9 Raman vibrational spectrum of PPhy BHs The same basic info

9. Raman vibrational spectrum of PPhy BHs. The same basic information is observed in the infrared spectrum (however our infrared spectrometer cannot observe peaks below 650 cm 60 424 439 1 476 495 1 504 102740 1104 26 1131 5 1160 13 1182 11 1309 2 1333 1 1433 3 14781 1572 16 1585 54 50 40 616 623 702 8 10 30 854 1 919 929 2 999 101 20 10 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 Wavenumbers (cm) What key absorption peaks in the Raman spectrum above allow for the unequivocal proof of the B-P covalent bond in PPh3*BHs? Consult the provided references.

Solution

Peak at 476cm-1 gives the proof of B-P covalent bond in the given spectrum. As per the reference the polar B-P Covalent bind absorbs at 556 cm-1 in substituted PR3•BR3 but due to the replacement of R with H the bond length increased and the wavelength decreased to 476 cm-1.