Nucleophilic behaviour of dioxo- and thiooxophosphorane complexes [MoCp(CO)₂{E,P-EP(O)(2,4,6-C₆H₂^tBu₃)}]⁻(E = O, S)

Abstract

ARTICLEThe structure of two of these products (X = C(O)C 2 H 3 , SiMe 3 ) was determined by single-crystal X-ray diffraction studies. Density functional theory (DFT) calculations of the title anions and some of their derivatives indicated that attachment of an external electrophile to the terminal O atom of the thiooxophosphorane ligand is favoured under conditions of charge control, while the sulphur atom is the favoured site under conditions of orbital control, although it leads to less stable products. IntroductionDioxophosphoranes (RPO 2 ) and thiooxophosphoranes (RPOS) are unstable molecules generated during thermolysis of a great variety of suitable organophosphorus precursors. These transient molecules display a strongly electrophilic character located at their positively-polarized phosphorus(V) atom, this enabling their use as strong phosphorylating agents upon reaction with many different organic substrates while, in the absence of external reagents, they usually evolve through polymerization or intramolecular activation of CH bonds. 1 Only under very favourable conditions can these species be detected directly, as it is the case of MePO 2 when generated in the gas phase under high vacuum. 2 It might be conceived that substantial stabilization of these elusive molecules could be achieved through coordination to metal centres, which in turn would allow for a more detailed study of their chemical behaviour. However, the coordination chemistry of these molecules is virtually unknown, with just one example described for a dioxophosphorane complex. 3 In a preliminary study we found that the anionic oxophosphinidene complex (H-(1), (R* = 2,4,6-C 6 H 2 t Bu 3 ; Cp= and thiooxophosphorane (H-DBU)[MoCp(CO) 2 {S,P-SP(O)R*}] (3) derivatives (Scheme 1). 4 Because of the negative charge of the latter complexes, the acid-base chemistry of their phosphorus ligands is reversed, so they can now behave as nucleophiles. Indeed our preliminary study on the reactivity of the thiooxophosphorane complex 3 indicated that methylation could occur easily at either the S and O sites, to give unprecedented thiolophosphinide (PR(O)(SMe)) and phosphonothiolate (PR(OMe)S) derivatives, respectively. 4 Therefore it was of interest exploring the potential of anions 2 and 3 in the generation of novel P-donor entities. In this paper we give full details of the above reactions, which we have now extended to the dioxophosphorane complex 2 and also to other electrophilic reagents, including the proton and some metalbased electrophiles. As it will be shown, most electrophiles add to the terminal oxygen atom of the phosphorus ligand of the above anions, an event favoured on steric, electrostatic and thermodynamic grounds, according to our theoretical calculations. Addition to the sulphur site of the thiooxophosphorane ligand is an orbital-favoured event only observed in the methylation reactions of 3. Scheme 1Results and Discussion Synthesis and structure of dioxo-and thiooxophosphorane complexesThe oxophosphinidene complex 1 reacts readily at...

Carbodiphosphorane-Stabilized Parent Dioxophosphorane: A Valuable Synthetic HO2P Source

“…have generated considerable scientific interest due to their potential as phosphorylation/phosphonylation reagents − as well as their participation as intermediates/final products of combustion reactions involving warfare agents and flame retardants. , Dioxyphosphorane ( 1 , Figure ) and cis / trans -alkoxyphosphanone ( 2 , 3 ) are the structural isomers that these molecules are capable of adopting. The former, formally a P­(V) species, is thermodynamically more favorable for all species regardless of the nature of the R substituent − ,− with the exception of the parent compound (i.e., R = H). − In fact, parent dioxophosphorane 1a has been predicted to be more than 40 kJ/mol less stable than the cis-isomer of hydroxyphosphanone ( 2a ), − and it was then not surprising that this least thermodynamically stable isomer (i.e., HPO 2 ) was only recently detected via infrared spectroscopy among several products formed during 193/266 nm laser photolysis of 2a in the Ar matrix at 2.8 K …”

Molecules containing lewis acidic phosphorus - sites

“…ppm. [199,201] The significant upfield shift for our product (compared to these compounds), indicates higher nucleophilicity of the P central in 17, most likely due to the carbone ligand's donor properties and the absence of back-donation to the metal, which is the case in previously reported metal-complexes. It is notable that the position of the phosphorus shift in 31 P NMR was highly dependent on the solvent choice.…”

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

“…As a result, the sulfur atom is attacked by an electrophile under the conditions of orbital control, while the oxygen atom favors the attachment of an incoming electrophile under the conditions of charge control (Figure 9). 301 The reactivity of 359), R = Cy; M = Mo, R = tBu (360); Figure 9) was extensively studied with a broad variety of electrophiles, including, for instance, the nitrosyl complex [Re(η 5 -C 5 H 4 Me)-(CO) 2 (NO)] + , Brønsted and carboxylic acids, SnClPh 3 , [AuCl(PR 3 )] (R = iPr, p-tol), PbClPh 3 , MeI, BnCl, PClR′ 2 (R′ = tBu, Et, Cy), PCl(O)(OPh) 2 , and P 4 . 178,302−304 In 2017, the related lighter analogue [Mo 2 (η 5 -Cp) 2 (μ-PtBu 2 )(μ-CO) 2 ] − (360) was reported, which was used to obtain new unsaturated hydride and alkyl derivatives with very distinctive chemical properties due to the presence of the bulky PtBu 2 − ligand.…”

“…Ruiz and co-workers have extensively investigated the chemistry of the anionic phosphinidene and phosphinidene oxide complexes illustrated in Figure . − A more extensive review of the chemistry of compounds 349 and 350 (and related compounds) was published by Ruiz in 2013, while the rich chemistry of the P 4 activation products [M 2 Cp 2 (μ-PCy 2 )­(CO) 2 (μ–κ 2 :κ 2 -P 2 )] − [M = Mo ( 351 ), W ( 352 )] and their corresponding methylation products [M 2 Cp 2 (μ-PCy 2 )­(CO) 2 (μ–κ 2 :κ 2 -P 2 Me)] [M = Mo ( 353 ), W ( 354 )] was reviewed by Caporali, Wolf and co-workers in 2021. , …”