Four-Coordinate Group-14 Elements in the Formal Oxidation State of Zero
FULL PAPER
solids. Single crystals of 1a and 1d were obtained within 3 d by
applying the method described below.
pyrimidine
as
a
spectroscopic
probe
in
[{(CO)5M}2Sn(bpmd)] (M ϭ Cr, W) this process of partial
de-coordination is more directly evident from dynamic H-
NMR spectroscopy.
1
Bis(pentacarbonylmolybdenum)(2,2Ј-bipyridine)tin, [{(CO)5Mo}2-
Sn(bipy)] (1b), and Bis(pentacarbonylmolybdenum)(1,10-phen-
anthroline)tin, [{(CO)5Mo}2Sn(phen)] (1e): A yellow solution of
Na2[{(CO)5Mo}2SnCl2], obtained by salt metathesis reaction of
[Ph4P]2[{(CO)5Mo}2SnCl2] (1340 mg; 1 mmol) with Na[BPh4] (684
mg; 2 mmol)[4], was filtered through Kieselgur (3 cm) into a
Schlenk tube which already contained solid 2,2Ј-bipyridine (156
mg; 1 mmol) or solid 1,10-phenanthroline (180 mg; 1 mmol),
respectively. The resulting deep red solution was filtered through
Kieselgur (3 cm) and taken to dryness. The resulting red oil was
redissolved in THF (3 ml) and slowly chromatographed (max. 50
drops/min) on silica gel (20 cm; Ø ϭ 3 cm; diethyl ether). Two
bands were obtained by elution with diethyl ether. The first yellow
band was identified by IR spectroscopy to be [Mo(CO)6][29]. The
second pink band was also characterized by spectroscopic compari-
The financial support by the Deutsche Forschungsgemeinschaft
(SFB 247) and the Fonds der Chemischen Industrie is gratefully
acknowledged.
Experimental Section
General: All manipulations were carried out under argon by
means of standard Schlenk techniques at 20°C unless mentioned
otherwise. All solvents were dried by standard methods and de-
stilled under argon. [D6]acetone used for the NMR spectroscopic
1
son (IR[30], H-, and 13C-NMR spectra) and found to be [(CO)4-
measurements was degassed by three successive “freeze-pump-
˚
Mo(bipy)] or [(CO)4Mo(phen)], respectively. A third red-brown
band, containing the compound 1b or 1d, was eluted with THF.
From the red-brown solution 310 mg (41%) of 1b or 290 mg (38%)
of 1d, respectively, were obtained by removing the solvent in vacuo.
Applying the method described below gave single crystals of 1b and
1d within 3 d.
thaw” cycles and dried over 4-A molecular sieves. Silica gel (Kiesel-
gel z. A. 0.06Ϫ0.2 mm, J. T. Baker Chemicals B.V.) used for chro-
matography and Kieselgur (Kieselgur, gereinigt, geglüht, Erg. B.6,
Riedel de Haen AG) used for filtration were degassed at 1 mbar at
180°C for 12 h and saturated with argon. Ϫ NMR: Bruker Avance
DPX 200 at 200.13 MHz (1H), 50.323 MHz (13C{1H}), 74.631
MHz (119Sn{1H}); chemical shifts (δ) in ppm with respect to [D6]-
acetone (1H: δ ϭ 2.04; 13C: δ ϭ 29.8) as internal standards and to
Bis(pentacarbonyltungsten)(2,2Ј-bipyridine)tin, [{(CO)5W}2-
Sn(bipy)] (1c), and Bis(pentacarbonyltungsten)(1,10-phenanthroli-
ne)tin, [{(CO)5W}2Sn(phen)] (1f). Ϫ Method A: The disodium
salt Na2[{(CO)5W}2SnCl2] (442 mg; 0.5 mmol) was dissolved in
THF (30 ml). Solid 2,2Ј-bipyridine (78 mg; 0.5 mmol) or solid 1,10-
phenanthroline (90 mg; 0.5 mmol), respectively, was added in one
portion. The orange solution turned deep red immediately. After
stirring for 30 min, the solvent was evaporated in vacuo. The oily
red residue was redissolved in THF (3 ml) and chromatographed
on silica gel (20 cm; Ø ϭ 3 cm; diethyl ether). Elution with diethyl
ether gave two bands. The first yellow band was found to contain
[W(CO)6], the second pink band contained [(CO)4W(bipy)] or
[(CO)4W(phen)], respectively. These compounds were characterized
by comparison of spectroscopic data[29][30] (IR, 1H-, and 13C-NMR
spectra). 1c or 1f were eluted with THF as a third red-brown band.
The resulting solution was taken to dryness leaving 310 mg (67%)
of 1c or 350 mg (71%) of 1f, respectively, as red microcrystalline
powders.
SnMe4 (
119Sn: δ ϭ 0 at 25°C), respectively, as external standard.
Ϫ IR: Bruker FT-IR IFS-66; CaF2 cells. Ϫ UV/Vis/NIR: Perkin
Elmer Lambda 19; cells (0.2 cm; Hellma 110 suprasil). Ϫ MS (FAB
or EI): Finnigan MAT 8400; Nibeol (4-nitrobenzyl alcohol) or
TEA (triethanol amine) matrices, respectively. Ϫ Elemental analy-
ses: microanalytical laboratory of the Organisch-Chemisches Insti-
tut, Universität Heidelberg. Ϫ Melting points: Gallenkamp MFB-
595 010; the values are not corrected. Ϫ Cyclic voltammetry:
Methrohm “Universal Meß- und Titriergefäß”, Methrohm GC
electrode RDE 628, platinum electrode, SCE electrode, Princeton
Applied Research potentiostat Model 273, 10Ϫ3 in 0.1
nBu4NPF6/CH3CN. Ϫ The dinuclear sodium salts of the compo-
sition Na2[{(CO)5M}2EX2] (E ϭ Sn: M ϭ Cr, Mo, W; X ϭ Cl;
E ϭ Pb: M ϭ Cr; X ϭ OOCCH3) were prepared by salt metathesis
reaction from the corresponding stable phosphonium salts
[Ph4P]2[{(CO)5M}2EX2] as described[4]. The biimidazole[27] and the
metallates Na2[M2(CO)10] (M ϭ Cr, Mo, W) were prepared as re-
ported[28]. All other chemicals were commercially obtained and
used without further purification.
Method B: To a stirred orange solution of the disodium metallate
Na2[W2(CO)10] (347 mg; 0.5 mmol) in ethanol (30 ml) was added
solid SnCl2 (95 mg; 0.5 mmol) in one portion. The solution turned
deep red immediately. After stirring for 30 min, the solution was
filtered through Kieselgur (3 cm). By addition of solid 2,2Ј-bipyri-
dine (78 mg; 0.5 mmol) or solid 1,10-phenanthroline (90 mg; 0.5
mmol), respectively, the corresponding chelate complex precipi-
tated. After additional stirring for 30 min, the red solid was sepa-
rated from the mother liquor by filtration, washed with ethanol (2
ϫ 5 ml) and diethyl ether (2 ϫ 5 ml), and taken to dryness. Yields:
1c: 260 mg (57%); 1f: 270 mg (56%).
Bis(pentacarbonylchromium)(2,2Ј-bipyridine)tin, [{(CO)5Cr}2-
Sn(bipy)] (1a), and Bis(pentacarbonylchromium)(1,10-phenanthro-
line)tin, [{(CO)5Cr}2Sn(phen)] (1d): Na2[{(CO)5Cr}2SnCl2] (310
mg; 0.5 mmol) was dissolved in THF (30 ml) and solid 2,2Ј-bipyri-
dine (78 mg; 0.5 mmol) or solid 1,10-phenanthroline (90 mg; 0.5
mmol), respectively, was added in one portion. The clear orange
solution turned deep red immediately. After stirring for 30 min, the
solvent was removed in vacuo. The resulting red oil was dissolved
in THF (3 ml) and chromatographed on silica gel (20 cm; Ø ϭ 3
cm; diethyl ether). Elution with diethyl ether gave two bands. The
first yellow band was identified by IR spectroscopy to be
[Cr(CO)6][29]. The second pink band was also characterized by
Single crystals of 1c or 1f were obtained within 3 d by applying
the method described below.
Bis(pentacarbonylchromium)bis(pyridine)tin,
Sn(py)2] (1g), and Bis(pentacarbonyltungsten)bis(pyridine)tin,
stirred orange solution of
[{(CO)5Cr}2-
spectroscopic comparison (IR[30], 1H-, and 13C-NMR spectra) and [{(CO)5W}2Sn(py)2] (1h): To
a
found to be [(CO)4Cr(bipy)] or [(CO)4Cr(phen)], respectively. A
third red-brown band which contained the compound 1a or 1d was
eluted with THF. The resulting solution was taken to dryness leav-
Na2[{(CO)5Cr}2SnCl2] (620 mg; 1 mmol) or Na2[{(CO)5W}2SnCl2]
(884 mg; 1 mmol), respectively, was added pyridine (316 mg; 4
mmol) in one portion. No colour change of the solution was ob-
ing 1a (230 mg; 71%) or 1d (230 mg; 68%), respectively, as red served upon the addition. After 30 min of stirring, the solution was
Eur. J. Inorg. Chem. 1998, 703Ϫ720 715
Kircher, Peter
