Geometries and energy separations of the various low-lying electronic states of Pt-5 with different structural arrangements have been investigated. The complete active space multiconfiguration self-consistent-field (CASMCSCF) method followed by large-scale multiconfiguration singles plus doubles configuration interaction (MRSDCI) that included up to 1.64 million configuration spin functions have been used to compute several electronic states. A B-1(2) (C-2v) electronic state of a distorted tetragonal pyramid equilibrium structure was found to be the minimum energy geometry. We also compared our MRSDCI results with density functional as well as Moller-Plesset second-order perturbation calculations. The dissociation and atomization energies have been computed and the results, together with our previous findings for the smaller Pt-n (n=2-4) clusters, were compared with other group 10 member clusters viz., Ni-n (n=2-5) and Pd-n (n=2-5) and the experimental findings.