Syntheses and X-ray structures of monocyclic, bicyclic, and spirocyclic gallium and indium boraamidinates

Article abstract of DOI:10.1021/ic0206286

The reactions of {Li₂[PhB(N^tBu)₂]}₂ with GaCl₃ in various stoichiometries yield [Li(thf)₄][PhB(μ-N^tBu)₂ GaCl₂·GaCl₃] (1), [PhB(μ-N^tBu)₂GaCl]₂ (2), and {μ-Li(OEt₂)[PhB(N^tBu)₂]Ga} (3a), a series of complexes in which the three chloride ligands are successively replaced by the dianion [PhB(N^tBu)₂]^2-. The X-ray structures of 1, 2, and 3a show that the boraamidinate ligand adopts an N,N′-chelating mode. In the ion-separated complex 1, one of the nitrogen atoms is coordinated to a GaCl₃ molecule. The related indium complexes [μ-LiCl(thf)₂][PhB(μ-N^tBU)₂ lnCl]₂ (4) and {μ-Li(OEt₂)[PhB(μ-N^tBu)₂]ln} (3b) were obtained in a similar manner. Complex 4 is the indium analogue of 2 with the incorporation of a bissolvated LiCl molecule. In 3a and 3b the spirocyclic {[PhB(μ-N^tBu)₂]₂M}^- (M = Ga, In) anions are N,N′-chelated to the [Li(OEt₂)]⁺ counterion. Prolonged reactions result in the formation of [PhB(μ- N^tBu)₂GaCl][^tBuN(H)GaCl₂] (5) and {[PhB(μ-N^tBu)₂lnCl][^tBuN(H) lnCl₂][μ-LiCl(OEt₂)₂]} (6), respectively. The X-ray structures of 5 and 6 reveal bicyclic structures which formally involve the entrapment of the monomers ^tBuN(H)-MCl₂ by a four-membered BN₂M ring (M = Ga, ln). The synthesis and X-ray structure of Cl₂Ga[μ-N(H)^tBu]₂GaCl₂ are also reported.

Full text of DOI:10.1021/ic0206286

Inorg. Chem. 2003, 42, 2084−2093
Syntheses and X-ray Structures of Monocyclic, Bicyclic, and Spirocyclic
Gallium and Indium Boraamidinates
Tristram Chivers,* Chantall Fedorchuk, Gabriele Schatte, and Masood Parvez
Department of Chemistry, UniVersity of Calgary, Calgary, Alberta, Canada T2N 1N4
Received October 16, 2002
t
t
The reactions of {Li2[PhB(NBu)2]}2 with GaCl3 in various stoichiometries yield [Li(thf)4][PhB(µ-NBu)2GaCl2‚GaCl3]
t
t
(1), [PhB(µ-NBu)2GaCl]2 (2), and {µ-Li(OEt2)[PhB(NBu)2]Ga} (3a), a series of complexes in which the three chloride
ligands are successively replaced by the dianion [PhB(NBu)2]2-. The X-ray structures of 1, 2, and 3a show that
t
the boraamidinate ligand adopts an N,N′-chelating mode. In the ion-separated complex 1, one of the nitrogen
t
atoms is coordinated to a GaCl3 molecule. The related indium complexes [µ-LiCl(thf)2][PhB(µ-NBu)2InCl]2 (4) and
t
{µ-Li(OEt2)[PhB(µ-NBu)2]In} (3b) were obtained in a similar manner. Complex 4 is the indium analogue of 2 with
t
the incorporation of a bissolvated LiCl molecule. In 3a and 3b the spirocyclic {[PhB(µ-NBu)2]2M}- (M ) Ga, In)
anions are N,N′-chelated to the [Li(OEt2)]+ counterion. Prolonged reactions result in the formation of [PhB(µ-
t
t
NBu)2GaCl][tBuN(H)GaCl2] (5) and {[PhB(µ-NBu)2InCl][tBuN(H)InCl2][µ-LiCl(OEt2)2]} (6), respectively. The X-ray
structures of 5 and 6 reveal bicyclic structures which formally involve the entrapment of the monomers tBuN(H)-
MCl2 by a four-membered BN M ring (M ) Ga, In). The synthesis and X-ray structure of Cl2Ga[µ-N(H)Bu]2GaCl2
t
2
are also reported.
Introduction
recently we have discovered a potentially versatile route to
alkyl or aryl boraamidinates that involves the reaction of
trisaminoboranes B(NHR′)3 with 3 equiv of an organolithium
reagent RLi (R ) alkyl, aryl).9 In addition to effecting
dilithiation, the RLi reagents serve as a nucleophile in the
displacement of one NHR′ group by the substituent R. The
Complexes of amidinate anions [RC(NR′)2]- with main
group elements1a or transition metals1a,b have been studied
extensively. Recent work on group 13 systems has revealed
novel structural chemistry for In2 and catalytic activity for
cationic Al or Ga complexes.3 By contrast, previous inves-
tigations of the coordination chemistry of the isoelectronic
boraamidinate dianion [RB(NR′)2]2- have been limited to
group 4 for the transition metals and groups 14-16 in the
case of p-block elements.4 The most common route to aryl
boraamidinate complexes has involved the preparation of
{Li2[PhB(NR′)2]}x (R ) Pr, Bu) by dilithiation of PhB-
(NHR′)2 with LinBu followed by lithium-halogen exchange
with the appropriate transition-metal or main group element
halide.5-7 This approach has also been applied to the
pentafluorophenyl derivative C6F5B(µ-NtBu)2SnMe2.8 More
n
dilithium derivatives {Li2[RB(NR′)2]}x (R ) Me, Bu, Ph;
R′ ) tBu) have dimeric (x ) 2) cluster structures,7,9 although
a trimer (x ) 3) has also been structurally characterized for
t
R ) Me, R′ ) Bu.7
Although the use of the reagents {Li2[RB(NR′)2]}x in
metathetical reactions is the most versatile route to bora-
amidinate complexes,5-7 several other synthetic approaches
have been reported. These include the preparation of (a) the
dimeric Sn(II) complex [PhB(µ-NtBu)2Sn]2 by the reaction
of SnCl2 with Me3SiN(Li)BMe2,10 (b) sulfur(II) complexes
i
t
* Author to whom correspondence should be addressed. Phone: (403)
220-5741. Fax: (403) 289-9488. E-mail: chivers@ucalgary.ca.
(1) (a) Edelmann, F. T. Coord. Chem. ReV. 1994, 137, 403. (b) Barker,
J.; Kilner, M. Coord. Chem. ReV. 1994, 133, 219.
(2) (a) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 1423. (b) Zhou,
Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 2448.
(5) (a) Heine, A.; Fest, D.; Stalke, D.; Habben, C. D.; Meller, A.;
Sheldrick, G. M. J. Chem. Soc., Chem. Commun. 1990, 742. (b) Fest,
D.; Habben, C. D.; Meller, A.; Sheldrick, G. M.; Stalke, D.; Pauer, F.
Chem. Ber. 1990, 123, 703.
(6) Koch, H.-J.; Roesky, H. W.; Besser, S.; Herbst-Irmer, R. Chem. Ber.
1993, 126, 571.
(3) Dagome, S.; Guzei, I. A.; Coles, M. P.; Jordan, R. F. J. Am. Chem.
Soc. 2000, 122, 274 and references therein.
(4) For a review, see: Blais, P.; Brask, J. K.; Chivers, T.; Fedorchuk, C.;
Schatte, G. ACS Symposium Series 822; American Chemical Soci-
ety: Washington, DC, 2002; Chapter 14, pp 195-207.
(7) Brask, J. K.; Chivers, T.; Fedorchuk, C.; Schatte, G. Can. J. Chem.
2002, 80, 821.
(8) Habben, C. D.; Heine, A.; Sheldrick, G. M.; Stalke, D. Z. Naturforsch.
1992, 47b, 1367.
(9) Brask, J. K.; Chivers, T.; Schatte, G. Chem. Commun. 2000, 1805.
2084 Inorganic Chemistry, Vol. 42, No. 6, 2003
10.1021/ic0206286 CCC: $25.00 © 2003 American Chemical Society
Published on Web 02/21/2003

Syntheses of Gallium and Indium Boraamidinates
(NO3)3 in D2O, and 1.0 M LiCl in D2O, respectively. FTIR spectra
were obtained as Nujol mulls between KBr plates on a Mattson
4030 FTIR or Nicolet Nexus 470 spectrometer in the range 4000-
350 cm-1. Elemental analyses and mass spectra were obtained by
the Analytical Services Laboratory, Department of Chemistry,
University of Calgary.
of the type RB(µ-NR′)(µ-NR′′)S by treatment of sulfur(IV)
12
diimides with RB(SMe)2,11 (c) C6F5B(µ-NtBu)2CPh2 and
tBuB(µ-NtBu)2PtBu(NtBu)13 by [2 + 2] cycloaddition reac-
t
tions of the appropriate iminoborane with BuNdCPh2 or
tBuNdPtBu, respectively, (d) MesB(µ-NtBu)2Si(Mes)SiMe3
by the reaction of the iminoborane Me3Si(tBu)NBdNtBu
with the photochemically generated silylene SiMes2,14 (e)
MeB(µ-NAr)2SiMe2 (Ar ) 2,6-diisopropylphenyl) from the
isomerization of ArNdBN(Ar)SiMe3 formed by the lithiation
of Ar(H)NB(F)N(R)SiMe3 with LitBu,15 and (f) PhB(µ-
NtBu)2TeNtBu by the reaction of PhBCl2 with {Li2[Te-
(NtBu)3]}2.16
Preparation of (thf)4Li{[PhB(µ-NtBu)2GaCl2]GaCl3} (1). A
colorless solution of Li2[PhB(NtBu)2] (0.541 g, 2.215 mmol) in thf
(20 mL) was added to solid GaCl3 (0.780 g, 4.430 mmol) cooled
to -78 °C, whereupon a dark purple solution was obtained. The
reaction mixture was allowed to reach 23 °C after 30 min, and a
colorless solution was obtained after another 30 min. After 3.5 h
the volatile materials were removed under vacuum to give a sticky
white solid. Et2O (10 mL) was added, and the pale yellow solution
was filtered through a PTFE filter disk into a Schlenk glass tube to
remove LiCl. The formation of two phases was observed. The upper
colorless phase was removed and discarded. The remaining yellow
liquid was transferred into a test tube. Colorless blocklike crystals
of 1 (0.764 g, 0.907 mmol, 82% based on GaCl3) were obtained
In view of the current interest in the catalytic activity of
aluminum and gallium amidinates, as well as the potential
importance of group 13 complexes of nitrogen-centered
ligands as precursors of electronic materials such as gallium
nitride, we have initiated an investigation of boraamidinate
complexes of group 13 metals. In this paper we describe
the synthesis, spectroscopic characterization, and X-ray
structures of [Li(thf)4][PhB(µ-NtBu)2GaCl2‚GaCl3] (1), [PhB-
(µ-NtBu)2GaCl]2 (2), [µ-Li(OEt2){PhB(µ-NtBu)2}2M] (3a, M
) Ga; 3b, M ) In), and [µ-LiCl(thf)2][PhB(µ-NtBu)2InCl]2
(4), the first boraamidinate complexes of group 13 elements.
The spectroscopic and structural characterizations of the
novel bicyclic complexes {[PhB(µ-NBut)2GaCl][tBuN(H)-
GaCl2]} (5) and {[PhB(µ-NBut)2InCl][ButN(H)InCl2][µ-LiCl-
(OEt2)2]} (6) and the dimer Cl2Ga[µ-N(H)tBu]2GaCl2 (7) are
also reported.
1
after 7 d at -19 °C. H NMR (C4D8O, 23 °C, δ): 7.78-7.15 (m,
5 H, C6H5), 3.60 (m, 16 H, CH2CH2O), 1.75 (m, 16 H, CH2CH2O),
1.25 (s, 18 H, C4H9). 13C NMR (C4D8O, 23 °C, δ): 134.35, 127.95,
127.34 (C6H5), 56.12 (br) (CMe3), 33.82 (CMe3). 11B NMR (C4D8O,
23 °C, δ): 36.4. 71Ga NMR (C4D8O, 23 °C, δ): 247.8 (∆ν1/2 ) 49
Hz). 7Li NMR (C4D8O, 23 °C, δ): -0.71. Several attempts to obtain
CHN analyses gave inconsistent results owing to the loss of thf
from the complex.
From a second crystallization colorless platelike crystals of (thf)3-
(Et2O){Li[PhB(NtBu)2]GaCl2‚GaCl3} were obtained. 1H NMR
(C4D4O, 23 °C, δ): 7.85-7.18 (m, 5 H, C6H5), 3.63 (m, 12 H,
CH2CH2O), 3.36 (q, 4 H, CH3CH2O), 1.78 (m, 12 H, CH2CH2O),
1.308 (s, 18 H, C4H9), 1.11 (t, 6 H, CH3CH2O). 13C NMR (C4D8O,
23 °C, δ): 134.51, 127.78, 127.29 (C6H5), 68.27 (CH2CH2O), 66.36
(CH3CH2O), 56.05 (CMe3), 33.88 (CMe3), 26.43 (CH2CH2O), 15.72
(CH3CH2O). 11B NMR (C4D8O, 23 °C, δ): 37.4. 71Ga NMR: 247.8.
7Li NMR (C4D8O, 23 °C, δ): 0.91.
Experimental Section
Reagents and General Procedures. Solvents were dried and
distilled before use: tetrahydrofuran, toluene, n-hexane, diethyl ether
t
(all from Na/benzophenone); n-pentane (Na). BuNH2 (99.5%),
nBuLi (2.5 M solution in hexanes), PhBCl2 (97%), GaCl3 (99.99%),
and InCl3 (99.999%) were commercial samples (Aldrich) and used
as received. The reagent Li2[PhB(NtBu)2] was prepared from PhB-
(NHtBu)2 and 2 equiv of LinBu7 or by the reaction of B(NHtBu)3
with 3 equiv of LiPh.7 The handling of air- and moisture-sensitive
reagents was performed under an atmosphere of argon gas using
Schlenk techniques or a glovebox.
Preparation of {[PhB(µ-NtBu)2]GaCl}2 (2). A colorless solu-
tion of Li2[PhB(NtBu)2] (0.500 g, 2.049 mmol) in thf (20 mL) was
added to solid GaCl3 (0.360 g, 2.049 mmol) cooled to -78 °C.
The formation of a pink solution was observed. The reaction mixture
was allowed to reach 23 °C over a period of 50 min and then stirred
for 3 h. The volatile materials were removed under vacuum, and
Et2O (5 mL) was added. The solution was filtered through a syringe
filter PTFE disk (pore size 0.45 µm). The solution was concentrated
to 3 mL and filtered again, and n-pentane was added, whereupon
a white microcrystalline precipitate was formed. The solution was
stored at -20 °C to give an additional amount of white crystalline
solid. The total yield was 0.223 g. The product was a mixture of 2
and (Et2O)Li[PhB(µ-NtBu)2]2 (3). Attempts to separate the two
products through fractional crystallization were unsuccessful. The
NMR resonances for 2 were identified by subtraction of those for
1
Instrumentation. H NMR spectra were collected on Bruker
AM-200 and Bruker DRX 400 spectrometers operating at 200 and
400 MHz, respectively, and chemical shifts are reported relative
7
to that of Me4Si in CDCl3. 11B, 13C, 71Ga, and Li NMR spectra
were measured at 25 °C in C6D6 or C4D8O on a Bruker DRX 400
spectrometer using a 5 mm broad-band (BBO) probe operating at
128.336, 100.594, 122.014, and 155.459 MHz, respectively. Chemi-
cal shifts are reported relative to those of BF3‚Et2O in C6D6, Ga-
1
3 (vide infra). H NMR (C4D8O, 23 °C, δ): 7.5-7.1 (m, C6H5),
1.29 (s, C4H9). 13C NMR (C4D8O, 23 °C, δ): 133.0, 128.8, 128.4
(C6H5), 54.1 (CMe3), 34.4 (CMe3). 11B NMR (C4D8O, 23 °C, δ):
35.0.
(10) Fussstetter, H.; No¨th, H. Chem. Ber. 1979, 112, 3672.
(11) (a) Habben, C. D.; Heine, A.; Sheldrick, G. M.; Stalke, D.; Bu¨hl, M.;
von R. Schleyer, P. Chem. Ber. 1991, 124, 47. (b) Habben, C. D.;
Herbst-Irmer, R.; Noltemeyer, M. Z. Naturforsch. 1991, 46b, 625.
(12) Paetzold, P.; Richter, A.; Thijssen, T.; Wurtenburg, S. Chem. Ber.
1979, 112, 3811.
Preparation of (Et2O)µ-Li{Ga[PhB(µ-NtBu)2]2}2 (3a). A col-
orless solution of Li2[PhB(NtBu)2] (0.500 g, 2.049 mmol) in Et2O/
n-hexane (30 mL, 2:1) was added to solid GaCl3 (0.180 g, 1.024
mmol) cooled to -78 °C. An immediate exothermic reaction
occurred, and the formation of a dark purple solution was observed.
The reaction mixture was allowed to reach 23 °C after 15 min.
After 4.5 d the pale yellow solution was filtered through an Acrodisc
syringe PTFE filter to remove LiCl. Solvent was removed under
(13) Gudat, D.; Niecke, E.; Nieger, M.; Paetzold, P. Chem. Ber. 1988, 121,
565.
(14) Paetzold, P.; Hahnfeld, D.; Englert, U.; Wojnowski, W.; Dreczewski,
B.; Pawelec, Z.; Walz, L. Chem. Ber. 1992, 125, 1073.
(15) Luthin, W.; Stratmann, J.-G.; Elter, G.; Meller, A.; Heine, A.;
Gornitzka, H. Z. Anorg. Allg. Chem. 1995, 621, 1995.
(16) Chivers, T.; Gao, X.; Parvez, M. Angew. Chem., Int. Ed. Engl. 1995,
34, 2549.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2085

Chivers et al.
vacuum to give sticky white crystals. Addition of diethyl ether (5
mL) followed by cooling to -19 °C gave blocklike crystals of 3a
in two crops (0.254 g, 0.371 mmol, 36%). Anal. Calcd for C32H56B2-
GaLiN4O: C, 62.91; H, 9.25; N, 9.18. Found: C, 62.28; H, 9.62;
N, 9.06. 1H NMR (C4D8O, 23 °C, δ): 7.38-6.92 (m, 10 H, C6H5),
3.38 (q, 4 H, OCH2CH3), 1.11 (t, 6 H, OCH2CH3), 1.05 (s, 36 H,
C4H9). 13C NMR (C4D8O, 23 °C, δ): 133.6, 126.5, 124.3 (C6H5),
to remove LiCl. Concentration (ca. 15 mL) by removal of solvent
in vacuo and subsequent cooling (0 °C for 18 h) of the resulting
yellow solution yielded colorless crystals of 6 (0.26 g, 0.31 mmol,
48%). Anal. Calcd for BC26Cl4H53In2LiN3O2: C, 37.67; H, 6.45;
N, 5.07. Found: C, 36.68; H, 6.32; N, 5.03. A 1 mL aliquot of the
initial Et2O reaction mixture was pumped to dryness in vacuo and
taken up in C6D6. 1H NMR (C6D6, 23 °C): δ 7.60-7.21 (m, C6H5,
5 H), 2.28 (br s, NH), 1.54 (s, C4H9), 1.47 (s, C4H9), 1.35 (s, C4H9).
66.3 (OCH2CH3), 50.9 (CMe3), 36.3 (CMe3), 15.7 (OCH2CH3). 11
B
NMR (C4D8O, 23 °C, δ): 32.5. 7Li NMR (C4D8O, 23 °C, δ): -0.67.
Preparation of Li(OEt2){PhB(µ-NtBu)2}2In (3b). The addition
of a solution of Li2[PhB(NtBu)2] (1.00 g, 4.10 mmol) in Et2O (50
mL) to a stirred solution of InCl3 (0.50 g, 2.26 mmol) in Et2O (50
mL) at -78 °C produced a cloudy, bright pink solution. The reaction
mixture was heated at reflux for 18 h, and then the resulting cloudy,
yellow solution was filtered to remove LiCl. Concentration (ca. 80
mL) by removal of solvent in vacuo and subsequent cooling (0 °C
for 18 h) of the resulting yellow solution yielded colorless crystals
of 3b (0.42 g, 0.73 mmol, 32%). Anal. Calcd for C32H56B2-
InLiN4O: C, 58.57; H, 8.60; N, 8.54. Found: C, 58.24; H, 8.96;
7
11B NMR (C6D6, 23 °C): δ 31.7 (s). Li NMR (C6D6, 23 °C): δ
-1.48 (s). IR (cm-1): 3217 [ν(N-H)].
Preparation of Cl2Ga[N(H)tBu]2GaCl2 (7a). A slurry of Li-
[N(H)tBu] (0.288 g, 3.640 mmol) in diethyl ether (20 mL) was
added to a solution of gallium trichloride (0.641 g, 3.640 mmol) in
diethyl ether (30 mL) at -78 °C. The reaction mixture was allowed
to reach room temperature, whereupon a white precipitate formed.
After 20 h LiCl was removed by filtration through a PTFE syringe
filter disk (pore size 0.45 µm). Solvent was removed under vacuum
to give 7a as a white solid (0.678 g, 1.593 mmol, 88%). Anal.
Calcd for C4H10Cl2GaN: C, 22.58; H, 4.74; N, 6.58. Found: C,
22.33; H, 4.78; N, 6.23. NMR data indicated the presence of two
1
N, 8.62. H NMR (C6D6, 23 °C): δ 7.32 (m, 10 H, C6H5,), 3.17
1
(q, 4 H, OCH2CH3), 1.31 (s, 36 H, C4H9,), 0.89 (t, 6 H, OCH2CH3).
isomers (cis and trans). H NMR (C7D8, 23 °C): δ 2.46 (s, NH),
7
11B NMR (C6D6, 23 °C): δ 36.0 (br s). Li NMR (C6D6, 23 °C):
2.23 (s, NH), 1.07 (s, C4H9), 1.06 (s, C4H9). 13C NMR (C7D8, 23
°C): 56.8 [s, C(CH3)3], 56.6 [s, C(CH3)3], 31.1 [s, C(CH3)3], 30.7
[s, C(CH3)3]. IR (cm-1): 3245, 3192 [ν(N-H)]. Recrystallization
of the product from diethyl ether at -20 °C gave X-ray-quality
crystals of the trans isomer.
δ 0.71 (s).
Preparation of [µ-LiCl(thf)2][PhB(µ-NtBu)2InCl]2 (4). The
addition of a solution of Li2[PhB(NtBu)2] (0.50 g, 2.05 mmol) in
thf (50 mL) to solid InCl3 (0.45 g, 2.05 mmol) at -78 °C produced
a cloudy, bright pink solution. The reaction mixture was allowed
to stir for 3 h at 23 °C, whereupon the solvent was removed in
vacuo to give a pale gray residue. This residue was redissolved in
Et2O, and after filtration, a clear yellow filtrate was obtained.
Concentration (ca. 30 mL) by removal of solvent in vacuo and
subsequent cooling (0 °C for 18 h) of the resulting yellow solution
yielded colorless crystals of 4 (1.26 g, 1.40 mmol, 68%). 1H NMR
(C6D6, 23 °C, δ): 7.51-7.20 (m, 10 H, C6H5), 3.55 (m, 8 H, OCH2-
CH2), 1.39 (m, 8 H, OCH2CH2), 1.34 (s, 36 H, C4H9). 13C NMR
(C6D6, 23 °C, δ): 132.7, 127.8 (C6H5), 67.8 (OCH2CH2), 54.75
(br, CMe3), 35.29 (CMe3), 25.42 (OCH2CH2). 11B NMR (C6D6, 23
X-ray Structure Determinations. Single crystals of 1, 2, 3a,
3b, 4, 5, 6, and 7a were coated with Paratone 8277 oil (Exxon),
mounted onto thin glass fibers or inside a mounted CryoLoop
(Hampton Research, diameter of the nylon fiber 20 and 10 µm),
and quickly frozen in the cold nitrogen stream of the goniometer.
Measurements for 2, 3a, 3b, and 4 were made on a Nonius CCD
four-circle Kappa FR540C diffractometer using graphite-mono-
chromated Mo KR radiation (λ ) 0.71073 Å). Data were measured
using φ and ω scans. Data reduction was performed by using the
HKL DENZO and SCALEPACK software.17 A multiscan absorp-
tion correction was applied to the data (SCALEPACK).17 The X-ray
data for 1, 5, and 6 were collected on a Bruker AXS Platform/
Smart 1000 CCD diffractometer using graphite-monochromated Mo
KR radiation (λ ) 0.71073 Å). In each case three series of frames
were collected at a fixed ø angle of 54.79° and at values for φ
equal to 0°, 90°, and 180°, respectively. Data reduction was
performed by using the SAINT software.18 An empirical absorption
correction was applied (SADABS).19
7
°C, δ): 35.7. Li NMR (C6D6, 23 °C, δ): 0.25. Several attempts
to obtain CHN analyses gave inconsistent results owing to loss of
thf from the complex.
Preparation of {PhB(µ-NtBu)2GaCl[tBuN(H)]GaCl2} (5). The
addition of a solution of Li2[PhB(NtBu)2] (0.500 g, 2.049 mmol)
in toluene (10 mL) to a solution of GaCl3 (0.361 g, 2.049 mmol)
in toluene (10 mL) at -78 °C produced a colorless solution with
small amounts of a white precipitate (LiCl). The reaction mixture
was allowed to reach 23 °C very slowly and then heated to 55 °C
Relevant parameters for the data collections and crystallographic
data for 1, 2, 3a, 3b, 4, 5, 6, and 7a are summarized in Tables 1
and 2. The structures were solved by direct methods (2, 3b, SIR-
92;20a 1, 3a, 4, 5, 6, 7a, SIR-9720b) and refined by a full-matrix
1
for 18 h. The completeness of the reaction was monitored by H
NMR spectroscopy. LiCl was separated by filtration through an
Acrodisc syringe filter, and removal of solvent under vacuum
produced a sticky white solid. Recrystallization from Et2O at -19
°C gave 5 (0.392 g, 0.715 mmol, 70% based on GaCl3) as a white
(17) HKL DENZO and SCALEPACK v1.96: Otwinowski, Z.; Minor, W.
Processing of X-ray Diffraction Data Collected in Oscillation Mode;
Methods in Enzymology, Vol. 276: Macromolecular Crystallography,
Part A; Carter, C. W., Jr., Sweet, R. M., Eds.; Academic Press: San
Diego, CA, 1997; pp 307-326.
(18) SAINT V 5.0, Software for the CCD Detector System; Bruker AXS,
Inc.: Madison, WI, 1998.
(19) SADABS, V 2.01 (WindowsNT, SerVice Pack 6), Software for Area-
Detector Absorption and other Corrections; Bruker AXS, Inc.:
Madison, WI, 2000.
(20) (a) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. SIR-
92, A package for crystal structure solution by direct methods and
refinement. J. Appl. Crystallogr. 1993, 26, 343. (b) Altomare, A.;
Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.;
Burla, M. C.; Polidori, G.; Camalli, M.; Spagna, R. SIR 97, A package
for crystal structure solution by direct methods and refinement; Italy,
1997.
1
solid. H NMR (C4D8O, 23 °C, δ): 7.86-7.16 (m, 5 H, C6H5),
2.29 (s, 1 H, NH), 1.30 (s, 27 H, C4H9). 13C NMR (C4D8O, 23 °C,
δ): 133.6, 133.1, 126.9 (C6H5), 56.1 (br) (CMe3), 35.7 (CMe3).
11B NMR (C4D8O, 23 °C, δ): 37.4. 71Ga NMR (in C4D8O, 23 °C,
δ): 248.8 (∆ν1/2 ) 49 Hz). Anal. Calcd for C18H33BCl3Ga2N3: C,
39.44; H, 6.07; N, 7.67. Found: C, 38.00; H, 6.05; N, 7.07.
Preparation of {[PhB(µ-NtBu)2InCl][tBuN(H)InCl2][µ-LiCl-
(OEt2)2]} (6). The addition of a solution of Li2[PhB(NtBu)2] (0.16
g, 0.66 mmol) in Et2O (15 mL) to a stirred solution of InCl3 (0.15
g, 0.66 mmol) in Et2O (15 mL) at 23 °C produced a cloudy, pale
pink solution. The reaction mixture was allowed to stir for 18 h at
23 °C, whereupon the resulting cloudy, yellow solution was filtered
2086 Inorganic Chemistry, Vol. 42, No. 6, 2003

Syntheses of Gallium and Indium Boraamidinates
Table 1. Crystallographic Data for 1, 2, 3a, and 3b
1
2
3a
3b
empirical formula
fw
C30H55BCl5Ga2LiN2O4
842.20
C28H46B2Cl2Ga2N4
670.65
C32H56B2GaLiN4O
611.09
C32H56B2InLiN4O
656.19
space group
a, Å
b, Å
P21/c
P21/c
Pbcn
C2/c
13.9213(13)
11.6036(11)
25.361(2)
99.0474(19)
4045.7(7)
4
10.0624(2)
13.6143(3)
12.1416(3)
104.3800(10)
1611.20(6)
2
15.7660(5)
11.9720(9)
18.6330(9)
90a
3517.0(3)
4
11.1322(2)
16.7074(3)
20.3868(4)
103.3140(10)
3689.83(12)
4
c, Å
â, deg
V, Å3
Z
T (°C)
λ, Å
-80(2)
-100(2)
0.71073
1.382
18.62
0.0345
-100(2)
0.71073
1.154
8.11
0.0549
-100(2)
0.71073
1.181
6.7
0.04
0.71073
1.383
d
calcd, g cm-3
µ, cm-1
16.95
0.0413
0.1005
Rb
Rw
c
0.0912
0.1293
0.115
a R ) â ) γ ) 90°. b R ) ∑||Fo| - |Fc||/∑|Fo| [I g 2.00σ(I)]. c Rw ) {[∑w(Fo - Fc )2]/[∑w(Fo )2]}1/2 (all data).
2
2
2
Table 2. Crystallographic Data for 4, 5, 6, and 7a
4
5
6
7a
empirical formula
fw
C36H62B2Cl3In2LiN4O2
947.45
C18H33BCl3Ga2N3
548.07
C26H53BCl4In2LiN3O2
828.90
C8H20Cl4Ga2N2
425.50
space group
a, Å
b, Å
P21/c
P21/c
P21/n
P21/n
13.5690(2)
20.2680(2)
20.4090(2)
127.7511(5)
4437.92(9)
4
13.8474(12)
12.4157(11)
14.2062(11)
91.0080(18)
2449.0(4)
4
18.1901(14)
10.4585(8)
20.3996(15)
106.2219(13)
3726.6(5)
4
6.4670(2)
11.8600(5)
10.7420(5)
97.3790(14)
818.80(6)
2
c, Å
â, deg
V, Å3
Z
T (°C)
λ, Å
-100(2)
-80(2)
-80(2)
-100(2)
0.71073
1.726
39.22
0.0392
0.71073
0.71073
1.491
0.71073
d
calcd, g cm-3
1.418
12.53
0.0482
0.1249
1.478
15.50
0.0295
0.0666
µ, cm-1
25.43
0.0333
0.0825
Ra
Rw
b
0.0976
2
-
2
2
a R ) ∑||Fo| - |Fc||/∑|Fo| [I g 2.00σ(I)]. b Rw ) {[∑w(Fo
Fc )2]/[∑w(Fo )2]}1/2 (all data).
least-squares method based on F2 using SHELXL-97.21 The non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
included at geometrically idealized positions (C-H bond distances
0.95 Å) and were not refined. The NH protons in 5, 6, and 7a
were initially located in the difference Fourier map and then
included at geometrically idealized positions (N-H bond distances
0.95 Å) and were not refined. The isotopic thermal parameters of
the hydrogen atoms were fixed at 1.2 times that of the preceding
carbon or nitrogen atom.
Two carbon atoms [labeled as C(73), C(74), C(73′), and C(74′)]
in one of the four coordinating thf molecules in 1 were disordered
over two sites. The disorder was modeled using the split-atom
model, and the carbon atoms were refined using the SAME and
SIMU contraints. The partial occupancy factors for these atoms
were refined to 0.658(19) and 0.342(19), respectively. From a
second crystallization colorless thin-plate crystals of (thf)3-
(Et2O){Li[PhB(µ-NtBu)2GaCl2(GaCl3)]}, which belong to the space
group P21/c, were obtained. The cell dimensions are a ) 17.1100(4)
Å, b ) 13.8690(4) Å, c ) 13.0020(6) Å, â ) 113.7170(14)°, V )
4128.3(2) Å3, and Z ) 4. The coordinated thf and Et2O molecules
show severe disorder. The bond distances and bond angles for the
[PhB(µ-NtBu)2GaCl2(GaCl3)]}- anion are essentially identical to
those obtained for the anion in 1. Therefore, structural data for (thf)3-
(Et2O){Li[PhB(µ-NtBu)2GaCl2(GaCl3)]} will not be discussed
further.
axis with partial occupancy factors of 0.582(15) and 0.418(15),
respectively. The SAME and SIMU constraints were used to refine
these atoms. A disordered Et2O molecule was also located on a
special position in 3b with a partial occupancy factor of 0.50. The
carbon atoms of this Et2O molecule could only be refined
isotropically, and the isotropic displacement parameters were
constrained to be equal for the two CH3 and two CH2 carbon atoms,
respectively. The O-C and C-C bond distances were restrained
to 1.480(5) and 1.500(5) Å. In 4 one of the carbon atoms [C(84),
C(84′)] of one of the coordinated thf molecules was disordered over
two positions with partial occupancy factors of 0.56(4) and 0.44(4),
respectively. The SAME and SIMU constraints were used to refine
this atom. The atoms of one of the two Et2O molecules in 6 were
disordered over two sites [labeled as O(2A), C(61A), C(62A),
C(63A), C(64A), O(2B), C(61B), C(62B), C(63B), and C(64B)].
The occupancy factors of these atoms were refined initially and
then set to 0.60 and 0.40, respectively.
Results and Discussion
Formation and X-ray Structures of Gallium Bora-
amidinates. The reaction of Li2[PhB(NtBu)2] with GaCl3 was
carried out under a variety of conditions with variations in
stoichiometry, solvent, and reaction time. All products were
characterized by X-ray crystal structures in addition to their
The carbon atoms [labeled as C(31), C(32), C(31′), and C(32′)]
of the Et2O molecule in 3a were disordered around a 2-fold screw
7
multinuclear (1H, 13C, 11B, and, where appropriate, Li and
71Ga) NMR spectra. An interesting feature of these reactions
is the formation of intensely colored solutions when the
boraamidinate reagent is added to the group 13 metal halide.
(21) Sheldrick, G. M. SHELXL97-2: Program for the Solution of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2087

Chivers et al.
Figure 1. Molecular structure of the anion [PhB(µ-NtBu)2GaCl2‚GaCl3]-
in 1. The cation [Li(thf)4]+ is not shown.
Scheme 1
Figure 2. Molecular structure of 2.
thf in thf solution. The lack of a 71Ga resonance for GaCl3‚
thf has been attributed to quadrupole broadening.23 This
suggestion is consistent with the equivalence of the two NtBu
1
environments revealed in the H and 13C NMR spectra.
The reaction of GaCl3 with an equimolar amount of
Li2[PhB(NtBu)2] in thf produces a mixture of [PhB(µ-
NtBu)2GaCl]2 (2) and the spirocyclic complex [Li{PhB(µ-
NtBu)2}2Ga] (vide infra). As a result of the similar solubilities
of these two products it was not possible to isolate a pure
sample of 2 from this route. Crystals of 2 suitable for X-ray
analysis were obtained, however, from the reaction of 1 with
Li2[PhB(NtBu)2]. The dimeric structure of 2 (Figure 2) is
comparable to those of the previously reported tin(II)10 and
lead(II)5a boraamidinates.
The colors, which are more intense in the reaction with GaCl3
(purple) than that with InCl3 (pink), are tentatively attributed
to the formation of radicals.22
When the stoichiometry of the reaction of Li2[PhB(NtBu)2]
with GaCl3 is changed to 2:1, the spirocyclic compound [Li-
(OEt2){PhB(µ-NtBu)2}2Ga] (3a) is obtained in 20% yield.
The X-ray structural analysis of 3a (Figure 3) showed that
the spirocyclic anion [{PhB(µ-NtBu)2}2Ga]- is N,N′-chelated
to a monosolvated lithium cation.24 This anion and the indium
analogue in 3b are isoelectronic with the corresponding
neutral spirocyclic Ge(IV) and Sn(IV) derivatives, respect-
ively.5b Since 3a and 3b are isostructural, only the molecular
When the reaction of Li2[PhB(NtBu)2] with GaCl3 is
carried out in a 1:2 molar ratio in thf, the ion-separated
complex [Li(thf)4][PhB(µ-NtBu)2GaCl2‚GaCl3] (1) is ob-
tained in 82% yield (Scheme 1). The coordination of the
gallate anion [PhB(µ-NtBu)2GaCl2]- to a neutral GaCl3
molecule was established by an X-ray crystal structure of 1
1
(Figure 1). The H NMR spectrum of 1 in d8-thf shows
resonances corresponding to the Ph and NtBu groups, as well
as the coordinated thf ligands, with the appropriate relative
intensities. A singlet is observed at δ -0.71 in the 7Li NMR
spectrum. Surprisingly, only one resonance is observed in
the 71Ga NMR spectrum. This observation may indicate
dissociation into [Li(thf)4][PhB(µ-NtBu)2GaCl2] and GaCl3‚
1
structure of 3a is shown in Figure 3. The H NMR spectra
of 3a and 3b in d8-thf show resonances for the Ph and NtBu
groups, in addition to the coordinated OEt2 ligand, with the
(23) The 71Ga resonance for a thf solution of GaCl3 has a half-width of
19000 Hz. Bo¨ck, S.; No¨th, H.; Wietelmann, A. Z. Naturforsch. 1990,
45b, 979.
(22) Detailed EPR investigations of the radicals formed from {Li2[PhB(Nt-
Bu)2]}2 upon air oxidation and in reactions with main group element
halides are in progress. Boere´, R. T.; Chivers, T.; Fedorchuk, C.;
Schatte, G. Unpublished observations.
(24) The first spirogallane [Li(thf)‚12-crown-4][PhCdCPhPhCdCPh]2. It
is a solvent-separated ion pair with Ga-C bonds. Su, J.; Goodwin, S.
D.; Li, X.-W.; Robinson, G. H. J. Am. Chem. Soc. 1998, 120, 12994.
2088 Inorganic Chemistry, Vol. 42, No. 6, 2003

Syntheses of Gallium and Indium Boraamidinates
Figure 4. Molecular structure of 4. For clarity, only the R-carbon atoms
t
of Bu groups and the O atoms of thf ligands are shown.
Scheme 2
Figure 3. Molecular structure of 3a. For clarity, only the R-carbon atoms
t
of Bu groups and the O atoms of Et2O ligands are shown.
appropriate relative intensities. The equivalence of all four
1
NtBu environments in 3a and 3b indicated by the H and
13C NMR spectra at 23 °C suggest the occurrence of an
exchange process in which the chelation of Li+ changes
rapidly from N(1)/N(1)* to N(2)/N(2)*. Such fluxional
processes in lithium derivatives of polyimido anions of
p-block elements have low activation energies.25 Singlets are
observed in the 7Li NMR spectra of 3a and 3b at δ 0.40 and
0.71, respectively.
In summary, a series of gallium boraamidinates in which
each of the three chlorides attached to gallium is replaced
successively by the dianionic [PhB(NtBu)2]2- ligand may be
prepared by varying the stoichiometry of the reaction of
Li2[PhB(NtBu)2] and GaCl3.
and {[PhB(µ-NtBu)2InCl][tBuN(H)InCl2][µ-LiCl(OEt2)2] (6)
were obtained from the reaction of Li2[PhB(NtBu)2] (prepared
from B(NHtBu)3 and PhLi) with GaCl3 or InCl3 in a 1:1
molar ratio when long reaction times (ca. 18 h) were
employed. Apart from the incorporation of the bissolvated
LiCl molecule in 6, these two complexes have the same
bicyclic framework, which is formally comprised of a tBuN-
(H)ECl2 (E ) Ga, In) monomer coordinated to the four-
membered rings PhB(µ-NtBu)2ECl as depicted in Figures 5
and 6. tert-Butylamidolithium is a byproduct in the prepara-
tion of Li2[PhB(NtBu)2] from B(NHtBu)3 and 3 equiv of
PhLi.7 Thus, it is conceivable that [tBuN(H)ECl2]n could be
generated in situ from the reaction of ECl3 with LiN(H)tBu
impurity present in the boraamidinate reagent. The subse-
quent reaction of [tBuN(H)ECl2]n (E ) Ga, In) with 2 or 4
may generate 5 or 6, respectively.
We have prepared Cl2Ga[N(H)R]2GaCl2 (7a, R ) tBu) by
the reaction of GaCl3 with LiN(H)tBu in thf. However,
attempts to make the indium analogue of 7a by a similar
method gave a mixture of products that could not be
separated. The dimeric trimethylsilylamido derivative 7b (R
) SiMe3) has been structurally characterized as the trans
isomer.25 In C7D8 solution, however, 1H NMR spectra
revealed that 7b consists of a mixture of cis and trans dimers
Formation and X-ray Structures of Indium Bora-
amidinates. As indicated in Scheme 2, indium analogues
of 2 and 3a are obtained from the reaction of Li2[PhB(NtBu)]2
and InCl3. When equimolar amounts of these two reagents
are allowed to react in thf, the complex [µ-LiCl(thf)2][PhB-
(µ-NtBu)2InCl]2 (4) is isolated in 68% yield. Complex 4 can
be viewed as the indium analogue of the dimeric gallium
system 2 with the incorporation of a bissolvated lithium
chloride molecule in the indium complex (Figure 4). The
1H NMR spectra of 3 in d6-benzene show resonances for
the Ph and NtBu groups, in addition to the coordinated thf
ligand, with the expected intensities. As in the case of 2 the
apparent equivalence of the NtBu environments may indicate
the formation of a solvated monomer in thf solution. A singlet
7
is observed in the Li NMR spectrum at δ 0.25.
When the reaction of Li2[PhB(NtBu)2] and InCl3 is carried
out in a 2:1 molar ratio in boiling diethyl ether, the
spirocyclic complex 3b, the indium analogue of 3a, is
isolated in 32% yield.
Formation of the Bicyclic Complexes 5 and 6. The
bicyclic complexes [PhB(µ-NtBu)2GaCl][tBuN(H)GaCl2] (5)
(25) Brask, J. K.; Chivers, T. Angew. Chem., Int. Ed. 2001, 40, 3960.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2089

Chivers et al.
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for 1
Ga(1)-N(2)
Ga(1)-N(1)
Ga(1)-Cl(1)
Ga(1)-Cl(2)
Ga(2)-N(1)
Ga(2)-Cl(4)
Ga(2)-Cl(3)
Ga(2)-Cl(5)
1.880(2)
2.048(2)
2.1718(10) C(31)-B(1)
2.1834(9)
1.966(2)
N(1)-B(1)
N(2)-B(1)
1.565(4)
1.377(4)
1.592(4)
1.911(7)
1.923(6)
1.913(6)
1.921(7)
O(1)-Li(1)
O(2)-Li(1)
2.1792(10) O(3)-Li(1)
2.1875(9)
O(4)-Li(1)
2.1876(10)
N(2)-Ga(1)-N(1)
74.13(9)
C(10)-N(1)-B(1)
115.8(2)
N(2)-Ga(1)-Cl(1) 122.77(8)
N(1)-Ga(1)-Cl(1) 118.51(7)
N(2)-Ga(1)-Cl(2) 117.48(8)
N(1)-Ga(1)-Cl(2) 120.70(7)
Cl(1)-Ga(1)-Cl(2) 102.82(4)
N(1)-Ga(2)-Cl(4) 112.88(7)
N(1)-Ga(2)-Cl(3) 118.45(7)
Cl(4)-Ga(2)-Cl(3) 105.27(4)
N(1)-Ga(2)-Cl(5) 106.65(7)
Cl(4)-Ga(2)-Cl(5) 108.79(4)
Cl(3)-Ga(2)-Cl(5) 104.20(4)
C(10)-N(1)-Ga(2) 116.00(17)
B(1)-N(1)-Ga(2)
C(10)-N(1)-Ga(1) 116.23(17)
B(1)-N(1)-Ga(1) 83.37(15)
110.75(17)
Ga(2)-N(1)-Ga(1) 110.37(11)
B(1)-N(2)-C(20)
B(1)-N(2)-Ga(1)
133.5(2)
95.23(18)
Figure 5. Molecular structure of 5. For clarity, only the R-carbon atoms
t
of Bu groups are shown.
C(20)-N(2)-Ga(1) 130.97(19)
N(2)-B(1)-N(1)
N(2)-B(1)-C(31)
N(1)-B(1)-C(31)
107.2(2)
129.1(3)
123.6(2)
Table 4. Selected Bond Lengths (Å) and Bond Angles (deg) for 2
Ga(1)-N(2)
Ga(1)-N(1)a
Ga(1)-N(1)
Ga(1)-Cl(1)
1.8967(19) N(1)-B(1)
1.9657(18) N(2)-B(1)
2.0421(18)
1.552(3)
1.394(3)
2.1554(7)
N(2)-Ga(1)-N(1)a 118.73(8)
B(1)-N(2)-C(20)
B(1)-N(2)-Ga(1)
131.9(2)
94.10(15)
C(20)-N(2)-Ga(1) 133.81(15)
N(2)-Ga(1)-N(1)
74.11(8)
89.92(7)
N(1)a-Ga(1)-N(1)
N(2)-Ga(1)-Cl(1) 118.99(6)
N(1)a-Ga(1)-Cl(1) 117.89(6)
N(1)-Ga(1)-Cl(1) 126.29(6)
N(1)-B(1)-C(1)
N(2)-B(1)-C(1)
N(2)-B(1)-N(1)
125.1(2)
127.3(2)
107.42(19)
C(10)-N(1)-B(1)
115.72(18)
Figure 6. Molecular structure of 6. For clarity, only the R-carbon atoms
t
C(10)-N(1)-Ga(1) 123.54(14)
of Bu groups and the O atoms of OEt2 ligands are shown.
B(1)-N(1)-Ga(1)
84.03(13)
90.08(7)
Ga(1)a-N(1)-Ga(1)
a Symmetry transformations used to generate equivalent atoms: *-x,
-y + 1, -z.
In view of the difficulties of obtaining pure 2 (vide supra),
we were unable to determine whether the reaction of 2 with
7a is a viable source of 5. As an alternative, we carried out
the reaction of an equimolar mixture of Li[N(H)tBu] and
Li2[PhB(NtBu)2] with 2 equiv of GaCl3. Fractional crystal-
lization of the mixture of products from diethyl ether at -20
°C led to the isolation of colorless crystals of 2 after 2 d.
Complex 2 was identified by determination of unit cell
constants. After an additional 20 d, blocklike crystals were
obtained and identified as pure 5 by XRD (cell constants)
Figure 7. Molecular structure of 7a.
1
and by H and 13C NMR spectra.
in equilibrium with a trimer.26 By contrast, the H and 13C
1
NMR of 7a indicate a mixture of cis and trans isomers in
C7D8, but no resonances for the corresponding trimer are
observed. Recrystallization of 7a from toluene or diethyl
ether produced the pure trans isomer as established by an
X-ray structure (Figure 7). The bond lengths and bond angles
for 7a and 7b are compared in Table 8.
In view of the close similarity of the structural parameters
for these two derivatives, further discussion is not warranted.
It is noted, however, that the mean Ga-N and Ga-Cl
distances in the mesityl derivative 7c (R ) Mes) are ca. 0.03
and 0.08 Å longer than those in 7a and 7b,27 presumably as
a result of a combination of steric and electronic factors.
Structural Trends for Boraamidinate Complexes of
Gallium and Indium. Selected bond lengths and bond angles
for the individual boraamidinate complexes 1, 2, 3a, 3b, 4,
5, and 6 are summarized in Tables 3-7. In the discussion
of these structures the focus will be on general trends within
(26) Nult, W. R.; Anderson, J. A.; Odom, J. D.; Williamson, M. M.; Rubin,
(27) Kopp, M. R.; Kra¨uter, T.; Dashti-Mommertz, A.; Neumu¨ller, B. Z.
Naturforsch. 1999, 54b, 627.
B. H. Inorg. Chem. 1985, 24, 159.
2090 Inorganic Chemistry, Vol. 42, No. 6, 2003

Syntheses of Gallium and Indium Boraamidinates
Table 5. Selected Bond Lengths (Å) and Bond Angles (deg) for 3a and 3b
3a (M ) Ga)
3b (M ) In)
3a (M ) Ga)
3b (M ) In)
M(1)-N(1)
M(1)-N(2)
B(1)-N(1)
B(1)-N(2)
1.974(3)
1.887(3)
1.491(5)
1.423(5)
2.195(2)
2.069(2)
1.472(3)
1.424(4)
Li(1)-N(1)
Li(1)-O(1)
2.101(7)
1.926(10)
2.109(4)
1.885(8)
N(2)a-M(1)-N(2)
N(2)a-M(1)-N(1)
N(2)-M(1)-N(1)
N(1)-M(1)-N(1)a
C(10)-N(1)-B(1)
C(10)-N(1)-M(1)
B(1)-N(1)-M(1)
C(10)-N(1)-Li(1)
B(1)-N(1)-Li(1)
M(1)-N(1)-Li(1)
140.92(19)
131.31(14)
75.07(13)
106.01(18)
122.5(3)
131.5(3)
86.0(2)
104.2(3)
128.0(3)
78.4(2)
157.51(13)
128.70(8)
68.28(8)
98.31(10)
121.8(2)
127.52(18)
86.93(14)
107.15(17)
126.58(17)
78.93(15)
B(1)-N(2)-C(20)
B(1)-N(2)-M(1)
C(20)-N(2)-M(1)
N(2)-B(1)-N(1)
N(2)-B(1)-C(1)
N(1)-B(1)-C(1)
O(1)-Li(1)-N(1)
N(1)a-Li(1)-N(1)
135.1(4)
91.3(2)
135.0(2)
93.20(15)
131.56(18)
111.6(2)
125.3(2)
123.3(2)
128.09(15)
103.8(3)
133.4(3)
107.7(4)
125.9(4)
126.4(4)
131.4(2)
97.3(4)
1
3
a Symmetry transformations used to generate equivalent atoms: *-x + 1, y, -z + /2 (3a); -x + 1, y, -z + /2 (3b).
Table 6. Selected Bond Lengths (Å) and Bond Angles (deg) for 4
these dimeric complexes or, in the case of 1, to the
coordination of one N atom to a GaCl3 molecule. The B-N
bonds involving 3-coordinate nitrogen atoms are consistently
shorter than those involving 4-coordinate nitrogen atoms.
Consistently we note that the B-N bond distances are
approximately equal in the monomers PhB(µ-NtBu)2TeNtBu16
and PhB(µ-NtBu)2PBr,7 in which both nitrogen atoms are
3-coordinate. The Ga-Cl bond lengths in 1 fall within the
narrow range 2.172(1)-2.188 (1) Å (Table 3). These values
are typical for 4-coordinate Ga complexes.28 Interestingly,
the endocyclic Ga-N bond involving the 4-coordinate N(1)
atom is ca. 0.07 Å longer than the exocyclic Ga(2)-N(1)
bond, suggesting contributions from both resonance forms
1A and 1B to the overall structure.
In(1)-N(1)
In(1)-N(2)
In(1)-N(4)
In(1)-Cl(1)
In(2)-N(2)
In(2)-N(3)
In(2)-N(4)
In(2)-Cl(2)
In(2)-Cl(3)
2.105(3)
2.243(3)
2.114(3)
N(1)-B(1)
N(2)-B(1)
N(3)-B(2)
1.393(5)
1.538(5)
1.404(5)
1.497(5)
2.417(11)
2.345(10)
1.925(13)
1.913(12)
2.3730(10) N(4)-B(2)
2.191(3)
2.099(3)
2.566(3)
Cl(2)-Li(1)
Cl(3)-Li(1)
O(1)-Li(1)
2.4550(11) O(2)-Li(1)
2.5408(12)
N(1)-In(1)-N(4)
N(1)-In(1)-N(2)
N(4)-In(1)-N(2)
124.01(2)
67.07(11)
96.61(12)
B(2)-N(3)-C(30) 131.5(3)
B(2)-N(3)-In(2) 103.7(2)
C(30)-N(3)-In(2) 124.8(3)
B(2)-N(4)-C(40) 121.3(3)
N(1)-In(1)-Cl(1) 113.28(9)
N(4)-In(1)-Cl(1) 119.74(9)
N(2)-In(1)-Cl(1) 122.87(8)
B(2)-N(4)-In(1)
112.0(2)
C(40)-N(4)-In(1) 117.4(2)
B(2)-N(4)-In(2) 82.1(2)
N(3)-In(2)-N(2)
112.20(12)
N(3)-In(2)-Cl(2) 121.20(9)
N(2)-In(2)-Cl(2) 118.88(8)
N(3)-In(2)-Cl(3) 109.39(9)
N(2)-In(2)-Cl(3) 104.45(8)
C(40)-N(4)-In(2) 131.0(3)
In(1)-N(4)-In(2)
N(1)-B(1)-N(2)
84.47(10)
110.2(3)
N(1)-B(1)-C(51) 126.7(3)
N(2)-B(1)-C(51) 123.1(3)
Cl(2)-In(2)-Cl(3)
N(3)-In(2)-N(4)
N(2)-In(2)-N(4)
Cl(2)-In(2)-N(4)
84.64(4)
61.20(11)
85.94(10)
94.75(7)
N(3)-B(2)-N(4)
112.2(3)
N(3)-B(2)-C(61) 126.5(4)
N(4)-B(2)-C(61) 121.3(3)
Cl(3)-In(2)-N(4) 168.49(7)
O(2)-Li(1)-O(1)
110.1(5)
Li(1)-Cl(2)-In(2)
Li(1)-Cl(3)-In(2)
92.9(2)
92.5(3)
O(2)-Li(1)-Cl(3) 111.3(5)
O(1)-Li(1)-Cl(3) 112.2(5)
O(2)-Li(1)-Cl(2) 108.7(6)
O(1)-Li(1)-Cl(2) 123.0(5)
The central Ga2N2 ring in the step-shaped dimer 2 (Figure
2 and Table 4) is planar with unequal Ga-N distances of
1.966 and 2.042 Å (cf. 2.001 and 2.054 Å for the related
dimer [Me2Si(µ-NtBu)2GaCl]2).29 The Ga-N distance of
1.897 Å involving the 3-coordinate nitrogen atom [N(1)] is
significantly shorter than the mean value of 2.004 Å for the
Ga-(λ4)N bonds. The Ga-Cl bond length of 2.155 Å in 2
is similar to the reported literature values for d(Ga-Cl) in
complexes with 4-coordinate gallium in a N3Cl environ-
ment.29,30 The distorted tetrahedral geometry at gallium
involves bond angles in the range 74.1-126.3° with -N-
Ga-N ) 74.1° and 89.9° in the four-membered GaN2B and
Ga2N2 rings, respectively.
B(1)-N(1)-C(10) 134.5(3)
B(1)-N(1)-In(1)
96.0(2)
C(10)-N(1)-In(1) 129.3(2)
C(20)-N(2)-B(1) 117.8(3)
C(20)-N(2)-In(2) 118.3(2)
Cl(3)-Li(1)-Cl(2)
89.9(3)
B(1)-N(2)-In(2)
115.1(2)
C(20)-N(2)-In(1) 121.2(2)
B(1)-N(2)-In(1)
In(2)-N(2)-In(1)
86.5(2)
91.02(10)
this series of closely related group 13 complexes. In addition,
the significant features of individual structures will be
addressed.
The boron atom in all these boraamidinate complexes
adopts a trigonal planar geometry (∑-B ) 360.0 ( 0.2°)
with bond angles -N-B-N in the range 106.5-110.2°.
Consistently their 11B NMR chemical shifts all fall within a
narrow range (δ 32-36). As indicated in Table 9 there is a
significant difference in the two B-N bond distances in the
planar, four-membered BN2M (M ) Ga, In) rings, ranging
from ca. 0.05 to 0.19 Å. This disparity, which is also
observed for [Pb(µ-NtBu)2BPh]2,5a can be related to the
different coordination numbers of the two nitrogen atoms in
Complex 4 can be viewed as the indium analogue of 2 in
which one In-Cl unit has trapped a bissolvated LiCl
molecule (Figure 4 and Table 6). As expected the mean In-
(28) Beachley, O. T., Jr.; Gardinier, J. R.; Churchill, M. R.; Churchill, D.
G.; Keil, K. M. Organometallics 2002, 21, 946.
(29) Veith, M.; Swamy, K. C. K.; Huch, V. Phosphorus, Sulfur Silicon
Relat. Elem. 1995, 103, 25.
(30) Schranz, I.; Moser, D. F.; Stahl, L.; Staples, R. J. Inorg. Chem. 1999,
38, 5814.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2091

Chivers et al.
Table 7. Selected Bond Lengths (Å) and Bond Angles (deg) for 5 and 6
5 (M ) Ga)
6 (M ) In)
5 (M ) Ga)
6 (M ) In)
B(1)-N(1)
B(1)-N(2)
B(1)-C(41)
M(1)-N(1)
M(1)-N(2)
M(1)-N(3)
M(2)-N(2)
M(2)-N(3)
1.395(4)
1.563(4)
1.586(5)
1.879(2)
2.035(2)
1.978(2)
1.973(2)
1.995(2)
1.401(4)
1.508(4)
1.599(4)
2.100(2)
2.457(2)
2.208(2)
2.137(2)
2.179(2)
M(1)-Cl(1)
M(1)-Cl(4)
M(2)-Cl(2)
M(2)-Cl(3)
Li(1)-Cl(1)
Li(1)-Cl(4)
Li(1)-O(1)
Li(1)-O(2A)
2.1437(8)
2.4450(8)
2.4973(7)
2.3643(9)
2.3800(8)
2.425(5)
2.389(5)
1.929(6)
2.029(10)
2.1619(8)
2.1776(8)
N(1)-M(1)-N(3)
N(1)-M(1)-N(2)
N(3)-M(1)-N(2)
N(1)-M(1)-Cl(1)
N(3)-M(1)-Cl(1)
N(2)-M(1)-Cl(1)
N(1)-M(1)-Cl(4)
N(3)-M(1)-Cl(4)
Cl(1)-M(1)-Cl(4)
N(2)-M(2)-N(3)
N(2)-M(2)-Cl(2)
N(3)-M(2)-Cl(2)
N(2)-M(2)-Cl(3)
N(3)-M(2)-Cl(3)
Cl(2)-M(2)-Cl(3)
108.42(10)
74.49(10)
89.78(9)
124.81(8)
119.97(7)
127.12(7)
102.88(9)
62.81(8)
83.63(8)
133.73(7)
115.83(6)
96.17(5)
107.42(6)
105.02(6)
86.77(2)
83.63(8)
115.56(6)
106.07(7)
121.85(6)
116.80(6)
103.52(3)
B(1)-N(1)-C(10)
B(1)-N(1)-M(1)
C(10)-N(1)-M(1)
C(20)-N(2)-B(1)
C(20)-N(2)-M(2)
B(1)-N(2)-M(2)
C(20)-N(2)-M(1)
B(1)-N(2)-M(1)
M(2)-N(2)-M(1)
C(30)-N(3)-Ga(1)
C(30)-N(3)-Ga(2)
Ga(1)-N(3)-Ga(2)
N(1)-B(1)-N(2)
N(1)-B(1)-C(41)
N(2)-B(1)-C(41)
133.9(2)
132.3(2)
94.78(18)
130.37(19)
119.5(2)
100.77(17)
126.86(18)
122.9(2)
120.00(17)
110.69(16)
125.25(18)
83.97(16)
89.05(9)
129.80(16)
106.89(17)
120.80(16)
106.89(17)
88.30(8)
91.10(9)
120.59(7)
116.06(7)
114.46(7)
105.72(7)
107.47(3)
123.95(17)
124.50(17)
90.03(9)
123.63(19)
121.26(17)
93.97(9)
106.5(3)
110.7(2)
128.8(3)
125.0(2)
124.7(2)
124.2(2)
Table 8. Bond Lengths (Å) and Bond Angles (deg) for 7a and 7b
7a
7ba
7a
7ba
Ga(1)-N(1)
Ga(1)-N(1)
1.976(3)
1.979(3)
1.974(4)
1.964(4)
Ga(1)-Cl(1)
Ga(1)-Cl(2)
2.1605(9)
2.1439(11)
2.150(2)
2.136(2)
N(1)-Ga(1)-N(1)
N(1)-Ga(1)-Cl(2)
N(1)-Ga(1)-Cl(2)
N(1)-Ga(1)-Cl(1)
86.79(12)
110.37(9)
118.75(9)
119.47(8)
89.0(1)
111.7(1)
116.0(1)
115.8(1)
N(1)-Ga(1)-Cl(1)
Cl(2)-Ga(1)-Cl(1)
Ga(1)-N(1)-Ga(1)
109.91(8)
110.26(5)
93.21(12)
110.8(1)
111.9(1)
91.0(1)
a Data taken from ref 25.
Table 9. B-N Bond Lengths (Å) in Complexes of the Boraamidinate
distorted trigonal bipyramidal (tbp) with a bond angle -Cl-
(3)-In(2)-N(4) ) 168.49(7)° and ∑-In(2) ) 352.3° for
the equatorial-equatorial bond angles. The values of the
bond angles -N-In-N in the four-membered InN2B rings
are ca. 61.2° and 67.1° for 5-coordinate and 4-coordinate
indium, respectively.
In contrast to their neutral, isoelectronic Ge(IV) and Sn-
(IV) analogues, the spirocyclic structures in 3a and 3b are
distorted by N,N′-chelation of the anion to the monosolvated
Li+ counterion (Figure 3). The bond angles at the central
group 13 element deviate markedly from tetrahedral [ranges
ca. 75-141° (3a) and ca. 68-157.5° (3b)] (Table 5). As
expected, there are significant differences in M-N distances
involving the 3- and 4-coordinate nitrogen atom [0.09 Å (M
) Ga) and 0.13 Å (M ) In)].
Ligand [PhB(NtBu)2]2-
a
complex
d(B-N)
∆
ref
1
2
3a
3b
4
1.377, 1.565
1.394, 1.552
1.423, 1.491
1.424, 1.472
1.404, 1.538
1.395, 1.563
1.401, 1.508
1.393(10), 1.498(8)
1.422(24), 1.484(27)
1.453(9), 1.475(10)
1.440(4), 1.440(4)
1.439(2), 1.439(2)
1.413(8), 1.448(5)
1.447(3), 1.447(3)
0.188
0.158
0.068
0.048
0.134
0.168
0.107
0.105
0.062
0.022
0
this work
this work
this work
this work
this work
this work
this work
5a
10
5b
7
11a
5
6
{Pb[(µ-NtBu)2BPh]2}2
{Sn[(µ-NtBu)2BPh]2}2
Cp2Ti[(µ-NtBu)2BPh]
BrP[(µ-NtBu)2BPh]
S[(µ-NtBu)2BPh]
0
b
Te[(µ-NtBu)2BPh]2
0.035
0
6
7
c
[Cl2Te[(µ-NtBu)2BPh]]2
a Difference (Å) between short and long B-N bonds. b All N atoms are
3-coordinate in this spirocyclic complex with pseudo-tbp geometry. The
shorter B-N bonds involve the N atoms in the axial positions, i.e., the
longer Te-N bonds. c This complex dimerizes through weak Te‚‚‚Cl
interactions. All N atoms are 3-coordinate.
The final pair of complexes 5 and 6 have closely related
bicyclic structures, which formally involve the entrapment
t
of a monomeric BuN(H)MCl2 unit by a BN2M (M ) Ga,
In) four-membered ring (Figures 5 and 6). The fold angles
between the two four-membered rings in 5 and 6 are 70.36-
(8)° and 74.11(7)°, respectively. In the indium complex 6
the InCl unit is coordinated to a bissolvated LiCl molecule.31
This gives rise to a 5-coordinate geometry at In(1) similar
to that described for In(2) in 4. Thus, the bond angle N(20)-
In(1)-Cl(1) ) 168.6°, and the sum of the bond angles in
the trigonal plane is 352.4° (Table 5). The geometry at the
4-coordinate indium atom In(2) is distorted tetrahedral with
bond angles in the range 92.4-121.9°. The In-Cl distances
for In(2) are ca. 0.07 Å shorter than those involving In(1).
Cl bond lengths involving the 5-coordinate indium atom are
longer (by ca. 0.13 Å) than that involving the 4-coordinate
indium atom (cf. d(λ5)In-Cl ) 2.405(1) Å in the forma-
midinate complex [HC(µ-NCy)2InCl]2).2a The In-N bonds
follow the trend of increasing bond length as the coordination
number of N and/or In increases. However, the value of
2.566(3) Å for In(2)-N(4) is exceptionally long, even
allowing for the fact that this bond occupies one of the axial
positions of a tbp (cf. |d(In-N)| ) 2.237 Å for the axial
bonds in [HC(µ-NCy)2InCl]2).2a The geometry at In(2) is
2092 Inorganic Chemistry, Vol. 42, No. 6, 2003

Syntheses of Gallium and Indium Boraamidinates
The most significant feature of the structure of 6 is the long
transannular In(1)-N(2) bond, 2.457(2) Å. The weakness
of this interaction is highlighted by the observation that this
bond is 0.25 Å longer than the other bond [In(1)-N(3)]
involving 5-coordinate indium and 4-coordinate nitrogen. A
similar, but much less pronounced, trend is observed for 5
in which the transannular Ga(2)-N(2) bond is significantly
longer than the other Ga-N bonds, 2.035(2) Å vs 1.879(2)-
1.995(2) Å. In 5, however, both gallium atoms are 4-coor-
dinate with bond angles in the ranges 74.5-127° [Ga(1)]
and 91-120.6° [Ga(2)] and typical Ga-Cl bond lengths.
ligand via metathetical reactions. The complexes with M-Cl
functionalities, e.g., 2 and 4, are suitable precursors for alkyl
derivatives with Lewis acidic centers. The Lewis base
properties of the BN2Ga ring toward GaCl3 in 1 may be
significant in future studies of the catalytic behavior of group
13 boraamidinates. The oxidation of the spirocyclic anions
in 3a and 3b to the corresponding neutral radicals is an
intriguing possibility that is being pursued.
Acknowledgment. We thank Dr. R. MacDonald (Uni-
versity of Alberta) for the X-ray data collections of 5 and 6
and the NSERC (Canada) for financial support.
Conclusions
The chloride substituents in MCl3 (M ) Ga, In) can be
successively replaced by an N,N′-chelating boraamidinate
Supporting Information Available: X-ray crystallographic files
in CIF format for 1, 2, 3a, 3b, 4, 5, 6, and 7. This material is
available free of charge via the Internet at http://pubs.acs.org.
(31) For recent examples of the entrapment of LiCl by amidinate complexes,
see: Chivers, T.; Downard, A.; Parvez, M. Inorg. Chem. 1999, 38,
4347.
IC0206286
Inorganic Chemistry, Vol. 42, No. 6, 2003 2093