Molybdenum dinitrogen complexes facially coordinated by linear tridentate PEP ligands (E = N or P): impact of the central E donor in trans-position to N2.

The syntheses of molybdenum dinitrogen complexes supported by the tridentate PEP ligands (E = N, P) prPP(Ph)P = (Ph2PCH2CH2CH2)2P(Ph), prPPHP = (Ph2PCH2CH2CH2)2PH, PN(Ph)P = (Ph2PCH2CH2)2N(Ph) and prPN(Ph)P = (Ph2PCH2CH2CH2)2N(Ph) are reported. Together with the coligand dmpm = (CH3)2PCH2P(CH3)2 dinitrogen complexes of the type [Mo(N2)(PEP)(dmpm)] are formed. The new systems are characterized by IR and NMR spectroscopy and compared with the literature-known complex [Mo(N2)(dpepp)(dmpm)] (1) (dpepp = PhP(CH2CH2PPh2)2). The consequences of the substitution of the central P-donor of dpepp by N and the replacement of its C2 by C3 linkages as well as the exchange of the EPh by an EH function are investigated with respect to the stability of the corresponding N2-complexes. Importantly, the activation of the N2 ligand drastically increases upon replacing the trans-phosphine with a trans-amine donor.