[1]Metallocenophanes (M = Fe, Ru) of Heavier Group 13 Elements (E = Al, Ga):  Synthesis, Characterization, and Ring-Opening Polymerization

Two new [1]ruthenocenophanes, Ru(η5-C5H4)2E(Me2Ntsi) (Me2Ntsi = C(SiMe3)2SiMe2NMe2; E = Al, Ga), bridged by aluminum (3a) and gallium (3b), were synthesized by reaction of dilithioruthenocene with (Me2Ntsi)ECl2 in good to moderate yields (3a, 80%; 3b, 36%). Both species were analyzed by standard techniques (multinuclear NMR spectroscopy, elemental analysis, UV−vis, MS), and their molecular structures were deduced from single-crystal X-ray analysis. Compared to the analogous [1]ferrocenophanes 2a,b, compounds 3a,b showed an increased ring tilt as indicated by the tilt angle α (2a, α = 14.33(14)°; 3a, α = 20.31(19)°; 2b, α = 15.83(19)°; 3b, α = 20.91(19)°). Ring-opening polymerization (ROP) with previously published aluminum- and gallium-bridged [1]ferrocenophanes Fe(η5-C5H4)2E(Pytsi) (Pytsi = C(SiMe3)2SiMe2(2-C6H4N); E = Al (1a), Ga (1b)) and Fe(η5-C5H4)2E(Me2Ntsi) (E = Al (2a), Ga (2b)) and the [1]ruthenocenophanes 3a,b (this paper) has been shown to be very sluggish or unsuccessful. Only the ROP of 1b with [Pd(dba)2] (2 mol %, toluene, 25 °C, 48 h) resulted in polymeric material (GPC analysis: M w = 2.11 × 104, PDI = 3.0).