Molybdenum complexes containing mixed disubstituted organohydrazido(1 - ) and organohydrazido(2 - ) ligands, [Mo(NHNPhR)-(NNPhR)(acac)Cl2], R=Ph (I), R=Me (II), react in acetonitrile with sodium hydridotris(pyrazolyl)borate, NaTp, or in toluene with potassium hydridotris(3,5-dimethylpyrazolyl)borate, KTp*, to afford the neutral six-coordinated species formulated as [TpMo(NNPhR)2Cl], R=Ph (III), R=Me (FV) and [Tp*Mo(NNPhR)2Cl], R=Ph (V), R=Me (VI). These compounds have been characterized by elemental analysis, by IR, UV - visible, 1H and 13C NMR spectroscopy, and by mass spectrometry. The electrochemical behavior of complexes III-VI has also been studied by cyclic voltammetry. The X-ray crystal structure of IV has been determined. Crystals are parallelepiped, space group Pbnm, with a=7.468(2), b=18.483(3), c=19.052(3) Ä, α=β=γ=90° and Z=4. The structure was solved and refined by full-matrix, least-squares methods to R and Rw values of 0.038 and 0.049, respectively. The complex displays a distorted octahedral geometry with symmetrical organohydrazido(2 - ) ligands adopting the nearly linear mode (Mo-N-N=169.4(3)°). This linearity and the short bond distances (Mo-N = 1.771(4), N-N = 1.308(5) Å) indicate an extensive π-electronic delocalization throughout the Mo-N-N fragment.