Heterometallic Second-Row Transition Metal Chain Compounds in Two Charge States: Syntheses, Properties, and Electronic Structures of [Mo–Mo–Ru]^6+/7+ Chains

Reaction of Mo2(dpa)4 (dpa = 2,2′-dipyridylamido) with 1/2 equiv of [Ru­(CO)3Cl2]2 in molten naphthalene at 250 °C provides facile access to the first all-second-row transition metal heterometallic chain compound, MoMoRu­(dpa)4Cl2 (1). The one-electron oxidized compound [MoMoRu­(dpa)4Cl2]­(OTf) (2) is synthesized by reaction of 1 with FeCp2(OTf). X-ray crystallography reveals a contraction of the Mo–Ru bond distance from 2.38 Å in 1 to 2.30 Å in 2, and an elongation of the Mo–Mo bond distance from 2.12 Å in 1 to 2.21 Å in 2. The short Mo–Ru bond distances indicate significant electron delocalization along the Mo–Mo–Ru chain, which is quantified by density functional theory (DFT) calculations. Molecular orbital analyses of both compounds based on DFT results reveal full delocalization of the orbitals of σ and π symmetry for both compounds. Additionally, δ orbital delocalization is observed in 2.