Mixed-metal cluster chemistry. 2.1 site-selective substitution of CpWIr3(CO)11 by phosphines: X-ray crystal structures of CpWIr3(μ-CO)3(CO)7(PPh3), CpWIr3(μ-CO)3(CO)6(PPh3) 2, and CpWIr3(μ-CO)3(CO)7(PMe3)

Article abstract of DOI:10.1021/om950554o

Reactions of CpWIr₃(CO)₁₁ (1) with stoichiometric amounts of phosphines afford site-selective products CpWIr₃(μ-CO)₃(CO)_8-x(L)_x (L = PPh₃, x = 1 (2), 2 (3), or 3 (4); L = PMe₃, x = 1 (5), 2 (6), or 3 (7)) in fair to excellent yields (38-63%). These products exhibit ligand fluxionality in solution, resolvable at low temperature into the constituent interconverting isomers. The structures of three of the species, namely 2a, 3a, and 5a, have been determined by X-ray diffraction studies. The single-crystal X-ray studies reveal that ligand substitution induces a rearrangement in the cluster coordination sphere from the all-terminal carbonyl ligand geometry of CpWIr₃(CO)₁₁ to one in which the three edges of a WIr₂ face of the tetrahedral core contain bridging carbonyls (2a, 3a) or one in which the three edges of the triiridium face are bridged by carbonyl ligands (5a). The triphenylphosphine in 2a ligates radially to the carbonyl-bridged WIr₂ face; a similar site for one of the phosphines is found in 3a, with the second triphenylphosphine coordinated in an axial position with respect to this face. The trimethylphosphine ligand in 5a is located in an axial site with respect to the basal carbonyl-bridged triiridium plane. Information from the crystallographically-verified isomers, the ligand substitution pattern in the related tetrairidium system, and chemical shifts of signals in the ³¹P NMR spectra has been used to suggest coordination geometries for the isomeric forms of the complexes above and for other reported derivatives.

Full text of DOI:10.1021/om950554o

934
Organometallics 1996, 15, 934-940
Mixed -Meta l Clu ster Ch em istr y. 2.1 Site-Selective
Su bstitu tion of Cp WIr 3(CO)11 by P h osp h in es: X-r a y
Cr ysta l Str u ctu r es of Cp WIr 3(µ-CO)3(CO)7(P P h 3),
Cp WIr 3(µ-CO)3(CO)6(P P h 3)2, a n d
Cp WIr 3(µ-CO)3(CO)7(P Me3)
Susan M. Waterman and Mark G. Humphrey*
Department of Chemistry, Australian National University, Canberra, ACT 0200, Australia
Vicki-Anne Tolhurst
Department of Chemistry, University of New England, Armidale, NSW 2351, Australia
Brian W. Skelton and Allan H. White
Department of Chemistry, University of Western Australia, Nedlands, WA 6907, Australia
David C. R. Hockless
Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
Received J uly 20, 1995X
Reactions of CpWIr3(CO)11 (1) with stoichiometric amounts of phosphines afford site-
selective products CpWIr3(µ-CO)3(CO)8-x(L)x (L ) PPh3, x ) 1 (2), 2 (3), or 3 (4); L ) PMe3,
x ) 1 (5), 2 (6), or 3 (7)) in fair to excellent yields (38-63%). These products exhibit ligand
fluxionality in solution, resolvable at low temperature into the constituent interconverting
isomers. The structures of three of the species, namely 2a , 3a , and 5a , have been determined
by X-ray diffraction studies. The single-crystal X-ray studies reveal that ligand substitution
induces a rearrangement in the cluster coordination sphere from the all-terminal carbonyl
ligand geometry of CpWIr3(CO)11 to one in which the three edges of a WIr2 face of the
tetrahedral core contain bridging carbonyls (2a , 3a ) or one in which the three edges of the
triiridium face are bridged by carbonyl ligands (5a ). The triphenylphosphine in 2a ligates
radially to the carbonyl-bridged WIr2 face; a similar site for one of the phosphines is found
in 3a , with the second triphenylphosphine coordinated in an axial position with respect to
this face. The trimethylphosphine ligand in 5a is located in an axial site with respect to
the basal carbonyl-bridged triiridium plane. Information from the crystallographically-
verified isomers, the ligand substitution pattern in the related tetrairidium system, and
chemical shifts of signals in the 31P NMR spectra has been used to suggest coordination
geometries for the isomeric forms of the complexes above and for other reported derivatives.
In tr od u ction
The chemistry of mixed-metal clusters has been the
subject of great interest.2 Although site selectivity
investigations of mixed-metal clusters with phosphines
have been widespread,2a,3 most of these studies have
been with mixed-metal clusters containing metals from
the same group or from adjacent groups.
Results from work with tetrahedral clusters have
been summarized.3j Although the least sterically hin-
dered sites are the radial carbonyl sites (Figure 1), most
F igu r e 1.
* To whom correspondence should be addressed.
monosubstituted homometallic or pseudotetrahedral
heterometallic clusters have ligands in an axial site,
presumably an electronic effect. Homometallic cluster
substitution then proceeds at a different basal metal to
afford bis-substituted derivatives with diaxial coordina-
tion for small ligands or radial, axial coordination for
sterically encumbered ligands. The third incoming
ligand occupies a basal coordination site to minimize
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
(1) Part 1: Lee, J .; Humphrey, M. G.; Hockless, D. C. R.; Skelton,
B. W.; White, A. H. Organometallics 1993, 12, 3457.
(2) (a) Gladfelter, W. L.; Fox, J . R.; Smegal, J . A.; Wood, T. G.;
Geoffroy, G. L. 1981, 20, 3223. (b) Roberts, D. A.; Geoffroy, G. L. In
Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G.
A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1982; Vol. 6, p
763. (c) Bruce, M. I. J . Organomet. Chem. 1983, 242, 147. (d) Bruce,
M. I. J . Organomet. Chem. 1985, 17, 399. (e) Sappa, E.; Tiripicchio,
A.; Braunstein, P. Coord. Chem. Rev. 1985, 65, 219.
0276-7333/96/2315-0934$12.00/0 © 1996 American Chemical Society

Mixed-Metal Cluster Chemistry
Organometallics, Vol. 15, No. 3, 1996 935
although no special precautions were taken to exclude air
during workup. The reaction solvent dichloromethane was
dried over CaH2, and tetrahydrofuran (THF) was distilled from
sodium/benzophenone under argon prior to use; all other
solvents were reagent grade and used as received. Petroleum
ether refers to a fraction of boiling point range 40-70 °C. The
products of thin-layer chromatography were separated on 20
× 20 cm glass plates coated with Merck GF254 silica gel (0.5
4
mm). The clusters CpWIr3(CO)11 and CpWIr3(µ-CO)3(CO)7-
(PPh3)1 were prepared by the published procedures. Tri-
phenylphosphine (Aldrich) and trimethylphosphine (Aldrich,
1 M solution in THF) were purchased commercially and used
as received.
P h ysica l Mea su r em en ts. Infrared spectra were recorded
on a Perkin-Elmer Model 1600 Fourier transform spectropho-
tometer with CaF2 optics. 1H and 13C NMR spectra were
recorded on a Varian Gemini 300 spectrometer (1H spectra at
300 MHz, 13C at 75 MHz). The 13C NMR spectra were proton
decoupled and recorded using ca. 0.02 M Cr(acac)3 as a
relaxation agent. 31P NMR spectra were recorded on a Varian
VXR300S spectrometer (121 MHz) and are proton decoupled.
Spectra were run in CDCl3 (Aldrich) or acetone-d6 (Aldrich);
chemical shifts in ppm are referenced to internal residual
solvent for 1H and 13C NMR spectra and external 85% H3PO4
for 31P NMR spectra.
Mass spectra were obtained either at the University of
Adelaide on a VG ZAB 2HF mass spectrometer (FAB source
of argon at 10-6 mbar, FAB gun voltage 7.5 kV, current 1 mA,
ion accelerating potential 8 kV, matrix 3-nitrobenzyl alcohol,
ca. 0.5 M solutions in dichloromethane) or at the Australian
National University on a VG ZAB 2SEQ instrument (30 kV
Cs+ ions, current 1 mA, accelerating potential 8 kV, matrix
3-nitrobenzyl alcohol). Peaks were recorded as m/ z based on
183W assignments and are reported in the following form: m/ z
(assignment, relative intensity). Elemental microanalyses
were performed by the Microanalysis Service Unit in the
Research School of Chemistry, Australian National University,
or by the Microanalysis Service Unit in the Department of
Chemistry, University of Queensland. Decomposition tem-
peratures and melting points were measured in sealed capil-
laries using a Gallenkamp melting point apparatus.
F igu r e 2. Common substitution geometries for tetrahedral
clusters with edge-bridging carbonyls about one face.
steric effects, to usually give a diradial, axial derivative.
The fourth ligand substitutes at the apical metal, forcing
the two ligands of the basal metals on the Mapical(Mbasal 2
)
face to axial sites and the other ligand into a radial site
(Figure 2). For mixed-metal hydrido clusters of this
geometry, the hydride occupies a face-capping site below
the basal plane, displacing the radial carbonyls toward
the apical metal and increasing available space at the
axial site; both mono- and disubstitution are commonly
axial.
By contrast with the studies above, investigations
with mixed-metal clusters employing widely differing
metals are comparatively rare. We have previously
reported site-specific products from reaction between
CpWIr3(CO)11 (1) and equimolar PPh3, dppm, dppe, or
dppa and structural studies on CpWIr3(µ-L)(µ-CO)3(CO)6
(L ) dppm, dppe, dppa).1 We report herein the reactiv-
ity of 1 toward 1, 2, or 3 equiv of PPh3 or PMe3 and the
characterization by single-crystal X-ray studies of three
of the site-selective reaction products, CpWIr3(µ-CO)3-
(CO)7(PPh3) (2a ), CpWIr3(µ-CO)3(CO)6(PPh3)2 (3a ), and
CpWIr3(µ-CO)3(CO)7(PMe3) (5a ).
Rea ction of Cp WIr 3(CO)11 w ith 2 equ iv of P P h 3. An
orange solution of CpWIr3(CO)11 (30.3 mg, 0.0267 mmol) and
PPh3 (14.0 mg, 0.0534 mmol) in CH2Cl2 (20 mL) was stirred
at room temperature for 24 h. The dark orange solution
obtained was evaporated to dryness. The resultant orange
residue was dissolved in CH2Cl2 (ca. 1 mL) and chromato-
graphed (3:2 CH2Cl2/petroleum ether eluant). Three bands
were obtained. The contents of the first band were identified
as CpWIr3(µ-CO)3(CO)7(PPh3) (2.3 mg, 6%) by solution IR
spectroscopy. The second band contained a small amount of
an unidentified green compound. Crystallization of the con-
tents of the third band, Rf 0.48, from CH2Cl2/MeOH afforded
orange crystals of CpWIr3(µ-CO)3(CO)6(PPh3)2, 3 (12.0 mg,
45%, mp 167 °C (dec)). Analytical data for 3: IR (c-C6H12) 2059
vs, 2027 w, 2009 s, 2001 vs, 1986 s, 1958 m, 1904 m, 1815 m
Exp er im en ta l Section
Gen er a l In for m a tion . All reactions were performed under
an atmosphere of dry nitrogen (high-purity grade, CIG),
(3) (a) Lindsell, W. E.; Walker, N. M.; Boyd, A. S. F. J . Chem. Soc.,
Dalton Trans. 1988, 675. (b) Pursiainen, J .; Ahlgren, M.; Pakkanen,
T.; Valkonen, J . J . Chem. Soc., Dalton Trans. 1990, 1147. (c) Curnow,
O. J .; Kampf, J . W.; Curtis, M. D. Organometallics 1991, 10, 2546. (d)
Ojima, I.; Clos, N.; Donovan, R. J .; Ingallina, P. Organometallics 1991,
10, 3211. (e) Le Grand, J .-L.; Lindsall, W. E.; McCullough, K. J . J .
Organomet. Chem. 1991, 413, 321. (f) Le Grand, J .-L.; Lindsall, W. E.;
McCullough, K. J .; McIntosh, C. H.; Meiklejohn, A. G. J . Chem. Soc.,
Dalton Trans. 1992, 1089. (g) Fox, J . R.; Gladfelter, W. L.; Wood, T.
G.; Smegal, J . A.; Foreman, T. K.; Geoffroy, G. L.; Tavanaiepour, I.;
Day, V. W.; Day, C. S. Inorg. Chem. 1981, 20, 3214. (h) Horvath, I. T.
Organometallics 1986, 5, 2333. (i) Sappa, E.; Marchino, M. L. N.;
Predieri, G.; Tiripicchio, A.; Camellini, M. T. J . Organomet. Chem.
1986, 307, 97. (j) Bojczuk, M.; Heaton, B. T.; J ohnson, S.; Ghilardi, C.
A.; Orlandini, A. J . Organomet. Chem. 1988, 341, 473. (k) Pakkanen,
T. A.; Pursianen, J .; Vena¨la¨inen, T.; Pakkanen, T. T. J . Organomet.
Chem. 1989, 372, 129. (l) Pursianen, J .; Pakkanen, T. A. Acta. Chem.
Scand. Ser. A 1989, 43, 463. (m) Matsuzaka, H.; Kodama, T.; Uchida,
Y.; Hidai, M. Organometallics 1988, 7, 1608. (n) Pursiainen, J .;
Pakkanen, T. A.; J a¨a¨skela¨inen, J . J . Organomet. Chem. 1985, 290, 85.
(o) Bahsoun, A. A.; Osborn, J . A.; Voelker, C.; Bonnet, J . J .; Lavigne,
G. Organometallics 1982, 1, 1114. (p) Eshtiagh-Hosseini, H.; Nixon,
J . F. J . Organomet. Chem. 1978, 150, 129. (q) Labroue, D.; Queau, R.;
Poilblanc, R. J . Organomet. Chem. 1980, 186, 101. (r) Huie, B. T.;
Knobler, C. B.; Kaesz, H. D. J . Am. Chem. Soc. 1978, 100, 3059. (s) Le
Grand, J .-L.; Lindsall, W. E.; McCullough, K. J . J . Organomet. Chem.
1989, 373, C1.
cm-1 1H NMR (CDCl3) δ 7.58-7.29 (m, 30H, C6H5), 4.87 (s
;
(br), 5H, C5H5); 13C NMR (CDCl3) δ 133.9-128.0 (C6H5), 87.5
(C5H5); 31P NMR (CDCl3) δ 27.3 (s, 2P), 25.1 (s, 1P), -7.7 (s,
1P); FAB MS 1602 ([M]+, 57), 1574 ([M - CO]+, 54), 1546 ([M
- 2CO]+, 69), 1518 ([M - 3CO]+, 100), 1490 ([M - 4CO]+, 42),
1462 ([M - 5CO]+, 100), 1434 ([M - 6CO]+, 64), 1406 ([M -
7CO]+, 58), 1378 ([M - 8CO]+, 40). Anal. Calcd: C, 37.48;
H, 2.20. Found: C, 37.44; H, 2.22%.
Rea ction of Cp WIr 3(CO)11 w ith 3 equ iv of P P h 3. An
orange solution of CpWIr3(CO)11 (21.5 mg, 0.0190 mmol) and
PPh3 (14.9 mg, 0.0568 mmol) in CH2Cl2 (25 mL) was stirred
at room temperature for 18 h and then evaporated to dryness.
The resultant dark orange residue was redissolved in CH2Cl2
(4) Shapley, J . R.; Hardwick, J .; Foose, D. S.; Stucky, G. D. J . Am.
Chem. Soc. 1981, 103, 7383.

936 Organometallics, Vol. 15, No. 3, 1996
Waterman et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for 2a , 3a , a n d 5a
(ca. 1 mL) and chromatographed (3:2 CH2Cl2/petroleum ether
eluant) to afford two products, one of which was in trace
amounts. The major product, Rf 0.29, was crystallized (CHCl3/
EtOH at -20 °C) to afford red crystals of CpWIr3(µ-CO)3(CO)5-
(PPh3)3, 4 (16.2 mg, 46%, mp 145 °C (dec)).5 Analytical data
for 4: IR (c-C6H12) 2059 m, 2027 w, 2009 s, 2000 vs, 1986 s,
1958 m, 1904 m, 1815 m cm-1; 1H NMR (acetone-d6) δ 8.02 (s,
0.66H, CHCl3), 7.57-7.37 (m, 45H, C6H5), 4.82 (s, 5H, C5H5);
31P NMR (CDCl3) δ 31.8 (s, 2P), -17.9 (s, 1P); FAB MS 1420
([M - PPh3 - 2Ph]+, 43), 1392 ([M - PPh3 - 2Ph-CO]+, 39),
2a
3a
5a
chem formula
fw
space group
cryst system
a, Å
C33H20Ir3O10PW C50H35Ir3O9P2W C18H14Ir3O10PW
1367.9
P1h (No. 2)
triclinic
15.174(7)
11.792(4)
9.774(5)
79.33(4)
83.28(4)
78.77(3)
1680
1602.2
1181.8
P1h (No. 2)
triclinic
9.486(2)
17.058(4)
30.590(6)
100.08(2)
94.60(2)
89.63(2)
4857
P21/c (No. 14)
monoclinic
15.262(3)
10.808(5)
28.92(2)
b, Å
c, Å
R, deg
â, deg
98.38(5)
1364 ([M - PPh3 - 2Ph - 2CO]+, 100), 1336 ([M - PPh3
-
γ, deg
2Ph - 3CO]+, 84), 1308 ([M - PPh3 - 2Ph - 4CO]+, 58). Anal.
Calcd: C, 42.42; H, 2.67. Found: C, 42.16; H, 2.38.
V, Å3
4720
F
calcd, g cm-3
2.70
2.25
3.231
Z
2
15.4
4
11.0
8
21.3
Rea ction of Cp WIr 3(CO)11 w ith 1 equ iv of P Me3. An
orange solution of CpWIr3(CO)11 (21.0 mg, 0.0185 mmol) and
PMe3 (20 µL, 1 M solution in THF, 0.020 mmol) in THF (20
mL) was stirred at room temperature for 18 h after which
solvent was removed from the resulting dark orange solution
in vacuo. The orange residue was dissolved in CH2Cl2 (ca. 1
mL) and chromatographed (3:2 CH2Cl2/petroleum ether eluant)
to afford two products, one of which was in trace amounts.
The major product, Rf 0.19, was crystallized (CHCl3/MeOH)
to afford orange crystals of CpWIr3(µ-CO)3(CO)7(PMe3), 5 (8.2
mg, 38%, mp 143 °C). Analytical data for 5: IR (c-C6H12) 2070
s, 2040 vs, 2030 m, 2021 s, 2003 s, 1992 vs, 1958 w, 1920 m,
µ, mm-1
spec size, mm 0.084 × 0.45
0.064 × 0.037
× 0.18
1.3, 1.9
50
8283
3068
0.22 × 0.10
× 0.16
1, 3.2
50
17 219
8921
× 0.12
A*(min, max) 3.2, 6.5
2θmax, deg
60
N
9805
7362
0.043
0.049b
No
R
0.071
0.039
a
Rw
0.070b
0.034c
a
2 1/2 b
Rw(Fo) ) (∑w(|Fo| - |Fc|)2/∑wFo
)
.
Statistical weights de-
rivative of σ2(I) ) σ2(Idiff) + 0.0004σ4(Idiff); useful data were limited
in consequence of specimen size, supporting meaningful anisotro-
pic thermal parameter refinement for Ir, W, and P only. c w ) 4Fo
/
2
1
1840 w cm-1; H NMR (CDCl3) δ 5.03 (s, 5H, C5H5), 1.91 (d,
σ2(Fo2), where σ2(Fo2) ) [σ2(C + 4B) + (pFo2)2]/Lp2 (s ) scan rate,
C ) peak count, B ) background count, p ) 0.007 determined
experimentally from standard reflections).
J HP ) 11 Hz, 6H, CH3); 13C NMR (acetone-d6) δ 84.0 (s, C5H5),
20.4 (d, J CP ) 38 Hz, CH3), 20.1 (s, CH3); 31P NMR (acetone-
d6) δ -26.1 (s, 1P), -30.2 (s, 1P); FAB MS 1182 ([M]+, 6), 1154
([M - CO]+, 38), 1126 ([M - 2CO]+, 42), 1098 ([M - 3CO]+,
69), 1070 ([M - 4CO]+, 100), 1042 ([M - 5CO]+, 31), 1028 ([M
- 5CO - CH3]+, 10), 1012 ([M - 5CO - 2CH3]+, 55), 997 ([M
- 5CO - 3CH3]+, 11), 984 ([M - 6CO - 2CH3]+, 46), 969 ([M
- 6CO - 3CH3]+, 32), 954 ([M - 6CO - 4CH3]+, 15). Anal.
Calcd: C, 18.29; H, 1.19. Found: C, 18.24; H, 0.80.
3CO]+, 75), 1166 ([M - 4CO]+, 100), 1138 ([M - 5CO]+, 45),
1110 ([M - 6CO]+, 80), 1082 ([M - 7CO]+, 40), 1067 ([M -
7CO - CH3]+, 50), 1052 ([M - 7CO - 2CH3]+, 45), 1037 ([M -
7CO - 3CH3]+, 30), 1024 ([M - 8CO - 2CH3]+, 25), 1009 ([M
- 8CO - 3CH3]+, 21), 994 ([M - 8CO - 4CH3]+, 20).
Satisfactory analyses could not be obtained due to sample
decomposition over days.
X-r a y Cr ysta llogr a p h y. Crystals of compounds 2a , 3a ,
and 5a suitable for diffraction analyses were grown by slow
diffusion of methanol into either dichloromethane (2a , 3a ) or
chloroform (5a ) solutions at room temperature. Unique dif-
fractometer data sets were measured at ∼295 K within the
specified 2θmax limit (2θ/θ scan mode; monochromatic Mo KR
radiation (λ ) 0.71073 Å)) yielding N independent reflections.
No of these with I > 3σ(I) were considered “observed” and used
in the full-matrix/large block least-squares refinements after
analytical absorption correction. Anisotropic thermal param-
Rea ction of Cp WIr 3(CO)11 w ith 2 equ iv of P Me3. An
orange solution of CpWIr3(CO)11 (22.9 mg, 0.0203 mmol) and
PMe3 (40 µL, 1 M solution in THF, 0.040 mmol) in THF (20
mL) was stirred at room temperature for 18 h, after which
the solvent was removed from the dark orange solution in
vacuo. The resultant orange residue was dissolved in CH2Cl2
(ca. 1 mL) and chromatographed (3:2 CH2Cl2/petroleum ether
eluant) to afford two products, one of which was in trace
amounts. The major product, Rf 0.40, was crystallized (CHCl3/
MeOH) to afford orange crystals of CpWIr3(µ-CO)3(CO)6-
(PMe3)2, 6 (9.6 mg, 41%, 159 °C). Analytical data for 6: IR
(c-C6H12) 2044 m, 2004 vs, 1988 vs, 1977 m, 1965 m, 1955 m,
eters were refined for the non-hydrogen atoms; (x, y, z, Uiso
)
H
1
1807 w cm-1; H NMR (CDCl3) δ 5.06 (s, 5H, C5H5), 1.97 (d,
were included, constrained at estimated values. Conventional
residuals R, Rw on |F| at convergence are given. Neutral atom
complex scattering factors were used, computation using the
XTAL 3.2 program system (2a , 3a ),6 implemented by Hall, or
teXsan (5a ).7 Pertinent results are given in the figures and
tables. Individual variants are noted in Table 1.
J HP ) 10 Hz, 3H, CH3); 13C NMR (acetone-d6) δ 88.3 (s, C5H5),
20.5 (d, J CP ) 38 Hz, CH3), 20.3 (s, CH3); 31P NMR (acetone-
d6) δ -20.8 (s, 2P), -22.7 (s, 1P), -38.7 (s, 1P); FAB MS 1202
([M - CO]+, 12), 1174 ([M - 2CO]+, 24), 1146 ([M - 3CO]+,
100), 1118 ([M - 4CO]+, 37), 1090 ([M - 5CO]+, 14), 1062 ([M
- 6CO]+, 37), 1034 ([M - 7CO]+, 23). Anal. Calcd: C, 19.55;
H, 1.89. Found: C, 19.49; H, 1.91.
Resu lts a n d Discu ssion
Rea ction of Cp WIr 3(CO)11 w ith 3 equ iv of P Me3. An
orange solution of CpWIr3(CO)11 (22.3 mg, 0.0198 mmol) and
PMe3 (60 µL, 1 M solution in THF, 0.060 mmol) in THF (20
mL) was stirred at room temperature for 18 h, after which
the solvent was removed from the dark orange solution in
vacuo. The resultant orange residue was dissolved in CH2Cl2
(ca. 1 mL) and chromatographed (3:2 CH2Cl2/petroleum ether
eluant) to afford one product. The orange band, Rf 0.56, was
crystallized (CHCl3/MeOH) to afford orange crystals of CpWIr3-
(µ-CO)3(CO)5(PMe3)3, 7 (8.2 mg, 63%). Analytical data for 7:
Syn th eses a n d Ch a r a cter iza tion . The reactions
of CpWIr3(CO)11 (1) with n equiv of PPh3 (n ) 1, 2, or
3) or PMe3 (n ) 1, 2, or 3) proceed in dichloromethane
at room temperature to afford the clusters CpWIr3(µ-
CO)3(CO)8-n(PPh3)n (n ) 1, 2; n ) 2, 3; n ) 3, 4) or
CpWIr3(µ-CO)3(CO)8-n(PMe3)n (n ) 1, 5; n ) 2, 6; n )
3, 7), respectively, as the major or sole reaction products
in fair to excellent yields (38-63%). The products have
1
been characterized by a combination of IR and H, 13C,
IR (c-C6H12) 2002 s, 1966 vs, 1957 s, 1949 vs, 1815 vw cm-1
;
and 31P NMR spectroscopies, FAB MS, and satisfactory
1H NMR (CDCl3) δ 4.89 (s, 5H, C5H5), 1.54 (d, J HP ) 10 Hz,
9H, CH3); 31P NMR (CDCl3) δ -27.1 (s, 1P), -45.2 (s, 1P),
-83.4 (s, 1P); FAB MS 1222 ([M - 2CO]+, 80), 1194 ([M -
(6) Hall, S. R.; Flack, H. D.; Stewart, J . M. The Xtal 3.2 Reference
Manual; Universities of Western Australia, Geneva, and Maryland:
Nedlands, Western Australia, Geneva, Switzerland, and College Park,
MD, 1992.
(5) Complex 4 has been isolated and formulated previously: McA-
teer, C. H.; Shapley, J . R. Unpublished results.
(7) teXsan; Single Crystal Structure Analysis Software, version 1.6c;
Molecular Structure Corp.: The Woodlands, TX, 1993.

Mixed-Metal Cluster Chemistry
Organometallics, Vol. 15, No. 3, 1996 937
Ta ble 2. Im p or ta n t Bon d Len gth s (Å) for
Com p lexes 2a a n d 3a
2a
3a
2a
3a
Ir(1)-Ir(2) 2.6775(9) 2.708(3) Ir(2)-C(21) 1.87(1)
Ir(1)-Ir(3) 2.734(1) 2.778(3) Ir(2)-C(22) 1.87(1) 1.73(5)
Ir(2)-Ir(3) 2.685(1) 2.725(3) Ir(3)-C(31) 1.94(1) 1.82(4)
Ir(1)-W(4) 2.813(1) 2.785(3) Ir(3)-C(32) 1.92(1) 1.97(5)
Ir(2)-W(4) 2.841(1) 2.918(3) Ir(3)-C(33) 1.90(1) 1.81(5)
Ir(3)-W(4) 2.896(1) 2.869(3) W(4)-C(2) 2.09(1) 2.19(5)
Ir(1)-P(1)
Ir(2)-P(2)
Ir(1)-C(1) 2.08(1)
Ir(1)-C(3) 2.10(1)
Ir(1)-C(11) 1.85(1)
Ir(2)-C(1) 2.14(1)
Ir(2)-C(2) 2.17(1)
2.330(3) 2.34(1) W(4)-C(3) 2.17(1) 2.09(5)
2.32(1) W(4)-C(41) 1.97(1) 1.88(4)
2.12(4) W(4)-C(01) 2.31(2) 2.29(5)
2.04(4) W(4)-C(02) 2.32(1) 2.24(7)
1.74(5) W(4)-C(03) 2.34(2) 2.30(7)
2.00(4) W(4)-C(04) 2.30(2) 2.26(5)
2.09(5) W(4)-C(05) 2.27(2) 2.23(5)
Ta ble 3. Im p or ta n t Bon d Len gth s (Å) for
Com p lex 5a
mol A
mol B
mol C
mol D
Ir(1)-Ir(2)
Ir(1)-Ir(3)
Ir(2)-Ir(3)
Ir(1)-W(1)
Ir(2)-W(1)
Ir(3)-W(1)
Ir(3)-P(1)
Ir(1)-C(1)
Ir(1)-C(3)
Ir(1)-C(11)
Ir(1)-C(12)
Ir(2)-C(1)
Ir(2)-C(2)
Ir(2)-C(21)
Ir(2)-C(22)
Ir(3)-C(2)
Ir(3)-C(3)
Ir(3)-C(31)
W(1)-C(41)
W(1)-C(42)
W(1)-C(01)
W(1)-C(02)
W(1)-C(03)
W(1)-C(04)
W(1)-C(05)
2.756(1)
2.739(1)
2.753(2)
2.855(1)
2.839(1)
2.894(1)
2.312(7)
2.10(2)
2.13(2)
1.85(2)
1.93(3)
2.12(2)
2.13(3)
1.81(3)
1.94(2)
2.11(2)
2.12(2)
1.81(3)
1.98(2)
1.99(3)
2.30(2)
2.28(2)
2.38(3)
2.41(3)
2.31(3)
2.733(1)
2.739(1)
2.757(1)
2.838(1)
2.837(1)
2.897(1)
2.322(7)
2.09(3)
2.06(3)
1.87(2)
1.90(2)
2.14(2)
2.13(2)
1.88(3)
2.01(3)
2.07(2)
2.05(2)
1.86(3)
2.00(2)
1.94(3)
2.29(2)
2.34(2)
2.40(2)
2.38(2)
2.31(2)
2.734(1)
2.748(1)
2.750(1)
2.846(1)
2.836(1)
2.886(1)
2.313(7)
2.10(2)
2.10(3)
1.94(3)
1.92(2)
2.11(3)
2.13(2)
1.93(3)
1.95(2)
2.06(2)
2.09(2)
1.87(3)
1.96(3)
1.99(2)
2.29(3)
2.31(2)
2.36(3)
2.37(2)
2.32(2)
2.738(1)
2.747(1)
2.745(1)
2.838(1)
2.843(1)
2.892(1)
2.322(7)
2.14(3)
2.10(3)
1.89(2)
1.95(2)
2.12(2)
2.12(3)
1.81(3)
1.92(3)
2.06(2)
2.07(2)
1.87(3)
1.95(3)
2.00(3)
2.26(2)
2.28(2)
2.39(3)
2.39(2)
2.32(2)
F igu r e 3. Molecular structure and atomic labeling scheme
for CpWIr3(µ-CO)3(CO)7(PPh3), 2a . Thermal envelopes of
20% probability are shown for the non-hydrogen atoms;
hydrogen atoms have arbitrary radii of 0.1 Å.
by single-crystal X-ray studies are consistent with the
formulations given above, define the substitution sites
for these derivatives, and aid interpretation of the 31P
NMR spectra (see below). A summary of crystal and
refinement data is found in Table 1, and selected bond
distances are listed in Tables 2 (2a and 3a ) and 3 (5a ).
ORTEP plots showing the molecular geometry and
atomic numbering scheme are shown in Figures 3 (2a ),
4 (3a ) and 5 (5a ).
microanalyses. Infrared spectra suggest the presence
of edge-bridging carbonyl ligands in all complexes
(ν(CO) 1840-1807 cm-1), which contrasts with the all-
terminal precursor 1. In combination with the X-ray
structural results detailed below, the number of bands
in the terminal carbonyl ligand ν(CO) region is indica-
Complexes 2a and 3a have the WIr3 pseudotetrahe-
dral framework of the precursor cluster 1 and possess
η5-cyclopentadienyl groups, three bridging carbonyls
arranged about a WIr2 plane, six (3a ) or seven (2a )
terminal carbonyl ligands, and one (2a ) or two (3a )
iridium-ligated triphenylphosphine ligands. The WIr3
core distances (W-Irav ) 2.85 Å, 2a , and 2.86 Å, 3a ;
Ir-Irav ) 2.699 Å, 2a , and 2.737 Å, 3a ) can be compared
to those of 1 (W-Irav ) 2.82 Å, Ir-Irav ) 2.699 Å) and
possibly suggest some slight core expansion; core dis-
tances of the diphosphine-substituted complexes Cp-
WIr3(µ-dppe)(µ-CO)3(CO)6, CpWIr3(µ-dppm)(µ-CO)3(CO)6,
and CpWIr3(µ-dppa)(µ-CO)3(CO)6 are also larger than
those of 1.1 As previously observed in the diphosphine
clusters, the longest W-Ir distance in 2a is effectively
trans to the Cp group, although that in 3a is on the WIr2
face to which the Cp group is inclined. In 3a , the
shortest Ir-Ir bonds are between the phosphine-
coordinated iridiums, the longest Ir-Ir vector in both
CpWIr3(µ-dppe)(µ-CO)3(CO)6 and CpWIr3(µ-dppm)(µ-
CO)3(CO)6. The cyclopentadienyl groups in 2a and 3a
are inclined toward the WIr2 faces containing the
bridging carbonyl ligands. Carbonyl distances and
angles for 3a are relatively imprecise and will not be
tive of the presence of isomers. The H and 13C NMR
1
(where appropriate) spectra contain signals assigned to
Cp and Ph groups for 2-4, and Cp and Me groups for
5-7. Discussion of the 31P NMR spectra is deferred
until the solid state structures are presented (see below),
but the spectra indicate the presence of interconverting
isomers in solution; the crystallographically observed
isomers of 2, 3, and 5 are labeled a . The FAB mass
spectra of complexes 2, 3, and 5 have molecular ions,
stepwise loss of carbonyls, and isotope patterns consis-
tent with the presence of three iridium atoms and one
tungsten atom; in some cases, loss of Ph is competitive
with loss of the last few carbonyl ligands. The FAB
mass spectra of derivatives 4, 6, and 7 do not contain
molecular ions. Although mass spectra for 6 and 7
exhibit loss of carbonyls from the molecular ion, that of
4 shows initial loss of a phosphine ligand, followed by
loss of carbonyls, possibly a result of steric factors.
X-r a y Str u ctu r a l Stu d ies of 2a , 3a , a n d 5a . The
molecular structures of 2a , 3a , and 5a as determined

938 Organometallics, Vol. 15, No. 3, 1996
Waterman et al.
the increase in electron density (and capacity for back-
donation) at Ir(1) resultant upon phosphine substitu-
tion. Complexes 2a and 3a are the first examples from
the tungsten-iridium system with bridging carbonyls
at a WIr2 face. The Ir-P distances (2.330(3) Å (2a ), 2.33
Å (3a ) (average)) are unexceptional, as are the intra-
phosphine bond lengths and angles. Formal electron
counting reveals that 2a and 3a have 60 e, electron
precise for tetrahedral clusters.
Single-crystal X-ray diffraction of 5a revealed the
presence of four independent molecules per asymmetric
unit, each molecule differing only slightly from the
others. No chemically significant differences exist in
the four independent molecules; a representative mol-
ecule is depicted in Figure 5. As with 2a , complex 5a
also possesses a WIr3 pseudotetrahedral framework
with η5-cyclopentadienyl groups, phosphine ligand, and
seven terminal carbonyl ligands but instead has three
bridging carbonyls arranged around the triiridium
plane, a structural type found previously with the
bidentate ligand derivatives CpWIr3(µ-L)(µ-CO)3(CO)6
(L ) dppm, dppe, dppa).1 The WIr3 core distances (W-
Irav 2.863 Å, Ir-Irav 2.749 Å) are comparable to 2a and
3a ; as with 2a , the longest W-Ir distance for 5a is
effectively trans to the Cp group, and the shortest Ir-
Ir bond is that effectively trans to the phosphine ligand.
The cyclopentadienyl group is inclined toward a WIr2
face; three W-C distances (average 2.30 Å) are shorter
than the two W-C distances (average 2.40 Å) involving
the carbons closest to the Ir-Ir vector. Ir-CO(terminal)
interactions (1.81(5)-1.94(1) Å) and W-CO interactions
(1.98(2)-1.99(3) Å) are normal. Cluster 5a is also
electron precise with 60 e.
F igu r e 4. Molecular structure and atomic labeling scheme
for CpWIr3(µ-CO)3(CO)6(PPh3)2, 3a . Thermal envelopes of
20% probability are shown for the non-hydrogen atoms;
hydrogen atoms have arbitrary radii of 0.1 Å.
Discu ssion . As mentioned above, the IR spectra in
the terminal carbonyl ligand ν(CO) region are indicative
of the presence of isomers. This is also true of the 31P
NMR spectra. The room-temperature 31P NMR spec-
trum of 2 contains a broad resonance at about -0.5 ppm,
which decoalesces to give resonances (ratio approxi-
mately 4:5) at 4.7 and -5.1 ppm at 228 K. Similarly,
the room-temperature spectrum of 3 contains two broad
resonances, which sharpen on cooling to 230 K to give
three resonances at 27.3, 25.1, and -7.7 ppm in the ratio
2:1:1. The room-temperature 31P NMR spectra of the
complexes 4-7 were found to have either broad reso-
nances or no signals at all. Lowering the temperature
to 230 K sharpened the resonances, suggesting fluxion-
ality in each of the derivatives. In analogous tetrairi-
dium clusters, Shapley has assigned downfield 31P NMR
resonances to radially-coordinated phosphines and up-
field signals to axially-coordinated phosphines, with
respect to the plane of the bridging carbonyl ligands.9
F igu r e 5. Molecular structure and atomic labeling scheme
for CpWIr3(µ-CO)3(CO)7(PMe3), 5a . Thermal envelopes of
50% probability are shown for the non-hydrogen atoms;
hydrogen atoms have arbitrary radii of 0.1 Å.
discussed here. Ir-CO(terminal) interactions for 2a
(1.85(1)-1.94(1) Å) and W-CO(terminal) distances
(1.97(1) Å) are comparable to those reported in other
tungsten-iridium carbonyl complexes;4,8 the M-C-O
angles are in the normal range for terminal carbonyl
groups (171(1)-178(1)°). In 2, carbonyls 1 and 3 bridge
asymmetrically toward Ir(1), with Ir(1)-CO(1) 2.08(1)
Å, Ir(2)-CO(1) 2.14(1) Å, Ir(1)-CO(3) 2.10(1) Å, and
W(4)-CO(3) 2.17(1) Å; CO(2) is displaced toward tung-
sten [W(4)-CO(2) 2.09(1) Å, Ir(2)-CO(2) 2.17(1) Å]. The
asymmetry in bridging carbonyls presumably reflects
1
This has been generalized and extended; in the H, 13C,
and 31P NMR spectra of tetrairidium cluster compounds,
the chemical shifts of the ligands decrease in the
following positional sequence: bridging > radial > axial
≈ apical.10a Resonances of the phosphine-substituted
tungsten-iridium clusters, and their suggested sites of
substitution, are listed in Table 4. As detailed below,
these substitution sites have been assigned by utilizing
information from (a) the crystallographically-verified
isomers, (b) the substitution pattern in the tetrairidium
system (see Introduction), and (c) chemical shifts in the
31P NMR spectra.
(8) (a) Churchill, M. R.; Bueno, C.; Hutchinson, J . P. Inorg. Chem.
1982, 21, 1359. (b) Churchill, M. R.; Biondi, L. V. J . Organomet. Chem.
1989, 366, 265. (c) Churchill, M. R. J . Organomet. Chem. 1985, 280,
C63.
(9) Stuntz, G. F.; Shapley, J . R. J . Am. Chem. Soc. 1976, 99, 607.

Mixed-Metal Cluster Chemistry
Organometallics, Vol. 15, No. 3, 1996 939
Ta ble 4. 31P NMR Da ta for Cp WIr 3(µ-CO)3(CO)11-x (P R3)x (R ) P h , Me; x ) 1, 2, or 3)
suggested site of PR3 substitution,
with respect to (µ-CO)3 plane
isomer
ratio
complex
n ) 1, R ) PPh3
31P NMR chem shifts
4.7a
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7
radialc
4
5
1
1
-5.1a
axial
n ) 2, R ) PPh3
n ) 3, R ) PPh3
n ) 1, R ) PMe3
n ) 2, R ) PMe3
25.1, -7.7 (1:1)a
27.3a
radial, axialc
diradial
31.8, -17.9 (2:1)a
diaxial, apical
diradial, apical
axialc
radial
radial, axial
diradial
-30.2b
3
2
4
5
-26.1b
-22.7, -38.7 (1:1)b
-20.8b
n ) 3, R ) PMe3
-27.1, -45.2, -83.4 (1:1:1)b
radial, axial, apical
a
b
CDCl3, 230 K. Acetone-d6, 230 K. c Crystallographically confirmed.
F igu r e 6. Possible configurations for 2-4.
F igu r e 7. Possible configurations for 5-7.
Geometries of possible isomers of 2-4 are given in
Figure 6. The crystallographically observed 2a has Cp
occupying an axial site and PPh3 occupying a radial site
(radial, axial isomer). The axially coordinated phos-
phine is consistent with the other isomer adopting
diaxial or radial, axial geometries, but we favor the
latter (2b); diaxial coordination is unlikely with bulky
ligands (cone angles: Cp 136°, PPh3 145°). Isomer 3a
is the crystallographically observed radial, diaxial form.
The other isomer presumably adopts the diradial, axial
structure 3b, which would minimize steric repulsion
from the Cp ligand. All previous structurally confirmed
tetrasubstituted tetrahedral tetrairidium clusters adopt
radial, diaxial, apical geometries.9,10bc Assuming that
this substitution pattern (which minimizes steric repul-
sion) is maintained, a signal of intensity 2 downfield of
a signal of intensity 1 suggests that the phosphines are
located at axial and apical sites in 4a , with the Cp in a
radial position. The alternative, consistent with the
chemical shift data, but involving a new tetrasubsti-
tuted coordination geometry, is for the phosphines to
occupy diradial, apical sites as in 4b. Structure 4b
involves greater steric repulsion of phosphine ligands
than that in the ideal tetrasubstituted radial, diaxial,
apical geometry; consistent with assignment as struc-
ture 4b is that 4 (i) loses phosphine in solution over
hours (which has precluded an X-ray structural study)
and (ii) does not have a molecular ion in the FAB MS
but rather [M - PPh3]+.
Isomer assignment requires a crystallographic un-
derpinning to be solid; the suggested geometries of
trimethylphosphine derivatives are necessarily cautious,
given that only one crystallographically verified example
exists. Geometries of possible isomers of 5-7 are
displayed in Figure 7. Isomer 5a is the crystallographi-
cally observed form, with an axial PMe3. Considering
the Cp coordination site also, it is a disubstituted cluster
of axial, apical geometry. Only trans axial, apical
geometries as in 5a have been crystallographically
confirmed;11 a cis axial apical isomer is conceivable, but
the observation of only one 31P NMR resonance for
diaxially-coordinated diphosphine clusters CpWIr3(µ-L)-
(µ-CO)3(CO)6 (L ) dppe, dppm) where the crystal
structure shows ligated P both trans and cis to the apical
Cp suggests that CpW(CO)2 tripodal rotation is rapid
in solution and that such trans and cis isomers are
indistinguishable on the NMR timescale. Alternative
5b, with a carbonyl-bridged WIr2 face as in the tri-
phenylphosphine complexes above, is most probable; the
radial, axial form as drawn minimizes phosphine cy-
clopentadienyl repulsion. The combination of 31P NMR
shifts observed for 6 and 7 and tri- and tetrasubstituted
geometries structurally characterized in previous work
with tetrahedral clusters lead us to postulate geometries
6a , 6b, and 7. Trisubstituted geometries are invariably
radial, diaxial or diradial, axial; NMR data are consis-
tent with 6a adopting the former and 6b the latter
geometries. NMR data for 7 combined with the previ-
ously characterized radial, diaxial, apical geometries for
(10) (a) Ros, R.; Scrivanti, A.; Albano, V. G.; Braga, D. J . Chem.
Soc., Dalton Trans. 1986, 2411. (b) Darensbourg, D. J .; Baldwin-
Zuschke, B. J . Inorg. Chem. 1981, 20, 3846. (c) Blake, A. J .; Osborne,
A. G. J . Organomet. Chem. 1984, 260, 227.
(11) Keller, E.; Vahrenkamp, H. Chem. Ber. 1981, 114, 1111.

940 Organometallics, Vol. 15, No. 3, 1996
Waterman et al.
tetrasubstitution are only consistent with the radial,
axial, apical assignment displayed. Clearly, further
structural data for phosphine-substituted tungsten-
iridium clusters are needed to support these tentative
assignments; in particular, the isolation and structural
characterization of clusters with Ir3 and WIr2 edge-
bridged faces suggests that the assignments above
should be treated with caution. The 31P NMR data
support WIr2-edge bridged geometries for 6 and 7; the
possibility therefore exists that the crystallographically
verified 5a is a minor isomer not observed in the 31P
NMR and that the resonance at -30.2 ppm is from an
analogue of 2b with a WIr2-edge bridged structure.
Our investigations extend previous work on ligand
substitution at tetrairidium clusters and structural
studies on the resultant species10,12 into the mixed-metal
domain. Replacement of Ir(CO)3 by isolobal CpW(CO)2
in the tetrahedral core immediately introduces possible
isomers in the carbonyl-bridged form; the Cp ligand can
occupy axial, radial or apical sites, and we have now
structurally characterized examples of the axial and
apical forms, although the radial has thus far proved
elusive.
Related structurally-characterized mixed-metal clus-
ters containing one metal from group 6 and three metals
from group 9 in the carbonyl-bridged form, i.e. CpMoCo3-
13
(µ-CO)3(CO)8 and CpMoIr3(µ-CO)3(CO)8,14 have the
basal plane containing the lighter metals, i.e. Co3(µ-CO)3
for the former, MoIr2(µ-CO)3 for the latter. Neither
tungsten nor iridium favor the carbonyl-bridged geom-
etry (which in general becomes increasingly less likely
on descending a group); as a consequence, both WIr2-
(µ-CO)3 and Ir3(µ-CO)3 basal planes are accessible in this
system. Although CpWIr3(CO)11 adopts the all-terminal
geometry in the solid state,4 its 13C NMR spectrum
(169.2 ppm (11 CO)) suggests carbonyl exchange over
all positions, presumably by way of bridged intermedi-
ates.14 The present investigation provides examples of
edge-bridging species as putative models for carbonyl
scrambling intermediates in CpWIr3(CO)11.
(12) (a) Tranqui, D.; Durif, A.; Nasr Eddine, M. Acta Crystallogr.
1982, B38, 1920. (b) Strawczynski, A.; Ros, R.; Roulet, R.; Braga, D.;
Gradella, C.; Grepioni, F. Inorg. Chim. Acta 1990, 170, 17. (c) Flo¨rke,
U.; Haupt, H.-J . Z. Kristallogr. 1990, 191, 149. (d) Clucas, J . A.;
Harding, M. M.; Nicholls, B. S.; Smith, A. K. J . Chem. Soc., Chem.
Commun. 1984, 319. (e) Albano, V.; Bellon, P.; Scatturin, V. Chem.
Commun. 1967, 730. (f) Strawczynski, A.; Ros, R.; Roulet, R. Helv.
Chim. Acta 1988, 71, 867. (g) Albano, V. G.; Braga, D.; Ros, R.;
Scrivanti, A. J . Chem. Soc., Chem. Commun. 1985, 866. (h) Braga, D.;
Grepioni, F.; Guadalupi, G.; Scrivanti, A.; Ros, R.; Roulet, R. Organo-
metallics 1987, 6, 56. (i) Shapley, J . R.; Stuntz, G. F.; Churchill, M.
R.; Hutchinson, J . P. J . Am. Chem. Soc. 1979, 101, 7425. (j) Churchill,
M. R.; Hutchinson, J . P. Inorg. Chem. 1979, 18, 2451.
Ack n ow led gm en t. We thank the Australian Re-
search Council for support of this work and J ohnson-
Matthey Technology Centre for the loan of IrCl3. M.G.H.
is an ARC Australian Research Fellow.
Su p p or tin g In for m a tion Ava ila ble: Tables giving final
values of all refined atomic coordinates, all calculated atomic
coordinates, all anisotropic and isotropic thermal parameters,
and all bond lengths and angles (100 pages). Ordering
information is given on any current masthead page.
(13) Schmidt, G.; Bartl, K.; Boese, R. Z. Naturforsch. B 1977, 32,
1277.
(14) Churchill, M. R. J . Organomet. Chem. 1986, 312, 121.
OM950554O