[ω‐(Phosphanyl)alkyl]cyclopentadienyl Complexes

Abstract

The syntheses and characterisation of the [a-(phosphany1)alkyl]cyclopentadienyl anions 2,3,6-8,10, and 11 are described. These anions form metallocenes 12-15 and 11-19 with FeC1, 2 THF and with ZrC1, . 2 THF, respectively. With ICO(CO)~ chelated carbonyl complexes 23-25, 28, and 29 are formed. The unchelated intermediate 20 has been detected by IR spectroscopy. The carbonyl chelate complexes are thermally stable. Under photochemical conditions, ligand exchange reactions are possible which in the case of 1,5-cyclooctadiene proceed with decomplexation of the phosphane arm. This does not prevent a reaction at the cobalt(1) atom, treatment of 35 with diphenylethyne gives the corresponding tetraphenylcyclobutadiene complex 36 in good yield, the phosphane arm remaining uncoordinated.Transition metal complexes with cyclopentadienyl ligands have been intensively studied since their initial synthesis in 1951 ['I. Special aspects of their chemistry are ring-slippage reactions1'] in which the usual -q5 bonding mode changes to an q3 bonding with temporary decomplexation of one double bond. This raised the question in how far chemical reactions with participation of the temporarily decoordinated double bond might be possible. One result of our work was the ring opening reaction of a (bicyclo[3.2.0]hepta-1,3-dienyl)cobalt(I) complex followed by a cycloaddition of the intermediate ortho-quinodimethane speciesL3]. In these ringslippage reactions the cyclopentadienyl ligand can formally be regarded as a bidentate "allyl-ene" ligand, whose "ene" fragment decoordinates in the course of the change in hapticity from q5 to q3 and is recoordinated later. The process reversibly generates a vacant coordination site, which is capable of participating in chemical reactionsr3].Vacant coordination sites are usually generated by decomplexation of a ligand. If the ligand is not present in large excess in the reaction mixture, it will normally not be recoordinated after use of the vacant coordination site for further reaction. However, if the decomplexed ligand is still attached to the complex by other means than by coordination to the metal atom, it will not leave the molecule as a whole and can be later recoordinated. The ring slippage of a cyclopentadienyl ("allyl-ene") ligand mentioned is a very special case, and more generally this line of thought leads to the use of bi-or multidentate ligands. Most bidentate ligands are combinations of two ligands of the same nature, e.g. diphosphanes, bipyridyl derivatives and similar systems. In contrast, heterobidentate ligands should allow use to be made of the different coordination properties of the two ligands involved. In this context we became interested in combinations of cyclopentadienyl and phosphane ligands, which are among the most thoroughly studied ligands in organometallic chemistry. To avoid any interference from resonance interactions we envisaged a connection of the ligands by an alkyl chain. The two partial ligands have rather different properties: whereas the cyclopentadienyl system ...

New cyclopentadienylethylphosphane chelate complexes with unsymmetrical phosphane substitution

“…The data obtained resemble those of the closely related di-tert-butyl substituted complex. 28,29 Subsequent treatment of rac-5 with sodium amalgam (1%) and ethene in THF at À78 1C followed by warming to 25 1C gave ethene chelate complex rac-6 in 40% yield.…”

“…49 Similar to the formation of rac-5 and rac-6 the corresponding tert-butyl(cyclohexyl) substituted complexes rac-9 and rac-10 are obtained in moderate yields from spiro[2.4]hepta-4,6-diene [65][66][67][68] Cole-Hamilton et al, 69 Lalinde et al, 70 and Whitby et al…”

Syntheses and Structures of Sterically Congested Linear and Branched Cobalta[n]triangulanes

“…[18] A convenient route to such complexes is the reductive complexation starting from the paramagnetic chloro complex 5 in the presence of sodium amalgam and the new ligand. [19] This method was selected for the preparation of linear cobalta[n]triangulanes from carbocyclic methylenetriangulanes and spirocyclopropanated bicyclopropylidenes (Scheme 1).…”

Dimethylphosphanylethylcyclopentadienyl Complexes of Lanthanum and Yttrium

“…At Ϫ90°C the 31 P{ 1 H}-NMR shows two signals at δ ϭ Ϫ39.91 and δ ϭ Ϫ51.24 of intenOnly a restricted number of phosphanylcyclopentadienyl complexes have been reported so far and only a few are sity 2:1 which coalesce at Ϫ50°C, and at room temperature only one broad singlet at δ ϭ Ϫ43.62 is observed. This is characterized by X-ray structure determinations [16] [17] [18] [19] [20] . Several independent routes have been explained by a fast exchange of two coordinated and one "dangling" phosphano groups with the low-field signal beapplied for the synthesis of phosphanoalkyl-substituted cyclopentadienyl ligands, depending on the length of the ing assigned to the coordinating phosphane ligands and the signal at δ ϭ Ϫ51.24 being assigned to the noncoordinating alkyl chain connecting the cyclopentadienyl and the phosphane functionality.…”

“…Only a few complexes with neutral phosphane ligands are found in ligands with R ϭ Ph, iPr, tBu are known [18] . The ligand Li[C 5 H 4 (CH 2 ) 2 P(CH 3 ) 2 ] (1) .…”