Supramolecular chemistry of gold(I) thiocyanate complexes with thiophene, phosphine and isocyanide ligands, and the structure of 2,6-dimethylphenyl isocyanide

Article abstract of DOI:10.1039/b100117p

The reaction of equivalent quantities of (L)AuCl (L = tetrahydrothiophene, trimethylphosphine, 2,6-xylyl isocyanide or mesityl isocyanide) and KSCN in CH₂Cl₂-water gave (L)Au(SCN) in excellent yield. The products were formed through Cl ? (SCN) anion exchange in the two-phase systems. Crystals of (THT)Au(SCN) contain short inter-ion Au···Au contacts (3.006 A) within chain polymers of alternating cations [Au(THT)₂]⁺ and anions [(NCS)₂Au]^-. The crystal structure of (Me₃P)Au(SCN) exhibits dimers based on short Au···Au contacts of 3.099 A. The dimers appear to aggregate further by long Au···S contacts giving a tetrameric motif. Molecules of (2,6-Me₂C₆H₃NC)Au(SCN) crystallise as flat, centrosymmetric dimers with long intermolecular Au···Au and Au···S contacts. Although the general aurophilic motif of (2,4,6-Me₃C₆H₂NC)Au(SCN) is similar to (2,6-Me₃C₆H₃NC)Au(SCN), its structure has two different dimers formed from similar monomers. The crystal structure of 2,6-Me₂C₆H₃NC was also characterised and (consistent with bonding theory of metal isocyanides) exhibited a C≡N bond which is slightly longer than in the gold(I) complex.

Full text of DOI:10.1039/b100117p

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Supramolecular chemistry of gold(I) thiocyanate complexes with
thiophene, phosphine and isocyanide ligands, and the structure of
2,6-dimethylphenyl isocyanide
Trevor Mathieson, Annette Schier and Hubert Schmidbaur*
Anorganisch-chemisches Institut, Technische Universität München, Lichtenbergstrasse 4,
D-85747 Garching, Germany
Received 2nd January 2001, Accepted 15th February 2001
First published as an Advance Article on the web 20th March 2001
The reaction of equivalent quantities of (L)AuCl (L = tetrahydrothiophene, trimethylphosphine, 2,6-xylyl isocyanide
or mesityl isocyanide) and KSCN in CH2Cl2–water gave (L)Au(SCN) in excellent yield. The products were formed
through Cl
(SCN) anion exchange in the two-phase systems. Crystals of (THT)Au(SCN) contain short inter-
ion Au ؒ ؒ ؒ Au contacts (3.006 Å) within chain polymers of alternating cations [Au(THT)2]ϩ and anions [(NCS)2Au]Ϫ.
The crystal structure of (Me3P)Au(SCN) exhibits dimers based on short Au ؒ ؒ ؒ Au contacts of 3.099 Å. The dimers
appear to aggregate further by long Au ؒ ؒ ؒ S contacts giving a tetrameric motif. Molecules of (2,6-Me2C6H3NC)-
Au(SCN) crystallise as flat, centrosymmetric dimers with long intermolecular Au ؒ ؒ ؒ Au and Au ؒ ؒ ؒ S contacts.
Although the general aurophilic motif of (2,4,6-Me3C6H2NC)Au(SCN) is similar to (2,6-Me3C6H3NC)Au(SCN),
its structure has two different dimers formed from similar monomers. The crystal structure of 2,6-Me2C6H3NC was
᎐
also characterised and (consistent with bonding theory of metal isocyanides) exhibited a C᎐N bond which is slightly
᎐
longer than in the gold() complex.
ϩ
anion has been structurally characterised with the AsPh4
Introduction
counter cation,6 again with no observable aurophilicity. In
contrast, intramolecular Au ؒ ؒ ؒ Au contacts have been
observed, for example in the [Au4(dpmp)2(SCN)2]2ϩ [dpmp =
bis(diphenylphosphinomethyl)phenylphosphine] cation.7
Representative neutral ligands L were chosen from the
thioether, tertiary phosphine and isocyanide groups. The
studied molecules therefore exhibited a variety of steric prop-
erties, which in turn led to the observation of distinctive
supramolecular motifs for each. The specific donor/acceptor
properties of the neutral ligands may also influence the inherent
aurophilicity.
Current research in Crystal Engineering is endeavouring to
understand the process of molecular crystallisation to the point
where structural prediction is feasible. However, the topic is
very complicated in that one must consider an intricate blend of
contributions from efficient space packing to energetically
optimised multidimensional intermolecular contacts.1
Gold() complexes of the type L–Au–X (L = neutral, X =
anionic ligand) feature linear two-coordinate gold centres and
are monomers in solution and in the gas phase. These molecules
have considerable potential as model building blocks for
supramolecular structures because of their relatively simple
molecular structure and shape. Furthermore, there is growing
structural evidence for ready association into dimers, oligomers
and polymers as a result of attractive intermolecular Au ؒ ؒ ؒ Au
interactions. This aurophilic bonding in the crystalline state is
associated with short, sub-van der Waals metal–metal distances
(generally ca. 3.00 Å) and surprisingly high bond energies
(5–15 kcal molϪ1), similar or even higher than for hydrogen
bonding.2
As the number of characterised L–Au–X structures increases,
it is hoped that clear trends will emerge regarding relationships
between molecular properties (steric and electronic) and the
observed supramolecularity. In contribution to this, we describe
herein a series of gold() thiocyanate structures that exhibit
aurophilic contacts. The thiocyanate anion is known to form a
sharp Au–S–C angle when bound to gold() centres,3 which
together with the small steric influence of the neighbouring
cyanide group leaves the gold atom exposed to an approach of
neighbouring molecules.
Isocyanide ligands (RNC) do not accept appreciable electron
density from the metal centres to which they are attached. The
RNC bonding lone pair is antibonding with respect to the C᎐N
bond, therefore co-ordination to metal centres characterist-
᎐
᎐
᎐
ically results in an increase in the infrared C᎐N stretching
᎐
frequency.8 For comparison, CO co-ordination is generally
reliant on back donation from the metal centre into orbitals
᎐
that are antibonding with respect to the C᎐O bond, hence
᎐
9
᎐
the general observation of ν(C᎐O) reduction upon ligation.
᎐
᎐
ν(C᎐N) figures have been reported for a series of (Me C H -
᎐
2
6
3
NC)AuX (X = Cl, Br, I or CN) and Me2C6H3NC.10 The “free”
ligand had the lowest stretching frequency, with the values
for the complexes being proportional to the electronegativity of
the trans anionic ligand. In this paper we report the crystal
structure of both free 2,6-Me2C6H3NC and the complex
(2,6-Me2C6H3NC)Au(SCN), which allows a direct structural
᎐
comparison of the isocyanide C᎐N bond length.
᎐
Intermolecular Au ؒ ؒ ؒ Au contacts involving coordinated
SCN anions appear to have no precedent in the literature.
(Ph3P)Au(SCN), for example, is a monomer in the crystal.3 This
could be attributed to the large size of the phosphine, although
multiple phenyl embraces4 are an alternative influence in the
Preparative results
The preparations of the complexes were carried out by reaction
of the corresponding gold chloride complex L–Au–Cl and
potassium thiocyanate in the dichloromethane–water two-
phase system at room temperature, eqn. (1). The products were
Ϫ
crystal packing of (Ph3P)AuX complexes.3,5 The Au(SCN)2
1196
J. Chem. Soc., Dalton Trans., 2001, 1196–1200
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b100117p

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Fig. 2 Tetrameric aggregates of the dinuclear units of complex 1.
Au2 ؒ ؒ ؒ S1Ј 3.771(2) Å.
Fig. 1 Molecular structure of the dimers of compound 1 (ORTEP11
drawing with 50% probability ellipsoids; H atoms omitted for clarity).
Selected bond lengths [Å] and angles [Њ] (the corresponding values of
the second molecule are given in parentheses): Au1 ؒ ؒ ؒ Au2 3.0994(5),
Au1–P1 2.263(2) [2.252(2)], Au–S1 2.334(2) [2.329(2)], S1–C1 1.673(11)
[1.669(9)] and C1–N1 1.167(14) [1.160(12)]; P1–Au1–S1 175.76(8)
[168.57(8)], Au1–S1–C1 102.7(3) [103.4(3)] and S1–C1–N1 175.6(10)
[176.8(9)].
L–Au–X ϩ KSCN → L–Au–SCN ϩ KCl
1: L = PMe3
(1)
2: L = S(CH2)4
3: L = 2,6-Me2C6H3NC
4: L = 2,4,6-Me3C6H2NC
Fig. 3 Molecular structure of the ligand 2,6-Me2C6H3NC (only one of
the two independent molecules is shown, details as in Fig. 1). Selected
bond lengths [Å] and angles [Њ] (the corresponding values of the second
molecule are given in parentheses): N1–C9 1.160(3) [1.161(2)] and
N1–C1 1.399(2) [1.401(2)]; C1–N1–C9 179.4(2) [178.9(2)].
obtained in ca. 85% yield from the dried organic phase by
precipitation with pentane. They are soluble in dichloro-
methane, chloroform and tetrahydrofuran, but insoluble in
pentane and other non-polar solvents. The products were
characterised by elemental analysis, NMR spectroscopy and
mass spectrometry (see Experimental section). The crystals of
all of the compounds are stable under ambient conditions,
except for the thiophene complex which was stored at Ϫ25 ЊC
in the dark.
two independent molecules in the unit cell which differ only
marginally in their structural details. Although not strictly
imposed by crystal symmetry, the molecules obey very closely
the requirements of point group C2v (Fig. 3). For both mole-
cules all non-hydrogen atoms are coplanar and each of the two
methyl pairs has one hydrogen atom in the molecular plane.
This conformation minimises steric repulsion between the
isocyanide and the methyl groups. The axes C1–N1–C9/C10–
N2–C18 are linear [179.4(2)/178.9(2)Њ] and the distances
C9–N1/C18–N2 of the functional groups are 1.160(3)/1.161(2)
Å. Both data suggest a description with sp hybridised atoms
C9/C18 and N1/N2 and a high bond order, close to a triple
bond. The values are similar to standard reference data.15
Crystals of 2,6-Me2C6H3NC–Au–SCN 3 are triclinic, space
Crystal and molecular structures
Crystals of Me3PAu(SCN) 1 are monoclinic, space group P21/c,
with Z = 8 formula units in the unit cell. There are two
independent monomers in the asymmetric unit which are
associated into dimers through short aurophilic contacts
[Au1 ؒ ؒ ؒ Au2 3.0994(5) Å] (Fig. 1). As shown by the dihedral
angle S1–Au1–Au2–S2 112.2Њ, the molecular axes of the two
monomers are crossed, possibly in order to minimise steric
repulsion. The molecular axes are both bent with angles
S1–Au1–P1 175.76(8) and S2–Au2–P2 168.57(8)Њ to get the
metal atoms closer together. The overall structural motif is
similar to that of the [(Me3P)AuX]2 dimers (X = SMe12 or I13).
A close inspection of the environment of the dimer 1 reveals
that there are also Au ؒ ؒ ؒ S contacts to neighbouring dimers,
which may be significant even though the distances Au2 ؒ ؒ ؒ S1Ј/
Au2Ј ؒ ؒ ؒ S1 3.771(2) Å are close to the sum of the covalent radii
of the partner atoms. In the resulting tetramer (Fig. 2) the
atoms are related by a crystallographic centre of inversion.
Other (Me3P)AuX complexes are known to form their own
isostructural set (X = Cl, Br, CN, NO3 or CF3CO2), in this case
polymeric.14
¯
group P1, with Z = 2 molecules in the unit cell. The monomers
have a seven-atom chain which is sharply bent at S1 [Au1–S1–
C1 100.9(3)Њ] and a distinct curvature for the sequence S1–Au1–
C2–N1–C3 (Fig. 4) resulting from angles S1–Au1–C2 176.0(2),
Au1–C2–N1 175.5(7) and C2–N1–C3 178.4(8)Њ. The atoms of
the seven-atom chain are all very near to the molecular plane
with maximum deviations of only 0.4 Å.
The distance N1–C2 of the isocyanide group in complex 3
is 1.119(12) Å and differs very little from that in the “free”
ligand. However, the data do indicate that there is a significant
shortening of the isocyanide bond upon co-ordination, which is
consistent with conclusions from IR vibrational studies (see
Introduction).
Crystals of the ligand 2,6-Me2C6H3NC are triclinic, space
group P1, with Z = 4 formula units in the unit cell. There are
The monomers of complex 3 are associated into centro-
symmetrical dimers mainly via intermolecular Au–S contacts.
¯
J. Chem. Soc., Dalton Trans., 2001, 1196–1200
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Fig. 4 Molecular structure of compound 3 (details as in Fig. 1).
Selected bond lengths [Å] and angles [Њ]: Au1–S1 2.282(2), Au1–C2
1.970(9), S1–C1 1.672(8), C1–N2 1.160(12), C2–N1 1.119(12) and N1–
C3 1.420(11); C3–N1–C2 178.4(8), N1–C2–Au1 175.5(7), C2–Au1–S1
176.0(2), Au1–S1–C1 100.9(3) and S1–C1–N2 175.7(8).
Fig. 6 Molecular structure of compound 4 (only one of the two
independent molecules is shown, details as in Fig. 1). Selected bond
lengths [Å] and angles [Њ] (the corresponding values of the second mole-
cule are given in parentheses): Au1–S1 2.289(2) [2.284(2)], S1–C12
1.685(7) [1.685(7)], C12–N12 1.134(9) [1.156(10)], Au1–C11 1.951(7)
[1.949(7)] and N11–C13 1.374(8) [1.395(9)]; C13–N11–C11 178.2(6)
[177.3(6)], N11–C11–Au1 176.4(6) [178.1(6)], C11–Au1–S1 174.6(2)
[176.8(2)], Au1–S1–C12 102.9(3) [101.2(3)] and S1–C12–N12 175.3(7)
[174.2(7)].
Fig.
5
Association of molecules of compound 3 into dimers.
Au1 ؒ ؒ ؒ S1Ј 3.459(2), Au1 ؒ ؒ ؒ Au1Ј 3.983(1).
Fig. 7 Aggregation of molecules of compound 4 into dimers (only one
dimer is shown, the corresponding values for the second dimer being
given in parentheses). Au1 ؒ ؒ ؒ SЈ 3.938(2) [3.719(2)], Au1 ؒ ؒ ؒ Au1Ј
3.397(1) [5.125(1)] Å.
The atoms Au1, S1, Au1Ј, S1Ј form a parallelogram with
Au ؒ ؒ ؒ SЈ edges of 3.459(2) Å and an Au ؒ ؒ ؒ AuЈ diagonal of
3.983(1) Å (Fig. 5). This general motif was also observed for
(Me3P)Au[SC(O)CCl3],16 which is a molecule with considerable
differences in steric properties. It appears that a slippage of
the two parallel L–Au–S axes in opposite directions, length-
ening the Au ؒ ؒ ؒ Au contacts, but shortening the Au ؒ ؒ ؒ S
contacts, is associated with only minor changes in energy.
The nature of the substituents may therefore induce such a
shift in either direction. The structure of 3 is one of seven
distinct motifs observed in combination with the group
(2,6-Me2C6H3NC)AuX (X = Cl, Br, I, CN, NO3 or CCPh).10,17
In contrast, (Me3P)AuX (X = Cl, Br, O2CCF3, CN or NO3)
and (ButNC)AuX (X = Cl, Br, CN or NO3) form two isostruc-
tural series based on the steric properties of the neutral
ligand.14
Fig. 8 The structure of compound 2 featuring a chain of cations
[(C4H8S)2Au]ϩ and anions [Au(SCN)2]Ϫ. This structure is a preliminary
result owing to experimental difficulties (see text). Au1 ؒ ؒ ؒ Au2 3.0054
and Au1 ؒ ؒ ؒ Au2Ј 3.0064 Å; Au2–Au1–Au2Ј 151.11 and Au1–Au2–
Au1Ј 158.98Њ.
Crystals of (2,4,6-Me3C6H2NC)Au(SCN) 4 are also triclinic,
¯
space group P1, but with four formula units in the unit cell. The
asymmetric unit contains two independent molecules (Fig. 6)
each of which is associated into centrosymmetrical dimers.
While the two independent monomers differ very little in their
structural details, their individual mode of aggregation is very
different. The Au12S12 parallelogram has an Au1 ؒ ؒ ؒ Au1Ј
distance of 3.397(1) Å as the shortest intermolecular contact,
but in the Au22S22 parallelogram the corresponding distance
Au2 ؒ ؒ ؒ Au2Ј is exceedingly long (5.125(1) Å), and contacts
Au2 ؒ ؒ ؒ S2Ј (3.719(2) Å) are the only close approach of the two
molecules (Fig. 7).
As already indicated for complex 3, the relative positioning
of the C–Au–S atom sequence of neighbouring RNC–Au–SCN
molecules appears to be very flexible. Indeed, it is intriguing
that introduction of only one methyl group in the p position
(converting the 2,6-xylyl into the 2,4,6-mesityl group on going
from 3 to 4) is sufficient to induce such changes in the molecular
packing.
In the crystals of complexes 1, 3 and 4 there are no further
intermolecular contacts other than those shown in Figs. 2, 5
and 7.
Crystals of compound 2 were of poor quality and did not
allow an unambiguous determination of the space group. The
data obtained gave a good solution in the acentric monoclinic
space group C2 which clearly revealed the constitution of the
complex (Fig. 8), but further efforts to refine the structure to a
satisfactory convergence were not successful. The preliminary
data show the complex to be an ionic isomer composed
of bis(tetrahydrothiophene)gold() cations18 and bis(thio-
cyanato)gold() anions. The [Au(SCN)2]Ϫ anion was discovered
previously, but with a distinctly different conformation (differ-
ent dihedral angle C–S–Au–S–C).6 The cations and anions
alternate to form a chain with short Au ؒ ؒ ؒ Au contacts of
1198
J. Chem. Soc., Dalton Trans., 2001, 1196–1200

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Table 1 Crystal data for compounds 1, 3 and 4 and 2,6-Me2C6H3NC
1
3
4
Ligand
Empirical formula
M
C4H9AuNPS
331.12
C10H9AuN2S
386.22
C11H11AuN2S
400.24
C9H9N
131.17
Crystal system
Space group
Monoclinic
P21/c
Triclinic
P1
Triclinic
P1
Triclinic
P1
¯
¯
¯
a/Å
b/Å
c/Å
α/Њ
9.625(1)
9.438(1)
18.677(1)
6.077(1)
8.324(1)
11.000(1)
98.626(2)
95.504(2)
97.452(4)
541.67(5)
2
8.4855(2)
11.6095(3)
14.1815(4)
102.144(1)
106.554(2)
110.128(2)
1181.65(5)
4
7.551(1)
8.888(2)
12.820(2)
83.39(2)
72.87(1)
64.87(1)
744.3(2)
4
β/Њ
103.78(1)
γ/Њ
U/Å3
1649.9(7)
8
181.9
143
Z
µ(Mo-Kα)/cmϪ1
T/K
137.3
153
125.94
133
0.69
173
Measured reflections
Unique reflections
Refined parameters
R1 [I > 2σ(I)]
wR2
7022
2647
2647
128
0.0472
0.1248
26554
6843 [Rint = 0.0474]
272
0.0445
0.1172
6437
3533 [Rint = 0.0731]
145
0.0442
0.1104
3217 [Rint = 0.0474]
254
0.0621
0.1676
3.0054 (Au1 ؒ ؒ ؒ Au2) and 3.0064 Å (Au1 ؒ ؒ ؒ Au2Ј) and Au–Au–
Au angles of 151.11Њ at Au1 and 158.98Њ at Au2.
Preparations
(THT)Au(SCN). To (THT)AuCl (110 mg, 0.34 mmol) in 5 mL
of CH2Cl2 was added KSCN (33 mg, 0.34 mmol) in 5 mL of
water. The two-phase mixture was stirred vigorously for three
hours. The CH2Cl2 phase was separated, washed with 5 mL of
water and dried over anhydrous MgSO4. The CH2Cl2 phase was
then treated with pentane affording a colourless, heat and/or
light sensitive, solid (81 mg, 70%).
Conclusion
Two-co-ordinate complexes, (L)AuSCN (L = tetrahydrothio-
phene (THT), trimethylphosphine or xylyl and mesityl iso-
cyanide), are readily prepared in high yield by anion exchange
reactions between (L)AuCl and KSCN. For each complex
a different structure is observed. The crystal structure of
(THT)Au(SCN) exhibits aurophilic contacts of 3.006 Å within
a chain polymer of alternating cations [(THT)2Au]ϩ and anions
[Au(SCN)2]Ϫ. Neutral molecules of (Me3P)Au(SCN) form
dimers based on Au ؒ ؒ ؒ Au contacts of 3.099 Å. The overall
structure appears to be tetrameric, which is possibly the result
of favourable Au ؒ ؒ ؒ S contacts during crystallisation. The
crystal structures of (2,6-Me2C6H3NC)Au(SCN) and (2,4,6-
Me3C6H2NC)Au(SCN) exhibit flat, centrosymmetric dimers,
with relatively long intermolecular contacts. The (2,4,6-
Me2C6H2NC)Au(SCN) structure is particularly noteworthy,
in that it contains two crystallographically independent
dimers.
(Me3P)Au(SCN). As for (THT)Au(SCN); from (Me3P)AuCl
(220 mg, 0.71 mmol) and KSCN (80 mg, 0.82 mmol) in 5 mL
of water affording 195 mg (83%). Found: C, 15.17; H, 2.75;
N, 4.05. Calc. for C4H9AuPNS: C, 14.50; H, 2.71; N, 4.22%.
FAB-MS: m/z 273.2, (Me3P)Auϩ. 1H NMR δ 1.5, d, 2J(HP) 11.0
Hz, CH3. 13C-{1H} NMR: δ 16.0, s, CH3. 31P-{1H} NMR:
δ Ϫ4.2, P(CH3)3.
(2,6-Me2C6H3NC)Au(SCN). As for (THT)Au(SCN); from
(2,6-Me2C6H3NC)AuCl (180 mg, 0.50 mmol) and KSCN (50
mg, 0.51 mmol) in 5 mL of water affording 173 mg (90%).
Found: C, 31.69; H, 2.12; N, 7.06. Calc. for C10H9AuN2S:
C, 31.08; H, 2.33; N, 7.25%. FAB-MS: m/z 459.6, (2,6-Me2-
C6H3NC)2Auϩ. 1H NMR: δ 2.53, s, ortho-CH3; 7.25, d, 3J(HH)
The observed structures of (2,6-Me2C6H3NC)Au(SCN) and
(2,4,6-Me2C6H2NC)Au(SCN) appear to contain only very weak
intermolecular contacts. However, the positioning of the gold
and sulfur centres is proposed to be significant, particularly
since the sterically distinct (Me3P)Au[S(O)CCCl3] molecule
adopts a similar motif.
7.5, meta-H; and 7.42, d, J(HH) 7.5 Hz, para-H. 13C-{1H}
3
NMR: δ 18.7, s, CH3; 128.0, s, ipso-C; 134.3, s, ortho-C; 128. 5,
s, meta-C; 131.9, s, para-C; and 157.1, s, C᎐N.
᎐
᎐
(2,4,6-Me2C6H2NC)Au(SCN). As for (THT)Au(SCN); from
(2,4,6-Me3C6H2NC)AuCl (200 mg, 0.53 mmol) and KSCN (55
mg, 0.57 mmol) in 5 mL of water affording 180 mg (85%).
Found: C, 33.78; H, 3.22; N, 7.01. Calc. for C11H11AuN2S:
C, 33.00; H, 2.75; N, 7.00%. FAB-MS: m/z 487.5, (Mes-
NC)2Auϩ. 1H NMR: δ 6.99, s, meta-H; 2.41, s, ortho-CH3; and
2.34, s, para-CH3. 13C-{1H} NMR: δ 121.0, t, 1J(CN) = 13.8 Hz,
ipso-C; 136.1, s, ortho-C; 129.3, s, meta-C; 142.3, s, para-C; 18.6,
s, ortho-CH3; and 21.5, s, para-CH3.
The comparison of non-ligated 2,6-Me2C6H3NC and (2,6-
Me2C6H3NC)Au(SCN) structures is consistent with the theory
᎐
of isocyanide coordination to metals, in that the C᎐N bond
᎐
length is shorter in the complex.
Experimental
The isocyanide ligands RNC (R = xylyl or mesityl) were
prepared by two-phase carbene addition.18 (THT)AuCl was
prepared by the addition of two equivalents of THT to HAuCl4ؒ
3H2O in MeOH.19 The LAuCl compounds (L = Me3P or RNC)
were prepared by reaction of L with (THT)AuCl,20 LAuSCN
compounds by anion exchange during the reaction of LAuCl
and KSCN in a two-phase CH2Cl2–water mixture.21 Single
crystals were obtained by slow diffusion of pentane into
CH2Cl2 solutions. Crystals of 2,6-Me2C6H3NC were obtained
by slow evaporation of a CH2Cl2 solution. NMR spectra (ppm)
were measured from CDCl3 solutions using a JEOL-GX
400 spectrometer; 1H 399.8, 13C-{1H} 100.5, 31P-{1H}161.8
MHz.
X-Ray crystallography
Specimens of suitable size of compounds 1, 3, 4, 5 and of 2,6-
Me2C6H3NC were mounted on the ends of quartz fibers in
F06206R oil and used for intensity data collection on Nonius
DIP2020 (3, 4, 5) and CAD4 (1 and 2,6-Me2C6H3NC) diffract-
ometers, respectively, using graphite-monochromated Mo-Kα
radiation. Data of compounds 1, 3, and 4 were corrected for
absorption effects (DELABS from PLATON).22 The structures
were solved by a combination of direct methods (SHELXS
97)23 and Fourier-difference syntheses and refined by full matrix
J. Chem. Soc., Dalton Trans., 2001, 1196–1200
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least-squares calculations on F2 (SHELXL 97).24 The thermal
motion was treated anisotropically for all non-hydrogen atoms.
All hydrogen atoms were calculated and allowed to ride on
their parent atoms with fixed isotropic contributions. The
poor quality of the crystals of compound 5 did not allow an
unambigous determination of the space group. The obtained
data set gave a good solution in the acentric space group C2
which clearly revealed the constitution of the complex, but fur-
ther efforts to refine the structure to a satisfactory convergence
were not successful. Further information on crystal data, data
collection and structure refinement is summarised in Table 1.
CCDC reference numbers 155748–155750 and 159216.
4 I. Dance and M. Scudder, J. Chem. Soc., Dalton Trans., 1998, 1341.
5 J.-C. Wang, N. I. Khan and J. P. Fackler, Acta Crystallogr., Sect. C,
1989, 45, 1008.
6 P. Schwerdtfeger, P. D. W. Boyd, A. K. Burrell, W. T. Robinson and
M. J. Taylor, Inorg. Chem., 1990, 29, 3593.
7 D. Li, C.-M. Che, S.-M. Peng, S.-T. Liu, Z.-Y. Zhou and T. C. W.
Mak, J. Chem. Soc., Dalton Trans., 1993, 189.
8 P. M. Treichel, Adv. Organomet. Chem., 1973, 11, 21; E. Singleton
and H. E. Oosthuizen, Adv. Organomet. Chem., 1983, 209.
9 S. H. Strauss, J. Chem. Soc., Dalton Trans., 2000, 1.
10 H. Ecken, M. M. Olmstead, B. C. Noll, S. Attar, B. Schlyer and
A. L. Balch, J. Chem. Soc., Dalton Trans., 1998, 3715.
11 C. K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge
National Laboratory, Oak Ridge, TN, 1976.
12 A. Sladek, K. Angermaier and H. Schmidbaur, Chem. Commun.,
1996, 1959.
13 S. Ahrland, B. Aurivillius, K. Dreisch, B. Norén and Å Oskarsson,
Acta Chem. Scand., Ser. A, 1992, 46, 262.
See http://www.rsc.org/suppdata/dt/b1/b100117p/ for crystal-
lographic data in CIF or other electronic format.
14 T. Mathieson, A. Schier and H. Schmidbaur, J. Chem. Soc., Dalton
Trans., 2000, 3881.
15 D. Britton, J. Konnert and S. Lam, Acta Crystallogr., Sect. C, 1978,
7, 445; D. Lentz and D. Preugschat, Acta Crystallogr., Sect. C, 1993,
49, 52; D. Britton, J. Crystallogr. Spectrosc. Res., 1993, 23, 689.
16 M. Preisenberger, A. Schier and H. Schmidbaur, J. Chem. Soc.,
Dalton Trans., 1999, 1645.
17 T. Mathieson, A. G. Langdon, N. B. Milestone and B. K. Nicholson,
J. Chem. Soc., Dalton Trans., 1999, 201; H. Xiao, K.-K. Cheung and
C.-M. Che, J. Chem. Soc., Dalton Trans., 1996, 3699.
18 G. W. Gokel, R. P. Widera and W. P. Weber Org. Synth., 1976, 55,
98.
19 R. Uson, A. Laguna and M. Laguna Inorg. Synth., 1989, 26, 85.
20 F. Bonati and G. Minghetti, Gazz. Chim. Ital., 1973, 103, 373.
21 W. Schneider, K. Angermaier, A. Sladek and H. Schmidbaur,
Z. Naturforsch., Teil B, 1996, 51, 790.
Acknowledgements
The authors wish to thank Deutscher Forschungsgemeinschaft,
Fonds der Chemischen Industrie and Alexander von Humboldt
Foundation (T. M.) for generous support. The donation of
chemicals by Degussa-Hüls AG and Heraeus GmbH is grate-
fully acknowledged.
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