Low-Coordinate Magnesium Sulfide and Selenide Complexes

The reactions of [{( (iPrDip)NacNac)Mg}(2)] 1 ((iPrDip)nacnac = HC(iPrCNDip)(2)) with Ph3P=O at 100 degrees C afforded the phosphinate complex [((iPrDip)NacNac)Mg(OPPh3)(OPPh2)] 3. Reactions of 1 with Ph3P=E (E = S, Se) proceeded rapidly at room temperature to low-coordinate chalcogenide complexes [{((iPrDip)NacNac)Mg}2(mu-S)] 4 and [{((iPrDip)NacNac)Mg}(2)(mu-Se)] 5, respectively. Similarly, reactions of (NHC)-N-R=S ((MeCNR)2C=S with R = Me, Et, or iPr) with 1 afforded NHC adducts of magnesium sulfide complexes, [{((iPrDip)NacNac)Mg((NHC)-N-R)}(mu-S){Mg((iPrDip)NacNac)}] 6, that could alternatively be obtained by adding the appropriate RNHC to sulfide complex 4. Complex 4 reacted with 1-adamantylazide (AdN(3)) to give [{((iPrDip)NacNac)Mg}(2)(mu-SN(3)Ad)] 7 and can form various simple donor adducts in solution, of which [((iPrDip)NacNac)Mg(OAd)}(2)(mu-S)] 8a (OAd = 2-adamantanone) was structurally characterized. The nature of the ionic Mg-E-Mg unit is described by solution and solid-state studies of the complexes and by DFT computational investigations.