A family of scandium and yttrium tris((trimethylsilyl)methyl) complexes with neutral N3 donor ligands

Article abstract of DOI:10.1021/om050209r

The synthesis and reactivity scandium and yttrium tris((trimethylsilyl)methyl) complexes family with neutral N₃ donor ligands were studied. The effective synthetic routes to the first group 3 organometallic and coordination compounds containing the tris(pyrazolyl) methane and triazacyclohexane ligands were described. All manipulations were carried out under standard Schlenk line or drybox techniques under an atmosphere of argon or of dinitrogen. The stoitiometric and catalytic chemistry of cationic alkyl and related complexes derived from the new classes of compounds were also studied.

Full text of DOI:10.1021/om050209r

3136
Organometallics 2005, 24, 3136-3148
A Family of Scandium and Yttrium
Tris((trimethylsilyl)methyl) Complexes with Neutral N3
Donor Ligands
Cara S. Tredget, Sally C. Lawrence, Benjamin D. Ward, Robert G. Howe,
Andrew R. Cowley, and Philip Mountford*
Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K.
Received March 19, 2005
The first group 3 organometallic compounds containing the tris(3,5-dimethylpyrazolyl)-
methane (HC(Me2pz)3) and 1,3,5-trimethyltriazacyclohexane (Me3[6]aneN3) ligands are
reported, together with the homologous 1,4,7-triazacyclononane-supported compounds and
trichloride derivatives for many of the ligands. Reaction of M(CH2SiMe3)3(THF)2 (M ) Sc,
Y) with Me3[9]aneN3 (1,4,7-trimethyltriazacyclononane), HC(Me2pz)3, or Me3[6]aneN3 gave
the corresponding tris((trimethylsilyl)methyl) derivatives M(Me3[9]aneN3)(CH2SiMe3)3 (M
) Sc (1), Y (2)), M{HC(Me2pz)3}(CH2SiMe3)3 (M ) Sc (3), Y (4)), and M(Me3[6]aneN3)(CH2-
SiMe3)3 (M ) Sc (12), Y (13)). Reaction of 3 with 2,6-dimethylphenol (ArOH) gave the tris-
(aryloxide) derivative Sc{HC(Me2pz)3}(OAr)3 (9), and reaction of HC(Me2pz)3 with MCl3 gave
M{HC(Me2pz)3}Cl3 (M ) Sc (5), Y(6)). Attempts to prepare tris((trimethylsilyl)methyl)
i
complexes with the more sterically demanding tris(3-R-pyrazolyl)methanes (R ) Pr, Ph,
tBu) or the related tris(pyrazolyl)methylsilane ligand were unsuccessful. However, the
trichlorides M{HC(iPrpz)3}Cl3 (M ) Sc (7), Y (8)) and M{MeSi(Me2pz)3}Cl3 (M ) Sc (10), Y
(11)) could be made. In related studies the reaction of ScCl3(THF)3 with Me3[6]aneN3 afforded
Sc(Me3[6]aneN3)Cl3 (14), but the yttrium congener could not be prepared. The compounds
1, 3, 4, 9, 11, and 14 have been crystallographically characterized. Competitive ligand
exchange reactions for the tris(alkyl) compounds M(L)(CH2SiMe3)3 established the binding
preference L ) Me3[9]aneN3 > Me3[6]aneN3 > HC(Me2pz)3 for M ) Sc and L ) Me3[9]aneN3
> HC(Me2pz)3 > Me3[6]aneN3 for M ) Y. Reaction of ScR3(THF)2 (R ) CH2SiMe3, Ph) with
1-(3,5-di-tert-butyl-2-hydroxybenzyl)-4,7-dimethyltriazacyclononane (HL1) or 1-(3,5-di-tert-
butyl-2-hydroxybenzyl)-4,7-diisopropyltriazacyclononane (HL2) gave organoscandium deriva-
tives of mono(phenoxy)-substituted triazacyclononane ligands, namely Sc(L1)R2 (R )
CH2SiMe3 (15), Ph (17)) and Sc(L2)(CH2SiMe3)2 (16). Reaction of 15 with 2 equiv of TolOH
(Tol ) p-tolyl) afforded Sc(L1)(OTol)2 (18), which was crystallographically characterized.
Introduction
yttrium tris((trimethylsilyl)methyl) complexes sup-
ported by a family of neutral fac-coordinated N3 donor
ligands, together with some related systems. Bercaw8
reported the first group 3 complexes of 1,4,7-trimeth-
yltriazacyclononane (Me3[9]aneN3; see Chart 1 for the
ligands used herein and the nomenclature adopted),
namely M(Me3[9]aneN3)X3 (I in Chart 2; M ) Sc, Y; X
Non-cyclopentadienyl organometallic compounds of
group 3 (and the lanthanide 4f elements) are currently
attracting considerable attention. A range of neutral and
(especially) anionic supporting ligands have recently
been employed in these efforts, and this work has
recently been comprehensively reviewed.1-3 One par-
ticular emphasis has been on the synthesis and reactiv-
ity (including olefin polymerization catalysis4-6) of
cationic alkyl derivatives; Okuda has very recently
reviewed the latter rapidly evolving area.7 Our present
contribution reports the development of scandium and
) Cl, Me). Reaction of Sc(Me3[9]aneN3)Me3 with BArF
3
(ArF ) C6F5) in THF-d8 afforded a species (not isolated)
which was formulated as Sc(Me3[9]aneN3)Me2(µ-Me)-
BArF3. The NMR spectra of this compound were broad,
but the compound nonetheless “proved competent” for
ethylene polymerization at 80 °C (no activity data were
given). Hessen subsequently disclosed the triazacy-
clononane-amide group 3 complexes II (Chart 2, M )
Y,9 La10). Activation of the yttrium congener with
* To whom correspondence should be addressed. E-mail:
philip.mountford@chem.ox.ac.uk.
(1) Piers, W. E.; Emslie, D. J. H. Coord. Chem. Rev. 2002, 233-
234, 131.
[PhNMe2H][BArF ] forms a cationic alkyl complex which
4
(2) Edelmann, F. T.; Freckmann, D. M. M.; Schumann, H. Chem.
Rev. 2002, 102, 1851.
is active for the polymerization of ethylene.9 Okuda has
(3) Mountford, P.; Ward, B. D. Chem. Commun. 2003, 1797 (feature
article review).
(8) Hajela, S.; Schaefer, W. P.; Bercaw, J. E. J. Organomet. Chem.
1997, 532, 45.
(4) Gromada, J.; Carpentier, J.-F.; Mortreux, A. Coord. Chem. Rev.
2004, 248, 397.
(9) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben,
J. H. Chem. Commun. 2001, 637.
(5) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283.
(6) Hou, Z.; Wakatsuki, Y. Coord. Chem. Rev. 2002, 231, 1.
(7) Arndt, S.; Okuda, J. Adv. Synth. Catal. 2005, 347, 339.
(10) Tazelaar, C. G. J.; Bambirra, S.; van Leusen, D.; Meetsma, A.;
Hessen, B.; Teuben, J. H. Organometallics 2004, 23, 936.
10.1021/om050209r CCC: $30.25 © 2005 American Chemical Society
Publication on Web 05/20/2005

Sc and Y Complexes with Neutral N3 Donor Ligands
Organometallics, Vol. 24, No. 13, 2005 3137
Chart 1
the synthesis and stoichiometric and catalytic chemistry
of cationic alkyl systems will be reported in a future
contribution.
In this paper we report the synthesis and structural
characterization of new organo-scandium and -yttrium
complexes of Me3[9]aneN3, as well as the first group 3
organometallic and coordination complexes of HC(Me2-
pz)3 and 1,3,5-trimethyltriazacyclohexane (Me3[6]aneN3).
We also report the first group 3 complexes of MeSi(Me2-
pz)3 as well as organoscandium derivatives of mono-
(phenoxy)-substituted triazacyclononane ligands (L1 and
L2; Chart 1). This family of compounds forms the basis
for exploring further the stoichiometric and catalytic
chemistry of group 3 neutral and cationic alkyl com-
plexes.18
Results and Discussion
The syntheses of the new tris((trimethylsilyl)methyl)
complexes of scandium and/or yttrium are summarized
in Scheme 1. All start from the readily available M(CH2-
SiMe3)3(THF)2 starting materials19 and previously re-
ported face-capping ligands.20-23
Compounds with Me3[9]aneN3 Ligands. Triaza-
cyclononanes and their N-functionalized derivatives
have been used as effective face-capping ligands across
the full range of transition, main-group, and lanthanide
metals. However, their organometallic chemistry in
group 3 is comparatively underdeveloped, as discussed
above. The compounds M(Me3[9]aneN3)(CH2SiMe3)3 (M
) Sc (1), Y (2)) were readily obtained as pale air- and
moisture-sensitive solids in ca. 60-70% isolated yield.
The NMR spectra of the new compounds suggest C3v
symmetry. The “up” and “down” (with respect to the
metal) ring methylene protons appear as mutually
coupled second-order multiplets consistent with the
macrocycle being κ3 bound to the M(CH2SiMe3)3 frag-
ment, the methylene and SiMe3 protons of which appear
as singlets. As shown by 1H NMR spectroscopy in C6D6,
the reactions to form 1 and 2 are quantitative. The X-ray
structure of 1 has been determined and is discussed
below. However, for this compound (and 2 and some
other alkyl complexs reported herein) we have been
unable to gain satisfactory elemental analysis, espe-
cially for carbon. For example, diffraction-quality crys-
tals of 1 consistently gave lower than expected carbon
analysis (in three different analytical laboratories), even
when combustion aids were used. We believe that on
the basis of the NMR spectra and several X-ray crystal
structures that the compounds are authentic and ana-
lytically pure but that either their lability on heating
or incomplete combustion is responsible for the disap-
pointing elemental analyses.
recently employed crown ethers (O donors) to stabilize
both neutral and cationic lanthanide (trimethylsilyl)-
methyl complexes such as III (Chart 2), which was the
first structurally characterized cationic lanthanide-
alkyl complex.11 However, the cationic crown ether
complexes were not catalytically active. In a recent
communication12 we reported that the tris((trimethyl-
silyl)methyl) complexes Sc(L)(CH2SiMe3)3 (L ) Me3[9]-
aneN3, HC(Me2pz)3) formed highly active ethylene
polymerization catalysts on activation with BArF .
3
These are the most active ethylene polymerization
catalysts reported to date for cationic scandium
systems. Furthermore, Sc{HC(Me2pz)3}(CH2SiMe3)3
was the first group 3 organometallic compound of
HC(Me2pz)3,13 which is the neutral analogue of the very
widely exploited tris(pyrazolyl)hydroborate ligand,
[HB(Me2pz)3]-.14-16 The CH2SiMe3 ligands appear to be
critical to good catalyst activity, since Bercaw’s Sc(Me3-
[9]aneN3)Me3 gave about 15% of the activity under
otherwise identical conditions.17 The cationic alkyl
complex [Sc{HC(Me2pz)3}(CH2SiMe3)2(THF)]+ was iso-
-
lated as its [BArF
]
4
salt.12 Full details of our work on
Chart 2

3138 Organometallics, Vol. 24, No. 13, 2005
Tredget et al.
Table 1. Selected Bond Lengths (Å) and Angles
(deg) for Sc(Me3[9]aneN3)(CH2SiMe3)3 (1)a
Scheme 1. Synthesis of New
Tris((trimethylsilyl)methyl) Complexes of
Me3[9]aneN3, HC(Me2Pz)3, and Me3[6]aneN3
Sc(1)-N(1)
2.4688(15)
2.4604(14)
2.4726(14)
2.2887(17)
2.2970(17)
2.2574(18)
71.81(5)
[2.4537(14)]
[2.4664(14)]
[2.4583(14)]
[2.2799(17)]
[2.2952(16)]
[2.2572(18)]
[71.30(5)]
Sc(1)-N(2)
Sc(1)-N(3)
Sc(1)-C(10)
Sc(1)-C(14)
Sc(1)-C(18)
N(1)-Sc(1)-N(2)
N(1)-Sc(1)-N(3)
N(2)-Sc(1)-N(3)
N(1)-Sc(1)-C(10)
N(2)-Sc(1)-C(10)
N(3)-Sc(1)-C(10)
N(1)-Sc(1)-C(14)
N(2)-Sc(1)-C(14)
N(3)-Sc(1)-C(14)
C(10)-Sc(1)-C(14)
N(1)-Sc(1)-C(18)
N(2)-Sc(1)-C(18)
N(3)-Sc(1)-C(18)
C(10)-Sc(1)-C(18)
C(14)-Sc(1)-C(18)
Sc(1)-C(10)-Si(1)
Sc(1)-C(14)-Si(2)
Sc(1)-C(18)-Si(3)
71.21(5)
[72.20(5)]
70.87(5)
158.16(6)
90.90(6)
90.85(6)
91.34(6)
[71.52(5)]
[160.02(6)]
[92.94(6)]
[91.49(6)]
[90.53(5)]
159.42(5)
92.89(6)
102.20(6)
94.13(7)
93.17(6)
[158.01(6)]
[91.52(5)]
[101.62(6)]
[97.34(6)]
[94.79(6)]
160.83(6)
100.20(7)
99.93(7)
131.02(9)
135.87(9)
141.35(10)
[164.70(6)]
[96.12(7)]
[99.88(6)]
[125.38(9)]
[138.36(9)]
[142.31(10)]
a Values in brackets correspond to the other crystallographically
independent molecule in the asymmetric unit.
ported24,25 ranges (distances, range 2.166-2.295, aver-
age 2.232 Å; angles, range 115.5-149.8, average 131.7°)
for compounds containing a Sc-CH2SiR3 ligand (R3 )
Me3 or Me2Ph), they are certainly among the largest
reported to date. However, precise comparisons cannot
be made, since there is no six-coordinate tris((triorga-
nosilyl)methyl) derivative among the 15 compounds
containing a Sc-CH2SiR3 linkage listed on the current
Cambridge Crystallographic Database.24,25 The struc-
turally characterized compounds closest to 1 (and also
to 3 described below) are Piers’ Sc(CH2SiMe2Ph)3(THF)2
(average Sc-CH2 ) 2.251 Å, average Sc-CH2-Si )
123.4°)26 and Sc{HB(Me2pz)3}(CH2SiMe3)2(THF) (aver-
age Sc-CH2 ) 2.251 Å, average Sc-CH2-Si ) 134.9°),
the latter being formally zwitterionic with a positive
charge at Sc and a negative charge at boron.27 The
Crystals of 1 contain two independent molecules in
the asymmetric unit, and there are no significant
differences between them. One of the two molecules is
represented in Figure 1, and selected bond lengths and
angles for both of them are listed in Table 1. The
geometry at Sc is approximately octahedral, and while
the Sc-CH2 distances (average 2.279 Å) and Sc-CH2-
Si angles (average 135.7°) are within previously re-
(11) Arndt, S.; Zeimentz, P. M.; Spaniol, T. P.; Okuda, J.; Honda,
M.; Tatsumi, K. Dalton 2003, 3622.
(12) Lawrence, S. C.; Ward, B. D.; Dubberley, S. R.; Kozak, C. M.;
Mountford, P. Chem. Commun. 2003, 2880.
(13) For an up-to-date review see: Bigmore, H. R.; Lawrence, S. C.;
Mountford, P.; Tredget, C. S. Dalton 2005, 635.
(14) Trofimenko, S. Chem. Rev. 1993, 93, 943.
(15) Trofimenko, S. The Coordination Chemsitry of Pyrazole-Derived
Ligands; Wiley: New York, 1986.
(16) Trofimenko, S. Chem. Rev. 1972, 72, 497.
(17) Tredget, C. S.; Mountford, P. Unpublished results.
(18) Note added during manuscript revision: Gade has very recently
reported a tris(oxazoline) organoscandium compound akin to some of
the compounds we report herein: Ward, B. D.; Bellemin-Laponnaz,
S.; Gade, L. H. Angew. Chem., Int. Ed. 2005, 44, 1668.
(19) Lappert, M. F.; Pearce, R. J. Chem. Soc., Chem. Commun. 1973,
126.
(20) Madison, S. A.; Batal, D. J. (Unilever PLC, U.K.; Unilever NV)
U.S. Patent 5,284,944, 1994.
(21) Hoerr, C. W.; Rapkin, E.; Brake, A. E.; Warner, K. N.; Harwood,
H. J. J. Am. Chem. Soc. 1956, 78, 4667.
(22) Reger, D. L.; Grattan, T. C.; Brown, K. J.; Little, C. A.; Lamba,
J. J. S.; Rheingold, A. L.; Sommer, R. D. J. Organomet. Chem. 2000,
607, 120.
(23) Pullen, E. E.; Rheingold, A. L.; Rabinovich, D. Inorg. Chem.
Commun. 1999, 194.
(24) Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993,
8, 1, 31.
Figure 1. Displacement ellipsoid plot (25% probability)
of one of the two crystallographically independent mol-
ecules of Sc(Me3[9]aneN3)(CH2SiMe3)3 (1). H atoms are
omitted for clarity.
(25) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J. J. Chem. Inf.
Comput. Sci. 1996, 36, 746.
(26) Emslie, D. J. H.; Piers, W. E.; Parvez, M.; McDonald, R.
Organometallics 2002, 21, 4226.

Sc and Y Complexes with Neutral N3 Donor Ligands
Organometallics, Vol. 24, No. 13, 2005 3139
relatively long Sc-CH2 distances and obtuse Sc-CH2-
Si angles in 1 are attributed to the six-coordinate,
comparatively crowded environment in this compound.
While there is some variation between the individual
Sc-CH2 distances and Sc-CH2-Si angles, it is not clear
why this should be, on the basis of the intermolecular
disposition of the CH2SiMe3 groups. The Sc-N distances
(average 2.463 Å) are considerably longer than in
Bercaw’s Sc(Me3[9]aneN3)Cl3 (average 2.337 Å),8 due to
the additional steric crowding in 1 and the better donor
ability of CH2SiMe3 in comparison to Cl.
Compounds with Tris(pyrazolyl)methane and
Tris(pyrazolyl)methylsilane Ligands. Tris(pyrazolyl)-
methane ligands13 are the neutral analogues of
the tris(pyrazolyl)hydroborates,14-16 among which [HB-
(Me2pz)3]- (“Tp*”) is the most widely used. Tris(pyra-
zolyl)hydroborate derivatives of the group 3 (and lan-
thanide) elements in general are extremely well-
known,28 and within group 3 the organometallic com-
pounds Y{HB(Me2pz)3}R2(THF) (R ) CH2SiMe3, Ph),29
Sc{HB(Me2pz)3}(CH2SiMe3)2(THF), and Sc{HB(tBu,-
Mepz)3}(CH2SiMe3)227 have recently been described by
Bianconi (yttrium) and Piers. In contrast, only one tris-
(pyrazolyl)methane compound of the rare-earth metals
has so far been described, namely Ce{HC(pz)3}(NO3)4,
which was disclosed in a crystallographic report in
2002,30 and no rare-earth tris(pyrazolyl)silane com-
pound has been reported at all.
Figure 2. Displacement ellipsoid plot (25% probability)
of Sc{HC(Me2pz)3}(CH2SiMe3)3 (3). H atoms and toluene
molecules of crystallization are omitted for clarity.
As summarized in Scheme 1, the compounds M{HC-
(Me2pz)3}(CH2SiMe3)3 (M ) Sc (3), Y (4)) are readily
prepared from M(CH2SiMe3)3(THF)2 in ca. 60-70%
isolated yields as pale-colored solids. Their NMR spectra
feature resonances attributed to coordinated HC(Me2-
pz)3 groups as well as CH2SiMe3 ligands and are
consistent with C3v-symmetrical products. NMR tube-
scale syntheses are quantitative.
Attempts to prepare homologues of 3 and 4 using the
different ring 3-substituted ligands HC(Rpz)3 (R ) iPr,
t
Ph, Bu; see Chart 1) gave either ill-defined mixtures
i
(R ) Pr or Ph) or no reaction at all. The complexation
Figure 3. Displacement ellipsoid plot (25% probability)
of Y{HC(Me2pz)3}(CH2SiMe3)3 (4). H atoms are omitted for
clarity.
reactions therefore appear to be rather sensitive to the
nature of the pyrazolyl ring 3-substituent. For compari-
son and completeness we also attempted to prepare
trichloride derivatives of the HC(Me2pz)3 and HC(Rpz)3
ligands (eq 1). The compounds M{HC(Me2pz)3}Cl3 (M
products were again formed with HC(Phpz)3, while no
reaction at all occurred with the most sterically de-
manding ligand, HC(tBupz)3. The compounds 5-8 are
the first group 3 trichloride compounds of tris(pyra-
zolyl)methane, and their NMR spectra show the ex-
pected C3v symmetry. A structurally characterized
tris(pyrazolyl)methylsilane analogue is discussed later;
the tris(pyrazolyl)methane complexes are assumed to
have comparable molecular structures.
The X-ray structures of the tris((trimethylsilyl)m-
ethyl) compounds 3 and 4 have been determined.
Displacement ellipsoid plots are shown in Figures 2 and
3, and selected distances and angles are listed in Tables
2 and 3. The structures are broadly similar but will be
discussed in turn.
Molecules of 3, like those of 1, feature an approxi-
mately octahedral scandium center. The average Sc-N
distance (2.420 Å) is somewhat shorter than that in 1
(2.463 Å), but this could to some extent be a consequence
of the change in N atom hybridization from sp3 in Me3-
[9]aneN3 to sp2 in Me2pz and the associated reduction
in covalent radius. Further discussion of the differences
) Sc (5), Y(6)) were readily isolated (ca. 75% yield), as
were the ring 3-isopropyl-substituted homologues M{HC-
(iPrpz)3}Cl3 (M ) Sc (7), Y(8)). However, ill-defined

3140 Organometallics, Vol. 24, No. 13, 2005
Tredget et al.
Table 2. Selected Bond Lengths (Å) and Angles
Y-CH2-SiMe3 angle in 4 (132.9°) is rather similar to
that in 3 (130.8°) and also in Evans’ 6-coordinate Y(CH2-
(deg) for Sc{HC(Me2Pz)3}(CH2SiMe3)3 (3)
33
SiMe3)3(THF)3 (average 134.6°) and Okuda’s 7-coor-
Sc(1)-N(1)
Sc(1)-N(3)
Sc(1)-N(5)
2.3996(17)
2.4422(17)
2.4173(17)
Sc(1)-C(17)
Sc(1)-C(21)
Sc(1)-C(25)
2.291(2)
2.269(2)
2.281(2)
dinate Y(CH2SiMe3)3(12-crown-4)11 (average 129.2°).
These last two compounds (being the only two previ-
ously reported structurally authenticated tris((trimeth-
ylsilyl)methyl)yttrium complexes) have average Y-CH2
distances of 2.427 and 2.417 Å, respectively, which are
comparable to that of 4 (average 2.420 Å).
As for the Me3[9]ane systems 1 and 2, the combustion
analyses for crystallographically authenticated 3 and
4 were reproducibly poor (note, however, that the
trichlorides 5-8 did not exhibit this problem). To gain
further support for the authenticity of these compounds,
the alcoholoysis reaction of 3 with ArOH (3 equiv; Ar )
2,6-C6H3Me2) was carried out to form analytically pure
Sc{HC(Me2pz)3}(OAr)3 (9) in 81% isolated yield (eq 2).
N(1)-Sc(1)-N(3)
N(1)-Sc(1)-N(5)
N(3)-Sc(1)-N(5)
76.63(6)
77.76(6)
70.83(6)
C(17)-Sc(1)-C(21) 99.87(8)
N(1)-Sc(1)-C(25)
N(3)-Sc(1)-C(25)
90.20(7)
89.34(7)
158.61(7)
N(1)-Sc(1)-C(17) 168.87(7) N(5)-Sc(1)-C(25)
N(3)-Sc(1)-C(17) 93.98(7)
N(5)-Sc(1)-C(17) 93.63(8)
N(1)-Sc(1)-C(21) 87.50(7)
C(17)-Sc(1)-C(25) 95.72(9)
C(21)-Sc(1)-C(25) 105.89(9)
Sc(1)-C(17)-Si(1) 122.37(11)
N(3)-Sc(1)-C(21) 158.13(7) Sc(1)-C(21)-Si(2) 134.55(12)
N(5)-Sc(1)-C(21) 91.35(7) Sc(1)-C(25)-Si(3) 135.52(12)
Table 3. Selected Bond Lengths (Å) and Angles
(deg) for Y{HC(Me2Pz)3}(CH2SiMe3)3 (4)
Y(1)-N(1)
Y(1)-N(3)
Y(1)-N(5)
2.601(2)
2.563(2)
2.596(2)
Y(1)-C(17)
Y(1)-C(21)
Y(1)-C(25)
2.434(3)
2.448(3)
2.420(4)
N(1)-Y(1)-N(3)
N(1)-Y(1)-N(5)
N(3)-Y(1)-N(5)
70.80(8)
70.11(8)
70.59(8)
C(17)-Y(1)-C(21) 99.42(11)
N(1)-Y(1)-C(25)
N(3)-Y(1)-C(25)
90.75(11)
89.60(11)
155.84(11)
N(1)-Y(1)-C(17) 160.68(10) N(5)-Y(1)-C(25)
N(3)-Y(1)-C(17) 97.10(10)
N(5)-Y(1)-C(17) 91.91(10)
N(1)-Y(1)-C(21) 87.94(10)
C(17)-Y(1)-C(25) 104.51(13)
C(21)-Y(1)-C(25) 104.31(12)
Y(1)-C(17)-Si(1) 136.35(16)
N(3)-Y(1)-C(21) 154.89(10) Y(1)-C(21)-Si(2) 125.32(16)
N(5)-Y(1)-C(21) 90.02(9) Y(1)-C(25)-Si(3) 137.0(2)
in Sc-N distances between 1 and 3 is limited by the
paucity of crystallographic data for pairs of homologous
complexes M(Me3[9]aneN3)(L)n and M{HC(Me2pz)3}(L)n.
Data for just one pair of such compounds are available,
namely Ti(Me3[9]aneN3)(NtBu)Cl2 (average Ti-Nmacro
-
cycle ) 2.377 Å)31 and Ti{HC(Me2pz)3}(NtBu)Cl232 (aver-
age Ti-NMe pz ) 2.291 Å). In these two compounds there
is also a de2crease in metal-N distance on going from
the Me3[9]aneN3 to the HC(Me2pz)3 ligand.
The average Sc-CH2 distance in 3 (2.280 Å) is
indistinguishable from that in 1 (2.279 Å), but the
average Sc-CH2-Si angle (130.8°) and range of values
(122.37(11)-135.52(12)°) is somewhat less than those
in 1 (average 135.7°, range 125.38(9)-142.31(10)°). A
closer inspection of 3 shows that two of the SiMe3 groups
(containing Si(2) and Si(3)) are oriented “up” toward the
HC(Me2pz)3 ligand and are partially accommodated in
the clefts between pairs of Me2pz rings. The other SiMe3
(Si(1)) is oriented “down”, and this has the smaller Sc-
CH2-Si angle (122.37(11)° subtended at C(17)), possibly
indicative of reduced steric repulsion for this individual
moiety (but see below).
The structure of 4 is very similar to that of 3 but
features one SiMe3 (Si(1)) oriented “up” and two “down”.
However, in this case the angle subtended at C(17)
(136.35(16)°, associated with the “up” SiMe3) is indis-
tinguishable from that at C(25) for one of the “down”
SiMe3 groups, and so it is probably unsafe to advance a
simple explanation of the trends in M-CH2-SiMe3
angles in the compounds reported herein. The average
When it was followed on an NMR tube scale (CD2Cl2),
the reaction was quantitative and the sole side product
was SiMe4. The room-temperature 1H and 13C NMR
spectra of 9 showed broad resonances for the ortho and
meta groups of the Ar substituent, consistent with
restricted rotation about the Sc-OAr bonds. At -20 °C
the fluxional process was frozen out and the spectra
were consistent with the solid-state structure, as de-
termined by X-ray crystallography (Figure 4, with
selected bond distances and angles given in Table 4)
showing, for example, two o-methyl group environments
for the OAr ligands at δ 2.48 ppm (“down”, away from
the HC(Me2pz)3 ligand) and 1.19 ppm (“up”). The
relatively high field shift of the “up” o-Me resonance is
attributed to the shielding ring-current effects of nearby
Me2pz ligands.
In the solid state, molecules of 9 lie on crystal-
lographic 3-fold rotation axes which render all three OAr
(and also Me2pz rings) strictly equivalent. The Sc-N
distance of 2.3543(19) Å is significantly shorter than the
average value of 2.420 Å for Sc{HC(Me2pz)3}(CH2-
SiMe3)3 (3), reflecting the reduced trans influence of OAr
in comparison with CH2SiMe3. The Sc-O distance of
(27) Blackwell, J.; Lehr, C.; Sun, Y.; Piers, W. E.; Pearce-Batchilder,
S. D.; Zaworotko, M. J.; Young, V. G., Jr. Can. J. Chem. 1997, 75, 702.
(28) Marques, N.; Sella, A.; Takats, J. Chem. Rev. 2002, 102, 2137.
(29) Long, D. P.; Bianconi, P. A. J. Am. Chem. Soc. 1996, 118, 12453.
(30) Chen, S. J.; Li, Y. Z.; Chen, X. T.; Shi, Y. J.; You, X. Z. Acta
Crystallogr., Sect. E 2002, E58, m753.
(31) Wilson, P. J.; Blake, A. J.; Mountford, D. P.; Schro¨der, M. Chem.
Commun. 1998, 1007.
(32) Lawrence, S. C., D.Phil. Thesis, University of Oxford, 2003.
(33) Evans, W. J.; Brady, J. C.; Ziller, J. W. J. Am. Chem. Soc. 2001,
123, 7711.

Sc and Y Complexes with Neutral N3 Donor Ligands
Organometallics, Vol. 24, No. 13, 2005 3141
Figure 5. Displacement ellipsoid plot (25% probability)
of one of the two crystallographically independent mol-
ecules of Y{MeSi(Me2pz)3}Cl3 (11). H atoms and dichlo-
romethane molecule of crystallization are omitted for
clarity.
Figure 4. Displacement ellipsoid plot (25% probability)
of Sc{MeSi(Me2pz)3}(OAr)3 (9). H atoms and benzene
molecules of crystallization are omitted for clarity. Atoms
carrying the suffixes A and B are related to their counter-
parts by the symmetry operators -y, x - y + 1, z and -x
+ y - 1, -x, z, respectively.
Table 5. Selected Bond Lengths (Å) and Angles
(deg) for Y{MeSi(Me2Pz)3}Cl3 (11)
Y(1)-Cl(1)
2.5527(10)
2.5782(10)
2.5678(10)
2.454(3)
2.466(3)
2.488(3)
97.68(4)
98.13(4)
95.93(4)
163.75(7)
90.32(7)
95.06(7)
91.67(7)
166.34(7)
92.56(7)
78.26(10)
87.53(7)
92.10(7)
169.45(7)
78.02(9)
78.32(10)
[2.5768(9)]
[2.5775(10)]
[2.5528(10)]
[2.448(3)]
[2.481(3)]
[2.447(3)]
[96.64(3)]
[100.67(3)]
[103.16(4)]
[168.27(7)]
[90.74(7)]
[86.42(7)]
[90.71(7)]
[167.65(7)]
[85.11(7)]
[80.52(9)]
[92.02(7)]
[92.36(7)]
[158.53(7)]
[78.53(9)]
[77.42(9)]
Y(1)-Cl(2)
Y(1)-Cl(3)
Y(1)-N(1)
Y(1)-N(3)
Table 4. Selected Bond Lengths (Å) and Angles
Y(1)-N(5)
(deg) for Sc{MeSi(Me2Pz)3}(OAr)3 (9)a
Cl(1)-Y(1)-Cl(2)
Cl(1)-Y(1)-Cl(3)
Cl(2)-Y(1)-Cl(3)
Cl(1)-Y(1)-N(1)
Cl(2)-Y(1)-N(1)
Cl(3)-Y(1)-N(1)
Cl(1)-Y(1)-N(3)
Cl(2)-Y(1)-N(3)
Cl(3)-Y(1)-N(3)
N(1)-Y(1)-N(3)
Cl(1)-Y(1)-N(5)
Cl(2)-Y(1)-N(5)
Cl(3)-Y(1)-N(5)
N(1)-Y(1)-N(5)
N(3)-Y(1)-N(5)
Sc(1)-O(1)
1.9615(16)
Sc(1)-N(1)
2.3543(19)
N(1)-Sc(1)-N(1A)
O(1)-Sc(1)-N(1)
75.20(7) Sc(1)-N(1)-N(2) 123.41(13)
85.92(7) Sc(1)-N(1)-C(1) 131.84(16)
O(1)-Sc(1)-O(1A) 103.74(6) Sc(1)-O(1)-C(7) 174.41(17)
a Atoms carrying the suffix A are related to their counterparts
by the symmetry operator -y, x - y + 1, z.
1.9615(16) Å is within known ranges for such linkages
(range, 1.853-2.149; average 1.975 Å for eight ex-
amples).24,25
We also attempted to prepare analogous tris((trim-
ethylsilyl)methyl) compounds using the homologous
silicon-capped ligand MeSi(Me2pz)3 in reaction with
M(CH2SiMe3)3(THF)2. There have been only three re-
ports of complexes of this ligand to date, and none from
group 3.23,34,35 Surprisingly, these reactions gave rather
complicated mixtures on both the preparative and NMR
tube scales. However, the trichloride derivatives M{MeSi-
(Me2pz)3}Cl3 (M ) Sc (10), Y (11)) could readily be
prepared in 79 and 54% isolated yields, respectively (eq
1), and, being the first group 3 complexes of this ligand,
are included here for completeness. Attempted alkyla-
tions of these compounds with LiCH2SiMe3 have so far
been inconclusive.
Diffraction-quality crystals containing two indepen-
dent molecules of 11 per asymmetric unit (together with
two CH2Cl2 molecules of crystallization) were grown
from a dichloromethane solution. There are no substan-
tial differences between the two molecules, and the
structure of one of them is shown in Figure 5. Selected
bond lengths and angles for both molecules are listed
in Table 5. Compound 11 possesses an approximately
octahedral yttrium center with average Y-N and Y-Cl
distances of 2.464 and 2.568 Å, respectively, which
are within the known ranges. However, a more detail-
ed comparison with literature data is limited by the
paucity of relevant systems. Just one structure contain-
ing a six-coordinate “YN3Cl3” core has been reported,
this being a very poor quality determination (e.g. R )
0.139) of the tris(pyrazolyl)hydroborate-supported anion
[Y{HB(Me2pz)3}Cl3]-, which has average Y-N and
Y-Cl distances of 2.434 and 2.572 Å, respectively.36
Only one paper describing structures of tris(pyrazolyl)-
silane complexes has appeared, this being for the M(0),
d6 compounds M{MeSi(Me2pz)3}(CO)3 (M ) Cr, Mo,
W).35
Compounds with Me3[6]aneN3 Ligands. 1,3,5-
Triazacyclohexane ligands have smaller ring sizes than
their R3[9]aneN3 homologues, and their coordination
(34) Vepachedu, S.; Stibrany, R. T.; Knapp, S.; Potenza, J. A.;
Schugar, H. J. Acta Crystallogr. 1995, C51, 423.
(35) Pullen, E. E.; Rabinovich, D.; Incarvito, C. D.; Concolino, T. E.;
Rheingold, A. L. Inorg. Chem. 2000, 39, 1561.
(36) Roitershtein, D.; Domingos, A.; Pereira, L. C. J.; Ascenso, J.
R.; Marques, N. Inorg. Chem. 2003, 42, 7666.

3142 Organometallics, Vol. 24, No. 13, 2005
Tredget et al.
chemistry in general is less extensively developed in
comparison (although in general their syntheses are
much more straightforward and the scope for easy
variation of the N substituents potentially limitless37).
Recently, Ko¨hn and co-workers have shown how R3[6]-
ane-supported chromium complexes can be highly ef-
fective mimics of the Phillips-type catalysts,38 and so
we have chosen to target group 3 tris(alkyl) complexes
of Me3[6]aneN3. Only one report of rare-earth complexes
supported by triazacyclohexane ligands has so far
appeared,39 these being the recently described praseo-
dynium species Pr(Me3[6]aneN3)2(OTf)3 and [Pr2(Et3[6]-
aneN3)2(OTf)4(µ-OTf)3]-.
As in the previous syntheses (Scheme 1), reaction of
Me3[6]aneN3 with M(CH2SiMe3)3(THF)2 afforded the
corresponding products M(Me3[6]aneN3)(CH2SiMe3)3 (M
) Sc (12), Y (13)) as pale yellow solids in ca. 70-80%
isolated yield. The reactions were again quantitative on
the NMR tube scale in C6D6. The NMR spectra suggest
C3v-symmetric products, and the fac-κ3 coordination of
the Me3[6]aneN3 is indicated by the presence of a pair
of mutually coupled doublets for the ring methylene
protons in the 1H NMR spectra. We have not been able
to obtain diffraction crystals of 12 and 13, but their
structures are supported by that of the trichloride Sc-
(Me3[6]aneN3)Cl3 (14), which was prepared in 66%
isolated yield according to eq 3. Reaction of 14 with
Figure 6. Displacement ellipsoid plot (30% probability)
of Sc(Me3[6]aneN3)Cl3 (14). H atoms are omitted for clarity.
Atoms carrying the suffix A are related to their couterparts
3
by the symmetry operator x, /2 - y, z.
Table 6. Selected Bond Lengths (Å) and Angles
(deg) for Sc(Me3[6]aneN3)Cl3 (14)a
Sc(1)-Cl(1)
Sc(1)-Cl(2)
2.3829(5)
2.3727(3)
Sc(1)-N(1)
Sc(1)-N(2)
2.3306(15)
2.3331(9)
Cl(1)-Sc(1)-Cl(2) 105.721(14) Cl(2)-Sc(1)-N(2)
Cl(2)-Sc(1)-Cl(2A) 106.67(2)
92.97(2)
Cl(2)-Sc(1)-N(2A) 147.95(3)
Cl(1)-Sc(1)-N(1)
Cl(2)-Sc(1)-N(1)
Cl(1)-Sc(1)-N(2)
147.05(4)
93.56(3)
92.48(3)
N(1)-Sc(1)-N(2)
N(2)-Sc(1)-N(2A)
59.46(4)
59.47(5)
a Atoms carrying the suffix A are related to their counterparts
3
by the symmetry operator x,
/ - y, z.
2
are seen in the homologous pair40,41 Fe(Me3[n]aneN3)-
Cl3 (n ) 6, 9): average Fe-Cl ) 2.249 (n ) 6) and 2.303
Å; average Fe-N ) 2.254 (n ) 6) and 2.246 Å; average
N-Fe-N ) 61.0 (n ) 6) and 78.0°.
Competitive Binding Studies. Having prepared
the new families of organo-group 3 complexes (i.e. the
HC(Me2pz)3- and Me3[6]aneN3-supported systems), as
well as the homologous compounds with Me3[9]aneN3,
it was of interest to compare the experimental relative
binding preferences of the M(CH2SiMe3)3 fragments for
the various ligands. Such factors may be relevant in the
design of catalytic systems based on fac-N3 ligands. We
probed the binding preferences through a series of
competitive NMR tube scale reactions in C6D6 in which
each M(fac-L3)(CH2SiMe3)3 complex in Scheme 1 was
treated with 1 equiv of another of the fac-L3 donor
ligands. The results for the yttrium and scandium
systems are described in turn.
For the yttrium compounds 2, 4, and 13 the ligand
binding preference is Me3[9]aneN3 > HC(Me2pz)3 > Me3-
[6]aneN3, with a ligand higher in the binding order
being able to quantitatively displace a ligand from lower
down the order (reaction times at room temperature
were in the range 1-24 h). The binding preference of
Me3[9]aneN3 over Me3[6]aneN3 may be rationalized in
terms of coordination bite angle, with the larger ligand
matching the metal better (Ko¨hn has described the
metal-ligand orbital directional mismatch typically
associated with R3[6]ane systems38). It is also consistent
with our previous work on the titanium imido systems
LiCH2SiMe3 (3 equiv) in C6D6 on an NMR tube scale
afforded complete conversion to 12. Attempts to prepare
an yttrium analogue of 14 have so far been unsuccessful.
The molecular structure of 14 is shown in Figure 6,
and selected bond distances and angles are listed in
Table 6. The molecules lie across crystallographic mirror
planes and contain an octahedral Sc center and fac-
coordinated Me3[6]aneN3 ligand. Compound 14 is analo-
gous to Bercaw’s Sc(Me3[9]aneN3)Cl3, and key param-
eters between the two can be compared: average Sc-
Cl ) 2.378 (14) and 2.406 Å; average Sc-N ) 2.332 (14)
and 2.337 Å; average N-Sc-N ) 59.5 (14) and 74.9°.
The longer Sc-Cl distance in Sc(Me3[9]aneN3)Cl3 is
attributed to the fact that the N donors of the macro-
cycle lie more strictly trans to the Sc-Cl bonds (average
N-Sc-Cltrans ) 163.7°) than in 14 (average N-Sc-
Cltrans ) 145.5°) and so exert a larger trans influence.
The smaller average N-Sc-N angle in 14 is because of
the smaller ring size of Me3[6]aneN3. Analogous trends
(37) For an example and leading references see: Ko¨hn, R. D.; Haufe,
M.; Kociok-Ko¨hn, G.; Grimm, S.; Wasserscheid, P.; Keim, W. Angew.
Chem., Int. Ed. 2000, 39, 4337-4339.
(38) Ko¨hn, R. D.; Haufe, M.; Mihan, S.; Lilge, D. Chem. Commun.
2000, 1927.
(39) Ko¨hn, R. D.; Pan, Z.; Kociok-Ko¨hn, G.; Mahon, M. F. Dalton
2002, 2344.
(40) Ko¨hn, R. D.; Kociok-Ko¨hn, G. Angew. Chem., Int. Ed. 1994.
(41) Silver, G. C.; Trogler, W. C. J. Am. Chem. Soc. 1995, 117, 3983.

Sc and Y Complexes with Neutral N3 Donor Ligands
Organometallics, Vol. 24, No. 13, 2005 3143
Ti(Me3[n]aneN3)(NtBu)Cl2 (n ) 6, 9),31,42 in which Me3-
[9]aneN3 quantitatively displaced coordinated Me3[6]-
aneN3. The binding preference of Me3[9]aneN3 over
HC(Me2pz)3 (which both appear to have a similar match
at the metal in terms of bite angle) may be attributed
in general terms to the “macrocylic effect”.43 This
expression embraces a number of contributing factors,
enthalpic and entropic, and further studies would be
needed to unravel the various contributions.
and alkoxy-functionalized triazacyclononane ligands,
including compounds derived from the previously re-
ported52,54 protio ligands HL1 and HL2 (Chart 1). Fol-
lowing Hessen’s work on the triazacyclononane-amide
systems II, we were interested to prepare group 3 com-
pounds based on triazacyclononane-phenoxide ligands.
Reaction of the protio ligands HL1 and HL2 with
Sc(CH2SiMe3)3(THF)2 in cold benzene afforded the
compounds Sc(L1)(CH2SiMe3)2 (15) and Sc(L2)(CH2-
SiMe3)2 (16) in ca. 50-70% isolated yields (eq 4). The
The scandium systems 1, 3, and 12 show a different
binding order among the N3 donor ligands. In this case
the preference is Me3[9]aneN3 > Me3[6]aneN3 > HC(Me2-
pz)3, and again a ligand higher in the binding order is
able to displace quantitatively a ligand from lower down
the order. The relative positions of Me3[9]aneN3 and
Me3[6]aneN3 can be rationalized as above, on the basis
of ligand ring size. However, it was surprising that Me3-
[6]aneN3 would, over the course of several hours at room
temperature, quantitatively displace HC(Me2pz)3 from
3 to form 12. It appears that there may be a delicate
balance between bite angle and steric and (for Me3[6]-
aneN3) macrocyclic/preorganization effects for the two
ligands Me3[6]aneN3 and HC(Me2pz)3 in the scandium
and yttrium systems. We note in this context that Piers
has reported27 that the related tris(pyrazolyl)hydrobo-
rate scandium complexes are prone to fac-N3 ligand
displacement (albeit with anionic alkyl reagents). Bi-
anconi has reported that this is not apparently the case
for congeneric yttrium systems.29 However, Carpentier
has recently reported (in contrast to Bianconi’s findings)
that reaction of Y{HB(Me2pz)3}Cl2(THF) with a range
of lithium or potassium salts (including LiCH2SiMe3)
led essentially to the formation of M[HB(Me2pz)3] (M )
Li, K).44 It appears that the stability of fac-N3 donor
ligands toward displacement from group 3 metals may
be sensitive to a number of subtle experimental factors.
Organoscandium Complexes of Pendant Arm
Functionalized Triazacyclononanes. Although pen-
dant arm functionalized macrocycles have a rich and
extensive coordination chemistry (e.g., in the areas of
selectiveionbinding,sensors,andbioinorganicchemistry),43,45-47
they have only recently started to be employed in
organometallic and related chemistry. As mentioned
above, Hessen has described catalytic and stoichiometric
chemistry arising from triazacyclononane-amide group
3 complexes II (Chart 2). Recently Arnold48 and Peters49
have reported cyclopentadienyl-functionalized triaza-
cyclonane ligands, and Meyer has used a series of
uranium complexes of tris(hydroxybenzyl)-substituted
triazacyclononanes to considerable effect in the small-
molecule binding chemistry of uranium.50,51 We have
recently reported52,53 work on neutral and cationic
organoaluminum and -indium complexes of phenoxy-
corresponding reaction of HL1 with ScPh3(THF)2 gave
Sc(L1)Ph2 (17) in 38% isolated yield, but reaction of HL1
with Y(CH2SiMe3)3(THF)2 did not give a clean product
on either the preparative or NMR tube scale (C6D6). Use
of the more sterically demanding protio ligand HL2 (N-
isopropyl-substituted homologue) appeared to give an
yttrium congener of 16, but the data for this compound
were somewhat ambiguous. Unlike the rather simple
NMR spectra of C3v-symmetric M(Me3[9]aneN3)(CH2-
SiMe3)3 (1 and 2), those of 15-18 show (as expected)
no molecular symmetry and are consistent with the
structures proposed in eq 4, in which a deprotonated
hydroxybenzyl arm is coordinated to the metal center.
Furthermore, compounds 15 and 16 showed the ap-
propriate molecular ions (correct m/z and isotope dis-
tribution pattern) in their EI mass spectra. We were
unable to grow diffraction-quality crystals of the orga-
nometallic compounds. However, the protonolysis reac-
tion of 15 with TolOH (2 equiv, Tol ) p-tolyl) cleanly
afforded SiMe4 (identified in an NMR tube scale reac-
tion) and Sc(L1)(OTol)2 (18, eq 5), which has been
(42) Wilson, P. J.; Blake, A. J.; Mountford, P.; Schro¨der, M. J.
Organomet. Chem. 2000, 600, 71.
(43) Lindoy, L. F. The Chemistry of Macrocyclic Ligand Complexes;
Cambridge University Press: Cambridge, U.K., 1989.
(44) Kunrath, F. A.; Casagrande, O. L.; Toupet, L.; Carpentier, J.-
F. Polyhedron 2004, 23, 2437.
(45) Wainwright, K. P. Coord. Chem. Rev. 1997, 166, 35.
(46) Chaudhuri, P.; Wieghardt, K. Prog. Inorg. Chem. 1987, 35, 329.
(47) Costamagna, J.; Ferraudi, G.; Matsuhiro, B.; Campos-Vallette,
M.; Canales, J.; Villagran, M.; Vargas, J.; Aguirre, M. J. Coord. Chem.
Rev. 2000, 196, 125.
(48) Giesbrecht, G. R.; Cui, C.; Shafir, A.; Schmidt, J. A. R.; Arnold,
J. Organometallics 2002, 21, 3841.
(49) Qian, B.; Henling, L. M.; Peters, J. C. Organometallics 2000,
19, 2805.

3144 Organometallics, Vol. 24, No. 13, 2005
Tredget et al.
azacyclononane-scandium systems8,46 with aryloxy or
halide coligands (range 2.328-2.412, average 2.356 Å
for three examples) but are clearly shorter than those
in 1 (average 2.463). The angles subtended at the
nonchelating aryloxide oxygen atoms are similar at
158.5(4) and 162.5(4)°, whereas the angle subtended at
O(1) (part of the pendant arm) is more acute at 141.1-
(4)°, due to the constraining nature of the pendant arm.
Conclusions
In this paper we have described effective synthetic
routes to the first group 3 organometallic and coordina-
tion compounds containing the tris(pyrazolyl)methane
and triazacyclohexane ligands. Together with the new
triazacyclononane analogues M(Me3[9]aneN3)(CH2SiMe3)3
(1 and 2) these tris((trimethylsilyl)methyl) compounds
form the basis for a comprehensive study of the sto-
ichiometric and catalytic chemistry of cationic alkyl and
related complexes derived from the new classes of com-
pound as a function of macrocycle ring size (R3[6]aneN3
vs R3[9]aneN3 systems), topology (the podand-like HC-
(Me2pz)3 vs macrocyclic R3[9]aneN3), and face-capping
ligand substitution in general. Such studies are under-
way and will be reported in due course, together with
investigations of related M(fac-L3)R3 (R ) alkyl) com-
plexes of the lanthanides. The syntheses and structures of
15-18 are analogous to those of Hessen’s triazacyclo-
nonane-amide systems II. Reports on the chemistry of
these new complexes will also be described at a later date.
Figure 7. Displacement ellipsoid plot (20% probability)
of Sc(L2)(OTol)2 (18). H atoms and benzene molecule of
crystallization are omitted for clarity.
Table 7. Selected Bond Lengths (Å) and Angles
(deg) for Sc(L2)(OTol)2 (18)
Sc(1)-N(1)
Sc(1)-N(4)
Sc(1)-N(7)
2.367(5)
2.411(6)
2.360(5)
Sc(1)-O(1)
Sc(1)-O(2)
Sc(1)-O(3)
1.981(4)
1.949(4)
1.963(5)
Experimental Section
N(1)-Sc(1)-N(4)
N(1)-Sc(1)-N(7)
N(4)-Sc(1)-N(7)
N(1)-Sc(1)-O(1)
N(4)-Sc(1)-O(1)
N(7)-Sc(1)-O(1)
N(1)-Sc(1)-O(2)
N(4)-Sc(1)-O(2)
N(7)-Sc(1)-O(2)
73.3(2)
74.6(2)
73.2(2)
82.9(2)
92.8(2)
156.1(2)
161.3(2)
89.8(2)
93.4(2)
O(1)-Sc(1)-O(2)
N(1)-Sc(1)-O(3)
N(4)-Sc(1)-O(3)
N(7)-Sc(1)-O(3)
O(1)-Sc(1)-O(3)
O(2)-Sc(1)-O(3)
Sc(1)-O(1)-C(17)
Sc(1)-O(2)-C(26)
Sc(1)-O(3)-C(33)
106.2(2)
91.3(2)
158.7(2)
88.7(2)
100.0(2)
102.8(2)
141.1(4)
162.5(4)
158.5(4)
General Methods and Instrumentation. All manipula-
tions were carried out using standard Schlenk line or drybox
techniques under an atmosphere of argon or of dinitrogen.
Protio solvents were predried over activated 4 Å molecular
sieves, purged with N2, and dried either by refluxing over an
appropriate alkali metal or alloy or (HPLC grade, nonstabilized
as appropriate) by passage through a column of activated
alumina.55 Deuterio solvents were predried over activated 4
Å molecular sieves and were refluxed over the appropriate
drying agent, distilled, and stored under dinitrogen in Teflon
valve ampules. NMR samples were prepared under dinitrogen
in 5 mm Wilmad 507-PP tubes fitted with J. Young Teflon
valves. 1H, 13C{1H} and 13C NMR spectra were recorded on
Varian Mercury-VX 300 and Varian Unity Plus 500 spectrom-
eters. 1H and 13C assignments were confirmed when necessary
with the use of DEPT-135, DEPT-90, and two-dimensional 1H-
1H and 13C-1H NMR experiments. 1H and 13C spectra were
referenced internally to residual protio solvent (1H) or solvent
(13C) resonances and are reported relative to tetramethylsilane
(δ 0 ppm). Chemical shifts are quoted in δ (ppm) and coupling
constants in hertz. Infrared spectra were prepared as KBr
pellets or as Nujol mulls between NaCl plates and were
recorded on Perkin-Elmer 1600 and 1710 series FTIR spec-
trometers. Infrared data are quoted in wavenumbers (cm-1).
Mass spectra were recorded by the mass spectrometry service
of the Chemistry Laboratory Oxford and elemental analyses
by the analytical services of the University of Oxford Inorganic
Chemistry Laboratory, by Mikroanalytisches Labor Pascher,
Germany, or by the Elemental Analysis Service, London
Metropolitan Univeristy.
crystallographically characterized (see below). The NMR
spectra of 18 are analogous to those of 15, except that
the resonances for the two inequivalent CH2SiMe3
groups are replaced by resonances for two OTol ligands.
The molecular structure of 18 is illustrated in Figure
7, and selected distances and angles are listed in Table
7. Molecules of 18 possess the expected C1 symmetry
in the solid state and contain approximately octahedral
scandium centers. The triazacyclononane ligand moiety
is coordinated facially, and the OTol ligands are in
different environments, one being trans to the macro-
cycle nitrogen N(1) bearing the phenoxide pendant arm
of the macrocycle ligand and the other being trans to
an NMe. The Sc-O bond lengths (average 1.964 Å) are
within the known ranges24,25 and are identical within
error to that in 9 (1.9615(16) Å). The Sc-N bond lengths
(average 2.379 Å) are within previous ranges for tri-
(50) Castro-Rodriguez, I.; Olsen, K.; Gantzel, P.; Meyer, K. J. Am.
Chem. Soc. 2003, 125, 4565.
(51) Castro-Rodriguez, I.; Nakai, H.; Zakharov, L. N.; Rheingold,
A. L.; Meyer, K. Science 2004, 305, 1757.
Literature Preparations and Other Starting Materi-
als. The compounds M(CH2SiMe3)3(THF)2 (M ) Sc, Y),19 ScPh3-
(THF)2,56 Me3[9]aneN3,20 Me3[6]aneN3,21 HC(Me2pz)3 and HC-
(Rpz)3 (R ) iPr, Ph, tBu),22 MeSi(Me2pz)3,23 1-(3,5-di-tert-butyl-
(52) Bylikin, S. Y.; Robson, D. A.; Male, N. A. H.; Rees, L. H.;
Mountford, P.; Schro¨der, M. Dalton 2001, 170.
(53) Robson, D. A.; Bylikin, S. Y.; Cantuel, M.; Male, N. A. H.; Rees,
L. H.; Mountford, P.; Schro¨der, M. Dalton 2001, 157.
(54) Halfen, J. A.; Jazdzewski, B. A.; Mahapatra, S.; Berreau, L.
M.; Wilkinson, E. C.; Que, L., Jr.; Tolman, W. B. J. Am. Chem. Soc.
1997, 119, 8217.
(55) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.

Sc and Y Complexes with Neutral N3 Donor Ligands
Organometallics, Vol. 24, No. 13, 2005 3145
2-hydroxybenzyl)-4,7-dimethyl-triazacyclononane (HL1),52 and
1-(3,5-di-tert-butyl-2-hydroxybenzyl)-4,7-diisopropyltriazacy-
clononane (HL2)54 were prepared according to published
methods. All other compounds and reagents were purchased
and used without further purification.
was filtered. The resulting solid was re-extracted into benzene
(10 mL) and addition of hexane (20 mL) afforded 4 as a light
brown solid. Yield: 0.28 g (58%). Diffraction-quality crystals
were grown from a saturated toluene solution. 1H NMR
(C6D6, 500.0 MHz, 298 K): 6.99 (1H, s, HC(Me2pz)3), 5.18 (3H,
s, 4-N2C3Me2H), 2.61 (9H, s, 3-N2C3Me2H), 1.32 (9H, s,
5-N2C3Me2H), 0.33 (27H, s, SiMe3), -0.02 (6H, d, JHY ) 2.8
Hz, CH2SiMe3). 13C{1H} NMR (CD2Cl2, 125.7 MHz, 298 K):
154.3 (3-N2C3Me2H), 138.5 (5-N2C3Me2H), 107.6 (3-N2C3Me2H),
67.9 (HC(Me2pz)3), 32.4 (YCH2, JCY ) 33 Hz), 15.7 (3-
N2C3Me2H), 10.2 (5-N2C3Me2H), 5.0 (SiMe3). IR (NaCl plates,
Nujol): 2360 (m), 2342 (w), 1959 (w), 1618 (w), 1562 (w), 1459
(m), 1413 (w), 1261 (s), 1093 (s), 1020 (s), 863 (w), 800 (s), 705
(w), 669 (w) cm-1. Anal. Found (calcd for C28H55N6Si3Y): C,
49.9 (51.8); H, 7.9 (8.5); N, 12.3 (13.0).
Sc(Me3[9]aneN3)(CH2SiMe3)3 (1). Sc(CH2SiMe3)3(THF)2
(152 mg, 0.34 mmol) was dissolved in cold (7 °C) benzene (15
mL) and stirred for the dropwise addition of a solution of Me3-
[9]aneN3 (58 mg, 0.34 mmol) in benzene (15 mL). The mixture
was warmed to room temperature and stirred for 30 min. The
volatiles were removed under reduced pressure to afford 1 as
a pale yellow solid. Yield: 94 mg (59%). Diffraction-quality
crystals were grown from slow diffusion of pentane into a
saturated toluene solution. 1H NMR (C6D6, 500.0 MHz, 293
K): 2.32 (9 H, s, NMe), 2.26 (6 H, m, NCH2), 1.56 (6 H, m,
NCH2), 0.42 (27 H, s, SiMe3), -0.23 (6 H, s, ScCH2). 13C{1H}
NMR (C6D6, 125.7 MHz, 293 K): 53.6 (NCH2CH2N), 48.1
(NMe), 2.5 (SiMe3); CH2SiMe3 not observed. IR (KBr pellet):
2940 (s), 2894 (s), 2860 (s), 2822 (m), 1494 (m), 1464 (s), 1424
(w), 1384 (w), 1366 (m), 1300 (m), 1246 (s), 1234 (s), 1206 (w),
1154 (w), 1126 (w), 1080 (m), 1068 (m), 1008 (s), 876 (s), 852
(s), 818 (s), 774 (w), 748 (m), 720 (m), 666 (m), 604 (w), 578
(w), 450 (m), 420 (w), 402 (w) cm-1. FI-HRMS for [Sc-
(Me3[9]aneN3)(CH2SiMe3)2]+: found (calcd for C17H43N3ScSi2)
m/z 390.2561 (390.2555). Anal. Found (calcd for C21H54N3-
ScSi3): C, 50.3 (52.8); H, 11.2 (11.4); N, 8.5 (8.8).
Y(Me3[9]aneN3)(CH2SiMe3)3 (2). Y(CH2SiMe3)3(THF)2 (290
mg, 0.587 mmol) was dissolved in cold (7 °C) benzene (15 mL)
and stirred for the dropwise addition of a solution of Me3[9]-
aneN3 (101 mg, 0.587 mmol) in benzene (15 mL). The mixture
was allowed to warm to room temperature and stirred for 30
min. The volatiles were removed under reduced pressure to
afford 2 as a white solid. Yield: 207 mg (68%). 1H NMR (C6D6,
500.0 MHz, 293 K): 2.30 (9 H, s, NMe), 2.20 (6 H, m, NCH2),
1.56 (6 H, m, NCH2), 0.41 (27 H, s, SiMe3), -0.67 (6 H, d, YCH2,
JHY ) 2.6 Hz) ppm. 13C{1H} NMR (C6D6, 125.7 MHz, 293 K):
54.4 (NCH2), 47.8 (NMe), 35.3 (YCH2, JCY ) 36 Hz), 4.9 (SiMe3)
ppm. IR (KBr pellet): 2822 (s), 1492 (m), 1464 (s), 1366 (m),
1302 (w), 1246 (m), 1234 (m), 1208 (w), 1154 (w), 1128 (w),
1068 (m), 1008 (s), 858 (s), 818 (m), 744 (m), 716 (m), 668 (m),
572 (w), 572 (w), 424 (w), 408 (w) cm-1. Anal. Found (calcd for
C21H54N3Si3Y): C, 40.4 (48.3); H, 8.4 (10.4); N, 8.5 (8.1).
Sc{HC(Me2pz)3}(CH2SiMe3)3 (3). To a yellow solution of
Sc(CH2SiMe3)3(THF)2 (0.100 g, 0.24 mmol) in benzene (10 mL)
was added a solution of HC(Me2pz)3 (0.070 g, 0.24 mmol) in
benzene (5 mL) to give an orange solution. After the mixture
was stirred at room temperature for 4 h, the volatiles were
removed under reduced pressure to give an orange solid, which
was washed with benzene (2 × 10 mL) to afford 3 as a pale
orange solid. Yield: 0.09 g (65%). Diffraction-quality crystals
were grown from a toluene-pentane mixture. 1H NMR
(C6D6, 500.0 MHz, 298 K): 7.03 (1H, s, HC(Me2pz)3), 5.21 (3H,
s, 4-N2C3Me2H), 2.66 (9H, s, 5-N2C3Me2H), 1.35 (9H, s,
3-N2C3Me2H), 0.60 (6H, s, ScCH2), 0.27 (27H, s, SiMe3) ppm.
13C{1H} NMR (C6D6, 500.0 MHz, 298 K): 154.2 (5-N2C3Me2H),
137.7 (3-N2C3Me2H), 107.8 (4-N2C3Me2H), 67.5 (HC(Me2pz)3),
38.2 (ScCH2), 16.3 (5-N2C3Me2H), 10.2 (3-N2C3Me2H), 4.8
(SiMe3) ppm. IR (NaCl plates, Nujol): 1562 (w), 1412 (w), 1321
(w), 1261 (s), 1093 (s), 1021 (s), 863 (w), 863 (w), 801 (s), 701
(w) cm-1. Anal. Found (calcd for C28H55N6ScSi3): C, 50.3 (55.6);
H, 7.7 (9.2); N, 13.7 (13.9).
Sc{HC(Me2pz)3}Cl3 (5). A suspension of ScCl3 (0.057 g,
0.38 mmol) in THF (10 mL) was refluxed for 10 min to give a
colorless solution, which was cooled. To this was added a yellow
solution of HC(Me2pz)3 (0.110 g, 0.38 mmol) in THF (10 mL),
and the mixture was stirred at room temperature for 4 h. The
resultant white solid was filtered away from the colorless
1
solution and dried to afford 5. Yield: 0.14 g (77%). H NMR
(CD2Cl2, 500.0 MHz, 298 K): 7.91 (1H, s, HC(Me2pz)3), 6.09
(3H, s, 4-N2C3Me2H), 2.72 (9H, s, 5-N2C3Me2H), 2.54 (9H, s,
3-N2C3Me2H). 13C{1H} NMR (CD2Cl2, 125.5 MHz, 298 K):
158.6 (5-N2C3Me2H), 142.2 (3-N2C3Me2H), 111.0 (4-N2C3Me2H),
70.2 (HC(Me2pz)3) 17.5 (5-N2C3Me2H), 13.3 (3-N2C3Me2H). IR
(NaCl plates, Nujol): 1619 (w), 1563 (m), 1413 (w), 1305 (w),
1261 (m), 1065 (m), 1044 (m), 910 (w), 862 (w), 706 (w), 407
(w) cm-1. Anal. Found (calcd for C16H22N6ScCl3‚1.1THF): C,
46.2 (46.3); N, 15.7 (15.9); H, 6.4 (5.9). EI+ MS: m/z 413 [M -
Cl]+, 60%.
Y{HC(Me2pz)3}Cl3 (6). To a suspension of YCl3 (0.048 g,
0.25 mmol) in THF (10 mL) was added a solution of HC(Me2-
pz)3 (0.080 g, 0.25 mmol) in THF (10 mL) at room temperature.
The mixture was stirred at room temperature for 16 h,
resulting in a white precipitate and yellow supernatant. Fil-
tration afforded [YCl3{HC(Me2pz)3}] as a white solid. Yield:
0.09 g (74%). 1H NMR (CD2Cl2, 500.0 MHz, 298 K): 7.91 (1H,
s, HC(Me2pz)3), 6.08 (3H, s, 4-N2C3Me2H), 2.65 (9H, s,
3-N2C3Me2H), 2.52 (9H, s, 5-N2C3Me2H). 13C{1H} NMR (CD2-
Cl2, 125.7 MHz, 298 K): 156.1 (3-N2C3Me2H), 140.9 (5-N2C3-
Me2H), 108.7 (4-N2C3Me2H), 67.9 (HC(Me2pz)3), 14.0 (3-
N2C3Me2H), 10.5 (5-N2C3Me2H). IR (NaCl plates, Nujol): 1562
(m), 1413 (m), 1304 (m), 1261 (m), 1064 (m), 1042 (m), 905
(m), 861 (m), 801 (m), 706 (m) cm-1. Anal. Found (calcd for
C16H22Cl3N6Y‚1.1THF): C, 42.7 (42.8); N, 14.8 (14.7); H, 5.7
(5.4). EI+ MS: m/z 456 [M - Cl - H]+, 70%; 457 [M - Cl]+,
50%.
Sc{HC(iPrpz)3}Cl3 (7). A suspension of ScCl3(THF)3 (0.100
g, 0.272 mmol) in THF (20 mL) was refluxed for 30 min to
give a colorless solution, which was then cooled. To this was
added a 0.15 M solution of HC(iPrpz)3 (0.272 mmol) in benzene.
The reaction mixture was stirred at room temperature for ca.
12 h, during which time a white precipitate formed. The
reaction volume was then reduced to ca. 10 mL, and pentane
(10 mL) was added. The precipitate was isolated and dried to
afford 7 as a white solid. Yield: 0.085 g (64%). 1H NMR
(C5D5N, 300.0 MHz, 298 K): 9.122 (1H, s, HC(3-iPrpz)3), 7.915
(3H, d, 3J ) 2.6 Hz, HC(NCHCHC(iPr)N)3), 6.275 (3H, d, 3J )
2.4 Hz, HC(NCHCHC(iPr)N)3), 2.95 (3H, sept., 3J ) 3.1 Hz,
Me2CH), 1.18 (18H, d, 3J ) 7.0 Hz, HCMe2). 13C NMR (C5D5N,
75 MHz, 298 K): 161.2 (HC(NCHCHC(iPr)N)3), 130.9 (HC-
(NCHCHC(iPr)N)3), 104.79 (HC(NCHCHC(iPr)N)3), 84.04 (HC(3-
iPrpz)3), 28.53 (Me2CH), 22.91 (Me2CH). IR (NaCl plates,
Nujol): 1529 (w), 1461 (m), 1377 (m), 1243 (m), 1018.8 (m),
856 (w), 801 (m) cm-1. Anal. Found (calcd for C19H28N6Cl3Sc):
C, 46.6 (46.4); N, 17.1 (17.1); H, 5.8 (5.7).
Y{HC(Me2pz)3}(CH2SiMe3)3 (4). To a colorless solution of
Y(CH2SiMe3)3(THF)2 (0.370 g, 0.74 mmol) in benzene (10 mL)
was added a solution of HC(Me2pz)3 (0.220 g, 0.74 mmol) in
benzene (10 mL). The resulting dark brown solution was
allowed to stir at room temperature for 1 h. The volume of
the solution was reduced to 10 mL and hexane (30 mL) was
added resulting in the formation of a brown precipitate which
Y{HC(iPrpz)3}Cl3 (8). A suspension of YCl3(THF)3 (0.500
g, 1.22 mmol) in THF (50 mL) was refluxed for 30 min to give
a colorless solution, which was then cooled. To this was added
(56) Putzer, M. A.; Bartholomew, G. P. Z. Anorg. Allg. Chem. 1999,
625, 1777.

3146 Organometallics, Vol. 24, No. 13, 2005
Tredget et al.
a 0.15 M solution of HC(iPrpz)3 in benzene (1.22 mmol), and
the resulting mixture was stirred at 40 °C for 4 days to give a
white precipitate. The reaction mixture was reduced in volume
to ca. 20 mL, and pentane (25 mL) was added. The white
precipitate was isolated by filtration and dried to afford 8 as
a white solid. Yield: 0.490 g (75%). 1H NMR (C5D5N, 500.0
MHz, 298 K): 9.10 (1H, s, HC(3-iPrpz)3), 7.91 (3H, d, 3J ) 2.3
Hz, HC(NCHCHC(iPr)N)3), 6.27 (3H, d, 3J ) 2.7 Hz, HC-
(NCHCHC(iPr)N)3), 2.93 (1H, sept, 3J ) 3.1 Hz, Me2CH), 1.40
(18H, d, 3J ) 6.7 Hz, HCMe2). 13C NMR (C5D5N, 75 MHz, 298
K): 160.3 (HC(NCHCHC(iPr)N)3), 130.0 (HC(NCHCHC(i-
Pr)N)3), 103.9 (HC(NCHCHC(iPr)N)3), 83.2 (HC(3-iPrpz)3), 27.7
(Me2CH), 22.0 (Me2CH). IR (NaCl plates, Nujol): 1530 (m),
1460 (m), 1331 (w), 1240 (m), 1198 (w), 1083 (m), 1018 (m),
853 (w) cm-1. Anal. Found (calcd for C19H28N6Cl3Y): C, 42.7
(42.6); N, 15.7 (15.7); H, 5.7 (5.3).
(w) cm-1. Anal. Found (calcd for C16H24N6SiCl3Y‚CH2Cl2): C,
33.3 (33.5); N, 13.6 (13.8); H, 4.3 (4.3). EI+ MS: m/z 523 [M]+,
1%.
Sc(Me3[6]aneN3)(CH2SiMe3)3 (12). To a solution of Sc-
(CH2SiMe3)3(THF)2 (400 mg, 0.887 mmol) in cold (0 °C) toluene
(20 mL) was added dropwise a solution of Me3(6)aneN3 (125
µL, 0.887 mmol) in toluene (10 mL). The reaction mixture was
stirred at for 3 h at 0 °C, after which time the volatiles were
removed under reduced pressure to afford 12 as a pale yellow
1
solid. Yield: 313 mg (80%). H NMR (C6D6, 300.0 MHz, 293
K): 3.32 (3 H, d, J ) 9.0 Hz, NCH2), 1.82 (3 H, d, J ) 8.8 Hz,
NCH2), 1.61 (9 H, s, NCH3), 0.45 (27 H, s, SiMe3), -0.21 (6 H,
s, CH2SiMe3). 13C{1H} NMR: (C6D6, 75.0 MHz, 293 K): 76.6
(NCH2), 38.5 (NCH3), 4.5 (SiMe3) (CH2SiMe3 not observed). IR
(NaCl plates, Nujol): 1468 (m), 1268 (s), 1235 (s), 1169 (m),
1117 (s), 1015 (m), 940 (m), 864 (s), 745 (m), 670 (m) cm-1
.
EI-MS: m/z 348 (100%) [M - CH2SiMe3]+, 261 (40%) [M - 2
CH2SiMe3]+. Anal. Found (calcd for C18H48N3ScSi3): C, 49.5
(49.6); H, 11.1 (11.1); N, 9.6 (9.6).
Sc{HC(Me2pz)3}(OAr)3 (9). To a pale orange solution of 3
(0.110 g, 0.18 mmol) in THF (10 mL) was added a solution of
2,6-dimethylphenol (0.060 g, 0.53 mmol) in THF (10 mL) at
room temperature. The mixture was stirred at room temper-
ature for 2 h, and the volume was reduced to 5 mL. Pentane
(15 mL) was added and a white solid formed. Filtration
afforded 9 as a white solid. Yield: 0.10 g (81%). 1H NMR (CD2-
Cl2, 500.0 MHz, 253 K): 7.88 (1H, s, HC(Me2pz)3), 6.83 (2H,
d, 3J ) 7.1 Hz, m-OC6H3Me2 “down”), 6.63 (2H, d, 3J ) 7.1
Y(Me3[6]aneN3)(CH2SiMe3)3 (13). To a solution of YCH2-
SiMe3)3(THF)2 (150 mg, 0.303 mmol) in cold (0 °C) toluene (20
mL) was added dropwise a solution of Me3(6)aneN3 (42 µL,
0.303 mmol) in toluene (10 mL). The reaction mixture was
stirred at for 3 h at 0 °C, after which time the volatiles were
removed under reduced pressure to afford 13 as a pale yellow
1
solid. Yield: 100 mg (68%). H NMR (C6D6, 300.0 MHz, 293
3
Hz, m-OC6H3Me2 “up”), 6.34 (1H, apparent t, apparent J )
2
2
K): 3.28 (3 H, d, J ) 9.5 Hz, NCH2), 1.77 (3 H, d, J ) 8.2
Hz, NCH2), 1.59 (9 H, s, NCH3), 0.46 (27 H, s, SiMe3), -0.62
(6 H, d, JHY ) 2.6 Hz, CH2SiMe3). 13C{1H} NMR: (C6D6, 75.0
MHz, 293 K): 76.5 (NCH2), 38.6 (NCH3), 36.2 (CH2SiMe3, JCY
) 34.7 Hz), 4.8 (SiMe3) ppm. IR (NaCl plates, Nujol): 1456
(m), 1113 (m), 939 (w), 859 (s), 667 (m) cm-1. EI-MS: m/z 392.1
(27%) [M - CH2SiMe3]+, 304 (25%) [M - 2CH2SiMe3]+. Anal.
Found (calcd for C18H48N3Si3Y): C, 45.0 (45.0); H, 10.0 (10.1);
N, 8.6 (8.8).
7.1 Hz, p-OC6H3Me2), 5.87 (3H, s, 4-N2C3Me2H), 2.54 (9H, s,
5-N2C3Me2H), 2.48 (9H, s, OC6H3Me2 “down”), 1.88 (9H, s,
3-N2C3Me2H), 1.19 (9H, s, OC6H3Me2 “up”). 13C{1H} NMR (CD2-
Cl2, 125.7 MHz, 253 K): 162.5 (ipso-OC6H3Me2), 155.1 (3-N2C3-
Me2H), 138.4 (5-N2C3Me2H), 127.6 (o-OC6H3Me2 “down”), 127.4
(o-OC6H3Me2 “up”), 114.9 (p-OC6H3Me2), 108.1 (4-N2C3Me2H),
67.2 (HC(Me2pz)3), 18.4 (OC6H3Me2 “down”), 16.3 (OC6H3Me2
“up”), 12.9 (3-N2C3Me2H), 11.0 (5-N2C3Me2H). IR (NaCl plates,
Nujol): 2852 (s), 2316 (w), 1590 (m), 1563 (m), 1378 (m), 1304
(m), 1260 (s), 1238 (w), 1092 (m), 1042 (w), 867 (w), 800 (m)
cm-1. Anal. Found (calcd for C40H49N6O3Sc): C, 68.0 (68.0);
N, 11.8 (11.9); H, 6.9 (7.0). FI+ MS: m/z 706 [M]+, 10%.
Sc{MeSi(Me2pz)3}Cl3 (10). To a slurry of ScCl3(THF)3
(0.100 g, 0.277 mmol, 1.0 equiv) in toluene (10 mL), a solution
of MeSi(Me2pz)3 (0.089 g, 0.277 mmol, 1.0 equiv) in toluene
(10 mL) was added. The reaction mixture was stirred at room
temperature for ca. 15 h, during which time a white precipitate
was formed. The white solid was isolated by filtration, wash-
ed with toluene, and dried to give 10 as a white solid. Yield:
106 mg (79%). 1H NMR (CD2Cl2, 300 MHz, 298 K): 6.11 (3H,
s, 4-N2C3Me2H), 2.85 (9H, s, 3- N2C3Me2H), 2.44 (9H, s,
5-N2C3Me2H), 1.65 (3H, s, MeSi(Me2pz)3). 13C{1H} NMR (CD2-
Cl2, 75 MHz, 298 K): 161.98 (3-N2C3Me2H), 149.36 (5-N2C3-
Me2H), 113.00 (4-N2C3Me2H), 16.89 (3-N2C3Me2H), 14.70 (5-
N2C3Me2H), 1.30 (MeSi(Me2pz)3). IR (NaCl plates, Nujol): 3135
(w), 3098 (w), 1602 (w), 1567 (s), 1451 (s), 1276 (m), 1295 (s),
1035 (s), 985 (m), 803 (s), 739 (m) cm-1. Anal. Found for C16H24-
Cl3N6ScSi‚0.9C7H8: C, 47.5 (47.6); N, 14.7 (14.9); H, 5.6 (5.6).
Y{MeSi(Me2pz)3}Cl3 (11). To a slurry of YCl3(THF)3 (0.100
g, 0.243 mmol, 1.0 equiv) in toluene (10 mL) was added a
solution of MeSi(Me2pz)3 (0.080 g, 0.243 mmol, 1.0 equiv) in
toluene (10 mL). The reaction mixture was stirred at room
temperature for ca. 15 h, during which time a white precipitate
was formed. The white solid was isolated by filtration, washed
with toluene, and dried. A residual impurity was removed by
sublimation to leave 11 as a white solid. Yield: 68 mg (54%).
1H NMR (CD2Cl2, 300 MHz, 298 K): 6.03 (3H, s, 4-N2C3Me2H),
2.68 (9H, s, 3- N2C3Me2H), 2.34 (9H, s, 5-N2C3Me2H), 1.53 (3H,
s, MeSi(Me2pz)3). 13C{1H} NMR (CD2Cl2, 75 MHz, 298 K):
161.46 (3-N2C3Me2H), 150.39 (5-N2C3Me2H), 112.68 (4-N2C3-
Me2H), 15.93 (3-N2C3Me2H), 14.76 (5-N2C3Me2H), 1.59 (MeSi-
(Me2pz)3). IR (NaCl plates, Nujol): 3277 (w), 1564 (m), 1457
(s), 1377 (m), 1323 (w), 1263 (s), 1147 (s), 983 (w), 799 (s), 729
Sc(Me3[6]aneN3)Cl3 (14). To a solution of ScCl3(THF)3 (125
mg, 0.395 mmol) in MeCN (5 mL) was added Me3[6]aneN3
(47.7 µL, 0.395 mmol). The reaction mixture was stirred at
room temperature for 3 h. Pentane (10 mL) was added and
the resulting solid isolated by filtration to afford 14 as a white
solid. Yield: 64 mg (66%). Diffraction-quality crystals were
grown from a saturated dichloromethane solution. 1H NMR
2
(CD2Cl2, 300 MHz, 293 K): 4.23 (3 H, d, J ) 8.8 Hz, NCH2),
3.52 (3 H, s, 2J ) 7.6 Hz, NCH2), 2.57 (9 H, s, NCH3) ppm.
13C{1H} NMR (CD2Cl2, 75 MHz, 293 K): 76.98 (NCH2), 39.58
(NCH3) ppm. IR (NaCl plates, Nujol): 1113 (s), 1181 (m), 936
(m) cm-1. EI-MS: m/z 244 (35%) [M - Cl]+, 209 (3%) [M - 2
Cl]+, 129 (30%). Anal. Found (calcd for C6H15Cl3N3Sc): C, 25.7
(25.7); H, 5.4 (5.4); N, 14.6 (14.9).
Sc(L1)(CH2SiMe3)2 (15). To a solution of Sc(CH2SiMe3)3-
(THF)2 (280 mg, 0.62 mmol) in cold (7 °C) benzene (20 mL)
was added dropwise a solution of HL1 (232 mg, 0.62 mmol) in
cold benzene. The solution was warmed to room temperature
and stirred for a further 1 h. The volatiles were removed under
reduced pressure to afford 15 as a pale yellow solid. Yield: 252
mg (68%). 1H NMR (C6D6, 500.0 MHz, 293 K): 7.60 (1H, d, 4J
t
4
t
) 1.9 Hz, 4-C6H2 Bu2), 7.00 (1H, d, J ) 1.9 Hz, 6-C6H2 Bu2),
2
2
4.49 (1H, d, J ) 12.2 HzCH2Ar), 3.15 (1H, td, J ) 10.8 Hz,
3J ) 5.6 Hz, NCH2CH2N), 3.05 (1H, td, 2J ) 10.8 Hz, 3J ) 5.6
Hz, NCH2CH2N), 2.87 (1H, d, J ) 12.2 Hz, CH2Ar), 2.50 (3H,
s, NMe), 2.14-1.22 (9H, overlapping m, NCH2CH2N), 2.10 (3H,
s, NMe), 1.80 (9H, s, CMe3), 1.35 (9H, s, CMe3), 0.89 (1H, d, J
) 12.4 Hz, NCH2CH2N), 0.46 (9H, s, SiMe3), 0.34 (9H, s,
SiMe3), -0.20 (1H, d, J ) 11.5 Hz, ScCH2), -0.29 (1H, d, J )
11.5 Hz, ScCH2), -0.36 (1H, d, J ) 11.5 Hz, ScCH2), -0.50
(1H, d, J ) 11.5 Hz, ScCH2). 13C{1H} NMR: (C6D6, 125.7 MHz,
t
t
293 K): 161.5 (2-C6H2 Bu2), 137.4 (3- or 5-C6H2 Bu2), 136.2 (5-
t
t
t
or 3-C6H2 Bu2), 125.4 (6-C6H2 Bu2), 124.5 (4-C6H2 Bu2), 124.1
(1-C6H2 Bu2), 64.3 (NCH2Ar), 58.8 (NCH2CH2N), 57.6 (NCH2-
t
CH2N), 55.8 (NCH2CH2N), 52.5 (NCH2CH2N), 52.3 (NCH2-
CH2N), 50.3 (NMe), 49.7 (NMe), 49.1 (NCH2CH2N), 35.6

Sc and Y Complexes with Neutral N3 Donor Ligands
Organometallics, Vol. 24, No. 13, 2005 3147
Table 8. X-ray Data Collection and Processing Parameters for Sc(Me3[9]aneN3)(CH2SiMe3)3 (1),
Sc{HC(Me2Pz)3}(CH2SiMe3)3‚2C7H8 (3‚2C7H8), Y{HC(Me2Pz)3}(CH2SiMe3)3 (4), Sc{HC(Me2Pz)3}(OAr)3‚4C6H6
(9‚4C6H6), Y{MeSi(Me2Pz)3}Cl3‚CH2Cl2 (11‚CH2Cl2), and Sc(Me3[6]aneN3)Cl3 (14)and Sc(L2)(OTol)2‚C6H6
(18‚C6H6)
1
3‚2C7H8
4
9‚4C6H6
11‚CH2Cl2
14
18‚C6H6
empirical
formula
fw
temp/K
wavelength/Å
space group
a/Å
C
21H54N3Sc-
C
28H55N6ScSi3
C
28H55N6Si3Y
C40H49N6O3-
Sc‚4C6H6
1019.29
150
0.710 73
P31c
14.7505(6)
14.7505(6)
15.4170(4)
90
90
120
2905.0(2)
2
C
16H24Cl3N6-
C6H15Cl3-
N3Sc
280.52
150
0.710 73
P21/m
7.5676(2)
12.1539(4)
7.8780(2)
90
118.5146(14)
90
636.69(3)
2
C
37H54N3O3-
Si3‚2C17H8
SiY‚CH2Cl2
Sc‚C6H6
477.89
150
0.710 73
P21/c
19.2407(2)
18.5432(2)
18.6490(2)
90
115.6548(5)
90
5997.74(11)
8
1.058
0.377
789.28
150
0.710 73
P21/c
12.4871(2)
16.0885(2)
24.0879(3)
90
101.2652(4)
90
4745.99(11)
4
1.105
0.264
648.95
150
0.710 73
P1h
11.0526(2)
11.6252(2)
17.1350(3)
81.8126(9)
85.5181(8)
71.3772(7)
2063.86(6)
2
608.69
150
0.710 73
P21/n
10.0211(1)
30.7707(3)
16.9809(2)
90
95.1016(3)
90
5215.42(10)
8
1.550
2.812
711.93
150
0.71073
P21/c
13.3324(5)
14.1401(7)
21.400(1)
90
90.670(3)
90
4034.0(9)
4
1.17
0.22
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
d(calcd)/Mg m-3
abs coeff/mm-1
R indicesa
R1
1.044
1.522
1.165
0.18
1.463
1.172
0.0349
0.0418
0.0452
0.0536
0.0489
0.0529
0.0507
0.0557
0.0373
0.0428
0.0271
0.0379
0.0658
0.0636
wR2
2
a R indices with I > nσ(I); n ) 3 except for 18‚C6H6, where n ) 2. R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑w(|Fo| - |Fc|)2/∑(w|Fo| )}1/2
.
(CMe3), 34.2 (CMe3), 32.1 (CMe3), 30.8 (CMe3), 4.7 (SiMe3), 4.4
(SiMe3), 1.4 (ScCH2). IR (KBr plates, Nujol): 1605 (s), 1317
(m), 1286 (s), 1261 (m), 1235 (s), 1104 (s), 1017 (m), 879 (s),
813 (m), 773 (m), 749 (m), 723 (m), 667 (w), 548 (w), 475 (w)
cm-1. EI-HRMS for [Sc(L1)(CH2SiMe3)]+: found (calcd for
C27H51N3OScSi) m/z 506.3348 (506.3361). Anal. Found (calcd
for C31H62N3OScSi2): C, 60.0 (62.7); H, 9.3 (10.5); N, 6.2 (7.1).
Sc(L2)(CH2SiMe3)2 (16). To a stirred solution of Sc(CH2-
SiMe3)3(THF)2 (119 mg, 0.29 mmol) in cold (7 °C) benzene (15
mL) was added a solution of HL2 (123 mg, 0.29 mmol) in cold
benzene (15 mL). The solution was warmed to room temper-
ature and stirred for 30 min. The volatiles were removed under
reduced pressure to afford 16 as a pale yellow solid. Yield: 96
mg (51%). 1H NMR (C6D6, 500.0 MHz, 293 K): 7.6 (1H, d, J )
to afford 17 as a white solid. Yield: 62 mg (38%). 1H NMR
(C6D6, 500.0 MHz, 293 K): 8.44 (2 H, d, J ) 7.3 Hz, 2-C6H5),
t
8.15 (2 H, d, J ) 7.3 Hz, 2-C6H5), 7.63 (1 H, s, 4-C6H2 Bu2),
7.49 (2 H, t, J ) 7.3 Hz, 3-C6H5), 7.35 (1 H, t, J ) 7.3 Hz,
4-C6H5), 7.29 (2 H, t, J ) 7.3 Hz, 3-C6H5), 7.16 (1 H, t, J ) 7.3
t
Hz, 4-C6H5), 6.92 (1 H, s, 6-C6H2 Bu2), 4.53 (1 H, d, J ) 12.2
Hz, NCH2Ar), 3.36 (1 H, m, NCH2CH2N), 3.27 (1 H, m, NCH2-
CH2N), 2.68 (3 H, s, NMe), 2.55 (1 H, d, J ) 12.2 Hz, NCH2-
Ar), 2.20-1.20 (9 H, overlapping m, NCH2CH2N), 2.00 (3 H,
s, NMe), 1.87 (9 H, s, CMe3), 1.39 (9 H, s, CMe3), 0.93 (1 H, m,
NCH2CH2N). 13C{1H} NMR (C6D6, 75.5 MHz, 293 K): 161.3
t
(2-C6H2 Bu2), 138.6 (2-C6H5), 138.0 (2-C6H5), 137.9 (3- or
t
t
5-C6H2 Bu2), 136.5 (5- or 3-C6H2 Bu2), 126.6 (3-C6H5), 126.5 (3-
t
C6H5), 125.5 (4-C6H5), 125.4 (4-C6H5), 125.0 (6-C6H2 Bu2), 124.5
t
t
t
t
(4-C6H2 Bu2), 124.3 (1-C6H2 Bu2), 64.6 (NCH2Ar), 58.9 (NCH2-
CH2N), 57.5 (NCH2CH2N), 56.0 (NCH2CH2N), 53.0 (NMe), 52.4
(NMe), 49.9 (NCH2CH2N), 49.5 (NCH2CH2N), 35.7 (CMe3), 34.2
(CMe3), 32.2 (CMe3), 30.6 (CMe3) ppm (not observed: 2 ×
1-C6H5). IR (KBr pellet, cm-1): 3038 (w), 2952 (s), 2902 (s),
2864 (s), 2826 (w), 1724 (w), 1700 (w), 1602 (w), 1476 (s), 1438
(m), 1412 (m), 1384 (m), 1362 (m), 1314 (s), 1284 (s), 1262 (m),
1240 (m), 1202 (w), 1168 (w), 1136 (w), 1104 (w), 1105 (m),
1006 (m), 992 (m), 878 (w), 840 (m), 810 (w), 800 (w), 772 (w),
722 (w), 706 (m), 680 (m), 634 (w), 610 (w), 546 (m), 504 (w),
490 (w), 472 (w), 440 (w), 422 (w), 408 (w) cm-1. Anal. Found
(calcd for C35H50N3OSc‚0.4C6H6): C, 74.4 (74.3); H, 8.9 (8.7);
N, 7.2 (7.0).
2.4 Hz, 4-C6H2 Bu2), 7.0 (1H, d, J ) 2.2 Hz, 6-C6H2 Bu2), 4.7
(1H, d, J ) 12.7 HzNCH2Ar), 3.78 (1H, app sept, J ) 5.6 Hz,
CHMe2), 3.33 (1H, app sept, J ) 6.5 Hz, CHMe2), 3.14 (1H,
m, NCH2CH2N), 2.90 (1H, d, J ) 12.7 Hz, NCH2Ar), 2.48 (2H,
m, NCH2CH2N), 2.14-1.34 (9H, overlapping m, NCH2CH2N),
1.86 (9H, s, CMe3), 1.40 (3H, d, J ) 6.4 Hz, CHMe2), 1.37 (9H,
s, CMe3), 0.72 (3H, d, J ) 6.6 Hz, CHMe2), 0.57 (3H, d, J )
6.3 Hz, CHMe2), 0.48 (9H, s, SiMe3), 0.40 (3H, d, J ) 6.4 Hz,
CHMe2), 0.24 (9H, s, SiMe3), -0.01 (1H, d, 2J ) 11.2 Hz,
2
2
ScCH2), -0.09 (1H, d, J ) 11.2 Hz, ScCH2), -0.19 (1H, d, J
) 11.2 Hz, ScCH2), -0.30 (1H, d, J ) 11.2 Hz, ScCH2). 13C-
2
{1H} NMR (C6D6, 125.7 MHz, 293 K): 160.1 (2-C6H2 Bu2),
t
t
t
t
137.4 (3-C6H2 Bu2), 136.4 (5-C6H2 Bu2), 124.6 (6-C6H2 Bu2),
t
t
Sc(L1)(OTol)2 (18). To a stirred solution of Sc(L1)(CH2-
SiMe3)2 (15; 90 mg, 0.14 mmol) in cold (7 °C) benzene (20 mL)
was added dropwise TolOH (20 mg, 0.28 mmol) in cold benzene
(20 mL). The solution was warmed to room temperature and
stirred for 1 h before removing the volatiles under reduced
pressure to afford 18 as a white powder. Yield: 40 mg (49%).
Diffraction-quality crystals were grown from a saturated
124.5 (4-C6H2 Bu2), 123.9 (1-C6H2 Bu2), 65.8 (NCH2Ar), 56.0
(CHMe2), 55.1 (CHMe2), 54.6 (NCH2CH2N), 54.2 (NCH2CH2N),
51.7 (NCH2CH2N), 43.1 (NCH2CH2N), 42.8 (NCH2CH2N), 35.8
(CMe3), 34.2 (CMe3), 32.1 (CMe3), 31.4 (CMe3), 23.4 (CHMe2),
21.2 (CHMe2), 14.1 (CHMe2), 13.9 (CHMe2), 4.8 (SiMe3), 4.3
(SiMe3) ppm (not observed: 2 × ScCH2). IR (KBr pellet): 2948
(s), 2900 (s), 2866 (m), 2818 (w), 1604 (w), 1478 (s), 1440 (m),
1414 (m), 1384 (m), 1362 (m), 1312 (s), 1286 (m), 1264 (w),
1236 (m), 1204 (w), 1160 (w), 1148 (w), 1134 (w), 1118 (w),
1080 (w), 1062 (w), 1016 (w), 968 (w), 948 (w), 900 (m), 876
(s), 844 (s), 812 (m), 748 (m), 730 (m), 666 (m), 646 (w), 598
(w), 586 (w), 546 (m), 466 (w), 452 (w), 404 (w) cm-1, EI-MS:
m/z 649 (50%) [M]+. Anal. Found (calcd for C35H70N3OScSi2):
C, 63.3 (64.7); H, 10.9 (10.9); N, 6.5 (6.5).
1
benzene solution at room temperature. H NMR (C6D6, 500.0
t
MHz, 293 K): 7.59 (1 H, d, J ) 2.4 Hz, 4-C6H2 Bu2), 7.14 (2 H,
m, C6H4Me), 7.08 (2 H, d, J ) 6.3 Hz, C6H4Me), 6.98-6.92 (5
t
H, overlapping m, 6-C6H2 Bu2, C6H4Me), 4.55 (1 H, d, J ) 12.7
2
3
Hz, CH2Ar), 3.34 (1 H, td, J ) 12.7 Hz, J ) 5.4 Hz, NCH2-
CH2N), 2.95 (1 H, td, 2J ) 12.7 Hz, 3J ) 5.4 Hz, NCH2CH2N),
2.87 (1 H, d, J ) 12.7, CH2Ar), 2.50 (3 H, s, NMe), 2.26 (3 H,
s, C6H4Me), 2.25 (3 H, s, C6H4Me), 2.24-1.24 (9 H, m, NCH2-
CH2N), 2.15 (3 H, s, NMe), 1.77 (9 H, s, CMe3), 1.40 (9 H, s,
CMe3), 1.05 (1 H, d, J ) 10.3 Hz, NCH2CH2N). 13C{1H} NMR
(C6D6, 125.7 MHz, 293 K): 163.3 (1-C6H4Me), 163.0 (1-C6H4-
Sc(L1)Ph2 (17). To a stirred solution of ScPh3(THF)2 (115
mg, 0.27 mmol) in cold (7 °C) benzene (15 mL) was added a
solution of HL2e (102 mg, 0.27 mmol) in cold benzene (15 mL).
The solution was warmed to room temperature and stirred for
30 min. The volatiles were removed under reduced pressure
t
t
Me), 161.4 (2-C6H2 Bu2), 137.1 (3- or 5-C6H2 Bu2), 136.5 (5- or

3148 Organometallics, Vol. 24, No. 13, 2005
Tredget et al.
t
3-C6H2 Bu2), 130.2 (4-C6H4Me), 128.2 (4-C6H4Me), 125.4 (4-
eters of all non-hydrogen atoms were refined. Hydrogen atoms
were positioned geometrically, except for the CH2SiMe3 atoms
of 1 and 3, which were located from Fourier difference
syntheses and positionally and isotropically refined.
t
t
C6H2 Bu2), 125.0 (C6H4Me), 124.7 (6-C6H2 Bu2), 124.4 (C6H4-
Me), 123.7 (1-C6H2 Bu2), 119.5 (C6H4Me), 119.3 (C6H4Me), 64.3
t
(NCH2Ar), 57.8 (NCH2CH2N), 56.1 (NCH2CH2N), 56.0 (NCH2-
CH2N), 52.6 (NCH2CH2N), 51.5 (NCH2CH2N), 48.7 (NCH2-
CH2N), 48.5 (NMe), 48.1 (NMe), 35.6 (CMe3), 34.2 (CMe3), 32.2
(CMe3), 30.6 (CMe3), 20.9 (C6H4Me), 20.8 (C6H4Me). IR (KBr
plates, Nujol): 1606 (s), 1504 (s), 1414 (m), 1350 (w), 1286 (s),
1260 (m), 1204 (w), 1164 (m), 1102 (m), 1074 (m), 1008 (m),
992 (w), 876 (s), 840 (m), 808 (m), 770 (m), 746 (m), 722 (m),
544 (s), 516 (w), 470 (w), 422 (w), 404 (w) cm-1. EI-HRMS for
[Sc(L2)(OTol)]+: found (calcd for C30H47N3O2Sc) m/z 526.3204
(526.3227). A satisfactory combustion analysis was not ob-
tained, even from the single crystals.
Crystal Structure Determinations of Sc(Me3[9]aneN3)-
(CH2SiMe3)3 (1), Sc{HC(Me2pz)3}(CH2SiMe3)3‚2C7H8 (3‚
2C7H8), Y{HC(Me2pz)3}(CH2SiMe3)3 (4), Sc{HC(Me2pz)3}-
(OAr)3‚4C6H6 (9‚4C6H6), Y{HC(Me2pz)3}Cl3‚CH2Cl2 (11‚
CH2Cl2), Sc(Me3[6]aneN3)Cl3 (14), and Sc(L2)(OTol)2‚C6H6
(18‚C6H6). Crystal data collection and processing parameters
are given in Table 8. Crystals were mounted on a glass fiber
using perfluoropolyether oil and cooled rapidly to 150 K in a
stream of cold N2 using an Oxford Cryosystems CRYOS-
TREAM unit. Diffraction data were measured using an Enraf-
Nonius KappaCCD diffractometer. Intensity data were pro-
cessed using the DENZO-SMN package.57 The structures were
solved using the direct-methods program SIR92,58 which
located all non-hydrogen atoms. Subsequent full-matrix least-
squares refinement was carried out using the CRYSTALS
program suite.59 Coordinates and anisotropic thermal param-
Additional Comments on the Crystal Structures. Crys-
tals of 1 have two crystallographically independent molecules
in the asymmetric unit which adopt very similar geometries.
One of the trimethylsilyl groups (that of Si(3)) of 4 was
disordered, and this was modeled as being due to the presence
of two conformers related by rotation about the Si(3)-C(25)
bond; coordinates, anisotropic displacement parameters, and
site occupancies of the disordered carbon atoms were refined,
subject to restraint of the Si-C bond lengths to 1.90(2) Å and
of the C-Si-C angles to 109.5(2)°; similarly, restraints were
applied to the displacement parameters of the C atoms and
those of Si(3). Moleclues of 14 are located on crystallographic
mirror planes. Crystals of 18‚C6H6 were weak diffractors, and
despite an extended data collection time (36 h), a data to
parameter ratio of only ca. 7:1 (threshold I > 2σ(I)) was
achieved; the C6H6 molecule of crystallization was disordered
and was refined in a rigid-body approximation.
Full listings of atomic coordinates, bond lengths and angles,
and displacement parameters have been deposited at the
Cambridge Crystallographic Data Center. See Notice to Au-
thors, Issue No. 1.
Acknowledgment. We thank the EPSRC and Le-
verhulme Trust for support. S.C.L. is the recipient of a
European Scatcherd Scholarship. C.S.T. thanks St.
Edmund Hall, Oxford, for a Graduate Scholarship.
(57) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode; Methods in Enzymology; Academic
Press: New York, 1997.
(58) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27,
435.
(59) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P.
W.; Cooper, R. I. CRYSTALS, issue 11; Chemical Crystallography
Laboratory, Oxford, U.K., 2001, 2001.
Supporting Information Available: X-ray crystallo-
graphic files in CIF format for the seven structure determina-
tions. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM050209R