Reactions of the phosphinidene-bridged complexes [Fe2(η 5-C5H5)2(μ-PR)(μ-CO)(CO) 2] (R = Cy, Ph, 2,4,6-C6H2 tBu 3) with diazoalkanes. Formation and rearrangements of phosphadiazadiene-bridged derivatives

Article abstract of DOI:10.1021/om100345e

The phosphinidene complexes [Fe₂Cp₂(μ-PR)(μ-CO) (CO)₂] (Cp = η⁵-C₅H₅; R = Cy, Ph, Mes*; Mes* = 2,4,6-C₆H₂^tBu ₃) react readily with diazoalkanes N₂CR′R″ (R′ = H, R″ = H, CO₂Et, SiMe₃; R′ = R″ = Ph) in dichloromethane solution at room temperature or below to give the corresponding P:P-bridged phosphadiazadiene derivatives [Fe ₂Cp₂(μ-RPN₂CR′R″)(μ-CO)(CO) ₂] (2) with high yield. The diazomethane derivative (Fe-Fe = 2.6198(6) A) is protonated selectively with HBF₄· OEt₂ at the P-bound nitrogen atom to yield the aminophosphide derivative [Fe₂Cp₂(μ-CyPNHNCH₂)(μ-CO)(CO) ₂](BF₄) (Fe-Fe = 2.6126(5) A). Compounds 2 decompose upon heating in toluene solution at 363 K to give the dimer [Fe ₂Cp₂(CO)₄] as the only organometallic product. The same result was obtained when irradiating with visible-UV light toluene solutions of the phenylphosphinidene-derived compounds. In contrast, relatively selective decarbonylations could be induced photochemically when R = Cy, Mes*. The reaction products, however, were strongly dependent on the nature of all substituents present in compounds 2. The diazomethane derivative yielded a mixture of the P:N-bound phosphadiazadiene complex [Fe ₂Cp₂(μ-CyPN₂CH₂)(μ-CO) ₂] (major) and the phosphaalkene derivative [Fe₂Cp ₂(μ-CyPCH₂)(μ-CO)(CO)] (minor). In contrast, the ethyldiazoacetate derivative gave the paramagnetic complex [Fe ₂Cp₂{μ-CyPN₂CH(CO₂Et)}(μ-CO) (CO)], possibly containing a μ-P:P,C-phosphadiazadiene ligand, which upon chromatography fully rearranges into the aminophosphide-iminoacyl complex [Fe₂Cp₂{μ-CyPNHNC(CO₂Et)}(μ-CO)(CO)] (Fe-Fe = 2.6261(8) A), possibly through a protonation/deprotonation sequence on the alumina surface. The trimethylsilyldiazomethane derivative instead gave directly the analogous aminophosphide-iminoacyl complex [Fe ₂Cp₂{μ-CyPN(SiMe₃)NCH}(μ-CO)(CO)], now resulting from an unusual 1,3-shift of the SiMe₃ group along the ligand backbone. Finally the photochemical treatment of the ethyldiazoacetate derivative of the supermesithylphosphinidene substrate gave the complex [Fe ₂Cp₂{μ-Mes*PN₂CH(CO ₂Et)}(μ-CO)₂] (Fe-Fe = 2.514(1) A), containing a P:N-bridged phosphadiazadiene ligand bound to the dimetal center in a novel coordination mode, this involving the P-bound nitrogen atom, instead of the C-bound nitrogen.

Full text of DOI:10.1021/om100345e

5140 Organometallics 2010, 29, 5140–5153
DOI: 10.1021/om100345e
Reactions of the Phosphinidene-Bridged Complexes
t
[Fe2(η5-C5H5)2(μ-PR)(μ-CO)(CO)2] (R = Cy, Ph, 2,4,6-C6H2 Bu3)
with Diazoalkanes. Formation and Rearrangements of
Phosphadiazadiene-Bridged Derivatives†
ꢀ
M. Angeles Alvarez, M. Esther Garcıa, Rocıo Gonzalez, and Miguel A. Ruiz*
´ ꢀ ꢀ
Departamento de Quımica Organica e Inorganica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain
Received April 26, 2010
The phosphinidene complexes [Fe2Cp2(μ-PR)(μ-CO)(CO)2] (Cp = η5-C5H5; R = Cy, Ph, Mes*;
t
Mes*=2,4,6-C6H2 Bu3) react readily with diazoalkanes N2CR0R00 (R0 = H, R00 = H, CO2Et, SiMe3;
R0=R00=Ph) in dichloromethane solution at room temperature or below to give the corresponding
P:P-bridged phosphadiazadiene derivatives [Fe2Cp2(μ-RPN2CR0R00)(μ-CO)(CO)2] (2) with high
˚
yield. The diazomethane derivative (Fe-Fe=2.6198(6) A) is protonated selectively with HBF4 OEt2
3
at the P-bound nitrogen atom to yield the aminophosphide derivative [Fe2Cp2(μ-CyPNHNCH2)-
(μ-CO)(CO)2](BF4) (Fe-Fe = 2.6126(5) A). Compounds 2 decompose upon heating in toluene
˚
solution at 363 K to give the dimer [Fe2Cp2(CO)4] as the only organometallic product. The same
result was obtained when irradiating with visible-UV light toluene solutions of the phenylphos-
phinidene-derived compounds. In contrast, relatively selective decarbonylations could be induced
photochemically when R = Cy, Mes*. The reaction products, however, were strongly dependent on
the nature of all substituents present in compounds 2. The diazomethane derivative yielded a mixture
of the P:N-bound phosphadiazadiene complex [Fe2Cp2(μ-CyPN2CH2)(μ-CO)2] (major) and the
phosphaalkene derivative [Fe2Cp2(μ-CyPCH2)(μ-CO)(CO)] (minor). In contrast, the ethyldiazo-
acetate derivative gave the paramagnetic complex [Fe2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO)(CO)],
possibly containing a μ-P:P,C-phosphadiazadiene ligand, which upon chromatography fully re-
arranges into the aminophosphide-iminoacyl complex [Fe2Cp2{μ-CyPNHNC(CO2Et)}(μ-CO)(CO)]
˚
(Fe-Fe = 2.6261(8) A), possibly through a protonation/deprotonation sequence on the alumina
surface. The trimethylsilyldiazomethane derivative instead gave directly the analogous aminophos-
phide-iminoacyl complex [Fe2Cp2{μ-CyPN(SiMe3)NCH}(μ-CO)(CO)], now resulting from an unu-
sual 1,3-shift of the SiMe3 group along the ligand backbone. Finally the photochemical treatment of
the ethyldiazoacetate derivative of the supermesithylphosphinidene substrate gave the complex
˚
[Fe2Cp2{μ-Mes*PN2CH(CO2Et)}(μ-CO)2] (Fe-Fe = 2.514(1) A), containing a P:N-bridged phos-
phadiazadiene ligand bound to the dimetal center in a novel coordination mode, this involving the
P-bound nitrogen atom, instead of the C-bound nitrogen.
Introduction
making them useful in the synthesis of numerous organophos-
phorus compounds.1 In contrast, the chemistry of binuclear
complexes having phosphinidene bridges has remained com-
paratively little explored until recently, even though the pre-
sence of multiple M-P bonds or lone pairs at phosphorus in
their different coordination modes (C to E in Chart 1) should
The study of phosphinidene complexes is a fruitful area of
research within the current organometallic chemistry.1 Most
of the work in this active area has been carried out so far on
the bent-terminal complexes, these having a nonbonding
electron pair at a low-coordination phosphorus atom and a
metal-phosphorus bond that can be described as essentially
single or double, depending on the metal environment (A and B
in Chart 1), all of which makes these complexes highly reactive
toward a great variety of unsaturated organic molecules, then
(1) Reviews: (a) Aktas, H.; Slootweg, J. C.; Lammerstma, K. Angew.
Chem., Int. Ed. 2010, 49, 2. (b) Waterman, R. Dalton Trans. 2009, 18. (c)
Mathey, F. Dalton Trans. 2007, 1861. (d) Lammertsma, K. Top. Curr.
Chem. 2003, 229, 95. (e) Streubel, R. Top. Curr. Chem. 2003, 223, 91. (f)
Mathey, F. Angew. Chem., Int. Ed. 2003, 42, 1578. (g) Lammertsma, K.;
Vlaar, M. J. M. Eur. J. Org. Chem. 2002, 1127. (h) Mathey, F.; Tran-Huy,
N. H.; Marinetti, A. Helv. Chim. Acta 2001, 84, 2938. (i) Stephan, D. W.
Angew. Chem., Int. Ed. 2000, 39, 314. (j) Shah, S.; Protasiewicz, J. D.
Coord. Chem. Rev. 2000, 210, 181. (k) Schrock, R. R. Acc. Chem. Res.
1997, 30, 9. (l) Cowley, A. H. Acc. Chem. Res. 1997, 30, 445. (m) Cowley,
A. H.; Barron, A. R. Acc. Chem. Res. 1988, 21, 81. (n) Huttner, G.; Knoll, K.
Angew. Chem., Int. Ed. Engl. 1987, 26, 743. (o) Huttner, G.; Evertz, K. Acc.
Chem. Res. 1986, 19, 406.
† Part of the Dietmar Seyferth Festschrift. This work is dedicated to Prof.
Dietmar Seyferth, in recognition for his outstanding contribution to organo-
metallic chemistry, both as an original researcher and as an efficient and kind
editor of the prime specialized journal in the field.
*To whom correspondence should be addressed. E-mail: mara@
uniovi.es.
r
pubs.acs.org/Organometallics
Published on Web 06/22/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 21, 2010 5141
Chart 1
Chart 3
Chart 2
(A, B) or trigonal-bridging (C, D) phosphinidene ligands.7 In
this paper we report a complete study on the reactions of the
phosphinidene complex 1a toward different diazoalkanes
N2CR0R00 (R0 =H, R00 = H, CO2Et, SiMe3; R0 =R00 = Ph)
and the rearrangements induced by the decarbonylation of the
products initially formed in these reactions. In order to examine
the influence of the substituent at the phosphorus atom, we
have also studied some reactions using the phenylphosphini-
dene complex 1b, as well as the supermesithylphosphinidene
complex [Fe2Cp2(μ-PMes*)(μ-CO)(CO)2] (1c) (Mes*=2,4,6-
make these complexes quite reactive toward unsaturated or-
ganic molecules or other metal complexes.2,3 Recent work from
our lab2,4 and the group of Carty3f,g,i has shown that this is
indeed the case for several complexes exhibiting trigonal-
phosphinidene bridges of the types C and D, but apparently
the reactivity of binuclear complexes having bent (or
pyramidal) phosphinidene bridges (E in Chart 1) toward
organic molecules has not been explored to date, with the
exception of the transient species [Fe2{μ-P(NiPr2)}2(CO)6].5
Recently we developed a high-yield route to the diiron com-
pounds [Fe2Cp2(μ-PR)(μ-CO)(CO)2] (Cp=η5-C5H5; R = Cy
(1a), Ph (1b), Chart 2), these exhibiting a quite nucleophilic
bent-bridging phosphinidene ligand.6 A preliminary study
revealed that the cyclohexylphosphinidene complex 1a reacted
with 1-alkynes and some unsaturated N-containing molecules
such as trimethylsilyldiazomethane and benzyl azide to give
products involving novel transformations not observed in
comparable reactions of complexes having bent-terminal
t
C6H2 Bu3), the latter being a sterically congested molecule
recently reported by us.8
It is well known that phosphines (PR3) react easily with
diazoalkanes to give the corresponding adducts R3PN2-
CR0R00,9 and it might be then anticipated that bent-terminal
and bent-bridging phosphinidene complexes might analo-
gously react with diazoalkanes to give initially coordinated
phosphadiazadiene (or phosphazine) RPN2CR0R00 ligands, a
type of molecule unknown in the free state, and perhaps
phosphaalkene ligands (RPdCR0R00), if spontaneous deni-
trogenation could take place afterward. Surprisingly, how-
ever, the reactions of phosphinidene complexes toward
diazolkanes have been explored only recently and even so
to a limited extent. In particular, it has been shown on one
hand that the mononuclear electrophilic complexes [ML-
(CO)x(PNiPr2)]þ (M= Fe, Cr, Mo, W; L=Cp, Cp*; x = 2, 3]
(type A) react with N2CPh2 to give P- or P,N,N-bound
phosphadiazadiene derivatives depending on the metal
(modes P and Q in Chart 3), while the iron complex also
reacts with N2CHSiMe3 to give the corresponding phos-
phaalkene, thus implying a fast denitrogenation reaction in
that case.10 On the other hand, the binuclear complex [Mn2-
(μ-PNiPr2)(CO)8], having a trigonal-phoshinidene bridge of
type C, has been shown to react with N2CPh2 to give the P:N-
bridged derivative [Mn2(μ-iPr2NPN2CPh2)(CO)8], thus pro-
viding a third coordination mode for the phosphadiazadiene
ligand (R in Chart 3).3i No other reactions of phosphinidene
complexes with diazoalkanes appear to have been investi-
gated previously. Therefore, the reactions of complexes 1a-c
reported in this work constitute the first study on this matter
involving bent-bridging phosphinidene complexes (type E in
Chart 1). As it will be seen below, this has allowed the isola-
tion of complexes having phosphadiazadiene ligands exhibiting
ꢀ
(2) Amor, I., Garcıa, M. E., Ruiz, M. A., Saez, D., Hamidov, H.,
Jeffery, J. C. Organometallics 2006, 25, 4857, and references therein.
(3) For recent work on binuclear phosphinidene complexes, see: (a)
Scheer, M.; Kuntz, C.; Stubenhofer, M.; Zabel, M.; Timoshkin, A. Y.
Angew. Chem., Int. Ed. 2010, 49, 188. (b) Stubenhofer, M.; Kuntz, C.;
ꢀ
Balazs, G.; Zabel, M.; Scheer, M. Chem. Commun. 2009, 1745. (c) Scheer,
M.; Himmel, D.; Kuntz, C.; Zhan, S.; Leiner, E. Chem. Eur. J. 2008, 14,
9020. (d) Cui, P.; Chen, Y.; Xu, X.; Sun, J. Chem. Commun. 2008, 5547. (e)
Masuda, J. D.; Jantunen, K. C.; Ozerov, O. V.; Noonan, J. T.; Gates, D. P.;
Scott, B. L.; Kiplinger, J. L. J. Am. Chem. Soc. 2008, 130, 2408. (f) Graham,
T. W.; Udachin, K. A.; Carty, A. J. Inorg. Chim. Acta 2007, 360, 1376. (g)
Graham, T. W.; Udachin, K. A.; Carty, A. J. Chem. Commun. 2006, 2699. (h)
Bai, G.; Pingrong, W.; Das, A. K.; Stephan, D. W. Dalton Trans. 2006, 1141.
(i) Graham, T. W.; Udachin, K. A.; Carty, A. J. Chem. Commun. 2005, 4441.
(j) Shaver, M. P.; Fryzuk, M. D. Organometallics 2005, 24, 1419. (k) Driess,
M.; Aust, J.; Merz, K. Eur. J. Chem. 2005, 866. (l) Scheer, M.; Vogel, U.;
€
Becker, U.; Balazs, G.; Scheer, P.; Honle, W.; Becker, M.; Jansen, M. Eur. J.
Chem. 2005, 135. (m) Sanchez-Nieves, J.; Sterenberg, B. T.; Udachin, K. A.;
Carty, A. J. Can. J. Chem. 2004, 82, 1507. (n) Termaten, A. T.; Nijbacker,
T.; Ehlers, A. W.; Schakel, M.; Lutz, M.; Spek, A. L.; McKee, M. L.;
Lammertsma, K. Chem. Eur. J. 2004, 10, 4063. (o) Sanchez-Nieves, J.;
Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. Inorg. Chim. Acta 2003, 350,
486. (p) Blaurock, S.; Hey-Hawkins, E. Eur. J. Inorg. Chem. 2002, 2975.
ꢀ
(4) (a) Garcıa, M. E.; Riera, V.; Ruiz, M. A.; Saez, D.; Vaissermann,
J.; Jeffery, J. C. J. Am. Chem. Soc. 2002, 124, 14304. (b) Amor, I.; García-
ꢀ
ꢀ
Vivo, D.; García, M. E.; Ruiz, M. A.; Saez, D.; Hamidov, H.; Jeffery, J. C.
Organometallics 2007, 26, 466. (c) Alvarez, M. A.; Amor, I.; García, M. E.;
ꢀ
García-Vivo, D.; Ruiz, M. A. Inorg. Chem. 2007, 46, 6230. (d) Alvarez,
ꢀ
(8) Alvarez, M. A.; Garcıa, M. E.; Gonzalez, R.; Ramos, A.; Ruiz,
M. A. Organometallics 2010, 29, 1875.
(9) (a) Bethell, D.; Bourne, R.; Kasran, M. J. Chem. Soc., Perkin
Trans. 2 1994, 2081, and references therein. (b) Khaskin, B. A.; Molodova,
O. D.; Torgasheva, N. A. Russ. Chem. Rev. 1992, 61, 306.
(10) Graham, T. W.; Udachin, K. A.; Carty, A. J. Chem. Commun.
2005, 5890.
M. A.; Amor, I.; García, M. E.; Ruiz, M. A. Inorg. Chem. 2008, 47, 7963.
(5) (a) King, R. B. J. Organomet. Chem. 1998, 557, 29. (b) King, R. B.;
Bitterwolf, T. E. Coord. Chem. Rev. 2000, 206-207, 563.
ꢀ
(6) Alvarez, C. M.; Alvarez, M. A.; Garcıa, M. E.; Gonzalez, R.;
Ruiz, M. A.; Hamidov, H.; Jeffery, J. C. Organometallics 2005, 24, 5503.
ꢀ
(7) Alvarez, M. A.; Garcıa, M. E.; Gonzalez, R.; Ruiz, M. A.
Organometallics 2008, 27, 1037.

5142 Organometallics, Vol. 29, No. 21, 2010
Alvarez et al.
Chart 4
three new coordination modes, as well as the observation of
unusual migratory processes in these ligands, resulting in novel
aminophosphide-iminoacyl derivatives.
Results and Discussion
Figure 1. ORTEP diagram (30% probability) of compound
2a.1, with the Cy ring (except the C1 atom) and H atoms
(except those bound to C4) omitted for clarity.
Reactions of Compounds 1 with Diazoalkanes. Structural
Characterization of P:P-Bridged Phosphadiazadiene Deriva-
tives. The cyclohexylphosphinidene complex 1a reacts ra-
pidly (in a few minutes) with the diazoalkanes N2CR0R00 (R0=
H, R00=H, CO2Et, R0=R00=Ph) in dichloromethane solution
at room temperature or below to give the corresponding P:P-
bridged phosphadiazadiene derivatives [Fe2Cp2(μ-CyPN2-
CR0R00)(μ-CO)(CO)2] (2a.1 to 2a.4) with good yield (Chart 4).
The presence of electron-withdrawing groups in the diazoalkane
seems to be beneficial for this reaction to proceed at a high
rate, since that with trimethylsilyldiazomethane requires ca.
16 h for completion under comparable conditions, even
when the corresponding reaction product (2a.3) has the same
structure as the other products. A similar reaction takes
place with the phenylphosphinidene complex 1b to give the
corresponding derivatives [Fe2Cp2(μ-PhPN2CR0R00)(μ-CO)-
(CO)2] (2a.2 to 2a.4), although the reaction now occurs at a
higher rate (cf. 2 h for completion in the case of N2CHSi-
Me3). The steric effects seem to have little influence in this
reaction, since the reaction of ethyldiazoacetate with the
supermesithylphosphinidene complex 1c still proceeds ra-
pidly at room temperature to give the corresponding phos-
phadiazadiene derivative [Fe2Cp2{μ-Mes*PN2CH(CO2Et)}-
(μ-CO)(CO)2] (2c.2). All these products could be isolated as
dark green solids of medium to high sensitivity to air.
˚
Table 1. Selected Bond Lengths (A) and Angles (deg) for
Compound 2a.1
Fe(1)-Fe(2)
Fe(1)-P(1)
Fe(2)-P(1)
Fe(1)-C(3)
Fe(2)-C(3)
Fe(1)-C(1)
Fe(2)-C(2)
P(1)-N(1)
N(1)-N(2)
N(2)-C(4)
2.6198(6)
2.2180(8)
2.2359(8)
1.939(3)
1.931(3)
1.749(3)
1.750(3)
1.612(2)
1.403(3)
1.278(4)
Fe(1)-P(1)-Fe(2)
Fe(1)-C(3)-Fe(2)
Fe(1)-Fe(2)-C(2)
Fe(2)-Fe(1)-C(1)
P(1)-Fe(1)-C(1)
P(1)-Fe(2)-C(2)
C(3)-Fe(1)-C(1)
C(3)-Fe(2)-C(2)
P(1)-Fe(1)-C(3)
Fe(1)-P(1)-N(1)
P(1)-N(1)-N(2)
N(1)-N(2)-C(4)
72.06(2)
85.2(1)
100.2(1)
98.8(1)
90.1(1)
91.3(1)
89.3(1)
90.0(1)
100.3(1)
124.5(1)
117.5(2)
116.1(3)
observed in the formation of the mentioned oxophosphinidene
complex.6 Yet all these values are within the range of single-
bond lengths. To our knowledge, compound 2a.1 represents
the first example of a complex displaying a bridging phospha-
diazadiene ligand bound to the metal centers exclusively
through the phosphorus atoms. This expectedly leads to Fe-P
distances longer than in the terminal mode (þP in Chart 3, cf.
i
2.1691(4) A in [FeCp(CO)2( Pr2NPN2CPh2)] ).10 Yet, the P-
˚
˚
N, N-N, and N-C distances of ca. 1.60, 1.40, and 1.30 A,
respectively, are comparable in both complexes. Taking into
account the reference values for the respective single and
double bonds, as well as the effect of hybridization,11 these
distances can be taken as indicative of the presence of essen-
tially double, single, and double bonds, respectively, which
is also in agreement with the values of the P-N-N and
N-N-C angles, close to 120°. Finally, we should remark that
the PNNC skeleton adopts a transoid, almost planar config-
uration (torsion angle 166°) perpendicular to the intermetallic
bond, perhaps just to minimize the repulsive interactions with
the cyclopentadienyl ligands.
Spectroscopic data in solution for the eight compounds of
type 2 prepared are similar to each other (Table 2 and
Experimental Section), thus indicating that they all share
the same structure, comparable to that of 2a.1 in the crystal.
In particular, their IR spectra exhibit a low-frequency band
The structure of the diazomethane derivative 2a.1 was
established by an X-ray study (Figure 1 and Table 1) and can
be related to the structure of the phosphinidene complexes
1b,c, and even more closely to that of the oxophosphinidene
derivative [Fe2Cp2{μ-P(O)Cy}(μ-CO)(CO)2].6,8 The mole-
cule is built up from two cyclopentadienylcarbonyliron fra-
gments placed in a cisoid relative arrangement, these being
bridged by a carbonyl and by a phosphadiazadiene ligand
bound to the iron centers through its P atom, with the cyclo-
hexyl group pointing away from the cyclopentadienyl ligands,
as found in the phosphinidene precursor. The environment
around the iron atoms is pseudooctahedral, and the interme-
˚
tallic distance of 2.6198(6) A is comparable to those measured
˚
in the mentioned compounds (cf. 2.601(2) A for the oxopho-
sphinidene complex) and consistent with the single Fe-Fe
bond proposed for all these molecules according to the EAN
rule. The major perturbation on the metal environment de-
rived from the binding of the diazoalkane molecule to the
phosphorus atom concerns the Fe-P bond lengths, which are
(11) (a) Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chem-
istry: Principles of Structure and Reactivity, 4th ed.; HarperCollins College
Publishers: New York, 1993. (b) Allen, F. H.; Kennard, O.; Watson, D. G.;
Brammer, L.; Orpen, G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
˚
˚
reduced from ca. 2.26 A in 1b to ca. 2.22 A in 2a.1, as also

Article
Organometallics, Vol. 29, No. 21, 2010 5143
Table 2. Selected IR and 31P{1H} NMR Data for New Compounds
ν(CO)a
b
δP
c
compound
δC(JCP)
[Fe2Cp2(μ-CyPN2CH2)(μ-CO)(CO)2] (2a.1)
[Fe2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO)(CO)2] (2a.2)
[Fe2Cp2{μ-CyPN2CH(SiMe3)}(μ-CO)(CO)2] (2a.3)
[Fe2Cp2(μ-CyPN2CPh2)(μ-CO)(CO)2] (2a.4)
[Fe2Cp2{μ-PhPN2CH(CO2Et)}(μ-CO)(CO)2] (2b.2)
[Fe2Cp2{μ-PhPN2CH(SiMe3)}(μ-CO)(CO)2] (2b.3)
[Fe2Cp2(μ-PhPN2CPh2)(μ-CO)(CO)2] (2b.4)
[Fe2Cp2{μ-Mes*PN2CH(CO2Et)}(μ-CO)(CO)2] (2c.2).
[Fe2Cp2(μ-CyPNHNCH2)(μ-CO)(CO)2](BF4) (3)
[Fe2Cp2(μ-CyPN2CH2)(μ-CO)2] (4)
cis-[Fe2Cp2(μ-κ1:η2-CyPCH2)(μ-CO)(CO)] (cis-5)
trans-5
[Fe2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO)(CO)] (6)
cis-[Fe2Cp2{μ-CyPNHNC(CO2Et)}(μ-CO)(CO)] (cis-7e)
trans-7e
cis-[Fe2Cp2{μ-CyPN(SiMe3)NCH}(μ-CO)(CO)] (cis-7f)
trans-7f
cis-[Fe2Cp2(μ-CyPNHNCH)(μ-CO)(CO)] (cis-7g)
trans-7g
cis-[Fe2Cp2(μ-CyPNHNHCH)(μ-CO)(CO)](BF4) (cis-8j)
trans-8j
cis-[Fe2Cp2(μ-CyPNHNMeCH)(μ-CO)(CO)](I) (cis-8k)
trans-8k
[Fe2Cp2(μ-Mes*PN2CH2)(μ-CO)2] (9)
1980 (vs), 1946 (w), 1780 (m)
1988 (vs), 1955 (w), 1791 (m), 1684 (m)
1980 (vs), 1947 (w), 1782 (m)
1980 (vs), 1947 (w), 1781 (m
1998 (vs), 1965 (w), 1797 (m), 1687 (m)
1991 (vs), 1955 (w), 1785 (m)
1990 (vs), 1956 (w), 1786 (m)
1998 (vs), 1968 (w), 1782 (m), 1678 (m)
2012 (vs), 1982 (w), 1825 (m)
1780 (w), 1745 (vs)
307.6
332.4d
304.8
301.0
315.0d
292.7
289.0
318.3
313.7
204.8d
208.2
193.0
133.7 (51)
130.0 (55)d
126.3 (61)
20.3 (4)
1939 (vs), 1860 (w, br)e
1895 (vs)e,f
1936 (vs), 1783 (s), 1683 (m)g
1967 (vs), 1788 (s), 1697 (m)
1942 (vs), 1788 (s), 1697 (m)
1953 (vs), 1782 (s)g
334.8
326.0
352.7
344.6
334.5h
315.4g
320.6
313.6
322.8
315.0
328.6
191.9 (11)
182.5 (11)
191.8 (11)
188.9 (5)
1934 (vs)g, f
1960 (vs), 1771 (s)
1934 (vs)f
1990 (vs), 1803 (s)
220.4 (16)
222.2 (18)
133.9 (27)
1966 (vs)f
1984 (vs), 1798 (s)
1960 (vs)f
1794 (w), 1764 (vs), 1710 (w)i
a Recorded in dichloromethane solution, C-O stretching bands (ν(CO)) in cm-1; in complexes with CO2Et groups, the band at the lowest frequency is
due in each case to the corresponding CdO stretch. b Recorded in CD2Cl2 solutions at 290 K and 121.50 MHz; δ in ppm relative to external 85% aqueous
H3PO4. c 13C NMR resonance for the methylenic carbon of the former diazoalkane molecule, recorded in CD2Cl2 solutions at 290 K and 75.48 MHz; δ in
ppm relative to internal TMS and JCP in Hz. d In CDCl3 solution. e In tetrahydrofuran solution. f The band at lower frequency could not be identified in
the spectrum, it being obscured by the lower frequency band of the major isomer. g In toluene solution. h Recorded at 162.00 MHz (31P) or 100.62 MHz
(
13C) and 253 K. i Recorded in petroleum ether solution.
at ca. 1780 cm-1 corresponding to the bridging carbonyl, and
two high-frequency bands at ca. 1980 and 1950 cm-1, with
relative intensities (strong and weak, in order of decreasing
frequencies) characteristic of M2(CO)2 oscillators with al-
most parallel carbonyl ligands.12 Compounds 2 exhibit 31P
NMR resonances in the range 290-330 ppm, a bit more
shielded than the related oxophosphinidene complexes
(315-345 ppm),6,8 with the ethyldiazoacetate derivatives
giving the most deshielded resonances. In any case, these
values are comparable or somewhat higher than that re-
ported for the terminal phosphadiazadiene complex [FeCp-
(CO)2(iPr2NPN2CPh2)]þ (291 ppm),10 which is somewhat
unexpected since, for instance, bridging phosphines (μ-PR3)
give rise to 31P resonances more shielded than comparable
terminal ligands.13 This suggests that the 31P shielding in the
phosphadiazadiene complexes is most likely determined by
the presence of substantial multiplicity in the P-N bond.
The uncoordinated methylenic groups in compounds 2 give
rise to 1H NMR resonances at ca. 7.5 ppm, as expected, and
to 13C resonances at ca. 130 ppm, a characteristic shift for sp2
C atoms. The latter resonances exhibit large three-bond
couplings to phosphorus (50-60 Hz), comparable to those
measured for the phosphine adducts of diazoalkanes (e.g., 50
Hz for Ph3PN2CPh(CN)).14 In the case of the diazomethane
derivative 2a.1, the coupling between the methylenic hydro-
gens (15 Hz) is much higher than expected for a geminal
coupling at a conventional sp2 carbon atom (0-3 Hz),
although we note that, for instance, the geminal couplings
in allenes are substantially higher (ca. 9 Hz).15 All the above
data might be suggestive of the presence of some delocaliza-
tion of the π bonding along the PNNC chain, which itself
would not be inconsistent with the geometrical data found in
the solid state for 2a.1.
Solid-State and Solution Structure of the Aminophosphide
Derivative 3. The presence of lone electron pairs at the N
atoms in complexes 2 should allow further functionalization
of these molecules through the reactions with suitable elec-
trophiles. Indeed this seems to be the case since, for instance,
the diazomethane derivative 2a.1 is instantaneously proto-
nated by HBF4 OEt2 in dichloromethane solution to give
3
the corresponding salt [Fe2Cp2(μ-CyPNHNCH2)(μ-CO)-
(CO)2](BF4) (3) in quantitative yield (Chart 4). A single-
crystal X-ray study confirmed the incorporation of the added
proton to the nitrogen atom bound to phosphorus (Figure 2
and Table 3), which otherwise caused little perturbation to
the overall structure of the complex. The most significant
˚
differences found in 3 are a slight contraction (by ca. 0.04 A)
of the Fe-P lengths and perhaps a more significant elonga-
˚
tion of the P-N distance (to 1.669(2) A), now approaching
the single-bond figures. In contrast, the N-N and N-C
lengths in the ligand chain remain unperturbed after proton-
ation. This can be explained by considering that the phos-
phinidene-diazoalkane interaction present in compound 2
must be biphilic in nature, as found for the phosphine/
diazoalkane adducts,9a then having σ (P to N) and π (N to
P) components. Because of the positive charge developed at
the P-bound nitrogen upon protonation, the π contribution
would be greatly diminished, leaving an essentially single
P-N bond. As a result, the new P-donor group might be
better described now as an aminophosphide ligand. The
degree of pyramidalyzation of the protonated nitrogen,
however, seems to be small, as indicated by the sum of bond
(12) Braterman, P. S. Metal Carbonyl Spectra; Academic Press:
London, U.K., 1975.
(13) (a) Pechmann, T.; Brandst, C. D.; Werner, H. Chem. Eur. J.
2004, 10, 728. (b) Werner, H. Angew. Chem., Int. Ed. 2004, 43, 938.
(14) Molina, P; Lopez-Leonardo, C.; Llamas-Botıa, J.; Foces-Foces,
ꢀ
~
€
C.; Fernandez-Castano, C. Tetrahedron 1996, 52, 9629.
(15) Pretsch, E; Buhlmann, P.; Badertscher, M. Structural Determi-
nation of Organic Compounds, 4th ed.; Springer: Heidelberg, Germany,
2009.

5144 Organometallics, Vol. 29, No. 21, 2010
Alvarez et al.
Chart 5
Chart 6
Figure 2. ORTEP diagram (30% probability) of the cation in
compound 3, with the Cy ring (except the C1 atom) and H atoms
(except those bound to N and C4) omitted for clarity.
˚
Table 3. Selected Bond Lengths (A) and Angles (deg) for
Compound 3
Fe(1)-Fe(2)
Fe(1)-P(1)
Fe(2)-P(1)
Fe(1)-C(3)
Fe(2)-C(3)
Fe(1)-C(1)
Fe(2)-C(2)
P(1)-N(1)
N(1)-N(2)
N(2)-C(14)
N(1)-H(2)
2.6126(5)
2.1855(6)
2.1772(7)
1.935(2)
1.948(2)
1.763(2)
1.766(2)
1.669(2)
1.388(2)
1.269(3)
0.81(2)
Fe(1)-P(1)-Fe(2)
Fe(1)-C(3)-Fe(2)
Fe(1)-Fe(2)-C(2)
Fe(2)-Fe(1)-C(1)
P(1)-Fe(1)-C(1)
P(1)-Fe(2)-C(2)
C(3)-Fe(1)-C(1)
C(3)-Fe(2)-C(2)
P(1)-Fe(1)-C(3)
Fe(1)-P(1)-N(1)
P(1)-N(1)-N(2)
N(1)-N(2)-C(14)
73.57(2)
84.6(1)
100.2(1)
100.7(1)
90.9(1)
92.0(1)
90.5(1)
88.9(1)
99.3(1)
121.1(1)
119.9(2)
116.3(2)
When heating toluene solutions of compounds 2, a pro-
gressive decomposition takes place in all cases to give the
dimer [Fe2Cp2(CO)4] as the only organometallic product, the
transformations being typically completed in ca. 1-2 h at
363 K. A similar result was obtained when irradiating with
visible-UV light toluene solutions of the phenyl compounds
2b.2 to 2b.4. In contrast, relatively selective decarbonylations
could be induced photochemically on the cyclohexyl (except
2a.4) and supermesithyl compounds. The reaction products,
however, were strongly dependent on the substituents at
either the P atom or the methylenic carbon. Thus the
diazomethane derivative 2a.1 yielded a mixture of the P:N-
bound phosphadiazadiene complex [Fe2Cp2(μ-CyPN2CH2)-
(μ-CO)2] (4) and the phosphaalkene derivative [Fe2Cp2(μ-
CyPCH2)(μ-CO)(CO)] (5) (Chart 5). In contrast, the ethyl-
diazoacetate derivative gave the paramagnetic complex
[Fe2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO)(CO)] (6), possibly
containing a μ-P:P,C-phosphadiazadiene ligand (Chart 6).
Finally, the trimethylsilyldiazomethane derivative instead
gave selectively the aminophosphide-iminoacyl complex
[Fe2Cp2{μ-CyPN(SiMe3)NCH}(μ-CO)(CO)] (7f) (Chart 6).
As for the influence of the substituent at phosphorus on these
reactions, we note that the decarbonylation of the ethyldi-
azoacetate derivative 2c.2 gave the complex [Fe2Cp2{μ-Mes*
PN2CH(CO2Et)}(μ-CO)2] (9), containing a μ-P:N-phospha-
diazadiene ligand bound to the dimetal center through the
P-bound nitrogen atom (Chart 8).
angles around nitrogen (356.5°). This figure, however, must
be taken with caution, due to the low precision of the angles
involving the H atom and the involvement of the latter in
a strong hydrogen-bond interaction with the BF4 anion
˚
(H F ca. 2.18 A).
3 3 3
-
Spectroscopic data in solution for 3 are fully consistent
with the structure in the crystal just discussed. In particular,
the pattern of the C-O stretching bands is identical to that in
the precursor 2a.1, with average C-O stretching frequencies
some 40 cm-1 higher, as expected. In contrast, the 31P chemi-
cal shift of 3 is comparable to that of its precursor in spite of
the substantial modifications occurring at the phosphorus
site, an observation that can be explained only if different
effects (e.g., charge and P-N bond order) counterbalance
their respective influences.
Decarbonylation Reactions of Phosphadiazadiene Com-
plexes. Since the P:P-bound bridging ligands in compounds
2 still have several potentially donor centers, such as the
nitrogen atoms or even the NdCR0R00 bond, it was of interest
to examine whether these donor centers would be involved in
bonding with the dimetal site when creating a coordination
vacant in the latter by removal of a CO molecule. A second
point of interest was to check whether denitrogenation could
also be induced in these complexes, to give phosphaalkene
derivatives. With this purpose, we studied the behavior of
compounds 2 under conditions of thermal and photochemical
activation.
Solution Structure of the Diazomethane Derivatives 4 and 5.
Although the complexes 4 and 5 differ in a molecule of
nitrogen, they were always obtained by us in a similar ratio
(ca. 3:1). Modifications in solvent (toluene vs tetrahydro-
furan), temperature (288 vs 263 K), or reaction time caused
no significant changes in this ratio. Thus, it is concluded that
compound 5 is not formed from 4, but through an indepen-
dent reaction pathway.

Article
The presence of two nitrogen atoms in 4 is unambiguously
Organometallics, Vol. 29, No. 21, 2010 5145
13C and 1H NMR spectra, in positions comparable to those
of the structurally characterized dicobalt complex [Co2(CO)4-
(μ-iPr2NPCH2)(μ-dppm)]3i and other phosphaalkene-bridged
complexes.19 Interestingly, the dicobalt complex was directly
obtained in the reaction of diazomethane with the trigonal-
phosphinidene complex [Co2(CO)4(μ-PNiPr2)(μ-dppm)]
(dppm=Ph2PCH2PPh2). The phosphorus resonances of both
isomersof 5 (δP 208.2 and193.0ppm) also appearin a position
comparable to that of the mentioned dicobalt complex (δP 247
ppm). Finally, the presence of semibridging and terminal
carbonyls in the major isomer of 5 is substantiated by the
appearance of quite differently deshielded 13C resonances
for these ligands, at 237.8 and 219.3 ppm, respectively, with
the latter being within the typical range of terminal ligands
(210-220 ppm) and the other being significantly shifted
toward the usual region of bridging carbonyls (255-280 ppm).
Solution Structure of the Paramagnetic Complex 6. The
magnetic susceptibility of 6 was measured in CD2Cl2 solu-
tion by the NMR method developed by Evans,20 yielding an
effective magnetic moment of 2.75 μB, which is very close to
the spin-only value for a complex with two unpaired elec-
trons (2.83 μB). On the other hand, its IR spectrum displays
C-O stretching bands indicative of the presence of one
terminal and one bridging carbonyl. Actually, these bands
are comparable to those of its diamagnetic derivative trans-
7e (Table 2), which we have fully characterized (see below).
For this reason, we propose that the phosphadiazadiene
ligand in 6 displays a coordination mode comparable to that
of its aminophosphide-iminoacyl derivative 7e, with the
methylenic carbon occupying the vacant position left by
the carbonyl ligand being removed. As a result of the strong
electronic rearrangement implied, the phosphadiazadiene
ligand would then become a sort of phosphide-alkyl ligand
(Chart 6), although, due to the scarce spectroscopic data
available, this structural proposal must be obviously taken
with great caution. Unfortunately, all our attempts to obtain
good-quality crystals of 6 for an X-ray study were unsuccess-
ful. Yet, another puzzling question is the presence of un-
paired electrons in this molecule, a feature very unusual for
binuclear carbonyl complexes of the transition metals, which
are generally able to form strong intermetallic bonds. We
trust that, for some reason, the Fe-Fe bond in 6 might be
particularly weak so as to yield singlet and triplet spin states
of comparable energy. For instance, the 32-electron complex
[Fe2Cp*2(μ-CO)3] is paramagnetic (μeff = 2.5 μB in the solid
state), in this case due to a symmetry-imposed triplet spin
state,21 and even a more complex situation (several singlet
and triplet states of comparable energies) has been recently
uncovered computationally for the isoelectronic cyclobuta-
diene complex [Fe2(η4-C4H4)2(μ-CO)2(CO)2].22
established by the microanalytical data. In addition, its IR
spectrum exhibits two C-O stretching bands in the region of
the bridging ligands, with relative intensities characteristic of
M2(μ-CO)2 oscillators with almost antiparallel CO ligands,12
as usually found for diphosphine-bridged (L2) complexes of
the type [Fe2Cp2(μ-CO)2(μ-L2)]. Actually, the 31P chemical
shift of the bridging ligand in 4 (204.8 ppm) is not much
higher than those of the mentioned diiron complexes when
the diphosphine ligand has P-O or P-N bonds, such as
(EtO)2POP(OEt)2 (179.1 ppm)16 or R2PN(Me)PNR2 (160-
180 ppm).17 Thus we propose that the phosphadiazadiene
ligand in 4 is bridging the dimetal center through the
phosphorus and C-bound nitrogen atoms (mode R in
Chart 3), as crystallographically determined for the diman-
ganese complex [Mn2(μ-iPr2NPN2CPh2)(CO)8].3i The latter
complex, however, exhibits a more deshielded 31P resonance
(δ 285 ppm), a difference for which we cannot give a satis-
1
factory explanation at the moment. Finally, the H NMR
spectrum of 4 displays inequivalent cyclopentadienyl and
methylenic resonances, in agreement with the proposed
structure. Yet, the latter resonances (δ ca. 4 ppm) are more
shielded than expected for an uncoordinated NdCH2 group.
Unfortunately, we could not obtain a satisfactory 13C NMR
spectrum of 4 to gain further structural information on this
molecule, due to its low solubility in most common solvents.
The microanalytical data for 5 clearly reveal the absence of
nitrogen in this molecule, while the NMR data denote the
presence of cis and trans isomers in solution (Chart 5), with
their relative ratio (ca. 10:1) being unaffected by changes in
solvent or temperature. The IR spectrum of 5 in petroleum
ether solution displays two sharp C-O stretching bands of
strong and weak intensities at 1955 and 1906 cm-1 and a
broad weak band at 1865 cm-1. The first and third band are
then assigned to the major isomer, and the low frequency and
broadness of the weaker band is suggestive of the presence of
a semibridging carbonyl in this isomer, in agreement with the
13C NMR data to be discussed later on. The minor isomer
possibly displays a similar pattern, although only the sharp
band at higher frequency can be identified in the spectrum of
the mixture. By comparison with the IR data of the cis and
trans isomers of the structurally related phosphide-acyl
complex [Fe2Cp2{μ-κ1:κ1,η1-CyPCHC(p-tol)C(O)}(μ-CO)-
(CO)],7 we can identify the isomer giving rise to the more
energetic terminal C-O stretch as the cis isomer. As it will be
seen later, cis and trans isomers are also observed for com-
plexes 7 and 8, and they also seem to follow the same
spectroscopic trend, which, incidentally, is the same trend
observed for the cis and trans isomers of the phosphine
complexes of general formula [Fe2Cp2(μ-CO)2(CO)(PR3)].18
The presence of a phosphaalkene ligand bridging the
dimetal center in an μ-η1:η2-alkenyl-like fashion is denoted
in the major isomer by the presence of quite shielded
resonances for the methylene group in the corresponding
Formation and Solid-State and Solution Structure of Com-
pounds 7. Upon column chromatography on alumina, the
paramagnetic complex 6 fully rearranges into the diamag-
netic isomer [Fe2Cp2{μ-CyPNHNC(CO2Et)}(μ-CO)(CO)]
(7e), which contains an aminophosphide-iminoacyl ligand
formally derived from a 1,3-shift of the methylenic hydrogen
up to the P-bound nitrogen atom. Since this transformation
ꢀ
(16) Alvarez, C. M.; Galan, B.; Garcıa, M. E.; Riera, V.; Ruiz, M. A.;
Bois, C. Organometallics 2003, 22, 3039.
(17) Wang, N.; Wang, M.; Liu, T.; Li, P.; Zhang, T.; Darensbourg,
M. Y.; Sun, L. Inorg. Chem. 2008, 47, 6948.
(18) (a) Haines, R. J.; du Preez, A. L. Inorg. Chem. 1969, 8, 1459. (b)
Klasen, C.; Lorenz, I. P.; Schmid, S.; Beuter, G. J. Organomet. Chem. 1992,
428, 363. (c) Zhang, S.; Brown, T. L. Organometallics 1992, 11, 4166.
(19) (a) Lang, H.; Leise, M. J. Organomet. Chem. 1993, 456, C4. (b)
Weber, L.; Schumann, I.; Stammler, H. G.; Neumann, B. Organometallics
1995, 14, 1626. (c) Davies, J. E.; Mays, M. J.; Raithby, P. R.; Woods, A. D. J.
Chem. Soc., Chem. Commun. 1999, 2455.
(20) (a) Evans, J. J. Am. Chem. Soc. 1960, 2003. (b) Grant, D. H. J.
Chem. Educ. 1995, 72, 39.
(21) Blaha, J. P.; Bursten, B. E.; Dewan, J. C.; Franke, R. B.;
Randolph, C. L.; Wilson, B. A.; Wrighton, M. S. J. Am. Chem. Soc.
1985, 107, 4561.
(22) Wang, H.; Xie, Y.; King, R. B.; Schaefer, H. F., III. Organome-
tallics 2008, 27, 3113.

5146 Organometallics, Vol. 29, No. 21, 2010
Alvarez et al.
Table 4. Selected Bond Lengths and Angles for Compound 7e
Fe(1)-Fe(2)
Fe(1)-P(1)
Fe(2)-P(1)
Fe(1)-C(2)
Fe(2)-C(2)
Fe(1)-C(1)
Fe(2)-C(3)
P(1)-N(1)
N(1)-N(2)
N(1)-H(1)
N(2)-C(3)
C(3)-C(4)
2.6261(8)
2.186(1)
2.114(1)
2.039(4)
1.879(4)
1.756(5)
1.959(4)
1.697(4)
1.407(5)
0.87(6)
Fe(1)-P(1)-Fe(2)
Fe(1)-C(2)-Fe(2)
Fe(1)-Fe(2)-C(3)
Fe(2)-Fe(1)-C(1)
P(1)-Fe(1)-C(1)
P(1)-Fe(2)-C(3)
C(2)-Fe(1)-C(1)
C(2)-Fe(2)-C(3)
P(1)-Fe(1)-C(2)
Fe(1)-P(1)-N(1)
Fe(2)-P(1)-N(1)
P(1)-N(1)-N(2)
N(1)-N(2)-C(3)
N(2)-C(3)-Fe(2)
75.27(4)
84.1(2)
91.0(1)
88.9 (1)
93.5(1)
79.6(1)
95.9 (2)
89.8(2)
95.5(1)
118.2(1)
104.8(1)
110.8(3)
114.0(4)
125.6(3)
1.301(5)
1.508(6)
Figure 3. ORTEP diagram (30% probability) of one of the two
independent molecules found in the crystal lattice of compound
7e, with the Cy ring (except the C1 atom) and H atoms (except
H1) omitted for clarity.
could not be induced by either thermal or photochemical
activation of 6, it does not seem to be intramolecular in
nature, but possibly results from a protonation/deprotona-
tion sequence on the alumina surface. In contrast, the
photochemical treatment of the trimethylsilyl compound
2a.3 gives directly the dicarbonyl [Fe2Cp2{μ-CyPN(SiMe3)-
NCH}(μ-CO)(CO)] (7f), having a related bridging ligand
now derived from a 1,3-shift of the SiMe3 group (presumably
intramolecular) up to the P-bound nitrogen atom. In turn,
the SiMe3 group in 7f is easily hydrolyzed either by addition
of water (30 min upon addition of 2 equiv of H2O to a toluene
solution) or upon column chromatography on alumina
(activity IV), to give almost quantitatively the corresponding
derivative [Fe2Cp2(μ-CyPNHNCH)(μ-CO)(CO)] (7g).
The compounds 7e-g exhibit in solution cis and trans
isomers differing in the relative orientation of the cyclopen-
tadienyl ligands with respect to the Fe2P plane (Chart 6), as
found for the phosphaalkene complex 5. However, the
relative proportion and possibility of interconversion be-
tween isomers strongly depend on the substituents present at
the PNNC chain, and no simple conclusion can be extracted
from the observed ratios (see the Experimental Section).
We have now determined the crystal structure of the trans
isomer of compound 7e (Figure 3 and Table 4), while the
structure of the cis isomer of compound 7f was reported in
our preliminary communication (Figure 4).7 Both structures
are similar, except for the relative orientation of the FeCp-
(CO) moiety, with interatomic distances differing by less
Figure 4. ORTEP diagram (30% probability) of compound 7f
(reproduced from ref 7), with the Cy ring (except the C1 atom),
Me groups, and H atoms (except H3) omitted for clarity.
˚
Selected bond lengths (A): Fe(1)-Fe(2) = 2.5890(8), Fe(1)-
P(1) = 2.149(1), Fe(2)-P(1) = 2.203(1), Fe(1)-C(1) = 1.856(4),
Fe(2)-C(1) = 2.016(4), Fe(2)-C(2) = 1.743(5), Fe(1)-C(3) =
1.936(4), C(3)-N(2) = 1.284(5), N(2)-N(1) = 1.437(5), N(1)-
P(1) = 1.711(4), N(1)-Si(1) = 1.760(4).
7
bond length of 1.967(3) A. The interatomic distances within
˚
the PNNC chain in both complexes are similar to each other,
˚
˚
˚
with values of ca. 1.70 A (P-N), 1.42 A (N-N), and 1.29 A
(N-C), comparable to those measured in 3 and indicative of
the presence of essentially single, single, and double bonds,
respectively. As for the P-bound nitrogen, this bonding des-
cription should imply a pyramidal environment, which is in
agreement with the angles around this atom for compound
7e, adding up 343°. For the SiMe3 compound 7f, however,
the environment around N(1) is trigonal, with the corre-
sponding angles adding up 360°, possibly a steric effect
minimizing the repulsions of the bulky SiMe3 group.
˚
than ca. 0.03 A from each other. Both molecules can be
described as two iron cyclopentadienyl fragments connected
˚
by a single metal-metal bond (ca. 2.60 A) and two bridging
The spectroscopic data in solution for compounds 7
(Table 2 and Experimental Section) are fully consistent with
the solid-state structures just discussed. In particular, the IR
spectra display for each isomer two C-O stretching bands at
ca. 1965-1935 and 1780 cm-1, corresponding respectively to
the terminal and bridging carbonyls, which correlates with
the appearance of resonances at ca. 212 and 268 ppm,
respectively, in the corresponding 13C NMR spectra. The
stretching frequency for the terminal carbonyl in the isomers
cis is systematically some 20 cm-1 higher than those for the
corresponding isomers trans, as noted above. The amino-
phosphide ligands in all these molecules give rise to a 31P
NMR resonance in the range 315-350 ppm, a position
ligands: a carbonyl and an aminophosphide group. The
coordination spheres around the iron atoms are completed
by the terminal binding of an iminoacyl group (Fe-C ca.
˚
1.95 A) and a carbonyl ligand, placed in either a trans or cis
relative arrangement. The better donor properties of the
carbonyl ligand (compared to the iminoacyl donor) are
counterbalanced by the bridging groups, placed closer to
˚
the acyl-bound iron atom (by ca. 0.06 A in the case of
˚
phosphorus and by 0.15 A for the carbonyl bridge). This
structural effect was also observed in the related phosphide-
acyl complex [Fe2Cp2{μ-κ1:κ1,η1-CyPCHC(p-tol)C(O)}-
(μ-CO)(CO)], which also displays a comparable Fe-C(acyl)

Article
Organometallics, Vol. 29, No. 21, 2010 5147
Chart 7
Chart 8
Figure 5. ORTEP diagram (30% probability) of compound 9,
with H atoms (except H13) omitted for clarity.
˚
Table 5. Selected Bond Lengths (A) and Angles (deg) for
Compound 9
reasonable for a N-substituted phosphide group (cf. 265 ppm
for the mentioned phosphide-acyl complex). On the other
hand, the presence of the terminally bound iminoacyl donor
is revealed by the appearance in the 13C NMR spectra of a
resonance at ca. 190 ppm in all cases, a position substantially
more shielded than that of the mentioned phosphide-acyl
complex (ca. 260 ppm),7 as expected. The observed chemical
shifts, in fact, are comparable (if we allow for the change in
metal) to that of the iminoacyl 13C resonance in the mono-
nuclear phosphine-iminoacyl complex [MoCp(CO)2{tBu2-
PNHNC(CO2Et)}] (171.3 ppm).23 Interestingly, the latter
complex is formed by a route related to that leading to
complexes 7, a matter to be addressed later.
Fe(1)-Fe(2)
Fe(1)-P(1)
Fe(1)-C(1)
Fe(1)-C(2)
Fe(2)-C(1)
Fe(2)-C(2)
Fe(2)-N(1)
P(1)-N(1)
2.514(1)
2.096(2)
1.976(5)
1.942(6)
1.856(6)
1.877(5)
2.028(5)
1.643(4)
1.372(6)
1.279(7)
1.492(7)
0.96(6)
Fe(1)-C(1)-Fe(2)
Fe(1)-C(2)-Fe(2)
Fe(1)-Fe(2)-N(1)
Fe(2)-Fe(1)-P1)
Fe(1)-P(1)-N(1)
P(1)-N(1)-Fe(2)
P(1)-N(1)-N(2)
P(1)-Fe(1)-C(1)
P(1)-Fe(1)-C(2)
N(1)-N(2)-C(13)
N(2)-C(13)-C(14)
N(2)-C(13)-H(13)
81.9(2)
82.3(2)
79.5(1)
76.11(5)
102.4(2)
101.9(2)
121.3(4)
85.2(2)
N(1)-N(2)
N(2)-C(13)
C(13)-C(14)
C(13)-H(13)
84.5(2)
116.2(4)
118.7(5)
120(3)
protons, whereas, in the case of 8k, the new methyl group
gives rise to a resonance at 3.61 ppm.
Cationic Derivatives of Compound 7g. The presence of a
lone electron pair at the C-bound nitrogen atom of the
bridging ligand of complexes 7 still should allow for further
functionalization of these molecules through the reactions
with suitable electrophiles. Indeed the unsubstituted complex
Solid-State and Solution Structure of Compound 9. The
molecular structure of this compound in the crystal (Figure 5
and Table 6) displays two iron cyclopentadienyl moieties
bridged by two carbonyls and a phosphadiazadiene ligand,
the latter being bound through phosphorus to one metal and
through the contiguous nitrogen atom to the second metal.
This establishes the main difference from the coordination
mode proposed for 4 and crystallographically determined for
[Mn2(μ-iPr2NPN2CPh2)(CO)8]3i (mode R in Chart 3) and,
therefore, constitutes a novel coordination mode of the
phosphadiazadiene ligands. The bridging carbonyls in 9
define an almost planar Fe2C2 rhombus, and the PNNC
chain of the bridging ligand defines a second plane perpen-
dicular to the former plane and containing the metals. The
overall coordination sphere of the metals in 9 is thus very
similar to that displayed by the isoelectronic diphosphine-
bridged complexes of the type [Fe2Cp2(μ-CO)2(μ-L2)], and
7g reacts instantaneously with HBF4 OEt2 in dichloro-
3
methane solution to give the salt [Fe2Cp2(μ-CyPNHNHCH)-
(μ-CO)(CO)](BF4) (8j) inquantitative yield, whilethe reaction
with MeI proceeds analogously to give the corresponding salt
[Fe2Cp2(μ-CyPNHNMeCH)(μ-CO)(CO)]I (8k) in ca. 1 h at
room temperature (Chart 7).
The NMR data available for compounds 8 (Table 2 and
Experimental Section) reveal a close structural relation with
their precursor 7g. In particular, these complexes are also
obtained as a mixture of the corresponding cis and trans
isomers (Chart 7), although the cis/trans ratio is different
from that in 7g (ca. 10:1 in dichloromethane), and only in the
case of the methyl derivative is this ratio dependent on the
solvent. Apart from this, the pattern of the C-O stretching
bands for the major isomer (the bands for the minor isomers
are barely visible) in compounds 8 is analogous to that of the
major (cis) isomer of 7g, but shifted some 25-30 cm-1
upward, thus indicating the retention of one terminal and
one bridging ligand. This is paralleled by the observation of
carbonyl resonances at ca. 211 and 262 ppm, respectively, in
the corresponding 13C NMR spectra, which also display
a now more deshielded iminoacyl resonance at ca. 215 ppm.
Finally, the 1H NMR spectra display the expectedly de-
shielded resonances for the corresponding CH and NH
˚
accordingly, the intermetallic separation of 2.514(1) A is
comparable (ca. 2.51 A for L2=(EtO)2POP(OEt)2,16 Ph2P-
˚
(CH2)2PPh2).24 The Fe-P distance of 2.096(1) A is some-
˚
what shorter than those measured for the above complexes
or for related phosphine and phosphite complexes of the type
[Fe2Cp2(μ-CO)2(CO)(L)],18b,25 with values of ca. 2.11-2.21 A,
˚
and also shorter than those in the aminophosphide complexes
˚
7e,f (2.11-2.20 A). Thus it would be tempting to interpret this
(24) Shade, J. E.; Pearson, W. H.; Brown, J. E.; Bitterwolf, T. E.
Organometallics 2005, 14, 157.
(25) (a) Cotton, F. A.; Frenz, B. A.; White, A. J. Inorg. Chem. 1974,
€
ꢀ
(23) Malisch, W.; Grun, K.; Fried, A.; Reich, W.; Pfister, H.;
13, 1407. (b) Alvarez, C. M.; Galan, B.; García, M. E.; Riera, V.; Ruiz, M. A.;
Huttner, G.; Zsolnai, L. J. Organomet. Chem. 1998, 566, 271.
Vaissermann, J. Organometallics 2003, 22, 5504.

5148 Organometallics, Vol. 29, No. 21, 2010
Alvarez et al.
Table 6. Crystal Data for New Compounds
3
2a.1
7e
9 0.5C6H14
3
mol formula
mol wt
cryst syst
C20H23Fe2N2O3P
482.07
monoclinic
P21/n
0.71073
12.018(2)
11.601(2)
14.223(2)
90
91.310(3)
90
1982.5(6)
4
1.615
1.568
120(2)
C20H24BF4Fe2N2O3P
569.89
orthorhombic
P212121
0.71073
10.723(2)
12.889(2)
16.683(3)
90
90
90
2305.7(7)
4
1.642
1.385
120(2)
C22H27Fe2N2O4P
526.13
triclinic
P1
0.71073
11.0876(3)
13.7702(4)
15.7119(5)
72.167(2)
72.183(2)
77.026(2)
2151.32(11)
4
C37H52Fe2N2O4P
731.48
monoclinic
C2/c
1.54184
19.9691(18)
10.0163(8)
36.114(3)
90
98.256(8)
90
7148.6(11)
8
1.359
7.252
100(2)
space group
˚
radiation (λ, A)
˚
a, A
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Z
calcd density, g cm-3
absorp coeff, mm-1
temperature, K
1.624
1.456
100(2)
θ range (deg)
2.19-26.45
-14, 15; 0, 14; 0, 17
22 694
4286 (0.0602)
2990
R1 = 0.0339
wR2 = 0.0681b
R1 = 0543
wR2 = 0.0733b
1.033
2.0-27.2
-13, 13; 0,16; 0, 21
36 457
5128 (0.0471)
4689
R1 = 0.0238
wR2 = 0.0496c
R1 = 0.0281
wR2 = 0.051c
1.083
0/311
0.255, -0.248
1.41-26.02
-12, 13; -15, 16; 0, 19
34 016
8466 (0.0582)
5364
R1 = 0.0548
wR2 = 0.1372 d
R1 = 0.0956
wR2 = 0.1523 d
1.078
0/626
1.234, -1.21
4.47-74.21
-21, 23; -11, 11; -43, 44
26 811
6640 (0.0826)
4576
R1 = 0.0655
wR2 = 0.1431 e
R1 = 0.0996
wR2 = 0.1587 e
1.04
0/430
0.818, -0.772
index ranges (h, k, l )
no. of reflns collected
no. of indep reflns (Rint
reflns with I > 2σ(I )
)
R indexes [data with I > 2σ(I )]a
R indexes (all data)a
GOF
no. of restraints/params
ΔF(max., min.), e A
0/261
0.427, -0.342
-3
˚
P
P
P
P
2
a R =
Fo| - |Fc
/
|Fo|. wR = [ w(|Fo|2 - |Fc|2)2/ w|Fo|2]1/2. w = 1/[σ2(Fo2) þ (aP)2 þ bP] where P = (Fo þ 2Fc2)/3. b a = 0.0280, b = 1.1802.
c a = 0.0213, b = 0.5229. d a = 0.0815, b = 0.0000. e a = 0.0420, b = 64.8613.
shortening effect as an indication of the presence of some
multiplicity in the Fe-P bond. Actually, the fact that the 31P
chemical shift in 9 is some 120 ppm higher than that in 4
reinforces this interpretation. Moreover, the presence of some
multiplicity in the Fe-P bond would possibly be accompanied
by a reduction in the multiplicity of the P-N bond. Indeed, the
C-O stretching bands in the region of the bridging ligands,
with the pattern characteristic of M2(μ-CO)2 oscillators with
almost antiparallel CO ligands, as found for 4. Finally, the
NMR data indicate the retention of an effective symmetry
plane containing the Fe and P atoms, while the uncoordi-
nated methylenic group in 9 displays chemical shifts (δC
133.9 ppm, δH 6.22 ppm) comparable to those of complexes 2.
Pathways in the Photochemical Reactions of the Phospha-
diazadiene Complexes 2. In the preceding sections we have
seen that the photochemical treatment of complexes 2 can
induce many different rearrangements involving the phos-
phadiazadiene ligand. Although we have detected no inter-
mediates in these reactions, we can propose reasonable
elemental steps to account for the formation of all the
isolated products, including their stereochemistry (Schemes 1
and 2).
First of all, it should be recognized that the residual donor
ability of the P:P-bound phosphadiazadiene ligand in com-
pounds 2 is not restricted to their lone-pair-bearing N atoms,
but also might involve its methylenic carbon. This can be
grasped by taking into account the different canonical forms
contributing to the electronic structure of the ligand (Chart 9).
In particular the formal charges in R3 illustrate the electron-
rich nature of this carbon atom while emphasizing the electro-
philic properties of the P atom.
˚
value of 1.64(3) A for the P-N(1) length in 9 is intermediate
˚
between the values measured for compound 2a.1 (1.612(1) A,
˚
˚
formally a double bond) and compounds 7e,f (ca. 1.70 A,
formally a single bond). As for the N-Fe length of 2.028(5) A,
it can be considered as normal for a single bond involving sp2-
hybridized N atoms, being comparable to the corresponding
length in the phosphinimine complex [Fe2(μ-Cl)2Cl2{N-
i
26
˚
(P Pr3)CH2SPh)2] (2.033(2) A) and related iron complexes.
Due to the different donor properties of the P and N ligand
sites in 9, the electron density at the metal centers has to be
balanced by a slightly asymmetric coordination of the bridging
carbonyls, closer to Fe(2), the iron atom bearing the poorer
donor. The interatomic N-N and N-C separations (1.372(6)
˚
and 1.279(7) A, respectively) are comparable to those in the
complexes 2a.1 and 7e,f previously discussed and, therefore,
can be considered consistent with the formulation of single and
double bonds, respectively.
The spectroscopic data in solution for 9 are consistent with
its solid-state structure. We have already mentioned the
strong deshielding of the P nucleus compared to that in
complex 4, this being attributed to the different coordination
modes that the phosphadiazadiene ligand adopts in these
two molecules, and the striking difference in the colors of
these compounds (purple for 4, green for 9) might have a
similar origin. As expected, the IR spectrum exhibits two
In order to explain the formation of the phosphaalkene
complex 5, we first propose that, at least under photochemi-
cal conditions, the complexes 2 would partially rearrange
into the corresponding isomers having the P-donor ligand
coordinated in a terminal fashion (A in Scheme 1). This is
completely analogous to the thermal equilibrium recently
observed between the terminal and bridged isomers of the
oxophosphinidene complex [Fe2Cp2(CO)3{P(O)Mes*}].8
The intermediate A, having now a low-coordination P
center, might then undergo an intramolecular attack of the
(26) (a) LePichon, L.; Stephan, D. W. Inorg. Chem. 2001, 40, 3827. (b)
Mai, H. J.; Wocadlo, S.; Kang, H. C.; Massa, W.; Dehnicke, K.; Maichle-
€
€
Moossmer, C.; Strahle, J.; Fenske, D. Z. Anorg. Allg. Chem. 1995, 621, 705.

Article
Scheme 1. Denitrogenation Pathway in the Photochemical
Reactions of Compounds 2
Organometallics, Vol. 29, No. 21, 2010 5149
Chart 9
before, compound 5 is obtained as a mixture of cis and trans
isomers in a ratio cis/trans of ca. 10:1. This is likely to follow
from a photochemically induced and reversible trans/cis
isomerization in the final product, comparable to those
previously observed in related species such as phosphide-
and thiolate-bridged complexes of the type [Fe2Cp2(μ-H)-
(μ-PR2)(CO)2] (trans to cis)27,28 and [Fe2Cp2(μ-SR)2(CO)2]
(cis to trans).29
The generation of significant amounts of the terminal
isomer A upon photolysis of compounds 2 also gives a
rationale for the observed photochemical decomposition of
these complexes to yield variable amounts of [Fe2Cp2(CO)4].
Due to the absence of a bridging P atom in the intermediate
A, it might be anticipated that this isomer might easily
undergo, under photolytic conditions, the homolytic clea-
vage of the Fe-Fe bond to yield, inter alia, FeCp(CO)2
radicals that would rapidly recombine to give the iron dimer,
thus paralleling the extensively studied photochemistry of
the latter species.30
Scheme 2. Reaction Pathways in the Photochemical Formation
of Compounds 4-9
In the presence of a substituent at the methylenic carbon in
the intermediate A, the cyclization step preceding denitro-
genation might be disfavored possibly by the steric hindrance
induced by this substituent at intermediate B. As a result, the
photochemically activated compound 2 would rather dis-
sociate a CO molecule to give an unsaturated intermediate E
(Scheme 2). This process would be also operative for the
unsubstituted compound 2a.1 (in fact it seems to be the
dominant pathway even in that case). The nature of the pro-
ducts finally isolated suggests that the intermediates E would
eliminate its coordinative and electronic deficiency in three
different ways, depending on the substituents at the bridging
ligand. For cyclohexyl compounds, in the absence of sub-
stituents at the methylenic carbon, the phosphadiazadiene
ligand might coordinate its C-bound nitrogen atom, to give a
P:P,N-bridged intermediate F structurally related to com-
plexes 7, but having a strained four-membered PNNFe ring,
which then would rearrange into its P:N-bridged isomer 4,
with an unstrained five-membered PN2Fe2 ring.
When a substituent is present at the methylenic carbon, the
formation of the corresponding intermediate F would be
disfavored because of the implied close approach of the
substituent to a cyclopentadienyl ligand. Then, the unsatura-
tion at the intermediate E would be eliminated by the
electron-rich methylenic carbon to phosphorus, to yield a
phosphine ligand having a very strained four-membered
PNNC ring (B in Scheme 1). This would force its denitro-
genation to give a P-bound phosphaalkene complex C,
which, under the action of UV light, would dissociate a CO
molecule to give the phosphaalkene-bridged complex 5,
initially in its trans-dicarbonyl form. However, as noted
(27) (a) Brunner, H.; Peter, H. J. Organomet. Chem. 1990, 393, 411.
€
(b) Brunner, H.; Rotzer, M. J. Organomet. Chem. 1992, 425, 119.
(28) Alvarez, C. M.; Garcıa, M. E.; Ruiz, M. A.; Connelly, N. G.
Organometallics 2004, 23, 4750.
(29) Bitterwolf, T. E.; Scallorn, W. B.; Li, B. H. Organometallics 2000,
19, 3280.
(30) Bitterwolf, T. E. Coord. Chem. Rev. 2000, 206-207, 419.

5150 Organometallics, Vol. 29, No. 21, 2010
Alvarez et al.
coordination of the nucleophilic methylenic carbon in a ter-
minal way, thus giving the isolable complex 6 (R=CO2Et) or
a similar but unstable intermediate G (R=SiMe3). Initially,
these species should display a transoid arrangement of the
terminal ligands, which seems to be the case of the major
isomer for 6 according to the IR spectrum of this complex, as
discussed above. Finally, the intermediate G would undergo
a fast 1,3-shift of the SiMe3 group to yield the aminopho-
sphide-iminoacyl derivative 7f, initially in its transoid form.
As discussed for 5, under photochemical activation, a rever-
sible trans to cis isomerization would finally account for the
observed mixture of isomers. Incidentally, this in agreement
with the fact that the major isomer in the related complex 7e,
which is not formed photochemically, but through a thermal
reaction of 6 on the surface of alumina, exhibits the same
arrangement of terminal ligands (trans) as its precursor 6.
Although the 1,3-shift responsible for the formation of 7f is
not a common rearrangement, there are some precedents of
related SiMe3 shifts involving two N atoms or C and N
atoms, and even 1,4-shifts between O and N atoms.31 Besides
this, we should note the parallelism between the formation of
the phosphide-iminoacyl complex 7f (reaction of the phos-
phinidene 1a with a diazoalkane followed by photochemi-
cally induced decarbonylation and 1,3-SiMe3 shift) and the
thermal formation of the mononuclear phosphine-iminoacyl
complex [MoCp(CO)2{tBu2PNHNC(CO2Et)}] from a term-
inal phosphide complex with ethyldiazoacetate followed by
decarbonylation and 1,3-H shift at the presumed (unde-
tected) diazoalkane adduct initially formed.23 In the forma-
tion of compounds 7, however, no 1,3-H shift seems to be
feasible at the intermediate stages 6/G without apparent
reason, although it is clear that the observed SiMe3 shift
yields an isomer having the bulky silyl group pointing away
from the dimetal center, therefore much more favored on
steric grounds.
The third possible way to remove the unsaturation in the
intermediate E is the coordination of the P-bound nitrogen
atom. This might be viewed as the least likely alternative, but
it is the one keeping a substituted methylenic group as far
away as possible from the rest of the molecule, and therefore
perhaps the least disfavored option in the presence of a really
bulky substituent at phosphorus such as the supermesithyl
group. Thus, in the case of compound 2c.2 the corresponding
intermediate E would first give a P:P,N-bridged intermediate
H with a structure related to that of the phosphaalkene
complex 5, then rearranging into the P:N-bridged isomer 9,
now having a less strained four-membered FePNFe ring. The
fact that compound 9 displays a structure different from
those of 4, 6, or 7 might be thus explained on kinetic grounds.
In addition, an analysis of the crystal structure of 9 reveals
the presence of close contacts between the ortho tBu groups
of the substituent at phosphorus and the cyclopentadienyl
ligand bound to the same metal atom. Therefore it can be
guessed that any hypothetical structure for this compound
analogous to that of 4 would be thermodynamically dis-
favored too, because of the strong Mes*/Cp repulsions
derived from the closer approach between these groups.
Concluding Remarks
The phosphinidene complexes [Fe2Cp2(μ-PR)(μ-CO)-
(CO)2] react readily with different diazoalkane molecules
N2CR0R00 to yield the corresponding derivatives [Fe2Cp2-
(μ-RPN2CR0R00)(μ-CO)(CO)2], which display a novel P:P-
bridging coordination mode of the phosphadiazadiene li-
gand resulting from a biphilic P-N interaction of the
phosphinidene with the terminal nitrogen of the diazoalk-
ane. Under photochemical activation, the new complexes
undergo decarbonylation and different rearrangements of
the phosphadiazadiene ligands that are strongly influenced
by the steric effects of the substituents present at phosphorus
and at the methylenic carbon of the former diazoalkane
molecule. The diazomethane derivative, having the smallest
steric demands, can evolve in two different ways, one of them
implying the nucleophilic attack of the methylenic carbon to
the phosphorus atom and eventually releasing dinitrogen to
yield a phosphaalkene derivative. The formation of all other
products can be explained by assuming the photochemical
generation of a common unsaturated dicarbonyl intermediate
that, as the steric demands of the substituents there present
increase, reaches its electronic saturation through the coordi-
nation to the metal center of the following atoms (in order of
preference): C-bound nitrogen<methylenic carbon<P-bound
nitrogen. The two last options lead to novel bridging coordi-
nation modes of the phosphadiazadiene ligand. Moreover, the
coordination of the methylenic carbon to the metal center
facilitates 1,3-shifts between the C and N atoms of the ligand to
yield novel aminophosphide-iminoacyl derivatives.
Experimental Section
General Procedures and Starting Materials. All manipulations
and reactions were carried out under a nitrogen (99.995%)
atmosphere using standard Schlenk techniques. Solvents were
purified according to literature procedures and distilled prior to
use.32 Petroleum ether refers to that fraction distilling in the
range 338-343 K. Dichloromethane solutions of the com-
pounds [Fe2Cp2(μ-PR)(μ-CO)(CO)2] (Cp = η5-C5H5; R = Cy
t
(1a), Ph (1b), 2,4,6-C6H2 Bu3 (1c)) were prepared in situ as
described previously.6,8 Diethyl ether solutions of diazomethane
were prepared in situ also by literature methods,33 and diphe-
nyldiazomethane was prepared as reported previously.34 All
other reagents were obtained from the usual commercial sup-
pliers and used as received. Photochemical experiments were
performed using jacketed quartz or Pyrex Schlenk tubes, cooled
by tap water (ca. 288 K). A 400 W mercury lamp placed ca. 1 cm
away from the Schlenk tube was used for all the experiments.
Chromatographic separations were carried out using jacketed
columns cooled by tap water (ca. 288 K) or by a closed
2-propanol circuit, kept at the desired temperature with a
cryostat. Commercial aluminum oxide (activity I, 150 mesh)
was degassed under vacuum prior to use. The latter was mixed
under nitrogen with the appropriate amount of water to reach
the activity desired. IR C-O stretching frequencies were mea-
sured in solution and are referred to as ν(CO). Nuclear magnetic
resonance (NMR) spectra were routinely recorded at 300.13
(1H), 121.50 (31P{1H}), or 75.48 MHz (13C{1H}) at 290 K in
CD2Cl2 solutions unless otherwise is stated. Chemical shifts (δ)
are given in ppm, relative to internal tetramethylsilane (1H, 13C)
(31) (a) Cole, M. L.; Junk, P. C. Dalton Trans. 2003, 2109. (b)
Hitchcock, P. B.; Lappert, M. F.; Wei, X. H. J. Organomet. Chem. 2003,
683, 83. (c) Tobita, H.; Matsuda, A.; Hashimoto, H.; Ueno, K.; Ogino, H.
Angew. Chem., Int. Ed. 2004, 43, 221. (d) Yu, X.; Xue, Z. L. Inorg. Chem.
2005, 44, 1505. (e) Wang, Z. X.; Chai, Z. Y.; Li, Y. X. J. Organomet. Chem.
2005, 690, 4252. (f) Ito, S.; Miyake, H.; Yoshifuji, M. Eur. J. Inorg. Chem.
2007, 22, 3491.
(32) Armarego, W. L. F.; Chai, C. Purification of Laboratory Che-
micals, 5th ed.; Butterworth-Heinemann: Oxford, U.K., 2003.
(33) Vogel, A. I. Texbook for Practical Organic Chemistry, 4th ed.;
Longman: London, U.K., 1978.
(34) Millar, J. B. J. Org. Chem. 1959, 24, 560.

Article
Organometallics, Vol. 29, No. 21, 2010 5151
or external 85% aqueous H3PO4 (31P). Coupling constants (J)
are given in Hz. The magnetic susceptibility of compound 6 was
measured in CD2Cl2 solution by the NMR method developed by
Evans.20 The molar magnetic susceptibility thus obtained (χe)
was then corrected for the diamagnetic contribution as esti-
mated from atomic susceptibilities.35 The resulting value (χc)
was then used for calculating the effective magnetic moment
(μeff) as usual.
Preparation of [Fe2Cp2(μ-CyPN2CH2)(μ-CO)(CO)2] (2a.1).
A large excess of a freshly prepared Et2O solution of N2CH2 was
added to a freshly prepared solution of complex 1a (ca. 0.050 g,
0.114 mmol) in dichloromethane (5 mL) at 273 K, and the
mixture was stirred at that temperature for 15 min to give a dark
green solution. The solvent was then removed under vacuum,
and the residue was washed with petroleum ether (2 ꢀ 3 mL) to
give compound 2a.1 as a green microcrystalline solid (0.051 g,
91%). The crystals used in the diffractometric study were grown
by the slow diffusion of a layer of petroleum ether into a toluene
solution of the complex at 253 K. Anal. Calcd for C20H23Fe2-
N2O3P: C, 49.83; H, 4.81; N, 5.81. Found: C, 49.62; H, 4.68; N,
5.67. 1H NMR: δ 7.10 (dd, JHH = 15, JHP = 2, 1H, CH2), 6.43
(d, JHH = 15, 1H, CH2), 5.11 (s, 10H, Cp), 2.42-1.18 (m, 11H,
Cy). 13C{1H} NMR: δ 270.1 (s, μ-CO), 212.1 (d, JCP = 11,
FeCO), 133.7 (d, JCP=51, CH2), 87.4 (s, Cp), 55.5 [d, JCP = 53,
C1(Cy)], 32.1 [d, JCP = 6, C2(Cy)], 27.8 [d, JCP = 11, C3(Cy)],
26.5 [s, C4(Cy)].
89%). Anal. Calcd for C23H21Fe2N2O5P: C, 50.40; H, 3.86; N,
5.11. Found: C, 50.17; H, 3.66; N, 5.02. H NMR (CDCl3):
δ 7.90 (m, 2H, Ph), 7.51 (s, 1H, CH), 7.48-7.37 (m, 3H, Ph),
5.27 (s, 10H, Cp), 4.22 (q, JHH = 7, 2H, OCH2), 1.29 (t, JHH = 7,
3H, Me).
1
Preparation of [Fe2Cp2{μ-PhPN2CH(SiMe3)}(μ-CO)(CO)2]
(2b.3). The procedure is identical to that described for com-
pound 2a.3, but using complex 1b (ca. 0.030 g, 0.069 mmol) and
a reaction time of 2 h. This gave compound 2b.3 as an air-
1
sensitive green solid (0.045 g, 89%). H NMR: δ 7.88 (m, 2H,
Ph), 7.74 (s, CH), 7.44-7.20 (m, 3H, Ph), 5.25 (s, 10H, Cp), 0.14
(s, 9H, SiMe3).
Preparation of [Fe2Cp2(μ-PhPN2CPh2)(μ-CO)(CO)2] (2b.4).
The procedure is identical to that described for compound 2a.4,
but using complex 1b (ca. 0.030 g, 0.069 mmol). This gave
compound 2b.4 as a green microcrystalline solid (0.039 g,
92%). Anal. Calcd for C32H25Fe2N2O3P: C, 61.18; H, 4.01; N,
4.46. Found: C, 60.97; H, 3.79; N, 4.23. 1H NMR (400.13 MHz):
δ 7.87 (m, 2H, Ph), 7.52-7.16 (m, 13H, Ph), 5.25 (s, 10H, Cp).
Preparation of [Fe2Cp2{μ-Mes*PN2CH(CO2Et)}(μ-CO)(CO)2]
(2c.2). The procedure is identical to that described for compound
2a.2, but using complex 1c (ca. 0.040 g, 0.066 mmol). This gave
compound 2c.2 as a green microcrystalline solid (0.043 g, 90%).
Anal. Calcd for C35H45Fe2N2O5P: C, 58.68; H, 3.91; N, 6.33.
Found: C, 58.56; H, 4.05; N, 6.09. 1H NMR (400.13 MHz): δ 7.36
(s, 1H, CH), 7.17(d, JHP =2, 2H, C6H2), 5.25 (s, 10H, Cp), 4.24 (q,
Preparation of [Fe2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO)(CO)2]
(2a.2). Neat N2CH(CO2Et) (10 μL, 0.095 mmol) was added to a
freshly prepared solution of complex 1 (ca. 0.040 g, 0.091 mmol)
in dichloromethane (5 mL), and the mixture was stirred at room
temperature for 5 min to give a dark green solution. Workup as
described for 2a.1 gave compound 2a.2 as a green microcrystal-
line solid (0.048 g, 95%). Anal. Calcd for C25H27Fe2N2O5P: C,
J
HH = 7, 2H, OCH2), 1.67 (s, 18H, o-tBu), 1.32 (t, JHH = 7, 3H,
Me), 1.11 (s, 9H, p-tBu). 13C{1H} NMR (100.62 MHz): δ 269.1 (s,
μ-CO), 210.4 (d, JCP = 9, FeCO), 166.6 (s, CO2Et), 155.0 [d, JCP
=
7, C2(C6H2)], 149.8 [s, C4(C6H2)], 137.2 [d, JCP = 71, C1(C6H2)],
126.3 (d, JCP = 61, CH), 123.5 [d, JCP = 12, C3(C6H2)], 90.2 (s,
Cp), 59.9 (s, OCH2), 41.8 [s, C1(o-tBu)], 34.3 [s, C2(o-tBu)], 31.2 [s,
C1(p-tBu)], 30.8 [s, C2(p-tBu)], 14.8 (s, Me).
1
49.85; H, 4.91; N, 5.06. Found: C, 49.69; H, 4.87; N, 5.98. H
Preparation of [Fe2Cp2(μ-CyPNHNCH2)(μ-CO)(CO)2](BF4)
NMR (CDCl3): δ 7.75 (s, 1H, CH), 5.13 (s, 10H, Cp), 4.21 (c,
JHH = 7, 2H, OCH2), 2.47 (m, 1H, Cy), 2.25 (m, 2H, Cy), 1.90
(m, 2H, Cy), 1.70-1.20 (m, 6H, Cy), 1.27 (t, JHH = 7, 3H, Me).
13C{1H} NMR (100.62 MHz, CDCl3): δ 267.5 (s, μ-CO), 210.8
(d, JCP = 13, FeCO), 166.0 (s, CO2Et), 130.0 (d, JCP = 55, CH),
87.6 (s, Cp), 59.6 (s, OCH2), 53.6 [d, JCP=47, C1(Cy)], 31.6 [d,
(3). A slight excess of HBF4 OEt2 (12 μL of a 54% solution in
3
Et2O, 0.087 mmol) was added to a dichloromethane solution
(5 mL) of compound 2a.1 (0.040 g, 0.083 mmol), and the mixture
was stirred at room temperature for 5 min to give a red solution.
The solvent was then removed under vacuum, and the residue
was washed with Et2O (3 ꢀ 4 mL) and then petroleum ether (2 ꢀ
4 mL) to give compound 3 as a red microcrystalline solid
(0.044 g, 93%). The crystals used in the diffractometric study
were grown by the slow diffusion of layers of toluene and
petroleum ether into a dichloromethane solution of the complex
at 253 K. Anal. Calcd for C20H24BFe2F4N2O3P: C, 42.15; H,
4.24; N, 4.92. Found: C, 41.98; H, 4.05; N, 4.77. 1H NMR: δ 8.80
(d, JHP=17, 1H, NH), 7.43 (d, JHH = 11, 1H, CH2), 6.68 (d,
J
CP=7, C2(Cy)], 27.2 [d, JCP = 11, C3(Cy)], 25.7 [s, C4(Cy)], 14.5
(s, Me).
Preparation of [Fe2Cp2{μ-CyPN2CH(SiMe3)}(μ-CO)(CO)2]
(2a.3). A solution of N2CH(SiMe3) (70 μL of a 2 M solution in
petroleum ether, 0.140 mmol) was added to a freshly prepared
solution of complex 1 (ca. 0.040 g, 0.091 mmol) in dichloro-
methane (5 mL), and the mixture was stirred at room tempera-
ture for 16 h to give a dark green solution. Workup as described
for 2a.1 gave compound 2a.3 as a green microcrystalline solid
(0.045 g, 90%). Anal. Calcd for C23H31Fe2N2O3PSi: C, 49.84;
H, 5.64; N, 5.05. Found: C, 49.60; H, 5.59; N, 4.90. 1H NMR:
δ 7.75 (s, 1H, CH), 5.13 (s, 10H, Cp), 2.50-1.10 (m, 11H, Cy),
0.15 (s, 9H, Me).
Preparation of [Fe2Cp2(μ-CyPN2CPh2)(μ-CO)(CO)2] (2a.4).
A solution of N2CPh2 (0.025 g, 0.13 mmol) in dichloromethane
(2 mL) was added to a freshly prepared solution of complex 1
(ca. 0.040 g, 0.091 mmol) in dichloromethane (5 mL), and the
mixture was stirred at room temperature for 5 min to give a dark
green solution. Workup as described for 2a.1 gave compound
2a.4 as a green microcrystalline solid (0.052 g, 90%). Anal.
Calcd for C32H31Fe2N2O3P: C, 60.60; H, 4.93; N, 4.42. Found:
C, 60.51; H, 4.87; N, 4.28. 1H NMR: δ 7.56-7.18 (m, 10H, Ph),
5.13 (s, 10H, Cp), 2.25-1.58 (m, 11H, Cy).
J
HH = 11, 1H, CH2), 5.24 (s, 10H, Cp), 2.53-0.90 (m, 11H, Cy).
Photochemical Decarbonylation of Compound 2a.1. A toluene
solution (7 mL) of compound 2a.1 (0.200 g, 0.415 mmol) was
irradiated with visible-UV light in a quartz Schlenk tube while
keeping a gentle N2 (99.9995%) purge at 288 K for 4 h to give a
purple solution. The solvent was then removed under vacuum,
and the residuewasdissolvedina minimum of dichloromethane-
petroleum ether (1:1) and chromatographed through an alumina
column (activity IV) at 288 K. Elution with the same solvent
mixture yielded a green fraction. Removal of solvents under
vacuum from this fraction gave a 10:1 mixture of the cis and trans
isomers of complex [Fe2Cp2(μ-κ1:η2-CyPCH2)(μ-CO)(CO)] (5) as
a green microcrystalline solid (0.039 g, 22%). Anal. Calcd for
C19H23Fe2O2P: C, 53.56; H, 5.44. Found: C, 53.23; H, 5.15.
Elution with dichloromethane-petroleum ether (5:1) yielded a
purple fraction. Removal of solvents under vacuum from this
fraction gave complex [Fe2Cp2(μ-CyPN2CH2)(μ-CO)2] (4) as a
purple microcrystalline solid (0.115 g, 61%) of low solubility in
common solvents. Anal. Calcd for C19H23Fe2N2O2P:C, 50.26; H,
5.11; N, 6.17. Found: C, 49.98; H, 5.02; N, 5.89. Spectroscopic
Preparation of [Fe2Cp2{μ-PhPN2CH(CO2Et)}(μ-CO)(CO)2]
(2b.2). The procedure is identical to that described for com-
pound 2a.2, but using complex 1b (ca. 0.040 g, 0.092 mmol). This
gave compound 2b.2 as a green microcrystalline solid (0.045 g,
1
data for compound 4: H NMR (400.13 MHz, CDCl3): δ 4.70,
4.69 (2s, 2 ꢀ 5H, Cp), 4.21, 3.98 (2d, JHH = 7, 2 ꢀ 1H, CH2), 3.10
(35) Oliver, K. Molecular Magnetism; Wiley: New York, 1992; Chap-
ter 1.
(m, 1H, Cy), 2.10-1.31 (m, 10H, Cy). Spectroscopic data for

5152 Organometallics, Vol. 29, No. 21, 2010
Alvarez et al.
cis-5: 1H NMR (400.13 MHz): δ 4.59 (d, JHP = 1, 5H, Cp), 4.50
(s, 5H, Cp), 2.70 [qt, JHH = JHP = 12, JHH =3, 1H, HC1(Cy)],
2.50, 2.23 (2 m, 2 ꢀ 1H, Cy), 2.08-1.37 (m, 8H, Cy), 1.52 (dd,
[d, JCP = 14, C5,3(Cy)], 26.6 [s, C4(Cy)], 1.2 (s, Me). Spectro-
scopic data for trans-7f: 1H NMR (400.13 MHz): δ 8.20 (d,
JHP = 6, 1H, CH), 4.60, 4.34 (2s, 2 ꢀ 5H, Cp), 3.57 [m, 1H,
HC1(Cy)], 2.70-1.25 (m, 10H, Cy), 0.38 (s, 9H, Me). 13C{1H}
NMR (100.63 MHz): δ 269.8 (d, JCP = 6, μ-CO), 211.7 (d,
JHH = 7, JHP = 9, 1H, PCH2), -0.40 (dd, JHH = 7, JHP = 6, 1H,
PCH2). 13C{1H} NMR (100.62 MHz): 237.8 (d, JCP = 3, μ-CO),
219.3 (d, JCP = 33, FeCO), 81.3, 78.4 (2s, Cp), 43.2 [d, JCP = 1,
C1(Cy)], 34.1 [s, C2,6(Cy)], 33.2 [d, JCP = 3, C6,2(Cy)], 27.6 [d,
J
CP=21, FeCO), 191.8 (d, JCP=11, CH), 88.1, 85.5 (2s, Cp), 46.0
[d, JCP=16, C1(Cy)], 33.2 [d, JCP=2, C2,6(Cy)], 30.9 [d, JCP = 4,
C6,2(Cy)], 26.4 [s, C4(Cy)], 2.1 (s, Me); other resonances for this
isomer were obscured by those of the major isomer.
J
CP = 6, C3,5(Cy)], 27.5 [d, JCP = 8, C5,3(Cy)], 26.5 [s, C4(Cy)],
20.3 (d, JCP = 4, PCH2). Spectroscopic data fortrans-5: 1H NMR
(400.13 MHz): δ 4.79, 4.48 (2s, 2 ꢀ 5H, Cp). 13C{1H} NMR
(100.62 MHz): 81.1, 79.5 (2s, Cp); other resonances of this minor
isomer could not be identified in the corresponding spectra due to
its low proportion and/or superposition with the resonances of
the major isomer.
Preparation of [Fe2Cp2(μ-CyPNHNCH)(μ-CO)(CO)] (7g).
Degassed water (4 mL, 0.222 mmol) was added to a toluene
solution (5 mL) of compound 7f (0.065 g, 0.124 mmol), and the
mixture was stirred for 30 min to give a green solution. The
solvent was then removed under vacuum, and the residue was
dissolved in a minimum of dichloromethane-petroleum ether
(1:1) and chromatographed through an alumina column
(activity IV) at 288 K. Elution with dichloromethane yielded a
green fraction. Removal of solvents under vacuum from this
fraction gave a mixture of the cis and trans isomers of complex
7g as a green microcrystalline solid (0.051 g, 91%). These
isomers interconvert in dichloromethane solution, with the
equilibrium ratio being ca. 4:1 at 253 K. Anal. Calcd for
C19H23Fe2N2O2P: C, 50.26; H, 5.11; N, 6.17. Found: C, 50.18;
H, 4.89; N, 6.12. Spectroscopic data for cis-7g: 1H NMR (400.13
MHz): δ 7.82 (s, br, 1H, CH), 6.42 (s, br, 1H, NH), 4.67, 4.61 (2s,
2 ꢀ 5H, Cp), 2.95 (m, 1H, Cy), 2.73, 2.56 (2 m, 2 ꢀ 1H, Cy),
2.24-1.42 (m, 8H, Cy). 1H NMR (400.13 MHz, 253 K): δ 7.78
(d, JHP = 5, 1H, CH), 6.61 (s, br, 1H, NH), 4.71, 4.65 (2s, 2 ꢀ
5H, Cp), 2.88 (m, 1H, Cy), 2.74, 2.50 (2 m, 2 ꢀ 1H, Cy),
2.24-1.42 (m, 8H, Cy). 13C{1H} NMR (100.62 MHz): δ 266.4
(s, μ-CO), 214.4 (d, JCP = 21, FeCO), 188.9 (s, CH), 85.0, 84.5
(2s, Cp), 49.8 [d, JCP = 22, C1(Cy)], 31.9 [m, C2, C6(Cy)], 27.9 [d,
Preparation of [Fe2Cp2{μ-CyPN2CH(CO2Et)}(μ-CO)(CO)]
(6). A toluene solution (5 mL) of complex 2a.2 (0.060 g, 0.108
mmol) was irradiated with visible-UV light at 288 K in a quartz
Schlenk tube for 1.5 h, while keeping a gentle N2 purge, to give a
dark green solution, which was filtered using a canula. The
solvent was then removed from the filtrate under vacuum, and
the residue was washed with petroleum ether (3 ꢀ 4 mL) to give
the paramagnetic complex 6 as a green microcrystalline solid
(0.054 g, 97%). Anal. Calcd for C22H27Fe2N2O4P: C, 50.22; H,
5.17; N, 5.32. Found: C, 50.07; H, 5.04; N, 5.13. μeff (CD2Cl2) =
2.75 μB.
Preparation of cis- and trans-[Fe2Cp2{μ-CyPNHNC(CO2-
Et)}(μ-CO)(CO)] (7e). Compound 6 (0.054 g, 0.105 mmol)
was dissolved in a minimum of dichloromethane-petroleum
ether (1:2) and chromatographed through an alumina column
(activity IV) at 263 K. Elution with dichloromethane yielded
a green-brown fraction. Removal of solvents under vacuum
from this fraction gave complex trans-7e as a green-brown solid
(0.049 g, 86%). The crystals used in the diffractometric study
were grown by the slow diffusion of layers of toluene and
petroleum ether into a dichloromethane solution of the complex
at 253 K. Elution with tetrahydrofuran-petroleum ether (1:1)
yielded a pale green fraction, which gave analogously complex
cis-7e as a green solid (0.005 g, 8%). Data for trans-7e: Anal.
Calcd for C22H27Fe2N2O4P: C, 50.22; H, 5.17; N, 5.32. Found:
C, 50.10; H, 5.07; N, 5.26. 1H NMR: δ 7.40 (d, br, JHP=5, 1H,
NH), 4.58, 4.41 (2s, 2 ꢀ 5H, Cp), 4.15, 4.09 (2dq, JHH =13,
7, 2 ꢀ 1H, OCH2), 3.06 (m, 1H, Cy), 2.60-1.97 (m, 5H, Cy), 1.90
(m, 1H, Cy), 1.65-1.43 (m, 4H, Cy), 1.31 (t, JHH = 7, 3H, Me).
J
CP = 8, C3,5(Cy)], 27.4 [d, JCP = 9, C5,3(Cy)], 26.0 [s, C4(Cy)].
Spectroscopic data for trans-7g: 1H NMR (400.13 MHz): δ 4.54,
4.37 (2s, 2 ꢀ 5H, Cp). 1H NMR (400.13 MHz, 253 K): δ 8.21 (s,
1H, CH), 4.59, 4.43 (2s, 2 ꢀ 5H, Cp). 13C{1H} NMR (100.63
MHz): δ 88.1, 86.6 (2s, Cp); other resonances for this isomer
were obscured by those of the major isomer.
Preparation of [Fe2Cp2(μ-CyPNHNHCH)(μ-CO)(CO)](BF4)
(8j). A slight excess of HBF4 OEt2 (16 μL of a 54% solution in
3
Et2O, 0.116 mmol) was added to a dichloromethane solution
(5 mL) of compound 7g (0.050 g, 0.110 mmol), and the mixture
was stirred at room temperature for 5 min to give a red solution.
The solvent was then removed under vacuum, and the residue
was washed with Et2O (3 ꢀ 4 mL) and then petroleum ether (2 ꢀ
4 mL) to give a mixture of the cis and trans isomers of complex 8j
as a red microcrystalline solid (0.058 g, 97%). The cis/trans ratio
was measured to be 10:1 in CD2Cl2 solution. Anal. Calcd for
C19H24BFe2F4N2O2P: C, 42.11; H, 4.46; N, 5.17. Found: C,
42.02; H, 4.52; N, 4.98. Spectroscopic data for cis-8j: 1H NMR:
δ 10.82 (dd, JHP = 19, JHH =4, 1H, NH), 8.94 (dd, JHP =6,
JHH = 4, 1H, CH), 7.65 (s, br, 1H, PNH), 4.90, 4.86 (2s, 2 ꢀ 5H,
Cp), 3.00 [m, 1H, HC1(Cy)], 2.71, 2.45 [2 m, 2 ꢀ 1H, HC2(Cy)],
2.21-1.49 (m, 8H, Cy). 13C{1H} NMR: δ 261.7 (d, JCP = 4, μ-
CO), 220.4 (d, JCP = 16, CH), 210.2 (d, JCP = 19, FeCO), 86.3,
86.2 (2s, Cp), 49.9 [d, JCP = 24, C1(Cy)], 32.3 [d, JCP = 6,
13C{1H} NMR (100.62 MHz): δ 266.0 (s, μ-CO), 211.1 (d, JCP
=
13, FeCO), 191.9 (d, JCP = 11, CCO2Et), 170.3 (s, CO2Et), 88.3,
86.2 (2s, Cp), 60.3 (s, OCH2), 47.2 [d, JCP = 23, C1(Cy)], 33.0 [s,
C2,6(Cy)], 32.0 [s, C6,2(Cy)], 28.0, 27.7 [2d, JCP = 13, C3 and
C5(Cy)], 26.4 [s, C4(Cy)], 14.8 (s, Me). Data for cis-7e: Anal.
Calcd for C22H27Fe2N2O4P: C, 50.22; H, 5.17; N, 5.32. Found:
C, 50.17; H, 5.14; N, 5.21. 1H NMR: δ 6.78 (d, br, JHP = 7, 1H,
NH), 4.70, 4.66 (2s, 2 ꢀ 5H, Cp), 4.15, 3.99 (2 m, 2 ꢀ 1H, OCH2),
2.96, 2.92, 2.56 (3 m, 3 ꢀ 1H, Cy), 2.27-1.50 (m, 8H, Cy), 1.26 (t,
JHH=7, 3H, Me).
Preparation of [Fe2Cp2{μ-CyPN(SiMe3)NCH}(μ-CO)(CO)]
(7f). A toluene solution (6 mL) of complex 2a.3 (0.065 g, 0.117
mmol) was irradiated with visible-UV light at 288 K in a quartz
Schlenk tube for 1 h, while keeping a gentle N2 purge, to give a
dark green solution, which was filtered using a canula. The
solvent was then removed from the filtrate under vacuum, and
the residue was washed with petroleum ether (2 ꢀ 3 mL) to give a
3:1 mixture (by NMR) of the cis and trans isomers of complex 7f
as a green microcrystalline solid (0.060 g, 97%). Anal. Calcd for
C22H31Fe2N2O2PSi: C, 50.21; H, 5.94; N, 5.32. Found: C, 49.98;
H, 5.76; N, 5.12. Spectroscopic data for cis-7f: 1H NMR (400.13
MHz): δ 7.66 (d, JHP=6, 1H, CH), 4.73, 4.56 (2s, 2 ꢀ 5H, Cp),
3.55 [m, 1H, HC1(Cy)], 2.70-1.25 (m, 10H, Cy), 0.25 (s, 9H,
Me). 13C{1H} NMR (100.63 MHz): δ 266.5 (d, JCP = 5, μ-CO),
214.1 (d, JCP = 21, FeCO), 182.5 (d, JCP=11, CH), 85.5, 83.6
(2s, Cp), 50.2 [d, JCP = 10, C1(Cy)], 33.6 [d, JCP = 3, C2,6(Cy)],
30.6 [d, JCP = 2, C6,2(Cy)], 27.9 [d, JCP = 11, C3,5(Cy)], 27.7
C
2,6(Cy)], 32.0 [d, JCP = 6, C6,2(Cy)], 27.9 [d, JCP = 10, C3,5
-
(Cy)], 27.4 [d, JCP=11, C5,3(Cy)], 26.0 [s, C4(Cy)]. Spectroscopic
data for trans-8j: 1H NMR: δ 10.69 (d, br, JHP = 16, 1H, NH),
9.21 (dd, JHP = 6, JHH = 4, 1H, CH), 8.26 (s, br, 1H, PNH),
4.78, 4.67 (2s, 2 ꢀ 5H, Cp), 3.04-1.49 (m, 11H, Cy). 13C{1H}
NMR: δ 88.8, 87.2 (2s, Cp); other resonances for this isomer
were obscured by those of the major isomer.
Preparation of [Fe2Cp2(μ-CyPNHNMeCH)(μ-CO)(CO)](I)
(8k). Neat MeI (100 μL, 1.607 mmol) was added to a dichloro-
methane solution (5 mL) of compound 7g (0.050 g, 0.110 mmol),
and the mixture was stirred at room temperature for 1 h to
give a red solution. The solvent was then removed under
vacuum, and the residue was washed with petroleum ether (2 ꢀ
4 mL) to give a mixture of the cis and trans isomers of complex

Article
Organometallics, Vol. 29, No. 21, 2010 5153
8k as a red microcrystalline solid (0.063 g, 95%). The cis/trans
ratio in solution was measured to be 10:1 (CD2Cl2), 7:1 (CDCl3),
and 16:1 (Me2CO-d6). Anal. Calcd for C20H26Fe2F4IN2O2P: C,
40.30; H, 4.40; N, 5.70. Found: C, 40.63; H, 4.52; N, 4.86.
Spectroscopic data for cis-8k: 1H NMR: δ 9.97 (s, 1H, CH), 8.50
(s, 1H, NH), 4.90, 4.82 (2s, 2 ꢀ 5H, Cp), 3.61 (s, 3H, Me), 3.13
(m, 1H, Cy), 2.66-1.70 (m, 10H, Cy). 13C{1H} NMR (Me2CO-
in the Fourier maps. All hydrogen atoms were given an overall
isotropic thermal parameter. Further details of the data collec-
tion and refinements are given in Table 6.
X-ray Structure Determination of Compound 7e. The X-ray
intensity data were collected on a Kappa-Apex-II Bruker dif-
fractometer using graphite-monochromated Mo KR radiation
at 100 K. The software APEX40 was used for collecting frames
with the omega/phi scan measurement method. The Bruker
SAINT software was used for the data reduction,36 and a
multiscan absorption correction was applied with SADABS.37
Using the program suite WinGX,38 the structure was solved by
Patterson interpretation and phase expansion and refined with
full-matrix least-squares on F2 using SHELXL97.39 Two inde-
pendent molecules were found to be present in the asymmetric
unit. The FeCp moiety, the cyclohexyl group, and O(34) and
C(36) atoms on the second independent molecule were highly
disordered and were modeled in two positions (occupancy
factor = 0.5/0.5, except for C(36) = 0.6/0.4). Non-H atoms
were refined anisotropically except for a number of atoms
involved in the disorder, which were refined isotropically be-
cause some of their temperature factors were persistently non-
positive definites. Not all hydrogen atoms were found in Fourier
maps, so all hydrogen atoms were fixed at calculated geometric
positions in the last least-squares refinements, except for the
N-H atoms (H(1) and H(3)), which could be located in the
Fourier maps, and their positions were refined satisfactorily. All
hydrogen atoms were given an overall isotropic thermal para-
meter. Further details of the data collection and refinements are
given in Table 6.
d6): δ 263.3 (s, μ-CO), 222.2 (d, JCP = 18, CH), 212.8 (d, JCP
=
20, FeCO), 87.2, 86.9 (2s, Cp), 49.6 [d, JCP = 23, C1(Cy)], 48.7 (s,
Me), 32.3 [m, C2, C6(Cy)], 28.3 [d, JCP=12, C3,5(Cy)], 27.6 [d,
J
CP = 13, C5,3(Cy)], 26.2 [s, C4(Cy)]. Spectroscopic data for
trans-8k: 1H NMR: δ 10.44 (s, 1H, CH), 8.74 (s, 1H, NH), 4.82,
4.76 (2s, 2 ꢀ 5H, Cp), 3.71 (s, 3H, Me), 2.66-1.70 (m, 11H, Cy).
Preparation of [Fe2Cp2{μ-Mes*PN2CH(CO2Et)}(μ-CO)2]
(9). A toluene solution (5 mL) of compound 2c.2 (0.060 g,
0.084 mmol) was irradiated with visible-UV light in a quartz
Schlenk tube while keeping a gentle N2 (99.9995%) purge at
288 K for 50 min to give a green solution. The solvent was then
removed under vacuum, and the residue was dissolved in a
minimum of dichloromethane-petroleum ether (1:8) and chro-
matographed through an alumina column (activity IV) at 263 K.
Elution with the same solvent mixture yielded a red fraction
containing some [Fe2Cp2(CO)4]. Elution with dichloromethane-
petroleum ether (1:3) yielded a green fraction. Removal of sol-
vents under vacuum from this fraction gave compound 9 as a
green microcrystalline solid (0.049 g, 85%). The crystals used in
the diffractometric study were grown from a concentrated
petroleum ether solution of the complex at 253 K. Anal. Calcd
for C34H45Fe2N2O4P: C, 59.32; H, 6.59; N, 4.07. Found: C,
1
59.13; H, 6.56; N, 3.88. H NMR (400.13 MHz,): δ 7.34 (d,
X-ray Structure Determination of Compound 9. Data collec-
tion was performed on an Oxford Diffraction Xcalibur Nova
single-crystal diffractometer, using Cu KR radiation. Images
were collected at a 65 mm fixed crystal-detector distance, using
the oscillation method, with 1° oscillation and variable exposure
time per image (1-30 s). Data collection strategy was calculated
with the program CrysAlis Pro CCD.41 Data reduction and cell
refinement were performed with the program CrysAlis Pro
RED.41 An empirical absorption correction was applied using
the SCALE3 ABSPACK algorithm as implemented in the pro-
gram CrysAlis Pro RED.41 Using the program suite WinGX,38
the structure was solved by direct methods and refined with full-
matrix least-squares on F2 using SHELXL97.39 This compound
was found to crystallize with half a molecule of hexane placed on
an element of symmetry described by the operation -xþ3/2,
-yþ3/2, -zþ1. During the final stages of the refinement, all the
positional parameters and the anisotropic temperature factors
of all the non-H atoms were refined anisotropically. All hydro-
gen atoms were geometrically placed and refined using a riding
model, except for H(13), which was located in the Fourier maps
and refined isotropically. Further details of the data collection
and refinements are given in Table 6.
J
HP=2, 2H, C6H2), 6.22 (s, 1H, CH), 4.74, 4.72 (2s, 2 ꢀ 5H, Cp),
4.00 (q, JHH=7, 2H, OCH2), 1.42 (s, 18H, o-tBu), 1.27 (s, 9H,
p-tBu), 1.10 (t, JHH = 7, 3H, Me). 13C{1H} NMR (100.62 MHz):
δ 279.9 (d, JCP = 25, μ-CO), 164.5 (s, CO2Et), 155.1 [s, C2-
(C6H2)], 154.0 [s, C4(C6H2)], 134.4 [d, JCP = 37, C1(C6H2)],
133.9 (d, JCP = 27, CH), 122.6 [d, JCP = 12, C3(C6H2)], 89.9 (d,
J
CP = 2, Cp), 85.3 (s, Cp), 60.7 (s, OCH2), 38.0 [s, C1(o-tBu)],
32.9 [s, C2(o-tBu)], 32.4 [s, C1(p-tBu)], 31.1 [s, C2(p-tBu)], 14.3
(s, Me).
X-ray Structure Determination of Compounds 2a.1 and 3. The
X-ray intensity data were collected on a Smart-CCD-1000
Bruker diffractometer using graphite-monochromated Mo KR
radiation at 120 K. Cell dimensions and orientation matrixes
were initially determined from least-squares refinements on
reflections measured in three sets of 30 exposures collected in
three different ω regions and eventually refined against all
reflections. The software SMART36 was used for collecting
frames of data, indexing reflections, and determining lattice
parameters. The collected frames were then processed for
integration by the software SAINT,36 and a multiscan absorp-
tion correction was applied with SADABS.37 Using the program
suite WinGX,38 the structure was solved by Patterson interpre-
tation and phase expansion and refined with full-matrix least-
squares on F2 using SHELXL97.39 All non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were fixed at
calculated geometric positions in the last least-squares refine-
ments, except for H(4a) and H(4b) (for compound 2a.1) and
H(2), H(14a), and H(14b) (for compound 3), which were located
Acknowledgment. We thank the DGI of Spain (Pro-
jects CTQ2006-01207 and CTQ2009-09444) and the COST
action CM0802 ‘‘PhoSciNet’’ for supporting this work, and
the MEC of Spain for a grant (to R.G.).
Supporting Information Available: CIF file giving the crystal-
lographic data for the structural analysis of compounds 2a.1, 3,
7e, 7f, and 9. This material is available free of charge via the
Internet at http://pubs.acs.org.
(36) SMART & SAINT Software Reference Manuals, Version 5.051
(Windows NT Version); Bruker Analytical X-ray Instruments: Madison, WI,
1998.
(37) Sheldrick, G. M. SADABS, Program for Empirical Absorption
€
€
Correction; University of Gottingen: Gottingen, Germany, 1996.
(38) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(39) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.
(40) APEX 2, version 2.0-1; Bruker AXS Inc: Madison, WI, 2005.
(41) CrysAlis Pro; Oxford Diffraction Ltd.: Oxford, U.K., 2006.