Structure and reactivity of (.eta.5-C5H5)Mn(CO)2 in room-temperature solution. Evidence for formation of a dinuclear intermediate detected by flash photolysis and time-resolved infrared spectroscopy

Abstract

UV laser flash photolysis (308 nm, 15 ns) with UV/vis monitoring and with time-resolved IR spectroscopy has been used to characterize two transient species formed by the photolysis of CpMn(CO)3 (Cp = v5-C5H5) in alkane solution. The fiist species has been identified as CPM~(CO)~S where S = cyclohexane or n-heptane, from both its kinetic behavior and its IR spectrum. CpMn(C0)&3 reacts with CO, Nz, and PPh3 with bimolecular rate constants similar to those previously published for the corresponding reactions of the group 6 metal pentacarbonyls. The second transient species CpzMnz(CO)5 is formed by the reacton of CpMn(C0)2S with unphotolyzed C~M n ( c 0 )~. 13C0 enrichment and IR spectroscopy are used to establish that CpzMnz(C0)5 has a single bridging CO group. The formation of Cp,Mn,(CO), can be suppressed by reagents, e.g. PPh,, added to the solution.

Investigation into the reactivity of M(η5-C5R5)(CO)2(alkane) (M = Mn or Re; R = H, Me or Ph; alkane = n-heptane or cyclopentane) and Re(η5-C5H5)(CO)2(Xe) in solution at cryogenic and room temperature

“…The photochemistry of the Group VI hexacarbonyls has been widely exploited to generate unstable organometallic alkane complexes, both at cryogenic temperatures in matrices and at room temperature. For example, photolysis of W(CO) 6 has been used to generate W(CO) The generation of unstable organometallic alkane complexes in solution has also been observed for M(η 5 -C 5 H 5 )(CO) 3 -(n-C 7 H 16 ) 29 (M = V, Nb or Ta) and M(η 5 -C 5 H 5 )(CO) 2 (L) [30][31][32] (M = Mn or Re; L = n-C 7 H 16 or c-C 6 H 12 (Mn only)) in solution at room temperature. Organometallic alkane complexes have also been generated from non-carbonyl precursors.…”

The photochemistry of (η3-2-R-C3H4)Fe(CO)(NO)(X) (R=H or Cl; X=CO or PPh3) in room temperature solution or frozen gas matrixes

“…6). The formation of dinuclear species by the reaction of COloss intermediates with the parent compound is frequently observed following flash photolysis of metal carbonyl compounds in the absence of trapping ligands such as CO [9]. The formation of a dinuclear species could be responsible for the additional features observed in the IR spectrum reported here.…”

Binuclear Cyclopentadienylmanganese Carbonyl Thiocarbonyls: Four‐Electron Donor Bridging Thiocarbonyl Groups of Two Types and a Bridging Acetylenedithiolate Ligand

“…In the [Cp 2 Mn 2 (CS) 2 ] singlet 20-7 with an MnMn single bond, the Mn 2 C 2 unit forms a tetrahedron and each manganese atom has a formal 16-electron configuration. The Mn 2 C 2 tetrahedron in 20-7 is analogous to the Co 2 C 2 tetrahedron found in the well-known [(alkyne)-Co 2 (CO) 6 ] complexes, first synthesized in 1956. [53][54][55] In the [Cp 2 Mn 2 (CS) 2 ] triplet 20-2T with no Mn-Mn bond, the Mn 2 C 2 unit forms a butterfly structure (two triangles sharing an edge) and each manganese atom has a formal 15-electron configuration.…”

“…However, [(η 5 3 ] in heptane solution. [6] The isovalent binuclear cyclopentadienylrhenium carbonyl chemistry is considerably more extensive. Thus [(η 5 -Me 5 C 5 ) 2 -Re 2 (CO) 4 (µ-CO)] with a bridging CO group and formal Re-Re single bond, [7] [(η 5 -Me 5 C 5 ) 2 Re 2 (CO) 2 (µ-CO) 2 ] with two terminal CO groups and two semibridging CO groups and a formal Re=Re double bond, [8] and [(η 5 -Me 5 C 5 ) 2 -Re 2 (µ-CO) 3 ] with three bridging CO groups and a formal ReϵRe triple bond [9] have all been synthesized as stable compounds that have been structurally characterized by Xray crystallography.…”