Reactions of Late First-Row Transition Metal (Fe-Zn) Dichlorides with a PGeP Pincer Germylene.

The reactivity of the PGeP germylene 2,2'-bis(di-isopropylphosphanylmethyl)-5,5'-dimethyldipyrromethane-1,1'-diylgermanium(II), Ge(pyrmPiPr2 )2 CMe2 , with late first-row transition metal (Fe-Zn) dichlorides has been investigated. All reactions led to PGeP pincer chloridogermyl complexes. The reactions with FeCl2 and CoCl2 afforded paramagnetic square planar complexes of formula [MCl{κ3 P,Ge,P-GeCl(pyrmPiPr2 )2 CMe2 }] (M=Fe, Co). While the iron complex maintained an intermediate spin state (S1 ; μeff =3.0 μB ) over the temperature range 50-380 K, the effective magnetic moment of the cobalt complex varied linearly with temperature from 1.9 μB at 10 K to 3.6 μB at 380 K, indicating a spin crossover behavior that involves S1/2 (predominant at T<180 K) and S3/2 (predominant at T>200 K) species. Both cobalt(II) species were detected by electron paramagnetic resonance at T<20 K. The reaction of Ge(pyrmPiPr2 )2 CMe2 with [NiCl2 (dme)] (dme=dimethoxyethane) gave a square planar nickel(II) complex, [NiCl{κ3 P,Ge,P-GeCl(pyrmPiPr2 )2 CMe2 }], whereas the reaction with CuCl2 involved a redox process that rendered a mixture of the germanium(IV) compound GeCl2 (pyrmPiPr2 )2 CMe2 and a binuclear copper(I) complex, [Cu2 {μ-κ3 P,Ge,P-GeCl(pyrmPiPr2 )2 CMe2 }2 ], whose metal atoms are in tetrahedral environments. The reaction of the germylene with ZnCl2 led to the tetrahedral derivative [ZnCl{κ3 P,Ge,P-GeCl(pyrmPiPr2 )2 CMe2 }].