Several new polyhydride complexes of rhenium containing the tridentate phosphine PhP(CH(2)CH(2)CH(2)PCy(2))(2) (Cyttp) were synthesized and characterized by H-1 and P-31{H-1} NMR and IR spectroscopy. The solid state structure of the previously reported ReH5(Cyttp) (1) was determined by X-ray crystallography. 1 crystallizes in the space group P2(1)/m with the following unit cell parameters : a = 8.582(2) Angstrom, b = 19.690(2) Angstrom, c = 10.800(2) Angstrom, beta = 95.57(1)degrees, and Z = 2. The molecule adopts a classical polyhydride, triangulated dodecahedral structure, with the three phosphorus atoms and one hydrogen atom occupying the B sites, and the remaining hydrogen atoms occupying the A sites. 1 is protonated by HSbF6 (or HBF4) to yield [ReH4(eta(2)-H-2)(Cyttp)]SbF6 (3), which was shown by X-ray diffraction techniques (space group , unit cell parameters : a 9.874(2) Angstrom, b = 14.242(4) A, c 16.198(2) Angstrom, a = 99.12(2)degrees, beta = 98.85(2)degrees, gamma = 109.42(2)degrees, and Z = 2) to contain a nonclassical polyhydride cation with a triangulated dodecahedral structure in the solid. The same structure is suggested in solution by H-1 NMR data (including T-1 measurements). 3 is inert to loss of H-2 and is unaffected by CO, t-BuNC, and P(OMe)(3) at room temperature. In contrast, 1 reacts with a variety of reagents to afford classical tetrahydride complexes which are thought also to possess a triangulated dodecahedral structure, with the hydrogens in the A sites, from spectroscopic evidence. Accordingly, CS2 p-O2NC6H4NCS, and EtOC(O)NCS (X=C=S) insert into an Re-Ii bond to yield ReH4(SCH=X)(Cyttp) (5-7, respectively). Mel cleaves one Re-H bond to afford ReH4I(Cyttp) (8), and [C7H7]BF4 abstracts hydride in the presence of MeCN, t-BuNC, CyNC, or P(OMe)(3) (L) to give [ReH(4)L-(Cyttp)]BF4 (9-12, respectively). A related pentahydride, ReH5(ttp) (2, ttp = PhP(CH(2)CH(2)CH(2)PPh(2))(2)), also reacts with HSbF6 to yield [ReH6(ttp)]SbF6 (4), which appears to be a nonclassical polyhydride in solution by T-1 measurements.