THE ENTHALPIES OF FORMATION OF BIS(DIMETHYLAMINO)CYANOPHOSPHINE, (DIMETHYLAMINO)DICYANOPHOSPHINE, AND TRICYANOPHOSPHINE

]The standard molar enthalpies of formation at the temperature 298.15 K of {(CH3)(2)N}2PCN(1), (CH3)(2)NP(CN)(2)(I), and P(CN)(3)(cr) have b een determined by reaction calorimetry as -(0.4 +/- 3.2) kJ . mol(-1), (189.3 +/- 5.0) kJ . mol(-1), and (373.1 +/- 6.8) kJ . mol(-1), respe ctively. Enthalpies of vaporization have been obtained from vapour-pre ssure measurements for the first two compounds and the corresponding v alues of Delta(f)H(m)(o)(g)/(kJ . mol(-1)) derived as (54.2 +/- 3.5), (228.7 +/- 5.5), and (448.4 +/- 7.4), respectively. The values of the bond enthalpies D(P-CN) in the cyanophosphines are discussed.