π-Electron-cesium interactions in cesium triorganofluorometalates

Article abstract of DOI:10.1021/om960220e

The reaction of MMes₃ (M = Ga, In; Mes = 2,4,6-Me₃C₆H₂) with CsF in acetonitrile yields the trimesitylfluorometalates [{Cs(MeCN)₂}{Mes₃MF}]₂·2MeCN ([1]₂·6MeCN, M = Ga; [2]₂· 6MeCN, M = In). Ga(CH₂Ph)₃ gives with CsF under the same conditions the salt [Cs{(PhCH₂)₃GaF}]₂·2MeCN ([3]₂·2MeCN). The treatment of 1 equiv CsF with 2 equiv of GaMes₃ does not lead to Cs[Mes₃GaFGaMes₃] but to [1]₂·6MeCN and the adduct [Mes₃Ga-(MeCN)] (4). [1]₂·6MeCN-4 have been characterized by NMR, IR, and MS techniques as well as by X-ray analyses. [1]₂-6MeCN and [2]₂·6MeCN are solvated ion pairs in acetonitrile, while [3]₂·2MeCN shows a monomer-dimer equilibrium. According to the X-ray structure determinations, [1]₂·6MeCN and [2]₂·6MeCN are isostructural and contain Cs-F four-membered rings. The fluorine centers at the rings are bound to the metallane groups. Each cesium cation is coordinated by two molecules of acetonitrile and by one mesityl group in a η³-fashion. The basic structural feature of [3]₂·2MeCN is also a Cs-F four-membered ring; however, the cations in [3]₂·2MeCN are surrounded by three phenyl groups of the benzyl substituents. The three η⁶-bound phenyl rings are contributed from two different metallane units. 4 possesses a distorted tetrahedral coordination sphere with a low pyramidalization of the Ga center (angular sum: 355°).

Full text of DOI:10.1021/om960220e

3746
Organometallics 1996, 15, 3746-3751
π-Electr on -Cesiu m In ter a ction s in Cesiu m
Tr ior ga n oflu or om eta la tes
Bert Werner, Thomas Kra¨uter, and Bernhard Neumu¨ller*
Fachbereich Chemie der Universita¨t Marburg,
Hans-Meerwein-Strasse, D-35032 Marburg, Germany
Received March 25, 1996X
The reaction of MMes3 (M ) Ga, In; Mes ) 2,4,6-Me3C6H2) with CsF in acetonitrile yields
the trimesitylfluorometalates [{Cs(MeCN)2}{Mes3MF}]2‚2MeCN ([1]2‚6MeCN, M ) Ga; [2]2‚
6MeCN, M ) In). Ga(CH2Ph)3 gives with CsF under the same conditions the salt
[Cs{(PhCH2)3GaF}]2‚2MeCN ([3]2‚2MeCN). The treatment of 1 equiv CsF with 2 equiv of
GaMes3 does not lead to Cs[Mes3GaFGaMes3] but to [1]2‚6MeCN and the adduct [Mes3Ga-
(MeCN)] (4). [1]2‚6MeCN-4 have been characterized by NMR, IR, and MS techniques as
well as by X-ray analyses. [1]2‚6MeCN and [2]2‚6MeCN are solvated ion pairs in acetonitrile,
while [3]2‚2MeCN shows a monomer-dimer equilibrium. According to the X-ray structure
determinations, [1]2‚6MeCN and [2]2‚6MeCN are isostructural and contain Cs-F four-
membered rings. The fluorine centers at the rings are bound to the metallane groups. Each
cesium cation is coordinated by two molecules of acetonitrile and by one mesityl group in a
η3-fashion. The basic structural feature of [3]2‚2MeCN is also a Cs-F four-membered ring;
however, the cations in [3]2‚2MeCN are surrounded by three phenyl groups of the benzyl
substituents. The three η6-bound phenyl rings are contributed from two different metallane
units. 4 possesses a distorted tetrahedral coordination sphere with a low pyramidalization
of the Ga center (angular sum: 355°).
Although triorganofluorometalates have been known
tions also in cesium triorganofluorometalates Cs[R3MF]
(R ) Me, M ) Al, Ga, In;14 R ) Et, i-Pr, M ) Ga, In15).
The important structural motifs are Cs2F2 four-mem-
bered rings connected to puckered layers, infinite lad-
der-type chains, or heterocubane units.
In the present work we have investigated the influ-
ence of electronic π-systems on the generation of the
Cs-F skeleton, particularly on the environment of the
Cs+ ions.
for 35 years, reports about their structures in the solid
state are sparse. The aluminum derivatives1-3 as well
as the later published derivatives of the higher homo-
loges gallium and indium, K[Me3GaF],4 K[Et3GaF],4-6
[NMe4][Et3GaF],5 [Me3NCH2Ph][Et3GaF],6,7 [Et3NCH2-
Ph][Et3GaF],7 and [Me3NCH2Ph][Me3InF],8 supposedly
consist of linear polymer chains of [R3MF]- units with
a distorted trigonal-bipyramidal coordination sphere. In
this case the cations should not be included into strong
interionic interactions as it has been found for the salts
K[Et3AlFAlEt3]9 and K[Me3AlFAlMe3]‚C6H6.10 This ar-
rangement, however, does not appear likely in the case
of the alkali triorganofluorometalates because of our
findings during the structural studies of the metalates
Cs[(PhCH2)2GaF2],11 Cs[MesGaF3],12 and [{Cs(MeCN)2}-
{F(i-Pr2InF)5}].13 In these salts Cs-F contacts domi-
nate the structure.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were carried out
under an atmosphere of argon using Schlenk techniques.
Purification and drying of the organic solvents were performed
using standard methods.16 GaMes3,17 InMes3,18 and Ga(CH2-
11,19
Ph)3
were prepared following literature procedures.
The 1H, 13C, and 19F NMR spectra were recorded on a Bruker
spectrometer AC-300 (1H, 300.134 MHz; 13C, 75.469 MHz; 19F,
282.409 MHz). The standards were TMS (external; H, 13C)
1
More recently, we have shown strong Cs-F interac-
and CFCl3 (external; 19F) with δ ) 0.0 ppm. The IR spectra
were obtained using a Bruker instrument IFS-88 (Nujol mulls,
CsI disks for the range 4000-500 cm-1; polyethylene disks for
the range 500-100 cm-1). For the EI mass spectra a Varian
CH7a mass spectrometer (70 eV) was used. The melting
points were measured with a Dr. Tottoli (Bu¨chi) melting point
apparatus in sealed capillaries under argon (values not cor-
rected).
X Abstract published in Advance ACS Abstracts, J uly 15, 1996.
(1) Ziegler, K.; Ko¨ster, R.; Lehmkuhl, H.; Reinert, K. Liebigs Ann.
Chem. 1960, 629, 33.
(2) Frey, F. W., J r.; Kobetz, P.; Robinson, G. C.; Sistrunk, T. O. J .
Org. Chem. 1961, 26, 2950.
(3) Bastide, J . P.; El Hajri, J .; Claudy, P.; El Hajbi, A. Synth. React.
Inorg. Met.-Org. Chem. 1995, 25, 1037.
(4) Wilson, I. L.; Dehnicke, K. J . Organomet. Chem. 1974, 67, 229.
(5) Eisch, J . J . J . Am. Chem. Soc. 1962, 84, 3605.
(6) Do¨tzer, R. Chem.-Ing. Tech. 1964, 36, 613.
(7) Do¨tzer, R. Ger. 1,200,817, Siemens-Schuckertwerke AG, 1965;
Chem. Abstr. 1965, 63, 15896d.
Syn t h esis of [{Cs(MeCN)2}{Mes3Ga F }]2‚2MeCN, [1]2‚
6MeCN. A 1.77 g (11.65 mmol) amount of CsF was added to
a solution of 3.56 g (8.32 mmol) of GaMes3 in 40 mL of MeCN
(8) Fr. 1,461,819, Siemens-Schuckertwerke AG, 1966; Chem. Abstr.
1967, 67, 17386m.
(9) (a) Natta, G.; Allegra, G.; Perego, G.; Zambelli, A. J . Am. Chem.
Soc. 1961, 83, 5033. (b) Allegra, G.; Perego, G. Acta Crystallogr. 1963,
16, 185.
(10) Atwood, J . L.; Newberry, W. R., III. J . Organomet. Chem. 1974,
66, 15.
(11) Neumu¨ller, B.; Gahlmann, F. Chem. Ber. 1993, 126, 1579.
(12) Neumu¨ller, B.; Gahlmann, F. Z. Anorg. Allg. Chem. 1993, 619,
1897.
(13) Neumu¨ller, B.; Gahlmann, F. Z. Anorg. Allg. Chem. 1993, 619,
718.
(14) Werner, B.; Neumu¨ller, B. Chem. Ber. 1996, 129, 355.
(15) Werner, B.; Kra¨uter, T.; Neumu¨ller, B. Inorg. Chem. 1996, 35,
2977.
(16) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals, 2nd ed.; Pergamon Press: Oxford, U.K., 1980.
(17) Beachley, O. T., J r.; Churchill, M. R.; Pazik, J . C.; Ziller, J . W.
Organometallics 1986, 5, 1814.
(18) Leman, J . T.; Barron, A. R. Organometallics 1989, 8, 2214.
(19) Viktorova, J . M.; Sheverdina, N. J .; Kocheshkov, K. A. J . Gen.
Chem. USSR 1967, 37, 2547.
S0276-7333(96)00220-8 CCC: $12.00 © 1996 American Chemical Society

Cesium Triorganofluorometalates
Organometallics, Vol. 15, No. 17, 1996 3747
in one portion at room temperature. The colorless suspension
was stirred for 4 days, heated to 60 °C and filtered at this
temperature. The filtrate was cooled to 5 °C yielding colorless
crystals of [1]2‚6MeCN [3.92 g, 82% yield based on GaMes3,
mp >270 °C (solvent-free material 1)]. 1H NMR (CD3CN,
ppm): 2.20 (s, 3 H, CH3-C4), 2.23 (s, 6 H, CH3-C2/6), 6.63 (s, 2
H, H-C3/5). 13C NMR (CD3CN, ppm): 21.0 (CH3-C4), 24.9 (CH3-
C2/6), 127.1 (C3/5), 134.9 (C4), 145.8 (C2/6), 155.4 (C1). 19F NMR
(CD3CN, ppm): -167.8. IR (cm-1): 2726 (w), 2292 (w), 2260
(w), 1735 (w), 1598 (m), 1542 (m), 1256 (m), 1169 (w), 1019
(m), 943 (w), 922 (w), 876 (s), 581 (m), 546 (vs), 496 (w), 421
(vs), 350 (s), 285 (m), 257 (s), 194 (s). EI-MS [m/ z (rel. int.)
fragment]: 503 (3) (CsFGaMes3 - 5Me)+, 429 (8) (CsFGaMes2
- 2Me)+, 415 (3) (CsFGaMes2 - 3Me + H)+, 401 (2) (CsF-
GaMes2 - 4Me + 2H)+, 355 (18) (CsFGaMesMe)+, 341 (8)
(CsFGaMes + H)+, 325 (7) (FGaMes2 - H)+, 307 (62) (GaMes2)+,
281 (51) (FGaMes2 - 3Me)+, 267 (6) (FGaMes2 - 4Me + H)+,
221 (12) (FGaMesMe - H/CsFGas)+, 207 (100) (FGaMes)+, 191
(9) (FGaMes - Me - H)+, 147 (22) (CsMe - H)+, 133 (9) Cs+,
119 (4) (Mes)+, 69 (28) Ga+. Anal. Calcd: C, 55.99; H, 5.74;
Cs, 22.95; F, 3.28. Found: C, 55.76; H, 5.82; Cs, 22.68; F, 3.16
(solvent-free material 1).
Syn t h esis of [{Cs(MeCN)2}{Mes3In F }]2‚2MeCN, [2]2‚
6MeCN. A 1.13 g (7.44 mmol) amount of CsF was added to a
solution of 2.34 g (4.95 mmol) of InMes3 in 50 mL in one portion
at room temperature. The colorless suspension was stirred
for 70 h, heated to 60 °C, and filtered at this temperature.
The filtrate was cooled to 5 °C yielding colorless crystals of
[2]2‚6MeCN [2.60 g, 84% yield based on InMes3, mp 191 °C
(solvent-free material 2)]. 1H NMR (CD3CN, ppm): 2.10 (s, 3
H, CH3-C4), 2.20 (s, 6 H, CH3-C2/6), 6.69 (s, 2 H, H-C3/5). 13C
NMR (CD3CN, ppm): 21.0 (CH3-C4), 25.9 (CH3-C2/6), 126.6
(C3/5), 135.8 (C4), 140.7 (C2/6), 146.4 (C1). 19F NMR (CD3CN,
ppm): -173.4. IR (cm-1): 2728 (m), 1712 (vw), 1609 (w), 1594
(w), 1306 (m), 1225 (m), 1156 (m), 1032 (m), 969 (m), 940 (m),
890 (w), 845 (m), 836 (m), 687 (m), 604 (m), 577 (m), 538 (m),
488 (w), 462 (w), 446 (w), 402 (w), 391 (w), 297 (w), 239 (w),
190 (m), 146 (w), 135 (w), 125 (w). EI-MS [m/ z (rel. int.)
fragment]: 372 (1) (FInMes2)+, 353 (2) (InMes2)+, 253 (2)
(FInMes)+, 234 (3) (InMes)+, 134 (3) (InF)+, 133 (7) Cs+, 119
(71) (Mes)+, 115 (3) In+, 105 (100) (MesH - Me)+, 91 (9)
(Mes - 2Me)+, 77 (12) (C6H5)+. Anal. Calcd: C, 51.95; H, 5.33;
Cs, 21.29; F, 3.04. Found: C, 51.69; H, 5.42; Cs, 21.18; F, 3.12
(solvent-free material 2).
(2.6 mmol) of GaMes3 in 10 mL of MeCN was treated with 5
mL of n-pentane. The mixture was cooled to 5 °C yielding
colorless crystals [0.96 g, 79%, mp 193 °C]. 1H NMR (CD3-
CN, ppm): 1.89 (s, 3 H, CH3CN), 2.11 (s, 6 H, CH3-C2/6), 2.13
(s, 3 H, CH3-C4), 6.67 (s, 2 H, H-C3/5). 13C NMR (CD3CN,
ppm): 1.2 (CH3CN), 20.9 (CH3-C4), 24.9 (CH3-C2/6), 121.2
(CH3CN), 128.1 (C3/5), 138.7 (C4), 145.1 (C2/6), 148.0 (C1). IR
(cm-1): 2728 (w), 2306 (w), 2279 (w), 1600 (m), 1569 (m), 1304
(m), 1225 (m), 1169 (m), 969 (m), 932 (m), 890 (m), 847 (s),
836 (s), 687 (m), 596 (w), 581 (m), 558 (m), 544 (m), 523 (w),
490 (w), 463 (m), 447 (m), 399 (m), 345 (m), 338 (m), 327 (m),
279 (w), 247 (m), 226 (vw), 194 (m-s), 170 (vw), 151 (m), 118
(m), 105 (w). EI-MS [m/ z (rel. int.) fragment]: 426 (10)
(GaMes3)+, 307 (90) (GaMes2)+, 188 (33) (GaMes)+, 119 (100)
(Mes)+, 105 (21) (Mes - Me)+, 91 (4) (Mes - 2Me)+, 69 (45)
Ga+, 41 (31) (MeCN)+. Anal. Calcd: C, 74.36; H, 7.76; N, 2.99.
Found: C, 74.18; H, 7.48; N, 2.98.
X-r a y Str u ctu r e Deter m in a tion s of [1]2‚6MeCN-4. The
crystals were covered with a high-boiling paraffin oil and
mounted on the top of a glass capillary under the flow of cold
gaseous nitrogen. The orientation matrix and preliminary unit
cell dimensions were determined from 25 reflections on a four-
circle diffractometer with graphite-monochromated Mo KR
radiation (λ ) 0.710 73 Å; [1]2‚6MeCN, 4, Siemens P4; [2]2‚
6MeCN, [3]2‚2MeCN, Enraf-Nonius CAD4). The final cell
parameters were determined with 25 high-angle reflections.
The intensities have been corrected for Lorentz and polar-
ization effects (cell parameters and collecting of the intensities;
see Table 1). The structure of [1]2‚6MeCN has been solved by
the Patterson method, and the structures of [3]2‚2MeCN and
4 have been solved by direct methods using the program
SHELXTL-Plus.20 The structure of [2]2‚6MeCN is isostruc-
tural to [1]2‚6MeCN; the coordinates of the non-hydrogen
atoms of [1]2‚6MeCN have been used for the first refinement
cycles. The structures were refined against F2 by full-matrix
least-squares with the program SHELXL-93.21 The positions
of the hydrogen atoms were calculated for ideal positions and
refined with a common displacement parameter. The calcula-
tion of the bond lengths, bond angles, and Ueq values was
performed using the program PLATON.22
Selected bond lengths and angles of [1]2‚6MeCN-4 are listed
in Table 2. Table 3 shows additional metal-carbon contacts
in [1]2‚6MeCN-[3]2‚2MeCN. A comparison of bond lengths
for selected organogallium(indium) compounds is given in
Table 4.
Syn th esis of [Cs{(P h CH2)3Ga F }]2‚2MeCN, [3]2‚2MeCN.
A 0.75 g (4.94 mmol) amount of CsF was added to a solution
of 1.14 g (3.32 mmol) of Ga(CH2Ph)3 in 25 mL of MeCN in one
portion at room temperature. The colorless suspension was
stirred for 48 h, heated to 60 °C, and filtered at this temper-
ature. The filtrate was cooled to 5 °C yielding colorless crystals
of [3]2‚2MeCN [1.49 g, 91% yield based on Ga(CH2Ph)3, mp
132 °C (dec, solvent-free material 3)]. 1H NMR (CD3CN, ppm,
rel. integral): 1.65 (s, 0.79, CH2Ph, dimer), 1.64 (s, 1.57, CH2-
Ph, dimer), 1.77 (s, 1, CH2Ph, monomer), 6.78-7.40 (m, 8.57,
H-phenyl, monomer and dimer). 13C NMR (CD3CN, ppm):
22.6 (br, CH2Ph, monomer), 24.4 (CH2Ph, dimer), 24.6 (CH2-
Resu lts a n d Discu ssion
The cesium triorganofluorometalates [{Cs(MeCN)2}-
{Mes3MF}]2‚2MeCN ([1]2‚6MeCN, M ) Ga; [2]2‚6MeCN,
M ) In) have been synthesized by the reaction of the
corresponding metallanes with CsF in acetonitrile at
room temperature according to eq 1.
2MMes3 + 2CsF + 6MeCN f
[{Cs(MeCN)2}{Mes3MF}]2‚2MeCN (1)
[1]2‚6MeCN, M ) Ga
Ph, dimer), 121.2 (C4, dimer), 122.6 (C4, monomer), 127.8 (C3/5
dimer), 128.4 (C3/5, monomer), 128.7 (C2/6, dimer), 128.9 (C2/6
,
,
monomer), 147.3 (C1, monomer), 150.7 (C1, dimer). 19F NMR
(CD3CN, ppm, rel. integral): -167.7 (s, 2.2, dimer), -173.1
(s, 1.0, monomer). IR (cm-1): 2717 (m), 2667 (m), 2008 (vw),
1980 (vw), 1858 (vw), 1808 (vw), 1590 (s), 1306 (m), 1267 (w),
1206 (vs), 1177 (m), 1071 (s), 1043 (s), 994 (s), 901 8m), 797
(m), 755 (vs), 699 (vs), 619 (w), 567 (w), 544 (m), 521 (m), 477
(s), 446 (s), 331 (m), 246 (s), 228 (s), 206 (s), 181 (m), 136 (vw).
EI-MS [m/ z (rel. int.) fragments]: 555 (1) [Cs2F2Ga(CH2Ph)2]+,
403 (1) [CsFGa(CH2Ph)2]+, 342 (1) [Ga(CH2Ph)3]+, 330 (1)
[CsF2GaCH2Ph - H]+, 251 (33) [Ga(CH2Ph)2]+, 91 (100) (CH2-
Ph)+, 69 (55) Ga+. Anal. Calcd: C, 50.95; H, 4.27; Cs, 26.85;
F, 3.84. Found: C, 50.79, H, 4.35; Cs, 26.59; F, 4.04 (solvent-
free material 3).
[2]2‚6MeCN, M ) In
The choice of CsF as fluoridation agent is based on
its highest fluoridation potential among the alkali
fluorides and the highest enthalpy of complexation for
the salts M′[R3MF] (M′ ) Li, Na, K, Rb, Cs; M ) Al,
Ga, In; R ) alkyl groups).1 Another reason is the
possibility of obtaining crystals of high quality. Other
(20) Sheldrick, G. M. SHELXTL-Plus, Release 4.2 for Siemens R3
Crystallographic Research Systems, Siemens Analytical X-ray Instru-
ments, Inc., Madison, WI, 1990.
(21) Sheldrick, G. M. SHELXL-93, Go¨ttingen, 1993.
(22) Spek, A. L. PLATON-94, Utrecht, 1994.
Syn th esis of [Mes3Ga (MeCN)], 4. A solution of 1.12 g

3748 Organometallics, Vol. 15, No. 17, 1996
Werner et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for th e Com p ou n d s [1]2‚6MeCN-4
compd
[1]2‚6MeCN
[2]2‚6MeCN
[3]2‚2MeCN
4
formula
fw
cryst size (mm)
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
space group
No.43
C66H84Cs2F2Ga2N6
1404.69
0.6 × 0.3 × 0.2
10.359(2)
13.319(3)
25.498(5)
101.58(1)
3446(1)
P21/c
C66H84Cs2F2In2N6
1494.89
0.6 × 0.5 × 0.1
10.341(1)
13.424(1)
25.711(2)
101.03(1)
3503.2(5)
P21/c
C46H48Cs2F2Ga2N2
1072.16
0.45 × 0.4 × 0.38
12.503(2)
19.755(1)
9.122(1)
93.05(1)
2249.9(5)
P21/c
C29H36GaN
468.33
0.4 × 0.08 × 0.2
8.219(2)
22.844(5)
13.834(3)
101.63(1)
2544(1)
P21/c
14
14
14
14
Z
F
2
2
2
4
calc (g/cm3)
1.354
223
numerical
18.7
1.417
213
empirical
17.3
4.4-50
1.583
203
no
28.3
1.222
223
no
11.0
temp (K)
abs corr
µ (cm-1
)
2θ range (deg)
h,k,l values
2-50
5.0-50
4-50
-1 e h e 12, -1 e k e 15, -12 e h e 12, 0 e k e 15, -14 e h e 14, -23 e k e 0, -1 e h e 9, -1 e k e 27,
-30 e l e 30
0 e l e 30
0 e l e 10
-16 e l e 16
scan
ω-scan
1.4
7772
6050
2990
ω-scan
0.58 + 0.43 tan θ
6588
6149
5063
ω-scan
0.96 + 0.46 tan θ
4334
3937
3103
ω-scan
1.2
5939
4481
1824
scan width (deg)
no. of refls
unique refls
refls with Fo > 4σ(Fo)
for R1
params
353
353
0.0267
0.0741
0.0422, 1.12
0.42/-0.49
345
0.0277
0.0712
0.0346, 1.01
0.63/-0.56
282
0.0501
0.0967
0.0286, 0
0.37/-0.43
a
R1
wR2
0.0578
0.1879
0.0958, 0
b
weight fact. a, b
max/min resid electron 1.27/-1.94
density (e/Å3)
a
b
2
c
R1 ) ∑||Fo - Fc||/∑|Fc|. wR2 ) {[∑w(Fo - Fc2)2]/∑w(Fo2)2]}1/2
.
w ) 1/[σ2(Fo2) + (aP)2 + bP].
alkali cations like K+ give crystalline material suitable
for a single-crystal X-ray structure determination only
in a few cases, e.g., for the compound K[MesInBr3].12,23
The coordination of MeCN at cesium centers can be
excluded for compounds of the general formula
M′[R4-nGaFn] (n ) 1, 2) in the case of benzyl substitu-
ents as shown in eq 2 for n ) 1.
Earlier investigations of the saltlike compounds Cs-
[(PhCH2)2GaF2],11 Cs[MesGaF3],12 and Cs[R3MF] (R )
Me, Et, i-Pr; M ) Al, Ga, In)14,15 showed similar results.
The 19F NMR spectra of 1 and 2 exhibit one resonance
at -167.8 and -173.4 ppm, respectively. The two
signals at -167.7 and -173.2 ppm for 3 in acetonitrile
may be caused by a monomer-dimer equilibrium. The
1H and 13C NMR spectra of 3 verify this assumption.
The monomer gives one signal at 1.77 (1H) and 22.6 ppm
(13C), while the dimer gives rise to two peaks at 1.64
and 1.65 ppm (1H) as well as at 24.4 and 24.6 ppm (13C).
However, the ratio of the signals for the dimer is 1:2.
This can be explained by the X-ray analysis, which
shows that the three benzyl groups are coordinated to
two different Cs centers. Therefore, two benzyl groups
are chemically equivalent. The molar dimer-monomer
2Ga(CH2Ph)3 + 2CsF + 2MeCN f
[Cs{(PhCH2)3GaF}]2‚2MeCN (2)
[3]2‚2MeCN
The treatment of 1 equiv CsF with 2 equiv of MR3
does not lead to the dimetalla fluorides Cs[R3MFMR3]
as was observed for M[R3AlFAlR3] (M ) alkali metal,
R ) alkyl),1,9,10 [NMe4][R3GaFGaR3] (R ) Me,4 Et4,6,7),
and [NMe4][Me3TlFTlMe3].24 Only [1]2‚6MeCN-[3]2‚
2MeCN and, in the case of GaMes3, the adduct [Mes3-
Ga(MeCN)], 4, could be isolated. One reason which
could serve to explain this finding is the reduced Lewis
acidity of gallanes and indanes compared to that of
allanes on the one hand and the strong cesium-fluorine
interaction on the other hand. A salt of general formula
A[R3MFMR3] with M ) Ga, In, and Tl should exist only
when A+ is a bulky nonpolarizing cation such as [NR4]+
or [PR4]+.
1
ratio determined from the H spectrum is 1.18:1 at 25
°C. A VT-19F-NMR study in the range -40 to 40 °C
(CD3CN) shows only a slight temperature dependence
of the dimer-monomer ratio.
1
The H and 13C resonances for the coordinated aceto-
nitrile molecule in 4 at 1.89 (1H) and 1.2 and 121.2 ppm
(13C) show typical values compared with the spectra of
compounds with MeCN ligands coordinated to group 13
metal centers.25,26 In all cases, 1-4, the organic groups
1
give H and 13C NMR signals which are characteristic
for Mes and CH2Ph ligands, attached to MF fragments
The title compounds are oxygen and moisture sensi-
tive and soluble in donor solvents such as MeCN and
THF. Solutions of 1 and 2 in acetonitrile contain
solvated ion pairs of the type [Cs(MeCN)n][Mes3MF].
(M ) Ga, In).11-13,25,27
The small rings in [1]2‚6MeCN-[3]2‚2MeCN allow a
reliable assignment of IR bands to the corresponding
(23) For gallium and indium compounds, see: Gmelin Handbook of
Inorganic Chemistry, Gallium, Organogallium Compounds; Springer:
Berlin, 1987; Part 1. Weidlein, J . In Gmelin Handbook of Inorganic
Chemistry, Organoindium Compounds; Springer: Berlin, 1991; Part
1.
(25) Neumu¨ller, B.; Gahlmann, F. Z. Anorg. Allg. Chem. 1992, 612,
123.
(26) Cowley, A. H.; Carrano, C. J .; Geerts, R. L.; J ones, R. A.; Nunn,
C. M. Angew. Chem., Int. Ed. Engl. 1988, 27, 277.
(27) Neumu¨ller, B.; Gahlmann, F. J . Organomet. Chem. 1991, 414,
271.
(24) Ehemann, T.; Dehnicke, K. J . Organomet. Chem. 1974, 71, 191.

Cesium Triorganofluorometalates
Organometallics, Vol. 15, No. 17, 1996 3749
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
Ta ble 3. Ad d ition a l Meta l-Ca r bon Con ta cts in
[1]2‚6MeCN-[3]2‚2MeCN (Å)
(d eg) of [1]2‚6MeCN-4
Compound [1]2‚6MeCN
Compound [1]2‚6MeCN
Cs1-F1
Cs1-F1a
Cs1-N1
Cs1-N2
Ga1-F1
3.207(6)
2.880(5)
3.18(1)
3.11(1)
1.903(5)
Ga1-C1
Ga1-C2
Ga1-C3
N1-C4
N2-C5
2.024(9)
2.03(1)
2.02(1)
1.13(2)
1.10(2)
Cs1‚‚‚C2
3.49(1)
3.31(1)
3.56(1)
4.00(1)
Cs1‚‚‚C24
Cs1‚‚‚C25
Cs1‚‚‚C36
4.17(1)
3.94(1)
3.59(1)
Cs1‚‚‚C21
Cs1‚‚‚C22
Cs1‚‚‚C23
Compound [2]2‚6MeCN
F1-Cs1-F1a
F1-Cs1-N1
F1-Cs1-N2
N1-Cs1-N2
N1-Cs1-F1a
N2-Cs1-F1a
F1-Ga1-C1
F1-Ga1-C2
F1-Ga1-C3
86.4(1)
119.0(3)
121.3(4)
119.6(4)
105.0(3)
82.1(3)
105.5(3)
96.0(3)
103.6(4)
C1-Ga1-C2
C1-Ga1-C3
C2-Ga1-C3
Cs1-F1-Ga1
Cs1-F1-Cs1a
Ga1-F1-Cs1a
Cs1-N1-C4
Cs1-N2-C5
113.3(4)
114.4(4)
130.3(4)
109.7(2)
93.6(1)
156.4(3)
160(1)
3.508(3)
4.243(4)
3.988(4)
3.663(5)
3.360(3)
3.761(4)
4.123(4)
Compound [3]2‚2MeCN
Cs1‚‚‚C11a
Cs1‚‚‚C12a
Cs1‚‚‚C13a
Cs1‚‚‚C14a
Cs1‚‚‚C15a
Cs1‚‚‚C16a
3.700(4)
3.641(4)
3.549(5)
3.477(5)
3.479(5)
3.592(4)
3.29
3.670(4)
3.697(4)
3.651(5)
3.556(5)
Cs1‚‚‚C25
Cs1‚‚‚C26
3.497(5)
3.553(5)
3.30
3.617(4)
3.550(5)
3.526(5)
3.545(5)
3.581(5)
3.614(5)
3.29
135(1)
Cs1‚‚‚C21-C26a
Cs1‚‚‚C31
Compound [2]2‚6MeCN
Cs1‚‚‚C32
Cs1-F1
Cs1-F1a
Cs1-N1
Cs1-N2
In1-F1
3.040(2)
2.852(2)
3.224(4)
3.139(4)
2.113(2)
In1-C1
In1-C2
In1-C3
N1-C4
N2-C5
2.202(3)
2.213(3)
2.212(3)
1.128(6)
1.112(6)
Cs1‚‚‚C33
Cs1‚‚‚C11a-C16aa
Cs1‚‚‚C21
Cs1‚‚‚C34
Cs1‚‚‚C35
Cs1‚‚‚C22
Cs1‚‚‚C36
Cs1‚‚‚C23
Cs1‚‚‚C31-C36a
Cs1‚‚‚C24
F1-Cs1-F1a
F1-Cs1-N1
F1-Cs1-N2
N1-Cs1-N2
N1-Cs1-F1a
N2-Cs1-F1a
F1-In1-C1
F1-In1-C2
F1-In1-C3
82.26(5)
121.83(9)
119.5(1)
118.7(1)
106.9(1)
80.9(1)
103.97(9)
93.9(1)
103.0(1)
C1-In1-C2
C1-In1-C3
C2-In1-C3
Cs1-F1-In1
Cs1-F1-Cs1a
In1-F1-Cs1a
Cs1-N1-C4
Cs1-N2-C5
115.1(1)
116.2(1)
119.3(1)
109.41(7)
97.74(5)
152.75(9)
160.0(5)
137.4(4)
a
Ring centroid.
tion at 338 cm-1 for 4 is caused by the M-N streching
vibration. Interesting are the CtN bands. A CtN
vibration for [1]2‚6MeCN and [2]2‚6MeCN has been
observed only for [1]2‚6MeCN because of the weakly
bound MeCN molecules. In [1]2‚6MeCN the acetonitrile
molecule is attached to Cs+, while 4 possesses a slightly
stronger donor-acceptor Ga-N bond. Nevertheless, in
both cases the resonance ν(CtN) is split by Fermi
resonance. In addition, a shift of the values to higher
wavenumbers should be observable ([1]2‚6MeCN, 2292,
2260; 4, 2306, 2279; MeCN, 2294, 2254 cm-1).30 [1]2‚
6MeCN and 4 exhibit only a small splitting of the band
and no significant shift of the values as it was found in
[{B(CH2Ph)3}0.92{Ga(CH2Ph)3}0.08(MeCN)] (2336, 2314,
2291 cm-1).25 The spectroscopic data and the results
of the X-ray analyses confirm that [1]2‚6MeCN, [2]2‚
6MeCN, and 4 are compounds with weak metal-
nitrogen bonds.
Compound [3]2‚2MeCN
Cs1-F1
Cs1-F1a
Ga1-F1
2.872(2)
2.838(2)
1.864(2)
Ga1-C1
Ga1-C2
Ga1-C3
2.013(4)
2.007(5)
2.021(5)
F1-Cs1-F1a
F1-Ga1-C1
F1-Ga1-C2
F1-Ga1-C3
C1-Ga1-C2
84.85(6)
105.0(1)
104.3(2)
104.6(2)
112.3(2)
C1-Ga1-C3
C2-Ga1-C3
Cs1-F1-Ga1
Cs1-F1-Cs1a
Ga1-F1-Cs1a
112.6(2)
116.6(2)
119.8(1)
95.15(7)
132.9(1)
Compound 4
Ga1-N1
Ga1-C1
Ga1-C2
2.207(5)
2.014(5)
1.999(5)
Ga1-C3
N1-C4
1.988(5)
1.111(6)
N1-Ga1-C1
N1-Ga1-C2
N1-Ga1-C3
C1-Ga1-C2
96.6(2)
94.2(2)
101.0(2)
119.3(2)
C1-Ga1-C3
C2-Ga1-C3
Ga1-N1-C4
N1-C4-C41
118.1(2)
118.0(2)
171.2(5)
178.4(7)
The EI mass spectra exhibit only fragments for the
dimers [1]2‚6MeCN-[3]2‚2MeCN. m/ z ) 503 (CsF-
GaMes3 - 5Me)+, m/ z ) 372 (FInMes2)+, and m/ z )
555 [Cs2F2Ga(CH2Ph)2]+ are the highest observed sig-
nals.
vibrations. Monomer CsF and the dimer (CsF)2 inves-
tigated by matrix isolation techniques exhibit IR bands
at 313 (monomer) and 251, 205, and 76 cm-1 (dimer),
respectively.28 The absorptions at 194 ([1]2‚6MeCN) and
190 cm-1 ([2]2‚6MeCN) can be attributed to the vibra-
tions νas(Cs2F2). The bands at 228, 206, and 181 cm-1
for the ring vibrations in [3]2‚2MeCN are observed at
higher wavenumbers because of the lower coordination
number of the Cs+ ion. The Ga(In)-F stretching
vibrations have been observed at 420 ([1]2‚6MeCN), 402
([2]2‚6MeCN), and 447 cm-1 ([3]2‚2MeCN); the higher
value for [3]2‚2MeCN in comparison to [1]2‚6MeCN is
in good agreement with the shorter Ga-F bond length
in [3]2‚2MeCN compared to that in [1]2‚6MeCN. We
assign the bands at 581 ([1]2‚6MeCN), 538 ([2]2‚
6MeCN), 477 ([3]2‚2MeCN), and 581 cm-1 (4) to M-C
vibrations. However, the M-Mes fragments lead to a
mixing of M-C and aryl-ring vibrations.29 The absorp-
Centrosymmetric four-membered CsF rings are the
dominating structural motif for the solid structures of
[1]2‚6MeCN-[3]2‚2MeCN. In comparable derivatives
such as Cs[Me3MF] and Cs[i-Pr3MF] (M ) Ga, In)14,15
the Cs2F2 rings are connected by additional Cs-F
interactions. In [1]2‚6MeCN-[3]2‚2MeCN the π-elec-
tron systems of aryl substituents and, in part, aceto-
nitrile molecules have to substitute the Cs-F contacts
to saturate the coordination sphere of the Cs+ ions.
However, the interactions of π-electron systems with
Cs+ ions can be understood as an electrostatic one.
Comparable aryl-Cs(Rb) features are known from or-
ganometallic compounds such as [Cs(C6H6)3{C(Si-
Me3)3}].31,32 The structures of [1]2‚6MeCN and [2]2‚
(29) Kainz, B; Schmidt, A. Spectrochim. Acta 1990, 46A, 1361.
(30) Weidlein, J .; Mu¨ller, U.; Dehnicke, K. Schwingungsfrequenzen
I; Thieme: Stuttgart, Germany, 1981.
(31) Eaborn, C.; Hitchcock, P. B.; Izod, K.; Smith, J . D. Angew.
Chem., Int. Ed. Engl. 1995, 34, 687.
(28) Martin, T. P.; Schaber, H. J . Chem. Phys. 1978, 68, 4299.

3750 Organometallics, Vol. 15, No. 17, 1996
Werner et al.
Ta ble 4. Com p a r ison of Bon d Len gth s (Å) in Selected Or ga n oga lliu m (in d iu m ) Com p ou n d s
compd
Cs-F
Ga(In)-F
1.903(5)
Ga(In)-C
Ga-N
ref
[1]2‚6MeCN
[3]2‚2MeCN
Cs[Me3GaF]
Cs[i-Pr3GaF]
Cs[(PhCH2)2GaF2]
Cs[MesGaF3]
2.880(5), 3.207(6)
2.838(2), 2.872(2)
2.96a
2.02a
b
b
14
15
11
12
1.864(2)
2.01a
1.919(3), 1.922(3)
1.970(4)
1.99a
2.924(2)
1.998(5)
3.18a
1.84a
1.97a
3.11a
1.784(7)
1.941(8)
1.807(4)
[Mes2GaF]2‚THF
[(PhCH2)3Ga(THF)]
GaMes3
[Mes2GaCl]2
4
[Mes2Ga(F)(t-BuNH2)]‚2.5THF
[Mes6Ga6F4O4]‚THF
[Me3Ga(t-BuNH2)]
[Me3Ga{(C6H11)2NH}]
[t-Bu3Ga(PhNH2)]
[2]2‚6MeCN
Cs[Me3InF]
Cs[i-Pr3InF]
[{Cs(MeCN)2}{F(i-Pr2InF)5}]
[(MesInF2)10MgF2]‚5tol
[Mes2InF]3
1.947(2)c
1.949(5)
1.981(6)
1.968(4)
1.972(3)
2.00a
44
11
17
45
b
46
44
36
38
37
b
14
15
13
13
46
18
18
2.207(5)
2.049(4)
1.838(3)
2.23a,d
1.991(5)
1.93a
1.95(1), 2.01(1)
1.97a
2.12(1)
2.151(6)
2.246(9)
2.00(1)
2.852(2), 3.040(2)
2.94a
2.113(2)
2.21a
2.148(9), 2.149(8)
2.168(3)
2.18a
2.889(2)
2.199(4)
2.96a
2.28a,c,d
2.15a
2.12a,c,d
2.14a
2.12a,c
2.13a
InMes3
[Mes2InCl]2
2.163(5), 2.170(5)
2.146(9), 2.17(1)
a
b
c
d
Average. This work. Contains µ2-bridging F atoms to two Ga(In) centers. Contains µ3-bridging F atoms to three Ga(In) centers.
F igu r e 1. Molecule [{Cs(MeCN)2}{Mes3InF}]2 in [2]2‚
6MeCN. The carbon and nitrogen atoms are drawn as balls
for clarity (Cs, In, and F with 50% probability level; without
H atoms).
F igu r e 2. Molecule [Cs{(PhCH2)3GaF}]2 in [3]2‚2MeCN
(50% probability level; without H atoms).
combined effects cause closer Cs-F contacts with stron-
ger electrostatic forces. A Cs-F distance of 3.005 Å has
been reported for crystalline CsF.33
6MeCN are isostructural (Figure 1), but all three Cs-F
four-membered rings show the same rhombic distortion
[F1-Cs1-F1a, Cs1-F1-Cs1a: 86.4(1), 93.6(1)° ([1]2‚
6MeCN); 82.26(5), 97.74(5)° ([2]2‚6MeCN); 84.85(6),
95.15(7)° ([3]2‚2MeCN)].
Decreasing Cs-F distances in a group of substances
with the same ligand sphere but different group 13
metals have been observed recently.14,15 We have
observed an analogous effect for [1]2‚6MeCN and [2]2‚
6MeCN. [1]2‚6MeCN shows Cs-F contacts of 3.207(6)
and 2.880(5) Å while [2]2‚6MeCN exhibits interactions
of 2.852(2) and 3.040(2) Å. This is caused by the
synergetic effect of an increase of M-F(C) bond lengths
(M ) Ga f In) on the one hand and an increase in the
ionic character of the M-F bond on the other. These
Longer Cs-C ([1]2‚6MeCN, 3.75 Å; [2]2‚6MeCN, 3.83
Å; mean values) and Cs-N distances ([1]2‚6MeCN,
3.11(1), 3.18(1) Å; [2]2‚6MeCN, 3.139(4), 3.224(4) Å) go
along with the reduction of the Cs2F2 ring sizes. The
Cs2F2M2 cores of [1]2‚6MeCN and [2]2‚6MeCN are
almost planar (angular sum at F1, 360°), while the Ga
atoms in [3]2‚2MeCN have a distinct distance from the
Cs2F2 plane (0.88 Å; angular sum at F1, 348°; Figure
2).
The Ga-F distances depend on the number of elec-
tronegative substituents at the metal center. The
observed values of 1.903(5) ([1]2‚6MeCN) and 1.864(2)
Å ([3]2‚2MeCN) are between those of 1.80 Å in Cs-
[MesGaF3] or 1.84 Å in Cs[(PhCH2)2GaF2] and that of
1.947(2) Å in [Mes2GaF]2‚THF with µ2-bridging F- ions.
An analogous rule cannot be developed for the softer In
(32) For alkali metal-C interactions see e.g.: (a) Eaborn, C.; Izod,
K.; Smith, J . D. J . Organomet. Chem. 1995, 500, 89. (b) Bock, H.;
Hauck, T.; Na¨ther, C. Organometallics 1996, 15, 1527. (c) Mecozzi, S.;
West, A. P., J r.; Dougherty, D. A. J . Am. Chem. Soc. 1996, 118, 2307.
(d) Dougherty, D. A. Science 1996, 271, 163 and references therein.
(33) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Oxford
Science Publications: Oxford, U.K., 1990.

Cesium Triorganofluorometalates
Organometallics, Vol. 15, No. 17, 1996 3751
center. The In-F bond length in [2]2‚6MeCN of
2.113(2) Å is shorter than the 2.15 Å (average) in Cs-
[Me3InF] or the 2.168(3) Å in Cs[i-Pr3InF] but in the
same region than the 2.12 Å observed in [Mes2InF]3 with
µ2-bridging F centers.
A nonlinear arrangement of the Cs-NCMe moities
like in [1]2‚6MeCN and [2]2‚6MeCN with similar Cs-N
bond lengths has been found in [{Cs(MeCN)2}{F(i-Pr2-
InF)5}].13,34 In all cases the acetonitrile molecules
coordinated to Cs+ ions are only loosely bound. The
nonlinear CsNC sequence is probably due to packing
effects. [1]2‚6MeCN-[3]2‚2MeCN contain, in addition
to the coordinated solvent, MeCN molecules occupying
lattice sites without any metal nitrogen interactions.
Therefore, [1]2‚6MeCN-[3]2‚2MeCN lose the solvent
already in a weak flow of argon under efflorescence.
As can be concluded from the Cs-C distances, only
the atoms C2, C21, and C22 of the phenyl ring belong
to the coordination sphere of the Cs+ ion (sum of the
van der Waals radii: 4.17 Å); the corresponding Mes
ligands are rotated around the M-C2 axis (M ) Ga,
In) to enable this Cs-C contacts.
F igu r e 3. Stereoscopic view of the unit cell of [3]2‚2MeCN.
In contrast to [1]2‚6MeCN and [2]2‚6MeCN, the aryl
rings in [3]2‚2MeCN must be described as η6-bound,
although the interaction mode is likewise an ionic one.
The mean values are 3.57 (C11 f C16), 3.60 (C21 f
C26), and 3.57 Å (C31 f C36). This is about 0.20 Å
longer than in Cs[InMe4]35 but 0.10-0.15 Å shorter than
the Cs-C distances in Cs[(PhCH2)2GaF2].11 Cs[(PhCH2)2-
GaF2] consists of a polymeric chain of Cs2F2 rings
shielded by η6-bound phenyl rings. The additional
phenyl ring in [3]2‚2MeCN leads to a complete coverage
of the Cs-F four-membered ring. The coordination
geometry of the Cs center in [3]2‚2MeCN can be de-
scribed as a distorted square-pyramidal environment,
if one counts a phenyl ring as one ligand.
All mentioned salts Cs[R4-nMFn] (n ) 1-3) possess
an identical construction principle: The center of the
formed structure is reserved for the interionic Cs-F
interactions, while the periphery is occupied by the
organic ligands, protecting the center. The number of
organic ligands per group 13 metal, the steric demand
of the ligands, and the M-F(C) bond lengths decide the
long-range order, whether rings, strings, layers, or
molecules of the heterocubane type are formed (Figure
3).
F igu r e 4. Computer-generated plot of 4 (50% probability
level; without H atoms).
The increase of the coordination number (CN) 3 at
GaMes3 (Ga-C: 1.968(4) Å 17) to CN 4 at 4 leads to a
weakening of the Ga-C bonds causing longer metal-
carbon distances [Ga-C: 2.00 Å]. The average values
for [1]2‚6MeCN (2.02 Å), [2]2‚6MeCN (2.21 Å), and [3]2‚
2MeCN (2.01 Å) can be unterstood in this context. An
exception is the 1.941(8) Å observed for Cs[MesGaF3],12
which can be attributed to the cumulation of electro-
negative bonding partners.
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie.
A long Ga-N distance of 2.207(5) Å and a low
pyramidalization of the metal center, recognizable by
the sum of the C-Ga-C angles of 355°, infer a weak
donor-acceptor bond for 4 (Figure 4). An average
Ga-N distance of 2.15 Å and an angular sum of 347° is
typical for known adducts [R3Ga(NR′3)]. A common rule
concerning the bulk of the substituents, the Ga-N bond
lengths, and the rate of pyramidalization does not
appear to exist.36-42
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates, bond lengths and angles, and iso-
tropic or anisotropic displacement parameters for all atoms
in [1]2‚6MeCN-4 (26 pages). Ordering information is given
on any current masthead page.
OM960220E
(34) For Cs‚‚‚NCR contacts, see: Bock, H.; Ruppert, K. Inorg. Chem.
1992, 31, 5094.
(35) Hoffmann, K.; Weiss, E. J . Organomet. Chem. 1973, 50, 17.
(36) Atwood, D. A.; J ones, R. A.; Cowley, A. H.; Bott, S. G. Atwood,
J . L. J . Organomet. Chem. 1992, 434, 143.
(41) Bradford, A. M.; Bradley, D. C.; Hursthouse, M. B.; Motevalli,
M. Organometallics 1992, 11, 111.
(42) Byers, J . J .; Pennington, W. T.; Robinson, G. H. Acta Crystal-
logr. 1992, 48C, 2023.
(37) Atwood, D. A.; J ones, R. A.; Cowley, A. H.; Bott, S. G.; Atwood,
J . L. Polyhedron 1991, 10, 1897.
(38) Bradley, D. C.; Dawes, H. M.; Hursthouse, M. B.; Smith, L. M.;
Thornton-Pett, M. Polyhedron 1990, 9, 343.
(43) International Tables for Crystallography, 2nd ed.; Kluwer
Academic Publishers: Dordrecht, The Netherlands, 1989; Vol. A.
(44) Neumu¨ller, B.; Gahlmann, F. Angew. Chem., Int. Ed. Engl.
1993, 32, 1701.
(39) Krause, H.; Sille, K.; Hausen, H.-D.; Weidlein, J . J . Organomet.
Chem. 1982, 235, 253.
(40) Hallock, R. B.; Hunter, W. E.; Atwood, J . L.; Beachley, J r., O.
T. Organometallics 1985, 4, 547.
(45) Petrie, M. A.; Power, P. P.; Dias, H. V. R.; Ruhlandt-Senge, K.;
Waggoner, K. M.; Wehmschulte, R. J . Organometallics 1993, 12, 1086.
(46) Kra¨uter, T.; Neumu¨ller, B. Z. Anorg. Allg. Chem. 1995, 621,
597.