Coordination Chemistry of [E(Idipp)]2+ Ligands (E = Ge, Sn): Metal Germylidyne [Cp*(CO)2W≡Ge(Idipp)]+ and Metallotetrylene [Cp*(CO)3W-E(Idipp)]+ Cations

The synthesis and full characterization of the NHC-stabilized tungstenochlorostannylene [Cp*(CO)(3)W-SnCl-(Idipp)] (1Sn), the NHC-stabilized chlorogermylidyne complex [Cp*(CO)(2)W=GeCl(Idipp)] (2), the tungsten germylidyne complex salt [Cp*(CO)(2)W equivalent to Ge(Idipp)][B(C6H3-3,5-(CF3)(2))(4)] (3), and the cationic metallostannylene [Cp*(CO)(3)W-Sn-(Idipp)][Al(OC(CF3)(3))(4)] (4Sn) are reported (Idipp = 2,3-dihydro -1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-2-ylidene, Cp* = eta(5)-C5Me5). Metathetical exchange of SnCl2(Idipp) with Li[Cp*W(CO)(3)] afforded selectively 1Sn. Photolytic decarbonylation of the Ge analogue [Cp*(CO)(3)W-GeCl(Idipp)] (1Ge) afforded the NHC-stabilized chlorogermylidyne complex (2), featuring a trigonal-planar coordinated germanium center and a W-Ge double bond (W-Ge 2.3496(5) (A) over circle). Chloride abstraction from 2 with Na[B(C6H3-3,5-(CF3)(2))(4)] yielded the germylidyne complex salt 3, which contains an almost linear W-Ge-Cl linkage (angle at Ge = 168.7(1)degrees) and a W-Ge triple bond (2.2813(4) (A) over circle). Chloride elimination from 1Ge afforded the tungstenogermylene salt [Cp*(CO)(3)W-Ge(Idipp)][B(C6H3-3,5-(CF3)(2))(4)] (4Ge), which in contrast to 1Ge could not be decarbonylated to form 3 despite the less strongly bound carbonyl ligands. The tin compounds 1Sn and 4Sn did not afford products bearing multiple W-Sn bonds. Treatment of 4Ge with Me2NC=-CNMe2 yielded unexpectedly the neutral germyl complex 5 containing a pendant 1-germabicyclo-[3,2,0]-hepta-2,5-diene ligand instead of the anticipated [2 + 1]-cycloaddition product at the Ge-center.