Heterobimetallic Nitrido Complexes of Group 8 Metalloporphyrins.

Heterobimetallic nitrido porphyrin complexes with the [(L)(por)M-N-M'(LOEt )Cl2 ] formula {por2- = 5,10,15,20-tetraphenylporphyrin (TPP2- ) or 5,10,15,20-tetra(p-tolyl)porphyrin (TTP2- ) dianion; LOEt - = [Co(η5 -C5 H5 ){P(O)(OEt)2 }3 ]- ; M = Fe, Ru, or Os; M' = Ru or Os; L = H2 O or pyridine} have been synthesized, and their electrochemistry has been studied. Treatment of trans-[Fe(TPP)(py)2 ] (py = pyridine) with Ru(VI) nitride [Ru(LOEt )(N)Cl2 ] (1) afforded Fe/Ru μ-nitrido complex [(py)(TPP)Fe(μ-N)Ru(LOEt )Cl2 ] (2). Similarly, Fe/Os analogue [(py)(TPP)Fe(μ-N)Os(LOEt )Cl2 ] (3) was obtained from trans-[Fe(TPP)(py)2 ] and [Os(LOEt )(N)Cl2 ]. However, no reaction was found between trans-[Fe(TPP)(py)2 ] and [Re(LOEt )(N)Cl(PPh3 )]. Treatment of trans-[M(TPP)(CO)(EtOH)] with 1 afforded μ-nitrido complexes [(H2 O)(TPP)M(μ-N)Ru(LOEt )Cl2 ] [M = Ru (4a) or Os (5)]. TTP analogue [(H2 O)(TTP)Ru(μ-N)Ru(LOEt )Cl2 ] (4b) was prepared similarly from trans-[Ru(TTP)(CO)(EtOH)] and 1. Reaction of [(H2 O)(por)M(μ-N)M(LOEt )Cl2 ] with pyridine gave adducts [(py)(por)M(μ-N)Ru(LOEt )Cl2 ] [por = TTP, and M = Ru (6); por = TPP, and M = Os (7)]. The diamagnetism and short (por)M-N(nitride) distances in 2 [Fe-N, 1.683(3) Å] and 4b [Ru-N, 1.743(3) Å] are indicative of the MIV ═N═M'IV bonding description. The cyclic voltammograms of the Fe/Ru (2) and Ru/Ru (4b) complexes in CH2 Cl2 displayed oxidation couples at approximately +0.29 and +0.35 V versus Fc+/0 (Fc = ferrocene) that are tentatively ascribed to the oxidation of the {LOEt Ru} and {Ru(TTP)} moieties, respectively, whereas the Fe/Os (3) and Os/Ru (5) complexes exhibited Os-centered oxidation at approximately -0.06 and +0.05 V versus Fc+/0 , respectively. The crystal structures of 2 and 4b have been determined.