An ionic edge-sharing bioctahedral (ESBO) species has been prepared having a tetramethylated bicyclic guanidinate with two fused six-membered rings characterized by a fairly flat N-C(N)-N skeleton and abbreviated as TMhpp. The anion has two W-IV atoms bridged by two oxo groups; the metal atoms are also spanned by two bridging guanidinate ligands, and each has two monodentate chlorine atoms. The complex formulated as (H(2)TMhpp)(2)[W(mu-O)(mu-TMhpp)Cl-2](2) has the shortest W-W distance (2.3318(8) angstrom) of any species with a sigma(2)pi(2) electronic configuration. The anion and cations are connected by hydrogen bonds. To unambiguously ascertain the existence of the double-bonded W-2(mu-O)(2) entity, density functional theory calculations and natural bond orbital analyses were done on an analogous but hypothetical species with a W-2(mu-OH)(2) core having trivalent tungsten atoms and a possible sigma(2)pi(2)delta(2) electronic configuration. The calculations decidedly support the presence of tungsten-oxo instead of tungsten-hydroxo groups and thus the existence of the double-bonded W-2(mu-O)(2) core. The strong bonding interaction between metal atoms is a clear indication that under certain circumstances the two octahedra in ESBO species do not behave as the sum of two mononuclear compounds.