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(NHEt2)2] (2), [NH2Et2][Mo2Cl7(NHEt2)2] (3), [NH2Et2]2[MoCl5(NHEt2)] (4), and [NH2Et2]3[Mo2Cl8(NEt2)] (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.