The O,C,O-coordinating pincer-type ligand {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2} - in organotin chemistry. Halide exchange, cyclization, and novel coordination mode

Article abstract of DOI:10.1021/om0103714

Reactions in solution of the hypercoordinated organotin chlorides {2,6-[P(O)(OEt)₂]₂-4-t-Bu-C₆H₂} SnCl₂X (X = Ph, Cl) with fluoride ions have been studied using temperature-dependent ¹¹⁹Sn

Full text of DOI:10.1021/om0103714

Organometallics 2001, 20, 4647-4653
4647
Th e O,C,O-Coor d in a tin g P in cer -Typ e Liga n d
{2,6-[P (O)(OEt)2]2-4-t-Bu -C6H2}- in Or ga n otin Ch em istr y.
Ha lid e Exch a n ge, Cycliza tion , a n d Novel Coor d in a tion
Mod e†
Michael Mehring, Ioannis Vrasidas, Dagmar Horn, Markus Schu¨rmann, and
Klaus J urkschat*
Lehrstuhl fu¨r Anorganische Chemie II der Universita¨t Dortmund, 44221 Dortmund, Germany
Received May 7, 2001
Reactions in solution of the hypercoordinated organotin chlorides {2,6-[P(O)(OEt)2]2-4-t-
Bu-C6H2}SnCl2X (X ) Ph, Cl) with fluoride ions have been studied using temperature-
dependent 119Sn and 31P NMR spectroscopy and electrospray mass spectrometry. The
syntheses and molecular structures of the novel intramolecularly coordinated diorganotin
difluoride {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnF2Ph‚0.5H2O (1), the heterocyclic compound
{[1(Sn),3(P)-PhClSnOP(O)(OEt)-5-t-Bu-7-P(O)(OEt)2]C6H2}2 (3), and the monoorganotin
difluoride hydroxide {{2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnF2OH}2 (6) are reported. In the
crystal lattice, compound 1 forms an adduct composed of two tin moieties and a water
molecule which are linked via F‚‚‚H-O-H‚‚‚F hydrogen bridges. The intramolecularly
coordinated benzoxaphosphastannole derivative 3 is formed by intramolecular cyclization
of {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl2Ph with elimination of ethyl chloride and dimeriza-
tion. The organotin difluoride hydroxide derivative 6 is a dimer in the solid state as a result
of intermolecular hydroxide bridges. Also present are intramolecular Sn-O-H‚‚‚OdP
hydrogen bonds. The configuration at tin is best described as a monocapped octahedron.
In tr od u ction
structure analyses of organofluorostannanes containing
more than one covalent Sn-F bond are still scarce.18
To date only one monoorganotin trifluoride19 and two
diorganotin difluorides2,7 have been structurally char-
acterized.
Organofluorostannanes usually form strong intermo-
lecular tin-fluorine bonds which often give poorly
soluble polymeric compounds.1-5 Higher solubility of
this type of compounds is achieved by the introduction
of bulky organic substituents and/or intramolecular or
intermolecular coordination with additional Lewis bases,
making it possible to study the structure of organotin
fluorides in solution.6-17 Nevertheless, X-ray crystal
For some time we have been interested in the syn-
thesis and structural characterization, including dy-
namic stereochemistry, of intramolecularly coordinated
organotin fluorides such as N(CH2CH2CH2)3SnF6 and
[Me2N(CH2)3]2SnF2.7 Recently, we have reported the
synthesis of a series of organotin and organosilicon
compounds containing the O,C,O-coordinating pincer-
type ligand {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}-,20-23 and
in continuation of these studies we now report our
attempts to prepare novel intramolecularly coordinated
organofluorostannanes containing this ligand. The single-
crystal structure analyses of the novel organotin dif-
luorides {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnF2Ph (1) and
{{2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnF2OH}2 (6) and of
the intramolecularly coordinated benzoxaphosphastan-
†This work includes parts of the Ph.D. thesis of M.M., Dortmund
University, 1998, and of the Diploma thesis of I.V., Dortmund
University, 1997.
(1) Clark, H. C.; O’Brien, R. J .; Trotter, J . J . Chem. Soc. 1964, 2332.
(2) Schlemper, E. O.; Hamilton, W. C. Inorg. Chem. 1966, 5, 995.
(3) Tudela, D.; Gutierrez-Puebla, E.; Monge, A. J . Chem. Soc., Dalton
Trans. 1992, 1069.
(4) Tudela, D.; Fernandez, R.; Belsky, V. K.; Zavodnik, V. E. J .
Chem. Soc., Dalton Trans. 1996, 2123.
(5) J agirdar, B. R.; Murphy, E. F.; Roesky, H. W. Prog. Inorg. Chem.
1998, 48, 351.
(6) Kolb, U.; Dra¨ger, M.; Dargatz, M.; J urkschat, K. Organometallics
1995, 14, 2827.
(7) Pieper, N.; Klaus-Mrestani, C.; Schu¨rmann, M.; J urkschat, K.;
Biesemanns, M.; Verbruggen, I.; Martins, J . C.; Willem, R. Organo-
metallics 1997, 16, 1043.
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Organometallics 1995, 14, 2512.
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10, 2737.
(17) Mercier, F. A. G.; Meddour, A.; Gielen, M.; Biesemans, M.;
Willem, R. Organometallics 1998, 17, 5933.
(18) Cambridge Crystallographic Database 2001, Release 5.1.
(19) Dostal, S.; Stoudt, S. J .; Fanwick, P.; Sereatan, W. F.; Kahr,
B.; J ackson, J . E. Organometallics 1993, 12, 2284.
(20) Mehring, M.; Schu¨rmann, M.; J urkschat, K. Organometallics
1998, 17, 1227.
(21) Mehring, M.; Lo¨w, C.; Schu¨rmann, M.; J urkschat, K. Eur. J .
Inorg. Chem. 1999, 887.
(22) Mehring, M.; Schu¨rmann, M.; J urkschat, K. Main Group Met.
Chem. 1998, 21, 635.
(15) Blunden, S. J .; Hill, R. J . Organomet. Chem. 1989, 371, 145.
(16) J ang, M.; J anzen, A. F. J . Fluorine Chem. 1994, 66, 129.
(23) Mehring, M.; Lo¨w, C.; Schu¨rmann, M.; Uhlig, F.; J urkschat,
K.; Mahieu, B. Organometallics 2000, 19, 4613.
10.1021/om0103714 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 09/22/2001

4648 Organometallics, Vol. 20, No. 22, 2001
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 1, 3 a n d 6
Mehring et al.
1
3
6
formula
fw
C
24H36F2O6P2Sn‚0.5H2O
C44H62Cl2O12P4Sn2
1215.10
C36H64F4O14P4Sn2‚2CH2Cl2
1327.98
648.17
cryst syst
cryst size, mm
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
triclinic
0.15 × 0.10 × 0.10
P1h
triclinic
0.20 × 0.15 × 0.10
P1h
triclinic
0.29 × 0.13 × 0.10
P1h
9.298(1)
11.247(1)
14.978(1)
73.516(1)
81.568(1)
87.871(1)
1485.7(2)
2
9.751(1)
11.361(1)
24.075(1)
101.414(1)
97.153(1)
95.182(1)
2575.7(2)
2
9.884(1)
11.346(1)
14.043(1)
73.849(1)
79.668(1)
74.396(1)
1447.6(2)
1
Z
F
calcd, Mg/m3
1.449
1.015
662
1.567
1.254
1232
1.528
1.226
672
µ, mm-1
F(000)
θ range, deg
index ranges
2.92-25.66
-9 e h e 9
-13 e k e 13
-17 e l e 18
20 538
2.94-27.45
-12 e h e 12
-14 e k e 14
-31 e l e 0
27 963
3.04-25.67
-10 e h e 10
-12 e k e 13
-16 e l e 17
16 257
no. of rflns collcd
completeness to θmax
no. of indep rflns/Rint
no. of reflns obsd with (I > 2σ(I))
no. of refined params
GOF (F2)
92.8
5232/0.027
3668
389
0.953
97.2
11 442/0.048
5245
586
0.826
90.9
4977/0.041
3090
362
0.947
R1(F) (I > 2σ(I))
0.0335
0.0872
0.001
0.488 / -0.349
0.0415
0.0737
0.001
0.649 / -0.672
0.0485
0.1239
0.001
0.384 / -0.512
wR2(F2) (all data)
(∆/ σ)max
largest diff peak/hole, e/Å3
nole derivative {[1(Sn),3(P)-PhClSnOP(O)(OEt)-5-t-Bu-
7-P(O)(OEt)2]C6H2}2 (3) are discussed.
Resu lts a n d Discu ssion
Compound 1 was synthesized by treatment of a CH2-
Cl2 solution of the corresponding dichloride with aque-
ous potassium fluoride (eq 1) and isolated in 80% yield
as colorless crystals.
F igu r e 1. General view (SHELXTL-PLUS) of 1 showing
30% probability displacement ellipsoids and the atom-
numbering scheme (symmetry transformations used to
generate equivalent atoms: (A) 1 - x, -y, 1 - z).
The molecular structure of the diorganotin difluoride
1 is shown in Figure 1, relevant crystallographic pa-
rameters are listed in Table 1, and selected bond lengths
and angles are given in Table 2. Compound 1 crystal-
lizes with 0.5 mol of water, i.e., two molecules of 1 are
connected via unsymmetrical hydrogen bonds of the
type F‚‚‚H-O-H‚‚‚F (F(1)-O(3) ) 2.589(15) Å, F(1a)-
O(3) ) 2.668(14) Å). The tin atom in 1 adopts a
distorted-octahedral configuration with the carbon,
fluorine, and oxygen atoms, respectively, mutually
trans. The distortion from the ideal octahedral geometry
is reflected especially in the O(1)-Sn(1)-O(2) angle of
159.8(1)° and is the result of the ligand constraint. The
intramolecular Sn(1)-O(1) and Sn(1)-O(2) distances of
2.244(2) and 2.243(2) Å are comparable to those of the
corresponding dichloro-substituted derivative. The Sn-
(1)-F(1) and Sn(1)-F(2) bond lengths of 2.017(2) and
2.012(2) Å are shorter as compared to those of six-
coordinate [Me2N(CH2)3]2SnF2‚2H2O (Sn-F ) 2.084(6)
Å),7 Me2SnF2 (Sn-F ) 2.12(1) Å),2 and (NH4)2(Me2SnF4)
(Sn-F ) 2.121(5), 2.126(3), 2.135(4) Å).24
The octahedral coordination geometry at tin in the
diorganotin difluoride 1 is retained in its toluene solu-
tion, as is evidenced by observation of a triplet of triplets
119Sn NMR resonance. The Sn-F bonds in 1 are kineti-
cally inert on the 119Sn NMR time scale to about 70 °C.
1
Above this temperature loss of J (119Sn-19F) coupling
is observed. The electrospray mass spectrum (ESMS)
(24) Tudela, D. J . Organomet. Chem. 1994, 471, 63.

A Pincer-Type Ligand in Organotin Chemistry
Organometallics, Vol. 20, No. 22, 2001 4649
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for 1 a n d 6a
was not isolated, but its monocation was detected as the
most prominent species ([2 - F]+ m/z 1163.5) in the
ESMS of an NMR sample of 2 from which the solvent
was stripped off in vacuo. Interestingly, the monomeric
fluoride adduct of compound 2 was detected as the most
prominent species ([1/2 2 + F]- m/z 611.1) of a solution
of the diorganotin difluoride 1 to which had been added
an excess of Bu4NF‚3H2O. The interpretation of the
aforementioned NMR spectra is further supported by
the results obtained from the chlorine-substituted ana-
logue of compound 1 (see below).
1: X ) C(11)
6: X ) O(3), Y ) O(3a)
Sn(1)-C(1)
Sn(1)-F(1)
Sn(1)-F(2)
Sn(1)-X
2.135(3)
2.017(2)
2.012(2)
2.116(3)
2.192(5)
1.951(3)
1.947(4)
2.157(4)
2.069(4)
2.186(3)
3.364(3)
1.480(4)
1.450(4)
Sn(1)-Y
Sn(1)-O(1)
Sn(1)-O(2)
P(1)-O(1)
P(2)-O(2)
F(1)-O(3)
F(1a)-O(3)
O(2)-Y
2.244(2)
2.243(2)
1.489(2)
1.489(3)
2.589(15)
2.668(14)
2.592(5)
In analogy to compound 1, the ESMS of {2,6-[P(O)-
(OEt)2]2-4-t-Bu-C6H2}SnCl2Ph in acetonitrile/CH2Cl2
reveals formation of the diorganotin halide cation {{2,6-
[P(O)(OEt)2]2-4-t-Bu-C6H2}SnClPh}+ (m/z 637.3). Heat-
ing of the diorganotin dichloride in toluene/xylene at 110
°C for 2 weeks (Scheme 1) provided a crude reaction
mixture, the 31P NMR spectrum of which displayed two
major resonances at δ 15.0 (4J (31P-31P) ) 5 Hz, J (31P-
119Sn) ) 176 Hz, J (31P-119Sn) ) 96 Hz, integral 43%)
and δ 27.7 (4J (31P-31P) ) 5 Hz, J (31P-119Sn) ) 100 Hz,
integral 43%), which are assigned to the benzoxaphos-
phole derivative 3. In addition, there are 10 minor
resonances at δ 11.3 (integral 0.5%), δ 12.3 (J (31P-31P)
) 5 Hz, integral 0.5%), δ 15.3 (integral 3%), δ 16.2
(integral 3%), δ 16.8 (J (31P-31P) ) 5 Hz, integral 0.5%),
δ 19.0 (integral 1%), δ 25.4 (4J (31P-31P) ) 5 Hz, integral
0.5%), δ 27.8 (integral 3%), and δ 28.0 (integral 2%).
The benzoxaphosphole derivative 3 was isolated from
the reaction mixture in 80% yield as a colorless crystal-
line solid. The resonance at δ 19.0 is assigned to 1,3-
[P(O)(OEt)2]2-5-t-Bu-C6H3. The remaining signals could
not be assigned but might belong to other isomers of 3.
The 119Sn NMR spectrum of pure 3 shows a doublet
of doublets of doublets at δ -474 (J (119Sn-31P) ) 98 Hz,
J (119Sn-31P) ) 100 Hz, J (119Sn-31P) ) 176 Hz). The
ESMS of a CH3CN/CH2Cl2 solution of 3 displays mass
clusters centered at m/z 1179.3 and 609.1, which are
assigned to the dimeric organotin cation [3 - Cl]+ and
the monomeric cation [1/2 3 + H]+, respectively.
C(1)-Sn(1)-F(1)
C(1)-Sn(1)-F(2)
C(1)-Sn(1)-X
89.1(1)
86.9(1)
177.2(1)
96.7(2)
165.8(2)
90.3(2)
105.6(2)
78.2(2)
88.5(2)
172.9(1)
85.1(2)
98.5(1)
86.6(2)
84.2(2)
C(1)-Sn(1)-Y
X-Sn(1)-Y
F(1)-Sn(1)-F(2)
F(1)-Sn(1)-X
176.0(1)
92.4(1)
91.6(1)
F(2)-Sn(1)-X
F(1)-Sn(1)-Y
F(2)-Sn(1)-Y
C(1)-Sn(1)-O(1)
C(1)-Sn(1)-O(2)
X-Sn(1)-O(1)
Y-Sn(1)-O(1)
X-Sn(1)-O(2)
F(1)-Sn(1)-O(1)
F(1)-Sn(1)-O(2)
F(2)-Sn(1)-O(1)
F(2)-Sn(1)-O(2)
O(1)-Sn(1)-O(2)
C(2)-P(1)-O(1)
C(6)-P(2)-O(2)
P(1)-O(1)-Sn(1)
P(2)-O(2)-Sn(1)
F(1)-O(3)-F(1a)
Sn(1)-O(3)-Sn(1a)
80.0(1)
80.0(1)
79.7(1)
86.5(1)
161.6(1)
102.4(1)
88.0(1)
95.6(1)
82.0(1)
89.8(1)
91.5(1)
89.4(1)
159.8(1)
107.5(1)
108.8(2)
117.7(1)
116.4(1)
111.1(5)
108.8(2)
114.7(2)
115.9(2)
101.8(2)
a
Symmetry transformations used to generate equivalent at-
oms: (a) 1 - x, -y, 1 - z.
Ch a r t 1
The monoorganotin trichloride {2,6-[P(O)(OEt)2]2-4-
t-Bu-C6H2}SnCl3 undergoes an analogous cyclization to
give the dichloro-substituted 2,3,1-benzoxaphosphast-
annole {[1(Sn),3(P)-Cl2SnOP(O)(OEt)-5-t-Bu-7-P(O)-
(OEt)2]C6H2}2 (A).21 Remarkably and in contrast to the
diorganotin dichloride {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}-
SnCl2Ph, the reaction time required to give A by heating
at reflux a toluene solution of the organotin trichloride
is only several hours.
of 1 in acetonitrile/CH2Cl2 reveals formation of {{2,6-
[P(O)(OEt)2]2-4-t-Bu-C6H2}SnFPh}+ (m/z 621.4).
Heating of a solution of 1 in toluene at 110 °C for 2
weeks gave a reaction mixture, the 31P NMR spectrum
of which showed resonances at δ 27.7 (ν1/2 ) 30 Hz,
integral 48), δ 20.1 (t, ν1/2 ) 22 Hz, J (31P-117/119Sn) )
60 Hz, signal a ), and several overlapping resonances
centered at δ 15.5 (signals b) and at δ 13.6 (ν1/2 ) 25
Hz, J (31P-117/119Sn) ) 60 Hz, signal c) with the total
integral of the signals a -c adding up to 52. The 119Sn
NMR spectrum of the same solution showed a doublet
of doublet of doublet of doublets resonance at δ -521
(1J (119Sn-19F) ) 2920 Hz, J (119Sn-31P) ) 100, 103, 162,
integral 70) and broad resonances of minor but equal
intensity at -503 (ν1/2 ) 330 Hz), -517 (ν1/2 ) 310 Hz),
-523 (ν1/2 ) 250 Hz), and -535 (ν1/2 ) 300 Hz). The
major 31P and 119Sn resonances are assigned with
caution to the dimeric fluorine-substituted benzox-
aphosphole 2 (Chart 1), whereas the low intense signals
might belong to structural isomers of 2. Compound 2
The formation of the monomeric diphenyl-substituted
2,3,1-benzoxaphaphastannole derivative [1(Sn),3(P)-Ph2-
SnOP(O)(OEt)-5-t-Bu-7-P(O)(OEt)2]C6H2 (B) by reaction
of the intramolecularly coordinated tetraorganotin com-
pound {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnPh3 with HCl
proceeds even faster and to the extent that the inter-
mediate triorganotin chloride {2,6-[P(O)(OEt)2]2-4-t-Bu-
C6H2}SnPh2Cl could not be isolated under the reaction
conditions applied.21 As suggested in a previous paper21
-
and proven in the meantime25 by isolation, as its PF6
salt, of the intramolecularly coordinated cation [{2,6-
[P(O)(O-i-Pr)2]2-4-t-Bu-C6H2}SnPh2]+, the first step in
the cyclization process involves heterolytic cleavage of
a tin-halogen bond. This is likely being followed by
(25) Mehring, M.; Lo¨w, C.; J urkschat, K. Unpublished results.

4650 Organometallics, Vol. 20, No. 22, 2001
Mehring et al.
Sch em e 1
Table 3. The structure of compound 3 resembles that of
previously reported {[1(Sn),3(P)-Cl2SnOP(O)(OEt)-5-t-
Bu-7-P(O)(OEt)2]C6H2}2 (A),21 and both compounds are
characterized by intermolecular and intramolecular
O-Sn interactions resulting in formation of dimers. The
tin centers in 3 adopt distorted-octahedral coordination
geometries, with cis angles ranging from 80.03(13) to
102.43(13)° and trans angles ranging from 161.35(9) to
177.11(7)°. The intramolecular O(2)-Sn(1) and O(12)-
Sn(2) distances amount to 2.251(3) and 2.274(3) Å,
respectively, and lie between the values for the corre-
sponding dative bonds in A (2.204(3) Å) and B (2.396-
(4) Å). These interatomic distances reflect the increasing
Lewis acidity of the tin fragments in the order Ph2Sn
< PhClSn < Cl2Sn. The intermolecular dative bonds
O(1)-Sn(2) (2.219(3) Å) and O(11)-Sn(1) (2.222(3) Å)
in 3 are longer than the corresponding interatomic
distances in A (O-Sn ) 2.140(3) Å), the latter being
comparable with typical O-Sn single-bond lengths (2.15
Å).26 The shortest O-Sn distances in 3 are found for
O(1′)-Sn(1) and O(11′)-Sn(2), which amount to 2.175-
(3) and 2.177(2) Å, respectively.
F igu r e 2. General view (SHELXTL-PLUS) of 3 showing
30% probability displacement ellipsoids and the atom-
numbering scheme.
The 119Sn NMR spectrum at -40 °C of a freshly
prepared CD2Cl2 solution of {2,6-[P(O)(OEt)2]2-4-t-Bu-
C6H2}SnCl3 to which had been added 3 mol equiv of Bu4-
NF‚3H2O displays a triplet of triplets at δ -596
(1J (119Sn-19F) ) 2250 Hz, J (119Sn-31P) ) 194 Hz) and
a doublet of triplets of triplets at δ -638 (1J (119Sn-19F)
nucleophilic attack of the halide ion at the methylene
carbon of the ethoxy group and release of ethyl halide
(Scheme 1). The very different rates at which the
cyclization reactions take place suggest the tendency of
intramolecularly coordinated organotin chlorides to
undergo Sn-Cl dissociation to follow the sequence
RSnPh2Cl > RSnCl3 > RSnPhCl2 (R ) {2,6-[P(O)-
(OEt)2]2-4-t-Bu-C6H2}), provided that the rate of the
subsequent attack of the halide ion is not or only little
influenced by the substituent pattern at tin.
1
) 2098 Hz, J (119Sn-19F) ) 2398 Hz, J (119Sn-31P) )
200 Hz) with an integral ratio of approximately 1:2.5.
The triplet of triplets resonance is assigned to {2,6-
[P(O)(OEt)2]2-4-t-Bu-C6H2}SnClF2 (4), and the doublet
of triplets of triplets is assigned to the organotin
trifluoride {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnF3 (5). On
The molecular structure of 3 is shown in Figure 2,
relevant crystallographic parameters are listed in Table
1, and selected bond lengths and angles are given in
(26) Harrison, P. G. In Chemistry of Tin, 2nd ed.; Smith, P. J ., Ed.;
Blackie: London, 1998.

A Pincer-Type Ligand in Organotin Chemistry
Organometallics, Vol. 20, No. 22, 2001 4651
Ta ble 3. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for 3
Sn(1)-C(1)
Sn(1)-Cl(1)
Sn(1)-C(21)
Sn(1)-O(11)
Sn(1)-O(1′)
Sn(1)-O(2)
P(1)-O(1)
P(1)-O(1′)
P(1)-O(1′′)
P(2)-O(2)
P(2)-O(2′)
P(2)-O(2′′)
P(1)-C(2)
2.122(4)
2.4802(12)
2.097(4)
2.222(3)
2.175(3)
2.251(3)
1.493(3)
1.524(3)
1.582(3)
1.505(3)
1.558(3)
1.557(3)
1.799(4)
1.786(4)
Sn(2)-C(11)
Sn(2)-Cl(2)
Sn(2)-C(31)
Sn(2)-O(1)
Sn(2)-O(11′)
Sn(2)-O(12)
P(3)-O(11)
P(3)-O(11′)
P(3)-O(11′′)
P(4)-O(12)
P(4)-O(12′)
P(4)-O(12′′)
P(3)-C(12)
P(4)-C(16)
2.117(4)
2.4967(12)
2.116(4)
2.219(3)
2.177(2)
2.274(3)
1.501(3)
1.523(3)
1.578(3)
1.497(3)
1.550(3)
1.558(3)
1.793(4)
1.783(4)
P(2)-C(6)
C(1)-Sn(1)-Cl(1)
C(1)-Sn(1)-C(21)
C(1)-Sn(1)-O(1′)
C(1)-Sn(1)-O(2)
C(1)-Sn(1)-O(11)
Cl(1)-Sn(1)-C(21)
Cl(1)-Sn(1)-O(1′)
Cl(1)-Sn(1)-O(2)
90.74(11) C(11)-Sn(2)-Cl(2)
89.80(11)
176.75(17) C(11)-Sn(2)-C(31) 174.42(16)
82.14(13) C(11)-Sn(2)-O(11′)
80.41(13) C(11)-Sn(2)-O(12)
89.02(13) C(11)-Sn(2)-O(1)
92.39(12) Cl(2)-Sn(2)-C(31)
81.56(13)
80.03(13)
88.18(13)
93.86(11)
92.92(7)
F igu r e 3. General view (SHELXTL-PLUS) of 6 showing
30% probability displacement ellipsoids and the atom-
numbering scheme (symmetry transformations used to
generate equivalent atoms: (A) 1 - x, -y, 1 - z).
95.22(8)
91.45(8)
Cl(1)-Sn(1)-O(11) 177.11(7)
Cl(2)-Sn(2)-O(11′)
Cl(2)-Sn(2)-O(12)
Cl(2)-Sn(2)-O(1)
89.99(7)
175.44(7)
C(21)-Sn(1)-O(1′)
C(21)-Sn(1)-O(2)
C(21)-Sn(1)-O(11)
O(1′)-Sn(1)-O(2)
O(1′)-Sn(1)-O(11)
O(2)-Sn(1)-O(11)
O(1)-P(1)-O(1′)
O(1)-P(1)-O(1′′)
O(1′)-P(1)-O(1′′)
O(1)-P(1)-C(2)
O(1′)-P(1)-C(2)
O(1′′)-P(1)-C(2)
O(2)-P(2)-O(2′)
O(2)-P(2)-O(2′′)
O(2′)-P(2)-O(2′′)
O(2)-P(2)-C(6)
O(2′)-P(2)-C(6)
O(2′′)-P(2)-C(6)
P(1)-O(1′)-Sn(1)
P(1)-O(1)-Sn(2)
P(2)-O(2)-Sn(1)
98.44(13) C(31)-Sn(2)-O(11′) 102.43(13)
98.62(14) C(31)-Sn(2)-O(12)
87.81(13) C(31)-Sn(2)-O(1)
95.74(13)
87.87(13)
nected by two asymmetric oxygen bridges of 2.157(4)
and 2.069(4) Å. Similar structural motifs were reported
for [EtSn(OH)Cl2(H2O)]2,27 [Me2Sn(OH)(NO3)]2,28 and
[t-Bu2Sn(OH)X]2,29 with Sn-O distances ranging from
2.012(5) to 2.237(9) Å.29 The octahedral configuration
at tin is distorted, as is manifested by the deviation of
the trans angles C(1)-Sn(1)-F(2) (165.8(2)°), F(1)-Sn-
(1)-O(3) (172.9(1)°), and O(1)-Sn(1)-O(3a) (161.6(1)°)
from the ideal value of 180°. The Sn(1)-O(1) distance
of 2.186(3) Å is shorter than the corresponding value
in the diorganotin difluoride 1 as well as in the orga-
notin trichloride {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl3
(2.225(3)/2.221(3) Å)21 and reflects a strong intramo-
lecular Sn-O coordination. The oxygen O(2) of the Pd
O group forms a hydrogen bridge with the tin-bonded
hydroxide (O(2)‚‚‚O(3A) 2.592(5) Å) resulting in a seven-
membered ring and, simultaneously, exhibits a weak
Sn(1)‚‚‚O(2) interaction of 3.364(3) Å. The latter distance
is shorter than the sum of the van der Waals radii of
tin and oxygen (3.7 Å).30 In fact, the proton attached to
O(3a) competes with the tin atom Sn(1) for the Lewis
basic O(2). The nonequivalence of the PdO groups is
also reflected in the different PdO bond lengths of
1.480(4) and 1.450(4) Å as well as in two ν(PdO)
absorptions at 1169 and 1236 cm-1 in the IR spectrum
of 6. Taking the weak Sn(1)‚‚‚O(2) interaction into
account, the geometry at Sn(1) can also be described as
a monocapped octahedron with the O(2) approaching the
tin center via the C(1), F(1), O(3a) face. The Sn(1)-F(1)
and Sn(1)-F(2) distances of 1.951(3) and 1.947(4) Å,
respectively, are rather short and correspond to the
Sn-F single bond length of 1.96 Å, as reported for
tetracoordinated triorganotin fluorides.31,32 On the other
hand, the Sn(1)-C(1) and Sn(1)-O(3) distances of 2.192-
161.38(9)
87.60(9)
O(11′)-Sn(2)-O(12) 161.35(9)
O(1)-Sn(2)-O(11′)
90.82(9)
85.64(9)
116.45(16)
85.67(10) O(1)-Sn(2)-O(12)
114.93(16) O(11)-P(3)-O(11′)
107.78(17) O(11)-P(3)-O(11′′) 104.13(15)
110.21(16) O(11′)-P(3)-O(11′′) 110.24(15)
112.27(17) O(11)-P(3)-C(12)
106.39(17) O(11′)-P(3)-C(12)
104.80(18) O(11′′)-P(3)-C(12) 108.97(18)
111.86(17)
105.12(17)
115.31(17) O(12)-P(4)-O(12′)
114.49(19) O(12)-P(4)-O(12′′)
114.22(18)
115.25(16)
98.6(2)
107.07(18) O(12)-P(4)-C(16)
110.9(2) O(12′)-P(4)-C(16)
O(12′)-P(4)-O(12′′) 100.17(18)
107.56(18)
108.88(18)
110.42(19) O(12′′)-P(4)-C(16) 110.55(18)
117.33(14) P(3)-O(11′)-Sn(2)
135.03(16) P(3)-O(11)-Sn(1)
117.05(16) P(4)-O(12)-Sn(2)
118.82(14)
139.47(17)
116.33(15)
the basis of the 1J (119Sn-19F) couplings being indicative
of terminal Sn-F bonds,17 both compounds are sug-
gested to be monomeric in solution. Under the reaction
conditions employed, attempts at isolating the intramo-
lecularly coordinated monorganotin trifluoride 5 failed,
and regardless of the synthetic procedure (eq 2) the
monoorganotin hydroxide difluoride {{2,6-[P(O)(OEt)2]2-
4-t-Bu-C6H2}SnF2OH}2 (6) was isolated instead.
(27) Lecomte, C.; Protas, J .; Devaud, M. Acta Crystallogr. 1976, B32,
923.
(28) Domingos, A. M.; Sheldrick, G. M. J . Chem. Soc., Dalton Trans.
1974, 475.
(29) Puff, H.; Hevendehl, H.; Ho¨fer, K.; Reuter, H.; Schuh, W. J .
Organomet. Chem. 1985, 287, 163.
(30) Bondi, A. J . Phys. Chem. 1964, 68, 441.
(31) Al-J uaid, S. S.; Dhaher, S. M.; Eaborn, C.; Hitchcock, P. B.;
Smith, J . D. J . Organomet. Chem. 1987, 325, 117.
(32) Bai, H.; Harris, R. K.; Reuter, H. J . Organomet. Chem. 1991,
408, 167.
The molecular structure of 6 (Figure 3) shows a
centrosymmetric dimer in which two, at first approxi-
mation, octahedrally configurated tin atoms are con-

4652 Organometallics, Vol. 20, No. 22, 2001
Mehring et al.
0.2 M. Electrospray mass spectra were recorded in the positive
mode on a Thermoquest-Finnigan instrument using CH3CN/
CH2Cl2 (10:1) as the mobile phase. The compounds were
dissolved in dichloromethane and then diluted with the mobile
phase to give a solution of approximate concentration 0.1 mM.
The sample was introduced via a syringe pump operating at
15 µL/min. The capillary voltage was 4.5 kV, while the cone-
skimmer voltage was varied between 50 and 250 V. Identifica-
tion of all major ions was assisted by comparison of experi-
mental and calculated isotope distribution patterns. The m/z
values reported correspond to that of the most intense peaks
in the corresponding isotope pattern.
(5) and 2.157(4) Å, respectively, are rather long and
reflect the strong trans influence of F(2) and F(1).
The 119Sn NMR spectrum of 6 in toluene-d8 at -60
°C shows a doublet of doublets of doublets of doublets
resonance at δ -602 (J (119Sn-31P) ) 142, J (119Sn-31P)
1
1
) 288 Hz, J (119Sn-19F) ) 1513, J (119Sn-19F) ) 2832
Hz), and in the 31P NMR spectrum at -60 °C two
resonances of equal intensity at δ 19.7 (J (31P-119Sn) )
4
142 Hz, J (31P-31P) ) 11 Hz, J (31P-19F) ) 4 Hz) and δ
27.7 (J (31P-119Sn) ) 282 Hz, 4J (31P-31P) ) 11 Hz,
J (31P-19F) ) 12 Hz) are observed, which are indicative
of a weakly and a strongly coordinating phosphonate
group, respectively. These data are consistent with the
structure in solution of 6 being rather similar to that
observed in the solid state. The 31P NMR spectrum
exhibits a further broad resonance of minor intensity
(about 15% of the major signals) at δ 23.6 (ν1/2 > 50 Hz),
for which no assignment was made. At ambient tem-
perature, compound 6 is kinetically labile on the 119Sn
NMR time scale; i.e., no signal is observed. The 31P NMR
spectrum at room temperature displayed one resonance
at δ 22.9 (J (31P-119Sn) ) 212 Hz, ν1/2 ) 38 Hz), which
hints at intra- and/or intermolecular dynamics, the
details of which were not investigated further.
Syn t h esis of {[2,6-Bis(d iet h oxyp h osp h on yl)-4-ter t-
bu tyl]p h en yl}p h en yltin Diflu or id e, {2,6-[P (O)(OEt)2]2-4-
t-Bu -C6H2}Sn F 2P h ‚0.5H 2O (1). At room temperature, a
solution of KF (2.300 g, 39.66 mmol) in H2O (20 mL) was added
dropwise to a solution of {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}-
SnPhCl2 (0.330 g, 0.50 mmol) in CH2Cl2 (20 mL). After the
reaction mixture was stirred for 24 h, the organic phase was
separated and dried over Na2SO4. The latter was filtered, and
the CH2Cl2 of the filtrate was evaporated in vacuo. The residue
was recrystallized from toluene/hexane to give 0.256 g (80%)
1
of 1 as a colorless solid: mp >340 °C. H NMR (400.13 MHz,
CDCl3): δ 1.35 (t, 12 H, CH3), 1.41 (s, 9 H, CH3), 4.15-4.44
(complex pattern, 8 H, CH2), 7.37-8.12 (complex pattern, 7
H, Haryl). 31P{1H} NMR (161.98 MHz, CDCl3): δ 28.7 (J (31P-
119Sn) ) 97 Hz). 119Sn{1H} NMR (149.18 MHz, toluene-d8): δ
-522 (tt, J (119Sn-31P) ) 104 Hz, J (119Sn-19F) ) 3072). IR
(KBr): ν 1176 cm-1 (PdO), 3496 cm-1 (OH). Anal. Calcd for
In contrast to the diorganotin dichloride derivative
{2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl2Ph, the correspond-
ing monoorganotin trichloride is sensitive toward hy-
drolysis. The 119Sn NMR spectrum of a CDCl3 solution
of {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl3 to which had
been added a few droplets of water showed, after 1 day,
a triplet at δ -526 (J (119Sn-31P) ) 281 Hz) assigned to
the starting material and a triplet at δ -499 (J (119Sn-
31P) ) 280 Hz) which is likely to belong to the monoor-
ganotin hydroxide dichloride {2,6-[P(O)(OEt)2]2-4-t-Bu-
C6H2}SnCl2OH. After 3 days, the low-frequency reson-
ance disappeared. The ESMS of {2,6-[P(O)(OEt)2]2-4-t-
Bu-C6H2}SnCl3 in CH2Cl2/CH3CN to which had been
added a few droplets of water showed peaks with
isotopic patterns indicative of {{2,6-[P(O)(OEt)2]2-4-t-
Bu-C6H2}SnCl2}+ (m/z 595.1) and {{2,6-[P(O)(OEt)2]2-
4-t-Bu-C6H2}SnClOH}+ (m/z 577.0). However, attempts
at isolating the monoorganotin hydroxide dichloride
{2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl2OH failed.
C
24H36F2O6P2Sn‚0.5H2O (648.23): C, 44.5; H, 5.8. Found: C,
45.0; H, 6.1.
Syn th esis of Bis(5-ter t-bu tyl-1-ch lor o-1-p h en yl-7-(d i-
et h oxyp h osp h on yl)-3-et h oxy-3-oxo-2,3,1-b en zoxa p h os-
p h a sta n n ole), {[1(Sn ),3(P )-P h ClSn OP (O)(OEt)-5-t-Bu -7-
P (O)(OEt)2]C6H2}2 (3). A solution of {2,6-[P(O)(OEt)2]2-4-t-
Bu-C6H2}SnPhCl2 (0.300 g, 0.45 mmol) in a 1:1 mixture of
toluene and xylene was heated at 110 °C for 2 weeks. The
solvent was removed in vacuo, and the residue was redissolved
in CDCl3. The 31P NMR spectrum of this solution was recorded
(see Results and Discussion). The CDCl3 was removed in vacuo,
and the residue was crystallized from CHCl3/hexane to give
1
0.219 g (80%) of 3 as colorless crystals, mp >300 °C. H NMR
(400.13 MHz, CDCl3): δ 1.02 (s, 18 H, CH3), 1.07 (t, 6 H, CH3),
1.21 (t, 6 H, CH3), 1.31 (t, 6 H, CH3), 3.72-3.82 (complex
pattern, 2 H, CH2), 3.99-4.38 (complex pattern, 10 H, CH2),
3
7.30-7.38 (complex pattern, 6 H, Haryl), 7.40 (d, 2 H, J (1H-
31P) ) 13 Hz, 4J (1H-119Sn) ) 31 Hz, Haryl), 7.72 (d, 2 H, 3J (1H-
31P) ) 13 Hz, 4J (1H-119Sn) ) 32 Hz, Haryl), 7.90 (d, 4 H, 3J (1H-
119Sn) ) 123 Hz, Haryl). 31P{1H} NMR (161.98 MHz, CDCl3): δ
Compound 6 is the first example in which the ligand
{2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}- is only bidentate with
respect to a metal center. Additionally, the results
suggest that stabilization of organotin dihydroxidess
or even trihydroxidessmight be possible by employing
intramolecular hydrogen bridges to appropriate func-
tionalities such as PdO groups.
15.0 (d, 4J (31P-31P) ) 5 Hz, J (31P-119Sn) ) 176 Hz, J (31P-119
-
Sn) ) 96 Hz), δ 27.7 (d, 4J (31P-31P) ) 5 Hz, J (31P-119Sn) )
100 Hz). 119Sn{1H} NMR (149.18 MHz, CDCl3): δ -474 (ddd,
J (119Sn-31P) ) 98 Hz, J (119Sn-31P) ) 100 Hz, J (119Sn-31P) )
176 Hz). IR (KBr): ν 1123, 1166 cm-1 (PdO). Anal. Calcd for
C
22H31ClO6P2Sn (607.58): C, 43.5; H, 5.1. Found: C, 43.3; H,
5.2.
Syn t h esis of {[2,6-Bis(d iet h oxyp h osp h on yl)-4-ter t-
Exp er im en ta l Section
b u t yl]p h en yl}t in Diflu or id e H yd r oxid e, {{2,6-[P (O)-
(OEt)2]2-4-t-Bu -C6H2}Sn F 2OH}2 (6). A solution of KF (2.600
g, 44.75 mmol) in H2O (20 mL) was added dropwise to a
solution of {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl3 (0.350 g, 0.56
mmol) in CH2Cl2 (20 mL) at room temperature. After the
reaction mixture was stirred for 12 h, the organic phase was
separated, dried over Na2SO4, and filtered. The CH2Cl2 of the
filtrate was evaporated in vacuo. The residue was recrystal-
lized from CH2Cl2/toluene/hexane at 4 °C to give 0.105 g (32%)
of 6 as colorless crystals; mp 108-113 °C. 1H NMR (400.13
MHz, CDCl3): δ 1.34 (broad, 42 H, CH3), 3.94-4.37 (broad,
16 H, CH2), 7.95 (d, 4 H, Haryl). 1H NMR (400.13 MHz, CD2-
Cl2, -60 °C): δ 1.10-1.45 (complex pattern, 42 H, CH3), 3.78-
4.48 (complex pattern, 16 H, CH2), 7.91-8.14 (complex pattern,
Gen er a l Rem a r k s. Literature procedures were used to
prepare {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl2Ph20 and {2,6-
[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl3.21 IR spectra were obtained
from a Bruker FTIR IFS 113v spectrometer. 119Sn, 29Si, 13C,
1H, and 31P NMR spectra were recorded on Bruker DRX 400
and DPX 300 spectrometers. Chemical shifts δ are given in
ppm and were referenced against Me4Sn (119Sn), Me4Si (1H,
13C, 29Si), and 85% H3PO4 (31P). 119Sn NMR spectra of the NMR
experiments were recorded for sample solutions prepared from
appropriate molar ratios of tetrabutylammonium fluoride
trihydrate (Bu4NF‚3H2O) and {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}-
SnX2Ph (X ) Cl, F) or {2,6-[P(O)(OEt)2]2-4-t-Bu-C6H2}SnCl3.
Typically, the concentration of the organotin halides was 0.1-

A Pincer-Type Ligand in Organotin Chemistry
Organometallics, Vol. 20, No. 22, 2001 4653
4 H, Haryl), 9.30 (s, 2 H, Sn-OH). 31P{1H} NMR (161.98 MHz,
CDCl3): δ 22.9 (J (31P-119Sn) ) 212 Hz). 31P{1H} NMR (161.98
MHz, CD2Cl2, -60 °C): δ 19.7 (J (31P-119Sn) ) 142 Hz, 4J (31P-
31P) ) 11 Hz, J (31P-19F) ) 4 Hz, 42.5%), 23.6 (broad, v1/2 > 50
refined with a common isotropic temperature factor (C-Hprim
) 0.96 Å, C-Hsec ) 0.97 Å; C-Haryl ) 0.93 Å; Uiso ) 0.170(5)
Å2 (1), Uiso ) 0.225(10) Å2 (6)) and for 3 with Uiso constrained
at 1.2 for nonmethyl groups and 1.5 for methyl groups times
Ueq of the carrier C atom.
Disordered atoms were found in 1 (C(8), C(9), C(22), C(24),
C(25) (sof 0.65); C(10), C(10′), C(27), C27′ (sof 0.5); C(8′), C(9′),
C(22′), C(24′), C(25′) (sof 0.35)), in 6 (Sn(1), F(1), F(2) (sof 0.85);
C(10), C(10′), C(41), C(45), C(46), C(41′), C(45′), C(46′) (sof 0,5);
Sn(1′), F(1′), F(2′) (sof 0.15)), and in 3 (C(53), C(53′) (sof 0.5)).
Atomic scattering factors for neutral atoms and real and
imaginary dispersion terms were taken from ref 35. The
figures were created by SHELXTL.36 Crystallographic data are
given in Table 1 and selected bond distances and angles in
Table 2.
4
Hz, 15%), 27.7 (J (31P-119Sn) ) 282 Hz, J (31P-31P) ) 11 Hz,
J (31P-19F) ) 12 Hz, 42.5%). 119Sn{1H} NMR (149.18 MHz, CD2-
Cl2, -60 °C): δ -602 (dddd, J (119Sn-31P) ) 142, 288 Hz,
1J (119Sn-19F) ) 1513, 2832 Hz). IR (KBr): ν 1169, 1236 cm-1
(PdO), 3480 cm-1 (OH). Anal. Calcd for C36H64F4O14P4Sn2
(1158.26): C, 37.3; H, 5.6. Found: C, 36.7; H, 5.6.
Cr ysta llogr a p h y. Intensity data for the colorless crystals
were collected on a Nonius KappaCCD diffractometer with
graphite-monochromated Mo KR (0.71069 Å) radiation at 291
K (1, 6) and 173 K (3). The data collection covered almost the
whole sphere of reciprocal space with 360 (1, 6) and 351 (with
four sets at different κ angles 3) frames via ω-rotation (∆/ω )
1°) at 2 times 10 s (3), 15 s (1), and 20 s (6) per frame. The
crystal-to-detector distances were 2.7 cm (1, 6) and 3.4 cm (3).
Crystal decay was monitored by repeating the initial frames
at the end of data collection. When the duplicate reflections
were analyzed, there was no indication for any decay. The data
were not corrected for absorption effects. The structures were
solved by direct methods (SHELXS9733) and successive dif-
ference Fourier syntheses. Refinement applied full-matrix
least-squares methods (SHELXL9734).
Ack n ow led gm en t. We gratefully acknowledge sup-
port of this work by the Deutsche Forschungsgemein-
schaft and the Fonds der Chemischen Industrie.
Su p p or tin g In for m a tion Ava ila ble: Tables of all atomic
coordinates, anisotropic displacement parameters, and geo-
metric data for compounds 1, 3 and 6. This material is
available free of charge via the Internet at http://pubs.acs.org.
The H atoms were placed in geometrically calculated
positions, except for O(3) in compound 6. For 1 and 6 they were
OM0103714
(35) International Tables for Crystallography; Kluwer Academic:
Dordrecht, The Netherlands, 1992; Vol. C.
(36) Sheldrick, G. M. SHELXTL Release 5.1 Software Reference
Manual, Bruker AXS: Madison, WI.
(33) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(34) Sheldrick, G. M. SHELXL97; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1979.