Schneider, Jorg J.; Czap, Norbert; Blaser, Dieter; Boese, Roland; Ensling, Jurgen; Gutlich, Philipp; Janiak, Christoph:

Experimental and theoretical investigations on the synthesis, structure, reactivity, and bonding of the stannylene-iron complex bis{{bis(2-tert-butyl-4,5,6-trimethyl-phenyl)}Sn}Fe(h6-toluene) (Sn-Fe-Sn).

In: Chemistry--A European Journal, Jg. 6 (2000) ; Nr. 3, S. 468-474
ISSN: 0947-6539
Zeitschriftenaufsatz / Fach: Chemie
The p-(arene)bis(stannylene) complex bis{{bis(2-tert-butyl-4,5,6-trimethylphenyl)}Sn}Fe(h6-toluene) (Sn-Fe-Sn, 15) is accessible in high yields by a metal-atom-mediated synthesis between Fe atoms, toluene, and the stannylene [{bis(2-tert-butyl-4,5,6-trimethylphenyl)}Sn] (3). Complex 15 has a half-sandwich structure with short Fe-Sn bonds (2.432(1) .ANG.) and a trigonal-planar coordination at both the Fe and Sn atoms. The distance between the two Sn centers is 3.56 .ANG.. Complex 15 is stable under ambient conditions and displays a p-arene lability, so far rarely obsd. for (arene)iron complexes; this leads to an irreversible substitution of the arene and formation of 5-fold-coordinated zerovalent Fe complexes. The p-arene lability of the title compd. is a result of the Fe-Sn bonding situation, which can be interpreted, from an EHMO calcn., as being solely a donation of the 5s lone-pair of Sn into empty or half-filled acceptor d orbitals on Fe. As the calcns. reveal, there is little backbonding from the Fe to the Sn, and the strong s donation leads to an increased occupation of the p-antibonding orbitals of the h6-arene, which are mainly responsible for the exptl. obsd. arene lability. Fe and Sn Mossbauer spectra support the polar character of Snd+ -> Fed- with strong s donation from Sn to Fe, but significantly low Fe-to-Sn p backdonation.