Copper Clusters Containing Hydrides in Trigonal Pyramidal Geometry

Structurally precise copper hydrides [Cu11H2{S2P((OPr)-Pr-i)(2)}(6)(C CR)(3)], R = Ph (1), C6H4F (2), and C6H4OMe (3), were first synthesized from the polyhydrido copper cluster [Cu20H11{S2P((OPr)-Pr-i)(2)}(9)] with nine equivalents of terminal alkynes. Later, their isolated yields were significantly improved by direct synthesis from [Cu(CH3CN)(4)](PF6), [NH4][S2P((OPr)-Pr-i)(2)], NaBH4, and alkynes along with NEt3 in THF. 1, 2, and 3 were fully characterized by single-crystal X-ray diffraction, ESI-MS, and multinuclear NMR spectroscopy. All three clustershave 11 copper atoms, adopting 3,3,4,4,4-pentacapped trigonal prismatic geometry, with two hydrides inside the Cu-11 cage, the position of which was ascertained by a single-crystal neutron diffraction structure of cluster 1 co-crystallized with a [Cu-7(H){S2P((OPr)-Pr-i)(2)}(6)] (4) cluster. Six dithiophosphate and three alkynyl ligands stabilize the Cu11H2 core in which the two hydrides adopt a trigonal pyramidal coordination mode. This coordination mode is so far unprecedented for hydride. The H-1 NMR resonance frequency of the two hydrides appears at 4.8 ppm, a value further confirmed by H-2 NMR spectroscopy for their deuteride derivatives [Cu-11(D)(2){S2P((OPr)-Pr-i)(2)}(6)(CCR)(3)]. A DFT investigation allows understanding the bonding within this new type of copper(I) hydrides.