Abiotic and biotic degradation of five aromatic organosilicon compounds in aqueous media-Structure degradability relationships.

Silicones have many applications and are produced in large quantities. Despite their potential toxicity, information on their environmental mineralisation is scarce. Therefore, we investigated a group of five organosilicon compounds (o-MeOCHSiMe (1), p-MeOCHSiMe (2), (p-MeOCH)SiMe (3), o-MeNCHSiMe (4) and p-MeNCHSiMe (5)), recently developed to be 'benign by design' based on their readily degradable core structure.

Reversible transformation of a stable monomeric silicon(II) compound into a stable disilene by phase transfer: experimental and theoretical studies of the system {[(Me3Si)2N](Me5C5)Si}n with n = 1,2.

The salt (eta(5)-pentamethylcyclopentadienyl)silicon(II) tetrakis(pentafluorophenyl)borate (5) reacts at -78 degrees C with lithium bis(trimethylsilyl)amide in dimethoxyethane (DME) as solvent to give quantitatively the compound [bis(trimethylsilyl)amino][pentamethylcyclopentadienyl]silicon(II) 6A in the form of a colorless viscous oil. The reaction performed at -40 degrees C leads to the silicon(IV) compound 7, the formal oxidative addition product of 6A with DME. Cycloaddition is observed in the reaction of 6A with 2,3-dimethylbutadiene to give the silicon(IV) compound 8.

Novel pi-complexes of divalent silicon: mixed substituted neutral sandwich compounds and the half-sandwich cation (iPr5C5)Si+.

The pentamethylcyclopentadienylsilicon(II) cation, Me5C5Si+, opens up access to novel silicocene derivatives; the penta-iso-propylcyclopentadienylsilicon(II) cation, iPr5C5Si+, is obtained by reaction of the mixed silicocene (iPr5C5)(Me5C5)Si with H(OEt2)2+ Al[OC(CF3)3]4-.

The (Me5C5)Si+ cation: a stable derivative of HSi+.

The reaction of decamethylsilicocene, (Me5C5)2Si, with the proton-transfer reagent Me5C5H2+B(C6F5)4- produces the salt (Me5C5)Si+ B(C6F5)4(2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic pi complex with an eta5-pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29Si nuclear magnetic resonance at very high field (delta = - 400.