Mesitylpseudohalogermanes Mes2Ge(CN)2 and Mes3GeX (X=CN, NCS, N3, NCO and OH; Mes=2,4,6-trimethylphenyl): Syntheses, crystal and molecular structures

Article abstract of DOI:10.1016/S0022-328X(99)00725-1

The crystal and molecular structures of the mesitylpseudohalogermanes, Mes₂Ge(CN)₂ (Mes=2,4,6-trimethylphenyl) and Mes₃GeX (X=CN, NCS, N₃, NCO, or OH), have been determined by X-ray diffraction methods; the isocyanate and hydroxide crystallise as a 1:1 hydrogen-bonded complex. All are covalent monomers free from pseudohalogen bridging, and all except the cyanides and hydroxide are N-bonded to germanium. Each Ge atom is four-coordinate in a distorted tetrahedral geometry, as evident from (mes)-Ge-(mes) angles between 112 and 120°, which are attributed to the sterically demanding mesityl groups. The greatest distortion is displayed by Mes₂Ge(CN)₂, for which the NC-Ge-CN angle of 97.8(3)° and (mes)-Ge-(mes) angle of 119.8(3)° are also consistent with the bulky mesityl groups and the small steric requirements of the cyano groups. The Ge-N-Y angles show a distinctive trend, decreasing from 173.3(5)° for the isothiocyanate (Y=CS), through 153.5(5)° for the isocyanate (Y=CO), to 119.0(7)° for the azide (Y=NN), an effect attributed to differences in electronic structure of the pseudohalo ligands. The geometries of the compounds examined here are compared with those of some other tri- and dimesityl-Group 14 metal derivatives as well as related phenylgermanium compounds.

Full text of DOI:10.1016/S0022-328X(99)00725-1

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Journal of Organometallic Chemistry 598 (2000) 276–285
Mesitylpseudohalogermanes Mes2Ge(CN)2 and Mes3GeX
(X=CN, NCS, N3, NCO and OH; Mes=2,4,6-trimethylphenyl):
syntheses, crystal and molecular structures
Goro Hihara a,1, Rosemary C. Hynes a, Anne-Marie Lebuis a,
Monique Rivie`re-Baudet b, Ivor Wharf* a,2, Mario Onyszchuk* a,3
a Department of Chemistry, McGill Uni6ersity, Montreal, Que´bec, H3A 2K6, Canada
b Laboratoire He´te´rochemie Fondamentale et Applique´e, UPRES(A) no 5069 du CNRS, Uni6ersite´ Paul Sabatier,
F-31062 Toulouse Ce´dex, France
Received 22 October 1999; received in revised form 21 November 1999
Abstract
The crystal and molecular structures of the mesitylpseudohalogermanes, Mes2Ge(CN)2 (Mes=2,4,6-trimethylphenyl) and
Mes3GeX (X=CN, NCS, N3, NCO, or OH), have been determined by X-ray diffraction methods; the isocyanate and hydroxide
crystallise as a 1:1 hydrogen-bonded complex. All are covalent monomers free from pseudohalogen bridging, and all except the
cyanides and hydroxide are N-bonded to germanium. Each Ge atom is four-coordinate in a distorted tetrahedral geometry, as
evident from (mes)ꢀGeꢀ(mes) angles between 112 and 120°, which are attributed to the sterically demanding mesityl groups. The
greatest distortion is displayed by Mes2Ge(CN)2, for which the NCꢀGeꢀCN angle of 97.8(3)° and (mes)ꢀGeꢀ(mes) angle of
119.8(3)° are also consistent with the bulky mesityl groups and the small steric requirements of the cyano groups. The GeꢀNꢀY
angles show a distinctive trend, decreasing from 173.3(5)° for the isothiocyanate (Y=CS), through 153.5(5)° for the isocyanate
(Y=CO), to 119.0(7)° for the azide (Y=NN), an effect attributed to differences in electronic structure of the pseudohalo ligands.
The geometries of the compounds examined here are compared with those of some other tri- and dimesityl-Group 14 metal
derivatives as well as related phenylgermanium compounds. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Organogermanium; Pseudohalides; Mesityl; Bulky ligand; Crystal structures; Molecular structures; Syntheses
NCO, N3) [5]. Bulky mesityl groups on Ge shield the
germanium atom from attack and thus tend to stabilise
small molecules that otherwise are thought to be un-
stable or exist only as transient species [6–8]. Of equal
interest are the effects of bulky mesityl groups on
molecular conformations as exemplified by the struc-
tures of Mes3SiH and Mes3GeH [9]. Moreover when
the unhindered phenyl analogs of mesityl compounds
also exist, the steric crowding of the o-CH3 groups of
the mesityls attached to the central metal atom can
cause significant changes in geometry, as was found
when comparing the structures of Mes3SnI and Ph3SnI
[10]. Here we report the structures of Mes3GeX (X=
CN, NCS, N3, NCO, OH), and Mes2Ge(CN)2 and
compare them with those of related organo-silicon and
-germanium compounds.
1. Introduction
In contrast to the wealth of information on
organogermanium halides, rather less is known about
the corresponding pseudohalides [1–3]. More recently
our interest in organogermanium pseudohalides was
piqued through a study of the reactions of Mes3GeNH2
(Mes=2,4,6-(CH3)3C6H2) [4], following which we re-
ported the synthesis of several Mes3GeX (X=NCS,
1 Permanent address: Department of Chemistry, Josai University,
Saitama, Japan.
2 *Corresponding author. Tel.: +1-514-398-6233; fax: +1-514-
398-3797; wharf@chemistry.mcgill.ca
3 *Corresponding author. Tel.: +1-514-398-6233; fax: +1-514-
398-3797.
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00725-1

G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
277
2. Results and discussion
Platon [11] plots (without H-atoms) giving the number-
ing schemes are shown in Figs. 1–5 for Mes3GeCN (A),
Mes3GeNCS (B), Mes3GeN3 (C), Mes3GeNCO·
Mes3GeOH (D) and Mes2Ge(CN)2 (E), respectively (see
Section 5).
2.1. Syntheses
Although silver thiocyanate easily converts
Mes3GeCl to Mes3GeNCS in high yield [4], we found
that AgCN would not react with Mes3GeCl or
Mes2GeCl2 under a variety of conditions. Instead, ex-
change reactions between Mes3SiCN and Mes3GeCl or
Mes2GeCl2 were required to obtain the corresponding
mesitylgermyl cyanides in good yield. The other trime-
sitylgermyl pseudohalides, i.e. the azide, isocyanate and
isothiocyanate, were obtained earlier [5] by the reaction
of Mes3GeCl with NaN3, KOCN, and KSCN, respec-
tively, in a mixture of 18-crown-6-ether and n-hexane at
60°. Recrystallising Mes3GeCN from THF gave X-ray-
quality crystals of the solvate Mes3GeCN·(1/2)THF but
the isocyanate was only obtained as single-crystals from
diethyl ether as the 1:1 hydrogen-bonded adduct,
Mes3GeNCO·Mes3GeOH in spite of using ‘dried’
ether.
2.2.1. Mes3GeX (X=CN, NCS, N3) and
Mes3GeNCO·Mes3GeOH
The pseudohalides A–C are clearly monomeric and
there is no evidence of intermolecular interactions as
the shortest non-bonding contacts are all greater than
the sum of the relevant van der Waals radii. Moreover
the central Ge atom in each compound is four-coordi-
nate but with a configuration seriously distorted from
tetrahedral geometry. It is unlikely that crystal packing
requirements are the main cause of the distortions in
molecular geometry that are detailed below. The
(mes)ꢀGeꢀ(mes) bond angles lie in the range of
112.4(4)–118.7(4)° all significantly greater than the te-
trahedral angle, while as expected the relevant
(mes)ꢀGeꢀX angles are correspondingly less than tetra-
hedral, in the range 100.2(2)–104.4(4)°, perhaps aided
by the low steric requirements of the NꢀGe bond in
these compounds. Similar distortions occur in
Mes3GeNH2 [4] with (mes)ꢀGeꢀ(mes) angles of
116.6(1), 113.0(1) and 112.0(1)°, and even more so for
2.2. Single-crystal X-ray diffraction studies
Crystal data are listed in Table 1 while selected
structural parameters are summarised in Table 2; the
Table 1
Crystal data and structure solution details
Compound
Mes3GeCN·(1/2)THF
(A)
Mes3GeNCS
(B)
Mes3GeN3
(C)
Mes3GeNCO·Mes3GeOH
(D)
Mes2Ge(CN)2
(E)
Formula
C30H37N1O0.5Ge
492.22
Monoclinic
C2/c
C28H33NSGe
488.22
Monoclinic
P21/c
C27H33N3Ge
472.17
Monoclinic
P21/n
C55H67NO2Ge2
919.32
Triclinic
C20H22N2Ge
362.99
Orthorhombic
Pcan
4 (1/2)
0.33×0.25×0.10
9.523(2)
11.037(2)
17.250(3)
90
Formula weight
Crystal system
Space group
Z (Z%)
(
P1
8 (1)
4 (1)
4 (1)
2 (1)
Crystal size (mm)
0.33×0.33×0.08
40.384(15)
8.643(5)
16.442(7)
90
108.99(3)
90
5427(4)
1.13
0.33×0.30×0.30
8.3034(20)
22.847(5)
13.7258(23)
90
99.962(16)
90
2564.6(9)
1.27
0.40×0.25×0.10
13.729(3)
11.6125(14)
15.714(3)
90
94.856(16)
90
2496.3(8)
1.23
0.40×0.15×0.13
8.2410(7)
16.374(2)
18.872(2)
97.668(10)
97.233(8)
100.352(9)
2453.0(5)
1.78
,
a (A)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
90
90
1813.0(6)
1.67
3
,
V (A )
v (mm−1
)
Reflections measured
Unique reflections
Rint
3619
3556
0.044
3615
3341
0.011
3016
2859
0.028
15712
7304
0.052
1347
1186
0.026
Significant reflections
|
1796
2.5
2488
2.5
1644
2.5
5745
2.0
734
2.5
Parameters used
a Rf
287
0.060
0.059
290
0.047
0.050
281
0.055
0.053
542
0.055
0.051
105
0.037
0.040
b Rw
Transmission range
Goodness-of-fit
0.7111 to 0.7535
2.11
0.5277 to 0.6458
2.29
0.5992 to 0.7523
1.79
1.82
1.79
a Rf=ꢀ[ꢁFoꢁ−ꢁFcꢁ]/ꢀ[ꢁFoꢁ].
b Rw={ꢀw[Fo−Fc]2/ꢀwF2o}1/2; w=[|2(F)+KF2]−1
.

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G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
Table 2
Selected structural parameters (e.s.d.) for Mes3GeX (X=CN, NCS, N3, NCO, and OH) and Mes2Ge(CN)2
,
Bond distances (A)
GeꢀX
GeꢀMes
Pseudohalide
1.962(9); 1.979(8); 1.942(9) CN, 1.149(15)
(A) Mes3GeCN
(B) Mes3GeNCS
(C) Mes3GeN3
1.975(11)
1.888(4)
1.895(9)
1.957(5); 1.976(5); 1.961(5) NC, 1.138(7); CS, 1.634(7)
1.942(11); 1.913(10);
1.988(10)
1.960(5); 1.962(5); 1.962(5) NC, 1.125(11); CO,
1.356(12)
1.973(5); 1.970(5); 1.974(5)
N1N2, 1.210(15); N2N3,
1.171(16)
(Da) a Mes3GeNCO 1.812(4)
(Db) a Mes3GeOH
(E) Mes2Ge(CN)2
1.805(3)
1.944(6)
1.956(6)
CN, 1.121(10)
Bond angles (°)
(A) Mes3GeCN
(B) Mes3GeNCS
(mes)ꢀGeꢀ(mes)
116.3(4); 115.7(4); 115.5(4)
115.4(2); 116.7(2); 117.1(2)
XꢀGeꢀ(mes)
Geꢀ(NꢀY)
103.0(4); 102.5(4); 100.4(4) 176.4(10) b
101.79(21); 100.22(20);
173.3(5) [Y=CS]
101.18(21)
(C) Mes3GeN3
118.7(4); 115.7(4); 112.4(4)
104.4(4); 101.4(4); 100.9(4) 119.0(7) [Y=NN]
(Da) a Mes3GeNCO 115.53(19); 115.17(19); 114.31(19) 101.8(2); 104.6(2); 103.1(2) 153.5(5) [Y=CO]
(Db) a Mes3GeOH
115.84(19); 113.44(19); 114.7(2)
105.12(18);
103.71(18);101.90(18)
103.7(3); 115.0(3)
(E) Mes2Ge(CN)2
119.8(3); [97.8(3)] c
173.9(6) b
a As the Mes3GeNCO·Mes3GeOH hydrogen-bonded adduct.
b Angle Geꢀ(CꢁN).
c Angle (NC)ꢀGeꢀ(CN).
Mes3GeNHCOtBu [12] with (mes)ꢀGeꢀ(mes) angles of
106.3(4), 117.0(4) and 117.8(4)°, while the same angles
in Mes3GeNꢂCꢂNGeMes3 are 115.0(1), 114.7(1) and
113.3(1)° for Ge(1) and 115.0(1), 114.7(1) and 113.3(1)°
for Ge(2) [13].
hydrogen bonds in Ph3GeOH [16], average d(O···O)=
,
2.63(1) A, are even stronger, showing that the O-atom
of GeꢀOH is a stronger H-bond acceptor than the end
oxygen of a terminal isocyanate group.
In A–C, Geꢀ(mes) bond distances vary from
The structure of C with d(N1N2) apparently greater
than d(N2N3) and 119.0(7)° for the GeꢀN1ꢀN2 angle, is
more like that of an organic azide [17–19] when com-
pared with that of its silicon analog [20]. The bonding
of covalent azides, R3MꢀN3, may be discussed in terms
of two canonical forms (Ia) and (Ib), with the contribu-
tion of each
,
1.913(10) to 1.988(10) A, similar to those in
Mes3GeNH2 [4], Mes3GeNHCOtBu [12] and
Mes3GeNꢂCꢂNGeMes3 [13], while B and C have GeꢀN
distances close to that found in Mes3GeNHCOtBu
,
(1.899(6) A). Angles formed by the linear pseudohalide
groups with Ge (designated as GeꢀCꢀN or GeꢀNꢀY in
Table 2) are about 180° for A and B but in Mes3GeN3
the angle is 119.0(7)°. The more encumbered azide,
GeN3[N(SiMe3)2][N(Mes)(SiMe3)]2, has a GeꢀNꢀN an-
gle of 125.5(4)° [14], but interestingly its GeꢀN(1),
N(1)ꢀN(2), and N(2)ꢀN(3) bond distances are similar to
those in Mes3GeN3. Trimesitylgermanium isocyanate
(Da) and hydroxide (Db) are found as a 1:1 hydrogen
bonded complex D (Fig. 4). Both Da and Db have bond
lengths and angles similar to those of the other pseudo-
halides (Table 2) but the most distinctive feature is the
unexpected hydrogen bonding between the two
form dependent on the R3M moiety. For Mes3SiN3
with d(N1N2) apparently less than d(N2N3) and with
angle SiꢀN1ꢀN2 of 125.8(2)°, form Ia appears to con-
tribute more than in the case of C or organic azides
[20]. This is clearly one more example of the tendency
of germanium to resemble carbon more than silicon
[21]. The noted increase of the Geꢀ(NꢀY) angle in
Mes3GeX as (NꢀY)ꢂNꢀNN is replaced by NꢀCO and
then NꢀCS or CꢁN, suggests that the following canoni-
cal forms determine the bond angles:
,
molecules. The oxygen to oxygen H-bond of 3.036(7) A
,
appears longer than the value (2.89(8) A) found in the
ostensibly analogous tin system, Me3SnNCO·Me3-
SnOH, also formed by adventitious hydrolysis of the
isocyanate [15]. However, in this adduct, chains of
Me3Sn groups are formed using alternating 1,1-iso-
cyanate and hydroxide bridges, which are then con-
nected by ꢀNCO···HꢀOꢀ hydrogen bonds. In D the
weaker H-bond is between terminal isocyanate and
hydroxide groups. In comparison, the

G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
279
Fig. 1. Platon view of the molecule of A showing the numbering scheme adopted. Ellipsoids are drawn at 40% probability level.
with II for Da intermediate between Ia–b for C and III
for B which is equivalent to the expected structure of A.
The similar GeꢀNCO angles for Da and Ph3GeNCO
[150.7(9)°] [22], and B and Ph3SiNCS (178.8(3)°) [23],
would suggest that electronic effects of this type are the
structure determinants rather than the steric effects of
the distal o-CH3 groups, which do not extend beyond
the a-pseudohalide atom bound to M. When consider-
ing a given Ar3MX pair (Ar=Ph or Mes) it was
predicted earlier [24] that with M=C and X=H, the
steric strain caused by replacing ortho-H atoms
by methyl groups would result in larger values for
d(MꢀC) and ArꢀMꢀAr angles. The effects of repulsions
between ortho-methyls on adjacent mesityl groups in
Mes3MX systems may also be monitored by the dihe-
dral angles defined by the plane of one ring and the
CiꢀMꢀCi* plane involving another ring*, and shown
below as h and i in Newman projections P, Q and R
[9].
Ideally Ar3MX systems are considered to have trigonal
symmetry, with the two most symmetric arrangements
having each ring plane perpendicular to the CiꢀMꢀX
plane P or rotated through 90° as seen in R. Both
geometries give rise to extreme steric strain, which must
be relieved by the rotation (ƒ) of each ring within the
range 0–90°, giving the intermediate geometry seen in
Q. In this case ƒ=(h+30o) or (i−30°). In fact, very
few Ar3MX systems have exact trigonal symmetry, so
averaged values of the structural parameters listed
above are given in Table 3 for the Mes3GeX systems
A–Db as well as for several other Mes3MX (M=Si,
Ge) 1–5 [9]. Indeed all Mes3MX deviate so much from

280
G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
Fig. 2. Platon view of the molecule of B showing the numbering scheme adopted. Ellipsoids are drawn at 40% probability level.
trigonal symmetry that h and i provide two different
numbers for the rotation (ƒ). Thus the average value,
ƒ=0.5[(h+30°)+(i−30°)] is listed instead.
with Ph3GeOH [1.791(8); 107.1(4)] [16] and
Mes3GeNCO [1.812(4); 103.2(2)] with Ph3GeNCO
[1.83(2); 105.7(6)] [22], although for the second pair
(X=NCO) only the angle change is significant at the
error level of the triphenyl structure.
The wide ranges of average d(GeꢀC) and ArꢀGeꢀAr
,
angles found for A–Db and 2 [1.95–1.98 A and 113.9–
116.4°] are effectively the same as those found for
All compounds in Table 3 have very similar mean
rotations (ƒ) ranging from 41.6 to 45.0°, the exceptions
being 5 and 6. For structures A–Db and 1 and 2 the
average dihedral angles (h) and (i) are all within
narrow ranges, (21.0–22.7°) and (62.7–68.5°), respec-
tively while the average deviations from trigonal sym-
metry given by [h−(ƒ−30°)] and [i−(ƒ+30°)] are
also very similar. Thus to relieve the interactions due to
the ortho-methyls, the mesityl groups rotate and the
molecules distort from trigonal symmetry, on average,
by nearly the same amount regardless of the metal M
or group X. Compound 3 is similar with less distortion,
but 4 and 5 do not fit this picture at all. Thus while (ƒ)
values are in the same range as before, the distortion
from trigonal symmetry is the reverse of that noted
,
Ph3GeX (X=Br [26], NCO [22], OH [16]), 1.93–1.95 A
and 118.6–112.6°. However, the comparison of average
,
values of d(SiꢀC) and ArꢀSiꢀAr angles for 1 (1.89 A,
,
114.0°) and 3 (1.91 A, 112.9°) with data for Ph3SiNCS
,
,
[23] (1.85 A, 112.4°) and Ph3SiOH [27] (1.86 A, 110.5°)
shows the trends predicted by Mislow, the changes in
angles being particularly significant. Together with
these changes should also be observed a concomitant
lengthening of the MꢀX bond and a significant lessen-
ing of the ArꢀMꢀX angle and these trends were ob-
served when comparing Mes3SnI with Ph3SnI [10]. The
,
same trends in d(GeꢀX) (A) and average ArꢀGeꢀX
angles (°) are also seen for the systems studied here.
Thus we may compare Mes3GeOH [1.805(3); 103.6(2)]

G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
281
Fig. 3. Platon view of the molecule of C showing the numbering scheme adopted. Ellipsoids are drawn at 40% probability level.
above. Furthermore the steric strain appears to be
accommodated by a drastic increase in d(MꢀC) rather
than any change in ArMAr angles. This is in contrast
to the structure of Mes3CH (6) [25], which is consistent
with those of the other Mes3MX in Table 3.
(Mes2GeNCN)4, 112.5(3)° [31], as well as the three-
membered ring compound
where the (mes)ꢀGeꢀ(mes) angles of 110.6(3) and
109.4(1)° are almost tetrahedral [32]. The cyano groups
in Mes2Ge(CN)2 subtend an angle of 97.8(3)° at Ge,
which may be the result of crowding by the sterically
demanding mesityl groups against the less bulky cyano
groups. However, electronic effects should not be dis-
counted since almost the same angles (MeꢀGeꢀMe,
120.9(8)°; NCꢀGeꢀCN, 100.9(7)°) are found in
Me2Ge(CN)2 [33]. In this case, the distortion from
tetrahedral geometry was ascribed to the relative elec-
tronegativities of the CH3ꢀ and NCꢀ groups as well as
2.2.2. Mes2Ge(CN)2
Like the preceding pseudohalides, Mes2Ge(CN)2 is
four-coordinate in a highly (Fig. 5) distorted geometry
but the molecule is symmetric since the Ge atom lies on
a crystallographic twofold axis. The mesityl groups
subtend an angle at Ge of 119.8(3)°, which is signifi-
cantly larger than that found in other compounds
having the Mes2Ge unit, e.g. Mes2GeꢂPar%, 112.9(4)°
[28],
,
a weak intermolecular CN···Ge interaction (3.28(2) A)
causing an increase from 4- to 5-coordination for
109.6(5)° [29], Mes2Ge(H)R*, 113.4(2) [30], and the
cyclic oligomers (Mes2GeNCN)3, 115.9(2)° and
Me2Ge(CN)2. For E, the same intermolecular contact
,
(5.397(7) A) is too long to suggest bridging by cyano

/
598
(
276
285
Fig. 4. Platon view of the hydrogen-bonded dinuclear molecule of D showing the numbering scheme adopted. Ellipsoids are drawn at 40% probability level.

G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
283
either Bruker AC 80 or AC 200 instruments. Infared
spectra were measured on a Perkin–Elmer 451, while
mass spectra were obtained with a Nermag R10-10H
instrument. Elemental analyses were done by the Ana-
lytical Services Laboratory of Josai University (Japan).
Literature procedures were used to prepare
Mes3GeCl [34], Mes2GeCl2 [35], as well as colourless
crystals of Mes3GeNCS (B) [5], and Mes3GeN3 (C)
[5,36]. Since Mes3GeCN and Mes3GeNCO were ob-
tained by new methods and Mes2Ge(CN)2 is a new
compound, the preparation and characterization of
these three is described in detail below.
3.1.1. Preparation of Mes3GeCN (A)
Cyanotrimethylsilane (1.31 g; 13.1 mmol) was added
slowly to a stirred solution of Mes3GeCl (0.968 g; 2.08
mmol) in THF (100 ml) and the mixture was refluxed at
60°C for 48 h, then cooled to 0°C and solid product
filtered; yield, 64%; m.p. 215–216°C. Anal. Calc. for
C28H33NGe: C, 73.73; H, 7.29; N, 3.00; Found: C,
73.93; H, 7.53; N, 2.91%. IR [w(CN)]: 2225 cm−1
.
1H-NMR (CDCl3, 80 MHz): 2.23 (s, 18H, o-Me); 2.27
(s, 6H, p-Me); 6.85 (s, 6H, CHar). 13C-NMR (CDCl3,
50.3 MHz): 24.18 (o-Me); 21.09 (p-Me); 131.58 (C1);
139.89 (C2); 129.84 (C3); 143.58 (C4); 128.48 (CꢁN).
MS (DCi–CH4: m/z,%): 456 [M+−1, 19]; 338 [M+−
mes, 50]; 431 [M+−CN, 100]. Colourless single crys-
tals of the hemi-solvate resulted from the filtrate kept at
ambient temperature in a Petri dish.
Fig. 5. Platon view of the molecule of E showing the numbering
scheme adopted. Ellipsoids are drawn at 40% probability level.
3.1.2. Preparation of Mes3GeNCO (Da)
Silver cyanate (0.500 g; 1.07 mmol) was added slowly
to a stirred solution of Mes3GeCl (0.161 g; 1.07 mmol)
in THF (8 ml). Since the reaction was incomplete after
16 h, an excess of AgNCO was added. The mixture was
agitated for another 20 h after which the liquid phase
was cannulated and the THF evaporated, leaving white
crystals of Mes3GeNCO; yield 83%; m.p. 161–164°C.
groups. A similar comparison of averaged angles can be
made
between
A
[MesꢀGeꢀMes,
115.9(4)°;
NCꢀGeꢀCN, 102.0(4)°] and Me3Ge(CN) [34] with
MeꢀGeꢀMe=116(2)° and NCꢀGeꢀCN=103(2)°. In
the latter compound there is
a relatively short
,
intermolecular CN···Ge interaction (3.57 A) which
suggests an incipient interaction might be there, but in
.
IR [was(NCO)]: 2268 cm−1 1H-NMR (CDCl3, 80
MHz): 2.27 (s, 18H, o-Me); 2.21 (s, 6H, p-Me); 6.83 (s,
6H, CHar); in C6D6: 2.30 (s, 18H, o-Me); 2.05 (s, 6H,
p-Me); 6.68 (s, 6H, CHar). 13C-NMR (CDCl3, 50.3
MHz): 23.78 (o-Me); 21.07 (p-Me); 134.96 (C1); 148.19
(C2); 129.77 (C3); 139.58 (C4); 124.30 (NCO). MS (EI:
m/z,%) 472 [M++1]; 431 [M+−NCO]; 353 [M+−
Mes]. Recrystallising the sample from diethyl ether gave
twinned crystals. A second recrystallisation produced
colourless single crystals suitable for X-ray diffraction
measurements, which revealed the crystals to be the 1:1
H-bonded adduct, Mes3GeNCO·Mes3GeOH (D), pre-
sumably due to traces of water remaining in the dried
diethyl ether.
,
A the same datum is 5.53(3) A, again too long to
suggest bridging by the cyano group.
3. Experimental
3.1. Syntheses
All manipulations were done under nitrogen using
standard Schlenk techniques. Solvents were degassed,
dried with Na–K alloy and distilled, stored over molec-
ular sieves, and distilled again immediately before use.
Proton and 13C-NMR data (l ppm) were obtained on

284
G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
Table 3
Summary of averaged structural parameters for various Mes3MX
(h) a (°)
(i) a (°)
(ƒ) a (°)
,
M
X
d(MꢀCi) (A)
BArMAr (°)
A
B
C
Ge
Ge
Ge
Ge
Ge
Si
Ge
Si
Ge
Si
CN
NCS
N3
NCO
OH
N3
NH2
CH2R c
H
1.961
1.965
1.948
1.961
1.972
1.889
1.978
1.909
2.047
2.02
115.8
116.4
115.6
115.0
114.6
114.0
113.9
112.9
109.0
105
21.0
22.7
22.7
22.3
21.3
21.8
19.1
14.2
3.0
62.7
62.7
64.7
65.3
68.0
68.1
68.5
69.0
81.8
87
41.8
42.7
43.7
43.8
44.6
45.0
43.8
41.6
42.4
48
Da
Db
1b
2b
3b
4b
5b
6d
H
H
9
22.3
C
1.539
115.9
82.3
52.3
a See text.
b Ref. [9].
c ꢀR=ꢀCHꢂCH2.
d Ref. [26].
4. Conclusions
3.1.3. Preparation of Mes2Ge(CN)2 (E)
To Mes2GeCl2 (1.185 g; 3.10 mmol) dissolved in
THF (10 ml) was added (CH3)3SiCN 7(1.699 g; 17.1
mmol) and the mixture was refluxed for 24 h before it
was cooled to 0°C and the precipitate filtered; yield,
100%. Colourless crystals for analysis were obtained
from toluene; m.p. 239°C. Anal. Calc. for C20H22N2Ge:
C, 66.18; H, 6.11; N, 7.72; Found: C, 65.92; H, 6.20; N,
Single-crystal X-ray diffraction measurements show
that Mes3GeX (X=CN, NCS, N3, NCO and OH) and
Mes2Ge(CN)2 are molecular, free from pseudohalo-
bridging, and with Ge atoms four-coordinate in a dis-
torted tetrahedral geometry. Distortions are assigned to
steric hindrance by the bulky mesityl groups. Angles
formed by the linear pseudohalides with Ge decrease
from about 180 to 120° in the order ꢀNCS\ꢀNCO\
ꢀN3, an effect attributed to differences in electronic
structures of the pseudohalides. The H-bonded adduct
1
7.62%. IR [w(CN]): 2186 cm−1. H-NMR (CDCl3, 80
MHz): 2.30 (s, 6H, p-Me); 2.48 (s, 12H, o-Me); 6.94 (s,
4H, CHar). 13C-NMR (CDCl3, 50.3 MHz): 23.75 (o-
Me); 21.14 (p-Me); 123.66 (C1); 143.30 (C2); 130.35
(C3); 142.37 (C4); 122.00 (CꢁN). MS (DCi,CH4: m/z,%)
365 (M++1, 20); 393 (M++29, 5); 405 (M++41, 2);
338 (M+ −CN, 100).
Mes3GeNCO·Mes3GeOH
was
obtained
when
Mes3GeNCO was recrystallized from diethyl ether that
was not sufficiently dry. In each unit of the adduct,
(mes)ꢀGeꢀ(mes) bond angles and Geꢀ(mes) bond dis-
tances are similar to those of the other pseudohalides,
confirming that the H-bonded components retain their
molecularity in the adduct.
3.2. X-ray structure analysis
X-ray crystallographic measurements were made on a
Rigaku AFC6S diffractometer using the ꢀꢀ2q scan
mode at 2191°C; D was measured using Cu–Ka radi-
,
ation (u=1.54056 A), all others used Mo–Ka radiation
,
(u=0.70930 A). Structures were solved by direct meth-
5. Supplementary material
ods; hydrogens were included in calculated positions
while all non-hydrogen atoms were refined anisotropi-
cally. Computations were done with NRCVAX [37]; ab-
sorption corrections were done using „-scans. The
sulfur atom of the NCS unit in B is disordered in two
positions at 50% occupancy each. Compound A has
four THF molecules per unit cell, each disordered
about the twofold axis; each THF molecule exhibits
multiple orientations, presumably due to tumbling of
the solvent molecule in the cell cavity, thus the disorder
was not modelled further.
Crystallographic material has been deposited with
the Cambridge Crystallographic Data Centre, Cam-
bridge CB2 1EZ, UK; CCDC no. 136047, E; 136048, A;
136049, B; 136050, C; and 136051, D. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.
cam.ac.uk).

G. Hihara et al. / Journal of Organometallic Chemistry 598 (2000) 276–285
285
[13] M. Dahrouch, M. Rivie`re-Baudet, H. Gornitzka, G. Bertrand, J.
Organomet. Chem. 562 (1998) 191.
Acknowledgements
[14] J. Pfeiffer, W. Maringgele, M. Notlemeyer, A. Meller, Chem.
Ber. 122 (1989) 245.
[15] J.B. Hall, D. Britton, Acta Crystallogr. Sect. B 28 (1972) 2133.
[16] G. Ferguson, J.F. Gallagher, D. Murphy, T.R. Spalding, C.
Glidewell, H.D. Holden, Acta Crystallogr. Sect. C 48 (1992)
1228.
[17] A. Treinin, in: S. Patai (Ed.), The Chemistry of the Azide
Group, Wiley–Interscience, New York, 1972, pp. 1–52.
[18] E.F.V. Scriven, Azides and Nitrenes: Reactivity and Utility,
Academic Press, New York, 1984.
[19] M. Kaftory, in: S. Patai, Z. Rappoport (Eds.), The Chemistry of
Halides, Pseudohalides, and Azides, Wiley, New York, 1983, pp.
1254–1258.
The financial support of the Ministe`re de l’Education
du Que´bec (Fonds FCAR) and of the CNRS (France)
is gratefully acknowledged, as is a major equipment
grant in 1989 from the Natural Sciences and Engineer-
ing Research Council of Canada for the purchase of
X-ray equipment. G.H. is especially grateful to Josai
University (Japan) for sabbatical leave at McGill Uni-
versity, and M.O. thanks McGill University (Montreal)
for sabbatical leave at Universite´ Paul Sabatier
(Toulouse).
[20] S.S. Zigler, K.J. Haller, R. West, M.S. Gordon, Organometallics
8 (1989) 1656.
References
[21] J.E. Huheey, E.A. Keiter, R.L. Keiter, Inorganic Chemistry, 4th
edition, Harper Collins, New York, 1993, p. 877. A.L. Allred,
E.G. Rochow, J. Inorg. Nucl. Chem. 5 (1958) 269.
[22] T.N. Tarkhova, L.E. Nikolaeva, E.V. Chuprinov, M.A. Si-
monov, N.V. Belov, Sov.-Phys. Crystallogr. 21 (1976) 216.
[23] G.M. Sheldrick, R. Taylor, J. Organomet. Chem. 87 (1975)
145.
[1] M. Lesbre, P. Mazerolles, J. Satge´, The Organic Compounds of
Germanium, Wiley, London, 1971, Chapters 5 and 8.
[2] J.J. Zuckerman, in: A.G. MacDiarmid (Ed.), Organometallic
Compounds of the Group IV elements, Vol. 2, Part II, Marcel
Dekker, New York, 1972, Chapter 2.
[3] B.J. Aylett, Organometallic Compounds, 4th edition, Vol. 1,
Part 2, Chapman and Hall, London, 1979, Chapter 3.
[4] M. Rivie`re-Baudet, A. More`re, J.F. Britten, M. Onyszchuk, J.
Organomet. Chem. 423 (1992) C5. M. Rivie`re-Baudet, A. Mor-
e`re, M. Onyszchuk, J. Satge´, Phosphorus, Sulfur and Silicon 70
(1992) 75.
[5] G. Hihara, M. Nakamura, H. Kobayashi, H. Miyamae, I.
Wharf, M. Onyszchuk, P. Rivie`re, M. Rivie`re, Chromatography
16 (1995) 31.
[6] J. Barrau, J. Escudie´, J. Satge´, Chem. Rev. 90 (1990) 283.
[7] J. Escudie´, C. Couret, H. Ranaivonjatovo, J. Satge´, J. Coord.
Chem. 130 (1994) 427.
[8] P. Rivie`re, M. Rivie`re-Baudet, J. Satge´, in: E.W. Abel, F.G.A.
Stone, G. Wilkinson, A.G. Davies (Eds.), Comprehensive
Organometallic Chemistry, 2nd edition, Vol. 2, Pergamon, Ox-
ford, 1995, chaper 5.
[9] J.B. Lambert, C.L. Stern, Y. Zhao, W.C. Tse, C.E. Shawl, K.T.
Lentz, L. Kania, J. Organomet. Chem. 568 (1998) 21.
[10] M.G. Simard, I. Wharf, Acta Crystallogr. Sect. C 50 (1994) 397.
[11] A.L. Spek, Platon — A multipurpose crystallographic tool, Acta
Crystallogr. Sect. A 50 (1990) C-34; Version 190499.
[12] A. More`re, M. Rivie`re-Baudet, J.F. Britten, M. Onyszchuk,
Main Group Met. Chem. 15 (1992) 141.
[24] J.D. Andose, K. Mislow, J. Am. Chem. Soc. 96 (1974) 2168.
[25] J.F. Blunt, K. Mislow, Tetrahedron Lett. (1974) 909.
[26] H. Preut, F. Huber, Acta Crystallogr. Sect. B 35 (1979) 83.
[27] H. Puff, K. Braun, H. Reuter, J. Organomet. Chem. 409 (1991)
119.
[28] M. Dra¨ger, J. Escudie´, C. Couret, H. Ranaivonjatovo, J. Satge´,
Organometallics 7 (1988) 1010.
[29] M. Lazraq, C. Couret, J.P. Declercq, A. Dubourg, J. Escudie´,
M. Rivie`re-Baudet, Organometallics 9 (1990) 845.
[30] M. Lazraq, J. Escudie´., C. Couret, J. Satge´, M. Drager, R.
Dammel, Angew Chem. Int. Ed. Engl. 27 (1988) 828.
[31] M. Dahrouch, M. Rivie`re, J. Satge´, M. Mauzac, C.J. Cardin,
J.H. Thorpe, Organometallics 17 (1998) 623.
[32] T. Tsumuraya, S. Sato, W. Ando, Organometallics 7 (1988)
2015.
[33] J. Konnert, D. Britton, Y.M. Chow, Acta Crystallogr. Sect. B 28
(1972) 180.
[34] O. Schlemper, D. Britton, Inorg. Chem. 5 (1966) 511.
[35] P. Rivie`re, M. Rivie`re-Baudet, Organomet. Syn. 4 (1988) 542.
[36] T. Tsumaraya, W. Ando, Chem. Lett. (1989) 1043.
[37] E.J. Gabe, Y. Le Page, J.P. Charland, F.C. Lee, P.S. White, J.
Appl. Crystallogr. 22 (1989) 384.
.