Synthesis and structures of salen-supported borates containing siloxides

Article abstract of DOI:10.1021/ic9812003

The ligand N,N″-bis(2-hydroxybenzylidene)diethylenetriamine (SalenN₃H₃) was used to prepare the compound SalenN₃H{B(OMe₂)}₂ (1) which could, in turn, be used in the formation of SalenN₃H{B(OSiPh₃)₂}₂ (2). For comparative purposes, the compounds Salben{B(OSiPh₃)₂}₂ (3) (Salben = N,N-butylenebis(2-hydroxybenzylideneamine), Salen(^tBu){B(OSiPh₃)₂}₂ (4) (Salen(^tBu) = N,N′-ethylenebis(3,5-di-tert-butyl-2-hydroxybenzylideneamine) and Salben(^tBu){B(OSiPh₃)₂}₂ (5) (Salben(^tBu) = N,N′-butylenebis(3,5-di-tert-butyl-2-hydroxy-benzylideneamine) were prepared. In reactions where the siloxide is (HO)₂SiPh₂, unique dimeric siloxide-bridged compounds result, [Salpten(^tBu){B(O₂SiPh₂}]₂ (6) and [SalenN₃H{B(O₂SiPh₂)}]₂ (7). Compound 6 possesses a zeolite-like cavity having a volume of 157 ?³. All of the compounds were characterized by physical (mp, analyses) and spectroscopic techniques (¹H and ¹¹B NMR, IR) and, in the case of 1, 3, 4, and 6, by X-ray crystallography.

Full text of DOI:10.1021/ic9812003

3914
Inorg. Chem. 1999, 38, 3914-3918
Synthesis and Structures of Salen-Supported Borates Containing Siloxides
Pingrong Wei, Timothy Keizer, and David A. Atwood*
Department of Chemistry, The University of Kentucky, Lexington, Kentucky 40506-0055
ReceiVed October 9, 1998
The ligand N,N′′-bis(2-hydroxybenzylidene)diethylenetriamine (SalenN3H3) was used to prepare the compound
SalenN3H{B(OMe2)}2 (1) which could, in turn, be used in the formation of SalenN3H{B(OSiPh3)2}2 (2). For
comparative purposes, the compounds Salben{B(OSiPh3)2}2 (3) (Salben ) N,N′-butylenebis(2-hydroxybenzyli-
deneamine), Salen(tBu){B(OSiPh3)2}2 (4) (Salen(tBu) ) N,N′-ethylenebis(3,5-di-tert-butyl-2-hydroxybenzyli-
deneamine) and Salben(tBu){B(OSiPh3)2}2 (5) (Salben(tBu) ) N,N′-butylenebis(3,5-di-tert-butyl-2-hydroxy-
benzylideneamine) were prepared. In reactions where the siloxide is (HO)2SiPh2, unique dimeric siloxide-bridged
compounds result, [Salpten(tBu){B(O2SiPh2}]2 (6) and [SalenN3H{B(O2SiPh2)}]2 (7). Compound 6 possesses a
zeolite-like cavity having a volume of 157 Å3. All of the compounds were characterized by physical (mp, analy-
ses) and spectroscopic techniques (1H and 11B NMR, IR) and, in the case of 1, 3, 4, and 6, by X-ray crystallog-
raphy.
Introduction
The potentially tetradentate Salen ligands (Figure 1a,b)
incorporate a wide range of unique structures and reactivity with
transition and main group metals.1,2 For the group 13 elements
these most often are monometallic and incorporating aluminum.
Examples include cations,3-5 five-coordinate alkyls,6,7 alkox-
ides,8 amides,9 and siloxides.7 Relatively few monometallic
gallium10 and indium11 derivatives are known although they are
clearly accessible. A few bimetallic aluminum,12 gallium,13,14
and indium15 complexes are also known. By comparison to its
heavier congeners the Salen chemistry of boron remains
relatively unexplored. The one report describing Salen-boron
combinations reveals the resulting complexes to be bimetallic
Figure 1. General depiction of the types of Salen ligands mentioned
with four-coordinate boron atoms.16 They are formed through
in the text: Salen (a); Salen(tBu) (b); SalenN3H3 (c).
alcoholysis, and the resulting complexes have consequently
contained alkoxide groups. The oxygens of these alkoxides
might be associated with combinations between the Salen
partake in both intra- and intermolecular hydrogen bonding,
ligands and boron. This will involve varying the hydrogen-
leading to unusual extended structures. The impetus for the
bonding potential of the ligand as well as the type of alkoxide
present work is to explore the supramolecular chemistry that
on the boron atom.
(1) Holm, R. H.; Everett, G. W., Jr.; Chakravorty, A. Prog. Inorg. Chem.
1966, 7, 83.
(2) Hobday, M. D.; Smith, T. D. Coord. Chem. ReV. 1972, 9, 311.
(3) Atwood, D. A.; Jegier, J. A.; Rutherford, D. J. Am. Chem. Soc. 1995,
117, 6779.
(4) Davidson, M. G.; Lambert, C.; Lopez-Solera, I.; Raithby, P. R.; Snaith,
R. Inorg. Chem. 1995, 34, 3765.
(5) Atwood, D. A.; Jegier, J. A.; Rutherford, D. Inorg. Chem. 1996, 35,
63.
(6) Dzugan, S. J.; Goedken, V. L. Inorg. Chem. 1986, 25, 2858.
(7) Atwood, D. A.; Hill, M. S.; Jegier, J. A.; Rutherford, D. Organome-
tallics 1997, 16, 2659.
(8) Gurian, P. L.; Cheatham, L. K. Ziller, J. W.; Barron, A. R. J. Chem.
Soc., Dalton Trans. 1991, 1449.
(9) Rutherford, D.; Atwood, D. A. Organometallics 1996, 15, 4417.
(10) Hill, M. S.; Atwood, D. A. Eur. J. Inorg. Chem. 1998, 67.
(11) Hill, M. S.; Atwood, D. A. Main Group Chem. 1998, in press.
(12) Atwood, D. A.; Liu, S.; Munoz-Hernandez, M.-A.; Wei, P. Organo-
metallics, submitted for publication.
The ligand, N,N′′-bis(2-hydroxybenzylidene)diethylenetriamine
(SalenN3H3) (Figure 1c) appeared useful in this context since
it contained a central NH group capable of hydrogen bonding
(or protonation). It is used to prepare the compound SalenN3H-
{B(OMe2)}2 (1) which could, in turn, be used in the formation
of SalenN3H{B(OSiPh3)2}2 (2). For comparison, the compounds
Salben{B(OSiPh3)2}2 (3) (Salben ) N,N′-butylenebis(2-hy-
droxybenzylideneamine), Salen(tBu){B(OSiPh3)2}2 (4) (Salen-
(tBu) ) N,N′-ethylenebis(3,5-di-tert-butyl-2-hydroxybenzylide-
neamine), and Salben(tBu){B(OSiPh3)2}2 (5) (Salben(tBu) )
N,N′-butylenebis(3,5-di-tert-butyl-2-hydroxybenzylideneam-
ine) were prepared. In reactions where the siloxide is (HO)2SiPh2,
unique dimeric siloxide-bridged compounds result, [Salpten(t-
Bu){B(O2SiPh2}]2 (6) and [SalpenN3H{B(O2SiPh2)}]2 (7).
(13) Chong, K. S.; Rettig, S. J. Storr, A. Trotter, J. Can. J. Chem. 1977,
55, 2540.
Results and Discussion
(14) Hill, M. S.; Wei, P.; Atwood, D A. Polyhedron 1998, 17, 811.
(15) Atwood, D. A.; Jegier, J. A.; Rutherford, D. Bull. Chem. Soc. Jpn.
1997, 70, 2093.
Due to the strong, covalent nature of the B-C bond alkane
eliminations (with BR3, for instance) are not useful in preparing
chelated boron complexes. However, alcohol eliminations work
(16) Wei, P.; Atwood, D. A. Inorg. Chem. 1998, 37, 4934.
10.1021/ic9812003 CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/04/1999

Salen-Supported Borates Containing Siloxides
Inorganic Chemistry, Vol. 38, No. 17, 1999 3915
Figure 2. Molecular structure and atom numbering for SalenN3H-
{B(OMe)2}2 (1).
Scheme 1. General Synthesis of the Bimetallic Borate
Derivatives 1-7
Figure 3. View of the hydrogen bonding for SalenN3H{B(OMe)2}2
(1).
were occasionally intramolecular for ligands containing short
alkylene “backbones” (with Salen(tBu){B(OEt)2}2 for example)
but were predominantly intermolecular, especially with longer
alkylene groups in the ligand backbone (for (CH2)n with n )
4-6). These hydrogen-bonding contacts produced interesting
extended structures, most often in the form of infinite sheets.
The SalenN3H3 ligand was chosen for the present study in order
to explore what effect the additional NH group might have on
the resulting structure. The NH group of 1 does form intermo-
lecular hydrogen bonds (Figure 3). There is one to the OMe
group (2.52 Å), which also has the expected imine contact (2.50
Å). This latter contact is also observed at the other end of the
molecule (2.38 Å). The extended structure of 1 consists of
infinite sheets organized by these three hydrogen-bonding
contacts (see unit cell view in the Supporting Information). This
arrangement is exactly what had been observed for the Salen
ligands (without the extra NH)12 so the effect of the NH is not
significant in this structure.
In previous work involving the Saltren ligand (tris(((2-
hydroxybenzyl)amino)ethyl)amine) attempts to synthesize the
bis(siloxide)s (Saltren{B(OSiPh3)2}2 were unsuccessful.18 Rather,
the reactions led to the isolation of a complex, SaltrenH3-
{B(OSiPh3)3}3, where the ligand acts as a Lewis base toward
the neutral B(OSiPh3)3 group. Thus, it was interesting to find
that high yields of the bis(siloxide)s 2-5 were readily available
for various Salen ligands (Scheme 1b). For these compounds
well provided the reaction is heated for a reasonable period of
time. This was the route used to prepare a range of bimetallic
borates supported by the Salen16 and related Schiff base17
ligands. The choice of alkyl group on the borate (whether Me,
Et, nPr, or nBu) apparently has no influence on the outcome of
the reaction. Good yields of 1 are isolated in this manner
(Scheme 1a). The 1H NMR spectrum reveals a symmetric
solution state geometry with singlets for the OMe (δ 3.01 ppm)
and NdCH (δ 8.26 ppm) groups. The NH is silent in the NMR
but apparent in the IR (ν 3200 cm-1).
A crystal structure of 1 reveals its arrangement in the solid
(Figure 2). The boron atoms are chelated by the ligand and two
alkoxides in an overall Td geometry. The B-O(ligand) distance
(1.496(5) Å) is marginally longer than the B-OMe distances
(average 1.417(8) Å). The Salen-supported bimetallics usually
adopt trans geometries in which the two B(OR)2 groups are
oriented away from one another.16 Often these structures contain
a center of inversion. Why 1 takes a less symmetric geometry
without a center of inversion can be attributed to hydrogen-
bonding interactions. Structurally characterized Salen{B(OR)2}
complexes have been shown to possess a wide range of
hydrogen bonding involving predominantly the imine groups
(NdCH) in contact with an oxygen of the B(OR)2 group.16 The
distances for these contacts ranged from 2.4 to 2.6 Å. They
1
the NdCH groups appear as sharp singlets in the H NMR in
the region expected (∼7.8 ppm). The PhH resonances were
somewhat complicated and appeared as a mass of mutiplets in
the range 6.5-7.5 ppm. By comparison, the Si-Ph protons of
the monomeric SalenAl(OSiPh3) compounds were easily dis-
cerned as equivalent with the appropriate coupling.7 The
difference may be attributed to the fact that there are six of
these groups to consider in 2-5. There are single broad
resonances in the 11B spectra of all of the compounds. For 2-5
these resonances occur in the narrow window, δ 0.08-0.72 ppm,
in the region for Td boron.19
Supporting the solution data, the crystal structures of 3 and
4 show that the two chelate-B(OSiPh3)2 units are related by a
center of symmetry (Figures 4 and 5, respectively). This gives
each of the complexes a trans orientation. By comparison to 1
(18) Wei, P.; Atwood, D. A. J. Organomet. Chem. 1998, 563, 87.
(19) Kidd, R. G. In NMR of Newly Accessible Nuclei; Laszlo, P., Ed.;
Academic Press: San Diego, CA, 1983; Vol. 2, Chapter 3.
(17) Wei, P.; Atwood, D. A. Inorg. Chem. 1997, 36, 4060.

3916 Inorganic Chemistry, Vol. 38, No. 17, 1999
Wei et al.
Table 1. Selected Bond Distances (Å) and Angles (deg) for
Compouds
SalenN3H[B(OMe)2]2 (1)
B(1)-O(3)
1.422(5)
1.496(5)
1.416(5)
1.480(5)
B(1)-O(4)
B(1)-N(1)
B(2)-O(5)
B(2)-N(3)
1.411(5)
1.614(5)
1.425(5)
1.610(5)
B(1)-O(1)
B(2)-O(6)
B(2)-O(2)
O(3)-B(1)-O(4)
O(4)-B(1)-O(1)
O(4)-B(1)-N(1)
O(6)-B(2)-O(5)
O(5)-B(2)-O(2)
O(5)-B(2)-N(3)
106.0(3)
110.9(3)
111.7(3)
106.8(3)
112.6(3)
108.8(3)
O(3)-B(1)-O(1)
O(3)-B(1)-N(1)
(1)-B(1)-N(1)
O(6)-B(2)-O(2)
O(6)-B(2)-N(3)
O(2)-B(2)-N(3)
112.7(3)
109.8(3)
105.9(3)
111.1(3)
110.5(3)
107.0(3)
Salben[B(OSiPh3)2]2 (3)
B(1)-O(2)
B(1)-O(1)
1.418(4)
1.481(4)
B(1)-O(3)
B(1)-N(1)
1.429(4)
1.618(5)
O(2)-B(1)-O(3)
O(3)-B(1)-O(1)
O(3)-B(1)-N(1)
113.3(3)
111.3(3)
105.0(3)
O(2)-B(1)-O(1)
O(2)-B(1)-N(1)
O(1)-B(1)-N(1)
110.8(3)
110.4(3)
105.5(3)
Figure 4. Molecular structure and atom numbering for Salben-
{B(OSiPh3)2}2 (3).
Salen(tBu)[B(OSiPh3)2]2 (4)
B(1)-O(2)
B(1)-O(1)
1.411(6)
1.479(6)
B(1)-O(3)
B(1)-N(1)
1.431(6)
1.635(6)
O(2)-B(1)-O(3)
O(3)-B(1)-O(1)
O(3)-B(1)-N(1)
114.8(4)
112.3(4)
105.7(4)
O(2)-B(1)-O(1)
O(2)-B(1)-N(1)
O(1)-B(1)-N(1)
110.9(4)
107.6(4)
104.9(4)
[Salpten(tBu){B(O2SiPh2)}2]2 (6)
B(1)-O(3)
B(1)-O(1)
B(2)-O(6)
B(2)-O(2)
1.424(11)
1.474(12)
1.394(13)
1.512(11)
B(1)-O(5)
B(1)-N(1)
B(2)-O(4)
B(2)-N(2)
1.418(11)
1.641(12)
1.449(11)
1.609(11)
O(3)-B(1)-O(5)
O(5)-B(1)-O(1)
O(5)-B(1)-N(1)
O(6)-B(2)-O(4)
O(4)-B(2)-O(2)
O(4)-B(2)-N(2)
115.7(8)
109.5(9)
108.6(8)
116.9(8)
107.6(9)
106.7(8)
O(3)-B(1)-O(1)
O(3)-B(1)-N(1)
O(1)-B(1)-N(1)
O(6)-B(2)-O(2)
O(6)-B(2)-N(2)
O(2)-B(2)-N(2)
110.3(8)
107.2(8)
105.0(7)
114.3(9)
105.4(8)
104.9(7)
Figure 5. Molecular structure and atom numbering for Salen(tBu)-
{B(OSiPh3)2}2 (4).
SiO2 unit bridges two metals21,22 rather than chelating just one.23
Likewise, this type of bonding is observed in phosphonate RPO-
(OH)2 derivatives of the group 13 elements.24-26 In these
compounds eight-membered rings form that contain the group
13 element, two oxygens, and the heteroatom (either Si or P)
(Figure 6a). This arrangement is important in that it is also found
in group 13 silicate and phosphate solid-state materials. This
type of bonding is revealed in the crystal structure of 6 (Figure
7). However, unlike the previously reported examples, the eight-
membered, (BO2Si)2 units in 6 are connected to one another by
the length of the ligand backbone rather than an oxygen (Figure
6b). The O-B-O angles (107.6(9)-115.7(8)°) and B-O
distances (1.394(13)-1.512(11) Å) are close to the values
observed in [tBuPO3BsBu]4 (∼108° and ∼1.48 Å).26 For the
six-membered ring [(PhBO)(Ph2SiO)2],27 the distance is similar
(1.3696(2) Å) but the angles are wider (120.79(21)°). The angles
and distances for eight-membered ring compounds incorporating
(106.0(3)°) the angles between the ligands are somewhat
widened in 3 and 4 (average 114(1)°). This reflects the mild
steric effect of the Ph3Si group. However, the B-O(ligand)
distances are comparable for all of the compounds (1, 3, and 4)
(Table 1). In keeping with the electronegativity difference
between oxygen and nitrogen, the B-N distances are lengthened
(average for the three compounds, 1.623(5) Å). Overall the bond
distances are similar to those for other four-coordinate bo-
rates.16,17 For instance, these distances in two diarylboroxazo-
lidines average 1.65(5) and 1.477(4) Å, respectively.20 There
is no inter- or intramolecular hydrogen bonding in compounds
3 and 4. The three phenyl groups of the Ph3SiO- unit effectively
shield the oxygen atom and prevent any contact. On the basis
of the similarity of these two compounds, it is clear that the
Ph-tBu groups of 4 do not have a significant effect on how
the ligand coordinates the boron atom. However, these groups
do significantly improve the solubility of this complex in
nonpolar solvents.
The combination of Ph2Si(OH)2 with Salpten(tBu)[B(OMe)2]2
(reported in ref 12) and 1 leads to 6 and 7, respectively (Scheme
(21) Montero, M. L.; Uson, I.; Roesky, H. W. Angew. Chem., Int. Ed. Engl.
1994, 33, 2103.
(22) Montero, M. L.; Voigt, A.; Teichert, M.; Uson, I.; Roesky, H. W.
Angew. Chem., Int. Ed. Engl. 1995, 34, 2504.
1
1c). The solution H NMR data show that the NdCH groups
of both compounds are equivalent. For 7 the NCH2 groups
appeared as a multiplet. Notably, νN-H is not observed in the
IR spectrum of 6 and 7 perhaps due to hydrogen bonding
involving this group. From these data it is uncertain whether
the BO2 unit is attached to one ligand or bridged across two. In
aluminum derivatives containing the RSi(OH)3 group the (OH)-
(23) Unless condensation unites two of the siloxy units: Veith, M.; Jarczyk,
M.; Huch, V. Angew. Chem., Int. Ed. Engl. 1998, 37, 105.
(24) Mason, M. R.; Mashuta, M. S.; Richardson, J. F. Angew. Chem., Int.
Ed. Engl. 1997, 36, 239.
(25) Yang, Y.; Walawalkar, M. G.; Pinkas, J.; Roesky, H. W.; Schmidt,
H.-G. Angew. Chem., Int. Ed. Engl. 1998, 37, 96.
(26) Walawalkar, M. G.; Murugavel, R.; Roesky, H. W.; Uson, I.;
Kraetzner, R. Inorg. Chem. 1998, 37, 473.
(27) Foucher, D. A.; Lough, A. J.; Manners, I. Inorg. Chem. 1992, 31,
3034.
(20) Rettig, S. J.; Trotter, J. Can. J. Chem. 1976, 54, 3130.

Salen-Supported Borates Containing Siloxides
Inorganic Chemistry, Vol. 38, No. 17, 1999 3917
1 or 2 cations. Realistically, however, the potential for forming
soluble molecular inclusion complexes with 6 may be impeded
by the steric requirements of the Ph2Si group. A more likely
cage would be one in which the silicon contains smaller groups
such as Me. Further efforts to accomplish this are in progress,
as are efforts to deprotonate the NH groups of 7 with large atoms
such as Rb and Cs.
Experimental Section
General Considerations. All manipulations were conducted using
Schlenk techniques in conjunction with an inert-atmosphere glovebox.
All solvents were rigorously dried prior to use. NMR data were obtained
on JEOL-GSX-400 and -270 instruments at 270.17 MHz (1H) and 32.08
MHz (11B) and are reported relative to SiMe4 and BF3‚OEt2, respectively
(in ppm). Samples were run in CDCl3 for all compounds except 7 which
was run in C6D6. Elemental analyses were obtained on a Perkin-Elmer
2400 analyzer and were satisfactory for all compounds. Infrared data
were recorded as KBr pellets on a Matheson Instruments 2020 Galaxy
Series spectrometer and are reported in cm-1. The reagent 3,5-di-tert-
butyl-2-hydroxybenzaldehyde28 was prepared according to the literature.
X-ray data (2θ ) 45°) for 1, 3, 4, and 6 were collected on a Siemens
SMART-CCD unit (Table 2). The hydrogen atoms in these complexes
were placed in ideal positions with a C-H distance of 0.90 Å. Being
involved in hydrogen bonding, these distances could conceivably be
somewhat longer, but in the absence of neutron diffraction data they
cannot be quantitatively determined. However, they are clearly within
the sum of the van der Waals radii for hydrogen (1.20 Å) and oxygen
(1.50 Å)29 and in keeping with distances observed in other systems
containing such hydrogen bonds.30
Figure 6. Frameworks of borosilicate molecules (a and b) and the
cylinder represented by compound 6 (c).
SalenN3H[B(OMe)2]2 (1). To a solution of SalenN3H3 (1.00 g, 3.21
mmol) in toluene (30 mL) was added trimethylborate (1.34 g, 12.84
mmol). The resulting solution was refluxed for 6 h. After filtration
and concentration, yellow crystals were grown at 25 °C (1.10 g, 76%):
1
Mp 116 °C (dec); H NMR δ 3.01 (m, 4H, CH2CH2), 3.22 (s, 12H,
OCH3), 3.67 (m, 4H, CH2CH2), 6.65 (m, 2H, PhH), 6.94 (m, 4H, PhH),
7.43 (m, 2H, PhH), 8.26 (s, 2H, NCH); 11B NMR δ 2.45 (W1/2, 238.63
Hz); IR ν 3283 (m), 3067 (w), 2960 (m), 2823 (m), 1977 (w), 1892
(w), 1807 (w), 1641 (s), 1612 (w), 1562 (m), 1483 (m), 1467 (m),
1419 (w), 1371 (w), 1317 (m), 1211 (m), 1130 (m), 977 (m), 833 (w),
783 (w), 756 (m), 549 (w), 468 (w). Anal. Calcd for C22H31N3O6B2:
C, 40.67; H, 4.77. Found: C, 40.38; H, 4.65.
Figure 7. Molecular structure and atom numbering scheme for
[Salpten{B(O2SiPh2)}] 2 (6).
SalenN3H[B(OSiPh3)2]2 (2). To a solution of SalenN3H[B(OMe)2]2
(0.75 g, 1.65 mmol) in toluene (30 mL) was added triphenylsilanol
(1.82 g, 6.60 mmol). The resulting solution was refluxed for 5 h. After
filtration and concentration, a pale yellow solid was obtained from a
toluene/hexane (1/5) solution (1.80 g, 78%): Mp 63 °C (dec); 1H NMR
δ 2.49 (m, 4H, CH2CH2), 3.10 (m, 4H, CH2CH2), 6.45 (m, 2H, PhH),
6.62 (m, 2H, PhH), 7.01 (m, 2H, PhH), 7.14 (m, 32H, SiPhH, PhH),
7.50 (m, 30H, SiPhH), 7.72 (d, 2H, NCH); 11B NMR δ 0.72 (W1/2
,
356.41 Hz); IR ν 3065 (m), 3047 (m), 2998 (w), 2849 (w), 1959 (w),
1892 (w), 1828 (w), 1643 (s), 1610 (w), 1560 (m), 1483 (m), 1427
(m), 1315 (w), 1234 (w), 1116 (br s), 1026 (w), 964 (m), 891 (w), 798
(w), 742 (w), 702 (m), 513 (m), 426 (w). Anal. Calcd for C90H79N3O6B2-
Si4: C, 75.49; H, 5.52. Found: C, 75.36; H, 5.48.
Salben[B(OSiPh3)2]2 (3). To a solution of Salben[B(OEt)2]2 (0.67
g, 1.35 mmol) in toluene (30 mL) was added triphenylsilanol (1.50 g,
5.40 mmol). The resulting solution was refluxed for 5 h. After filtration
and concentration, yellow crystals were grown at 25 °C (1.70 g, 89%):
Figure 8. Molecular framework for [Salpten{B(O2SiPh2)}]2 (6).
1
Mp 153 °C (dec); H NMR δ 1.45 (m, 4H, CH2CH2), 2.95 (m, 4H,
aluminum ([tBuPO3AliBu]4)25 are 105.2(1)-114.2(2)° and 1.762-
(4) Å, and those for gallium ([PhPO3GatBu]4)24 are 103.9(1)°
and 1.835(7) Å.
The framework of 6 (Figure 8) can be represented by a
cylinder that is 9.8 Å long (the average of the Si1-Si2a and
Si2-Si1a distances), 4 Å wide (the Si1-Si2 distance), and 4
Å deep (the B1-B2 distance) (Figure 6c). A crude estimate of
the volume within this cavity would then be 157 Å3, large
enough to accommodate solvent molecules or a couple of group
NCH2), 6.45 (d, 2H, PhH), 6.56 (d, 2H, PhH), 7.11-7.52 (m, 60H,
SiPhH), 7.73 (d, 2H, NCH); 11B NMR δ 0.22 (W1/2, 236.89 Hz); IR ν
3067 (w), 2984 (w), 2866 (w), 1959 (w), 1886 (w), 1820 (w), 1643
(s), 1612 (w), 1564 (m), 1483 (m), 1464 (w), 1427 (m), 1317 (m),
1261 (w), 1236 (w), 1113 (s), 1028 (m), 960 (m), 883 (w), 777 (w),
(28) Casiraghi, G.; Casnati, G.; Puglia, G.; Sartori, G.; Terenghi, G. J.
Chem. Soc., Perkin Trans. 1980, 1862.
(29) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(30) Desiraju, G. R. Acc. Chem. Res. 1991, 24, 290.

3918 Inorganic Chemistry, Vol. 38, No. 17, 1999
Wei et al.
Table 2. Data Collection and Processing Parameters for Compounds
compounds
1
3
4
6
formula
fw
color, habit
cryst size (mm3)
cryst system
space group
a (Å)
C22H31N3O6B2
455.12
yellow prism
0.50 × 0.25 × 0.20
monoclinic
C2/c
27.997(2)
6.200(1)
31.071(2)
90
116.53(1)
90
4825.3(6)
8
C45H39NO3BSi2
708.76
yellow block
0.10 × 0.18 × 0.22
triclinic
P1h
13.627(1)
13.657(1)
14.051(1)
65.83(1)
61.10(1)
64.21(1)
1994.9(2)
2
C59H56NO3BSi2
894.04
yellow block
0.40 × 0.35 × 0.25
triclinic
P1h
13.862(1)
14.045(1)
15.249(1)
82.36(1)
80.10(1)
62.32(1)
2585.4(3)
2
C66H80N2O6B2Si2
1075.12
yellow prism
0.50 × 0.30 × 0.25
triclinic
P1h
13.127(1)
13.748(1)
19.705(2)
78.26(1)
80.96(1)
68.00(1)
3216(2)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
F(000)
1936
1.253
0.089
2571
2571
298
0.054
0.129
746
1.180
0.129
4100
4100
469
0.046
0.119
948
1.148
0.113
4386
4374
595
0.060
0.153
1152
1.110
0.104
3635
3594
650
0.075
0.169
D(calcd) (g cm-3
)
µ (mm-1
)
unique data measd
obsd data, n [F g 4σ(F)]
no. of variables, p
R1a
wR2b
S (goodness of fit)c
1.12
0.87
1.00
1.33
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [(∑w(|Fo| - |Fc|)2/∑wFo )]1/2
.
c S ) [(∑w(|Fo| - |Fc|)2/n - m)]1/2
.
2
1
711 (m), 584 (w), 520 (w), 493 (w). Anal. Calcd for C90H78N2O6B2-
Si4: C, 76.29; H, 5.51. Found: C, 76.15; H, 5.39.
°C (dec); H NMR δ 1.29 (s, 18H, CCH3), 1.37 (s, 18H, CCH3), 1.42
(m, 12 H, CH2CH2), 1.55 (m, 4H, CH2CH2), 6.89 (d, 2H, PhH), 7.06
(d, 2H, PhH), 7.15-7.47 (m, 20H, SiPhH), 7.71 (d, 2H, NCH); 11B
NMR δ 0.60 (W1/2, 243.06 Hz); IR ν 3045 (w), 2953 (w), 2868 (w),
1957 (w), 1894 (w), 1826 (w), 1645 (s), 1591 (w), 1566 (m), 1471
(m), 1429 (m), 1392 (w), 1361 (w), 1043 (m), 954 (m), 912 (w),
873 (w), 805 (m), 773 (w), 717 (m), 642 (w), 572 (w), 513 (w), 495
(w). Anal. Calcd for C118H144N4O12B4Si4: C, 72.12; H, 7.33. Found:
C, 72.01; H, 7.28.
Salen(tBu)[B(OSiPh3)2]2 (4). To a solution of Salen(tBu)[B(OEt)2]2
(0.80 g, 1.15 mmol) in toluene (30 mL) was added triphenylsilanol
(1.27 g, 4.60 mmol). The resulting solution was refluxed for 5 h. The
filtrate was concentrated to incipient crystallization and let stand at 25
°C for 24 h to afford the product as yellow crystals (0.53 g, 30%):
1
Mp >260 °C; H NMR δ 1.13 (s, 18H, CCH3), 1.26 (s, 18H, CCH3),
3.55 (m, 2H, NCH2), 3.79 (m, 2H, NCH2), 6.24 (d, 2H, PhH), 6.66 (d,
2H, PhH), 7.21-7.50 (m, 60H, SiPhH), 7.82 (d, 2H, NCH); 11B NMR
δ 0.08 (W1/2, 260.21 Hz); IR ν 3049 (w), 2957 (m), 2870 (w), 1959
(w), 1897 (w), 1828 (w), 1637 (s), 1566 (m), 1460 (w), 1427 (s), 1357
(m), 1313 (s), 1261 (w), 1166 (w), 1120 (s), 1028 (w), 958 (m), 740
(w), 709 (m), 513 (w), 451 (w). Anal. Calcd for C104H106N2O6B2Si4:
C, 77.43; H, 6.57. Found: C, 77.58; H, 6.51.
[SalenN3H{B(O2SiPh2)}2]2 (7). To a solution of SalenN3H-
[B(OMe)2]2 (0.85 g, 1.87 mmol) in toluene (30 mL) was added
diphenylsilanediol (0.81 g, 3.74 mmol). The resulting solution was
refluxed for 5 h. After filtration and concentration, yellow solid was
isolated from a toluene/hexane (1/5) solution (1.30 g, 77%): Mp 103
1
°C (dec); H NMR δ 2.49 (m, 4H, CH2CH2), 2.53 (m, 4H, NCH2),
Salben(tBu)[B(OSiPh3)2]2 (5). To a solution of Salben(tBu)-
[B(OMe)2]2 (0.53 g, 0.80 mmol) in toluene (30 mL) was added
triphenylsilanol (0.88 g, 3.20 mmol). The resulting solution was refluxed
for 5 h. After filtration and concentration, yellow crystals were grown
3.30 (m, 4H, CH2CH2), 6.48 (m, 2H, PhH), 6.61 (m, 2H, PhH), 6.75
(m, 2H, PhH), 7.16 (m, 12H, SiPhH, PhH), 7.83 (m, 10H, SiPhH),
8.01 (d, 2H, NCH); 11B NMR δ 0.98 (W1/2, 277.86 Hz); IR ν 3067
(w), 3047 (w), 2968 (w), 2841 (w), 1957 (w), 1892 (w), 1830 (w),
1645 (s), 1610 (w), 1560 (m), 1481 (m), 1465 (w), 1429 (m), 1330
(m), 1261 (w), 1234 (w), 1116 (br, s), 1024 (w), 964 (w), 800 (w),
756 (w), 700 (m), 551 (w), 507 (m), 407 (w) cm-1. Anal. Calcd for
C84H78N6O12B4Si4: C, 66.43; H, 5.14. Found: C, 66.26; H, 5.05.
1
at 25 °C (0.80 g, 62%): Mp 230 °C (dec); H NMR δ 1.12 (s, 18H,
CCH3), 1.33 (s, 18H, CCH3), 1.47 (m, 4H, CH2CH2), 2.76 (m, 4H,
NCH2), 6.50 (d, 2H, PhH), 6.58 (d, 2H, PhH), 7.17-7.52 (m, 60H,
SiPhH), 7.72 (d, 2H, NCH); 11B NMR δ 0.70 (W1/2, 270.76 Hz); IR ν
3086 (w), 2962 (m), 2868 (w), 1961 (w), 1900 (w), 1822 (w), 1647
(s), 1464 (w), 1429 (m), 1361 (w), 1261 (m), 1153 (w), 1111 (s), 1026
(w), 952 (w), 891 (w), 806 (m), 702 (s), 570 (w), 513 (w), 422 (w).
Anal. Calcd for C106H110N2O6B2Si4: C, 77.57; H, 6.70. Found: C, 77.65;
H, 6.77.
Acknowledgment. Gratitude is expressed to the Petroleum
Research Fund (Grant 31901-AC3), administered by the Ameri-
can Chemical Society, and the National Science Foundation
(CAREER award, 1996-2000) for generous support.
[Salpten(tBu){B(O2SiPh2)}2]2 (6). To a solution of Salpten(tBu)-
[B(OMe)2]2 (0.74 g, 1.09 mmol) in toluene (30 mL) was added
diphenylsilanediol (0.47 g, 2.18 mmol). The resulting solution was
refluxed for 5 h. The filtrate was concentrated to 5 mL and stand at 25
°C for 2 weeks to yield pale yellow crystals (0.85 g, 79%): Mp 160
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determinations of 1, 3, 4, and 6. This
material is available free of charge via the Internet at http://pubs.acs.org.
IC9812003