1,1′-diphosphaferrocene derivatives for labeling of molecules of biological interest. The X-ray molecular structures of 4-oxo-4-(3,3′,4, 4′-tetramethyl-1,1′-diphosphaferrocen-2-yl)butanoic acid and its bis-W(CO)5 complex

Article abstract of DOI:10.1021/om9803117

3,3′,4,4′-Tetramethyl-1,1′-diphosphaferrocene (1) reacts with succinic anhydride in the presence of AlCl₃ to give 4-oxo- 4-(3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocen-2-yl)butanoic acid (2) in 80% yield. This complex treated with 1 equiv of W(CO) ₅(THF) gave a mixture of the products in which the W(CO)₅ moiety is coordinated to P(1′) (3a) and to P(1) (3b) in the ratio ～ 7:1. With two equiv of W(CO)₅(THF) the bis-W(CO)₅ adduct (4) was obtained and transformed into the corresponding N-succinimidyl ester (5) by treatment with N-hydroxysuccinimide in dichloromethane in the presence of DCC (dicyclohexylcarbodiimide). This activated ester reacts with benzylamine and glycine methyl ester to give the corresponding amides in good yields. The crystal structures of 2 and 4 have been determined by X-ray diffraction. Both structures show unexpected conformations with short intramolecular P- - -P distances, indicating secondary bonding between phosphorus atoms. This contrasts with the X-ray structure of 1 displaying longer P- - -P distance (no secondary bonding) and theoretical calculations showing destabilizing, repulsive P- - -P interactions in the 1,1′-diphosphaferrocene system (Ashe, A. J., III; Al-Ahmad, S. Adv. Organomet. Chem 1996, 39, 325, and references therein). Apparently, conformational preferences of 1,1′-diphosphaferrocenes are small, since they are so easily changed by small changes in the substitution. Furthermore, the structure of 2 shows intermolecular P- - -P secondary bonding, giving rise to the formation of stacking columns along the z axis. The structural differences between 2 and 4 and between the W(CO)₅ moiety in 4 and this moiety coordinated to nitrogen in W(CO)₅-(azaferrocene) complexes have also been analyzed.

Full text of DOI:10.1021/om9803117

5880
Organometallics 1998, 17, 5880-5886
1,1′-Dip h osp h a fer r ocen e Der iva tives for La belin g of
Molecu les of Biologica l In ter est. Th e X-r a y Molecu la r
Str u ctu r es of 4-Oxo-4-(3,3′,4,4′-tetr a m eth yl-
1,1′-d ip h osp h a fer r ocen -2-yl)bu ta n oic Acid a n d Its
Bis-W(CO)5 Com p lex
J anusz Zakrzewski* and Arkadiusz Kłys
Department of Organic Chemistry, University of Ło´dz´, 90-136 Ło´dz´, Narutowicza 68, Poland
Maria Bukowska-Strzyz˘ ewska* and Anita Tosik
Institute of General and Ecological Chemistry, Technical University of Ło´dz´, 90-924 Ło´dz´,
Z˙ wirki 36, Poland
Received April 23, 1998
3,3′,4,4′-Tetramethyl-1,1′-diphosphaferrocene (1) reacts with succinic anhydride in the
presence of AlCl3 to give 4-oxo- 4-(3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocen-2-yl)butanoic
acid (2) in 80% yield. This complex treated with 1 equiv of W(CO)5(THF) gave a mixture of
the products in which the W(CO)5 moiety is coordinated to P(1′) (3a ) and to P(1) (3b) in the
ratio ∼ 7:1. With two equiv of W(CO)5(THF) the bis-W(CO)5 adduct (4) was obtained and
transformed into the corresponding N-succinimidyl ester (5) by treatment with N-hydroxy-
succinimide in dichloromethane in the presence of DCC (dicyclohexylcarbodiimide). This
activated ester reacts with benzylamine and glycine methyl ester to give the corresponding
amides in good yields. The crystal structures of 2 and 4 have been determined by X-ray
diffraction. Both structures show unexpected conformations with short intramolecular
P- - -P distances, indicating secondary bonding between phosphorus atoms. This contrasts
with the X-ray structure of 1 displaying longer P- - -P distance (no secondary bonding) and
theoretical calculations showing destabilizing, repulsive P- - -P interactions in the 1,1′-
diphosphaferrocene system (Ashe, A. J ., III; Al-Ahmad, S. Adv. Organomet. Chem 1996, 39,
325, and references therein). Apparently, conformational preferences of 1,1′-diphosphafer-
rocenes are small, since they are so easily changed by small changes in the substitution.
Furthermore, the structure of 2 shows intermolecular P- - -P secondary bonding, giving rise
to the formation of stacking columns along the z axis. The structural differences between 2
and 4 and between the W(CO)5 moiety in 4 and this moiety coordinated to nitrogen in W(CO)5-
(azaferrocene) complexes have also been analyzed.
In tr od u ction
cal and medicinal interest such as proteins, peptides,
nucleic acids, and currently used medications.1-4 Such
complexes can be used as labeling reagents in studies
of high-affinity interactions such as hormone-receptor,
enzyme-substrate, and antigen (hapten)-antibody in-
teractions, in DNA hybridization tests or as carriers of
radioisotopes in nuclear medicine. The bioconjugates can
Recently, there has been considerable interest toward
the synthesis of organo-transition metal complexes
which form stable conjugates with molecules of biologi-
(1) (a) Ryabov, A. D. Angew. Chem., Int. Ed. Engl. 1991, 30, 931.
(b) J aouen, G.; Vessieres, A.; Butler, I. S. Acc. Chem. Res. 1993, 26,
361. (c) Kramer, R. Angew. Chem., Int. Ed. Engl. 1996, 35, 1197.
(2) (a) Beaucourt, J . P.; Le Borgne, F. Tetrahedron Lett. 1988, 29,
5649. (b) Sasaki, N. A.; Potier, P.; Savignac, M.; J aouen, G. Tetrahedron
Lett. 1988, 29, 5759. (c) Varenne, A.; Salmain, M.; Brisson, C.; J aouen,
G. Bioconjugate Chem. 1992, 3, 471. (d) Salmain, M.; Gunn, M.; Gorfti,
A.; Top, S.; J aouen, G. Bioconjugate Chem. 1993, 4, 425. (e) Salmain,
M.; Malisza, K. L.; Top, S.; J aouen, G.; Senechechal-Tocquer, M.-C.;
Senechal, D.; Caro, B. Bioconjugate Chem. 1994, 5, 655. (f) Rudolf, B.;
Zakrzewski, J . Tetrahedron Lett. 1994, 35, 9611. (g) Malisza, K. L.;
Top, S.; Vaissermann, J .; Caro, B.; Senechal-Tocquer, M.-C.; Senechal,
D.; Saillard, J .-Y.; Triki, S.; Kahlal, S.; Britten, J . S.; McGlinchey, M.
J .; J aouen, G. Organometallics 1995, 14, 5273. (h) El Amouri, H.;
Canceil, S.; Besace, Y.; Ricard, L. Organometallics 1996, 15, 2303. (i)
Osella, D.; Ravera, M.; Vincenti, M.; Salmain, M.; J aouen, G. Orga-
nometallics 1996, 15, 3037. (j) Blanalt, S.; Salmain, M.; Malezieux,
B.; J aouen, G. Tetrahedron Lett. 1996, 37, 6561. (k) Rudolf, B.;
Zakrzewski, J . J . Organomet. Chem. 1996, 322, 313. (l) Kazimierczak,
A.; Zakrzewski, J .; Salmain, M.; J aouen, G. Bioconjugate Chem. 1997,
8, 489.
(3) (a) Wang, Z.; Roe, B. A.; Nicholas, K. M.; White, R. L. J . Am.
Chem. Soc. 1993, 115, 4399. (b) Dalla Riva Toma, J . M.; Bergstrom,
D. E. J . Org. Chem. 1994, 59, 2418. (c) Sloop, F. V.; Brown, G. M.;
Sachleben, R. A.; Garrity, M. L.; Elbert, J . E.; J acobson, K. B. New J .
Chem. 1994, 18, 317. (d) Mucic, R. C.; Herrlein, M. K.; Mirkin, C. A.;
Letsinger, R. L. J . Chem. Soc., Chem. Commun. 1996, 555.
(4) (a) Scutaru, D.; Tataru, L.; Mazilu, I.; Vata, M.; Lixandru, T.;
Simonescu, C. Appl. Organomet. Chem. 1993, 7, 225. (b) Limoges, B.;
Dagrand C.; Brossier, P.; Blankespoor, R. L. Anal. Chem. 1993, 65,
1054. (c) Top, S.; El Hafa, H.; Vessieres, A.; Quivy, J .; Vaissermann,
J .; Hughes, D. W.; McGlinchey, M. J .; Mornon, J .-P.; Thoreau, E.;
J aouen., G. J . Am. Chem. Soc. 1995, 117, 8372. (d) Lavastre, I.;
Besancon, J .; Moise, C.; Brossier, P. Bull. Soc. Chim. Fr. 1995, 132,
188. (e) Kowalski, K.; Zakrzewski, J . Polyhedron 1998, 17, 2563.
(5) (a) Cais, M.; Dani, S.; Eden, I.; Gandalfi, O.; Horn, M.; Isaacs,
E.; J osephy, I.; Saar, I.; Slovin, E.; Snarsky, L. Nature 1977, 534. (b)
Cais, M. In Methods in Enzymology; Longone, J . J ., Van Vunakis, H.,
Eds.; Academic Press: New York, 1983.
10.1021/om9803117 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 12/03/1998

1,1′-Diphosphaferrocene Derivatives
Organometallics, Vol. 17, No. 26, 1998 5881
be readily detected and quantified by various techniques
including atomic absorption spectroscopy (AAS),5 elec-
trochemical methods,6 and Fourier transform IR spec-
troscopy.7 In the latter case metal carbonyl labels are
used, detectable in the region of the stretching vibra-
tions of coordinated CO (2100-1850 cm-1), where bio-
molecules and biological matrixes are practically trans-
parent. An immunoassay technique using metal carbonyl
markers (carbonylmetalloimmunoassay, CMIA) was
recently introduced and successfully applied for simul-
taneous quantification of two or three haptenes.7c,d
Th e fer r ocen e m oiety has been coupled with redox
enzymes such as glucose and galactose oxidases to
enable electronic communication between the enzyme
and an electrode (“wiring” of enzymes)8 and with a
variety of medications to afford tracers for electroim-
munoassays.9 Ferrocenyl amino acids have also been
synthesized for incorporation into a polypeptide chain
to study the role of the peptidic backbone in electron-
transfer processes.10 Finally, ferrocene probes are widely
used in studies of molecular recognition processes.11
The last two decades have witnessed a remarkable
progress in synthetic methods and in the understanding
of the structure and reactivity of 1,1′-diheteroferrocenes
of the group 15 elements.12 Similarly to ferrocene, these
complexes display more or less reversible redox chem-
istry, but additionally they are able to bind one or two
metal centers through the heteroatom lone pairs.13 In
our opinion these features make them particularly
interesting as versatile labeling reagents for in vitro
assays, with potential applications in redox enzyme
assays or electroctrochemical immunoassays, carbonyl-
metalloimmunoassays (when a metal carbonyl fragment
is bound to the heterometallocene), and radioimmuno-
therapy (when a suitable radioactive metal fragment is
bound to the heterometallocene moiety linked, for
example, to an antibody). Obviously these anticipated
applications will require a detailed knowledge of biologi-
cal properties of 1,1′-diheteroferrocenes such as their
stability in biological media, ability to cross biological
membranes, or toxicity.
In this paper we describe the synthesis, starting from
the readily available 3,3′4,4′-tetramethyl-1,1′-diphos-
phaferrocene (1),14 of 4-oxo-4-(3,3′,4,4′-tetramethyl-1,1′-
diphospha-2-ferrocenyl)butanoic acid (2), its mono-
W(CO)5 complexes 3a and 3b, the bis-W(CO)5 complex
4, and corresponding active N-succinimidyl (NS) ester
5.
This ester is a potential metallocarbonyl diphospha-
ferrocenyl labeling reagent for biomolecules containing
amino groups. Its reactivity was tested toward model
compounds: benzylamine and glycine methyl ester.
Finally, we have determined the X-ray structures of 2
and 4. These structures shed new light on the hitherto
unclear conformational preference in the 1,1′-diphos-
phaferrocene system and on secondary bonds involving
phosphorus atoms.
Exp er im en ta l Section
Gen er a l Rem a r k s. All reactions were carried out under
an atmosphere of argon. Solvents were dried by using standard
procedures. Chromatographic purifications were carried out
on Silica gel 60 (230-400 mesh ASTM), purchased by Merck,
using chloroform as eluent. The NMR spectra were determined
1
on Varian Gemini 200 BB (200 MHz for H) in CDCl3 solutions.
They were calibrated by using internal Me4Si (1H and 13C) or
external 85% H3PO4 (31P) references. IR spectra were run on
a Specord 75 IR spectrometer. The combustion analyses were
determined by Analytical Services of the Center of Molecular
and Macromolecular Studies of the Polish Academy of the
Sciences (Ło´dz´). 3,4,3′,4′-Tetramethyl-1,1′-diphosphaferrocene
(1) was prepared according to the earlier published proce-
dure.14
4-Oxo-4-(3,3′,4,4′-tetr a m eth yl-1,1′-d ip h osp h a -2-fer r oce-
n yl)bu ta n oic Acid , 2. To a stirred and cooled to 0 °C
suspension of succinic anhydride (0.324 g, 3.24 mmol) in
dichloromethane (10 mL) was added AlCl3 (0.573 g, 4.32 mmol)
in one portion, and then a solution of DPF (0.600 g, 2.16 mmol)
in dichloromethane (5 mL) was slowly added (addition time
approximately 45 min). The resulting mixture was refluxed
for 3.5 h and hydrolyzed with a mixture of 2 M HCl (15 mL)
with ice. The organic layer was separated, and the water layer
was extracted with chloroform (3 × 15 mL). The combined
extracts were dried with sodium sulfate and evaporated to
dryness. Column chromatography (eluent chloroform) and
crystallization (dichloromethane-hexanes) afforded pure 2.
(6) (a) Osella, D.; Gambino, O.; Dutto, G. C.; Nervi, C.; J aouen,
Vessieres, A. Inorg. Chim. Acta 1994, 218, 207. (b) La Gal La Salle,
A.; Limoges, B.; Degrand, C.; Brossier, P. Anal. Chem.1995, 67, 1245.
(b) Limoges, B.; Degrand, C. Anal. Chem. 1996, 68, 4141.
(7) (a) Salmain, M.; Vessieres, A.; J aouen, G.; Butler, I. S. Anal.
Chem. 1991, 63, 2323. (b) Varenne, A.; Vessieres, A.; Brossier, P.;
J aouen, G. Res. Commun. Chem. Pathol. Pharmacol. 1994, 84, 81. (c)
Varenne, A.; Vessieres, A.; Salmain, M.; Brossier, P.; J aouen, G.
Immunoanal. Biol. Spectrosc. 1994, 9, 205. (d) Varenne, A.; Vessieres,
A.; Salmain, M.; Durand, S.; Brossier, P.; J aouen, G. Anal. Biochem.
1996, 242, 172.
(8) (a) Degani, Y.; Heller, A. J . Phys. Chem. 1987, 91, 1285. (b)
Degani, Y.; Heller, A. J . Am. Chem. Soc. 1988, 110, 2615. (c) Heller,
A. J . Chem. Phys. 1992, 96, 3579.
(9) (a) La Gal La Salle, A.; Limoges, B.; Degrand, C.; Brossier, P.
Anal. Chem. 1995, 67, 1245.
1
Yield: 0.650 g (80%). Mp: 146-148 °C (decomp). H NMR: δ
3.99 (d, J P-H ) 36.6 Hz, 1H, H-5); 3.73 and 3.69 (dd, J P-H
)
36.0 Hz, J H-H ) 2.0 Hz, 1H, 1H, H-2′ and H-5′); 2.99 (m, 2H,
CH2); 2.62 (m, 2H, CH2); 2.39, 2.10, 2.06, 1.98 (singlets, each
3H, Me’s).13 C NMR: δ 205.2 (d, J C-P ) 21.7 Hz, CO-ketone);
178.2 (s, CO-acid); 102.6 (d, J C-P ) 7.6 Hz), 99.27 (d, J C-P
)
7.3 Hz), 99.08 (d, J C-P ) 7.2 Hz) and 97.38 (d, J C-P ) 5.0 Hz);
C3,C3′, C4,′C4′, 84.1-82.4 (m, C2,C2′,C5,C5′); 37.32 (d, J C-P
) 12.3 Hz, CH2), 28.41 (br s CH2), 15.40, 14.58, 14.04, (s, Me’s).
31P NMR: δ -68.68 (td, J P-P ) 14.9 Hz, J P-H ) 36.0, P1′);
-53.15 (dd, J P-P ) 14.9 Hz, J P-H ) 36.6 Hz, P1). IR (CHCl3):
3300, 2080, 1995, 1720, 1670. Anal. Calcd for C16H20P2FeO3:
C, 50.82; H, 5.33. Found: C, 50.43; H, 5.41.
(10) Kraatz, H.-B.; Lusztyk, J .; Enright, G. D. Inorg. Chem. 1997,
36, 2400.
(11) For a recent survey see: Beer, D. Acc. Chem. Res. 1998, 31, 71.
(12) (a) Mathey, F. New J . Chem. 1987, 11, 585. (b) Mathey, F. J .
Organomet. Chem. 1990, 400, 149. (c) Dillon, K. B.; Mathey, F.; Nixon,
J . F. Phosphorus: The Carbon Copy; J . Wiley; Chichester, 1998. (d)
Ashe, A. J ., III; Kampf, J . W.; Pilotek, S.; Rousseau, R. Organometallics
1994, 13, 4067. (e) Ashe, A. J ., III; Al-Ahmad, S.; Pilotek, S.; Puranik,
D. B.; Elschenbroich, C.; Behrendt, A. Organometallics 1995, 14, 2689.
(f) Ashe, A. J ., III; Al-Ahmad, S. Adv. Organomet. Chem. 1996, 39,
325. (g) Kostic, N.; M.; Fenske, R. Organometallics 1983, 2, 1008. (h)
Guimon, C.; Gonbeau, D.; Pfister-Guillouzo, G.; de Lauzon, G.; Mathey,
F. Chem. Phys. Lett. 1984, 3, 1303. (i) Su, M.-D.; Chu, S.-Y. J . Phys.
Chem. 1989, 93, 6043.
Rea ction of 2 w ith W(CO)5(THF ). A solution of W(CO)5-
(THF) was prepared by irradiation through Pyrex (external
200 W high-pressure mercury lamp) of W(CO)6 (0.352 g, 1.0
mmol) in THF (150 mL) at room temperature for 1.5 h. In a
separate experiment this solution was treated with pyridine.
The amount of W(CO)5(py) isolated by column chromatography
indicated that 0.79 mmol of W(CO)5(THF) was generated
(assuming that reaction with pyridine proceeds quantitatively).
(13) Deschamps, B.; Mathey, F.; Fischer, J .; Nelson, J . H. Inorg.
Chem. 1984, 23, 3455.
(14) Mathey, F.; De Lauzon, G. Organometallic Synthesis; Elsevi-
er: Amsterdam, 1986; p 259.

5882 Organometallics, Vol. 17, No. 26, 1998
Zakrzewski et al.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Deta ils
The photolyte was treated with 2 (0.095 mg, 0.25 mmol), and
the resulting solution was stirred at room temperature for 2
h. Removal of solvent, column chromatography (eluent chlo-
roform), and crystallization (CH2Cl2-hexanes) afforded pure
4. Yield: 0.227 g (88%). Mp: 137-139 °C.
2
4
Crystal Data
16H20FeO3P2
formula
C
C26H20FeO13P2W2
1H NMR: δ 4.47 (dd, J P-H ) 33.1 Hz, J H-H ) 1.4 Hz, 1H,
H2′ or H5′); 4.16 (dt, J C-P ) 32.8 Hz, J H-H ) 1.4 Hz, 1H, H5);
3.52 (dd, J P-H ) 33.1 Hz, J H-H ) 1.4 Hz, 1H, H2′ or H5′), 2.92
(m, 2H, CH2) 2.70 (m, 2H, CH2); 2.37, 2.19, 2.13, 1.95 (singlets,
each 3H, Me’s). 13C NMR: δ 201.22 (d, J C-P ) 16.4 Hz, CO-
source of material
red irregular pillars
red irregular pillars
and habit
crystal dimens, mm
space group
Z
a, Å
b, Å
c, Å
0.15 × 0.2 × 0.2
P21/n
8
11.367(2)
22.166(3)
14.129(3)
112.36(1)
3292(1)
1.12
0.15 × 0.2 × 0.3
P21/c
4
11.548(2)
11.201(2)
24.902(5)
95.31(3)
3207(1)
7.76
ketone); 196.80 (d, J
) 33.9 Hz) and 196.69 (d, J C-P ) 32.7
C-P
Hz); W-CO trans to P; 194.27(d, J C-P ) 8.2 Hz, W-CO cis to
P) and 193.92(d, J C-P ) 8.5 Hz, W-CO cis to P); 178.08, (s,
CO-acid); 99.61, 99.39, 97.76, 94.98 (doublets, J C-P ) 4.2 Hz,
C3,C4,C3′,C4′); 86.16 (d, J C-P ) 9.9 Hz, C1); 79.35, 79.14, 77.49
(singlets, C1′, C4,C4′); 39.47, 27.82 (singlets, CH2CH2); 16.40
(d, J C-P ) 4.8 Hz, Me), 13.9 (m, Me’s). 31P NMR: δ -27.78 (d,
J P-H ) 32.8 Hz, satellite bands J W-C ) 266.1 Hz, P1); -36.98
(t J P-H ) 33.1, satellite bands J W-C ) 264.5 Hz, P1′). IR
(CHCl3): 2080, 1995, 1960, 1720, 1670. Anal. Calcd for
â, deg
V, Å3
linear abs coeff (µ),
mm-1
Data Collection
Siemens P3
Mo KR (0.710 73)
293(2)
ω/2θ
1.8-48.0
diffractometer
radiation type (λ), Å
temp, K
scan type
2θ scan range, deg
Siemens P3
Mo KR (0.710 73)
293(2)
ω/2θ
1.8-48.0
-15 e h e 14;
0 e k e 14;
0 e l e 32
4940
4818 (Rint ) 0.0173)
4155
C
26H20O13P2FeW2: C, 30.44; H, 1.96. Found: C, 30.80; H, 2.11.
data collected (h, k, l) -13 e h e 14;
-28 e k e 0;
-18 e l e 0
5236
5024 (Rint ) 0.0182)
3674
N-Su ccin im id yl Ester 5. A solution of 4 (0.102 g, 0.1
mmol), N-hydroxysuccinimide (0.012 g, 0.1 mmol), and N,N′-
dicyclohexylcarbodiimide (DCC, 0.1 mL of 1.0 M solution in
dichloromethane) in dichloromethane (5 mL) was stirred 45
min at room temperature TLC showed complete disappearance
of 4 and formation of a product. The solid formed was filtered
off and the filtrate evaporated to dryness and chromatographed
(chloroform) to give 5 as an orange-red oil. Yield: 109 mg
(96%).
1H NMR: δ 4.46 (dd, J H-P ) 33.0 Hz, J H-H ) 1.5 Hz, 1H,
H2′ or H5′); 4.15 (dt, J H-P ) 33.1 Hz, J H-H ) 1.3 Hz, 1H, H5);
3.53 (dd, J P-H ) 33.3 Hz, J H-H ) 1.8 Hz, 1H, H2′ or H5′); 3.0
(m, 4H, CH2CH2); 2.84 (s, 4H, succinimide), 2.37, 2.19, 2.14,
1.95 (singlets, each 3H, Me’s). IR (CHCl3): 2080, 2000,1975,
1790, 1745, 1680.
no of reflns collected
no. of ind reflns
no. of reflns with
Fo > 4σ(Fo)
Solution and Refinement
system used
soln
SHELXS-97, SHELXL-97
direct methods
refinement method
H atoms
(∆/σ)max
full-matrix least-squares on F2
refined isotropically using riding model
0.003
0.080
0.171c
0.001
0.049
0.107d
R(F)a
wR(F2)b
R(F)a
0.055 for 3674 reflns 0.039 for 4155 reflns
wR(F2)b
0.148 for 3674 reflnsc 0.096 for 4155 reflnsd
a
R(F) ) ∑(|Fo - Fc|)/∑|Fo|. b wR(F2) ) [∑(w|Fo - Fc|)2/∑w(Fo)2]1/2
.
c w ) 1/[σ2 (Fo2) + (0.111P)2 + 7.39P)]. w ) 1/[σ2 (Fo2) + (0.0685P)2
d
Rea ction of 5 w ith Ben zyla m in e. A solution of N-
succinimidyl ester 5 (106 mg, 0.094 mmol) and benzylamine
(15 mg, 0.14 mmol) in dichloromethane (5 mL) was stirred
overnight at room temperature The solvent was evaporated
and the residue chromatographed using chloroform as eluent
to give 6a as an orange solid. Yield: 71 mg (62%). Mp: 64-66
°C.
+ 5.65P)], where P ) (max(Fo2, 0) + 2Fc2)/3.
evaporated to dryness and the residue chromatographed to
give 5b as an orange solid. Yield: 78 mg (71%). Mp: 61-63
°C.
1H NMR: δ 6.12 (t, J H-H ) 5.0 Hz, 1H, NH); 4.41 (dd, J H-P
) 32.7 Hz; J H-H ) 1.4 Hz, 1H, H2′ or H5 ′); 4.20 (t, J H-H ) 1.2
Hz, 0.5 H, a half of the H5 signal), 4.02 (d, J H-H ) 5.0 Hz,
1.5H, glycine CH2 + half of the H5 signal); 3,76 (s, 3H,
COOMe); 3.56 dd, (J H-P ) 33.1 Hz, J H-H ) 1.8 Hz, H2′ or H5′);
3.0 (m. 2H, CH2); 2.55 (m, 2H, CH2); 2.39, 2.19, 2.14, 1.99
(singlets, each 3H, Me’s). 13C NMR: δ 202.1 (d, J C-P ) 15.5
Hz, CO ketone); 197.0 (d, J C-P ) 34.5 Hz, W-CO trans to P);
1H NMR: δ 7.30 (m, 5H, Ph); 5.90 (t, J H-H ) 5.9 Hz, 1H,
NH); 4.48 (dd, J H-H ) 11.5 Hz, 5.9 Hz, 1H, CH2 benzyl); 4.36
(dd, J H-H ) 11.5 Hz, 5.9 Hz, 1H, CH2 benzyl); 4.44 (d, J H-P
)
34.1 Hz; J H-H ) 1.7 Hz, H2′ or H5′); 4.14 (dt, J P-H ) 33.2 Hz,
J H-H ) 1.7 Hz, H5); 3.54 (dd, J H-P ) 33.4 Hz, J H-H ) 1.7 Hz,
1H, H2′ or H5′); 3.1 (m, 1H CH2); 2.9 (m, 1H CH2; 2.6, m, 2H,
CH2); 2.40, 2.19, 2.13, 1.93 singlets, each 3H, Me’s). 13C NMR:
δ 202.2 (d, J C-P ) 15.6 Hz, CO ketone); 197.2 (d, J C-P ) 34.5
Hz, W-CO trans to P); 196.8 (d, J C-P ) 32.0 Hz, W-CO trans
to P); 194.3 (d, J C-P ) 8.3 Hz, W-CO cis to P); 194.0 (d, J C-P
) 8.5 Hz, W-CO cis to P); 171.2 (s, CO amide); 138.1, 128.7,
127.7, 127.5 (singlets, Ph); 99.6, 99.4, 97.8 (singlets, C4,C3′C4′);
94.0 (d, J C-P ) 4.4 Hz, C3); 87.1 (d, J C-P ) 8.8 Hz, C2); 79.1-
77.3 (m, C2′,C5,C5′); 43.6, 39.7, 30.1 (singlets, methylene
carbons); 16.4 (d, J C-P ) 4.7 Hz, Me); 14.0 (m, Me’s). 31P
NMR: δ -32.2 (d, J P-H ) 33.2 Hz, satellites 183W, J P-W ) 267.3
Hz, P1); -45.7 (t, J P-H ) 33.9 Hz, satellites 183W, J P-W ) 264.0
Hz, P1′). IR (CHCl3): 2080, 2000, 1995, 1700, 1680. Anal. Calcd
for C33H27NO12P2FeW2: C, 35.55; H, 2.44; N, 1.26; P, 5.56.
Found: C, 35.86; H, 2.72; N, 1.45; P, 5.66.
196.8 (d, J C-P ) 32.5 Hz, W-CO trans to P); 194.3 (d, J C-P
)
8.2 Hz, W-CO cis to P); 194.0 (d, J C-P ) 8.4 Hz, W-CO cis to
P); 171.4 (s, CO); 170.3 (s, CO); 99.6, 99.4, 97.8 (singlets,
C4,C3′,C4′); 94.2 (d, J C-P ) 4.4 Hz, C3); 87.1 (d, J C-P ) 8.8
Hz, C2); 79.1-77.3 (m, C2′,C5,C5′); 52.4 (s, OMe) 41.3, 39.6,
29.7 (singlets, methylene carbons); 16.4 (d, J C-P ) 4.7 Hz, Me);
14.0 (m, Me’s). 31P NMR: δ -23.9 (d, J P-H ) 33.0 Hz, satellites
183W, J P-W ) 266.8 Hz, P1); -36.5 (t, J P-H ) 33.0 Hz, satellites
183W, J P-W ) 264.2 Hz, P1′). IR (KBr): 2080, 2000, 1960. Anal.
Calcd for C29H25NO14P2FeW2‚1/3C6H14: C, 33.08; H, 2.66; N,
1.24; P, 5.50. Found: C, 33.15; H, 2.61; N, 1.50; P, 5.70.
X-r a y Str u ctu r e Deter m in a tion s. A summary of crystal-
lographic data collection parameters and refinement param-
eters are collected in Table 1. In the final least-squares full-
matrix refinement, all non-hydrogen atoms for both structures
were refined with anisotropic thermal displacement param-
eters. Hydrogen atoms were included as riding atoms with an
idealized geometry (C-H(CH3) ) 0.96, C-H(CH2) ) 0.97,
C-H(CH) ) 0.98, UH ) 1.5 UC). Only H atoms of the OH
groups were localized from the difference map. UH were refined
isotropically.
Rea ction of 5 w ith Glycin e Meth yl Ester . 5 (106 mg,
0.094 mmol) was dissolved in dichloromethane (2 mL). To this
solution was added a solution of glycine methyl ester hydro-
chloride (14 mg, 0.11 mmol) in dichloromethane (2 mL)
containing 2 drops of triethylamine, and the resulting solution
was stirred overnight at room temperature. The solvent was

1,1′-Diphosphaferrocene Derivatives
Organometallics, Vol. 17, No. 26, 1998 5883
Sch em e 1. (i) Su ccin ic An h yd r id e/AlCl3; (ii)
W(CO)5(THF ), 1 equ iv; (iii) N-Hyd r oxysu ccin im id e/
N,N′-Dicycloh exylca r bod iim id e; (iv) Ben zyla m in e
(Glycin e Meth yl Ester ); NS ) N-Su ccin im id yl
whereas the latter, a doublet of doublets (J P-H ) 35.6
Hz, J P-P ) 8.9 Hz), corresponds to P(1). Only the signal
of P(1′) shows characteristic satellite bands due to 183
W
(J P-W ) 262.1 Hz). The major product of the reaction is
therefore 3a . On the same basis the minor product of
the reaction, displaying signals at -29.7 (this signal
shows 183W satellites (J P-W ) 267.5 Hz)), and -60.2
ppm was identified as 3b. The ratio of 3/3b of 7:1
indicates that the -COCH2CH2COOH chain renders
coordination to P(1) slighty more difficult, presumably
by combination of steric and electronic effects.
Treatment of 2 with two or more equivalents of
W(CO)5(THF) gave the bis-W(CO)5 adduct (4) in good
yield. This complex was isolated and characterized by
spectral and elemental analysis data as well as by X-ray
structure determination (vide infra). Its 31P NMR
spectrum displays the 183W satellites at both signals
(-27.78, -36.98 ppm). In contrast to mono-W(CO)5
complexes 3a and 3b no coupling between 31P nuclei is
observed in the spectrum.
The complex 4 was then transformed into the corre-
sponding N-succinimidyl ester 5 by a standard treat-
ment with N-hydroxysuccinimide (NHS) and N,N′-
dicyclohexylcarbidiimide (DCC) in dichloromethane. We
1
characterized this compound only by IR and H NMR
spectra.
Once the synthesis and characterization of 5 was
completed, it was still necessary to verify its reactivity
toward amino groups since inactivation of organome-
tallic NS-esters toward nucleophiles has been re-
ported.15 Therefore, we tested the reactivity of 5 toward
model amines: benzylamine and glycine methyl ester
(the latter can be considered as a model of the terminal
amino function in peptides and proteins).
The reaction of 5 with these amines procceded
smoothly and completely in dichloromethane at room
temperature to give the corresponding amides 6a and
6b isolated in 62-71% yield (Scheme 1). This means
that reactivity of the activated ester function in 5 is
quite normal. Obviously, coupling of 5 with peptides or
proteins should be carried out in water or mitures of
water with organic solvent. Although 5 is almost totally
insoluble in water, we hope than it will work similarly
to an osmium cluster studied by Osella et al. in water-
organic solvent mixtures.2i Another possibility is offered
by the reverse micelle systems.16
It is worthy to note that the IR spectra of derivatives
4-6a ,b are quite similar in the region 2100-1900 cm-1
(region of stretching vibrations of coordinated carbon
monoxide). The lack of the influence of the modification
of the organic chain means that IR spectra represent
good fingerprints for the presence of the diphosphafer-
rocene-W(CO)5 marker in biomolecules.
Resu lts a n d Discu ssion
Syn th eses a n d Ch a r a cter iza tion . Earlier studies
by Mathey and his group12a-c showed that 1,1′-diphos-
phaferrocenes display high reactivity toward electro-
philes and undergo typical Friedel-Crafts acetylation
when treated with acetyl chloride in the presence of
AlCl3. We have found that 1 reacts under mild condi-
tions with succinic anhydride and AlCl3 in dichlo-
romethane to give 2 in 80% yield (Scheme 1).
The structure of 2 was confirmed by the spectral as
well as elemental analysis data. We have also deter-
mined its X-ray structure (vide infra).
We were interested in the coordinating properties of
2 toward photochemically generated W(CO)5(THF). Li-
gating properties of 1 toward various metal centers,
including M(CO)5(THF), where M ) Cr, Mo, W, have
earlier been studied by Mathey et al.13 However, 2
contains two nonequivalent P atoms, and therefore the
problem of the selectivity of the complexation arises. We
have found that when 2 was treated with 1 molar equiv
of W(CO)5(THF) at room temperature for 2 h, two
products are formed in the ratio ∼7:1 along with some
amount of unreacted 2. We were unable to separate
them, but analysis of the 31P NMR spectrum of their
mixture made possible their identification. The signals
assigned to the major product appear at -40.2 and
-47.9 ppm. In the 1H undecoupled spectrum the former
The unit cell of 2 contains two crystallographically
independent, almost identical, molecules (2a /2b). A view
of the molecule 2a (with its numbering scheme) is given
in Figure 1.
The atoms in molecule 2b are numbered 20 + X,
where X is the number of the corresponding atom in
(15) (a) Gorfti, A.; Salmain, M.; J ouen, G. J . Chem. Soc., Chem.
Commun. 1994, 433. (b) El Mautassim, B.; Elamouri, H.; Vaissermann,
J .; J aouen, G. Organometalics 1995, 14, 3296.
(16) Ryabov, A. D.; Trushkin, A. M.; Baksheera, l. I.; Gorbatova, R.
K.; Kubrakova, I. V.; Mozhaev, V. V.; Gnedenko, B. B.; Levashov, A.
V. Angew. Chem., Int. Ed. Engl. 1992, 31, 789.
signal is a triplet of doublets (J P-H ) 33.2 Hz, J P-P
8.9 Hz) and therefore should be assigned to P(1′),
)

5884 Organometallics, Vol. 17, No. 26, 1998
Zakrzewski et al.
F igu r e 3. Possible conformations of 1,1′-diheterofer-
rocenes as a function of angle θ. E ) P, As, Sb, Bi; θ is the
dihedral angle between the planes normal to each C4H4E
ring that contain both Fe and E atoms.
F igu r e 1. Ortep plot of 2a (30% probability level) showing
the adopted numbering scheme. View along the vector
perpendicular to the phospholyl rings.
F igu r e 4. Molecular packing of 2.
conformation in comparison to C2 conformations with θ
> 100°. The X-ray structures of 3,3′,4,4′-tetramethyl-
1,1′-diphosphaferrocene17 and 3,3′,4,4′-tetramethyl-2,2′-
diphenyl-1,1′-diphosphaferrocene18 are in full agreement
with these results (θ ) 145° for the former and θ > 100°
for the latter). Hovewer, the eclipsed conformation was
recently reported for crystalline 2,2′,5,5′-tetraphenyl-
1,1′-diphosphaferrocene19 and explained as a result of
intramolecular π-π interactions of the phenyl substit-
uents providing an extra stabilization energy. The C2v
conformation is also forced for 1,1′-diphosphaferrocene
chelate complexes in which both lone pairs of the
phosphorus atoms are ligated to a metal center.13,20 In
contrast to 1,1′-diphosphaferrocenes, their analogues
containing heavier heteroatoms (especially Sb or Bi)
show a tendency to adopt in the solid state the eclipsed
conformation, which was explained as a result of a
secondary bonding between heteroatoms (defined as a
covalent bond with fractional bond order which involves
interatomic distances longer than the sum of the
covalent, but shorter than the sum of the van der Waals
radii).12d,f,21
F igu r e 2. Ortep drawing of 4 (30% probability level). View
along the vector perpendicular to the phospholyl rings.
the molecule 2a . The view of molecule 4, also along the
vector perpendicular to the phospholyl planes, is given
in Figure 2.
Taking account of all these facts, we were surprised
to find that molecules 2a and 2b display nearly eclipsed
conformations with low values of θ: 28.4(3)° and 27.9-
(3)°, respectively. The intramolecular distance between
the phosphorus atoms is 3.522(2) and 3.513(2) Å in 2a
and 2b, respectively, indicating a secondary bonding.
Conformations of 1,1′-diheteroferrocenes, (C4H4E)2Fe,
can be conveniently described as a function of the
dihedral angle θ, defined as the angle between the
planes normal to each C4H4E ring that contain both Fe
and E atoms.12c,e When the heteroatoms are syn-eclipsed
(C2v symmetry), θ ) 0°. When they are anti (C2h
symmetry), θ ) 180°. The intermediate gauche or
partially eclipsed conformations of C2 symmetry have
0° < θ < 180°.
(17) De Lauzon, G.; Deschamps, B.; Fischer, J.; Mathey, F.; Mitschler,
A. J . Am. Chem. Soc. 1980, 102, 994.
(18) Qiao, S.; Hoic, D. A.; Fu, G. C. Organometallics 1998, 17, 773.
(19) Hitchcock, P. B.; Lawless, G. A.; Marziano, I. J . Organomet.
Chem. 1997, 527, 305.
(20) Atwood, D. A.; Cowley, A. H.; Dennis, S. M. Inorg Chem. 1993,
32, 1527.
(21) (a) Chiche, L.; Gally, J .; Thiollet, G.; Mathey, F. Acta Crystal-
logr. 1980, B36, 344. (b) Ashe, A. J ., III; Kampf, J . W.; Al-Taweel, S.
M. Organometallics 1992, 11, 1491. (c) Ashe, A. J ., III; Kampf, J . W.;
Puranik, D. B.; Al-Taweel, S. M. Organometallics 1992, 11, 2743.
The computational studies (using extended Hu¨ckel,12d,h,i
Fenske-Hall,12g and MS XR12i methods) on 1,1′-diphos-
phaferrocene showed destabilization of the eclipsed

1,1′-Diphosphaferrocene Derivatives
Organometallics, Vol. 17, No. 26, 1998 5885
Ta ble 2. Selected Bon d Len gth s [Å] a n d An gles [d eg] a n d Th eir Aver a ge Va lu esa
molecule
bond
2a
2b
av in 2a and 2b
4
av in 4
Phospholyl Rings
1.426(8)
1.416(7)
C(2 or 22)-C(3 or 23)
1.418(8)
1.422(7)
1.433(7)
1.397(8)
1.410(8)
1.423(9)
1.805(5)
1.753(6)
1.744(7)
1.743(7)
88.4(3)
1.414(12)
1.419(12)
1.432(11)
1.411(12)
C(3 or 23)-C(4 or 24)
C(4 or 24)-C(5 or 25)
1.427(7)
1.417(2)
1.419(5)
C(12 or 32)-C(13 or 33)
C(13 or 33)-C(14 or 34)
C(14 or 34)-C(15 or 35)
P(1 or 21)-C(5 or 25)
1.395(8)
}
1.421(8)
1.421(9)
1.808(5)
1.750(6)
1.751(6)
1.748(7)
88.4(3)
1.429(13)
1.411(12)
1.778(8)
1.745(7)
1.749(9)
}
1.806(4)
1.748(3)
P(1 or 21)-C(2 or 22)
P(11 or 31)-C(12 or 32)
P(11 or 31)-C(15 or 35)
C(2 or 22)-P(1 or 21)-C(5 or 25)
C(12 or 32)-P(11 or 31)-C(15 or 35)
W(1 or 2)-P(1 or 11)-C(2 or 12)
W(1 or 2)-P(1 or 11)-C(5 or 15)
1.748(5)
90.2(3)
}
}
}
1.751(9)
90.0(4)
}
88.8(3)
89.0(3)
88.7(2)
130.9(3)
136.5(2)
90.3(4)
128.8(3)
137.2(3)
Fe Coordination
2.280(2)
2.289(2)
2.074(2)
2.081(5)
2.083(5)
2.082(5)
2.083(5)
Fe(1 or 2)-P(1 or 21)
Fe(1 or 2)-P(11 or 31)
Fe(1 or 2)-C(2 or 22)
Fe(1 or 2)-C(3 or 23)
Fe(1 or 2)-C(4 or 24)
Fe(1 or 2)-C(5 or 25)
Fe(1 or 2)-C(12 or 32)
Fe(1 or 2)-C(13 or 33)
Fe(1 or 2)-C(14 or 34)
Fe(1 or 2)-C(15 or 35)
2.282(2)
2.290(2)
2.073(5)
2.081(5)
2.087(5)
2.076(5)
2.085(6)
2.081(5)
2.066(6)
2.067(6)
2.257(2)
2.262(2)
}
}
2.285(1)
2.078(7)
2.259(1)
2.091(3)
2.089(8)
2.081(7)
2.098(8)
2.078(1)
2.077(7)
2.111(8)
2.080(5)
2.080(5)
2.066(5)
}
}
2.101(8)
2.094(8)
Intramolecular P‚‚‚P Secondary Bonds
P(1)(21)‚‚‚P(11)(31)
3.522(2)
3.513(2)
3.737(2)
Intermolecular P‚‚‚P Secondary Bonds
P(1)‚‚‚P(21)i
3.498(2)
3.723(2)
P(11)‚‚‚P(31)ii
W Coordination in 4
W(1)-P(1)
2.448(2)
W(2)-P(11)
W(2)-C(23)
W(2)-C(24)
W(2)-C(25)
W(2)-C(27)
W(2)-C(26)
2.457(2)
2.054(11)
2.060(13)
2.048(13)
2.033(12)
2.019(10)
2.452(1)
W(1)-C(18)
W(1)-C(19)
W(1)-C(20)
W(1)-C(22)
W(1)-C(21)
2.029(11)
2.032(12)
2.049(12)
2.038(14)
2.002(11)
2.043(4)
2.011(7)
}
}
a
Symmetry code: (i) x, y, 1-z; (ii) x, y, 1+z.
Structures of 2a and 2b show also an intermolecular
P‚‚‚P secondary bonding, giving rise to formation of
stacking columns along the z axis (see Figure 4).
Figure 5 shows a view of this column along the y axis.
Molecules 2a and 2b are situated alternately in the
chain. They are two kinds of intermolecular P- - -P
interactions: the first between phosphorus atoms be-
longing to more substitued rings and the second be-
tween P atoms belonging to less substituted rings. The
intermolecular distances P(1)- - -P(21) and P(11)- - -P-
(31)i are 3.498(2) and 3.723(2) Å, respecively. The
interacting phospholyl rings are nearly parallel. The
intra- and intermolecular angles between their four-
carbon planes are from 1.3(2)° to 1.7(2)°. In the column
Fe atoms are not ideally collinear. The angle formed by
three succeeding Fe atoms is 159.8(5)°. The distances
Fe(1)-Fe(2) and Fe(2)-Fe(1)i are 7.177(2) and 7.175(2)
Å, respecively. The structure of 2 provides the first
example of intermolecular secondary interactions be-
tween P atoms in the diphosphaferrocene system.
However, such interactions were reported for a heavier
diheteroferrocene system: octamethyl-1,1′-distibafer-
rocene.12d In our opinion this type of crystal may show
interesting electrical properties.
tween the W(CO)5 groups. The intramolecular P1-P11
distance of 3.737(2) Å indicates weaker secondary
bonding.
The above results clearly show that secondary bond-
ing between heteroatoms exists not only in heterofer-
rocenes containing heavy pnictogens such as As, Sb, and
Bi but also in 1,1′-diphosphaferrocenes. The latter
system can populate conformers with low values of θ
(<53°) and short intramolecular separations between
the heteroatoms even in the absence of such factors as
intramolecular interactions between substituents or
constraints due to coordination of two phosphorus atoms
to a metal center. The most reasonable conclusion to
be drawn from these facts is that conformational prefer-
ences in 1,1′-diphosphaferrocenes are small, and they
can be easily changed by small changes in the substitu-
tion. Thus it would seem that the prior (using extended
Hu¨ckel,12d,h,i Fenske-Hall,12g and MS XR12i methods)
computational studies on 1,1′-diphosphaferrocene do not
give a correct description of the conformational prefer-
ences of this system, and higher level computation work
is called for.
In the molecule 4 both W atoms display a distorted
octahedral coordination with similar W-P bond lengths
of 2.448(2) and 2.457(2) Å. These bonds are distinctly
shorter than the W-P bonds in W(CO)5(triphen-
The structure of 4 shows a larger value of θ, 52.6(4)°.
This may be attributed to the steric interactions be-

5886 Organometallics, Vol. 17, No. 26, 1998
Zakrzewski et al.
Ta ble 3. Hyd r ogen Bon d in g Geom etr y [Å, d eg]a
D-H‚‚‚A
D-Hb H‚‚‚Ab
D‚‚‚A
D-H‚‚‚Ab
Crystals of 2
O(1)-H(1)‚‚‚O(22)i
O(21)-H(21)‚‚‚O(2)ii
C(8)-H(8A)‚‚‚O(3)
C(28)-H(28A)‚‚‚O(23)
0.93
0.93
1.08
1.08
1.77
1.72
2.39
2.42
2.642(6)
2.642(6)
2.782(7)
2.772(7)
153
167
100
98
Crystals of 4
0.93 1.81
O(1)-H(1)‚‚‚O(2)iii
2.690(12)
155
a
Symmetry codes: (i) 1-x, y, 1-z; (ii) 1+x, y, 1+z; (iii) 1-x,
b
-y, -z. Values normalized following: J effrey, A.; Lewis, L.
Carbohydr. Res. 1978, 60, 179. Taylor, R.; Kennard, O. Acta
Crystallogr. 1983, B39, 133.
shows less tendency for π-back-bonding to CO than in
the azaferrocene complexes. This fact, together with
relatively short W-P bonds, suggests significant π-ac-
ceptor properties of the 1,1′-diphosphaferrocene system.
It is worthy noting that such properties were already
suggested by Mathey et al.13 on the basis of IR spectral
data.
The conformation of the COCH2CH2COOH chain in
2 and 4 is different. In 4 carbonyl oxygen O(3) and P(1)
are in trans conformation with respect to the C(5)-C(6)
bond, whereas in 4 the same atoms are in cis conforma-
tion. Furthermore the P-W coordination of the phosp-
hole ring disturbs the coplanarity of this ring with the
CdO carbonyl bond (in 4 the torsion angle P(1)-C(5)-
C(6)-O(3) is 26.9(1.1)°, and in 2 the average value of
this angle is - 173.0(4)°). In 4 certain reduction of π
electron delocalization between C(5)-C(6) and C(6)-
O(3) bonds can be observed. The lengths of these bonds
in 4 are 1.476(12) and 1.201(11) Å, respectively, and in
2 their average values are 1.459(7) and 1.224(6) Å.
There are intermolecular short O-H‚‚‚O hydrogen
bonds between neighboring carboxylate groups and in
2 also intramolecular C-H‚‚‚O hydrogen bonds. Table
3 gives the geometry of these bonds. The molecules of 4
form centrosymmetrical dimers by two O-H‚‚‚O bonds,
which gives nearly eclipsed conformation on the C(8)-
C(9) bond with the O(2)-C(9)-C(8)-C(7) torsion angle
of 5.6(1.7)°. In the crystals of 2 O-H‚‚‚O hydrogen bonds
are formed between molecules 2a and 2b from neigh-
boring stacking columns of molecules connected by
intermolecular secondary P‚‚‚P bonds. They also gener-
ate the eclipsed conformation on the C(8)(28)-C(9)(29)
bonds with the torsion angles O(2)(22)-C(9)(29)-C(8)-
(28)-C(7)(27) of 19.8(8)° and 18.4(8)°, respectively. The
COCH2CH2COOH groups in the molecules 2a and 2b
have an eclipsed conformation also on the C(6)(26)-
C(7)(27) bonds caused by the C(8)(28)-H‚‚‚O(3)(23)
hydrogen bonds. The torsion angles C(8)(28)-C(7)(27)-
C(6)(26)-O(3)(23) are 15.6(8)° and 14.1(7)°, respectively.
F igu r e 5. View along y axis on the stacking column of
molecules 2a and 2b. H atoms and CH3 groups are omitted
for clarity.
ylphosphine) and W(CO)5(trimethylphosphine) com-
plexes, where the mean W-P bond lengths are 2.545-
(1) and 2.516(3) Å, respectively.22a,b They are also
shorter than normalized to W-P, W-N bonds observed
in W(CO)5(azaferrocene) complexes,23 where the average
W-N bond is 2.271(5) Å, which after normalization to
W-P gives 2.67 Å (as the difference between rP-rN
Pauling’s atomic radii is 0.40 Å). Thus W-P bonds in 4
are short and strong. In both W(CO)5P moieties the
W-P bonds are not exactly coplanar with the phospholyl
rings. The deviations of W(1) and W(2) atoms from the
least-squares planes of these rings are 0.579(9) and
0.714(10) Å, respectively, and the angles between the
W(1)-P(1) and W(2)-P(11) bonds and the normal to
these rings are 76.7(3)° and 73.6(3)°, respectively. These
angles may be considered as the measure of the steric
hindrance on binding to W(CO)5. The W-C bonds cis
to phosphorus in 4 are equivalent with the mean value
of 2.043(4) Å, which is nearly identical to the values
observed in W(CO)5(azaferrocene) and other W(CO)5L
complexes.22,23 However, the trans W-C bonds with the
mean value 2.011(7) Å are distinctly longer than the
average value of these bonds of 1.962(4) Å observed in
W(CO)5(azaferrocene) complexes.23 The W-P and trans
W-C bond lengths provide information on the coordi-
nating properties of the 1,1′-diphosphaferrocene system.
The long trans W-C bonds in 4 indicate that the W
atom in W(CO)5(1,1′-diphosphaferrocene) complexes
Ack n ow led gm en t. This research was financially
supported from the University of Ło´dz´ and Technical
University of Ło´dz´ Research Grants.
Su p p or tin g In for m a tion Ava ila ble: Crystal data for 2
and 4 (19 pages). Ordering information is given on any current
masthead page.
(22) (a) Aroney, M. J .; Buys, I. E.; Davies, M. S.; Hambley, T. W. J .
Chem. Soc., Dalton Trans. 1994, 2827. (b) Cotton, F. A.; Darensbourg,
D. J .; Kothamer, B. W. S. Inorg. Chem. 1981, 20, 4440.
(23) Silver, J .; Zakrzewski, J .; Tosik, A.; Bukowska-Strzyz˘ ewska,
M. J . Organomet. Chem. 1997, 540, 169.
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