REACTIONS OF 2-COORDINATE PHOSPHINES WITH ACETYLENES - SYNTHESIS OF NEW ALLENIC AND ACETYLENIC PHOSPHINES

The two-coordinate phosphines (Me3Si)2NP=ESiMe3 (1, E = N; 2, E = CH) reacted smoothly with 2-butyne via an ene process (instead of the expected cycloaddition reaction) to give the novel allenic phosphines H2C=C=C-(CH3)P[E(H)SiMe3]N(SiMe3)2(3,E=N,4,E=CH). Similarly,treatment of the iminophosphine 1 with 1-hexyne (in benzene solution at 80-degrees-C) afforded the analogous allene derivative CH3CH2CH2CH=C=CHP[N(H)SiMe3]N-(SiMe3)2 (5). Under different conditions (no solvent, 25-degrees-C), however, the reaction of 1 with 1-hexyne occurred via a unique 1,2-addition of the terminal H-C bond to the P=N linkage, thus affording the acetylene isomer CH3CH2CH2CH2C=CP[N(H)SiMe3]N(SiMe3)2 (6). Other terminal acetylenes, PhC=CH and Me3SiC=CH, reacted with 1 via this 1,2-addition pathway to give the acetylenic phosphines RC=CP[N(H)SiMe3]N(SiMe3)2 (7, R = Ph; 8, R = SiMe3). These new allenic (3-5) and acetylenic (6-8) phosphines were obtained in good yields (50-82%) as thermally stable liquids and were fully characterized by NMR (H-1, C-13, P-31) spectroscopy and elemental analysis.