Divergent reactivity of [(κ3-L)ThCl2(dme)] with Grignard reagents: Alkylation, ancillary ligand transfer to magnesium, and halide exchange caught in the act

Article abstract of DOI:10.1016/j.jorganchem.2010.08.048

Reaction of [(BDPP)ThCl₂(dme)] (1) with 2 equivalents of MeMgBr in OEt₂, followed by filtration and layering a toluene solution with hexanes at -30 °C yielded a single large crystal of [{(BDPP)ThX(μ-X) ₂Mg(OEt₂)

Full text of DOI:10.1016/j.jorganchem.2010.08.048

Journal of Organometallic Chemistry 695 (2010) 2798e2803
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Journal of Organometallic Chemistry
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Divergent reactivity of [(
ancillary ligand transfer to magnesium, and halide exchange caught in the actq
k
3-L)ThCl2(dme)] with Grignard reagents: Alkylation,
,
a
,
,b
Carlos A. Cruz a, Terry Chu a, David J.H. Emslie a , Hilary A. Jenkins b, Laura E. Harrington a
,
*
,
b
James F. Britten a
a Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
b McMaster Analytical X-Ray Diffraction Facility, Hamilton, Ontario, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of [(BDPP)ThCl2(dme)] (1) with 2 equivalents of MeMgBr in OEt2, followed by filtration and
layering a toluene solution with hexanes at ꢀ30 ꢁC yielded a single large crystal of [{(BDPP)ThX
Received 17 May 2010
Received in revised form
5 August 2010
(
m
-X)2Mg(OEt2)(
m
-Me)}2]$2 toluene (X ¼ Br0.73e0.87/Cl0.13e0.27; 3$2 toluene). This product is the result of
halide exchange to form a partially brominated neutral thorium species, which is adducted with
MeMgX(OEt2). The complex is then tetrametallic as a result of MgeMeeMg bridges. The structure of
complex 3 provides direct insight into the process by which halide exchange takes place between
electrophilic metal halide complexes and Grignard reagents. This reactivity stands in stark contrast to
the reactions of 1 and [(XA2)ThCl2(dme)] (2) with PhCH2MgCl. In these cases the expected dialkyl
products, [LTh(CH2Ph)2] [L ¼ BDPP (4) and XA2 (5)], were formed under most conditions. However,
addition of a PhCH2MgCl solution to 2 at ꢀ78 ꢁC and warming to room temperature after 5 minutes
gave [(XA2)Mg(dme)] (6), the product of ancillary ligand transfer from thorium to magnesium, in 30
e50% yield.
Accepted 12 August 2010
Keywords:
Thorium complexes
Grignard reactivity
Halide exchange
Alkylation
Ancillary ligand transfer
Magnesium complexes
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
LiCH2SiMe3 or PhCH2MgCl allowed access to [LTh(CH2SiMe3)2]
(L ¼ BDPP and XA2),[14] and [LTh(CH2Ph)2] [L ¼ BDPP (4) and XA2
Much of early organometallic actinide chemistry has been
(5)] from which the first examples of non-cyclopentadienyl
thorium alkyl cations were prepared [15,18]. However, caution is
drawn to the expected outcome in reactions with PhCH2MgCl
(vide infra).
ꢀ
2ꢀ
dominated by carbocyclic ancillary ligand (e.g. C5R5 or C8R8
)
complexes [1]. However, non-carbocyclic ligands have recently
seen a flurry of activity in this area (Fig. 1) [2e20] and offer a wide
range of opportunities with respect to modification of metal
complex geometry, coordination number, steric and electronic
properties, and reactivity. Our research has focused on the rigid,
planar and tridentate BDPP [2,6-bis(2,6-diisopropylanilidomethyl)
pyridine] [21] and XA2 [4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-
butyl-9,9-dimethylxanthene] [14] dianions (Fig. 1) [22], and
reaction of Li2[BDPP], Na2[XA2] or K2(dme)2[XA2] with
[ThCl4(dme)2] [23] provided [LThCl2(dme)] [L ¼ BDPP (1) or XA2
To explore the impact of alkyl group variation on complex
stability and reactivity, the synthesis of n-butyl, methyl and benzyl
complexes was undertaken. Thermally stable [(BDPP)ThnBu2]
proved readily accessible by reaction of 1 with nBuLi, while reac-
tion of 1 with MeLi was only useful as a direct route to the ‘ate’
complex [(BDPP)ThMe(
complex was subsequently prepared by reaction of [(BDPP)ThMe
-Me)2Li(dme)] with 0.5 equiv. of 1) [16]. In this work, the reac-
m-Me)2Li(dme)] (the neutral dimethyl
(m
(2)] in good yield. Subsequent reaction of
1
and
2
with
tions of [LThCl2(dme)] [L ¼ BDPP (1) or XA2 (2)] with MeMgBr and
PhCH2MgCl [15,18] are discussed, and the unexpected products
[{(BDPP)ThX(
m
-X)2Mg(OEt2)(
m
-Me)}2] (X ¼ Br0.73e0.87/Cl0.13e0.27; 3)
and [(XA2)Mg(dme)] (6) are reported. Grignard reagents are
commonly employed for the alkylation of d- and f-block metal
halide complexes, especially when there exists the potential
for reduction or ate-complex formation with more aggressive
alkylating agents (e.g. RLi).
q
L represents the ancillary ligands 2,6-bis(2,6-diisopropylanilidomethyl)pyridine
(BDPP) and 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene
(XA2).
* Corresponding author. Tel.: þ1 905 525 9140; fax: þ1 905 522 2509.
E-mail address: emslied@mcmaster.ca (D.J.H. Emslie).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.08.048

C.A. Cruz et al. / Journal of Organometallic Chemistry 695 (2010) 2798e2803
2799
Fig. 1. Selected Multidentate Non-Carbocyclic Ligands in Alkyl Actinide Chemistry:
1,10-Bis(amido)ferrocene [17,19,20], Amidinate [2], Tris- or Tetrakis(pyrazolyl)borate
[3e8], 2,6-Bis(amidomethyl)pyridine (BDPP) [14e17], Tris(2-amidoethyl)amine, [9,10],
Bis(amidodimethylsilyl)ether Bis(2-amidoethyl)ether, [11e13], and 4,5-Bis(amido)
xanthene (XA2) [14,15,18] ligands.
Scheme 1. Reaction of 1 with MeMgBr to form the fully brominated analogue of
complex 3.
alkylation, allylation or arylation reactions. For example, reaction of
[{O(SiMe2NtBu)2}UCl2]2 with MeMgBr resulted in the formation of
2. Results and discussion
[{O(SiMe2NtBu)2}UBr1.46Cl0.54 2
] rather than the expected methyl
2.1. Reactions of [(BDPP)ThCl2(dme)] with MeMgBr
uranium complex. By contrast, [{O(SiMe2NtBu)2}UCl2]2 reacted
with (C3H5)MgBr to give the expected diallyl complex, and closely
related [{O(SiMe2NtBu)2}UCl(Cp*)] reacted with MeMgBr to give
the anticipated methyl complex [11]. These reactions illustrate the
extent to which Grignard reactivity (alkylation versus halide
exchange) is influenced by subtle changes in the nature of the
Grignard reagent and the metal halide complex. Another example
of halide exchange in actinide chemistry is the reaction of [Cp*2ThCl
Reaction of [(BDPP)ThCl2(dme)] (1) with 2 or 3 equivalents of
MeMgBr (3.0 M in OEt2) in OEt2 or toluene yielded 1H NMR spectra
similar to those of the starting materials, but substantially broad-
ened. Attempts to isolate an organometallic complex from these
mixtures were in most instances unsuccessful. However, on one
occasion, reaction of 1 with MeMgBr (2 equiv.) in diethylether,
filtration, and layering a toluene solution with hexanes at ꢀ30 ꢁC
yielded a single large (w4 ꢂ 4 ꢂ 2 mm) X-ray quality crystal. The
(
h2-tBuNSPh)] with MeMgBr to form [Cp*2ThBr( 2-tBuNSPh)] [24].
h
Halide redistribution reactivity has also been reported for a range of
lanthanide and group 3 complexes. For example, [(P2N2)YCl]2
[P2N2 ¼ PhP(CH2SiMe2NSiMe2CH2)2PPh] reacted with PhMgBr,
p-tolylMgBr or p-biphenylMgBr to afford exactly the same mixture
of products: the dinuclear dichloride, the mixed chloride/bromide
and the dibromide [25,26].
In the X-ray crystal structure of complex 3, thorium adopts
a distorted octahedral geometry, while magnesium is trigonal
bipyramidal. Of the three TheX bond lengths, TheX(1) and TheX(2)
are very similar [2.856(2) and 2.887(2) Å, respectively], even though
X(1) is terminal while X(2) bridges between thorium and magne-
sium. These bond distances fall in the usual range for thorium
bromide complexes (2.8e2.9 Å) [27e34]. However, at 3.007(2) Å,
TheX(3) is significantly longer than TheX(1) and TheX(2). Further,
on magnesium, the MgeX and MgeC bond distances in the trigonal
plane [MgeX(3) ¼ 2.538(5) Å; MgeC(32) ¼ 2.177(10) Å] are much
shorter than those in the apical sites [MgeX(2) ¼ 2.913(6) Å; Mg(1)e
C(320) ¼ 2.355(12) Å]. Based on these bond lengths, the structure can
be viewed as twomolecules of (BDPP)ThX2 interacting with a central
solid state structure of this product, [{(BDPP)ThX(m-X)2Mg(OEt2)
(m-Me)}2]$2 toluene (X ¼ Br0.73e0.87/Cl0.13e0.27; 3$2 toluene; Scheme
1, Fig. 2), revealed that alkylation had not takenplace; instead, halide
exchange and adduct formation between the resulting [(BDPP)ThX2]
moiety and XMgMe(OEt2) had occurred. The product is then tetra-
metallic as a result of MgeMeeMg bridges. Generation of the fully
brominated analogue of 3 would require reaction of 1 with 3
equivalents of MeMgBr, releasing 2 equivalents of MeMgCl per
thorium centre (Scheme 1). It is of note that the formation of [(BDPP)
ThMe2] must not occur to any significant extent given that the
thorium dimethyl complex decomposes rapidly at room tempera-
ture in solution to form a mixture of products [16], none of which
were observed in reactions of 1 and MeMgBr.
Although the reaction of 1 with MeMgBr did not provide
reproducible access to complex 3, this product presents substantial
insight into the type of intermediates involved in halide exchange
reactivity between metal halide precursors and Grignard reagents.
Such reactivity is relatively common for f-element complexes, and
is generally observed as an undesirable outcome in attempted

2800
C.A. Cruz et al. / Journal of Organometallic Chemistry 695 (2010) 2798e2803
Fig. 2. Solid state structure of 3$2 toluene with thermal ellipsoids at 50%. Lattice solvent and hydrogen atoms are omitted for clarity. X(1) ¼ Br0.865(8)/Cl0.135(8); X(2) ¼ Br0.735(8)
/
Cl0.265(8); X(3) ¼ Br0.814(9)/Cl0.186(9). Selected bond lengths (Å) and angles (ꢁ): TheN(1) 2.501(10), TheN(2) 2.259(8), TheN(3) 2.250(9), TheX(1) 2.856(2), TheX(2) 2.887(2), TheX(3)
3.007(2), Mg(1)eO(1) 1.995(11), Mg(1)eC(32) 2.177(10), Mg(1)eC(32)0 2.355(12), Mg(1)eX(2) 2.913(6), Mg(1)eX(3) 2.538(5), N(1)eTheX(3) 164.9(2), N(2)eTheN(3) 127.1(4), X
(1)eTheX(2) 158.36(5), X(3)eMg(1)eO(1) 114.8(4), C(32)eMg(1)eO(1) 124.1(5), C(32)eMg(1)eX(3) 117.5(4), C(32)0eMg(1)eX(2) 169.9(3), TheX(3)eMg(1) 102.83(13), TheX(2)e
Mg(1) 97.00(11), Mg(1)eC(32)eMg(1)0 77.5(4).
Grignard core, itself composed of two trigonal planar MeMgX(OEt2)
units linked by MgeCeMg bridges.
Complex 3 also highlights the potential compatibility of magne-
sium alkyls with metal halides; both bridging and terminal. A
proposed reaction pathway for the conversion of 1 to the fully
brominated analogue of 3 is provided in Scheme 1 [47]. A related
pathway was previously proposed by Cooper et al. to explain the
The MgeCeMg angles in 3 are acute [77.5(4)ꢁ], but are typical for
sterically uncluttered complexes containing a Mg(
for example [{Mg( -Np)2}3Mg(
-Me)2}n] [75ꢁ] [35], [({Mg(
[74.1 and 74.9ꢁ] [36], [{Br2Mg( -Me)}2]2ꢀ [73.7ꢁ] [37] and [{(
{(CH2)2NMe2}2)Mg(
-Me)}2]2þ [80.8 and 80.3ꢁ] [38]. The asymme-
try of the Mg(
-Me)2Mg core in 3 [MgeC ¼ 2.177(10) and 2.355
(12) Å] is also not uncommon; while [{Mg( -Me)2}n] and [{Br2Mg
-Me)}2]2ꢀ adopt much more symmetrical structures
m
-alkyl)2Mg core,
-Br)2)n]
3-MeN
m
m
m
k
m
formation of [Cp{h
5-C5H4(CH2CH]CH2)}WHBr] in the reaction of
m
[Cp2WCl2] with H2C]CHCH2MgBr [48].
m
m
2.2. Reactions of [LThCl2(dme)] with PhCH2MgCl
(m
[MgeC ¼ 2.24 Å in the former; MgeC ¼ 2.26 and 2.28 Å in the latter]
The reactivity of 1 and 2 with PhCH2MgCl stands in stark
contrast to the reactivity of 1 with MeMgBr; with PhCH2MgCl (2
equiv. in toluene), the expected dialkyl products, [LTh(CH2Ph)2]
[L ¼ BDPP (4) and XA2 (5); previously reported] were obtained in
high yield (Scheme 3) [15,18]. However, the reaction to form 5 is
best performed: (a) with addition of PhCH2MgCl at 20 ꢁC, or (b)
with addition of PhCH2MgCl at ꢀ78 ꢁC, followed by stirring at 0 ꢁC
for 3 h. If the addition of PhCH2MgCl to 2 was performed at ꢀ78 ꢁC,
and the reaction was allowed to warm to room temperature after 5
minutes, a substantial amount (30e50%) of a new product, [(XA2)
Mg(dme)] (6), was formed in addition to complex 5 (Scheme 4)
[49]. This product is a result of ancillary ligand transfer from
thorium to magnesium, and was characterized by 1H and 13C NMR
spectroscopy, elemental analysis and X-ray crystallography. Inter-
estingly, [(XA2)Th(CH2Ph)2] (5) does not react with MgCl2 or
PhCH2MgCl at room temperature in toluene or OEt2, so the reaction
pathway responsible for formation of 6 must involve either
complex 2, or a mixed benzyl/chloride thorium intermediate.
[35,37], MgeC bond distances from 2.23 to 2.34 Å were observed in
[{(
from 2.20 to 2.42 Å were observed in [({Mg(
k m
3-MeN{(CH2)2NMe2}2)Mg( -Me)}2]2þ [38], and MgeC distances
m-Np)2}3Mg(m-Br)2)n]
[36]. The long MgeC distances and acute MgeCeMg angle in 3 are
consistent with a 3-centre 2-electron interaction, and confirm that
the atoms bridging between Mg(1) and Mg(10) are carbon, not
oxygen. For comparison, MgeO distances and MgeOeMg angles are
1.94e1.99 Å and 103e106ꢁ, respectively, in the three crystallo-
graphically characterized m2-hydroxy magnesium complexes;
[{(
[Mg4(THF)4(OMes)6(
The MgeX(3) distance in 3 [2.538(5) Å] [34] is similar to those
k
3-TpAr,Me)Mg(
m-OH)}2],
[{(nacnac)Mg(THF)(
m
-OH)}2]
and
m-OH)(m4-OH)] [39e41].
observed in dinuclear [{LMgEt(m-Br)}2] complexes (2.56 Å for
L ¼ NEt3 and 2.58 Å for L ¼ OiPr2) [42,43] and in [(THF){(Me3Si)3C}
Mg(m-Br)2Li(THF)2] (2.52 and 2.55 Å) [44]. By contrast, at 2.913(6) Å,
MgeX(2) is extremely long [34]. A similar bonding situation was
observed in the weakly bound dimer [{(tBuCN){(Me3Si)2HC}Mg
(m-Br)}2], with MgeBr distances of 2.56 and 2.93 Å [45].
Complex 3 is a rare example of an adduct between a d- or f-block
metal complex and a Grignard reagent, and is the first example of
such a complex containing a terminal halide ligand (on the d- or
f-block metal). The only other well-characterized d- or f-element
Grignard adduct (containing an MeXeMgeR linkage) is [Cp*(COT)
t
Th(m
-Cl)2Mg(CH2 Bu)(THF)], formed via the reaction of [Cp*(COT)
ThCl(THF)] with tBuCH2MgCl (Scheme 2) [46]. However, adduct
formation and halide exchange has to the best of our knowledge
only been observed in 3. As such, complex 3 provides direct insight
into the type of intermediates responsible for halide exchange.
Scheme 2. Synthesis of [Cp*(COT)Th( -Cl)2Mg(CH2tBu)(THF)] [46].
m

C.A. Cruz et al. / Journal of Organometallic Chemistry 695 (2010) 2798e2803
2801
Scheme 3. Reactions of complexes 1 and 2 with PhCH2MgCl to form 4 and 5.
In the solid state structure of 6$hexane (Fig. 3), the geometry at
magnesium is intermediate between square pyramidal and trigonal
bipyramidal [N(1)eMgeN(2) ¼ 138.8(1)ꢁ; N(1)eMgeO(3) ¼ 112.9
(1)ꢁ; N(2)eMgeO(3)
¼
104.2(1)ꢁ], which requires significant
bending of the xanthene backbone of the XA2 ligand;
pln1 e pln2 ¼ 41ꢁ (pln1 ¼ plane through C1eC4, C10 and C11;
pln2 ¼ plane through C5eC8, C12 and C13). For comparison, in the
chemistry of thorium, the backbone of the XA2 ligand is invariably
more planar (e.g. pln1 ꢀ pln2 ¼12ꢁ and 19ꢁ for the two independent
molecules in the X-ray crystal structure of 5) [18]. However, for both
the thorium and magnesium complexes, the two methyl groups on
C(9) are equivalent in the room temperature 1H and 13C NMR
spectra, indicating that rapid inversion of the bend in the XA2 ligand
occurs in solution.
Surprisingly, given the large binding pocket of the XA2 ligand, the
MgeN bond distances of 2.054(2) Å in 6 also lie within the expected
range (cf. 2.055(2) Å in [(Ph2N)2Mg(hmpa)2] and 2.013(3) Å in
[(Ph2N)2Mg(THF)2]) [50,51]. This is achieved through appreciable
distortion of the ligand framework to bring the two amido donors
closer to one another [C(1)/C(8) ¼ 4.87 Å, C(4)/C(5) ¼ 4.40 Å and N
(1)/N(2) ¼ 3.85 Å]. The MgeO distances in 6 [2.047(2)e2.096(2) Å]
also fall in the usual range (cf. MgeO distances of 2.047(5) Å in [Mg
{P(SiMe3)2}2(dme)] [52], 2.124(4) Å in [Mg(SiMe3)2(dme)] [53],
2.084(7) and 2.096(6) Å in [Mg(tBuNSiMe2(C6H4)OMe-o}2] [54], and
2.052(2) and 2.087(2) Å in [(diglyme)Mg(BH4)2] [55]), although
due to constraints imposed by the rigid XA2 ligand, MgeO(1) is
somewhat shorter than might be expected for coordination to
Fig. 3. The solid state structure of 6$hexane with thermal ellipsoids at 50% probability.
Lattice solvent and hydrogen atoms are omitted for clarity. In view B, isopropyl and
tert-butyl groups are also omitted for clarity. Selected bond lengths (Å) and angles (ꢁ):
MgeN(1) 2.054(2), MgeN(2) 2.054(2), MgeO(1) 2.047(2), MgeO(2) 2.084(2), MgeO(3)
2.096(2), O(1)eMgeO(2) 172.07(7), N(1)eMgeN(2) 138.79(8), N(1)eMgeO(3) 112.92
(7), N(2)eMgeO(3) 104.18(7).
a
diarylether ligand; other crystallographically characterized
Mgediarylether complexes are not available for comparison.
Several examples of ancillary ligand transfer from a rare earth
element to magnesium have previously been reported. For
3. Summary and conclusions
The formation of [{(BDPP)ThX(m-X)2Mg(OEt2)(m-Me)}2]
example, [(nacnac)LaBr2(THF)2] or [(nacnac)La(THF)(
m-Cl)3LaCl
(X ¼ Br0.73e0.87/Cl0.13e0.27; 3) from [(BDPP)ThCl2(dme)] (1) involves
both halide exchange (Cl for Br) and adduct formation with
MeMgX. As such, complex 3 can be considered to provide a snap-
shot of the process responsible for halide exchange between highly
electrophilic metal halide complexes and Grignard reagents. The
composition of 3 also highlights the compatibility of magnesium
alkyls with certain metal halides; both bridging and terminal. In
contrast to the reaction of 1 with MeMgBr, reactions of 1 and [(XA2)
ThCl2(dme)] (2) with PhCH2MgCl provided the expected dibenzyl
complexes, [LTh(CH2Ph)2] [L ¼ BDPP (4) and XA2 (5); previously
reported] under most reaction conditions [15,18]. However, addi-
tion of PhCH2MgCl to 1 at ꢀ78 ꢁC and warming to room temper-
ature after 5 min yielded a significant amount of [(XA2)Mg(dme)]
(6), the product of ancillary ligand transfer from thorium to
magnesium. This reaction outcome further highlights the diversity
of behaviour accessible in the reactions of f-element halides with
Grignard reagents.
(nacnac)] [nacnac ¼ N,N-bis(2,6-diisopropylphenyl)-
b
-diketimi-
nate] reacted with RMgCl (R ¼ Me or allyl) to form [(nacnac)MgR
(THF)] and [LaX3(THF)n] (X ¼ Cl or Br) [40,56]. Similarly, the yttrium
complex [(PNP)2Y(
[(PNP)Y(C3H5)(
m
-Cl)]2 [PNP ¼ N(SiMe2CH2PMe2)2] yielded
m
-Cl)]2 and [Mg(PNP)2] when treated with either
(C3H5)MgCl or Mg(C3H5)2(dioxane) [57,58]. The temperature
sensitivity of the reactions of 2 with PhCH2MgCl is remarkable, and
the absence of ancillary ligand transfer to magnesium in reactions
of similarly ligated 1 with PhCH2MgCl highlights the extent to
which this reaction manifold is sensitive to the specific steric and
electronic properties of the ligands involved.
4. Experimental
General details: An argon-filled MBraun UNIlab glove box was
employed for the manipulation and storage of all oxygen and
moisture sensitive compounds, and all compounds were stored in
Scheme 4. Reaction of complex 2 with PhCH2MgCl (ꢀ78 ꢁC for 5 min, then stirring at
room temperature for 1 h) to form 6.

2802
C.A. Cruz et al. / Journal of Organometallic Chemistry 695 (2010) 2798e2803
4
4
a ꢀ30 ꢁC freezer within the glove box. Commonly utilized specialty
glassware includes double manifold high vacuum lines, swivel frit
assemblies, J-Young NMR tubes, and thick walled flasks equipped
with Teflon stopcocks (Chemglass and Toonen Glassblowing) [59].
Any residual oxygen and moisture was removed from the argon
stream by passage through an Oxisorb-W scrubber from Matheson
Gas Products.
Hexanes and toluene were initially distilled under nitrogen from
CaH2 and sodium, respectively, prior to storage under vacuum over
Na/Ph2CO (toluene) or Na/Ph2CO/tetraglyme (hexanes). C6D6 was
purchased from ACP chemicals and dried over Na/Ph2CO. All
solvents were introduced into reactions or storage flasks by
vacuum transfer with condensation at ꢀ78 ꢁC. MeMgBr (3.0 M in
OEt2) and PhCH2MgCl (1.0 M in OEt2) were purchased from Aldrich.
[(BDPP)ThCl2(dme)] (1) and [(XA2)ThCl2(dme)] (2) were prepared
as previously reported [14].
Ar-Hpara), 6.62 (d, 2H, JHeH 1.7 Hz, CH3), 6.24 (d, 2H, JHeH 1.7 Hz,
CH1), 3.55 (sept, 4H, 3JHeH 6.7 Hz, CHMe2), 2.79 (s, 6H, OMe), 2.58 (s,
3
4H, OCH2), 1.70 (s, 6H, CMe2), 1.27, 1.12 (d, 2 ꢂ 12H, JHeH 6.7 Hz,
CHMe2). 13C{1H} NMR (C6D6, 125 MHz):
d 148.8 (Ar-CHortho), 148.2,
147.0, 132.1 (Xanth-Q), 146.1 (Ar-Cipso), 123.5 (Ar-CHpara), 123.8 (Ar-
CHmeta), 109.1 (CH1), 103.0(CH3), 69.4 (OCH2), 59.9 (OMe), 36.5
(CMe2), 35.1 (CMe3), 28.8 (CMe2), 32.0 (CMe3), 28.2 (CHMe2), 26.0,
24.4 (CHMe2). Anal. Calcd. for: C51H72MgN2O3: C, 77.99; H, 9.24; N,
3.57. Found: C, 78.43; H, 9.71; N, 3.48.
Acknowledgements
D. J. H. E. thanks NSERC of Canada for a Discovery Grant, and
Canada Foundation for Innovation (CFI) and Ontario Innovation
Trust (OIT) for New Opportunities Grants. C. A. C. thanks the
Government of Ontario for an Ontario Graduate Scholarship (OGS)
and NSERC of Canada for a PGS-D scholarship.
Combustion elemental analyses were performed on a Thermo
EA1112 CHNS/O analyzer. X-ray crystallography was performed on
suitable crystals coated in Paratone oil and mounted on either: (a)
a P4 diffractometer with a Bruker Mo rotating-anode generator and
a SMART1K CCD area detector, or (b) a SMART APEX II diffractom-
eter with a 3 kW Sealed tube Mo generator in the McMaster
Analytical X-ray (MAX) Diffraction Facility.
Appendix A. Supporting information
Supplementary data associated with this article (X-ray crystal-
lographic data in PDF format) can be found in the online version at
doi:10.1016/j.jorganchem.2010.08.048.
NMR spectroscopy [1H, 13C{1H}, DEPT-135, COSY, HSQC, HMBC]
was performed on a Bruker AV-600 spectrometer. All 1H NMR and
13C NMR spectra were referenced to SiMe4 through a resonance of
the deuterated solvent or proteo impurity of the solvent (C6D6):
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3
3
d
7.27 (d, 4H, JHeH 7.4 Hz, Ar-Hmeta), 7.20 (t, 2H, JHeH 7.4 Hz,

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