Abstract
We report the first examples of intramolecular phosphine-stabilized tetra-coordinated germanium(iv) di-cationic compounds: [L(iPr)(2)Ge][CF(3)SO(3)](2)3(iPr) and [L(Ph)(2)Ge][CF(3)SO(3)](2)3(Ph) (L(iPr) = 6-(diisopropylphosphanyl)-1,2-dihydroacenaphthylene-5-ide; L(Ph) = 6-(diphenylphosphanyl)-1,2-dihydroacenaphthylene-5-ide). The step wise synthetic strategy involves the isolation of neutral and mono-cationic Ge(iv) precursors: [L(iPr)(2)GeCl][X] (X = GeCl(3)1(iPr), OTf 2(iPr)), [L(Ph)(2)GeCl(2)] 1(Ph) and [L(Ph)(2)GeCl][OTf] 2(Ph). Both 3(iPr) and 3(Ph) exhibit constrained spiro-geometry. DFT studies reveal the dispersion of di-cationic charges over P-Ge-P sites. Anion or Lewis base binding occurs at the Ge site resulting in relaxed distorted trigonal bipyramidal/tetrahedral geometry. 3(iPr) and 3(Ph) activate the Si-H bond initially at the P-site. The hydride ultimately migrates to the Ge-site rapidly giving [L(Ph)(2)GeH][CF(3)SO(3)] 3(Ph)H, while sluggishly forming [L(iPr)(2)GeH][CF(3)SO(3)] 3(iPr)H. Compounds 3(iPr) and 3(Ph) were tested as catalysts for the hydrosilylation of aromatic aldehydes. While catalytic hydrosilylation proceeded via the initial Et(3)Si-H bond activation in the case of 3(iPr), compound 3(Ph) as a catalyst showed a masked Frustrated Lewis Pair (FLP) type reactivity in the catalytic cycle.