Unprecedented formation of ethylene during the synthesis of a NbRh bimetallic complex: molecular structure of Cp′2Nb(μ-PPh2)2RhC2H4

Reaction between Cp′2Nb(PPh2)2Li and (ClRhCOD)2 (COD = cyclooctadiene) in tetrahydrofuran followed by the treatment of the reaction product with Et2O leads to the unprecedented formation of coordinated ethylene to give the new heterobimetallic complexes Cp′2Nb(PPh2)2RhC2H4 (Cp = C5H5 (1a); Cp′ = C5H4CH3 (1b)) and LiCl. The structure of 1 was established spectroscopically (for 1a), and by X-ray diffraction (for 1b). 1b: P-1 (Z = 2) with a = 10.363(2) A, b = 10.605(2) A, c = 17.629(4) A, α = 77.11(3)°, β = 74.66(3)°, γ = 61.51(3)° and V = 1631.37 A3, R = 6.07, Rw = 6.38 and G = 3.734. The geometry at rhodium is pseudotriangular, the Nb(μ-P2)RhC2 fragment being almost planar; the NbRh bond distance is 2.869(2) A.