M. Gorol, N. C. Mösch-Zanetti, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt
FULL PAPER
of the cationic iridium complex [Ir(C8H12)(PPh3)2]ϩ in the
presence of weakly coordinating anions is well-known.[14]
In addition, the appearance of the [SiF5]Ϫ anion is not un-
expected, if reactions involving HF are carried out in glass
vessels.[20] Thus, the reaction of 1 in THF with an excess of
aqueous HF in a glass vessel affords 4 in quantitative yield,
after two equiv. of triphenylphosphane were added
(Scheme 1). The 1H NMR spectrum of 4 shows three reson-
ances of equal intensity for the protons of the cyclooc-
tadiene ligand [δ ϭ 4.20 (br. s, 4 H), δ ϭ 2.33 (m, 4 H) and
δ ϭ 1.97 ppm (m, 4 H)]. These values are similar to δ ϭ
4.14 (s, 4 H) and δ ϭ 2.12 ppm (m, 8 H) found in
[Ir(C8H12)(PPh3)2][BF4].[24] The formation of the cationic
bisphosphane complex is best documented by its 13C NMR
spectrum. The resonance for the carbon atoms of the
ϭCHϪ groups of the cyclooctadiene ligand appears as a
triplet [δ ϭ 87.40 ppm (t, J ϭ 5.58 Hz)] indicative of coup-
ling to two phosphorus nuclei, whereas the ϪCH2Ϫ groups
show a singlet at δ ϭ 31.37 ppm. In the 19F NMR spectrum
a broad resonance (δ ϭ Ϫ139.1 ppm) is observed. This is
in good agreement with that reported (δ ϭ Ϫ139 ppm) for
the [SiF5]Ϫ anion in [Au(PPh3)3][SiF5].[18] The 31P NMR
resonance is shifted upfield in comparison to that of com-
pound 3 and appears as a singlet at δ ϭ 17.4 ppm. Com-
Figure 2. Molecular structure of the [Ir(C8H12)(PPh3)2]ϩ cation in
4 with 50% probability ellipsoids and the labelling scheme; selected
bond lengths (pm) and angles (°): Ir(1)ϪC(1) 221.5(11), Ir(1)ϪC(2)
223.5(10), Ir(1)ϪC(5) 216.5(11), Ir(1)ϪC(6) 219.5(11), Ir(1)ϪP(1)
233.1(3), Ir(1)ϪP(2) 235.3(3), C(1)ϪC(2) 140.8(16), C(5)ϪC(6)
132.3(19), P(1)ϪC(11) 184.1(11), P(1)ϪC(21) 180.6(11),
P(1)ϪC(31) 181.4(10), P(2)ϪC(41) 183.0(11), P(2)ϪC(51)
184.3(10), P(2)ϪC(61) 183.9(11); C(1)ϪIr(1)ϪP(1) 153.7(3),
C(2)ϪIr(1)ϪP(1) 168.7(3), C(5)ϪIr(1)ϪP(1) 95.6(3), C(6)ϪIr(1)Ϫ
P(1) 89.5(3), C(1)ϪIr(1)ϪP(2) 93.9(3), C(2)ϪIr(1)ϪP(2) 86.7(2),
˜
pound 4 gives rise to bands in the infrared spectrum at (ν ϭ
879, 790, 479 and 448 cmϪ1 CsI plates), due to SiϪF modes
similar to those reported in the literature.[16]
C(5)ϪIr(1)ϪP(2)
152.0(4),
C(6)ϪIr(1)ϪP(2)
170.4(4),
Single crystals suitable for X-ray diffraction analyses of
4 were obtained by slow diffusion of pentane into a concen-
trated CH2Cl2 solution. Compound 4 crystallises in the
monoclinic space group P21/c. A structure determination
showed one [Ir(C8H12)(PPh3)2]ϩ cation, one non-coordi-
nated [SiF5]Ϫ anion and a solvent molecule CH2Cl2 in the
asymmetric unit. The cation is depicted in Figure 2 together
with selected bond lengths and angles. The iridium-phos-
phorus bond lengths [Ir(1)ϪP(1) 233.1(3) and Ir(1)ϪP(2)
235.3(3) pm] are similar to those of IrϪP(1) 236.7(2) and
IrϪP(2) 232.6(3) pm found in [Ir(C8H12)(PPh3)2][PF6].[14]
The [SiF5]Ϫ anion is not coordinated to an iridium atom
(shortest Ir···F distance is 461.1 pm). The geometry of the
silicon atom is regular bipyramidal. The SiϪFeq bond
lengths are Si(1)ϪF(1) 158.4(10), Si(1)ϪF(3) 159.8(10) and
Si(1)ϪF(5) 158.3(10) pm. The SiϪFax distances are longer,
with values of Si(1)ϪF(2) 162.3(10) and Si(1)ϪF(4)
162.5(11) pm. The bond lengths and angles for the [SiF5]Ϫ
anions in the compounds [Au(PPh3)3][SiF5], [Ir(CO)2-
(PtBu2Ph)2][SiF5] and [Ir(H)2(CO)2(PtBu2Ph)2][SiF5], are in
the same range as those for compound 4.[18,19]
P(1)ϪIr(1)ϪP(2) 94.43(9)
tributable to a ν˜CO mode. These data lead to the assumption
that one of the products of the decomposition of 3 is the
Vaska complex IrF(CO)(PPh3)2. The formation of a car-
bonyl complex is in agreement with reports of the ability
of rhodium() systems to abstract carbon monoxide from
oxygen-containing organic solvents.[25]
Conclusion
The present study describes the synthesis and characteris-
ation of IrF(C8H12)(PPh3) and provides the first crystallo-
graphic data for an organoiridium() fluoro complex. The
reaction of [Ir(µ-OH)(C8H12)]2 with concentrated aqueous
HF yields the fluoro complex, only in Teflon tubes, whereas
the use of glass vessels led to [Ir(C8H12)(PPh3)2][SiF5]. The
X-ray diffraction analysis of this iridium() complex salt
shows that the rather unstable [SiF5]Ϫ anion can be trapped.
Once compound 3 has been isolated it does not interact
with the glass surface. Evidence for that is derived from
NMR and IR spectroscopic data obtained from the oily
residue, formed in a glass vessel, as a result of the decompo-
sition of 3 after some weeks. In the 19F NMR spectrum a
triplet (δ ϭ Ϫ256.3 ppm, t, J ϭ 28.8 Hz) and in the 31P{H}
NMR spectrum a doublet (δ ϭ 24.5 ppm, d, J ϭ 28.7 Hz)
suggest the formation of a complex, which has one fluorine
atom and two phosphane groups bonded to the iridium
Experimental Section
General Remarks: Solvents were dried and distilled under nitrogen
prior to use. All reactions were carried out under dry nitrogen,
using standard Schlenk techniques. NMR spectra were recorded
using a Bruker Avance 200, Bruker MSL 400 or a Bruker Avance
500 spectrometer and referenced to the resonances of the residual
atom. The IR spectrum exhibits a band at 1945 cmϪ1 at- protons in deuterated benzene or CD2Cl2. 1H NMR: external
Eur. J. Inorg. Chem. 2004, 2678Ϫ2682