Phospha(III)guanidinate complexes of titanium(IV) and zirconium(IV) amides

Article abstract of DOI:10.1016/j.poly.2010.05.017

Two procedures for the synthesis of group 4 phosphaguanidine compounds M(R₂PC{NR′}₂)(NR″₂)₃ (M = Ti, Zr; R = Ph, Cy; R′ = ⁱPr, Cy; R″ = Me, Et) are described. Spectroscopic characterization indicated symmetrical bonding of the phosphaguanidinate ligand in solution for the P-diphenyl derivatives whereas the P-dicyclohexyl analogs adopt a more rigid geometry with inequivalent N _amidine substituents within the phosphaguanidinate ligand. X-ray diffraction studies show exclusively monomeric tbp metal centers for a series of derivatives, with a chelating phosphaguanidinate ligand that spans an axial and an equatorial position. Two different conformers have been identified in the solid-state that differ in the relative orientation of the phosphorus R ₂P?C substituents with respect to the equatorial plane of the tbp metal. The synthetic protocol was extended to the bimetallic complex, [PhP(C{NⁱPr}₂Ti{NMe₂}₃)CH ₂?]₂, which was characterized by crystallography as the meso-form.

Full text of DOI:10.1016/j.poly.2010.05.017

Polyhedron 29 (2010) 2481–2488
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Phospha(III)guanidinate complexes of titanium(IV) and zirconium(IV) amides
*
Natalie E. Mansfield, Joanna Grundy, Martyn P. Coles , Peter B. Hitchcock
Department of Chemistry, University of Sussex, Falmer, Brighton, BN1 9QJ, UK
a r t i c l e i n f o
a b s t r a c t
Two procedures for the synthesis of group 4 phosphaguanidine compounds M(R2PC{NR0}2)(NR00
)
2 3
Article history:
(M = Ti, Zr; R = Ph, Cy; R0 = iPr, Cy; R00 = Me, Et) are described. Spectroscopic characterization indicated
symmetrical bonding of the phosphaguanidinate ligand in solution for the P-diphenyl derivatives
whereas the P-dicyclohexyl analogs adopt a more rigid geometry with inequivalent Namidine substituents
within the phosphaguanidinate ligand. X-ray diffraction studies show exclusively monomeric tbp metal
centers for a series of derivatives, with a chelating phosphaguanidinate ligand that spans an axial and an
equatorial position. Two different conformers have been identified in the solid-state that differ in the rel-
ative orientation of the phosphorus R2P–C substituents with respect to the equatorial plane of the tbp
metal. The synthetic protocol was extended to the bimetallic complex, [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2,
which was characterized by crystallography as the meso-form.
Received 6 April 2010
Accepted 19 May 2010
Available online 1 June 2010
Keywords:
Coordination compounds
Titanium amides
Zirconium amides
Phosphaguanidinates
Crystal structure
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
j1-N,N0-bonding mode observed at aluminum [21], and more
recently at lanthanum (E) [20]. Chelating
j
1-P,N-coordination,
The phosphaguanidinate anion, [R2PC{NR0}2]ꢀ, is a versatile li-
gand that continues to elicit attention since it was first investigated
by Thewissen et al. in 1980 [1]. In the original studies, the rhodium
and iridium phosphine complexes A were reported (Fig. 1), for
which spectroscopic data indicated a square planar metal with a
originally deduced from spectroscopic data to be present in A, is re-
ported in the homoleptic Co(II) compound [22], with related bond-
ing reported in the patent literature for ethylene polymerization
pre-catalysts containing bulky phospha(III)guanidinate ligands
[23]. The base-free lithium salt derived from the P-dicyclohexyl
derivative Cy2PC{NR0}{NHR0} [24], crystallized as a bridging ligand
chelating
j
1-P,N-bonding mode. The first structurally character-
ized example, ZrCp02[(Me3Si)2PC{NPh}2]Cl (B), was synthesized by
carbodiimide insertion into a terminal phosphide to afford the che-
lating j1-N,N0-phosphaguanidinate [2,3], reminiscent of traditional
amidinate and guanidinate bonding [4–9,10].
with
j
1-P,N-bonding to one metal and secondary Nimineꢁ ꢁ ꢁLi bonds,
generating cyclic hexamer (F) [22]. Finally Jones and co-workers
have observed a novel chelating mode for phosphaguanidinate
[Cy2PC{NAr}2]ꢀ (Ar = 2,6iPr2C6H3) at Tl(I) and In(I) centers
[25,26]. The metal is coordinated in an
nitrogen, with an approximately
3-interaction with the aryl
substituent of the other nitrogen (G).
We became interested in this area as an extension of our work
with metal guanidine [11] and guanidinate complexes [10], initially
developing a synthetic route to the neutral, P-diphenyl substituted
ligand precursors Ph2PC{NR0}{NHR0} [12], via lithium phosphagua-
g
1-fashion by the amido
g
One of the driving forces behind our research was to develop
multi-metallic complexes through simultaneous amidinate and
phosphine coordination. This was recently demonstrated with
the structurally characterized mixed aluminum/copper compound,
CuBr(Ph2PC{NiPr}2AlMe2)2 (H) [27], indicating that only minor per-
turbations occur to the bonding within the ligand when combining
with two metal fragments (Fig. 2). We have also developed alkyl-
bridged bis-phosphaguanidines [28]. The bimetallic aluminum
complex, [PhP(C{NiPr}2AlMe2)CH2–]2 (I) was isolated as a mixture
of the rac- and meso-products that could be separated by fractional
crystallization.
Gathering further information on the types of complex that
these versatile ligands adopt remains a worthwhile pursuit and,
as such, we wish to report in this contribution the synthesis and
structural characterization of a series of titanium and zirconium
amides supported by examples of the phosphaguanidinate ligand.
nidinates
C and D [13]. Synthesis of the bulky derivatives
i
R2PC{NAr}{NHAr} (Ar = 2,6 Pr2C6H3, R = Ph, Cy) has recently been
described using a similar synthetic procedure [14]. Building on this
work, other groups have demonstrated that tetra-substituted phos-
pha(III)guanidines may be obtained catalytically from the reaction
of carbodiimides with secondary phosphines in the presence of al-
kali-metal reagents [15,16], group 2 metal amides [17,18], transi-
tion metal phosphides [19] or lanthanide compounds [20].
Crystallographic characterization of phosphaguanidinate com-
plexes has demonstrated versatility in the bonding. The P-diphenyl
substituted lithium salts C and D exhibit the
j
1-P,N- and
j
1,2-N-j1
-
N0-bonding modes, respectively, with the more conventional
* Corresponding author. Tel.: +44 0 1273 877339; fax: +44 0 1273 677196.
E-mail address: m.p.coles@sussex.ac.uk (M.P. Coles).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.05.017

2482
N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
iPr
THF
Ph
iPr
Ph
P
N
Ph
Ph
P
Me2
N
Cl
P
N
P
Ph3P
Ph3P
iPr
Ph
N
Zr
Li
Li
N
N
Li
M
iPr
N
N
N
iPr
THF
N
Ar
N
Ph
Ph
Ar
Me2
SiMe3
Ph
N
Ph
P
Ph
SiMe3
iPr
(M = Ir, Rh)
C
A
B
D
iPr
iPr
Me2Si
iPr
N
Cy
Cy
N
La
N
N
N
iPr
OEt2
iPr
Cy
Cy
P
Li
Ar
Pri
iPr
iPr
Li
N
P
N
Li
M
N
N
P
Cy
Ar'
N
N
P
Cy
iPr
Ph
M = Tl(I), In(I)
P
iPr
Ph
Cy
Ar = 2,6-iPr2C6H3
Cy
Ar = 2,4,6-Me3C6H2
E
F
G
Fig. 1. Examples of different bonding modes in phosphaguanidinate metal complexes.
2.2. General synthesis – procedure 1
iPr
iPr
N
iPr
N
Me
Ph
P
Ph
P
Ph
Me
Ph
nBuLi (1 equiv.) was added dropwise via syringe to a stirred
solution of the neutral phosphaguanidine in THF at 0 °C. After stir-
ring at ambient temperature for 1 h the volatiles were removed un-
der reduced pressure and the resultant white solid was washed
with hexane (2 ꢂ 10 mL). The residual solid was dissolved in tolu-
ene added dropwise to a solution of ‘M(NMe2)3Cl’ in toluene at
ꢀ78 °C. The reaction mixture was allowed to warm to ambient
temperature affording a clear solution and a white precipitate. Re-
moval of the volatiles and extraction with hexane, followed by con-
N
Al
Ph
iPr
N
R"
R"
R"
R"
Al
Al
N
iPr
P
P
N
iPr
N
iPr
Cu
Ph
Al
N
Me
Me
Br
iPr
H
I
Fig. 2. Examples of bimetallic and linked phosphaguanidinate complexes.
centration and storage at ꢀ30 °C yielded the product as
a
crystalline solid.
2. Experimental
2.3. General synthesis – procedure 2
2.1. General considerations
A clear solution of the appropriate metal-amide in hexanes was
added dropwise via syringe to a clear colorless solution of the neu-
tral phosphaguanidine in toluene at ambient temperature. The
resulting solution was stirred for ꢃ15 h. Removal of the volatile
component, followed by storage of a concentrated hexane solution
at ꢀ30 °C yielded the product as a crystalline solid.
All manipulations were carried out under dry nitrogen using
standard Schlenk-line and cannula techniques, or in a conventional
nitrogen-filled glovebox. Solvents were dried over appropriate dry-
ing agents and degassed prior to use. NMR spectra were recorded
using a Bruker Avance DPX 300 MHz spectrometer at 300.1 (1H),
75.4 (13C{1H}) and 121.4 (31P{1H}) MHz and a Bruker AMX
500 MHz spectrometer at 500.1 (1H), 125.7 (13C{1H}) and 202.4
2.3.1. Ti(Ph2PC{NiPr}2)(NMe2)3 (3a)
31P{1H}) MHz, from samples at 25 °C in [2H6]-benzene, unless
Compound 3a was made according to procedure 2, using the
following amounts: Ti(NMe2)4 (1.60 mL of a 0.20 M solution in
hexanes, 0.32 mmol) and Ph2PC{NiPr}{NHiPr} (0.10 g, 0.32 mmol).
The compound was isolated as yellow crystals. Yield 0.08 g (52%).
1H NMR (300 MHz): d 7.65 (t, J = 7.1, 4H, m-C6H5), 7.13–7.03 (m,
6H, o- and p-C6H5), 4.20 (sept, J = 6.2, 2H, CHMe2), 3.31 (s, 18H,
NMe2), 0.92 (d, J = 6.2, 12H, CHMe2). 13C NMR (75 MHz): d 173.2
(d, J = 56, PCN2), 134.7 (d, J = 16, C6H5), 132.5 (d, J = 18, C6H5),
128.9 (d, J = 6, C6H5), 128.5 (C6H5), 50.7 (d, J = 17, CHMe2), 46.4
(NMe2), 24.9 (CHMe2). 31P NMR (121 MHz): d ꢀ23.0.
(
otherwise stated. Coupling constants are quoted in Hz. Proton
and carbon chemical shifts were referenced internally to residual
solvent resonances; phosphorus chemical shifts were referenced
externally to H3PO4 (aq). Elemental analyses were performed by
S. Boyer at London Metropolitan University.
Zr(NMe2)4 [29], Ph2PC{NR0}{NHR0} (1) [12], Cy2PC{NR0}{NHR0}
(2) [24], [PhP(C{NiPr}{NHiPr})CH2–]2 (7) [28] were made according
to literature procedures. The corresponding lithium phosphaguani-
dinate species ‘[Li(R2PC{NR}2)(solvent)n]x’ were prepared in situ by
reacting 1 and 2 with nBuLi [13,22]. TiCl4, ZrCl4, Ti(NEt2)4 and
Ti(NMe2)4 were purchased from Sigma–Aldrich; 0.20 M stock solu-
tions of the tetraamide were made by diluting the neat compound
with the appropriate amount of hexane. A 1.0 M solution of ‘Ti(N-
Me2)3Cl’ and ‘Zr(NMe2)3Cl’ in toluene/hexane were made by com-
bining the appropriate molar quantities of the metal tetraamide
and tetrachloride [30]. Compounds listed in inverted commas indi-
cate that they were not isolated and used in situ; for the purposes
of calculating yields and reaction stoichiometries, the yield was as-
sumed to be quantitative.
2.3.2. Ti(Ph2PC{NCy}2)(NMe2)3 (3b)
Compound 3b was made according to procedure 1, using the
following amounts: nBuLi (0.44 mL of a 2.5 M solution in hexanes,
1.1 mmol), Ph2PC{NCy}{NHCy} (0.39 g, 1.0 mmol), ‘Ti(NMe2)3Cl’
(1.00 mL of a 1.0 M solution in toluene/hexane, 1.0 mmol). The
compound was isolated as dark yellow crystals. Yield 0.07 g (50%).
Compound 3b was also made according to procedure 2, using
the following amounts: Ti(NMe2)4 (1.25 mL of a 0.20 M solution
in hexanes, 0.25 mmol) and Ph2PC{NCy}{NHCy} (0.10 g,

N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
2483
0.25 mmol). The compound was isolated as yellow crystals. Yield
2.3.8. Zr(Cy2PC{NiPr}2)(NMe2)3 (6a)
0.07 g (50%). 1H NMR (300 MHz): d 7.66 (t, J = 8.4, 4H, m-C6H5),
Compound 6a was made according to procedure 2, using the
following amounts: Zr(NMe2)4 (0.09 g, 0.32 mmol) and Cy2-
PC{NiPr}{NHiPr} (0.10 g, 0.32 mmol). The compound was isolated
as colorless crystals. Yield 0.10 g (58%). 1H NMR (300 MHz): d
4.82 (m, 1H, CHMe2), 3.91 (m, 1H, CHMe2), 3.12 (s, 18H, NMe2),
1.68–1.26 (m, 22H, Cy-CH2), 1.19 (br d, J = 5.9, 12H, CHMe2). 13C
NMR (125 MHz): d 50.3 (d, J = 16, CHMe2), 42.5 (NMe2), 35.5 (d,
7.13–7.02 (m, 6H, o- and p-C6H5), 3.76 (m, 2H, Cy-H ), 3.34 (s,
a
18H, NMe2), 1.59–0.99 (m, 20H, Cy-CH2). 13C NMR (75 MHz): d
173.3 (d, J = 56, PCN2), 135.0 (d, J = 16, C6H5), 132.5 (d, J = 18,
C6H5), 128.9 (d, J = 6, C6H5), 128.3 (C6H5), 58.9 (d, J = 17, Cy-C ),
a
46.5 (NMe2), 35.5 (N-Cy), 26.2 (N-Cy), 26.1 (N-Cy). 31P NMR
(121 MHz): d ꢀ22.1.
J = 17, Cy-C ), 31.6 (d, J = 14, Cy-CH2), 27.1, 27.0, 26.9, 26.4
a
2.3.3. Ti(Ph2PC{NiPr}2)(NEt2)3 (3a0)
(Cy-CH2), 25.1 (CHMe2). PCN2 and CHMe2 resonances not
observed due to broadening and low solubility. 31P NMR
(121 MHz): d ꢀ7.4.
Heating an equimolar mixture of Ph2PC{NiPr}{NHiPr} and
Ti(NEt2)4 to 120 °C in toluene afforded a small number of yellow
crystals that were analyzed by elemental analysis and X-ray crys-
tallography. Insufficient pure material was isolated for spectro-
scopic analysis.
2.3.9. Zr(Cy2PC{NCy}2)(NMe2)3 (6b)
Compound 6b was made according to procedure 2, using the
following amounts: Zr(NMe2)4 (0.07 g, 0.32 mmol) and Cy2-
PC{NCy}{NHCy} (0.10 g, 0.32 mmol). The compound was isolated
as colorless crystals. Yield 0.13 g (67%). 1H NMR (300 MHz): d
2.3.4. Zr(Ph2PC{NiPr}2)(NMe2)3. (4a)
Compound 4a was made according to procedure 2, using the
following amounts: Zr(NMe2)4 (0.09 g, 0.31 mmol) and
Ph2PC{NiPr}{NHiPr} (0.10 g, 0.31 mmol). The compound was iso-
lated as colorless crystals. Yield 0.11 g (58%). 1H NMR (300 MHz):
d 7.62 (t, J = 7.7, 4H, m-C6H5), 7.11–7.02 (m, 6H, o- and p-C6H5),
4.20 (sept, J = 6.1, 2H, CHMe2), 3.12 (s, 18H, NMe2), 0.93 (d,
J = 6.1, 12H, CHMe2). 13C NMR (125.5 MHz): d 134.4 (d, J = 16,
C6H5), 132.3 (d, J = 18, C6H5), 128.9 (d, J = 6, C6H5), 128.6 (C6H5),
50.5 (d, J = 18, CHMe2), 42.6 (NMe2), 24.8 (CHMe2). PCN2 resonance
not observed due to low solubility. 31P NMR (121 MHz): d ꢀ20.8.
4.32 (br m, 1H, NCy-H ), 3.48 (br m, 1H, NCy-H ), 3.14 (s, 18H,
a
a
NMe2), 1.80–1.16 (m, 42H, Cy). 13C NMR (75 MHz): d 178.9 (d,
J = 54, PCN2), 58.4, 58.2 (br, NCy-C ), 42.7 (s, NMe2), 36.1 (d,
a
J = 17, PCy-C ), 36.0 (N-Cy), 33.2 (d, J = 23, PCy-CH2), 31.8 (d,
a
J = 12, PCy-CH2), 27.4, 27.2, 27.1, 26.4, 26.2 (P- and NCy-CH2). The
NCy-CH2 resonances are not clear due to overlap with the PCy-
CH2 signals and broadening of the signals. 31P NMR (121 MHz): d
ꢀ8.7.
2.3.10. [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2 (8a)
2.3.5. Zr(Ph2PC{NCy}2)(NMe2)3 (4b)
Compound 4a was made according to procedure 2, using the fol-
Compound 8a was made according to procedure 2, using the
following amounts: Ti(NMe2)4 (2.00 mL of a 0.2 M solution in hex-
anes, 0.40 mmol) and [PhP(C{NiPr}{NHiPr})CH2–]2 (0.10 g,
0.20 mmol). The compound was isolated as yellow crystals. Yield
0.08 g (47%). 1H NMR (300 MHz, CDCl3): d 7.59–7.37 (m, 20H,
C6H5 major and minor isomers), 4.16 (m, 2H, CHMe2 major), 3.31
(s, 18H, NMe2 minor), 3.30 (s, 18H, NMe2 major), 2.20 (d, J = 6.4,
4H, C2H4 major) 2.76 (m, 2H, CHMe2 minor), 1.30 (d, J = 6.0, 4H,
C2H4 minor), 1.20 (d, J = 6.3, 12H, CHMe2 minor), 0.89 (d, J = 6.3,
lowing
amounts:
Zr(NMe2)4
(0.07 g,
0.25 mmol)
and
Ph2PC{NCy}{NHCy} (0.10 g, 0.25 mmol). The compound was iso-
lated as colorless crystals. Yield 0.12 g (67%). 1H NMR (300 MHz):
d 7.64 (t, J = 7.2, 4H, m-C6H5), 7.11–7.01 (m, 6H, o- and p-C6H5),
3.77 (m, 2H, Cy-H ), 3.15 (s, 18H, NMe2), 1.57–0.93 (m, 20H, Cy-
a
CH2). 13C NMR (125 MHz): d 175.2 (d, J = 55, PCN2), 134.7 (d,
J = 16, C6H5), 132.4 (d, J = 19, C6H5), 128.9 (d, J = 6, C6H5), 128.6
(C6H5), 58.1 (d, J = 17, Cy-C ), 42.7 (NMe2), 35.6, 26.1, 26.0 (Cy-
a
CH2). 31P NMR (121 MHz): d ꢀ20.6.
12H, CHMe2 major). 31P NMR (121 MHz): d –30.6 (meso), –31.8
*
*
(rac). Due to the sparing solubility of this compound in hydrocar-
2.3.6. Ti(Cy2PC{NiPr}2)(NMe2)3 (5a)
bon and decomposition in chlorinated solvents, over extended
time periods, it was not possible to obtain accurate 13C NMR data.
Compound 5a was made on an NMR scale in C6D6 according to
procedure 2, using the following amounts: Ti(NMe2)4 (0.007 g,
0.032 mmol) and Cy2PC{NiPr}{NHiPr} (0.010 g, 0.032 mmol). A con-
version of ꢃ90% was noted from the integration of the 1H NMR
spectrum. 1H NMR (300 MHz): d 4.67 (m, 1H, CHMe2), 4.40 (m,
1H, CHMe2), 3.10 (s, 18H, NMe2), 1.70–1.24 (m, 22H, Cy), 1.18 (d,
J = 6.3, 12H, CHMe2). 13C NMR (75 MHz): d 178.0 (d, J = 57, PCN2),
2.4. Details of crystallographic study
Details of the crystal data, intensity collection and refinement
for complexes 3a0, 3b and 4b are collected in Table 1 and for 5a,
6a, 6b and 8a in Table 2. Crystals were covered in an inert oil
and suitable single crystals were selected under a microscope
and mounted on a Kappa CCD diffractometer. Data was collected
50.2 (CHMe2), 42.3 (NMe2), 35.7 (d, J = 17, Cy-C ), 33.3 (d, J = 23,
a
Cy-CH2), 31.6 (d, J = 12, Cy-CH2), 27.2, 27.1, 26.9, 26.6 (Cy-CH2),
25.2 (CHMe2). 31P NMR (121 MHz): d ꢀ9.8.
at 173(2) K using Mo K
a radiation at 0.71073 Å. The structures
were refined with SHELXL-97 [31]. In all cases, the H-atom on the
amine nitrogen was refined with other H-atoms in riding mode.
Additional features of note are described below:
2.3.7. Ti(Cy2PC{NCy}2)(NMe2)3 (5b)
Compound 5b was made according to procedure 2, using the
following amounts: Ti(NMe2)4 (1.25 mL of a 0.2 M solution in hex-
anes, 0.25 mmol) and Cy2PC{NCy}{NHCy} (0.10 g, 0.25 mmol). The
compound was isolated as yellow crystals. Yield 0.07 g (48%). 1H
2.4.1. Zr(Cy2PC{NCy}2)(NMe2)3 (6b)
There are two independent molecules of the Zr complex and
one poorly defined hexane solvate disordered about an inversion
center present in the unit cell. The hexane was included with a
common isotropic displacement parameter for carbon and with
DFIX and FLAT geometry restraints.
NMR (300 MHz): d 4.48 (m, 1H, NCy-H ), 4.26 (m, 1H, NCy-H ),
a
a
3.32 (s, 18H, NMe2), 2.18–1.14 (m, 42H, P- and NCy-CH2). 13C
NMR (75 MHz): d 178.1 (d, J = 57, PCN2), 59.3 (br, NCH), 46.4
(NMe2), 36.2 (d, J = 17, PCy-C ), 35.8 (br, NCy-CH2), 33.2 (d, J = 22,
a
PCy-CH2), 32.0 (d, J = 13, PCy-CH2), 27.4, 27.3, 27.1, 26.6, 26.5,
26.2, 26.1 (P- and NCy-CH2). The NCy-CH2 resonances are not clear
due to overlap with the PCy-CH2 signals and broadening of the sig-
nals. 31P NMR (121 MHz): d ꢀ11.0.
2.4.2. [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2 (8a)
The molecule is located on an inversion center.

2484
N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
Table 1
Crystal structure and refinement data for Ti(Ph2PC{NiPr}2)(NEt2)3 (3a0), Ti(Ph2PC{NCy}2)(NMe2)3 (3b) and Zr(Ph2PC{NCy}2)(NMe2)3 (4b).
3a0
3b
4b
Formula
C
31H54N5PTi
C31H50N5PTi
571.63
C31H50N5PZr
614.95
Formula weight
Crystal size (mm)
Crystal system
Space group
a (Å)
575.66
0.40 ꢂ 0.35 ꢂ 0.15
0.15 ꢂ 0.15 ꢂ 0.02
0.40 ꢂ 0.40 ꢂ 0.05
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1 (no.2)
P1 (no.2)
P1 (no.2)
9.1768(2)
11.0815(2)
17.3647(3)
104.301(1)
92.406(1)
100.157(1)
1677.54(6)
2
8.4743(2)
11.8215(2)
18.1375(4)
72.333(2)
76.752(2)
69.214(2)
1603.50(7)
2
8.5324(2)
11.9182(2)
18.1919(3)
72.164(1)
76.872(1)
69.529(1)
1634.90(5)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg mꢀ3
)
1.14
0.33
1.18
0.34
1.25
0.41
Absorption coefficient (mmꢀ1
)
h Range for data collection (°)
Reflections collected
3.71–25.02
17 624
3.75–25.00
16 771
3.73–25.05
17 517
Independent reflections (Rint
)
5826 (0.040)
5097
5533 (0.066)
4130
5679 (0.039)
5188
Reflections with [I > 2 (I)]
r
Data/restraints/parameters
5826/0/343
0.992
5533/0/349
1.057
5679/0/349
1.023
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.040; wR2 = 0.102
R1 = 0.048; wR2 = 0.108
0.52 and ꢀ0.33
R1 = 0.052; wR2 = 0.098
R1 = 0.084; wR2 = 0.110
0.34 and ꢀ0.37
R1 = 0.027; wR2 = 0.063
R1 = 0.032; wR2 = 0.065
0.26 and ꢀ0.41
Largest difference in peak and hole (e Åꢀ3
)
Table 2
Crystal structure and refinement data for Ti(Cy2PC{NiPr}2)(NMe2)3 (5a), Zr(Cy2PC{NiPr}2)(NMe2)3 (6a), Zr(Cy2PC{NCy}2)(NMe2)3 (6b) and [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2 (8a).
5a
6a
6b
8a
Formula
C
25H54N5PTi
C25H54N5PZr
546.92
C31H62N5PZrꢁ0.25(C6H14
648.59
)
C40H78N10P2Ti2
856.86
Formula weight
Crystal size (mm)
Crystal system
Space group
a (Å)
503.60
0.10 ꢂ 0.10 ꢂ 0.10
monoclinic
P21/n (no. 14)
8.3493(2)
11.9892(3)
29.5480(6)
90
91.342(1)
90
2956.99(12)
4
0.10 ꢂ 0.05 ꢂ 0.02
monoclinic
P21/n (no. 14)
8.4070(1)
11.9812(2)
29.9250(4)
90
91.462(1)
90
3013.24(7)
4
0.30 ꢂ 0.25 ꢂ 0.20
0.25 ꢂ 0.20 ꢂ 0.20
triclinic
triclinic
ꢀ
ꢀ
P1 (no. 2)
P1 (no. 2)
10.4685(1)
10.9017(2)
33.5824(5)
97.719(1)
90.236(1)
104.032(1)
3681.83(9)
4
8.5743(3)
10.4422(2)
13.7172(4)
90.085(2)
98.748(1)
98.265(2)
1200.93(6)
1
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg mꢀ3
)
1.13
0.36
1.21
0.44
1.17
0.37
1.19
0.44
Absorption coefficient (mmꢀ1
)
h Range for data collection (°)
Reflections collected
3.40–26.02
21 559
3.40–26.04
29 821
3.44–26.03
43 811
3.41–26.06
18 286
Independent reflections (Rint
)
5779 (0.050)
4439
5929 (0.048)
4857
14 375 (0.054)
10 895
4735 (0.043)
4027
Reflections with [I > 2 (I)]
r
Data/restraints/parameters
5779/0/295
1.017
5929/0/295
0.680
14 375/11/717
1.071
4735/0/250
1.053
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.042; wR2 = 0.093
R1 = 0.064; wR2 = 0.102
0.40 and ꢀ0.31
R1 = 0.036; wR2 = 0.096
R1 = 0.051; wR2 = 0.112
0.32 and ꢀ0.42
R1 = 0.050; wR2 = 0.102
R1 = 0.076; wR2 = 0.113
1.00 and ꢀ0.52 (near solvate)
R1 = 0.034; wR2 = 0.078
R1 = 0.044; wR2 = 0.082
0.31 and ꢀ0.30
Largest difference in peak and hole (e Åꢀ3
)
The corresponding group 4 amides, M(R2PC{NR0}2)(NR200)3, were
therefore targeted. Reaction of in situ generated lithium phospha-
3. Results and discussion
guanidinate with M(NR00)3Cl (M = Ti, Zr) successfully afforded the
Attempted preparation of group
4
metal chlorides M(R2-
2
PC{NR0}2)Cl3 by the transmetallation reaction between in situ
generated lithium phosphaguanidinate and MCl4 or MCl4(THF)2
(M = Ti, Zr) met with limited success. Whilst an analogous proce-
dure has been successful for a range of ‘conventional’ guanidi-
desired complexes, although the yield was typically less than 30%
(Scheme 1). The amine elimination route between the neutral
phosphaguanidines 1a,b and 2a,b and the metal tetrakis(amides)
M(NR00)4, however, afforded the desired products in considerably
2
higher yields (48–67%). It was noted that reactions with Ti(NEt3)4
required heating to promote amine elimination, in contrast with
the corresponding Ti(NMe2)4 reactions which proceeded at room
temperature.
Compounds 3–6 were isolated as yellow (Ti) or colorless (Zr)
crystalline materials after purification. In each case 31P NMR spec-
troscopy showed a single resonance, in the range d ꢀ22.1 to ꢀ20.0
nate complexes of group
4
metals [32–41,42], reactions
involving the P-diphenyl derivatives Ph2PC{NR0}{NHR0} (1a,
R0 = iPr; 1b, R0 = Cy) led to complicated mixtures of products.
31P NMR spectroscopy indicated the presence of tetraphenyldi-
phosphine in the crude reaction mixture [dP ꢀ14.8 ppm, C6D6,
162 MHz] consistent with degradation of the phosphaguanidine
via rupture of the P–Camidine bond.

N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
2485
R'
N
R'
N
P
N1
nBuLi
THF
C1
N2
P
P
[Li(solvent)n]
N
R'
N3
N4
M
R
R
R
R
N R'
H
N5
1 R = Ph
2 R = Cy
Fig. 3. Key for bond length and angle tables.
a R' = iPr b R' = Cy
M
Ti
Ti
Ti
Zr
Zr
Ti
Ti
Zr
Zr
R
R' R"
tempted preparation of bis-guanidinate, Ti[(Me3Si)2NC{NiPr}2]2
(NMe2)2, via salt metathesis [42].
'M(NR"2)3Cl'
3a
Ph iPr Me
Ph iPr Et
Ph Cy Me
M(NR"2)4
3a'
3b
4a
4b
5a
5b
6a
6b
X-ray diffraction data have been solved for a number of com-
pounds,3 and the molecular structures of representative examples
are presented in Figs. 4 and 5; crystal structure and refinement data
is collected in Tables 1 and 2, and bond lengths and angles in Tables
3 and 4. Fig. 3 presents a generic atomic numbering scheme for the
compounds described in this study to facilitate comparison between
data for different derivatives.
iPr
Cy
iPr
Cy
iPr
Cy
Ph
Ph
Cy
Cy
Cy
Cy
Me
Me
Me
Me
Me
Me
R'
N
R
R
P
NR"2
NR"2
N
M
R'
NR"2
All compounds contain a five-coordinate metal center in what is
best described as a highly distorted trigonal bipyramidal geometry,
Scheme 1. Synthetic procedures used in the synthesis of group 4 metal phospha-
guanidinate complexes described in this work.
with
s-values [52] in the range 0.55–0.70. As expected for early
transition metals, the phosphaguanidinate is present as a j1
-
N,N0-chelating ligand (B and E, Fig. 1), with axial and equatorial
Namidine atoms. The acute bite angle of the phosphaguanidinate li-
gand [ave. 59.3°] is the primary cause of the distortion from tbp-
geometry, resulting in a significantly reduced Nax–M–Nax bond an-
gle [range 155.52(11)°–162.78(7)°], as noted in related five-coordi-
for P-diphenyl derivatives (3 and 4) and d ꢀ11.0 to ꢀ7.4 for P-dicy-
clohexyl species (5 and 6). 1H NMR data indicated a phosphaguani-
dinate:amide ratio of 1:3, consistent with formation of M(L)(NR00)3
2
(L = phosphaguanidinate). One set of resonances was observed for
each the NR0 substituents of the phosphaguanidinate ligands for
compounds 3 and 4, with a single environment for the amide sub-
stituents. This is attributed to a fluxional trigonal bipyramidal
complex in solution with fast exchange between the axial and
equatorial positions.1 Low temperature NMR (198 K) did not re-
solve the spectra, indicating a low-energy barrier to this fluxional
process. In contrast, data for the P-dicyclohexyl derivatives 5 and
6 showed different environments for the Namidine substituents, con-
sistent with a more rigid solution-state structure.
nate metal containing structures [42,53–56]. We note
a
consistently shorter C–Nax bond compared to the C–Neq (range of
DCN [57]: 0.030–0.046 Å), consistent with partial localization with-
in the amidine unit. This has previously been noted in five-coordi-
nate aluminum compounds supported by amidinate ligands [58],
and reflects a greater contribution to the overall bonding from
the resonance structure B (Fig. 6).
The orientation of the R2P-group with respect to the approxi-
mate equatorial plane differs within this series of compounds. In
the P-diphenyl compounds 3b and 4b the phosphide group is
positioned such that the phenyl substituents point away from
The 1H, 13C and 31P NMR spectra were consistent with the pro-
posed structures M(R2PC{NR0}2)(NR200)3.2 However, combustion
analysis results were consistently inaccurate for the formulated
compounds, despite repeated attempts on recrystallized samples.
Whilst we can not completely rule out the presence of NMR silent
contaminants (e.g., metal oxides) an alternative explanation for
these erroneous results is the formation of non-volatile metal ni-
tride/carbonitride (or possibly phosphide) materials during the
combustion. This is not without precedent, given the all nitrogen
coordination environment at the metal centers in these com-
pounds. Indeed, in the last couple of years, conventional guanidi-
nate ligands have been successfully utilized for the stabilization
of molecular precursors in the (MO)CVD of a number of nitrogen
containing materials including tantalum [43–45,46], niobium
[47], tungsten [46,48–50] and gadolinium nitride [51], and tita-
nium carbonitride [42], where the source of the nitrogen typically
arises from the guanidinate ligand.
the MN3-plane (a-form, Fig. 7), whilst in the P-dicyclohexyl substi-
tuted examples, the phosphorus groups point towards the equator
(b-form). The structure of 3a0, being the only diethylamido deriva-
tive structurally examined, differs from the other P-diphenyl
examples with respect to its P-substituent orientation, crystallizing
as the b-form (Fig. 4). In this case, the M–Naxial–C angles suggest
that the increased steric influence of the NEt2 ligands force the Nax-
substituent back towards the phenyl groups on phosphorus,
ial
destabilizing the a
-form (Fig. 7).4 Whilst it is recognized that these
data are from the solid-state structures, and that in solution free
rotation about the P–C bond is likely, energetic preferences for a
specific orientation of this group will have important consequences
in the development of multi-metallic compounds [13,27].
Given the inherent stability of chelating bis-phosphines, and the
aforementioned potential application of the compounds described
in this manuscript as metal-functionalized phosphines, we were
keen to explore the possibility of synthesizing a bimetallic group
Reactions between two equivalents of the neutral P-dic-
yclohexylphosphaguanidine and M(NR00)4 yielded only the mono-
substituted product species, even after prolonged reflux in toluene
solution. This is likely due to the steric crowding at the metal cen-
ter upon mono-substitution, preventing protonolysis of additional
metal-amide bonds; a similar restriction has been noted in the at-
4
compound incorporating our previously reported linked
bis(phosphaguanidine) [28]. The 1:2 reaction of [PhP(C{NiPr}
{NHiPr})CH2–]2 (7), with Ti(NMe2)4 was therefore carried out,
affording yellow crystals (8a) upon crystallization from toluene
1
Although this spectroscopic data is also consistent with a square-based pyramid
3
in which the phosphaguanidinate forms two of the basal ligands and the three amides
fluctuate between basal and apical positions, this is unlikely given the strong
preference for five-coordinate early transition-metals to adopt trigonal bipyramidal
geometries. This would also contradict the solid-state data for these complexes.
The crystal structures of Ti(Ph2PC{NCy}2)(NMe2)3 (3b) and Zr(Cy2PC-
{NiPr}2)(NMe2)3 (6a) have also been solved. ORTEPs have been included in the
Supplementary data.
4
It is noted that the Namidine substituents also differ when comparing 30a, 3b and
2
Representative 1H, 13C and 31P NMR spectra are provided in the Supplementary
4b. However, previous studies have indicated that these groups have a minimal effect
data.
on the metrical paramaters associated with the bonding in compounds of this type.

2486
N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
Fig. 4. ORTEP of the molecular structures of Ti(Ph2PC{NiPr}2)(NEt2)3 (3a0) and Zr(Ph2PC{NCy}2)(NMe2)3 (4b). Ellipsoids drawn at 30% probability; hydrogens omitted.
Fig. 5. ORTEP of the molecular structures of Ti(Cy2PC{NiPr}2)(NMe2)3 (5a) and one of the independent molecules of Zr(Cy2PC{NCy}2)(NMe2)3 (6b). Ellipsoids drawn at 30%
probability; hydrogens and, in the case of 6b the solvate, omitted.
Table 3
Selected bond lengths (Å) for the compounds M(R2PC{NR0}2)(NR200 )3. Atomic labeling scheme taken from Fig. 3 to facilitate comparisons of equivalent bonds.
3a0
3b
4b
5a
6a
6b
N1–M
N2–M
N3–M
N4–M
N5–M
C1–N1
C1–N2
C1–P
2.251(2)
2.099(2)
1.922(2)
1.908(2)
1.960(2)
1.311(2)
1.351(2)
1.888(2)
2.231(2)
2.087(2)
1.895(3)
1.897(2)
1.999(2)
1.311(3)
1.342(3)
1.890(3)
2.3396(14)
2.2302(15)
2.0340(16)
2.0304(16)
2.0935(16)
1.316(2)
2.2363(17)
2.0878(16)
1.9007(18)
1.9030(17)
1.9682(17)
1.309(3)
2.333(2)
2.227(2)
2.044(2)
2.037(2)
2.096(2)
1.320(3)
1.352(3)
1.892(3)
2.349(3)/2.336(2)
2.218(2)/2.220(2)
2.043(3)/2.050(3)
2.042(3)/2.027(3)
2.087(3)/2.085(3)
1.315(4)/1.316(4)
1.356(4)/1.350(4)
1.895(3)/1.895(3)
1.346(2)
1.8914(18)
1.355(3)
1.892(2)
Table 4
Selected bond angles (°) for the compounds M(R2PC{NR0}2)(NR200 )3. Atomic labeling scheme taken from Fig. 3 to facilitate comparisons of equivalent bonds.
3a0
3b
4b
5a
6a
6b*
N1–M–N5
N1–M–N2
N1–M–N3
N1–M–N4
N5–M–N2
N5–M–N3
N5–M–N4
N2–M–N3
N2–M–N4
N3–M–N4
162.78(7)
60.91(6)
92.88(7)
93.67(7)
101.93(7)
96.29(7)
95.43(7)
115.44(7)
123.27(7)
115.64(7)
161.24(9)
60.81(9)
94.66(10)
94.94(9)
100.43(9)
94.75(10)
94.81(10)
118.97(10)
118.69(10)
118.34(11)
157.22(6)
57.73(5)
96.44(6)
95.16(6)
99.49(6)
95.49(6)
95.87(6)
118.07(6)
118.46(7)
119.15(7)
160.30(7)
60.84(6)
94.31(7)
96.03(7)
99.60(7)
94.74(8)
95.64(7)
121.85(7)
118.05(7)
116.06(8)
155.64(9)
57.86(8)
94.70(9)
97.74(9)
98.25(9)
94.71(9)
97.97(10)
121.60(9)
117.29(9)
116.76(10)
155.57(11)/157.37(10)
57.92(9)/57.82(9)
98.43(10)/97.15(10)
96.52(12)/95.66(11)
97.85(11)/99.56(10)
96.46(12)/94.83(11)
94.43(14)/96.53(12)
118.76(11)/120.69(10)
122.29(11)/119.78(10)
115.42(12)/115.11(11)
*
Two independent molecules in the unit cell.

N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
2487
Table 5
R'
N
R'
N
R
Selected bond lengths (Å) and angles (°) for [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2 (8a).
Atomic labeling scheme taken from Fig. 3 to facilitate comparisons of equivalent
bonds.
P
R
P
R
N
R'
R
M
N
M
R'
N1–Ti
N2–Ti
N3–Ti
N4–Ti
2.2631(14)
2.0689(14)
1.9130(16)
1.8941(15)
N5–Ti
C1–N1
C1–N2
C1–P
1.9440(15)
1.308(2)
1.353(2)
A
B
Fig. 6. Resonance structures contributing to the bonding in M(R2PC{NR0}2)ðNR200 )3.
1.8917(16)
N1–M–N5
N1–M–N2
N1–M–N3
N1–M–N4
N5–M–N2
161.38(6)
60.94(5)
94.50(6)
95.36(6)
100.50(6)
N5–M–N3
N5–M–N4
N2–M–N3
N2–M–N4
N3–M–N4
94.12(7)
95.18(7)
120.40(6)
117.97(6)
117.70(7)
R
R'
N
R'
N
R
P
R
R
P
N
M
N M
R'
R'
α-form
β-form
iPr
N
Cy
Cy
N
Ph
Ph
Ph
Ph
144.38°
NEt2
141.19°
139.27°
P
P
N
P
Ph
Ph
NMe2
NMe2
NMe2
NMe2
N
Ti
NEt2
3'a (β-form)
N
Ti
NMe2
3b (α-form)
N
Zr
NMe2
4b (α-form)
iPr
Cy
Cy
NEt2
Fig. 7. Conformational differences between a- and b-forms of the ligand.
(Scheme 2). The 31P NMR spectrum showed resonances at d ꢀ30.6
and ꢀ31.8, assigned to the rac- and meso- forms of the complexes,
arising from the chiral phosphine group. The 1H NMR spectrum
was complicated by the presence of both forms in solution,
although groups of peaks corresponding to the expected reso-
nances were observed. Once again, elemental analysis failed to give
a result consistent with the expected formulation of 8a.
Fig. 8. ORTEP of the molecular structure of [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2 (8a).
Ellipsoids drawn at 30% probability; hydrogens omitted.
The molecular structure of 8a is illustrated in Fig. 8; crystal
structure data is collected in Table 2 and selected bond lengths
and angles in Table 5. Compound 8a crystallizes from toluene as
the meso-form with both ends of the molecule related by an inver-
sion center. The ligand binds to each titanium as the N,N0-chelate
In the solid-state the metals adopt a trigonal bipyramidal geom-
etry with the N,N0-chelate spanning an axial and equatorial posi-
tion. Unequal contribution to the bonding from different
resonance forms results in localization within the amidine unit,
with the greater CN bond-order to the Naxial atom. Two conformers
are found that differ in the position of the phosphorus substituents,
related by rotation about the R2P–CN2 bond. It is probable that sub-
tle steric effects involving the amide, amidine and phosphorus sub-
stituents dictate which of these forms has the lowest energy. This
methodology was also extended to the bimetallic complex,
[PhP(C{NiPr}2Ti{NMe2}3)CH2–]2, which crystallized as the meso-
compound, with similar bonding parameters to those observed in
the mono-phosphaguanidinates. We are currently examining the
suitability of these compounds to act as metal-functionalized li-
gands in the development of multi-metallic systems for tandem
catalysis.
forming the expected distorted tbp-geometry, with a s-value of
0.68 and the phosphorus substituents in the b-position. With the
exception of minor variations, the bonding parameters of 8a mirror
those in the mono-phosphaguanidinate complexes described ear-
lier, suggesting that the metals are sufficiently far apart that they
do not have a strong influence on the bonding at the other end
of the molecule.
In summary, we have demonstrated a clean route to the mono-
phosphaguanidinate complexes, M(R2PC{NR0}2)(NR200)3, via amine
elimination. The P-diphenyl compounds are fluxional in solution
with a rapid exchange of axial and equatorial positions consistent
with a low-energy pathway converting these positions in a trigonal
bipyramidal geometry, whereas the P-dicyclohexyl derivatives are
more rigid in solution. No further reactivity with a second equiva-
lent of phosphaguanidine could be induced, suggesting a crowded
metal center that restricts the approach of additional neutral li-
gand precursor.
Acknowledgements
The University of Sussex and the EPSRC are thanked for finan-
cial support.
NMe2
H
iPr
iPr
Ph
iPr
N
iPr
N
N
NMe2
NMe2
N
2 Ti(NMe2)4
Ti
Ph
P
P
P
Ph
- 2 NHMe2
N
N
iPr
P
Me2N
Me2N
Ti
iPr
N
N
iPr
Ph
iPr
H
NMe2
7
8a
Scheme 2. Synthesis of the bimetallic compound [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2 (8a).

2488
N.E. Mansfield et al. / Polyhedron 29 (2010) 2481–2488
[28] N.E. Mansfield, M.P. Coles, A.G. Avent, P.B. Hitchcock, Organometallics 25
Appendix A. Supplementary data
(2006) 2470.
[29] D.C. Bradley, I.M. Thomas, J. Chem. Soc. (1960) 3857.
[30] D.G. Dick, R. Rousseau, D.W. Stephan, Can. J. Chem. 69 (1991) 357.
[31] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structures,
Göttingen, 1997.
[32] D. Wood, G.P.A. Yap, D.S. Richeson, Inorg. Chem. 38 (1999) 5788.
[33] P.J. Bailey, K.J. Grant, L.A. Mitchell, S. Pace, A. Parkin, S. Parsons, J. Chem. Soc.,
Dalton Trans. (2000) 1887.
[34] M.P. Coles, P.B. Hitchcock, J. Chem. Soc., Dalton Trans. (2001) 1169.
[35] A.P. Duncan, S.M. Mullins, J. Arnold, R.G. Bergman, Organometallics 20 (2001)
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[37] P. Bazinet, D. Wood, G.P.A. Yap, D.S. Richeson, Inorg. Chem. 42 (2003) 6225.
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CCDC 659262, 659263, 659264, 659265, 659266, 659267 and
659268 contain the supplementary crystallographic data for 3a0,
3b, 4b, 5a, 6a, 6b and 8a. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.ca-
m.ac.uk. Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.poly.2010.05.017.
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