Influence of aromatic ring substituents and co-ligand on the binding mode of a phosphine-borane-stabilized carbanion; crystal structures of [[(Me3Si)2{Ph2P(BH3)}C]KLn]2[Ln = (OEt

Article abstract of DOI:10.1016/j.jorganchem.2007.07.040

The phosphine-borane adduct (Me₃Si)₂CHPPh₂(BH₃) (1) is readily prepared from the reaction between (Me₃Si)₂CHPCl₂ and 2 equiv of PhMgBr in refluxing THF, followed by treatment wit

Full text of DOI:10.1016/j.jorganchem.2007.07.040

Journal of Organometallic Chemistry 692 (2007) 5060–5064
www.elsevier.com/locate/jorganchem
Influence of aromatic ring substituents and co-ligand on the
binding mode of a phosphine–borane-stabilized carbanion;
crystal structures of [[(Me Si) {Ph P(BH )}C]KL ] [L = (OEt ) ,
3
0
2
00
2
3
n 2
n
2 2
00
pmdeta; pmdeta = N,N,N ,N ,N -pentamethyldiethylenetriamine]
*
Keith Izod , Corinne Wills, William Clegg, Ross W. Harrington
Main Group Chemistry Laboratories, Department of Chemistry, School of Natural Sciences, Bedson Building, University of Newcastle,
Newcastle upon Tyne NE1 7RU, UK
Received 18 June 2007; received in revised form 18 July 2007; accepted 23 July 2007
Available online 1 August 2007
Abstract
The phosphine–borane adduct (Me
of PhMgBr in refluxing THF, followed by treatment with BH
cleanly to give [[(Me Si) {Ph P(BH )}C]K] (2), which may be crystallized in the presence of pmdeta to give the corresponding adduct
3
Si)
2
CHPPh
2
3
(BH ) (1) is readily prepared from the reaction between (Me
3 2 2
Si) CHPCl and 2 equiv
3
ÆSMe . The reaction between 1 and MeK in cold diethyl ether proceeds
2
3
2
2
3
0
00
00
[
[(Me
3
Si)
2
{Ph
2
P(BH
3
)}C]K(pmdeta)]
2
(2a) [pmdeta = N,N,N ,N ,N -pentamethyldiethylenetriamine]. Treatment of 1 with MeK, fol-
Si) {Ph P(BH )}C]K(OEt (2b). X-ray crystallography reveals that in
lowed by crystallization from cold diethyl ether, gives [[(Me
3
2
2
3
2 2 2
) ]
both 2a and 2b the phosphine–borane-stabilized carbanion ligand binds to the metal centers via its BH hydrogen atoms; there are
3
no short contacts between the potassium ions and the carbanion centers. In 2b the ligand also binds the potassium ion through an
5
g -aryl interaction; in 2a this contact is absent.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Alkali metal; Organometallic; Crystal structure; Carbanion
1
. Introduction
mode (VI). In addition, Schmidbaur and co-workers have
reported the separated ion pair compound [Li(tme-
da) ][CH{PMe (BH )} ], in which there are no close con-
In spite of the frequent application of phosphine–bor-
2
2
3
2
ane-stabilized carbanions for the synthesis of both chiral
and achiral mono- and polyphosphines [1,2], little is known
about the structures of these species. In a recent extended
study we have shown that alkali and alkaline earth metal
complexes of these ligands exhibit a remarkable structural
diversity; these compounds crystallize as molecular species,
ate complexes, one-dimensional polymers, ribbon-type
polymers and two-dimensional sheets [3–8]. There is also
a remarkable diversity of ligand binding modes in these
compounds; we have observed a chelating mode (I), a vari-
tacts between the cation and the carbanion [9], and
Kobayashi and co-workers have reported a phosphine–
borane-stabilized carbanion complex of lithium in which
there is a C–Li contact but no B–Hꢀ ꢀ ꢀLi contacts [10].
Me
P
SiMe
P
Me
P
2
3
2
SiMe3
SiMe3
BH3
M
M
H B
H B
3
3
Me
2
M
M
M
SiMe3
SiMe
SiMe3
3
II
I
III
M
Me Si
3
SiMe3
Me
P
ety of bridging modes (II–V), and a terminal BH -donor
2
3
Me
P
2
BH3
M
P
M
H B
3
CH2
Me
BH3
M
2
M
M
Me Si
3
SiMe
M
3
*
Corresponding author.
IV
V
VI
E-mail address: k.j.izod@ncl.ac.uk (K. Izod).
0
022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.07.040

K. Izod et al. / Journal of Organometallic Chemistry 692 (2007) 5060–5064
5061
It is well known that alkali metal cations are able to
form moderately strong interactions with aromatic rings
11]. This has important consequences both for the struc-
[
tural chemistry of alkali metal complexes, where metal–aryl
contacts compete with more traditional metal-lone pair
interactions [12], and in biology, where alkali metal–arene
contacts are thought to play a significant role in the molec-
ular conformation of proteins [13]. Alkali metal–arene
contacts are a frequent feature of organo-alkali metal com-
pounds and so we were interested to see whether such
interactions would have any significant effect on the coor-
dination behavior of phosphine–borane-stabilized carba-
nions with these metals. We report herein the synthesis of
a new phenyl-substituted phosphine–borane adduct, and
the synthesis and structural characterization of two potas-
sium derivatives of this compound.
Fig. 1. Molecular structure of 2a with 40% probability ellipsoids and with
H atoms bonded to carbon omitted for clarity.
2
. Results and discussion
The reaction between {(Me Si) CH}PCl and 2 equiv of
3
2
2
PhMgBr in refluxing THF yields the tertiary phosphine
(Me Si) CH}PPh [14]. Treatment of this compound with
diethyl ether in the absence of co-ligands gives pale yellow
blocks of the complex [[(Me Si) {Ph P(BH )}C]K(OEt ) ]
3 2 2 3 2 2 2
{
3
2
2
BH Æ SMe in THF gives the phosphine–borane adduct
(2b) in moderate yield. The coordinated diethyl ether in 2b
is slowly lost under vacuum, although solid samples of 2b
are stable enough that, by careful manipulation of the crys-
talline solid, accurate elemental analyses could be obtained.
3
2
{
(Me Si) CH}P(BH )Ph (1) as a colorless solid in good
3 2 3 2
yield and purity, after a straightforward aqueous work-
1
13
1
11
1
31
1
up (Scheme 1). The H, C{ H}, B{ H} and P{ H}
1
NMR spectra of 1 are as expected; the BH group gives rise
However, despite repeated attempts, H NMR spectra of
3
to a broad quartet at 1.22 ppm, which collapses to a broad
2b consistently show low, but variable, amounts of diethyl
ether present.
1
1
doublet (J = 15.3 Hz) on decoupling the B nucleus.
PH
11
1
31
1
The B{ H} and P{ H} spectra consist of a broad dou-
The solid state structures of 2a and 2b were determined
by X-ray crystallography; the molecular structures of 2a
and 2b are shown in Figs. 1 and 2, respectively, and
selected bond lengths and angles for both 2a and 2b are
given in Table 1.
blet and a poorly resolved quartet at ꢁ37.1 and 14.0 ppm,
respectively (J = 66.1 Hz).
PB
Compound 1 reacts cleanly with a small excess of MeK
in diethyl ether to give the corresponding potassium salt
[
(Me Si) {Ph P(BH )}C]K (2). Complete metalation of 1
Both 2a and 2b crystallize as discrete centrosymmetric
dimers. The potassium ions in 2a are coordinated by the
3
2
2
3
3
1
1
was confirmed by a P{ H} NMR spectrum of the crude
reaction mixture, which exhibited a single poorly-resolved
quartet at 16.0 ppm (JPB = 107.3 Hz), and by the lack of
a signal due to the PSi CH group in the H{ B} NMR
spectrum of 2 [cf. 1.39 ppm (d, J = 19.2 Hz) for this
three nitrogen atoms of the pmdeta co-ligand, and by
2
two g -BH
groups, one from each ligand in the dimer.
group in each phosphine–borane-stabilized
3
3
1
11
Thus the BH
carbanion ligand forms a l -g :g bridge between the
2
2
2
2
2
PH
group in 1]. As observed in previous cases, metalation of
two potassium ions in the dimer. The coordination sphere
of each potassium ion is completed by three short agostic-
type interactions with three of the methyl groups in the
pmdeta co-ligand, one on each nitrogen; the Kꢀ ꢀ ꢀC(Me)
the neutral phosphine–borane adduct leads to a near dou-
3
1
11
bling of the P– B coupling constant [3–8].
Treatment of 2 with pmdeta followed by recrystalliza-
tion from hot toluene yields the corresponding complex
˚
distances [3.222(8)–3.458(8) A] are typical for this type of
˚
[
[(Me Si) {Ph P(BH )}C]K(pmdeta)] (2a) as pale yellow
contact, which usually falls in the range 3.30–3.70 A [15].
3
2
2
3
2
0
00
00
needles [pmdeta = N,N,N ,N ,N -pentamethyldiethylene-
triamine]. In contrast, recrystallization of 2 from cold
There are no short contacts between the potassium ions
and the essentially planar carbanion centers [sum of angles
MeK/
pmdeta
[[(Me Si) {Ph P(BH )}C]K(pmdeta)] (2a)
3 2 2 3 2
1
. 2PhMgBr/THF
{
(Me Si) CH}PCl
{(Me Si) CH}P(BH )Ph
3
2
2
3
2
3
2
2
. BH SMe /THF
3.
2
(1)
MeK/
[[(Me Si) {Ph P(BH )}C]K(Et O) ] (2b)
3
2
2
3
2
2 2
Et O
2
Scheme 1.

5062
K. Izod et al. / Journal of Organometallic Chemistry 692 (2007) 5060–5064
(
BH )}C]K] (3)[4], [[(Me Si) {Me P(BH )}C]K(THF) ]
3 3 2 2 3
1
0.5 1
(4) [8], and [[(Me Si) {Me P(BH )}C]K(pmdeta)] (5) [8]
3
2
2
3
2
˚
whichare 1.735(5)and 1.735(5) A (forthe two crystallograph-
ically different carbanions in the asymmetric unit), 1.750(2)
and 1.745(2) A, and 1.742(2) A, respectively. The shorter
C1–P distances in 2a and 2b are clearly associated with
increased delocalization of charge from the carbanion center
via negative hyperconjugation in these compounds and the
˚
˚
3
change in hybridization of the carbanion center from sp to
sp .
2
˚
The K–H distances of 2.64(7) and 2.88(7) A in 2a and
˚
2
.77(2) and 2.91(3) A in 2b are similar to K–H distances
found in potassium salts of borohydride anions; for exam-
ple, the K–H distances in [K(H B–t-Bu )(pmdeta)] are
2
2
2
˚
2
.56(2), 2.67(1) and 3.06(2) A [15].
Fig. 2. Molecular structure of 2b with 40% probability ellipsoids and with
minor disorder components and H atoms bonded to carbon omitted for
clarity.
The structures of 2a and 2b are markedly different from
those adopted by the potassium salts of the closely related
carbanion (Me Si) {Me P(BH )}C , in which methyl
ꢁ
3
2
2
3
in the PCSi skeleton = 359.8°]. In contrast, the potassium
2
groups replace the phenyl rings found in (Me Si) {Ph P
3 2 2
2
ꢁ
ions in 2b are coordinated by two g -BH groups, one from
3
(BH )}C . The solvent-free compound 3 crystallizes with
3
each ligand in the dimer, two oxygen atoms from the ether
a complex two-dimensional sheet structure, whereas the
THF adduct 4 crystallizes as a ribbon-type polymer; in
both compounds there are both K–H(B) and K–C con-
tacts. The pmdeta adduct 5 crystallizes as a centrosymmet-
ric dimer related to 2a and 2b, however, in 5 the
phosphine–borane-stabilized carbanion ligands bind the
ligands, a short agostic-type Kꢀ ꢀ ꢀC(Me) contact to one of
5
˚
the ether ligands [Kꢀ ꢀ ꢀC(Me) 3.510(3) A], and an g -phenyl
group from the carbanion ligand. The Kꢀ ꢀ ꢀC distances
5
to the g -phenyl rings in 2b range from 3.194(2) to
5
˚
3
.524(2) A [the typical range for Kꢀ ꢀ ꢀg -phenyl distances
˚
2
2
is 2.96–3.30 A [12]; the K–C12 distance is greater than
potassium ions via both their BH groups (in a l -g :g
3 2
˚
3
.56 A]. Once again, there are no short contacts between
fashion) and their carbanion centers, generating pseudo-
four-membered chelate rings. The different coordination
behavior of these two closely related ligands may be attrib-
uted to a combination of steric and electronic effects. In 2a
and 2b, the phenyl rings engender greater steric hindrance
about the carbanion center, favoring coordination by the
the potassium ions and the essentially planar carbanion
centers [sum of angles in the PCSi skeleton = 359.49°].
2
˚
The C1–P distances of 1.718(5) and 1.7084(19) A in 2a and
2
b, respectively, are significantly shorter than the C1–P dis-
tances in the closely related compounds [[(Me Si) {Me P
3
2
2
Table 1
Selected bond lengths (A) and angles (°) for 2a and 2b
˚
2
a
0
0
K–H1A
K–H1C
K–N1
2.64(7)
2.67(5)
2.900(5)
3.222(8)
1.718(5)
1.951(6)
K–H1B
K ꢀ ꢀ ꢀ B
K–N2
2.88(7)
K–H1B
2.95(7)
0
3.215(7)
2.865(5)
3.411(7)
1.837(5)
1.831(5)
K ꢀ ꢀ ꢀ B
3.269(7)
2.883(5)
3.458(8)
1.848(5)
1.823(5)
K–N3
K ꢀ ꢀ ꢀ C24
K ꢀ ꢀ ꢀ C27
K ꢀ ꢀ ꢀ C21
P–C14
P–C1
P–C8
P–B
C1–Si1
C1–Si2
N1–K–N2
B ꢀ ꢀ ꢀ K ꢀ ꢀ ꢀ B
P–C1–Si1
61.98(15)
87.73(16)
120.4(3)
N2–K–N3
P–C1–Si2
Si1–C1–Si2
62.39(14)
120.1(3)
119.3(3)
0
2
b
0
K–H1A
K–H1C
K–O1
K–C9
K–C12
P–C1
2.77(2)
2.64(3)
K–H1B
K ꢀ ꢀ ꢀ B
K–O2
K–C10
K–C13
P–C2
2.91(3)
K–H1A
K ꢀ ꢀ ꢀ B
2.90(2)
0
0
3.296(3)
2.7021(18)
3.339(2)
3.421(2)
1.839(2)
1.826(2)
3.094(2)
3.2316(19)
3.524(2)
3.510(3)
1.843(2)
1.939(2)
2.675(2)
3.194(2)
3.568(2)
1.7084(19)
1.826(2)
K–C8
K–C11
K ꢀ ꢀ ꢀ C27
P–C8
C1–Si1
C1–Si2
P–B
0
O1–K–O2
P–C1–Si2
Si1–C1–Si2
106.07(7)
120.17(11)
120.39(10)
B ꢀ ꢀ ꢀ K ꢀ ꢀ ꢀ B
85.98(7)
118.93(11)
P–C1–Si1

K. Izod et al. / Journal of Organometallic Chemistry 692 (2007) 5060–5064
5063
BH groups; in addition, the phenyl rings are likely to facil-
itate the delocalization of charge away from the carbanion
center, making this center less nucleophilic and a poorer
(27.9 mL, 68.4 mmol), dropwise. The resulting solution
was heated under reflux for 1 h, and then stirred for 16 h
at room temperature, during which time a white solid
formed. Deoxygenated water (50 mL) was cautiously
added; the organic layer was decanted and dried over acti-
3
donor in comparison to the BH group.
3
˚
3
. Conclusions
vated 4 A molecular sieves. The solution was filtered and
the solvent was removed in vacuo from the filtrate to yield
The ready availability of the phosphine–borane adduct
and its facile metalation provide a useful opportunity to
study the effect of phenyl substituents on the structures
adopted by phosphine–borane-stabilized carbanions. We
find that such substituents have a marked effect on the
structural preferences of these carbanions, leading, in
{(Me Si) CH}PPh as an off-white solid. Isolated yield
10.32 g, 87.6%. NMR data for this compound were essen-
tially identical to those reported previously [14].
3
2
2
1
{(Me Si) CH}P(BH )Ph (1): To
a
solution of
3
2
3
2
{(Me Si) CH}PPh (4.25 g, 12.3 mmol) in THF (40 mL)
3
2
2
was added BH Æ SMe (6.17 mL, 12.3 mmol). The resulting
3
2
the example studied, to a BH -donor coordination mode
solution was stirred for 16 h then the solvent was removed in
vacuo to yield 1 as a white solid. Isolated yield 4.31 g, 97.8%.
3
with no metal–carbanion center contacts. In addition, it
appears that, in the presence of weaker, monodentate
ligands such as diethyl ether, there is significant competi-
tion for coordination of the potassium ions by the aryl
rings of the phosphine–borane-stabilized carbanion. This
clearly has important implications for the use of such car-
banions for the synthesis of chiral phosphines, since there
1
11
H{ B} NMR (CDCl ): d ꢁ0.02 (s, 18H, SiMe ), 1.22 (d,
3
3
2
2
J
= 15.3 Hz, 3H, BH ), 1.39 (d, J = 19.2 Hz, 1H,
, PH
PH
3
1
3
1
CH), 7.36–7.84 (m, 10H, Ph). C{ H} NMR (CDCl ): d
3
3
2.67 (SiMe ), 10.57 (CH), 128.47 (d, J = 9.9 Hz, m-Ph),
130.57 (p-Ph), 132.19 (d, J = 9.4 Hz, o-Ph), 133.61 (d,
3
PC
2
PC
1
1
11
JPC = 52.6 Hz, ipso-Ph). B{ H} NMR (CDCl ): d ꢁ37.1
3
3
1
1
is the possibility that, where a BH -donor mode is
(d, J = 66.1 Hz). P{ H} NMR (CDCl ): d 14.0 (q,
PB 3
3
adopted, the presence of chiral diamines such as (ꢁ)-spar-
teine at the metal center will have little influence on the
stereochemical outcome of any reaction at the carbanion
center.
JPB = 66.1 Hz).
[[(Me Si) {Ph P(BH )}C]K(OEt ) ] (2b): A solu-
3
2
2
3
2 2 2
tion of {(Me Si) CH}P(BH )Ph (1.97 g, 5.50 mmol) in
3
2
3
2
cold (ꢁ10 °C) diethyl ether (30 mL) was added to solid
MeK (0.34 g, 6.28 mmol). The mixture was allowed to
attain room temperature and was stirred for 16 h. The
slightly turbid solution was filtered to give a yellow solu-
tion and cooling of this filtrate (ꢁ30 °C) for several hours
yielded pale yellow blocks of [[(Me Si) {Ph P(BH )}C]K(-
4
. Experimental
All manipulations were carried out using standard
Schlenk techniques under an atmosphere of dry nitrogen.
THF, diethyl ether and toluene were distilled under
nitrogen from sodium, potassium or sodium/potassium
alloy. THF was stored over activated 4 A molecular
sieves; all other solvents were stored over a potassium
film. Deuterated toluene was distilled from potassium
3
2
2
3
OEt ) ] (2b) suitable for X-ray crystallography. Isolated
2
2 2
yield 1.01 g, 46%. Anal. Calc. for C H BKO PSi
2
2
7
51
2
(544.74): C, 59.53; H, 9.44. Found: C, 59.39; H, 9.52%.
1
11
H{ B} NMR (toluene-d ): d 0.20 (s, 18H, SiMe ), 0.65
8
3
(d, JPH = 14.0 Hz, 3H, BH ), 0.99 (t, 4H, CH CH ), 3.15
3
2
3
and CDCl3 was distilled from CaH ; both deuterated
(q, 2H, OCH CH ), 6.99 (m, 2H, p-Ph), 7.10 (m, 4H, m-
2 3
2
1
3
1
solvents were deoxygenated by three freeze–pump–thaw
cycles and were stored over activated 4 A molecular
sieves. Pmdeta was dried over CaH2 and was distilled
Ph), 7.94 (m, 4H, o-Ph). C{ H} NMR (toluene-d ): d
8
7.98 (SiMe ), 11.74 (Si CP), 16.37 (OCH CH ), 66.70
3
2
2
3
(OCH CH ), 128.94 (m-Ph), 131.64 (p-Ph), 133.64 (d,
2
3
2
1
3
1
under
nitrogen
before
use;
MeK
[16]
and
J
= 8.3 Hz, o-Ph), 144.08 (d, J = 49.6 Hz, ipso-Ph).
PC PC
B{ H} NMR (toluene-d ): d -27.5 (d, J = 107.3 Hz).
8 PB
P{ H} NMR (toluene-d ): d 16.0 (q, J = 107.3 Hz).
8 PB
1
1
(
Me Si) CHPCl [17] were prepared by previously pub-
3
2
2
1
1
lished procedures. PhMgBr was supplied by Aldrich as
a 2.45 M solution in THF; BH ÆSMe was supplied by
[[(Me Si {Ph P(BH )}C]K(pmdeta)] (2a): A solu-
3 2 2 3 2
3
2
Aldrich as a 2.0 M solution in THF.
H, C{ H}, P{ H} and B{ H} NMR spectra were
recorded on a JEOL Lambda500 spectrometer operating at
tion of {(Me Si) CH}P(BH )Ph (0.82 g, 2.29 mmol) in
3 2 3 2
1
13
1
31
1
11
1
cold (ꢁ10 °C) diethyl ether (30 mL) was added to solid
MeK (0.12 g, 2.29 mmol). The mixture was allowed to
attain room temperature and was stirred for 16 h. The
slightly turbid solution was filtered, then pmdeta
(0.48 mL, 2.29 mmol) was added. The resulting solution
was stirred for 30 min, and then the solvent was removed
in vacuo to yield a yellow oil. The oil was dissolved in
hot toluene, and allowed to cool to room temperature to
give pale yellow needles of [[(Me Si) {Ph P(BH )}-
1
5
00.16, 125.65, 202.35 and 160.35 MHz, respectively; H,
13
and C chemical shifts are quoted in ppm relative to tetra-
methylsilane, P and B chemical shifts are quoted in ppm
relative to 85% H PO and BF OEt , respectively. Elemen-
3
1
11
3
4
3
2
tal analyses were obtained by the Elemental Analysis Ser-
vice of London Metropolitan University.
{
(Me Si) CH}PPh : This compound was prepared by
3 2 2
3
2
2
3
an alternative, higher yielding procedure to that previously
reported [14]. To a solution of {(Me Si) CH}PCl (8.94 g,
C]K(pmdeta)] (2a) suitable for X-ray crystallography. Iso-
2
lated yield 0.60 g, 49%. Anal. Calc. for C H BKN PSi
2
3
2
2
28 54
3
3
4.2 mmol) in THF (50 mL) was added PhMgBr
(569.80): C, 59.02; H, 9.55; N, 7.37. Found: C, 58.89; H,

5064
K. Izod et al. / Journal of Organometallic Chemistry 692 (2007) 5060–5064
Table 2
Appendix A. Supplementary material
Crystallographic data for 2a and 2b
Compound
2a
2b
CCDC 650314 and 650315 contain the supplementary
Formula
M
C
56
H
108
B
2
K
2
N
6
P
2
Si
4
C
54
H
102
B
2
K
O
2 4
P
2
Si
4
crystallographic data for 2a and 2b. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223 336 033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2007.07.040.
1139.6
Monoclinic
P2 /n
17.495(3)
10.1310(16)
19.931(3)
90.117(2)
3532.7(10)
2
1089.5
Monoclinic
P2 /n
12.773(2)
14.652(3)
18.649(4)
106.181(3)
3351.8(11)
2
Crystal system
Space group
1
1
˚
a (A)
˚
b (A)
˚
c (A)
b (°)
V (A )
˚
3
Z
ꢁ1
l (mm
)
0.283
0.298
Data collected
Unique data
29649
4628
29180
8081
References
R
int
0.064
4350
349
0.061
0.132
1.318
0.35, ꢁ0.41
0.028
6214
346
0.048
0.130
1.055
0.54, ꢁ0.32
2
[1] For recent reviews see: (a) M. Ohf, J. Holz, M. Quirmbach, A.
Borner, Synthesis (1998) 1391;
Data with F > 2r
Refined parameters
R (on F, F > 2r)
R
2
(b) J.M. Brunel, B. Faure, M. Maffei, Coord. Chem. Rev. 178–180
(1998) 665;
(c) B. Carboni, L. Monnier, Tetrahedron 55 (1999) 1197;
2
w
(on F , all data)
2
Goodness of fit on F
Minimum, maximum
(
d) R.T. Paine, H. N o¨ th, Chem. Rev. 95 (1995) 343;
˚
ꢁ
3
(e) A.C. Gaumont, B. Carboni, in: D. Kaufmann, D.S. Matteson (Eds.),
Science of Synthesis, Vol. 6, Thieme, Stuttgart, 2004, pp. 485–512.
2] For examples see: (a) A.R. Muci, K.R. Campos, D.A. Evans, J. Am.
Chem. Soc. 117 (1995) 9075;
(b) T. Imamoto, Pure Appl. Chem. 65 (1993) 655.
3] K. Izod, W. McFarlane, B.V. Tyson, W. Clegg, R.W. Harrington,
Chem. Commun. (2004) 570.
electron density (e A
)
[
[
1
11
9
.43; N, 7.24%. H{ B} NMR (toluene-d ): d 0.32 (s, 18H,
8
SiMe ), [BH protons not observed], 1.76 (s, 3H, NMe),
3
3
1
.83 (s, 12H, NMe ), 1.84 (m, 4H, NCH ), 1.85 (m, 4H,
2 2
[4] K. Izod, C. Wills, W. Clegg, R.W. Harrington, Organometallics 25
(2006) 38.
NCH ), 7.00 (m, 2H, p-Ph), 7.14 (m, 4H, m-Ph), 8.13 (m,
4
1
2
1
3
1
[
5] K. Izod, C. Wills, W. Clegg, R.W. Harrington, Organometallics 25
2006) 5326.
6] K. Izod, C. Wills, W. Clegg, R.W. Harrington, Inorg. Chem. 46
2007) 4320.
H, o-Ph). C{ H} NMR (toluene-d ): d 8.23 (SiMe ),
8 3
(
5.27 (Si CP), 42.82 (NMe), 46.20 (NMe2), 56.58
2
[
3
(
NCH ), 58.17 (NCH ), 128.39 (d, J = 8.3 Hz, m-Ph),
2 2 PC
(
4
2
1
33.44 (d, J = 8.3 Hz, p-Ph), 133.90 (d, J = 8.8 Hz,
PC PC
[7] K. Izod, C. Wills, W. Clegg, R.W. Harrington, Organometallics 26
(2007) 2861.
1
11
1
o-Ph), 145.32 (d, JPC = 51.64 Hz, ipso-Ph).
B{ H}
3
1
1
[
[
8] K. Izod, C. Wills, W. Clegg, R.W. Harrington, Dalton Trans. (2007) 3669.
9] H. Schmidbaur, E. Weiss, B. Zimmer-Gasser, Angew. Chem., Int.
Ed. Engl. 18 (1979) 782.
NMR (toluene-d ): d ꢁ27.2 (d, J = 104.8 Hz). P{ H}
8
PB
NMR (toluene-d ): d 18.1 (q, J = 104.8 Hz).
8
PB
Crystal structure determinations of 2a and 2b: Measure-
ments were made at 150 K on a Bruker AXS SMART CCD
diffractometer using graphite-monochromated MoKa radi-
[
10] X.-M. Sun, K. Manabe, W.W.-L. Lam, N. Shiraishi, J. Kobayashi,
M. Shiro, H. Utsumi, S. Kobayashi, Chem. Eur. J. 11 (2005) 361.
[11] (a) J.L. Wardell, in: G. Wilkinson, F.G.A. Stone, E.W. Abel (Eds.),
Comprehensive Organometallic Chemistry, Vol. 1, Pergamon,
Oxford, 1982, pp. 43–120;
˚
ation (k = 0.71073 A). For both compounds cell parame-
ters were refined from the observed positions of all strong
reflections in each data set. Intensities were corrected
semi-empirically for absorption, based on symmetry-equiv-
alent and repeated reflections. The structures were solved
(
b) D.S. Wright, M.A. Beswick, in: G. Wilkinson, F.G.A. Stone,
E.W. Abel (Eds.), Comprehensive Organometallic Chemistry II, Vol.
, Pergamon, Oxford, 1995, pp. 1–34.
1
[12] For examples see: (a) C. Schade, P.vonR. Schleyer, Adv. Organomet.
Chem. 27 (1987) 169;
2
by direct methods and were refined on F values for all
(
b) J.D. Smith, Adv. Organomet. Chem. 43 (1999) 267.
13] (a) D.A. Dougherty, Science. 271 (1996) 163;
b) D. Sun, V.L. Davidson, Biochemistry. 40 (2001) 12285.
unique data. Table 2 gives further details. All non-hydro-
gen atoms were refined anisotropically, and H atoms were
constrained with a riding model, except those bound to
boron, which were freely refined; U(H) was set at 1.2 (1.5
for methyl groups) times Ueq for the parent atom. Disorder
was resolved for the diethyl ether in 2b. The crystal of 2a
was twinned (37% minor component) and high angle data
were very weak. Programs were Bruker AXS SMART
[
[
(
14] C. Eaborn, N. Retta, J.D. Smith, J. Chem. Soc., Dalton Trans. (1983)
905.
15] J. Knizek, H. N o¨ th, J. Organomet. Chem. 614–615 (2000) 168.
16] (a) E. Weiss, G. Sauermann, Angew. Chem., Int. Ed. Engl. 7 (1968)
[
[
1
33;
(
(
b) E. Weiss, G. Sauermann, Chem. Ber. 103 (1970) 265;
c) C. Eaborn, P.B. Hitchcock, K. Izod, A.J. Jaggar, J.D. Smith,
(
control) and SAINT (integration), and SHELXTL for structure
Organometallics 13 (1994) 753.
[
[
17] M.J.S. Gynane, A. Hudson, M.F. Lappert, P.P. Power, H. Gold-
white, J. Chem. Soc. Dalton Trans. (1980) 2428.
18] (a) SMART and SAINT software for CCD diffractometers; Bruker AXS
Inc., Madison, WI, 2004 and 1997;
solution, refinement, and molecular graphics [18].
Acknowledgement
(
b) Sheldrick, G.M. SHELXTL user manual, version 6; Bruker AXS Inc.
The authors thank the Royal Society for support.
Madison, WI, 2001.