Metallacrown Ethers: Unique Organometallic Ligands
- 1 March 1995
- journal article
- research article
- Published by Taylor & Francis in Comments on Inorganic Chemistry
- Vol. 17 (2) , 95-114
- https://doi.org/10.1080/02603599508035784
Abstract
Metallacrown ethers are a unique class of complexes that form when R2PX-(CH2CH2O)nCH2CH2XPR2 (X = –, O; R = Ph, alkoxy; n = 3–5) ligands chelate to transition metals. Metallacrown ethers with cis-coordinated phosphines (cis-metallacrown ethers) contain a crown ether-like pocket and exhibit size-selective binding of alkali metal cations similar to that observed with the crown ethers. Binding of Li+ and Hg2+ to cis-Mo(CO)4{R2PX(CH2CH2O)nCH2CH2XPPh2P,P′} metallacrown ethers can, under certain circumstances, activate the carbonyl ligands cis to the phosphines to nucleophilic attack or dissociation. The cis-metallacrown ethers are also capable of binding water via coordination to the metal center and hydrogen bonding to the ethers. Recently, octahedral metallacrown ethers with trans-coordinated phosphines (trans-metallacrown ethers) have been prepared. The conformations of these complexes are quite different from those of the cis-metallacrown ethers with more extended metallacrown ether chains and the ether oxygens closer to the ligands on the octahedral metal center. The metal centers in the trans-metallacrown ethers appear to spin freely within the metallacrown ether cavity, indicating that the barriers to rotation about the P–M–P axes are low. Dimetallacrown ethers in which the R2PX(CH2CH2O)nCH2CH2XPR2 ligands bridge two metal centers have also been isolated. These complexes contain two separate crown ether sites and may be able to coordinate two metal cations. The above results suggest that metallacrown ethers containing platinum-group metal centers could exhibit quite different catalytic activities and selectivities from those of related complexes with simple phosphorusdonor ligands.Keywords
This publication has 46 references indexed in Scilit:
- Syntheses and reactions of the cis-PtCl2{Ph2P(CH2CH2O)nCH2CH2PPh2-P,P'} (n = 3-5) metallacrown ether complexes. The x-ray crystal structures of the n = 4 and 5 complexes and of [cis-Pt{Ph2P(CH2CH2O)4CH2CH2PPh2-P,P',O}(H2O)](BF4)2Inorganic Chemistry, 1992
- Synthesis and chemistry of a molybdenum carbonyl phosphinite complex containing a ditopic macrocyclic ligand with chelating phosphorus-donor and crown ether characteristicsOrganometallics, 1992
- cis-Mo(CO)4{Ph2P(CH2CH2O)nCH2CH2PPh2} (n = 3-5) metallacrown ethers. X-ray crystal structure of cis-Mo(CO)4{Ph2P(CH2CH2O)3CH2CH2PPh2}Inorganic Chemistry, 1991
- Synthesis, isomer separation, and metal complexation studies of aza- and oxaphosphands, a class of hard/soft dinucleating phosphine macrocyclesInorganic Chemistry, 1990
- Synthesis of Group 6 metalla-(aza)-crown ether tetracarbonyl complexes with potentially anionic amido groups. The influence of Li+, Mg2+, and Al3+ cations on the susceptibility of the carbonyl ligand to nucleophilic addition of alkyl/aryl carbanions and hydrideOrganometallics, 1989
- Synthesis of Group 6 metal carbonyls with hybrid P-donor crown ether and aza-crown ether ligands and the effect of phosphorus substituents on their reaction with RLi reagentsOrganometallics, 1989
- Less common modes of coordination in α,ω‐bis(di‐tert‐butylphosphino)alkane and α,ω‐bis(di‐tert‐butylphosphino) (poly)ether complexes of rhodium(I)Recueil des Travaux Chimiques des Pays-Bas, 1988
- Reactions of di-µ-chloro-bis[cyclo-octa-1,5-dienerhodium(I)] with carbon mono-oxide and mono-, di-, or tri-tertiary phosphines, or 1,2-bis(diphenylarsino) ethaneJ. Chem. Soc., Dalton Trans., 1977
- Rhodium phosphinoether complexes. Part 2. Crystal and molecular structures of trans-[1,8-bis(diphenylphosphino)-3,6-dioxaoctane-P,P′]-carbonyl(ethanol)rhodium(I) hexafluorophosphate and trans-[1,5-bis(diphenylphosphino)-3-oxapentane-P,P′]carbonylchlororhodium(I) dimerJ. Chem. Soc., Dalton Trans., 1977
- Large-ring complexes of platinum and palladium of the type trans-[{MCl2[But 2P(CH2) n PBut 2]} x ]J. Chem. Soc., Dalton Trans., 1976