Group 1 and 13 complexes of aryl-substituted bis(phosphinimino)methyls

Article abstract of DOI:10.1016/j.jorganchem.2003.11.030

The organolithium reagent [{HC(Ph₂PNC₆ H₂Me₃-2,4,6)₂}Li(OEt₂)] was easily obtained by deprotonation of H₂C(Ph₂ P=NC₆H₂Me₃-2,4,6)₂ with nBuLi in diethyl ether solution. The crystal structure of [{HC(Ph₂PNC₆H₂Me₃-2,4,6) ₂}Li(OEt₂)] has been determined and shown to consist a monomeric chelate structure that contains a distorted, trigonal planar lithium centre. The ligand precursor has also been deprotonated with both Me₃Al and Me₂AlCl to yield the tetrahedral organoaluminium complexes, [{HC(Ph₂ PNC₆H₂Me₃-2,4,6)₂}AlMe ₂] and [{HC(Ph₂PNC₆H₂Me ₃-2,4,6)₂}Al(Cl)Me]. Reaction of [{HC(Ph₂PNC₆H₂Me₃-2,4,6) ₂}Li(OEt₂)] with either AlX₃ (X=Cl, Br, I) or GaCl₃ yielded a series of dihalo derivatives [{HC(Ph₂PNC₆H₂Me₃-2,4,6) ₂}MX₂] all of which have been shown to exist as similar monomeric species containing four-coordinate group 13 centres.

Full text of DOI:10.1016/j.jorganchem.2003.11.030

Journal of Organometallic Chemistry 689 (2004) 722–730
www.elsevier.com/locate/jorganchem
Group 1 and 13 complexes of aryl-substituted
bis(phosphinimino)methyls
a,
b
b
Michael S. Hill *, Peter B. Hitchcock , Sophia M.A. Karagouni
a
Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, UK
School of Chemistry, Physics and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QJ, UK
b
Received 14 October 2003; accepted 19 November 2003
Abstract
The organolithium reagent [{HC(Ph2PNC6H2Me3-2,4,6)2}Li(OEt2)] was easily obtained by deprotonation of H2C(Ph2P@
NC6H2Me3-2,4,6)2 with nBuLi in diethyl ether solution. The crystal structure of [{HC(Ph2PNC6H2Me3-2,4,6)2}Li(OEt2)] has been
determined and shown to consist a monomeric chelate structure that contains a distorted, trigonal planar lithium centre. The ligand
precursor has also been deprotonated with both Me3Al and Me2AlCl to yield the tetrahedral organoaluminium complexes,
[{HC(Ph2PNC6H2Me3-2,4,6)2}AlMe2] and [{HC(Ph2PNC6H2Me3-2,4,6)2}Al(Cl)Me]. Reaction of [{HC(Ph2PNC6H2Me3-2,4,6)2}
Li(OEt2)] with either AlX3 (X ¼ Cl, Br, I) or GaCl3 yielded a series of dihalo derivatives [{HC(Ph2PNC6H2Me3-2,4,6)2}MX2] all of
which have been shown to exist as similar monomeric species containing four-coordinate group 13 centres.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Bis(phosphinimino)methyl; Group 13; X-ray structures
1. Introduction
We were struck by the close resemblance, in both
steric demands and denticity, between the aryl-substi-
tuted bis(phosphinimino)methanes, II and III [31],
and ligands of type I. The trimethylsilyl-substituted
bis(phosphinimino)methane, IV, has been the subject of
a number of recent publications [32–38], most notably in
its doubly deprotonated form for the synthesis of Ôpin-
cerÕ carbene complexes of the group 4 elements [39]. Use
of the N-aryl substituted variants II and III however is
restricted to a single account of their application as
ancillary ligands for Co(II)- and Ni(II)-based olefin
polymerisation catalysts [31] and our recent reports of
their application in the support of three-coordinate mid
and late first row (Mn–Zn) transition metal amides and
alkoxides [1]. A number of group 13 derivatives of I and
IV which include, as yet unique, examples of two-
coordinate Al(I) and Ga(I), have also recently been
described [40–42], while cationic aluminium alkyl com-
plexes supported by IV have been identified as transition
metal-free ethylene polymersation catalysts [43]. We
now wish to report our syntheses of a range of group 13
complexes derived from II (Scheme 1). This study allows
detailed structural comparisons to be made with related
We have recently initiated a program of research that
aims to apply bulky and kinetically stabilising ligand
systems to the study of low-coordinate metal centres
[1,2]. A review of the recent literature revealed a wide-
spread use of chelating, anionic ligands derived by de-
protonation of bulky aryl-substituted b-aminoimines
such as I and related ligands bearing other flanking N-
substituents, which have the potential for precise steric
and electronic ÔtuningÕ of a reactive metal site. Ligands
of this type have been used to support a variety of low-
coordinate transition metal [3–13], main group element
[14–20] and f-element complexes [21,22]. Furthermore,
many of these systems have shown great utility in, for
example, ring opening polymerisation catalysis [23–26]
or as synthetic mimics for low-coordinate metal envi-
ronments encountered in biological systems [27–30].
* Corresponding author. Tel.: +44-207-594-5709; fax: +44-207-594-
5804.
E-mail address: mike.hill@imperial.ac.uk (M.S. Hill).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.11.030

M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
723
Scheme 1. Reagents: Path A ; 3, Me3Al; 4 Me2AlCl: Path B ; 5 AlCl3; 6
AlBr3; 7 AlI3; 8 GaCl3.
Fig. 1. The molecular structure of II (only hydrogen atoms attached to
C(1) illustrated for clarity). 50% probability ellipsoids.
Table 1
ꢀ
Selected bond lengths (A) and angles (°) for compounds II, 1, and 2
II
1
2
M–N(1)
M–N(2)
1.952(5)
1.979(4)
1.953(7)a
2.036(7)b
1.941(6)c
2.061(6)d
2.521(6)e
1.598(3)
1.593(3)
1.740(3)
1.702(3)f
1.731(3)
1.763(3)g
Fig. I, II, III and IV.
M–Cl/N(3)/O
P(1)–N(1)
P(2)–N(2)
P(1)–C(1)
1.965(5)
1.597(2)
1.585(2)
1.725(2)
1.518(4)
1.534(4)
1.842(5)
derivatives and a further evaluation of the ligating be-
haviour of II toward electropositive metal centres (Figs.
I, II, III and IV).
P(2)–C(1)
1.837(5)
1.713(2)
N(1)–M–O/Cl/I
N(2)–M–O/Cl/I
N(1)–M–N(2)
122.9(2)
122.1(2)
114.9(2)
166.3(4)h
134.0(3)i
76.2(2)j
2. Results and discussion
115.5(3)k
97.1(2)l
M–N(1)–P(1)
M–N(2)–P(2)
N(1)–P(1)–C(1)
111.72(17)
110.69(17)
112.90(12)
The N-mesityl-substituted bis(diphenylphosphini-
mino)methane II (mesityl ¼ 2,4,6-trimethylphenyl) was
synthesised according to the literature method [31].
Crystallisation from diethyl ether resulted in colourless
crystals which were subjected to an X-ray diffraction
analysis. The molecular structure of II along with the
numbering scheme used is illustrated in Fig. 1; selected
bond lengths and angles are given in Table 1 and details
of the X-ray analysis are given in Table 2. The structure
is unremarkable and the observed P–N and P–C bond
distances are comparable to values determined in other
structurally characterised phosphiniminomethanes and
bis(phosphinimino)methanes [1a,44].
Treatment of II with nBuLi in diethyl ether and
crystallisation from a diethyl ether/hexane solvent sys-
tem (ꢀ10:1) at )30°C resulted in the isolation of 1 as
large colourless block crystals suitable for X-ray dif-
fraction analysis. The molecular structure of 1 along
with the numbering scheme used is illustrated in Fig. 2.
Selected bond lengths and angles are given in Table 1
and details of the X-ray analysis are given in Table 2. 1
is a monomeric lithium derivative of II in which the
lithium centre is three-coordinate. This comprises a six-
102.5(2)m
106.90(15)
107.84(15)n
106.12(14)
130.74(19)
118.71(19)o
114.3(2)
N(2)–P(2)–C(1)
P(1)–C(1)–P(2)
119.0(2)
115.8(2)
111.51(12)
134.58(16)
a Li(1)–N(1).
b Li(1)–N(3).
c Li(2)–N(2).
d Li(2)–N(3).
e Li(2)–P(4).
f P(3)–C(44).
g P(4)–C(44).
h N(1)–Li(1)–N(3).
i N(2)–Li(2)–N(3).
j N(1)–Li(1)–C(1).
k N(3)–Li(1)–C(1).
l Li(1)–N(1)–P(1).
m Li(1)–N(3)–P(3).
n N(3)–P(3)–C(44).
o P(3)–C(44)–P(4).
membered metallocyclic structure in which the bis
(phosphinimino)methyl ligand behaves as a strictly bid-
entate chelate and the lithium coordination is completed

724
M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
Table 2
Selected crystallographic and data collection parameters for compounds II, 1, 2, 3 and 4
II
1
2
3
4
Chemical formula
C43H44N2P2
C47H53LiN2OP2
C77H75Li2N3P4 ꢁ 0.5
C45H49AlN2P2 ꢁ 1.5
(C7H8)
844.98
C44H46AlClN2P2 ꢁ 2
(C7H8)
911.47
(C6H14
)
Formula weight
T (K)
Crystal size (mm3)
Crystal system
Space group
650.74
173(2)
730.79
173(2)
1223.25
173(2)
173(2)
0.30 ꢂ 0.20 ꢂ 0.20
173(2)
0.30 ꢂ 0.30 x 0.20
0.10 ꢂ 0.10 ꢂ 0.02 0.40 ꢂ 0.40 ꢂ 0.30 0.40 ꢂ 0.30 ꢂ 0.30
Monoclinic
P21=n (No.14)
11.2554(16)
23.545(5)
13.5408(14)
90
Triclinic
ꢁ
Monoclinic
P21=n (No.14)
11.9297(3)
24.1662(7)
24.0715(7)
90
Triclinic
ꢁ
Triclinic
ꢁ
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
ꢀ
a (A)
10.5227(5)
11.2575(6)
18.5988(10)
86.539(3)
81.331(3)
70.183(3)
2
12.4197(8)
12.8777(8)
16.3104(11)
92.107(2)
108.078(3)
101.181(4)
2
12.2018(2)
15.1001(3)
15.7376(4)
110.008(1)
93.998(1)
109.626(1)
2
ꢀ
b (A)
ꢀ
c (A)
a (deg)
b (deg)
c (deg)
Z
87.871(9)
90
91.497(2)
90
4
4
3
ꢀ
V (A )
3586.0(10)
1.21
0.15
2049.0(2)
1.19
0.14
6937.3(3)
1.17
0.15
2419.6(3)
1.16
0.15
2509.86(9)
1.21
0.20
dc (Mg mꢃ3
l (mmꢃ1
)
)
h range (deg)
4.16–21.97
0.066, 0.117
0.124, 0.135
3.71–21.96
0.045, 0.109
0.055, 0.116
9581/4833/
0.049
3.77–23.00
0.056, 0.133
0.079, 0.147
29,125/9563/
0.060
3.78–23.02
0.095, 0.241
0.118, 0.258
15,200/6309/
0.091
3.76–24.84
0.065, 0.161
0.088, 0.174
26,622/8576/
0.056
R1; wR2½I > 2rðIÞꢄ
R1; wR2 all data
Measured/independent 13,185/4338/
Reflections/Rint
Reflections with
I > 2rðIÞ
0.123
2759
4142
7282
5010
6613
cated by the sum of angles subtended by the bonds
around lithium [Rangles ¼ 359:9ð2Þ°], the lithium coordi-
nation geometry is effectively trigonal planar and only
slightly distorted by the ÔbiteÕ of the chelated ligand
[N(1)–Li–N(2) ¼ 14.9(2)°]. The Li–N and Li–O bond
lengths are within the range of those previously ob-
served for three-coordinate lithium bound to amide and
ether ligands and are similar to those reported for che-
lated b-diketiminate derivatives [14]. This latter obser-
vation illustrates the similar donation of charge that
results from the two ligand types. The P–N and P–C
bond lengths indicate considerable charge delocalisation
around the chelate structure; the P–C(1) bonds are
shortened in comparison to those of II while the P–N
bonds are elongated.
The preparation of 1 was repeated on several occa-
sions during the course of this study. Although yields
were consistently high, in one instance, a small number
of colourless crystals with a different needle-like mor-
phology were observed to have formed along with the
bulk product. Although a pure bulk sample could not be
isolated for complete analytical and NMR spectroscopic
characterisation, a further X-ray analysis revealed them
to be the dimeric lithium derivative 2. The structure of
compound 2 is illustrated in Fig. 3, while selected bond
lengths and angles are given in Table 1 and details of the
X-ray analysis are given in Table 2. 2 consists of a de-
protonated molecule of II which has co-aggregated along
with the lithium derivative of the mixed P(III)/P(V)
methane derivative V. We have previously reported V as
an intermediate in the synthesis of an asymmetrically
Fig. 2. The molecular structure of 1 (hydrogen atoms removed for
clarity). 20% probability ellipsoids.
by a single molecule of diethyl ether. Although the
chelated ligand adopts a boat conformation, the dis-
tance between the carbanionic methine carbon C(1) and
ꢀ
the lithium centre is too long (2.999 A to suggest any
significant interaction. This is in contrast to our obser-
vations of similar three-coordinate derivatives of the
later first row (Mn–Zn) transition elements where M–
ꢀ
C(1) distances <2.4 A have been observed [1]. As indi-

M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
725
Fig. V.
respectively. X-ray crystallographic analyses were un-
dertaken upon crystals of both compounds grown from
toluene solution. Details of both analyses are given in
Table 2. Crystals of the dimethylaluminium derivative 3
diffracted only weakly at higher angle resulting in high
final R indices. The X-ray analysis of 4, although re-
sulting in acceptable residuals after refinement, was
hampered by disorder of the chlorine and methyl groups
with relative occupancy 0.71:0.29. Although detailed
discussion of bond lengths and angles are not justifiable,
the structures are unambiguous. Like the previously
reported [{HC(Ph2PNSiMe3)2}AlMe2] [49], both struc-
tures are monomers in which the phosphinimine units of
the anionic ligands chelate to the four-coordinate alu-
minium centres to form a six-membered N–P–C–P–N–
Al metallocyclic ring. Each ring adopts a distorted boat
conformation, although the Al–C(1) distances are too
Fig. 3. The molecular structure of 2 (hydrogen atoms removed for
clarity). 20% probability ellipsoids.
substituted bis(phosphinimino)methane [1], while several
examples of (phosphinimino)methyl phosphines have
been reported in the literature [45]. On this occasion we
reason that a small contaminating quantity of V was
present in our sample of II and that the deprotonated V
forms 2 when crystallised in the presence of 1. The di-
nuclear molecule contains two three-coordinate lithium
ions. Li(1) is coordinated by the N(1) centre of the de-
protonated bis(phosphinimino)methyl ligand and N(3)
of the phosphinimino arm of the P(III)/P(V) fragment,
subtending a N–Li–N angle of 166.3(4)°. This deviation
from linearity is due to an additional Li(1)–C(1) inter-
ꢀ
long [3: 3.36; 4: 3.24 A] to formulate either structure as
containing direct Al–C(1) bonds which would effectively
raise the coordination number of each Al centre to five.
A wide range of unusual cationic and low valent
group 13 complexes have been reported which employ a
b-diketiminate ligand as a sterically demanding and
solubilising reaction platform [40–42,50–55]. Many of
these interesting species employ dihalo-aluminium or
gallium compounds as starting materials [50,56]. We
therefore undertook the synthesis of analogous com-
pounds derived from II through metathesis of 1 and
the appropriate aluminium or gallium trihalide in di-
ethyl ether solution. Compounds 5–8, of the general
form [{HC(Ph2PNC6H2Me3-2,4,6)2}MX2] (5: M ¼ Al,
X ¼ Cl; 6: M ¼ Al, X ¼ Br; 7: M ¼ Al, X ¼ I; 8: M ¼ Ga,
X ¼ Cl) were synthesised straightforwardly in this
manner and obtained as colourless crystalline solids in
high yield after crystallisation from diethyl ether solu-
tion at low temperature. In contrast to the methyl
substituted organoaluminium compounds 3 and 4, each
of the dihalo derivatives displayed only limited solubility
ꢀ
ꢀ
action of 2.362(7) A. There are no short contacts (<3 A
to the P(III)/P(V)-bridging C(44) methyl centre. Li(2)
bridges the N(2) and N(3) positions of the two ligand
moieties and is further ligated by the trivalent P(4) centre
to form a five-membered metallocyclic P–C–P–N–Li
chelate. The Li–N distances, while all falling within the
normal range observed for lithium amides and lithium
iminophosphoranes, reflect the differing coordination
numbers of the nitrogen centres [46], as does the P(3)–
ꢀ
N(3) bond length [1.635(3) A] in comparison to the P(1)–
ꢀ
N(1) [1.598(3) A] and P(2)–N(2) [1.593(3) A] distances.
ꢀ
ꢀ
The Li(2)–P(4) distance of 2.521(6) A is typical of Li–P
interactions observed in other phosphorus-substituted
methyl anions such as [Li(thf)C(SiMe3)2{SiMe2CH
ꢀ
[Li(thf)2]PPh2}] [2.517(8) A] [47] and [LiC(SiMe3)2
ꢀ
PMe2]2 [2.519(4) A] [48] (Fig. V).
Reaction of II with either Me3Al or Me2AlCl in tol-
uene also resulted in deprotonation of the ligand and
resulted in high yielding syntheses of the organoalu-
minium compounds 3 and 4 respectively. In both cases
31P NMR spectra of the final reaction mixtures dem-
onstrated that quantitative consumption of II had oc-
curred, presenting sharp singlets at 30.3 and 31.9 ppm
1
in toluene or benzene precluding collection of H, 13C
and 31P NMR data in these solvents. This necessitated
the use of more polar d8-THF for the collection of
quality solution-state data which were consistent with
time averaged C2v-symmetric structures.
Crystals suitable for X-ray crystallographic analyses
of all four dihalo complexes were isolated from con-
centrated diethyl ether solution. Selected bond lengths
and angles are presented in Table 3 and crystal data
are summarised in Table 4. While only compounds 5
and 6 are crystallographically isostructural, all four

726
M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
Table 3
ꢀ
Selected bond lengths (A) and angles (°) for compounds 5, 6, 7 and 8
5
6
7
8
M–N(1)
M–N(2)
1.873(2)
1.881(2)
2.1602(9)
2.1369(9)
1.650(2)
1.647(2)
1.711(2)
1.700(2)
1.880(3)
1.868(3)
1.327(1)
2.297(1)
1.648(3)
1.649(3)
1.701(3)
1.713(3)
1.865(5)
1.867(5)
2.599(2)
2.531(2)
1.648(5)
1.651(5)
1.713(5)
1.707(5)
1.915(3)
1.914(3)
2.199(1)
2.169(1)
1.642(3)
1.642(3)
1.710(4)
1.700(4)
M–Cl/Br/I(1)
M–Cl/Br/I(2)
P(1)–N(1)
P(2)–N(2)
P(1)–C(1)
P(2)–C(1)
N(1)–M–Cl/Br/I(1)
N(2)–M–Cl/Br/I(2)
Cl/Br/I(1)–M–Cl/Br/I(2)
N(1)–M–N(2)
M–N(1)–P(1)
M–N(2)–P(2)
N(1)–P(1)–C(1)
N(2)–P(2)–C(1)
P(1)–C(1)–P(2)
109.69(6)
106.64(6)
106.46(4)
113.01(8)
116.98(10)
117.91(10)
109.45(10)
107.14(10)
134.83(14)
112.38(9)
108.73(9)
104.2(4)
110.77(15)
107.92(16)
103.78(6)
111.8(2)
119.2(3)
119.4(3)
109.5(3)
108.7(3)
136.2(3)
111.70(9)
107.11(9)
105.91(4)
111.21(13)
118.91(17)
118.53(17)
109.59(18)
109.48(17)
136.9(2)
113.90(13)
117.15(15)
116.26(15)
106.77(15)
108.97(15)
134.9(2)
Table 4
Selected crystallographic and data collection parameters for compounds 5, 6, 7 and 8
5
6
7
8
Chemical formula
Formula weight
T (K)
C45H43AlCl2N2P2 ꢁ (C4H10O) C43H43AlBr2N2P2 ꢁ (C4H10O) C45H43AlI2N2P2 ꢁ 2(C4H10O)
C43H43Cl2GaN2P2
790.35
173(2)
821.73
173(2)
910.65
173(2)
1078.75
173(2)
Crystal size (mm3)
Crystal system
Space group
0.40 ꢂ 0.40 ꢂ 0.40
Monoclinic
P21=c (No. 14)
12.0797(5)
19.2571(9)
19.0409(5)
90
0.40 ꢂ 0.40 ꢂ 0.35
Monoclinic
P21=c (No.14)
12.0912(2)
19.3900(4)
19.2706(3)
90
0.10 ꢂ 0.10 ꢂ 0.10
Orthorhombic
Pna21 (No. 33)
30.8796(9)
15.8994(5)
10.2388(2)
90
0.20 ꢂ 0.20 ꢂ 0.05
Monoclinic
P21=c (No.14)
19.9063(7)
11.7084(7)
17.7565(10)
90
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a (deg)
b (deg)
c (deg)
Z
100.329(2)
90
99.288(1)
90
90
90
109.871(3)
90
4
4
4
4
3
ꢀ
V (A )
4357.5(3)
1.25
0.28
4458.7(1)
1.36
1.95
5026.9(2)
1.43
1.37
3892.1(3)
1.35
0.96
dc (Mg mꢃ3
l (mmꢃ1
)
)
h range (deg)
3.72–25.02
0.044, 0.106
0.057, 0.114
16,777/7241/
0.046
3.73–25.68
0.048, 0.082
0.077, 0.091
35,556/7852/
0.061
3.80–25.04
0.042, 0.079
0.058, 0.085
19,788/8265/
0.055
3.73–23.03
0.047, 0.093
0.066, 0.103
15,136/5387/
0.064
R1; wR2½I > 2rðIÞꢄ
R1; wR2 all data
Measured/independent
Reflections/Rint
Reflections with I > 2rI
5955
5925
6829
4185
compounds display similar features and only the struc-
tures of the diiodoaluminium dervivative 7 and the di-
chlorogallium derivative 8 are illustrated in Figs. 4 and
5. All four complexes adopt monomeric distorted tet-
rahedral structures with chelating bis(phosphinimino)
methyl ligands. The N–M–N bite angles show little
variation with changing metal or halide identity and
range from 111.21(13)° in 8 to 113.9(13)° in 6. These
values are somewhat higher than those observed in re-
lated b-diketiminate derivatives such as the dichloroal-
uminium derivative of I [99.36(4)°] [56]. We have
previously made similar observations with regard to
three-coordinate mid and late transition metal deriva-
tives of II [1]. Despite this feature, both the M–N and
M–X bond lengths of compounds 5–8 are very similar to
those observed in analogous diketiminato derivatives
indicating that charge donation from the deprotonated
II is similar to that of the b-diketiminate ligand. The
increased bite angle provided by the bis(phosphini-
mino)methyl ligand also results in a compression of the
X–M–X bond angles by some 4–5° in comparison to
similar b-diketiminate derivatives [50,56]. We have pre-
viously noted that three-coordinate metallated deriva-
tives of II display close C(1)–M contacts. These result in

M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
727
less than 1 ppm of O2. Solvents were purified by distil-
lation from an appropriate drying agent (toluene and
THF from potassium, diethyl ether from Na/benzo-
phenone and hexane from Na/K alloy). NMR spectra
were recorded at 300.13 (1H), 125.8 (13C), 194.5 (7Li)
and 121.5 MHz (31P) from samples in C6D6 at 25 °C
unless otherwise stated. Chemical shifts are relative to
1
SiMe4 for H and 13C NMR. 31P and 7Li NMR spectra
were referenced externally to aqueous H3PO4 and LiCl
respectively. Mass spectra were obtained at 70 eV.
Mesityl azide and II, were synthesised in high yield by
established literature procedures [31,57]. A sample of II
suitable for a single crystal X-ray diffraction analysis
was isolated from a concentrated diethyl ether solution
at 5 °C.
Fig. 4. The molecular structure of 7 (hydrogen atoms removed for
clarity). 20% probability ellipsoids.
3.2. [{HC(Ph2PNC6H2Me3-2,4,6)2}Li(OEt2)] (1)
nBuLi (0.62 ml of a 2.5 M solution in hexane) was
added at room temperature to a stirred solution of II
(1.0 g, 1.54 mmol) in diethyl ether (30 ml). This resulted
in gas evolution and the formation of a pale yellow so-
lution that was stirred for a further 1 h. At this point the
solution was concentrated to about 10 ml and then
cooled to )30 °C. Storage at this temperature for one
week produced 1 as colourless block crystals suitable for
an X-ray diffraction analysis (0.99 g, 88%). In an anal-
ogous preparation, 2 was identified as a minor product
by its contrasting morphology as colourless needles. A
single crystal was mechanically separated and used in a
further X-ray diffraction study. Analytical and spectro-
scopic data for 1. Anal. Calc. for C47H53LiN2OP2: C,
77.24; H, 7.32; N, 3.83. Found: C, 77.35; H, 7.22; N,
3.85. 1H NMR: d 1.13 (t, 6H, Et2O), 1.27 (t, 1H, P2CH,
2JPH ¼ 4.2 Hz), 1.84 (s, 12H, o-CH3), 2.10 (s, 6H, p-
CH3), 3.34 (q, 4H, Et2O), 6.56 (s, 4H, mesityl), 7.19 (m,
12H, m, p,-PhP), 7.70 (m, 8H, o-PhP). 13C{1H} NMR: d
Fig. 5. The molecular structure of 8 (hydrogen atoms removed for
clarity). 20% probability ellipsoids.
the adoption of a pronounced boat conformation of the
chelating ligand but without major disruption of the
overall metal coordination geometry [1]. As was the case
for the methylaluminium derivatives 3 and 4, the four
coordinate dihalo derivatives 5–8 display no M–C(1)
1
15.7 (p-CH3), 18.9 (t, JPC ¼ 150:1 Hz, PCH), 20.8
2
(Et2O), 21.4 (o-CH3), 66.3 (Et2O), 127.8 (dd, JPC ¼ 9:4
3
Hz, o-Ph), 129.5 (p-Ph), 132.9 (dd, JPC ¼ 9:4 Hz, m-
Ph), 134.8, 140.6, 141.8, 144.6, 147.9. 31P{1H} NMR: d
7
ꢀ
14.1. Li NMR: d-0.52.
interactions <3 A.
We are continuing to explore the reactivity of these
compounds, particularly as synthons en route to cat-
ionic alkoxo and amido derivatives for application in
the ring opening polymerisation of cyclic ethers and
esters [1a].
3.3. [{HC(Ph2PNC6H2Me3-2,4,6)2}AlMe2] (3)
A solution of trimethylaluminium (2.0 M in hexanes,
2.3 ml, 4.6 mmol) was added to II (3.00 g, 4.6 mmol) in
toluene (30 ml) and the mixture was stirred at room
temperature overnight. Concentration and cooling (5
°C) of this solution afforded 3 as colourless crystals.
Reproducible CHN combustion analysis for this com-
pound could not be obtained due to varying amounts of
3. Experimental section
3.1. General considerations
1
toluene solvate. Yield: 2.57 g, 80%. H NMR; d-0.25 (s,
6H, Me-Al), 1.80 (s, 12H, o-CH3), 2.08 (s, 6H, p-CH3),
6.69 (s, 4H, mesityl), 7.05 (m, 12H, m, p,-PhP), 7.79
(m, 8H, o-PhP). 13C{1H}NMR: d 2.1 (CH3-Al), 20.08
All reactions were conducted under an atmosphere of
dry argon and manipulated either on a double manifold
vacuum line or in a dinitrogen-filled drybox operating at

728
M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
1
(p-Me), 21.3 (o-Me), 21.8 (t, JPC ¼ 150:1 Hz, CHP),
125.2 (Ar), 128.4 (Ar), 130.2 (Ar), 134.6 (Ar), 136.5 (Ar),
140.2 (Ar). 31P{1H} NMR: d 30.3. M.S. m=z: 691 [45%,
Mþ], 335 [20%, Ph2PCH2NMesH], 91 [100%, NPh].
m-Ph). 13C{1H} NMR (d8-thf, 25 °C): d 20.9 (p-Me),
21.8 (o-Me), 25.0 (PCH), 128.7 (p-C, mes), 130.3 (o-C,
Ph), 132.6 (m-C, mes), 134.0 (p-C, Ph), 134.57 (m-C, Ph),
134.57 (i-C, Ph), 135.21 (o-C, mes), 139.0 (i-C, mes). 31
{1H} NMR (d8-thf, 25 °C): d 32.8.
P
3.4. [{HC(Ph2PNC6H2Me3-2,4,6)2}Al(Cl)Me] (4)
3.7. [{HC(Ph2PNC6H2Me3-2,4,6)2}AlI2] (7)
A solution of Me2AlCl (1.0 M in hexanes, 4.6 ml, 4.6
mmol) was added to II (3.00 g, 4.6 mmol) in toluene (30
ml) and the mixture was stirred at room temperature
overnight. Concentration and cooling (5 °C) afforded 4
as colourless crystals. Yield: 2.02 g, 60%. Anal. Calc.
for C44H46AlClN2 P2 ꢁ 2(C7H8): C, 76.42; H, 6.80; N
3.09. Found: C, 76.01; H, 6.51; N, 3.08. 1H NMR:
d-0.50 (s, 3H, Me-Al), 1.84 (s, 12H, o-CH3), 2.021 (s,
6H, p-CH3), 2.30 (s, 1H, PCHP) 6.60 (s, 4H, mesityl),
7.40 (m, 12H, m, p,-PhP), 7.90 (m, 8H, o-PhP). 13C{1H}
NMR: d 1.4 (CH3-Al), 20.7 (p-Me), 20.9 (o- Me), 21.3
(CHP), 125.6 (Ar), 127.4 (Ar), 128.2 (Ar), 130.9 (Ar),
133.4 (Ar), 135.9 (Ar), 140.00 (Ar). 31P{1H} NMR:
d 31.9. M.S. m=z: 711 [100%, HC(Ph2PNMes)2AlCl],
594 [75%, HC(Ph2PNMes)2AlClH2], 183 [45%].
This was synthesised in an analogous manner from I
(0.77 mmol) and AlI3 (0.32 g, 0.78 mmol). Yield: 0.58 g,
80%. Anal. Calc. for C43H43N2P2Al2I2: C, 52.42; H,
1
5.90; N, 2.60%. Found: C, 52.30; H, 4.91; N, 2.51%. H
NMR (d8-thf, 25 °C): d 1.45 (s, 12H, o-Me), 1.72 (s, 6H,
2
p-Me), 2.95 (d, PCHP, JPH ¼ 6:95 Hz), 6.26 (s, 4H,
mes), 6.96 (t, 8H, o-Ph), 7.09 (t, 4H, p-Ph), 7.44(t, 8H,
m-Ph). 13C{1H} NMR (d8-thf, 25 °C): d 20.78 (p-Me),
21.05 (o-Me), 22.7 (PCH2), 128.7 (p-C, mes), 129.9 (o-C,
Ph), 130.4 (m-C, mes), 132.6 (p-C, Ph), 134.1 (m-C, Ph),
134.2 (i-C, Ph), 135.3 (o-C, mes), 139.3 (i-C, mes). 31P
{1H} NMR (d8-thf, 25 °C): d 30.1. M.S. m=z: 929 [10%,
Mþ], 803 [55%, {HC(Ph2PNmes)AlI}], 440 [35%,
Ph2PCH2PNmes], 202 [100%], 318[45%, Ph2PNmes],
134 [45%, HNmes], 91 [45%, NPh].
3.5. [{HC(Ph2PNC6H2Me3-2,4,6)2}AlCl2] (5)
3.8. [{HC(Ph2PNC6H2Me3-2,4,6)2}GaCl2](8)
A solution of 1 (1.08 mmol) in Et2O (20 ml) was
added to a stirred suspension of AlCl3 (0.14 g, 1.08
mmol) in Et2O (20 ml) at )78 °C. This was allowed to
warm to room temperature to produce a pale yellow
solution and a colourless precipitate. Filtration and
concentration to ꢀ10 ml produced 5 as an Et2O solvate
in the form of pale yellow needles (0.64 g, 80 %). Anal.
Calc. for C47H53N2AlOP2: C, 68.69; H, 6.45; N, 3.41.
This was synthesised in an analogous manner from I
(2.00 mmol) and GaCl3 (0.35 g, 2.00 mmol). Yield: 0.86
g, 54%. Anal. Calc. for C43H43N2P2 GaCl2: C, 65.34; H,
1
5.50; N, 3.55%. Found: C, 64.90; H, 5.00; N, 3.02%. H
NMR (d8-thf, 25 °C): d 2.01 (s, 12H, o-Me), 2.10 (s, 6H,
p-Me), 2.30 (t, PCHP), 6.49 (s, 4H, Mes), 6.79 (t, 8H, o-
Ph), 7.57 (t, 4H, p-Ph), 8.02 (t, 8H, m-Ph). 13C{1H}
NMR (d8-thf, 25 °C): d 20.3 (p-Me), 21.0 (o-Me), 21.7
(PCH2), 128.1 (p-C, Mes), 129.3 (o-C, Ph), 130.5 (m-C,
Mes), 132.1 (p-C, Ph), 134.1 (m-C, Ph), 134.3 (i-C, Ph),
135.1 (o-C, Mes), 139.3 (i-C, Mes). 31P{1H} NMR
(d8-thf, 25 °C), d: 36.0. M.S. m=z: 790 [5%, Mþ], 755
[2%, Mþ-Cl], 440 [15%, Ph2PCH2PNMes], 317 [30],
318 [30%, Ph2PNMes], 134 [100%, HNMes], 91 [45%,
NPh].
1
Found: C, 68.61; H, 6.57; N, 3.38. H NMR (d8-THF,
25 °C): d 1.12 (t, 6H, Et2O), 1.85 (s, 12H, o-CH3), 2.16
(s, 6H, p-CH3), 3.37 (q, 4H, Et2O), 6.64 (s, 4H, mesityl),
7.38 (m, 12H, m, p,-PhP), 7.85 (m, 8H, o-PhP). 13C{1H}
1
NMR (d8-THF, 25 °C): d 12.0 (t, JPC ¼ 135:9 Hz,
PCH), 15.7 (p-CH3), 20.8 (Et2O), 21.4 (o-CH3), 66.3
(Et2O), 128.6 (dd, 2J ¼ 18:1 Hz, o-Ph), 130.2 (m-C,
Mes), 132.5 (p-C, Ph), 134.5 (m-C, Ph), 135.4 (i-C, Ph),
138.0 (o-C, Mes), 138.8 (i-C, Mes). 31P {1H} NMR (d8-
thf, 25 °C), d: 31.4. M.S., m=z: 746 [55%, Mþ], 440 [60%,
Ph2PCH2NMes], 317 [100%, Ph2NmesH], 240 [35%],
210 [45%], 183 [80%], 164 [25%, PNMes], 121
[50%,MesH2], 91 [40%, NPh].
3.9. Crystallography
Data were collected at 173 K on a Nonius Kappa
ꢀ
CCD diffractometer, kðMo KaÞ ¼ 0:71073 A; details are
given in Tables 2 and 4. The structures were solved by
direct methods (SHELXS-97) [58] and refined by full
matrix least squares (SHELXL-97) [59] with non-H at-
oms anisotropic and H atoms included in riding mode.
Crystals of 3 diffracted very weakly at high angle. The
chlorine and methyl group attached to Al in 4 were
disordered 0.71:0.29. One toluene molecule was also
disordered and was refined with bond length constraints
(SADI) with hydrogens omitted. In 7 two poorly defined
molecules of diethyl ether were refined with bond length
3.6. [{HC(Ph2PNC6H2Me3-2,4,6)2}AlBr2] (6)
This was synthesised in an analogous manner from I
(2.00 mmol) and AlBr3 (0.53 g, 2.00 mmol). Yield: 0.552
g, 33%. Anal. Calc. for C43H43N2P2 Al2Br2: C, 61.99; H,
5.88; N, 3.08%. Found: C, 61.83; H, 5.93; N, 3.01%. 1H
NMR (d8-thf, 25 °C): d 1.86 (s, 12H, o-Me), 1.92 (s, 6H,
2
p-Me), 3.32 (d, PCHP, JPH ¼ 7:02 Hz), 6.75 (s, 4H,
mes), 7.41 (t, 8H, o-Ph), 7.56 (t, 4H, p-Ph), 7.85 (t, 8H,

M.S. Hill et al. / Journal of Organometallic Chemistry 689 (2004) 722–730
729
[19] Y. Ding, H. Hao, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt,
Organometallics 20 (2001) 4806.
constraints. An absorption correction (MULTISCAN)
was applied to 5–8.
[20] Y. Ding, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt, P.P.
Power, Organometallics 20 (2001) 1190.
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4. Supplementary Information
[22] P.B. Hitchcock, J. Hu, M.F. Lappert, S. Tian, J. Organomet.
Chem. 536 (1997) 473.
Crystallographic data for the structural analyses of
II, 1–8 have been deposited with the Cambridge Crys-
tallographic Data Centre, CCDC no. 209814–209822.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://www.
ccdc.cam.ac.uk).
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