Synthesis and reactivity of low-valent group 14 element compounds

Article abstract of DOI:10.1002/zaac.201000029

The tetravalent germanium and tin. compounds of the general formulae Ph*EX₃ (Ph* = C₆H₃Trip-2,6, Trip = C₆H₂iPr₃-2,4,6; E = Sn, X = Cl (la), Br (lb); E = Ge, X = Cl (2)) are synthesized by reaction of Ph*Li·OEt ₂ with EX₄. The subsequent reaction of 1a,b with LiP(SiMe₃)₂ leads to Ph*EP(SiMe₃) ₂ (E = Sn (3), Ge (4)) and the diphosphane (Me₃Si) ₂PP(SiMe₃)₂ by a redox reaction, In an alternative approach 3 and 4 are synthesized by using the corresponding divalent compounds Ph*ECl (E = Ge, Sn) in the reaction with LiP(SiMe ₃)₂. The reactivity of Ph*SnCl is extensively investigated to give with LiP(H)Trip a tin(II)-phosphane derivative Ph*SnP(H)Trip (6) and with Li₂PTrip a proposed product [Ph*SnPTrip]^- (7) with multiple bonding between tin and phosphorus. The latter feature is confirmed by DFT calculations on a model compound [PhSnPPh]^-. The reaction with Li[H₂PW(CO) ₅] gives the oxo-bridged tin compound [Ph*Sn{W(CO) ₅}(μ-O)₂SnPh*] (8) as the only isolable product. However, the existence of 8 as the bis-hydroxo derivative [Ph*Sn{W(CO) ₅}(μ-OH)₂SnPh*]] (8a) is also possible. The Sn^IV derivatives Ph*Sn(OSiMe₃)₂Cl (9) and [Ph*Sn(μ-O)Cl]₂ (10) are obtained by the oxidation of Ph*SnCl with bis(trimethylsilyl)peroxide and with Me₃NO, respectively. Besides the spectroscopic characterization of the isolated products compounds la, 2, 3, 4, 8, and 10 are additionally characterized by X-ray diffraction analysis.

Full text of DOI:10.1002/zaac.201000029

ARTICLE
DOI: 10.1002/zaac.201000029
Synthesis and Reactivity of Low-Valent Group 14 Element Compounds
Brian P. Johnson,[a] Stefan Almstätter,[a] Fabian Dielmann,[a] Michael Bodensteiner,[a] and
Manfred Scheer*[a]
Dedicated to Professor Gerd Becker on the Occasion of His 70th Birthday
Keywords: Germanium; Tin; Phosphorus; Multiple bonding; Density functional calculations
Abstract. The tetravalent germanium and tin compounds of the gen- between tin and phosphorus. The latter feature is confirmed by DFT
eral formulae Ph*EX3 (Ph* = C6H3Trip-2,6, Trip = C6H2iPr3-2,4,6; E = calculations on a model compound [PhSnPPh]–. The reaction with
Sn, X = Cl (1a), Br (1b); E = Ge, X = Cl (2)) are synthesized by Li[H2PW(CO)5]
gives
the
oxo-bridged
tin
compound
reaction of Ph*Li·OEt2 with EX4. The subsequent reaction of 1a,b with [Ph*Sn{W(CO)5}(μ-O)2SnPh*] (8) as the only isolable product. How-
LiP(SiMe3)2 leads to Ph*EP(SiMe3)2 (E = Sn (3), Ge (4)) and the ever, the existence of
8
as the bis-hydroxo derivative
diphosphane (Me3Si)2PP(SiMe3)2 by a redox reaction. In an alternative [Ph*Sn{W(CO)5}(μ-OH)2SnPh*] (8a) is also possible. The SnIV deriv-
approach 3 and 4 are synthesized by using the corresponding divalent atives Ph*Sn(OSiMe3)2Cl (9) and [Ph*Sn(μ-O)Cl]2 (10) are obtained
compounds Ph*ECl (E = Ge, Sn) in the reaction with LiP(SiMe3)2. by the oxidation of Ph*SnCl with bis(trimethylsilyl)peroxide and with
The reactivity of Ph*SnCl is extensively investigated to give with Me3NO, respectively. Besides the spectroscopic characterization of the
LiP(H)Trip a tin(II)-phosphane derivative Ph*SnP(H)Trip (6) and with isolated products compounds 1a, 2, 3, 4, 8, and 10 are additionally
Li2PTrip a proposed product [Ph*SnPTrip]– (7) with multiple bonding characterized by X-ray diffraction analysis.
PSiR'3 and R2Si=PPR'2 [12]. A novel chapter of multiple-bond
chemistry was opened, when the so-called ‘terphenyl’ substitu-
ent was introduced in main group chemistry. Thus, a novel
stannaacetylene, Ph*Sn≡CSiiPr3 (Ph* = C6H3Trip2-2,6), was
proposed to exist as a reactive intermediate [13], and the asym-
metric dipnictenes Ph*E=PMes (E = As, Sb) were synthesized
by Power et al. [14]. Moreover, novel arsa-Wittig reagents 2,6-
Ph'2-C6H3As=PMe3 (Ph' = Mes, Trip) were developed by Pro-
tasiewicz and co-workers, whereby the phosphorus atom is in
the +5 oxidation state [15].
Introduction
Almost three decades ago Becker et al. succeeded in the syn-
thesis of the first stable phosphaalkyne, tert-butylphosphaalk-
yne [1], which through an improved synthesis [2] gave a gen-
eral approach to this class of P≡C triply bound compounds
on a preparative scale, and many representatives have since
appeared [3]. In contrast, arsaalkynes are extremely rare, with
the first stable compounds, Mes*C≡As, reported in 1986 [4].
A recent development was reported by the synthesis of the
borate derivatives [(F3C)3BC≡P]– and [(F3C)3BC≡As]– repre-
senting phosphaethynyl and arsaethynyl systems [5]. The reac-
Our long-term engagement in phosphaalkyne chemistry [16]
tion behavior of phosphaalkynes was intensively investigated presents the question of whether group 14 elements other than
both for phosphaorganic [6] and coordination chemistry [7]
purposes. Moreover, the discovery of Becker opened up the
research field of multiple bonding of the heavier main-group
elements [8]. Compounds of the type R2E = PR' with heavier
group 14 elements were isolated having Si=P [9], Ge=P [10],
and Sn=P [11] double bonds, which were stabilized kinetically
by bulky aryl groups (Mes (C6H2Me3-2,3,6); Trip (C6H2iPr3-
2,3,6); Mes* (C6H2tBu3-2,3,6)); or by bulky aliphatic groups
(t-Bu or CH(SiMe3)2) at both phosphorus and the group 14
element atom. Additionally, P-silyl and P-phosphanyl deriva-
tives were successfully prepared in compounds of type R2Si=
carbon can be used for the synthesis of compounds with a
triple bond to phosphorus. Compounds featuring an E≡P (E =
Si, Ge, Sn, Pb) triple bond have not yet been detected or iso-
lated. Only a compound with a Si≡P triple bond is tentatively
proposed as an unobserved intermediate, the identity of which
is suggested based solely on the nature of the isolated product
(Scheme 1) [17]. Matrix isolation studies show the access to
H3SiP and its isomers [18]. Moreover, a phosphasilene, RR'Si=
PH (R = Ph*, R' = tBu3Si), and its zinc salt were synthesized
by Driess et al. [19] and Cp*(Cl)2EP(SnMe3)2 (E = Si, Ge)
was synthesized by Niecke and Pietschnig [20]. All these com-
pounds are on the way to realizing stable derivatives with an
E≡P triple bond. Interestingly, the stability of triply bonded
RSn≡P systems has been predicted by quantum chemical cal-
culations only for examples in which R represents a bulky ter-
phenyl group [21].
* Prof. Dr. M. Scheer
Fax: +49-941-943-4441
E-Mail: manfred.scheer@chemie.uni-regensburg.de
[a] Institut für Anorganische Chemie
Universität Regensburg
93040 Regensburg, Germany
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B. P. Johnson, S. Almstätter, F. Dielmann, M. Bodensteiner, M. Scheer
ARTICLE
with Ph*GeCl. The arrangement around the group 14 element
atom is a distorted tetrahedron with the chloride ligands
pinched toward each other and away from the Ph* ligand, pre-
sumably a result of the bulkiness of the Ph* ligand.
Scheme 1. Reaction pathway of thermolysis of Mes*Si(F)2P{Li(thf)3}SiMe3
and proposed generation of intermediate Mes*Si≡P [17].
Thus, the use of bulky terphenyl substituents like, e.g., Ph*
(Ph* = C6H3Trip2-2,6; Trip = C6H2iPr3-2,4,6) on tin or germa-
nium (E) provides a unique heteroleptic template for preparing
element–phosphorus compounds with low-coordination ar-
rangements. With the relatively stable E–Caryl bond anchoring
the group 14 atom at one site, reactivity with phosphorus com-
pounds is probed at the remaining coordination sites. As a re-
sult, a heteroleptic terphenyl-tin or germanium phosphanide
would represent an optimal precursor for the synthesis of E≡P
triple-bond compounds of the type Ph*E≡P (E = Sn, Ge). The
experiments reported in the following are partly directed to-
ward this goal. Moreover, the results described give insight
into the reaction behavior of low-valent tin compounds.
Figure 1. Molecular structure of Ph*ECl3 (1a: E = Sn, 2: E = Ge) in
the crystal. Hydrogen atoms are omitted for clarity. Selected bond
lengths /Å and angles /° for 1a: Sn–C1 2.155(5), Sn–Cl1 2.322(3), Sn–
Cl2 2.321(3), Sn–Cl3 2.328(2); C1–Sn–Cl1 119.89(13), C1–Sn–Cl2
122.05(13), C1–Sn–Cl3 109.26(14), Cl1–Sn–Cl2 98.12(7), Cl1–Sn–
Cl3 102.96(8), Cl2–Sn–Cl3 101.67(8) [58].
Formation of Group 14 Element/Phosphorus Compounds
An interesting aspect of the synthesized reagents 1a and 2 is
the potential use as starting materials for the synthesis of Sn/
Ge–P compounds in the oxidation state +4 of the group 14
element. Compound 1a was treated with LiP(SiMe3)2·1.8THF
in Et2O at low temperature. The 31P NMR spectrum of the
crude reaction mixture reveals the formation of
Ph*SnP(SiMe3)2 (3) (δ(31P) = –123.1) and (Me3Si)2PP(SiMe3)2
(δ(31P) = –216 [23]) in an approximate 1:1 ratio as the main
phosphorus-containing products [Equation (2)]. As the reduc-
tion potential for germanium is generally lower than that for
tin, compound 2 reacted with LiP(SiMe3)2·1.8THF in Et2O at
low temperature in order to give Ph*GeCl2P(SiMe3)2. How-
ever, the same result was achieved and, along with of the for-
Results and Discussion
Synthesis of Terphenyl-Trihalogeno-Germanium(IV)- and
Tin(IV) Compounds
The most direct preparation of compounds of the formulae
Ph*EX3 (Ph* = C6H3Trip-2,6, Trip = C6H2iPr3-2,4,6) is
achieved by treating Ph*Li·OEt2 with EX4 in a mixture of n-
hexane and Et2O [Equation (1)]. Colorless crystals of the pro-
ducts are obtained after work-up and recrystallization from n-
hexane in moderate yields of 37–45 %. The oxidation of
Ph*SnCl (3) by PCl3 gives a higher yield of 1a (68 %). How-
ever, the current transmetalation method saves the step of pre-
paring Ph*SnCl and allows the synthesis of 1a in a larger
scale. Saito et al. obtained a yield of 45 % by oxidizing
Ph*SnCl with CCl4 [22].
mation of (Me3Si)2PP(SiMe3)2 as
a
side-product,
Ph*GeP(SiMe3)2 (4) was isolated [Equation (2)]. Obviously,
metal–halogen exchange reactions play a decisive role which
is also unavoidable using higher reaction temperatures (up to
0 °C). Similar results are obtained if reaction (2) is carried
out under the conditions of the multiple P–P bond formation
reactions [24], for which an excess of LiP(SiMe3)2 has to be
present to assure the autometalation reaction of the silylphos-
phorus atom by LiP(SiMe3)2 with formation of P(SiMe3)3. In
order to ascertain whether a heavier alkali-metal phosphanide
can induce preferential salt elimination over reduction, the
¯
Compound 1a crystallizes in the triclinic space group P1, analogous reaction was carried out with 1a and KP(SiMe3)2.
and 2 crystallizes in the orthorhombic space group C2221. The The 31P NMR spectrum of the crude reaction mixture reveals
molecular structure of 1a and 2 is shown in Figure 1. The the same phosphorus-containing products as that with
structure of 2 is disordered due to contamination of the product LiP(SiMe3)2·1.8THF.
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Synthesis and Reactivity of Low-Valent Group 14 Element Compounds
The reduction of 1a and 2 by LiP(SiMe3)2 and P–P bond
formation are unexpected in light of the reports on the reaction
of Ph*SiF3 with LiP(SiMe3)2 to give the silane-elimination
product shown in Scheme 1 [17]. Clearly, the relative stability
of divalent stannylenes and germylenes over silylenes plays a
key role in the differing redox behavior of 1a and 2 in reactions
with the lithium phosphanide.
A byproduct-free synthesis of 3 and 4 is achieved, if the
corresponding group 14 starting material is already in the oxi-
dation state +2. Thus, Ph*ECl (E = Sn [25], Ge) was treated
with LiP(SiMe3)2·1.8THF in n-hexane at low temperature. Ac-
cording to the 31P NMR spectra of the reaction mixtures only
Ph*SnP(SiMe3)2 (3) (δ(31P) = –123.1) and Ph*GeP(SiMe3)2
(4) (δ(31P) = –48.5), respectively, are detected as the main
phosphorus-containing products along with traces of
HP(SiMe3)2 (δ(31P) = –236.3), resulting from hydrolysis of
LiP(SiMe3)2 [Equation (3)]. From these reactions X-ray quality
violet crystals of 3 and dark red crystals of 4 are obtained.
Interestingly, the isolated yields are similar to the ones ob-
tained by reaction (2).
Figure 2. Molecular structures of Ph*EP(SiMe3)2 (3: E = Sn, 4: E =
Ge) in the crystal. Hydrogen atoms are omitted for clarity. Selected
bond lengths /Å and angles /° for 3: C7–Sn 2.229(3), Sn–P 2.527(1),
P–Si1 2.244(2), P–Si2 2.243(4); C7–Sn–P 105.61(8), Sn–P–Si1
97.40(5), Sn–P–Si2 110.02(5), Si1–P–Si2 110.58(6). Selected bond
lengths /Å and angles /° for 4: C7–Ge 2.018(5), Ge–P 2.291(4), P–Si1
2.240(5), P–Si2 2.248(1); C7–Ge–P 106.89(5), Ge–P–Si1 119.53(2),
Ge–P–Si2 97.49(2), Si1–P–Si2 109.87(3).
chlorides/anhydrides [29], and chalcogens [30], among others,
to give well-defined SnIV addition products, it is expected that
chemical oxidation of Ph*SnP(SiMe3)2 would be feasible. A
variety of reagents bearing halides or pseudohalides were se-
lected such that either spontaneous or thermal silane elimina-
tion would be viable upon oxidation and formation of
Ph*Sn≡P or similar products would be conceivable. However,
low-temperature reactions of Ph*SnP(SiMe3)2 with C2Cl6,
Cp2Ti(OTf)2, Hg(OTf)2, Tl(OOCCF3)3, benzoyl chloride,
Me3NO, and tropylium tetrafluoroborate each results in cleav-
age of the Sn–P bond and generation of an intractable mixture
of products, according to 31P NMR spectra of the respective
crude reaction mixtures. Reaction of Ph*SnP(SiMe3)2 with
BrCH2CH2Br at low temperature results in gradual discolora-
tion of the violet solution to clear beige. The 31P NMR spec-
The molecular structure of the compounds 3 and 4 are de-
picted in Figure 2. Compound 3 crystallizes in the triclinic
¯
space group P1 and 4 in the monoclinic space group P21/c. In
the crystal structure of Ph*EP(SiMe3)2 (3: E = Sn, 4: E = Ge)
the group 14 atom has a coordination number of two and lies
in a bent arrangement (Cipso–Ge–P: 106.88°, Cipso–Sn–P:
105.56(9)°), which is a characteristic feature for structurally
characterized stannylene/germylene compounds. The phospho-
rus atom is located in a distorted trigonal-pyramidal geometry
between the group 14 atom and two silicon atoms. Since the
phosphorus atom does not approach planarity, it can be con-
cluded that the phosphorus lone pair does not participate sig-
nificantly in donation to the group 14 element atom. This cor-
relates well with the tin–phosphorus coupling constants of
compound 3 (1JP117Sn = 1396, 1JP119Sn = 1453 Hz), which are
well below the range for compounds known to exhibit tin–
phosphorus double bonding (1JPSn ≈ 2000 Hz). The bulky na-
ture of the Ph* ligand allows the isolation of the terminal stan-
nylene phosphanide 3 and the terminal germylene phosphanide
4. This is in contrast to the well-established field of phospha-
stannylenes and -germylenes usually representing phosphan-
ido-bridged dimers [26] or donor-stabilized monomers [27].
trum reveals a main phosphorus-containing product (> 65 %)
1
at –167.2 ppm with tin satellites (1JP117Sn = 1719, JP119Sn
=
1799 Hz). Work-up of the solution and crystallization from n-
hexane afforded only colorless crystals of Ph*Br [31], as iden-
tified by X-ray diffraction experiments.
Reactivity of Ph*SnCl (5)
Moreover, the reactivity of the divalent compound Ph*SnCl
(5) was of interest and the reactions shown in Scheme 2 were
carried out.
The reaction of 5 with LiP(H)Trip was carried out in Et2O
at low temperature and afforded the monomeric arylstannylene
phosphanide, Ph*SnP(H)Trip (6), with a Trip group and a re-
active proton at the phosphorus atom. The 31P{1H} NMR spec-
trum of the crude reaction mixture reveals a relatively clean
Reactivity of Ph*SnP(SiMe3)2 (3)
reaction with a slightly broadened main signal (ca. 70 %,
1
Given the wealth of oxidative reactions of bivalent tin am- Δν1/2 = 150 Hz) attributable to 6 (δ = –70.9, JP117/119Sn
ides with organic halides, transition-metal halides [28], acid 934 Hz), which is split into a doublet upon proton coupling
=
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B. P. Johnson, S. Almstätter, F. Dielmann, M. Bodensteiner, M. Scheer
ARTICLE
Scheme 2. Reactivity of Ph*SnCl (5) with (a) LiP(H)Trip in Et2O at –78 °C; (b) Li2PTrip in Et2O at –78 °C; (c) Li[H2PW(CO)5] in n-hexane
at –78 °C; (d) Me3SiO–OSiMe3 in Et2O at 0 °C; (e) Me3NO in Et2O at 0 °C.
(1JPH = 186 Hz), along with traces of Trip(H)P–P(H)Trip The low-field 31P NMR shift of the proposed compound 7
1
(–113.9 ppm) and TripPH2 (–158.3 ppm) as the only other (Scheme 2) and the large JP117/119Sn coupling constants sig-
phosphorus-containing products. The color of the proposed nify a situation of multiple bonding between tin and phospho-
product 6 is intense violet, the same color as for the analogous rus. The bonding about tin and phosphorus in the anionic moi-
bis(trimethylsilyl)phosphanide 3. In the 31P{1H} NMR spec- ety [Ph*SnPTrip]– is isoelectronic to the neutral compound
trum of 6 a singlet with unresolved 117/119Sn satellites is ob- Ph*Sb=PMes with a known double bond [32]. [Ph*SnPTrip]–
served, which in the proton-coupled 31P NMR splits into a can also be thought of as isolobal to the doubly reduced acety-
doublet with two sets of unresolved 117/119Sn satellites. The lene analogue [Ph*Sn=SnPh*]2–, which has been suggested as
observation of unresolved 117/119Sn satellites is reminiscent of having a Sn=Sn double bond [33], as well as isolobal to the
the poorly resolved satellites observed in the 31P signal for general family of dipnictenes RE=ER (E = P, As, Sb), each
5. Owing to the same excellent solubility of the byproducts with undisputed double-bond character [34]. The bonding be-
compound 6 can not be isolated in analytically pure form.
tween tin and phosphorus is tentatively represented in
Experiments aimed at deprotonating in situ generated 6 with Scheme 2 with a bond order greater than one, with the possi-
n-BuLi produced a mixture of unidentified products according bility that double bonding is the more accurate description for
to 31P NMR spectroscopy. In recognition of the possibility of anionic compounds of the form [PhRSnPPhR]–.
nucleophilic attack of n-BuLi on the tin atom, a route was
chosen to circumvent the direct use of n-BuLi with the stannyl-
Theoretical Considerations for Li+[Ph*SnPTrip]– (7)
ene. Thus, TripPH2 was twice deprotonated by n-BuLi, and the
resulting doubly lithiated phosphanide Li2PTrip was added to
A SnII compound in which both the tin and phosphorus at-
5. According to 31P NMR, a mixture of products was generated oms are two-coordinated is so far unprecedented, as all known
by this protocol, from which Trip(H)P–P(H)Trip could be doubly bonded Sn=P species are three-coordinated at the tin
identified (ca. 20 %). The main product (ca. 40 %) was ob- atom. As noted above, the Sn–P bonding in the anionic com-
served as a broad downfield signal proposed tentatively to be pound 7 is expected to be isolobal to dianionic [PhRSnSnPhR]2–
1
Li+[Ph*SnPTrip]– (7) (δ(31P) = 229.7, Δν1/2 = 280, JP117Sn
=
or neutral [PhRPPPhR]. Three interesting considerations for 7
1735, 1JP119Sn = 2004 Hz). The broadness of the observed sig- are the energetically lowest molecular geometry about tin and
nal is a characteristic indicator for lithium-coordinated anions, phosphorus, the appearance of the frontier molecular orbitals,
where the lithium shifts rapidly between ion-contact and ion- and the charge distribution within the anionic compound. Cal-
separated forms. No P–H coupling is observed in the proton- culations were carried out on the model compound [PhSnPPh]–
coupled spectrum. Attempts to produce 7 by lithiation of 6 (7') using the Gaussian 03 program [35] at the DFT-B3LYP
with n-BuLi did not result in the observation of the downfield level with the SDD basis set consisting of an pseudorelativistic
signal observed in the reaction of Ph*SnCl (5) with Li2PTrip. effective core potential for the tin atom and Dunning/Huzinaga
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Synthesis and Reactivity of Low-Valent Group 14 Element Compounds
full double zeta basis set for all other atoms. In the current ally became light red, and overnight stirring produced a beige-
study, the lithium counterion is not considered in order to rule red solution. The 31P{1H} and 31P NMR spectra for the crude
out influence of contacts between the lithium cation and ani- reaction mixture reveal an array of six main phosphorus-con-
onic portions of [PhSnPPh]–.
taining products in approximately equal proportions. One sig-
The calculated structure of [PhSnPPh]– results in a trans- nal at δ = –187 ppm bears tungsten satellites (1JPW = 213 Hz)
bent orientation of the phenyl substituents, which are slightly and is split into a quartet in the proton-coupled spectrum
rotated relative to one another. The Caryl–Sn–P and Sn–P–Caryl (1JPH = 342 Hz) and is assigned as [H3PW(CO)5]. Each of the
angles in the optimized structure are 94.3° and 103.2°, respec- remaining five signals is split into triplets in the proton-cou-
tively. The angle about tin is considerably less obtuse than that pled 31P NMR spectra, indicating preservation of the intact
in compound 3 (105.56(9)°), which could be attributed par- PH2 unit. Decanting the mother liquor away from
tially to the lower degree of steric bulk of Ph in comparison [H3PW(CO)5] and storage of the highly concentrated solution
to Ph*. In Figure 3, the orbital iso-surfaces for the frontier at –25 °C for several weeks resulted in deposition of a few
molecular orbitals are represented. The HOMO–1 (lower right) orange crystals, alongside co-crystallized [H3PW(CO)5], from
and HOMO (upper right) are of the bonding σ and π types, which one was selected for an X-ray diffraction experiment.
respectively, while the LUMO (upper left) is of the antibond- [Ph*Sn{W(CO)5}(μ-O)2SnPh*] (8) crystallizes in the ortho-
ing π* type. This situation is in agreement with the view of rhombic space group Pnma, in which one of the tin atoms is
[PhSnPPh]– having an Sn=P double bond, though a concrete coordinated to a tungsten pentacarbonyl fragment. The mole-
bond order cannot be assigned from these data. Furthermore, cular structure and selected bond lengths and angles are shown
the molecular orbital representations reveal participation of the in Figure 4. The formation of 8 comes apparently as a result
phenyl groups in the Sn–P bonding, particularly in the π-type of contamination with moisture or oxygen, likely due to the
and π*-type orbitals, which is an indication of the stabilization excess handling and long crystallization period. The most nota-
which aryl groups offer to such multiply bonded systems. The ble feature of 8 is the coordination of tin to the W(CO)5 frag-
Mulliken atomic charges in [PhSnPPh]– are calculated to be ment, which had been introduced into the reaction mixture as
+0.12 for tin and –0.25 for phosphorus, whereas the remainder a phosphorus-coordinated adduct. The bridging oxygen atoms
of the overall negative charge is distributed throughout the are slightly bowed in the same direction and the Ph* groups
phenyl groups (av. charge on C: –0.23; av. charge on H: lie in trans-bent arrangement.
+0.20). The negative charge is weighted slightly more heavily
toward the phosphorus-bound phenyl group (total = –0.45)
than the tin-bound phenyl group (total = –0.42). The distribu-
tion of charge throughout the phenyl groups also demonstrates
an aspect of the stabilization of aryl groups in multiply bonded
anionic main-group moieties.
Figure 4. Molecular structure of [Ph*Sn{W(CO)5}(μ-O)2SnPh*] (8)
in the crystal. The hydrogen atoms and o-Trip groups are omitted for
clarity. Selected bond lengths /Å and angles /°: W1–Sn1 2.743(2),
Sn1–C1 2.183(9), Sn2–C20 2.183(9), Sn1–O1 2.140(5), Sn2–O1
2.224(5), W1–Ctrans 1.978(15), W1–Ccis 2.058(14) (mean value is
given); O1–Sn1–O1 73.0(3), O1–Sn2–O1 69.9(3), O1–Sn1–W1
111.57(14), Sn1–O1–Sn2 105.6(2), C1–Sn1–W1 137.9(3), C1–Sn1–
O1 101.9(3), C20–Sn2–O1 99.2(3).
Figure 3. Iso-surfaces of the molecular orbitals for model compound
[PhSnPPh]– (7'). Upper left: LUMO; upper right: HOMO; lower left:
graphical representation of anion considered; lower right: HOMO–1.
The large Caryl–Sn1–W1 angle (137.9(3)°) illustrates the steric
crowding about Sn1 in 8 as does the pronounced pinching of the
Synthesis of Tin-Oxo Derivatives
In order to probe the possibility of preparing a monomeric oxygen atoms about the tin atoms (O1–Sn1–O1: 73.0(3)°; O1–
aryl stannylene with reactive P–H bonds and without organic Sn2–O1: 69.9(3)°). The Sn–W bond length (2.743(2) Å) falls
substituents at phosphorus, 5 was treated with Li[H2PW(CO)5] within the range of other known tungstenpentacarbonyl-coordi-
in n-hexane at –78 °C (Scheme 2). The orange solution gradu- nated stannylene complexes (compare: [(salen)SnW(CO)5]
Z. Anorg. Allg. Chem. 2010, 1275–1285
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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B. P. Johnson, S. Almstätter, F. Dielmann, M. Bodensteiner, M. Scheer
ARTICLE
(salen = 2,2'-N,N'-bis(salicylidene)ethylenediamine) (2.712(1) Å) structure with bridging silyloxy ligands, are found. Thus, the
2–
[36a]; [(CO)5WSn(Cl)Fe(CO)4]2
[Mes*(R)Sn=W(CO)5] (R
(2.799(1) Å) [36b]; structure is proposed to be monomeric, as shown in Scheme 2.
=
CH2CMe2C6H3 tBu2-3,5)
In an attempt to prepare the kinetically stabilized heavier
(2.751(1) Å) [36c]; [(o-C6H4CH2E)2SnW(CO)5] (E = NMe2, Group 14 acid halide analogue Ph*Sn(O)Cl, 5 was treated with
PPh2) (2.749(1) and 2.762(1) Å [36d]). A most conspicuous fea- solid trimethylamine N-oxide, Me3NO, at 0 °C in Et2O
ture of the structure of 8 is the tricoordinate tin atom, Sn2. (Scheme 2). Immediately upon mixing the orange solution un-
Whereas the donation to W(CO)5 designates Sn1 as a divalent derwent rapid discoloration and colorless crystals of [Ph*Sn(μ-
atom, the logical description of Sn2 as tetravalent does not agree O)Cl]2 (10) were isolated by crystallization from the filtered
well with Sn2 being only tricoordinate, unless multiple Sn–O reaction mixture. 10 formally represents a dimerization of the
bonding is involved. The Sn–O bond lengths (Sn1–O1: targeted acid halide analogue, Ph*Sn(O)Cl, a compound class
2.140(5) Å, Sn2–O1: 2.224(5) Å) differ slightly from one an- which has yet not been described experimentally for tin. The
other, but are considerably longer than the Sn–O bonds in cyclo- clean addition of oxygen to SnII to form 10 stands in contrast
[Trip2SnO]3 (1.956(2) Å, 1.970(2) Å), which contains exclu- to attempts to prepare a ketone analogue for tin by Power et
sively Sn–O single bonds [37]. The elongated Sn–O bonds in 8 al., in which the reaction of Ph'2Sn (Ph' = C6H3Mes2-2,6) with
can be attributed to the steric crowding about the tin atoms Me3NO resulted in the formal addition of H2O to the expected
caused by the bulky terphenyl substituents and the W(CO)5 unit. product Ph2Sn=O and led instead to the dihydroxy compound
Thus, the most logical bonding scheme which fits the existence Ph'2Sn(OH)2 [40]. Compound 10 crystallizes in the triclinic
¯
of the tricoordinate tin atom is one in which the Sn2–O bond is space group P1. The molecular structure and selected bond
represented by a double bond, and this oxygen ligand further lengths and angles are shown in Figure 5.
donates to the stannylene center, Sn1. One resonance form for
this description is depicted in Scheme 3. The structure proposal
of 8 in Scheme 3 is not consistent with the Sn–O bond lengths,
since the Sn2–O bond should be a multiple bond by this descrip-
tion but is longer than the Sn1–O bond. An explanation for this
discrepancy may be the constrained geometry of the core in 8
caused by steric repulsion from the W(CO)5 group. However,
the existence of a bis-hydroxo derivative 8a (Scheme 3) can not
be excluded, since a residue electron density is found close to
the O1 atoms (Figure 4). Yet, the experimental distance found of
0.58 Å is too short for an O–H bond. Nevertheless, in view of a
recent report on hydroxo-bridged SnII dimers (Ph'SnOH)2 (Ph' =
C6H3-2,6(C6H3-2,6-iPr2)2) by Power et al. [38], for which Sn–O
bond lengths of 2.145(2) and 2.149(1) Å were found, the exis-
tence of 8a is also an appropriate description.
Figure 5. Molecular structure of [Ph*Sn(μ-O)Cl]2 (10) in the crystal.
Hydrogen atoms are omitted for clarity. Selected bond lengths /Å and
angles /°: Sn1–O1 1.994(2), Sn1–Cl1 2.343(1), Sn1–Cipso 2.137(3);
Sn1–O1–Sn1 95.38(9), O1–Sn1–O1 84.62(9), Cl1–Sn1–O1 108.47(6),
Cl1–Sn1–O1 106.36(7), Cipso–Sn1–O1 117.28(10), Cipso–Sn1–O1
119.98(9), Cl1–Sn1–Cipso 115.76(8).
Scheme 3. Proposed bonding scheme in Sn2O2{W(CO)5} core of 8
and its alternative existence as a bis-hydroxy derivative 8a.
The molecular structure of 10 is located on an inversion cen-
Treatment of 5 with trimethylsilylperoxide, Me3SiOOSiMe3 ter, such that the central Sn2O2 unit is a planar rhombus and
[39], at 0 °C in Et2O resulted in immediate discoloration of only one unique Sn–O bond length results. The planarity of
the orange solution (Scheme 2). Ph*Sn(OSiMe3)2Cl (9) was the Sn2O2 core mirrors that of [R2Sn(μ-O)]2 (R = CH(SiMe3)2)
isolated as a sticky oil and is highly soluble in common hydro- [41] and analogues having heavier chalcogenide ligands, as in
1
carbons. The H NMR spectrum of 9 reveals a sharp signal [tBu2Sn(μ-E)]2 (E = S, Se, Te) [42] or [(Trip2Sn)2(μ-O)(μ-S)]
at 0.13 ppm for the trimethylsiloxy groups along with a few [43]. However, whereas all Sn–O bonds in 10 have the same
neighboring peaks likely resulting from impurity or unreacted length, the Sn–O bonds in [{(Me3Si)2CH}2Sn(μ-O)]2 are of
trimethylsilylperoxide. The iPr protons on the tertiary carbon varying lengths, such that a non-rhomboidal parallelogram
atoms overlap and give a broad multiplet. In the EI mass spec- form of the Sn2O2 core results. The tin atoms are in distorted
trum a peak corresponding to the molecular ion minus one tetrahedral arrangement with the
Cipso–Sn1–O1 angles
methyl group is found, along with further peaks signaling suc- (117.28(10)°, 119.98(9)°) significantly larger than the Cl–Sn–
cessive loss of the silyloxy ligands and fragmentation of the O angles (106.36(7)°, 108.47(6)°), which is likely a result of
Ph* ligand. No higher peaks, which could indicate a dimeric steric repulsion from the Ph* ligands. The O–Sn–O angles
1280
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 1275–1285

Synthesis and Reactivity of Low-Valent Group 14 Element Compounds
Method B: PCl3 (45 μL, 72 mg, 0.52 mmol) was added by pipette to
a solution of Ph*SnCl (5) (333 mg, 0.52 mmol) in n-hexane (20 mL)
at –78 °C. The solution turned immediately from orange to colorless.
The solution was allowed to warm to room temperature and stirred
overnight, after which a colorless solution with yellow precipitate
(probably (PCl)n) was observed. The solution was filtered through a
plug of Kieselgur, and the filtrate was concentrated to 5 mL under
vacuum. Storage at –25 °C for five days afforded colorless crystals of
1a (249 mg, 68 %).
(84.62(9)°) are considerably more acute than the Sn–O–Sn an-
gles (95.38(9)°) in 10. The Sn–O bond length (1.994(2) Å) is
significantly shorter than those in compound 8 (2.140(5) Å,
2.224(5) Å) and compares well with the Sn–O bond lengths
in cyclo-[(Me3Si)3CSn(OH)O]3 (Sn–Oring: 1.965 Å; Sn–OOH
:
1.968 Å) [44], but is longer than those of
[{(Me3Si)2CH}2Sn(μ-O)]2 (1.94(2) Å, 1.98(1) Å). The Sn–
Cipso bond length (2.137(3) Å) is considerably shorter than the
Sn–Cipso bond length (2.226(4) Å) in 3, reflecting the differ-
ence in a tetravalent aryl stannane and a divalent aryl stannyl-
ene.
1a: MS (EI, 70 eV, 160 °C): m/z = 706.2 (M+, 13 %), 671.2 (M+
–
Cl, 4 %), 481.4 (M+ – SnCl3, 99 %), 466.3 (M+ – SnCl3 – CH3, 34 %),
438.4 (M+ – SnCl3 –C3H7, 14 %). Element. Analysis: C36H49SnCl3
(706.2 g·mol–1): C 62.10 (calcd. 61.20); H 6.41 (6.99)%. 1H NMR
3
(C6D6, 25 °C): δ = 1.04 (d, JHH = 6.9 Hz, 12 H, o-CH(CH3)2), 1.23
Conclusions
3
3
(d, JHH = 6.9 Hz, 12 H, o-CH(CH3)2), 1.44 (d, JHH = 6.9 Hz, 12 H,
3
p-CH(CH3)2), 2.82 (m, CH(CH3)2), 7.07 (t, JHH = 7.7 Hz, 1 H, p-
The results showed that the reaction of tetravalent trichloro-
germanium and -tin compounds containing a bulky terphenyl
substituent Ph*ECl3 with LiP(SiMe3)2 did not result in low-
valent products possessing element-phosphorus triple bonds.
Instead, redox reactions proceed and the divalent group 14/
phosphanide products Ph*EP(SiMe3)2 (E = Sn, Ge) were iso-
lated and structurally characterized. These products were also
obtained by using the divalent compounds Ph*ECl. Compre-
hensive studies of the reaction behavior of Ph*SnCl were car-
ried out resulting in novel low valent tin–phosphorus and tin–
oxygen derivatives. Some of them reveal unprecedented bond-
ing features. The reaction pattern shown clearly reveals the
high potential of the bulky terphenyl substituent in low-valent
group 14 element chemistry.
C6H3), 7.22 (s, 4 H, m-Trip), 7.24 (br., 2 H, m-C6H3). 13C NMR
(75.47 MHz, C6D6): δ = 23.01 (s, CH(CH3)2), 24.12 (s, CH(CH3)2),
26.04 (s, CH(CH3)2), 31.41 (s, CH(CH3)2), 34.96 (s, CH(CH3)2),
122.07 (s), 131.11 (s), 131.63 (s), 134.77 (s), 141.50 (s), 147.66 (s),
147.97 (s), 151.18 (s). 119Sn{1H} NMR (149.21 MHz, C6D6): δ = –
113.8 (s).
Ph*SnBr3 (1b): Ph*SnBr3 (1b) was prepared using the same proce-
dure as for 1a (Method A) starting from SnBr4 (326 mg, 0.74 mmol)
and Ph*Li·OEt2 (418 mg, 0.74 mmol) to give colorless crystals of 1b
in two crops (248 mg, 40 %).
1b: MS (EI, 70 eV): m/z = 837.9 (M+, 7 %), 796.9 (M+ – C3H7,
3.5 %), 759.0 (M+ – Br, 19 %), 481.4 (M+ – SnBr3, 100 %), 466.3
(M+ – SnBr3 – CH3, 16 %), 43.0 (C3H7 , 14 %). Element. Analysis:
+
C36H49SnBr3 (837.9 g·mol–1): C 53.11 (calcd. 51.49); H 6.11 (5.88)%.
3
1H NMR (C6D6, 25 °C): δ = 1.04 (d, JHH = 6.6 Hz, 12 H, o-
CH(CH3)2), 1.23 (d, 3JHH = 6.6 Hz, 12 H, o-CH(CH3)2), 1.46 (d, 3JHH
=
=
Experimental Section
3
6.8 Hz, 12 H, p-CH(CH3)2), 2.87 (m, CH(CH3)2), 7.03 (t, JHH
7.6 Hz, 1 H, p-C6H3), 7.21 (s, 4 H, m-Trip). 13C NMR (75.47 MHz,
C6D6): δ = 23.39 (s, CH(CH3)2), 24.16 (s, CH(CH3)2), 26.11 (s,
CH(CH3)2), 31.40 (s, CH(CH3)2), 34.97 (s, CH(CH3)2), 122.15 (s),
130.65 (s), 132.10 (s), 134.35 (s), 139.37 (s), 147.30 (s), 147.82 (s),
151.02 (s). 119Sn{1H} NMR (149.21 MHz, C6D6): δ = –332.6 (s).
General Remarks
All manipulations were performed in an atmosphere of dry argon using
standard glovebox and Schlenk techniques. Solvents were purified and
degassed by standard procedures. NMR spectra were recorded with
either a Bruker AMX 300 or Bruker Avance 400 spectrometer with δ
referenced to external SiMe4 (1H, 13C), H3PO4 (31P), or SnMe4 (119Sn).
The substances LiP(SiMe3)2·1.8THF [45], Ph*I [46], Ph*Li·OEt2 [46],
Ph*GeCl [47], and Ph*SnCl [48] were prepared according to literature
methods. Due to the sensibility of the compounds and, in some cases,
the lack of material no elemental analyses of 2–10 could be performed.
However, in most cases the MS analyses reported the composition of
the products.
Ph*GeCl3 (2): GeCl4 (0.67 mL, 1.265 g, 5.9 mmol) was dissolved in
Et2O (10 mL). A solution of Ph*Li·OEt2 (3.318 g, 5.9 mmol) in Et2O
(50 mL) was afterwards added dropwise at –78 °C. The solution was
slowly allowed to warm to room temperature and was stirred over-
night. The solvent was removed under reduced pressure, and the white
residue extracted with n-hexane (40 mL). Upon filtration through Kie-
selgur, the filtrate was concentrated under vacuum until the onset of
crystallization. Storage at –25 °C for five days afforded colorless crys-
tals of 2. The mother liquor was decanted, and the crystals were dried
under vacuum (1.752 g, 45 %).
Syntheses
2: MS (EI, 70 eV): m/z = 660 (M+, 26 %), 645 (M+ – CH3, 3 %), 481
(M+ – GeCl3, 71 %), 466 (M+ – GeCl3 – CH3, 22 %). 1H NMR
Ph*SnCl3 (1a): Method A: SnCl4 (0.90 mL, 2.0 g, 7.7 mmol) was dis-
solved in n-hexane (5 mL). Et2O (5 mL) was added, and the resulting
white suspension was cooled to –78 °C. A solution of Ph*Li·OEt2
(4.319 g, 7.7 mmol) in Et2O (50 mL) was afterwards added dropwise.
The reaction mixture was slowly allowed to warm to room temperature
and stirred overnight. The solvent was removed in vacuo, and the white
residue was extracted with n-hexane (40 mL). Upon filtration through
Kieselgur, the filtrate was concentrated under reduced pressure to
about 15 mL and stored at –25 °C, whereby colorless microcrystals of
3
(300 MHz, C6D6, 25 °C): δ = 1.24 (d, JHH = 6.9 Hz, 12 H, p-
CH(CH3)2), 1.29 (d, 3JHH = 6.9 Hz, 12 H, o-CH(CH3)2), 1.32 (d, 3JHH
=
3
6.9 Hz, 12 H, o-CH(CH3)2), 2.89 (sept, JHH = 6.9 Hz, 2 H, p-
3
CH(CH3)2), 3.56 (sept, JHH = 6.9 Hz, 4 H, o-CH(CH3)2), 7.05 (s, 4
3
3
H, m-Trip), 7.31 (d, JHH = 6.9 Hz, 2 H, m-Phenyl), 7.39 (t, JHH
6.9 Hz, 1 H, p-Phenyl).
=
1a precipitated overnight. The mother liquor was decanted, and the Ph*SnP(SiMe3)2 (3): Method A: A solution of Ph*SnCl3 (1a)
crystals were dried under vacuum (2.01 g, 37 %). (1.452 g, 2.06 mmol) in Et2O (40 mL) was cooled to –78 °C.
Z. Anorg. Allg. Chem. 2010, 1275–1285
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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B. P. Johnson, S. Almstätter, F. Dielmann, M. Bodensteiner, M. Scheer
ARTICLE
LiP(SiMe3)2·1.8THF (677 mg, 2.06 mmol) was added as a solid, and 78 °C. The solution was allowed to warm slowly to room temperature,
the solution slowly turned violet. The solution was allowed to stir over- whereby the orange solution slowly became brown. After stirring over-
night at room temperature, and then filtered through Kieselgur. A ali- night, the solution was filtered through Kieselgur and the solvent re-
quot of the filtrate (5 mL) was taken for 31P NMR spectroscopic analy- moved. The resulting brown residue was analyzed by 31P NMR spec-
sis, while the rest was concentrated to ca. 5 mL under reduced pressure troscopy, which indicated formation of Trip(H)P–P(H)Trip (ca. 20 %)
and was stored at –25 °C for one week, after which colorless crystals and 6 (ca. 70 %) alongside unreacted TripPH2 (ca. 10 %).
of 3 deposited (750 mg, 46 %).
1
6: 31P NMR (162 MHz, C6D6): δ = –70.9 (br., Δν1/2 = 150, JPH
=
186, JP117/119Sn = 934 Hz; 117/119Sn satellites could not be resolved,
1
Method B: Ph*SnCl (1.356 g, 2.1 mmol) was dissolved in n-hexane
(20 mL) and cooled to –78 °C. KP(SiMe3)2 (465 mg, 2.1 mmol) was
added as a solid. Upon warming to room temperature, the color
changed from orange to deep violet. The solution was stirred overnight
and filtered through Kieselgur. The filtrate was concentrated to about
5 mL under vacuum and stored at –25 °C, whereby violet crystals of
3 deposited after one week (799 mg, 49 %). Compound 3 can also be
synthesized from 5 and LiP(SiMe3)2·1.8THF by an analogous proce-
dure in approximately the same yield.
total Sn satellite intensity = 12 %).
Li+[Ph*SnPTrip]– (7, proposed): To a solution of TripPH2 (64 mg,
0.27 mmol) in Et2O (10 mL) was added a solution of nBuLi (0.34 mL,
1.6 m in n-hexane, 0.54 mmol) at –78 °C. The resulting solution was
allowed to warm to room temperature and stirred for 3 hours. The
yellow solution of Li2PTrip was added slowly to a solution of Ph*SnCl
(5) (171 mg, 0.27 mmol) in Et2O (10 mL) at –78 °C. The resulting
solution was allowed to warm slowly to room temperature, whereby
the orange color gradually became brown. After overnight stirring, the
solution was filtered through Kieselgur and the solvent removed. The
resulting brown residue was analyzed by 31P NMR spectroscopy,
whereby a mixture of signals indicated formation of Trip(H)P–
P(H)Trip (ca. 20 %) and Li+[Ph*SnPTrip]– (7, proposed, ca. 40 %).
3: MS (EI, 70 eV, 120 °C): m/z = 778.2 (M+, 2.2 %), 763.2 (M+
–
CH3, 0.3 %), 705.1 (M+ – SiMe3, 0.3 %), 690.2 (M+ – SiMe3 – CH3,
1.5 %), 675.3 (M+ – SiMe3 – 2 CH3, 1.6 %), 601.1 (M+ – P(SiMe3)2,
70 %), 482.4 (M+ – SnP(SiMe3)2, 100 %), 467.3 (M+ – SnP(SiMe3)2 +–
CH3, 47 %), 439.3 (M+ – SnP(SiMe3)2 – C3H7, 14 %), 73 (SiMe3
,
=
+
1
3
4 %), 43.1 (C3H7 3 %). H NMR (C6D6, 25 °C): δ = 0.16 (d, JHP
7: 31P NMR (162 MHz, C6D6): δ = 229.7 (br., Δν1/2 = 280, 1JP117Sn
1735, JP119Sn = 2004 Hz, total Sn satellite intensity = ca. 14 %).
=
3
4.0 Hz, 18 H, Si(CH3)3), 1.13 (d, JHH = 6.7 Hz, 12 H, o-CH(CH3)2),
1
3
3
1.23 (d, JHH = 6.9 Hz, 12 H, o-CH(CH3)2), 1.46 (d, JHH = 6.7 Hz,
12 H, p-CH(CH3)2), 2.79 (sept, 3JHH = 6.9 Hz, 2 H, p-CH(CH3)2), 3.28
3
(sept, JHH = 6.8 Hz, 4 H, o-CH(CH3)2), 7.14 (s, 4 H, m-Trip). 13C
[Ph*Sn{W(CO)5}(μ-O)2SnPh*] (8): A solution of Ph*SnCl (5)
(198 mg, 0.31 mmol) in n-hexane (10 mL) was added dropwise to a
vigorously stirred suspension of Li[H2PW(CO)5] (113 mg, 0.31 mmol)
in n-hexane (5 mL) at –78 °C. The resulting pale red-brown suspen-
sion was allowed to warm to room temperature and stirred overnight.
The solution was filtered through Kieselgur, and the volume was re-
duced under vacuum to 1 mL. Storage at –25 °C for several weeks
yielded a mixture of colorless, yellow, and orange crystals, from which
an orange crystal was selected for an X-ray diffraction experiment and
determined crystallographically to be compound 8. Among the mixture
of crystals the presence of [H3PW(CO)5] was shown by EI mass spec-
trometry, but no other compounds could be unambiguously identified.
The synthesis of 8 could not be reproduced, thus preventing prepara-
tive isolation and further spectroscopic characterization. The mass
spectrometric data given below were measured for the actual crystal
that was used in the X-ray experiment.
2
NMR (62.90 MHz, C6D6): δ = 6.50 (d, JCP = 9.5 Hz), 24.25 (s,
CH(CH3)2), 25.09 (s, CH(CH3)2), 27.95 (s, CH(CH3)2), 32.01 (s,
CH(CH3)2), 35.54 (s, CH(CH3)2), 122.81 (s), 127.73 (s), 131.90 (s),
136.10 (s), 146.28 (s), 147.69 (s), 150.10 (s), 181.31 (s, ipso-C6H3).
29Si{1H} NMR (49.69 MHz, C6D6): δ = 4.08 (d, 1JSiP = 38.5 Hz). 29Si
NMR (49.69 MHz, C6D6): δ = 4.08 (dm, 1JSiP = 38.5, 2JSiH = 6.6 Hz).
31P NMR (101.36 MHz, C6D6): δ = –123.1 (s, 1JP117Sn = 1396,
1JP119Sn = 1453 Hz, total Sn satellite intensity = 12 %). 119Sn NMR
1
(112.02 MHz, C6D6): δ = 1919 (d, JSnP = 1453 Hz).
Ph*GeP(SiMe3)2 (4): Method A: A solution of LiP(SiMe3)2 (499 mg,
1.52 mmol) in Et2O (20 mL) was added dropwise to a solution of
Ph*GeCl3 (2) (1 g, 1.52 mmol) in Et2O (40 mL) at –78 °C. Upon
warming to room temperature, the color changed from orange to deep
red. The solution was allowed to warm to room temperature and was
stirred for 16 h. After filtration through Kieselgur the filtrate was con-
centrated under vacuum to about 5 mL and stored at –25 °C, whereby
red crystals of 4 deposited after two weeks (70 mg, 7 %).
8: MS (EI, 70 eV, 380 °C): m/z = 594.5 ([Sn2O2W(CO)5]+, 11 %),
566.5 ([Sn2O2W(CO)4]+, 33 %), 538.5 ([Sn2O2W(CO)3]+, 38 %),
510.5 ([Sn2O2W(CO)2]+, 16 %), 43.1 ([C3H7]+, 54 %).
Method B: Ph*GeCl (897 mg, 1.52 mmol) was dissolved in Et2O
(40 mL) and cooled to –78 °C. A solution of LiP(SiMe3)2 (499 mg,
1.52 mmol) in Et2O (20 mL) was added dropwise. Upon warming to
room temperature, the color changed from orange to deep red. The
solution was stirred overnight and filtered through Kieselgur. Red crys-
tals of Ph*GeP(SiMe3)2 (4) were obtained in similar yield as for
method A.
Ph*Sn(OSiMe3)2Cl (9): Excess trimethylsilylperoxide (0.2 mL, ca.
200 mg, ca. 1.1 mmol) was added by pipette to a solution of Ph*SnCl
(5) (560 mg, 0.88 mmol) in Et2O (10 mL) at 0 °C. The color changed
immediately from orange to colorless. The solution was allowed to
warm to room temperature and stirred for one hour. After filtration
through Kieselgur, the filtrate was concentrated under reduced pressure
to 2 mL and stored at –25 °C. Colorless crystals formed after one
week, were separated from the mother liquor by decantation, and dried
under vacuum (172 mg, 24 %).
4: MS (EI, 70 eV): m/z = 733 (M+, 40 %), 719 (M+ – CH3, 4 %), 677
(M+ – iPr, 13 %). 31P NMR (101.36 MHz, C6D6): δ = –48.6 (s).
Ph*SnP(H)Trip (6): TripPH2 (57 mg, 0.24 mmol) was dissolved in 9: MS (EI, 70 eV, 120 °C): m/z = 799.1 (M+ – CH3, 1 %), 741.0 (M+ –
Et2O (10 mL) and cooled to –78 °C. A solution of nBuLi (0.15 mL, SiMe3, 1.2 %), 725.1 (M+ – OSiMe3, 1.6 %), 652.1 (M+ – OSiMe3 –
1.6 m in n-hexane, 0.24 mmol) was added slowly by pipette. The mix- SiMe3, 1.3 %), 636.1 (M+ – 2 OSiMe3, 0.8 %), 601.1 (M+ – 2
ture was allowed to warm to room temperature and stirred for one hour. OSiMe3 – Cl, 1.2 %), 482.2 (M+ – Sn(OSiMe3)2Cl, 100 %), 467.2
The resulting LiP(H)Trip solution was added dropwise to a solution of (M+ – Sn(OSiMe3)2Cl – CH3, 100 %), 439.1 (M+ – Sn(OSiMe3)2Cl –
1
Ph*SnCl (5) (154 mg, 0.24 mmol) in Et2O (8 mL) and cooled to – C3H7, 46 %), 424.2 (M+ – Sn(OSiMe3)2Cl – C3H7 – CH3, 20 %). H
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Synthesis and Reactivity of Low-Valent Group 14 Element Compounds
3
NMR (C6D6, 25 °C): δ = 0.13 (d, 18 H, Si(CH3)3), 1.07 (d, JHH
=
toluene solution): m/z = 1304.6 (M+, 100 %). 1H NMR (C6D6, 25 °C):
3
3
3
6.9 Hz, 12 H, o-CH(CH3)2), 1.20 (d, JHH = 6.8 Hz, 12 H, o- δ = 1.02 (d, JHH = 6.9 Hz, 12 H, CH(CH3)2), 1.36 (d, JHH = 6.8 Hz,
CH(CH3)2), 1.30 (d, 3JHH = 6.9 Hz, 12 H, p-CH(CH3)2), 2.91 (m, 6 H, 12 H, CH(CH3)2), 1.46 (d, JHH = 6.9 Hz, 12 H, CH(CH3)2), 2.86 (m,
3
CH(CH3)2), 7.06 (t, JHH = 7.5 Hz, 1 H, p- C6H3), 7.18 (s, 4 H, m- 6 H, CH(CH3)2), 7.22 (s, 4 H, m-Trip). 13C NMR (75.48 MHz, C6D6):
3
Trip), 7.21 (br., 2 H, m- C6H3).
δ = 23.45 (s, CH(CH3)2), 24.20 (s, CH(CH3)2), 26.17 (s, CH(CH3)2),
31.34 (s, CH(CH3)2), 34.75 (s, CH(CH3)2), 121.64 (s), 127.71 (s),
130.17 (s), 131.08 (s), 136.59 (s), 147.22 (s), 147.90 (s), 149.88 (s).
[Ph*Sn(μ-O)Cl]2 (10): Trimethylamine N-oxide (59 mg, 0.79 mmol)
was added as a solid to a solution of Ph*SnCl (500 mg, 0.79 mmol)
in Et2O (15 mL) at 0 °C. The color changed within 30 minutes from
orange to colorless. The solution was allowed to warm to room temper-
ature and stirred for two hours, after which the solution had become
cloudy. Et2O was added by Teflon cannula until the solution became
clear (ca. 15 mL). After filtration through Kieselgur, the filtrate was
concentrated under reduced pressure until the onset of crystallization
and stored at –25 °C. Colorless crystals formed after four days, were
separated from the mother liquor by decantation, and dried under vac-
uum (216 mg, 42 %).
Crystal Structure Analysis
The crystal structure analyses were performed on an Oxford Diffrac-
tion Gemini R Ultra CCD (2, 4) using Cu-Kα radiation (λ = 1.54184 Å)
and a STOE IPDS diffractometer (1a, 3, 8, 10) using Mo-Kα radiation
(λ = 0.71073 Å), respectively. Semi-empirical absorption corrections
from equivalents (multi-scan) were applied for 2 and 4 [49]. For 1a,
3, 8 and 10 numerical absorption corrections from crystal faces were
carried out [50]. 1a, 3, 8 and 10 were solved by direct methods with
10: IR(KBr): ν = 3053 (m), 2860 (m), 1962 (w), 1760 (m), 1605 (s), the program SIR-97 [51]. Compound 2 could not be solved by direct
˜
1564 (s), 1385 (s), 1362 (s), 1318 (s), 1251 (s), 1240 (s), 1188 (m),
1164 (vs), 1154 (m), 1100 (vs), 1080 (s), 1071 (s), 1055 (s), 916 (s),
methods or Patterson methods. Hence it was solved using charge-flip-
ping algorithms from SUPERFLIP [52]. Full matrix least-square re-
875 (s), 805 (s), 776 (s), 750 (s), 654 (s), 497 (s) cm–1. MS (FD, finement on F2 in SHELXL-97 [53] was performed with anisotropic
Table 1. Crystallographic Data for compounds 1a, 2, 3, 4, 8, and 10.
1a
2
3
4
8
10
Empirical
formula
C36Cl3H49Sn
C36Cl2H49Ge
C42H67PSi2Sn
C42H67PSi2Ge
C77H98O7Sn2W
C72Cl2H98O2Sn2
Formula
mass /g·mol–1 706.81
625.26
123(1)
777.82
200(1)
731.72
123(1)
1556.81
203(1)
1303.82
173(1)
T /K
203(2)
Crystal
dimensions
/mm
0.12 × 0.10 × 0.03 0.29 × 0.09 × 0.08 0.20 × 0.20 × 0.02 0.24 × 0.11 × 0.11 0.20 × 0.20 × 0.06 0.22 × 0.16 × 0.12
Crystal
system
Triclinic
Orthorhombic
C2221
11.017(9)
12.212(6)
25.526(3)
90
Triclinic
Monoclinic
P21/c
Orthorhombic
Pnma
Triclinic
¯
¯
¯
Space group P1
P1
P1
a /Å
b /Å
c /Å
α /°
β /°
γ /°
8.479(1)
9.280(1)
13.240(3)
19.576(4)
83.19(3)
88.44(3)
70.83(3)
2255.7(9)
2
15.279(7)
16.004(8)
18.090(5)
90
18.983(4)
18.340(4)
23.227(5)
90
9.887(9)
12.945(9)
15.833(8)
66.61(8)
87.09(8)
86.62(5)
1856.3(3)
1
13.799(3)
16.691(3)
70.59(3)
85.67(3)
72.24(3)
1753.4(8)
2
90
90
103.60(9)
90
90
90
V /Å3
Z
3434.7(6)
4
4299.8(2)
4
8086(3)
4
Dcalc /g·cm–3 1.339
1.209
1.145
1.130
1.279
1.166
μ /mm–1
F(000)
0.980
732
Mo-Kα
2.40–25.94
2.788
0.680
2.031
2.077
0.783
1324
824
1576
3160
680
radiation
θ range
Cu-Kα
3.41–62.21
Mo-Kα
2.32–26.00
Cu-Kα
Mo-Kα
2.06–25.90
Mo-Kα
2.46–25.81
3.41–66.73
reflections
collected
unique
12082
6320
12127
16260
20851
34356
13161
reflections
2639
1.094
0.0485
8232
1.029
0.0359
7497
1.062
0.0272
7703
1.056
0.0750
6646
0.949
0.0234
GOF on F2 1.034
Rinat)
0.0617
0.0532
0.1263
–
R1
[I > 2s(I)]
0.0927
0.0409
0.1073
–
0.0331
0.0883
–
0.0554
0.1308
–
0.0317
0.0709
–
b)
wR2
(all data)
Flack para-
meter
0.2515
0.50(7)
Max/min
Δρ /e·Å–3
0.713/–0.902
1.287/–1.633
0.651/–0.730
2 2 ½
0.464/–0.243
1.030/–1.515
1.488/–0.310
2
2 2
a) R1 = Σ|Fo|–|Fc||/Σ|Fo|. b) wR2 = [Σω(Fo –Fc ) ]/[Σ (Fo ) ] .
Z. Anorg. Allg. Chem. 2010, 1275–1285
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1283

B. P. Johnson, S. Almstätter, F. Dielmann, M. Bodensteiner, M. Scheer
ARTICLE
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in idealized positions and refined isotropically according to the riding
model. In 8 and 10 isopropyl groups are disordered over two positions.
Thus, several constraints and restraints were used for refinement. Dis-
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CCDC-760737 (1a), -760738 (2), -760739 (3), -760740 (4), -760741
(8), and -760736 (10) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK, Fax: +44-1223-
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Acknowledgement
This work is comprehensively supported by the Deutsche Forschungs-
gemeinschaft and the Fonds der Chemischen Industrie. F. Dielmann
thanks the Studienstiftung des Deutschen Volkes for a PhD fellowship.
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Received: January 12, 2010
Published Online: May 20, 2010
Z. Anorg. Allg. Chem. 2010, 1275–1285
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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