Oxidative-addition of the N–H bond of saccharin (sacH) to a triosmium centre: Synthesis, structure and reactivity of Os3(CO)10(μ-H)(μ-sac)

Abstract

Saccharin (sacH) is a widely-used sweetener and consequently its chemistry has been extensively studied, but here we report a rare example of its reactivity towards a multinuclear metal centre. Lightly-stabilized Os3(CO)10-n(NCMe)n (n = 1, 2) react with sacH to afford Os3(CO)10(μ-H) (μ-sac) (1) in which the sac ligand bridges an osmium–osmium vector via nitrogen and the carbonylic oxygen (μ-N,O). The reactivity of 1 towards monodentate phosphines, PR3 (R = Ph, Th, Fu), has been investigated. Carbonyl substitution affords both mono- and bis-phosphine substituted derivatives Os3(CO)9(PR3) (μ-H) (μ-sac) (2) and Os3(CO)8(PR3)2(μ-H) (μ-sac) (3) respectively. In the mono-substituted derivatives, the phosphine occupies an equatorial position on the osmium that is directly bonded to the carbonylic oxygen of saccharinate, while in the bis-(phosphine) substituted derivatives the second phosphine is bound to the remote osmium also occupying an equatorial site. In all complexes the saccharinate ligand remains in the bidentate N,O coordination mode thus playing a directing spectator role in these reactions.