RESUMO
Three types of tetradentate phosphine ligands with different central methylene chains and configurations, meso- and rac-Ph2PCH2P(Ph)(CH2) nP(Ph)CH2PPh2 ( n = 2, meso- and rac-dpmppe; n = 3, meso-dpmppp) were utilized to synthesize a new series of tri- and tetranuclear copper hydride complexes. Reactions of meso-dpmppe or meso-dpmppp with CuCl/NH4PF6 or [Cu(CH3CN)4]PF6 in the presence of NaBH4 afforded trinuclear copper hydride complexes, [Cu3(µ3-H)( meso-dpmppe)2](PF6)2 (1) and [Cu3(µ3-H)( meso-dpmppp)2](PF6)2 (2), while a similar reaction with rac-dpmppe resulted in the formation of a tetranuclear copper dihydride complex, [Cu4(µ3-H)2( rac-dpmppe)2](PF6)2 (5). Complexes 1 and 5 further reacted with RNC (R = tBu, Cy, Xyl) to give [Cu3(µ3-H)( meso-dpmppe)2(XylNC)](PF6)2 (3), [Cu4(µ3-H)2( meso-dpmppe)2(RNC)2](PF6)2 (R = tBu (4a), Cy (4b)) and [Cu4(µ3-H)2( rac-dpmppe)2(RNC)2](PF6)2 (R = tBu (6a), Cy (6b), Xyl (6c)), respectively. Complexes 1-6 were characterized by ESI-MS and 1H and 31P NMR spectroscopy and X-ray diffraction analyses, demonstrating that a hydride ligand is located at the center of triangular Cu3 plane of 1-3, while two µ3-hydride-capped Cu3 planes are fused to result in rhombic Cu4H2 structures in 4a,b, 5, and 6a-c. Complexes 1-6 in CD3CN solutions notably showed high thermal stability and no reactivity toward H2O and CO2. DFT calculations indicated an interesting correlation between the Wiberg bond indices (WBI) of Cu-H bonds and their natural atomic charge (NAC), where the isocyanide ligands had an appreciable influence on the Cu-H interactions.