Syntheses, Structures, and Reactivity of Divalent Germanium and Tin Compounds Containing a Diketiminato Ligand

Abstract

In this thesis, diketiminato ligands have been employed as a supporting moiety for germanium and tin compounds. The experimental results demonstrate that steric bulk and additional intramolecular coordination of the ligand can stabilize some unusual and unique compounds. In addition, these compounds may be useful as starting materials for further reactions. The precursors, the Ge (II) chloride [{HC(CMeNAr)2}GeCl], (3) and Sn (II) chloride [{HC(CMeNAr)2}SnCl], (5) were synthesized in high yields and structurally characterized. The single crystal X-ray structures of 3 and 5 shows that both compounds are monomeric. The ligand is chelated to the metals and the metal centers adopt three coordinated sites and reside in distorted tetrahedral environments with one vertex occupied by a lone pair of electrons. This is the basic structural feature of these compounds. [{HC(CMeNAr)2}GeF] (8), the first structural characterized divalent organo germanium fluoride, was synthesized from the reaction of compound 3 with Me3SnF. The reactivity of the electron lone pair on the germanium atom of 8 was examined with Me3SiN3. Treatment of 3 with NaBH4 in THF under reflux led to the formation of [{HC(CMeNAr)2}Ge(H)BH3] (11); for the first time a Ge(II) hydride was prepared successfully. The coordinated BH3 in 11 can be easily removed with PMe3 yielding the free hydride [{HC(CMeNAr)2}GeH] (13). Reaction of 11 with tBuLi in diethyl ether led to [{HC(C(CH2)NAr)CMeNAr}Ge(H)BH3]Li(Et2O)3 (Ar = 2,6-iPr2C6H3) (14), in which a hydrogen of one of the Me groups was eliminated, and this consequently resulted in the formation of a methylene group. Distinct difference in the NMR and IR spectra of compounds 11, 13 and 14 from those of the Ge(IV) congeners were found. Oxidative addition of elemental sulfur to compound 3 gave the example with a formal double bond between group 14 and 16 bearing a halide, [{HC(CMeNAr)2}Ge(S)Cl] (Ar = 2,6-iPr2C6H3 (15)). The fluoro analogue [{HC(CMeNAr)2}Ge(S)F] (16) has been generated by two routes: from 15 by fluorination with Me3SnF or from 8 by oxidative addition with elemental sulfur. The reactivity of 15 was preliminarily investigated using the smallest alkylation reagent MeLi to yield [{HC(CMeNAr)2}Ge(S)Me] (Ar = 2,6-iPr2C6H3 (17)). The so far known structurally characterized double bonded heavier main group elements are bound to bulky ligands. With this reaction a small alkyl group was introduced into such a system for the first time. The chemistry of heavier organoelement main group compounds bearing a halide and a double bond was also successfully extended to the selenium analogues of 15 * 17. The compounds [{HC(CMeNAr)2}Ge(Se)X] (Ar = 2,6-iPr2C6H3, X = Cl (18), F (19), nBu (20)) were obtained and 18 and 20 were structurally characterized. The small alkyl substituted Ge(II) compounds stabilized by a diketiminato ligand, [{HC(CMeNAr)2}GeR] (Ar = 2,6-iPr2C6H3, R = Me (21), nBu (22)), were prepared and their structures determined by single crystal X-ray diffraction analyses. Compounds [{HC(CMeNAr)2}Ge(Se)Me] (23), [{HC(C(CH2)NAr)CMeNAr}Ge(Me)N(H)SiMe3] (24), and [{HC(CMeNAr)2}Ge(Me2)I] (25) were synthesized from 21 and appropriate reaction partners. Selected substrates were reacted with the compound [{HC(CMeNAr)2}SnCl] (5) to synthesize Sn(II) diketiminato complexes with ligands other than chlorine. The resulting derivatives [{HC(CMeNAr)2}2Sn] (26), [{HC(CMeNAr)2}SntBu] (27), [{HC(CMeNAr)2}SnOSO2CF3] (28), and [{HC(CMeNAr)2}SnN3] (29) were fully characterized. The solid state structures of 26 and 28 were determined, and the structure of 27 was derived from its 119Sn NMR.