Abstract Depending on the solvent and the bulkiness of the substituents, Iithiated aminofluorosilanes are dimers, monomers, or LiF-adducts of iminosilanes. In the crystal structure of the dimeric lithium derivative of di-tert-butyl(rm-butylamino)fluorosilane, each lithium atom is coordinated by one fluorine and two nitrogen atoms. LiF-elimination leads - if sterically possible - to dimerisation. The limits of dimerisation are reached with the dimer diisopropyl(tri-tert-butylphenyI- imino)silane, for which the crystal structure analysis shows severe steric distortions. Fluorine- chlorine-cxchange occurs in reactions of lithiated (tri-tert-butylphenylimino)fluorosilanes with Me3SiCl. Iminosilanes are obtained by thermal LiCl-elimination from the resulting salts.

(PhAsNSN)2 (1) reacts with M(CO)4(C7H8) (M = a Cr. b Mo) to yield (PhAsNSN)2M(CO)4 (2). 2a and 2b are dark red air stable complexes. 2b was characterized by X-ray diffraction. Crystals of 2b are monoclinic, space group C2/c, with a = 2884.7(4). b = 1166.2(2), c = 1344.1(2) pm, fβ = 104.81(2)° and Z = 8. The molecule exhibits approximate mm (C2v) symmetry with mean bond lengths: Mo-As 255.1. Mo-C 201.8. As-N 186.2 and S -N 152.8 pm.

Abstract In an acid medium di-tert-butylsilanediol reacts with acyl chlorides to give the di-tert-butylchlorosilanol (2) and the carboxylic acid. A lithium salt of a silanol-carboxylic acid ester (5) is formed in the reaction of the lithiated diol with 2,2-dimethylpropionyl chloride. 5 reacts with phenylacetyl chloride to give the first mixed dicarboxyl-silane. The crystal structure determination of 5 shows a Li-O-cubane with C = 0 ···Li chelate bonds.

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Lithiation of the aminofluorosilanes (IIIa)‐(IIId) affords iminosilanes.