Selective Syntheses of Homo- and Hetero-dimetal Complexes with the Tetramethyltetraazaannulene Ligand of the Type [(ML,M‘L‘)(TMTAA)], Where M and M‘ Are Rh(I) or Ir(I) and L and L‘ Are COD or (CO)₂

Abstract

The tetraazamacrocycle, tmtaaH 2, reacts with [M 2 (COD) 2 (μ-OH) 2 ], M = Rh or Ir, to give [M(tmtaaH)(COD)], which give the dicarbonyl derivatives, [M(tmtaaH)(CO) 2 ], on exposure to CO. The COD and dicarbonyl derivatives, M = Rh, are methylated with MeOTf at the β-carbon site of the imidinate ring, giving [Rh(tmtaaHMe)(L 2 )] +, where L 2 = COD or (CO) 2 . The crystal structure of [Rh(tmtaaHMe)(CO) 2 ][OTf] shows that the site of methylation is the imidinate ring that contains the Rh(CO) 2 fragment. Protonation by HOTf also occurs at the β-carbon site of the imidinate ring, assumed to be the ring that contains the Rh(L 2 ) fragment. The dicarbonyls are deprotonated by LiN(SiMe 3 ) 2 in thf, giving [M(CO) 2 (tmtaa)Li(thf)]. A crystal structure of M = Rh shows an intramolecular Li−Rh distance of 2.635(10) Å and an intermolecular Rh···Rh contact distance between two molecular units of 3.198(1) Å that align along their molecular z -axis. Addition of MeI to [M(CO) 2 (tmtaa)Li(thf)] yields [M(tmtaaMe)(CO) 2 ], where the methyl group is attached to the imidinate ring that contains the Li(thf) fragment, as shown by X-ray crystallography. The [M(tmtaaH)(CO) 2 ] reacts with half an equivalent of [M 2 (COD) 2 (μ-OH) 2 ] to give the mixed dimetal complexes [M(CO) 2 (tmtaa)M‘(COD)], where M,M‘ is either Rh,Rh or Rh,Ir, which react with CO to give [MM‘(tmtaa)(CO) 4 ].