Synthesis and structures of titanaoxacyclobutanes

Synthesis and kinetics of decomposition of tungsten(VI) and molybdenum(VI) 2-oxametallacyclobutane complexes and the x-ray structure of trans-Mo[CH(tert-Bu)CH(C6F5)O](NAr)(O-tert-Bu)2

“…The result shown in eq 6 can be explained on the basis of the findings so far; 2a-trans decomposes quantitatively Ar 2a-trans t-Bu + la + W(0)(NArXO-t-Bu)2 (6) to Mo(0)(NAr)(0-t-Bu)2 and frans-PhFCH=CH(t-Bu) and Mo(0)(NAr)(0-t-Bu)2 then reacts quantitatively with lb. Note that no cis-PhpCH=CH(t-Bu) is formed (not detectable by 500-MHz NMR), as one would expect if some PhpCHO were lost from 2a-trans and would then react three times faster with lb than it would back-react with la.…”

“…Mo(CH-i-Bu)(NAr)(0-t-Bu)2 (150 mg, 3.07 X 10"4 mol) in octane (500 mL). The solution was kept at -40 °C for approximately 48 h to give the product as bright orange crystals (96 mg, 46%) suitable for X-ray analysis: *H NMR (toluene-d8, 263 K) 6.96 (m, 3, Ha,), 6.62 (d, 1, « = 8.5, Cs), 4.41 (sept, 2, CHMe2), 2.45 (d, 1, JHh = 8.5), 1.55 (s, 9, OCMe3), 1.45 (s, 9, OCMe3), 1.38 (d, 6, CHMe2), 1.32 (d, 6, CHAfe2), 1.08 (s, 9, CHCMe3); 13C (125.7…”

“…NMR of 2b-trans: 7.04 (d, 2, Hm), 6.96 (t, 1, Cp), 6.53 (d, 1, Hg), 4.15 (septet, 2, CHMe2), 2.27 (d, 1 Ha, «W = 8), 1.46 (s, 9, OCMe3), 1.41 (s, 9, OCMe3), 1.40 (d, 6, CHMe2), 1.34 (d, 6, CHMe2), 1.08 (s, 9, CHCMe3).…”

Bis(cyclopentadienyl)-3,3-dimethyltitanacyclobutane

“…Most titanacyclobutanes, including (2a-e), thermally cleave by a 'retro 2 + 2' process to liberate alkene and afford the reactive methylidene species 'Cp 2 Ti=CH 2 ', or an alkene complex thereof, as shown in eq 3. 17 This methylenation chemistry has been the subject of a recent comprehensive review. 1c For example, the titanium methylidene so produced affords vinyl ethers from a wide range of esters (eq 3), a conversion which is not possible using Wittig alkylidene phosphorane reagents.…”

Addition of a carbonyl functionality to titanium carbenes. A study of the mechanism and intermediates in the Tebbe reaction

“…They prepared 4 and 5 either by reaction of a titanium ketene with dimethylsulfonium methanide (4) or by exchange of a ketene with the alkene of 3-tert-butyltitanacyclobutane (5). 7 Reaction of (cp),Ti=C=CR, with ketones or aldehydes has been proposed to involve the formation of the isomeric 3-exomethylenetitanaoxetane complex 6." However, this was not detectable by NMR spectroscopy, as are the 4-exo-methylene substituted compounds 4 and 5.…”