Organophosphines are organophosphorus compounds with the formula PRH, where R is an organic substituent.  These compounds can be classified according to the value of n: primary phosphines (n = 1), secondary phosphines (n = 2), tertiary phosphines (n = 3). All adopt pyramidal structures. Organophosphines are generally colorless, lipophilic liquids or solids.  The parent of the organophosphines is phosphine (PH).