The first silyl- and germylboryl complexes: synthesis from novel (dichloro)silyl- and (dichloro)germylboranes, structure and reactivity

A series of silyl- and germyl( dichloro) boranes Cl2B-ER3(5, ER3=Si(SiMe3)(3); 6, ER3=Ge(SiMe3)(3); 7, ER3=Si(SiMe3)(2)-Si(SiMe3)(3); 8, ER3=SiPh3) was obtained in good yields from the corresponding bis(dimethylamino) boranes (Me2N)(2)B-ER3(1, ER3=Si(SiMe3)(3;) 2, ER3=Ge(SiMe3)(3); 3, ER3=Si(SiMe3)(2)-Si(SiMe3)(3); 4, ER3=SiPh3) upon reaction with BCl3, and fully characterised in solution. These compounds proved to be versatile starting materials for the synthesis of the first silyl- and germylboryl complexes by salt elimination reactions starting from anionic transition metal complexes of the type Na[(eta(5)-C5R5)Fe(CO)(2)] and K[(eta(5)-C5R5)Mn(H)(CO)(2)]. The novel iron and manganese boryl complexes [(eta(5)-C5R4R')(OC)(2)Fe-B(Cl)Si(SiMe3)(3)] (9a, R=R'=H; 9b, R=H, R'=Me; 9c, R=R'=Me), [(eta(5)-C5H5)(OC)(2)Fe-B(Cl)Ge(SiMe3)(3)] (9d), [(eta(5)-C5H5)(OC)(2)Fe-B(Cl)Si(SiMe3)(2)Si(SiMe3)(3)] (9e), [(eta(5)-C5H4Me)(OC)(2)(H)Mn-B(Cl)Si(SiMe3)(3)] (10a) and [(eta(5)-C5H4Me)(OC)(2)(H)Mn-B(Cl)Ge(SiMe3)(3)](10b) were obtained in yields between 35 and 70%, fully characterised in solution and in the case of 9a, d, and 10a also in the crystalline state. They are all characterised by metal-boron sigma-bonds without indication of any metal-to-boron pi-backdonation. There is, however, spectroscopical and structural evidence for the presence of a Mn-H-B bridge in the case of the manganese complexes 10a, b. The first transhalogenation of a metal coordinated boryl ligand was achieved by reaction of 9a with TlF affording the fluoroboryl complex [(eta(5)-C5H5)(OC)(2)Fe-B(F)Si(SiMe3)(3)] (11), which was characterised in solution and in the solid state.