The majority of cytochrome P450 enzymes (CYPs) predominantly operate as monooxygenases, but recently a class of P450 enzymes was discovered, that can act as peroxygenases (CYP152). These enzymes convert fatty acids through oxidative decarboxylation, yielding terminal alkenes, and through α- and β-hydroxylation to yield hydroxy-fatty acids. Bioderived olefins may serve as biofuels, and hence understanding the mechanism and substrate scope of this class of enzymes is important. In this work, we report on the substrate scope and catalytic promiscuity of CYP OleTJE and two of its orthologues from the CYP152 family, utilizing α-monosubstituted branched carboxylic acids. We identify α,β-desaturation as an unexpected dominant pathway for CYP OleTJE with 2-methylbutyric acid. To rationalize product distributions arising from α/β-hydroxylation, oxidative decarboxylation, and desaturation depending on the substrate’s structure and binding pattern, a computational study was performed based on an active site complex of CYP OleTJE containing the heme cofactor in the substrate binding pocket and 2-methylbutyric acid as substrate. It is shown that substrate positioning determines the accessibility of the oxidizing species (Compound I) to the substrate and hence the regio- and chemoselectivity of the reaction. Furthermore, the results show that, for 2-methylbutyric acid, α,β-desaturation is favorable because of a rate-determining α-hydrogen atom abstraction, which cannot proceed to decarboxylation. Moreover, substrate hydroxylation is energetically impeded due to the tight shape and size of the substrate binding pocket.

The reactions of a number of rare-earth (RE) trichlorides and an oligosilanylene diide containing a siloxane unit in the backbone in DME are described. The formed products of the type [(DME) 4 ·K][(DME)·RE(Cl) 2 {Si(SiMe 3 ) 2 SiMe 2 } 2 O] (RE = Y, La, Ce, Pr, Sm, Tb, Dy, and Er) are disilylated dichloro metalate complexes and include the first examples of Si–La and Si–Pr compounds as well as the first structurally characterized example of a Si–Dy complex. A most intriguing aspect of the synthesis of these complexes is that they offer entry into a systematic study of the still largely unexplored field of silyl RE complexes by the possibility of ligand exchange reactions under preservation of the Si–RE interaction. This was demonstrated by the conversion of [(DME) 4 ·K][(DME)·RE(Cl) 2 {Si(SiMe 3 ) 2 SiMe 2 } 2 O] to [(DME) 4 ·K][Cp 2 Y{Si(SiMe 3 ) 2 SiMe 2 } 2 O].

Extending the chemistry of disilene fluoride adducts studied earlier by us, we investigated the formation of 1,1-bis(trimethylsilyl)fluorodiphenylsilylsilanide, which was prepared by reaction of (Me 3 Si) 3 SiSiPh 2 F with KO t Bu. The formed FPh 2 SiSi(Me 3 Si) 2 K displays distinctively different structural and spectroscopic features compared to the earlier reported F(Me 3 Si) 2 SiSi(SiMe 3 ) 2 K. While the latter eliminates metal fluoride upon reaction with MgBr 2 , the respective magnesium silanide is formed from FPh 2 SiSi(Me 3 Si) 2 K. Reaction of (Me 3 Si) 3 SiSiPh 2 Cl with KO t Bu proceeded similarly, but the formed ClPh 2 SiSi(Me 3 Si) 2 K easily undergoes potassium chloride elimination to the disilene Ph 2 SiSi(SiMe 3 ) 2 . Compared to F(Me 3 Si) 2 SiSi(SiMe 3 ) 2 K, which can be regarded as a disilene fluoride adduct, structural, spectroscopic, and reactivity properties of FPh 2 SiSi(Me 3 Si) 2 K distinguish it as a β-fluorodisilanide.

Our recent study on formal halide adducts of disilenes led to the investigation of the synthesis and properties of β-fluoro- and chlorodisilanides. The reaction of the functionalized neopentasilanes (Me3Si)3SiSiPh2NEt2 and (Me3Si)3SiSiMe2OMe with KOtBu in the presence of 18-crown-6 provided access to structurally related β-alkoxy- and amino-substituted disilanides. The obtained Et2NPh2Si(Me3Si)2SiK·18-crown-6 was converted to a magnesium silanide and further on to Et2NPh2Si(Me3Si)2Si-substituted ziroconocene and hafnocene chlorides. In addition, an example of a silanide containing both Et2NPh2Si and FPh2Si groups was prepared with moderate selectivity. Also, the analogous germanide Et2NPh2Si(Me3Si)2GeK·18-crown-6 could be obtained.

Reaction of a 2,5‐dilithiated silole with excess dichlorodimethylsilane gives the respective 2,5‐bis(chlorodimethylsilyl) substituted silole. This compound can be converted to 2,5‐bis(oligosilanyl) substituted siloles by addition of a suitable oligosilanide. In the UV spectra of the thus obtained compounds the lowest energy absorptions are bathochromically shifted compared to the absorptions of the two constituents, namely the 2,5‐disilyl substituted silole and a trisilane. The bathochromic shift is interpreted as being caused by a mixed σ‐conjugation/cross‐hyperconjugation. This assumption is supported by TD‐DFT calculations, which show a significant contribution from Si−Si bonds to the HOMO of the molecule.