Synthesis, structures and stabilities of thioanisole-functionalised phosphido-borane complexes of the alkali metals

Article abstract of DOI:10.1039/c1dt11368b

Treatment of the secondary phosphine {(Me₃Si) ₂CH}PH(C₆H₄-2-SMe) with BH₃· SMe₂ gives the corresponding phosphine-borane {(Me ₃Si)₂CH}PH(BH₃)(C₆H

Full text of DOI:10.1039/c1dt11368b

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PAPER
Synthesis, structures and stabilities of thioanisole-functionalised
phosphido-borane complexes of the alkali metals†
Keith Izod,* James M. Watson, William Clegg and Ross W. Harrington
Received 20th July 2011, Accepted 1st September 2011
DOI: 10.1039/c1dt11368b
Treatment of the secondary phosphine {(Me3Si)2CH}PH(C6H4-2-SMe) with BH3·SMe2 gives the
corresponding phosphine-borane {(Me3Si)2CH}PH(BH3)(C6H4-2-SMe) (9) as a colourless solid.
Deprotonation of 9 with n-BuLi, PhCH2Na or PhCH2K proceeds cleanly to give the corresponding
alkali metal complexes [[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]ML]n [ML = Li(THF), n = 2 (10); ML =
Na(tmeda), n = • (11); ML = K(pmdeta), n = 2 (12)] as yellow/orange crystalline solids. X-ray
crystallography reveals that the phosphido-borane ligands bind the metal centres through their sulfur
and phosphorus atoms and through the hydrogen atoms of the BH3 group in each case, leading to
dimeric or polymeric structures. Compounds 10–12 are stable towards both heat and ambient light;
however, on heating in toluene solution in the presence of 10, traces of free phosphine-borane 9 are
slowly converted to the free phosphine {(Me3Si)2CH}PH(C6H4-2-SMe) (5) with concomitant formation
of the corresponding phosphido-bis(borane) complex [{(Me3Si)2CH}P(BH3)2(C6H4-2-SMe)]Li (14).
complexes,3e,f intermediates in catalytic P–C cross-coupling reac-
tions, and Wagner and co-workers have reported the synthesis and
crystal structure of an iron(II) complex of a novel bis(phosphido-
borane) dianion.3g
Introduction
Phosphido-borane anions, [R2P(BH3)]- (alternatively known as
phosphanylborohydrides or mono(borane)phosphides) are useful
intermediates for the synthesis of a variety of chiral phos-
phines and for the generation of polymeric main group element
materials;1,2 however, almost without exception, these anions are
generated and used in situ and few attempts have been made to
isolate and characterise them. Since phosphido-borane anions
are isoelectronic with the corresponding silyl anions [R2MeSi]-,
which have a well-developed coordination chemistry, it is perhaps
surprising that relatively few complexes of these anions have been
reported. Recently, however, a small number of research groups
have noted their potential and a nascent coordination chemistry
for these ligands has begun to emerge.3–6
Of the few crystallographically-characterised complexes of
phosphido-borane anions the majority are of the transition metal
centres Fe, Ru, Pd and Pt.3 For example, Manners and co-
workers have reported the structures of several late transition
metal complexes, prepared either via metathesis reactions between
a transition metal halide and an alkali metal phosphido-borane
complex or via oxidative addition of a phosphine-borane adduct to
a low oxidation state transition metal complex; these compounds
are effective catalysts for the dehydrocoupling of phosphine-
borane adducts to give poly(phosphinoborane) materials.3a–d In
addition, Brown and Gaumont have isolated a small number of Pd
Main group derivatives are limited to complexes of lithium,
potassium and aluminium.4 The first structurally authenticated
complexes of this type were reported in 2003 by Mu¨ller and
Brand, who described the synthesis and structural charac-
terisation of the lithium complexes [{Me2P(BH3)}Li(tmeda)]•
(1) and [{Ph(t-Bu)P(BH3)}Li{(-)-sparteine}]• (2) and of the
aluminium complexes [Li(tmeda)2][Al{Me2P(BH3)}4] (3) and
[[Li(t-BuOMe)][Al{Me2P(BH3)}4]]• (4) [tmeda = N,N,N¢,N¢-
tetramethylethylenediamine].4a Subsequently, Wagner and co-
workers reported the potassium complexes [K(18-crown-
6)][R2P(BH3)] [R = Ph, t-Bu].4b,c In addition, a small number of al-
kali metal complexes of the related phosphido-bis(borane) anions
[R2P(BH3)2]- [R = Ph, t-Bu] and [(2,4,6-t-Bu3C6H4)PH(BH3)2]-
have been structurally characterised.5 More recently, Lancaster
and co-workers have reported a series of lithium and aluminium
complexes with perfluorophenyl-substituted phosphido-borane
and phosphido-bis(borane) ligands.6
Phosphido-borane anions have the potential to coordinate
metal ions through the formally anionic phosphorus centre
and/or the hydrogen atoms of the adjacent borane group and
so represent an interesting class of ambidentate ligands. As such,
phosphido-boranes may adopt a variety of coordination modes,
including terminal P- or BH3-donor modes (I and II), a bidentate
coordination mode (III) and bridging modes (IV, V). In complexes
containing soft transition metal centres phosphido-borane ligands
typically adopt a P-donor coordination mode, whereas hard alkali
metal cations usually favour a BH3-donor mode.
Main Group Chemistry Laboratories, School of Chemistry, Bedson Building,
University of Newcastle, Newcastle upon Tyne, UK, NE1 7RU. E-mail:
k.j.izod@ncl.ac.uk
† CCDC reference numbers 836010–836012. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt11368b
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In order to understand better this unusual behaviour we have
embarked on a programme to study systematically the deproto-
nation of thioether-substituted phosphines and the stability of
the corresponding phosphide complexes. In this contribution we
report the synthesis of the borane adduct of 5 and the synthesis,
structural characterisation and photolysis/thermolysis behaviour
of its lithium, sodium and potassium derivatives.
Results and Discussion
Treatment of a solution of 5 in diethyl ether with one equivalent
of BH3.SMe2 yields the air stable phosphine-borane adduct
{(Me3Si)2CH}PH(BH3)(C6H4-2-SMe) (9) as a viscous oil, which
may be crystallised from cold n-hexane as colourless needles in
We have a long-standing interest in the coordination chemistry
of donor-functionalised phosphides of type A and have isolated
numerous main group and lanthanide metal derivatives of these
ligands.7,8 In the course of these studies we discovered that
the thioanisole-substituted phosphine {(Me3Si)2CH}PH(C6H4-2-
SMe) (5) exhibits rather unusual behaviour towards alkyllithium
reagents.8 The reaction between 5 and one equivalent of n-BuLi in
diethyl ether yields, after crystallisation in the presence of tmeda,
half an equivalent of the dianion complex [{(Me3Si)2CH}P(C6H4-
2-S)][Li(tmeda)]2 (6) (Scheme 1). Compound 6 results from
concurrent deprotonation and demethylation of the phosphine,
leaving half an equivalent of 5 unchanged; compound 6 may be ac-
cessed cleanly through the reaction between 5 and two equivalents
of n-BuLi under the same conditions. In contrast, the reaction
between 5 and one equivalent of n-BuLi in diethyl ether in the
presence of tmeda cleanly yields the expected lithium phosphide
[{(Me3Si)2CH}P(C6H4-2-SMe)][Li(tmeda)] (7). Perhaps more in-
triguingly, exposure of toluene solutions of 7 to ambient light
rapidly leads to isomerisation to the corresponding phosphine-
thiolate [{(Me3Si)2CH}P(Me)(C6H4-2-S)][Li(tmeda)] (8).
1
1
good yield. The 31P{ H} and 11B{ H} NMR spectra of 9 consist
of a broad quartet at -15.7 ppm and a broad doublet at -40.1 ppm,
respectively (1JPB = 49.0 Hz), while in the 1H NMR spectrum the
PH proton gives rise to a complex doublet of quartets of doublets
3
3
centred at 6.04 ppm (1JPH = 375.2 Hz, JHH = 6.5 Hz, JHH¢
=
2.8 Hz); this signal does not change significantly in appearance on
decoupling the 11B nucleus.
The reaction between 9 and one equivalent of n-BuLi in
THF proceeds cleanly to give the corresponding phosphido-
borane complex [[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]Li(THF)]2
(10), which was crystallised from cold toluene/THF as colourless
blocks suitable for X-ray crystallography (Scheme 2). Similarly,
the reaction between 9 and one equivalent of either PhCH2Na
or PhCH2K in THF yields the corresponding alkali metal
salts, which were crystallised from cold toluene in the presence
of one equivalent of either tmeda or pmdeta, respectively,
as the adducts [[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]Na(tmeda)]•
(11) and [[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]K(pmdeta)]2 (12)
[pmdeta = N,N,N¢,N¢¢,N¢¢-pentamethyldiethylenetriamine]. These
straightforward reactions contrast with the corresponding reac-
tion between 5 and n-BuLi, which, in the absence of tmeda, leads
to both deprotonation and demethylation to give the phosphido-
thiolate 6;8 no such dianionic products were observed in the
syntheses of 10–12. Compounds 10–12 are soluble in ethereal
solvents and are moderately soluble in aromatic hydrocarbons,
but have limited solubility in aliphatic solvents.
Scheme 2 [R = CH(SiMe3)2].
Upon metalation the 31P{ H} NMR signal shifts significantly
1
Scheme 1 [R = CH(SiMe3)2].
upfield from -15.7 ppm for 9 to between -58.3 and -59.5 ppm for
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1
10–12. Although there is only a marginal difference in the 31P{ H}
chemical shifts of the metalated compounds, the magnitude of
the 31P–11B coupling constants decreases steadily with decreasing
electronegativity of the cation [1JPB = 49.0 (9), 39.2 (10), 29.4 (11),
and 19.6 Hz (12)].
Compound 10 crystallises as discrete centrosymmetric dimers;
the molecular structure of 10 is shown in Fig. 1, along with
selected bond lengths and angles. Each lithium ion is coordinated
by the P and S atoms of the phosphido-borane ligand to give
a five-membered chelate ring [P–Li–S bite angle 77.28(7)◦]. The
coordination about lithium is completed by a molecule of THF
2
and by an h -BH3 contact with a borane group from the adjacent
phosphido-borane ligand in the dimer to give a pseudo-tetrahedral
geometry at lithium. Thus, the two halves of the dimer are linked
via an essentially planar, pseudo-six-membered [PLi(BH3)]2 ring.
Fig. 2 Part of the polymeric structure of 11 with 40% probability
ellipsoids and with H atoms bound to carbon omitted for clarity. Selected
◦
˚
bond lengths (A) and angles ( ): P(1)–Na(1) 2.9661(17), P(2)–Na(2)
2.9474(16), S(1)–Na(1) 3.0441(19), S(2)–Na(2) 3.0735(18), N(1)–Na(1)
2.542(3), N(2)–Na(1) 2.498(3), N(3)–Na(2) 2.523(3), N(4)–Na(2) 2.533(3),
Na(1)–H(2B) 2.64(3), Na(1)–H(2C) 2.35(3), Na(1) ◊ ◊ ◊ B(2) 2.694(4),
Na(2)–H(1A¢) 2.54(3), Na(2)–H(1B¢) 2.63(3), Na(2)–H(1C¢) 2.51(4),
Na(2) ◊ ◊ ◊ B(1¢) 2.646(4), C(17) ◊ ◊ ◊ Na(1) 3.126(4), P(1)–B(1) 1.951(4),
P(2)–B(2) 1.957(4), P(1)–C(1) 1.888(3), P(1)–C(8) 1.833(4), P(2)–C(21)
1.887(3), P(2)–C(28) 1.837(4), P(1)–Na(1)–S(1) 62.93(4), P(2)–Na(2)–S(2)
63.43(4). The prime indicates
translation).
a symmetry-generated atom (lattice
a chelating molecule of tmeda. The coordination about Na(1)
2
is completed by h -coordination of the hydrogen atoms of a
borane group from an adjacent unit in the chain and by a short
contact to one of the methylene carbon atoms of the tmeda co-
Fig. 1 Molecular structure of 10 with 40% probability ellipsoids
˚
ligand [Na(1) ◊ ◊ ◊ C(17) 3.126(4) A], whereas the coordination of
and with H atoms bound to◦ carbon omitted for clarity. Selected
3
Na(2) is completed by h -coordination of a BH3 group from an
˚
bond lengths (A) and angles ( ): P–Li 2.527(3), S–Li 2.608(2), O–Li
adjacent unit in the chain. The P–Na distances of 2.9661(17)
1.910(3), Li–H(1A¢) 2.053(14), Li–H(1B¢) 1.905(4), Li ◊ ◊ ◊ B¢ 2.403(3),
P–B 1.9617(18), P–C(1) 1.8682(14), P–C(8) 1.8459(13), P–Li–S 77.28(7),
P–Li–O 124.52(12), P–Li ◊ ◊ ◊ B¢ 121.84(11), O–Li–S 108.78(11), O–Li ◊ ◊ ◊ B¢
107.95(12), S–Li ◊ ◊ ◊ B¢ 109.83(10). The prime indicates a symmetry-gener-
ated atom (inversion).
˚
and 2.9474(16) A are similar to the P–Na distances in related
sodium phosphide complexes;9 for example, the P–Na distances
11
˚
in [Na(PHCy)(pmdeta)]2 are 2.884(8) and 2.936(7) A, while the
P–Na distances in [Na{P(C6H4-2-OMe)2}(diglyme)]2 range from
12
˚
˚
2.861(2) to 3.047(2) A. The Na(1) ◊ ◊ ◊ B(2) distance [2.694(4) A]
2
˚
The P–Li distance of 2.527(3) A in 10 is somewhat shorter than
is also similar to other h -BHn-Na distances [for example, the
˚
the corresponding distance in 1 [2.620(4) A], and slightly longer
Na ◊ ◊ ◊ B distance in [[(Me3Si)2CPMe2(BH3)]Na(THF)2].1 PhMe is
2
8
13
˚
˚
˚
than the P–Li distance in 7 [2.508(3) A], but lies in the range of
2.766(3) A], while the Na(2) ◊ ◊ ◊ B(1B) distance [2.646(4) A] is
similar to other h -BHn-Na distances [for example, the Na ◊ ◊ ◊ B
distances in [Na(BH4)(morpholine)2] are 2.640 A].
3
typical P–Li distances for lithium phosphide complexes;9 the S–Li
14
˚
˚
distance in 10 [2.608(2) A] is slightly longer than the corresponding
˚
distance in 7 [2.543(3) A]. The Li–H distances in 10 [2.053(14) and
Compound 12 crystallises as discrete centrosymmetric dimers
in which the phosphido-borane ligands adopt a tridentate coor-
dination mode; the structure of 12 is shown in Fig. 3, along with
selected bond lengths and angles. Each phosphido-borane ligand
binds the adjacent potassium ion through its P and S atoms and,
˚
1.905(14) A] are similar to Li–H distances in complexes which
2
˚
possess a h -BH3-Li contact; the Li ◊ ◊ ◊ B¢ distance of 2.403(3) A is
2
also typical of an h -Li–BHn interaction. For example, the Li–H
distances and the Li ◊ ◊ ◊ B distance in Li(h -BH4)(py)3 are 2.06 and
1.90 A, and 2.401(7) A, respectively.
2
10
2
˚
˚
in an h manner, through its borane hydrogen atoms, which bridge
Compound 11 represents the first example of a sodium complex
of a phosphido-borane anion to be crystallographically char-
acterised. This compound crystallises as an essentially linear
polymer with two crystallographically independent monomer
units per asymmetric unit; the structure of 11 is shown in Fig.
2, along with selected bond lengths and angles. Both sodium
ions are coordinated by the P and S atoms of a phosphido-
borane ligand to give a five-membered chelate ring [P–Na–S
bite angles 62.93(4) and 63.43(4)◦], and by the N atoms of
the two potassium ions in the dimer. The third hydrogen atom
1
of each borane group is h -bonded to the second potassium ion,
2
3
such that each borane group acts as a m2-h :h bridge between
the two potassium ions, forming a rhombus-shaped pseudo-four-
membered K2(BH3)2 ring. The coordination about each potassium
ion is completed by the three nitrogen atoms of a molecule
of pmdeta and by a short contact between potassium and the
central methyl group of the pmdeta ligand [K ◊ ◊ ◊ C(19) 3.266(2)
˚
A], making the potassium ions pseudo-eight-coordinate.
11714 | Dalton Trans., 2011, 40, 11712–11718
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during sample preparation) disappeared gradually over the course
of a few hours, to be replaced by a peak at -68.0 ppm due to
the secondary phosphine 5 and a broad peak at -6.9 ppm due to
a new phosphine-borane species. We attribute this behaviour to
a borane redistribution process, whereby the anionic phosphido-
borane ligand in 10 removes a borane group from the less electron-
rich, neutral phosphine-borane 9 to give one equivalent each of
the free phosphine 5 and the corresponding lithium phosphido-
bis(borane) (14), the latter of which gives rise to the peak at
1
-6.9 ppm in the 31P{ H} NMR spectrum (Scheme 3). We were,
unfortunately, unable to separate a pure sample of the phosphido-
bis(borane) complex 14 from these thermolysis reactions; however,
1
1
1H, 31P{ H} and 11B{ H} NMR spectra of samples taken directly
from the reaction solution are consistent with this formulation.
Fig. 3 Molecular structure of 12 with 40% probability ellipsoids and
with H atoms bound to carbon omitted for clarity. Selected bond lengths
◦
˚
(A) and angles ( ): K–P 3.6617(6), K–S 3.7568(7), K–N(1) 2.9039(17),
K–N(2) 2.8912(16), K–N(3) 2.9099(17), K–H(1A) 3.01(2), K–H(1C)
2.77(2), K ◊ ◊ ◊ B 3.243(2), K–H(1A¢) 3.00(2) K–H(1B¢) 2.97(2), K–H(1C¢)
2.74(2), K ◊ ◊ ◊ B¢ 3.047(2), K ◊ ◊ ◊ C(19) 3.266(2), P–B 1.975(2), P–C(1)
1.8852(18), P–C(8) 1.8473(18), P–K–S 49.666(12). The prime indicates
a symmetry-generated atom (inversion).
Scheme 3 [R = CH(SiMe3)2].
In order to confirm the identity of 14 we prepared this
compound by a more straightforward route. The reaction between
10 and one equivalent of BH3.SMe2 in THF yields crude 14 as a
colourless solid after a straightforward work-up. Treatment of a
solution of this crude material in toluene with one equivalent of
12-crown-4 and addition of a few drops of diethyl ether leads, on
standing, to the deposition of pure {(Me3Si)2CH}P(BH3)2(C6H4-
2-SMe)Li(12-crown-4) (14a) as a colourless solid. With the
The P–K–S bite angle of 49.666(12)◦ is significantly smaller
than the bite angles in 10 and 11, consistent with the greater ionic
radius of potassium than sodium and lithium. The “tridentate”
S,P,BH3 binding mode of the phosphido-borane ligand in 12 is
also consistent with the greater size of the potassium cation; a
“bidentate” P,BH3 binding mode has previously been observed
only in the related potassium salt [Ph2P(BH3)]K(18-crown-6) (13).4
exception of the expected signals for 12-crown-4, the 1H, 31P{ H}
1
and 11B{ H} NMR spectra of this deliberately prepared sample
1
˚
The P–K distance of 3.6617(6) A in 12 is significantly greater than
˚
are indistinguishable from those observed during the attempted
the corresponding distance in 13 [3.320(2) A]. The K ◊ ◊ ◊ B distance
˚
thermolysis of 10.
in 12 [3.243(2) A] is somewhat longer than the corresponding
2
˚
distance in 13 [3.162 A], in spite of the similar h -BH3 binding
modes in both cases; however, the intra-dimer K ◊ ◊ ◊ B¢ distance
Experimental
˚
[3.047(2) A] is significantly shorter than the K ◊ ◊ ◊ B distance in
3
13, consistent with the h -BH3 coordination mode in the former
All manipulations were carried out using standard Schlenk
techniques under an atmosphere of dry nitrogen. Diethyl ether,
THF, light petroleum (b.p. 40–60 ◦C), n-hexane and toluene were
dried prior to use by distillation under nitrogen from sodium,
potassium or sodium/potassium alloy as appropriate. THF was
stored over activated 4A molecular sieves; all other solvents were
stored over a potassium film. Deuterated THF was distilled from
potassium and CDCl3 was distilled from CaH2 under nitrogen and
both solvents were deoxygenated by three freeze-pump-thaw cycles
and were stored over activated 4A molecular sieves. Benzylsodium
and benzylpotassium were prepared by previously published
procedures;15 n-butyllithium was purchased from Aldrich as a
2.5 M solution in hexanes and BH3.SMe2 was purchased from
Aldrich as a 2.0 M solution in THF. 12-Crown-4 was dried over
activated 4A molecular sieves before use; tmeda and pmdeta were
distilled from CaH2 under nitrogen and were stored over activated
4A molecular sieves. All other compounds were used as supplied
by the manufacturer.
compound.
The ready isolation of compounds 10–12 and the unusual
photolytic rearrangement previously observed for 7 prompted us
to explore their behaviour on exposure to light and heat. We
observe that, while the phosphide complex 7 rapidly rearranges
on exposure to ambient light to give the corresponding tertiary
phosphine-functionalised thiolate (8), compound 10 undergoes
no such isomerisation; exposure of solutions of 10 in toluene or
THF to light (either ambient light or a 10 W fluorescent lamp)
for extended periods resulted in no change. Similarly, 11 and 12
are unaffected by exposure to light. It therefore appears that the
presence of boron directly adjacent to phosphorus in 10–12, which
effectively ties up the phosphorus lone pair present in 7, inhibits
rearrangement to the corresponding thiolate.
Compound 10 is also stable towards thermolysis: flame-sealed
samples of 10 in d8-THF which were heated to 60 ◦C for 16
h showed no evidence for decomposition. However, during the
course of these experiments, we noted that a small peak at -15.8
1
1H and 13C{ H} NMR spectra were recorded on a JEOL
ppm in the 31P{ H} NMR spectrum (due to the presence of free
ECS500 spectrometer operating at 500.16 and 125.65 MHz,
respectively, or a Bruker Avance300 spectrometer operating at
1
phosphine-borane 9, caused by a small amount of hydrolysis of 10
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300.15 and 75.47 MHz, respectively; chemical shifts are quoted in
benzylsodium (167 mg, 1.46 mmol) in diethyl ether (15 ml). After
stirring at room temperature for 1 h the solvent was removed
in vacuo, yielding a yellow powder. This powder was dissolved
in toluene (5 ml) and tmeda (0.20 ml, 1.33 mmol) was added.
Upon cooling to 5 ◦C colourless crystals of 11 suitable for X-ray
crystallography were deposited. Yield: 0.48 g, 94%. C 51.48, H
ppm relative to tetramethylsilane. 31P{ H}, 11B{ H} and 7Li{ H}
NMR spectra were recorded on a JEOL ECS500 spectrometer op-
erating at 202.35, 160.16 and 194.38 MHz, respectively; chemical
shifts are quoted in ppm relative to external 85% H3PO4, BF3·Et2O,
and 0.1 M LiCl, respectively. Elemental analyses were obtained
by the Elemental Analysis Service of London Metropolitan
University.
1
1
1
◦
11
9.72% Found C 51.38, H 9.76%. 1H{ B} NMR (d8-THF, 25 C):
2
d -0.06 (s, 9H, SiMe3), 0.09 (s, 9H, SiMe3), 0.71 (d, JPH = 6.4
2
Hz, 3H, BH3), 0.86 (d, JPH = 5.5 Hz, 1H, Si2CH), 2.15 (s, 12H,
3
NMe2), 2.30 (s, 4H, NCH2), 2.33 (s, 3H, SMe), 6.83 (t, JHH
=
{(Me3Si)2CH}PH(BH3)(C6H4-2-SMe) (9)
3
7.1 Hz, 1H, ArH), 6.92 (m, 2H, ArH), 7.82 (d, JHH = 6.9 Hz,
To
a
solution of {(Me3Si)2CH}PH(C6H4-2-SMe) (6.64 g,
◦
1H, ArH). 13C{ H} NMR (d8-THF, 25 C): d 0.08 (d, JPC = 5.4
Hz, SiMe3), 1.99 (s, SiMe3), 5.06 (PCH), 16.16 (d, 4JPC = 11.5 Hz,
SMe), 46.20 (NMe), 58.90 (NCH2), 123.57 (d, 3JPC = 3.7 Hz, ArC),
1
3
21.11 mmol) in THF (15 ml) was added BH3·SMe2 (10.6 ml,
21.20 mmol). After stirring for 1 h the solvent was removed in
vacuo to yield an off-white oil which was crystallised from cold
1
124.04, 125.88, 132.72, 134.86 (Ar◦C), 143.45 (d, JPC = 22.6 Hz,
◦
(-30 C) n-hexane (30 ml) as colourless microcrystals. The solid
ArC). 11B{ H} NMR (d8-THF, 25 C): d -33.5 (d, br, 1JBP = 29.4
1
was washed with cold light petroleum (3 ¥ 10 ml) and residual
solvent was removed in vacuo, to yield 9 as a white crystalline
◦
Hz). 31P{ H} NMR (d8-THF, 25 C): d -58.4 (q, br, JPB = 29.4
1
1
Hz).
1
solid. Isolated crystalline yield: 7.22 g, 83%. H NMR (CDCl3,
25 ◦C): d -0.06 (s, 9H, SiMe3), 0.32 (s, 9H, SiMe3), 0.92 (q, 1JBH
=
[[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]K(pmdeta)]2 (12)
2
3
7.1 Hz, 3H, BH3), 1.46 (dd, JPH = 20.6 Hz, JHH = 2.8 Hz, 1H,
1
3
Si2CH), 2.56 (s, 3H, SMe), 6.04 (m, JPH = 375.2 Hz, JHH = 6.5
To a solution of {(Me3Si)2CH}PH(BH3)(C6H4-2-SMe) (0.55 g,
1.67 mmol) in diethyl ether (15 ml) was added a slurry of
benzylpotassium (224 mg, 1.72 mmol) in diethyl ether (15 ml).
This mixture was stirred at room temperature for 1 h and then
solvent was removed in vacuo to give a white powder. This powder
was dissolved in toluene (5 ml) and pmdeta (0.3 ml, 1.44 mmol) was
added. Upon cooling to 5 ◦C colourless crystals of 12 suitable for
X-ray crystallography were deposited. Yield: 0.57 g, 93%. Anal.
Calcd. for [[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]K(pmdeta)]2: C
3
3
Hz, JHH¢ = 2.8 Hz, 1H, PH), 7.24 (t, JHH = 7.8 Hz, 1H, ArH),
7.29 (d, 3JHH = 6.9 Hz, 1H ArH), 7.46 (t, 3JHH = 7.6 Hz, 1H, ArH),
8.02 (dd, 3JPH = 13.8 Hz, 3JHH = 6.0 Hz, 1H, ArH). 13C{ H} NMR
1
◦
3
3
(CDCl3, 25 C): d 1.53 (d, JPC = 3.8 Hz, SiMe3), 2.18 (d, JPC
=
2.8 Hz, SiMe3), 6.34 (CHP), 16.59 (SMe), 125.25 (d, JPC = 12.5
Hz, ArC), 126.02 (d, JPC = 4.8 Hz, ArC), 125.25 (d, JPC = 4.9, Hz
ArC), 132.08 (d, JPC = 1.9 Hz, ArC), 136.14 (d, JPC = 18.2 Hz,
◦
1
ArC), 143.08 (ArC), 11B{ H} NMR (CDCl3, 25 C): d -40.1 (br
◦
d, 1JBP = 49.0 Hz). 31P{ H} NMR (CDCl3, 25 C): d -15.7 (br q,
1
11
51.18, H 9.71, N 7.78%. Found C 51.09, H 9.75, N 7.74%. 1H{ B}
1JPB = 49.0 Hz).
NMR (d8-THF, 25 ◦C): d 0.01 (s, 9H, SiMe3), 0.04 (s, 9H, SiMe3),
3
3
0.73 (d, JPH = 5.5 Hz, 3H, BH3), 0.83 (d, JPH = 4.2 Hz, 1H,
Si2CH), 2.16 (s, 12H, NMe2), 2.19 (s, 3H, NMe), 2.31 (m, 4H,
CH2N), 2.32 (s, 3H, SMe), 2.42 (m, 4H, CH2N), 6.84 (t, 3JHH = 7.4
Hz, 1H, ArH), 6.90 (d, 3JHH = 6.9 Hz, 1H, ArH), 6.95 (t, 3JHH = 7.6
[[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]Li(THF)]2 (10)
To a solution of {(Me3Si)2CH}PH(BH3)(C6H4-2-SMe) (0.47 g,
1.43 mmol) in diethyl ether (15 ml) was added n-BuLi (0.7 ml,
1.75 mmol) and this mixture was stirred at room temperature
for 1 h. Solvent was removed in vacuo to yield a white powder,
which was crystallised from cold (5 ◦C) toluene (5 ml) containing
a few drops of THF as colourless blocks of 10 suitable for
X-ray crystallography. Yield: 0.34 g, 58%. Anal. Calcd. for
[[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]Li(THF)]: C 50.29, H 8.74.
Found C 50.40, H 8.65. 1H NMR (d8-THF, 25 ◦C): d -0.03 (s, 9H,
1
Hz, 1H, ArH), 7.75 (d, 3JHH = 7.8 Hz, 1H, ArH). 13C{ H} NMR
(d8-THF, 25 ◦C): d 2.36 (d, 3JPC = 6.7 Hz, SiMe3), 3.73 (d, 3JPC
1.9 Hz, SiMe3), 8.03 (d, JPC = 47.0 Hz, Si2CH), 15.75 (d, JPC
=
=
1
4
13.4 Hz, SMe), 43.15 (NMe), 46.16 (NMe2), 57.24 (NCH2), 58.70
3
(NCH2), 122.03 (d, JPC = 3.8 Hz, ArC), 122.45, 125.78, 134.25
(ArC), 143.48 (d, 2JPC = 22.0 Hz, A◦rC), 150.42 (d, 1JPC = 27.8 Hz,
1
ArC). 11B{ H} NMR (d8-THF, 25 C): d -30.6 (d, br, 1JPB = 19.6
◦
1
1
Hz). 31P{ H} NMR (d8-THF, 25 C): d -58.3 (q, br, JPB = 19.6
1
SiMe3), 0.07 (s, 9H, SiMe3), 0.59 (q, JBH = 87.0 Hz, 3H, BH3),
Hz).
0.85 (s, 1H, PCH), 1.77 (m, 4H, THF), 2.32 (s, 3H, SMe), 3.62
(m, 4H, THF), 6.80 (m, 1H, ArH), 6.91 (m, 2H, ArH), 7.76 (d,
◦
1
3JHH = 7.3 Hz, 1H, ArH). 13C{ H} NMR (d8-THF, 25 C): d 1.50
[{(SiMe3)2CH}P(BH3)2(C6H4-2-SMe)][Li(12-crown-4)] (14a)
3
1
(d, JPC = 6.7 Hz, SiMe3), 2.88 (SiMe3), 7.52 (d, JPC = 48.0 Hz,
CH), 15.05 (d, 4JPC = 13.4 Hz, SMe), 25.27 (THF), 68.12 (THF),
122.28 (ArC), 122.52 (ArC), 124.68 (ArC), 133.51 (ArC), 143.35
To a solution of 9 (0.57 g, 1.74 mmol) in THF (10 ml) was added
n-BuLi (0.7 ml, 1.75 mmol). This mixture was stirred for 1 h, after
which BH3·SMe2 (0.90 ml, 1.80 mmol) was added, whereupon the
mixture became colourless. This mixture was stirred for a further
1 h and then the solvent was removed in vacuo to yield a colourless
solid. This solid was dissolved in toluene (10 ml) and 12-crown-4
(0.3 ml, 1.84 mmol) was added followed by a few drops of diethyl
ether. The solution was filtered and the filtrate was allowed to
stand at room temperature for 16 h, whereupon 14a precipitated
as a colourless solid. Isolated yield: 0.55 g, 60%. Anal. Calcd. for
[{(Me3Si)2CH}P(BH3)2(C6H4-2-SMe)][Li(12-crown-4)]: C 50.29,
(d, 2JPC = 24.0 Hz, ArC), 149.95 (d, 1JPC = 32.6 Hz, ArC). 11B{ H}
1
◦
NMR (d8-THF, 25 C): d -32.9 (d, br, JBP = 39.2 Hz). 31P{ H}
1
1
◦
1
7
1
NMR (d8-THF, 25 C): d -59.5 (q, br, JPB = 39.2 Hz). Li{ H}
NMR (d8-THF, 25 ◦C): d 2.3.
[[{(Me3Si)2CH}P(BH3)(C6H4-2-SMe)]Na(tmeda)]• (11)
To a solution of {(Me3Si)2CH}PH(BH3)(C6H4-2-SMe) (0.48 g,
1.46 mmol) in diethyl ether (15 ml) was added a slurry of
11716 | Dalton Trans., 2011, 40, 11712–11718
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Table 1 Crystallographic data for 10, 11, and 12
Compound
10
11
12
Formula
Mw
C36H74B2 Li2O2P2S2Si4
812.9
0.32 ¥ 0.30 ¥ 0.30
Monoclinic
P21/c
13.4504(5)
16.2605(5)
11.2638(4)
C20H45BN2NaPSSi
466.6
C46H104B2K2N6P2S2Si4
1079.6
Cryst. size/mm
Cryst. syst.
Space group
0.12 ¥ 0.10 ¥ 0.08
0.30 ¥ 0.20 ¥ 0.20
Triclinic
Triclinic
¯
¯
P1
P1
˚
a/A
11.3566(9)
13.2652(10)
21.1564(18)
93.397(7)
104.760(7)
97.552(6)
3040.9(4)
4
11.1081(6)
12.0772(7)
14.3398(7)
101.977(4)
108.829(5)
105.691(5)
1658.67(15)
1
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
103.732(4)
3
˚
V/A
2393.08(14)
2
0.306
0.908–0.914
15640
5823
0.031
4054
245
0.032
Z
m/mm-1
0.261
0.969–0.979
26610
10697
0.083
4259
551
0.048
0.095
3.238
0.443–0.564
8950
5133
0.022
4426
314
0.032
0.085
Trans. coeff. range
Reflns. measd.
Unique reflns.
Rint
Reflns. with F2>2s
Refined parameters
R (on F, F2>2s)a
Rw (on F2, all data)a
Goodness of fita
0.076
0.914
0.61, -0.37
0.698
0.33, -0.24
1.026
0.41, -0.23
-3
˚
Max, min electron density/e A
2
2
a Conventional R = RꢀFo| - |Fcꢀ/R|Fo|; Rw = [Rw(Fo - Fc2)2/Rw(Fo2)2]1/2; S = [Rw(Fo - Fc2)2/(no. data - no. params)]1/2 for all data.
◦
11
H 9.40. Found C 50.13, H 9.39. 1H{ B} NMR (d8-THF, 25 C):
Acknowledgements
2
d 0.07 (s, 18H, SiMe3), 0.34 (d, JPH = 8.3 Hz, 1H, CH), 0.80 (d,
2JPH = 10.5 Hz, 6H, BH3), 2.42 (s, 3H, SMe), 3.74 (s, 16H, 12-
The authors are grateful to the EPSRC for support.
crown-4), 6.93 (m, 1H, ArH), 7.09 (m, 1H, ArH), 7.22 (m, 1H,
◦
1
ArH), 8.11 (m, 1H, ArH). 13C{ H} NMR (d8-THF, 25 C): d 3.09
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and refined on F2 values for all unique data. Table 1 gives further
details. All non-hydrogen atoms were refined anisotropically, and
C-bound H atoms were constrained with a riding model, while
B-bound H atoms were freely refined; U(H) was set at 1.2 (1.5
for methyl groups) times Ueq for the parent C atom. Disordered
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occupancy, the solvent being presumably readily lost even on brief
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©

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11718 | Dalton Trans., 2011, 40, 11712–11718
This journal is
The Royal Society of Chemistry 2011
©