Coordination chemistry of an asymmetric P,N,O tridentate ligand containing primary phosphine, amine and alcohol donors

Article abstract of DOI:10.1016/j.jorganchem.2011.01.031

The asymmetric, heterodonor tridentate ligand 2(S)-amino-4-phosphinobutan- 1-ol, S-PNO, has been prepared from (S)-aspartic acid and some aspects of its coordination chemistry with a number of metal complexes investigated. Reaction of S-PNO with appropriate metal precursors led to the isolation of the complexes fac-Cr(CO)₃(κ³-S-PNO), 1, fac-[Mn(CO) ₃(κ³-S-PNO)]PF₆, 2, and fac-[Re(CO) ₃(κ³-S-PNO)]BF₄, 3. The alcohol and amine donors in fac-Cr(CO)₃(κ³-S-PNO) were substituted upon addition of trivinylphosphine to 1 to give the complex fac-Cr(CO) ₃(κ¹-P-S-PNO){P(C₂H₃) ₃}₂, 4. Addition of base to 4 gave a coordinated linear tridentate P₃ ligand through the formation of two new chelate rings via hydrophosphination of one vinyl group on each coordinated P(C ₂H₃)₃ with the P-H bonds of the complexed S-PNO. The alcohol donor in fac-[Re(CO)₃(κ³-S-PNO)] BF₄ is labile and can be substituted with tris(2-fluorophenyl) phosphine, PAr₃^F, to give fac-[Re(CO)₃(κ ²-P,N-S-PNO)(PAr₃^F)]BF₄, 5. Attempts to form a macrocyclic ligand through addition of base to fac-[Re(CO) ₃(κ²-P,N-S-PNO)(PAr₃^F)]BF ₄ were unsuccessful due to loss of PAr₃^F prior to any ring-closure. All the complexes have been fully characterised by spectroscopic and analytical techniques including a single-crystal X-ray structure analysis of 2.

Full text of DOI:10.1016/j.jorganchem.2011.01.031

Journal of Organometallic Chemistry 696 (2011) 1652e1658
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Coordination chemistry of an asymmetric P,N,O tridentate ligand containing
primary phosphine, amine and alcohol donors
*
*
Peter G. Edwards , Paul D. Newman , Andreas Stasch
School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The asymmetric, heterodonor tridentate ligand 2(S)-amino-4-phosphinobutan-1-ol, S-PNO, has been
prepared from (S)-aspartic acid and some aspects of its coordination chemistry with a number of metal
complexes investigated. Reaction of S-PNO with appropriate metal precursors led to the isolation of the
Received 29 November 2010
Received in revised form
21 January 2011
complexes fac-Cr(CO)3(
alcohol and amine donors in fac-Cr(CO)3(
1 to give the complex fac-Cr(CO)3(
1-P-S-PNO){P(C2H3)3}2, 4. Addition of base to 4 gave a coordinated linear
k k k
3-S-PNO), 1, fac-[Mn(CO)3( 3-S-PNO)]PF6, 2, and fac-[Re(CO)3( 3-S-PNO)]BF4, 3. The
Accepted 27 January 2011
k
3-S-PNO) were substituted upon addition of trivinylphosphine to
k
Keywords:
Heterodonor
Asymmetric
Tridentate
Phosphine
Amine
tridentate P3 ligand through the formation of two new chelate rings via hydrophosphination of one vinyl
group on each coordinated P(C2H3)3 with the PeH bonds of the complexed S-PNO. The alcohol donor in
fac-[Re(CO)3(
give fac-[Re(CO)3(
base to fac-[Re(CO)3(
k
3-S-PNO)]BF4 is labile and can be substituted with tris(2-fluorophenyl)phosphine, PArF3, to
k
2-P,N-S-PNO)(PAr3F)]BF4, 5. Attempts to form a macrocyclic ligand through addition of
k
2-P,N-S-PNO)(PAr3F)]BF4 were unsuccessful due to loss of PArF3 prior to any ring-
Alcohol
closure. All the complexes have been fully characterised by spectroscopic and analytical techniques
including a single-crystal X-ray structure analysis of 2.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
different donor types should enable access to a range of coordi-
nation compounds showing metal ion dependent denticity and
Fac-[M(CO)3]nþ fragments are useful structural units for the
template-assisted synthesis of small-ring P3, P2C and PN2 macro-
cycles [1]. The success of these systems relies on a number of
features including the facility to add, in a sequential manner,
different donors at preferred positions in the coordination sphere
prior to the cyclisation event. As part of a continued interest in
small, facially capping macrocycles we are seeking new ligands
bearing primary phosphine functions in addition to other potential
donor types with the two-fold aim of making mixed-donor mac-
rocycles and/or to access P3 macrocycles bearing functionalised
pendant arms. The inclusion of secondary donors exo- to the main
macrocyclic ring is an attractive one as it is conceivable that such
donors can be used to bind other metals to give hetero-bimetallic
compounds. To this end we have synthesised the P,N,O containing
ligand 2(S)-amino-4-phosphinobutan-1-ol (S-PNO) as a potential
precursor to one or other of the aforementioned coordination
systems. S-PNO is part of an under-represented ligand class that
combine classically soft donors (P) with harder donors of two
different types (in this case N and O). The availability of three
selectivity in the lower dentate modes. The current paper examines
some aspects of the chemistry of S-PNO with low-valent middle
transition metals in an attempt to explore the possibility of selec-
tive coordination of one or more donors and also highlights some
preliminary efforts to synthesise P2N macrocycles from the S-PNO
complexes.
2. Experimental
The complexes were synthesised under dinitrogen using stan-
dard Schlenk line techniques. All solvents were freshly distilled
from sodium (toluene, 40/60 petroleum ether), sodium/benzo-
phenone (diethyl ether, tetrahydrofuran) or calcium hydride
(acetonitrile, ethanol) under dinitrogen before use. The 31P NMR
spectra were recorded on a Jeol Eclipse 300 spectrometer operating
at 121.7 MHz and referenced to 85% H3PO4 (
d
¼ 0 ppm). 1H (500 or
300 MHz) and 13C (125.8 or 75.6 MHz) NMR spectra were obtained
on Bruker 500 and Jeol Eclipse 300 spectrometers and are refer-
enced to tetramethylsilane (
d
¼ 0 ppm). Mass spectra were
obtained on a Waters LCT Premier XE mass spectrometer. All other
chemicals were of reagent grade and were used as supplied unless
otherwise stated. The precursors to S-PNO and R,S-S-PiPrNO were
prepared as described by Burgess et al. [2]. Fac-[Cr(CO)3(MeCN)3]
* Corresponding authors. Tel.: þ44 29 20870464; fax: þ44 29 20874030.
E-mail address: newmanp1@cardiff.ac.uk (P.D. Newman).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.01.031

P.G. Edwards et al. / Journal of Organometallic Chemistry 696 (2011) 1652e1658
1653
[3], fac-[Mn(CO)3(MeCN)3]PF6 [4] and LiP(SiMe3)2 [5] were
prepared by literature methods.
121.7 MHz)
d
ꢀ56.3 ppm 1H NMR (CD2Cl2, 500 MHz)
d
4.41 (1H,
d br, 1JHeP ¼ 330 Hz, PH), 4.35 (1H, dm, 1JHeP ¼ 310 Hz, PH), 3.46
(1H, d br, CH2OH), 3.12 (1H, br, CH2OH), 2.82 (1H, br, OH), 2.42 (1H,
m br, CH2PH2), 2.39 (1H, m br, R2CHNH2), 1.88 (1H, m br, CH2), 1.65
(2H, m br, CH2PH2, NH2), 1.08 (2H, m br, CH2, NH2) ppm. 13C DEPT
2.1. 2(S)-amino-4-phosphinobutan-1-ol, S-PNO
To a solution of propan-2-yl 5-(2-hydroxyethyl)-2,2-dimethyl-
1,3-oxazolidine-3-carboxylate tosylate (12 g, 0.03 mol) in Et2O
(250 ml) at ꢀ78 ꢁC was added slowly a solution of LiP(SiMe3)2
(6.25 g, 0.034 mol) in THF (100 ml) over a period of 1 h. The mixture
was stirred at ꢀ78 ꢁC for 2 h then allowed to warm slowly to room
temperature and stirred overnight. The mixture was filtered,
methanol added (20 ml) and the volatiles removed in vacuo to give
a sticky residue. The residue was dissolved in 5% aq. MeOH (100 ml)
and stirred with Dowex-X8 cation exchange resin in the Hþ-form
(5 g) for 24 h. The solution was filtered and taken to dryness before
repeating with fresh resin and solvent. After filtering again the
volatiles were removed in vacuo and the residue stirred with 1.5 M
HCl in MeOH (100 ml) for 24 h. The volatiles were removed, the
residue dissolved in H2O (10 ml) and made slightly basic by the
addition of aq. NaOH. The solution was taken to dryness in vacuo
and the residue extracted into THF (2 ꢂ 150 ml), dried over MgSO4,
filtered and the volatiles removed to give S-PNO as a white solid.
NMR (CD2Cl2, 125.8 MHz)
J ¼ 15.0 Hz, CO), 217.5 (d, J ¼ 15.0 Hz, CO), 67.2 (s, CH2OH), 58.2 (s,
R2CHNH2), 28.0 (s, CH2), 13.7 (d, J ¼ 18.8 Hz, CH2PH2) ppm. IR: CO
(CH2Cl2) 1942 s, 1887 vs, 1846 s; OH (KBr) 3572 m; NH2 (KBr)
3334 m, 3265 m;
PH (KBr) 2354 m, 2336 m cmꢀ1. Anal.: Calc. for
d
224.0 (d, J ¼ 12.6 Hz, CO), 217.8 (d,
y
y
y
y
C7H12NO4PCr: C, 32.69; H, 4.71; N, 5.45%. Found: C, 32.3; H, 4.9; N,
5.3%. MS: 258 ([M þ Hþ], 20%), 230 ([M þ Hþ e CO], 35%).
2.4. fac-[Mn(CO)3(k
3-S-PNO)]PF6, 2
To a stirred solution of fac-[Mn(CO)3(MeCN)3]PF6 (120 mg,
2.95 ꢂ 10ꢀ4 mol) in CH2Cl2 (10 ml) was added S-PNO (0.8 ml of a 5%
solution in THF, 1.1 mol equiv.) and the solution stirred overnight.
The solution was taken to dryness and the solid residue treated
with CH2Cl2 (15 ml), filtered and the filtrate allowed to stand at 4 ꢁC
overnight. The precipitated crystals of 2 were isolated by filtration.
A second crop was obtained upon leaving the filtrate to stand.
Yield ¼ 2.7 g (74%). 31P{1H} NMR (CDCl3, 121.7 MHz)
d
ꢀ135.3 ppm
Yield
d
¼
62 mg (52%). 31P{1H} NMR (CD3NO2, 121.7 MHz)
1H NMR (CDCl3, 500 MHz)
d
3.52 (1H, dd, J ¼ 10.5, 4.0 Hz, CH2OH),
ꢀ58.4 ppm 1H NMR (CD3NO2, 500 MHz)
d 4.65 (1H, br, NH2/OH),
3.23 (1H, dd, J ¼ 10.5, 7.7 Hz, CH2OH), 2.80 (1H, m, R2CHNH2), 2.65
4.60 (1H, d br, 1JHeP ¼ 365 Hz, PH), 4.45 (1H, dd, 1JHeP ¼ 345 Hz,
J ¼ 11.5 Hz, PH), 4.02 (1H, d, J ¼ 10.3 Hz, CH2OH), 3.65 (1H, d,
J ¼ 10.3 Hz, CH2OH), 3.61 (1H, s br, R2CHNH2), 3.30 (1H, br, NH2/OH),
2.42 (1H, m, CH2PH2), 2.10 (3H, m, CH2PH2, CH2, NH2/OH), 1.82 (1H,
(2H, dm, 1JHeP ¼ 198 Hz, PH2), 1.88 (3H, m br, NH2, OH), 1.56 (2H, m,
CH2), 1.43 (2H, m, CH2) ppm. 13C DEPT NMR (CDCl3, 125 MHz)
d 66.4
(s, CH2OH), 53.3 (s, CHNH2), 37.8 (s br, CH2), 10.3 (d, J ¼ 8.1 Hz,
CH2PH2) ppm.
m, CH2) ppm. 13C DEPT NMR (CD3NO2, 125.8 MHz)
d
210.3 (br, CO),
206.9 (br, CO), 200.0 (br, CO), 68.5 (s, CH2OH), 51.4 (s, R2CHNH2),
32.6 (s, CH2), 12.2 (d, J ¼ 20.0 Hz, CH2PH2) ppm. IR (KBr): CO 2039
NH2 3350 m, 3312 m; PH
2.2. 2(S)-amino-4-(2-propylphosphino)butan-1-ol, R,S-S-PiPrNO
y
vs, 1945 vs, 1915 sh;
yOH 3509 m;
y
y
The reaction was performed as detailed for S-PNO above except
using 6 g (0.015 mol) of tosylate and the appropriate amount of LiP
(SiMe3)2. The hemiaminal primary phosphine was dissolved in
1.6 M HCl in MeOH (100 ml) and the solution refluxed for 18 h. The
volatiles were removed in vacuo, and the residue dissolved in THF
(200 ml) to which was added LiAlH4 (1 g) portionwise with stirring.
The mixture was stirred overnight and then hydrolysed by the
dropwise addition of O2-free water (1 ml) then degassed 12% NaOH
solution (1 ml) and finally O2-free water (3 ml). The mixture was
filtered, the THF solution dried over MgSO4, filtered once more and
the volatiles removed in vacuo to give a colourless oil which was
distilled under dynamic vacuum (bp ¼ 90-5ꢁ, 0.05 mm Hg).
2380 w, 2351 w cmꢀ1. Anal.: Calc. for C7H12NP2O4F6Mn: C, 20.75; H,
2.99; N, 3.46%. Found: C, 20.2; H, 2.9; N, 3.3%. MS: 301
([Mþ] þ MeCN, 60%), 260 ([Mþ], 15%).
2.5. fac-[Re(CO)3(k
3-S-PNO)]BF4, 3
To a stirred solution of Re(CO)5Cl (186 mg, 5.14 ꢂ 10ꢀ4 mol) in
MeCN (20 ml) was added AgBF4 and the solution stirred for 10 min
in the absence of light. Subsequent addition of S-PNO (0.68 ml of
a 10% solution in THF, 1.1 mol equiv.) caused an immediate dark-
ening of the solution with precipitation of a black solid. The mixture
was filtered and the very pale yellow solution taken to dryness. The
solid residue was triturated with MeOH (20 ml), filtered to remove
a small amount of Re(CO)5Cl and the filtrate taken to dryness to give
3 as a white solid. Yield ¼ 62 mg (52%). 31P{1H} NMR (CD3NO2,
Yield ¼ 1.2 g (49%). 31P{1H} NMR (C7D8, 121.7 MHz)
d
ꢀ29.3,
ꢀ29.4 ppm 1H NMR (C6D6, 400 MHz)
3.26 (1H, dd, J ¼ 10.4, 4.0 Hz,
d
CH2OH), 2.96 (1H, dd, J ¼ 10.4, 7.5 Hz, CH2OH), 2.90 (1H, dm,
1JHeP ¼ 193 Hz, PH), 2.41 (1H, m, CHNH2), 1.63 (1H, m, CHMe2), 1.48
(3H, s br, NH2, OH), 1.4e1.0 (4H, m, 2 ꢂ CH2), 0.96 (1.5H, d, J ¼ 7.0 Hz,
121.7 MHz)
d
ꢀ88.8 ppm 1H NMR (CD3NO2, 500 MHz)
d 6.60 (2H, br,
NH2/OH), 4.75 (2H, d m, 1JHeP ¼ 369 Hz, PH2), 4.00 (1H, dd, J ¼ 10.3,
4.1 Hz, CH2OH), 3.75 (1H, dd, J ¼ 10.4, 7.9 Hz, CH2OH), 3.61 (1H, s br,
R2CHNH2), 3.23 (1H, br, NH2/OH), 2.25 (1H, m, CH2PH2), 2.18 (2H, m,
CH3), 0.93 (3H, d, J ¼ 7.0 Hz, CH3), 0.89 (1.5H, d, J ¼ 7.0 Hz) ppm. 13
C
DEPT NMR (C6D6, 125.8 MHz)
d
66.2 (s, CH2), 54.0 (d, J ¼ 8.1 Hz, CH),
53.9 (d, J ¼ 7.9 Hz, CH), 33.1 (d, J ¼ 10.0 Hz, CH2), 22.2 (d, J ¼ 8.9 Hz,
CH), 21.4 (d, J ¼ 3.2 Hz, CH3), 21.3 (d, J ¼ 3.2 Hz, CH3), 21.2 (d,
J ¼ 6.7 Hz, CH3), 21.1 (d, J ¼ 7.0 Hz, CH3),15.8 (d, J ¼ 2.5 Hz, CH2),15.7
(d, J ¼ 2.6 Hz, CH2) ppm.
CH2) ppm. 13C DEPT NMR (CD3NO2, 75.6 MHz)
d 185.7 (d,
J ¼ 10.4 Hz, CO), 185.6 (d, J ¼ 58.9 Hz, CO), 183.9 (d, J ¼ 6.9 Hz, CO),
66.6 (s, CH2OH), 56.2 (br, R2CHNH2), 30.6 (d, J ¼ 6.9 Hz, CH2),14.5 (d,
J ¼ 33.5 Hz, CH2PH2) ppm. IR (KBr):
y
CO 2000 vs, 1940 vs;
yOH
3559 m, 3463 m; yNH2 3259 m, 3199 m; y
PH 2379 w cmꢀ1. Anal.:
2.3. fac-Cr(CO)3(
k
3-S-PNO), 1
Calc. for C7H12NPO4BF4Re: C, 17.58; H, 2.53; N, 2.93%. Found: C, 17.9;
H, 2.7; N, 2.9%. MS: 452 ([Mþ] þ CH3NO2, 100%), 391 ([Mþ], 20%).
To stirred solution of fac-[Cr(CO)3(MeCN)3] (0.39 g,
a
1.50 ꢂ 10ꢀ3 mol) in CH2Cl2 (20 ml) was added S-PNO (1.9 ml of
a 10% solution in THF, 1.05 mol equiv.) and the solution stirred
overnight. The solution was filtered to remove some unwanted
green precipitate and all volatiles removed in vacuo to give a sticky
orange solid that crystallised upon continued application of
dynamic vacuum. Yield ¼ 0.37 g (88%). 31P{1H} NMR (CD2Cl2,
2.6. fac-Cr(CO)3(
k
3-P,P,P-S-P3NO), 4
To
a
stirred solution of fac-[Cr(CO)3(MeCN)3] (0.09 g,
3.47 ꢂ 10ꢀ4 mol) in CH2Cl2 (40 ml) was added S-PNO (0.84 ml of
a 5% solution in THF, 1.0 mol equiv.) and the solution stirred for
20 min whereupon a solution of trivinylphosphine (0.78 ml of a 10%

1654
P.G. Edwards et al. / Journal of Organometallic Chemistry 696 (2011) 1652e1658
ppm. 1H NMR (CD3NO2, 500 MHz)
d 6.9e6.1 (12H, m, ArH), 4.25 (1H,
d br, 1JHeP ¼ 359 Hz, PH2), 3.98 (1H, d br, 1JHeP ¼ 364 Hz, PH2), 3.93
(1H, d br, J ¼ 10.4 Hz, CH2OH), 3.72 (1H, br, CH2OH), 3.62 (1H, s
br, R2CHNH2), 3.21 (1H, br, NH2/OH), 2.30 (1H, m, CH2PH2), 2.08 (2H,
O
O
O
O
i
P(SiMe3)2
OTs
N
O
N
O
m, CH2) ppm. 13C DEPT NMR (CD3NO2, 75.6 MHz)
d 164.6 (d,
J ¼ 248.2 Hz, CF), 136.5 (d, J ¼ 10.4 Hz, CH), 135.8 (s, CH), 129.9
(d, J ¼ 54.3 Hz, C), 126.0 (d, J ¼ 9.2 Hz, CH), 117.7 (d, J ¼ 21.9 Hz, CH),
60.1 (s, CH2OH), 56.6 (d, J ¼ 10.4 Hz, R2CHNH2), 30.8 (d, J ¼ 7.5 Hz,
II
I
ii
CH2), 14.7 (dd, J ¼ 31.2, 10.1 Hz, CH2PH2) ppm. IR (KBr):
y
CO 2036
vs, 1955 vs, 1911 vs;
yPH 2360 w . Anal.: Calc. for
cmꢀ1
O
O
C25H24NP2O4BF7Re: C, 37.80; H, 3.05; N, 1.76%. Found: C, 37.2; H,
O
2.9; N, 1.7%. MS: 740 ([Mþ] e CO þ CH3NO2, 100%), 707 ([Mþ], 10%).
O
iii
PH2
PH2
N
O
N
H
3. Crystallography
HO
III
IV
Single crystal X-ray diffraction data were collected at 150 K on
a Nonius Kappa CCD diffractometer using graphite monochromated
iv
v
Mo-K
a
radiation (
l
¼ 0.71073 Å) and an Oxford Cryostream cooling
apparatus. The data was corrected for Lorentz and polarization
effects and for absorption using SORTAV [6]. Structure solution was
achieved by Patterson methods (Dirdiff-99 program system) [7].
Structure solution and full-matrix least-squares refinement on F2
were performed using SHELX-97 [8] with all non hydrogen atoms
assigned anisotropic displacement parameters. Hydrogen atoms
attached to carbon atoms were placed in idealised positions and
a riding model used during subsequent refinement.
PH2
P
H
H2N
HO
H2N
HO
O
S-PNO
V
vi
P
H2N
HO
H
4. Results and discussion
R,S-PiPrNO
4.1. Ligand syntheses
Scheme 1. i) LiP(SiMe3)2, THF, ꢀ78 ꢁC; ii) MeOH; iii) Dowex-X50 (Hþ); iv) 1.5 M HCl in
MeOH, RT; v) 1.5 M HCl in MeOH, reflux; vi) LiAlH4, THF.
The preparation of the ligand is highlighted in Scheme 1. The
starting point of the synthesis, namely the protected tosylate I was
prepared by the method of Burgess [2]. Subsequent reaction of I
with LiP(SiMe3)2 at low temperature gives the N,O-protected
species II which is desilylated quantitatively in MeOH to the
primary phosphine compound III. The dimethylmethyl hemiaminal
protecting group is selectively removed upon treatment of III with
cation exchange resin (Hþ - form) in methanol at room temperature
to give the N-Boc protected phosphino alcohol IV. Subsequent
treatment of IV with 1.5 M HCl in MeOH leads to removal of the Boc
group and isolation of the primary phosphine derivative S-PNO as
a low-melting solid.1 Efforts to remove both protecting groups
simultaneously by refluxing a solution of III in methanolic HCl led
only to the 2-propylphosphine oxide derivative V; this occurs even
when air has been vigorously excluded suggesting that the source
of the oxygen in the product comes from the methanol or from
traces of water in the methanolic HCl. Water is more than likely
present in the methanolic HCl hence the generation of acetone after
cleavage of the hemiaminal protecting group is expected. The
solution in THF, 2 mol equivs.) was added and the whole stirred
overnight. The solution was concentrated to one third volume and
stirred for a further 3 days at RT. The solution was taken to dryness
in vacuo and the solid residue dissolved in THF (25 ml) to which was
added 2 mol equivalents of KtOBu causing an immediate precipi-
tation. The mixture was stirred overnight, filtered and the volatiles
removed to leave a bright yellow solid which was washed with
water (1 ꢂ 5 ml) then dry diethyl ether and dried under vacuum.
Yield ¼ 0.57 g (34%). 31P{1H} NMR (CDCl3, 121.7 MHz)
d 114.2 (t,
2
2JPeP ¼ 17.9 Hz), 68.7 (d, JPeP ¼ 17.9 Hz) ppm. 1H NMR (CDCl3,
500 MHz)
d 6.3e5.4 (12H, m), 3.50 (3H, br), 2.90 (1H, br), 2.1e1.1
(12H, br) ppm. 13C DEPT NMR (CD2Cl2, 125.8 MHz)
d 234.0 (br, CO),
229.9 (br, CO), 135.2 (m, CH), 134.8 (d, J ¼ 20.4 Hz, CH), 134.5 (d,
J ¼ 20.5 Hz, CH), 128.0 (s, CH2), 127.2 (s, CH2), 125.4 (s, CH2), 125.1 (s,
CH2), 65.3 (br, CH2OH), 53.0 (br, R2CHNH2), 28.2 (br, CH2), 26.4 (br,
CH2), 24.9 (br, CH2), 10.5 (br, CH2PH2) ppm. IR (KBr): yCO 1940 s,
1860 vs br cmꢀ1. MS: 482 ([M þ Hþ], 25%), 454 ([M þ Hþ e CO],
acetone could react with the primary phosphine to give an
a-
55%).
hydroxyphosphine species which rearranges by a 1,2 migration of
the hydroxyl function to give the observed product [9]. The resul-
tant P(V) species is readily reduced back to the potential ligand 2
(S)-amino-4-(R,S-2-propyl-phosphino)butan-1-ol, R,S-S-PiPrNO, by
LiAlH4 reduction and the secondary phosphine obtained by high-
vacuum distillation.
Compound S-PNO is very soluble in water and alcohols,
moderately soluble in CH2Cl2 and CHCl3 and poorly soluble in
diethyl ether and acetonitrile. The 31P{1H} NMR spectrum of S-PNO
consists of a singlet at dP ¼ ꢀ135.3 ppm and the 1H NMR spectrum
2.7. fac-[Re(CO)3(k
2-P,N-S-PNO)(PArF3)]BF4, 5
To a stirred solution of 3 (80 mg, 1.67 ꢂ 10ꢀ4 mol) in CH3NO2
(5 ml) was added one mol equivalent of tris(2-fluorophenyl)phos-
phine (53 mg, 1.67 ꢂ 10ꢀ4 mol) and the solution heated at 80 ꢁC for
30 min. The solution was concentrated to small volume and diethyl
ether slowly added through vapour diffusion. The initial precipitate
was filtered off and discarded. The filtrate was removed in vacuo to
give a pale yellow solid which was triturated in toluene, isolated by
filtration and dried in vacuo. Yield ¼ 70 mg (53%). 31P{1H} NMR
1
On occasion some contamination (<10%) with the oxide of R,S-S-PiPrNO was
(CD3NO2, 121.7 MHz)
d
ꢀ10.4 (d, J ¼ 26.8 Hz), ꢀ72.3 (d, J ¼ 26.8 Hz)
observed.

P.G. Edwards et al. / Journal of Organometallic Chemistry 696 (2011) 1652e1658
1655
shows the expected pattern of peaks with the diastereotopic
hydrogens to the alcohol group being observed as two doublets of
ring especially when bound as a tridentate ligand [10] and it may be
that there is some strain within the ligand framework when bound
through all three donors as indicated in the molecular structure of
the manganese complex (see below). The 1H NMR spectrum of 1 is
broadened, but all the peaks are identifiable and assignable
through a combination of 1D and 2D techniques. The outstanding
feature of the 1H NMR spectrum is the presence of two separate
resonances for the two hydrogens directly bonded to the phos-
phorus atom, one of which is observed as a slightly broadened
doublet at dP ¼ 4.33 ppm (1JHeP ¼ 330 Hz) and the other as
a doublet of multiplets at dP ¼ 4.31 ppm (1JHeP ¼ 310 Hz). Both these
signals are shifted downfield of their position in the 1H NMR
spectrum of the free ligand. The remaining resonances show
smaller coordination shifts as noted in the experimental section.
The 13C{1H} NMR spectrum of 1 does not suffer from broadening
and all the pertinent CeP coupling constants are readily obtained.
There are the expected three signals at low field assignable to the
a
doublets at 3.52 and 3.23 ppm respectively, the PH2 hydrogens as
a doublet of multiplets at 2.65 ppm with a large 1JHeP of 198 Hz, the
amine and alcohol protons as a broad composite peak at 1.88 ppm
and the remaining methylene hydrogens as multiplets at 1.56 and
1.43 ppm. The 13C{1H} NMR spectrum has the anticipated four
signals, two of which show clear coupling with the 31P nucleus and
one of which is broadened. The relative simplicity of the NMR
spectra of S-PNO contrast with those for R,S-S-PiPrNO which clearly
show the presence of two diastereomers namely P(R)-PiPrNO and
P(S)-PiPrNO. This is evident from the 31P{1H} NMR spectrum which
shows two singlets at dP ¼ ꢀ29.3 and ꢀ29.4 ppm and the 1H NMR
spectrum which is complex in the region of the 2-propyl methyls.
The 13C{1H} NMR spectrum of R,S-S-PiPrNO shows a number of
duplicated peaks particularly for those carbons in closer proximity
to the phosphorus centre (see experimental) confirming the dia-
stereomeric nature of the product.
2
three distinct carbonyls at 224.0, 217.9 and 217.5 ppm with JCeP
coupling constants of 12.6, 15.0 and 15.0 Hz respectively. The signal
showing the greatest downfield shift and smallest absolute value of
2JCeP is assigned to the CO group trans to the P-donor in accord with
previous observations on Cr(CO)5(PR3) systems [11]. Of the four
aliphatic signals in the 13C{1H} NMR spectrum of 1 only the
methylene carbon (dC ¼ 13.7 ppm) directly bonded to the P-atom
4.2. Complexes of S-PNO
As stated above, S-PNO has the potential to bind through one,
two or three donors at a single-metal centre and it is anticipated
that all three modes will be accessible through appropriate choice
of metal ion. Further metal-dependent isomerism is possible as the
ligand has the option of binding solely though the phosphine,
amine or alcohol donor in the monodentate mode and via P/N, P/O
or N/O combinations when coordinated through two donors. We
were interested in incorporating the phosphorus centre into a P-
containing macrocycle and thus chose metal precursors that favour
P-coordination and also have accessible sites cis to the phosphine
ligand; it was envisaged that the ideal systems would be those that
1
shows any coupling to the phosphorus: JCeP ¼ 18.8 Hz. The solu-
tion (CH2Cl2) infrared spectrum of complex 1 shows three bands in
the region of CO absorption at 1942s, 1887vs and 1846 s cmꢀ1. The
lower energy bands are less well resolved in the solid-state IR
spectrum recorded as a KBr disk where peaks are seen at 1877vs,
1835vs and 1821 cmꢀ1. The observation of three bands reflects the
low symmetry of the complex. Other observable bands in the solid-
state spectrum are assigned to PeH stretching (2354 and
2336 cmꢀ1), the OeH stretch (3572 cmꢀ1) and NeH stretching
(3334 and 3265 cmꢀ1).
possessed tridentate
substituted) M-NH2R and M-OHR bonds. To this end the complexes
fac-Cr(CO)3(
3-S-PNO), fac-[Mn(CO)3( 3-S-PNO)]BF4 and fac-[Re
(CO)3(
k
3-S-PNO with relatively weak (easily
The cationic complexes fac-[Mn(CO)3(
[Re(CO)3(
3-S-PNO)]BF4, 3, are made in an analogous manner to the
chromium species by displacement of three acetonitrile ligands from
the fac-[M(CO)3(MeCN)3]X precursors. Fac-[Mn(CO)3(
3-S-PNO)]PF6,
k
3-S-PNO)]PF6, 2, and fac-
k
k
k
3-S-PNO)]BF4 were sought through displacement of labile
k
acetonitrile ligands from the familiar fac-[M(CO)3(MeCN)3]nþ
starting materials.
k
2, can be crystallised from CH2Cl2 at low temperature to give yellow
crystals suitable for analysis by single-crystal X-ray methods. The
molecular structure of the cation is shown in Fig. 1. As expected, the
complex adopts a distorted octahedral geometry with the carbonyl
groups and the S-PNO ligand occupying opposing faces of the octa-
hedron. The tridentate ligand consists of two fused rings, a six-
membered C3PMnO cycle and a five-membered C2NMnO ring. The
former adopts a chair conformation while the latter is an asymmetric
The synthesis of the complexes is shown in Scheme 2. In all
cases, complete substitution of the poorly bound MeCN ligands
occurred giving the desired complexes. Fac-Cr(CO)3(k
3-S-PNO), 1,
could be crystallised as orange prisms from CH2Cl2 at low
temperature. The 31P{1H} NMR spectrum of 1 consists of a singlet at
dP ¼ ꢀ56.3 ppm which splits into a triplet of multiplets in the
proton-coupled spectrum with an absolute 1JPeH coupling constant
of 320 Hz. The coordination shift (
D
31P ¼ dcoord P
ꢀ
duncoord P) is
envelope with the
(12) Å is slightly shorter than that of 2.3419(6) Å observed in the
related mixed N,O,P-donorcomplex (
2-P,N-(2-NMe2-3-PiPr2-indene)
Mn(CO)3(OTf) [12]. The Mn-O {2.089(3) Å} and Mn-N {2.091(3) Å}
bond lengths are close to those observed in (
2-P,N-(2-NMe2-3-PiPr2-
l conformation. The Mn-P bond length of 2.3121
smaller than that observed in related fac-Cr(CO)3(PRH2)3 systems
1
but the magnitude of the JPeH coupling is comparable [1f]. The
relatively small D
31P is unexpected as phosphine donors which are
k
part of a chelate ring(s) tend to show enhanced coordination shifts
compared to monodentate analogues. However triphosphorus
ligands with the same carbon skeleton as S-PNO also show similar
reduced coordination shifts for the phosphorus in the 6-membered
k
indene)Mn(CO)3(OTf) where MneN is 2.209(2) Å and Mn-O 2.094(2)
Å [12]. The largest angular distortion about the metal occurs for the
NeMneO angle which is compressed to 78.92(11)ꢁ, the two
remaining chelate rings have angles of 85.64(9) (PeMneN) and 83.68
(8)ꢁ (PeMneO) respectively. All of these angles are smaller than in
related systems such as [Mn(dppe)(CO)3(H2O)]þ [13] Mn(dppp)
(CO)3X [14] and Re(dppb)(CO)3(H) [15] where bite angles of 84.24(4)ꢁ,
90 ꢃ 2ꢁ and 92.99ꢁ are observed for the 5-, 6- and 7-membered
chelates respectively. Tripodal phosphines do show some angular
contraction compared to those forming single chelates. For example
fac-[Mn(CO)3{MeC(CH2PPh2)3}]þ has PeMneP angles ranging from
85.89(6) to 89.14(6) [16]. The PeMneO angle in 2 is particularly
constrained for a seven-membered chelate which may explain in part
the unusual chemical shift of the compound (and indeed the other
n+
H
H
CO
M
[M(CO)3(MeCN)3]n+
PH2
P
CO
CO
H2N
HO
NH2
OH
S-PNO
1, M = Cr, n = 0
2, M = Mn, n = 1
3, M = Re, n = 1
Scheme 2. Synthesis of the metal complexes.

1656
P.G. Edwards et al. / Journal of Organometallic Chemistry 696 (2011) 1652e1658
The colourless complex fac-[Re(CO)3(k
3-PNO)]BF4, 3, shares
many of the features already discussed for the analogous manga-
nese compound, although the coordination shift in the 31P{1H}
NMR spectrum is less with a signal being observed 46.5 ppm
downfield of the uncoordinated ligand at ꢀ88.8 ppm. The 1H NMR
spectrum of 3 is also better resolved with all the resonances bar
that for the NH2 and OH hydrogens showing appropriate coupling.
The CO resonances in the 13C{1H} NMR spectrum of 3 are seen as
three separate doublets at 185.7 (2JCeP
¼
10.4 Hz), 185.6
(2JCeP ¼ 58.9 Hz) and 183.9 (2JCeP ¼ 6.9 Hz) ppm. The signal with
the large coupling constant is assigned to the carbonyl trans to the
P-donor in accordance with the similar system {2-(CH3CO)-C4H3N}
Re(PPh3)(CO)3 where a value of 55.5 Hz is observed for the trans
2JCeP coupling [20]. The IR spectrum of 3 recorded as a KBr disk
shows two strong absorbances for the CO stretches at 2000 and
1940 cmꢀ1 which compare with values of 2048, 1967 and
1933 cmꢀ1 for fac-[Re(PPh3)(CO)3(pyC(H) ¼ O)][OTf] [20], 2024,
1931 and 1875 cmꢀ1 for fac-{ 3-P,N,O-Ph2PC6H4C(H)N(C6H4O}Re
k
(CO)3 [21] and 2022, 1923, 1892 cmꢀ1 for {2-(CH3CO)-C4H3N}Re
(PPh3)(CO)3 [20].
Fig. 1. Ortep view of the molecular structure of 2. Thermal ellipsoids are drawn at 50%
probability, hydrogens are omitted for clarity. Selected bond lengths (Å) and angles(ꢁ)
for 2: Mn1-P1 2.3121(12), Mn1-N1 2.091(3), Mn1-O1 2.089(3), Mn1-C5 1.843(4), Mn1-
C6 1.815(4), Mn1-C5 1.789(4), N1-Mn1-P1 85.64(9), O1-Mn1-P1 83.68(8), N1-Mn1-O1
78.92(11).
4.3. Further reactions of 1, 2 and 3
The coordinated primary phosphine group in the metal
complexes of S-PNO was susceptible to chlorination when solutions
of the complexes in CHCl3 were left to stand. This observation,
along with more typical reactivity such as the ready methylation of
the phosphine with MeI, suggested that the coordinated phosphine
is reactive and that the amino group when unbound may be
assisting the generation of a metal-bound phosphido group. This is
the type of reactivity we wished to exploit for the formation of
mixed-donor macrocycles containing two P-donors and one other
(N or O) donor. As a first step, we were interested in examining
whether complex 1, 2 or 3 would undergo selective replacement of
one donor of S-PNO by another phosphine ligand that possessed
substituents capable of undergoing further reaction to enable
access to macrocyclic systems. The two approaches we hoped to
exploit are summarised in Scheme 3. The alcohol is believed to be
the most weakly bound of the donors for two reasons; firstly the
nature of the metal ions is such that they prefer softer donors and
secondly, if the phosphine is most strongly bound the resulting 6-
membered P,N chelate should be more stable than the 7-membered
complexes containing k
3-S-PNO) observed in the 31P NMR spectrum.
It is notable that the MneCO bond length to the carbonyl group trans
to the phosphine donor is somewhat longer at 1.843(4) Å than those
trans to the amine and alcohol donors which have values of 1.815(4)
and 1.789(4) Å respectively. However, this pattern resembles closely
that seen in (k
2-P,N-(2-NMe2-3-PiPr2-indene)Mn(CO)3(OTf) where
the appropriate MneC bond lengths are 1.859(2), 1.806(2) and 1.779
(3) Å [12].
The IR spectrum of 2 recorded as a KBr disk shows a strong
y(CO)
stretch at 2040 cmꢀ1 and a very strong carbonyl stretch at
1945 cmꢀ1 with
a low-energy shoulder at approximately
1915 cmꢀ1. These compare to values of 2052, 1956 and 1919 cmꢀ1 in
fac-{Mn(CH3CN)(CO)3[H(pzAnMe)]}(PF6) where H(pzAnMe) is 2-
(pyrazolyl)-4-toluidine [17], 2031s, 1961s, and 1915s cmꢀ1 in fac-
[(CO)3Mn{(PhF)2PC6H4P(PhF)2}(CH3CN)]PF6 [18], and those of 2036,
1957 and 1916 cmꢀ1 in
(k
2-P,N-(2-NMe2-3-PiPr2-indene)Mn
(CO)3(OTf) [12], but differ somewhat from the values of 2049, 1980
and 1944 cmꢀ1 reported for fac-[Mn(PPh3)(CO)3(pyC(H) ¼ O)][OTf]
[19]. In addition to the carbonyl stretches, the IR spectrum of 2
shows three peaks at 3509, 3350 and 3312 cmꢀ1 assignable to the
OeH and NeH stretches and two weak peaks at 2380 and
2351 cmꢀ1 for the PeH stretches. The 31P{1H) NMR spectrum of 2
consists of a singlet at ꢀ58.4 ppm in addition to the septet for the
PFꢀ6 anion at ꢀ143.6 ppm. The resonance for the coordinated
phosphine splits into a triplet of multiplets (1JPeH ¼ 375 Hz) in the
31P NMR spectrum. The 1H NMR spectrum recorded in CD3NO2
shows the anticipated number of signals but all are broadened to
a varying degree. The two chemically inequivalent PH hydrogens
P,O chelate. Initial studies focussed on the neutral fac-Cr(CO)3(k
3-S-
PNO), 1, system. Attempted introduction of the poorly donating tris
(2-fluorophenyl)phosphine ligand was unsuccessful as only
complex 1 and uncoordinated PArF3 were observed by 31P{1H} NMR
under the reaction conditions. Thus, the nature of the incoming
phosphine was changed to the more strongly donating divinyl-
benzylphosphine. 31P{1H} NMR analysis of a solution prepared by
adding one mol equivalent of P(CH2Ph)(C2H3)2 to a solution of 1 in
CH2Cl2 showed, in addition to the singlets for free P(CH2Ph)(C2H3)2
and 1, a triplet at e 29.4 ppm (2JPeP ¼ 38.7 Hz) and three doublets at
37.0 (2JPeP ¼ 35.7 Hz), 34.4 (2JPeP ¼ 38.7 Hz) and e 34.3
(2JPeP ¼ 35.7 Hz) ppm respectively. The two furthest upfield peaks
1
are seen as two distinct doublets with large JHeP coupling
1
constants of 365 and 345 Hz; both are w1.7 ppm downfield of their
gave large triplets in the 31P NMR spectrum with JPeH coupling
position in the 1H NMR spectrum of S-PNO and the upfield reso-
constants of around 310 Hz confirming their assignment as primary
phosphines whereas the downfield peaks were tertiary phos-
phines. The 2JPeP coupling constants suggest that the peaks at 37.0
and ꢀ34.3 ppm belong to one species while the remaining peaks
belong to a second species. The presence of a triplet for the primary
phosphine for one of the complexes in the 31P{1H} NMR spectrum
of the solution indicates coupling to two divinylbenzylphosphine
2
nance shows a JHeH coupling of small magnitude (11.5 Hz). The
resonances for the methylene hydrogens
a to the alcohol function
also show downfield coordination shifts and are observed at 4.02
and 3.65 ppm, respectively. The 13C{1H} NMR spectrum of 2 is also
broadened in the region of the CO resonances where three peaks
with no resolved 31P coupling are seen at 210.3, 206.9 and
200.0 ppm. The remaining resonances in the 13C{1H} NMR spec-
trum are sharp singlets with the exception of the RCH2PH2 carbon
ligands and hence this species must be fac-Cr(CO)3(
(CH2Ph)(C2H3)2}2 while the second complex is most likely fac-Cr
(CO)3(
2-P,N-S-PNO){P(CH2Ph)(C2H3)2}. Thus it would appear that
k
1-P-S-PNO){P
1
which is a doublet at 12.2 ppm with an absolute JCeP of 20.0 Hz.
k

P.G. Edwards et al. / Journal of Organometallic Chemistry 696 (2011) 1652e1658
1657
n+
n+
n+
CO
Cr
CO
Cr
CO
M
CO
CO
CO
P
CO
N
CO
CO
H
H
PR(C2H3)2
base
H2P
NH2
H2P
NH2
H
M = Cr,
n = 0
P
R
O
H
P
R
O
O
H
PArF
3
M = Re,
n = 1
n+
n+
CO
Re
CO
Re
CO
CO
CO
P
CO
N
H
H
H2P
F
NH2
F
base
O H
H
P
O
P
F
F
Scheme 3. Proposed synthesis of chiral P2N macrocycles.
selective introduction of one P(CH2Ph)(C2H3)2 ligand to 1 is not
achieved under these conditions. When the reaction was per-
formed in THF a similar outcome resulted. Addition of KOtBu to the
THF solution gave a 31P{1H} NMR spectrum that consisted of four
a second mol equivalent of trivinylphosphine led to the predomi-
nance of the species giving the doublet at 32.1 ppm and the triplet
at ꢀ31.2 ppm which is assigned to the complex fac-Cr(CO)3(
k
1-P-S-
PNO){P(C2H3)3}2. After removal of the solvent, the residue was
dissolved in THF, 2 mol equivalents of KOtBu added thereto, and the
reaction monitored by 31P{1H} NMR spectroscopy. The peaks
peaks: two triplets at 113.1 (2JPeP
¼
20.8 Hz) and 112.3
(2JPeP ¼ 17.9 Hz) ppm, a multiplet at 73.9 ppm and a doublet at 72.7
(2JPeP ¼ 17.9 Hz) ppm all of which are tertiary phosphines as
deduced upon inspection of the 31P NMR spectrum. The chemical
shift of these resonances would suggest that the low-field peaks at
assigned to fac-Cr(CO)3(k
1-P-PNO){P(C2H3)3}2 were lost after
addition of the base and replaced by new peaks at 115.1 (t,
2
2JPeP ¼ 17.9 Hz) and 70.7 (d, JPeP ¼ 17.9 Hz) ppm both of which
dP > 100 ppm represent coordinated P-donors that are constituents
represent tertiary phosphines. The downfield shifts and decreased
2
of two chelate rings whereas the higher field signals at w73 ppm
are tertiary phosphines that are part of a single chelate [22]. The
presence of more than one resonance around 113 ppm reflects an
isomeric mixture of two closely similar species most likely resulting
from isomerism at the terminal phosphine(s) as shown in Fig. 2.
The isomeric complication present in the reaction of 1 with
divinylbenzylphosphine prompted an investigation of the same
chemistry with trivinylphosphine where no such complexity is
possible. Addition of one mol equivalent of P(C2H3)3 to a solution of
1 in CH2Cl2 gave a mixture which, upon inspection by 31P{1H} NMR
spectroscopy, showed a pattern closely similar to that observed
magnitude of JPeP is indicative of the formation of new chelate
rings with the peak at 115.1 ppm being assigned to the central
phosphine of a linear tridentate triphosphine and the doublet to
the two equivalent terminal phosphines of the coordinated P3
ligand. This suggests that the new complex is fac-Cr(CO)3(k
3-P,P,P-
S-P3NO), 4 as shown in Fig. 3. The complex was isolated as a yellow
solid in modest yield. The 1H NMR spectrum of the isolated
complex was complex in the region of the alkenic protons as all 12
of the hydrogens are chemically inequivalent and was broad in the
region of the aliphatic protons. The aliphatic signals in the 13C{1H}
NMR spectrum were also broad but two new peaks for the CH2
groups of the chelate backbones were evident at dC ¼ 26.2 and
25.0 ppm. In addition, two broad carbonyl peaks were seen at 234.1
and 231.1 ppm, along with a multiplet at 135.2 for two of the
with P(CH2Ph)(C2H3)2, i.e. three doublets at dP
¼
44.7
(2JPeP ¼ 38.7 Hz), 32.1 (2JPeP ¼ 35.7 Hz) and ꢀ27.9 (2JPeP ¼ 38.7 Hz)
ppm and a triplet at ꢀ31.2 ppm (2JPeP ¼ 35.7 Hz) [in addition to
peaks for 1 and some other minor signals]. It is clear from the
distribution of species here and in the case of the same reaction
with P(CH2Ph)(C2H3)2 that selective substitution of one of the
donors of S-PNO by one tertiary phosphine ligand is not occurring
and that a competitive binding of a second P(CH2Ph)(C2H3)2 or P
alkenyl carbons
134.7 and 134.5 ppm for the other two
a
to the phosphorus atom and two doublets at
a
-carbons with 1JCeP values
of 21.3 and 23.5 Hz respectively. Thus although hydro-
phosphination is observed in these systems the desired P2N mac-
rocycle highlighted in the upper part of Scheme 3 was not obtained.
Although identified in solution, the desired complex of type Cr
(C2H3)3 is frustrating attempts to get the desired fac-Cr(CO)3(k2
P,N-S-PNO){P(R)(C2H3)2} where R ¼ CH2Ph or C2H3. Addition of
-
(CO)3(
k
2-P,N-S-PNO){P(R)(C2H3)2} was not isolable (or indeed
bz
bz
CO
Cr
P
bz
CO
Cr
P
CO
P
P
CO
CO
P
P
CO
CO
P
P
Cr
P
H2N
CO
bz
H2N
H2N
CO
bz
OH
bz
OH
OH
Fig. 2. Possible isomers from the base-induced cyclisation of fac-Cr(CO)3(k
1-P-S-PNO){P(CH2Ph)(C2H3)2}2.

1658
P.G. Edwards et al. / Journal of Organometallic Chemistry 696 (2011) 1652e1658
which shows, in addition to the expected 1JCeP coupling of 31.2 Hz,
a 3JCeP coupling to the PArF phosphorus of 10.1 Hz.
CO
Cr
P
3
P
P
CO
CO
Efforts to form new chelate rings by nucleophilic substitution at
one or two of the 2-fluoro carbons of the coordinated PArF by
3
H2N
metal-bound phosphido/amido nucleophiles were unsuccessful.
Addition of base (Et3N or KOtBu) to a suspension of 5 in THF or in
nitromethane generally led to
a darkening of the solution
OH
(complete dissolution of 5 was not observed in THF) which, upon
examination by 31P{1H} NMR, showed loss of the PArF3 ligand from
the metal centre. Other peaks were present in the 31P{1H} NMR
spectrum of the reaction performed in CH3NO2, some of which
were assignable to various S-NOP complexes of Re while others
were not. Clearly if deprotonation had occurred the resultant
Fig. 3. Likely structure of the product from the intramolecular cyclisation of fac-Cr
(CO)3(
1-P-S-PNO){P(C2H3)3}2.
k
complex(es) underwent loss of PArF before any template cyclisa-
useful for transformation into a P2N macrocycle) due to the non-
selectivity of the tertiary phosphine substitution. The extra bulk of
tris-(2-fluorophenyl)phosphine should prevent coordination of
3
tion could result and the desired macrocyclic complex shown in the
lower part of Scheme 3 was not obtained.
a second PArF ligand if a complex of type [M(CO)3( 2-P,N-S-PNO)
k
3
(PArF3)]nþ could be accessed. As noted above this proved to be
difficult for the chromium system but we have shown previously
that the ligand can be coordinated to both Mn(I) and Re(I) tri-
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yCO stretching
frequencies in the IR spectra of 3 and 5 shows a shift to high
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s
-donor is
replaced by a
p-acceptor. However, the highest energy absorbance
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2
two doublets at dP ¼ ꢀ10.4 and ꢀ72.3 ppm with a JPeP coupling
constant of 26.8 Hz. The high field peak is further split into a large
triplet in the 31P NMR spectrum with 1JPeH of 360 Hz. The position
of this peak is downfield that of the k
3-S-PNO as noted in the Mn(I)
systems above. The 19F NMR spectrum had two singlets at
ꢀ95.4 ppm and ꢀ150.3 for the coordinated PArF and the BF4ꢀ
3
counterion respectively. The 1H NMR spectrum of 5 is largely
uninformative with the expected mass of peaks in the aromatic
region and some broadening in the aliphatic, but the 13C{1H} NMR
spectrum has some distinguishing features notably the large
doublet for the C-F carbon at 164.6 ppm and the presence of
a doublet of doublets for the CH2PH2 carbon of S-PNO at 14.7 ppm