Conformationally Rigid Chelate Rings in Metal Complexes of Pyridyloxy-Substituted 2,2‘-Dioxybiphenyl-Cyclotetra- and Cyclotriphosphazene Platforms

Abstract

Divalent metal halides react with pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotri- and cyclotetraphosphazene ligands to form the complexes, [MLX2] [M=Co or Cu; L=(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotriphosphazene (L1) or (2,2'-dioxybiphenyl)tetrakis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L2); X=Cl or Br], [ZnLCl2] [L=bis(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotriphosphazene (L3) or bis(2,2'-dioxybiphenyl)bis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L4)], [MLCl2] [M=Cu or Hg; L=tris(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotetraphosphazene (L5)] and [Cu2LCl4] (L=trans-bis(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotetraphosphazene (L6)]. Single-crystal X-ray structures show the L2 ligand complexes to have a N3Cl2 five-coordinate, trigonal-bipyramidal donor set with the phosphazene ring and pendant pyridyloxy nitrogens binding to the metal ions. The coordinated L2 ligand in the complex, [CoL2Cl2], slowly hydrolyses in acetonitrile with the loss of a pyridine pendant arm to form a dimetallic species, which has been characterized by crystallography as [{CoL2aCl}]2.4MeCN (L2a=[N3P3(biph)(OPy)3(O)]-, biph=2,2'-dioxybiphenyl, OPy=2-oxopyridine). The ligands, L3, L4, L5, and L6, bind to the metal halides via gem-substituted pyridyloxy nitrogens only. The resulting rigid eight-membered chelate rings all have distorted boat conformations, which force distorted-tetrahedral N2Cl2 coordination environments onto the metal ions. The spectroscopic (ESR and electronic) and magnetic properties of the complexes are reported.

Chiral configurations in cyclophosphazene chemistry

“…The crystal structures of a number of mono-BP derivatives are given in below (164a [34e], 164b and c [191], 164d [192], 165 [193], 166 [34e], 167a and b [194], 167c and 168 [195], 169a-d [136]). Except for the crystal structures 168 [195] where the racemic configurational properties were stated as RS (or SR), none of the other structures of mono-spiro BP derivatives recorded that the molecule was racemic.…”

“…The bis-BP motif is very common in metallocyclophosphazenes but the stereogenic properties were only stated in one study where the racemic form of bis-BP was observed (180 [203]). In order to understand the structural properties of the metallo-cyclophosphazene in the other studies, it may be important to know that the bis-BP motif is racemic (181-183 [199]) or meso (184 [204], 185a,b and 186 [205], 187 and 188 [194]). M a n u s c r i p t …”

“…The structures of a number of BP derivatives of cyclotetraphosphazene have been characterized by X-ray crystallography [194,206]. There are two structures of bis-BP tetramers (189 [206] and 190 [94]) where the BP units exist in the meso configuration, and three structures of tris-BP tetramers (191 [206], 192a,b [194]) where the BP units are necessarily racemic (RRS/SSR etc.).…”

“…There are two structures of bis-BP tetramers (189 [206] and 190 [94]) where the BP units exist in the meso configuration, and three structures of tris-BP tetramers (191 [206], 192a,b [194]) where the BP units are necessarily racemic (RRS/SSR etc.). …”

Phosphorus–nitrogen compounds: part 30. Syntheses and structural investigations, antimicrobial and cytotoxic activities and DNA interactions of vanillinato-substituted NN or NO spirocyclic monoferrocenyl cyclotriphosphazenes

“…The trans-N 3 P 3 Cl 4 R 2, trans-N 3 P 3 Cl 3 R 3 and trans-N 3 P 3 Cl 2 R 4 structures are likely to display the possibility of optical isomerism as the enantiomers of these compounds [12]. On the other hand, it was found that the aryloxides react with Cl atoms to yield partly and fully substituted phosphazenes regio-and stereoselectively via generally the non-geminal pathway [12,13]. But, our group observed that tetrachloro mono and bisferrocenylphosphazenes with potassium vanillinate gave both of the geminal and nongeminal products [14].…”