SYNTHESIS AND X-RAY STRUCTURE OF AN ANIONIC CHELATING PHOSPHINE ACYL DERIVATIVE OF TUNGSTEN, [PPH4][W(CO)4C(O)CH2CH2CH2PPH2], AND THE REACTIVITY OF ITS DECARBONYLATED ANALOG WITH CARBON-DIOXIDE
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Thesynthesis of an anionic chelating phosphine-acyl derivative of tungsten, (CO)4WC(O)CH2CH2CH2PPh2, is described. The complex was prepared from the reaction of Na2W(CO)5 and PPh2CH2CH2CH2Cl in tetrahydrofuran. This complex undergoes decarbonylation in refluxing THF to afford the five-membered phosphametal cycloalkane derivative (CO)4WCH2CH2CH2PPh2-. Upon pressurizing this metal alkyl species with carbon dioxide (400 psi) at ambient temperature the carboxylate derivative (CO)4WOC(O)CH2CH2CH2PPh2- was formed. The rate of carbon dioxide insertion into the W-C bond of this phosphine substitution derivative was qualitatively faster than the analogous process involving CH3W(CO)5, indicative of a rate enhancement by the phosphine ligand. All compounds were characterized by infrared and NMR (13C) spectroscopy. Single crystals of [PPh4][W(CO)4C(O)-CH2CH2CH2PPh2] are monoclinic of space group P21/n with a = 9.444 (1) , b = 22.654 (5) , c = 21.279 (4) , = 96.00 (1), and Z = 4. The structure was solved and refined by using 2831 unique, observed reflections measured on a Nicolet P3 diffractometer to R and Rwvalues of 0.0699 and 0.0787. The six-membered chelate ring assumes a chain conformation with the acyl groups' oxygen atom lying 0.940 from the equatorial plane of the metals' coordination sphere. The W-C(O)-and W-P bond distances were found to be 2.260 (19) and 2.504 (6) , respectively. 1985, American Chemical Society. All rights reserved.