Reductive Coupling of CO: Formation of a 1:1 Adduct of η²‐Ketone‐ and Enediolato‐Complex upon Carbonylation of Bis(cyclopentadienyl)hafnacyclobutane

Abstract

complex [{(qs-CsHS)Ni}2(p,q5-CSHS)]*.1141 In contrast to 1 (Ass middle deck), in which a p,q4-coordination of the five-membered ring is discussed on the basis of the large differences in the As-As bond lengths (2.389(2)-2.762(3) A),"] in 5 the Ps ring forms a regular pentagon (cf. the pentagonal columns of phosphorus atoms in Hittorfs phosphorus and the polyphosphides derivable therethe mean value of the P-P bond lengths differs very little from that in the P6 middle deck of 2,I2I and is of an order of magnitude which has also been found in the triple-decker complexes stabilized by triphosphorus ligands (triphos = for example l,l,l-tris(dipheny1phosphi-nomethy1)ethane) with p,q3-P3

Insertion of Isonitriles into the Zr–CH3 Bond of Cp*2Zr(CH3)2 and Electrophilic Cleavage of the Remaining Methyl Group

“…A stoichiometric reaction (1:1) in CD 2 Cl 2 gave quantitative conversion to ionic 5 (both 11 B and 19 F NMR confirmed the generation of [MeB(C 6 F 5 ) 3 ] − ). An SC-XRD structure (only one of the two independent molecules in the unit cell is shown in Figure 4) showed no evidence of interaction between the Zr cation and the weakly coordinating [MeB(C 6 F 5 ) 3 ] − (which is obviously less coordinating than [CpCr(CO) 3 ] − ).…”

“…Full experimental details, 1 H, 13 C, 11 B, and 19 F NMR spectra, HRMS spectra, ATR-FTIR data, kinetic plots, and crystallographic data (PDF)…”

“…The insertion of CO into the M–C bonds of group 4 complexes is a useful strategy in the construction of C–C bonds. − The mechanistic and stereochemical aspects of CO insertion have been discussed quite extensively. , In 1976, Floriani reported that the reaction of CO with Cp 2 Zr­(CH 3 ) 2 led to the monoacyl complex Cp 2 Zr­(acyl)­CH 3 (eq ). SC-XRD analysis revealed that the resulting acyl ligand adopts η 2 coordination, with the O atom positioned in the middle of the acyl and methyl ligands (“O-inside” isomer) .…”

Highly Modular Synthesis of 1,2-Diketones via Multicomponent Coupling Reactions of Isocyanides as CO Equivalents

“…Multicomponent one-pot reactions offer efficiency and sustainability in organic synthesis and are increasingly being employed to build complexity in pharmaceutical and fine chemical synthesis. − Of particular value are highly modular unions of widely available building blocks to access novel structural motifs. 1,2-Diketones are useful intermediates in synthetic organic chemistry, often used in the synthesis of medicinally relevant heterocycles, such as imidazoles, pyrazines, and quinoxalines as well as natural products. − They are also used in materials chemistry , and as ligands for various metal complexes. − Despite their widespread synthetic utility, 1,2-diketone synthesis is typically achieved via lengthy linear sequences and oxidative protocols. − These approaches are often limited to (symmetrical) dibenzylic 1,2-diketones and suffer poor compatibility with heteroaryl substrates, preventing efficient access to large libraries of these highly versatile derivatives (Scheme ).…”

Transition‐Metal Complexes with Singly Reduced 1,2‐Diketone Radical Ligands

“…Indeed, until recently only 1,2-diketone complexes containing the ligand in its two-electron-reduced diolate form with an early transition metal or main-group element had been isolated. [21] Complexes of bis(1-methylimidazol-2yl)glyoxal with late transition metals have been shown by EPR spectroscopy, to undergo reduction at the ligand, although these intermediates have not been isolated and are thought to be coordinated through the imidazolyl moiety. [22] The one-electron-reduced form has been implicated by EPR spectroscopy in the adducts formed by the reaction of 1,2-diketones with in situ photolyzed manganese carbonyl…”