Iron(II) Complexes Containing the 1,2-Diphospholanoethane Ligand

Article abstract of DOI:10.1021/ic9701928

The synthesis and crystal structure of cis-Fe(BPE5)₂Cl₂ (BPE5 = 1,2-diphospholanoethane), the first symmetrical cis-Fe(PP)₂Cl₂ (PP = bidentate phosphine), is reported (monoclinic, P2₁/n, a = 12.084(3) ?, b = 14.059(2) ?, c = 17.665(2) ?, β = 101.77(1)°, Z = 4). The overall structure and Fe-P and Fe-Cl bond lengths of cis-Fe-(BPE5)₂Cl₂ more closely resemble those in Fe(PP₃)Cl₂ complexes (PP₃ = tripodal, tetradentate phosphine ligand) than in other Fe(PP)₂Cl₂ complexes. In solution, cis-Fe(BPE5)₂Cl₂ exhibits temperature-dependent paramagnetic behavior due to reversible dissociation of chloride. The dissociation of chloride was exploited in the synthesis of Fe(BPE5)₂X₂ (X = Br, I) and [Fe(BPE5)₂(L)(Cl)]⁺ (L = CO, PMe₃). The crystal structure of [cis-Fe(BPE5)₂-(CO)(Cl)][BPh₄] is reported (monoclinic, P2₁/a, a = 12.938(3) ?, b = 29.647(4) ?, c = 13.131(3) ?, β = 107.89(2)°, Z = 4). The relative chelation strength of BPE5 in Fe(PP)₂Cl₂ complexes is BPE5 ≈ DMPE > DEPE > DPrPE [DMPE = 1,2-bis(dimethylphoshino)ethane; DEPE = 1,2-bis(diethylphoshino)ethane; DPrPE = bis(di-n-propylphosphino)ethane].

Full text of DOI:10.1021/ic9701928

612
Inorg. Chem. 1998, 37, 612-618
Ar ticles
Iron(II) Complexes Containing the 1,2-Diphospholanoethane Ligand
Leslie D. Field,*,† Iain P. Thomas,† Trevor W. Hambley,‡ and Peter Turner‡
Divisions of Organic Chemistry and Inorganic Chemistry, School of Chemistry, University of Sydney,
NSW 2006, Australia
ReceiVed February 20, 1997
The synthesis and crystal structure of cis-Fe(BPE5)2Cl2 (BPE5 ) 1,2-diphospholanoethane), the first symmetrical
cis-Fe(PP)2Cl2 (PP ) bidentate phosphine), is reported (monoclinic, P21/n, a ) 12.084(3) Å, b ) 14.059(2) Å,
c ) 17.665(2) Å, â ) 101.77(1)°, Z ) 4). The overall structure and Fe-P and Fe-Cl bond lengths of cis-Fe-
(BPE5)2Cl2 more closely resemble those in Fe(PP3)Cl2 complexes (PP3 ) tripodal, tetradentate phosphine ligand)
than in other Fe(PP)2Cl2 complexes. In solution, cis-Fe(BPE5)2Cl2 exhibits temperature-dependent paramagnetic
behavior due to reversible dissociation of chloride. The dissociation of chloride was exploited in the synthesis
of Fe(BPE5)2X2 (X ) Br, I) and [Fe(BPE5)2(L)(Cl)]+ (L ) CO, PMe3). The crystal structure of [cis-Fe(BPE5)2-
(CO)(Cl)][BPh4] is reported (monoclinic, P21/a, a ) 12.938(3) Å, b ) 29.647(4) Å, c ) 13.131(3) Å, â )
107.89(2)°, Z ) 4). The relative chelation strength of BPE5 in Fe(PP)2Cl2 complexes is BPE5 ≈ DMPE >
DEPE > DPrPE [DMPE ) 1,2-bis(dimethylphoshino)ethane; DEPE ) 1,2-bis(diethylphoshino)ethane; DPrPE
) bis(di-n-propylphosphino)ethane].
Introduction
Scheme 1
The study of metal complexes of the MP4X2 type (M ) Fe,
Ru, Os; P ) phosphine; X ) halide, hydride) has been extensive,
and the chemistry exhibited by metal phosphines depends to a
large extent on the nature of the phosphine ligand(s) that they
contain.1 MP4X2 systems have been employed in many types
of reactions including intramolecular2 and intermolecular3 C-H
activation and as catalysts in organic synthesis.4 The most
frequently studied MP4X2 systems have incorporated two
bidentate ligands (e.g. R2PCH2CH2PR2, R ) Ph,5 Me,2a,3a-d,3f,6,7
and Et8).
R ) Ph,9 Me,3g,10 Cy11) have been used; i.e., when the
phosphines are constrained to occupy adjacent coordination sites.
In this paper we report the synthesis of the first cis-FeP4Cl2
complex with two bidentate bisphosphines (PP), cis-Fe(BPE5)2-
Cl2 (cis-1; BPE5 ) 1,2-diphospholanoethane12 (2)). The
geometry adopted by cis-1 is probably influenced by the steric
bulk of the diphospholano ligands 2.
To date, the existence of FeP4Cl2 complexes in which the
chloride ligands occupy a cis geometry has only been observed
when tetradentate phosphine ligands (P((CH2)nPR2): n ) 2, 3;
† Division of Organic Chemistry.
‡ Division of Inorganic Chemistry.
(1) See for example: Mayer, H. A.; Kaska, W. C. Chem. ReV. 1994, 1239.
(2) (a) Jones, W. D.; Foster, G. P.; Putinas, J. M. Inorg. Chem. 1987, 26,
2120. (b) Antberg, M.; Dahlenberg, L. Angew. Chem., Int. Ed. Engl.
1986, 25, 260.
(3) (a) Jones, W. D.; Feher, F. Organometallics 1983, 2, 562. (b) Baker,
M. V.; Field, L. D. J. Am. Chem. Soc. 1986, 108, 7433. (c) Baker, M.
V.; Field, L. D. J. Am. Chem. Soc. 1986, 108, 7436. (d) Baker, M.
V.; Field, L. D. J. Am. Chem. Soc. 1987, 109, 2825. (e) Antberg, M.;
Dahlenberg, L.; Frosin, K. M.; Ho¨ck, N. Chem. Ber. 1988, 121, 859.
(f) Field, L. D.; George, A. V.; Messerle, B. A. J. Chem. Soc., Chem.
Commun. 1991, 19, 1339. (g) Bampos, N.; Field, L. D.; Messerle, B.
A. Organometallics 1993, 12, 2529.
Results and Discussion
Synthesis of cis-Fe(BPE5)2Cl2 (cis-1). On addition of 2
equiv of BPE5 (2) to a THF solution of anhydrous iron(II)
chloride, a burgundy solution formed, from which dark red
crystals of cis-Fe(BPE5)2Cl2 (cis-1) precipitated as the sole
isolated product (Scheme 1). The complex cis-1 is soluble in
(9) (a) Bianchini, C.; Peruzzini, M.; Zanobini, F. J. Organomet. Chem.
1988, 354, C19. (b) Bianchini, C.; Peruzzini, M.; Polo, A.; Vacca,
A.; Zanobini, F. Inorg. Chem. 1991, 30, 279. (c) Bianchini, C.; Perez,
P. J.; Peruzzini, M.; Zanobini, F.; Vacca, A. Inorg. Chem. 1991, 30,
279.
(4) (a) Jones, W. D.; Kosar, W. P. J. Am. Chem. Soc. 1986, 108, 5640.
(b) Hsu, G. C.; Kosar, W. P.; Jones, W. D. Organometallics 1994,
13, 385.
(5) Hata, G.; Kondo, H.; Miyake, A. J. Am. Chem. Soc. 1968, 90, 2278.
(6) Chatt, J.; Watson, H. R. J. Chem. Soc. 1962, 2545.
(7) Burn, M. J.; Fickes, M. G.; Hollander F. J.; Bergman, R. G.
Organometallics 1995, 14, 137.
(10) (a) Bampos, N.; Field, L. D. Inorg. Chem. 1989, 29, 587. (b) Bampos,
N.; Field, L. D.; Messerle, B. A. Magn. Reson. Chem. 1991, 29, 36.
(11) Jia, G.; Drouin, S. D.; Jessop, P. G.; Lough, A. J.; Morris, R. H.
Organometallics 1993, 12, 906.
(8) Chatt, J.; Hayter, R. G. J. Chem. Soc. 1961, 5507.
(12) Field, L. D.; Thomas, I. P. Inorg. Chem. 1996, 35, 2546.
S0020-1669(97)00192-4 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/28/1998

Fe-BPE5 Complexes
Inorganic Chemistry, Vol. 37, No. 4, 1998 613
in cis-1 is slightly wider (1-2°) and the Fe-P bond lengths
shorter (∼6%). The Fe-P bond lengths are short when trans
to Cl, reflecting the weaker σ-donor ability of the chloride
ligand. The cis disposition of the chloro ligands distinguishes
cis-1 from 3-6 and is presumably responsible for the distortion
from octahedral geometry evident in Table 1. In cis-1, the BPE5
ligands interact significantly with the chlorine atoms and this
undoubtedly contributes to the distortion from octahedral
geometry.
In complex cis-1, the Fe-Cl bonds are slightly longer than
in complexes 3-6 but very similar to those of cis-Fe(P((CH2)3-
PMe2)3)Cl2 (7)16 (Table 2). The chloride ligands of complexes
cis-1, 7, and 8 are all trans to strong σ-donor phosphine ligands,
whereas, in complexes 3-6, the two chloride ligands are
mutually trans.
Figure 1. ORTEP plot (25% thermal ellipsoids, non-hydrogen atoms)
of cis-Fe(BPE5)2Cl2 (cis-1).
Table 1. Bond Lengths (Å) and Angles (deg) about the Iron Atom
of cis-Fe(BPE5)2Cl2 (cis-1)a
Bond Lengths
Fe-Cl(1)
Fe-Cl(2)
Fe-P(1)
2.384(3)
2.403(3)
2.181(3)
Fe-P(2)
Fe-P(3)
Fe-P(4)
2.225(3)
2.185(3)
2.223(3)
Bond Angles
Cl(1)-Fe-Cl(2)
Cl(1)-Fe-P(1)
Cl(1)-Fe-P(2)
Cl(1)-Fe-P(4)
P(1)-Fe-P(2)
89.4(1)
88.4(1)
87.1(1)
88.4(1)
86.5(1)
P(3)-Fe-P(4)
P(1)-Fe-P(4)
P(2)-Fe-P(3)
P(1)-Fe-P(3)
P(2)-Fe-P(4)
86.1(1)
98.2(1)
98.2(1)
94.3(1)
173.4(1)
a Errors in the least significant figures are presented in parentheses.
The phospholane rings at the two trans phosphines P(2) and
P(4) of complex cis-1 are in essentially envelope conformations
(minimum torsion angles of 5.6 and 1°, respectively), in which
the carbon atoms â to phosphorus (C(8) and C(18)) lie out of
plane with respect to the rest of their respective rings. The ring
at P(3) is the most planar (no torsion angle exceeds 11°), and
the ring at P(1) is puckered.
Solution-State Temperature Dependent Paramagnetism
of cis-Fe(BPE5)2Cl2 (cis-1). At room temperature, no signal
was detected in the 31P{1H} NMR spectra of cis-1 in either THF
or methanol solution. However, on cooling, two broad reso-
nances were observed, and at 233 K these were resolved as
two sharp apparent triplets.
The broadness of the 31P resonances of cis-1 is due to
paramagnetism probably originating from reversible dissociation
of chloride to form a five-coordinate paramagnetic complex [Fe-
(BPE5)2Cl]+ (9). Methanol or THF solutions of cis-1 which
were saturated with sodium chloride gave well-resolved sharp
signals in the 31P{1H} NMR spectra recorded at 300 K.
Temperature-dependent paramagnetism has been observed for
complexes 4 and 5 and in these complexes was attributed to
reversible dissociation of one end of the bulky bidentate
methanol, ethanol, and benzene but only sparingly soluble in
THF. Recrystallization of cis-1 from THF afforded crystals
suitable for X-ray diffraction.
The 31P{1H} NMR spectrum of the filtered reaction mixture
(recorded at 233 K) indicated that cis-1 was the predominant
product (two apparent triplets at 93.2 and 106.7 ppm, splitting
) 40 Hz); a second product (91.8 ppm, singlet) is assigned as
the isomeric trans complex trans-Fe(BPE5)2Cl2 (trans-1; ∼90:
10 cis-1/trans-1). On addition of n-hexane to the THF solution,
a dark red solid precipitated, and this was insoluble in most
organic solvents, including alcohols and THF. The product is
probably oligomeric or polymeric but has not been further
characterized. Attempts to isomerize pure cis-1 to trans-1 in
refluxing methanol and benzene, by irradiation at ambient and
low (233 K) temperatures, and by heating in the solid state were
unsuccessful.
cis-Fe(BPE5)2Cl2 (cis-1) crystallizes with 1 mol of THF as a
slightly distorted octahedral complex in which the two chloride
ligands are mutually cis (Figure 1). Selected structural data
for complex cis-1 are reported in Table 1. In comparison with
related trans-Fe(PP)2Cl2 complexes [PP ) DMPE (3),13 DEPE
(4),13,14 DPrPE (5),14 BPE6 (6),15 BPE6 ) 1,2-bis(1-phos-
phorinano)ethane; Table 2], the P-Fe-P chelation bite angle
(14) Baker, M. V.; Field, L. D.; Hambley, T. W. Inorg. Chem. 1988, 27,
2872-2876.
(15) Field, L. D.; Thomas, I. P.; Hambley, T. W.; Turner, P. Submitted
for publication.
(13) Di Vaira, M.; Midollini, S.; Sacconi, L. Inorg. Chem. 1981, 20, 3430.
(16) Antberg, M.; Dahlenburg, L. Inorg. Chim. Acta 1985, 104, 51.

614 Inorganic Chemistry, Vol. 37, No. 4, 1998
Field et al.
Table 2. Average Fe-Cl and Fe-P Bond Lengths (Å) and Chelate P-Fe-P Angles (deg) about the Iron Centers of Fe(PP)2Cl2 Complexes
(cis-1, 3-8, and 15)
Fe-Cl
Fe-Pa
Fe-Pb
P-Fe-Pc
ref
cis-Fe(BPE5)2Cl2 (cis-1)
trans-Fe(DMPE)2Cl2 (3)
trans-Fe(DEPE)2Cl2 (4)
trans-Fe(DPrPE)2Cl2 (5)
trans-Fe(BPE6)2Cl2 (6)
cis-Fe(P(CH2)3PMe2)3Cl2 (7)
2.394b, j
2.183 j
2.224j
86.3
85.8
85.3
84.6
85.2
95.4, 97.1, 88.9
this work
13
13,14
14
15
16
2.352(1)a
2.344(1)a
2.345(2)a
2.361(2)a
2.388(5)d
2.410(4)e
2.341b, j
2.235 j
2.260 j
2.268 j
2.251 j
2.202(5) f
2.231(5)g
2.237(8)
2.260(8)i
2.322g,h,j
2.234 j
[cis-Fe(BPE5)2(CO)(Cl)]+ (15)
85.7
this work
a Trans to chloride. b Trans to phosphorus. c Chelate angle. d Trans to apical phosphorus atom. e Trans to terminal phosphorus atom. f Apical
phosphorus atom. g Terminal phosphorus atom. h Average of two mutually trans phosphorus atoms. i Trans to CO. j Average values.
phosphine ligand to generate paramagnetic five-coordinate iron
complexes with P3Cl2 donor sets.14
as a green microcrystalline solid. In both cases, substitution
presumably occurs by stepwise reversible dissociation of
chloride and association of halide (Br- or I-) and the reaction
is driven to completion by the precipitation of the insoluble
products. Substitution by bromide or iodide was too rapid to
allow partially substituted complexes Fe(BPE5)2ClX to be
observed by 31P NMR spectroscopy.
The dibromide complex cis-13 does not exhibit paramagnetic
properties like those of complex cis-1. In refluxing toluene,
an equilibrium mixture of cis-13 and trans-13 was established
(∼1:1.8) which on cooling reverted to cis-13. Gentle heating
of solid cis-13 to 220 °C gave trans-13 as a green crystalline
solid, which on dissolution in toluene gave rise to a green
solution that darkened over approximately 20 min and from
which cis-13 precipitated. In the solid state trans-13 was air
stable and maintained its isomeric integrity over an indefinite
period.
The diiodide complex 14 was insoluble in most organic
solvents. The isotropic region of the solid-state 31P{1H} MAS
NMR spectrum of 14 is essentially a singlet resonance with
two symmetrical shoulders giving the peak the appearance of a
broadened triplet (Figure 2) and demonstrates 14 to be of trans
geometry. Maricq et al.21 and Wu et al.22 have shown that MAS
NMR resonances of crystallographically equivalent but magneti-
cally inequivalent nuclei that are dipolar-coupled exhibit mul-
tiplet structure. The isotropic regions of the 31P{1H} MAS
NMR spectra of cis-1 and cis-13 consist of complicated
resonances (Figure 2). The crystal structure of cis-1 (Figure 1)
shows the four 31P nuclei to be crystallographically inequivalent
and therefore part of an AMQX spin system in the solid state.
The extreme insolubility of 14 prevented the growth of crystals
suitable for crystallographic analysis.
Chloride Ligand Substitution Reactions of cis-Fe(BPE5)2Cl2
(cis-1) by CO and PMe3. The cationic complex [cis-Fe-
(BPE5)2(CO)(Cl)]+ (15) was formed when a methanol solution
of complex cis-1 was stirred under an atmosphere of CO
(Scheme 2). The complex was isolated as its bright yellow
tetraphenylborate salt. Displacement of chloride by CO was
not observed in less polar solvents such as THF and benzene.
The ease with which one of the chloride ligands of complex
cis-1 apparently dissociates is probably not only due to the fact
that it is trans to a phosphine ligand. The related complexes
716 and 817 are diamagnetic under similar conditions. Coordina-
tion of bulky tetradentate ligands P((CH2)2PPh2)3 and P(o-C6H4-
PPh2)3 to iron(II) chloride has only resulted in the isolation of
paramagnetic cationic monochloride cations [Fe(P((CH2)2-
PPh2)3)Cl]+ (10)18 and [Fe(P(o-C6H4PPh2)3)Cl]+ (11),19 respec-
tively. The existence of monochloride cations 10 and 11 has
been attributed to the greater rigidity of the tetradentate ligands
in which the chelate bite angles are restricted to 84 ( 2°;16
however, this rationalization is not consistent with the structure
of the dichloride complex 817 in which the chelate bite angles
are similarly restricted to 85.8 ( 1°. It is more likely that bulky
phosphine ligands are better accommodated in five-coordinate
monochloride complexes,20 and the steric bulk of the BPE5
ligands contributes significantly to the lability of chloride in
cis-1.
Addition of excess phosphine (BPE5, DMPE, or PMe3) to
complex cis-1 in THF solution also suppressed paramagnetism
and was accompanied by isomerization of the complex to form
an equilibrium mixture of cis-1 and trans-1 (ca. 90:10).
Addition of DMPE also led to phosphine exchange, and the
complex containing one DMPE and one BPE5 ligand [Fe-
(DMPE)(BPE5)Cl2] was characterized by NMR spectroscopy
(see below). No charged [FeP5Cl]+ (P ) phosphine) cationic
complexes were detected in THF solution; however, the cation
[Fe(BPE5)2(PMe3)Cl]+ (12) has been isolated from more polar
solvents (see below).
cis-1 is stable with respect to cis/trans isomerization in the
absence of free phosphines, and this suggests that the mechanism
of isomerization is probably via chloride dissociation from cis-1
followed by coordination of free phosphine to give a cation of
the type [FeP5Cl]+. Reversible loss of a phosphine donor
provides an avenue for isomerization and also ligand exchange.
Chloride Ligand Substitution Reactions of cis-Fe(BPE5)2Cl2
(cis-1) by Halides. Reaction of complex cis-1 in methanol
solution with an excess of the appropriate sodium or potassium
halide resulted in almost instantaneous precipitation of the
corresponding iron dihalide complexes cis-Fe(BPE5)2Br2 (cis-
13) as a dark purple crystalline solid or trans-Fe(BPE5)2I2 (14)
The crystal structure of complex 15 (Figure 3) resembles that
of cis-1. The complex is of slightly distorted octahedral
geometry in which the CO and chloride ligands are mutually
cis. Selected bond lengths and bond angles for complex 15
are reported in Table 3. The P-Fe-P chelation angles of 15
are only slightly smaller than in the dichloride cis-1 (Table 2).
The Fe-P bond lengths are longer and the Fe-Cl bond lengths
(17) (a) Smernik, R. J. Ph.D. Thesis, University of Sydney, 1996. (b) Field,
L. D.; Messerle, B. A.; Smernik, R. J.; Hambley, T. W.; Turner, P.
Inorg. Chem. 1997, 36, 2884.
(18) King, R. B.; Kapoor, R. N.; Saran, M. S.; Kapoor, P. N. Inorg. Chem.
1971, 10, 1851.
(19) Halfpenny, M. T.; Hartley, J. G.; Venanzi, L. N. J. Chem. Soc. A
1967, 627.
(20) Venanzi, L. N.; Angew. Chem., Int. Ed. Engl. 1964, 3, 453.
(21) Maricq, M. M.; Waugh, J. S. J. Chem. Phys. 1979, 70, 3300.
(22) Wu, G.; Wasylishen, R. E. Inorg. Chem. 1994, 33, 2774 and references
therein.

Fe-BPE5 Complexes
Inorganic Chemistry, Vol. 37, No. 4, 1998 615
Table 3. Bond Lengths (Å) and Angles (deg) about the Iron Atom
of [cis-Fe(BPE5)2(CO)(Cl)]+ (15)a
Bond Lengths
Fe(1)-Cl(1)
Fe(1)-C(1)
Fe(1)-P(1)
2.341(9)
1.93(3)
Fe(1)-P(2)
Fe(1)-P(3)
Fe(1)-P(4)
2.237(8)
2.260(7)
2.231(8)
2.237(7)
Bond Angles
Cl(1)-Fe(1)-P(1)
Cl(1)-Fe(1)-P(2)
Cl(1)-Fe(1)-P(3)
Cl(1)-Fe(1)-P(4)
Cl(1)-Fe(1)-C(1)
P(1)-Fe(1)-P(2)
P(1)-Fe(1)-P(3)
P(1)-Fe(1)-P(4)
174.8(4)
89.3(3)
88.7(3)
86.3(3)
89(1)
P(1)-Fe(1)-C(1)
P(2)-Fe(1)-P(3)
P(2)-Fe(1)-P(4)
P(2)-Fe(1)-C(1)
P(3)-Fe(1)-P(4)
P(3)-Fe(1)-C(1)
P(4)-Fe(1)-C(1)
90(1)
96.9(3)
174.8(3)
91(1)
85.7(3)
172(1)
87(1)
85.7(3)
92.9(2)
98.7(3)
a Errors in the least significant figures are presented in parentheses.
tetraphenylborate salts and could not be separated by fractional
recrystallization. The ratio of isomers did not alter on refluxing
in methanol (prior to isolation) or in acetone (after isolation).
The coordination environments of cis-16 and trans-16 are both
[FeP5Cl]+ in which the chloride ligands are necessarily trans
to phosphine. The greater proportion of cis-16 probably
primarily reflects lesser steric encumbrance in this isomer.
In similar reactions, treatment of a methanol solution of cis-1
with the bidentate phosphines BPE5 (2) or DEPE resulted in
complex mixtures of monomeric and dimeric complexes. No
reaction was observed between cis-1 and triphenylphosphine,
and this is probably due to the great steric bulk of this phosphine.
Figure 2. 31P MAS NMR spectra (121 MHz, spin rate 10 kHz): (a)
trans-Fe(BPE5)2I2 (14); (b) cis-Fe(BPE5)2Br2 (cis-13); (c) cis-Fe(BPE5)2-
Cl2 (cis-1).
Phosphine Ligand Displacement Reactions of cis-Fe-
(BPE5)2Cl2 (cis-1). A series of ligand substitution reactions
using the bidentate phosphine ligands BPE5 (2), DMPE (17),
DEPE (18), and DPrPE (19) were performed with complexes
cis-1 and 3-5 to assess the relative chelation strength of BPE5
(2). Ligand substitution was monitored by 31P NMR spectros-
copy.
The bidentate phosphines 18 and 19 did not displace BPE5
(2) from cis-1. After prolonged heating at 70 °C, an equilibrium
concentration of complex trans-1 was established. At 70 °C,
17 displaced BPE5 (2) from cis-1 in approximately 20 min to
give Fe(DMPE)2Cl2 (3). BPE5 (2) readily displaced DEPE and
DPrPE ligands from their respective Fe(PP)2Cl2 complexes (4,
5) at ambient temperature, but displacement of DMPE from 3
to give complexes cis-1 and trans-1 was slow at ambient
temperature but more rapid at 70 °C. The relative chelation
strength of the bidentate phosphines in Fe(PP)2Cl2 complexes
is BPE5 ≈ DMPE > DEPE >DPrPE.
Figure 3. ORTEP plot (25% thermal ellipsoids, non-hydrogen atoms)
-
of the cation [cis-Fe(BPE5)2(CO)(Cl)]+ (15), BPh4 salt.
Where phosphine substitution occurred, the intermediate
mixed-ligand complexes Fe(BPE5)(PP)Cl2 were detected. Com-
plexes Fe(BPE5)(DMPE)Cl2 (20) and Fe(BPE5)(DEPE)Cl2 (21)
are solely trans complexes. The predominant isomer of complex
Fe(BPE5)(DPrPE)Cl2 (22) is also trans; however, an unsym-
metrically substituted cis complex was also detected as a minor
product (<5%) and is assigned as cis-Fe(BPE5)(DPrPE)Cl2 (cis-
22). The propensity for the mixed-ligand complexes 20-22 to
exhibit trans geometries reflects the lesser steric bulk and greater
flexibility of the terminal alkyl groups of ligands 17-19
compared with BPE5 (2); only DPrPE, the bulkiest of the
bidentate ligands studied, gives rise to a cis mixed-ligand
complex (cis-22).
Scheme 2
are shorter in 15 than corresponding bond lengths in cis-1 (Table
2), and this is consistent with the cationic nature of 15. The
phospholane rings adopt almost envelope conformations with
minimum torsion angles in each ring of 2° (P(1)), 5° (P(2)), 0°
(P(3)), and 6° (P(4)).
Treatment of a methanol solution of complex cis-1 with PMe3
gave an equilibrium mixture of the cationic complexes [cis-Fe-
(BPE5)2(PMe3)(Cl)]+ (cis-16) and [trans-Fe(BPE5)2(PMe3)-
(Cl)]+ (trans-16) (∼3:1). The isomers were isolated as the
The characteristic 31P{1H} NMR spectra of the AA′XX′ spin

616 Inorganic Chemistry, Vol. 37, No. 4, 1998
Field et al.
Table 4. 31P NMR Chemical Shifts and Coupling Constants for the AA′XX′ Spin Systems of the Mixed Ligand Complexes
Fe(BPE5)(DMPE)Cl2 (20), Fe(BPE5)(DEPE)Cl2 (21), and Fe(BPE5)(DPrPE)Cl2 (trans-22) and Related Complexes
a
a
complex
δ(PAA′
)
δ(PXX′
)
JAA′, JXX′
JAX ) JA′X
JAX′ ) JA′X
Fe(BPE5)(DMPE)Cl2
Fe(BPE5)(DEPE)Cl2
Fe(BPE5)(DPrPE)Cl2
Fe(DMPE)(DEPE)Cl2
92.84
87.34
87.20
67.74
63.25
63.06
80.61
75.05
57.28
66.18
62.43
55.78
55.99
57.96
9.59
+41.2(1), +41.3(3)
+40.7(2), +41.0(4)
+41.2(1), +41.3(3)
+40.0(7), +40.2(6)
+39.9(2), +39.8(2)
+40.1(3), +40.4(2)
+37.9(3), +44.5(3)
+37.7(3), +44.0(3)
+50.2(3)
+47.6(3)
+46.6(3)
+50.4(5)
+50.2(2)
+47.5(2)
+57.3(2)
+56.5(3)
-144.3(3)
-132.4(3)
-132.5(3)
-132.3(7)
-132.5(2)
-121.4(2)
-150.8(2)
-151.6(3)
b
b
Fe(DMPE)(DPrPE)Cl2
c
Fe(DEPE)(DPrPE)Cl2
b
Fe(DEPE)(DHPE)Cl2
b
Fe(DPrPE)(DHPE)Cl2
9.41
a Chemical shifts of ligands appear in order, with respect to the complex notation in the left-hand column. 31P{1H} NMR spectra were recorded
at 162 MHz and 300 K, in THF unless otherwise stated. Chemical shifts (δ) are referenced to external, neat trimethyl phosphite (taken as δ 140.85
ppm). Coupling constants (in Hz, with uncertainties in parentheses) were determined by computer simulation. JAA′ and JXX′ could not be individually
assigned with the available data. The signs of the coupling constants were assigned by analogy with the complexes reported in ref 14. b In toluene
at 223 K (taken from ref 14). c 223 K (taken from ref 14).
systems of 20, 21, and trans-22 were simulated23 to establish
the chemical shifts and coupling constants of the mixed-ligand
cycles before distillation from potassium benzophenone ketyl under
static high-vacuum conditions (toluene-d8). All bulk compressed gases
were obtained from British Oxygen Co. (BOC Gases). Argon
systems (Table 4).
(>99.99%), nitrogen (>99.5%), and carbon monoxide (>99.5%) were
used as supplied without further purification.
Conclusions
Mass spectra of organometallic complexes were recorded on a
Finnigan MAT TSQ-46 mass spectrometer (San Jose, CA) fitted with
a desorption probe and using chemical ionization (CI, UHP methane
The BPE5 ligand 2 is a strongly chelating ligand of similar
chelation strength to DMPE (17) in Fe(PP)2Cl2 complexes. The
relatively rigid steric bulk of 2 is probably responsible for the
tendency of the Fe(BPE5)2X2 (X ) halide) and [Fe(BPE5)2-
(L)Cl]+ (L ) phosphine or CO) complexes to exhibit cis
coordination geometries. The crystal structures of cis-1 and
15 show that the presence of two BPE5 diphospholane ligands
significantly crowds the remaining two coordination sites. One
chloride ligand of cis-Fe(BPE5)2Cl2 (cis-1) is notably labile
probably due to the steric bulk of the diphospholane ligands in
the complex and also because it is located trans to a phosphine
ligand. The reversible dissociation of chloride from cis-1
accounts for the observed temperature-dependent paramagnetism
and for the ease with which one chloride can be substituted by
other ligands.
> 99.999% or UHP ammonia > 99.999%) with a source temperature
of 140 °C and an electron energy of 100 eV. Data are quoted in the
form x (y), where x is the mass/charge ratio (m/z) and y is the percentage
abundance relative to the base peak. Mass spectra were recorded
scanning mass ranges greater than that of the free phosphine ligand,
typically m/z > 250. Peaks of low intensity are not quoted unless
deemed significant.
Infrared spectra were obtained on a Perkin-Elmer 1600 series FTIR
spectrophotometer. Melting points were determined using a Gallen-
kamp melting point apparatus and are uncorrected. Melting points of
air-sensitive compounds were performed in capillary tubes sealed under
argon. Microanalyses were carried out at the University of New South
Wales, Sydney, Australia.
1H, 31P, and 13C NMR spectra were recorded on a Bruker AMX400
NMR spectrometer at 400.13, 161.98, and 100.61 MHz, respectively,
or on a Bruker AMX600 NMR spectrometer at 600.13 MHz (1H) and
242.94 MHz (31P). All spectra were recorded at 300 K unless otherwise
stated. 1H and 13C NMR spectra are referenced to residual solvent
resonances. 31P NMR spectra are referenced to external neat trimethyl
phosphite taken as 140.85 ppm at the temperature quoted. Chemical
shifts (δ) are quoted in ppm with the downfield direction being taken
as positive. For [cis-Fe(BPE5)2(CO)(Cl)][BPh4] (15), the four distinct
P nuclei were not unambiguously assigned but they were labeled PA-
Experimental Section
All manipulations of air-sensitive phosphines, metal complexes, and
reagents were carried out using standard Schlenk or vacuum tech-
niques24 or in a Vacuum Atmospheres argon-filled drybox.
Anhydrous iron(II) dichloride was prepared by following the
procedure of Leigh et al.25 The phosphines DMPE (17), DEPE (18),
and DPrPE (19) were purchased from Strem and used without further
purification. The iron complexes Fe(DMPE)2Cl2 (3), Fe(DEPE)2Cl2
(4), and Fe(DPrPE)2Cl2 (5) were prepared by literature methods.26 The
ligand BPE5 was prepared as described previously.12
Diethyl ether, tetrahydrofuran, benzene, and toluene were stored over
sodium wire and were distilled under nitrogen from sodium benzo-
phenone ketyl27 immediately prior to use. Absolute methanol was
distilled from magnesium turnings.28 NMR solvents were obtained from
Merck and Cambridge Isotopes and were used as supplied (methanol-
d4 and acetone-d6) or degassed by at least three freeze-pump-thaw
P
D for the purpose of reporting shifts and coupling constants, with PA
and PC being mutually trans. Solid-state 31P MAS NMR spectra were
recorded on a Bruker MSL300 NMR spectrometer at 121.44 MHz at
293 K with a spin rate of 10 kHz. Spectra were referenced to NH4H2-
PO4 taken as δ 1.00 ppm.
cis-Fe(BPE5)2Cl2 (cis-1). A solution of BPE5 (2) (721 mg, 3.57
mmol) in THF (∼5 mL) was added dropwise over 20 min to a solution
of iron(II) chloride (226 mg, 1.78 mmol) in THF (∼15 mL). Upon
addition, the solution turned dark red. The mixture was stirred for 30
min and cis-1 was precipitated from solution. The crude product was
isolated by filtration and recrystallized fromTHF/methanol to give cis-1
as a maroon crystalline solid, mp dec > 119 °C. Yield: 728 mg (77%).
31P{1H} NMR (162 MHz, methanol-d4, 233 K): 93.2, 106.7 (apparent
triplets, splitting ) 40.0 Hz) ppm. 1H{31P} NMR (400 MHz, methanol-
d4, 233 K): 1.36, 1.72, 2.05, 2.17 (8H, 2 PCH2CH2P), 1.44-2.20 (m,
28H), 2.80 (m, 2H), 3.76 (m, 2H) ppm. 13C{1H,31P} NMR (100 MHz,
methanol-d4, 233 K): 26.6, 26.9, 27.1, 27.4, 28.4, 28.5, 29.2, 30.0,
31.6, 33.6 (CH2) ppm. MS (CI, NH3): m/z > 400, 548 (10%,
[Fe(BPE5)235Cl2]NH3+), 533 (56, [Fe(BPE5)235Cl37Cl]H+), 531 (63,
[Fe(BPE5)235Cl2]H+), 497 (34, [Fe(BPE5)237Cl]+), 496 (24, [Fe-
(BPE5)235Cl]H+), 495 (100, [Fe(BPE5)235Cl]+), 460 (23, [Fe(BPE5)2]+),
425 (23); m/z > 300, 348 (65, [Fe(BPE5)35Cl35Cl]NH4+), 346 (100,
(23) Simulations were performed using the computer program PANIC,
Parameter Adjustment in NMR by Iteration and Calculation (Bruker
Spectrospin Pty Ltd.), executed on a Bruker ASPECT 3000 data
station.
(24) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air SensitiVe
Compounds; John Wiley & Sons: New York, 1986.
(25) Hughes, D. L.; Leigh, G. J.; Jimenez-Tenorio, M.; Rowley, A. T. J.
Chem. Soc., Dalton Trans. 1993, 75.
(26) Burt, R. J.; Hussain, W.; Leigh, G. J. J. Organomet. Chem. 1979,
182, 203.
(27) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: London, 1988.
(28) Furnis, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. Vogel’s
Textbook of Practical Organic Chemistry, 5th ed.; Longmans: London,
1989.

Fe-BPE5 Complexes
Inorganic Chemistry, Vol. 37, No. 4, 1998 617
Table 5. Crystal data for cis-Fe(BPE5)2Cl2 (cis-1) and
[Fe(BPE5)35Cl2]NH4+). Anal. Calcd for C20H40P4Cl2Fe: C, 45.22; H,
7.59. Found: C, 45.0; H, 7.8.
[cis-Fe(BPE5)2(CO)(Cl)][BPh4] (15)
cis-Fe(BPE5)2Br2 (cis-13). A deep red solution of cis-1 (275 mg,
518 mol) in methanol (∼10 mL) was treated with a solution of lithium
bromide (88 mg, 2.1 mmol, ∼4 equiv) in methanol (∼2 mL). The
color of the solution turned dark purple almost immediately, and a
purple crystalline solid precipitated from solution. The crude product
was recrystallized from hot toluene to give cis-Fe(BPE5)2Br2‚H2O (cis-
13) as large purple air-stable cubic crystals, mp dec > 306 °C. Yield:
238 mg (75%). 31P{1H} NMR (162 MHz, toluene-d8): 86.7, 106.6
(apparent triplets, splitting ) 37.5 Hz) ppm. 1H{31P} NMR (400 MHz,
toluene-d8): 0.89 (m, 2H), 1.03 (m, 2H), 1.08 (m, 2H), 1.42 (m, 2H),
1.56-1.81 (m, 12H), 1.87 (m, 2H), 1.91-2.37 (m, 16H), 3.82 (m, 2H)
ppm. 13C{1H,31P} NMR (100 MHz, toluene-d8): 27.2, 28.4, 28.5, 28.6,
29.3, 30.1, 30.2, 32.4, 32.7, 34.4 (CH2) ppm. MS (CI, CH4): m/z >
350, 623 (9, [Fe(BPE5)281Br2]H+), 622 (33, [Fe(BPE5)281Br2]+), 621
(23, [Fe(BPE5)279Br81Br]H+), 620 (73, [Fe(BPE5)279Br81Br]+), 619 (17,
cis-Fe(BPE5)2Cl2
[cis-Fe(BPE5)2(CO)-
(Cl)][BPh4] (15)
(cis-1)
empirical formula
fw, g mol-1
space group
a, Å
b, Å
c, Å
C24H48Cl2FeP4O
603.29
C45H60BClFeO1.25P4
846.97
P21/n (#14)
12.084(3)
14.059(2)
17.665(2)
101.77(1)
2938.0(8)
1.364
P21/a (#14)
12.938(3)
29.647(4)
13.131(3)
107.89(2)
4793(2)
1.174
â, deg
cell vol, Å3
calcd density, g cm-3
Z
4
4
λ(Cu KR), Å
1.541 78
79.66
0.072
1.541 78
45.30
0.092
µ, cm-1
R(Fo)a
Rw(Fo)a
0.068
0.087
[Fe(BPE5)279Br2]H+), 618 (45, [Fe(BPE5)279Br2]+), 542 (23, [Fe(BPE5)281
-
Br]H+), 541 (89, [Fe(BPE5)281Br]+), 540 (28, [Fe(BPE5)279Br]H+), 539
(100, [Fe(BPE5)279Br]+), 420 (21, [Fe(BPE5)81Br2]+), 418 (44,
[Fe(BPE5)79Br 81Br2]+), 416 (25, [Fe(BPE5)79Br2]+). Anal. Calcd for
C20H40P4Br2Fe‚H2O: C, 37.64; H, 6.64. Found: C, 37.7; H, 6.9.
trans-Fe(BPE5)2Br2 (trans-13). A round bottom flask containing
dark purple crystals of anhydrous cis-13 (65 mg, 100 mol) was heated
gently to 225 °C under vacuum (to prevent aerial oxidation). At 220-
221 °C, the solid turned green and trans-13 was isolated as a bright
green air stable solid, mp dec > 306 °C. Yield: 65 mg (100%). 31P-
{1H} NMR (162 MHz, toluene-d8): 92.5 (s) ppm. 1H{31P} NMR (400
MHz, toluene-d8): 1.90-2.12 (m, 24H), 2.22 (s, 8H, PCH2CH2P), 2.38
(m, 8H) ppm. 13C{1H,31P} NMR (100 MHz, toluene-d8): 28.8, 29.1
(PCH2CH2), 31.0 (PCH2CH2P) ppm.
a R ) ∑(||Fo| - |Fc||)/∑|Fo|; Rw ) (∑w(|Fo| - |Fc|)2/∑wFo )1/2; w
2
) 1/σ2(Fo).
188 mol) in methanol (∼5 mL). The deep red solution turned pale
red, from which a dark pink solid was precipitated on addition of excess
sodium tetraphenylborate in methanol. Recrystallization of the pre-
cipitate from acetone gave [Fe(BPE5)2(PMe3)Cl][BPh4] (16) as a pink
microcrystalline solid consisting of two isomers cis-16 and trans-16
(∼3:1), mp dec > 228 °C. Yield: 162 mg (97%). 31P{1H} NMR
(162 MHz, acetone-d6): cis-16, 9.7 (1P, complex m, PMe3) 85.8 (2P,
complex m), 88.6 (1P, complex m), 93.4 (1P, complex m) ppm; trans-
2
16, 24.5 (1P, p, JP-PMe ) 48.8 Hz, PMe3), 91.0 (4P, d) ppm. 1H-
3
{31P} NMR (400 MHz, acetone-d6): cis-16: 1.58-2.47 (m, -CH2-),
1.75 (s, 9H, P(CH3)3), 6.92 (m, 4H, BArHpara), 7.07 (m, 8H, BArHmeta),
7.48 (m, 8H, BArHortho) ppm. 13C{1H,31P} NMR (100 MHz, acetone-
d6): 22.7 (d, 1JP-Me ) 21.0, PCH3), 26.2, 26.6, 27.0, 27.9, 28.0, 28.6,
28.7, 28.8, 29.0, 29.0, 29.0, 29.1, 29.4, 30.7, 32.0, 31.4, 31.7, 32.3,
33.3, 34.3 (CH2), 122.6 (ArCpara BPh4-), 126.3 (ArCortho, BPh4-), 137.5
(ArCmeta, BPh4-), 165.5 (m, ArCipso, BPh4-) ppm. MS (CI, CH4): m/z
> 400, 572 (1%, [Fe(BPE5)2(PMe3)35Cl]+), 537 (9, [Fe(BPE5)2(PMe3)]-
H+), 536 (8, [Fe(BPE5)2(PMe3)]+), 498 (10, [Fe(BPE5)237Cl]H+), 497
(37, [Fe(BPE5)237Cl]+), 496 (25, [Fe(BPE5)235Cl]H+), 495 (100,
[Fe(BPE5)235Cl]+). Anal. Calcd for C47H69P5BClFe: C, 63.35; H, 7.80.
Found: C, 63.1; H, 7.9.
trans-Fe(BPE5)2I2 (14). A deep red solution (∼10 mL) of cis-1
(103 mg, 194 mol) in methanol (∼10 mL) was treated with a solution
of excess sodium iodide (120 mg, 800 mol, ∼4 equiv) in methanol
(∼2 mL). The color of the solution turned royal blue, and a green
solid was precipitated within 30 s. The solid was isolated by filtration
and washed with methanol to give trans-Fe(BPE5)2I2 (14) as a green
microcrystalline solid, mp dec > 352 °C. Yield: 71 mg (64%). 31P-
{1H} MAS NMR (121 MHz, 293 K): 93.2 ppm. MS (CI, CH4): m/z
> 350, 715 (22%, [Fe(BPE5)2I2]H+), 714 (100, [Fe(BPE5)2I2]+), 588
(24, [Fe(BPE5)2I]H+), 587 (53, [Fe(BPE5)2I]+), 513 (12, [Fe(BPE5)-
I2]H+), 512 (30, [Fe(BPE5)I2]+), 384 (42, [Fe(BPE5)I]+). Anal. Calcd
for C20H40P4I2Fe: C, 33.64; H. 5.65. Found: C, 33.6; H, 5.9.
[cis-Fe(BPE5)2(CO)(Cl)][BPh4] (15). A solution of cis-1 (98 mg,
180 mol) in methanol (∼5 mL) was stirred under an atmosphere of
carbon monoxide for approximately 30 min. The color of the deep
red solution gradually turned yellow. A yellow solid was precipitated
from solution on addition of excess sodium tetraphenylborate in
methanol. The crude product was isolated by filtration and recrystal-
X-ray Crystallography. The crystal data for complexes cis-1 and
15 are reported in Table 5. The crystals of each complex (cis-1 and
15) were obtained by slow evaporation of THF/methanol and acetone
solutions, respectively. Crystals of each complex were inserted into
glass capillaries and mounted on a Rigaku AFCR7 diffractometer
employing a graphite-monochromated Cu KR radiation.
Primitive monoclinic cell constants for the dichloride complex cis-1
were obtained from a least-squares refinement using the setting angles
of 25 reflections in the range 19.47 < 2θ < 27.36°. ω scans of several
intense reflections, made prior to data collection, had an average width
at half-height of 0.16°. Data were collected with ω/2θ scans (0.79 +
0.35 tan θ) at a speed of 32.0°/min (ω). The weak reflections
(I < 15.0σ(I)) were rescanned (maximum of 10 scans), and the counts
were accumulated. Stationary background counts were recorded on
each side of the reflection, and the ratio of peak counting time to
background counting time was 2:1. The intensities of three representa-
tive reflections measured every 150 reflections decreased by 10.1%,
and accordingly a linear correction was applied to the data. An
empirical absorption correction based on azimuthal scans of three
reflections resulted in transmission factors ranging from 0.84 to 0.99.
The data were corrected for Lorentz and polarization effects, and a
small correction for secondary extinction was also applied (coefficient
) 2.44 × 10-6).
lized from acetone to give [cis-Fe(BPE5)2(CO)(Cl)]+BPh4 (15) as a
-
yellow, air-stable microcrystalline solid, mp dec > 303 °C. Yield: 136
mg (96%). Cation 15 was also synthesized in methanol-d4 and was
characterized by NMR spectroscopy without isolation. 31P{1H} NMR
(243 MHz, methanol-d4, 233 K): 80.5 (1P, ddd, 2JP(A)-P(D) ) 40.0 Hz,
2JP(B)-P(D) ) 60.0 Hz, 2JP(C)-P(D) ) 53.2 Hz, PD), 87.2 (1P, ddd, 2JP(B)-P(C)
2
2
) 23.6 Hz, JP(A)-P(C) ) 106.3 Hz, PC), 92.2 (1P, ddd, JP(A)-P(B)
)
33.3 Hz, PB), 93.0 (1P, ddd, PA) ppm. 1H{31P} NMR (600 MHz,
methanol-d4, 233 K): 1.46, 1.48, 1.89, 2 2.04, 2.10, 2.20, 2.28 ppm
(8H, 2 PCH2CH2P); 1.51-2.17 ppm (m, 28H, CH2); 2.33 (m, 1H,
CHH), 2.39 (m, 1H, CHH), 2.60 (m, 2H, CH2) ppm. 13C{1H,31P} NMR
(100 MHz, methanol-d4, 233 K): 26.8, 27.0, 27.4, 27.5, 27.7, 27.8,
28.5, 28.6, 2 28.7, 29.2, 29.4, 29.5, 29.7, 30.1, 30.3, 30.4, 31.0, 31.7,
32.4 (CH2), 185.0 (CO) ppm. MS (CI, CH4): m/z > 400, 523 (3%,
[Fe(BPE5)2(CO)35Cl]+), 498 (4, [Fe(BPE5)237Cl]H+), 497 (20, [Fe-
35
(BPE5)237Cl] +), 496 (20, [Fe(BPE5)235Cl]H+), 495 (67, [Fe(BPE5)2
-
Cl]+), 489 (56, [Fe(BPE5)2(CO)]H+), 488 (100, [Fe(BPE5)2(CO)]+),
461 (7, [Fe(BPE5)2]H+), 460 (4, [Fe(BPE5)2]+). IR (νmax, Nujol): 1965
(s, CO) cm-1. Anal. Calcd for C45H60P4BClOFe: C, 64.12; H, 7.18.
Found: C, 63.7; H, 7.1.
Primitive monoclinic cell constants for complex 15 were obtained
from a least-squares refinement using the setting angles of 25 reflections
in the range 20.37 < 2θ < 40.00°. ω scans of several intense
reflections, made prior to data collection, had an average width at half-
height of 0.33°. Data were collected with ω/2θ scans (1.00 + 0.35
tan θ) at a speed of 8.0°/min (ω). The weak reflections (I < 15.0σ(I))
[Fe(BPE5)2(PMe3)(Cl)][BPh4] (16). Trimethylphosphine (20 mg,
270 mol, 1.4 equiv) was condensed into a solution of cis-1 (100 mg,

618 Inorganic Chemistry, Vol. 37, No. 4, 1998
Field et al.
were rescanned up to 10 times, and the counts were accumulated.
Background counts were calculated using a Lehmann-Larsen routine.29
The intensities of three representative reflections measured every 150
reflections did not change significantly during the data collection. An
analytical absorption correction was applied to the data, and the data
were also corrected for Lorentz and polarization effects.
In the crystals of 1 and 15, both enantiomers were observed and the
crystals contain racemic mixtures. All calculations were performed
using the teXsan30 crystallographic software package. The structures
were solved by direct methods31 and expanded using Fourier tech-
niques.32 With the exception of a solvate oxygen in complex 15, the
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. In complex 15,
no hydrogen atoms were attached to the solvate oxygen atom, the
population of which was initially refined and then fixed at 0.25. The
refinements converged, with the largest parameter shift to estimated
standard deviation ratio being 0.01 in both cases. The structure of
complex 15 is of poor quality, with the carbonyl group being particularly
ill-defined. The short CdO bond and the near nonpositive definite
nature of the carbonyl carbon may simply reflect the poor crystal quality
but may also be the result of a minor mixed occupancy of the carbonyl
and chloro sites. Neutral atom scattering factors were taken from
Cromer and Waber.33 Anomalous dispersion effects were included in
the structure factor calculation,34 and the values for ∆f ′ and ∆f ′′ were
those of Creagh and McAuley.35a The values for the mass attenuation
coefficients are those of Creagh and Hubbell.35b
Acknowledgment. We gratefully acknowledge financial
support from the Australian Research Council.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for complexes cis-Fe(BPE5)2Cl2 (cis-1) and [cis-Fe-
(BPE5)2(CO)(Cl)][BPh4] (15) are available on the Internet only. Access
information is given on any current masthead page.
(29) Lehman, M. S.; Larsen, F. K. Acta Crystallogr. 1974, A30, 580.
(30) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corp.: The Woodlands, TX, 1985, 1992.
(31) SIR92: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr. 1993,
26, 343.
IC9701928
(33) 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.
(32) 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 of the Crystallography Laboratory;
University of Nijmegen: Nijmegen, The Netherlands, 1994.
(34) Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(35) (a) Creagh, D. C.; McAuley, W. J. International Tables for Crystal-
lography; Kluwer Academic Publishers: Boston, MA, 1992; Vol. C,
Table 4.2.6.8, pp 219-222. (b) Ibid., Table 4.2.4.3, pp 200-206.