Chemical and structural effects of bulkness on bent-phosphinidene bridges: Synthesis and reactivity of the diiron complex [Fe2Cp 2{μ-P(2,4,6-C6H2tBu 3)}(μ-CO)(CO)2]

Article abstract of DOI:10.1021/om100137d

The steric pressure introduced by the 2,4,6-C₆H₂ ^tBu₃ group (R*) in the complex [Fe ₂Cp₂(μ-PR*)(μ-CO)(CO)₂] (Cp = η⁵-C₅H₅) has pronounced effects

Full text of DOI:10.1021/om100137d

Organometallics 2010, 29, 1875–1878 1875
DOI: 10.1021/om100137d
Chemical and Structural Effects of Bulkness on Bent-Phosphinidene
Bridges: Synthesis and Reactivity of the Diiron Complex
t
[
Fe Cp {μ-P(2,4,6-C H Bu )}(μ-CO)(CO) ]
2
2
6
2
3
2
M. Angeles Alvarez, M. Esther Garcıa, Rocı
´ ´
o Gonz ꢀa lez, Alberto Ramos, and
Miguel A. Ruiz*
Departamento de Quı´mica Org aꢀ nica e Inorg aꢀ nica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain
Received February 22, 2010
t
5
Summary: The steric pressure introduced by the 2,4,6-C H Bu
6
(Cp=η -C H ) having bent phenyl- or cyclohexylphosphini-
5 5
5
2
3
group (R*) in the complex [Fe Cp (μ-PR*)(μ-CO)(CO) ] (Cp =
η -C H ) has pronounced effects with regard to its synthesis,
structure, thermal stability, and general reactivity of the bent
phosphinidene bridge, enabling it, for instance, to react with
hydrogen under mild conditions (ca. 4 atm, 290 K).
dene bridges. These compounds are themselves stable at
room temperature but are also highly reactive under mild
conditions toward a great variety of electrophilic molecules
ranging from simple alkyl halides or chalcogens to alkenes,
alkynes, diazo compounds, and organic azides, to give in
some cases novel or unexpected organophosphorus ligands
coordinated at the diiron center. It was thus of interest to
examine the influence of steric effects in all this rich chem-
istry, which we have done by using a quite bulky aryl group
2
2
2
5
5
5
It is well-known that steric effects have a pronounced
influence not only on the structure but also on the stability
and reactivity of chemical species in general, and examples of
the consequences of introducing bulky groups in molecules can
be found in all areas of chemistry. Within the realm of
organometallic chemistry, for instance, we can quote the use
5
,6
t
(
R*=2,4,6-C H Bu ) as substituent in the phosphinidene
3
6
2
ligand. In this communication we report the preparation and
a preliminary study of the reactivity of the corresponding
diiron complex [Fe Cp (μ-PR*)(μ-CO)(CO) ] (3). As will be
5
5
of η -C Me instead of η -C H ligands or of phosphine
ligands PR having very bulky instead of “normal-sized” R
5
5
5
5
2
2
2
3
shown below, the increased steric demands of the R* group
have pronounced effects at all levels, since significant differ-
ences (when compared to the complexes having PCy and PPh
ligands) are found for compound 3 concerning its synthesis,
structure, thermal stability, and general reactivity.
groups. In this way, novel structures and novel reactivity can
be found that would be otherwise impossible to reach. Recent
outstanding achievements of this strategy are the use of very
bulky aryl (Ar) or silyl (X) groups to build the first examples of
1
stable quintuply bonded dimetal complexes (Cr Ar ) and of
2
2
2
The mentioned phosphinidene complex can be prepared
through a two-step procedure (Scheme 1). First, a double oxi-
dation coupled to deprotonation is induced on the correspond-
triply bonded disilicon species (Si X ), respectively.
2
2
Bulky substituents have been used also in the very active
3
area of phosphinidene (PR) complexes, mainly to stabi-
7
3
d,i,l,m
4
ing arylphosphine complex [Fe Cp (μ-CO) (CO)(PR*H )] (1)
2
2
2
2
lize mononuclear species,
Recently, we reported a high-yield synthetic procedure
but also binuclear species.
by reacting it with 2 equiv of [FeCp ]BF in the presence of
2
4
NaHCO , to give with high yield the cationic phosphide-bridged
3
for the new diiron complexes [Fe Cp (μ-PR)(μ-CO)(CO) ]
2
2
2
8
complex [Fe Cp (μ-PR*H)(μ-CO)(CO) ]BF (2), which dis-
2
2
2
4
plays two terminal CO ligands almost parallel to each other, as
observed for the PCy or PPh complexes. Here we find, however,
the first important effect of the R* group, since the less bulky
phosphide complexes are not formed via two-electron oxidation
of their phosphine complexes, but just following a single-electron
*
To whom correspondence should be addressed. E-mail: mara@
uniovi.es.
(1) Nguyen, T.; Sutton, A. D.; Brynda, M.; Fettinger, J. C.; Long, G.
J.; Power, P. P. Science 2005, 310, 844.
(
(
2) Sekiguchi, A.; Kinjo, R.; Ichinohe, M. Science 2004, 305, 1755.
3) Reviews: (a) Aktas, H.; Slootweg, J. C.; Lammerstma, K. Angew.
5
oxidation/dehydrogenation sequence. Apparently, the radical
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. Engl. 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. Engl. 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.
complex emerging from the first oxidation step of 1 is stabilized
by the bulky R* group enough to prevent its spontaneous
dehydrogenation, a matter to be studied in detail in the future.
(
(
(6) Alvarez, M. A.; Garcı
Organometallics 2008, 27, 1037.
(7) Compound 1 was prepared as reported in ref 5 for the related
complexes [Fe Cp (μ-CO) (CO)(PRH )] (R = Ph, Cy). Selected spec-
troscopic data for 1: ν(CO) (CH Cl ) 1936 (m), 1772 (w), 1732 (vs) cm
) δ -21.3 ppm; H NMR (CD
δ 4.71 (s, 5H, Cp), 4.44 (d, JHP = 343, 2H, P-H), 3.99 (s, 5H, Cp) ppm.
(8) Preparation of 2: solid [FeCp ]BF (0.400 g, 1.467 mmol) was
slowly added to a stirred suspension of NaHCO (1.0 g, 11.9 mmol) in a
´
a, M. E.; Gonz ꢀa lez, R.; Ruiz, M. A.
(
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,
2
2
2
2
-
1
2
2
;
3
1
1
1
4
06.
P{ H} NMR (CD
2
Cl
2
2 2
Cl , trans isomer)
(4) (a) Arif, A. M.; Cowley, A. H.; Norman, N. C.; Orpen, A. G.;
Pakulski, M. Organometallics 1988, 7, 309. (b) García, M. E.; Riera, V.;
Ruiz, M. A.; S ꢀa ez, D.; Vaissermann, J.; Jeffery, J. C. J. Am. Chem. Soc. 2002,
2
4
3
1
24, 14304. (c) Sanchez-Nieves, J.; Sterenberg, B. T.; Udachin, K. A.; Carty,
dichloromethane solution (30 mL) of compound 1 (0.400 g, 0.662 mmol)
at 243 K, and the mixture was further stirred for 2 h at the same
temperature to give a red solution yielding compound 2 (0.420 g,
A. J. Inorg. Chim. Acta 2003, 350, 486. (d) 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.
92%) after workup. Selected spectroscopic data: ν(CO) (CH
2
Cl
) δ 181.7 ppm; H
) δ 9.88 (d, JHP = 385, 1H, P-H), 5.32 (s, 10H, Cp) ppm.
2
) 2028
-1
31
1
1
(
5) Alvarez, C. M.; Alvarez, M. A.; Garcı
´
a, M. E.; Gonz ꢀa lez, R.;
(vs), 2000 (w), 1825 (m) cm
2 2
; P{ H} NMR (CD Cl
Ruiz, M. A.; Hamidov, H.; Jeffery, J. C. Organometallics 2005, 24, 5503.
NMR (CD Cl
2
2
r 2010 American Chemical Society
Published on Web 03/24/2010
pubs.acs.org/Organometallics

1
876 Organometallics, Vol. 29, No. 8, 2010
Alvarez et al.
Scheme 2
Figure 1. ORTEP diagram of compound 3, with H atoms and the
t
p- Bu group omitted for clarity. Selected bond lengths (A) and
˚
angles (deg): Fe(1)-Fe(2) = 2.5763(5), Fe(1)-C(1) = 1.758(3),
Fe(2)-C(2) = 1.762(3), Fe(1)-C(3) = 1.911(3), Fe(2)-C(3) =
1.915(3), Fe(1)-P(1) = 2.305(1), Fe(2)-P(1) = 2.306(1), P(1)-
C(14) = 1.893(2); C(1)-Fe(1)-Fe(2) = 100.8(1), C(2)-Fe(2)-
Fe(1)=98.1(1), C(1)-Fe(1)-C(3)=85.6(1), C(2)-Fe(2)-C(3) =
8
6.4(1), C(1)-Fe(1)-P(1)=94.3(1), C(2)-Fe(2)-P(1)=94.0(1),
Fe(1)-P(1)-Fe(2)=67.9(1), Fe(1)-P(1)-C(14)=113.5(1), Fe-
2)-P(1)-C(14) = 113.2(1).
(
terminal carbonyls away from the aryl group. All these effects
can be considered as indicative of the presence of a severe steric
crowding introduced by the bulky R* group in this complex.
We also note that, although the boat deformation of the R*
group has been previously found in other sterically over-
crowded molecules, that observed in 3 seems particularly
large, as indicated by the tip angles for the ipso and para carbon
atoms of the ring (ca. 22 and 10°, respectively).
The steric crowding in compound 3 is perhaps behind its low
thermal stability. Indeed, this complex rearranges slowly
Scheme 1
11
(conversion ca. 80% after 4 day) in toluene solution at room
temperature by undergoing intramolecular insertion of the P
t
atom into a C-H bond of one of the close o- Bu groups
˚
H = ca. 2.55 A in the crystal), to give the phosphine deri-
(P
3
3 3
t
12
vative [Fe Cp (μ-CO) (CO){PH(CH CMe )C H Bu }] (4),
2
2
2
2
2
6
2
2
the latter having a structure comparable to that of the phos-
phine complex 1(Scheme 2). Expectedly, thistransformationis
much faster at higher temperatures, and it can be completed in
ca. 1 h at 338 K in toluene solution. As found for 1, complex 4
exists in solution as an equilibrium mixture of trans and cis
isomers, these differing in the relative orientation of the Cp or
(CO/phosphine) ligands, with the former being the major
isomers, as is usually found for phosphine derivatives of the
The second step in the preparation of the phosphinidene
complex 3 is a more conventional deprotonation of the P-H
bond remaining in the phosphide-bridged cation 2, which can
be quantitatively accomplished in dichloromethane solution
using solid K(OH) and other strong bases. The presence of the
phosphinidene ligand in 3 is denoted by the strong deshielding
31
9
of its P nucleus and has been further confirmed through an
10
X-ray study (Figure 1). The structure is qualitatively similar
5
type [Fe Cp
2
(μ-CO) (CO)(PR )]. The C-H bond cleavage of
2 2 3
t
the Bu group in a PR* ligand to yield the free or metal-bound
to that of the corresponding phenylphosphinidene complex,
but there are significant quantitative differences concerning the
t
phosphine PH(CH
ported to occur on a few transient mononuclear complexes.
CMe )C H Bu has been previously re-
2 2 6 4 2
13
bent (or pyramidal) phosphinidene ligand in 3: (a) Fe-P and
˚
P-C(aryl) lengths ca. 0.05 A longer, (b) a strong deviation of
the aryl ring from planarity, to adopt an incipient boat con-
(11) (a) Aktas, H.; Slootweg, J. C.; Schakel, M.; Ehlers, A. W.; Lutz,
M.; Spek, A. L.; Lammertsma, K. J. Am. Chem. Soc. 2009, 131, 6666.
t
formation that takes the ortho Bu groups away from the
(
b) Jutzi, P.; Schmidt, H.; Neumann, B.; Stammler, H. G. Organometallics
˚
terminal cyclopentadienyl (H H = ca. 2.2 A) and carbonyl
3
3 3
1996, 15, 741and references therein.
(12) Preparation of 4: a toluene solution (5 mL) of compound 1 (0.050 g,
˚
C/O = ca. 2.6 A) ligands, and (c) a slight bending of the
(
H
3
3 3
0.083 mmol) was placed in a Schlenk tube equipped with a Young valve, and
it was stirred at 338 K for 1 h to give a brown-green mixture yielding
compound 4 (0.036 g, 71%) after chromatographic separation. Selected
(9) Preparation of 3: solid KOH (ca. 0.1 g, excess) was added to a
-
1
dichloromethane solution (6 mL) of compound 2 (0.050 g, 0.072 mmol)
at room temperature, and the mixture was vigorously stirred for 5 min to
give a wine red solution which yielded compound 3 (0.042 g, 95%) after
spectroscopic data: ν(CO) (CH
2
Cl
) δ 36.8 (trans), 37.5 (cis) ppm; H NMR (C
isomer trans) δ 4.56 (dd, JHP = 348, JHH = 5, 1H, P-H), 4.47, 4.09 (2s, 2 Â
2
) 1934 (m), 1772 (w), 1730 (vs) cm .
31
1
1
P{ H} NMR (C
6
D
6
6 6
D ,
workup. Selected spectroscopic data: ν(CO) (CH
2
Cl
2
) 1991 (vs),
5H, Cp), 2.53, 1.99 (2 m, 2 Â 1H, CH ), 1.66, 1.00 (2s, 2 Â 3H, Me) ppm.
2
-1
31
1
P{ H} NMR (CD
1
1
958 (w), 1769 (m) cm
;
2
Cl
2
) δ 593.4 ppm;
H
(13) (a) Champion, D. H.; Cowley, A. H. Polyhedron 1985, 4, 1791.
(b) Arif, A. M.; Cowley, A. H.; Pakulski, M.; Pearsall, M. A.; Clegg, W.;
Norman, N. C.; Orpen, A. G. J. Chem. Soc., Dalton Trans. 1988, 2713.
(c) Hey-Hawkins, E.; Kurz, S. J. Organomet. Chem. 1994, 479, 125.
(d) Masuda, J. D.; Jantunen, K. C.; Ozerov, O. V.; Noonan, K. J. T.; Gates,
D. P.; Scott, B. L.; Kiplinger, J. L. J. Am. Chem. Soc. 2008, 130, 2408.
NMR (CD Cl ) δ 4.86 (s, 10H, Cp) ppm.
2
2
˚
10) X-ray data for 3: red crystals, triclinic (P1), a = 9.7459(4) A, b =
(
˚
˚
1
7
1.4820(5) A, c = 13.4931(6) A, R = 73.027(2)°, β = 85.188(2)°, γ =
6.050(2) , V = 1401.4(1) A , T = 100 K, Z = 2, R = 0.0358 (observed
o 3
˚
data with I > 2σ(I)), GOF = 1.045.

Communication
Organometallics, Vol. 29, No. 8, 2010 1877
˚
similarly short P-O length of ca. 1.48 A but a substantially
˚
shorter Fe-P length of ca. 2.10 A. The latter figure can
be compared to the value of ca. 2.22 A for the mentioned
˚
5
˚
diiron complex or to values of ca. 2.13-2.21 A for different
phosphite and phosphine (L) complexes of the type [Fe -
Cp (μ-CO) (CO)(L)]. All of the above data suggest the
2
18
2
2
presence of substantial multiplicity in the Fe-P bond of 5T,
3
1
also consistent with the strong deshielding of its P nucleus (δP
ca. 433 ppm, to be compared to 312 ppm for the isomer 5B). We
should stress that compound 5 is the first Fe complex having a
terminal oxophosphinidene ligand to be reported, with pre-
19a
19b
vious comparable species being restricted so far to Cr, Re,
2
0
and Mo compounds. Because of this paucity of suitable
complexes, the chemistry of the phosphinidene oxide ligand
remains largely unknown at present, and compound 5 thus
offers an excellent opportunity to explore this chemistry at an
iron center, currently under way.
Figure 2. ORTEP diagram of compound trans-5T, with H
t
atoms and the p- Bu group omitted for clarity. Selected bond
˚
lengths (A) and angles (deg): Fe(1)-Fe(2) = 2.556(1), Fe(1)-C-
Although the reactions discussed above are indeed singu-
lar in the context of the isolable phosphinidene complexes,
the most remarkable observation concerning the chemical
behavior of 3, not paralleled by other phosphinidene com-
plexes of any type, lies however in its ability to react with
hydrogen under mild conditions. Thus, upon stirring a
toluene solution of 3 under hydrogen (ca. 4 atm) at room
temperature for ca. 20 h, a mixture containing the phosphine
complex 1 as the major product is obtained, along with small
amounts of free phosphine PR*H , the dimer [Fe Cp (CO) ],
(
1) = 1.760(8), Fe(1)-C(2) = 1.910(7), Fe(1)-C(3) = 1.923(6),
Fe(2)-C(2) = 1.936(7), Fe(2)-C(3) = 1.926(6), Fe(2)-P(1) =
.091(2), P(1)-O(4) = 1.484(4), P(1)-C(14) = 1.840(7); C(1)-
Fe(1)-Fe(2) = 96.2(2), C(1)-Fe(1)-C(2) = 94.6(3), C(1)-Fe-
1)-C(3) = 96.3(3), P(1)-Fe(2)-C(2) = 97.6(2), P(1)-Fe(2)-
2
(
C(3) = 90.4(2), P(1)-Fe(2)-Fe(1) = 98.1(1), Fe(2)-P(1)-O-
(
(
4) = 129.5(2), Fe(2)-P(1)-C(14) = 118.6(2), O(4)-P(1)-C-
14) = 111.6(3).
Interestingly, we recently proposed that the dimolybdenum
complex [Mo Cp (μ-PR*)(CO) ], having a trigonal (four-elec-
2
2
2
4
2
2
4
and complex 4. Most of the last complex is surely formed
from the slow thermal rearrangement of 3 discussed above,
while a separate experiment revealed that compound 1 in
turn decomposes slowly in dichloromethane solution at
room temperature to give free phosphine PR*H2 and
[Fe Cp (CO) ] as major products. Thus, it seems that the
tron-donor) PR* bridge, undergoes a related C-H bond clea-
vage reaction via a photoexcited state having a pyramidal (two-
1
4
electron-donor) PR* bridge. The observable transformation3/
4
thus provides indirect support for the above proposal.
The structural effects imposed by the bulky R* group on
2
2
4
the reaction products arising from complex 3 are illustrated
through its reaction with oxygen. The latter takes place
rapidly at room temperature in the presence of air to give ini-
tially the oxophosphinidene-bridged derivative [Fe Cp {μ-
hydrogenation of 3 is quite selective and gives mainly the
phosphine complex 1 through a formal oxidative addition of
the H-H bond to the lone-pair-bearing P atom. This is a
remarkable reaction since, to our knowledge, no other
phosphinidene complex has ever been reported to add hydro-
gen. Actually, even free phosphines and related P-donor
molecules fail to react with hydrogen under ordinary condi-
tions. In this context we note that the first example of the
oxidative addition of the relatively unreactive H-Si bond of
silanes to a phosphinidene complex has been reported only
2
2
1
5
P(O)R*}(μ-CO)(CO) ] (5B), thus resembling the behavior
2
5
of the related PPh and PCy complexes. However, this
product slowly rearranges at room temperature to reach an
equilibrium with its isomer [Fe Cp (μ-CO) (CO){P(O)R*}]
2
2
2
(
5T), the latter having a terminally bound oxophosphinidene
1
6
ligand. Compound 5T is the major species in all solvents
examined, and in turn it exists in solution as a mixture of the
corresponding trans and cis isomers, as found for com-
pounds 1 and 4 (see the Supporting Information). An
2
1
very recently. Further work is currently under progress to
get a more precise picture of the remarkable hydrogenation
of compound 3 and its potential relation with the steric
demands of the PR* group.
1
7
X-ray study confirmed the structure of trans-5T (Figure 2).
In comparison to the geometrical parameters of the oxopho-
In summary, we have shown that the steric pressure intro-
t
sphinidene-bridged complex [Fe Cp {μ-P(O)Cy}(μ-CO)-
duced by the 2,4,6-C H Bu group in the complexes [Fe -
6
2
2
2
3
2
(
CO) ], we note that the terminal ligand in 5T exhibits a
Cp (μ-PR)(μ-CO)(CO) ] having bent phosphinidene bridges
2 2
2
has pronounced effects concerning its synthesis (stabilization
of radical intermediates toward dehydrogenation), structure
(
14) Amor, I.; Garcı
Jeffery, J. C. Organometallics 2006, 25, 4857.
15) Preparation of compound 5: a dichloromethane solution (10 mL)
´
a, M. E.; Ruiz, M. A.; S ꢀa ez, D.; Hamidov, H.;
(
(18) (a) Cotton, F. A.; Frenz, B. A.; White, A. J. Inorg. Chem. 1974,
13, 1407. (b) Klasen, C.; Lorenz, I. P.; Schmid, S.; Beuter, G. J. Organomet.
Chem. 1992, 428, 363. (c) Alvarez, C. M.; Gal ꢀa n, B.; García, M. E.; Riera, V.;
Ruiz, M. A.; Vaissermann, J. Organometallics 2003, 22, 5504.
(19) (a) Niecke, E.; Engelmann, M.; Zorn, H.; Krebs, B.; Henkel, G.
Angew. Chem., Int. Ed. Engl. 1980, 19, 710. (b) Hitchcock, P. B.; Johnson, J.
A.; Lemos, M. A. N. D. A.; Meidine, M. F.; Nixon, J. F.; Pombeiro, A. J. L.
J. Chem. Soc., Chem. Commun. 1992, 645.
of compound 3 (0.100 g, 0.188 mmol) was stirred in contact with air at
room temperature for 1.5 h to give a brown solution yielding compound
5
(0.063 g, 61%) as a mixture of three isomers. Selected spectroscopic
) 1997 (vs), 1965 (w), 1774 (m) cm
-
1 31 1
;
data for 5B: ν(CO) (CH
NMR (CD
ppm.
2
Cl
2
P{ H}
1
2 2 2 2
Cl ) δ 312.0 ppm; H NMR (CD Cl ) δ 4.93 (s, 10H, Cp)
(
16) Selected spectroscopic data for trans-5T: ν(CO) (CH
2
Cl
2
) 1964
-1
31
1
P{ H} NMR (CD
(m), 1802 (w), 1769 (vs) cm
ppm; H NMR (CD
17) X-ray data for trans-5T: red crystals, monoclinic (P2
˚ ˚ ˚
0.8126(8) A, b = 13.0255(11) A, c = 20.5208(17) A, β = 91.402(4) ,
3
;
2
Cl
2
, 233 K) δ 432.5
(20) (a) Alonso, M.; Garcıa, M. E.; Ruiz, M. A.; Hamidov, H.;
´
1
2
Cl
2
, 233 K) δ 5.01, 4.20 (2s, 2 Â 5H, Cp) ppm.
Jeffery, J. C. J. Am. Chem. Soc. 2004, 126, 13610. (b) Alonso, M.; Alvarez,
M. A.; García, M. E.; Ruiz, M. A.; Hamidov, H.; Jeffery, J. C. J. Am. Chem.
Soc. 2005, 127, 15012.
(21) Vaheesar, K.; Bolton, T. M.; East, A. L. L.; Sterenberger, B. T.
Organometallics 2010, 29, 484.
(
1
/c), a =
o
1
˚
V = 2889.3(4) A , T = 100 K, Z = 4, R = 0.0805 (observed data with
I > 2σ(I)), GOF = 1.039.

1
878 Organometallics, Vol. 29, No. 8, 2010
Alvarez et al.
(
geometrical distortions and changes in the coordina-
Acknowledgment. We thank the DGI of Spain (Project
CTQ2006-01207) and the COST action CM0802 ‘‘PhoS-
ciNet’’ for supporting this work and the MEC of Spain
for a grant (to R.G.)
tion mode of ligands), thermal stability (intramolecular
C-H bond activation), and general reactivity (hydrogena-
tion, oxygenation). Further studies on the chemical behavior
of compound 3 are now in progress to examine in detail
the effects of steric pressure on the wide reactivity of this
sort of phosphinidene complexes having bent phosphi-
nidene bridges, with special emphasis on their intriguing
ability for the activation of rather inert (H-H, H-C) single
bonds.
Supporting Information Available: Text giving experimental
procedures and spectroscopic data for new compounds and CIF
files giving crystallographic data for compounds 3 and 5T. This
material is available free of charge via the Internet at http://
pubs.acs.org.