Zur Umsetzung von Bis(alkinyl)-Titanocenen mit Übergangsmetall-Verbindungen von Cu(II), Pd(II), Pt(II), Fe(III) und Au(III)

The reaction behaviour of the bis(alkynyl) titanocenes [Ti](CCR1)(CCR2) {[Ti]=(η5-C5H4SiMe3)2Ti; 1: R1=R2=Fc, Fc=(η5-C5H4)Fe(η5-C5H5); 5a: R1=R2=SiMe3; 5b: R1=R2=C6H5; 5c: R1=SiMe3, R2=C6H5} towards MX2 (M=Pd, Pt; X=Cl; M=Cu; X=Cl, Br, OAc, acac) and MCl3 (M=Fe, Au) is described. All reactions are dominated by redox processes. Generally, the reaction of 1 or 5a–5c with AuCl3 or MCl2 (M=Cu, Pd, Pt) produces the titanocene dichloride [Ti]Cl2 (3a) along with the corresponding butadiynes R1CCCCR2 (4: R1=R2=Fc; 7a: R1=R2=SiMe3; 7b: R1=R2=C6H5; 7c: R1=SiMe3, R2=C6H5) and M(0) (M=Cu, Au, Pd, Pt). As key intermediates the heterobimetallic tweezer complexes {[Ti](CCR1)(CCR2)}MCl2 (M=Cu, Pd, Pt) are formed. These reactions are strongly solvent dependent. While {[Ti](CCFc)2}CuCl2 (2) is readily formed as the main product when 1 is reacted with CuCl2 in diethyl ether, it is found that 2 affords 3a, 4 and Cu(0) on prolonged stirring in tetrahydrofuran. In contrast, complexes 5a–5c produce with equimolar amounts of CuX2 (X=Cl, Br) the compounds [Ti]X2 (3a: X=Cl, 3b: X=Br), R1CCCCR2 (7a: R1=R2=SiMe3; 7b: R1=R2=C6H5; 7c: R1=SiMe3, R2=C6H5), {[Ti](CCR1)(CCR2)}CuX (6a: R1=R2=SiMe3, X=Cl; 6b: R1=R2=SiMe3, X=Br; 6c: R1=R2=C6H5, X=Cl; 6d: R1=SiMe3; R2=C6H5, X=Cl) as well as 1/n[CuX]n (X=Cl, Br). However, when 5a is treated with Cu(OAc)2 or Cu(acac)2 in a 1:1 ratio, heterobimetallic {[Ti](CCSiMe3)2}CuX (6e: X=OAc, 6f: X=acac) is the only isolated species. Possible mechanisms for the reactions presented are described.