Structural investigations on new iron-acyl derivatives of B(C 6F5)3

Article abstract of DOI:10.1016/j.jorganchem.2004.07.013

B(C₆F₅)₃ adducts of the iron-acetyl complexes [Fe(η-C₅H₅)(COCH₃)(CO)(L)] (where L = PPh₃ (1), PMe₃ (2), PPhMe₂ (3), PCy ₃ (4), CO (5)) have been prepared and invesigated. Studies using density function theorem, DFT, of several model compounds containing the systems [Fe-acyl] and [Fe-acyl-BF₃] provide into their electronic structure. Reactions between [Fe(η-C₅H₅)(MeCO)(CO)(L)], L = PPh₃ (1), PMe₃ (2), PPhMe₂ (3), PCy₃ (4), CO (5), and B(C₆F₅)₃ give new complexes [Fe(η-C₅H₅){MeCOB(C₆F₅) ₃}(CO)(L)] L = PPh₃ (7), PMe₃ (8), PPhMe ₂ (9), PCy₃ (10), CO (11), where B(C₆F ₅)₃ coordinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(η-C₅H₅){HOB(C ₆F₅)₃}(CO)(PPh₃)] (6). The X-ray structures of 6, 8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system. Both effects lead to a lengthening of the acyl C-O bond thus π populations cannot be inferred from the distance changes.

Full text of DOI:10.1016/j.jorganchem.2004.07.013

Journal of Organometallic Chemistry 689 (2004) 4407–4419
www.elsevier.com/locate/jorganchem
Structural investigations on new iron-acyl derivatives of B(C6F5)3
*
Grant D.W. Anderson, Oliver J. Boys, Andrew R. Cowley, Jennifer C. Green ,
*
Malcolm L.H. Green , Simon A. Llewellyn, Carlo Maresca von Beckh,
1
Sofia I. Pascu , Ino C. Vei
Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
Received 15 June 2004; accepted 5 July 2004
Available online 6 August 2004
Abstract
Reactions between [Fe(g-C5H5)(MeCO)(CO)(L)], L = PPh3 (1), PMe3 (2), PPhMe2 (3), PCy3 (4), CO (5), and B(C6F5)3 give new
complexes [Fe(g-C5H5){MeCOB(C6F5)3}(CO)(L)] L = PPh3 (7), PMe3 (8), PPhMe2 (9), PCy3 (10), CO (11), where B(C6F5)3 coor-
dinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(g-C5H5){HOB(C6F5)3}(CO)(PPh3)] (6). The X-ray structures of 6,
8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group
on Lewis acid coordination is more significant in the r than the p system. Both effects lead to a lengthening of the acyl C–O bond
thus p populations cannot be inferred from the distance changes.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Fischer–Tropsch reactions; Tris(perfluorophenyl)borane; Lewis acids; Catalysis; Fe-acyls complexes; Fischer carbenes; Density functi-
onal theory
1. Introduction
bonylation and reduction could then lead to carbon
chain homologation.
The transition metal catalysed reductive polymerisa-
tion of carbon monoxide by dihydrogen to form hydro-
carbons, the Fischer–Tropsch (FT) synthesis, has
received renewed interest in recent years [1]. However,
the search for a homogenous Fischer–Tropsch catalyst
has been unfruitful. A possible model for a homogene-
ous FT catalyst could be found in two centre/bridging
systems such as M–CO ! Z, where Z is an electron-
poor and oxophilic metal or a Lewis acid [2] (Scheme
1). Here, the metal centre M is proposed to act as a sup-
port for chain growth, while Z activates the M-acyl
functionality towards hydrogenation. Successive car-
The [Fe(g-C5H5)(CO)2] moiety and its congeners, in
which (g-C5(CH3)5) or (g-indenyl) replace (g-C5H5),
have been extensively investigated [3,4]. In particular,
a large body of research has centred on the use of such
systems as chiral auxillaries [5–7]. However, catalytic
hydrogenation of metal–carbonyl ligands such as M–
CO, M–CHO, M–COR has not been established. The
reduction of the metal-coordinated CO in the com-
pounds [M(g-C5H5)(CO)3(PPh3)]+ (M = Mo, W) with
NaBH4 gives the methyl complexes [M(g-C5H5)
(CH3)(CO)2(PPh3)] [8]. The strong reducing agent
BH3THF has also been used for the reduction of metal-
acyl groups [9]. The reduction by lithium aluminium
hydride of a terminal CO group in [Fe(g-C5(CH3)5)
*
(PMe3)(CO)2]+
gives
[Fe(g-C5(CH3)5)(PMe3)(CO)
Corresponding authors. Tel.: +44-1865-272637; fax: +44-1865-
272690.
(CH3)] [10]. Akita et al. [11] have shown that the reac-
tion of the acetyl compound [Fe(g-C5H5)(MeCO)
(CO)(PPh3)] with H2SiPh2 and the catalyst
E-mail address: jennifer.green@chem.ox.ac.uk (J.C. Green).
1
Present address: Department of Chemistry, University of Cam-
bridge, Lensfield Road, CB4 1EW.
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.07.013

4408
G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
Z
O
O
R
O
R
+2H2
CO
Z
M
MCH2
R
M
M
-H2O
-LA
CH2R
etc
Z = Lewis acid
Scheme 1. A possible mechanism for homogeneous FT reactions.
[RhCl(PPh3)3] gives [Fe(g-C5H5)(Et)(CO)(PPh3)]. Sub-
sequent treatment with CO and [Fe(g-C5H5)2][BF4]
gives [Fe(g-C5H5)(EtCO)(CO)(PPh3)]. This sequence
of reduction and insertion can be repeated to give
the pentanoyl complex [Fe(g-C5H5)(COC4H9})(CO)-
(PPh3)]. Treatment of [Fe(g-C5H5)(MeCO)(CO)(PPh3)]
with HBF4 or R3OþBF4ꢀ, (where R = Me, Et), results
in selective attack at the acyl-O atom giving [Fe(g-
C5H5)(MeCOR)(CO)(PPh3)][BF4] [12]. Davies et al.
have demonstrated that treatment of [Fe(g-
C5H5)(CO)(PPh3)(COEt) with trimethyloxonium tera-
fluoroborate led to the formation of [Fe(g-C5H5)
CO
Fe
O
C
(i) Na/Hg, THF
(ii) CH3I, THF
L
Fe
OC
Fe
Fe
O
C
O
L
OC
Me
OC
OC
Me
L = PPh3 (1), PMe3(2), PMe2Ph (3), PCy3 (4)
(i) Na/Hg, THF
(ii) CH3C(O)Cl, THF
B(C6F5)3
O
Fe
OC
OC
B(C6F5)3
Fe
Me
O
L
5
OC
Me
B(C6F5)3
L = PPh3 (7), PMe3 (8), PMe2Ph (9), PCy3 (10)
B(C6F5)3
Fe
O
OC
OC
Me
11
H2O
B(C6F5)3
Fe
+
Fe
HC(O)Me
OH
O
Ph3P
Ph3P
OC
OC
B(C6F5)3
Me
6
7
Scheme 2. Formation of compounds 1–5 and 7–11.

G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
4409
(CO)(PPh3)(‚COMe)Et]+, which underwent reduction
on treatment with hydride reagents to give [Fe(g-C5
H5)(CO)(PPh3)(CH(OMe)Et)] [13]. [Fe(g-C5H5)(CO
CH3)(CO)2] has been shown to react with BF3 gives
the acetyl O-coordinated adduct [Fe(g-C5H5)(CO
{BF3}CH3)(CO)2] [14].
Recently, B(C6F5)3 (a strong Lewis acid) has been
used as a catalyst for the hydrosilylation of aromatic
and aliphatic carbonyls [15]. Unlike BF3, the pentafluor-
ophenyls of B(C6F5)3 are not readily detached from the
boron centre. Therefore, we set out to prepare and study
B(C6F5)3 adducts of the iron-acetyl complexes [Fe(g-
C5H5)(COCH3)(CO)(L)] (where L = PPh3 (1), PMe3
(2), PPhMe2 (3), PCy3 (4), CO (5)). Studies using density
functional theory (DFT) of several model compounds
containing the systems [Fe-acyl] and [Fe-acyl-BF3] pro-
vide insight into their electronic structure.
the compounds [Fe(g-C5H5)(COCH3)(CO)(L)], where L
is a tertiary phosphine or CO, showed that only adducts
of the type [Fe(g-C5H5){MeCOB(C6F5)3}(CO)(L)] were
formed. The larger scale reactions between complexes 1–
5 and B(C6F3)3 in toluene also led in all cases to forma-
tion of the acyl-B(C6F5)3 adducts 7–11 in good yields.
The complex [Fe(g-C5H5){HOB(C6F5)3}(CO)(PPh3)]
(6) was formed as a result of the hydrolysis of 7, when
the product was purified by chromatography over silica.
A proposed pathway for the formation of 6 is shown in
Scheme 3. The adduct [H2OB(C6F5)3] [19] is presumably
formed initially. This strong acid would be expected to
protonate the [Fe-acyl] group to form a Fischer-
carbe ne-type intermediate [12]. Subsequent dissociation
with elimination of HC(O)Me gives the observed
[Fe(g-C5H5){HOB(C6F5)3}(CO)(PPh3)] (6).
2.2. Spectroscopic data
2. Results and discussion
The IR spectra (in Nujol for 1–5 and 7–11 and in d8-
1
toluene for 6), and the H, 31P{1H}, 11B{1H}, and 19F
2.1. Reactions
NMR spectra are given in Table 1. The IR spectra of
compounds 1–11 all show sharp bands in the region
characteristic for CO stretching frequencies. In all cases,
the coordination of B(C6F5)3 to the acyl oxygen results
in a significant lowering of the carbonyl stretching fre-
quency, which made them unobservable as Nujol emul-
sions. This is consistent with increased single-bond
character of the acyl-C–O. There is a rise in the terminal
carbonyl absorption of ca. 55 cmꢀ1 as a consequence of
the reduced electron density on the cationic iron centre
of the B(C6F5)3 adducts. The IR spectra of [Fe(g-
C5H5){MeCOB(C6F5)3}(CO)(PCy3)] (10) and the other
Scheme 2 shows synthetic routes used for the com-
pounds 1–11. The complexes [Fe(g-C5H5)(MeCO)
(CO)(L)], where L is PPh3 (1), PMe3 (2), PPhMe2 (3),
PCy3 (4), and CO (5) have been described previously
[12,16,17]. These compounds were synthesized using
modifications of the reported routes and then reacted
with B(C6F5)3. It has been shown that B(C6F5)3 reacts
with [Fe(g-C5H5)Me(CO)2] [18] to give the unexpected
complex [Fe-s-C6F4(2-C(O)Me)](g-C5H5)(CO)]. How-
ever, NMR scale reactions of B(C6F5) in d8-toluene with
B(C6F5)3
O
O
H2O
H2O
B(C6F5)3
+
[Fe]
CH3
O
[Fe]
CH3
H
H
O
[Fe]
CH3
HO B(C6F5)3
[Fe]
CH3
HO
B(C6F5)3
O
H
CH3
H
O
[Fe]
B(C6F5)3
Scheme 3. Proposed pathway for the formation of 6.

Table 1
IR (Nujol, m in cmꢀ1) and NMR data (d8-toluene unless otherwise specified, d in ppm, J in Hz) at room temperature
Compound
IR (tCO
)
1H
31P{1H} 11B{1H} 19F-ortho
19F-meta
19F-para
Terminal Acyl
[Fe(g-C5H5)(MeCO)(CO)(PPh3)]a (1)
1902s
1600 m 2.60 (3H, s, COMe)
3
4.28 (5H, d, JPH 1, Cp)
77.6
7.06 (9H, m, m + p-Ph)
7.74 (6H, m, o-Ph)
2
[Fe(g-C5H5)(MeCO)(CO)(PMe3)]b (2)
[Fe(g-C5H5)(MeCO)(CO)(PMe2Ph)] (3)
1914s
1916s
1604 m 1.22 (9H, d, JPH = 10, PMe3) 44.8
2.41 (3H, s, COMe)
4.35 (5H, b, Cp)
2
1605 m 1.41 (6H, d, JPH 8.7, PMe3)
2.48 f(3H, b, COMe)
4.31 (5H, s, Cp)
52.0
7.32 (3H, s, m + p-Ph)
7.48 (2H, s, o-Ph)
[Fe(g-C5H5)(MeCO)(CO)(PCy3)] (4)
1914s
1623 m 2.51 (33H, m, PCy3)
2.58 (3H, s, COMe)
4.53 (5H, s, Cp)
75.3
[Fe(g-C5H5)(MeCO)(CO)2] (5)
2023s
1966s
1666 m 2.37 (3H, s, COMe)
4.68 (5H, s, Cp)
–
[Fe(g-C5H5){HOB(C6F53)}(CO)(PPh3)]a (6)
1973s
–
2.60 (1H,b, HO)
4.18 (5H, s, Cp)
7.00 (15H, m, Ph)
69.0
ꢀ0.68
ꢀ14.0
ꢀ141.3 (b)
ꢀ165.5 (b)
ꢀ156.9 (b)
3
3
3
[Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PPh3)] (7)
1957s
–
2.21 (3H, s, COMe)
78.66
ꢀ132.9 (d, JFF 17)
ꢀ167.1 (td, JFF ꢀ160.9 (t, JFF 20.3)
4
21.1, JFF 5.6)
4.18 (5H, s, Cp)
7.00 (9H, s, m + p-Ph)
7.22 (6H, s, o-Ph)
2
0.81 (9H, d, JPH 7, PMe3)
3
3
3
[Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PMe3)] (8)
1948s
–
–
43.1
36.7
ꢀ13.9
ꢀ19.2
ꢀ133.2 (d, JFF 22.5) ꢀ164.1 (td, JFF ꢀ157.5 (t, JFF 21.2)
4
22.5, JFF 11.3)
2.34 (3H, s, COMe)
4
3.98 (5H, d, JPH 2, Cp)
2
1.85 (6H, d, JPH 1, PMe2)
3
3
[Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PMe2Ph)] (9) 1952s
ꢀ139.9 (d, JFF 21.3) ꢀ172.5 (b)
ꢀ165.8 (t, JFF 20.2)
2.09 (3H, s, COMe)
3.73 (5H, s, Cp)
6.78 (3H, m, m + p-Ph)
6.88 (2H, m, o-Ph)

G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
4411
related adducts with bulky tertiary phosphine ligands
show two bands in the C–O stretching region indicating
two distinct terminal carbonyl stretches. These are as-
signed to the presence of conformational isomers [20].
The complex 6, shows a broadband at 3229 cmꢀ1 that
may be assigned to the H–O stretching vibration of
[HOB(C6F5)3]. The terminal CO absorption, lies at a
higher wave number than for the neutral parent [Fe(g-
C5H5)(COCH3)(CO)(PPh3)], as is expected for a weakly
bonded [HOB(C6F5)3]ꢀ adduct. Facile separation into
the ion pair [Fe(g-C5H5)(CO)(PPh3)]+[HOB(C6F5)3]ꢀ
may occur in solution.
The 1H NMR spectra of 7–11 show a decrease of the
chemical shift of COMe upon coordination of B(C6F5)3
to the acyl-oxygen. In all cases, the C5H5-resonances are
found up-field compared with the parent compounds,
the most shielded being 7 and 9. The increase may be
caused the electron withdrawing effect of B(C6F5)3.
The 19F NMR spectra of 7–11, show an upfield shift
in the para-fluorine (ca. 12 ppm) compared to uncoordi-
nated B(C6F5)3. The 11B NMR spectra are particularly
diagnostic since the 11B resonances differ substantially
between the three-coordinate borane and the four-coor-
dinate boron in the Lewis acid–base adducts. The latter
resonances are shifted up-field with respect to B(C6F5)3
by ca. 50 ppm [19,21–23].
2.3. X-ray crystallography
Table 2 contains selected molecular parameters. A
summary of the X-ray crystallographic data for com-
pounds 6, 8 and 11 is given in Table 3. The ORTEP dia-
grams are presented in Fig. 1 (compound 8), Fig. 2
(compound 11) and Fig. 3 (compound 6). Cif files are gi-
ven in supporting information and have been deposited
at the Cambridge Crystallographic Data Centre (deposi-
tion numbers CCDC 230809–230811). In all three com-
pounds, coordination about the B atom is almost
tetrahedral. Coordination about the Fe centre is typical
of ‘‘half sandwich’’ mono(cyclopentadienyl)metal com-
plexes [26,27]. The X-ray crystal structure determina-
tions confirm that for both compounds 8 and 11, the
oxygens of the initial acyl groups are connected through
˚
a C–O–B system with O–B of 1.559(3) A, 8 and 1.570(3)
˚
˚
A, 11, and C–O of 1.297(3), 8 and 1.254(3) A, 11. The
attachment of the B(C6F5)3 lengthens the original dou-
ble acyl carbonyl bond and shortens the Fe–C(acyl)
bond. The Fe–C(acyl) and (acyl)C‚O bond lengths in
˚
the adduct 8 (1.904(2) and 1.297(3) A, respectively) are
intermediate between those found in typical Fe-acyl
compounds (i.e. [Fe(g-C5H5)(COCH3)(CO){PPh3}],
˚
[24] with Fe–C(acyl) bond 1.917(8) A, (acyl)C‚O bond
˚
1.234(7) A and [Fe(g-C5H5)(COCH3)(CO){PPhMe2}]
˚
[25] with Fe–C bond 1.948(4) A, (acyl)C‚O bond
˚
1.214(4) A) and Fischer-carbenes (i.e. [Fe(g-C5H5)I{Ph-
˚
C(OEt)}(CO)] [26] with Fe–C bond 1.849(10) A,

4412
G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for compounds 6, 8 and 11
Compound
Bond lengths
Bond angles
6
O(1)–B(1)
1.508(2)
2.0403(13)
2.768(2)
2.762(2)
O(1)–Fe(1)–P(1)
C(19)–Fe(1)–P(1)
O(1)–B(1)–C(1)
C(1)–B(1)–C(7)
Fe(1)–O(1)–H(1)
B(1)–O(1)–H(1)
Fe(1)–O(1)–B(1)
O(1)–Fe(1)–C(19)
92.13(4)
89.29(6)
Fe(1)–O(1)
O(1)ꢁ ꢁ ꢁF(1)
O(1)ꢁ ꢁ ꢁF(15)
112.83(14)
104.72(14)
109.4(20)
112.9(20)
136.83(11)
97.42(7)
8
Fe(1)–C(90)
Fe(1)–C(10)
Fe(1)–P(1)
C(10)–O(2)
O(2)–B(1)
1.745(3)
1.904(2)
2.185(8)
1.297(3)
1.559(3)
C(10)–Fe(1)–P(1)
C(10)–Fe(1)–C(90)
C(90)–Fe(1)–P(1)
92.55(8)
94.36(13)
90.76(11)
11
Fe(1)–C(8)
C(8)–O(3)
O(3)–B(1)
Fe(1)–C(1)
Fe(1)–C(2)
1.919(2)
1.254(3)
1.570(3)
1.774(3)
1.763(3)
C(8)–O(3)–B(1)
C(1)–Fe(1)–C(8)
O(3)–B(1)–C(16)
138.11(18)
89.7(1)
114.48(18)
˚
(acyl)C‚O bond 1.344(14) A). Similarly, for 11 the
Fe(1)–C(8) distance is 1.919(2) and (acyl)C‚O is
creases that of the Fe–C bond. Such resonance struc-
tures are normally taken to imply a shift of p electrons
(Scheme 4). To reduce computational time, in modelling
the B(C6F5)3 derivatives all C6F5 groups were substi-
tuted by fluorine atoms and C6H5 groups by hydrogen.
Though in the isolated molecules the bonding in planar
BF3 and B(C6F5)3 differs, in that the former has a strong
p component, when tetrahedrally coordinated the B–F p
bonding in BF3 is considerably reduced. Such a substitu-
tion has been used successfully in a number of studies
[21,30]. Geometry optimisations were carried out for
the iron-acyl species: [Fe(C5H5)(MeCO)(CO)2] (I),
[Fe(C5H5)(MeCO)(CO)(PH3)] (II) and [Fe(C5H5)(Me-
CO)(CO)(PMe3)] (III), and for their respective Lewis
acid adducts: [Fe(g-C5H5){MeCOBF3}(CO)2] (I0),
[Fe(C5H5){MeCOBF3}(CO)(PH3)] (II0) and [Fe(C5H5)
{MeCOBF3}(CO)(PMe3)] (III0). Fragment analyses
were performed to analyze the bonding between the iron
centre and the acyl carbon atom. [Fe(g-C5H5)(MeCO)
(CO)(L)] (L = CO and PMe3) were split into [Fe(g-
C5H5)(CO)(L)] and [MeCO] and [Fe(g-C5H5)(Me-
COBF3)(CO)(L)] into [Fe(g-C5H5)(CO)(L)] and
[MeCOBF3].
˚
1.254(3) A.
The ORTEP diagram showing the molecular
structure of 6 is given in Fig. 3. There are only three pre-
viously structurally characterised examples of coordi-
nated [HOB(C6F5)3] [27–29]. [PtMe{HOB(C6F5)3}
(bipy)] [28] and [InMe{HOB(C6F5)3}{1,2-(NiPr)2C8H5}]
[29] are believed to be formed by analogous reaction
pathways to that proposed above, due to the presence
of adventitious H2O. The B–O bond length in the free
anion [HOB(C6F5)3]ꢀ increases upon coordination to a
metal centre from 1.487(3) in [NEt4][HOB(C6F5)3] to
˚
˚
1.508(2) A in 6, 1.526(3) A in [PtMe{HOB(C6F5)3}
˚
(bipy)] or 1.528(3) A in [InMe{HOB(C6F5)3}{1,2-
(NiPr)2C8H5}]. The structure of 6 shows a weak interac-
tion of the hydroxyl proton with the two fluorine atoms
F(1) and F(15). The O atom is relatively close to one flu-
orine atom of two of the pentafluorophenyl groups
˚
˚
(O(1)ꢁ ꢁ ꢁF(1) 2.768(2) A, O(1)ꢁ ꢁ ꢁF(15) 2.762(2) A). The
hydroxyl group does not project directly towards either
F and it is thus not clear whether any hydrogen bond is
present. However, they cause the slight elongation of the
˚
corresponding C–F bonds to 1.362(2) and 1.361(2) A,
˚
compared to the average of ca. 1.35 A.
The results of all geometry optimisations are given in
Table 4 together with experimental (X-ray diffraction)
values for comparison. Reasonable agreement between
calculated and experimental distances confirms that, in
general, replacement of B(C6F5)3 with BF3, and that
of PPh3 with PH3 provided accurate models. Table 5
shows the total energy gain upon coordination of BF3
to Fe-acyls. The gas phase formation of O-acyl coordi-
nated BF3-adducts was found to be energetically favour-
able in all cases. The binding energy increases with the
donor character of L. Examination of bond lengths
2.4. DFT calculations
Electronic structure calculations were undertaken to
investigate the causes of the bond length changes on
coordination of B(C6F5)3. Consideration of resonance
structures for the Lewis acid coordinated iron-acyl com-
pound would suggest that the coordination decreases
the double bond character of the C–O bond and in-

Table 3
Crystallographic data for compounds 6, 8 and 11
6
8
11
Chemical formula
Formula weight
Temperature (K)
C
49H29BF15FeO2P
C29H17BF15FeO2P
780.05
C27H8BF15FeO3
731.99
1032.37
150
0.71073
150
0.71073
150
0.71073
˚
Wavelength (A)
Crystal system
Space group
Triclinic
ꢀ
Monoclinic
P21/n
Monoclinic
C2/c
P1
10.5856(3)
˚
a (A)
a = 12.1985(2)
b = 18.6027(3)
26.3586(3)
12.9606(2)
˚
b (A)
14.0834(4)
16.0926(5)
˚
c (A)
c = 13.4403(2)
90
19.6149(3)
90
a (ꢁ)
b (ꢁ)
c (ꢁ)
94.7028(10)
108.2310(11)
102.8671(8)ꢁ
90
2973.4
128.3594(7)
90
5254.4
107.8446(12)
2126.7
3
˚
Cell volume (A )
Z
2
1.612
4
1.742
8
1.851
Calculated density (Mg/m3)
Absorption coefficient (mmꢀ1
F0 0 0
)
0.501
1041.305
0.685
1552
0.713
2884.362
Crystal size (mm)
Absorption correction
0.08 · 0.14 · 0.16
Semi-empirical from equivalent reflections
0.42 · 0.2 · 0.1
Semi-empirical from equivalent reflections
0.08 · 0.12 · 0.22
Semi-empirical from equivalent reflections
Transmission coefficients (min and max)
h Range for data collection (ꢁ)
Index ranges
0.92 and 0.96
5.0 6 h 6 27.5
0.87 and 0.93
3.6 6 h 6 27.5
0.85, 0.94
5.0 6 h 6 27.5
ꢀ13 6 h 6 12, ꢀ18 6 k 6 18, 0 6 l 6 20
ꢀ15 6 h 6 15, ꢀ21 6 k 6 24, ꢀ17 6 l 6 17
ꢀ34 6 h 6 26, 0 6 k 6 16, 0 6 l 6 25
Reflections measured
Unique reflections
Rint
28,893
9645
13,012
6809
41,307
6227
0.035
7198
0.020
4509
0.042
4348
Observed reflections (I > 3r(I))
Refinement method
Parameters refined
Weighting scheme
Goodness-of-fit
Full-matrix least-squares on F
626
Full-matrix least-squares on F
550
Full-matrix least-squares on F
424
Chebychev 3-term polynomial
1.0461
Chebychev 3-term polynomial
1.0199
Chebychev 3-term polynomial
1.0425
R1
0.0348
0.0397
0.0406
0.0492
0.0369
0.0419
wR2
ꢀ3
˚
Residual electron density (min and max) (eA
)
ꢀ0.35, 0.41
ꢀ0.38 and 0.66
ꢀ0.40, 0.57

4414
G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
_
BArF
_
BArF
+
O
O
3
3
+
Fe
Fe
Scheme 4. Resonances structures for [Fe(g-C5H5){MeCOB(C6F5)3}
(CO)(L)].
shown in Table 4 shows that the acyl C–O distances in-
˚
crease upon coordination by BF3 (0.05 A on average)
and Fe–C (acyl bond) shortens by an average of 0.06
˚
A compared with parent acyl compound. The O–B dis-
tances in the Fe-(l-CO)B unit show significant variation
in the order L = CO > PH3 > PMe3 and the B–F dis-
tances correlate inversely with the B–O distances. Com-
pounds I, I0, III and III0 were chosen for fragment
analysis, as these represent the electronic extremes for
the system. The movement of charge on coordination
of BF3 is shown in Fig. 4. The charge on the [Fe(g-
C5H5)(CO)(L)] fragment is positive and is greater for
L = PMe3 than L = CO. On binding BF3 there is a trans-
fer of electron density from both the Fe centre and the
acyl fragment, towards the BF3 moiety. There is thus a
correlation between the charge transfer and the binding
energy, both increasing with the donor power of L.
The HOMO of [Fe(g-C5H5)(MeCO)(CO)(L)] is
shown in Fig. 5 for L = CO and PMe3. In both cases
the HOMO is the principal Fe-acyl bonding orbital.
However it is not localised in the Fe–C bond but has a
contributions from the O pp orbital lying in the acyl
plane and from the C–Me bond. The six Fe d electrons
occupy the next three orbitals. It is the HOMO that is
the source of the electron pair donation to the Lewis
acidic BF3 and O that acts as the donor atom. Conse-
quently the O–B bond is formed in the plane of the acyl
group and at an angle of ca. 125ꢁ to the C–O bond.
Binding of the acyl group to [Fe(g-C5H5)(CO)(L)] in-
volves principally the acyl HOMO and to a certain ex-
tent its LUMO. As the acyl group is planar the
orbitals may be classified as r for the HOMO and p
for the LUMO. The HOMO has an outward pointing
lobe directed towards the Fe but also has a contribution
from the O p orbital in the C–C–O plane. The acyl
Fig. 1. ORTEP of compound 8.
F(12)
F(7)
C(5)
F(13)
C(6)
C(4)
C(24)
C(7)
F(11)
F(6)
C(25)
C(18)
C(3)
C(26)
F(14)
C(1)
C(17)
O(1)
C(8)
C(23)
Fe(1)
C(22)
F(8)
C(19)
C(27)
O(3)
F(15)
B(1)
C(16)
C(21)
C(2)
C(9)
C(20)
C(10)
O(2)
F(5)
F(9)
F(1)
C(11)
C(12)
F(10)
C(15)
C(14)
F(4)
F(2)
C(13)
F(3)
Fig. 2. ORTEP of compound 11.
F(3)
F(7)
F(2)
C(4)
C(22)
C(23)
F(1)
C(3)
C(2)
C(21)
F(6)
C(8)
C(5)
C(29)
F(4)
C(24)
C(28)
C(20)
C(6)
C(1)
C(9)
Fe(1)
C(30)
C(25)
HOMO is C–O antibonding. The LUMO is a p C–O
*
O(1)
C(27)
B(1)
F(5)
F(8)
antibonding orbital (Scheme 5).
C(7)
P(1)
C(10)
C(11)
C(13)
C(19)
Orbital occupancies for the acyl HOMOs and LU-
MOs in [Fe(g-C5H5)(MeCO)(CO)(L)] are given in Table
6. When L = CO the acyl HOMO has an occupancy of
1.0 electrons and the LUMO one of 0.09 electrons, indi-
cating little p bonding by the Fe centre to the acyl lig-
and. For L = PMe3 both the HOMO and LUMO
occupancy are slightly greater at 1.1 and 0.19 respec-
tively. As both the acyl HOMO and LUMO are C–O
antibonding the C–O distance is longer in III than I
C(32)
F(15)
C(26)
C(12)
C(18)
F(10)
O(2)
F(11)
C(31)
C(33)
C(37)
C(14)
C(42)
C(38)
C(34)
C(15)
C(17)
C(36)
F(14)
C(41)
F(12)
C(39)
C(35)
C(16)
C(40)
F(13)
Fig. 3. ORTEP of compound 6.

Table 4
Selected distances (A) and angles (ꢁ) calculated for I-III, I -III
0
0
˚
Compound
Fe–C (acyl)
Fe–P
Fe–C (carbonyl)
O‚C (acyl)
B–O (acyl)
C„O
BAF
Fe–C(acyl)–O
Fe–C(acyl)–C
C(acyl)–O–B
I
1.958
1.932
1.914
1.891
1.869
1.850
1.917(8)
1.725, 1.722
1.715
1.705
1.206
1.213
1.226
1.253
1.263
1.276
1.234(7)
1.156, 1.160
1.161
1.164
122.2
124.3
126.0
119.4
120.5
121.0
123.2(6)
116.6
117.2
119.2
119.1
121.6
122.9
122.8(2)
II
III
I0
II0
2.216
2.137
1.734, 1.732
1.722
1.710
1.593
1.571
1.546
1.149, 1.154
1.156
1.160
1.352, 1.371, 1.378
1.355, 1.370, 1.378
1.360, 1.375, 1.380
124.2
124.5
125.3
2.121
2.156
2.202(2)
III0.
[Fe(g-C5H5)(MeCO)-
(CO)(PPh3)]a
1.708(8)
1.171(6)
[Fe(g-C5H5)(MeCO)-
(CO)(PPhMe2)]
1.948(4)
2.180(1)
2.185(8)
1.725(4)
1.214(4)
1.161(4)
123.0(3)
133.4(6)
120.7(3)
122.6(8)
b
[Fe(g-C5H5)I{PhC-
1.849(10)
1.758(13)
1.344(14)
1.157(15)
(OEt)}(CO)]c
8
11
1.904(2)
1.919(2)
1.745(3)
1.774(3) 1.763(3)
1.297(3)
1.254(3)
1.559(3)
1.570(3)
1.155(4)
1.140(3) 1.142(3)
116.1(2)
118.04(16)
122.77(17)
122.13(16)
131.65(19)
138.11(18)
Where available, experimental distances of related derivatives are given for comparison. Calculated Cp(C–C) and Fe–C(Cp) distances are all within expected range.
a
Ref. [24].
Ref. [25].
Ref. [26].
b
c

4416
G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
Table 6
Occupancies of fragment MOs (FMOs) for I, I0, III and III0
Compound
Fragment
FMO
Occupancy
[Fe(g-C5H5)(MeCO)(CO)2] (I)
MeCO
MeCO
HOMO
LUMO
HOMO
1.03
0.09
1.03
Fe(g-C5H5)(CO)2
Fe(g-C5H5){MeCOBF3}(CO)2] (I0)
{MeCOBF3}
{MeCOBF3}
HOMO
LUMO
HOMO
1.25
0.14
0.83
Fe(g-C5H5)(CO)2
[Fe(g-C5H5)(MeCO)(CO)(PMe3)] (III)
[Fe(g-C5H5){MeCOBF3}(CO)(PMe3)] (III0)
MeCO
MeCO
HOMO
LUMO
HOMO
1.13
0.19
0.92
Fe(g-C5H5)(CO)(PMe3)
{MeCOBF3}
{MeCOBF3}
HOMO
LUMO
HOMO
1.3
0.29
0.78
Fe(g-C5H5) (CO)(PMe3)
by resonance structures, as it is shown to be a combi-
nation of both r and p effects, both the r HOMO
and the p LUMO of the acyl group increasing their
occupancy on BF3 coordination and both and C–O
antibonding. Thus p populations cannot be inferred
from distance changes.
O
Me
BF3
Me
BF3
LUMO
HOMO
Scheme 6. HOMO and LUMO of the acyl-BF3 fragment.
4. Experimental
acyl-BF3 HOMO from 1.0 to 1.2. The acyl-BF3 LUMO
also increases its occupancy to 0.14. This represents a
movement of electron density from the metal. The shift
is greater in the r framework than in the p. When
L = PMe3 a similar shift occurs of 0.2 electrons in the
r system and 0.1 in the p. In both cases these shifts re-
sult in a lengthening of the CO bond and a shortening of
the Fe–C bond on BF3 coordination.
Thus the simple resonances structures, as presented,
are deceptive in so far as they are taken to indicate shifts
in p population. The bond length changes on BF3 coor-
dination are as much, if not more, due to changes in r
occupancy. The acyl r HOMO is CO antibonding and
increase in its occupancy increases the CO bond length.
All reactions were carried out under N2, using con-
ventional Schlenk-line techniques. The compounds
[Fe(g-C5H5)(Me)(CO)2] [31], PMe3 [32], B(C6F5)3 [33],
[Fe(g-C5H5)(Me)(CO)(PPh3)] [34], and [Fe(g-C5H5)
(Me)(CO)(PMe3)] [35] (2) were prepared according to
the literature methods. The compunds [Fe(g-C5H5)(l-
CO)2(CO)], PPh3, PPhMe2, PPh2Me, PCy3, MeCOCl,
Mel and alumina (activated, neutral, Brockmann I,
Std Grade, 150 mesh) were purchased from Aldrich
Chemical Co. and used as received. NMR spectra were
recorded on either a 300 MHz Varian Mercury or a
500 MHz Varian Unity spectrometer, referenced inter-
nally using the residual protio-solvent, and chemical
shifts were reported with respect to SiMe4 (1H and
13C, d = 0), BF3 Æ Et2O (11B, d = 0), H3PO4 (31P, d = 0)
and CFCl3 (19F, d = 0). All chemical shifts are quoted
in d (ppm) and coupling constants in Hz. Infrared spec-
tra were recorded on either a Perkin–Elmer 1710 IR FT
spectrometer or a Perkin–Elmer 1600 FTIR. GC–MS
chromatographs and spectra were recorded using a
Hewlett–Packard 5890 Gas Chromatograph fitted with
a non-polar column connected to a Trio-1000 Mass
Spectrometer operating Electron Impact (70 eV) and
Chemical Ionisation (CI) mode (NH3) and detecting
positively charged species. The temperature profile for
the GC is shown below. Elemental analyses and mass
spectra were provided by the Microanalytical Services
of the Inorganic Chemistry Laboratory, Oxford.
3. Conclusions
The reactivity of [Fe(g-C5H5)(MeCO)(CO)(L)] to-
wards B(C6F5)3 has been investigated. New complexes
incorporating the [Fe-acyl-B(C6F5)3] unit have been
prepared, characterised and their electronic structure
investigated. DFT calculations indicate that formation
of O-acyl-coordinated adducts of BF3 is thermody-
namically favourable both the binding energy and
the charge transfer increasing with the donor power
of the other ligands bound to Fe. The lengthening
of the C–O bond and shortening of the Fe–C bond
on B(C6F5)3 coordination is not precisely described

G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
4417
The spectroscopic data are: for [Fe(g-C5H5)(Me)
(CO)(PPh3)] 1, IR (Nujol): 1902s, 1600s [C‚O stretch].
stirring. The mixture was left at ꢀ78 ꢁC for 20 min then
left to return to room temperature. Solvent was then re-
moved under reduced pressure, the resulting oil dis-
solved in toluene and filtered. Drying under reduced
pressure gave [Fe(g-C5H5)(MeCO)(CO)2] as a yellow-
brown powder that was purified by sublimation (52 ꢁC
and 0.1 bar). Yield 40%. IR (Nujol): 2023 s, 1956 s,
1656 m [C‚O Stretch].
1
NMR (C6D6): H: 2.60 [3H, s, COCH3], 4.28 [5H, d,
3J(H,P) = 1.2 Hz, C5H5], ꢂ7.06 [9H, m, p-/m-(C6H5)3],
7.74 [6H, m, o-(C6H5)3]. 13C{1H}: 51.6 [d,
3J(C,P) = 6.4 Hz, COCH3], 85.4 [d, 2J(C,P) = 0.8 Hz,
C5H5], 128.2 [d, 3J(C,P) = 9.7 Hz, m-(C6H5)3], 129.8
4
2
[d, J(C,P) = 2.3 Hz, p-(C6H5)3], 133.8 [d, J(C,P) = 9.4
1
1
Hz, o-(C6H5)3], 137.4 [d, J(C,P) = 42.4 Hz, i-(C6H5)3],
NMR (d8-toluene): H: 2.37 [3H, s, COCH3], 4.68
221.2 [d, 2J(C,P) = 31.3 Hz, CO], 269.5 [d,
2J(C,P) = 23.0 Hz, COCH3]. 31P{1H}: 77.6 [s,
P(C6H5)3].
[5H, s, C5H5].
4.1.4.
[Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PPh3)]
For [Fe(g-C5H5)(Me)(CO)(PMe3)] (2) IR (Nujol):
1914 s, 1604 m [C‚O Stretch]. NMR (CDCl3): 1H:
1.22 [9H, d, J(P,H) = 9.7 Hz, P(CH3)3], 2.41 [3H, s,
(7) and [Fe(g-C5H5){HOB(C6F5)3}(CO)(PPh3)] (6)
NMR scale. A solution of B(C6F5)3 (0.017 g, 0.033
mmol) in C6D6 was added dropwise to a solution of
[Fe(g-C5H5)(MeCO)(CO)(PPh3)] (0.015 g, 0.033 mmol)
in C6D6. The combined solution was transferred to a
Youngꢀs Tap NMR tube and monitored by 1H, 19F,
31P and 11B NMR spectroscopy.
2
COCH3], 4.35 [5H, s, C5H5]; 31P{H}: 44.8 [s, PMe3].
4.1. Preparation
4.1.1. Fe(g-C5H5)(MeCO)(CO)(PPhMe2)] (3)
PPhMe2 (0.4 cm3, 2 mmol) was added to a solution of
[Fe(g-C5H5)(CH3)(CO)2] (0.35 g, 2 mmol) in toluene (10
cm3) and refluxed under N2 for 2 h. The solvent was re-
moved under reduced pressure and the resultant solid
purified by chromatography on silica. The first fraction
(yellow) was collected with light petrol and the second
(orange) with 50% diethyl ether and 50% tetrahydrofu-
ran. The solvent was removed from the second fraction,
the product extracted from light petrol and then dried
under reduced pressure to give [Fe(g-C5H5)(MeCO)(-
CO)(PPhMe2)] as an orange-brown solid. Yield: 30%.
Elemental Analysis: C11H17FeO2P Found (Calc.) %C
49.4 (49.3), %H 6.7 (6.4), %P 10.1 (11.6). IR (Nujol):
1916 s, 1605 m [C‚O Stretch].
Preparative scale. A solution of B(C6F5)3 (0.225 g,
0.44 mmol) in toluene (20 cm3) was added dropwise,
with stirring, over 10 min to a solution of [Fe(g-
C5H5)(CH3CO)(CO)(PPh3)] (200 mg, 0.44 mmol) in
toluene (20cm3) at ꢀ78ꢁC. The orange mixture was
stirred for 1 h at ꢀ78ꢁC. The cooling bath was re-
moved and the solution allowed to warm to room
temperature whilst stirring for a further hour. Re-
moval of solvents yielded [Fe(g-C5H5){MeCOB-
(C6F5)3}(CO)(PPh3)], (7), as a yellow solid. Yield:
99%. Elemental Analysis: Found (Calculated) %C
54.7 (54.7), %H 2.9 (2.4) IR (Nujol): 1957s, 1517m
[C‚O stretch]. NMR (d8-toluene): 1H: 2.21 [3H, s,
COCH3], 4.18 [5H, s, C5H5], 7.00 [9H, s, m-/p-
C6H5], 7.22 [6H, s, o-C6H5]; 13C{H}: 49.82 [1C, s,
COCH3], 87.12 [5C, s, C5H5], 130.76 [6C, s, m-C6
H5], 133.60 [3C, s, p-C6H5], 134.20 [6C, s, o-C6H5],
133.24 [3C, s, i-C6H5]; 218.01[1C, d, 2J(P,C) =
28.7 Hz, CO].
NMR (d8-toluene): 1H: 1.41 [3H, d, 1J(P,H) = 8.7 Hz,
P(CH3)2], 2.48 [3H, s, COCH3], 4.31 [5H, s, C5H5], 7.32
[3H, s, m-/p-C6H5], 7.48 [2H, s, o-C6H5]; 31P{1H}: 52.0
[s, PPhMe2].
19F: ꢀ167.1 [6F, td J(F,F) = 21.1 Hz J(F,F) = 5.6
Hz, m-C6F5], ꢀ160.9 [3F, t 3J(F,F) = 21.09 Hz, p-
C6F5], ꢀ134.0 [6F, d 3J(F,F) = 16.9 Hz, o-C6F5];
31P{1H}:67.3 [s, PPh3]; 11B{1H}: ꢀ14.0.
3
4
4.1.2. Fe(g-C5H5)(MeCO)(CO)(PCy3)] (4)
The procedure described for the synthesis of 3 was
followed, using PCy3 (4.2 g, 10 mmol) and [Fe(g-
C5H5)(CH3)(CO)2] (1.95 g, 15 mmol) to give [Fe(g-
C5H5)(COCH3)(CO)(PCy3)] as a yellow-brown solid.
Yield: 70%. IR (Nujol): 1914 s, 1623 m [C‚O Stretch].
NMR (d8-toluene): 1H: 2.51 [33H, m, P(C6H11)3],
2.58 [3H, s, COCH3], 4.53 [5H, s, C5H5]; 31P{H}: 75.3
[s, PCy3].
FAB+. m/z (Intensity %), [Assignment]: 411 (9),
[Fe(PPh3)(C5H5)(CO)]+, 383 (100), [Fe(PPh3)(C5H5)]+,
121 (20), [Fe(C5H5)+].
Attempted purification of [Fe(g-C5H5){CH3 COB-
(C6F5)3}(CO)(PPh3)] by chromatography on silica in
THF led only to formation of the hydrolysis product
[Fe(g-C5H5){HOB(C6F5)3}(CO)(PPh3)] (6). Yield 20%.
IR (Nujol): 3229 m [H-O stretch], 1973 s [C”O stretch]
4.1.3. Fe(g-C5H5)(MeCO)(CO)2] (5)
[Fe2(g-C5H5)2(l-CO)2(CO)2] (3.54 g, 10 mmol) in
THF (50 cm3) was added to ꢂ3% sodium amalgam
(0.98 g, 0.021 mol Na + 35 g Hg) and occasionally
swirled over three hours. The solution was then filtered
in to another flask and cooled to ꢀ78 ꢁC before
CH3COCl (1.6 ml, 10 mol) was added dropwise with
1
NMR (d8-toluene): H: 2.00 [3H, s, COCH3], 3.84 [5H,
s, C5H5], 7.00 [9H, s, m-/p-C6H5], 7.13 [6H, s, o-C6H5];
19F: ꢀ165.5 [6F, td 3J(F,F) = 22.6 Hz 4J(F,F) = 5.6
Hz, m-C6F5], ꢀ156.92 [3F, s, p-C6F5], ꢀ141.34 [6F, s,
o-C6F5]; 31P: 68.6 [s, PPh3].

4418
G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
Mass Spec.(EI+) m/z(Intensity %) [Assignment]:
612(10) [Fe{HOB(C6F5)3}(CO)]+, 528(10) [HOB
(C6F5)3+], 383(100) [Fe(C5H5)(PPh3)]+.
31.0 [18C, s, P(C6H11)3], 41.2 [1C, s, COCH3], 86.2
[5C, s, C5H5], 126 [3C, s, i-C6F5], 128 [3C, m-C6F5],
129 [6C, p-C6F5], 136 [6C, o-C6F5]; 11B{1H}: ꢀ14.1;
[3F, s, p-C6F5], ꢀ133.5 [6F, d 3J(F,F) = 22.6 Hz, o-
C6F5]; 31P{H}: 80.1 [s, PCy3]. FAB+: m/z (Intensity %)
[Assignment]: 984(1) [Fe(C5H5){MeCOB(C6F5)3}(CO)-
(PCy3)]+, 401(97) [Fe(MeCO)(CO)(PCy3)]+.
3
19F: ꢀ170.0 [6F, d J(F,F) = 22.6 Hz, m-C6F5], ꢀ167.5
4.1.5. Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PMe3)] (8)
NMR scale. A solution of B(C6F5)3 (0.029 g, 0.056
mmol) in C6D6 was added dropwise to a solution of
[Fe(g-C5H5)(COCH3)(CO){P(CH3)3}] (0.015 g, 0.056
mmol) in C6D6. The combined solution was transferred
to a Youngꢀs tap NMR tube and monitored by 1H, 19F,
31P{1H} and 11B{1H} NMR spectroscopy.
Preparative scale. This synthesis was performed in the
same manner as described for 7, using [Fe(g-C5H5)(Me-
CO)(CO)(PMe3)] (0.134 g, 5 mmol) and B(C6F5)3 (0.256
g, 5 mmol). [Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PMe3)]
was obtained as a green powder. Yield 85%. Elemental
Analysis: Found (Calculated) %C 44.4 (44.6), %H 2.6
(2.2). IR (Nujol): 1948 s [C”O stretch], 1520 m [C‚O
4.1.8. [Fe(g-C5H5){MeCOB(C6F5)3}(CO)2] (11)
This synthesis was performed in the same manner as
described for 7, using [Fe(g-C5H5)(MeCO)(CO)2] (0.110
g, 5 mmol) and B(C6F5)3 (0.256 g, 5 mmol). [Fe(g-
C5H5){MeCOB(C6F5)3}(CO)2] was obtained as a green
powder, with 92% yield. Elemental Analysis: Found
(Calculated) %C 44.1 (44.3), %H 1.3 (1.1). IR (Nujol):
2052 s 1994 s [C”O stretch], 1517 m [C‚O stretch].
1
NMR (d8-toluene): H: 2.04 [3H, s, COCH3], 3.88 [5H,
stretch] NMR (d8-toluene): 1H: 0.81 [9H,
d
s, C5H5]; 13C{H}:44.8 [1C, s, COCH3], 89.1 [5C, s,
C5H5]; 19F: ꢀ163.8 [6F, td 3J(F,F) = 22.7 Hz
4J(F,F) = 7.3 Hz, m-C6F5], ꢀ156.9 [3F, t, 3J(F,F) =
1J(H,P) = 6.8 Hz, P(CH3)3], 2.34 [3H, s, COCH3], 3.98
3
[5H, d J(H,P) = 2 Hz, C5H5]; 11B: ꢀ13.9; 19F: ꢀ164.1
3
4
[6F, td J(F,F) = 22.5 Hz J(F,F) = 11.3 Hz, m-C6F5],
3
20.5 Hz, p-C6F5], ꢀ134.5 [6F, d J(F,F) = 20.9 Hz, o-
3
ꢀ157.5 [3F, t J(F,F) = 21.2 Hz, p-C6F5], ꢀ133.2 [6F,
C6F5] FAB+: m/z (Intensity %) [Assignment]: 665(19),
[Fe(CO)2{MeCOB(C6F5)3}]+, 221(88) [Fe(C5H5)(Me-
CO)(CO)2]+.
d
3J(F,F) = 22.5 Hz, o-C6F5]; 31P{H}: 43.1 [s,
P(CH3)3]. FAB+: m/z (Intensity %) [Assignment]:
585(3) [Fe (C5H5){MeCOB(C6F5)3}(PMe3)]+, 444(2)
[Fe(C5H5){MeCOB(C6F5)3}(PMe3)]+.
4.1.9. X-ray crystallography
In each case, a single crystal was selected under inert
atmosphere, encased in perfluoro-polyether oil, and
mounted on the end of a glass fibre. The fibre, secured
on a goniometer head was then placed under a stream
of cold nitrogen maintained at 150 K. Data was col-
lected on an Enraf-Nonius DIP2000 image plate diffrac-
tometer (complex 8) or a Nonius KCCD diffractometer
(complexes 6 and 11), using graphite monochromated
4.1.6. [Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PPhMe2)]
(9)
This synthesis was performed in the same manner as
described for 7, using [Fe(g-C5H5)(MeCO) (CO)
(PPhMe2)] (0.165 g, 5 mmol) and B(C6F5)3 (0.256g,
5 mmol). [Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PPhMe2)]
was obtained as a green-brown powder. Yield: 89%.
Elemental Analysis: Found (Calculated) %C 47.93
(48.46), %H 2.90 (2.26)IR (Nujol): 1952 s [C”O stretch],
1518 m [C‚O stretch]. NMR (d8-toluene): 1H: 1.85 [6H,
d 1J(P,H) = 14 Hz, P(CH3)2], 2.09 [3H, s, COCH3], 3.73
[5H, s, C5H5], 6.78 [3H, s, m-/p-C6H5], 6.88 [2H, s, o-
C6H5]; 19F: ꢀ172.49 [6F, m-C6F5], ꢀ165.83 [3F, t
3J(F,F) = 20.2 Hz, p-C6F5], ꢀ139.9 [6F, d 3J(F,F) =
21.3 Hz, o-C6F5]; 31P{H}:36.7 [s, PPhMe2].
˚
Mo Ka radiation (k = 0.71069 A). The images were
processed with the DENZO and SCALEPACK programs32.
Corrections for Lorentz and polarisation effects were
performed. All solution, refinement, and graphical cal-
culations were performed using the CRYSTALS [36] and
CAMERON [37] software packages. The structures were
solved by direct methods using the SIR92 [38] program
and refined by full-matrix least squares procedure on
F. All non-hydrogen atoms were refined with aniso-
tropic displacement parameters. All hydrogen atoms
were generated and allowed to ride on their correspond-
ing carbon atoms with fixed thermal parameters. An
empirical absorption correction was applied [38]. The
crystallographic data are summarised in Table 3. The
crystal structure of 8 was modelled as disordered over
two positions, with refined occupancies. A 9:1 distribu-
tion of the two enantiomers of 8 suggests that disorder
arises in the crystal packing when 10% of one enantio-
mer occupies sites usually occupied by the other enanti-
omer, and vice-versa.
4.1.7. Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PCy3)](10)
This synthesis was performed in the same manner as
described for 7, using [Fe(g-C5H5)(MeCO)(CO)(PCy3)]
(0.236 g, 5 mmol) and B(C6F5)3 (0.256 g, 5 mmol).
[Fe(g-C5H5){MeCOB(C6F5)3}(CO)(PCy3)] was ob-
tained as a yellow-brown powder. Yield: 85%.
Elemental Analysis: Found (Calculated) %C 54.0
(53.7), %H 5.0 (4.2). IR (Nujol): 2048 s 2005 s [C”O
stretches], 1509 m [C‚O stretch]. NMR (d8-toluene):
1H: 1.52 [33H, broad m, P(C6H11)3], 2.72 [3H, s,
COCH3], 4.23 [5H, s, C5H5]; 13C{H}: 26.5 27.6 30.8

G.D.W. Anderson et al. / Journal of Organometallic Chemistry 689 (2004) 4407–4419
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Acknowledgements
We thank Dr. Neale G. Jones for helpful discussions,
the Oxford Supercomputing Centre for use of its facili-
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ship (S.I.P), the AG Leventis Foundation (I.C.V) and
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