Since the end of the 20th century, complexes of the alkaline earth elements have emerged as viable catalysts for a wide variety of molecular transformations. Being both earth abundant and environmentally benign, these elements hold obvious appeal as candidates for the development of future sustainable chemical technologies. Despite a history that stretches to the earliest days of main group organometallic chemistry, the factors governing the reactivity of the group 2 elements, in particular those heavier than magnesium, are only now starting to emerge. A single and effectively unchangeable 2+ oxidation state signifies that the reaction chemistry of these significantly ionic species is totally dependent on polarized heterolytic pathways for substrate bond activation. Despite this ostensible limitation, significant variability in both reaction mechanism and absolute reactivity has arisen. This article will attempt to highlight these variations through a broad survey of reaction type and substrate class.