The gas-phase photoelectron spectrum of Re/sub 3/Cl/sub 9/ has been measured at ca. 800/sup 0/K. The first vertical ionization potential occurs at 8.85 eV. Results of a discrete variational Hartree-Fock-Slater calculation suggest that this ionization be attributed to a /sup 2/E'' state. Spin-orbit splitting of the first ionization band also supports this assignment. Charge density contributions to this orbital are distributed over the Re 5d, bridging Cl 3p, and axial Cl 3p orbitals in a 5:2:3 ratio. Remaining features in the photoelectron spectrum and the proposed orbital assignments are as follows: 9.80 eV, 22e''; 9.90 eV, 18a/sub 2/'', 12a/sub 2/', 40e'; 10.47 eV, 21e''; 10.83 eV, 39e', 17a/sub 2/'', 5a/sub 1/''; 11.09 eV, 28a/sub 1/', 20e'', 38e'; 11.83 eV, 16a/sub 2/'', 37e'; 12.21 eV, 11a/sub 2/', 36e'; 13.06 eV, 27a/sub 1/'; 13.39 eV, 15a/sub 2/'', 19e'', 26a/sub 1/'; 13.86 eV, 35e'. A unique feature of bonding in this complex is the great stability of 25a/sub 1/', the cluster sigma-bonding orbital. Chemically, this manifests itself in a trans effect at the vertices of the trinuclear cluster framework. To allow a fair comparison between Re/sub 3/Cl/sub 9/ and the well-studied Re/sub 2/Cl/sub 8//sup 2 -/ ion, a calculation of the latter complex'smore » electronic structure was also performed. A detailed comparison of the valence orbitals in these two molecules follows. 25 references, 5 figures, 3 tables.« less