R. Rupp, G. Huttner, H. Lang, K. Heinze, M. Büchner, E. R. Hovestreydt
FULL PAPER
LiCϵCPh (2 mmol) in Et2O (5 mL) was added at Ϫ80 °C. The re-
action mixture was stirred for 10 min at this temperature and then
allowed to warm to 25 °C resulting in a colour change from beige
to red-brown. The solvent was evaporated and the residue dissolved
in CH2Cl2. Ph4PCl (1 mmol, 375 mg) was added and the reaction
mixture stirred for 20 min. After removal of the solvent under re-
duced pressure, the residue was redissolved in toluene and filtered
to remove LiCl. Evaporation of the solvent produced PPh4ϩ2a؊ as
a red-brown, air-sensitive powder. Ϫ 1H NMR (CD2Cl2): δ ϭ 1.28
(br. s, 3 H, CH3), 2.46 (br. s, 6 H, CH2), 7.07Ϫ7.48 (m, 60 H, Har).
observed that they undergo one-electron oxidation which
results in oxidative coupling of the alkynyl ligands to pro-
duce 1,3-diynes and concomitant reduction of CoII to CoI
to produce [tripodCo(η2-RCϵCCϵCR)]ϩ (5).
Experimental Section
General Remarks: Unless otherwise noted, all manipulations were
carried out under argon by means of standard Schlenk techniques
All solvents were dried by standard methods and distilled under
argon.[18] The CD2Cl2 used for NMR spectroscopic measurements
was degassed by three successive ‘‘freeze-pump-thaw’’ cycles and
Ϫ
31P NMR (CD2Cl2): δ ϭ 26.8 (s, PPh4ϩ), 32.1 (s, CH2ϪP). Ϫ
IR (KBr): ν(CC) ϭ 2049 (w) cmϪ1. Ϫ MS (FAB-negative): m/z ϭ
885 [MϪ]. Ϫ C81H69CoP4 (1225.27): calcd. C 79.40, H 5.68; found
C 78.21, H 5.82. Ϫ M.p. 145 °C (dec.).
˚
dried with 4 A molecular sieves. Ϫ EPR: Bruker ESP 300 E, X-
General Procedure for the Synthesis of Compounds 4: Compound 2
(1 mmol) was dissolved in toluene and treated with a threefold ex-
cess of Ni(CO)4. The reaction mixture was stirred for 2 h. No col-
our change took place, but a slow gas evolution was observed. The
solvent was removed under reduced pressure and the residue recrys-
tallised from CH2Cl2. After evaporation of the solvent, compounds
4 were obtained as black-brown microcrystalline powders.
band, standard cavity ER 4102, temperature control unit Euro-
therm B-VT 2000, external standard dipenylpicrylhydrazyl
(DPPH); Simulation: XSophe Computer Simulation Software
Suite, Version 1.0.4b, 1993Ϫ1999; XEPRView, Version 1.0, 1999;
Bruker Analytik, Rheinstetten, Germany. Ϫ NMR: Bruker Avance
DPX 200 at 200.12 MHz (1H), 50.323 MHz (13C{1H}),
81.015 MHz (31P{1H}), T ϭ 303 K; chemical shifts (δ) are given in
ppm with respect to CD2Cl2 (1H: δ ϭ 5.32; 13C: δ ϭ 53.8) as in-
ternal standard. 31P chemical shifts (δ) are given in ppm with re-
spect to 85% H3PO4 (31P: δ ϭ 0) as external standard. Ϫ IR:
Bruker IFS-66, KBr disks. Ϫ MS: Finnigan MAT 8230; Fast-atom
bombardment (FAB) xenon, matrix: 4-nitrobenzyl alcohol. Ϫ HR-
MS (FAB) JEOL JMS 700, matrix: 4-nitrobenzyl alcohol. Ϫ Mag-
netic measurements: Faraday balance with a Bruker electromagnet
B-E 15 C8, Bruker Field Controller B-H 15, Sartorius vacuum-
microbalance M25 D-S, Oxford Temperature Control Unit ITC-4;
calibration with K3[Fe(CN)6]. Ϫ Molecular weight determinations:
Knauer vapor-pressure osmometer No. 7311100000; calibration
with dibenzil. Ϫ Elemental analyses: Microanalytical Laboratory
of the Organisch-Chemisches Institut, Universität Heidelberg. Ϫ
Melting points: Gallenkamp MFB-595 010, melting points are not
corrected. Ϫ Cyclic voltammetry: Metrohm ‘‘Universal Meß- und
Titriergefäß’’, Metrohm GC electrode RDE 628, platinum elec-
trode, SCE electrode, Princeton Applied Research potentiostate
Model 273, 10Ϫ3 in 0.1 nBu4NPF6/CH2Cl2.
CV (4b, CH2Cl2, vs. SCE): E1/2 ϭ 605 mV (rev.), ∆E ϭ 90 mV.
General Procedure for the Synthesis of Compounds 5: Compound 2
(1 mmol) was dissolved in acetone (25 mL) and treated with
(Cp2Fe)PF6 (1 mmol, 332 mg). The colour immediately changed
from black-brown to green. The solvent was removed under re-
duced pressure and the resulting green residue was purified by chro-
˚
matography on SiO2 (ICN 32Ϫ63, 60 A) with PE (boiling range
40Ϫ60 °C)/CH2Cl2 (5:1). After evaporation of the solvent, the PF6
salts 5aϪc were obtained as fine black-green powders. Single crys-
tals of compound 5b suitable for X-ray diffraction were obtained
after three months by diffusion of PE (boiling range 40Ϫ60 °C)
into a solution of 5b in THF.
Preparation of 5a·Co2(CO)6: Compound 5a (0.1 mmol, 103 mg)
was dissolved in acetone (10 mL). [Co2(CO)8] (0.15 mmol, 52 mg)
was added and the reaction mixture was stirred for 1.5 h. A
darkening of the solution was evident after a few minutes. The solv-
ent was removed under reduced pressure and the residue was
washed three times with Et2O. After evaporation of the solvent, the
Co2(CO)6 adduct of 5a was obtained as a black microcrystalline
powder.
General Procedure for the Synthesis of Compounds 2: Alkyne
(2 mmol) was dissolved in Et2O (5 mL) and deprotonated with
nBuLi (0.8 mL, 2.5 in n-hexane) at Ϫ80 °C. After 5 min, the reac-
tion mixture was allowed to warm to room temperature. [tri-
podCoCl2] (1 mmol, 753 mg) was dissolved in THF (25 mL) and
cooled to Ϫ80 °C. The acetylide was added at Ϫ80 °C with a syr-
inge, and a brown solution was immediately formed. After 10 min
at Ϫ80 °C, the reaction mixture was allowed to warm to room
temperature and the solvent was removed under reduced pressure.
The resulting black-brown residue was dissolved in toluene and
filtered to remove LiCl. After evaporation of the solvent, com-
pounds 2 were obtained as microcrystalline black-brown powders.
Attempts to obtain crystals suitable for X-ray crystallography were
unsuccessful. Compounds 2 are highly soluble in organic solvents
such as hexane, toluene, Et2O, and methanol such that crystallis-
ation by diffusion is unfeasible; slow evaporation of the solvent
leaves them as microcrystalline powders only. Cooling the solutions
down to Ϫ80 °C also did not result in single crystals.
31P NMR (CD2Cl2): δ ϭ 36.9 (s, CH2ϪP). Ϫ IR (KBr): ν(CO) ϭ
2100 (s), 2083 (s), 2054 (s), 2034 (s) cmϪ1. Ϫ MS (FAB): m/z ϭ
1171 [Mϩ], 1143 [Mϩ Ϫ CO], 1115 [Mϩ Ϫ 2CO], 1087 [Mϩ
3CO], 1059 [Mϩ Ϫ 4CO], 1031 [Mϩ Ϫ 5CO], 885 [Mϩ
Co2(CO)6].
Ϫ
Ϫ
X-ray Crystallographic Study: The measurement was carried out on
a Siemens AXS Smart CCD diffractometer using graphite-mono-
chromated Mo-Kα radiation. All calculations were performed us-
ing the SHELXT PLUS software package. The structure was solved
by direct methods with the SHELXS-97 program and refined with
the SHELXL-97 program.[19] Graphical handling of the structural
data during solution and refinement was performed with
XPMA.[20] Atomic coordinates and anisotropic thermal parameters
of the non-hydrogen atoms were refined by full-matrix least-squares
calculations. Table 5 lists the data for the structure determination.
µeff (2a, 25 °C) ϭ 1.8 BM; osmometric determination of the mo-
lecular mass of compound 2a: calcd./found: 885/887.
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Preparation of PPh4[tripodCoI-(CϵCPh)2], PPh4ϩ2a؊: [tri-
podCoCl] (3) (1 mmol, 718 mg) was suspended in THF (20 mL). Crystallographic Data Centre as supplementary publication
1958 Eur. J. Inorg. Chem. 2000, 1953Ϫ1959