Ethylenediamine (en) solutions of E-7(3-) (E = P, AS) react with Pt(PPh3)(2)(C2H4) in the presence of 4,7,13,16,21,24-hexaoxa-1,10-diazobicyclo[8.8.8]hexacosane (2,2,2-crypt) to give the transition-metal Zintl ion complexes [P7PtH(PPh3)(2-) (1) and [As7PtH(PPh3)(2-) (2) as isomorphic [K(2,2,2-crypt)](+) salts, respectively. The hydride ligand originates from the solvent, and deuterium labeling studies show that the order of hydrogen sources follows the sequence en > CH3CN > DMSO > DMF in the synthesis of 1. The [E7PtH(PPh3)](2-) anions have C-1 point symmetry with unperturbed nortricyclane-like E-7(3-) ligands bound eta (2) to square planar (PtH)-H-pi(PPh3)(+) centers. Complex 1 is dynamic in solution whereby the PtH(PPh3)(+) fragment shifts from the top to bottom of the P-7 cluster (an eta (2) -> eta (4) -> eta (2) shift) and spins in the P-4 face in a concerted process to give apparent C-2 nu symmetry. We have shown that P-31 EXSY NMR experiments at -78 degreesC permit the separation of the two processes and show that shifting is similar to 20 times faster than spinning (k(shift) = 160 s(-1), k(spin) = 8 s(-1)).