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ChemInform Abstract The sequential reactions of the acyl complexes (I) shown in the scheme give crystalline vinylidene complexes as mixture of the geometric isomers (II) and (III). The thermodynamic synclinal isomers (II) are favored at room temperature. In CD2Cl2 these geometric isomers equilibrate. Photolysis gives (50:50) photostationary states. An X-ray structure analysis of the PF6 salt of the synclinal complex cation (IId) (space group C2/c, Z = 8) confirms the naphthyl substituent to be anti to the bulky PPh3 ligand. Reactions of (II)/(III) with base yield the acetylide complexes (IV). These react with TFA at -78 rc C (assayed by NMR) to give 98:2, > 99:1, and > 99:1 mixtures of (IIIb)/(IIb), (IIIc)/(IIc), and (IIId)/(IId). Kinetic and activation parameters for the thermal isomerization of (III) to (II) are determined. Analogous Cβ methylation reactions of (IV) are similarly stereospecific; (IVb) gives (VI). The structure of (IVb) (P1-, Z=2) is established by X-ray analysis. Reactions of (IIb), (IIIb), and its dimethyl analogue (VI) with PMe3 (IX) produce the α-phosphoniovinyl complexes (VII) indicating preferential attack on the Cα face opposite to PPh3.

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Three bimetallic anionic formyl complexes, Li+[Mn2(CO)9(CHO)]~(2), Li+[ReMn(CO)9(CHO)]' (3), and Li+[m-Re2(CO)9(CHO)]' (4), are prepared by the reaction of Li(C2H5)3BH with the corresponding neutral metal carbonyl dimers MM'(CO)10. Whereas 2 has a half-life of ca. 8 min at room temperature, 4 is stable for days and is easily isolated as a THE solvate. When 2-4 are treated with electrophiles such as benzaldehyde, Fe(CO)s, and «-octyl iodide, hydride transfer occurs to give benzyl alcohol (after protonation), Li+[Fe(CO)4(CHO)]', and octane, respectively. Heterobimetallic formyl 3 is a weaker hydride donor than 2 and 4. Reaction of 4 with CH3I gives CH4 (ca. 50%). However, complex reactions occur when 2 and 4 are treated with CH3SG3F and strong acids, contrary to our original report of CH4 and H2 evolution.