Syntheses, electrochemistry, photophysics and photochemistry of nitridorhenium(V) diphosphine complexes and related nitridorhenium(V) organometallics; crystal structure of [ReVN(C
CBut)2(PPh3)2]
Abstract
A series of nitrido complexes [ReNL2X]n[L = dppe(Ph2PCH2CH2PPh2), X = F, Cl, Br, NCS, NCO or N3(n= 1) or MeCN (n= 2); L = dppbz(Ph2PC6H4PPh2-o), X = Cl (n= 1) or MeCN (n= 2)] have been synthesized and shown to exhibit long-lived photoluminescence in both the solid state and fluid solution, derived from the [(dxy)1(dπ*)1] triplet (dπ*= dxz, dyz). The positions of the d–d absorption and emission bands have been found to be dependent on the identity of X. The luminescence quantum yields of [ReNL2(MeCN)]2+ are greatly enhanced with respect to their chloro analogues. Cyclic voltammetric studies show that the [ReNL2X]+ complexes display an irreversible reduction couple at Epc of ca.–2.0 to –2.3 V and an irreversible oxidation couple at Epa of ca.+1.3 to +1.9 V vs. the ferrocenium–ferrocene couple in MeCN (0.1 mol dm–3 NBu4PF6). An additional irreversible reduction couple is observed at ca.–1.67 and –1.63 V for [ReN(dppe)2(MeCN)]2+ and [ReN(dppbz)2(MeCN)]2+, respectively. The reactivities of the nitrido complexes toward trifluoroacetic acid and electron donors such as alkoxybenzenes and organic amines have been investigated by Stern–Volmer quenching experiments and transient absorption difference spectroscopy. The electrochemical and spectroscopic properties of [ReNL2X]n+ have been compared with those of organorhenium(V) nitro complexes [ReNR2(PPh3)2](R = CCBut or C6H4Me-p). The crystal structure of [ReN(C
CBut)2(PPh3)2] has been determined: monoclinic, space group P21/n, a= 13.708(8), b= 19.161(6), c= 17.246(3)Å, β= 109.49(4)°, U= 4270(3)Å3, Z= 4. A Re
N distance of 1.63(2)Å has been measured.