From a Diphosphanegermylene to Nickel, Palladium, and Platinum Complexes Containing Germyl PGeP Pincer Ligands

The PGeP pincer-type germylene Ge(NCH₂ PtBu₂ )C₆ H₄ (1) has been used to prepare a family of group 10 metal complexes, namely, [MCl{κ³ P,Ge,P-GeCl(NCH₂ PtBu₂ )₂ C₆ H₄ }] (M=Ni (2_Ni ), Pd (2_Pd ), Pt (2_Pt )), featuring a chloridogermyl PGeP pincer ligand and a Cl-Ge-M-Cl bond sequence. Their reactivity is not initially centered on the metal atom but on their Ge atom. Complexes 2_Ni and 2_Pd easily led to the hydrolyzed products [Ni₂ Cl₂ {μ-(κ³ P,Ge,P-Ge(NCH₂ PtBu₂ )₂ C₆ H₄ )₂ O}], which features a Cl-Ni-Ge-O-Ge-Ni-Cl bond sequence, and [PdCl{κ³ P,Ge,P-Ge(OH)(NCH₂ PtBu₂ )₂ C₆ H₄ }], which contains a hydroxidogermyl PGeP pincer ligand (2_Pt is reluctant to undergo hydrolysis). Simple chloride exchange reactions led to the methoxidogermyl, methylgermyl, and phenylgermyl derivatives [MCl{κ³ P,Ge,P-GeR(NCH₂ PtBu₂ )₂ C₆ H₄ }] (M=Pd, Pt; R=OMe, Me, Ph). Whereas the palladium complexes [PdCl{κ³ P,Ge,P-GeR(NCH₂ PtBu₂ )₂ C₆ H₄ }] (R=Me, Ph) reacted with more MeLi or PhLi to give palladium black and GeR₂ (NCH₂ PtBu₂ )₂ C₆ H₄ (R=Me, Ph), similar reactions with the analogous platinum complexes afforded the transmetalation derivatives [PtR{κ³ P,Ge,P-GeR(NCH₂ PtBu₂ )₂ C₆ H₄ }] (R=Me, Ph). The short length of the CH₂ PtBu₂ arms of the PGeP pincer ligands forces the metal atoms of all these complexes to be in a very distorted square-planar ligand environment. The reactivity results have been rationalized with theoretical calculations.