CO, Isocyanide, Alkene, and Alkyne Insertions into Platinaoxetane Pt−O Bonds

Abstract

Platinaoxetanes Pt(COD)(C7H10O) (1) and Pt(PEt3)2(C7H10O) (2) undergo insertion of CO into their Pt−O bonds to afford Pt(COD)(C(O)OC7H10) (3) and Pt(PEt3)2)(C(O)OC7H10) (4), respectively. Complex 4 is also available from 3 and PEt3. Platinaoxetanes [Pt(COD)(C7H10O)Pt(COD)Cl)]+ (5) and Pt(COD)(C7H10OBF3) (6), with Lewis acids bonded to the platinaoxetane ring oxygen atom, give free norbornene when treated with CO. Treatment of 3 with BF3·Et2O immediately gives 6. Both types of platinaoxetanes are inert to CO2. Treatment of 1 with tetracyanoethylene (TCNE) yields Pt(COD)(TCNEOC7H10) (7) by alkene insertion into the Pt−O bond, while 1 shows no reactivity with ethylene or isobutylene. Similarly 1 reacts with diethylacetylenedicarboxylate (DEAD) to give a rare alkyne M−O bond insertion product Pt(COD)(DEADOC7H10) (8) but is inert to diphenylacetylene. Reaction of 1 with isocyanide in a 1:3 molar ratio gives Pt(ButNC)2(C7H10OButNC) (9), a result of COD displacement by 2 isocyanides and insertion of another isocyanide into the Pt−O bond. Complex 3 was characterized by single-crystal X-ray crystallography.

Ring expansion of a 2-rhodaoxetane: insertion chemistry with unsaturated molecules

“…Interestingly, the peaks of the axial methylene protons of the equivalent TPA arms have shifted dramatically downfield from [1] + (δ = 5.18 ppm, d[AB], 2 J H,H = 15.3 Hz) to [2b] + (δ = 5.96 ppm, d[AB], 2 J H,H = 16.3 Hz), which could be because of close contact with the nearby carbonyl moiety (vide infra). 13 C NMR spectroscopy also supported the proposed structure of [2b] + , notably showing a doublet for C1 (δ = 29.48 ppm, 1 J Rh,C = 26.9 Hz) and for C4 (δ = 141.52 ppm, 1 J Rh,C = 34.5 Hz), although the latter is, not surprisingly, of low intensity. 10 Full characterization of [2b] + was completed with the use of 2D NMR spectroscopic techniques such as COSY, NOESY, HSQC and HMBC, as well as HRMS to confirm the empirical formula.…”

“…Despite the fact that similar reactions of [1] + have been proposed to be acid catalysed, 7 the rate of alkyne insertion was found to be unaffected by the presence of Na 2 CO 3 . The insertions of these acetylene dicarboxylates into rhodium-alkoxide bonds 12 as well as the Pt-O bond of a platinaoxetane 13 are known, although the insertion of diethylacetylene dicarboxylate into [1] + , which is complete after 1 hour, is notably faster than the corresponding platinaoxetane reaction, which requires 20 hours. This transformation is also in contrast to that of the ruthenaoxetane reported by Chakravorty, 14 where insertion occurs across the Ru-C bond and electron-rich alkynes react faster than electron-deficient ones.…”

Effects of ligands on the migratory insertion of alkenes into rhodium–oxygen bonds

“…For example, tetrauoroethene inserts into the platinum(II)-methoxo bond of Pt(DPPE)(OMe)(Me) (Scheme 1A), 33 acrylonitrile inserts into the platinum(II)-phenoxo bond in Pt(PEt 3 ) 2 (OPh)(H), 34 and tetracyanoethene inserts into the Pt(II)-O bond of a platinaoxetane. 35 Yet, the only direct observation of the insertion of an unactivated alkene into a transition-metal-alkoxo bond is the reaction of PEt 3 -ligated rhodium(I) alkoxo complexes that insert coordinated alkenes (Scheme 1B). 36 No discrete complexes of any metal containing other types of ancillary ligands have been reported that undergo this elementary reaction.…”

Deoxygenation of Epoxides with Carbon Monoxide

“…The IR spectrum (ATR) confirms this with characteristicb ands at 2014 (CO) and 1630 cm À1 (IrCO 2 R). Thel atter value is similart ot he one of a2platina-g-lactone (1644 cm À1 (NaCl)), the only structurally characterized 2-metalla-g-lactone in literature, [34] and to an acyclic iridaester( 1638( benzene) and 1650 cm À1 (KBr)). [35] When monitoring the catalytic reactionN MR-spectroscopically (with Lewis acid) at 60 8Co ver ap eriod of 23 h, this intermediate can also be detected.…”