A dinuclear palladium complex haVing bridging diphenylgermyl ligands, [{Pd(PCy 3 )} 2 (µ-HGePh 2 ) 2 ] (1), was obtained from the reaction of Ph 2 GeH 2 with [Pd(PCy 3 ) 2 ]. X-ray crystallographic results and NMR spectra of 1 reVealed coordination of the Ge ligands to two Pd centers Via a Ge-H-Pd three-center-two-electron bond and a Ge-Pd σ bond. The reaction of Ph 2 GeH 2 with [Pt(PCy 3 ) 2 ] produces the (germyl)hydridoplatinum complexes cis-[Pt(H)(GeHPh 2 )(PCy 3 ) 2 ] (cis-3) and trans-[Pt(H)(GeHPh 2 )(PCy 3 ) 2 ] (trans-3) as the kinetic and thermodynamic products, respectiVely.

A complex with a planar hexagonal Pd(4)Ge(3) core, [Pd{Pd(dmpe)}(3)(μ(3)-GePh(2))(3)], was synthesized and characterized by X-ray and NMR measurements as well as by DFT calculations. 4-tert-Butylbenzenethiol converted the Pd(4) complex into a hexapalladium complex, [{Pd(3)(μ-GePh(2))(2)(μ-H)(μ(3)-GePh(2)(SC(6)H(4)(t)Bu-4))}(2)(μ-dmpe)], composed of two Pd(3)Ge(3) units bridged by a dmpe ligand. The addition of CuI or AgI to the Pd(4) complex yielded [Pd(μ-MI){Pd(dmpe)}(3)(μ(3)-GePh(2))(3) ] (M = Cu, Ag), in which Cu or Ag bridges a Pd-Pd bond of the Pd(4)Ge(3) core. The CuI adducts in solution undergo a pivot motion of the CuI on the surface of the Pd(4)Ge(3) plane on the NMR time scale.

Heating a toluene solution of bis(germyl)palladium complex [Pd(GeHPh2)2(dmpe)] (2) (dmpe = 1,2-bis(dimethylphosphino)ethane) at 70 °C produced a mixture of dipalladium complexes, one with bridging digermene and germylene ligands, [{Pd(dmpe)}2(μ-GePh2)(μ-Ge2Ph4)] (3), and also a mononuclear tetragermapalladacyclopentane, [Pd(GePh2GePh2GePh2 GePh2)(dmpe)] (4), in 92:8 molar ratio, respectively. The reaction of H2GePh2 with 2 in 10:1 molar ratio formed complex 4 as the main product (3:4 = 4:96). Complexes 3 and 4 were isolated from the above reactions and characterized by X-ray crystallography and NMR spectroscopy. Complex 3 reacted with H2GePh2 (Pd:Ge = 1:10) at 80 °C to yield 4 quantitatively, whereas simple heating of 3 at the same temperature did not form 4 at all. Reaction pathways for the Ge−Ge bond formation are discussed.

The dinuclear palladium(I) complexes [L(Ar2 HGe)Pd(μ-GeAr2 )2 Pd(GeHAr2 )L] (Ar=Ph, p-Tol; L=PMe3 , tBuNC) contain terminal germyl and bridging germylene ligands with the experimentally observed Ge⋅⋅⋅Ge bond lengths of 2.8263(4) Å (L=PMe3 ) and 2.928(1) Å (L=tBuNC), which are close to the longest Ge-Ge bond reported to date [2.714(1) Å]. Significant Ge⋅⋅⋅Ge interactions between the germylene and germyl ligands (PMe3 complexes > tBuNC complexes) are supported by DFT calculations, Wiberg bond indices (WBI), and natural bond orbital (NBO) analyses. Exchanging tBuNC for PMe3 ligands increases the Ge⋅⋅⋅Ge interaction, and simultaneously activates two Pd-Ge bonds. Adding the chelating diphosphine 1,2-bis(diethylphosphino)ethane (depe) to the PMe3 complexes results in the intramolecular coupling of germyl and germylene ligands followed by extrusion of a digermane.

The bis(germyl)platinum complex [Pt(GeHPh2)2(dmpe)] (1) (dmpe = 1,2-bis(dimethylphosphino)ethane) reacts with a small excess of H2GePh2 at 90 °C to produce four-membered germaplatinacycle [Pt(GePh2GePh2 GePh2)(dmpe)] (2). Further reaction of 2 with excess H2GePh2 at 90 °C forms tetragermaplatinacyclopentane [Pt(GePh2GePh2GePh2 GePh2)(dmpe)] (3), while 3 is obtained also by the direct reaction of excess H2GePh2 with 1 for a prolonged period. Complexes 1−3 were characterized by X-ray crystallography and NMR spectroscopy. Germaplatinacycles 2 and 3 react with H3GePh to cause cleavage of the Pt−Ge bonds and formation of the oligogermanes H(GePh2)3H and H(GePh2)4H, respectively.