TRIMETHYLINDIUM BASED PHOSPHINOINDANES - SYNTHESIS AND MOLECULAR-STRUCTURE OF [ME2IN-PPH2]3 - AN INTERESTING IN3P3 TRIMER

The trimeric phosphinoindane [Me2In-PPh2]3 was prepared from the room temperature reaction of trimethylindium with diphenylphosphine in toluene. The highly toluene soluble crystalline phosphinoindane was characterized by H-1 NMR, P-31 NMR, 'partial elemental analyses, and single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group C2/c (No. 15) with unit cell parameters a = 43.130(5) angstrom, b = 11.461(1) angstrom, c = 18.887(2) angstrom, beta = 107.591(8)degrees D(calcd) = 1.48 g cm-3, and V = 8899(1) angstrom3 for Z = 8. Refinement converged at R = 0.025, R(w) = 0.031. The crystal structure reveals that the title compound resides about an In3P3 six-membered ring in a virtually perfect chair conformation, possessing approximate C3 symmetry. The coordination about both indium and phosphorus may be described as distorted tetrahedral. The mean In-P bond distance is found to be 2.62(1) angstrom, while the corresponding mean In-C distance is 2.17(1) angstrom. The title compound represents the first higher-order phosphinoindane oligomer derived from trimethylindium, the simplest indium alkyl.