Alternativ-Liganden XXXVIII. [1] Neue Versuche zur Synthese von Pd(0)- und Pt(0)-Komplexen des Tripod-Phosphanliganden FSi(CH₂CH₂PMe₂)₃ / Alternative Ligands XXXVIII. [1] Further Attempts to Synthesize Pd(0) and Pt(0) Complexes with the Tripod Phosphane Ligand FSi(CH₂CH₂PMe₂)₃

Abstract

The tripod phosphane ligand FSi(CH 2 CH 2 PMe 2 ) 3 (1) has been prepared again and attempts to generate F 3 CSi(CH 2 CH 2 PMe 2 ) 3 (2) were undertaken for the preparation of transition metal cage compounds of the type A(CCP) 3 M or A(CCP) 3 M-L (A = FSi, F 3 CSi). The photochemical addition of dimethylphosphane to trifluoromethyl-trivinylsilane, however, gave 1 instead of the expected CF 3 Sitripod ligand 2, obviously due to difluorocarbene elimination. 1 was used to prepare the chromium carbonyl derivative (CO) 3 Cr[(Me 2 PCH 2 CH 2 ) 3 SiF] (3) from Cr(CO) 3 CHT, and 3 was characterized by NMR and IR spectroscopy. The novel complex FSi(CH 2 CH 2 PMe 2 ) 3 Pd (4) and its PPh 3 derivative [FSi(CH 2 CH 2 PMe 2 ) 3 Pd]PPh 3 (5) have been obtained by reacting 1 with Pd(PPh3)4 and were characterized by NMR (4) and X-ray diffraction (5). The data prove the expected Pd→Si interaction by characteristic coordination shifts and a Pd-Si distance of 3.875 Å which is smaller than the Ni-Si distance in the corresponding nickel compound (3.92 Å ). The preparation of the analogous platinum complex from the precursors Pt(PPh 3 ) 4 , Pt(C 7 H 10 ) 3 , or (Ph 3 P) 2 Pt(η 2 -C 2 H 4 ) failed, whereas the reaction of 1 with Pt(PEt 3 ) 4 was successful, but surprisingly led to the trinuclear complex [FSi(CH 2 CH 2 PMe 2 ) 3 Pt] 3 (PMe 2 CH 2 CH 2 ) 3 SiF (6) with three cages of type 4 and an additional ligand 1 as a bridging unit. Complex 6 was isolated and characterized spectroscopically. Quantum chemical calculations have been used to elucidate the coordination geometry expected for 4, 5 and the corresponding platinum cage 4′ in 6. The calculations support the structure of 5 within the expected limitations of the experimental and theoretical methods and - in spite of the extremely soft coordination sphere of the studied cages - are in accord with the spectroscopic results.