Reactions of alkynes with [Fe2(CO)6(μ-PPh2){μ-η 1:η2α,β=(H)C α=Cβ=CγH2}]: Formation of diphenylvinylphosphine-functionalized vinyl carbenes via carbon-carbon and carbon-phosphorus bond formation and hydrogen migration

Article abstract of DOI:10.1021/om0005147

Reaction of [Fe₂(CO)₆(μ-PPh₂){μ-η ¹:η²_α,β-(H)C _α=C_β=C_γH₂}] (1) with PhC=CPh results in allenyl-alkyne-phosphido coupling to give [Fe₂(CO)₆(μ-PPh₂){μ-η ¹(P):η³(C):η ¹(C)-C(Ph)C-(Ph)C(H)C(=CH₂)PPh₂}] (2), bridged by a diphenylvinylphosphine-substituted vinyl carbene. Under similar conditions 1 reacts with PhC=CMe to give an equal mixture of the two possible regioisomers

Full text of DOI:10.1021/om0005147

Organometallics 2000, 19, 4557-4562
4557
Rea ction s of Alk yn es w ith
[F e2(CO)6(µ-P P h 2){µ-η1:η2r,â-(H)CrdCâdCγH2}]: F or m a tion
of Dip h en ylvin ylp h osp h in e-F u n ction a lized Vin yl
Ca r ben es via Ca r bon -Ca r bon a n d Ca r bon -P h osp h or u s
Bon d F or m a tion a n d Hyd r ogen Migr a tion
Simon Doherty,*,†,‡ Graeme Hogarth,§ Mark Waugh,‡ William Clegg,‡ and
Mark R. J . Elsegood‡
Department of Chemistry, Bedson Building, The University of Newcastle upon Tyne,
Newcastle upon Tyne, NE1 7RU, U.K., and Department of Chemistry, University College
London, 20 Gordon Street, London WC1H 0AJ , U.K.
Received J une 19, 2000
Reaction of [Fe2(CO)6(µ-PPh2){µ-η1:η2R,â-(H)CRdCâdCγH2}] (1) with PhCtCPh results in
allenyl-alkyne-phosphido coupling to give [Fe2(CO)6(µ-PPh2){µ-η1(P):η3(C):η1(C)-C(Ph)C-
(Ph)C(H)C(dCH2)PPh2}] (2), bridged by a diphenylvinylphosphine-substituted vinyl carbene.
Under similar conditions 1 reacts with PhCtCMe to give an equal mixture of the two possible
regioisomers, [Fe2(CO)6(µ-PPh2){µ-η1(P):η3(C):η1(C)-C(Ph)C(Me)C(H)C(dCH2)PPh2}] (3a ) and
[Fe2(CO)6(µ-PPh2){µ-η1(P):η3(C):η1(C)-C(Me)C(Ph)C(H)C(dCH2)PPh2}] (3b ). In contrast, 1
reacts with 2 equiv of PhCtCH to give the vinyl carbene bridged [Fe2(CO)6(µ-PPh2){µ-η1-
(P):η3(C):η1(C)-(Ph)CCC(H)MeCHdCPhC(PPh2)}] (4), which results from a complex sequence
of carbon-carbon and carbon-phosphorus bond formation and hydrogen migration steps.
In tr od u ction
functionalization. A survey of the literature reveals only
two examples of alkyne-allenyl coupling. The first, a
comparative study by Carty, examined the reactivity of
σ-η-allenyl and σ-η-acetylide complexes of group 8
with internal alkynes, and in both cases unusual η5-
cyclopentadienyl complexes formed via alkyne-allenyl
and alkyne-acetylide coupling, respectively.4 In the
second, reaction of the trinuclear allenyl cluster [Ru3-
(CO)8(µ-PPh2){µ3-η2-C(Pri)CdCH2}] with alkynes results
in allenyl-alkyne coupling to give a “wrap-around” five-
carbon penta-1,4-dien-2,3,5,-triyl hydrocarbon.5
We have recently undertaken a detailed study of
the reactivity of [Fe2(CO)6(µ-PPh2){µ-η1:η2R,â-(H)CRd
CâdCγH2}] and reported a number of diverse and
interesting transformations including the synthesis of
diiron-coordinated R,â-unsaturated carbonyl compounds
via nucleophile-carbonyl-allenyl coupling with alkyl-
lithium reagents,6 amines,7 and alcohols;8 dealkylation
of trialkyl phosphites to give a R,â-unsaturated phos-
phonates;9 the first examples of nucleophilic addition
to the R-carbon atoms of a σ-η-coordinated allenyl;10
and a host of unusual transformations involving phos-
The reactivity of homobinuclear σ-η-coordinated al-
lenyl/propargyl complexes is dominated by the electro-
philic character of the C3 ligand, and examples of
addition of protic and nonprotic nucleophiles to CR, Câ,
and Cγ are well documented.1 However, several recent
articles have reported nucleophilic reactivity for bi-
nuclear allenyl complexes,2,3 which include addition of
p-toluenesulfonyl isocyanate to Cγ to give modified σ,η-
allenyl derivatives,2a formation of a [3+2] cycloaddition
adduct,2a and protonation at Câ to afford a binuclear
µ-vinylcarbene.3 In contrast, the reactivity of alkynes
with bi- and multinuclear allenyl complexes is less well
developed, somewhat surprising considering that the
product of alkyne-allenyl coupling would be highly
unsaturated and potentially reactive toward further
This paper is dedicated to Professor Arthur J . Carty on the
occasion of his 60th birthday.
† E-mail: simon.doherty@newcastle.ac.uk.
‡ University of Newcastle upon Tyne.
§ University College London.
(1) For selected reviews see: (a) Wojcicki, A. New J . Chem. 1994,
18, 61. (b) Doherty, S.; Corrigan, J . F.; Carty, A. J .; Sappa, E. Adv.
Organomet. Chem. 1995, 37, 39. (c) Chen, J .-Y. Coord. Chem. Rev. 1999,
192, 1168. For examples see: (d) Breckenridge, S. M.; Taylor, N. J .;
Carty, A. J . Organometallics 1991, 10, 837. (e) Breckenridge, S. M.;
Carty, A. J .; Pellinghelli, M. A.; Tiripicchio, A.; Sappa, E. J . Organomet.
Chem. 1994, 471, 211. (f) Meyer, A.; McCabe, D. J .; Curtis, M. D.
Organometallics 1987, 6, 1491. (g) McLain, M. D.; Hay, M. S.; Curtis,
M. D.; Kampf, J . W. Organometallics 1994, 13, 4377. (h) Amouri, H.;
Besace, Y.; Vaissermann, J .; Ricard, L. Organometallics 1997, 16, 2160.
(i) Henrick, K.; McPArtlin, M.; Deeming, A. J .; Hasso, S.; Manning, P.
J . Chem. Soc., Dalton Trans. 1982, 899.
(2) (a) Calligaris, W. R. R.; Faleschini, P.; Gallucci, J . C.; Wojcicki,
A. J . Organomet. Chem. 2000, 594, 465. (b) Willis, R. R.; Calligaris,
M.; Faleschini, P.; Wojcicki, A. J . Cluster Sci. 2000, 11, 233.
(3) Ogoshi, S.; Tsutsumi, K.; Ooi, M.; Kurosawa, J . J . Am. Chem.
Soc. 1995, 117, 10415.
(4) (a) Blenkiron, P.; Breckenridge, S. M.; Taylor, N. J .; Carty, A.
J .; Pellinghelli, Tiripicchio, A.; Sappa, E. J . Organomet. Chem. 1996,
506, 229. (b) Randall, S. M.; Taylor, N. J .; Carty, A. J .; Ben Haddah,
T.; Dixneuf, P. H. J . Chem. Soc., Chem. Commun. 1988, 870.
(5) Nucciarone, D.; Taylor, N. J .; Carty, A. J . Organometallics 1988,
7, 127.
(6) Doherty, S.; Elsegood, M. R. J .; Clegg, W.; Rees, N. H.; Scanlan,
T. S.; Waugh, M. Organometallics 1997, 16, 3221.
(7) Doherty, S.; Elsegood, M. R. J .; Clegg, W.; Waugh, M. Organo-
metallics 1996, 15, 2688.
(8) Doherty, S.; Elsegood, M. R. J .; Clegg, W.; Mampe, D. Organo-
metallics 1997, 16, 1186.
(9) Doherty, S.; Elsegood, M. R. J .; Clegg, W.; Ward, M. F. W.;
Waugh, M. Organometallics 1997, 16, 4251.
10.1021/om0005147 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/23/2000

4558 Organometallics, Vol. 19, No. 22, 2000
Doherty et al.
phorus- and nitrogen-based nucleophiles.11 In a continu-
ation of these studies we have now extended the range
of nucleophiles to include alkynes and herein report that
1 reacts with alkynes to give vinyl-carbene-bridged
products via carbon-carbon and carbon-phosphorus
coupling.
Resu lts a n d Discu ssion
Thermolysis of a solution [Fe2(CO)6(µ-PPh2){µ-η1:η2
-
R,â
(H)CRdCâdCγH2}] (1) with an excess of diphenylacetyl-
ene in toluene at 90 °C for 6 h results in the formation
of [Fe2(CO)6(µ-PPh2){µ-η1(P):η3(C):η1(C)-C(Ph)C(Ph)C-
(H)C(dCH2)PPh2}] (2) as the major product (eq 1). The
reaction of 1 with unsymmetrical alkynes offers the
possibility of regioselective insertion in the carbon-
carbon coupling step as there are two possible regio-
isomers. Under conditions similar to those used to
prepare 2, PhCtCMe reacts with 1 to generate a
mixture of two compounds, identified by 1H and 31P
NMR spectroscopy as the two possible regioisomers
[Fe2(CO)6(µ-PPh2){µ-η1(P):η3(C):η1(C)-C(Ph)C(Me)C(H)C-
(dCH2)PPh2}] (3a ) and [Fe2(CO)6(µ-PPh2){µ-η1(P):η3-
(C):η1(C)-C(Me)C(Ph)C(H)C(dCH2)PPh2}] (3b) in a 1:1
ratio. Attempts to separate 3a and 3b by column chro-
matography proved unsuccessful, although fractional
crystallization from a hexamethyldisiloxane solution
yielded orange crystals of a single regioisomer, 3a .
F igu r e 1. Molecular structure of [Fe2(CO)6(µ-PPh2){µ-η1-
(P):η3(C):η1(C)-C(Ph)C(Ph)C(H)C(dCH2)PPh2}] (2). Phenyl
hydrogen atoms have been omitted. Carbonyl carbons have
the same numbers as oxygen atoms. Ellipsoids are at the
50% probability level.
Me).15 The central carbon atom of the C3-bridge appears
as a doublet at δ 110.8 (3J PC ) 15.6 Hz) and the terminal
vinylic carbon as a doublet at δ 65.3 (2J PC ) 21.7 Hz).
The remaining two carbons of the C5-hydrocarbon,
namely, those of the diphenylvinylphosphine unit, ap-
pear as a doublet and singlet at δ 174.5 (1J PC ) 25.8
Hz) and 118.3, respectively. This value of 1J PC is similar
to that reported by Knox and co-workers for closely
related complexes of σ-vinyl phosphines generated dur-
ing the thermal and photochemical cleavage of the 1,1-
bis(diphenylphosphino)ethene ligand in [Fe2(CO)6(µ-
CO){µ-(Ph2P)2CdCH2}].16 The 1H and 13C{1H} NMR
spectra of 3a and 3b are strikingly similar to those of 2
and strongly support our formulation. The 31P{1H} NMR
spectrum of 3a ,b showed an approximately equal mix-
ture of isomers and confirms the complete lack of
selectivity in the alkyne insertion step.
To establish precise details of the connectivity and,
in the case of 3a ,b to assign the spectroscopic data to
their respective regioisomers, single-crystal X-ray analy-
ses of 2 and 3a were undertaken, the results of which
are illustrated in Figures 1 and 2, respectively. A
selection of bond lengths and angles for both compounds
is listed in Table 1. The most striking feature of 2 is
the newly formed hydrocarbyl bridge, which can most
aptly be considered as a σ-η2-diphenylvinylphosphine-
substituted vinyl carbene. The two iron atoms are
separated by 2.6772(4) Å and bridged by a three-carbon
hydrocarbon, σ-bonded to Fe(2) [Fe(2)-C(1) ) 2.033(2)
Å], and η3-bonded to Fe(1) [Fe(1)-C(1) ) 2.072(2) Å,
Fe(1)-C(2) ) 2.088(2) Å, Fe(1)-C(3) ) 2.113(2) Å].
Similar three-carbon bridging fragments have been
The 31P{1H} NMR spectrum of 2 contains a singlet
at δ 45.8, shifted to high-field compared to that of 1 and
consistent with a transformation involving coupling of
the phosphido bridge with a hydrocarbyl fragment. The
1H NMR spectrum contains doublets at δ 5.97 (3J PH
)
28.8 Hz) and 4.96 (3J PH ) 13.4 Hz), which correspond
to the vinylic protons, and another at δ 4.39 (3J PH
)
25.3 Hz), associated with the proton attached to the
terminal carbon atom of the bridging vinyl carbene. In
the 13C{1H} NMR spectrum a low-field signal at δ 154.3
corresponds to the bridging alkylidene carbon and
appears in the same region as that previously reported
for related vinyl carbene complexes including [Fe2(CO)4-
(µ-dppm){µ-η1:η3-HCC(Me)dC(Me)PPh2}],12 [Fe2(CO)(µ-
CO)Cp2{µ-η1:η3-(E)-CHC(Me)dCHMe}],13 [Fe2(CO)(µ-
CO)Cp2{µ-η1:η3-(E)-C(CO2Me)C(CO2Me)dCHMe}],14 and
[Ru2(CO)(µ-CO)Cp2{µ-η1:η3-CHC(R)dCH2}] (R ) H,
(10) (a) Doherty, S.; Elsegood, M. R. J .; Clegg, W.; Mampe, D.
Organometallics 1996, 15, 5302. (b) Doherty, S.; Hogarth, G.;
Waugh, M.; Scanlan, T. H.; Clegg, W.; Elsegood, M. R. J . Organo-
metallics 1999, 18, 3178. (c) Doherty, S.; Elsegood, M. R. J .; Clegg,
W.; Scanlan, T. H.; Rees, N. H. Chem. Commun. 1996, 1545.
(11) (a) Doherty, S.; Waugh, M.; Scanlan, T. H.; Elsegood, M. R. J .;
Clegg, W. Organometallics 1999, 18, 679. (b) Doherty, S.; Hogarth, G.;
Elsegood, M. R. J .; Clegg, W.; Rees, N. H.; Waugh, M. Organometallics
1998, 17, 3331.
(13) (a) Casey, C. P.; Woo, K. L.; Fagan, P. J .; Palermo, R. E.; Adams,
B. R. Organometallics 1987, 6, 447. (b) Casey. C. P.; Meszaros, M. W.;
Fagan, P. J .; Bly, R. K.; Marder, S. R.; Austin, E. A. J . Am. Chem.
Soc. 1986, 108, 4043.
(14) Dyke, A. F.; Knox, S. A. R.; Naish, P. J .; Taylor, G. E. J . Chem.
Soc., Chem. Commun. 1980, 203.
(15) Elsenstadt, A.; Efraty, A. Organometallics 1982, 1, 1101.
(16) Grist, N. J .; Hogarth, G.; Knox, S. A. R.; Lloyd, B. R.; Morton,
D. A. V.; Orpen, A. G. J . Chem. Soc., Chem. Commun. 1988, 673.
(12) Hogarth, G.; Shukri, K.; Doherty, S.; Carty, A. J .; Enright, G.
D. Inorg. Chim. Acta 1999, 291, 178.

Formation of Phosphine-Functionalized Vinyl Carbenes
Organometallics, Vol. 19, No. 22, 2000 4559
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles (d eg) for 2, 3a , a n d 4
3a a
2
4
Fe(1)-Fe(2)
Fe(1)-C(2)
Fe(1)-C(1)
Fe(1)-C(3)
Fe(2)-C(1)
Fe(2)-P(1)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(4)-P(1)
2.6772(4)
2.088(2)
2.072(2)
2.113(2)
2.033(2)
2.2640(6)
1.419(3)
1.441(3)
1.469(3)
1.334(3)
1.806(2)
Fe(1)-Fe(2)
Fe(1)-C(3)
Fe(1)-C(4)
Fe(1)-C(6)
Fe(2)-C(6)
Fe(2)-P(1)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(4)-C(6)
C(2)-P(1)
2.6668(3)
2.1128(18)
2.0917(17)
2.0804(16)
2.0308(16)
2.2578(5)
1.336(2)
1.462(2)
1.442(2)
1.515(2)
1.415(2)
Fe(1)-Fe(2)
Fe(1)-C(7)
Fe(1)-C(11)
Fe(1)-C(12)
Fe(2)-C(12)
Fe(2)-P(1)
C(7)-C(11)
C(11)-C(12)
C(7)-C(8)
2.6182(6)
2.166(3)
2.082(3)
2.070(3)
2.041(3)
2.2433(8)
1.432(4)
1.407(4)
1.494(4)
1.342(4)
1.495(4)
1.516(4)
C(8)-C(9)
C(9)-C(10)
C(10)-C(11)
1.8095(17)
Fe(1)-Fe(2)-P(1)
Fe(1)-C(1)-Fe(2)
Fe(1)-Fe(2)-C(1)
Fe(2)-Fe(1)-C(1)
Fe(2)-C(1)-C(2)
Fe(1)-C(1)-C(2)
C(1)-C(2)-C(3)
C(3)-C(4)-C(5)
P(1)-C(4)-C(5)
92.386(18)
81.41(8)
49.94(6)
Fe(1)-Fe(2)-P(1)
Fe(1)-C(6)-Fe(2)
Fe(1)-Fe(2)-C(6)
Fe(2)-Fe(1)-C(6)
Fe(2)-C(6)-C(4)
Fe(1)-C(6)-C(4)
C(6)-C(4)-C(3)
C(6)-C(4)-C(5)
C(4)-C(3)-C(2)
C(3)-C(2)-C(1)
C(3)-C(2)-P(1)
C(1)-C(2)-P(1)
C(2)-P(1)-Fe(2)
91.278(14)
80.87(6)
50.37(5)
48.75(4)
126.61(12)
70.60(9)
119.36(14)
122.47(15)
125.83(15)
122.77(16)
114.31(12)
122.91(14)
107.74(6)
Fe(1)-Fe(2)-P(1)
Fe(1)-C(12)-Fe(2)
Fe(1)-Fe(2)-C(12)
Fe(2)-Fe(1)-C(12)
Fe(2)-C(12)-C(11)
Fe(1)-C(12)-C(11)
C(12)-C(11)-C(7)
C(12)-C(11)-C(10)
C(11)-C(7)-C(8)
C(7)-C(8)-C(9)
75.71(2)
79.12(10)
50.93(7)
49.95(8)
115.9(2)
70.67(15)
118.1(2)
132.4(3)
106.9(2)
108.3(3)
113.5(3)
101.7(2)
48.65(6)
125.86(15)
70.67(12)
118.74(19)
122.4(2)
124.34(17)
C(8)-C(9)-C(10)
C(9)-C(10)-C(11)
a
Data for one of two similar molecules in the asymmetric unit.
The similarity in the carbon-carbon bond lengths C(1)-
C(2) [1.419(3) Å] and C(2)-C(3) [1.441(3) Å] and the
difference in Fe-C bond lengths to C(1) (∆Fe-C ) 0.039
Å) favor the σ-η3-allylic structure. The terminal carbon
atom of the bridging C3-fragmant is substituted with a
diphenylvinylphosphine group which coordinates to
Fe(2) via the phosphorus atom [Fe(2)-P(1) ) 2.2640(6)
Å]. The C(4)-C(5) bond length of the pendent vinylic
substituent [1.334(3) Å] is similar to those previously
reported for [Os3(CO)11(Ph2PCHdCH2)] and [Ru3(µ-H)-
(CO)8(Ph2PCHdCH2)(µ3-Ph2PCHdCH2)]17 and close to
that expected for an uncoordinated C-C double bond.
Knox and co-workers have reported that ethyne inserts
into the M-C bond of the alkylidene carbon in [M2(CO)2-
(µ-CO)Cp2(µ-CHMe)] (M ) Fe, Ru) to give the vinyl
carbene derivative [M2(CO)(µ-CO)Cp2{µ-η1:η3-C(H)C-
(H)dCHMe}].14 For M ) Fe, the bridging carbon is
equidistant from both metal centers and the vinyl
fragment is asymmetrically bonded to one metal atom.
In the case of M ) Ru, a second insertion gave [Ru2-
(CO)(µ-CO)Cp2{µ-C(H)C(H)dC(H)C(H)dCHMe}], which
is bridged by a vinyl carbene containing a pendent
vinylic unit similar to that in 2.18 The solid-state
structure of 3a , shown in Figure 2, is qualitatively
similar to that of 2 in that it contains a diphenyl-
vinylphosphine-substituted vinylcarbene, σ-bonded to
Fe(2) [Fe(2)-C(6) ) 2.0308(16) Å], and η3-bonded
to Fe(1) [Fe(1)-C(6) ) 2.0804(16) Å, Fe(1)-C(4) )
2.0917(17) Å, Fe(1)-C(3) ) 2.1128(18) Å]. The remain-
ing structural features associated with the metal atom
framework and supporting ligands are similar to those
of 2 and will not be discussed further.
F igu r e 2. Molecular structure of [Fe2(CO)6(µ-PPh2){µ-η1-
(P):η3(C):η1(C)-C(Ph)C(Me)C(H)C(dCH2)PPh2}] (3a ). Phen-
yl hydrogen atoms have been omitted. Carbonyl carbons
have the same numbers as oxygen atoms. Ellipsoids are
at the 50% probability level.
generated from the insertion of an alkyne into an M-C
bond of a bridging alkylidene, and in each case struc-
tural features have suggested contributions from three
possible resonance forms: a µ-η2-vinyl carbene I, a σ-η3-
coordinated 1-metallallyl II, and a dimetallacyclopen-
tene III in which the ethylenic bond is η2-bound to Fe(2).
The overall transformation of 1 into 2 most likely
involves initial phosphorus-carbon bond formation via
an intramolecular 1,3-migration of the phosphido bridge
(17) Gobetto, R.; Sappa, E.; Tiripicchio, A.; Tiripicchio Camellini,
M.; Mays, M. J . J . Chem. Soc., Dalton Trans. 1989, 807.
(18) Adams, P. Q.; Davies, D. L.; Dyke, A. F.; Knox, S. A. R.; Mead,
K. A.; Woodward, P. J . Chem. Soc., Chem. Commun. 1983, 222.

4560 Organometallics, Vol. 19, No. 22, 2000
Doherty et al.
Sch em e 1
to Câ of the σ-η-coordinated allenyl fragment, to give a
coordinatively unsaturated alkylidene-bridged interme-
diate such as IV, followed by 1,2-insertion of the
coordinated alkyne into the Fe-CR bond of the bridging
alkylidene, V, to generate 2 (Scheme 1). However, we
cannot exclude an alternative pathway involving initial
1,2-migratory insertion of the alkyne into the Fe-CR
bond of the bridging allenyl, to give VI, prior to the
phosphorus-carbon coupling step. However, we favor
the former mechanism since there are a number of
reports of 1,3-migration of bridging phosphido groups
to coordinated hydrocarbyl ligands. Such insertions are
relatively common place and may well occur via a
transient terminal phosphido group that results from
M-P bond cleavage.19 For instance, addition of PPh2Cl
to [Mo2(CO)4(µ-R1CtCR2)Cp2] results in P-Cl bond
cleavage to give [Mo2(CO)2(µ-Cl){µ-C(R1)C(R2)PPh2}-
Cp2], which presumably involves coupling of the result-
ing phosphido group with the alkyne.20 Moreover, the
vacant site for alkyne coordination is generated as a
natural consequence of 1,3-phosphido migration in the
former pathway, whereas it is not clear how alkyne
coordination and migratory insertion would be facili-
tated in the latter pathway.
31P{1H} NMR spectrum again suggests phosphido-
hydrocarbyl coupling, while the 1H NMR spectrum
contains a doublet at 6.04 (1H, 3J HH ) 2.5 Hz), a quartet
3
of doublets at 3.91 (1H, J HH ) 2.5 Hz), and a doublet
3
at δ 0.72 (3H, J HH ) 7.1 Hz). It is clear from this
pattern of resonances that formation of 4 involves (i)
incorporation of two PhCtCH fragments, (ii) migration
of both acetylenic protons to the allenyl fragment, and
(iii) phosphorus-carbon bond formation. The uncer-
tainty in the exact nature of this transformation
prompted a single-crystal X-ray analysis using syn-
chrotron radiation, due to the small size of the crystals.
A perspective view of the molecular structure is shown
in Figure 3, and selected bond lengths and angles
are listed in Table 1. The molecular structure identi-
fies 4 as [Fe2(CO)6(µ-PPh2){µ-η1(P):η3(C):η1(C)-(Ph)C-
The use of terminal alkynes offers alternative reaction
pathways including carbon-hydrogen activation and
hydrogen migration with the possibility of generating
more elaborate products. With this in mind, the reaction
of 1 toward phenyl ethyne was investigated to establish
whether the coupling sequence described above could
be extended to include terminal alkynes. Thermolysis
of a toluene solution of 1 and excess PhCtCH at 90 °C
resulted in a darkening of the solution and disappear-
ance of 1 to give low yields of 4 as the only isolable
product (eq 2). It is clear from the pattern of CO
absorptions in the IR spectrum that 4 is not the
PhCtCH analogue of 2. A singlet at δ 58.0 in the
CC(H)MeCHdCPhC(PPh2)}]. The bridging hydrocarbyl
fragment in 4 bears a close similarity to those in 2 and
3a in that it can be considered as an asymmetrically
bridging substituted alkylidene [Fe(2)-C(12) ) 2.041(3)
Å, Fe(1)-C(12) ) 2.070(3) Å]. The vinylic substituent
C(7)-C(11) [1.432(4) Å] attached to C(12) coordinates
to Fe(1) [Fe(1)-C(11) ) 2.082(3) Å, Fe(1)-C(7) )
2.166(3) Å] and forms part of a 2-diphenylphosphino-
5-methylcyclopentadiene ring and shows the expected
elongation upon coordination to a metal center. The
remaining carbon-carbon bond lengths in the cyclo-
pentadiene ring show that the uncoordinated double
bond C(8)-C(9) [1.342(4) Å] is localized21 and that C(7)-
C(8), C(9)-C(10), and C(10)-C(11) are all single bonds
[1.494(4), 1.495(4), 1.516(4) Å, respectively] and similar
to those found in other η2-cyclopentadiene complexes,22
as is the planarity of the cyclopentadiene ring (maxi-
(19) (a) Regragui, R.; Dixneuf, P. H.; Taylor, N. J .; Carty, A. J .
Organometallics 1984, 3, 814. (b) Regragui, R.; Dixneuf, P. H.; Taylor,
N. J .; Carty, A. J . Organometallics 1990, 9, 2234. (c) Edwards, A. J .;
Martin, A.; Mays, A. J .; Nazar, D.; Raithby, P. R.; Solan, G. A. J . Chem.
Soc., Dalton Trans. 1993, 355.
(20) Conole, G.; Hill, K. A.; McPartlin, M.; Mays, M. J .; Morris, M.
J . J . Chem. Soc., Chem. Commun. 1989, 688. Caffyn, A. J . M.; Mays,
M. J .; Solan, G. A.; Conole, G.; Tiripicchio, A. J . Chem. Soc., Dalton
Trans. 1993, 2345.
(21) Bennett, M. J .; Cotton, F. A.; Davison, A.; Faller, J . W.; Lippard,
S. J .; Moorehouse, S. M. J . Am. Chem. Soc. 1966, 88, 4371.

Formation of Phosphine-Functionalized Vinyl Carbenes
Organometallics, Vol. 19, No. 22, 2000 4561
by using standard Schlenk line techniques. Diethyl ether and
hexane were distilled from Na/K alloy, tetrahydrofuran was
distilled from potassium, and dichloromethane was distilled
from CaH2. CDCl3 was predried with CaH2, vacuum trans-
ferred, and stored over 4 Å molecular sieves. Reactions were
monitored by thin-layer chromatography (Baker flex silica gel,
1B-F). Column chromatography was carried out with alumina
purchased from Aldrich Chemical Co. and deactivated with
6% w/w water prior to loading. Alkynes were purchased from
Aldrich Chemical Co. and used without further purification.
The diiron complex [Fe2(CO)6(µ-PPh2){µ-η1:η2-(H)CdCdCH2}]
(1) was prepared as previously described.6
P r ep a r a tion of [F e2(CO)6(µ-P P h 2){µ-η1(P ):η3(C):η1(C)-
C(P h )C(P h )C(H)C(dCH2)P P h 2}] (2). [Fe2(CO)6(µ-PPh2){µ-
η1:η2R,â-(H)CdCdCH2}] (1) (0.20 g, 0.4 mmol) and diphenyl
ethyne (0.71 g, 4.0 mmol) were dissolved in toluene (20 mL),
and the solution was heated to 90 °C for 6 h, after which time
the toluene was removed in vacuo. The resulting oily residue
was extracted into dichloromethane (2-3 mL) and the solution
absorbed onto deactivated alumina, desolvated, placed on a
300 × 30 mm column, and eluted with n-hexane/dichloro-
methane (90:10 v/v) to give orange-red 2 in 40% yield (0.11 g).
Crystallization from n-hexane gave X-ray quality crystals. IR
(ν(CO), cm-1, C6H14): 2054 m, 2011 s, 1992 m, 1977 w, 1959
F igu r e 3. Molecular structure of bridged [Fe2(CO)6(µ-
P P h 2){µ-η1(P ):η3(C):η1(C)-(P h )CCC(H )MeCH dCP h C-
(PPh2)}] (4). Phenyl hydrogen atoms have been omitted.
Carbonyl carbons have the same numbers as oxygen atoms.
Ellipsoids are at the 50% probability level.
1
w. 31P{1H} (202.35 MHz, CDCl3, δ): 45.8 (s, PPh2). H NMR
(500.1 MHz, CDCl3, δ): 7.75-6.66 (m, 10H, C6H5), 5.97 (d, 3J PH
) 28.8 Hz, 1H, trans-Ph2PCdCH{H}), 4.96 (d, 3J PH ) 13.4 Hz,
mum deviation from the best least-squares plane of
0.010 Å). The bridging hydrocarbon in 4 could alterna-
tively be described as a η2-coordinated cyclopentadiene,
tethered to the binuclear metal center through diphen-
ylphosphine and alkylidene substituents. The 2-diphen-
ylphosphine substituent coordinates to a single metal
center [Fe(2)-P(1) ) 2.2433(8) Å] to form a four-
membered dimetallaphosphacycle containing Fe(1),
Fe(2), P(1), and C(7). In contrast, coordination of the
diphenylphosphine group in 2 and 3 forms a five-
membered metalacycle. The allenyl fragment of 1
provides two of the cyclopentadiene ring carbons and
the 5-methyl substituent, while the two molecules of
phenyl ethyne provide the remaining three carbons of
the ring and the bridging alkylidene carbon atom via
tail-to-tail coupling. A related alkylidene-bridged com-
plex, [Fe2(CO)4(µ-dppm){µ-η1:η3-HCC(Me)dC(Me)PPh2}],
is the major product of the reaction between [Fe2(CO)6-
(µ-PPh2){µ-(H2CdCMe)CdCH2}] and dppm.12
In summary, the reaction of alkynes with [Fe2(CO)6-
(µ-PPh2){µ-η1:η2-(H)CdCdCH2}] (1) results in carbon-
carbon and carbon-phosphorus bond formation to give
a range of vinyl carbene bridged complexes. Diphenyl
acetylene and 1-phenyl propyne react in a similar
manner, although insertion of the latter lacks regiose-
lectivity and gives an equal mixture of the two possible
regioisomers. In contrast, phenyl acetylene reacts via
multiple insertions coupled with hydrogen transfer to
give an unusual diphenylphosphine-alkylidene-substi-
tuted cyclopentadiene. These studies suggest that it
should be possible to prepare a more elaborate range of
hydrocarbons simply by extending these coupling reac-
tions to include diynes, enynes, ynenitriles, yneones, and
variously functionalized alkynes.
3
1H, cis-Ph2PCdCH{H}), 4.39 (d, J PH ) 25.3 Hz, 1H, CHCd
CH{H}). 13C{1H} NMR (125.65 MHz, CDCl3, δ): 213.1 (br, CO),
174.5 (d, 1J PC ) 25.8 Hz, PhCC{Ph}HCPh2PCdCH2), 154.3 (s,
1
PhCC{Ph}HCPPh2CdCH2), 144.8 (d, J PC ) 25.8 Hz, C6H5),
133.1-124.3 (m, C6H5), 118.3 (s, PhCC{Ph}HCPPh2CdCH2),
2
110.8 (d, J PC ) 15.6 Hz, PhCC{Ph}HCPPh2CdCH2), 65.3 (d,
2J PC ) 21.7 Hz, PhCC{Ph}HCPPh2CdCH2). Anal. Calcd for
C
35H23Fe2O6P: C, 61.62; H, 3.40. Found: C; 61.59; H, 3.24.
[Fe2(CO)6(µ-P P h 2){µ-η1(P ):η3(C):η1(C)-C(P h )C(Me)C(H)C-
(dCH2)P P h 2}] (3a ) a n d [F e2(CO)6(µ-P P h 2){µ-η1(P ):η3-
(C):η1(C)-C(Me)C(P h )C(H)C(dCH2)P P h 2}] (3b). A toluene
solution of [Fe2(CO)6(µ-PPh2){µ-η1:η2-(H)CdCdCH2}] (1) (0.20
g, 0.4 mmol) and 3-phenylpropyne (0.5 mL, 4.0 mmol) was
heated to 90 °C. After 8 h all the starting material had been
consumed and the toluene was removed in vacuo to leave a
dark oily residue. This residue was dissolved in a minimum
amount of dichloromethane, absorbed onto deactivated alu-
mina, desolvated, and placed on a 300 × 30 mm column.
Elution with n-hexane/dichloromethane (90:10 v/v) gave 3a ,b
as an orange-red solid in 20% yield (0.05 g), which was
crystallized from neat hexamethyldisiloxane to give orange-
red crystals of 3a , leaving the mother liquor enriched in 3b.
Complex 3a : IR (ν(CO), cm-1, C6H14): 2054 m, 2009 s, 1994
m, 1969 w, 1957 w. 31P{1H} (202.35 MHz, CDCl3, δ): 52.1 (s,
1
PPh2). H NMR (500.1 MHz, CDCl3, δ): 7.69-6.97 (m, C6H5),
3
5.54 (d, J PH ) 28.6 Hz, 1H, trans-PPh2CdCH{H}), 5.17 (d,
3
3J PH ) 12.5 Hz, 1H, cis-Ph2PCdCH{H}), 3.87 (d, J PH ) 25.6
Hz, 1H, HCPPh2CdCH{H}), 2.85 (d, 5J PH ) 1.8 Hz, 3H, PhCC-
{CH3}HCPh2PCdCH2). 13C{1H} NMR (125.65 MHz, CDCl3,
1
δ): 211.0-212.1 (br, CO), 174.4 (d, J PC ) 28.0 Hz, {Ph}CC-
1
{Me}HCPh2PCdCH2), 145.9 (d, J PC ) 33.5 Hz, C6H5), 145.1
1
(d, J PC ) 44.5 Hz, C6H5), 141.0 (s, {Ph}CC{Me}HCPh2PCd
CH2), 134.4-124.7 (m, C6H5), 114.2 (s, {Ph}CC{Me}HCPh2-
2
PCCH2), 111.9 (d, J PC ) 16.6 Hz, {Ph}CC{Me}HCPh2PCd
CH2), 65.9 (d, 2J PC ) 22.8 Hz, {Ph}CC{Me}HCPh2PCCH2), 37.6
(s, Me). Anal. Calcd for C35H23Fe2O6P: C, 58.11; H, 3.41.
Found: C; 58.43; H, 3.21. Complex 3b: IR (ν(CO), cm-1
,
C6H14): 2054 m, 2009 s, 1994 m, 1969 w, 1957 w. 31P{1H}
(202.35 MHz, CDCl3, δ): 48.3 (s, PPh2). 1H NMR (500.1 MHz,
CDCl3, δ): 7.69-6.97 (m, 10H, C6H5), 5.72 (d, 3J PH ) 29.0 Hz,
Exp er im en ta l Section
Gen er a l P r oced u r es. Unless otherwise stated all manipu-
lations were carried out in an inert atmosphere glovebox or
3
1H, HCPh2PCdCH{H}), 4.71 (d, J PH ) 13.7 Hz, 1H, HCPh2-
PCdCH{H}), 4.15 (d, 3J PH ) 24.7 Hz, 1H, HCPh2PCdCH{H}),
1.49 (d, 4J PH ) 0.9 Hz, 3H, {CH3}CC{Ph}HCPh2PCdCH2). 13C-
{1H} NMR (125.65 MHz, CDCl3, δ): 211.0-212.0 (br, CO),
(22) (a) Akita, M.; Kato, S.; Terada, M.; Masaki, Y.; Tanaka, M.;
Moro-oka, Y. Organometallics 1997, 16, 2392. (b) Rheingold, A. L.;
Guangzhong, W.; Heck, R. F. Inorg. Chim. Acta. 1987, 131, 147.

4562 Organometallics, Vol. 19, No. 22, 2000
Ta ble 2. Su m m a r y of Cr ysta l Da ta a n d Str u ctu r e Deter m in a tion for 2, 3a , a n d 4
Doherty et al.
2
3a
4
mol form
fw
C
35H23Fe2O6P
C30H21Fe2O6P
620.14
C37H25Fe2O6P
708.24
682.20
cryst size, mm
temperature, K
cryst syst
space group
a, Å
0.40 × 0.22 × 0.16
0.78 × 0.58 × 0.29
0.10 × 0.04 × 0.04
160(2)
160(2)
160(2)
orthorhombic
Pbca
20.8592(12)
10.3433(6)
28.1509(15)
triclinic
Ph1
monoclinic
P21/c
15.3078(19)
9.5600(12)
21.656(3)
12.5509(6)
15.3144(8)
15.9483(8)
109.143(2)
99.880(2)
104.577(2)
2692.3(2)
4
b, Å
c, Å
R, deg
â, deg
91.133(3)
γ, deg
V, Å3
6073.6(6)
8
1.492
1.054
2784
3168.5(7)
4
1.485
1.013
1448
Z
D
calcd, g cm-3
1.530
1.180
1264
µ, mm-1
F(000)
θ range, deg
1.75-28.89
27, 13, 37
36 167
7452
5514
0.753-0.928
0.0535
0.0295, 4.3513
0.0415
0.0833
1.41-29.03
17, 20, 21
22 404
12 746
9987
0.460-0.726
0.0159
0.0440, 0.00
0.0302
0.0736
2.21-29.49
21, 13, 30
22 243
8859
max. indices: h, k, l
no. reflns measd
no. reflns unique reflns
no. reflns with F2>2σ(F2)
transmn coeff range
Rint (on F2)
5372
0.578-0.962
0.0664
0.0635, 0.00
0.0526
0.1220
416
weighting paramsa a, b
Rb
c
Rw
no. of params
407
1.046
0.476, -0.352
711
0.984
0.545, -0.347
GOFd on F2
0.890
1.385, -0.534
max, min diff map e Å -3
w-1 ) σ2(Fo2) + (aP)2 + bP, where P ) (Fo + 2Fc2)/3. Conventional R ) ∑||Fo| - |Fc||/∑|Fo|. For “observed” reflections having Fo
>
a
2
b
2
2σ(Fo2). c Rw ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2 for all data. GOF ) [∑w(Fo - Fc2)2/(no. unique reflns - no. of params)]1/2
.
2
d
2
175.2 (d, 1J PC ) 25.9 Hz, {Me}CC{Ph}HCPh2PCdCH2), 154.4
by direct methods (Patterson synthesis for 3a ) and refined on
F2 values for all unique data by full-matrix least squares. Table
2 gives further details. All non-hydrogen atoms were refined
anisotropically. H atoms, located in difference maps, were
constrained with a riding model except for those attached to
C(3) and C(5) in 2 and C(3) and C(33) in 3a , which had their
coordinates freely refined because of nonstandard geometry;
U(H) was set to 1.2 (1.5 for methyl groups) times Ueq for the
parent atom. Programs used were Bruker AXS SMART and
SAINT for diffractometer control and frame integration,24
Bruker SHELXTL for structure solution, refinement, and
molecular graphics,25 and local programs.
1
(s, {Me}CC{Ph}HCPh2PCdCH2), 145.9 (d, J PC ) 33.5 Hz,
C6H5), 145.9 (d, 1J PC ) 43.5 Hz, C6H5), 134.4-124.7 (m, C6H5),
2
117.5 (s, {Me}CC{Ph}HCPh2PCdCH2{PPh2}), 105.4 (d, J PC
2
) 14.5 Hz, {Me}CC{Ph}HCPh2PCdCH2), 64.1 (d, J PC ) 20.7
Hz, {Me}CC{Ph}HCPh2PCdCH2), 25.9 (s, Me).
P r ep a r a tion of [F e2(CO)6(µ-P P h 2){µ-η1(P ):η3(C):η1(C)-
(P h )CCC(H)MeCHdCP h C(P P h 2)}] (4). A toluene solution
of [Fe2(CO)6(µ-PPh2){µ-η1:η2-(H)CdCdCH2}] (1) (0.20 g, 0.4
mmol) and phenyl ethyne (0.44 mL, 4.0 mmol) was heated to
90 °C for 8 h, after which time the solvent was removed to
leave a dark oily residue. This was dissolved in 2-3 mL of
dichloromethane, absorbed onto deactivated alumina, desol-
vated, placed on a column, and eluted with n-hexane/dichloro-
methane (90:10 v/v) to give 4 as an orange-red solid in 10%
yield (0.03 g). Small X-ray quality crystals of 4 were grown
from n-hexane at room temperature. IR (ν(CO), cm-1, C6H14):
2058 m, 2015 s, 1994 w, 1977 s, 1967 w. 31P{1H} (202.35
Ack n ow led gm en t. We thank the University of
Newcastle upon Tyne for financial support, the Nuffield
Foundation and the Royal Society for grants (S.D.), and
the EPSRC for funding for a diffractometer (W.C.) and
beamtime at Daresbury Laboratory (M.R.J .E.)
1
MHz, CDCl3, δ): 58.0 (s, PPh2). H NMR (500.1 MHz, CDCl3,
3
Su p p or tin g In for m a tion Ava ila ble: For 2, 3a , and 4
details of structure determination, non-hydrogen atomic po-
sitional parameters, full listings of bond distances and angles,
anisotropic displacement parameters, and hydrogen atomic
coordinates. This material is available free of charge via the
Internet at http://pubs.acs.org. Observed and calculated struc-
ture factor tables are available from the authors upon request.
δ): 7.48-6.81 (m, 10H, C6H5), 6.04 (d, J HH ) 2.5 Hz, 1H,
3
3
PhCdCHC{H}CH3), 3.91 (qd, J HH ) 2.5 Hz, J HH ) 7.1 Hz,
3
1H, PhCdCHC{H}CH3), 0.72 (d, J HH ) 7.1 Hz, 3H, PhCd
CHC{H}CH3). Anal. Calcd for C35H23Fe2O6P: C, 62.71; H, 3.56.
Found: C, 62.97; H, 3.40.
Cr ysta l Str u ctu r e Deter m in a tion of 2, 3a , a n d 4. All
measurements were made on a Bruker AXS SMART CCD
area-detector diffractometer using graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å) and narrow frame exposures
(0.3° in ω) for 2 and 3a and using silicon 111 monochromated
synchrotron radiation at Daresbury SRS station 9.8 (λ )
0.6890 Å; 0.2° frames) for 4, as reported previously.23 Intensi-
ties were corrected semiempirically for absorption and for 65%
X-ray beam decay in the case of 4. The structures were solved
OM0005147
(23) Clegg, W.; Elsegood, M. R. J .; Teat, S. J .; Redshaw, C.; Gibson,
V. C. J . Chem. Soc., Dalton Trans. 1998, 3037.
(24) SMART and SAINT software for CCD diffractometers; Bruker
AXS Inc.: Madison, WI, 1994.
(25) Sheldrick, G. M. SHELXTL user manual, version 5; Bruker
AXS Inc.: Madison, WI, 1994.