Cycloaddition reactions of isocyanides with bis[tris(trimethylsilyl)methyl]diphosphene

The [2 + 1] cycloaddition reactions of isocyanoacetonitrile (1a), pc nt aca rbonyl(diisocyanomethane)chromium (1b), and 2,2,2-trifluoroethylisocyanide (1c) with the diphosphene R-P=P-R (R = C[Si(CH3)(3)]) (2) yield the expecte d diphosphirane imines 3a-c. All compounds an thermally very stable and sho w no evidence for a [2 + 1] cycloreversion reaction. The structures of 3a: triclinic, <P(1)over bar >, a = 918.0(2), b = 1174.7(4), c = 1821.9(5)pm, a lpha = 93.83(2), beta = 97.22(2)degrees, gamma = 97.08(2)degrees, Z = 2. R- 1 =0.069; 3c: monoclinic, P2(1), a = 928.6(2), b = 1659.8(3), c = 1261.2(3) pm, beta = 107.65(2)degrees, Z = 2, R-1 = 0.073, and 1,2-Bis[tris(trimethyl silyl)]methyl-N-trifluormethyl-3-diphosphiranimin: monoclinic, P2(1)/n, a = 1374.6(3), b = 1685.9(1), c = 1658.6(5)pm, beta = 108.99(9)degrees, Z = 4, R-1 = 0.092, were elucidated by X-ray crystallography. All three compounds possess a similar three membered PCP ring system with an exocyclic C-N dou ble bond.