180839-70-7Relevant articles and documents
Dirhenium Polyhydrides Containing Bridging 2-Mercaptoquinoline Ligands
Ondracek, Andrea L.,Wu, Wengan,Fanwick, Phillip E.,Walton, Richard A.
, p. 5249 - 5253 (1996)
The dirhenium polyhydride complex [Re2H6(μ-mq)2(PPh3) 4](BF4)2 (1), where mq represents the 2-mercaptoquinoline ligand, can be deprotonated in two steps to afford the diamagnetic complexes [Re2H5(μ-mq)2(PPh3) 4]BF4 (2) and Re2H4μ-mq)2(PPh3)4 (3) through the use of the bases PMe3 and DBU, respectively. The treatment of 2 and 3 with HBF4·Et2O regenerates 1. The basic structure of the [Re2(μ-mq)2(PPh3)4] unit is retained throughout these deprotonations/protonations as demonstrated by 1H and 31P{'H} NMR spectroscopy. The neutral tetrahydrido complex 3 undergoes a two-electron oxidation when treated with the oxidants [(η5-C5H5)2Fe]BF4 and [(η5-C5H5)2-Fe]PF6 to afford the salts [Re2H4(μ-mq)2(PPh3) 4](BF4)2 (4a) and [Re2H4(μ-mq)2(PPh3) 4](PF6)2 (4b), respectively. The [Re2H4(μ-mq)2(PPh3) 4]2+/Re2H4(μ-mq) 2(PPh3)4 couple has an E1/2 value of -0.47 V vs Ag/AgCl as measured by the cyclic voltammetric technique on solutions of 3 and 4 in 0. l M Bu4NPF6/CH2Cl2. The chemical reversibility of this process has been confirmed by the use of (η5-C5H5)2Co to reduce 4a back to 3. An X-ray crystal structure on a salt of the [Re2H4(μ-mq)2(PPh3) 4]2+ cation, established that this complex is very similar structurally to 1 (see J. Am. Chem. Soc., 1995, 117, 9715). The most important structural differences are (1) the different numbers of hydrido ligands present and (2) the presence of a Re-Re single bond in 4a (the Re-Re distance is 3.000(1) A? compared to 3.9034(8) A? in [Re2H6(μ-mq)2(PPh3) 4)2+. Crystal data for [Re2H4(μ-mq)2(PPh3) 4]-(ReO4)1.18(BF4) 0.82·3CH2Cl2 at 203 K: monoclinic space group P21/n (No. 14) with a = 14.716(4) A?, b = 43.908(13) A?, c = 14.860(3) A?, β= 110.164(19)°, V = 9013(4) A?3, Z = 4. The structure was refined to R = 0.071 (Rw = 0.159) for 14128 data (Fo2> 2σ(Fo2)).
