Reactivity Studies on a Binuclear Ruthenium(0) Complex Equipped with a Bridging κ2N,Ge-Amidinatogermylene Ligand

The amidinatogermylene-bridged diruthenium(0) complex [Ru2{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(CO)7] (2; iPr2bzam = N,N′-bis­(iso-propyl)­benzamidinate; HMDS = N­(SiMe3)2) reacted at room temperature with tBuNC and PMe3 to give [Ru2{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(L)­(CO)6] (L = tBuNC, 3; PMe3, 4), which contain the new ligand in an axial position on the Ru atom that is not attached to the amidinato fragment. At 70 °C, 2 reacted with PPh3, PMe3, dppm, and dppe to give the equatorially substituted derivatives [Ru2{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(L)­(CO)6] (L = PPh3, 5; PMe3, 6) and [Ru2{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(μ–κ2P,P′-L2)­(CO)5] (L2 = dppm, 7; dppe, 8). HSiEt3 and HSnPh3 were oxidatively added to complex 2 at 70 °C, leading to the coordinatively unsaturated products [Ru2(ER3)­(μ-H)­{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(CO)5] (ER3 = SiEt3, 9; SnPh3, 10), which easily reacted with tBuNC and CO to give the saturated derivatives [Ru2(ER3)­(μ-H)­{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(tBuNC)­(CO)5] (ER3 = SiEt3, 11; SnPh3, 12) and [Ru2(ER3)­(μ-H)­{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­(CO)6] (ER3 = SiEt3, 13; SnPh3, 14), respectively. Compounds 9–14 have their ER3 group on the Ru atom that is not attached to the amidinato fragment. In contrast, the reaction of 2 with H2 at 70 °C led to the unsaturated tetranuclear complex [Ru4(μ-H)2{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}2(CO)10] (15), which also reacted with tBuNC and CO to give the saturated derivatives [Ru4(μ-H)2{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}2(L)2(CO)10] (L = tBuNC, 16; CO, 17). All tetraruthenium complexes contain an unbridged metal–metal connecting two germylene-bridged diruthenium units. Under CO atmosphere, complex 17 reverted to compound 2. All of the coordinatively unsaturated products (9, 10, and 15) have their unsaturation(s) located on the Ru atom(s) that is­(are) attached to the amidinato fragment(s). In the absence of added reagents, the thermolysis of 2 in refluxing toluene led to [Ru4{μ–κ2Ge,N-Ge­(iPr2bzam)­(HMDS)}­{μ3−κGe-Ge­(HMDS)}­(μ–κ3N,C,N′-iPr2bzam)­(μ-CO)­(CO)8] (18), which contains two new ligands, a triply bridging germylidyne and a bridging benzamidinate, and that results from the condensation of two molecules of 2 and the activation of the Ge–N bond of the benzamidinatogermylene ligand of 2.