distance in square-planar [Ni(CH2SiMe3)2(PMe3)2]6 is 2.158(4)
Å and in the square pyramidal [Ni(CN)2{P(CH2OH)Ph2}3]7
they are 2.229(4), 2.246(4) and 2.400(3) Å.
Solvents were dried by standard procedures8 and distilled under
N2 prior to use. The commercial products NiBr2 (99.99%, H2O
< 100 ppm), CH3COBr (99%), PhPH2 (98%), CH2Br2 (99%),
formaldehyde (37 wt% solution in water) were used as received
except that the solids were dried in vacuum. N,N,NЈ,NЈ-tetra-
ethyl- and tetramethyl-methanediamine were refluxed over
The 1H NMR resonances of IV were slightly broadened, due
to the paramagnetism of the sample, but did not shift to higher
1
frequencies as compared with [PhP(CH2NHEt2)2]Br2. The H
NMR spectrum (Fig. 4) shows that the CH2NHCH2 units in the
complex are magnetically non-equivalent, as each distinct pro-
ton nucleus produces two resonances. The assignments were
confirmed by saturation-transfer and selective-decoupling
experiments. The non-equivalence is due to the rigidity of the
NH ؒ ؒ ؒ Br bonds, which keep the methylenes in constrained
positions. Saturation-transfer experiments at 45 ЊC showed
exchange between two CH3 groups but no exchange between
the two PCH2N methylene groups. The 1H NMR spectrum
showed no significant changes in the temperature range Ϫ30 to
ϩ100 ЊC
sodium and distilled under dinitrogen prior to use. (Me N᎐
᎐
2
CH2)Br9 and (Et N᎐CH )Br10 were prepared by literature
᎐
2
2
methods in 60% and 95% yields, respectively.
Microanalyses were carried out at the University of Surrey
using a Leenan CE 440 CHN elemental analyzer or by
MEDAC, Brunel Science Centre, Surrey. IR spectra were
recorded on a Perkin-Elmer Spectrum One model FT-IR
spectrometer, from Nujol mulls prepared under argon. NMR
spectra were obtained in the appropriate deuterated solvents
using a Brüker 300 or 500 MHz instrument. (13C, 1H)-
1
HETCOR NMR and variable temperature H NMR experi-
ments were carried out by Dr Tony Avent, University of Sussex.
Mass spectra were recorded by Dr Ali Abdul-Sada, at the
University of Sussex, using a Kratos M580RF instrument for
FAB spectra (and 3-nitrobenzyl alcohol as a matrix material)
and a Fisons VG Autospec for EI spectra.
X-Ray crystal structure data were collected by the 2θ–ω scan
method at 173(2) K using an Enraf-Nonius Kappa CCD
diffractometer and Mo-Kα radiation (λ = 0.71073 Å). During
processing, the data were corrected for absorption by semi-
empirical methods. The structures were solved by direct
methods in SHELXS and refined by full-matrix least-square
methods in SHELXL.11 All non-hydrogen atoms were refined
anistropically. Diagrams of the molecular structures of the
complexes were drawn with the ORTEP package.12 Details of
the crystal structure determinations are shown in Table 5.
CCDC reference numbers 201299–201301.
Fig. 4 The 1H NMR spectrum of [NiBr4{PhP(CH2NHEt2)2}2][[NiBr4]
(IV), in d3-acetonitrile at room temperature.
lographic data in CIF or other electronic format.
The 31P NMR spectrum of IV in d3-acetonitrile showed no
detectable resonances at room temperature, probably because
of relaxation caused by proximity to the paramagnetic Ni
centres. The 13C{1H} NMR spectrum, with assignments con-
firmed by 13C and 13C-DEPT NMR experiments, showed no
signals for C(1) and C(17) of the Ph rings presumably because
they too are close to the paramagnetic Ni centres.
[PhP(CH2NHEt2)2]Br2 (I) and [PhP(O)(CH2NHEt2)2]/
[PhP(CH2NHEt2)2]Br2 (II)
PhPH2 (0.50 cm3, 4.6 mmol) was added to a white suspension
of (Et N᎐CH )Br (0.82 g, 4.9 mmol) in thf (25 cm3). The reac-
᎐
2
2
tion mixture was heated for ca. 5 h under reflux, and then left
stirring overnight. The mixture was then filtered, giving a white
powder (compound I, 0.70 g, 35% yield) and a colourless
filtrate. The solid was recrystallised from a dichloromethane
solution layered with hexane to yield colourless crystals of
[PhP(CH2NHEt2)2]Br2 (I). Found: C, 42.9; H, 7.2; N, 6.3.
C16H31Br2N2P requires: C, 43.4; H, 7.0; N, 6.3%.
The filtrate was layered with hexane to yield colourless
crystals of [PhP(O)(CH2NHEt2)2]/[PhP(CH2NHEt2)2]Br2 (II).
IR for I (cmϪ1): 697(s), 726(s), 749(w), 768(w), 810(s), 861(w),
873(w), 916(w), 930(w), 968(w), 1030(s), 1071(w), 1097(w),
1166(w), 1261(s), 1299(w), 2485(s), 2620(s).
Conclusions
This work was originally carried out to clarify some aspects of
the chemistry of triamine complexes. Although the reactions
described did not yield the desired triamine NiII species, we have
now isolated an NPN analogue from a reaction that might
have been expected to generate a triphosphacyclohexane ring.
Although [PhP(CH2NHEt2)2]Br2 is a phosphorus donor to
nickel(), the nitrogen might also be a donor were the quaternis-
ing protons to be removed. This mixed-donor proligand, which
may bind either by phosphorus or by nitrogen, will probably
not allow all three donors to coordinate to the same metal ion
owing to the single methylene spacers between the donor
centres. This offers potential to use ligands such as this to
explore metal ion hard/soft character, and to generate dimetal
species.
This work extends the known NCH2(NR)CH2N and
NCH2OCH2N compounds to a novel variant of the NCH2-
(PR)CH2N series. Although such compounds are potentially
obtainable by other routes, the chemistry displayed here dem-
onstrates just how much we have yet to learn about these
systems.
Reaction of NiBr2 with [PhP(CH2NHEt2)2]Br2
(1) Anhydrous NiBr2 (0.020 g, 0.10 mmol) and [PhP(CH2-
NHEt2)2]Br2 (0.16 g, 0.36 mmol) were suspended in thf (30 cm3)
and heated under reflux for 5 h. During this period, a slow
change to light green and then to purple was observed. The
mixture was cooled slowly to room temperature and left stir-
ring overnight. A white solid (0.11 g) was then filtered off.
The filtrate was layered with hexane to yield light red crystals,
analysed as [{Ni3Br6(thf )5}n] (III). Found: C, 22.5; H, 4.0; N,
0.3. C20H40Br6Ni3O5 requires: C, 23.6; H, 4.0; N, 0.0%.
(2) Tetrahydrofuran (40 cm3) was added to the mixture of
NiBr2 (0.52 g, 2.3 mmol) and [PhP(CH2NHEt2)2]Br2 (1.08 g,
2.4 mmol). The reaction mixture was left stirring for 72 h at
room temperature in the glove-box. A large amount of a pale
green powder (compound IV) was filtered off from a dark green
solution. The solid was recrystallised from a CH3CN solution
Experimental
All operations were carried out under an inert atmosphere in an
argon-filled box or with use of standard Schlenk techniques.
D a l t o n T r a n s . , 2 0 0 3 , 2 2 7 6 – 2 2 7 9
2278
Hitchcock, Peter B.
