Carben- und Carbin-Komplexe des Technetiums und Rheniums - Synthese, Struktur und Reaktionen / Carbene and Carbyne Complexes of Technetium and Rhenium - Synthesis, Structure and Reactions

Abstract

Abstract Synthesis, structure and reactions of technetium and rhenium complexes bearing metal-carbon multiple bonds are reported. Addition of LiPh to Cp*M (CO)3 (1a : M = Tc; 1b: M = Re) (Cp* = η5-C5Me5) in Et2O yields the acyl complexes Li[Cp*(CO)2MC(O)Ph]·Et2O (2a: M = Tc; 2 b: M = Re). These are converted with Et3OBF4 into the carbene complexes Cp*(CO)2M = C(OEt)Ph (3a, 3b). Reaction of 3a and 3 b with BCl3 affords the carbyne complexes [Cp*(CO)2M ≡ CPh]BCl4 (4a, 4b) in high yield. The acyl complex 2b can be directly converted into the carbyne complex [Cp*(CO)2Re ≡ CPh]Br (5b), when it is treated with oxalyl bromide. Nucleophiles add at the carbynecarbon atoms of 4a and 4b, as demonstrated by the reaction with NaOCy (Cy = cyclohexyl) to afford the carbene complexes Cp*(CO)2M = C(OCy)Ph (6a, 6b). Similarly, reaction of P(OMe)3 with [Cp*(CO)2Re ≡ CPh]Cl (5b'), the latter being generated in situ from 2b and oxalyl chloride, gives the ylide complex {Cp*(CO)2Re = C[P(OMe)3]Ph}Cl (7b'). In comparison, addition of P(OMe)3 to [Cp*(CO)2Tc ≡ CPh]Cl (5a'), generated in situ from 2a and oxalyl chloride, induces a carbvne-carbonvl coupling reaction resulting in the formation of the ketenyl complex . Thermolysis of the compounds 2a, 2b, 4a, 4b and 7b' has been studied in vacuo and the products of decomposition identified by IR spectroscopy. The solid-state structure of the carbene complexes 3 a and 3 b was determined by single crystal X-ray diffraction studies. Both compounds crystallize in the monoclinic space group P21/n with very similar unit cell data. Striking feature of the isostructural carbene complexes is the nearly perpendicular orientation of the carbene ligand relative to the Cp* ring.