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Synthesis, structure and reactions of technetium and rhenium complexes are reported bearing metal-carbon multiple bonds. Addition of LiPh to Cp(*)M(CO)(3) (1a: M = Tc; 1b: M = Re) (Cp(*) = eta(5)-C(5)Me(5)) in Et(2)O yields the acyl complexes Li[(*)Cp(CO)(2)MC(O)Ph].Et(2)O (2a: M = Tc; 2b: M = Re). These are converted with Et(3)OBF(4) to the carbene complexes (*)Cp(CO)(2)M=C(OEt)Ph (3a,3b).Reaction of 3a and 3b with BCl(3) affords the carbyne complexes [(*)Cp(CO)(2)M=CPh]BCl(4) (4a,4b) in high yield. The acyl complex can be directly converted to the carbyne complex [(*)Cp(CO)(2)Re=CPh]Br, when it is treated with oxalyl bromide. Nucleophiles add at the carbyne-carbon of, as demonstrated by the reaction with NaOCy (Cy = cyclohexyl), to afford the carbene complexes (*)Cp(CO)(2)M=C(OCy)Ph. Similarly, reaction of P(OMe)(3) with [(*)Cp(CO)(2)Re=CPh]Cl, the latter being generated in situ from 2b and oxalyl chloride, gives the ylide complex {(*)Cp(CO)(2)Re=C[P(OMe)(3)]Ph}Cl (7b'). In comparison, addition of P(OMe)(3) to [(*)Cp(CO)(2)Tc=CPh]Cl, generated in situ from 2a and oxalyl chloride, induces a carbyne-carbonyl 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 infrared (IR) spectroscopy. The solid-state structure of the carbene complexes 3a and 3b was determined by single-crystal X-ray diffraction studies. Both compounds crystallize in the monoclinic space group and have very similar unit cell constants. Striking feature of the isostructural carbene complexes is the nearly perpendicular orientation of the carbene ligand relative to the Cp(*) ring.

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Authors: FISCHER E O, Technischen Universität München, Anorganisch-Chemisches Institut (DE);APOSTOLIDIS C ET AL, Forschungszentrum Karlsruhe GmbH (DE);DORNBERGER E ET AL, Kernforschungszentrum Karlsruhe, Institut für Heiße Chemie (DE);FILIPPOU A CT ET AL, Humboldt-Universität zu Berlin, Institut für Anorganische und Allgemeine Chemie (DE)
Bibliographic Reference: Article: Zeitschrift für Naturforschung (1995)