Unusual coordination mode for 1,3-diphosphete ligands towards a Cr-Cr quintuple bond complex

Abstract

The reaction of LCr^5̲CrL (L = N₂C₂₅H₂₉, 1) with the phosphaalkynes R-C≡P (R = tBu, Me, Ad) yields the neutral dimerisation compounds [L₂Cr₂(μ,η¹:η¹:η²:η²-P₂C₂R₂)] (R = tBu (2), Me (3)) and the tetrahedrane complex [L₂Cr₂(μ,η²:η²-PCAd)] (4). The 1,3-diphosphete ligands in complexes 2 and 3 are the first to possess this structural feature spanned over a metal-metal multiple bond, while the slightly bigger adamantyl phosphaalkyne remains a monomer in 4 with a side-on coordination mode.