15689-01-7Relevant academic research and scientific papers
Synthesis and reactivity of cyclohexenylmanganese tricarbonyl, a complex containing a two-electron, three-center Mn?H?C interaction
Brookhart,Lamanna,Pinhas, Allan R.
, p. 638 - 649 (2008/10/08)
The cation (benzene)Mn(CO)3+ undergoes stepwise, vicinal addition of 2 equiv of hydride in an exo fashion to yield a unique transition-metal anion, (1,3-cyclohexadiene)Mn(CO)3-. The diene anion is highly reactive. Exposure to oxygen results in oxidation of the metal and liberation of free 1,3-cyclohexadiene. Protonation yields an unusual, bridged (cyclohexenyl)Mn(CO)3 species possessing an aliphatic, endo C-H bond that is activated via coordination to manganese. The three-center Mn?H?C interaction in this complex renders the bridging hydrogen acidic and permits facile removal by base to regenerate the diene anion. Alkylation with MeI or MeOSO2CF3 results in methyl addition to the endo side of the ring and coordination of a second endo C-H bond. A second deprotonation/alkylation sequence can be achieved to give ring-dialkylated cyclohexenyl products. The coordinated C-H bond of the bridged cyclohexenyl species is replaced by external ligands L (L = CO, P(OMe)3) to give (cyclohexenyl)Mn(CO)3L adducts. Hydride addition to the π-allyl unit of the tetracarbonyl species results in reduction of the polyolefin to cyclohexene. Thermolysis of the phosphite adduct causes loss of CO and formation of the bridged complex (cyclohexenyl)Mn(CO)2P(OMe)3. The parent complex C6H9Mn(CO)3 reacts with diazomethane in an unexpected fashion providing an alternate and complimentary method of ring methylation. Reactions with activated olefins appear to proceed via a free radical mechanism resulting in transfer of H2 across the double bond.
Bimetallic anionic formyl complexes: Synthesis and properties
Tam, Wilson,Marsi, Marianne,Gladysz
, p. 1413 - 1421 (2008/10/08)
Three bimetallic anionic formyl complexes, Li+[Mn2(CO)9(CHO)]- (2), Li+[ReMn(CO)9(CHO)]- (3), and Li+[cis-Re2(CO)9(CHO)]- (4), are prepared by the reaction of Li(C2H5)3BH with the corresponding neutral metal carbonyl dimers MM′(CO)10. Whereas 2 has a half-life of ca. 8 min at room temperature, 4 is stable for days and is easily isolated as a THF solvate. When 2-4 are treated with electrophiles such as benzaldehyde, Fe(CO)5, and n-octyl iodide, hydride transfer occurs to give benzyl alcohol (after protonation), Li+[Fe(CO)4(CHO)]-, and octane, respectively. Heterobimetallic formyl 3 is a weaker hydride donor than 2 and 4. Reaction of 4 with CH3I gives CH4 (ca. 50%). However, complex reactions occur when 2 and 4 are treated with CH3SO3F and strong acids, contrary to our original report of CH4 and H2 evolution. Formyl 2 is stabilized by added (C2H5)3B and decomposes disproportionatively to Mn2(CO)10 (0.5 equiv), Li+[Mn(CO)5]- (1.0 equiv), and H2 (0.5 equiv). An initial Mn-Mn bond cleavage step is proposed. The only characterizable product from the thermolysis of 4 is Re2(CO)10, but photolysis gives Li+[Re2(CO)9(H)]-. When K+[Re2(CO)9(CHO)]- is treated with 1 equiv of K(sec-C4H9)3BH, reduction to formaldehyde (21%) and K2[Re2(CO)9] (92%) occurs.
