Phosphine-Stabilized Pnictinidenes.

The reaction of the intramolecular germylene-phosphine Lewis pair (o-PPh2 )C6 H4 GeAr* (1) with Group 15 element trichlorides ECl3 (E=P, As, Sb) was investigated. After oxidative addition, the resulting compounds (o-PPh2 )C6 H4 (Ar*)Ge(Cl)ECl2 (2: E=P, 3: E=As, 4: E=Sb) were reduced by using sodium metal or LiHBEt3 . The molecular structures of the phosphine-stabilized phosphinidene (o-PPh2 )C6 H4 (Ar*)Ge(Cl)P (5), arsinidene (o-PPh2 )C6 H4 (Ar*)Ge(Cl)As (6) and stibinidene (o-PPh2 )C6 H4 (Ar*)Ge(Cl)Sb (7) are presented; they feature a two-coordinate low-valent Group 15 element. After chloride abstraction, a cyclic germaphosphene [(o-PPh2 )C6 H4 (Ar*)GeP] [B(C6 H3 (CF3 )2 )4 ] (8) was isolated. The 31 P NMR data of the germaphosphene were compared with literature examples and analyzed by quantum chemical calculations. The phosphinidene was treated with [iBu2 AlH]2 , and the product of an Al-H addition to the low-valent phosphorus atom (o-PPh2 )C6 H4 (Ar*)Ge(H)P(H)Al(C4 H9 )2 (9) was characterized.

Germaborenes: Borylene Transfer Agents for the Synthesis of Iminoboranes.

Halide and phenyl substituted germaborenes were shown to react with azides at room temperature and transfer a borylene moiety to give iminoboranes. This iminoborane synthesis based on a borylene transfer route was investigated computationally in the case of the phenyl substituted germaborene.

Phosphine-Stabilized Germasilenylidene: Source for a Silicon-Atom Transfer.

A phosphine-stabilized germasilenylidene is synthesized following the pathway of SiCl4 oxidative addition at a germylene-phosphine Lewis pair. Low-temperature reduction using {(MesNacnac)Mg}2 resulted in a chlorosilylene intermediate and finally a molecule exhibiting a Ge═Si: motif. Inside the chelating phosphine-germylene, a low-valent silicon atom is stabilized and was transferred to diazabutadiene to give N-heterocyclic silylenes. Because of the high reactivity of the phosphine-stabilized germasilenylidene, a reaction of two Ge═Si: units was found to yield a Si2Ge2-ring molecule exhibiting a germasilene substituted with a silylene.

Ge=B π-Bonding: Synthesis and Reversible [2+2]†Cycloaddition of Germaborenes.

Phosphine-stabilized germaborenes featuring an unprecedented Ge=B double bond with short B⋅⋅⋅Ge contacts of 1.886(2) (4) and 1.895(3) Š(5) were synthesized starting from an intramolecular germylene-phosphine Lewis pair (1). After oxidative addition of boron trihalides BX3 (X=Cl, Br), the addition products were reduced with magnesium and catalytic amounts of anthracene to give the borylene derivatives in yields of 78 % (4) and 57 % (5). These halide-substituted germaborenes were characterized by single-crystal structure analysis, and the electronic structures were studied by quantum-chemical calculations. According to an NBO NRT analysis, the dominating Lewis structure contains a Ge=B double bond. The germaborenes undergo a reversible, photochemically initiated [2+2] cycloaddition with the phenyl moiety of a terphenyl substituent at room temperature, forming a complex heterocyclic structure with GeIV in a strongly distorted coordination environment.