Oxidative decarbonylation of Mo(CO) 6 with [–Se(Se)P(O i-Pr) 2] 2 generates the mixed-valent tetranuclear cluster Mo 4(μ 3-Se) 4[Se 2P(O i-Pr) 2] 6 and a cationic trinuclear cluster [Mo 3(μ 3-Se)(μ 2-Se 2) 3{Se 2P(O i- Pr) 2} 3] +

Abstract

Oxidative decarbonylation of Mo(CO) 6 with [–Se(Se)P(O i-Pr) 2] 2 yielded a novel tetranuclear, mixed-valent (Mo III/IV) Mo 4(μ 3-Se) 4[Se 2P(O i-Pr) 2] 6 cluster 1 (dark brown), and a trinuclear, [Mo 3(μ 3-Se)(μ 2-Se 2) 3{Se 2P(O i- Pr) 2} 3][Se 2P(O i-Pr) 2] cluster 2a (orange).The uncoordinated Se 2P(O i-Pr) 2anion of 2a was replaced by halide anions to yield [Mo 3(μ 3-Se)(μ 2-Se 2) 3{Se 2P(O i- Pr) 2} 3](X) (X = Cl, 2b; Br, 2c; I, 2d) via the anion exchange reactions.In cluster 1, each Mo atom is bonded to two Se atoms from one chelating dsep ( dsep = diselenophosphates) ligand, one Se from bridging dsep and to three, triply bridging μ 3-Se atoms with Mo–μ 3-Se bond distances, 2.4580–2.503 Å, and Mo–( 1η-Se) bond distances, 2.691–2.729 Å.The cyclic voltammogram of 1 reveals one quasi-reversible one-electron oxidation wave ( E 1/2 = 0.67 V), corresponding to the formation of the Mo 4 Se 4 7 + state, and two quasi-reversible one-electron reduction waves ( E 1/2 = −0.23 and −1.09 V), suggesting the formation of Mo 4 Se 4 5 + and Mo 4 Se 4 4 + cores. In cluster cation, 2, three Mo atoms form an equilateral triangle which is capped by a μ 3-Se 2− anion, and each Mo atom is further coordinated to two μ 2 - Se 2 2 - ligands and a chelated dsep ligand. Interestingly, clusters 2a–2d exhibited unusual, intermolecular Se⋯Se interactions to produce infinite chains. All “sandwiched” halides are attached to three Se ax atoms of one Mo 3 unit and one Se eq atom of the neighboring unit in clusters 2b–2d and these distances are far shorter than the sum of the van der Waals radii.