Chemistry of phosphido-bridged dimolybdenum complexes. Part 3. Reinvestigation of the reaction between [Mo₂(η-C₅H₅)₂(CO)₆] and P₂Ph₄; X-ray structures of [Mo₂(η-C₅H₅)₂(µ-PPh₂)₂(CO)₂], [Mo₂(η-C₅H₅)₂(µ-PPh₂)₂(µ-CO)], and trans-[Mo₂(η-C₅H₅)₂(µ-PPh

Abstract

ChemInform Abstract The thermal title reaction gives the bis(phosphido)-bridged Mo2 complex (III) (space group P1, Z=2) containing a Mo-Mo double bond. Further decarbonylation leads to the µ-carbonyl derivative (IV) ( P21/n, Z=4) with a Mo-Mo triple bond. Protonation of (III) occurs across the Mo-Mo bond to give the µ-hydrido derivative (V). Oxidation of (III) results in the formation of the trans and cis isomers (VIIa) (P1, Z=2) and (VIIb); the same oxidation products are obtained similarly from (IV) in 1.9 and 52% yield.

Protonation reactions of the oxo complex cis-[Mo2(η5-C5H5)2(O)(μ-PPh2)2(CO)]. Hydroxo and tetrafluoroborate derivatives

“…(2) is reached instantaneously (Scheme 2). This is revealed by the observation of IR bands attributable to both 1 [3] and 2 (1921 cm À1 ), with the latter being somewhat higher than that of its ditungsten analogue (1904 cm À1 [2]), as expected when comparing related Mo and W complexes. Upon standing at room temperature, a band at 1997 cm À1 grows at the expense of the former, which might arise from the corresponding oxohydride isomer [Mo 2 Cp 2 (m-H)(O)(m-PPh 2 ) 2 (CO)](BAr 0 4 ) (3) (cf.…”

“…If, however, these solutions were further left standing over longer periods of time at room temperature (ca. 12 h), then the starting material 1 was completely replaced by its isomer trans-1 [3], while the amount of oxohydride 3 remained unchanged. This suggests the occurrence of a slow cis/trans isomerisation of the hydroxo complex 2, not further investigated by us.…”

“…We should note that we have retained for the oxohydride 3 the formulation of a twoelectron donor oxo ligand (formal MoeO double bond), as originally proposed for 1 and its ditungsten analogue [2,3]. However, it should be kept in mind that more recent work from our lab indicates that the oxo ligand in related carbonyl complexes might be instead considered as a four-electron donor (formal MoeO triple bond) [7].…”

“…Thus, it seemed of interest to attempt the preparation of the analogous dimolybdenum complex, so as to examine the influence of the metal on the reactivity of these unsaturated cations. In this paper we report a detailed study of the protonation reactions of the dimolybdenum complex cis-[Mo 2 Cp 2 (O)(mPPh 2 ) 2 (CO)] (1), a compound described previously by Mays and coworkers [3]. As it will be discussed, these reactions turned to be far more complex than those of the ditungsten complex, and eventually led to the formation of a quite labile tetrafluoroborate complex when using HBF 4 $OEt 2 as protonation agent.…”

Diphosphorus-bridged heterometallic anions and hydrides derived from reactions of complex [Mo2Cp2(μ-PCy2)(μ-κ2:κ2-P2)(CO)2]− with precursors of 16-electron metal carbonyl fragments

“…0.25 Å shorter than those measured for the electron-precise neutral derivatives of 1 [2], and close to the values measured in isoelectronic dimolybdenum complexes bridged by two P-donor ligands, such as [Mo 2 Cp 2 (m-PPh 2 ) 2 (CO) 2 ] (ca. 2.71 Å, [13]) or the phosphide-bridged [Mo 2 WCp 2 (m 3 -P)(m-PCy 2 )(CO) 7 ] (2.749(2) Å [5a]). The PeP distance of 2.043(2) Å is somewhat shorter than the values of ca.…”