B=P Double Bonds Relieved from Steric Encumbrance: Matrix-Isolation Infrared Spectroscopy of the Phosphaborene F2B−P=BF and the Triradical B=PF3

Free phosphaborenes have a labile boron-phosphorus double bond and therefore require extensive steric shielding by bulky substituents to prevent isomerisation and oligomerisation. In the present work, the small free phosphaborene...