Solution multinuclear and multidimensional NMR analyses of the [(triphos)Rh(?1:?2-P4RR)]n+ complex cations [triphos = MeC(CH2PPh2)3; R = H, Me, Ph; R = lone pair, H, Me; n = 0, 1] confirm the same primary structure determined by X-rays in the solid state. In addition, 2D 1H NOESY and 31P{1H} exchange NMR spectroscopy show that these complexes are nonrigid on the NMR time-scale over the 253-318 K temperature range. A dynamic process that involves the terminal phosphane groups of the triphos ligand is displayed by each compound. The NMR spectroscopic data indicate a slow Introduction White phosphorus is a cheap chemical largely used in the manufacturing of organophosphorus compounds.[1] These industrially important derivatives are generally produced by the reaction of PCl3 or PCl5 with suitable organic reagents. The industrial process is not very environmentally sustainable as the reaction involves gaseous chlorine and releases huge amounts of hydrochloric acid into the atmosphere. Therefore, the discovery of new and efficient methods for the preparation of organophosphorus derivatives from P4 through non-chlorine routes remains a challenging task for the industry.[2] Moreover, the underpinnings of the formation of P-C and P-H bonds need to be understood in more detail.[2,3] Advances in this area entail the use of transition metal systems that are suitable for the activation of both the P4 tetrahedron and the organic substrate. On the other hand, a recent breakthrough in the area has been presented by Bertrand et al. who have reported on the reactivity of alkyl amino carbenes with P4. This process does not lead to the formation of any metal intermediate and leads to very reactive P-C bonds.[4] Another important advancement in P4 activation/functionalization was our previous finding that some rhodium [a] Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti OrganoMetallici, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy E-mail: maurizio.peruzzini@iccom.cnr.it © 2008 Wiley-VCH Verlag 1392 GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2008, 1392-1399 scrambling motion in which the P4R unit tumbles with respect to the (triphos)Rh moiety. DFT calculations outline a possible turnstile mechanism involving the threefold and twofold rotors into which the complex is subdivided. The process goes through a transition state in which the axial and equatorial dispositions of the PRR and P=P donating groups of the P4RR ligand are inverted with respect to the ground state.
Dynamic Behaviour of the [(Triphos)Rh(·1:·2-P4RR')]n+ Complexes [Triphos = MeC(CH2PPh2)3; R = H, Alkyl, Aryl; R' = Lone Pair, H, Me; n = 0, 1]: NMR and Computational Studies
Barbaro Pierluigi;Caporali Maria;Ienco Andrea;Mealli Carlo;Peruzzini Maurizio;Vizza Francesco
2008
Abstract
Solution multinuclear and multidimensional NMR analyses of the [(triphos)Rh(?1:?2-P4RR)]n+ complex cations [triphos = MeC(CH2PPh2)3; R = H, Me, Ph; R = lone pair, H, Me; n = 0, 1] confirm the same primary structure determined by X-rays in the solid state. In addition, 2D 1H NOESY and 31P{1H} exchange NMR spectroscopy show that these complexes are nonrigid on the NMR time-scale over the 253-318 K temperature range. A dynamic process that involves the terminal phosphane groups of the triphos ligand is displayed by each compound. The NMR spectroscopic data indicate a slow Introduction White phosphorus is a cheap chemical largely used in the manufacturing of organophosphorus compounds.[1] These industrially important derivatives are generally produced by the reaction of PCl3 or PCl5 with suitable organic reagents. The industrial process is not very environmentally sustainable as the reaction involves gaseous chlorine and releases huge amounts of hydrochloric acid into the atmosphere. Therefore, the discovery of new and efficient methods for the preparation of organophosphorus derivatives from P4 through non-chlorine routes remains a challenging task for the industry.[2] Moreover, the underpinnings of the formation of P-C and P-H bonds need to be understood in more detail.[2,3] Advances in this area entail the use of transition metal systems that are suitable for the activation of both the P4 tetrahedron and the organic substrate. On the other hand, a recent breakthrough in the area has been presented by Bertrand et al. who have reported on the reactivity of alkyl amino carbenes with P4. This process does not lead to the formation of any metal intermediate and leads to very reactive P-C bonds.[4] Another important advancement in P4 activation/functionalization was our previous finding that some rhodium [a] Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti OrganoMetallici, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy E-mail: maurizio.peruzzini@iccom.cnr.it © 2008 Wiley-VCH Verlag 1392 GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2008, 1392-1399 scrambling motion in which the P4R unit tumbles with respect to the (triphos)Rh moiety. DFT calculations outline a possible turnstile mechanism involving the threefold and twofold rotors into which the complex is subdivided. The process goes through a transition state in which the axial and equatorial dispositions of the PRR and P=P donating groups of the P4RR ligand are inverted with respect to the ground state.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
