Chirale Tripodliganden: Die Eintopfreaktion MeC(CH2PPh2)3 MeC(CH2P(Ph)(R))3; Zwischenstufen, diastereoselektive Kontrolle und Komplexchemie

Article abstract of DOI:10.1016/0022-328X(93)80458-N

The tripod ligand H3CC(CH2PPh2)3, 1, reacts with lithium metal to produce H3CC(CH2PPhLi)3, 2, in good yields.Compound 2 crystallizes in the form of 2*4THF*MeN(CH2CH2NMe2)2.The crystal structure of this adduct shows bridging as well as terminal phosphorous-coordination of lithium.Compound 2 reacts with electrophiles RX to give H3CC(CH2P(Ph)(R))3, 3 (R = H, Me, Et, ⁱPr, CH2Ph, 3a-e).The transformation 1 <*> 2 <*> 3 can be performed in a one-pot reaction.While the chiral compounds 3 may be characterized as such, their reaction with (CH3CN)3Mo(CO)3 yields theeasy-to-characterize coordination compounds H3CC(CH3P(Ph)(R))3Mo(CO)3, 5.NMR analysis of 3 and 5 shows that from the two diastereomeric forms of 3 (the enantiomeric pair SSR/RRS and the pair SSS/RRR) only the SSR/RRS-diastereomer is formed with R = CH2Ph (3e, 5e).In the other cases (R = H, Me, Et, ⁱPr) a statistical 3:1 mixture of the two diastereomers is formed.These findings are further corroborated by X-ray analyses of H3CC(CH2P(Ph)(Et))3Mo(CO)3, 5c, and H3CC(CH2P(Ph)(CH2Ph))3Mo(CO)3, 5e.The remarkable facts reported in this paper are the ease with which the chiral tripod ligands H3CC(CH2P(Ph)(R))3, 3, are prepared, and the evidence that their formation may well involve diastereoselective control.