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Making the True “CP” Ligand

“…A doublet of quintets in the 1 H NMR spectrum at d = À8.13 ppm (trans-2 J H-P = 122.1 Hz, cis-2 J H-P = 17.0 Hz) for the ruthenium hydride was most diagnostic for the formation of 4. The signal for the a-carbon atom of the coordinated phosphaalkyne was observed at d = 175.1 ppm in the 13 C NMR spectrum with a significantly larger C-P coupling constant of J C-P = 71.4 Hz as compared to 3.…”

“…While phosphaalkynes (R À C P) have been known for some time, [1][2][3] the terminal MÀCP has only been reported as a transient species. [4,5] Other C-functionalized XÀCP compounds (X = R 3 Si, [6] R 2 N, [7,8] RO, [8] F, [9] Cl, [10] ), anionic species [XÀCP] À (X = R 3 B, [11] RN, [8] O, [12] S [13] ), and the cationic phosphonio phosphaalkyne [R 3 P À C P] + , [14] have been synthesized, but the vast majority of reports deal with tert-butyl, [15] adamantyl, [16] 2,4,6-trimethylphenyl [17] and 2,4,6-tri-tert-butylphenyl [18] phosphaalkynes. Recently, we devised a very simple method for accessing the kinetically stable crystalline triphenylmethyl (trityl)-substituted phosphaalkyne, Ph 3 CC P (1), which allowed for the economical metal-promoted synthesis of phosphorus heterocycles.…”

“…In the 31 P NMR spectrum of 3, a deshielded signal at d = 111 ppm was observed. The a-carbon atom, which gives a signal at d = 193.3 ppm (d, J C-P = 16.4 Hz) in the 13 C NMR spectrum, was also shifted significantly downfield compared to other phosphaalkynes. [20] Attempts to isolate 3 were unfortunately unsuccessful.…”

“…If a solution of 3 was concentrated, a red precipitate formed which gave no detectable 31 P NMR signal upon redissolving in more polar solvents. However, the lifetime of 3 in toluene or diethyl ether (t 1/2 % 1 day at 23 8C) was sufficiently long so that 31 P and 13 C NMR data could be acquired and, more importantly, coordination of 3 to [RuH(dppe) 2 ]OTf was successful. Addition of a solution of 3 in toluene to 0.5 equiv of [RuH(dppe) 2 ]OTf in CH 2 Cl 2 resulted in a color change from dark red to yellow-orange.…”

“…In a selective 1 H{ 31 P} NMR experiment, the 31 P NMR signal at d = 165 ppm coupled with the hydride to form a doublet with J P-H = 19.5 Hz, while the signal at d = 65.2 ppm coupled with the hydride to give a quintet with J P-H = 20.5 Hz. Finally, a 13 C-1 H HMQC experiment with phosphorus decoupling centered at d = 65 ppm, detected a crosspeak for a quaternary carbon atom at d = 287.1 ppm in the 13 C dimension, which correlated with the hydride. Coupling between the phosphorus and carbon centers corresponded to 1 J C-P % 90 Hz.…”