Penn Chemistry (@pennchemistry.bsky.social)

Isonitrile Insertion into Titanium Neopentylidene Alkyl Complexes Yields a Bifurcated Pathway to Form κ1-N-vinylamido or κ2-C,N-azaalleneyl Fragments Three organometallic ligand scaffolds resulting from the insertion of 1-adamantyl isonitrile (C≡NAd; Ad = C10H15) into titanium neopentylidene complexes, [(PNP)Ti═CHtBu(X)] are described herein. Treatment of the titanium neopentylidene complex (PNP)Ti═CHtBu(OTf) (1-OTf, PNP– = N[2-PiPr2-4-methylphenyl]2–, OTf = trifluoromethanesulfonate–) with one equivalent of C≡NAd leads to the formation of a titanium η2-C,N-ketenimine, (PNP)Ti(η2-C,N-AdNCCHtBu)(OTf) (2-OTf). However, when the titanium neopentylidene neopentyl complex (PNP)Ti═CHtBu(CH2tBu) (1-Np) is added one equivalent of C≡NAd, a titanium neopentylidene κ1-N-vinylamido complex (PNP)Ti═CHtBu(κ1-N-AdNCHCHtBu) (3) is formed. In contrast, the titanium neopentylidene methyl complex (PNP)Ti═CHtBu(CH3) (1-Me) reacts with one equivalent of C≡NAd to produce a rare chelating κ2-C,N-azaalleneyl ligand, in the complex (PNP)Ti(κ2-C,N-AdNCCtBu) (4), with concurrent extrusion of methane. Independently, it is shown that treatment of 2-OTf with one equivalent of neopentyl lithium (LiNp, Np– = CH2tBu) or a half equivalent of dimethyl magnesium (MgMe2) smoothly forms complex 3 or 4, respectively, and suggests that the η2-C,N-ketenimine ligand in 2-OTf might be an intermediate ligand enroute to the neopentylidene κ1-N-vinylamido or κ2-C,N-azaalleneyl complexes. Complexes 2-OTf, 3 and 4 have been structurally and spectroscopically characterized and a proposed mechanism for the formation of complexes 3 and 4 is also described. https://pubs.acs.org/doi/10.1021/acs.organomet.4c00442?utm_source=SendGrid_ealert&utm_medium=ealert&utm_campaign=ASAP_orgnd7_v0_i0