A new cubic binary phase was recently discovered in tin monosulfide and tin monoselenide.  The structure and properties of this new phase including mechanical and thermodynamic stability and bandgap width are studied ab-initio across the monochalcogenide systems of groups IV-VI. The structure is interpreted in terms of a distorted Rock Salt structure and the bonding between the 64 atoms of the unit cell is elucidated.  It is found that the π phase is mechanically stable in germanium sulfide and germanium selenide and unstable in the tellurides.  The energy differences from the stable orthorhombic structures are found to be very small, suggesting that the π phase could be thermodynamically accessible in the form of nanoparticles.  The bandgaps of the new phases are found to range from 1.0-1.4 eV which may be attractive for a variety of photovoltaic and photosensing applications