Reactions of cyclic and linear alkynols with a phosphinic iron(II) centre

Article abstract of DOI:10.1016/S1387-7003(02)00690-1

Treatment of a MeOH solution of trans-[FeBr₂(depe)₂] (depe = Et₂PCH₂CH₂PEt₂) with HC≡CC₆H₁₀OH or HC≡C(CH₂)_n OH (n = 1 or 2), in the presence of NaBPh₄, forms the cyclic allenylidene trans-[FeBr(=C=C=C₆H₁₀)(depe)₂] [BPh₄] or the alkyne trans-[FeBr{η²-HC≡C(CH₂) _nOH}(depe)₂][BPh₄] (n = 1 or 2) complexes, respectively.

Full text of DOI:10.1016/S1387-7003(02)00690-1

Inorganic Chemistry Communications 6 (2003) 94–96
www.elsevier.com/locate/inoche
Reactions of cyclic and linear alkynols with a phosphinic
iron(II) centre q
a
Ana I.F. Venancio , Luısa M.D.R.S. Martins , Joao J.R. Frausto da Silva ,
a,b
a
^
ꢀ
~
*
ꢀ
a,
Armando J.L. Pombeiro
a
Centro de Quꢀımica Estrutural, Complexo I, Instituto Superior Teꢀcnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
b
Seccßa~o de Quꢀımica Inorga^nica, DEQ, ISEL, R. Conselheiro Emꢀıdio Navarro, 1949-014 Lisboa, Portugal
Received 26 July 2002; accepted 3 October 2002
Abstract
Treatment of a MeOH solution of trans-[FeBr2ðdepeÞ2] (depe ¼ Et2PCH2CH2PEt2) with HCBCC6H10OH or HCBCðCH2ÞnOH
(n ¼ 1 or 2), in the presence of NaBPh4, forms the cyclic allenylidene trans-½FeBrð@C@C@C6H10ÞðdepeÞ2Š½BPh4Š or the alkyne
trans-½FeBrfg2-HCBCðCH2ÞnOHgðdepeÞ2Š½BPh4Š (n ¼ 1 or 2) complexes, respectively.
Ó 2002 Elsevier Science B.V. All rights reserved.
Keywords: Iron; Alkynes; Allenylidenes; Alkynols; Propargyl alcohols; Phosphinic complexes
1. Introduction
alcohols) and derived organometallic species [13,21–23],
we have now obtained, at an Fe(II) phosphinic centre,
two different kinds of products from alkynol reactions:
cyclic allenylidene (upon loss of a water molecule) and
alkyne (without water liberation) complexes. Their syn-
thesis, spectroscopic and FAB-MScharacterization are
now reported. Both types of complexes are not common,
being usually mentioned in the literature as intermedi-
ates, e.g., in the formation of cycloalkenylvinylidene and
hydroxyvinylidene complexes, respectively.
Since the middle of the seventies, when the first al-
lenylidene complex was synthesized [1], the interest in
the chemistry of these compounds has noticeably grown.
The dehydration of propargyl alcohols by transition
metal centres [2] provides a general method for the
synthesis of compounds containing extended multiple
carbon–carbon bonds and, in particular, of allenylidene
complexes with the M@C@C@C— group. The interest of
these compounds can arise not only from their material
properties but also from their potential capacity to be-
have as building blocks for the synthesis of unsaturated
organic molecules and for the access to metal-containing
copolymers [3,4]. They also have several applications in
homogeneous catalysis [5]. However, examples of Fe(II)
allenylidene complexes are still relatively rare [6–13].
Within our interest on the activation, by coordina-
tion, of alkynes [14–20] and alkynols (propargyl
2. Results and discussion
Treatment of a MeOH solution of trans-[FeBr2
ðdepeÞ2], in the presence of NaBPh4, with 1-ethynyl-1-
cyclohexanol, HCBCC6H10OH, leads to the formation of
the allenylidene complex trans-½FeBrð@C@C@C6H10Þ
ðdepeÞ2Š½BPh4Š 1 (reaction 1, Scheme 1), isolated as a red
1
1
solid and formulated on basis oþf IR, H, 31P–f Hg and
13C NMR spectroscopies, FAB -MSspectrometry and
elemental analysis. In the IR spectrum, the characteristic
asymmetric stretching vibration mðC@C@CÞ is observed
as a medium intensity band at 1920 cmꢀ1 and in the
q Work presented at the 35th International Conference on Coordi-
nation Chemistry held in Heidelberg, Germany from 21 to 26 July
2002.
* Corresponding author. Tel.: +351-2184-19237; fax: +351-2184-
64457.
E-mail address: pombeiro@alfa.ist.utl.pt (A.J.L. Pombeiro).
1
13C–f Hg NMR spectra the carbon atoms from the cu-
mulenic chain are observed at: d 319.3 ppm (qt, JCP ¼ 35:0
1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved.
PII: S1387-7003(02)00690-1

A.I.F. Ven^ancio et al. / Inorganic Chemistry Communications 6 (2003) 94–96
95
Scheme 1.
Hz, Ca), 218.6 ppm (qt, JCP ¼ 3:6 Hz, Cc with the lowest
JCP value, in comparison with those for Ca and Cb) and
169.4 ppm (qt, JCP ¼ 5:3 Hz, Cb). The FABþ-MSspec-
trum of 1 exhibits the molecular ion (m/z 655/653 ½MŠþ)
and its fragmentation pattern initiated by the stepwise
eliminaþtion of the allenylidene (m/zþ549/547 ½M–C@C@
C6H10Š ), bromide (m/z 574 ½M–BrŠ ) or depe (m/z 449/
447 ½M–depeŠþ) ligands. The trans geometry of this
complex and those below is assigned on the basis of the
ðg2-HCBCHÞðPMe2PhÞ2Š½BF4Š (3JHP ¼ 6:7 Hz) [27],
thus also corroborating our proposed g2-alkyne ligand
formulation. Further, in the FABþ-MSspectra of 2a it
þ
is observed the molecular ion ½MŠ [m/z 605/603
81
ð Br=79BrÞ], its fragmentation pattern namely byþloss of
the ligands (e.g., m/z 549/547 ½M–HCBCCH2OHŠ , 399/
397 ½M–depeŠþ) anþd by dehydration of the alkynol (m/z
587/585 ½M–H2OŠ ), the latter process conceivably
leading to the corresponding allenylidene complex under
FABþ-MSconditions. The hypothesis of formation of
an hydroxyvinylidene complex was also discarded by IR
data, since the characteristic vinylidene mðC@CÞ band
at ca. 1660–1500 cmꢀ1, as known, e.g., for trans-
[ReXð@C@CHRÞðdppeÞ2] (X ¼ Cl, F) [19,20] and
½RuClð@C@CHCH2OHÞðdppmÞ2Š½PF6Š [28], was not
observed.
1
singlet observed in their 31P–f Hg NMR spectra.
However, alkyne complexes are obtained from pri-
mary alkynols which are stable towards dehydration. In
fact, treatment of a MeOH solution of trans-[FeBr2
ðdepeÞ2] with HCBCðCH2ÞnOH (n ¼ 1 or 2), in the
presence of NaBPh4, yields (reaction 2, Scheme 1) trans-
½FeBrfg2-HCBCðCH2ÞnOHgðdepeÞ2Š½BPh4Š (n ¼ 1 2a
or 2 2b) which were isolated, although in low yields in
view of their low stability, as orange (2a) or green (2b)
Hence, the work now reported shows the uncommon
ability of the fFeBrðdepeÞ2gþ centre to bind either an
alkynol or a derived allenylidene, depending on the
properties of the alkynol, and the extension of the study
to other alkynols and the investigation of further reac-
tivity of such products are under way.
1
solids and characterized by IR, 1H and 31P–f Hg NMR
spectroscopies, FABþ-MSspectrometry and elemental
analysis. Hence, for example, in the IR spectra, the al-
kynol ligands present m(OH) at ca. 3500 (w, br) cmꢀ1
,
m(CBC) at ca. 2085 (m/w) cmꢀ1 (corresponding to co-
ordination shifts of ca. 30 cmꢀ1 to lower wavenumbers)
and mðC–OÞ at ca. 1085 (s) cmꢀ1 also indicative that
there was no dehydration of the alkynol. In the 1H
NMR spectrum of compound 2a, the acetylenic proton
(g2-HCBCðCH2ÞnOH) is observed as a quintet with
3JHP ¼ 8:2 Hz, a value that is considerably higher than
3. Experimental
All manipulations and reactions were carried out
using standard inert gas flow or high-vacuum tech-
niques. The complex trans-[FeBr2ðdepeÞ2] was prepared
by a published method [29], the alkynols were used as
purchased from Aldrich. The solvents were purified and
dried by standard methods and freshly distilled under
dinitrogen. The IR (KBr) spectra were recorded on a
4
those of JHP exhibited by the vinylidene proton, e.g.,
in trans-[ReClð@C@CHRÞðdppeÞ2] (R ¼ alkyl or aryl,
dppe ¼ Ph2PCH2CH2PPh2) (4JHP ¼ 3–5 Hz range)
[19,20], [Ruðg5-C5Me5Þð@C@CHCH2OHÞðPEt3Þ2Š½BPh4]
(4JHP ¼ 1:8 Hz) [24] and ½Ruðg5-C5Me5ÞðPMe2PhÞ2
ð@C@CHCH2OHފ½PF6Š (4JHP ¼ 2:2 Hz) [25]. More-
Bio-Rad FTS3000 instrument and NMR (CDCl
)
3
spectra on a Varian UNITY 300 spectrometer. FABþ-
MSspectra were obtained on a Trio 2000 instrument in
3-nitrobenzyl alcohol matrices. C and H elemental
analyses (which, for all the complexes, agree with the
3
over, our JHP value is within those of other 1-alkyne
complexes such as ½Ruðg5-C5H5Þðg2-HCBCMeÞðPMe3Þ2Š
½PF6Š (3JHP ¼ 10:5 Hz) [26] and ½Ruðg5-C5H5Þ

96
A.I.F. Ven^ancio et al. / Inorganic Chemistry Communications 6 (2003) 94–96
expected values) were carried out by the Microanalytical
ꢀ
References
Service of the Instituto Superior Tecnico.
Abbreviations: w ¼ weak, m ¼ medium, s ¼ strong,
€
[1] (a) E.O. Fischer, H.-J. Kalder, A. Frank, F.H. Kohler, G.
Huttner, Angew. Chem., Int. Ed. Engl. 15 (1976) 623;
(b) H. Berke, Angew. Chem., Int. Ed. Engl. 15 (1976) 624.
[2] J.P. Selegue, Organometallics 1 (1982) 217.
[3] M.I. Bruce, Chem. Rev. 98 (1998) 2797.
[4] V. Cadierno, M.P. Gamasa, J. Gimeno, Eur. J. Inorg. Chem.
(2001) 571.
qt ¼ quintet, m ¼ multiplet.
3.1. Allenylidene complex trans-½FeBrð@C@C@C6H10Þ
ðdepeÞ Š ½BPh4Š 1
2
[5] A. Furstner, M. Liebl, C.W. Lehmann, M. Picquet, R. Kunz, C.
Bruneau, D. Touchard, P.H. Dixneuf, Chem. Eur. J. 6 (2000)
1847.
To a solution of trans-½FeBr2ðdepeÞ2Š (0.20 g, 0.32
mmol) in MeOH (50 cm3) was added HCBCC6H10OH
(0.059 g, 0.478 mmol) and the mixture was stirred at 40
°C for ca. 5 h whereafter a MeOH solution (5 cm3) of
NaBPh4 (equimolar amount) was added. It was taken to
dryness by evaporation of the solvent in vacuo. Ex-
traction with CH2Cl2 (20 cm3) followed by filtration,
concentration in vacuo and addition of diethyl ether (10
cm3) led to the precipitation of the product which was
isolated by decantation, washed with diethyl ether and
dried in vacuo (0.23 g, 75% yield). Relevant IR, NMR
and FABþ-MSdata: see text.
[6] C. Gauss, D. Veghini, O. Omara, H. Berke, J. Organomet. Chem.
541 (1997) 19.
[7] V. Guilaume, P. Thominot, F. Coat, A. Mari, C. Lapinte, J.
Organomet. Chem. 565 (1998) 75.
[8] E. Gatto, G. Gervasio, D. Marabello, E. Sappa, J. Chem. Soc.,
Dalton Trans. (2001) 1485.
[9] G. Albertin, P. Agnoletto, S. Antoniutti, Polyhedron 21 (2002)
1755.
[10] Y. Nishibayashi, Y. Inada, M. Hidai, S. Uemura, J. Am. Chem.
Soc. 124 (2002) 7900.
[11] S. Nakanishi, K. Goda, S. Uchiyama, Y. Otsuji, Bull. Chem. Soc.
Jpn. 65 (1992) 2560.
€
[12] H. Berke, V. Grossmann, G. Huttner, L. Zsolnai, Chem. Ber. 117
(1984) 3432.
^
ꢀ
[13] A.I.F. Venancio, L.M.D.R.S. Martins, J.J.R. Frausto da Silva,
A.J.L. Pombeiro, Port. Electrochim. Acta 19 (2001) 361.
[14] A.J.L. Pombeiro, J. Organomet. Chem. 632 (2001) 215.
[15] A.J.L. Pombeiro, Chemistry and electrochemistry of alkyne- and
isocyanide-derived carbyne complexes of rhenium, molybdenum
and tungsten, in: F.R. Kreissl (Ed.), Transition Metal Carbyne
Complexes (NATO Advanced Research Workshop), NATO ASI
Series, Kluwer Academic Publishers, Dordrecht, The Netherlands,
1993, p. 105.
3.2. Alkyne complexes trans-½FeBrfg2-HCBCðCH2Þn
OHgðdepeÞ Š½BPh4Š ðn ¼ 1 2a or 2 2bÞ
2
To a solution of trans-[FeBr2ðdepeÞ2] (0.20 g, 0.32
mmol) in MeOH (50 cm3) was added a stoichiometric
amount of the alkynol [18.5 ll (HCBCCH2OH) or
24.0 ll (HCBCðCH2Þ2OH)] and the mixture was stir-
red at 40 °C for ca. 1 h whereafter NaBPh4 (equimolar
amount) in MeOH (5 cm3) was added. Cooling to ca.
)18 °C led to the precipitation of 2a or 2b which were
isolated by decantation, washed with diethyl ether and
dried in vacuo (0.090 g, 31% 2a and 0.070 g, 23% 2b
[16] M. Kuznetsov, A.J.L. Pombeiro, A.I. DementÕev, J. Chem. Soc.,
Dalton Trans. (2000) 4413.
[17] M.F.N.N. Carvalho, A.J.L. Pombeiro, G. Wagner, B. Pedersen,
R. Herrmann, Z. Naturforsch. B 54 (1999) 725.
[18] M.F.N.N. Carvalho, S.S.P.R. Almeida, A.J.L. Pombeiro, R.A.
Henderson, Organometallics 16 (1997) 5441.
[19] S.S.P.R. Almeida, A.J.L. Pombeiro, Organometallics 16 (1997)
4469.
1
3
yield, respectively). 2a: H NMR: d 4.2 (qt, 1H, JHP
¼
8:2 Hz, g2-HCBCCH2OH), 4.0 (m, 2H, g2-HCBCCH2
OH). 2b: 1H NMR: d 3.8 (m, 1H, g2-HCBCðCH2Þ2
[20] A.J.L. Pombeiro, S.S.P.R. Almeida, M.F.C. Guedes da Silva,
J. Chem. Soc., Dalton Trans. (1989) 2381.
1
OHÞ, 3.2 (m, 2H, g2-HCBCCH2 CH2OH). 13C–f Hg
ꢀ
[21] L. Zhang, M.P. Gamasa, J. Gimeno, R.J. Carbajo, F. Lopez-
Ortiz, M.F.C. Guedes da Silva, A.J.L. Pombeiro, Eur. J. Inorg.
Chem. (2000) 341.
and 13C NMR: no reliable spectra could be
obtained due to the unstability of the complexes in the
usual solvents. Relevant IR and FABþ-MSdata: see
text.
[22] L. Zhang, M.P. Gamasa, J. Gimeno, M.F.C. Guedes da Silva,
A.J.L. Pombeiro, C. Graiff, M. Lanfranchi, A. Tiripicchio, Eur.
J. Inorg. Chem. (2000) 1707.
[23] L. Zhang, M.F.C. Guedes da Silva, M.L. Kuznetsov, M.P.
ꢀ
Gamasa, J. Gimeno, J.J.R. Frausto, A.J.L. Pombeiro, Organo-
metallics 20 (2001) 2782.
[24] E. Bustelo, M.J. Tenorio, M.C. Puerta, P. Valerga, Organomet-
allics 18 (1999) 4563.
Acknowledgements
€
[25] R. Le Lagadec, E. Roman, L. Toupet, U. Muller, P.H. Dixneuf,
Organometallics 13 (1994) 5030.
This work has been partially supported by the
^
[26] R.M. Bullock, J. Chem. Soc., Chem. Commun. (1989) 165.
[27] J.R. Lomprey, J.P. Selegue, J. Am. Chem. Soc. 114 (1992) 5518.
[28] D. Touchard, P. Haquette, N. Pirio, L. Toupet, P.H. Dixneuf,
Organometallics 12 (1993) 3132.
~
Fundaßcao para a Ciencia e Tecnologia (FCT), and the
PRAXISXXI and POCTI Programmes. We also thank
^
Dr. M. Candida N. Vaz for the elemental analysis ser-
vice and Mr. Indalecio Marques for running the MS
ꢀ
[29] D.J. Evans, R.A. Henderson, A. Hills, D.L. Hughes, K.E. Oglive,
J. Chem. Soc., Dalton Trans. (1992) 1259.
spectra.