NORMAL-COORDINATE ANALYSIS OF DISILENES AND DIPHOSPHENES - THE UPSILON(SI=SI) AND UPSILON(P=P) STRETCHING VIBRATIONS

Normal coordinate analysis (NCA) of some disilene and diphosphene mole cules has been performed and compared with NCA of corresponding alkene s. For various models of disilenes containing the C2Si=SiC2 moiety, NC A shows that Si=Si and Si-C stretching coordinates are heavily mixed, their in-phase combination resulting in a normal mode in the region 45 0-550 cm(-1), while their out-of-phase combination is in the region 60 0-750 cm(-1). In contrast, the results of NCA for diphosphenes show th at the vibration at approximate to 600 cm(-1) is well localized, being predominantly nu P=P stretch ( approximate to 90% in PED). (C) 1997 E lsevier Science B.V.