The open-chain triphosphanes RMe2SiCH2P(PR′ 2)2 (R = Me, Ph; R′ = SiMe3, Cy, Ph)

Article abstract of DOI:10.1039/c1dt11499a

The triphosphanes RMe₂SiCH₂P(PR′₂) ₂ (R = Me, Ph; R′ = SiMe₃, Cy) are synthesised in good yield via metathesis of organodichlorophosphanes and LiPR′ ₂, while for R′ = Ph a propensity to form (Ph ₂P)₂ precludes isolation of the in situ characterised triphosphanes. Where R = Me and R′ = SiMe₃ the triphosphane has also been characterised by single crystal X-ray diffraction and exhibits a single geometric conformer in the solid state, though solution-phase NMR spectra are indicative of facile conformational exchange across a wide temperature range. All of the described triphosphanes exhibit comparable behaviour, with their respective ³¹P{¹H} NMR spectra manifesting anomalous 'second-order' characteristics, which are considered using full spin-Hamiltonian simulation. Preliminary studies of coordination chemistry and ancillary reactivity of the triphosphanes are described. The Royal Society of Chemistry.

Full text of DOI:10.1039/c1dt11499a

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PAPER
The open-chain triphosphanes RMe2SiCH2P(PR¢2)2 (R = Me, Ph;
R¢ = SiMe3, Cy, Ph)†
Charlotte E. Averre, Martyn P. Coles, Ian R. Crossley* and Iain J. Day
Received 8th August 2011, Accepted 21st September 2011
DOI: 10.1039/c1dt11499a
The triphosphanes RMe2SiCH2P(PR¢2)2 (R = Me, Ph; R¢ = SiMe3, Cy) are synthesised in good
yield via metathesis of organodichlorophosphanes and LiPR¢2, while for R¢ = Ph a propensity
to form (Ph2P)2 precludes isolation of the in situ characterised triphosphanes. Where R = Me and
R¢ = SiMe3 the triphosphane has also been characterised by single crystal X-ray diffraction and exhibits
a single geometric conformer in the solid state, though solution-phase NMR spectra are indicative
of facile conformational exchange across a wide temperature range. All of the described triphosphanes
1
exhibit comparable behaviour, with their respective 31P{ H} NMR spectra manifesting anomalous
‘second-order’ characteristics, which are considered using full spin-Hamiltonian simulation. Preliminary
studies of coordination chemistry and ancillary reactivity of the triphosphanes are described.
As part of a study targeting reactive molecules bearing P–P and
Introduction
P–Si functionalities, we report herein the synthesis of a series of
triphosphanes built around the “RMe2SiCH2P” core. We further
discuss selected spectroscopic facets and outline preliminary
reactivity studies.
Open-chain polyphosphanes1 have been studied for over 50 years,
both as polydentate chelates for application to homogeneous
catalysis,2 and as ‘building blocks’ for more elaborate organophos-
phorus molecules.3 While research toward both goals is currently
being dominated by compounds of low-coordinate phosphorus,
e.g. phosphinines,4 triphosphabenzenes,5 polyphospholides6 and
complexes and cages derived from these,7 in addition to recent
advances in the controlled activation of the P4 molecule by
transition metals8 and amino-stabilised carbenes,9 the study of
classical polyphosphanes remains an active field.
Results and discussion
Applying a classical approach to triphosphanes, the low-
temperature metathesis between LiPR¢2 and RMe2SiCH2PCl2
(R = Me 1, Ph 2)‡ offered facile access to crude samples of
the compounds RMe2SiCH2P(PR¢2)2 (R = Me, R¢ = SiMe3 (3),
Cy (4); R = Ph, R¢ = SiMe3 (5) Cy (6), Scheme 1), obtained as
viscous oils. Each compound was readily formulated on the basis
of characteristic NMR spectroscopic data, consistent with their
constituent functionalities, the core ‘P3’ unit being apparent from
Notwithstanding, open-chain triphosphanes remain the least
well studied of such materials, though recent notable reports
have included isolation of the stable 1,3-dihydrotriphosphane
(TbtHP)2PFc (Fc = ferrocenyl, Tbt = 2,4,6-{CH(SiMe3)2}3-
C6H2),10 extrusion of DmpP(PPh2)2 (Dmp = 2,6-Mes2C6H3) from
the terminal zirconium phosphinidene [Cp2Zr PDmp(PMe3)]
with Ph2PCl,11 formation of HP{P(H)(tBu)→W(CO)5}2 via a
Cp* ring-expansion protocol12 and the electrophilic ring-opening
1
two distinctive 31P{ H}-NMR resonances (2 : 1 ratio), seemingly
exhibiting the ‘simple’ doublet-of-doublet multiplicities (1JPP 300–
330 Hz) of an AMM¢ spin-system (vide infra). The relative
positions of said resonances vary between the compounds in
accordance with the differing influence of alkyl vs. silyl substituents
(e.g. for 3 dP -162.2, 2P, -58.0, 1P; cf. 4, dP -3.4, 2P, -84.1, 1P).
Analytically pure samples of 3, 4 and 6 were furnished by
slow cooling, to -80 ◦C, of concentrated n-pentane solutions,
whereby 3 and 4 were obtained in moderate yield (~ 40%) as
white solids, the former as X-ray quality single crystals (vide
of (tBuP)3As to afford BuP(PtBuR)2 (R = Me, benzyl, allyl).13
t
Typically, however, the triphosphanes are ancillary to the prevail-
ing foci, thus relatively few examples have been comprehensively
characterised. This is particularly so with respect to more reactive
species bearing hydride or silyl substituents at phosphorus, the
range of which is limited to (TbtHP)2PFc,10 Me3SiP{PR2}2 (R =
NiPr2,14 Ph,14 tBu15) and P{PMe(SiMe3)}3.16
‡ The synthesis of 1 from Me3SiCH2MgCl and PCl3 is documented17 and
typically requires treatment with anhydrous HCl to destroy the presumed
complex 1.MgCl2 and furnish acceptable yields (40–60%). We, however,
have found that the latter step can be dispensed with by permitting the
reaction to stir (-10 ◦C → r.t.) over 12 h before isolation. In this fashion we
have routinely achieved yields in excess of 75%. Comparable methodology
has been applied to the synthesis of the novel derivative 2 (see experimental
section).
Department of Chemistry, University of Sussex, Falmer, Brighton, UK.
E-mail: i.crossley@sussex.ac.uk; Fax: +44 1273 876687; Tel: +44 1273
877302
† Electronic supplementary information (ESI) available. Crystal data for 3
(CCDC reference number 835037) in CIF format, phosphorus spectra and
simulations for compounds 3 to 10. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt11499a
278 | Dalton Trans., 2012, 41, 278–284
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Scheme 1 Reagents and conditions: i) Mg, Et2O, r.t., 12 h.; ii) PCl3; iii)
2 LiP(SiMe3)2, -78 ◦C→r.t., 2 h.; iv) 2 LiPCy2, -78 ◦C→r.t., 2 h.; v) 2
LiPPh3, -78 ◦C→r.t., 1 h.; vi) 12 h.
Fig. 1 Molecular structure of Me3SiCH2P{P(SiMe3)2}2 (3) with Me3Si
based hydrogen atoms omitted for clarity and thermal ellipsoids at the
˚
50% probability level. Selected bond distances (A) and angles (deg.):
infra). In contrast, the yield of pure 6 was below 5%, though
appreciable quantities remained in solution in admixture with
P2Cy4 (dP -21.3;18 ratio of 6 : P2Cy4 = 2 : 1) as the sole contaminant;
this mixture is, however, adequate for pursuit of coordination
chemistry, 6 reacting preferentially. Attempts to obtain 5 in
analytical purity were unsuccessful, this material being heavily
contaminated by numerous species including P(SiMe3)3 (dP -252).
The diphenylphosphino compounds RMe2SiCH2P(PPh2)2 were
similarly pursued, but with limited success; indeed, only for
R = Me (7) was the desired product obtained. However, though
spectroscopically identifiable in the crude mixture, 7 is unstable
both in solution and the solid state, decomposing over several
hours to P2Ph4 (dP -14.8)18 and intractable by-products, even at
-80 ◦C. The proclivity for P2Ph4 extrusion from triphosphanes
is documented,19 and can be ascribed to predominant electronic
influences, given that the more sterically encumbered 4 and 6 are
solution-stable, albeit that traces of P2Cy4 form alongside 6.
P1–P2 2.2197(5), P2–P3 2.1951(5), P1–Si1 2.2608(5), P1–Si2 2.2553(5),
P3–Si4 2.2540(5), P3–Si5 2.2558(5), P2–C7 1.8491(15), P1–P2–P3
110.877(9), P1–P2–C7 108.49(5), P3–P2–C7 102.93(5), Si1–P1–Si2
103.98(2), Si4–P3–Si5 108.06(2).
Fig. 2 Conformational arrangements of compound 3; conformations
3a to c are ‘in-plane’, involving coplanarity of the lone pairs, while 3d
involves staggering of the lone pairs in an ‘out-of-plane’ arrangement.
Conformation 3a alone is adopted in the solid state.
(3d) state.§ These data do not, however, indicate retention of the
3a conformation in solution, as this would impose chirality at
the central phosphorus atom, rendering the methylenic protons
(Me3SiCH2P-) diastereotopic, a scenario that is not observed.
Rather, one must conclude facile equilibration of the magnetic
environment of each terminal phosphido unit across the observed
temperature range.
Structural features of the triphosphanes
The solid-state structure of the pyrophoric triphosphane 3
(Fig. 1) is based around a pyramidal phosphorus centre, with P–P
distances being typical of the limited range of previously studied
triphosphanes. Appreciable disparity is noted between the two
˚
NMR spectroscopic features
P–P linkages (0.025 A), as is often observed for such materials,
though in 3 this is more extreme than the norm (ca. 0.002 A)20 and
˚
Given these data, the apparent observation of an AMM¢ phos-
phorus spin system (Fig. 3), a ubiquitous assertion within the
triphosphane literature,12,23 is anomalous and warrants further
comment. In lieu of magnetic inequivalence of the terminal
phosphido units, the origin of second-order behaviour (i.e. such as
gives rise to an apparent AMM¢ pattern) must, necessarily, derive
from the spin–spin coupling interaction between these (M2) and
16
˚
exceeded only by the related P{PMe(SiMe3)}3 (0.039 A).
In common with Me3SiP{P(NiPr2)2}2,14 Me3SiP(PtBu2)2,15
P{PMe(SiMe3)}3,16 and the trigonal planar P(PtBu3)3,21 the ter-
minal ‘P(SiMe3)2’ moieties of compound 3 adopt exclusively a
syn–anti arrangement22 with respect to their lone-pairs (Fig. 2,
3a). This is significant in that DFT studies (B3LYP/6-311+G**)
reveal an alternative out-of-plane syn–syn arrangement (3d) to
be energetically accessible, lying just 12 kJ mol-1 higher in energy
than 3a. However, no evidence for the 3d conformation is apparent,
1
§ The 31P{ H}-NMR spectra were recorded with a measured S/N ratio of
at least 200/1. At this level, species populations of 2 mol% (approximate
level derived from the 12 kJ mol-1 energy separation) should be readily
observable. The lack of observable 3d species presumably reflects a slightly
higher energy separation in solution vs. gas phase.
even in solution, the 31P{ H}-NMR spectra remaining invariant
1
◦
◦
in the temperature range -80 C to 100 C, thus precluding any
dynamic interchange or population variance of the higher energy
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1
Fig. 3 31P{ H}-NMR resonances associated with the A (top) and M2 (bottom) phosphorus centres of 3.
the central phosphorus (A) atom. Under normal circumstances,
first-order spectra (i.e. a triplet and doublet for an AM2 spin-
system) would be observed where the frequency separation of the
resonances is significantly greater the magnitude of their mutual
coupling, viz. DnA/M ꢀ |JAM| – a manifestation of the ‘Secular
approximation’. Under this so-called weak coupling regime, off-
diagonal elements of the spin Hamiltonian, which correspond to
small differences in eigenvalues, can be discounted and simple
first-order spectra are observed.
Scheme 2 Reagents: i) [PtCl2(PEt3)2], CH2Cl2/C5H12, 1 h. r.t.
significant coordination shifts, while cis-chelation is confirmed
by the presence of 195Pt satellites on the terminal phosphido
resonances (1JPtP = 2998 Hz 8; 2995 Hz 9). All other spectroscopic
data (1H, 13C, 29Si, 195Pt) are internally consistent. It is, however,
In the cases of 3 to 7 inclusive, DnP > 10|JPP|, hence, the
weak coupling regime is anticipated and first order spectra
1
would be observed. Indeed, if the 31P{ H}-NMR spectra of
3
noteworthy that an unusually large JPH coupling (~ 20 Hz),
3 to 7 are simulated as AM2 spin-systems under an imposed
‘weak-coupling’ regime, classical first-order spectra are predicted
(Fig. 4 and ESI†). However, only when the full spin Hamiltonian,
corresponding to the strong-coupling regime, is imposed, do the
predicted spectra mirror precisely the second-order behaviour that
is observed experimentally. It would thus seem that the universal
arbitrary assignment to triphosphanes of AMM¢ spin systems,
with presumed diasterotopicity of the terminal phosphido units, is
likely erroneous in most instances; rather, the observed behaviour
arises as a deficiency of the Secular approximation insofar as it is
applied to the trivial interpretation of experimental spectra.
noted in the free ligands between the central phosphorus atom
and cyclohexyl CH units, has been lost upon coordination,
presumably as a consequence of conformational change. Though
not further studied, we believe this to reflect Karplus behaviour
(i.e. bond mediated), rather than a lone-pair mediated ‘through-
space’ interaction.24
The behaviour of the polysilylated 3 is somewhat more complex.
Its stoichiometric combination with solutions of [PtCl2(SEt2)2]
results in immediate precipitation of a black residue (which is
insoluble and defies characterisation), while notable quantities
of 3 alone are retained in the supernatant liquor. The same be-
haviour is encountered with a range of metal substrates, including
3
[MCl2(NCPh)2] (M = Pd, Pt), [PdCl(h -C3H4R)]2 (R = H, Me),
Coordination chemistry and reactivity studies
3
4
[TpPd(h -C3H5)], [RhCl(h -C8H12)]2 and [RuHCl(CO)(PPh3)3];
even with [W(CO)5(thf)] no evidence for coordination of 3 in any
mode was obtained. In an attempt to probe this behaviour, the re-
Since triphosphanes 3 to 6 would be anticipated to engage readily
in cis-chelation to metal centres, representative examples were
sought. Both 4 and 6 conform to expectation, reacting with
1
4
action between 3 and [RhCl(h -C8H12)]2 was repeated in a sealed
2
2
[PtCl2(SEt2)2] to give cis-[k -P1,P3-{RMe2SiCH2P(PCy2)2}PtCl2]
NMR tube with an internal standard (OPPh3). This revealed
that 70% of 3 is consumed within minutes (concomitant with
formation of the precipitate), the remaining material gradually
degrading over prolonged standing (~ 50% per day). Significantly,
no phosphorus-containing by-products can be observed, while
(R = Me 8, Ph 9, Scheme 2) in high yield. Though single crystals
of 8 and 9 have thus far proven elusive, their identity is clear
from spectroscopic data. Both retain the characteristic AM2
1
coupling patterns in their 31P{ H}-NMR spectra, though with
280 | Dalton Trans., 2012, 41, 278–284
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Fig. 4 Simulated resonances for 3, (A left, B right) imposing strong (top) and weak (bottom) coupling.
1
the H-NMR spectrum confirms the presence in solution of the
free cyclooctadiene ligand and exhibits a resonance consistent
with a Me3Si moiety, though lacking any discernible coupling to
phosphorus. While no further data are available, we suggest that
the rapid degradation of 3 and the metal complex follows from
a P–Si cleavage process, presumably affording a polymeric metal
phosphide species, though this remains unconfirmed.
Cleavage of the P–Si linkages of 3 is indeed facile, as
is evident from its rapid degradation by air and moisture.
Moreover, when combined under ambient conditions, 3 and
dichlorophosphane 1 (1 : 1) undergo rapid condensation (with
liberation of Me3SiCl) to afford the cyclic tetraphosphane
Me3SiCH2P{P(SiMe3)}2PCH2SiMe3 (10, Scheme 3). Initially en-
countered during attempts to prepare Me3SiCH2P(Cl)P(SiMe3)2
from 1 and LiP(SiMe3)2, which afforded instead a mixture of 1, 3
and 10, the origin of the latter was conclusively demonstrated via
a quantitative NMR-scale reaction (PPh3 internal standard).
Fig. 5 AA¢BB¢ phosphorus spin system of 10.
formation of P(SiMe3)3 is often encountered when working
with LiP(SiMe3)2, and we cannot exclude the intermediacy of
Me3SiCH2P(Cl)P(SiMe3)2 in our initial observation of 10, the
defined condensation process is unequivocal and stands as a
viable alternative, perhaps competitive, pathway for each scenario,
given the presence of a dichlorophosphane starting material in all
instances.
Conclusions
We have reported the synthesis and characterisation of several
new triphosphanes, including the solid state structure of the
polysilylated Me3SiCH2P{P(SiMe3)2}2 (3). This has led us to
investigate the anomalous NMR spectroscopic patterns exhibited
by such molecules, from which we conclude that the ubiqui-
tous assignment of AMM¢ spin systems is erroneous, a more
appropriate description being AM2 under a regime of ‘strong-
coupling’; i.e. for such molecules, the accepted precept that for
DnA/M ꢀ |JAM| first-order spectra are obtained does not hold.
Finally, we have demonstrated that while the alkyl-substituted
triphosphanes readily engage in chelation to metal centres,
polysilylated 3 preferentially degrades to an intractable (presumed
polymeric) material, behaviour attributable to facile P–Si cleavage.
This also leads to 3 reacting with dichlorophosphanes to afford
cyclic tetraphosphanes under mild conditions, chemistry that we
continue to explore.
Scheme 3 Reagents and conditions: i) 1 equiv. LiP(SiMe3)2, -78 ◦C → r.t.,
2 h.; ii) Me3SiCH2P{P(SiMe3)2}2 (3), C6D6, r.t., 16 h.
Formation of 10 was thus monitored over the course of
16 h. at ambient temperature, with an eventual yield of 78%
(by NMR). Though unisolated, the identity of 10 was conclusively
1
established from its characteristic 31P{ H}-NMR resonances (dP
-101.3, -106.3; Fig. 5), both by simulation of the AA¢BB¢ spin-
system, and comparison to those previously reported.25
Though 10 and related systems are well documented,23a,25,26
their formation is not well understood, being ascribed to: i)
◦
Experimental
thermal instability of RP(Cl){P(SiMe3)2} above 0 C,22a,26 result-
ing in loss of Me3SiCl to generate the transient RP PSiMe3,
which spontaneously dimerise, or ii) the mechanistically ill-
defined elimination of P(SiMe3)3 from RP{P(SiMe3)2}2, induced
by the presence of excess LiP(SiMe3)2.25 While the inexplicable
General methods
Standard Schlenk and vacuum line techniques were employed
throughout, operating under an inert Ar atmosphere; sensitive
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1
C1(C6H5)). 31P (161.7 MHz): dP 203.4 (t, 2JPH = 15.5 Hz). 29Si{ H}
materials were stored and manipulated in a dry-nitrogen filled
MBraun glovebox. Solvents were distilled under dinitrogen from
appropriate drying agents and stored over either molecular sieves
(chlorinated and THF) or potassium mirrors (non-halogenated).
PCl3, Me3SiCH2Cl and ClMe2SiCH2Cl were obtained from com-
mercial vendors, distilled from appropriate drying agents and
stored under Ar. Bis(trimethylsilyl)phosphane was prepared by
literature procedure.27 NMR spectra were recorded on a Varian
VNMRS 400 (1H 399.5 MHz, 13C 100.46 MHz, 29Si 79.37 MHz, 31P
161.71 MHz) or 600 (1H 599.69 MHz, 13C 150.81 MHz, 195Pt 128.39
MHz) spectrometer, referenced to external Me4Si, 85% H3PO4
and K2PtCl6 as appropriate. Carbon-13 NMR assignments were
confirmed by recourse to the 2D (HSQC, HMBC) spectra. The 31P-
NMR spectrum for compound 10 was simulated using Spinworks
v3,28 iterating against experimental spectra. Mass spectrometric
data were recorded by Dr A.-A. Sada of the departmental service,
microanalyses were performed by Mr S. Boyer of the London
Metropolitan University Elemental Analysis Service.
(79.4 MHz): dSi = -6.40 (d, 1JSiP = 17.5 Hz). Anal. Found: C, 42.73;
H, 5.10. Calcd. for C28H47P3Si: C, 43.04; H, 5.22.
Me3SiCH2P{P(SiMe3)2}2 (3). To a cold (-78 ◦C) solution of
1 (148.9 mg, 0.79 mmol) in ether (5 cm3) was added dropwise an
ethereal solution of LiP(SiMe3)2 (14.7 cm3, 0.107 M, 1.57 mmol),
prepared from HP(SiMe3)2 and n-BuLi. During addition a slight
yellow hue is assumed by the reaction mixture. The mixture was
then stirred while warming slowly to ambient temperature over
3 h., after which the solvent was removed under reduced pressure.
The off-white residue was extracted with n-pentane and filtered
via cannula to remove the LiCl by-products. Concentration of the
filtrate at reduced pressure affords a deep yellow solution, storage
of which at -80 ◦C (12 h.) leads to deposition of 3 as white crystals.
◦
The supernatant solution was filtered off at -78 C, and◦3 dried
1
in vacuo. Isolated yield: 133 mg, 35%. NMR (C6D6, 30 C). H
(399.5 MHz): dH = 0.23 (s, br, (hhw = 3. Hz), 9H, Me3SiCH2),
2
0.41 (d, JPH = 2 Hz, 36H, Me3SiP), 1.62 (dt, JPH = 12.0 Hz,
3JPH = 2.8 Hz, 2H, Me3SiCH2P). 13C (100.5 MHz): dC 0.30 (d,
3JPC = 5 Hz, Me3SiCH2), 3.29 (ddd, 2JPC = 10.0 Hz, 3JPC = 6.5 Hz,
4JPC = 3.5 Hz, P(SiMe3)2), 1.62 (dt, 1JPC = 46.7 Hz, 2JPC = 15.0 Hz,
Synthetic details
Me3SiCH2PCl2 (1). In a modification of literature pro-
cedures,17 excess of finely divided magnesium (4.00 g, 165 mmol)
was suspended in diethyl ether (ca. 50 cm3) in a flask equipped
with a water-cooled reflux condenser. An ethereal (ca. 50 cm3)
solution of Me3SiCH2Cl (11.27 g, 91.8 mmol) was added slowly,
resulting (upon ca 30% addition) in a self-initiated Grignard
reaction; subsequent addition was conducted at a rate to maintain
controlled reflux, and was complete after 45 min. The mixture
was stirred under Ar while cooling to ambient temperature (2 h.),
then cautiously filtered (cannula) directly into a solution of PCl3
(7.75 cm3, 91.5 mmol) in diethyl ether (ca. 50 cm3) held around
-20 ◦C; a white precipitate forms immediately. After complete
addition the mixture was stirred overnight, while slowly attaining
ambient temperature. After filtration, residual MgX2 was washed
thoroughly with ether (3 ¥ 30 cm3), the extracts combined and
solvent removed under reduced pressure (6 mbar) to afford crude
1 as yellow oil. Distillation at reduced pressure (50 ◦C, 1.7 mbar)
yields pure 1 as a colourless liquid that fumes in air. Yield 14 g,
Me3SiCH2P). 31P{ H} (161.7 MHz): dP -58.0 (dd, 1JPP = 320 Hz,
1
317 Hz, 2JSiP = 11.0 Hz, 1P, CH2P{P(SiMe3)2}2), -162.6 (dd, 1JPP
=
320 Hz, 317 Hz, JSiP = 20.0 Hz, 2P, P(SiMe3)2). 29Si (79.4 MHz,
indirect observe): dSi = 0.92 (Me3SiCH2P), 3.88 (P(SiMe3)2). High-
res ESI+ MS: m/z 473.1831 [MH]+ (Err = 4.45 ppm). EI+ MS: m/z
472 [M]+, 457 [M - Me]+, 399 [M - SIMe3]+, 327 [M - 2(SiMe3)]+,
295 [M - P(SiMe3)2]+, 73 [SiMe3]+ Crystal data: C16H47P3Si5. Mw =
1
¯
˚
◦
˚
472.90, triclinic, P1(No 2), a = 10.3093(3) A, b = 10.3617(2) ◦A, c =
◦
˚
˚
15.8740(4) A, a = 93.564(1) , b = 90.351(1) , g = 118.183(1) . V =
3
-3
-1
1490.55(6) A . Z = 2, Dc = 1.05 Mg m , m(Mo-Ka) = 0.4 mm , T =
173(2)K, 5774 independent reflections, full-matrix F2 refinement
R1 = 0.027, wR2 = 0.071 on 5328 independent absorption corrected
reflections [I > 2s(I); 2qmax = 52◦], 232 parameters, R1 = 0.031,
wR2 = 0.073 on all data. CCDC 835037. Crystals were covered
in an inert oil and suitable single crystals were selected under a
microscope and mounted on a Kappa CCD diffractometer. Data
˚
were collected at 173(2) K using Mo-Ka radiation at 0.71073 A.
◦
The structures were refined with SHELXL-97.29
1
80%. NMR (C6D6, 30 C); H (399.5 MHZ): dH = -0.08 (s, 9H,
Me3Si), 1.56 (d, JPH = 15.8 Hz, 2H, CH2). 13C (100.5 MHz): dC
2
Me3SiCH2P(PCy2)2 (4). As for 3, with 497.5 mg, (2.63 mmol)
of 1 and a THF solution of LiPCy2 (42 cm3, 0.125 M, 5.3 mmol).
Workup, extraction into pentane and overnight storage at -80 ◦C
yiel◦ded 4 as a white precipitate. Yield: 600 mg, 45%. NMR (C6D6,
0.06 (d, 3JPC = 5 Hz, 1JSiC = 52 Hz, Me3Si), 35.4 (d, 1JPC = 61.2 Hz,
1JSiC = 39.6 Hz, CH2). 31P (161.7 MHz): dP 205.4 (t, JPH = 15.3
2
Hz). 29Si (79.4 MHz, indirect observe): dSi = -0.6.
1
PhMe2SiCH2PCl2 (2). Analogously to 1, the new dichloro-
phosphane 2 was prepared from PhMe2SiCH2Cl (19.4 g,
105 mmol), itself obtained from ClMe2SiCH2Cl and PhMgBr.
The Grignard reagent was separated from excess magnesium by
filtration and stored under Ar prior to use. Slow addition to
8.9 cm3 (105 mmol) PCl3 in ether at -20 ◦C afforded, after workup,
crude 2 as a slightly discoloured viscous liquid. Distillation at
reduced pressure (94 ◦C, 0.59 mbar) yielded 20.69 g (78%) of 2
as a clear, colourless liqui◦d that is moderately air and moisture
sensitive. NMR (C6D6, 30 C). 1H (399.5 MHz): dH = 0.15 (s, 6H,
30 C). H (599.69 MHz): dH = 0.26 (s, br, (hhw = 2 Hz), 9H,
Me3SiCH2), 1.21 (unres. m, 2H, SiCH2P), 1.22 (tdt, J = 12.0,
7.5, 2.6 Hz, 4H, PCH(CH2-CH2)2CHH), 1.30 (dtt, J = 12.6, 12.5,
3 Hz, 8H, PCy-(CH2)2), 1.58 (m, 4H, PCy-CHH), 1.60 (m, 4H,
PCy-CHH), 1.63 (m, 4H, PCH(CH2CH2)2CHH), 1.78 (t, J = 15.0
Hz, 8H, PCH(CH2)2-C3H6), 2.03 (d, J = 12.2 Hz, 4H, PCy-CHH),
2.09 (br. s. hhw = 30 Hz, 4H, PCHC5H10), 2.17 (d, J = 13.2 Hz,
4H, PCy-CHH). 13C (150.81 MHz): dC 0.75 (dt, JPC = 4.9 Hz,
3
4JPC = 1.5 Hz, CH3, Me3SiCH2), 7.38 (dt, JPC = 45.0 Hz, JPC
=
1
2
11.3 Hz, CH2, Me3SiCH2P), 26.9 (s, CH2, PCH-(CH2CH2)2CH2),
27.9 (dt, JPC = 13.6, 4.5 Hz, CH2, PCH-(CH2)2C3H6), 32.0 (dt,
JPC ~ 5.0 Hz, CH2, PCH(CH2CH2)-(C2H4)CH2), 32.9 (dt, JPC
~ 7.5 Hz, CH2, PCH(C2H4)(CH2CH2)-CH2), 34.2 (br. m., CH,
2
Me2PhSi), 1.77 (d, JPH = 15.5 Hz, 2H, CH2), 7.25–7.20 (m, Ar,
2H, 2,6-C6H4SiMe2), 7.15–7.10 (m, Ar, 3H PhMe2Si). 13C (100.5
MHz): dC -1.72 (d, 3JPC = 4.5 Hz, 1JSiC = 54.2 Hz, Me2PhSi), 34.7
(d, JPC = 62.2 Hz, JSiC = 41.1 Hz, CH2), 128.3 (s, C4(C6H5)),
PCH(C5H10)). 31P{ H} (161.7 MHz): dP -3.4 (dd, JPP = 308 Hz,
1
1
1
1
129.9 (s, C3,5(C6H5)), 133.83 (s, C2,6(C6H5)), 136.85 (s, 1JCP = 4 Hz,
306 Hz, 2P, PCy2), -84.1 (dd, 1JPP = 308 Hz, 306 Hz, 2JSiP = 21.0
282 | Dalton Trans., 2012, 41, 278–284
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1
2
1
Hz, 1P, Me3SiCH2P). 29Si{ H} (79.4 MHz): dSi = 1.96 (d, JSiP
=
(CH2, Cy), 34.54 (CH, PCH(C5H10). 31P{ H} (161.7 MHz): dP
21 Hz, Me3SiCH2P). Anal. Found: C, 65.42; H, 10.91. Calcd. for
C28H55P3Si: C, 65.59; H, 10.81.
-6.6 (dd, 1JPP = 172 Hz, 168 Hz, 2JSiP = 22.0 Hz, 2JPtP = 129 Hz, 1P,
Me3SiCH2P), -46.1 (dd, 1JPP = 172 Hz, 168 Hz, JPtP = 2998 Hz,
2
2P, Pt-PCy2P). 29Si (79.4 MHz, indirect obs.): dSi = 2.80. 195Pt{ H}
1
PhMe2SiCH2P{P(SiMe3)2}2 (5). As for 3, however, 5 fails to
precipitate from pentane at low-temperature, and is isolable only
as an impure oil, characterized spectroscopically. NMR (C6D6,
(128.4 MHz): dPt -3832 (td, 1JPtP = 2998 Hz, 2JPtP = 129 Hz). EI+
MS: m/z 778 [M]+, 743 [M-Cl]+. Anal. Found: C, 42.97; H, 6.97.
Calcd. for C28H55Cl2P3PtSi: C, 43.19; H, 7.12.
◦
1
30 C). H (399.5 MHz): dH = 0.37 (m, br, (hhw = 6 Hz), 36H,
{P(SiMe3)2}2), 0.53 (br. S. (hhw = 2 Hz), 6H, PhMe2SiCH2P), 1.92
(ddd, 2JPH ~ 12 Hz, 3JPH = 3 Hz, 2H, PhMe2SiCH2P), 7.23 (m., 3H,
cis-[j2-{Me2PhSiCH2P(PCy2)2}PtCl2] (9). As for 8, but using
200 mg (0.45 mmol) PtCl2(SEt2)2 and excess of 6 (crude), as solu-
tion in pentane. After stirring overnight, workup and purification
afforded 9 as◦a yellow solid. Yield: 230 mg, 61% (wrt Pt). NMR
Ph-H4, H3,5), 7.61 (m., 2H, Ph-H2,6). 31P{ H} (161.7 MHz): dP -58.1
1
(dd, 1JPP = 323 Hz, 316.9 Hz, 2JSiP = 11.7 Hz, 1P, PhMe2SiCH2P),
-162.7 (dd, 1JPP = 323 Hz, 316.9 Hz, 1JSiP = 21.6 Hz, 2P, P(SiMe3)2).
29Si (79.4 MHz, indirect obs.): dSi = -4.26 (PhMe2SiCH2P), 4.28
(P(SiMe3)2).
1
(CD2Cl2, 30 C). H (399.5 MHz): dH = 0.48 (s, br, (hhw = 3.
Hz), 6H, PhMe2SiCH2), 1.12–2.40 (m. ¥ 4, poorly resolved, 46H,
Cy ¥ 4, PhMe2SiCH2P {1.32 ppm by HSQC}), 7.42 (m., 3H, Ph-
H4, H3,5), 7.54 (m., 2H, Ph-H2,6). 13C (100.5 MHz): dC -2.17 (s,
CH3, Me2PhSi), 7.55 (CH2, Me2PhSiCH2), 25.50 (CH2, Cy), 26.20
(CH2, Cy), 26.50 (CH2, Cy), 35.04 (CH, PCH(C5H10)), 128.76 (CH,
Ph- C3,5), 130.86 (CH, Ph-C4), 134.62 (CH, Ph-C2,6), 136.46 (CH,
PhMe2SiCH2P(PCy2)2 (6). As for 4. Low yields of analytically
pure 6 precipitate from pentane at -80 ◦C; the bulk was used
crude in subsequent chemistry. NMR (C6D6): H (599.69 MHz):
1
dH = 0.59 (s, br, (hhw = 2 Hz), 6H, PhMe2SiCH2), 1.21 (tt,
J ~ 12.0, 2.6 Hz, 4H, PCH(CH2CH2)2-CHH), 1.27 (br. dt. m.,
J ~ 12.5 Hz, 8H, PCH(CH2)2C3H6), 1.45 (t, JPH = 7.7 Hz, 2H,
SiCH2P), 1.52 (m, 4H, PCy-CHH), 1.56 (m, 4H, PCy-CHH), 1.62
(br. d., J ~ 13 Hz, 4H, PCH(CH2CH2)2-CHH), 1.75 (m, 8H,
PCH(CH2)2C3H6), 1.99 (d, J = 13.0 Hz, 4H, PCy-CHH), 2.04
(br. s. hhw = 30 Hz, 4H, PCHC5H10), 2.12 (d, J = 13.2 Hz, 4H,
PCy-CHH), 7.19 (m., 1H, p-PhMe2Si), 7.24 (m, 2H, o-PhMe2Si),
Ph-C1). 31P{ H} (161.7 MHz): dP -9.65 (dd, JPP = 173 Hz, 168
1
1
Hz, 2JPtP = 138 Hz, 1P, Me2PhSiCH2P), -45.9 (dd, 1JPP = 172 Hz,
168 Hz, JPtP = 2995 Hz, 2P, Pt-PCy2P). 29Si (79.4 MHz, indirect
2
obs.): dSi = -3.46. 195Pt{ H} (128.4 MHz): dPt -3830 (td, JPtP
=
1
1
2995 Hz, 2JPtP = 138 Hz). Anal. Found: C, 45.66; H, 5.85. Calcd.
for C33H57Cl2P3PtSi: C, 47.14; H, 6.83.
Simulated 31P-NMR spectroscopic parameters for 10. dP (161.7
MHz) -101.3, -106.3; |1JPaPb| = 99.84 Hz; |1JPa¢Pb¢| = 97.59 Hz;
|2JPaPa¢| = 8.01 Hz; |2JPbPb¢| = 7.93 Hz. All spin–spin coupling
constants are of the same sign. RMS = 2.3%.
¯
¯
7.64 (d. m, J ~ 8 Hz, 2H, m-PhMe2Si). 13C (150.81 MHz): dC
¯
-0.84 (dt, 3JPC = 5.2 Hz, 4JPC = 1.7 Hz, CH3, PhMe2SiCH2), 6.84
1
2
(dt, JPC = 46.2 Hz, JPC = 11.6 Hz, CH2, PhMe2SiCH2P), 26.9
(s, CH2, PCH(CH2CH2)2CH2), 27.9 (dt, JPC = 14.0, 4.6 Hz, CH2,
PCH(CH2)2C3H6), 32.0 (dt, JPC ~ 5.0 Hz, CH2, PCH(CH2CH2)-
(C2H4)-CH2), 32.8 (dt, JPC ~ 8 Hz, CH2, PCH(C2H4)(CH2CH2)-
CH2), 34.2 (br. m., CH, PCH(C5H10)), 129.3 (s, CH, Ph-C3,5), 134.2
Computational details
DFT calculations. DFT studies were performed using Gaus-
sian 03 W, Rev. E0.1 (multi-processor version)30 running on an
Intel Core 2 Quad Q9550 with 4 GB RAM, and visualised
using GausView 4.1. Geometries were initially optimized at the
B3LYP/6-311G level before addition of diffuse and polarization
functions; the final stationary points (B3LYP/6-311+G(d,p)) were
characterized as minima on the basis of frequency calculations
yielding zero imaginary frequencies. Energies were used compar-
atively at the same level of theory, negating the need for ZPE
correction.
(s, CH, Ph-C2,6) 140.2(d, JPC = 5 H, Ph-C4). 31P{ H} (161.7 MHz):
1
dP -2.52 (dd, 1JPP = 305, 303 Hz, 2P, PCy2), -85.2 (dd, 1JPP = 305
Hz, 303 Hz, P, PhMe2SiCH2P). 29Si (79.4 MHz, indirect observe):
dSi = -3.83 (PhMe2SiCH2P). Anal. Found: C, 69.05; H, 10.15.
Calcd. for C33H57P3Si: C, 68.95; H, 10.00.
Me3SiCH2P(PPh2)2 (7). Analogously to 3 and 4, using 1 (92.7
mg, 0.49 mmol) and two equivalents of LiPPh2, generated in situ
from HPPh2 and n-BuLi. Workup afforded a deep yellow oil,
which was spectroscopically characterized and found to contain
7 in appreciable amounts. Purification was unsuccessful. Selected
crude NMR data (C6D6): 1H (599.69 MHz): dH = 0.83 (t, JPH = 8
Simulation of 31P{ H} NMR spectra. The 31P-NMR spectra
1
of the RMe2SiCH2P(PR¢2)2 triphosphanes were simulated using
the approach outlined by Levitt,31 considering them as IS2 spin
systems, with the following spin Hamiltonian, constructed in the
rotating frame:
Hz, Me3SiCH2). 31P{ H} (161.7 MHz): dP -14.5 (dd, JPP = 232
1
1
1
Hz, 223 Hz, 2P, PPh2), -52.6 (dd, JPP = 232 Hz, 223 Hz, 1P,
Me3SiCH2P).
cis-[j2-{Me3SiCH2P(PCy2)2}PtCl2] (8). To a dichlorometh-
ane (10 cm3) solution of [PtCl2(SEt2)2] (88 mg, 0.2 mmol) was
added a solution of 4 (100 mg, 0.2 mmol) in pentane (2 cm3). The
mixture was stirred for 1 h. then the solvent removed under reduced
pressure. The crude product was purified by re-precipitation from
dichloromethane with n-hexane, to affo◦rd 8 as a pale yellow solid.
ˆ
ˆ
ˆ
ˆ
ˆ
H = wI Iz + ws(SAz + SBz) + 2pJISHJ
The individual spin operators were constructed in the Zeeman
product basis, using the appropriate Kronecker products of the
Pauli spin matrices for a spin-21 particle. The scalar coupling term
(HJ ) in the spin Hamiltonian was constructed in two forms to
allow investigation of the strong versus weak coupling regimes.
ˆ
Yield: 105 mg, 68%. NMR (CD2Cl2, 30 C). 1H (399.5 MHz): dH
=
The full form of the different scalar coupling terms used was:
0.19 (s, br, (hhw = 3. Hz), 9H, Me3SiCH2), 1.21 (td, JPH = 11, 5
Hz, 2H, Me3SiSCH2P), 1.325–2.50 (m ¥ 4, poorly resolved, 44H,
Cy ¥ 4). 13C (100.5 MHz, indirect): dC -0.97 (CH3, Me3SiCH2),
7.92 (CH2, Me3SiCH2P), 26.40 (CH2, Cy), 25.50 (CH2, Cy), 26.70
1
2
1
2
strong
ˆ
HJ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
= IzSAz + IzSBz
+
I SA − + I−SA + +
I SB− + I−SB+
(
)
(
)
+
+
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weak
ˆ
ˆ ˆ
ˆ ˆ
Al-Ktaifani, M. P. Coles, I. R. Crossley, L. T. J. Evans, P. B. Hitchcock,
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HJ = IzSAz + IzSBz
The strong coupling regime includes the full isotropic coupling
Hamiltonian written in terms of ladder operators, whereas in weak
coupling, typically defined to be when |Dw| ꢀ 2pJ, only the z
components are retained.
The eigenvalues Xp and normalized eigenvectors xp of the
Hamiltonian were determined using the linear algebra routines
of the Scipy library.32 The spectral peak frequencies correspond to
the frequencies of the coherences between the eigenvalues, given
by:
Xpq = -Xp+ Xq
while the peak amplitudes correspond to the square of the matrix
elements of the transition moment:
14 H. R. G. Bender, M. Nieger and E. Niecke, Z. Naturforsch. Tiel B.
T
+
2
Chem Sci., 1993, 48, 1742.
ˆ
apq = |xp · I · xq|
with the raising operator being constructed in the same basis as:
15 I. Kovacs, H. Krautscheid, E. Matern, E. Sattler, G. Fritz, W. Honle, H.
Borrmann and H. G. V. Schnering, Z. Anorg. Allg. Chem., 1996, 622,
1564.
+
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
16 M. Kopan and G. M. Reisner, Acta Crystallogr., Sect. C: Cryst. Struct.
I = (Ix + SAx + SBx) + i(Iy + SAy + SBy)
Commun., 1990, 46, 349.
17 D. Seyferth and W. Freyer, J. Org. Chem., 1961, 26, 2604.
18 R. Appel and R. Milker, Chem. Ber., 1975, 108, 1783.
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deference to related 1,3-donor systems such as carboxylates: J. B. Huff,
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The NMR spectra were then synthesized by placing
Lorentzian lines of width w and intensities apq at positions
Xpq.
Acknowledgements
We thank the Royal Society and University of Sussex for financial
support. IRC gratefully acknowledges the award of a Royal Society
University Research Fellowship.
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284 | Dalton Trans., 2012, 41, 278–284
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