Preparation and reactivity of stannyl and germyl complexes of cobalt

Article abstract of DOI:10.1016/j.jorganchem.2012.07.045

Trichlorostannyl complex Co(SnCl₃)(CO)₂(PPh ₃)₂ (1) was prepared by allowing the chloro compound CoCl(CO)₂(PPh₃)₂ to react with SnCl ₂·2H₂O. Instead, treatment of the iodo complex CoI(CO)₂[PPh(OEt)₂]₂ with SnCl ₂·2H₂O afforded a mixture of Co(SnCl ₂I)(CO)₂[PPh(OEt)₂]₂ (2a) and Co(SnCl₃)(CO)₂[PPh(OEt)₂]₂ (2b) derivatives. Trichlorogermyl complexes Co(GeCl₃)(CO) ₂L₂ (3, 4) [L = PPh₃, PPh(OEt)₂] were prepared by allowing halo compounds CoX(CO)₂L₂ (X = Cl, I) to react with GeCl₂·dioxane. Treatment of trihalostannyl complexes Co(SnCl₂X)(CO)₂L₂ (1, 2) (X = Cl, I) with NaBH₄ in ethanol yielded tin trihydrido derivatives Co(SnH₃)(CO)₂L₂ (5, 6). Instead, reaction of Co(SnCl₂X)(CO)₂[PPh(OEt)₂] ₂ (2) with LiAlH₄ in THF yielded the hydrido CoH(CO) ₂[PPh(OEt)₂]₂ (7). Trimethylstannyl Co(SnMe₃)(CO)₂L₂ (8, 9) and trialkynylstannyl derivatives Co[Sn(C≡CPh)₃](CO)₂L₂ (10, 11) were prepared by allowing trihalostannyl compounds Co(SnCl ₂X)(CO)₂L₂ (1, 2) to react with MgBrMe and with Li⁺(PhC≡C)^-, respectively, in THF. The complexes were characterised by spectroscopy (IR and ¹H, ³¹P, ¹³C, ¹¹⁹Sn NMR) and by X-ray crystal structure determination of Co(SnCl₂X)(CO)₂[PPh(OEt) ₂]₂ (2) and Co(GeCl₃)(CO)₂[PPh(OEt) ₂]₂ (4).

Full text of DOI:10.1016/j.jorganchem.2012.07.045

Journal of Organometallic Chemistry 718 (2012) 108e116
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Preparation and reactivity of stannyl and germyl complexes of cobalt
,
a
b
Gabriele Albertin a , Stefano Antoniutti , Jesús Castro
*
a Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy
b Departamento de Química Inorgánica, Universidade de Vigo, Facultade de Química, Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Trichlorostannyl complex Co(SnCl3)(CO)2(PPh3)2 (1) was prepared by allowing the chloro compound
CoCl(CO)2(PPh3)2 to react with SnCl2$2H2O. Instead, treatment of the iodo complex CoI(CO)2[PPh(OEt)2]2
with SnCl2$2H2O afforded a mixture of Co(SnCl2I)(CO)2[PPh(OEt)2]2 (2a) and Co(SnCl3)(CO)2[PPh(OEt)2]2
(2b) derivatives. Trichlorogermyl complexes Co(GeCl3)(CO)2L2 (3, 4) [L ¼ PPh3, PPh(OEt)2] were prepared
by allowing halo compounds CoX(CO)2L2 (X ¼ Cl, I) to react with GeCl2$dioxane. Treatment of triha-
lostannyl complexes Co(SnCl2X)(CO)2L2 (1, 2) (X ¼ Cl, I) with NaBH4 in ethanol yielded tin trihydrido
derivatives Co(SnH3)(CO)2L2 (5, 6). Instead, reaction of Co(SnCl2X)(CO)2[PPh(OEt)2]2 (2) with LiAlH4 in
THF yielded the hydrido CoH(CO)2[PPh(OEt)2]2 (7). Trimethylstannyl Co(SnMe3)(CO)2L2 (8, 9) and tri-
alkynylstannyl derivatives Co[Sn(C^CPh)3](CO)2L2 (10, 11) were prepared by allowing trihalostannyl
compounds Co(SnCl2X)(CO)2L2 (1, 2) to react with MgBrMe and with Liþ(PhC^C)ꢀ, respectively, in THF.
The complexes were characterised by spectroscopy (IR and 1H, 31P, 13C, 119Sn NMR) and by X-ray crystal
structure determination of Co(SnCl2X)(CO)2[PPh(OEt)2]2 (2) and Co(GeCl3)(CO)2[PPh(OEt)2]2 (4).
Ó 2012 Elsevier B.V. All rights reserved.
Received 25 June 2012
Received in revised form
25 July 2012
Accepted 31 July 2012
Keywords:
Cobalt
Stannyl and germyl complexes
Trihydridostannyl ligand
Synthesis
1. Introduction
preparation of the first trihydridostannyl complex of cobalt, are
reported here.
Stannyl complexes of transition metals continue to be studied
not only from a fundamental point of view [1e3], but also because
the introduction of a stannyl ligand often changes the properties of
the complexes and may modify the activity of noble metal catalysts
[4].
2. Experimental section
2.1. General comments
Another reason for interest in stannyl complexes stems from the
variety of reactions they may undergo, including ligand substitu-
tion at the tin centre, to yield stannyl complexes with novel func-
tionalities [1e3].
All synthetic work was carried out in an appropriate atmosphere
(Ar, N2) using standard Schlenk techniques or a vacuum atmo-
sphere dry-box. All solvents were dried over appropriate drying
agents, degassed on a vacuum line, and distilled into vacuum-tight
storage flasks. Anhydrous CoI2 and CoCl2 were Alfa Aesar (USA)
products, used as received. GeCl2$dioxane, anhydrous SnCl2,
SnCl2$2H2O and CoCl2$6H2O were Aldrich products, used as
received. Phosphite PPh(OEt)2 was prepared by the method of
Rabinowitz and Pellon [8]. Other reagents were purchased from
commercial sources in the highest available purity and used as
received. Infrared spectra were recorded on PerkineElmer Spec-
trum One FT-IR spectrophotometer. NMR spectra (1H, 31P, 13C, 119Sn)
were obtained on AC200 or AVANCE 300 Bruker spectrometers at
temperatures between ꢀ80 and þ30 ꢁC, unless otherwise noted.1H
and 13C spectra are referred to internal tetramethylsilane; 31P{1H}
chemical shifts are reported with respect to 85% H3PO4 and 119Sn
ones with respect to Sn(CH3)4, and in both cases downfield shifts
are considered positive. The COSY, HMQC and HMBC NMR experi-
ments were performed using their standard programs. The iNMR
software package [9] was used to treat NMR data. The conductivity
We are interested in the chemistry of stannyl complexes of
transition metals and have reported the synthesis and reactivity of
trihydridostannyl [M]eSnH3 and triorganostannyl [M]eSnR3
derivatives [R ¼ Me, C(OOMe)¼CH2, C^CPh] of manganese [5]
and iron [6] triads stabilised by several ligands, including CO, PR3,
P(OR)3, h
5-C5H5, tris(pyrazolyl)borate (Tp) and p-cymene.
The interesting properties shown by both trichloro- [M]eSnCl3
and trihydridostannyl [M]eSnH3 ligands in these complexes
prompted us to extend study to cobalt, as the chemistry of stannyl
complexes [7] is less well developed than that of other metals
[1e3]: our aim was to test whether cobalt fragments can also sta-
bilise trihydridostannyl derivatives. The results, which included the
* Corresponding author.
E-mail address: albertin@unive.it (G. Albertin).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.07.045

G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
109
of 10ꢀ3 mol dmꢀ3 solutions of the complexes in CH3NO2 at 25 ꢁC
were measured with a Radiometer CDM 83. Elemental analyses
were determined in the Microanalytical Laboratory of the Diparti-
mento di Scienze Farmaceutiche of the University of Padua, Italy.
triturated with ethanol (3 mL) until a yellow solid separated out,
which was filtered and crystallised from CH2Cl2 and ethanol. Yield:
560 mg (45%). IR (KBr pellet): nCO ¼ 2005 (m), 1949 (s) cmꢀ1
.
1H
NMR (CD2Cl2, 25 ꢁC):
d
¼ 7.70e4.41 (m, 30 H, Ph) ppm. 31P{1H} NMR
(CD2Cl2, 25 ꢁC):
d
¼ 51.9 (s br); (ꢀ90 ꢁC): 52.0 (s br) ppm.
2.2. Synthesis of complexes
C38H30Cl3GeO2P2Co (818.52): C 55.76, H 3.69, Cl 12.99; found C
55.94, H 3.60, Cl 12.79%.
Complexes CoX(CO)2(PPh3)2 (X ¼ Cl, I) and CoI(CO)2[PPh(OEt)2]2
were prepared following the methods previously reported [10,11].
2.2.4. Co(GeCl3)(CO)2[PPh(OEt)2]2 (4)
In a 25-mL three-necked round-bottomed flask were placed
2.2.1. Co(SnCl3)(CO)2(PPh3)2 (1)
0.30 g (0.47 mmol) of CoI(CO)2[PPh(OEt)2]2, an excess of
In a 50-mL three-necked round-bottomed flask were placed
solid samples of CoCl(CO)2(PPh3)2 (1.0 g, 1.48 mmol), an excess of
SnCl2$2H2O (1.33 g, 5.9 mmol) and 30 mL of ethanol. The reaction
mixture was stirred at room temperature for 24 h and then
concentrated to about 5 mL by evaporation of the solvent at
reduced pressure. A yellow solid separated out, which was filtered
and crystallised from CH2Cl2 and ethanol. Yield: 0.77 g (60%). IR
(KBr pellet): nCO ¼ 2006 (m), 1953 (s) cmꢀ1. 1H NMR (CD2Cl2, 25 ꢁC):
GeCl2$dioxane (0.27 g, 1.18 mmol) and 10 mL of CH2Cl2. The reac-
tion mixture was stirred for 5 h and then the solvent was removed
under reduced pressure. The oil obtained was triturated with n-
hexane (10 mL) giving a yellow solid which was filtered and crys-
tallised from toluene and n-hexane. Yield: 280 mg (85%). IR (KBr
pellet): nCO ¼ 2008, 1950 (s) cmꢀ1
.
1H NMR [(CD3)2CO, 25 ꢁC]:
d
¼ 7.65e7.49 (m, 10 H, Ph), 3.79 (m, 8 H, CH2), 1.20 (t, 12 H, CH3)
ppm. 31P{1H} NMR [(CD3)2CO, 25 ꢁC]:
d
¼
166.6 (s br)
d
¼ 7.54 (m, 30 H, Ph) ppm. 31P{1H} NMR (CD2Cl2, 25 ꢁC):
d
¼ 53.73
[(CD3)2CO, ꢀ90 ꢁC]: 166.0 (br) ppm.13C{1H} NMR [(CD3)2CO, 25 ꢁC]:
(s br); (ꢀ90 ꢁC) 53.2, 52.9 (br) ppm. 119Sn NMR (CD2Cl2, 25 ꢁC):
d
¼ 198.7 (br, CO), 137e128 (m, Ph), 63.0 (d br, CH2), 15.9 ppm (s br,
d
¼ ꢀ139 (t br) ppm. C38H30Cl3O2P2SnCo (864.59): C 52.79, H 3.50,
CH3, JCP ¼ 3.4 Hz). C22H30Cl3GeO6P2Co (690.35): C 38.28, H 4.38, Cl
Cl 12.30; found C 52.62, H 3.35, Cl 12.03%.
15.41; found C 38.11, H 4.47, Cl 15.23%.
2.2.2. Co(SnCl2I)(CO)2[PPh(OEt)2]2 (2a) (w33%) and
2.2.5. Co(SnH3)(CO)2(PPh3)2 (5) and Co(SnH3)(CO)2[PPh(OEt)2]2 (6)
Co(SnCl3)(CO)2[PPh(OEt)2]2 (2b) (w66%)
An excess of NaBH4 (0.24 g, 6.3 mmol) in ethanol (5 mL) was
Method A: in a 50-mL three-necked round-bottomed flask were
placed solid samples of CoI(CO)2[PPh(OEt)2]2 (0.50 g, 0.78 mmol),
an excess of anhydrous SnCl2 (0.60 g, 3.2 mmol) and 20 mL of
CH2Cl2 and the reaction mixture was stirred for 4 h. After filtration
to remove unreacted SnCl2, the solution was evaporated to dryness
to give an oil, which was triturated with ethanol (3 mL). A yellow
solid slowly separated out, which was filtered and crystallised from
CH2Cl2 and ethanol. Yield: 508 mg (85%).
Method B: in a 25-mL three-necked round-bottomed flask were
placed solid samples of CoI(CO)2[PPh(OEt)2]2 (0.50 g, 0.78 mmol),
an excess of SnCl2$2H2O (0.72 g, 3.2 mmol) and 10 mL of ethanol.
The reaction mixture was stirred at room temperature for 6 h and
then the solvent was removed under reduced pressure to half
volume (about 5 mL). The yellow solid which separated out was
filtered and crystallised from CH2Cl2 and ethanol. Yield: 479 mg
(80%). Crystallisation by slow diffusion at 5 ꢁC of ethanol into
a dichloromethane solution of the complex gives only one type of
crystals containing, by X-ray analysis, and a mixture of 2a and 2b in
about 1:3 ratio. As fractional crystallisation does not allow their
separation, we attempted chromatographic separation of the two
compounds on a silica gel column. Unfortunately, with all the
solvents used as eluent (e.g., diethyl ether, petroleum ether,
benzene, dichloromethane, ethanol, and mixtures of them) the
complexes decomposed in the column, preventing their separation.
IR (KBr pellet): nCO ¼ 2002, 1947 (s) cmꢀ1. 1H NMR (CD3C6D5, 25 ꢁC):
added to a suspension of the appropriate trihalostannyl
Co(SnCl2X)(CO)2L2 (1, 2) [X ¼ Cl, I; L ¼ PPh3, PPh(OEt)2] (0.63 mmol)
in ethanol (5 mL) cooled to ꢀ196 ꢁC. The reaction mixture was
brought to 0 ꢁC and, at this temperature, the solvent was removed
under reduced pressure. The hydridostannyl complex was extrac-
ted from the oil obtained with three 10-mL portions of toluene,
using a cellulose column (5 cm) for filtration. The extracts were
evaporated to dryness under reduced pressure giving an oil, which
was triturated with n-hexane:ethanol (10:1 ratio) (5 mL) until
a yellow solid separated out, which was filtered and dried under
vacuum. Yield: 220 mg (45%) for 5, 200 mg (50%) for 6.
5: IR (KBr pellet): nCO ¼ 1969, 1913 (s); nSnH ¼ 1806 (m br) cmꢀ1
.
1H NMR (CD2Cl2, 25 ꢁC):
d
¼ 7.80e6.98 (m, 30 H, Ph), 4.36 (t br, 3 H,
SnH3) ppm. 31P{1H} NMR (CD2Cl2, 25 ꢁC):
d
¼ 51.3 (s br) ppm. 119Sn
NMR (CD2Cl2, 25 ꢁC):
d
¼ ꢀ287 (br) ppm.C38H33O2P2SnCo (761.26):
C 59.95, H 4.37; found C 60.14, H 4.49%.
6: IR (KBr pellet): nCO ¼ 1967, 1913 (s); nSnH ¼ 1788, 1768 (m)
cmꢀ1. 1H NMR (CD3C6D5, 25 ꢁC):
d
¼ 7.64, 7.08 (m, 10 H, Ph), 4.32 (t,
3 H, SnH3, JPH ¼ 8.7, J117Sn1H ¼ 1594 Hz), 3.74, 3.57 (m, 8 H, CH2), 1.01
31
(t, 12 H, CH3) ppm. P{1H} NMR (CD3C6D5, 25 ꢁC):
d
¼ 180.4 (br);
(ꢀ90 ꢁC): 179.5 ppm (br, J117Sn31P ¼ 144.0 Hz). 119Sn NMR (CD3C6D5,
e50 ꢁC):
d
¼ A2MX3 spin system, dM ꢀ274.7 ppm, JAM ¼ 148.5,
JAX ¼ 8.7, JMX ¼ 1656 Hz C22H33O6P2SnCo (633.08): C 41.74, H 5.25;
found C 41.58, H 5.36%.
d
¼ 7.50, 7.01 (m, 10 H, Ph), 3.56 (m, 8 H, CH2), 0.95, 0.92 (t, 12 H,
2.2.6. CoH(CO)2[PPh(OEt)2]2 (7)
CH3) ppm. 31P{1H} NMR (CD3C6D5, 25 ꢁC):
d
¼ 170.9, 169.2 (br);
A solution of the mixture of compounds Co(SnCl2X)(CO)2[P-
Ph(OEt)2]2 (2a and 2b) (X ¼ Cl, I) (0.4 g, about 0.52 mmol) in 15 mL
of THF was transferred by needle into a suspension of LiAlH4
(0.20 g, 5.2 mmol) in 10 mL of THF cooled to ꢀ196 ꢁC. The reaction
mixture was brought to room temperature and then the solvent
removed under reduced pressure leaving an oily product. The
complex was extracted from the oil with three 5-mL portions of
toluene, using a cellulose column (3 cm) for filtration. The extracts
were evaporated to dryness giving an oil, which was triturated with
ethanol (2 mL) until a yellow solid separated out, which was filtered
and dried under vacuum. Yield: 180 mg (65%). IR (KBr pellet):
[(CD3)2CO, ꢀ90 ꢁC]: 170.8, 169.0 (s br) ppm. 13C{1H} NMR (CD3C6D5,
25 ꢁC):
d
¼ 199.4 (t br, CO, J13C31P about 68 Hz), 137e124 (m, Ph),
63.9 (d br, CH2), 15.8 (s br, CH3) ppm. 119Sn NMR (CD3C6D5, 25 ꢁC):
421.0; (2b)
d
¼ A2M spin system (2a) dM ꢀ366.6, JAM ¼
dM ꢀ197.5 ppm, JAM ¼ 398.0 Hz.
2.2.3. Co(GeCl3)(CO)2(PPh3)2 (3)
In a 50-mL three-necked round-bottomed flask were placed
solid samples of CoCl(CO)2(PPh3)2 (1.0 g, 1.48 mmol), an excess of
GeCl2$dioxane (0.86 g, 3.7 mmol) and 30 mL of CH2Cl2. The reaction
mixture was stirred at room temperature for 20 h and then the
solvent removed under reduced pressure. The oil obtained was
nCO ¼ 1989, 1931 (s) cmꢀ1. 1H NMR (CD3C6D5, 25 ꢁC):
d
¼ 7.75, 7.71,
6.97 (m, 10 H, Ph), 3.86, 3.71 (m, 8 H, CH2), 1.07 (t, 12 H, CH3),

110
G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
e10.63 ppm (t, 1 H, CoH, JPH ¼ 22.1 Hz). 31P{1H} NMR (CD3C6D5,
2.3. X-ray data collection and refinement
25 ꢁC):
d
¼ 183.0 (br); (ꢀ90 ꢁC): 182.0 (br) ppm.C22H31O6P2Co
(512.36): C 51.57, H 6.10; found C 51.71, H 6.01%.
Crystallographic data were collected on a Bruker Smart 1000
CCD diffractometer at CACTI (Universidade de Vigo) using graphite
ꢀ
2.2.7. Co(SnMe3)(CO)2(PPh3)2 (8) and Co(SnMe3)(CO)2[PPh(OEt)2]2
(9)
monochromated Mo-K
a
radiation (
l
¼ 0.71073 A), and were cor-
rected for Lorentz and polarisation effects. The software SMART
[12] was used for collecting frames of data, indexing reflections, and
the determination of lattice parameters, SAINT [13] for integration
of intensity of reflections and scaling, and SADABS [14] for empirical
absorption correction.
An excess of MgBrMe (1.12 mmol, 0.80 mL of a 1.4 mol dmꢀ3
solution in THF) was added to a suspension of the appropriate tri-
halostannyl complex Co(SnCl2X)(CO)2L2 (1, 2) [X ¼ Cl, I; L ¼ PPh3,
PPh(OEt)2] (0.18 mmol) in THF (7 mL) cooled to ꢀ196 ꢁC. The
reaction mixture was brought to room temperature, stirred for 2 h,
and then the solvent removed under reduced pressure leaving an
oil. The complex was extracted from the oil obtained with three 5-
mL portions of toluene, using a cellulose column (3 cm) for filtra-
tion. The extracts were evaporated to dryness to give an oil, which
was triturated with ethanol (2 mL). A yellow solid slowly separated
out, which was filtered and dried under vacuum. Yield: 90 mg (60%)
for 8, 80 mg (65%) for 9.
The crystallographic treatment of the compounds was per-
formed with the Oscail program [15]. The structures were solved by
direct methods. Then, they were refined by a full-matrix least-
squares based on F2 [16]. Non-hydrogen atoms were refined with
anisotropic displacement parameters. Hydrogen atoms were
included in idealized positions and refined with isotropic
displacement parameters. For 2, one of the supposed chlorine
atoms gave a thermal displacement out of the expected range so
a new iodine atom was included sharing the coordination position
to the tin atom. The factor occupancy of both atoms was refined
given a value close to 33/66%. The substitutional disorder of
halogen atoms in the asymmetric unit is a well-known effect,
specially in pure inorganic solids, but also in molecules [17]. Details
of crystal data and structural refinement are given in Table 1.
CCDC 881506 (for 2) and 881507 (for 4) contain the supple-
mentary crystallographic data for this paper (Table 2). These data
can be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
8: IR (KBr pellet): nCO ¼ 1932 (s br) cmꢀ1
.
1H NMR (CD2Cl2,
25 ꢁC):
d
¼ 8.86 (m br, 30 H, Ph), 0.19 (s, 9 H, CH3) ppm. 31P{1H} NMR
(CD2Cl2, 25 ꢁC):
d
¼ 59.9 (s br); (ꢀ90 ꢁC): 60.3 (s br) ppm.13C{1H}
NMR (CD2Cl2, 25 ꢁC):
d
¼ 201.2 (t br, CO), 138e129 (m, Ph), e3.0 (s,
CH3) ppm. 119Sn NMR (CD2Cl2, 25 ꢁC):
d
¼ 280.9 (m); 119Sn{1H}: A2M
spin syst, dM 280.9 ppm, JAM ¼ 241.0 Hz C41H39O2P2SnCo (803.34):
calcd. C 61.30, H 4.89; found C 61.22, H 4.95%.
9: IR (KBr pellet): nCO ¼ 1952, 1901 (s) cmꢀ1
.
1H NMR (CD2Cl2,
25 ꢁC):
d
¼ 7.79e7.37 (m, 10 H, Ph), 4.08, 3.68 (m br, 8 H, CH2), 1.15
(m br, 12 H, CH3 phos), 0.28 (s, 9 H, SnCH3) ppm. 31P{1H} NMR
(CD2Cl2, 25 ꢁC):
d
¼ 180.5 (br); (ꢀ90 ꢁC): 180.8 (s br) ppm.13C{1H}
NMR (CD2Cl2, 25 ꢁC):
d
¼ 204.0 (t br, CO), 141e128 (m, Ph), 61.7 (s,
3. Results and discussion
CH2), 16.4 (s, CH3 phos), ꢀ3.0 ppm (s, SnCH3, J13C119Sn ¼ 258 Hz).
119Sn NMR (CD2Cl2, 25 ꢁC):
d
¼ 295 (m br); 119Sn{1H}: 295 (br) ppm.
3.1. Preparation of stannyl and germyl complexes
C25H39O6P2SnCo (675.16): calcd. C 44.47, H 5.82; found C 44.29, H
5.90%.
The chlorodicarbonyl complex CoCl(CO)2(PPh3)2 was reacted
with SnCl2$2H2O in ethanol to give the trichlorostannyl derivative
Co(SnCl3)(CO)2(PPh3)2 (1), which was isolated as a yellow solid and
characterised (Scheme 1).
2.2.8. Co[Sn(C^CPh)3](CO)2(PPh3)2 (10) and Co
[Sn(C^CPh)3](CO)2[PPh(OEt)2]2 (11)
An excess of Liþ(PhC^C)ꢀ (1.2 mmol, 0.80 mL of a 1.5 mol dmꢀ3
solution in THF) was added to a suspension of the appropriate tri-
halostannyl complex Co(SnCl2X)(CO)2L2 (1, 2) [X ¼ Cl, I; L ¼ PPh3,
PPh(OEt)2] (0.20 mmol) in THF (10 mL) cooled to ꢀ196 ꢁC. The
reaction mixture was brought to room temperature, stirred for
90 min, and then the solvent removed under reduced pressure
leaving an oil. The complex was extracted from the oil obtained
with three 7-mL portions of toluene, using a cellulose column
(3 cm) for filtration. The extracts were evaporated to dryness to give
an oil, which was triturated with ethanol (3 mL). A yellow solid
slowly separated out, which was filtered and dried under vacuum.
Yield: 95 mg (45%) for 10, 90 mg (50%) for 11.
The reaction proceeded with the insertion of SnCl2 into the
CoeCl bond, yielding trichlorostannyl derivative 1. Anhydrous
SnCl2 in dichloromethane may also be used as a reagent with
CoCl(CO)2(PPh3)2, affording 1 in good yields.
The reaction of the related iodo-derivative CoI(CO)2(PPh3)2 with
SnCl2$2H2O was studied in various conditions, but no stable species
was isolated. Surprisingly, the complex containing two phenyl-
diethoxyphosphine instead of two triphenylphosphine ligands,
CoI(CO)2[PPh(OEt)2]2, did react with an excess of both anhydrous
and hydrate SnCl2 to give an orange solid, which was characterised,
by X-ray analysis, as a mixture of the two compounds Co(Sn-
Cl2I)(CO)2[PPh(OEt)2]2 (2a) and Co(SnCl3)(CO)2[PPh(OEt)2]2 (2b) in
a ratio of about 1:3 (Scheme 2).
The formation of the two derivatives 2a and 2b may be
explained as due to the insertion of SnCl2 into the CoeI bond to give
the dichloroiodostannyl complex Co(SnCl2I)(CO)2[PPh(OEt)2]2 (2a).
The metathetic exchange of Iꢀ by Clꢀ in the SnCl2I group, due to the
presence of an excess of SnCl2, afforded trichlorostannyl derivative
2b. However, a reaction of CoI(CO)2L2 with SnCl2 to give the chloro
complex CoCl(CO)2L2 followed by the insertion of SnCl2 into the
CoeCl bond, yielding Co(SnCl3)(CO)2L2 (2b) is also plausible. In
every case, this halide exchange reaction was rather slow and the
solid which separated from the reaction mixture contained 20e40%
of 2b. Even with longer reaction times at room temperature and
a large excess of SnCl2, trichlorostannyl [Co]eSnCl3 (2b) was never
obtained in pure form, but always as a mixture with 2a. Unfortu-
nately, the compound CoCl(CO)2[PPh(OEt)2]2 cannot be prepared,
10: IR (KBr pellet): nC^C ¼ 2134 (m); nCO ¼ 1972, 1924 (s) cmꢀ1
.
1H NMR (CD2Cl2, 25 ꢁC):
d
¼ 7.81e7.22 (m, 45 H, Ph) ppm. 31P{1H}
NMR (CD2Cl2, 25 ꢁC):
d
¼ 48.0 (br); (ꢀ90 ꢁC): 47.8 (br) ppm.13C{1H}
¼ 207.5 (t br, CO), 134e125 (m, Ph), 106.8 (s,
NMR (CD2Cl2, 25 ꢁC):
d
C
b
), 96.3 ppm (s, C
a
, J13C119Sn ¼ 240 Hz). 119Sn NMR (CD2Cl2, 25 ꢁC):
d
¼ A2M spin syst, dM ꢀ241.3 ppm, JAM ¼ 268.0 Hz C62H45O2P2SnCo
(1061.61): calcd. C 70.14, H 4.27; found C 70.35, H 4.39%.
11: IR (KBr pellet): nC^C ¼ 2134 (m); nCO ¼ 1986, 1930 (s) cmꢀ1
.
1H NMR (CD2Cl2, 25 ꢁC):
d
¼ 7.89e7.20 (m, 25 H, Ph), 3.75 (m br, 8 H,
CH2), 1.21 (t, 12 H, CH3) ppm. 31P{1H} NMR (CD2Cl2, 25 ꢁC):
d
¼ 175.9
(br); (ꢀ90 ꢁC): 175.5 (s br) ppm.13C{1H} NMR (CD2Cl2, 25 ꢁC):
d
¼ 201.2 (t br, CO), 132e125 (m, Ph), 108.5 (s, C , J13C119Sn ¼ 51.0),
b
92.0 (s, C
a
, J13C119Sn ¼ 241.0 Hz), 62.5 (d, CH2), 16.5 (d, CH3) ppm.
119Sn NMR (CD2Cl2, 25 ꢁC):
d
¼ A2M spin syst, dM ꢀ247.3 ppm,
JAM ¼ 330.0 Hz C46H45O6P2SnCo (933.44): calcd. C 59.19, H 4.86;
found C 59.02, H 4.98%.
so
preventing
the
synthesis
of
pure
samples
of

G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
111
Table 1
Crystal data and structure refinement.
Identification code
2
4
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C22H30Cl2.67 0.33
766.78
I
O6P2SnCo
C22H30Cl3O6P2GeCo
690.27
293(2) K
293(2) K
ꢀ
ꢀ
0.71073 A
Monoclinic
P21/n
0.71073 A
Monoclinic
P21/n
ꢀ
ꢀ
Unit cell dimensions
a ¼ 11.3294(7) A
a ¼ 11.1798(19) A
ꢀ
ꢀ
b ¼ 15.8913(10) A
b ¼ 15.670(3) A
ꢀ
ꢀ
c ¼ 17.8950(11) A
c ¼ 17.889(3) A
b
¼ 99.4920(10)ꢁ
b
¼ 98.821(3)ꢁ
3
3
ꢀ
ꢀ
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
3177.7(3) A
3096.7(9) A
4
4
1.603 Mg/m3
1.481 Mg/m3
1.900 mmꢀ1
1400
1.987 mmꢀ1
1520
Crystal size
0.30 ꢂ 0.22 ꢂ 0.17 mm
0.47 ꢂ 0.29 ꢂ 0.27 mm
q
range for data collection
1.72e28.05ꢁ
1.74e28.04ꢁ
Index ranges
ꢀ14 ꢃ h ꢃ 14; ꢀ20 ꢃ k ꢃ 20; ꢀ23 ꢃ l ꢃ 23
30,215
ꢀ14 ꢃ h ꢃ 14; ꢀ18 ꢃ k ꢃ 20; ꢀ23 ꢃ l > 19
20,088
Reflections collected
Independent reflections
Reflections observed (>2
Data Completeness
Absorption correction
7636 [R(int) ¼ 0.0543]
7411 [R(int) ¼ 0.0460]
s)
3989
3586
0.991
0.987
Semi-empirical from equivalents
0.728 and 0.5871
Full-matrix least-squares on F2
7636/0/329
Semi-empirical from equivalents
0.7456 and 0.6530
Full-matrix least-squares on F2
7411/0/320
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
1.016
1.015
Final R indices [I > 2
R indices (all data)
Largest diff. peak and hole
s
(I)]
R1 ¼ 0.0477 wR2 ¼ 0.1330
R1 ¼ 0.0640 wR2 ¼ 0.1882
R1 ¼ 0.1180 wR2 ¼ 0.1853
R1 ¼ 0.1420 wR2 ¼ 0.2474
ꢀꢀ3
ꢀꢀ3
1.005 and ꢀ0.931 e A
1.760 and ꢀ0.689 e A
Co(SnCl3)(CO)2[PPh(OEt)2]2 (2b) from the reaction with SnCl2.
Halide exchange in trihalidestannyl complexes of cobalt has some
precedents in the reaction of Co(
Br, I) with SnX2 [7e,18], but the ratio between isomers was deter-
mined only spectroscopically.
h
5-C5H5)LX2 (L ¼ CO, PPh3; X ¼ Cl,
Table 2
ꢁ
ꢀ
Selected bond lengths [A] and angles [ ].
2
4
The easy reaction of complexes CoX(CO)2L2 with SnCl2 to give
cobalt stannyl derivatives 1 and 2 prompted us to extend study to
GeCl2$dioxane. Results showed that both dicarbonyls CoCl(-
CO)2(PPh3)2 and CoI(CO)2[PPh(OEt)2]2 react with an excess of
GeCl2$dioxane to give the trichlorogermyl derivatives Co(GeCl3)(-
CO)2(PPh3)2 (3) and Co(GeCl3)(CO)2[PPh(OEt)2]2 (4), as shown in
Scheme 3.
The reaction proceeds with the insertion of GeCl2 into the CoeCl
bond of CoCl(CO)2(PPh3)2 to give the derivative [Co]eGeCl3 (3).
Insertion of GeCl2 into the CoeI bond of CoI(CO)2[PPh(OEt)2]2 may
yield the intermediate [Co]eGeCl2I which, by metathetic exchange
of Iꢀ with Clꢀ, gives the final [Co]eGeCl3 (4) derivative. However, an
initial halido exchange of CoI(CO)2L2 to give CoCl(CO)2L2, which
undergoes insertion of GeCl2 to afford 4, cannot be excluded. In
every case, metathetic exchange of Iꢀ with Clꢀ must be fast, because
the reaction of CoI(CO)2L2 [L ¼ PPh(OEt)2] did not yield a mixture of
products, as observed with SnCl2 (2a and 2b), but exclusively the
trichlorogermyl complex Co(GeCl3)(CO)2[PPh(OEt)2]2 (4).
CoeC(1)
CoeC(2)
CoeP(1)
CoeP(2)
CoeSn
C(1)eO(1)
C(2)eO(2)
SneCl(1)
1.751(7)
1.759(8)
2.1585(17)
2.1831(17)
2.4590(9)
1.146(8)
1.145(8)
2.358(8)
2.378(2)
2.4570(18)
2.708(4)
119.1(4)
91.7(2)
CoeC(1)
CoeC(2)
CoeP(1)
CoeP(2)
CoeGe
C(1)eO(1)
C(2)eO(2)
GeeCl(3)
GeeCl(2)
GeeCl(1)
1.771(9)
1.753(8)
2.1665(18)
2.192(2)
2.2940(11)
1.144(9)
1.149(9)
2.193(2)
2.228(2)
2.3290(19)
SneCl(3)
SneCl(2)
SneI(1)
C(1)eCoeC(2)
C(1)eCoeP(1)
C(2)eCoeP(1)
C(1)eCoeP(2)
C(2)eCoeP(2)
P(1)eCoeP(2)
C(1)eCoeSn
C(2)eCoeSn
P(1)eCoeSn
P(2)eCoeSn
O(1)eC(1)eCo
O(2)eC(2)eCo
Cl(1)eSneCl(3)
Cl(1)eSneCl(2)
Cl(3)eSneCl(2)
CoeSneCl(1)-
CoeSneCl(2)
CoeSneCl(3)-
CoeSneI(1)
Cl(2)eSneI(1)
Cl(3)eSneI(1)
O(1)eC(1)eCo
O(2)eC(2)eCo
C(1)eCoeC(2)
C(2)eCoeP(1)
C(1)eCoeP(1)
C(2)eCoeP(2)
C(1)eCoeP(2)
P(1)eCoeP(2)
C(2)eCoeGe
C(1)eCoeGe
P(1)eCoeGe
P(2)eCoeGe
119.4(4)
91.2(3)
91.3(2)
120.5(3)
119.7(3)
93.31(7)
85.8(2)
87.2(2)
175.31(7)
91.30(6)
92.5(2)
119.7(3)
120.5(3)
93.87(7)
86.2(2)
87.4(2)
177.48(6)
88.36(5)
176.9(9)
178.6(7)
103.1(4)
98.1(4)
96.09(8)
121.7(4)
110.88(5)
121.72(6)
124.53(15)
99.77(17)
98.48(16)
176.9(9)
178.6(7)
Cl(1)eGeeCl(3)
Cl(1)eGeeCl(2)
Cl(3)eGeeCl(2)
CoeGeeCl(1)
CoeGeeCl(2)
CoeGeeCl(3)
100.56(9)
100.31(8)
98.10(10)
121.68(6)
111.77(7)
120.32(7)
PPh3
exc. SnCl2•2H2O
EtOH
CO
CO
Cl
CoCl(CO)2(PPh3)2
Ph3P
Cl
Co
Sn
Cl
1
O(1)eC(1)eCo
O(2)eC(2)eCo
178.6(8)
177.7(7)
Scheme 1.

112
G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
exc. SnCl2
CH2Cl2
L
L
CO
CO
Cl
CO
CO
Cl
CoI(CO)2L2
L
Co
Sn
L
Co
Sn
exc. SnCl2•2H2O
EtOH
I
Cl
Cl
Cl
2a
2b
Scheme 2. L ¼ PPh(OEt)2.
These reactions on cobalt(I) carbonyl complexes highlight the
of Co(SnCl2X)(CO)2[PPh(OEt)2]2 (2) and Co(GeCl3)(CO)2[PPh(OEt)2]2
(4), the ORTEPs of which are shown in Figs. 1 and 2.
parallel behaviour of SnCl2 and GeCl2 species towards the CoeX
bond, allowing the synthesis of stable trichlorostannyl and tri-
chlorogermyl cobalt derivatives.
Germyl complexes of cobalt are rare [19] and, apart from the
pioneering works of Mackay [20] and Graham [21], only one paper
has been published recently [7b]. The insertion reaction of GeCl2
into the CoeX bond of dicarbonyl precursors CoX(CO)2L2 allowed
new trichlorogermyl complexes to be prepared.
Trihalostannyl complexes Co(SnCl3)(CO)2L2 (1, 2b) and Co(Sn-
Cl2I)(CO)2L2 (2a) reacted with NaBH4 in ethanol to give trihy-
dridostannyl derivatives Co(SnH3)(CO)2L2 (5, 6), which were
isolated as yellow solids and characterised (Scheme 4).
The reaction proceeded with the substitution of all three halides
bonded to tin by Hꢀ yielding trihydridostannyl derivatives.
However, performing the reaction at 0 ꢁC with a short reaction time
(2e3 min) was crucial for successful synthesis. Otherwise, large
amounts of decomposition products are obtained, which prevent
purification of the complexes.
The reaction of trihalostannyl complexes 1, 2 was also extended
to LiAlH4 in THF, but in this case no trihydridostannyl complex was
formed. Complex Co(SnCl2X)(CO)2[PPh(OEt)2]2 (2) (X ¼ Cl, I)
quickly reacted with LiAlH4 to afford a yellow solid characterised as
the hydrido complex CoH(CO)2[PPh(OEt)2]2 (7) (Scheme 5). Instead,
the related triphenylphosphine derivative Co(SnCl3)(CO)2(PPh3)2
(1) gave only an intractable oil in the reaction with LiAlH4, which
was not characterised (Scheme 5).
Both compounds consist of a cobalt atom coordinated by two
carbonyl ligands, two phosphonite PPh(OEt)2 ligands and a trihali-
destannyl or trihalidegermyl ligand in a trigonal bipyramidal
fashion. The carbonyl ligands are in the equatorial location and
axial sites are occupied by the stannyl (2) or germyl (4) and one of
the two phosphonite ligands. The CoeP bonds [2.158(2) and
ꢀ
ꢀ
2.183(2) A for the stannyl and 2.167(2) and 2.192(2) A for the germyl
ꢀ
compound] differ 0.025 A (longer than in the equatorial site). These
values are smaller than those found in the square pyramidal
Co(CO)2(PPh3)2(SiMePh2) [22], but a similar difference was found
between the two kinds of CoeP bonds, equatorial or axial. The
CoeC bonds lengths with the carbonyl ligands are 1.751(7) and
ꢀ
ꢀ
1.759(8) A for the stannyl and 1.753(8) and 1.771(9) A for the
germyl compound, similar to those found in [CoI(CO)2(PEt3)2] [23],
but clearly shorter than those of Co(CO)3(PMe3)2 [24]. The trihali-
demetal ligand is located in an axial site, with a SneCo bond
ꢀ
ꢀ
distance of 2.4590(9) A or GeeCo distance of 2.294(1) A. It is worth
noting the difference of 0.165 A between both compound, accord-
ing to the different covalent radii (0.19 A) [25]. The CoeSn bond
ꢀ
ꢀ
value is shorter than that found in the compound Cl3SnCo(CO)4 [26]
and similar to the short bonds found for the anion trans-
[(Cl3Sn)2Co(CO)3]ꢀ [27] or the anionic [CoCp*(SnCl3)3]ꢀ [28], con-
firming the strength of the trihalide SneCo bond. Also, the CoeGe
ꢀ
bond value 2.294(1) A is slightly shorter than that of the few
ꢀ
examples found in the literature, e.g., 2.31 A in Cl3GeCo(CO)4 [29].
Therefore, the reaction with NaBH4 results a facile procedure to
prepare a new class of cobalt complexes containing tin trihydrido as
a ligand.
Trichlorogermyl complexes Co(GeCl3)(CO)2L2 (3, 4) were also
treated with both NaBH4 in ethanol and LiAlH4 in THF, but no
reaction was observed and the starting compounds could be
recovered unchanged after several hours of reaction at room
temperature. In refluxing conditions, some decomposition
occurred, but no evidence of the formation of the expected trihy-
dridogermyl derivatives was seen.
The new stannyl and germyl complexes 1e6 were isolated as
yellow or orange solids relatively stable in air and in solution of
common organic solvents, where they behave as non-electrolytes.
Their formulation is supported by analytical and spectroscopic
data (IR, 1H, 31P, 119Sn) and by X-ray crystal structure determination
It is interesting to note the disposition of the various ligands
around the cobalt atom in trigonal bipyramidal geometries of
formula [CoL(CO)2(PR3)2]. Co(CO)3(PMe3)2 has a trigonal bipyra-
midal configuration with two axial trimethylphosphine ligands,
whereas three carbonyl ligands are located in the equatorial plane
[24]. The cation [Co(PMe3)3(CO)2]þ [30] also has its carbonyl
ligands in the equatorial plane. In compounds [Co(SR)(CO)2(PEt3)2]
[31] and [CoI(CO)2(PEt3)2] [32] both phosphines are in axial sites
and the iodine or thiol lie in the equatorial plane. [Co(Si-
MePh2)(CO)2(PPh3)2] is best described as square pyramidal [22].
However, compounds [Co(SbCl2)(CO)2P(OR)3] (R ¼ Me or Ph) were
crystallised with one of the phosphines in the equatorial sites but,
in solution, at least for one of them, two isomers were found. Lastly,
acylcobaltcarbonyl complex Co(MeCO)(CO)2(PPh2H)(PPh2OMe)
crystallises in such a way that one phosphine lies in an axial site and
L
L
L
exc. GeCl2•dioxane
exc. NaBH4
EtOH, 0 °C
CO
CO
Cl
CO
CO
Cl
CO
CO
H
CoX(CO)2L2
L
Co
Ge
L
Co
Sn
L
Co
Sn
Cl
X
H
Cl
Cl
H
3, 4
1, 2
5, 6
Scheme 3. L ¼ PPh3 (3), PPh(OEt)2 (4); X ¼ Cl, I.
Scheme 4. L ¼ PPh3 (5), PPh(OEt)2 (6); X ¼ Cl, I.

G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
113
L
L
LiAlH4
THF
CO
CO
Cl
CO
L
Co
Sn
L
Co
CO
H
X
Cl
7
L = PPh(OEt)2
L
LiAlH4
THF
CO
CO
Cl
L
Co
Sn
oily product
X
Cl
L = PPh3
Scheme 5.
the other in the equatorial plane, and the acyl ligand is in an axial
site, like our Co(SnCl2X)(CO)2[PPh(OEt)2]2 (2) and Co(GeCl3)(-
CO)2[PPh(OEt)2]2 (4).
Fig. 2. ORTEP drawn of 4 at 30% probability level. P1 and P2 represent PPh(OEt)2
groups.
The angles around cobalt atoms are very regular for a trigonal
bipyramid. The axial bond angles range from 175.31(7) to
177.48(6)ꢁ, the former being the more distorted germyl compound.
All other angles are not more than 5ꢁ from the expected 120 or 90ꢁ,
showing slight bending of the axis towards the smaller CO ligands
and away from the equatorial phosphonite ligand. A similar (but
stronger) effect was found for the cation [Co(PMe3)3(CO)2]þ [30].
Substituents in axial positions are eclipsed conformations,
although two carbonyl ligands and the phosphorus atom are
located in staggered positions with respect to the two axial ligands
The CleEeCl and especially the CleEeCo angles (E ¼ Sn or Ge)
are of particular interest [27]. The former range from 103.1(4) to
96.09(8)ꢁ (around 100ꢁ), but the latter compose two groups, one
with angles of 110.8(1)ꢁ (Sn) and 111.7(1)ꢁ (Ge) and two with angles
of about 120ꢁ. The acute Cl-E-Co bond corresponds with the
pseudo-trans bond with the phosphonite ligand [across
CleEeCoeP, dihedral angle of 177.59(7)ꢁ (E ¼ Sn) and 179.9(1)ꢁ
(E ¼ Ge)] so is the less sterically affected for this ligand.
The IR spectra of trihalidestannyl complexes Co(SnCl2X)(CO)2L2
ꢀ
(see Fig. 3). The cobalt atom lies slightly below [0.088(3) A in the Sn
(1, 2) (X
¼
Cl, I) show two bands of strong intensity at
ꢀ
complex and 0.063(4) A in the Ge one] of the plane formed by
2006e1947 cmꢀ1, attributed to the nCO of the two carbonyls in
mutually cis position. The 31P{1H} NMR spectra of Co(SnCl3)(-
CO)2(PPh3)2 (1) show a broad signal at 20 ꢁC, which changed as
temperature was lowered, but did not resolve into a fine structure
even at the lowest attained temperature (ꢀ90 ꢁC). However, the
donor atoms in the equatorial plane, since the carbonyl ligands
bend towards the EX3 moiety, like other CoeSn complexes [7a,32].
Fig. 3. The germyl compound 4 drawn along the GeeCoeP axis. In first plane filled
lines are bonds around P(1) atom, second plane bonds open lines are bonds around Co
atom and GeeCl bonds as dotted lines in a third plane.
Fig. 1. ORTEP drawn of 2 at 30% probability level. X1 represents either iodine (33%) or
chlorine (66%) (see text). P1 and P2 represent PPh(OEt)2 groups.

114
G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
appearance of two broad signals at ꢀ90 ꢁC indicated that the low-
exchange spectrum was approaching an AB spin system, fitting the
magnetic inequivalence of the two phosphine ligands. At room
temperature, the 119Sn spectrum of 1 appears as a broad signal
at ꢀ139.0 ppm, which did not resolve even at ꢀ90 ꢁC but which
does support the presence of the trichlorostannyl SnCl3 ligand.
According to these data, it is plausible to propose a type I geometry
in solution for complex 1 (Scheme 1), like that found in the solid
state for the related compound 2.
At room temperature, the 31P{1H} NMR spectra of Co(SnCl2X)(-
CO)2[PPh(OEt)2]2 (2) show two slightly broad singlets, attributable
to the two isomers [Co]eSnCl2I (2a) and [Co]eSnCl3 (2b) present in
the sample. The 119Sn spectra show two triplets at ꢀ366.0 and at-
197.5 ppm, with an intensity ratio of about 1:3, attributed to the
signals of compounds 2a and 2b. The multiplicity of signals is due to
coupling of the 119Sn with 31P nuclei of the two phosphines which,
at room temperature, appear magnetically equivalent. Lowering the
sample temperature caused some variations in both 31P and 119Sn
spectra, but even at ꢀ90 ꢁC no fine structure was observed.31P
Spectra still appear as two broad singlets, and the 119Sn ones as two
slightly broad triplets, so that geometry in solution cannot be
proposed.
Fig. 4. 119Sn NMR spectrum of complex Co(SnH3)(CO)2[PPh(OEt)2]2 (6) in toluene-d8 at
223 K (J119Sn1H ¼ 1656 Hz): high, simulated; low, experimental.
at about 183 ppm, thus preventing the unambiguous attribution of
a geometry in solution, but confirming the proposed formulation
for the complex.
The IR spectra of germyl complexes Co(GeCl3)(CO)2L2 (3, 4)
show two strong bands at 2008e2005 and 1950e1949 cmꢀ1
,
indicating two carbonyl ligands in a mutually cis position. Unfor-
tunately, the 31P spectra do not give any conclusive information on
the geometry of the complex but, even at ꢀ90 ꢁC, broad signals at
52.0 (3) and 166.0 ppm (4). This suggests that the exchange process,
at this temperature, is still rapid on the NMR time scale, preventing
any geometry in solution to be established.
3.2. Reactivity
The facile substitution of Xꢀ by Hꢀ in the trihalostannyl ligand of
compounds [Co]eSnCl2X (1, 2) (X ¼ Cl, I) to give trihydridostannyl
species [Co]eSnH3 (5, 6) prompted us to extend the reactivity
studies to other nucleophilic reagents to test whether new orga-
nostannyl cobalt complexes could be prepared. The results showed
that both the Grignard reagent MgBrMe and lithium acetylide
Liþ(PhC^C)ꢀ react with trihalostannyl complexes Co(SnCl2X)(-
CO)2L2 (1, 2) to give both trimethylstannyl Co(SnMe3)(CO)2L2 (8, 9)
and trialkynylstannyl derivatives Co[Sn(C^CPh)3](CO)2L2 (10, 11),
as shown in Scheme 6.
Reactions quickly proceeded in THF at room temperature with
the substitution of the tin-bonded halides by either methyl or
acetylide, to afford the new organostannyl derivatives 8e11 in good
yields. Cobalt complexes containing organostannyl groups SnR3 as
ligands are rare and were obtained by oxidative addition of
RnSnX4ꢀn (X ¼ Cl, H; n ¼ 2, 3) tin(IV) species [7b,h]. The use of
trihalostannyl complexes Co(SnCl2X)(CO)2L2 (1, 2) as precursors
yielded new examples of organostannyl [Co]eSnR3 derivatives by
means of a substitution reaction.
The IR spectra of tin hydrido complexes Co(SnH3)(CO)2L2 (5, 6)
show two strong nCO bands between 1969 and 1913 cmꢀ1, indi-
cating a cis arrangement of the two carbonyl ligands. The spectra
also show two bands of medium intensity, at 1788 and 1768 cmꢀ1
,
for 6, and only one broad band at 1806 cmꢀ1 for 5, which were
attributed to nSneH of the trihydridostannyl group. However, the
presence of the SnH3 ligand was confirmed by the 1H NMR spectra,
which show a triplet at 4.36 (5) and at 4.32 ppm (6) with the
characteristic 119Sn and 117Sn satellites due to the hydrido reso-
nance of the SnH3 group coupled with two phosphites magnetically
equivalent. Further support comes from the proton-coupled 119Sn
spectrum of 6, which displays a quartet of triplets simulable with an
A2MX3 model (A ¼ 31P; M ¼ 119Sn; X ¼ 1H) with the parameters
reported in Experimental section. The good fit between calculated
and experimental spectra (Fig. 4) strongly support the presence of
the trihydridostannyl ligand in 5 and 6.
At room temperature, the 31P NMR spectra of complexes
Co(SnH3)(CO)2L2 (5, 6) show a broad singlet, which does not resolve
into a fine structure at the lowest attained temperature (ꢀ90 ꢁC),
thus preventing any conclusive attribution of geometry in solution
for the complexes.
Stannyl complexes of cobalt have been reported with either tri-
chloro- SnCl3 or triorganostannyl SnR3 (R ¼ alkyl or aryl) ligands [7],
but, to the best of our knowledge, no examples of trihydridostannyl
derivatives [Co]eSnH3 have been previously reported. The reaction
with NaBH4 of trihalostannyl complexes Co(SnCl2X)(CO)2L2 is an
easy procedure for a new class of cobalt complexes containing SnH3
as a ligand.
The IR spectrum of hydrido complex CoH(CO)2[PPh(OEt)2]2 (7)
shows two strong nCO bands at 1989 and 1931 cmꢀ1, due to two
carbonyls in a mutually cis position. Besides the signals of phos-
phites, the 1H NMR spectrum shows a triplet at ꢀ10.63 ppm,
attributed to the hydrido ligand coupled with two magnetically
equivalent phosphine ligands. In the temperature range
between þ20 and-90 ꢁC, the 31P NMR spectra show a broad singlet
CO
Co
Me
CO
Me
MgBrMe
THF, RT
L
L
Sn
Me
CO
Co
Cl
L
8, 9
CO
Cl
X
CPh
C
L
Sn
CPh
CO
Co
L
C
CO
L
1, 2
Li+C CPh–
THF, RT
Sn
C
10, 11
CPh
Scheme 6. L ¼ PPh3 (8, 10), PPh(OEt)2 (9, 11); X ¼ Cl, I.

G. Albertin et al. / Journal of Organometallic Chemistry 718 (2012) 108e116
115
Complexes
Co(SnMe3)(CO)2L2
(8,
9)
and
Co
References
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formulation.
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