Backbone modified small bite-angle diphosphines: Synthesis and molecular structures of [M(CO)4{X2PC(R1R2)PX2}] (M = Mo, W; X = Ph, Cy; R1 = H, Me, Et, Pr, allyl, R2 = Me, allyl)

Article abstract of DOI:10.1016/j.jorganchem.2007.09.024

A range of new small bite-angle diphosphine complexes, [M(CO)₄{X₂PC(R¹R²)PX₂}] (M = Mo, W; X = Ph, Cy; R¹ = H, Me, Et, Pr, allyl, R² = Me, allyl), have been prepared via elaboration of the methylene backbones in [M(CO)₄(X₂PCH₂PX₂)] as a result of successive deprotonation and alkyl halide addition. When X = Ph it proved possible to replace both methylene protons but for X = Cy only one substitution proved possible. This is likely due to the electron-releasing nature of the cyclohexyl groups but may also be due to steric constraints. Attempts to prepare the bis(allyl) substituted complex [Mo(CO)₄{Ph₂PC(allyl)₂PPh₂}] were only moderately successful. The crystal structures of nine of these complexes are presented.

Full text of DOI:10.1016/j.jorganchem.2007.09.024

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5655–5670
www.elsevier.com/locate/jorganchem
Backbone modified small bite-angle diphosphines: Synthesis
and molecular structures of [M(CO)4{X2PC(R1R2)PX2}] (M = Mo,
W; X = Ph, Cy; R1 = H, Me, Et, Pr, allyl, R2 = Me, allyl)
*
Graeme Hogarth , John Kilmartin
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
Received 28 August 2007; received in revised form 19 September 2007; accepted 25 September 2007
Available online 1 October 2007
Abstract
A range of new small bite-angle diphosphine complexes, [M(CO)4{X2PC(R1R2)PX2}] (M = Mo, W; X = Ph, Cy; R1 = H, Me, Et, Pr,
allyl, R2 = Me, allyl), have been prepared via elaboration of the methylene backbones in [M(CO)4(X2PCH2PX2)] as a result of successive
deprotonation and alkyl halide addition. When X = Ph it proved possible to replace both methylene protons but for X = Cy only one
substitution proved possible. This is likely due to the electron-releasing nature of the cyclohexyl groups but may also be due to steric
constraints. Attempts to prepare the bis(allyl) substituted complex [Mo(CO)4{Ph2PC(allyl)2PPh2}] were only moderately successful.
The crystal structures of nine of these complexes are presented.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Diphosphine; Chelating; Dppm; Backbone modified; Molybdenum; Tungsten
R
N
1. Introduction
base
ð1Þ
2 Ar2PCl
+ RNH2
- 2 HCl
Diphosphines are an important class of ligand that find
widespread use in transition metal chemistry and catalysis.
A subclass of these is small bite-angle diphosphines in
which the two phosphorus centres are separated only by
a single atom linker unit, the archetypal example being
bis(diphenylphosphino)methane (dppm) [1–3]. Metal coor-
dination of small bite-angle diphosphines has been shown
to often lead to complexes that show unusual behaviour
and recently this has been exploited with applications in
a range of catalytic processes [4–24]. A wide range have
been synthesised predominantly with carbon and nitrogen
backbone atoms. Since the latter are prepared using pri-
mary amines as the source of the NR group (Eq. (1))
[25–40], a large number of backbone modified examples
have been prepared, while phosphorus functionalisation
appears to be limited to aryl groups.
PAr2
Ar2P
In contrast, carbon-linked varieties are predominantly
functionalised at phosphorus [41–57], with backbone func-
tionalisation being far less widely studied [58–64]. This is
due to the synthetic methods widely utilised (Eqs. (2)–(4))
since in all three the methylene backbone is a key compo-
nent of one of the precursors.
H
H
H
H
4 RMgX
ð2Þ
ð3Þ
ð4Þ
PCl2
Cl2P
- 4 MgXCl
PR2
R2P
H
H
R2 PCl, Δ
H
H
2
R1 P
- Ph3SnCl
PR2
R1 P
SnPh3
2
2
2
H
H
H
H
2 Ar2PM
- 2 MCl
*
PAr2
Corresponding author.
Ar2P
Cl
Cl
E-mail address: g.hogarth@ucl.ac.uk (G. Hogarth).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.09.024

5656
G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
In theory, all three methods should be adaptable to give
yet been made to assess how steric and electronic changes
to the backbone substituents might effect the performance
of the catalyst. With this in mind, we decided to return
to Shaw’s on-metal backbone derivatisation studies of
dppm with the aim of preparing hitherto unknown asym-
metrically disubstituted derivatives, Ph2PC(R1R2)PPh2,
and also to see if this methodology could be extended to
the more basic bis(dicyclohexylphosphino)methane
(dcpm).
backbone substituted derivatives, however, in practice,
backbone functionalised derivatives of Cl2PCH2PCl2 and
R12PCH2SnPh3 are not known. Eq. (4) is potentially the
most widely utilisable towards this aim since geminal diha-
lides can be readily prepared upon reduction of the corre-
sponding aldehydes or ketones using PCl5. Indeed, this
route has been utilised towards the preparation of methyl
substituted compounds, Ph2PCH(Me)PPh2 [58–61] and
Ph2PC(Me)2PPh2 [62]. However, even in these instances
yields are relatively low when compared to the analogous
synthesis of dppm via this method and a large number of
side-products are observed by 31P NMR spectroscopy.
These possibly result from the competing reduction of the
geminal dihalide and indeed this has been developed for
the stereoselective reduction of geminal-dichlorocyclopro-
panes [65].
2. Results and discussion
2.1. Synthesis of mono-substituted complexes
[M(CO)4{Ph2PCH(R)PPh2}] (2–9): structural
characterisation of [Mo(CO)4{Ph2PCH(Pr)PPh2}] (4)
As detailed in the introduction, Shaw and co-work-
ers have previously shown that [Mo(CO)4(dppm)] (1)
can be readily deprotonated by n-BuLi, subsequent
addition of alkyl halides leading to the formation
of mono-substituted derivatives. In this way,
[Mo(CO)4{Ph2PCH(Me)PPh2}] (2) can be prepared in
moderate yields [66], being available in similar amounts
In the early 1980s, Shaw and co-workers developed
an on-metal route to the backbone functionalisation of
dppm [66–72]. This utilises the enhanced acidity of the
methylene protons upon coordination of the diphosphine
to a low-valent metal centre, those with electron-with-
drawing ligands being particularly suitable. For example,
they
showed
that
addition
of
n-BuLi
to
upon
addition
of
Ph2PCH(Me)PPh2
to
cis-
[Mo(CO)4(dppm)] followed by treatment of the in situ
generated anion with alkyl halides lead to the formation
[Mo(CO)4(NHC5H10)2]. In both cases the yields we
recorded were for the recrystallised product and by
31P NMR spectroscopy the reactions are essentially
quantitative. Other mono-substituted complexes 3–6
were prepared analogously via the deprotonation
method in crystalline yields of between 58% and 78%.
Attempts to prepare 6 using allyl bromide gave poor
of
backbone
substituted
derivatives
[Mo(CO)4-
{Ph2PCH(R)PPh2}], and when excess MeLi was used
as the base a double deprotonation can occur to afford
[Mo(CO)4{Ph2PC(Me)2PPh2}] after quenching with MeI.
More recently we have adapted this procedure towards
the on-metal backbone functionalisation of (o-
tolyl)2PCH2P(o-tolyl)2 [51]. In this case, only a single
methylene proton can be replaced even under forcing
conditions, an observation attributed to both the steric
demands of the ortho-tolyl groups and also their better
electron-releasing ability.
In a number of recent publications and patents, small
bite-angle diphosphine complexes have been shown to be
excellent catalysts for a number of different catalytic pro-
cesses including the polymerisation and oligomerisation
of ethylene [7,14], the selective co-trimerisation of ethylene
and styrene co-monomers [8] and the asymmetric hydroge-
yields, large amounts of
1 being reclaimed after
work-up. We were also frustrated in trying to extend
this simple methodology to bulkier alkyl iodides such
as CyI, iPrI, iBuI and tBuI. In these cases, after
work-up only 1 was reclaimed suggesting that either
the anion generated is not nucleophilic enough to
attack the sterically hindered and more electron-rich
carbon centres or a competing elimination process sim-
ply regenerates the starting material. The tungsten com-
plexes 8 and 9 were prepared in an analogous fashion
from [W(CO)4(dppm)] (7) and were isolated in moder-
ate crystalline yields.
CO
CO
Ph
Ph
2
2
2
2 R = Me
3 R = Et
4 R = Pr
5 R = Bu
6 R = allyl
CO
P
CO
CO
P
H
H
(i) BuLi
(ii) RI
H
R
Mo
Mo
CO
P
CO
P
Ph
Ph
2
CO
1
nation of a range of substrates [15,16]. A wide range of
ligands have been used in these studies, however, for those
based on a carbon backbone, while a number of phospho-
rus functionalised ligands have been tested, no attempt has
All mono-substituted complexes are air-stable, pale yel-
low solids soluble in a range of organic solvents and char-
acterisation was straightforward. They show three
carbonyl absorptions in the IR spectrum, the positions of

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
5657
which do not vary significantly with changes to the substi-
tuent. 31P NMR spectroscopy is useful in assessing the con-
version of the dppm complexes, substituent addition
resulting in a downfield shift of the singlet resonance from
tonation of 1 by MeLi followed by quenching with MeI
[68]. One of our goals of this work was the preparation
of unsymmetrically disubstituted complexes and with this
in mind we followed a similar procedure starting with
mono-alkyl-substituted 2–6 leading to the preparation of
disubstituted complexes 11–14 in moderate crystalline
yields. In all cases, addition of a slight excess of MeLi
resulted in a darkening of the reaction solution which
we associated with formation of the deprotonated species.
1
2.6 ppm in 1 to 22.6–25.6 ppm in 2–6. In the H NMR
spectra, the characteristic triplet patterns shown by the
methylene protons in 1 and 7 are replaced by a multiplet
centred around a similar chemical shift range of d 4.50–
4.73.
CO
CO
Ph
2
Ph
P
2
2
CO
P
CO
CO
H
H
(i) BuLi
(ii) RI
H
R
8 R = Me
9 R = allyl
W
W
P
CO
P
Ph
Ph
2
CO
CO
7
In order to probe the structural consequences of back-
bone substitution, the crystal structure of 4 was carried
out (Fig. 1) in order to compare it with that of 1 which
has previously been reported [73]. Key structural parame-
ters are shown in Table 1. As expected, the backbone has
been functionalized with a propyl group. In solution, this
splits the four equivalent phenyl groups in 1 into two sets,
while in the solid state all four are inequivalent. Addition
of the propyl group to the backbone leads to a small increase
in the P–C–P angle (ca. 0.7ꢁ) and concomitant decrease in
the P–Mo–P bite-angle (ca. 0.5ꢁ), changes broadly consis-
tent with an increased repulsion between the alkyl and
diphenylphosphino groups. Molybdenum–phosphorus dis-
tances vary only slightly between 1 and 4, as do the molyb-
denum–carbon distances to the carbonyls lying cis to the
diphosphines. There is, however, a very marked difference
in the molybdenum–carbon distances to the trans carbonyls
However, no attempts were made to isolate these or char-
acterise them in any way. Initially we stirred these solu-
tions at room temperature for ca. 1 h in order to allow
the reactions to proceed to completion. Subsequent addi-
tion of MeI then afforded the required unsymmetrically
1
disubstituted complexes. However, by 31P and H NMR
spectroscopy it was clear that under these conditions a
mixture of three complexes resulted; namely the unreacted
starting material, the expected product and the dimethyl-
substituted complex 10. Formation of the latter suggests
that nucleophilic substitution of the methine proton
may compete with deprotonation. We initially considered
that the presence of starting mono-substituted complexes
may result from their poor deprotonation; however,
increasing the amount of MeLi or reaction time had little
effect on its consumption. We then considered that the
highly reactive nature of the generated anions, and their
subsequent reaction with adventitious water, may be to
blame. Consequently, addition of MeLi followed by
almost immediate quenching with MeI was adopted. This
indeed gave better conversion to the desired products and
the sequence was sometimes repeated in order to enhance
this conversion. We also attempted to prepare 11–13 from
[Mo(CO)4{Ph2PCH(Me)PPh2}] (2) upon successive addi-
tion of MeLi and the required alkyl iodide. This was gen-
erally disappointing with only small amounts of the
required disubstituted products being generated, even
after successive additions. We attribute this to the rela-
tively high reactivity of MeI as compared to other alkyl
iodides.
˚
which are elongated by an average of ca. 0.6 A in 4 as com-
pared to 1. Since the same bonds in other substituted com-
plexes (Table 1) are more in line with the values measured
in 4 this difference may simply be a result of the relatively
poor quality of the literature X-ray data for 1 [73].
2.2. Synthesis of disubstituted complexes
[Mo(CO)4{Ph2PCMe(R)PPh2}] (10–14),
[Mo(CO)4{Ph2PC(allyl)2PPh2}] (15) and
[W(CO)4{Ph2PC(Me2)PPh2}] (16): structural
characterisation of 11–13
Al-Jibori and Shaw have previously prepared
[Mo(CO)4{Ph2PC(Me2)PPh2}] (10) via the double depro-
CO
CO
10 R = Me
Ph
2
Ph
2
CO
P
CO
CO
11 R = Et
12 R = Pr
13 R = Bu
14 R = allyl
P
R
H
(i) MeLi
(ii) MeI
R
Mo
CO
Mo
CO
P
CO
Me
P
Ph
Ph
2
2
2-6

5658
G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
Fig. 1. Molecular structure and numbering scheme for [Mo(CO)4{Ph2PCH(Pr)PPh2}] (4) (hydrogen atoms omitted for clarity).
t
The allyl–methyl derivative 14 was produced upon
CH(allyl)PPh2}] (6) by BuLi (MeLi was avoided since 14
would be a by-product) followed by addition of excess allyl
iodide resulted in the slow generation of a new peak in the
31P NMR spectrum at d 49.9 being consistent with the for-
mation of a disubstituted diphosphine. After eight succes-
sive deprotonation–quench cycles, conversion was around
66% by 31P NMR. Unfortunately, we were unable to iso-
late a pure sample of 15 since all attempts to separate it
from 6 were unsuccessful. Nevertheless, we are confident
on the basis of spectroscopic data (see below) that this
was formed.
deprotonation of 2 by MeLi followed by addition of excess
allyl bromide. This method gave around 80% conversion of
2 in one-step, although a significant amount (ca. 10%) of
the dimethyl complex 10 was also produced. Nevertheless,
the relative success of the latter route spurred us on to
attempt the synthesis of the diallyl complex
[Mo(CO)4{Ph2PC(allyl)2PPh2}] (15). The latter was a tar-
get for us as we hoped to be able to use a ring-closing
metathesis route to prepare a diphosphine based on a cyclic
backbone. Repeated deprotonation of [Mo(CO)4{Ph2P-

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
5659
CO
CO
Mo
Ph
P
2
Ph
P
CO
CO
2
2
CO
CO
(i) tBuLi
(ii) allylI
Mo
P
H
P
Ph
Ph
2
CO
CO
15
6
All unsymmetrically disubstituted complexes are air-sta-
ble, pale yellow crystalline complexes with good solubility
in a range of organic solvents. Their formation is easily
shown by 31P NMR spectroscopy, the observed singlet
being shifted to ca. 25 ppm downfield of that observed in
the analogous mono-substituted complexes. Again, IR
spectra vary little from that of 1 and their mono-substi-
tuted precursors suggesting that even disubstitution of
the backbone has little effect on the electron-donating nat-
ure of the diphosphine and the unsymmetrical nature of the
backbone substitution leads to the maintained inequiva-
lence of the phenyl groups above and below the MoPCP
plane as easily seen by 1H NMR spectroscopy. For the pre-
viously reported dimethyl complex, [Mo(CO)4{Ph2PC(-
Me2)PPh2}] (10) [68], the methyl groups are equivalent
and appear as a triplet at d 1.46 (JP–H = 13.2), while the
aromatic region is also relatively simple due to the symmet-
rical nature of the diphosphine. For [Mo(CO)4{Ph2PC(al-
lyl)2PPh2}] (15), a similar equivalence of the two allyl
groups is clearly seen in the H NMR spectrum, with the
appearance of resonances in the expected regions.
1
Crystallographic studies were carried out on three of
these complexes, namely 11–13, in order to compare the
metric parameters with those of 1 and 4, and also to assess
the arrangement of the phenyl rings upon disubstitution.
Data are summarized in Table 1, and the molecular struc-
ture of [Mo(CO)4{Ph2PCMe(Et)PPh2}] (11) as a representa-
tive example is shown in Fig. 2. Bond lengths in all three
structures do not vary significantly from those found in 4,
nor do the observed P–Mo–P bite-angles of between
67.495(12)ꢁ and 67.941(12)ꢁ. As might be expected, how-
ever, the P–C–P angle is reduced upon disubstitution rang-
ing from 94.50(6)ꢁ to 94.65(6)ꢁ, being around 1.7ꢁ smaller
than that in 4. This shows that while the addition of a second
substituent has a marked effect on the angle at the diphos-
phine backbone this is not passed on to the metal centre,
Table 1
1
2
˚
Selected bond lengths (A) and angles (ꢁ) for [M(CO)4{X2PC(R R )PX2}]
˚
˚
˚
M–CO (cis) (A)
M–CO (trans) (A)
M–P (A)
P–M–P (ꢁ)
P–C–P (ꢁ)
[Mo(CO)4(Ph2PCH2PPh2)]a
2.07(1)
1.92(1)
2.501(2)
67.3(1)
95.6(4)
2.02(2)
1.94(1)
2.535(3)
[Mo(CO)4{Ph2PCH(Pr)PPh2}] (4)
[Mo(CO)4{Ph2PCMe(Et)PPh2}] (11)
[Mo(CO)4{Ph2PCMe(Pr)PPh2}] (12)
[Mo(CO)4{Ph2PCMe(allyl)PPh2}] (13)
[Mo(CO)4(Cy2PCH2PCy2)] (17)
2.0328(15)
2.0485(15)
2.0310(14)
2.0349(15)
2.0292(16)
2.0379(16)
2.029(2)
2.038(2)
2.027(2)
2.041(2)
2.025(3)
2.036(3)
2.025(3)
2.040(3)
2.020(3)
2.030(3)
2.030(2)
2.032(2)
2.028(5)
2.051(5)
1.993(8)
2.042(8)
2.021(3)
2.031(4)
1.9807(14)
2.0010(15)
1.9907(15)
1.9976(15)
1.9833(16)
1.9937(15)
1.993(2)
1.998(2)
1.985(2)
1.989(2)
1.987(3)
1.988(3)
1.993(3)
1.995(3)
1.986(2)
1.986(2)
1.990(2)
1.997(2)
1.979(4)
1.981(5)
1.972(5)
1.972(5)
1.963(4)
1.990(3)
2.4954(3)
2.5132(3)
2.5132(4)
2.5185(4)
2.5024(4)
2.5395(4)
2.5070(5)
2.5289(5)
2.5241(5)
2.5410(5)
2.5187(6)
2.5324(6)
2.5187(7)
2.5207(7)
2.5338(6)
67.829(11)
67.941(12)
67.495(12)
67.917(16)
67.397(17)
67.20(2)
96.29(6)
94.50(6)
94.60(6)
94.65(8)
98.81(10)
98.21(13)
97.61(12)
97.12(14)
98.66(6)
99.2(2)
[W(CO)4(Cy2PCH2PCy2)] (18)
[Mo(CO)4{Cy2PCH(Me)PCy2}] (19)
[Mo(CO)4{Cy2PCH(Et)PCy2}] (20)
[Mo(CO)4{Cy2PCH(allyl)PCy2}] (21)
[Mo(CO)4{(o-tolyl)2PCH2P(o-tolyl)2}]b
[Mo(CO)4{(o-tolyl)2PCH(Me)P(o-tolyl)2}]b
[Mo(CO)4{(o-tolyl)2PCH(Bz)P(o-tolyl)2}]b
67.95(2)
67.06(3)
2.5214(5)
2.5453(5)
2.5338(11)
2.5561(10)
2.5502(12)
2.5502(12)
2.5378(8)
2.5767(9)
67.804(16)
67.20(3)
67.66(5)
97.6(3)
66.58(3)
96.33(13)
a
Reference [73].
Reference [51].
b

5660
G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
Fig. 2. Molecular structure and numbering scheme for [Mo(CO)4{Ph2PCMe(Et)PPh2}] (11) (hydrogen atoms omitted for clarity).
presumably due to the flexibility of the Mo–P–C angles. The
orientation of the phenyl groups is very similar in all three
complexes 11–13, and also bears a close resemblance to that
found in 4. Thus, one of the groups [C(9)–C(14) in 11] is
rotated significantly with respect to the other three, lying
approximately perpendicular to them and this group always
lies on the same side of the diphosphine as the longest of the
backbone substituents.
As alluded to above, the known tungsten dimethyl com-
plex 16 [68] was easily prepared in high yield (94%) upon

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
5661
deprotonation of 8 by MeLi followed by quenching with
MeI. An attempt was also made to prepare the diallyl-
substituted [W(CO)4{Ph2PC(allyl)2PPh2}] via deprotona-
tion of the mono-allyl complex 9 followed by addition of
allyl bromide. While some evidence was gleaned for the
generation of the latter, the use of MeLi as the deprotonat-
ing agent (see above) was unfortunate and lead to the for-
[Mo(CO)4(dcpm)] (17) and [W(CO)4(dcpm)] (18) in moder-
ate isolated yields upon thermolysis of the free ligand and
cis-[M(CO)4(NHC5H10)2] in dichloromethane. Both are
easily characterised, IR spectra showing the characteristic
tetracarbonyl pattern being shifted by around 12–15 cmꢀ1
to lower wavenumbers as compared to the analogous dppm
complexes, a result of the more electron-releasing nature of
the alkyl phosphines.
mation of
a mixture containing methyl-substituted
H
CO
M
CO
Cy2
CO
CO
CO
N
P
Cy2PCH2PCy2
H
17 M = Mo
18 M = W
M
CH2Cl2, Δ
N
H
P
CO
Cy2
CO
CO
H
products along with the desired diallyl derivative. Further
attempts to prepare the diallyl complex using BuLi as a
base are currently in progress.
The molecular structures of both 17 and 18 were inves-
tigated by X-ray crystallography. The complexes are iso-
structural (Table 2). Data are summarized in Table 1 and
the molecular structure of [Mo(CO)4(dcpm)] (17) is shown
in Fig. 3. Few significant differences are seen between the
structure of 17 and that of the related phenyl-functional-
ised complexes. For example, the bite-angle of the diphos-
phine at 67.397(17)ꢁ is indistinguishable from that found in
1, although as might be expected, the P–C–P angle of
98.81(10)ꢁ is over 3ꢁ larger than that found in 1. A note-
worthy feature of the orientation of the cyclohexyl rings
is that they those on either phosphorus atom lie approxi-
mately perpendicular to one another while on either side
of the diphosphine pairs of cyclohexyl groups are approx-
imately parallel. This suggests that the greatest steric inter-
action between cyclohexyl rings is between those on the
same phosphorus atom.
In order to prepare the first examples of backbone
functionalised dcpm ligands we treated 17 sequentially
with n-BuLi and RI leading to formation the new
diphosphine complexes 19–21 in moderate crystalline
yields. Formation of 19 and 20 proceeded relatively
straightforwardly, but conversion of 17 to 21 was less
efficient and the procedure was repeated twice in order
to generate significant product. All display very similar
spectroscopic properties to 17, the remaining methine
proton appearing as a multiplet at between d 3.18 and
3.47.
t
CO
W
CO
W
Ph2
P
Ph2
P
CO
CO
CO
CO
Me
H
(i) MeLi
(ii) MeI
Me
Me
P
P
Ph2
Ph2
CO
CO
16
8
2.3. Synthesis and structural characterisation of cyclohexyl-
substituted complexes [M(CO)4{Cy2PCH(R)PCy2}]
(16–20)
The coordination chemistry of bis(dicyclohexylphos-
phino)methane (dcpm) has been explored to a far lesser
extent than that of the related bis(diphenylphos-
phino)methane (dppm) [46,74–80]. This is in part to its
more challenging synthesis and air sensitivity in solution.
As far as we are aware, backbone-functionalised deriva-
tives of dcpm are currently unknown. They should be avail-
able via the method developed by Rothwell and co-workers
for the catalytic hydrogenation of arylphosphines using for
example, Ph2PCH(Me)PPh2 or Ph2PC(Me2)PPh2 as start-
ing materials. We were interested to see if Shaw’s method-
ology, to date only applied to dppm, could be extended to
this more bulky and electron-donating diphosphine. Some-
CO
CO
Cy
2
Cy
2
CO
CO
19 R = Me
20 R = Et
21 R = allyl
P
P
(i) BuLi
(ii) RI
H
R
H
H
Mo
CO
Mo
P
CO
P
CO
Cy
Cy
2
2
CO
17
what surprisingly, we could not find reference to the syn-
thesis of any of the group VI tetracarbonyl complexes of
The crystal structures of all three new molybdenum
complexes were carried out (Table 1) and the molecular
structure of [Mo(CO)4{Cy2PCH(allyl)PCy2}] 21 as a
dcpm
so
consequently
we
initially
prepared

Table 2
Crystal data and collection and refinement details for new complexes
Compound
4
11
12
13
17
18
19
20
21
Empirical formula
Formula weight
Crystal system
Space group
C
634.42
Monoclinic
P21/c
32H28MoO4P2
C32H28MoO4P2
634.42
Monoclinic
P21/c
C33H30MoO4P2
648.45
Monoclinic
P21/c
C33H28MoO4P2
646.43
Monoclinic
P21/c
C29H46MoO4P2
616.54
Orthorhombic
Pbca
C29H46WO4P2
704.45
Orthorhombic
Pbca
C123H188Mo4O19P8 C31H50MoO4P2
C32H50MoO4P2
656.60
Monoclinic
P21/c
2602.25
Monoclinic
P21/c
644.59
Monoclinic
P21/m
Temperature (K)
293(2)
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
˚
a (A)
9.4418(6)
17.3456(11)
18.3159(11)
100.731(1)
2932.1(3)
4
12.1290(6)
13.7921(7)
18.0899(10)
104.982(1)
2923.3(3)
4
17.8552(12)
9.6650(6)
19.4329(13)
114.159(1)
3059.8(3)
4
11.8877(11)
13.9578(13)
18.6855(18)
107.163(1)
2962.3(5)
4
18.3477(13)
15.5405(11)
21.3580(15)
90
6089.9(7)
8
18.3539(11)
15.4842(9)
21.3638(12)
90
6071.5(6)
8
18.7960(13)
15.8810(11)
21.9585(16)
101.677(1)
6418.9(8)
2
8.7614(7)
20.7393(15)
9.6466(7)
113.424(1)
1608.4(2)
2
11.3002(9)
16.5626(13)
17.1139(13)
94.743(1)
3192.1(4)
4
˚
b (A)
˚
c (A)
b(ꢁ)
Volume (A )
3
˚
Z
Dcalc (Mg mꢀ1
F(000)
)
1.437
1296
1.442
1296
1.408
1328
1.449
1320
1.345
2592
1.541
2848
1.346
2732
1.331
680
1.336
1384
Crystal size (mm) 0.34 · 0.28 · 0.16 0.28 · 0.28 · 0.26 0.28 · 0.26 · 0.15 0.28 · 0.24 · 0.04 0.28 · 0.14 · 0.12 0.38 · 0.20 · 0.20 0.36 · 0.30 · 0.16
0.26 · 0.18 · 0.16 0.26 · 0.18 · 0.17
h Range (ꢁ)
Reflections
collected
1.63–28.30
25346
1.74–28.28
25127
2.12–28.29
26117
1.85–28.30
25319
1.92–28.26
50988
1.91–28.33
50714
1.69–28.30
54803
1.96–28.28
1.71–28.27
14204
27570
Independent
reflections
6993 (0.0158)
6933 (0.0138)
7319 (0.0174)
7040 (0.0190)
7427 (0.0331)
7397 (0.0242)
15279 (0.0258)
3958 (0.0204)
7645 (0.0198)
(Rint
)
Data/restraints/
parameters
Goodness-of-fit
on F2
6993/0/352
1.045
6933/1/352
1.056
7319/0/361
1.035
7040/0/361
1.127
7427/0/325
1.041
7397/0/325
1.072
15279/0/678
1.019
3958/0/187
1.033
7645/0/352
1.074
Final R indices
[I > 2r(I)]
R1 = 0.0218,
wR2 = 0.0559
R1 = 0.0232,
wR2 = 0.0593
R1 = 0.0249,
wR2 = 0.0631
R1 = 0.0298,
wR2 = 0.0752
R1 = 0.0345,
wR2 = 0.0825
R1 = 0.0248,
wR2 = 0.0307
R1 = 0.0457,
wR2 = 0.1214
R1 = 0.0377,
wR2 = 0.0933
R1 = 0.0312,
wR2 = 0.0813
Largest difference 0.409 and ꢀ0.220 0.658 and ꢀ0.288 0.492 and ꢀ0.337 0.626 and ꢀ0.585 0.845 and ꢀ0.429 1.387 and ꢀ0.491 1.856 and ꢀ0.788
0.802 and ꢀ0.631 1.588 and ꢀ0.510
in peak aꢀn3d
˚
hole (e A
)

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
5663
Fig. 3. Molecular structure and numbering scheme for [Mo(CO)4(dcpm)] (17) (hydrogen atoms omitted for clarity).
representative example is shown in Fig. 4. Introduction of
the substituent leads to no significant changes in bond
lengths and angles as compared to 17 with P–C–P and P–
Mo–P angles over the three structures lying on either side
of those found in 17. In 19 and 20 the observed relative ori-
entations of the cyclohexyl groups is maintained (it is crys-
tallographically imposed in 20 as a result of the mirror
plane that includes the metal, backbone carbon and cis car-
bonyls), however, in 21 it is somewhat different being more
randomly orientated.
Repeated attempts to add a second substituent to the
backbone of dcpm met only with failure. A range of
bases were attempted but all failed to result in significant
deprotonation as evidenced by the high yield of starting
materials reclaimed. We attribute this to the decreasing
acidity of the remaining backbone proton and also to
steric difficulties for the addition of the incoming electro-
phile. Thus it seems that at the molybdenum carbonyl
stabilized centre the dcpm cannot be further functional-
ized. As alluded to above, such ligands should be

5664
G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
Fig. 4. Molecular structure and numbering scheme for [Mo(CO)4{Cy2PCH(allyl)PCy2}] (21) (hydrogen atoms omitted for clarity).
accessible upon hydrogenation of Ph2PC(R2)PPh2 or per-
haps via the double deprotonation of more electron-defi-
cient dcpm complexes, and with this in mind we are
currently investigating the reactivity of the diborane com-
plex of dcpm.
3. Conclusions
This contribution has developed work previously
reported by Shaw and co-workers [66–72], showing that
the backbone of the readily available small bite-angle

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
5665
diphosphine dppm can be readily modified when coordi-
nated to the molybdenum and tungsten tetracarbonyl cen-
tres. Importantly, asymmetric disubstituted complexes
unavailable via standard methods can be prepared in this
manner. The diphosphines bind strongly to the low-valent
centres and appear to be indefinitely stable both in the solid
state and solution. Infra-red spectra suggest that backbone
functionalisation does not significantly affect the donor
properties of the diphosphine but the introduction of steric
bulk at this position should have a significant effect on the
stability of chelate versus bridge coordination modes, while
also restricting the rotation about the P–Ar bonds and thus
allowing a more well-defined coordination environment
about the metal centre. While we have not shown the latter
directly here we have previously demonstrated this for
related ortho-tolyl diphosphines [51]. We have also shown
for the first time that the more basic dcpm ligand can also
be backbone modified, although somewhat disappointingly
addition of only a single substituent appears to be possible.
This is likely due to the more basic nature of this ligand but
also to the enhanced steric bulk at phosphorus and corre-
sponds with the situation found for the ortho-tolyl deriva-
tive where again only a single substituent could be added
[51]. The high stability of the prepared complexes suggests
that these ligands will bind strongly to a wide-range of low-
valent metal centres and thus may have applications in
homogeneous catalysis. No attempts were made to liberate
the free diphosphines from their group VI complexes. This
is likely only to be achievable under highly oxidising condi-
tions, which would almost certainly lead to the oxidation
(or destruction) of the diphosphines. A goal of our work
is the preparation of the free diphosphines and with this
in mind we are now developing related chemistry of the
borane-protected diphosphines. These are easily prepared
from the diphosphine and BH3 Æ thf and the strong Lewis
acidity of the borane group should render the backbone
protons acidic and thus susceptible to substitution. Unlike
the low-valent metal centre, the borane unit is easily
removed upon addition of excess base and this route
should allow preparation of the free diphosphines. Studies
in this area are ongoing and will be reported in due course.
VG ZAB-SE high resolution mass spectrometer and ele-
mental analyses were performed in house.
Synthesis of Ph2PCH(Me)PPh2. 1,1-Dibromoethane
(2.15 ml, 0.025 mol) was added dropwise to the stirred
solution of LiPPh2 (ca. 0.05 mol) under nitrogen leading
to a colour change from red to yellow. After stirring for
1 h, methanol (ca. 20 ml) was added, the solution was
transferred to a round bottom flask and volatiles were
removed by rotary evaporation to a give yellow-grey solid.
This was dissolved in dichloromethane (ca. 100 ml) and
washed with water (3 · 50 ml). The dichloromethane solu-
tion was dried with magnesium sulphate, filtered and vola-
tiles were removed under reduced pressure to leave a crude
orange product. This was washed with a small amount of
ethanol to give a fine white powder. Crystallisation upon
adding ethanol to a concentrated dichloromethane solution
gave Ph2PCH(Me)PPh2 as a fine white solid (4.48 g, 45%).
1H NMR (CDCl3) d 7.54–7.27 (m, 20H, Ph), 3.21 (q,
J = 6.94, 1H, CH), 1.01 (dt, J = 10.3, J = 7.01, 3H, Me);
31P NMR (CDCl3) d ꢀ6.5 (s).
Synthesis of Ph2PC(Me2)PPh2. A thf (10 ml) solution of
2,2-dichloropropane (5.64 g, 0.05 mol) was added to a stir-
red solution of LiPPh2 (ca. 0.10 mol) in thf (150 ml). After
stirring overnight the solution turned from deep red to
orange and upon addition of methanol (ca. 10 ml) the solu-
tion turned straw yellow. After removal of volatiles under
reduced pressure, the dry solid was dissolved in dichloro-
methane (ca. 100 ml) and washed with water (3 · 50 ml).
After drying the dichloromethane portion with magnesium
sulphate, removal of volatiles gave an orange oil. This was
washed with a small amount of ethanol to give a white pre-
cipitate (7.59 g, 39% yield). 1H NMR (CDCl3) d 7.8–7.4 (m,
20H, Ph), 1.25 (t, J = 10.3, 6H, 2Me); 31P NMR (CDCl3) d
12.8 (s).
Synthesis of [Mo(CO)4{Ph2PCH(Me)PPh2}] (2).
[Mo(CO)4(NHC5H10)2] (1.00 g, 2.64 mmol) and Ph2PCH-
(Me)PPh2 (1.05 g, 2.64 mmol) were refluxed in dichloro-
methane (40 ml) for 1 h. The solution was filtered and con-
centrated on a rotary evaporator and crystals were
obtained upon adding methanol and placing the mixture
in a freezer overnight. More crystals were obtained by con-
centrating the reaction solution and placing back in the
freezer. Total yield: 0.61 g (40%). Alternatively, 1 (0.43 g,
0.72 mmol) was dissolved in toluene (20 ml) and TMEDA
(0.16 ml, 1.08 mmol) and n-BuLi (0.43 ml, 1.08 mmol) were
added causing the solution to turn from yellow to dark red-
orange. This was stirred for 1 h, MeI (0.089 ml, 1.44 mmol)
was added and the mixture was stirred overnight. The solu-
tion turned cloudy yellow-brown and volatiles were
removed to give a grey-brown solid. This was dissolved
in dichloromethane (ca. 20 ml) and washed with water
(3 · 30 ml). The dichloromethane portion was dried over
magnesium sulphate and concentrated on a rotary evapo-
rator. Methanol was added and the solution was placed
in a freezer to give pale yellow crystals (0.34 g, 77%).1H
NMR (CDCl3) d 7.61–7.35 (m, 20H, Ph), 4.70 (m, 1H,
CH), 1.15 (dt, J = 13.0, J = 7.6, 3H, Me); 31P NMR
4. Experimental
All reactions were carried out under a nitrogen atmo-
sphere in dried degassed solvents unless otherwise stated.
cis-[M(CO)4(NHC5H10)2] (M = Mo, W) and [M(CO)4-
(dppm)] (M = Mo, W) [81,82] were prepared by the litera-
ture method and bis(dicyclohexylphosphino)methane was
purchased from Aldrich and used as supplied. NMR spec-
tra were run on a Bruker AMX400 spectrometer and refer-
enced internally to the residual solvent peak (1H) or
externally to P(OMe)3 (31P). Infrared spectra were run on
Nicolet 205 or Shimadzu 8700 FT-IR spectrometers in a
solution cell fitted with calcium fluoride plates, subtraction
of the solvent absorptions being achieved by computation.
Fast atom bombardment mass spectra were recorded on a

5666
G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
(CDCl3) d 22.6 (s). Anal. Calc. for 2: C, 57.42, H, 4.67.
Found: C, 57.54, H, 3.86%. IR m(CO) (CH2Cl2) 2020s,
(0.50 ml, 2.80 mmol). The solution turned dark orange
and was stirred for 2 min. Allyl iodide (1.02 ml, 11.2 mmol)
was then added causing another colour change to dark
brown-orange. This was stirred for 15 min and then vola-
tiles were removed under vacuum leaving a viscous
brown-orange oil. This was dissolved in dichloromethane
(50 ml) and washed with water (3 · 40 ml). The dichloro-
methane portion was then dried over magnesium sulphate
and filtered. Orange crystals were obtained by layering a
concentrated solution of the product in dichloromethane
with methanol and leaving the solution to mix slowly
(0.19 g, 78%). 1H NMR (CDCl3) d 7.65–7.25 (m, 20H,
Ph), 5.40 (qt, J = 10.1, 6.9, 1H, CH), 4.90 (dd, J = 10.1,
1.1, 1H, @CH2), 4.73 (dd, J = 18.4, 1.1, 1H, @CH2), 4.67
(m, 1H, PCHP), 2.24 (m, 2H, CH2); 31P NMR (CDCl3) d
1907s, 1882s cmꢀ1
.
Synthesis of [Mo(CO)4{Ph2PCH(Et)PPh2}] (3). To 1
(0.18 g, 0.30 mmol) in thf (40 ml) was added TMEDA
(0.07 ml, 0.51 mmol) and n-BuLi in hexane solution
(0.3 ml, 0.75 mmol). The solution turned orange and was
then stirred for 1 h before EtI (0.18 g, 1.17 mmol) was
added and the mixture left stirring overnight. Removal of
volatiles gave an oily solid which was dissolved in dichloro-
methane (30 ml) and washed with water (3 · 40 ml). The
dichloromethane portion was then dried over magnesium
sulphate, filtered and concentrated under vacuum. Metha-
nol was added to give pale yellow crystals (0.11 g, 58%). 1H
NMR (CDCl3) d 7.60–7.36 (m, 20H, Ph), 4.52 (m, 1H,
CH), 1.54 (m, 2H, CH2), 0.77 (t, J = 7.3, 3H, Me); 31P
NMR (CDCl3) d 24.7 (s); IR m(CO) (CH2Cl2) 2019s,
25.6 (s); IR m(CO) (CH2Cl2) 2019s, 1908s, 1884s cmꢀ1
.
Synthesis of [W(CO)4{Ph2PCH(allyl)PPh2}] (9). To
7 (0.21 g, 0.31 mmol) in thf (20 ml) was added n-BuLi
(0.62 ml, 1.5 mmol) in hexane, the solution turning dark
orange. This was stirred for 15 min and allyl bromide
(0.16 ml, 1.8 mmol) was added. After 2 h removal of vola-
tiles under vacuum gave an orange solid. This solid was dis-
solved in dichloromethane (20 ml), washed with water
(3 · 30 ml), dried with magnesium sulphate and filtered.
This solution was concentrated under vacuum and layered
with methanol. Slow mixing of the solvents yielded crystals
(0.98 g, 89%). 1H NMR (CDCl3) d 7.71–7.38 (m, 20H, Ph),
5.5 (m, 1H, CH), 5.03 (d, J = 10.5, 1H, CH2), 4.73 (d,
J = 17.5, 1H, CH2), 2.19 (m, 2H, CH2); 31P NMR (CDCl3)
d 1.1 (s, JW–P = 102.4); IR m(CO) (CH2Cl2) 2015s, 1897s,
1905s, 1878s cmꢀ1
.
Synthesis of [Mo(CO)4{Ph2PCH(Pr)PPh2}] (4). To 1
(0.41 g, 0.69 mmol) in thf (30 ml) was added n-BuLi
(0.55 ml, 1.40 mmol) resulting in a colour change from
light yellow to dark brown-orange. This was stirred for
30 min and PrI (2.65 ml, 0.26 mmol) was added. The mix-
ture was left to stir overnight forming a dark brown solu-
tion. Removal of volatiles gave an oily solid that was
dissolved in dichloromethane (30 ml), washed with water
(3 · 40 ml) and dried with magnesium sulphate. Removal
of volatiles gave a yellow-brown solid which was dissolved
in the minimum amount of dichloromethane and layered
with methanol to give crystals (0.31 g, 72%). 1H NMR
(CDCl3) d 7.53–7.25 (m, 20H, Ph), 4.60 (tt, J = 10.8, 6.8,
1H, CH), 1.45 (m, 2H, CH2), 1.20 (sextet, J = 7.9, 2H,
CH2), 0.61 (t, J = 7.3, 3H, Me); 31P NMR (CDCl3) d
1878s cmꢀ1
.
Synthesis of [Mo(CO)4{Ph2PC(Me)2PPh2}] (10)
[68]. [Mo(CO)4(NHC5H10)2] (1.048 g, 2.72 mmol) and
Ph2PC(Me)2PPh2 (1.165 g, 2.82 mmol) were refluxed in
dichloromethane (40 ml) for 1 h. The solution was then
allowed to cool before being filtered. It was then concen-
trated on a rotary evaporator before adding methanol
and placing the mixture in a freezer overnight to obtain
10 as yellow crystals (0.25 g, 16%). Alternatively, to 2
(0.26 g, 0.43 mmol) in thf (20 ml) was added MeLi
(1.35 ml, 2.17 mmol) causing the solution to turn from yel-
low to dark red-orange. This was stirred for 1 h before add-
ing MeI (0.13 ml, 2.17 mmol) which caused an immediate
colour change to brown-orange. After stirring overnight,
volatiles were removed under vacuum to leave a dark
brown-orange solid. This was dissolved in dichloromethane
(20 ml) and washed with water (3 · 30 ml). The dichloro-
methane solution was then over magnesium sulphate and
filtered. The solution was then concentrated on a rotary
evaporator before adding methanol and placing the mix-
ture in the freezer to obtain crystals (0.24 g, 89%). 1H
NMR (CDCl3) d 7.62–7.37 (m, 20H, 4Ph), 1.46 (t,
J = 13.2, 6H, Me); 31P NMR (CDCl3) d 44.5 (s); IR
25.1 (s); IR m(CO) (CH2Cl2) 2019s, 1906s, 1881s cmꢀ1
.
Anal. Calc. for 4: C, 60.57, H, 4.45. Found: C, 59.16, H,
4.37%.
Synthesis of [Mo(CO)4{Ph2PCH(Bu)PPh2}] (5). To 1
(0.41 g, 0.69 mmol) in thf (40 ml) was added n-BuLi
(0.55 ml, 1.40 mmol). This was stirred for 30 min and then
BuI (0.30 ml, 2.68 mmol) was added and the solution was
allowed to stir overnight turning dark brown. Removal
of volatiles gave a solid which was dissolved in dichloro-
methane (40 ml) and washed with water (3 · 30 ml). The
dichloromethane portion was dried with magnesium sul-
phate and pumped down. Crystals were obtained by dis-
solving the washed and pumped down solid in the
minimum amount of dichloromethane and adding a little
methanol (0.33 g, 73%). 1H NMR (CDCl3) d 7.52–7.36
(m, 20H, Ph), 4.60 (m, 1H, CH), 1.45 (m, 2H, CH2), 1.12
(quintet, J = 7.3, 2H, CH2), 0.97 (sextet, J = 7.3, 2H,
CH2), 0.59 (t, J = 7.3, 3H, Me); 31P NMR (CDCl3) d
25.1 (s); IR m(CO) (CH2Cl2) 2018s, 1906s, 1881s cmꢀ1
.
Anal. Calc. for 5: C, 61.12, H, 4.66. Found: C, 60.58, H,
4.76%. Mass spectrum (FAB): m/z 650 (M+), 592
(M+ꢀ2CO), 538, (M+ꢀ4CO).
m(CO) (CH2Cl2) 2019s, 1905s, 1881s cmꢀ1
.
Synthesis of [Mo(CO)4{Ph2PCMe(Et)PPh2}] (11).
To 3 (0.142 g, 0.2341 mmol) in thf (50 ml) was added MeLi
(0.73 ml, 1.171 mmol) in diethyl ether. This caused the
Synthesis of [Mo(CO)4{Ph2PCH(allyl)PPh2}] (6). To
1 (0.23 g, 0.39 mmol) in thf (50 ml) was added n-BuLi

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
5667
solution to turn yellow-orange. After stirring for 1 h, EtI
(0.093 ml, 1.171 mol) was added via syringe. There was lit-
tle colour change upon its addition. The reaction mixture
was allowed to stir for 3 days before removal of volatiles
which gave a viscous yellow-orange oil. This was dissolved
in dichloromethane (50 ml), washed with water (3 · 40 ml),
dried over magnesium sulphate and filtered to give a clear
yellow solution. This was concentrated on a rotary evapo-
rator and the resulting solution was layered with methanol
to yield 11 as yellow crystals (0.137 g, 92%). 1H NMR
(CDCl3) d 7.77–7.32 (m, 20H), 2.30 (m, 2H, Et), 1.15 (t,
J = 16.3, 3H, Me), 0.94 (t, J = 7.4, 3H, Me); 31P NMR
(CDCl3) d 48.5 (s); IR m(CO) (CH2Cl2) 2018s, 1903s,
1880s cmꢀ1. Anal. Calc. for 11: C, 60.60, H, 4.45. Found:
C, 60.02, H, 4.46%.
an oily solid. This was dissolved in dichloromethane
(20 ml) and washed with water (3 · 30 ml). The dichloro-
methane portion was then dried over magnesium sulphate,
filtered and concentrated on a rotary evaporator. This solu-
tion was layered with methanol and the two solutions were
1
allowed to mix slowly, yielding crystals (0.34 g, 82%). H
NMR (CDCl3) d 7.78–7.30 (m, 20H, Ph), 5.64 (m, 1H,
CH), 5.08 (d, J = 9.7, 1H, CH2), 4.79 (d, J = 17.7, 1H,
CH2), 3.01 (m, 2H, CH2), 1.18 (t, J = 16.0, 3H, Me); 31P
NMR (CDCl3) d 49.3 (s); IR m(CO) (CH2Cl2) 2019s,
1905s, 1881s cmꢀ1. Anal. Calc. for 14: C, 61.31, H, 4.37.
Found: C, 60.68, H, 4.35%.
Synthesis of [Mo(CO)4{Ph2PC(allyl)2PPh2}] (15). To
6 (0.25 g, 0.39 mmol) in thf (20 ml) was added t-BuLi
(0.23 ml, 0.39 mmol) to give an orange solution. This was
stirred for 1 min and then allyl iodide (0.10 ml, 1.18 mmol)
was added. The solution turned yellow and was stirred for
15 min. After removal of volatiles, NMR analysis revealed
a poor conversion to the desired product. Hence, the oily
solid was redissolved in dry thf, and t-BuLi (0.93 ml,
1.57 mmol) and allyl iodide (0.22 ml, 2.37 mmol) were
again added. This procedure was carried out a further five
times. At this stage removal of volatiles gave a viscous oil
which was dissolved in dichloromethane (20 ml), washed
with water (3 · 30 ml) and dried with magnesium sulphate.
After filtration this gave a dry solid which was washed with
a hexane (5 ml). This was redissolved in the minimum
amount of dichloromethane and layered with methanol
to give a yellow crystalline solid. 31P NMR showed this
Synthesis of [Mo(CO)4{Ph2PCMe(Pr)PPh2}] (12).
To 4 (0.31 g, 0.487 mmol) in thf (50 ml) was added MeLi
(1.5 ml, 2.443 mmol) the solution turning dark brown. This
was stirred for 1 h followed by addition of MeI (0.18 ml,
2.931 mmol). This caused the solution to turn dark
brown-orange. After 3 days the solution was evaporated
to give a viscous brown oil. This was dissolved in dichloro-
methane (50 ml), washed with water (3 · 40 ml) and the
dichloromethane portion was dried over magnesium sul-
phate. After filtration and concentration under vacuum it
was layered with methanol. As the solvents slowly mixed,
1
crystals were obtained (0.25 g, 80%). H NMR (CDCl3) d
7.54–7.33 (m, 20H, Ph), 2.16 (m, 2H, CH2), 1.35 (m, 2H,
CH2), 0.86 (t, J = 7.2, 3H, Me), 1.18 (t, J = 16.4, 3H,
Me);31P NMR (CDCl3) d 48.9 (s); IR m(CO) (CH2Cl2)
2018s, 1903s, 1880s cmꢀ1. Anal. Calc. for 12: C, 58.21,
H, 4.49. Found: C, 57.82, H, 5.02.
1
to be a mixture of 6 and 15 (ca. 1:2). H NMR (CDCl3)
d 7.78–7.42 (m, 20H, Ph), 5.23 (qt, J = 10.0, 6.9, 2H,
CH), 4.71 (dd, J = 10.6, 1.1, 2H, @CH2), 4.42 (dd,
J = 17.0, 1.4, 2H, @CH2), 2.97 (dt, J = 12.4, J = 6.7, 4H,
CH2);31P NMR (CDCl3) d 49.8 (s); IR m(CO) (CH2Cl2)
Synthesis of [Mo(CO)4{Ph2PCMe(Bu)PPh2}] (13).
To 5 (0.33 g, 0.588 mmol) in thf (50 ml) was added MeLi
in diethyl ether (1.59 ml, 2.54 mmol) causing the reaction
mixture to turn dark brown. After 1 h, MeI (0.21 ml,
3.52 mmol) was added, the reaction mixture turning dark
brown-orange. This was stirred for 3 days and volatiles
removed to give a sticky dark brown-orange oil. This was
dissolved in dichloromethane (50 ml) and washed with
water (3 · 40 ml). The dichloromethane portion was dried
over magnesium sulphate and filtered. Crystals were
obtained upon layering a concentrated dichloromethane
solution with methanol and allowing the two layers to
mix very slowly. Further crystals were obtained upon slow
evaporation of the solvent (0.23 g, 68%). 1H NMR (CDCl3)
d 7.55–7.32 (m, 20H, Ph), 1.45 (t, J = 13.3, 2H, CH2), 1.25–
1.08 (m, 2H, CH2), 0.75 (t, J = 7.2, 3H, Me), 0.58 (t,
J = 3H, Me); 31P NMR (CDCl3) d 48.9 (s); IR m(CO)
(CH2Cl2) 2018s, 1903s, 1880s cmꢀ1. Anal. Calc. for 13:
C, 61.38, H, 4.87. Found: C, 60.48, H, 4.86%.
2019s, 1904s, 1888s cmꢀ1
.
Synthesis of [W(CO)4{Ph2PC(Me2)PPh2}] (16) [68].
To 7 (0.20 g, 0.32 mmol) in thf (35 ml) was added MeLi
(0.99 ml, 1.6 mmol) giving rise to a colour change from
yellow to bright yellow. This was allowed to stir for
15 min before adding MeI (0.12 ml, 1.9 mmol). Heat
was evolved upon the addition of MeI and the solution
turned orange. The reaction mixture was then left to stir
for 2 h. The solvent was then removed under vacuum
leaving a dry solid. Analysis of the solid by 31P NMR
spectroscopy showed that only a moderate conversion
to 16 so the solid was redissolved in dry thf and the pro-
cedure repeated. The reaction mixture was then pumped
down to a solid and dissolved in dichloromethane (ca.
20 ml). This solution was washed with aliquots of water
(3 · 30 ml) and dried with anhydrous magnesium sul-
phate. The solution was filtered and concentrated on a
rotary evaporator. Crystals were yielded by layering the
dichloromethane solution with methanol and then leav-
ing the mixture to allow the two solvents to mix slowly
Synthesis of [Mo(CO)4{Ph2PCMe(allyl)PPh2}] (14).
To 6 (0.41 g, 0.64 mmol) in thf (20 ml) was added MeLi
(0.11 ml, 1.8 mmol) causing it to turn bright orange. This
was stirred for 30 min and MeI (0.11 ml, 1.8 mmol) added
causing the solution to turn orange-yellow. The mixture
was stirred overnight and volatiles were removed to give
1
(0.20 g, 94%). H NMR (CDCl3) d: 7.63–7.37 (m, 20H,
Ph), 1.45 (t, J = 13.6, 6H, Me); 31P NMR (CDCl3) d
21.2 (s, JP–W = 103.9).

5668
G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
Synthesis of [Mo(CO)4(dcpm)] (17). dcpm (0.170 g,
Me);31P NMR (CDCl3) d 36.6 (s); IR m(CO) (CH2Cl2)
2007s, 1887s, 1867s cmꢀ1. Anal. Calc. for 20: C, 57.76, H,
7.82. Found: C, 56.51, H, 7.64%. Mass spectrum (FAB):
m/z 646 (M+), 618 (M+ꢀCO).
0.41 mmol) and cis-[Mo(CO)4(NHC5H10)2] (0.158 g,
0.41 mmol) were refluxed in dichloromethane (10 ml) for
212 h. The solution was cooled to room temperature before
being filtered. Methanol (15 ml) was added and the mixture
was placed in the freezer overnight yielding pale yellow
crystals (0.15 g, 55%). 1H NMR (CDCl3) d 2.87 (t,
J = 8.0, 2H, CH2), 1.91–1.25 (m, 44H, Cy); 31P NMR
(CDCl3) d 13.2 (s); IR m(CO) (CH2Cl2) 2008s, 1891s,
1866s cmꢀ1. Anal. Calc. for 17: C, 56.49, H, 7.52. Found:
C, 54.34, P, 9.95%. Mass spectrum (FAB): m/z 616
(MH+), 530 (M+ꢀ2CO).
Synthesis of [Mo(CO)4{Cy2PCH(allyl)PCy2}] (21).
To 17 (0.19 g, 0.3 mmol) in thf (20 ml) was added n-
BuLi (0.49 ml, 1.2 mmol) causing the solution to turn
dark yellow. This was stirred for 1 min and allyl iodide
(0.17 ml, 1.8 mmol) added, turning the mixture dark
red. This was stirred for 15 min and volatiles were
removed to give a dark solid. A31P NMR spectrum
revealed that there had not been full conversion so
the solid was redissolved in thf and the procedure
was repeated. After this, removal of volatiles gave an
oily solid which was dissolved in dichloromethane
(20 ml) and washed with water (3 · 30 ml). The dichlo-
romethane solution was then dried over magnesium sul-
phate, filtered and volatiles removed to give a dry
solid. Crystals were obtained by dissolving the solid
in the minimum amount of dichloromethane and then
layering the solution with methanol (0.19 g, 92%). 1H
NMR (CDCl3)d: 5.71 (m, 1H, CH), 5.06 (t, J = 5.00,
J = 11.0, 2H, CH2), 3.47 (m, 1H, CH), 2.53 (quin,
J = 8.09, 2H, CH2), 2.15–0.85 (m, 44H, Cy); 31P
NMR (CDCl3) d 37.1 (s); IR m(CO) (CH2Cl2) 2008s,
1889s, 1868s cmꢀ1. Anal. Calc. for 21: C, 58.53, H,
7.67. Found: C, 58.91, H, 8.25%.
Synthesis of [W(CO)4(dcpm)] (18). dcpm (0.175 g,
0.43 mmol)
and
cis-[W(CO)4(NHC5H10)]
(0.202 g,
0.43 mmol) were refluxed in dichloromethane (10 ml) for
412 h. After cooling, the reaction mixture was filtered and
methanol (20 ml) was added. The dark orange solution
was then put in the freezer. The crystals that formed were
removed and the solution was concentrated on a rotary
evaporator before being returned to the freezer to obtain
1
a second batch (0.267 g, 90%). H NMR (CDCl3) d 3.26
(t, J = 8.33, 2H, CH2), 1.92–1.26 (m, 44H, Cy); 31P
NMR (CDCl3) d ꢀ10.6 (s, JP–W = 96.7); IR m(CO)
(CH2Cl2) 2004s, 1880s, 1860s cmꢀ1. Anal. Calc. for 18:
C, 49.44, H, 6.58, P, 8.79. Found: C, 48.94, H, 6.62, P,
8.94%. Mass spectrum (FAB): m/z 704 (M+), 616
(M+ꢀ3CO), 409 (LH+).
Synthesis of [Mo(CO)4{Cy2PCH(Me)PCy2}] (19).
To 17 (0.180 g, 0.29 mmol) in thf (25 ml) was added n-BuLi
(0.18 ml, 0.29 mmol) and this was stirred for 1 h. MeI
(0.07 ml, 1.15 mmol) was then added to the dark yellow reac-
tion mixture causing it to turn dark orange. After stirring
overnight, volatiles were removed down to give an orange
solid. This solid was dissolved in dichloromethane (20 ml),
washed with water (3 · 30 ml), dried over magnesium sul-
phate and concentrated on a rotary evaporator. Methanol
was then added and the mixture placed in a freezer overnight,
yielding small orange crystals (0.164 g, 82%). These were iso-
lated and washed with petrol before drying under vacuum.
1H NMR (CDCl3) d 3.52 (m, 1H, CH), 2.17–1.27 (m, 47H,
Cy and Me); 31P NMR (CDCl3) d 32.7 (s); IR m(CO)
(CH2Cl2) 2006s, 1886s, 1866s cmꢀ1. Anal. Calc. for 19: C,
57.01, H, 7.67. Found: C, 55.15, H, 7.54%.
X-ray data collection and solution. Single crystals were
mounted on glass fibres and all geometric and intensity data
were taken from these samples using a Bruker SMART
APEX CCD diffractometer using graphite-monochromated
˚
Mo Ka radiation (k = 0.71073 A) at 150 2 K. Data reduc-
tion was carried out with SAINT+ [83] and absorption correc-
tion applied using the program SADABS [84]. Structures were
generally solved by direct methods [85] and developed [86]
using alternating cycles of least-squares refinement and dif-
ference-Fourier synthesis. All non-hydrogen atoms were
refined anisotropically except for the two disordered mole-
cules of methanol in 19 which were refined only isotropically.
In 20 the methyl carbon of the backbone, C(6), was disor-
dered over two sites (50:50). Hydrogens were generally
placed in calculated positions (riding model) but in 19 the
hydrogen atoms were not located or fixed on the methanol
molecules, while hydrogen atoms were also omitted from
the ethyl group in 20. Structure solution used SHELXTL-PLUS
V6.10 program package [87]. Full structural details are sum-
marized in Table 2.
Synthesis of [Mo(CO)4{Cy2PCH(Et)PCy2}] (20). To
17 (0.151 g, 0.244 mmol) in thf (50 ml) was added n-BuLi
(0.2 ml, 0.32 mmol) turning the solution dark yellow. EtI
(0.078 ml, 0.976 mmol) was added to give a dark orange-
brown solution which was stirred overnight. Removal of vol-
atiles gave an oily brown solid which was dissolved in dichlo-
romethane (50 ml) and washed with water (3 · 25 ml). The
dichloromethane portion was dried over magnesium sul-
phate, filtered and pumped down. Crystals were obtained
by redissolving the solid in the minimum amount of dichlo-
romethane and layering this with methanol (0.075 g, 48%).
After mixing, slow evaporation yielded crystals suitable for
Acknowledgements
We thank Dr. Derek A. Tocher for crystallographic
advice.
Appendix A. Supplementary material
1
X-ray diffraction. H NMR (CDCl3) d 3.18 (m, 1H, CH),
CCDC 658767, 658768, 658769, 658770, 658771,
658772, 658773, 658774 and 658775 contain the supple-
1.89–1.25 (m, 46H, CH2 and Cy), 0.98 (t, J = 7.4, 3H,

G. Hogarth, J. Kilmartin / Journal of Organometallic Chemistry 692 (2007) 5655–5670
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