Reversible π-coordination of triallylphosphine in a trinuclear ruthenium carbonyl cluster

Article abstract of DOI:10.1016/j.inoche.2003.12.032

The triallylphosphine-substituted clusters [Ru₃(CO) ₁₁{P(CH₂CH=CH₂)₃}], [Ru ₃(CO)₁₀{P(CH₂CH=CH₂) ₃}₂] and [Ru₃(CO)₁₀{σ;π- CH₂=CHCH₂P(CH₂CH=CH₂)₂}] have been prepared; reaction of [Ru₃(CO)₁₀{σ;π- CH₂=CHCH₂P(CH₂CH=CH₂)₂}] with phosphines/phosphites leads to cleavage of the Ru-allyl π-bond and formation of [Ru₃(CO)₁₁{P(CH₂CH=CH ₂)₃}(PR₃)].

Full text of DOI:10.1016/j.inoche.2003.12.032

Inorganic Chemistry Communications 7 (2004) 443–446
www.elsevier.com/locate/inoche
Reversible p-coordination of triallylphosphine
in a trinuclear ruthenium carbonyl cluster q
a
Anders Thapper , Emma Sparr , Brian F.G. Johnson , Jack Lewis ,
b
c
c
d
Paul R. Raithby , Ebbe Nordlander
a,
*
a
Inorganic Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden
Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden
b
c
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
d
Department of Chemistry, University of Bath, Bath BA2 7AY, UK
Received 27 December 2003; accepted 31 December 2003
Published online: 4 February 2004
Abstract
The triallylphosphine-substituted clusters [Ru3(CO)11{P(CH2CH@CH2)3}], [Ru3(CO)10{P(CH2CH@CH2)3}2] and [Ru3(CO)10
{r;p-CH2@CHCH2P(CH2CH@CH2)2}] have been prepared; reaction of [Ru3(CO)10{r;p-CH2@CHCH2P(CH2CH@CH2)2}] with
phosphines/phosphites leads to cleavage of the Ru–allyl p-bond and formation of [Ru3(CO)11{P(CH2CH@CH2)3}(PR3)].
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Cluster; Hemilabile ligand; Allylphosphine
The use of lightly stabilizing ligands, e.g. acetonitrile
[1] or cyclooctene [2], is well established in transition
metal carbonyl cluster chemistry. Reversal of the coor-
dination of polydentate ligands or ligand moieties is
another useful method to generate potential coordina-
tion sites in polynuclear metal complexes [3]. An ex-
ample of the latter phenomenon that involves a
transition metal carbonyl cluster is [Ru3(l-H)(CO)9(l-
PPh2)] [4] which is formally unsaturated but where the
vacant coordination site is proposed to be lightly sta-
bilized by a weak Ru–P–C interaction. Although it is
unclear whether this interaction remains in solution, the
cluster is reactive and adds phosphorus nucleophiles to
form the electron–precise cluster [Ru3(l-H)(CO)9(l-
PPh2)] [4]. Intramolecular stabilization of labilised spe-
cies by polydentate and hemilabile ligands has the added
advantage that it may be feasible to ‘‘mask’’ several
coordination sites and/or labilise a metal complex in
repeated steps [5]. We are investigating the systematic
preparation of labilised clusters using potentially
polydentate/hemilabile phosphorus ligands and have
previously attempted to use vinyldiphenylphosphine [6]
for this purpose. Here, we wish to describe the prepa-
ration of the stable, yet chemically reactive cluster
[Ru3(CO)10{r;p-CH2@CHCH2P(CH2CH@CH2)2}] – in
which the ligand triallylphosphine is coordinated via the
phosphorus atom as well as one p-coordinated allyl
moiety – and the facile cleavage of the Ru–allyl p-bond
of this cluster through addition of suitable nucleophiles.
Reaction of [Ru3(CO)12] with an excess of triallyl-
phosphine in dichloromethane in the presence of Na/
Ph2CO [7] leads to formation of the clusters
[Ru3(CO)12 ꢀ n{P(CH2CH@CH2)3}n] [n ¼ 1 (1), 2 (2)]
which have been characterized by IR and NMR
q Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.inoche.2003.12.032.
* Corresponding author. Tel.: +46-46-222-8118; fax: +46-46-222-
4439.
E-mail address: Ebbe.Nordlander@inorg.lu.se (E. Nordlander).
1387-7003/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2003.12.032

444
A. Thapper et al. / Inorganic Chemistry Communications 7 (2004) 443–446
"
"
- CO
Ru
Ru
Ru
P
Ru
P
1
Ru
Ru
Ru
Ru
+ PR3
Ru
P
P(CH2CH=CH2)3
R3P
Ru
Ru
Ru
3
Scheme 1. A schematic outline of the mechanisms of coordination and decoordination of one of the allyl moieties of the triallylphosphine ligand in
[Ru3(CO)11{P(CH2CH@CH2)3}] (1)/[Ru3(CO)10{r;p-CH2@CHCH2P(CH2CH@CH2)2}] (3).
spectroscopy, mass spectrometry and elemental analy-
1
sis. A third, dark red compound, whose IR spectrum
There is no evidence for coordination of the phos-
phine allyl moieties in the above-mentioned clusters but
reaction of 1 with one equivalent of trimethylamine N-
oxide results in the formation of the dark orange-red
compound [Ru3(CO)10{r;p-CH2@CHCH2P(CH2CH@
indicates that it is [Ru3(CO)9{P(CH2CH@CH2)3}3] [8],
is also formed but this cluster has not yet been fully
characterised. The IR spectra of 1 and 2 resemble those
reported for similar Ru3–phosphine complexes [9,10]
and suggest that the phosphorus ligands are equatorially
coordinated in both 1 and 2.
1
CH2)2}] (3) in relatively good yield (65%). A possible
mechanism for the formation of 3 is the initial decarb-
onylation of 1 by Me3NO to form ‘‘[Ru3(CO)10
{P(CH2CH@CH2)3}]’’ followed by coordination of an
allyl group of the phosphine (Scheme 1). Coordination
of an allyl moiety is evident from the 1H NMR spectrum
of 3 (Fig. 1) which is relatively complicated in compar-
ison to that of 1 and 2 as all protons of the three allyl
groups are chemically and magnetically inequivalent in
3. There are thus fifteen resonances, as shown in Fig. 1;
the individual resonances have been assigned on the
1
Spectroscopic and analytical data for new complexes
[Ru3(CO)11{P(CH2CH@CH2)3}] (1): IR mC–O/cmꢀ1 (CH2Cl2) 2096 m,
2043 (s), 2025 (s, sh), 2013 (vs) MS (FABþ): m=z 765 (calc. 765) 1H
NMR (CDCl3): d ¼ 5:79 (m, Hb, {P(CH2CH@CH2)3}), 5.38 (dd,
4
3JHc–Hb ꢁ 10.4, JP–Hc ꢁ 3.5, Hc, {P(CH2CH@CH2)3}, cis to Hb), 5.26
3
4
(dd, JHd–Hb ꢁ 16, JP–Hd ꢁ 2.4, Hd, {P(CH2CH@CH2)3}, trans to Hb),
2
2
2.70 (ÔtÕ (dd), JP–Ha ꢁ JHb–Ha ꢁ 10, Ha, {P(CH2CH@CH2)3}) 31P
NMR (CDCl3, P(OMe)3: d ¼ 0, downfield positive: )127.7 (s,
{P(CH2CH@CH2)3}) anal. C20H15O11PRu3: Calc. C 32.10, H 2.63, P
4.30; found C 31.37, H 1.96, P 4.05%.
1
basis of a H–1H COSY experiment. As has been ob-
served for related ligands, e.g. vinyldiphenylphosphine
[11], the resonances attributable to the coordinated allyl
moiety are shifted upfield by 2–3 ppm. We note that the
related complex [(l-H)Os3(l-OCNMe2)(CO)9(PPh2CH2
CH@CH2)] does not undergo any transformation (e.g.
isomerization, chelation of the allylphosphine ligand)
when heated in solution [12], but it is possible to prepare
the osmium analogue of 3 by a synthetic method similar
to that described above [13].
[Ru3(CO)10{P(CH2CH@CH2)3}2] (2): IR mC–O/cmꢀ1 (CH2Cl2): 2070
(mw), 2016 (s), 1993 (vs, br) 1H NMR (CDCl3): d ¼ 5:86 (m, Hb,
3
4
{P(CH2CH@CH2)3}), 5.28 (dd, JHc–Hb ꢁ 9.6, JP–Hc ꢁ not resolved,
3
Hc, {P(CH2CH@CH2)3}, cis to Hb), 5.22 (dd, JHd–Hb ꢁ 17,
4JP–Hd ꢁ not resolved, Hd, {P(CH2CH@CH2)3}, trans to Hb), 2.69 (ÔtÕ
2
(dd),
C
2JP–Ha ꢁ JHb–Ha ꢁ 8,
Ha,
28H30O10P2Ru3: Calc. C 37.7, H 3.42, P 6.9; found. C 37.8, H 4.22, P
{P(CH2CH@CH2)3})
anal.
6.2%.
[Ru3(CO)10{r;p-CH2@CHCH2P(CH2CH@CH2)2}] (3): IR: mC–O
/
X-ray crystallography confirms the proposed struc-
2
ture of 3. The molecular structure of this cluster is
cmꢀ1 (CH2Cl2): 2087 (ms), 2025 (s, sh), 2016 (vs), 2003 (vs), 1958 (m)
1H NMR (CDCl3): d ¼ 6:62 (m, Ha), 5.81 (m, Hb), 5.71 (m, Hc), 5.44
(dd, Hd), 5.36 (dd, He), 5.35 (dd, Hf ), 5.27 (dd, Hg), 3.00 (m, Hh), 2.93
(ddd, Hi), 2.91 (m, Hj), 2.78 (m, Hk), 2.60 (m, Hl), 2.44 (m, Hm), 2.20
(ddd, Hn), 1.71 (m, Ho) (see text and Fig. 2) 31P NMR (CDCl3,
P(OMe)3: d ¼ 0, downfield positive: )142.3 (s, {P(CH2CH@CH2)3})
MS (FABþ, m=z): 737 (Mþ ¼ 737, based on Ru ¼ 101) C19H15O10PRu3:
2
Crystal data: C20H15O11PRu3, M ¼ 765:50, monoclinic, space
ꢀ
ꢀ
ꢀ
Calc. C 30.9, H 2.0, P 4.2; found C 40.0, H 2.1, P 4.5 [Ru3(CO)10
-
group P21=n, a ¼ 8:429ð2Þ A; b ¼ 26:106ð5Þ A, c ¼ 11:597ð2Þ A,
{P(CH2CH@CH2)3}(PPh3)] IR: mC–O/cmꢀ1 (CH2Cl2): 2058 (m), 2040
(mw), 2020 (mw), 1967 (vs), 1950 (s, sh) 1H NMR (CDCl3):
d ¼ 7:49–7:32 (m, P(C6H5)3) 5.79 (m, Hb, {P(CH2CH@CH2)3}), 5.17
b ¼ 104:48ð3Þ°, U ¼ 2470:8ð9Þ A , Z ¼ 4, Dc ¼ 2:058 Mg/m3,
3
ꢀ
F ð000Þ ¼ 1480, l ¼ 1:931 mmꢀ1, Mo Ka radiation (k ¼ 0:71069 A),
ꢀ
1:56 < h < 27:56°, T ¼ 290ð2Þ K, 3885 reflections (I P 2rðIÞ) used in
structure solution (SHELXS-86 [15] SHELXL-93 [16]), R (on F 2)
0.0487, wR2 (on F 2) 0.1309.
3
4
(dd, JHc–Hb ꢁ 9, JP–Hc ꢁ not resolved, Hc, {P(CH2CH@CH2)3}, cis to
3
4
Hb), 5.12 (dd, JHd–Hb ꢁ 17, JP–Hd ꢁ 3.7, Hd, {P(CH2CH@CH2)3}).

A. Thapper et al. / Inorganic Chemistry Communications 7 (2004) 443–446
445
Fig. 1. The 1H NMR spectrum (CD2Cl2, 400 MHz) of [Ru3(CO)10{r;p-CH2@CHCH2P(CH2CH@CH2)2}] (3).
shown in Fig. 2. The Ru(1)–Ru(2) and Ru(2)–Ru(3)
symmetrical fashion, with the distances Ru(1)–
ꢀ
bonds [2.8687(10) A and 2.8556(10) A] are slightly
ꢀ
ꢀ
ꢀ
C(012) ¼ 2.286(7) A and Ru(1)–C(013) ¼ 2.244(8) A.
These distances are similar to those observed in the
related cluster [Rh6(CO)14(r;p-PPh2(CH2CH@CH2)]
ꢀ
longer than the Ru(1)–Ru(3) bond [2.8472(10) A].
This may be explained by the fact that the latter bond
is bridged by the triallylphosphine moiety. The
bridging allyl group is p-bonded in an approximately
ꢀ
[Rh–C ¼ 2.32(2) and 2.366(14) A] [14]. The alkene
bond in 3 is significantly longer [C(012)–C(013) ¼
ꢀ
1.391(11) A] than the corresponding bonds in the
ꢀ
uncoordinated allyl moieties (1.13 and 1.11 A). This
indicates that the bond order in the p-coordinated
bond is reduced upon coordination to the metal, as
may be expected.
Reaction of 3 with nucleophiles, such as P(OMe)3 or
PPh3, under mild conditions (CH2Cl2, room tempera-
ture) leads to the reversal/cleavage of the allyl p-coordi-
nation and formation of the clusters [Ru3(CO)10
{P(CH2CH@CH2)3}(PR3)] (R ¼ OMe, Ph), demonstrat-
ing that triallylphosphine may indeed act as a hemilabile
ligand in polynuclear complexes. In the presence of ex-
cess phosphine, direct substitution of carbonyl ligands to
form [Ru3(CO)9{P(CH2CH@ CH2)3} (PR3)2] as a minor
product is also observed. The fact that the allyl p-bond
has been broken is evident from the 1H NMR spectra of
the products which show only the expected four reso-
nances attributable to terminally (P-) coordinated trial-
Fig. 2. An ORTEP drawing of the molecular structure of [Ru3(CO)10
{r;p-CH2@CHCH2P(CH2CH@CH2)2}] (3) showing the atom label-
ling scheme. Thermal ellipsoids are drawn at the 30% probability level.
1
lylphosphine. As of yet, we have not determined
ꢀ
Selected bond distances (A) and bond angles (°): Ru(1)–Ru(2)
whether the addition of nucleophiles to 3 is an associative
or dissociative process, but a kinetic investigation of the
reactivity of its osmium analogue indicates that this type
of reaction is associative. The reaction of 3 with carbon
monoxide is currently being investigated.
2.8687(10), Ru(1)–Ru(3) 2.8472(10), Ru(2)–Ru(3) 2.8556(10), Ru(3)–P
2.324(2), P–C(011) 1.860(8), C(012)–C(011) 1.504(11), C(012)–C(013)
1.391(11), Ru(1)–Ru(2)–Ru(3)1 59.66(3), Ru(1)–Ru(3)–Ru(2) 60.40(3),
Ru(2)–Ru(1)–Ru(3) 59.94(2), Ru(3)–P–C(011) 111.2(2), P–C(011)–
C(012) 111.2(5), C(011)–C(012)–C(013) 121.8(8).

446
A. Thapper et al. / Inorganic Chemistry Communications 7 (2004) 443–446
[8] M.I. Bruce, M.J. Lidell, O. bin Shawkataly, C.A. Hughes, B.W.
Acknowledgements
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