Syntheses and crystal structures of P-transition-metalated iminophosphoranes, Cp*(CO)2M{P(NPh)(OMe)2} (M = Fe and Ru)

Article abstract of DOI:10.1021/om0110484

The reaction of[Cp*(CO)₂Fe{P(NHPh)(OMe)₂}]PF₆ with NaNH₂ yielded the P-iron-bonded iminophosphorane Cp*(CO)₂Fe{P(NPh)(OMe)₂}, with deprotonation from the NHPh group on the phosphorus. The ruthenium analogue, Cp*(CO)₂Ru{P(NPh(OMe)₂}, was also prepared in a similar manner. The spectroscopic properties of the metallaiminophosphoranes are quite similar to those of their P=O analogue, i.e., phosphonate complexes. The X-ray structure analyses revealed that the P-N bond in Cp*(CO)₂Fe{P(NPh)(OMe)₂} is comparable in length to that of the ruthenium analogue, Cp*(CO)₂Ru{P(NPh)(OMe)₂}, and both are considerably shorter than a P-N single bond. These observations strongly suggest that the P-N bonds in the P-metalated iminophosphoranes have substantial double-bond character. The structural features of the metallaiminophosphorane of iron resemble those of the starting cation complex, indicating that their electronic structures are basically similar. The iron-iminophosphorane is thermally stable compared with its Cp analogue, which is not stable enough to isolate, suggesting that both steric and electronic factors are responsible for the stability of the Cp* complexes.

Full text of DOI:10.1021/om0110484

1942
Organometallics 2002, 21, 1942-1948
Syn th eses a n d Cr ysta l Str u ctu r es of
P -Tr a n sition -Meta la ted Im in op h osp h or a n es,
Cp *(CO)2M{P (NP h )(OMe)2} (M ) F e a n d Ru )
Kazuyuki Kubo, Hiroshi Nakazawa,* Hiroyasu Inagaki, and Katsuhiko Miyoshi*
Department of Chemistry, Graduate School of Science, Hiroshima University,
Higashi-Hiroshima 739-8526, J apan
Received December 10, 2001
The reaction of [Cp*(CO)2Fe{P(NHPh)(OMe)2}]PF6 with NaNH2 yielded the P-iron-bonded
iminophosphorane Cp*(CO)2Fe{P(NPh)(OMe)2}, with deprotonation from the NHPh group
on the phosphorus. The ruthenium analogue, Cp*(CO)2Ru{P(NPh)(OMe)2}, was also prepared
in a similar manner. The spectroscopic properties of the metallaiminophosphoranes are quite
similar to those of their PdO analogue, i.e., phosphonate complexes. The X-ray structure
analyses revealed that the P-N bond in Cp*(CO)2Fe{P(NPh)(OMe)2} is comparable in length
to that of the ruthenium analogue, Cp*(CO)2Ru{P(NPh)(OMe)2}, and both are considerably
shorter than a P-N single bond. These observations strongly suggest that the P-N bonds
in the P-metalated iminophosphoranes have substantial double-bond character. The
structural features of the metallaiminophosphorane of iron resemble those of the starting
cation complex, indicating that their electronic structures are basically similar. The iron-
iminophosphorane is thermally stable compared with its Cp analogue, which is not stable
enough to isolate, suggesting that both steric and electronic factors are responsible for the
stability of the Cp* complexes.
In tr od u ction
zirconium,10 iron,11 cobalt,12 palladium,13 and plati-
num,14 most of them were obtained unexpectedly in the
Compounds bearing a phosphorus-nitrogen bond
have attracted considerable attention in heteroatom
chemistry.1 In particular, iminophosphoranes (R3PdNR),
which make up an isoelectronic series with phosphorus
ylides (R3PdCR2) and phosphine oxides (R3PdO), have
been extensively studied due to not only the basic
interests in their structures and reactivity but also their
availability as reagents for organic synthesis2 and, more
recently, as precursors to inorganic polymers.3,4 In
addition, they have also been of great interest in
coordination chemistry as ligands for transition metals.
Iminophosphoranes bonded to a transition metal in η1
fashion can be classified into three types: (i) N-coordi-
nated iminophosphoranes with an N-metal dative
bond,5-7 (ii) N-metalated iminophosphoranes with an
N-metal covalent bond,6-8 and (iii) P-metalated imino-
phosphoranes with a P-metal covalent bond.
(5) For example, see: (a) Vicente, J .; Arcas, A.; Bautista, D.; Ram´ırez
de Arellano, M. C. Organometallics 1998, 17, 4544, and references
therein. (b) Ackermann, H.; Geiseler, G.; Harms, K.; Leo, R.; Massa,
W.; Weller, F.; Dehnicke, K. Z. Anorg. Allg. Chem. 1999, 625, 1500.
(c) Ackermann, H.; Leo, W.; Massa, W.; Dehnicke, K. Z. Anorg. Allg.
Chem. 2000, 626, 608. (d) Krieger, M.; Gould, R. O.; Harms, K.;
Greiner, A.; Dehnicke, K. Z. Anorg. Allg. Chem. 2001, 627, 747. (e)
LePichon, L.; Stephan, D. W. Inorg. Chem. 2001, 40, 3827. (f) Stephens,
J . C.; Khan, M. A.; Houser, R. P. Inorg. Chem. 2001, 40, 5064.
(6) For a review article, see: Dehnicke, K.; Krieger, M.; Massa, W.
Coord. Chem. Rev. 1999, 182, 19.
(7) For example, see: (a) Schlecht, S.; Deubel, D. V.; Frenking, G.;
Geiseler, G.; Harms, K.; Magull, J .; Dehnicke, K. Z. Anorg. Allg. Chem.
1999, 625, 887. (b) Gro¨b, T.; Seybert, G.; Massa, W.; Dehnicke, K. Z.
Anorg. Allg. Chem. 2000, 626, 349.
(8) For recent examples, see: (a) Gue´rin, F.; Stephan, D. W. Angew.
Chem., Int. Ed. 2000, 39, 1298. (b) Gro¨b, T.; Seybert, G.; Massa, W.;
Weller, F.; Palaniswami, R.; Greiner, A.; Dehnicke, K. Angew. Chem.,
Int. Ed. 2000, 39, 4373. (c) Williams, V. C.; Mu¨ller, M.; Leech, M. A.;
Denning, R. G.; Green, M. L. H. Inorg. Chem. 2000, 39, 2538. (d) Sung,
R. C. W.; Courtenay, S.; McGarvey, B. R. Stephan, D. W. Inorg. Chem.
2000, 39, 2542. (e) Carraz, C.-A.; Stephan, D. W. Organometallics 2000,
19, 3791. (f) Gro¨b, T.; Seybert, G.; Massa, W.; Harms, K.; Dehnicke,
K. Z. Anorg. Allg. Chem. 2000, 626, 1361. (g) Dietrich, A.; Neumu¨ller,
B.; Dehnicke, K. Z. Anorg. Allg. Chem. 2000, 626, 1837. (h) Kickham,
J . E.; Gue´rin, F.; Stewart, J . C.; Urbanska, E.; Stephan, D. W.
Organometallics 2001, 20, 1175. (i) Courtenay, S.; Stephan, D. W.
Organometallics 2001, 20, 1442. (j) Raab, M.; Sundermann, A.; Schick,
G.; Loew, A.; Nieger, M.; Schoeller, W. W.; Niecke, E. Organometallics
2001, 20, 1770. (k) Yue, N. L. S.; Stephan, D. W. Organometallics 2001,
20, 2303. (l) Balakrishna, M. S.; Teipel, S.; Pinkerton, A. A.; Cavell,
R. G. Inorg. Chem. 2001, 40, 1802. (m) Gro¨b, T.; Seybert, G.; Massa,
W.; Dehnicke, K. Z. Anorg. Allg. Chem. 2001, 627, 304. (n) Balakrishna,
M. S.; Teipel, S.; Pinkerton, A. A.; Cavell, R. G. Inorg. Chem. 2001,
40, 1802. (o) Gue´rin, F.; Beddie, C. L.; Stephan, D. W.; Spence, R. E.
v. H.; Wurz, R. Organometallics 2001, 20, 3466. (p) Yue, N.; Hollink,
E.; Gue´rin, F.; Stephan, D. W. Organometallics 2001, 20, 4424.
(9) A few P-metalated cyclic polyiminophosphoranes were reported
by Allcock et al. For a review article, see: Allcock, H. R.; Desorcie, J .
L.; Riding, G. H. Polyhedron 1987, 6, 119.
In contrast to many reports on the former two, those
on the latter type are relatively rare.9 Although several
P-metalated iminophosphoranes have been reported for
(1) (a) Emsley, J .; Hall, D. In The Chemistry of Phosphorus; Harper
& Row: New York, 1976; Chaper 10. (b) Corbridge, D. E. C. In
Phosphorus. An Outline of its Chemistry, Biochemistry and Technology;
Elsevier: New York, 1980; Chaper 5.
(2) For review articles, see: (a) Gololobov, Y. G.; Kasukhin, L. F.
Tetrahedron 1992, 48, 1353. (b) Molina, P.; Vilaplana, M. J . Synthesis
1994, 1197.
(3) Wisian-Neilson, P., Allcock, H. R., Wynne, K. J ., Eds. In
Inorganic and Organic Polymers II. Advanced Materials and Interme-
diates; ACS Symposium Series 572; American Chemical Society:
Washington, DC, 1994; Neilson, R. H., J inkerson, D. L., Kucera, W.
R., Longlet, J . J ., Samuel, R. C., Wood, C. E., Chapter 18; White, M.
L., Matyjaszewski, K., Chapter 24.
(4) For a review article, see: Manners, I. Angew. Chem., Int. Ed.
Engl. 1996, 35, 1602.
(10) For a review article, see: Majoral, J .-P.; Igau, A. Coord. Chem.
Rev. 1998, 176, 1.
10.1021/om0110484 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 04/03/2002

P-Transition-Metalated Iminophosphoranes
Organometallics, Vol. 21, No. 9, 2002 1943
Ch a r t 1
particular reactions. Therefore, the procedures adopted
there have not been applied as a general synthetic
method. In the case of the palladium complexes,13 the
anionic compound [Ph2PNP(O)Ph2]- was allowed to
react with palladium complexes, yielding P-palladium-
bonded iminophosphoranes. In this reaction, the anion
serves as iminophosphoranide. This simple approach
would be one of the good routes to the metalated
iminophosphoranes. However, iminophosphoranide is
usually in equilibrium with phosphinoamide, as shown
in eq 1, and thus it also has the possibility of giving
phosphinoamide complexes as well.
whereas an NH proton was not observed any longer.
These observations strongly suggest that the N-H
proton in 1a was abstracted to form an electrically
neutral complex with a P(V) fragment, that is, the
P-iron-bonded iminophosphorane, Cp*(CO)2Fe{P(NPh)-
(OMe)2} (1b) (68% yield). In addition, the X-ray crystal-
lographic study (vide infra) confirmed the formation of
1b.
The synthetic method presented here seems to be
applicable to a wide range of transition-metal com-
plexes. The cationic ruthenium-phosphite complex
[Cp*(CO)2Ru{P(NHPh)(OMe)2}]BF4 (2a ), which can be
easily obtained from the reaction of Cp*(CO)2RuCl with
P{NPh(SiMe3)}(OMe)2, AgBF4, and then H2O, is con-
verted into the P-ruthenium-bonded iminophosphorane
Cp*(CO)2Ru{P(NPh)(OMe)2} (2b) (60% yield), in a man-
ner similar to that of 1a . Complex 2b is the first
example of a P-metalated iminophosphorane of ruthe-
nium.
In this paper, we report the syntheses of P-metalated
iminophosphoranes of iron and ruthenium by another
simple and convenient procedure, which involves proton
abstraction from cationic complexes having a P{(NHPh)-
(OMe)2} ligand. Although the similar deprotonation
from phosphonium salts is known to be a facile route
to organic iminophosphoranes, the reaction presented
here is, to our knowledge, the first application to the
preparation of transition-metalated iminophosphoranes.
The spectroscopic and structural properties of the
P-metalated iminophosphoranes are also reported.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of Cp *(CO)2M-
{P (NP h )(OMe)2} (M ) F e a n d Ru ). The cationic iron-
phosphite complex [Cp*(CO)2Fe{P(NHPh)(OMe)2}]PF6
(1a ) (Cp* stands for η5-C5Me5), which was prepared in
the reaction of [Cp*(CO)2Fe(THF)]PF6 with P{NPh-
(SiMe3)}(OMe)2 and then with H2O, was dissolved in
THF and then treated with an excess amount of NaNH2.
During a few minutes stirring, the color of the solution
changed from yellow to yellowish orange. The mixture
was then worked up to give a yellow powder (eq 2). The
31P NMR spectrum of the product showed a singlet at
122.3 ppm, which is at higher field than the chemical
shift of the starting phosphite complex (161.5 ppm). No
resonance due to the PF6 counterion was observed. The
two absorption bands (2016 and 1967 cm-1) assignable
to νCO in the IR spectrum appeared at lower frequency
than those of the starting cation (2036 and 1991 cm-1).
Although deprotonation from an aminophosphonium
salt has been utilized in the preparation of a variety of
organic iminophosphoranes,1 there is no report so far
on the deprotonation reaction of an aminophosphite
coordinated to a cationic transition-metal complex. In
this reaction, the phosphorus valence changes formally
from P(III) to P(V), and the coordination mode of the
phosphorus ligand concomitantly changes from dative
to covalent. Since the starting complex has the phos-
phorus atom already bonded to the transition metal, the
deprotonation from the nitrogen leads naturally to the
exclusive formation of a P-metalated iminophosphorane.
Sp ectr oscop ic P r op er ties of P -Meta la ted Im in o-
p h osp h or a n es. The 31P NMR chemical shifts of
Cp*(CO)2M{P(NPh)(OMe)2} (122.3 ppm for M ) Fe (1b),
103.8 ppm for M ) Ru (2b)) are at lower field than those
of the corresponding organic iminophosphoranes (-3
1
In the H NMR spectrum, the resonances attributed to
C5(CH3)5, OCH3, and NC6H5 protons were observed,
(11) Newton, M. G.; King, R. B.; Chang, M.; Gimeno, J . J . Am. Chem.
Soc. 1978, 100, 326.
(12) Pohl, D.; Ellermann, J .; Knoch, F. A.; Moll, M. J . Organomet.
Chem. 1995, 495, C6.
15
ppm for P(NPh)(OMe)3 and 16.7 ppm for PhP(NMe)-
(13) Smith, M. B.; Slawin, A. M. Z. Polyhedron 2000, 19, 695.
(14) Slawin, A. M. Z.; Smith, M. B.; Woollins, J . D. J . Chem. Soc.,
Dalton Trans. 1996, 4567.
(15) Bellan, J .; Sanchez, M.; Marre-Mazieres, M. R.; Murillo, B. A.
Bull. Soc. Chim. Fr. 1985, 491.

1944 Organometallics, Vol. 21, No. 9, 2002
Kubo et al.
F igu r e 2. ORTEP drawing of 2b showing the non-
hydrogen atoms as 50% probability thermal ellipsoids with
the numbering scheme. All hydrogen atoms are omitted
for clarity.
F igu r e 1. ORTEP drawing of 1b showing the non-
hydrogen atoms as 50% probability thermal ellipsoids with
the numbering scheme. All hydrogen atoms are omitted
for clarity.
(OMe)216), but they are close to that of the corresponding
phosphonate complex Cp*(CO)2FeP(O)(OMe)2 (113.5
ppm).17 The IR data are also comparable to those of the
phosphonate complex (νCO: 2016 and 1967 cm-1 for 1b,
2029 and 1976 cm-1 for 2b, 2014 and 1962 cm-1 for
Cp*(CO)2FeP(O)(OMe)217). Therefore, it can be said that
the iminophosphorane and phosphonate ligands provide
similar electronic environments around the metal cen-
ter. Comparison between νCO values of 1b and 2b in the
IR spectra and of chemical shifts in the 31P NMR spectra
reveals that the ruthenium complex has more electron-
rich phosphorus and more electron-poor metal than does
1
the iron complex. Indeed, the H NMR spectrum of 2b
shows that the methyl protons in η5-C5(CH3)5 are
observed at slightly lower field, whereas the protons in
the OMe groups on the phosphorus are observed at
slightly higher field than those of 1b. A similar tendency
has been observed for the corresponding iron- and
ruthenium-phosphonate complexes.18
X-r a y Str u ctu r es of 1a , 1b, a n d 2b. The X-ray
crystal structures of P-metalated iminophosphoranes 1b
and 2b were determined. The ORTEP drawings are
given in Figures 1 and 2, respectively. For comparison,
the X-ray structure of 1a was also determined. In this
case, the unit cell has two crystallographically inde-
pendent molecules. The ORTEP drawing of one of the
two is shown in Figure 3. The crystallographic data and
selected bond distances and angles are summarized in
Tables 1 and 2.
All complexes have typical piano-stool configurations
with a Cp*, two carbonyls, and a phosphorus ligand all
coordinated to the transition-metal center. The struc-
tural parameters of 1b resemble closely those of 2b,
though each corresponding metal-ligand bond is longer
for 2b, probably due to the greater atomic radius of
ruthenium. It should be emphasized that the P(1)-N(1)
bond for 1b (1.574(1) Å) is comparable in length to that
for 2b (1.575(2) Å), and both are considerably shorter
F igu r e 3. ORTEP drawing of one of the independent
molecules of 1a showing the non-hydrogen atoms as 50%
probability thermal ellipsoids with the numbering scheme.
All hydrogen atoms and the PF6 counterion are omitted
for clarity.
than a usual P-N single bond (ca. 1.78 Å).1a These
observations strongly suggest that the P-N bonds in
1b and 2b have substantial double-bond character.
Furthermore, it should be noted that the P-N bond in
1a (1.672(2) or 1.658(2) Å) is also relatively short,
suggesting that it has already partial double-bond
character. These three complexes take the common
conformations around the M-P, P-N, and N-C bonds
with the N atom sp2-hybridized (P(1)-N(1)-C(15)
angles: 1b, 130.2(1)°; 2b, 128.8(2)°; 1a , 125.1(2)° or
127.4(2)°). In all complexes, the Cp* and the two
carbonyls on the transition-metal fragment are located
in a staggered position around the M-P bond to the
three substituents on the phosphorus fragment. The
imino group is gauche to the Cp* ring and thus is trans
to one of the two carbonyls (N(1)-P(1)-Fe(1)-C(11)
torsion angle: 1b, 174.1(1)°; 2b, 172.4(1)°; 1a, -172.7(1)°
or -172.2(1)°). Similar conformational features were
observed in the iron-phosphonate complexes Cp(CO)2-
Fe{P(O)(OEt)2}19 and Cp(CO)2Fe{P(O)(CF3)2}20 (Cp
(16) Goldwhite, H.; Gysegem, P.; Schow, S.; Swyke, C. J . Chem. Soc.,
Dalton Trans. 1975, 12.
(17) Spectroscopic data for Cp*(CO)2Fe{P(O)(OMe)2}: IR (νCO, KBr
disk): 2014, 1962 cm-1. 1H NMR (δ, in CDCl3): 1.88 (s, 15H, C5(CH3)5),
3.57 (d, J PH ) 12.0 Hz, 6H, OCH3). 31P NMR (δ, in THF): 113.5 (s).
Nakazawa, H.; Ichimura, S.; Nishihara, Y.; Miyoshi, K.; Nakashima,
S.; Sakai, H. Organometallics 1998, 17, 5061.
(19) Nakazawa, H.; Morimasa, K.; Kushi, Y.; Yoneda, H. Organo-
metallics 1988, 7, 458.
(18) Nakazawa, H.; Fujita, T.; Kubo, K.; Miyoshi, K. J . Organomet.
Chem. 1994, 473, 243.
(20) (a) Barrow, M.; Sim, G. A. J . Organomet. Chem. 1974, 69, C4.
(b) Barrow, M.; Sim, G. A. J . Chem. Soc., Dalton Trans. 1975, 291.

P-Transition-Metalated Iminophosphoranes
Organometallics, Vol. 21, No. 9, 2002 1945
Ta ble 1. Su m m a r y of Cr ysta l Da ta for 1a , 1b, a n d 2b
1a
20H27O4NP2F6Fe
1b
2b
formula
fw
C
C20H26O4NPFe
431.25
C20H26O4NPRu
476.47
577.22
color, habit
cryst dimens, mm
cryst syst
unit cell dimens
a, Å
yellow, plate
0.30 × 0.30 × 0.25
orthorhombic
yellow, stick
0.28 × 0.25 × 0.30
triclinic
yellow, plate
0.38 × 0.15 × 0.08
triclinic
23.3290(4)
8.7940(1)
24.3940(2)
8.4470(3)
10.2390(4)
12.8300(5)
84.362(2)
73.617(2)
78.521(2)
1042.26(7)
P1h (#2)
2
8.5940(2)
10.3780(3)
12.7040(4)
84.358(1)
74.460(2)
77.377(2)
1064.29(5)
P1h (#2)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
5004.56(9)
Pca21 (#29)
8
space group
Z
D
calcd, g m-3
1.532
1.374
1.487
F(000)
2368.00
8.01
55.9
452.00
8.24
55.8
488.00
2.36
55.5
µ, cm-1
2θmax, deg
no. of reflns
measd
obsd (I > 3σ(I))
struct soln
12 146
10742
direct methods
(SIR92)
615
4615
4236
direct methods
(SAPI91)
349
4648
4362
Patterson methods
(DIRDIF92 PATTY)
349
0.034
0.052
no. of params
Ra
Rw
0.041
0.065
0.034
0.057
b
a
b
2
2
2
2 -1
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w||Fo| - |Fc|| /∑w|Fo| ]1/2 and w ) 1/σ2(Fo) ) [σc (Fo) + (p2/4)Fo
] .
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) w ith Esd ’s in P a r en th eses for 1a , 1b, a n d 2b
1a
1b
2b
Fe(1)-P(1)
Fe(1)-C(11)
Fe(1)-C(12)
P(1)-O(3)
P(1)-O(4)
P(1)-N(1)
N(1)-C(15)
2.1864(6) Fe(1′)-P(1′)
2.1854(6) Fe(1)-P(1)
2.2218(4) Ru(1)-P(1)
2.3189(5)
1.883(3)
1.889(3)
1.615(2)
1.625(2)
1.575(2)
1.381(3)
1.784(2)
1.780(3)
1.590(2)
1.592(2)
1.672(2)
1.410(3)
Fe(1′)-C(11′)
Fe(1′)-C(12′)
P(1′)- O(3′)
P(1′)- O(4′)
P(1′)- N(1′)
N(1′)- C(15′)
1.775(3)
1.776(3)
1.580(2)
1.590(2)
1.658(2)
1.414(3)
Fe(1)-C(11)
Fe(1)-C(12)
P(1)-O(3)
P(1)-O(4)
P(1)-N(1)
N(1)-C(15)
1.765(2)
1.758(2)
1.618(1)
1.628(1)
1.574(1)
1.376(2)
Ru(1)-C(11)
Ru(1)-C(12)
P(1)-O(3)
P(1)-O(4)
P(1)-N(1)
N(1)-C(15)
P(1)-Fe(1)-C(11)
P(1)-Fe(1)-C(12)
91.37(8)
93.21(9)
C(11)-Fe(1)-C(12) 93.9(1)
P(1′)-Fe(1′)-C(11′)
P(1′)-Fe(1′)-C(12′)
90.57(8)
93.65(9)
C(11′)-Fe(1′)-C(12′) 94.7(1)
P(1)-Fe(1)-C(11)
P(1)-Fe(1)-C(12)
87.45(6)
90.12(7)
C(11)-Fe(1)-C(12) 95.25(9)
P(1)-Ru(1)-C(11)
P(1)-Ru(1)-C(12)
86.48(8)
88.79(8)
C(11)-Ru(1)-C(12) 92.3(1)
Fe(1)-P(1)-O(3)
Fe(1)-P(1)-O(4)
Fe(1)-P(1)-N(1)
O(3)-P(1)-O(4)
O(3)-P(1)-N(1)
O(4)-P(1)-N(1)
P(1)-N(1)-C(15)
118.20(7) Fe(1′)-P(1′)-O(3′)
117.92(8) Fe(1)-P(1)-O(3)
107.29(8) Fe(1)-P(1)-O(4)
121.89(8) Fe(1)-P(1)-N(1)
106.9(1)
94.0(1)
107.5(1)
127.4(2)
105.98(5) Ru(1)-P(1)-O(3)
106.03(7)
104.79(7)
123.54(8)
103.5(1)
104.0(1)
113.1(1)
128.8(2)
106.63(7) Fe(1′)-P(1′)-O(4′)
122.21(8) Fe(1′)-P(1′)-N(1′)
107.02(9) O(3′)-P(1′)-O(4′)
103.65(5) Ru(1)-P(1)-O(4)
125.10(6) Ru(1)-P(1)-N(1)
103.06(8) O(3)-P(1)-O(4)
104.27(7) O(3)-P(1)-N(1)
112.62(8) O(4)-P(1)-N(1)
O(3)-P(1)-O(4)
O(3)-P(1)-N(1)
O(4)-P(1)-N(1)
P(1)-N(1)-C(15)
94.6(1)
106.90(9) O(4′)-P(1′)-N(1′)
125.1(2) P(1′)-N(1′)-C(15′)
O(3′)-P(1′)-N(1′)
130.2(1)
P(1)-N(1)-C(15)
stands for η5-C5H5), in which the phosphoryl oxygen is
trans to one of the two carbonyls, suggesting that this
conformation is general for the complexes of the type
[(η5-C5R5)(CO)2M{P(E)R′2}]n+ (M ) Fe, Ru; E ) O, NR,
NHR; n ) 0, 1), irrespective of steric demands of
substituents on the phosphorus and of the charge on
the molecule. Therefore, it seems that some preferable
orbital interactions are responsible for the common
conformation, and this implies that 1a and 1b (and also
2b) have closely related electronic structures. In other
words, even though the deprotonation from the amino
group in 1a leads to formal changes in phosphorus
valency from P(III) to P(V) and in a metal-phosphorus
bonding from dative to covalent, the basic molecular
orbital compositions would not be significantly changed.
The Fe(1)-P(1) bond is slightly longer in 1b (2.2218(4)
Å) than in 1a (2.1864(6) or 2.1854(6) Å). Thus, it can be
proposed that the deprotonation from 1a to give 1b
causes slight weakening of the metal-phosphorus bond,
although the anionic iminophosphoranide ligand in 1b
may be greater in σ-donacity than the electrically
neutral phosphite ligand in 1a . This observation can be
rationally explained as follows. As mentioned above, 1a
and 1b might have similar electronic structure with
somewhat larger P-N double-bond character in 1b, and
the π bond is made up of the filled π orbital on the N
atom and the empty σ* orbital on the P atom. Therefore,
the stronger π bonding in 1b would lead to greater
electron distribution into the σ* orbital, leading to the
weaker phosphorus-substituent (other than the imino
group) bonds in 1b. Indeed, the P-OMe bonds are also
slightly longer in 1b than in 1a .
Sta bility a n d Rea ctivity of P -Meta la ted Im in o-
p h osp h or a n es.The metalated iminophosphoranes 1b
and 2b are both air- and/or moisture-sensitive but
neither decomposition nor rearrangement is observed
under an inert atmosphere and at least up to 60 °C in
benzene. In contrast, a P-zirconium-bonded iminophos-
phorane has been reported to be converted into a
phosphinoamide complex at 25 °C via migration of the

1946 Organometallics, Vol. 21, No. 9, 2002
Kubo et al.
zirconium fragment from P to N (eq 3).21 The difference
complex was supported by 31P NMR considerations. Our
previous study on the metallaphosphorane Cp(CO)LFe-
{P(OC6H4NH)2}, containing highly polarized P-Oapical
bonds, revealed that the π back-donation from the
transition-metal fragment increases the polarization of
the phosphorus-substituent bond to accumulate a posi-
tive charge on the phosphorus, leading to the downfield
shift in the 31P NMR.23 Similar explanations could be
applied to the present case. That is, the Cp* complex
1b resonates at lower field (122.3 ppm) than its Cp
analogue (99.8 ppm), because the greater π back-
donation in 1b polarizes the PdN bond more, leading
to more positive charge on the phosphorus.
It was previously reported that a protonated iron-
phosphonate complex, i.e., a cationic phosphite complex,
can be deprotonated by relatively mild bases such as
pyridine.19 In contrast, the protonated 1b, i.e., 1a , is not
deprotonated by pyridine (eq 4) under similar condi-
tions. This suggests that the nitrogen atom in 1b is more
in the thermal stability can be rationalized from the
HSAB concept. That is, the anionic ligand [R2PNR]- can
be described as a resonance hybrid of iminophosphor-
anide and phosphinoamide (eq 1), though a theoretical
study revealed that the latter prevails in equilibrium
in usual cases.22 Since the zirconium fragment ([Cp2-
ZrCl]+) would serve as a hard acid, it prefers hard
N-coordination to soft P-coordination, resulting eventu-
ally in exclusive formation of a phosphinoamide com-
plex. In contrast, the iron and ruthenium fragments
([Cp*(CO)2M]+) may serve as a soft acid, and so they
would preferably coordinate to the phosphorus atom to
give P-metalated iminophosphoranes. Thus, it could be
proposed that fragments of the late transition metals
in a low oxidation state are stabilized by P-coordination
of the iminophosphoranide, while those of early transi-
tion metals in a high oxidation state by N-coordination
of phosphinoamides. Indeed, the anionic compound
[Ph2PNP(O)Ph2]- reacted with palladium complexes,
i.e., soft acids, to yield not N- (nor O-) coordinated
complexes but P-palladium-bonded iminophosphor-
anes.14
To examine the stability of the metalated iminophos-
phorane having a Cp ligand in place of a Cp* ligand,
the preparation of the Cp analogue of 1b, Cp(CO)2Fe-
{P(NPh)(OMe)2}, was attempted. Since the reaction of
NaNH2 with the cationic complex [Cp(CO)2Fe{P(NHPh)-
(OMe)2}]PF6 gave many unknown products, LiN(SiMe3)2
was then used as a milder base. The reaction mixture
at -78 °C showed a resonance at 99.8 ppm in the 31P
NMR spectrum as a sole product. This chemical shift
was indicative of the formation of the metalated imi-
nophosphorane Cp(CO)2Fe{P(NPh)(OMe)2}. However,
the product is not stable enough to isolate, and decom-
position took place at room temperature. Therefore, it
can be considered that the Cp* ligand plays an impor-
tant role in the stabilization of the present metalated
iminophosphoranes. In addition to the kinetic stabiliza-
tion due to the bulkiness of the Cp* ligand, an electronic
factor also seems to be responsible. Since the Cp* ligand
is a stronger electron donor than Cp, it makes the
transition-metal center more electron-rich. Therefore,
the back-donation from the metal center to the imino-
phosphoranide ligand is greater for the Cp* complex,
leading to a stronger metal-phosphorus bond. The
presence of this greater back-donation in the Cp*
basic than the phosphoryl oxygen in the phosphonate
complex. A similar trend is generally observed between
organic iminophosphoranes and phosphonates.1b There-
fore, it can be expected that the P-metalated iminophos-
phoranes are more reactive toward electrophiles than
the corresponding phosphonate complexes.24 This means
that the P-metalated iminophosphoranes could serve as
good ligands to provide novel binuclear transition-metal
complexes with N-coordination as in type (i) and (ii) in
Chart 1.
Exp er im en ta l Section
All reactions were carried out under an atmosphere of dry
nitrogen using standard Schlenk techniques. Column chro-
matography was done quickly in the air. THF, diethyl ether,
and benzene were distilled from sodium metal, whereas CH2Cl2
was distilled from P2O5, and then they were stored under a
dry nitrogen atmosphere. Other organic solvents, AgBF4 and
(23) Kubo, K.; Nakazawa, H.; Mizuta, T.; Miyoshi, K. Organo-
metallics 1998, 17, 3522.
(24) (a) Nakazawa, H.; Kadoi, Y.; Itoh, T.; Mizuta, T.; Miyoshi, K.
Organometallics 1991, 10, 766. (b) Kubo, K.; Nakazawa, H.; Nakahara,
S.; Yoshino, K.; Mizuta, T.; Miyoshi, K. Organometallics 2000, 19, 4932.
(21) (a) Igau, A.; Dufour, N.; Mahieu, A.; Majoral, J .-P. Angew.
Chem., Int. Ed. Engl. 1993, 32, 95. (b) Mahieu, A.; Igau, A.; J aud, J .;
Majoral, J .-P. Organometallics 1995, 14, 944.
(22) Trinquier, G.; Ashby, M. T. Inorg. Chem. 1994, 33, 1306.

P-Transition-Metalated Iminophosphoranes
Organometallics, Vol. 21, No. 9, 2002 1947
NaNH2, were obtained from common commercial sources and
used without further purification. HNPh(SiMe3),25 [Cp*(CO)2-
Fe(THF)]PF6,26 and Cp*(CO)2RuCl27 were prepared in ac-
cordance with published procedures.
components were removed under vacuum. The residue was
dissolved in a small amount of CH2Cl2 and loaded on a silica
gel column, and then all the eluents with a mixture of CH2Cl2/
acetone (4/1) were collected and dried. The pure Cp*(CO)2Ru-
{P(NHPh)(OMe)2} (2a ) was finally obtained by GPLC sepa-
ration as a white powder (182 mg, 0.32 mmol, 46% yield). Anal.
Calcd for C20H27O4NBF4PRu: C, 42.57; H, 4.82; N, 2.48.
Found: C, 42.69; H, 4.90; N, 2.41. IR (νCO, in THF): 2050, 1002
HPLC was performed using a J AI LC-908 recycling pre-
parative HPLC instrument with J AIGEL-1H and -2H columns
and with CHCl3 as eluent. IR spectra were recorded on either
a Shimadzu FTIR-8100A or a Perkin-Elmer Spectrum One
spectrometer. A J EOL LA-300 multinuclear spectrometer was
1
cm-1. H NMR (δ, in CDCl3): 1.85 (s, 15H, C5(CH3)5), 3.72 (d,
1
used to obtain H, 13C, and 31P NMR spectra. 1H and 13C NMR
J PH ) 12.3 Hz, 6H, OCH3), 6.97-7.29 (m, 5H, C6H5). The signal
due to the NH proton was not observed, probably because of
broadening and/or overlapping with the multiplet due to
phenyl protons. 13C NMR (δ, in CDCl3): 10.09 (s, C5(CH3)5),
53.91 (d, J CP ) 7.5 Hz, OCH3), 103.35 (s, C5(CH3)5), 119.28 (d,
J CP ) 6.8 Hz, C6H5), 122.96 (s, C6H5), 129.54 (s, C6H5), 138.64
(d, J CP ) 3.7 Hz, C6H5), 197.51 (d, J CP ) 30.4 Hz, CO). 31P
NMR (δ, in CDCl3): 136.7 (s).
data were referenced to Me4Si, and 31P NMR data were
referenced to 85% H3PO4. Elemental analysis data were
obtained on a Perkin-Elmer 2400 CHN elemental analyzer.
P r ep a r a tion of P {NP h (SiMe3)}(OMe)2. The ether solu-
tion (80 mL) of LiNPh(SiMe3) was prepared from the reaction
of HNPh(SiMe3) (10.22 g, 61.8 mmol) with n-BuLi (2.47 M
hexane solution, 25.0 mL, 61.8 mmol) at -78 °C. To the
solution was added the ether solution (100 mL) of P(OMe)2Cl
(5.6 mL, 62.6 mmol) at -78 °C, which was prepared by
overnight stirring of PCl3 (1.8 mL, 20.6 mmol) with P(OMe)3
(4.0 mL, 33.9 mmol) at room temperature. After stirring for 2
h at room temperature, the volatile components were removed
under vacuum. Finally, distillation at 80 °C under reduced
pressure (60 Pa) provided P{NPh(SiMe3)}(OMe)2 (6.85 g, 26.6
mmol, 43% yield) with a small amount of impurities. It can
be used in the following reactions without further purification.
1H NMR (δ, in CDCl3): 0.29 (d, J PH ) 1.5 Hz, 9H, SiCH3), 3.55
(d, J PH ) 12.6 Hz, 6H, OCH3), 7.08-7.37 (m, 5H, C6H5). 13C
NMR (δ, in CDCl3): 1.19 (d, J PC ) 7.5 Hz, SiCH3), 50.41 (d,
J PC ) 18.0 Hz, OCH3), 124.93 (s, C6H5), 128.18 (s, C6H5), 130.12
(d, J PC ) 3.1 Hz, C6H5), 140.65 (d, J PC ) 3.7 Hz, C6H5). 31P
NMR (δ, in CDCl3): 145.35 (s).
P r ep a r a tion of Cp *(CO)2F e{P (NP h )(OMe)2} (1b). To a
yellow solution of 1a (419 mg, 0.73 mmol) in THF (30 mL)
was added an excess amount of NaNH2, and the mixture was
stirred at room temperature for 30 min. The color of the
solution changed to yellowish orange. After volatile compo-
nents were removed under reduced pressure, the product was
extracted with pentane from the residue. Finally the solvent
was removed in vacuo to give Cp*(CO)2Fe{P(NPh)(OMe)2} (1b)
as an orange-yellow powder (213 mg, 0.49 mmol, 68% yield).
When the product has reddish color, it should be washed with
a small amount of hexane. Anal. Calcd for C20H26O4NPFe: C,
55.70; H, 6.08; N, 3.25. Found: C, 55.81; H, 5.63; N, 3.11. IR
1
(νCO, in THF): 2016, 1967 cm-1. H NMR (δ, in CDCl3): 1.71
(s, 15H, C5(CH3)5), 3.65 (d, J PH ) 11.4 Hz, 6H, OCH3), 6.61-
7.12 (m, 5H, C6H5). 13C NMR (δ, in CDCl3): 9.44 (s, C5(CH3)5),
51.61 (d, J CP ) 8.7 Hz, OCH3), 98.16 (s, C5(CH3)5), 116.58 (s,
C6H5), 122.96 (d, J CP ) 17.4 Hz, C6H5), 128.63 (s, C6H5), 150.60
(d, J CP ) 6.26 Hz, C6H5), 214.47 (d, J CP ) 35.18 Hz, CO). 31P
NMR (δ, in CDCl3): 122.3 (s).
P r epar ation of [Cp*(CO)2Fe{P (NHP h )(OMe)2}]P F6 (1a).
[Cp*(CO)2Fe(THF)]PF6 (3.68 g, 7.92 mmol) was dissolved in
CH2Cl2 (75 mL) and treated with P(OMe)2{NPh(SiMe3)} (2.10
mL, 7.92 mmol) at room temperature. The mixture was stirred
overnight, and then a few drops of H2O were added. After
stirring for an additional 2 h, the mixture was loaded on a
silica gel column and eluted with CH2Cl2 and then with
CH2Cl2/acetone, 1:4. A pale yellow band eluted with 1:4
CH2Cl2/acetone was collected and dried under vacuum to give
a yellow oil. The oil was dissolved in a small amount of THF,
and then a large amount of ether was added to form a pale
yellow precipitate. After washing with ether several times, the
precipitate was dried under reduced pressure to give [Cp*(CO)2-
Fe{P(NHPh)(OMe)2}]PF6, 1a , as a yellow powder (3.07 g, 5.32
mmol, 67% yield). Anal. Calcd for C20H27O4NP2F6Fe: C, 41.62;
H, 4.71; N, 2.43. Found: C, 41.67; H, 4.70; N, 2.36. IR (νCO, in
P r ep a r a tion of Cp *(CO)2Ru {P (NP h )(OMe)2} (2b). Using
2a (182 mg, 0.32 mmol) as a starting material, Cp*(CO)2Ru-
{P(NPh)(OMe)2} (2b) was prepared as a yellow powder by a
procedure similar to that for 1b (92 mg, 0.19 mmol, 60% yield).
Anal. Calcd for C20H26O4NPRu: C, 50.42; H, 5.50; N, 2.94.
Found: C, 49.83; H, 5.74; N, 2.66. IR (νCO, in THF): 2029, 1976
1
cm-1. H NMR (δ, in CDCl3): 1.83 (s, 15H, C5(CH3)5), 3.57 (d,
J PH ) 12.1 Hz, 6H, OCH3), 6.64-7.11 (m, 5H, C6H5). 13C NMR
(δ, in CDCl3): 9.88 (s, C5(CH3)5), 50.59 (d, J CP ) 6.2 Hz, OCH3),
101.86 (s, C5(CH3)5), 116.37 (s, C6H5), 122.99 (d, J CP ) 18.0
Hz, C6H5), 128.57 (s, C6H5), 150.83 (d, J CP ) 9.9 Hz, C6H5),
200.59 (d, J CP ) 18.6 Hz, CO). 31P NMR (δ, in CDCl3): 103.8
(s).
1
THF): 2036, 1991 cm-1. H NMR (δ, in CDCl3): 1.74 (s, 15H,
C5(CH3)5), 3.82 (d, J PH ) 12.1 Hz, 6H, OCH3), 6.22 (br d, J PH
) 3.9 Hz, 1H, NH), 7.08-7.30 (m, 5H, C6H5). 13C NMR (δ, in
CDCl3): 9.17 (s, C5(CH3)5), 54.12 (d, J CP ) 8.7 Hz, OCH3),
100.42 (s, C5(CH3)5), 119.27 (d, J CP ) 6.2 Hz, C6H5), 123.46 (s,
C6H5), 129.81 (s, C6H5), 138.03 (d, J CP ) 4.9 Hz, C6H5), 211.05
(d, J CP ) 34.10 Hz, CO). 31P NMR (δ, in CDCl3): 161.5 (s, Fe-
P), -143.9 (sep, J PF ) 712.0 Hz, PF6-).
P r epar ation of [Cp*(CO)2Ru {P (NHP h )(OMe)2}]BF4 (2a).
To the mixture of Cp*(CO)2RuCl (232 mg, 0.71 mmol) and
AgBF4 (138 mg, 0.71 mmol) in 15 mL of CH2Cl2 was added
dropwise 10 mL of a CH2Cl2 solution of P(OMe)2{NPh(SiMe3)}
(1.19 mL, 0.71 mmol) at room temperature. After stirring for
1.5 h, the mixture was filtered and the volatile components
were removed from the filtrate under reduced pressure. The
residue was washed with ether several times and dissolved
in 15 mL of CH2Cl2, and then a few drops of H2O were added.
The mixture was stirred for 1.5 days, and then the volatile
X-r a y Str u ctu r e Deter m in a tion for 1a , 1b, a n d 2b. A
suitable crystal of 1a was obtained through recrystallization
from CH2Cl2, while those of 1b and 2b were obtained from
benzene, and then they were separately mounted on a glass
fiber. All measurements were made on a Mac Science DIP2030
diffractometer with graphite-monochromated Mo Ka radiation
(λ ) 0.710 73 Å) at 200 K. Crystal data, data collection
parameters, and results of the analyses are summarized in
Table 1.
The structures were solved by direct methods with the
program SIR9228 for 1a and SAPI9129 for 1b and by the
Patterson method for 2b with the program DIRDIF92 PATTY30
and then were expanded using Fourier techniques.31 Positions
(28) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. J . Appl. Crystallogr. 1994,
27, 435.
(29) Fan, H.-F. Structure Analysis Programs with Intelligent Control;
Rigaku Corporation: Tokyo, J apan, 1991.
(25) Randall, E. W.; Zuckerman, J . J . J . Am. Chem. Soc. 1968, 90,
3167.
(26) Catheline, D.; Astruc, D. Organometallics 1984, 3, 1094.
(27) Blockmore, T.; Cotton, J . G.; Bruce, M. I.; Stone, F. G. A. J .
Chem. Soc. A 1968, 2931.
(30) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF program system; Technical Report of the Crystallography
Laboratory; University of Nijmegen: Nijmegen, The Netherlands,
1992.

1948 Organometallics, Vol. 21, No. 9, 2002
Kubo et al.
of hydrogen atoms of 1a were calculated by assuming idealized
geometries, whereas those of 1b and 2b were determined from
subsequent difference Fourier maps. The non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were not refined
for 1a , but they were refined isotropically for 1b and 2b. An
extinction correction was applied in each case. Neutral atom
Creagh and Hubbel.35 All calculations were performed using
the program package teXsan.36
Ack n ow led gm en t. This work was supported by
Grants-in-Aid for Scientific Research (Nos. 11740371
and 12640539) from the Ministry of Education, Culture,
Sports, Science and Technology of J apan.
scattering factors were taken from Cromer and Waber.32
33
Anomalous dispersion effects were included in Fcalc
;
the
Su p p or tin g In for m a tion Ava ila ble: Details of X-ray
crystal structure determination of 1a , 1b, and 2b including
tables of intensity collection and refinement details, atomic
coordinates and thermal parameters, and bond distances and
angles. This material is available free of charge via the
Internet at http://pubs.acs.org.
values for ∆f ′ and ∆f′′ were those of Creagh and McAuley.34
The values for the mass attenuation coefficients are those of
(31) 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.
(32) Cromer, D. T.; Waber, J . T. In International Tables for X-ray
Crystallography; The Kynoch Press: England, 1974; Vol. IV, Table
2.2A.
(33) Ibers, J . A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(34) Creagh, D. C.; McAuley, W. J . In International Tables for
Crystallography; Wilson, A. J . C., Ed.; Kluwer Academic Publishers:
Boston, 1992; Vol. C, Table 4.2.6.8.
OM0110484
(35) Creagh, D. C.; Hubbel, J . H. In International Tables for
Crystallography; Wilson, A. J . C., Ed.; Kluwer Academic Publishers:
Boston, 1992; Vol. C, Table 4.2.4.3.
(36) teXsan,
A Crystal Structure Analysis Package; Molecular
Structure Corporation: The Woodlands, TX, 1985 and 1992.