Synthesis and thermal behavior of dimethyl scandium complexes featuring anilido-phosphinimine ancillary ligands

Article abstract of DOI:10.1016/j.jorganchem.2007.08.037

A family of N,N donor ligands [1-(NHAr)-2-(PR₂{double bond, long}NAr′)C₆H₄] (1a-d; Ar = 2,6-ⁱPr₂-C₆H₃, R = Me, Ph, Ar′ = 2,4,6-Me₃-C₆H₂, 2-ⁱPr-C₆H₄, 2,6-ⁱPr₂-C₆H₃) has been prepared and fully characterized by multinuclear NMR spectroscopy and X-ray crystallography. Lithiation of the N-H unit and subsequent salt metathesis protocols with ScCl₃THF₃ provides an avenue to organometallic scandium complexes. The resultant base-free monomeric dichlorides LScCl₂, 3a-d, have been fully characterized by NMR spectroscopy as well as X-ray crystallography (3a,c,d). Alkylation of the dichlorides using LiMe results in clean formation of dialkyl complexes LScMe₂ 4a-c. Thermolysis of these materials under argon and hydrogen leads to decomposition products as a result of C-H activation of the ligand. Analysis of these results provides a qualitative assessment of the metalative resistance of each ligand framework.

Full text of DOI:10.1016/j.jorganchem.2007.08.037

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 834–846
www.elsevier.com/locate/jorganchem
Synthesis and thermal behavior of dimethyl scandium
complexes featuring anilido-phosphinimine ancillary ligands
Korey D. Conroy, Warren E. Piers ,1, Masood Parvez
*
Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
Received 11 August 2007; received in revised form 28 August 2007; accepted 28 August 2007
Available online 6 September 2007
Abstract
A family of N,N donor ligands [1-(NHAr)-2-(PR2@NAr0)C6H4] (1a–d; Ar = 2,6-iPr2-C6H3, R = Me, Ph, Ar0 = 2,4,6-Me3-C6H2,
2-iPr-C6H4, 2,6-iPr2-C6H3) has been prepared and fully characterized by multinuclear NMR spectroscopy and X-ray crystallography.
Lithiation of the N–H unit and subsequent salt metathesis protocols with ScCl3THF3 provides an avenue to organometallic scandium
complexes. The resultant base-free monomeric dichlorides LScCl2, 3a–d, have been fully characterized by NMR spectroscopy as well as
X-ray crystallography (3a,c,d). Alkylation of the dichlorides using LiMe results in clean formation of dialkyl complexes LScMe2 4a–c.
Thermolysis of these materials under argon and hydrogen leads to decomposition products as a result of C–H activation of the ligand.
Analysis of these results provides a qualitative assessment of the metalative resistance of each ligand framework.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Scandium; Chelating ligands; Anilido-phosphinimine ligands; Thermal stability
1. Introduction
parts tend to be less robust, and decompose via C–H acti-
vation of one of the ortho-groups of the N-aryl units. This
deactivation mode also operates for the organoyttrium
congeners [10] and, thus, alternatives to NacNac were
pursued.
Ligand design is a regular exercise for organometallic
chemists attempting to generate novel coordination envi-
ronments, stabilizing particular oxidation states and
preparing robust catalysts. With respect to group 3 chem-
istry [1], recent efforts have focused on the synthesis and
reactivity of metal cations [2], hydrides [3] and metal to ele-
ment double bonds [4]. In that regard, the b-diketiminato,
or ‘‘NacNac’’ ligand (I) has been firmly established as a
cyclopentadienide (‘‘Cp’’) surrogate for organotransition
metal chemistry [5] due to the steric and electronic [6]
tunability of the ligand scaffold and its relatively straight-
forward synthesis [7]. This ancillary, featuring 2,6-disubsti-
tution of the N-aryl groups, has proven an appropriate
support for neutral [8] and cationic [9] organoscandium
complexes. While neutral scandium bis-alkyl complexes
exhibit moderate thermal stability, their cationic counter-
R
R
R
H
P R
N
NH
N
Ar
Ar
NH
NH
N
Ar
Ar
Ar'
Ar'
I
II
III
We recently reported a new anilido-imine system (II),
which was deployed as a support for organoyttrium cations
[11]. Attempts to prepare organoyttrium hydride com-
plexes from the same dialkyl starting materials were perpet-
ually hampered by nucleophilic attack by the hydride at the
imine carbon generating an undesirable dianionic ligand.
To eliminate this possibility, the anilido-imine framework
was modified through incorporation of a phosphinimine
*
Corresponding author. Tel.: +1 403 220 5746; fax: +1 403 289 9488.
E-mail address: wpiers@ucalgary.ca (W.E. Piers).
S. Robert Blair Professor of Chemistry (2005–2010).
1
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.037

K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
835
unit [12] in place of the imine, producing a new ancillary III
[13]. The institution of the phosphorus(V) center should
eliminate any nucleophilic attack of the ligand backbone,
and the PN unit should allow for facile steric and electronic
tunability. This system has been effectively utilized as a sta-
bilizing ligand for neutral and cationic organoaluminum
complexes [13] and recently for organoyttrium alkyls [14].
In this paper, we describe the synthesis of a family of ani-
lido-phosphinimine ligands highlighting the modularity of
the ligand framework. The thermal stability of the corre-
sponding scandium dimethyl complexes is evaluated, as
well as their ability to support organoscandium hydrides.
similar yields whether the lithium anilide is added stoichio-
metrically or in slight excess. All of the ligands are obtained
analytically pure as colorless crystals upon recrystallization
from hot methanol in overall yields of 37–45% starting
from bromo-2-fluorobenzene. This modular synthesis
allows for a wide array of ligands to be prepared depending
on the phosphine, azide and N-aryl substituents utilized;
the current study will focus on the Dipp analide family
depicted in Scheme 1.
Ligands 1a–d have been comprehensively characterized
by combustion analysis and multinuclear NMR spectros-
copy (1H, 13C, 31P). Signature spectral features include
1
the N–H shift downfield of 9 ppm in the H NMR spectra
2. Results and discussion
and singlets in the 31P{1H} NMR spectra between 0 and
6 ppm for 1a–c which shifts further downfield when the
more electron donating methyl groups are installed on
phosphorus for 1d. The X-ray structure of 1a has been
reported previously [13] and those of 1b and 1c are shown
in Figs. 1 and 2, respectively; comparative metrical data for
the three ligands whose structures have been determined
are presented in Table 1.
The solid state structure of 1b (Fig. 1) illustrates the
characteristic twist within the ligand backbone with a
C(27)–C(22)–P–N(1) torsion angle of 50.8(2)ꢁ which is even
greater (c.f. 53.5(1)ꢁ) in the bulkier system 1c (Fig. 2 and
Table 1). Both angles are notably larger than the 44.1(2)ꢁ
reported previously for 1a [13], perhaps a result of the
enhanced steric bulk of the aryl substituents on the phos-
phinimine nitrogen. As a result the aryl group of the PN
unit is oriented significantly out of the plane while the ani-
lido Dipp group lies orthogonal to the N–C–C–P plane.
The phenyl rings on phosphorus occupy pseudoaxial and
equatorial positions relative to the backbone plane. This
ligand geometry contrasts with related N,N-bidentate
2.1. Synthesis and characterization of anilido-phosphinimine
ligands 1a–d
The synthesis of ligand 1a has been previously reported
[13] and follows the slightly modified sequence outlined in
Scheme 1. Of note, the preparation of o-C6H4FPR2
(R = Me, Ph [15]) gives consistently higher yields when
THF instead of diethyl ether (as originally reported) is
employed. The lithiation step is kinetically much slower
in ether, and the in situ generated aryl lithium begins to pre-
cipitate prior to addition of the phosphorus electrophile,
which significantly lowers the yield. In THF however, the
lithiation is very efficient and the aryl lithium remains dis-
solved in the more coordinating solvent at ꢀ78 ꢁC. Oxida-
tion of the phosphines under Staudinger conditions [16]
can be performed in air with diethyl ether instead of under
anaerobic conditions in MeCN and the resultant phosphin-
imines o-C6H4FP(R2)@NAr0(R = Me, Ph; Ar0 = Mes,
Mipp, Dipp) can be recrystallized from hexane. Incorpora-
tion of the formally P(V) center activates the ortho fluorine
towards nucleophilic aromatic substitution, which gives
1. nBuLi, THF
Br
2. R2PCl
PR2
F
F
ArN3, Et2O
- N2
NHLi
PR2
N
PR2
N
THF, reflux
- LiF
N
F
Dipp
H
Ar
Ar
R
Ar
1a Ph
1b Ph
1c Ph
1d Me
Mes
Mipp
Dipp
Dipp
Mes = 2,4,6-Me3C6H2
Mipp = 2-iPr-C6H4
Fig. 1. Thermal ellipsoid diagram of 1b at 50% probability. Selected bond
lengths (A) and angles (ꢁ): P–N(1), 1.575(2); P–C(22), 1.810(2); N(2)–
Dipp = 2,6-iPr2-C6H3
˚
C(27), 1.381(2); N(2)–C(27)–C(22)–P, 5.4(3); C(27)–C(22)–P–N(1),
Scheme 1.
50.8(2).

836
K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
anilido-imine [11] scandium complexes. Compound 1a
has been shown to react with AlMe3 and AlH3 Æ NMe3 to
produce dimethyl- and dihydrido-aluminum complexes
with concomitant loss of CH4 and H2 [13]. Attempts to pre-
pare diakyl scandium complexes using alkane elimination
protocols [18] with 1a–d were unsuccessful, and thus a
more traditional salt metathesis procedure was developed.
Treatment of 1a–d with nBuLi in toluene quantitatively
generates the lithium salts 2a–d that can be isolated as pale
yellow solids by filtration and washing with hexanes
(Scheme 2). Lithiated ligands 2a–d are air and moisture
sensitive materials but are stable indefinitely under argon
at room temperature. Characterization by multinuclear
NMR spectroscopy reveals the loss of the diagnostic N–
1
H signal in the H NMR spectra, and a downfield shift
in the 31P{1H} NMR spectra to 18–20 ppm. The phosphin-
imine nitrogen chelates the lithium ion, effectively deshiel-
ding the phosphorus center leading to the downfield shift
[13].
Fig. 2. Thermal ellipsoid diagram of 1c at 50% probability. Selected bond
lengths (A) and angles (ꢁ): P–N(1), 1.558(2); P–C(25), 1.817(2); N(2)–
C(30), 1.383(2); N(2)–C(30)–C(25)–P, 6.2(2); C(30)–C(25)–P–N(1),
53.5(1).
˚
The anilido-phosphinimine scaffold can be attached to
scandium by refluxing toluene solutions of 2a–d with
ScCl3THF3 for 8–10 h forming compounds LScCl2 3a–d
in moderate yields of 70–95% as off-white solids upon
work-up. Compounds 3 are soluble in aromatic and halo-
genated solvents but largely insoluble in all aliphatic media.
Spectroscopic analysis of 3a–d indicates complete loss of
coordinated THF donors and the 31P{1H} NMR spectra
indicate a further downfield shift to the range of 29–
33 ppm. Whereas the spectra for 3a,c,d all exhibit sharp,
resolved signals in the 1H NMR spectrum, the mixed
Mipp–Dipp dichloride 3b exhibits broad signals for the
Dipp isopropyl methynes and all of the isopropyl methyls
at room temperature. Cooling C7D8 solutions below
ꢀ30 ꢁC freezes out the exchange processes and sharp sep-
tets and doublets are resolved. Presumably this behavior
is a result of hindered rotation of the Dipp group and at
Table 1
Selected metrical parameters for 1a–c
R
C2
H
R
C1
N2
P
N1
Dipp
Ar
Param
1a [13]
1b
1c
˚
Bond distances (A)
N(2)–C(1)
C(2)–P
1.382(3)
1.817(2)
1.563(2)
1.381(2)
1.810(2)
1.575(2)
1.383(2)
1.817(2)
1.558(1)
P–N(1)
Bond angles (ꢁ)
N(2)–C(1)–C(2)
C(2)–P–N(1)
120.1(2)
120.45(16)
116.57(9)
121.30(13)
113.87(7)
116.45(10)
Torsion angles (ꢁ)
N(2)–C(1)–C(2)–P
C(1)–C(2)–P–N(1)
3.7(3)
44.1(2)
5.4(3)
50.8(2)
6.2(2)
53.5(1)
nBuLi, tol.
PR2
N
PR2
N
N
N
Li
2a-d
Dipp
H
Dipp
Ar
Ar
ligands like the b-diketiminates [5] and imine-anilido sys-
tems [11,17] where the flanking aryl groups are parallel to
each other and perpendicular to the ligand plane. In the
anilido-phosphinimine systems, the coordination core is
protected on the PN flank by the phosphinimine aryl group
and the pseudoaxial phenyl group on phosphorus. The P–
ScCl3THF3
tol., reflux
- LiCl
˚
˚
N(1) contact at 1.575(2) A for 1b and 1.558(2) A for 1c are
typical for P@N bonds of this type.
PR2
N
PR2
N
2 MeLi, tol.
- 2 LiCl
2.2. Dichloro- and dimethylscandium complexes
N
N
Dipp
Sc
Dipp
Sc
Cl
Ar
Ar
With a family of well characterized ligands in hand, we
sought to evaluate their ability to support monomeric,
base-free dichloro- and dimethylscandium complexes
related to our previous work with b-diketiminato-[8] and
Me
Me
Cl
3a-d
4a-d
Scheme 2.

K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
837
room temperature the compound is at the onset of the fast
exchange regime.
Concentrated benzene solutions of 3a and 3c afford X-
ray quality crystals when cooled to 0 ꢁC and the molecular
structures of these two compounds are shown in Figs. 3
and 4, respectively. The structure of 3a is dimeric with
the two distorted trigonal bypramidal scandium atoms
each possessing two bridging chlorides and one terminal
chloride within its coordination sphere, in addition to the
chelating nitrogens of the ligand framework. It is presumed
that this aggregation exists in benzene solution as well,
since 3a is only sparingly soluble in C6D6, which contrasts
the other dichlorides studied here. As in the free ligand, the
backbone atoms are not co-planar as illustrated by the
C(13)–C(14)–P–N(2) torsion angle of 22.5(7)ꢁ, though it
is much more planar than in 1a (44.1(2)ꢁ) and 1b
(53.6(2)ꢁ). This is likely a result of the congested core of
the dimer, necessitating the two ligands to arrange them-
selves approximately orthogonal to each other to minimize
‘‘across dimer’’ steric repulsions. The P–N contact is elon-
Fig. 4. Thermal ellipsoid diagram of 3c at 50% probability. Selected bond
lengths (A) and angles (ꢁ): P–N(2), 1.630(2); Sc–N(1), 2.071(2); Sc–N(2),
2.106(2); Sc–Cl(1), 2.3373(7); Sc–Cl(2), 2.3341(6); P–C(25), 1.783(2); N(1)–
C(26), 1.386(2); N(1)–Sc–N(2), 91.59(6); N(1)–C(26)–C(25)–P, 8.7(2);
C(26)–C(25)–P–N(2), 48.1(2).
˚
still consistent with a PN double bond. The terminal Sc–
˚
˚
gated from the free ligand to 1.628(5) A indicating strong
Cl contact of 2.345(2) A is shorter than those in the bridg-
donation from the phosphinimine unit, but the distance is
ing chlorides; these are asymmetrically bound, with Sc–Cl
˚
˚
bond distances of 2.466(2) A and 2.633(2) A. This suggests
that aggregation is weak and indeed addition of THF to
C7D8 suspensions of 3a promotes complete dissolution,
1
giving rise to new H and 31P{1H} signals corresponding
to a five-coordinated monomeric scandium dichloride with
one THF donor. The Sc–N contacts are equivalent within
experimental error which highlights the strong donating
capacity of the phosphinimine moiety (vide infra).
When the mesityl group is replaced by the bulkier Dipp
group in 3c a monomeric dichloride structure is obtained
(Fig. 4). The four-coordinate scandium adopts a distorted
tetrahedral geometry and does not retain any THF mole-
˚
cules. The P–N bond distance of 1.630(2) A is comparable
to that observed for 3a however the ligand twist of 48.1(2)ꢁ
is more reminiscent of the free ligand than of the dimer 3a.
The phenyl groups at phosphorus adopt the predicted axial
and equatorial orientations, with the axial group and the
adjacent Dipp group serving to protect regions of space
above and below the ligand plane about the metal center.
The inequivalent Sc–N contacts indicate asymmetric ligand
binding with the anilide nitrogen more closely bound to the
˚
˚
metal. The Sc–Cl distances of 2.3341(6) A and 2.3373(7) A
are unremarkable.
Dichlorides 3 represent precursors to base-free dialkyl
scandium complexes. Treatment of 3a-c with ethereal solu-
tions of methyl lithium at 0 ꢁC produce dimethylscandium
species 4a–c in good yields following removal of LiCl by fil-
tration. Addition of precisely 2 equiv. of MeLi is important
as any excess produces lithiated ligands 2 which are difficult
to remove from samples of 4. Purified dimethyls 4 are sta-
ble indefinitely at room temperature under argon as solids,
but show degrees of decomposition over time in solution
(vide infra). Solution NMR spectra reveal 31P shifts reside
in the same region (ꢁ30 ppm) as their dichloride precur-
sors. The 1H spectra of 4 are analogous to 3 with the
Fig. 3. Thermal ellipsoid diagram of 3a at 50% probability. The dimeric
structure is shown in (a) and the monomer moiety is shown in (b). Selected
˚
bond lengths (A) and angles (ꢁ): P–N(2), 1.628(5); Sc–N(1), 2.107(5); Sc–
N(2), 2.101(5); Sc–Cl(1), 2.466(2); Sc–Cl(2), 2.345(2); Sc–Cl(10), 2.633(2);
P–C(14), 1.767(7); N(1)–C(13), 1.385(7); N(1)–Sc–N(2), 92.5(2); N(1)–
C(13)–C(14)–P, 16.9(9); C(13)–C(14)–P–N(2), 22.5(7).

838
K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
exception that the ScMe groups give rise to resonances
1
upfield of 0 ppm. Once again, the room temperature H
NMR spectrum of 4b is broadened, however the spectrum
becomes resolved below ꢀ30 ꢁC (Fig. 5). Although the
ligand provides an environment that lacks left–right, or
top–bottom symmetry, the ScMe groups, which reside in
chemically equivalent orientations, resonate as a singlet,
even at temperatures below ꢀ80 ꢁC. This suggests that
the twist in the backbone is not static, and a dynamic pro-
cess must exist in solution with a low barrier to inversion at
scandium. 13C{1H} NMR spectra do not always reveal the
ScMe resonance due to the close proximity to the quadru-
polar scandium (I = 7/2); however, these resonances can be
detected using an 1H–13C HMQC experiment, and they fall
in the range 23–25 ppm. While 3a is dimeric in the solid
state, 4a is likely a monomer due to the observed chemical
shift of ꢀ0.26 ppm for the Sc–Me carbons, which is in the
same range as the other monomeric dimethyl derivatives
(vide infra).
Fig. 6. Thermal ellipsoid diagram of 4b at 50% probability. Selected bond
˚
lengths (A) and angles (ꢁ): P–N(1), 1.616(3); Sc–N(1), 2.145(3); Sc–N(2),
2.134(3); Sc–C(1), 2.206(4); Sc–C(2), 2.211(5); P–C(3), 1.785(4); N(2)–
C(4), 1.383(5); N(1)–Sc–N(2), 89.8(1); N(2)–C(4)–C(3)–P, 6.5(5); C(4)–
C(3)–P–N(1), 43.4(4).
X-ray quality crystals of 4b and 4c were grown from
concentrated hexane solutions cooled to ꢀ35 ꢁC and their
molecular structures are shown in Figs. 6 and 7, respec-
tively. Complexes 4b and 4c reveal four-coordinate,
distorted tetrahedral scandium centers with distinct Sc–N
the ligand derived from 1c. In all cases, closer Sc–Nanilide
contacts are observed vs. the Sc–Nphosphinimine highlighting
the charge localization in that position. Nevertheless, the
˚
disparities in the bond lengths (0.015–0.035 A) is signifi-
˚
˚
bond distances of 2.134(3) A and 2.145(3) A for 4b and
cantly smaller than for our previously reported yttrium
complexes featuring the anilido-imine ligand (II) where
the Y–Nanilide contact was consistently shorter than the
˚
˚
2.127(2) A and 2.160(2) A for 4c with the shorter contacts
arising from the anilide nitrogens indicating a moderate
charge localization within the ligand backbone. The
Sc–C distances are statistically equivalent and average
˚
Y–Nimine by P0.130 A [11]. This suggests the phosphini-
mine unit possesses enhanced basicity vs. the imine func-
tion, making it an effective donor [12]. For 3c and 4c that
feature chloride and methyl ligands, respectively, the two
observed Sc–E contacts are statistically equivalent and
does not suggest that a particular coordination site is more
or less hindered.
Whereas the ligand systems with phenyl groups on phos-
phorus react cleanly with MeLi to afford dimethyl scan-
dium complexes, the preparation of 4d, in which the
˚
2.209(4) A which is in agreement with other dimethylscan-
dium complexes [8]. A similar coordination environment is
observed for 4c which is isostructural to 3c. As seen in the
structure of 4b, the Sc–N contacts are elongated in 4c
relative to 4b, however, N–Sc–N bond angle remains essen-
tially unchanged.
Table 2 summarizes the metrical parameters of the three
scandium-containing complexes (3c, 4c and 5c) featuring
Fig. 5. Variable temperature 400 MHz 1H NMR spectra of 4b in C7D8 ( ).
*

K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
839
resonance intensity are indicative of a metalation process
(see below and Scheme 3) wherein a methyl group is lost
through C–H activation of the ligand. The presence of four
well resolved isopropyl methynes indicates that metalation
is not occurring at either of the Dipp groups, and must
originate at the phosphorus methyls. The typical doublet
for the P(Me)2 is absent from the proton NMR spectrum
and replaced with a complex multiplet characteristic of dia-
stereotopic methylene protons. This was confirmed by a
structural determination of the product (5d), and the struc-
ture is shown in Fig. 8.
Metalated product 5d is a dimeric structure with the
scandium methyls adopting a symmetric bridging geometry
between the two distorted trigonal bipyramidal scandium
centers. As the spectroscopy showed, the axial methyl
group on phosphorus has succumbed to metalation, form-
Fig. 7. Thermal ellipsoid diagram of 4c at 50% probability. Selected bond
˚
lengths (A) and angles (ꢁ): P–N(2), 1.629(2); Sc–N(1), 2.127(2); Sc–N(2),
˚
2.160(2); Sc–C(1), 2.208(2); Sc–C(2), 2.209(2); P–C(25), 1.788(2); N(1)–
C(26), 1.386(2); N(1)–Sc–N(2), 91.52(6); N(1)–C(26)–C(25)–P, 5.2(2);
C(26)–C(25)–P–N(2), 47.1(2).
ing a tuck-in species with a Sc–C(2) distance of 2.338(3) A
˚
that is 0.06 A shorter than the bridging Sc–C(1) length of
˚
2.399(3) A. The N(2)–P–C(2)–Sc ring possesses a butterfly
conformation with a torsion angle of 31.6(1)ꢁ. The back-
bone twist is in the range of the dimethyl complexes 4b,c
at 52.1(3)ꢁ, and has pushed the phosphinimine Dipp group
away from the scandium allowing for dimerization. The
N(1)–Sc–N(2) angle is approximately 5ꢁ more obtuse than
in the dimethyl analogues with the scandium drawn into
the ligand core by the metalated methylene unit.
phenyl groups have been replaced with methyls, is not pos-
sible under the same conditions. Here, an asymmetric com-
plex is obtained with a scandium methyl resonance at
0.5 ppm, which integrates to 3H and not the predicted
6H. The loss of symmetry and lower than expected methyl
Table 2
2.3. Thermal stability of scandium dialkyl complexes 4a–c
Selected metrical parameters for 3c, 4c and 5c
The thermal instability of putative complex 4d towards
loss of methane is somewhat surprising given that the sp2
hybridized C–H bonds of the phosphorus phenyl groups
in compounds 4a–c might be expected to be kinetically
more prone [19] to such decomposition pathways. Given
the potential of monomeric dialkyl scandium complexes
in catalysis [9,20] and as precursors for elusive monomeric
scandium hydrides [3,21] we were therefore interested in the
thermal stability of compounds 4a–c and their reactivity
towards dihydrogen.
R
C2
Sc
R
C1
N2
P
N1
Dipp
Ar
E2
E1
Param.a
3c
4c
5cb
˚
Bond distances (A)
Sc–E(1)
Sc–E(2)
Sc–N(1)
Sc–N(2)
N(2)–C(1)
C(1)–C(2)
C(2)–P
2.3373(7)
2.3341(6)
2.106(2)
2.071(2)
1.386(2)
1.431(3)
1.783(2)
1.630(2)
2.208(2)
2.209(2)
2.160(2)
2.127(2)
1.386(2)
1.427(3)
1.788(2)
1.629(2)
2.365(3)
2.307(4)
2.170(3)
2.155(3)
1.393(4)
1.427(5)
1.777(3)
1.608(3)
PPh2
N
PPh2
N
RT
N
N
- CH4
Dipp
Dipp
Sc
Dipp
Sc
Me
Mes
P–N(1)
Me
Me
4a
Bond angles (ꢁ)
N(1)–Sc–N(2)
E(1)–Sc–E(2)
N(2)–Sc–E(1)
N(2)–Sc–E(2)
N(1)–Sc–E(1)
N(1)–Sc–E(2)
No metalation
observed for 4b,c
5a
91.59(6)
104.08(2)
113.34(5)
121.44(5)
119.24(5)
107.73(4)
91.52(6)
100.99(9)
112.52(8)
125.37(8)
116.49(8)
110.93(8)
89.32(10)
88.64(13)
107.16(12)
94.93(12)
161.48(13)
81.41(11)
PMe2
N
PMe
Δ
N
N
N
- CH4
Sc
Dipp
Sc
Dipp
Dipp
Torsion angles (ꢁ)
N(2)–C(1)–C(2)–P
C(1)–C(2)–P–N(1)
a
8.7(2)
48.1(2)
5.2(2)
47.1(2)
4.4(4)
50.2(3)
Me
Me
Me
2
4d
5d
E = Cl for 3c and C for 4c and 5c.
b
E(2) = C(42) from Fig. 9.
Scheme 3.

840
K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
Ph
P
N
PPh2
N
H2
N
N
- CH4
Dipp
- H2
Sc Dipp
Dipp
Sc
Dipp
Me
5c
Me
Me
2
H2
4c
-CH4
PPh2
N
N
Dipp
Sc
Dipp
H
Me
4c'
Scheme 4.
Fig. 8. Thermal ellipsoid diagram of 5d at 50% probability. The dimeric
structure with iso-propyl groups removed is shown in (a) and the
˚
monomer moiety is shown in (b). Selected bond lengths (A) and angles (ꢁ):
P–N(2), 1.641(2); Sc–N(1), 2.082(2); Sc–N(2), 2.144(2); Sc–C(1), 2.399(3);
Sc–C(2), 2.338(3); P–C(4), 1.800(3); N(1)–C(9), 1.398(4); N(1)–Sc–N(2),
95.53(9); N(1)–C(9)–C(4)–P, 0.7(4); C(9)–C(4)–P–N(2), 52.1(3); N(2)–P–
C(2)–Sc, 31.6(1).
Solutions of P@N mesityl substituted 4a were found to
decompose readily at room temperature through C–H
bond activation of a mesityl methyl group (Scheme 3)
and its chemistry was not examined further in this regard.
In contrast, when C6D6 solutions of 4b,c were heated at
65 ꢁC in a J-Young NMR tube no decomposition was
observed spectroscopically over 24 h. Given their promis-
ing thermal stability, compounds 4b and 4c were subjected
to reaction with dihydrogen in an attempt to generate reac-
tive scandium hydrides.
Fig. 9. Thermal ellipsoid diagram of 5c at 50% probability. The dimeric
structure with iso-propyl groups removed is shown in (a) and the
monomer moiety is shown in (b). Selected bond lengths (A) and angles (ꢁ):
˚
P–N(2), 1.608(3); Sc–N(1), 2.155(3); Sc–N(2), 2.170(3); Sc–C(1), 2.322(4);
Sc–C(10), 2.365(3); Sc–C(42), 2.307(4); P–C(25), 1.777(3); N(1)–C(26),
1.393(4); N(1)–Sc–N(2), 89.3(1); N(1)–C(26)–C(25)–P, 4.4(4); C(26)–
C(25)–P–N(2), 50.2(3); P–C(37)–C(42)–Sc, 25.6(3).
2.4. Hydrogen catalyzed C–H activation of 4c
Alkyl- and dialkylscandium complexes have been
known for some time to react readily with dihydrogen to
produce hydrides [3,22] although well-defined monomeric
hydrides have not been structurally verified and represent
an attractive target. Stirring a hexane solution of 4c under
4 atm of hydrogen at room temperature for 4 days (Scheme
4) leads to a pale yellow precipitate which can be isolated
1
by filtration. The H NMR spectrum of a C7D8 solution
of 5c suggests a complete loss of symmetry in the molecule
as all of the isopropyl methyl signals become diastereotopic
and a new signal arises at 0.52 ppm for the Sc–Me group

K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
841
which integrates to 3H. An upfield shift in the 31P NMR
experiment is observed as a new resonance appears at
27.7 ppm. X-ray quality crystals of 5c were grown from a
layered solution of toluene and hexane at ꢀ35 ꢁC and the
molecular structure is shown in Fig. 9.
employed solvent, 2H to external Si(CD3)4 at 0.0 ppm,
11B spectra to external BF3 Æ OEt2 at 0.0 ppm and 19F
spectra to CFCl3 using an external standard of hexaflu-
orobenzene (d ꢀ163.0 ppm) in C6D6. NMR data are pro-
vided in ppm; 13C resonances for the C6F5 groups are not
3
The solid state structural analysis of 5c shows that it
adopts a dimeric conformation which is structurally akin
to 5d, with a pair of bridging methyl groups linking the
two scandium atoms. As in the P-methyl ligand supported
system, an axial phenyl group on phosphorus assumes a
non-innocent role [14] and an ortho-C–H bond engages in
a r-bond metathesis reaction with a putative scandium
hydride 4c0 (Scheme 4). Thus, dihydrogen serves as a cata-
lyst for the metalation of 4c to give dimer 5c. The Sc–C(42)
reported. The coupling constants (i.e. JH–H) for the iso-
propyl groups on the ligand range between 6.4 and
7.2 Hz, and thus, are not reported in the NMR analysis
of the compounds. Elemental analyses were performed
by Mrs. Roxanna Smith and Mrs. Dorothy Fox in the
microanalytical laboratory at the University of Calgary.
Complexes containing scandium (i.e. 3–5) were consis-
tently low in carbon; possibly a result of metal-catalyzed
silicon carbide formation leading to incomplete combus-
tion [26]. X-ray data were collected on a Bruker P4/
RA/SMART 1000 CCD diffractometer [27] using Mo
Ka radiation at ꢀ80 ꢁC.
˚
distance of 2.307(4) A is slightly shorter than the Sc–C(1) at
0
˚
˚
2.322(4) A and Sc–C(1 ) at 2.365(3) A. There is also a large
torque observed for the metalated phenyl group with a P–
C(37)–C(42)–Sc torsion angle of 25.6(3)ꢁ.
4.2. Syntheses of complexes
3. Conclusions
4.2.1. General procedure for 1-F-2-PR2C6H4
An optimized synthesis of a versatile anilido-phosphini-
mine ligand is reported; these ligands can be readily affixed
to scandium using standard salt metathesis protocols.
While the ligand is a competent donor to scandium, it is
susceptible to ligand deactivation either under thermal con-
ditions for 4a,d or in the presence of dihydrogen, 4c. The
rapid conversion of the intermediate hydride 4c0, is sugges-
tive of a highly reactive hydride species and efforts are cur-
rently underway to capture this system by developing more
metalatively robust ligand scaffolds.
The following is a modification to a published procedure
[15]. A solution of 1-bromo-2-fluorobenzene (6.77 mL,
62 mmol) in 200 mL was cooled to ꢀ78 ꢁC and nBuLi
(2.5 M, 24.8 mL, 62 mmol) was added via syringe is stirred
for 15 min. A solution of Me2PCl (4.9 mL, 62 mmol) in
25 mL of THF was then added via cannula and the solu-
tion was stirred for 4 h at ꢀ78 ꢁC, then slowly warmed to
room temperature overnight. The red solution was
quenched with 100 mL of 1 M HCl and extracted with
ether, washed twice with 100 mL of water, then with
50 mL of brine. Combined organic fractions were dried
over MgSO4, filtered, and volatiles removed in vacuo to
afford a pale yellow oil (1-F-2-PMe2C6H4). Yield: 6.62 g
(69%).
4. Experimental
4.1. General methods
All manipulations were performed either in an Innova-
tive Technologies System One inert atmosphere glovebox
or on greaseless vacuum lines equipped with Teflon needle
valves (Kontes) using swivel-frit type glassware. Toluene,
THF and hexanes were dried and purified using the Grub-
bs/Dow purification system, [23] and stored in evacuated
bombs. Bromobenzene and bromobenzene-d5 were pre-
dried over CaH2, and hexamethyldisiloxane, THF-d8 Ben-
zene-d6 and toluene-d8 were dried and stored over sodium/
benzophenone. All were distilled prior to use.
The following reagents were synthesized using literature
protocols: mesityl azide [24], 2-isopropylphenyl azide [25]
and 2,6-diisopropylphenyl azide [25]. Lithio ligands 2b–d
were prepared according to the protocol developed in this
lab for 2a [13]. Phosphine reagents were obtained from
Strem and all other materials were obtained from Aldrich
and used as received.
4.2.2. General procedure for 1-F-2-(PR2@NAr)C6H4
A solution of 1-F-2-PMe2C6H4 (6.55 g, 42 mmol) in
50 mL of Et2O was added to a solution of DippN3
(8.54 g, 42 mmol) in 50 mL of Et2O and stirred at room
temperature for 2 h, or until N2 effervescence is complete.
Volatiles were removed in vacuo to afford a pale yellow
oil which was recrystallized from refluxing hexane (1-F-2-
(PMe2@NDipp)C6H4). Yield: 13.26 g (95%).
4.2.3. Characterization of 1-(NHDipp)-2-(PPh2@
NMipp)C6H4 (1b)
1
Yield: 41%. H NMR (C6D6): d 9.03 (s, 1H, NH), 7.87
(m, 4H, m-P-(C6H5)2), 7.31 (m, 1H, PNC6H4), 7.12–7.09
(m, 3H, NC6H3), 7.02–6.87 (m, 10H, o,p-P(C6H5)2,
PNC6H4, PC6H4N), 6.44 (m, 1H, PC6H4N), 6.27 (m, 1H,
PC6H4N), 4.13 (sp, 1H, CHMe2), 3.00 (sp, 2H, CHMe2),
1.35 (d, 6H, CH(CH3)2), 0.99 (d, 6H, CH(CH3)2), 0.84
(d, 6H, CH(CH3)2). 13C NMR (C6D6): d 153.6, 148.9 (2
quaternary aromatic), 148.1 (1Ph), 142.4 (1 quaternary
aromatic), 134.8 (1Ph), 133.7 (1 quaternary aromatic),
133.3, 132.7, 132.6, 131.5 (4Ph), 131.3 (1 quaternary
Samples were analyzed by NMR spectroscopy on Bru-
ker AMX-300 and DRX-400 spectrometers at room tem-
perature unless otherwise specified. 1H and 13C were
referenced to Si(CH3)4 through the residual peaks of the

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K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
aromatic), 128.6, 126.1, 125.8, 124.1, 121.1, 118.9, 116.0,
113.3 (8Ph), 112.1, 110.8 (2 quaternary aromatic) 28.6
(CHMe2), 28.4 (CHMe2), 24.3 (CH(CH3)2), 23.8
(CH(CH3)2), 23.2 (CH(CH3)2). 31P{1H} NMR (C6D6): d
6.8. Anal. Calc. for C39H43N2P: C, 82.07; H, 7.59; N,
4.91. Found C, 82.13; H, 7.47, N, 4.99%.
(2 quaternary aromatic) 28.4 (CHMe2), 27.8 (CHMe2),
25.7 (CH(CH3)2), 24.1 (CH(CH3)2), 23.2 (CH(CH3)2).
31P{1H} NMR (C6D6):
d
21.6. Anal. Calc. for
C39H42LiN2P: C, 81.23; H, 7.34; N, 4.86. Found C,
81.44; H, 7.12, N, 4.60%.
4.2.7. Characterization of 1-(NLiDipp)-2-(PPh2@NDipp)-
C6H4 (2c)
4.2.4. Characterization of 1-(NHDipp)-2-(PPh2@
NDipp)C6H4 (1c)
Yield: 94%. 1H NMR (C6D6): d 7.47 (m, 4H, m-P-
(C6H5)2), 7.28-7.25 (m, 4H, PNC6H4, NC6H3), 7.09–6.97
(m, 7H, NC6H3, o,p-P(C6H5)2, PNC6H3, PC6H4N), 6.83
(m, 1H, NC6H3), 6.08 (m, 1H, PC6H4N), 5.99 (m, 1H,
PC6H4N), 3.34 (sp, 2H, CHMe2), 2.62 (sp, 2H, CHMe2),
1.31 (d, 6H, CH(CH3)2), 1.11 (d, 6H, CH(CH3)2), 1.06
(d, 6H CH(CH3)2) 0.85 (d, 6H, CH(CH3)2). 13C NMR
(C6D6): d 162.9, 150.6 (2 quaternary aromatic), 145.1,
144.9, 144.8 (3Ph), 134.5 (1 quaternary aromatic), 133.7
(1Ph), 133.2 (1 quaternary aromatic), 131.8 (1Ph), 130.7
(1 quaternary aromatic), 128.5, 124.4, 124.1, 123.5 (4Ph),
122.6, 117.2, 110.8 (3 quaternary aromatic), 108.0 (1Ph)
29.4 (CHMe2), 27.9 (CHMe2), 26.9 (CH(CH3)2), 24.9
(CH(CH3)2). 31P{1H} NMR (C6D6): d 19.4. Anal. Calc.
for C42H48LiN2P: C, 81.53; H, 7.82; N, 4.53. Found C,
81.22; H, 7.95, N, 4.36%.
1
Yield: 45%. H NMR (C6D6): d 9.06 (s, 1H, NH), 7.73
(m, 4H, m-P-(C6H5)2), 7.19–7.15 (m, 6H, PNC6H4,
NC6H3), 7.02–6.97 (m, 8H, NC6H3, o,p-P(C6H5)2,
NC6H3, PC6H4N), 6.4 (m, 2H, PC6H4N), 3.77 (sp, 2H,
CHMe2), 3.13 (sp, 2H, CHMe2), 1.11 (d, 6H, CH(CH3)2),
1.03 (d, 12H, CH(CH3)2), 0.95 (d, 6H, CH(CH3)2). 13C
NMR (C6D6): d 154.4 (1 quaternary aromatic), 148.0
(1Ph), 144.2 (1 quaternary aromatic), 143.2 (1Ph), 135.7,
135.2, 134.7, 133.9, 133.3 (5 quaternary aromatic), 133.1,
132.9, 131.5, 128.9, 124.7, 124.1, 120.9, 116.5, 114.6
(9Ph), 112.0 (1 quaternary aromatic) 29.7 (CHMe2), 28.8
(CHMe2), 25.0 (CH(CH3)2), 24.7 (CH(CH3)2), 24.4
(CH(CH3)2). 31P{1H} NMR (C6D6): d 1.2. Anal. Calc.
for C42H49N2P: C, 82.32; H, 8.06; N, 4.57. Found C,
82.26; H, 8.46, N, 4.61%.
4.2.5. Characterization of 1-(NHDipp)-2-(PMe2@NDipp)-
C6H4 (1d)
4.2.8. Characterization of 1-(NLiDipp)-2-(PMe2@NDipp)-
C6H4 (2d)
Yield: 37%. 1H NMR (C6D6): d 10.35 (s, 1H, NH), 7.20
(m, 5H, NC6H3), 7.06 (m, 1H, PC6H4N), 6.96 (t, 1H,
NC6H3), 6.81 (m, 1H, PC6H4N), 6.52 (m, 1H, PC6H4N),
6.38 (m, 1H, PC6H4N), 3.78 (sp, 2H, CHMe2), 3.45 (sp,
Yield: 91%. H NMR (C6D6): d 7.31 (m, 2H, NC6H3),
1
7.19 (m, 3H, NC6H3, PC6H4N), 7.04 (m, 1H, PC6H4N),
6.97 (t, 1H NC6H3) 6.76 (m, 1H, PC6H4N), 6.22 (m, 2H,
PC6H4N), 3.51 (sp, 2H, CHMe2), 3.29 (sp, 2H, CHMe2),
2
2
2H, CHMe2), 1.29 (d, JH–P = 14 Hz 6H, P(CH3)2), 1.23
1.39 (d, JH–P = 14 Hz 6H, P(CH3)2), 1.30 (d, 6H,
(d, 12H, CH(CH3)2), 1.18 (d, 6H, CH(CH3)2), 1.15 (d,
6H, CH(CH3)2). 13C NMR (C6D6): d 153.7, (1 quaternary
aromatic), 147.5 (1Ph), 144.3 (1 quaternary aromatic),
143.9 (1Ph), 136.3, 133.1 (2 quaternary aromatic), 130.0,
127.7, 124.6, 123.6 (4Ph), 121.4 (1 quaternary aromatic),
116.6, 113.6 (2Ph), 113.3 (1 quaternary aromatic) 29.1
(CHMe2), 28.8 (CHMe2), 25.3 (CH(CH3)2), 24.8
(CH(CH3)2), 23.7 (CH(CH3)2), 16.9 (P(CH3)2). 31P{1H}
NMR (C6D6): d 8.6. Anal. Calc. for C34H51N2P: C,
78.72; H, 9.91; N, 5.40. Found C, 79.04; H, 10.11, N,
5.33%.
CH(CH3)2), 1.21 (m, 18H, CH(CH3)2). 13C NMR (C6D6):
d 161.3, 150.1, 145.6 (3 quaternary aromatic), 144.9,
144.0, 132.8 (3Ph), 129.0 (1 quaternary aromatic), 124.0,
123.6, 122.7, 122.4 (4Ph), 115.3, 110.8 (2 quaternary aro-
matic), 108.3 (1Ph), 28.3 (CHMe2), 28.2 (CHMe2), 25.2
(CH(CH3)2), 25.1 (CH(CH3)2), 25.1 (CH(CH3)2), 24.7
(CH(CH3)2), 13.6 (P(CH3)2). 31P{1H} NMR (C6D6): d
19.2. Anal. Calc. for C34H50LiN2P: C, 77.83; H, 9.61; N,
5.34. Found C, 77.97; H, 9.52, N, 5.30%.
4.2.9. Synthesis of [1-(NDipp)-2-(PPh2@NMes)C6H4]-
ScCl2 (3a)
4.2.6. Characterization of 1-(NLiDipp)-2-(PPh2@NMipp)-
C6H4 (2b)
The following is a representative procedure for 3a–d. A
50 mL bomb was charged with 2a (2.26 g, 3.9 mmol) and
ScCl3THF3 (1.43 g, 3.9 mmol) and 25 mL of toluene was
condensed. The mixture was stirred overnight at 110 ꢁC
and upon cooling to room temperature, was transferred
to a swivel frit apparatus and filtered. Removal of toluene
in vacuo followed by sonication in hexanes and filtration
Yield: 98%. 1H NMR (C6D6): d 7.61 (m, 4H, m-P-
(C6H5)2), 7.24–7.19 (m, 5H, PNC6H4, NC6H3), 7.07–6.88
(m, 10H, o,p-P(C6H5)2, PNC6H4, PC6H4N), 6.21 (m,
1H, PC6H4N), 6.27 (m, 1H, PC6H4N), 3.26 (sp, 1H,
CHMe2), 2.92 (sp, 2H, CHMe2), 1.18 (d, 6H, CH(CH3)2),
1.11 (d, 6H, CH(CH3)2), 0.96 (d, 6H, CH(CH3)2). 13C
NMR (C6D6): d 149.6, 147.7 (2 quaternary aromatic),
144.3 (1Ph), 142.9 (1 quaternary aromatic), 135.4 (1Ph),
133.7 (1 quaternary aromatic), 133.1, 132.4, 131.5, 131.1
(4Ph), 129.6 (1 quaternary aromatic), 128.5, 126.6,
125.8, 124.9, 123.8, 122.9, 121.0, (7Ph), 115.6, 108.1
1
afforded a white powder. Yield: 2.55 g (95%). H NMR
(C7D8): d 7.58 (m, 4H, m-P-(C6H5)2), 7.24 (m, 3H,
PC6H4N, NC6H3), 7.10 (m, 4H, o-P(C6H5)2), 7.01–6.92
(m, 5H, p-P(C6H5)2, NC6H3, PC6H4N) 6.55 (s, 2H,
PNC6H2), 6.23 (m, 2H, PC6H4N), 3.32 (sp, 2H, CHMe2),
2.23 (s, 6H, NC6H2Me-2,6), 1.99 (s, 3H, NC6H2Me-4)

K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
843
1.42 (d, 6H, CH(CH3)2), 1.02 (d, 6H, CH(CH3)2). 13C
NMR (C7D8): d 147.8 (1 quaternary aromatic), 137.2
(1Ph), 137.1, 135.8, 135.3 (3 quaternary aromatic), 134.9,
134.8 (2Ph), 134.5 (1 quaternary aromatic), 133.2, 130.7,
129.0, 128.7 (4Ph), 127.9 (1 quaternary aromatic), 125.8
(1Ph), 119.2, 115.8 (2 quaternary aromatic) 29.1 (CHMe2),
26.9 (CH(CH3)2), 25.1 (CH(CH3)2), 21.3 (C6H2Me-2,6),
21.1 (C6H2Me-4). 31P{1H} NMR (C7D8): d 29.4. Anal.
Calc. for C39H42Cl2N2PSc: C, 68.32; H, 6.17; N, 4.09.
Found C, 67.62; H, 6.35, N, 3.67%.
145.8, 133.8, 133.6 (3 quaternary aromatic), 129.4, 128.1,
127.9 (3Ph), 126.7 (1 quaternary aromatic), 126.2, 124.6,
117.2, 116.1 (4Ph), 111.5 (1 quaternary aromatic) 29.5
(CHMe2), 29.0 (CHMe2), 26.7 (CH(CH3)2), 25.4
(CH(CH3)2), 24.7 (CH(CH3)2), 24.1 (CH(CH3)2), 13.1
(P(CH3)2). 31P{1H} NMR (C6D6): d 34.2. Anal. Calc. for
C32H44Cl2N2PSc: C, 63.68; H, 7.35; N, 4.64. Found C,
62.96; H, 7.08, N, 4.79%.
4.2.13. Synthesis of [1-(NDipp)-2-(PPh2@NMes)C6H4]-
ScMe2 (4a)
4.2.10. Characterization of [1-(NDipp)-2-(PPh2@NMipp)-
C6H4]ScCl2 (3b)
The following is a representative synthesis of 4a–d. A
50 mL flask was charged with 3a (200 mg, 0.29 mmol)
and 20 mL of toluene was condensed. The solution was
cooled to 0 ꢁC and nBuLi (1.6 M, 0.36 mL, 0.58 mmol)
was introduced dropwise via syringe. The reaction was
warmed to room temperature and stirred for one hour,
then the LiCl was removed by filtration and the toluene
removed to afford a pale yellow solid. Yield 160 mg
(85%). 1H NMR (C7D8): d 7.53 (m, 4H, m-P-(C6H5)2),
7.27 (m, 3H, PC6H4N, NC6H3), 7.10–7.06 (m, 4H, o-
P(C6H5)2), 7.02–6.93 (m, 5H, p-P(C6H5)2, NC6H3,
PC6H4N) 6.64 (s, 2H, PNC6H2), 6.16 (m, 2H, PC6H4N),
3.13 (sp, 2H, CHMe2), 2.18 (s, 6H, NC6H2Me-2,6), 2.03
(s, 3H, NC6H2Me-4) 1.22 (d, 6H, CH(CH3)2), 0.99 (d,
6H, CH(CH3)2) ꢀ0.26 (s, 6H, Sc(CH3)2). 31P{1H} NMR
(C7D8): d 28.2. 13C NMR resonances were not assigned
due to metalative decomposition during acquisition.
Yield: 70%. 1H NMR (C6D6): d 7.63 (m, 4H, m-P-
(C6H5)2), 7.32–7.29 (m, 4H, PNC6H4, NC6H3), 7.13–6.81
(m, 11H, o,p-P(C6H5)2, PNC6H4, PC6H4N), 6.32 (m, 1H,
PC6H4N), 6.24 (m, 1H, PC6H4N), 3.73 (sp, 1H, CHMe2),
3.5 (br s, 2H, CHMe2), 1.49 (br s, 6H, CH(CH3)2), 1.16
(br s, 12H, CH(CH3)2). 13C NMR (C6D6): d 159.4, 148.1
(2 quaternary aromatic), 148.0 (1Ph), 138.3, 134.2 (2 qua-
ternary aromatic), 135.4, 134.7, 134.3, 134.2 (4Ph), 133.3,
129.7 (2 quaternary aromatic), 128.6, 128.5, 127.1, 126.5,
125.6 (5Ph), 117.9 (1 quaternary aromatic), 116.2 (1Ph),
28.9 (CHMe2), 28.2 (CHMe2), 26.4 (CH(CH3)2), 24.5
(CH(CH3)2). 31P{1H} NMR (C6D6): d 32.6. Anal. Calc.
for C39H42Cl2N2PSc: C, 68.32; H, 6.17; N, 4.09. Found
C, 67.97; H, 6.32, N, 4.22%.
4.2.11. Characterization of [1-(NDipp)-2-(PPh2@NDipp)-
C6H4]ScCl2 (3c)
4.2.14. Characterization of [1-(NDipp)-2-(PPh2@NMipp)-
C6H4]ScMe2 (4b)
Yield: 76%. 1H NMR (C6D6): d 7.51 (m, 4H, m-P-
(C6H5)2), 7.30–7.26 (m, 3H, PNC6H4, NC6H3), 7.06–6.91
(m, 9H, NC6H3, o,p-P(C6H5)2, PNC6H3), 6.80 (m, 2H,
PC6H4N), 6.24 (m, 1H, PC6H4N), 6.16 (m, 1H, PC6H4N),
3.77 (sp, 2H, CHMe2), 3.07 (sp, 2H, CHMe2), 1.60 (d, 6H,
CH(CH3)2), 1.38 (d, 6H, CH(CH3)2), 1.00 (d, 6H
CH(CH3)2) 0.83 (d, 6H, CH(CH3)2). 13C NMR (C6D6): d
158.1 (1 quaternary aromatic), 149.4, 146.2 (2Ph), 139.7
(1 quaternary aromatic), 128.7, 128.5, 128.3 (3Ph), 126.5
(1 quaternary aromatic), 125.7 (1Ph), 124.5 (1 quaternary
aromatic), 118.1, 118.0, 115.7, 115.5 (4Ph), 110.4 (1 quater-
nary aromatic) 29.4 (CHMe2), 28.6 (CHMe2), 26.9
(CH(CH3)2), 25.6 (CH(CH3)2), 24.0 (CH(CH3)2), 23.5
(CH(CH3)2). 31P{1H} NMR (C6D6): d 33.6. Anal. Calc.
for C42H48Cl2N2PSc: C, 69.32; H, 6.65; N, 3.85. Found
C, 70.44; H, 6.80, N, 3.43%.
1
Yield: 86%. H NMR (C6D6): d 7.81–7.30 (m, 8H, m-P-
(C6H5)2, PNC6H4, NC6H3), 7.17–7.14 (m, 3H, NC6H3,
PNC6H4) 7.05–6.95 (m, 8H, o,p-P(C6H5)2, PNC6H4,
PC6H4N), 7.72 (m, 1H, PC6H4N), 6.31 (m, 1H, PC6H4N),
6.22 (m, 1H, PC6H4N), 3.95 (sp, 1H, CHMe2), 3.36 (br s,
2H, CHMe2), 1.29 (br s, 6H, CH(CH3)2), 1.15 (br s, 12H,
CH(CH3)2), ꢀ0.38 (s, 6H Sc(CH3)2). 13C NMR (C6D6): d
160.2 (1 quaternary aromatic), 148.9 (1Ph), 148.0, 138.6,
137.6 (3 quaternary aromatic), 137.5, 135.0, 134.5 (3Ph),
134.0, 133.2 (2 quaternary aromatic), 129.3.6, 128.8,
128.5, 127.4 (4Ph), 126.6, 126.2 (2 quaternary aromatic),
125.6, 125.4, 117.6, 113.9 (4Ph), 106.4 (1 quaternary aro-
matic) 28.9 (CHMe2), 28.4 (CHMe2), 26.5 (CH(CH3)2),
23.9 (Sc(CH3)2) 23.3 (CH(CH3)2). 31P{1H} NMR (C6D6):
d 28.2. Anal. Calc. for C41H48N2PSc: C, 76.38; H, 7.50;
N, 4.34. Found C, 75.48; H, 7.41, N, 4.65%.
4.2.12. Characterization of [1-(NDipp)-2-(PMe2@NDipp)-
C6H4]ScCl2 (3d)
4.2.15. Characterization of [1-(NDipp)-2-(PPh2@NDipp)-
C6H4]ScMe2 (4c)
Yield: 74% 1H NMR (C6D6): d 7.32–7.29 (m, 3H,
NC6H3, PC6H4N), 7.06 (m, 3H, NC6H3), 7.04 (m, 1H,
PC6H4N), 6.78 (t, 1H, NC6H3) 6.49 (m, 1H, PC6H4N),
6.31 (m, 1H, PC6H4N), 6.03 (m, 1H, PC6H4N), 3.58 (sp,
4H, CHMe2), 1.62 (d, 6H, CH(CH3)2), 1.47 (d, 6H,
Yield: 72%. 1H NMR (C6D6): d 7.48 (m, 4H, m-P-
(C6H5)2), 7.36–7.31 (m, 3H, PNC6H4, NC6H3), 7.09–
6.75 (m, 11H, NC6H3, o,p-P(C6H5)2, PNC6H3, PC6H4N),
6.18 (m, 2H, PC6H4N), 3.80 (sp, 2H, CHMe2), 3.12 (sp,
2H, CHMe2), 1.53 (d, 6H, CH(CH3)2), 1.24 (d, 6H,
CH(CH3)2), 1.06 (d, 6H CH(CH3)2) 0.90 (d, 6H,
CH(CH3)2), ꢀ0.01 (s, 6H, Sc(CH3)2). 13C NMR (C6D6):
2
CH(CH3)2), 1.36 (d, JH–P = 12 Hz 6H, P(CH3)2), 1.09 (d,
6H, CH(CH3)2), 1.03 (d, 6H, CH(CH3)2). 13C NMR
(C6D6): d 156.6 (1 quaternary aromatic), 149.8 (1Ph),

844
K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
d 158.8 (1 quaternary aromatic), 148.7, 146.2 (2Ph),
139.6, 137.8 (2 quaternary aromatic), 134.0 (1Ph),
133.5, 133.4, 133.3 (3 quaternary aromatic), 132.5,
128.3 (2Ph), 125.6 (1 quaternary aromatic), 125.1,
124.2, 117.8, 113.2 (4Ph), 110.1 (1 quaternary aromatic)
29.0 (CHMe2), 28.2 (CHMe2), 26.6 (CH(CH3)2), 25.2
(CH(CH3)2), 24.7 (Sc(CH3)2) 23.9 (CH(CH3)2), 23.6
(CH(CH3)2). 31P{1H} NMR (C6D6): d 29.7. Anal. Calc.
for C44H54N2PSc: C, 76.94; H, 7.92; N, 4.08. Found C,
75.84; H, 7.47, N, 3.84%.
Table 3
Summary of data collection and structure refinement details for 1b,c, 3a,c
1b
1c
3a
3c
Color
Habit
Size (mm3)
Formula
Colorless
Prismatic
.22 · .20 · .18
Colorless
Block
.24 · .16 · .11
C42H49N2P
612.80
11.494(2)
12.772(2)
14.673(3)
64.625(10)
82.333(10)
66.033(8)
Triclinic
Colorless
Block
.20 · .20 · .18
C78H84Cl4P2Sc2
1371.14
18.776(4)
21.772(5)
25.481(6)
Colorless
Prismatic
.26 · .12 · .12
C42H48Cl2N2PSc
739.71
10.1450(10)
13.417(2)
18.882(4)
84.210(5)
83.171(5)
73.196(9)
Triclinic
C
39H43N2P
Molecular weight
570.72
10.762(3)
21.353(5)
14.131(3)
90
90.776(14)
90
Monoclinic
P21/n
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
101.028(19)
Crystal system
Space group
Z
Monoclinic
C2/c
8
10244(4)
173 (2)
0.315
ꢀ
ꢀ
P1
P1
4
2
2
3
˚
V (A )
3247.0(14)
273(2)
0.114
1776.2(6)
173(2)
0.11
2436.9(7)
173(2)
0.33
T (K)
l (mmꢀ1
)
Transmission factors
h Range (ꢁ)
Data/restraints/parameters
GoF
.9798–.9754
2.4–27.5
7413/0/385
1.01
.988–.974
3.6–27.5
8072/0/406
1.00
.945–.940
3.0–25.0
8974/0/531
1.03
.961–.919
3.2–27.3
10885/0/541
1.01
R1 (I > 2r(I))
0.053
0.048
0.098
0.044
wR2 (all data)
0.117
0.123
0.255
0.103
Table 4
Summary of data collection and structure refinement details for 4b,c, and 5c,d
4b
4c
5c
5d
Color
Habit
Size (mm3)
Formula
Colorless
Block
.20 · .16 · .08
C48H56N2PSc
736.88
10.266(3)
13.478(6)
16.188(8)
73.84(2)
Colorless
Prismatic
.16 · .15 · .10
C44H54N2PSc
686.82
19.364(2)
18.661(4)
21.813(3)
Yellow
Colorless
Needle
.12 · .08 · .06
C72H102N4P2Sc2
1175.44
46.690(2)
12.035(4)
27.799(4)
Prismatic
.12 · .08 · .07
C49H64N2PSc
756.95
17.779(3)
20.047(4)
24.459(7)
Molecular weight
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
84.07(3)
79.50(3)
94.162(7)
118.945(7)
Crystal system
Space group
Z
Triclinic
Orthorhombic
Pbca
Monoclinic
C2/c
8
8695(3)
173(2)
0.240
Monoclinic
C2/c
16
13669(5)
173(2)
0.287
ꢀ
P1
2
8
3
˚
V (A )
2112.0(15)
173(2)
0.246
7882(2)
173(2)
0.259
T (K)
l (mmꢀ1
)
Transmission factors
h Range (ꢁ)
Data/restraints/parameters
GoF
.981–.953
2.9–25.1
7415/0/466
1.06
.975–.960
3.2–27.6
8951/0/443
1.04
.983–.972
1.5–25.0
7619/0/478
1.00
.983–.966
1.9–25.1
12047/0/739
1.03
R1 (I > 2r(I))
0.074
0.046
0.058
0.052
wR2 (all data)
0.186
0.106
0.145
0.127

K.D. Conroy et al. / Journal of Organometallic Chemistry 693 (2008) 834–846
845
4.2.16. Synthesis of {[j3-1-(NDipp)-2-(PPh(C6H4)@
NDipp)C6H4]ScMe}2 (5c)
scholarship to K.D.C. (PGS-A and CGS-D). K.D.C. also
thanks Alberta Ingenuity for a Studentship Award.
A
50 mL bomb was charged with 4c (200 mg,
0.29 mmol) and 15 mL of hexane was condensed. The flask
was evacuated and hydrogen (4 atm) was condensed. The
flask was sealed and the yellow solution was stirred at
room temperature at which point a white precipitate was
observed. The mixture was transferred to a swivel frit appa-
ratus and the solid collected by filtration. Yield: 138 mg
(71%). 1H NMR (C6D6): d 7.45–6.48 (m, 17H, m-P-
(C6H5)2, PNC6H4, NC6H3), o,p-P(C6H5)2, PC6H4N, 6.30
(m, 1H, PC6H4N), 5.94 (m, 1H, PC6H4N), 3.88 (ov sp,
2H, CHMe2), 3.52 (sp, 1H, CHMe2), 3.16 (sp, 1H,
CHMe2), 1.70–0.65 (br m, 18H, CH(CH3)2), 0.52 (s, 3H,
Sc(CH3)2) 0.25 (d, 6H, CH(CH3)2). 31P{1H} NMR
(C6D6): d 27.7. Anal. Calc. for C43H50N2PSc: C, 76.99;
H, 7.51; N, 4.18. Found C, 76.71; H, 7.77, N, 4.45%.
Appendix A. Supplementary material
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2007.08.037.
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[27] Programs for diffractometer operation, data collection, data reduc-
tion, and absorption correction were those supplied by Bruker.