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Aldehydes and Ketones. Acyl Addition Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
An ylid is a neutral compound with a negatively charged carbon atom directly bonded to a positively charged atom of phosphorus, sulfur, and nitrogen, primarily. It is noted that ylid can also be spelled ylide. What is a phosphine?
New stable phosphorus ylide (p-tolyl)3P = CHCOC6H4 (p-CN) and its metal complexes: Crystal and molecular structure, theoretical study and antibacterial investigation
Published in Journal of Coordination Chemistry, 2020
Leila Vatannavaz, Seyyed Javad Sabounchei, Asieh Sedghi, Mehdi Bayat, Kristof Van Hecke, Abdolkarim Chehregani Rad
Phosphorus ylides have high versatility in the applications as pharmaceutical and biological active agents and also a wide scope of suitability in industrial and chemical processes [1–7]. Thus, synthesis and application of the metalated phosphorus ylides has attracted attention. The stability of the phosphonium ylides with the formula [R3P = CHCOR]+ can be attributed to the ambidentate nature and this property guarantees their applications as ligands with two sites for coordination (C and O coordination sites). In previously reported keto-stabilized ylides with soft metal ions such as Hg(II), Pd(II), Pt(II), Ag(I), Au(I) and Au(III), coordination through carbon atom is more predominant [8–12] and there are few examples of O-coordinated ylides [13–16]. Some of these examples are including O-coordinated ylide to a hard metal center, very oxophilic metal center, such as Sn(IV) [13, 14] or group four metals with a high oxidation number e.g., Ti(IV), Zr(IV) and Hf(IV) [15]. Only in W(0) complexes of the type [W(CO)5L] where L is ylide [16] and Pd(II) complexes of the stoichiometry [Pd(C6F5)L2)(APPY)](ClO4) [17] (APPY = Ph3CCOMe; L = PPh3, PBu3; L2 = bipy) contain stable ylides O-linked to a soft metal center. The resonance form of a typical ambidentate phosphonium ylide is depicted in Scheme 1. In the α-keto-stabilized ylides, coordination through carbon is more perfect and is observed with soft metal ions, e.g. Hg(II), Ag(I), Cd(II) [8, 18, 19]. In these types of phosphonium ylides, according to the Pearson acid-base theory [20], it can be concluded that the soft metal ions will be coordinated via the soft ylidic carbon site as opposed to the hard carbonyl oxygen atom in the ligands which will coordinate to the hard metal ions.