New tin(II) and tin(IV) amidophenolate complexes

Article abstract of DOI:10.1016/j.inoche.2006.03.012

Treatment of tin amalgam with 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (imQ) in THF results in formation of bis-(4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophenolato)tin(IV ) tetrahydrofuranate (1). The exchange reaction of

Full text of DOI:10.1016/j.inoche.2006.03.012

Inorganic Chemistry Communications 9 (2006) 612–615
www.elsevier.com/locate/inoche
New tin(II) and tin(IV) amidophenolate complexes
*
Alexandr V. Piskunov , Igor A. Aivaz’yan, Georgii K. Fukin, Evgenii V. Baranov,
Andrey S. Shavyrin, Vladimir K. Cherkasov, Gleb A. Abakumov
G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Laboratory of Organoelement Compounds,
49 Tropinina Street, 603950 Nizhny Novgorod, Russia
Received 13 February 2006; accepted 10 March 2006
Available online 24 March 2006
Abstract
Treatment of tin amalgam with 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (imQ) in THF results in formation
of bis-(4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophenolato)tin(IV) tetrahydrofuranate (1). The exchange reaction of imQ dil-
ithium derivative with tin dichloride dioxanate in THF solution produces bis-[(4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophe-
nolato)tin(II)] (2). Stannylene (2) reacts with imQ in THF to give 1. Structures of 1 and 2 were determined by X-ray analysis.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: o-iminoquinone; Amidophenolate; Stannylene; Tin; X-ray diffraction
Metal complexes containing o-quinone type ligands are
well known class of compounds. The ability of o-quinones
to exist in three different redox states causes their rich
coordination chemistry [1]. Particularly, they proved to
be convenient objects for EPR investigations [2]. Substitu-
tion in such compounds of one oxygen atom for nitrogen,
conducing to iminoquinone derivatives, allows to enter
asymmetry into the electronic structure of corresponding
metal complexes. Due to a magnetism of 14N nuclei these
derivatives seem to be very promising in terms of EPR
spectroscopy.
Introduction of bulky substitutes at nitrogen atom of
o-iminobenzoquinones allows to obtain low-coordinated
metal complexes having coordination vacancies accessi-
ble for light-weight species. Such complexes are of inter-
est as potential reagents in organic synthesis, especially
for addition, activation or transfer of small molecules.
Thus, antimony amidophenolate derivative has shown
to be able to reversible addition of atmospheric oxygen
[3].
By now, a number of transition metal complexes con-
taining substituted o-iminoquinone ligands are synthesized
[4]. To the contrary, the chemistry of iminoquinone com-
plexes of non-transition elements still stays insufficiently
explored. Particularly, there were described few o-imino-
quinone derivatives of magnesium, germanium and tin
[5]. All of them include five- or six-coordinate metal center
due to substitutes [5a] or additional coordination binding
[5b,5c], whereas coordination unsaturation is needed for
high reactivity.
In the present work, we have synthesized and
characterized the first tin(II) and tin(IV) derivatives con-
taining amidophenolate ligands on the basis of 4,6-di-
tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone
(imQ).
The direct interaction of o-quinones with metal amal-
gams in aprotic solvents was shown to be a convenient
method to synthesize o-semiquinonate and catecholate
derivatives [6]. The interaction of imQ with tin amalgam
in THF [7] results in formation of new five-coordinate
bis(amidophenolato)tin(IV) complex 1.
*
Corresponding author. Tel.: +7 8312 626782; fax: +7 8312 627497.
E-mail addresses: pial@imoc.sinn.ru (A.V. Piskunov), gogo@imoc.
sinn.ru (I.A. Aivaz’yan), gera@imoc.sinn.ru (G.K. Fukin), cherkasov@
imoc.sinn.ru (V.K. Cherkasov), gleb@imoc.sinn.ru (G.A. Abakumov).
1387-7003/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.03.012

A.V. Piskunov et al. / Inorganic Chemistry Communications 9 (2006) 612–615
613
t-Bu
t-Bu
Ar
N
THF
Sn
O
N
O
t-Bu
Sn/Hg
THF
(1)
t-Bu
t-Bu
N
O
Ar
Ar
t-Bu
1
Ar = 2,6-di-iso-propylphenyl
The crystal structure of 1 has been determined by single-
crystal X-ray diffraction.1 Tin(IV) atom in 1 has a distorted
tetragonal pyramidal coordination with two nitrogen and
two amidophenolate oxygen atoms in the base and with
THF oxygen atom at the apical site (Fig. 1). Deviation of
˚
Sn(1) from the O(1)N(1)O(2)N(2) plane is 0.223 A. Dihe-
dral angle between two amidophenolate metallocycles
amounts to 152.02(6)ꢁ.
Fig. 1. PLATON presentation [18] of the molecular structure of 1. The
hydrogen atoms, THF and methyls of i-Pr groups carbon atoms are
˚
The distances Sn(1)–O(1) (2.010(2) A) and Sn(1)–O(2)
˚
(2.019(2) A) are quite close to the sum of covalent radii
˚
omitted for clarity. Selected bond lengths (A) and angles (ꢁ): Sn(1)–O(1)
˚
of tin and oxygen atoms (2.06 A [8]), and are similar to
2.010(2), Sn(1)–N(2) 2.012(2), Sn(1)–N(1) 2.018(2), Sn(1)–O(2) 2.019(2),
Sn(1)–O(3) 2.151(2), C(1)–O(1) 1.366(3), N(1)–C(2) 1.405(3), N(1)–C(15)
1.431(3), O(2)–C(27) 1.368(3), N(2)–C(28) 1.399(3), N(2)–C(41) 1.426(3)
and O(1)–Sn(1)–N(2) 96.54(7), O(1)–Sn(1)–N(1) 82.69(7), N(2)–Sn(1)–
N(1) 152.41(9), O(1)–Sn(1)–O(2) 178.35(7), N(2)–Sn(1)–O(2) 82.63(7),
N(1)–Sn(1)–O(2) 98.71(7), O(1)–Sn(1)–O(3) 89.55(7), N(2)–Sn(1)–O(3)
104.40(8), N(1)–Sn(1)–O(3) 103.18(8), O(2)–Sn(1)–O(3) 89.27(7), C(1)–
O(1)–Sn(1) 111.94(14), C(2)–N(1)–Sn(1) 111.45(16), C(27)–O(2)–Sn(1)
111.88(14), C(28)–N(2)–Sn(1) 111.52(15).
those observed for tin(IV) catecholate complexes (1.995–
˚
˚
2.080 A [9]). The bond lengths Sn(1)–N(1) (2.018(2) A)
˚
and Sn(1)–N(2) (2.012(2) A) are slightly less then the sum
of covalent radii of nitrogen and tin (2.10 A [8]). These
˚
bonds are also shorter then for tin(IV) diamide derivative
˚
distance
(2.071–2.073 A
(2.151(2) A) is quite close to typical range of donor–accep-
tor bond lengths between tin(IV) and coordinated THF in
[10]).
The
Sn(1)–O(3)
˚
˚
catecholate complexes (2.186–2.379 A [11]). Distances C–O
˚
(1.366(3) and 1.368(3) A) and C–N (1.405(3) and
˚
1.399(3) A) in amidophenolate ligands are close to those
observed for antimony amidophenolate derivative (1.351
˚
and 1.408 A correspondingly [3]).
The exchange reaction between imQ dilithium salt
(obtained from lithium and imQ in THF solution) and
dioxane complex of tin dichloride [12] leads to three-coor-
dinate tin(II) amidophenolate derivative 2.
t-Bu
t-Bu
t-Bu
O
SnCl2•diox,
THF
O
OLi
Li, THF
t-Bu
Sn
(2)
- LiCl
t-Bu
N
t-Bu
N
NLi
Ar
2
Ar
Ar
2
1
X-ray data for 1: C62H96N2O3Sn, crystal size 0.33 · 0.25 · 0.15 mm,
˚
˚
Fig. 2. PLATON presentation [18] of the molecular structure of 2. The
M = 1036.10, orthorhombic, a = 16.4135(9) A, b = 16.5902(9) A, c =
3
˚
˚
˚
hydrogen atoms are omitted for clarity. Selected bond lengths (A) and
21.7037(12) A, a = 90ꢁ b = 90ꢁ, c = 90ꢁ, V = 5910.0(6) A , space group
P2(1)2(1)2(1), Z = 4, T = 100(2) K, F(000) = 2224, dcalc. = 1.164 g cmÀ3
,
angles (ꢁ): Sn(1)–N(1) 2.100(2), Sn(1)–O(1) 2.170(2), Sn(1)–O(2) 2.240(2),
O(1)–C(1) 1.399(3), O(1)–Sn(2) 2.235(2), N(1)–C(2) 1.404(3), N(1)–C(15)
1.430(3), Sn(2)–N(2) 2.105(2), Sn(2)–O(2) 2.162(2), O(2)–C(27) 1.400(3),
N(2)–C(28) 1.398(3), N(2)–C(41) 1.431(3), Sn(1)–Sn(2) 3.350(4) and N(1)–
Sn(1)–O(1) 76.33(6), N(1)–Sn(1)–O(2) 91.30(7), O(1)–Sn(1)–O(2) 80.70(5),
C(1)–O(1)–Sn(1) 111.47(12), Sn(1)–O(1)–Sn(2) 99.03(6), C(2)–N(1)–Sn(1)
113.46(14), N(2)–Sn(2)–O(1) 92.11(6), N(2)–Sn(2)–O(2) 76.08(6), O(2)–
Sn(2)–O(1) 80.99(6), C(27)–O(2)–Sn(2) 112.15(12), Sn(2)–O(2)–Sn(1)
99.08(6), C(28)–N(2)–Sn(2) 113.72(15).
l = 0.475 mmÀ1, h = 1.54–25.00ꢁ, reflection collected 32,855, independent
reflection 10,392 (Rint = 0.0289), GOF (F2) = 0.999, R1 = 0.0278
[I > 2r(I)], wR2 = 0.0691 (all data). The structure was solved by direct
method and refined anisotropically on F2 by full matrix least squares using
SHELXTL [17]. The H atoms were placed in calculated positions and
2
˚
refined in the ‘‘riding-model’’(Uiso(H) = 1.2Ueq(carbon) A for aromatic
2
˚
hydrogen and 1.5Ueq(carbon) A for alkyl hydrogen). One solvent
molecule of hexane was found in asymmetric unit.

614
A.V. Piskunov et al. / Inorganic Chemistry Communications 9 (2006) 612–615
The X-ray analysis2 of 2 has shown that in the crystal it
t-Bu
t-Bu
Ar
N
THF
Sn
has a dimeric structure and tin atoms have a distorted tri-
gonal pyramidal environment (Fig. 2). The O(1), N(1),
O(2) and O(2), N(2), O(1) atoms form the bases of trigonal
pyramids, respectively for Sn(1) and Sn(2). The skeletons
of amidophenolate ligands are plane and these ligands
are the practically parallel to each other. Dihedral angle
between ones is 3.87(9)ꢁ. Dihedral angles between the
planar central Sn(1)O(1)Sn(2)O(2) fragment and the
five-membered metallocycles are 101.7(1)ꢁ and 98.9(1)ꢁ,
respectively for Sn(1)O(1)N(1)C(1)C(2) and Sn(2)O(2)-
N(2)C(27)C(28) fragments. The bending angles along
O. . .N lines in metallocycles have an opposite direction
and are 23.13(8)ꢁ and 21.72(8)ꢁ. Probably, it is caused by
the nonbonding repulsion between the tin atoms, which
O
O
N
t-Bu
THF
+
2
(3)
t-Bu
N
t-Bu
O
Ar
Ar
t-Bu
1
Supplementary material
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic Data
Centre, CCDC No. 297394 for compound 1 and CCDC
No. 297395 for compound 2. Copies of this information
may be obtained free of charge from The Director, CCDC,
12, Union Road, Cambridge CB2 1EZ, UK [fax: +44 1223
336033]; e-mail deposit@ccdc.cam.ac.uk or http://www.
ccdc.cam.ac.uk.
˚
are separated from each other by 3.350(4) A.
˚
The
Sn(1)–O(1)
(2.170(2) A)
and
Sn(2)–O(2)
˚
(2.162(2) A) distances are significantly shorter then bonds
˚
˚
Sn(2)–O(1) and Sn(1)–O(2) (2.235(2) A and 2.240(2) A)
which have donor–acceptor nature. Also these distances
are shorter then in tin(II) catecholate (2.201(4)–
Acknowledgements
˚
2.334(4) A [13]), but are comparable with Sn–O bonds
We are grateful to the Russian Foundation for Basic Re-
search (Grant 04-03-32413), Russian President Grant sup-
porting scientific schools (Grant 4947.2006.3) and Russian
Science Support Foundation for financial support of this
work.
lengths observed for dimeric tin(II) phenolates and alcoho-
˚
lates (2.169–2.173 A [14]). Values of Sn–N distances
˚
(2.010(2) and 2.105(2) A) lie in the range typical for diva-
˚
lent tin diamide derivatives (2.084–2.102 A [15]), and it is
in clear agreement with the sum of covalent radii of nitro-
˚
gen and tin (2.10 A [8]). It should be noted that existence of
dimer divalent tin derivatives having such Sn–O bonding is
rather usual [16].
References
˚
In contrast to 1, distances C–O (1.399(3) A and
[1] (a) C.G. Pierpont, Coord. Chem. Rev. 216–217 (2001) 99;
(b) C.G. Pierpont, Coord. Chem. Rev. 219–221 (2001) 415.
[2] V.K. Cherkasov, G.A. Abakumov, Organomet. Chem. USSR 3
(1990) 426.
[3] G.A. Abakumov, A.I. Poddel’sky, E.V. Grunova, V.K. Cherkasov,
G.K. Fukin, Yu.A. Kurskii, L.G. Abakumova, Angew. Chem. Int.
Ed. 44 (2005) 2767.
˚
˚
˚
1.400(3) A) and C–N (1.404(3) A and 1.398(3) A) in 2 are
equalized and have no noticeable difference, so their values
lie between those observed for antimony amidophenolate
˚
derivative (1.351 and 1.408 A correspondingly [3]), but clo-
ser to N–C distance.
[4] (a) G.A. Abakumov, A.I. Poddel’sky, M.P. Bubnov, G.K. Fukin,
L.G. Abakumova, V.N. Ikorskii, V.K. Cherkasov, Inorg. Chim. Acta
358 (2005) 3829, and references therein;
Complexes 1 and 2 are both stable in solid state under
excluding air and moisture conditions.
Complex 1 can be easily obtained from derivative 2.
Interaction of equimolar quantities of 2 and imQ in THF
results in tin(IV) amidophenolate 1 formation. The equiva-
lence of the products obtained by two different ways (reac-
tions (1) and (3)) was shown using melting point
determination and NMR data.
(b) E. Bill, E. Bothe, P. Chaudhuri, K. Chlopek, D. Herebian, S.
Kokatam, K. Ray, T. Weyhermuller, F. Neese, K. Wieghardt, Chem.
Eur. J. 11 (2005) 204, and references therein.
[5] (a) V.M. Jımenez-Perez, C. Camacho-Camacho, M. Guizado-
¨
Rodrıguez, H. No¨th, R. Contreras, J. Organomet. Chem. 614–615
(2000) 283;
(b) S. Bruni, A. Caneschi, F. Cariati, C. Delfs, A. Dei, D. Gatteschi, J.
Am. Chem. Soc. 116 (1994) 1388;
(c) A.Y. Girgis, A.L. Balch, Inorg. Chem. 14 (1975) 2724.
[6] A.V. Piskunov, S.V. Maslennikov, I.V. Spirina, V.P. Maslennikov,
Russ. J. Coord. Chem. 28 (2002) 808.
[7] The imQ (1.52 g, 4 mmol) dispersion in THF (30 ml) was added to tin
(4.75 g, 40 mmol) amalgam and reaction mixture was shacked for
about 3 h. During the reaction color of solution turned from red to
transparent brown. After reaction had been finished (the color of
reaction mixture did not change any more), THF was evaporated
under vacuum conditions and after that hexane was added. After
cooling of hexane solution, light brown crystals of 1 were obtained.
Additional quantities of 1 were produced by the same way from
mother liquor in three steps. The total yield is 2.37 g (83.4%) of the
analytically pure compound. M.p. 206 ꢁC (dec.). Point of crystal
hexane loss is 119 ꢁC. Anal. Calc. for C62H96N2O3Sn C, 73.00; H,
2
X-ray data for 2: C52H74N2O2Sn2, crystal size 1.50 · 0.60 · 0.40 mm,
˚
˚
M = 996.51, monoclinic, a = 26.2216(19) A, b = 8.8081(6) A, c =
3
˚
˚
23.0711(17) A, a = 90ꢁ b = 109.9830(10)ꢁ, c = 90ꢁ, V = 5007.7(6) A , space
group Cc, Z = 4, T = 100(2) K, F(000) = 2064, dcalc. = 1.322 g cmÀ3
,
l = 1.036 mmÀ1, h = 2.53–25.00ꢁ, reflection collected 17974, independent
reflection 8677 (Rint = 0.0154), GOF (F2) = 1.046, R1 = 0.0237 [I > 2r(I)],
wR2 = 0.0648 (all data). The structure was solved by direct method and
refined anisotropically on F2 by full matrix least squares using SHELXTL
[17]. The H atoms were located from Fourier synthesis and refined
isotropically.

A.V. Piskunov et al. / Inorganic Chemistry Communications 9 (2006) 612–615
615
9.49; Sn, 11.64%. Found: C, 72.95; H, 9.42; Sn, 11.67%. 1H NMR
(200 MHz, toluene d8) d, ppm: 0.89 (t, 6H, 6.4 Hz, 2CH3, hexane),
1.03 (d, 6H, 6.7 Hz, 2CH3 groups of Pri), 1.16 (d, 6H, 6.7 Hz, 2CH3
groups of Pri), 1.19 (s, 18H, 2But), 1.25 (m, 8H, 4CH2, hexane), 1.26–
1.28 (m, 4Hb, 2CH2 groups of THF), 1.31 (d, 6H, 6.7 Hz, 2CH3
groups of Pri), 1.33 (s, 18H, 2But), 1.35 (d, 6H, 6.7 Hz, 2CH3 groups
of Pri), 3.27 (septet, 2H, 6.7 Hz, 2CH groups of Pri), 3.39 (septet, 2H,
6.7 Hz, 2CH groups of Pri), 3.74 (m, 2Ha, CH2 group of THF), 4.03
(m, 2Ha, CH2 group of THF), 6.29 (d, 2H, 2.3 Hz, 2CH aromatic,
J(H–117,119Sn) = 11.6 Hz), 6.85 (d, 2H, 2.3 Hz, 2CH aromatic), 7.15–
7.37 (m, 6H, 6CH aromatic). Assignment of NMR signals was defined
more exactly using 2D COSY NMR.
(0.83 g, 3 mmol) and THF (10 ml) cooled to À10 ꢁC, and at the same
time reaction mixture turned orange. THF was replaced with hexane
and solution was separated from white deposit of lithium chloride by
filtration. Cooling of hexane solution resulted in the formation of
light yellow crystals of 2. After separation of solid phase mother
liquor was additionally concentrated and cooled to isolate the
product more quantitatively. The total yield is 0.86 g (57.6%) of the
analytically pure compound. M.p. 176 ꢁC. Anal. calc. for
C
52H74N2O2Sn2 C, 62.67; H, 7.48; Sn, 23.82%. Found: C, 62.60; H,
7.42; Sn, 23.95%. 1H NMR (200 MHz, toluene d8) d, ppm: 0.97 (d,
12H, 6.8 Hz, 4CH3 groups of Pri), 0.99 (d, 12H, 6.8 Hz, 4CH3 groups
of Pri), 1.31 (s, 9H, 2But), 1.81 (s, 9H, 2But), 2.72 (septet, 2H, 6.8 Hz,
2CH groups of Pri), 6.30 (d, 1H, 2.3 Hz, CH aromatic), 7.14 (d, 1H,
2.3 Hz, CH aromatic), 7.18 (m, 3H, 3CH aromatic).
[13] A.V. Piskunov, A.V. Lado, G.K. Fukin, E.V. Baranov, L.G.
Abakumova, V.K. Cherkasov, G.A. Abakumov, Heteroatom. Chem.
17 (2006), in press.
[8] J. Emsley, The Elements, Clarendon Press, Oxford, 1991, p. 256.
[9] (a) T.A. Annan, B.R. McGarvey, A. Ozarowski, D.G. Tuck, R.K.
Chadha, J. Chem. Soc., Dalton Trans. (1989) 439–446;
(b) T.A. Annan, R.K. Chadha, D.G. Tuck, K.D. Watson, Can. J.
Chem. 65 (1987) 2670.
[10] M. Weidenbruch, M. Sturmann, H. Kilian, S. Pohl, W. Saak, Chem.
Ber. 130 (1997) 735.
[14] (a) M.J. McGeary, K. Folting, K.G. Caulton, Inorg. Chem. 28 (1989)
4051;
[11] (a) A.V. Lado, A.I. Poddel’sky, A.V. Piskunov, G.K. Fukin, E.V.
Baranov, V.N. Ikorskii, V.K. Cherkasov, G.A. Abakumov, Inorg.
Chim. Acta 358 (2005) 4443;
(b) B.G. McBurnett, A.H. Cowley, Chem. Commun. (1999) 17.
[15] T. Gans-Eichler, D. Gudat, M. Nieger, Angew. Chem. 114 (2002)
1966.
(b) A.V. Lado, A.V. Piskunov, V.K. Cherkasov, G.K. Fukin, G.A.
Abakumov, Russ. J. Coord. Chem. 32 (2006) 173.
[16] N.N. Zemlyanskii, I.V. Borisova, M.S. Nechaev, V.N. Khrustalev,
V.V. Lunin, M. Yu. Antipin, Yu.A. Ustynyuk, Russ. Chem. Bull. 53
(2004) 980.
[17] G.M. Sheldrick, SHELXTL v. 6.12, Structure Determination Soft-
ware Suite, Bruker AXS, Madison, Wisconsin, USA, 2000.
[18] A.L. Spek, PLATON A Multipurpose Crystallographic Tool, Utrecht
University, Utrecht, The Netherlands, 2000.
[12] The imQ (1.14 g, 3 mmol) dispersion in THF (20 ml) was added to
excess (0.5 g, 71 mmol) of granulated lithium metal and shacked until
solution became light yellow indicating lithium amidophenolate
formation. When reaction finished, solution was filtered and added
to the ampoule containing 1,4-dioxane complex of tin dichloride