Oxidative addition of group 13 and 14 metal halides and alkyls to Ga(DDP) (DDP = bulky bisimidinate)

Article abstract of DOI:10.1021/ic800690z

The oxidative addition of a variety of group 13 and group 14 halides and alkyls R_aMX to the mono valent group 13 bis-imidinate Ga(DDP) (DDP = 2-{(2,6-diisopropyl-phenyl)amino}-4-{(2,6-diisopropylphenyl)imino}-2-pentene) is reported. Accordingly

Full text of DOI:10.1021/ic800690z

Inorg. Chem. 2008, 47, 7279-7285
Oxidative Addition of Group 13 and 14 Metal Halides and Alkyls to
Ga(DDP) (DDP ) Bulky Bisimidinate)
Andreas Kempter, Christian Gemel, and Roland A. Fischer*
Anorganische Chemie II - Organometallics & Materials, Ruhr-UniVersita¨t Bochum,
D-44780 Bochum, Germany
Received April 17, 2008
The oxidative addition of a variety of group 13 and group 14 halides and alkyls RaMX to the mono valent group
13 bis-imidinate Ga(DDP) (DDP ) 2-{(2,6-diisopropyl-phenyl)amino}-4-{(2,6-diisopropylphenyl)imino}-2-pentene)
is reported. Accordingly, the insertion of Ga(DDP) into the Ga-Me bond of GaMe3 yield in the complexes
[{(DDP)GaMe}GaMe2] (1) and [{(DDP)GaMe}2GaMe] (2), respectively, which show a temperature-dependent
equilibrium between 1 at higher temperatures and 2 at lower temperatures. In the case of GaCl3, the only isolable
product is [{(DDP)GaCl}2GaCl] (3). The related reaction of SnMe2Cl2 with Ga(DDP) yields the compound
[Me2Sn{ClGa(DDP)}2] (4), whereas SnMe4 behaves inert. In the case of SiCl4, only the monoinsertion product
[Cl3Si{ClGa(DDP)}] (5) was observed. Finally, [(CH3)3C{ClGa(DDP)}] (6) is synthesized by insertion of Ga(DDP)
into the C-Cl bond of ClC(CH3)3. All new compounds were fully characterized by elemental analysis, NMR-
spectroscopy, and single-crystal X-ray diffraction analysis.
Introduction
Ma(ER)b.18–20 Quite recently, Power, Roesky, and Hill added
a new class of compounds to the series ER, that is the bulky
bisimidinates E(DDP) (DDP ) 2-{(2,6-diisopropyl-pheny-
l)amino}-4-{(2,6-diisopropylphenyl)imino}-2-pen-
tene).21–23 Additionally, the related borylene complex
[B{ArNCH}2]Li was reported by Segawa et al. in 2006.24
The chemistry of these compounds has proven to be very
prosperous and especially in the case of Al(DDP) a variety
of coordination, oxidation and insertion reactions were
studied in some detail.25–28 Thus, the aluminum center in
Al(DDP) has been shown to be rather Lewis acidic,
The chemistry of monovalent group 13 compounds ER is
a fascinating part of modern inorganic chemistry and has
been explored extensively in the past 20 years.1–14 Their
coordination chemistry to electron-rich transition metals is
very rich, especially for R ) Cp*, ranging from classical
organometallic reactions such as C-H or C-C bond
activation reactions,15–17 to unprecedented product classes,
for example, homoleptic cluster compounds of the type
* To whom correspondence should be addressed. E-mail: roland.fischer@
ruhr-uni-bochum.de. Fax: (+49)234 321 4174.
(1) Uhl, W. Angew. Chem. 1993, 105, 1449.
(16) Steinke, T.; Cokoja, M.; Gemel, C.; Kempter, A.; Krapp, A.; Frenking,
G.; Zenneck, U.; Fischer, R. A. Angew. Chem., Int. Ed. 2005, 44,
2943.
(2) Loos, D.; Schno¨ckel, H. J. Organomet. Chem. 1993, 463, 37.
(3) Dohmeier, C.; Loos, D.; Schno¨ckel, H. Angew. Chem., Int. Ed. 1996,
35, 129.
(17) Steinke, T.; Gemel, C.; Cokoja, M.; Winter, M.; Fischer, R. A. Angew.
Chem., Int. Ed. 2004, 43, 2299.
(4) Haubrich, S. T.; Power, P. P. J. Am. Chem. Soc. 1998, 120, 2202.
(5) Niemeyer, M.; Power, P. P. Angew. Chem. 1998, 110, 1291.
(6) Murugavel, R.; Chandrasekhar, V. Angew. Chem., Int. Ed. 1999, 38,
1211.
(18) Steinke, T.; Gemel, C.; Winter, M.; Fischer, R. A. Chem.sEur. J.
2005, 11, 1636.
(19) Steinke, T.; Gemel, C.; Winter, M.; Fischer, R. A. Angew. Chem.,
Int. Ed. 2002, 41, 4761.
(7) Murugavel, R.; Chandrasekhar, V. Angew. Chem. 1999, 111, 1289.
(8) Fischer, R. A.; Weiss, J. Angew. Chem., Int. Ed. 1999, 38, 2831.
(9) Fischer, R. A.; Weiss, J. Angew. Chem. 1999, 111, 3002.
(10) Twamley, B.; Power, P. P. Angew. Chem. 2000, 112, 3643.
(11) Braunschweig, H.; Colling, M. Coord. Chem. ReV. 2001, 223, 1.
(12) Braunschweig, H.; Colling, M. Eur. J. Inorg. Chem. 2003, 393.
(13) Hardman, N. J.; Wright, R. J.; Phillips, A. D.; Power, P. P. J. Am.
Chem. Soc. 2003, 125, 2667.
(20) Steinke, T.; Gemel, C.; Winter, M.; Fischer, R. A. Angew. Chem. 2002,
114, 4955.
(21) Hardman, N. J.; Eichler, B. E.; Power, P. P. Chem. Commun. 2000,
1991.
(22) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao, H.;
Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4274.
(23) Hill, M. S.; Hitchcock, P. B. Chem. Commun. 2004, 1818.
(24) Segawa, Y.; Yamashita, M.; Nozaki, K. Science 2006, 314, 113.
(25) Baker, R. J.; Jones, C. Coord. Chem. ReV. 2005, 249, 1857.
(26) Roesky, H. W. Inorg. Chem. 2004, 43, 7284.
(27) Roesky, H. W.; Kumar, S. S. Chem. Commun. 2005, 4027.
(14) Gemel, C.; Steinke, T.; Cokoja, M.; Kempter, A.; Fischer, R. A. Eur.
J. Inorg. Chem. 2004, 4161.
(15) Steinke, T.; Gemel, C.; Cokoja, M.; Winter, M.; Fischer, R. A. Angew.
Chem. 2004, 116, 2349.
10.1021/ic800690z CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 16, 2008 7279
Published on Web 07/17/2008

Kempter et al.
Scheme 1. Synthesis of [{(DDP)GaMe}GaMe2] (1) and [{(DDP)GaMe}2GaX] (X ) Me (2), Cl (3))
coordinating also weak donors such as the aromatic C-F
group of a B(C6F5)3 moiety.29 Also, acetylene is coordinating
strongly to the aluminum center leading to a metallacyclo-
propene structure through backbonding of Al(I) to the
coordinating acetylene.30 Al(DDP) is easily oxidized by a
variety of reagents, P4 or S8 for example, leading to the
dimeric aluminacycles [(DDP)Al]2P431 and [(DDP)Al]2S6.32
In the case of Ga(DDP), the latter reaction leads to the
dimeric sulfide [(DDP)Ga]2S, whereas oxidation of Ga(DDP)
by N2O leads to the structurally analogous oxide.33
Whereas the chemistry of the neutral compounds E(DDP)
is mainly studied in the context of nonmetallic main group
element substrates as outlined above, the anionic NHC
congener [Ga{[N(Ar)C(H)]2}]- (Ar ) 2,6-iPr2C6H3) has been
shown to form very stable bonds to electropositive elements
such as Ca, Mg, Nd, Pb, Ge, or Sn.34–36 In many cases, these
compounds are prepared by salt metathesis reactions of
substrates containing M-X bonds, which on reaction with
[K(tmeda)][Ga{[N(Ar)C(H)]2}] lead to M-Ga complexes
under elimination of KX. The anionic intermediates of these
reactions, that is the initial products formed by coordination
or oxidative addition of M-X to the gallium heterocycle,
have not been reported so far. However, the general
possibility for oxidative addition of group 14 elements to
gallium(I) heterocycles has been reported by Jones et al.37,38
Against this background of previous work, we became
interested in the coordination behavior of Ga(DDP) to
electropositive main group element halides and alkyls. The
fact that the Ga(I) center in this compound is easily oxidized
suggests the use of substrates, which are intrinsically more
difficult to reduce, such as Ga(III), Si(IV), or Sn(IV). In fact,
the rich redox chemistry of Ga(DDP) could be an entry into
M-Ga compounds also of the more electropositive main
group metals, in analogy to the insertion reactions of
Ga(DDP) into transition-metal halide bonds, which has been
studied by us and others in more detail.39–41 In this article,
we present the reactions of Ga(DDP) with GaMe3, GaCl3,
SiCl4, ClC(CH3)3, and Me2SnCl2. In all cases, oxidative
addition of M-X to Ga(DDP) is observed, leading to a
variety of new main group metal-gallium compounds.
Results and Discussion
Oxidative Addition of GaR3 (R ) CH3, Cl) to Ga(DDP).
When adding 1 equiv of GaMe3 (as a 0.25 M solution in
hexane) to a yellow solution of Ga(DDP) in hexane under
vigorous stirring, the color of the solution turns to intense
yellow. On storing, the resulting mixture at -30 °C
overnight, bright-yellow crystals of [{(DDP)GaMe}Ga-
Me2] (1) can be obtained in 81% yield (Scheme 1). 1 is quite
air sensitive but stable in an inert gas atmosphere for several
days and can be dissolved in non polar organic solvents such
as hexane or toluene.
The 1H NMR spectrum of 1 in C6D6 at room temperature
shows the typical set of signals for a Ga(DDP) moiety with
reduced (CS) symmetry, which is a result of the insertion of
Ga(DDP) in one Ga-Me bond of GaMe3 and is known for
the insertion into transition-metal halide bonds (e.g., in
[(Ph3P)AuCl] and [(COE)2RhCl]2).39,40 Additionally, signals
at 0.37 ppm (6H) and -0.25 ppm (3H) can be assigned to
the methyl protons of the GaMe2 moiety and the GaMe(DDP)
ligand, respectively. The 13C NMR spectrum is in good
agreement with this result, showing two distinct signals for
{MeGa(DDP)} (1.4 ppm) and {GaMe2} (-6.1 ppm), re-
spectively.
(28) Hardman, N. J.; Phillips, A. D.; Power, P. P. ACS Symposium Series
2002, 822, 2.
(29) Yang, Z.; Ma, X.; Oswald, R. B.; Roesky, H. W.; Zhu, H.; Schulzke,
C.; Starke, K.; Baldus, M.; Schmidt, H.-G.; Noltemeyer, M. Angew.
Chem., Int. Ed. 2005, 44, 7072.
(30) Zhu, H.; Chai, J.; Fan, H.; Roesky, H. W.; He, C.; Jancik, V.; Schmidt,
H.-G.; Noltemeyer, M.; Merrill, W. A.; Power, P. P. Angew. Chem.,
Int. Ed. 2005, 44, 5090.
(31) Peng, Y.; Fan, H.; Zhu, H.; Roesky, H. W.; Magull, J.; Hughes, C. E.
Angew. Chem., Int. Ed. 2004, 43, 3443.
(32) Peng, Y.; Fan, H.; Jancik, V.; Roesky, H. W.; Herbst-Irmer, R. Angew.
Chem., Int. Ed. 2004, 43, 6190.
(33) Hardman, N. J.; Power, P. P. Inorg. Chem. 2001, 40, 2474.
(34) Jones, C.; Mills, D. P.; Platts, J. A.; Rose, R. P. Inorg. Chem. 2006,
45, 3146.
Single crystals for X-ray diffraction could be obtained from
a saturated solution of 1 in hexane at -30 °C. The molecular
structure of 1 is shown in Figure 1 (left).
1 consists of a gallium atom, which is coordinated in a
trigonal-planar geometry by two methyl and one {(DDP)-
(35) Arnold, P. L.; Liddle, S. T.; McMaster, J.; Jones, C.; Mills, D. P.
J. Am. Chem. Soc. 2007, 129, 5360.
(36) Green, S. P.; Jones, C.; Lippert, K.-A.; Mills, D. P.; Stasch, A. Inorg.
Chem. 2006, 45, 7242.
(37) Jones, C.; Mills, D. P.; Rose, R. P. J. Organomet. Chem. 2006, 691,
3060.
(39) Kempter, A.; Gemel, C.; Fischer, R. A. Inorg. Chem. 2005, 44, 163.
(40) Kempter, A.; Gemel, C.; Hardman, N. J.; Fischer, R. A. Inorg. Chem.
2006, 45, 3133.
(38) Jin, G.; Jones, C.; Junk, P. C.; Stasch, A.; Woodul, W. D. New J. Chem.
2008, 32, 835.
7280 Inorganic Chemistry, Vol. 47, No. 16, 2008

Ga(DDP) (DDP ) Bulky Bisimidinate)
Figure 1. Molecular structure of [{(DDP)GaMe}GaMe2] (1) (left) and [{(DDP)GaMe}2GaMe] (2) (right). Selected bond length (angstroms) and angles
(degrees) for 1: Ga1-Ga2 2.4508(18), Ga1-N1 1.981(5), Ga1-N2 2.001(6), Ga1-C30 1.981(6), Ga2-C31 1.815(7), Ga2-C32 1.990(7); N1-Ga1-N2
93.0(2), C30-Ga1-Ga2 113.8(2), C31-Ga2-Ga1 121.8(3), C32-Ga2-Ga1 121.2(2), C31-Ga2-C32 116.9(4), C30-Ga1-Ga2-C3 22.5. Selected bond
length (angstroms) and angles (degrees) for 2: Ga1-Ga2 2.5030(18), Ga1-Ga2* 2.5062(17), Ga2-N1 2.006(8), Ga2-N2 2.005(8), Ga2*-N1 2.048(8),
Ga2*-N2 2.037(7), Ga1-C30 2.000(9), Ga2-C31 1.981(7), Ga2*-C3* 1.996(7); Ga2-Ga1-Ga2* 138.37(5), C30-Ga1-Ga2 122.5(3), C31-Ga1-Ga2*
124.7(3), C31-Ga2-Ga1 112.2(2), C31*-Ga2*-Ga1 121.0(2), N1-Ga1-N2 91.7(3), N1-Ga2-N2 92.1(3), C30-Ga1-Ga2-C31 179.8(4),
C31-Ga2-Ga2*-C31* 0.08.
GaMe} ligand, respectively. The Ga-Ga bond distance
(2.4508(18) Å) is comparable to other covalent Ga-Ga
interactions such as [Cp*Ga(GaCp*Cl2)] (2.4245(3) Å)42 or
[{(CSiMe3)GaBr}2] (2.43 Å).43
On slow addition of GaMe3 to 2 equiv of Ga(DDP) in
hexane, the color changes to orange after the addition is
completed. Stirring the reaction mixture for 1 h at room
temperature and cooling it to -30 °C overnight leads to a
mixture of bright-yellow single crystals of 1 (as proven by
single-crystal X-ray diffraction analysis) and deep-orange
crystals of [{(DDP)GaMe}2GaMe] (2) (Scheme 1). The
overall yield of 2 is rather low (22-25%) and could only
be determined by manual separation of the crystals. 2 is stable
in the solid state in an inert gas atmosphere for several days
without decomposition, but readily dissociates to 1 and
Ga(DDP) on redissolving in all common organic solvents at
Interestingly, the Ga-C bond length of the methyl groups
cis to each other are quite similar with 1.981(6) Å (Ga1-C30)
and 1.990(7) Å (Ga2-C32) and thus is comparable to
those in [(DDP)GaMe2] (1.970(2) and 1.979(2) Å)44 or
[(DDP)GaMeCl] (1.956(2) Å),45 respectively. In contrast, the
bond length of the methyl group cis to the DDP backbone
is distinctly shorter (Ga2-C31: 1.815(7) Å). However,
similar bond distances can be found for example in [(Me3Ga)4-
(C6N4)] (1.837 Å; C6N4 ) hexamethylenetetramine, N4,
adamantane).46
The insertion of the Ga(DDP) moiety into the Ga-Me
bond is reflected by the distorted tetrahedral geometry at the
gallium center, coordinated by the DDP-backbone, the
methyl, and the GaMe2 moiety, respectively (angular sum
Ga-N-N-Me: 319.55), with a dihedral angle between the
C3N2 and the GaN2 arrays of 25.67°. The Ga-N bond
distances are 1.981(5) Å and 2.001(6) Å, which is consistent
with an electron rich gallium center. Similar Ga-N bond
distances can be found for example in [{(DDP)Ga}-
Au{Ga(DDP)Cl}] (1.936(5)-1.995(5) Å)39 or [(coe)(η6-
benzene)Rh{(DDP)GaCl}] (1.974(3) Å and 2.018(3) Å).
1
room temperature, as proven by H NMR spectroscopy.
Therefore, variable-temperature 1H NMR spectroscopy of a
2:1 mixture of Ga(DDP) and Me3Ga in toluene was
performed (Supporting Information).
At 50 °C, only signals for free Ga(DDP) (5.18 ppm) and
1 (4.83 ppm) are observed. On cooling the solution to room
temperature, new signals at 4.74, 0.42, and -0.01 ppm
appear, which can be assigned to the γ-CH of the DDP
backbone and the two distinct GaMe groups of 2. On further
cooling the solution to -40 °C, the signals for free Ga(DDP)
and 1 vanish, and only the signals for 2 remain. Thus, a
temperature-dependent equilibrium between 2, 1, and Ga(D-
DP) exists, which is shifted toward 2 at lower temperature
(Scheme 1).
(41) Kempter, A.; Gemel, C.; Cadenbach, T.; Fischer, R. A. Inorg. Chem.
2007, 46, 9481.
j
2 crystallizes in the triclinic space group P1 with half of
(42) Jutzi, P.; Neumann, B.; Reumann, G.; Schebaum, L. O.; Stammler,
H.-G. Organometallics 2001, 20, 2854.
the molecule in the unit cell. Figure 1 (right) shows the
molecular structure of 2, which consists of a central GaMe
moiety, which is coordinated by a methyl and two {(DDP)-
GaMe} moieties in a trigonal planar geometry (angular sum
Ga-Ga-Ga-Me: 360.0°). The two Ga-Ga bonds of
2.5030(18) and 2.5062(17) Å are slightly longer than in 1
(2.4508(18)) but within the range of Ga-Ga distances in
other trigallanes (e.g., 2.451(1) and 2.460(1) Å in [{(PEt3)-
(43) Uhl, W.; Ei-Hamdan, A.; Geiseler, G.; Harms, K. Z. Anorg. Allg. Chem.
2004, 630, 821.
(44) Stender, M.; Eichler, B. E.; Hardman, N. J.; Power, P. P.; Prust, J.;
Noltemeyer, M.; Roesky, H. W. Inorg. Chem. 2001, 40, 2794.
(45) Singh, S.; Ahn, H.-J.; Stasch, A.; Jancik, V.; Roesky, H. W.; Pal, A.;
Biadene, M.; Herbst-Irmer, R.; Noltemeyer, M.; Schmidt, H.-G. Inorg.
Chem. 2006, 45, 1853.
(46) Hill, J. B.; Eng, S. J.; Pennington, W. T.; Robinson, G. H. J.
Organomet. Chem. 1993, 445, 11.
Inorganic Chemistry, Vol. 47, No. 16, 2008 7281

Kempter et al.
Table 1. Crystallographic Data for 1-6
1
2
3
4
5
6
empirical formula
fw
C32H50Ga2N2
602.18
105(2)
C59H85Ga3N4
1059.47
113(2)
C58H82Cl3Ga3N4
1150.83
113(2)
0.71073
Monoclinic
P21/c
14.5470(14)
20.3303(18)
24.2913(14)
90.00
104.506(7)
90.00
6955.0(10)
2
1.273
C60H88Cl2Ga2N4Sn
1197.43
113(2)
0.71073
monoclinic
P21/c
22.3307(10)
12.8162(5)
32.5680(18)
90.00
118.894(4)
90.00
8160.5(7)
4
1.047
C29H41Cl4GaN2Si
657.25
113(2)
0.71073
monoclinic
P21/m
9.0848(5)
20.4648(15)
9.6349(6)
90.00
114.738(6)
90.00
1626.92(18)
2
1.342
C33H50ClGaN2
579.92
113(2)
0.71073
monoclinic
P21/c
10.203(12)
26.884(8)
13.510(12)
90.00
120.31(6)
90.00
temperature [K]
wavelength [Å]
cryst syst
space group
a (Å)
0.71073
triclinic
0.71073
Triclinic
j
j
P1
P1
11.025(5)
12.214(5)
14.119(6)
65.03(4)
68.78(4)
70.49(4)
1569.3(12)
2
1.274
1.738
636
8.957(5)
b (Å)
c (Å)
12.996(12)
14.388(7)
85.47(6)
80.28(5)
80.24(6)
1625(2)
1
1.083
1.269
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
3199(5)
2
1.204
0.966
Z
δcalcd [g cm-3
]
µ [mm-1
F (000)
]
1.311
2800
1.058
2688
1.232
684
623
1240
2θ range [deg]
3.05 - 27.56
-14 e h e 10
-15 e k e 15
-18 e l e 16
7148
3.36 - 27.56
-11 e h e 10
-16 e k e 16
-18 e l e 18
7417
2.71 - 27.58
-18 e h e 18
-25 e k e 26
-24 e l e 31
15 967
2.62 - 27.59
-24 e h e 29
-16 e k e 24
-14 e l e 42
18 841
2.66 - 27.58
-10 e h e 11
-23 e k e 26
-12 e l e 11
3867
3.08 - 25.10
-9 e h e 12
-30 e k e 31
-16 e l e 16
5641
index ranges
reflns collected
reflns unique
2275
0.751
4517
1.016
3569
0.478
6188
0.721
2754
0.983
4233
1.163
GOF on F2
final R indices [I > 2σ(I)]
R1 ) 0.0667
wR2 ) 0.0966
R1 ) 0.2123,
wR2 ) 0.1300
R1 ) 0.0637
wR2 ) 0.1635
R1 ) 0.0996,
wR2 ) 0.1754
R1 ) 0.0436
wR2 ) 0.527
R1 ) 0.02155,
wR2 ) 0.678
R1 ) 0.0466
wR2 ) 0.1156
R1 ) 0.1276,
wR2 ) 0.1254
R1 ) 0.0451
wR2 ) 0.1214
R1 ) 0.0662,
wR2 ) 0.1377
R1 ) 0.0642
wR2 ) 0.1060
R1 ) 0.0868,
wR2 ) 0.1120
R indices (all data)
GaI2}2Ga(I)(PEt3)],47 2.4071(9) Å in [GaH2(Ga{NC(R)C-
(H)}2)2][K(tmeda)]48 or 2.5267(7) and 2.879(1) in
[(tBu3Si)4Ga3]49). The gallium atoms and the methyl groups
are coplanar (torsion angles 0.20° and 0.24°) and coordinated
trans to each other, giving a Y-shaped arrangement
(Ga-Ga-Ga angle: 138.37°).
The DDP backbones are both orientated perpendicular
toward the GaMe plane. Obviously due to steric interactions,
only one (DDP)Ga ring is planar (Ga1), whereas in the
second one the GaN2 and C3N2 planes adopt an angle of
35.7°. This tilting is within the range of other sterically
crowded Ga(DDP) complexes, for example [{(DDP)Ga}Au-
{Ga(DDP)Cl}] (22.4°)39 or [(COE)(η6-benzene)Rh{(DDP)-
GaCl}] (29.8°). The Ga-N bond distances in 2 (2.005(8) Å
to 2.048(8) Å) are slightly longer than those in 1 (1.981(5)
Å and 2.001(6) Å).
By using GaCl3 instead of GaMe3, the only isolable
product is [{(DDP)GaCl}2GaCl] (3), independent of the
reaction conditions or the ratio of the reactants used (Scheme
1). 3 is soluble in common organic solvents and can be stored
without decomposition in an inert gas atmosphere for several
weeks. The 1H NMR spectrum of 3 in C6D6 at room
temperature does not show the expected splitting of the DDP-
proton signals for a Cs symmetric DDP-ligand; instead only
one septet signal at 3.43 ppm as well as two doublet signals
at 1.42 and 1.10 ppm can be observed, indicating a fast
exchange of the chlorine atoms in solution. Additionally, the
13C NMR spectrum is in good agreement with this result.
Crystals suitable for single-crystal X-ray analysis could
be grown from a saturated solution of 3 in hexane at -30
°C overnight. The molecular structure is similar to that of 2
with chlorine atoms instead of methyl groups coordinating
the gallium centers. A mercury plot as well as a table with
selected bond lengths and angles can be found in the
Supporting Information. The Ga-Ga bond distances of
2.4376(7) Å and 2.4436(8) Å are shorter than those in 2,
but still in the range of Ga3 chains known in literature (vide
supra). The distinctly shorter Ga-N bond distances of 3
(1.929(4) to 1.948(4) Å) as compared to 2 (2.005(8) Å to
2.048(8) Å) are explained by the substantial polarization and
thus enhanced electrophilicity of the gallium centers caused
by the chloride ligands.
On reaction of AlMe3 with Ga(DDP) in toluene, no
oxidative addition reaction can be observed. Instead, single
crystals of pure ligand can be isolated when cooling the
1
reaction mixture. However, the H NMR spectrum of the
reaction mixture shows a clear shift of the resonances for
free Ga(DDP), indicating the formation of a donor-acceptor
bond between Ga(DDP) and AlMe3. However, all attempts
to grow single crystals of this adduct failed.
Oxidative Addition of Group 14 halides R3ECl (E )
C, Si, Sn) to Ga(DDP). Ga(DDP) readily reacts with
[SnMe2Cl2] in hexane at room temperature, giving [Me2Sn-
{ClGa(DDP)}2] (4) as colorless crystals after crystallization
from hexane at -30° (Scheme 2). 4 readily dissolves in all
common organic solvents such as hexane or THF and can
be stored in an inert gas atmosphere for several days, whereas
immediate decomposition occurs upon contact with air. The
reaction of less than 2 equiv Ga(DDP) with [SnMe2Cl2] only
reduces the yield of 4 and does not lead to different products.
Interestingly, only the insertion into the Sn-Cl bonds of
(47) Schnepf, A.; Doriat, C.; Moellhausen, E.; Schnoeckel, H. Chem.
Commun. 1997, 2111.
(48) Baker, R. J.; Jones, C.; Kloth, M.; Platts, J. A. Angew. Chem., Int.
Ed. 2003, 42, 2660.
(49) Wiberg, N.; Blank, T.; Amelunxen, K.; Noth, H.; Knizek, J.;
Habereder, T.; Kaim, W.; Wanner, M. Eur. J. Inorg. Chem. 2001,
1719.
7282 Inorganic Chemistry, Vol. 47, No. 16, 2008

Ga(DDP) (DDP ) Bulky Bisimidinate)
Scheme 2. Synthesis of [Me2Sn{ClGa(DDP)}2] (4)
SnMe2Cl2 occurs, probably because of kinetic reasons. It
should be noted, that SnMe4 behaves inert against Ga(DDP)
and no reaction is observed as indicated by 119Sn NMR
spectroscopy.
1
The H NMR spectrum of 4 at room temperature shows
signals for a Ga(DDP) ligand with Cs symmetry. The signal
for the protons of the SnMe2 moiety can be found at -0.76
ppm, showing the expected 119Sn satellites with a coupling
constant of 21.7 Hz. The 119Sn-NMR spectrum shows a
resonance at 1189 ppm relative to SnMe4. This large
downfield-shift compared to the resonances for the Sn-
Ga complexes [K(tmeda)][Sn{CH(SiMe3)2}2Ga{[N(Ar)C-
(H)]2}]-(δ ) -97.9ppm)and[K(tmeda)][(Ar′)2SnGa{[N(Ar)-
C(H)]2}]- (Ar′ ) C6H2Pri3-2,4,6; δ ) -306.7 ppm) is not
surprising considering the anionic nature of the latter
complexes, which can be compared to trialkyl stannate anions
(e.g., LiSnMe3; δ ) -189 ppm).50 Comparable shifts to 4
are reported for the neutral complexes [(Giso)SnGa-
{[N(Ar)C(H)]2}] (δ ) 455 ppm; Giso ) [Pri2NC{N(Ar)}2]-)
or the related NHC complex [(NHC)Sn(Ar′)2] (δ ) 710
ppm).51
Figure 2. Molecular structure of [Me2Sn{ClGa(DDP)}2] (4). Selected bond
lengths (angstroms) and angles (degrees); Sn-C60 2.175(5), Sn-C61
2.178(5), Sn-Ga1 2.6236(7), Sn-Ga2 2.6328(7), Ga1-Cl1 2.2471(15),
Ga2-Cl2 2.2470(15), Ga1-N11 1.977(4), Ga1-N12 1.969(4), Ga2-N21
1.979(4), Ga2-N2 1.962(4); C60-Sn-C61 103.4(2), Ga1-Sn-Ga21
21.27(2),N11-Ga1-N1294.14(18),N21-Ga2-N2294.78(18),Sn-Ga1-Cl11
15.77(4), Sn-Ga2-Cl2 116.72(4).
4 crystallizes in the monoclinic space group P21/c. The
molecular structure is depicted in Figure 2 and consists of a
central SnMe2 moiety in a distorted tetrahedral coordination
environment surrounded by two {ClGa(DDP)} and two
methyl groups. The Sn-Ga bond distances are almost
identical with 2.6236(7) Å and 2.6328(7) Å, which are
significantly shorter than the reported Sn-Ga bond distances
in the anionic complexes [R2SnGa{[N(Ar)C(H)]2}]- (2.7186(6)
Å) and [RSn[Ga{[N(Ar)C(H)]2}]2] (2.6361(5) Å and 2.6610(5)
Å) (R ) CH(SiMe3)2).36 Also, the neutral complex
[(Giso)SnGa{[N(Ar)C(H)]2}] exhibits longer bond distances
(2.6888(6) Å). The distorted tetrahedral coordination envi-
ronment at the tin center is reflected in a comparably large
Ga-Sn-Ga bond angle of 127° and a rather small angle of
103° for the Me-Sn-Me arrangement. The gallium centers
of the Ga(DDP) ligands are also tetrahedrally coordinated
by the nitrogen atoms of the DDP backbone, the tin and the
chlorine atoms, leading to dihedral angles between the C3N2
and the GaN2 arrays of 35.87° (Ga1) and 23.34° (Ga2),
respectively. The Ga-Cl bond distances (av. 2.247 Å) are
similar to those in [(DDP)GaCl2] (2.228(1) Å and 2.218(1)
Å)44 but slightly shorter than in [(COE)(η6-benzene)-
Rh{(DDP)GaCl}] (2.321(2) Å).40
Figure 3. Molecular structure of [Cl3Si{ClGa(DDP)}] (5). Selected bond
lengths (angstroms) and angles (degrees): Ga-Si 2.3860(13), Si-Cl2
1.999(2), Si-Cl3 2.0135(15), Ga-N1 1.917(2), Ga-Cl1 2.1980(11);
N1-Ga-N1* 98.46(14), Cl1-Ga-Si 103.71(5), Cl2-Si-Cl3 105.75(8),
Cl3-Si-Cl3 105.04(16), Cl2-Si-Ga 121.80(8).
Scheme 3. Synthesis of [Cl3Si{ClGa(DDP)}] (5)
Upon mixing Ga(DDP) with SiCl4 in a ratio of 1:1 in
hexane or toluene (Scheme 3), a colorless precipitate is
formed. On recrystallization, colorless crystals of [Cl3Si-
{ClGa(DDP)}] (5) are obtained in high yields. It should be
noted that the 1:1 reaction product 5 is formed also in the
presence of excess of Ga(DDP). 5 is soluble in several
organic solvents (hexane, toluene, benzene) and stable at
room temperature in an inert gas atmosphere for several
weeks without decomposition (Figure 3).
(50) Reimann, W.; Kuivila, H. G.; Farah, D.; Apoussidis, T. Organome-
tallics 1987, 6, 557.
(51) Schaefer, A.; Weidenbruch, M.; Saak, W.; Pohl, S. J. Chem. Soc.,
Chem. Commun. 1995, 1157.
Inorganic Chemistry, Vol. 47, No. 16, 2008 7283

Kempter et al.
Ga-CtBu bond distance very similar to that in [(tBu){Ga-
(DDP)}(CN)] (1.994(5) Å).55 The Ga-Cl bond distance
(2.251(2) Å) is slightly longer than in [(DDP)Ga(Me)Cl]
(2.223(1) Å) or [Cl3Si{ClGa(DDP)}] (5, 2.1980(11) Å). The
Ga-N bond distances (1.953(4) Å and 1.965(3) Å) are
significantly longer than in [(DDP)GaCl2] (1.906(3) Å and
1.926(3) Å)44 or 5 (1.962(4)-1.979(4) Å).
Conclusion
In this article, we have shown that oxidative addition of a
variety of group 13 and group 14 halides and alkyls is a
suitable way for the preparation of compounds with
metal-gallium bonds. Thus, the insertion into the Ga-Me
bond of GaMe3 yield in the complexes [{(DDP)GaMe}-
GaMe2] (1) and [{(DDP)GaMe}2GaMe] (2), respectively,
which show a temperature-dependent equilibrium between
1 (at higher temperatures) and 2 (at lower temperatures). In
the case of GaCl3, the only isolable product is [{(DDP)-
GaCl}2GaCl] (3). In accordance to that, the reaction of
[SnMe2Cl2] with Ga(DDP) yields the compound [Me2Sn-
{ClGa(DDP)}2] (4). In the related reaction with SiCl4, only
a monoinsertion can be observed giving [Cl3Si{ClGa-
(DDP)}] (5). These results show that oxidative addition of
M-X of appropriate precursors to monovalent group 13
fragments can be regarded as a general pathway for the
formation of metal complexes featuring a {(DDP)Ga}-M
bond also in the case of more electropositive metals.
Figure 4. Molecular structure of [(DDP)Ga(tBu)(Cl)] (6). Selected bond
lengths (angstroms) and angles (degrees): Ga1-N1 1.943(6), Ga1-N2
1.956(6), Ga1-Cl 2.251(2), Ga1-C30 2.029(8), Ga1-C31 1.997(7),
N3-C30 1.141(9); N1-Ga1-N2 95.4(2), N1-Ga1-C30 102.1(3),
N1-Ga1-C31 122.4(3), N2-Ga1-C30 101.8(3), N2-Ga1-C31 121.5(3),
C31-Ga1-C30 110.3(3).
Scheme 4. Synthesis of [{(DDP)Ga}(tBu)Cl] (6)
1H NMR and 13C NMR spectra are in good agreement
with the solid-state structure described below and will not
be discussed here in more detail.
Experimental Section
5 crystallizes in the monoclinic space group P21/m. The
gallium center is coordinated in a distorted tetrahedral
geometry and lies significantly above the C3N2 plane
(0.639Å), causing a dihedral angle of 30.13°. The Ga-Cl
bond length of 2.1980(11) Å is shorter than those in
[(DDP)GaCl2] (2.228(1) Å and 2.218(1) Å)44 but well within
the range for other Ga-Cl bond distances reported in
literature. The Ga-Si bond length of 2.3860(13) Å is
significantly shorter than that in the Ga(I) tetramer
[{(tBu3Si)Ga}4] (2.45 Å)52 or the Ga(III) dihalide
[(tBu3Si)GaCl2(THF)] (2.42 Å).53 Similar bond distances are
reported for example for the dimeric compound [{(Me3Si)3-
SiGaMeCl}2].54
Methods and Techniques. All manipulations were carried out
in an atmosphere of purified argon using standard Schlenk and
glovebox techniques. Hexane and toluene were dried using an
mBraun Solvent Purification System. The final H2O content in all
solvents was checked by Karl Fischer titration and did not exceed
5 ppm. Ga(DDP)56 was prepared according to literature methods.
GaMe3 (Strem), GaCl3, AlMe3, SiCl4, tBuCl (Aldrich), and
SnMe2Cl2 (Fluka) were used as purchased. Elemental analyses were
performed by the Microanalytical Laboratory of the Ruhr-Univer-
sita¨t Bochum. NMR spectra were recorded on a Bruker Avance
DPX-250 spectrometer (1H, 250.1 MHz; 13C, 62.9 MHz) in C6D6
at 298 K, if not stated otherwise. Chemical shifts are given relative
to TMS and were referenced to the solvent resonances as internal
standards.
All crystal structures were measured on an Oxford Excalibur 2
diffractometer using Mo KR radiation (λ ) 0.71073 Å). The
structures were solved by direct methods using SHELXS-97 and
refined against F2 on all data by full-matrix least-squares with
SHELXL-97. CCDC 693184 (1), CCDC 693185 (2), CCDC 693186
(3), CCDC 693187 (4), CCDC 693188 (5), and CCDC 693189 (6)
contain the supplementary crystallographic data for this article.
These data can be obtain free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: (+44)1223-
336-033; or deposit@ccdc.cam.uk).
Whereas no reaction of Ga(DDP) is observed in the
presence of fluorobenzene or chlorobenzene, decomposition
and undefined products are obtained with CH2Cl2 and CHCl3.
In contrast to that, the reaction of Ga(DDP) with tBuCl yields
[{(DDP)Ga}(tBu)Cl] (6) as colorless crystals (Scheme 4).
1
The H NMR and 13C spectra of 6 in C6D6 at room
temperature show the expected signals for a DDP-moiety
with reduced (Cs) symmetry and will not be discussed here
in more detail.
The molecular structure of 6 (Figure 4) consists of a
distorted tetrahedrally coordinated gallium center with a
Synthetic Procedures and Analytical Data. [{(DDP)GaMe}-
GaMe2] (1). Ga(DDP) (200 mg, 0.41 mmol) was dissolved in 5
mL of hexane at room temperature. A solution of GaMe3 (1.65
(52) Wiberg, N.; Amelunxen, K.; Lerner, H. W.; Noth, H.; Ponikwar, W.;
Schwenk, H. J. Organomet. Chem. 1999, 574, 246.
(53) Wiberg, N.; Blank, T.; Westerhausen, M.; Schneiderbauer, S.;
Schnockel, H.; Krossing, I.; Schnepf, A. Eur. J. Inorg. Chem. 2002,
351.
(55) Kempter, A.; Gemel, C.; Fischer, R. A. Chem.sEur. J. 2007, 13, 2990.
(56) Hardman, N. J.; Eichler, B. E.; Power, P. P. Chem. Commun. 2000,
1991.
(54) Wochele, R.; Schwarz, W.; Klinkhammer, K. W.; Locke, K.; Weidlein,
J. Z. Anorg. Allg. Chem. 2000, 626, 1963.
7284 Inorganic Chemistry, Vol. 47, No. 16, 2008

Ga(DDP) (DDP ) Bulky Bisimidinate)
mL, 0.2489 M) in hexane was slowly added. The reaction mixture
turned to deep yellow and was stirred for an additional 1 h at room
temperature. The solvent was reduced to ca. 2 mL and stored at
-30 °C overnight to give deep-yellow crystals of 1 in 200 mg yield
(81%). 1H NMR (C6D6, 25 °C): δ 7.15-6.95 (m, 6H), 4.78 (s, 1H,
γ -CH), 3.52 (sept, 2H, CH(Me)2), 3.04 (sept, 2H, CH(Me)2), 1.52
(s, 6H, CH3), 1.35 (d, 6H, CH(Me)2), 1.13 (d, 12H, CH(Me)2), 1.08
(d, 6H, CH(Me)2), 0.37 (br, 6H, GaMe2), -0.25 (s, 3H, GaMe).
13C NMR (C6D6, 25 °C): δ 168.0 (CN), 143.7 (CMe), 143.6 (Ar),
142.2 (Ar) 126.6 (Ar), 124.3 (Ar), 124.2 (Ar), 96.2 (γ-C), 28.6
(CHMe2), 25.7 (CHMe2), 24.8 (CMe), 24.6 (CMe), 23.9 (CHMe2).
23.2 (CHMe2), 1.4 (GaMe), -6.1 (GaMe2). Elemental Anal. Calcd
(found) for C32H50Ga2N2: C, 63.82 (63.89); H, 8.37 (8.41); N, 4.65
(5.08).
the solution to -30 °C overnight gave 4 as colorless crystals. Yield:
125 mg (86%). 1H NMR (C6D6, RT): δ 7.20 - 6.96 (6H), 4.96 (s,
1H, γ-CH), 3.84 (sept, 2H, CH(Me)2), 3.10 (sept, 2H, CH(Me)2),
1.48 (s, 6H, CH3), 1.31 (d, 6H, CH(Me)2), 1.24 (d, 6H, CH(Me)2),
1.21 (d, 6H, CH(Me)2), 0.93 (d, 6H, CH(Me)2), -0.76 (SnMe J )
21.7 Hz). 13C NMR (C6D6, RT): δ 169.0, 146.5, 142.3, 125.5, 123.4,
99.3, 29.5, 28.7, 28.1, 24.8, 24.2, 24.1, 24.0, -12.4. Elemental Anal.
Calcd (found) for C60H88Cl2Ga2N4Sn: C, 60.33 (60.35); H, 7.43
(7.80); N, 4.69 (4.54).
[Cl3Si{ClGa(DDP)}] (5). Ga(DDP) (0.41 mmol, 200 mg) were
dissolved in 5 mL hexane, and an excess of SiCl4 (1 mL) was added
via a syringe to the solution. Heating the solution to reflux and
stirring for 10 min at room temperature afforded a colorless
precipitate. All volatiles were removed in vacuo, the colorless
precipitate redissolved in 3 mL hexane, and again heated to reflux
and slowly cooled to room temperature to give colorless crystals.
[{(DDP)GaMe}2GaMe] (2). Ga(DDP) (0.031 mmol, 150 mg)
was dissolved in 5 mL of hexane at room temperature. On slow
addition of 0.49 mL of a 0.2489 M solution of GaMe3 in hexane,
the color of the solution turns to intense yellow (after the addition
1
Yield: 130 mg (48%). H NMR (C6D6, RT): δ 7.16-7.04 (6H),
4.88 (s, 1H, γ-CH), 3.74 (sept, 2H, CH(Me)2), 3.18 (sept, 2H,
CH(Me)2), 1.54 (s, 6H, CH3), 1.51 (d, 6H, CH(Me)2), 1.38 (d, 6H,
CH(Me)2), 1.18 (d, 6H, CH(Me)2), 0.99 (d, 6H, CH(Me)2). 13C NMR
(C6D6, RT): δ 170.9, 145.9, 142.6, 140.2, 126.7, 124.1, 123.6, 98.5,
29.9, 28.2, 26.6, 24.9, 24.5, 23.8, 23.5. Elemental Anal. Calcd
(found) for C29H41Cl4GaN2Si: C, 52.99 (53.75); H, 6.29 (5.89); N,
4.26 (4.00).
1
of /2 equiv of GaMe3) and changes to orange after the addition
was completed. After stirring the reaction mixture for 1 h at room
temperature and cooling it to -30 °C overnight, a mixture of bright-
yellow and deep-orange crystals were obtained. Separating the
1
orange crystals of 2 manually gave a yield of 29 mg (25%). H
NMR (C6D6, -40 °C): δ 7.15-6.95 (br, m, 12H), 4.64 (s, 2H,
γ-CH), 3.35 (br, sept, 8H, CH(Me)2), 1.41 (br, s, 12H, CH3), 1.09
(br, d, 48H, CH(Me)2), 0.63 (br, 6H, (DDP)GaMe), 0.03 (br, s,
3H, GaMe). 13C NMR (C6D6, -40 °C): δ 169.7 (CN), 146.7 (CMe),
146.4 (CMe), 145.5 (CMe), 145.2 (CMe), 140.1 (Ar), 128.9 (Ar),
126.9 (Ar), 126.7 (Ar), 126.2 (Ar), 98.8 (γ -C), 37.6 (CHMe2),
35.0 (CHMe2), 31.3 (CHMe2), 31.2 (CHMe2), 30,7 (CHMe2), 29.8
(CHMe2), 28.2 (CHMe2), 27.4 (CHMe2), 27.1 (CHMe2), 26.4
(CHMe2), 26.2 (CHMe2), 26.1 (CHMe2), 17.4 (CMe), 14.6 (CMe),
4.1 (GaMe), 0.86 (GaMe). Elemental Anal. Calcd (found) for
C61H91Ga3N4: C, 67.24 (67.24); H, 8.42 (8.37); N, 5.17 (5.41).
[{(DDP)GaCl}2GaCl] (3). Ga(DDP) (0.0205 mmol, 100 mg) and
18 mg GaCl3 (0.01 mmol) were dissolved in 5 mL of hexane at
room temperature. After stirring the solution for 15 min, the solvent
was concentrated and stored at -30 °C overnight to yield pale-
yellow/colorless crystals of 3. Yield: 71 mg (60%). 1H NMR (C6D6):
δ 7.15-7.07 (br, m, 24H), 4.74 (s, 2H, γ-CH), 3.43 (sept, 8H,
CH(Me)2), 1.49 (s, 12H, CH3), 1.42 (d, 24H, CH(Me)2), 1.10 (d,
24H, CH(Me)2). 13C NMR (C6D6): δ 174.1 (CN), 144.4 (Ar), 141.2
(Ar), 127.5 (Ar), 99.6 (γ -C), 31.5 (CHMe2), 28.1 (CHMe2), 27.4
(CHMe2), 26.4 (CMe). Elemental Anal Calcd (found) for
C58H82Cl3Ga3N4: C, 60.53 (60.56); H, 7.18 (6.89); N, 4.87 (5.41).
[Me2Sn{ClGa(DDP)}2] (4). [SnMe2Cl2] (0.205 mmol, 45 mg)
and 200 mg Ga(DDP) (0.41 mmol) were dissolved in toluene at
room temperature. The color of the former yellow solution turns
slightly orange after several minutes. Concentrating and cooling
[(DDP)Ga(tBu)(Cl)] (6). Ga(DDP) (220 mg, 0.45 mmol) was
t
dissolved in hexane (10 mL) at room temperature. Excess BuCl
(1 mL, 1,5 mmol) was added via a syringe. The reaction mixture
was heated to 60 °C and stirred for 20 min. All volatiles were
removed in vacuo and the crude product recrystallized from hexane
1
(-30 °C, overnight). Yield 195 mg (89%). H NMR (C6D6, RT):
δ 7.15 - 7.01 (6H), 4.97 (s, 1H, γ -CH), 3.92 (sept, 2H, CH(Me)2),
3.30 (sept, 2H, CH(Me)2), 1.61 (s, 6H, CH3), 1.50 (d, 6H, CH(Me)2),
1.31 (d, 6H, CH(Me)2), 1.17 (d, 6H, CH(Me)2), 1.00 (d, 6H,
CH(Me)2), 0.84 (s, 9H, tBu). 113C NMR (C6D6, RT): δ 169.7, 145.9,
142.6, 142.5, 125.6, 123.6, 98.3, 30.8, 29.6, 28.0, 25.7, 25.0, 24.9,
23.7, 23.4. Elemental Anal. Calcd (found) for C33H50ClGaN2: C,
68.34 (67.86); H, 8.69 (8.83); N, 4.83 (5.56)
Acknowledgment. This work was supported by the Fonds
der Chemischen Industrie, Germany. A.K. is grateful for a
Ph.D. fellowship granted by the Fonds.
Supporting Information Available: Crystallographic data files
of the 1-6 in CIF format, temperature-depending NMR spectra of
1 and 2, mercury plot and table with selected bond length and angles
of 3. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC800690Z
Inorganic Chemistry, Vol. 47, No. 16, 2008 7285