The reaction of Me 3SiCCSiMe 3 (bd1}), L nMCSiMe 3 ( 4a, L nMCp(CO) 2Fe; 4b, L nMCp(CO) 3Mo] and E(CCR) 2 ( 6, EMe 2Si; 8, E( η 5-C 5H 4SiMe 3) 2Ti; R is a singly bonded organic ligand) with CuX ( 2) (X is a halide or pseudohalide) is described. 1 and 4 react CuX ( 2a, XCl; 2b, XBr; 2c, XI; 2d, XOSO 2CF 3) to yield the dimeric compounds [( η 2-Me 3SiCCSiMe 3)CuX] 2 ( 3a, XCl 3b, XBr; 3c, XI; 3d, XOSO 2CF 3) or [( η 2-L nMCCSiMe 3)CuX] 2 ( 5a, L nMCp(CO) 2Fe, XCl; 5b, L nMCp(CO) 3Mo, XCl) respectively. In these compounds the C 2 building block is η 2-coordinated to a CuX moiety and by the formation of copper-X-bridges (Cu 2X 2) a dimer is formed. However, the reaction of Me 2Si(CCSiMe 3) (CCR) ( 6a, RSiMe 3; 6b, RH) with CuX ( 2) (XCl, Br, OSO 2CF 3, O 2CMe) affords polymeric Me 2 Si[ η 2-CCSiMe 3})( η 2-CCRCu 2X 2] n ( 7a RSiMe 3, XCl; 7b, RSiMe 3, XBr; 7c, RH, XCl; 7d, RH, XBr; 7e, RSiMe 3, XOSO 2CF 3; 7f, RSiMe 3, XO 2CMe) in high yields. In 7a– 7f each alkynyl fragment is η 2-coordinated to a CuX unit. While the reaction of 6a or 6b with CuX yields polymeric 7a– 7f, the organometallic 1,4-diyne RCC-[Ti]-CCR ([Ti]( η 5-C 5H 4SiMe 3) 2Ti; 8a, RPh; 8b, RSiMe 3) affords with CuX ( 2a, XCl; 2b, XBr; 2c, XI; 2e, XCN; 2f, XSCN) the dinuclear compounds [( η 5-C 5H 4SiMe 3) 2Ti(CCR) 2]CuX ( 9a, RPh, XCl; 9b RSiMe 3, XCl; 9c, RSiMe 3, XBr; 9d, RSiMe 3, XI; 9e, RSiMe 3, XCN; 9f, RSiMe 3, XSCN). Compounds 9a– 9f feature a monomeric copper(I) halide or copper(I) pseudohalide moiety, which is stabilized by the chelating effect of the alkynyl ligands in [Ti](CCR) 2. [( η 5-C 5H 4SiMe 3) 2Ti(CCSiMe 3) 2]CuCl ( 9b) reacts with AgX (XCN, SCN, O 2CMe, O 2CPh) to yield [( η 5-C 5H 4SiMe 3) 2Ti(CCSiMe 3) 2CuX ( 9e, XCN; 9f, XSCN; 9g, XOC(O)Me; 9h, XOC(O)Ph) by precipitation of AgCl. In addition, the bis(alkynyl)- ansa-titanocene [( η 5-C 5H 4)Me 2Si( η 5-C 5H 3SiMe 3)]Ti(CCSiMe 3) 2 ( 10) yields with CuCl ( 2a) the dinuclear species {[ η 5-C 5H 4)Me 2Si( η 5-C 5H 3SiMe 3})]Ti(CCSiMe 3) 2 CuCl ( 11). The identity of compounds 3, 5, 7, 9 and 11 is confirmed by analytical and spectroscopic (IR, MS, 1H, 13C NMR) data, and that of [( η 5-C 5H 4SiMe 3) 2Ti(CCPh) 2]CuCl ( 9a) is confirmed by X-ray analysis. Crystals of 9a are monoclinic, space group Pc with cell constant a = 992.6(7), b = 1210(1), c = 1335.5(7) pm, β = 105.75(5)°, V = 1543(2) × 10 6 pm 3 and Z = 2.