Octa(m 3 -selenido)hexarhenium( iii ) Complexes Containing Axial Monodentate Diphosphine or Diphosphine – Monoxide Ligands Zhong-Ning Chen, Takashi Yoshimura, Masaaki Abe, Kiyoshi Tsuge, Yoichi Sasaki,* Shoji Ishizaka, Haeng-Boo Kim, and Noboru Kitamura [a] Abstract: A series of the octahedral hexarhenium( iii ) complexes containing a variable number of diphosphine (di- phos) or diphosphine – monoxide (di- phosO) ligands have been prepared by the substitution of the diphosphine Ph 2 P(CH 2 ) n PPh 2 (n  1 to 5) for the iodide ions in the parent octa- hedral hexarhenium cluster compound [Re 6 Se 8 I 6 ] 3 . The diphosphine Ph 2 P- (CH 2 ) n PPh 2 ligands adopt an h 1 -bonding mode with the Re 6 (m 3 -Se) 8 core, and the P donor atom in the pendant arm is noncoordinated and oxygenated in most cases. The series of new hexarhenium( iii ) complexes have been well-defined by 1 H, 13 C, and 31 P NMR spectroscopic and FAB-MS data. Four compounds among the series were characterized by X-ray structural determination. Geometrical isomers were identified by NMR spec- troscopy as well as by the structural determinations. The apical ligand sub- stitution induces significant change in the redox potentials and the photophys- ical properties of the Re 6 (m 3 -Se) 8 core. The E 1/2 value of the reversible process Re III 6 /Re III 5 Re IV becomes more positive with the increasing number of the coor- dinated P donors. The phosphine-sub- stituted hexarhenium( iii ) derivatives are highly luminescent, with microsecond scale emissive lifetime at ambient tem- perature, and the fully substituted derivatives with the formula [Re 6 Se 8 - (h 1 -diphosO) 6 ] 2 display the strongest luminescence with the longest emission lifetimes. Keywords: cluster compounds · luminescence · P ligand · redox chemistry · rhenium Introduction In recent years, much attention has been paid to octahedral hexametal cluster complexes [M 6 (m 3 -E) 8 L 6 ] q (M  transition metal, E  chalcogenide or halide, L  axial ligand) with respect to ligand substitution and redox reactions, photo- physical properties, and M 6 (m 3 -E) 8 core-based supramolecular design. [1] These hexametal cluster cores can be regarded as giant octahedral centers, and various organic ligands may be introduced into the apical sites to produce different M 6 (m 3 -E) 8 core-based derivatives. [2–15] Axial ligand substitution offers an excellent means to control the chemical and physical proper- ties by introducing organic ligands. [11d, 13, 14] It also provides the ways to use the hexametal cores as potential building blocks for aggregated cluster complexes with higher nuclearity or for molecular materials with specific function. [4b, 5b, 11a–c, 12d, 15] Diverse neutral and anionic ligands with various donors, the former including phosphine, [3, 7, 11] pyridine, [8, 13] and solvent molecules, [4a, 11b] and the latter embracing cyanide, [4b, 9, 12] alkyl oxide, [6] and carboxylate, [5] have been introduced into the apices of hexametal octahedrons. The hexarhenium cluster complexes [Re 6 (m 3 -E) 8 X 6 ] q (E  S, Se; L  Cl, Br, I; q  3, 4) [10] have been developed very recently, the substitution character of the axial ligands allows designed synthesis based on the hexarhenium core and the chemistry of these clusters is more versatile than the other hexametal complexes. To the best of our knowledge, the substitution chemistry of bi- or multidentate ligands for the axial ligand L in [Re 6 (m 3 -E) 8 L 6 ] q (E  S, Se) octahedral hexametal complexes has not been studied previously. [13b, 14] Herein we report on the stepwise substitution reactions of the bidentate diphosphine ligands Ph 2 P(CH 2 ) n PPh 2 (n  1 – 5) for the iodide ions in the parent compound [Re 6 (m 3 -Se) 8 I 6 ] 3 (1), as well as on the preparation of a series of octahedral hexarhenium derivatives [Re 6 (m 3 -E) 8 I (6m) L m ] (3m) (m  3– 6), in which L is a monodentate diphosphine or a diphos- phine – monoxide ligand. We have also prepared the com- pound containing Ph 2 P(CH 2 ) 6 PPh 2 with the “bridge-chelate” coordination mode around the octahedral hexarhenium cluster core. [14] The substitution reaction can not only be controlled in a stepwise manner, but also the substitution mode (whether monodentate or bridge-chelate) is adjustable by altering the number of the methylene spacer groups in the diphosphine Ph 2 P(CH 2 ) n PPh 2 . We report herein the detailed [a] Prof. Dr. Y. Sasaki, Dr. Z.-N. Chen, Dr. T. Yoshimura, Dr. M. Abe, Dr. K. Tsuge, Dr. S. Ishizaka, Prof. Dr. H.-B. Kim, Prof. Dr. N. Kitamura Division of Chemistry, Graduate School of Science Hokkaido University, Kita-ku, Sapporo 060-0810 (Japan) Fax: ( 81)11-706-3447 FULL PAPER Chem. Eur. J. 2001, 7 , No. 20  WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001 0947-6539/01/0720-4447 $ 17.50+.50/0 4447