Copper hydride clusters of the type ((PNP)-P-R-P-H)(n)Cu2nH2n ((PNP)-P-R-P-H = HN(CH2CH2PR2)(2); n = 2 and 3) have been synthesized from the reaction of ((PNP)-P-R-P-H)CuBr with (KOBu)-Bu-t under H-2 or in one pot from a 1:2:2 mixture of (PNP)-P-R-P-H, CuBr, and (KOBu)-Bu-t under H-2. With medium-sized phosphorus substituents (R = Pr-i and Cy), the phosphine ligands stabilize both hexanuclear and tetranuclear clusters; however, the smaller clusters are kinetic products and aggregate further over time. Use of a bulkier ligand (PNP)-P-tBu-P-H leads to the formation of only a tetranuclear cluster. Crystallographic studies reveal a distorted octahedral Cu-6 unit in ((PNP)-P-iPr-P-H)(3)Cu6H6 (2a) and ((PNP)-P-Cy-P-H)(3)Cu6H6 (2b), while a tetrahedral Cu-4 unit exists in ((PNP)-P-Cy-P-H)(2)Cu4H4 (2b') and ((PNP)-P-tBu-P-H)(2)Cu4H4 (2c'), all furnished with face-capping hydrides and bridging (PNP)-P-R-P-H ligands. The aggregations are maintained in solution, although hydrides are fluxional. These copper clusters are capable of reducing aldehydes and ketones to the corresponding copper alkoxide species. Ranking their reactivity toward N-methyl-2-pyrrolecarboxaldehyde gives 2b' > 2a, 2b >> 2c', which correlates inversely with the order of thermal stability (against decomposition and cluster expansion).