Preparation and molecular structures of benzyl- and phenylacetylcobalt carbonyls

Article abstract of DOI:10.1016/S0022-328X(99)00157-6

The benzyl-type cobalt carbonyl complexes (para-^tBuC₆H₄CH₂)Co(CO) ₃PPh₃ (4) and [para-ClC₆H₄CH₂C(O)]Co(CO)₃PPh ₃ (5) were prepared and

Full text of DOI:10.1016/S0022-328X(99)00157-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 586 (1999) 61–69
Preparation and molecular structures of benzyl- and
phenylacetylcobalt carbonylsꢀ
Claudia Zucchi a,*, Andrea Cornia a, Roland Boese b, Erich Kleinpeter c,
Howard Alper d, Gyula Pa´lyi a
a Department of Chemistry, Uni6ersity of Modena, Via Campi 183, I-41100 Modena, Italy
b Institute of Inorganic Chemistry, Uni6ersity of Essen, Uni6ersita¨tstrasse 5/7, D-45117 Essen, Germany
c Department of Chemistry, Uni6ersity of Potsdam Am Neuen Palais 10, D-14469 Potsdam, Germany
d Department of Chemistry, Uni6ersity of Ottawa, 10 Marie Curie, Ottawa, Ont K1N 6N5, Canada
Received 12 November 1998; received in revised form 15 February 1999
Dedicated to: Professor La´szlo´ Marko´ (Veszpre´m, Hungary) on the occasion of his 70th birthday.
Abstract
The benzyl-type cobalt carbonyl complexes (para-tBuC6H4CH2)Co(CO)3PPh3 (4) and [para-ClC6H4CH2C(O)]Co(CO)3PPh3 (5)
were prepared and characterized by analyses, spectra and X-ray single-crystal diffraction. The overall structures both of the
alkylcobalt-type 4 and the acylcobalt-type 5 display trigonal bipyramidal geometry, with the two noncarbonyl ligands in the two
axial positions. The relevance of the stereochemistry of complexes 4 and 5 to the supposed mechanism of the CO insertion/dein-
sertion on cobalt is discussed. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Molecular structures; Benzylcobalt carbonyls; Phenylacetylcobalt carbonyls
+CO
RCo(CO)4−XCORC(O)Co(CO)4
1. Introduction
(1)
2
1
The inventory of experimental and theoretical back-
ground behind the generally accepted mechanism of
equilibrium (1) consists of:
1. Early experiments of Heck [4] and Marko´ [5]
providing proofs for the intermediacy of alkyl- and
acylcobalt tetracarbonyls 1 and 2 in carbonylations
catalyzed by cobalt.
2. Kinetic studies of Marko´ and Ungva´ry [6] showing
quantitative details of reaction (1), of the formation
of complexes 1 and of subsequent formation of
complexes 2.
Carbon–carbon bond forming processes figure
prominently in transition metal-catalyzed carbonyla-
tion and in hydroformylation reactions, and are one
of the main driving forces behind the explosive devel-
opment of transition metalorganic chemistry in the
last decades [2]. It is surprising, in this context, to
note the scarcity of publications on mechanistic spec-
ulations about the C–C bond making step (the ‘inser-
tion’ of CO) in reactions catalyzed by cobalt (Eq.
(1)), which is one of the earliest and even nowadays a
widely used catalyst for these reactions [3]:
3. Preparative and spectroscopic studies of Cotton and
Calderazzo [7] as well as of Flood [8] with alkyl- and
acyl- manganese pentacarbonyls, suggesting the mi-
gratory character of the CO insertion into the
metal–Calkyl bond (intermediate 3):
ꢀ Alkylcobalt carbonyls, Part 13 (for Part 12 see Ref. [1]).
* Corresponding author. Tel: +39-59-378443; fax: +39-59-
373543.
E-mail address: zucchi@unimo.it (C. Zucchi)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00157-6

62
C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
2. Experimental
Starting materials were of commercial origin, their
purity was determined by GLC, and they were distilled,
if necessary, before use. Dicobalt octacarbonyl,
Co2(CO)8, was made by the method of Marko´ et al. [14].
All operations were performed according to standard
Schlenk techniques [15].
IR spectra were recorded with a Bruker FT-IR IFS113
V spectrometer, 1H- 13C- and 31P-NMR experiments were
performed with a Bruker AMX-400 instrument.
4. EHMO calculations of Hoffmann [9] supporting the
involvement of 3 in the mechanism.
5. Preparative and isotopic studies on cobalt complexes
performed by Marko´, Bor et al. [10] providing proofs for
5.1. the equilibrium nature of equation (1) and
5.2. showing that the ‘inserted’ CO is one of the
carbonyl ligands already coordinated to Co.
6. The recent report of Kova´cs, Szalontai and Ungva´ry
[11] on the spectroscopic detection of cis-
MeOC(O)CH2Co(CO)3PPh3 providing the first direct
evidence for the alkyl-migratory character of CO
‘insertion’ on Co, while all other reports indicate
axial-1 and -2 as well as trans-RCo(CO)3PPh3 or
RC(O)Co(CO)3PPh3 isomers [1,10b,12].
2.1. Preparation of benzyl- and phenylacetylcobalt
tetracarbonyls
Essentially the procedures described in Refs. [10,16]
were followed.
Consensus has been reached assuming [13] that in all
cases, except (6), the primary (equatorial or cis) isomers
were undergoing a fast rearrangement both in carbony-
lation or in decarbonylation. The complexity of the
picture is shown in Scheme 1.
Prompted by the encouraging results under (5) and (6),
we prepared and structurally characterized two benzyl-
derived cobalt carbonyls, an alkyl-derivative: para-
tBuC6H4CH2Co(CO)3PPh3 (4) and an acyl-derivative:
para-ClC6H4CH2C(O)Co(CO)3PPh3 (5). The results of
this study are reported here.
2.1.1. [para-(CH3)3CC6H4CH2]Co(CO)3PPh3 (4)
Co2(CO)8 (342 mg,
1 mmol) was reduced to
Na[Co(CO)4] in 20 ml of Et2O by Na/Hg. This solution
of Na[Co(CO)4] (2 mmol) was filtered into a Schlenk
vessel under Ar atmosphere and then cooled to −20°C.
To this cold solution, while stirred, para-tbutylbenzyl
chloride (330 mg, 0.39 ml, 2 mmol) was added at once.
The formation of a white precipitate (NaCl) was ob-
served immediately. The stirring was continued for 4 h.
The gradual development of a yellow and then a brown
color was observed. After this period the solution was left
Scheme 1. Full arrows, experimentally proven; dotted arrows, supposed.

C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
63
Table 1a
CC6H4CH2Co(CO)3PPh3). This product was character-
ized by spectra (Table 1(a–c)), elemental analyses and
single crystal X ray diffraction.
FT-IR of the intermediates and of complexes 4 and 5 [(h3-ben-
zyl)Co(CO)3 (a), RCo(CO)4 (b) and RC(O)Co(CO)4 (c)] (n-hexane)
Anal. Calc. for C32H30CoO3P: C, 69.6; H, 5.5; Co,
10.7. Found: C, 69.0; H, 5.5; Co, 10.4%.
4a
4b
4c
5a
5b
5c
1975 s, 1989 s, 2053 s
2014 vs, 2031 m, 2097 m
1746 m, 2043 s, 2105 m
1972 s, ca. 1990 s, 2054 vs
2013 vs, br, 2035 s, 2099 m
1742 m, 2020 vs, br, 2107 m
2.1.1.1. X-ray diffraction structure determination of
complex (4). C32H30CoO3P, crystal dimensions 0.34×
0.25×0.18 mm3, measured on a Siemens SMART dif-
fractometer with Mo–Ka radiation at T=298 K. Data
collection of 12 125 intensities (2qmax=51.47°), 8464
independent (Rmerg=0.0246), 6796 observed [Fo]
4|(F)], structure solution with direct methods
(Siemens-SHELXS) and refinement on F2 (Siemens-
SHELXTL 5.03) (667 parameters), the hydrogen atom
positions were calculated and refined as rigid groups
with the 1.2-fold (1.5 for methyl groups) Uiso-values of
the corresponding C-atoms. R1=0.0610, wR2 (all
data)=0.1815, w−1=|2(F2o)+(0.1P)2+2.47P, where
4
5
1957 vs, 1983 s, 2049 m
ca. 1725 br, vw, 1964 s, 1988 s, 2051 w
to warm to room temperature (r.t.) and then stirring
was continued for 1 h at r.t. A sample was taken (1 ml),
and analyzed by IR spectroscopy in the 1600–2200
cm−1 range. The analysis showed the disappearance of
the strong band of [Co(CO)4]− and the appearance of
a band system which corresponded to a mixture of
(h3-benzyl)Co(CO)3 (4a), RCo(CO)4 (4b) and
RC(O)Co(CO)4 (4c) complexes in a ratio of ca.
60:30:10% (in a separate experiment these complexes
P=[max (F2o)+(2F2c)]/3, maximum residual electron
−3
,
density 0.903 e A
.
Drawing was performed with the ORTEP plotting
program [17]. The crystal structure determination con-
ditions are given in Table 2, final fractional coordinates
and equivalent thermal parameters are shown in Table
3, while selected interatomic distances and angles are
collected in Table 4. Tables showing full listings of
interatomic distances and angles, anisotropic thermal
parameters, final hydrogen coordinates and equivalent
thermal parameters are available as supplementary ma-
terial. For availability of deposited crystallographic
data, see Section 4.
were characterized by IR, H- and 13C-NMR spectra in
1
low-polarity solvents, see Table 1(a–c)). The solution
was then filtered and to the filtrate, containing a total
of ca. 2 mmol of these mononuclear cobalt complexes
triphenylphosphine, P(C6H5)3 (524 mg, 2 mmol) was
added at once. Stirring was continued for an additional
3 h during which period a gradual color change from
brown to yellow was observed. At this point a sample
was taken and analyzed by 31P-NMR spectroscopy.
The two bands observed were assigned to
RCo(CO)3PR3 (56.2 ppm) and RC(O)Co(CO)3PR3
(47.2 ppm) type complexes on the basis of literature
analogies [11a], indicating a ca. 2:1 ratio of these prod-
ucts. Then stirring was continued at r.t. for 6 h during
which time the spectroscopic analysis showed a gradual
decarbonylation of the acyl-compound. At the end of
this period the solvent was evaporated. The crude
product was recrystallized from Et2O with layered n-
hexane. The yield of the analytically pure (twice recrys-
tallized) product was 818 mg (74% as (CH3)3-
2.1.2. (para-ClC6H4CH2)COCo(CO)3PPh3 (5)
Na[Co(CO)4] (4 mmol) was prepared in 60 ml of
Et2O and to this solution 4-chlorobenzylchloride (612
mg, 3.8 mmol) was added under a CO atmosphere at
r.t. This solution was stirred and samples were taken
after each 1 h and were analyzed by IR spectroscopy.
The IR w(CꢀO) spectra indicated after 4 h the disap-
pearance of the strong band of [Co(CO)4]− and a band
Table 1b
1H- and 13C-NMR spectra of the intermediates of complexes 4 and 5 (benzene-d6)
C(CH3)3
p-C
m-CH
o-CH
Cipso
CH2
COcoord.
204.1
COacyl
4a
4b
4c
5b
5c
1H
1.13
6.23, 6.80
123.4, 125.7
7.24–7.05
129.5
7.24–7.05
13C
1H
31.3, 31.2, 30.6, 48.6
1.24
121.9
97.1
2.4
13C
1H
151.3
1.19
7.24–7.05
4.20
13C
1H
6.98
129.0
7.02
6.87
129.7
6.65
131.0
2.9
18.4
3.73
67.9
13C
1H
131.6
133.7
146.0
131.8
198.7
196.6
13C
128.9
223.7

64
C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
Table 2
Crystal data and structure refinement for complex 4
Empirical formula
Formula weight
Temperature (K)
C32H30CoO3P
552.46
298(2)
,
Wavelength (A)
0.71073
Triclinic
Crystal system
Space group
(
P1
Unit cell dimensions
,
a (A)
13.8850(3)
14.1339(2)
15.7905(3)
,
b (A)
,
c (A)
h (°)
i (°)
101.1189(8)
108.8935(5)
90.0641(7)
2870.12(9)
4
1.279
0.683
1152
k (°)
3
,
V (A )
Z
Dcalc. (g cm−3
)
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
q range for data collection (°)
0.34×0.25×0.18
1.81–25.73
Index ranges
−85hB16, −175k516,
−145l519
12 125
8464 [Rint=0.0246]
Full-matrix least-squares on
F2
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I))
R indices (all data)
8463/0/667
1.079
Rl=0.0610, wR2=0.1555
Rl=0.0764, wR2=0.1816
Largest difference peak and hole 0.903 and −0.260
−3
,
(e A
)
system which corresponds approximately to the mixture
of 20% RCo(CO)4 (5b) and 80% RC(O)Co(CO)4 (5c).
Then, to the reaction mixture, PPh3 (1.48 g, 4 mmol)
was added at once, with stirring. Vigorous CO evolu-
tion was observed for 10–20 min while the reddish
brown color of the solution changed to yellow. The
resulting solution was then filtered and chilled to −
80°C and an equal volume of cold (−80°C) n-pentane
was added. A yellow microcrystalline substance was
obtained, yield 1.44 g (68%) which was purified by
recrystallization from its saturated solution in Et2O by
diffusion of n-hexane, yield 870 mg (41%). The recrys-
tallized material was then characterized.
Anal. Calc. for C29H21O4ClCoP: C, 62.3; H, 3.8; Cl,
6.3; Co, 10.5; P, 5.5. Found: C, 62.5; H, 3.9; Cl, 6.3;
Co, 10.4; P, 5.4%.
The spectra of complex 5 together with those of
intermediates 5a, 5b and 5c are shown in Table 1(a–c).
2.1.2.1. X-ray structure determination of complex 5. The
intensity data for {(4-chlorophenyl)acetyl}cobalt tricar-
bonyl triphenylphosphine (5) were collected at r.t. on a
Siemens P4/RA automatic diffractometer with graphite-
monochromated Mo–Ka radiation. Details on crystal

C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
65
Table 3
Table 3
Atomic coordinates (×10−4) and equivalent isotropic displacement
Atomic coordinates (×10−4) and equivalent isotropic displace-
2
3
2
3
,
ment parameters (A ×10 ) for complex 4
,
parameters (A ×10 ) for complex 4
a
a
x
y
z
Ueq
x
y
z
Ueq
C(20%)
C(21%)
C(22%)
C(23%)
C(24%)
C(25%)
C(26%)
C(27%)
C(28%)
C(29%)
C(30%)
C(31%)
C(32%)
−8870(4)
−7046(3)
−7406(4)
−6906(5)
−6059(5)
−5680(5)
−6181(4)
−8934(3)
−8971(5)
−9837(7)
3902(4)
2161(3)
1975(4)
1381(4)
961(4)
1141(4)
1737(3)
2234(4)
1226(4)
690(6)
127(3)
−154(3)
524(3)
1102(4)
1011(4)
347(4)
72(1)
56(1)
75(1)
89(2)
86(2)
85(2)
68(1)
66(1)
88(2)
125(3)
139(4)
125(3)
90(2)
Co(1)
P(1)
C(1)
O(1)
C(2)
O(2)
C(3)
O(3)
C(4)
C(5)
C(6)
C(7)
C(8)
−5923(1)
−6738(1)
−6765(4)
−7298(3)
−4784(4)
−4043(4)
−6182(3)
−6365(3)
−5101(3)
−4249(3)
−4381(3)
−3592(4)
−2627(3)
−2488(4)
−3279(3)
−1755(4)
−799(6)
−1539(6)
−2107(6)
−6448(3)
−6303(4)
−6100(5)
−6049(5)
−6201(5)
−6396(4)
−8133(4)
−8614(4)
−9676(5)
−10 238(6)
−9750(6)
−8713(5)
−6419(5)
−7131(6)
−6843(11)
−5856(13)
−5130(9)
−5420(6)
−7003(1)
−7729(1)
−5766(4)
−4952(3)
−7890(4)
−8461(3)
−7318(3)
−7546(3)
−6321(4)
−6978(3)
−6918(4)
−7493(4)
−8169(4)
−8237(4)
−7656(4)
−8820(5)
−9297(11)
−8106(8)
−9411(13)
−8006(3)
−7293(4)
−7419(5)
−8281(6)
−8994(5)
−599(1)
−3809(1)
−4187(1)
−4743(3)
−5316(2)
−3855(4)
−3880(4)
−2759(3)
−2093(3)
−3481(3)
−2604(3)
−1811(3)
−985(3)
−902(3)
−1694(3)
−2524(3)
19(3)
54(1)
58(1)
63(1)
92(1)
77(1)
129(2)
62(1)
90(1)
60(1)
55(1)
65(1)
68(1)
62(1)
66(1)
63(1)
76(1)
155(4)
114(2)
112(2)
61(1)
79(2)
90(2)
92(2)
90(2)
71(1)
72(1)
91(2)
118(3)
135(4)
132(3)
97(2)
74(2)
101(2)
147(4)
157(5)
138(4)
102(2)
53(1)
53(1)
62(1)
87(1)
69(1)
110(2)
62(1)
86(1)
66(1)
61(1)
73(1)
80(2)
70(1)
76(1)
73(1)
98(2)
311(10)
177(4)
372(12)
59(1)
72(1)
94(2)
98(2)
88(2)
−2051(1)
−151(3)
169(3)
−1132(4)
−1465(3)
−308(3)
−132(3)
761(3)
970(3)
1479(3)
1692(3)
1376(3)
880(3)
682(3)
1593(4)
1103(7)
2683(5)
1219(5)
−2904(3)
−3868(4)
−4478(4)
−4135(5)
−3190(4)
−2576(4)
−2077(4)
−1266(5)
−1298(7)
−2119(9)
−2921(8)
−2900(5)
−2672(3)
−2845(4)
−3266(5)
−3516(6)
−3358(5)
−2921(4)
3382(1)
2928(1)
3691(3)
3893(3)
4297(4)
4863(3)
2235(4)
1511(3)
3832(4)
−246(3)
−1586(3)
−1745(4)
−2349(5)
−2793(5)
−2633(5)
−2036(4)
−10 651(7)
−10 645(5)
−9777(4)
1130(9)
2116(9)
2683(5)
C(9)
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
Co(1%)
P(1%)
C(1%)
O(1%)
C(2%)
O(2%)
C(3%)
O(3%)
C(4%)
C(5%)
C(6%)
C(7%)
C(8%)
C(9%)
C(10%
C(11%)
C(12%)
C(13%)
C(14%)
C(15%)
C(16%)
C(17%)
C(18%)
C(19%)
−25(5)
321(4)
727(4)
data and experimental parameters are reported in Table
5. Corrections for Lorentzian polarization and absorp-
tion („ scans) were applied.
−5082(3)
−5056(4)
−5774(4)
−6510(4)
−6552(4)
−5850(3)
−4603(3)
−4361(4)
−4692(6)
−5244(6)
−5475(5)
−5163(4)
−3232(3)
−2827(4)
−2062(6)
−1709(5)
−2105(5)
−2869(4)
−1875(1)
−933(1)
−1063(3)
−576(2)
−2077(3)
−2191(3)
−2643(3)
−3153(3)
−2779(3)
−3752(3)
−4408(3)
−5320(3)
−5624(3)
−4975(3)
−4062(3)
−6638(4)
−6861(5)
−7211(5)
−6947(7)
−137(3)
268(3)
The structure was solved by direct methods (SIR-92
[18]) and refined on Fo2 by the SHELX-97 program
package [19]. All atoms in the structure were located in
DF maps and subsequent refinement cycles. All nonhy-
drogen atoms were refined anisotropically, while hydro-
gen atoms were treated isotropically. Drawing was
performed with the ORTEP plotting program [17]. Major
calculations were carried out on an Alpha 3000/800S
computer. Final fractional coordinates and equivalent
thermal parameters are given in Table 6, while selected
interatomic distances and angles are collected in Table
7. Tables showing full listings of selected interatomic
distances and angles, anisotropic thermal parameters,
final hydrogen coordinates and equivalent thermal
parameters are available as supplementary material (see
Section 4).
3. Results and discussion
The main goal of the present work was to obtain
alkyl- and acylcobalt type tricarbonyltriphenylphos-
phine complexes with benzyl-derived organyl ligands,
which can be crystallized in satisfactory quality for
X-ray crystal and molecular structure determination.
This goal has been set in the light of the reports listed
under (5) and (6) in Section 1, aiming to get unequivo-
cal structural information about the overall geometry
of such complexes, which represent the bulk of the
analytically pure products in the crystalline phase. We
hope then to use the solution behavior of these com-
plexes as reference for future spectroscopic studies.
In the light of our earlier experience with benzyl-
3717(3)
2935(4)
2839(4)
3506(4)
4284(4)
4387(3)
3361(5)
4232(11)
3236(8)
2458(11)
3916(3)
4695(4)
5425(4)
5387(5)
934(4)
1190(4)
792(4)
4645(5)

66
C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
Table 6
Table 4
Atomic coordinates (104) and equivalent isotropic displacement
,
Selected bond lengths (A) and angles (°) for complex 4
2
3
,
parameters (A ×10 ) for complex 5
Bond
Molecule Aa
Molecule Ba
a
x
y
z
Ueq
Bond lengths
Co–C(O) av.
CO–P
P–C(Ph) av.
Co–C(4)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(8)–C(11)
C(4)–C(5)
Co
P
Cl
O(2)
C(2)
O(3)
C(3)
O(1)
C(1)
O(4)
C(4)
C(5)
8521(1)
8135(1)
9314(1)
3711(1)
5115(1)
6496(1)
6497(1)
5557(1)
6746(1)
6654(1)
5048(1)
5617(1)
7734(1)
7242(1)
6483(2)
6424(1)
6316(2)
6122(1)
5479(1)
5304(1)
5774(1)
6412(1)
6577(1)
7207(1)
7871(1)
8430(1)
8334(2)
7680(2)
7117(2)
5709(1)
5232(1)
4618(2)
4480(2)
4944(2)
5560(1)
6551(1)
6634(1)
6692(1)
6664(1)
6582(1)
6517(1)
36(1)
35(1)
107(1)
74(1)
46(1)
100(1)
54(1)
75(1)
47(1)
125(1)
53(1)
60(1)
47(1)
59(1)
61(1)
56(1)
59(1)
53(1)
40(1)
54(1)
70(1)
75(1)
84(1)
63(1)
43(1)
64(1)
80(1)
75(1)
72(1)
60(1)
38(1)
49(1)
58(1)
57(1)
55(1)
45(1)
1.779
2.2497(13)
1.825
2.120(4)
1.138(5)
1.142(6)
1.142(6)
1.537(6)
1.477(6)
1.782
2.2313(13)
1.824
2.136(5)
1.142(5)
1.125(6)
1.145(5)
1.535(7)
1.488(6)
−1790(1)
4157(2)
4004(2)
3522(2)
3598(2)
3208(1)
3405(1)
2240(1)
2456(1)
1777(2)
881(1)
10 099(1)
9483(1)
8053(2)
8224(1)
7740(1)
8032(1)
9463(1)
8836(1)
8214(1)
8485(1)
8787(2)
9040(2)
8998(1)
8704(2)
8452(1)
8505(1)
8521(1)
8766(2)
8994(2)
8985(2)
8742(2)
8389(1)
7857(2)
8080(2)
8819(2)
9353(2)
9142(2)
7125(1)
6834(1)
6068(1)
5593(1)
5873(1)
6638(1)
Bond angles
C(O)–Co–C(O) av.
C(O)–Co–C(Ph) av.
C(O)–Co–P av.
C(4)–Co–P
C(Ph)–P–C(Ph) av.
O–C(O)–Co av.
C(5)–C(4)–Co
119.8
87.2
92.9
177.44(14)
104.1
119.7
86.8
93.1
179.23(14)
103.8
C(6)
C(7)
C(8)
C(9)
725(2)
−95(2)
−756(1)
−622(2)
202(2)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
178.4
116.1(3)
177.5
116.5(3)
5796(1)
5459(2)
5961(2)
6797(2)
7142(2)
6650(2)
5686(1)
5993(2)
6373(2)
6448(2)
6149(2)
5769(2)
5280(1)
6111(2)
6231(2)
5526(2)
4699(2)
4574(2)
a Atoms of molecule B are indicated in Fig. 1 by (%), e.g. Co(1%)–
C(1%).
Table 5
Crystal data and structure refinement for complex 5
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C29H21ClCoO4P
558.81
298(2)
0.71069
,
Monoclinic
C2/c (no. 15)
Unit cell dimensions
,
a (A)
17.8350(10)
15.3040(10)
19.3090(10)
90
,
b (A)
,
c (A)
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
h (°)
i (°)
91.759(7)
k (°)
90
5267.8(5)
8
1.409
0.847
2288
3
,
V (A )
cobalt
carbonyls
we
have
chosen
(para-
Z
tbutylbenzyl)cobalt tricarbonyl triphenylphosphine (4)
as representative of the former and [(para-
chlorophenyl)acetyl]cobalt tricarbonyl triphenylphos-
phine (5) as representative of the latter type.
Dcalc. (Mg m−3
)
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
q range for data collection (°)
0.3×0.2×0.2
2.66–28.5
The preparation of complexes 4 and 5 proceeded
smoothly by using metathesis of [Co(CO)4]− with the
corresponding benzyl halides. The h3-benzylcobalt tri-
carbonyl (a) h1-benzylcobalt tetracarbonyl (b) h1-
phenylacetylcobalt tetracarbonyl (c) type intermediates
could be identified spectroscopically on the basis of
earlier experience [10,16,20].
The X-ray diffraction crystal and molecular structure
determinations show that the overall molecular ge-
ometries of complexes 4 (Fig. 1) and 5 (Fig. 2) are
nearly ideal trigonal bipyramidal with the two noncar-
bonyl ligands in the axial positions. The P–Co–Calkyl
Index ranges
−235h523, 05k520,
05l525
7169
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I))
6646 [Rint=0.0160]
Full-matrix least-squares
6646/0/410
1.068
R1=0.0386,
wR2=0.1024
R1=0.0584,
wR2=0.1105
0.498 and −0.478
R indices (all data)
Largest difference peak and hole (e
−3
,
A
)

C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
67
and P–Co–Cacyl axes are slightly bent (4: 177.44(14)°
and 179.23(14)° 5: 175.90(7)°) as has been observed also
for the known alkyl- [1,6,10b,12a,b,d,e] and acylcobalt
carbonyl [10b,12b,c] structures, e.g. RCo(CO)3PPh3,
R=ClCH2: 177.6(1)° [12b], R=iPrOC(O)CH2: (two
independent molecules) 176.2(2)° and 178.1(2)° [21];
RC(O)Co(CO)3PPh3, R=ClCH2: 174.5(1)° [12b], =
2,6-dichlorophenylCH2: 178.9(1)° [10b], R=nBuO:
177.1(1)° [12c]. The three carbonyl groups are nearly
coplanar, with a slight bending towards the organic
ligand (4: Calkyl–Co–Ccoord av. 87.0°; 5: Cacyl–Co–
Ccoord av. 87.1°), a phenomenon which was predicted
on the basis of a sophisticated analysis of the IR
w(CꢀO) stretching vibrations of MeCo(CO)4 [22].
The crystal structure of complex 4, has the fairly
interesting feature of two independent molecules in the
unit cell. This effect may be correlated to the surprising
Table 7
,
Selected bond lengths (A) and angles (°) for complex 5
Bond lengths
Co–C(3)
Co–C(2)
Co–P
P–C(24)
Cl–C(9)
O(3)–C(3)
O(4)–C(4)
C(5)–C(6)
C(5)–H(5B)
1.769(2)
1.791(2)
2.2564(5)
1.8251(18)
1.736(2)
1.139(3)
1.168(3)
1.505(3)
1.05(4)
Co–C(1)
Co–C(4)
P–C(18)
P–C(12)
O(2)–C(2)
O(1)–C(1)
C(4)–C(5)
C(5)–H(5A)
1.771(2)
2.008(2)
1.823(2)
1.829(2)
1.132(3)
1.137(3)
1.530(3)
1.06(3)
Bond angles
C(3)–Co–C(1)
C(1)–Co–C(2)
C(1)–Co–C(4)
C(3)–Co–P
127.87(11)
114.87(10)
87.07(10)
90.68(8)
C(3)–Co–C(2)
C(3)–Co–C(4)
C(2)–Co–C(4)
C(1)–Co–P
116.43(11)
85.23(10)
88.94(9)
95.35(7)
C(2)–Co–P
93.03(7)
C(4)–Co–P
175.90(7)
105.00(10)
111.81(7)
116.13(6)
178.1(3)
C(18)–P–C(24)
C(24)–P–C(12)
C(24)–P–Co
O(2)–C(2)–Co
O(1)–C(1)–Co
O(4)–C(4)–Co
C(6)–C(5)–C(4)
104.67(9)
102.28(9)
115.66(7)
177.3(2)
177.7(2)
122.30(19)
114.54(19)
C(18)–P–C(12)
C(18)–P–Co
C(12)–P–Co
O(3)–C(3)–Co
O(4)–C(4)–C(5) 120.6(2)
C(5)–C(4)–Co
C(6)–C(5)
Fig. 1. ORTEP view of complex 4 with atom labels and 30% probabil-
ity thermal ellipsoids. The hydrogen atoms are omitted for clarity.
117.10(15)
111.0(15)
stereochemistry observed for the crystals of
ROC(O)CH2Co(CO)3PPh3 complexes [12d,21], how-
ever, the organic ligand in 4 is symmetric and thus
direct comparison with the ester derivatives is not possi-
ble. This point merits additional efforts using asymmet-
rically (ortho- and/or meta-) substituted benzyl
derivatives.
–H(5A)
C(6)–C(5)
C(4)–C(5)–H(5A) 108.0(15)
C(4)–C(5)–H(5B) 108(2)
112(2)
103(3)
–H(5B)
H(5A)–C(5)
–H(5B)
In alkyl- and acylcobalt carbonyls the Corganic–Co

68
C. Zucchi et al. / Journal of Organometallic Chemistry 586 (1999) 61–69
of the alkoxycarbonyl derivative, which merits a sepa-
rate study.
We can conclude that the structural rearrangement of
the supposed primary cis-alkyl/acylcobalt tricarbonyl
phosphine complexes [6,7,8,11a,12a,13] should be fast
(or at least faster than the formation of the crystalline
phase) also in the case of the benzylcobalt family. On
the other hand we regard the results obtained in the
present work as a solid basis for solution studies in an
attempt at extending the highly interesting observations
of Kova´cs et al. [11a] to additional alkyl- and acyl-
cobalt carbonyls. It should be pointed out [23] that the
benzyl-type (present work and Refs. [10,16]) as well as
the
alkoxycarbonylmethyl-type
(ROC(O)CH2Co-
(CO)3L, L=CO, PR%; [6,11a,12a,d,21,24]) complexes
3
possess a great structural advantage: CO insertion stud-
ies are not complicated by b-H elimination and con-
nected isomerization [6,12a,25,26] reactions [27].
4. Supplementary material
Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as
supplementary publication nos. CCDC-119403 (4) and
CCDC-119397 (5). Copies of the data can be obtained
free of charge on application to The Director, CCDC,
12 Union Road, Cambridge CB21EZ, UK (fax: int.
code +(1223) 336-033; e-mail: deposit@chemcrys.
cam.ac.uk).
Fig. 2. ORTEP view of complex 5 with atom labels and 30% probabil-
ity thermal ellipsoids. The hydrogen atoms of the triphenylphosphine
ligand are omitted for clarity.
and Co–P distances are the most sensitive to structural
changes in the organic ligand or in the phosphine. The
Calkyl–Co separation in 4 is slightly longer than the
average in numerous alkylcobalt complexes (2.120(4)
,
,
and 2.136(5) A vs. 2.1 A), probably due to the ‘tension’
generated by the bulky organic ligand. Similarly the
Co–P distances (2.2213(13) and 2.2313(13)) also show a
slight increment with respect to the average of the
Acknowledgements
This research is supported by the Department of
Chemistry of the University of Modena (Ricerca avan-
zata, 1997 and postdoctoral fellowship to C.Z. 1994/6).
Discussions with Dr I. Kova´cs (Montreal), Professor E.
Rosenberg (Missoula), Dr M.C. Rossi (Modena) and
Professor L. Schenetti (Modena) are acknowledged.
,
alkylcobalt complexes (2.212 A), approaching the value
observed for butoxycarbonylcobalt tricarbonyl
,
triphenylphosphine (2.229(1) A [12c]). In the acylcobalt
derivative 5 these trends are different. The Cacyl–Co
bond is significantly shorter (by ca. 0.1 A) than the ca.
A values observed for alkylcobalt carbonyls
[10b,12], but fairly similar to values found at the acyl
complexes cited above, with Co–Cacyl distances ranging
from 1.967 to 1.999 A. The Co–P distances show even
less consistency: the 2.2564(5) A value found in the
present study is similar only to the values found at the
(2,6-dichlorophenyl)acetyl- (2.259(1)
chloroacetylcobalt (2.254(1) A [12b]) complexes, but
significantly longer than the Co–P distances found at
the butoxycarbonyl (2.229(1) A [12c]) or the alkyl-
derivatives (av. 2.212 A). Generally it can be deduced
that the negative inductive effect in the organic group
causes shortening of the Co–Cacyl distance and in-
creases the Co–P distance, with the exception of 4 and
,
,
2.1
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