ORGANOMETALLIC TRANSFORMATIONS FROM AN ETA(3)-PROPARGYL OR ETA(3)-ALLENYL LIGAND TO ETA(3)-HYDROXYALLYL, ETA(3)-HETEROTRIMETHYLENEMETHANE, AND ETA(6)-DIALLYL ETHER SPECIES

A Abstraction of bromide ion from the allenyl complex trans-Pt(eta(1)-CHCCH2)(Br)(PPh(3))(2) (1) with AgBF4 leads to the formation of the new cationic unsubstituted eta(3)-propargyl complex [Pt(eta(3)-CH2CCH)(PPh(3))(2)](BF4) (2(BF4)). Unlike 1, which is stable to air, complex 2 is highly susceptible to regioselective addition of water at the propargyl central carbon to form the hydroxyallyl complex [Pt(eta(3)-CH2C(OH)CH2)(PPh(3))(2)](BF4) (3). Further addition of 3 to 2 gives the cationic eta(6)-diallyl ether dinuclear complex [(PPh(3))(2)Pt(eta(3)-(CH2)(2)C)](2)(O)(BF4)(2) (4(BF4)(2)). The reaction of ethylenediamine with 2 yields the eta(3)-azatrimethylenemethane complex [Pt(eta(3)-CH2C(NHCH2CH2NH2)CH2)(PPh(3))(2)](BF4) (6a(BF4)), but that with 1 yields [Pt(eta(1)-CHCCH2)-(en)(PPh(3))](Br) (5). Such reactions suggest that the eta(3)-propargyl ligand could be subjected to direct external attack at its central carbon by a nucleophile. The eta(1)-allenyl complex, however, requires preceding coordination of the nucleophile to first result in a pi-allene intermediate that then undergoes nucleophilic addition. Treatment of complex 3 with base gives the neutral eta(3)-oxatrimethylenemethane complex Pt(eta(3)-CH2C(O)CH2)(PPh(3)>(2) (7). Addition of acid to 7 reverts it to 3. Complex 4 reacts with Et(2)NH to produce 7 along with 1 equiv of[Pt(eta(3)-CH2C(NEt(2))CH2)(PPh(3))(2)](BF4) (6b), presumably via regioselective nucleophilic substitution at the allyl central carbon. The X-ray single-crystal structures of 1 and 3 are provided.