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

The amidinatogermylene-bridged diruthenium(0) complex [Ru-2{mu-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(CO)(7)] (2; (i)Pr(2)bzam = N,N'-bis(iso-propyl)benzamidinate; HMDS = N(SiMe3)(2)) reacted at room temperature with (BuNC)-Bu-t and PMe3 to give [Ru-2{mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(L)(CO)(6)] (L = (BuNC)-Bu-t, 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 degrees C, 2 reacted with PPh3, PMe3, dppm, and dppe to give the equatorially substituted derivatives [Ru-2{mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(L)(CO)(6)] (L = PPh3, 5; PMe3, 6) and [Ru-2{mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(mu-kappa P-2,P'-L-2)(CO)(5)] (L-2 = dppm, 7; dppe, 8). HSiEt3 and HSnPh3 were oxidatively added to complex 2 at 70 degrees C, leading to the coordinatively unsaturated products [Ru-2(ER3)(mu-H){mu-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(CO)(5)] (ER3 = SiEt3, 9; SnPh3, 10), which easily reacted with (BuNC)-Bu-t and CO to give the saturated derivatives [Ru-2(ER3)(mu-H){mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)-(HMDS)}((BuNC)-Bu-t)(CO)(5)] (ER3 = SiEt3, 11; SnPh3, 12) and [Ru-2(ER3)(mu-H){mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)-(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 H-2 at 70 degrees C led to the unsaturated tetranuclear complex [Ru-4(mu-H)(2){mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(2)(CO)(10)] (15), which also reacted with tBuNC and CO to give the saturated derivatives [Ru-4(mu-H)(2){mu 0-kappa Ge-2,N-Ge((i)Pr(2)bzam)(HMDS)}(2)(L)(2)(CO)(10)] (L = (BuNC)-Bu-t, 16; CO, 17). All tetraruthenium complexes contain an unbridged metal0-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 [Ru-4{mu 0-kappa Ge-2,N-Ge((t)Pr(2)bzam)(HMDS)}{mu(3)-kappa Ge-Ge(HMDS)}(mu 0-kappa N-3,C,N'-(i)Pr(2)bzam)(mu-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.