Coordination diversity of aluminum centers molded by triazole based chalcogen ligands

Article abstract of DOI:10.1021/ic900166u

Equimolar and excess ratio reactions of AIMe₃ and AI'Bu ₃ with the ligands 4,5-(P(E)Ph₂)₂tzH (tz = 1,2,3-triazole; E = O (1), S (2), Se(3)) were performed, showing a vast variety of coordination modes. The produ

Full text of DOI:10.1021/ic900166u

5874 Inorg. Chem. 2009, 48, 5874–5883
DOI: 10.1021/ic900166u
Coordination Diversity of Aluminum Centers Molded by Triazole Based Chalcogen
Ligands
†
†
‡
†
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´
´
Jocelyn Alcantara-Garcıa, Vojtech Jancik, Joaquın Barroso, Sandra Hidalgo-Bonilla,
†
†
,†
ꢀ
ꢀ
Raymundo Cea-Olivares, Ruben A. Toscano, and Monica Moya-Cabrera*
†
´
ꢀ
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Instituto de Quımica, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria,
‡
ꢀ
ꢀ
ꢀ
´
04510, Mexico D.F., Mexico, and Centro de investigacion en Polımeros, Grupo COMEX, Marcos Achar
ꢀ
ꢀ
Lobaton 2, 55885 Tepexpan, Mexico
Received January 26, 2009
Equimolar and excess ratio reactions of AlMe3 and AliBu3 with the ligands 4,5-(P(E)Ph2)2tzH (tz = 1,2,3-triazole;
E = O (1), S (2), Se(3)) were performed, showing a vast variety of coordination modes. The products obtained,
i
[AlR2{κ2-O,O0-[4,5-(P(O)Ph2)2tz]}] (R = Me (4), Bu (5)), [AlR2{κ3-N,N0,S-[4,5-(P(S)Ph2)2tz]}(μ-tz)]2 (R = Me (6),
R = iBu (7)), [AlMe2{κ2-N,Se-[4,5-(P(Se)Ph2)2tz]}] (8), [Al{κ2-N,Se-[4,5-(P(Se)Ph2)2tz]}3] (9), [AlR2{κ2-O,O0-[4,5-(P(O)-
Ph2)2tz]}-(N0-AlR3)] (R = Me (10), iBu (11)), and [AlR2{κ2-N,S-[4,5-(P(S)Ph2)2tz]}-(N0-AlR3)] (R = Me (12), R = iBu (13)),
were characterized by spectroscopic methods, and the structures of 1, 4, 6, 7, 9, 10, and 12 were obtained through
X-ray diffraction studies. Theoretical calculations were performed on the deprotonated ligands and on selected
compounds to obtain information regarding the coordination variety observed for these compounds.
Introduction
donor atoms along with the highly delocalized charge on the
backbone of these ligands are accountable for this behavior.
In this regard, multidentate amido and imido ligands have
been amply used in the preparation of aluminum complexes.
Indeed, there is a fairly extensive literature on the interaction
of AlR3 with five-membered nitrogen heterocycles. In this
regard, 1,2-azole rings react readily with aluminum alkyls
forming compounds bearing M2N4 rings and their structural
outcome depends on the steric bulk present on both the azole
ring and the alkyl groups.7-10
The chemistry of the heavy elements of group 13, namely,
gallium and indium, has been substantially explored through
N[P(E)R2]2- (E = S, Se) ligands.1 However, the correspond-
ing aluminum complexes remain scarce and so far, are yet to
be structurally characterized. This contrasts with the con-
siderable number of structurally characterized aluminum
compounds bearing ligands with PdNR and CdN units,
that span from bis(diphenylphosphine)methane,2,3 amidi-
nate4 to β-diketimidato compounds.5,6 The high Lewis
acid character of Al(III) and the hardness of the nitrogen
We have recently reported on the preparation of indium
compounds bearing 4,5-bis(diphenylphosphoranyl)-1,2,3-
triazole ligands (4,5-(P(E)Ph2)2tzH).11 These ligands were
first introduced by Trofimenko and used selectively in
*To whom correspondence should be addressed. E-mail: monica.moya@
correo.unam.mx. Phone: +52 (55) 56 22 44 01. Fax: + 52 (55) 56 16 22 17.
(1) Silvestru, C.; Drake, J. E. Coord. Chem. Rev. 2001, 223, 117–216.
(2) (a) Aparna, K.; McDonald, R.; Cavell, R. G. J. Am. Chem. Soc. 2000,
122, 9314–9315. (b) Cavell, R. G.; Aparna, K.; Kamalesh, B. R. P.; Wang, Q.
J. Mol. Catal. 2002, 189, 137–143. (c) Aparna, K.; McDonald, R.; Ferguson,
M.; Cavell, R. G. Organometallics 1999, 18, 4241–4243.
::
(7) (a) Zheng, W.; Mosch-Zanetti, N. C.; Roesky, H. W.; Hewitt, M.;
Cimpoesu, F.; Schneider, T. R.; Stasch, A.; Prust, J. Angew. Chem., Int. Ed.
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2000, 39, 3099–3102. (b) Zheng, W.; Hohmeister, H.; Mosch-Zanetti, N.;
Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Inorg. Chem. 2001, 40,
(3) (a) Ong, C. M.; McKarns, P.; Stephan, D. W. Organometallics 1999,
18, 4197–4204. (b) Hill, M. S.; Hitchcock, P. B.; Karagouni, S. M. A.
J. Organomet. Chem. 2004, 689, 722–730.
(4) (a) Aeitls, S. L.; Coles, M. P.; Swenson, D. C.; Jordan, R. F.; Young,
V. G. Jr. Organometallics 1998, 17, 3265–3270. (b) Coles, M. P; Swenson, D.
C.; Jordan, R. F.; Young, V. G.Jr. Organometallics 1997, 16, 5183–5194.
(c) Coles, M. P.; Jordan, R. F. J. Am. Chem. Soc. 1997, 119, 8125–8126.
(5) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem. Rev. 2002, 102,
3031–3065.
(6) (a) Roesky, H. W. Inorg. Chem. 2004, 43, 7284–7293. (b) Roesky, H.
W.; Kumar, S. S. Chem. Commun. 2005, 4027–4038. (c) Roesky, H. W.;
Singh, S. S.; Jancik, V.; Chandrasekhar, V. Acc. Chem. Res. 2004, 37, 969–
981.
2363–2367.
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(8) (a) Lewinski, J.; Zachara, J.; Gos, P.; Grabska, E.; Kopec, T.;
Madura, I.; Marciniak, W.; Prowotorow, I. Chem.-Eur. J. 2000, 6, 3215–
3227. (b) Lewinski, J.; Zachara, J.; Gos, P.; Kopec, T.; Madura, I.;
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Prowotorow, I. Inorg. Chem. Commun. 1999, 2, 131–134.
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(9) Cortes-Llamas, S. A.; Hernandez-Perez, J. M.; Ho, M.; Munoz-
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Hernandez, M. A. Organometallics 2006, 25, 588–595.
(10) (a) Yu, Z.; Knox, J. E.; Korolev, A. V.; Heeg, M. J.; Schlegel, H. B.;
Winter, C. H. Eur. J. Inorg. Chem. 2005, 330–337. (b) Sirimanne, C. T.;
Yu, Z.; Heeg, M. J.; Winter, C. H J. Organomet. Chem. 2006, 691, 2517–
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r
2009 American Chemical Society
pubs.acs.org/IC
Published on Web 06/10/2009

Article
Inorganic Chemistry, Vol. 48, No. 13, 2009 5875
1H (300 MHz), 31P (121.6 MHz), and 27Al (78.3 MHz) NMR
spectra were recorded on a JEOL X300 spectrometer at 25 °C,
unless otherwise stated. Chemical shifts are reported in ppm
with reference to TMS (internal), H2PO3 85% (external), or Al-
3+
(H2O)6
(external). IR spectra were recorded on a Bruker
Tensor 27 in the range 400-4000 cm-1 as KBr discs. Mass
spectra (EI) data were obtained on a JEOL JMS-AX505HA
(70 eV) utility. Elemental analyses (C, H, N) were performed on
a CE-440 Exeter Analytical Instrument. Melting points were
measured in sealed glass tubes on a Melt Temp II apparatus
and are not corrected. The ligands 4,5-(P(E)Ph2)2tzH [E=O (1),
S(2), Se(3)] were prepared according to the literature proce-
dures.12,13,17,18
Figure 1. Coordination modes reported for ligands 1- 3.
the preparation of transitional (Pd, Ni, Rh, Co) and f-block
(La, U) complexes, with Mg being the only main group metal
explored.12,13 The coordination patterns observed with these
metals include the formation of a seven-membered ring
(Figure 1, I) or the formation of a five-membered heterocycle
(II), depending on either the metal or the chalcogen atom
present on the ligand. However, in the case of the indium
compounds only the formation of dinuclear species was
observed (III).
Preparation of [AlMe2{K2-O,O0-[4,5-(P(O)Ph2)2tz]}] (4). To a
suspension of 1 (0.41 g, 0.87 mmol) in 10 mL of toluene
was added a 2.0 M solution of AlMe3 in hexanes (0.44 mL,
0.88 mmol) at ambient temperature. Evolution of gas was
observed, and within a few minutes a colorless solution resulted.
After stirring for 2 h, the volatiles were removed under vacuum
and the white solid was washed with 5 mL of hexanes. Yield
(0.43 g, 82%). Mp 184-185 °C. IR (KBr, cm-1): v (P-O) 854.
The multifunctionality of the 4,5-bis(diphenylphosphora-
nyl)-1,2,3-triazoles, 4,5-(P(E)Ph2)2tzH [E=O (1), S (2), Se
(3)], make them an interesting type of ligand for the prepara-
tion of aluminum complexes. This is due to their wide variety
of coordination modes and the presence of both hard and soft
donor atoms. In this regard, the coordination of a hard Lewis
acid, such Al(III), to soft donor atoms (S, Se) can lead to a
change in the acid properties of the metal center in the
complexes obtained, and thus, to an overall modification of
their chemical behavior. Indeed, there is a reduced number of
examples of structurally characterized aluminum complexes
that contain sulfur donor atoms in a chelating ancillary
ligand.14 Moreover, in the case of selenium, such types
of aluminum compounds are extremely rare.15,16 In this
work, we describe the reaction of trialkylaluminum com-
pounds (AlR3, R=Me, iBu) in different molar ratios with 4,5-
bis(diphenylphosphoranyl)-1,2,3-triazole ligands. The struc-
tures obtained include mono- and dinuclear aluminum com-
pounds displaying a noticeable variety of coordination
modes, with Al-E (E=O, S, Se) bonding as their most
important feature. Additionally, theoretical calculations
were performed on the deprotonated forms of the ligands,
as well as on selected complexes.
~
1H NMR (C6D6, 25 °C, ppm): δ 7.60 [m, 8H, (o-C6H5)], 6.80 [m,
12H, (m, p-C6H5)], -0.41 [s, 6H, Al(CH3)2]. 31P NMR (C6D6,
25 °C, ppm): δ 35.5. No 27Al NMR signals were observed.
EI-MS (70 eV): m/z 510 (M+-Me). Anal. Calcd For
C28H26AlN3P2O2 (525.46) C, 64.0; H, 5.0; N, 8.0. Found: C,
64.1; H, 5.2; N, 7.8.
Preparation of [AliBu2{K2-O,O0-[4,5-(P(O)Ph2)2tz]}] (5). A
similar procedure as for 4 was used starting from 1 (0.30 g, 0.64
mmol) in 10 mL of toluene and a 1.0 M solution of AliBu3 (0.65
mL, 0.65 mmol) in toluene. After 2 h of vigorous stirring, all
volatiles were removed under vacuum, and the white solid was
washed with 5 mL of hexanes. Yield (0.27 g, 69%). Mp
~
1
198 °C. IR (KBr, cm-1): v 832 (P-O). H NMR (C6D6, 25 °C,
ppm): δ 7.84 [m, 8H, (o-C6H5)], 6.85 [m, 12H, (m-, p-C6H5)2], 2.05
[m, 2H, CH2CH(CH3)2], 1.11 [d, 3J = 6.3 Hz, 12H, CH2CH-
(CH3)2], 0.31 [d, 3J=7.2 Hz, 4H, CH2CH(CH3)2]. 31P NMR
(C6D6, 25 °C, ppm): δ 37.3. No 27Al NMR signals were observed.
EI-MS (70 eV): m/z 552 (M+-iBu). Anal. Calcd for C34H38AlN3-
P2O2 (609.62): C, 67.0; H, 6.3; N, 6.9. Found: C, 67.2; H, 6.2;
N, 6.6.
Preparation of [AlMe2{K3-N,N0,S-[4,5-(P(S)Ph2)2tz]}(μ-tz)]2
(6). To a suspension of 2 (0.49 g, 0.98 mmol) in 10 mL of tol-
uene was added a 2.0 M solution of AlMe3 in hexanes (0.49 mL,
0.98 mmol) at ambient temperature. Evolution of gas was
observed and after stirring for 2 h, the volatiles were removed
under vacuum, and the white solid was washed with 10 mL of
hexanes. Yield (0.46 g, 84%). Mp 168-170 °C (dec). IR (KBr,
cm-1): v~ 681(P=S), 654 (P-S). 1H NMR (C6D6, 25 °C, ppm):
δ 7.85 [m, 8H, (o-C6H5)], 6.95 [m, 12H, (m-,p-C6H5)], -0.12 [m,
6H, Al(CH3)2]. 31P NMR (C6D6, 25 °C, ppm): δ 28.3 (P=S),
37.0 (P-S(Al)). No 27Al NMR signals were observed. EI-MS
(70 eV): m/z 1084 (M+-2Me). Anal. Calcd for C56H52-
Al2N6P4S4 (1115.17): C, 60.3; H, 4.7; N, 7.5. Found: C, 60.1;
H, 4.5; N, 7.2.
Experimental Section
General Comments. All reactions and handling of reagents
were performed under an atmosphere of dry nitrogen using
standard Schlenk techniques and a glovebox. All glassware was
oven-dried at 140 °C for at least 24 h, assembled hot under
a stream of nitrogen prior to use. Toluene, hexanes, pentane,
and tetrahydrofuran (Na/benzophenone ketyl) were dried
and distilled prior to use. A 2.0 M solution of AlMe3 in
hexanes was purchased from Aldrich, and a 1.0 M solution
of AliBu3 in toluene was prepared from neat AliBu3 (Aldrich).
Preparation of [AliBu2{K3-N,N0,S-[4,5-(P(S)Ph2)2tz)}(μ-tz)]2
(7). A similar procedure as for 6 was used starting from 2 (0.56 g,
1.08 mmol) in 10 mL of toluene and a 1.0 M solution of AliBu3
(1.10 mL, 1.10 mmol) in toluene. After 2 h of stirring, all
volatiles were removed under vacuum, and the white solid was
washed with 10 mL of hexanes. Yield (0.51 g, 72%). Mp 198 °C.
(12) Rheingold, A. L.; Liable-Sands, L. M.; Trofimenko, S. Angew.
Chem., Int. Ed. 2000, 39, 3321–3324.
(13) Rheingold, A. L.; Liable-Sands, L. M.; Trofimenko, S. Inorg. Chim.
Acta 2002, 303, 38–43.
IR (KBr, cm-1): v 668 (P=S), 640 (P-S). 1H NMR (C6D6,
~
(14) (a) Haagenson, D. C.; Moser, D. F.; Stahl, L.; Staples, R. J. Inorg.
Chem. 2002, 41, 1245–1253. (b) McMahon, C. N.; Francis, J. A.; Bott, S. G.;
Barron, A. R. J. Chem. Soc., Dalton Trans. 1999, 67–72. (c) Coles, M. P.;
Swenson, D. C.; Jordan, R. F.; Young, V. G.Jr. Organometallics 1998, 17,
4042–4048. (d) Kang, Y.; Yang, N.; Kang, S. O.; Ko, J.; Lee, C. -H.; Lee, Y.-
H. Organometallics 1997, 16, 5522–5527.
25 °C, ppm): δ 7.75 [m, 8H, (o-C6H5)], 6.85 [m, 12H, (m-,
(17) Trofimenko, S.; Rheingold, A. L.; Incarvito, C. D. Angew. Chem.,
Int. Ed. 2003, 42, 3506–3509.
(18) (a) Charrier, C.; Chadokiewicz, W.; Cadiot, P. Bull. Soc. Chim. Fr.
1966, 1002–1011. (b) Hartmann, V. H.; Beermann, C.; Czempik, H. Z.
Anorg. Allg. Chem. 1956, 46, 261–272.
(15) Han, H.; Johnson, S. A. Organometallics 2006, 25, 5594–5602.
(16) Briand, G. G.; Chivers, T.; Krahn, M.; Parvez, M. Inorg. Chem. 2002,
41, 6808–6815.

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Alcantara-Garcıa et al.
5876 Inorganic Chemistry, Vol. 48, No. 13, 2009
3
p-C6H5)], 2.09 [m, 2H, CH2CH(CH3)2], 1.09 [d, J = 6.6 Hz,
12H, CH2CH(CH3)2], 0.59 [d, 3J=6.9 Hz, 4H, CH2CH(CH3)2].
31P NMR (C6D6, 25 °C, ppm): δ 27.5 (P=S), 38.1 (P-S(Al)).
27Al NMR (C6D6, 25 °C, ppm): δ 31 (s, ω1/2=130 Hz). EI-MS
(70 eV): 584 [(1/2M+)-iBu]. Anal. Calcd for C68H76Al2N6-
P4S4 (1283.49): C, 63.6; H, 6.0; N, 6.5. Found: C, 63.9; H, 6.2;
N, 6.8.
552 (M+-AliBu3-iBu). Anal. Calcd for C46H65Al2N3O2P2
(807.95): C, 68.4; H, 8.1; N, 5.2. Found: C, 68.3; H, 8.0; N, 4.8.
Preparation of [AlMe2{K2-N,S-[4,5-(P(S)Ph2)2tz]}-(N0-Al-
Me3)] (12). To a suspension of 2 (0.42 g, 0.84 mmol) in
10 mL of toluene was added a 2.0 M solution of AlMe3 in
hexanes (0.84 mL, 1.68 mmol) at ambient temperature. Evolu-
tion of gas was observed, and after 2 h of stirring, all volatiles
were removed under vacuum and the white solid obtained was
washed with 10 mL of hexanes. Yield (0.36 g, 68%). Mp 303-
305 °C (dec). IR (KBr, cm-1): v~683 (P=S), 642 (P-S). 1H NMR
(C6D6, 25 °C, ppm): δ 7.67, 7.50 [m, 8H, (o-C6H5)], 6.87, 6.68 [m,
12H, (m-,p-C6H5)], -0.20 [s, 6H, Al(CH3)2 ], -0.31 [s, 9H, Al-
(CH3)3]. 31P NMR (C6D6, 25 °C, ppm): δ 27.5 (P=S), 36.5 (P-S
(Al)). 27Al NMR (C6D6, 25 °C, ppm): δ 154 (br s), 165 (br s). EI-
MS (70 eV): m/z 542 (M+-AlMe3-Me). Anal. Calcd for
C31H35Al2N3P2S2 (629.67): C, 59.1; H, 5.6; N, 6.7. Found: C,
59.2; H, 5.8; N, 6.5.
Preparation of [AlMe2{K2-N,Se-[4,5-(P(Se)Ph2)2tz]}] (8). To
a suspension of 3 (0.42 g, 0.70 mmol) in 10 mL of toluene
was added a 2.0 M solution of AlMe3 in hexanes (0.36 mL,
0.72 mmol) at ambient temperature. After 2 h of vigorous
stirring, all of the volatiles were removed under vacuum, and a
white solid was precipitated with 10 mL of hexanes and then
filtered and dried under vacuum. Yield (0.40 g, 87%). Mp 127-
128 °C. IR (KBr/cm-1): v 601 (P=Se), 564 (P-Se). H NMR
1
~
(C6D6, 25 °C, ppm): δ 7.80 [m, 8H, (o-C6H5)], 6.77 [m, 12H, (m-,
p-C6H5)], -0.18 [m, 6H, Al(CH3)2]. 31P NMR (C6D6, 25 °C,
=
ppm): δ 21.9 (1JP-Se = -750 Hz) (P=Se), 23.5 (1JP-Se
Preparation of [AliBu2{K2-N,S-[4,5-(P(S)Ph2)2tz]}-(N0-Ali-
Bu3)] (13). A similar procedure as for 12 was used starting from
2 (0.35 g, 0.70 mmol) in 10 mL of toluene and a 1.0 M solution of
AliBu3 (1.40 mL, 1.40 mmol) in toluene. After 2 h of vigorous
stirring, volatiles were removed under vacuum, and the white
solid was washed with 10 mL of hexanes. Yield (0.51 g, 86%).
-594 Hz) (P-Se(Al)). 27Al NMR (C6D6, 25 °C, ppm): δ 165
(br s, ω1/2=3130 Hz). 77Se NMR (C6D6, 25 °C, ppm): δ -91.9
1
1
(d, JSe-P=-594 Hz) (Se-Al), -244.9 (d, JSe-P=-750 Hz)
(P-Se(Al)). EI-MS (70 eV): m/z 636 (M+-Me). Anal. Calcd for
C26H26AlN3P2Se2 (651.38): C, 51.6; H, 4.0; N, 6.4. Found: C,
51.4; H, 4.2; N, 6.3.
Mp 274-277 °C (dec). IR (KBr, cm-1): v 661(P=S), 634 (P-S).
~
Preparation of [Al{K2-N,Se-[4,5-(P(Se)Ph2)2tz]}3] (9). A simi-
lar procedure as for 8 was used starting from 3 (0.44 g, 0.74
mmol) in 10 mL of toluene and a 1.0 M solution of AliBu3 (0.75
mL, 0.75 mmol) in toluene. After stirring vigorously for 2 h, all
volatiles were removed under vacuum, and the white solid was
washed with 8 mL of hexanes. Yield (0.43 g, 98%). Mp 273-278
°C (dec). IR (KBr, cm-1): v~ 611 (P=Se), 537 (P-Se). 1H NMR
(C6D6, 25 °C, ppm): δ 7.8-8.1 [m, 60H, o-, m-, p-(C6H5)]. 31P
NMR (C6D6, 25 °C, ppm): δ 18.3 (1JP-Se=-749 Hz) (P=Se),
19.4 (1JP-Se=-562 Hz) (P-Se(Al)). 27Al NMR (C6D6, 25 °C,
ppm): δ 15 (s, ω1/2=45 Hz). 77Se NMR (C6D6, 25 °C, ppm): δ -
86.5 (d, 1JSe-P=-562 Hz) (Se-Al), -243 (d, 1JSe-P = -749 Hz)
(SedP). EI-MS (70 eV): m/z 955 (C40H31AlN6P3Se3). No ele-
mental analysis data was obtained because of the highly sensi-
tive nature of this compound and its extremely pungent odor.
Preparation of [AlMe2{K2-O,O0-[4,5-(P(O)Ph2)2tz]}-(N0-Al-
Me3)] (10). To a suspension of 1 (0.33 g, 0.69 mmol) in
10 mL of toluene was added a 2.0 M solution of AlMe3 in
hexanes (0.70 mL, 1.40 mmol) at ambient temperature. Evolu-
tion of gas was observed, and after 2 h of vigorous stirring, all
volatiles were removed under vacuum and the white solid
obtained was washed with 5 mL of hexanes. Yield (0.34 g,
75%). Mp 184-185 °C. IR (KBr, cm-1): v~ 810 (P-O). 1H
NMR (C6D6, 25 °C, ppm): δ 7.79 [m, 8H, (o-C6H5)], 6.88 [m,
12H, (m-, p-C6H5)], 0.27 [s, 9H, Al(CH3)3], 0.33 ppm [s, 6H, Al-
(CH3)2]. 31P NMR (C6D6, 25 °C, ppm): δ 36.9. No 27Al NMR
signals were observed; EI-MS (70 eV): m/z 510, (M+-AlMe3-
Me). Anal. Calcd for C31H35Al2N3O2P2 (597.55): C, 62.3 H, 5.9;
N, 7.0. Found: C, 61.9; H, 6.2; N, 6.9.
1H NMR (C6D6, 25 °C, ppm): δ 7.67, 6.81 [m, 8H, (o-C6H5)],
7.07 [m, 12H, (m-,p-C6H5)], 3.11 [m br 3H, Al{CH2CH-
(CH3)2}3], 2.09 [m br 2H, Al{CH2CH(CH3)2}2], 0.99 [unre-
solved resonance signal, 30H, Al{CH2CH(CH3)2}3, Al{CH2-
CH(CH3)2}2, 0.18 [unresolved resonance signal, 10H, Al{CH2-
CH(CH3)2}3, Al{CH2CH(CH3)2}2]. 31P NMR (C6D6, 25 °C):
δ 30.8 (P=S), 31.2 (P-S(Al)). No 27Al NMR signals were
observed. EI-MS (70 eV): 584 (M+-AliBu3-iBu). Anal. Calcd
for C46H65Al2N3P2S2 (840.0): C, 65.8 H, 7.8; N, 5.0. Found: C,
65.9; H, 7.6; N, 4.8.
NMR Follow-up for the Formation of 9. NMR samples
were prepared according to the following procedure by dupli-
cate. A 0.10 mL portion of a 1.0 M solution of AliBu3 (0.020 g,
0.100 mmol) in C6D6 was added to a 0.40 mL portion of a 0.25 M
solution of 3 (0.60 g, 0.100 mmol) in C6D6 at 25 °C. The reaction
mixture was followed for 10 h by 1H NMR and by 31P, 27Al, and
77Se NMR spectroscopy in a parallel experiment. 1H NMR
measurements were taken every 10 min for the first 2 h, followed
by one-hour intervals for the next 8 h. The 31P NMR experi-
ments were taken every 30 min for the first 2 h followed by one-
hour intervals for the next 8 h. The 27Al and 77Se NMR
measurements were taken every 2 h for 10 h.
Characterization of Transient [AliBu2{K2-N,Se-[4,5-(P(Se)-
Ph2)2tz]}] in Solution. 1H NMR (C6D6, 25 °C, ppm): δ 7.77
(m, 8 H, o-C6H5), 7.31 (m, 4H, p-C6H5), 7.42 (m, 8H, m-C6H5),
3
1.98 [m, 2H, Al{CH2CH(CH3)2}2], 0.94 [d, J=6.2 Hz, 12H,
Al{CH2CH(CH3)2}2], 0.35 [d, 3J = 6.4 Hz, 4H, Al{CH2CH-
=
(CH3)2}2]. 31P NMR (C6D6, 25 °C, ppm): δ 18.1 (1JP-Se
-766 Hz) (P=Se), 19.6 (1JP-Se = -634 Hz) (P-Se(Al)). No
27Al NMR signals were observed. 77Se NMR (C6D6, 25 °C,
=
Preparation of [AliBu2{K2-O,O0-[4,5-(P(O)Ph2)2tz]}-(N0-Ali-
Bu3)] (11). A similar procedure as for 10 was used starting from
1 (0.30 g, 0.64 mmol) and a 1.0 M solution of AliBu3 (1.30 mL,
1.30 mmol) in toluene. Evolution of gas was observed, and after
stirring for 2 h, all volatiles were removed under vacuum and an
oily product remained. Ten milliliters of pentane were added to
the product, and it was stirred for 1 h, after which the solvent
was decanted and the product was dried under vacuum leaving a
yellow oil. Yield (0.28 g, 96%). IR (KBr, cm-1): v~821 (P-O). 1H
NMR (C6D6, 25 °C, ppm): δ 7.74 [m, 8H, (o-C6H5)], 6.94 [m,
12H, (m-, p -C6H5)], 2.36 [m, 3H, Al{CH2CH(CH3)2}3], 2.00 [m,
2H, Al{CH2CH(CH3)2}2], 1.28 [d, 3J=6.3 Hz, 18H, Al{CH2CH-
(CH3)2}3], 1.16 [d, 3J=6.6 Hz, 12H, Al{CH2CH(CH3)2}2], 1.07
ppm): δ -85.8 (d, 1JSe-P=-634 Hz) (Se-Al), -253.8 (d, 1JSe-P
-766 Hz) (SedP).
Computational Methods. Ab initio calculations at RHF/
3-21G** (for the deprotonated ligands [4,5-(P(O)Ph2)2tz]-(1a),
[4,5-(P(S)Ph2)2tz]-(2a), and [4,5-(P(Se)Ph2)2tz]-(3a)), RHF/
6-31G**(4 and 6) and RHF/LANL2DZ (9) levels of theory were
performed on the selected compounds. All calculations were
carried out with the GAUSSIAN 0319 suite of programs at the
Hartree-Fock level of theory. Natural Bond Orbitals (NBO)20
(19) For a full description of the theoretical methods used and the full
reference for GAUSSIAN 03 suite of programs please see the Supporting
Information.
(20) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899–
926.
3
3
[d, J=6.9 Hz 4H, Al{CH2CH(CH3)2}2], 0.77 [d, J=6.6 Hz,
6H, Al{CH2CH(CH3)2}3]. 31P NMR (C6D6, 25 °C, ppm): δ 36.3.
No 27Al NMR signals were observed. EI-MS (70 eV): m/z

Article
Inorganic Chemistry, Vol. 48, No. 13, 2009 5877
Table 1. Crystal Data and Structure Refinement for Compounds 4a, 6, 7, 9, 10, and 12
compound
4a
6 toluene
7 2 toluene
9 toluene
10c
12
3
3
3
formula
fw
C
28H26AlN3-
O2P2
C63H60Al2N6-
P4S4
1207.25
orthorhombic
Pca21
C82H92Al2-
N6P4S4
1467.70
triclinic
P1
C85H68AlN9-
P6Se6
1902.04
triclinic
P1
C60.81H66.44Al4-
Cl1.19N6O4P4
1219.23
orthorhombic
Pca21
100(2)
C31H35Al2N3-
P2S2
629.64
triclinic
P1
173(2)
0.71073
8.159(2)
12.158(3)
18.367(3)
95.56(2)
96.66(3)
104.70(3)
1735.2(7)
2
525.44
triclinic
P1
173(2)
0.71073
8.765(2)
11.598(2)
14.047(4)
102.35(3)
100.14(3)
104.43(2)
1311(1)
crystal system
space group
temp, K
173(2)
173(2)
0.71073
173(2)
0.71073
˚
λ, A
0.71073
20.329(4)
17.450(3)
17.352(3)
90
90
90
6156(2)
4
1.303
0.71073
˚
a, A
9.656(2)
14.175(2)
15.895(3)
64.44(2)
85.80(3)
88.35(3)
1957.4(7)
1
16.048(2)
16.886(2)
18.437(3)
115.85(2)
90.51(2)
112.88(2)
4045(2)
2
1.561
2.894
1896
18.963(3)
18.529(2)
17.960(2)
90
90
90
6311(1)
4
1.283
0.276
2550
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Ζ
F
2
1.331
0.231
548
calcld., g cm-3
1.245
0.273
1.205
0.320
3
μ, mm-3
F(000)
0.332
2520
776
0.30 ꢀ 0.20 ꢀ
660
0.35 ꢀ 0.11 ꢀ
crystal size, mm3
0.32 ꢀ 0.18 ꢀ
0.35 ꢀ 0.27 ꢀ
0.23 ꢀ 0.09 ꢀ
0.52 ꢀ 0.44 ꢀ
0.03
0.27
0.14
0.06
0.15
0.06
θ range for data collection, deg
index ranges
1.53 to 25.51
-10 e h e 10
-13 e k e 13
-16 e l e 16
13491
1.17 to 25.37
-24 e h e 24
-21 e k e 20
-20 e l e 20
50062
1.59 to 25.03
-11 e h e 11
-16 e k e 16
-18 e l e 18
20318
1.68 to 25.39
-19 e h e 19
-20 e k e 20
-22 e l e 22
55802
1.54 to 25.36
-22 e h e 22
-22 e k e 20
-21 e l e 16
24992
1.13 to 25.05
-9 e h e 9
-14 e k e 14
-21 e l e 21
14139
no. of reflns collected
no. of indep. reflns (Rint
no. of data/restraints/
parameters
)
4827 (0.0372)
4827/0 /327
11286 (0.0657)
11286/352/780
6887 (0.0564)
6887/381/548
14792 (0.0473)
14792/ 653/1074
10366 (0.0631)
10366/30/727
6098 (0.0343)
6098/0/366
GoF on F2
1.052
0.0490, 0.1102
0.0612, 0.1158
1.024
1.022
0.0480, 0.1094
0.0678, 0.1192
1.036
0.0394, 0.0968
0.0543, 0.1044
0.999
1.033
0.0458, 0.1093
0.0614, 0.1172
R1,awR2b (I > 2σ(I))
R1,awR2b (all data)
abs. struct. par.
0.0412, 0.0901
0.0468, 0.0932
-0.03(5)
0.0534, 0.1082
0.0693, 0.1156
0.08(8)
-3
˚
largest diff. peak/hole, e A
0.462/-0.249
0.409/-0.187
0.339/-0.255
1.440/-0.611
0.779/-0.375
0.380/-0.258
3
P
P
P
P
a R1 =
Fo| - |Fc
/
|Fo|. b wR2 = [ w(Fo2 - Fc2)2/ (Fo2)2]1/2. c Although there are two independent molecules in the asymmetric unit, they have
different content of chlorine (0.52 and 0.65, for details see the text), and thus, formula, fw, Z, and F(000) are reported for the sum of both molecules; thus
the real Z is 8.
analyses were performed on the optimized wave functions to
assess the electronic density distribution in a localized manner
over all the molecules considered. A frequencies analysis was
carried out after every geometry optimization to assert the
presence of a minimum on the potential energy surface. No
imaginary frequencies were found for any of the compounds
studied herein. All graphics were generated using the Molekul
visualization package.21
Information, Table S1 (1, 4b). Selected interatomic distances
and angles for all the compounds are provided in Tables 2 (4a,
6, 7, 9, 10, and 12) and Supporting Information, Tables S2-S4
(1, 4b).
Results and Discussion
Equimolar Reactions. Compounds 4- 9 were synthe-
sized in a straightforward manner by addition of trialk-
ylaluminum compounds to the corresponding 4,5-(P(E)-
Ph2)2tzH [E = O (1), S (2), Se (3); tz = 1,2,3-triazole]
ligands at ambient temperature (Scheme 1). All com-
pounds are air and moisture-sensitive and readily soluble
at ambient temperature in most common organic solvents
(toluene, benzene, CH2Cl2, diethylether, THF, etc.) but
insoluble in pentane and hexanes.
X-ray Crystallography. Single crystals were removed from
Schlenk flasks under a stream of nitrogen and immediately
covered with a thin layer of hydrocarbon oil. A suitable crystal
was selected, attached to a nylon loop, and quickly placed in a
low temperature stream of nitrogen. The diffraction data for
all the compounds were collected on a Bruker-APEX three-
˚
circle diffractometer using MoKR radiation (λ = 0.71073 A)
at 173 or 100 K. The structures were solved by direct methods
(SHELXS-97)22 and refined against all the data by full-matrix
least-squares on F2 using SHELXL-97.23 The hydrogen atoms
of C-H bonds were placed in idealized positions and refined
isotropically with a riding model. The non-hydrogen atoms
were refined anisotropically. The hydrogen atom attached
to the nitrogen atom in 1 was located from the difference
electron density map and refined with Uij tied to the parent
atom. Crystallographic data and refinement details are sum-
marized in Table 1 (4a, 6, 7, 9, 10, and 12) and in Supporting
Reaction of 4,5-(P(O)Ph2)2tzH (1) with AlMe3 and
AliBu3 yielded compounds 4 and 5, respectively; both
compounds are highly soluble in toluene and were recrys-
tallized from a mixture of toluene/hexane. The mass
spectra for 4 and 5 reveal the peaks corresponding
i
to the loss of one alkyl group [M+- R] (R=Me, Bu).
1
The H NMR spectra for these compounds show the
characteristic pattern owing to the deprotonated ligand
along with the signals corresponding to the alkyl groups
attached to the aluminum atoms. Examination of these
compounds by 31P NMR shows single signals corre-
sponding to a symmetric coordination, thus suggesting
the formation of a seven-membered ring system (I). The
::
::
(21) Flukiger, P.; Luthi, H. P.; Portmann, S.; Weber, J. MOLEKEL 4.3;
Swiss Center for Scientific Computing: Manno, Switzerland, 2000.
(22) SHELXS-97, Program for Structure Solution; Sheldrick, G. M. Acta
Crystallogr. 1990, A46, 467-473.
(23) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Re-
finement; Universitat Gottingen: Gottingen, Germany, 1997.
::
::
::

ꢀ
Alcantara-Garcıa et al.
5878 Inorganic Chemistry, Vol. 48, No. 13, 2009
˚
Table 2. Selected Bond Lengths (A) and Angles (deg) for Compounds 4a, 6, 7, 9, 10, and 12
Compound 4a (triclinic)
Compound 10
1.830(3) Al(3)-O(3)
Al(1)-O(1)
Al(1)-O(2)
Al(1)-C(27)
Al(1)-C(28)
P(1)-O(1)
1.817(2)
1.808(2)
1.948(3)
1.946(3)
1.522(2)
1.514(2)
143.2(1)
Al(1)-O(2)-P(2)
O(1)-Al(1)-O(2)
O(1)-Al(1)-C(27)
O(2)-Al(1)-C(27)
O(1)-Al(1)-C(28)
O(2)-Al(1)-C(28)
C(28)-Al(1)-C(27)
143.8(1)
99.0(1)
molecule a
molecule b
Al(1)-O(1)
Al(1)-O(2)
Al(2)-N(2)
1.826(3)
1.819(3)
2.000(3)
1.939(5)
1.948(4)
111.1(1)
106.6(1)
108.5(1)
110.5(1)
119.3(1)
1.850(3)
1.964(3)
1.931(5)
1.938(4)
1.937(4)
1.991(4)
Al(3)-O(4)
Al(4)-N(5)
Al(3)-C(58)
Al(3)-C(59)
Al(1)-C(27)
Al(1)-C(28)
P(2)-O(2)
Al(1)-O(1)-P(1)
Al(2)-C(29)
Al(4)-C(60)
1.945(4)
1.998(4)
Al(2)-C(30)
Al(4)-C(61)
Compound 6 toluene
3
Al(1)-S(1)
2.652(1)
1.997(2)
2.147(2)
1.964(3)
1.951(3)
1.972(1)
1.938(1)
94.5(1)
Al(2)-S(3)
2.736(1)
1.988(2)
2.101(2)
1.946(3)
1.970(3)
1.966(1)
1.940(1)
93.4(1)
Al(2)-C(31)
Al(2)-Cl(1)
1.975(4)
2.129(2)
1.513(3)
1.507(3)
136.2(2)
137.0(2)
98.6(1)
107.7(1)
109.2(2)
107.5(2)
111.5(2)
120.2(2)
103.4(2)
101.0(2)
105.0(2)
104.8(1)
114.5(2)
Al(4)-C(62)
1.949(4)
2.148(2)
1.510(3)
1.516(3)
142.6(2)
140.9(2)
98.1(2)
Al(1)-N(1)
Al(2)-N(4)
Al(4)-Cl(2)
Al(1)-N(5)
Al(2)-N(2)
P(1)-O(1)
P(3)-O(3)
P(4)-O(4)
Al(1)-C(27)
Al(2)-C(55)
P(2)-O(2)
Al(1)-C(28)
Al(2)-C(56)
Al(1)-O(1)-P(1)
Al(1)-O(2)-P(2)
O(1)-Al(1)-O(2)
O(1)-Al(1)-C(27)
O(1)-Al(1)-C(28)
O(2)-Al(1)-C(27)
O(2)-Al(1)-C(28)
C(27)-Al(1)-C(28)
N(2)-Al(2)-C(29)
N(2)-Al(2)-C(30)
N(2)-Al(2)-C(31)
Cl(1)-Al(2)-N(2)
Cl(1)-Al(2)-C(29)
Al(3)-O(3)-P(3)
Al(3)-O(4)-P(4)
O(3)-Al(3)-O(4)
O(3)-Al(3)-C(58)
O(3)-Al(3)-C(59)
O(4)-Al(3)-C(58)
O(4)-Al(3)-C(59)
C(58)-Al(3)-C(59)
N(5)-Al(4)-C(60)
N(5)-Al(4)-C(61)
N(5)-Al(4)-C(62)
Cl(2)-Al(4)-N(5)
Cl(2)-Al(4)-C(60)
P(1)-S(1)
P(3)-S(3)
P(2)-S(2)
P(4)-S(4)
Al(1)-S(1)-P(1)
S(1)-Al(1)-N(1)
S(1)-Al(1)-N(5)
N(1)-Al(1)-N(5)
S(1)-Al(1)-C(27)
S(1)-Al(1)-C(28)
N(1)-Al(1)-C(27)
N(1)-Al(1)-C(28)
N(5)-Al(1)-C(27)
N(5)-Al(1)-C(28)
C(27)-Al(1)-C(28)
Al(2)-S(3)-P(3)
S(3)-Al(2)-N(4)
S(3)-Al(2)-N(2)
N(2)-Al(2)-N(4)
S(3)-Al(2)-C(55)
S(3)-Al(2)-C(56)
N(4)-Al(2)-C(55)
N(4)-Al(2)-C(56)
N(2)-Al(2)-C(55)
N(2)-Al(2)-C(56)
C(55)-Al(2)-C(56)
110.8(2)
105.6(2)
107.3(2)
108.7(2)
123.5(2)
102.5(2)
99.2(2)
106.3(2)
102.8(1)
112.9(1)
82.4(1)
80.8(1)
168.4(1)
88.3(1)
88.1(1)
166.6(1)
89.7(1)
93.4(1)
92.8(1)
85.4(1)
117.3(1)
112.4(1)
90.0(1)
97.2(1)
130.0(2)
111.9(1)
120.6(1)
99.0(1)
91.4(1)
126.4(2)
Cl(1)-Al(2)-C(31)
110.6(1)
114.6(2)
Cl(2)-Al(4)-C(62)
112.4(2)
114.0(2)
C(29)-Al(2)-C(30)
C(60)-Al(4)-C(61)
Compound 7 2toluene
3
Al(1)-S(1)
2.739(1)
1.996(2)
2.138(2)
1.968(3)
1.971(3)
1.960(1)
1.940(1)
92.7(1)
S(1)-Al(1)-N(2)#1
170.7(1)
91.1(1)
93.4(1)
87.0(3)
110.9(1)
117.3(2)
94.8(1)
90.8(3)
131.3(2)
C(29)-Al(2)-C(31)
C(30)-Al(2)-C(31)
117.1(2)
113.3(2)
C(60)-Al(4)-C(62)
C(61)-Al(4)-C(62)
118.0(2)
113.8(2)
Al(1)-N(1)
N(1)-Al(1)-N(2)#1
S(1) -Al(1)-C(27)
S(1)-Al(1)-C(31)
N(1)-Al(1)-C(27)
N(1)-Al(1)-C(31)
N(2)#1-Al(1)-C(27)
N(2)#1-Al(1)-C(31)
C(27)-Al(1)-C(31)
Al(1)-N(2)#1
Al(1)-C(27)
Al(1)-C(31)
P(1)-S(1)
P(2)-S(2)
Al(1)-S(1)-P(1)
S(1)-Al(1)-N(1)
Compound 12
Al(1)-S(1)
Al(1)-N(1)
Al(2)-N(2)
Al(1)-C(27)
Al(1)-C(28)
Al(2)-C(29)
Al(2)-C(30)
2.382(1)
1.994(2)
2.055(2)
1.940(3)
1.938(3)
1.968(3)
1.960(3)
S(1)-Al(1)-C(27)
S(1)-Al(1)-C(28)
N(1)-Al(1)-C(27)
N(1)-Al(1)-C(28)
C(27)-Al(1)-C(28)
N(2)-Al(2)-C(29)
N(2)-Al(2)-C(30)
109.1(1)
103.8(1)
110.3(1)
112.4(1)
125.5(2)
104.4(1)
103.2(1)
82.0(1)
Compound 9 toluene
3
Al(1)-Se(1)
Al(1)-Se(3)
Al(1)-Se(5)
P(1)-Se(1)
2.557(1)
2.559(1)
2.539(1)
2.150(1)
2.096(1)
2.161(1)
2.100(1)
2.157(1)
2.100(1)
1.981(3)
1.978(3)
1.966(3)
95.0(1)
Se(1)-Al(1)-Se(3)
89.5(1)
87.9(1)
85.8(1)
88.7(1)
178.3(1)
91.8(1)
90.5(1)
89.0(1)
175.4(1)
175.0(1)
92.7(1)
89.8(1)
89.8(1)
90.6(1)
Al(2)-C(31)
P(1)-S(1)
1.954(3)
2.004(1)
1.939(1)
94.2(1)
N(2)-Al(2)-C(31)
C(29)-Al(2)-C(30)
C(29)-Al(2)-C(31)
C(30)-Al(2)-C(31)
100.6(1)
117.1(2)
115.1(2)
113.6(2)
Se(1)-Al(1)-Se(5)
Se(3)-Al(1)-Se(5)
Se(1)-Al(1)-N(1)
Se(1)-Al(1)-N(4)
Se(1)-Al(1)-N(7)
Se(3)-Al(1)-N(1)
Se(3)-Al(1)-N(4)
Se(3)-Al(1)-N(7)
Se(5)-Al(1)-N(1)
Se(5)-Al(1)-N(4)
Se(5)-Al(1)-N(7)
N(7)-Al(1)-N(4)
N(1)-Al(1)-N(4)
P(2)-S(2)
P(1)-S(1)-Al(1)
S(1)-Al(1)-N(1)
P(2)-Se(2)
89.2(1)
P(3)-Se(3)
P(4)-Se(4)
P(5)-Se(5)
P(6)-Se(6)
Al(1)-N(1)
Al(1)-N(4)
Al(1)-N(7)
Al(1)-Se(1)-P(1)
Al(1)-Se(3)-P(3)
94.2(1)
#1 2 - x, 1 - y, -z.
Scheme 1. Preparation of Compounds 4-8

Article
Inorganic Chemistry, Vol. 48, No. 13, 2009 5879
Figure 3.
Figure 2. Perspectiveviewof4a(triclinic)withthermalellipsoidsat50%
probability. All hydrogen atoms are omitted for clarity.
signals of the 27Al NMR spectra appear to be too broad
for observation. However, crystals of two polymorphic
forms of 4, suitable for X-ray diffraction studies, were
obtained when allowing a saturated toluene solution
to slowly cool from 80 °C to ambient temperature
(4a, triclinic P1) or crystallized at -30 °C, (4b, monoclinic
P21/c). In both polymorphs there is one molecule in the
asymmetric unit. The conformations of both seven mem-
bered-rings in these polymorphs are nearly identical
(Supporting Information, Figure S1) and thus only the
data for 4a will be discussed, as they have better quality.
The molecular structure of 4a reveals a non-planar seven-
Figure 4. Perspective view of 6 with thermal ellipsoids at 50% prob-
ability. All hydrogen atoms are omitted for clarity.
˚
membered ring (mean deviation from the plane = 0.16 A)
(Figure 2). The geometry around the metal center corre-
sponds to a distorted tetrahedron; the Al-O bond dis-
tances (1.817(2) and 1.808(2) A) are within the normal
˚
values for Al-O(P) bond lengths for tetracoordinate
aluminum atoms.24
It is noteworthy that during the isolation of 4 and 5,
we obtained a polymorph form of the ligand 1 (Support-
ing Information, Figure S3). The crystal structure of
1 exhibits two molecules bounded by two intermolecu-
lar hydrogen interactions N-H O (IV, Figure 3), as
3 3 3
opposed to the molecular structure reported previously
by Trofimenko (V).12 The protropic behavior of 1 (IV and
V) is also observed in solution and is strongly depen-
dent on the solvent used. Thus, the 31P NMR spectrum of
1 shows two signals in CDCl3, while in (CD3)2CO only
one signal is observed.
Reaction of 4,5-(P(S)Ph2)2tzH (2) with AlMe3 and
AliBu3 gave the dimeric compounds 6 and 7, respectively
(Scheme 1). The H NMR spectra of 6 and 7 exhibit
1
Figure 5. Perspective view of 7 with thermal ellipsoids at 50% prob-
ability. All hydrogen atoms, and carbon atoms from the phenyl groups,
except the ipso, are omitted for clarity.
signals assigned to the PPh2 moieties and to the aluminum
alkyl groups. In addition, the 31P NMR spectra exhibit
for 6 and 7 doublets signals for each compound. The 27Al
NMR spectrum of 7 shows a broad signal at δ 31 ppm,
corresponding to a pentacoordinate aluminum atom.
However, in the case of 6, the signal appears to be too
broad for observation. The spectroscopic data suggest
the existence of dimeric-like metallacycles compris-
ing asymmetric coordination modes to the ligand (III).
Furthermore, the composition of these compounds was
unequivocally established by X-ray diffraction studies.
Single crystals of 6 and 7 were obtained from their
saturated toluene solutions at ambient temperature.
Compound 6 crystallizes in the orthorhombic system,
space group Pca21 with one molecule of 6 and one
molecule of toluene in the asymmetric unit, while 7
crystallizes in the triclinic system, space group P1 with
one-half of the molecule of 7 and one molecule of toluene
in the asymmetric unit (Figures 4 and 5).
(24) For a full account of Al-O(P) bond lengths see the Al-O(P) bond
length histogram for tetracoordinate Al atoms from CCDC in the Support-
ing Information, Figure S2.

ꢀ
Alcantara-Garcıa et al.
5880 Inorganic Chemistry, Vol. 48, No. 13, 2009
Scheme 2. Formation of 9
The molecular structures of 6 and 7 exhibit dimeric-like
arrangements achieved through bridging triazole groups.
The metal centers coordinate to the sulfur and nitrogen
atoms of one ligand moiety, as well as to the central
nitrogen atom of a second ligand moiety. This coordina-
tion mode results in the formation of five fused hetero-
cycles with a central Al2N4 core. The Al2N4 core is non-
moiety. The 31P NMR spectrum displays two signals at
δ 21.9 and 23.5, indicating two different phosphorus
environments. While the 27Al NMR spectrum displays a
broad signal at δ 165 (ω1/2 = 3130 Hz), which suggests
a tetracoordinate aluminum atom in solution. Further-
more, the 77Se NMR spectrum exhibits two double signals
at δ -91.9 (1JSe-P = -594 Hz) and -244.9 ppm (1JSe-P
=
˚
planar for 6 (mean deviation = 0.22 A) and considered
˚
planar for 7 (mean deviation = 0.08 A). Moreover, the
-750 Hz). The difference between the chemical shifts and
coupling constants of these signals clearly denotes the
coordination of one selenium atom to the aluminum
center. Finally, the mass spectra of 8 shows the peak with
the highestm/z at 636, assignedtothe fragment [M+-Me],
which indicates a coordination mode corresponding to II.
On the other hand, the reaction of 4,5-(P(Se)Ph2)2tzH
(3) with AliBu3 in a 1:1 ratio gave the trischelate 9 in
a quantitative yield (98% on the basis of the mmol of
3 present). The reaction was repeated at ambient tem-
perature in a 3:1 (ligand/metal) ratio, to examine if
the formation of the trischelate could be optimized.
However, only free ligand and an inseparable mixture
of products containing 9 were observed. Accordingly, the
formation of 9, starting from 3 and AliBu3, was followed
by NMR experiments (1H, 31P and 27Al), and the alumi-
num monochelate [AliBu2{κ2-N, Se-[4,5-(P(Se)Ph2)2tz]}]
was identified as a transient product. Indeed, upon gentle
heating (50 °C) of the monochelate, a rapid conversion to
9 was observed along with the formation of AliBu3, thus
confirming the mechanism proposed in Scheme 2. As
mentioned earlier, aluminum compounds bearing multi-
dentate ligands with selenium donor atoms are extremely
scarce, to such a degree that 9 is to our knowledge the first
example of a structurally characterized hexacoordinate
aluminum compound bearing a Al-Se bond. Surpris-
ingly, even pentacoordinate aluminum compounds bear-
ing Al-Se bonds are unknown.
Al2N4 six-membered ring in 6 shows a twisted conforma-
tion with an angle of 26.9° between the planes defined
by Al(1)-N(1)-N(2) and Al(2)-N(4)-N(5). With the
exception of the Al2N4 ring conformation, the structural
traits in 6 and 7 are closely related. The aluminum centers
in these two compounds are in distorted trigonal-bipyr-
amid environments with the sulfur atom and the central
nitrogen atoms from a second triazole moiety occupying
the axial positions. The equatorial Al-N bond distances
˚
˚
(1.988(2) and 1.997(2) A for 6 and 1.996(2) A for 7) are
comparable to the values observed in similar aluminum
complexes bearing Al2N4 rings.7-10 The axial Al-N bond
˚
distances with 2.101(2) and 2.147(2) A for 6 and
˚
2.138(2) A for 7 are significantly longer than those of
the above-mentioned Al2N4 compounds. The Al-S bond
˚
˚
lengths, with 2.652(1) and 2.736(1) A for 6 and 2.739(1) A
for 7, are comparable with those observed in the penta-
coordinate aluminum compounds:25 [MeAl(xytbmp),
(xytbmp = o-xylylenedithio-bis(6-tBu-4-methylphenol)]
26
(2.621(1) A), [(MeAl)2(μ-tbop), tbop=2,20-thiobis {4-
˚
(1,1,3,3-tetramethylbutyl)phenolato}] (2.675(2) A)27 and
˚
˚
[R2Al(μ-OC6H4-2-SMe)]2 [R=Me (av. 2.738(5) A), R=
iBu (2.778(1))].28
The equimolar reactions of 4,5-(P(Se)Ph2)2tzH (3) with
aluminum alkyls gave compounds with different coordina-
tion behavior (Scheme 2). The reaction of 3 with AlMe3
yielded the monomeric compound 8. The structural arr-
angement of 8 in solution was determined on the basis of its
1H, 31P, 27Al, and 77Se NMR data. The 1H NMR spectrum
shows the pattern corresponding to the deprotonated
ligand, along with the high-field signal owing to the AlMe2
Compound 9 is highly soluble in toluene and extremely
air- and moisture-sensitive with a strong pungent odor.
Yellowish twinned crystals of 9 were obtained from a
saturated toluene solution at ambient temperature. Com-
pound 9 crystallizes in a triclinic, space group P1 with one
molecule of 9 and one molecule of toluene in the asym-
metric unit (Figure 6).
(25) For a full account of Al-S bond lengths see the Al-S bond length
histogram for pentacoordinate Al atoms from CCDC in Supporting In-
formation, Figure S4.
(26) Ma, H.; Melillo, G.; Oliva, L.; Spaniol, T. P.; Englert, U.; Okuda, J.
Dalton Trans. 2005, 721–727.
(27) Janas, Z.; Jerzykiewicz, L. B.; Sobota, P.; Szczegot, K.; Wioeniewska,
D. Organometallics 2005, 24, 3987–3994.
(28) Hendershot, D. G.; Barber, M.; Kumar, R.; Oliver, J. P. Organome-
The aluminum center in 9 displays an octahedral
geometry with slightly distorted “trans” angles N-Al-
Se (175.0(1), 175.4(1) and 178.3(1)°). The Al-N bond
˚
lengths in 9 (1.981(3), 1.978(3), 1.966(3) A) are the
shortest observed for the compounds in this study. More-
over, the relatively short Al-Se bond lengths (2.557(1),
2.559(1), 2.539(1) A) present in this hexacoordinate
˚
tallics 1991, 10, 3302–3309.

Article
Inorganic Chemistry, Vol. 48, No. 13, 2009 5881
Figure 7. Perspective view of molecule a of 10 with thermal ellipsoids at
50% probability. All hydrogen atoms are omitted for clarity.
Scheme 3. Preparation of Compounds 10-13
Figure 6. Perspective view of 9 with thermal ellipsoids at 50% prob-
ability. Carbonatoms fromthe phenylgroups, excepttheipso, areomitted
for clarity.
aluminum compound are comparable to those observed
in the tetracoordinate aluminum complexes Me2Al[PhP-
t
t
(Se)(N Bu)(NH Bu)], (2.510(1) and 2.187(1) A)
15
˚
and
(Me2Al)3[P(CH2NPh)2Se]2(AlMe3) (2.510(1) and 2.239-
16
˚
(2)A). Furthermore, the three five-membered C-P-
Se-Al-N heterocycles display planar arrangements
(mean deviation from the plane = 0.04 A), with angles
˚
tion of the ligand with its hydrochloride salt.29 Com-
pound 10 exhibits two tetracoordinate aluminum atoms
with different coordination environments. The aluminum
atom from the AlMe2 moiety is coordinated to both
oxygen atoms while the second aluminum atom from
the AlMe3 group coordinates through a dative bond to
the central nitrogen atom from the triazole ring. The
seven-membered ring displays a mean deviation from
of 2.8, 11.0, and 11.1° between the planes defined by the
C-P-Se-Al-N heterocycles and the triazole rings.
Excess Ratio Reactions. Reactions of 4,5-(P(O)-
Ph2)2tzH (1) and 4,5-(P(S)Ph2)2tzH (2) with 2 equiv of
i
AlR3 (R= Me, Bu) gave the organometallic adducts
[AlR2{κ2-O,O0-[4,5-(P(O)Ph2)2tz]}-(N0-AlR3)] (R = Me
(10), iBu (11)) and [AlR2{κ2-N,S-[4,5-(P(S)Ph2)2tz]}-(N0-
AlR3)] (R = Me (12), Bu (13)), respectively, in good
i
˚
the plane = 0.32 A, while the triazole ring remains planar.
˚
yields (Scheme 3). The reaction of 4,5-(P(Se)Ph2)2tzH (3)
with 2 equiv of AlMe3 gave the monometallic compound
8, while reaction of the former with an excess of AliBu3
produced an inseparable mixture of products.
The Al-O bond lengths, with 1.830(3) and 1.850(3) A, are
similar to those observed in 4 (1.817(2) and 1.808(2) A).
˚
Furthermore, the reaction of 4,5-(P(S)Ph2)2tzH (2)
with 2 equiv of AlMe3 and AliBu3 gave the dinuclear
compounds 12 and 13, respectively. The 1H NMR spectra
of 12 and 13 show similar patterns for the corresponding
AlR2 and AlR3 groups as those observed in 10 and 11.
However, the 31P NMR spectra of 12 and 13 display two
different coordination environments for the two phos-
phorus atoms. The 27Al NMR spectrum of 12 was silent;
however, that of 13 showed two broad signals that over-
lap, which is in agreement with the existence of two
chemically different tetracoordinate aluminum atoms.
Suitable crystals for X-ray diffraction studies were
obtained for 12 upon allowing its saturated toluene
solution to slowly cool from 80 °C to ambient tempera-
ture. Compound 12 crystallizes in the triclinic system P1
space group, with one molecule in the asymmetric unit
(Figure 8).
Although X-ray quality crystals of 11 were not
obtained, the spectroscopic evidence strongly supports
the structure depicted in Scheme 3. The 1H NMR spectra
of 10 and 11 show two sets of signals for the AlR2 and
AlR3 groups and their 31P NMR spectra reveal single
signals corresponding to symmetric coordination modes.
Attempts to grow X-ray quality crystals from the recrys-
tallized products were unsuccessful. However, single
crystals of a lower quality of 10 were obtained when using
a toluene/hexane mixture. Compound 10 crystallized as
two independent molecules in the orthorhombic Pca21
space group (Figure 7). The crystal structure of 10
revealed positional disorder between the C(30) and Cl-
(1) atoms with the occupancy ratio of 48:52. The presence
of the chlorine atom is most probably due to contamina-
Compound 12 exhibits two tetracoordinate aluminum
atoms with different coordination environments. The
aluminum atom from the AlMe2 moiety is coordinated
(29) During the isolation of the free form of the ligand, the addition of a 10
M solution of HCl is required for precipitation, followed by thorough
washing with distilled water.

ꢀ
Alcantara-Garcıa et al.
5882 Inorganic Chemistry, Vol. 48, No. 13, 2009
Figure 9. Molecular structure of compound 13.
deprotonated ligands [4,5-(P(E)Ph2)2tz]-(E = O(1a), S-
(2a), Se(3a)) (Figure 10) shows the highest occupied
molecular orbitals (HOMOs) distributed over the triazole
ring (1a) and on both chalcogen atoms (2a and 3a). This
suggests that an orbital controlled process is not favored
in the formation of their respective aluminum complexes.
Furthermore, NBO calculations show that the stron-
gest negative electrostatic potentials for compounds 1a-
3a are located over the N-N-N fragments (Supporting
Information, Figures S6-S8). However, in 1a the natural
charges for the oxygen atoms have values of -1.129 and
-1.112, while those for the N(1), N(2), and N(3) atoms
are -0.393, -0.137, and -0.285, respectively. This sug-
gests that a charge control bonding process predominates
over an orbital controlled bonding process in the forma-
tion of compounds 4 and 5. On the other hand, the natural
charges for the chalcogen atoms in 2a and 3a exhibit the
strongest negative value in these molecules, -0.683 (S)
and -0.605 (Se), respectively. While for the N(1) atom,
the values of -0.351 and -0.318 are observed for 2a and
3a, respectively (Supporting Information, Figure S9).
Therefore, the driving force in the formation of com-
pounds 6- 8, where the bonding to the metal center
occurs through the chalcogen and nitrogen atom, can
be attributed to the formation of the five-membered
chelate rings.
Furthermore, the electrostatic potential mapped onto
the electronic density surfaces for 4 and one-half of 6
(Supporting Information, Figures S10 and S11) yield the
most negative potentials on the nitrogen atoms in the
triazole rings. This can account for the formation of the
adduct-like compounds 10-13, when 1 and 2 are treated
with an excess of aluminum alkyls. Furthermore, the
NBO analysis on one-half of 6 shows a highly electrostatic
nature of the metal-ligand interaction, since the Wiberg
bond indexes for Al are very small. The Wiberg bond
index31 for the Al-C bonds is 0.563, whereas for the Al-
N(1) bond it is only about half (0.261) and for the Al-S
bond the value is 0.441. This is unexpected from the point
of view of the HSAB32 theory by which the harder N(2)
atom should be more strongly bound to the hard Al atom.
This in turn may be explained by the fact that there is a
Figure 8. Perspective view of 12 with thermal ellipsoids at 50% prob-
ability. All hydrogen atoms are omitted for clarity.
to sulfur and nitrogen atoms while the second aluminum
atom from the AlMe3 group coordinates through a dative
bond to the central nitrogen atom from the triazole ring.
Furthermore, the core of 12 can be viewed as two fused
five-membered rings with a non-planar arrangement.
However, the P(1) and Al(1) atoms are coplanar to the
˚
triazole ring, whereas, the S(1) atom lies 0.87 A above the
˚
plane. The Al-S(P) bond length (2.382(1) A) is longer
than the mean value for Al-S bond lengths for tetra-
coordinate aluminum atoms (2.303 A),30 but significantly
˚
shorter than those observed for the dimeric compounds 6
˚
˚
(2.652(1) and 2.736(1) A) and 7 (2.737(1) A). The N(1)-
Al(1)-S(1) angle is 89.2(1)°, more obtuse than those
observed in 6 (82.4°(1)) and 7 (82.0°(1)). The Al(1)-N(1)
˚
bond length (1.994(2) A) in 12 is closely related to those
˚
˚
observed in 6 (1.997(2) and 1.988(2) A) and 7 (1.996(2) A)
and comprehensively shorter than the Al(2)-N(2) dative
bond (2.055(2) A). The structure of 12 contrasts signifi-
˚
cantly with that of the adduct reported by Jordan and
co-workers, [AlMe2[κ2-N,S-{S(NAd)CMe}]-(S-AlMe3)]
(Ad = adamantyl).14c In the latter, the coordination of
the AlMe3 group occurs through the sulfur atom rather
than through the nitrogen atom of the thioamidate ligand
because of the steric bulk of the adamantyl group. While
in 12, the N(2) position is preferred over the N(3), in great
part because of the steric bulk that the phenyl groups
exerted over the N(3) atom.
Although the quality of the X-ray data for 13 did not
allow a full structural characterization, a model of this
compound was attained (Figure 9). Compound 13 shows
the same coordination features as those observed in 12,
regardless of the difference in the steric bulk of the alkyl
groups on the aluminum atom.
Theoretical Calculations. To gain insight into the
coordination behavior of these ligands, theoretical calcu-
lations were carried out using the GAUSSIAN 03 suite
of programs.19 A plot of the frontier orbitals for the
(30) For a full account of Al-S bond lengths see the Al-S bond length
histogram for tetracoordinate Al atoms from CCDC in Supporting Infor-
mation, Figure S5.
(31) Wiberg, K. B. Tetrahedron 1968, 24, 1083–1096.
(32) Pearson, R. G. J. Am. Chem. Soc. 1963, 85, 3533–3539.

Article
Inorganic Chemistry, Vol. 48, No. 13, 2009 5883
Figure 10. Frontier orbitals plot for the deprotonated ligands 1a-3a calculated at the RHF/3-21G** level of theory (All hydrogen atoms omitted for
clarity).
strong delocalization of the electron density over the
triazole ring, making it less available for bond formation
with the metal. Natural charges for compound 6 reflect
this feature by exhibiting values of 1.83 for the Al atom,
-0.624 for S(1), and -0.535 for N(1).
as the nature of the donor atoms and the steric protection of
the metal center. Compounds 4 and 5, which bear a seven-
membered ring system, are formed through the involvement
of both oxygen atoms. The oxygen atoms are highly electro-
negative and exhibit the strongest negative charges in the
deprotonated ligands. Therefore, the structural traits of these
compounds can be viewed as a token of the high oxophility of
aluminum(III) centers. On the other hand, 6-8 exhibit κ3
coordination through a combination of hard and soft donor
atoms, allowing the chelation of the aluminum centers by
forming stable five- and six-membered ring systems, which
provides sufficient electronic relief for the hard aluminum
center. Furthermore, the highest negative potential in the
N-N-N fragment of the triazole moieties calculated for 4
and 6 can account for the formation of adduct-like com-
pounds 10- 13. Finally, the high covalent character of the
Al-Se bonds combined with the essentially electrostatic
nature of the Al-N bonds in 9 may explain the relative
stability of this uncommon trischelate arrangement. The
structural diversity observed in these compounds can be
viewed as an example of charge control versus orbital control
during the bond formation process.
NBO analysis on compound 9 suggest that the Al-Se
bonds have a higher covalent character than Al-N
bonds, as reflected by their Wiberg bond indexes (0.49
vs 0.18). Moreover, the analysis of the natural charges
of the N (-0.623, -0.623, and -0.618) and Se atoms
(-0.390, -0.383, -0.387) bonded to the Al atom suggests
the existence of essentially Al-N electrostatic interac-
tions in this compound. Furthermore, there is little
electron transfer from N to Al as observed by the second
order perturbation theory analysis in which the delocali-
zation energy is assessed. The energy for the electronic
transfer from Se to Al is 134.04 kcal/mol, which is large
when compared to regular delocalization energy in aro-
matic compounds.33 The delocalization energy from N to
Al in compound 9 is only 42.36 kcal/mol. This further
supports the idea that covalent bonding is mainly carried
out by Se atoms rather than by N atoms.
Conclusions
Acknowledgment. We thank the UNAM-DGAPA
(Grant IN205708) and CONACyT (Grant 058484) for
financial support and M. N. Zavala-Segovia for her
technical assistance. J.A.-G. acknowledges the CONA-
CyT for her Ph.D. fellowship.
The structural outcome of the compounds synthesized is
essentially the result of the interaction of the hard Al(III)
centers in different fashion, depending on the relative
importance of the electrostatic ligand-metal interactions
regarding the overlap of frontier orbitals. The reactivity
and stability of these compounds are reflected in factors such
Supporting Information Available: Figures S1-S11, histo-
grams from CCDC and X-ray data (CIF) for 1, 4a, 4b, 6, 7, 9, 10,
and 12. This material is available free of charge via the Internet
at http://pubs.acs.org.
(33) The delocalization energy for the BD(C-C) bond to a BD*(C-C)
one in a phenyl group is typically in the range 200 to 300 kcal/mol.