Penta(cyclopentadienyl)-η 5-cyclopentadienylmanganesetricarbonyl: Structure and laser-induced conversion to fullerenes

Article abstract of DOI:10.1016/S0022-328X(98)00940-1

The title compound [Cp₅CpMn(CO)₃], 1, has been characterized by X-ray crystallography and shown by laser-induced desorption/ionization (LDI) to undergo dissociative coalescence to fullerene C₆₀ and other carbon clusters.

Full text of DOI:10.1016/S0022-328X(98)00940-1

Journal of Organometallic Chemistry 572 (1999) 135–139
Preliminary communication
5
Penta(cyclopentadienyl)-p -cyclopentadienylmanganesetricarbonyl:
structure and laser-induced conversion to fullerenes
a
b
b
b
Mark P. Barrow , J. Kevin Cammack , Matthias Goebel , Ian M. Wasser ,
b,1
a,
K. Peter C. Vollhardt , Thomas Drewello *
a
Department of Chemistry, Uni6ersity of Warwick, Co6entry CV4 7AL, UK
b
Department of Chemistry, Uni6ersity of California at Berkeley and the Chemical Sciences Di6ision, Lawrence Berkeley National Laboratory,
Berkeley, CA 94720, USA
Received 3 July 1998; received in revised form 28 August 1998
Abstract
The title compound [Cp CpMn(CO) ], 1, has been characterized by X-ray crystallography and shown by laser-induced
5
3
desorption/ionization (LDI) to undergo dissociative coalescence to fullerene C60 and other carbon clusters. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Oligocyclopentadienylmetals; Manganese; Fullerenes; Laser-induced desorption/ionization
Laser desorption/ionization experiments represent a
powerful tool to obtain insight into the formation,
structure and reactivity of carbon clusters. The historic
approach, using laser vaporisation of graphite to pro-
duce fullerenes [1], has prompted numerous new devel-
opments and applications of this method. Replacing the
graphite target with fullerenes, such as C , C or C84,
led to the observation of gas-phase coalescence reac-
tions in which higher fullerenes could be formed as
multiples of the initial precursor [2,3]. The reactivity
with regards to coalescence shows a strong dependence
on modifications of the fullerene surface. Oxygenated
carbon spheres, for instance, were found to undergo
fusion reactions at lower laser powers than pure fullere-
nes [4] and laser-ablated organic ligand-bearing deriva-
tives resulted in products with an uneven number of
carbon atoms [5]. The laser-induced fullerene formation
from non-fullerene precursors is also of intense current
research interest [6]. Illustrative examples include the
production of metallofullerenes by laser ablation of
pyrolysed dried algae residues [7] and the fullerene
formation in coalescence reactions of cyclo[n]carbons
[8] or dodecahedrane derivatives [9]. These investiga-
tions clearly show that the precursor material must not
only provide a sufficient amount of carbon to drive the
coalescence reaction, but that certain structural features
seem to facilitate the laser-induced formation of
fullerenes.
60
70
In
[Cp
this
CpMn(CO)
connection,
the
title
compound
], 1 [10], seemed an intriguing substrate
5
3
as its y-ligand provides a C30 unit with a topography
similar to semi-buckminsterfullerene, C30 10 [11], in
H
which the arrangement of six pre-formed five-mem-
bered carbon moieties ideally satisfies the isolated pen-
tagon rule [12]. Upon laser-induced desorption/
ionization (LDI) intramolecular fusion might be envis-
aged to lead to the generation of this elusive species
perhaps in metal-complexed form [13], or to
coalescence via a dimer to (potentially metallated)
*
Corresponding author. E-mail: t.drewello@warwick.ac.uk.
Also corresponding author. E-mail: vollhard@cchem.berkeley.edu
1
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00940-1

136
M.P. Barrow et al. / Journal of Organometallic Chemistry 572 (1999) 135–139
˚
Fig. 1. Molecular structure of 1 in the crystal. Selected bond distances (A): C(4)ꢀC(9) 1.475(6), C(9)ꢀC(10) 1.459(6), C(10)ꢀC(11) 1.378(7),
C(11)ꢀC(12) 1.410(8), C(12)ꢀC(13) 1.489(6), C(9)ꢀC(13) 1.357(7), C(8)ꢀC(29) 1.478(6), C(29)ꢀC(30) 1.480(7), C(30)ꢀC(31) 1.446(7), C(31)ꢀC(32)
1.371(7), C(32)ꢀ(33) 1.469(7), C(29)ꢀC(33) 1.354(6).
[
14] fullerene C . This paper reports the X-ray struc-
to induce coalescence reactions of fullerenes and
fullerene derivatives, such as highly fluorinated fullere-
nes [17]. The mass spectra shown here represent the
accumulation of 200 single-laser-shot data. Since it was
found that the precursor material degraded over a
period of several days at r.t., the target compound was
either freshly prepared for the investigation or stored at
low temperatures. For the experiments, the complex
was deposited onto a stainless steel target slide in the
form of a dichloromethane solution and dried before
the introduction into the ion source.
6
0
ture of 1 and LDI experiments that reveal the occur-
rence of such coalescence processes.
Although 1 is obtained as a mixture of equilibrating
,3- and 1,4-cyclopentadiene tautomers [10], slow crys-
1
tallisation of one isomer occurred at −20°C in hexanes
as yellow crystals amenable to (routine) X-ray analysis
(
tomeric pattern of the five appended Cp rings with
C(14), C(19) and C(29) constituting carbons marking
the terminus of the diene unit, C(9) and C(24) constitut-
ing their internal analogs [16]. Most notable is the lack
of coplanarity of the Cp substituents, with dihedral
angles ranging from 42.2° to 46.4° and bending angles
Fig. 1) [15]. The molecule shows an alternating tau-
Fig. 2 shows the positive ion LDI mass spectrum,
obtained for 1 with laser power adjusted just above the
threshold for ion formation. The spectrum is character-
ised by four major signal groups, each consisting of
several peaks spaced by one mass unit, indicating the
loss of hydrogen and with the most intense signals
observed at m/z 317 (C H ), m/z 385 (Cp Cp), m/z
[
of the carbons of attachment from the least-squares
plane of C(4)ꢀC(8)] averaging 10° (away from the
metal). While the average distance of the h-carbons in
neighbouring Cp substituents is ca. 3.3 A, Spartan
˚
25
17
5
modelling of the all-coplanar conformer narrows it to
ca. 2.2 A.
440 (Cp CpMn) and m/z 493 ([Cp CpMn(CO) ꢀH ]).
5
5
2
2
˚
The assignment of these signals was further supported
by investigating fully deuterated C D Mn(CO) ,
A nitrogen laser was used for LDI, operating at
u=337 nm with a pulse length of 3 ns. Cations gener-
ated as the result of the LDI process were accelerated
by a potential difference of 20 kV and analysed by
reflectron time-of-flight mass spectrometry (ref-TOF).
The mass spectrometer, which has been described in
more detail elsewhere [17], has been successfully applied
30
25
3
which showed the expected mass shifts due to the
presence of deuterium. For both precursors, the molec-
ular ion could not be detected and the only abundantly
observed CO-containing fragment ion resulted from the
loss of one CO unit. This fragment ion forms the only
species of moderate intensity, together with Cp CpMn,
5

M.P. Barrow et al. / Journal of Organometallic Chemistry 572 (1999) 135–139
137
Fig. 2. Positive ion LDI mass spectrum of 1 with the laser power adjusted to just above the threshold for the ion formation.
which still contain the metal atom attached to the
carbon framework of the Cp ligand. For comparison,
under electron impact conditions (70 eV), the molecular
ion is with 56% relative intensity perfectly detectable
ters could not be detected; their abundance remained
below the detection limit of the experimental set-up.
Only by applying an ion gate was it possible to
obtain the spectrum in Fig. 3. The ion gate consists of
two charged plates parallel to the ion flight path that
allows the selection of one particular ion for further
investigations (tandem mass spectrometry, post source
decay) [20] and provides higher sensitivity for the detec-
tion of the gated ions, as saturation of the detector is
prevented by decreasing the total number of ions reach-
ing it. Fig. 3 clearly shows the formation of carbon
clusters in the C60 region. However, semi-buckminster-
fullerene and metallofullerenes could not be detected.
The overall abundance of the fullerenes generated in
this manner is at least two orders of magnitude lower
than that observed in the laser-induced fusion of C60
under similar conditions. Repeated runs revealed C60
and the Cp CpMn fragment ion represents the base
5
peak. Thus, LDI under the applied conditions leads to
a more pronounced dissociation behaviour. This is
further corroborated by increasing the laser power in
order to promote coalescence reactions. Coalescence
reactions of fullerene-based material were found to
occur efficiently only if a sufficient amount of target
material is ablated into the gas-phase [18] and if the
dissociation leads to energised fragments, which act as
the initialising particles for these reactions [19]. Upon
increasing the laser power more fragmentation occurs,
due to the dissociation of the Cp Cp ligand. Under
5
these conditions, ions correlating to higher carbon clus-

138
M.P. Barrow et al. / Journal of Organometallic Chemistry 572 (1999) 135–139

M.P. Barrow et al. / Journal of Organometallic Chemistry 572 (1999) 135–139
139
[
[
[
[
[
3] B. Kubler, E. Millon, J.J. Gaumet, J.F. Muller, Full. Sci. Tech.
(1996) 1247.
4] R.D. Beck, C. Stoermer, C. Schulz, R. Michel, P. Weis, G.
Br a¨ uchle, M.M. Kappes, J. Chem. Phys. 101 (1994) 3243.
5] R.D. Beck, P. Weis, A. Hirsch, I. Lamparth, J. Phys. Chem. 98
(1994) 9683.
6] F.G. Hopwood, K.J. Fisher, P. Greenhill, G.D. Willett, R.
Zhang, J. Phys. Chem. 101 (1997) 10704.
7] H.R. Rose, I.G. Dance, K.J. Fisher, D.R. Smith, G.D. Willett,
M.A. Wilson, J. Chem. Soc. Chem. Commun. (1993) 941.
always as the slightly dominant signal but also a
plethora of higher carbon clusters. The overall cluster
distribution varied for different experimental runs,
which might indicate a moderate degree of fragmenta-
tion of the initially formed coalescence products. The
instrumental resolution does not allow the exclusion of
a possible contamination of the carbon clusters with
hydrogen. The width of the particular peaks, however,
suggests that the amount of hydrogen possibly still
bonded to the fullerene ions is rather low.
4
[8] S.W. McElvany, M.M. Ross, N.S. Goroff, F. Diederich, Science
259 (1993) 1594.
[
9] E.E.B. Campbell, R. Tellgmann, F. Wahl, H. Prinzbach, Int. J.
Mass Spectr. Ion Proc. 136 (1994) 209.
In summary, it appears that LDI-induced coalescence
of 1 occurs after the strategically positioned central
metal atom has been removed from the ligand. The low
fullerene yield may be due to the tendency of the ligand
itself to undergo facile fragmentation by the loss of Cp,
which makes a simple fusion of two intact ligands
rather unlikely. The high degree of |-bonded hydrogen
atoms possibly plays a further unfavourable role, con-
sistent with the distinctly attenuated tendency for
C H to undergo coalescence in comparison with that
[
[
10] R. Boese, G. Br a¨ unlich, J.-P. Gottel, J.-T. Hwang, C. Troll,
K.P.C. Vollhardt, Angew. Chem. Int. Ed. Engl. 35 (1996) 995,
and references therein.
11] (a) R. Liu, X. Zhou, N.L. Allinger, J. Phys. Org. Chem. 7 (1994)
5
51. (b) A. H. Abdourazak, Z. Marcinow, A. Sygula, R. Sygula,
P.W. Rabideau, J. Am. Chem. Soc. 117 (1995) 6410. (c) P.W.
Rabideau, A. Sygula, Acc. Chem. Res. 29 (1996) 235.
12] J. Aihara, J. Am. Chem. Soc. 117 (1995) 4130.
[13] For a leading reference on metallated ‘buckybowls’, see: R.M.
Shaltout, R. Sygula, A. Sygula, F.R. Fronczek, G. G. Stanley,
P.W. Rabideau, J. Am. Chem. Soc. 120 (1998) 835.
14] For organic approaches to endohedral metallofullerenes, see: (a)
Y. Rubin, Chem. Eur. J. 3 (1997) 1009. (b) R.W. Saalfrank,
Nature 383 (1996) 124.
[
6
0
36
of pure C60 [21].
[
Acknowledgements
[15] Crystal data for 1, C33
H
25
O
3
Mn, M=524.50, triclinic, space
˚
group P1
(
(No. 2), a=9.578(2), b=10.278(2), c=15.284(4) A,
˚
3
h=93.49(2), i=101.29(2), k=116.79(1)°, U=1298.0 (1) A ,
This work was supported by the EPSRC, the Lever-
hulme Trust and the Director, Office of Energy Re-
search, Office of Basic Energy Sciences, Chemical
Sciences Division of the US Department of Energy
under Contract DE-AC03-76SF00098. The authors
thank Erik Williams of Micromass Ltd. for obtaining
the spectrum in Fig. 2 with the TofSpec-E. M.G. ac-
knowledges a postdoctoral fellowship by the Deutsche
Forschungsgemeinschaft.
−
3
−1
Z=2, Dcalc.=1.342 g cm , v=5.41 cm . Measured reflec-
tions, 5491; unique reflections, 3656; 2561 reflections with I \
o
3|(I ) used in refinement, R=0.050, R =0.057. There is ca.
o
w
10% disorder in the conformation of the Mn(CO)
02 751.
group. CCDC
3
1
[
16] The positions of the double bonds are readily ascertained by
inspection of the CꢀC bond lengths. The positions of the hydro-
gens were calculated but not refined.
[17] R. Cozzolino, O. Belgacem, T. Drewello, L. K a¨ seberg, R.
Herzschuh, S. Suslov, O.V. Boltalina, Eur. Mass Spectr. 3 (1997)
4
07.
[
[
18] K.R. Lykke, D. Holmes Parker, P. Wurz, Int. J. Mass Spectr.
Ion Proc. 138 (1994) 149.
19] R. Mitzner, B. Winter, C. Kusch, E.E.B. Campbell, I.V. Hertel,
Z. Phys. D 37 (1996) 89.
References
[
[
1] H.W. Kroto, J.R. Heath, S.C. O’Brian, R.F. Curl, R.E. Smalley,
Nature 318 (1985) 162.
2] C. Yeretzian, K. Hansen, F. Diederich, R.L. Whetten, Nature
[20] R. Kaufmann, D. Kirsch, B. Spengler, Int. J. Mass Spectr. Ion
Proc. 131 (1994) 355.
[21] M. M o¨ der, M. N u¨ chter, G. Czira, K. V e´ key, M.P. Barrow, T.
Drewello, in preparation.
3
59 (1992) 44.
.