Alkinstabilisierte monomere Organo-Kupfer(I)-Verbindungen als Organyl-Transfer Reagenzien

The reaction chemistry of the monomeric organo-copper(I) species {[Ti](CCR1)2}CuR {[Ti]=(η5-C5H4SiMe3)2Ti; R1=SiMe3: 1a, R=CH3; 1b, R=C6H5; 1c, R=C6H4OMe-4; 1d, R=CCtBu; 1e, R=CCSiMe3; R1=tBu: 8a, R=CCSiMe3; 8b, R=CH3} towards different inorganic and organic reagents is described. On treatment of 1a–1e with one equivalent of X2 (2a: X=Br, 2b: X=I) selective cleavage of the copper–carbon σ-bond is observed, producing {[Ti](CCSiMe3)2}CuX (4a: X=Br, 4b: X=I) along with RX (X=Br: 3a, R=CH3; 3b, R=C6H5; 3c, R=C6H4OMe-4; 3d, R=CCtBu; 3e, R=CCSiMe3; X=I: 3f, R=CCSiMe3; 3g, R=CCtBu). Treatment of {[Ti](CCSiMe3)2}CuCCR3 (1d: R3=tBu, 1e: R3=SiMe3) with ICN (7) produces {[Ti](CCtBu)2}CuCN (9) and 3f or 3g. Copper–carbon σ-bond cleavage is also obtained, when 1a or 8b is treated with stoichiometric amounts of HX (10a: X=Br, 10b: X=Cl), NH4Cl or NEt3HCl. In contrast, a carbon–carbon coupling is observed when {[Ti](CCR1)2}CuR (1, 8) is reacted with R2X (R2=CH3, CH2CH3, CH2C6H5, CCSiMe3; X=Cl, Br, I) in a 1:1 molar ratio. This yields R2R and {[Ti](CCR1)2}CuX (R1=SiMe3: 4a, X=Br; 4b: X=I; 4c: X=Cl; R1=tBu: 11a: X=Cl; 11b: X=Br; 11c: X=I). The latter molecules can be transformed into the corresponding starting materials 1 or 8 by their reaction with, e.g., LiR (5). However, when aromatic halides, such as IC6H4Me-4, are added to {[Ti](CCSiMe3)2}CuCCR3 (1d: R3=tBu, 1e: R3=SiMe3), elimination of Me3SiCCR3 takes place and the titanium(IV)–copper(I) acetylide {[Ti](CCSiMe3)(CCCu)}2 (15) is formed. In addition, organo copper(I) compounds can be considered as key molecules in the decarboxylative bromination of copper(I) carboxylates: heating the copper(I)-carboxylate {[Ti](CCSiMe3)2}CuO2CR2 (6a: R2=CH3, 6b: R2=C6H5) to 100°C produces the organo copper(I) species 1a and 1b by loss of CO2. On treatment of 1a and 1b with equimolar amounts of Br2, oxidative cleavage of the CuC σ-bond is induced and {[Ti](CCSiMe3)2}CuBr (4a) as well as R2Br are formed. Complex 4a can be transformed to the starting material 6a or 6b by subsequent reaction with AgO2CR2 (R2=CH3, C6H5) on precipitation of AgBr. All compounds synthesized were characterized by elemental analysis and spectroscopy (IR, 1H-NMR, 13C{1H}-NMR). The organic products were characterized additionally by GC–mass spectrometry.