Iron Complexes Containing the Tripodal Tetraphosphine Ligand P(CH2CH2PMe2)3

Article abstract of DOI:10.1021/ic970030b

The preparation and characterization of iron(II) complexes containing the tripodal tetraphosphine ligand tris [2(dimethylphosphino)ethyl]phosphine, P(CH₂CH₂PMe₂)₃ (PP₃, 1), are reported. The complex FeCl₂(PP₃) (2) was formed by the reaction of PP₃ with anhydrous iron(II) chloride. The complexes FeHCl(PP₃) (3) and FeH₂(PP₃) (4) were formed by the reaction of 2 with lithium aluminum hydride. Likewise, the complexes FeMeCl(PP₃) (5) and FeMe₂(PP₃) (6) were formed by the reaction of 2 with methyllithium or dimethylmagnesium. Reaction of 2 with CO afforded a mixture of isomeric carbonyl chloride complexes [Fe(CO)Cl(PP₂)]⁺ (7 and 8). Reaction of 2 with PPh₃ afforded [Fe(PPh₃)Cl(PP₃)]⁺ (9). The air-sensitive complexes 2-9 were characterized by multinuclear NMR spectroscopy, and 9 was characterized by X-ray crystallography. Crystals of 9 (BPh₄ salt), C₅₄H₆₅BClFeP₅, M 971.09, are monoclinic, space group P2₁/c, a = 13.246(3) ?, b = 30.314(2) ?, c= 14.338(2) ?,β= 100.92(2)°, Z = 4; R = 0.058.

Full text of DOI:10.1021/ic970030b

2884
Inorg. Chem. 1997, 36, 2884-2892
Iron Complexes Containing the Tripodal Tetraphosphine Ligand P(CH2CH2PMe2)3
Leslie D. Field,* Barbara A. Messerle,* Ronald J. Smernik, Trevor W. Hambley, and
Peter Turner
School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
ReceiVed January 10, 1997X
The preparation and characterization of iron(II) complexes containing the tripodal tetraphosphine ligand tris[2-
(dimethylphosphino)ethyl]phosphine, P(CH2CH2PMe2)3 (PP3, 1), are reported. The complex FeCl2(PP3) (2) was
formed by the reaction of PP3 with anhydrous iron(II) chloride. The complexes FeHCl(PP3) (3) and FeH2(PP3)
(4) were formed by the reaction of 2 with lithium aluminum hydride. Likewise, the complexes FeMeCl(PP3) (5)
and FeMe2(PP3) (6) were formed by the reaction of 2 with methyllithium or dimethylmagnesium. Reaction of 2
with CO afforded a mixture of isomeric carbonyl chloride complexes [Fe(CO)Cl(PP3)]+ (7 and 8). Reaction of
2 with PPh3 afforded [Fe(PPh3)Cl(PP3)]+ (9). The air-sensitive complexes 2-9 were characterized by multinuclear
NMR spectroscopy, and 9 was characterized by X-ray crystallography. Crystals of 9 (BPh4 salt), C54H65BClFeP5,
M 971.09, are monoclinic, space group P21/c, a ) 13.246(3) Å, b ) 30.314(2) Å, c ) 14.338(2) Å, â ) 100.92(2)°,
Z ) 4; R ) 0.058.
Introduction
Although the related “hybrid” of ligands 10 and 11, P(CH2-
CH2PMe2)3 (PP3, 1), has been known since 1975,7 its reported
coordination chemistry has been limited to that of a single
complex, [NiCl(PP3)]+,8 presumably due to the difficult and low-
yielding synthesis of 1. We have recently reported9 a new,
efficient and high-yielding synthesis of 1, which has facilitated
the current investigation of iron complexes of 1.
In this paper we report the synthesis of the iron(II) complexes
FeXY(PP3) (X ) Cl, Y ) Cl (2); X ) Cl, Y ) H (3); X ) H,
Y ) H (4); X ) Cl, Y ) Me (5); X ) Me, Y ) Me (6); X )
Cl, Y ) CO (7); X ) CO, Y ) Cl (8); and X ) PPh3, Y ) Cl
(9)). Complexes 2-9 have been completely characterized by
multinuclear NMR spectroscopy, and 9 was structurally char-
acterized by X-ray crystallography.
Metal complexes containing polydentate phosphine ligands
are an important class of organometallic compounds, and many
metal phosphine complexes facilitate C-H activation and act
as catalysts for organic transformations.1 Phosphines are strong
donor ligands, and the polydentate architecture provides stability
and restricts the arrangement of donors in the ligand sphere. In
octahedral complexes, tripodal tetradentate phosphine ligands
enforce a cis geometry of the two remaining ligands. One of
the most thoroughly studied tripodal tetradentate phosphine
ligands is P(CH2CH2PPh2)3 (10), and metal complexes of 10
act as catalysts for a variety of organic transformations.2
Ruthenium and iron complexes of the related ligand P(CH2-
CH2CH2PMe2)3 (11) undergo C-H insertion reactions with
alkene and arene substrates.3 In the molecular hydrogen
complexes [M(P4)H(H2)]+ (M ) Fe, Ru; P4 ) P(CH2CH2PPh2)3
(10),4 P(CH2CH2CH2PMe2)3 (11),5 P(CH2CH2PCy2)3 (12)6), the
interaction between the hydride and dihydrogen ligands con-
strained in cis coordination sites has led to speculation of the
existence of complexes of the ligand “H3”.
Experimental Section
All synthetic manipulations involving air-sensitive materials were
carried out under an inert atmosphere of argon in an argon-filled drybox
or under a nitrogen atmosphere using standard Schlenk techniques.
Lithium aluminum hydride was obtained from Aldrich and used as a
THF solution (approximately 1 M). Methyllithium was used as a
solution in hexane (approximately 2.4 M) as supplied by Aldrich.
Dimethylmagnesium was prepared as a THF solution (approximately
1 M) using the procedure of Ludher et al.10 THF, benzene, toluene,
pentane, and hexane were dried over sodium before distillation from
sodium and benzophenone under nitrogen. Ethanol and methanol were
distilled from magnesium under nitrogen.
X Abstract published in AdVance ACS Abstracts, May 1, 1997.
(1) See, for example: Mayer, H. A.; Kaska, W. C. Chem. ReV. 1994, 94,
1239 and references therein.
(2) (a) Bianchini, C. Pure Appl. Chem. 1991, 63, 829. (b) Bianchini, C.;
Meli, A.; Peruzzini, M.; Vizza, F.; Zanobini, F. Coord. Chem. ReV.
1992, 120, 193.
(3) (a) Antberg, M.; Dahlenburg, L. Angew. Chem., Int. Ed. Engl. 1986,
25, 260. (b) Antberg, M.; Dahlenburg, L.; Frosin, K.-M.; Ho¨ck, N.
Chem. Ber. 1988, 121, 859. (c) Bampos, N.; Field, L. D.; Messerle,
B. A. Organometallics 1993, 12, 2529.
(4) (a) Bianchini, C.; Perez, P. J.; Peruzzini, M.; Zanobini, F.; Vacca, A.
Inorg. Chem. 1991, 30, 279. (b) Bianchini, C.; Peruzzini, M.; Polo,
A.; Vacca, A.; Zanobini, F. Gazz. Chim. Ital. 1991, 121, 543. (c)
Bianchini, C.; Peruzzini, M.; Zanobini, F. J. Organomet. Chem. 1988,
354, C19.
(5) Bampos, N.; Field, L. D. Inorg. Chem. 1990, 29, 587.
(6) Jia, G.; Drouin, S. D.; Jessop, P. G.; Lough, A. J.; Morris, R. H.
Organometallics 1993, 12, 906.
(7) King, R. B.; Cloyd, J. C., Jr. J. Am. Chem. Soc. 1975, 97, 53.
(8) King, R. B.; Cloyd, J. C., Jr. Inorg. Chem. 1975, 14, 1550.
(9) Bampos, N.; Field, L. D.; Messerle, B. A.; Smernik, R. J. Inorg. Chem.
1993, 32, 4084.
(10) Ludher, K.; Nehls, D.; Madeja, K. J. Prakt. Chem. 1983, 325, 1027.
S0020-1669(97)00030-X CCC: $14.00 © 1997 American Chemical Society

Fe-P(CH2CH2PMe2)3 Complexes
Inorganic Chemistry, Vol. 36, No. 13, 1997 2885
-
Table 1. Crystallographic Data for [Fe(PPh3)Cl(PP3)]+ 9 (BPh4
Salt)
coefficient for the complex with Mo KR radiation is 4.9 cm-1, and an
absorption correction was not applied to the data. The data were
corrected for Lorentz and polarization effects.
A. Crystal Data
All calculations were performed using the teXsan11 crystallographic
software package. The structure was solved by direct methods12 and
expanded using Fourier techniques.13 Neutral atom scattering factors
were taken from Cromer and Waber.14 Anomalous dispersion effects
were included in the structure factor calculation,15 and the values for
∆f ′ and ∆f ′′ were those of Creagh and McAuley.16 The values for
the mass attenuation coefficients are those of Creagh and Hubbel.17
Non-hydrogen atoms were refined anisotropically, and the hydrogen
atoms were included in the full matrix least squares refinement at
calculated positions with group temperature factors. An ORTEP18
representation of the structure is provided in Figure 8.
empirical formula
formula wt
cryst color, habit
cryst dimens
cryst syst
lattice type
no. of rflns used for unit cell
determination (2θ range)
lattice params
C54H65BClFeP5
971.09
red, prism
0.50 × 0.38 × 0.38 mm
monoclinic
primitive
24 (19.12-24.24°)
a ) 13.246(3) Å
b ) 30.314(2) Å
c ) 14.338(2) Å
â ) 100.92(2)°
V ) 5653(1) Å3
P21/c (No. 14)
4
FeCl2(PP3) (2). Solutions of anhydrous iron(II) chloride (50 mg,
0.39 mmol) in THF (10 mL) and 1 (110 mg, 0.37 mmol) in THF (10
mL) were simultaneously added to THF (50 mL), with rapid stirring.
The resulting deep red solution deposited a small quantity of an orange-
brown precipitate during the reaction, and this was removed by filtration.
Removal of the THF in Vacuo left a red solid, which was extracted
into benzene (10 mL). The addition of hexane (50 mL) resulted in the
precipitation of the product, which was collected by filtration. 2 was
obtained as a red-purple crystalline solid (116 mg, 74%; mp 145-151
°C dec).
space group
Z value
Dcalc
F000
µ(Mo KR)
1.141 g/cm3
2048.00
4.87 cm-1
B. Intensity Measurements
temperature
2θmax
21.0 °C
44.9°
-14 to 14, -1 to 32, -1 to 15
hkl range
no. of rflns measd
total
31P{1H} NMR spectrum (162 MHz, THF-d8, 233 K): δ 179.3 (dt,
2
2
8884
1P, PC, JP(C)-P(T) ) 24.8 Hz, JP(C)-P(U) ) 32.4 Hz); 53.2 (dd, 2P, PT,
2JP(T)-P(U) ) 47.7 Hz); 83.1 (dt, 1P, PU).
unique
7557 (Rint ) 0.080)
1H{31P} NMR spectrum (400 MHz, THF-d8, 233 K): δ 1.81, 1.97,
2.20, 2.54 (4 × m, 4 × 2H, -PCCHHCHHPT-); 1.51, 1.74 (2 × m, 2
× 2H, -PCCH2CH2PU-); 1.50, 1.72 (2 × s, 2 × 6H, 2 × PT(CH3));
1.31 (s, 6H, PU(CH3)2).
C. Structure Solution and Refinement
function minimized
least squares wts
no. of observations (I > 2.00σ(I))
no. of variables
∑w(|Fo| - |Fc|)2
1/σ2(Fo)
5097
560
13C{1H} NMR spectrum (101 MHz, THF, 233 K): δ 14.1 (t, PTCH3,
rfln:param ratio
residuals: R; Rw
goodness-of-fit indicator
max peak in final diff map
min peak in final diff map
9.10
1
1JP(T)-C ) 6.7 Hz); 19.0 (t, PTCH3, JP(T)-C ) 11.0 Hz); 18.6 (d, PU-
0.058; 0.057
3.01
(CH3)2, 1JP(U)-C ) 18.6 Hz); 24.5 (m, -PCCH2CH2PT-); 31.2 (m, -PC-
CH2CH2PT-); 27.7 (dd, -PCCH2CH2PU-, 1JP(C)-C ) 26.2 Hz, 2JP(U)-C
) 11.4 Hz); 31.5 (m, -PCCH2CH2PU-).
0.77 e/Å3
-0.37 e/Å3
MS (+CI, CH4) m/z >200: 424 (Fe35Cl2(PP3) + 1, 3), 392 (Fe37-
Cl(PP3) + 1, 5), 391 (Fe37Cl(PP3), 21), 390 (Fe35Cl(PP3) + 1, 15), 389
(Fe35Cl(PP3), 65), 354 (Fe(PP3), 14), 331 ((PP3)O2, 27), 327 (32), 315
((PP3)O, 25), 300 ((PP3) + 2, 15), 299 ((PP3) + 1, 100), 283 ((PP3) -
CH3, 24), 209 (P(CH2CH2PMe2)2, 11).
1H, 13C, and 31P NMR spectra were recorded on Bruker AMX400
or AMX600 spectrometers at the temperatures quoted. 1H and 13C
chemical shifts were internally referenced to residual solvent resonances.
31P spectra were referenced to external neat trimethyl phosphite at
140.85 ppm. Infrared spectra were recorded on a Perkin-Elmer 1600
series FTIR; all frequencies are quoted in cm-1. EI (electron ionization)
mass spectra (both low and high resolution) were recorded on a Kratos
MS9/MS50 double-focusing mass spectrometer with an accelerating
voltage of 8000 V, a source temperature of 150-350 °C, and an electron
energy of 70 eV. Perfluorokerosene was used as a calibrant for high-
resolution spectra. Chemical ionization (CI) mass spectra were recorded
on a Finnigan MAT TSQ-46 mass spectrometer (San Jose, CA) fitted
with a desorption probe, with a source temperature of 140 °C and an
electron energy of 100 eV. The ionization gas, methane (>99.999%)
or ammonia (>99.999%), is as quoted. Elemental analyses were carried
out at the Joint Elemental Analysis Facility, The University of Sydney.
Melting points were recorded on a Gallenkamp heating stage and are
uncorrected.
FeHCl(PP3) (3). A THF solution of lithium aluminum hydride was
added dropwise to a solution of 2 (116 mg, 0.27 mmol) in THF (30
mL), resulting in a color change from deep red to bright yellow. The
reaction was rapid at room temperature, and the color change allowed
the end point to be determined accurately. The reaction mixture was
filtered, the solvent removed in Vacuo, and the residue extracted into
benzene (20 mL). The volume of the solution was reduced in Vacuo
to approximately 3 mL, and the addition of hexane (10 mL) resulted
in the precipitation of the product, which was collected by filtration. 3
was obtained as bright yellow needles (83 mg, 78%; mp 176.5-177.5
°C).
(11) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corporation: The Woodlands, TX, 1985, 1992.
(12) SIR92: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr., in
preparation.
(13) DIRDIF94: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman,
W. P.; de Gelder, R.; Israel, R..; Smits, J. M. M. The DIRDIF-94
program system. Technical Report; Crystallography Laboratory:
University of Nijmegen, The Netherlands, 1994.
(14) Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystal-
lography; The Kynoch Press: Birmingham, England, 1974; Vol. IV,
Table 2.2 A.
(15) Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(16) Creagh, D. C.; McAuley, W. J. In International Tables for Crystal-
lography; Wilson, A. J. C., Ed.; Kluwer Academic Publishers: Boston,
1992; Vol. C, Table 4.2.6.8, pp 219-222.
(17) Creagh, D. C.; Hubbell, J. H. In International Tables for Crystal-
lography; Wilson, A. J. C., Ed.; Kluwer Academic Publishers: Boston,
1992; Vol. C, Table 4.2.4.3, pp 200-206.
(18) Johnson C. K. ORTEP, A Thermal Ellipsoid Plotting Program; Report
ORNL-5138; Oak Ridge National Laboratories: Oak Ridge, TN, 1976.
Crystal Structure Determination. The crystallographic data for
9 (BPh4 salt) are summarized in Table 1. The complex decayed rapidly
on exposure to the atmosphere. Accordingly, a red prism of C54H65-
BClFeP5 having approximate dimensions of 0.50 × 0.38 × 0.38 mm
was coated with a heavy hydrocarbon oil and inserted in a thin glass
capillary. The capillary was then mounted on an Enraf-Nonius CAD4
diffractometer employing graphite-monochromated Mo KR radiation.
Cell constants obtained from a least-squares refinement using the setting
angles of 24 reflections in the range 19.12° < 2θ < 24.24° corresponded
to a primitive monoclinic cell, and systematic absences of h0l, l * 2n,
and 0k0, k * 2n, uniquely determined the space group to be P21/c
(No. 14). Diffraction data were collected at a temperature of 21 ( 1
°C using ω/θ scans to a maximum 2θ value of 44.9°. The intensities
of three representative reflections measured every 2 h decreased by
10.1% during the course of the data collection, and a linear correction
factor was accordingly applied to the data. The linear absorption

2886 Inorganic Chemistry, Vol. 36, No. 13, 1997
Field et al.
31P{1H} NMR spectrum (162 MHz, toluene-d8, 300 K): δ 184.8
FeMe2(PP3) (6). A solution of 5 in THF was prepared as above.
A hexane solution of methyllithium was added, resulting in a color
change from deep orange to pale yellow. The reaction was rapid at
room temperature, and the color change allowed the end point to be
determined accurately. The reaction mixture was filtered, the solvent
removed in Vacuo, and the residue extracted into benzene (20 mL).
The solvent was removed in Vacuo, affording 6 (52 mg, 82% from 5),
as a waxy, air-sensitive, yellow solid.
2
2
(dt, 1P, PC, JP(C)-P(T) ) 30.5 Hz, JP(C)-P(U) ) 22.9 Hz); 61.3 (dd, 2P,
2
PT, JP(T)-P(U) ) 22.9 Hz); 60.0 (dt, 1P, PU).
1H{31P} NMR spectrum (600 MHz, toluene-d8, 303 K): δ -11.63
1
(s, H, FeH); 1.30, 1.70 (2 × m, 2 × 2H, -PCCH2CHHPT-); 1.21,
1.34 (2 × m, 2 × 2H, -PCCHHCH2PT-); 1.07 (m, 2H, -PCCH2-
CH2PU-); 1.22 (m, 2H, -PCCH2CH2PU-); 1.40, 1.88 (2 × s, 2 × 6H,
2 × PT(CH3)); 1.45 (s, 6H, PU(CH3)2).
31P{1H} NMR spectrum (162 MHz, toluene-d8, 220 K): δ 179.8 (t,
13C{1H} NMR spectrum (101 MHz, benzene-d6) δ 25.1 (dt, PT(CH3),
2
2
3
1JP(T)-C ) 16.3 Hz, JP(U)-C ) 6.8 Hz); 18.7 (m, PT(CH3)); 19.1 (dt,
1P, PC, JP(C)-P(T) ) 14.4 Hz, JP(C)-P(U) ) 0 Hz); 69.5 (dd, 2P, PT,
2JP(T)-P(U) ) 27.4 Hz); 67.5 (t, 1P, PU).
1
3
PU(CH3)2, JP(U)-C ) 10.5 Hz, JP(T)-C ) 3.4 Hz); 27.1 (ddt, -PT-
CH2CH2PC-, 1JP(C)-C ) 22.6 Hz, 2JP(T)-C ) 8.9 Hz, 3JP(U)-C ) 1.6 Hz);
34.4 (dt, -PTCH2CH2PC-, JP(T)-C ) 15.3 Hz, JP(C)-C ) 15.3 Hz);
27.7 (dd, -PUCH2CH2PC-, JP(C)-C ) 18.4 Hz, JP(U)-C ) 18.4 Hz);
1H{31P} NMR spectrum (600 MHz, toluene-d8, 303 K): δ -0.88,
0.12 (2 × s, 2 × 3H, 2 × FeCH3); 1.38, 2.13 (2 × m, 2 × 2H, -PC-
CH2CHHPT-); 1.59, 1.61 (2 × m, 2 × 2H, -PCCHHCH2PT-); 1.26,
1.26 (m, 2 × 2H, -PCCH2CH2PU-); 1.14, 1.41 (2 × s, 2 × 6H, 2 ×
PT(CH3)); 1.23 (s, 6H, PU(CH3)2).
1
2
1
2
1
2
33.4 (dd, -PUCH2CH2PC-, JP(U)-C ) 25.8 Hz, JP(C)-C ) 15.3 Hz).
MS (EI) m/z: 392 (FeH37Cl(PP3), 16), 391 (Fe37Cl(PP3), 21), 390
(FeH35Cl(PP3), 45), 389 (Fe35Cl(PP3), 44), 388 (15), 354 (Fe(PP3), 49),
338 (Fe(PP3) - CH4, 59), 300 ((PP3) + 2, 59), 283 ((PP3) - CH3, 30),
272 (26), 238 (42), 211 (34), 209 (P(CH2CH2PMe2)2, 66), 61 (100).
HRMS: Calcd for C12H3135ClFeP4 390.0414; found 390.0428.
Anal. Calcd for C12H31ClFeP4: C, 36.90; H, 8.00. Found: C, 36.5;
H, 8.0.
13C{1H,31P} NMR spectrum (101 MHz, benzene-d6, 300 K): δ 1.8,
2.5 (2 × s, 2 × FeCH3); 12.5, 21.7 (2 × s, 2 × PT(CH3)); 22.9 (s,
PU(CH3)2); 24.8 (s, -PTCH2CH2PC-); 35.7 (s, -PTCH2CH2PC-); 29.2
(s, -PUCH2CH2PC-); 36.0 (s, -PUCH2CH2PC-).
MS (+CI, CH4) m/z >135: 385 (M + 1, 13), 384 (M, 95), 369
(FeMe(PP3), 98), 354 (Fe(PP3), 11), 353 (Fe(PP3) - 1, 19), 299 ((PP3)
+ 1, 21), 181 (15), 153 (13), 135 (100).
FeH2(PP3) (4). A THF solution of 3 was prepared as above. A
THF solution of lithium aluminum hydride was added dropwise,
resulting in a distinct color change from bright to very pale yellow.
The reaction mixture was filtered and the solvent removed in Vacuo,
leaving a pale yellow gum, which was extracted into benzene (15 mL).
The benzene extract was filtered and the solvent removed in Vacuo.
The residue was extracted into hexane (10 mL) and the resultant mixture
filtered. Removal of the hexane in Vacuo afforded 4 (68 mg, 90%
from 3) as a highly air-sensitive, waxy, pale yellow solid.
[Fe(CO)Cl(PP3)]+ (7 and 8). An atmosphere of carbon monoxide
was introduced over a solution of 2 (30 mg, 71 µmol) in ethanol (5
mL), resulting in a rapid color change from deep red to bright yellow.
A solution of sodium tetraphenylborate (40 mg, 120 µmol) in ethanol
(2 mL) was added immediately, resulting in the formation of a yellow
precipitate, which was isolated by filtration. The crude product was
washed with ethanol (10 mL) and dried in Vacuo to give 7 (BPh4 salt)
as a pale yellow powder (35 mg, 67%; mp 285-290 °C dec).
Heating of an ethanol solution of 7 (chloride salt) resulted in the
formation of a second product, assigned as the isomeric carbonyl
chloride complex 8. The reaction could not be forced to completion,
apparently reaching equilibrium (ratio 7:8 ) 1:5) on heating at 60 °C
for 10 days. A solution of sodium tetraphenylborate (10 mg, 29 µmol)
in ethanol (2 mL) was added, resulting in the formation of a yellow
precipitate, which was isolated by filtration, washed with ethanol (10
mL), and dried in Vacuo to afford a mixture of the carbonyl chloride
complexes 7 and 8 (BPh4 salts).
31P{1H} NMR spectrum (162 MHz, toluene-d8, 300 K): δ 187.2 (q,
2
1P, PC, JP(C)-P(E) ) 20.9 Hz); 68.7 (d, 3P, PE).
31P{1H} NMR spectrum (162 MHz, toluene-d8, 198 K): δ 185.6
(br, 1P, PC); 67.7 (br, 2P, PT); 70.5 (br, 1P, PU).
1H{31P} NMR spectrum (400 MHz, benzene-d6, 300 K): δ -11.03
(s, 2H, FeH); 1.62 (m, 6H, -PCCH2CH2PE-), 1.55 (m, 6H, -PC-
CH2CH2PE-); 1.54 (s, 18H, PECH3).
1H{31P} NMR spectrum (high-field region only, 400 MHz, toluene-
1
d8, 198 K): δ -14.20, -7.70 (2 × br, 2 × H, 2 × FeH).
A. [Fe(CO)Cl(PP3)]+ (7) (Kinetic Product, CO Trans to PU). 31P-
13C{1H} NMR spectrum (101 MHz, benzene-d6, 300 K) δ 26.6 (m,
PECH3); 38.8 (m, -PECH2CH2PC-); 27.9 (m, -PECH2CH2PC-).
MS (EI) m/z: 356 (M, 1), 355 (FeH(PP3), 5), 354 (Fe(PP3), 29),
283 ((PP3) - CH3, 14), 266 (11), 210 (HP(CH2CH2PMe2)2, 12), 209
(P(CH2CH2PMe2)2, 33), 31 (100).
{1H} NMR spectrum (BPh4 salt, 162 MHz, acetone-d6, 300 K): δ 163.9
2
2
(dt, 1P, PC, JP(C)-P(T) ) 19.8 Hz, JP(C)-P(U) ) 44.3 Hz); 44.4 (dd, 2P,
2
PT, JP(T)-P(U) ) 54.9 Hz); 58.6 (dt, 1P, PU).
1H{31P} NMR spectrum (BPh4 salt, 600 MHz, acetone-d6, 288 K):
δ 2.25, 2.74 (2 × m, 2 × 2H, -PCCH2CHHPT-); 2.14, 2.71 (2 × m,
2 × 2H, -PCCHHCH2PT-); 2.40 (m, 2H, -PCCH2CH2PU-); 2.28 (m,
2H, -PCCH2CH2PU-); 1.85, 2.01 (2 × s, 2 × 6H, 2 × PT(CH3)); 1.83
(s, 6H, PU(CH3)2); 7.46 (br, 8H, BPhortho); 7.08 (t, 8H, 3JH-H ) 7.1 Hz,
BPhmeta); 6.93 (t, 4H, BPhpara).
FeMeCl(PP3) (5). A hexane solution of methyllithium was added
dropwise to a solution of 2 (100 mg, 0.24 mmol) in THF (30 mL),
resulting in a color change from deep red to orange. The reaction was
rapid at room temperature and the color change allowed the end point
to be determined accurately. The reaction mixture was filtered, the
solvent removed in Vacuo, and the residue extracted into benzene (20
mL). The solvent was removed in Vacuo, affording 5 (67 mg, 70%)
as an orange-yellow powder.
13C{1H} NMR spectrum (BPh4 salt, carbonyl region of 13CO-labeled
complex, 101 MHz, acetone-d6, 300 K): δ 212.9 (ddt, FeCO, 2JP(C)-C
2
2
) 15.9 Hz, JP(T)-C ) 45.1 Hz, JP(U)-C ) 31.8 Hz).
13C{1H} NMR spectrum (chloride salt, 101 MHz, MeOH, 300 K):
δ 14.5 (t, PTCH3, 1JP(T)-C ) 10.0 Hz); 17.3 (dt, PTCH3, 1JP(T)-C ) 15.3
Hz, 3JP(U)-C ) 3.8 Hz); 15.3 (dt, PU(CH3)2, 1JP(U)-C ) 24.3 Hz, 3JP(T)-C
31P{1H} NMR spectrum (162 MHz, benzene-d6, 300 K): δ 188.4
2
2
(dt, 1P, PC, JP(C)-P(T) ) 30.0 Hz, JP(C)-P(U) ) 11.4 Hz); 64.1 (dd, 2P,
2
PT, JP(T)-P(U) ) 25.4 Hz); 59.8 (dt, 1P, PU).
1
2
1H{31P} NMR spectrum (600 MHz, benzene-d6, 303 K): δ -0.10
(s, 3H, FeCH3); 1.24, 2.08 (2 × m, 2 × 2H, -PCCH2CHHPT-); 1.37,
1.37 (2 × m, 2 × 2H, -PCCHHCH2PT-); 0.99 (m, 2H, -PCCH2-
CH2PU-); 1.17 (m, 2H, -PCCH2CH2PU-); 1.38, 1.80 (2 × s, 2 × 6H,
2 × PT(CH3)); 1.56 (s, 6H, PU(CH3)2).
) 3.8 Hz); 26.0 (dt, -PCCH2CH2PT-, JP(C)-C ) 30.0 Hz, JP(T)-C
)
6.7 Hz); 30.5 (dt, -PCCH2CH2PT-, 1JP(T)-C ) 15.7 Hz, 2JP(C)-C ) 8.1
1
2
Hz); 24.8 (dd, -PCCH2CH2PU-, JP(C)-C ) 25.7 Hz, JP(U)-C ) 13.8
Hz); 31.5 (dd, -PCCH2CH2PU-, JP(U)-C ) 31.0 Hz, JP(C)-C ) 9.5
Hz).
1
2
MS (+CI, NH3) m/z >200: 437 (FeCO37Cl(PP3) + NH4, 4), 435
(FeCO35Cl(PP3) + NH4, 11), 391 (Fe37Cl(PP3), 18), 390 (Fe35Cl(PP3)
+ 1, 33), 389 (Fe35Cl(PP3), 78), 384 (FeCO(PP3) + 2, 12), 383 (FeCO-
(PP3) + 1, 100), 377 (11), 376 (53), 370 (12), 354 (Fe(PP3), 12), 299
((PP3) + 1, 38), 279 (25), 260 (28), 259 (13).
13C{1H,31P} NMR spectrum (101 MHz, benzene-d6, 300 K) δ 2.0
(s, FeCH3); 13.1, 20.4 (2 × s, 2 × PT(CH3)); 22.0 (s, PU(CH3)); 32.1
(s, -PTCH2CH2PC-); 25.5 (s, -PTCH2CH2PC-); 33.2 (s, -PUCH2-
CH2PC-); 28.7 (s, -PUCH2CH2PC-).
MS (+CI, CH4) m/z >300: 407 (Fe37ClMe(PP3) + 1, 4), 405 (Fe35-
ClMe(PP3) + 1, 11), 391 (Fe37Cl(PP3), 11), 390 (12), 389 (Fe35Cl-
(PP3), 44), 363 ((PP3)O4 + 1, 15), 359 (17), 355 (Fe(PP3) + 1, 16),
347 ((PP3)O3 + 1, 30), 343 (17), 332(13), 331 ((PP3)O2 + 1, 100),
329 (16), 327 (41), 316 (15), 315 ((PP3)O + 1, 100), 313 (12), 311
(10).
IR νmax (BPh4 salt, Nujol): 1952 cm-1
.
Anal. Calcd for C37H50BClFeOP4: C, 60.31; H, 6.84. Found: C,
60.2; H, 7.4.
B. [Fe(CO)Cl(PP3)]+ (8) (Thermodynamic Product, CO Trans
to PC). 31P{1H} NMR spectrum (BPh4 salt, 162 MHz, acetone-d6, 300

Fe-P(CH2CH2PMe2)3 Complexes
Inorganic Chemistry, Vol. 36, No. 13, 1997 2887
Scheme 1
Figure 1. 31P{1H} NMR spectrum (162 MHz, 233 K, THF-d8) of 2.
2
2
K): δ 168.9 (dt, 1P, PC, JP(C)-P(T) ) 30.5 Hz, JP(C)-P(U) ) 38.1 Hz);
2
60.5 (dd, 2P, PT, JP(T)-P(U) ) 40.1 Hz); 77.9 (dt, 1P, PU).
Scheme 2
1H{31P} NMR spectrum (BPh4 salt, 600 MHz, acetone-d6, 283 K):
δ 2.35, 2.81 (2 × m, 2 × 2H, -PCCH2CHHPT-); 2.74, 2.74 (2 × m,
2 × 2H, -PCCHHCH2PT-); 2.55 (m, 2H, -PCCH2CH2PU-); 2.16 (m,
2H, -PCCH2CH2PU-); 1.85, 1.93 (2 × s, 2 × 6H, 2 × PT(CH3)); 1.58
(s, 6H, PU(CH3)2); 7.46 (br, 8H, BPhortho); 7.08 (t, 8H, 3JH-H ) 7.1 Hz,
BPhmeta); 6.93 (t, 4H, BPhpara).
13C{1H} NMR spectrum (BPh4 salt, carbonyl region of 13CO-labeled
complex, 101 MHz, acetone-d6, 300 K): δ 214.5 (ddt, FeCO, 2JP(C)-C
2
2
) 43.9 Hz, JP(T)-C ) 17.2 Hz, JP(U)-C ) 21.0 Hz).
13C{1H} NMR spectrum (chloride salt, 101 MHz, MeOH, 300 K):
δ 15.8 (dt, PTCH3, 1JP(T)-C ) 17.6 Hz, 3JP(U)-C ) 1.9 Hz); 19.0 (t, PTCH3,
1JP(T)-C ) 11.4 Hz); 19.1 (dt, PU(CH3)2, 1JP(U)-C ) 28.1 Hz, 3JP(T)-C
)
2.4 Hz); 24.0 (dt, -PCCH2CH2PT-, 1JP(C)-C ) 26.7 Hz, 2JP(T)-C ) 8.1
temperatures (Figure 1). Similar behavior has been noted for
the octahedral iron dichloride complexes containing the hindered
bis(phosphine) ligands DEPE and DPrPE, and the spectral
broadness was attributed to temperature dependent paramagnet-
ism.19 At 233 K, the 31P{1H} NMR spectrum of 2 contains
three sharp multiplet resonances at δ 179.3 (dt), 83.1 (dt), and
53.2 (dd) ppm in the ratio 1:1:2, respectively (Figure 1). The
central phosphorus of the tripodal ligand (PC) is easily identified
as the resonance at δ 179.3 ppm due to its extreme low-field
shift, which is due to PC being at the bridgehead of three fused
five-membered chelate rings.20 An apparent plane of symmetry
through the iron and two chloro ligands renders two of the three
terminal phosphorus atoms equivalent (PT), and these are
assigned to the resonance at δ 53.2 ppm. The remaining
resonance at δ 83.1 ppm was assigned to the remaining unique
terminal phosphorus (PU). The 1H NMR spectrum of 2 contains
three methyl and six methylene resonances and was assigned
by analysis of the 2D COSY spectrum.
1
2
Hz); 32.3 (dt, -PCCH2CH2PT-, JP(T)-C ) 15.7 Hz, JP(C)-C ) 11.4
1
2
Hz); 24.9 (dd, -PCCH2CH2PU-, JP(C)-C ) 27.2 Hz, JP(U)-C ) 12.9
1
2
Hz); 32.9 (dd, -PCCH2CH2PU-, JP(U)-C ) 30.5 Hz, JP(C)-C ) 12.4
Hz).
IR νmax (BPh4 salt, Nujol): 1913 cm-1
.
[FeCl(PPh3)(PP3)]+ (9). Triphenylphosphine (50 mg, 191 µmol)
was added to a solution of 2 (50 mg, 118 µmol) in methanol (10 mL).
The resultant red solution was indistinguishable in color from the
starting complex. A solution of sodium tetraphenylborate (50 mg, 146
µmol) in methanol (2 mL) was added, resulting in the formation of a
red precipitate, which was isolated by filtration. The crude product
was washed with methanol (10 mL) and dried in Vacuo to afford 9
(BPh4 salt) as a red crystalline solid (87 mg, 76%; mp 181-182 °C
dec).
31P{1H} NMR spectrum (BPh4 salt, 162 MHz, acetone-d6, 300 K):
2
2
δ 167.6 (ddt, 1P, PC, JP(C)-P(T) ) 28.6 Hz, JP(C)-P(U) ) 32.4 Hz,
2JP(C)-PPh3 ) 104.9 Hz); 39.6 (ddd, 2P, PT, JP(T)-P(U) ) 36.2 Hz,
2
2JP(T)-PPh3 ) 36.2 Hz); 56.9 (ddt, 1P, PU, JP(U)-PPh3 ) 34.3 Hz); 41.8
2
(ddt, 1P, PPh3).
1H{31P} NMR spectrum (BPh4 salt, 600 MHz, acetone-d6, 283 K):
δ 2.09, 2.35 (2 × m, 2 × 2H, -PCCH2CHHPT-); 2.41, 2.43 (2 × m,
2 × 2H, -PCCHHCH2PT-); 2.14 (m, 2H, -PCCH2CH2PU-); 2.73 (m,
2H, -PCCH2CH2PU-); 0.61, 1.57 (2 × s, 2 × 6H, 2 × PT(CH3)); 1.14
(s, 6H, PU(CH3)2); 7.72 (m, 2H, PPhortho); 7.68 (m, 3H, PPhmeta, PPhpara);
7.46 (br, 8H, BPhortho); 7.08 (t, 8H, 3JH-H ) 7.1 Hz, BPhmeta); 6.93 (t,
4H, BPhpara).
Crystals of 2 were obtained by slow cooling of a saturated
benzene/hexane solution to approximately 0 °C. The solid was
extremely air- and moisture-sensitive, and X-ray diffraction data
were collected at low temperature (-55 °C). The data could
not be fully refined, and although only a poor quality structure
was obtained, it nonetheless supports the proposed structure of
2.21
13C{1H} NMR spectrum (chloride salt, 101 MHz, EtOH, 300 K): δ
14.9 (t, PTCH3, 1JP(T)-C ) 13.7 Hz); 19.5 (t, PTCH3, 1JP(T)-C ) 8.2 Hz);
1
20.0 (d, PU(CH3)2, JP(U)-C ) 19.2 Hz); 24.1 (dt, -PCCH2CH2PT-,
Other tripodal tetraphosphine ligands with ethylene (-CH2-
CH2-) linkages between the central and terminal phosphorus
atoms react with iron(II) chloride to give trigonal bipyramidal
monochloride complexes (Scheme 2) rather than octahedral
complexes analogous to 2. Reaction of the cyclohexyl-
substituted tripodal ligand P(CH2CH2PCy2)3 (12) or the phenyl-
substituted tripodal ligand P(CH2CH2PPh2)3 (10) with iron(II)
chloride in dichloromethane affords the cationic complexes
[FeP(CH2CH2PR2)3Cl]+, 136 or 14,22 respectively (Scheme 2).
1JP(C)-C ) 28.4 Hz, JP(T)-C ) 6.2 Hz); 35.2 (m, -PCCH2CH2PT-);
2
1
2
24.5 (dd, -PCCH2CH2PU-, JP(C)-C ) 24.3 Hz, JP(U)-C ) 10.2 Hz);
37.6 (dm, -PCCH2CH2PU-, 1JP(U)-C ) 33.6 Hz); 137.5 (d, PPhipso, 1JP-C
) 28.4 Hz); 129.3 (d, PPh, JP-C ) 8.2 Hz); 135.5 (d, PPh, JP-C ) 9.7
Hz); 131.4 (d, PPhpara, JP-C ) 1.7 Hz).
Crystal data for 9 (BPh4 salt) are summarized in Table 1. The atom
4
numbering is given in Figure 8.
Results and Discussion
Preparation of 2. The iron(II) dichloride complex 2 was
synthesized by the simultaneous, dropwise addition of a THF
solution of 1 and a THF solution of anhydrous iron(II) chloride
to rapidly stirring THF (Scheme 1). This procedure resulted
in the instantaneous formation of a deep red solution with some
orange-brown precipitate, which was removed by filtration.
At 300 K, only broad resonances were detected in the 31P
NMR spectrum of 2. Sharper resonances were detected at lower
(19) Baker, M. V.; Field, L. D.; Hambley, T. W. Inorg. Chem. 1988, 27,
2872.
(20) (a) Garrou, P. E. Inorg. Chem. 1975, 14, 1435. (b) Garrou, P. E. Chem.
ReV. 1981, 81, 229.
(21) Details of crystal structure determination for 2: C12H30Cl2FeP4, M )
425.02, red, space group P21/a, a ) 15.312(6) Å, b ) 16.398(8) Å,
c ) 15.469(5) Å, â ) 93.12(4)°, V ) 3878(2) Å3, Dcalc ) 1.456 g
cm-3, Z ) 8, F(000) ) 1776.00, R ) 11.5%.

2888 Inorganic Chemistry, Vol. 36, No. 13, 1997
Field et al.
Figure 2. 31P{1H} NMR spectrum (162 MHz, 300 K, MeOH) of 17.
Figure 3. Schematic representation showing significant NOESY
interactions between the hydride ligand and the PP3 ligand in 3. The
thickness of the arrows indicates the relative intensity of the NOESY
cross peak.
Both 13 and 14 are paramagnetic, and 13 was reported to
give no 31P NMR spectrum.6 In contrast, at low temperatures
(233 K), the iron dichloride complex [FeP(CH2CH2PMe2)3Cl2]
(2) gives rise to sharp 31P NMR spectra in all solvents, including
methanol. However, the addition of a methanol solution of
sodium tetraphenylborate to a methanol solution of 2 resulted
in the immediate precipitation of a red solid, which has not been
further characterized.23
Scheme 3
Byproducts in the Preparation of 2. Simultaneous addition
of iron(II) chloride and the ligand P(CH2CH2PMe2)3, where
neither species was in excess of the other, gave the highest yields
of 2. When either species is in excess, a larger quantity of the
orange-brown precipitate is formed, and this has been attributed
to the multi-iron complexes 17 containing bridging PP3 ligands.
Decomposition is more rapid at higher temperatures, occurring
within seconds at 150 °C in the solid state. The phosphorus
atoms of the bridging PP3 ligand in 17 are bound strongly to
the metal and cannot easily be displaced in subsequent reactions.
Preparation of 3 and 4. The iron chloro hydride complex
3 was synthesized by the careful reduction of the dichloride
complex 2 with lithium aluminum hydride in THF, and more
forcing reduction conditions afforded the dihydride 4 (Scheme
3). A THF solution of LiAlH4 was added dropwise to a THF
solution of 2, resulting in a color change from red to bright
yellow. The reaction was rapid at room temperature, and the
color change allowed the end point to be determined accurately.
Complex 3 is soluble in most organic solvents, although it reacts
with methanol and haloalkanes.24 The complex is least soluble
in alkanes and can be recrystallized from alkane solvent (pentane
or hexane) to afford bright yellow, needle-like crystals.
The multinuclear complex 17 is not a single compound, and its
structure is poorly defined. The material is soluble in alcohol
solvents (methanol and ethanol) and was precipitated as the
tetraphenylborate salt by the addition of sodium tetraphenylbo-
rate. In 17, the bridging phosphorus could be either the central
or a terminal phosphorus of PP3, and there are a number of
possible isomeric tetranuclear complexes (or complexes of
higher nuclearity). As would be expected, the 31P NMR
spectrum contains broad signals resulting from the overlap of a
number of similar environments. The 31P NMR spectrum of
17 contains four broad resonances at δ 169.2, 67.4, 47.8, and
19.0 ppm (Figure 2). The resonances at δ 169.2 (PC, PC′), 67.4
(PT, PT′), and 47.8 (PU, PU′) ppm are assigned to the PP3
phosphorus atoms complexed to a single iron center, while the
resonance at δ 19.0 ppm is assigned to the bridging PP3 ligand
(PB, PB′). The low-field shift for the central phosphorus of the
nonbridging PP3 ligand is consistent with all four phosphorus
atoms of this ligand being bound to the same metal center.
The dichloride complex 2 is thermally unstable, and it
decomposes to give 17 both in the solid state and in solution.
This decomposition is slow at ambient temperature in the solid
state, allowing 2 to be stored for days with little degradation.
31P{1H} NMR of 3 indicated the presence of a single product
giving rise to three multiplets at δ 184.8 (dt, PC), 61.3 (dd, PT),
and 60.0 (dt, PU) ppm in the ratio 1:2:1, respectively. Complete
1
assignment of the H NMR resonances of 3 was achieved by
analysis of the 1H and 1H{31P} NMR spectra as well as the 2D
COSY and NOESY spectra. The resonance due to the hydride
ligand of 3 appears at δ -11.63 ppm and in the phosphorus-
coupled spectrum is split into a doublet of doublets of triplets
(ddt) by the 31P nuclei. Assignment of heteronuclear P-H
couplings was achieved by selective 31P decoupling (2JH-P(C)
2
2
) 44.4 Hz, JH-P(T) ) 69.1 Hz, JH-P(U) ) 44.1 Hz).
There are two possible stereoisomers of 3 which can be
formed, with the hydride either cis or trans to the central
phosphorus atom, PC. The position of the hydride was
determined from the NOESY spectrum. Strong correlations
were observed between the hydride resonance and MeA, H1,
and H2 (Figure 3). A very weak correlation was observed
between the hydride and MeB, and no correlation was observed
(22) King, R. B.; Kapoor, R. N.; Saran, M. S.; Kapoor, P. N. Inorg. Chem.
1971, 10, 1851.
(23) The 31P{1H} NMR spectrum of the red solid, at low temperature (203
K), in acetone-d6, shows the presence of at least three complexes.
Major product (ca. 65%) 31P{1H} NMR spectrum (162 MHz, acetone-
d6, 203 K): δ 167.3 (br, 1P, PC), 86.8 (br, 1P, PU), 51.4 (br, 2P, PT).
Minor product (ca. 30%) 31P{1H} NMR spectrum (162 MHz, acetone-
2
2
d6, 203 K): δ 172.6 (dt, 1P, PC, JP(C)-P(U) ) 24.4 Hz, JP(C)-P(T)
)
2
21.4 Hz), 78.8 (dt, 1P, PU, JP(T)-P(U) ) 42.7 Hz), 48.7 (dd, 2P, PT);
minor product (ca. 5%) 31P{1H} NMR spectrum (162 MHz, acetone-
2
2
d6, 203 K): δ 171.1 (dt, 1P, PC, JP(C)-P(U) ) 30.5 Hz, JP(C)-P(T)
)
(24) Details of the chemistry of alkoxy complexes will be published
elsewhere.
2
22.9 Hz), 77.4 (dt, 1P, PU, JP(T)-P(U) ) 42.7 Hz), 49.5 (dd, 2P, PT).

Fe-P(CH2CH2PMe2)3 Complexes
Inorganic Chemistry, Vol. 36, No. 13, 1997 2889
Scheme 4
Figure 4. Variable temperature 31P{1H} NMR spectra (162 MHz,
toluene-d8) of FeH2(PP3) 4.
modeled the exchange in terms of the concerted “tetrahedral
jump” mechanism.27 However, the bulky, monodentate phos-
phite ligands are quite different from PP3. Alternative mech-
anisms include the reversible loss of a hydride ligand or the
temporary detachment of one of the bound phosphines to give
a five-coordinate complex which could undergo facile pseu-
dorotation before recoordination of the pendant phosphine.
Facile substitution of a phosphine trans to hydride is not
unexpected since hydride ligands have a strong trans effect.
The observed exchange of hydride ligands and phosphine
ligands occurs at approximately the same rate. This may be
because they are part of the same process; however, separate
mechanisms for each exchange process occurring at similar rates
cannot be ruled out.
Figure 5. Variable temperature 1H NMR spectra (400 MHz, toluene-
d8) of 4 (hydride region only). The inset is an expansion of the hydride
resonance showing fine structure at 300 K.
between the hydride and MeC. This clearly locates the hydride
cis to the central phosphorus atom, since if it were trans, a
NOESY correlation would be expected between the hydride and
the methyl groups on the unique phosphorus (MeC).3c
Reaction of a THF solution of the chloro hydride complex 3
with lithium aluminum hydride afforded the dihydride complex
4 (Scheme 3). Extraction into an aromatic solvent (benzene or
toluene) followed by extraction into an alkane solvent (pentane
or hexane) afforded 4 as a very pale yellow, highly air-sensitive
solid which was soluble in most organic solvents.
When dissolved in methanol or ethanol, the dihydride 4
affords an equilibrium mixture of [FeH(H2)(PP3)]+ and the
alkoxy hydride complexes FeH(OMe)(PP3) or FeH(OEt)(PP3),
respectively. The alkoxy complexes are unstable and on
standing or heating undergo further reactions.24
Preparation of 5 and 6. The iron methyl chloride complex
5 was prepared by the reaction of the iron dichloride complex
2 with either dimethylmagnesium or methyllithium, in THF
solution (Scheme 4). A THF solution of either dimethylmag-
nesium or methyllithium was added dropwise to a THF solution
of 2, resulting in a color change from red to orange. The
reaction was rapid at room temperature, and the color change
allowed the end point to be determined accurately. The chloro
methyl complex 5 is soluble in most organic solvents, although
it reacts rapidly with alcohols or other protic solvents.
In the monomethylation of 2, there are two possible isomers
which could be formed, i.e., with the methyl ligand either cis
or trans to the central phosphorus atom, PC. 31P{1H} NMR
indicated the presence of a single isomer giving rise to three
multiplets at δ 188.4 (dt, PC), 64.1 (dd, PT), and 59.8 (dt, PU)
ppm in the ratio 1:2:1, respectively.
The 31P{1H} NMR spectrum of 4, at 300 K, contains only
two sharp resonances, at δ 187.2 (q, PC) and 68.7 ppm (d, PT
and PU) in the ratio 1:3, with a 31P-31P coupling constant of
20.9 Hz (Figure 4). This spectrum is consistent with fast
exchange occurring between the terminal phosphorus environ-
ments, PT and PU. At 223 K the exchange was slowed, causing
significant broadening of the resonances due to PT and PU. At
198 K, two broad resonances were observed for the terminal
phosphorus nuclei, at δ 70.5 (PU) and 67.7 (PT) ppm in the ratio
1:2, respectively.
The 1H NMR spectrum of 4 shows similar exchange (Figure
5), with the two hydride resonances in fast exchange at 300 K
and giving rise to a single sharp multiplet resonance at δ -11.03
2
2
ppm (dq, JH-P(C) ) 44.9 Hz, JH-P(terminal) ) 7.2 Hz). At 243
K, the hydride resonance is very broad. At 198 K, two broad
resonances are apparent at δ -7.70 and -14.21 ppm.
1
Complete assignment of the H NMR spectrum of 5 was
1
1
achieved by analysis of the H and H{31P} NMR spectra as
well as the 2D COSY and NOESY spectra. The resonance due
to the methyl ligand of 5 appears at δ -0.26 ppm and in the
phosphorus-coupled spectrum is split (ddt) by the 31P nuclei.
Selective 31P decoupling allowed the assignment of 31P-CH3
couplings (3.2, 9.7, and 1.6 Hz to PC, PT, and PU, respectively).
The position of the iron-bound methyl relative to the central
phosphorus atom was established from the NOESY spectrum.
Strong NOEs were observed between the iron-bound methyl
The broadness of the resonances precluded the measurement
of 31P-31P and 31P-1H coupling constants and also precluded
the use of 2D COSY and/or NOESY experiments to make
unambiguous assignment of the two hydride resonances. The
1
31P and H spectra of 4 are very similar to those reported for
FeH2[(PCH2CH2PPh2)3].25,26
There are a number of possible mechanisms for the observed
exchange between hydride and terminal phosphine resonances.
Studies of tetraphosphite dihydride complexes of iron have
(27) (a) Tebbe, F. N.; Meakin, P.; Jesson, J. P.; Muetterties, E. L. J. Am.
Chem. Soc. 1970, 92, 1068. (b) Meakin, P.; Muetterties, E. L.; Tebbe,
F. N.; Jesson, J. P. J. Am. Chem. Soc. 1971, 93, 4701. (c) Meakin, P.;
Muetterties, E. L.; Jesson, J. P. J. Am. Chem. Soc. 1973, 95, 75. (d)
Jesson, J. P.; Meakin, P. Acc. Chem. Res. 1973, 6, 269.
(25) Bianchini, C.; Laschi, F.; Peruzzini, M.; Ottaviani, F. M.; Vacca, A.;
Zanello, P. Inorg. Chem. 1990, 29, 3394.
(26) Heinekey, D. M.; van Roon, M. J. Am. Chem. Soc. 1996, 118, 12134.

2890 Inorganic Chemistry, Vol. 36, No. 13, 1997
Field et al.
Preparation of 7 and 8. Substitution of a chloro ligand of
the iron(II) dichloride complex 2 by carbon monoxide yielded
two isomeric iron(II) carbonyl chloride complexes 7 and 8
(Scheme 5). The introduction of an atmosphere of carbon
monoxide over a degassed ethanol solution of the dichloride
complex 2 resulted in a rapid color change from red to yellow.
The addition of an ethanol solution of sodium tetraphenylborate
precipitated 7 as the tetraphenylborate salt. The 31P NMR
spectrum contained three signals at δ 163.9 (dt, PC), 58.6 (dt,
PU), and 44.9 (dd, PT) ppm in the ratio 1:1:2, respectively.
By using 13C-labeled carbon monoxide, 31P-13C coupling
Figure 6. Variable temperature 31P{1H} NMR spectra (162 MHz,
toluene-d8) of 6.
constants to the carbonyl ligand were determined from the 31
P
and 13C NMR spectra. The 31P NMR spectrum of the 13CO-
labeled complex contained an extra doublet coupling in each
2
2
2
resonance; JC-P(C) ) 15.9 Hz, JC-P(U) ) 31.8 Hz, JC-P(T)
)
45.1 Hz. The 13CO ligand gave rise to a ddt resonance at δ
212.9 ppm in the 13C NMR spectrum.
Heating an ethanol solution of the carbonyl chloride complex
7 (chloride salt) at 60 °C resulted in the formation of another
product, assigned as the isomeric carbonyl chloride complex 8.
This reaction was followed by 31P NMR, which showed the
depletion of the signals due to 7 in favor of the three new signals
of 8 at δ 168.9 (dt, PC), 77.9 (dt, PU), and 60.5 (dd, PT) ppm.
The reaction could not be forced to completion, the two
complexes, 7 and 8, apparently reaching equilibrium after
heating at 60 °C for 10 days with a ratio 8:7 of 5:1.
Figure 7. Schematic representation showing significant NOESY
interactions between the methyl ligands and the PP3 ligand in 6.
and MeA, H1, and H2. No correlations were observed to MeB
or MeC. This set of results unambiguously places the iron-
bound methyl cis to the central phosphorus atom, the same site
as the hydride ligand occupies in the chloro hydride complex
3.
The use of 13CO confirmed that this second product also has
one carbonyl ligand. The 13C-31P coupling constants (2JC-P(C)
2
2
) 43.9 Hz, JC-P(U) ) 21.0 Hz, JC-P(T) ) 17.2 Hz) are very
different from those of 7. The 13C NMR spectrum contained a
ddt resonance at δ 213.3 ppm assigned to the carbonyl ligand
of 8. The relative stereochemistry of 7 and 8 was tentatively
assigned from the relative magnitudes of their 13C-31P coupling
constants.28
Reaction of dimethylmagnesium or methyllithium with the
methyl chloride complex 5 or reaction of excess methylating
reagent with the dichloride complex 2 afforded the dimethyl
complex 6 (Scheme 4). The 31P NMR spectrum of 6 at 300 K
contains two complex multiplet resonances, centered at δ 179.7
ppm, due to the central phosphorus, PC, and at δ 67.8 ppm, due
to the terminal phosphorus atoms, PT and PU, in the ratio 1:3.
The appearance of only one terminal phosphorus resonance in
this complex is due to the near coincidence of the chemical
shifts of PT and PU. The chemical shift of PU is notably
temperature dependent, and first-order 31P spectra are clearly
resolved at lower temperatures (Figure 6).
Preparation of 9. The preparation of 9 was achieved by
the addition of triphenylphosphine to a methanol solution of 2
(Scheme 6). No notable color change occurred, the resultant
solution being essentially indistinguishable from the red color
of 2. The addition of a methanol solution of sodium tetraphe-
nylborate resulted in the precipitation of the tetraphenylborate
salt of 9, which was soluble in acetone.
The 31P NMR spectrum of 9 contained four resonances at δ
167.6, 56.9, 41.8, and 39.6 ppm in the ratio 1:1:1:2, respectively.
The central phosphorus, PC, was assigned to the resonance at δ
167.6 ppm due to its extreme low-field shift. PT was also easily
assigned to the resonance at δ 39.6 ppm by reference to the
relative integrated intensities. The resonance at δ 41.8 ppm
was assigned to the bound triphenylphosphine due to the large,
104.9 Hz coupling to PC, which is characteristic of the trans
31P-31P coupling constant. The resonance at δ 56.9 ppm was
assigned to PU.
1
Two iron-bound methyl resonances appear in the H NMR
spectrum, at 0.12 ppm (Me1) and -0.88 ppm (Me2), each
appearing as a ddt. 31P couplings to Me1 were 1.4, 8.7, and
8.7 Hz to PC, PT, and PU, respectively. 31P couplings to Me2
were 5.9, 9.7, and 8.3 Hz to PC, PT, and PU, respectively.
1
The resonances of the PP3 ligand in the H NMR spectrum
of 6 were assigned using the 2D COSY and NOESY spectra in
a fashion analogous to that used for the chloro hydride complex
3. The positions of the methyl ligands relative to PC were
determined from the NOESY spectrum. Strong correlations
were observed between Me1 and all three methyl groups MeA,
MeB, and MeC, showing Me1 to be trans to the central
phosphorus, PC. Strong correlations between Me2 and MeA,
H1, and H2 showed Me2 to be cis to the central phosphorus, PC
(Figure 7).
The full assignment of the 1H NMR spectrum of 9 was
achieved using 2D COSY and NOESY experiments. The
NOESY spectrum contained roughly equal enhancements from
the ortho phenyl protons of the bound triphenylphosphine to
all three PP3 methyl resonances, confirming that the tri-
phenylphosphine is trans to PC.
Scheme 5

Fe-P(CH2CH2PMe2)3 Complexes
Inorganic Chemistry, Vol. 36, No. 13, 1997 2891
Table 3. Selected Bond Angles (deg) for Iron(II) Complexes 9
(This Work), 15,31 and 1632
9
15
16
PC-Fe-PU
83.85(9)
83.24(9)
83.66(9)
82.14(9)
174.5(1)
93.40(9)
98.71(9)
165.22(9)
101.59(8)
161.07(9)
80.32(8)
84.41(8)
97.40(8)
94.37(8)
92.52(8)
97.1(2)
95.4(2)
88.9 (2)
85.6(2)
179.0(2)
99.7(2)
95.3(2)
176.9(2)
83.7(2)
168.8(2)
81.5(2)
83.2(2)
83.7(2)
91.5(2)
93.6(2)
85.3(1)
86.3(1)
82.7(1)
a
PC-Fe-PT
PC-Fe-PT
a
PC-Fe-Cl[1]
PC-Fe-Cl[2]/PPh3
a
PU-Fe-PT
PU-Fe-PT
97.1(1)
98.9(1)
a
PU-Fe-Cl[1]
PU-Fe-Cl[2]/PPh3
PT-Fe-PT
159.7(2)
PT-Fe-Cl[1]a
PT-Fe-Cl[1]a
a
PT-Fe-Cl[2]/PPh3
PT-Fe-Cl[2]/PPh3
a
Cl[1]-Fe-Cl[2]/PPh3
a Two trans terminal phosphines, PT.
Figure 8. ORTEP plot (25% thermal ellipsoids, non-hydrogen atoms)
of the complex cation of 9 (BPh4 salt).
ligands containing phosphine groups separated by an ethylene
bridge. For example, the chelation angle in the iron dichloride
complexes of the diphosphines DMPE,30 DEPE,18 and DPrPE18
are 85.8°, 85.3°, and 84.6°, respectively. The chelation angles
in 9 (Table 3) are 83.9° and 83.5° for PC-Fe-PU and PC-
Fe-PT (average), respectively. The distortion is most noticeable
in the angle between the trans phosphines (161.07°), nearly 20°
from the ideal octahedral angle. Many octahedral iron(II)
complexes of 10 have been synthesized, and an X-ray diffraction
structure of the η2-pentynato complex 16 has been reported.32
The Fe-P bond lengths and angles for 16 are included in Tables
2 and 3.
Scheme 6
Table 2. Selected Bond Lengths (Å) for Iron(II) Complexes 9
(This Work), 15,31 and 1632
9
15
16
Fe-PC
Fe-PU
2.202(2)
2.234(2)
2.312(2)
2.312(2)
2.356(2)
2.361(2)
2.202(5)
2.231(5)
2.338(5)
2.306(5)
2.388(4)
2.410(4)
2.151(3)
2.224(3)
2.259(4)
2.297(3)
a
Fe-PT
Fe-PT
a
Fe-Cl[1]
Fe-Cl[2]/PPh3
a Two trans terminal phosphines, PT.
X-ray Crystal Structure of 9 (BPh4 Salt). Crystals of 9,
suitable for X-ray diffraction, were obtained by cooling a
saturated acetone solution of 9 to 5 °C. The structure deter-
mination confirmed the trans arrangement of PC and tri-
phenylphosphine (Figure 8). The crystal data parameters are
summarized in Table 1. Selected bond lengths and angles are
listed in Tables 2 and 3, respectively.
The four phosphorus atoms of the PP3 ligand and the two
chloro ligands of 9 are arranged in a distorted octahedron. The
distortion from an octahedral arrangement is due to the natural
bite angle29 of PP3 being less than the required 90°. Chelation
angles of less than 90° are also observed in complexes of other
The Fe-P bond lengths of 16 on average are slightly shorter
than those of 9 and 15, due to the presence of the harder
carboxylate ligand. The P-Fe-P bond angles for 16 are very
similar to those for 9; in both cases the chelation angles are
significantly less than 90°.
Comparison of 9 with the iron dichloride complex 1531 of
the related tripodal tetraphosphine ligand, 11, with three carbon
links between the phosphorus atoms, highlights the differences
imparted to complexes by the two ligands (Table 3). Whereas
1 has a natural bite angle of less than 90°, 11 has a natural bite
angle of greater than 90°. In 15, the trans phosphines are bent
toward the front chloro ligand (Cl[1]) by 11.2°, whereas in 9
they are bent by 18.9°, essentially away from the chloro and
triphenylphosphine ligands.
(28) The related iron(II) carbonyl complexes [FeH(CO)(PP3)]+ and [FeMe-
(CO)(PP3)]+ have also been prepared.33 The carbonyl ligand in both
these complexes was shown (unambiguously) to be trans to PC using
1H-1H NOESY experiments. The magnitudes of the 13C-31P coupling
constants for the 13CO-labeled complexes are as follows: [FeH(CO)-
(PP3)]+, 2JC-P(C) ) 31.5 Hz, 2JC-P(T) ) 20.0 Hz, 2JC-P(U) ) 17.2 Hz;
2
2
2
[FeMe(CO)(PP3)]+, JC-P(C) ) 40.7 Hz, JC-P(T) ) 19.6 Hz, JC-P(U)
) 16.0 Hz. The similarity of these coupling constants to those of the
second (thermodynamically favored) carbonyl chloride complex 8
(2JC-P(C) ) 43.9 Hz, JC-P(T) ) 17.2 Hz, JC-P(U) ) 21.0 Hz) and
their marked difference from those of the first (kinetically favored)
carbonyl chloride complex 7 (2JC-P(C) ) 15.9 Hz, 2JC-P(T) ) 45.1 Hz,
2JC-P(U) ) 31.8 Hz) indicate that the carbonyl is trans to PC in 8 and
trans to PU in 7. The synthesis and full characterization of [FeH(CO)-
(PP3)]+ and [FeMe(CO)(PP3)]+ will be reported elsewhere.
2
2
(30) Di Vaira, M.; Midollini, S.; Sacconi, L. Inorg. Chem. 1981, 20, 3430.
(31) Antberg, M.; Dahlenburg, L. Inorg. Chim. Acta. 1985, 104, 51.
(32) Linn, K.; Masi, D.; Mealli, C.; Bianchini, C.; Peruzzini, M. Acta
Crystallogr. 1992, C48, 2220.
(29) Casey, C. P.; Whittaker, G. T. Isr. J. Chem. 1990, 30, 299.
(33) Smernik, R. J. Ph.D. Thesis, University of Sydney, 1996.

2892 Inorganic Chemistry, Vol. 36, No. 13, 1997
Field et al.
Conclusions
Acknowledgment. We gratefully acknowledge financial
support from the Australian Research Council, the Australian
Government for an Australian Postgraduate Award (R.J.S.), and
the University of Sydney for an H. B. and F. M. Gritton Award
(R.J.S.).
Iron(II) complexes containing the tripodal tetraphosphine
ligand P(CH2CH2PMe2)3 (1) were synthesized. Reaction of the
dichloride complex FeCl2(PP3) (2) with LiAlH4 afforded FeHCl-
(PP3) (3) and FeH2(PP3) (4); reaction of 2 with Me2Mg or MeLi
afforded FeMeCl(PP3) (5) and FeMe2(PP3) (6). Reaction of 2
with CO afforded the isomeric carbonyl hydride complexes
[FeCOCl(PP3)]+ (7 and 8); and reaction of 2 with PPh3 afforded
[Fe(PPh3)Cl(PP3)]+ (9). The structure of 9 was determined by
X-ray crystallography, and the core structure was significantly
distorted from octahedral coordination due to the small natural
bite angle of the PP3 ligand. The dihydride complex FeH2(PP3)
Supporting Information Available: Listings of atom coordinates,
anisotropic thermal parameters, bond lengths and angles, torsion angles,
nonbonded contacts, and details of least squares planes for [Fe(PPh3)-
Cl(PP3)]+ (9) (BPh4 salt) (15 pages). Ordering information is given
on any current masthead page.
(4) shows dynamic NMR behavior in both the H and 31P
spectra.
1
IC970030B