om5005918_si_002.cif (83.62 kB)

From Unsymmetrically Substituted Benzamidinato and Guanidinato Dichlorohydridosilanes to Novel Hydrido N‑Heterocyclic Silylene Iron Complexes

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posted on 13.10.2014, 00:00 by Burgert Blom, Markus Pohl, Gengwen Tan, Daniel Gallego, Matthias Driess
Starting from the unsymmetric N,N′-substituted thiourea compounds (R)­N­(H)­C­(S)­N­(H)­(tBu) (1, R = Dipp: 2,6-iPr2-C6H3; 2, R = 1-adamantyl), the corresponding asymmetric carbodiimines (R)­NCN­(tBu) (3, R = Dipp; 4, R = 1-adamantyl) are readily accessible in high yields upon reduction with LiHMDS (Li­[N­(SiMe3)2]). The reaction of compound 3 with PhLi followed by SiCl4 afforded, in a one-pot reaction, the asymmetric benzamidinato-stabilized trichlorosilane [PhC­{(NtBu)­(NDipp)}]­SiCl3 (5). Similarly, silanes [PhC­{(NtBu)­(NDipp)}]­SiHCl2 (6), [(NMe2)­C­{(NtBu)­(NDipp)}]­SiHCl2 (7), and [PhC­{(NtBu)­(NAd)}]­SiHCl2 (8) could also be isolated. All novel trichloro- or dichlorohydridosilanes were fully spectroscopically characterized and studied by single-crystal X-ray diffraction analyses, the latter revealing in all cases a distorted-trigonal bipyramidal five-coordinate silicon center. The reactions of silanes 58 with K2[Fe­(CO)4] were also explored: In the case of the reaction of silane 5 with K2[Fe­(CO)4], no reaction was observed even after prolonged heating. However, in the case of the silanes 68, the selective formation of the corresponding hydrido SiII:→Fe0 complexes [[R1C­{(NtBu)­(NR2)}]­(H)­Si:→Fe­(CO)4] (9, R1 = Ph, R2 = Dipp; 10, R1 = NMe2, R2 = Dipp; 11, R1 = Ph, R2 = 1-adamantyl) could be achieved. Complexes 911 represent unprecedented hydrido-N-heterocyclic silylene complexes, bearing asymmetric ligand backbones. Complexes 911 were fully spectroscopically characterized, and in addition the single-crystal X-ray structure analysis of compound 10 is reported.