17-electron Cation Research Articles

Preparation of new (η 5-C 5H 4CH 3)Mn(NO)(PPh 3) and (η 7-C 7H 7)Mo(CO)-(PPh 3) complexes

The complex (η 5-C 5H 4CH 3)Mn(NO)(PPh 3)I has been prepared by the reaction of NaI with [(η 5-C 5H 4CH 3)Mn(NO)(CO)(PPh 3)] + and also by the reaction of [(η 5-C 5H 4CH 3)Mn(NO)(CO) 2] + with NaI followed by PPh 3. This iodide compound reacts with NaCN to yield (η 5-C 5H 4CH 3)Mn(NO)(PPh 3)CN which is ethylated by [(C 2H 5) 3O]BF 4 to yield [(η 5-C 5H 4CH 3)Mn(NO)(PPh 3)(CNC 2H 5)] +. Both [(η 5-C 5H 4CH 3)Mn(NO)(CO) 2] + and [(η 5-C 5H 4CH 3)Mn(NO)(PPh 3)(CO)] + react with NaCN to yield [(η 5-C 5H 4CH 3)Mn(NO)(CN) 2] −. This anion reacts with Ph 3SnCl to yield cis-(η 5-C 5H 4CH 3)Mn(NO)(CN) 2SnPh 3 and with [(C 2-H 5) 3O]BF 4 to yield [(η 5-C 5H 4CH 3)Mn(NO)(CNC 2H 5) 2] +. The reaction of (η 5-C 5-H 4CH 3)Mn(NO)(PPh 3)I with AgBF 4 in acetonitrile yields [(η 5-C 5H 4CH 3)Mn-(NO)(PPh 3)(NCCH 3)] +. The complex (η 5-C 5H 4CH 3)Mn(NO)(CO)I, produced in the reaction of [(η 5-C 5H 4CH 3)Mn(NO)(CO) 2] + with NaI, is not stable and decomposes to the dimeric complex (η 5-C 5H 4CH 3) 2Mn 2(NO) 3I for which a reasonable structure is proposed. Similar dimers can be prepared from the other halide salts. The reaction of (η 7-C 7H 7)Mo(CO)(PPh 3)I with NaCN yields (η 7-C 7-H 7)Mo(CO)(PPh 3)CN which is ethylated by [(C 2H 5) 3O]BF 4 to yield [(η 7-C 7H 7)-Mo(CO)(PPh 3)(CNC 2H 5)] +. The interaction of this molybdenum halide complex with AgBF 4 in acetonitrile and pyridine yields [(η 7-C 7H 7)Mo(CO)(PPh 3)-(NCCH 3)] + and [(η 7-C 7H 7)Mo(CO)(PPh 3)(NC 5H 5)] +, respectively. Both (η 5-C 5-H 4CH 3)Mn(NO)(PPh 3)I and (η 7-C 7H 7)Mo(CO)(PPh 3)I are oxidized by NOPF 6 to the respective 17-electron cations in acetonitrile at −78°C but revert to the neutral halide complex at room temperature. This result is supported by electrochemical data.

ChemInform Abstract: ANODIC OXIDATION OF METAL CARBONYLS IN TRIFLUOROACETIC ACID, STABILITIES OF SOME 17‐ELECTRON CATIONS

AbstractDurch elektrochemische Oxidation der 18‐Elektronen‐Carbonyle Hexacarbonyl‐Cr, Cyclopentadienyltricarbonyl‐Mn, Pentacarbonyl‐Fe und Bromopentacarbonyl‐Mn in Trifluoressigsäure/Tetrabutylammoniumtetrafluoroborat entstehen die entsprechenden 17‐Elektronen‐Kationen, von denen die ersten beiden in diesem Medium einige Sekunden bei Raumtemperatur beständig sind.

Anodic oxidation of metal carbonyls in trifluoroacetic acid; stabilities of some 17-electron cations

The electrochemical oxidation of some metal carbonyls at a Pt electrode in trifluoroacetic acid–tetrabutylammonium tetrafluoroborate (0.2 mol dm–3) is reported. It is shown that the 17-electron cations [Cr(CO)6]+, [Fe(CO)5]+, [Mn(η-C5H5)(CO)3]+ and [MnBr(CO)5]+ may be prepared form their parent 18-electron carbonyls and that each has some stability in this medium. The complex [Mn2(CO)10] undergoes a two-electron oxidation and the product is [Mn(CO)5(O2CCF3)]. This latter product can also be prepared by direct air oxidation.

Arene–molybdenum chemistry: reactions of di-µ-chloro-bis[(η-allyl)-(η-arene)molybdenum] with cyclic olefins

The violet solutions formed form (AlEtCl2)2 and the compounds [{Mo(η-C3H5)(η-arene)Cl}2](arene = C6H6, C6H5Me, or C6H3Me3-1,3,5) react with norbornadiene (nbd), cyclo-octa-1,3,5,7-tetraene(cot), or cyclohepta-1,3,5-triene (cht), and the corresponding cations [Mo(η-C3H5)(η-arene)(η-olefin)]+ have been is olated from the hydrolysed reaction mixtures. Prolonged reaction with cht yields the cycloheptatrienly sandwich compounds [Mo(η-C7H7)(η-arene)][PF6]. The comound [Mo(η-C3H5)(η-C6H6)(cht)][PF6] undergoes deprotonation on an alumina column to the neutral compound [Mo(η-C3H5)(η-C6H6)(η3-C7H7)]. The violet solution reacts with cyclopentene and hydrolysis of the product in the presence of lithium chloride or alkaline sodium dithionite gives [Mo(η-C5H5)(η-C6H6)Cl] or paramagnetic [Mo(η-C5H5)(η-C6H6)] respectively; with cyclohexene the 17-electron cation [Mo(η-C6H6)2]+ is formed in high yield.