Reactions of a dicarboxylate-substituted allene with activated dirhenium carbonyl complexes

The compound Re(CO)(4)[C(CH(2)CO(2)Me)=C(H)CO(2)Me], 1, was obtained in 83% yield when a mixture of Re-2(CO)(9)(NCMe) and MeO(2)C(H)C=C=C(H)CO(2)Me in a hexane solution was heated to reflux for 1.5 h. The addition of one hydrogen atom to the allene grouping was shown to be derived from adventitious water. The reaction of 1 with PMe(2)Ph yielded the derivative fac-Re(CO)(3)(PMe(2)Ph)[C(CH(2)CO(2)Me)=C(H)CO(2)Me], 2, in 98% yield. The reaction of Re-2(CO)(8)(PMe(2)Ph)(NCMe) with MeO(2)C(H)C=C=C(H)CO(2)Me yielded two isomeric products mer-Re-2(CO)(6)(PMe(2)Ph)[mu-eta(3)-eta(1)-MeO(2)C(H)CCC(H)CO(2)Me], 3 (31%), and fac-Re-2(CO)(6)(PMe(2)-Ph)[mu-eta(3)-eta(1)-MeO(2)C(H)CCC(H)CO(2)Me], 4 (22%), which contain bridging eta(3)-eta(1)-MeO(2)C(H)CCC(H)CO(2)Me dicarboxylateallene ligands and small amounts of three mononuclear nuclear products: fac-Re(CO)(3)(PMe(2)Ph)[MeO(2)CCH(2)CC(H)CO(2)Me], 2 (8%), mer-Re(CO)(3)(PMe(2)Ph)(MeO(2)CCH(2)CCHCO(2)Me), 5 (5%), and a trace of 1, The carbonyl oxygen atom of one of the carboxylate-groups is coordinated to one of the metal atoms in 3 and 4. Compound 3 slowly isomerizes to 4 at 25 degrees C, and compound 5 isomerizes to 2 when heated, The reaction of 4 with EtO(2)CN=C=S produced two products: 2 (20%) and fac-Re(CO)(3)(PMe(2)Ph)[MeO(2)-CCH2CC(CO(2)Me)C=SN(H)CO(2)Et], 6 (28%). Water may be involved in the formation of both products. Compound 6 contains a MeO(2)CCH(2)C=C(CO(2)Me)C=S)N(H)CO(2)Et grouping that is chelated to the rhenium atom by the sulfur and alkenyl carbon atom to form a five-membered Re-C=C-C=S ring, with Re-S = 2.443(3) Angstrom and Re-C(1) = 2.12(1) Angstrom.