Effect of peripheral donor substituents on the binding modes of phosphinomethanide ligands. Synthesis and crystal structures of alkali metal derivatives of an O-functionalised phosphinomethanide ligand

Article abstract of DOI:10.1039/b502416a

The O-functionalised tertiary phosphine {(Me₃Si) ₂CH}P(C₆H₄-2-CH₂OMe)₂ (9) is accessible via the reaction of {(Me₃Si)₂CH}PCl ₂ with two equivalents of in si

Full text of DOI:10.1039/b502416a

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F U L L P A P E R
Effect of peripheral donor substituents on the binding modes of
phosphinomethanide ligands. Synthesis and crystal structures of
alkali metal derivatives of an O-functionalised phosphinomethanide
ligand
Keith Izod,* Jonathan Young, William Clegg and Ross W. Harrington
Department of Chemistry, School of Natural Sciences, Bedson Building, University of
Newcastle, Newcastle upon Tyne, UK NE1 7RU. E-mail: k.j.izod@ncl.ac.uk
Received 2nd February 2005, Accepted 17th March 2005
First published as an Advance Article on the web 4th April 2005
The O-functionalised tertiary phosphine {(Me3Si)2CH}P(C6H4-2-CH2OMe)2 (9) is accessible via the reaction of
{(Me3Si)2CH}PCl2 with two equivalents of in situ generated 2-LiC6H4CH2OMe. Phosphine 9 is readily deprotonated
by BunLi to give the lithium phosphinomethanide [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Li] (13), which undergoes
metathesis reactions with the alkoxides MOR [M = Na, K, R = But; M = Rb, R = 2-ethylhexyl] to give the heavier
alkali metal phosphinomethanides [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]M]n in good yields [M = Na (14), n = 2; M =
K (15), Rb (16), n = ∞]. Compounds 9, [{(Me3Si)2CH}P(C6H4-2-CH2OMe)2LiBr]2 (10), and 14–16 have been
studied by X-ray crystallography; in the solid state 14 adopts a dimeric structure, whereas 15 and 16 crystallise as
one-dimensional polymers.
group adjacent to phosphorus to give a tetrameric phosphi-
Introduction
nomethanide complex [LiCH2P(C6H4-2-CH2NMe2)2]4·(PhMe)3
Phosphorus-stabilised carbanions (phosphinomethanides,
(8).5 The benzyllithium species 7 isomerises slowly in toluene
[R2P–CR2]−) constitute an interesting class of ambidentate
solution to give 8; both 7 and 8 are unstable in THF, yielding the
ligands. Their ambidentate nature may be attributed to extensive
delocalisation of charge from the carbanion to the phosphorus
centre(s) and the similar electronegativities of phosphorus and
carbon, allowing the P and C atoms to compete as nucleophiles
same secondary phosphide complex [MeP{C6H4-2-CH(C6H4-2-
CH2NMe2)}Li(THF)2] via an unusual Smiles rearrangement.6
The foregoing prompted us to consider to what extent
changing the peripheral donor groups in these ligands from
for metal centres. Phosphinomethanides thus adopt a wide
nitrogen- to oxygen-donors would affect their reactivities and
variety of coordination modes in their complexes with main
structures. We herein report the synthesis and structural char-
group and transition metals, ranging from monodentate
acterisation of the new O-functionalised tertiary phosphine
2
3
C- or P-donation through to g -PC and g -PCP heteroallyl
coordination and bridging modes.1 The coordination mode
adopted is dependent on a variety of factors, including the
nature of the substituents at the P and C centres, the nature of
the metal and the presence of co-ligands. In addition, we have
recently shown that the incorporation of donor functionality at
the periphery of tertiary phosphines has a dramatic effect on
both their deprotonation behaviour and the binding modes of
the subsequent phosphinomethanide ligands.2
In this context, we have reported that the amino-
functionalised tertiary phosphine {(Me3Si)2CH}P(C6H4-2-
CH2NMe2)2 undergoes complete deprotonation on treatment
with BunLi in a matter of minutes at room temperature.2a This
is in stark contrast to {(Me3Si)2CH}PMe2, which undergoes
deprotonation with BunLi only over a period of several days
in refluxing hexane.3 The peripheral amino groups also en-
gender a novel PN2-coordination mode in the correspond-
ing phosphinomethanide derivatives, [{(Me3Si)2C}P(C6H4-2-
CH2NMe2)2M(L)n]x [M = Li (1), n = 0, x = 1; M = Na (2),
(L)n = (Et2O)0.5(DME)0.5, x = 1; M = K (3), Rb (4), n = 0, x =
∞; M = Cs (5), (L)n = (PhMe), x = ∞], enabling the synthesis
of the first complexes (2–5) containing a direct bond between a
heavier alkali metal and a formally tertiary phosphine centre.2b–d
There is a remarkable structural diversity amongst these alkali
metal complexes, which range from non-solvated monomers to
one-dimensional polymers.
{(Me3Si)2CH}P(C6H4-2-CH2OMe)2 (9) and its alkali metal
derivatives [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]M]n [M = Na,
K, Rb].
Results and discussion
Metalation of 2-bromobenzyl methyl ether with BunLi at 0 C
◦
cleanly gives the corresponding lithium salt, which reacts in situ
with half an equivalent of (Me3Si)2CHPCl2 to give the tertiary
phosphine{(Me3Si)2CH}P(C6H4-2-CH2OMe)2 (9) in good yield,
according to eqn. (1).
(Me3Si)2CHPCl2 + 2[Li(C6H4-2-CH2OMe)]
◦
Et O(0 C)
2
−−−−−−→ {(Me3Si)2CH}P(C6H4-2-CH2OMe)2(9) + 2LiCl (1)
Compound 9 is isolated as a viscous oil which slowly crystallises
on standing for several days at room temperature. In contrast to
previous reports,7 we found that, if the reaction between BunLi
and 2-bromobenzyl methyl ether was allowed to warm to room
temperature, a side reaction occurred that greatly diminished
the yield of 9. This is most likely due to the formation of butyl-
substituted benzyl ethers and LiBr; interestingly, isolation of
the expected tertiary phosphine from these reactions yielded a
novel tertiary phosphine–LiBr adduct [{(Me3Si)2CH}P(C6H4-2-
CH2OMe)2LiBr]2 (10) as a significant by-product.
1
In addition, we have demonstrated that the related tertiary
phosphine MeP(C6H4-2-CH2NMe2)2 (6) undergoes selective
deprotonation at a benzylic site on treatment with ButLi to
give the unusual dimer [MeP{C6H4-2-CH(Li)NMe2}(C6H4-2-
CH2NMe2)]2 (7),4 but that treatment of 6 with BunLi under
the same conditions results in deprotonation at the methyl
The 1H and 31P{ H} NMR spectra of 9 and 10 in CDCl3 are
essentially identical, suggesting that the LiBr fragment in 10 is
only weakly bound by the ligand; indeed, dissolution of 10 in this
solvent is accompanied by the precipitation of a small amount
of solid, which we attribute to the elimination of LiBr under
these conditions. Compounds 9 and 10 were characterised by
1 6 5 8
D a l t o n T r a n s . , 2 0 0 5 , 1 6 5 8 – 1 6 6 3
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 5
©

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benzylamine- or naphthylamine-substituted tertiary phosphines
such as P(C6H4-2-CH2NMe2)3 (11) and P(C10H6-8-NMe2)3 (12),
for which X-ray crystallography suggests significant P · · · N
contacts.8,9 For example, compound 11 crystallises in four,
structurally different, forms which have either two or three
P · · · N contacts, giving a pseudo-hexacoordinate or pseudo-
heptacoordinate phosphorus centre.9 The lack of any corre-
sponding P · · · O contact in 9 is most likely due to the weaker
donor strength of the ether O atom and the large degree of steric
hindrance about the phosphorus atom in this compound.
Compound 10 crystallises as discrete dimers with a crystallo-
graphic centre of inversion and a central Li2Br2 rhombus-shaped
core. It is to be expected that the hard lithium cations will
favour interactions with the hard oxygen donor groups over
interactions with the soft tertiary phosphine centres and, in
accord with this, there are no short contacts between the lithium
and phosphorus atoms in 10. The coordination sphere of each
lithium is comprised of two bromide ions and two oxygen atoms
from the benzyl ether substituents of an adjacent phosphine,
giving a four-coordinate, distorted tetrahedral lithium centre.
Thus, the tertiary phosphine ligands chelate the lithium atoms
via their two ether donor groups, generating 10-membered
˚
chelate rings. The Li–Br distances of 2.465(4) and 2.482(4) A
˚
and the Li–O distances of 1.940(4) and 1.963(5) A are typical
for these types of contact.
Treatment of 9 with one equivalent of BunLi in diethyl
ether yields a red solution containing the lithium phosphi-
nomethanide [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Li] (13). De-
spite repeated attempts, we were unable to obtain a sample
of 13 suitable for analysis; this compound is always isolated
as a viscous oil. However, the identity of 13 may be inferred
from the large change in 31P chemical shift from −46.6 to
−11.8 ppm on metalation of 9 with BunLi and the subsequent
successful isolation of the heavier alkali metal compounds
[[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]M]n via the in situ formation
of 13 (Scheme 1) [M = Na (14), n = 2; M = K (15), Rb (16), n =
∞]. In contrast to 1, 31P–7Li coupling was not resolved in either
Fig. 1 Molecular structures of (a) 9 and (b) 10 with 40% probability
ellipsoids and with H atoms omitted for clarity.
X-ray crystallography; the molecular structures of 9 and 10 are
shown in Fig. 1 and details of bond lengths and angles are given
in Table 1. The structure of 9 is as expected; the P atom is three-
coordinate with P–C bond lengths of 1.8480(14), 1.8529(14)
˚
and 1.8514(14) A [P–C(1), P–C(8), and P–C(16), respectively].
This contrasts with the crystal structures of several related
7
the 31P or Li NMR spectra of crude solutions of 13 in either
◦
˚
toluene or THF.2a
Table 1 Selected bond lengths (A) and angles ( ) for 9 and 10
A straightforward metathesis reaction between in situ formed
13 and the alkali metal alkoxides MOR [M = Na, K, R =
But; M = Rb, R = 2-ethylhexyl] yields the heavier alkali
metal phosphinomethanides 14–16 as orange crystalline solids,
after work-up (Scheme 1). A similar reaction between 13 and
caesium 2-ethylhexoxide yields an orange oil, which we were
9
P(1)–C(1)
P(1)–C(16)
Si(1)–C(2)
Si(1)–C(4)
Si(2)–C(5)
Si(2)–C(7)
1.8480(14) P(1)–C(8)
1.8514(14) Si(1)–C(1)
1.8619(17) Si(1)–C(3)
1.8719(18) Si(2)–C(1)
1.8699(18) Si(2)–C(6)
1.8710(17)
1.8529(14)
1.9126(15)
1.8696(17)
1.9063(15)
1.8730(17)
1
unable to crystallise, but which has H and 31P NMR spectra
consistent with the formation of a caesium phosphinomethanide
[[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Cs]. Compounds 14–16 are
soluble in ethereal and aromatic solvents but are insoluble in
light petroleum and were obtained as single crystals suitable for
X-ray crystallography from hot toluene.
C(1)–P(1)–C(8)
C(8)–P(1)–C(16)
Si(1)–C(1)–Si(2)
105.59(6)
97.17(6)
113.34(7)
C(1)–P(1)–C(16)
P(1)–C(1)–Si(1)
P(1)–C(1)–Si(2)
105.56(6)
107.53(7)
112.94(7)
10
1
1
The 31P{ H}, 13C{ H} and 1H NMR spectra of 14–16 are con-
sistent with the formation of solvent-free phosphinomethanide
Br(1)–Li(1)
P(1)–C(1)
P(1)–C(16)
Si(1)–C(2)
Si(1)–C(4)
Si(2)–C(5)
Si(2)–C(7)
O(1)–C(15)
O(2)–C(22)
O(2)–Li(1)
2.482(4)
1.854(2)
1.855(2)
1.877(3)
1.858(3)
1.867(3)
1.871(3)
1.427(3)
1.448(3)
1.963(5)
Br(1)–Li(1A)
P(1)–C(8)
2.465(4)
1.854(2)
1.906(2)
1.872(3)
1.908(2)
1.867(2)
1.433(3)
1.940(4)
1.427(3)
complexes; the 31P{ H} spectra exhibit singlets at −12.4, −6.2
1
and −17.1 ppm, respectively, whereas the 1H NMR spectra are
very broad at room temperature, consistent with the operation
of one or more dynamic processes in solution. This behaviour
parallels that of the amino-functionalised compounds 1–5 and
may be attributed to rapid, reversible M–O or M–P cleavage
and/or changes in chelate ring conformation.2b
Si(1)–C(1)
Si(1)–C(3)
Si(2)–C(1)
Si(2)–C(6)
O(1)–C(14)
O(1)–Li(1)
O(2)–C(23)
Compound 14 crystallises from toluene as solvent-free cen-
trosymmetric dimers containing an Na2O2 rhombus-shaped
core; the molecular structure of 14 is shown in Fig. 2 and details
of bond lengths and angles are given in Table 2. Each sodium
is bound by the phosphorus and the two ether oxygen atoms
of a phosphinomethanide ligand, generating two puckered six-
membered chelate rings [O–Na–P bite angles: 81.57(5) and
86.48(5)◦]. Each sodium is further coordinated by an oxygen
atom from an adjacent ligand in the dimer; thus one ether
oxygen in each ligand acts as a bridge between the two sodium
Li(1)–Br(1)–Li(1A)
C(1)–P(1)–C(16)
P(1)–C(1)–Si(1)
Si(1)–C(1)–Si(2)
Br(1)–Li(1)–O(1)
Br(1)–Li(1)–O(2)
O(1)–Li(1)–O(2)
76.12(15) C(1)–P(1)–C(8)
104.16(10) C(8)–P(1)–C(16)
107.42(11) P(1)–C(1)–Si(2)
103.51(10)
98.09(10)
114.99(11)
113.34(11) Br(1)–Li(1)–Br(1A) 103.88(15)
115.2(2)
Br(1A)–Li(1)–O(1)
113.69(19)
110.21(19)
111.37(19) Br(1A)–Li(1)–O(2)
102.7(2)
Symmetry operator (inversion): A, 2 − x, 2 − y, −z.
D a l t o n T r a n s . , 2 0 0 5 , 1 6 5 8 – 1 6 6 3
1 6 5 9

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Scheme 1 M = Na, K, R = But; M = Rb, R = 2-ethylhexyl [principal contacts only shown].
◦
˚
˚
Table 2 Selected bond lengths (A) and angles ( ) for 14
[Na · · · C(12A) 2.859(2), Na · · · C(13A) 2.945(2) A]. There is no
contact between the sodium atom and the essentially planar
carbanion centre [sum of angles at C(1) = 357.94◦].
Compounds 15 and 16 are both isostructural and isomor-
phous and crystallise from hot toluene as one-dimensional
polymers. The polymeric structure of 15 is shown in Fig. 3 and
details of bond lengths and angles for both 15 and 16 are given
in Table 3.
P(1)–Na(1)
P(1)–C(8)
2.8144(16)
1.866(2)
1.8198(18)
1.887(2)
P(1)–C(1)
1.7499(18)
1.8501(19)
1.897(2)
1.883(2)
1.876(2)
1.893(2)
2.4543 (18)
2.859(2)
P(1)–C(16)
Si(1)–C(2)
Si(1)–C(4)
Si(2)–C(5)
Si(2)–C(7)
Na(1)–O(1A)
Na(1)–C(12A)
Si(1)–C(1)
Si(1)–C(3)
Si(2)–C(1)
Si(2)–C(6)
Na(1)–O(1)
Na(1)–O(2)
Na(1)–C(13A)
1.829(2)
1.886(2)
2.4327(17)
2.3182(18)
2.945(2)
P(1)–Na(1)–O(1)
P(1)–Na(1)–O(2)
O(1)–Na(1)–O(2)
Na(1)–O(1)–Na(1A) 95.63(6)
P(1)–C(1)–Si(2) 124.79(10)
86.48(5)
81.57(5)
102.79(6)
P(1)–Na(1)–O(1A) 96.04(5)
O(1)–Na(1)–O(1A) 84.37(6)
O(1A)–Na(1)–O(2) 172.24(5)
P(1)–C(1)–Si(1)
Si(1)–C(1)–Si(2)
114.43(10)
118.72(10)
Symmetry operator (inversion): A, −x, 1 − y, −z.
Fig. 3 Structure of 15 with 40% probability ellipsoids and with H atoms
omitted for clarity.
The coordination mode of the phosphinomethanide ligands
in 15 and 16 is significantly different from the PO2 coordination
mode observed in 14. Each ligand binds the potassium or
rubidium atom via its phosphorus and one of its oxygen atoms
to give a single, puckered, six-membered chelate ring [P–M–
O bite angle 58.10(6)◦ (15), 57.58(4)◦ (16)]; in addition, the
2
metal has an g -interaction with two of the aryl carbons of this
ligand. The metal atoms are further coordinated by the oxygen
atom of a second ligand in the polymeric chain, and have short
contacts to the carbanion centre and to one methyl from each
of the two SiMe3 groups of this second ligand, along with an
2
g -interaction with an aryl ring in the second ligand. Thus, the
overall binding mode of the ligand more closely resembles the
bridging mode observed in the cyclic tetramer [LiCH2P(C6H4-2-
CH2NMe2)2]4·(PhMe)n (8), in which each amino-functionalised
arm of the ligand binds a different metal centre, than the doubly
chelating PN2/PO2 modes observed in 1–5 and 14.
Fig. 2 Molecular structure of 14 with 40% probability ellipsoids and
with H atoms omitted for clarity.
˚
The M–P(1) distances of 3.6836(15) and 3.7328(8) A for
15 and 16, respectively are substantially longer than the
˚
atoms. The Na–P distance of 2.8144(16) A is somewhat longer
corresponding distances in the amino-functionalised phosphi-
2d
2c
˚
˚
than the same distance in 2 [2.8004(10) A], but is shorter
nomethanides 3 and 4 [3.2227(5) and 3.3437(8) A, respectively],
than the Na–P distances in the only other reported sodium
phosphinomethanides [{CH2C(PR2)2}NaL]2 [R = Ph, L =
pmdeta; R = Pri, L = (THF)3; pmdeta = N,N,Nꢀ,Nꢀꢀ,Nꢀꢀ-
consistent with the significantly different binding mode, but lie
within the range of distances typically found for potassium and
rubidium phosphides.1a The M · · · C(1) distances of 3.291(4) A
˚
˚
pentamethyldiethylenetriamine], which range from 2.877(2) to
(15) and 3.418(3) A (16) are at the longer end of the usual
10,11
˚
3.0451(11) A;
the Na–P distance falls in the typical range of
range for K–C and Rb–C r-bonds [K–C 2.91–3.10, Rb–C 3.29–
distances found for Na–P contacts in sodium phosphides.1a
In addition to these contacts there is a short intramolecular
Si–Me · · · Na contact to one of the SiMe3 groups in the chelating
3.51 A]12 and the carbanion centres are essentially planar in both
˚
compounds [sum of angles at C(1) = 359.2 (15), 358.9◦ (16);
displacement of C(1) from the PSi2 plane towards K/Rb: 0.094
2
˚
˚
ligand [Na · · · C(2) 3.003(2) A] and an g -interaction between
(15), 0.108 (16) A]; this suggests that any M · · · carbanion inter-
the sodium and an aryl ring in the other half of the dimer
actions in these compounds are relatively weak. For comparison,
1 6 6 0
D a l t o n T r a n s . , 2 0 0 5 , 1 6 5 8 – 1 6 6 3

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◦
˚
Table 3 Selected bond lengths (A) and angles ( ) for 15 (M = K) and 16 (M = Rb)
15
16
15
16
M(1)–C(1A)
M(1)–O(2A)
M(1)–C(13)
M(1)–C(16A)
M(1)–P(1)
P(1)–C(1)
3.291(4)
2.669(3)
3.258(4)
3.630(4)
3.6836(15)
1.767(4)
1.879(4)
1.887(4)
1.892(4)
1.894(5)
1.879(4)
3.418(3)
2.783(2)
3.326(3)
3.677(3)
3.7328(8)
1.769(3)
1.875(3)
1.891(3)
1.902(3)
1.883(3)
1.889(3)
M(1)–C(21A)
M(1)–O(1)
M(1)–C(8)
M(1)–C(14)
M(1)–P(1A)
P(1)–C(16)
Si(1)–C(1)
Si(1)–C(3)
Si(2)–C(1)
Si(2)–C(6)
3.604(4)
2.825(3)
3.293(4)
3.580(4)
3.8948(15)
1.846(4)
1.832(4)
1.898(4)
1.837(4)
1.883(4)
3.657(3)
2.973(2)
3.335(3)
3.729(3)
3.9979(8)
1.849(3)
1.836(3)
1.891(3)
1.834(3)
1.888(4)
P(1)–C(8)
Si(1)–C(4)
Si(1)–C(2)
Si(2)–C(5)
Si(2)–C(7)
O(2A)–M(1)–O(1)
O(2A)–M(1)–C(1A)
O(2A)–M(1)–P(1)
O(2A)–M(1)–P(1A)
C(1A)–M(1)–P(1A)
P(1)–C(1)–Si(2)
144.61(10)
84.92(10)
123.52(8)
61.07(7)
26.81(7)
110.6(2)
145.49(7)
82.65(7)
129.45(5)
59.60(5)
26.13(5)
110.90(15)
C(1A)–M(1)–P(1)
O(1)–M(1)–C(1A)
O(1)–M(1)–P(1)
O(1)–M(1)–P(1A)
Si(2)–C(1)–Si(1)
P(1)–C(1)–Si(1)
149.42(8)
106.42(9)
58.10(6)
132.87(6)
121.8(2)
126.8(2)
146.14(5)
103.75(7)
57.58(4)
129.56(4)
121.66(17)
126.37(18)
1
2
1
2
Symmetry operator (screw axis): A, 1 − x, y −
,
− z.
6
Elemental analyses were obtained by the Elemental Analysis
Service of London Metropolitan University.
the sum of angles at the carbanion centre in {(Me3Si)3C}Cs(g -
C6H6)3, which contains a genuine C–Cs r-bond, is 351.79◦ and
˚
the central C atom is displaced some 0.304 A out of the Si3 plane
towards the Cs ion.13
The P–C(1) distances in 14, 15, and 16 [1.7499(18), 1.767(4)
and 1.769(3) A, respectively] are considerably shorter than
Preparation of {(Me3Si)2CH}P(C6H4-2-CH2OMe)2 (9)
˚
To a cold (0 ◦C) solution of 2-BrC6H4CH2OMe (2.5 g, 12 mmol)
in ether (50 ml) was added BunLi (4.8 ml, 12 mmol). The
temperature of the reaction mixture was maintained at 0 ◦C
for 3 h whilst stirring and then a solution of {(Me3Si)2CH}PCl2
(1.3 g, 5 mmol) in ether (30 ml) was added, dropwise. This
mixture was allowed to attain room temperature and was stirred
for 12 h. The solution was filtered and solvent was removed
in vacuo. The oily product was extracted into light petroleum
(30 ml), filtered and solvent was removed in vacuo from the
filtrate to yield 9 as a viscous pale yellow oil, which crystallised
on standing at room temperature for several days. Isolated yield
1.69 g (78%). 1H NMR (C6D6 at 25 ◦C): d 0.10 (s, 18H, SiMe3),
1.40 (d, 2J(P,H) = 1.42 Hz, 1H, CHP), 3.35 (s, 6H, OMe), 4.97
(dd, 2J(H,H) = 12.48 Hz, 4J(P,H) = 1.94 Hz, 2H, CH2O), 5.09
(dd, 2J(H,H) = 12.48 Hz, 4J(P,H) = 2.36 Hz, 2H, CH2O), 7.13–
expected for a P–C single bond, consistent with some degree
of multiple bond character, associated with the extensive delo-
calisation of charge from the carbanion centre to phosphorus
via negative hyperconjugation. For comparison, the P–C(8)
˚
distances in 14, 15 and 16 are 1.866(2), 1.879(4) and 1.875(3) A,
respectively and the P–C(1) distances in the tertiary phosphine
˚
9 and its LiBr complex 10 are 1.8480(14) and 1.854(2) A,
respectively.
In summary, we have shown that subtle changes in the
donor groups at the periphery of a phosphinomethanide ligand
can have significant consequences for the binding mode and
aggregation state of its complexes. The coordination chemistry
of these ligands with alternative metal centres is currently under
investigation.
7.64 (m, 8H, ArH). 13C{ H} NMR (CDCl3 at 25 ◦C): d 0.85
1
(SiMe3), 12.07 (d, 1J(P,C) = 25.50 Hz, CHP), 56.31 (OMe), 72.52
(d, 3J(P,C) = 14.63 Hz, CH2O), 123.72 (Ar), 125.72 (d, 2J(P,C) =
3.00 Hz, Ar), 128.81, 130.71 (Ar), 136.09, (d, 2J(P,C) = 10.05 Hz,
Experimental
All manipulations were carried out using standard Schlenk
techniques under an atmosphere of dry nitrogen or argon. THF,
diethyl ether, toluene and light petroleum (bp 40–60 ◦C) were
distilled under nitrogen from potassium or sodium/potassium
alloy. THF was stored over activated 4A molecular sieves; all
other solvents were stored over a potassium film. Deuterated
toluene, THF and benzene were distilled from potassium
and CDCl3 was distilled from CaH2; all NMR solvents were
deoxygenated by three freeze–pump–thaw cycles and were
stored over activated 4A molecular sieves. The compounds
{(Me3Si)2CH}PCl214 and 2-BrC6H4CH2OMe15 were prepared by
previously published procedures. Rubidium 2-ethylhexoxide was
prepared by the direct reaction between rubidium metal and 2-
ethylhexanol in THF. BunLi was purchased from Aldrich as a
2.5 M solution in hexanes. All other compounds were used as
supplied by the manufacturer.
1
Ar), 139.92 (d, 1J(P,C) = 12.79 Hz, Ar). 31P{ H} NMR (CDCl3
at 22 ◦C): d −46.6 (br).
Preparation of [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Na]2 (14)
To a solution of 9 (2.6 g, 6.02 mmol) in ether (30 ml) was
added BunLi (2.4 ml, 6.02 mmol) and this mixture was stirred for
1 hour. This solution was added to a solution of NaOBut (0.58 g,
6.02 mmol) in ether (30 ml) and was stirred for 3 h. Solvent was
removed in vacuo to leave a brown solid which was washed with
light petroleum (3 × 20 ml) and residual solvent was removed
in vacuo. Crystals of 14 suitable for X-ray crystallography were
obtained from cold (−30 ◦C) toluene. Isolated yield 2.13 g (78%).
1
Found (%): C, 60.85; H, 8.00. Calc. (%) C, 60.76; H, 7.98. H
1H and 13C NMR spectra were recorded on a Jeol Lambda 500
spectrometer operating at 500.16 and 125.78 MHz, respectively,
or a Bruker Avance 300 spectrometer operating at 300.15 and
75.47 MHz, respectively; chemical shifts are quoted in ppm
relative to tetramethylsilane. 31P NMR spectra were recorded
on a Jeol Lambda 500 spectrometer operating at 202.35 MHz
and chemical shifts are quoted relative to external 85% H3PO4.
NMR (d8-toluene at 21 ◦C): d 0.45 (br s, 18H, SiMe3), 2.92
(br s, 6H, OMe), 4.87 (s, 4H, CH2O), 7.05–7.50 (m, 8H, ArH).
13C{ H} NMR (d8-THF at 25 ◦C): d 2.54 (SiMe3); 10.99 (d,
1
1
1J(P,C) = 26.07 Hz, PCH), 58.61 (OMe), 73.58 (d, J(P,C) =
7.26 Hz, CH2O), 127.76 (Ar), 128.54, 129.35, 133.91 (Ar), 139.21
(d, 2J(P,C) = 10.11 Hz, Ar); 143.58 (d, 1J(P,C) = 12.88 Hz, Ar).
◦
1
31P{ H} NMR (d8-toluene at 21 C): d −12.4 (br).
D a l t o n T r a n s . , 2 0 0 5 , 1 6 5 8 – 1 6 6 3
1 6 6 1

View Article Online
Table 4 Crystallographic data for 9, 10, 14, 15 and 16
Compound
9
10
14
15
16
Formula
M
C23H37O2PSi2
432.7
C46H74Br2Li2O4P2Si4
1039.1
Monoclinic
P21/c
12.0404(6)
9.4535(5)
C46H72Na2O4P2Si4
909.3
C23H36KO2PSi2
470.8
Orthorhombic
P212121
11.0925(19)
14.177(3)
C23H36O2PRbSi2
517.1
Orthorhombic
P212121
11.122(1)
Crystal system
Triclinic
Triclinic
¯
¯
Space group
P1
P1
˚
a/A
7.2142(4)
11.2764(6)
16.3272(8)
73.502(1)
86.635(1)
77.341(1)
1242.57(11)
2
9.235(4)
11.043(4)
13.945(7)
85.58(4)
80.06(4)
69.33(3)
1310.4(10)
1
˚
b/A
14.430(1)
16.248(1)
˚
c/A
24.4234(12)
16.388(3)
a/◦
b/◦
c /◦
95.371(1)
3
˚
V/A
2767.8(2)
2
1.645
23677
6579
2577.1(8)
4
0.377
13124
4511
2607.6(3)
4
2.068
20240
5239
Z
l/mm−1
0.223
11239
5839
0.229
7484
4388
Data collected
Unique data
Rint
0.023
261
0.035
0.095
1.037
0.32, −0.19
0.045
279
0.036
0.086
1.028
0.78, −0.49
0.018
270
0.032
0.083
1.042
0.32, −0.19
0.068
270
0.050
0.102
0.050
270
0.037
0.061
Refined parameters
R (on F, F2 > 2r)
Rw (on F2, all data)
Goodness of fit on F2
1.071
1.064
−3
˚
min, max electron density/e A
Absolute structure parameter
0.32, −0.28
0.31, −0.33
−0.06(7)
−0.014(5)
corrected semi-empirically for absorption, based on symmetry-
equivalent and repeated reflections. The structures were solved
by direct methods and were refined on F2 values for all unique
data. Table 4 gives further details. All non-hydrogen atoms were
refined anisotropically, and H atoms were constrained with a
riding model; U(H) was set at 1.2 (1.5 for methyl groups) times
Ueq for the parent atom. None of the structures is disordered.
Compounds 15 and 16 are both isostructural and isomorphous
(in space group P212121), the relationship between the reported
coordinates for these compounds is such that (x, y, z) for 15
Preparation of [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]K]n (15)
To a solution of 9 (2.4 g, 5.56 mmol) in ether (30 ml) was added
BunLi (2.2 ml, 5.56 mmol). This solution was added to a solution
of KOBut (0.62 g, 5.56 mmol) in ether (30 ml) and this mixture
was stirred for 3 h. After this period the ether was removed
in vacuo to leave a brown solid. This was washed with light
petroleum (3 × 20 ml) and residual solvent was removed in
vacuo to give 15 as an orange solid. Single crystals of 15 suitable
for X-ray crystallography were obtained from cold (−30 ◦C)
toluene. Yield 1.63 g (62%). Found (%): C, 57.35; H, 7.84. Calc.
1
transforms as (x, − y, z) for 16.
(%) C, 58.68; H, 7.71. H NMR (d8-toluene at 21 ◦C): d 0.36
1
Programs were 2Bruker AXS SMART (control) and SAINT
(integration), Nonius COLLECT and associated HKL DENZO
and SCALEPACK, and SHELXTL for structure solution,
refinement, and molecular graphics.16
(br s, 18H, SiMe3), 3.38 (br s, 6H, OMe), 4.00 (br s, 2H, CH2O),
4
4.27 (br d, J(P,H) = 6.10 Hz, 2H, CH2O), 7.05–7.49 (m, 8H,
◦
1
ArH). 13C{ H} NMR (d8-toluene at 21 C): d 2.62 (SiMe3), 11.02
(d, 1J(P,C) = 25.1 Hz, CHP), 58.36 (OMe), 75.59 (d, 1J(P,C) =
4.58 Hz, CH2O), 128.31, 131.43, 133.41, 138.94 (Ar), 142.80 (d,
CCDC reference numbers 263835–263839.
See http://www.rsc.org/suppdata/dt/b5/b502416a/ for cry-
stallographic data in CIF or other electronic format.
2J(P,C) = 12.93 Hz, Ar), 150.24 (d, J(P,C) = 13.73 Hz, Ar).
1
◦
31P{ H} NMR (d8-toluene at 21 C): d − 6.17 (br).
1
Preparation of [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Rb]n (16)
Acknowledgements
To a solution of 9 (2.6 g, 6.02 mmol) in ether (30 ml) was added
BunLi (2.41 ml, 6.02 mmol) and this mixture was stirred for 1 h.
The resulting solution was added to rubidium 2-ethylhexoxide
(6.02 mmol, 6.02 ml of a 1.0 M solution in THF) and stirred
overnight. Solvent was removed in vacuo and the sticky solid
was washed with light petroleum (3 × 20 ml). The resulting
dark red solid was recrystallised from cold (−30 ◦C) toluene.
Yield 1.2 g (39%). Found (%): C, 53.20; H, 6.67. Calc. (%) 53.42;
The authors thank the Royal Society, the EPSRC and the
University of Newcastle for support.
References
1 For recent reviews see: (a) K. Izod, Adv. Inorg. Chem., 2000, 50, 33;
(b) K. Izod, Coord. Chem. Rev., 2002, 227, 153.
2 (a) W. Clegg, S. Doherty, K. Izod and P. O’Shaughnessy, Chem.
Commun., 1998, 1129; (b) M. N. S. Hill, K. Izod, P. O’Shaughnessy
and W. Clegg, Organometallics, 2000, 19, 4531; (c) W. Clegg, K. Izod
and P. O’Shaughnessy, Organometallics, 1999, 18, 2939; (d) K. Izod,
W. Clegg and S. T. Liddle, Organometallics, 2001, 20, 367.
3 H. H. Karsch, K. Zelner, P. Mikulcik, J. Lachmann and G. Mu¨ller,
Organometallics, 1990, 9, 190.
4 W. Clegg, K. Izod, W. McFarlane and P. O’Shaughnessy,
Organometallics, 1999, 18, 3950.
5 K. Izod, P. O’Shaughnessy, W. Clegg and S. T. Liddle,
Organometallics, 2001, 20, 648.
H, 7.02. H NMR (d8-toluene at 21 ◦C): d 0.37 (br s, 18H,
1
SiMe3), 2.90 (br s, 6H, OMe), 4.27 (br d, 2H, CH2O), 4.92
1
(d, 2H, CH2O), 7.10–7.52 (m, 8H, ArH). 13C{ H} NMR (d8-
toluene at 21 ◦C): d 2.06 (SiMe3), 10.76 (d, 1J(P,C) = 25.45 Hz,
CHP), 58.12 (OMe), 73.42 (d, 1J(P,C) = 2.65 Hz, CH2O), 127.21,
129.50, 131.46, 137.61 (Ar), 138.61 (d, 2J(P,C) = 10.13 Hz, Ar),
1
142.98 (d, 1J(P,C) = 12.95 Hz, Ar). 31P{ H} NMR (toluene/light
petroleum at 21 ◦C): d −17.1 (br).
6 K. Izod, P. O’Shaughnessy and W. Clegg, Organometallics, 2002, 21,
641.
Crystal structure determinations of 9, 10, 14, 15 and 16
7 K. Kobayashi, Y. Kajimura, K. Maeda, T. Uneda, O. Morikawa and
H. Konishi, Heterocycles, 1997, 45, 1593.
8 (a) C. Chuit, R. J. P. Corriu, P. Monforte, C. Reye´, J.-P. Declercq
and A. Dubourg, Angew. Chem., Int. Ed. Engl., 1993, 32, 1430; (b) F.
Carre´, C. Chuit, R. J. P. Corriu, P. Monforte, N. Nayyar and C. Reye´,
J. Organomet. Chem., 1995, 499, 147; (c) C. Chuit, R. J. P. Corriu,
Measurements were made at 150
SMART or Nonius KappaCCD diffractometers using graphite-
K on Bruker AXS
˚
monochromated Mo-Ka radiation (k = 0.71073 A). For all
compounds cell parameters were refined from the observed
positions of all strong reflections in each data set. Intensities were
1 6 6 2
D a l t o n T r a n s . , 2 0 0 5 , 1 6 5 8 – 1 6 6 3

View Article Online
P. Monforte, C. Reye´, J.-P. Declercq and A. Dubourg, J. Organomet.
Chem., 1996, 511, 171.
9 A. Chandrasekaran, N. V. Timosheva, R. O. Day and R. R. Holmes,
Inorg. Chem., 2002, 41, 5235.
14 M. J. S. Gynane, A. Hudson, M. F. Lappert, P. P. Power and H.
Goldwhite, J. Chem. Soc., Dalton Trans., 1980, 2428.
15 S. P. Khanapure and E. R. Biehl, J. Org. Chem., 1990, 55,
1471.
10 W. Clegg, K. Izod, W. McFarlane and P. O’Shaughnessy,
Organometallics, 1998, 17, 5231.
11 K. Izod, W. McFarlane, B. V. Tyson, W. Clegg, R. W. Harrington and
S. T. Liddle, Organometallics, 2003, 22, 3684.
12 J. D. Smith, Adv. Organomet. Chem., 1999, 43, 267.
13 C. Eaborn, P. B. Hitchcock, K. Izod and J. D. Smith, Angew. Chem.,
Int. Ed. Engl., 1995, 34, 687.
16 (a) SMART and SAINT software for CCD diffractometers, Bruker
AXS Inc., Madison, WI, 1997; (b) COLLECT software, Nonius BV,
Delft, The Netherlands, 2000; (c) Z. Otwinowski and W. Minor,
Methods in Enzymology, ed. C. W. Carter, Jr. and R. M. Sweet,
Academic Press, New York, 1997, vol. 276, pp. 307–326; (d) G. M.
Sheldrick, SHELXTL user manual, version 6, Bruker AXS Inc.,
Madison, WI, 2001.
D a l t o n T r a n s . , 2 0 0 5 , 1 6 5 8 – 1 6 6 3
1 6 6 3