Novel (silylimino)diarylphosphoranyl(trimethylsilyl)methyl-C,N ligands [CH(SiMe3)PPh2=NSiMe3]- ([LL′]-) and [CH(SiMe3) {Ph(1,2-C6H4)P=NSiMe2}]- (

Article abstract of DOI:10.1039/a700609h

Metal complexes containing the ligands [CH(SiMe₃)PPh₂=NSiMe₃]^- {≡[LL′]^-} and [CH(Si-Me₃){Ph(1,2-C₆H₄)P=NSiMe ₂}]^- {≡[LL″]^-} are report

Full text of DOI:10.1039/a700609h

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Novel (silylimino)diarylphosphoranyl(trimethylsilyl)methyl-C,N ligands
[CH(SiMe3)PPh2NNSiMe3]2 ([LLA]2) and
[CH(SiMe3){Ph(1,2-C6H4)PNNSiMe2}]2 ([LLB]2) and the structures of
[Li(LLB)]2 and [Pb(LLA)2]†
Peter B. Hitchcock, Michael F. Lappert* and Zhong-Xia Wang
The Chemistry Laboratory, University of Sussex, Brighton, UK BN1 9QJ
Metal
complexes
containing
the
ligands
5 or the colourless Pb(LLB)2 6. The yields shown in Scheme 1
refer to isolated, pure, crystalline (or for 3, powder) 2–6.
The conversion of 2 to 4 (Scheme 1, step iii) probably
proceeded via an ortho-lithiated intermediate, followed by an
intramolecular displacement of Me2 at silicon by the aromatic
anion, as shown in 7. In a separate experiment (Scheme 1, step
iv) it was shown that the transformation 2 to 4 was effected
catalytically using 0.2 mol excess of LiBun.
Each of the compounds 2–6 (except 3), were hydrocarbon-
soluble, gave satisfactory microanalytical, as well as 1H,
13C{1H}, 31P{1H}, 7Li{1H} (2 and 4) and 207Pb{1H} (5 and 6)
NMR‡ and EI mass spectra {which showed as the highest ion
[M 2 Li (or K) + 1]+ (ca. 30% for 2 or 3), [M 2 Li]+ (58% for
4) and M+ (1% for 5 and 5% for 6)} (thf = OC4H8, M = the
mononuclear molecular ion). Single-crystal X-ray diffraction
data§ established the molecular structures of 4 (Fig. 1), 5
(Fig. 2) and 6; the structure of 6 will be presented in the full
paper.
[CH(SiMe3)PPh2NNSiMe3]2 {·[LLA]2} and [CH(Si-
Me3){Ph(1,2-C6H4)PNNSiMe2}]2 {·[LLB]2} are reported
[from, as initial precursor, CH2(SiMe3)PPh2NNSiMe3]:
Li(LLA), K(LLA), [Li(LLB)]2 4, Pb(LLA)2 5 and Pb(LLB)2; mass
and multinuclear NMR spectra and single-crystal X-ray
diffraction data for 4 (a fused tricyclic complex having a
central LiNLiN ring) and 5 are presented.
We report the synthesis and characterisation of five lithium,
potassium and lead(ii) homoleptic derivatives of two novel C,N-
centred (iminophosphoranyl)methyl ligands, including the
X-ray structures of two of them.
Treatment of the phosphinimine CH2(SiMe3)PPh2NNSiMe3
11 with LiBun yielded (Scheme 1, step i) colourless [Li{CH-
(SiMe3)PPh2NNSiMe3}]2 {·[Li(LLA)]2} 2, which with KOBut
in hexane afforded (Scheme 1, step ii) the insoluble, pale yellow
K(LLA) 3, which was soluble in thf or pyridine. Reacting 2
with LiBun gave (Scheme 1, step iii) the colourless ortho-
Noteworthy features of the NMR spectra‡ include the
demonstration of (i) long-range phosphorus–silylmethyl cou-
pling in the 13C{1H} NMR spectrum of 2, 3J(13C–31P) 3.5, 4.6
silylated product [Li(CH(SiMe3){Ph(1,2-C6H4)PNNSiMe2})]2
{N[Li(LLB)]2} 4, which was also accessible (Scheme 1, step iv)
C(10)
from 1 and 1.2 equiv. of LiBun. The product obtained (Scheme
C(11)
1, step v) from PbCl2 and either 2 or 4 was the yellow Pb(LLA)2
C(15)
C(9)
C(7)
C(6)
C(14)
C(8)
Si(1)
C(12)
C(13)
C(1)
SiMe3
SiMe3
N
SiMe3
C(2)
P
C(5)
N
K
CH
N
Li
CH
i
ii
C(16)
Ph2P
Ph2P
Ph2P
CH2
C(4)
C(3)
Li
SiMe3
N
SiMe3
SiMe3
Si(2)
3, 75%
1 (ref. 1)
2, 85%
N′
Li′
v
iv
iii
C(18)
C(17)
1
– Pb[CH(SiMe3)PPh2=NSiMe3]2
2
5, 50%
Li +
–
Me2
Si
Me2
1.699(3)
P
SiMe2
Si
Me
C(1)
1.628(2)
N
N
2.081(6) N
v
N
2.232(6)
1
1
–
2
– Pb
2
P
P
Li
Li
P
Ph
Ph
CH
1.978(5)
CH
SiMe3
6, 50%
Ph
CH
Li′
C′
N′
SiMe3
SiMe3
2
2
7
4, 70%
P′
4a
Scheme
1
Synthesis of (silylimino)diarylphosphoranyl(trimethyl-
silyl)methyl-C,N]metal complexes 2–6. Reagents and conditions: i, LiBun,
hexane, 220 °C to room temp., 3 h; ii, KOBut, hexane, room temp., 3 h; iii,
LiBun, hexane, reflux, 4 h; iv, 1.2 equiv. LiBun, hexane, 220 °C to room
temp., 5 d; v, 1/2 PbCl2, Et2O, 245 to ca. 20 °C.
Fig. 1 The molecular structure of crystalline complex 4. Selected bond
lengths (Å) (see also 4a) and angles (°): N–Li–C(1) 80.1(2), N–Li–NA
103.8(2), NA–Li–C(1) 135.0(3), N–P–C(1) 113.18(14), P–N–Li 86.2(2),
P–N–LiA 126.4(2), P–C(1)–Li 79.9(2), Li–N-LiA 76.2(2).
Chem. Commun., 1997
1113

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Hz for the two SiMe3 groups; (ii) separate (axial and equatorial)
Si–Me 1H signals due to the endocyclic SiMe2 group in 4 and 6;
and (iii) 2J(31P–207Pb) and 2J(207Pb–31P) in 5 and 6.
The new ligands [LLA]2 and [LLB]2 should have an extensive
coordination chemistry. Using Li(LLA) 2 or Li(LLB) 4, we have
made inter alia Sn(LLA)2, Sn(LLB)2, [Sn(LLA)]2, Pb(LLB)2 and
The structures of crystalline [Li{CH2PMe2NNSiMe3}]4 8 and
[Fe(LLA)3], as well as some analogues of Li, K, SnII, FeII and
[Li{CMe2PPri2NNSiMe3}]2 9 have the lithium atoms bridged
by carbon.2 It is surprising, therefore, that the dinuclear
crystalline 4 (Fig. 1) has the imido nitrogen atoms bridging the
lithium atoms, the skeletal structure being ladder-shaped, 4a.
CoII.
We thank the Chinese Government and the British Council
for the award of a studentship to Z.-X. W. and the EPSRC for
other support.
The central LiNLiANA ring is planar, with the angle at N
Footnotes
narrower [76.2(2)°] than that at Li, 103.8(2)°. The terminal
LiNPC rings are puckered, Li lying 0.26 Å out of the NPC
plane. The bond angles at the three-coordinate Li range from
80.1(2) [N–Li–C(1)] to 135.0(3)° [NA–Li–C(1)], the sum of the
angles at Li being ca. 319°. The six bond angles at N (av. 108°)
vary from 76.2(2) to 129.6(2)° [Si(2)–N–Li]. The Li–N and Li–
C bond lengths are unexceptional,3 while the Li···P contact of
2.556(5) Å is similar to the 2.56 (av.), 2.58 (av.) or 2.520(9) Å
found in [{Li(thf)2}2{PhPCH2CH2PPh}],4 [{Li(tmen)}2-
C6H4(PPh)2-1,2}],5 or Li(thf)2[{N(SiMe3)}2PPh2],6 respec-
tively [tmen = (Me2NCH2)2]. The average Li–N and Li–C
distances are 2.03 (8) and 1.928 (9), and 2.39 (8) and 2.27 (9),
* E-mail: M.F.Lappert@sussex.ac.uk
† No reprints available.
‡ Selected NMR data [1H 360.1, 7Li{1H} 97.3, 31P{1H} 101.3, 207Pb{1H}
52.1 MHz; 298 K; C5D5N for 3, C6D6 for 2 and 4–6; J, Hz]. 2: 1H d 0.10
(s, 9 H, SiMe3), 0.13 (s, 9 H, SiMe3), 0.17 (d, 1 H, CH, J 13.8), 7.19 (s, Ph),
7.21 (s, Ph), 7.84–7.89 (m, Ph); 7Li{1H} d 2.23; 31P{1H} d 33.32. 3: 1H d
0.26 (s, 9 H, SiMe3), 0.29 (s, 9 H, SiMe3), 7.20–7.58 (m, Ph), 8.18–8.22 (m,
Ph); 31P{1H} d 20.23. 4: 1H d 20.02 (s, 9 H, SiMe3), 0.32 (s, 3 H, SiMe),
0.59 (s, 3 H, SiMe), 0.92 (d, 1 H, CH, J 4.9), 7.03–7.15 (m, 5 H, Ph),
7.44–7.56 (m, 2 H, C6H4), 7.77–7.83 (m, 2 H, C6H4); 7Li{1H} d 2.05;
1
31P{1H} d 48.70. 5: H d 20.01 (s, 18 H, SiMe3), 0.20 (s, 18 H, SiMe3),
1.37 (d, 2 H, CH, J 15.8), 7.00–7.05 (m, Ph), 7.15–7.22 (m, Ph), 7.64–7.69
(m, Ph), 7.79–7.85 (m, Ph); 31P{1H} d 19.52 (s, with satellite peaks, J 308);
207Pb{1H} d 2787.63 (t, J 306). 6: 1H d 0.31 (s, 18 H, SiMe3), 0.53 (s, 6 H,
SiMe), 0.69 (s, 6 H, SiMe), 1.43 (d, 2 H, CH, J 9.5), 7.06–7.25 (m, Ph +
C6H4), 7.54–7.65 (m, Ph + C6H4); 31P{1H} d 40.27 (s, with satellite peaks,
respectively.2 The X-ray structure of [Li{2-C6H4PPh2NNSi-
Me3}2Li(OEt)2] is available.7
Crystalline 5 is mononuclear, Fig. 2. The four-coordinate
lead has a stereochemically active lone pair of electrons. The
phosphorus approximates to its having tetrahedral geometry. A
simplified bonding pattern is shown in 5a. The P–N bond length
of 1.569(4) Å indicates a double bond, while the mean
endocyclic P–C distance of 1.757(6) Å is slightly shorter than
usual for a PV–C single bond. The average Pb–N distance of
2.678 Å is much longer than in anionic nitrogen-centred lead(ii)
compounds, e.g., 2.24(2) Å in Pb[N(SiMe3)2]2,8 or 2.465 Å
(av.) in Pb[{N(SiMe3)}2PPh2]2,9 while the mean Pb–C(sp3)
bond length of 2.448 Å in 5 may be compared with the Pb–
C(sp2) distance of 2.336 Å in Pb[C6H2(CF3)3-2,4,6]2.10
J 311.8); 207Pb{1H} d 1998.26 (t, J 313.3).
–
§ Crystal data: 4, C36H50Li2N2P2Si4: M = 699.0, triclinic, space group P1
(no. 2), a = 9.904(1), b = 10.259(3), c = 11.175(1) Å, a = 109.10(2),
b = 95.79(1), g = 104.44(2)°, U = 1018.2(2) Å3, F(000) = 372; Z = 1,
Dc = 1.14 g cm23, specimen 0.3 3 0.3 3 0.3 mm, 3578 independent
reflections, 2706 reflections with [ıF2ı
> = 0.054,
2s(F2)]; R1
wR2 = 0.152 (for all data). 5, C38H58N2P2PbSi4: M = 924.4, triclinic, space
–
group P1 (no. 2), a = 10.767(2), b = 14.091(2), c = 16.775(2) Å,
a
= 87.07(1), b = 72.01(1), g = 69.77(1)°, U =
2266.9(6) Å3,
F(000) = 936; Z = 2, Dc = 1.35 g cm23, specimen 0.3 3 0.3 3 0.1 mm,
13179 independent reflections, 7752 reflections with [ıF2ı > 2s(F2)];
R1 = 0.056, wR2 = 0.102 (for all data).
Intensities were measured to qmax 25° (for 4) or 30° (for 5) on an Enraf-
Nonius CAD4 diffractometer using monochromated Mo-Ka (m = 0.25 mm
4, 3.92 mm 5) radiation (l = 0.71073 Å); absorption correction from y scan
for 5. Structure refinements were by SHELXL-93, with H atoms in riding
mode. Atomic coordinates, bond lengths and angles, and thermal parame-
ters have been deposited at the Cambridge Crystallographic Data Centre
(CCDC). See Information for Authors, Issue No. 1. Any request to the
CCDC for this material should quote the full literature citation and the
reference number 182/455.
C(30)
C(25)
C(6)
C(26)
C(28)
C(7)
C(24)
C(5)
Si(1)
Si(4)
C(31)
C(29)
C(17)
C(16)
C(32)
N(1)
C(18)
C(27)
C(33)
C(15)
C(20)
C(19)
C(14)
P(2)
P(1)
Pb
References
C(38)
C(34)
C(1)
C(36)
C(37)
1 J. C. Wilburn and R. H. Neilson, Inorg. Chem., 1979, 18, 347.
2 A. Mu¨ller, B. Neumu¨ller and K. Dehnicke, Chem. Ber., 1996, 129,
253.
C(8)
C(35)
N(2)
C(13)
C(9)
3 cf. K. Gregory, P. v. R. Schleyer and R. Snaith, Adv. Inorg. Chem., 1991,
37, 47; W. N. Setzer and P. v. R. Schleyer, Adv. Organomet. Chem.,
1985, 24, 353.
4 D. M. Anderson, P. B. Hitchcock, M. F. Lappert and I. Moss, Inorg.
Chim. Acta, 1988, 141, 157.
C(23)
Si(3)
Si(2)
C(12)
C(11)
C(2)
C(10)
C(4)
C(21)
C(3)
C(22)
b
5 D.M. Anderson, P. B. Hitchcock, M. F. Lappert, W.-P. Leung and
J. A. Zora, J. Organomet. Chem., 1987, 333, C13.
6 A. Steiner and D. Stalke, Inorg. Chem., 1993, 32, 1977.
7 A. Steiner and D. Stalke, Angew. Chem., Int. Ed. Engl., 1995, 34,
1752.
Pb
2.701(4)
N(1)
a
d
2.449(6)
c
C(20)
P(2)
1.569(4)
P(1) C(1)
1.759(5)
N(2)
8 T. Fjeldberg, H. Hope, M. F. Lappert, P. P. Power and A. J. Thorne,
J. Chem. Soc., Chem. Commun., 1983, 639.
5a
9 U. Kilimann, M. Noltemeyer and F. T. Edelmann, J. Organomet. Chem.,
1993, 443, 35.
[a, 62.52(14); b, 107.6(2);
c, 107.2(2); d, 167.27(11)°]
10 S. Brooker, J.-K. Buijink and F. T. Edelmann, Organometallics, 1991,
10, 25.
Fig. 2 The molecular structure of crystalline complex 5. Selected bond
lengths (Å) and angles (°) (see also 5a): Pb–C(20) 2.447(5), Pb–N(2)
2.654(4), P(2)–C(20) 1.756(5), P(2)–N(2) 1.569(4); C(20)–Pb–C(1)
88.2(2), C(20)–Pb–N(2) 63.6(2), C(1)–Pb–N(2) 106.69(14), C(20)–Pb–
N(1) 107.6(2), N(2)–Pb–N(1) 167.27(11), N(2)–P(2)–C(20) 108.1(2).
Received in Basel, Switzerland, 27th January 1997; Com.
7/00609H
1114
Chem. Commun., 1997