Computational results reveal that the most accurate structural parameters can be predicted at the B2PLYP/SDD level of theory. <...> AIM and NBO analyses are performed to investigate the nature of the Mo—W and the metal-carbonyl interaction in . <...> It is confirmed that there is a Mo—W bond and a semi-bridging carbonyl group in the complex. <...> The formation of the Mo—W bond accompanies the dominant charge transfer interactions: BD(1)Mo1—W2 BD*(1)Mo1—W2 and BD(2)Mo1—W2 BD*(2)Mo1—W2. <...> The real interaction between W and the CO ligand coordinated to molybdenum explains the observed IR (CO) band at 1876 cm–1 at room temperature and q(13CO) at 218.69 ppm at 210 K. DOI: 10.15372/JSC20160523 Keywords: DFT, metal-metal bond, semi-bridging carbonyl, AIM, NBO. <...> One special feature of the heterobimetallic phosphido-bridged complexes is the influence of the metal—metal bond on the reactivity [ 1 ]. <...> The dative metal-metal bond functions as a switch to control the reaction in order to obtain the desired complex. <...> This behavior provides not only an empty site for further ligand coordination to the binuclear complex when the metal—metal bond opens but also a driving force for a further reaction when the metal-metal bond reforms. <...> Such directional opening of the dative metal—metal bond was demonstrated by the addition of a Lewis base to the heterobimetallic phosphido-bridged and arsino-bridged complexes [ 2 ]. <...> This property can also be considered as a cooperative effect of two adjacent metals in the binuclear complex. <...> The theory of atoms in molecules (AIM) and NBO analysis have become the paradigm for interpreting theoretical and experimental electron density distributions [ 5, 6 ]. <...> It proved to be appropriate to retrieve the physical and chemical significance of bond paths for very weak or supposedly repulsive interactions [ 8 ]. <...> AIM and NBO analyses were then performed to investigate the nature of the Mo—W bond and the metal—carbonyl interactions in the binuclear complex. <...> All the minimization procedures and the corresponding frequency calculations were carried out through HF [ 9 ], B3LYP [ 10 ], B3PW91 [11 ], MPW1PW91 [ 12 ], and B2PLYP [13 ] with LAN2DZ, CEP-31G, and SDD basis sets, respectively, without any geometrical constrains for the complex. <...> AIM analysis <...>