A Terminally Bound Niobium Methylidyne

Complex (PNP)­Nb­(CH3)2(OAr) (PNP = N­[2-PiPr2-4-methylphenyl]2–, Ar = 2,6-iPr2C6H3), prepared from treatment of (PNP)­NbCl3 with NaOAr followed by 2 equiv of H3CMgCl, can be oxidized with [FeCp2]­[OTf] to afford (PNP)­Nb­(CH3)2(OAr)­(OTf). While photolysis of the latter resulted in formation of a rare example of a niobium methylidene, (PNP)­NbCH2(OAr)­(OTf), treatment of the dimethyl triflate precursor with the ylide H2CPPh3 produced the mononuclear group 5 methylidyne complex, (PNP)­NbCH­(OAr). Adding a Brønsted base to (PNP)­NbCH2(OAr)­(OTf) also resulted in formation of the methylidyne. Solid-state structural analysis confirms both methylidene and methylidyne moieties to be terminal, having very short Nb–C distances of 1.963(2) and 1.820(2) Å, respectively. It is also shown that methylidyne for nitride cross-metathesis between (PNP)NbCH(OAr) and NCR (R = tert-butyl or 1-adamantyl) results in formation of a neutral and mononuclear niobium nitride, (PNP)­NbN­(OAr), along with the terminal alkyne HCCR.