Nucleophilicity and P–C Bond Formation Reactions of a Terminal Phosphanido Iridium Complex

Abstract

The diiridium complex [{Ir(ABPN2)(CO)}2(μ-CO)] (1; [ABPN2](-) = [(allyl)B(Pz)2(CH2PPh2)](-)) reacts with diphenylphosphane affording [Ir(ABPN2)(CO)(H) (PPh2)] (2), the product of the oxidative addition of the P-H bond to the metal. DFT studies revealed a large contribution of the terminal phosphanido lone pair to the HOMO of 2, indicating nucleophilic character of this ligand, which is evidenced by reactions of 2 with typical electrophiles such as H(+), Me(+), and O2. Products from the reaction of 2 with methyl chloroacetate were found to be either [Ir(ABPN2)(CO)(H)(PPh2CH2CO2Me)][PF6] ([6]PF6) or [Ir(ABPN2)(CO)(Cl)(H)] (7) and the free phosphane (PPh2CH2CO2Me), both involving P-C bond formation, depending on the reaction conditions. New complexes having iridacyclophosphapentenone and iridacyclophosphapentanone moieties result from reactions of 2 with dimethyl acetylenedicarboxylate and dimethyl maleate, respectively, as a consequence of a further incorporation of the carbonyl ligand. In this line, the terminal alkyne methyl propiolate gave a mixture of a similar iridacyclophosphapentanone complex and [Ir(ABPN2){CH═C(CO2Me)-CO}{PPh2-CH═CH(CO2Me)}] (10), which bears the functionalized phosphane PPh2-CH═CH(CO2Me) and an iridacyclobutenone fragment. Related model reactions aimed to confirm mechanistic proposals are also studied.

Addition of Re‐Bonded Nucleophilic Ligands to Activated Alkynes: A Theoretical Rationalization

“…[51,52] This last reaction is remarkable because of the inertness of coordinated bipy and phen. Furthermore, this result stands in contrast with the Pcco-type products reported for the reaction towards activated alkynes of Fe, Mo, W, and Ir complexes containing the same PPh2 phosphanido ligand [55][56][57] and with Pins-type product detected in case of a Nb complex. [58] It is also believed that the reaction of a stannylphosphole complex with DMAD evolves through an intermediate resulting from the alkyne insertion into the P-Sn bond.…”

Rhodium Complexes in P−H Bond Activation Reactions

“…Interestingly, the values of J (P,Rh) for the terminal phospanido ligand (63 and 62 Hz) were found to be smaller than those corresponding to the phosphane ligands (136 and 138 Hz). It can be attributed to a substantial reduction in the σ‐orbital character of the Rh−PR 2 bond as compared to the Rh−phosphane, and thus provides a useful tool for the identification of the terminal phosphanide ligand.…”

Insights on the Reactivity of Terminal Phosphanido Metal Complexes toward Activated Alkynes from Theoretical Computations

“…2,3 This kind of product stands in contrast with other experimental results. 4−10 On the one hand, the reaction of [CpFe(CO) 2 (PR 2 )] (Cp = η 5 -C 5 H 5 ; R = Ph, C 6 F 5 ) (2 and 3, respectively), 4 [CpM- (CO) 3 (PPh 2 )] (Cp = η 5 -C 5 H 5 ; M = Mo, W) (4 and 5, respectively), 5 and [Ir(ABPN 2 ) (CO)(H) (PPh 2 )] (ABPN 2 = (allyl)B(Pz) 2 (CH 2 PPh 2 ); Pz = pyrazolate) (6) 6 with HMAD and/or DMAD gives rise to the formation of metallacyclic complexes, which contain a five-membered chelate ring formed by the linkage of the phosphanido group, the alkyne, and the CO ligand (see P2 in Scheme 1). Analogous five-membered metallacyclic products were also reported both when replacing carbonyls by other ancillary ligands like alkyl or aryl isocyanides in certain Nb complexes 7 and when using iron carbonyl complexes containing acetyl and deprotonated phosphanido ligands.…”

“…9 On the other hand, a nonconcerted process has been suggested for the formation of P1-type product from the 1 complex 2,3 and of P2type products when using the 4, 5, and 6 complexes. 6,8 As seen in Scheme 2, the first step would imply the attack of the nucleophilic phosphanido ligand on one of the acetylenic carbon atoms to form a zwitterionic intermediate. In this species, the other carbon of the initially acetylenic moiety would present a negative charge.…”