Dehydrogenative Formation and Reactivity of the Unsaturated Benzylidyne-Bridged Complex [Mo₂Cp₂(μ-CPh)(μ-PCy₂)(μ-CO)]: C−C and C−P Coupling Reactions

Synthesis and DFT Study of a Diphenylsilanone‐Bridged Dimolybdenum Complex

“…Surprisingly, compound 3 is easily accessible by a two-step procedure involving the selective oxidation with molecular O2 of an intermediate silylene complex [Mo2Cp2(-CPh)(-PCy2)(-SiPh2)] (2), which in turn is generated in situ from the readily available 30-electron benzylidyne-bridged complex [Mo2Cp2(-CPh)(-PCy2)(-CO)] (1). [14] As shown below, our results reveal for the first time the potential of silanones as bridging ligands in polynuclear transition metal complexes, as well as its unprecedented ability to fine-tune their electron donation properties to further stabilize electronically unsaturated complexes by using oxygen lone pairs for -bonding with the metal atoms. The silylene-bridged compound 2 can be conveniently prepared in high yield (ca.…”

“…0.1 Å) of the Mo-Mo bond in 3 (2.571(1) Å), when compared with the parent carbonyl complex 1 (2.465 Å). [14] Although bonding in the central Mo2SiO skeleton of 3 might be described in principle through several canonical forms (Figure 3), the above structural parameters suggest that a combination of the canonical forms II and III would best describe the actual bonding within the Mo2SiO ring, which then would approach the extreme description of a dimetallacyclosiloxane, a view also supported by DFT calculations. Finally, we note that all available NMR data for 3 indicate that the solid state structure is essentially retained in solution.…”

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)

“…Unfortunately, the photolysis of compound 1 in presence of these complexes only rendered partial transformation of 1 into its ketenyl derivative [Mo 2 Cp 2 {-C(Ph)CO}(-PCy 2 )(CO) 2 ] [3]. This is obviously due to reaction of 1 with the carbon monoxide generated by the photolytic process, and is in contrast with the behaviour of the related methoxycarbynebridged complex [Mo 2 Cp 2 (-COMe)(-PCy 2 )-CO)], which gave the trinuclear complexes [Mo 2 MnCp 2 L(-COMe)(-PCy 2 )CO) 4 ] under similar conditions [7]. In contrast, compound 1 reacts at room temperature with [Fe 2 (CO) 9 ], or with [Ru 3 (CO) 12 ] under visible-UV irradiation, to give the corresponding trinuclear clusters .…”

“…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.…”

“…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.…”