Multiple Bonds between Transition Metals and Main-Group Elements. 73.1a Synthetic Routes to Rhenium(v) Alkyl and Rhenium(VII) Alkylidyne Complexes. X-ray Crystal Structures of (η5-C5Me5)Re(=O)(CH3)[CH2C(CH3)3] and (η5-C5Me5)(Br)3Re≡CC(CH3)3

Wolfgang A. Herrmann, Josef K. Felixberger, Reiner Anwander, Eberhardt Herdtweck, Paul Kiprof, Jürgen Riede

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Abstract

Dialkyloxo(η5-pentamethylcyclopentadienyl)rhenium(V) complexes (η5-C5Me5)Re(═O)(CH3)Rʹ [Rʹ = C2H5, CH2Si(CH3)3, CH2C(CH3)3], 1c-e, have become accessible through alkylation of (η5-C5Me5)Re(═O)(Cl)(CH3) (7) with RʹMgCl. 1c-e are the first rhenium complexes containing different alkyl ligands. The neopentyl derivative 1e [Rʹ = CH2C(CH3)3] crystallizes in the orthorhombic space group Pbca with a = 960.7 (2), b = 2844.5 (4), c = 1260.7 (2) pm, and Z = 8. The X-ray crystal structure was refined to Rw = 3.9%. The chiral molecule shows a distorted tetrahedral geometry around the rhenium center. The coordination of the aromatic ring ligand is highly unsymmetric due to the pronounced trans influence of the oxo ligand, with the Re‒Cring bond distances varying from 217.8 (5) to 249.3 (7) pm. Different products arise from halogenation of (η5-C5Me5)Re(═O)(R)2 (1) with (η5-C5H5)TiX3 (4). Chlorination of If (R = CH3) with 4a (X = Cl) results in formation of (η5-C5Me5)Re(Cl)2(CH3)2 (9). Chlorination of 1a (R = C2H5) and 1h [R = CH(CH3)2] with 2 equiv of 4a finally yields the reduced binuclear complexes [(η5-C5Me5)Re(Cl)2(µ-Cl)]2 (11) and [(η5-C5Me5)Re(Cl)(µ-Cl)]2 (12) of rhenium(IV) and rhenium(III), respectively. By way of contrast, chlorination of dialkyl complexes 1 lacking β-hydrogen atoms leads to rhenium alkylidyne complexes. Reaction of li [R = CH2C(CH3)3] with 2 equiv of 4 yields the unique paramagnetic rhenium(VI) complex (η5-C5Me5)(X)2Re≡CC(CH3)3 (2). Carbyne complexes 2 are quantitatively oxidized by a stoichiometric amount of the respective halogen to yield the rhenium(VII) compounds (η5-C5Me5)(X)3Re≡CCMe3 (3). The tribromide 3b has been structurally characterized. Brown crystals of 3b belong to space group P21/c with unit cell dimensions a = 1311.5 (2), b = 723.0 (1), c = 1901.6 (2) pm, β = 92.68 (1)°, and Z = 4. The structure refinement yielded a final R value of Rw = 3.3%. The structure exhibits a “four-legged piano stool” geometry with no trans influence of the neopentylidyne ligand to the bromine atom. The rhenium‒carbyne bond length is 175.5 (6) pm, typical of a rhenium‒carbon triple bond. The “carbine” angle Re≡C—C of 179.1 (5)° corresponds to an ideal “sp geometry”. Chlorination of the benzyl derivative 1g (R = CH2C6H5) provides the new binuclear complex [(η5-C5Me5)ReCl]2(µ-Cl)(µ-CC6H5) (14a), formally a rhenium(IV) system.

Original languageEnglish (US)
Pages (from-to)1434-1443
Number of pages10
JournalOrganometallics
Volume9
Issue number5
DOIs
StatePublished - Jan 1 1990

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