Weak unsupported single hydrogen bridges in Cp2Zr((mu-H)B(X)CH2Ph)((mu-H)2BX) (X = C5H10, C4H8)

The compounds Cp2Zr((mu-H)B(X)CH2Ph)((mu-H)2BX), where X = C5H10, C4H8, have been synthesized by reacting Cp2ZrCl((mu-H)2BX) with PhCH2MgCl. The reactions were performed on a standard high-vacuum line or in a drybox under an atmosphere of nitrogen. Single-crystal x-ray diffraction studies reveal that these compounds have unsupported Zr-H-B bonds. NMR spectra in solution at low temperature support this finding. However, NMR spectra at room temperature show the hydrogen bridge decomposes to Cp2ZrH((mu-H)2BC5H10) and B(C5H10)CH2Ph when X = C5H10 and Cp2ZrH((mu-H)2BC4H8) and B(C4H8)CH2Ph when X = C4H8.