Synthesis and structural characterisation of heavy alkaline earth N,N′-bis(aryl)formamidinate complexes

Article abstract of DOI:10.1039/b602210c

Treatment of calcium or strontium with 2.0 equivalents of N,N′-bis(o-methylphenyl)formamidine (o-TolFormH), N,N′-bis(2,6-dimethylphenyl)formamidine (XylFormH) or N,N′-bis(o-phenylphenyl)formamidine (o-PhPhFormH) in the presence of 1.0 equivalent of Hg(C

Full text of DOI:10.1039/b602210c

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Synthesis and structural characterisation of heavy alkaline earth
ꢀ
N,N -bis(aryl)formamidinate complexes
Marcus L. Cole,a,b Glen B. Deacon, Craig M. Forsyth, Kristina Konstas and Peter C. Junk*
a
a
a
a
Received 14th February 2006, Accepted 13th April 2006
First published as an Advance Article on the web 27th April 2006
DOI: 10.1039/b602210c
ꢀ
Treatment of calcium or strontium with 2.0 equivalents of N,N -bis(o-methylphenyl)formamidine
ꢀ
ꢀ
(
o-TolFormH), N,N -bis(2,6-dimethylphenyl)formamidine (XylFormH) or N,N -bis(o-phenylphenyl)-
formamidine (o-PhPhFormH) in the presence of 1.0 equivalent of Hg(C in tetrahydrofuran (thf)
affords the bis(formamidinate) complexes [Ca(o-TolForm) (thf) ] (1), [Ca(XylForm) (thf) ] (2),
] (4), [Sr(XylForm) (thf)
]·3thf (5) and
]·2thf (6). Analogous reactions with barium were generally unsatisfactory but
]·2thf (7) was successfully prepared. Compounds 1–7 have been characterised
6
F
)
5 2
2
2
2
2
[Ca(o-PhPhForm)
[Sr(o-PhPhForm)
[Ba(o-PhPhForm)
2
(thf)
(thf)
(thf)
2
]·thf (3), [Sr(o-TolForm)
2
(thf)
3
2
3
2
3
2
3
1
13
1
by various spectroscopic methods ( H, C{ H} NMR and IR), elemental analyses and, for 1, 2 and
4
–6, X-ray crystallography. The calcium complexes are monomeric and six-coordinate with either
transoid octahedral or trigonal prismatic geometry, whilst the larger radius of strontium accommodates
an additional thf solvent donor to give seven-coordinate structures with two types of coordination
polyhedra.
Introduction
Herein we report the use of redox transmetallation/ligand
exchange reactions for the synthesis of some heavy alkaline earth
The challenge of preparing and characterising highly reactive
heavy alkaline earth organometallics and organoamides is attract-
ing increasing attention. Commonly used synthetic methods
are metathesis from the anhydrous halides and protolysis of
ꢀ
species with the moderately bulky organoamide ligands N,N -
ꢀ
bis(o-methylphenyl)formamidine (o-TolFormH), N,N -bis(2,6-
1
–5
ꢀ
dimethylphenyl)formamidine (XylFormH) and N,N -bis(o-
phenylphenyl)formamidine (o-PhPhFormH). Formamidinate lig-
1
–5
suitable reactants, most usually the bis(trimethylsilyl)amides,
1
2
−
1
2
ands ([R NC(H)NR ] , where R and R = alkyl or aryl)
1
,4
which also pose a synthetic challenge. For metathesis reactions
the anhydrous chlorides and bromides have the disadvantage of
low solubility in common polar organic solvents, whilst the more
suitable high purity anhydrous iodides are extremely expensive.
Syntheses based on the highly reactive metals analogous to
reactions of lanthanoid metals offer an alternative approach, and
the metals in liquid ammonia have been particularly successful,
for example giving bis(trimethylsilyl)amides. More recently the
direct reaction of the metals with phenols and pyrazoles at
elevated temperatures has provided a number of phenolate and
pyrazolate complexes. Redox transmetallation/ligand exchange
between a metal, a diarylmercurial, and a protonated ligand (eqn
have demonstrated excellent coordination flexibility with tran-
sition and alkali metals
application to the alkaline earths. We have shown that the
extremely bulky formamidinate with 2,6-diisopropylphenyl N-
substituents (DippForm) produces complexes with the alkaline
17–24
but have experienced only limited
15
1
6
earth metal in a sterically frustrated environment, in this instance
1
–3
15
[
M(DippForm)
2
(thf)
n
]; M = Ca, n = 1; M = Sr or Ba, n = 2. In
7
principle, use of the moderately bulky ligands o-TolFormH and
XylFormH will give the metal greater control of coordination
number and geometry, and will therefore allow us to probe
whether two ortho-methyl groups (XylForm) do indeed provide
greater steric hindrance than a single ortho-methyl substituent
8
9
6
,10–13
(
1)), a route notably successful for the lanthanoid elements,
(
o-TolForm). This is of interest as we have recently observed
offers particular promise for the more electropositive alkaline
earth metals.
that XylForm adopts a conformation in binding to lithium and
sodium where the xylyl groups lie perpendicular to the plane
of the MNCN metallacycle to avoid disfavourable buttressing
M + HgR
2
+ 2 HL → ML
2
+ 2 RH + Hg
(1)
17g
with the formamidinate backbone methine. By contrast, the
Alkaline earth 3,5-diphenylpyrazolates have been obtained as
both thf and dme (1,2-dimethoxyethane) complexes employing
o-tolyl groups of o-TolForm can and sometimes do adopt co-
planarity with the MNCN metallacycle permitting the o-methyl
14
ꢀ
17b,25
this method, as have complexes of the very bulky N,N -bis(2,6-
to project towards the metal.
As the latter conformation is
15
diisopropylphenyl)formamidinate ligand and pentafluorophenyl
inaccessible to the XylForm ligand, it is conceivable that the o-
complexes stabilised by ‘super’ bulky and p-bonding triazenide
ligands.
TolForm ligand can exert greater steric influence on the metal
16
ꢀ
coordination environment. The hitherto neglected N,N -bis(o-
26,27
phenylphenyl)formamidinate ligand,
with the potential for
different conformations (owing to the planarity of the phenyl
group) and p-phenyl binding, has been explored with calcium,
strontium and barium. Accordingly, its coordination chemistry is
reported here for the first time.
a
School of Chemistry, Monash University, Victoria, 3800, Australia.
E-mail: peter.junk@sci.monash.edu.edu.au; Fax: +61 (0)3 9905 4597
b
School of Chemistry and Physics, The University of Adelaide, Adelaide,
South Australia, 5005, Australia
3
360 | Dalton Trans., 2006, 3360–3367
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Results and discussion
XylForm complexes 2 and 5 and o-PhPhForm complexes 3, 6 and 7
(
see Experimental section). The change in chemical shift is typical
Freshly filed calcium and strontium metal react cleanly with two
equivalents of o-TolFormH, XylFormH or o-PhPhFormH in thf in
the presence of one equivalent of bis(pentafluorophenyl)mercury
17a
of deprotonation of the formamidine. Analogous appropriate
shifts of the methine carbons were observed for all complexes.
1
For compounds 1, 2 and 4 the H NMR spectra and microanal-
to afford the compounds [M(o-TolForm)
n = 2 (1) and M = Sr; n = 3 (4), [M(XylForm)
where M = Ca; n = 2; m = 0 (2) and M = Sr; n = 3; m =
(5), and [M(o-PhPhForm) (thf)
2
(thf)
n
], where M = Ca;
yses support the ratio of solvent to ligand observed in the crystal
structure (see below), but for 5 the lattice thf is removed by drying
of the bulk material in vacuo to give a thf to formamidinate ratio
2
(thf)
n
]·mthf,
3
2
n
]·mthf, where M = Ca; n = 2;
1
of 3 : 2 as confirmed by metal analysis and H NMR data. In
m = 1 (3) and M = Sr; n = 3; m = 2 (6), in good yield (see
the case of 6, a microanalysis on single crystals was consistent
Scheme 1). By contrast, reactions of o-TolFormH and XylFormH
with their composition as [Sr(o-PhPhForm)
sample prepared for acquisition of H NMR data showed loss
2
(thf)
3
]·2thf but the
with barium were unsatisfactory but [Ba(o-PhPhForm)
7) was successfully isolated. The absence of a m(N–H) absorption
in the infrared spectra and the lack of a NH resonance in the
2
(thf)
3
]·2thf
1
(
of lattice thf. Compound 3, which was not obtained as single
1
crystals, had microanalyses and a H NMR spectrum indicative
1
H NMR spectra of the bulk vacuum dried materials in C
6
D
6
of a thf to formamidinate ratio of 3 : 2. For 7, also not obtained
indicated complete deprotonation of the formamidine reagents in
the isolated complexes. The methine proton resonance (NC(H)N)
in the spectra of 1 and 4 is shifted significantly to higher frequencies
from those of the neutral ligand (7.72 ppm for o-TolFormH to
1
as single crystals, both microanalyses and H NMR data suggest
a thf to formamidinate ratio of 5 : 2. Only a single, symmetrical
1
formamidinate environment is evident in the H NMR spectra
of 1–7, indicating either symmetrically bound ligands or a rapidly
8
.39 ppm (1) and 8.80 ppm (4)). The same trend is observed for
28
1
13
1
exchanging system. Variable-temperature H and C{ H} NMR
spectra of arguably the most sterically crowded compound, 2,
◦
in C
7
D
8
over the regime −60 to +80 C exhibit no significant
differences.
X-Ray crystallographic studies
Colourless crystalline samples of compounds 1, 2 and 4–6 of
suitable quality for X-ray structure determination were grown
from thf and proved to be extremely air-sensitive and prone to
solvent loss. However, satisfactory X-ray data were obtained and
the structure solutions show all compounds to be mononuclear
species with two chelating formamidinate ligands (see Fig. 1–5,
POV-RAY illustrations, 40% thermal ellipsoids). Table 1 contains a
summary of crystallographic data for all compounds characterised
by X-ray methods, while Table 2 provides selected bond lengths
Scheme 1 Reagents and conditions: (i) R = o-Me, 2.0 eq. o-TolFormH,
.0 eq. Hg(C H, 1;
, 1.0 eq. M, thf, room temperature, 48 h, −2 C
M = Ca, n = 2, 4; M = Sr, n = 3. (ii) R = 2,6-Me , 2.0 eq. XylFormH, 1.0 eq.
Hg(C H, 2; M = Ca,
, 1.0 eq. M, thf, room temperature, 48 h, −2 C
n = 2, 5; M = Sr, n = 3. (iii) R = 2-Ph, 2.0 eq. o-PhPhFormH, 1.0 eq.
Hg(C H, 3; M = Ca,
, 1.0 eq. M, thf, room temperature, 48 h, −2 C
n = 2, 6; M = Sr, n = 3, 7; M = Ba, n = 3.
1
6
F
5
)
2
6 5
F
2
6
F
5
)
2
6 5
F
6
F
5
)
2
6 5
F
◦
˚
(A), angles and interplanar angles ( ).
Table 1 Summary of crystallographic data for all compounds characterised by single-crystal X-ray structure determination
[
(
Ca(o-TolForm)
1)
2
(thf)
2
]
[Ca(XylForm)
(2)
2
(thf)
2
]
[Sr(o-TolForm)
(4)
2
(thf)
3
]
[Sr(XylForm)
3thf (5)
2
(thf)
3
]·
[Sr(o-PhPhForm)
2thf (6)
2
(thf)
3
]·
Mol. formula
M
C
630.87
123(2)
P2
11.2249(3)
16.7282(9)
19.6462(10)
90
105.930(3)
90
3547.3(3)
4
38
H
46CaN
4
O
2
C
686.98
123(2)
C2/c
19.3852(3)
11.1831(2)
18.1765(4)
90
101.7590(10)
90
3857.73(12)
4
1.183
42
H
54CaN
4
O
2
C
42
H
54
N
4
O
3
Sr
C
58
H
86
N
4
O
6
Sr
70 78 4 5
C H N O Sr
750.51
123(2)
Cc
21.4128(8)
9.8514(4)
18.7930(8)
90
100.313(3)
90
3900.3(3)
4
1.278
1.425
15560
7223
455
1022.93
123(2)
P2
1142.98
123(2)
Pccn
T/K
Space group
a/A˚
1
/c
1
/c
10.9388(3)
26.6486(4)
b/A˚
c/A˚
33.5561(10)
16.2284(5)
90
109.591(2)
90
5612.0(3)
4
1.211
10.17120(10)
21.9266(3)
90
90
90
5943.17(13)
4
1.277
0.962
49571
6710
◦
a/
b/
◦
◦
c /
V/A˚
3
Z
−
3
D
c
/g cm
l/mm
1.181
0.214
23008
8358
−
1
0.202
12570
4599
1.012
Reflections collected
Unique reflections
Parameters varied
34805
12813
640
411
226
390
R
int
0.0665
0.0510
0.1357
0.0572
0.0574
0.1331
0.1114
0.0605
0.1159
0.0880
0.0763
0.1458
0.1274
0.0783
0.1374
R
1
wR
2
This journal is © The Royal Society of Chemistry 2006
Dalton Trans., 2006, 3360–3367 | 3361

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◦
Table 2 Selected bond lengths ( A˚ ), angles and interplanar angles ( ) for compounds 1, 2 and 4–6
1
2
4
5
(6)
M–N(1)
M–N(2)
M–N(3)
M–N(4)
M–O(1)
M–O(2)
M–O(3)
2.415(2)
2.442(2)
2.4244(19)
2.425(2)
2.3668(16)
2.3688(17)
—
1.332(3)
1.317(3)
1.319(3)
1.330(3)
2.415(2)
2.442(2)
2.415(2)
2.442(2)
2.4013(19)
2.4013(19)
—
2.595(5)
2.666(5)
2.623(5)
2.674(5)
2.585(4)
2.640(4)
2.654(4)
1.330(8)
1.320(8)
1.311(8)
1.327(8)
2.631(3)
2.642(3)
2.652(3)
2.657(3)
2.571(3)
2.586(3)
2.630(3)
1.322(5)
1.321(5)
1.319(5)
1.317(5)
2.661(4)
2.704(3)
2.661(4)
2.704(3)
2.565(3)
2.622(4)
2.565(3)
1.326(5)
1.325(5)
1.326(5)
1.325(5)
b
b
c
c
b
c
a
N(1)–CNCNa
1.327(3)
1.319(3)
1.327(3)
N(2)–CNCN
a
b
c
c
N(3)–CNCNꢀ
N(4)–CNCNꢀ
a
b
1.319(3)
N(1)–M–N(2)
N(3)–M–N(4)
56.41(6)
56.29(6)
169.87(7)
93.69(6)
91.48(6)
—
89.67(6)
85.73(6)
—
174.04(6)
—
—
94.90(7)
91.06(7)
—
89.60(6)
93.58(6)
—
87.34(6)
90.37(6)
—
88.95(6)
85.20(6)
—
7.92(11)
39.25(7)
57.00(7)
86.36(7)
48.66(6)
23.95(8)
65.56(6)
56.58(7)
56.58(7)
129.20(11)
118.54(7)
100.36(7)
—
100.36(7)
118.54(7)
—
79.90(9)
—
—
145.42(7)
94.52(7)
52.22(17)
51.65(16)
116.66(18)
141.88(16)
83.32(15)
105.93(15)
101.41(16)
128.92(16)
94.27(16)
70.58(15)
71.40(14)
126.62(17)
121.15(17)
85.06(16)
83.91(15)
152.10(15)
81.59(16)
127.55(15)
110.10(16)
154.24(16)
75.02(16)
88.24(16)
103.37(15)
111.44(15)
89.62(14)
49.06(20)
42.41(21)
83.18(16)
27.73(27)
35.38(23)
35.84(26)
51.97(10)
51.65(11)
144.25(11)
90.70(11)
93.30(11)
108.99(10)
91.17(11)
87.93(11)
106.75(10)
174.33(10)
85.53(10)
89.37(10)
95.27(11)
86.62(11)
83.80(10)
87.88(11)
97.47(10)
134.40(10)
84.67(11)
92.12(11)
81.30(10)
95.76(10)
85.85(10)
132.37(10)
20.14(24)
69.46(15)
65.55(12)
73.52(14)
66.06(12)
65.37(14)
68.73(12)
51.17(10)
51.17(10)
152.29(14)
103.04(10)
103.86(7)
82.85(10)
103.04(10)
b
c
c
a
b
C
C
C
C
C
C
C
NCN–M–CNCNꢀ
a
NCN–M–O(1)
NCN–M–O(2)
NCN–M–O(3)
NCNꢀ –M–O(1)
NCNꢀ –M–O(2)
NCNꢀ –M–O(3)
a
a
b
c
c
a
b
a
a
b
c
103.86(7)
82.85(10)
77.79(7)
155.58(14)
77.79(7)
c
c
O(1)–M–O(2)
O(1)–M–O(3)
O(2)–M–O(3)
N(1)–M–O(1)
N(1)–M–O(2)
N(1)–M–O(3)
N(2)–M–O(1)
N(2)–M–O(2)
N(2)–M–O(3)
N(3)–M–O(1)
N(3)–M–O(2)
N(3)–M–O(3)
N(4)–M–O(1)
N(4)–M–O(2)
N(4)–M–O(3)
MNCN–MNCN
MNCN–N(1)Ar
MNCN–N(2)Ar
N(1)Ar–N(2)Ar
MNCN–N(3)Ar
MNCN–N(4)Ar
c
89.74(10)
79.74(7)
b
c
85.94(10)
111.85(10)
128.58(7)
92.48(7)
108.13(7)
—
94.52(7)
145.42(7)
—
108.13(7)
92.48(7)
—
71.07(7)
74.39(7)
80.44(8)
64.60(8)
74.39(7)
80.44(8)
64.60(8)
b
c
83.78(9)
b
c
c
85.94(10)
b
c
79.74(7)
89.74(10)
b
c
83.78(9)
128.58(7)
b
c
c
c
111.85(10)
32.68(11)
40.09(13)
43.60(12)
51.98(11)
40.09(13)
43.60(12)
51.98(11)
d
b
d
d
d
d
d
b
c
c
c
b
d
b
N(3)Ar–N(4)Ar
a
b
C
NCN and CNCNꢀ refer to the lowest numbered and highest numbered “NCN” methine carbon, respectively. N(3), N(4), O(2) and CNCNꢀ are symmetry
3
generated equivalents of N(1)#, N(2)#, O(1)# and CNCN#, respectively. Symmetry transformation used to generate equivalent atoms: 1 − x, y, − z.
2
c
N(3), N(4), O(3) and CNCNꢀ are symmetry generated equivalents of N(1)#, N(2)#, O(1)# and CNCN#, respectively. Symmetry transformation used to
3
3
d
generate equivalent atoms: 2 −x 2 −y, z. MNCN refers to a metallacyclic plane directly associated with an aryl ring (N(#)Ar).
Calcium formamidinates
Compound 1 exhibits two transoid thf donor molecules com-
plementing two formamidinate ligands, giving the calcium metal
centre a coordination number of six (Fig. 1). The calcium atom and
the four formamidinate nitrogen atoms lie in a plane with the two
thf ligands normal to this plane. Compound 1 can be described as
having a distorted octahedral geometry, with the NCN backbones
in the equatorial plane and the two transoid thf molecules in axial
◦
positions (O(1)–Ca(1)–O(2) 174.04(6) ). The ortho-methyl groups
are placed to avoid clash with the methine hydrogen, and occupy
the space on either side of the two thf ligands. This produces
˚
close Ca(1) · · · C(Me) distances (3.6467(23)–4.2372(23) A) that
Fig. 1 Molecular structure of [Ca(o-TolForm)
ellipsoids). All hydrogen atoms omitted for clarity.
2
(thf)
2
] (1) (40% thermal
are nevertheless too long to be considered bonding/agostic
1,3,4,5b
˚
interactions (ca. 3.0 A).
Compound 1 displays a similar
3
362 | Dalton Trans., 2006, 3360–3367
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2 3
Fig. 3 (a) Molecular structure of [Sr(o-TolForm) (thf) ] (4) (40% thermal
ellipsoids). All hydrogen atoms omitted for clarity. (b) Orientation of 4
depicting the pseudo-square based pyramidal geometry of the central
C O Sr unit (40% thermal ellipsoids). Refer to Table 2 for selected angles.
2 3
Fig. 2 (a) Molecular structure of [Ca(XylForm)
ellipsoids). All hydrogen atoms omitted for clarity. (b) Orientation of
depicting the distorted trigonal prismatic geometry of the central
2 2
(thf) ] (2) (40% thermal
2
CaN
4
O
2
unit (40% thermal ellipsoids). Selected distances ( A˚ ), interplanar
and twist angles ( ): N(1)–N(2)/N(1)#–N(2)# 2.2999(27), O(1)–O(1)#
◦
˚
˚
˚
2.37 A, ꢁCa–Nꢂ 2.43 A; 2 ꢁCa–Nꢂ 2.43 A), however the Ca–O
3
2
.0800(35), N(2)O(1)N(1)#:N(2)#O(1)#N(1) interplanar; 17.49(5), twist;
4.47(47), centroid–Ca(1)–centroid’ (centroid = centre of each trigonal
bond lengths of both [Ca{C(Ph){N(SiMe )} } (thf) ] and 1 are
3
2
2
2
˚
marginally shorter than those of 2 (2.401(2) A) due to the increased
bulk of XylForm.
face) 175.26(71). Symmetry transformation used to generate ‘#’ atoms:
1
3
2
− x, y, − z.
A proposal for the structure of compound 3, which has the
empirical formulation Ca(o-PhPhForm)
basis of the coordination numbers of both 1 and 2, which have two
coordinated thf molecules. Further, comparison of the strontium
2
(thf) , can be made on the
3
2
5
arrangement to its magnesium analogue despite the larger ionic
2
+
29
˚
radius of Ca (six-coordinate; 0.28 A increase).
Compound 2, which crystallises with half a molecule in the
asymmetric unit and the calcium on a two-fold rotation axis, also
exhibits six-coordination about its metal centre (Fig. 2). Unlike
the transoid octahedral geometry of 1, the metal centre of 2 is
considered cisoid octahedral owing to its O(1)–Ca(1)–O(1)# angle
compounds [Sr(XylForm)
2
(thf)
3
] (5) and [Sr(o-PhPhForm)
2
(thf) ]
3
(
6) vide infra suggests the coordination geometries adopted by
complexes bearing these particular formamidinates are similar.
Accordingly, compound 3 is reasonably formulated as [Ca(o-
PhPhForm)
2
(thf)
2
]·thf.
◦
of 79.90(9) . However, closer inspection of the bond angles about
Ca(1) suggests the geometry of 2 is best described as a distorted
trigonal prism (Fig. 2(b)). The two triangular faces of this prism,
composed of O(1)#, N(1) and N(2)# and N(2), O(1) and N(1)#,
Strontium formamidinates
In compound 4 the strontium atom is seven-coordinate and
bound to two formamidinate and three thf ligands (Fig. 3). The
increase in coordination number from 1 is consistent with the
◦
◦
are twisted by 24.47(47) and are not parallel (17.49(5) ) due
to the small bite angles of the two XylForm ligands. The two
centroids of the triangular faces and Ca(1) are approximately
2
+
2+ 29
˚
increase in ionic radius (0.21 A) of Sr relative to Ca . The
◦
linear (175.26(71) ).
corresponding lengthening of the Sr–O bonds in compound 4
˚
˚
˚
A calcium amidinate complex closely related to 1 is octahedral
(ꢁSr–Oꢂ 2.63 A; cf. 1 ꢁCa–Oꢂ 2.37 A) is 0.05 A larger than
[
Ca{C(Ph){N(SiMe
3
)}
2
}
2
(thf)
2
], where the thf molecules are trans
expected on the basis of ionic radii and coordination number
29
and the benzamidinate ligands chelate to calcium in the equatorial
positions. The average Ca–O and Ca–N bond lengths of this
differences. Further, the coordination geometry of 4, though
irregular, can be described as a pseudo-square-based pyramid
(Fig. 3(b)), formed by the thf oxygen atoms and the methine
carbons of the NCN fragments, with C(30) as the apex. The square
30
˚
˚
compound (ꢁCa–Oꢂ 2.38 A, ꢁCa–Nꢂ 2.43 A) are similar to those
of compound 1 and the Ca–N bond length of 2 (1; ꢁCa–Oꢂ
This journal is © The Royal Society of Chemistry 2006
Dalton Trans., 2006, 3360–3367 | 3363

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Fig. 5 (a) Molecular structure of [Sr(PhPhForm)
ellipsoids). All hydrogen atoms and lattice thf omitted for clarity. (b)
Orientation of 6 depicting the distorted trigonal pyramidal C Sr
polyhedron (40% thermal ellipsoids). Refer to Table 2 for selected angles.
2 3
(thf) ] (6) (40% thermal
2
O
3
3
2
3
Fig. 4 (a) Molecular structure of [Sr(XylForm)
ellipsoids). All hydrogen atoms and lattice thf omitted for clarity.
b) Orientation of 5 depicting the distorted trigonal pyramidal C Sr
2
(thf)
3
] (5) (40% thermal
Symmetry transformation used to generate ‘#’ atoms: − x, 2 − y, z.
(
2 3
O
polyhedron (40% thermal ellipsoids). Refer to Table 2 for selected angles.
addition of an o-methyl to o-TolForm (giving XylForm). The
most striking difference between 5 and 6 is the greater bending
of the Oapical–Sr–Oapical angle (5; 174.3(1) , 6; 155.6(1) ), which
presumably arises from the differing steric effects of planar o-
phenyl and the 2,6-dimethyl substituents (Fig. 4, 5). The phenyl
substituents are somewhat directed towards the metal, but the
base places O(2) and O(3), and C(15) and O(1), trans to one
another, with Sr–O(2,3) bond distances significantly longer (ca
◦
◦
˚
0.06 A) than Sr–O(1). The increased average Sr–O bond length
˚
(
2.63 A) over the average reported Sr–O bond length for seven
31
˚
coordination (2.59 A) suggests significant steric crowding in 4
owing to the positioning of the ortho-methyl groups (see below).
˚
closest approach at 3.7050(38) A (Sr(1)–C(20)/C(20)#) is far too
1,3,4,5b
˚
The Sr–N bond lengths of 4 (ꢁ2.64 Aꢂ) are expectedly longer than
distant to be considered a bonding interaction.
Accordingly,
˚
the Ca–N bond lengths of compound 1 (ꢁ2.43 Aꢂ). Two related
exploration of p-phenyl · · · M interactions with o-PhPhForm,
where M = Ca, Sr or Ba, would appear to require the preparation
of homoleptic complexes.
benzamidinate compounds, trans-[Sr{C(Ph){N(SiMe
3
)}
2
}
2
(thf) ]
(diglyme)] (seven-
2
(
six-coordinate) and [Sr{C(Ph){N(SiMe
3
)}
2
}
2
32
˚
˚
coordinate), have mean Sr–N bond lengths (2.58 A, 2.60 A)
shorter than the mean of analogous bonds in 4.
The clearest evidence of a structural difference between 4 and
compounds 5 and 6 is that the latter pair have a maximum O–Sr–O
◦
Mononuclear 5 and 6 (Fig. 4, 5), which crystallise with one and
one half molecule in the asymmetric unit, respectively (the latter
with the strontium on a two-fold rotation axis), differ only in the
number of lattice thf molecules, and have seven coordinate (two
chelating formamidinates and three thf ligands) strontium metals
with distorted trigonal bipyramidal arrangements (Fig. 4(b) and
angle in excess of 150 (see above) while 4 possesses a maximum
◦
O–Sr–O angle of 126.6(2) . Furthermore, the variation in Sr–N
˚
distances for 5 and 6 (0.03 and 0.04 A, respectively) is much less
˚
than that of 4 (0.08 A). Comparing Sr–O distances, 4 has one Sr–O
bond significantly shorter than the other two (2.585(4), 2.640(4),
˚
2.654(4) A) whereas for 5 and 6 there is a significantly longer Sr–
O distance for the equatorial thf of the SrO unit (5; 2.571(3),
5
(b)) of oxygen atoms and NCN methine carbon atoms. In both,
3
C
2
˚
˚
two thf molecules are apical and two NCN methine carbons and
one thf oxygen are equatorial. This contrasts with the square
pyramidal arrangement in 4 (Fig. 3(b)) suggesting, at least for
strontium, that the replacement of the methyl of o-TolForm with
a phenyl group (giving o-PhPhForm) has a similar effect to the
2.586(3), 2.630(3) A, 6; 2.565(3), 2.565(3), 2.622(4) A). Comparing
2 and 5, with their common XylForm ligand, the average Ca–N
(2.43 A) and Sr–N (2.65 A) bond lengths, and the average Ca–O
˚
˚
˚
˚
(2.401(2) A) and Sr–O (2.60 A) bond lengths differ as expected
29
˚
(0.21 A) for ionic radius differences.
3
364 | Dalton Trans., 2006, 3360–3367
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A structural proposal for the sole barium complex, 7, is
speculative in the absence of a crystal structure. However, since the
thf to formamidinate ratio of 5 : 2 is the same as that of the struc-
formamidinate bonding with the residual coordination sphere
occupied by thf, the extent of which is dependent on metal
ionic radius. A variety of subtle steric effects are observed upon
progression from o-TolForm to o-PhPhForm or XylForm without
alteration of coordination number.
turally characterised compound [Sr(o-PhPhForm)
2
(thf)
3
]·2thf (6)
a similar structure is probable. It is noteworthy that the DippForm
(
see Introduction) complexes [M(DippForm)
2
(thf)
2
], M = Sr or
15
2+
Ba, are isostructural despite the difference in six-coordinate Sr
and Ba ionic radii (0.17 A).
Experimental
2
+
29
˚
ꢀ
ꢀ
N,N -Bis(o-methylphenyl)formamidine (o-TolFormH) and N,N -
Comparison of formamidinates
bis(2,6-dimethylphenyl)formamidine (XylFormH) were synthe-
33
sised according to a modified published procedure. The
The bite angles of the formamidinate ligands appear unaffected
ꢀ
known ligand precursor N,N -Bis(o-phenylphenyl)formamidine
by the addition of a CH
3
group in the ortho-phenyl position of
26,27
(
o-PhPhFormH)
was prepared by the same procedure as o-
o-TolForm to give Xylform (calcium compounds, 1; 56.41(6),
TolFormH and XylForm. As this represents a new synthesis of
o-PhPhFormH, details are given below. Calcium, strontium, bar-
ium, o-phenylaniline, 2,6-dimethylaniline, o-toluidine and triethyl
orthoformate were purchased from Aldrich. The alkaline earth
metals were stored under purified nitrogen and freshly filed prior to
◦
◦
5
5
6.29(6) , 2; 56.58(7) , strontium compounds, 4; 52.22(17),
◦
◦
1.65(16) , 5; 51.97(10), 51.65(11) ). Likewise, replacement of
the o-methyl of o-TolForm with a phenyl group to give o-
PhPhForm has only a marginal effect (6; 51.17(10) ). In contrast,
◦
the interplanar angles of the arene rings with respect to the
MNCN metallacycle plane are significantly affected (Table 2).
Whilst compounds 1 and 4 (with the o-TolForm ligand) show
variable twisting of tolyl rings out of the MNCN plane (1;
6,34
use. Bis(pentafluorophenyl)mercury was prepared as reported.
Tetrahydrofuran (thf) was pre-dried over sodium wire and freshly
distilled over sodium benzophenone ketyl under nitrogen. All
manipulations were performed using conventional Schlenk and
glovebox techniques under an atmosphere of purified nitrogen.
◦
◦
2
3.95(8)–57.00(7) , 4; 27.73(27)–49.06(20) ) compounds 2 and 5
(
with the XylForm ligand) exhibit consistently more substantial
−1
Infrared spectra (4000–500 cm ) of Nujol mulls were recorded
◦
twisting of the arene rings (2; 74.39(7)–80.44(8) , 5; 65.37(14)–
with a Perkin Elmer 1600 Fourier transform infrared spectrometer.
◦
6
9.46(15) ). The analogous twisting exhibited for the o-PhPhForm
1
H NMR spectra were recorded at 300.13 or 400.13 MHz, and
C{H} NMR spectra were recorded at 75.47 or 100.62 MHz using
◦
compound 6 (40.09(13)–43.60(12) ) is less variable compared to
the o-TolForm and XylForm compounds. This may be attributed
to the ordered packing of the o-phenyl rings within the structure,
which is also consistent with the low variation in biaryl C–
13
a Br u¨ ker AC 300 spectrometer or a Br u¨ ker AC 400 spectrometer,
respectively. Chemical shifts were referenced to the residual H
and C resonances of the solvent deuterobenzene or deutero-
1
13
◦
C interplanar angles (54.35(16) and 55.19(14) ). The related
toluene. All microanalyses were conducted by the Campbell
Microanalytical Laboratory, Chemistry Department, University
of Otago, Dunedin, New Zealand. Metal analyses were determined
magnesium complex trans-[Mg(p-TolForm)
2
(thf)
2
] (p-TolForm =
ꢀ
25
N,N -bis(para-tolyl)formamidinate), with no ortho substituents,
exhibits arene rings that are notably closer to coplanar with the
MNCN metallacyclic plane (4.65(17)–38.49(11) ) than those of 1,
35
according to a literature procedure following acid digestion.
◦
Melting points were determined in sealed glass capillaries under
nitrogen and are uncalibrated. The mass spectrometric analysis
of o-PhPhFormH was conducted at low resolution electro spray
ionisation (ESI) on a micromass platform spectrometer (QMS-
Quadrupole Mass electrospray). The predominate ion peak (m/z)
is reported [M] to denote the molecular ion.
2
and 4–6.
All the present calcium complexes are six-coordinate and the
strontium complexes are seven coordinate despite the contrasting
formamidinate ligands. These are one higher than the respective
DippForm complexes [M(DippForm)
2
5
(thf)
n
], where M = Ca, n =
1
1
; M = Sr, n = 2; M = Ba, n = 2, reflecting the lesser steric
demand of the current ligands. All the calcium and strontium
bis(formamidinate) compounds, including those containing the
DippForm ligand, display longer M–N bonds to the anionically
charged ligand than the corresponding M–O bonds to neutral thf.
ortho-PhPhFormH
Ten drops of acetic acid were added to a round bottom flask
charged with o-phenylaniline (10.00 g, 59.1 mmol) and triethyl or-
thoformate (4.38 g, 29.6 mmol). The clear colourless solution was
heated to reflux for 6 h and cooled to ambient temperature, where-
upon crude o-PhPhFormH precipitated. Collection of the precip-
itate by filtration followed by recrystallisation from hot methanol
gave pure ortho-PhPhFormH as a colourless powder (8.75–9.47 g,
However, [Ba(DippForm)
2
(thf) ], which is both isostructural and
2
isomorphous with the strontium analogue, displays Ba–N bond
˚
distances (ꢁ2.73 Aꢂ) that are commensurate with the Ba–O lengths
2
+
˚
(
ꢁ2.72 Aꢂ), presumably because the larger Ba relieves the steric
15
strain within the six-coordinate complex.
◦
◦
26
◦
27
8
(
1
5–92%), mp 163–165 C (lit. 156.5–157.5 C and 162 C ). IR
Nujol): m˜ 1661s, 1587m, 1488 sh w, 1461s, 1428m, 1309s, 1260m,
202m, 1112w, 1074w, 1052w, 1000w, 910w, 827w, 763m, 743m,
Conclusion
−
1
1
The redox transmetallation/ligand exchange reaction of the heavy
alkaline earth metals Ca, Sr and Ba with bis(pentafluorophenyl)-
mercury and the formamidines o-TolFormH, XylFormH and o-
PhPhFormH provides a versatile route to a variety of new alkaline
earth bis(formamidinate) complexes with limitations for barium.
726s, 694s cm ; H NMR (300.13 MHz, C
6
D , 300 K): d 7.35 (br
6
d, 4H; ArH), 7.21 (br d, 2H; ArH), 7.18–7.14 (m, 2H; ArH), 7.12
(br s, 2H; ArH), 7.09–6.95 (m, 7H; ArH + NC(H)N), 6.97 (br
1
3
1
dd, 2H; ArH), 6.58 (br s, 1H; NH); C{ H} NMR (75.47 MHz,
C
6
6
D , 300 K) d 147.3 (s, NC(H)N), 142.2 (s, Ar–C), 139.9 (s,
ꢀ
X-Ray crystallographic studies show exclusively N,N -chelating
Ar–CH), 133.5 (s, Ar–C), 130.7 (s, Ar–CH), 130.0 (s, Ar–CH),
This journal is © The Royal Society of Chemistry 2006
Dalton Trans., 2006, 3360–3367 | 3365

View Article Online
1
28.6 (s, Ar–CH), 127.2 (s, Ar–CH), 123.5 (s, Ar–CH), 119.5 (s,
123.2 (s, Ar–CH), 121.7 (s, Ar–CH), 68.3 (s, OCH
CH , thf).
2
, thf), 25.9 (s,
+
Ar–CH), 114.1 (s, Ar–C); ESMS: m/z 349 (100, [M + H] ).
2
◦
[
Sr(o-TolForm)
2
(thf)
3
] (4). (0.42 g, 70%), mp 153–156 C,
General procedure
◦
decomp. > 200 C. Calc. (%) for C42
H
54
N
4
3
O Sr: C 67.21, H 7.25,
3
N 7.46, Sr 11.67. Found: C 65.81, H 6.90, N 7.72, Sr 11.39. IR
Nujol): m˜ 1667m, 1593m, 1573w, 1314s, 1224s, 1185m, 1154m,
Tetrahydrofuran (40 cm ) was added to a Schlenk flask charged
(
with freshly filed alkaline earth metal (Ca; 0.035 g, 8.59 mmol, Sr;
.035 g, 3.99 mmol, Ba; 0.035, 2.55 mmol), o-TolFormH (0.35 g,
.60 mmol), XylFormH (0.35 g, 1.38 mmol) or o-PhPhFormH
0.35 g, 1.05 mmol) and bis(pentafluorophenyl)mercury (o-
TolFormH; 0.42 g, 0.80 mmol Hg(C , XylFormH; 0.36 g,
.69 mmol Hg(C , o-PhPhFormH; 0.28 g, 0.52 mmol
Hg(C ) under purified nitrogen. The slurry was stirred at
ambient temperature for 48 h before the light brown solution was
filtered from the deposit of elemental mercury and excess Ca,
1
110s, 1039s, 990s, 926s, 884s, 838m, 796w, 778m, 755s, 722s,
0
1
(
−
1
1
698m, 666mw cm ; H NMR (400.13 MHz, C
6
D
6
, 300 K): d
8
.80 (s, 2H; NC(H)N), 7.16–6.90 (m, 16H; ArH), 3.46 (m, 12H;
1
3
1
OCH
2
, thf), 2.26 (s, 12H; CH
, 300 K): d 162.5 (s, CN(H)N), 151.3 (s,
Ar–C), 130.2 (s, Ar–CH), 129.3 (s, Ar–C), 126.9 (s, Ar–CH), 120.8
3
), 1.19 (m, 12H; CH
2
, thf); C{ H}
6
F
)
5 2
NMR (100.13 MHz, C
6
D
6
0
6
F
)
5 2
6
F
)
5 2
(
s, Ar–CH), 117.9 (s, Ar–CH), 67.9 (s, OCH
2
, thf), 25.0 (s, CH
2
,
thf), 18.9 (s, CH ).
3
3
Sr or Ba metal. The solution was concentrated (to ca. 4 cm )
[
Sr(XylForm)
2
(thf)
3
]·3thf (5). (0.31 g, 56% [Sr(XylForm)
2
-
and, after standing at ambient temperature for several hours,
yielded colourless rectangular crystals (1, 2 and 4–6) or a colourless
powder (3 and 7).
◦
◦
(
C
thf)
3
]), mp 155–158 C, decomp. 200 C. Calc. (%) for
Sr: Sr 10.86. Found: Sr 11.07. IR (Nujol): m˜ 1651m,
46
H
62
N
4
O
3
1
597m, 1538s, 1298s, 1201s, 1074s, 1043s, 982m, 914s, 823w, 759s,
−
1
1
◦
732w, 667m, 598w, 500w cm ; H NMR (300.13 MHz, C
6
D
6
,:
[
Ca(TolForm)
2
(thf)
2
] (1). (0.31 g, 61%), mp 166–170 C, de-
comp. > 200 C. Calc. (%) for CaC38
.88, Ca 6.35. Found: C 71.02, H 7.05, N 8.99 Ca 6.77. IR (Nujol): m˜
668m, 1588m, 1304s, 1227s, 1183m, 1107m, 1034m, 987m, 953m,
◦
300 K) d 7.72 (br s, 2H; NC(H)N), 6.99 (d, 8H; ArH, J 7.5 Hz),
H
46
N
4
O : C 72.34, H 7.35, N
2
6
.90 (t, 4H; ArH, J 7.5 Hz), 3.45 (br s, 12H; OCH
2
, thf), 2.21 (s,
, thf); C{ H} NMR (75.47 MHz,
, 300 K) d 179.6 (s, NC(H)N), 154.7 (s, Ar–C), 133.9 (s, Ar–
C), 129.3 (s, Ar–CH), 128.7 (s, Ar–CH), 68.4 (s, OCH , thf), 25.1
8
1
8
1
3
1
2
4H; CH
3
), 1.24 (br s, 12H; CH
2
−
1
1
C
6
D
6
83m, 838w, 776m, 752s, 721m, 700m, 671w, 611w cm ; H NMR
, 300 K): d 8.39 (s, 2H; NC(H)N), 7.13–6.67
m, 16H; ArH), 3.52 (m, 8H; OCH , thf), 2.21 (s, 12H; CH ), 1.23
, thf); C{ H} NMR (75.47 MHz, C , 300 K) d
62.1 (s, NC(H)N), 151.8 (s, Ar–C), 130.3 (s, Ar–CH), 129.4 (s,
Ar–C), 125.9 (s, Ar–CH), 120.7 (s, Ar–CH), 117.4 (s, Ar–CH),
7.3 (s, OCH , thf), 24.2 (s, CH , thf), 17.4 (s, CH ).
2
(
(
(
300.13 MHz, C
6
D
6
(
s, CH
2
, thf), 20.2 (s, CH ).
3
2
3
1
3
1
m 8H; CH
2
6
D
6
[
Sr(o-PhPhForm)
2
(thf)
3
]·2thf (6). (0.33 g, 56%), mp 135–
Sr: C 73.56,
1
◦
◦
1
40 C, decomp. >300 C. Calc. (%) for C70
H
78
N
4
O
5
H 6.88, N 4.90. Found: C 73.46, H 7.34, N 5.01. IR (Nujol): m˜
6
2
2
3
1
1
6
662s, 1597m, 1567w, 1520s, 1310s, 1261m, 1202m, 1155w, 1108w,
071s, 1039m, 1008w, 936w, 912w, 883m, 778m, 761m, 744s, 700s,
◦
[
Ca(XylForm)
2
(thf)
decomp. 170 C. Calc. (%) for CaC42
N 8.16, Ca 5.83. Found: C 72.59, H 8.07, N 8.35, Ca 6.20. IR
Nujol): m˜ 1651m, 1595m, 1531m, 1294s, 1200s, 1160m, 1090s,
2
] (2). (0.34 g, 72%), mp 156–158 C,
−
1 1
69w cm ; H NMR (400.13 MHz, C
6
D
6
, 300 K): d 9.14 (br s, 2H;
, thf),
, 300
K) d 161.0 (s, NC(H)N), 149.3 (s, Ar–C), 144.4 (s, Ar–C), 134.3
s, Ar–C), 130.7 (s, Ar–CH), 129.6 (s, Ar–CH), 129.1 (s, Ar–CH),
28.7 (s, Ar–CH), 127.4 (s, Ar–CH), 120.8 (s, Ar–CH), 116.2 (s,
Ar–CH), 67.8 (s, OCH , thf), 25.7 (s, CH , thf).
◦
H
54
N
4
O
2
: C 73.43, H 7.92,
NC(H)N), 7.36–6.85 (m, 36H; ArH), 3.62 (m, 12H; OCH
1
2
1
3
1
.47 (m, 12H; CH
2
, thf); C{ H} NMR (100.62 MHz, C
6
D
6
(
1
6
033s, 995m, 955m, 931m, 917 shw, 878s, 765s, 732w, 698m,
71w cm ; H NMR (300.13 MHz, C
H; NC(H)N), 7.09–6.71 (m, 12H; ArH), 3.53 (m, 8H; OCH ,
), 1.31 (m, 8H; CH
, 300 K) d 174.7 (s, NC(H)N), 154.2 (s,
Ar–C), 127.6 (s, Ar–C), 127.4 (s, Ar–CH), 127.1 (s, Ar–CH),
(
1
−
1
1
6
6
D , 300 K): d 7.75 (br s,
2
2
1
3
1
2
2
thf), 2.19 (s, 24H; CH
3
2
, thf); C{ H} NMR
◦
(75.47 MHz, C
6
D
6
[Ba(o-PhPhForm) (thf) ]·2thf (7). (0.35 g, 56%), mp 76–80 C,
◦
70 78 4 5
2
3
decomp. >300 C. Calc. (%) for BaC H N O : C 70.49, H 6.59, N
1
6
6.8 (s, OCH
300.13 MHz, C
H; ArH, J 7.5 Hz), 6.85 (t, 4H; ArH, J 7.5 Hz), 3.57 (m, 8H;
2
, thf), 24.3 (s, CH
2
, thf), 17.1 (s, CH
3
); H NMR
4.70. Found: C 70.21, H 6.48, N 4.79. IR (Nujol): m˜ 1662s, 1596m,
(
7
D
8
, 300 K): d 7.79 (br s, 2H; NC(H)N), 6.95 (d,
1565m, 1526s, 1306s, 1262w, 1208m, 1156w, 1112w, 1071m, 1047m,
−
1 1
8
1009w, 929w, 883m, 826w, 765m, 758m, 743s, 703s cm ; H NMR
1
3
1
OCH
NMR (75.47 MHz, C
Ar–C), 133.7 (s, Ar–C), 127.6 (s, Ar–CH), 127.1 (s, Ar–CH), 68.5
2
, thf), 2.14 (s, 24H; CH
3
), 1.37 (m, 8H; CH
2
, thf); C{ H}
(400.13 MHz, C D , 300 K): d 9.26 (br s, 2H; NC(H)N), 7.31–6.72
6
6
7
D
8
, 300 K) d 174.7 (s, NC(H)N), 152.5 (s,
(m, 36H; ArH), 3.57 (m, 20H; OCH , thf), 1.41 (m, 20H; CH , thf);
2
2
1
3
1
C{ H} NMR (100.62 MHz, C D , 300 K) d 159.8 (s, NC(H)N),
6
6
(
s, OCH
2
, thf), 25.8 (s, CH
2
, thf), 20.0 (s, CH
3
).
151.0 (s, Ar–C), 145.3 (s, Ar–C), 134.6 (s, Ar–C), 130.7 (s, Ar–CH),
1
1
30.0 (br s, 2 Ar–CH), 129.7 (br s, 2 Ar–CH), 120.7 (s, Ar–CH),
15.7 (s, Ar–CH), 68.1 (s, OCH , thf), 26.1 (s, CH , thf).
[
Ca(o-PhPhForm)
2
(thf)
2
]·thf (3). (0.30 g, 61%), mp 160–
: C 78.28,
2
2
◦
◦
1
64 C, decomp. 200 C. Calc. (%) for CaC62
H
62
N
4
O
3
H 6.57, N 5.89. Found: C 78.59, H 6.67, N 5.95. IR (Nujol): m˜
X-Ray structure determinations
1
663m, 1594w, 1522m, 1316s, 1210w, 1072w, 1034w, 934w, 882m,
−
1
1
764m, 742m, 696m cm ; H NMR (400.13 MHz, C
6
D
6
, 300
Crystalline samples of compounds 1, 2 and 4–6 were mounted on
◦
K): d 8.65 (br s, 2H; NC(H)N), 7.17–6.74 (m, 36H; ArH), 3.35
glass fibres in silicone oil at −150(2) C (123 (2) K). A summary of
1
3
1
(
(
1
br s, 12H; OCH
100.62 MHz, C
44.0 (s, Ar–C), 134.6 (s, Ar–C), 131.5 (s, Ar–CH), 129.7 (s,
Ar–CH), 129.5 (s, Ar–CH), 129.0 (s, Ar–CH), 126.9 (s, Ar–CH),
2
, thf), 1.26 (br s, 12H; CH
2
, thf); C{ H} NMR
crystallographic data can be found in Table 1. Data were collected
on an Enraf-Nonius Kappa CCD diffractometer using graphite-
6
D
6
, 300 K) d 171.0 (s, NC(H)N), 150.9 (s, Ar–C),
˚
monochromated Mo-Ka X-ray radiation (k = 0.71073 A). Data
36
were corrected for absorption by the DENZO-SMN package.
3
366 | Dalton Trans., 2006, 3360–3367
This journal is © The Royal Society of Chemistry 2006

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Lorentz polarization and absorption corrections were applied.
Structural solution and refinement was carried out using the
SHELX suite of programs with the graphical interface X-seed.
12 G. B. Deacon and C. M. Forsyth, Chem. Eur. J., 2004, 10, 1798.
1
1
3 G. B. Deacon and C. M. Forsyth, Organometallics, 2003, 22, 1349.
4 J. Hitzbleck, A. Y. O’Brien, C. M. Forsyth, G. B. Deacon and K.
Ruhlandt-Senge, Chem. Eur. J., 2004, 10, 3315.
37
38
1
1
5 M. L. Cole and P. C. Junk, New J. Chem., 2005, 29, 135.
6 S.-O. Hauber, F. Lissner, G. B. Deacon and M. Niemeyer, Angew.
Chem., Int. Ed., 2005, 117, 6021; S.-O. Hauber, F. Lissner, G. B. Deacon
and M. Niemeyer, Angew. Chem., Int. Ed., 2005, 44, 5871.
Variata
For compound 1, modelling of disorder for one thf methylene
carbon (C(32)) was attempted but failed to give satisfactory
thermal parameters.
1
7 (a) M. L. Cole, P. C. Junk and L. M. Louis, J. Chem. Soc., Dalton Trans.,
2
002, 3906; (b) J. Baldamus, C. Berghof, M. L. Cole, D. J. Evans, E.
Hey-Hawkins and P. C. Junk, Eur. J. Inorg. Chem., 2002, 2878; (c) J.
Baldamus, C. Berghof, M. L. Cole, D. J. Evans, E. Hey-Hawkins and
P. C. Junk, J. Chem. Soc., Dalton Trans., 2002, 4185; (d) J. Baldamus,
C. Berghof, M. L. Cole, D. J. Evans, E. Hey-Hawkins and P. C. Junk,
J. Chem. Soc., Dalton Trans., 2002, 2802; (e) M. L. Cole, D. J. Evans,
P. C. Junk and M. K. Smith, Chem. Eur. J., 2003, 9, 415; (f) M. L. Cole
and P. C. Junk, J. Organomet. Chem., 2003, 666, 55; (g) M. L. Cole,
A. J. Davies, C. Jones and P. C. Junk, J. Organomet. Chem., 2004, 689,
For compound 4, inversion of the structure gave a Flack
39
parameter of 0.943(15) suggesting the absolute configuration is
that chosen (Flack parameter −0.004(9)).
For compound 5, modelling of disorder for several thf methylene
carbons (C(41), C(44), C(47), C(48) and C(49)) was attempted but
only gave acceptable thermal parameters for C(44). The disorder
of this atom was modelled over two sites of partial occupancy (62 :
3
093.
18 (a) For reviews, see: T. Ren, Coord. Chem. Rev., 1998, 175, 43; (b) J.
Barker and M. Kilner, Coord. Rev., 1994, 133, 219.
3
8%) and the remaining atoms were left as is.
1
9 (a) J. L. Eglin, C. Lin, T. Ren, L. Smith, R. J. Staples and D. O. Wipf,
Eur. J. Inorg. Chem., 1999, 2095; (b) F. A. Cotton, L. M. Daniels, C. A.
Murillo and P. Schooler, J. Chem. Soc., Dalton Trans., 2000, 2001.
For compound 6, the thf of solvation was found to reside over
two partially coincident sites. These were modelled with partial
occupancies of 60 : 40% (C(33) and O(3) : C(37) and C(39)).
CCDC reference numbers 298094–298098.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b602210c
20 F. A. Cotton, L. M. Daniels and C. A. Murillo, Inorg. Chem., 1993, 32,
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987, 2687.
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3 M. G. B. Drew and J. D. Wilkins, J. Chem. Soc., Dalton Trans., 1974,
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This journal is © The Royal Society of Chemistry 2006
Dalton Trans., 2006, 3360–3367 | 3367