Reaction of metallophosphanide anions with MLnX (X = halide) species as a simple route to heterometallic transition metal complexes

Article abstract of DOI:10.1039/b211243d

The reaction of metallophosphanides with ML_nX leads to the formation of mixed-metal clusters via complexes that consist of a metallophosphine coordinated through the lone pair on the phosphorus atom to another metal fragment. This synthetic strategy has been employed to initially form trinuclear complexes with the general formula [(Ph₂PML _n)(OC)₂Co(μ-DMAD)Mo(CO)₂Cp] (ML_n = Mn(CO)₅ 3, WCp(CO)₂ 4, FeCp(CO)₂ 5; DMAD = dimethylacetylene-dicarboxylate) from the reaction of the anion [(Ph ₂P)(OC)₂Co(n-DMAD)Mo(CO)₂Cp]^-, 2, with metal halide complexes, ML_nX (X = Cl, Br). The complexes 3, 4 and 5 have been characterised spectroscopically, and an X-ray crystal structure of 5 shows that the Ph₂PFe(CO)₂Cp unit has coordinated to the cobalt centre through the lone pair on the phosphorus centre. Subsequent heating of 3 leads to carbonyl loss, and metal-metal bond formation, to yield [(OC)₆CpCoMnMo(μ-CO)(μ-PPh₂)(μ₃- η²(II)-DMAD)], 6. An X-ray structure determination of 6 confirms that it contains a 'closed' metal triangle. In a related series of reactions the cluster anion [Os₃(CO)₁₀(μ-PPh₂)] ^- was treated with a variety of metal-containing synthons, ML _nX. With [FeCp(CO)₂Cl] the cluster [Os₃(CO) ₁₀FeCp(CO)(μ-PPh₂)(μ-CO)] 9 was obtained in good yield, and has been shown crystallographically to consist of an osmium triangle 'spiked' by an iron atom, with the Os-Fe bond bridged by the PPh₂ group and a carbonyl ligand. With [(Ph₃P)MCl] (M = Ag, Au) the tetranuclear 'butterfly' clusters [Os₃(CO)₁₀(μ-PPh ₂)(μ-MPR₃)] (10: M = Au, R = Ph; 11: M = Ag, R = Me) are obtained. These two complexes have been characterised spectroscopically and crystallographically.

Full text of DOI:10.1039/b211243d

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Reaction of metallophosphanide anions with MLnX (X ؍ halide)
species as a simple route to heterometallic transition metal
complexes
Birte Ahrens,a,b Jacqueline M. Cole,a Jonathan P. Hickey,a James N. Martin,a Martin J. Mays,a
Paul R. Raithby,b Simon J. Teatc and Anthony D. Woods*a
a Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge,
UK CB2 1EW
b Department of Chemistry, University of Bath, Bath, UK BA2 7AY
c CLRC Daresbury Laboratory, Daresbury, Claverton Down, Warrington, UK WA4 4AD
Received 13th November 2002, Accepted 19th February 2003
First published as an Advance Article on the web 4th March 2003
The reaction of metallophosphanides with MLnX leads to the formation of mixed-metal clusters via complexes that
consist of a metallophosphine coordinated through the lone pair on the phosphorus atom to another metal fragment.
This synthetic strategy has been employed to initially form trinuclear complexes with the general formula [(Ph2PMLn)-
(OC)2Co(µ-DMAD)Mo(CO)2Cp] (MLn = Mn(CO)5 3, WCp(CO)2 4, FeCp(CO)2 5; DMAD = dimethylacetylene-
dicarboxylate) from the reaction of the anion [(Ph2P)(OC)2Co(µ-DMAD)Mo(CO)2Cp]Ϫ, 2, with metal halide
complexes, MLnX (X = Cl, Br). The complexes 3, 4 and 5 have been characterised spectroscopically, and an X-ray
crystal structure of 5 shows that the Ph2PFe(CO)2Cp unit has coordinated to the cobalt centre through the lone pair
on the phosphorus centre. Subsequent heating of 3 leads to carbonyl loss, and metal–metal bond formation, to yield
[(OC)6CpCoMnMo(µ-CO)(µ-PPh2)(µ3-η2(//)-DMAD)], 6. An X-ray structure determination of 6 confirms that it
contains a ‘closed’ metal triangle. In a related series of reactions the cluster anion [Os3(CO)10(µ-PPh2)]Ϫ was treated
with a variety of metal-containing synthons, MLnX. With [FeCp(CO)2Cl] the cluster [Os3(CO)10FeCp(CO)(µ-PPh2)-
(µ-CO)] 9 was obtained in good yield, and has been shown crystallographically to consist of an osmium triangle
‘spiked’ by an iron atom, with the Os–Fe bond bridged by the PPh2 group and a carbonyl ligand. With [(Ph3P)MCl]
(M = Ag, Au) the tetranuclear ‘butterfly’ clusters [Os3(CO)10(µ-PPh2)(µ-MPR3)] (10: M = Au, R = Ph; 11: M = Ag,
R = Me) are obtained. These two complexes have been characterised spectroscopically and crystallographically.
ated phosphanides towards many organic electrophiles over
Introduction
recent years,11,12 there have been surprisingly few reactions of
Interest in trimetallic species has grown for several reasons;
such phosphanides with metal salts.
including the possibility of using clusters as potential models
for the chemisorption of unsaturated hydrocarbons on metallic
surfaces.1 More recently the catalytic properties of such tri-
Results and discussion
metallic complexes have been studied with a view to organic
Deprotonation of a solution of [(Ph2PH)(OC)2Co(µ-DMAD)-
synthesis2 since heterometallic clusters should have additional
n
Mo(CO)2Cp], 1, with BuLi proceeds smoothly at Ϫ78 ЊC to
enantio- and diastereoselective properties.3 Investigating
yield [(Ph2P)(OC)2Co(µ-DMAD)Mo(CO)2Cp]Ϫ (DMAD
=
rational routes to heterometallic clusters, therefore, remains an
active area of research. One strategy that is often employed in
the preparation of such complexes is vertex exchange of isolo-
bal metal fragments; such routes usually involve thermolysis
with metal carbonyls, and unsurprisingly yields and product
ratios are variable.4
dimethylacetylendicarboxylate), 2, which was used without any
further purification in subsequent reactions.
Reactions with Mn(CO)5, WCp(CO)2 and FeCp(CO)2
Stirring a THF solution of 2 with MLnCl at room temperature,
for 1 h, gave one new orange product, [(Ph2PMLn)(OC)2-
Co(µ-DMAD)Mo(CO)2Cp] (MLn = Mn(CO)5, 3; WCp(CO)2, 4;
FeCp(CO)2, 5) in moderate to high yield (Scheme 1).
It was noted that solutions of 3 on being allowed to stand
for several hours slowly turned green, and it was assumed
that metal–metal bond formation was occurring to yield a
metal triangle. In order to confirm this hypothesis it was
decided to thermolyse a solution of 3. Thus heating a toluene
solution of 3 at 50 ЊC for 1 h led to the formation of a green
solution. Separation by preparative TLC yielded green
[(OC)6CpCoMnMo(µ-CO)(µ-PPh2)(µ3-η2(//)-DMAD)], 6, in
which metal–metal bond formation had occurred (// signifies
parallel coordination).
Somewhat surprisingly, closure of the metal triangles of 4
and 5 proved to be rather difficult; thus heating a toluene
solution of 5 at 60 ЊC for 3h led to the isolation of brown
[(OC)4CpCoFeMo(µ-CO)(µ-PPh2)(µ3-η2(//)-DMAD)], 7, in low
(15%) yield, and thermolysis of toluene solutions of 4 led only
to decomposition (Scheme 2). It is assumed that it is harder to
The ability to introduce an additional metal fragment into
the coordination sphere of a complex by bonding it to a two-
electron donor that can substitute a carbonyl group seems a
particularly appealing methodology. Metallophosphines such
as [Ph2PMoCp(CO)3] are well known,5 but these complexes are
not particularly stable. They dimerize readily on heating, and
often cannot be isolated in the solid state.5,6 This precludes them
from being used to add metal fragments to other complexes by
simple substitution reactions, since the conditions required to
effect substitution may also lead to dimerization of the phos-
phine and thus poor yields of the substituted complexes are
obtained. Vahrenkamp and co-workers chose to use the
metalloarsines, Me2As[MLn] in an attempt to circumvent the
problem of dimerization and discovered a rational route to
many tri- and tetra-nuclear clusters.7–10 It seemed to us that a
different strategy would be to substitute a metal complex with
Ph2PH, and then to deprotonate this phosphine in order to
facilitate reaction with a different metal complex. Despite a
growing interest in the reactivity of transition metal coordin-
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 1 3 8 9 – 1 3 9 5
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Table 1 Selected bond lengths (Å) and angles (Њ) for 5
Mo(1)–Co(1)
Mo(1)–C(12)
Co(1)–C(12)
C(11)–C(12)
2.6924(5)
2.187(3)
1.968(3)
1.358(4)
Mo(1)–C(11)
Co(1)–C(11)
Co(1)–P(1)
Fe(1)–P(1)
2.169(3)
1.929(3)
2.2794(9)
2.3266(9)
Mo(1)–Co(1)–C(12)
Mo(1)–C(11)–C(10) 121.2(2)
Mo(1)–C(12)–C(8)
Mo(1)–Co(1)–C(11)
Co(1)–C(11)–C(12)
53.27(8)
Mo(1)–C(11)–C(12)
Mo(1)–C(11)–Co(1)
Mo(1)–C(12)–Co(1)
Mo(1)–Co(1)–P(1)
Co(1)–C(11)–C(10)
72.5(2)
81.9(1)
80.59(9)
150.71(3)
138.5(2)
133.7(2)
52.91(9)
71.1(2)
Table 2 Selected bond lengths (Å) and angles (Њ) for 6
Mo(1)–Co(1)
Mo(1)–C(10)
Mo(1)–C(6)
Mn(1)–C(11)
Co(1)–C(10)
Co(1)–P(1)
2.6351(9)
2.210(3)
1.974(5)
1.999(3)
1.965(3)
2.1958(9)
Mo(1)–Mn(1)
Mo(1)–C(11)
Mn(1)–Co(1)
Mn(1)–P(1)
C(10)–C(11)
Co(1)–C(6)
2.883(1)
2.296(3)
2.7013(7)
2.257(1)
1.394(5)
2.3245(4)
Scheme 1 Reaction of [(Ph2P)(OC)2Co(µ-DMAD)Mo(CO)2Cp]Ϫ, 2,
with metal salts.
Mo(1)–C(10)–C(11)
Mo(1)–C(10)–Co(1)
Mo(1)–C(11)–C(10)
O(7)–C(7)–Mo(1)
75.4(2)
78.0(1)
68.6(2)
168.8(3)
43.60(8)
Mo(1)–C(10)–C(9)
Mo(1)–C(11)–C(12) 126.2(2)
O(6)–C(6)–Mo(1)
Mn(1)–Mo(1)–C(10)
Mn(1)–Co(1)–C(10)
118.6(2)
165.9(4)
64.59(8)
71.2(1)
Mn(1)–Mo(1)–C(11)
Mn(1)–C(11)–C(10) 108.7(2)
Co(1)–Mo(1)–C(11)
Co(1)–Mn(1)–C(11)
C(10)–C(11)–C(12)
67.84(9)
70.3(1)
125.9(3)
The crystal structure of [(OC)6CpCoMnMo(µ-CO)(µ-PPh2)-
(µ3-η2(//)-DMAD)], 6, consists of well separated molecular
units. The molecular structure of 6 is shown in Fig. 2, and
relevant bond lengths (Å) and angles (Њ) are included in Table 2.
Within the molecular structure the ligand geometry is well
defined but the metal triangle is disordered in a 4 : 1 ratio with
the Mn and Co atoms each occupying both ‘lighter atom’ metal
sites, and the molybdenum occupying two sites separated by
0.63 Å. Because of the inability to locate any light atoms
associated with the second (approximately 20%) orientation of
the metal triangle except for a slight movement in the position
of the carbon atoms of the bridging carbonyls in the plane of
the metal triangle, only the structure of the major (ca. 80%
orientation) of the complex will be discussed in any detail.
Scheme 2 Thermolysis of 3 and 5.
cause the closure of the metal triangle for 4 and 5 because, as
compared with 3, the P–MLn fragment has less labile carbonyl
ligands which can be displaced in order to permit metal–metal
bond formation.
1
Complexes 3 to 7 have been characterised by IR, H NMR,
and 31P NMR spectroscopy; satisfactory FAB MS and micro-
analytical data were also obtained. Additionally 5 and 6 were
characterised by single crystal X-ray diffraction studies. The
molecular structure of 5 is shown in Fig. 1, with relevant bond
lengths (Å) and angles (Њ) given in Table 1.
Fig. 2 Molecular structure of [(OC)6CpCoMnMo(µ-CO)(µ-PPh2)-
(µ3-η2(//)-DMAD)], 6.
Fig.
1
Molecular structure of [{Ph2PFeCp(CO)2}(OC)2Co-
(µ-DMAD)Mo(CO)2Cp], 5.
In 6 the alkyne is bound in µ3-η2-// fashion, with the η2
coordination to the molybdenum atom being in accord with the
work of Einstein.16 The C(10)–C(11) vector is approximately
parallel to the Co(1)–Mn(1) edge (3.1Њ deviation) with C(11)
being located slightly closer to Mo(1). The dihedral angle
between the Mn–P–Co and Mn–Co–Mo planes is 10.9Њ and
that between the Mn–Co–Mo and Mo–Co–C(6) planes is 7.8Њ.
Using the Wade–Mingos15 electron counting scheme complex 6
The alkyne is coordinated transverse to the Mo–Co vector as
expected for a µ-η2 donor. The bond lengths and angles are all
in the normal range for such core geometries.13,14 Using the
Wade–Mingos electron counting scheme15 the core of 5 may be
described as a nido-M2C2 cluster (based on the removal of one
vertex from a trigonal bipyramid).
D a l t o n T r a n s . , 2 0 0 3 , 1 3 8 9 – 1 3 9 5
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Table 3 Selected bond lengths (Å) and angles (Њ) for 9
can thus be described as a nido-M3C2 cluster possessing seven
skeletal electron pairs. As such, the bond lengths and bond
angles are of the same order of magnitude as those observed in
other nido M3C2 clusters.16 As is customary,17 the M–C bonds
in the pseudo square plane Mn–Co–C(10)–C(11) (maximum
deviation from plane 0.0282 Å) are all shorter [C(11)–Mn(1)
1.999(3) Å, C(10)–Co(1) 1.965(3) Å] than those to the capping
Mo unit [C(10)–Mo(1) 2.210(3) Å, C(11)–Mo(1) 2.296(3) Å]. It
has previously been noted by Einstein et al.16 that in such hetero-
metallic square-based pyramids the thermodynamically pre-
ferred isomer has the most electron attracting fragments located
in the ‘basal’ position, and the most electropositive metal at the
apical site. Calculations have shown that this preference is based
on a stronger bonding interaction between the alkyne and
the two metals in the basal plane.18 This proves to be true in the
present case, with the Mo atom occupying the apical site of the
square-based pyramid.
The formation of the metal triangle leads to an increase in
the Co–Mo bond length from 2.6351(9) Å in 5 to 2.7059(6) Å in
6. Unsurprisingly, the change in the mode of coordination of
the alkyne from µ-η2-⊥ to µ3-η2-// leads to a lengthening of the
C(10)–C(11) bond length from 1.358(4) Å in 5 to 1.394(5) Å in 6
(⊥ signifies perpendicular coordination).
A semi-bridging carbonyl group is present on the molyb-
denum atom, as determined from the Mo–C(7)–O(7) bond
geometry [Mo(1)–C(7)–O(7) 168.8(3)Њ]. The carbonyl carbon
atom is in close contact with the two other metal centres [C(7)–
Mn(1) 2.937 Å, C(7)–Co(1) 2.966 Å]. Semi-bridging carbonyl
atoms are a common feature in hetero-trimetallic alkyne-
bridged complexes. However, in the majority of these cases
although the triangle electron count is the expected 48, the indi-
vidual metals do not conform to the eighteen-electron rule.16
It has been argued that in such cases the formation of a semi-
bridging carbonyl group helps to offset the disparity between
the formal individual electron counts of each metal centre.
Os(1)–Os(2)
Os(1)–Os(3)
Os(3)–P(1)
Os(1)–C(11)
2.8686(14)
2.8736(13)
2.322(3)
Os(2)–Os(3)
Os(3)–Fe(1)
Fe(1)–P(1)
2.8924(16)
2.7325(16)
2.199(3)
1.970(9)
Fe(1)–C(11)
2.135(9)
Os(1)–Os(2)–Os(3)
Os(2)–Os(1)–Os(3)
Os(3)–C(11)–Fe(1)
59.84(4)
60.49(4)
83.4(4)
Os(1)–Os(3)–Os(2)
Os(3)–P(1)–Fe(1)
Os(1)–Os(3)–Fe(1) 152.18(6)
59.67(3)
74.32(8)
Os(2)–Os(3)–Fe(1) 147.41(5)
W) and RuCp(CO)2Cl all appeared to proceed smoothly but the
compounds decomposed during attempted chromatographic
separation.
The molecular structure of 9 was confirmed by a single-
crystal X-ray diffraction study and is shown in Fig. 3, and rele-
vant bond lengths (Å) and angles (Њ) are included in Table 3.
The core consists of an iron spiked-Os3 triangle, with the Fe–Os
bond being bridged by a CO and PPh2 group. Simple spiked Os3
triangles are scarce, other examples being [Os3Pt(µ-CH2)(CO)11-
(PPh3)2],20 [Os4H2(CO)15],21 [Os4H3Br(CO)13]22 and [Os4(CO)15-
PMe3].23 The four metal atoms are not quite planar, the Fe atom
lying 0.266 Å above the plane of the Os3 triangle, with the
dihedral angle between the Os3 plane and Os1Os3Fe1 plane
being 8.9Њ; by contrast the dihedral angle between the planes in
[Os4(CO)15PMe3] is 2.9Њ. The Os–Os bonds within the core
[range 2.8686(14) to 2.8924(16) Å] compare closely with those
in [Os3Pt(µ-CH2)(CO)11(PPh3)2] [range 2.857(3) to 2.882(4) Å],20
and to the average Os–Os bond length of 2.877 Å in
[Os3(CO)12].24
Reactions of [Os3(CO)10(ꢀ-PPh2)]؊ with [MLnX]
In order to extend the general applicability of these reactions it
was decided to investigate the reactivity of [Os3(CO)11PPh2H] 8
to Mϩ synthons. Colbran and co-workers had previously
demonstrated that 8 may be readily deprotonated but during
this procedure a geometric change occurs yielding [Os3(CO)10-
(µ-PPh2)]Ϫ in which the phosphanide has adopted a bridging
position; reprotonation thus yields [Os3(CO)10(µ-PPh2)(µ-H)].19
Treatment of a dichloromethane solution of 8 with DBU
(DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) followed by addi-
tion of FeCp(CO)2Cl led to an immediate colour change from
yellow to deep red to orange. Separation of the mixture
by preparative TLC yielded one new product, [Os3(CO)10-
FeCp(CO)(µ-PPh2)(µ–CO)], 9, in high yield (Scheme 3).
Surprisingly, this proved to be the only reaction of its class
which yielded isolable products. In contrast, the reaction of
[Os3(CO)10(µ-PPh2]Ϫ with Mn(CO)5Br, MCp(CO)3Cl (M = Mo,
Fig. 3 Molecular structure of [Os3(CO)10FeCp(CO)(µ-PPh2)(µ-CO)],
9.
The bulk of documented Fe–Os bonds are found either in
mixed metal FenOs3Ϫn triangles or as dative bonds between a
bis-cyclopentadienyl coordinated Fe atom and an Os atom of
an Os3 triangle. Unsurprisingly, such dative bonds are long,
being typically in the range of 2.813 to 2.995 Å,25 whereas the
mean Fe–Os separation in [Fe2Os(CO)12] is 2.742 0.005 Å,26
both these separations being significantly longer than in the
current case [Os–Fe 2.7325(16) Å]. The CO group bridging the
Fe and an Os is asymmetric [Os(3)–C(11) 1.970(9) Å; Fe(1)–
C(11) 2.135(9) Å]. Thus the Os–C separation is only marginally
longer than that of a terminal Os–CO separation [range
1.88(1)–1.95(1) Å] whereas the Fe–C separation is significantly
longer than the terminal Fe(1)–C separation of 1.756 (10) Å,
although it is comparable with bridging Fe–C separations in
Fe2Os(CO)12 [range 1.92(1) to 2.22(2) Å].26
Reactions with [M(PR3)Cl] [M = Ag, Au; R = Me, Ph]
The reaction of [Os3(CO)10(µ-PPh2)]Ϫ with [MPR3Cl] in the
presence of Tl(OAc), which acts as a halide abstractor, led to
the formation of [Os3(CO)10(µ-PPh2)(µ-MPR3)] (10: M = Au,
R = Ph; 11: M = Ag, R = Me). This reaction may simply be
Scheme 3 Reaction of Os3(CO)11(PPh2H) with metal salts.
D a l t o n T r a n s . , 2 0 0 3 , 1 3 8 9 – 1 3 9 5
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Fig. 4 Molecular structures of [Os3(CO)10(µ-PPh2)(µ-MPR3)] [10: M = Au, R = Ph (left); 11: M = Ag, R = Me (right)].
Table 4 Selected bond lengths (Å) and angles (Њ) for 10 Table 5 Selected bond lengths (Å) and angles (Њ) for 11
Os(1)–Os(2)
Os(2)–Os(3)
Os(2)–Au(1)
Os(1)–P(1)
2.9568(3)
2.8995(3)
2.7864(3)
2.3688(14)
Os(1)–Au(1)
Os(1)–Os(3)
Os(2)–P(1)
2.7910(3)
2.8947(3)
2.3643(13)
Os(1)–Os(2)
Os(2)–Os(3)
Os(2)–Ag(1)
Os(1)–P(1)
2.9694(4)
2.8829(4)
2.8153(7)
2.3692(19)
Os(1)–Ag(1)
Os(1)–Os(3)
Os(2)–P(1)
2.7802(7)
2.9068(4)
2.3712(19)
Os(1)–Os(2)–Os(3) 59.236(7)
Os(1)–Os(3)–Os(2) 61.369(7)
Os(2)–Os(1)–Os(3)
Os(1)–Au(1)–Os(2) 64.030(7)
59.395(7)
Os(1)–Os(2)–Os(3) 59.541(10)
Os(1)–Os(3)–Os(2) 61.710(10)
Os(2)–Os(1)–Os(3) 58.749(10)
Os(1)–Ag(1)–Os(2) 64.099(14)
Os(1)–P(1)–Os(2)
77.32(4)
Os(1)–P(1)–Os(2)
77.57(6)
viewed as the isolobal analogue of the reaction reported by
Colbran and co-workers.19 Both complexes were characterised
spectroscopically and in addition have been the subjects of
single crystal X-ray diffraction studies (Fig. 4).
one, the unsaturated cluster [{Os3(CO)10H}2Ag]Ϫ, has been
crystallographically characterised.32
Gold bridged Os–Os bond lengths seem to be particularly
dependent on the other ligands present. Thus the clusters
[Os3(CO)10(µ-Cl)(µ-AuPPh3)],31 [Os6(CO)18(µ6-P)(µ-AuPPh3)]33
and [Os3(CO)9(µ-C3H5)(µ-AuPEt3)]34 show bridged Os–Os
separations of 2.880(2), 2.932(5) and 3.014(1) Å respectively cf.
2.9568(3) Å in 10. The Os–Au separations in 10 fall within the
normal range, and the Au fragment bridges symmetrically. The
lack of similar structures incorporating Ag precludes any com-
parative discussion, although it is interesting to note that the
bridged Os–Os bond length of 11 is 0.01 Å longer than that of
10 whereas in the two unsaturated compounds [{Os3(CO)10H}2-
Ag]Ϫ and [{Os3(CO)10H}2Au]Ϫ the corresponding bond length
is 0.02 Å shorter in the Ag bridged complex.32
Complexes 10 and 11 consist of butterfly Os3M cores in
which the hinge Os–Os bond is bridged by a PPh2 group. The
dihedral angle of 113.1Њ between the Os3 and Os(1)–Os(2)–P(1)
planes of 10 is virtually identical to the value of 113.4Њ recorded
in [Os3(CO)10(µ-PPh2)(µ-H)],27 but is larger than that in
[Os3(CO)9{P(OMe)3}(µ-H)(µ-PPh2)]28 and [Os3(CO)9(CF3-
CO2)3(µ-H)2(µ-PPh2)] (∼110Њ).29 The plane of the endo-Ph group
in 10, i.e. the Ph group lying above the Os3 plane, lies approxi-
mately parallel to the Os(1)–Os(2) edge in order to minimise
steric repulsion with the CO groups. However, its close prox-
imity to the axial carbonyl of Os(3) [C(33)–Phcentroid 3.548 Å;
O(33)–Phcentroid 3.028 Å] forces a marked deviation from the
preferred linear CO geometry [Os(3)–C(33)–O(33) 169.6(6)Њ].
The endo and exo Ph groups are approximately perpendicular
to each other; such a conformation has been assigned in similar
structures by Deeming et al. on the basis of NMR spectroscopy
studies.30 The dihedral angle of 115.2Њ between the Os3 and
Os(1)–Os(2)–P(1) planes in 11 is larger than that in 10 presum-
ably due to the lower steric demands of the bridging Ag–PMe3
moiety. This greater dihedral angle manifests itself in a slightly
lower distortion of the geometry of the axial CO groups
[Os(3)–C(33)–O(33) 171.4(7)Њ] caused by the steric repulsion of
the endo-Ph group of the µ-PPh2 moiety. By comparison, the
dihedral angle of 125.1Њ between the Os3 and Os(1)–Os(2)–
Ag(1) planes is significantly greater than the corresponding
angle of 113.1Њ between the Os3 and Os(1)–Os(2)–Au(1) planes
in 10 thus supporting the argument that the smaller AgPMe3
group creates less steric-repulsion. In both 10 and 11 the
bridged Os–Os bond lengths are ∼0.06 Å longer than the
unbridged Os–Os bonds (see Tables 4 and 5) both of which are
similar to the Os–Os bond lengths in [Os3(CO)12]. Furthermore
the bridged bonds [10: 2.9568(3) Å, 11: 2.9694(4) Å] are mark-
edly longer than the corresponding separation of 2.916(1) Å in
[Os3(CO)10(µ-H)(µ-PPh2)]. It has been noted previously that the
bond lengthening effect of a bridging coinage metal is greater
than that of a bridging hydride.31 To the authors’ knowledge,
despite several other Ag containing triangles being known, only
Conclusions
We have demonstrated that deprotonation of a coordinated
PPh2H moiety followed by reaction with a Mϩ synthon repre-
sents a general method to introduce an additional metal frag-
ment into the coordination sphere of a cluster. Such reactions
frequently result on metal–metal bond formation and, as such,
represent an excellent route to heterometallic compounds.
Experimental
Unless otherwise stated all experiments were carried out under
an atmosphere of dry, oxygen-free nitrogen, using conventional
Schlenk line techniques, and solvents freshly distilled from
the appropriate drying agent. NMR spectra were recorded in
CDCl3 using a Bruker DRX 400 spectrometer, with TMS as an
external standard for 1H and 13C spectra and H3PO4 as an
external standard for 31P NMR spectra. Infrared spectra were,
unless otherwise stated, recorded in dichloromethane solution
in 0.5 mm NaCl solution cells, using a Perkin Elmer 1710
Fourier Transform spectrometer. FAB mass spectra were
obtained using a Kratos MS 890 instrument, using 3-nitro-
benzyl alcohol as a matrix. Preparative TLC was carried out on
1 mm silica plates prepared at the University of Cambridge.
Column chromatography was performed on Kieselgel 60
D a l t o n T r a n s . , 2 0 0 3 , 1 3 8 9 – 1 3 9 5
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Table 6 X-Ray crystallographic data for the new complexes
Complex
5
6
9
10
11
Empirical formula
Weight
Crystal system
Space group
C35H28Cl2CoFeMoO10P
921.16
C30H21CoMnMoO11P
798.25
Monoclinic
P21/c
C32H22FeO12Os3P
1255.92
Monoclinic
P21/c
C40H25AuO10Os3P2
1495.11
C25H19AgO10Os3P2
1219.81
Monoclinic
P21/n
Triclinic
Triclinic
¯
¯
P1
P1
a/Å
b/Å
c/Å
α/Њ
10.3658(4)
10.7100(4)
18.1348(6)
81.443(2)
80.052(2)
66.061(2)
1805.49(11)
180(2)
15.2152(5)
10.9665(3)
19.4998(4)
90
108.314(2)
90
8.9577(19)
10.834(2)
34.169(7)
90
94.537(10)
90
10.0320(2)
13.9040(2)
16.4300(4)
94.6710(12)
103.7790(9)
111.1271(12)
2040.47(7)
180(2)
17.4362(2)
8.7998(1)
20.0377(3)
90
93.038(1)
90
β/Њ
γ/Њ
V/Å3
3088.9(2)
180(2)
3305.7(12)
150(2)
3070.17(7)
150(2)
T /K
Z
2
4
4
2
4
Abs coefficient/mmϪ1
F(000)
1.441
924
1.445
1592
12.036
2316
13.028
1364
13.159
2216
Reflections measured
Independent reflections
Rint
Final R1, wR2
R1, wR2 (all data)
20615
8217
0.0704
0.0411, 0.0760
0.0779, 0.1034
25149
7053
0.0606
0.0436, 0.0877
0.0649, 0.3235
22341
8711
0.0430
0.0559, 0.0935
0.0786, 0.0973
26465
8336
0.0666
0.0333, 0.0857
0.0368, 0.0880
40543
7038
0.0655
0.0488, 0.1186
0.0578, 0.1411
(70–230 mesh ASTM). Unless otherwise stated, all reagents
were obtained from commercial suppliers and used without fur-
ther purification. [(Ph2PH)(OC)2Co(µ-DMAD)Mo(CO)2Cp],14
[Os3(CO)11(PPh2H)],19 [CpW(CO)3Cl]35 and [CpFe(CO)2Cl]36
were prepared by the literature methods.
and angle constraints. A summary of data collection and data
refinement details is given in Table 6.
CCDC reference numbers 197610–14.
See http://www.rsc.org/suppdata/dt/b2/b211243d/ for crystal-
lographic data in CIF or other electronic format.
Preparation of [(Ph2P)(OC)2Co(ꢀ-DMAD)Mo(CO)2Cp]؊, 2
Crystal structure determinations
Single-crystal X-ray diffraction data for 5, 6, 10 and 11 were
collected using a Nonius-Kappa CCD diffractometer, equipped
with an Oxford Cryosystems cryostream and employing MoKα
(0.71069 Å) irradiation from a sealed tube X-ray source. Cell
refinement, data collection and data reduction were performed
with the programs DENZO37 and COLLECT38 and multi-scan
absorption corrections were applied to all intensity data with
the program SORTAV.39 The crystal structure of 9 was deter-
mined using the single-crystal diffraction Station 9.8 at the
Synchrotron Radiation Source, Daresbury, UK. This houses
a Bruker SMART diffractometer, equipped with an Oxford
Cryosystems cryostream. A Si(111) monochromator enabled
X-ray irradiation of λ = 0.6923 Å onto the sample. Cell refine-
ment and data collection were performed using the SMART40
software whilst the SAINT41 and SADABS42 programs were
used for data reduction and absorption correlations respect-
ively. All structures were solved and refined with the programs
SHELXS97 and SHELXL97,43 respectively. The structures of 6
and 9 show disorder. In 6 two positions of the Mo(1) atom were
observed in an approximately 4 : 1 ratio. The two positions were
refined with the total occupancy of the site summing to unity.
Also, it was not possible to distinguish between the Mn and Co
sites, and partial occupancies of each atom type were assigned
to each position, with the atom positions of the Mn and Co
atoms on each site constrained to be the same; again the partial
occupancies on each site summed to unity. Slight differences in
the position of the carbon atom of the bridging carbonyls, C(3)
and C(6), in the plane of the metal triangle were also noted, and
refined in conjunction with the difference in the Mo atom pos-
ition using the same occupancy ratio. In the structure of 9 the
Os triangle was disordered in a 96 : 4 ratio, with the low occu-
pancy triangle showing a slight rotation about an approximate
three-fold axis perpendicular to the triangle compared to the
major component. Related Os atom sites were refined with the
occupancies summed to unity. Because of the relative weakness
of the data additional restraints were placed on the phenyl and
cyclopentadienyl rings in order to stabilise the refinement. The
crystal structure of 9 also contains a molecule of hexane sol-
vent in the lattice that was disordered across a centre of sym-
metry. This molecule was refined with appropriate bond length
To a solution of [(Ph2PH)(OC)2Co(µ-DMAD)Mo(CO)2Cp]
(250 mg, 0.38 mmol) in THF (40 ml) at Ϫ78 ЊC was added 1.7
t
M BuLi (0.25 ml, 1.1 eq) leading to an immediate colour
change from orange to deep brown to yield [(Ph2P)(OC)2-
Co(µ-DMAD)Mo (CO)2Cp]Ϫ 2, which was used without
further purification.
Reaction of 2 with Mn(CO)5Br
To a solution of 2 (250 mg, 0.38 mmol) in THF (40 ml) at
Ϫ78 ЊC was added Mn(CO)5Br (115 mg, 1.1 eq); the resulting
solution was warmed to RT and stirred for 1 h. The solvent was
removed in vacuo, the residue redissolved in the minimum
of dichloromethane and applied to the base of TLC plates.
Elution with 2 : 1 hexane/ethyl acetate yielded orange
[{Ph2PMn(CO)5}(OC)2Co(µ-DMAD)Mo(CO)2Cp], 3 (245 mg,
78%), as the sole product.
IR (ν CO/cmϪ1): 2094 (w), 2019 (s), 1992 (s), 1963 (m), 1940
1
(m), 1913 (m); H NMR δ: 7.81 to 7.34 (m, 10H, Ph), 3.53 (s,
6H, COOMe); 31P NMR δ: 48.22 (s, br, Co–PPh2Mn); FAB m/z:
854 Mϩ; Mϩ–nCO (n = 1 to 3); analysis calculated (found) for
CoMoMnC32H21O13P: C 45.21 (44.99), H 2.52 (2.47), P 3.58
(3.62).
Reaction of 2 with CpW(CO)3Cl
Using an analogous procedure to that above 2 was reacted with
CpW(CO)3Cl (132 mg, 1.1 eq) to give orange [{Ph2PWCp-
(CO)3}(OC)2Co(µ-DMAD)Mo(CO)2Cp] (164 mg, 44%). IR
(ν CO/cmϪ1): 2007 (vs), 1964 (vs); 1H NMR δ: 7.7–7.2 (m, 10H,
Ph), 5.35 (s, 5H, Cp), 3.5 (s, 3H, COOMe), 3.3 (s, 3H, COOMe);
31P NMR δ 38.7; FAB m/z: 1029 Mϩ, Mϩ–nCO (n = 1 to 3);
analysis calculated (found) for CoMoWC35H26O11: C 40.38
(40.90), H 2.46 (2.55), P 3.06 (3.01).
Reaction of 2 with CpFe(CO)2Cl
Using an analogous procedure to that in the above reaction
250 mg of 2 was treated with CpFe(CO)2Cl (90 mg, 1.1 eq) to
yield red [{Ph2PFeCp(CO)2}(OC)2Co(µ-DMAD)Mo(CO)2Cp],
5 (292 mg, 92%), as the sole product. IR (ν CO/cmϪ1): 2054 (w),
D a l t o n T r a n s . , 2 0 0 3 , 1 3 8 9 – 1 3 9 5
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1
2033 (m), 2014 (s), 1991 (vs), 1980 (s), 1956 (m), 1948 (m); H
Data for 10
NMR δ: 7.70–7.10 (m, 10H, Ph), 5.25 (s, 5H, Mo–Cp), 4.85 (s,
5H, Fe–Cp), 3.50 (s, 6H, COOMe); 31P NMR δ: 52.31 (s, br,
Co–PPh2Fe); FAB m/z: 836 Mϩ, Mϩ–nCO (n = 1 to 6); analysis
calculated (found) for CoMoFeC34H26O10: C 48.84 (48.74),
H 3.13 (3.67), P 3.72 (3.70).
IR (ν CO/cmϪ1): 2088 (m), 2027 (s), 2005 (ms), 1977 (sh), 1958
(m); 1H NMR δ: 7.98–7.04 (m, 25H, Ph); 31P NMR δ: 132.26 (s,
µ-PPh2); FAB m/z: 1498 Mϩ, Mϩ–nCO (n = 1 to 6); analysis
calculated (found) for Os3AuC40H25O10P2: C 32.01 (32.13), H
1.64 (1.69), P 4.22 (4.14).
Reaction of 2 with Mn(CO)5Br at 50 ؇C
Data for 11
Following the above procedure but heating the reaction at 50 ЊC
for 1.5 h and work up by the above method gave orange
[{Ph2PMn(CO)5}(OC)2Co(µ-DMAD)Mo(CO)2Cp], 3 (25 mg,
8%), and green [(OC)6CpCoMnMo(µ-CO)(µ-PPh2)(µ3-η2(//)-
DMAD)], 6 (140 mg, 46%). IR (ν CO/cmϪ1): 2054 (m), 2013 (s),
1998 (s), 1953 (s), 1941 (s), 1882 (w, br); 1H NMR δ: 8.15–7.49
(m, 10H, Ph), 5.03 (s, 5H, Cp), 3.75 (s, 3H, COOMe), 3.64 (s,
3H, COOMe); 31P NMR δ: 57.00 (s, vbr, CoMnµ-PPh2); FAB
m/z: 798 Mϩ, Mϩ–nCO (n = 1, 3 to 7); analysis calculated
(found) for CoMoMnC30H21O11P: C 45.80 (45.14), H 2.80
(2.65), P 3.86 (3.88).
IR (ν CO/cmϪ1): 2155 (w), 2125 (w), 2086 (m), 2054 (mw), 2018
(s), 2003 (ms), 1973 (sh), 1951 (m), 1945 (m); 1H NMR δ: 6.95–
8.12 (m, 10H, Ph), 1.49 (d, 9H, Me); 31P NMR δ: 71.02 (s,
µ-PPh2), 18.88 (s, 1P, PMe3); FAB m/z: 1222 MHϩ; analysis
calculated (found) for Os3AgC25H19O10P2: C 25.00 (24.61),
H 1.68 (1.57), P 5.04 (5.08).
Acknowledgements
We acknowledge the financial support of the EPSRC (J.N.M.,
A.D.W. and for the purchase of the Nonius Kappa CCD dif-
fractometer). A.D.W. and J.M.C. are grateful to St Catharine’s
College, Cambridge, for the award of Research Fellowships and
additionally, J.M.C. thanks the Royal Society for a University
Research Fellowship. The award of a DAAD grant (Gemein-
sames Hochschulsonderprogramm III von Bund und Ländern)
to B.A. is gratefully acknowledged. Dr John E. Davies is
thanked for crystal structure determinations. Johnson Matthey
PLC is thanked for the loan of metal salts.
Thermolysis of [{Ph2PFeCp(CO)2}(OC)2Co(ꢀ-DMAD)-
Mo(CO)2Cp], 5
A solution of 5 (100 mg, 0.12 mmol) in toluene (50 ml) was
heated at 60 ЊC for 3 h. The solvent was removed in vacuo, the
residue redissolved in the minimum of dichloromethane and
applied to the base of TLC plates. Elution with 2 : 1 hexane/
ethyl acetate yielded brown [(OC)3Cp2CoFeMo(µ-CO)(µ-PPh2)-
(µ3-η2(//)-DMAD)], 7 (14 mg, 15%), as the sole isolable product.
IR (ν CO/cmϪ1): 2012 (vs), 1990 (s), 1950 (m), 1940 (s), 1883
(m); 1H NMR δ: 7.73–7.20 (m, 10H, Ph), 5.45 (s, 5H, Mo–Cp),
5.18 (s, 5H, Fe–Cp), 3.86 (s, 3H, COOMe), 3.57(s, 3H,
COOMe); 31P NMR δ: Ϫ27.14 (s, CoFeµ-PPh2); FAB m/z: 780
Mϩ, Mϩ–nCO (n = 4, 5); analysis calculated (found) for CoMo-
FeC32H26O8: C 49.33 (49.26), H 3.30 (3.36), P 3.95 (3.96).
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