Utilization of Redox and Acid/Base Chemistry for the Deprotection of a Mn(dmpe)2(C⋮CSiMe3)2 Complex

The reaction of the low-spin d 5 complex Mn(dmpe) 2 (C⋮CSiMe 3 ) 2 ( 1 ) (dmpe = 1,2-bis(dimethylphosphino)ethane) with [NBu 4 ][Ph 3 F 2 M] (M = Si or Sn) yields the SiMe 3 metathesis products Mn(dmpe) 2 (C⋮CMPh 3 ) 2 (M = Si 2a, Sn 2b ). When the Mn(II) species 1 was dissolved in MeOH in the presence of NaBF 4, disproportionation occurred with formation of the Mn(I) products Mn(dmpe) 2 (C⋮CSiMe 3 )(C CH 2 ) ( 3a ) and [Mn(dmpe) 2 (C⋮CSiMe 3 )(⋮C−CH 3 )][BF 4 ] ( 5a ) and the cationic Mn(III) complex [Mn(dmpe) 2 (C⋮CSiMe 3 ) 2 ][BF 6 ] ( 4a ). In a similar way 1 was transformed into [Mn(dmpe) 2 (C⋮CSiMe 3 ) 2 ][H 2 F 3 ] ( 4b ) and [Mn(dmpe) 2 (C⋮CSiMe 3 )(⋮C−CH 3 )][H 2 F 3 ] ( 5b ) by its reaction with excess of HF·pyridine. The reaction of 1 with Li or Na in toluene at 100 °C gave the new d 6 cis -bisalkynyl complexes [Mn(dmpe) 2 (C⋮CSiMe 3 ) 2 ][M] (M = Li 6a, Na 6b ). The trans -alkynylvinylidene derivatives Mn(dmpe) 2 (C⋮CSiMe 3 )(C C(E)SiMe 3 ) (E = H 3b, SnMe 3 3c ) were obtained by the reaction of species 6 with stoichiometric MeOH or ClSnMe 3 . In MeOH/KOH solutions complex 3b or 3c was converted into the trans -alkynylvinylidene species 3a . The reaction of complex 3a with HBF 4 or HF·pyridine produced the carbyne complexes [Mn(dmpe) 2 (C⋮CSiMe 3 )(⋮C−CH 3 )][A] (A = BF 4 5a, H 2 F 3 5b ). These new compounds have been characterized by NMR and IR spectroscopy and elemental analyses, and for 2a, 2b, 3a, 4b, and 6b X-ray diffraction studies have been performed.