F:I -qEVIER Journal of Organometallic Chemistry 540 (1997) 83-88 O ~ ' c Synthesis and characterization of new oligosilane derivatives of iron and molybdenum Wolfram Palitzsch, Uwe Btihme, Gerhard Roewer * Technische Universitiit Bergakademie Freiberg, lnstitut fiir Anorganische Chemie, Leipziger Strafle 29, D-09596 Freiberg, Germany Received 8 November 1996 AlmraO By use of salt elimination, the transition metal suhstitmed oligosilaaes (r/5-csme4Et)Fe(CO)2Sime2SiMe2Cl 1, (7/5- CsMe4Et)Mo(CO)3SiMe2SiMe2Br 2, (r/5-CsMe4Et)Fe(CO)2(SiMe2)6(CO)2Fe(r/5-CsMe4Et) 3 and (r/s-CsMe4Et)Fe(CO)2(SiMe2)6Br 4 were prepared and characterized. Compound 1 is well crystallized from pentane and its structure has been determined by X-ray diffraction analysis. © 1997 Elsevier Science S.A. Keywords: Iron; Molybdenum; Oligosilanes; Transition metal silicon compounds Within the last few years transition metal silicon complexes with silane ligands have been the focus of much a_rtention [1]. The chemistry of transition metal silylene complexes is researched very intensively [2]. Furthermore, triphonylsilyl and tris(trimethylsilyl)silyl ligands are applied to stabilize transition metal com- pounds due to their steric properties [3] (also, see for instance Ref. [4]). Transition metal silicon compounds are useful as precursors in metal silicide CVD processes [5], they are involved in a number of syntheses, for instance in hydrosilylation reactions [6], and in o-bond metathesis processes [7] like the catalytic dehydrocoupling of silanes [8]. Organosilicon polymers in which silicon atoms are joined with transition metals represent an area of considerable current interest, since unusual physical and chemical properties are to be expected of the resul- tant materials [9]. The chemistry of transition metal oligosilanes, i.e. one transition metal centre bonded to a chain with at least two silicon atoms, is not very well explored. There are a number of c o ~ of this type derived from CpFe(CO) 2 (Fp) [10]. The Fp-fragnmnt seems to be an ideal substrate to join with oligosilanes, * Corresponding author. 0022-328X/97/$17.00 © 1997 Elsevier Science S.A. All fights reserved. PII S0022-328X(97)00106-X but there exist only a few examples of transition metal oligosilanes with transition metal centres other than iron [11,12]. In 1974, Malisch reported about the difficulties with the production of Group VlB-metal silicon com- pounds [12]. These transition metal substinue~d disilanes are in fact very sensitive to light, heat and air. We are presently re-investigating this area of chemistry and our aim was to ~ mo~-stable and well-crystallized compounds. For this mason we selected ligand systems other than cyclopentadiene, like the steric pretentious ethyltetramethylcyclopentadiene, which should enable us to synthesize transition metal substituted disilanes with improved stability. A conceptually simple way in which an M-Si bond may be formed is the reaction between a metallate complex and a silicon halide with elimination of one equivalent of a salt [13]. Halogeno-oligosilane complexes of the type LnM- (SiMe2)mX (X -- CI, Br) are interesting as synthons for metal-containing polysilanes. For that purpose reactive halide groups are highly recommended. 2.1. Synthesis of (~15-C5 Me4 Et)Fe(CO)2 SiMe2SiMe2CI 1 The reaction of one equivalent of Na[(~ 5- CsMe4Et)Fe(CO)2] with CIMe2SiSiMe2C1 in THF-