Germanium(II) and tin(II) complexes of a sterically demanding phosphanide ligand

Article abstract of DOI:10.1021/ic1003534

The reaction between PhPCl₂ and 1 equiv of RLi, followed by in situ reduction with LiAlH₄ and an aqueous workup yields the secondary phosphane PhRPH [R = (Me₃Si)₂CH]. Treatment of PhRPH with n-BuLi in diethyl ether generates the lithium phosphanide (RPhP)Li(Et ₂O)_n [15(Et₂O)], which may be crystallized as the tetrahydrofuran (THF) adduct (RPhP)Li(THF)₃ [15(THF)]. Compound 15(Et₂O) reacts with 1 equiv of either NaO-tBu or KO-tBu to give the corresponding sodium and potassium phosphanides (RPhP)Na(Et₂O) _n (16) and (RPhP)K(Et₂O)_n (17), which may be crystallized as the amine adducts [(RPhP)Na(tmeda)]₂ [16(tmeda)] and [(RPhP)K(pmdeta)]₂ [17(pmdeta)], respectively. The reaction between 2 equiv of 17 and GeCl₂(1,4-dioxane) gives the dimeric compound [(RPhP)₂Ge]₂'Et₂O (18'Et₂O). In contrast, the reaction between 2 equiv of 15 and SnCl₂ preferentially gives the ate complex (RPhP)₃SnLi(THF) (19) in low yield; 19 is obtained in quantitative yield from the reaction between SnCl₂ and 3 equiv of 15. Crystallization of 19 from n-hexane/THF yields the separated ion pair complex [(RPhP)₃Sn][Li(THF)₄] (19a); exposure of 19a to vacuum for short periods leads to complete conversion to 19. Treatment of GeCl₂(1,4-dioxane) with 3 equiv of 15 yields the contact ion pair (RPhP)₃GeLi(THF) (20), after crystallization from n-hexane/THF. Compounds 15(THF), 16(tmeda), 17(pmdeta), 18'Et₂O, 19a, and 20 have been characterized by elemental analyses, multielement NMR spectroscopy, and X-ray crystallography. While 15(THF) is monomeric, both 16(tmeda) and 17(pmdeta) are dimeric in the solid state. The diphosphagermylene 18'Et₂O adopts a dimeric structure in the solid state with a syn,syn-arrangement of the phosphanide ligands, and this structure appears to be preserved in solution. The ate complex 19a crystallizes as a separated ion pair, whereas the analogous ate complex 20 crystallizes as a discrete molecular species. The structures of 19 and 20 are retained in non-donor solvents, while dissolution in THF yields the separated ion pairs 19a and [(RPhP)₃Ge][Li(THF)₄] (20a).

Full text of DOI:10.1021/ic1003534

4698 Inorg. Chem. 2010, 49, 4698–4707
DOI: 10.1021/ic1003534
Germanium(II) and Tin(II) Complexes of a Sterically Demanding
Phosphanide Ligand
Keith Izod,* John Stewart, Ewan R. Clark, William Clegg, and Ross W. Harrington
Main Group Chemistry Laboratories, School of Chemistry, Bedson Building, University of Newcastle,
Newcastle upon Tyne, NE1 7RU, U.K.
Received February 22, 2010
The reaction between PhPCl2 and 1 equiv of RLi, followed by in situ reduction with LiAlH4 and an aqueous workup
yields the secondary phosphane PhRPH [R = (Me3Si)2CH]. Treatment of PhRPH with n-BuLi in diethyl ether
generates the lithium phosphanide (RPhP)Li(Et2O)n [15(Et2O)], which may be crystallized as the tetrahydrofuran
(THF) adduct (RPhP)Li(THF)3 [15(THF)]. Compound 15(Et2O) reacts with 1 equiv of either NaO-tBu or KO-tBu to
give the corresponding sodium and potassium phosphanides (RPhP)Na(Et2O)n (16) and (RPhP)K(Et2O)n (17),
which may be crystallized as the amine adducts [(RPhP)Na(tmeda)]2 [16(tmeda)] and [(RPhP)K(pmdeta)]2
[17(pmdeta)], respectively. The reaction between 2 equiv of 17 and GeCl2(1,4-dioxane) gives the dimeric compound
[(RPhP)2Ge]2 Et2O (18 Et2O). In contrast, the reaction between 2 equiv of 15 and SnCl2 preferentially gives the ate
3
3
complex (RPhP)3SnLi(THF) (19) in low yield; 19 is obtained in quantitative yield from the reaction between SnCl2 and
3 equiv of 15. Crystallization of 19 from n-hexane/THF yields the separated ion pair complex [(RPhP)3Sn][Li(THF)4]
(19a); exposure of 19a to vacuum for short periods leads to complete conversion to 19. Treatment of GeCl2(1,4-
dioxane) with 3 equiv of 15 yields the contact ion pair (RPhP)3GeLi(THF) (20), after crystallization from n-hexane/
THF. Compounds 15(THF), 16(tmeda), 17(pmdeta), 18 Et2O, 19a, and 20 have been characterized by elemental
3
analyses, multielement NMR spectroscopy, and X-ray crystallography. While 15(THF) is monomeric, both 16(tmeda)
and 17(pmdeta) are dimeric in the solid state. The diphosphagermylene 18 Et2O adopts a dimeric structure in the
3
solid state with a syn,syn-arrangement of the phosphanide ligands, and this structure appears to be preserved in
solution. The ate complex 19a crystallizes as a separated ion pair, whereas the analogous ate complex 20 crystallizes
as a discrete molecular species. The structures of 19 and 20 are retained in non-donor solvents, while dissolution in
THF yields the separated ion pairs 19a and [(RPhP)3Ge][Li(THF)4] (20a).
Introduction
Pb; Tripp =2,4,6-iPr3C6H2]3 reported by Driess and co-
workers, although Power and co-workers have reported the
spectroscopically characterized monomeric diphosphastanny-
lene [{2,6-(2,4,6-Me3C6H2)2C6H3}(Ph)P]2Sn (3) (Chart 1).4
The remaining crystallographically characterized diphospha-
tetrylenes, {(tBu2P)2Pb}2 (4),5 {((Me3Si)2P)2Pb}2 (5),6 and
{(iPr2P)2Ge}2 (6),7 are dimeric both in the solid state and in
solution. In addition, the ate complexes (tBu2P)E(μ-tBu2P)2-
Li(THF) [E = Sn (7), Pb (8)] have been reported,8 along
with the heteroleptic species {(μ2-tBu2P)GeCl}2 (9)7 and the
β-diketiminate-supported phosphagermylenes [CH{(CMe)-
(2,6-iPr2C6H3N)}2]Ge(PR2) [PR2 = PH2, PH(SiMe3),
P(SiMe3)2, 1/2(PH-PH)];9 a range of homometallic Sn(II)
phosphinidene clusters and heterometallic Ca/Sn or Ba/Sn
phosphanide and phosphinidene clusters are also known.10
We have recently begun to explore the use of sterically
demanding, donor-functionalized phosphanides such as
[{(Me3Si)2CH}(C6H4-2-(CH2)nNMe2)P]- (n = 0, 1) as ligands
for low oxidation state group 14 centers. In our initial
experiments we have shown that the compounds [{(Me3Si)2-
CH}(C6H4-2-CH2NMe2)P]2E [E = Ge (10),11 Sn (11)12] and
Whereas the heavier group 14 analogues of diaminocar-
benes [diaminotetrylenes; (R2N)2E, E = Si, Ge, Sn, Pb] have
been known for many years and are well established, the
corresponding diphosphatetrylenes [(R2P)2E] have been less
well explored.1,2 Structurally characterized monomeric di-
phosphatetrylenes are limitedtothe highlystericallyhindered
compounds [{(Tripp)2FSi}(iPr3Si)P]2E [E = Ge (1), Sn (2),
*To whom correspondence should be addressed. E-mail: k.j.izod@ncl.
ac.uk.
(1) For recent reviews of heavier tetrylene chemistry see: (a) Barrau, J.;
Rima, G. Coord. Chem. Rev. 1998, 178-180, 593. (b) Tokitoh, N.; Okazaki, R.
Coord. Chem. Rev. 2000, 210, 251. (c) Kira, M. J. Organomet. Chem. 2004,
689, 4475. (d) Weidenbruch, M. Eur. J. Inorg. Chem. 1999, 373. (e) Klinkhammer,
K. W. In Chemistry of Organic Germanium, Tin and Lead Compounds;
Rappoport, Z., Ed; Wiley: New York, 2002; Vol. 2, pp 283-357. (f) Veith, M.
Angew. Chem., Int. Ed. Engl. 1987, 26, 1. (g) Hill, N. J.; West, R. J. Organomet.
Chem. 2004, 689, 4165. (h) Gehrhus, B.; Lappert, M. F. J. Organomet. Chem.
2001, 617, 209. (i) K€uhl, O. Coord. Chem. Rev. 2004, 248, 411. (j) Zemlyanskii,
N. N.; Borisova, I. V.; Nechaev, M. S.; Khrustalev, V. N.; Lunin, V. V.; Antipin, M.
Yu.; Ustynyuk, Yu. A. Russ. Chem. Bull. Int. Ed. 2004, 53, 980. (k) Zabula, A. V.;
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r
pubs.acs.org/IC
Published on Web 04/14/2010
2010 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 10, 2010 4699
Chart 1
[{(Me3Si)2CH}(C6H4-2-NMe2)P]2E [E = Ge (12), Sn (13)]13
are monomeric both in the solid state and in solution by
virtue of the intramolecular coordination of one of the
peripheral amino substituents in each case. Compounds
10-13 are highly dynamic in solution; detailed NMR studies
and density functional theory (DFT) calculations suggest
that these compounds are subject to both epimerization via
inversion at one or more of the phosphorus centers and
interconversion between the chelating and terminal phospha-
nide ligands. Low temperature NMR spectra indicate that
compound 13 adopts a pseudotrigonal bipyramidal structure
(13a) in solution which corresponds to the intermediate
proposed for exchange of the chelating and terminal phos-
phanide ligands via an associative pathway.
We now report the synthesis of a related sterically hindered
phosphane, {(Me3Si)2CH}(Ph)PH (14), which does not con-
tain additional donor functionality, the preparation and
crystal structures of its lithium, sodium and potassium
derivatives, and the reactions between these derivatives and
either GeCl2(1,4-dioxane) or SnCl2 to give either diphos-
phatetrylenes or ate complexes.
Results and Discussion
The reaction between PhPCl2 and 1 equiv of [(Me3Si)2-
CH]Li in diethyl ether yields the monochlorophosphane
{(Me3Si)2CH}(Ph)PCl, which, on treatment with LiAlH4,
gives the secondary phosphane {(Me3Si)2CH}(Ph)PH (14) in
good yield as a colorless oil. Treatment of 14 with n-BuLi in
diethyl ether gives the lithium phosphanide [{(Me3Si)2CH}-
(Ph)P]Li(Et2O)n [15(Et2O)] as an orange oil which may be
crystallized from cold n-hexane/tetrahydrofuran (THF) as the
adduct [{(Me3Si)2CH}(Ph)P]Li(THF)3 [15(THF)] (Scheme1).
The reaction between in situ prepared 15(Et2O) and either
NaO-tBu or KO-tBu in diethyl ether gives the corresponding
heavier alkali metal phosphanides [{(Me3Si)2CH}(Ph)P]M
[M = Na (16); M = K (17)], which may be crystallized as
the adducts [[{(Me3Si)2CH}(Ph)P]Na(tmeda)]2 [16(tmeda)]
and [[{(Me3Si)2CH}(Ph)P]K(pmdeta)]2 [17(pmdeta)] from
methylcyclohexane containing 1 equiv of either tmeda or
pmdeta, respectively [tmeda = N,N,N0,N0-tetramethylethy-
lenediamine, pmdeta = N,N,N0,N00,N00-pentamethyldiethyl-
enetriamine]. The 1H, 13C{1H}, and 31P{1H} NMR spectra of
14, 15(THF), 16(tmeda), and 17(pmdeta) are as expected.
Whereas the SiMe3 groups of 14 are diastereotopic, giving
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4700 Inorganic Chemistry, Vol. 49, No. 10, 2010
Izod et al.
Figure 2. Molecular structure of 16(tmeda) with 40% probability ellip-
˚
soids and with H atoms omitted for clarity. Selected bond lengths (A) and
Figure 1. Molecular structure of 15(THF) with 40% probability ellip-
soids and with H atoms and minor disorder components omitted for
clarity. Selected bond lengths (A) and angles (deg): Li-P 2.551(3),
Li-O(1) 1.994(3), Li-O(2) 1.936(3), Li-O(3) 1.941(3), P-C(1)
1.8913(16), P-C(8) 1.7985(17), C(1)-Si(1) 1.8729(17), C(1)-Si(2)
1.8643(16), P-Li-O(1) 102.43(12), P-Li-O(2) 118.08(13), P-Li-O(3)
124.01(14), O(1)-Li-O(2) 106.15(15), O(1)-Li-O(3) 101.23(14),
O(2)-Li-O(3) 102.49(14).
angles (deg): Na(1)-P(1) 2.9701(9), Na(1)-P(2) 2.9627(9), Na(2)-P(1)
2.9386(9), Na(2)-P(2) 2.9341(9), Na(1)-N(1) 2.4868(18), Na(1)-N(2)
˚
2.5169(18), Na(2)-N(3) 2.4921(18), Na(2)-N(4) 2.4712(18), Na(1) C(32)
3 3 3
3.100(3), Na(2) C(34) 3.125(3), Na(1)-P(1)-Na(2) 84.71(2), Na(1)-
3 3 3
P(2)-Na(2) 84.92(2), P(1)-Na(1)-P(2) 94.52(2), P(1)-Na(2)-P(2)
95.79(2), N(1)-Na(1)-N(2) 74.65(6), N(3)-Na(2)-N(4) 74.94(6).
Scheme 1. [R = (Me3Si)2CH]
Figure 3. Molecular structure of 17(pmdeta) with 40% probability
ellipsoids and with H atoms and minor disorder components omitted
1
rise to two signals in the H spectrum, the SiMe3 groups in
˚
for clarity. Selected bond lengths (A) and angles (deg): K-P 3.4862(15),
15(THF), 16(tmeda), and 17(pmdeta) are equivalent on the
NMR time-scale because of rapid intermolecular exchange
via P-M cleavage and re-coordination.
K-P0 3.3351(12), K-N(1) 3.053(3), K-N(2) 2.905(3), K-N(3) 2.874(3),
K-C(2) 3.222(3), K-C(3) 3.162(3),
K
C(18) 3.445(4), P-C(1)
3 3 3
1.893(3), P-C(2) 1.809(3), C(1)-Si(1) 1.884(3), C(1)-Si(2) 1.880(3),
P-K-P0 81.47(3), K-P-K0 98.53(3), N(1)-K-N(2) 61.29(8), N(2)-
K-N(3) 62.99(8). A prime indicates an inversion-generated atom.
Compound 15(THF) crystallizes as discrete monomers in
which the lithium ion is coordinated by the phosphorus atom
of the phosphanide ligand and the oxygen atoms of three
molecules of THF in a distorted tetrahedral geometry. The
molecular structure of 15(THF) is shown in Figure 1, along
with selected bond lengths and angles. The Li-P distance of
the Li-P distances in [(Ph2P)Li(DME)]¥ are 2.563(3) and
16
˚
2.541(3) A.
Compounds 16(tmeda) and 17(pmdeta) crystallize as
dimers containing rhombus-shaped P2M2 cores. The mole-
cular structures of 16(tmeda) and 17(pmdeta) are shown in
Figures 2 and 3, respectively, along with selected bond
lengths and angles. In 16(tmeda) each sodium ion is
coordinated by the P atoms of two phosphanide ligands
and the N atoms of a molecule of tmeda to give a four-
coordinate distorted tetrahedral metal center; in addition
2.551(3) A is typical of such contacts,14a and is similar to the
˚
corresponding distances in the closely related compounds
[(2,4,6-Me3C6H2)PH]Li(THF)3 [2.533(9) A],14b [{(Me3Si)2CH}-
˚
14c
˚
(C6H4-2-CH2NMe2)P]Li(THF)2 [2.535(8) and 2.535(7) A]
and [{(Me3Si)2CH}(C6H4-2-NMe2)P]Li(THF)2 [2.498(5) and
2.505(5) A]15 and in other lithium phosphanides; for example,
˚
(14) (a) Izod, K. Adv. Inorg. Chem. 2000, 50, 33. (b) Bartlett, R. A.;
Olmstead, M. M.; Power, P. P.; Sigel, G. A. Inorg. Chem. 1987, 26, 1941.
(c) Clegg, W.; Doherty, S.; Izod, K.; Kagerer, H.; O’Shaughnessy, P.; Sheffield,
J. M. J. Chem. Soc., Dalton Trans. 1999, 1825.
(15) Izod, K.; Stewart, J. C.; Clegg, W.; Harrington, R. W. Dalton Trans.
2007, 257.
(16) Steiglitz, G.; Neumuller, B.; Dehnicke, K. Z. Naturforsch. B 1993, 48,
156.
€

Article
Inorganic Chemistry, Vol. 49, No. 10, 2010 4701
Scheme 2. [R = (Me3Si)2CH]
there are short contacts between each sodium ion and one
of the methyl groups from the adjacent tmeda ligand
˚
[Na(1) C(23) 3.100(3), Na(2) C(34) 3.125(3) A]. The
3 3 3
3 3 3
dimeric molecule of 16(tmeda) has no crystallographically
imposed symmetry, but is essentially centrosymmetric;
the P-Na distances lie in the range 2.9341(9)-2.9701(9)
˚
A and are somewhat longer than the corresponding dis-
tances in the monomeric compounds [{(Me3Si)2CH}(C6H4-
14c
˚
2-CH2NMe2)P]Na(tmeda) [2.8189(8) A]
and [{(Me3-
15
˚
Si)2CH}(C6H4-2-NMe2)P]Na(tmeda) [2.8396(9) A], but
are similar to the Na-P distances in the phosphanide-
bridged dimer [{(C6H4-2-OMe)2P}Na(diglyme)]2 [2.861(2)-
17
˚
3.047(2) A]. Each potassium ion in 17(pmdeta) is coordi-
nated by the phosphorus atoms of two phosphanide ligands
and by the three N atoms of a molecule of pmdeta, affording
a five-coordinate metal center; in addition, there are short
contacts between each potassium ion and two of the carbon
atoms in the phenyl ring of one phosphanide ligand [K-
Figure 4. Molecular structure of one of the two independent molecules
of 18 Et2O with 40% probability ellipsoids; H atoms and solvent of
3
˚
C(2) 3.222(3), K-C(3) 3.162(3) A] and between each potas-
˚
crystallization omitted for clarity. Selected bond lengths (A) and angles
sium and the central methyl group of the pmdeta ligand
˚
(deg) for the independent molecule shown: Ge(1)-P(1) 2.4151(13), Ge-
(1)-P(2) 2.4362(13), Ge(1)-P(4) 2.4361(12), Ge(2)-P(2) 2.4442(12),
Ge(2)-P(3) 2.4153(13), Ge(2)-P(4) 2.4369(13), Ge(1)-P(2)-Ge(2)
90.78(4), Ge(1)-P(4)-Ge(2) 90.95(4), P(1)-Ge(1)-P(2) 96.86(4), P-
(1)-Ge(1)-P(4) 107.65(4), P(2)-Ge(1)-P(4) 80.62(4), P(3)-Ge(2)-P-
(2) 104.89(4), P(3)-Ge(2)-P(4) 99.54(4), P(2)-Ge(2)-P(4) 80.44(4).
[K C(18) 3.445(4) A]. The P-K distances in the strictly
3 3 3
centrosymmetric dimer of 17(pmdeta) [3.4862(15) and
˚
3.3351(12) A] are somewhat longer than the P-K distances
inmonomeric[{(Me3Si)2CH}(C6H4-2-CH2NMe2)P]K(pmdeta)
14c
˚
[3.2326(6) A]
and [{(Me3Si)2CH}(C6H4-2-NMe2)P]K-
15
˚
(pmdeta) [3.2198(10) A], but are similar to the P-K
distances in a range of potassium phosphanide complexes
containing μ2-briding phosphanide ligands; for example,
the P-K distances in polymeric [{(Me3Si)2P}K(THF)]n
Et2O (18 Et2O) suitable for X-ray crystallography (Scheme 2).
3
Compound 18 Et2O crystallizes with two independent mole-
3
cules of 18 in the asymmetric unit with opposite PtRPtR and
PtSPtS stereochemistry (where Pt and Pbr refer to the terminal and
bridging phosphorus atoms, respectively (see below)), which
differ only trivially in their bond lengths and angles, along with
two molecules of diethyl ether; for brevity, the following discus-
sion relates to molecule 1. The structure of molecule 1 of 18 is
shown in Figure 4, along with selected bond lengths and angles.
Although the structure is racemic, this is not a necessary
consequence of the space group symmetry, which could equally
well support an enantiopure structure, for example, by sponta-
neous resolution on crystallization.
18
˚
are 3.3169(7), 3.4063(8), and 3.4272(8) A. In both 16-
(tmeda) and 17(pmdeta) the phosphanide ligands adopt
an anti arrangement, which minimizes steric interactions
between the bulky (Me3Si)2CH groups.
The reaction between GeCl2(1,4-dioxane) and 2 equiv of
17 in THF yields the phosphagermylene [[{(Me3Si)2CH}-
(Ph)P]2Ge]2 (18), after a simple workup, as a sticky, orange-
brown solid, which may be crystallized from cold hexam-
ethyldisiloxane containing a few drops of diethyl ether as
orange blocks of the solvate [[{(Me3Si)2CH}(Ph)P]2Ge]2
The solvent of crystallization in 18 Et2O is only weakly
3
3
held, and 1H NMR spectra obtained from crystalline samples
which had been exposed to vacuum for a few minutes
exhibited signals due to sub-stoichiometric amounts of di-
(17) Aspinall, H. C.; Tillotson, M. R. Inorg. Chem. 1996, 35, 5.
(18) Englich, U.; Hassler, K.; Ruhlandt-Senge, K.; Uhlig, F. Inorg. Chem.
1998, 37, 3532.
ethyl ether. Similarly, a sample of 18 Et2O which had been
3

4702 Inorganic Chemistry, Vol. 49, No. 10, 2010
Izod et al.
exposed to vacuum for 15 min had an elemental (C and H)
composition corresponding to the dimer with no solvent of
crystallization.
Given the similar steric properties of the ligands in 10 and
18 Et2O it is clear that, in the absence of intramolecular
3
coordination of the Ge center by a peripheral amino sub-
stituent, the germanium center remains sufficiently Lewis
acidic that dimerization occurs. In such systems the electron
deficiency of Ge(II) or Sn(II) centers may alternatively be
alleviated through the formation of ate complexes. In this
regard, we find that treatment of SnCl2 with 2 equiv of 15 in
THF preferentially yields the ate complex [{(Me3Si)2CH}-
(Ph)P]3SnLi(THF) (19), rather than the expected homoleptic
complex [{(Me3Si)2CH}(Ph)P]2Sn. Repeated experiments
reveal that complex 19 is formed irrespective of the ratio of
SnCl2:15 employed or the conditions used; presumably the
LiCl side product is contaminated in these cases with un-
reacted SnCl2. In contrast, the reaction between 2 equiv of the
potassium salt 17 and SnCl2 results in the formation of the
diphosphane {(Me3Si)2CH}(Ph)P-P(Ph){CH(SiMe3)2} and
elemental tin; we have previously observed similar behavior
in the reactions of SnCl2 or PbCl2 with other potassium
phosphanides.19
Compound 18 Et2O crystallizesasdiscrete dimers inwhich
3
two phosphanide ligands bridge in a μ2-fashion between the
two germanium centers, generating a butterfly shaped Ge2P2
core. The Ge-Pbr distances within this core range from
˚
2.4361(12) to 2.4442(12) A and compare with Ge-P distances
7
˚
of 2.4261(11) and 2.4217(11) A in the Ge2P2 core of 6. The
t
˚
Ge-P distances in 18 Et2O of 2.4151(13) and 2.4153(13) A
3
are slightly shorter than the Ge-Pbr distances but are similar
11
˚
to the Ge-P distances in 10 [2.4023(4) and 2.4114(4) A].
The germanium centers possess a stereochemically active lone
pair and adopt a trigonal pyramidal geometry [sum of angles
at Ge(1) 285.14, Ge(2) 284.87ꢀ].
The dimers crystallize with a syn, syn-arrangement, in which
the two terminal phosphanides lie on the same side of the
P2Ge2 core and the bridging phosphanide ligands are arranged
such that the bulky (Me3Si)2CH groups lie on the same side of
the P2Ge2 core. This arrangement enables the planar phenyl
substituents of the bridging ligands to adopt a configuration
which minimizes steric interactions with the bulky (Me3Si)2CH
substituents of the terminal phosphanide ligands and positions
the bulky (Me3Si)2CH substituents of the bridging ligands on
theoppositesideoftheP2Ge2 core to the terminal phosphanide
ligands. Steric interactions between the terminal phosphanide
ligands are minimized by a puckering of the P2Ge2 core (the
angle between the P(2)-Ge(1)-P(4) and P(2)-Ge(2)-P(4)
planes is 138.0ꢀ). This configuration contrasts with the config-
uration adopted by the closely related dimer 6, in which the
terminal phosphanide ligands are positioned anti to one
another.7 The difference between the configurations of
Rational synthesis of 19 may be achieved through the
reaction between SnCl2 and 3 equiv of 15; this gives 19 in
good yield as orange crystals, after recrystallization from
methylcyclohexane. Similarly, we find that treatment of
GeCl2(1,4-dioxane) with 3 equiv of 15 gives the corres-
ponding ate complex [{(Me3Si)2CH}(Ph)P]3GeLi(THF)
(20) in good yield. Unfortunately, we were unable to obtain
single crystals of 19 suitable for X-ray crystallography;
however, elemental analyses and NMR spectroscopy un-
ambiguously confirm the identity of this compound (see
below). In contrast, single crystals of the germanium
analogue 20 suitable for X-ray crystallography were ob-
tained from cold n-hexane/THF.
18 Et2O and 6 may be attributed to the steric properties of
3
the unsymmetrical bridging ligands in the former, which favor
the syn, syn arrangement, whereas the symmetrical bridging
ligands in the latter do not influence the arrangement of the
terminal ligands and so these adopt a configuration which
minimizes terminal-terminal ligand interactions.
Compound 20 is chiral at each of the phosphorus centers
and crystallizes as discrete cage-like molecules; the crystal
studied contains the PRPRPR stereoisomer and its PSPSPS
enantiomer, since the structure, with glide planes, is non-
centrosymmetric, but achiral. The molecular structure of 20
is shown in Figure 5, along with selected bond lengths and
angles; 3-fold disorder of the whole molecule about the
Ge-Li axis was reasonably modeled by inclusion of a minor
component of all three P atoms, disorder of the hydrocarbon
substituents remaining unresolved. The three phosphorus
atoms of the phosphanide ligands form μ2-bridges between
the germanium and lithium centers to give a trigonal bipyra-
midal GeP3Li core, affording a trigonal pyramidal geo-
metry at the germanium center. The coordination sphere
of the lithium ion is completed by a molecule of THF,
giving the lithium ion a distorted tetrahedral geometry. The
The dimeric structure of 18 appears to remain intact in
solution, even in the donor solvent THF. The 31P{1H} NMR
spectrum of 18 in d8-THF consists of a dominant pair of
triplets at -58.1 (A) and -37.3 ppm (B) (JPP = 17.4 Hz),
consistent with the dimeric structure observed in the solid
state. In addition, small poorly resolved triplets are observed
at -50.5 (C), -43.3 (D), -36.7 (E), and -26.4 ppm (F) with
approximately 10% relative intensity compared to the major
signals A and B. A 31P-31P COSY spectrum shows correla-
tions between the pairs of peaks A and B, C and F, and D and
E, suggesting that the low intensity signals may be assigned to
two additional dimeric species. However, variable tempera-
˚
Ge-P distances of 2.4609(18), 2.4449(19), and 2.4497(19) A
1
ture H, 31P{1H} and 31P-31P EXSY NMR experiments
(taking only the major disorder component) lie between
7
the Ge-Pbr distances in 6 [2.4261(11) and 2.4217(11) A]
˚
reveal that the three species present in solution are not
undergoing exchange; the 1H and 31P{1H} NMR spectra of
18 in d8-THF are invariant over the temperature range -50
to 50 ꢀC. The formation of three independent dimeric
species in solution is supported by the NMR spectra of
batches of 18 from different preparations, which show
different proportions of the minor components, although
these minor components always comprise <10% of the total
product. While it is not possible to unambiguously attribute
these minor signals to specific species, it is likely that one of
the low concentration dimeric species is the alternative PtRPtS
diastereomer of 18.
and the Ge-Pbr distances in the heteroleptic phosphanide-
7
˚
bridged dimer 9 [2.4876(8) and 2.4926(8) A]. The Li-P
˚
distances of 2.663(9), 2.591(10), and 2.593(10) A are typical
of such contacts; for example, the Li-P distances in the
phosphanide-bridged dimer [(Ph2P)Li(tmeda)]2 range from
2.574(19) to 2.629(20) A.20 The P-Ge-P angles in 20 lie in
˚
(19) Blair, S.; Izod, K.; Taylor, R.; Clegg, W. J. Organomet. Chem. 2002,
656, 43.
(20) Mulvey, R. E.; Wade, K.; Armstrong, D. R.; Walker, G. T.; Snaith,
R.; Clegg, W.; Reed, D. Polyhedron 1987, 6, 987.

Article
Inorganic Chemistry, Vol. 49, No. 10, 2010 4703
Figure 6. Structure of the anion of 19a with 40% probability ellipsoids
˚
and with H atoms omitted for clarity. Selected bond lengths (A) and
angles (deg): Sn-P 2.649(2), P-C(1) 1.905(7), P-C(8) 1.849(7), Li-O(1)
1.929(11), Li-O(2) 1.94(3), P-Sn-P0 91.41(6), O(1)-Li-O(2) 110.8(7),
O(1)-Li-O(10) 108.1(8). The prime denotes a symmetry-generated atom.
Figure 5. Molecular structure of 20 with 40% probability ellipsoids and
with H atoms and minor disorder components omitted for clarity.
Selected bond lengths (A) and angles (deg): Ge-P(1) 2.4609(18), Ge-
˚
P(2) 2.4449(19), Ge-P(3) 2.4497(19), Li-P(1) 2.663(9), Li-P(2)
2.591(10), Li-P(3) 2.593(10), Li-O 1.955(9), Ge-P(1)-Li 80.82(19),
Ge-P(2)-Li 82.6(2), Ge-P(3)-Li 82.5(2), P(1)-Ge-P(2) 85.11(6),
P(1)-Ge-P(3) 84.82(6), P(2)-Ge-P(3) 84.54(6), P(1)-Li-P(2) 78.3(2),
P(1)-Li-P(3) 78.1(2), P(2)-Li-P(3) 78.9(2), P(1)-Li-O 127.8(4),
P(2)-Li-O 134.9(5), P(3)-Li-O 136.2(5).
Chart 2. [R = (Me3Si)2CH]
Scheme 3
Figure 7. Proximity of the methine H atoms to the adjacent aromatic
rings in 19 and 20.
latter compounds (Scheme 3). This transition state clearly
bears a strong resemblance to 20.
Although we were unable to obtain single crystals of the tin
analogue of 20, recrystallization of 19 from cold methyl-
cyclohexane/THF gives single crystals of the solvent-separated
ion pair [[{(Me3Si)2CH}(Ph)P]3Sn][Li(THF)4] (19a) suitable
for X-ray crystallography. The molecular structure of the
anion of 19a is shown in Figure 6, along with selected bond
lengths and angles; the structure of the cation is unexceptional
and is not shown. Compound 19a crystallizes in the non-
centrosymmetric cubic space group F43c as a separated ion
pair consisting of an anion containing a tin atom coordinated
by three phosphanide ligands, in a trigonal pyramidal geo-
metry, and a cation containing a lithium ion coordinated by
four molecules of THF in a distorted tetrahedral geometry.
The cation and anion have exact, crystallographic, C3 sym-
metry; the cation is therefore subject to 3-fold disorder about
the Li-O(2) axis. Each phosphanide ligand is chiral, and the
crystal studied was of the PSPSPS and PRPRPR stereoisomers,
the structure being racemic as a result of 4 improper rotation
the small range 84.54(6) to 85.11(6)ꢀ, while the P-Li-P
angles fall in the range 78.1(2) to 78.9(2)ꢀ.
The molecular structure of 20 closely resembles that of the ate
complex [{(Me3Si)2CH}(C6H4-2-CH2NMe2)P]3GeK (21),11
which we reported previously, but which has additional
N-donor groups that bind the potassium ion (Chart 2); this
compound contains a GeP3K core similar to the GeP3Li
core observed in 20. However, the structure of 20 differs
markedly from that of the ate complexes (tBu2P)E(μ2-
tBu2P)2Li(THF) [E = Sn (7), Pb (8)],8 in which only two
phosphanide ligands bridge between the lithium and group
14 element centers. It is notable, however, that Cowley,
Jones, and co-workers propose a transition state of the
form E(μ2-tBu2P)3Li(THF) (7a/8a), in which all three
phosphanide ligands bridge the lithium and tin (or lead)
atoms, to account for the rapid dynamic equilibrium
between the bridging and terminal phosphanides in these
˚
axes and glide planes. The Sn-P distance of 2.649(2) A is

4704 Inorganic Chemistry, Vol. 49, No. 10, 2010
Izod et al.
Figure 8. 31P{1H} NMR spectra of 19 in (a) d8-toluene and (b) d8-THF.
somewhat longer than the corresponding distance in the mono-
satellites due to coupling to 117Sn/119Sn (JPSn = 747 and 780 Hz)
(Figure 8a), while the 7Li{1H} spectrum consists of a binomial
quartet at 3.4 ppm; the 119Sn{1H} spectrum consists of a
binomial quartet centered at -105 ppm (JPSn = 780 Hz). As
was observed for 20, inthe1H NMR spectrum of 19 the methine
protons exhibit an unusual high field chemical shift of -1.16
ppm because of the proximity of these protons to the face of the
adjacent aromatic rings. These spectra are clearly consistent
with the presence in solution of a cage-like ate complex having a
SnP3Li core similar to the GeP3Li core observed in the solid
state structure of 20.
˚
meric diphosphastannylene 2 [average Sn-P 2.567(1) A], but is
similar to the Sn-P distances in the ate complex 7 [2.684(4),
˚
2.702(3), and 2.671(4) A]. In spite of the increased size of Sn
compared to Ge, the P-Sn-P angle of 91.41(6)ꢀ is substantially
wider than the P-Ge-P angle in 20 [84.82(6)-85.11(6)ꢀ],
consistent with the constraints associated with the formation
of a contact ion pair in the latter compound. Although voids of
3
˚
about 1000 A can be identified in the crystal structure, the
SQUEEZE procedure of PLATON finds little electron density
in them and gives only a minor reduction in R factor, so any
solvent must be only loosely held and is largely lost, even in the
brief handling and transfer of a crystal from the mother liquor
to the cold gas stream of the diffractometer. The original, rather
than SQUEEZE-generated, data have been used for the results
reported here.
Exposure of the separated ion pair complex 19a to vacuum
for short periods leads to loss of THF and complete conver-
sion to the cage-like form 19, as established by elemental
analyses and NMR spectroscopy. However, NMR spectra
consistent with the separated ion pair form 19a may be
obtained from solutions of 19 in d8-THF. The 31P{1H}
NMR spectrum of 19 in d8-THF (Figure 8b) consists of a
singlet at -46.6 ppm exhibiting well-resolved satellites due to
coupling to 117Sn/119Sn (JPSn = 995 and 1038 Hz); the
7Li{1H} NMR spectrum of 19 in this solvent consists of a
singlet at 2.3 ppm and the 119Sn{1H} NMR spectrum consists
of a binomial quartet at 62 ppm (JPSn = 1038 Hz). The lack
of 31P-7Li coupling and the large downfield shift of the 119Sn
signal are consistent with the presence of separated ion pairs
The 31P{1H} NMR spectrum of 20 in d8-toluene consists of
a 1:1:1:1 quartet at -32.2 ppm because of coupling to a single
7Li nucleus (JPLi = 50.0 Hz); the 7Li{1H} spectrum consists
of a binomial quartet at 3.18 ppm. These spectra clearly
suggest that the cage-like structure observed in the solid state
persists in non-donor solvents. Consistent with this, the 1H
NMR spectrum of 20 exhibits a singlet at -1.32 ppm because
of the methine proton of the phosphanide ligand, two equal
intensity singlets at 0.04 and 0.17 ppm, because of the
diastereotopic SiMe3 groups, along with signals due to the
phenyl rings and THF. The unusually high-field chemical
shift of the methine proton of the phosphanide ligand may be
attributed to chemical shift anisotropy associated with the
presence of a nearby aromatic ring. Examination of the solid
state structure of 20 clearly shows that the position of the
methine proton of each phosphanide ligand is fixed directly
over the face of the phenyl ring of an adjacent ligand, and so
these protons experience an upfield shift due to a substantial
ring current effect (Figure 7).
7
in this solvent. Similarly, the 31P{1H} and Li{1H} NMR
spectra of 20 in d8-THF consist of singlets at -42.3 and
2.5 ppm, respectively, consistent with the presence of a
separated ion pair species [[{(Me3Si)2CH}(Ph)P]3Ge][Li-
(THF)4] (20a). Removal of solvent in vacuo from THF
solutions of 20a results in complete conversion to the contact
ion pair form 20.
For both 19a and 20a the 1H NMR spectra are as expected.
The methine protons give rise to signals at 1.04 and 0.68 ppm,
respectively; free rotation about the P-E bond on removal of
the “capping” lithium ion ineachcase has the result that these
protons are no longer constrained to lie over an adjacent
The 31P{1H} NMR spectrum of 19 consists of a 1:1:1:1
quartet at 47.3 ppm (JPLi = 50.9 Hz), with well-resolved

Article
Inorganic Chemistry, Vol. 49, No. 10, 2010 4705
aromatic ring and so no longer experience any significant
chemical shift anisotropy.
31P{1H}, 7Li{1H}, and 119Sn{1H} NMR spectrawere recorded
on a JEOL ECS500 spectrometer operating at 202.35, 194.38,
and 186.50 MHz, respectively; chemical shifts are quoted in
ppm relative to external 85% H3PO4, external 0.1 M LiCl,
and external Me4Sn, respectively. Elemental analyses were
obtained by the Elemental Analysis Service of London
Metropolitan University.
Conclusions
The sterically demanding secondary phosphane {(Me3Si)2-
CH}(Ph)PH (14), which lacks a peripheral donor group, is
readily accessible and undergoes deprotonation on treatment
with n-BuLi to give the monomeric phosphanide [{(Me3Si)2-
CH}(Ph)P]Li(THF)3 [15(THF)], after crystallization. The di-
meric sodium and potassium derivatives [[{(Me3Si)2CH}-
(Ph)P]Na(tmeda)]2 [16(tmeda)] and [[{(Me3Si)2CH}(Ph)P]K-
(pmdeta)]2 [17(pmdeta)] may also be obtained in good yields
after crystallization in the presence of the corresponding tertiary
amine.
Whereas reactions between GeCl2(1,4-dioxane) and either
of the donor-functionalized compounds [{(Me3Si)2CH}-
(C6H4-2-NMe2)P]Kor[{(Me3Si)2CH}(C6H4-2-CH2NMe2)P]K
yield the corresponding monomeric, base-stabilized diphospha-
germylenes [{(Me3Si)2CH}(C6H4-2-(CH2)nNMe2)P]2Ge [n = 0
(12), 1 (10)], the corresponding reaction between 2 equiv of
17(Et2O) and GeCl2(1,4-dioxane) yields the dimeric complex
{(Me3Si)2CH}(Ph)PH (14). A solution of [(Me3Si)2CH]Li
(3.56 g, 21.4 mmol) in diethyl ether (30 mL) was added, drop-
wise, to a cold (-78 ꢀC) solution of PhPCl2 (3.83 g, 21.4 mmol)
in diethyl ether (20 mL). The reaction mixture was allowed to
warm to room temperature and was stirred for 2 h. The solvent
was removed in vacuo giving a white solid, which was redis-
solved in THF (30 mL). Solid LiAlH4 (0.81 g, 21.4 mmol) was
cautiously added, and the reaction mixture was heated under
reflux for 2 h. The reaction mixture was allowed to cool to room
temperature, and excess LiAlH4 was quenched by the careful
addition of deoxygenated water (30 mL). The organic layer was
decanted, and the aqueous layer was extracted into diethyl ether
(3 ꢀ 20 mL). The combined organic extracts were dried over 4A
molecular sieves, the solution was filtered, and the solvent was
removed in vacuo from the filtrate to give 14 as a colorless oil.
Yield: 3.72 g, 64.9%. 1H NMR (CDCl3, 294 K): δ 0.07 (s, 9H,
SiMe3), 0.15 (s, 9H, SiMe3), 0.47 (m, 1H, CHP), 4.37 (dd, 3JHH
= 5.0 Hz, JPH = 205.4 Hz, 1H, PH), 7.30-7.55 (m, 5H, Ph).
[[{(Me3Si)2CH}(Ph)P]2Ge]2.Et2O (18 Et2O). This clearly de-
3
13C{1H} NMR (CDCl3, 294 K): δ 0.02 (SiMe3), 7.24 (d, JPC
=
monstrates that, in the absence of peripheral donor functionali-
zation, the steric demands of these ligands are insufficient to
prevent oligomerization.
42.3 Hz, CHP), 127.37, 127.53 (Ph), 132.92 (d, JPC = 17.7 Hz,
Ph), 138.04 (d, JPC = 16.3 Hz, Ph). 31P NMR (CDCl3, 294 K): δ
-60.2 (d, JPH = 205.4 Hz).
Unexpectedly, the reaction between SnCl2 and the lithium
complex 15(Et2O) yields the ate complex [{(Me3Si)2CH}-
(Ph)P]3SnLi(THF) (19), irrespective of the reaction stoichio-
metry. This compound and its germanium analogue (20)
retains its structure in toluene solution, but forms the
separated ion pair complex [[{(Me3Si)2CH}(Ph)P]3Sn]-
[Li(THF)4] (19a) on crystallization from n-hexane/THF.
[[{(Me3Si)2CH}(Ph)P]Li(THF)3] [15(THF)]. To a stirred
solution of 14 (0.92 g, 3.43 mmol) in diethyl ether (20 mL) was
added n-BuLi (1.37 mL, 3.43 mmol), and this mixture was
stirred at room temperature for 1 h. The solvent was removed
in vacuo giving an orange, viscous oil which was crystallized
from cold (-30 ꢀC) n-hexane containing a few drops of THF as
yellow blocks of 15(THF) suitable for X-ray crystallography.
Yield: 1.32 g, 78.4%. Anal. Calcd. for C25H48LiO3PSi2: C,
61.13; H, 9.78%. Found: C, 60.95; H, 9.58%. 1H NMR
(C6D6, 296 K): δ 0.38 (s, 18H, SiMe3), 0.64 (s, 1H, CHP), 1.27
(m, 12H, THF), 3.45 (m, 12H, THF), 6.72-7.53 (m, 5H, Ph).
Experimental Section
All manipulations were carried out using standard Schlenk
techniques under an atmosphere of dry nitrogen. Diethyl
ether, THF, n-hexane, methylcyclohexane, and light petro-
leum (bp 40-60 ꢀC) were dried prior to use by distillation
under nitrogen from sodium, potassium, or sodium/potas-
sium alloy; hexamethyldisiloxane was dried by distillation
under nitrogen from calcium hydride. THF and hexamethyl-
disiloxane were stored over activated 4A molecular sieves;
diethyl ether, n-hexane, methylcyclohexane and light petro-
leum were stored over a potassium film. Deuterated toluene
and THF were distilled from potassium and deoxygenated by
three freeze-pump-thaw cycles and were stored over acti-
vated 4A molecular sieves. Germanium(II) chloride was
prepared as its 1,4-dioxane adduct by a previously published
procedure;21 [(Me3Si)2CH]Li was prepared as previously
described.22 Tin(II) chloride was dried with chlorotrimethyl-
silane prior to use; potassium tert-butoxide and sodium tert-
butoxide were dried under vacuum at 100 ꢀC/10-2 mmHg for
3 h before use. All other compounds were used as supplied by
the manufacturer.
13C{1H} NMR (C6D6, 296 K): δ 1.48 (SiMe3), 2.55 (d, JPC
=
52.8 Hz, CHP), 25.15 (THF), 68.12 (THF), 117.85(Ph), 126.16
(d, JPC = 17.3 Hz, Ph), 133.77 (d, JPC = 17.3 Hz, Ph), 157.73 (d,
J
PC = 45.1 Hz, Ph). 31P{1H} NMR (C6D6, 296 K): δ -77.3.
[[{(Me3Si)2CH}(Ph)P]Na(tmeda)]2 [16(tmeda)]. To a solution
of 14 (1.23 g, 4.60 mmol) in diethyl ether (20 mL) was added
n-BuLi (1.84 mL, 4.60 mmol), and this mixture was stirred for
1 h. The resulting solution was added to a slurry of NaO-t-Bu
(0.44 g, 4.60 mmol) in diethyl ether (20 mL), and this mixture
was stirred at room temperature for 1 h. The solvent was
removed in vacuo giving a sticky yellow solid which was washed
with light petroleum (3 ꢀ 20 mL) and dried in vacuo, yielding a
yellow, pyrophoric solid (16). Crystals of the adduct 16(tmeda)
suitable for an X-ray crystallographic study were obtained from
cold (-30 ꢀC) methylcyclohexane containing 1 equiv of tmeda.
Yield: 1.01 g, 54.2%. Anal. Calcd. for C19H40NaN2PSi2: C,
56.07; H, 9.84; N, 6.89%. Found: C, 55.90; H, 9.75; N, 6.72%.
1H NMR (d8-THF, 296 K): δ 0.20 (s, 18H, SiMe3), 0.30 (s, 1H,
CHP), 2.18 (s, 12H, NMe2), 2.35 (s, 4H, CH2N), 6.28-7.29
(m, 5H, Ph). 13C{1H} NMR (d8-THF, 296 K): δ 0.89 (SiMe3),
2.46 (d, JPC = 59.1 Hz, CHP), 45.56 (NMe2), 58.08 (CH2N)
115.00, 125.41, 126.77 (Ph), 162.73 (d, JPC = 56.7 Hz, Ph).
31P{1H} NMR (d8-THF, 296 K): δ -67.8.
1H and 13C{1H} NMR spectra were recorded on a JEOL
ECS500 spectrometer operating at 500.16 and 125.65 MHz,
respectively, or a Bruker Avance300 spectrometer operating
at 300.15 and 75.47 MHz, respectively; chemical shifts are
quoted in parts permillion (ppm) relative to tetramethylsilane.
[[{(Me3Si)2CH}(Ph)P]K(pmdeta)]2 [17(pmdeta)]. To a solu-
tion of 14 (0.94 g, 3.51 mmol) in diethyl ether (20 mL) was added
n-BuLi (1.40 mL, 3.51 mmol), andthismixturewas stirredatroom
temperature for 1 h. The resulting solutionwas added to a solution
of KO-t-Bu (0.39 g, 3.51 mmol) in diethyl ether (20 mL), and this
mixture was stirred at room temperature for 1 h. Solvent was
(21) Benet, S.; Cardin, C. J.; Cardin, D. J.; Constantine, C. P.; Heath, P.;
Rashid, H.; Teixeira, S.; Thorpe, J. H.; Todd, A. K. Organometallics 1999,
18, 389.
€
(22) Wiberg, N.; Wagner, G.; Muller, G.; Riede, J. J. Organomet. Chem.
1984, 271, 381.

4706 Inorganic Chemistry, Vol. 49, No. 10, 2010
Izod et al.
Table 1. Crystallographic Data for 15(THF), 16(tmeda), 17(pmdeta), 18 Et2O, 19a, and 20
3
15(THF)
16(tmeda)
17(pmdeta)
18 Et2O
3
19a
20
formula
Mw
C25H48LiO3PSi2
490.7
C38H80N4Na2P2Si4 C44H94K2N6P2Si4 C56H106Ge2OP4Si8 C55H104LiO4P3Si6Sn C43H80GeLiOP3Si6
954.1
813.3
959.8
1289.2
1216.5
cryst. size/mm
cryst. syst.
T/K
0.40 ꢀ 0.40 ꢀ 0.24 0.45 ꢀ 0.40 ꢀ 0.40 0.25 ꢀ 0.20 ꢀ 0.20 0.50 ꢀ 0.50 ꢀ 0.40 0.42 ꢀ 0.30 ꢀ 0.30
0.40 ꢀ 0.40 ꢀ 0.20
orthorhombic
150
triclinic
150
P1
triclinic
160
P1
monoclinic
160
P21/c
orthorhombic
150
P212121
cubic
150
space group
˚
F43c
39.504(10)
Pna21
a /A
9.1099(9)
10.7582(11)
17.2892(18)
77.1493(16)
80.0929(16)
65.3595(15)
1495.6(3)
2
11.8928(12)
13.3060(13)
17.8681(18)
93.371(2)
100.996(2)
111.007(2)
2566.1(4)
2
13.538(3)
13.331(3)
17.801(3)
21.4695(13)
22.5652(13)
29.9365(18)
14.464(5)
21.109(3)
18.2313(14)
˚
b /A
˚
c /A
R /deg
β /deg
γ /deg
111.225(14)
3
˚
V /A
Z
2994.9(11)
2
0.323
14503.1(15)
8
1.082
61649(27)
32
0.521
5566(2)
4
0.794
μ/mm-1
0.194
0.223
trans. coeff. range
reflns. measd.
unique reflns.
Rint
0.927-0.955
13338
6926
0.906-0.916
22965
11925
0.022
9215
0.924-0.938
13750
5206
0.057
3448
0.614-0.671
130441
35168
0.065
26086
0.811-0.860
36004
4471
0.058
2961
0.742-0.857
49063
9694
0.053
8332
0.020
reflns. with F2 > 2σ 5321
parameters
R (on F, F2 > 2σ)a
324
0.042
471
0.048
0.118
1.077
324
0.058
0.129
1.075
1332
0.051
0.121
1.140
235
0.055
0.146
1.109
526
0.054
0.146
1.070
Rw (on F2, all data)a 0.112
goodness of fita
max, min electron
1.040
0.42, -0.31
0.39, -0.41
0.33, -0.27
1.42, -0.59
0.49, -0.37
1.16, -0.53
-3
˚
density/e A
P
P
P
P
P
a Conventional R = ||Fo| - |Fc||/ |Fo|; Rw = [ w(Fo2 - Fc2)2/ w(Fo2)2]1/2; S = [ [w(Fo2 - Fc2)2]/(no. data - no. params)]1/2 for all data.
removed in vacuo giving a sticky brown solid which was washed
with light petroleum (3 ꢀ 20 mL) and dried in vacuo, yielding a
yellow-orange pyrophoric solid (17). Crystals of the adduct
17(pmdeta) suitable for an X-ray crystallographic study were
obtained from hot methylcyclohexane containing 1 equiv of
pmdeta. Yield: 0.97 g, 59.5%. Anal. Calcd. for C22H47KN3PSi2:
C, 55.01; H, 9.79; N, 8.75%. Found: C, 54.79; H, 9.60; N, 8.60%.
1H NMR (d8-THF, 297 K): δ 0.07 (s, 18H, SiMe3), 0.13 (s, 1H,
CHP), 2.15 (s, 12H, NMe2), 2.19 (s, 3H, NMe), 2.31 (m, 4H,
CH2N), 2.42 (m, 4H, CH2N), 5.96-6.83 (m, 5H, Ph). 13C{1H}
NMR (d8-THF, 297 K): δ 0.84 (SiMe3), 3.83 (d, JPC = 66.2 Hz,
CHP), 42.33 (NMe), 45.30 (NMe2) 56.42 (CH2N), 57.89 (CH2N)
111.61, 124.14, 126.47 (Ph), 166.72 (d, JPC = 68.1 Hz, Ph).
31P{1H} NMR (d8-THF): δ -51.3.
The filtrate was cooled to -30 ꢀC to give orange microcrystals
of 19. Yield: 0.51 g, 69.0%. Anal. Calcd. for C43H80LiOP3Si6Sn:
C, 51.64; H, 8.06%. Found: C, 51.47; H, 7.91%. 1H NMR
(d8-toluene, 297 K): δ -1.16 (s, 3H, CHP), 0.13 (s, 54H, SiMe3),
1.59 (br s, 4H, THF), 4.00 (br s, 4H, THF), 6.99-7.97 (m, 15H,
Ph). 13C{1H} NMR (d8-toluene, 297 K): δ 3.03 (SiMe3), 4.04
(SiMe3), 8.24 (d, JPC = 24.9 Hz, CHP), 25.26 (THF), 68.91
(THF), 139.14, 140.28 (Ph, remaining signals obscured by
7
solvent). Li{1H} NMR (d8-toluene, 297 K): δ 3.4 (q, JPLi
=
=
50.8 Hz). 31P{1H} NMR (d8-toluene, 297 K): δ -47.3 (q, JPLi
50.8 Hz, JPSn = 747 and 780 Hz). 119Sn{1H} NMR (d8-toluene,
297 K): δ -105 (q, JSnP = 780 Hz).
[[{(Me3Si)2CH}(Ph)P]3Sn]-[Li(THF)4]þ (19a). Dissolution
of 19 in n-hexane containing a few drops of THF and cooling
to 5 ꢀC for several hours yields crystals of the contact ion pair
[[{(Me3Si)2CH}(Ph)P]3Sn]-[Li(THF)4]þ (19a). This compound
rapidly reverts to 19 on exposure to vacuum, but NMR data
[[{(Me3Si)2CH}(Ph)P]2Ge]2 Et2O (18 Et2O). To a stirred
3
3
solution of GeCl2(1,4-dioxane) (0.45 g, 1.94 mmol) in THF
(20 mL) was added a solution of 17 (1.19 g, 3.89 mmol) in THF
(20 mL), and this mixture was stirred at room temperature for
16 h. Solvent was removed in vacuo, and the sticky brown solid
was extracted into light petroleum (20 mL) and filtered. Solvent
was removed in vacuo from the filtrate, and the sticky solid was
crystallized from cold (-30 ꢀC) hexamethyldisiloxane contain-
ing a few drops of diethyl ether as orange blocks of the solvate
1
corresponding to 19a may be obtained in d8-THF. H NMR
(d8-THF, 297 K): δ 0.06 (s, 54H, SiMe3), 1.04 (s, 3H, CHP), 1.81
(br s, 16H, THF), 3.64 (br s, 16H, THF), 6.73-7.73 (m, 15H,
Ph). 13C{1H} NMR (d8-THF, 297 K): δ 2.84 (SiMe3), 6.20
(d, JPC = 30.7 Hz, CHP), 24.43 (THF), 66.59 (THF), 122.63,
125.67, 134.86 (Ph), 149.34 (d, JPC = 39.4 Hz, Ph). Li{1H}
7
18 Et2O. Yield: 0.76 g, 60.8%. Anal. Calcd. for C52H96Ge2P4Si8
NMR (d8-THF, 297 K): δ 2.3 (s). 31P{1H} NMR (d8-THF,
297 K): δ -46.6 (s, JPSn = 995 and 1038 Hz). 119Sn{1H} NMR
(d8-THF, 297 K): δ 62 (q, JSnP = 1038 Hz).
3
(empirical formula without solvent of crystallization): C, 51.40; H,
7.96%. Found: C, 51.27; H, 8.14%. 1H NMR (d8-THF, 323 K): δ
-0.03 (s, 18H, SiMe3), 0.07 (s, 18H, SiMe3), 0.13 (s, 18H, SiMe3),
0.24 (br s, 18H, SiMe3), 0.44 (m, 2H, CHP), 0.53 (m, 2H, CHP),
1.11 (t, ca. 6H, Et2O), 3.39 (q, ca. 4H, Et2O), 6.73-8.01 (m, 20H,
Ph). 31P{1H} NMR (d8-THF, 323 K): δ -26.4 (br s, minor), -36.7
(t, 2JPP2= 36.0 Hz, minor), -37.3 (t, 2JPP =17.4Hz, major), -43.2
[[{(Me3Si)2CH}(Ph)P]3GeLi(THF)] (20). To a stirred solu-
tion of GeCl2(1,4-dioxane) (0.28 g, 1.21 mmol) in THF (20 mL)
was added a solution of 15(THF) (1.78 g, 3.63 mmol) in THF
(20 mL), and this mixture was stirred at room temperature for
16 h. Solvent was removed in vacuo, and the sticky brown solid
was extracted into diethyl ether (20 mL) and filtered. Solvent
was removed in vacuo from the filtrate, and the sticky solid was
crystallized from cold (-30 ꢀC) n-hexane containing a few drops
of THF as orange blocks of 20. Yield: 0.61 g, 52.8%. Anal.
Calcd. for C43H80GeLiOP3Si6: C, 54.13; H, 8.45%. Found: C,
54.08; H, 8.40%. 1H NMR (d8-toluene, 295 K): δ -1.32 (s, 3H,
CHP), 0.04 (s, 27H, SiMe3), 0.17 (s, 27H, SiMe3), 1.58 (br m, 4H,
THF), 3.93 (br m, 4H, THF), 7.01-8.10 (m, 15H, Ph). 13C{1H}
NMR (d8-toluene, 296 K): δ 2.97 (SiMe3), 4.33 (SiMe3), 8.48
2
(br t, JPP = ca. 36 Hz, minor), -50.5 (br t, JPP = ca. 33 Hz,
minor), -58.1 (t, 2JPP = 17.4 Hz, major).
[[{(Me3Si)2CH}(Ph)P]3SnLi(THF)] (19). To a stirred solu-
tion of SnCl2 (0.14 g, 0.74 mmol) in cold (-78 ꢀC) THF (20 mL)
was added a solution of 15(THF) (1.09 g, 2.22 mmol) in THF
(20 mL), excluding light as much as possible. The reaction
mixture was allowed to attain room temperature and was stirred
for 16 h. Solvent was removed in vacuo, and the sticky brown
solid was extracted into methylcyclohexane (20 mL) and filtered.

Article
Inorganic Chemistry, Vol. 49, No. 10, 2010 4707
(d, JPC = 23.9 Hz, CHP), 25.29 (THF), 68.78 (THF), 127.65,
128.36, 138.92, 140.13 (Ph). 7Li{1H} NMR (d8-toluene, 296 K):
δ 3.2 (q, JLiP = 50.4 Hz). 31P{1H} NMR (d8-toluene, 296 K): δ
-32.1 (q, JPLi = 50.4 Hz).
U(H) was set at 1.2 (1.5 for methyl groups) times Ueq for the
parent atom. Minor disorder was resolved for the two THF
ligands in 15(THF) and for the pmdeta ligand in 17(pmdeta).
In 19a one THF ligand isdisorderedbya crystallographicC3 axis,
so the structural model contains one component with 1/3 occu-
pancy. Inallthree ofthesestructures the disorder does not include
the coordinating N or O atoms and so does not impact on the
metal coordination geometry. In 20, there is only one crystallo-
graphically independent phosphanide ligand, and this is dis-
ordered equally over two orientations. The C and H atoms could
not be resolved, as the two components overlap closely, but two
alternative positions were successfully refined for the P atom with
unequal occupancy; unresolved C/H atom disorder is apparent in
large anisotropic displacement parameters. Refinement of dis-
order components was aided by geometrical similarity restraints
for 19a, and restraints on displacement parameters for 19a and
20, but these were unnecessary for the other structures. Programs
were Bruker AXS SMART and SAINT or Nonius COLLECT
and EvalCCD, and SHELXTL for structure solution, refine-
ment, and molecular graphics.23
[[{(Me3Si)2CH}(Ph)P]3Ge]-[Li(THF)4]þ (20a). Although the
separated ion pair complex [[{(Me3Si)2CH}(Ph)P]3Ge]-[Li-
(THF)4]þ (20a) could not be isolated in the solid state because
of rapid desolvation to give the contact ion pair 20, NMR data
recorded in d8-THF are consistent with the presence of the
1
former: H NMR (d8-THF, 296 K): δ -0.12 (s, 54H, SiMe3),
0.68 (m, 3H, CHP), 1.78 (br m, 16H, THF), 3.62 (br m, 16H,
THF), 6.86-8.04 (m, 15H, Ph). 13C{1H} NMR (d8-THF, 297
K): δ 2.75 (SiMe3), 6.29 (d, JPC = 38.4 Hz, CHP), 24.41 (THF),
66.49 (THF), 124.07, 125.78, 137.73, 147.69 (Ph). 7Li{1H} NMR
(d8-THF, 297 K): δ 2.5 (s). 31P{1H} NMR (d8-THF, 297 K): δ
-42.3 (s).
Crystal Structure Determinations of 15(THF), 16(tmeda),
17(pmdeta), 18 Et2O, 19a and 20. Measurements were made
3
on either a Bruker AXS SMART or a Nonius KappaCCD
diffractometer using graphite-monochromated MoKR radiation
˚
(λ = 0.71073 A). Cell parameters were refined from the observed
Acknowledgment. The authors are grateful to the EPSRC
for support.
positions of all strong reflections. Intensities were corrected
semiempirically for absorption, based on symmetry-equivalent
and repeated reflections. The structures were solved by direct
methods and refined on F2 values for all unique data. Table 1
gives further details. All non-hydrogen atoms were refined aniso-
tropically, and H atoms were constrained with a riding model;
Supporting Information Available: For 15(THF), 16(tmeda),
17(pmdeta), 18 Et2O, 19a, and 20 details of structure determi-
3
nation, atomic coordinates, bond lengths and angles, and dis-
placement parameters in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org. Observed
and calculated structure factor details are available from the
authors upon request.
(23) (a) COLLECT; Nonius B. V.: Delft, The Netherlands, 1998.
(b) SMART and SAINT; Bruker AXS Inc.: Madison, WI, 2004 and 1997;
(c) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.