Both Pt-Mg•TMEDA and Pt-Zn could be isolated as crystalline solids. X-ray diffraction studies confirmed that the coordination geometry at the transition metal is square planar. In the solid state, the four hydride ligands of Pt-Zn are organised in a near symmetric configuration around the transition metal and sit in the same plane as both the Pt and Zn atoms. The hydride atoms were located within the Fourier difference map and their positions confirmed by DFT calculations. The geometry at Zn is near tetrahedral and the -diketiminate chelate twisted and orthogonal to the plane created by the hydrides. The Pt---Zn distance in Pt-Zn is 2.4466(4) Å. Despite being close to the sum of the covalent radii (Pauling, 2.53Å; Pyykkö, 2.38 Å), computational analysis of the bonding suggests weak metal-metal interactions at best (vide infra), which supports assignment of the geometry at Pt as 4-coordinate square planar. The average H-Pt-H angle across all unique solid-state structures for Pt-Mg•TMEDA and Pt-Zn is 89.9(3) (74.2(3)-105.7(3)). This tetrahydride core is reminiscent of a Ru-Zn2 tetrahydride complex reported by Fischer and coworkers, in which the four hydride ligands are arranged in the equatorial plane, but two phosphine ligands make the central Ru octahedral. Pt-Mg•TMEDA appears as a dimer in the solid state due to the ability of TMEDA to act as a bridging ligand. As a result, there are some differences in the heterometallic core of Pt-Mg•TMEDA compared to Pt-Zn. Increasing the coordination at one magnesium site results in a distortion of the position of the -diketiminate ligand and induces an asymmetry in the Pt---Mg distances. These take values of 2.5605(15) and 2.7124(15) Å to the 4-and 5-coordinate magnesium centres respectively, with the longer distance consistent with the higher coordination number at Mg. Ternary hydrides of s-block and group 10 metals have been reported and characterised by neutron diffraction, and one homometallic complex featuring a [Ni3H4] 2-core has been reported. The bonding in a series of heterometallic tetrahydride complexes (M 1 = Ni-Pt; M 2 = Mg or Zn) was investigated by computational methods. Superficially this structural type resembles that of 1, in that it contains six co-planar atoms closely arranged around a palladium centre.