Synthesis and structure of bulky phosphiniminato complexes of zirconium and hafnium: Aryl groups as non-innocent substituents in electrophilic systems

Article abstract of DOI:10.1016/j.ica.2006.03.013

Sterically highly hindered phosphiniminato complexes MCl₃(NCP) were prepared from MCl₄ and Li[NPC] in toluene [M = Zr or Hf; NPC = 4-Bu^tC₆H₄C(SiMe₃)P(Ph)₂ {double bond, long}NC₆H₂Me₃-2,4,6]. Reaction with methyl lithium readily affords the corresponding zirconium and hafnium trimethyl complexes. The structures of representative zirconium and hafnium complexes MX₃(NPC) (X = Cl, M = Zr, Hf; X = Me, M = Hf) were determined by X-ray diffraction. In all cases the NPC ligand acts as C-N chelate, with an additional bonding contribution from the ipso-carbon atom of the C-bound aryl substituent, which results in a η¹:η²-coordination mode. The reaction of the hafnium trimethyl complex with CPh₃⁺ salts of perfluoroarylborate anions results either in the diastereoselective formation of the binuclear cation [{(NPC)HfMe₂}₂(μ-Me)]⁺ or in the formation of the mononuclear cation [(NPC)HfMe₂]⁺, depending on the molar ratio of reagents.

Full text of DOI:10.1016/j.ica.2006.03.013

Inorganica Chimica Acta 360 (2007) 1354–1363
www.elsevier.com/locate/ica
Synthesis and structure of bulky phosphiniminato complexes
of zirconium and hafnium: Aryl groups as ‘‘non-innocent’’
substituents in electrophilic systems
b
a
a,
*
Musa Said a,1, Mark Thornton-Pett , David L. Hughes , Manfred Bochmann
a
Wolfson Materials and Catalysis Centre, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, UK
b
Pakuranga College, Bucklands Beach, Aukland 1704, New Zealand
Received 10 February 2006; accepted 16 March 2006
Available online 24 March 2006
Dedicated to Professor Mike Lappert with affection and appreciation of his many seminal and inspiring contributions to organometallic chemistry.
Abstract
Sterically highly hindered phosphiniminato complexes MCl3(NCP) were prepared from MCl4 and Li[NPC] in toluene [M = Zr or Hf;
NPC = 4-ButC6H4C(SiMe3)P(Ph)2@NC6H2Me3-2,4,6]. Reaction with methyl lithium readily affords the corresponding zirconium and
hafnium trimethyl complexes. The structures of representative zirconium and hafnium complexes MX3(NPC) (X = Cl, M = Zr, Hf;
X = Me, M = Hf) were determined by X-ray diffraction. In all cases the NPC ligand acts as C–N chelate, with an additional bonding
contribution from the ipso-carbon atom of the C-bound aryl substituent, which results in a g1:g2-coordination mode. The reaction of the
þ
hafnium trimethyl complex with CPh3 salts of perfluoroarylborate anions results either in the diastereoselective formation of the binu-
clear cation [{(NPC)HfMe2}2(l-Me)]+ or in the formation of the mononuclear cation [(NPC)HfMe2]+, depending on the molar ratio of
reagents.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Zirconium; Hafnium; Catalysis; Chelating ligand; Phosphiniminato complex
1. Introduction
D [6–8] and E [9], while Stephan and Cavell have
described a number of mono- and binuclear dimetallated
compounds of type F and G [10,11]. The flexible coordi-
nation of the NPC framework is rather reminiscent of
that of the well-known azaallyls [12–15], with the excep-
tion that the presence of the phosphorus heteroatom pre-
cludes p-type g3-coordination that is prevalent for
[RNCR1CHR2]ꢁ complexes.
C–N chelating ligands based on phosphiniminato
anions ½CHR1APR2 @NR3ꢀꢁ [1] show great coordinative
2
versatility. Many complexes are typified by structures of
type A (Chart 1), although in the case of M = Li alterna-
tive and more varied structures have also been found, as
in B and C [2–5]. Some time ago we reported a number
of early and late transition metal complexes of bi- and
tridentate phosphiniminato NCN chelates, for example
The type of complex formed on reaction of group 4 metal
halides with alkylphosphinimines H2R1CAPR2 @NR3 or
2
the corresponding anion strongly depends on the substitu-
ents; e.g. if R3 = SiMe3 dehalosilylation may be preferred
to give products of type H, while with R3 = mesityl the car-
bon atom is metallated to form A. The steric environment
of the carbon atom, too, is important. As we have recently
*
Corresponding author.
E-mail address: m.bochmann@uea.ac.uk (M. Bochmann).
New address: Hellesdon High School, 187 Middleton’s Lane, Norwich
1
NR6 5SB, UK.
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.03.013

M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
1355
SiMe3
Me3Si
Pri2
P
H
N
Me3Si
Ph2P
H
R1
N
R1
C
N
Me
Me
C
H
Li
C
P
Li
Li
PPh2
Me
Me
R2
C
R3
C
Li
M
N
SiMe3
Ln
P
N
Pri2
Me3Si
SiMe3
A
B
C
R1
R1
P
R1
R1
R1
P
R1
R1
P
R1
H
R1
R1
H
C
R1
P
P
R1
P
N
R2
N
R2
R2
N
M
R2
N
N
N
Ln
M
R2
M
R2
Ln
Ln
F
E
D
R1
R1
Ln
M
PPh2
N
Ar
P
R2
N
N
R2
C
TiCl3
P
M
Ln
R1
R1
G
H
Chart 1.
reported [16], the bulky ligand 4-ButC6H4CH(SiMe3)-
P(Ph)2@Nmes (mes = C6H2Me3-2,4,6), as well as its
N-SiMe3 analogue, demonstrates a remarkably varied
coordination chemistry towards metals like lithium, with
aryl substituents involved in various types of p-bonding to
the metal (I–K, Chart 2), a coordination behaviour of the
aryl substituents that was however absent in the zirconium
NPC complex Zr(NMe2)3{4-ButC6H4CHP(Ph)2 @Nmes.
It was of interest to see to what extent this ability of aryl
substituents to interact with electrophilic metal centres in a
‘‘wrap-around’’ fashion by p-interactions extended to early
transition metal chemistry, and we report here the synthe-
sis, structures and reactivity of zirconium and hafnium
complexes of the [4-ButC6H4C(SiMe3)P(Ph)2@NC6H2-
Me3-2,4,6]ꢁ anion.
2. Results and discussion
The complexes MCl3(NCP) [NCP = 4-ButC6H4C-
(SiMe3)P(Ph)2@Nmes, M = Zr 1, M = Hf 2] were
synthesized in good yields by heating Li[NCP] and MCl4
in toluene to 80 ꢁC (Scheme 1). Recrystallisation from light
petroleum afforded the compounds as colourless crystals.
The choice of solvent turned out to be important since
reactions conducted in diethyl ether or tetrahydrofuran
did not afford clean products. The reactions of 1 and 2 with
methylmagnesium chloride proceeded cleanly to yield the
corresponding metal trimethyl derivatives 3 and 4. The
presence of SiMe3 group in this ligand appears to increase
the thermal stability of these complexes when compared to
those reported earlier without the SiMe3 substituent [8].
SiMe3
PPh2
Ph
N
SiMe3
Ph
Me
C
N
SiMe3
Me3Si
Ar
P
But
C
PPh2
C
SiMe3
Li
Li
Li
(THF)2
N
Li
N
Me3Si
(THF)2
C
mes
Me
PPh2
SiMe3
J
K
I
Chart 2.

1356
M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
Ph
Ph
N
Ph
Ph
Me3Si
MCl4
P
Me3Si
P
C
C
N
toluene
Li
(THF)2
M
Cl
Cl
1, M = Zr; 2, M = Hf
Cl
MeMgCl
Ph
C
Ph
Me3Si
P
N
M
Me
Me
Me
3, M = Zr; 4, M = Hf
Scheme 1.
1
In all four cases the H NMR spectra in C6D6 showed
three singlets for the methyl groups on the mesityl ring,
indicating that rotation of the C6H2Me3 group around
the N–C bond is slow on the NMR time scale at room tem-
perature. As is expected for such low symmetry com-
pounds, the methyl derivatives 3 and 4 show three
separate methyl signals in the 1H NMR spectrum at
ꢁ80 ꢁC (CD2Cl2) but only one signal at room temperature
(C6D6), at d 0.96 (3) and 0.61 (4) (Table 1).
slightly wider than in {4-ButC6H4CHP(Ph)2@Nmes}-
Zr(NMe2)3 (63.93(9)ꢁ) reported earlier [8]. The N–P–C
angle in the free ligand of 110.62(7)ꢁ is reduced in 1 to
101.10(14)ꢁ and in 4 to 103.4(4)ꢁ. The Me–Hf–Me angles
are subject to considerable variation, 88.1(4)ꢁ, 93.4(4)ꢁ and
107.1(4)ꢁ. Similarly, in 1 the Cl–Zr–Cl are different,
88.44(3)ꢁ, 94.22(3)ꢁ and 110.68(3)ꢁ. The P–N bonds in 1
˚
˚
[1.644(3) A] and 4 [1.649(3) A] are longer than that in the
˚
free ligand [1.562(13) A] [8].
The molecular structures of 1, 2 and 4 were determined
by single-crystal X-ray diffraction. Since 1 and 2 are iso-
structural, only that of 2 is shown (Fig. 1). The hafnium tri-
methyl analogue 4 is shown in Fig. 2 for comparison.
Selected bond lengths and angles are collected in Table 2.
Compound 1 contains 0.3 molecules of CH2Cl2 of
crystallisation.
The structures of 1 and 2 are best described as distorted
square pyramids, with C, N and two Cl atoms forming the
base of the pyramid, while the third Cl atom occupies the
apical position. However, a sixth coordination position is
occupied by the ipso-C atom C(21) of the C-aryl substituent,
i.e. the phosphorane C-C6H4But moiety acts as an as g2
ligand, with the M–C(ipso) distances being only ca. 4.5
(Zr) and 5.8% (Hf) longer than the M–C(SiMe3) bonds.
Even though the metal centre in the hafnium trimethyl com-
plex 4 is less Lewis acidic, here too the NPC ligand adopts
the same g1:g2 tridentate bonding mode. The ipso-carbons
are almost trans to one of the chloride or methyl ligands
in all three cases, with C(ipso)–M–Cl(Me) angles close to
171ꢁ. The phosphiniminato ligands have narrow bite angles,
with C–M–N angles of ca. 67–69ꢁ, although these are
NMR studies of mixtures of MMe3{4-ButC6H4C(Si-
Me3)P(Ph)2@Nmes} (M = Hf or Zr) and [CPh3][B(C6F5)4]
or [CPh3][B(C6F5)3CNB(C6F5)3] were carried out at low
temperature in CD2Cl2 by weighing each component
directly into an NMR tube in a glove box. The NMR tube
was cooled to ꢁ78 ꢁC in a Schlenk tube, followed by the
addition of cooled CD2Cl2. The sample was then shaken
quickly at ca. ꢁ40 ꢁC to ensure adequate mixing before
inserting the sample into the cooled NMR probe. Samples
for studies at room temperature were prepared from C6D6
or C7D8, in which case the precipitation of ionic species as
orange-red oils was unavoidable. Assignments were made
1
on the basis of H–13C HET-COR experiments.
Compound 4 was treated with [CPh3][CN{B(C6F5)3}2]
in a 2:1 molar ratio in dichloromethane-d2 (Scheme 2).
The spectrum at ꢁ70 ꢁC shows the formation of the binu-
clear cation [{(NPC)HfMe2}2(l-Me)]+, characterised by a
signal for the bridged methyl ligand at d ꢁ1.95, as the
[CN{B(C6F5)3}2]ꢁ salt (5a). Because of the low symmetry
of the NPC ligand, four separate singlets for the terminal
Hf–Me groups are expected, and indeed at low temperature
all four signals are resolved, alongside the typical high-field

M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
1357
Table 1
1H, 13C{1H} and 31P NMR data of zirconium and hafnium complexes
Complex
d (1H)
Assignt
d (13C)
Assignt
d (31P)
Solvent, temp.
C6D6, 20 ꢁC
0.10 (s, 9H)
1.21 (s, 9H)
1.83 (s, 3H,)
1.99 (s, 3H)
2.13 (s, 3H)
SiMe3
CMe3
p-CH3
o-CH3
o-CH3
aryl
4.58
20.36
21.50
21.93
31.26
34.68
127.45–156.03
SiMe3
p-CH3
o-CH3
o-CH3
CMe3
CMe3
aryl
23.1
Me3Si
Ph2P
6.63–7.84 (m,16H).
ZrCl3
HfCl3
ZrMe3
N
1
2
3
0.12 (s, 9H)
1.21 (s, 9H)
1.87 (s, 3H)
2.05 (s, 3H)
2.11 (s, 3H)
6.63–7.84 (m, 16H)
SiMe3
CMe3
p-CH3
o-CH3
o-CH3
aryl
2.75
20.58
20.94
21.93
31.11
34.14
125.35–150.00
SiMe3
p-CH3
o-CH3
o-CH3
CMe3
CMe3
aryl
21.9
C6D6, 20 ꢁC
Me3Si
Ph2P
N
0.09 (s, 9H)
0.96 (s, 9H)
1.31 (s, 9H)
1.85 (s, 3H)
2.19 (s, 3H)
2.98 (s, 3H)
6.76–7.49 (m, 16H).
SiMe3
ZrMe3
CMe3
p-CH3
o-CH3
o-CH3
aryl
4.75
20.43
21.1
21.45
31.42
34.30
49.56
127.49–150.45
SiMe3
p-CH3
o-CH3
o-CH3
CMe3
CMe3
ZrMe3
aryl
20.77
C6D6, 20 ꢁC
Me3Si
Ph2P
N
ꢁ0.79 (s, 3H)
ꢁ0.38 (s, 9H)
0.09 (s, 3H,)
0.52 (s, 3H,)
1.23 (s, 9H,)
1.29 (s, 3H,)
1.47 (s, 3H,)
2.10 (s, 3H,)
6.87–8.64 (m, 16H)
ZrMe
SiMe3
ZrMe
ZrMe
CMe3
p-CH3
o-CH3
o-CH3
aryl
CD2Cl2, ꢁ80 ꢁC
0.07 (s, 9H)
0.61 (s, 9H)
1.26 (s, 9H)
1.79 (s, 3H)
2.00 (s, 3H)
2.14 (s, 3H)
6.72–7.95 (m, 16H).
SiMe3
HfMe3
CMe3
p-CH3
o-CH3
o-CH3
aryl
19.4
C6D6, 20 ꢁC
Me3Si
Ph2P
HfMe3
N
4.74
20.51
21.11
21.57
31.69
34.75
58.93,
127.49–150.69
SiMe3
p-CH3
o-CH3
o-CH3
CMe3
CMe3
HfMe3
aryl
CD2Cl2, 20 ꢁC
4
(continued on next page)
(continued on next page)

1358
M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
Table 1 (continued)
Complex
d (1H)
Assignt
d (13C)
Assignt
d (31P)
Solvent, temp.
ꢁ1.10 (s, 3H,)
ꢁ0.37 (s, 9H)
ꢁ0.16 (s, 3H)
0.21 (s, 3H,),
1.23 (s, 9H)
1.28 (s, 3H)
1.55 (s, 3H)
2.13 (s, 3H)
6.60–7.73 (m, 16H)
HfMe3
SiMe3
HfMe3
HfMe3
CMe3
p-CH3
o-CH3
o-CH3
aryl
CD2Cl2, ꢁ80 ꢁC
ꢁ1.95 (s, 3H)
ꢁ1.38 (s, 3H)
ꢁ0.82 (s, 3H)
ꢁ0.37 (s,18H)
0.15 (s, 3H)
0.16 (s, 3H,)
1.29 (br s, 30H)
2.12 (s, 3H)
Hf–CH3–Hf
Hf–CH3
Hf–CH3
SiMe3
Hf–CH3
Hf–CH3
C(CH3)3 + 4CH3
Ph3CCH3
CH3
6.51
21.73
22.83
32.46
33.47
36.04
54.58
61.60
62.37
64.31
66.54
128.52–156.52
6.64
21.61
22.93
32.57
33.53
SiMe3
CH3
CH3
Ph3CCH3
CMe3
CMe3
Ph3CMe
Hf–CH3–Hf
Hf–Me
Hf–Me
Hf–Me
aryl
SiMe3
CH3
CH3
21.9
CD2Cl2, ꢁ70 ꢁC
+
SiMe3
PPh2
Me3Si
Me
Me
Me
Hf
Ph2P
Hf
Me
N
Me
N
2.18 (s, 6H)
6.51–7.79 (m, 32H)
aryl
[CN{B(C6F5)3}2]-
5
ꢁ0.23 (s, 18H)
0.01 (s, 15H)
1.33 (s, 18H)
1.37 (s, 6H)
SiMe3
Hf–CH3
CMe3
CH3
CD2Cl2, 0 ꢁC
Ph3CCH3
CMe3
1.49 (s, 6H)
CH3
2.17 (s, 3H)
2.19 (s, 6H)
6.65–7.48 (m, 32H)
Ph3C Me
CH3
aryl
37.07
54.78
63.54
128.34–156.35
CMe3
Ph3CMe
Hf–Me
aryl
0.09 (s, 18H)
0.37 (s, 15H)
1.19 (s, 18H)
1.61 (s, 12H)
2.07 (s, 3H)
SiMe3
Hf–CH3
CMe3
o-CH3
Ph3CCH3
p-CH3
aryl
19.4
C6D6, 20 ꢁC
2.15 (s, 6H)
6.70–7.45 (m, 32H)
ꢁ1.75 (s, 3H)
ꢁ1.11 (s, 3H)
ꢁ0.79 (s, 3H)
0.39 (s, 18H)
0.06 (s, 3H)
0.56 (s, 3H)
1.23 (s, 18H)
1.46 (s, 12H,)
2.10 (s, 3H),
2.16 (s, 6H)
6.47–7.76
Zr–CH3–Zr
Zr–CH3
Zr–CH3
SiMe3
Hf–CH3
Hf–CH3
CMe3
o-CH3
Ph3CCH3
p-CH3
4.44
19.83
21.02
31.63
31.84
34.11
52.64
126.61–149.41
SiMe3
CH3
CH3
Ph3CMe
CMe3
CMe3
Ph3CCH3
aryl
CD2Cl2, ꢁ70 ꢁC
+
SiMe3
Me
Me3Si
Ph2P
Me
Me
Me
Zr
Zr
PPh2
N
Me
N
aryl
[B(C6F5)4]-
6
+
ꢁ0.80 (s, 3H)
ꢁ0.21 (s, 9H)
0.72 (s, 3H)
Hf–CH3
SiMe3
Hf–CH3
CMe3
6.02
22.84
23.03
23.76
SiMe3
CH3
CH3
CD2Cl2, ꢁ70 ꢁC
Me3Si
Ph2P
1.22 (s, 9H)
CH3
Me
Me
1.44 (s, 6H)
2.10 (s, 6H)
6.69–8.20 (m, 16H)
CH3
Ph3CCH3 + CH3
aryl
32.50
33.27
36.08
Ph3CCH3
C Me3
CMe3
Hf
N
54.62
64.36
73.83
126.38–151.73
Ph3CCH3
Hf–CH3
Hf–CH3
aryl
[CN{B(C6F5)3}2]-
7a
(continued on next page)

M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
1359
Table 1 (continued)
Complex
d (1H)
Assignt
d (13C)
Assignt
d (31P)
Solvent, temp.
ꢁ0.22 (s, 9H)
0.21 (br, 6H)
1.09 (s, 9H)
SiMe3
Hf–CH3
CMe3
15.8
C7D8, 20 ꢁC
1.52 (s, 6H)
2.13 (s, 3H)
2.15 (s, 3H)
6.61–7.55 (m, 16H)
o-CH3
Ph3CCH3
p-CH3
aryl
+
ꢁ0.84 (s,3H)
ꢁ0.23 (s, 9H)
0.77 (s, 3H)
1.29 (s, 9H)
1.41 (s, 6H)
2.12 (s, 3H)
2.14 (s, 3H)
6.65–8.05
Hf–CH3
SiMe3
Hf–CH3
CMe3
o-CH3
Ph3CCH3
p-CH3
aryl
4.19
21.02
21.14
21.37
30.53
31.39
34.07
52.64
SiMe3
CH3
CH3
CH3
Ph3CCH3
CMe3
CD2Cl2, ꢁ70 ꢁC
Me3Si
Me
Ph2P
Hf
Me
N
CMe3
Ph3CCH3
Hf–CH3
Hf–CH3
aryl
62.41
70.92
126.62–149.79
[B(C6F5)4]-
7b
C(45)
C(44)
C(13)
C(33)
C(32)
C(12)
C(11)
C(43)
C(34)
C(46)
Si(1)
C(1)
C(41)
C(42)
C(35)
P(1)
C(36)
N(1)
C(21)
C(26)
C(25)
C(59)
C(22)
C(51)
C(56)
C(55)
C(29)
Hf
C(23)
C(57)
C(24)
C(52)
Cl(3)
C(53)
C(27)
C(54)
C(58)
C(30)
Cl(1)
Cl(2)
C(28)
Fig. 1. Molecular structure of HfCl3{4-ButC6H4C(SiMe3)P(Ph)2@Nmes} (2), showing the atomic numbering scheme.
singlet for the bridging methyl ligand. Upon heating the
solution to 0 ꢁC, the Hf–Me peaks coalesce to one peak
at d ꢁ0.01 ppm. In C7D8 or C6D6 at room temperature,
the methyl signals appear at d 0.14 and 0.26, respectively.
A very similar product was obtained from 4 and
[CPh3][B(C6F5)4] (2:1) (5b); since the NMR spectra are very
similar, only the data for 5a have been included in Table 1.
Mixtures of the zirconium complex 3 and [CPh3][B(C6F5)4]
in a 2:1 molar ratio in CD2Cl2 at ꢁ70 ꢁC gave the analo-
gous compound [{(NPC)ZrMe2}2(l-Me)]+[B(C6F5)4]ꢁ (6).
The phosphoranyl–carbon atom in ligands of the type
Ar1C(ꢁ)(SiMe3)PR2@NAr2 is chiral. In the methyl-bridged
binuclear cations this, together with several possible ligand
rotamers, leads to the possibility of 12 diastereomers. How-
ever, the assignment of the NMR spectra proved quite
straightforward, and evidently only one major diastereo-
mer predominates.
Treatment of 4 with [CPh3][CN{B(C6F5)3}2] or [CPh3]-
[B(C6F5)4] in a 1:1 ratio (dichloromethane-d2, ꢁ78 ꢁC) affor-
ded mainly salts of the monomeric hafnium dimethyl cation,

1360
M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
C(314)
C(313)
C(12)
C(315)
C(11)
C(316)
C(323)
C(13)
C(311)
Si(1)
C(325)
C(2)
C(21)
C(421)
P(3)
C(22)
N(4)
C(43)
C(23)
Hf
C(41)
C(45)
C(5)
C(24)
C(25)
C(244)
C(242)
C(461)
C(441)
C(7)
C(241)
C(243)
Fig. 2. Molecular structure of HfMe3{4-ButC6H4C(SiMe3)P(Ph)2@Nmes} (4), showing the atomic numbering scheme. Hydrogen atoms are omitted for
clarity.
[(NCP)HfMe2]+Xꢁ [7a, X = CN{B(C6F5)3}2; 7b, X =
B(C6F5)4]. There are no signals in the H NMR spectra
ligand acts in tridentate g1:g2 fashion. Reaction with
[CPh3][CN{B(C6F5)3}2] or [CPh3][B(C6F5)4] in a 2:1 molar
ratio, binuclear methyl-bridged cations are formed. The
reaction is highly diastereoselective. A similar reaction in
a 1:1 ratio affords mononuclear hafnium dimethyl cations.
By contrast, attempts to form zwitterionic species by reac-
tion of (NCP)HfMe3 with B(C6F5)3 led to rapid CH3/C6F5
ligand scrambling. However, although the chemistry of Zr
and Hf methyl complexes of NPC ligands shows many sim-
ilarities to catalytically active metallocene methyls [17],
these complexes activated by methylaluminoxane (MAO)
at room temperature showed negligible ethene polymerisa-
tion activity.
1
high-field of ꢁ1 ppm, indicative of the absence of bridging
methyl ligands. As expected for a C1 symmetric cation, there
are two singlets for the two Hf–Me ligands, one of which is
high-field shifted to d ꢁ0.8 due to the magnetic anisotropy
of the neighbouring C6H4But substituent, 1.5 ppm higher
than the second Hf–Me signal. The complex is fluxional,
and in toluene-d8 at room temperature only one Hf–Me res-
onance is found, at d 0.21.
In contrast to the clean formation of ionic products
from trityl salts, the reaction between 4 and one equivalent
of B(C6F5)3 in C6D6 in an NMR tube at room temperature
gave rise to a mixture of products. The 11B NMR shows
clearly the formation of [MeB(C6F5)3]ꢁ (d ꢁ12.07). It also
shows the formation of BMe3 and Me2B(C6F5) (d 89.2 and
83.6, respectively). It is evident, therefore, that the mixture
undergoes facile methyl/C6F5 ligand exchange, and no
clean product could be isolated.
4. Experimental
4.1. General considerations
All manipulations were performed under a dinitrogen
atmosphere using standard vacuum line techniques. Sol-
vents were distilled under N2 over sodium benzophenone
(THF and diethyl ether), sodium (toluene), or sodium–
potassium alloy (light petroleum, b.p. 40–60 ꢁC). NMR
solvents were dried over activated molecular sieves and
degassed through several freeze–thaw cycles. NMR spectra
were recorded on a Bruker Avance DPX300 spectrometer.
Chemical shifts are reported in ppm and referenced to
residual solvent resonances (1H, 13C). 31P NMR chemical
shifts are relative to external 85% H3PO4. 4-ButC6H4CH
(SiMe3)P(Ph)2@Nmes and Li[4-ButC6H4C(SiMe3)P(Ph)2
@Nmes] (mes = 2,4,6-C6H2Me3) were prepared according
to the literature procedures [8]. ZrCl4 and HfCl4 were
Ethene polymerisation tests conducted with 1 and 3 acti-
vated with methylaluminoxane (Al:Zr = 1000 :1) in toluene
at room temperature under 1 bar monomer pressure dis-
played negligible activity.
3. Conclusion
Sterically highly hindered phosphiniminates act as effec-
tive C, N chelating ligands and form 1:1 complexes with
group 4 metals, including thermally stable zirconium and
hafnium trimethyl species. The aryl substituent of the C-
atom further stabilises the complexes by g1-coordination
of the ipso-carbon atom to the metal centre, such that the

M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
1361
Table 2
1.84 mmol) were charged into a 100 mL Schlenk flask. Tol-
uene (40 mL) was added, the mixture was stirred for 3 h,
followed by stirring for 5 h at 80 ꢁC. LiCl was filtered off,
the solvent was reduced to 5 mL and light petroleum was
added (10 mL). Colourless crystals formed within 30 min
at room temperature, yield 1.1 g (81%). Anal. Calc. for
C35H43Cl3NPSiZr: C, 57.24; H, 5.90; N, 1.91; Cl, 14.48.
Found: C, 58.12; H, 6.56; N, 2.05; Cl, 13.83%.
˚
Selected bond length (A) and angles (ꢁ) for (NPC)MX3 complexes
{4-ButC6H4C(SiMe3)P(Ph)2@Nmes}ZrCl3 (1)
Zr(1)–N(1)
Zr(1)–Cl(3)
Zr(1)–C(3)
N(1)–C(11)
2.149(3)
2.4014(9)
2.490(3)
1.453(4)
Zr(1)–Cl(1)
Zr(1)–Cl(2)
Zr(1)–C(311)
N(1)–P(2)
2.3684(8)
2.4152(9)
2.604(3)
1.644(3)
N(1)–Zr(1)–Cl(1)
Cl(1)–Zr(1)–Cl(3)
Cl(1)–Zr(1)–Cl(2)
N(1)–Zr(1)–C(3)
Cl(3)–Zr(1)–C(3)
N(1)–Zr(1)–C(311)
Cl(3)–Zr(1)–C(311) 171.40(7)
C(3)–Zr(1)–C(311)
C(11)–N(1)–Zr(1)
109.10(7)
N(1)–Zr(1)–Cl(3)
N(1)–Zr(1)–Cl(2)
Cl(3)–Zr(1)–Cl(2)
Cl(1)–Zr(1)–C(3)
Cl(2)–Zr(1)–C(3)
Cl(1)–Zr(1)–C(311)
Cl(2)–Zr(1)–C(311)
P(2)–N(1)–Zr(1)
C(16)–C(11)–N(1)
N(1)–P(2)–C(3)
88.88(7)
140.21(7)
88.44(3)
122.63(8)
89.73(8)
88.76(7)
98.06(7)
101.48(13)
121.7(3)
101.10(14)
94.22(3)
110.68(3)
68.48(10)
140.96(7)
82.53(10)
4.3. Preparation of {4-ButC6H4C(SiMe3)P(Ph)2@Nmes}-
HfCl3 (2)
Following the procedure described for 1, the compound
was made from Li[4-ButC6H4C(SiMe3)LiP(Ph)2@Nmes]
(0.70 g, 1.29 mmol) and HfCl4 (0.41 g, 1.29 mmol) in tolu-
ene (40 mL), yield 1.50 g, (66%). Anal. Calc. for
C35H43Cl3NPSiHf: C, 51.16; H, 5.28; N, 1.70; Cl, 12.94.
Found: C, 52.25; H, 5.65; N, 1.40; Cl, 12.30%.
34.27(9)
133.9(2)
C(16)–C(11)–C(12) 119.4(3)
{4-ButC6H4C(SiMe3)P(Ph)2@Nmes}HfCl3 (2)
Hf–N(1)
Hf–Cl(1)
Hf–C(1)
C(1)–C(21)
C(1)–Si(1)
2.129(4)
2.3834(12) Hf–Cl(3)
2.465(5)
1.511(7)
1.915(5)
Hf–Cl(2)
2.3502(13)
2.3994(13)
2.608(5)
1.754(5)
1.644(4)
Hf–C(21)
C(1)–P(1)
P(1)–N(1)
4.4. Preparation of {4-ButC6H4C(SiMe3)P(Ph)2@Nmes}-
ZrMe3 (3)
N(1)–Hf–Cl(2)
Cl(2)–Hf–Cl(1)
Cl(2)–Hf–Cl(3)
N(1)–Hf–C(1)
Cl(1)–Hf–C(1)
N(1)–Hf–C(21)
Cl(1)–Hf–C(21)
C(21)–C(1)–Si(1)
C(21)–C(1)–Hf
Si(1)–C(1)–Hf
C(22)–C(21)–Hf
C(51)–N(1)–P(1)
P(1)–N(1)–Hf
108.51(11)
94.95(5)
N(1)–Hf–Cl(1)
N(1)–Hf–Cl(3)
Cl(1)–Hf–Cl(3)
Cl(2)–Hf–C(1)
Cl(3)–Hf–C(1)
Cl(2)–Hf–C(21)
Cl(3)–Hf–C(21)
P(1)–C(1)–Si(1)
P(1)–C(1)–Hf
89.14(11)
142.21(11)
88.35(5)
122.66(11)
90.02(11)
88.56(11)
97.43(11)
120.2(3)
To a solution of 1 (1.0 g, 1.36 mmol) in toluene (20 mL)
was added slowly methylmagnesium chloride (1.4 mL,
4.20 mmol, 3.0 M in THF) at ꢁ78 ꢁC. The mixture was stir-
red overnight and subsequently heated for 2 h at 50 ꢁC.
After filtration the volume was reduced. On addition of light
petroleum (15 mL) small crystals of 3 were obtained, yield
0.32 g (35%). Anal. Calc. for C38H52NPSiZr: C, 67.81; H,
7.79; N, 2.08. Found: C, 67.40; H, 8.25; N, 1.75%.
109.27(5)
68.87(15)
140.42(12)
82.79(15)
171.87(11)
110.5(3)
77.9(3)
138.0(2)
110.3(3)
124.0(3)
86.51(18)
91.8(3)
100.5(2)
C(26)–C(21)–Hf
N(1)–P(1)–C(1)
C(51)–N(1)–Hf
134.5(3)
4.5. Preparation of {4-ButC6H4C(SiMe3)P(Ph)2@Nmes}-
HfMe3 (4)
101.48(19)
{4-ButC6H4C(SiMe3)P(Ph)2@Nmes}HfMe3 (4)
Hf–C(2)
Hf–C(21)
Hf–P(3)
Hf–N(4)
C(2)–P(3)
2.596(9)
2.687(9)
2.986(7)
2.175(7)
1.729(9)
Hf–C(5)
Hf–C(6)
Hf–C(7)
P(3)–N(4)
2.243(10)
2.238(9)
2.208(9)
1.649(7)
Following the procedure described for 3, the compound
was prepared from 2 (2.75 g, 3.35 mmol) and MeMgCl
(10.05 mmol, 3.35 mL, 3 M solution in THF), yield 1.1 g
(43%). Anal. Calc. for C38H52NPSiHf: C, 60.02; H, 6.89;
N, 1.84. Found: C, 59.65; H, 6.68; N, 1.78%.
C(2)–Hf–C(21)
C(5)–Hf–C(2)
C(6)–Hf–C(2)
C(7)–Hf–C(2)
C(21)–Hf–P(3)
N(4)–Hf–C(21)
C(5)–Hf–C(21)
C(6)–Hf–C(21)
C(7)–Hf–C(21)
N(4)–P(3)–Hf
P(3)–N(4)–Hf
33.2(3)
141.4(3)
92.2(4)
123.0(3)
58.7(2)
81.1(3)
170.7(3)
99.1(4)
90.1(3)
45.5(2)
101.8(3)
N(4)–Hf–P(3)
N(4)–Hf–C(2)
N(4)–Hf–C(5)
N(4)–Hf–C(6)
N(4)–Hf–C(7)
C(6)–Hf–C(5)
C(7)–Hf–C(5)
C(7)–Hf–C(6)
N(4)–P(3)–C(2)
C(41)–N(4)–P(3)
C(41)–N(4)–Hf
32.7(2)
66.9(3)
89.6(3)
141.4(3)
111.5(3)
88.1(4)
4.6. Generation of [{(NPC)HfMe2}2(l-Me)]+-
[CN{B(C6F5)3}2]ꢁ (5a)
An NMR tube was charged with 4 (48 mg, 63.13 lmol)
and [Ph3C][CN{B(C6F5)3}2] (41 mg, 31.56 lmol), cooled,
and cold (ꢁ78 ꢁC) CD2Cl2 was added. The NMR tube
was quickly shaken at room temperature until a clear solu-
tion was formed and then inserted into a pre-cooled NMR
probe at ꢁ70 ꢁC.
93.4(4)
107.1(4)
103.4(4)
125.8(5)
132.1(5)
purified by sublimation under argon immediately prior to
use.
4.7. Generation of [{(NPC)HfMe2}2(l-Me)]+-
[B(C6F5)4]ꢁ (5b)
4.2. Preparation of {4-ButC6H4C(SiMe3)P(Ph)2@Nmes}-
ZrCl3 (1)
The compound was generated in situ by mixing 4 (7 mg,
9.21 lmol) and [Ph3C][B(C6F5)4] (4.25 mg, 4.60 lmol) in
C6D6. The NMR tube was shaken to give a clear solution,
and NMR spectra were recorded at room temperature.
In an inert atmosphere drybox Li[4-ButC6H4C(SiMe3)-
LiP(Ph)2@Nmes] (1.0 g, 1.84 mmol) and ZrCl4 (0.43 g,

1362
M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
Ph
C
Ph
Me3Si
P
N
N
0.5 CPh3+X-
N
X
Hf
Hf
Me
Me
C
C
Hf
But
Me
Me
Me
Me
Me
Me
5a, X = CN{B(C6F5)3}2
5b, X = B(C6F5)4
4
CPh3+X-
Ph
Ph
Me3Si
P
C
N
mes
X
Hf
But
Me
Me
7a, X = CN{B(C6F5)3}2
7b, X = B(C6F5)4
Scheme 2.
Table 3
Crystal data and structure refinement data for 1, 2 and 4
Compound
1
2
4
Empirical formula
Formula weight
Size (mm)
C
759.81
0.28 · 0.17 · 0.06
150(2)
triclinic
35H43Cl3NPSiZr Æ 0.3CH2Cl2
C35H43Cl3HfNPSi
821.6
0.42 · 0.14 · 0.07
150(2)
C38H52HfNPSi
760.4
0.5 · 0.4 · 0.15
140(2)
orthorhombic
P212121 (no. 19)
11.396(1)
15.064(1)
21.664(1)
90
90
90
3719.0(4)
4
1.358
Temperature (K)
Crystal system
Space group
triclinic
ꢀ
ꢀ
P1
P1
˚
a (A)
11.8825(5)
12.8506(6)
15.0503(6)
65.000(3)
74.572(3)
69.120(2)
1927.89(14)
2
11.8801(9)
12.8445(5)
15.0611(9)
64.976(3)
74.513(3)
69.180(4)
1928.0(2)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg/m3)
1.309
0.631
785
1.415
3.009
824
l (mmꢁ1
F(000)
)
2.905
1552
Independent reflections [Rint
]
7565 [0.053]
5939
7565/0/413
1.069
7541 [0.0788]
6782
7541/0/389
1.051
5608 [0.059]
5482
5608/0/391
1.059
Number of observed reflections [I > 2r(I)]
Data/restraints/parameters
Goodness-of-fit
R1[I > 2r(I)], R1 (all data)
wR2 (all data)
0.044, 0.063
0.117
0.046, 0.051
0.119
0.053, 0.054
0.149
4.8. Generation of [{(NPC)ZrMe2}2(l-Me)]+-
[B(C6F5)4]ꢁ (6)
spectrum the Zr–Me signals could not be unequivocally
identified.
The compound was generated in situ by charging an
NMR tube with 3 (16 mg, 23.77 lmol) and [Ph3C]-
[B(C6F5)4] (10.96 mg, 11.88 lmol) and dissolving the mix-
ture in cold CD2Cl2. Spectra were recorded at ꢁ70 ꢁC.
4.9. Generationof[(NPC)HfMe2]+[CN{B(C6F5)3}2]ꢁ (7a)
Following the procedure described for 5a, the compound
was made from 4 (50 mg, 65.76 lmol) and [Ph3C]-
[CN{B(C6F5)3}2] (85.0 mg, 65.76 lmol) in cold CD2Cl2.
Spectra were recorded at ꢁ70 ꢁC. For room temperature
1
Although the H NMR spectrum demonstrated that the
structure of 6 is analogous to that of 5, in the 13C NMR

M. Said et al. / Inorganica Chimica Acta 360 (2007) 1354–1363
1363
spectra, 4 (5.0 mg, 6.56 mol) and [Ph3C][CN{B(C6F5)3}2]
Acknowledgement
(8.5 mg, 6.56 lmol) were dissolved in toluene-d8 at room
temperature.
This work was supported by the Engineering and Phys-
ical Sciences Research Council.
4.10. Generation of [(NPC)HfMe2]+[B(C6F]5)4]ꢁ (7b)
References
Following the procedure for 7a, the compound was
made from 4 (20 mg, 26.3 lmol) and [Ph3C][B(C6F5)4]
(24.3 mg, 26.3 lmol) in cold CD2Cl2. The NMR tube was
shaken quickly until the solution became clear, and spectra
were recorded at ꢁ70 ꢁC.
[1] H. Schmidbaur, G. Jonas, Chem. Ber. 100 (1967) 1120.
´
´
´
[2] F. Lopez-Ortiz, E. Pelaez-Arango, B. Tejerina, E. Perez-Carreno, S.
˜
´
Garcıa-Granda, J. Am. Chem. Soc. 117 (1995) 9972.
[3] A. Muller, B. Neumuller, K. Dehnicke, Chem. Ber. 129 (1996) 253.
¨
¨
[4] P.B. Hitchcock, M.F. Lappert, Z.X. Wang, Chem. Commun. (1997)
1113.
[5] P.B. Hitchcock, M.F. Lappert, P.G.H. Uiterweerd, Z.X. Wang, J.
Chem. Soc., Dalton Trans. (1999) 3413.
4.11. X-ray crystallography
Suitable crystals of 1, 2 and 4 were coated in an inert
perfluoropolyether oil and mounted in a nitrogen stream
at 150(2) K on a Nonius Kappa CCD area-detector diffrac-
tometer (1 and 2) or a Rigaku R-Axis-IIc image plate dif-
fractometer at 140(2) K (for 4). Data collections were
[6] M.J. Sarsfield, M. Thornton-Pett, M. Bochmann, J. Chem. Soc.,
Dalton Trans. (1999) 3329.
[7] M. Sarsfield, M. Said, M. Thornton-Pett, L.A. Gerrard, M. Boch-
mann, J. Chem. Soc., Dalton Trans. (2001) 822.
[8] M. Said, M. Thornton-Pett, M. Bochmann, J. Chem. Soc., Dalton
Trans. (2001) 2844.
˚
performed using Mo Ka radiation (k = 0.71073 A). The
[9] S. Al-Benna, M.J. Sarsfield, M. Said, M. Thornton-Pett, D.L.
raw data of 1 and 2 were processed using the program
DENZO-SMN [18] and corrected for absorption with
SORTAV [19]. Data for 4 were processed in DENZO/SCALEPACK
[18]. All structures were solved either by heavy-atom or
direct methods using SHELXS-97 and were refined by
full-matrix least squares (on F2) in SHELX-97 [20]. All non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were constrained to idealized
positions. Crystallographic data for compounds 1, 2 and 4
are summarized in Table 3.
`
Ormsby, P.J. Maddox, P. Bres, M. Bochmann, J. Chem. Soc., Dalton
Trans. (2000) 4247.
[10] C.M. Ong, D.W. Stephan, J. Am. Chem. Soc. 121 (1999) 2939.
[11] Review R.G. Cavell, R.P. Kamalesh, K. Aparna, J. Organomet.
Chem. 617–618 (2001) 158.
[12] (a) Reviews M.F. Lappert, D.S. Liu, J. Organomet. Chem. 500 (1995)
203;
(b) C.F. Caro, M.F. Lappert, P.G. Merle, Coord. Chem. Rev. 219-
221 (2001) 605.
[13] L. Bourget-Merle, P.B. Hitchcock, M.F. Lappert, Phosphorus,
Sulfur, Silicon 168 (2001) 609.
[14] P.B. Hitchcock, M.F. Lappert, X.H. Wei, J. Organomet. Chem. 683
(2003) 83.
[15] A.G. Avent, P.B. Hitchcock, M.F. Lappert, R. Sablong, J.R. Severn,
Organometallics 23 (2004) 2591.
5. Supplementary material
[16] M. Said, M. Thornton-Pett, M. Bochmann, Organometallics 20
(2001) 5629.
Full tables of bond lengths and angles, tables of non-
hydrogen and hydrogen atomic coordinates and anisotropic
thermal parameters for non-hydrogen atoms are available
from the Cambridge Crystallographic Data Centre, quoting
CCDC deposition numbers 297358 (1), 297359 (2) and
297360 (4). Copies of the 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 http://www.ccdc.cam.ac.uk.
[17] Review M. Bochmann, J. Organomet. Chem. 689 (2004) 3982.
[18] Z. Otwinowski, W. Minor, Processing of X-ray diffraction data
collected in oscillation mode, in: C.W. CarterJr., R.M. Sweet (Eds.),
Methods in Enzymology, Macromolecular Crystallography, Part A,
vol. 276, Academic Press, New York, 1997, pp. 307–326.
[19] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33.
[20] G.M. Sheldrick, SHELX-97 – Programs for Crystal Structure Deter-
mination (SHELXS) and Refinement (SHELXL), University of Go¨ttingen,
Germany, 1997.