The nonprotonated member, 1 ( n = 6), of the previously established nanosized nu(3)-octahedral [ H6-nPt6Ni38( CO) 48](n-) series ( n = 3 -6) has been isolated from an aprotic synthetic route and stabilized as the crystal-ordered cyclohexane/acetonitrile-solvated [ NMe4](+) salt. A highly precise X-ray determination ( cubic; Pa (3) over barh; Z = 4 with 1 possessing -3 site symmetry) has allowed a comparative analysis of the nonprotonated pseudo-D-3d structure of 1 with the monoprotonated structure of 2 ( n = 5), which constitutes the only previously reported complete geometry of any member of this extraordinary Pt-6-encapsulated nu(3)-octahedral Pt6Ni38 cluster series.