Acyl‐Functionalized Molybdenum Compounds [(η³‐C₃H₅)(η⁵‐Cp′)Mo(CO)₂]: An Experimental Study Including the X‐ray Structure of a Rare endo Conformer

Abstract

A series of new acyl‐functionalized molybdenum(II) complexes [(η3‐C3H5)(η5‐C5H4COR)Mo(CO)2] have been successfully synthesized and crystallographically characterized, and the relationship between the reactivity and electronic properties of these organometallic compounds has been studied in detail. The X‐ray analysis revealed [(η3‐C3H5)(η5‐C5H4COCF3)Mo(CO)2] to exist as a rare endo conformer, the first time that this structure has been observed in the crystal lattice of a [(η3‐C3H5)(η5‐Cp′)Mo(CO)2] (Cp′ = substituted Cp) complex without any disorder. It has also been demonstrated that the derivatives bearing very strong electron‐withdrawing acyl groups (e.g., ‐CHO, ‐COCF3) show different outcomes in the protonation reactions compared with the parent cyclopentadienyl compound or derivatives bearing less electron‐withdrawing groups (e.g., ‐COMe, ‐COPh). This study has also revealed the increased reactivity of the formyl derivative [(η3‐C3H5)(η5‐C5H4CHO)Mo(CO)2] towards aromatic amines. An IR spectroscopic analysis revealed that the aldimine‐functionalized products formed very quickly even under the mild conditions that fulfill the basic rules of click chemistry.

Stabilization of η3-indenyl compounds by sterically demanding N,N-chelating ligands in the molybdenum coordination sphere

“…The structural parameters, describing the coordination sphere of molybdenum, are in line with data of structurally related cyclopentadienyl and indenyl compounds described previously. 13,14,[44][45][46] The reaction of 2 with lower than stoichiometric amount of bpy or phen gives a material insoluble in common organic solvents that strongly contrasts with properties of the starting compounds as well as the products 4a and 5a. Elemental analysis of the products together with their insolubility suggests an appearance of the ionic pair consisting of a large complex cation and a large complex anion [(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 ( N,N L)] [(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 Cl 2 ] (4b-9: N,N L ¼ bpy, 5b-9: N,N L ¼ phen), see Scheme 5.…”

“…13,14,[44][45][46] The reaction of 2 with lower than stoichiometric amount of bpy or phen gives a material insoluble in common organic solvents that strongly contrasts with properties of the starting compounds as well as the products 4a and 5a. The structural parameters, describing the coordination sphere of molybdenum, are in line with data of structurally related cyclopentadienyl and indenyl compounds described previously.…”

Indenyl Compounds with Constrained Hapticity: The Effect of Strong Intramolecular Coordination

“…Since the compound 14 gives one set of sharp signals at room, consistent with C1 molecular symmetry, fluxional behavior is not expected in solution. According to previous studies on indenyl compounds without substituents in five-membered ring, [10,12,13] 3 . This experiment unambiguously revealed η 3 -coordination mode of the indenyl ligand that was confirmed in solid state by X-ray diffraction analysis (Fig.…”

“…for C23H17ClMoN2O2: C,56.98;H,3.54;N,5.78. Found: C,57.18;H,3.45;N,500.20 MHz): δ = 3.82,4.21 (2 × d,3 X-ray crystallography: The X-ray data for the crystals of the compounds 4', 7, 9, 10, 11, 12, 13, 14·CH2Cl2, 15, 16· 1 /2Me2CO and 18 were obtained at 150 K using an Oxford Cryostream low-temperature device on a Nonius KappaCCD diffractometer with Mo Kα radiation (λ = 0.71073 Å) and a graphite monochromator. Data reductions were performed with DENZO-SMN.…”

“…[2] The variations in cyclopentadienyl ligand periphery often result in dramatic changes in physical, chemical and biological properties of the corresponding compounds. [3] These changes can be, in particular cases, attributed to electronic and steric effects caused by the partial or full replacement of the hydrogen atoms by other groups. [4] A formal replacement of the cyclopentadienyl ligand with indenyl, a congener with annulated benzene ring (Ind = C9H7), usually accelerates the rates of substitution reactions due to a lower energetic barrier of the haptotropic shift of the π-ligand.…”