From tetragermacyclobutene to tetragermacyclobutadiene dianion to tetragermacyclobutadiene transition metal complexes.

The reaction of 3,4-dichlorotetragermetene derivative 2 with Na(2)[Fe(CO)(4)] in THF produced a (tetragermacyclobutadiene)tricarbonyliron complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]Fe(CO)(3)4, which has a slightly folded Ge(4) ring perhaptocoordinated to the Fe center. Structural and spectral characteristics of 4 show a remarkable π-donating ability of the tetragermacyclobutadiene ligand toward the transition metal, surpassing that of tetrasilacyclobutadiene and cyclobutadiene ligands. Reduction of 2 with KC(8) resulted in exclusive formation of the dipotassium salt of the tetragermacyclobutadiene dianion derivative 3(2-)·[K(+)(thf)(2)](2), representing a rare example of a 6π-electron compound that, on the basis of its structural and magnetic properties, was recognized as a nonaromatic species.

A two-and-a-half-layer sandwich: potassium salt of anionic (η(4)-tetrasilacyclobutadiene)(η(5)-cyclopentadienyl)ruthenium.

An anionic ruthenium sandwich complex featuring the tetrasilacyclobutadiene ligand, [η(4)-tetrakis(di-tert-butylmethylsilyl)tetrasilacyclobutadiene](η(5)-pentamethylcyclopentadienyl)ruthenium was synthesized and isolated as its potassium salt [(η(4)-R(4)Si(4))RuCp*](-)·[K(+)(thf)(2)] (R = SiMet-Bu(2), Cp* = η(5)-Me(5)C(5)), 1(-)·[K(+)(thf)(2)], by the reaction of the tetrasilacyclobutadiene dianion dipotassium salt [R(4)Si(4)](2-)·[K(+)(thf)(2)](2) with 0.25 equiv. of [Cp*RuCl](4) in THF.

Base-free molybdenum and tungsten bicyclic silylene complexes stabilized by a homoaromatic contribution.

Unprecedented base-free bicyclic silylene complexes of molybdenum and tungsten 3a,b (a, M = Mo; b, M = W) were prepared by the reaction of the calcium salt of 1,2,3,4-tetrakis(di-tert-butylmethylsilyl)tetrasilabicyclo[1.1.0]butane-2,4-diide 2(2-) x Ca(2+) with Cp(2)MCl(2) (M = Mo, W).

Tetrasilacyclobutadiene ((t)Bu(2)MeSi)(4)Si(4): a new ligand for transition-metal complexes.

The anionic complex of [tetrakis(di-tert-butylmethylsilyl) tetrasilacyclobutadiene]dicarbonylcobalt, [(R4Si4)Co(CO)2]-.K+ (R = SiMetBu2) 2-.K+, was synthesized by the reaction of tetrasilacyclobutadiene dianion dipotassium salt [R4Si4]2-.

Cyclobutadiene dianions consisting of heavier group 14 elements: synthesis and characterization.

The first "heavy" cyclobutadiene dianions (CBD2-), tetrakis(di-tert-butylmethylsilyl)-1,2-disila-3,4-digermacyclobutadiene dianion 22- and tetrakis(di-tert-butylmethylsilyl)tetrasilacyclobutadiene dianion 42-, have been synthesized by the reductive dehalogenation of the corresponding precursors with potassium graphite in THF. Structural characterization of [K+(thf)2]2.22- and [K+(thf)2]2.

A chemical trick: how to make a digermene from a disilene, formation of 3delta-1,2,3,4-disiladigermetene.

The unexpected reaction of tetrakis[di-tert-butyl(methyl)silyl]disilagermirenes (1a and 1b) with GeCl2.dioxane results in the quantitative formation of trans-1,2-dichloro-1,2,3,4-tetrakis[di-tert-butyl(methyl)silyl]-3Delta-1,2,3,4-disiladigermetene, 2, representing the first cyclotetrametallene containing two different heavier group 14 elements and the first digermene incorporated in a four-membered ring. trans-1,2-Dichloro-1,2,3,4-tetrakis[di-tert-butyl(methyl)silyl]-3Delta-1,2,3,4-disilagermastannetene (8), with a Ge=Sn double bond, was also prepared by the reaction of 1 with SnCl2.