Phosphinomacrocycles. 16. Complexation of the nickel(II) triad with 14-membered macrocyclic P4-nSn (n = 2, 1, 0) ligands. Study of the effects on coordination of the relative configuration at the phosphines and the number and placement of thioether sites

Abstract

049ChemInform Abstract The complexation of Ni, Pd, and Pt with the title ligands (I)-(III), each having the phenyl groups on phosphorus either in cis or in trans position, is studied. 22 complexes (18-76% yield) are obtained by reaction of the macrocycles in CH2Cl2 of THF with the metal salts in EtOH or CH2Cl2. The coordinating ability of the macrocyclic ligands is determined by solution-phase competition experiments and found to depend on the metal species, the nature, number and disposition in the ring of the heteroatoms, and the relative stereochemistry of the substituents on the phosphine sites. The complexes (IV)-(VII) are characterized by an X-ray diffraction study. They all crystallize in the space group P21/c with Z=4.

Characteristics of Nickel(0), Nickel(I), and Nickel(II) in Phosphino Thioether Complexes: Molecular Structure andS-Dealkylation of (Ph2P(o-C6H4)SCH3)2Ni0

“…That is, consumption of one electron by the nickel(II) complex [ 2 ](BF 4 ) 2 produces a nickel(I) species of structure close to that of the original square planar nickel(II) complex, and subsequently, a tetrahedral twist of this intermediate yields a nickel(I) species close in structure to the tetrahedral nickel(0) complex 1 . The distorted tetrahedral structure of the Ni I complex has been previously suggested for bidentate phosphine and macrocyclic tetradentate P,S donor ligands from similar electrochemical data. , Interestingly, the second reduction, the Ni I/0 couple of [ 2 ](BF 4 ) 2 , is scan rate independent and fully reversible ( i pa / i pc ≈ 1.0), indicating that the major structural change has occurred following addition of the first electron.…”

“…These spectroscopic parameters are solvent dependent, probably indicative of solvent or counterion interactions at nickel, the most dramatic of which is shown by the 31 P{ 1 H} NMR spectra of [ 2 ](BF 4 ) 2 . In CD 2 Cl 2 solution the 31 P{ 1 H} chemical shift of 51.8 ppm is typical of other four-coordinate Ni II complexes with P,S-donor atom ligands (typically around 50 ppm), ,, whereas in CD 3 CN solution, a very broad resonance is barely discernible at −13.0 ppm (indicative of free ligand). Incremental additions of CD 2 Cl 2 to the CD 3 CN solution of [ 2 ](BF 4 ) 2 resulted in the broadening of the resonance at 52 ppm, with growth of the high-field −13.0 ppm resonance.…”

Pendant Functionalised Triphosphamacrocycles

“…40−60 °C. The compounds [Mo(CO) 3 (12aneP 3 H 3 )] and [Cr(CO) 3 (12aneP 3 H 3 )],2 and 6a and 6b 11 were prepared as previously described. All other chemicals were obtained from the Aldrich Chemical Company and used without further purification, except alkyl halide reagents, which were dried over molecular sieves and deoxygenated by freeze‐thaw degassing.…”

“…We have previously reported the template synthesis and P‐atom functionalisation of 1,5,9‐triphosphacyclododecane to give a number of tritertiary derivatives (12aneP 3 R 3 ), which can be liberated from their Mo 0 and Cr 0 templates by oxidation of the metal centre followed by base digestion 1. Unlike the only other triphosphorus macrocycle known as the free ligand,2 our synthetic procedure is stereospecific (for the syn ‐ syn isomer) producing ligands with identical bridging backbone functions and hence achiral phosphorus atoms. A feature of these ligands is that they are ideally suited to coordinating a trigonal face in metal coordination polyhedra; the phosphorus atoms are clearly restricted to a mutually all cis arrangement which in turn locates the remaining active sites at the metal to also be mutually cis (at least for coordination numbers of six or less).…”

The Dianion Cyclization Strategy for the Synthesis of Dibenzoheterocycles

“…Phosphorus heterocycles containing another heteroatom in the ring was not included till 1976. 17 Since phosphorus is a well-established atom for stabilization of low oxidation state transition metal complexes, 18 crown ethers incorporating phosphorus atoms in different valences have become a important area of chemistry. 19 Thus, in view of the synthetic and catalytic importance of the ligand and in continuation of our work 20−26 on the chemistry of heterocycles, we herein report the synthesis and characterization of some new organosilicon, organotin, and organophosphorus macroheterocycles via dianion-mediated cyclizations.…”