Mixed Chloride/Amine Complexes of Dimolybdenum(II). 1. Preparation, Characterization, and Crystal structure of Mo₂Cl₄(NHEt₂)₄: A Quadruply-Bonded Dimolybdenum Compound with Diethylamine Ligands

Reaction of the molybdenum(III) complex Mo₂Cl₆,(THF)₃ with diethylamine at room temperature causes reduction of the starting compound to produce the dimolybdenum(II) complex Mo₂Cl₄(NHEt₂)₄ (1). It was shown that the Cl^- anions released by the substitution with amine can react with more of the starting material to give side products of molybdenum(III). Four such products were isolated and characterized: [NH₂Et₂][MoCl₄(NEt₂)] (2), [NH₂Et₂][Mo₂Cl₇(NHEt ₂)₂] (3), [NH₂Et₂]₂[MoCl₅(NHEt₂)] (4), and [NH₂Et₂]₃[Mo₂Cl₈(NEt ₂)] (5). The crystal structures of all complexes 1-5 have been investigated by X-ray diffraction. The structure of 1 consists of two trans-MoCl₂(NHEt₂)₂ units joined by a quadruple Mo-Mo bond (2.1330(6) Å). The crystallographic parameters for compounds 1-5 are as follows: for 1, monoclinic space group C2/c with a = 20.846(1) Å, b = 7.044(1) Å, c = 19.868(3) Å, β = 118.72(2)°, and Z = 4; for 2, triclinic space group P1̄ with a = 9.820(3) Å, b = 10.305(1) Å, c = 11.510(1) Å, α = 95.779(8)°, β= 97.80(2)°, γ = 111.17(1)°, and Z = 2; for 3, monoclinic space group p2₁/n with a = 13.847(5) Å, b = 10.448(4) Å, c = 22.091(4) Å, β= 96.68(2)°, and Z = 4; for 4, monoclinic space group P2₁/c with a = 11.710(2) Å, b = 12.363(2) Å, c = 30.272(7) Å, β= 95.87(2)°, and Z = 8; for 5, monoclinic space group P2₁/n with a = 10.335(1) Å, b = 18.061(1) Å, c = 16.775(1) Å, β = 95.558(8)°, and Z = 4.