Photodriven Elimination of Chlorine From Germanium and Platinum in a Dinuclear Pt^II→Ge^IV Complex

Abstract

Searching for a connection between the two‐electron redox behavior of Group‐14 elements and their possible use as platforms for the photoreductive elimination of chlorine, we have studied the photochemistry of [(o‐(Ph2P)C6H4)2GeIVCl2]PtIICl2 and [(o‐(Ph2P)C6H4)2ClGeIII]PtIIICl3, two newly isolated isomeric complexes. These studies show that, in the presence of a chlorine trap, both isomers convert cleanly into the platinum germyl complex [(o‐(Ph2P)C6H4)2ClGeIII]PtICl with quantum yields of 1.7 % and 3.2 % for the GeIV–PtII and GeIII–PtIII isomers, respectively. Conversion of the GeIV–PtII isomer into the platinum germyl complex is a rare example of a light‐induced transition‐metal/main‐group‐element bond‐forming process. Finally, transient‐absorption‐spectroscopy studies carried out on the GeIII–PtIII isomer point to a ligand arene–Cl. charge‐transfer complex as an intermediate.

Photoreductive Elimination of PhCl Across the Dinuclear Core of a [GePt]VI Complex

“…The same geometrical constraints affect the tetrahedral coordination geometry of the germanium atom as indicated by the larger than expected C6− Ge−C20 angle of 118.08(7)°. The Pt−Ge and Pt−Cl bond distances of 2.3572(5) and 2.3915(7) Å are similar to those of the previously reported complex 1-Cl (2.3338(4) and 2.3891(8) Å, respectively), 7 as well as the PGeP pincer complexes E and F (Figure 2) reported by Cabeza (Pt−Ge distances 2.3017(5) Å and 2.3140(8) Å), 10,11 as well as that seen in [ClPtGe(o-dppp) 3 ] (G, Figure 2) described by Braun (Ge−Pt distance = 2.3545(2) Å). 12 Oxidation of 1-Ph with one equivalent of PhICl 2 in CH 2 Cl 2 affords the target complex 2-Ph quantitatively.…”

“…The Pt−Ge bond length of 2.4135(8) Å in this complex is slightly longer than that in 2-Cl (2.3892(6) Å), and the Pt−Cl1 and Pt−Cl3 bond lengths of 2.3213(17) Å and 2.3353(16) Å are similar to the corresponding distances in 2-Cl (2.3472(11) Å and 2.3075(11) Å, respectively). 7 The stronger trans influence of the germyl moiety, however, results in the Pt−Cl2 linkage (2.4718(16) Å) being longer than the other Pt−Cl bonds, similar to the effect observed in its analog 2-Cl. 7 Analysis of the electronic structure of 1-Ph using the Natural Bond Orbital (NBO) method shows that the Pt−Ge σ-bond is mainly covalent (Figure 3c).…”

“…7 The stronger trans influence of the germyl moiety, however, results in the Pt−Cl2 linkage (2.4718(16) Å) being longer than the other Pt−Cl bonds, similar to the effect observed in its analog 2-Cl. 7 Analysis of the electronic structure of 1-Ph using the Natural Bond Orbital (NBO) method shows that the Pt−Ge σ-bond is mainly covalent (Figure 3c). In fact, a Natural Localized Molecular Orbital (NLMO) analysis indicates that contributions from Ge (46.02%) and Pt (53.98%) are close to one another, further supporting the covalent nature of this bond.…”

“…As an entry point, we targeted complex 1-Ph (Figure 1). dppp) 2 GeCl]PtCl (2-Cl), 7 which shows a single peak at 57.8 ppm ( 1 J Pt−P = 2885 Hz), as well as the PGeP pincer complex [PtCl{κ 3 P,Ge,P-GeCl(NCH 2 P t Bu 2 ) 2 C 6 H 4 }] (E, Figure 2)…”

“…6 A similar observation was made in the case of the Pt II − Ge IV system D, which can be photoreduced into 1-Cl, presumably through the intermediacy of 2-Cl (Figure 1). 7 To better understand the role played by the germanium substituents in these complexes, we have now decided to synthesize and investigate the properties 2-Ph, an analog of 2-Cl in which the germanium-bound chlorine atom is replaced by a phenyl group.…”