Complex 3a was characterised by X-ray diffraction crystallography, along with multinuclear NMR and IR spectroscopy. The 1 H NMR spectrum shows characteristic signals in the hydride region at δ = -15.98 ppm (2H). The IR also exhibited bands at 1780 and 1810 cm -1 for the bridging hydrides and at 1948 cm -1 for the CO group. The structure was confirmed after obtaining crystals suitable for X-ray diffraction studies from the reaction mixture of 1a and [Fe(η 5 -C5H5)(CO)2]2 (Figure ). Two molecules co-crystallized in the same unit cell, one corresponding to the Zn-Fe adduct (2a) and the other to the dihydride complex (3a). The Zn-Fe distance of 2.384(1) Å in complex 2a is elongated to 2.404(1) Å in complex 3a due to the presence of two bridging hydrides (Figure ). The hydrogen atoms were located in the Fourier difference map during X-ray experiments and their positions confirmed by DFT calculations (Table ).