Reactivity of lithium n-butyl amidinates towards group 14 metal(ii) chlorides providing series of hetero- and homoleptic tetrylenes

Article abstract of DOI:10.1039/c2dt12472f

The new class of homo- and heteroleptic n-butyl-N,N′-disubstituted amidinato group 14 metal(ii) complexes were prepared by salt elimination from starting lithium amidinates and metal(ii) chlorides both in stoichiometric ratio 2:1 and 1:1, respectively. The target amidinates contain less bulky isopropyl or cyclohexyl as well as a sterically demanding aromatic substituent. Desired 1:1 Pb(ii) complexes are not accessible by the described procedure. Ligand transfer from Pb to Sn is taking place if homoleptic Pb(ii) compounds are reacted with SnCl₂. Prepared tetrylenes were characterized by ¹H, ¹³C, ¹¹⁹Sn and ²⁰⁷Pb NMR spectroscopy in C₆D₆ or THF-d₈. X-Ray diffraction studies of one heteroleptic Ge(ii) monomeric where the coordination polyhedron of the three coordinated germanium atoms is a trigonal pyramid, two different dimeric structures of heteroleptic Sn(ii) complexes, one amidine hydroiodide byproduct and the oxidation product of the heteroleptic chloro Sn(ii) amidinate as a tetranuclear species with two Sn(iv) and two Sn(ii) atoms in central Sn₂O₂ planar ring were performed on appropriate single crystals. The dimer of one of the heteroleptic stannylenes reveals a new type of monomeric units connection, weak Sn-Cl contact and an interaction of the tin atom with delocalized N-C(C)-N system of the amidinato ligand of the second molecule. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt12472f

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PAPER
Reactivity of lithium n-butyl amidinates towards group 14 metal(II) chlorides
providing series of hetero- and homoleptic tetrylenes†
Tomáš Chlupatý,a Zdeňka Padělková,a Antonín Lyčka,b Jiří Brusc and Aleš Růžička*a
Received 22nd December 2011, Accepted 16th February 2012
DOI: 10.1039/c2dt12472f
The new class of homo- and heteroleptic n-butyl-N,N′-disubstituted amidinato group 14 metal(II)
complexes were prepared by salt elimination from starting lithium amidinates and metal(II) chlorides both
in stoichiometric ratio 2 : 1 and 1 : 1, respectively. The target amidinates contain less bulky isopropyl or
cyclohexyl as well as a sterically demanding aromatic substituent. Desired 1 : 1 Pb(II) complexes are not
accessible by the described procedure. Ligand transfer from Pb to Sn is taking place if homoleptic Pb(II)
compounds are reacted with SnCl2. Prepared tetrylenes were characterized by 1H, 13C, 119Sn and 207Pb
NMR spectroscopy in C6D6 or THF-d8. X-Ray diffraction studies of one heteroleptic Ge(II) monomeric
where the coordination polyhedron of the three coordinated germanium atoms is a trigonal pyramid, two
different dimeric structures of heteroleptic Sn(II) complexes, one amidine hydroiodide byproduct and the
oxidation product of the heteroleptic chloro Sn(II) amidinate as a tetranuclear species with two Sn(IV) and
two Sn(II) atoms in central Sn2O2 planar ring were performed on appropriate single crystals. The dimer of
one of the heteroleptic stannylenes reveals a new type of monomeric units connection, weak Sn–Cl
contact and an interaction of the tin atom with delocalized N–C(C)–N system of the amidinato ligand of
the second molecule.
alkyne10 analogues. With a lone electron pair and a vacant
π-orbital on the central atom they can be seen as Lewis ampho-
1. Introduction
The amidinates,1 formally N′,N-disubstituted amidoimides, have
become very popular ligands especially for stabilization/specific
ters. Particular attention has been paid to the reactivity of these
compounds in oxidative addition reactions,11 in activation of
small molecules,12 in use as carbene analogues for complexa-
activation of low valent metal centres of a whole periodic
system, within the last decade. The f- and d-element3 com-
plexes are frequently studied because of their catalytic activity of
various processes, s-element4 complexes as precursors for other
metal complexes or reducing agents. The investigation of new p-
block metal or metalloid complexes,5,3f especially of group 14
elements6 is a current topic in this field. The stabilization of
lower oxidation states of these elements through the formation of
unsaturated four-membered diazametalla ring(s) produces inter-
esting complexes with remarkable properties.7 The heavier
elements of group 14 metal complexes with the metal atom in a
lower oxidation state are widely accepted as carbene,8 radical9 or
2
tion13 of transition metal complexes and in reductions to metal
clusters.14 Two types of these metal complexes with group 14
elements in the oxidation state of II (tetrylenes) are known. The
first one is the homoleptic type of compounds (Scheme 1A) con-
taining the same amidinato ligands in the molecule. To the best
of our knowledge there exist no reactivity studies of these com-
pounds. On the other hand the reactivity of the second type, het-
eroleptic one (Scheme 1B), where the only one amidinato unit is
employed, with various reducing agents is the subject of numer-
ous papers.15,6g These reduced amidinato complexes or their
aDepartment of General and Inorganic Chemistry, Faculty of Chemical
Technology, University of Pardubice, Studentská 573, CZ-532 10
Pardubice, Czech Republic. E-mail: ales.ruzicka@upce.cz; Fax: +420-
466037068
bResearch Institute for Organic Syntheses (VUOS), Rybitví 296, CZ-533
54 Pardubice, Czech Republic
cInstitute of Macromolecular Chemistry, Academy of Science of the
Czech Republic, Heyrovský Sqr. 2, 162 06, Praha 6, Czech Republic
†Electronic supplementary information (ESI) available: 13C CP/MAS
NMR spectrum and details of the coordination sphere of tin atoms of
5a; molecular structure of LCyHI. CCDC 858674 (for 7), 858678 (for
8), 858676 (for 9), 858677 (for 5a) and 858675 (for LCyHI·C6H6). For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c2dt12472f
Scheme 1 Homoleptic (A) and heteroleptic (B) type of tetrylene
amidinates.
5010 | Dalton Trans., 2012, 41, 5010–5019
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precursors can activate unsaturated systems16,6b,6h or small
molecules.17,15c
NMR in solution. When the reaction time was prolonged to 4 h,
the reaction mixture contains no plumbylenes but the molar ratio
of corresponding homo- and heteroleptic stannylenes was 1 : 1.
Surprisingly, after two days the equilibrium of the reaction was
moved towards the excess of homoleptic stannylene to 3 : 1.
Similar reactions of 15 with SnCl2 led after 4 h to the homoleptic
stannylene 14 as the sole product. After 3 days at the same con-
ditions the ratio of homo-(14) and heteroleptic (7) stannylenes
was changed to 1 : 3. The PbCl2 was detected (δ(207Pb) ca.
−1730 ppm)21 in the solid residue using 207Pb MAS NMR spec-
troscopy after all reactions.
Accidentally, when the stopcock of the Schlenk tube was not
sufficiently greased, the insoluble colourless crystalline material
of 5a as the oxidation product of 5 was obtained by slow diffu-
sion of air. The process is fully reproducible and is described in
the Experimental section. The formation of 5a could be under-
stood as the reaction of four molecules of heteroleptic stannylene
5 with a molecule of oxygen (Scheme 2). There is obvious oxi-
dation of two tin(II) atoms to tin(IV) only. The migration of the
amidinato units from tin(II) to tin(IV) atoms takes place and the
formation of the central 1,3-Sn2O2 ring is the main structural
motif of this compound (for more details of NMR and X-ray
studies see below).22 5a is one of the rare examples of com-
pounds where both stable oxidation states are present23 but the
only example of a compound where low-valent tin atoms are
connected together as well as with tin(IV) atoms by oxygen
bridges.
This paper deals with the preparation and structural studies of
n-butyl amidinato N′,N-disubstituted (formally derivatives of
pentanoic acid) complexes of Ge, Sn and Pb in the oxidation
state II. Only one homoleptic N,N′-diisopropyl n-butylamidinato
germanium(II) complex is reported as MOCVD precursor of ger-
manium compounds.18 The main objective of this study is to
prepare such complexes that contain a rather flexible aliphatic
chain which could facilitate further reactivity studies in respect
of higher solubility of products in comparison to used
amidinates.
2. Results and discussion
2.1. Synthesis
The preparation of desired complexes via the salt elimination
reactions from various lithium n-butyl amidinates19 and GeCl2·-
dioxane complex (1 : 1), SnCl2 and PbCl2, respectively, in molar
ratio 1 : 1 or 2 : 1 has been performed according to Fig. 1 in
rather good yields. The preliminary attempts to prepare germa-
nium(II) amidinates from GeI2 as a germanium source led to the
mixture of rather insoluble products from which only a minor
part crystallizes the adduct of free ligand with HI (LCyHI, for the
crystal structure see ESI†). These problems were eliminated by
the use of GeCl2·dioxane complex instead of GeI2. The reactions
of lithium n-butyl amidinates with PbCl2 in both stoichiometric
ratios 1 : 1 and 2 : 1 led to the same product, formation of homo-
leptic plumbylenes only. On the other hand, there is only one
amidinato lead complex described until now, and in a series of
related guanidinato complexes, the only reported types are a few
heteroleptic complexes.20 All reactions of lithium amidinate pre-
cursors with PbCl2 have to be conducted in the dark because of
the instability of lead amidinates on the light which is reflected
in an elimination of elemental Pb from the solution.
2.2. NMR spectroscopic studies in solution
Compounds 4–18 were investigated by multinuclear NMR
approach in solution with a view to elucidating their structural
1
behaviour. The H NMR spectra reveal one set of signals for
each symmetry independent group in C6D6 as well as in THF-d8,
as an example of a coordinating solvent, for an aliphatic chain or
ring substituted heteroleptic amidinates 4–7, while the N,N′-
cyclohexyl substituted compounds 6 and 7 show broadening of
aliphatic signals. The bulky aromatic group substituted hetero-
leptic compounds 8, 9 and homoleptic 16–18 have dynamic be-
havior in solution, and, thus, the 1H NMR spectra are quite
Attempts to prepare heteroleptic plumbylenes from SnCl2 and
LiPr2Pb (12) or LCy2Pb (15), respectively, were made. When 12
was stirred with equimolar amount of SnCl2 in THF at room
temperature for 20 min, the desired heteroleptic plumbylene was
not observed but a mixture of corresponding homo- and hetero-
leptic stannylenes 18 : 1 has been detected with the help of 119Sn
1
complex. On the other hand, from the H NMR spectra of the
rest of the homoleptic compounds 10–15 the deduction about
the higher symmetry of compounds in solution is made on the
basis of simple spectral patterns.
In the 13C NMR spectra of heteroleptic compounds 4–9 the
signals for the central ipso carbon atom are found around
176 ppm, while the lowest values of ca. 174 ppm are attributed
to the germylenes 4 and 6 in C6D6 solution. For compounds 5
and 9 little decreases by 2 ppm are caused by changing of the
solvent to THF-d8 and contrasted with all 13C NMR spectral
Fig. 1 Reagents and conditions: (i) Et2O, −60 °C to RT, −LiCl; (ii)
Et2O, RT, −2LiCl (darkness in the case of Pb).
Scheme 2 Reaction route leading to 5a.
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Table 1 Selected NMR spectra parameters
13
Compound
Solvent
δ (
C
)
ipso
δ (119Sn/207Pb)
LiPrGeCl (4)
L
C6D6
C6D6
THF-d8
C6D6
C6D6
THF-d8
C6D6
C6D6
THF-d8
C6D6
C6D6
C6D6
THF-d8
C6D6
C6D6
C6D6
THF-d8
C6D6
C6D6
C6D6
THF-d8
174.2
178.1
176.2
174.8
177.8
177.9
177.2
179.2
175.9
165.8
168.2
168.8
169.5
166.1
168.8
168.6
169.8
169.8
171.7
170.4
171.3
—
78.9
69.1
—
75.7
69.7
—
29.4
−124.0
—
−252.3
1734.8
1743.5
—
−255.3
1729.0
1745.6
—
iPrSnCl (5)
LCyGeCl (6)
CySnCl (7)
L
LDippGeCl (8)
LDippSnCl (9)
LiPr2Ge (10)
LiPr2Sn (11)
LiPr2Pb (12)
LCy2Ge (13)
LCy2Sn (14)
LCy2Pb (15)
LDipp2Ge (16)
LDipp2Sn (17)
LDipp2Pb (18)
−341.3
1541.3
1540.1
Fig. 2 Molecular structure of LDippGeCl (8) (ORTEP view, 50% prob-
ability level). Hydrogen atoms are omitted for clarity. Selected intera-
tomic distances [Å] and angles [°]: N1–C1 1.322(5); N1–C2 1.436(4);
N1–Ge1a 2.029(3); N2–C1 1.339(5); N2–C14 1.429(5); N2–Ge1a 2.019
(3); C1–C26 1.493(5); C1–Ge1a 2.475(4); Ge1a–Cl1a 2.2400(13); N1–
C1–N2 108.9(3); N1–Ge1a–N2 64.69(12); C1–Ge1a–Cl1a 102.63(11);
C14–C1–C2 164.1(2).
parameters of the remaining heteroleptic stannylene 7 which are
solvent independent. These values of the specified ipso carbon
atom are in line with the appropriate values for known t-butyla-
midinato substituted germylene (∼176 ppm)24 and stannylene
(∼180 ppm).25 The values of the same parameter of homoleptic
compounds 10–18 are much lower ∼168 ppm than in compar-
able heteroleptic compounds, all are solvent independent, and
the increase in these values in the row from germylenes to plum-
bylenes is quite significant. The highest chemical shifts are
found for bulky Dipp substituted compounds 16–18.
The 13C and 119Sn MAS NMR spectra of 5a were measured
(see ESI†), a rather simple 13C NMR spectrum reveals all the
carbon signals in a similar range found for 5 in solution, except
of the amidinato ipso carbon signal which is located at 164 ppm.
Surprisingly, only the signal for tin(IV) atoms is observed at
−600 ppm which indicates the coordination number of the tin
atoms to be six, the resonance for tin(II) remains silent.
119Sn NMR spectroscopy, which is very significant in the
investigation of coordination polyhedra of tin s,26 has been used
in studies of compounds 5, 7, 9, 11, 14 and 17. The tin chemical
shifts of all heteroleptic stannylenes except for 9 are found to be
solvent independent at similar values in C6D6 and THF-d8 (see
Table 1). The appropriate value for Dipp substituted stannylene
9 is a bit lower (29.4 ppm) in C6D6, when dissolved in THF-d8 a
high field shift of ca. 150 ppm is observed, probably caused by
increase of the coordination number of the tin atom to four. For
homoleptic stannylenes 11, 14 and 17 a direct comparison with
the compounds bearing the same substituent can be made, the
δ(119Sn) decrease of ∼350 ppm is seen for each pair of hetero-
and homoleptic stannylenes. The same trend was also observed
in the literature for related methyl and t-butyl amidinato
stannylenes.6d,25
2.3. Crystal structure determination by X-ray diffraction
For five of the compounds studied the crystal structure has been
determined by means of X-ray diffraction techniques on single
crystalline material. Three of the molecular structures are of het-
eroleptic germylene and stannylenes. The common feature of the
heavier elements heteroleptic tetrylenes is an easy formation of
dimeric structures either via chlorido or amido bridges.29–31 On
the other hand, related silylenes and germylenes tend to be
monomeric.
The germanium atom in the molecular structure of 8 (Fig. 2)
is three-coordinated with the coordination polyhedra of trigonal
pyramid as reported for analogues of monomeric t-butyl/phenyl
amidinatogermylenes [Dipp-NC(t-Bu)N-Dipp]GeCl and [t-Bu-
NC(Ph)N-t-Bu]GeCl, respectively.24,32 Based on the comparison
of interatomic distances and angles in these three structures, a
conclusion about the same structure is made.
On the other hand, tin atoms in amidinato or guanidinato sub-
stituted stannylenes are ready to increase their coordination
number to four by an interaction with adjacent donor groups as
for example halides, to form infinite chains6d or dimers in the
solid state.31
Compound 9 is an asymmetric dimer in the solid state
(Fig. 3). The amidinato units are nearly symmetrically bonded to
the tin atoms together with one covalently bonded chlorine
There is no literature comparison for 207Pb NMR spectra in
solution of amidinato plumbylenes 12, 15 and 18 but it could be
a generally helpful tool for further structural studies of amidi-
nato, guanidinato and formamidinato plumbylenes in solution.
The δ(207Pb) around 5000 ppm are found for lead bisamides27
where the lead coordination number is two, for four-coordinated
complexes of lead(II) a decrease of the chemical shift is found
28
(2624 ppm and 1816 ppm 29). In compounds 12, 15 and 18
solvent independent 207Pb chemical shifts were found in a
similar range while for aliphatic group substituted plumbylenes
12 and 15 the ∼200 ppm higher chemical shift were observed.
5012 | Dalton Trans., 2012, 41, 5010–5019
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Fig. 3 Molecular structure of [LDippSnCl]2 (9) (ORTEP view, 50%
probability level). Hydrogen atoms are omitted for clarity. Selected
interatomic distances [Å] and angles [°]: N1–C1 1.322(11); N1–C2
1.422(12); N2–C1 1.316(12); N2–C14 1.419(13); C1–C26 1.523(13);
N3–C101 1.320(12); N4–C101 1.342(12); N3–C102 1.427(12); N4–
C114 1.426(12); C101–C126 1.487(13); N1–Sn1 2.192(8); N2–Sn1
2.251(9); N3–Sn2 2.248(9); N4–Sn2 2.198(8); C1–Sn1 2.662(9); C101–
Sn2 2.678(9); Cl1–Sn1 2.482(2); Cl2–Sn1 2.986(3); Cl2–Sn2 2.484(2);
Cl1–Sn2 3.033(3); N1–C1–N2 112.3(8); N3–C101–N4 111.1(8); C2–
C1–C14 167.4(5); C102–C101–C114 166.3(5); N1–Sn1–N2 59.0(3);
N4–Sn2–N3 59.2(3); C1–Sn1–Cl1 96.33(19); C101–Sn2–Cl2 96.89
(19); Sn1–Cl1–Sn2 101.98(9); Cl1–Sn1–Cl2 77.80(8).
Fig. 4 Molecular structure of LCySnCl (7) (ORTEP view, 50% prob-
ability level). Hydrogen atoms are omitted for clarity. Selected intera-
tomic distances [Å] and angles [°]: N1–C1 1.325(4); N1–C2 1.459(4);
N1–Sn1 2.195(3); N1a–C1 1.325(4); N1a–C2a 1.459(4); N1a–Sn1
2.195(3); C1–Sn1 2.661(6); Sn1–Cl1 2.4823(18); C1–C8 1.506(7);
Cl1–Sn1b 3.4089(19); C1b–Sn1 3.597(6); N1–C1–N1a 110.4(4); N1–
Sn1–N1a 59.40(10); C1–Sn1–Cl1 96.67(13); C1–C8–C9 113.2(4);
C2a–C1–C2 165.8(3); Sn1–Cl1–Sn1b 97.96(6); Sn1–C1b–Sn1b 90.32
(17).
atom. The coordination polyhedra are completed by a weak inter-
action with the second type of chlorine atoms. The interactions
between the tin atoms and coordinated chlorine atoms Sn1–Cl2
and Sn2–Cl1 are much longer than the covalent bonds Sn–Cl
but still in the range of the sum of the van der Waals radii of
both atoms. The intermolecular interaction Sn–Cl in [t-Bu-NC
(Ph)N-t-Bu]SnCl6d which forms an infinite linear chain is even
weaker (3.602 Å) than the same type of connection in 9. The
rest of interatomic distances and angles is comparable with the
same values found in the previously published monomeric het-
eroleptic amidinato stannylene [Dipp-NC(t-Bu)N-Dipp]SnCl.25
The new type of intermolecular connection is responsible for
the formation of a dimer of 7. The molecules are interconnected
by one weak Sn1b–Cl1 contact and an interaction of the tin atom
Sn1 with a delocalized N1c–C1b(C8b)–N1b system of the ami-
dinato ligand of the second molecule. To the best of our knowl-
edge, this type of interaction has not been known up until now
in the chemistry of amidinato and related ligands of the main
group metals. The saturation of the tin empty orbitals with
π-electrons of the second amidinato unit is probably the reason
for this interaction. The shape of coordination polyhedra of the
tin atom in 7 is quite similar to the shape of the polyhedra in 9.
The characteristic C1–Sn1–Cl1 angle and the covalent Sn–Cl
bond distances in stannylene 7 and 9 are comparable with the
same parameters in the known heteroleptic stannylenes [Dipp-
NC(t-Bu)N-Dipp]SnCl25 (96.64(3)°; 2.4282(6) Å) and [t-Bu-NC
(Ph)N-t-Bu]SnCl6d (95.43(7)°; 2.4831(9) Å). On the other hand,
the changing of these parameters (shortening of the bonding dis-
tance and extension of the interatomic angle) going from the dis-
cussed stannylenes to germylenes 8, [Dipp-NC(t-Bu)N-Dipp]
GeCl (104.61(18)°; 2.174(2) Å) and [t-Bu-NC(Ph)N-t-Bu]GeCl
(100.21(5)°; 2.2572(13) Å) is caused by the difference in
covalent radii of both central atoms (Fig. 3 and 4).
Fig. 5 Molecular structure of {[LiPr2SnCl]-μ2-(OSnCl)}2 (5a) (ORTEP
view, 50% probability level). Hydrogen atoms are omitted for clarity.
Selected interatomic distances [Å] and angles [°]: N1–C1 1.322(9); N1–
C2 1.456(9); N2–C1 1.340(8); N2–C5 1.467(9); C1–C8 1.516(8); N3–
C12 1.338(8); N4–C12 1.339(8); N3–C13 1.482(8); N4–C16 1.475(7);
C12–C19 1.339(8); N1–Sn1 2.203(5); N2–Sn1 2.141(5); N3–Sn1 2.200
(5); N4–Sn1 2.153(5); C1–Sn1 2.611(6); C12–Sn1 2.633(7); Cl1–Sn1
2.4287(17); O1–Sn1 2.028(4); O1–Sn2 2.117(5); Cl2–Sn2 2.4801(19);
O1–Sn2a 2.134(3); N1–C1–N2 112.3(5); N3–C12–N4 111.0(6); C2–
C1–C5 169.7(3); C13–C12–C16 169.1(4); N1–Sn1–N2 61.15(19); N4–
Sn1–N3 60.93(18); C1–Sn1–Cl1 93.49(13); C12–Sn1–O1 95.05(19);
C1–Sn1–C12 119.4(2); O1–Sn2–Cl2 95.35(13); O1–Sn1–Cl1 89.20
(12); Sn2–O1–Sn2a 103.00(17); Sn2–Sn2a–Cl2a 97.78(9).
The tetranuclear structure of 5a consists of the central Sn2O2
planar ring where the tin atoms are in the oxidation state +II with
the coordination vicinity of a trigonal pyramid. Each of the tin
(Sn2, Sn2a) coordination polyhedra is constructed of two brid-
ging oxygens, one chlorine atom at the base of the pyramid and
the lone electron pair situated in an apical position. The arrange-
ment of this fragment as well as the interatomic distances and
angles (see Fig. 5) are very close to the reported compounds
This journal is © The Royal Society of Chemistry 2012
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Table 2 Crystallographic data for 7, 8, 9, 5a and LCyHI·C6H6
Compound reference
LCySnCl (7)
LDippGeCl·1/18 Et2O (8)
[LDippSnCl]2 (9) {[LiPr2SnCl]OSnCl}2 (5a) LCyHI·C6H6
Chemical formula
Formula mass
Crystal system
a/Å
b/Å
c/Å
α (°)
C17H31ClN2Sn C29H43ClGeN2·1/18(C4H10O) C58H86Cl2N4Sn2 C44H92Cl4N8O2Sn4
C23H39N2I
470.46
Monoclinic
10.5760(9)
15.2480(6)
15.1009(11)
90
417.58
Orthorhombic
17.1751(9)
12.4098(11)
8.8522(9)
90
540.05
1147.59
Monoclinic
9.8450(10)
28.878(2)
10.6540(8)
90
1381.82
Monoclinic
23.5241(9)
17.8710(11)
16.6439(7)
90
Hexagonal
40.6731(2)
40.6731(2)
9.5350(4)
90
β (°)
γ (°)
90
90
1886.7(3)
150(1)
Cmc21
4
1.493
9173
2211
0.0354
0.0270
0.0554
1.127
90
120
13 660.5(7)
150(1)
ˉ
R3
104.068(7)
90
2938.1(4)
150(1)
P21
123.122(12)
90
5860.0(3)
150(1)
C2/c
98.247(7)
90
2410.0(3)
150(1)
P21/c
Unit cell volume/Å3
T/K
Space group
No. of formula units per unit cell, Z
Absorption coefficient, μ/mm−1
No. of reflections measured
No. of independent reflections
Rint
Final R1 values (I > 2σ(I))
Final wR(F2) values (I > 2σ(I))
Goodness of fit on F2
18
2
4
4
1.114
31 427
6764
0.0683
0.0675
0.1210
1.076
0.979
1.907
47 387
6389
0.0594
0.0491
0.0690
1.188
1.337
17 797
5456
0.0355
0.0301
0.0571
1.139
27 606
12 365
0.0982
0.0707
0.1534
1.075
a Ri2nt = ∑ |Fo2 − Fo,mean2|/∑Fo . b S = [∑(w(Fo2 − Fc ) )/(Ndiffr. − Nparam.)]1/2
.
c Weighting scheme: w = [σ2(Fo ) + (w1P)2 + w2P]−1, where P = [max
2
2 2
2
(Fo ) + 2Fc ], R(F) = ∑||Fo| − |Fc||/∑|Fo|, wR(F2) = [∑(w(Fo2 − Fc ) )/(∑w(Fo ) )]1/2
.
2
2 2
2 2
33
[SnCl-μ2-(OtBu)]2 and {SnCl-μ2-[OCr(NMe2)2Cl2(THF)]}2.34
The only difference is the larger deviation of Sn–Cl bonds from
the perpendicular arrangement with the central Sn2O2 plane
(Sn2–Sn2a–Cl2a 97.78(9)°). Two tin(IV) atoms on the periphery
of the molecule are joined to two tin(II) atoms by a three-centric
oxygen bridge in an alternating fashion – 0.314 Å below and
above the central plane, respectively. These tin atoms (Sn1,
Sn1a) are pseudo-octahedrally coordinated by two asymmetri-
cally bonded amidinato ligands in bidentate mode, chlorine and
oxygen atom. The Sn1–Cl1 bond is parallel to the central Sn2O2
plane and shortened in comparison to the Sn2–Cl2 bond by ca.
0.05 Å. The asymmetrical bonding of the amidinato units, which
are mutually nearly parallel (85.47(9)°), is probably caused by
the stronger trans-effect of oxygen and chlorine atoms, where
the differences in Sn–N distances are about 0.05 Å.
obtained by dissolving of approximately 40 mg (100 mg for
207Pb measurements) of each compound approximately in 0.5 ml
of deuterated solvents. H chemical shifts were calibrated to an
1
internal standard—tetramethylsilane (δ(1H) = 0.00) or to residual
signals of benzene (δ(1H) = 7.16) and THF (δ(1H) = 3.58 or
1.73). The values of 13C chemical shifts were calibrated to
signals of THF (δ(13C) = 67.6) and benzene (δ(13C) = 128.4).
All 13C NMR spectra were measured using a standard proton-
decoupled experiment and CH and CH3 vs. C and CH2 were dif-
ferentiated using the APT method.36 The 119Sn and 207Pb chemi-
cal shifts are referred to as external neat tetramethylstannane (δ =
0.0) and tetraethyllead (δ = 0.0), respectively, and measured
using the inverse gated proton broad band decoupling mode.
The solid state NMR spectra were measured at 11.7 T using a
Bruker Avance 500 WB/US NMR spectrometer in a double-res-
onance 4-mm probe head. Direct-polarization MAS NMR exper-
iments with a high-power dipolar decoupling (TPPM) and
sufficiently long recycle delays (RD) were preformed to obtain
quantitative NMR spectra. 207Pb MAS NMR spectra were
acquired at 104.52 MHz; the spinning frequency was ωr/2π = 11
and 13 kHz; 90° pulse width was 3 μs; recycle delay of 10 s; and
the number of scans was 2048. The spectra were referenced to
Pb(NO3)2 at 0.0 ppm. 119Sn MAS NMR spectra were acquired at
186.49 MHz; the spinning frequency was ωr/2π = 11 and 13
kHz; 90° pulse width was 3 μs; a recycle delay of 15 s; and the
number of scans was 8200. The 119Sn chemical shifts were cali-
brated indirectly using tetracyclohexyl tin (δ = −97.35 ppm).
The 119Sn NMR chemical shift was allocated approximately in
the centre of gravity of the signal.
Compound 5a is the third example of the tin(IV)bisamidinato
substituted complex but the mutual comparison with previously
reported bisamidinato tin sulfides is not very interesting because
of the highly disordered structure with a strongly polarized
double tin–sulfur bond in the first case and the less electrophilic
sulfur substituents of the octahedral tin atom in the other one.35
3. Experimental
3.1 General methods
3.1.1 NMR spectroscopy. The NMR spectra of the com-
pounds measured were recorded from solutions in benzene-d6
and THF-d8 on a Bruker Avance 500 spectrometer (equipped
with Z-gradient 5mm probe) at frequencies for 1H
(500.13 MHz), 13C{1H} (125.76 MHz), and 119Sn{1H}
(186.50 MHz) at 295 K and on a Bruker Avance II 400 spec-
3.1.2 Elemental analyses. The compositional analyses were
determined under an inert atmosphere of argon on the automatic
analyzer EA 1108 by FISONS Instruments.
1
trometer operating at 400.13 MHz for H, and 81.49 MHz for
207Pb at 295 K. All deuterated solvents were degassed and then
stored over a K-mirror under argon atmosphere. Solutions were
3.1.3 Crystallography. The X-ray data (Table 2) obtained
from colourless crystals for all compounds were acquired at
5014 | Dalton Trans., 2012, 41, 5010–5019
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150 K using an Oxford Cryostream low-temperature device on a
Nonius KappaCCD diffractometer with Mo-Kα radiation (λ =
0.71073 Å), a graphite monochromator, and in the ϕ and χ scan
mode. Data reductions were performed with DENZO-SMN.37
The absorption was corrected using integration methods.38 The
structures were solved by direct methods (Sir92)39 and refined
by a full matrix least-square based on F2 (SHELXL97).40 Hydro-
gen atoms were mostly localized on a difference Fourier map,
but in order to ensure uniformity of the crystal treatment, all
hydrogen atoms were recalculated into idealized positions
(riding model) and assigned temperature factors Hiso(H) =
1.2Ueq(pivot atom) or of 1.5Ueq for the methyl moiety with C–H
= 0.96, 0.97, 0.98 and 0.93 Å for methyl, methylene, methine
and hydrogen atoms in aromatic rings and 0.86 Å for N–H,
respectively. The positional disorder of Ge and Cl atoms in 8 is
split into two positions with approximate ratio 9 : 1 and treated
by standard SHELXL9740 procedures. Higher residual electron
density in 9 was treated using several methods but no better
results of refinement were obtained, this maximum gave no
chemical significance.
Et2O. 1.13 g (92%) of colourless oily matter of 4. 1H NMR
(C6D6, 500 MHz, 295 K) δ: 3.41 (m, 2H, CH); 1.81 (t, J = 7.9
3
Hz, 2H, α-CH2(Bu)); 1.26 (m, 2H, β-CH2(Bu)); 1.15 (m, 2H,
3
γ-CH2(Bu)); 1.02 (br s, 12H, (CH3)2); 0.93 (t, 3H, J = 7.3 Hz,
CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 174.2 (NvC(Bu)–
N); 46.1 (CH); 28.6 (α-CH2(Bu)); 25.3 (β-CH2(Bu)); 23.3 (br s,
(CH3)2); 22.5 (γ-CH2(Bu)); 13.5 (CH3). Elemental Anal. Calcd
(%) for C11H23ClGeN2: C 45.34; H 7.96; N 9.61. Found: C
45.12; H 7.85; N 9.78.
3.2.2 Preparation of N,N′-di(propan-2-yl)n-butylamidinato-
tin(II) chloride (LiPrSnCl) (5). 1.22 g of 1 (6.3 mmol), 1.19 g of
SnCl2 (6.3 mmol), 30 ml of Et2O. 1.83 g (84%) of colourless
1
oily matter of 5. H NMR (C6D6, 500 MHz, 295 K) δ: 3.57 (m,
3
2H, CH); 1.82 (t, J = 8.1 Hz, 2H, α-CH2(Bu)); 1.31 (m, 2H,
3
β-CH2(Bu)); 1.15 (m, 2H, γ-CH2(Bu)); 1.00 (d, 12H, J = 6.3
3
Hz, (CH3)2); 0.77 (t, 3H, J = 7.3 Hz, CH3). 13C NMR (C6D6,
125 MHz, 295 K) δ: 178.1 (NvC(Bu)–N); 46.6 (CH); 29.9
(α-CH2(Bu)); 27.4 (β-CH2(Bu)); 26.1 ((CH3)2); 23.5
(γ-CH2(Bu)); 14.3 (CH3). 119Sn NMR (C6D6, 186 MHz, 295 K)
1
δ: 78.9. H NMR (THF-d8, 500 MHz, 295 K) δ: 3.88 (m, 2H,
CH); 2.25 (t, 3J = 8.0 Hz, 2H, α-CH2(Bu)); 1.58 (m, 2H,
3
3.2 Synthesis
β-CH2(Bu)); 1.45 (m, 2H, γ-CH2(Bu)); 1.12 (d, 12H, J = 6.3
Hz, (CH3)2); 0.96 (t, 3H, 3J = 7.3 Hz, CH3). 13C NMR (THF-d8,
125 MHz, 295 K) δ: 176.2 (NvC(Bu)–N); 45.0 (CH); 28.5
(α-CH2(Bu)); 25.6 (β-CH2(Bu)); 24.2 ((CH3)2); 21.7
(γ-CH2(Bu)); 12.4 (CH3). 119Sn NMR (THF-d8, 186 MHz,
295 K) δ: 69.1. Elemental Anal. Calcd (%) for C11H23ClN2Sn:
C 39.15; H 6.87; N 8.30. Found: C 39.33; H 6.69; N 8.36.
All syntheses were performed using the standard Schlenk tech-
niques under inert argon atmosphere. Solvents and reactants
were purchased from commercial sources. Solvents were distilled
over K/Na alloy, degassed and then stored over a K-mirror under
argon atmosphere. Single crystals suitable for X-ray diffraction
analyses were obtained under argon from corresponding satu-
rated solutions of products in Et2O or hexane cooled to −30 °C.
The melting points were measured in inert perfluoroalkylether
and were uncorrected. Preparations of starting lithium N,N′-di
(propan-2-yl)n-butylamidinate (1), lithium N,N′-bis(cyclohexyl)
n-butylamidinate (2) and lithium N,N′-bis[2,6-di(propan-2-yl)
phenyl]n-butylamidinate (3) are reported elsewhere.19
3.2.3 Oxidation product of 5 – {[LiPr2SnCl]-μ2-(OSnCl)}2
(5a). After standing of 1.2 g of 5 in 50 ml of Et2O in a not well
greased Schlenk tube at −30 °C for three weeks, about 150 mg
of insoluble colorless solid of 5a has been reproducibly crystal-
lized. Mp 112–113 °C. 13C CP/MAS NMR (125 MHz, 295 K)
δ: 164.1; 47.6; 44.7; 30.1; 22.0; 14.2. 119Sn CP/MAS NMR
(186 MHz, 295 K) δ: −598.1. Elemental Anal. Calcd (%) for
C44H92Cl4N8O2Sn4: C 38.24; H 6.71; N 8.11. Found: C 38.52;
H 6.39; N 8.45.
General procedure of preparation of heteroleptic tetrylene
amidinates LRMCl (4–9)
To a white suspension of metal(II) chloride in Et2O cooled
down to −60 °C, one equivalent of pure starting lithium N,N′-
disubstituted n-butylamidinate precursor 1–3 dissolved in Et2O
was added. The reaction mixtures were slowly heated up to room
temperature and stirred overnight. After that they were filtered
from forming lithium chloride and Et2O was evaporated under
vacuo to give products of heteroleptic tetrylenes 4–9 in good
yields.
3.2.4 Preparation of N,N′-bis(cyclohexyl)n-butylamidinato-
germanium(II) chloride (LCyGeCl) (6). 1.86 g of 2 (6.8 mmol),
1.59 g of GeCl2 dioxane complex (1 : 1) (6.8 mmol), 40 ml of
Et2O. 2.29 g (90%) of white solid of 6. Mp 97–98.5 °C. 1H
NMR (C6D6, 500 MHz, 295 K) δ: 3.28 (m, 2H, CyH); 2.01 (t,
3
2H, J = 8.0 Hz, α-CH2(Bu)); 1.86 (s, 4H, CyH); 1.72 (m, 4H,
CyH); 1.52–1.41 (m, 10H, CyH + β-CH2(Bu)); 1.27–1.06 (m,
General procedure of preparation of homoleptic tetrylene
3
6H, CyH + γ-CH2(Bu)); 0.85 (t, 3H, J = 7.2 Hz, CH3). 13C
amidinates (LR)2M (10–18)
NMR (C6D6, 125 MHz, 295 K) δ: 174.8 (NvC(Bu)–N); 54.4
(Cy); 37.0 (Cy); 29.7 (α-CH2(Bu)); 26.1 (β-CH2(Bu)); 26.0
(Cy); 25.7 (Cy); 23.2 (γ-CH2(Bu)); 14.2 (CH3). Elemental Anal.
Calcd (%) for C17H31ClGeN2: C 54.96; H 8.41; N 7.54. Found:
C 55.13; H 8.63; N 7.37.
To a white suspension of metal(II) chloride in Et2O at room
temperature, two equivalents of pure colorless Et2O solution of
starting lithium precursor 1–3 were added (reactions with lead
dichloride have to be performed in the dark because of elimin-
ation of elemental Pb). The reaction mixtures were stirred over-
night, filtered from forming lithium chloride and Et2O was
evaporated under vacuo. Pure products of homoleptic tetrylenes
10–18 in good yields were obtained.
3.2.5 Preparation of N,N′-bis(cyclohexyl)n-butylamidinato-
tin(II) chloride (LCySnCl) (7). 3.58 g of 2 (13.3 mmol), 2.51 g
of SnCl2 (13.3 mmol), 60 ml of Et2O. Washed with 10 ml of
pentane. 4.72 g (85%) of white solid of 7. Mp 88.5–90.5 °C.
Single crystalline material suitable for XRD analyses were
obtained under argon from saturated solution of 7 in Et2O cooled
3.2.1 Preparation of N,N′-di(propan-2-yl)n-butylamidinato-
germanium(II) chloride (LiPrGeCl) (4). 0.81 g of 1 (4.2 mmol),
0.97 g of GeCl2 dioxane complex (1 : 1) (4.2 mmol), 30 ml of
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1
to −30 °C. H NMR (C6D6, 500 MHz, 295 K) δ: 3.31 (m, 2H,
NMR (THF-d8, 125 MHz, 295 K) δ: 175.9 (NvC(Bu)–N);
148.2 (Ar); 145.5 (br s, Ar); 140.5 (Ar); 126.3 (Ar); 124.2 (Ar);
123.6 (Ar); 31.6 (α-CH2(Bu)); 29.4 (CH); 29.3 (br s, CH); 29.1
(CH); 27.8 (β-CH2(Bu)); 26.7 ((CH3)2); 24.0 ((CH3)2); 23.7
(γ-CH2(Bu)); 13.8 (CH3). 119Sn NMR (THF-d8, 186 MHz,
295 K) δ: −124.0. Elemental Anal. Calcd (%) for
C29H43ClN2Sn: C 60.70; H 7.55; N 4.88. Found: C 60.72; H
7.48; N 4.59.
CyH); 1.92 (t, 2H, 3J = 8.0 Hz, α-CH2(Bu)); 1.77 (m, 4H, CyH);
1.61 (m, 4H, CyH); 1.48–1.36 (m, 4H, CyH + β-CH2(Bu));
3
1.25–1.01 (m, 12H, CyH + γ-CH2(Bu)); 0.77 (t, 3H, J = 7.3
Hz, CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 177.8 (NvC
(Bu)–N); 54.3 (Cy); 36.9 (Cy); 30.2 (α-CH2(Bu)); 27.4
(β-CH2(Bu)); 26.1 (Cy); 25.8 (Cy); 23.4 (γ-CH2(Bu)); 14.3
(CH3). 119Sn NMR (C6D6, 186 MHz, 295 K) δ: 75.7. H NMR
1
(THF-d8, 500 MHz, 295 K) δ: 3.41 (m, 2H, CyH); 2.19 (t, 2H,
3J = 7.4 Hz, α-CH2(Bu)); 1.64 (m, 6H, CyH); 1.50 (m, 4H,
CyH); 1.38 (m, 2H, β-CH2(Bu)); 1.27–1.05 (m, 12H, CyH +
γ-CH2(Bu)); 0.89 (t, 3H, 3J = 7.3 Hz, CH3). 13C NMR (THF-d8,
125 MHz, 295 K) δ: 177.9 (NvC(Bu)–N); 54.5 (Cy); 37.0
(Cy); 30.6 (α-CH2(Bu)); 27.5 (β-CH2(Bu)); 26.5 (Cy); 26.1
(Cy); 23.7 (γ-CH2(Bu)); 14.4 (CH3). 119Sn NMR (THF-d8,
186 MHz, 295 K) δ: 69.7. Elemental Anal. Calcd (%) for
C17H31ClN2Sn: C 48.89; H 7.48; N 6.71. Found: C 48.96; H
7.25; N 6.56.
3.2.8 Preparation of bis[N,N′-di(propan-2-yl)n-butyl-amidi-
nato]germanium(II) (LiPr2Ge) (10). 1.68 g of 1 (8.8 mmol),
1.02 g of GeCl2 dioxane complex (1 : 1) (4.4 mmol), 40 ml of
1
Et2O. 1.54 g (79%) of pale yellow oily matter of 10. H NMR
3
(C6D6, 500 MHz, 295 K) δ: 3.70 (m, 4H, CH); 2.11 (t, J = 8.1
Hz, 4H, α-CH2(Bu)); 1.42 (m, 4H, β-CH2(Bu)); 1.36 (d, 24H, 3J
3
= 6.5 Hz, (CH3)2); 1.21 (m, 4H, γ-CH2(Bu)); 0.83 (t, 6H, J =
7.3 Hz, CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 165.8
(NvC(Bu)–N); 47.3 (CH); 29.7 (α-CH2(Bu)); 25.4
(β-CH2(Bu)); 25.2 ((CH3)2); 22.9 (γ-CH2(Bu)); 13.6 (CH3).
Elemental Anal. Calcd (%) for C22H46GeN4: C 60.15; H 10.56;
N 12.75. Found: C 60.43; H 10.32; N 12.63.
3.2.6 Preparation of N,N′-bis[2,6-di(propan-2-yl)phenyl]n-
butylamidinato-germanium(II) chloride (LDippGeCl) (8). 2.43 g
of 3 (5.7 mmol), 1.32 g of GeCl2 dioxane complex (1 : 1)
(5.7 mmol), 50 ml of Et2O. 2.81 g (93%) of pale yellow solid of
8. Mp 161–162 °C. Single crystalline material suitable for XRD
analyses were obtained under argon from saturated solution of 8
in Et2O cooled to −30 °C. 1H NMR (C6D6, 500 MHz, 295 K) δ:
7.26–7.16 (m, 6H, ArH); 4.02 (m, 2H, CH); 3.48 (m, 2H, CH);
3.2.9 Preparation of bis[N,N′-di(propan-2-yl)n-butyl-amidi-
nato]tin(II) (LiPr2Sn) (11). 0.73 g of 1 (3.8 mmol), 0.36 g of
SnCl2 (1.9 mmol), 30 ml of Et2O. 0.81 g (88%) of colourless
oily matter of 11. 1H NMR (C6D6, 500 MHz, 295 K) δ: 3.77 (m,
3
4H, CH); 2.10 (t, 4H, J = 8.1 Hz, α-CH2(Bu)); 1.44 (m, 4H,
3
β-CH2(Bu)); 1.31 (d, 24H, J = 6.5 Hz, (CH3)2); 1.24 (m, 4H,
3
3
2.05 (t, J = 8.2 Hz, 2H, α-CH2(Bu)); 1.52 (d, J = 6.3 Hz, 6H,
3
γ-CH2(Bu)); 0.85 (t, 6H, J = 7.3 Hz, CH3). 13C NMR (C6D6,
(CH3)2); 1.39 (d, 3J = 6.4 Hz, 6H, (CH3)2); 1.33 (d, 3J = 6.6 Hz,
6H, (CH3)2); 1.29 (m, 2H, β-CH2(Bu)); 1.21 (d, J = 6.4 Hz,
125 MHz, 295 K) δ: 168.2 (NvC(Bu)–N); 47.4 (CH); 29.8
(α-CH2(Bu)); 25.8 (β-CH2(Bu)); 25.7 ((CH3)2); 23.0
(γ-CH2(Bu)); 13.7 (CH3). 119Sn NMR (C6D6, 186 MHz, 295 K)
δ: −252.3. Elemental Anal. Calcd (%) for C22H46N4Sn: C
54.44; H 9.55; N 11.54. Found: C 54.71; H 9.83; N 11.34.
3
6H, (CH3)2); 0.76 (m, 2H, γ-CH2(Bu)); 0.50 (t, 3J = 7.2 Hz, 3H,
CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 177.2 (NvC(Bu)–
N); 147.2 (Ar); 144.5 (Ar); 136.8 (Ar); 127.7 (Ar); 124.9 (Ar);
124.0 (Ar); 29.8 (α-CH2(Bu)); 29.0 (β-CH2(Bu)); 27.1 (CH);
27.0 (CH); 23.6 ((CH3)2); 23.4 ((CH3)2); 23.1 (γ-CH2(Bu)); 13.7
(CH3). Elemental Anal. Calcd (%) for C29H43ClGeN2: C 66.00;
H 8.21; N 5.31. Found: C 66.22; H 8.25; N 5.12.
3.2.10 Preparation of bis[N,N′-di(propan-2-yl)n-butyl-ami-
dinato]lead(II) (LiPr2Pb) (12). 0.87 g of 1 (4.6 mmol), 0.63 g of
PbCl2 (2.3 mmol), 30 ml of Et2O. 1.08 g (82%) of colourless
oily matter of 12. 1H NMR (C6D6, 500 MHz, 295 K) δ: 4.53 (m,
3
3.2.7 Preparation of N,N′-bis[2,6-di(propan-2-yl)phenyl]n-
butylamidinatotin(II) chloride (LDippSnCl) (9). 6.29 g of 3
(14.7 mmol), 2.79 g of SnCl2 (14.7 mmol), 60 ml of Et2O. Crys-
tallized from hexane and Et2O (1 : 1). 5.56 g (66%) of white
solid of 9. Mp 193–195 °C. Single crystalline material suitable
for XRD analyses were obtained under argon from a saturated
solution of 9 in Et2O cooled to −30 °C. 1H NMR (C6D6,
500 MHz, 295 K) δ: 7.10 (br s, 6H, ArH); 3.98 (br s, 2H, CH);
4H, CH); 2.09 (t, 4H, J = 8.1 Hz, α-CH2(Bu)); 1.56 (m, 4H,
3
β-CH2(Bu)); 1.30 (m, 4H, γ-CH2(Bu)); 1.29 (d, 24H, J = 6.3
3
Hz, (CH3)2); 0.88 (t, 6H, J = 7.3 Hz, CH3). 13C NMR (C6D6,
125 MHz, 295 K) δ: 168.8 (NvC(Bu)–N); 47.9 (CH); 30.7
(α-CH2(Bu)); 30.0 (β-CH2(Bu)); 26.7 ((CH3)2); 23.7
(γ-CH2(Bu)); 14.1 (CH3). 207Pb NMR (C6D6, 81 MHz, 295 K)
δ: 1734.8. 1H NMR (THF-d8, 500 MHz, 295 K) δ: 4.48 (m, 2H,
CH); 2.14 (t, 4H, 3J = 8.1 Hz, α-CH2(Bu)); 1.53 (m, 4H,
3
3
3.68 (m, 1H, CH); 3.55 (m, 1H, CH); 1.91 (t, J = 8.1 Hz, 2H,
β-CH2(Bu)); 1.40 (m, 4H, γ-CH2(Bu)); 1.13 (d, 24H, J = 6.3
Hz, (CH3)2); 0.94 (t, 6H, 3J = 7.3 Hz, CH3). 13C NMR (THF-d8,
125 MHz, 295 K) δ: 169.5 (NvC(Bu)–N); 48.6 (CH); 31.4
(α-CH2(Bu)); 30.5 (β-CH2(Bu)); 26.9 ((CH3)2); 24.4
(γ-CH2(Bu)); 14.5 (CH3). 207Pb NMR (THF-d8, 81 MHz,
295 K) δ: 1743.5. Elemental Anal. Calcd (%) for C22H46N4Pb:
C 46.05; H 8.08; N 9.76. Found: C 46.01; H 8.23; N 9.63.
α-CH2(Bu)); 1.28 (br s, 24H, (CH3)2); 1.15 (m, 2H, β-CH2(Bu));
3
0.60 (m, 2H, γ-CH2(Bu)); 0.39 (t, J = 7.3 Hz, 3H, CH3). 13C
NMR (C6D6, 125 MHz, 295 K) δ: 179.2 (NvC(Bu)–N); 147.6
(Ar); 145.1 (Ar); 138.6 (Ar); 127.0 (Ar); 124.8 (Ar); 124.1 (Ar);
31.5 (α-CH2(Bu)); 29.2 (br s, CH); 27.3 (β-CH2(Bu)); 27.1 (br
s, CH); 23.6 (br s, (CH3)2); 23.2 (γ-CH2(Bu)); 13.7 (CH3). 119Sn
NMR (C6D6, 186 MHz, 295 K) δ: 29.4. 1H NMR (THF-d8,
500 MHz, 295 K) δ: 7.15 (s, 4H, ArH); 7.08 (m, 2H, ArH); 3.57
3.2.11 Preparation of bis[N,N′-bis(cyclohexyl)n-butyl-amidi-
nato]germanium(II) (LCy2Ge) (13). 0.93 g of 2 (3.4 mmol),
0.39 g of GeCl2 dioxane complex (1 : 1) (1.7 mmol), 30 ml of
3
(s, 2H, CH); 3.29 (m, 1H, CH); 3.17 (m, 1H, CH); 1.87 (t, J =
3
8.4 Hz, 2H, α-CH2(Bu)); 1.29 (d, 12H, J = 6.9 Hz, (CH3)2);
3
1
1.24 (d, 12H, J = 6.7 Hz, (CH3)2); 1.16 (m, 2H, β-CH2(Bu));
Et2O. 0.86 g (84%) of pale yellow oily matter of 13. H NMR
3
3
0.87 (m, 2H, γ-CH2(Bu)); 0.52 (t, J = 7.3 Hz, 3H, CH3). 13C
(C6D6, 500 MHz, 295 K) δ: 3.28 (m, 4H, CyH); 2.20 (t, 4H, J
5016 | Dalton Trans., 2012, 41, 5010–5019
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3.2.15 Preparation of bis[N,N′-bis[2,6-di(propan-2-yl)phenyl]-
n-butylamidinato]tin(II) (LDipp2Sn) (17). 4.61 g of 3 (10.8 mmol),
1.02 g of SnCl2 (5.4 mmol), 50 ml of Et2O. Extracted with
30 ml of hexane. 3.89 g (75%) of white solid of 17. Mp
= 7.7 Hz, α-CH2(Bu)); 1.87–1.71 (br m, 20H, CyH); 1.59–1.43
(br m, 8H, CyH + β-CH2(Bu)); 1.35–1.15 (br m, 20H, CyH +
3
γ-CH2(Bu)); 0.85 (t, 6H, J = 7.3 Hz, CH3). 13C NMR (C6D6,
125 MHz, 295 K) δ: 166.1 (NvC(Bu)–N); 56.2 (Cy); 35.7
(Cy); 30.0 (α-CH2(Bu)); 26.2 (β-CH2(Bu)); 25.8 (Cy); 25.1
(Cy); 22.8 (γ-CH2(Bu)); 13.7 (CH3). Elemental Anal. Calcd (%)
for C34H62GeN4: C 68.11; H 10.42; N 9.35. Found: C 68.03; H
10.61; N 9.58.
1
63–65 °C. H NMR (C6D6, 500 MHz, 295 K) δ: 7.14–6.97 (br
m, 12H, ArH); 3.70 (s, 4H, CH); 3.35 (s, 2H, CH); 3.15 (m, 2H,
CH); 1.86 (s, 4H, α-CH2(Bu)); 1.48–1.11 (br m, 52H,
3
β-CH2(Bu) + (CH3)2); 0.48 (m, 4H, γ-CH2(Bu)); 0.36 (t, J =
7.3 Hz, 6H, CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 171.7
(NvC(Bu)–N); 145.0 (Ar); 144.4 (Ar); 142.2 (Ar); 126.0 (Ar);
123.9 (Ar); 123.7 (Ar); 32.0 (α-CH2(Bu)); 28.5 (br s, CH); 27.2
(β-CH2(Bu)); 25.1 (br s, CH); 23.8 (br s, (CH3)2); 23.3
(γ-CH2(Bu)); 13.6 (CH3). 119Sn NMR (C6D6, 186 MHz, 295 K)
δ: −341.3. Elemental Anal. Calcd (%) for C58H86N4Sn: C
72.71; H 9.05; N 5.85. Found: C 72.59; H 9.24; N 5.63.
3.2.12 Preparation of bis[N,N′-bis(cyclohexyl)n-butyl-amidi-
nato]tin(II) (LCy2Sn) (14). 2.18 g of 2 (8.1 mmol), 0.76 g of
SnCl2 (4.0 mmol), 40 ml of Et2O. 2.11 g (82%) of colourless
oily matter of 14. 1H NMR (C6D6, 500 MHz, 295 K) δ: 3.38 (m,
3
4H, CyH); 2.19 (t, 4H, J = 7.8 Hz, α-CH2(Bu)); 1.92–1.73 (br
m, 20H, CyH); 1.67–1.48 (br m, 8H, CyH + β-CH2(Bu));
3
1.38–1.10 (br m, 20H, CyH + γ-CH2(Bu)); 0.87 (t, 6H, J = 7.3
Hz, CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 168.8 (NvC
(Bu)–N); 56.6 (Cy); 36.5 (Cy); 30.2 (α-CH2(Bu)); 26.3
(β-CH2(Bu)); 26.0 (Cy); 25.9 (Cy); 23.1 (γ-CH2(Bu)); 13.9
(CH3). 119Sn NMR (C6D6, 186 MHz, 295 K) δ: −255.3.
Elemental Anal. Calcd (%) for C34H62N4Sn: C 63.25; H 9.68; N
8.68. Found: C 63.46; H 9.52; N 8.39.
3.2.16 Preparation of bis[N,N′-bis[2,6-di(propan-2-yl)phenyl]-
n-butylamidinato]lead(II) (LDipp2Pb) (18). 0.77
g
of
3
(1.8 mmol), 0.25 g of PbCl2 (0.9 mmol), 30 ml of Et2O. 0.82 g
(87%) of colourless oily matter of 18. 1H NMR (C6D6,
3
500 MHz, 295 K) δ: 7.09 (br s, 8H, ArH); 7.09 (t, 4H, J = 7.5
Hz, ArH); 3.46 (br s, 8H, CH); 1.88 (s, 4H, α-CH2(Bu)); 1.30
(br s, 48H, (CH3)2); 1.06 (m, 4H, β-CH2(Bu)); 0.59 (m, 4H,
3
γ-CH2(Bu)); 0.37 (t, J = 7.2 Hz, 6H, CH3). 13C NMR (C6D6,
3.2.13 Preparation of bis[N,N′-bis(cyclohexyl)n-butyl-amidi-
nato]lead(II) (LCy2Pb) (15). 1.92 g of 2 (7.1 mmol), 0.98 g of
PbCl2 (3.5 mmol), 40 ml of Et2O. 2.31 g (90%) of colourless
oily matter of 15. 1H NMR (C6D6, 500 MHz, 295 K) δ: 4.08 (m,
125 MHz, 295 K) δ: 170.4 (NvC(Bu)–N); 146.9 (Ar); 142.5
(Ar); 138.6 (Ar); 124.7 (Ar); 123.4 (Ar); 123.2 (Ar); 33.9
(α-CH2(Bu)); 28.0 (br s, CH); 26.8 (β-CH2(Bu)); 23.2 (br s,
(CH3)2); 23.0 (γ-CH2(Bu)); 12.9 (CH3). 207Pb NMR (C6D6,
81 MHz, 295 K) δ: 1541.3. 1H NMR (THF-d8, 500 MHz,
3
4H, CyH); 2.15 (t, 4H, J = 8.0 Hz, α-CH2(Bu)); 1.88–1.75 (br
m, 16H, CyH); 1.65–1.54 (br m, 16H, CyH + β-CH2(Bu));
3
3
1.36–1.22 (br m, 16H, CyH + γ-CH2(Bu)); 0.89 (t, 6H, J = 7.2
295 K) δ: 7.04 (br s, 8H, ArH); 6.88 (t, 4H, J = 7.6 Hz, ArH);
Hz, CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 168.6 (NvC
(Bu)–N); 56.2 (Cy); 36.9 (Cy); 30.4 (α-CH2(Bu)); 29.4
(β-CH2(Bu)); 26.0 (Cy); 25.8 (Cy); 23.1 (γ-CH2(Bu)); 13.7
(CH3). 207Pb NMR (C6D6, 81 MHz, 295 K) δ: 1729.0. 1H NMR
(THF-d8, 500 MHz, 295 K) δ: 4.01 (m, 4H, CyH); 2.17 (t, 4H,
3J = 7.7 Hz, α-CH2(Bu)); 1.74–1.65 (br m, 18H, CyH);
1.57–1.37 (br m, 16H, CyH + β-CH2(Bu)); 1.34–1.15 (br m,
3.29 (m, 8H, CH); 1.69 (s, 4H, α-CH2(Bu)); 1.21 (br s, 48H,
(CH3)2); 0.92 (m, 4H, β-CH2(Bu)); 0.67 (m, 4H, γ-CH2(Bu));
3
0.38 (t, J = 7.3 Hz, 6H, CH3). 13C NMR (THF-d8, 125 MHz,
295 K) δ: 171.3 (NvC(Bu)–N); 148.2 (Ar); 143.6 (Ar); 139.4
(Ar); 125.6 (Ar); 124.3 (Ar); 123.6 (Ar); 34.9 (α-CH2(Bu)); 29.0
(br s, CH); 27.9 (β-CH2(Bu)); 24.1 (γ-CH2(Bu)); 23.7 (br s,
CH); 13.6 (CH3). 207Pb NMR (THF-d8, 81 MHz, 295 K) δ:
1540.1. Elemental Anal. Calcd (%) for C58H86N4Sn: C 66.56; H
8.28; N 5.35. Found: C 66.48; H 8.12; N 5.38.
3
14H, CyH + γ-CH2(Bu)); 0.95 (t, 6H, J = 7.2 Hz, CH3). 13C
NMR (THF-d8, 125 MHz, 295 K) δ: 169.8 (NvC(Bu)–N); 57.4
(Cy); 37.9 (Cy); 31.5 (α-CH2(Bu)); 30.4 (β-CH2(Bu)); 26.9
(Cy); 26.8 (Cy); 24.2 (γ-CH2(Bu)); 14.8 (CH3). 207Pb NMR
(THF-d8, 81 MHz, 295 K) δ: 1745.6. Elemental Anal. Calcd (%)
for C34H62N4Pb: C 55.63; H 8.51; N 7.63. Found: C 55.58; H
8.36; N 7.75.
4. Conclusions
A series of homo- and heteroleptic Ge(II), Sn(II) and homoleptic
Pb(II) N,N′-disubstituted n-butyl amidinates were prepared and
characterized. In the solid state the heteroleptic Ge(II) amidinate
is a monomer, Sn(II) amidinate with bulky Dipp substituents is a
dimer via chlorine bridges and the cyclohexyl N,N′-disubstituted
Sn(II) chloride reveals a unique dimeric structure via one Cl
bridge and Sn to an amidinate π-system contact. Accidental but
reproducible oxidation of heteroleptic Sn(II) chloride led to the
tetranuclear linear complex containing two Sn(II) and two Sn(IV)
atoms formed by migrations of two ligands.
3.2.14 Preparation of bis[N,N′-bis[2,6-di(propan-2-yl)phenyl]-
n-butylamidinato]-germanium(II) (LDipp2Ge) (16). 1.38 g of 3
(3.2 mmol), 0.37
g of GeCl2 dioxane complex (1 : 1)
(1.6 mmol), 30 ml of Et2O. 1.19 g (82%) of pale yellow oily
1
matter of 16. H NMR (C6D6, 500 MHz, 295 K) δ: 7.24–6.94
(m, 12H, ArH); 3.76 (m, 4H, CH); 3.35 (m, 2H, CH); 3.22 (m,
2H, CH); 2.13 (s, 4H, α-CH2(Bu)); 1.29 (m, 4H, β-CH2(Bu));
3
1.36 (s, 48H, (CH3)2); 0.80 (m, 4H, γ-CH2(Bu)); 0.35 (t, 6H, J
= 7.3 Hz, CH3). 13C NMR (C6D6, 125 MHz, 295 K) δ: 169.8
(NvC(Bu)–N); 147.6 (Ar); 142.5 (Ar); 141.0 (Ar); 126.8 (Ar);
123.9 (br s, Ar); 29.3 (α-CH2(Bu)); 28.8 (β-CH2(Bu)); 28.4 (br
s, CH); 23.3 (br s, (CH3)2); 22.8 (γ-CH2(Bu)); 13.6 (CH3).
Elemental Anal. Calcd (%) for C58H86GeN4: C 76.39; H 9.51; N
6.14. Found: C 76.58; H 9.86; N 5.88.
Acknowledgements
The authors would like to thank the Grant Agency of the Czech
Republic (grant no. 104/09/0829) for financial support.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 5010–5019 | 5017

View Article Online
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