Binuclear Pd(II) and Pt(II) complexes supported by rac-dpmppm (bis[(diphenylphosphinomethyl)phenylphosphino]methane) in a triply-bridged Z-form, [M2Cl4(rac-dpmppm)] (M = Pd (3a), Pt (3b)), readily reacted with 2,6-xylyl isocyanide (XylNC) in the presence of NH4PF6 to afford [M2Cl2(rac-dpmppm)(XylNC)2](PF6)2 (M = Pd (4a), Pt (4b)), in which each metal center accommodates one isocyanide ligand at the trans position to the inner P atom of dpmppm. Similarly, treatment of 3a and 3b with axially chiral (R/S)-1,1′-binaphthyl-2,2′-bisisocyanide (rac-Binac) in the presence of NH4OTf gave cyclic tetranuclear complexes, [{M2Cl2(rac-dpmppm)(rac-Binac)}2](OTf)4 (M = Pd (5), Pt (8)), where two {M2Cl2(rac-dpmppm)}2+ fragments are connected by two rac-Binac ligands through chirality sorting of (R*,R*)-dpmppm and (R*)-Binac. Complex 5 could be transformed into the halide exchanged tetranuclear complexes, [{Pd2X2(rac-dpmppm)(rac-Binac)}2](OTf)4 (X = Br (6), I (7)), to show that the rectangular arrangement of four Pd(II) ions is elongated by repulsive interaction between halide ligands. By using (R)- and (S)-Binac, enantiopure Pd4 complexes, [{Pd2Cl2((R*,R*)-dpmppm)((R*)-Binac)}2](OTf)4 (5 RR/R and 5 SS/S ), were successfully isolated as pure crystalline forms, from which enantiopure (R,R)- and (S,S)-dpmppm were obtained by treatment with NaCN aqueous solution. Namely, optical resolution of rac-dpmppm was established through the tetranuclear Pd complexes, which is the first example for methylene-bridged polyphosphines, R2P(CH2PR) n CH2PR2 (n > 0). Furthermore, chiral octapalladium chains, [Pd8((R*,R*)-dpmppm)4(NCCH3)2](BF4)4 (2 RR and 2 SS ), were synthesized by reacting enantiopure P-chiral dpmppm with [Pd2(CH3CN)6](BF4)2 and [Pd2(dba)3]·C6H6 and were characterized by spectroscopic and X-ray crystallographic analyses, to determine the absolute configurational structures. The Pd8 chains are the longest enantiopure chiral single-metal-atom chains structurally characterized, thus far, and the electronic structures were examined on the basis of DFT calculations of 2 RR .
Reaction of[Cu(MeCN) 4 ]BF 4 with rac-Ph 2 -PCH 2 P(Ph)CH 2 P(Ph)CH 2 PPh 2 (rac-dpmppm) gave [Cu 2 (μ-racdpmppm)(MeCN) 4 ](BF 4 ) 2 (1), and that of CuCl with rac-dpmppm in the presence of 2,6-xylyl isocyanide (XylNC) and NH 4 PF 6 afforded [Cu 2 (μ-rac-dpmppm)(XylNC) 4 ](PF 6 ) 2 (2). Complex 1 was converted by treatment with diimino ligands (N^N) to a series of Cu I 2 complexes, [Cu 2 (μ-rac-dpmppm)(N^N) 2 ] 2+ (N^N = phen (3), 4-Mephen (4), 4,7-Me 2 phen (5), 5,6-Me 2 phen (6), 2,9-Me 2 phen (7), 3,4,7,8-Me 4 phen (8), 4,7-Ph 2 phen (9), bpy (10), 4,4′-Me 2 bpy (11), and 1,8-naphtyridine (nap) (12)), where phen = 1,10-phenanthroline and bpy = 2,2′-bipyridyl. The isolated complexes were characterized by spectroscopic and X-ray crystallographic analyses to reveal that two Cu I ions are triply bridged by a rac-dpmppm ligand in κ 2 ,κ 2 fashion resulting in robust Z-form dicopper structures, where the Cu···Cu distances vary from 4.2 to 5.6 Å depending on the ancillary ligands through altering conformation of the fused six-membered che- [a]
Invited for the cover of this issue is the group of Tomoaki Tanase at Nara Women's University, Japan. The cover image shows a dinuclear copper(I) complex triply bridged by rac‐dpmppm with a series of diimino ligands as a “dicopper firefly” that switches its luminescence mechanisms to emit rapid fluorescence in dichloromethane solution and 3MLCT phosphorescence in the solid state.
The Front Cover shows dinuclear copper(I) complexes triply bridged by a tetraphosphine rac‐dpmppm ligand in Z‐form with a series of diimino ligands, which emit rapid fluorescence from loosely coordinated diimino ligands in CH2Cl2 solution and 3MLCT phosphorescence in the solid state. The “dicopper firefly” switches the luminescence mechanisms by fluxional flipping of the diimino ligands. More information can be found in the Full Paper by T. Tanase et al. For more on the story behind the cover research, see the Cover Profile.
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