Synthesis and characterization of cobaloxime dendrimer precursors

Article abstract of DOI:10.1016/j.ica.2004.01.043

Reactions of bromobutyl or bromohexyl cobaloxime complexes with 3,5-dihydroxybenzyl alcohol in the presence of potassium carbonate gave, in both cases, mono- and di-cobalt complexes. These complexes were characterized largely by their NMR spectra. In addition, a new dimeric alkylcobaloxime complex was formed in these reactions by HBr elimination from the bromoalkyl complexes. This dimer was fully characterized and its X-ray crystal structure was determined. A zero generation dendrimer containing three cobaloxime groups was obtained by reaction of the bromobutyl cobaloxime with the core molecule 1,1,1-tris(4-hydroxyphenyl)ethane.

Full text of DOI:10.1016/j.ica.2004.01.043

Inorganica Chimica Acta 357 (2004) 2748–2754
www.elsevier.com/locate/ica
Note
Synthesis and characterization of cobaloxime dendrimer precursors
a,b,
a
a,
a
Ipe J. Mavunkal
*, Meredith A. Hearshaw , John R. Moss *, John Bacsa
a
Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
Department of Chemistry, University of Botswana, P. Bag 0704, Gaborone, Botswana
b
Received 9 July 2001; accepted 28 January 2004
Available online 6 May 2004
Abstract
Reactions of bromobutyl or bromohexyl cobaloxime complexes with 3,5-dihydroxybenzyl alcohol in the presence of potassium
carbonate gave, in both cases, mono- and di-cobalt complexes. These complexes were characterized largely by their NMR spectra.
In addition, a new dimeric alkylcobaloxime complex was formed in these reactions by HBr elimination from the bromoalkyl
complexes. This dimer was fully characterized and its X-ray crystal structure was determined. A zero generation dendrimer con-
taining three cobaloxime groups was obtained by reaction of the bromobutyl cobaloxime with the core molecule 1,1,1-tris(4-hy-
droxyphenyl)ethane.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Cobaloxime complexes; Dendrimer; Dimer
1. Introduction
Our research laboratory has focussed on the synthesis
of dendrimers containing metal carbon r-bonds. We have
successfully built up dendrimers containing Fe, Ru and
Re functionalities at the periphery of the dendrimer
[12,13]. Our aim was to try and extend this work to cobalt
and build a first-generation dendrimer with cobaloxime
units at the surface that might have potential in catalysis.
One current aspect of dendrimer synthesis focuses on
the preparation of dendrimers with specific functions [1].
Various organometallic dendrimers with functional
groups at the periphery [2], the core [3] or throughout
the dendritic structure have been reported [4]. Increasing
the number of functional centres, particularly metal
centres, in a dendrimer is expected to alter the properties
of the dendrimer significantly. There is a good literature
precedent for the use of cobaloximes as Vitamin B12
model compounds [5]. Cobaloximes have potential uses
as catalysts in organic reactions, for example as metal-
intermediates in intramolecular radical processes which
could lead to the synthesis of complex carbocyclic
frameworks [6]. Cobalt containing organometallic den-
drimers have been reported with various cobalt units
occupying different positions in the dendritic scaffold
[7–10]. Some of these complexes are reported to be po-
tential precursors to the formation of metal oxide nan-
ospheres [11].
2. Experimental
All reactions were carried out under nitrogen using
standard Schlenk techniques.
Solvents were dried by standard methods and distilled
under nitrogen before use. 3,5-Dihydroxybenzyl alcohol
was prepared by literature methods [14] and also pur-
chased from Sigma–Aldrich. Potassium carbonate was
dried at 100 °C before use. Silica gel (Merck, 60) was
used for column chromatography. All other reagents
were obtained commercially, unless otherwise stated.
The bromoalkyl cobaloxime complexes [Co(DH)2py
(CH2)nBr] (DH ¼ monoanion of dimethylglyoxime,
py ¼ pyridine) (n ¼ 4; 6) were synthesized according to
literature procedures [15] and characterized by m.p., IR
* Corresponding authors.
E-mail addresses: mavunkal@mopipi.ub.bw (I.J. Mavunkal),
jrm@science.uct.ac.za (J.R. Moss).
1
and H NMR spectroscopy. The reaction vessels were
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.01.043

I.J. Mavunkal et al. / Inorganica Chimica Acta 357 (2004) 2748–2754
2749
covered with aluminium foil to protect the compounds
from light.
CH2OH), 3.77 (br, 2H, CH2O), 2.10 (s, 12H, DH), 1.6
(m, CH2), dCfHg(100 MHz, CDCl3) 157.77, 149.89,
139.10, 106.33, 101.59 (Ar), 149.29 (C@N, DH), 149.91,
137.42, 125.13 (py), 67.81 (CH2OAr), 65.22 (ArCH2),
29.98, 26.33, 26.10 (CH2), 11.98 (CH3), m/z (FAB) 561
(Mþ ) 3H).
Elemental analyses were obtained from the Micro-
analytical Laboratory at the University of Cape Town.
Infrared spectra were recorded on a Perkin–Elmer Par-
agon 1000 FT-IR spectrometer as hexane or CH2Cl2
1
solutions. H and 13C NMR spectra were recorded on
either a Varian Unity-400 or a Varian VXR-200 NMR
spectrometer in CDCl3 solutions at ambient tempera-
ture. The chemical shifts are reported relative to TMS
(d 0:00). Low resolution electron mass spectra were
recorded on a Kratos MS 80 RFA spectrometer, oper-
ating at 70 eV ionizing voltage and the electrospray mass
spectra were run on a Finnigan LCQ DECA mass
spectrometer.
2.2. Synthesis of compounds 4 and 6
A mixture of the bromohexyl cobaloxime 2 (1.00 g,
1.88 mmol), 3,5-dihydroxybenzylalcohol (0.13 g, 0.94
mmol), potassium carbonate (0.78 g, 5.64 mmol), 18-
crown-6 (0.10 g, 0.38 mmol) and dry acetone (20 ml) was
heated under reflux and stirred vigorously for 96 h. The
products 4 and 6 were isolated using a similar procedure
to that described above. Compound 4: Recrystallized
from CH2Cl2/hexane to give 4 as a crystalline yellow/
orange solid at )15 °C (Yield 0.43 g, 45%). Melting
point 180 °C (dec). Anal. Calc. C45H68N10O11Co2: C,
51.8; H, 6.6. Found C, 50.9; H, 7.2%. dH(200 MHz,
CDCl3) 18.08 (br s, 4H, OH. . .O, DH), 8.58 (d, J(CH) 5
Hz, 4H, o-H, py), 7.66 (t, J(CH) 6 Hz, 2H, p-H, py), 7.22
(t, J(CH) 4 Hz, 4H, m-H, py), 6.48 (m, 2H, ArH), 6.30
(d, J(CH) 2 Hz, 1H, ArH), 4.58 (d, J(CH) 12 Hz, 2H,
CH2OH), 3.83 (t, J(CH) 7 Hz, 4H, CH2O), 2.10 (s, 24H,
CH3, DH) 1.61(q, J(CH) 8 Hz, 4H, CH2), 1.52 (m, 4H,
CoCH2,) 1.24, (m, 8H, CH2), 0.86 (m, 4H, CoCH2CH2);
dCfHg(50 MHz, CDCl3) 160.46, 143.37, 105.13, 101.11
(Ar), 149.13 (C@N, DH), 149.96, 137.34, 125.10 (py),
70.21 (CH2OAr), 65.32 (ArCH2), 31.88, 32.71, 30.44,
29.64, 28.60 (CH2), 11.96 (CH3;DH); m/z (FAB) 1042
(Mþ ) H).
Compound 6: (Yield 0.30 g, 27%); dH(200 MHz,
CDCl3) 18.08 (br, 2H, OHꢀ ꢀ ꢀO, DH), 8.58 (d, J(CH) 5
Hz, 2H, o-H, py), 7.66 (t, J(CH) 6 Hz, 1H, p-H, py), 7.22
(t, J(CH) 4 Hz, 2H, m-H, py), 6.46 (s, 1H, ArH), 6.37 (s,
1H, ArH), 6.31 (s, 1H, ArH), 4.58 (d, J ¼ 12 Hz, 2H,
CH2OH), 3.83 (t, J(CH) 7 Hz, 2H, CH2O), 2.10 (s, 12H,
CH3, DH), 1.52 (m, 2H, CoCH2,) 1.21, (m, 8H, CH2);
dCfHg(50 MHz, CDCl3) 158.12, 151.06, 143.37, 106.35,
100.63 (Ar), 149.36 (C@N, DH), 149.96, 137.26, 125.10
(py), 68.08 (CH2OAr), 65.32 (ArCH2), 31.68, 30.13,
29.80, 29.26, 25.33 (CH2), 12.53 (CH3); m/z (FAB) 580
(Mþ + 3H).
2.1. Synthesis of compounds 3 and 5
A mixture of the bromobutyl cobaloxime 1 (1.00 g,
1.98 mmol), 3,5-dihydroxybenzylalcohol (0.14 g, 0.99
mmol), potassium carbonate (0.82 g, 5.94 mmol), 18-
crown-6 (0.11 g, 0.40 mmol) and dry acetone (20 ml) was
heated under reflux and stirred vigorously for 96 h. The
reaction was monitored by TLC eluting with ethyl ace-
tate. Two new spots for the ‘‘di-substituted’’ 3 and
‘‘mono-substituted’’ 5 benzyl alcohols were observed.
The solvent was removed in vacuo to give a brownish
residue that was extracted with ethyl acetate and filtered.
The filtrate was concentrated and purified by column
chromatography on silica gel. The polarity of the eluting
solvent was gradually increased from 30% ethyl acetate/
hexane to pure ethyl acetate. Unreacted starting mate-
rial was eluted first followed by the ‘‘mono-substituted’’
benzyl alcohol 5 with ethyl acetate. The ‘‘di-substituted’’
product 3 was eluted with acetone. The yellow/orange
bands were collected and the solvent removed in vacuo
to give yellow/orange solids. An additional product, a
cobaloxime dimer 7, contaminated the benzyl alcohols
and hindered the isolation of the products in pure form.
Compound 3: (Yield 0.39 g, 40%). Melting point 113–
115 °C, dH(400 MHz, CDCl3) 8.54 (d, J(CH) 5 Hz, 4H,
o-H, py), 7.67 (m, 2H, p-H, py), 7.28 (t, J(CH) 6 Hz, 4H,
m-H, py), 6.41 (m, 2H, ArH), 6.24 (br, 1H, ArH), 4.56
(s, 2H, CH2OH), 3.82 (t, J(CH) 6 Hz, 4H, CH2O), 2.08
(s, 24H, CH3, DH), 1.60 (t, J(CH) 7 Hz, 12H,
CoCH2 + CH2), 1.01 (q, 4H, CoCH2CH2), dCfHg(100
MHz, CDCl3) 160.41, 143.20, 105.13, 100.11 (Ar),
149.22 (C@N, DH), 149.86, 137.37, 125.09 (py), 67.68
(CH2OAr), 65.25 (ArCH2), 30.76, 30.10, 26.67 (CH2),
11.95 (CH3, DH).
2.3. Synthesis of compound 7
A mixture of bromobutyl cobaloxime 1 (1.00 g, 1.98
mmol), K2CO3 (0.82 g, 5.94 mmol), 18-crown-6 (0.05 g,
0.20 mmol) and acetone (15 ml) was heated under reflux
and stirred vigorously for 48 h. The solvent was re-
moved after cooling the reaction mixture and purified by
column chromatography. Unreacted 1 was eluted with
30% ethyl acetate in hexane and the reddish band that
tailed on the column was eluted with pure ethyl acetate.
The solvent was removed under reduced pressure to
Compound 5: (Yield 0.28 g, 25%). Anal. Calc.
C24H34N5O7Co: C, 51.1; H, 6.1; N, 12.4. Found: C,
50.0; H, 6.1; N, 12.4%. Melting point 87–90 °C, dH(200
MHz, CDCl3) 8.53 (d, J(CH) 2 Hz, 2H, o-H, py), 7.69 (t,
J(CH) 8 Hz, 1H, p-H, py), 7.26 (t, J(CH) 7 Hz, 2H, m-
H, py), 6.44, 6.34, 6.25 (s, 3H, ArH), 4.52 (s, 2H,

2750
I.J. Mavunkal et al. / Inorganica Chimica Acta 357 (2004) 2748–2754
yield a dark reddish powder. The solid was further pu-
rified by recrystallization from CH2Cl2/hexane at )4 °C.
(Yield 0.375 g, 55%); m.p 192–194 °C (dec); Anal. Calc.
C24H42N8O8Co2 ꢀ 1/2CH2Cl2: C, 40.28; H, 5.93; N,
15.34. Found: C, 40.20; H, 5.84; N, 14.89%. dH(400
MHz, CDCl3) 4.91 (m, 2H, CH2), 3.69 (m, 2H, CH2),
2.35 (s, 3H, CH3), 2.21 (s, 3H, CH3), 2.19 (m, 2H, CH2),
2.05 (s, 3H, CH3), 1.84 (s, 3H, CH3), 1.60 (m, 2H, CH2),
1.56 (m, 2H, CH2), 1.42 (m, 2H, CH2), 0.47 (m, 4H,
CH2); dCfHg(100 MHz, CDCl3), 160.16 (C@N), 158.85
(C@N), 150.97 (C@N), 150.22 (C@N), 71.62 (CH2O),
29.90 (CH2), 29.41 (CH2), 20.17 (CH2), 14.27 (CH3),
13.12 (CH3), 13.04 (CH3), 12.85 (CH3); m/z (ES): 688
[Mþ], 572 [Mþ ) DH], 344.9 [Mþ ) 1/2M]. Depending
upon the solvent, used peaks at different m/z values
higher than the expected molecular ion peak were ob-
served in the mass spectra. We believe that the cob-
aloxime dimer upon ionization in the mass spectrometer
interacts with solvent molecules giving rise to the higher
mass peaks observed in the different mass spectral ex-
periment carried out.
sure times of 17 s per frame and scan widths of 1° were
used throughout the data collection. Three sets of data
were collected: a 180° phi scan and several omega scans.
The frames that were measured contained 32 480
reflections.
The four sets of data were scaled and reduced using
Denzo-SMN [17]. Unit cell dimensions were refined on
all data. The space group F 222 was chosen for merging
data and Friedel pairs were kept separate [crystal mo-
saicity ¼ 0.38(1); number of reflections ¼ 32 480 (before
merging), 4618 (after merging)]. The unique space group
Fdd2 was chosen on the basis of systematic absences.
This space group is polar and there are two possible
enantiomers. The structure that yielded a Flack pa-
rameter close to zero was chosen. A semi-empirical ab-
sorption correction was applied using the program
PLATON. The structure was solved and refined using
SHELXL97 [18]. Hydrogen atoms, except those belong-
ing to atoms O2 and O6, were placed in calculated po-
sitions and included in the model during later stages of
the refinement. Hydrogen atoms H2 and H6 were lo-
cated from difference maps and allowed to refine. Plots
of the molecular structure were obtained with ORTEP
[19] and PLATON [20].
2.4. Synthesis of compound 8
A mixture of 1 (0.50 g, 0.99 mmol), K2CO3 (0.41 g,
2.97 mmol), 18-crown-6 (0.05 g, 0.20 mmol), 1,1,1-tris(4-
hydroxyphenyl) ethane (1.05 g, 0.3 mmol) and dry ace-
tone (20 ml) was refluxed under nitrogen for 48 h. The
reaction was monitored by TLC eluting with a 40% ethyl
acetate/acetone mixture. The crude product was chro-
matographed on silica eluting with ethyl acetate/acetone
(70:30) and the solvent removed to give 8 as a yellow/
orange solid (Yield 0.11 g, 20%), m.p. >110 °C (dec);
dH(200 MHz, CDCl3) 8.53 (d, J(CH) 2 Hz, 6H, oH, py),
7.69 (t, J(CH) 8 Hz, 3H, pH, py), 7.26 (t, J(CH) 7 Hz,
6H, mH, py), 6.94 (d, J(CH) 9 Hz, 6H, Ar), 6.70 (d,
J(CH) 9 Hz, 6H, ArH), 3.84 (t, J(CH) 7 Hz, 6H, CH2O),
2.10 (s, 12H, CH3, DMGO), 1.54 (m, 12H,
CoCH2 + CH2), 1.05 (m, 6H, CoCH2CH2); dCfHg(100
MHz, CDCl3) 158.36, 137.25, 129.42, 113.64 (Ar),
149.10 (C@N, DH), 149.92, 137.13, 125.02 (py), 67.97
(CH2OAr), 31.16 (CH3), 30.48, 27.23, 23.03 (CH2),
12.53 (CH3, DH); m/z (ES) 1577 (M)þ.
3. Results and discussion
3.1. Preparation of the cobaloxime complexes
The convergent approach, as described previously
[11], was used to build up the cobaloxime dendritic
wedges. Scheme 1 shows the synthesis of the ‘‘di-
substituted’’ and ‘‘mono-substituted’’ dendritic wedges.
Thus, the bromoalkyl complex 1 or 2 was heated
under reflux with 3,5-dihydroxybenzyl alcohol in ace-
tone for 96 h in the presence of 18-crown-6 and potas-
sium carbonate (Scheme 1). (Iodoalkyl analogues of 1
and 2 can also be used). TLC was used to monitor the
reactions. In both these cases, two main products were
obtained. The major product was identified as the ‘‘di-
substituted’’ benzyl alcohols, 3 and 4, respectively, by
1H NMR spectroscopy. The minor products were also
identified by 1H NMR spectroscopy as the ‘‘mono-
substituted’’ benzyl alcohols, 5 and 6. These ‘‘mono-
substituted’’ products form first as intermediates on
route to the ‘‘di-substituted’’ products. An additional
product, a cobaloxime dimer, e.g., 7 was also observed
to form in these reactions.
2.5. X-ray structure analyses for complex 7
A small crystal of 7 with well-formed faces and
roughly equal dimensions was selected for X-ray anal-
ysis. This crystal was coated with paratone oil and
mounted on a glass fibre. Data were collected at 171 K
on a Nonius Kappa CCD using 1.5 kW graphite
monochromated Mo radiation. The strategy for the data
collection was evaluated using the COLLECT Software
[16]. The diffraction patterns could be indexed using a
face-centred orthorhombic cell. The detector to crystal
distance during the data collection was 77 mm. Expo-
Column chromatography was used to separate and
purify the compounds. The products tended to tail on
silica; this made separation of the product from any
unreacted starting material difficult. The oily solids ob-
tained after column chromatography were crystallized
from CH2Cl2/hexane mixtures. The dark orange solids
were subsequently dried in vacuo.

I.J. Mavunkal et al. / Inorganica Chimica Acta 357 (2004) 2748–2754
2751
Scheme 1.
Bromination of the benzyl alcohols 3 and 4 was at-
tempted using two reagents: (i) CBr4/PPh3 and (ii) PBr3.
Decomposition was observed with both brominating
agents and the expected benzyl bromides could not be
isolated or fully characterized. As we were unable to
synthesize the cobaloxime benzyl bromides, we could
not use the convergent approach to prepare a first
generation dendrimer with six cobaloxime units at the
periphery of a dendrimer. We did, however, succeed in
synthesizing a zero generation dendrimer 8 with three
cobaloxime units at the periphery in a single step which
is effectively a divergent approach. However, compound
8 cannot be expanded further using a sequential diver-
gent strategy. Thus, the bromobutyl cobaloxime com-
plex 1 was reacted with a CORE molecule, 1,1,1-tris(4-
hydroxyphenyl)ethane, under reflux in acetone for 48 h.
The product was isolated as yellow orange solid in low
yield (20%) (Scheme 2). Previously, we made no dis-
tinction to differentiate the zero generation dendrimers
synthesized in our laboratory as they were forming part
of a series synthesized by a convergent approach.
3.2. The cobaloxime dimer 7
A cobaloxime dimer, e.g., 7 was formed during the
synthesis of the dendritic wedges 3–6. This dimer was
synthesized independently by refluxing the bromobutyl
cobaloxime compound in acetone with K2CO3 and
Scheme 2.

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I.J. Mavunkal et al. / Inorganica Chimica Acta 357 (2004) 2748–2754
18-crown-6. The product was characterized by analyti-
cal and spectroscopic methods (see experimental). The
presence of OH groups on the dimethylglyoximato li-
gand led to the formation of the cobaloxime dimer 7.
Thus, the base presumably deprotonates one of the OH
groups on the dimethylglyoximato ligands with sub-
sequent elimination of HBr and the formation of a new
carbon–oxygen bond. One of the oxygens of the dim-
ethylglyoximato ligand replaces the pyridine from an-
other cobaloxime molecule forming a bridge between
the two metal atoms. The second bridge is presumably
formed in a similar way (see Fig. 1).
A similar intramolecular reaction was reported for a
rhodoxime complex but, in this case no dimeric com-
pounds were formed [21]. The presence of strong coor-
dinating ligand PPh3 on the rhodoxime may not favour
the formation of a dimer similar to that observed in the
cobaloxime case.
3.3. Description of the structure of 7
Fig. 2. ORTEP diagram of compound 7 with selected bond lengths and
bond angles. Co1–O5 2.067(6); Co1–N1 1.929(6); Co1–N2 1.896(6);
Co1–N3 1.946(6); Co1–N4 1.900(7); Co1–C12 2.012(8); N1–O1
1.335(7); N5–O5 1.354(8); N1–Co–O5 88.7(2) and O5–Co1–N3
90.6(2).
We have crystallized the dimer 7 and a single crystal
X-ray analysis was carried out to completely charac-
terize the product. The structure of 7 with atom labelling
is shown in Fig. 2 and details of the data collection and
structure refinement are listed in Table 1.
The Co atoms display a distorted octahedral co-or-
dination, with the two modified dimethylglyoximato li-
gands in the equatorial plane. One of the oxygen atoms
from the ligand serves to bridge to the other cobalt
atom. An additional 7-membered ring is formed be-
tween the butyl chain and one of the oxygen atoms from
the modified dimethylglyoximato ligand. The volume of
the unit cell is found to be very large containing 16
molecules. Also, solvated CH2Cl2 molecules are located
with each cobaloxime dimer; CH2Cl2 is also seen in the
1H NMR and inferred from elemental analysis results.
gration, in the aromatic region (phenyl protons of the
1
benzyl group) of the H NMR spectra confirmed either
the ‘‘mono-substituted’’ (3 peaks) or ‘‘di-substituted’’
benzyl alcohol (2 peaks). The triplet at 3.82 ppm (as-
signed to the CH2OAr protons) confirms the formation
of the first generation benzyl alcohol.
In compound 3 the different environments of the
phenyl carbons can clearly be seen by the four aromatic
carbon peaks (160.41, 143.20, 105.13 and 100.11 ppm).
A peak at 67.68 ppm for the benzyl carbon confirms the
formation of the cobaloxime benzyl alcohol. Elemental
analysis on the new cobaloxime dendrimer precursors
was attempted, but the complexes were dried under high
vacuum for three to five hours, varying amounts of
solvent still remained included in the crystals and sat-
isfactory analyses could not be obtained in most cases.
3.4. Characterization
1H and 13C NMR spectroscopy were the main
methods used for characterization of the compounds
synthesized. The number of peaks, as well as the inte-
4. Conclusions
Several new cobaloxime dendrimer precursors have
been synthesized and characterized as fully as possible.
The butyl- and hexyl-cobaloxime benzyl alcohols, 3 and
4 were found to undergo considerable amount of de-
composition upon attempted activation with a CBr4/
PPh3 mixture or PBr3. Thus, our attempts to prepare the
first generation cobaloxime dendrimer were unsuccess-
ful, but we were able to synthese a zero generation
dendrimer, 8, by a divergent synthetic strategy. The X-
ray structure of a cobaloxime dimer 7 was determined.
Fig. 1. Line drawing representation of the cobaloxime dimer 7.

I.J. Mavunkal et al. / Inorganica Chimica Acta 357 (2004) 2748–2754
2753
Table 1
Crystal data and structure refinement for compound 7
Identification code
Empirical formula
Formula weight
Temperature (K)
compound 7
Co2C24H42N8 O8.1/2 (CH2Cl2)
729.97
173(2)
ꢁ
Wavelength (A)
0.71074
orthorhombic
Fdd2
Crystal system
Space group
Unit cell dimensions
ꢁ
a (A)
37.803(2)
40.574(3)
ꢁ
b (A)
ꢁ
c (A)
8.3540(7)
90
a (°)
b (°)
c (°)
90
90
3
ꢁ
Volume (A )
12813.5(19)
16
Z
Density (calculated) (Mg mꢁ3
Absorption coefficient (mmꢁ1
)
1.516
1.177
)
F ð000Þ
6096
0.33 ꢂ 0.30 ꢂ 0.23
3.86–27.47
Crystal size (mm3)
h range for data collection (°)
Index ranges
Reflections collected
ꢁ49 6 h 6 39, ꢁ52 6 k 6 29, ꢁ8 6 l 6 8
32 480
Independent reflections
Completeness to h ¼ 27.47° (%)
Reflections collected
4618 ½Rint ¼ 0:0278ꢃ
78.4
32 480
Independent reflections
Completeness to h ¼ 27.47° (%)
Maximum and minimum transmission
Refined method
4659 ½Rint ¼ 0:0277ꢃ
78.9
0.7736 and 0.6975
full-mixed least-squares on F2
4659/1/410
Data/restraints/parameters
Goodness-of-fit on F2
1.057
Final R indices ½I > 2rðIÞꢃ
R indices (all data)
R1 ¼ 0:0570, wR2 ¼ 0:1532
R1 ¼ 0:0669, wR2 ¼ 0:1615
)0.01(3)
0.00000(5)
2.767 and )0.500
Absolute structure parameter
Extinction coefficient
Largest difference peak and hole (e A
ꢁ3
ꢁ
)
[4] K. Onitsuka, M. Fujimoto, N. Oshiro, S. Takahashi, Angew.
Chem., Int. Ed. Eng. 111 (1999) 689.
5. Supplementary material
[5] G.N. Schrauzer, Angew. Chem., Int. Ed. Engl. 15 (1976) 417.
[6] I. Das, S. Chowdhury, K. Ravikumar, S. Roy, B.D. Gupta, J.
Organomet. Chem. 532 (1997) 101.
Atomic coordinates, thermal parameters, and bond
lengths and angles for compound 7 are available from
the authors.
€
[7] R. Moors, F. Vogtle, Chem. Ber. 126 (1993) 2133.
[8] E.C. Constable, O. Eich, C.E. Housecroft, L.A. Johnston, Chem.
Commun. (1998) 2661.
[9] D. Seyferth, T. Kugita, A.L. Rheingold, G.P.A. Yap, Organo-
metallics 14 (1995) 5362.
Acknowledgements
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