Synthesis and structures of new binuclear zinc alkyl, aryl and aryloxo complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.10.043

The synthesis of a series of binuclear zinc complexes with Cl, N and O bridges is reported. The reaction of EtZnCl with B(C₆F₅)₃ in the presence of hexamethylbenzene affords the arene complex [Zn(μ-Cl)(C₆F₅)(η-C₆Me₆)]₂ in which the C₆Me₆ ligand may be regarded as η³-bonded. The comproportionation of Zn[N(SiMe₃)₂]₂ with ZnBu^t₂ or Zn(C₆F₅)₂ · toluene gave [Bu^tZn{μ-N(SiMe₃)₂}]₂ and [C₆F₅Zn{μ-N(SiMe₃)₂}]₂, respectively, with three-coordinate zinc. The reaction of ZnEt₂ with C₆F₅OH in the presence of pyridine gave [EtZn(μ-OC₆F₅)(py)]₂, while ZnMe₂ and C₆F₅OH followed by recrystallisation from THF gave [Zn(OC₆F₅)(μ-OC₆F₅)(THF)₂]₂ with five-coordinate zinc in a trigonal-bipyramidal geometry. The structures of these compounds have been determined.

Full text of DOI:10.1016/j.jorganchem.2007.10.043

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1494–1501
www.elsevier.com/locate/jorganchem
Synthesis and structures of new binuclear zinc alkyl, aryl
and aryloxo complexes
Yann Sarazin, Joseph A. Wright, Duncan A.J. Harding, Eddy Martin,
*
Timothy J. Woodman, David L. Hughes, Manfred Bochmann
Wolfson Materials and Catalysis Centre, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, UK
Received 28 August 2007; accepted 26 October 2007
Available online 1 November 2007
In memoriam Professor F. Albert Cotton.
Abstract
The synthesis of a series of binuclear zinc complexes with Cl, N and O bridges is reported. The reaction of EtZnCl with B(C6F5)3 in
the presence of hexamethylbenzene affords the arene complex [Zn(l-Cl)(C6F5)(g-C6Me6)]2 in which the C6Me6 ligand may be regarded as
g3-bonded. The comproportionation of Zn[N(SiMe3)2]2 with ZnBu2t or Zn(C6F5)2 Æ toluene gave [ButZn{l-N(SiMe3)2}]2 and
[C6F5Zn{l-N(SiMe3)2}]2, respectively, with three-coordinate zinc. The reaction of ZnEt2 with C6F5OH in the presence of pyridine gave
[EtZn(l-OC6F5)(py)]2, while ZnMe2 and C6F5OH followed by recrystallisation from THF gave [Zn(OC6F5)(l-OC6F5)(THF)2]2 with five-
coordinate zinc in a trigonal-bipyramidal geometry. The structures of these compounds have been determined.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Zinc; Amide complex; Phenoxide; Arene p-bonding; Binuclear complex; Crystal structure analysis
1. Introduction
the copolymerisation of epoxides with CO2 [6,7]. We have
been interested in zinc complexes in various coordination
environments as catalysts for ring-opening polymerisations
of esters and ethers [8] and for isobutene polymerisations
and copolymerisations [9]. In the course of these studies a
number of zinc amido and aryloxo complexes were pre-
pared as convenient starting materials, and we report here
the syntheses and structural characterisation of a series of
binuclear zinc alkyl, aryl and aryloxide complexes.
Interest in organometallic zinc compounds has persisted
for over 150 years. Since Frankland’s synthesis of EtZnI
[1], a multitude of applications have been found for such
simple reagents in various fields of chemistry. For instance,
alkylzinc iodides are used for Simmons–Smith cyclopropa-
nation [2], alkylzinc bromides are used for nickel-catalyzed
Negishi reactions [3] and EtZnCl generated in situ has been
shown to be a good chain transfer agent in the polymerisa-
tion of olefins [4]. Zinc alkoxides and mixed-ligand species
Zn(X)(Y), where X = bulky ligand and Y = alkyl, amide
or alkoxide, are effective catalysts for the ring-opening
polymerisation of lactide [5], while a number of related spe-
cies as well as zinc bis(aryloxide)zinc compounds catalyze
2. Results and discussion
The reaction of [EtZnCl] [10] with B(C6F5)3 in toluene
1
in the presence of hexamethylbenzene gave a mixture of
products as a white precipitate from which some colourless
crystals could be isolated by manual separation. These
crystals were identified by single-crystal X-ray diffraction
as the arene complex [Zn(l-Cl)(C6F5)(g-C6Me6)]2 (1); it
crystallises with one molecule of CH2Cl2 (Scheme 1).
*
Corresponding author.
E-mail address: M.Bochmann@uea.ac.uk (M. Bochmann).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.10.043

Y. Sarazin et al. / Journal of Organometallic Chemistry 693 (2008) 1494–1501
1495
F
F
F
F
C6Me6
Cl
Cl
EtZnCl + B(C6F5)3
F
Zn
Zn
F
F
toluene
F
F
F
1
Scheme 1.
Complex 1 consists of a Zn2Cl2 four-membered ring
with almost equal Zn–Cl distances, a hexamethyl ligand
and a terminal C6F5 substituent (Fig. 1). The geometry
around the metal centre is distorted tetrahedral, with the
fourth coordination position being occupied by a hexa-
methylbenzene ligand which is unsymmetrically bound to
interaction of zinc with the more electron-rich C6Me6 mol-
ecule than was found for toluene. We have pointed out
earlier the difficulty of assigning defined hapticity to arene
bonds of this kind [12]; in the case of 1 the bonding is prob-
ably best described as g1 with a tendency towards an
g3-interaction. The Zn–C(aryl) bond of 1.977(13) is slightly
longer than that in the related three-coordinate toluene
˚
the metal centre. The distance Zn–C(7) is 2.448(3) A,
˚
whereas the distances to C(8) and C(12) are 2.714(3) and
complexes Zn(C6F5)2(g-toluene) (1.9436(14) A) and
˚
˚
2.767(3) A, respectively. We have recently reported first
Zn(C6F4–2-C6F5)2(g-toluene) (1.951(3) A).
examples of crystallographically characterised toluene
complexes of zinc in which the arene ligand was rather
Further examples of binuclear zinc complexes are read-
ily accessible as outlined in Scheme 2.
weakly bound; Zn(C6F5)2(g-toluene) displayed
a
The comproportionation of Zn[N(SiMe3)2]2 with ZnBu2t
or Zn(C6F5)2 Æ toluene gives the three-coordinate amido-
bridged complexes [ButZn{l-N(SiMe3)2}]2 (2) and
[C6F5Zn{l-N(SiMe3)2}]2 (3), respectively, in good yields
as colourless crystals. [ButZn{l-N(SiMe3)2}]2 is very solu-
ble in hydrocarbons, ethers and chlorinated solvents and
˚
Zn–C(toluene) distance of 2.6847(15) A, whereas the tolu-
ene ligand in Zn(C6F4–2-C6F5)2(g-toluene) was bonded
slightly more strongly, with a shortest distance to the arene
˚
of 2.524(3) A [11,12]. By comparison, the Zn–C(arene) vec-
tor in 1 is remarkably short, indicative of a much stronger
Fig. 1. Molecular structure of [Zn(l-Cl)(C6F5)(g-C6Me6)]2 (1) showing the atomic numbering scheme and 50% probability ellipsoids; hydrogen atoms
˚
have been omitted for clarity. Selected bond lengths (A) and angles (ꢁ) with estimated standard deviations: Zn(1)–C(1) 1.977(3), Zn(1)–Cl(1) 2.3319(7),
0
0
˚
Zn(1)–Cl(1 ) 2.3426(8), Zn(1)–C(7) 2.448(3), Zn(1)–C(8) 2.714(3), Zn(1)–C(12) 2.767(3) A; C(1)–Zn(1)–Cl(1) 119.60(8), C(1)–Zn(1)–Cl(1 ) 117.64(8),
Cl(1)–Zn(1)–Cl(10) 91.97(3).

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Y. Sarazin et al. / Journal of Organometallic Chemistry 693 (2008) 1494–1501
SiMe3
Zn
SiMe3
Zn
Me3Si
Zn
Me3Si
Zn
N
N
N
N
ZnBut2
Zn(C6F5)2
C6F5
C6F5
Zn[N(SiMe3)2]2
Me3Si
SiMe3
Me3Si
SiMe3
3
2
C6F5
C6F5
O
C6F5
O
THF
THF
py
Et
O
Et
R = Me or C6F5
R = Et
Zn
Zn
Zn
ZnR2
Zn
THF
THF
1 C6F5OH
pyridine
py
O
O
2 C6F5OH
O
C6F5
C6F5
C6F5
4
5
Scheme 2.
is very air-sensitive. [C6F5Zn{l-N(SiMe3)2}]2 is sparingly
soluble in hydrocarbons but soluble in chlorinated solvents
and in ethers. It is relatively air-stable and as a solid can be
briefly handled in air with no visible sign of degradation.
Interestingly, attempts to use similar comproportiona-
tion reactions to prepare the mixed-ligand zinc alkyl aryls
RZn(C6F5) from Zn(C6F5)2 Æ C7H8 and either ZnEt2 or
ZntBu2 did not give the desired products; with ZnEt2, no
reaction took place and Zn(C6F5)2 Æ C7H8 was recovered
The structures of 2 and 3 are shown in Figs. 2 and 3,
respectively. In both cases the metal centres are three-coor-
dinate. The Zn2N2 cores of both molecules are almost com-
pletely planar. The structure of 2 exhibits no obvious
contacts between the zinc centres and any non-bonded
atoms. Indeed, there are no short contacts with the struc-
ture using the standard definition (the sum of the van der
Waals radii of the atoms). Compound 2 resembles the pre-
viously reported (low quality) structure [MeZn{l-
N(SiMe3)2}]2 [8d]. The crystals showed reactivity with air
1
(as confirmed by H and 19F NMR), and with ZntBu2 a
small amount of intractable oily material was obtained.
Fig. 2. Molecular structure of [ButZn{l-N(SiMe3)2}]2 (2), showing 50%
Fig. 3. Molecular structure of [C6F5Zn{l-N(SiMe3)2}]2 (3), showing 50%
probability ellipsoids; hydrogen atoms have been omitted for clarity.
Selected bond lengths (A) and angles (ꢁ) with estimated standard
probability ellipsoids; hydrogen atoms and one molecule of toluene have
been omitted for clarity. Selected bond lengths (A) and angles (ꢁ) with
˚
˚
deviations: Zn(1)–C(60) 2.019(3), Zn(2)–C(50) 2.021(3), Zn(1)–N(1)
2.084(2), Zn(1)–N(2) 2.096(2), Zn(2)–N(1) 2.109(2), Zn(2)–N(2) 2.086(2),
Zn(1)ꢀ ꢀ ꢀZn(2) 2.9026(5); N(1)–Zn(1)–N(2) 92.34(9), N(1)–Zn(2)–N(2)
91.91(9), C(50)–Zn(2)–N(2) 132.79(12), C(50)–Zn(2)–N(1) 135.29(12),
Zn(1)–N(1)–Zn(2) 87.62(9), Zn(1)–N(2)–Zn(2) 87.91(9).
estimated standard deviations: Zn(1)–N(1) 2.048(2), Zn(1)–N(2) 2.048(2),
Zn(2)–N(1) 2.044(2), Zn(2)–N(2) 2.051(2), Zn(1)–C(50) 1.983(3), Zn(2)–
C(60) 1.988(3); N(1)–Zn(1)–N(2) 94.00(8), N(1)–Zn(2)–N(2) 94.00(8),
C(50)–Zn(1)–N(1) 132.85(11), C(60)–Zn(2)–N(1) 134.65(11), Zn(1)–
N(1)–Zn(2) 86.09(8), Zn(1)–N(2)–Zn(2) 85.91(9).

Y. Sarazin et al. / Journal of Organometallic Chemistry 693 (2008) 1494–1501
1497
even when under vacuum oil; this accounts for the high
value of Rint for the data set obtained.
The Zn–N bond lengths in 3 are significantly shorter
than those in 2, a reflection of the presence of the strongly
electron-withdrawing C6F5 ligand. On the other hand, in
spite of the very different nature of the bridging atoms
and the different coordination numbers, the Zn–C(aryl)
distance in 3 is almost identical to that in 1, 1.977(3) vs.
˚
1.983(3) A.
The protonolysis of dialkyl of diaryl zinc compounds
with pentafluorophenol gives the corresponding aryloxide
complexes. The reaction of diethyl zinc with pentafluoro-
phenol in a molar ratio of 1:1 leads to the expected alkyl-
zinc aryloxide which can be stabilised by donor ligands;
e.g. ZnEt2 and C6F5OH in the presence of pyridine gave
crystals of the complex [EtZn(l-OC6F5)(py)]2 (4), with tet-
rahedral metal cores. On the other hand, the reaction of 2
equivalents of C6F5OH with either ZnMe2 or Zn(C6F5)2 Æ
toluene afforded [Zn(OC6F5)2]n as a white precipitate
which, on recrystallisation from tetrahydrofuran, afforded
colourless crystals of the THF adduct [Zn(OC6F5)(l-
OC6F5)(THF)2]2 (5). The structures of these compounds
are shown in Figs. 4 and 5, respectively.
Fig. 5. Molecular structure of [Zn(OC6F5)2(THF)2]2 (5). Thermal ellip-
The two halves of the molecules in both 4 and 5 are
related by an inversion centre. The geometry about the zinc
atom in 4 is distorted tetrahedral. The Zn–Et bond length
is closely comparable to the Zn–C distances in 1 and 3 but
significantly shorter than in tert-butyl complex 2, even
though the latter is coordinatively less saturated. The aryl-
soids are drawn at the 30% probability level. Hydrogen atoms in the THF
ligands have been omitted for clarity. Selected bond lengths (A) and angles
˚
(ꢁ) with estimated standard deviations: Zn–O(1) 1.975(2), Zn–O(10)
2.136(2), Zn–O(2) 1.918(3), Zn–O(3) 2.148(2), Zn–O(4) 2.050(2); O(1)–
Zn–O(2) 140.51(11), O(1)–Zn–O(3) 90.98(9), O(1)–Zn–O(4) 121.91(10),
O(1)–Zn–O(10) 76.01(10), O(2)–Zn–O(3) 91.92(11), O(2)–Zn–O(4)
97.51(11), O(2)–Zn–O(10) 98.67(11), O(3)–Zn–O(10) 166.96(9), O(4)–Zn–
O(3) 89.35(9), O(4)–Zn–O(10) 96.73(10), Zn–O(1)–Zn0 103.99(10), C(11)–
O(1)–Zn 130.3(2), C(21)–O(2)–Zn 130.3(2), C(11)–O(1)–Zn0 125.1(2).
oxide bridges are distinctly asymmetric, with Zn–O dis-
˚
tances of 2.0595(12) and 2.0858(13) A, unlike the amido
complexes 2 and 3 which have almost identical Zn–N bond
lengths.
In contrast to the complexes discussed so far, the zinc
atom in 5 is sufficiently strongly Lewis acidic to bind two
THF ligands. This results in pentacoordination with a dis-
torted trigonal-bipyramidal pattern in which one of the
OC6F5 ligands lies in an apical site on one Zn atom and
bridges to the second Zn, where it occupies an equatorial
site. The aryloxide ligands form highly asymmetric bridges,
˚
with Zn–O bond distances of 1.975(2) and 2.136(2) A. The
normal to the C6 ring of the bridging ligand is almost per-
pendicular to that of the central Zn2O2 ring plane, and the
terminal OC6F5 ligands lie almost parallel to, and overlap-
ping, the bridging OC6F5 groups. The THF ligands are
well-resolved, one occupying an apical site, the other an
equatorial site. The five-membered rings of both these
ligands have ‘half-chair’ conformations in which the mini-
mum torsion angles are 7.4(4) and 10.8(4)ꢁ; in an envelope
conformation, there is one torsion angle of 0ꢁ.
Fig. 4. Molecular structure of [EtZn(l-OC6F5)(py)]2 (4). Displacement
ellipsoids are shown at the 50% probability level. Hydrogen atoms have
been omitted for clarity. The two halves of the molecule are symmetry
˚
related by an inversion centre. Selected bond lengths (A) and angles (ꢁ)
with estimated standard deviations: Zn(1)–C(21) 1.968(2), Zn(1)–O(10)
2.0595(12), Zn(1)–N(11) 2.0776(15), Zn(1)–O(1) 2.0858(13), C(21)–Zn(1)–
O(10) 127.41(8), C(21)–Zn(1)–N(11) 123.38(8), O(10)–Zn(1)–N(11)
96.58(6), C(21)–Zn(1)–O(1) 121.56(7), O(10)–Zn(1)–O(1) 78.00(5), N(11)–
Zn(1)–O(1) 98.65(6).
Compound 5 is closely related to Darensbourg’s
[Zn(OAr)2(THF)]2 (Ar = 2,6-F2C6H3) [7a] which, how-
ever, contains tetrahedral zinc binding to only one THF

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Y. Sarazin et al. / Journal of Organometallic Chemistry 693 (2008) 1494–1501
Table 1
40–60 ꢁC) or calcium hydride (dichloromethane). NMR
Comparison of geometric parameters of binuclear zinc complexes
˚
solvents were dried over activated 4 A molecular sieves
Compound
E–Zn–E angle Zn–E–Zn
Znꢀ ꢀ ꢀZn
˚
and degassed by several freeze-thaw cycles. NMR spectra
were recorded using a Bruker Avance DPX-300 spectrom-
eter. Chemical shifts are reported in ppm. 1H NMR spectra
(300.13 MHz) are referenced to the residual protons of the
deuterated solvent used. 13C{1H} NMR spectra (75.47
MHz) were referenced internally to the D-coupled 13C res-
onances of the NMR solvent. 19F (282.38 MHz) NMR
spectra were referenced externally to CFCl3. Hexamethyl-
benzene was purchased from Aldrich (99%) and sublimed
under dynamic vacuum prior to use. Compounds EtZnCl
[10], Zn[N(SiMe3)2]2 [13] and Zn(C6F5)2 Æ C6H7 [11] were
prepared according to the literature methods.
(ꢁ)
(ꢁ)
distance (A)
1, E = Cl
2, E = N
91.97(3)
92.34(9),
91.91(9)
Two at
88.03(3)
87.62(9)
3.2481(8)
2.9026(5)
3, E = N
86.09(8)
2.7930(6)
3.2216(4)
94.00(8)
78.00(5)
76.01(10)
4, E = O
5, E = O
[Zn(OC6H3F2)2(THF)]2 80.07(19)
102.00(5)
103.99(10) 3.2409(9)
99.93(19) 3.0497(16)
ligand. By contrast, a number of other bis-THF adducts of
zinc aryloxides proved to be tetrahedral monomers,
Zn(OAr)2(THF)2 [7b]. Evidently the pentafluorophenyl
substituents in 5 lead to a sufficient increase in the Lewis
acidity of the metal to favour the higher coordination num-
ber. In line with this, the bond lengths to the THF and ter-
minal aryloxide ligands in 5 are slightly longer than in
[Zn(OC6H3F2-2,6)2(THF)]2.
In spite of the structural similarities of the compounds
described here, closer inspection shows that they fall into
two categories: those with E–Zn–E angles <80ꢁ, and those
with >90ꢁ (where E is the bridging atom). Table 1 summa-
rises a number of pertinent geometric features. The results
show that the nature of the bridging ligand influences the
structure of the Zn2E2 core more than the coordination
number of the metal centres. The non-bonding Zn–Zn dis-
tances show significant variation, even if the bridging
atoms are identical (e.g. see 2 and 3).
4.2. Synthesis of ZnBu2t
ZnBut2 was prepared by modification of a method avail-
able in the literature [14]. A solution of ButLi in pentane
(85 mL, 1.76 M, 149.6 mmol) was added at 0 ꢁC over a per-
iod of 1 h to a solution of ZnCl2 (10.2 g, 74.8 mmol) in
diethyl ether (200 mL). After the addition was complete,
the reaction mixture was allowed to warm slowly to room
temperature and stirring was then continued for another
hour. The precipitate of LiCl was removed by filtration
through Celite, and the solvent was removed at room tem-
perature under vacuum to yield a yellow viscous material.
ZnBut2 was obtained from this oil as colourless crystals
by careful sublimation under partial vacuum at room tem-
perature, by using two traps connected in series (the first in
an acetone/dry ice bath, and the second in a liquid nitrogen
bath). Yield 7.1 g, 53%.
3. Conclusions
4.3. Synthesis of [ButZnN(SiMe3)2]2 (2)
Mixed-ligand zinc complexes of the type [Zn(X)(Y)]2 are
readily accessible by a variety of routes. Only highly Lewis
acidic compounds like [ZnCl(C6F5)]2 and Zn(C6F5)2 show
a pronounced tendency to form stable complexes with such
weak donors as arenes. Amido-bridged species are three-
coordinate, whereas the more open aryloxo-bridged com-
plexes adopt tetrahedral or trigonal-bipyramidal geometry,
depending on the electron-withdrawing character of the
aryl substituents, and readily bind donors like THF or
puridine. All contain planar Zn2E2 cores; however, these
fall into two geometric categories; those with E–Zn–E
angles >90ꢁ (E = Cl, N) and those with E–Zn–E 680ꢁ
(E = O).
Solid Zn[N(SiMe3)2] (2.3 g, 5.9 mmol) was added at
room temperature to a colourless solution of ZnBu2t
(1.0 g, 5.6 mmol) in light petroleum (40 mL), and the
resulting solution was stirred overnight. The volatiles were
then pumped off to yield a white powder which was dried in
vacuo to constant weight. The target compound was
obtained free of any residual Zn[N(SiMe3)2] by recrystalli-
sation from a concentrated light petroleum solution
(5.0 mL) stored overnight at 4 ꢁC. X-ray quality crystals
of 2 were obtained in high yield (2.8 g, 10.0 mmol, 89%)
as colourless plates. The structure of the compound was
determined by X-ray diffraction. 1H NMR (CD2Cl2,
300.13 MHz, 25 ꢁC): d 1.15 (s, 9H, CMe3), 0.09 (s, 18H,
SiMe3). 13C{1H} NMR (CD2Cl2, 75.47 MHz, 25 ꢁC): d
31.2 (C(CH3)3), 26.3 (C(CH3)3), 4.8 (SiMe3). Anal. Calc.
for C10H27NSi2Zn: C, 42.46; H, 9.62; N, 4.95. Found: C,
42.28; H, 9.78; N, 4.79%.
4. Experimental
4.1. General procedures
All manipulations were performed under argon using
standard Schlenk techniques. Solvents were pre-dried,
and distilled under inert atmosphere over sodium (low-sul-
phur toluene), sodium–benzophenone (diethyl ether,
THF), sodium–potassium alloy (light petroleum, b.p.
4.4. Synthesis of [(C6F5)ZnN(SiMe3)2]2 (3)
Zn[N(SiMe3)2] (0.5 g, 1.3 mmol) was added at room tem-
perature to a solution of Zn(C6F5)2 Æ C6H7 (0.6 g, 1.2 mmol)

Y. Sarazin et al. / Journal of Organometallic Chemistry 693 (2008) 1494–1501
1499
in toluene (15 mL). Small amounts of a white precipitate
formed within minutes. Stirring was continued at room tem-
perature overnight, which resulted in the precipitation of a
large amount of white solid which was filtered off, washed
with light petroleum (3 · 5 mL) and dried under vacuum.
Single-crystals of 3 suitable for X-ray crystallography were
isolated as colourless rods by recrystallisation from a con-
centrated toluene solution (10 mL) kept overnight at
ꢁ26 ꢁC, yield 0.8 g, (2.0 mmol, 83%). Analytical data were
300.13 MHz, 25 ꢁC): d 0.42 (s, 18H, Me). 13C{1H} NMR
(CD2Cl2, 75.47 MHz, 25 ꢁC): d 150.7, 148.0, 143.1, 139.8,
138.7, 135.4 (all aryl-C6F5), 5.8 (SiMe3). 19F NMR (CD2Cl2,
282.40 MHz, 25 ꢁC): d –114.2 (m, 2F, o-F), –155.2 (t, 1F,
JFF = 19.8 Hz, p-F), ꢁ162.3 (m, 2F, m-F). Anal. Calc. for
C12H18F5NSi2Zn: C, 36.69; H, 4.62; N, 3.57. Found: C,
36.55; H, 4.47; N, 3.42%.
N(SiMe3)2}]2 Æ C7H8 (3 Æ C7H8) were collected in the cold
nitrogen stream on an Oxford Diffraction Xcalibur Sap-
phire 3 diffractometer equipped with a Spellman DF3
molybdenum sealed-tube source operating at ꢁ50 kV,
and fitted with Enhance X-ray optics. Crystals were coated
in perfluorinated polyether oil, mounted on a glass fibre
and fixed in the cold nitrogen stream. Data were collected
at 140(2) K. Data collection and reduction was carried out
using CrysAlis CCD and RED [15]. The structures were
determined by direct methods using SIR92 [16] and refined
on F2 using SHELXL [17].
The data collection for [EtZn(l-OC6F5)(C5H5N)]2 (4)
was performed on in the cold nitrogen strem of an
Enraf–Nonius Kappa CCD area detector diffractometer
equipped with 10 cm confocal mirrors (Mo Ka radiation).
The crystal was handled as for 1–3. Data collection was
carried out using the COLLECT package; data reduction were
carried out using the software packages DENZO and SCALE-
PACK [17]. The structure was solved using SHELXS [17] and
refined on F2 using SHELXL [17].
1
collected solid after drying in vacuo. H NMR (CD2Cl2,
4.5. Synthesis of [EtZn(OC6F5)(C5H5N)]2 (4)
A solution of pentafluorophenol (210 mg, 1.14 mmol) in
hexane (3 mL) was added to a hexane solution of diethyl zinc
(1.1 mmol) containing pyridine (0.17 mL, 2.2 mmol). The
mixture was stirred for 1 h at 20 ꢁC. Removal of volatiles left
a solid which was recrystallised from toluene at ꢁ37 ꢁC to
For the data collection of (5), from a sample under oil a
fragment was cut from a large crystal, mounted on a glass
fibre, fixed in the cold nitrogen stream and mounted on a
Rigaku R-Axis II image plate diffractometer equipped with
a rotating anode X-ray source (Mo Ka radiation) and
graphite monochromator. Using 4ꢁ oscillations, 48 expo-
sures of 30 min. each were made. Data were processed
using the DENZO and SCALEPACK [18] programs. The struc-
ture was determined by the direct methods routines in the
XS program [19] and refined by full-matrix least-squares
methods, on F2 in SHELXL [17]. Scattering factors for neu-
tral atoms were taken from reference [20].
1
afford colourless crystals (0.28 g, 72%). H NMR (CDCl3,
300.13 MHz, 25 ꢁC): d 8.66 (4H, dd, J = 4.8 Hz, 1.6 Hz);
7.96 (2H, dd, J = 7.6 Hz, 1.6 Hz); 7.55 (ddd, J = 7.6 Hz,
4.8 Hz, 1.3 Hz); 1.25 (6H, t, J = 8 Hz); 0.42 (4H, q,
J = 8 Hz). 19F NMR (CDCl3,282 MHz): ꢁ163.76 (4F, br
s), ꢁ167.27 (2F, t, J = 20.6 Hz), ꢁ177.04 (4F, br s). Anal.
Calc. for C26H20F10N2O2Zn2: C, 43.79, H, 2.83; N, 3.93.
Found: C, 43.78; H, 2.76; N, 3.92%.
In all cases non-hydrogen atoms were refined with
anisotropic thermal parameters. Hydrogen atoms were
included in idealised positions and their Uiso values were
set to ride on the Ueq values of the parent carbon atoms.
Crystal data for 1 Æ CH2Cl2: [ZnCl(C6F5)(C6Me6)]2 Æ
CH2Cl2, C36H36Cl2F10Zn2 Æ CH2Cl2, colourless plate of
dimensions 0.20 · 0.10 · 0.04 mm, formula weight 945.21,
4.6. Synthesis of [Zn(OC6F5)2(THF)2]2 (5)
Method A: A solution of ZnMe2 (2.0 M in petroleum,
3.11 mL, 6.22 mmol) was added to a solution of C6F5OH
(2.29 g, 12.44 mmol) in petroleum (100 mL). A very gelati-
nous precipitate formed immediately.
Method B: C6F5OH (0.45 g, 2.44 mmol) in toluene
(20 mL) was added to a solution of Zn(C6F5)2 Æ toluene
(1.20 g, 2.44 mmol) in toluene (50 mL). At the end of addi-
tion, a white micro-crystalline precipitate began to form.
19F (CD2Cl2): ꢁ170.06 (tt, 1F, J = 5.2 Hz, 21.7 Hz),
ꢁ162.24 (ꢂt, 2F, J = 21.7 Hz), ꢁ164.27 (ꢂdd, 2F, 5.2
Hz, 17.5 Hz).
Recrystallisation from tetrahydrofuran at 5 ꢁC afforded
colourless crystals of 5 (2.0 g, 60%) from which crystals
were selected for X-ray diffraction. Anal. Calc. for
C40H32F20O8Zn2: C, 41.73; H, 2.80. Found: C, 40.85; H,
2.40%.
ꢀ
triclinic, space group P1, lattice constants a = 9.5738(10)
˚
˚
˚
A, b = 9.9797(10) A, c = 10.7795(10) A, a = 93.751(8)ꢁ,
3
˚
b = 90.247(8)ꢁ, c = 113.233(10)ꢁ, V = 943.86(18) A , Z =
1, l(Mo Ka) = 1.631 mmꢁ1, h range 4.13–27.50ꢁ; 4305
independent reflections collected (Rint = 0.0440) of which
3159 were considered observed (I > 2r(I)). Final R-factors
were R1 = 0.041 (I > 2r(I)) wR2 = 0.080 (all data).
Crystal data for 2: [ButZn{l-N(SiMe3)2}]2, C20H54-
N2Si4Zn2, colourless plate 0.60 · 0.20 · 0.10 mm, formula
weight 565.75, orthorhombic, space group Pbca, lattice
˚
˚
constants a = 16.5540(12) A, b = 21.7318(17) A, c =
3
˚
˚
17.0151(15) A, V = 6121.2(8) A , Z = 8; l(Mo Ka) =
1.733 mmꢁ1, h range 3.56–27.74ꢁ; 7112 independent reflec-
tions collected (Rint = 0.1572) of which 4254 were consid-
4.7. X-ray crystallography
ered observed (I
>
2r(I)). Final R-factors were
R1 = 0.042 (I > 2r(I)) wR2 = 0.074 (all data).
The diffraction data for [ZnCl(C6F5)(C6Me6)]2 Æ CH2Cl2
(1 Æ CH2Cl2), [ButZn{l-N(SiMe3)2}]2 (2), and [C6F5Zn{l-
Crystal data for 3 Æ C7H8: [C6F5Zn{N(SiMe3)2}]2 Æ C7H8,
C24H36F10N2Si4Zn2 Æ C7H8, colourless rods, crystal size

1500
Y. Sarazin et al. / Journal of Organometallic Chemistry 693 (2008) 1494–1501
(e) M.H. Chisholm, N.W. Eilerts, J.C. Huffman, S.S. Iyer, M. Pacold,
K. Phomphrai, J. Am. Chem. Soc. 122 (2000) 11845;
(f) M.H. Chisholm, J. Gallucci, K. Phomphrai, Chem. Commun.
(2003) 48;
(g) M.H. Chisholm, C.-C. Lin, J.C. Gallucci, B.-T. Ko, Dalton
Trans. (2003) 406;
(h) M.H. Chisholm, J.C. Gallucci, K. Phomphrai, Inorg. Chem. 44
(2005) 8004;
(i) H.-Y. Chen, H.-Y. Tang, C.-C. Lin, Macromolecules 39 (2006)
3745;
0.40 · 0.07 · 0.05 mm, formula weight 877.78, triclinic,
ꢀ
˚
space group P1, lattice constants a = 10.9731(13) A, b =
˚
˚
12.5736(7) A, c = 16.422(3) A, a = 106.771(9)ꢁ, b =
3
˚
98.792(12)ꢁ, c = 112.112(9)ꢁ, V = 1920.5(5) A , Z = 2;
l(Mo Ka) = 1.447 mmꢁ1, h range 3.50–27.56ꢁ; 8732 inde-
pendent reflections collected (Rint = 0.0559) of which
5330 were considered observed (I > 2r(I)). Final R-factors
were R1 = 0.038 (I > 2r(I)) wR2 = 0.065 (all data).
Crystal data for 4: [EtZn(l-OC6F5)(C5H5N)]2, C26H20-
F10N2O2Zn2, colourless plates, crystal size 0.16 · 0.14 ·
(j) C.K. Williams, L.E. Breyfogle, S.K. Choi, W. Nam, V.G. Young,
M.A. Hillmyer, W.B. Tolman, J. Am. Chem. Soc. 125 (2003)
11350;
(k) C.K. Williams, N.R. Brooks, M.A. Hillmyer, W.B. Tolman,
Chem. Commun. (2002) 2132;
ꢀ
0.05 mm, formula weight 713.2, triclinic, space group P1,
˚
˚
lattice constants a = 7.5547(2) A, b = 9.5722(3) A, c =
˚
9.9370(3) A, a = 108.0070(10)ꢁ, b = 99.419(2)ꢁ, c =
(l) T.R. Jensen, L.E. Breyfogle, M.A. Hillmyer, W.B. Tolman, Chem.
Commun. (2004) 2504;
3
˚
96.476(2)ꢁ, V = 663.88(3) A , Z = 1; l(Mo Ka) = 1.906
mmꢁ1, h range 3.2–27.5ꢁ; 3029 independent reflections col-
lected (Rint = 0.038) of which 2825 were considered
observed (I > 2r(I)). Final R-factors were R1 = 0.027
(I > 2r(I)) wR2 = 0.059 (all data).
(m) B. Lian, C.M. Thomas, O.L. Casagrande Jr., C.W. Lehmann, T.
Roisnel, J.-F. Carpentier, Inorg. Chem. 46 (2007) 328.
[6] (a) S. Inoue, H. Koinuma, T. Tsuruta, J. Polym. Sci., Polym. Lett.
Ed. 7 (1969) 287;
(b) M. Cheng, E.B. Lobkovsky, G.W. Coates, J. Am. Chem. Soc. 120
(1998) 11018;
(c) M. Cheng, D.R. Moore, J.J. Reczek, B.M. Chamberlain, E.B.
Lobkovsky, G.W. Coates, J. Am. Chem. Soc. 123 (2001) 8738;
(d) D.R. Moore, M. Cheng, E.B. Lobkovsky, G.W. Coates, Angew.
Chem., Int. Ed. 41 (2002) 2599;
Crystal data for 5: [Zn(OC6F5)2(THF)2]2, C40H32F20-
O8Zn2, colourless blocks, crystal size 0.17 · 0.17 · 0.20,
ꢀ
formula weight = 1151.4, triclinic, space group P1, lattice
˚
˚
constants a = 9.865(1) A, b = 10.182(2) A, c = 10.935(1)
˚
A,
a = 88.78(1)ꢁ,
b = 83.74(1)ꢁ,
c = 80.21(1)ꢁ,V =
(e) D.R. Moore, M. Cheng, E.B. Lobkovsky, G.W. Coates, J. Am.
Chem. Soc. 125 (2003) 11911;
1075.9(3) A . Z = 1, l (Mo Ka) = 1.25 mmꢁ1, h range
3
˚
1.9–25.4ꢁ, 3648 independent reflections collected (Rint
0.100) of which 3083 were considered observed (I
2r(I)). Final R-factors were R1 = 0.056 (I > 2r(I)) wR2 =
=
>
(f) C.M. Byrne, S.D. Allen, E.B. Lobkovsky, G.W. Coates, J. Am.
Chem. Soc. 126 (2004) 11404;
(g) M.H. Chisholm, J.C. Gallucci, H. Zhen, J.C. Huffman, Inorg.
Chem. 40 (2001) 5051;
(h) R. Eberhardt, M. Allmendinger, G.A. Luinstra, B. Rieger,
Organometallics 22 (2003) 211.
0.140 (all data).
Acknowledgement
[7] (a) D.J. Darensbourg, J.R. Wildeson, J.C. Yarbrough, J.H. Reibens-
pies, J. Am. Chem. Soc. 122 (2000) 12487;
(b) D.J. Darensbourg, M.W. Holtcamp, G.E. Struck, M.S. Zimmer,
S.A. Niezgoda, P. Rainey, J.B. Robertson, J.D. Draper, J.H.
Reibenspies, J. Am. Chem. Soc. 121 (1999) 107;
(c) D.J. Darensbourg, J.R. Wildeson, J.C. Yarbrough, Organometal-
lics 20 (2001) 4413;
This work was supported by the Engineering and Phys-
ical Sciences Research Council. DAJH thanks Lanxess
Inc., Canada, for a fellowship.
(d) D.J. Darensbourg, M.W. Holtcamp, Macromolecules 28 (1995)
7577.
Appendix A. Supplementary material
[8] (a) M.D. Hannant, M. Schormann, M. Bochmann, J. Chem. Soc.,
Dalton Trans. (2002) 4071;
CCDC 658162, 658163, 658164, 658160 and 658161 con-
tain the supplementary crystallographic data for
1 Æ CH2Cl2, 2, 3, 4 and 5. These data can be obtained free
of charge from The Cambridge Crystallographic Data Cen-
tre via www.ccdc.cam.ac.uk/data_request/cif, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-
mail: deposit@ccdc.cam.ac.uk.
(b) M.D. Hannant, M. Schormann, D.L. Hughes, M. Bochmann,
Inorg. Chim. Acta 358 (2005) 1683;
(c) R.H. Howard, M. Bochmann, J.A. Wright, Acta Crystallogr. C
26 (2006) m293;
(d) D.A. Walker, T.J. Woodman, M. Schormann, D.L. Hughes, M.
Bochmann, Organometallics 22 (2003) 797;
(e) Y. Sarazin, M. Schormann, M. Bochmann, Organometallics 23
(2004) 3296;
(f) Y. Sarazin, R.H. Howard, D.L. Hughes, S.M. Humphrey, M.
Bochmann, Dalton Trans. (2006) 340.
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