Crystalline metal (Li, Mg, Ca, Sr, Ba, Sn, Pb) complexes of the new chelating N,N′-dianionic [1,2-N(R)C6H4(CH 2NR)]2- ligand (R = SiMe3, CH 2But)

Article abstract of DOI:10.1039/c1dt10574d

2-Aminomethylaniline was converted into the N,N′-bis(pivaloyl) (1) or -bis(trimethylsilyl) (2) derivative, using 2 Bu^tC(O)Cl or 2 Me ₃SiCl ( RCl), respectively, with 2 NEt₃, or for 2 from successively using 2 LiBuⁿ

Full text of DOI:10.1039/c1dt10574d

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PAPER
Crystalline metal (Li, Mg, Ca, Sr, Ba, Sn, Pb) complexes of the new chelating
N,N¢-dianionic [1,2-N(R)C6H4(CH2NR)]2- ligand (R = SiMe3, CH2But)†‡
Catherine F. Caro, Martyn P. Coles, Peter B. Hitchcock, Michael F. Lappert* and Luc J.-M. Pierssens
Received 4th April 2011, Accepted 15th June 2011
DOI: 10.1039/c1dt10574d
2-Aminomethylaniline was converted into the N,N¢-bis(pivaloyl) (1) or -bis(trimethylsilyl) (2) derivative,
using 2 ButC(O)Cl or 2 Me3SiCl ( RCl), respectively, with 2 NEt3, or for 2 from successively using 2
LiBun and 2 RCl. N,N¢-Bis(neopentyl)-2-(aminomethyl)aniline (3) was prepared by LiAlH4 reduction
of 1. From 2 or 3 and 2 LiBun, the appropriate dilitiodiamide {2-[{N(Li)R}C6H4{CH2N(Li)R}(L)]2 (L
absent, 4a; or L = THF, 4b) or the N,N¢-bis(neopentyl) analogue (5) of 4a was prepared. Treatment of
4a with 2 ButNC, 2 (2,6-Me2C6H3NC) or 2 ButCN ( L¢) furnished the corresponding adduct
[2-N{Li(L¢)R}C6H4{CH2N(Li)R}] (4c, 4d or 4e, respectively), whereas 4b with 2 PhCN afforded
[2-{N(Li)R}C6H4{CH2C(Ph) = NLi(NCPh)}] (6). The dimeric bis(amido)stannylene
[Sn{N(R)C6H4(CH2NR)-1,2}]2 (7) was obtained from 4a and [Sn(m-Cl)NR2]2, while the
N,N¢-bis(neopentyl) analogue 8 of 7 was similarly derived from [Sn(m-Cl)NR2]2 and 5. Reaction of two
equivalents of the diamine 2 with Pb(NR2)2 yielded 9, the lead homologue of 7. Oxidative addition of
sulfur to 7 led to the dimeric bis(diamido)tin sulfide 10. Treatment of 2 successively with ‘MgBu2’ in
C5H12 and THF gave [Mg{N(R)C6H4(CH2NR)}(THF)]2 (11a), which by displacement of its THF by an
equivalent portion of ButCN or PhCN produced [Mg{N(R)C6H4(CH2NR)}(CNR’)n] [R¢ = But, n = 1
(11b); R¢ = Ph, n = 2 (11c)]. The Ca (12), Sr (13) or Ba (14) analogues of the Mg compound 11a were
isolated from 2 and either the appropriate compound M(NR2)2 (M = Ca, Sr, Ba), or successively 2
LiBun and 2 M(OTos)2. The new compounds 1–14 were characterized by microanalysis (C, H, N; not
for 1, 2, 3, 5), solution NMR spectra, nmax (C N) (IR for 4c, 4d, 4e, 6, 11b, 11c), selected EI-MS peaks
(for 1, 2, 3, 7, 8, 9, 10), and single crystal X-ray diffraction (for 4a, 4b, 11a).
C6H4{N(H)R}-1,2 (R = SiMe3).4 The dianionic ligand of A, or the
Introduction
N,N¢-bis(neopentyl) [C6H4(NR¢)2; R¢ = CH2But] analogue, has
Amides [N(R¢)(R¢¢)]- (R¢ and R¢¢ are the same or different and
each is an alkyl, aryl or silyl group) represent possibly the most
ubiquitous of all ligands and are found in compounds of all
the elements except the lighter rare gases.1 They may be bound
to a metal of metalloid in a terminal or bridging (double or
single) fashion. This paper continues our long held involvement
in metal and metalloid amide chemistry. Simple N,N¢-dianionic
chelating ligands have been found inter alia in carbenes2 and
silylenes.3 More directly relevant to the present paper are the
1,3-, 1,4- and particularly 1,2-benzene(diamido) ligands. The first
example of the latter appears to have been in the pentacyclic
featured in complexes of Li,5 Si,6 Ca,7 Al,8 Zn,7 Ga,9 Ge,10 Y, 5 Zr,5
Mo,11 Sn,12 Hf,13 Ta,13 W, 10 and Pb.12 The references 2 to 13 are
of relatively recent date and are intended to be illustrative rather
than comprehensive.
Results and discussion
The objective of this research was to begin to explore the synthesis
and structures of metal complexes of the new N,N¢-dianionic
ligands [1,2-N(R or R¢)C6H4{CH2N(R or R¢)}]2- (R = SiMe3, R¢ =
CH2But). A new feature of such a chelating bis(amido) ligand is its
asymmetry, one N-centre being aromatic and the other aliphatic.
This distinction is of particular significance in a bi- or oligo-
nuclear [bis(amido)metal]n complex in determining the preferred
bridge(s).
dimeric magnesium complex Mg[N(R)C6H4N(R)-1,2] (
obtained from the hydrocarbon-soluble dibutylmagnesium and
A),
Department of Chemistry, University of Sussex, Falmer, Brighton, UK.
E-mail: m.f.lappert@sussex.ac.uk; Fax: +44 1273876687; Tel: +44 1273
678316
† CCDC reference numbers 819594–819596. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt10574d
Synthesis and structures of the dilithiodiamides 4a, 4b and 5
2-Aminobenzylamine with pivaloyl or trimethylsilyl chloride in the
presence of triethylamine was N,N¢-bis(acylated) or -bis(silylated)
‡ This paper is dedicated to our friend and esteemed colleague Professor
H. Schno¨ckel
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yielding compounds 1 or 2, respectively. The latter was also pre-
pared from the diamine by successive dilithiation and quenching
with 2 Me3SiCl. The N,N¢-bis(neopentyl)diamine 3 was obtained
by reduction of 1. Compounds 2 and 3 were each N,N¢-dilithiated,
furnishing the crystalline dimer 4a (or its THF–adduct 4b) and 5.
The routes to 4a, 4b and 5 are summarized in Scheme 1.
Fig. 1 (a) Molecular structure of crystalline 4a (30% thermal ellipsoids,
hydrogens except [{N(Li)SiMe3}C6H4{CH2N(Li)SiMe3}] omitted). (b)
Schematic representation of the core structure of 4a.
71.0 0.9◦ than the two at the periphery N1 and N3 at 74.8 0.2◦.
The endocyclic angles at the lithium atoms range from the 104.4
0.2◦ at Li1 and Li3 in the outer rhombi to the 110.45 0.05◦
in their corresponding inner rhombi. The dihedral angle between
the Li1N2Li3N4 rhombus and its Li1N1Li2N4 and Li3N2Li4N3
counterparts is 63.6(2)◦ and 63.7(2)◦, respectively. Each of the five-
coordinate alkyl nitrogen atoms N2 and N4 has short contacts
Scheme 1 Synthesis of the dilithiodiamides 4a, 4b and 5 (R = SiMe3, R¢ =
CH2But).
Each of the crystalline compounds 1, 4a, 4b and 5, or the
distillable liquids 2 and 3, were isolated in good yield and
characterized by 1H NMR spectroscopy, and for 4a and 4b by C,
1
1
H and N microanalysis. The 13C{ H} and 7Li{ H} NMR spectra
were recorded for 4a, 4b and 5 and the 29Si{ H} spectra for 4a
to three lithium atoms (at av. 2.05 A), as well as bonds to its
1
˚
3
and 4b. Selected EI-mass spectral peaks are listed for 1, 2 and 3.
The molecular structures of the dilithium diamides 4a and 4b were
firmly established from single crystal X-ray diffraction.
attached Csp and Si atoms. Each of the four-coordinate aryl
nitrogen atoms N1 and N3 bridges two lithium atoms at distances
2
˚
of 1.945 and 2.035 0.006 A, and binds to its adjacent Csp and
The 1H NMR spectrum of 4a in C7D8 at 298 K was com-
pletely assigned by NOE experiments. The CH2 protons were
inequivalent, with doublets at d 3.72 and 3.97 ppm; their relative
proportions were invariant of concentration or temperature, ruling
out an equilibrium. The major isomer was found to exchange with
the minor, by saturation transfer experiments.
Si atoms. Each of the four lithium atoms is in a three-coordinate
environment; in the case of the peripheral Li atoms, Li2 and Li4,
˚
this is by virtue of having short contacts of 2.33 0.03 A to the
C19 and C6 atoms, respectively. These values may be compared
˚
with the Li ◊ ◊ ◊ C contacts of ca. 2.69, 2.34 or 2.27 A found in Li{m-
N(CH2Ph)}3,14 [{Li(NBut)}2SiMe2]2,15 or [Li2{NR)2C6H4-1,2}]2,16
respectively. Selected geometric parameters for 4a are listed in
Table 1.
The 1H NMR spectrum of 4b in C7D8 at 298 K showed a broad
peak at d 4.18 ppm, assigned to the CH2 protons, which did not
◦
1
split upon cooling to -78 C. Likewise the 7Li{ H} NMR spectral
An ORTEP representation of the molecular structure of the
crystalline 4b is shown in Fig. 2. It is closely similar to that
of 4a, except that the peripheral lithium atoms Li3 and Li4 are
attached to O1 and O2, respectively (rather than the C19 and C6
near to Li2 and Li4, respectively in 4a). The central rhombus of
4b, Li1N2Li2N4, is fused to the Li1N1Li3N4 and Li2N2Li4N3
rings. The endocyclic angles centred at the nitrogen atoms range
signal at d 1.5 ppm at 298 K was unchanged at -78 ◦C.
The molecular structure of the crystalline compound 4a is
illustrated as an ORTEP diagram in Fig. 1a. Its core is a ladder
like arrangement of three (LiN)2 rhombi; a central Li1N2Li3N4
is flanked by Li1N1Li2N4 and Li3N2Li4N3, as shown in Fig. 1b.
Four of the endocyclic angles at the nitrogen atoms are narrower at
9822 | Dalton Trans., 2011, 40, 9821–9830
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◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for 4a
Li1–N1
Li1–N2
Li1–N4
Li2–N1
Li2–N4
Li2 ◊ ◊ ◊ C19
N1–C1
N2–C7
N3–C14
N4–C20
C6–C7
2.030(6)
2.015(6)
2.075(6)
1.945(6)
2.040(6)
2.314(7)
1.405(4)
1.491(4)
1.414(4)
1.501(4)
1.504(5)
1.423(4)
Li3–N2
Li3–N3
Li3–N4
Li4–N3
Li4–N2
Li4 ◊ ◊ ◊ C6
N1–Si1
N2–Si2
N3–Si3
N4–Si4
C19–C20
C14–C19
2.083(6)
2.026(6)
2.050(6)
1.943(6)
2.041(6)
2.353(7)
1.702(3)
1.711(3)
1.709(3)
1.716(3)
1.504(5)
1.420(5)
C1–C6
N1–Li1–N2
N1–Li1–N4
N2–Li1–N4
N1–Li2–N4
N1–Li2–C19
N4–Li2–C19
Li1–N1–Li2
Li1–N1–C1
Li2–N1–C1
Li1–N1–Si1
Li2–N1–Si1
C1–N1–Si1
Li1–N2–Li3
Li1–N2–Li4
Li3–N2–Li4
Li1–N2–C7
Li3–N2–C7
Li4–N2–C7
Li1–N2–Si2
Li3–N2–Si2
Li4–N2–Si2
C7–N2–Si2
N1–C1–C6
N1–C1–C2
C1–C6–C7
N2–C7–C6
109.0(3)
104.6(3)
110.5(3)
109.2(3)
137.0(3)
68.6(2)
N2–Li3–N3
N2–Li3–N4
N3–Li3–N4
N3–Li4–N2
N3–Li4–C6
N2–Li4–C6
Li3–N3–Li4
Li3–N3–C14
Li4–N3–C14
Li3–N3–Si3
Li4–N3–Si3
C14–N3–Si3
Li1–N4–Li2
Li2–N4–Li3
Li1–N4–Li3
Li3–N4–C20
Li1–N4–C20
Li2–N4–C20
Li1–N4–Si4
Li2–N4–Si4
Li3–N4–Si4
C20–N4–Si4
N3–C14–C15
N3–C14–C19
C14–C19–C20
N4–C20–C19
104.2(3)
108.8(3)
110.4(3)
108.9(3)
140.8(3)
68.1(2)
74.6(2)
75.0(2)
109.2(2)
112.6(3)
117.8(2)
112.7(2)
121.0(2)
70.6(2)
106.4(3)
71.8(2)
88.3(2)
148.1(3)
92.7(2)
123.9(2)
97.9(2)
122.1(2)
113.8(2)
121.4(3)
122.4(3)
120.4(3)
111.5(3)
107.6(2)
108.1(3)
118.1(2)
121.0(2)
118.8(2)
71.7(2)
106.4(2)
70.1(2)
86.6(2)
Fig. 2 Molecular structure of crystalline 4b (30% thermal ellipsoids,
hydrogens except [{N(Li)SiMe3}C6H4{CH2N(Li)SiMe3}] omitted).
Reactions of the dilithiodiamide 4a or 4b with a nitrile or an
isonitrile
The outcome of the four reactions between the dilithiodiamide 4a
or 4b and two equivalents of a nitrile or an isonitrile is summarized
in Scheme 2. Thus, simple ligand addition from 4a (or ligand
substitution from 4b) led to the isolation in high yield of the
crystalline compounds 4c, 4d and 4e. However, from 4b and two
equivalents of benzonitrile, the product 6 was the 1 : 1-benzonitrile
adduct of the dilithium salt of a 2-ureidomethylanilide; evidently
one of the PhCN reactants had inserted into the CH2N(R)-Li
bond, while the other was found ligated to that lithium cation.
145.5(3)
92.1(2)
101.6(2)
123.0(2)
124.6(2)
112.7(2)
121.4(3)
121.5(3)
121.0(3)
110.2(3)
Dihedral Angles
Li1–N2–Li3–N4 and Li1–N1–Li2–N4
Li1–N2–Li3–N4 and Li3–N2–Li4–N3
N1–Li1–N2 and N1–Li1–N4
N3–Li3–N4 and N3–Li3–N2
N1–Li1–N2 and N2–Li1–N4
63.6(2)
63.7(2)
61.8(2)
66.3(3)
65.6(3)
66.3(3)
N3–Li3–N4 and N2–Li3–N4
from 68.7 0.1◦ at N2 and N4 of Li1N2Li2N4, through 72.2
0.3◦ at these atoms in the adjacent rhombi, to 76.0 0.2◦ at
N1 and N3. The endocyclic angles at the lithium atoms range
from 103.5 0.6◦ at Li3 and Li4 (the peripheral atoms), through
108.3 0.6◦ at Li1 and Li2 (the outer rhombi), to 111.4 0.6◦
in Li1N2Li2N4. The dihedral angle between the Li1N2Li2N4
plane and the Li1N1Li3N4 or Li2N2Li4N3 is 50.8(2)◦ or 51.9(3)◦,
respectively. Each of the five-coordinate alkyl nitrogen atoms N2
˚
and N4 has Li ◊ ◊ ◊ N contacts of an av. 2.06 0.01 A (ranging from
3
˚
2.030 to 2.118 A), as well as bonds to the attached Csp and Si
atoms. Each of the four-coordinate aryl nitrogen atoms N1 and
N3 is a bridge between two Li atoms at distances of 1.957 0.007
Scheme
2
Reactions of 4a/4b with ButNC, ButCN, PhCN or
2,6-Me2C6H3NC (R = SiMe3).
˚
and 2.017 0.015 A. Each of the central lithium atoms, Li1 and
Li2, has only three nitrogen atoms as near neighbours, whereas
each of the peripheral equally three-coordinate lithium atoms Li3
and Li4 is also joined to an oxygen atom of tetrahydrofuran.
Selected geometric parameters for 4b are listed in Table 2.
Each of the yellow compounds 4c, 4d, 4e and 6 was characterized
by C, H and N microanalysis, NMR spectra in C6D6 [1H and
1
1
1
13C{ H} for each; 7Li{ H} for 4d and 6; 29Si{ H} for 4e and 6] and
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◦
midinate [Li{N(R)C(Ph)NR}];18 for other examples of dimeric
crystalline N-trimethylsilylated lithium benzamidinates, see ref. 19
The compound [Li(m-NR2)(CNPh)]2 shows an isonitrile behaving
as a ligand (cf. 4c, 4d), rather than inserting into an Li–NR2 bond.20
˚
Table 2 Selected bond lengths (A) and angles ( ) for 4b
Li1–N1
Li1–N2
Li1–N4
Li3–N1
Li3–N4
N1–C1
N2–C7
Li3–O1
N1–Si1
N2–Si2
C6–C7
1.963(7)
2.032(8)
2.030(8)
2.032(8)
2.118(7)
1.409(5)
1.492(5)
1.979(8)
1.698(3)
1.711(3)
1.506(5)
Li2–N2
Li2–N3
Li2–N4
Li4–N2
Li4–N3
N3–C14
N4–C20
Li4–O2
N3–Si3
N4–Si4
C19–C20
2.051(8)
1.950(8)
2.041(8)
2.096(8)
2.002(8)
1.423(5)
1.492(5)
1.973(8)
1.707(3)
1.704(3)
1.510(5)
Synthesis of the tin(II) (7, 8), tin(IV) (10) and lead(II) (9) compounds
The dimeric crystalline pentacyclic 1,2-bis(phenylenediamido)-
stannylenes 7 and 8 were obtained from the interaction of equiv-
alent portions of the dinuclear amido(m-chloro)stannane and the
appropriate dilithiodiamide 4a and 5, respectively. The crystalline
lead analogue 9 of 7 was prepared by the amine elimination reac-
tion between the diamine 2 and bis[bis(trimethylsilyl)amido]lead.
Treatment of 7 with two equivalents of sulfur in toluene afforded
the crystalline dimeric trans-bis(phenylenediamido)tin(IV) sulfide
10. These syntheses are summarized in Scheme 3. The new
colourless complexes 7–10 were isolated as crystals in excellent
(10) or satisfactory yields. The pathway from 7→10 is presumed
to implicate successive dissociation of 7, oxidation of the monomer
furnishing Sn(S)[N(R)C6H4(CH2NR)] (7¢) and dimerisation of the
latter.
N1–Li1–N2
N1–Li1–N4
N2–Li1–N4
N1–Li3–N4
N1–Li3–O1
N4–Li3–O1
Li1–N1–Li3
Li1–N1–C1
Li3–N1–C1
Li1–N1–Si1
Li3–N1–Si1
C1–N1–Si1
Li1–N2–Li2
Li1–N2–Li4
Li2–N2–Li4
Li2–N2–C7
Li4–N2–C7
Li1–N2–C7
Li1–N2–Si2
Li2–N2–Si2
Li4–N2–Si2
C7–N2–Si2
C1–N1–Si1
N1–C1–C6
C1–C6–C7
C5–C6–C7
N2–C7–C6
115.0(4)
108.8(3)
112.0(3)
102.9(3)
121.9(4)
130.0(4)
75.8(3)
104.8(3)
110.5(3)
120.6(3)
116.9(3)
119.9(3)
68.6(3)
N2–Li2–N3
N2–Li2–N4
N3–Li2–N4
N2–Li4–N3
N2–Li4–O2
N3–Li4–O2
Li2–N3–Li4
Li2–N3–C14
Li4–N3–C14
Li2–N3–Si3
Li4–N3–Si3
C14–N3–Si3
Li1–N4–Li2
Li2–N4–Li3
Li1–N4–Li3
Li1–N4–C20
Li3–N4–C20
Li2–N4–C20
Li2–N4–Si4
Li1–N4–Si4
Li3–N4–Si4
C20–N4–Si4
N3–C14–C15
N3–C14–C19
C14–C19–C20
C18–C19–C20
N4–C20–C19
107.7(4)
110.8(3)
114.4(4)
104.1(3)
129.5(4)
122.3(4)
76.1(3)
106.1(3)
112.8(3)
121.4(3)
115.1(3)
118.2(3)
68.8(3)
116.4(3)
71.9(3)
144.8(3)
95.5(3)
117.2(3)
72.4(3)
145.2(3)
96.2(3)
89.9(3)
89.3(3)
117.3(3)
100.5(3)
117.4(3)
114.2(3)
120.9(4)
122.8(3)
121.9(4)
118.5(4)
113.7(6)
119.9(3)
100.6(3)
114.3(3)
113.8(3)
121.4(4)
121.7(4)
122.5(4)
118.6(4)
113.3(3)
Dihedral Angles
Li1–N2–Li2–N4 and
Li1–N1–Li3–N4
Li1–N2–Li2–N4 and
Li2–N2–Li4–N3
50.8(2)
51.9(3)
N1–Li1–N2 and N1–Li1–N4
N3–Li2–N4 and N3–Li2–N2
N1–Li1–N2 and N2–Li1–N4
N3–Li2–N4 and N2–Li2–N4
53.5(4)
56.4(3)
55.2(4)
58.1(4)
IR n(N C) stretching frequencies. These data firmly establish the
structures of 4c, 4d and 4e. The formulation is not so definitive
for 6. The spectral data for the latter showed that one of the
two benzonitriles had behaved as a ligand (thus displacing THF
from 4b), whereas the other had been inserted into an RN–Li
bond. More detailed NMR spectral studies of 6 (NOE, saturation
transfer and 2D experiments) did not unambiguously establish the
site of insertion; the assignment shown for 6 in Scheme 2 is based
on the notion that PhCN would preferentially insert into the more
basic amido groups: thus implicating the CH2N–Li rather than
the ArN–Li bond.
The formation of a ButCN, ArNC or a ButNC adduct of
the dilithium diamide 4c, 4d or 4e, respectively, is attributed
to steric constraints to the alternative of insertion of the ni-
trile or isonitrile into one of its Li–N bonds. In support, it
is noted that treatment of LiNR2 with ButCN yielded [Li(m-
NR2)(NCBut)]2,17 while with PhCN the product was the benza-
Scheme 3 Synthesis of the crystalline dimeric bis(amido)-group 14
metallenes 7, 8 and 9 and the cyclodi[tin(IV)sulfide] 10 (R = SiMe3, R¢ =
CH2But).
Each of the compounds 7 to 10 was identified by C, H and N
microanalysis, NMR spectra in C6D6 [1H, 13C{ H}, 29Si{ H} (not
1
1
1
1
8), 119Sn{ H} (not 9) and 207Pb{ H} for 9] and EI-mass spectra
(selected highest m/z signals). The highest m/z peak in the mass
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spectrum of both 8 and 9 showed in low intensity a signal attributed
to the dimeric molecular ion. The same degree of molecular
aggregation of 7 and 9 in solution in C6D6 at 298 K is reflected in
Sr (13), Ba (14)] were prepared from the diamine 2 and the
appropriate group 2 metal reagent by an elimination reaction
[of C4H10 (11a); or of HNR2 (12, 13, 14)]. Alternatively, 12,
13 and 14 were obtained from 2 and successively 2 LiBu and
M(OTos)2. Compound 11a with 2 ButCN or 2 PhCN gave Mg[{2-
N(R)C6H4(CH2NR)}(NCR¢)n] [R¢ = But, n = 1 (11b); R¢ = Ph, n =
2 (11c)]; the 1 : 1 rather than the 1 : 2 (as for 11c) stoichiometry for
11b is noteworthy.
1
1
the values of the 119Sn{ H} (7) and 207Pb{ H} (9) chemical shifts;
cf . Wrackmeyer’s equation for isostructural Sn/Pb compounds:
1
dPb = 3.30 (dSn) + 2336.21 The H NMR spectrum of 8 in C6D6
at 298 K showed a distinctive pattern of doublets, assigned to
magnetically inequivalent CH2 protons from both the benzyl and
neopentyl moieties. A pair of doublets and triplets from the
C6H4 protons was assigned by a two-dimensional (COSY) and
a saturation transfer experiment.
Each of the compounds of Scheme 5 was characterized by C, H
1
1
and N microanalysis and 1H, 13C{ H} and 29Si{ H} NMR spectra
in C6D6 at 298 K. The CN stretching frequencies for 11b and
11c were located at a higher wave number than in the free nitrile
(ButCN at 2136 cm-1 and PhCN at 2115 cm-1). The nitrile adducts
11b and 11c dissociated upon heating above 70 ◦C; no evidence of
insertion of R¢CN into a Mg–N bond was observed.
1
A variable temperature 119Sn{ H} NMR spectroscopic study
for 8 in PhMe + C6D6 indicated reversible equilibria. At 298 K, a
single signal at d 3.0 ppm was recorded, whereas at 168 K separate
signals assigned to both 8 and 8¢ were observed (Scheme 4).
Scheme 4 Solution-state equilibria of 8 and 10.
The crystalline dimeric diamidotin(IV) sulfide 10 has the trans
configuration, but in hydrocarbon solution it exists as a mixture
of the trans-(10) and the cis-(10¢)-dimers; the more abundant is
probably the former (Scheme 4). Thus, the 1H NMR spectrum in
PhMe + C6D6 at 298 K showed two pairs of SiMe3 resonances in a
ratio of ca. 5 : 2. Correspondingly, there were four distinct signals
Scheme 5 Synthesis of the dimeric bis(amido)-group 2 metallenes 11a,
12, 13 and 14 and the conversion of 11a into the nitrile adducts 11b and
11c (R = SiMe3).
1
1
in both the 13C{ H} and 29Si{ H} NMR spectra attributed to
1
four inequivalent SiMe3 groups. The 119Sn{ H} spectrum showed
signals at d -75 (major) and -72 ppm, each with a set of satellites
due to the 2J(119Sn –117Sn) coupling of ca. 700 Hz. These data may
The molecular structure of the crystalline compound 11a, com-
prising discrete dimers lying across a crystallographic inversion
centre, is represented by the ORTEP of Fig. 3; selected bond
lengths and angles are listed in Table 3. There is a central
MgN1Mg¢N1¢ rhombus with the endocyclic angle at the metal
slightly wider than at the aliphatic nitrogen atom and the Mg–N1
1
2
be compared with the d 119Sn{ H} of -106.6 ppm with J(119Sn–
117Sn) of 609 Hz for [Sn(NR2)(m-S)]2 in C6D6 at 298 K.22 The route
from crystalline 10 to a mixture of 10 and 10¢ in solution is likely
to implicate 7¢ as an intermediate.
˚
˚
bond ca. 0.02 A shorter than the Mg¢– N1¢ (which is ca. 0.08 A
longer than the bond between Mg and the aryl nitrogen atom
N2). This rhombus is at the centre of an array of five fused rings:
the adjacent puckered MgN1C7C1C2N2 to which is attached the
aromatic ring via its C1 and C2 atoms. The endocyclic angles at
Synthesis and structures of the group 2 metal complexes 11a, 11b,
11c, 12, 13 and 14
The crystalline pentacyclic bis(1,2-phenylenediamido)metal sol-
vates [M{2-N(R)C6H4(CH2NR)}(THF)]2 [M = Mg (11a), Ca (12),
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◦
˚
Table 3 Selected bond lengths (A) and angles ( ) for 11a
The structures of the crystalline dinuclear magnesium diamides
[Mg{(NR)2C6H4-1,2}(OEt2)]2 (C),4 [Mg(m-NR2)(NR2)]2 (D)23 and
[Mg{(NPh)2CH2CH2}(THF)1.5]2 (E)24 are available for compari-
son with that of compound 11a. Like the latter, C has distorted
tetrahedrally centred Mg atoms, but in D and E the magnesium
Mg–N1
Mg–N2
Mg–N1¢
Mg–O
2.099(2)
2.035(2)
2.116(2)
2.078(2)
1.419(2)
N1–C7
N2–C2
N1–Si1
N2–Si2
C1–C7
1.150(3)
1.396(3)
1.731(2)
1.717(2)
1.510(3)
C1–C2
atoms are in a three- and five-coordinate environment, respectively.
4
˚
˚
Their Mg–N bond lengths are 1.997(7) and 2.082(7) A in C,
Mg–N1–Mg¢
N1–Mg–N1¢
N1–Mg–N2
N1¢–Mg–N2
Mg–N1–C7
Mg–N2–C2
Mg¢–N1–C7
Mg–N1–Si1
Mg¢–N1–Si1
88.61(8)
91.39(8)
N1–C7–C1
C7–C1–C2
N2–C2–C1
Mg–O–C14
Mg–O–C17
Si1–N1–C7
O–Mg–N1
O–Mg–N1¢
O–Mg–N2
117.5(2)
121.1(2)
121.2(2)
133.3(2)
118.3(2)
114.5(2)
115.36(8)
110.57(8)
102.15(8)
23
24
˚
1.975(7) and 2.145(5) A in D and 2.040(2) and 2.290(2) A in E.
The N–Mg–N¢ angles are 87.8(3) and 93.9(3)◦ in C,4 95.5(2) and
102.31(9)
134.60(9)
97.54(13)
111.85(2)
105.30(14)
121.19(11)
124.22(10)
96.1(2)◦ in D,23 and 84.22(8) and 127.58(9)◦ in E.24 The Mg–O
4
˚
˚
bond lengths are 2.041(7) A in C, and 2.083(2) and 2.167(2) A in
E.24
Conclusions
Distance from plane
O
Si
˚
˚
Metal
complexes
of
the
new
asymmetric,
N,N¢-
1.721(1) A out of Mg–N1–Mg¢–N1¢ plane
1.134(4) A out of Mg–N1–Mg¢–N1¢ plane
chelating, dianionic ligands [N(R)C6H4(CH2NR)-1,2]2- and
[N(R¢)C6H4(CH2NR¢)-1,2]2- (R = SiMe3, R¢ = CH2But) have been
prepared and characterized. The particularity of these ligands
lies in the chemically different nature of its amido groups: one
being aliphatic and the other aromatic. In the dimeric crystalline
compounds it is the former which feature as bridges in the central
MNM¢N¢ rhomboid [M = Li (4a, 4b), M = Mg (11a)].
Dihedral Angles
N2–Mg–N1 and N1–Mg–N1¢ 43.6(1)
C7–N1–Mg and Mg–N1–Mg¢ 74.8(1)
C3–C2–C1 and C1–C2–N2 0.0(5)
C1–C2–N2 and C2–N2–Mg 26.0(4)
C2–C1–C7 and C1–C7–N1 68.7(2)
Symmetry transformations used to generate equivalent atoms for 11a: ‘-x,
-y, -z
Experimental
General remarks
Syntheses were carried out under an atmosphere of argon or in a
vacuum, using Schlenk apparatus and vacuum line techniques. The
solvents used were reagent grade or better and were freshly distilled
under dry nitrogen gas and then freeze–thaw degassed prior to
use. Solvents were dried and distilled from sodium benzophenone
(PhMe, Et2O, THF) or sodium–potassium alloy (C5H12, C6H14).
The C6D6, C7D8, CDCl3 and C5D5N for NMR spectroscopy were
˚
stored over molecular sieves (4 A) under an argon atmosphere.
The NMR spectrometers were Bruker AC-P 250, WM 300 and
DPX 300. IR Spectra were recorded as KBr discs on a Perkin
Elmer 1720 instrument. The EI mass spectra were taken from
solid samples using a Kratos MS 80 RF machine. Melting points
were measured of samples in sealed capillaries. Elemental analyses
were obtained from Brunel University. The following compounds
were commercial samples (and were redistilled where appropriate):
ButC(O)Cl, Me3SiCl, ButCN, PhCN, 2,6-Me2C6H3NC, Et3N, 2-
(NH2)C6H4CH2NH2, Li[AlH4], LiBun in C6H14 and “MgBu2” in
C6H14. The compounds M(NR2)2,25 M(OTos)2 (M = Ca, Sr, Ba),26
27
28
[Sn(m-Cl)NR2)]2 and Pb(NR2)2 (R = SiMe3) were prepared by
Fig. 3 Molecular structure of crystalline 11a (30% thermal ellipsoids,
hydrogens except [Mg{2-N(SiMe3)C6H4(CH2NSiMe3)}(THF)]2 omitted).
published procedures.
Preparation of 2-[N(H)R¢¢]C6H4[CH2N(H)R¢¢] (1) [R¢¢ = C(O)But]
the Mg and N1 atoms are ca. 10◦ wider in the six-membered ring
than in MgN1Mg¢N1¢, and that at N2 is an additional ca. 10◦
wider. The Mg, N1 and N2 atoms are in a distorted tetrahedral,
pyramidal and trigonal planar environment, respectively. The
A solution of pivaloyl chloride (27.6 g, 0.23 mol) in THF (75 cm3)
was added slowly to a stirring solution of 2-(NH2)C6H4CH2NH2
(1◦4.0 g, 0.12 mol) and Et3N (23.2, 0.23 mol) in THF (100 cm3) at
0 C. The mixture was heated under reflux for 2 h, then filtered.
The filtrate was concentrated in vacuo and cooled to -5 ◦C yielding
colourless needles of the diamide 1 (28.3 g, 85%), mp 160–162 ◦C.
1H NMR (CDCl3, 298 K): d 1.19, 1.39 (s, 9H, CH3), 4.29 (d, 2H,
CH2), 6.29 (s, 1H, NH), 7.11 (t, 1H, C6H4), 7.22 (d, 1H, C6H4),
7.30 (t, 1H, C6H4), 7.83 (d, 1H, C6H4), 9.23 ppm (s, 1H, NH).
˚
˚
atoms O and Si1 are 1.721(3) A and 1.134(4) A on the same side
of the MgN1Mg¢N1¢ plane, respectively. The angles between the
planes (i) N2MgN1 and N1MgN1¢, (ii) C7N1Mg and MgN1Mg¢,
(iii) C3C2C1 and C1C2N2, (iv) C1C2N2 and C2N2Mg, and (v)
C2C1C7 andC1C7N1 are 43.6(1)◦ (i), 74.8(1)◦ (ii), 0.0(5)◦ (iii),
26.0(4)◦ (iv) and 68.7(2)◦ (v), respectively.
9826 | Dalton Trans., 2011, 40, 9821–9830
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EI-MS [m/z (assignment and rel. intensity, %): [M]+, 25, 290; [M -
Me]+, 100, 276; [M - 2Me]+, 15, 261.
a yellow solid. Crystallisation from pentane (10 cm3) yielded pale
yellow crystals of 4b (1.36 g, 90%) (C34H64Li4N4O2Si4 requires C,
1
58.3; H, 9.14; N, 8.00. Found: C, 58.4; H, 9.03; N, 7.89%). H
NMR (C6D6, 298 K): d 0.18 (s, 9H, CH3), 0.30 (s, 9H, CH3), 1.26
(m, 4H, THF), 3.40 (m, 4H, THF), 4.15 (br s, 2H, CH2), 6.50 (t,
1H, 3J = 7.0 Hz), 6.92 (d, 1H, 3J = 6.8 Hz), 7.02 (t, 1H, 3J = 6.8 Hz),
Preparation of 2-[N(H)R]C6H4[CH2N(H)R] (2)
Method a. Me3SiCl (49.30 g, 0.46 mol) in PhMe (100 cm3) was
added to a stirring solution of 2-(NH2)C6H4CH2NH2 (27.73 g,
0.23 mol) and Et3N (45.94 g, 0.46 mol) in toluene (100 cm3) at 0 ◦C.
The mixture was heated at 100 ◦C for 2 h, then filtered. Volatiles
were removed from the filtrate in vacuo; distillation yielded the
3
1
7.09 ppm (d, 1H, J = 6.5 Hz); 13C{ H} NMR (C6D6, 298 K): d
2.5 (CH3), 2.7 (CH3), 25.5 (THF), 68.4 (THF); 105.4, 113.8, 122.1,
1
129.6, 135.4, 157.9 ppm (C6H4); 29Si{ H} NMR (C6D6, 298 K): d
1
-11.5, -8.5 ppm; 7Li{ H} NMR (C6D6, 298 K): d 1.5 ppm.
◦
1
colourless diamine 2 (45.4 g, 75%), bp 96–98 C/0.1 mmHg. H
NMR (CDCl3, 298 K): d 0.12, 0.28 (s, 9H, CH3), 3.85 (d, 2H, CH2),
3.86, 5.33 (s, 1H, NH), 6.66–6.76 (m, 2H, C6H4), 7.05–7.12 ppm
(m, 2H, C6H4). EI-MS [m/z (assignment and rel. intensity, %):
[M]+, 25, 266, [M - Me]+, 2, 251; [M - SiMe3]+, 100, 193.
Preparation of [2-{N(Li)R¢}C6H4{CH2N(Li)R¢}] (5)
LiBun (30 cm3 of a 1.6 mol dm-3 solution in hexane, 48.0 mmol)
was added to the diamide 3 (6.27 g, 24.0 mmol) in Et2O (50 cm3)
at 25 ◦C. After ca. 2 h volatiles were removed◦in vacuo, leaving
Method b. LiBun (82.9 cm3 of a 1.6 mol dm-3 hexane solution,
0.13 mol) was added to 2-(NH2)C6H4CH2NH2 (8.09 g, 0.07 mol)
in THF (250 cm3) at 0 ◦C. The mixture was stirred for 2 h at
1
the pale yellow solid 5 (6.22 g, 95%), mp 185 C (decomp.). H
NMR (C5D5N, 298 K): d 0.70, 0.96 (s, 9H, CH3), 2.44, 3.30 (s, 2H,
◦
ca. 20 ◦C, then cooled to 0 C. Me3SiCl (16.9 cm3, 0.13 mol)
CH2), 4.06 (s, 2H, CH2), 6.21 (d, 1H, C6H4), 6.92 (d, 1H, C6H4),
1
7.20–7.40 ppm (m, 2H, C6H4); 13C{ H} NMR (C5D5N, 298 K):
was slowly added. The mixture was heated under reflux for 3 h
and set aside with stirring for ca. 12 h. Volatiles were removed in
vac◦uo; distillation afforded the diamine 2 (14.2 g, 81%), bp 96–
d 28.03, 29.26, 31.36, 35.13 (Me3), 61.01, 62.62 (CH2Me3), 65.79
(CH2); 103.29, 108.88, 129.91, 131.56, 139.49, 162.48 ppm (C6H4);
1
1
7Li{ H} NMR (PhMe + C6D6, 298 K): d -1.7 ppm.
98 C/0.1 mmHg. The H NMR spectrum was identical to that
recorded for (a).
Reactions of [2-{N(Li)R}C6H4{CH2N(Li)R}]2 (4a) with a nitrile
Preparation of 2-[N(H)R¢]C6H4[CH2N(H)R¢] (3) (R¢ = CH2But)
or isonitriles
The N,N-pivaloyldiamide 1 (28.3 g, 0.10 mol) in THF (75 cm3) was
added dropwise to a stirring suspension of Li[AlH4] (7.41 g, 0.19
mol) in THF (100 cm3) at◦0 ◦C. The mixture was heated under
reflux for 10 h, cooled (0 C) and water (20 cm3) was carefully
added, then filtered. Removal of volatiles from the filtrate in vacuo
and distillation furnished the colourless diamine 3 (19.2 g, 75%),
bp 116–118 C/0.2 mmHg. H NMR (CDCl3, 298 K): d 1.52,
1.64 (s, 9H, CH3), 3.00, 3.51 (s, 2H, CH2But), 4.40 (d, 2H, CH2),
5.20, 6.70 (s, 1H, NH), 7.20–7.90 ppm (m, 4H, C6H4). EI-MS [m/z
(assignment and rel. intensity, %): [M]+, 29, 262; [M - Me]+, 2, 247;
[M - But]+, 100, 205.
tert-Butyl isocyanide (0.67 cm3, 6.47 mmol) was added to a
solution of 4a (0.89 g, 3.23 mmol) in pentane (50 cm3) at -78 ◦C.
A white precipitate developed immediately which dissolved when
set aside for 12 h at 25 ◦C. Volatiles were removed in vacuo to give
a yellow solid; pentane (5 cm3) was introduced and the resulting
solution was stored at 4 ◦C for 4 h, whereafter yellow crystals
of [2-{N(Li)R}C6H4{CH2N(Li)R.(CNBut)}] (4c) (0.99 g, 85%)
(C18H33Li2N3Si2 requires C, 59.8; H, 9.14; N 11.6. Found: C, 59.2;
◦
1
1
H, 9.11; N, 11.2%) were collected. H NMR (C6D6, 298 K): d
0.18 (s, 9H, SiCH3), 0.33 (s, 9H, SiCH3), 0.90 (s, 9H, CCH3), 3.77
(d, 1H, CH2), 4.54 (d, 1H, CH2), 6.32–7.21 ppm (m, 4H, C6H4);
1
13C{ H} NMR (C6D6, 298 K): d 3.1 and 3.4 (SiCH3), 29.6 and
Preparation of [2-{N(Li)R}C6H4{CH2N(Li)R}]2 (4a)
36.0 (CCH3 and CCH3), 49.7 (CH2); 117.2, 118.2, 127.6, 129.7
(C6H4), 134.5 (NCBut), 147.6 and 158.2 ppm (C6H4). IR: n(NC)
2161 cm-1.
LiBun (4.8 cm3 of a 1.6 mol dm-3 solution in hexane, 7.8 mmol) was
added to the diamide 2 (1.04 g, 3.2 mmol) in hexane (50 cm3) at
25 ◦C. After ca. 2 h volatiles were removed in vacuo, leaving a pale
yellow solid. Crystallisation from pentane (20 cm3) gave colourless
crystals of 4a (0.65 g, 87%) (C26H48Li4N4Si4 requires C, 56.1; H,
8.63; N, 10.1. Found: C, 55.7; H, 8.58; N, 9.97%). 1H NMR (C6D6,
298 K): d 0.50 (s, 9H, CH3), 0.22 (s, 9H, CH3), 3.69 (d, 1H, CH2),
2,6-Dimethyl(isocyano)benzene (0.12 g, 2.0 mmol) and 4a
(0.28 g, 1.0 mmol) in pentane (50 cm3) similarly afforded yellow
crystals of [2-{N(LiR)C6H4NR.(CNC6H3Me2-2,6)}] (4d) (0.40 g,
74%) (C22H33Li2N3Si3 requires C, 68.9; H, 7.78; N, 10.4. Found:
C, 68.8; H, 7.69; N, 10.5%). 1H NMR (C7D8, 298 K): d -0.13 (s,
9H, SiCH3), 0.13 (s, 9H, SiCH3), 2.01 (s, 6H, CH3), 3.26 (d, 1H,
CH2), 3.92 (d, 1H, CH2), 6.10 (d, 2H, 3J = 3.8 Hz, C6H4), 6.60 –
6.69 (m, 3H, C6H4), 6.91–7.01 (m, 3H, C6H4), 7.12 ppm (t, 2H,
3
4.21 (d, 1H, CH2), 6.27 (m, 1H, C6H4), 6.58 (t, 1H, J = 7.2 Hz,
C6H4), 6.81 (d, 1H, 3J = 6.81 Hz, C6H4), 6.94 ppm (t, 1H, 3J = 6.0
1
Hz, C6H4); 13C{ H} NMR (C6D6, 298 K): d 0.9 (CH3), 2.9 (CH3),
1
3J = 7.4 Hz, C6H4); 13C{ H} NMR (C7D8, 298 K): d 2.9 and 3.6
48.7 (CH2); 119.1, 125.7, 129.6, 131.6, 136.5, 157.2 ppm (C6H4);
1
1
29Si{ H} NMR (C6D6, 298 K): d -8.5, -4.4 ppm; 7Li{ H} (C6D6,
(SiCH3), 18.6 (CH3), 49.8 (CH2); 117.3, 118.3, 127.3, 129.2, 129.8,
130.2, 131.9, 135.1, 158.2 (C6H4, C6H3), 166.8 ppm (CNC6H3);
298 K): d 1.7 ppm.
1
7Li{ H} NMR (C7D8, 298 K): d 2.91, 2.93 ppm. IR: n(NC)
2144 cm-1.
Preparation of [2-{N(Li)R}C6H4{CH2N(Li)R}(THF)]2 (4b)
LiBun (5.38 cm3 of a 1.6 mol dm-3 solution in hexane, 8.6 mmol)
was added to the diamide 2 (1.15 g, 4.3 mmol) in THF (50 cm3)
at 25 ◦C. After ca. 4 h, volatiles were removed in vacuo affording
tert-Butyl cyanide (1 cm3) was added to 4a (0.14 g). The solution
was set aside for 2 h at 25 ◦C, whereafter volatiles were removed in
vacuo. The residue was washed with pentane (10 cm3) furnishing
the dark yellow adduct 4e (0.14 g, 79%) (C18H33Li2N3Si2 requires C,
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59.8; H, 9.14; N, 11.6. Found: C, 60.4; H, 9.19; N, 11.4%). 1H NMR
Preparation of [Pb{(NR)C6H4{CH2NR)-1,2}]2 (9)
(C6D6, 298 K): d 0.29 (s, 9H, SiMe3), 0.53 (s, 9H, SiMe3), 4.24 (br
The salt 4a (0.71 g, 2.70 mmol) was added to a stirring solution of
Pb(NR2)2 (1.41 g, 2.70 mmol) in hexane (80 cm3) at 25 ◦C. After
12 h the solution was concentrated in vacuo to ca. 5 cm3, from
which colourless crystals of the lead(II) diamide 9 (0.83 g, 65%)
(C26H48N4Pb2Si4 requires C, 33.1; H, 5.13; N, 5.94. Found: C, 33.0;
H, 5.10; N, 5.90%), mp 138–142 ◦C (decomp.), were isolated. 1H
NMR (C6D6, 298 K): d 0.00, 0.36 (s, 9H, CH3), 5.61 (s, 2H, CH2),
6.61 (t, 1H, C6H4), 7.00 (d, 1H, C6H4), 7.10 (d, 1H, C6H4), 7.30
3
s, 2H, CH2), 6.54 (t, 1H, J = 7.0 Hz), 7.06 – 7.20 ppm (m, 3H);
1
13C{ H} NMR (C6D6, 298 K): d 3.0 and 3.2 (SiCH3), 27.9 and 28.4
(CCH3 and CCH3), 52.7 (CH2); 111.8, 122.0 (C6H4), 125.49 (CN);
1
129.5, 133.1, 160.0 ppm (C6H4); 29Si{ H} NMR (C6D6, 298 K): d
-17.1, -11.1 ppm. IR: n(CN) 2255 cm-1.
Benzonitrile (0.82 cm3, 8.0 mmol) and 4a (1.12 g, 4.0 mmol)
in THF (50 cm3) were mixed at -40 ◦C. The resultant or-
ange solution was set aside at 25 ◦C for 2 h. Removal of
volatiles in vacuo furnished an orange–red solid, which was
washed with pentane (20 cm3). The residue was washed with
hot toluene (40 cm3); concentration of the extract in vacuo
and storage at -20 ◦C yielded pale yellow crystals of [2-
{N(Li)R}C6H4{CH2N(R)C(Ph)NLi.(NCPh)}] (6) (1.85 g, 95%)
(C27H34Li2N4Si2 requires C, 66.9; H, 7.02; N, 11.5. Found: C, 66.7,
H, 7.05; N, 11.2%). 1H NMR (C6D6, 298 K): d 0.15 (s, 9H, SiMe3),
0.34 (s, 9H, SiMe3), 4.30 (d, 1H, CH2), 4.51 (d, 1H, CH2), 6.64–
6.81 (m, 5H, C6H5), 7.14–7.35 (m, 5H, C6H5), 7.35 (d, 2H, 3J = 6.5
3
1
ppm (d, 1H, J = 7 Hz, C6H4); 13C{ H} NMR (C6D6 + PhMe,
298 K): d 1.5, 3.3 (CH3), 49.3 (CH2); 118.5, 125.4, 129.2, 131.0,
135.2, 153.3 ppm (C6H4); 29Si{ H} NMR (C6D6 + PhMe, 298 K):
1
d -0.4, 10.4 ppm; 207Pb{ H} NMR (C6D6 + PhMe, 298 K): d 2722
1
ppm. EI-MS [m/z (assignment and rel. intensity,%): [M]+, 5, 943;
[M - CH3]+, 10, 928.
Preparation of [Sn{(NR)C6H4(CH2NR)-1,2}(l-S)]2 (10)
A solution of the diamidotin(II) compound 7 (1.03 g, 1.34 mmol)
in toluene (50 cm3) was added to a stirring suspension of sulfur
(0.09 g, 2.70 mmol) in toluene (50 cm3) at -78 ◦C. After 12 h
at 25 ◦C the mixture was filtered. Removal of volatiles in vacuo
from the filtrate gave a colourless solid, which was extracted into
hexane (20 cm3). The extract was concentrated to ca. 5 cm3, from
which colourless crystals of the dimeric bis(amido)tin(IV) sulfide
10 (0.90 g, 80%) (C34H56N4S2Sn2 requires C, 37.6; H, 5.83; N, 6.75.
Found: C, 37.0; H, 5.72; N, 6.55%), mp 178–182 ◦C, were isolated.
1H NMR (C6D6, 298 K): d 0.30, 0.31 (2 s, 18H, CH3), 0.45, 0.46
(2 s, 18H, CH3), 4.04 (s, 4H, CH2), 6.79–7.19 ppm (m, 8H, C6H4).
1
Hz, C6H4), 7.59 ppm (d, 2H, 3J = 7.3 Hz, C6H4); 13C{ H} NMR
(C6D6, 298 K): d 3.2 and 3.3 (SiCH3), 53.0 (CH2); 111.1, 116.9;
124.6 (CN); 127.2, 129.1, 130.8, 132.1, 133.2, 136.5, 140.6, 157.8,
1
178.8 ppm (C6H4, C6H5, C N); 7Li{ H} NMR (C6D6, 298 K): d
1
1.4 and 1.8 ppm; 29Si{ H} NMR (C6D6, 298 K): d -8.7, -6.8 ppm.
Preparation of [Sn{(NR)C6H4(CH2NR)-1,2}]2 (7)
The salt (4a) (1.14 g, 4.10 mmol) in hexane (35 cm3) was added to
◦
[Sn(m-Cl)NR2]2 (2.58 g, 4.10 mmol) in hexane (35 cm3) at 25 C.
1
13C{ H} NMR (C6D6 + PhMe, 298 K): d 2.1, 2.2, 3.0, 3.7 (CH3);
The mixture was stirred for 12 h then filtered. The filtrate was
concentrated in vacuo to ca. 5 cm3 and set aside at -5 ◦C affording
colourless crystals of the diamide 7 (0.63 g, 40%) (C26H48N4Si4Sn2
requires C, 40.8; H, 6.31; N, 7.31. Found: C, 40.4; H, 6.35; N,
50.0, 50.2 (CH2); 123.2, 123.6, 138.2, 140.4, 147.6 ppm (C6H4);
1
29Si{ H} NMR (PhMe + C6D6, 298 K): d 9.6, 11.1, 12.1 ppm;
1
119Sn{ H} NMR (PhMe + C6D6, 298 K): d -72 ppm (2J = 6.85
and 7.10 Hz). EI-MS [m/z (assignment and rel. intensity, %): [M]+,
1, 830; [M - CH3]+, 1, 815; [M/2 - S]+, 15, 383.
◦
1
7.16%), mp 150–152 C (decomp.). H NMR (C6D6, 298 K): d
0.10, 0.39 (s, 9H, CH3), 4.17 (s, 2H, CH2); 6.73 (t, 1H, 3J = 7.0 Hz,
C6H7), 7.05 – 7.15 ppm (m, 3H, C6H4); 13C{ H} NMR (C6D6 +
Preparation of [Mg{2-N(R)C6H4(CH2NR)}(THF)]2 (11a)
1
PhMe, 298 K): d 0.6 and 2.7 (CH3), 48.9 (CH2); 118.3, 122.5, 127.8,
A solution of “MgBu2” (4 cm3 of a 1 mol dm-3 solution in hexane,
4.0 mmol) was added dropwise to a stirred solution of the diamine
2 (1.06 g, 4.0 mmol) at 0 ◦C, then set aside for 4 h at 25 ◦C.
Volatiles were removed in vacuo and the residue was dissolved
in THF (5 cm3). After 1 h, volatiles were again eliminated in
vacuo. The residue was crystallised from hot toluene yielding pale
yellow crystals of the dimeric bis(amido)magnesium-THF-solvate
11a (1.20 g, 83%) (C34H64Mg2N4O2Si4 requires C,56.7; H, 8.89; N,
7.78. Found: C, 55.4; H, 8.79; N, 7.82%). 1H NMR (C6D6, 298 K):
d 0.20 (s, 9H, CH3), 0.33 (s, 9H, CH3), 1.41 (m, 4H, THF), 3.52
(m, 4H, THF), 4.44 (d, 1H, CH2), 4.84 (d, 1H, CH2), 6.69 (t, 1H,
130.0, 132.7, 151.0 ppm (C6H4); 29Si{ H} NMR (C6D6 + PhMe,
1
298 K): d 4.4 and 15.8 ppm; 119Sn{ H} NMR (C6D6 + PhMe,
1
298 K): d 118.0 ppm. EI-MS [m/z (assignment and rel. intensity,
%): [M/2]+, 52, 383; [M/2 - (CH3 + 1)]+, 15, 367; [M/2 - SiMe3 +
1]+, 69, 311; [M/2 - SiMe3 - Me]+, 17, 296.
Preparation of [Sn{NR¢)C6H4(CH2NR¢)-1,2}]2 (8) (R¢ = CH2But)
As for 7, the salt 5 (1.20 g, 4.38 mmol) and [Sn(m-Cl)NR¢2]2 (27.5 g,
4.38 mmol) furnished the colourless crystalline diamide 8 (0.94 g,
56%) (C34H56N4Sn2 requires C, 53.9; H, 7.49; N, 7.39. Found: C,
54.0; H, 7.51; N, 7.31%), mp 195–197 ◦C. 1H NMR (C6D6, 298 K):
d 0.87, 0.90 (s, 9H, CH3), 2.23, 2.66 (d, 1H, 2J = 14.0 Hz, CH2But),
3
3J = 7.1 Hz, C6H4), 7.15 (d, 1H, J = 6.9 Hz, C6H4), 7.29 (t, 1H,
3J = 7.3 Hz, C6H4), 7.39 ppm (d, 1H, 3J = 7.9 Hz, C6H4); 13C{ H}
1
NMR (C6D6, 298 K): d 3.2, 3.3 (CH3), 25.4 (THF), 52.3 (CH2),
67.3 (THF); 113.5, 120.5, 128.5, 130.7, 132.7, 158.0 ppm (C6H4);
2
3.87, 4.30 (d, 1H, J = 11.0 Hz, CH2But); 6.65 (t, 1H, C6H4),
1
29Si{ H} NMR (C6D6, 298 K): d 1.1, 4.8 ppm.
3
1
7.07 (d, 1H, C6H4), 7.26 ppm (d, 1H, J = 7 Hz, C6H4); 13C{ H}
NMR (C6D6 + PhMe, 298 K): d 27.7, 29.9, 33.2 (CH3), 57.0,
57.7 (CH2But), 62.3 (CH2N); 114.3, 115.4, 133.7, 136.7, 136.9,
Reactions of [Mg{2-N(R)C6H4(CH2NR)}(THF)]2 (11a) with
nitriles
155.7 ppm (C6H4); 119Sn{ H} NMR (C6D6 + PhMe 298 K): d 3.0
1
ppm. EI-MS [m/z (assignment and rel. intensity,%): [M]+, 1, 758;
[M/2]+, 14, 380; [M/2 - But]+, 86, 323; [M/2 - Sn]+, 61, 260.
tert-Butyl cyanide (0.1 cm3, 1 mmol) was added to a solution
of 11a (0.18 g, 0.5 mmol) in tetrahydrofuran (30 cm3) at
9828 | Dalton Trans., 2011, 40, 9821–9830
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Table 4 Crystal data and structure refinement for 4a, 4b and 11a
Compound
4a
4b
11a
Formula
M
C26H48Li4N4Si4
556.8
Monoclinic
P21/n (non-standard No.14)
9.729(2)
21.316(5)
16.744(4)
90
97.90(2)
90
3439.5(14)
4
0.19
C34H64Li4N4O2Si4
701.0
C34H64Mg2N4O2Si4 (C7H8)
814.0
Crystal system
Monoclinic
P21/c (No.14)
19.787(7)
9.808(3)
21.951(9)
90
99.70(3)
90
4199(3)
4
0.17
5146, 0.069
3736
0.056, 0.132
0.086, 0.150
Triclinic
¯
Space group
P1(No.2)
˚
a (A)
10.380(5)
10.726(3)
11.752(4)
77.64(2)
66.68(3)
82.20(3)
1171.8(8)
1
˚
b (A)
˚
c (A)
a (◦)
b (◦)
g (◦)
V (A3)
Z
Absorption coefficient (mm-1)
Unique reflections, Rint
Reflections with I > 2s(I)
Final R indices I > 2s(I) R1, wR2
R indices (all data) R1, wR2
0.19
4120, 0.000
3392
0.047, 0.0123
0.059, 0.131
6025, 0.060
4032
0.056, 0.131
0.098, 0.154
-40 ◦C. The pale yellow solution was stored at 25 ◦C for
12 h. Volatiles were removed in vacuo to leave the pale yellow
solid [Mg{2-N(R)C6H4(CH2NR}(NCBut)] (11b) (0.25 g, 96%)
(C18H33MgN3Si2 requires C, 58.2; H, 8.89; N, 11.3. Found: C, 57.5;
H, 8.75; N, 11.6%). 1H NMR (C6D6, 298 K): d 0.27 (s, 9H, SiCH3),
0.39 (s, 9H, SiCH3), 0.77 (s, 9H, CCH3), 4.46 (d, 1H, CH2), 4.85
(d, 1H, CH2), 6.42 (d, 1H, 3J = 4.9 Hz, C6H4), 6.76 (t, 1H, 3J = 6.2
Hz, C6H4), 7.35 (t, 1H, 3J = 7.9 Hz, C6H4), 7.43 ppm (d, 1H, 3J =
67.4 (THF); 112.6, 126.6, 128.5, 129.1, 132.2, 159.3 ppm (C6H4);
1
29Si{ H} NMR (C6D6, 298 K): d -8.3, 2.3 ppm.
Compound 12 (1.00 g, 61%) was also obtained by successive
addition of Ca(OSO2C6H4Me-4)2 (1.64 g, 4.3 mmol) to the
dilithium salt 4b (1.2 g, 4.3 mmol) in tetrahydrofuran at 25 ◦C,
filtration, removal of volatiles from the filtrate, washing the residue
with pentane, and drying in vacuo.
1
7.8 Hz); 13C{ H} NMR (C6D6, 298 K): d 3.7, 3.8 (SiCH3), 27.8,
Preparation of [Sr{2-N(R)C6H4(CH2NR)}(THF)]2 (13)
28.2 (CCH3), 5.27 (CH2); 113.9, 116.3, 117.5 (C6H4); 120.9 (CN);
1
128.9, 131.1, 158.3 ppm (C6H4); 29Si{ H} NMR (C6D6, 298 K): d
Using similar procedures as for 12, the yellow solid strontium
salt 13 (0.25 g, 76%; or 1.66 g, 89%) was prepared either from
Sr(NR2)2 (0.45 g, 0.8 mmol) and the diamine 2 (0.20 g, 0.8 mmol),
or Sr(OSO2C6H4Me-4)2 (1.89 g, 4.4 mmol) and the dilithium salt
4b (1.22 g, 4.4 mmol), respectively. (C34H64Sr2N4O2Si4 requires C,
1.0, 4.9 ppm. IR: n(CN) 2276 cm-1.
Pale yellow crystals of [Mg{2-N(R)C6H4(CH2NR)}(NCPh)2]
(11c) (0.39 g, 90%) (C27H34MgN4Si2 requires C, 58.2; H, 8.89;
N, 11.3. Found: C, 57.5; H 8.75; N, 11.6%) were obtained from
benzonitrile (0.11 cm3, 1.1 mmol) and 11a (0.41 g, 1.1 mmol) in
1
48.2; H, 7.57; N, 6.62. Found: C, 47.9; H, 7.56; N, 6.64%). H
1
toluene (40 cm3), using procedures similar to those for 11b. H
NMR (C6D6, 298 K): d 0.16 (s, 9H, CH3), 0.22 (s, 9H, CH3), 1.41
(m, 4H, THF), 3.52 (m, 4H, THF), 4.41 (d, 1H, CH2), 4.61 (d,
NMR (C6D6, 298 K): d 0.04 (s, 9H, SiCH3), 0.35 (s, 9H, SiCH3),
3
3
4.84 (d, 1H, CH2); 6.65–6.78 (m, 5H, C6H4, 6.89–6.95 (m, 4H,
1H, CH2), 6.57 (t, 1H, J = 7.3 Hz, C6H4), 6.77 (d, 1H, J = 8.0
Hz, C6H4), 7.16 (t, 1H, 3J = 8.0 Hz, C6H4), 7.24 ppm (d, 1H, 3J =
3
C6H4),7.05 (d 1H, J = 1.4 Hz, C6H4), 7.25–7.45 ppm (m, 2H,
1
C6H4); 13C{ H} NMR (C6D6, 298 K): d 3.7, 4.0 (SiCH3), 52.7
6.8 Hz, C6H4); 13C{ H} NMR (C6D6, 298 K): d 2.8, 3.0 (SiCH3),
1
(CH2); 113.9 (C6H4), 120.9 (CN); 128.9, 131.1, 132.0, 132.3, 158.3
25.7 (THF), 54.0 (CH2), 67.7 (THF); 112.2, 121.5, 127.0, 129.2,
1
ppm + 2 others (C6H4, C6H5); 29Si{ H} NMR (C6D6, 298 K): d
132.5, 160.3 ppm (C6H4); 29Si{ H} NMR (C6D6, 298 K): d -8.3,
1
-8.4, 2.4 ppm. IR: n(CN) 2277 cm-1.
-4.4 ppm.
Preparation of [Ca{2-N(R)C6H4(CH2NR)}(THF)]2 (12)
Preparation of [Ba{2-N(R)C6H4(CH2NR)}(THF)]2 (14)
A solution of the diamine 2 (0.60 g, 2.2 mol) in pentane (30 cm3)
was added dropwise to a solution of Ca(NR2)2 (0.45 g, 2.2 mmol)
in pentane (50 cm3) at 0 ◦C, then set aside for 4 h at 25 ◦C.
Volatiles were removed in vacuo. The residue was dissolved in
tetrahydrofuran (10 cm3), then eliminated in vacuo. The residual
solid, upon crystallisation from hot toluene, yielded yellow crystals
of 12 (0.61 g, 74%) (C34H64Ca2N4O2Si4 requires C, 54.3; H, 8.51;
As for 12 or 13, the yellow solid barium salt 14 (0.34 g, 33%; or
1.39 g, 70%) was obtained either from Ba(NR2)2 (0.47 g, 1.6 mmol)
and the diamine 2 (0.42 g, 1.6 mmol), or Ba(OSO2C6H4Me-4)2
(2.00 g, 4.2 mmol) and the dilithium salt 4b (1.17 g, 4.2 mmol),
respectively. (C34H64Ba2N4O2Si4 requires C, 43.1; H, 6.77; N, 5.92.
1
Found: C, 42.9; H, 6.72, N, 5.87%). H NMR (C6D6, 298 K): d
0.01 (s, 9H, CH3), 0.19 (s, 9H, CH3), 1.22 (m, 4H, THF), 3.11
(m, 4H, THF), 3.71 (d, 1H, CH2), 4.22 (d, 1H, CH2), 6.72 (t, 1H,
3J = 6.4 Hz, C6H4), 6.86 (d, 1H, 3 J = 8.0 Hz, C6H4), 6.97 (d, 1H,
1
N, 7.45. Found: C, 53.5; H, 8.47; N, 7.41%). H NMR (C6D6,
298 K): d 0.25 (s, 9H, CH3), 0.55 (s, 9H, CH3), 1.11 (m, 4H, THF),
3.17 (m, 4H, THF), 4.13 (d, 1H, CH2), 4.32 (d, 1H, CH2), 6.60
(t, 1H, 3J = 7.1 Hz, C6H4), 6.91 (1H, 3J = 7.9 Hz, C6H4), 7.06 (t,
1
3J = 7.4 Hz, C6H4), 7.12 ppm (t, 1H, 3J = 6.1 Hz, C6H4); 13C{ H}
NMR (C6D6, 298 K): d 2.1, 2.7 (SiCH3), 25.4 (THF), 55.9 (CH2),
3
3
1
1
1H, J = 8.0 Hz, C6H4), 7.20 ppm (d, 1H, J = 7.3 Hz); 13C{ H}
67.7 (THF); 116.3, 117.5, 128.5, 129.9, 133.2, 157.7 ppm; 29Si{ H}
NMR (C6D6, 298 K): d 2.5, 2.6 (SiCH3), 25.3 (THF), 53.4 (CH2),
NMR (C6D6, 298 K): d -11.9, -8.5 ppm.
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X-Ray crystallographic studies for 4a, 4b and 11a
10 J. Pfeiffer, W. Maringgele, M. Noltemeyer and A. Meller, Chem. Ber.,
1989, 122, 245.
11 E. A. Ison, T. S. Cameron, K. A. Abboud and J. M. Boncella,
Organometallics, 2004, 23, 4070.
12 B. Gehrhus, P. B. Hitchcock and M. F. Lappert, J. Chem. Soc., Dalton
Trans., 2000, 3094.
Diffraction data were collected at 173(2) K on an Enraf–Nonius
CAD4 diffractometer using monochromated Mo-Ka radiation
˚
(l = 0.71073 A). Crystals were coated in oil and then directly
mounted on the diffractomer under a stream of cold nitrogen gas.
The structures were refined on all F2 with H atoms in riding mode
using SHELXL97.29 Further details are in Table 4.
13 G. J. Pindado, M. Thornton-Pett and M. Bochmann, J. Chem. Soc.,
Dalton Trans., 1998, 393.
14 D. R. Armstrong, R. E. Mulvey, G. T. Waller, D. Barr and R. Snaith,
J. Chem. Soc., Dalton Trans., 1988, 617.
15 D. J. Brauer, H. Bu¨rger and G. r. Liewald, J. Organomet. Chem., 1986,
308, 119.
16 S. Daniele, C. Drost, B. Gehrhus, S. M. Hawkins, M. F. Lappert, P. G.
Merle and S. G. Bott, Dalton Trans., 2006, 3179.
17 G. Boche, I. Langlotz, M. Marsch, K. Harms and G. Frenking, Angew.
Chem., Int. Ed. Engl., 1993, 32, 1171.
18 A. R. Sanger, Inorg. Nucl. Chem. Lett., 1973, 9, 351.
19 F. Antolini, P. B. Hitchcock, A. V. Khvostov and M. F. Lappert, Can.
J. Chem., 2006, 84, 269.
Acknowledgements
For financial support we thank EPSRC (C.F.C.) and the European
Commission (TMR grant for L.J-M.P.). We are grateful to
Professor Gang Li for help with the manuscript.
20 C. F. Caro, P. B. Hitchcock, M. F. Lappert and M. Layh, Chem.
Commun., 1998, 3179.
Notes and references
21 B. Wrackmeyer, C. Stader and K. Horchler, J. Magn. Reson., 1989, 83,
601–607.
1 M. F. Lappert, P. P. Power, A. R. Sanger and R. C. Srivastava, Metal
and Metalloid Amides, Ellis Horwood/John Wiley, Chichester, 1980;
M. F. Lappert, P. P. Power, A. V. Protchenko and A. L. Seeber, Metal
Amide Chemistry, Wiley, Chichester, 2009.
2 M. F. Lappert, J. Organomet. Chem., 2005, 690, 5467.
3 N. J. Hill and R. West, J. Organomet. Chem., 2004, 689, 4165; B.
Gehrhus, P. B. Hitchcock, R. Pongtavornpinyo and L. Zhang, Dalton
Trans., 2006, 1847.
4 A. W. Duff, P. B. Hitchcock, M. F. Lappert, R. G. Taylor and J. A.
Segal, J. Organomet. Chem., 1985, 293, 271.
5 P. B. Hitchcock, Q. Huang, M. F. Lappert, X.-H. Wei and M. Zhou,
Dalton Trans., 2006, 2991.
6 F. Antolini, B. Gehrhus, P. B. Hitchcock and M. F. Lappert, Chem.
Commun., 2005, 5112.
7 P. B. Hitchcock, M. F. Lappert and X.-H. Wei, Dalton Trans., 2006,
1181.
8 J.-P. Bezombes, B. Gehrhus, P. B. Hitchcock and M. F. Lappert, Chem.
Commun., 2005, 5112.
9 D. S. Brown, A. Decken and A. H. Cowley, Polyhedron, 1996, 15,
4109.
22 P. B. Hitchcock, E. Jang and M. F. Lappert, J. Chem. Soc., Dalton
Trans., 1995, 3179.
23 M. Westerhausen and W. Schwarz, Z. Anorg. Allg. Chem., 1992, 609,
39.
24 W. Clegg, L. Horsburgh, R. E. Mulvey, M. J. Ross, R. B. Rowlings and
V. Wilson, Polyhedron, 1998, 17, 1923.
25 P. B. Hitchcock, M. F. Lappert, G. A. Lawless and B. Royo, J. Chem.
Soc., Chem. Commun., 1990, 1141; F. G. N. Cloke, P. B. Hitchcock, M.
F. Lappert, G. A. Lawless and B. Royo, J. Chem. Soc., Chem. Commun.,
1991, 724; A. D. Frankland, P. B. Hitchcock, M. F. Lappert and G. A.
Lawless, J. Chem. Soc., Chem. Commun., 1994, 2436.
26 A. D. Frankland and M. F. Lappert, J. Chem. Soc., Dalton Trans., 1996,
4151.
27 R. W. Chorley, P. B. Hitchcock, B. S. Jolly, M. F. Lappert and G. A.
Lawless, J. Chem. Soc., Chem. Commun., 1991, 1302.
28 M. J. S. Gynane, D. H. Harris, M. F. Lappert, P. P. Power and Rivie´re-
Baudet, J. Chem. Soc., Dalton Trans., 1977, 2004.
29 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
9830 | Dalton Trans., 2011, 40, 9821–9830
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