The structure and chemical bonding of B-16(-) were studied using ab initio calculations and photoelectron spectroscopy. Its global minimum is found to be a quasi-planar and elongated structure (C-2h). Addition of an electron to B-16(-) resulted in a perfectly planar and closed shell B-16(2-) (D-2h), which is shown to possess 10 pi electrons with a pi-bonding pattern similar to that of naphthalene and can thus be considered as an "all-boron naphthalene", a new member in the growing family of hydrocarbon analogues of boron clusters.