Synthesis and structures of the dinuclear tin(II) complexes [R = Ph, X(Z) = CPh; R = SiMe3, X(Z) = PPh2] and of related compounds

Article abstract of DOI:10.1016/j.jorganchem.2009.06.025

Tin(II) compounds containing the ligands [CH(C₆H₃Me₂-2,5)C(Bu^t) NSiMe₃]^- (≡ L¹), [CH(Ph)C(Ph)NSiMe₃]^- (≡L²), [CH(SiMe₃)P(Ph)₂NSiMe₃]^- (≡ L³), {A figure is presented} (≡ L⁴), [C(Ph)C(Ph)NSiMe₃]^2- (≡ L⁵), and [C(SiMe₃)P(Ph)₂NSiMe₃]^2- (≡ L⁶) are reported: the transient SnBr(L¹) (1) and SnBr(L²) (2), Sn(L¹)₂ (3) [P.B. Hitchcock, J. Hu, M.F. Lappert, M. Layh, J.R. Severn, J. Chem. Soc., Chem. Commun. (1997) 1189], the labile Sn(L²)₂ (4), [Sn(L⁵)]₂ (5), SnCl(L³) (6), Sn(L³)₂ (7), [Sn(L⁶)]₂ (8), Sn(L⁴)₂ (9) and Pb(L⁴)₂ (10). They were prepared from (i) SnBr₂ and K(L¹) (1, 3) or K(L²) (2, 4, 5); (ii) SnCl₂ and Li(L³) (6-9); or (iii) PbCl₂ and Li(L⁴) (10). Each of 1, 3 and 5-10 has been characterised by multinuclear NMR spectra; 3, 5, 6, 8, 9 and 10 by EI-mass spectra, but only 3, 5, 8, 9 and 10 were isolated pure and furnished X-ray quality crystals. Of greatest novelty are the title binuclear fused tricyclic ladder-like compounds 5 and 8. Quantum chemical calculations, on alternative pathways to 5 from 2 and to 8 from 7, are reported.

Full text of DOI:10.1016/j.jorganchem.2009.06.025

Journal of Organometallic Chemistry 694 (2009) 3487–3499
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and structures of the dinuclear tin(II) complexes
[Sn{µ-C(R)X(Z)NSiMe3}]2
[R = Ph, X(Z) = CPh; R = SiMe3, X(Z) = PPh2] and of related compounds
b
a
a
Peter B. Hitchcock a, Michael F. Lappert a, , Mikko Linnolahti , John R. Severn , Patrick G.H. Uiterweerd ,
*
Zhong-Xia Wang a,1
a Department of Chemistry, University of Sussex, Brighton BN1 9QJ, UK
b Department of Chemistry, University of Joensuu, P.O. Box 111, 810101 Joensuu, Finland
a r t i c l e i n f o
a b s t r a c t
Tin(II) compounds containing the ligands [CH(C6H3Me2-2,5)C(But)NSiMe3]ꢀ (ꢁ L1), [CH(Ph)C(Ph)NSiMe3]ꢀ
Article history:
Received 6 May 2009
Received in revised form 13 June 2009
Accepted 19 June 2009
Available online 26 June 2009
4
(ꢁ L2), [CH(SiMe3)P(Ph)2NSiMe3]ꢀ (ꢁ L3),
(ꢁ L ), [C(Ph)C(Ph)-
−
[CH(SiMe3)P(Ph)=NSi(Me)2C6H4-1,2]
NSiMe3]2ꢀ (ꢁ L5), and [C(SiMe3)P(Ph)2NSiMe3]2ꢀ (ꢁ L6) are reported: the transient SnBr(L1) (1) and
SnBr(L2) (2), Sn(L1)2 (3) [P.B. Hitchcock, J. Hu, M.F. Lappert, M. Layh, J.R. Severn, J. Chem. Soc., Chem. Com-
mun. (1997) 1189], the labile Sn(L2)2 (4), [Sn(L5)]2 (5), SnCl(L3) (6), Sn(L3)2 (7), [Sn(L6)]2 (8), Sn(L4)2 (9) and
Pb(L4)2 (10). They were prepared from (i) SnBr2 and K(L1) (1, 3) or K(L2) (2, 4, 5); (ii) SnCl2 and Li(L3) (6–9);
or (iii) PbCl2 and Li(L4) (10). Each of 1, 3 and 5–10 has been characterised by multinuclear NMR spectra; 3,
5, 6, 8, 9 and 10 by EI-mass spectra, but only 3, 5, 8, 9 and 10 were isolated pure and furnished X-ray quality
crystals. Of greatest novelty are the title binuclear fused tricyclic ladder-like compounds 5 and 8. Quantum
chemical calculations, on alternative pathways to 5 from 2 and to 8 from 7, are reported.
Ó 2009 Elsevier B.V. All rights reserved.
Dedicated to Professor Jon R. Dilworth, as a
mark of respect and (for MFL) of friendship.
Keywords:
1-Azaallyls
Crystal structures
Dianionic C,N-centred ligands
Quantum chemical calculations
Silyliminodiphenylphospho-
ranylsilylmethyls
Tin(II) compounds
1. Introduction
group 14 metal(II) chemistry include b-diiminates [7]. More di-
rectly relevant to the present paper are tin(II) compounds contain-
Until the early 1970’s, most of the published work on the metal-
lic elements of Group 14 (Ge, Sn, Pb) concentrated exclusively on
the tetravalent state. Relatively few divalent germanium, tin or
lead compounds had been fully characterised due to their low sta-
bility or to their strong tendency towards polymerisation [1–4].
Over the next 10–15 years this previously neglected area of chem-
istry grew enormously as the crucial role of ligand design in the ki-
netic stabilization of compounds through steric effects was
recognised. The use of various sterically demanding ligands gave
thermally stable Ge(II), Sn(II) or Pb(II) monomers or dimers; a ser-
ies of such ligands was developed, which included amido, alkoxo,
aryloxo, alkylthio, alkyl, aryl and cyclopentadienyl ligands [3–6].
Monoanionic N-centred chelating ligands which have featured in
ing monoanionic, usually chelating, 1,3-N,X-centred ligands: (i)
X = N, the amidinates [8,9] and guanidinates [9] and quite specifi-
cally (ii) (X = C) the 1-azaallyls [10]. 1-Iminodiarylphosphoranyl-
methyls and some of their tin(II) derivatives, which like (ii) are
the focus of the present report, were previously unknown, but re-
lated compounds are A [11], B [12a] and C [12b]. Earlier publica-
tions [related to (ii)] dealt with the synthesis and structures of
the compounds D [13], E [14], F [14], G [15], and H [15,16]; the
structure of crystalline 3 (vide infra) has also been published
[15].
The present paper is a contribution to our pioneering studies on
novel divalent molecular compounds of tin. Four of the ligands
chosen (L1–L4) are 1,3-N,C-centred and potentially chelating, charac-
terised by having a potentially labile hydrogen attached to the 3-car-
bon atom; two of these (L2 and L4) are unprecedented and another
two (L1 and L3) have appeared only briefly in our prior
publications.
* Corresponding author. Tel.: +44 1273 678316; fax: +44 1273 876687.
E-mail address: m.f.lappert@sussex.ac.uk (M.F. Lappert).
1
Present address: Department of Chemistry, University of Science and Technology
of China, Hefei, Anhui 230026, PR China.
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.06.025

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P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
itant 1,3-C ? N shift of the SiMe3 group, is a variant of a
2. Results and discussion
general route described earlier [17]. Both the prior ambient
temperature lithiation of the SiMe3- and aryl-activated meth-
ane, and the ultimate conversion of the hydrocarbon-soluble
Li(L1 or L2) into the insoluble K(L1 or L2), have ample prec-
edent [18].
This paper deals with the synthesis and structures of tin(II)
compounds containing the ligands L1–L6. Each is an 1,3-C,N-chelat-
ing moiety having an NZC core; four are monoanionic having
Z = CR0 (L1, L2) or PPh(C6H4R00-2) (L3, L4), and two are dianionic with
Z = CPh (L5) or PPh2 (L6).
SiMe3
SiMe3
N
Me2Si
N
N
P
Ph
Ph
R1
P
C
(−)
(−)
(−)
Ph
C
C
C
R2
H
SiMe3
SiMe3
H
H
L3
L4
L1: R1 = But, R2 = C6H3Me2-2,5
L2: R1 = Ph = R2
SiMe3
N
SiMe3
N
P
Ph
Ph
C
Ph
(2−)
(2−)
C
C
Ph
SiMe3
L5
L6
2.1. The tin(II) compounds 1–5
The reaction of tin(II) bromide with two equivalents of K(L1) or
K(L2) gave the yellow crystalline complexes Sn(L1)2 (3) or [Sn(L5)]2
(5), respectively.Itissuggested(Scheme3)thattheformationofeach
proceded via the intermediate Sn(Br)L1 (1) or SnBr(L2) (2), respec-
tively, the latter furnishing first the labile Sn(L2)2 (4) which, being
sterically encumbered, eliminated H(L2) en route to 5. The structure
(but no other data) for crystalline 3 has previously been communi-
cated [15]; and selected geometrical parameters are shown in Fig. 1.
The 1-azaallylpotassium compounds K(L1) and K(L2) were
prepared in high yield, as shown in Schemes 1 and 2. The
procedure, in which the key step was the insertion of the
a
-hydrogen-free nitrile (ButCN or PhCN) into the appropriate
lithium
trimethylsilylalkyl
[LiCH(SiMe3)(C6H3Me2-2,5)
for
Li(L1) or LiCH-(SiMe3)Ph for Li(L2), respectively] with concom-

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
3489
1. LiBun, tmeda, C5H12
1. Mg, Et2O
2. Si(Cl)Me3
2,5-Me2C6H3CH2Cl
2,5-Me2C6H3CH2SiMe3
2. ButCN, KOBut
K[CH(C6H3Me2-2,5)C(But)NSiMe3]
K(L1)], 94%
[
Scheme 1.
LiBun, tmeda, C5H12
1. PhCN, C5H12
2. KOBut
Li[CH(SiMe3)Ph]
PhCH2SiMe3
K[CH(Ph)C(Ph)NSiMe3]
[
K(L2)], 74%
Scheme 2.
SiMe3
SiMe3
2 K(L1)
2 K(L2)
(− 2 KBr)
N
N
C
But
Ph
C
2
2 SnBr2
2
Sn
Sn
(− 2 KBr)
C
C
Br
Br
C6H3Me2-2,5
Ph
H
H
1
2
2 K(L2)
(− 2 KBr)
2 K(L2)
2 K(L1)
(− 2 KBr)
[− 2 KBr,
− 2 H(L2)]
2 [Sn{N(SiMe3)C(Ph)CH(Ph)}2]
But
Me3Si
4
C
Me3Si
Ph
Ph
N
N
C(H)
C(H)
[− 2 H(L2)]
C6H3Me2-2,5
C6H3Me2-2,5
N
Ph
C
2
Sn
Sn
C
C
C
Sn
C
N
Me3Si
But
Ph
SiMe3
3, 74% [15]
5, 23%
Scheme 3.
1.478(5)
3.151
1.349(5)
C2
C7
C1
N
1.435(4)
3.188
Sn
111.20(14)
101.2(2)
2.130(3)
N
117.4(3)
129.2(3)
Fig. 1. Selected structural parameters of crystalline Sn(L1)2 (3); core atoms only
[15].
Fig. 2. Molecular structure of [Sn(L5)]2 (5) in ORTEP representation.
Compounds 3 and 5 gave satisfactory C, H and N microanalyses.
The EI-mass spectra showed parent molecular cations for the
mononuclear 3 and the dinuclear 5 and appropriate fragment ions.
The multinuclear NMR spectra for 3 in C6D6 at ambient tempera-
ture were consistent with the crystal structure; the 119Sn{1H}
NMR chemical shift of d +61.5 ppm may be compared with the d
ꢀ387.2 and d ꢀ37.3 ppm for G and H, respectively [15], and the d
+148.4 (323 K) and +118.5 (213 K) for A [13].
Compound 5 was too sparingly soluble in hydrocarbon solvents
to locate 1H NMR spectral signals. However, solution 1H NMR data,

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P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
Table 1
ble structures of isomers 4a–4c of the latter and of the by-product
H(L2) as monomer or dimer. The calculations were carried out
using two methods: initially by the hybrid density functional
B3LYP/def2-SVP procedure, involving the screening of isomeric
possibilities. The final calculations, on the energetically preferred
isomers, were performed at the MP2/def-TZVP level. The use of
MP2 was necessary mainly because of dispersive interactions be-
tween the phenyl groups, which is one of the most well-known
problems of density functional theory. Also the possibility for the
side-product to form a hydrogen-bonded dimer was an issue.
Concerning the isomeric forms of 4, there are many possibilities
for the rings to arrange around the tin centre. Having calculated 12
different isomers (at B3LYP level), the energetically preferred are
illustrated in Fig. 3, with their energies and selected calculated
bond lengths and angles (MP2). As evident from Fig. 3, 4c lies
33.1 kJ/mol higher in energy than 4a; attempts to locate 4b
resulted in a transformation back to 4a.
Selected bond distances (Å) and angles (°) for 5.
Sn1–N1
Sn1–C2
Sn1–C20
N1–C1
C1–C2
2.216(5)
2.317(6)
2.318(7)
1.334(8)
1.406(9)
N1–Si1
C1–C3
C2–C9
Sn1ꢂ ꢂ ꢂSn10
1.742(6)
1.513(9)
1.466(9)
3.132(2)
N1–Sn1–C2
C2–Sn1–C20
N1–C1–C2
N1–C1–C3
N1–Sn1–C20
61.7(2)
95.0(2)
116.1(6)
121.7(6)
97.5(2)
Sn1–C2–C1
Sn1–C2–Sn10
Sn1–N1–Si1
C1–C2–C9
84.4(4)
85.0(2)
133.7(3)
126.1(6)
90.2(4)
C1–N1–Sn1
Symmetry transformations to generate equivalent atoms 0ꢀx + 1, ꢀy + 1, ꢀz + 1.
00ꢀx + 1, ꢀy, ꢀz + 1.
clearly of a diamagnetic material, were collected in C5D5N at ambi-
ent temperature; the signals, characteristic of the L2 ligand, were of
low intensity and consequently attempts to obtain spectral data for
other nuclei were unsuccessful. In the light of the microanalytical,
mass spectral and particularly the X-ray data (see next paragraph)
on crystalline 5, this NMR spectrum is attributed to 4 or H(L2)
rather than 5.
The molecular structure of the crystalline, centro-symmetric
fused tricyclic ladder compound [Sn(L5)]2 (5) is shown in an ORTEP
representation in Fig. 2. Selected bond lengths and angles are listed
in Table 1. The central rhomboidal Sn1C2Sn10C20 ring has the endo-
cyclic angles subtended at the tin atoms ca. 10° wider than those at
carbon. The transannular Snꢂ ꢂ ꢂSn0 distance is too long for there to
be significant bonding between them; tin–tin single bonds are gen-
erally in the range 2.75–2.92 Å [19]. The outer Sn1N1C1C2 and
Sn10N10C10C20 rings are puckered, the dihedral angle between the
Sn1N1C1 and Sn1C2C1 planes is 27.4° and that between the latter
and the Sn1C2Sn10 is 68.6°. Comparisons with the structure of 8 are
deferred to Section 2.2.
Four separate isomers of the monomeric side-product (HL2)
were calculated; the energetically preferred is illustrated in
Fig. 4, showing the relative arrangement of its two phenyl groups
and the localisation of the hydrogen atom attached to the nitrogen.
For the dimeric side-product, only one possibility was considered
as no reasonable alternative was envisaged. In the dimer the
arrangement of the phenyl groups is different and the hydrogen
atoms of (HL2)2 are located on carbon rather than nitrogen. The
Gibbs free energies as a function of temperature (illustrated in
the Supplementary data) for the dimerisation of HL2, showed that
HL2 exists as a dimer at temperature 6 210 K.
Fig. 5 shows the computed molecular structure of [Sn(L5)]2 (5)
with selected calculated and observed geometrical parameters.
The Gibbs free energy for the conversion of 4a into 5, with
monomeric and dimeric HL2 as co-products calculated over a range
of temperatures is illustrated in the Supplementary data. It is con-
cluded that these reactions are exothermic above 200 K.
To investigate possible reaction pathways further, quantum
chemical calculations studies were performed. Scheme 4 illustrates
the first pathway to 5 via 4 in more detail, and includes the possi-
Quantum chemical calculation studies were also carried out on
the alternative pathway to 5, from 2 without the intermediate of 4,
Me3Si
Ph
C
N
C
Ph
Sn
C
+ 2 H(L2)
C
N
2 [Sn{N(SiMe3)C(Ph)CH(Ph)}2]
Sn
4
Ph
Ph
SiMe3
5
Ph
Ph
Ph
H
H
Ph
Ph
H
Ph
Me3Si
Ph
Me3Si
Ph
C
C
Me3Si
Ph
C
Sn
C
C
N
H
C
N
H
C
N
H
N
C
N
N
C
Sn
C
Sn
C
C
SiMe3
SiMe3
SiMe3
Ph
4b
Ph
4c
Ph
4a
Ph
H
H
Ph
Me3Si
Ph
C
Me3Si
C
NH
or
N
H(L2)
=
N
H
C
C
C
SiMe3
C
H
Ph
H
Ph
Ph
1/2
Scheme 4.

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
3491
Fig. 3. MP2 calculated structure for isomer 4a and 4c, with selected bond angles and lengths.
Fig. 4. MP2 calculated structure for HL2 and its dimer.
Scheme 3. Four isomers of 2 were considered, possessing various
orientations of the phenyls and the Sn–Br bond; the energetically
favoured is represented in Fig. 6. The Gibbs free energy for the
transformation of two molecules of 2 into 5 via elimination of
2HBr was shown to be endothermic at all temperatures, as illus-
trated in the Supplementary data, indicating that 2 can not proceed
to 5 via this route. SCS-MP2/def2-TZVP computations were carried
out to confirm the validity of the MP2/def-TZVP calculations. Con-
cerning electronic energies (i.e., enthalpies without zero-point
vibrational corrections, and also
DG as G = H–TS and T = 0, so
G = H), the reaction is endothermic by 210.0 kJ/mol at the MP2,
and even more so at the SCS-MP2 level, 222.7 kJ/mol (B3LYP gives
the even much higher value of 342.2 kJ/mol).
Fig. 5. MP2 computed structure for 5, with selected calculated bond lengths and an
angle with crystal structural data in parentheses.

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P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
labile, the solid being stable only for ca. 3 weeks and a C6D6 solu-
tion only for ca. 4 d; whilst at ꢀ30 °C it suffered no deterioration,
either as solid or in hydrocarbon solution, after being stored at that
temperature for three months.
Surprisingly, from equivalent portions of SnCl2 and Li(L3) in
Et2O, then addition of an equivalent portion of LiBun in hexane, fol-
lowed by removal of solvent in vacuo, extraction of the residue
with hexane and concentration of the extract furnished colourless
crystals of Sn(L4)2 (9) in 54% yield [based on Li(L3)].
Evidence for SnCl(L3) (6) as an intermediate in these reactions
was realised by mass spectral data on the material obtained by
the following procedure. Equivalent portions of SnCl2 and Li(L3)
in Et2O were allowed to react for 15 h at ambient temperature,
then filtered, the filtrate was concentrated and hexane added
yielding a white solid, which contained 6 as judged by its EI-mass
spectrum, and its 1H NMR spectrum in C6D6.
Whereas 2 Li(L3) + PbCl2 at ꢀ45–0 °C in Et2O gave the X-ray-
characterised Pb(L3)2 [20], the same reagents under prolonged re-
flux furnished Pb(L4)2 (10), Eq. (1). It is likely that Pb(L3)2 was an
intermediate along the pathway to Pb(L4)2. The tin analogue 7 of
the latter, although not isolated pure, was obtained contaminated
with H(L3) as the first formed product en route to [Sn(L6)]2 (8).
Thus, the 1H NMR spectrum of freshly prepared 7 invariably
showed the presence of H(L3), doublets being observed at d 1.44
[H(L3)] and 1.71 (7) ppm. The production of H(L3) was not a result
of purification difficulties, because upon heating the CH signal at d
1.71 ppm disappeared whilst that at d 1.44 ppm increased in inten-
sity; furthermore, the 1H{31P} NMR spectrum showed singlet sig-
nals for the CH protons. A freshly prepared sample of 7 [with
H(L3)] revealed the expected triplet, due to 2J(119Sn–31P), in the
119Sn{1H} NMR spectrum at d 82.3 ppm which upon heating disap-
peared and concomitantly a new triplet signal at d 530.3 (attrib-
uted to 8) was observed. Similar features were found in the
31P{1H} NMR spectra: thus, initially the main P-containing constit-
uent was 7 [d 25.45 ppm], but upon heating this signal vanished,
whilst that at d 0.46 ppm of H(L3) progressively increased in inten-
sity as did a new signal at d 27.77 ppm (due to 8). Based on d(207Pb)
for Pb(L3)2 of 2788 ppm [20], the calculated value of d(119Sn) for
Sn(L3)2 (7) is 137 ppm based on the empirical correlation of
Eq. (2) (ref. [22]) [22], which, whilst not very close to the assigned
chemical shift of d 82.3 ppm, is of a similar order of magnitude
keeping in mind the very wide range of known 119Sn chemical
shifts. Selected NMR data for 7 and 8 are compared with those
for four related compounds in Table 2.
Fig. 6. MP2 calculated structure for 2.
2.2. The tin(II) compounds 6–9 and the lead(II) compound 10
The synthesis of the new crystalline tin(II) complexes, the yel-
low binuclear [Sn(L6)]2 (8) and the colourless mononuclear
Sn(L4)2 (9), is outlined in Scheme 5. The precursors were SnCl2
and the 1,3-bis(trimethylsilyl)-1-aza-2-diphenylphospha(V)allylli-
thium compound Li(L3). An in situ-prepared Li(L3) had been used
for the synthesis of the X-ray-characterised Pb(L3)2 (Fig. 7) [20];
the synthesis and X-ray structures of the crystalline complexes
Li(L3)(OEt2) and [Li(L3)]2 have been reported [21]. Treatment of
SnCl2 with two equivalents of an in situ-prepared portion of
Li(L3) in Et2O at ꢀ40 °C, removal of volatiles and extraction of the
residue with pentane afforded a high yield (based on SnCl2) of yel-
low crystals of 8. At ambient temperature 8 proved to be thermally
SiMe3
2 Li(L3) [20]
N
Ph
2
2 SnCl2
P
Sn
(− 2 LiCl)
Ph
C
Cl
SiMe3
H
(i) 2 Li(L3) [20]
6
2 Li(L3)
(ii) 2 LiBun
(− 2 LiCl)
(− 2 LiMe)
(− 2 LiCl)
[− 2 C4H10
]
SiMe3
Me3Si
SiMe3
Me2Si
N
Ph
N
N
P
Sn
C
P
Ph
Ph
SiMe3
2
2
Ph
P
P
Ph
Ph
Sn
[− 2 H(L3)]
C
Sn
Sn
Ph
SiMe3
9, 54% [20]
C
C
N
2
SiMe3
2
SiMe3
H
H
8, 96%
7
Scheme 5.

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
3493
Fig. 7. Selected structural parameters of crystalline Pb(L3)2: Pb–N1 2.701(4), Pb–N2 2.654(4), Pb–C1 2.449(6), Pb–C20 2.447(5) Å; N1–Pb–C1 62.52(14), N1–Pb–N2 162.27(1),
N1–Pb–C20 107.6(2), N2–Pb–C1 106.49(14), C1–Pb–C20 88.2(2)° [20].
Table 2
Selected solution NMR spectroscopic data in C6D6 or C7D8 for 7 and 8 and four reference compounds at ambient temperature.
H(L3)a
[Li(L3)(OEt2)]b
[Li(L3)]2
Sn(L3)2 (7)
Pb(L3)2
[Sn(L6)]2 (8)
b
c
Compound
1.44 (d)
15.2
1.48 (d)
14.7
1.47 (d)
13.8
1.71 (d)
15.7
1.37 (d)
15.8
–
–
d [31P{1H}/ppm
0.46
–
60.0
–
33.32
–
25.45
82.3 (t)
19.52
–
27.77
530.3 (t)
d [119Sn{1H}/ppm
a
Ref. [23].
Ref. [21].
Ref. [20].
b
c
Et2
O
Pbcl þ 2LiðL4Þ
2LiCl þ PbðL4Þ
ð1Þ
ð2Þðref:½22ꢃÞ
Satisfactory C, H, N microanalytical data were obtained for
[Sn(L6)]2 (8), Sn(L4)2 (9) and Pb(L4)2 (10). The d(31P) and d(119Sn)
NMR chemical shifts for 8 are listed in Table 2.
ƒƒ!
2
2
10;48%
dð207PbÞ ¼ 3:30½dð119SnÞꢃ þ 2336
Fig. 8. Selected structural parameters of crystalline [Sn(L6)]2 (8) (see also Fig. 12): C1–P 1.706(8), Sn–N 2.308(7), P–N 1.618(7) Å; Sn0–C1–P 110.5(4), C1–P–N 105.0(4),
C1–Sn0–N0 99.0(3), Sn–C10–P0 110.5(4), P–N–Sn 92.6(3)° [24].

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P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
b
c
a
Fig. 9. Comparative geometric data for the SnC1Sn0C10 fragment of 5 (a), I (b) [25] and 8 (c).
The 1H NMR spectral data for 9 in C6D6 at ambient temperature
This may be due to dispersive interactions between the phenyl
groups, as suggested by B3LYP calculations, which do not consider
dispersion adequately.
Selected results of the final calculations for complex 5, are
shown in Fig. 12, together with the appropriate experimental
X-ray data. Fig. 13 shows the MP2 calculated Gibbs free energies
for the conversion 7a or 7b into 8 over a range of temperatures.
includes a singlet (SiMe3) and a doublet (SiMe2); the latter is attrib-
uted to the exo- and endo-methyls of the CCPNSi ring. Likewise, the
13C{1H} NMR spectrum showed three sets of silylmethyl signals,
each a doublet due to J(13C-31P). The 119Sn{1H} NMR spectrum re-
vealed a triplet due to coupling to two equivalent 31P nuclei, whilst
the 31P{1H} NMR spectrum had 119/117Sn satellites. The 29Si{1H}
NMR spectrum contained a singlet with 119/117Sn satellites and a
doublet due to coupling to 31P.
The 1H and 13C{1H} NMR spectra of 10 in C6D6 showed three
sets of silylmethyl signals assigned (as for 9) to SiMe3 and
exo-/endo-SiMe2 methyls. The 31P{1H} and the 207Pb{1H} NMR
spectra revealed a singlet with 207Pb satellites and a triplet due
to 31P-coupling, respectively.
The molecular structure of the centro-symmetric crystalline 8 is
shown in Fig. 8, with selected geometrical parameters. It has a
fused tricyclic ladder-like skeleton. The central SnC1Sn0C10 ring is
planar and its geometric parameters are similar to those for the
corresponding in [Sn(L6)]2 (5) and Veith and Huch’s compound I
[25], as illustrated in Fig. 9. The Sn atom is outside the C1PN plane.
The Sn–N bond of 8 is longer than in Sn(II) amides {cf., 2.09(1) Å
in Sn[N(SiMe3)2]2 [26a]} or eneamides {cf., 2.130(3) Å in
Sn[N(SiMe3)C(But)@CH(C6H3Me2-2,5)]2 [15]}. Likewise, the Sn–C
bond of 8 is long {cf., 2.28 Å in Sn[CH(SiMe3)2]2 [26b]}.
The reaction leading to the dimeric product [Sn(L6)]2 (8) was
investigated using quantum chemical calculation techniques. Of
the twelve isomers of complex 7, two were considered further;
of these, 7a (Fig. 10), corresponds to that of the isoleptic lead com-
pound (Pb(L3)2), [20]. It is noteworthy that the phenyl rings on
adjacent phosphorus atoms, stack like the graphene layers in
graphite, which is due to dispersive interactions. However, 7a is
not the energetically favoured isomer. Isomer 7b, illustrated in
Fig. 11, where the nitrogens are on the same side, has weaker
Ph/Ph interaction. However, there is a clear interaction (see back
view) from hydrogen (up right) to phenyl (down right). Isomer
7b is favoured (MP2) over 7a by 28.0 kJ/mol.
As with complex 5, the energies for HL3 and its dimer were cal-
culated, with similar observations on the location of the hydrogen
as between the monomer and the dimer. From the calculation on
the dimerisation reaction it appears that the dimer is preferred
at 6470 K, indicating that there is a significant difference to the re-
lated dimerisation of HL2, (for which the temperature was 6210 K).
Fig. 10. MP2 calculated structure for 7a, with selected geometrical parameters.

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
3495
Fig. 13. MP2 calculated Gibbs free energy for reaction of 7a or 7b to 8 over a range
of temperatures.
From these data it is concluded that 7a, unlike 7b, is unstable with
respect to the reaction products 8 and HL3.
The molecular structures of the crystalline Sn(L4)2 (9) (Fig. 14)
and Pb(L4)2 (10) (Fig. 15) were determined by single crystal
X-ray diffraction [24]. Selected geometric parameters are listed in
Table 3 (9) and 4 (10). Each of 9 and 10 has the two L4 ligands
bound almost symmetrically about the pyramidal central M(II)
atom, as illustrated for 10 in Fig. 16.
3. Conclusions
Reactions of (i) SnBr2 with an equivalent portion of a 1-aza-
allylpotassium compound K(L1) or K(L2) and (ii) SnCl2 with an
equivalent portion of the 1-aza-2-diphenylphospha(V)allyllithium
compound Li(L3) are reported [L1 = CH(C6H3Me2-2,5)C(But)-
Fig. 11. MP2 calculated structure for 7b, with selected geometrical parameters.
N-(SiMe3);
L2 = CH(Ph)C(Ph)N(SiMe3);
L3 = CH(SiMe3)P(Ph)2-
N(SiMe3)]. Particularly noteworthy was the unexpected formation
of the X-ray-characterised crystalline fused tricyclic compounds
[Sn(L5)]2 (5) and [Sn(L6)]2 (8) from 2SnBr2 with 2 K(L2) and 2SnCl2
with 2Li(L3), respectively [L5 = C(Ph)C(Ph)N(SiMe3); L6 = C(Si-
Me3)P(Ph)2N(SiMe3)]. The formation of
5 and 8 from their
precursors has been modelled by quantum chemical calculations.
Six new mononuclear tin(II) complexes containing the ligands L1,
L2, L3 or L4 have been prepared and characterised (Table 4).
4. Experimental
4.1. General details
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 freeze/thaw degassed prior
to use. The drying agents employed were sodium benzophenone
(C6H6, Et2O, thf) or sodium-potassium alloy (C5H12, C6H14). The sol-
vents for NMR spectroscopy (C6D6, C5D5N) were stored over molec-
ular sieves (A4). Elemental analyses were obtained by Medac Ltd.,
Brunel University or The Metropolitan University, London. Melting
points were measured in sealed capillaries. The 1H, 13C, 31P and
119Sn NMR spectra were recorded using
a Bruker WM-360,
DPX300 or AMX500 instrument and were referenced internally
(1H, 13C) to residual solvent resonances or externally (31P with
85% aq. H3PO4 as standard; 119Sn with SnMe4 as standard). Electron
impact mass spectra were taken from solid samples, with a VG
Autospec or a Kratos MS 80RF instrument. The compounds H(L3)
[23], [Li(L3)(OEt2)2] [21], [Li(L3)]2 [21] [L3 = CH(SiMe3)P(Ph)2@
NSiMe3] were prepared by published procedures. Other chemical
Fig. 12. MP2 calculated structure for 5, with selected calculated bond angles and
lengths with crystal structure data in parentheses.

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P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
Fig. 14. ORTEP representation of the molecular structure of Sn(L4)2 (9) [24].
Fig. 15. ORTEP representation of the molecular structure of Pb(L+)2 (10) [24].
Table 3
90.1(2)
66.2(2)
Selected bond distances (Å) and angles (°) for 9 [24].
109.9(3)
Pb
Sn–C1
Sn–C19
Sn–N1
Sn–N2
P1–N1
P2–N2
P1–C1
2.335(7)
2.353(6)
2.480(6)
2.525(6)
1.599(6)
1.592(6)
1.751(7)
Si1–N1
Si3–N2
P1–C2
P2–C26
C2–C7
1.705(6)
1.711(6)
1.813(8)
1.830(7)
1.401(11)
1.395(10)
1.749(7)
C31
N1
P2
N2
P1
C13
146.0(2)
C26–C31
P2–C19
Fig. 16. Schematic representation of 10, showing the angular environment of the Pb
atom [24].
C1–Sn–N1
C19–Sn–N2
N1–Sn–C19
N2–Sn–C1
N1–Sn–N2
C1–Sn–C19
C1–P1–C2
C19–P2–C26
P1–C2–C7
68.4(2)
67.5(2)
89.3(2)
88.8(2)
146.7(2)
93.8(2)
117.1(3)
117.6(3)
111.5(7)
Sn–N1–P1
Sn–N2–P2
Sn–C1–P1
Sn–C19–P2
N1–P1–C1
N2–P2–C19
N1–Si1–C7
N2–Si3–C31
P2–C26–C31
90.6(2)
89.8(3)
91.9(3)
91.9(3)
107.9(3)
108.5(3)
97.9(4)
97.9(3)
111.1(5)
4.2. Preparation of K[CH(C6H3Me2-2,5)C(But)NSiMe3] [ꢁ K(L1)]
A solution of 2,5-dimethylbenzyl chloride (25.0 g, 162 mmol) in
diethyl ether (ca. 140 cm3) was slowly added to magnesium
(4.50 g, 192 mmol) suspended in Et2O (ca. 40 cm3). After ca. 12 h,
chlorotrimethylsilane (18.4 g, 162 mmol) was added dropwise at
ambient temperature. The mixture was stirred for ca. 12 h, where-
after water was added. The organic phase was separated and dried
(CaCl2). Distillation afforded 2,5-Me2C6H3CH2SiMe3 (17.0 g, 53%),
b.p. 46–56 °C/1 mmHg. LiBun in hexanes (25 cm3 of a 1.6 mol dmꢀ3
solution in hexane) was slowly added to the above silane (7.80 g,
starting materials were purchased (Aldrich) and rigorously dried
before use. Details of the X-ray diffraction data for [Sn(L6)]2 (8),
Sn(L4)2 (9) and Pb(L4)2 (10) are to be found in Ref. [24].

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
3497
1J(13C-1H) 118.5, Si(CH3)3], 20.27 [q, 1J(13C–1H) 125.8,
C6H3(CH3)2], 20.88 [q, 1J(13C–1H) 125.8, C6H3(CH3)2], 30.6 [q,
1J(13C–1H) 125.8, C(CH3)3], 41.84 [s, C(CH3)3], 104.4 [d, 1J(13C–1H)
151.9 Hz, C(H)]; 132.4, 134.5, 138.5 (C6-2,4,6), 151.1 ppm (CN);
29Si{1H} NMR: d 0.27 ppm; 119Sn{1H} NMR: d 61.5 ppm.
Table 4
Selected bond distances (Å) and angles (°) for 10 [24].
Pb–C13
Pb–C31
Pb–N1
Pb–N2
N1–P1
N2–P2
C13–P1
2.450(7)
2.429(7)
2.607(5)
2.594(6)
1.580(6)
1.599(6)
1.748(7)
N1–Si1
N2–Si3
P1–C1
P2–C19
C1–C2
1.706(6)
1.691(6)
1.815(8)
1.817(11)
1.395(10)
1.449(13)
1.762(6)
4.5. Preparation of
{ꢁ [Sn(L5)]2} (5)
[Sn{µ-C(Ph)C(Ph)NSiMe3}]2
C19–C20
C31–P2
Tin(II) bromide (0.51 g, 1.8 mmol) was added to a stirred sus-
pension of K(L2) (1.13 g, 3.70 mmol) in Et2O (ca. 50 cm3) at ambient
temperature and the mixture was set aside for 35 h with stirring.
The mixture was filtered. The yellow filtrate was concentrated to
ca. 20 cm3 and stored at ꢀ30 °C. After 3 weeks, pale yellow crystals
of 5 (0.36 g, 23%) (Anal. Calc. C34H38N2Si2Sn2: C, 53.1; H, 4.95; N,
3.64. Found: C, 52.6; H, 4.90; N, 3.67%), mp < 120 °C (decomp.)
were obtained. 1H NMR (C5D5N): d 0.21 [s, 9 H, Si(CH3)3], 5.71
(br s, 1 H, CH), 7.30 (m, 5 H, Ph), 7.75 ppm (m, 5 H, Ph). A small
amount (ca. 50 mg) of [Me3SiN@C(Ph)C(Ph)-]2 was identified in
the filtrate by 1H NMR spectroscopy.
C13–Pb–N1
C31–Pb–N2
N1–Pb–C31
N2–Pb–C13
N1–Pb–N2
C13–Pb–C31
C13–P1–C1
C31–P2–C19
P1–C1–C2
65.2(2)
66.2(2)
90.1(2)
90.8(2)
146.0(2)
92.7(2)
117.1(4)
115.0(4)
111.0(6)
Pb–N1–P1
Pb–N2–P2
90.4(2)
90.5(2)
92.0(3)
92.4(3)
109.9(3)
109.5(3)
97.0(3)
95.6(4)
107.7(9)
Pb–C13–P1
Pb–C31–P2
N1–P1–C13
N2–P2–C31
N1–Si1–C2
N2–Si3–C20
P2–C19–C20
40 mmol) and tmeda (6.0 cm3, 40 mmol) in light petroleum (b.p.
30–40 °C) at 0 °C. The mixture was stirred at ambient temperature
for ca. 2 h, then ButCN (4.4 cm3, 40 mmol) was added with stirring
which was continued for a further 2 h. Potassium tert-butoxide
(4.9 g, 40 mmol) was added and the mixture set aside for ca.
12 h, then filtered. The precipitate of K(L1) (11.5 g, 92%) was
washed with light petroleum (2 ꢄ 40 cm3) and dried in vacuo; 1H
NMR (C5D5N): d 0.56 (s, 9 H), 1.48 (s, 9 H), 2.27 and 2.31 (s, 3 H),
5.48 (s, 1 H), 6.54 (m, 1 H), 7.15 (d, 2 H).
4.6. Preparation of
Sn[CH(SiMe3)P(Ph)=NSi(Me)2C6H4-1,2]2
{ꢁ [Sn(L4)2]} (9)
Tin(II) chloride (0.58 g, 3.05 mmol) was added to a solution of
Li(L3) (1.10 g, 3.01 mmol) in Et2O (30 cm3) at ꢀ78 °C with stirring.
The mixture was allowed to warm at ambient temperature and
was stirred overnight. The stirred mixture was recooled to ꢀ78 C
and LiBun (1.9 cm3 of a 1.6 mol dmꢀ3 hexane solution, 3.04 mmol)
was added dropwise. Stirring was continued for 4 h at room temper-
ature. Solvent was removed in vacuo and the solid residue was ex-
tracted with hexane. The extract was filtered and the filtrate was
concentrated to afford colourless crystals of 9 [0.65 g, 54% based
on Li(L3)] (Anal. Calc. C36H50N2P2Si4Sn: C, 53.8; H, 6.27; N, 3.48.
Found: C, 53.0; H, 6.18; N, 3.13%), mp 183–186 °C. 1H NMR: d 0.27
[s, 18 H, Si(CH3)3], 0.43 [s, 6 H, Si(CH3)2], 0.69 [s, 6 H, Si(CH3)2],
1.77 [d, 2 H, 2J(1H–31P) 10.8 Hz]; 6.92–7.02 (m) and 7.39–7.49 (m)
ppm (C6H5 and C6H4); 13C{1H} NMR: d 0.74 [d, J(13C–31P) 6.2, SiCH3],
1.60 [d, J(13C–31P) 3.8, SiCH3], 2.63 [d, J(13C–31P) 2.1, SiCH3], 18.94 [d,
2J(13C–31P) 54.7, CH], 127.5 [d, J(13C–31P) 13.5], 128.5 [d, J(13C–31P)
10.0], 128.7 [d, J(13C–31P) 11.5], 129.1 [d, J(13C–31P) 10.5], 129.8 [d,
J(13C–31P) 2.6], 129.9 [d, J(13C–31P) 2.5], 131.6 [d, J(13C–31P) 16.5],
140.5 [d, 1J(13C–31P) 85.7], 148.3 [d, 1J(13C–31P) 75.3], 149.7 ppm
[d, J(13C–31P) 30.2 Hz]; 29Si{1H} NMR: d ꢀ0.42 [s, with satellites,
2J(29Si-119/117Sn) 53.5], 8.53 ppm [d, 2J(29Si–31P) 7.3 Hz]; 31P{1H}
4.3. Preparation of K[CH(Ph)C(Ph)NSiMe3] [ꢁ K(L2)]
A hexanes solution of LiBun (73 cm3 of a 1.6 mol dmꢀ3 solution)
was slowly added to benzyl(trimethyl)silane (19.0 g, 116 mmol)
and tmeda (17 cm3, 116 mmol) in light petroleum (b.p. 30–40 °C,
ca. 60 cm3) at ambient temperature. The mixture was stirred for
12 h, then filtered. The precipitate of Li{CH(SiMe3)Ph}(tmeda)
(27 g, 81%) was collected and dried. Benzonitrile (4.1 cm3,
41 mmol) was added by syringe to this lithium compound
(12.0 g, 42 mmol) in light petroleum (b.p. 60–80 °C, 40 cm3) at
ambient temperature. The mixture was stirred for 4 h, then KOBut
(5.1 g, 42 mmol) was added. The mixture was stirred for a further
4 h. The precipitate was collected and washed with Et2O (ca.
100 cm3) and dried in vacuo to give the pale yellow K(L2) (14.3 g,
94%). 1H NMR (C5D5N): d 0.24 (s, 9 H), 5.50 (s, 1 H), 6.81 (t, 1 H),
7.25 (m, 5 H), 7.72 (d, 2 H), 8.50 (d, 2 H).
NMR:
d
44.9 ppm [s, with satellites, 2J(31P–119/117Sn) 155.5,
162.3 Hz]; 119Sn{1H} NMR: d 121.4 ppm [t, 2J(119Sn–31P) 162.5 Hz].
4.4. Preparation of Sn[N(SiMe3)C(But)C(H)C6H3Me2-2,5]2 {ꢁ [Sn(L1)2]}
(3)
4.7. Preparation of
{ꢁ [Sn(L6)]2} (8)
[Sn{µ-C(SiMe3)P(Ph)2NSiMe3}]2
and Sn(L3)2 (7)
Tin(II) bromide (0.67 g, 2.50 mmol) was added to a stirred sus-
pension of K(L1) (1.50 g, 4.78 mmol) in Et2O (ca. 50 cm3) at ambi-
ent temperature for 16 h. The resulting yellow solution was
filtered off from the white precipitate and solvent removed from
the filtrate in vacuo. The bright yellow oily residue was then
washed twice with light petroleum (b.p. 30–40 °C, ca. 20 cm3) to
give a pale yellow, free-flowing solid, which was dissolved in tolu-
ene (ca. 15 cm3) and concentrated to ca. 5 cm3. The solution in a
Schlenk tube was then heated to ca. 80 °C, placed in a Dewar vessel
filled with warm (ca. 60 °C) water and allowed to cool slowly. After
3 d, the water was removed and replaced by acetone. The Dewar
vessel and Schlenk tube were cooled to ꢀ30 °C affording bright yel-
low crystals of complex 3 (1.23 g, 74%) (Anal. Calc. C34H56N2Si2Sn:
C, 61.1; H, 8.40; N, 4.19. Found: C, 60.9; H, 8.45; N, 4.23%), mp
87 °C. 1H NMR: d 0.24 [s, 9 H, Si(CH3)3], 1.02 [s, 9 H, C(CH3)3],
1.91 (s, 3 H, C6H3CH3-5), 2.15 (s, 3 H, C6H3CH3-2), 5.09 (br s, 1 H,
CH), 6.61–6.84 ppm [m, 3 H, C6H3(CH3)2]; 13C NMR: d 4.27 [q,
n-Butyllithium (2.25 cm3 of a 1.6 mol dmꢀ3 hexane solution,
3.52 mmol) was added dropwise to a solution of H(L3) (1.22 g,
3.40 mmol) in Et2O (30 cm3) at ꢀ20 °C, brought to ambient tem-
perature and set aside for 3 h. Tin(II) chloride (0.32 g, 1.68 mmol)
was added to the Li(L3) solution at ꢀ40 °C. The mixture was stirred
at ambient temperature for 12 h. Volatiles were removed in vacuo
and the residue was extracted with pentane (20 cm3). The extract
was concentrated to ca. 5 cm3, which after 12 h afford the yellow
crystalline complex 8 (0.77 g, 96%). (Anal. Calc. C38H56N2P2Si4Sn2:
C, 47.9; H, 5.92; N, 2.94. Found: C, 48.0; H, 5.94; N, 2.87%), mp
216–219 °C. Complex 8 was sparingly soluble in pentane or hexane
but soluble in benzene or diethyl ether. It was stable for only about
3 weeks in the solid state or 4 d in benzene at ambient tempera-
ture. The NMR spectra of a freshly prepared sample in C6D6 were
consistent with it being Sn(L3)2 (7); for selected 13C, 31P, 119Sn
NMR spectral data, see Table 2. 1H NMR: d 0.04 [s, 18 H, NSi(CH3)3],

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P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
Table 5
Mass spectral data (EI–70 eV) for 3, 5, 6, 8, 9a and 10.a
Compound
m/e (relative intensity, %), and assignment
Sn(L1)2
(3)
(5)
(6)
(8)
667 (100), [M]+; 652 (63), [M ꢀ Me]+; 594 (74), [M ꢀ SiMe3]+; 421 (65), [M ꢀ L1]+
767 (21), [M + 1]+; 695 (54), [M + 1 ꢀ SiMe3]+; 622 (44), [M + 1 ꢀ 2SiMe3]+; 174 (63), [Ph2C2]+
[Sn{µ-C(Ph)C(Ph)NSiMe3}]2
Sn(L3)Cl
513 (21), [M]+; 478 (8), [M ꢀ Cl]+; 422 (2), [M ꢀ Cl ꢀ SiMeCH]+; 359 (50), [L3]+
730 (1), [M + 1 ꢀ 2SiMe3 ꢀ Ph]+; 641 (2), [M + 1 ꢀ 2SiMe3 ꢀ 2Ph]+; 567 (6), [M + 1 ꢀ 3SiMe3 ꢀ 2Ph ꢀ N]+; 552(3),
[M + 1 ꢀ 3SiMe3 ꢀ 2Ph ꢀ N ꢀ Me]+
[Sn{µ-C(SiMe3)P(Ph)2NSiMe3}]2
920 (38), [2M ꢀ L3]+; 848 (4), [2M ꢀ L3 ꢀ SiMe3]+; 804 (1), [M]+; 578 (10), [M ꢀ Ph ꢀ C6H4 ꢀ SiMe3]+
(9)
Sn[CH(SiMe3)P(Ph)(1,2-C6H4)=NSiMe2]2
892 (5), [M]+; 550 (70), [M ꢀ L4]+; 472 (20), [M ꢀL4 ꢀ C6H4]+; 342 (100), [L4]+
(10)
Pb[CH(SiMe3)P(Ph)(1,2-C6H4)=NSiMe2]2
[M]+ represents the parent molecular ion; only the four highest m/e peaks are listed.
a
0.29 [s, 18 H, CSi(CH3)3], 1.71 [d, 2 H, 1J(1H–31P) 15.7 Hz, CH (con-
firmed by a DEPT experiment)], 6.95–6.98 (m), 7.15–7.10 (m),
7.57–7.63 (m), 7.79–7.84 ppm (m) (C6H5); 13C{1H} NMR: d 2.82
[d, J(13C–31P) 4.5, Si(CH3)3], 4.15 [d, J(13C–31P) 3.2, SiCH3], 24.76
[d, J(13C–31P) 62.8, CH]; 128.1 (s), 130.8 (d), 131.5 [d, J(13C–31P)
10.6], 132.0 [d, J(13C–31P) 10.5], 139.1 [d, J(13C–31P) 80.6],
4.10. Mass spectra of 3, 5, 6, 8, 9 and 10
The four highest m/e peaks of the EI-mass spectrum for each of
compounds 3, 5, 6, 8, 9 and 10 with assignments are listed in
Table 5.
139.2 ppm [d, J(13C–31P) 85.7 Hz] (Ph); 31P{1H} NMR:
d
25.45 ppm [s, with satellite peaks at 2J(31P–119/117Sn) 160.5,
167.1 Hz]; 119Sn{1H} NMR: d 82.3 ppm [t, 2J(119Sn–31P) 167.6 Hz].
4.11. X-ray crystallographic study of 5
Diffraction data were collected at 293(2) K on an Enraf-Nonius
CAD 4 diffractometer using monochromated Mo K
a radiation
4.8. Preparation of mixtures with H(L3) of
(k = 0.71069 Å). Crystals were mounted under an inert atmosphere
into a capillary which was then sealed. The structure was refined
on all F2 using SHELXL-97 [27]. Further details are in Table 6. There
are two independent molecules in the unit cell of essentially the
same geometry.
(7) and [Sn(L6)]2 (8)
Sn[CH(SiMe3)P(Ph)2NSiMe3]2
Solid tin(II) chloride (0.17 g, 0.897 mmol) was added to a stirred
solution of Li(L3) (0.68 g, 1.86 mmol) in hexane (40 cm3) at ꢀ40 °C,
to which Et2O (40 cm3) was added. The mixture was stirred for
21 h at ambient temperature, then filtered. Volatiles were removed
from the filtrate in vacuo yielding a mixture of 7 and H(L3) as a
sticky solid. The NMR data (integration of Ph signals excluded)
were as follows: 1H NMR: d 0.04 (s, 18 H, CSiMe3), 0.22 (s, 18 H,
NSiMe3), 1.71 [d, 2 H, 1J(1H–31P) 15.7 Hz], 6.94–7.81 ppm (m,
Ph); 31P{1H} NMR: d 25.45 ppm [s, with satellites 2J(31P–119Sn)
167 Hz]; 119Sn{1H} NMR: d 82.3 ppm [t, 2J(119Sn–31P) 167 Hz].
A solution of 7 in C6D6 was stored in an NMR tube for 28 d,
when all traces of signals of 7 had disappeared and the following
data (attributed to 8) were recorded: 1H NMR: d ꢀ0.25 (s, 9 H,
CSiMe3), 0.15 (s, 9 H, NSiMe3), 6.81–7.72 ppm (m, Ph); 31P{1H}
4.12. Quantum chemical calculations
All molecules were fully optimised by the MP2 method, utilising
the resolution of the identity (RI) technique [28] as implemented in
the TURBOMOLE version 5.10 [29]. A triple-zeta valence basis set
(def-TZVP) [30,31], together with the corresponding RI auxiliary
basis set [32], was applied for all atoms, and for tin a 46 electron
relativistic effective core potential (ECP) was used [33]. Symmetry
constraints were employed when applicable. Each structure was
verified as a true minimum in the potential energy surface by per-
forming vibrational frequency calculations, also required for
obtaining the Gibbs free energies.
NMR:
d
27.77 ppm [s, with satellites 2J(31P–119Sn) 138 Hz];
119Sn{1H} NMR: d 530.3 ppm [t, 2J(119Sn–31P) 147 Hz].
4.9. Preparation of
Pb[CH(SiMe3)P(Ph)(1,2-C6H4)=NSiMe2]2
{ꢁ [Pb(L4) 2} (10)
Table 6
Crystal and refinement for 5.
From lead(II) chloride (0.23 g, 0.82 mmol) and a solution of
Li(L4) (0.57 g, 1.63 mmol) in Et2O (20 cm3), using a procedure sim-
ilar to that for Sn(L4)2 (Section 4.6), there were obtained colourless
crystals of 10 (0.35 g, 48%) (Anal. Calc. C36H50N2P2Si4Pb: C, 48.5; H,
5.65; N, 3.14. Found: C, 47.9; H, 5.65; N, 3.09%), mp 90–92 °C. 1H
NMR: d 0.31 [s, 18 H, Si(CH3)3], 0.53 [s, 6 H, Si(CH3)2], 0.69 [s, 6
H, Si(CH3)2], 1.43 [d, 2 H, 2J(1H–31P) 9.5 Hz]; 7.06–7.25 (m) and
7.54–7.65 ppm (m, Ph, C6H4); 13C{1H} NMR: d 1.63 [d, J(13C–31P)
6.2, SiCH3], 2.01 [d, J(13C–31P) 3.9, SiCH3], 2.39 [d, J(13C–31P) 2.41,
SiCH3], 28.2 [d, 2J(13C–31P) 61.9, CH]; 127.0 [d, J(13C–31P) 13.4],
128.5 [d, J(13C–31P) 11.2], 129.1 [d, J(13C–31P) 10.2], 129.7 [d,
J(13C–31P) 2.8], 129.9 [d, J(13C–31P) 2.8], 131.1 [d, J(13C–31P) 16.5],
141.3 [d, 1J(13C–31P) 86.9], 148.0 [d, 1J(13C–31P) 30.8], 153.6 ppm
[d, J(13C–31P) 77.0 Hz]; 31P{1H} NMR: d 40.3 ppm [s, with satellites,
Formula
C34H38N2Si2Sn2
M
768.22
Triclinic
Crystal system
Space group
P1(No. 2)
12.369(3)
12.501(5)
13.058(4)
99.19(3)
116.55(3)
101.37(3)
1698.5(9)
2
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Absorption coefficient (mmꢀ1
Unique reflections,
)
1.57
5964
3962
R1 0.051, wR2 0.085
R1 0.095, wR2 0.100
Reflections with I > 2
r
(I)
J(31P–119Sn) 311.8 Hz]; 207Pb{1H} NMR:
2J(207Pb–31P) 313.3 Hz].
d
1998.3 ppm [t,
Final R indices [I > 2
r
(I)]
R indices (all data)

P.B. Hitchcock et al. / Journal of Organometallic Chemistry 694 (2009) 3487–3499
3499
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For financial support we thank EPSRC and SPECSBioSpecs
(J.R.S.), the Chinese Government and the British Council (Z.-X.W.)
and the European Commission (TMR grant for P.G.H.U.).
Appendix A. Supplementary data
CCDC 730721 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.jorganchem.
2009.06.025.
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