(TRIMETHYLSTANNYL)-LITHIUM AND (TRIBUTYLSTANNYLLITHIUM) - SOLUTION STRUCTURE IN ETHER, THF, AND HMPA

(Tributylstannyl)- and (trimethylstannyl)-lithium are momomeric in ether and THF solution; coordination between Sn and Li is indicated by the observation of large Li-Sn couplings. The addition of HMPA in ether produces an unusual dimeric structure, (Bu3SnLi)2(HMPA)3, in which each tin is coordinated by one lithium and the two lithiums are bridged by three molecules of HMPA. In both ether and THF, more than 2 equiv of HMPA produces separated ion pairs.