Abstract
The reactions of R~,(C0)~(i-Pr-Pyca) (la) [i-Pr-Pyca = pyridine-2-carbaldimine] with ethyne, methyl propynoate (MP), and dimethyl acetylenedicarboxylate (DMADC) and the reaction of Ru,(CO),(t-Bu-Pyca) (lb) with p-tolylacetylene (PTA) were studied. The reaction of la with MP and DMADC leads to C-C coupling between the Pyca and the alkyne via a direct attack of one of the alkyne C atoms on the $C=N coordinated imine moiety of 1. In the resulting complex RU~(CO)~(C~H~NCH(N-~-P~)~(~(~)OM~)=CR) [2a, R = C(0)OMe; 2b, R = HI, in which the Ru-Ru bond is absent, the second alkyne C atom is a-bonded to the Ru center to which both N atoms are bonded and the reduced alkyne bond is $-C=C coordinated to the second Ru center. Complex 2a thermally rearranges to RuZ(CO),(i-Pr-Pyca)(p2-DMADC) (3), of which the crystal structure-has been determined. Red crystals of 3 (Ru~C~~H~~N~~~~~ ~.~CH~C~~, 2 = 4) are triclinic, space group P1, and have cell constants a = 15.853 (3) A, b = 17.221 (4) A, c = 9.953 (2) A, a = 91.40 (l), @ = 95.56 (l), and y = 86.03 (2). A total 7113 reflections (Mo Ka, p = 12.50 cm-') were used in the refinement which converged to a final R value of 0.055. The structure shows a Ru(CO), and a Ru(CO),(i-Pr-Pyca) fragment (all CO ligands are terminally bonded) which are bridged by a p,-parallel bonded DMADC molecule and linked by a formally single Ru-Ru bond of 2.899 (3) A. Complex 3 reacts thermally with a second DMADC to give RU~~CO)~~~-P~-P~ ~~)((C(C(O)OM~)= C(C(O)OM~))~C=O) ~ (4a),
Published Version
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