PENTACOORDINATED MOLECULES - 122 - MOLECULAR-STRUCTURES OF 3-COORDINATE, 4-COORDINATE, AND 5-COORDINATE PHOSPHORUS-COMPOUNDS CONTAINING SALICYLATE LIGANDS

The new cyclic compound 2,2'-sulfurylbis(4-methyl-6-tert-butylphenyl) methyl 2-benzoate phosphite, O2S[(t-Bu)MeC6H4O](2)(OC6H4CO2Me)P (3), c ontaining a salicylate ligand was synthesized from 2,2'-sulfurylbis(4- methyl-6-tert-butylphenyl) chlorophosphite and methyl salicylate in th e presence of triethylamine in ether solution. X-ray analyses of bis(m ethyl salicylate-O)phenylphosphine, (OC6H4CO2Me)(2)PPh (1), and is(met hylsalicylato-O)phenyl(tetrachlorophenylene- 1,2-dioxy)phosphorane, (O 2C6Cl4)(OC6H4CO2Me)(2)PPh (2), as well as that for 3 were obtained. Th e phosphane 1 has a pseudo trigonal bipyramidal (TBP) structure due to coordination of a carbonyl oxygen atom at an axial site. The cyclic p hosphorane 2 and the phosphite 3 lack any coordination from salicylate ligands. This results in a TBP geometry and a pyramidal geometry resp ectively for 2 and 3. Comparisons with X-ray structures for carboxylat e-containing phosphorus compounds exhibiting oxygen coordination show the formation of four- and five-membered cyclic systems. Thus, 1 appea rs to be the first example of formation of a six-membered ring via car bonyl oxygen coordination. Reference is made to the tyrosyl-tRNA synth etase system where it is proposed that carbonyl oxygen atom coordinati on is a likely occurrence in the transition state on the basis of the analysis presented in this work.