Tri- and Tetranuclear Copper Hydride Complexes Supported by Tetradentate Phosphine Ligands

摘要

( ) Three types of tetradentate phosphine ligands with different central methylene chains and configurations, meso- and rac-Ph2PCH2P(Ph)(CH2)(n)P(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, [Cu-3(mu(3)-H)(meso-dpmppe)2](PF6)(2) (1) and [Cu-3(mu(3)-H)-(meso-dpmppp)(2)](PF6)(2) (2), while a similar reaction with rac-dpmppe resulted in the formation of a tetranuclear copper dihydride complex, [Cu-4(mu(3)-H)(2)(rac-dpmppe)(2)](PF6)(2) (5). Complexes 1 and 5 further reacted with RNC (R = Bu-t, Cy, Xyl) to give [Cu-3(mu(3)-H)(meso-dpmppe)(2)(XylNC)](PF6)(2) (3), [Cu-4(mu(3)-H)(2)(meso-dpmppe)(2) (RNC)(2)](PF6)(2) (R =Bu- t (4a), Cy (4b)) and [Cu-4(mu(3)-H)(2)(rac-dpmppe)(2)(RNC)(2)](PF6)(2) (R = Bu-t (6a), Cy (6b), Xyl (6c)), respectively. Complexes 1-6 were characterized by ESI-MS and H-1 and P-31 NMR spectroscopy and X-ray diffraction analyses, demonstrating that a hydride ligand is located at the center of triangular Cu, plane of 1-3, while two mu(3)-hydride-capped Cu-3 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.