Preparation and characterisation of cobalt (l) acyl compounds

Article abstract of DOI:10.1016/j.jorganchem.2005.02.031

The new cobalt (l) acyl compounds, [Co(PMe₃)(CO) ₃(COMe)] 1, [Co(PPhMe₂)(CO)₃(COMe)] 2, [Co(P(4-Me-C₆H₄)₃)(CO)₃(COMe)] 3 and [Co(P(4-F-C₆H₄)

Full text of DOI:10.1016/j.jorganchem.2005.02.031

Journal of Organometallic Chemistry 690 (2005) 2358–2364
www.elsevier.com/locate/jorganchem
Preparation and characterisation of cobalt (l) acyl compounds
*
Simon A. Llewellyn , Malcolm L.H. Green, Andrew R. Cowley
Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
Received 26 January 2005; revised 23 February 2005; accepted 25 February 2005
Available online 18 April 2005
Abstract
The new cobalt (l) acyl compounds, [Co(PMe3)(CO)3(COMe)] 1, [Co(PPhMe2)(CO)3(COMe)] 2, [Co(P(4-Me-C6H4)3)(CO)3-
(COMe)] 3 and [Co(P(4-F-C6H4)3)(CO)3(COMe)] 4, have been prepared from [Na(Co(CO)4)]. The compound [Co(PCy3)(CO)3-
(COMe)] 5 has been prepared from [Co(PCy3)(CO)3(Me)] 6. The crystal structures of 5 and 6 are reported.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Cobalt; Acyl; Phosphine
1. Introduction
2. Results and discussion
Cobalt (l) alkyl [1] and acyl [2] compounds of the
form [Co(L)(CO)3(R)] and [Co(L)(CO)(COR)] have
been extensively studied [3] with regard to the carbonyl-
ation and decarbonylation process. Their relevance to
commercial applications, most notably in the hydro-
formylation [4,5] of olefins, has ensured continued inter-
est. More recently, such acyl compounds have attracted
renewed interest following the discovery that
[Co(PPh3)(CO)3(COMe)] [6] and [Co(P(o-tolyl)3)-
(COMe)] [7] are pre-catalysts for aziridine/CO copoly-
merisation. However, despite the wealth of cobalt (l)
acyl compounds in the literature [3], there are compara-
tively few examples [2,7,8] of tertiary phosphine substi-
tuted tricarbonyl cobalt (l) acyls containing the simple
[COMe] moiety. Our interest in carbon–carbon bond
formation led us to prepare and characterise a number
of tertiary phosphine substituted cobalt (l) acyl com-
plexes, as described below.
2.1. Synthesis of [Co(L)(CO)3(COMe)] (L = PMe3
(1), PPhMe2 (2), P(4-Me-C6H4)3 (3), P(4-F-C6H4)3
(4), PCy3 (5)) and [Co(PCy3)(CO)3(Me)] (6)
The new cobalt (I) acyl complexes [Co(PMe3)(CO)3-
(COMe)] 1, [Co(PPhMe2)(CO)3(COMe)] 2, [Co(P(4-
Me-C6H4)3)(CO)3(COMe)] 3 and [Co(P(4-F-C6H4)3)-
(CO)3(COMe)] 4 were prepared by treating [Na(Co-
(CO)4)] with an excess of MeI and 1 equivalent the
appropriate tertiary phosphine in diethyl ether at either
0 ꢁC (3–4) or À78 ꢁC (1–2) (Scheme 1).
These syntheses are analogous to those used to pre-
pare [Co(PPh3)(CO)3(COMe)] [2]. Reduction of [Co-
(PCy3)(CO)3]2 over Na/Hg amalgam followed by
treatment with MeI (Scheme 2) gave [Co(PCy3)-
(CO)3(Me)] 6.
The compound [Co(PCy3)(CO)3(COMe)] 5 was syn-
thesised by passing CO through an ethereal solution of
6. Characterisation was achieved by IR and NMR spec-
troscopies, by mass spectrometry and by microanalysis.
These characterising data are summarised in Table 1.
The X-ray crystal structures of compounds 5 and 6 have
been determined.
*
Corresponding author. Tel.: +44 1865 272600; fax: +44 1865
272690.
E-mail address: simon.llewellyn@chem.ox.ac.uk (S.A. Llewellyn).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.02.031

S.A. Llewellyn et al. / Journal of Organometallic Chemistry 690 (2005) 2358–2364
2359
H3C
2.2. Spectroscopic data
O
C
Co
L
OC
OC
The IR spectra in Nujol of compounds 1–5 can be as-
signed by analogy with those of previously reported co-
balt (l) acyl complexes [3]. The compounds 1–5 all
exhibit three bands (see Table 1) in the region 1950–
2050 cmÀ1, assignable to m(CO)terminal. This is consistent
with C3V symmetry with the three terminal carbonyl
groups in the equatorial positions, and with a trans
L, MeI
Na [Co(CO)4]
CO
Diethyl ether
L = PMe3, PPhMe2, P(4-F-C6H4)3, P(4-Me-C6H4)3
Scheme 1. Synthetic route for direct synthesis of cobalt (I) acyl
compounds 1–4.
H3C
O
CH3
Co
PCy3
C
OC
i) Na/Hg,THF
OC
CO
Ether
[Co(PCy3)(CO)3]2
CO
Co
PCy3
CO
ii) MeI
OC
OC
Scheme 2. Synthetic route for compounds 5 and 6.
Table 1
Summary of analytical data for the compounds 1–6
Compounda
NMR datab
2
1 [Co(PMe3)(CO)3(COMe)]
Orange oil
1H: 1.45 [d, JPH = 9.71, 9H, P(CH3)3], 2.64 [s, 3H, C(O)CH3]
31P{1H}:10.87 [s, P(CH3)3]
3
C, 36.3 (36.7); H, 4.4 (4.6); N, 0 (0)
Mass (EI): 262 [M]+
IR: 1686m, 1954 s, 1976 s, 2046 w
13C{1H}: 19.17 [d, JPC = 27.62 Hz, P(CH3)3], 50.90 [d, JPC = 26.93, C(O)CH3],
2
200.03 [br s, CoCO], 240.67 [d, JPC = 32.4, C(O)CH3]
2
2 [Co(PPhMe2)(CO)3(COMe)]
Yellow solid
C, 48.3(48.2); H,4.5(4.4); N 0(0)
1H: 1.73 [d, JPH = 9.24, 6H PPh(CH3)2], 2.67 [s, 3H, C(O)CH3], 7.50 [m, 3H ArH],
7.64 [m, 2H ArH]
31P{1H}:20.10 [s, PPh(CH3)2]
Mass (FI): 296 [M À CO]+; 268 [M À (CO)2]+ 13C{1H}:16.93 [d,1JPC = 28.53, PPh(CH3)2], 49.39 [d, JPC = 25.14, C(O)CH3], 129.08 [m, ArC],
3
1
136.24 [d, JPC = 42.31, ArC] 200.38 [br s, CoCO], 240.68 [d, JPC = 33.43, C(O)CH3]
2
IR 1686 m, 1956 s, 1976 s, 2036 w
2
3
3 [Co(P(4-F-C6H4)3)(CO)3(COMe)]
Yellow solid
C, 55.2 (55.0), H, 3.2 (3.0), N 0 (0)
1H: 2.69 [s, 3H, C(O)CH3], 7.13 (dt, JHH = 8.51, JFH = 1.76, 2H, m-ArH),
7.33 (m, 2H, o-ArH)
19F{1H}:-108.36 [s, P(4-F-C6H4)3]
Mass (FI); 474 [M À CO]+, 445 [M À (CO)2]+ 31P{1H}:48.80 [s, P(4-F-C6H4)3]
3
IR: 1674 m, 1954 s, 1990 s, 2052 w
13C{1H}:49.43 [d, JPC = 28.72, 3H, C(O)CH3], 116.2 [m, ArC], 128.89 [d, J = 3.41, ArC],
129.46 [d, J = 3.41, ArC], 135.0[m, ArC], 162.65 [d, J = 1.97, ArC], 166.00 [d, J = 2.12, ArC],
2
199.68 [d, JPC = 18.98 Co(CO)3], 231.74 [d, JPC = 31.16, C(O)CH3]
2
4 Co(CO)3(P(4-Me-C6H4)3)(COMe)]
Yellow solid
C, 63.7 (63.3) H, 5.0 (5.0) N, 0 (0)
1H :2.37 [s, 9H, 4-CH3-C6H5]; 2.74 [s, 3H, C(O)CH3] ; 7.311[m, 12H, ArH]
31P{1H}:48.63 [s, P(CH3)3]
3
13C{1H}:21.45 [s, 4-CH3-C6H5], 50.32 [d, JPC = 26.28, C(O)CH3], 129.75 [d, JPC = 10.13, ArC],
Mass (FI): 462 [M À CO]+, 434 [M À (CO)2]+ 130.49 [d, JPC = 44.63, ArC], 130.40 [s, ArC], 130.99 [s, ArC], 141.59 [s, ArC],
2
199.80 [br s, CoCO], 238.70[d, JPC = 32.61, C(O)CH3]
IR: 1670 m, 1948 s, 1972 s, 2042 w
4
5 [Co(PCy3)(CO)3(COMe)]
Yellow solid
C, 59.6 (59.2) H, 8.6 (7.8) N, 0 (0)
1H ; 2.75 [d, JPH = 0.58, 3H, C(O)CH3], 1.04-1.89 [m, 33H, P(C6H11)3]
31P{1H}:60.91 [s, P(C6H11)3]
13C{1H}:26.31 [s,P(C6H11)], 27.62 [d, JPC = 10.1, P(C6H11)], 36.70 [d, JPC = 16.6, P(C6H11)],
Mass (FI): 438 [M À CO]+, 410 [M À (CO)2]+ 48.68 [d, JPC = 23.6, C(O)CH3], 201.54 [d, JPC = 15.90, CoCO],
IR: 1682 m, 1946 s, 1969 s, 2038 w
235.55 [d, JPC = 29.06, C(O)CH3]
6 [Co(PCy3)(CO)3(Me)]
Yellow solid
1H ; 0.26 [s,3H, CH3], 1.04-1.89 [m, 33H, P(C6H11)3]
31P{1H}:74.23 [s, P(C6H11)3]
C, 60.7 (60.3) H, 8.3 (8.3) N, 0 (0)
Mass (FI): 438 [M]+
IR: 1948 s, 2022 w
a
13C{1H}:-9.23 [d, JPC = 16.77, CoCH3], 26.31 [s,P(C6H11)], 27.62 [d, JPC = 10.1, P(C6H11)],
36.70 [d, JPC = 16.62, P(C6H11)], 48.68 [d, JPC = 23.6, C(O)CH3], 201.54 [d, JPC = 15.94, CoCO],
235.55 [d, JPC = 29.06, C(O)CH3]
Analytical data given as found (calculated) in %, IR data (cmÀ1) determined for Nujol mulls on KBr discs.
b
The NMR data (CD2Cl2, 298 K), 1–4, (C6D6, 298 K), 5 and 6, given as [multiplicity in Hz, relative intensity, assignment].

2360
S.A. Llewellyn et al. / Journal of Organometallic Chemistry 690 (2005) 2358–2364
position of the acyl and phosphine groups [9], along the
axis. Typically, the two strong bands are assigned to the
E mode and the weak band is assigned to the A1 totally
symmetric stretch [10]. In all instances, the E band is
split into two separate bands and this has been attrib-
uted to hindered rotation of the acyl group about the
Co–C bond, due to dp-pp bonding between the acyl
group and the cobalt centre [11]. A further band as-
signed to m(CO)acyl is observed between 1670 and
1686 cmÀ1, the lower stretching frequency reflecting
the lower bond order of the COacyl compared with the
ues were in the range 23–28 Hz. Coupling of the 31P{H}
nucleus to the carbon nucleus of COacyl was also ob-
served in all instances (2JPC = 29–33 Hz). Curiously,
the 13C{H} resonances attributed to the COterminal for
the compounds 1–4 showed broad singlets. This may
be due to quadropolar broadening. By contrast,
for compound 5 the 13C{H} resonance attributed to
COterminal is observed as a doublet, indicating coupling
with the 31P{H} nucleus. In this series of compounds,
the COterminal 13C{H} resonances are less susceptible
than the COacyl13C{H} resonances to steric and elec-
tronic influences of the appended ligand. The former
varying by a maximum of 1.5 ppm for the compounds
1–5, whereas the later showed variation of ca. 10 ppm.
This reflects the trans influence of the mutually axial
ligand and acyl group.
COterminal
.
The 1H NMR spectra for compounds 1–5 show char-
acteristic resonances between d 2.64 and d 2.76, which
are assigned to the acyl methyl group. The 13C{H} for
1–5 show characteristic COterminal (ca. d 200), COacyl
(ca. d 240) and CH3 (ca. d 50) resonances. In all in-
stances, the coupling of the 31P{H} nucleus to the
In all instances FI or ES+ spectra of compounds 1–5
showed either the [M]+ or [M À CO]+ and [M À 2CO]+
ions.
3
methyl carbon of the trans acyl was observed. JPC val-
Table 2
Summary of crystallographic data for the compounds 5 and 6
5
6
Empirical formula
Formula weight
Temperature (K)
C
23H36CoO4P
C22H36CoO3P
438.43
150
466.44
150
˚
Wavelength (A)
0.71073
Monoclinic
P 21/n
0.71073
Monoclinic
P 21/n
Crystal system
Space group
Unit cell dimensions
˚
a (A)
14.9641(2)
10.4925(2)
20.0898(3)
11.5044(2)
20.6298(3)
90
˚
b (A)
˚
c (A)
16.4305(3)
90
a (ꢁ)
b (ꢁ)
c (ꢁ)
113.5830(8)
90
2364.31(7)
111.0245(6)
90
3
˚
Cell volume (A )
4450.56(12)
8
1.309
Z
4
1.310
Calculated density (mg/m3)
Absorption coefficient (mmÀ1
F0 0 0
)
0.818
992
0.862
1872
Crystal size (mm)
Description of crystal
Absorption correction
0.16 · 0.24 · 0.24
Pale-yellow fragment
Semi-empirical from equivalent reflections
0.12 · 0.14 · 0.14
Pale-brown block
Semi-empirical from equivalent reflections
Transmission coefficients (min, max)
h Range for data collection (ꢁ)
Index ranges
0.82, 0.88
5.0 6 h 6 27.5
0.89, 0.90
5.0 6 h 6 27.5
À19 6 h 6 17, 0 6 k 6 13, 0 6 l 6 21
À26 6 h 6 24, À14 6 k 6 14, 0 6 l 6 26
Reflections measured
Unique reflections
Rint
24020
5649
20105
10617
0.036
3918
0.082
6644
Observed reflections (I > 3r (I))
Refinement method
Parameters refined
Weighting scheme
Goodness-of-fit
Full-matrix least-squares on F
262
Full-matrix least-squares on F
512
Chebychev 3-term polynomial
1.0837
Chebychev 3-term polynomial
1.0324
R
0.0266
0.0293
0.0490
0.0525
wR
˚
Residual electron density (min, max) (eA
À3
)
À0.27, 0.35
À0.55, 0.59

S.A. Llewellyn et al. / Journal of Organometallic Chemistry 690 (2005) 2358–2364
2361
Table 4
˚
Selected bond lengths (A) of cobalt (l) acyl compounds
2.3. X-ray crystallography of 5 and 6
˚
Bond lengths (A)
Compound
Crystals suitable for X-ray structure determination
were grown by cooling saturated pentane solutions of
5 and 6 to À80 ꢁC. Selected structural parameters for
compounds 5 and 6 are given in Table 2. A view of
the X-ray crystal structure of 5 is given in Fig. 1. Se-
lected bond lengths and angles for compound 5 are gi-
ven in Table 3. Table 4 lists selected bond lengths and
angles of similar cobalt (l) acyl complexes. The com-
pound 5 shows a distorted trigonal bipyramidal struc-
ture with three carbonyl groups in equatorial
positions, and the PCy3 and acyl groups occupying
mutually axial positions.
Co–Cacyl
Co–P
C@O(acyl)
[Co(PCy3)(CO)3(COMe)]
[Co(PPh3)(CO)3(COMe)] [7]
2.0149(17) 2.2753(4) 1.194(2)
1.988(6)
[Co(PPh3)(CO)3(C(O)CH2Cl)] [13] 1.999 (5)
2.249(4)
2.25(4)
2.229(1)
2.234a
1.195(7)
1.180a
[Co(PPh3)(CO)3(C(O)OnBu)] [10]
[Co(PPh3)(CO)3(C(O)OMe)] [14]
1.967(2)
1.976a
120.1(2)
1.196a
a
Esd not given.
The equatorial CO groups are slightly bent towards
the axial acyl group, with an average Ccarbonyl–Co–Cacyl
bond angle of 87.4ꢁ. This can be attributed to the more
sterically demanding nature of the phosphine ligand
compared with the smaller trans acyl group. A similar,
though more pronounced effect has been noted in
[Co(PPh3)(CO)3H] and [Co(PCy3)(CO)3H] [12] with
average C–Co–H bond angles of 81.6ꢁ and 81ꢁ, respec-
tively. In the related compound [Co(PPh3)(CO)3-
(COMe)] [7], the average Ccarbonyl–Co–Cacyl angle is
87.9ꢁ.
The crystal structure of 6 is somewhat unusual in that
two crystallographically distinct molecules are observed
in the unit cell. Views of these molecules are given in
Figs. 2a and b. Selected bond lengths and angles for 6
are given in Table 5. The distinct molecules differ by
the orientation of one of the cyclohexyl groups
(C(11)–C(16)/C(33)–C(39)), but the two molecules are
otherwise related by a non-crystallographic1 180ꢁ rota-
tion. A similar occurrence has been reported by Zucchi
t
et al. [15] in [Co(PPh3)(CO)3(CH2C6H4 Bu)], who noted
that this effect may be correlated to the unexpected
stereochemistry observed for [Co(PPh3)(CO)3(CH2(O)-
COR)] complexes. However, since [Co(PPh3)(CO)3-
t
(CH2C6H4 Bu)] and [Co(PCy3)(CO)3(Me)] both contain
Fig. 1. ORTEP diagram of the molecular structure of compound 5.
Thermal ellipsoids are drawn at 40%. Hydrogen atoms have been
omitted for clarity.
symmetrical organic ligands a direct comparison is not
possible. Compound 6 shows the expected distorted tri-
gonal bipyramidal geometry, with three terminal car-
bonyl groups in the equatorial positions, and the alkyl
and phosphine ligands in axial sites. The terminal car-
bonyl groups are bent towards the less sterically
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for 5
demanding methyl group, with an average Ccarbonyl
–
Compound 5
Co–Calkyl angle of 84.25ꢁ. This indicates an approxi-
mately 6ꢁ bend towards the alkyl group presumably
due to the more sterically demanding PCy3 ligand. In
general, the Co–Calkyl and Co–P bonds show the most
sensitivity to changes in the tertiary phosphine and or-
ganic ligand [15]. The lack of crystallinity/stability of
methyl substituted cobalt compounds makes direct com-
parisons difficult. However, Table 6 lists selected bond
lengths and angles for related cobalt (l) alkyl com-
Co(1)–C(1)
Co(1)–C(2)
Co(1)–C(3)
Co(1)–C(4)
Co(1)–P(1)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
1.8014(18)
1.7726(17)
1.7755(18)
2.0149(17)
2.2753(4)
1.141(2)
1.147(2)
1.150(2)
1.194(2)
C(4)–Co(1)–P(1)
C(1)–Co(1)–C(4)
C(2)–Co(1)–C(4)
C(3)–Co(1)–C(4)
172.95(6)
˚
pounds. In the compound 6, the 2.081(3) A Co–Calkyl
90.67(8)
84.52(7)
86.59(7)
1
i.e., not a symmetry element of the unit cell.

2362
S.A. Llewellyn et al. / Journal of Organometallic Chemistry 690 (2005) 2358–2364
Table 5
Selected bond lengths (A) and angles (ꢁ) for compound 6
˚
Molecule a
Molecule b
Co(1)–C(4)
Co(1)–P(1)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
Co(1)–C(1)
Co(1)–C(2)
Co(1)–C(3)
2.081(3)
2.2291(8)
1.131(4)
1.149(4)
1.146(4)
1.792(3)
1.772(3)
1.781(3)
Co(2)–C(26)
Co(2)–P(2)
C(23)–O(4)
C(24)–O(5)
C(25)–O(6)
Co(2)–C(23)
Co(2)–C(24)
Co(2)–C(25)
2.081(3)
2.2311(8)
1.136(4)
1.139(4)
1.141(4)
1.788(3)
1.783(4)
1.779(4)
C(4)–Co(1)–P(1)
C(1)–Co(1)–C(4)
C(2)–Co(1)–C(4)
C(3)–Co(1)–C(4)
175.03(12)
84.06(15)
85.90(15)
82.81(16)
C(26)–Co(2)–P(2)
C(23)–Co(2)–C(26)
C(24)–Co(2)–C(26)
C(25)–Co(2)–C(26)
177.89(14)
84.02(17)
84.43(17)
84.10(17)
The 2.2291(8)/2.2311(8) Co–P bond length is in the typ-
ical range observed for this type of compound.
3. Conclusion
New cobalt (l) acyl compounds, [Co(L)(CO)3-
(COMe)] (L = PMe3 1, PPhMe2 2, P(4-F-C6H4)3 3,
P(4-Me-C6H4)3 4, PCy3 5) and the alkyl complex
[Co(PCy3)(CO)3(Me)] 6 have been synthesised and
characterised.
4. Experimental
4.1. General procedures
All manipulations were carried out under N2, using
conventional Schlenk-line techniques. PMe3 [18], P(4-
Me-C6H4)3 [19] and [Na(Co(CO)4)] [20] were prepared
according to the literature methods. The compound
Co2(CO)8 was purchased from Strem and used as re-
ceived. PPh3, PPhMe2, P(4-F-C6H4)3, PCy3 and MeI
were purchased from Aldrich Chemical Co. and used
as received. [Co(PCy3)(CO)3]2 was synthesised by reflux-
ing Co2(CO)8 and PCy3 in toluene. 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, (1H and 13C,
d = 0), or externally BF3 Æ Et2O (11B, d = 0), H3PO4
Fig. 2. (a) ORTEP diagram of distinct molecule a of compound 6.
Thermal ellipsoids are drawn at 40%. Hydrogen atoms have been
omitted for clarity. (b) ORTEP diagram of distinct molecule b of
compound 6. Thermal ellipsoids are drawn at 40%. Hydrogen atoms
have been omitted for clarity.
bond is longer than is observed in most of the character-
ised PPh3 containing cobalt (l) alkyls, though shorter
t
than that observed for [Co(PPh3)(CO)3(CH2C6H4 Bu)].
Table 6
Selected bond lengths (A) of cobalt (l) alkyl compounds
˚
˚
Bond lengths (A)
Compound
Co–Calkyl
Co–P
C@O(terminal) ave
[Co(PCy3)(CO)3(Me)]
[Co(PPh3)(CO)3(CH2Cl)] [13]
2.081(3), 2.081(3)
2.022(3)
2.2291(8), 2.2311(8)
2.223(1)
1.142(4), 1.139(4)
1.138(3)
t
[Co(PPh3)(CO)3(CH2C6H4 Bu)] [15]
2.120(4), 2.136(5)
2.011(2)
1.953(6)
2.2213(13), 2.313(13)
2.2218(6)
2.235(1)
1.141(6), 1.137(6)
1.140(3)
1.174(7)
[Co(PPh3)(CO)3(C6F5)] [16]
[Co(PPh3)(CO)3(CF3)] [17]

S.A. Llewellyn et al. / Journal of Organometallic Chemistry 690 (2005) 2358–2364
2363
(31P, d = 0) and CFCl3 (19F, d = 0) and chemical shifts
were reported with respect to SiMe4. All chemical shifts
are quoted in d (ppm) and coupling constants in Hz.
Infrared spectra were recorded on a Perkin–Elmer
1600 FTIR. Elemental analyses and mass spectra were
provided by the Microanalytical Services of the Inor-
ganic Chemistry Laboratory, Oxford.
left a pale yellow powder, which was dried under vac-
uum. Yield = 548 mg (43.2%).
4.5. Preparation of [Co(P(4-Me-C6H4)3)-
(CO)3(COMe)] (4)
A solution of Na[Co(CO)4] (650 mg, 3.29 mmol) in
diethyl ether (40 ml) was cooled to 0 ꢁC. A solution of
P(4-Me-C6H4)3 (1000 mg, 3.29 mmol) in diethyl ether
(20 ml) was then added and the resulting solution left
stirring for 5 min. Neat MeI (1.6 ml, 25.4 mmol) was
then added and the solution left stirring at 0 ꢁC for 1 h
during which a white precipitate formed. The resulting
mixture was filtered and solvent was removed under re-
duced pressure. This resulting yellow solid was dissolved
in diethyl ether (10 ml) and filtered. Removal of solvents
under reduced pressure left a yellow solid that was
recrystallised from diethyl ether/pentane at À78 ꢁC and
dried under vacuum. Yield = 516 mg (32.3%).
4.2. Preparation of [Co(PMe3)(CO)3(COMe)] (1)
The compound Na[Co(CO)4] (500 mg, 2.54 mmol) in
diethyl ether (40 ml) at À78 ꢁC was treated with neat
PMe3 (0.32 ml, 2.54 mmol). The mixture was allowed
to warm to room temperature under stirring for
20 min and was then again cooled to À78 ꢁC and neat
MeI (1.6 ml, 25.4 mmol) was added. The solution was
allowed to warm to room temperature under stirring,
a white precipitate formed. After 30 min of stirring,
the mixture was filtered and solvents were removed un-
der reduced pressure to leave an oily yellow solid. This
was dissolved in diethyl ether (20 ml) and cooled to
À78 ꢁC. Pentane was added (10 ml) and yellow crystals
separated. These were isolated by filtration and dried
in vacuo. On warming to room temperature, the crystals
melted to give 7 as an orange oil. Yield = 269 mg
(40.5%).
4.6. Preparation of [Co(PCy3)(CO)3(COMe)] (5)
Carbon monoxide was passed through a solution of
[Co(PCy3)(CO)3(Me)] (100 mg, 0.228 mmol) in diethyl
ether (30 ml). Solvent was removed in vacuo and the
resulting yellow solid was recrystallised from pentane
at À80 ꢁC to give the desired product as yellow crystals.
These were isolated by filtration and dried under vac-
uum to yield 95.2 mg of 6. Crystals suitable for single
crystal X-ray diffraction were grown by cooling a satu-
rated pentane solution to À80 ꢁC. Yield = 95.2 mg
(89.5%).
4.3. Preparation of [Co(PPhMe2)(CO)3(COMe)] (2)
A solution of Na[Co(CO)4] (500 mg, 2.54 mmol) in
diethyl ether (40 ml) was cooled to À78 ꢁC. Neat
PPhMe2 (0.46 ml, 2.54 mmol) was added and the mix-
ture allowed to warm to room temperature under stir-
ring for 20 min. The solution was then cooled to
À78 ꢁC and neat MeI (1.6 ml, 25.4 mmol) was added.
The solution was again allowed to warm to room tem-
perature under stirring. During this time a white precip-
itate formed and the solution turned brown. After 1 h
stirring the mixture was filtered and solvents were re-
moved under reduced pressure to leave sticky brown
oil, which was recrystallised from pentane at À78 ꢁC
to give a yellow/brown solid. Yield = 411 mg (50.1%).
4.7. Preparation of [Co(PCy3)(CO)3(Me)] (6)
A solution of [Co(PCy3)(CO)3]2 (600 mg, 0.88 mmol)
in THF (20 ml) was stirred over excess of Na/Hg amal-
gam for 17 h. The resulting suspension was allowed to
settle before being transferred by cannular. MeI
(1.5 ml) was added to resulting brown solution, which
was stirred for 3 h. Removal of solvents yielded a dirty
brown solid. This was extracted into pentane and cooled
to À80 ꢁC. The resulting yellow crystalline solid was iso-
lated by filtration and dried under vacuum to yield
300 mg of 5. Crystals suitable for single crystal X-ray
diffraction were grown by cooling a saturated pentane
solution to À80 ꢁC. Yield = 300 mg (38.9%).
4.4. Preparation of [Co(P(4-F-C6H4)3)-
(CO)3(COMe)] (3)
A solution of Na[Co(CO)4] (500 mg, 2.54 mmol) in
THF (40 ml) was cooled to 0 ꢁC and P(4-F-C6H4)3
(802 mg, 2.54 mmol) was then added in one portion.
The mixture was stirred for 10 min during which time
the solution darkened. MeI (1.6 ml, 25.4 mmol) was
then added, leading to the formation of an orange solu-
tion. This was left stirring for 17 h and allowed to warm
to room temperature, leading to the formation of a pale
yellow mixture. This was filtered, leaving a pale yellow
solid. Recrystallisation from THF/pentane at À78 ꢁC
5. 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. Data were collected
at 150 K using an Enraf-Nonius KappaCCD diffractom-
eter (graphite-monochromated MoKa radiation,

2364
S.A. Llewellyn et al. / Journal of Organometallic Chemistry 690 (2005) 2358–2364
˚
k = 0.71073 A), as summarised in Table 2. The images
were processed with the DENZO and SCALEPACK programs
[21]. Corrections for all solution, refinement, and graph-
ical calculations were performed using the CRYSTALS [22]
program suite. The structures were solved by direct
methods using the SIR 92 [23] program and refined by
full-matrix least squares procedure on F. All non-hydro-
gen atoms were refined with anisotropic displacement
parameters. All hydrogen atoms were generated and al-
lowed to ride on their corresponding carbon atoms with
fixed thermal parameters. Data for compound 6 indi-
cated twinning of the crystal. The contributions of the
two twin components to those reflections for which both
diffraction patterns overlapped were included in the
refinement, giving volume fractions of 0.754(12) and
0.246(12). The methyl hydrogen atoms were located in
a difference Fourier map and their coordinates and iso-
tropic thermal parameters subsequently refined.
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We thank the EPSRC for a grant (S.A.L).