Silox Titanium(II) and Masked Ti(II) Derivatives (Silox = ^t Bu ₃ SiO): Titanacycles, Dinitrogen Species and Serendipitous Silicides

Exploration of Ti(II) or “masked” Ti(II), i.e. Ti(IV) derivatives that could electrophilically ring-open 1.1.1-propellane (111P) was conducted. Reduction of (silox)3Ti (1, silox = tBu3SiO) with KC8 generated [(silox)3Ti]K(OEt2)n (2-K), which degraded 111P, but exposure to N2 produced [(silox)3Ti](μ-N2)K(OEt2)3 (2-N2K, tentative), and diimide dianion [(silox)3Ti=N–N=Ti(silox)3][K2(18-c-6)3] (22-N2). Attempts to prepare a mononorbornene (NBE) complex upon KC8 reduction of (silox)2TiCl2 (3) instead reductively coupled two NBE to give the titanacycle (silox)2Ti(κ2-C,C–C14H20) (4), which converted to a benzyne/NBE titanacycle (silox)2Ti(κ2-C,C–C13H14) (7) of remarkable stability. Similar reductions in the presence of PMe2R (R = Me, Ph) afforded metastable (silox)2Ti(PMe2R)2 (8-PMe2R, R = Me, Ph) that serendipitously and sporadically degraded to (silox)2(PMe2R)Ti=Si=Ti(PMe2R)(silox)2 (9-PMe2R, R = Me, Ph); other isolated products included [(silox)2Ti]2(μ-C,P-CH2PMe2)2 (10), (silox)2ClTi(PMe2Ph) (11), and (silox)2(PMe3)Ti=NN=Ti(PMe3)(silox)2 (12). None of the reduced or masked Ti(II) species afforded the desired 3-exomethylenecyclobutanylidene complexes, thus providing provisional limits on the use of 111P as an alkylidene source.