The selectivity of formation of organometallic rings or [2]catenanes [{X(4-C 6 H 4 OCH 2 -CtCAu) 2 (µ-Ph 2 PZPPh 2 )} n ], n )1 or 2, respectively, has been studied as a function of the hinge group X and the diphosphine ligandas identified by NMR spectroscopy. The complexes with Z ) (CH 2 ) 4 exist in solution predominantly as the macrocycles and so do not form analogous mixed diacetylide complexes. When the hinge group contained a prochiral carbon center (X ) CHMe, CMePh, 1,1-indanylidene), only achiral macrocycles [X(4-C 6 H 4 OCH 2 CtCAu) 2 (µ-Ph 2 PZPPh 2 )] were formed in solution when Z ) (CH 2 ) 4 , but mixtures containing both achiral macrocycles and chiral [2]catenane were formed when Z ) (CH 2 ) 3 . In several cases, the solid-state structures of the isolated complexes were not representative of the structures in solution, with macrocycles being dominant in solution and [2]catenanes formed preferentially during crystallization.
The digold(I) diacetylides [4-RC 6 H 9 (4-C 6 H 4 OCH 2 CtCAu) 2 ], which contain a cyclohexylidene hinge group 4-RC 6 H 9 with R ) H or t-Bu, react with diphosphine ligands Ph 2 PZPPh 2 to give the corresponding macrocycles orBu, the bulky tert-butyl group locks the cyclohexane ring conformation and so provides a good NMR spectroscopic probe of the structure. The organogold(I) [2]catenane complexes are chiral when R ) t-Bu, and the complex with Z ) (CH 2 ) 4 gives an equilibrium in solution between ring, double-ring, and [2]catenane. When R ) H and Z ) (CH 2 ) 3 , the variabletemperature NMR spectra give new insight into the fluxionality in the [2]catenane complex, and when R ) H and Z ) (CH 2 ) 4 , it is shown that the complex exists in solution as the ring structure, although it crystallizes as a doubly braided [2]catenane.
Reactions of the bis(bidentate) Schiff-bases N,N'-bis(6-alkyl-2-pyridylmethylene)ethane-1,2-diamine (where alkyl = H, Me, iPr) (L) with tetrakis(acetonitrile)copper(I) hexafluorophosphate and silver(I) hexafluorophosphate afforded, respectively, the double-stranded, dinuclear metal helicates [T-4-(R,R)]-(+/-)-[M2L2](PF6)2 (M = Cu, Ag). The helicates were characterized by 1H and 13C NMR spectroscopy, conductivity, microanalysis, and single-crystal X-ray structure determinations on selected compounds. Intermolecular ligand exchange and intramolecular inversion rates for the complexes were investigated by 1H NMR spectroscopy. Reversible intermolecular ligand exchange between two differently substituted helicates followed first-order kinetics. The rate constants (k) and corresponding half-lives (t(1/2)) for ligand exchange for the dicopper(I) helicates were k = (1.6-1.8) x 10(-6) s(-1) (t(1/2) = 110-120 h) in acetone-d6, k = 4.9 x 10(-6) s(-1) (t(1/2) = 40 h) in dichloromethane-d2, and k> 2 x 10(-3) s(-1) (t(1/2) < 5 min) in acetonitrile-d3. Ligand exchange for the disilver(I) helicates occurred with k > 2 x 10(-3) s(-1) (t(1/2) < 5 min). Racemization of the dicopper(I) helicate by an intramolecular mechanism was investigated by determination of the coalescence temperature for the diastereotopic isopropyl-Me groups in the appropriate complex, and DeltaG() >> 76 kJ mol(-1) was calculated for the process in acetone-d6, nitromethane-d3, and dichloromethane-d2 with DeltaG() = 75 kJ mol(-1) in acetonitrile-d3. Complete anion exchange of the hexafluorophosphate salt of a dicopper(I) helicate with the enantiomerically pure Delta-(-)-tris(catecholato)arsenate(V) ([As(cat)3]-) in the presence of Dabco gave the two diastereomers (R,R)-[Cu2L2][Delta-(-)-[As(cat)3]]2 and (S,S)-[Cu2L2][Delta-(-)-[As(cat)3]]2 in up to 54% diastereomeric excess, as determined by (1)H NMR spectroscopy. The diastereomerically and enantiomerically pure salt (R,R)-[Cu(2)L2][Delta-(-)-[As(cat)3]]2 crystallized from the solution in a typical second-order asymmetric transformation. The asymmetric transformation of the dicopper(I) helicate is the first synthesis of a diastereomerically and enantiomerically pure dicopper(I) helicate containing achiral ligands.
The synthesis of achiral gold(I) macrocycles [RCH(4-C6H4OCH2C≡CAu)2(µ-Ph2PZPPh2)] and the corresponding chiral gold(I) [2]catenanes, bearing substituents R = 2-pyridyl, 4-pyridyl, and 4-(2,2′-bipyridyl), is reported. The gold(I) compounds form by self-assembly on reaction of oligomeric digold(I) diacetylides [{RCH(4-C6H4OCH2C≡CAu)2}n] or the isocyanide complexes [RCH(4-C6H4OCH2C≡CAuC≡N-t-Bu)2] with diphosphine ligands Ph2PZPPh2, Z = CC or (CH2)n with n = 25, or on reaction of [Au2(O2CCF3)2(µ-Ph2PZPPh2)] with diacetylenes RCH(4-C6H4OCH2C≡CH)2 in the presence of a base. The equilibrium between macrocycles and chiral [2]catenanes in solution was established by NMR spectroscopy, while the structures of several [2]catenanes in the solid state were established crystallographically. The coordination of the gold(I) compounds with R = 4-(2,2′-bipyridyl) to platinum(IV), by formation of the corresponding [PtIMe3(bipy)] units, is established, showing that organometallic [2]catenanes can act as ligands.Key words: gold, macrocycle, catenane, platinum.
The ligand 4,4'-bipyridine-N-monoxide, (BIPYMO) coordinates through the pyridine N-donor to Pt(II) and Pd(II) to form square planar [ML(4)](2+) complexes and to Cu(II) and Zn(II) to form octahedral trans-[M(H(2)O)(2)L(4)](2+) complexes. Single crystal X-ray structures show that these individual building blocks are organized via hydrogen bonding through the external N-oxide O-atoms to form 2D and 3D networks.
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