The antitumor agents cis-dichloro(octamethylcyclotetraphosphazene-N, N")platinum(II)-acetonitrile (compound 1) and the related salt, N, N"-dihydro(octamethylcyclotetraphosphazenium) tetrachloroplatinate (compound 2), have been subjected to X-ray structure analysis. Crystals of 1 were orthorhombic, with the space group P21mn and with a = 10.328 (6) Å, b = 11.439 (6) Å, c = 9.050 (3) Å, and Z=2. The structure was refined by full-matrix least-squares methods to a final R1= 0.048. The eight-membered phosphazene ring in 1 is puckered into a saddle conformation and is coordinated to platinum through two antipodal nitrogen atoms. The ring-platinum binding appears to be by a composite of σ-bonding and π-type interactions. Crystals of compound 2 were monoclinic, with the space group P21/c and with a = 14.911 (2) Å,b= 12.177 (2)Å, c = 11.760 (7)Å, β = 94.94 (2)°, and Z = 4. The structure was solved by heavy-atom methods and was refined by full-matrix least-squares methods to R1= 0.041 and R2= 0.052. The eight-membered phosphazene ring in 2 is protonated at two antipodal nitrogen atoms and is puckered into a distorted chair conformation. The tetrachloroplatinate dianion forms a hydrogen-bonded bridge between parallel sets of phosphazene rings via the protonated nitrogen atoms. The coordination of ring nitrogen atoms to platinum or hydrogen in 1 or 2 causes a lengthening of the P-N bonds that flank the coordination site.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry