Isolation and structural characterisation of two sterically crowded diphosphanes

Article abstract of DOI:10.1016/S0022-328X(02)01434-1

Under specific conditions the reduction of the chlorophosphanes R(Me₂NCH₂-2-C₆H₄)PCI or RPCl₂ [R = (Me₃Si)₂CH] with LiAlH₄ gives the diphosphanes PbI₂. Comp

Full text of DOI:10.1016/S0022-328X(02)01434-1

Journal of Organometallic Chemistry 656 (2002) 43ꢁ48
/
www.elsevier.com/locate/jorganchem
Isolation and structural characterisation of two sterically crowded
diphosphanes
Stuart Blair, Keith Izod *, Richard Taylor, William Clegg
Department of Chemistry, University of Newcastle, Bedson Building, Newcastle upon Tyne NE1 7RU, UK
Received 28 March 2002; received in revised form 28 March 2002; accepted 9 April 2002
Abstract
Under specific conditions the reduction of the chlorophosphanes R(Me2NCH2ꢀ
LiAlH4 gives the diphosphanes {R(Me2NCH2ꢀ2-C6H4)P}2 (2) and RPHꢀPHR (3), respectively, in moderate to good yields.
Compound 2 may be obtained in higher yield from the reaction of {R(Me2NCH2ꢀ2-C6H4)P}Li with PbI2. Compounds 2 and 3 have
/
2-C6H4)PCl or RPCl2 [Rꢀ/(Me3Si)2CH] with
/
/
/
been characterised by multi-element NMR spectroscopy and the meso-diastereomers of both compounds have been characterised by
X-ray crystallography. In the solid state both meso-2 and meso-3 adopt an antiperiplanar conformation. # 2002 Elsevier Science
B.V. All rights reserved.
Keywords: P-ligands; Crystal structures; Pꢀ
/
P bond; Reduction
1. Introduction
Diphosphanes RR?Pꢀ
with LiAlH4 in ethereal solvents. However, in several
recently reported instances it has been observed that
such reductions proceed to give high yields of dipho-
/
PRR? are accessible through a
variety of synthetic procedures including: (i) reduction
of a chlorophosphane with an alkali metal Eq. (1); (ii)
oxidative coupling of a lithium phosphanide by a
transition or main group metal centre Eq. (2); and (iii)
oxidative coupling of a lithium phosphanide mediated
by 1,2-dibromoethane Eq. (3). Such diphosphanes have
been the subject of detailed NMR studies in solution
and several have been structurally characterised by X-
sphane products, RP(H)ꢀ
/
P(H)R and R2Pꢀ
/
PR2, as well
as (or, in some cases, rather than) the expected
phosphanes [4,7]. For example, whereas the reaction of
{(2-C5H3Nꢀ
ether at ꢃ78 8C yields the corresponding primary
arsine {(2-C5H3Nꢀ6-Me)(Me3Si)2C}AsH2, treatment
of the dichlorophosphane {(2-C5H3Nꢀ6-Me)(Me3-
Si)2C}PCl2 with LiAlH4 under the same conditions
yields the disecondary diphosphane {(2-C5H3Nꢀ6-
6-
/6-Me)(Me3Si)2C}AsCl2 with LiAlH4 in
/
/
/
ray crystallography [1ꢁ6].
/
/
Me)(Me3Si)2C}P(H)ꢀ
/
P(H){C(SiMe3)2(2-C5H3Nꢀ
/
2RR?PClꢂ2Na 0 RR?PꢀPRR?ꢂ2NaCl
2(RR?P)LiꢂMnꢂ 0 RR?PꢀPRR?ꢂM(nꢃ2)ꢂ
[Mꢀe:g: ZrIV; HgII]
(1)
(2)
Me)} [5]. Notably, when this reaction is carried out
under the same conditions with THF as solvent the
complexes [{(2-C5H3Nꢀ
/6-Me)(Me3Si)2C}E(H)AlH2]2
2(RR?P)LiꢂBrCH2CH2Br 0 RR?PꢀPRR?
ꢂCH2ꢁCH2 ꢂ2LiBr
(EꢀP, As) are isolated [5], illustrating the sensitivity
/
of reductions mediated by LiAlH4 to the specific
reaction conditions. The LiAlH4-mediated oxidative
coupling of chlorophosphanes is seemingly favoured
when the chlorophosphane has sterically demanding
substituents. We now report that, under certain condi-
(3)
The reduction of dichlorophosphanes, RPCl2, and
chlorophosphanes, R2PCl, to the corresponding pri-
mary and secondary phosphanes RPH2 and R2PH is
typically achieved with high efficiency by their reaction
tions, reduction of the chlorophosphanes PCl(R)(C6H4ꢀ
2-CH2NMe2) and RPCl2 [Rꢀ(Me3Si)2CH] by LiAlH4
/
/
gives the corresponding diphosphanes as major by-
* Corresponding author. Fax: ꢂ
/
44-191-2226929
E-mail address: k.j.izod@ncl.ac.uk (K. Izod).
products.
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 4 3 4 - 1

44
S. Blair et al. / Journal of Organometallic Chemistry 656 (2002) 43ꢁ48
/
2. Results and discussion
both the re-dissolved crystalline materials and their
precursor solutions shows that for 2 the rac ꢁmeso ratio
/
We recently reported that the reaction of
is ca. 1:5, whilst for 3 this ratio is 2:3 and that these
ratios are essentially unchanged upon crystallisation.
The 1H-, 13C- and 31P-NMR spectra of 2 are as
expected and clearly show the presence of both diaster-
PCl{CH(SiMe3)2}(C6H4ꢀ
etherꢁTHF (2:5 ratio) under conditions of reflux gives
the expected secondary phosphane PH{CH(SiMe3)2}-
(C6H4ꢀ2-CH2NMe2) (1) in good yield [8]. However,
when this reduction is carried out at low temperature (ꢃ
/2-CH2NMe2) with LiAlH4 in
/
1
/
eomers, although in the H spectrum signals due to the
two diastereomers overlap in several instances. Unu-
/
sually, in the 13C-NMR spectrum of 2 31Pꢁ13
C coupling
/
78 8C) in the same solvent system in the presence of an
excess of LiAlH4, the diphosphane {P(CH[SiMe3]2)-
is resolved for the SiMe3 carbons in both diastereomers,
each signal appearing as a triplet due to coupling to the
two phosphorus atoms, both of which appear to have
(C6H4ꢀ/2-CH2NMe2)}2 (2) is formed in moderate yield,
along with variable amounts of 1Eq. (4). These two
products may be separated by crystallisation from cold
ether, from which pale yellow crystals of 2 suitable for
X-ray crystallography may be isolated after standing at
similar coupling constants [JPC(average)ꢀ5.1 and 2.7
/
Hz (meso-isomer) and 2.2 Hz (rac-isomer, the signal due
to the second of the diastereotopic SiMe3 groups is
obscured by signals due to the meso-diastereomer)].
The non-decoupled 31P-NMR spectrum of 3 com-
ꢃ
/
30 8C for 2 weeks. Compound 2 may be isolated
more easily from the reaction of Li[P{CH(SiMe3)2}-
(C6H4ꢀ2-CH2NMe2)] with PbI2 at low temperatures.
/
prises two sets of doublets of doublets, centred at ꢃ
/
96.0
This yields 2 as the major product, along with elemental
lead, lithium iodide and small amounts of the secondary
phosphane 1 Eq. (5). Although certain lead(II) phos-
and ꢃ88.3 ppm (assigned to the rac and meso
/
diastereomers, respectively), consistent with an AA?XX?
? spin system for each diastereomer [1JPH
ꢀ120.0 Hz
/
2
(rac), 136.4 Hz (meso); JPH
phanides Pb(PR2)2 are accessible [9ꢁ
noted that these are frequently thermally unstable,
decomposing to the diphosphane R2PꢀPR2 and ele-
mental lead. For example, the homoleptic, dimeric
lead(II) diphosphanide
{(Me3Si)2P}Pb{m-P(Si-
/
11], it has been
ꢀ65.5 Hz (rac), 58.1 Hz
/
(meso)] (Fig. 1). The multiplet signal due to the rac-
isomer also shows additional splitting due to coupling
between each phosphorus and the a-proton of the
/
adjacent CH(SiMe3)2 substituent [2JPH
ꢀ7.5 Hz]. The
/
corresponding 1H-NMR spectrum of 3 exhibits complex
doublet of doublet signals for the PH protons in both
Me3)2}2Pb{P(SiMe3)2} may be isolated at ambient
temperature; however, this compound decomposes to
{(Me3Si)2P}2 and elemental lead on heating under reflux
in benzene solution for 10ꢁ
between Li[P{CH(SiMe3)2}(C6H4ꢀ
PbI2 it appears that the lead(II) diphosphanide inter-
2-CH2NMe2)]2, is
/
15 min [9]. In the reaction
/
2-CH2NMe2)] and
mediate, Pb[P{CH(SiMe3)2}(C6H4ꢀ
/
thermally unstable even at temperatures below ambient,
decomposing to 2 and elemental lead in situ.
PClfCH(SiMe3)2g(C6H4ꢀ2-CH2NMe2)
ꢂLiAlH40xfP(CH[SiMe3]2)
 (C6H4ꢀ2-CH2NMe2)g2 (2)
ꢂy[PHfCH(SiMe3)2g(C6H4ꢀ2-CH2NMe2)] (1)
(4)
(5)
2Li[PfCH(SiMe3)2g(C6H4ꢀ2-CH2NMe2)]
ꢂPbI20fP(CH[SiMe3]2)
 (C6H4ꢀ2-CH2NMe2)g (2)ꢂ2LiIꢂPb0
2
The LiAlH4-mediated reduction of the related di-
chlorophosphane RPCl2 [Rꢀ(Me3Si)2CH] in ether
under reflux also gives substantial quantities of the
diphosphane RP(H)ꢀP(H)R (3), along with the expected
/
/
primary phosphane RPH2 (4). Compounds 3 and 4 are
both highly soluble in hydrocarbon and ethereal sol-
vents but may readily be separated by crystallisation
from the extremely poor solvent hexamethyldisiloxane,
from which colourless crystals of 3 may be isolated.
Both 2 and 3 crystallise as mixtures of rac and meso
1
diastereomers; integration of the H-NMR spectra of
Fig. 1. Non-decoupled 31P-NMR spectrum of 3 in d8-toluene.

S. Blair et al. / Journal of Organometallic Chemistry 656 (2002) 43ꢁ
/48
45
diastereomers; further splitting due to additional cou-
pling between the PH and Si2CH protons is also
observed on these signals, although this is not comple-
tely resolved.
X-ray crystal structures were obtained for the meso-
diastereomers of both 2 and 3 (in both cases crystals of
the rac and meso forms adopt the same habit and are
therefore impossible to distinguish by eye). The mole-
cular structures of 2 and 3 are shown in Figs. 2 and 3,
respectively and details of bond lengths and angles for
both compounds are listed in Table 1. As far as we are
aware 3 is only the third example of a disecondary
diphosphane to be crystallographically characterised.
Fig. 3. Molecular structure of 3 with 40% probability ellipsoids and
with H atoms omitted for clarity.
Table 1
˚
Selected bond lengths (A) and angles (8) for 2 and 3
The other two examples, (mes)PHꢀ
C5H3Nꢀ6-Me)(Me3Si)2C}P(H)ꢀ
C5H3Nꢀ6-Me)} [5], also contain relatively bulky sub-
stituents at phosphorus [mesꢀ2,4,6-Me3ꢀC6H2].
In spite of the large steric bulk of the substituents in 2
/PH(mes) [3] and {(2-
/
/
P(H){C(SiMe3)2(2-
2
3
/
˚
Bond lengths (A)
/
/
PꢀP?
2.2304(6)
PꢀP?
2.2086(8)
C(10)ꢀSi(1)
Si(1)ꢀC(12)
Si(2)ꢀC(15)
PꢀC(9)
C(10)ꢀSi(2)
Si(1)ꢀC(13)
Si(2)ꢀC(16)
PꢀC(10)
1.9125(12) C(1)ꢀSi(2)
1.8726(14) Si(1)ꢀC(4)
1.8725(14) Si(2)ꢀC(7)
1.8549(12) PꢀC(1)
1.8934(12) Si(1)ꢀC(2)
1.8690(15) Si(2)ꢀC(5)
1.8705(14) C(1)ꢀSi(1)
1.8813(12) Si(1)ꢀC(3)
1.8791(14) Si(2)ꢀC(6)
1.8755(14)
1.8892(15)
1.8697(18)
1.8673(18)
1.8679(15)
1.8600(18)
1.8676(18)
1.8819(15)
1.8711(18)
1.8685(17)
˚
and 3, the Pꢀ
respectively, are well within the range of distances found
for other diphosphanes, although, as expected, the Pꢀ
distance in the more sterically encumbered 2 is signifi-
cantly greater than that in 3. For example, the Pꢀ
/P distances of 2.2304(6) and 2.2086(8) A,
/P
/P
distances in (mes)2Pꢀ
/
P(mes)2, Cy2Pꢀ
/
PCy2 and Ph4C4Pꢀ
/
˚
PC4Ph4 are 2.260(1), 2.215(3) and 2.2051(11) A, respec-
tively. In contrast, in the recently reported, closely
S(1)ꢀC(11)
Si(2)ꢀC(14)
Bond angles (8)
P?ꢀPꢀC(10)
C(9)ꢀPꢀC(10)
PꢀC(10)ꢀSi(2)
P?ꢀPꢀC(9)
PꢀC(10)ꢀSi(1)
Si(1)ꢀC(10)ꢀSi(2)
related, ditertiary diphosphane R2Pꢀ
/
PR2 [Rꢀ
/
99.70(4)
107.80(5)
120.07(6)
99.93(4)
P?ꢀPꢀC(1)
100.14(5)
109.48(7)
109.43(8)
119.11(7)
˚
CH(SiMe3)2] the PꢀP distance is 2.3103(7) A, the
/
PꢀC(1)ꢀSi(2)
PꢀC(1)ꢀSi(1)
Si(1)ꢀC(1)ꢀSi(2)
longest such distance to be reported, possibly due to
steric interactions between the bulky substituents [2].
There is no contact between the N atoms of the
benzylamine substituents and the P atoms in 3.
111.88(6)
115.71(6)
accord with the majority of diphosphanes for which a
solid state structure has been obtained; for example,
Both 2 and 3 crystallise in an antiperiplanar con-
formation with a crystallographic centre of inversion
midway between the two phosphorus atoms. This is in
(mes)2Pꢀ
/
P(mes)2 crystallises in an essentially antiper-
iplanar conformation with a dihedral angle of 1588
between the nominal lone pair directions [1,12], whilst
(mes)PHꢀ/PH(mes) crystallises with a crystallographic
inversion centre [3] (however, there are several examples
of diphosphanes which adopt an anticlinal conforma-
tion in the solid state [13ꢁ16]). Such an antiperiplanar
/
arrangement is perhaps more likely in 2 and 3 due to the
size of the substituents at phosphorus, although detailed
NMR studies on the sterically encumbered diphosphane
(mes)2Pꢀ/P(mes)2 suggest that a synclinal conformation
is favoured in solution for this molecule, i.e. in the
absence of crystal packing forces [1]. The hydrogen
atoms bonded to phosphorus in 3 appear to be
disordered over the two possible positions that would
give a pyramidal geometry at P, with small electron
density peaks in these positions. These H atoms were
not included in the refinement.
Fig. 2. Molecular structure of 2 with 40% probability ellipsoids and
with H atoms omitted for clarity.

46
S. Blair et al. / Journal of Organometallic Chemistry 656 (2002) 43ꢁ48
/
Since the LiAlH4-mediated reduction of 3 gives
(SiMe3)2}(C6H4ꢀ
/
2-CH2NMe2)] [8] were prepared ac-
mixtures of primary phosphane and secondary dipho-
sphane we were interested to see whether alternative
reducing agents would have a similar effect on the
dichlorophosphine RPCl2. Alternative methods for the
synthesis of primary phosphanes include the reduction
of dichlorophosphanes with Bun3SnH [17]. We find that
cording to previously published procedures.
1H- and 13C-NMR spectra were recorded on a Bruker
Avance 300 spectrometer operating at 300.1 and 75.5
MHz, respectively, and chemical shifts are quoted in
ppm relative to Me4Si; 31P-NMR spectra were recorded
on a Bruker AC300 spectrometer operating at 121.5
MHz and are quoted in ppm relative to external 85%
H3PO4. Elemental analyses were obtained by Elemental
Microanalysis Ltd., Okehampton, UK.
treatment of RPCl2 [Rꢀ
Bun3SnH or Ph3SnH in ether yields a mixture of products
PHR and the known cyclic
/(Me3Si)2CH] with either
containing RPH2, RPHꢀ
/
triphosphane (RP)3 [18,19] in the approximate ratio
8:11:1 Eq. (6).
4.2. Preparation of {P(CH[SiMe3]2)(C6H4ꢀ
CH2NMe2)}2 (2)
/2-
RPCl2 ꢂ2Bun3SnH E0t2O xRPH2 ꢂyRPHꢀPHRꢂz(RP)3
4.2.1. Method (a)
[RꢀCH(SiMe3)2]
(6)
To
CH2NMe2) (0.87 g, 2.416 mmol) in etherꢁ
ml/25 ml) at ꢃ78 8C was added LiAlH4 (0.09 g, 2.371
a
solution of PCl{CH(SiMe3)2}(C6H4ꢀ
/
2-
We attribute the formation of these three species to the
radical-based nature of tin hydride reductions.
/
THF (10
/
mmol). This mixture was allowed to attain room
temperature (r.t.) and was stirred for 2 h. De-oxyge-
nated water was carefully added and the organic phase
was decanted and dried over activated 4A molecular
sieves. Evaporation of the solvent under reduced
pressure yielded a colourless oil containing both 1 and
2 from which crystals of 2 formed in ca. 10% yield after
standing for 2 weeks at r.t.
3. Conclusions
The products of the reduction of certain primary and
secondary chlorophosphanes with lithium aluminium
hydride are highly sensitive to the reaction conditions.
Changes to either the reaction temperature or solvent
may affect the ratio of the expected primary or
secondary phosphane in comparison to diphosphane
products: compound 2 may be isolated in moderate yield
from the reduction of the respective chlorophosphane
with LiAlH4 at low temperature, whilst the same
4.2.2. Method (b)
To a cold (ꢃ
mmol) in ether (30 ml) was added, dropwise, a solution
of Li[P{CH(SiMe3)2}(C6H4ꢀ2-CH2NMe2)] (1.19 g,
/
78 8C) suspension of PbI2 (0.91 g, 1.974
/
3.596 mmol) in ether (20 ml). This mixture was allowed
to warm to r.t. and was stirred for 12 h. The dark
reaction mixture was filtered and the filtrate was
reaction carried out in refluxing etherꢁTHF yields the
/
secondary phosphane 1 as the exclusive product. The
formation of diphosphane products appears to be
favoured by sterically demanding substituents at phos-
phorus.
concentrated to ca. 10 ml and cooled to ꢃ30 8C for
/
12 h. The pale yellow crystals of 2 were isolated by
filtration, washed with a little light petroleum and dried
in vacuo. Yield: 0.91 g, 78%. Anal. Found: C, 57.57; H,
9.93; N, 4.14. Calc. for C32H62N2P2Si4: C, 59.21; H,
4. Experimental
1
9.63; N, 4.32%. H-NMR (d8-C6H5CH3, 295 K): meso-
isomer: 0.10 (s, 9H, SiMe3), 0.16 (s, 9H, SiMe3), 0.41 (s,
4.1. General Comments
1H, Si2CH), 2.34 (s, 6H, NMe2), 3.87 (d, JHH
ꢀ/14.0 Hz,
1H, CH2N), 4.20 (d, JHH 14.0 Hz, 1H, CH2N), 7.19
ꢀ
/
All manipulations were carried out using standard
Schlenk techniques under an atmosphere of dry nitro-
(m, 2H, ArH), 7.72 (m, 1H, ArH), 8.42 (m, 1H, ArH);
rac-isomer: 0.14 (s, 9H, SiMe3), 0.44 (s, 9H, SiMe3), 0.77
gen. Ether, THF and light petroleum (b.p. 40ꢁ
/
60 8C)
(t, JPH
(d, JHH
ꢀ
ꢀ
/
3.6 Hz, 1H, Si2CH) 2.29 (s, 6H, NMe2), 3.62
13.3 Hz, 1H, CH2N), 3.80 (d, JHH 13.3 Hz,
1H, CH2N), 6.73 (m, 1H, ArH), 6.95 (m, 1H, ArH), 7.42
were distilled from sodiumꢁpotassium alloy under an
/
/
ꢀ
/
atmosphere of dry nitrogen and stored over a potassium
film (except THF which was stored over activated 4A
molecular sieves). Hexamethyldisiloxane was distilled
from CaH2 under an atmosphere of dry nitrogen and
was stored as for THF. Deuterated C6H5CH3 was
distilled from potassium and was deoxygenated by three
freeze-pump-thaw cycles and stored over activated 4A
(m, 1H, ArH), 7.65 (m, 1H, ArH). 13C{1H}-NMR (d8-
C6H5CH3, 295 K): meso-isomer: 1.59 (t, JPC
SiMe3), 2.17 (t, JPC 2.7 Hz, SiMe3), 9.46 (t, JPC
Hz, Si2C), 44.66 (s, NMe2), 62.23 (t, JPC 12.6 Hz,
CH2N), 125.24 (Ar)128.07 (t, JPC 3.0 Hz, Ar), 128.22
(Ar), 135.37 (t, JPC 12.1 Hz, Ar), 144.93 (t, JPC 13.8
Hz, Ar); rac-isomer: 2.39 (t, JPC 2.2 Hz, SiMe3), 8.27
(t, JPC 19.2 Hz, Si2C), 44.31 (NMe2), 61.18 (t, JPC
ꢀ/10.1 Hz,
ꢀ
/
ꢀ/27.1
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
molecular sieves. PCl{CH(SiMe3)2}(C6H4ꢀ
/
2-CH2-
NMe2) [8], {(Me3Si)2CH}PCl2 [20] and Li[P{CH-
ꢀ
/
ꢀ
/
ꢀ
/

S. Blair et al. / Journal of Organometallic Chemistry 656 (2002) 43ꢁ
/48
47
12.3 Hz, CH2N), 124.47, 127.39 (Ar), 135.50 (t, JPC
6.1 Hz, Ar), 144.01 (t, JPC
13.5 Hz, Ar). 31P{1H}-
NMR (d8-C6H5CH3, 295 K): meso-isomer: ꢃ21.3; rac-
isomer: ꢃ22.4.
ꢀ
/
C6H5CH3, 295 K): meso-isomer: 0.03 (SiMe3), 5.03 (t,
JPC 18.6 Hz, CHSi2); rac-isomer: ꢃ0.10 (SiMe3), 4.14
(d, JPC
19.7 Hz, CHSi2). 31P{1H}-NMR (d8-
C6H5CH3, 295 K): meso-isomer: ꢃ96.0; rac-isomer:
88.3.
ꢀ
/
ꢀ
/
/
/
ꢀ
/
/
/
ꢃ
/
4.3. Preparation of {PH(CH[SiMe3]2)}2 (3)
4.4. Reaction of {(Me3Si)2CH}PCl2 with Ph3SnH
To a solution of {(Me3Si)2CH}PCl2 (1.98 g, 7.58
mmol) in ether (20 ml) was added LiAlH4 (0.80 g, 21.1
mmol). This mixture was heated under reflux for 4 h,
cooled and then de-oxygenated water was added (25 ml).
The organic phase was extracted with light petroleum
To a solution of {(Me3Si)2CH}PCl2 (0.73 g, 2.79
mmol) in cold (0 8C) ether (10 ml) was added, dropwise,
a solution of Ph3SnH (1.96 g, 5.58 mmol) in ether (10
ml). This mixture was allowed to attain r.t. and was
stirred for 16 h. Light petroleum (5 ml) was added and
the solids were removed by filtration. The filtrate was
concentrated to ca. 5ml and a 31P{1H}-NMR spectrum
was obtained, revealing the presence of RPH2 (ca. 40%),
(3ꢄ
sieves. Solvent was removed in vacuo to give a colour-
less oil from which colourless crystals of rac ꢁmeso-3
/10 ml) and dried over activated 4A molecular
/
(ca. 2:3 ratio) appeared after standing for 16 h. Crystals
of 3 suitable for X-ray crystallography were obtained
RPHꢀ
(etherꢁ
Hz, (RP)3), ꢃ
Hz, (RP)3), ꢃ96.0 (s, meso-RPHꢀ
RPHꢀPHR).
/
PHR (ca. 55%) and (RP)3 (ca. 5%). 31P-NMR
from cold (ꢃ
crystalline rac ꢁ
/
30 8C) hexamethyldisiloxane. Yield of
meso-3: 0.67 g, 46%. Anal. Found: C,
/
light petroleum, 295 K): ꢃ
147.1 (s, RPH2), ꢃ128.3 (d, JPP
PHR), ꢃ88.3 (s, rac-
/
155.2 (t, JPP
ꢀ
/
198.5
/
/
/
ꢀ/198.5
41.12; H, 10.55. Calc. for C14H40P2Si4: C, 43.93; H,
/
/
/
1
10.53%. H-NMR (d8-C6H5CH3, 295 K): meso-isomer:
0.15 (s, 9H, SiMe3), 0.16 (s, 9H, SiMe3), 0.29 (s, 1H,
/
A similar reaction between {(Me3Si)2CH}PCl2 and
1
CHSi2), 3.11 (dd, JPH
2
136.4 Hz, JPH
ꢀ
/
ꢀ58.1 Hz, 1H,
/
Bun3SnH in ether at 0 8C gave substantially greater
PH); rac-isomer: 0.13 (s, 9H, SiMe3), 0.19 (s, 9H,
120.0
quantities of RPH2 contaminated with RPHꢀ
/PHR and
1
SiMe3), 0.32 (s, 1H, CHSi2), 3.43 (dd, JPH
ꢀ
/
(RP)3.
2
Hz, JPH
ꢀ
/
66.5 Hz, 1H, PH). 13C{1H}-NMR (d8-
4.5. Crystal structure determination of meso-2 and meso-
3
Table 2
Table 2
Crystallographic data for 2 and 3
Data were collected at 160 K on a Bruker AXS
2
3
SMART CCD diffractometer with graphite-monochro-
˚
Ka radiation (lꢀ0.71073 A). Structure
mated Moꢁ
/
/
Empirical formula
Formula weight
Crystal system
Space group
C32H62N2P2Si4
649.14
C14H40P2Si4
382.76
Triclinic
solution was by direct methods and refinement was by
full matrix least-squares on F2. Absorption correction
was by semi-empirical methods from equivalents and
repeated reflections. Further details of data collection
and refinement are given in Table 2 and in the
supporting information. Programs used: BRUKER AXS
SMART (diffractometer control), SAINT (data integra-
tion), and SHELXTL (structure solution and refinement).
Monoclinic
P21/n
¯
/
P1/
˚
a (A)
12.6787(8)
10.6897(7)
14.8800(9)
6.5376(7)
8.1120(9)
12.2027(13)
106.375(2)
93.835(2)
103.031(2)
598.99(11)
2
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
V (A )
Z
102.631(12)
3
˚
1967.9(2)
2
Dcalc. (g cmꢃ1
)
1.095
0.255
1.061
0.375
m (mmꢃ1
)
Crystal size (mm)
Reflections
0.70ꢄ0.65ꢄ0.20 0.55ꢄ0.32ꢄ0.22
5. Supplementary material
16 462
4658
5160
2732
Unique reflections
Reflections with F2ꢀ2s
Parameters
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 179744 and 179743 for
compounds 2 and 3, respectively. Copies of this
information are available free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: (int. code) ꢂ44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.ca-
m.ac.uk).
4085
189
2421
97
a
R, Rw [F2ꢀ2s]
0.0278, 0.0742
0.0333, 0.0776
1.042
0.0358, 0.1034
0.0395, 0.1064
1.077
a
R, Rw [all data]
Goodness-of-fit on F2 b
Largest difference peak/hole 0.32, ꢃ0.22
0.68, ꢃ0.54
ꢃ3
˚
(e A
)
/
a
Rꢀa jjFojꢃjFcjj/a jFoj;
/
Rw ꢀ[S w(Fo2 ꢃFc2)2=(S wFo2)2]1=2
:/

48
S. Blair et al. / Journal of Organometallic Chemistry 656 (2002) 43ꢁ48
/
[8] W. Clegg, S. Doherty, K. Izod, H. Kagerer, P. O’Shaughnessy,
J.M. Sheffield, J. Chem. Soc. Dalton Trans. (1999) 1825.
[9] S.C. Goel, M.Y. Chiang, D.J. Rauscher, W.E. Buhro, J. Am.
Chem. Soc. 115 (1993) 160.
Acknowledgements
This work was supported by the EPSRC and The
Royal Society.
[10] A.A. Arif, A.H. Cowley, R.A. Jones, J.M. Power, Chem.
Commun. (1986) 1446.
[11] M. Driess, R. Janoschek, H. Pritzkow, S. Rell, U. Winkler,
Angew. Chem. Int. Ed. Engl. 34 (1995) 1614.
References
[12] S.G. Baxter, A.H. Cowley, R.E. Davies, P.E. Riley, J. Am. Chem.
Soc. 103 (1981) 1699.
[1] W. McFarlane, N.H. Rees, L. Constanza, M. Patel, I.J. Colqu-
houn, J. Chem. Soc. Dalton Trans. (2000) 4453 (and references
therein).
[13] H. Westermann, M. Nieger, Inorg. Chim. Acta 177 (1990) 11.
[14] R. Richter, J. Kaiser, J. Sieler, H. Hartung, C. Peter, Acta
Crystallogr. Sect. B 33 (1977) 1887.
[2] S.L. Hinchley, C.A. Morrison, D.W.H. Rankin, C.L.B. Macdo-
nald, R.J. Wiacek, A.H. Cowley, M.F. Lappert, G. Gundersen,
J.A.C. Clyburne, P.P. Power, Chem. Commun. (2000) 2045.
[3] S. Kurz, H. Oessen, J. Sieler, E. Hey-Hawkins, Phosphorus Sulfur
Silicon 117 (1996) 189.
[15] C.J. Harlan, R.A. Jones, S.U. Koschmieder, C.M. Nunn, Poly-
hedron 9 (1990) 699.
[16] J.K. Vohs, P. Wei, J. Su, B.C. Beck, S.D. Goodwin, G.H.
Robinson, Chem. Commun. (2000) 1037.
[17] J. Escudie, C. Couret, H. Ranaivonjatovo, M. Lazraq, J. Satge,
Phosphorus Sulfur 31 (1987) 27.
[4] P.C. Andrews, S.J. King, C.L. Raston, B.A. Roberts, Chem.
Commun. (1998) 547.
[18] A.H. Cowley, J.E. Kilduff, S.K. Mehrotra, N.C. Norman, M.
Pakulski, Chem. Commun. (1983) 528.
[5] P.C. Andrews, C.L. Raston, B.A. Roberts, Chem. Commun.
(2000) 1961.
[6] S. Loss, C. Widauer, H. Grutzmacher, Angew. Chem. Int. Ed.
¨
[19] A. Baldy, J. Estienne, Acta Crystallogr. Sect. C. 44 (1988)
747.
Engl. 38 (1999) 3329.
[7] G. Bala´zs, H.J. Breunig, E. Lork, W. Offermann, Organometallics
20 (2001) 2666.
[20] M.J.S. Gynane, A. Hudson, M.F. Lappert, P.P. Power, H.
Goldwhite, J. Chem. Soc. Dalton Trans. (1980) 2428.