Synthesis of a tin(II) 1,3-benzobis(thiophosphinoyl)methanediide complex and its reactions with aluminum compounds

Article abstract of DOI:10.1021/om300345u

The synthesis of a tin(II) 1,3-benzobis(thiophosphinoyl)methanediide complex and its reactions with aluminum compounds are reported. The reaction of the 1,3-benzodiphosphole disulfide [1,3-C₆H₄(PhP=S) ₂CH₂] (4) with [Sn{N(SiMe₃)₂} ₂] in refluxing toluene afforded the tin(II) 1,3- benzobis(thiophosphinoyl)methanediide [{μ-1,3-C₆H ₄(PhP=S)₂C}Sn]₂ (5). The X-ray crystal structure of 5 shows that it has a 1,3-dimetallacyclobutane structure. The reaction of 5 with 1 equiv of AlCl₃ in CH₂Cl₂ afforded [1,3-C₆H₄(PhP=S)₂C(Sn){Sn(S=PPh) ₂C(AlCl₃)-1,3-C₆H₄}] (6). The reaction proceeds via an insertion of a AlCl₃ molecule into one of the Sn-C bonds in 5. The reaction of 5 with 2 equiv of AlCl₃ in CH₂Cl₂ afforded[1,3-C₆H₄(PhP=S) ₂C(Sn)(AlCl₃)] (7). The reaction appears to proceed via the formation of compound 6, which then undergoes an insertion with another AlCl₃ molecule to form compound 7. The transmetalation reaction of 5 with 2 equiv of AlMe₃ in CH₂Cl₂ afforded [1,3-C₆H₄(PhP=S)₂CAlMe]₂ (8), which contains a terminal C_methanediide-Al bond.

Full text of DOI:10.1021/om300345u

Article
pubs.acs.org/Organometallics
Synthesis of a Tin(II) 1,3-Benzobis(thiophosphinoyl)methanediide
Complex and Its Reactions with Aluminum Compounds
Yi-Fan Yang, Cechao Foo, Rakesh Ganguly, Yongxin Li, and Cheuk-Wai So*
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University,
637371 Singapore
S
* Supporting Information
ABSTRACT: The synthesis of a tin(II) 1,3-benzobis(thiophosphinoyl)methanediide complex and its reactions with aluminum
compounds are reported. The reaction of the 1,3-benzodiphosphole disulfide [1,3-C6H4(PhPS)2CH2] (4) with
[Sn{N(SiMe3)2}2] in refluxing toluene afforded the tin(II) 1,3-benzobis(thiophosphinoyl)methanediide [{μ-1,3-C6H4(PhP
S)2C}Sn]2 (5). The X-ray crystal structure of 5 shows that it has a 1,3-dimetallacyclobutane structure. The reaction of 5 with
1 equiv of AlCl3 in CH2Cl2 afforded [1,3-C6H4(PhPS)2C(Sn){Sn(SPPh)2C(AlCl3)-1,3-C6H4}] (6). The reaction proceeds
via an insertion of a AlCl3 molecule into one of the Sn−C bonds in 5. The reaction of 5 with 2 equiv of AlCl3 in CH2Cl2 afforded
[1,3-C6H4(PhPS)2C(Sn)(AlCl3)] (7). The reaction appears to proceed via the formation of compound 6, which then
undergoes an insertion with another AlCl3 molecule to form compound 7. The transmetalation reaction of 5 with 2 equiv of
AlMe3 in CH2Cl2 afforded [1,3-C6H4(PhPS)2CAlMe]2 (8), which contains a terminal Cmethanediide−Al bond.
complex [{μ-1,3-C6H4(PhPS)2C}Sn]2 (5), and (iii) the reactions
INTRODUCTION
■
of compound 5 with AlMe3 and AlCl3.
Low-valent group 14 metal bis(phosphinoyl)methanediide
complexes of composition [:MC(PPh2E)2]2 (M = Ge, Sn,
RESULTS AND DISCUSSION
Pb, E = NSiMe3, S) have attracted much attention in the past
decade.1 Moreover, the pyridine- and lutidene-functionalized
low-valent group 14 metal phosphinoylmethanediide com-
plexes have been reported.2 They have either a metal-
lavinylidene structure (A and B, Scheme 1) or a 1,3-dimetalla-
cyclobutane structure (C−F). The reactivity of low-valent
group 14 metallavinylidene derivatives has been well studied.
Leung et al. reported that the bis(germavinylidene)
[(Me3SiNPPh2)2CGe:]2 (A) acts as a Lewis base or
undergoes an 1,2-addition or cycloaddition toward various
transition-metal complexes and organic and inorganic sub-
strates.3 We have also reported the synthesis of the tin(II)
(iminophosphinoyl)(thiophosphinoyl)methanediide [(PPh2
NSiMe3)(PPh2S)CSn:]2 (B)1b and its reactions with sulfur,
isocyanates, and [RhCl(cod)]2.4 In contrast, the reactivity of
low-valent group 14 1,3-dimetallacyclobutane has been less studied.
Only one example was reported. Leung et al. showed that the
reaction of [Pb{μ-C(PPh2S)2}]2 with sulfur formed [PbS{C-
(PPh2S)2}], in which the sulfur atom is inserted into the
Cmethanediide−Pb bond.1c Since the group 14 elements in a low-valent
group 14 1,3-dimetallacyclobutane contain a lone pair of electrons,
we are highly interested in exploring their reactivities with Lewis
acids such as aluminum compounds. In this paper, we report (i)
the synthesis of the 1,3-benzodiphosphole disulfide [1,3-
C6H4(PhPS)2CH2] (4) from [CH2(PPh2S)2], (ii) the
synthesis of the tin(II) 1,3-benzobis(thiophosphinoyl)methanediide
■
Synthesis of the 1,3-Benzodiphosphole Disulfide [1,3-
C6H4(PhPS)2CH2]. The reaction of [CH2(PPh2S)2] (1)
with 1 equiv of BunLi in THF, followed by treatment with
1 equiv of ButOK in THF afforded [(PPh2S)2CHK] (2;
Scheme 2). Moreover, the reaction of 1 with 1 equiv of ButOK
and 1.2 equiv of BunLi in refluxing THF afforded the potassium
1,3-benzobis(thiophosphinoyl)methanide [1,3-C6H4(PhP
S)2CHK·3THF] (3). Furthermore, treatment of 2 with PhLi
or BunLi in refluxing THF afforded compound 3, which has
been confirmed by NMR spectroscopy. In contrast, there is no
reaction between 2 and ButOLi. According to these results, the
reaction of 1 with ButOK/BunLi in refluxing THF probably
proceeds via the formation of 2. Consequently, the ortho
position of the phenyl ring is lithiated by BunLi, followed by an
intramolecular displacement of a PhLi molecule to form 3
(Scheme 3). The PhLi molecule then is involved in the
lithiation of the ortho position of the phenyl ring. As a result, a
slight excess of BunLi (1.2 equiv) is enough to initiate the ortho
metalation of the phenyl ring. Similar ortho metalation of the
PPh2 moiety of the bis(iminophosphinoyl)methanediide and
(iminophosphinoyl)(trimethylsilyl)methanide ligands has been
reported.5
Received: April 26, 2012
© XXXX American Chemical Society
A
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Scheme 1. Low-Valent Metallavinylidene Derivatives (A and B) and 1,3-Dimetallacyclobutane Derivatives (C−F)
Scheme 2. Synthesis of 2−4
3 was then hydrolyzed by water in THF to form [1,3-
C6H4(PhPS)2CH2] (4). It is noteworthy that the PS
moieties are cis to each other in solution and in the solid state
(see below).
Compound 2 has been synthesized in situ for the preparation
of vinylidene phosphine sulfide.6 However, its isolation and
characterization were not reported. Compound 2 was isolated
as a highly air- and moisture-sensitive pale yellow crystalline
B
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Scheme 3. Proposed Mechanism for the Formation of 3
solid which is soluble in Et2O and THF. It is stable in the solid
state at room temperature under an inert atmosphere. The
K(1)···C(16) = 3.336(8) Å, K(1)···C(17) = 3.432(8) Å).7 In the
monomeric form, the K(1) atom is coordinated with the S(1)
and S(2) atoms of the thiophosphinoyl substituents to form a
twisted six-membered metallacycle. The C(1)···K(1) distance
(4.807(7) Å) is significantly longer than that in [(PPh2
NSiMe3)2CHK(THF)2] (4.145(2) Å),8 which indicates that
there is no contact between the C(1) and K(1) atoms. The
K(1)−S(1) (3.187(3) Å) and K(1)−S(2) bonds (3.234(3) Å)
are comparable with those in the potassium bis(thiophosphinoyl)-
amide [KN(PPh2S)2] (3.203(1), 3.279(1) Å).9 The P−S
bonds (1.982(2), 1.997(2) Å) are lengthened and the C−P
bonds (1.696(7), 1.718(7) Å) are shortened compared with
those in [CH2(PPh2S)2] (P−S, average 1.945 Å; P−C,
average 1.829 Å).10
1H NMR spectrum of 2 shows a triplet at δ 1.48 ppm (2JP−H
=
2.32 Hz) for the proton on the Cmethanide atom. The 13C{1H}
NMR spectrum shows a triplet at δ 20.12 ppm (JP−C = 107.3 Hz)
for the Cmethanide atom. The 31P{1H} NMR spectrum displays a
singlet at δ 38.03 ppm for the equivalent P nuclei.
The molecular structure of compound 2 is shown in Figure 1.
Selected bond lengths and angles of 2 are given in Table 1.
Compound 3 was isolated as a highly air- and moisture-
sensitive orange crystalline solid which is soluble only in THF.
It is stable in the solid state at room temperature under an inert
1
atmosphere. The H NMR spectrum of 3 shows a triplet at δ
1.35 ppm (2JP−H = 11.2 Hz) for the proton on the Cmethanide
atom. The 13C{1H} NMR spectrum shows a triplet at δ 26.0
ppm (JP−C = 101.1 Hz) for the Cmethanide atom. The 31P{1H}
NMR spectrum displays a singlet at δ 44.12 ppm for the
equivalent P nuclei.
The molecular structure of compound 3 (Figure 2, with
selected bond lengths and angles in Table 1) shows that the
K(1) atom is coordinated with the C(1), S(1), and S(2) atoms
of the ligand to form a couchlike conformation. The dihedral
angle between the C(8)C(13)P(2)C(1)P(1) and P(1)S(1)-
S(2)P(2) least-squares planes is 80.41°. The K(1)S(1)P(1)-
C(1)P(2)S(2) metallacycle adopts a pseudo-boat conformation
in which the C(1) and K(1) atoms are displaced from the
P(1)S(1)S(2)P(2) least-squares plane by 0.897 and 0.637 Å,
respectively. The coordination sphere on the K(1) atom is
further supplemented by coordinating with three THF
molecules. The K(1)−C(1) bond (3.196(6) Å) is comparable
to that in [(PPh2NSiMe3)(PPh2)CHK]n (3.166(7) Å),11
which suggests that there is a contact between the C(1) and
K(1) atoms. The K(1)−S(1) (3.2667(18) Å) and K(1)−S(2)
bonds (3.3622(19) Å) are comparable with those in 2.
Compound 4 was isolated as a pale yellow crystalline solid
which is soluble in toluene and THF. Its molecular structure is
shown in Figure 3. The PS moieties are cis to each other.
The result is in contrast to the X-ray crystal structure of
[CH2(PPh2S)2], in which the PS moieties are on opposite
sides.10 The C−P bonds (1.8229(14), 1.8373(14) Å) are
lengthened and the P−S bonds (1.9463(5), 1.9498(5) Å) are
shortened compared with those in 3 (C−P = 1.698(5),
1.721(5) Å; P−S = 1.9846(19), 1.987(2) Å).
Figure 1. Molecular structure of compound 2: (a) perspective view of
the molecule (50% thermal ellipsoids); (b) its polymeric form (15%
thermal ellipsoids). Hydrogen atoms are omitted for clarity.
Compound 2 has a polymeric structure by the electrostatic
interaction of the K(1) atoms with the thiophosphinoyl
substituents of the adjacent molecules. The coordination sphere
on the K(1) atoms is further supplemented by an η3 interaction
with the phenyl substituents (K(1)···C(15) = 3.453(8) Å,
Compound 4 also retains its solid-state structure in solution.
1
The H NMR spectrum displays a quartet at δ 3.26 (2JP−H
=
15.9 Hz) and a multiplet at δ 3.61 ppm for two nonequivalent
−PCH2P− protons. The 13C{1H} NMR spectrum shows a
C
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Table 1. Selected Bond Lengths (Å) and Angles (deg) for Compounds 2−8
[(PPh2S)2CHK] (2)
[1,3-C6H4(PhPS)2C(Sn){Sn(SPPh)2C(AlCl3)-1,3-C6H4}] (6)
K(1)−S(1)
K(1)−S(1C)
C(1)−P(1)
3.187(3)
3.137(3)
1.696(7)
1.997(2)
3.453(8)
3.432(8)
81.34(6)
119.7(2)
116.6(2)
K(1)−S(2)
3.234(3)
3.117(2)
1.718(7)
1.982(2)
3.336(8)
4.807(8)
103.65(9)
124.8(4)
C(1)−P(2)
1.670(15)
2.036(16)
2.297(4)
2.8055(11)
1.753(4)
2.0087(14)
123.1(3)
107.4(4)
81.34(10)
89.4(3)
P(1)−S(1)
2.059(8)
K(1)−S(2B)
C(1)−P(2)
P(2)−S(2)
K(1)−C(16)
C(1)···K(1)
K(1)−S(1)−P(1)
P(1)−C(1)−P(2)
P(2)−S(2)
C(20)−Sn(2)
Sn(2)−S(4)
C(20)−P(4)
C(20)−Sn(1)
Sn(2)−S(3)
C(20)−P(3)
P(3)−S(3)
2.310(4)
2.8152(11)
1.763(4)
P(1)−S(1)
K(1)−C(15)
K(1)−C(17)
S(1)−K(1)−S(2)
S(1)−P(1)−C(1)
C(1)−P(2)−S(2)
2.0091(15)
P(4)−S(4)
P(1)−C(1)−Al(1)
P(1)−C(1)−P(2)
C(20)−Sn(1)−S(2)
Sn(1)−S(1)−P(1)
P(2)−S(2)−Sn(1)
C(20)−Sn(2)−S(4)
Sn(2)−S(3)−P(3)
P(3)−C(20)−Sn(2)
P(3)−C(20)−P(4)
Sn(2)−C(20)−P(4)
P(4)−S(4)−Sn(2)
P(2)−C(1)−Al(1)
C(20)−Sn(1)−S(1)
S(1)−Sn(1)−S(2)
S(1)−P(1)−C(1)
C(1)−P(2)−S(2)
C(20)−Sn(2)−S(3)
S(3)−Sn(2)−S(4)
S(3)−P(3)−C(20)
P(3)−C(20)−Sn(1)
Sn(2)−C(20)−Sn(1)
C(20)−P(4)−S(4)
128.9(3)
81.7(3)
101.8(2)
[1,3-C6H4(PhPS)2CHK·3THF] (3)
117.8(4)
89.2(3)
118.3(6)
K(1)−C(1)
K(1)−S(2)
C(1)−P(2)
P(2)−S(2)
K(1)−O(2)
3.196(6)
3.3622(19)
1.721(5)
1.987(2)
2.662(5)
3.362(6)
59.02(10)
110.44(5)
119.50(19)
83.25(6)
92.6(2)
K(1)−S(1)
C(1)−P(1)
P(1)−S(1)
K(1)−O(1)
K(1)−O(3)
3.2667(18)
1.698(5)
73.18(10)
78.44(4)
99.33(17)
107.0(2)
99.21(16)
78.38(4)
73.18(9)
100.08(3)
109.05(14)
121.96(19)
100.38(14)
109.14(13)
1.9846(19)
2.714(4)
2.742(6)
K(1)−C(5)
C(1)−K(1)−S(1)
S(1)−K(1)−S(2)
S(1)−P(1)−C(1)
K(1)−S(2)−P(2)
P(2)−C(1)−K(1)
C(1)−K(1)−S(2)
K(1)−S(1)−P(1)
P(1)−C(1)−K(1)
S(2)−P(2)−C(1)
P(1)−C(1)−P(2)
58.35(10)
83.66(6)
90.4(2)
[1,3-C6H4(PhPS)2C(Sn)(AlCl3)] (7)
C(1)−Al(1)
Sn(1)−S(1)
C(1)−P(1)
1.963(3)
C(1)−Sn(1)
Sn(1)−S(2)
2.392(3)
119.2(2)
116.0(3)
2.6435(9)
1.758(3)
2.6364(9)
1.756(3)
C(1)−P(2)
[1,3-C6H4(PhPS)2CH2] (4)
P(1)−S(1)
2.0191(11)
74.22(8)
P(2)−S(2)
2.0164(11)
74.57(8)
C(1)−P(2)
P(1)−S(1)
P(1)−C(1)−P(2)
1.8229(14)
1.9463(5)
C(1)−P(1)
P(2)−S(2)
1.8373(14)
1.9498(5)
S(1)−Sn(1)−C(1)
S(1)−Sn(1)−S(2)
Al(1)−C(1)−P(1)
Sn(1)−S(1)−P(1)
P(1)−C(1)−P(2)
P(2)−S(2)−Sn(1)
S(2)−Sn(1)−C(1)
Sn(1)−C(1)−Al(1)
Al(1)−C(1)−P(2)
S(1)−P(1)−C(1)
C(1)−P(2)−S(2)
100.29(3)
123.27(18)
82.59(4)
102.33(13)
124.45(18)
107.22(11)
107.81(11)
110.41(7)
[{μ-1,3-C6H4(PhPS)2C}Sn]2 (5)
106.27(17)
82.26(4)
C(1)−Sn(1)
Sn(1)−S(1)
C(1)−P(2)
2.334(2)
2.7174(6)
1.766(2)
1.9618(8)
84.13(8)
C(1)−Sn(1A)
C(1)−P(1)
P(1)−S(1)
2.301(2)
1.750(2)
2.0111(8)
[1,3-C6H4(PhPS)2CAlMe]2 (8)
P(2)−S(2)
C(1)−Al(1)
Al(1A)-S(1)
1.9469(17)
2.3331(7)
1.7111(16)
2.0616(6)
108.07(5)
113.44(2)
125.68(9)
98.41(2)
C(2)−Al(1)
1.9547(18)
2.3312(6)
1.7102(16)
2.0596(6)
109.94(5)
116.56(8)
127.19(9)
115.75(6)
117.59(6)
C(1)−Sn(1)−C(1A)
P(1)−C(1)−P(2)
P(1)−C(1)−Sn(1A)
P(2)−C(1)−Sn(1A)
P(1)−S(1)−Sn(1)
C(1)−P(2)−S(2)
Sn(1)−C(1)−Sn(1A)
95.88(8)
96.71(10)
106.36(11)
106.13(8)
72.71(6)
Al(1A)-S(2)
110.28(12) P(1)−C(1)−Sn(1)
113.55(11) P(2)−C(1)−Sn(1)
127.50(11) C(1)−P(1)−S(1)
C(1)−P(1)
P(1)−S(1)
C(1)−P(2)
P(2)−S(2)
C(1)−Al(1)−S(1A)
S(1A)−Al(1)−S(2A)
Al(1)−C(1)−P(1)
Al(1A)−S(1)−P(1)
P(1)−C(1)−P(2)
P(2)−S(2)−Al(1A)
C(1)−Al(1)−S(2A)
C(2)−Al(1)−C(1)
Al(1)−C(1)−P(2)
S(1)−P(1)−C(1)
C(1)−P(2)−S(2)
79.63(2)
S(1)−Sn(1)−C(1)
114.43(8)
[1,3-C6H4(PhPS)2C(Sn){Sn(SPPh)2C(AlCl3)-1,3-C6H4}] (6)
C(1)−Al(1)
Sn(1)−S(2)
1.923(4)
Sn(1)−S(1)
C(1)−P(1)
2.685(8)
1.724(8)
104.37(9)
97.12(2)
2.7094(11)
triplet at δ 41.62 ppm (JP−C = 40.0 Hz) for the CPCP atom. The
31P{1H} displays a singlet at δ 45.80 ppm for the P nuclei.
Synthesis of the Tin(II) 1,3-Benzobis(thiophosphinoyl)-
methanediide [{μ-1,3-C6H4(PhPS)2C}Sn]2. The reaction
of compound 4 with [Sn{N(SiMe3)2}2] in refluxing tolu-
ene afforded [{μ-1,3-C6H4(PhPS)2C}Sn]2 (5; Scheme 4).
The X-ray crystal structure of 5 shows that it has a 1,3-
dimetallacyclobutane structure (see below). Similar tin(II)
and lead(II) bis(phosphinoyl)methanediide complexes [M{μ-
C(PPh2E)2}]2 (M = Sn, Pb; E = S, NSiMe3) with a 1,3-
dimetallacyclobutane structure have been reported by
Leung et al.1a,c
(2JSn−P = 47.7, 160.4 Hz). The results are not consistent with
the solid-state structure. It is suggested that the thiophosphi-
noyl substituents are fluxional in solution. Similar observations
can be found in [Sn{μ-C(PPh2S)2}]2.1c The 119Sn{1H} NMR
spectrum shows a triplet at δ 26.28 ppm (2JSn−P = 50.2 Hz).
On comparison of the 119Sn NMR signal of 5 with those of
[(PPh2NSiMe3)(PPh2S)CSn:]2 (δ 132.1 ppm)1b and the
6-stannapentafulvene [(Tbt)(Mes)SnCR2] (Tbt = 2,4,6-
{CH(SiMe3)2}3C6H2, Mes = 2,4,6-Me3C6H2, CR2 = fluorenylidene)
(δ 270 ppm),12 it is suggested that compound 5 does not have
a vinylidene structure in solution.
The molecular structure of 5 (Figure 4, with selected bond
lengths and angles in Table 1) is comparable to that of [Sn{μ-
C(PPh2S)2}]2.1c It has a 1,3-dimetallacyclobutane structure
in which the Sn(1) and Sn(1A) atoms are coordinated with two
Cmethanediide atoms (C(1), C(1A)). The Sn(1) and Sn(1A)
atoms are also coordinated with one of the thiophosphinoyl
substituents of the ligand and display a distorted-trigonal-
pyramidal geometry (sum of bond angles 254.02°). The results
illustrate that the Sn atoms possess a high-s-character lone pair.
Compound 5 was isolated as an air- and moisture-sensitive
1
yellow crystalline solid which is soluble in CH2Cl2. The H
NMR spectrum displays resonances for the phenyl protons. It is
noteworthy that the 13C NMR signal for the Cmethanediide atom
in 5 is not observed. Similarly, there is no 13C NMR resonance
for the Cmethanediide atom in [Sn{μ-C(PPh2E)2}]2 (E = S,
NSiMe3).1a,c The 31P{1H} NMR spectrum displays a singlet
with satellites due to coupling to 117/119Sn at δ 54.91 ppm
D
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The C(1)−Sn(1) (2.334(2) Å) and C(1A)−Sn(1) bonds
(2.301(2) Å) in 5 are longer than the Cmethanediide−Sn bond in
[(PPh2NSiMe3)(PPh2S)CSn:]2 (2.2094(9) Å).1b The
difference between the C−Sn bond lengths in 5 (0.033 Å) is
significantly smaller than that in [Sn{μ-C(PPh2S)2}]2
(2.327(3), 2.514(3) Å; Δ = 0.187 Å).1c It is noteworthy that
the PS moieties are cis to each other. The result is in contrast
to the X-ray crystal structure of [Sn{μ-C(PPh2S)2}]2, in
which the PS moieties are on opposite sides.1c
Reactivity of [{μ-1,3-C6H4(PhPS)2C}Sn]2 (5) toward
Aluminum Compounds. The reaction of 5 with 1 equiv of
AlCl3 in CH2Cl2 afforded [1,3-C6H4(PhPS)2C(Sn){Sn(S
PPh)2C(AlCl3)-1,3-C6H4}] (6). The results show that the low-
valent Sn atoms in 5 do not form any adduct with AlCl3.
Instead, the reaction appears to proceed via an insertion of
AlCl3 into one of the Sn−C bonds in 5 to form the
intermediate G. The C−Sn bond is then cleaved in order to
release the steric congestion between two 1,3-benzobis-
(thiophosphinoyl)methanediide ligands. The results illustrate
that the Cmethanediide−Sn bonds in 5 are polar and the
Cmethanediide atom is nucleophilic. Hence, the lone pair electrons
on the tin atoms are less favorable for bond formation.
Figure 2. Molecular structure of 3 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms and the disordered THF molecule
are omitted for clarity.
Compound 6 was isolated as a highly air- and moisture-
sensitive yellow crystalline solid which is soluble only in
1
CH2Cl2. The H NMR spectrum displays resonances for the
phenyl protons. The 13C{1H} NMR signal for the Cmethanediide
atom in 6 cannot be observed. The 31P{1H} NMR spectrum
displays two singlets with satellites due to coupling to the Sn
2
nuclei at δ 55.05 (2JSn−P = 47.7 Hz, JSn’‑P = 160.4 Hz) for the
PCP nuclei and δ 58.45 ppm (2JSn−P = 164.7 Hz) for the
PC(AlCl3)P nuclei. The 119Sn{1H} NMR spectrum displays
two triplets at δ 22.15 (2JSn−P = 48.1 Hz) for the Sn(2) atom
(see Figure 5 for the numbering scheme) and δ −160.40 ppm
(2JSn−P = 164.3 Hz) for the Sn(1) atom, which show a upfield
shift compared with those of 5. These indicate that the Sn
atoms have a positive charge.
The molecular structure of 6 is shown in Figure 5. Selected
bond lengths and angles of 6 are given in Table 1. The
Sn(1)S(1)P(1)C(1)P(2)S(2) and Sn(2)S(3)P(3)C(20)P(4)S(4)
Figure 3. Molecular structure of 4 with thermal ellipsoids at the 50%
probability level.
Scheme 4. Synthesis of 5−8
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Figure 5. Molecular structure of 6 with thermal ellipsoids at the 30%
probability level. Hydrogen atoms, disordered phenyl substituents,
P(1A), P(2A), and S(1A) atoms, and solvent molecules are omitted
for clarity.
Figure 4. Molecular structure of 5 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms and solvent molecules are omitted
for clarity.
metallacycles adopt a pseudo-boat conformation. The C(20)
atom is coordinated with the Sn(1) and Sn(2) atoms. The
C(20)−Sn(1) (2.310(4) Å) and C(20)−Sn(2) bond lengths
(2.297(4) Å) are comparable with those in 5. Each tin atom
is also coordinated with two thiophosphinoyl substituents
and adopts a distorted-trigonal-pyramidal geometry (Sn(1),
264.84°; Sn(2), 246.44°). These indicate that the tin atoms
possess a high-s-character lone pair. The C(1)···Sn(1) distance
(3.065(4) Å) is significantly longer than the C−Sn bond in
base-stabilized stannylenes such as [{C5H4N-2-C(SiMe3)2}Sn-
{N(SiMe3)2}] (2.356(8) Å) and [{2,6-(CH2NMe2)2C6H3}-
SnCl] (2.158(8) Å),13 but it is shorter than the sum of van der
Waals radii (ca. 3.87 Å). The results suggest that there is a
weak interaction between the C(1) and Sn(1) atoms. The
C(1)−Al(1) bond (1.923(4) Å) is slightly shorter than the
Al−Cmethanediide bonds in the aluminum (iminophosphinoyl)-
(thiophosphinoyl)methanediide complex [(PPh2S)(PPh2
NSiMe3)CAlMe]2 (1.976(1) Å).14 Moreover, the C(1)−P
bonds (1.670(15), 1.724(8) Å) are significantly shorter than
the C(20)−P bonds (1.753(4), 1.763(4) Å), while the P(1)−
S(1) (2.059(8) Å) and P(2)−S(2) (2.036(16) Å) bonds are
longer than the P(3)−S(3) (2.0091(15) Å) and P(4)−S(4)
bonds (2.0087(14) Å). On the basis of the theoretical studies of
the dilithium bis(thiophosphinoyl)methanediide complex,15 it
is suggested that the C(1) atom contains two lone pairs of
electrons (LP), as illustrated in Scheme 5. One of the LPs
Similarly, the reaction of 5 with 2 equiv of AlCl3 in CH2Cl2
afforded [1,3-C6H4(PhPS)2C(Sn)(AlCl3)] (7). The reaction
appears to proceed via the formation of compound 6, which
then undergoes an insertion with another AlCl3 molecule to
form compound 7.
Compound 7 was isolated as a highly air- and moisture-
sensitive colorless crystalline solid, which is soluble only in
1
CH2Cl2. The H NMR spectrum displays resonances for the
phenyl protons. The 13C{1H} NMR signal for the Cmethanediide
atom in 7 cannot be observed. The 31P{1H} spectrum shows a
singlet with satellites due to coupling to the Sn nuclei at δ 58.54
ppm (2JSn−P = 164.7 Hz). The 119Sn{1H} NMR spectrum
displays a triplet at δ −140.25 ppm (2JSn−P = 170.8 Hz), which
is comparable with that in the tin(II) β-diketiminate cation
[HC(CMeNAr)2Sn(OEt2)][MeB(C6F5)3] (Ar = 2,6-Pri2C6H3,
δ −139.50 ppm).16
The molecular structure of 7 (Figure 6, with selected bond
lengths and angles in Table 1) shows that the Sn(1) atom is
Scheme 5. Resonance Structure of the 1,3-
Benzobis(thiophosphinoyl)methanediide Ligand
Figure 6. Molecular structure of 7 with thermal ellipsoids at the 50%
probability level.
coordinated with the thiophosphinoyl substituents and the
Cmethanediide atom. The Sn(1)S(1)P(1)C(1)P(2)S(2) metalla-
cycle adopts a pseudo-boat conformation in which the C(1)
and Sn(1) atoms are displaced from the P(1)S(1)S(2)P(2)
least-squares plane by 1.049 and 1.667 Å, respectively.
Moreover, the geometry around the Sn(1) atom is distorted
donates to the vacant p orbital of the Al(1) atom. Another
LP is stabilized by the negative hyperconjugation with the
P−CPh and P−S σ* orbitals, which results in shortening the
C(1)−P bonds and lengthening the P(1)−S(1) and P(2)−
S(2) bonds.
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Scheme 6. Proposed Mechanism for the Formation of 8
trigonal pyramidal (sum of bond angles 249.08°). This
geometry indicates that the Sn(1) atom possesses a high-s-
character lone pair. The C(1)−Sn(1) bond (2.392(3) Å) is
comparable with those in 5 and 6. The C(1)−Al(1) bond
(1.963(3) Å) is longer than that in 6.
angles in Table 1).18 The Al(1) atom is bonded to the
Cmethanediide atom, the methyl substituent, and the thiophosphi-
noyl substituent of the adjacent ligand, which adopts a
tetrahedral geometry. The C(1)−Al(1) bond (1.9469(17) Å)
is slightly shorter than that in [(PPh2NSiMe3)(PPh2S)-
CAlMe]2 (1.976(1) Å)14 and [(PPh2S)2CAlCl]2 (1.975(2) Å).18
In addition, the Cmethanediide−Al bond in 8 is slightly shorter than
the CMe−Al bond (1.9547(18) Å). According to the theoretical
studies of [(PPh2NSiMe3)(PPh2S)CAlMe]2,14 it is sug-
gested that the Cmethanediide−Al bond in 8 is highly ionic and has
weak covalent binding.
In conclusion, the tin(II) 1,3-benzobis(thiophosphinoyl)-
methanediide [{μ-1,3-C6H4(PhPS)2C}Sn]2 (5) undergoes
an insertion reaction with AlCl3 to form [1,3-C6H4(PhP
S)2C(Sn){Sn(SPPh)2C(AlCl3)-1,3-C6H4}] (6) and [1,3-
C6H4(PhPS)2C(Sn)(AlCl3)] (7). Compound 5 also under-
goes a transmetalation reaction with 2 equiv of AlMe3 in
CH2Cl2 to afford [1,3-C6H4(PhPS)2CAlMe]2 (8).
The transmetalation reaction of 5 with 2 equiv of AlMe3 in
CH2Cl2 afforded [1,3-C6H4(PhPS)2CAlMe]2 (8). The by-
products are SnMe4 and Me3Sn−SnMe3, which were confirmed
by 119Sn{1H} NMR spectroscopy. The reaction appears to proceed
through the formation of [1,3-C6H4(PhPS)2C(Sn)AlMe3]
(Scheme 6). The methyl groups are then transferred from
the Al atom to the Sn atom, which leads to the formation of
8 and SnMe2. Subsequently, the reactive SnMe2 intermediate
may decompose to form SnMe4 and Me3Sn−SnMe3. The mech-
anism is similar to that proposed for the transmetalation reactions of
transition-metal bis(thiophosphinoyl)methanediide complexes.17
The X-ray crystal structure shows that compound 8 has a
terminal Cmethanediide−Al bond (see below), which is comparable
with those of other aluminum bis(phosphinoyl)methanediide
complexes such as [(PPh2NSiMe3)(PPh2S)CAlMe]214 and
[(PPh2S)2CAlCl]2.18
EXPERIMENTAL SECTION
■
All manipulations were carried out under an inert atmosphere of
nitrogen gas using standard Schlenk techniques. Et2O, THF, and
toluene were dried over and distilled over Na/K alloy prior to use.
CH2Cl2 was dried over and distilled over CaH2 prior to use. 1 was
Compound 8 was isolated as a highly air- and moisture-
sensitive colorless crystalline solid, which is soluble only in CH2Cl2.
1
The H NMR spectrum shows signals for the Me substituent
and phenyl protons. It is noteworthy that the 13C NMR signal
for the Cmethanediide atom cannot be observed. The 31P{1H}
spectrum displays a singlet at δ 52.43 ppm, which shows a
downfield shift compared with that of [(PPh2S)2CAlCl]2
(δ 32.24 ppm).18
prepared as described in the literature.15 The H, 13C, 31P, and 119Sn
1
NMR spectra were recorded on a JEOL ECA 400 spectrometer. The
chemical shifts δ are relative to SiMe4 for 1H and 13C, SnMe4 for 119Sn,
and 85% H3PO4 for 31P. Elemental analyses were performed by the
Division of Chemistry and Biological Chemistry, Nanyang Techno-
logical University. Melting points were measured in sealed glass tubes
and were not corrected.
The molecular structure of 8 is comparable to that of
[(PPh2S)2CAlCl]2 (Figure 7, with selected bond lengths and
[(PPh2S)2CHK] (2). BunLi (1.8 mL, 3.6 mmol, 2 M solution in
cyclohexane) was added slowly to a solution of 1 (1.57 g, 3.5 mmol) in
THF (20 mL) at −78 °C. The yellow solution was warmed to ambient
temperature and stirred overnight. The resulting solution was then
added dropwise to a solution of ButOK (0.39 g, 3.5 mmol) in THF
(5 mL) at −78 °C. The yellow solution was warmed to ambient
temperature and stirred for 24 h. Volatiles were removed under
reduced pressure. After washing with hexane, the residue was extracted
by Et2O/THF (1:1, 30 mL). The insoluble precipitate was filtered.
The filtrate was concentrated to give compound 2 as pale yellow
crystals. Yield: 1.24 g (73%). Mp: 305 °C. Anal. Calcd for
1
C25H21KP2S2: C, 61.71; H, 4.35. Found: C, 61.51; H 4.35. H NMR
2
(399.5 MHz, THF-d8, 21.5 °C): δ 1.48 (t, JP−H = 2.32 Hz, 1H,
PCHP), 7.18−7.21 (m, 12H, Ph), 8.00−8.05 ppm (m, 8H, Ph).
13C{1H} NMR (100.5 MHz, THF-d8, 21.5 °C): δ 20.12 (t, PCP, JP−C
=
3
107.3 Hz), 126.73 (t, JP−C = 5.75 Hz, Cmeta of Ph), 128.24 (s, Cpara of
2
Ph), 131.47 (t, JC−P = 5.76 Hz, Cortho of Ph), 142.97 ppm (dd, JP−C
=
3
96.9 Hz, JP′−C = 2.87 Hz, Cipso of Ph). 31P{1H} NMR (161.7 MHz,
THF-d8, 21.7 °C): δ 38.03 ppm.
[1,3-C6H4(PhPS)2CHK·3THF] (3). Method A. BunLi (1.8 mL,
3.6 mmol, 2 M solution in cyclohexane) was added slowly to a solu-
tion of 1 (1.34 g, 3.0 mmol) and ButOK (0.34 g, 3.0 mmol) in THF
(20 mL) at ambient temperature. The orange solution was refluxed at
70 °C overnight to give a reddish brown solution. Volatiles were
removed under vacuum, and Et2O was added to the residue to afford a
Figure 7. Molecular structure of 8 with thermal ellipsoids at the 50%
probability level. One of the two independent molecules in the
asymmetric unit is shown. Solvent molecules are omitted for clarity.
G
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red solid after 16 h. The red solid was then recrystallized in THF to
give compound 3 as orange crystals. Yield: 0.88 g (47%).
2JSn′−P = 160.4 Hz, PCP) and 58.45 ppm (2JSn−P = 164.7 Hz, PC(AlCl3)P).
2
119Sn{1H} NMR (147.6 MHz, CD2Cl2, 23.2 °C): δ 22.15 (t, JSn−P
=
2
Method B. PhLi (0.5 mL, 1.0 mmol, 2 M solution in dibutyl ether)
was added slowly to a solution of 2 (0.48 g, 1.0 mmol) in THF
(10 mL) at ambient temperature. The orange solution was refluxed at
70 °C overnight to give a reddish brown solution. Volatiles were re-
moved under vacuum, and the residue was extracted by Et2O. After
filtration, a red crystalline solid was obtained in the filtrate. The red
solid was then recrystallized in THF to give compound 3 as orange
crystals. Yield: 0.17 g (27%).
48.1 Hz), −160.40 ppm (t, JSn−P = 164.3 Hz).
[1,3-C6H4(PhPS)2C(Sn)(AlCl3)] (7). A solution of 5 (0.57 g,
0.6 mmol) in CH2Cl2 (30 mL) was added to a suspension of AlCl3
(0.13 g, 1.0 mmol) in CH2Cl2 (10 mL) at ambient temperature. The
resulting yellow suspension was stirred overnight to give a clear yellow
solution. After filtration, the filtrate was concentrated to give
compound 7 as colorless crystals. Yield: 0.39 g (63%). Mp 257 °C
dec. Anal. Calcd for C19H14AlCl3P2S2Sn: C, 36.77; H, 2.28. Found: C,
1
Mp: 274 °C dec. Anal. Calcd for C31H39KO3P2S2: C, 59.59; H, 6.30.
36.64; H, 2.17. H NMR (395.9 MHz, CDCl3, 22.7 °C): δ 7.51−7.63
Found: C, 59.54; H, 6.31. 1H NMR (399.5 MHz, THF-d8, 21.5 °C): δ
(m, 6H, Ph and C6H4), 7.69−7.76 (m, 4H, Ph and C6H4), 7.88−7.94 ppm
(m, 4H, Ph and C6H4). 13C{1H} NMR (99.5 MHz, CDCl3, 21.8 °C):
δ 128.64−129.06 (m, Cmeta of Ph and C6H4), 132.19−132.41 (m,
Cortho of Ph and C6H4), 133.85−133.93 (m, C6H4), 134.01 (s, Cpara of
Ph), 142.46 ppm (dd, JP−C = 80.11 Hz, JP′−C = 21.93 Hz, Cipso of Ph).
2
1.35 (t, JP−H = 11.2 Hz, 1H, PCHP), 7.22−7.33 (m, 8H, Ph and
C6H4), 7.52−7.58 (m, 2H, Ph and C6H4), 8.00−8.06 ppm (m, 4H, Ph
and C6H4). 13C{1H} NMR (100.5 MHz, THF-d8, 21.5 °C): δ 26.0 (t,
3
JP−C = 101.1 Hz, PCP), 127.76 (t, JP−C = 6.71 Hz, Cmeta of Ph),
31P{1H} NMR (160.3 MHz, CDCl3, 14.6 °C): δ 58.54 ppm (2JSn−P
=
2
128.90 (t, JP−C = 11.5 Hz, C6H4), 129.68 (s, Cpara of Ph), 130.14 (t,
2
3JP−C = 3.83 Hz, C6H4), 131.94 (t, JP−C = 4.79 Hz, Cortho of Ph),
164.7 Hz). 119Sn{1H} NMR (147.6 MHz, CDCl3, 23.2 °C): δ −140.25
ppm (2JSn−P = 170.8 Hz).
143.61 (t, JP−C = 44.1 Hz, Cipso of Ph/C6H4), 144.63 ppm (t, JP−C
=
52.7 Hz, Cipso of Ph/C6H4). 31P{1H} NMR (161.7 MHz, THF-d8,
21.9 °C): δ 44.12 ppm.
[1,3-C6H4(PhPS)2CAlMe]2 (8). AlMe3 (0.5 mL, 1.0 mmol, 2 M
solution in toluene) was added to a solution of 5 (0.57 g, 0.5 mmol) in
CH2Cl2 (30 mL) at 0 °C. The resulting orange solution was stirred
overnight. After filtration, the orange filtrate was concentrated to give
compound 8 as yellow crystals. Yield: 0.21 g (51%). Mp: 266 °C dec.
Anal. Calcd for C40H34Al2P4S4: C, 58.54; H, 4.18. Found: C, 58.21; H,
[1,3-C6H4(PhPS)2CH2] (4). Excess degassed H2O was added to a
solution of 3 (1.87 g, 3.0 mmol) in THF (20 mL) at room
temperature. The resulting pale yellow suspension was stirred at room
temperature for 1 h. Volatiles were removed under reduced pressure.
The residue was washed with 10 mL of toluene. The pale yellow
residue was then extracted by CH2Cl2/hexane (1/1). After filtration
and concentration of the filtrate, compound 4 was obtained as pale
yellow crystals. Yield: 0.93 g (84%). Mp: 172 °C. Anal. Calcd for
1
3.95. H NMR (399.5 MHz, CDCl3): δ −1.03 (s, 6H, AlMe), 7.45−
7.61 (m, 20H, Ph and C6H4), 7.92−7.97 ppm (m, 8H, Ph and C6H4).
13C{1H} NMR (100.5 MHz, CDCl3, 22.7 °C): δ 1.18 (s, AlMe),
3
127.90 (t, JP−C = 11.5 Hz, Cmeta of Ph), 128.43−128.57 (m, C6H4),
1
131.67−133.00 (m, Cortho of Ph and C6H4), 132.21 (s, Cpara of Ph),
133.74 (dd, JP−C = 84.8 Hz, 3JP′−C = 4.79 Hz, C6H4), 143.41 ppm (dd,
JP−C = 83.87 Hz, 3JP′−C = 23.0 Hz, Cipso of Ph). 31P{1H} NMR (161.7
MHz, CDCl3): δ 52.43 ppm.
C19H16P2S2: C, 61.62; H, 4.36. Found: C, 61.29; H, 4.29. H NMR
2
(395.9 MHz, CDCl3, 21.6 °C): δ 3.26 (quartet, JP−H = 15.9 Hz, 1H,
PCH2P), 3.61 (m, 1H, PCH2P), 7.12−7.18 (m, 4H, Ph and C6H4),
7.27−7.32 (m, 6H, Ph and C6H4), 7.73−7.79 (m, 2H, Ph and C6H4),
7.91−7.99 ppm (m, 2H, Ph and C6H4). 13C{1H} NMR (100.5 MHz,
X-ray Data Collection and Structural Refinement. Intensity
data for compounds 2−8 were collected using a Bruker APEX II
diffractometer. The crystals of 2−8 were measured at 103(2) K. The
structures were solved by direct phase determination (SHELXS-97)
and refined for all data by full-matrix least-squares methods on F2.19 All
non-hydrogen atoms were subjected to anisotropic refinement. The
hydrogen atoms were generated geometrically and allowed to ride on
their respective parent atoms; they were assigned appropriate isotopic
thermal parameters and included in the structure factor calculations.
The X-ray crystallographic data of 2−8 are summarized in Table S1
(see the Supporting Information).
THF-d8, 21.7 °C): δ 41.62 (t, JP−C = 40.0 Hz, PCP), 129.41 (d, 3JP−C
=
2
6.71 Hz, Cmeta of Ph), 131.49 (d, JP−C = 11.4 Hz, C6H4), 131.70 (t,
3JP−C = 10.5 Hz, C6H4), 132.43 (s, Cpara of Ph), 134.38 (d, 2JP−C = 11.4 Hz,
C
ortho of Ph), 135.60 (d, JP−C = 52.7 Hz, C6H4), 140.17 ppm (dd, JP−C
= 86.8 Hz, 3JP′−C = 15.3 Hz, Cipso of Ph). 31P{1H} NMR (160.2 MHz,
CDCl3, 21.8 °C): δ 45.80 ppm.
[{μ-1,3-C6H4(PhPS)2C}Sn]2 (5). Toluene (30 mL) was added
to a mixture of 4 (1.11 g, 3.0 mmol) and Sn[N(SiMe3)2]2 (1.40 g,
3.2 mmol) at ambient temperature. The orange suspension was then
refluxed at 140 °C overnight. After filtration, the residue was then
extracted by CH2Cl2. After filtration and concentration of the filtrate, 5
was isolated as yellow crystals. Yield: 1.42 g (83%). Mp: 230 °C dec.
Anal. Calcd for C38H28P4S4Sn2: C, 46.85; H, 2.90. Found: C, 46.79; H,
ASSOCIATED CONTENT
* Supporting Information
■
S
1
2.87. H NMR (395.9 MHz, CDCl3, 23.2 °C): δ 7.37−7.43 (m, 8H,
CIF files giving X-ray data for 2−8 and a table giving
crystallographic data of 2−8. This material is available free of
charge via the Internet at http://pubs.acs.org.
Ph and C6H4), 7.47−7.51 (m, 4H, Ph and C6H4), 7.61−7.73 ppm (m,
16H, Ph and C6H4). 13C{1H} NMR (99.5 MHz, CD2Cl2, 21.4 °C): δ
129.17 (m, Cmeta of Ph and C6H4), 130.84 (d, 2JC−P = 12.4 Hz, C6H4),
132.26 (s, Cpara of Ph), 137.11 (d, JC−P = 80.11 Hz, C6H4), 143.18 ppm
3
(dd, JP−C = 75.3 Hz, JP′−C = 23.8 Hz, Cipso of Ph). 31P{1H} NMR
AUTHOR INFORMATION
Corresponding Author
*E-mail: CWSo@ntu.edu.sg.
■
(161.7 MHz, CDCl3, 23.4 °C): δ 54.91 ppm (2JSn−P = 47.7, 160.4 Hz).
119Sn{1H} NMR (147.6 MHz, CDCl3, 23.2 °C): δ 26.28 ppm (t,
2JSn−P = 50.2 Hz).
Notes
[1,3-C6H4(PhPS)2C(Sn){Sn(SPPh)2C(AlCl3)-1,3-C6H4}] (6).
A solution of 5 (0.57 g, 0.6 mmol) in CH2Cl2 (30 mL) was added
to a suspension of AlCl3 (0.06 g, 0.5 mmol) in CH2Cl2 (10 mL) at
ambient temperature. The resulting yellow suspension was stirred
overnight to give a clear yellow solution. After filtration, the filtrate was
concentrated to give compound 6 as yellow crystals. Yield: 0.31 g
(56%). Mp 225 °C dec. Anal. Calcd for C38H28AlCl3P4S4Sn2: C, 41.20;
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Academic Research Fund Tier
1 (RG 57/11).
1
H, 2.55. Found: C, 41.13; H, 2.46. H NMR (395.9 MHz, CDCl3,
21.6 °C): δ 7.34−7.94 ppm (m, 28H, Ph and C6H4). 13C{1H} NMR
(99.5 MHz, CDCl3, 21.8 °C): δ 128.6−129.0 (m, Ph and C6H4),
130.3−130.4 (m, Cortho of Ph and C6H4), 131.68 (s, Cpara of Ph),
132.24−132.37 (m, C6H4), 133.81−134.09 ppm (m, Cipso of Ph).
31P{1H} NMR (160.3 MHz, CDCl3, 22.2 °C): δ 55.05 (2JSn−P = 47.7 Hz,
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Organometallics
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dx.doi.org/10.1021/om300345u | Organometallics XXXX, XXX, XXX−XXX