Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 45. Synthesis of the pentanuclear metal complexes [M′M₂Re₂(µ-CC₆H₄Me-4)₂(CO)₁₈](M′= Ni or Pt, M = Cr or W) and related compounds; X-ray crystal structure of [ReWPt(µ-CC₆H₄Me-4)(CO)₉(PMe₃)₂]

Effect of Transition Metal Fragments on the Reverse Fritsch–Buttenberg–Wiechell Type Ring Contraction Reaction of Metallabenzynes to Metal–Carbene Complexes

“…The plane of the five-membered ring in 2Os and 2Ir is parallel to the axial L–M–L plane (L axial –M–C1–C5 dihedral angle, θ, is 1.5 and 0.0°, respectively), while that of 2Re and 2Pt lies in between the axial (L–M–L) and the equatorial (L′–M–L′) planes of TBP geometry (L–M–C1–C5 dihedral angle, θ, is 29.6 and 14.6°, respectively). The calculated M–C1 bond lengths in 2M range from 1.970 to 1.885 Å, which are within the experimentally reported M–C double bond lengths ,− and are in between the M–C1 (1.871–1.790 Å) single and M–C5 triple bond lengths (2.163–2.041 Å) of 1M . The other isomers of 2M in which the five-membered ring is perpendicular to the axial ligands ( 2M′ , M′ = Re, Os, Ir) are higher-order saddle points (Figure ).…”

“…The optimized geometrical parameters of 1Re and 1Os are close to the experimentally reported geometrical parameters of osmabenzyne , and rhenabenzyne . The calculated M–C1 (1.817–1.790 Å) and M–C5 (2.163–2.041 Å) bond lengths in 1M are within the range of metal–carbon triple and single bond lengths, respectively. ,,− The six-membered C 5 H 4 M ring in 1M lies in the plane of L′–M–L′. The axial ligands in 1W and 1Pt are almost linear, with L–M–L bond angles of 176.8 and 175.8°, respectively.…”

Intramolecular Cyclizations via Carbenoid Intermediates in Complexation of Alkynyltungsten Compounds with Co2(CO)8: A New Route to the Pauson−Khand Reaction

“…The structure of C in Scheme represents a carbenoid equivalent, and E below is a plausible structure with the same formula as C . Several heteronuclear clusters have skeletons such as F are known …”