title: Synthesis of α-amino acidato derivatives of niobium and tantalum pentahalides and their conversion into iminium salts.
abstract: Dinuclear complexes of formula Nb2Cl9[O2CCH(R)NR'R″2-κO,κO] (R = CH2CHMe2, R' = R″ = H, 1a; R = CH2Ph, R' = R″ = H, 1b; R = CH2CH2SCH3, R' = R″ = H, 1c; R = R' = H, R″ = Me, 1d; R = CH2Ph, R' = R″ = Me, 1e; Nb2Cl9[O2C⌈CH(CH2)3NH⌉], 1f) were prepared by allowing NbCl5 to react in dichloromethane with the appropriate α-amino acid in 1:2 amino acid/Nb molar ratio. The 1:1 reactions between MX5 (M = Nb, Ta; X = Cl, Br) and a series of α-amino acids resulted in the formation of the iminium salts [(R)CH═NR'R″2][MX6] (R = CH2Ph, R' = R″ = Me: M = Nb, X = Cl, 2a; M = Nb, X = Br, 2b; M = Ta, X = Cl, 2c; M = Ta, X = Br, 2d; R = CH2Ph, R' = R″ = H, M = Nb: X = Cl, 3a; X = Br, 3b; R = CH2CHMe2, R' = R″ = H, M = Nb, X = Cl, 4; R = R' = H, R″ = Me, M = Nb, X = Cl, 5). The formate/amino acidate derivative NbCl3(O2CH)[O2CCH(CH2Ph)NMe2], 6, was isolated and identified as coproduct of the 1:1 reaction between NbCl5 and N,N-dimethyl-l-phenylalanine, leading to 2a. All of the compounds were characterized by analytical and spectroscopic methods and by X-ray diffractometry in the cases of 2a, 2b, and 2d. Moreover, density functional theory studies were carried out to shed light on mechanistic and structural aspects.
authors.affiliation: †Dipartimento di Scienze Molecolari e Nanosistemi, Ca' Foscari Università di Venezia, Dorsoduro 2137, 30123 Venezia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Bortoluzzi
authors.affiliation: §Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hayatifar
authors.affiliation: ‡Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 3, I-56124 Pisa, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Marchetti
authors.affiliation: ‡Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 3, I-56124 Pisa, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Pampaloni
authors.affiliation: §Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zacchini