Synthesis and reactivity of transition metal complexes containing halogenated boryl ligands

Article abstract of DOI:10.1016/S0022-328X(01)01427-9

The synthesis and characterization of iron and manganese complexes containing the tetrachlorocatecholboryl (BO₂C₆Cl₄) ligand are reported. Crystallographic study of the methylcyclopentadienyl derivative and reveals that th

Full text of DOI:10.1016/S0022-328X(01)01427-9

Journal of Organometallic Chemistry 649 (2002) 9–14
www.elsevier.com/locate/jorganchem
Synthesis and reactivity of transition metal complexes containing
halogenated boryl ligands
S. Aldridge a,*, R.J. Calder a, R.E. Baghurst a, M.E. Light b, M.B. Hursthouse b
a Department of Chemistry, Cardiff Uni6ersity, PO Box 912, Park Place, Cardiff CF10 3TB, UK
b Department of Chemistry, Uni6ersity of Southampton, Highfield, Southampton SO17 1BJ, UK
Received 12 October 2001; accepted 2 November 2001
Abstract
The synthesis and characterization of iron and manganese complexes containing the tetrachlorocatecholboryl (BO2C6Cl4) ligand
are reported. Crystallographic study of the methylcyclopentadienyl derivative (h5-C5H4Me)Fe(CO)2BO2C6Cl4 allows comparison
of structure and bonding with related complexes of the type (h5-C5R5)Fe(CO)2B(OR)2 and reveals that the relative orientation of
(h5-C5H4Me)Fe(CO)2 and BO2C6Cl4 moieties is influenced by intramolecular CꢀH···O hydrogen bonding. Additionally, an
alternative route to catecholboryl complexes from dilithiocatechol is reported. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Boryl; Boron; Iron; Manganese; Hydrogen bond; Substitution
p-symmetry; to what extent the nature of the MꢀB
bond can be altered by variation in the electronic
properties of X has been the subject of several studies
[16,17]. Ultimately a better understanding of the nature
of the MꢀB bond may help to rationalize the unusual
reactivity of such complexes.
1. Introduction
Transition metal boryl complexes (LnMꢀBX2) have
been the subject of intense recent research activity
[1–4], partly because of their involvement in the hydro-
and diboration of carbonꢀcarbon multiple bonds [5],
but also because of their implication in highly selective
stoichiometric and catalytic functionalization of alkanes
under either photolytic or thermal conditions [6–14].
The reactivity of boryl complexes towards a variety of
substrates has therefore been investigated in some
depth [2,4], although the intrinsic reactivity of the metal
boron bond is such that substitution reactions at the
boron centre that occur with retention of the MꢀB bond
are rare [2,4,15]. Such studies of reactivity have been
complimented by numerous structural investigations in
which the nature of the metal boron bond has been
probed by crystallographic, spectroscopic and computa-
tional methods [1–4,16,17]. One of the significant ques-
tions investigated by such studies is the potential for the
extremely strongly s-donor boryl ligand also to act as a
p acid by utilizing the vacant boron-based orbital of
We have recently begun a research program aimed at
a better understanding of the relationship between the
structure and reactivity of boryl ligands, which has
encompassed the investigation of new types of ligand
[18] and new modes of coordination [19,20], together
with novel methods for probing the nature of the metal
boron bond [17]. One approach has been to investigate
the effect on structure and reactivity of variation in
electronic properties within the boryl ligand framework
(e.g. by introduction of halogen substituents). Com-
plexes containing the BF2 ligand [21], or containing
boryl ligands bearing perhalogenated aryl substituents
have only recently been reported [18,22], and although
complexes containing the BCl2 ligand have been synthe-
sised by Roper and Wright [2,15], no structural data are
as yet available. We have therefore sought to synthesise
iron and manganese complexes containing the
BO2C6Cl4 (BcatCl4) ligand, which might offer useful
comparison with derivatives containing the more widely
exploited BO2C6H4 (Bcat) fragment. In addition, we
have sought to investigate the utility of iron complexes
Abbre6iations: st, strong; md, medium; w, weak; sh, shoulder; s,
singlet; m, multiplet; b, broad.
* Corresponding author. Tel.: +44-29-20875495; fax: +44-29-
20874030.
E-mail address: aldridges@cardiff.ac.uk (S. Aldridge).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01427-9

10
S. Aldridge et al. / Journal of Organometallic Chemistry 649 (2002) 9–14
containing the BCl2 ligand in the synthesis of other
metal boryl complexes.
topic pattern in agreement with that expected for 1B,
4Cl, 1Fe atom. Anal. Calc. for C13H5BCl4FeO4: C,
36.00; H, 1.16. Found: C, 35.58; H, 1.23%. Complex 2%
was prepared in an analogous fashion and crystals
suitable for X-ray diffraction grown by controlled cool-
ing of concentrated C6H5CH3 solutions. Spectroscopic
2. Experimental
1
All manipulations were carried out under a nitrogen
or argon atmosphere using standard Schlenk line or dry
box techniques. Solvents were pre-dried over Na wire
(hexanes, C6H5CH3) or molecular sieves (CH2Cl2) and
purged with nitrogen prior to distillation. Hexanes (K),
C6H5CH3 (Na), and CH2Cl2 (CaH2) were then distilled
from the appropriate drying agent before use. C6D6
(Goss) was degassed and dried over K prior to use.
BCl3 (1 M solution in heptanes, Aldrich) and nBuLi (2.5
M solution in hexanes, Aldrich) were used as received,
without further purification. Catechol (Aldrich) and
tetrachlorocatechol (Lancaster) were dried and sub-
limed prior to use. Dilithiocatechol, perchlorocatechol-
borane (1), (h5-C5H4R)Fe(CO)2Na (R=H, Me) and
NaMn(CO)5 were prepared by minor modification of
literature methods [23–25]. NMR spectra were mea-
sured on a Bruker AM-400 or JEOL Eclipse 300 Plus
FT-NMR spectrometer. Residual protons of solvent
data for 2%: H-NMR (400 MHz, C6D6): l 1.39 (3H, s,
h5-C5H4CH3), 4.06 (2H, m, h5-C5H4CH3), 4.17 (2H, m,
h5-C5H4CH3). 13C-NMR (76 MHz, C6D6): l 12.6 (h5-
C5H4CH3) 82.3, 84.6 (Cp CH), 102.3 (Cp quaternary),
115.1, 125.7, 146.4 (BO2C6Cl4), 213.3 (CO). 11B-NMR
(96 MHz, C6D6): l 53.4. IR (KBr) (cm−1): 2004 st,
1945 st [w(CO)].
2.2. [(OC)5MnBO2C6Cl4] (3)
Complex 3 was prepared in a manner analogous to
that described in Section 2.1 for 2, using NaMn(CO)5
as the organometallic reagent. Complex 3 was isolated
as pale yellow plate-like crystals in yields of up to 53%,
based on the amount of manganese reagent used and
has been characterized by 13C- and 11B-NMR, IR, MS
(including exact mass determination) and elemental
analysis. 13C-NMR (76 MHz, C6D6): l 106.9, 126.6,
146.0 (aromatic), 209.7 (b, CO). 11B-NMR (96 MHz,
C6D6): l 50.6. IR (KBr) (cm−1): 2120 md, 2036 st sh,
2014 st, 1990 st, 1972 md sh [w(CO)]. MS (EI): [M]+=
452 (100%), isotopic pattern in agreement with that
expected for 1B, 4Cl, 1Mn atom. Exact mass: Calc. for
C11BCl4MnO7 (m/z=449.8 isotopomer): 449.7872.
Found: 449.7867. Anal. Calc. for C11BCl4MnO7: C,
29.37; H, 0.00. Found: C, 29.02; H, 0.17%.
1
were used for reference for H- and 13C-NMR, while a
sealed tube containing a solution of [(nBu4N)(B3H8)] in
CDCl3 was used as an external reference for 11B-NMR.
IR spectra were measured for each compound either as
a KBr disk or as a solution in hexanes on a Nicolet 500
FT-IR spectrometer. Mass spectra were measured by
the EPSRC National Mass Spectrometry Service Cen-
tre, University of Wales Swansea and by the depart-
mental service. Perfluorotributylamine was used as the
standard for high-resolution EI mass spectra. Elemental
analyses were carried out both by the departmental
analysis service and by Warwick Analytical Service,
University of Warwick.
2.3. Alternati6e synthesis of
(p5-C5H5)Fe(CO)2BO2C6H4 (4)
To a suspension of 0.295 g (1.48 mmol) of (h5-
C5H5)Fe(CO)2Na in C6H5CH3 at −40 °C was added
one equivalent of BCl3 (1.48 mmol, 1.48 cm3 of a 1 M
solution in heptanes). The solution was warmed to r.t.
and stirred for 4 h, and the 11B-NMR spectrum of the
reaction mixture at this point revealed complete conver-
sion of BCl3 (lB 46.5) to a species with a single 11B
resonance at lB 90.7. The reaction mixture was then
filtered and added to a suspension of one equivalent of
dilithiocatechol in 10 cm3 C6H5CH3. After stirring for a
further 20 min at r.t., the 11B-NMR spectrum of the
reaction mixture revealed a single resonance at lB 51.0,
characteristic of (h5-C5H5)Fe(CO)2BO2C6H4 (4) [6]. Re-
moval of volatiles in vacuo at this point, extraction of
the resulting solid into hexanes and cooling to −30 °C
2.1. (p5-C5H4R)Fe(CO)2BO2C6Cl4 [R=H (2) and
R=Me (2%)]
To a suspension of (h5-C5H5)Fe(CO)2Na (274 mg,
1.37 mmol) in ca. 20 cm3 C6H5CH3 at room tempera-
ture (r.t.) was added to one equivalent of perchlorocat-
echolborane (1) (0.400 g, 1.37 mmol) in 10 cm3
C6H5CH3. The reaction mixture was stirred at r.t. for a
period of 12 h, volatiles removed in vacuo, and the
resulting solid recrystallized from either C6H5CH3 or
hexanes to yield 2 as pale yellow acicular crystals in
yields of up to 62%. Complex 2 has been characterized
by 1H-, 13C- and 11B-NMR, IR, MS and elemental
1
1
analysis. H-NMR (400 MHz, C6D6): l 4.07 (5H, s,
led to the crystallization of 4 in 48% isolated yield. H-,
h5-C5H5). 13C-NMR (76 MHz, C6D6): l 84.4 (h5-
C5H5), 115.7, 126.5, 146.9 (aromatic), 213.1 (CO). 11B-
NMR (96 MHz, C6D6): l 55.2. IR (KBr) (cm−1): 2008
st, 1949 st [w(CO)]. MS (EI): [M]+=435 (100%), iso-
13C-, 11B-NMR, IR and mass spectrometric data for 4
were consistent with those reported by Hartwig and
Huber [6]. Alternatively, if the reaction mixture is
worked up prior to the addition of dilithiocatechol,

S. Aldridge et al. / Journal of Organometallic Chemistry 649 (2002) 9–14
11
Scheme 1. Synthetic routes to boryl complexes 2–4 [LnMꢁ(h5-C5H5)Fe(CO)2, X=Cl (2); LnMꢁ(h5-C5H4Me)Fe(CO)2, X=Cl (2%);
LnMꢁ(OC)5Mn, X=Cl (3); LnMꢁ(h5-C5H5)Fe(CO)2, X=H (4)].
characterization of the intermediate species can be car-
ried out. Removal of volatiles in vacuo and recrystal-
lization from hexanes leads to the isolation of a pale
yellow microcrystalline material which has been charac-
methods and refined by full-matrix least-squares on F2
[29]. Non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were placed in idealised positions and
refined using a riding model; in the case of the methyl
group the torsion angle was allowed to vary to locate
the maximum electron density. The C6H5CH3 solvent
molecule was found to be disordered about a centre of
inversion and it was necessary to constrain its geometry
during refinement.
terized by H-, 13C- and 11B-NMR, IR and MS. H-
NMR (400 MHz, C6D6): l 4.07 (5H, s, h5-C5H5).
13C-NMR (76 MHz, C6D6): l 81.4 (h5-C5H5), 215.8
(CO). 11B-NMR (96 MHz, C6D6): l 90.7. IR (hexanes)
(cm−1): 2022 st, 1963 st [w(CO)]. MS (EI): [M]+=259
(28%), isotopic pattern in agreement with that expected
for 1B, 2Cl, 1Fe atom. Although spectroscopic data are
in agreement with the formulation of the intermediate
as (h5-C5H5)Fe(CO)2BCl2, further characterization (e.g.
by elemental analysis and X-ray diffraction) were ham-
pered by the fragility of the compound and its ready
decomposition to the dark red dimeric species [(h5-
C5H5)Fe(CO)2]2.
1
1
3. Results and discussion
The metathesis reaction between ClBO2C6Cl4 (1) and
the sodium salt of either [(h5-C5H4R)Fe(CO)2]− (R=
H, Me) or [Mn(CO)5]− results in the synthesis of the
(tetrachlorocatechol)boryl complexes (h5-C5H4R)Fe-
(CO)2BO2C6Cl4 [R=H (2), Me (2%)] and [(OC)5-
MnBO2C6Cl4] (3) in yields of 50–60% (Scheme 1). The
pale yellow solids are moderately air sensitive, but can
be stored indefinitely under argon at −30 °C. Com-
plexes 2 and 3 are characterized by 11B-NMR reso-
nances in the region typical of metal boryl complexes
containing two boron-bound oxygen substituents (e.g.
lB 55.2 and 50.6 ppm, respectively for 2 and 3, com-
pared to 51.8 and 49 ppm for (h5-C5H5)Fe(CO)2-
BO2C6H4 and (OC)5MnBO2C6H4 [6,7]). Other spectro-
scopic and analytical data for 2 and 3 are consistent
with the proposed formulation, and although single
crystals suitable for diffraction study could not be
obtained for either complex, the methylcyclopentadi-
enyl analogue of 2, (h5-C5H4Me)Fe(CO)2BO2C6Cl4 (2%)
could be obtained in suitable crystalline form by slow
cooling of a concentrated toluene solution.
It should be noted that careful repeated washing of
the (h5-C5H5)Fe(CO)2Na starting material with warm
C6H5CH3 is required to remove traces of THF (which is
a contaminant inherent in the synthetic route used).
Yields of 4 are otherwise significantly reduced and the
side product BCl3·THF is a major contaminant.
2.4. Crystallographic data for 2%
C14H7BCl4O4Fe·12(C7H8), Mr=493.72, T=120(2) K,
(
triclinic, space group P1, a=6.8564(6), b=10.6520(3),
,
c=13.7941(10) A, h=74.504(5), i=86.866(6), k=
76.658(4)°,V=944.59(11)A ,Z=2,zcalc=1.736gcm−3
,
3
,
v=1.386 mm−1, reflections collected: 6734, indepen-
dent reflections: 2544 (Rint=0.0639), final R indices
[I\2|(I)]: R1=0.0462, wR2=0.1041, R indices (all
data): R1=0.0798, wR2=0.1203.
Crystals of 2% suitable for single crystal X-ray diffrac-
tion were mounted on a Bruker Nonius KappaCCD
area detector equipped with a molybdenum rotating
anode. The initial cell determination was found to be
The X-ray structure analysis reveals the expected
half sandwich geometry at the iron centre with the
coordination sphere being completed by two carbonyls
and one (tetrachlorocatechol)boryl ligand (Fig. 1).
To our knowledge 2% represents only the second crystal-
lographically characterized complex containing this
ligand, and the first for iron [22]. The FeꢀB dis-
unreasonable and, using the program DIRAX [26], it
was possible to index all reflections on two smaller cells
related by a 180° rotation about a. The data collection
was carried out using COLLECT [27] and integration
performed by EvalCCD [28]. The reflection file con-
sisted of the non-overlapping reflections from the major
twin component. The structure was solved via direct
,
tance [1.967(6) A] is consistent with that found in
similar complexes containing catechol-based boryl
ligands {e.g. (h5-C5H5)Fe(CO)2BO2C6H4 [1.959(6) A],
,
5
(h5-C5Me5)Fe(CO)2BO2C6H4 [1.980(2) A], and (h -
,

12
S. Aldridge et al. / Journal of Organometallic Chemistry 649 (2002) 9–14
C5H5)Fe(CO)2BO2C6H2O2BFe(CO)2(h5-C5H5) [1.971(2)
troidꢀFeꢀB and BO2 planes is found to be 26.6(5)°
compared with values of 7.9, 26.7 and 82.2° found in
(h5-C5H5)Fe(CO)2BO2C6H4, (h5-C5Me5)Fe(CO)2BO2-
C6H4 and (h5-C5H5)Fe(CO)2BO2C6H2O2BFe(CO)2(h5-
C5H5), respectively [6,20]. The wide range of values
obtained for r for superficially similar compounds indi-
cates that the orientational preference of (h5-
C5H4R)Fe(CO)2 and BX2 units is not a strong one and is
consistent with a description of catecholboryl ligands as
strong s donors, but as relatively poor p acceptors. In
addition, it appears that the conformation adopted in 2%
is influenced by a weak CꢀH···O hydrogen bond between
H(6a) of the methyl group and O(4) of the boryl ligand
(Fig. 2). Although structural inferences based on the
position of the hydrogen atom must be viewed cau-
tiously, the C···O and O···H distances [3.279(7) and 2.52
,
A]} [6,20], and significantly shorter than the average
value found for Fp boryl complexes in general.1 By
analogy with these related complexes, the bond length is
therefore indicative of an (albeit weak) FeꢀB back-bond-
ing interaction [6,20]. Comparison of the carbonyl
stretching frequencies for 2 and 2% (2008, 1949 and 2004,
1945 cm−1, respectively) with those obtained for (h5-
C5H5)Fe(CO)2BO2C6H4 (2024 and 1971 cm−1), how-
ever, implies that the degree of back bonding is
somewhat reduced upon perchlorination of the catechol-
boryl ligand.
The torsion angle (r) between (h5-C5H5) cen-
,
A, respectively] and CꢀH···O angle (134.4°) are within
the ranges expected for hydrogen bonds of this sort
[30–32], being similar, for example, to those reported for
methyl CꢀH···OꢁC bonds in various geometries of the
DMF dimer [32]. The ability of a weak hydrogen
bonding interaction to influence the conformational
geometry is further indicative of the relatively shallow
potential surface for rotation about the FeꢀB bond.
Estimates of typical CꢀH···O hydrogen bond strengths
are of the order of 4–10 kJ mol−1 [30–32], whereas a
barrier to rotation of ca. 3 kJ mol−1 has been calculated
for the model catecholboryl complex (h5-C5H5)Fe-
(CO)2BO2C2H2 by DFT methods [17]. The assessment of
CꢀH···O hydrogen bond strengths as being comparable
to the energetics of conformational processes in small
molecules has previously been advanced by Desiraju
[30]. It should be noted however that there is no evidence
on the basis of spectroscopic data for the existence of
intramolecular hydrogen bonding in solution.
Fig. 1. Molecular structure of the tetrachlorocatecholboryl complex
,
2%. Relevant bond lengths (A) and angles (°): Fe(1)ꢀB(1) 1.967(6),
Fe(1)ꢀcentroid 1.721(5), Fe(1)ꢀC(7) 1.761(6), Fe(1)ꢀC(8) 1.731(6),
B(1)ꢀO(3) 1.423(7), B(1)ꢀO(4) 1.433(7), C(7)ꢀFe(1)ꢀC(8) 94.4(2),
Fe(1)ꢀB(1)ꢀO(3) 126.6(4), Fe(1)ꢀB(1)ꢀO(4) 125.6(4), O(3)ꢀB(1)ꢀO(4)
107.8(4), centroidꢀFe(1)ꢀB(1)ꢀO(4) 26.6(5).
The reaction of (h5-C5H5)Fe(CO)2Na with boron
trichloride followed by dilithiocatechol provides an al-
ternative route to catecholboryl derivatives of iron (see
Scheme 1). In this case the reaction is thought to proceed
via the dichloroboryl intermediate (h5-C5H5)Fe-
(CO)2BCl2 on the basis of multinuclear NMR, IR and
mass spectrometric data. Monitoring of the reaction by
11B-NMR reveals that the signal at lB 46.5 due to the
BCl3 starting material is quantitatively replaced by a
low-field signal at lB 90.7 over a period of 4 h. The
11B-NMR resonance for the intermediate species shows
the downfield shift (compared to the BCl3 starting
material) expected for replacement of Cl with the
(h5-C5H5)Fe(CO)2 fragment.2 In addition the mass
Fig. 2. Intramolecular CꢀH···O hydrogen bond between the methyl
CꢀH and catecholboryl oxygen O(4) in 2%. Relevant bond lengths (A)
and angles (°): C(6)···O(4) 3.279(7), H(6a)···O(4) 2.52, C(6)ꢀH(6a)
0.98, CꢀH···O 134.4.
,
2 Typically, downfield shifts of between 20 and 65 ppm are ob-
served for the 11B resonance on replacement of a chlorine (in X2BCl)
with a (h5-C5R5)Fe(CO)2 fragment [to give (h5-C5R5)Fe(CO)2BX2].
Larger shifts are generally observed for weaker p donor X sub-
stituents. For example: lB 29.0–51.0 for BX2=BO2C6H4 [37,6];
35.0–59.1 for B(NMe2)Cl [37,36]; 37.5–69.5 for B(NMe2)B(NMe2)Cl
[37,35]; 61.0–121.0 for BPh2 [37,6]; 59.1–121.5 for B(C6F5)2 [37,18].
1 The average FeꢀB bond length measured for crystallographically
characterised complexes of the type (h5-C5R5)Fe(CO)2BX2 containing
,
a three-coordinate boron centre is 2.008(6) A [6,18,20,34–36].

S. Aldridge et al. / Journal of Organometallic Chemistry 649 (2002) 9–14
13
spectrum displays
a
peak at m/z=259 [(h5-
Acknowledgements
C5H5)Fe(CO)2BCl+2 ], and the measured carbonyl
stretching frequencies [2022 and 1963 cm−1] are consis-
tent with the attachment at the iron centre of a moder-
ately p acidic boryl ligand such as BCl2. On addition of
one equivalent of dilithiocatechol, the signal at lB 90.7
is converted over a period of 20 min into a single
resonance at lB 51.0 characteristic of (h5-
C5H5)Fe(CO)2BO2C6H4 (4) [6]. The identity of the final
isolated product was confirmed by comparison of the
measured spectroscopic data with that originally re-
ported by Hartwig and Huber [6].
We would like to acknowledge the support of the
EPSRC, the Royal Society, the Nuffield Foundation
and Cardiff University for the funding of this project.
The assistance of the EPSRC National Mass Spec-
trometry Service Centre, University of Wales Swansea
is also gratefully acknowledged.
References
This reaction represents a rare example of substitu-
tion at X within a boryl (BX2) ligand, with retention of
the metal boron bond. This type of reactivity occurs
almost exclusively for BCl2 complexes (in which the
stabilization of the boron centre by p electron release is
relatively poor), and has also been reported by Roper
and Wright for osmium BCl2 derivatives [2,15]. Similar
chemistry has also been reported by Braunschweig for
bridging borylene complexes containing the BCl ligand
[33]. Attempts to develop the scope of this substitution
chemistry in the synthesis of novel iron boryl complexes
are ongoing.
[1] H. Wadepohl, Angew. Chem. Int. Ed. Engl. 36 (1997) 2441.
[2] G.J. Irvine, M.J.G. Lesley, T.B. Marder, N.C. Norman, C.R.
Rice, E.G. Robins, W.R. Roper, G. Whittell, L.J. Wright, Chem.
Rev. 98 (1998) 2685.
[3] H. Braunschweig, Angew. Chem. Int. Ed. Engl. 37 (1998) 1787.
[4] M.R. Smith, Prog. Inorg. Chem. 48 (1999) 505.
[5] See, for example: (a) H.C. Brown, B. Singaram, Pure Appl.
Chem. 59 (1987) 879;
(b) K. Burgess, M.J. Ohlmeyer, Chem. Rev. 91 (1991) 1179;
(c) C.N. Iverson, M.R. Smith, Organometallics 15 (1996) 5155;
(d) I. Beletskaya, A. Pelter, Tetrahedron 53 (1997) 4957.
[6] (a) J.F. Hartwig, S. Huber, J. Am. Chem. Soc. 115 (1993) 4908;
(b) K.M. Waltz, J.F. Hartwig, Organometallics 18 (1999) 3383.
[7] K.M. Waltz, X. He, C. Muhoro, J.F. Hartwig, J. Am. Chem.
Soc. 117 (1995) 11357.
[8] K.M. Waltz, J.F. Hartwig, Science 277 (1997) 211.
[9] H. Chen, J.F. Hartwig, Angew. Chem. Int. Ed. Engl. 38 (1999)
3391.
4. Conclusions
[10] H. Chen, S. Schlecht, T.C. Semple, J.F. Hartwig, Science 287
(2000) 1995.
[11] K.M. Waltz, J.F. Hartwig, J. Am. Chem. Soc. 122 (2000) 11358.
[12] K. Kawamura, J.F. Hartwig, J. Am. Chem. Soc. 123 (2001)
8422.
[13] C.N. Iverson, M.R. Smith, J. Am. Chem. Soc. 121 (1999) 7696.
[14] S. Shimada, A.S. Batsanov, J.A.K. Howard, T.B. Marder,
Angew. Chem. Int. Ed. Engl. 40 (2001) 2168.
[15] G.J. Irvine, C.E.F. Rickard, W.R. Roper, A. Williamson, L.J.
Wright, Angew. Chem. Int. Ed. Engl. 39 (2000) 948.
[16] K.T. Giju, M. Bickelhaupt, G. Frenking, Inorg. Chem. 39 (2000)
4776.
[17] A.A. Dickinson, D.J. Willock, R.J. Calder, S. Aldridge,
Organometallics, submitted.
[18] S. Aldridge, A. Al-Fawaz, R.J. Calder, A.A. Dickinson, D.J.
Willock, M.E. Light, M.B. Hursthouse, Chem. Commun. (2001)
1846.
[19] S. Aldridge, R.J. Calder, K.M.A. Malik, J.W. Steed, J.
Organomet. Chem. 614 (2000) 188.
Complexes of iron and manganese containing the
tetrachlorocatecholboryl (BO2C6Cl4) ligand can be syn-
thesised in reasonable yield by the reaction of the
appropriate organometallic anion with perchlorocate-
cholborane; in addition catecholboryl complexes of iron
can be synthesised by substitution at the boryl centre of
an initially-formed BCl2 complex. Crystallographic data
for (h5-C5H4Me)Fe(CO)2BO2C6Cl4 further emphasise
the description of such ligands as good s donors, but
poor p acceptors, with the relative orientation of (h5-
C5H4Me)Fe(CO)2 and BO2C6Cl4 moieties being influ-
enced by weak intramolecular CꢀH···O hydrogen
bonding.
[20] S. Aldridge, R.J. Calder, A.A. Dickinson, D.J. Willock, J.W.
Steed, Chem. Commun. (2000) 1377.
[21] (a) A. Kerr, T.B. Marder, N.C. Norman, A.G. Orpen, M.J.
Quayle, C.R. Rice, P.L. Timms, G.R. Whittell, Chem. Commun.
(1998) 319;
5. Supplementary material
(b) N. Lu, N.C. Norman, A.G. Orpen, M.J. Quayle, P.L.
Timms, G.R. Whittell, Dalton Trans. (2000) 4032.
[22] W. Clegg, F.J. Lawlor, G. Lesley, T.B. Marder, N.C. Norman,
A.G. Orpen, M.J. Quayle, C.R. Rice, A.J. Scott, F.E.S. Souza, J.
Organomet. Chem. 550 (1998) 183.
[23] M. Kira, K. Sato, H. Sakurai, J. Am. Chem. Soc. 110 (1988)
4599.
[24] D. Ma¨nnig, H. No¨th, J. Chem. Soc. Dalton Trans. (1985) 1689.
[25] R.B. King, Acc. Chem. Res. 3 (1970) 417.
[26] A.J.M. Duisenberg, J. Appl. Crystallogr. 25 (1992) 92.
Crystallographic data for the structural analysis of
compound 2% have been deposited with the Cambridge
Crystallographic Data Centre, CCDC no. 171824.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
email: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).

14
S. Aldridge et al. / Journal of Organometallic Chemistry 649 (2002) 9–14
[27] COLLECT: Data Collection Software, Nonius BV, 1999.
[28] A.J.M. Duisenberg, Reflections on Area Detectors, Thesis,
Utrecht, 1998.
[29] G.M. Sheldrick, SHELX-97: Programs for Crystal Structure
Analysis (Release 97-2), University of Go¨ttingen, Germany,
1998.
[33] H. Braunschweig, M. Colling, J. Organomet. Chem. 614 (2000)
18.
[34] H. Braunschweig, C. Kollann, M. Mu¨ller, Eur. J. Inorg. Chem.
(1998) 291.
[35] H. Braunschweig, B. Ganter, M. Koster, T. Wagner, Chem. Ber.
129 (1996) 1099.
[30] G.R. Desiraju, Acc. Chem. Res. 24 (1991) 290.
[31] G.A. Jeffrey, J. Mol. Struct. 485–486 (1999) 293.
[32] R. Vargas, J. Garza, D.A. Dixon, B.P. Hay, J. Am. Chem. Soc.
122 (2000) 4750.
[36] H. Braunschweig, C. Kollann, U. Englert, Eur. J. Inorg. Chem.
(1998) 465.
[37] G.R. Eaton, W.N. Lipscomb, NMR Studies of Boron Hydrides
and Related Species, Benjamin, 1969.