Pentacoordinate silicon compounds with SiO5 skeletons containing SiOH or SiOSi groups: Derivatives of the pentahydroxosilicate(1-) anion [Si(OH)(5)](-) and its anhydride [(HO)(4)Si-O-Si(OH)(4)](2-)

Three novel pentacoordinate silicon compounds with SiO5 skeletons containin g SiOH or SiOSi groups were synthesized: triethylammonium bis[benzilato(2-) -O-1,O-2]hydroxosilicate (1; isolated as rac-1), anilinium bis[benzilato(2- )-O-1,O-2]hydroxosilicate [2; isolated as a conglomerate consisting of (Lam bda)-2 . THF and (Delta)-2 . THF], and anilinium tetrakis[benzilato(2-)-O-1 ,O-2]-mu-oxo-disilicate (3; isolated as rac-3 . 2CH(3)CN). The lambda(5)Si- hydroxosilicate and lambda(5)Si,lambda(5)Si'-mu-oxo-disilicate anions of th ese salts formally derive from the pentahydroxosilicate-(1-) anion [Si(OH)( 5)](-) and its anhydride [(HO)(4)Si-O-Si(OH)(4)](2-) respectively. All comp ounds were characterized in solution (H-1, C-13 and Si-29 NMR) and in the s olid state (Si-29 VACP/MAS NMR, crystal structure analyses).