Insertion of the Ga(I) bis-imidinate Ga(DDP) into the metal halogen bonds of Rh(I) complexes. How electrophilic are coordinated Ga(DDP) fragments?

Article abstract of DOI:10.1021/ic0521731

The reactivity of Ga(DDP) (DDP = 2-((2,6-diisopropylphenyl)amino-4-((2,6-diisopropylphenyl)imino)-2-pentene) towards the rhodium-chloride bonds of [RhCl(PPh₃)₃] and [RhCl(COE)₂]₂ (COE = cyclooctene) is investigated. Reaction of the first complex leads to [(Ph₃P)₂Rh{Ga(DDP)}(μ-Cl)] (1), exhibiting a chloride bridging the gallium and the rhodium atoms, whereas the second complex leads to a full insertion of the Ga(DDP) ligand into the Rh-Cl bond giving [(COE)(benzene)Rh{(DDP)GaCl}] (2) on coordination of the solvent C₆H₆. Compounds 1 und 2 readily react with the halide abstracting reagent Tl[BAr^F] (BAr^F = B[3,5-(CF₃)₂C₆H₃]₄), yet the products could not be isolated and characterized because of their lability. The Au(I) complex [{(DDP)Ga}Au{Ga(DDP)}Cl] reacts with Na[BAr^F] giving the linear, symmetric cationic complex [{(DDP)Ga·THF}₂Au][BAr^F] (3.2THF), exhibiting two THF molecules coordinated to the Ga(DDP) moieties.

Full text of DOI:10.1021/ic0521731

Inorg. Chem. 2006, 45, 3133−3138
Insertion of the Ga(I) Bis-imidinate Ga(DDP) into the Metal Halogen
Bonds of Rh(I) Complexes. How Electrophilic Are Coordinated Ga(DDP)
Fragments?†
Andreas Kempter, Christian Gemel, Ned J. Hardman, and Roland A. Fischer*
Anorganische Chemie II, Organometallics & Materials Chemistry, Ruhr-UniVersita¨t Bochum,
D-44780 Bochum, Germany
Received December 22, 2005
The reactivity of Ga(DDP) (DDP
the rhodium chloride bonds of [RhCl(PPh3)3] and [RhCl(COE)2]2 (COE
the first complex leads to [(Ph3P)2Rh Ga(DDP) -Cl)] (1), exhibiting a chloride bridging the gallium and the rhodium
atoms, whereas the second complex leads to a full insertion of the Ga(DDP) ligand into the Rh Cl bond giving
[(COE)(benzene)Rh (DDP)GaCl ] (2) on coordination of the solvent C6H6. Compounds 1 und 2 readily react with
the halide abstracting reagent Tl[BArF] (BArF
B[3,5-(CF3)2C6H3]4), yet the products could not be isolated and
characterized because of their lability. The Au(I) complex [ (DDP)Ga Au Ga(DDP)
Cl] reacts with Na[BArF] giving
2Au][BArF] (3
2THF), exhibiting two THF molecules
)
2-((2,6-diisopropylphenyl)amino-4-((2,6-diisopropylphenyl)imino)-2-pentene) towards
−
)
cyclooctene) is investigated. Reaction of
{
}(µ
−
{
}
)
{
}
{
}
the linear, symmetric cationic complex [
coordinated to the Ga(DDP) moieties.
{(DDP)Ga‚THF
}
‚
Introduction
Ga-Cl-Ga bridges.9-11 Furthermore, a C-C bond rupture
process is taking place in the reaction of RhCp*(L)(CH3)2
with GaCp* giving the zwitterion RhCp*(C5Me4GaMe3). The
C-C bond activation was shown to topologically take place
at the gallium instead of the rhodium center.12,13 In the course
of these reactivity studies of reactive transition metal frag-
ments with EIR compounds we became interested in sterically
more encumbered ligands to stabilize coordinatively unsatur-
ated transition metal centers. Among numerous known bulky
Ga(I) compounds, P. P. Power’s bis-imidinate Ga(DDP) is
a very prominent and well-studied example.14-16 Recently,
we reported on the reaction of Ga(DDP) with AuCl(PPh3),
giving the linear insertion products [(PPh)Au{GaCl(DDP)}]
Low-valent group 13 element organyls of the general type
ECp* (E ) Al, Ga) have been widely used as ligands for
various transition metal centers.1-4 Their σ-donor capability
is rather strong, leading to a Lewis acidic group 13 metal
coordinated to an electron-rich transition metal in the
complexes.5,6 These intermetallic compounds have been
shown to undergo classical organometallic reactions such as
C-H, Si-H, or C-C bond activations in which the group
13 metal usually plays a crucial role being not only a
spectator ligand but actively taking part as a reaction
partner.7,8 Thus, GaCp* readily inserts into the metal-
halogen bonds of [RhCp*Cl2]2 and [Rh(p-cymene)Cl2]2
forming cagelike complexes with terminal Ga-Cl bonds and
(9) Steinke, T.; Gemel, C.; Cokoja, M.; Fischer, R. A. Dalton Trans. 2005,
55.
(10) Cokoja, M.; Gemel, C.; Steinke, T.; Schroeder, F.; Fischer, R. A.
Dalton Trans. 2005, 44.
(11) Steinke, T.; Gemel, C.; Cokoja, M.; Winter, M.; Fischer, R. A. Chem.
Commun. 2003, 1066.
(12) Cadenbach, T.; Gemel, C.; Schmid, R.; Fischer, R. A. J. Am. Chem.
Soc. 2005, 17068.
† Organo group 13 complexes of transition metals [XLII]; communication
[XLI], see ref 32.
* To whom correspondence should be addressed. Fax (+49)234 321
4174. E-mail: roland.fischer@ruhr-uni-bochum.de.
(1) Gemel, C.; Steinke, T.; Cokoja, M.; Kempter, A.; Fischer, R. A. Eur.
J. Inorg. Chem. 2004, 4161.
(2) Fischer, R. A.; Weiss, J. Angew. Chem. 1999, 111, 3002.
(3) Murugavel, R.; Chandrasekhar, V. Angew. Chem. 1999, 111, 1289.
(4) Dohmeier, C.; Loos, D.; Schno¨ckel, H. Angew. Chem. 1996, 108, 141.
(5) Uddin, J.; Boehme, C.; Frenking, G. Organometallics 2000, 19, 571.
(6) Uddin, J.; Frenking, G. J. Am. Chem. Soc. 2001, 123, 1683.
(7) Steinke, T.; Gemel, C.; Cokoja, M.; Winter, M.; Fischer, R. A. Angew.
Chem. 2004, 116, 2349.
(13) Cadenbach, T.; Gemel, C.; Schmid, R.; Block, S.; Fischer, R. A. Dalton
Trans. 2004, 3171.
(14) (a) Hardman, N. J.; Eichler, B. E.; Power, P. P. Chem. Commun. 2000,
1991. (b) Baker, R. J.; Jones, C. Coord. Chem. ReV. 2005, No. 17-
18, 1857-1869. (c) Power, P. ACS Symp. Ser. 2002, 822.
(15) Hardman, N.; Power, P. Inorg. Chem. 2001, 40, 2474.
(16) Hardman, N.; Power, P.; Gordon, J.; Macdonald, C. L. B.; Cowley,
A. H. Chem. Commun. 2001, 1866.
(8) Steinke, T.; Cokoja, M.; Gemel, C.; Kempter, A.; Krapp, A.; Frenking,
G.; Zenneck, U.; Fischer, R. A. Angew. Chem. 2005, 117, 3003.
10.1021/ic0521731 CCC: $33.50
Published on Web 03/09/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 7, 2006 3133

Kempter et al.
Scheme 1. Insertion of Ga(DDP) into the Rh-Cl Bond of
[RhCl(PPh3)3]
and [{(DDP)Ga}Au{Ga(DDP)}Cl].17 Ga(DDP) is by far
more bulky than GaCp*. However, its electronic features
are also distinctly different from the Cp* congener. The GaI
center in Ga(DDP) is isolobal to NHCs, the vacant p orbital
not being stabilized by additional π-electrons (as in the case
of GaCp*, which is stabilized by the strong π-donor Cp*)14,16
which leads to an increase of the electrophilicity of the
gallium center on coordination to transition metals. On the
other side, the oxidized species Ga(DDP)X2 is less acidic
than its counterpart GaCp*Cl2, leading to a different behavior
of the ligands toward transition metal halogenides and
alkyls.18 In this paper, we wish to report on insertion reactions
of Ga(DDP) into the metal-halogen bonds of rhodium(I)
complexes, as well as the creation of a cationic transition
metal Au(I)-Ga(DDP) complex by abstraction of a chloride
ion.
Figure 1. Molecular structure of 1. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Rh-Ga ) 2.3870(6), Ga-Cl
) 2.4853(11), Rh-Cl ) 2.4515(11), Rh-P1 ) 2.3062(11), Rh-P2 )
2.1927(12), Ga-N1 ) 1.996(3), Ga-N2 ) 1.989(3), Ga-Rh-Cl )
61.80(3), P1-Rh-P2 ) 103.24(4), P2-Rh-Ga ) 101.33(3), P1-Rh-Cl
) 93.35(4), Rh-Ga-Cl ) 60.38(3), N1-Ga-N2 ) 93.05(13).
Results and Discussion
Insertion Reaction of Ga(DDP) into Rh-Cl Bonds. The
reaction of [(Ph3P)3RhCl] with 1 equiv of Ga(DDP) in
toluene at room temperature gives a bright-red solution. After
removal of the solvent in vacuo and recrystallization of the
residue from a 3:1 mixture of hexane/THF at -30 °C, air-
sensitive red rhombohedric crystals of [(Ph3P)2Rh{Ga-
(DDP)}(µ-Cl] (1) are obtained in yields of around 60%
(Scheme 1). The complex dissolves well in aprotic organic
solvents and is stable at room temperature when stored in
an inert gas atmosphere.
Compound 1 crystallizes in the monoclinic space group
P21/c. The molecular structure (Figure 1) consists of a central
Rh atom in a distorted square planar coordination geometry,
surrounded by two Ph3P units and the {Ga(DDP)Cl} moiety
(angular sum of P-Rh-P, P-Rh-Ga, Ga-Rh-Cl, and Cl-
Rh-P is 359.7°).
The Rh-Ga bond distance (2.3870(6) Å) is similar to the
ones found in [Cp*Rh(GaCp*)3Cl2] (2.35-2.45 Å) or the
“all-hydrocarbon” complex [(Cp*Rh)2(GaCp*)3] (2.387-
2.405 Å).9
1
The H NMR spectrum shows one set of signals for the
DDP ligand, with a reduced (Cs) symmetry (e.g., two signals
The most interesting feature of this structure is the
chlorine-bridged Rh-Ga bond giving a triangular arrange-
ment of the atoms with similar Rh-Cl and Ga-Cl bond dis-
tances (Rh-Ga ) 2.3870(6), 2.4853(11) Å; Rh-Cl )
2.4515(11) Å). Obviously, the steric demand of the ligands
forbids the formation of a stable 16VE RhL4 complex leading
to a more electrophilic 14VE RhL3 center. Thus, two electro-
philic metal centers are competing for the electrons of the
basic chloride ligand, therefore “forcing” the chlorine as a 4VE
donor into the bridging position. The Ga-Cl bond length is
significantly longer than those in (DDP)GaCl2 (2.22 Å)18 or
the related gold compounds [{(DDP)Ga}Au{Ga(DDP)}Cl]
and [(Ph3P)Au{Ga(DDP)Cl}] (Ga-Cl ) 2.28-2.29 Å),17 but
it is comparable to the one in [Cp*Rh(GaCp*)3Cl2] (2.438
Å)9 or the bond length for bridging chlorides (Ga-Cl-Ga
motifs) found in the cluster compound [{(Cp′′Rh)2(µ-Ga)}2-
(µ4,η2-Ga2Cl3)2] (Ga-Cl ) 2.445(2) Å and 2.363(2) Å).19
In contrast, the Rh-Cl distance remains nearly
i
for the Pr-CH protons). This indicates the transfer of the
chloride from the rhodium to the gallium center in the course
of the reaction, as also found in the complexes [{(DDP)-
Ga}Au{Ga(DDP)Cl}] and [(Ph3P)Au{Ga(DDP)Cl}].17 The
iPr-CH3 groups show four distinct doublet-signals at 2.00,
1.16, 1.00, and 0.61 ppm (each d, 6H). The PPh3 moieties
give rise to a multiplet at 6.63-7.61 ppm, the total integral
indicating two PPh3 groups (i.e., the loss of one PPh3 ligand
in the course of the reaction). The unusual high-field shift
of one of the CH3 groups of the DDP ligand (2.00 ppm, d,
6H) can be best explained by an anisotropic interaction with
a phenyl group of a PPh3 moiety. The 31P NMR shows two
doublets of doublets at 53.1 and 41.5 ppm, pointing to an
asymmetric coordination environment with respect to the two
phosphine atoms. The 13C NMR spectrum shows the typical
sets of signals for coordinated Ga(DDP) and Ph3P ligands,
respectively.
(17) Kempter, A.; Gemel, C.; Fischer, R. A. Inorg. Chem. 2005, 44, 163.
(18) Stender, M.; Eichler, B. E.; Hardman, N.; Power, P.; Prust, J.;
Noltemeyer, M.; Roesky, H. Inorg. Chem. 2001, 40, 2794.
(19) Scheer, M.; Kaupp, M.; Virovets, A. V.; Konchenko, S. N. Angew.
Chem. 2003, 115, 5237.
3134 Inorganic Chemistry, Vol. 45, No. 7, 2006

Ga(I) Bis-imidinate Ga(DDP)
Scheme 2. Reaction of [Rh (COE)2Cl]2 with Ga(DDP)
unchanged, compared to the parent compound (Ph3P)3RhCl
(2.416 Å),20 indicating the strong Lewis acidity of the hypo-
thetical 14VE [Rh(PPh3)2{Ga(DDP)Cl}] complex. To the
best of our knowledge compound 1 represents the first exam-
ple of a halide-bridged transition metal-group 13 metal bond.
Hence, compound 1 can be regarded as a “frozen intermedi-
ate” of an insertion reaction of GaDDP into a Rh-Cl bond.
According to Scheme 2, reaction of the Rh(I) precursor
[Rh(COE)2Cl]2 (COE ) cyclooctene) with Ga(DDP) leads
to the replacement of one olefin by the Ga(I) ligand, full
migration of the chloride to the gallium center, and coordina-
tion of the solvent C6H6 forming [(COE)(η6-benzene)Rh-
{(DDP)GaCl}] (2). It should be noted that the reaction in
absence of C6H6 did not give defined products. Recrystal-
lization of the raw product from hexane gives 2 as a deep
green solid in a 60% yield.
Figure 2. Molecular structure of 2. Hydrogen atoms are omitted for clarity.
Selected bond length (Å) and angles (deg): Rh-Ga ) 2.4037(8), Ga-Cl
) 2.321(2), Ga-N1 ) 2.018(3), Ga-N2 ) 1.974(3), Rh-C30 ) 2.141(4),
Rh-C31 ) 2.113(4), Rh-Ga-Cl ) 112.08(4), N1-Ga-N2 ) 93.12(12),
N1-Ga-Rh ) 122.84(9), N2-Ga-Rh ) 129.12(9).
of the N1-N2-Ga-Rh plane is 345°). The Rh-Ga-Cl
bond angle of 112° is also in accordance with a complete
migration of the chlorine atom from the rhodium to the
gallium center in the course of the reaction. The Ga-Cl bond
distance (2.32 Å) is only slightly longer than those in the
gold compounds [{(DDP)Ga}Au{Ga(DDP)Cl}] and [(Ph3P)-
Au{Ga(DDP)Cl}] (Ga-Cl ) 2.28-2.29 Å).17 The Rh-Ga
distance (2.40 Å) is longer than in 1, but it is in the same
range as that found in the GaCp* compounds [Cp*Rh-
(GaCp*)2(GaCl3)] (Rh-Ga ) 2.34-2.41 Å) or the dimeric
complex [(Cp*Rh)2(GaCp*)3] (Rh-Ga ) 2.38-2.41 Å).9
The 1H NMR spectrum in C6D6 at room temperature shows
the expected signal set for a (DDP)GaCl moiety with two
i
distinct septets for the Pr-CH groups and four distinct
i
doublets for the Pr-CH3 groups, respectively. The COE
signals are found at 2.83 (2H), 1.89 (2H), 1.41 (4H), 1.20
(4H), and 1.00 ppm (2H). Interestingly, in C6D6 no signal
for coordinated C6H6 could be detected; instead, a singlet
for free C6H6 at 7.15 ppm integrating to about six protons is
found. Obviously, an exchange between coordinated C6H6
and the deuterated solvent C6D6 takes place. In accordance
with this, the 13C NMR spectrum of 2 in C6D6 shows a triplet
signal in the range of a coordinated C6D6 ligand (97.4 ppm).
Such arene exchange reactions are also known for other RhI
compounds (e.g., in [(Rh(η-ArH)(η-C8H14){SnCl(NR2)2}]
(ArH ) PhMe, C6H3Me3-1,3,5, or C6Me6)21 and [(Rh(η-
Arene)(P(OPh)3)2]ClO4 (ArH ) PhMe, C6H3Me3-1,3,5, or
Interestingly, the Rh-Colefin bond distances (Rh-Ccoe
)
2.113(4) and 2.141(4) Å) are significantly shorter than those
in the dimeric compound [RhCp*(C2H4)(µ2-GaCp*)]2 (Rh-
Cethylene ) 2.24-2.29 Å), pointing to a higher degree of
π-back-bonding in 2.9
Chloride Abstraction from 1 and 2, Cationic Ga(DDP)
Complexes. In several attempts to abstract the chlorine atoms
of both compounds 1 and 2 by TlBArF (BArF ) tetra-((3,5-
bis-triflourmethyl)phenyl)borate) to produce [(coe)Rh(C6H6)-
{Ga(DDP)}]+ or [(Ph3P)2Rh{Ga(DDP)}]+ did not lead to
products stable enough to be isolable, at least so far in our
hands. However, both compounds 1 and 2 were found to
readily react with TlBArF, as indicated by a significant
1
C6H6)).22 However, the H NMR spectrum of 2 in THF-d8
shows a sharp singlet signal at 5.65 ppm, assignable to a
coordinated C6H6 molecule.
Crystals suitable for X-ray analysis could be obtained by
slow evaporation of the solvent of a saturated benzene-
solution. Compound 2 crystallizes in the triclinic space group
P1h. The molecular structure (Figure 2) can be described as
a half-sandwich complex with a two-legged piano-stool
coordination sphere consisting of an η2-coordinated cy-
clooctene ligand and a {(DDP)GaCl} moiety. The covalent
Ga-Cl interaction is reflected by the only slightly distorted
tetrahedral environment of the gallium center (angular sum
1
change in the H NMR spectra and the formation of TlCl.
In the spectra of both compounds, the characteristic splitting
of the iPr-CH-signal of the {(DDP)GaCl} moiety disappears,
indicating the formation of a C2V symmetric (i.e., halogen-
free) Ga(DDP) moiety. In addition, the reaction products
were found to be soluble only in polar solvents such as THF
or fluorobenzene, which is in agreement with an ionic nature
of the products. Unfortunately, no crystals suitable for X-ray
analysis of either compound could yet be obtained. The
resulting species could also not be spectroscopically char-
acterized in more detail since all attempts to purify the
obviously very labile products failed and resulted in decom-
position.
(20) Bennett, M. J.; Donaldson, P. B. Inorg. Chem. 1977, 16, 655.
(21) Hawkins, S. M.; Hitchcock, P. B.; Lappert, M. F. Chem. Commun.
1985, 22, 1592.
(22) Bittersmann, E.; Hildenbrand, K.; Cervilla, A.; Lahuerta, P. J.
Organomet. Chem. 1985, 287, 255.
Inorganic Chemistry, Vol. 45, No. 7, 2006 3135

Kempter et al.
Figure 3. Molecular structure of 3‚2THF. Hydrogen atoms and the BArF anion are omitted for clarity. Selected bond length (Å) and angles (deg): Au1-
Ga1 ) 2.393, Au1-Ga2 ) 2.391, Ga1-N11 ) 1.956, Ga1-N12 ) 1.948, Ga1-O1 ) 2.178, Ga2-N21 ) 1.986, Ga2-N22 ) 1.958, Ga2-O2 ) 2.151,
Ga1-Au1-Ga2 ) 170.93, Au1-Ga1-O1 ) 105.09, N11-Ga1-N12 ) 95.38, N11-Ga1-Au1 ) 134.85, N12-Ga1-Au1 ) 119.61, Au1-Ga2-O2 )
105.6, N21-Ga2-N22 ) 95.50, N21-Ga2-Au1 ) 118.59, N22-Ga2-Au1 )137.68.
Scheme 3. Reaction of [{(DDP)Ga}Au{ClGa(DDP)}] with NaBArF
To prove the concept, we selected the related Au(I)
compound [{(DDP)Ga}Au{Ga(DDP)}Cl]17 which was treated
in the same manner with NaBArF in THF solution. Halide
abstraction from the coordinated {ClGa(DDP)} moiety
occurred as discussed above for the Rh congeners, and the
cationic compound [{(DDP)Ga‚THF}2Au][BArF] (3‚2THF)
was obtained. The 1H NMR spectrum in THF-d8 shows only
one C2V symmetric signal set for both coordinated Ga(DDP)
ligands, as well as signals for the [BArF] anion, in a ratio of
2:1. The 13C NMR spectrum is in total agreement with this
result. The spectroscopic features of the coordinated
Ga(DDP) ligand of 3‚2THF match the observation in the
case of the instable cationic Rh complexes.
Crystals of 3‚2THF, suitable for X-ray analysis, were
obtained by slow diffusion of hexane into a saturated THF
solution at room temperature. The molecular structure (Figure
3) of the cation consists of a central gold atom almost linearly
coordinated by two Ga(DDP) ligands (Ga1-Au-Ga2 )
170.89°). Both Ga-Au distances are equal (Ga-Au ) 2.392
Å) and are slightly shorter than the distances found for the
parent compound [{(DDP)Ga}Au{Ga(DDP)}Cl] (2.41 Å),17
but they are longer than the distances found for the equatorial
GaCp* units in the trimeric cluster [Au3(µ-GaI2)(Cp*Ga)5]
(Au-Ga ) 2.384 and 2.377 Å).23 A very interesting feature
of the solid-state structure of 3‚2THF is the weak coordina-
tion of THF to each of the gallium centers giving [(DDP)-
Ga(THF)] moieties. This is in agreement with an “electro-
philization” of the Ga(I) center of Ga(DDP) when coordinated
to a transition metal center, since such adducts are unknown
for free Ga(DDP). It should be noted, that a similar
observation was recently reported on the adduct (DDP)Al-
B(C6F5)3 showing intramolecular Al-F interactions in the
solid state.24 However, the Ga-O distances (2.14-2.17Å)
are significantly longer than in the Ga(III)-THF adduct
[(THF)GaCl3] (1.91 Å).25 Similarly elongated Ga-O bond
lengths are, for example, known for hypervalent trigonal-
pyramidal or octahedral gallium complexes for axially
coordinated THF ligands (e.g., GaX3(THF)2 Ga-O ) 2.11
(X ) Cl)26 and 2.14 Å (X ) Br)27), as well as for other
Ga(III) complexes with weakly acidic gallium centers. The
THF-free compound [{(DDP)Ga}2Au][BArF] (3) cannot be
synthesized analogously to its THF adduct by a simple one-
pot reaction in the absence of THF using a noncoordi-
(23) Anandhi, U.; Sharp, P. R. Angew. Chem., Int. Ed. Engl. 2004, 43,
6128.
(24) 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. 2005, 117, 7234.
(25) Scholz, S.; Lerner, H.-W.; Bolte, M. Acta Crystallogr. E 2002, 58,
m585.
(26) Niger, M.; Thomas, F. CCDC 181829, 2002, private communication.
(27) Nogai, S. D.; Schmidbaur, H. Dalton Trans. 2003, 2488.
3136 Inorganic Chemistry, Vol. 45, No. 7, 2006

Ga(I) Bis-imidinate Ga(DDP)
at 298 K. Chemical shifts are given relative to TMS and were
referenced to the solvent resonances as internal standards.
The crystals of 1, 2, and 3‚2THF were measured on a 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.
nating solvent (e.g., C6H5F). Instead, the well-known cation
[(Ph3P)2Au]+ 28 is formed in high yields. However, treatment
of pure [{(DDP)Ga}Au{ClGa(DDP)}] with Na[BArF] in
flourbenzene gives 3 in high yields (Scheme 3). Crystals of
3 suitable for X-ray analysis can also be obtained by
crystallization in the absence of THF, indeed showing an
undistorted, linear [Au{(GaDDP)}2] moiety as the cation.
However, the overall structural quality was poor because of
the twinning of the crystals, and thus a depiction of this
structure is not included herein.
[(Ph3P)2Rh{Ga(DDP)}µ-Cl] (1). [(Ph3P)3RhCl] (300 mg, 0.33
mmol) and Ga(DDP) (237 mg, 0.49 mmol) in 10 mL of toluene
were stirred at room temperature overnight. The solvent was
removed in vacuo. The red solid was recrystallized from 10 mL of
hexane/3 mL of THF at -30 °C to yield deep red crystals (235
1
Conclusions
mg, 63%). H NMR (C6D6, RT): δ 7.15 (ar, 36H), 5.06 (s, 1H,
CH), 3.99 (sept. 2H, CH(CH3)2), 2.93 (sept. 2H, CH(CH3)2), 2.00
(d, 6H, CH(CH3)2), 1.52 (s, 6H, CH3), 1.16 (d, 6H, CH(CH3)2),
1.00 (d, 6H, CH(CH3)2), 0.61 (d, 6H, CH(CH3)2). 13C NMR (C6D6,
RT): δ 168.82 (CN), 146.91 (ar), 144.25 (ar), 143.59 (ar), 136.39
(ar), 135.93 (ar), 135.73 (ar), 134.70 (ar), 134.51 (ar), 128.83 (ar),
127.64 (ar), 127.48 (ar), 127.29 (ar), 127.14 (ar), 125.34 (ar), 124.42
(ar), 100.23 (γ-C), 29.80 (CH(CH3)2), 29.07 (CH(CH3)2), 28.31
(CH(CH3)2), 24.73(CH(CH3)2), 24.60 (CH(CH3)2), 24.54(CH-
(CH3)2), 24.15 (CMe). 31P NMR (C6D6, RT): δ 53.1 (dd). 41.5
(dd). Anal. Calcd (found) for RhGaN2P2C65H71Cl: C, 67.03 (67.87);
H, 6.16 (6.22); N, 2.53 (2.44).
The rhodium complexes, [RhCl(PPh3)3] and [RhCl-
(COE)2]2, readily react with Ga(DDP) giving the insertion
products [(Ph3P)2Rh{Ga(DDP)}(µ-Cl)] (1) and [(COE)(η6-
benzene)Rh{(DDP)GaCl}] (2), respectively. Compound 1
exhibits a chloride bridging the gallium and the rhodium
atom, which is explained by the steric bulk of the DDP ligand
not allowing the coordination of additional ligands. The very
electrophilic rhodium center in the hypothetical 14VE
complex [(Ph3P)2Rh{GaCl(DDP)}] effectively competes with
the electrophilic Ga(I) center of the Ga(DDP) ligand for the
electrons of the chloride, finally leading to a Rh-Cl-Ga
bridge. In contrast, a full migration of the chloride from the
rhodium to the gallium center is observed on reaction of
[RhCl(COE)2]2 giving [(COE)(η6-benzene)Rh{(DDP)GaCl}]
(2) on coordination of the solvent C6H6.
Rh(COE)(C6H6)(µ-ClGa(DDP)) (2). [(COE)2RhCl)]2 (100 mg,
0.14 mmol) and Ga(DDP) (136 mg, 0.28 mmol) in 5 mL of benzene
were stirred at room temperature overnight. The solvent was
removed in vacuo. Recrystallization of the deep green solid out of
hexane at -30 °C gave deep green crystals in a 60% yield (135
1
mg). H NMR (C6D6, RT): δ 7.08-7.24 (ar, 12H), 5.12 (s, 1H,
Abstraction of the chloride from both 1 or 2 does not give
isolable products. However, reaction of the halide-abstracting
reagent Na[BArF] with the Au(I) complex [{(DDP)Ga}Au-
{ClGa(DDP)}] leads to the linear, symmetric cationic
complex [{(DDP)Ga}2Au][BArF] (3). The rather strong
electrophilicity of the coordinated gallium center in cation
3 becomes visible by crystallization of the product from a
saturated solution in THF, leading to a molecular structure
of 3‚2THF showing THF molecules axially coordinated to
each gallium center.
CH), 4.08 (m, 2H, CHCH3), 3.36 (m, 2H, CHCH3), 2.83 (d, 2H,
cyclooctene), 1.89 (d, 2H, cyclooctene), 1.69 (d, 6H, CHCH3), 1.68
(s, 6H, CCH3), 1.44 (d, 6H, CHCH3), 1.41 (m, 4H, cyclooctene),
1.25 (d, 6H, CHCH3), 1.20 (m, 4H, cyclooctene), 1.09 (d, 6H,
CHCH3), 1.00 (m, 2H, cyclooctene). 13C NMR (C6D6, RT): δ 166.9
(CN), 146.1 (ar), 144.9 (ar), 143.4 (ar), 128.1 (ar), 127.9 (ar), 126.8
(ar), 125.4 (ar), 123.4 (ar), 98.9 (γ-C), 97.4 (t, coord. C6D6), 57.0
(d, CdC, JC-Rh ) 14.6 Hz), 35.3 (br, cyclooctene), 32.6 (br,
cyclooctene), 29.8, 29.7, 28.0, 27.9, 26.6 (br, cyclooctene), 26.4,
26.3, 25.1, 25.0, 24.9, 24.8, 24.4, 24.3, 23.5, 23.4. 1H NMR (THF-
d8, RT): δ 7.14-7.30 (ar, 6H), 5.65 (s, 6H, C6H6), 5.19 (s, 1H,
CH), 3.80 (m, 2H, CHCH3), 3.28 (m, 2H, CHCH3), 2.67 (d, 2H,
cyclooctene), 1.83 (d, 2H, cyclooctene), 1.76 (s, 6H, CCH3), 1.43
(d, 6H, CHCH3), 1.41 (d, 6H, CHCH3), 1.22 (d + m, 12H, CHCH3
+ cyclooctene), 1.03 (d + m, 10H, CHCH3 + cyclooctene). 13C
NMR (THF-d8, RT): δ 167.4 (CN), 146.5 (ar), 145.5 (ar), 144.2
(ar), 129.1 (ar), 127.3 (ar), 125.7 (ar), 124.1 (ar), 99.2 (γ-C), 98.7
(d, C6H6, JC-Rh ) 2.14 Hz), 57.6 (d, C)C, JC-Rh ) 14.54 Hz),
35.7, 32.9, 30.4, 28.3, 27.6, 27.1, 26.5, 25.2, 25.1, 24.6, 23.8. Anal.
Calcd (found) for RhGa N2C43H61Cl: C, 63.44 (63.44); H, 7.55
(7.58); N, 3.44 (3.46).
[{(DDP)Ga}2Au][BArF] (3). [{(DDP)Ga}Au{ClGa(DDP)}] (90
mg, 0.075 mmol) and Na(BArF) (80 mg, 0.09 mmol) in 3 mL of
C6H5F were stirred at room temperature for 1 h. The white
precipitate of NaCl was filtered off, and the solvent of the resulting
yellow solution was removed in vacuo. The remaining colorless
solid was washed twice with hexane and dried in vacuo. Yield:
145 mg (95%). 1H NMR (C6H5F/C6D6, RT): δ 8.36 (br, 8H,
BArF), 7.65 (s, 4H, BArF), 7.34-6.34 (ar, 12H), 5.26 (s, 2H, CH),
2.50 (m, 8H, CHCH3), 1.61 (s, 12H, CCH3), 1.09 (d, 24H, CHCH3),
0.85 (d, 24H, CHCH3). 13C NMR: Because of the large 13C NMR
signals for the solvent, no satisfying 13C NMR spectrum of this
sample could be recorded.
Experimental Section
All manipulations were carried out in an atmosphere of purified
argon using standard Schlenk and glovebox techniques. Hexane
and THF were dried using an mBraun Solvent Purification System;
benzene and fluorbenzene were dried by distillation over standard
drying agents. The final H2O content in all solvents used was
checked by Karl Fischer titration and did not exceed 5 ppm.
[(COE)2RhCl]2,29 [(Ph3P)3RhCl],20 [(Ph3P)AuCl],30 Na[BArF],31
Ga(DDP),14 and [{(DDP)Ga}Au{ClGa(DDP)}]17 were prepared
according to literature methods. Elemental analyses were performed
by the Microanalytical Laboratory of the Ruhr-Universita¨t Bochum.
NMR spectra were recorded on a Bruker Avance DPX-250
spectrometer (1H, 250.1 MHz; 13C, 62.9 MHz) in C6D6 or THF-d8
(28) Malatesta, L.; Naldini, L.; Simonetta, G.; Cariati, F. Coord. Chem.
ReV. 1966, 1, 255.
(29) Van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28, 90.
(30) Braunstein, P.; Lehner, H.; Matt, D. Inorg. Synth. 1989, 27, 218.
(31) Reger, D. L.; Wright, T.; Little, C.; Lamba, J.; Smith, M. Inorg. Chem.
2001, 40, 3810.
(32) Buchin, B.; Gemel, C.; Cadenbach, T.; Schmid, R.; Fischer, R. A.
Angew. Chem. 2006, 118, 1091.
Inorganic Chemistry, Vol. 45, No. 7, 2006 3137

Kempter et al.
[{(DDP)Ga‚THF}2Au][BArF] (3‚2THF). The reaction was
performed in a manner similar to that described above using 47
mg of [(Ph3P)AuCl)] (0.1 mmol), 100 mg Ga(DDP) (0.2 mmol),
90 mg Na(BArF) (0.1 mmol), and THF. Yield: 150 mg (73%).
Crystals, suitable for X-ray analysis, were obtained by slow
diffusion of hexane into a saturated THF solution of 3‚2THF at
room temperature. 1H NMR (THF-d8, RT): δ 7.79 (m, 8H, BArF),
7.57 (s, 4H, BArF), 7.11-7.24 (ar, 12H), 5.36 (s, 2H, CH), 2.79
(m, 8H, CHCH3), 1.79 (s, 12H, CCH3), 1.11 (d, 24H, CHCH3),
0.95 (d, 24H, CHCH3). 13C NMR (THF-d8, RT): δ 168.8 (CN),
162.8 (q, BArF-ar), 144.3 (ar), 141.5 (ar), 135.6 (ar), 130.2 (q,
BArF-ar), 129.7 (q, BArF-ar), 128.0 (ar), 125.5 (q, JC-F ) 272
Hz, BArF-CF3), 125.0 (ar), 118.2 (BArF-ar), 99.7 (γ-C), 29.2
(CHCH3), 24.4 (CHCH3), 24.1 (CMe). 1H NMR (10:1 C6H5F/C6D6,
RT): δ 8.25 (m, 8H, BArF), 7.55 (s, 4H, BArF), 7.11-7.24 (ar,
overlaid by C6H5F), 5.17 (s, 2H, CH), 3.43 (m, 8H, THF), 2.43
(m, 8H, CHCH3), 1.53 (s, 12H, CCH3), 1.44 (m, 8H, THF), 1.02
(d, 24H, CHCH3), 0.77 (d, 24H, CHCH3). Anal. Calcd (found) for
AuGa2N4BO2C98H110F24: C, 54.01 (53.81); H, 5.09 (5.24); N, 2.57
(2.85).
Supporting Information Available: Crystallographic data files
in CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org.
IC0521731
3138 Inorganic Chemistry, Vol. 45, No. 7, 2006