Ein cyclisches Arsinoschwefeldiimid als intramolekularer Brückenligand: Synthese und Röntgenstrukturanalyse von Os3(CO)10[μ-(t-Bu)As(NSN)2As(t-Bu)]

A Cyclic Arsino Sulfur Diimide as an Intramolecular Bridging Ligand: Synthesis and X-Ray Structure Analysis of Os₃(CO)₁₀μ-(t-Bu)As(NSN)₂As(t-Bu)] The eight-membered sulfur diimide heterocycle (t-Bu)As(NSN)₂As(t-Bu) ( 8 ) can be incorporated into a trinuclear carbonylosmium cluster either as a mono- or as a bidentate ligand. Reaction of the kinetically labile acetonitrile complex Os₃(CO)₁₁(CH₃CN) with 8 in CH₂Cl₂ solution leads to a monosubstituted derivative of Os₃(CO)₁₂ of composition Os₃(CO)₁₁(t-Bu)As(NSN)₂As(t-Bu)] ( 9 ) which still contains one uncoordinated arsenic atom; addition of a second Os₃(CO)₁₁] fragment to 9 was not observed. However, Me₃NO-induced substitution of a carbonyl group in 9 results in coordination of the ligand 8 to the triosmium cluster through both arsenic atoms. The structure of the product Os₃(CO)₁₀μ-(t-Bu)As(NSN)₂As(t-Bu)](10)¹ was determined by an X-ray structure analysis. I n the triangulo-triosmiumcarbonyl cluster 10 , the ligand 8 occupies two equatorial positions at two adjacent osmium atoms, being coordinated through the arsenic atoms with O s ? As distances of 2.403(1) Å The cluster molecule 10 possesses a 2-symmetry of crystallographic origin. The Os₃(CO)₁₀] fragment and the eight-membered heterocyclic ligand are not changed significantly in their structures as compared with Os₃(CO)₁₀ and free 8 , respectively. Nevertheless, coordination of 8 imposes its lower 2-symmetry upon the Os₃(CO)₁₀] fragment. The reduction of mm2- to 2-symmetry (C_2v to C₂) for the cyclic arsino sulfur diimide 8 is more pronounced in the complex 10 than in the free state. The As …? As distance in 10 (8.878(4) A) is considerably enlarged its compared to 8 (3.683(1) Å).