Heptacoordinate Structures of Organotin Halides with Three Phosphine Donors: Halogen-Substituent Effect on Geometry

Article abstract of DOI:10.1002/ejic.201900524

Structural studies were performed on heptacoordinate compounds of triorganotin halides {(o-Ph₂P)C₆H₄}₃SnX [X = F (1), Cl (3), Br (4), I (5)] with three phosphine donors. The fluorostannane (1) has an unusual heptacoordinate geometry, in which the three phosphine donors interact with the Sn center around the opposite coordination site of the Sn–F bond (a form). In contrast, the chloro (3) and bromo (4) analogues have highly distorted pentagonal-bipyramidal geometries (b form), while the iodo analogue (5) has a tricapped tetrahedral geometry (c form). Although both b and c forms have two phosphine donors coordinating to the Sn center around the opposite site of the C_ipso atoms and one phosphine donor coordinating to the Sn atom trans to the halogen atom, the geometry around the Sn center is much more distorted from tetrahedral geometry in b form than in c form. Density functional theory (DFT) calculations indicate that the presence of the halogen atom on the Sn center facilitates access from the opposite side of the halogen due to the strong electrostatic and intramolecular donor–acceptor transfer interactions. The difference in electronegativity of the halogen atoms also appear to contribute to structural modification by altering the halogen substituent, because a strongly electronegative halogen facilitates the formation of a structure that is highly distorted from the tetrahedral geometry (Bent's rule).

Full text of DOI:10.1002/ejic.201900524

A Journal of
Accepted Article
Title: Heptacoordinate Structures of Organotin Halides with Three
Phosphine Donors: Halogen-Substituent Effect on Geometry
Authors: Hajime Kameo, Tatsuya Kawamoto, Shigeyoshi Sakaki,
Didier Bourissou, and Hiroshi Nakazawa
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201900524
Link to VoR: http://dx.doi.org/10.1002/ejic.201900524

10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
Heptacoordinate Structures of Organotin Halides with Three
Phosphine Donors: Halogen-Substituent Effect on Geometry
Hajime Kameo,*[a] Tatsuya Kawamoto,[b] Shigeyoshi Sakaki,[c] Didier Bourissou,[d] and Hiroshi
Nakazawa*[b]
Abstract: Structural studies were performed on heptacoordinate
compounds of triorganotin halides {(o-Ph2P)C6H4}3SnX (X = F (1), Cl
(3), Br (4), I (5)) with three phosphine donors. The fluorostannane (1)
has an unusual heptacoordinate geometry, in which the three
phosphine donors interact with the Sn center around the opposite
coordination site of the Sn−F bond (a form). In contrast, the chloro
(3) and bromo (4) analogues have highly distorted pentagonal-
bipyramidal geometries (b form), while the iodo analogue (5) has a
tricapped tetrahedral geometry (c form). Although both b and c
forms have two phosphine donors coordinating to the Sn center
around the opposite site of the Cipso atoms and one phosphine donor
coordinating to the Sn atom trans to the halogen atom, the geometry
around the Sn center is much more distorted from tetrahedral
geometry in b form than in c form. Density functional theory (DFT)
calculations indicate that the presence of the halogen atom on the
Sn center facilitates access from the opposite side of the halogen
due to the strong electrostatic and intramolecular donor-acceptor
transfer interactions. The difference in electronegativity of the
halogen atoms also appear to contribute to structural modification by
altering the halogen substituent, because a strongly electronegative
halogen facilitates the formation of a structure that is highly distorted
from the tetrahedral geometry (Bent’s rule).
Lewis bases using the *(E−R) orbital to form a hypercoordinate
geometry. The characteristics of the heavier group 14 elements
results in several and curious geometries involving not only penta-
and hexacoordination but also higher coordination.[2-6] These
geometries and bonding interactions would be useful for discussing
the reaction mechanisms and/or reasons for stereoselectivity.
Corriu’s group provided several pioneering examples of neutral
hepta-coordinate species (Figure 1).[2] They used a bidentate ligand
having a 2-electron donor moiety (L) at one end and a 1-electron
donor moiety (X) at the other. This type of ligand has been denoted
as an LX-type ligand hereafter. Corriu’s group reported that silane
compounds adopted a heptacoordinate geometry by forming three
LP(N)→*(Si−X) interactions (LP = lone pair) (type I in Figure 1).[2a]
Other types of heptacoordinate silane, germane, and stannane
compounds were also investigated by other groups using an L3X-
type ligand (type II).[4] Both types I and II form a tricapped tetrahedral
geometry around the central atom.
heptacoordinate geometry was reported for stannane systems. The
O,N,N,N,O-pentadentate[5a]
and cupferronato (N-nitroso-N-
A
different type of
phenylhydroxylaminato)[5b] ligands as well as the combination of
N,N,O-tridentate and N,O-bidentate ligands[5c] allowed the formation
of a pentagonal bipyramidal geometry (type III).
We have been interested in the use of a phosphine-based LX-
type ligand for the synthesis of novel hypercoordinate compounds
because of its strong multiple LP(P)→E donor-acceptor interactions
induced by the effective overlap between the larger lone pair orbital
of phosphine relative to a nitrogen donor and the *(E−X) orbital.[6−8]
Previously, we reported that fluorosilane and fluorogermane {o-
Introduction
The chemistry of hypercoordinate compounds of group 14 elements
has been developed due to their interesting geometries (similar to
transition states or intermediates of SN2-type reactions) and their
essential roles in molecular transformation and catalytic functions.[1]
An ER4 molecule of a heavier group 14 element (E) can interact with
(Ph2P)C6H4}3E(F) (E
= Si, Ge) adopted a different type of
heptacoordinate geometry, whereby one of the three phosphine
donors was coordinated to E at the coordination site trans to the E−F
bond owing to the significant LP(P)→*(E−X) interaction (type IV in
Figure 1).[6b] Furthermore, we found that tin fluorostannane {o-
(Ph2P)C6H4}3SnF (1) adopted an unusual heptacoordinate structure,
in which the three phosphine donors equivalently interacted with one
*(Sn−F) orbital.[6a] FSnC3 core in 1 strongly distorted from a
tetrahedral geometry and its structure adopted a trigonal pyramidal
geometry with the axial fluoride atom (∑(CSnC) = 358.23(7),
∑(CSnF) = 282.96(15)) (type V in Figure 1). In contrast, the hydride
[a]
[b]
Dr. H. Kameo
Department of Chemistry, Graduate School of Science, Osaka
Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai, Osaka 599-
8531, Japan
E-mail: h.kameo@c.s.osakafu-u.ac.jp
T. Kawamoto, Prof. H. Nakazawa
Department of Chemistry, Graduate School of Science, Osaka City
University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585,
Japan
analogue {o-(Ph2P)C6H4}3SnH (2) of
1
has
a
different
heptacoordinate geometry in which each phosphine donor
coordinates via the LP(P)→*(Sn−C) interactions in a way similar to
type I in Figure 1.[9] Note that the HSnC3 core adopts a less-distorted
tetrahedral geometry despite the presence of P→*(Sn−C)
interactions (∑(CSnC) = 314.86(12), ∑(CSnF) = 341.1(15)).
E-mail: nakazawa@sci.osaka-cu.ac.jp
Prof. Sakaki
Fukui Institute for Fundamental Chemistry, Kyoto University,
Takano-nishihiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan
Dr. D. Bourissou
[c]
[d]
Universitꢀ de Toulouse, UPS, Laboratoire Hꢀtꢀrochimie
Fondamentale Appliquꢀe, 118 route de Narbonne, F-31062
Toulouse, France
Such structural changes in heptacoordinate tin compounds
motivated us to investigate further on different halogen analogues of
1 to determine the different hypercoordinate structures and elucidate
the substituent effect on the heptacoordinate geometry. In this
contribution, we performed systematic studies on chloro, bromo, and
Supporting information for this article is given via a link at the end of
the document.
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
Figure 1. Representative examples of neutral heptacoordinate species featuring the heavier group 14 elements and a schematic representation of the associated
coordination patterns
iodo analogues {o-(Ph2P)C6H4}3SnX (3: X = Cl, 4: X = Br, 5: X = I)
of and demonstrated that these compounds adopted
modifying the procedure previously reported.[8o] The reaction of {o-
(Ph2P)C6H4}Li with one-third equivalents of SnCl4 provided 3 as a
white powder (Scheme 1). The bromo analogue {o-
(Ph2P)C6H4}3SnBr (4) was successfully synthesized in a way similar
to 3 using SnBr4 instead of SnCl4. Br/I exchange of 4 using excess
amount of KI provided the iodo analogue {o-(Ph2P)C6H4}3SnI (5).
X-ray diffraction studies of 3[10] and 4 were carried out using
single crystals obtained from the slow diffusion of n-hexane into
dichloromethane solution (Figure 2, Table 1). Structural analysis
showed that 3 and 4 have a similar structure but their geometries
were different from those of the fluoro and hydrido analogues (1
and 2). In 3 and 4, one phosphine donor (Pax) occupies the position
trans to the halogen X atom, and two phosphine donors (Peq) are
1
heptacoordinate geometries different from those of 1 and 2. In
addition, the origin of these structural modifications was
investigated by density functional theory (DFT) calculation.
Results and Discussion
Since the ortho-phenylene framework has been reported to be
useful for inducing an intramolecular P→Sn interaction,[8n] we used
this framework to fabricate three intramolecular P→Sn interactions.
The chloro analogue of 1, o-{(Ph2P)C6H4}3SnCl (3), was isolated by
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
Scheme 1. Synthesis of heptacoordinate organotin halides o-
(Ph2P)C6H4}3SnX (3: X = Cl, 4: X = Br, 5: X = I).
Figure 2. XRD structures of 3 and 4 with thermal ellipsoids set at 40%
probability. H atoms and phenyl groups except the ipso-carbons are omitted
for clarity. a) side view of 3. b) top view of 3. c) side view of 4. d) top view of 4.
located around the opposite coordination site of ipso-carbons,
where the subscripts “ax” and “eq” represent the axial and
equatorial positions, respectively. All the Sn−P distances (3.3039(7),
3.4119(7), 3.5087(7) Å for 3; and 3.2688(7), 3.4236(7), 3.5048(7) Å
for 4) are longer than the sum of the covalent radii (2.46 Å)[11] but
significantly shorter than the sum of the van der Waals radii (4.20
Å),[12] suggesting the presence of P→Sn interaction. The relatively
short distance of the Sn−P bond trans to the Sn−X bond (X = Cl,
Br) would be attributed to the strong LP(Pax)−*(Sn−X) CT
interaction. The other two Sn−P bonding interactions could be
formed by LP(Peq)−*(Sn−C) CT, but one Sn−Peq distance for ca.
3.41 Å is significantly shorter than that for ca. 3.51 Å. This is
probably because two phosphine donors around the opposite
coordination site to ipso-carbons (Peq) are differently oriented; one
slightly tilts downward and the other tilts upward as shown in
Figures 2a and 2c. Accordingly, the lone pairs on the phosphorus
atoms tilting upward are directed toward the regions of the
*(Sn−C) orbitals of the Sn center, while that on the phosphorus
tilting downward strays somewhat from the regions of the *(Sn−C)
orbitals. Consequently, a smaller overlap would be found between
this LP(P) and the *(Sn−C) orbitals, leading to the longer Sn−P
distance.
Table 1. Selected Distances (Å) and Angles (°) of 3, 4 and 5.
3 (X = Cl)
4 (X = Br)
5 (X = I)
Sn1−C1 (Å)
2.134(2)
2.136(3)
2.176(6)
2.148(6)
2.181(5)
3.265(2)
3.416(2)
3.4979(18)
2.7166(9)
117.5(2)
111.3(2)
110.9(2)
157.53(4)
80.19(4)
78.06(4)
Sn1−C19 (Å)
Sn1−C37 (Å)
Sn1−P1 (Å)
2.148(2)
2.154(2)
2.159(2)
2.157(3)
3.3039(7)
3.4119(7)
3.5087(7)
2.3732(7)
112.55(8)
128.53(9)
105.50(9)
157.89(2)
74.75(2)
3.2688(7)
3.4236(7)
3.5048(7)
2.5255(3)
112.94(9)
128.59(10)
105.66(10)
158.570(16)
75.484(16)
107.727(14)
Sn1−P2 (Å)
Sn1−P3 (Å)
Sn1−X (Å)
C1−Sn1−C19 (°)
C1−Sn1−C37 (°)
C19−Sn1−C37 (°)
X−Sn−P1 (°)
X−Sn−P2 (°)
X−Sn−P3 (°)
107.73(2)
Two Sn−C bonds (2.148(2) and 2.159(2) Å for 3; 2.154(2) and
2.157(3) Å for 4) participating in LP(P)−*(Sn−C) interactions are
longer than the other (2.134(2) Å for 3; 2.136(3) Å for 4), and the
Sn−X (X = Br, Cl) bonds are slightly longer in 3 and 4 (2.3732(7) Å
that 3 and 4 adopt a pentagonal bipyramidal geometry with a
Pax−Sn−X axis.
for 3; 2.5255(3)
Å
for 4) than the corresponding
Single crystals of the iodo analogue 5 were prepared from the
slow diffusion of n-hexane into the dichloromethane solution (Figure
3). The crystal lattice includes the solvent molecules CH2Cl2, which
weakly interact with H atom in Ph group through one of Cl atoms
(Figure S5). The structure of 5 is different from those of fluoro (1),
chloro (3) and bromo (4) analogues. One of the phosphine donors
is located at the position trans to the iodo atom, and two of the
phosphine donors are situated at the position trans to the ipso-
carbons. Although these geometrical features are similar to those of
halogenotriphenylstannanes Ph3SnX (2.360 Å for X = Cl[13a,13b]
;
2.495 Å for X = Br[13c]), suggesting that the LP(P)−*(Sn−C) and
LP(P)−*(Sn−X) interactions weaken the corresponding Sn−C and
Sn−X bonds. The sum of C−Sn−C angles in 3 and 4 are 346.58(15)
and 347.19(17), respectively, and the C−Sn−X angles in 3 and 4
range from 96.47(7) to 108.56(6)°. Also, Peq−Sn−X angles range
from 74.8 to 107.7°, and two Peq atoms as well as three ipso-
carbons are roughly situated on one plane. Further, the Pax−Sn−X
angle is considerably large (157.9 for 3; 158.6° for 4), indicating
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
3 and 4, both phosphine donors trans to the ipso-carbons tilt
downward unlike in 3 and 4 (Figure 3a). Accordingly, both lone
pairs on the phosphorus atoms are directed toward the regions of
the *(Sn−C) orbitals, presumably giving rise to a substantially
large orbital overlap between LP(P) and *(Sn−C) orbitals. The
three Sn−P distances (3.265(2), 3.416(2), and 3.4979(18) Å) are
significantly shorter than the sum of the van der Waals radii (4.20
Å),[12] suggesting the presence of P→Sn interactions. Similar to 3
and 4, the Sn−P distance trans to the Sn−I bond is the shortest
among the three Sn−P distances, which would be attributed to the
strong LP(P)→*(Sn−I) CT interaction. The two Sn−C bonds
(2.176(6) and 2.181(5) Å) in 5 trans to the phosphine donors are
longer than the other Sn−C bond (2.148(6) Å), and the Sn−I bond
(2.7166(19) Å) is somewhat elongated in comparison with that in
Ph3SnI (2.704 Å).[14] These results support the presence of
P→*(Sn−I) and P→*(Sn−C) interactions. The sum of the three
C−Sn−C angles (339.7(3)°) in 5 is significantly less than those of
fluoro (1), chloro (3), and bromo (4) analogues (358.32(5)° for 1;
346.58(15)° for 3; 347.19(17)° for 4), indicating that the SnC3I core
in 5 adopts a less-distorted tetrahedral geometry despite the
presence of LP(P)→*(Sn−I) and LP(P)→*(Sn−C) interactions.
( = −65 to −85 ppm).[13c,17] The 31P{1H} NMR spectrum showed one
singlet around 0 ppm ( = −1.2 ppm (w1/2 = 15.6 Hz) for 3;  = −2.2
ppm (w1/2 = 10.6 Hz) for 4;  = −3.1 ppm (w1/2 = 11.9 Hz) for 5 in a
4/1 mixture of THF-d8 and toluene-d8) (Figure S1 in ESI). At a low
temperature (−80 °C), one broad singlet was observed around 0
ppm ( = −1.5 ppm (w1/2 = 109.7 Hz) for 3;  = −3.7 ppm (w1/2 = 80.3
Hz) for 4;  = −5.3 ppm (w1/2 = 67.5 Hz) for 5), indicating the
presence of fast site exchange due to the rotation of ortho-
diphenylphosphinophenyl groups. Previously, the similar site
exchange was reported to take place more smoothly in {o-
(Ph2P)C6H4}3GeF than in the Si analogue because the longer Ge−C
bonds than the Si−C bonds facilitate the rotation of ortho-
diphenylphosphinophenyl groups.[6b] Similarly, the longer Sn−C
bonds may be responsible for the faster site exchange in 3 to 5
over NMR time scale. Further, the presence of an equilibrium
including other isomers may contribute to the broadening of the
signals.
To understand deeply the effect of the halogen substituent in
{o-(Ph2P)C6H4}3SnX (X = F, Cl, Br, I, H) on their geometries, DFT
calculations were carried out in a series of heptacoordinate species
1 to 5 and for their possible isomers, namely four types of
geometrical arrangements around the central Sn, a, b, c, and d
forms (see Tables S4-S5 and Figures S6-S10 in the ESI);
a form: Three phosphine donors interact with the tin center through
the same coordination site involving antibonding orbital of the Sn−X
bond (type V in Figure 1).
b and c forms: One phosphine coordinates at the position trans to
the Sn−X bond and two phosphines coordinate around the opposite
coordination site to the Sn−Cipso bond. SnC3 fragment in b form
builds parts of pentagonal planar (type III), while the SnC3 fragment
in c form adopts the tetrahedral geometry with a very small
deviation (type IV).
d form: Three phosphine donors coordinate to the tin center at
different position trans to the Sn−Cipso bond (type I)).
Figure 3. XRD structure of 5 with thermal ellipsoids set at 40% probability. H
atoms and phenyl groups except the ipso-carbons are omitted for clarity. a)
side view. b) top view.
For example, with 1, although the a form was observed in a solid
phase, we obtained the optimized structures of 1a-1d to investigate
the relative stability and understand its origin. We herein employed
PBE-D3 level of theory (SDD for Sn and I; 6-311G* for C and P; 6-
31G* for H (except for Hydride); 6-311+G* for F, Cl, Br, Hydride),
which well reproduced the key geometries such as Sn−P distances
in the X-ray structures of 3b, 4b, and 5c (Table S4 in the ESI).
Gibbs energies relative to d (in CH2Cl2) form are displayed in
Table 2 (the data in other solvents and in gas phase are shown in
Table S6 in the SPI), and data for (LP(P)−*(Sn−X) (X = F, Cl, Br, I,
H) and LP(P)−*(Sn−C)) donor-acceptor interactions are listed in
Table 3. In H analogues, the rotation of phosphine arms in 2d
provides little stabilization; the stability of 2d is comparable to other
isomers 2a-2c. This is consistent with the absence of significant
donor-acceptor interactions in 2a-2c. In contrast, the phosphine
rotation starting from d form provides significant stabilization in
halogen systems, and a-c forms are significantly more stable than
the d form. This is attributed to the presence of significant donor-
acceptor interactions between the lone pair of phosphine and the
anti-bonding orbital of the Sn−X bond.[18] Forms b and c resulting
from one phosphine arm are energetically comparable in all
systems, which is consistent with comparable CT interactions
Recently, Wagler and Bhargava reported that heptacoordinate
tin chloride {(o-Ph2P)C6F4}3SnCl, in which the o-(Ph2P)C6H4 in 3
was replaced with o-(Ph2P)C6F4, adopted a similar geometry to the
iodo analogue 5 but not to that of 3.[3e] Possibly, the acceptor ability
of (Ph2P)C6F4 which is better than that of o-(Ph2P)C6H4 may be
responsible for the formation of the geometry due to the large
orbital overlaps between LP(P) and *(Sn−C) orbitals.
The signal in the 119Sn{1H} NMR spectrum of 3 appears at  =
−121 ppm, which is at somewhat lower frequency than those of
Ar3SnCl derivatives (Ar = Ph ( = −44.8 ppm), Ar = o-MeO-C6H4 (
= −56.7 ppm), and Ar = 2,4,6-Me3C6H2: ( = −84.4 ppm)).[13,15] On
one hand, the 119Sn{1H} NMR chemical shifts of 4 ( = −126.6 ppm)
and 5 ( = −177.2 ppm) are within the ranges observed in those of
Ar3SnBr (Ar = Ph ( = −60.0 ppm), Ar = o-MeO-C6H4 ( = −74.3
ppm), Ar = 2,4,6-Me3C6H2: ( = −121.0 ppm))[13c,15] and Ar3SnI (Ar =
Ph ( = −113.4 ppm), Ar = o-MeO-C6H4 ( = −135.7 ppm), Ar =
2,4,6-Me3C6H2: ( = −217.1 ppm)),[13c,14,15] respectively.[16] These
results are contrast with the 119Sn{1H} NMR signal of 1 ( = −164.5
ppm), which is at significantly lower frequency than those of Ar3SnF
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
Table 2. Relative stabilities for four forms. Gibbs energies relative to that of
d form are given (in CH2Cl2 (PCM); kcal/mol).
Ar3SnX[a]
a form
b form
c form
d form
1 (X = F)
3 (X = Cl)
4 (X = Br)
5 (X = I)
−10.6 (1a)
−8.4 (3a)
−7.7 (4a)
−7.5 (5a)
1.2 (2a)
−4.5 (1b)
−4.7 (3b)
−4.2 (4b)
−4.9 (5b)
3.6 (2b)
−4.0 (1c)
−3.6 (3c)
−4.0 (4d)
−4.7 (5c)
2.1 (2c)
0.0 (1d)
0.0 (3d)
0.0 (4d)
0.0 (5d)
0.0 (2d)
Figure 4. Electrostatic potential of {(o-H)C6H4}3Sn(X) (X = F, Cl, Br, I, H) at
the position trans to the Sn−X bond.
2 (X = H)
Secondly, we investigated the electrostatic potential at the
position trans to the Sn−X bond (Figure 4). In the regions trans to
the Sn−X bond, the electronic potential is more positive in the
halogen systems (1, 3-5) than in the hydrogen system (2). Hence,
the electrostatic effect would also be an important factor for
stabilizing a-c forms containing the LP(P)−*(Sn−X) interaction (X =
F, Cl, Br, I).
[a] Ar = o-(Ph2P)C6H4.
Next, we investigated the effect of the electronegative
character of a halogen atom[19] on the sp hybridization of the central
Sn. According to Bent’s rule, the highly electronegative X atom
enhances the p character of Sn in the Sn−X bond and increases
the s character of the Sn in the Sn−C bond,[20] accordingly causing
large C−Sn−C angles. Wharf et al. reported that the s character of
Sn in the Sn−C bond in Ph3SnX (X = F, Cl, Br, I) increases in the
Table 3. Intramolecular donor-acceptor interactions of the lone pair of the
phosphine with the * antibonding MOs of Sn−X and Sn−C bonds (kcal/mol),
which were calculated by NBO analyses (second-order perturbation).[a]
1
order (H) < I < Br < Cl < F through the JSn−C coupling constant and
the geometrical features such as the sum of the three C−Sn−C
angles.[13c,21] These results indicate that a higher electronegative
halogen is expected to facilitate the formation of a more distorted
geometry from a tetrahedral one around the tin center.
Ar3SnX[b]
P = P1
a form
b form
c form
d form
7.7
7.7
7.5
17.6
2.6
17.9
3.2
2.6
2.6
2.5
As shown in Table 4, the sum of C−Sn−C angles increases in
the order d form < c form < b form < a form, and the average of
C−Sn−X angles (X = F, Cl, Br, I, H) decreases in the order d form >
c form > b form > a form for all systems. These calculations may
indicate that the relative stabilities of these forms are mainly
explained by the hybridization of tin, which is caused by X, rather
than CT interaction and electrostatic effect. The potential energy of
Ph3SnX (X = F, Cl, Br, I, H) was found to strongly depend on the
geometric environment around the tin center (Figure 5). For
1 (X = F)
3 (X = Cl)
4 (X = Br)
5 (X = I)
P = P2
P = P3
0.5
2.7
P = P1
P = P2
P = P3
9.8
9.9
9.2
21.2
3.7
20.8
3.5
4.7
3.7
1.7
0.7
3.4
P = P1
P = P2
P = P3
10.2
10.4
9.7
14.2
4.3
12.5
4.9
4.9
3.4
1.7
0.6
3.8
P = P1
P = P2
P = P3
8.2
8.3
7.9
17.5
4.6
17.3
4.4
4.1
3.6
3.8
0.5
3.9
P = P1
P = P2
P = P3
2.0
2.0
1.9
3.9
3.7
3.6
3.6
3.6
3.6
3.7
3.7
Table 4. Sum of three C−Sn−C angles and average of three C−Sn−F angles
in {o-(Ph2P)C6H4}3SnX (X = F (1), Cl (3), Br (4), I (5), H (2)) and their isomers.
2 (X = H)
[c]
−
Ar3SnX[a]
a form
b form
c form
d form
[a] Although each P→Sn interaction includes several LP(P)−*(Sn−C)
interactions in a similar way to the previously reported analysis on 1 and
2,[6a] trans P→*(Sn−X) and P→*(Sn−C) interactions play key roles for the
geometry changes. Therefore, only this donor-acceptor interaction per
P→Sn interaction is mentioned here. [b] Ar = o-(Ph2P)C6H4. [c] Not detected.
∑(CSnC)
358.4
94.3
350.0
100.7
349.1
101.0
348.7
101.3
347.4
101.8
337.3
106.2
342.5
104.1
341.2
104.6
340.2
105.0
339.2
105.4
327.6
109.7
334.5
107.4
316.6
113.3
315.1
113.8
315.8
113.4
322.1
112.4
1 (X = F)
3 (X = Cl)
4 (X = Br)
5 (X = I)
ave. (CSnF)
∑(CSnC)
357.3
95.4
ave. (CSnCl)
∑(CSnC)
357.9
95.9
ave. (CSnBr)
∑(CSnC)
356.2
96.5
ave. (CSnI)
∑(CSnC)
observed in b and c forms. Although the a form resulting from the
rotation of the three phosphine arms is the most stable in all
halogen systems, the stability of a form may be overestimated if the
solid-state structures of 3b, 4b, and 5c are considered. In addition,
we could not rule out the possibility that the packing effects
reflected the form observed in the solid-state.
351.5
99.8
2 (X = H)
ave. (CSnH)
[a] Ar = o-(Ph2P)C6H4.
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
over P2O5 and stored over 4-Å molecular sieves. The other reagents
used in this study were purchased from commercial sources and used
without further purification. 1H, 13C{1H} and 31P{1H} NMR spectra were
recorded with a JEOL JNM-AL 400 spectrometer. The 1H and 13C{1H}
NMR data were analyzed with reference to the residual peaks of the
solvent, and 31P{1H} NMR chemical shifts were referenced to an
external 85% H3PO4 (0 ppm) sample. Elemental analyses were
conducted using a J-Science Lab JM-10 or FISONS Instrument EA108
elemental analyzer. {o-(Ph2P)C6H4}Li∙Et2O[8o] was prepared as
described in the literature.
Preparation of {o-(Ph2P)C6H4}3Sn(Cl) (3). A Schlenk tube was charged
with 45.1 L of SnCl4 (0.386 mmol) and 5 mL of toluene, and the
solution was cooled to −78 ºC.
8 mL toluene solution of {o-
(Ph2P)C6H4}Li∙Et2O (413 mg, 1.21 mmol) was added slowly to the
prepared reaction solution, and the mixture was then allowed to warm to
room temperature. The reaction mixture was stirred at ambient
temperature for 15 h. After the resulting solution was filtered through a
Celite pad, the volatile materials were then removed under reduced
pressure to give a white solid. The residue was washed with hexane (5
mL × 2) and toluene (3 mL × 2) and dried under vacuum to afford 3
Figure 5. Potential energy of Ph3SnX (X = F, Cl, Br, I, H) for which the
average C−Sn−X angle in the optimized structure of Ph3SnX has been
progressively diminished to 90º.
example, the potential energy of Ph3SnF increases when the
average of the three C−Sn−F angles (104.7° in optimized geometry
of Ph3SnF) decreases in the order 1.0 kcal/mol (av. 100.7°) > 3.7
kcal/mol (av. 96.7°) > 8.3 kcal/mol (av, 92.7°) > 12.6 kcal/mol (av.
90°). Similarly, the potential energy of Ph3SnX (X = Cl, Br, I, H)
increases with decreasing C−Sn−X angles, and the destabilizations
increase in the order Ph3SnF << Ph3SnCl < Ph3SnBr ≈ Ph3SnI <
Ph3SnH. Accordingly, the highly electronegative halogen alleviates
the destabilization induced by the distortion around the tin atom.
This factor is, at least partially, responsible for the structural
modification by changing the halogen substituent.
1
(49.1 mg, 0.0523 mmol) in 14% yield as a white powder. H NMR (400
MHz, C6D6): δ 6.86−7.13 (m, 30H), 7.36−7.43 (m, 9H), 8.21−8.24 (m,
3H). 13C{1H} NMR (100 MHz, CDCl3):  128.1 (s), 129.7 (s), 133.2 (d,
JP−C = 5.8 Hz), 133.3 (d, JP−C = 5.0 Hz), 133.4 (m), 135.2 (s), 137.4 (m),
137.6 (m), 143.5 (s), 157.0 (m). 119Sn{1H} NMR (149 MHz, CDCl3): 
119
−121.4 (q, JP− Sn = 42.7 Hz). 31P{1H} NMR (163 MHz, C6D6): δ −1.4 (s,
JP−119Sn = 42.7 Hz). Anal. Calc. for C54H42ClP3Sn: C, 69.15; H, 4.51.
Found: C, 68.87; H, 4.53.
Preparation of {o-(Ph2P)C6H4}3Sn(Br) (4).
A Schlenk tube was
charged with 920 mg of {o-(Ph2P)C6H4}Li∙Et2O (2.69 mmol) and 10 mL
of toluene, and the solution was cooled to −78 ºC. SnBr4 (115 L,
0.0876 mmol) was added slowly to the prepared reaction solution, and
the mixture was then allowed to warm to room temperature. The
reaction mixture was stirred at ambient temperature for 15 h. After the
resulting solution was filtered through a Celite pad, the volatile materials
were then removed under reduced pressure to give a white solid. The
residue was washed with hexane (5 mL × 2), Et2O (3 mL), and toluene
(2 mL) and dried under vacuum to afford 4 (298 mg, 0.303 mmol) in
34% yield as a white powder. 1H NMR (400 MHz, CDCl3):  6.92-6.96
(m, 12H, Harom), 7.03-7.09 (m, 12H, Harom), 7.14-7.22 (m, 9H, Harom),
7.30-7.34 (m, 6H, Harom), 7.91-7.94 (m, 3H, Harom). 13C{1H} NMR (100
MHz, CDCl3):  128.2 (s), 128.2 (m), 129.0 (m), 129.7 (s), 133.3 (m),
Conclusions
We demonstrate the preparation of heptacoordinate bromo- (4) and
iodostannane (5) compounds featuring three P→Sn interactions.
Introduction of a different halogen at the tin center significantly
influences the heptacoordinate geometry in solid state. As
previously reported, fluorostannane (1) adopts a C3 symmetric
geometry, in which three phosphine donors interact with one
*(Sn−F) orbital, while the other halogeno analogues adopt a C1
symmetric geometry. The chloro (3) and bromo (4) analogues have
135.2 (2), 137.5 (m), 138.0 (m), 143.5 (s), 156.1 (m). 31P{1H} NMR (162
119
MHz, CDCl3):  −1.3 (s, JP−
= 46.9 Hz). 119Sn{1H} NMR (149 MHz,
Sn
119
CDCl3):  −126.6 (q, JP− Sn = 46.9 Hz). Anal. Calc. for C54H42BrP3Sn: C,
66.02; H, 4.31. Found: C, 66.18; H, 4.49.
a
distorted pentagonal bipyramidal geometry, and the iodo
analogue (5) adopts tri-capped tetrahedral geometry. The
a
Preparation of {o-(Ph2P)C6H4}3Sn(I) (5). A Schlenk tube was charged
with 152 mg of {o-(Ph2P)C6H4}3SnBr (4) (0.155 mmol), 924 mg of KI
(5.57 mmol), and 15 mL of THF, and the reaction mixture was stirred at
80° C for 72 h. The volatile materials were then removed under reduced
pressure, and the residue was extracted with benzene. After the solution
was filtered through a Celite pad, the volatile materials were then
removed under reduced pressure to give a white solid. The residue was
washed with hexane (5 mL × 2) and dried under vacuum to afford 5
(121 mg, 0.118 mmol) in 76% yield as a white powder. 1H NMR (400
MHz, CDCl3):  6.92-6.98 (m, 12H, Harom), 7.07-7.11 (m, 12H, Harom),
intramolecular donor-acceptor interaction, the electrostatic
interaction, and the hybridization of the tin center (Bent’s rule)
would be important factors for changes in geometry.
Experimental Section
General procedures. All experiments were performed under a dry
nitrogen atmosphere using standard Schlenk techniques. Benzene-d6,
toluene-d8, tetrahydrofuran-d8, and diethylether were dried over sodium
7.14-7.22 (m, 9H, Harom), 7.25-7.29 (m, 6H, Harom), 7.91-7.94 (m, 3H,
119
Harom). 31P{1H} NMR (162 MHz, CDCl3):  −1.7 (s, JP−
= 64.6 Hz).
= 64.6 Hz).
Sn
119
119Sn{1H} NMR (149 MHz, CDCl3):  −177.2 (q, JP−
benzophenone ketyl and distilled under
a dinitrogen atmosphere.
Sn
13C{1H} NMR (100 MHz, CDCl3):  128.1 (s), 128.3 (t, JP−C = 13.2 Hz),
129.4 (m), 129.7 (d, JP−C = 5.8 Hz), 133.4 (m), 135.2 (s), 137.4 (m),
Tetrahydrofuran, and n-hexane were purified using a two-column solid-
state purification system. Chloroform-d and dichloromethane were dried
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
138.5 (m), 143.4 (s), 154.2 (m). Anal. Calc. for C54H42IP3Sn: C, 63.00; H,
4.11. Found: C, 62.74; H, 4.30.
Organometallic, and Polymer Chemistry, John Wiley & Sons: New
York, 2000, pp. 97.
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Structure Determination by X-ray Diffraction. Single crystals suitable
for X-ray diffraction analysis were obtained as described above.
Diffraction intensity data were collected with a Rigaku/MSC Mercury
CCD diffractometer at 200 K(2), and
a semiempirical multi-scan
absorption[22] correction was performed. The space groups were chosen
based on the systematic absences in the diffraction data. The structures
were solved using SIR97[23] by subsequent difference Fourier synthesis,
and refined by full matrix least-squares procedures on F2. All non-
hydrogen atoms were refined with anisotropic displacement coefficients.
The hydrogen atoms were treated as idealized contributions and refined
in rigid group model. All software and sources of scattering factors are
contained in the SHELXL97 program package.[24] CCDC 1425640,
1425641, and 1425642 contain supplementary crystallographic data for
this paper. These data can be obtained free of charge from the
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Acknowledgments
H.K. acknowledges the financial support from the Foundation
for Interaction in Science & Technology and a Grant-in-Aid for
Scientific Research (C) (No. 18K05151). S.S. wishes to
acknowledge the support from the Ministry of Education,
Culture, Science, Sport and Technology through Grants-in-Aid
of Specially Promoted Science and Technology (No. 22000009)
and Japan Science and Technology Cooperation (CREST
‘Establishment of Molecular Technology towards the Creation
of New Functions’ Area).
Keywords: tin • heptacoordination • phosphorus • DFT
calculation • X-ray analysis
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
FULL PAPER
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Similarly, Peters[3c] and Braun[3d] reported that silicon and germane
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using crystal data of better crystals.
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119Sn NMR resonance (see references below). Such shifts were
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119
119
119
[16] The JP− Sn values of 3 (JP− Sn = 42.7 Hz), 4 (JP− Sn = 46.9 Hz), and
119
5 (JP−
= 64.6 Hz) are not very different from that of diphosphine-
Sn
119
dimethylstannane {(o-Ph2P)C6F4}2SnMe2 (JP−
=
40.4 Hz)[8r]
[26] J. M. L. Martin, A. Sundermann, J. Chem. Phys. 2001, 114, 3408.
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Sn
containing only very weak LP(P)→*(Sn−CMe) interactions. Therefore,
119
119
3JP− Sn interactions may determine the JP− Sn values.
[17] Although the 119Sn{1H} NMR signal of 1 was not available in the
previous work,[6a] it was detected in this study through several re-
examinations. (see Figure S2a)
[18] The most electronegative halogen (fluorine) does not cause the
strongest P→Sn interaction. A similar phenomenon was observed in
intramolecular N→Sn coordination: see U. Kolb, M. Dräger, M.
Dargatz, K. Jurkschat, Organometallics 1995, 14, 2827.
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10.1002/ejic.201900524
European Journal of Inorganic Chemistry
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Heptacoordination
Hajime Kameo,* Tatsuya Kawamoto,
Shigeyoshi Sakaki, Didier Bourissou,
Hiroshi Nakazawa*
Page No. – Page No.
Structural studies were performed on heptacoordinate compounds of organotin
halides {(o-Ph2P)C6H4}3SnX (X = F (1), Cl (3), Br (4), I (5)) with three phosphine
donors. Introduction of a different halogen at the tin center significantly influences the
heptacoordinate geometry in solid state. The origin of these structural modifications was
investigated by density functional theory (DFT) calculation.
Heptacoordinate Structures of
Organotin Halides with Three
Phosphine Donors: Halogen-
Substituent Effect on Geometry
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