ZUTIN et al.
Conclusions
cordance to the well established Chatt, Duncanson and
Levason synergistic model of bonding [20], and the in-
ternal stability of the a-framework of the a,b-unsatu-
rated ligand.
The thermal behaviour of the four complexes dis-
cussed in this work is perhaps difficult to understand
separately, but they show collectively that the
iron-enone entity is the primal feature for all these
compounds. This basic characteristic is clearly re-
flected by the last fragments that leave the metal un-
der the extreme conditions of temperature imposed
upon the compounds in the herewith called third step
of thermal decomposition.
References
1 D. H. R. Barton, A. A. L. Gunatilaka, T. Nakanishi,
H. Patin, W. A. Barton and B. R. Worth, J. C. S. Perkin I,
8
(1976) 821.
2
3
G. Sholes, C. R. Graham and M. Brookhart,
J. Am. Chem. Soc., 96 (1974) 5665.
Theoretically, (Table 2), the final residue re-
maining on the metal in the tricarbonyl(enone) com-
M. Brookhart, G. O. Nelson, G. Scholes and R. A. Watson,
J. C. S. Chem. Comm., 6 (1976) 195.
pounds have the basic composition ’C O’ (enone=ch)
3
and ’C O’ (enone=bda), which probably reflect
4
a,b-‘unsaturated substrates’ of the type ‘O=C–C=C’,
from the loss of both aromatic rings of ch, and
4 B. F. G. Johson, J. Lewis, P. McArdle and G. L. P. Randall,
Chem. Comm., 2 (1971) 177.
5 G. D. Sargent, N. Lowry and S. D. Reich,
J. Amer. Chem. Soc., 89 (1967) 5985.
‘
C–C(=O)–C=C’, from the loss of the unique aro-
6
7
C. R. Ganellin and R. Petit, J. Chem. Soc., 112 (1958) 576.
J. A. S. Howell, B. F. G. Johnson, P. L. Josty and J. Lewis,
J. Organomet. Chem., 39 (1972) 329.
matic ring available in bda. Of course, there is no pos-
sibility as yet to determine the kinds of bonds that still
hold those metal–organic fragments together, but they
shall be very different from the h -mode as observed
in the parent complexes [17–19].
The successive losses of pendant aromatic rings
and CO molecules from this class of complexes upon
heating is therefore a clear evidence of the strength of
the Fe(O=C–C=C) interactions; it should be stressed,
however, that the apparent stability of the s-frame-
4
8 E. J. S. Vichi, P. R. Raithby and M. McPartlin,
J. Organomet. Chem., 256 (1983) 111.
9
A. Vessieres and P. Dixneuf, Tetrahedron Lett.,
6 (1974) 1499.
1
10 B. F. G. Johnson, J. Lewis, G. R. Stephenson and
E. J. S. Vichi, J. Chem. Soc., Dalton Trans., 5 (1978) 369.
11 E. J. S. Vichi, F. Y. Fujiwara and E. Stein, Inorg. Chem.,
24 (1985) 286.
1
1
1
2 J. A. S. Howell, D. T. Dixon and J. C. Kole,
J. Organomet. Chem., 69 (1984) 266.
3 M. J. Calhorda and E. J. S. Vichi, Organometallics,
work H C–C(=O)–C(H)=C(H)– of dba (Table 2) may
3
be responsible for the TG suggested mechanism
where the loss of a phenylic residue seem to be more
important at the beginning of the decomposition path-
9
(1990) 1060.
4 V. M. Nogueira, A. V. Benedetti, E. J. S. Vichi and
E. Stein, J. Electroanal. Chem., 287 (1991) 761.
way of [Fe(bda)(CO)
CO molecule.
The presence of one molecule of coordinated
] than the loss of a coordinated
3
15 K. Zutin, V. M. Nogueira, A. E. Mauro, P. Melnikov and
A. Iluykhin, Polyhedron, 20 (2001) 1011.
triphenylphosphane in [Fe(enone)(CO) PPh ] does
2
16 P. S. Haddad, A. E. Mauro, V. M. Nogueira and
S. I. Klein, Trans. Metal Chem., 28 (2003) 899.
3
make very difficult any assumption regarding the ther-
mal fragmentation pathway for those compounds, after
the initial loss of one CO, regardless of the enone em-
ployed. Nevertheless, it is symptomatic that in the ch
case, where there is the possibility of thermal detach-
ment of two aromatic rings, as before, the final residue
seem to contain a residual phosphorous atom embed-
ded in the ubiquitous ‘O=C–C=C’ fragment (Table 2),
whereas for the bda analog, the final organic fragments
include that which can also be regarded as arising from
the metal-stabilized C–C(=O)–C=C. The combined re-
sults for the thermal decomposition of this whole fam-
ily of compounds seem therefore to be reflecting both
the metal to enone strong a and p interactions, in ac-
1
1
1
7 A. F. Clifford and A. K. Mukherjee, Inorg. Synth.,
(1966) 185.
8 F. M. Chaudari and P. L. Pauson, J. Organomet. Chem.,
(1966) 73.
8
5
9 R. Edwards, J. A. S. Howell, B. F. G. Johnson and
J. Lewis, J. Chem. Soc. Dalton Trans., 19 (1974) 2105.
20 J. Chatt and L. A. Duncanson, J. Chem. Soc., (1953) 2939.
Received: May 9, 2006
Accepted: September 20, 2006
OnlineFirst: December 18, 2006
DOI: 10.1007/s10973-006-7687-y
452
J. Therm. Anal. Cal., 87, 2007