The synthesis of the triply bonded tetramethyl complex Re2(CH3)4(μ-dppm)2 and its reaction with carbon monoxide to afford Re2(μ-CH2)2(CO)4(μ-dppm)2

The reaction of Re2Cl4(μ-dppm)2 (dppm=Ph2PCH2PPh2) with CH3Li in toluene affords Re2(CH3)4(μ-dppm)2 (1) in high yield. This is the first simple alkyl complex of the triply bonded dirhenium(II) core. The crystal structure of 1 (ReRe=2.2841(7) Å) shows it to be very closely related to that of Re2Cl4(μ-dppm)2. Compound 1 reacts with CO to produce the di-μ-methylene complex Re2(μ-CH2)2(CO)4(μ-dppm)2 (2) which is shown to have an edge-sharing bioctahedral structure on the basis of X-ray crystal structure determinations on crystals of composition 2·2THF and 2·1.734CH2Cl2. The dirhenium units have ReRe single bond distances 2.9931(5) and 2.8930(5) Å in these two crystals, and the [Re2(μ-dppm)2] units possess chair and boat conformations, respectively.