ZnEt]ꢀ have different back-
bone configurations, however, and these are depicted as
cartoons in Fig. 3. Although [(BDI-1)ZnEt] possesses a
trigonal planar arrangement around the zinc, [(BDI-
3)ZnEt]ꢀ and [(BDI-4)ZnEt]ꢀ attain distorted tetrahe-
dral geometries due to donation from the CN moiety.
˚
The CNÁZn bond is 2.15 A for [(BDI-3)ZnEt]ꢀ
/
(average of the three CNÁ
/
Zn bonds in the unit cell)
and 2.11 A for [(BDI-4)ZnEt]ꢀ, which are within the
expected limits for ZnÁN coordination bonds of this
type [10].
˚
/
Scheme 1.
[(BDI-3)ZnEt]ꢀ crystallizes with three (BDI-3)ZnEt
molecules and two molecules of toluene in the unit cell.
potential catalysts for other polymerizations and or-
ganic transformations [6cÁf]. We have previously seen
dramatic variation in catalytic activity depending on the
BDI ligand substituents. Herein we report the synthesis,
structure, and reactivity of several representative diimi-
nate zinc alkyl complexes.
/
The C(32)Á
/
N(3)ÁZn(1) angle is essentially linear at
/
179.18, which orients the BDI complexes perpendicular
to each other along the chain. Additionally, the steric
bulk of the aryl isopropyl groups causes each complex
along the chain to twist ꢁ
/
908 relative to the subsequent
BDI ligand plane (Fig. 1).
[(BDI-4)ZnEt]ꢀ crystallizes with only one molecule in
the asymmetric unit cell and has similar bond lengths
and angles as [(BDI-3)ZnEt]ꢀ. The major difference is
in the CN coordination to Zn which is significantly bent
2. Results and discussion
2.1. Synthesis and structure
with C(8)Á
/
N(3)Á
/
Zn(1)ꢀ151.98, unlike the linear co-
/
The synthesis and isolation of monomeric, low valent
zinc complexes is rare, but the use of bulky chelating
ligands such as BDI and tris(pyrazolyl)borate (TPB) [8]
has allowed for the study of such complexes. The
synthesis of (BDI)ZnR complexes is accomplished
through the reaction of (BDI)H with excess ZnR2
ordination of the CN group of [(BDI-3)ZnEt]ꢀ. The
lower steric bulk of the diethyl aryl groups does not
force the molecules along the chain to orient themselves
perpendicular to the chain and they remain parallel in a
‘zigÁzag’ pattern. The geometry about the Zn atom is a
/
similar distorted tetrahedron as [(BDI-3)ZnEt]ꢀ.
The crystallographic data are shown in Table 3, and a
comparison of these alkyl complexes with [(BDI-1)ZnEt]
is shown in Table 4. Even as coordination polymers, the
(RꢀEt, Me). Removal of the volatiles in vacuo yields
/
the (BDI)ZnR complexes (Scheme 1) in quantitative
1
conversions as observed by H-NMR spectroscopy.
We have previously reported the synthesis [6a,cÁ
/
e]
ZnÁ
[(BDI-4)ZnEt]ꢀ are very similar to [(BDI-1)ZnEt]. The
major difference is in the NÁZnÁN angle which is more
acute in both [(BDI-3)ZnEt]ꢀ and [(BDI-4)ZnEt]ꢀ by
about 68.
/
C and ZnÁN bond lengths in [(BDI-3)ZnEt]ꢀ and
/
and structure [6c] of monomeric, three-coordinate
(BDI)ZnEt compounds [9]. [(BDI-1)ZnEt] [6c] has
bond lengths and angles that are simliar to related zinc
alkyl complexes.
/
/
Typically, (BDI)ZnR complexes are oils or waxy
solids and highly soluble in common organic solvents.
As a result, crystallization is often difficult. (BDI)ZnR
complexes modified with CF3 groups on the backbone
(such as (BDI-5) and the related BDI ligands with all
ethyl or isopropyl aryl groups) are crystalline, but poor
crystal quality and twinning problems preclude data
collection. BDI ligands bearing cyano groups on the
three-position of the backbone, however, form highly
crystalline Zn alkyl complexes. The X-ray crystal
structures of [(BDI-3)ZnEt]ꢀ and [(BDI-4)ZnEt]ꢀ are
shown in Figs. 1 and 2, respectively, along with selected
bond lengths and angles in Tables 1 and 2. This high
crystallinity results from the formation of infinite one-
dimensional coordination polymers where the CN group
Given the bimetallic nature of epoxide/CO2 copoly-
merization using [(BDI)ZnOR]2 catalysts [6d], we have
synthesized a variation of the BDI ligands that can
accommodate two Zn centers. These b-oxo-d-diimine
(BODDI; Scheme 2) ligands have been known for quite
some time containing both N-alkyl [11] and N-aryl [12]
substituents.
Metal complexes of this class of ligands, however, are
limited to macrocyclic ligand dimers [13] where two
BODDI molecules are strapped together through the
nitrogens by a short alkyl chain. Monomeric, bimetallic
complexes of these ligands have yet to be explored. The
BODDI ligands were prepared through the reaction of
diacetylacetone with the desired aniline as shown in
Scheme 2 [14].

S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á
/
148
139
Fig. 1. ORTEP drawing of [(BDI-3)ZnEt]ꢀ (non-hydrogen atoms) with thermal ellipsoids drawn at the 40% probability level. Solvent molecules
omitted for clarity.
The reactivity of (BODDI-1)H2 is similar to the
reactivity of BDI ligands, and the ZnEt derivative can
be synthesized using the same method. The X-ray
structure of [(BODDI-1)(ZnEt)2] is shown in Fig. 4
with selected bond lengths and angles in Table 5.
[(BODDI-1)(ZnEt)2] crystallizes as a monomer with
two similar complexes in the unit cell, and has similar
bond lengths as the analogous [(BDI-1)ZnEt]. A com-
parison between the bond lengths and angles is shown in
Table 4. The extended BODDI backbone is planar as in
the BDI complexes. To alleviate the steric repulsions of
the neighboring ZnEt groups, each Zn atom sits on
opposite sides of the plane of the BODDI ligand. Zn(1)
by N(2), C(5) and O(1). This is also made evident by the
dihedral angles of C(3)ÁC(4)ÁO(1)ÁZn(1) and C(5)Á
C(4)ÁO(1)ÁZn(2) which are 24.19 and 23.688, respec-
tively. Both Zn atoms adopt a trigonal planar geometry.
The atoms C(8), N(1), O(1) and Zn(1) and C(10), N(2),
O(1) and Zn(2) are highly coplanar with the Zn atoms
/
/
/
/
/
/
˚
sitting only 0.04 A above their respective planes.
2.2. Reactivity
We have taken advantage of the reactivity of the ethyl
groups of [(BDI)ZnEt] complexes towards alcohols and
carboxylic acids as a synthetic route to the correspond-
˚
sits 0.62 A above the plane described by N(1), C(3), and
˚
O(1) while Zn(2) sits 0.50 A below the plane described
ing alkoxides and carboxylates (Scheme 3) [6a,cÁ
/
e]. BDI
ligands 1Á5 undergo clean reactions and high conver-
/
Fig. 2. ORTEP drawing of [(BDI-4)ZnEt]ꢀ (non-hydrogen atoms) with thermal ellipsoids drawn at the 40% probability level.

140
S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á148
/
Table 1
sions (50Á87%) to the corresponding acetates when
/
˚
Selected bond lengths (A) and bond angles (8) of [(BDI-3)ZnEt]ꢀ
reacted with acetic acid. Even the highly organized
coordination polymers of [(BDI-3)ZnEt]ꢀ and [(BDI-
4)ZnEt]ꢀ do not hinder the reaction with acetic acid and
form the corresponding acetate complexes in moderate
to high yields. These complexes crystallize as acetate-
bridged dimers, as shown in Scheme 3, and are mixtures
of monomers and dimers in solution, the ratio of which
depends on the ligand, solvent, concentration, and
temperature [6a,c,e,f]. Synthetically, this method is
superior to the previously used method of reacting
(BDI)Li with Zn(OAc)2 [6c].
[(BODDI-1)(ZnEt)2] reacts similarly with acetic acid
to yield the expected acetate complex [(BODDI-1)Zn2(m-
OAc)2] (Scheme 2). An X-ray crystal structure of this
complex is shown in Fig. 5 and selected bond lengths
and angles are shown in Table 6. [(BODDI-1)Zn2(m-
OAc)2] exists as a m,h2-diacetate complex in the solid
state. The Zn atoms in this complex are highly coplanar
with the ligand framework unlike [(BODDI-1)(ZnEt)2],
where the Zn atoms are on opposite sides of the ligand
Bond lengths
Zn(1)Á
Zn(1)Á
Zn(1)Á
Zn(1)Á
/
C(1)
N(1)
N(2)
N(3)
1.962(6)
2.044(5)
2.051(5)
2.136(5)
1.288(7)
1.310(7)
1.956(7)
2.033(4)
2.038(5)
Zn(2)Á
/
N(6)
2.160(5)
1.301(7)
1.311(7)
1.970(6)
2.045(5)
2.056(5)
2.154(5)
1.302(7)
1.307(7)
/
N(4)Á/C(36)
/
N(5)Á/C(38)
/
Zn(3)Á
Zn(3)Á
Zn(3)Á
Zn(3)Á
/
C(65)
N(7)
N(8)
N(9)
N(1)Á/C(4)
/
N(2)Á/C(6)
/
Zn(2)Á
Zn(2)Á
Zn(2)Á
/
C(33)
N(4)
N(5)
/
/
N(7)Á/C(68)
/
N(8)Á/C(70)
Bond angles
C(2)ÁC(1)Á
N(1)ÁZn(1)Á
C(32)ÁN(3)Á
C(8)ÁN(1)Á
C(20)ÁN(2)Á
C(34)ÁC(33)Á
N(4)ÁZn(2)ÁN(5)
/
/
Zn(1)
114.7(7)
C(40)Á
/
N(4)Á
N(5)Á
C(65)ÁZn(3) 117.2(5)
/
Zn(2)
115.1(3)
116.9(4)
/
/N(2)
91.85(19) C(52)Á
/
/Zn(2)
/
/Zn(1)
179.0(5)
113.7(4)
114.1(4)
C(66)Á
N(7)ÁZn(3)Á
C(96)ÁN(9)Á
C(72)ÁN(7)Á
91.49(18) C(84)ÁN(8)Á
/
/
/
/
Zn(1)
/
/N(8)
91.87(18)
176.4(5)
117.6(3)
114.9(3)
/
/Zn(1)
/
/
Zn(3)
Zn(3)
Zn(3)
/
/
Zn(2) 121.6(6)
/
/
/
/
/
/
Table 2
˚
Selected bond lengths (A) and bond angles (8) of [(BDI-4)ZnEt]ꢀ
˚
plane. Both Zn atoms only sit 0.007 A above the ligand
plane with dihedral angles of 1.6618 for Zn(1)ÁO(3)Á
C(3)ÁC(4) and 1.7378 for Zn(1A)ÁO(3)ÁC(3)ÁC(4A).
Bond lengths
/
/
Zn(1)Á
Zn(1)Á
Zn(1)Á
Zn(1)Á
N(1)Á
/
C(1)
1.995(5)
2.042(2)
2.042(3)
2.114(3)
1.308(4)
N(2)Á
C(5)ÁC(8)
N(3)Á
C(4)Á
C(5)Á
/C(6)
1.305(4)
1.418(4)
1.146(4)
1.436(4)
1.437(4)
/
/
/
/
/
N(1)
N(2)
N(3A)
/
The reactivity of (BDI)ZnR complexes with aliphatic
alcohols, however, is less predictable. Formation of
[(BDI)Zn(m-OMe)]2 is observed when the ZnEt com-
plexes of BDI ligands 1, 2 [6c] and 4 [6d] are reacted with
MeOH. On the other hand, reaction of MeOH with
either [(BDI-3)ZnEt]ꢀ or [(BDI-5)ZnEt] leads to
[{(BDI)Zn(m-OMe)}2Zn(m-OMe)2] (Scheme 3). [{(BDI-
/
/
C(8)
C(5)
C(6)
/
/
/
C(4)
/
Bond angles
C(1)ÁZn(1)Á
C(1)ÁZn(1)Á
C(1)ÁZn(1)Á
C(9)ÁN(1)Á
/
/N(1)
129.97(15) C(19)Á
124.26(17) N(1)ÁZn(1)Á
105.35(17) N(3)ÁC(8)ÁC(5)
113.36(18)
/
N(2)Á
/
Zn(1) 113.99(18)
/
/N(2)
/
/
N(2)
91.22(10)
177.7(4)
/
/N(3A)
/
/
/
/
Zn(1)
3)Zn(m-OMe)}2Zn(m-OMe)2]
OMe)}2Zn(m-OMe)2] are isolated in moderate crystal-
lized yields of 34Á57%, indicating they are not minor by-
and
[{(BDI-5)Zn(m-
/
Fig. 3. Depictions of the backbone orientations in [(BDI-3)ZnEt]ꢀ and [(BDI-4)ZnEt]ꢀ
.

S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á
/
148
141
Table 3
Crystal data and structure refinements for all structures
[(BDI-3)ZnEt]ꢀ
[(BDI-4)ZnEt]ꢀ
[(BODDI-1)(ZnEt)2]
[(BODDI-1)Zn2(m-OAc)2]
[{(BDI-3)Zn(m-OMe)}2
Zn(m-OMe)2]
Molecular formula
Formula weight
Temperature (K)
C
96H134N9Zn3×
/2C7H8
C28H37N3Zn
480.98
C70H104N4O2Zn4
1295.05
C35H48N2O5Zn2
707.49
C128H184N12O8Zn6×/C6H14
2497.26
1794.51
173(2)
173(2)
173(2)
173(2)
173(2)
˚
Wavelength (A)
0.71073
Monoclinic
P21/c
0.71073
Monoclinic
P21/c
0.71073
0.71073
0.71073
Triclinic
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
C2/c
¯
P1
Unit cell dimensions
˚
a (A)
˚
b (A)
14.739(4)
37.863(9)
19.329(5)
90
12.0199(15)
16.111(2)
14.3174(17)
90
15.3677(12)
13.8273(11)
32.591(3)
90
16.263(2)
13.6025(19)
17.052(3)
90
12.3899(3)
23.8946(5)
24.7560(6)
71.025(1)
78.747(1)
82.885(2)
6783.1(3)
2
˚
c (A)
a (8)
b (8)
102.324(4)
90
108.943(3)
90
99.8150(10)
90
108.257(7)
90
g (8)
3
V (A )
˚
10539(4)
4
2622.4(6)
4
6824.0(9)
4
3582.3(10)
4
Z
rcalc (Mg mꢂ3
)
1.131
1.218
1.261
1.312
1.223
m (Mo Ka) (mmꢂ1
)
0.726
0.955
1.433
1.379
1.100
F(000)
3852
1024
2752
1488
2660
Crystal size (mm3)
u Range (8)
Index ranges
0.50ꢃ
1.08Á20.82
145h5
375k 5
195l 519
/
0.10ꢃ
/
0.10
0.40ꢃ
2.19Á28.28
165h 5
185k 5
175l 519
/
0.30ꢃ
/
0.20
0.60ꢃ
1.27Á26.41
175h 5
85k 517,
405l 540
/
0.20ꢃ
/
0.10
0.40ꢃ
2.52Á26.37
155h 5
165k 5
215l 5
/
0.20ꢃ
/
0.10
0.20ꢃ
0.90Á23.82
145h 5
265k 5
285l 528
/
0.10ꢃ
/
0.05
/
/
/
/
/
ꢂ
/
/
/14,
ꢂ
/
/
/15,
ꢂ
/
/
/19,
ꢂ
/
/
/19,
ꢂ
/
/
/14,
ꢂ/
/
/7,
ꢂ/
/
/21,
ꢂ/
/
/
ꢂ/
/
/16,
ꢂ/
/
/26,
ꢂ/
/
/
ꢂ/
/
/
ꢂ/
/
/
ꢂ/
/
/9
ꢂ/
/
/
Data collected
Unique data
Rint
47471
11037
0.0781
1.283
18111
6510
39410
13919
0.0722
0.918
9384
44587
18608
0.0557
1.021
3300
0.0408
1.086
0.0593
1.047
Goodness-of-fit
Final R indices [I ꢂ
/
2s(I)]
R1ꢀ
wR2ꢀ
R1ꢀ0.1133,
wR2ꢀ0.1590
0.444 and ꢂ0.388
/
0.0917,
R1ꢀ
wR2ꢀ
R1ꢀ0.0830,
wR2ꢀ0.1351
0.893 and ꢂ0.778
/
0.0510,
R1ꢀ
wR2ꢀ
R1ꢀ0.1178,
wR2ꢀ0.1281
0.827 and ꢂ0.637
/
0.0501,
R1ꢀ
wR2ꢀ
R1ꢀ0.0739,
wR2ꢀ0.1198
1.014 and ꢂ0.677
/
0.0520,
R1ꢀ
wR2ꢀ
R1ꢀ0.0995,
wR2ꢀ0.1304
0.585 and ꢂ0.378
/
0.0566,
/0.1517
/0.1228
/0.1076
/
0.1119
/
0.1151
R indices (all data) [I ꢂ
/2s(I )]
/
/
/
/
/
/
/
/
/
/
ꢂ3
˚
rmax (e A
rmin
Á/
)
/
/
/
/
/
products. An X-ray crystal structure of [{(BDI-3)Zn(m-
OMe)}2Zn(m-OMe)2] is shown in Fig. 6 with selected
bond lengths and angles in Table 7.
there are two similar complexes in the unit cell as well
as a disordered molecule of hexane. The two ZnÁOÁ
ZnÁO moieties are nearly planar with a sum of the
/
/
/
These complexes consist of two [(BDI)Zn(m-OMe)]
molecules bridged by a Zn(mOMe)2. All Zn atoms are
distorted tetrahedra and the BDI ligands are arranged
so that they are nearly perpendicular to each other. X-
ray analysis reveals [{(BDI-3)Zn(m-OMe)}2Zn(m-OMe)2]
(Fig. 6) and [{(BDI-5)Zn(m-OMe)}2Zn(m-OMe)2] are
isostructural with only slight variations in bond lengths
and angles. In [{(BDI-3)Zn(m-OMe)}2Zn(m-OMe)2],
internal angles equal to 359.38. The planes intersect at
68.5 and 72.48 through the center Zn atom for [{(BDI-
3)Zn(m-OMe)}2Zn(m-OMe)2]
OMe)}2Zn(m-OMe)2], respectively. The distal Zn atoms
are distorted tetrahedra with compressed OÁZnÁO and
NÁZnÁN bond angles of 83 and 978 for [{(BDI-3)Zn(m-
and
[{(BDI-5)Zn(m-
/
/
/
/
OMe)}2Zn(m-OMe)2] and 82 and 988 for [{(BDI-5)Zn(m-
OMe)}2Zn(m-OMe)2]. The internal Zn atom is also a
Table 4
Comparison of zinc alkyl complexes
a
[(BDI-1)ZnEt]
[(BDI-3)ZnEt]ꢀ
[(BDI-4)ZnEt]ꢀ
[(BODDI-1)(ZnEt)2]
d(ZnÁ
d(ZnÁ
d(ZnÁ
NÁ
/
C)
1.963(5)
1.979(3)
1.943(3)
97.07(12)
1.963(3)
2.041(1)
2.048(8)
91.73(9)
1.995(5)
2.042(2)
2.042(3)
91.22(10)
1.956(5)/1.950(5)
1.922(3)
1.926(3)
92.92(13)/94.03(13) b
/N1)
/N2)
/
ZnÁ
/N
a
Bond lengths and angles are averages over the three molecules in the unit.
b
NÁ
/
ZnÁO angles.
/

142
S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á
/
148
Scheme 2.
Due to the unpredictable reactions of alcohols with
Table 5
(BDI)ZnR, facile and predictable routes to (BDI)ZnOR
complexes continue to be a goal. One route envisioned
was the reaction of an aldehyde or ketone with
(BDI)ZnR to give the corresponding alkoxide via
Scheme 4. The addition of alkyl Zn groups from ZnR2
across aldehydes and ketones is well-documented [15],
˚
Selected bond lengths (A) and bond angles (8) of [(BODDI-1)(ZnEt)2]
Bond lengths
Zn(1)Á
Zn(1)Á
Zn(1)Á
Zn(2)Á
Zn(2)Á
/
N(1)
C(8)
O(1)
N(2)
C(10)
1.922(3)
1.956(5)
2.007(3)
1.926(3)
1.950(5)
Zn(2)Á
O(1)ÁC(4)
N(1)Á
N(2)Á
/
O(1)
2.004(3)
1.334(5)
1.344(5)
1.332(5)
3.4026(8)
/
/
/
/
C(2)
C(6)
/
/
/
Zn(1)ÁZn(2)
/
but neither (BDI-1)ZnR nor (BDI-2)ZnR (RꢀMe, Et)
/
Bond angles
N(1)ÁZn(1)Á
N(2)ÁZn(2)Á
Zn(2)ÁO(1)Á
react with benzaldehyde to give the corresponding
alkoxide.
When reacted for extended amounts of time (about 24
/
/
O(1)
92.92(13) C(12)Á
/
N(1)Á
/
Zn(1)
116.5(3)
116.3(3)
/
/O(1)
94.03(13) C(24)Á
/
N(2)Á
/
Zn(2)
/
/Zn(1)
115.94(14)
24.3(5)
h) at room temperature, or at higher temperatures (]
/
Dihedral angles
C(3)ÁC(4)ÁO(1)Á
Zn(1)
50 8C), benzaldehyde undergoes a Tishchenko type
disproportionation in the presence of [(BDI)ZnR] to
1
yield benzyl benzoate (Scheme 4) [16]. H-NMR spec-
/
/
/
C(5)Á/C(4)Á
/O(1)Á
/
23.4(5)
Zn(2)
troscopy shows no change of the (BDI)ZnEt complex,
but the reaction goes to completion (even at ratios of
benzaldehyde:Zn of 100:1). These reactions are generally
initiated with metal alkoxides and it is our belief that
protic impurity or aldehyde insertion product is gen-
erating a small amount of zinc alkoxide which may be
initiating the reaction. This reaction does not occur
spontaneously in the absence of the Zn complex and it
occurs with other aldehydes. For example, the regioir-
distorted tetrahedron with bond angles of 83.0, 83.4,
130.3 and 140.48 for [{(BDI-3)Zn(m-OMe)}2Zn(m-
OMe)2], and 82.5, 82.5, 124.4 and 132.78 for [{(BDI-
5)Zn(m-OMe)}2Zn(m-OMe)2]. These complexes are ther-
mally stable in solution for days at elevated tempera-
tures. Heating a toluene solution of [{(BDI-5)Zn(m-
OMe)}2Zn(m-OMe)2] for five days at 110 8C does not
liberate free [Zn(OMe)2]ꢀ.
Fig. 4. ORTEP drawing of [(BODDI-1)(ZnEt)2] (non-hydrogen atoms) with thermal ellipsoids drawn at the 40% probability level.

S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á
/
148
143
Scheme 3.
regular polyester can be synthesized from benzene-1,4-
dicarboxaldehyde (Scheme 4) [17].
react with acetic acid to give the corresponding acetate
complexes in moderate to high yields. This synthetic
method is superior to previous routes using (BDI)Li and
Zn(OAc)2. The reaction of MeOH with [(BDI)ZnR]
complexes is unpredictable and the expected
[(BDI)Zn(m-OMe)]2 complex is only achieved with
some ligand sets, whereas with (BDI-3)H and (BDI-
5)H, [{(BDI)Zn(m-OMe)}2Zn(m-OMe)2] is formed in
moderate yields. New routes to BDI zinc complexes
with carboxylate and alkoxide initiators continue to be a
goal and further optimization of the synthetic routes to
2.3. Summary
In summary, we have reported the synthesis and
structure of several new BDI and BODDI zinc alkyl
complexes. BDI Zn alkyl complexes with cyano groups
on the backbone do not form the expected monomeric
species, but form coordination polymers in the solid
state. [(BDI)ZnEt] and [(BODDI)(ZnEt)2] complexes
Fig. 5. ORTEP drawing of [(BODDI-1)Zn2(m-OAc)2] (non-hydrogen atoms) with thermal ellipsoids drawn at the 40% probability level.

144
S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á148
/
Table 6
Table 7
˚
˚
Selected bond lengths (A) and bond angles (8) of [(BODDI-1)Zn2(m-
OAc)2]
Selected bond lengths (A) and bond angles (8) of [{(BDI-3)Zn(m-
OMe)}2Zn(m-OMe)2]
Bond lengths
Bond lengths
Zn(1)Á
Zn(1)Á
Zn(1)Á
/
O(1)
O(2)
O(3)
1.947(2)
1.970(2)
Zn(1)Á
/
N(1)
1.927(2)
1.448(4)
1.334(4)
1.322(4)
1.265(4)
Zn(1)Á
Zn(1)Á
Zn(2)Á
Zn(1)Á
Zn(1)Á
/
O(1)
O(2)
O(2)
N(1)
N(2)
1.963(3)
1.916(3)
1.968(3)
1.959(4)
1.985(4)
N(1)Á
/
C(29)
1.319(6)
1.147(7)
1.433(7)
2.8944(9)
/
N(1)Á
/
C(7)
C(5)
/
N(3)Á
/
C(33)
/
1.9387(16) N(1)Á
1.9387(16) O(3)Á
3.0450(8) O(1)Á
/
/
C(29)Á
Zn(1)Á
/C(30)
Zn(1A)Á
/
O(3)
/C(3)
/
/Zn(2)
Zn(1)ÁZn(1A)
/
/C(1A)
/
Bond angles
N(1)ÁZn(1)Á
O(1A)ÁC(1)Á
Zn(1)ÁO(3)ÁZn(1A) 103.50(11) C(5)Á
Bond angles
O(2)ÁZn(1)Á
N(1)ÁZn(1)Á
O(1)ÁZn(2)Á
Zn(1)Á
/
/
O(3)
95.55(9) O(3)Á
/
Zn(1)Á
Zn(1)Á
N(1)Á
/
O(1)
O(2)
105.14(7)
100.77(7)
121.9(2)
/
/
O(1)
83.74(14) Zn(2)Á
96.63(18) Zn(1)Á
83.06(14) C(5)ÁN(1)Á
C(17)ÁN(2)ÁZn(1) 118.0(3)
/
O(1)Á
/
Zn(1)
95.85(14)
96.36(14)
118.7(3)
/
/O(2)
125.7(3) O(3)Á
/
/
/
/
N(2)
O(2)
/O(2)Á
/
Zn(2)
/
/
/
/
Zn(1)
/
/
/
/Zn(1)
/
Zn(2)Á
/Zn(3) 164.01(3)
/
/
Dihedral angles
Zn(1)ÁO(3)ÁC(3)Á
C(4)
/
/
/
1.67(15)
Zn(1A)Á
C(4A)
/O(3)Á
/
C(3)Á
/
1.74(16)
techniques. 1H-NMR and 13C-NMR spectra were
recorded on Varian Inova 400 and Bruker AF 300
spectrometers and referenced versus residual non-deut-
erated solvent shifts. In some cases, 13C-NMR spectra
were not obtained due to low solubility.
these complexes is underway. Additionally, the catalytic
activity of the new class of [(BODDI)Zn2(m-OAc)2]
complexes is currently being investigated.
3. Experimental
3.2. Materials
3.1. General considerations
Solvents were purified over solvent columns. All
reagents were purchased from Aldrich and used without
further purification unless otherwise noted.
All manipulations of air- and/or water-sensitive
compounds were carried out under dry N2 using a
Braun Labmaster drybox or standard Schlenk line
Fig. 6. ORTEP drawing of [{(BDI-3)Zn(m-OMe)}2Zn(m-OMe)2] (non-hydrogen atoms) with thermal ellipsoids drawn at the 40% probability level.

S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á
/
148
145
3.3.3. N-(2,6-diethyl)phenyl-acetimine
2,6-Diethylaniline (20.0 g, 134 mmol), 2,2-dimethox-
˚
ypropane (19.1 g, 183 mmol) and activated 4 A
molecular sieves (12.5 g) were added to 20 ml dry
toluene. The mixture was heated for 2 days at 100 8C
then the sieves were filtered off and the volatiles were
removed in vacuo to leave a light yellow oil. The
product was isolated by vacuum distillation as a color-
1
less oil (23.4 g, 92%). H-NMR (C6D6, 300 MHz): d
7.00 (3H, m, ArÁ
CH3), 1.65 (3H, s, CH3), 1.15 (3H, s, CH3). 13C{1H}-
NMR (C6D6, 75 MHz): d 168.6 (CÄN), 147.9, 132.1,
126.0, 123.2 (aromatic C), 27.9, 24.6, 21.4, 14.1 (Etꢁ
/
H), 2.36 (4H, m, CH2CH3), 2.29 (3H, s,
/
/
Me).
Scheme 4.
3.3.4. N-(2,6-diisopropyl)phenyl-
trifluoromethylacetimidoyl chloride
3.3. Ligand synthesis
The preparation for this compound was accomplished
using a literature procedure in 80% isolated yield. [19]
BDI ligands 1 and 2 [6c] were prepared as previously
reported. BDI ligands 3 and 4 were prepared using a
modified procedure reported by Corey and Wang [18].
1H-NMR (C6D6, 300 MHz): d 7.21 (3H, s, ArÁ
/
H), 2.69
6.9 Hz, CHMe2), 1.21 (12H, m,
CHMeMe). 13C{1H}-NMR (C6D6, 75
MHz): d 141.2, 136.5, 127.2, 124.2 (aromatic C), 134.6
(2H, m, Jꢀ
/
CHMeMeꢁ
/
(q, 2JCF
ꢀ
/
43 Hz, Cꢀ
/
O), 121.0 (q, 1JCF
ꢀ264 Hz, CF3)
/
29.4, 23.3 (iPr).
3.3.1. (BDI-3)H
nBuLi (1.6 M in hexane, 1.0 ml, 1.6 mmol) was added
dropwise to a solution of (BDI-1)H (0.60 g, 1.43 mmol)
in THF (30 ml) at ꢂ
/
78 8C. After stirring at ꢂ78 8C for
/
3.3.5. (BDI-5)H
5 min, the solution was warmed to room temperature
(r.t.) and stirred for 1 h. The solution was cooled back
This compound was prepared using a modified
procedure reported by Andersson and co-workers [20].
nBuLi (1.6 M in hexane, 27.7 ml, 44.3 mmol) was added
to a solution of diisopropyl amine (4.48 g, 44.3 mmol) in
down to ꢂ78 8C and a solution of p-toluenesulfonyl-
/
cyanide (0.28 g, 1.5 mmol) in THF (10 ml) was added
dropwise. The solution was warmed to r.t. and stirred
for 10 h. The volatiles were removed in vacuo and the
light yellow residue was dissolved in CH2Cl2 (50 ml),
washed with brine, dried over Na2SO4, filtered, and the
solvent was removed in vacuo to leave a light yellow
THF (200 ml) at ꢂ78 8C. The solution was stirred for 30
/
min and N-(2,6-diethyl)phenyl-acetimine (4.0 g, 21.1.
mmol) was added in one portion. The solution was
stirred for 30 min at ꢂ78 8C, then warmed to 0 8C and
/
stirred for an additional 2 h. N-(2,6-diisopropyl)phenyl-
trifluoromethylacetimidoyl chloride (6.48 g, 22.2. mmol)
was added in one portion and stirred for 45 min at 0 8C.
The reaction was quenched with saturated NH4Cl
solution (100 ml) and EtOAc (200 ml) and water (100
ml) were added. The organic phase was separated,
solid. The crude material was crystallized from EtOH at
1
ꢂ
/
20 8C (0.48 g, 76%). H-NMR (C6D6, 300 MHz): d
14.14 (1H, s, NH) 7.07 (6H, m, ArH), 2.93 (4H, m, Jꢀ
6.5 Hz, CHMe2), 1.98 (6H, s, a-CH3), 1.02 (12H, d , Jꢀ
6.5 Hz, CHMeMeꢁ
CHMeMe). 13C{1H}-NMR (C6D6,
75 MHz): d 167.4 (iminate CÁN), 142.2, 139.0, 126.8,
123.9, 121.5 (aromatic CꢁCN), 81.4 (b-CH), 28.7, 24.2,
23.3, 19.8 (a-Meꢁi
Pr).
/
/
/
washed with 1ꢃ
/
100 ml NH4Cl, 1ꢃbrine, dried over
/
/
Na2SO4, filtered, and the solvent was removed in vacuo
to leave a yellow oil. The product was crystallized from
1
EtOH at r.t. to yield yellow needles (6.16 g, 66%). H-
/
/
NMR (C6D6, 300 MHz): d 12.18 (1H, s, NH), 7.05 (6H,
6.6 Hz,
m, ArH), 5.36 (1H, s, b-CH), 3.24 (2H, m, Jꢀ
/
3.3.2. (BDI-4)H
1H-NMR (C6D6, 300 MHz): d 14.0 (1H, s, NH), 6.94
(6H, m, ArH), 2.27 (8H, m, Jꢀ7.5 Hz, CH2CH3), 1.89
(6H, s, a-CH3), 0.98 (12H, t, Jꢀ7.5 Hz, CH2CH3).
13C{1H}-NMR (C6D6, 75 MHz): d 166.9 (iminate CÁ
N), 140.6, 126.6, 126.2, 121.5 (aromatic C), 81.0 (b-CH),
24.8, 19.3, 14.5 (a-MeꢁEt).
CHMe2), 2.42 (4H, m, Jꢀ7.5 Hz, CH2CH3), 1.41 (3H,
/
s, a-CH3), 1.29 (6H, d, Jꢀ
/
6.3 Hz, CHMeMe), 1.06
CH2CH3). 13C{1H}-NMR (C6D6,
/
(12H, m, CHMeMeꢁ
/
2
75 MHz): d 163.6, 149.4 (q, JCF
141.6, 140.3, 138.2, 126.6, 126.4, 125.9, 123.4 (aromatic
/
ꢀ
/
27.3, iminate CÁN)
/
/
1
C) 120.5 (q, JCF
ꢀ
/
284 Hz, CF3), 90.4 (b-CH), 28.8,
/
25.1, 24.7, 22.8, 20.5, 14.5 (a-Meꢁ
/
Etꢁi
/
Pr).

146
S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á148
/
3.3.6. (BODDI-1)H2
for X-ray analysis. 1H-NMR (C6D6, 300 MHz, 50 8C): d
6.90 (6H, br s, ArÁH), 2.48Á2.20 (8H, m, Jꢀ7.2 Hz,
CH2CH3), 2.05 (6H, s, a-Me), 1.1 (12H, t, Jꢀ7.2 Hz,
CH2CH3), 0.68 (3H, t, Jꢀ7.0 Hz, CH2CH3), 0.05 (2H,
q, Jꢀ
7.0 Hz, CH2CH3). 13C{1H}-NMR (C6D6, 75
MHz, 50 8C): d 171.34 (iminate CÁN), 145.26, 136.06,
127.60, 126.41, 123.00 (aromatic CꢁCN), 24.70, 22.00,
14.17, (Etꢁ Et). X-ray analysis
The preparation of this compound was accomplished
using a modified literature procedure [14]. Diacetylace-
tone [21] (2.32 g, 16.3 mmol) and 2,6-diisopropylaniline
(6.36 g, 35.8 mmol) were combined and heated until the
neat solution was homogeneous, then stirred overnight
at r.t. The light brown solution was dissolved in CH2Cl2
and dried with Na2SO4, filtered, and the volatiles were
/
/
/
/
/
/
/
/
/
a-Me) 11.40, -2.18 (ZnÁ
/
removed in vacuo. The product was crystallized from
1
revealed a coordination polymer as shown in Fig. 2.
EtOH at ꢂ
/
20 8C (5.26 g, 70%). H-NMR (C6D6, 300
MHz): d 12.32 (2H, b, NH), 7.04 (6H, m, ArH), 5.24
(2H, s, b-CH), 3.30 (4H, m, Jꢀ6.5 Hz, CHMe2), 1.49
(6H, s, a-Me), 1.10 (12H, d, Jꢀ6.5 Hz, CHMeMe),
1.08 (12H, d, Jꢀ
6.4 Hz, CHMeMe). 13C{1H}-NMR
(C6D6, 75 MHz) d 191.4, 159.0 (CÁNꢁCÄO), 147.2,
135.3, 128.1, 123.6 (aromatic C), 96.9 (b-CH), 28.8, 24.8,
22.7, 19.4 (a-Meꢁi
Pr).
3.4.5. [(BDI-5)ZnEt]
Bright yellow waxy solid. 1H-NMR (C6D6, 300
MHz): d 7.09 (3H, s, ArH), 6.97 (3H, s, ArH), 5.52
/
/
/
(1H, s, b-CH), 3.20 (2H, m, Jꢀ
Jꢀ7.5 Hz, CH2CH3), 1.44 (3H, s, a-CH3), 1.28 (6H, d,
Jꢀ6.7 Hz, CHMeMe), 1.20 (6H, d, Jꢀ6.7 Hz,
CHMeMe), 1.08 (6H, t, Jꢀ7.5 Hz, CH2CH3), 0.78
(3H, t, Jꢀ8.1 Hz, CH2CH3), 0.17 (2H, q, Jꢀ8.1 Hz,
CH2CH3). 13C{1H}-NMR (C6D6, 75 MHz): d 171.2
(iminate CÁN), 145.6, 142.3, 135.7, 127.9, 126.8, 126.4,
126.1, 123.5 (aromatic CꢁCF3), 91.2 (b-CH), 28.7, 25.0,
24.9, 23.0, 22.8 (a-Meꢁi
PrꢁEt), 14.2, 11.5 (ZnÁEt).
/
6.7 Hz), 2.33 (4H, m,
/
/
/
/
/
/
/
/
/
/
3.4. Complex synthesis
/
3.4.1. Synthesis of [(BDI)ZnR]
[(BDI-1)ZnMe], [(BDI-1)ZnEt] and [(BDI-2)ZnEt]
were prepared via literature procedures [6c] and corre-
1
lated with known H-NMR [6c,9c]. General procedure
for (BDI)ZnR: (BDI-2)H (1.0 g, 2.8 mmol) was dis-
solved in 20 ml toluene in a Schlenk tube in a drybox.
ZnMe2 (2.1 ml of a 2.0 M solution in toluene, 4.14
mmol) was added and the mixture was heated to 75 8C
for 18 h. After cooling to room temperature the volatiles
were removed in vacuo resulting in quantitative conver-
sion to [BDIZnR]. These complexes were used without
further purification unless otherwise noted.
/
/
/
/
3.4.6. [(BODDI-1)(ZnEt)2]
This complex was prepared as described for the
(BDI)ZnEt complexes. Crystallized from hexanes at
ꢂ
20 8C (54% yield). 1H-NMR (C6D6, 300 MHz): d
/
7.05 (6H, m, ArH), 5.04 (2H, s, b-CH), 3.16 (4H, septet,
Jꢀ7.0 Hz, CHMe2), 1.53 (6H, s, a-Me), 1.18 (6H, t,
Jꢀ8.0 Hz, CH2CH3), 1.12 (12H, d, Jꢀ7.0 Hz,
CHMeMe), 1.09 (12H, d, Jꢀ7.0 Hz, CHMeMe), 0.16
(4H, q, Jꢀ8.0 Hz, CH2CH3). X-ray analysis revealed
/
/
/
/
/
that the complex exists as a monomeric complex with
two Zn-Et moieties as shown in Fig. 4.
3.4.2. [(BDI-2)ZnMe]
Light yellow waxy solid. 1H-NMR (C6D6, 300 MHz):
d 7.03 (6H, b, ArH), 4.93 (1H, s, b-CH), 2.54 (8H, m,
3.4.7. Synthesis of [(BDI)Zn(m-OAc)]2
[(BDI-5)Zn(m-OAc)]2 was previously reported [6e].
Jꢀ
Jꢀ
NMR (C6D6, 75 MHz): d 167.2 (iminate CÁ
137.0, 126.8, 125.4 (aromatic C), 95.6 (b-CH), 25.2, 23.2
(a-MeꢁEt), 14.7 (ZnÁMe).
/
7.2 Hz, CH2CH3), 2.52 (6H, s, a-CH3), 2.45 (12H, t,
7.2 Hz, CH2CH3), ꢂ
0.67 (3H, s, CH3). 13C{1H}-
N), 146.6,
/
/
[(BDI)Zn(m-OAc)] for BDI ligands 1Á/4 were synthesized
/
with the following general procedure. [(BDI)ZnEt] was
dissolved in the appropriate solvent (hexanes for (BDI-
1) and (BDI-2); CH2Cl2 for (BDI-3) and (BDI-4)), the
solution was cooled to 0 8C, and acetic acid (1 equiv.)
was added dropwise. The solution was stirred overnight,
allowing gradual warming to r.t. then the volatiles were
removed in vacuo.
/
/
3.4.3. [(BDI-3)ZnEt]ꢀ
Light yellow powder. Slowly cooling a toluene solu-
tion of the complex yielded light yellow prisms suitable
1
for X-ray analysis. H-NMR (C6D6, 300 MHz): d 7.00
(6H, b, ArH), 2.88 (4H, m, Jꢀ
(6H, s, a-Me), 1.14 (12H, d, Jꢀ
1.00 (12H, d, Jꢀ7.0 Hz, CHMeMe), 0.71 (3H, t, Jꢀ
Hz, CH2CH3), 0.11 (2H, q, Jꢀ8.0 Hz, CH2CH3). X-ray
analysis revealed a coordination polymer as shown in
Fig. 1.
/
7.0 Hz, CHMe2), 2.14
7.0 Hz, CHMeMe),
8.0
3.4.8. [(BDI-1)Zn(m-OAc)]2
The white solid was crystallized from CH2Cl2 at
/
/
/
1
ꢂ
/
20 8C (87% yield). H and 13C{1H}-NMR correlate
to known spectra [6c].
/
3.4.9. [(BDI-2)Zn(m-OAc)]2
The white solid was crystallized from toluene at
3.4.4. [(BDI-4)ZnEt]ꢀ
Light yellow powder. Slowly cooling a toluene solu-
tion of the complex yielded light yellow prisms suitable
1
ꢂ
/
20 8C (85% yield). H and 13C{1H}-NMR correlate
to known spectra [6c].

S.D. Allen et al. / Journal of Organometallic Chemistry 683 (2003) 137Á
/
148
147
3.4.10. [(BDI-3)Zn(m-OAc)]2
The product was isolated as a microcrystalline powder
3.4.14. [{(BDI-5)Zn(m-OMe)}2Zn(m-OMe)2]
ZnEt2 (0.77 ml of a 1.1 M toluene, 0.84 mmol) was
added to a solution of (BDI-5)H (0.25 g, 0.56 mmol) in
toluene (5 ml) in the drybox at r.t. The solution was
heated to 75 8C for 16 h and the volatiles were removed
in vacuo to leave a waxy yellow solid, [(BDI-5)ZnEt],
which was used without further purification. The
complex was dissolved in 5 ml hexanes and MeOH (23
ml, 0.56 mmol) was added dropwise and stirred for 18 h
at r.t. The volatiles were removed in vacuo and the crude
yellow material was crystallized from hexanes to give
light yellow blocks, (0.26 g, 57% based on Zn). 1H-
NMR (C6D6, 300 MHz): d 7.06 (3H, s, ArH) 6.99 (3H,
s, ArH), 5.30 (2H, s, b-CH), 3.42 (4H, m, CHMe2), 3.09
from CH2Cl2 solution at ꢂ
(THF-d8, 400 MHz): d 7.12 (6H, b, ArH), 3.26 (4H,
septet, Jꢀ7.0 Hz, CHMe2), 2.00 (6H, s, a-Me), 1.63
(3H, s, OAc), 1.21 (12H, d, Jꢀ7.0 Hz, CHMeMe), 1.13
(12H, d, Jꢀ7.0 Hz, CHMeMe).
/
20 8C (50% yield). 1H-NMR
/
/
/
3.4.11. [(BDI-4)Zn(m-OAc)]2
The crude material was crystallized from toluene at
r.t. to give colorless blocks (84% yield). 1H-NMR
(60 8C, C6D6, 300 MHz): d 6.99 (3H, m, ArH), 6.88
(3H, m, ArH), 2.27 (8H, quartet, Jꢀ
1.96 (6H, s, a-Me), 1.46 (3H, b, OAc), 1.00 (12H, t, Jꢀ
7.5 Hz, CH2CH3). 13C{1H}-NMR (C6D6, 75 MHz), d
180.52 (iminate CÁN), 172.48, 144.47, 136.52, 125.95,
125.77, 123.60 (aromatic CꢁCN), 80.87 (b-CH), 23.38,
22.10, 13.55 (a-MeꢁEtꢁOAc).
/7.5 Hz, CH2CH3),
/
(12H, br, OCH3), 2.52 (8H, m, Jꢀ
1.37 (15H, m, CHMeMeꢁa-CH3) 1.28 (12H, d, Jꢀ
Hz, CHMeMe), 1.13 (12H, t, Jꢀ7.5 Hz, CH2CH3).
13C{1H}-NMR (C6D6, 75 MHz): d 172.4 (iminate CÁ
N), 143.1, 136.0, 127.4, 127.3, 127.2, 126.8, 126.5
(aromatic CꢁCF3), 91.2 (b-CH), 55.2 (OMe), 28.3,
25.6, 24.0, 23.90, 22.8, 13.7 (a-Meꢁ Pr).
Etꢁi
/
7.5 Hz, CH2CH3),
/
/
/
6.0
/
/
/
/
/
3.4.12. [(BODDI-1)Zn2(m-OAc)2]
/
To a solution of [(BODDI-1)(ZnEt)2] in a minimal
amount of hexanes was added one equivalent of acetic
acid at 0 8C. After stirring overnight allowing a gradual
temperature increase to r.t., the clear solution was dried
in vacuo to leave a yellow solid. The product was
crystallized from hexanes at r.t. to give brilliant fluor-
/
/
3.5. Reaction of [(BDI)ZnR] with benzaldehyde
[(BDI-n)ZnR] (nꢀ1, 2; RꢀMe, Et) (20 mg) was
/
/
dissolved in 1 ml C6D6. To the solution was added 1
equivalent of benzaldehyde. The solution was trans-
ferred to an NMR tube fitted with a Teflon stopcock,
and was allowed to react for 24 h at 50 8C. The reaction
1
escent yellow blocks (82% yield). H-NMR (C6D6, 400
MHz): d 7.12 (6H, m, ArH), 4.95 (2H, s, b-CH), 3.43
(4H, septet, Jꢀ6.8 Hz, CHMe2, 1.73 (6H, s, OAc), 1.58
/
1
(6H, s, a-Me), 1.30 (12H, d, Jꢀ
1.19 (12H, d, Jꢀ
6.8 Hz, CHMeMe). 13C{1H}-NMR
(C6D6, 75 MHz), d 181.23, 176.69 (CÁNꢁ O),
/6.8 Hz, CHMeMe),
was monitored via H-NMR and in all instances the
/
formation of benzylbenzoate was observed with no
change to the [(BDI)ZnR] complex. The polymerization
of 1,4-dicarboxaldehyde was accomplished using this
procedure.
/
/
CÄ
/
169.28, 143.95, 143.38, 126.24, 124.20 (aromatic C),
93.18 (b-CH), 27.93, 24.48, 24.24, 24.01, 23.54 (a-
Meꢁi
Pr). X-ray analysis revealed that this molecule
/
exists as a monomer with two m-OAc ligands bridging
the Zn atoms as shown in Fig. 5.
References
3.4.13. [{(BDI-3)Zn(m-OMe)}2Zn(m-OMe)2]
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NMR analysis showed only 25% conversion (based on
ZnEt peaks). Additional MeOH was added (about five
equivalents) in excess and the reaction was allowed to
proceed until all ZnEt peaks were reacted (about 2
days). The volatiles were removed in vacuo and the
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a-Me), 2.07 (6H, s, a-Me), 1.15 (12H, d, Jꢀ7.0 Hz,
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