Bis(diphosphino)methanide and hydride derivatives of Ir4(CO)I2

Article abstract of DOI:10.1039/a909881j

The reaction of [Ir₄(CO)₁₀(u-(Ph₂P)₂CH₂)] with dried KOH forms [Ir4(CO)10(n-(Ph2P)2CH)]~ which subsequently converts into [Ir₄(CO)9(u3-(Ph₂P)₂CH)]^-, a rare example of an Ir cluster with an Ir-C bond (average 2.274(8) A). The same reaction with the weaker base l,8-diazobicyclo[5.4.0]undec-7-ene or with K2CO3 in wet CH2C12 under CO affords the anion [HIr₄(CO)₉(u-(Ph₂P)₂CH2)]~, a hydride-cluster with an unusually long Ir-H distance (2.08(6) A at 90 K). Intramolecular CO scrambling is observed in CD2C12 solution above 200 K, preserving the terminal-axial position of the hydride ligand. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/a909881j

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Bis(diphosphino)methanide and hydride derivatives of Ir4(CO)12
Serena Detti,a Tito Lumini,a Raymond Roulet,*a Kurt Schenk,b Renzo Ros*c and
Augusto Tassanc
a Institut de Chimie Minérale et Analytique de l’Université, BCH, CH–1015 Lausanne,
Switzerland
b Institut de Crystallographie de l’Université, BSP, CH–1015 Lausanne, Switzerland
c Dipartimento di Processi Chimici dell’Ingegneria e Centro di Chimica Metallorganica del
CNR, Via Marzolo 9, I–35131 Padova, Italy
Received 16th December 1999, Accepted 31st March 2000
Published on the Web 27th April 2000
The reaction of [Ir4(CO)10(µ-(Ph2P)2CH2)] with dried KOH forms [Ir4(CO)10(µ-(Ph2P)2CH)]Ϫ which subsequently
converts into [Ir4(CO)9(µ3-(Ph2P)2CH)]Ϫ, a rare example of an Ir cluster with an Ir–C bond (average 2.274(8) Å).
The same reaction with the weaker base 1,8-diazobicyclo[5.4.0]undec-7-ene or with K2CO3 in wet CH2Cl2 under CO
affords the anion [HIr4(CO)9(µ-(Ph2P)2CH2)]Ϫ, a hydride-cluster with an unusually long Ir–H distance (2.08(6) Å at
90 K). Intramolecular CO scrambling is observed in CD2Cl2 solution above 200 K, preserving the terminal–axial
position of the hydride ligand.
The same reaction, but with a large excess of the weaker base
Introduction
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (or more slowly
with K2CO3) in wet CH2Cl2 under CO gave orange crystals of
the hydrido-cluster [PPN][HIr4(CO)9(µ-dppm)] (3) (yield 86%)
by the overall reaction:
The hydrido-derivatives of Ir4(CO)12 reported to date are the
anions [HIr4(CO)11]Ϫ,1 and [H2Ir4(CO)10]2Ϫ 2
,
as well as the
neutral orthometalled species [HIr (CO) (Ph PCH᎐CHPPh )-
᎐
4
7
2
2
(PhC H PCH᎐CHPPh )].3 The examples of clusters containing
᎐
6
4
2
Ir–C(alkyl) bonds are [Ir4(CO)11(CH2CO2CH3)]Ϫ and [Ir4-
[Ir4(CO)10(µ-dppm)] ϩ DBU ϩ H2O ϩ PPNCl →
[PPN][HIr4(CO)9(µ-dppm)] ϩ CO2 ϩ [DBUH]Cl
(CO)10(CH2CO2CH3)2]2Ϫ.4 Clusters containing Ir᎐C bonds are
᎐
the carbene complexes [Ir4(CO)12 Ϫ n(COCH2CH2O)n] (n = 1–3)
derived from the nucleophilic attack of the coordinated CO
ligands of Ir4(CO)12 by oxirane.5 The classical organometallic
reactions used for the preparation of metal alkyls failed to give
any well defined derivatives from Ir4(CO)12. An idea for obtain-
ing new clusters with Ir–C bonds is therefore to deprotonate
a methylene group which is part of a bidentate ligand already
bonded to Ir and form an Ir–C bond by intramolecular
displacement of carbon monoxide.
The bidentate ligand bis(diphenylphosphino)methane
(dppm) has widely been used in coordination and organometal-
lic chemistry.6 Its deprotonated form, bis(diphenylphosphino)-
methanide, [(Ph2P)2CH)]Ϫ, has also received some attention
because of its ability to act as a two-, four- or six-electron donor
ligand, being a versatile building block for the construction of
heterometallic species.7 We report here a simple way to obtain a
new class of methanide complexes derived from deprotonation
of the dppm ligand of [Ir4(CO)10(µ-dppm)]8 or alternatively,
depending on the choice of the base, a way to obtain new
hydrido derivatives of Ir4 clusters.
The crystal structures of 2 and 3 were determined by X-ray
analysis (see below).
Crystal structures of [PPN][Ir4(CO)9(ꢀ3-(Ph2P)2CH)]ؒCH2Cl2
and [PPN][HIr4(CO)9(ꢀ-dppm)]
The structure of the anionic part of 2 and the labelling scheme
are shown in Fig. 1. Some relevant interatomic distances are
reported in Table 1. Crystallographic data for 2ؒCH2Cl2 and 3
are reported in Table 2.
The anion of 2 has approximate Cs symmetry with all terminal
CO’s. The [(Ph2P)2CH)]Ϫ ligand is face bridging with the plane
P(3)–C(32)–P(2) eclipsed relative to the plane Ir(4)–Ir(2)–Ir(3).
The mean value of the Ir–Ir distances (2.700(1) Å) is signif-
Results and discussion
The reaction of [Ir4(CO)10(µ-dppm)] (1) with two equivalents of
bis(triphenyphosphoranylidene)ammonium chloride (PPNCl)
and an excess of KOH (dry powder) in CH2Cl2 at Ϫ20 ЊC gives
rapidly a first product which could only be observed in solution,
and was identified as [Ir4(CO)10(µ-(Ph2P)2CH)]Ϫ on the basis of
its NMR characteristics (see Experimental section). After ca. 30
minutes, intramolecular coordination of the methanide moiety
is completed, affording the yellow product [PPN][Ir4(CO)9-
(µ3-(Ph2P)2CH)] (2) (yield 76%) by the overall equation:
[Ir4(CO)10(µ-dppm)] ϩ 2 KOH ϩ PPNCl →
[PPN][Ir4(CO)9(µ3-(Ph2P)2CH)] ϩ KCl ϩ KHCO3
Fig. 1 ORTEP15 representation at the 30% probability level of
[Ir4(CO)9(µ3-(Ph2P)2CH)]Ϫ.
DOI: 10.1039/a909881j
J. Chem. Soc., Dalton Trans., 2000, 1645–1648
This journal is © The Royal Society of Chemistry 2000
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Table 1 Bond lengths [Å] for 2 and 3
2
3
Ir(1)–C(1)
1.864(12)
1.889(6)
1.888(7)
1.889(7)
2.7448(3)
2.7598(4)
2.7860(4)
Ir(1)–C(1A)
Ir(1)–C(1B)
Ir(1)–Ir(2)
Ir(1)–Ir(3)
Ir(1)–Ir(4)
Ir(2)–C(2C)
Ir(2)–C(2)
Ir(2)–C(23)
Ir(2)–C(24)
Ir(2)–P(2)
Ir(2)–Ir(4)
Ir(2)–Ir(3)
1.879(14)
1.917(13)
2.7066(5)
2.7080(5)
2.7179(6)
1.892(13)
1.899(12)
1.856(7)
2.053(6)
2.176(7)
2.275(2)
2.7426(4)
2.6847(3)
1.859(7)
2.287(2)
2.6703(6)
2.7359(5)
1.872(12)
1.873(12)
Ir(3)–C(3)
Ir(3)–C(3C)
Ir(3)–C(23)
Ir(3)–C(34)
Ir(3)–P(3)
Ir(3)–Ir(4)
Ir(4)–H(4)
2.103(6)
2.151(7)
2.291(2)
2.7276(4)
2.08(6)
2.299(2)
2.6620(6)
Fig. 2 ORTEP representation at the 50% probability level of
[Ir4(CO)9(µ-dppm)]Ϫ.
Ir(4)–C(4)
1.855(7)
icantly shorter than that found for [Ir4(CO)7(µ-CO)3-
(µ-(Ph2P)2CHMe)] (1Ј) (2.729(1) Å).9 A DFT calculation on
Rh4(CO)12 and IrRh3(CO)12 has shown that unbridged metal–
metal bonds are shorter than CO-bridged ones.10 This conclu-
sion seems to be also valid for the present, substituted clusters.
The metal tetrahedron is not regular, as the three Ir–Ir distances
of the Ir(2)–Ir(3)–Ir(4) face bearing the [(Ph2P)2CH)]Ϫ ligand
differ by more than 0.06 Å, the longest being that between the
Ir-atoms bearing the P-atoms and the shortest being the other
two bonds of that face. All the bond distances (and bond
angles) of the Ir2P2C ring are smaller than the corresponding
ones in 1Ј, probably denoting the better donor properties of the
deprotonated ligand relative to the neutral dppm ligand. As
expected, the average Ir–C distance (2.274(8) Å) is longer than
the Ir᎐C(carbene) distances of 1.94–2.06 Å in [Ir (CO)12 Ϫ n(CO-
Ir(4)–C(4B)
Ir(4)–C(4A)
Ir(4)–C(24)
Ir(4)–C(34)
Ir(4)–C(32)
Ir(4)–P(3)
1.869(12)
1.871(12)
2.046(7)
2.064(6)
2.274(8)
2.931(2)
2.956(2)
1.164(12)
1.178(13)
1.141(12)
1.137(12)
1.147(12)
Ir(4)–P(2)
O(1)–C(1)
1.168(8)
1.152(8)
1.131(8)
1.170(8)
O(1A)–C(1A)
O(1B)–C(1B)
O(2)–C(2)
O(2C)–C(2C)
O(23)–C(23)
O(24)–C(24)
O(3)–C(3)
O(3C)–C(3C)
O(34)–C(34)
O(4)–C(4)
O(4A)–C(4A)
O(4B)–C(4B)
P(2)–C(32)
C(32)–H(32A)
C(32)–H(32B)
P(2)–C(200)
P(2)–C(210)
P(3)–C(32)
P(3)–C(310)
P(3)–C(300)
C(32)–H(32)
1.173(7)
1.167(8)
1.160(8)
1.157(12)
1.168(12)
1.172(8)
1.153(9)
᎐
4
CH2CH2O)n] (n = 1–3),5 but also longer than the Ir–C distances
found in [Ir4(CO)11(CH2CO2Me)]Ϫ and [Ir4(CO)10(CH2CO2-
Me)2]2Ϫ (2.15–2.19 Å).4
1.150(12)
1.142(11)
1.786(9)
1.843(6)
0.97
0.97
1.829(6)
1.817(6)
1.829(6)
1.836(6)
1.841(6)
The anionic structure of 3 and the labelling scheme are
shown in Fig. 2. Some relevant interatomic distances are
reported in Table 1. The anion has approximate Cs symmetry
with the mirror plane defined by atoms Ir(1) and Ir(4), and the
methylene group. Three CO’s are edge-bridging, defining the
basal face Ir(2)–Ir(3)–Ir(4). The P-atoms of the dppm ligand
are in axial positions relative to the basal face. The comparison
between corresponding bond distances of 3 and 2 gives the
same trends as that described above between 1’ and 2. Due to
the presence of 3 edge-bridging CO’s, the mean value of the
Ir–Ir distance (2.769(3) Å) is longer than that of 2. Likewise,
the interatomic distances in the Ir2P2C ring (mean Ir–P 2.283,
mean P–C 1.836 Å) in 3 are longer than those in 2 (2.293 and
1.789 Å, respectively). The value for the Ir–H distance (2.08(6)
Å at 90 K) is unusually large, both relative to the range found in
monometallic complexes (1.5–1.9 Å)11 and to the calculated
range (1.54–1.60 Å).12 The temperature was low enough to
locate this H–atom during the refinement down to 4.16%.
However, a neutron diffraction experiment will be undertaken
to verify this value.
1.818(10)
1.840(10)
1.792(9)
1.822(9)
1.841(9)
1.01
Table 2 Crystallographic data for compounds 2ؒCH2Cl2 and 3
2ؒCH2Cl2
3
Formula
M
C71H53Cl2Ir4NO9P4
2027.72
C70H53Ir4NO9P4
1944.81
0.5 × 0.4 × 0.3
90(3)
Crystal size/mm
T/K
293(2)
Monoclinic
P21/n
12.6694(8)
26.479(2)
20.7990(13)
94.0210(10)
6960.4(8)
4
1.935
3840
7.848
51.0
Crystal system
Space group
Monoclinic
P21/c
a/Å
b/Å
c/Å
10.2149(8)
18.4724(13)
33.772(3)
94.578(9)
6352.3(8)
4
2.034
3680
8.259
51.88
β/Њ
V/Å3
Behaviour of clusters 2 and 3 in solution
Z
Complex 2 is thermally stable in CH2Cl2 solution up to room
temperature. It reverts back to 1 upon adding 1 equivalent of
HCl under CO. It converts to 3 upon adding excess DBU and
1 equivalent of H2O under CO, or to the deuterido-analog of
3 when replacing H2O by D2O.
Its geometry in solution is similar to that found in the solid,
as deduced from IR, 1H-, 31P- and 13C-NMR spectroscopy (see
Experimental section). A 2D–COSY spectrum of an enriched
Dc/g cmϪ3
F(000)
µ/mmϪ1
2θmax/Њ
Reflections collected/unique
28587/11402
821
0.0554
49085/12165
797
0.0412
Variables
R1
wR2
0.823
0.838
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Fig. 3 2D-COSY spectrum of 2 in CD2Cl2 at 193 K (see Fig. 4 for the
carbonyl labelling scheme).
Fig. 4 Experimental (left) and calculated (right) VT 13C-NMR spectra
of 2 in CD2Cl2.
sample of 2 in 13CO (ca. 30%) at 193 K (Fig. 3) shows the
pseudo-trans coupling between carbonyls d and f, the signal at
177.2 ppm being due to carbonyls d closest to the CHϪ group,
and shows also that the apical CO’s e and g (respectively at
163.4 and 160.4 ppm) are already in the slow exchange domain.
The only exchange mechanism in CD2Cl2 for compound 2,
noticeable above 203 K, is the rotation of the apical carbonyls,
as shown by the variable temperature 13C-NMR spectra (Fig. 4,
left) which were simulated using a two-site exchange matrix
(Fig. 4, right). Regression of the Eyring plot ln(k/T) vs. 1/T
gave a value of 43.1 0.6 kJ molϪ1 for the free enthalpy of
activation at 298 K for the rotation of the apical carbonyls
about the local C3 axis.
process of CO scrambling, starting at ca. 200 K, is the merry-
go-round of the basal carbonyls a, b, d and f.
The second process is the rotation of apical carbonyls, which
could not be simulated due to the similar δ values of carbonyls g
and e. Simulation of the merry-go-round was effected with a
four sites exchange matrix (Fig. 5, right). Regression of the
function ln(k/T) vs. 1/T gave a value of 39.4 1.4 kJ molϪ1 for
the free enthalpy of activation at 298 K, which is quite similar
to that found for anionic Ir4 clusters such as [Ir4(CO)11X]Ϫ
(X = Br, I, NCS, NO2).13
Experimental
The geometry of 3 in solution is similar to that found in
Unless otherwise stated, all the operations were carried out
under nitrogen, all solvents were dried by conventional methods
prior to use. PPNCl (Fluka) was used as received. KOH (Fluka)
was dried at 150 ЊC under reduced pressure (10Ϫ4 mm Hg).
DBU (Aldrich) was dried with KOH and distilled. [Ir4(CO)10-
(µ-dppm)] was prepared as described in the literature,8 as well as
13CO enriched derivatives of 2 and 3 (ca. 30% enrichment).14
Infrared spectra were recorded from 0.1 mm CaF2 cells prev-
iously purged with N2 on a Perkin-Elmer FT-IR 2000 spec-
trometer. Elemental analyses were performed at the Analytische
1
the solid, as deduced from IR, H-, 31P- and 13C-NMR spec-
troscopy (see Experimental section). The 1H-NMR spectrum at
210 K shows the CH2 group of the dppm ligand as an ABX2
spin system due to the inequivalence of the two methylene
protons: whereas the HB proton shows the expected chemical
shift at 2.69 ppm, the HA proton is abnormally deshielded at
6.03 ppm. This pattern is quite similar to that found for 1;8
therefore, the conformation of the dimetallacyclopentane ring
must be that found in solid 1Ј9 (where a methyl group replaces
the HB proton of dppm). The hydride ligand is coordinated in
an axial position, replacing the unique axial CO in 1 (Ϫ15.7
ppm). This is deduced from the presence of three resonances
in the 13C-NMR limiting spectrum of a 13CO enriched sample
of 3 (ca. 30% enrichment) in the region of radial CO’s (the
two P-atoms and the H-atom must therefore occupy axial
positions). Cluster 3 is fluxional in solution, as shown by the
variable temperature 13C-NMR spectra (Fig. 5, left). The first
1
Laboratorien, Lindlar, Germany. H-,31P- and 13C-NMR spec-
tra were recorded on a Bruker AC200 spectrometer, using
the residual proton peaks and carbon resonances of deuterated
1
solvents as chemical shift references for H- and 13C-NMR
spectra. 31P-NMR spectra were referenced to external 85%
H3PO4. 13C-NMR and 2D-13C-NMR spectra were recorded in
10 mm o.d. tubes on a Bruker WH360 spectrometer. COSY
experiment: 256 t1 increments with 2K transients, spectral
J. Chem. Soc., Dalton Trans., 2000, 1645–1648
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mmol) in CH2Cl2 (20 cm3) under CO was cooled to Ϫ10 ЊC and
DBU (600 µl, 4 mmol) was added. The solution was stirred for
2 h, then cold isopropanol (20 cm3) was added and the volume
of the mixture reduced by half. The orange precipitate was
recrystallised at Ϫ30 ЊC from CH2Cl2 (ϩPPNCl)/isopropanol
and the crystals of 3 were washed with cold isopropanol and
pentane (0.32 g, 87%) (Found: C, 43.08; H, 2.71; N, 0.69; P,
6.28; Ir, 39.70%. C70H53Ir4NO9P4 requires C, 43.23; H, 2.75; N,
0.72; P, 6.37; Ir, 39.53%). νmax/cmϪ1 (CH2Cl2): 2010m, 1960vs,
1827vs, 1766 m ν(CO). δH (CD2Cl2, 210 K): 7.6–7.0 (50 H; m,
Ph); 6.03 [1 H, dt, 2J(HA,HB) 12.8 Hz, 2J(P,H) 10.3 Hz, HA], 2.69
2
2
[1 H, dt, J(HA,HB) 12.8 Hz, J(P,H) 12.8 Hz, HB)], Ϫ15.7 (Ir-
H). δP (CD2Cl2, 210 K): 20.1 (PPNϩ), Ϫ52.9 (PPh2). δC (CD2Cl2,
200 K): 225.0 (2 CO; s, a), 224.5 (1 CO, s, b), 186.7 (1 CO, s, d),
185.1 (2 CO, s, f), 165.0 (1 CO, s, e) 164.9 (2 CO, m, g). Suitable
crystals of 3 for an X-ray diffraction study were obtained by
slow diffusion of hexane in a CH2Cl2 solution at 0 ЊC.
X-Ray crystallography
Compound 2. A yellow crystal was brought onto a Bruker
SMART CCD system equipped with Mo radiation. All non-
hydrogen atoms were refined anisotropically, and all hydrogens
were made to ride on their associated carbons.
Compound 3. An orange crystal of which the habitus
¯
¯
consisted of {100}, {001} pinacoids, (10, 2), (0, 1 0) pedions
and a (161) fracture plane was cooled, using an Oxford Cryo-
stream, to 90 K, the temperature of the data collection which
took place on a Stoe IPDS system equipped with Mo radiation.
All non-hydrogen atoms were refined anisotropically, and all
hydrogens but H4 were made to ride on their associated
carbons. The hydrogen H4 was difficult to find in difference
maps and isotropically refined to a position surprisingly far
away from Ir4 [2.08(6) Å].
CCDC reference number 186/1923.
See http://www.rsc.org/suppdata/dt/a9/a909881j/ for crystal-
lographic files in .cif format.
Fig. 5 Experimental (left) and calculated (right) VT 13C-NMR spectra
of 3 in CD2Cl2.
width 2840.9 Hz in the F2 domain and 1420.5 Hz in the
F1 domain.
Acknowledgements
We thank the Swiss National Science Foundation for financial
support.
Bis(triphenylphosphoranylidene)ammonium tetrahedro-nona-
carbonyl{ꢀ3-bis(diphenylphosphino)methanido}tetrairidate (2)
([PPN][Ir4(CO)9(ꢀ3-(Ph2P)2CH)])
References
Dry KOH powder (0.20 g) and PPNCl (0.37 g, 0.64 mmol) were
added to a solution of 1 (0.40 g, 0.28 mmol) in CH2Cl2 (15 cm3)
under N2 at Ϫ20 ЊC. After a few minutes the deprotonated
intermediate [Ir4(CO)10(µ-(Ph2P)2CH)]Ϫ was formed but could
not be isolated. δC (CD2Cl2, 210 K): 231.2 (1 CO, s), 214.7
(2 CO, m), 185.2 (2 CO, radial, s), 174.3 (1 CO, radial, s), 166.4
(1 CO, s), 159.8 (1 CO, s), 159.0 (2 CO, m). δP (CD2Cl2, 210 K):
Ϫ59.2 (PPh2). The suspension was stirred for 35 minutes,
filtered, and cold isopropanol (80 cm3) added. The yellow pre-
cipitate was recrystallised at Ϫ30 ЊC from CH2Cl2/isopropanol,
and the crystals of 2 washed with cold isopropanol and pentane
(0.41 g, 76%) (Found: C, 43.14; H, 2.69; N, 0.71; P, 6.32; Ir,
39.75%. C70H51Ir4NO9P4 requires C, 43.27; H, 2.65; N, 0.72; P,
6.38; Ir, 39.57%). νmax/cmϪ1 (CH2Cl2): 2034s, 1983vs, 1924w
ν(CO). δH (CD2Cl2, 298 K): 7.7–6.6 (50 H, m, Ph); 3.95 [1 H, t,
2J(P,H) 5.5 Hz, CH]. δP (CD2Cl2, 298 K): 21.0 (PPNϩ), Ϫ44.4
(PPh2). δC (CD2Cl2, 173 K): 177.1 (2 CO, s, d), 172.8 (2 CO, s, f),
167.0 (2 CO, s, c), 163.3 (1 CO, s, e), 160.2 (2 CO, m, g). Suitable
crystals of 2 for an X-ray diffraction study were obtained by
slow diffusion of hexane in a CH2Cl2 solution at 0 ЊC.
1 L. Malatesta and C. Caglio, Chem. Commun., 1967, 420; R. Bau,
M. Y. Chiang, C.-Y. Wei, L. Garlaschelli, S. Martinengo and T. F.
Koetzle, Inorg. Chim. Acta, 1984, 23, 4758; M. J. Davis and R.
Roulet, Inorg. Chim. Acta, 1992, 197, 15.
2 G. Ciani, M. Manassero, V. G. Albano, F. Canziani, G. Giordano,
S. Martinengo and P. Chini, J. Organomet. Chem., 1978, 150, C17.
3 V. G. Albano, D. Braga, R. Ros and A. Scrivanti, J. Chem. Soc.,
Chem. Commun., 1985, 866.
4 F. Ragaini, F. Porta and F. Demartin, Organometallics, 1991, 10, 185.
5 G. Bondietti, R. Ros, R. Roulet, F. Musso and G. Gervasio, Inorg.
Chim. Acta, 1993, 213, 301.
6 R. J. Puddephatt, Chem. Soc. Rev., 1983, 12, 99.
7 A. Laguna and M. Laguna, J. Organomet. Chem., 1990, 394, 743.
8 R. Ros, A. Scrivanti, V. G. Albano, D. Braga and L. Garlaschelli,
J. Chem. Soc., Dalton Trans., 1986, 2411; A. Strawczynski,
G. Suardi, R. Ros and R. Roulet, Helv. Chim. Acta, 1993, 76, 2210.
9 T. Lumini, G. Laurenczy, R. Roulet, A. Tassan, R. Ros, K. Schenk
and G. Gervasio, Helv. Chim. Acta, 1998, 81, 781.
10 K. Besançon, G. Laurenczy, T. Lumini, R. Roulet, R. Bruyndonckx
and C. Daul, Inorg. Chem., 1998, 37, 5634.
11 R. G. Teller and R. Bau (Editors), in Structure and Bonding,
Springer-Verlag, Berlin, 1981, vol. 44, pp. 1–82.
12 M. Casarrubios and L. Seijo, J. Chem. Phys., 1999, 110, 784.
13 R. Roulet, in The Synergy Between Dynamics and Reactivity at
Clusters and Surfaces, ed. L. J. Farrugia, Kluwer Academic
Publishers, Dordrecht, 1995, pp. 159–173.
14 R. Ros and A. Tassan, Inorg. Chim. Acta, 1997, 260, 89.
15 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National
Laboratory, Oak Ridge, TN, 1976.
Bis(triphenylphosphoranylidene)ammonium tetrahedro-nona-
carbonyl(hydrido){ꢀ-bis(diphenylphosphino)methane}tetra-
iridate (3) ([PPN][HIr4(CO)9(ꢀ-dppm)])
A solution of 1 (0.27 g, 0.19 mmol) and PPNCl (0.21 g, 0.37
1648
J. Chem. Soc., Dalton Trans., 2000, 1645–1648