Gene W. Wong, Jennifer L. Harkreader, Charles A. Mebi, and Brian J. Frost. University of Nevada, Reno, Reno, NV
The upper rim of 1,3,5-triaza-7-phosphaadamantane (PTA) has been modified for the first time via lithiation of PTA. The addition of n-butyl lithium to PTA resulted in deprotonation of an α-phosphorus methylene and formation of 1,3,5-triaza-7-phosphaadamantane-6-yllithium (PTA-Li). The first upper rim PTA derivative was synthesized by reacting PTA-Li with ClPPh2 resulting in the chiral phosphine, 6-(diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2). PTA-PPh2 has been fully characterized in solution by mass spectroscopy and multinuclear NMR spectroscopy, and in the solid state by X-ray crystallography. Unlike PTA, the new bidentate phosphine, PTA-PPh2 is insoluble in aqueous solutions. Two group six metal carbonyl complexes, M(CO)4(PTA-PPh2) (M = W, Mo), were synthesized by addition of PTA-PPh2 to M(CO)4(pip)2, and characterized by NMR spectroscopy, infrared spectroscopy, and X-ray crystallography. Also reported are the solid state structures of cis-W(CO)4(PTA)(PPh3) and W(CO)4DPPM (DPPM = diphenylphosphinomethane). From these tungsten complexes PTA-PPh2 appears to be sterically similar to and slightly more electron donating in comparison to DPPM.
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