Synthesis, Characterization and Stability of Spirodiene Complexes of Molybdenum(II): New Route to ansa‐Molybdenocene and Ring‐Functionalized Molybdenocene Compounds

Abstract

The reactions of [Mo(CO)2(Cp)(NCCH3)2][BF4] (1) with spiro[2.4]hepta‐4,6‐diene and spiro[4.4]nona‐1,3‐diene give the complexes [Mo{η4‐C5H4(CH2)2}(CO)2(Cp)][BF4] (3) and [Mo{η4‐C5H4(CH2)4}(CO)2(Cp)][BF4] (4), respectively. [Mo{η4‐C5H4(CH2)2}(CO)2(Cp)][BF4] (3) is stable towards ring opening at room temperature, but its formation is accompanied by small amounts of ring‐opening products [Mo(η5‐C5H4CH2‐η1‐CH2)(CO)(Cp)][BF4] (5) and [Mo{η5‐C5H4(CH2)2‐η1‐CO}(CO)(Cp)][BF4] (6). With 1,1‐dimethyl‐spiro[2.4]hepta‐4,6‐diene, two isomers with the formula [Mo{η4‐C5H4CH2C(CH3)2}(CO)2(Cp)][BF4] are formed (7 and 8). While the endo‐isomer 7 is stable towards ring opening, the exo‐isomer 8 slowly rearranges to the ring‐opened product [Mo{η5‐C5H4C(CH3)2CH2‐η1‐CO}(CO)(Cp)][BF4] (9). The reaction of [Mo(CO)2(Ind)(NCCH3)2][BF4] (2) with spiro[4.4]nona‐1,3‐diene also gives the diene coordinated species [Mo{η4‐C5H4(CH2)4}(CO)2(Ind)][BF4] (11), which is the first example of a structurally characterized, coordinated, unsubstituted spirodiene. In contrast, reaction of 2 with spiro[2.4]hepta‐4,6‐diene leads directly to the ansa‐cyclopentadienyl complex [Mo(η5‐C5H4CH2‐η1‐CH2)(CO)(Ind)][BF4] (12). Reaction of 12 with bromine or iodine leads to the formation of Cp‐substituted molybdenocene derivatives [Mo{η5‐C5H4(CH2)2X}(CO)(Ind)X][BF4] (13: X = Br, 14: X = I). The compounds [Mo(η5‐C5H4CH2‐η1‐CH2)(CO)(Ind)][BF4] (12) and [MoBr{η5‐C5H4(CH2)2Br}(CO)(Ind)][Br]·0.5H2O (13a) were structurally characterized, and they open the way to new functionalized molybdenocene complexes that have biological applications.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Kinetic Studies on the Oxidation of η5-Cyclopentadienyl Methyl Tricarbonyl Molybdenum(II) and the Use of Its Oxidation Products as Olefin Epoxidation Catalysts

“…Among the variety of efficient catalysts known today for olefin epoxidation are some organometallic oxides containing a metal in high oxidation state . Some of them can be conveniently synthesized from carbonyl precursors, such as Cp′Mo(CO) 3 R (R = alkyl group). − It has been found that the latter catalyze the epoxidation of olefins with tert -butyl hydroperoxide (TBHP) and other alkyl hydroperoxides as oxidants. , …”

“…In this particular case peroxo derivatives have been shown to be the active catalysts, and metal-attached η 2 -peroxo groups react with olefins when applied stoichiometrically. − Compounds of formula Cp′Mo(CO) 3 R and their oxidation products have not yet been examined in comparable detail, particularly with respect to mechanistic implications, and no active species beyond the Mo(VI)-dioxo species has been found or proposed to date. However, catalytic results show that their catalytic activity is considerable, and, in contrast to MTO they are both easier to derivatize and easier to immobilize. − , In this work, a detailed examination of the reaction mechanism of Cp′Mo(CO) 3 R-based olefin epoxidation with TBHP as the oxidizing agent is presented, based on kinetic experiments. It involves a comprehensive investigation of the system starting with (1) the tricarbonyl, (2) the dioxo, and (3) the oxo peroxo compounds after adding excess TBHP in the presence and absence of olefin.…”

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

“…[15][16][17][18][19][20][21] Recently, we have described a synthesis of [{(h 5 -Ind)Mo(CO) 2 (m-Cl)} 2 ] (1; Scheme 1) that was found to be a versatile synthon for various h 3 -indenyl compounds. 34,35 The aim of this study is to bring a detail description of the coordination properties of [{(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 (m-Cl)} 2 ] (2) in attempt to synthesize new h 3 -indenyl compounds structurally related with the well-known complexes bearing h 3 -allyl [(h 3 -C 3 H 5 )Mo(CO) 2 ( N,N L)Cl]. 24 Although the cyclopentadienyl and indenyl molybdenum compounds have oen a similar molecular structure, a different reactivity is expected since a replacement of the cyclopentadienyl ligand with the indenyl accelerates reaction rates due to a lower energetic barrier of the haptotropic shi of the p-ligand.…”

“…33 An activation of coordinated ligand was also observed for complexes with h 4 -bonded spiro- {h 4 -C 5 H 4 (CH 2 ) 2 }Mo(CO) 2 ][BF 4 ] is unusually stable, while the indenyl analogue undergoes a spontaneous and very fast ringopening to [(h 5 -Ind)(h 5 -C 5 H 4 CH 2 -h 1 -CH 2 )Mo(CO)][ BF 4 ]. 34,35 The aim of this study is to bring a detail description of the coordination properties of [{(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 (m-Cl)} 2 ] (2) in attempt to synthesize new h 3 -indenyl compounds structurally related with the well-known complexes bearing h 3 -allyl [(h 3 -C 3 H 5 )Mo(CO) 2 ( N,N L)Cl]. It will be shown that a steric congestion of the chelating ligand is critical for the stability of [(h 3 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 ( N,N L)Cl] and could be used for the control of the indenyl ring slippage.…”

Molybdenum complexes containing substituted cyclopenta[l]phenanthrenyl ligand

“…They serve as effective precursors for the synthesis of molybdenocenes substituted in one cyclopentadienyl ring [CpCp 0 MoL 2 ] n+ [1][2][3][4][5]. Protonation of [Cp 0 Mo(g 3 -C 3 H 5 )(CO) 2 ] with HBF 4 followed by cyclopentadiene coordination and oxidation gives dicationic complexes [CpCp 0 Mo(CO) 2 ] 2+ [1,2].…”