Scandium and yttrium complexes of the diamide-diamine donor ligand (2-C5H4N)CH2N(CH2CH2 NSiMe3)2: Chloride, primary and secondary amide, benzamidinate and alkyl functionalised de

Article abstract of DOI:10.1039/b111469g

Five- and six-coordinate scandium and yttrium complexes of the recently described diamide-diamine donor ligand N₂NN′ (where H₂N₂NN′ = (2-C₅H₄N)CH₂N{CH₂CH₂N (H)SiMe

Full text of DOI:10.1039/b111469g

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Scandium and yttrium complexes of the diamide–diamine donor
ligand (2-C5H4N)CH2N(CH2CH2NSiMe3)2: chloride, primary and
secondary amide, benzamidinate and alkyl functionalised
derivatives
Michael E. G. Skinner and Philip Mountford*
Inorganic Chemistry Laboratory, South Parks Road, Oxford, UK OX1 3QR.
E-mail: Philip.Mountford@chem.ox.ac.uk
Received 18th December 2001, Accepted 25th February 2002
First published as an Advance Article on the web 26th March 2002
Five- and six-coordinate scandium and yttrium complexes of the recently described diamide–diamine donor
ligand N2NNЈ (where H2N2NNЈ = (2-C5H4N)CH2N{CH2CH2N(H)SiMe3}2) are described. Reaction of ScCl3
with Li2N2NNЈ gave five-coordinate [ScCl(N2NNЈ)] 1 in excellent yield. The corresponding reaction with YCl3
in tetrahydrofuran (thf ) or pyridine (py) solution afforded “ate” complexes best described as [YCl(N2NNЈ)(L)]ؒ
1.5(LiCl) (L = thf 2 or py 3). The two chloride complexes 1 and 2 are useful starting materials for primary and
secondary amide, benzamidinate and alkyl complexes of Sc and Y supported by the N2NNЈ ligand. Thus reaction of
i
1 or 2 with LiN(SiMe3)2ؒEt2O, LiNMe2 or LiNHR (R = tBu or Ar, where Ar = 2,6-C6H3 Pr2) gave the corresponding
five-coordinate amide derivatives [M(NRRЉ)(N2NNЈ)] (M = Sc, R = RЉ = SiMe3 4 or Me 6, or R = H, RЉ = tBu 8 or Ar
9; M = Y, R = RЉ = SiMe3 5, or R = H, RЉ = Ar 10). The crystal structure of 5 is described. The σ-bond metathesis
reaction of [Sc(NMe2)(N2NNЈ)] 6 with ArFNH2 (ArF = C6F5) gave the corresponding primary flurophenylamide
derivative 7. The reaction of 1 or 2 with Li[PhC(NSiMe3)2] gave the fluxional, six-coordinate benzamidinate
derivatives [M{PhC(NSiMe3)2}(N2NNЈ)] (M = Sc 11 or Y 12), the crystal structures of which are reported.
Finally, reaction of 1 with LiCH2SiMe3 formed the alkyl derivative [Sc(CH2SiMe3)(N2NNЈ)] 13 in
reasonable yield; the crystal structure of 13 is described.
Introduction
While there is an extensive “classic” coordination chemistry of
scandium and yttrium in a wide range of ligand environments,
the organometallic and organometallic-related chemistry of
these Group 3 metals has generally been dominated by com-
pounds with cyclopentadienyl and related ligands.1 For
example, Group 3 metal complexes incorporating the cyclo-
pentadienyl ligand and its homologues can act as catalysts for
polymerisation,2 hydrogenation,3 hydroboration,4 hydrosilyl-
ation5 and hydroamination/cyclisation6 processes. Over the last
five to ten years the organometallic and organometallic-related
chemistry of scandium and yttrium in non-cyclopentadienyl
environments has grown enormously. New (or renewed) ligand
environments include the tetratolylporphyrins,7 tris(pyrazolyl)-
borates,8 variously functionalised benzamidinates,9 N2P2- and
NP2-donors,10 mixed amide–alkoxides,11 oxazolinates,12 and
Chart 1
functionalised triazacyclononanes13 or related macrocycles.14
Of particular relevance to this contribution are Group 3
t
complexes supported by a range of di- and tri-dentate bis(a-
mide) ligands.15 In addition, Scott and co-workers very recently
described Group 3 complexes of certain tetradentate triamide–
amine (“tren”) ligands, both as “ate” complexes I (Chart 1) and
as halide-free, trigonal monopyramidal complexes II obtained
upon high vacuum sublimation.16 Tren ligands have in general
been extremely successful in developing p-block, early- to mid-
transition metal, lanthanide and actinide chemistry.16,17 Despite
these successes, however, as a trianionic moiety the versatility of
this ligand is hampered in certain regards for developing new
lanthanide, and Group 3 since there are no metal electrons
remaining for binding additional anionic ligands in such
M(tren) fragments.
NSiMe2R)2 [R = Me (abbreviated as N2NNЈ) or Bu]18 which
support new five- and six-coordinate, coordination and
organometallic, Groups 4 and 5, singly- and multiply-bonded
complexes, examples of which are given as III and IV in Chart
1. Unlike established dianionic N4-donor ligands such as the
porphyrins19 and dibenzotetraaza[14]annulenes20 which pro-
mote square base pyramidal geometries for five-coordinate
complexes, the tetradentate N2NNЈ ligand gives “tren-like”
trigonal bipyramidal coordination geometries, as well as offer-
ing considerable scope for variation of the ligandЈs steric
and electronic characteristics close to the metal centre by
changing the amide nitrogen substituents. In this paper we
describe new scandium and yttrium complexes of the N2NNЈ
ligand. A preliminary account of part of this work has been
published.18a
As a kind of “dianionic tren” variant we have developed the
diamide–diamine donor ligands (2-C5H4N)CH2N(CH2CH2-
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DOI: 10.1039/b111469g

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free species such as “[YCl(N2NNЈ)]ؒ1.5(LiCl)”. Subsequent
addition of thf to this material resulted in the formation of 2.
Attempts to obtain salt-free compound of the type
[YCl(N2NNЈ)]x from 2 or 3 by high vacuum sublimation at tem-
peratures above 80 ЊC or by solvent extraction or by refluxing
in non-coordinating solvents led to decomposition products.
Alternative routes to compounds of the type [Y(X)(N2NNЈ)]
(X = I or OSO2CF3) from YI3 or Y(OSO2CF3)3 and Li2N2NNЈ
were unsuccessful.
Results and discussion
The dilithiated ligand precursor Li2N2NNЈ (where Li2N2NNЈ =
(2-C5H4N)CH2N{CH2CH2N(Li)SiMe3}2) was prepared in
multi-gram quantities from H2N2NNЈ according to previously
described procedures.18b Eqn. 1 summarises the synthesis of the
scandium and yttrium monochloride derivatives [ScCl(N2NNЈ)]
1 and[YCl(N2NNЈ)(L)]ؒ1.5(LiCl) (L = thf 2 or py 3).
a
The compounds [ScCl(N2NNЈ)] 1 and [YCl(N2NNЈ)(thf )]ؒ
1.5(LiCl) 2 are precursors to new primary or secondary amide,
benzamidinate or (for 1) alkyl complexes by substitution reac-
tions with the appropriate lithiated reagent. The new reactions
are summarised in Scheme 1. For the scandium derivatives it
is possible to start either from previously isolated 1 or from
samples of 1 prepared in situ (the latter method provides the
highest overall yield based on ScCl3). For the yttrium deriv-
atives it is much more convenient to use in situ prepared 2 owing
to the difficulties associated with isolating and handling this
compound.
(1)
Reaction of LiN(SiMe3)2ؒEt2O with thf solutions of 1 or
2 (prepared in situ) at Ϫ78 ЊC gave the pentane-soluble bis(tri-
methylsilylamide) derivatives [M{N(SiMe3)2}(N2NNЈ)] (M = Sc
4 or Y 5) in ca. 65% yields. The dimethylamide derivative
[Sc(NMe2)(N2NNЈ)] 6 was made in a similar way by reaction of
LiNMe2 with [ScCl(N2NNЈ)] 1 in benzene. Attempts to prepare
an yttrium analogue of 6 were unsuccessful, possibly because
the smaller NMe2 group does not allow sufficient steric protec-
tion of the metal centre. Diffraction-quality crystals of 5 were
grown from pentane and its molecular structure is illustrated in
Fig. 1, and selected bond lengths and angles are listed in Table 1.
Thus addition of Li2N2NNЈ to a white suspension of ScCl3 in
thf cooled to Ϫ78 ЊC and subsequent work-up gave 1 as a
well-defined, pentane-soluble cream-coloured powder in 91%
isolated yield. The corresponding reaction of Li2N2NNЈ with
YCl3 (or [YCl3(thf )3]) gave a benzene-soluble material tenta-
tively described as the “ate” complex [YCl(N2NNЈ)(thf )]ؒ
1.5(LiCl) 2 on the basis of its NMR spectra and by comparison
with the better characterised pyridine analogue 3 (vide infra).
Although samples of 2 as first obtained are soluble in
benzene, further handling or attempts to purify this highly
sensitive material led to apparent decomposition and the
formation of insoluble products; a satisfactory elemental
analysis could not be obtained. Speculating that loss of the
comparatively weak donor thf ligand might be a contributing
factor to the behaviour of 2 we prepared the pyridine
analogue from Li2N2NNЈ and YCl3 in pyridine as a solvent.
Subsequent work-up gave better-behaved and -defined
samples of the pentane-soluble “ate” complex formulated as
[YCl(N2NNЈ)(py)]ؒ1.5(LiCl) 3 in 71% yield.
The exact structural formulation of 2 and 3 are unknown as
it was not possible to obtain diffraction-quality crystals of
either compound. The 1H and 13C NMR spectra of 1–3 all show
resonances attributable to a tetra-coordinated N2NNЈ ligand
and the comparative simplicity of the spectra are consistent
with the compounds possessing Cs symmetry. Coordination of
the pyridyl moiety of N2NNЈ to the metal centres in 1–3 is
indicated by the substantial downfield chemical shifts (range
δ 9.33–9.85) of the pyridyl group ortho-hydrogens in com-
parison with that for the “free” protio ligand H2N2NNЈ (δ 8.47)
in the same solvent.18b By 1H NMR integration against the
N2NNЈ resonances there is one equivalent of thf or pyridine for
2 and 3, respectively. The presence of LiCl in 3 was established
Fig. 1 Molecular structure of [Y{N(SiMe3)2}(N2NNЈ)] 5. Displace-
ment ellipsoids are drawn at the 25% probability level. H atoms omitted
for clarity.
7
by Li NMR spectroscopy; the elemental analysis for 3 is also
consistent with the proposed formula. The difference in
behaviour between the five-coordinate, base-free scandium
compound 1 and the yttrium systems 2 and 3 is attributed to the
larger size and higher Lewis acidity of the heavier congener.
The close relationship between 2 and 3 was established by the
addition of an excess of pyridine to the thf adduct 2 which led
immediately to the formation of the pyridine adduct 3: the
sample of 3 prepared in this manner was indistinguishable from
those prepared directly from Li2N2NNЈ and YCl3 in pyridine.
Conversely, heating a sample of 3 to 80 ЊC under high vacuum
(1 × 10Ϫ6 mbar) led to the loss of pyridine and yielded a very
air- and moisture-sensitive pink compound. This could not be
unambiguously identified but is thought to be a Lewis base-
The geometry around the metal centre in 5 may best be
described as distorted trigonal bipyramidal in which the
yttrium metal centre is situated above the equatorial plane
defined by N(1), N(2) and N(3) of the N2NNЈ ligand which, in
turn, is bound in a tetradentate manner. The angle subtended at
Y(1) between the (formally) axial nitrogen atoms is consider-
ably distorted from the ideal value of 180Њ [N(4)–Y(1)–N(5) =
148.72(8)Њ] possibly due to steric interactions between the
trimethylsilyl groups of the N(SiMe3)2 moiety and those of the
N2NNЈ ligand.
The three Y–Namide bond lengths Y(1)–N(1) = 2.235(2) Å,
Y(1)–N(2) = 2.245(2) Å and Y(1)–N(5) = 2.289(2) Å differ only
slightly, although that to N(5) is the longest, possibly due to the
J. Chem. Soc., Dalton Trans., 2002, 1694–1703
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Scheme 1 For the following preparations the compounds 1 or 2 were prepared in situ according to eqn. 1: synthesis of 4, 5, 9, 10, 12. Reagents and
conditions. (i) for R = SiMe3: LiN(SiMe3)2ؒEt2O, thf, Ϫ78 ЊC then rt, 30–60 min, 62 or 67%; for R = Me: LiNMe2, benzene, rt, 61%; (ii) (from 6)
ArFNH2, benzene, rt, 20 min, 74%; (iii) LiCH2SiMe3, benzene, rt, 20 min, 58%; (iv) Li[PhC(NSiMe3)2], benzene (for M = Sc) or thf, rt or Ϫ78 ЊC then
rt, 15 min or 1 h, 83 or 70%; (v) LiNHtBu or LiNHAr, benzene or thf, rt or Ϫ78 ЊC then rt, 10–60 min, 57–76%.
The 1H and 13C NMR data for [Y{N(SiMe3)2}(N2NNЈ)] 5 are
Table 1 Selected bond distances (Å) and angles (Њ) for [Y{N(Si-
Me3)2}(N2NNЈ)] 5
consistent with the solid state structure; those of [Sc{N(Si-
Me3)2}(N2NNЈ)] 4 and [Sc(NMe2)(N2NNЈ)] 6 are analogous to
Y(1)–N(1)
Y(1)–N(2)
Y(1)–N(3)
Y(1)–N(4)
Y(1)–N(5)
2.235(2)
2.245(2)
2.473(2)
2.537(2)
2.289(2)
N(1)–Si(1)
N(2)–Si(2)
N(5)–Si(3)
N(5)–Si(4)
1.711(2)
1.716(2)
1.717(2)
1.703(2)
those of 5 and suggest that these compounds possess similar
structures. The SiMe3 groups of the N(SiMe3)2 ligand in 5 are
inequivalent in the solid, in both 4 and 5 they appear as a singlet
(integrating as 18 H) in the 1H NMR spectra at all temperatures
down to Ϫ80 ЊC implying that there is a low barrier to rotation
about the M–N(SiMe3)2 bonds. While the pyridyl group ortho-
hydrogens of 4 and 5 appear downfield of that in H2N2NNЈ as
is usually observed for bound pyridyl groups, in 6 the resonance
appears at 8.23 ppm, which is 0.24 ppm upfield of that in the
“free ligand”. While this direction of change in chemical shift is
relatively unusual, it has been seen in the zirconium dialkyl
complexes [ZrR2(N2NNЈ)] (R = CH2SiMe3, CH2CMe3 or CH2-
Ph)24 and is likely to be a result of anisotropic shielding effects.
Although Sc and Y compounds with secondary amide
ligands NR2, where R typically has a C or Si atom bound to
nitrogen, are ubiquitous in Group 3 amide chemistry, those
with primary amide ligands N(H)R are considerably less com-
mon (complexes with N–H functionalised amine ligands are
better known, however25). Examples in scandium chemistry are
N(1)–Y(1)–N(2)
N(1)–Y(1)–N(3)
N(2)–Y(1)–N(3)
N(1)–Y(1)–N(4)
N(2)–Y(1)–N(4)
N(3)–Y(1)–N(4)
N(1)–Y(1)–N(5)
N(2)–Y(1)–N(5)
N(3)–Y(1)–N(5)
N(4)–Y(1)–N(5)
112.87(9)
124.76(8)
91.71(8)
72.37(8)
75.91(8)
66.83(7)
109.14(9)
127.20(8)
89.55(8)
148.72(8)
Y(1)–N(1)–Si(1)
Y(1)–N(1)–C(1)
Si(1)–N(1)–C(1)
Y(1)–N(2)–Si(2)
Y(1)–N(2)–C(3)
Si(2)–N(2)–C(3)
Y(1)–N(5)–Si(3)
Y(1)–N(5)–Si(3)
Si(3)–N(5)–Si(4)
129.26(13)
115.28(17)
115.26(18)
133.04(12)
107.99(17)
112.86(18)
123.89(12)
114.42(12)
121.55(13)
presence of two SiMe3 substituents on this atoms. The Y–Namide
distances are similar to those previously observed for five-
coordinated yttrium compounds containing amide donor
atoms [range 2.250(6)–2.353(4) Å].15c,21 The amide nitrogen
atoms N(1), N(2) and N(5) are effectively sp2 hybridised with
the sums of the angles subtended at each of them being in the
range ca. 354–360Њ. The bond length to the pyridyl nitrogen
atom is shorter than that to the sp3 hybridised amine nitrogen
atom as expected. The Y(1)–N(4) bond length is unexceptional
and falls mid-range with regard to published values for
Y–N(sp3) dative bonds.22 With the amide nitrogen atoms all
potentially able to act as three electron donors, the complex
has a maximum formal valence electron count of 16 electrons
(subject to orbital availability).
The protons in closest proximity to the metal centre are
positioned more than ca. 3 Å away from the metal centre. These
distances are significantly longer than would be expected if
C–H ؒ ؒ ؒ Y agostic interactions were present.23 The notion that
no agostic interactions are present in the molecule is further
evidenced by the uniformity of all of the Si–C bond lengths and
the normality of the N–Si–C bond angles.
t
[Sc(η5-C5H5){N(SiMe2CH2PiPr2)2}(NHR)] (R = Bu or Ph)10c
and [Sc{PhC(NSiMe3)2}2(NHAr)] (hereafter Ar = 2,6-C6H3-
iPr2).9e We had speculated that primary amide complexes
[M(NHR)(N2NNЈ)] (M = Sc, Y) might be viable entry points to
anionic imido complexes [M(NR)(N2NNЈ)]Ϫ (imides are as yet
unknown in Group 3 chemistry) which would be isoeletronic
with the neutral Group 4 imido complexes [M(NR)(N2NNЈ)]
(M = Ti, R = tBu or Ar; M = Zr, R = Ar) that we have reported
elsewhere.18a,24 Ultimately our attempts to convert the Group 3
primary complexes [M(NHR)(N2NNЈ)] (vide infra) to the
corresponding amides were unsuccessful, but we nevertheless
report their syntheses and properties here since they are unusual
derivatives in Group 3 amide chemistry.
The perfluorinated primary arylamide complex [Sc(NHC6-
F5)(N2NNЈ)] 7 was made via a transamination (σ-bond meta-
thesis) reaction between [Sc(NMe2)(N2NNЈ)] 6 and ArFNH2
(ArF = C6F5) in benzene and was isolated in 74% yield as a pale
brown solid (Scheme 1). When the reaction was followed by 1H
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Table 2 Selected bond distances (Å) and angles (Њ) for [Sc{PhC(NSi-
NMR spectroscopy in benzene-d6 the conversion was quanti-
tative and the only by-product was NHMe2; there was no
evidence for protonolysis of the chelating (and presumably less
basic) N2NNЈ ligand to form H2N2NNЈ. The primary amide
complexes [M(NHR)(N2NNЈ)] where R = tBu or Ar were made
by transmetallation reactions between LiNHR and the metal
chloride 1 or 2. In the case of scandium these reactions yielded
[Sc(NHtBu)(N2NNЈ)] 8 and [Sc(NHAr)(N2NNЈ)] 9 in reason-
able yields. The yttrium analogue of 8 was not sufficiently stable
to be isolated, possibly due to inadequate steric protection, but
reaction of LiNHAr with in situ generated 2 at Ϫ78 ЊC gave
pentane-soluble [Y(NHAr)(N2NNЈ)] 10 as an orange micro-
crystalline powder in 76% yield after crystallisation at Ϫ30 ЊC.
The new compounds 7–10 give rise to the expected 1H, 13C and
(for 7) 19F NMR spectra. The N2NNЈ sub-spectra feature
molecular Cs symmetry and support the structures proposed in
Scheme 1. The 1H NMR spectra of the more sterically crowded
arylamide complexes 9 and 10 remain unchanged down to
Ϫ80 ЊC and feature a single pair of (mutually coupled) doublet
(12 H) and septet (2 H) resonances for the ring iso-propyl
groups at all temperatures examined. The primary amide N–H
resonance was clearly observed in all cases (range δ ca. 5.4–2.9).
For 7 and 8 a ν(N–H) band was observed in their IR spectra in
the range 3360–3380 cmϪ1. The values are in the region associ-
ated with amide groups which do not form an α-agostic inter-
action with the metal centre (namely ca. 3250–3450 cmϪ1).11a,26
For the arylamide compexes [M(NHAr)(N2NNЈ)] 9 and 10
ν(N–H) bands could not be confidently assigned.
Another class of ligand that has enjoyed recent attention in
Group 3 chemistry are the benzamidinates PhC(NSiMe3)2 and
their homologues.9 Indeed, benzamidinates have been widely
exploited as monoanionic, bidentate supporting ligands for both
maingroupandtransitionmetalcomplexes.27 Thesynthesesofthe
benzamidinatecomplexes[M{PhC(NSiMe3)2}(N2NNЈ)](M=Sc
11 or 12) are summarised in Scheme 1. Thus reaction of Li[PhC-
(NSiMe3)2] with [ScCl(N2NNЈ)] 1 in benzene, or with in situ
generated [YCl(N2NNЈ)(thf )]ؒ1.5(LiCl) 2 in thf at Ϫ78 ЊC, gave
the corresponding benzamidinate complexes in good to excel-
lent yields. For both compounds diffraction-quality crystals
were grown from pentane solution and the solid state X-ray
structures were determined. The molecular structures are
shown in Figs. 2 and 3, and selected bond lengths and angles are
listed in Tables 2 and 3.
Me3)2}(N2NNЈ)] 11
Sc(1)–N(1)
Sc(1)–N(2)
Sc(1)–N(3)
Sc(1)–N(4)
2.118(1)
2.118(1)
2.393(1)
2.431(1)
Sc(1)–N(5)
Sc(1)–N(6)
N(5)–C(17)
N(6)–C(17)
2.251(1)
2.269(1)
1.323(2)
1.334(2)
N(1)–Sc(1)–N(2)
N(1)–Sc(1)–N(3)
N(2)–Sc(1)–N(3)
N(1)–Sc(1)–N(4)
N(2)–Sc(1)–N(4)
N(3)–Sc(1)–N(4)
N(1)–Sc(1)–N(5)
N(2)–Sc(1)–N(5)
N(3)–Sc(1)–N(5)
N(4)–Sc(1)–N(5)
N(1)–Sc(1)–N(6)
N(2)–Sc(1)–N(6)
N(3)–Sc(1)–N(6)
N(4)–Sc(1)–N(6)
131.02(5)
113.18(5)
88.10(5)
73.82(5)
74.41(5)
68.63(5)
97.64(5)
91.26(5)
139.20(5)
149.31(5)
106.81(5)
119.14(5)
84.79(4)
150.31(5)
N(5)–Sc(1)–N(6)
Sc(1)–N(1)–Si(1)
Sc(1)–N(1)–C(1)
C(1)–N(1)–Si(1)
Sc(1)–N(2)–Si(2)
Sc(1)–N(2)–C(3)
C(3)–N(2)–Si(2)
Sc(1)–N(5)–Si(3)
Sc(1)–N(5)–C(17)
Si(3)–N(5)–C(17)
Sc(1)–N(6)–Si(4)
Sc(1)–N(6)–C(17)
Si(4)–N(6)–C(17)
60.26(4)
131.92(7)
120.4(1)
107.6(1)
130.38(7)
114.0(1)
112.7(1)
133.33(7)
91.45(9)
133.5(1)
139.89(7)
90.37(8)
127.1(1)
Table 3 Selected bond distances (Å) and angles (Њ) for [Y{PhC(NSi-
Me3)2}(N2NNЈ)] 12
Y(1)–N(1)
Y(1)–N(2)
Y(1)–N(3)
Y(1)–N(4)
2.262(3)
2.259(3)
2.525(3)
2.557(3)
Y(1)–N(5)
Y(1)–N(6)
N(5)–C(17)
N(6)–C(17)
2.380(3)
2.410(2)
1.330(4)
1.340(4)
N(1)–Y(1)–N(2)
N(1)–Y(1)–N(3)
N(2)–Y(1)–N(3)
N(1)–Y(1)–N(4)
N(2)–Y(1)–N(4)
N(3)–Y(1)–N(4)
N(1)–Y(1)–N(5)
N(2)–Y(1)–N(5)
N(3)–Y(1)–N(5)
N(4)–Y(1)–N(5)
N(1)–Y(1)–N(6)
N(2)–Y(1)–N(6)
N(3)–Y(1)–N(6)
N(4)–Y(1)–N(6)
127.5(1)
110.00(11)
86.95(11)
71.2(1)
71.3(1)
66.8(1)
102.1(1)
93.35(11)
139.1(1)
150.7(1)
110.6(1)
119.8(1)
87.5(1)
N(5)–Y(1)–N(6)
Y(1)–N(1)–Si(1)
Y(1)–N(1)–C(1)
Si(1)–N(1)–C(1)
Y(1)–N(2)–Si(2)
Y(1)–N(2)–C(3)
Si(2)–N(2)–C(3)
Y(1)–N(5)–Si(3)
Y(1)–N(5)–C(17)
Si(3)–N(5)–C(17)
Y(1)–N(6)–Si(4)
Y(1)–N(6)–C(17)
Si(4)–N(6)–C(17)
57.14(9)
128.51(15)
120.4(2)
111.0(2)
127.59(16)
120.4(2)
115.6(2)
131.95(15)
92.8(2)
133.9(2)
139.14(14)
91.29(19)
127.5(2)
152.1(1)
Fig. 3 Molecular structure of [Y{PhC(NSiMe3)2}(N2NNЈ)] 12. Dis-
placement ellipsoids are drawn at the 20% probability level. H atoms
omitted for clarity.
The solid state structures of 11 and 12 are isomorphous and
will be discussed together. Neither structure adopts an easily
categorised coordination geometry and both are best described
as distorted octahedral with the amide nitrogens of the N2NNЈ
Fig. 2 Molecular structure of [Sc{PhC(NSiMe3)2}(N2NNЈ)] 11. Dis-
placement ellipsoids are drawn at the 25% probability level. H atoms
omitted for clarity.
J. Chem. Soc., Dalton Trans., 2002, 1694–1703
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Table 4 Selected bond distances (Å) and angles (Њ) for [Sc(CH2Si-
Me3)(N2NNЈ)] 13
ligands occupying the formally axial coordination sites. In each
instance the N2NNЈ ligand is tetradentate and the sum of
the angles subtended at the amide nitrogens N(1) and N(2)
is approximately 360Њ implying sp2 hybridisation. As for the
five-coordinate compound [Y{N(SiMe3)2}(N2NNЈ)] 5, the M–
Npyridyl bond distances in 11 and 12 are significantly longer than
those for the M–Namine bonds. The PhC(NSiMe3)2 ligands in 11
and 12 are bound in a characteristic bidentate manner with no
significant differences between the internal PhC–N distances
implying that both coordination sites at the metal centre are
effectively equivalent.
Nonetheless, there is a small but significant difference
between the M–Namidinate bond lengths in the two compounds,
with the M–Namidinate distance for the nitrogen cis to the pyridyl
moiety being the longer. In both compounds the M–Namidinate
distances are at the long end of the range of values previously
reported for Group 3 benzamidinate complexes,9,28,29 presum-
ably reflecting the six-coordination of the metal centres and the
presence of the good amide donors of N2NNЈ.
Sc(1)–N(1)
Sc(1)–N(2)
Sc(1)–N(3)
Sc(1)–N(4)
2.0748(17)
2.0613(14)
2.3388(17)
2.3606(14)
Sc(1)–C(17)
N(1)–Si(1)
N(2)–Si(2)
C(17)–Si(3)
2.2885(17)
1.7096(17)
1.7014(16)
1.8347(17)
N(1)–Sc(1)–N(2)
N(1)–Sc(1)–N(3)
N(2)–Sc(1)–N(3)
N(1)–Sc(1)–N(4)
N(2)–Sc(1)–N(4)
N(3)–Sc(1)–N(4)
N(1)–Sc(1)–C(17)
N(2)–Sc(1)–C(17)
N(3)–Sc(1)–C(17)
110.94(7)
128.69(6)
101.74(6)
77.08(6)
80.96(6)
70.15(6)
105.85(6)
118.91(6)
90.52(6)
N(4)–Sc(1)–C(17)
Sc(1)–N(1)–C(1)
Sc(1)–N(1)–Si(1)
C(1)–N(1)–Si(1)
Sc(1)–N(2)–C(3)
Sc(1)–N(2)–Si(2)
C(3)–N(2)–Si(2)
Sc(1)–C(17)–Si(3)
155.43(6)
114.6(1)
124.85(9)
115.75(14)
112.04(12)
132.52(8)
114.74(12)
115.54(8)
Molecules of 11 and 12 are fluxional at room temperature on
the NMR timescale. Thus the N2NNЈ ligand sub-spectra indi-
cate apparent molecular Cs symmetry and the two SiMe3 groups
of the PhC(NSiMe3)2 ligands appear as single resonances (inte-
grating as 18 H with respect to N2NNЈ). This is not consistent
with the solid state structures which clearly place the latter
groups in very different environments. Furthermore, the
(Ph)CN2 core of the benzamidinate ligand is twisted with
respect to the approximate mirror plane passing through the
Npyridyl, Namine and M atoms of the M(N2NNЈ) fragments in 11
and 12 so that the two N2NNЈ ligand SiMe3 groups are also in
chemically slightly different environments. Cooling toluene-d8
solutions of 11 and 12 to Ϫ40 ЊC causes the fluxional process
(apparent rotation about the M ؒ ؒ ؒ C(Ph)N2 vector) that
exchanges the benzamidinate SiMe3 groups to be frozen out
while the two N2NNЈ SiMe3 groups remain equivalent on the
NMR timescale down to Ϫ90 ЊC suggesting that the PhC(N-
SiMe3)2 ligand is still “rocking” either side of the mirror plane
mentioned above at this temperature. Such fluxional behaviour
(apparent net rotation about a M ؒ ؒ ؒ C(Ph)N2 vector) is char-
acteristic of many benzamidinate complexes and sometimes can
never be frozen out on the NMR timescale.30
Finally we describe attempts to prepare organo-scandium
and -yttrium complexes with the N2NNЈ ligand. Of a wide
range of organo-lithium, -magnesium and -zinc reagents exam-
ined for the reactions of both in situ generated and previously
isolated examples of [ScCl(N2NNЈ)] 1 and [YCl(N2NNЈ)(thf )]ؒ
1.5(LiCl) 2, only the reaction of 1 with LiCH2SiMe3 gave
isolable products on the preparative scale (Scheme 1). Thus
addition of LiCH2SiMe3 to a benzene solution of 1 at room
temperature followed by standard work-up gave reasonable
yields of orange, pentane-soluble [Sc(CH2SiMe3)(N2NNЈ)] 13,
the crystal structure of which has been determined. The
molecular structure is shown in Fig. 4 and selected bond lengths
and angles are listed in Table 4.
Fig. 4 Molecular structure of [Sc(CH2SiMe3)(N2NNЈ)] 13. Displace-
ment ellipsoids are drawn at the 20% probability level. H atoms omitted
for clarity.
C(17)–Si(3) 115.54(8)Њ] into one of the “pockets” formed
between the pyridyl group and the N2NNЈ SiMe3 substituents.
The angles subtended at Si(3) are unexceptional and, combined
with the unexceptional Si(3)–CMe bond lengths, suggests that no
agostic interaction is present between any hydrogen atoms of
the alkyl ligand and the metal centre which has an apparent
valence electron count of 14 (assuming each amide nitrogen
1
donor is able to donate three electrons). The solution H and
13C NMR spectra are consistent with the solid state structure
and suggest that 13 possesses Cs symmetry on the NMR time-
scale. The mono-alkyl compound 13 is thermally stable at room
temperature for several days in benzene-d6 but decomposes
rapidly at temperatures above 60 ЊC.
Conclusion
The solid state structure of 13 features a five coordinate
metal centre with a tetradentate N2NNЈ ligand. The geometry
around the metal is a distorted trigonal bipyramid in which the
best equatorial plane is defined by N(1), N(2) and N(3). The
Sc–N distances are all somewhat shorter than those in [Sc{Ph-
C(NSiMe3)2}(N2NNЈ)] 11 (consistent with the higher coordin-
ation number and apparent valence electron count of the latter)
and are within normal ranges.28,29 The Sc–Npyridyl distance is
again slightly shorter than Sc–Namine. The sum of the angles
around N(1) and N(2) are 355.1 and 359.4Њ respectively indicat-
ing that they are effectively sp2 hybridised and therefore may
act as three electron donors. The Sc–CH2SiMe3 distance of
2.2885(17) Å is similar to those in other scandium complexes
containing a terminal alkyl ligand.28,29 None of the hydrogen
atoms (placed geometrically) are within bonding distance of
Sc(1). The SiMe3 group of the alkyl ligand is oriented [Sc(1)–
The diamide–diamine donor ligand N2NNЈ is a useful support-
ing ligand in scandium and yttrium chemistry. In all cases
examined the pyridyl donor remains firmly coordinated to the
metal centres of the the new chloride, primary and secondary
amide, benzamidinate and alkyl products reported. In its five-
coordinate complexes the N2NNЈ ligand promotes approximate
trigonal bipyramidal coordination geometries somewhat remin-
iscent of those of the trianionic “tren” ligands used widely for
early- to mid-transition metal chemistry.
Experimental
General methods and instrumentation
All manipulations of air- and/or moisture-sensitive compounds
were carried out under an atmosphere of dinitrogen or argon
1698
J. Chem. Soc., Dalton Trans., 2002, 1694–1703

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using standard Schlenk-line or dry-box techniques at room
temperature unless stated otherwise. Solvents were pre-dried
over activated molecular sieves and refluxed over an appro-
priate drying agent under an atmosphere of dinitrogen and
collected by distillation. NMR solvents for air- and/or
moisture-sensitive compounds were dried over appropriate
agents, distilled under reduced pressure and stored under N2 in
J. Young ampoules. NMR samples of air- and moisture-
sensitive compounds were prepared in the dry-box in 5 mm
Wilmad tubes, equipped with a Young’s Teflon valve.
a satisfactory elemental analysis could not be obtained. 1H
NMR (500.0 MHz, 298 K, benzene-d6): δ 9.69 (1 H, d, J =
3
4.5 Hz, 6-C5H4N), 6.81 (1 H, dd, 4-C5H4N), 6.42 (2 H, m, 3J =
4.5 Hz, 3-, 5-C5H4N), 3.74 (4 H, br s, 2-, 5-C4H8O), 3.48 (2 H,
m, NCH2CH2NSi), 3.44 (2 H, s, C5H4NCH2), 3.23 (2 H, m,
NCH2CH2NSi), 2.81 (2 H, m, NCH2CH2NSi), 2.29 (2 H, m,
NCH2CH2NSi), 1.43 (4 H, br s, 3-, 4-C4H8O), 0.28 (18 H, s,
Si(CH3)3). 13C-{1H} NMR (125.7 MHz, 298 K, benzene-d6):
δ 159.0 (2-C5H4N), 152.7 (6-C5H4N), 138.5 (4-C5H4N), 122.8
(5-C5H4N), 122.5 (3-C5H4N), 69.9 (2-, 5-C4H8O), 58.5 (NCH2-
CH2NSi), 57.2 (C5H4NCH2), 44.8 (NCH2CH2NSi), 25.5 (3-, 4-
C4H8O), 0.8 (Si(CH3)3). IR (CsBr plates, Nujol): 1607 (s), 1572
(m), 1489 (w), 1377 (s), 1346 (w), 1330 (w), 1309 (m), 1157 (w),
1145 (w), 1098 (s), 1066 (s), 1018 (s), 985 (w), 943 (m), 925 (m),
899 (m), 860 (w), 830 (s), 766 (m), 726 (m), 664 (s), 633 (w), 613
1H and 13C-{1H} NMR spectra were recorded on a Varian
Mercury 300 or Varian Unity Plus 500 spectrometer. 1H and 13
C
assignments were confirmed when necessary with the use of
DEPT-135, DEPT-90, and two dimensional 1H–1H and 13C-1H
correlation NMR experiments. All spectra were referenced
internally to residual protio-solvent (1H) or solvent (13C) reson-
ances, and are reported relative to tetramethylsilane (δ = 0).
Chemical shifts are quoted in ppm and coupling constants in
Hertz.
Infrared spectra were recorded on a Perkin–Elmer 1710
FTIR spectrometer. Infrared data are quoted in wavenumbers
(cmϪ1). Mass spectra were recorded by the mass spectro-
scopy services of the University of Oxford’s Dyson Perrins
Laboratory. Combustion elemental analyses were carried out
by the analytical services of the University of Oxford’s
Inorganic Chemistry Laboratory and Mikroanalytisches Labor
Pascher, Germany.
(w), 565 (m), 549 (w), 417 (m) cmϪ1
.
[YCl(N2NNЈ)(py)]ؒ1.5(LiCl) (3). To a mixture of solid YCl3
(271 mg, 1.39 mmol) and Li2N2NNЈ (486 mg, 1.39 mmol)
cooled to Ϫ78 ЊC was added pyridine (20 ml). The mixture was
allowed to warm to rt and stirred for a further 30 min before the
volatiles were removed under reduced pressure yielding a red
solid which was extracted into benzene (3 × 20 ml). After filter-
ing, the volatiles were removed under reduced pressure. The
remaining orange solid was triturated with pentane and dried to
give [YCl(N2NNЈ)(py)]ؒ1.5(LiCl) 3 as a pale pink solid. Yield:
590 mg (71%). 1H NMR (500.0 MHz, 298 K, benzene-d6):
δ 9.85 (1 H, d, 3J = 4.5 Hz, 6-C5H4N), 8.99 (2 H, br s, o-C5H5N),
6.93 (1 H, m, p-C5H5N), 6.77 (1 H, dd, 3J = 7.5, 8.0 Hz,
The compound Li2N2NNЈ was prepared as reported previ-
ously.18b Lithiated amides were prepared by reaction of the
n
3
corresponding amines with BuLi in either hexanes or diethyl
4-C5H4N), 6.68 (2 H, m, m-C5H5N), 6.42 (1 H, dd, J = 4.5,
3
ether.
8.0 Hz, 5-C5H4N), 6.36 (1 H, d, J = 7.5 Hz, 3-C5H4N), 3.58
(2 H, m, NCH2CH2NSi), 3.47 (2 H, s, C5H4CH2), 3.30 (2 H, m,
NCH2CH2NSi), 2.93 (2 H, m, NCH2CH2NSi), 2.36 (2 H, m,
NCH2CH2NSi), 0.84 (18 H, s, Si(CH3)3). 13C-{1H} NMR (125.7
MHz, 298 K, benzene-d6): δ 158.9 (2-C5H4N), 152.9 (6-C5H4N),
150.9 (o-C5H5), 138.4 (4-C5H4N), 137.3 (p-C5H5), 123.6
(5-C5H4N), 122.7 (m-C5H5), 122.4 (3-C5H4N), 58.4 (NCH2-
CH2NSi), 57.1 (C5H4NCH2), 46.1 (NCH2CH2NSi), 1.2
(Si(CH3)3). 7Li NMR (194.3 MHz, 298 K, benzene-d6): δ Ϫ0.49.
IR (CsBr plates, Nujol): 1600 (m), 1571 (w), 1307 (w), 1284 (w),
1246 (m), 1152 (w), 1140 (w), 1086 (s), 1058 (w), 1037 (m), 1002
(w), 945 (w), 928 (s), 843 (s), 791 (w), 757 (w), 727 (w), 697 (m),
670 (w), 624 (w), 582 (w), 551 (w) cmϪ1. EI mass spectrum: m/z
460 ([M Ϫ C5H5N, 1.5 LiCl]ϩ, 3%), 425 ([M Ϫ C5H5N, Cl, 1.5
LiCl]ϩ, 6%). Elemental analysis for C21H37ClN5Si2. 1.5 LiCl:
found (calculated): C, 41.4 (41.8); H, 6.7 (6.2); N, 11.8 (11.6)%.
Syntheses
[ScCl(N2NNЈ)] (1). To a suspension of ScCl3 (0.62 g, 4.12
mmol) in thf (20 ml) cooled to Ϫ78 ЊC was added dropwise a
solution of Li2N2NNЈ (1.44 g, 4.08 mmol) in thf (10 ml). The
reaction mixture was allowed to warm to rt and stirred for a
further 1 h after which time the volatiles were removed under
reduced pressure to yield a brown solid. This was extracted into
benzene (4 × 50 ml) and the extracts filtered. The volatiles were
removed under reduced pressure to give [ScCl(N2NNЈ)] 1 as a
cream solid. Yield: 1.55 g (91%). 1H NMR (300.1 MHz, 298 K,
3
benzene-d6): δ 9.33 (1 H, d, J = 4.8 Hz, 6-C5H4N), 6.67 (1 H,
3
3
dd, J = 7.5, 8.1 Hz, 4-C5H4N), 6.27 (1 H, t, J = 4.8, 7.5 Hz,
3
5-C5H4N), 6.14 (1 H, d, J = 8.1 Hz, 3-C5H4N), 3.44 (2 H, m,
NCH2CH2NSi), 3.18 (2 H, m, NCH2CH2NSi), 3.10 (2 H, s,
C5H4NCH2), 2.74 (2 H, m, NCH2CH2NSi), 2.21 (2 H, m,
NCH2CH2NSi), 0.52 (18 H, s, Si(CH3)3). 13C-{1H} NMR (75.5
MHz, 298 K, benzene-d6): δ 158.9 (2-C5H4N), 152.9 (6-C5H4N),
139.5 (4-C5H4N), 123.3 (5-C5H4N), 122.1 (3-C5H4N), 57.3
(NCH2CH2NSi), 56.9 (C5H4NCH2), 45.8 (NCH2CH2NSi), 1.9
(Si(CH3)3). IR (CsBr plates, Nujol): 1606 (m), 1572 (m), 1348
(w), 1309 (w), 1245 (s), 1157 (w), 1145 (w), 1082 (m), 1056 (m),
1039 (w), 1023 (m), 987 (w), 942 (s), 924 (m), 862 (w), 833 (m),
675 (w),662 (w), 645 (w), 633 (w), 619 (w), 570 (m), 551 (w),
484 (w), 452 (m), 430 (m) cmϪ1. EI mass spectrum: m/z 401
([M Ϫ CH3]ϩ, 6%), 371 ([M Ϫ 3 CH3]ϩ, 3%), 343 ([M Ϫ
Si(CH3)3]ϩ, 2%). Elemental analysis for C16H32ClN4ScSi2: found
(calculated): C, 46.5 (46.1); H, 8.0 (7.7); N, 13.4 (13.4)%.
[Sc{N(SiMe3)2}(N2NNЈ)] (4). To a suspension of ScCl3 (60
mg, 0.40 mmol) in thf (5 ml) cooled to Ϫ78 ЊC was added
dropwise a solution of Li2N2NNЈ (139 mg, 0.40 mmol) in thf
(5 ml). The solution was allowed to warm to rt and stirred for
a further 45 min before being recooled to Ϫ78 ЊC. A cooled
solution of LiN(SiMe3)2ؒEt2O (95.6 mg, 0.40 mmol) in thf
(5 ml) was added dropwise and the mixture was again allowed
to warm to rt. Stirring for a further 30 min resulted in a dark
red solution from which the volatiles were removed under
reduced pressure. The residues were extracted into pentane (3 ×
15 ml), filtered and the volatiles removed under reduced pres-
sure to give [Sc{N(SiMe3)2}(N2NNЈ)] 4. Yield: 144 mg (67%).
1H NMR (300.1 MHz, 298 K, benzene-d6): δ 9.10 (1 H, d, 3J =
3
[YCl(N2NNЈ)(thf )]ؒ1.5(LiCl) (2). To a mixture of solid YCl3
(153 mg, 0.78 mmol) and Li2N2NNЈ (275 mg, 0.78 mmol)
cooled to Ϫ78 ЊC was added thf (20 ml). The mixture was
allowed to warm to rt and stirred for a further 30 min before the
volatiles were removed under reduced pressure. The resulting
off-white, sticky solid was extracted into benzene (40 ml), and
filtered before the volatiles were removed under reduced pres-
sure to give [YCl(N2NNЈ)(thf )]ؒ1.5(LiCl) 2 as an off-white
solid. Yield: 218 mg (47%). Attempts to further handle or pur-
ify this material invariably lead to apparent decomposition and
5.4 Hz, 6-C5H4N), 6.79 (1 H, dd, J = 7.5, 7.8 Hz, 4-C5H4N),
3
3
6.60 (1 H, dd, J = 5.4, 7.5 Hz, 5-C5H4N), 6.24 (1 H, d, J =
7.8 Hz, 3-C5H4N), 3.37 (2 H, m, NCH2CH2NSi), 3.24 (2 H, s,
C5H4NCH2), 2.79 (2 H, m, NCH2CH2NSi), 2.65 (2 H, m,
NCH2CH2NSi), 2.27 (2 H, m, NCH2CH2NSi), 0.45 (18 H, s,
N(Si{CH3}3)2), 0.37 (18 H, s, NSi(CH3)3). 13C-{1H} NMR (75.5
MHz, 298 K, benzene-d6): δ 158.8 (2-C5H4N), 151.6 (6-C5H4N),
139.1 (4-C5H4N), 122.8 (5-C5H4N), 121.6 (3-C5H4N), 65.7
(NCH2CH2NSi), 64.2 (C5H4NCH2), 46.1 (NCH2CH2NSi), 6.2
(N(Si{CH3}3)2), 2.1 (NSi(CH3)3). IR (CsBr plates, Nujol): 1606
J. Chem. Soc., Dalton Trans., 2002, 1694–1703
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(m), 1572 (w), 1302 (w), 1245 (s), 1146 (w), 1066 (w), 1031 (w),
1017 (w), 945 (s), 929 (s), 876 (w), 834 (s), 783 (w), 756 (w), 742
(w), 665 (m), 621 (w), 578 (w), 559 (w), 527 (w), 482 (w), 438 (m)
cmϪ1. EI mass spectrum: m/z 541 ([M]ϩ, 2%), 526 ([M Ϫ CH3]ϩ,
6%), 381 ([M Ϫ N(Si{CH3}3)2]ϩ, 14%). Elemental analysis for
C22H50N5ScSi4: found (calculated): C, 48.5 (48.8); H, 9.3 (9.3);
N, 12.9 (12.9)%.
[Sc(NHArF)(N2NNЈ)] (7). To an orange solution of [Sc(N-
Me2)(N2NNЈ)] 6 (102 mg, 0.24 mmol) in benzene (5 ml) was
added a solution of ArFNH2 ( 44 mg, 0.24 mmol) in benzene
(5 ml) resulting in an immediate decrease in colour intensity
The solution was stirred at rt for 20 min before the volatiles
were removed under reduced pressure. The resulting light
brown material was redissolved in benzene (2 ml) and the benz-
ene then slowly removed under reduced pressure from a frozen
mixture giving [Sc(NHArF)(N2NNЈ)] 7 as a light brown solid.
Yield: 121 mg (74%). 1H NMR data (300.1 MHz, 298 K,
[Y{N(SiMe3)2}(N2NNЈ)] (5). To a mixture of solid YCl3
(110 mg, 0.56 mmol) and Li2N2NNЈ (197 mg, 0.56 mmol)
cooled to Ϫ78 ЊC was added thf (15 ml). The mixture was
allowed to warm to rt and stirred for a further 10 min to give an
orange solution. The solution was again cooled to Ϫ78 ЊC and
a solution of LiN(SiMe3)2ؒEt2O (122 mg, 0.51 mmol) in thf
(10 ml) was added dropwise. After complete addition the sol-
ution was allowed to warm to rt and stirred for a further 1 h
before the volatiles were removed under reduced pressure. The
resulting light orange solid was extracted into pentane (3 ×
15 ml), filtered, and the volatiles were removed under reduced
pressure to give [Y{N(SiMe3)2}(N2NNЈ)] 5 as an orange solid.
Yield: 183 mg (62%). Colourless single crystals suitable for
X-ray diffraction were grown from a saturated pentane solution
left standing in a vibration-free environment for 2 d. 1H NMR
3
benzene-d6): δ 8.33 (1 H, d, J = 4.8 Hz, 6-C5H4N), 6.78 (1 H,
dd, 3J = 8.1, 7.8 Hz, 4-C5H4N), 6.23 (1 H, dd, 3J = 4.8, 7.8 Hz,
3
5-C5H4N), 6.19 (1 H, d, J = 8.1 Hz, 3-C5H4N), 5.02 (1 H, s,
NH), 3.39 (2 H, m, NCH2CH2NSi), 3.13 (2 H, s, C5H4NCH2),
3.10 (2 H, m, NCH2CH2NSi), 2.62 (2 H, m, NCH2CH2NSi),
2.18 (2 H, m, NCH2CH2NSi), 0.31 (18 H, s, Si(CH3)3). 13C-{1H}
NMR (75.5 MHz, 298 K, benzene-d6): δ 158.9 (2-C5H4N), 150.0
(6-C5H4N), 149.2 (i-C6F5), 139.4 (4-C5H4N), 139.0 (o-C6F5, 1J =
1
1
245 Hz), 137.8 (p-C6F5, J = 234 Hz), 132.5 (m-C6F5, J = 197
Hz), 123.5 (5-C5H4N), 122.6 (3-C5H4N), 59.5 (NCH2CH2NSi),
58.3 (C5H4NCH2), 44.8 (NCH2CH2NSi), 1.2 (Si(CH3)3). 19F
NMR (282.3 MHz, 298 K, benzene-d6): δ Ϫ162.8 (2 F, m, o- or
m-C6F5), Ϫ167.9 (2 F, m, m- or o-C6F5), Ϫ183.8 (1 F, m,
p-C6F5). IR (CsBr plates, Nujol): 3366 (m), 1646 (m), 1608 (m),
1591 (w), 1572 (w), 1515 (s), 1504 (s), 1352 (w), 1299 (w), 1249
(s), 1158 (m), 1110 (w), 1068 (m), 1031 (w), 1006 (s), 967 (m),
938 (w), 927 (w), 870 (w), 835 (s), 792 (w), 770 (w), 735 (w), 676
(m), 629 (w), 572 (m), 487 (m), 453 (m), 437 (w) cmϪ1. EI mass
spectrum: m/z 235 ([M Ϫ 2 Si(CH3)3, NHC6F5]ϩ, 86%), 182
([NHC6F5]ϩ, 34%). Elemental analysis for C22H33F5N5ScSi2:
found (calculated): C, 47.2 (46.9); H, 6.2 (5.9); N, 12.1 (12.4)%.
3
(300.1 MHz, 298 K, benzene-d6): δ 9.04 (1 H, d, J = 4.8 Hz,
6-C5H4N), 6.77 (1 H, dd, 3J = 7.5, 8.1 Hz, 4-C5H4N), 6.46 (1 H,
3
3
dd, J = 4.8, 8.1 Hz, 5-C5H4N), 6.24 (1 H, d, J = 7.5 Hz,
3-C5H4N), 3.48 (2 H, m, NCH2CH2NSi), 3.15 (2 H, s,
C5H4NCH2), 2.96 (2 H, m, NCH2CH2NSi), 2.58 (2 H, m,
NCH2CH2NSi), 2.21 (2 H, m, NCH2CH2NSi), 0.44 (18 H, s,
N(Si{CH3}3)2), 0.31 (18 H, s, NSi(CH3)3). 13C-{1H} NMR (75.5
MHz, 298 K, benzene-d6): δ 159.3 (2-C5H4N), 150.6 (6-C5H4N),
139.3 (4-C5H4N), 122.9 (5-C5H4N), 122.6 (3-C5H4N), 65.0
(NCH2CH2NSi), 62.3 (C5H4NCH2), 45.0 (NCH2CH2NSi), 5.6
(N(Si{CH3}3)2), 1.9 (NSi(CH3)3). IR (CsBr plates, Nujol): 1608
(m), 1571 (w), 1343 (w), 1305 (w), 1270 (w), 1245 (s), 1165 (w),
1142 (w), 1078 (m), 1049 (w), 1030 (w), 1018 (w), 981 (s), 931
(s), 875 (w), 828 (s), 776 (m), 738 (m), 664 (m), 645 (w), 632 (w),
608 (m), 572 (w), 552 (w), 487 (w), 455 (w), 422 (m), 407 (m)
cmϪ1. EI mass spectrum: m/z 570 ([M Ϫ CH3]ϩ, 13%), 482
([M Ϫ N(Si{CH3}3)2]ϩ, 24%), 425 ([M Ϫ N(Si{CH3}3)2]ϩ,
24%). Elemental analysis for C22H50N5Si4Y: found (calculated):
C, 45.2 (45.1); H, 8.7 (8.6); N, 11.9 (12.0)%.
[Sc(NHtBu)(N2NNЈ)] (8). To a solution of [ScCl(N2NNЈ)] 1
(146 mg, 0.35 mmol) in benzene (10 ml) was added a solution of
LiNHtBu (27.7 mg, 0.35 mmol) in benzene (10 ml). The mixture
was stirred for 10 min to give an opaque orange/brown mixture
from which the volatiles were removed under reduced pressure.
The remaining orange solid was extracted into pentane and the
resulting orange solution was filtered. The volatiles were
removed under reduced pressure giving [Sc(NHtBu)(N2NNЈ)]
8 as a light brown solid. Yield: 102 mg (64%). 1H NMR
3
(300.1 MHz, 298 K, benzene-d6): δ 9.44 (1 H, d, J = 5.4 Hz,
6-C5H4N), 6.75 (1 H, dd, 3J = 8.1, 7.2 Hz, 4-C5H4N), 6.42 (1 H,
3
3
[Sc(NMe2)(N2NNЈ)] (6). To a solution of [ScCl(N2NNЈ)] 1
(120 mg, 0.29 mmol) in benzene (5 ml) was added a slurry of
LiNMe2 in benzene (5 ml) producing no immediate colour
change. The mixture was stirred for 25 min after which time the
volatiles were removed under reduced pressure. The remaining
brown solid was extracted into pentane (15 ml), filtered, and the
volatiles removed under reduced pressure. The orange oil was
dissolved in benzene (5 ml) and the volatiles were removed
under reduced pressure from a frozen mixture cooled to 0 ЊC to
afford [Sc(NMe2)(N2NNЈ)] 6 as a pale orange solid. Yield: 75
dd, J = 5.4, 7.2 Hz, 5-C5H4N), 6.22 (1 H, d, J = 8.1 Hz,
3-C5H4N), 3.46 (2 H, m, NCH2CH2NSi), 3.10 (2 H, s,
C5H4NCH2), 3.08 (2 H, m, NCH2CH2NSi), 2.89 (1 H, s, NH),
2.49 (2 H, m, NCH2CH2NSi), 2.10 (2 H, m, NCH2CH2NSi),
1.48 (9 H, s, C(CH3)3), 0.46 (18 H, s, Si(CH3)3). 13C-{1H} NMR
(75.5 MHz, 298 K, benzene-d6): δ 159.6 (2-C5H4N), 153.3 (6-
C5H4N), 139.0 (4-C5H4N), 122.5 (5-C5H4N), 122.3 (3-C5H4N),
61.3 (NCH2CH2NSi), 59.2 (C5H4NCH2), 52.8 (C(CH3)3), 44.7
(NCH2CH2NSi), 35.6 (C(CH3)3), 0.5 (Si(CH3)3). IR (CsBr
plates, Nujol): 3386 (w), 1606 (m), 1573 (w), 1300 (w), 1259 (w),
1240 (s), 1153 (w), 1083 (s), 1016 (m), 985 (w), 943 (s), 830 (s),
801 (w), 758 (w), 742 (w), 691 (w), 678 (w), 645 (w), 634 (w), 569
(w), 556 (w), 443 (m) cmϪ1. EI mass spectrum: m/z 453 ([M]ϩ,
1%), 438 ([M Ϫ CH3]ϩ, 2%), 381 ([M Ϫ NHC(CH3)3]ϩ, 65%).
Elemental analysis for C20H42N5ScSi2: found (calculated): C,
52.0 (53.0); H, 9.4 (9.3); N, 14.8 (15.4)%.
1
mg (61%). H NMR (300.1 MHz, 298 K, benzene-d6): δ 8.23
(1 H, d, 3J = 4.8 Hz, 6-C5H4N), 6.72 (1 H, dt, 3J = 7.5, 7.8 Hz,
4-C5H4N), 6.37 (1 H, t, 3J = 4.8, 7.5 Hz, 5-C5H4N), 6.17 (1 H, d,
3J = 7.8 Hz, 3-C5H4N), 3.41 (2 H, m, NCH2CH2NSi), 3.25 (2 H,
m, NCH2CH2NSi), 3.20 (6 H, s, N(CH3)2), 3.13 (2 H, s,
C5H4NCH2), 2.66 (2 H, m, NCH2CH2NSi), 2.19 (2 H, m,
NCH2CH2NSi), 0.51 (18 H, s, Si(CH3)3). 13C-{1H} NMR (75.5
MHz, 298 K, benzene-d6): δ 159.7 (2-C5H4N), 151.9 (6-C5H4N),
139.0 (4-C5H4N), 123.4 (5-C5H4N), 122.2 (3-C5H4N), 57.4
(overlapping NCH2CH2NSi and C5H4NCH2), 45.5 (NCH2-
CH2NSi), 44.7 (N(CH3)2, 1.7 (Si(CH3)3). IR (CsBr plates,
Nujol): 1606 (m), 1573 (w), 1297 (w), 1239 (s), 1147 (w), 1088
(m), 1016 (w), 932 (s), 867 (w), 830 (s), 758 (w), 741 (w), 677
(m), 549 (w), 524 (w), 446 (w) cmϪ1. EI mass spectrum: m/z 381
([M Ϫ N(CH3)2]ϩ, 45%) Elemental analysis for C18H38N5ScSi2ؒ
0.25 C5H12: found (calculated): C, 51.2 (52.1); H, 9.3 (9.3); N,
15.0 (15.8)%.
[Sc(NHAr)(N2NNЈ)] (9). To a suspension of ScCl3 (60 mg,
0.40 mmol) in thf (5 ml) cooled to Ϫ78 ЊC was added dropwise
a solution of Li2N2NNЈ (139 mg, 0.40 mmol) in thf (5 ml). The
reaction mixture was allowed to warm to rt and stirred for a
further 45 min after which time the orange/brown solution was
cooled to Ϫ78 ЊC before a solution of LiNHAr (73 mg, 0.40
mmol) in thf (5 ml) was added dropwise. The mixture was
allowed to warm to rt and stirred for a further 60 min after
which time the volatiles were removed under reduced pressure.
The resulting brown solid was extracted into pentane (30 ml),
1700
J. Chem. Soc., Dalton Trans., 2002, 1694–1703

View Article Online
filtered, concentrated to 5 ml and cooled to Ϫ80 ЊC afford-
ing [Sc(NHAr)(N2NNЈ)] 9 as an orange crystalline which was
isolated and dried in vacuo. Yield: 125 mg (57%). 1H
reduced pressure giving a brown solid which was extracted with
pentane (3 × 10 ml). The volatiles were removed under reduced
pressure affording [Sc{PhC(NSiMe3)2}(N2NNЈ)] 11 as an off-
white solid. Yield: 132 mg (83%). Colourless single crystals
suitable for X-ray diffraction were grown from a concentrated
3
NMR (300.1 MHz, 298 K, benzene-d6): δ 8.53 (1 H, d, J =
5.1 Hz, 6-C5H4N), 7.13 (2 H, d, 3J = 7.5 Hz, m-C6H3), 6.82 (1 H,
t, 3J = 7.5 Hz, p-C6H3), 6.63 (1 H, dd, 3J = 8.1, 7.2 Hz,
pentane solution over a period of 30 min. H NMR (300.1
1
3
4-C5H4N), 6.24 (1 H, d, J = 7.2 Hz, 3-C5H4N), 6.08 (1 H, dd,
MHz, 233 K, toluene-d8): δ 9.00 (1 H, br d, 6-C5H4N), 7.79 (2
H, br d, o-C6H5), 7.10 (3 H, br m, m-, p-C6H5), 6.80 (1 H, br t, 4-
C5H4N), 6.50 (1 H, br t, 5-C5H4N), 6.22 (1 H, br d, 3-C5H4N),
3.60 (2 H, br s, NCH2CH2NSi), 3.28 (2 H, s, C5H4NCH2), 3.20
(2 H, br s, NCH2CH2NSi), 2.73 (2 H, br s, NCH2CH2NSi), 2.09
(2 H, br s, NCH2CH2NSi), 0.42 (9 H, s, C6H5C(NSi{CH3}3)2),
0.37 (18 H, s, NSi(CH3)3), Ϫ0.08 (9 H, s, C6H5C(NSi{CH3}3)2).
13C-{1H} NMR (75.5 MHz, 233 K, toluene-d8): δ 183.0
(C6H5C), 158.2 (2-C5H4N), 150.2 (6-C5H4N), 143.7 (i-C6H5),
138.3 (4-C5H4N), 126.9 (o-C6H5), 123.2 (3-C5H4N), 121.8
(5-C5H4N), 59.1 (NCH2CH2NSi), 56.7 (C5H4NCH2), 46.5
(NCH2CH2NSi), 3.5 (C6H5C(NSi{CH3}3)2), 2.47 (C6H5C(N-
Si{CH3}3)2), 1.8 (NSi(CH3)3). IR (CsBr plates, Nujol): 2725
(w), 2678 (w), 1662 (m), 1607 (s), 1573 (m), 1306 (w), 1250 (s),
1167 (w), 1154 (m), 1145 (w), 1078 (m), 1064 (w), 1056 (w), 1036
(w), 1005 (w), 989 (m), 932 (m), 844 (s), 795 (w), 757 (m), 703
(m), 677 (m), 644 (w), 631 (w), 603 (w), 584 (w), 663 (m), 489 (s),
447 (w), 423 (s), 406 (w) cmϪ1. EI mass spectrum: m/z 644 ([M]ϩ,
1%), 571 ([M Ϫ Si(CH3)3]ϩ, 10%), 352 ([M Ϫ 4 Si(CH3)3]ϩ, 2%).
Elemental analysis for C29H55N6ScSi4: found (calculated): C,
53.1 (54.0); H, 9.1 (8.6); N, 13.0 (13.0)%.
3J = 5.1, 8.1 Hz, 5-C5H4N), 5.39 (1 H, s, NH), 3.44 (2 H, m,
NCH2CH2NSi), 3.24 (2 H, s, C5H4NCH2), 3.11 (4 H, m, over-
lapping NCH2CH2NSi and CH(CH3)2), 2.60 (2 H, m, NCH2-
3
CH2NSi), 2.22 (2 H, m, NCH2CH2NSi), 1.23 (12 H, d, J =
6.9 Hz, CH(CH3)2), 0.39 (18 H, s, Si(CH3)3). 13C-{1H} NMR
(75.5 MHz, 298 K, benzene-d6): δ 158.6 (2-C5H4N), 152.0
(i-C6H3), 151.7 (6-C5H4N), 139.1 (4-C5H4N), 133.4 (o-C6H3),
123.5 (5-C5H4N), 123.4 (m-C6H3), 121.9 (3-C5H4N), 115.0
(p-C6H3), 60.9 (NCH2CH2NSi), 59.2 (C5H4NCH2), 44.8
(NCH2CH2NSi), 30.1 (CH(CH3)2), 24.2 (CH(CH3)2), 1.5
(Si(CH3)3). IR (CsBr plates, Nujol): 1607 (m), 1589 (w), 1570
(w), 1333 (m), 1301 (w), 1255 (s), 1240 (s), 1157 (w), 1140 (w),
1121 (w), 1106 (w), 1074 (s), 1053 (w), 1031 (w), 1013 (m), 987
(w), 975 (w), 942 (s), 931 (s), 896 (w), 875 (m), 833 (s), 796 (m),
750 (m), 692 (w), 674 (m), 646 (w), 635 (w), 621 (w), 587 (w),
567 (m), 546 (w) 433 (m) cmϪ1. EI mass spectrum: m/z 557
([M]ϩ, 6%), 542 ([M Ϫ CH3]ϩ, 4%), 471 ([M Ϫ 2CH(CH3)2]ϩ,
35%), 381 ([M Ϫ NHC6H3(CH{CH3}2)2]ϩ, 100%). Elemental
analysis for C28H50N5ScSi2: found (calculated): C, 59.7 (60.3);
H, 9.2 (9.0); N, 12.3 (12.6)%.
[Y(NHAr)(N2NNЈ)] (10). To a mixture of YCl3 (113 mg, 0.58
mmol) and Li2N2NNЈ (203 mg, 0.58 mmol) cooled to Ϫ78 ЊC
was added thf (10 ml). The reaction mixture was stirred for 1
min before being allowed to warm to rt after which it was stirred
for a further 10 min. The resulting clear orange solution was
cooled to Ϫ78 ЊC and a solution of LiNHAr (106 mg, 0.58
mmol) in thf (5 ml) was added dropwise. The mixture was again
allowed to warm to rt and stirred for a further 45 min after
which time the volatiles were removed under reduced pressure.
The resulting orange solid was extracted into pentane (30 ml)
and filtered. Concentration of the solution to 5 ml followed by
cooling to Ϫ30 ЊC afforded [Y(NHAr)(N2NNЈ)] 10 as an orange
micro-crystalline solid which was isolated and dried in vacuo.
Yield: 264 mg (76%). 1H NMR (500.0 MHz, 298 K, benzene-d6):
δ 8.44 (1 H, d, 3J = 5.5 Hz, 6-C5H4N), 7.18 (2 H, d, 3J = 7.5 Hz,
m-C6H3), 6.82 (1 H, t, 3J = 7.5 Hz, p-C6H3), 6.62 (1 H, dd, 3J =
8.0, 7.5 Hz, 4-C5H4N), 6.22 (1 H, d, 3J = 8.0 Hz, 3-C5H4N), 6.06
(1 H, dd, 3J = 7.5, 5.5 Hz, 5-C5H4N), 4.60 (1 H, s, NH), 3.42 (2
H, m, NCH2CH2NSi), 3.21 (4 H, m, overlapping NCH2CH2NSi
and CH(CH3)2), 3.17 (2 H, s, C5H4NCH2), 2.61 (2 H, m, NCH2-
CH2NSi), 2.19 (2 H, m, NCH2CH2NSi), 1.27 (12 H, d, 3J = 7.0
Hz, CH(CH3)2), 0.35 (18 H, s, Si(CH3)3). 13C-{1H} NMR (125.7
MHz, 298 K, benzene-d6): δ 159.2 (2-C5H4N), 153.4 (i-C6H3),
151.2 (6-C5H4N), 139.3 (4-C5H4N), 133.0 (o-C6H3), 123.6 (5-
C5H4N), 123.2 (m-C6H3), 122.5 (3-C5H4N), 114.1 (p-C6H3), 60.1
(NCH2CH2NSi), 58.6 (C5H4NCH2), 44.5 (NCH2CH2NSi),
29.9 (CH(CH3)2), 23.9 (CH(CH3)2), 1.1 (Si(CH3)3). IR (CsBr
plates, Nujol): 1605 (m), 1589 (w), 1569 (w), 1426 (s), 1350 (w),
1341 (w), 1304 (w), 1260 (m), 1239 (m), 1158 (w), 1139 (w), 1085
(m), 1055 (w), 1034 (w), 1013 (m), 935 (s), 869 (m), 829 (s), 789
(w), 747 (m), 671 (m), 644 (w), 616 (w), 540 (w), 418 (m) cmϪ1. EI
mass spectrum: m/z 601 ([M]ϩ, 5%), 586 ([M Ϫ CH3]ϩ, 2%), 514
[Y{PhC(NSiMe3)2}(N2NNЈ)] (12). To a mixture of YCl3
(95 mg, 0.49 mmol) and Li2N2NNЈ (170 mg, 0.49 mmol) cooled
to Ϫ78 ЊC was added thf (10 ml). The mixture was warmed to rt
and stirred for a further 15 min before being cooled back to
Ϫ78 ЊC. To the orange reaction mixture a colourless solution of
Li[PhC(NSiMe3)2] (131 mg, 0.48 mmol) in thf (5 ml) was added.
The mixture was again allowed to warm to rt and after further
stirring for 1 h an orange/brown mixture persisted. After the
volatiles were removed under reduced pressure the remaining
solid was extracted into pentane (40 ml) and filtered. Concen-
trating the pentane solution to ca. 5 ml gave diffraction-quality,
colourless crystals of [Y{PhC(NSiMe3)2}(N2NNЈ)] 12. Yield:
235 mg (70%). 1H NMR (300.1 MHz, 233 K, toluene-d8): δ 8.87
3
3
(1 H, d, J = 4.8 Hz, 6-C5H4N), 7.61 (2 H, d, J = 6.9 Hz,
o-C6H5), 7.12 (3 H, m, m-, p-C6H5), 6.90 (1 H, dd, 3J = 7.8, 7.8
3
Hz, 4-C5H4N), 6.60 (1 H, dd, J = 4.8, 7.8 Hz, 5-C5H4N), 6.22
(1 H, d, 3J = 7.8 Hz, 3-C5H4N), 3.58 (2 H, br m, NCH2CH2NSi),
3.22 (4 H, br s, C5H4NCH2, NCH2CH2NSi), 2.73 (2 H, br m,
NCH2CH2NSi), 2.08 (2 H, br m, NCH2CH2NSi), 0.38 (27 H, s,
NSi(CH3)3, C6H5C(NSi{CH3}3)2), 0.0 (9 H, s, C6H5C(NSi-
{CH3}3)2). 13C-{1H} NMR (75.5 MHz, 233 K, toluene-d8):
δ 183.3 (C6H5C), 159.4 (2-C5H4N), 149.4 (6-C5H4N), 144.4
(i-C6H5), 138.6 (4-C5H4N), 126.5 (o-C6H5), 124.0 (3-C5H4N),
122.1 (5-C5H4N), 59.7 (NCH2CH2NSi), 56.3 (C5H4NCH2),
45.5 (NCH2CH2NSi), 3.3 (C6H5C(NSi{CH3}3)2), 2.4 (C6H5-
C(NSi{CH3}3)2), 1.2 (NSi(CH3)3). IR (CsBr plates, Nujol):
2720 (m), 2672 (w), 1646 (w), 1607 (s), 1572 (m), 1333 (w), 1308
(w), 1170 (w), 1154 (m), 1144 (m), 1130 (w), 1086 (s), 1057 (w),
1038 (m), 1003 (w), 987 (w), 931 (m), 839 (m), 791 (w), 756 (m),
704 (m), 678 (m), 644 (w), 629 (m), 619 (w), 603 (m), 577 (m),
554 (s), 481 (s), 439 (s), 418 (w) cmϪ1. EI mass spectrum:
m/z 586 ([M Ϫ NSi(CH3)3, CH3]ϩ, 3%), 538 ([M Ϫ C6H5,
Si(CH3)3]ϩ, 1%). Elemental analysis for C29H55N6Si4Y: found
(calculated): C, 49.5 (50.5); H, 8.7 (8.1); N, 11.4 (12.2)%.
([M
Ϫ
2CH{CH3}2]ϩ, 15%), 425 ([M
Ϫ
NHC6H3-
(CH{CH3}2)2]ϩ, 13%). Elemental analysis for C28H50N5Si2Y:
found (calculated): C, 55.9 (55.9); H, 8.4 (8.4); N, 11.5 (11.6)%.
[Sc(CH2SiMe3)(N2NNЈ)] (13). To
a solution of [ScCl-
[Sc{PhC(NSiMe3)2}(N2NNЈ)] (11). To a light brown solution
of [ScCl(N2NNЈ)] 1 (103 mg, 0.25 mmol) in benzene (5 ml) was
added a colourless solution of Li[PhC(NSiMe3)2] (65 mg,
0.25 mmol) in benzene (5 ml) to give immediately an orange
colouration to the opaque reaction mixture. The mixture was
stirred at rt for 15 min before the volatiles were removed under
(N2NNЈ)] 1 (119 mg, 0.29 mmol) in benzene (5 ml) was added a
solution of LiCH2SiMe3 in benzene (5 ml) to produce immedi-
ately an orange/brown clear solution. After 1 min the mixture
became slightly opaque and was allowed to stir for a further
20 min before the volatiles were removed under reduced
pressure. The brown solid was extracted into pentane (10 ml)
J. Chem. Soc., Dalton Trans., 2002, 1694–1703
1701

View Article Online
Table 5 X-Ray data collection and processing parameters for [Y{N(SiMe3)2}(N2NNЈ)] 5, [Sc{PhC(NSiMe3)2}(N2NNЈ)] 11, [Y{PhC(NSi-
Me3)2}(N2NNЈ)] 12 and [Sc(CH2SiMe3)(N2NNЈ)] 13
5
11
12
13
Formula
Formula weight
C22H50N5Si4Y
585.93
C29H55N6ScSi4
645.10
C29H55N6Si4Y
689.05
C20H43N4ScSi3
468.81
Crystal system
Space group
Orthorhombic
P212121
Monoclinic
P21/n
Monoclinic
P21/n
Orthorhombic
P212121
a/Å
b/Å
c/Å
α/Њ
9.281(1)
17.696(2)
19.399(2)
90.0
11.064(1)
20.177(2)
16.808(2)
90.0
11.4020(3)
20.0640(7)
16.8640(5)
90.0
12.131(1)
13.069(1)
17.548(1)
90.0
β/Њ
90.0
90.0
3186.0(6)
4
2.01
92.17(1)
90.0
3749.5(6)
4
0.35
19051
6145 [I > 3σ(I )]
0.0347, 0.0403
[I > 3σ(I )]
93.423(2)
90.0
3851.1(5)
4
1.67
17138
4702 [I > 3σ(I )]
0.0276, 0.0360
[I > 3σ(I )]
90.0
90.0
2782.1(3)
4
0.40
γ/Њ
V/Å3
Z
µ(Mo-Ks)/mmϪ1
Total reflections
Observed reflections
17528
15718
5692 [I > 3σ(I )]
0.0289, 0.0332
[I > 3σ(I )]
5037 [I > 3σ(I )]
0.0299, 0.0372
[I > 3σ(I )]
a
b
R1 , Rw
a R1 = Σ Fo| Ϫ |Fc /Σ|Fo|; b Rw = √{Σw(|Fo| Ϫ |Fc|)2/Σw|Fo|2}.
and the resulting orange solution was filtered before the volatiles
were removed under reduced pressure to give [Sc(CH2SiMe3)-
(N2NNЈ)] 13 as an orange solid. Yield: 77 mg (58%). Colour-
less diffraction-quality crystals of 13 were grown from a
saturated pentane solution allowed to stand in a vibrational-
free environment for 3 d. 1H NMR (300.1 MHz, 298 K,
Acknowledgements
This work was supported by the Leverhulme Trust and
University of Oxford. We thank Dr A. Vaughan (Exxon
Chemical Co.) for generous gifts of ScCl3.
3
benzene-d6): δ 8.80 (1 H, d, J = 5.4 Hz, 6-C5H4N), 6.77 (1 H,
References
dd, 3J = 7.5, 7.8 Hz, 4-C5H4N), 6.42 (1 H, dd, 3J = 5.4, 7.5 Hz,
3
1 P. R. Meehan, D. R. Aris and G. R. Willey, Coord. Chem. Rev., 1999,
181, 121; S. A. Cotton, Polyhedron, 1999, 18, 1691; F. T. Edelmann,
in Comprehensive Organometallic Chemistry, 2nd edn., eds. E. W.
Abel, F. G. A. Stone and G. Wilkinson, Pergamon, Oxford, 1995,
vol. 4, p. 10; F. A. Hart, in Comprehensive Coordination Chemistry,
eds. R. D. Gillard, J. A. McCleverty and G. Wilkinson, Pergamon,
Oxford, 1987, vol. 3, p. 1059; F. G. N. Cloke, in Comprehensive
Organometallic Chemistry, 2nd edn, eds. E. W. Abel, F. G. A. Stone
and G. Wilkinson, Pergamon, Oxford, vol. 4, p. 1.
2 G. Jeske, H. Lauke, H. Mauermann, P. N. Swepston, H. Schumann
and T. J. Marks, J. Am. Chem. Soc., 1985, 107, 8091; P. L. Watson,
J. Am. Chem. Soc., 1982, 104, 337; P. L. Watson and G. W. Parshall,
Acc. Chem. Res., 1985, 18, 51.
3 G. A. Molander and J. O. Hoberg, J. Org. Chem., 1992, 57, 3266;
G. Jeske, H. Lauke, H. Mauermann, H. Schumann and T. J. Marks,
J. Am. Chem. Soc., 1985, 107, 8111.
4 K. N. Harrison and T. J. Marks, J. Am. Chem. Soc., 1992, 114, 9220.
5 T. Sakakura, H.-J. Lautenschlager and M. Tanaka, J. Chem. Soc.,
Chem. Commun., 1991, 40.
6 V. M. Arredondo, F. E. McDonald and T. J. Marks, Organometallics,
1999, 18, 1949; M. R. Gagne, C. L. Stern and T. J. Marks, J. Am.
Chem. Soc., 1992, 114, 275; M. R. Gagne, L. Brard, V. P. Conticello,
M. A. Giardello, C. L. Stern and T. J. Marks, Organometallics, 1992,
11, 2003; Y. W. Li, P.-F. Fu and T. J. Marks, Organometallics, 1994,
13, 439.
7 J. Arnold, C. G. Hoffman, D. Y. Dawson and F. J. Hollander,
Organometallics, 1993, 12, 3645.
8 J. Blackwell, C. Lehr, Y. M. Sun, W. E. Piers, S. D. Pearce-Batchilder,
M. J. Zaworotko and V. G. Young, Can. J. Chem., 1997, 75,
702.
9 (a) R. Duchateau, C. T. van Wee, A. Meetsma, P. T. van Duijnen and
J. H. Teuben, Organometallics, 1996, 15, 2279; (b) R. Duchateau,
A. Meetsma and J. H. Teuben, Organometallics, 1996, 15, 1656;
(c) S. Bambirra, M. J. R. Brandsma, E. A. C. Brussee, A. Meetsma,
B. Hessen and J. H. Teuben, Organometallics, 2000, 19, 3197;
(d ) F. T. Edelmann and J. Richter, Eur. J. Solid State Inorg. Chem.,
1996, 33, 157; (e) J. R. Hagedorn and J. Arnold, Organometallics,
1996, 15, 984.
10 (a) M. D. Fryzuk, G. Giesbrecht and S. J. Rettig, Organometallics,
1996, 15, 3329; (b) M. D. Fryzuk, L. Jafarpour, F. M. Kerton, J. B.
Love, B. O. Patrick and S. J. Rettig, Organometallics, 2001, 20, 1387;
(c) M. D. Fryzuk, G. Giesbrecht and S. J. Rettig, Can. J. Chem.,
2000, 78, 1003.
5-C5H4N), 6.27 (1 H, d, J = 7.8 Hz, 3-C5H4N), 3.35 (2 H, m,
NCH2CH2NSi), 3.11 (2 H, s, C5H4NCH2), 3.07 (2 H,
m, NCH2CH2NSi), 2.41 (2 H, m, NCH2CH2NSi), 2.07 (2 H, m,
NCH2CH2NSi), 0.42 (18 H, s, NSi(CH3)3), 0.21 (9 H, s,
CH2Si(CH3)3), 0.05 (2 H, s, CH2Si(CH3)3). 13C-{1H} NMR
(75.5 MHz, 298 K, benzene-d6): δ 159.3 (2-C5H4N), 150.6
(6-C5H4N), 139.2 (4-C5H4N), 123.0 (5-C5H4N), 122.6
(3-C5H4N), 60.9 (NCH2CH2NSi), 58.8 (C5H4NCH2), 44.4
(NCH2CH2NSi), 30.7 (CH2Si(CH3)3), 4.5 (CH2Si(CH3)3), 1.8
(NSi(CH3)3). IR (KBr plates, Nujol): 1608 (s), 1572 (m), 1377
(w), 1344 (w), 1302 (w), 1242 (s), 1155 (w), 1143 (w), 1068 (m),
1017 (m), 985 (w), 945 (m), 924 (m), 834 (s), 784 (w), 759 (w),
740 (w), 678 (w), 669 (w), 646 (w), 633 (w), 570 (m), 557 (m),
455 (s) cmϪ1. EI mass spectrum: m/z 381 ([M Ϫ CH2Si(CH3)3]ϩ,
4%), 249 ([M Ϫ 3 Si(CH3)3]ϩ, 6%), 322 ([M Ϫ 2 Si(CH3)3,
CH2Si(CH3)3, H]ϩ, 87%). Elemental analysis for C20H43N4ScSi3:
found (calculated): C, 50.3 (51.2); H, 9.6 (9.3); N, 11.9 (12.0)%.
Crystal structure determinations for [Y{N(SiMe3)2}(N2NNЈ)]
(5), [Sc{PhC(NSiMe3)2}(N2NNЈ)] (11), [Y{PhC(NSiMe3)2}-
(N2NNЈ)] (12) and [Sc(CH2SiMe3)(N2NNЈ)] (13). Crystal data
collection and processing parameters are given in Table 5. Crys-
tals were immersed in a film of perfluoropolyether oil on a glass
fibre and transferred to an Enraf-Nonius DIP2000 image plate
diffractometer equipped with an Oxford Cryosystems low-
temperature device.31 Data were collected at low temperature
using Mo-Kα radiation; equivalent reflections were merged and
the images were processed with the DENZO and SCALEPACK
programs.32 Corrections for Lorentz-polarisation effects and
absorption were performed and the structures were solved by
direct methods using SIR92.33 Subsequent difference Fourier
syntheses revealed the positions of all other non-hydrogen
atoms. Hydrogen atoms were placed geometrically. Refinement
of an absolute structure (Flack) parameter34 for 5 and 13
yielded values of 0.01(10) and 0.03(2), respectively. Extinc-
tion corrections were applied as required.35 Crystallographic
calculations were performed using SIR9233 and CRYSTALS.36
CCDC reference numbers 170227 and 176539–176541.
11 R. Duchateau, T. Tuinstra, E. A. C. Brussee, A. Meetsma, P. T.
van Duijnen and J. H. Teuben, Organometallics, 1997, 16, 3511;
R. Duchateau, E. A. C. Brussee, A. Meetsma and J. H. Teuben,
Organometallics, 1997, 16, 5506.
See http://www.rsc.org/suppdata/dt/b1/b111469g/ for crystal-
lographic data in CIF or other electronic format.
1702
J. Chem. Soc., Dalton Trans., 2002, 1694–1703

View Article Online
12 H. W. Gorlitzer, M. Spiegler and R. Anwander, J. Chem. Soc.,
Dalton Trans., 1999, 4287.
13 S. Bambirra, D. van Leusen, A. Meetsma, B. Hessen and J. Teuben,
Chem. Commun., 2001, 637; S. Hajela, W. P. Schaefer and J. E.
Bercaw, J. Organomet. Chem., 1997, 532, 45; S. Y. Bylikin, D. A.
Robson, N. A. H. Male, L. H. Rees, P. Mountford and M. Schröder,
J. Chem. Soc., Dalton Trans., 2001, 170.
14 L. Lee, D. J. Berg and G. W. Bushnell, Organometallics, 1995, 14,
5021; L. Lee, D. J. Berg and G. W. Bushnell, Organometallics, 1995,
14, 8; L. Lee, D. J. Berg, F. W. Einstein and R. J. Batchelor,
Organometallics, 1997, 16, 1819.
15 (a) H. Noss, M. Oberthur, C. Fischer, W. P. Kretschmer and R.
Kempe, Eur. J. Inorg. Chem., 1999, 2283; (b) D. D. Graf, W. M. Davis
and R. R. Schrock, Organometallics, 1998, 17, 5820; (c) T. I.
Gountchev and T. D. Tilley, Organometallics, 1999, 18, 2896; (d )
T. I. Gountchev and T. D. Tilley, Organometallics, 1999, 18, 5661.
16 P. Roussel, N. W. Alcock and P. Scott, Chem. Commun., 1998, 801.
17 R. R. Schrock, Acc. Chem. Res., 1997, 30, 9; J. G. Verkade, Acc.
Chem. Res., 1993, 26, 483; P. Roussel, N. W. Alcock, R. Boaretto, A.
Kingsley, I. J. Munslow, C. P. Sanders and P. Scott, Inorg. Chem.,
1999, 38, 3651; P. Roussel and P. Scott, J. Am. Chem. Soc., 1998,
120, 1070; N. Kaltsoyannis and P. Scott, Chem. Commun., 1998,
1665.
18 (a) M. E. G. Skinner, D. A. Cowhig and P. Mountford, Chem.
Commun., 2000, 1167; (b) M. E. G. Skinner, Y. Li and P. Mountford,
Inorg. Chem., 2002, 41, in press.
19 H. Brand and J. Arnold, Coord. Chem. Rev., 1995, 140, 137;
P. J. Brothers, Adv. Organomet. Chem., 2001, 46, 224.
R. Weimann and J. Demtschuk, J. Organomet. Chem., 1997, 536,
541; P. C. Shao, D. J. Berg and G. W. Bushnell, Inorg. Chem., 1994,
33, 3452; H. Schumann, E. C. E. Rosenthal and J. Demptschuk,
Organometallics, 1998, 17, 5324.
23 W. A. Herrmann, F. C. Munck, G. R. J. Artus, O. Runte and
R. Anwander, Organometallics, 1997, 16, 682; W. A. Herrmann,
J. Eppinger, M. Spiegler, O. Runte and R. Anwander,
Organometallics, 1997, 16, 1813; W. T. Klooster, L. Brammer, C. J.
Schaverien and P. H. M. Budzelaar, J. Am. Chem. Soc., 1999, 121,
1381.
24 M. E. G. Skinner, D.Phil Thesis, University of Oxford, 2001.
25 See for example (and references therein): P. M. Fitzsimmons and
S. C. Jackels, Inorg. Chim. Acta, 1996, 246, 301; I. M. Hodzic
and S. R. Niketic, J. Serb. Chem. Soc., 2001, 66, 331; P. Indrasenan
and N. K. K. Raj, J. Indian Chem. Soc., 2000, 77, 259.
26 D. Hedden, D. M. Roundhill, W. C. Fultz and A. L. Rheingold,
Organometallics, 1986, 5, 336.
27 J. Barker and M. Kilner, Coord. Chem. Rev., 1994, 133, 219; F. T.
Edelmann, Coord. Chem. Rev., 1994, 137, 403.
28 The United Kingdom Chemical Database Service: D. A. Fletcher,
R. F. McMeeking and D. Parkin, J. Chem. Inf. Comput. Sci., 1996,
36, 746.
29 3D Search and Research using the Cambridge Structural Database:
F. H. Allen and O. Kennard, Chem. Des. Autom. News, 1993, 8, 1;
F. H. Allen and O. Kennard, Chem. Des. Autom. News, 1993, 8, 31.
30 See for example (and references therein): P. J. Stewart, A. J. Blake
and P. Mountford, Inorg. Chem., 1997, 36, 1982; P. J. Stewart, A. J.
Blake and P. Mountford, Inorg. Chem., 1997, 36, 3616.
31 J. Cosier and A. M. Glazer, J. Appl. Crystallogr., 1986, 19, 105.
32 D. Gewirth, The HKL Manual, written with the co-operation of the
program authors, Z. Otwinowski and W. Minor, Yale University,
CT, 1995.
20 P. Mountford, Chem. Soc. Rev., 1998, 27, 105; F. A. Cotton and
J. Czuchajowska, Polyhedron, 1990, 9, 2553.
21 W. J. Evans, M. A. Ansari, J. W. Ziller and S. I. Khan, Inorg. Chem.,
1996, 35, 5435; W. A. Herrmann, R. Anwander, F. C. Munck, W.
Scherer, V. Dufaud, N. W. Huber and G. R. J. Artus, Z. Naturforsch.,
Teil B, 1994, 49, 1789; A. C. Benniston, A. Harriman and V. M.
Lynch, J. Am. Chem. Soc., 1995, 117, 5275; K. C. Hultzsch, T. P.
Spaniol and J. Okuda, Angew. Chem., Int. Ed., 1999, 38, 227.
22 M. D. Rausch, D. F. Foust, R. D. Rogers and J. L. Atwood,
J. Organomet. Chem., 1984, 265, 241; M. Booij, N. H. Kiers,
A. Meetsma, J. H. Teuben, W. J. J. Smeets and A. L. Spek,
Organometallics, 1989, 8, 2454; H. Schumann, F. Erbstein,
33 A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi, M. C.
Burla, G. Polidori and M. Camalli, J. Appl. Crystallogr., 1994, 27,
435.
34 H. Flack, Acta Crystallogr., Sect. A, 1983, 39, 876.
35 A. C. Larson, Acta Crystallogr., 1967, 23, 664.
36 D. J. Watkin, C. K. Prout and J. R. Carruthers, P. W. Betteridge,
CRYSTALS Issue 10, Chemical Crystallography Laboratory,
University of Oxford, 1996.
J. Chem. Soc., Dalton Trans., 2002, 1694–1703
1703