81899-94-7Relevant academic research and scientific papers
Addition and cycloaddition reactions of the nucleophilic oxo and sulfido complexes [tmtaa]Ti=X (X = O, S; tmtaa = dianion of 7,16-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11] tetraazacyclotetradecine)
Housmekerides, Chris E.,Ramage, David L.,Kretz, Christine M.,Shontz, John T.,Pilato, Robert S.,Geoffroy, Gregory L.,Rheingold, Arnold L.,Haggerty, Brian S.
, p. 4453 - 4468 (2008/10/08)
The complexes [tmtaa]Ti=O (1) and [tmtaa]Ti=S (2) have highly reactive Ti=O and Ti=S linkages and are demonstrated to undergo a number of new addition and cycloaddition reactions, and complex 1 has been found to be involved in a series of acid-base equilibria. Treatment of 1 or 2 with excess RO3SCF3 (R = H, Me, SiMe3) yields the bis(triflate) complex [tmtaa]Ti(O3SCF3)2. This species in turn slowly reacts with water to displace the triflate ions and form the bis(aqua) complex [(tmtaa)Ti(OH2)2]2+ (5). Complex 1 reacts with 1 equiv of HO3SCF3 to form the oxo-bridged complex [(tmtaa)Ti-O-Ti(tmtaa)]2+ (8), and treatment of either 5 or 8 with [NH4]OH or wet Et3N regenerates 1. Deoxygenation of 1 occurs when it is treated with excess acetyl chloride to form [tmtaa] TiCl2 via a spectroscopically observed [tmtaa] Ti(Cl)(OC{O}Me) intermediate. Complex 1 also reacts with hexafluoroacetic, maleic, and phthalic anhydrides to form bis(carboxylate) complexes, and hexafluoropropylene oxide reacts with 1 to give a metallacycle formed by a net [3 + 2] cycloaddition reaction. Complex 1 undergoes [2 + 2] cycloaddition of the Ti=O bond across the C=O bond of electron deficient ketones to form the dioxatitanacyclobutanes [tmtaa]Ti(η2[02]-O2CRR′) (R = R′ = CF3; R = CH3, R′ = CF3 (16); R = CF3, R′ = Ph). Complex 2 undergoes an analogous [2 + 2] cycloaddition of its Ti=S bond across the C=O bond of O=C-(CF3)2 and O=C(CF3)CH3 to form similar metallacycles. The Ti=O bond of 1 also undergoes [2 + 2] cycloaddition across a C=O bond of [Cp*Re(CO)2(NO)]+ (20) to form the cationic heterobimetallic complex [(tmtaa)Ti-μ2,η3-O 2C)Re(CO)(NO)Cp*]+ (21), and both 20 and 21 were observed to react with Ph3P=NPh to form [Cp*Re(C≡NPh)2(NO)]+. Complex 1 also undergoes [2 + 2] cycloaddition reactions with SO2 and SO3 to form η2[O2]-sulfito (23) and η2[O2]-sulfato complexes, respectively. These same complexes result when the sulfido complex 2 is allowed to react with SO2 and SO3. Complex 1 reacts with COS to form the sulfido complex [tmtaa]Ti=S and CO2 by successive cycloaddition and retro-cycloaddition reactions. The corresponding reaction of 1 with CS2 gives a η2[S2]-CS3 complex via the intermediate formation of [tmtaa]Ti=S which was independently shown to give this product upon treatment with CS2. Complex 1 also reacts with Lawesson's reagent, 2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane 2,4-disulfide, to form the 4-membered non-carbon metallacycle [tmtaa]Ti(η2[O,S]-OSP(=S)(C6H4OMe)) (34). The reactions of 1 and [omtaa]Ti=O (omtaa = dianion of 7,16-dihydro-2,3,6,8,11,12,15,17-octamethyldibenzo[b,i][1,4,8,11] tetraazacyclotetradecine) with CO2 to form η2[ O2]-carbonate complexes have also been studied. The oxo group of complex 1 also displaces the labile acetonitrile and acetone ligands in Os3(CO)11(CH3CN), cis-[PtCl(PEt3)(acetone)]+, and trans-[Ir(CO)(PPh3)(CH3CN)]+ to form new μ2-oxo heterobimetallic complexes that possess dative Ti=O→Os, Ti=O→Pt, and Ti=O→Ir bonds, respectively. Complex 1 also reacts with Cp*W(O)2Cl to form the oxo-bridged heterobimetallic complex Cp*O2W(μ-O)Ti-(Cl)(tmtaa) which can also be produced by adding [Cp*WO3]- to (tmtaa)TiCl2. Complexes 5, 8,16, 21, 23, 34, and the complex, 11, formed between 1 and phthalic anhydride have been crystallographically characterized.
