Synthesis and structural characterization of base-stabilized oligomeric heterovinylidenes

Article abstract of DOI:10.1021/ic4011345

Metalation of the (iminophosphoranyl)phosphine PPh₂CH ₂(PPh₂=NSiMe₃) (1) with an equimolar amount of n-BuLi afforded the monolithium salt [Li{CH(PPh₂)(PPh ₂=NSiMe₃)}(THF)₂] (2). The reaction of 2 with GeCl₂·1,4-dioxane has led to the formation of a germavinylene moiety, which trimerized to form a new heterocyclic cage compound, [{(PPh ₂=NSiMe₃)(PPh₂)C=Ge:}{(PPh₂= NSiMe₃)(PPh₂)C}₂Ge→Ge:] (3). A similar reaction of the lithium methanide complex 2 with SnCl₂ afforded the stannavinylidene moiety, which underwent a head-to-tail cycloaddition to form a stable 1,3-distannacyclobutane, 4. A trapping reaction of 4 with diiron nonacarbonyl gave the novel iron stannavinylidene complex 5. The solid-state structure analysis of 5 reveals that it contains two stannavinylidene moieties bonded in a Sn-P head-to-tail fashion, with one of the tin(II) centers coordinating to a Fe(CO)₄ moiety. The X-ray structures of 2-5 have been determined by X-ray crystallography. In addition, the dynamic behavior of 5 has been studied by means of variable-temperature ³¹P and ¹¹⁹Sn NMR spectroscopy.

Full text of DOI:10.1021/ic4011345

Article
pubs.acs.org/IC
Synthesis and Structural Characterization of Base-Stabilized
Oligomeric Heterovinylidenes
Wing-Por Leung,* Wang-Kin Chiu, and Thomas C. W. Mak
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People’s Republic of China
S
* Supporting Information
ABSTRACT: Metalation of the (iminophosphoranyl)-
phosphine PPh2CH2(PPh2NSiMe3) (1) with an equimolar
amount of n-BuLi afforded the monolithium salt [Li{CH-
(PPh2)(PPh2NSiMe3)}(THF)2] (2). The reaction of 2 with
GeCl2·1,4-dioxane has led to the formation of a germavinylene
moiety, which trimerized to form a new heterocyclic cage
compound, [{(PPh2NSiMe3)(PPh2)CGe:}{(PPh2
NSiMe3)(PPh2)C}2Ge→Ge:] (3). A similar reaction of the
lithium methanide complex 2 with SnCl2 afforded the
stannavinylidene moiety, which underwent a “head-to-tail”
cycloaddition to form a stable 1,3-distannacyclobutane, 4. A
trapping reaction of 4 with diiron nonacarbonyl gave the novel
iron stannavinylidene complex 5. The solid-state structure analysis of 5 reveals that it contains two stannavinylidene moieties
bonded in a Sn−P “head-to-tail” fashion, with one of the tin(II) centers coordinating to a Fe(CO)4 moiety. The X-ray structures
of 2−5 have been determined by X-ray crystallography. In addition, the dynamic behavior of 5 has been studied by means of
variable-temperature 31P and 119Sn NMR spectroscopy.
complexes, stable heavier main group 14 vinylidene analogues
(:MC<) are still scarcely known. This is due to the high
reactivity of the CM: bond. In general, they are expected to
undergo oligomerization more readily. Until now, there are
only two examples of structurally characterized heavier group
14 metallavinylidene analogues (:MC<). The first example of
a bis(germavinylidene) was reported in 2001, which contains a
weak Ge−Ge interaction (Figure 1).7b So and co-workers
recently reported the synthesis of a tin(II) (iminophosphinoyl)-
(thiophosphinoyl)methanediide complex, [(PPh2NSiMe3)-
(PPh2S)CSn:]2 (Figure 1).16
INTRODUCTION
■
The chemistry of base-stabilized methanediide metal complexes
has been extensively studied in the past decades since the
report of a dilithium bis(iminophosphoranyl)methanediide
complex by Cavell et al. and Ong and Stephan.1−3 After that,
bis(iminophosphoranes) bearing tetramethylsilane,4 P(X)-
(OR)2,5 and sterically hindered aryl groups were synthesized.6
In particular, bis(iminophosphoranyl)methane CH2(PPh2
NSiMe3)24 has been used as a ligand precursor for the synthesis
of main-group,7 transition-metal,8 and lanthanide-metal9
methanediide complexes. By varying both the electronic and
steric properties of bis(phosphoranyl)methanes, Le Floch and
co-workers recently reported the direct synthetic routes to
mixed P−N ligands10 of the general formula (R2P−spacer−
PR2N−R) that incorporate both a phosphino group and an
iminophosphorane moiety. Cavell and co-workers have also
demonstrated that the controlled Staudinger reaction11 of
diphosphines with 1 equiv of azide can lead to the formation of
heterobifunctional phosphinophosphoranoimines
PPh2CH2(PPh2NR).12 Meanwhile, the (iminophos-
phoranyl)phosphine PPh2CH2(PPh2NSiMe3) (1) was em-
ployed by P. Roesky in the synthesis of potassium and
samarium phosphine(phosphinimino)methanide complexes.13
The closely related hemilabile ligands of the general
composition (Ph2PE)CH2(PPh2NSiMe3) (E = S, Se)
have been reported by individual research groups of So and
Cadierno in the synthesis of some metal complexes.14,15
Despite the recent advances in ligand development and the
coordination chemistry of base-stabilized metal methanide
Figure 1. Existing examples of base-stabilized germavinylidene and
stannavinylidene.
Received: May 6, 2013
Published: August 8, 2013
© 2013 American Chemical Society
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Here we report the synthesis and structural characterization
of a heterocyclic cage compound, [{(PPh2NSiMe3)(PPh2)-
CGe:}{(PPh2NSiMe3)(PPh2)C}2Ge→Ge:] (3), which
contains a phosphine-stabilized germavinylidene moiety. In
addition, the synthesis of a 1,3-distannacyclobutane, [Sn{μ2-
C(PPh2NSiMe3)(PPh2)}]2 (4), and its trapping reaction
with Fe2(CO)9 to give a novel iron stannavinylidene complex,
[{(PPh2NSiMe3)(PPh2)CSn:}{(PPh2NSiMe3)(PPh2)
CSn→Fe(CO)4}] (5), are described.
in the synthesis of bis(germavinylidene) from the reaction of
GeCl2·1,4-dioxane with [Li{CH(PPh2NSiMe3)2}(THF)].7b
Synthesis of an Iron Stannavinylidene Complex. The
reaction of 2 with SnCl2 afforded a 1,3-distannacyclobutane, 4,
with a “steplike” structure (Scheme 3). A similar reaction of the
lithium methanide complex [Li{CH(PPh2NSiMe3)2}-
(THF)] with SnCl2 also afforded 1,3-distannacyclobutane but
with an “open-box” structure.7b We have reported the synthesis
of a series of 1,3-distannacyclobutanes derived from different
ligands and proposed that the formation of these compounds
involves the “head-to-tail” cycloaddition of a highly reactive
stannavinylidene intermediate.17 However, attempts to trap the
transient stannavinylidene had been unsuccessful. We have
learned that several groups have used the donor−acceptor
strategy for stabilization of a highly reactive species in the
coordination spheres of transition metals or by formation of a
stable adduct with both Lewis acid or Lewis base.18 Inspired by
the results derived from this donor−acceptor stabilization
strategy, we anticipated isolating the unstable stannavinylidene
by the addition of 1 equiv of Fe2(CO)9 with 4. We have
successfully isolated the iron stannavinylidene complex 5.
Compound 5 represents the first example of a transition-metal
stannavinylidene complex. The solid-state structure of 5 reveals
that each molecule of 5 contains two stannavinylidene moieties
bonded in a Sn−P “head-to-tail” fashion with one of the tin(II)
centers coordinating to a Fe(CO)4 moiety. The other tin(II)
center remains with a stereoactive lone-pair electron uncoordi-
nated.
RESULTS AND DISCUSSION
■
Synthesis of Germavinylidene. The treatment of 1 with
n-BuLi in tetrahydrofuran (THF) at 0 °C afforded the lithium
phosphine(phosphinimino)methanide [Li{CH(PPh2)(PPh2
NSiMe3)}(THF)2] (2; Scheme 1).
Scheme 1. Synthesis of 2
The reaction of 2 with 0.5 equiv of GeCl2·1,4-dioxane
afforded a fused tricyclic germanium(II) methanediide complex,
3 (Scheme 2). The formation of 3 is proposed to involve three
molecules of unstable germavinylidene generated from reaction
with a lithium salt. Two of the germavinylidenes formed a
dimer via the Ge−P “head-to-tail” fashion. The other
germavinylidene transferred one methanediide ligand to one
of the germanium atoms, followed by rearrangement to form 3.
Delocalization of charge within the cyclic ring is based on the
structural data. The lithium salt 2 acted both as a ligand-transfer
reagent and as a base for dehydrochlorination. Formation of the
byproduct (iminophosphoranyl)phosphine was confirmed by a
31P NMR study. Similar dehydrochlorination has been reported
Spectroscopic Properties. Compounds 2−5 were isolated
as yellow or dark-red crystalline solids, which decompose
readily upon contact with air or moisture. They are soluble in
THF, ether, and toluene but sparingly soluble in hexane. The
1H NMR spectrum of 2 shows one doublet of doublets for the
2
methanide proton at δ 1.39 (2JP′−H = 11.6 Hz and JP−H = 5.6
Hz) due to the coupling of the methanide proton to two
nonequivalent phosphorus nuclei. The 31P{1H} NMR spectrum
displays two doublets at δ −19.3 and +25.8 (2JP−P′ = 129.6 Hz),
which is consistent with the presence of two different
Scheme 2. Synthesis of 3
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Scheme 3. Synthesis of 4 and 5
phosphorus environments. The 1H NMR spectrum of 3
displays two singlets with an intensity ratio of 1:2 due to the
three SiMe3 groups within the molecule. The 31P NMR
spectrum of 3 shows four signals and is consistent with the
structure that contains four different phosphorus environments.
four signals at δ 89.4, 100.7, 297.1, and 345.5. We propose that
in solution compound 5 is subjected to a dynamic equilibrium
that involves the breaking of the tin−phosphorus dative
interactions to give monomers 6 and 7 in a reversible manner
(Scheme 4). At room temperature, interconversion is at a
moderate rate and so broad signals were observed in the room
temperature 31P and 119Sn NMR spectra. At −80 °C, the
exchange rate slows down and the eight signals observed in the
31P NMR spectrum correspond to the eight different
phosphorus environments. The four signals observed in the
119Sn NMR spectrum at −80 °C are also consistent with the
proposed solution-state dynamic equilibrium. It is noteworthy
that the breaking of the Ge−Ge interaction in bis-
(germavinylidene) and the existence of monomeric germavi-
nylidene in the solution state have been demonstrated by the
trapping reactions of bis(germavinylidene).19
X-ray Structures. The molecular structures of 2−5 are
shown in Figures 3−6, respectively. Selected bond distances
(Å) and angles (deg) can be found in Tables 1−4 in the
Supporting Information. Compound 2 is a monomeric
compound containing a four-membered metallacycle Li(1)−
C(1)−P(1)−N(1). The anionic [Ph2PCH(PPh2NSiMe3)]−
ligand coordinates via the N−P−C backbone in a heteroallylic
fashion onto the lithium atom. The C(1)−Li(1) distance of
2.321(1) Å is shorter than that of 2.560(8) Å in the lithium
methanide complex [Li{CH(PPh2NSiMe3)2}(THF)]20 and
comparable to the C−Liavg distance of 2.386 Å in the dilithium
methanediide complex [Li2C(PPh2NSiMe3)2].2,3 The C(1)−
P bond distances of 1.715(6) and 1.753(6) Å are comparable to
those of the potassium methanide complex [K{CH(Ph2P)-
(PPh2NSiMe3)}]n [1.724(6) and 1.739(7) Å].13
1
The H NMR spectra of 4 and 5 display signals due to the
SiMe3 and phenyl protons. Similar to bis(germavinylidene)7b
and the tin(II) bis(phosphinoyl)methanediide complex,16 the
13C NMR signal for the carbenic carbon in 4 or 5 was not
observed. The 31P{1H} NMR spectrum of 4 displayed two
doublets at δ −13.6 and +32.2 (2JP−P′ = 24.3 Hz) due to two
different phosphorus environments. The 119Sn NMR spectrum
of 4 displays a signal at δ 284.6, which is consistent with the
solid-state structure. However, the 31P and 119Sn NMR spectra
of 5 at room temperature are not consistent with the solid-state
structure. There are two signals at δ 36.6 and 42.3 (2JP−P′ = 39.9
Hz), and one broad signal was observed at δ 2.5 in the 31P
NMR spectrum. In addition, the 119Sn NMR spectrum showed
a signal at δ 79.6 and a broad signal at δ 88.2. To get insight
into the structure of 5 in solution, we have carried out a
variable-temperature 31P NMR experiment of 5 (Figure 2). We
found that eight signals at δ −21.7, −19.4, +4.1, +6.1, +33.8,
+35.2, +39.5, and +45.5 were recorded at −80 °C. The 31P−31P
COSY and variable-temperature 119Sn NMR spectra were also
recorded. At −80 °C, the 119Sn NMR spectrum of 5 showed
The molecular structure of 3 is significantly different from
that of bis(germavinylidene) (Figure 1), which comprises of
two germavinylidenes [(Ph2PNSiMe3)2CGe:] bonded
together in a “head-to-head” manner.7b Compound 3 consists
of a germavinylidene [(PPh2NSiMe3)(PPh2)CGe:] moi-
ety on one side of the molecule stabilized by two other
phosphorus donor atoms from a germaallene moiety. The
eight-membered heterocyclic ring contains two germanium
atoms with a germanium(II)−germanium(II) donor−acceptor
interaction. The structure of compound 3 is symmetrical; it has
three different germanium environments. Ge(1) is three-
coordinate, and the sum of the bond angles at the Ge(1)
atom is 281.9°, which is consistent with the presence of a
stereoactive lone-pair electron at the germanium(II) center.
The Ge(3) atom is bonded with one methanediide carbon,
C(72), and two phosphorus atoms, P(2) and P(4), from the
other two ligands. The sum of the bond angles at the Ge(3)
Figure 2. Variable-temperature 31P{1H} NMR spectra (THF-d8) of 5.
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Scheme 4. Equilibrium of 5 in the Solution State
Figure 4. Molecular structure of 3. Hydrogen atoms are omitted for
clarity. 30% thermal ellipsoids are shown. Selected bond distances (Å)
and angles (deg): Ge(1)−Ge(2) = 2.427(1), Ge(2)−C(44) =
1.913(5), Ge(2)−C(16) = 1.943(5), Ge(3)−C(72) = 1.975(5),
Ge(2)−P(6) = 2.363(1), Ge(3)−P(2) = 2.526(1); N(1)−Ge(1)−
Ge(2) = 84.7(1), N(2)−Ge(1)−Ge(2) = 85.9(1), N(2)−Ge(1)−
N(1) = 111.3(2), C(16)−Ge(2)−Ge(1) = 106.0(1), C(44)−Ge(2)−
Ge(1) = 104.4(2), C(16)−Ge(2)−P(6) = 109.4(1), C(72)−Ge(3)−
P(4) = 102.1(2), C(72)−Ge(3)−P(2) = 100.2(2).
Figure 3. Molecular structure of 2. Hydrogen atoms are omitted for
clarity. 30% thermal ellipsoids are shown. Selected bond distances (Å)
and angles (deg): Li(1)−C(1) = 2.321(1), Li(1)−N(1) = 2.027(1),
P(1)−C(1) = 1.715(6), P(2)−C(1) = 1.753(6); P(1)−C(1)−Li(1) =
79.2(4), P(2)−C(1)−Li(1) = 123.0(4), P(1)−C(1)−P(2) = 123.1(4),
P(1)−N(1)−Li(1) = 123.0(4).
NHC-stabilized digermanium(0) complex [2.349(1) Å]23 and
much longer than the Ge−Ge triple bonds found in digermynes
[2.206(1)−2.285(1) Å].24 The Ge−Pavg distance of 2.460(1) Å
in 3 is in the range of 2.314(2)−2.526(1) Å observed for some
reported phosphinegermylene compounds.25
atom is 292.4°, which is consistent with a stereoactive lone pair
at the germanium(II) center.
The Ge(2)−C(16), Ge(2)−C(44), and Ge(3)−C(72) bond
distances of 1.943(5), 1.913(5), and 1.975(5) Å are comparable
to the Ge−C double-bond distances of 1.908(7) and 1.905(8)
Å in bis(germavinylidene)7b and significantly shorter than the
Ge−C single-bond distances in the 1,3-digermacyclobutane 1,3-
[Ge-{C(Pri2PNSiMe3)(2-Py)}]2 [2.107(3) and 2.132(3)
Å]17a and those in the germanium(II) methanediide complexes
[(Me3SiNPPh2)2C-GeW(CO)3(M(CO)5)] [2.046(4) Å]
and [(Me3SiNPPh2)2{(cod)Rh}C-GeCl] [2.076(3) Å].19 In
addition, the Ge−C bond distances of 3 are slightly longer than
the Ge−C double-bond distance in the germanium(IV)
bismethanediide complex [1.882(2) Å]21 because of the
lower oxidation state of germanium in 3. A rare germanium-
(II)−germanium(II) donor−acceptor interaction is also
observed in compound 3. The Ge(1)−Ge(2) bond distance
of 2.427(1) Å in the eight-membered heterocyclic ring is
comparable to the Ge−Ge bond distance of 2.483(1) Å in
bis(germavinylidene).7b It is shorter than the Ge−Ge single-
bond distances reported for germanium(I) dimers [2.506(1)−
2.709(1) Å]22 but longer than the Ge−Ge double bond in the
Compound 4 consists of two metal atoms bridged by two
methanediide carbon atoms, forming a 1,3-Sn2C2 four-
membered ring. Each imino nitrogen atom of the ligand
coordinates to the tetrahedral metal center to form a SnCPN
four-membered ring. In each molecule, the two SnCPN rings
together with the Sn2C2 ring form a “steplike” structure, which
is different from the “open-box” structure found in the 1,3-
distannacyclobutane [Sn{μ2-C(PPh2NSiMe3)2}]2.7b Notably,
the phosphorus atom of the diphenylphosphine group remains
uncoordinated. The C(1)−Sn(1) bond distance of 2.364(2) Å
in 4 is comparable to the distance of 2.376 Å in the 1,3-
7b
distannacyclobutane [Sn{μ2-C(PPh2NSiMe3)2}]2 and the
Sn−C single-bond distances of 2.373(4) and 2.362(2) Å
reported in the bis(phosphorus-stabilized)methanediide tin(II)
complexes.26
The molecular structure of compound 5 shows that it is
unsymmetrical and comprised of two stannavinylidene
[(PPh2NSiMe3)(PPh2)CSn:] moieties bonded together
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The C(1)−Sn(1) bond distance of 2.207(5) Å and the
C(29)−Sn(2) bond distance of 2.134(4) Å in 5 are both
significantly shorter than the Sn−C single-bond distances of
2.364(2) Å in 4 and the distance of 2.376 Å in the 1,3-
distannacyclobutane [Sn{μ2-C(PPh2NSiMe3)2}]2.7b
Although the C(1)−Sn(1) bond distance of 2.207(5) Å and
the C(29)−Sn(2) bond distance of 2.134(4) Å in 5 are
comparable to the Sn−C distances of 2.234(5) and 2.205(3) Å
in the four- and three-coordinate tin(II) complexes recently
reported by Jurkschat et al. and Ruzick
̌
a et al.,27,28 they are
̊
̌
significantly shorter than the Sn−C single-bond distances of
2.373(4) and 2.362(2) Å reported for the bis(phosphorus-
stabilized)methanediide tin(II) complexes.26 In addition, the
Sn−C bond distances in 5 are comparable to the distance of
2.2094(9) Å for the reported Sn−C double-bond distance of
the stannavinylidene derivative [(PPh2NSiMe3)(PPh2S)C
Sn:]2.16 This demonstrates that some double-bond character
exists in both of the C(1)−Sn(1) and C(29)−Sn(2) bonds.
The Sn−C distances in 5 are longer than those of the
stannaethene [{(Me3Si)2CH}2SnC{(Bt-Bu)2C(SiMe3)2}]
[2.025(4) Å],29 the 6-stannapentafulvene [(Tbt)(Mes)Sn
CR2] [2.016(5) Å],30 and the 2-stannaallene [Sn{C(PPh2
S)2}2] [2.063(2) Å]31 because of the lower oxidation state (+2)
of the tin atoms in 5.
Figure 5. Molecular structure of 4. Hydrogen atoms are omitted for
clarity. 30% thermal ellipsoids are shown. Selected bond distances (Å)
and angles (deg): Sn(1)−C(1) = 2.364(2), Sn(1)−N(1) = 2.247(2);
C(1)#1−Sn(1)−C(1) = 87.1(1), Sn(1)#1−C(1)−Sn(1) = 93.0(1),
P(1)−C(1)−Sn(1) = 107.2(1), P(2)−C(1)−Sn(1) = 101.9(1),
P(1)−C(1)−P(2) = 130.4(1), N(1)#1−P(1)−C(1) = 102.2(1).
Density functional theory calculations and natural bond
orbital analysis have been carried out in a similar
stannavinylidene complex, [(PPh2NSiMe3)(PPh2S)CSn:]2
(Figure 1). It was found that the electron densities of the σ
and π bonds are mostly occupied by the methanediide carbon
atom (85.3% electron density of the σ bond and 96.9% electron
density of the π bond).16 Topological analysis of the electron
densities shows that the Sn−C bond is polar and covalent and
can be viewed as between the resonance forms A and B
(Scheme 5).
Scheme 5. Resonance Forms A and B of the Sn−C Bonds in
Stannavinylidene Complexes
Figure 6. Molecular structure of 5. Hydrogen atoms are omitted for
clarity. 30% thermal ellipsoids are shown. Selected bond distances (Å)
and angles (deg): Fe(1)−Sn(2) = 2.505(1), Sn(1)−C(1) = 2.207(5),
Sn(2)−C(29) = 2.134(4), Sn(1)−N(1) = 2.252(4), Sn(2)−N(2) =
2.188(4), Sn(1)−P(4) = 2.690(1); C(29)−Sn(2)−Fe(1) = 132.4(1),
Fe(1)−Sn(2)−P(3) = 138.8(3), C(29)−Sn(2)−P(2) = 103.9(1),
P(2)−Sn(2)−P(3) = 108.2(1), C(1)−Sn(1)−N(1) = 70.0(2), C(1)−
Sn(1)−P(4) = 91.3(1), P(3)−C(29)−P(4) = 129.6(3), P(4)−
C(29)−Sn(2) = 131.3(2).
Meanwhile, the comparison of the Sn−C bond distances in
compound 5 also supports that the Sn−C bond in 5 can be
between the resonance forms A and B (Scheme 5). That the
C(29)−Sn(2) bond [2.134(4) Å] in 5 is shorter than the
C(1)−Sn(1) bond [2.207(5) Å] can be explained by the fact
that the Sn(2) atom forms a dative bond with Fe(1) and so the
electron density at Sn(2) is lowered, thereby making it more
electrophilic. The resonance form of the C(29)−Sn(2) bond
lies more to A form; hence, shortening of the Sn−C bond is
observed. The Sn(1)−N(1) [2.252(4) Å] and Sn(2)−N(2)
[2.188(4) Å] bonds are comparable to that of 4 [2.2469(19)
Å]. The Sn(1)−P(4) [2.6899(12) Å] and Sn(2)−P(2)
[2.6167(12) Å] bonds are comparable to the reported dative
Sn−P distances.32−34
in a Sn−P “head-to-tail” manner, with one of the tin(II) centers
coordinated to a Fe(CO)4 moiety. In addition to the iron atom
Fe(1), the tin atom Sn(2) is bonded to the methanediide
carbon atom C(29), one nitrogen atom, and one phosphorus
atom of each ligand. Therefore, the geometry around Sn(2) is
tetrahedral. As for the Sn(1) atom, it is bonded to the
methanediide carbon atom C(1), one nitrogen atom, and one
phosphorus atom of each ligand. The geometry around the
Sn(1) center is trigonal-pyramidal. The sum of the bond angles
at the tin atom is 272.0°, which is consistent with the presence
of a stereoactive lone-pair electron at the tin(II) center.
CONCLUSIONS
■
To summarize, we have prepared the lithium methanide
complex 2 from the (iminophosphoranyl)phosphine 1.
Compound 2 serves as a ligand-transfer and dehydrochlorina-
tion reagent in the synthesis of a cyclic germanium(II)
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Table 1. Crystallographic Data for Compounds 2−5
2
3
4
5
formula
Mr
C36H46LiNO2P2Si
621.71
C84H87Ge3N3P6Si3
1626.43
C56H58N2P4Si2Sn2
1176.48
C60H58FeN2O4P4Si2Sn2
1344.37
color
pale yellow
triclinic
yellow
yellow
red
cryst syst
space group
a (Å)
triclinic
monoclinic
P21/c
monoclinic
P21/n
P1
̅
P1
̅
10.7296(19)
10.880(2)
16.270(3)
95.857(4)
100.286(3)
96.741(3)
1841.1(6)
2
16.6973(8)
22.7980(11)
23.5002(12)
86.2080(10)
78.4490(10)
89.7510(10)
8745.0(7)
4
10.4080(3)
12.8655(4)
20.8788(7)
90
22.6265(13)
12.3720(7)
25.1730(15)
90
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
dcalcd (g cm−3
μ (mm−1
101.6420(10)
90
108.4570(10)
90
2738.24(15)
2
6684.3(7)
4
)
1.121
1.235
1.427
1.336
)
0.180
1.217
1.110
1.129
F(000)
664
3360
1192
2712
cryst size (mm)
2θ range (deg)
index range
0.40 × 0.30 × 0.20
1.28−25.00
0.50 × 0.40 × 0.30
0.89−25.25
0.40 × 0.30 × 0.20
1.87−27.97
0.50 × 0.40 × 0.30
1.90−25.25
−12 ≤ h ≤ 12, −12 ≤ k ≤ 12,
−20 ≤ h ≤ 19, −27 ≤ k ≤ 27,
−13 ≤ h ≤ 13, −16 ≤ k ≤ 15,
−27 ≤ h ≤ 26, −14 ≤ k ≤ 14,
−16 ≤ l ≤ 19
−28 ≤ l ≤ 28
−27 ≤ l ≤ 27
−30 ≤ l ≤ 30
no. of rflns collected 10061
no. of indep rflns 6450
R1, wR2 [I > 2(σ)I] 0.0845, 0.2129
97744
34465
54315
31621
6588
12002
0.0608, 0.1453
0.1097, 0.1623
0.899
0.0275, 0.0613
0.0439, 0.0687
1.023
0.0603, 0.1609
0.0712, 0.1721
1.042
R1, wR2 (all data)
0.2043, 0.3062
0.989
GOF, F2
no. of data/
restraints/param
6450/0/389
31621/0/1783
6588/0/298
12002/0/676
largest diff peaks, e
+0.377, −0.336
+1.895, −0.981
+0.399, −0.298
+1.434, −0.769
Å−3
Synthesis of C36H46LiNO2P2Si (2). n-BuLi (2.50 mL, 1.6 M in
hexane, 4.0 mmol) was added dropwise to a solution of
PPh2CH2(PPh2NSiMe3) (1; 1.89 g, 4.01 mmol) in THF (30 mL)
at 0 °C. The resultant yellow mixture was raised to ambient
temperature and stirred for 12 h. Volatiles from the mixture were
removed under reduced pressure, and the residue was then extracted
with diethyl ether (30 mL). The mixture was then filtered and
concentrated to 10 mL to give pale-yellow crystals of 2. Yield: 1.77 g
(71%). Mp: 87 °C. Anal. Calcd for C36H46LiNO2P2Si: C, 69.55; H,
7.46; N, 2.25. Found: C, 69.23; H, 7.47; N, 2.63. 1H NMR (THF-d8):
methanediide complex, 3, which also comprises a rare
germanium(II)−germanium(II) donor−acceptor interaction.
The reaction of 2 with SnCl2 has led to the formation of a
1,3-distannacyclobutane, 4. The trapping reaction of 4 with
Fe2(CO)9 afforded the first iron stannavinylidene complex, 5,
which contains two different stannavinylidene moieties, with
one of the tin(II) centers coordinating to a Fe(CO)4 moiety.
EXPERIMENTAL SECTION
δ −0.25 (s, 9H, SiMe3), 1.39 (dd, 1H, P2CH, 2JP′−H = 11.6 Hz, 2JP′−H
=
■
General Procedures. All manipulations were carried out under an
inert atmosphere of dinitrogen gas by standard Schlenk techniques.
Solvents were dried over and distilled from CaCl2 (hexane and
CH2Cl2) and/or Na (Et2O, toluene, and THF). Ph2PCH2(PPh2
5.6 Hz), 7.01−7.08 (m, 4H, Ph), 7.19−7.27 (m, 6H, Ph), 7.36−7.40
(m, 4H, Ph), 7.65−7.70 (m, 6H, Ph). 13C{1H} NMR (THF-d8): δ
2
1.26 (SiMe3), 20.46 (dd, PCP′, JP−C = 89.2 and 112.8 Hz), 24.13
(THF), 68.35 (THF), 123.4−136.9 (m, Ph). 31P{1H} NMR (THF-
35
NSiMe3)12,13 and Sn{N(SiMe3)2}2 were prepared according to
d8): δ −19.3, 25.8 (2JP−P′ = 129.6 Hz).
literature procedures. n-BuLi (1.6 M solution in hexane), GeCl2·1,4-
dioxane, SnCl2, and Fe2(CO)9 were purchased from Aldrich Chemical
Co. and used without further purification. The proton-decoupled
NMR spectra were recorded on Bruker 400 spectrometers in THF-d8.
The chemical shifts δ are relative to SiMe4 for 1H and 13C{1H} NMR,
85% H3PO4 and SnMe4 for 31P{1H} NMR, and 119Sn{1H} NMR,
respectively. Elemental analyses (duplicate trials) were performed by
MEDAC Ltd., United Kingdom. Electronic spectra of compounds 3−5
were recorded on a Varian Cary 5G UV−vis spectrophotometer.
General procedures of preparing samples in a drybox involved
weighing of the corresponding compound (3, 0.017 g; 4, 0.020 g; 5,
0.018 g), subsequent dissolution with 6 mL of THF, and the transfer
of 0.1 mL of the solution to a 1 cm cell. The solution was made up to 3
mL by adding 2.9 mL of THF.36 The electronic spectra of 3−5 can be
found in Figures 12−14 in the Supporting Information. For
measurement of the melting points, samples were sealed in glass
tubes under nitrogen, and their melting points were measured by an
electrochemical melting point apparatus and were uncorrected.
Synthesis of C84H87Ge3N3P6Si3 (3). A solution of 2 (0.62 g, 1.00
mmol) in diethyl ether (30 mL) was added slowly to a stirring
suspension of GeCl2·1,4-dioxane (0.12 g, 0.52 mmol) in diethyl ether
(10 mL) at 0 °C. The resultant orange suspension was warmed to
room temperature and stirred for another 24 h. The volatiles were
then removed under reduced pressure, and the residue was extracted
with toluene (20 mL). The extract was then added with 10 mL of
THF, and subsequent concentration of the extract to 4 mL of the
solution afforded yellow crystals of 3. Yield: 0.15 g (53%). Mp: 202
°C. Anal. Calcd for C84H87Ge3N3P6Si3: C, 62.02; H, 5.39; N, 2.58.
1
Found: C, 61.80; H, 5.55; N, 3.12. H NMR (THF-d8): δ −0.53 (s,
9H, SiMe3), −0.07 (s, 18H, SiMe3), 6.32−6.36 (m, 4H, Ph), 6.50−
6.58 (m, 10H, Ph), 6.69−6.73 (m, 8H, Ph), 6.85−7.08 (m, 14H, Ph),
7.26−7.40 (m, 20H, Ph), 8.33−8.37 (m, 4H, Ph). 13C{1H} NMR
(THF-d8): δ 3.91, 5.98 (SiMe3), 127.2−132.9 (m, Ph). 31P{1H} NMR
(THF-d8): δ 3.3, 11.1, 14.1, 38.4 (m).
Synthesis of C56H58N2P4Si2Sn2 (4). A solution of 1 (0.94 g, 1.99
mmol) in toluene (30 mL) was added slowly to a stirring solution of
9484
dx.doi.org/10.1021/ic4011345 | Inorg. Chem. 2013, 52, 9479−9486

Inorganic Chemistry
Article
Sn{N(SiMe3)2}2 (0.88 g, 2.00 mmol) in toluene (30 mL) at room
temperature. The resultant yellow mixture was refluxed for 1 day. The
mixture was filtered and then concentrated to 10 mL of the solution to
give yellow crystals of 4. Yield: 0.64 g (54%). Mp: 243 °C. Anal. Calcd
for C56H58N2P4Si2Sn2: C, 57.17; H, 4.97; N, 2.38. Found: C, 56.87; H,
5.05; N, 2.71. 1H NMR (THF-d8): δ −0.25 (s, 9H, SiMe3), 7.04−7.20
(m, 10H, Ph), 7.36−7.40 (m, 8H, Ph), 7.67−7.72 (m, 2H, Ph).
13C{1H} NMR (THF-d8): δ 1.79 (SiMe3), 126.4−134.9 (m, Ph).
31P{1H} NMR (THF-d8): δ −13.6, 32.2 (2JP−P′ = 24.3 Hz). 119Sn{1H}
NMR (THF-d8): δ 284.6.
Synthesis of 4 from SnCl2. A solution of 2 (0.98 g, 1.58 mmol) in
diethyl ether (40 mL) was added slowly to a stirring suspension of
SnCl2 (0.15 g, 0.79 mmol) in diethyl ether (15 mL) at 0 °C. The
resultant orange suspension was warmed to room temperature and
stirred for another 24 h. The volatiles were then removed under
reduced pressure, and the residue was extracted with toluene (20 mL).
The extract was then filtered and concentrated to 10 mL to give yellow
crystals. Yield: 0.28 g (56%).
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1
52.83; H, 4.96; N, 2.33. H NMR (THF-d8): δ −0.23 (s, 9H, SiMe3),
−0.15 (s, 9H, SiMe3), 6.44−7.15 (m, 16H, Ph), 7.16−7.49 (m, 20H,
Ph), 7.94−8.14 (m, 4H, Ph). 13C{1H} NMR (THF-d8): δ 2.81, 2.92
(SiMe3), 128.0−135.5 (m, Ph), 216.6 (CO). 31P{1H} NMR (THF-d8,
2
2
−80 °C): δ −21.7 (d, JP−P′ = 33.5 Hz), −19.4 (d, JP−P′ = 40.5 Hz),
4.1 (t, 3JP−P′ = 8.1 Hz), 6.1 (dt, 3JP−P′ = 6.2 Hz, 2JP−P′ = 38.9 Hz), 34.0
(d, 2JP−P′ = 40.5 Hz), 35.2 (dt, 3JP−P′ = 6.2 Hz, 2JP−P′ = 38.9 Hz), 39.5
(t, 3JP−P′ = 8.1 Hz), 45.5 (d, 2JP−P′ = 34.0 Hz). 119Sn{1H} NMR (THF-
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ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray crystallographic files in CIF format for the structure
determinations of 2−5, NMR and electronic spectra, and
selected bond distances and angles. This material is available
free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
■
Commun. 2010, 46, 1929.
Corresponding Author
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Research Grants Council of
The Hong Kong Special Administrative Region, China (Project
CUHK 402210).
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