2‐Phospha‐ and 2‐Arsaethynolates – Versatile Building Blocks in Modern Synthetic Chemistry

Abstract

2-Phosphaethynolates, particularly the sodium salts, Na(OCP), are exceedingly versatile nucleophiles, which renders these species important as precursors to phosphorus-containing π-conjugated heterocycles. Moreover, the 2-phosphaethynolate anion serves as a potent phosphide transfer reagent giving rise to the first stable phosphinidine among other prod-[a] Centrum für Molekulare Materialien, 2176 Scheme 3. Synthesis of [Na(dme) 2 (PCO)] 2 (2a) from 3by bond metathesis.philicity of carbon monoxide is considerably increased by ligation to the iron center, and where 2b was observed as the only P-containing product. [7] In keeping with this, heating a DMF solution of K 3 P 7 and [18]-crown-6 to 150°C under an atmosphere of CO led to the formation of [K([18]-crown-6)](PCO) 5 in addition to polyphosphides K 2 P 16 and K 3 P 21 . Aqueous work up allowed the isolation of 5 as a colorless solid in 38 % yield (Scheme 4). [9] Scheme 4. Synthesis of 5. Alkali Earth Metal 2-PhosphaethynolatesAttempts to emulate Becker's protocol for [Li(dme) 2 ](PCO) with alkaline earth metals was largely met with failure. Exposure of M[P(SiMe 3 ) 2 ] 2 to dimethyl carbonate in THF or DME afforded the corresponding magnesium (6), calcium (7), strontium (8) and barium (9) bis(2-phosphaethynolates), which slowly decomposed in the ethereal solvent. Rapid deterioration of the products was observed in hydrocarbon solvents or by removal of coordinating solvent molecules in vacuo.Solely in the case of the calcium derivative 7, where three DME ligands obviously imparted sufficient stability to the crystals full structural characterization was possible. Otherwise, identification of compounds 6-9 was restricted to NMR evidence (Scheme 5). [6d] Notably, combination of Sr[P(SiMe 3 ) 2 ] 2 with an excess of dimethyl carbonate yielded a few crystals of dinuclear 10, as confirmed by X-ray techniques. [6d] Eur. 2187 Scheme 32. Alkylation reactions of dianion 55 with 2-iodopropane and 4,4′,4′′-trimethoxyphenylmethyl chloride. Scheme 33. Preparation of Li(PCS) (58). 2193 Scheme 49. Synthesis of 98 from 99 and P(SiMe 3 ) 3 . Scheme 50. Synthesis of 98 from Na(OCP) or P 7 (SiMe 3 ) 3 . Scheme 51. Proposed mechanism for the formation of phosphaalkene 98′ from 101′ and (PCO) -(R = Me). Scheme 73. Synthesis of 145 {[K] + = [K{18}-crown-6] + }. 2201 Scheme 79. Synthesis of 153a and 154a. Scheme 80. Synthesis of 153b. Scheme 81. Preparation of 155 and 156 by deprotonation of 152c. Eur. J. Inorg. Chem. 2018, 2175-2227 www.eurjic.org Scheme 95. Formation of adducts 192a-e. Scheme 96. Reaction of 168 with N-heterocyclic carbenes 96 and 193b,c.

Indirect Access to Carbene Adducts of Bismuth- and Antimony-Substituted Phosphaketene and Their Unusual Thermal Transformation to Dipnictines and [(NHC)2OCP][OCP]

“…The utilization of the 2-phosphaethynolate anion, 3 [OCP] − , as a synthon has proved to be an effective way to access phosphaketenes via nucleophilic substitution. 4 However, these synthetic processes are not always straightforward, and phosphaketene stability and reactivity may be hampered by a number of complications. The most important of these are summarized as follows.…”

Quantum Chemical Calculations on CHOP Derivatives—Spanning the Chemical Space of Phosphinidenes, Phosphaketenes, Oxaphosphirenes, and COP− Isomers

“…It was Grützmacher who then described a novel approach to III using sodium phosphaethynolate Na[OCP] [14]. This new salt, bearing the OCP − (phosphaethynolate) anion [15,16], enabled a systematic exploration of its use in the field of P-heterocyclic chemistry [17]. Interestingly, the anion reacts as an ambident nucleophile, i.e., it could be used to form transient phosphaalkynes that underwent cyclotrimerization to yield 1,3,5-triphosphinines [18,19] or to obtain new phosphaketene derivatives [20].…”

Frontiers in the solution-phase chemistry of homoatomic group 15 Zintl clusters

“…[70][71][72] The subsequent chemistry of [PCO] − is now a separate field of study and has been reviewed by Grützmacher, Goicoechea, and Weber. 73,74…”