Multisite Reactivity of the Central Mo₂CP Core in the Unsaturated Carbyne-Bridged Complex [Mo₂(η⁵-C₅H₅)₂(μ-CPh)(μ-PCy₂)(CO)₂]

Abstract

The title compound reacted with HBF4·OEt2 at room temperature to give a mixture of the agostic-like, phosphine-bridged complex [Mo2Cp2(μ-CPh)(μ-κ1:η2-PHCy2)(CO)2]BF4 (major) and the carbene-bridged complex [Mo2Cp2(μ-η1:η2-CHPh)(μ-PCy2)(CO)2]BF4 (minor). It readily added a molecule of HCCCO2Me or a single Se atom at its Mo2C(carbyne) center to give with high yield the corresponding propenylylidene- or selenoacyl-bridged derivatives [Mo2Cp2{μ-η2:η3-CPhCHC(CO2Me)}(μ-PCy2)(CO)2] and [Mo2Cp2{μ-η,κ:η,κ-C(Ph)Se}(μ-PCy2)(CO)2], respectively. In contrast, the addition of a neat donor at the metal site can induce a reversible carbyne–carbonyl coupling, as observed in the reaction with N2CPh2 to give the ketenyl derivative [Mo2Cp2{μ-η1:η2-C(Ph)CO}(μ-PCy2)(CO)(κ1-N2CPh2)].

Heterometallic clusters derived from the unsaturated carbyne-bridged dimolybdenum complexes [Mo 2 (η 5 -C 5 H 5 ) 2 (μ-CPh) (μ-PCy 2 ) (CO) x ] (x = 1, 2)

“…In preliminary studies on the behaviour of compounds 1 and 2, we showed that both species display high reactivity under mild conditions towards many different reagents, usually involving participation of both the unsaturated dimetal centre and the carbyne ligand, whereby interesting C-C, C-P and C-H bond formation processes could be induced [4,5]. In this paper we explore reactions of compounds 1 and 2 with different metal complexes so as to examine their potential use in the rational synthesis of carbyne-bridged heterometallic clusters.…”

“…In a preliminary study we showed that the unsaturated benzylidyne complex 2 displayed a multisite reactivity on its central Mo 2 PC core, involving addition of a wide variety of electron donors, but also simple acceptors such as the proton itself [5].…”

“…Indeed, these complexes share almost the same 31 [27], cationic gold fragments can be added to electron-rich complexes having metalmetal bonds to give heterometallic derivatives alike to the corresponding hydride complexes following from protonation [28]. Since dicarbonyl 2 is nucleophilic enough to be protonated [5], it could be anticipated that it should be able to add gold(I) cations, although the output of these reactions proved to be different from protonation. ligand displays both isomers, with the anti isomer being the major species in solution.…”

“…Carbyne-bridged complexes have reduced metalcarbon bond orders (between one and two) and hence reduced reactivity; however, such reactivity can be significantly increased by the presence of metalmetal multiple bonds in the same molecule [2,3]. In this line of work, we recently initiated studies on the reactivity of the unsaturated benzylidyne-bridged complexes [Mo 2 Cp 2 (-CPh)(-PCy 2 )-CO)] (1) [4] and [Mo 2 Cp 2 (-CPh)(-PCy 2 )CO) 2 ] (2) [5] (Cp =  5 -C 5 H 5 ) (Chart 1), which combine multiple Mo-Mo and Mo-C bonds and therefore provide a platform for the analysis of the synergic effect of these functionalities on their chemical behaviour.…”

Chalcogenoacyl-bridged derivatives of the unsaturated carbyne complex [Mo 2 ( η 5 -C 5 H 5 ) 2 ( μ -CPh)( μ -PCy 2 )(CO) 2 ]

“…A preliminary exploration of its chemical behaviour revealed a multisite reactivity of its central Mo 2 PC core, involving the participation of MoMo, MoC and MoP bonds. Among other reactions, compound 1 was shown to add selenium atoms at the Mo 2 C face upon reaction with grey selenium, to build a selenoacyl ligand symmetrically bridging the metal atoms in a - 2 : 2 fashion [1]. In contrast, we later found that reaction of 1 with elemental oxygen instead promotes decarbonylation, to give the corresponding oxoderivative trans-[Mo 2 Cp 2 (-CPh)(O)(-PCy 2 )CO)] (2) (Scheme 1), a reaction taking place with retention of the overall stereochemistry of the binuclear substrate [2].…”