SYNTHESIS AND CHARACTERIZATION OF TRIANGULO COPPER(I) COMPLEXES CONTAINING MONOCAPPING AND BICAPPING SYSTEMS OF ASYMMETRIC MU(3)-ETA(1)-ACETYLIDE LIGANDS - MOLECULAR-STRUCTURES OF [CU3(MU(3)-ETA(1)-CCPH)(MU-DPPM)3][BF4]2, [CU3(MU(3)-ETA(1)-CCPH)2(MU-DPPM)3][BF4], AND U-DPPM)3][BF4][DPPM=BIS(DIPHENYLPHOSPHINO)METHANE]

Alkynyl-bridged trinuclear copper(I) complexes containing the triangul o framework Cu3(mu-dppm)3 [dppm = bis(diphenylphosphino)methane] have been prepared. Complexes [Cu3(mu3-eta1-C=CR)(mu-dppm)3][BF4]2 (R = Ph (1), (t)Bu (2), CH2OCH3 (3)) are obtained by treating [Cu2(mu-dppm)2(M eCN)2][BF4]2 with LiC=CR in a molar ratio of 3:2. The treatment of [Cu 2(mu-dPPM)2(MeCN)2][BF4]2 with HC=CR/KOH in CH2Cl2/MeOH (molar ratio 3 :4) yields the complexes [Cu3(mu3-eta1-C=CR)2(A-dppm)3][BF4] (R = Ph ( 4), (t)Bu (5), CH2OCH3 (6)). The reaction of [Cu3(AS-Cl)2(mu-dppm)3][B F4] with LiC=CR (1:1.5 molar ratio) in THF affords the double-bridged chloride-alkynyl complexes [Cu3(mu3-eta1-C=CR)(mu3-Cl)(mu-dppm)3][BF4] (R = Ph (7), (t)Bu (8), CH2OCH3 (9)) which are also formed from dichl oromethane solutions of 4-6 containing traces of acid. Complex 4 has a lso been directly obtained by treatment of [Cu3(mu3-Cl)2(mu-dppm)3][BF 4] with an excess of LiC=CPh. Crystal structures of the complexes 1 (C H2Cl2 solvate) (space group P2(1)/c, Z = 4, a = 25.02(1) angstrom, b = 13.752(1) angstrom, c = 24.207 (1) angstrom, beta = 93.375(4)-degrees , R = 0.080), 4 (space group P2(1)/c, Z = 4, a = 14.61(6) angstrom, b = 21.863(6) angstrom, c = 26.67 (1) angstrom, beta = 102.8(1)-degrees, R = 0.077), and 7 (space group P1BAR, Z = 2, a = 14.55(7) angstrom, b = 14.691(4) angstrom, c = 21.08(2) angstrom, alpha = 72.27(4)-degrees , beta = 71.29(4)-degrees, gamma = 68.72(8)-degrees, R = 0.105) have b een determined by X-ray diffraction methods. The structure determinati ons show that each cationic complex consists of an isosceles triangle of copper atoms with a dppm ligand bridging each edge to form a roughl y planar [Cu3P6] core. These triangulo copper(I) complexes contain mon o-and bicapping systems of mu3-eta1-acetylide ligands in which each ph enylethynyl ligand is C-bonded to the three copper atoms, showing an a symmetric mu3-eta1 bridging mode with the copper to carbon distances s ignificantly different.