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• 25875-19-8 K{iron(carbonyl)3nitrosyl} 

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Reactivity of cyclopalladated compounds. 9. Synthesis of trinuclear compounds with a carbonylmetalate anion as a bridging unit between two palladium(II) centers. Crystal and molecular structure of [(PdNMe2CH2C6H4) 2(μ-Cl)(μ-Co(CO)4)] and [(PdNMe2CH2C6 ...

Full title: Reactivity of cyclopalladated compounds. 9. Synthesis of trinuclear compounds with a carbonylmetalate anion as a bridging unit between two palladium(II) centers. Crystal and molecular structure of [(PdNMe2CH2C6H4) 2(μ-Cl)(μ-Co(CO)4)] and [(PdNMe2CH2C6H4) 2(μ-Cl){μ-Mo(CO)3(η5-C 5H5)}]. The cyclopalladated dimers of general formula [Pd(C N)Cl]2 (1a, C N = dmba, dimethylbenzylamine-C2,N; 1b, C N = dmat, 2-(dimethylamino)toluene-C,N; 1c, C N = 8-mq, 8-methylquinoline-C8,N) react with carbonylmetalate anions such as [Co(CO)4]-, [Fe(CO)3NO]-, and [M(CO)3Cp]- (M = Mo, Cr, W) to give trimetallic species where the metalate anion has replaced one bridging chloride in 1. Two of the resulting compounds were characterized by a single-crystal X-ray diffraction study. Crystals of [Pd(dmba)]2(μ-Cl)[μ-Co(CO)4] (2a) belong to the space group Pnma with a = 21.844 (4) A?, b = 11.947 (2) A?, c = 10.754 (2) A?, V = 2806 A?3, and Z = 4. The structure has been refined to R = 0.024 and Rω = 0.032. The molecule consists of two Pd(dmba) fragments bridged by a Cl atom and a Co(CO)4 moiety. The molecule, which has a noncrystallographic mirror of symmetry, may be viewed as an open book structure. The Co atom is located in the trans positions with respect to the N donor atom of the dmba chelates. Two CO groups are semibridging to the Pd atoms. Complex 4a [Pd(dmba)]2(μ-Cl)[μ-Mo(CO)3(η5-C 5H5)] crystallizes in the space group P21/n with a = 20.501 (9) A?, b = 15.624 (6) A?, c = 8.403 (4) A?, β= 99.83 (5)°, V = 2652 A?3, and Z = 4. The refinement of the structure led to R = 0.040 and Rω = 0.054. The molecular structure also shows that two cyclopalladated units are held together by a Cl atom and a Mo(CO)3Cp moiety. The Pd-Mo bond distances (2.832 (1) and 2.788 (1) A? are in accord with strong metal-metal interactions between these atoms. One CO group is semi triply bridging the Pd2Mo triangle whereas the two others are semibridging the Pd-Mo bonds. The degree of symmetry in this molecule is lower than in 2a since no mirror plane can be found. Here the Cl atom is again located trans to the σ-bonded carbon of the dmba Uganda. 1H NMR studies show that both 2a and 4a are fluxional molecules in solution. The slow exchange limit of the process can be easily reached for the latter compound. A systematic study on the compounds [Pd(dmba)]2(μ-Cl)[μ-W(CO)3Cp] (6a) and [Pd(dmat)]2(μ-Cl) [μ-M(CO)3Cp] (4b, M = Mo, 5, M = Cr, and 6b, M = W) reveals that the ΔG? value depends only on the nature of the σ-bonded carbon of the N C moiety: it is close to 70 kJ mol-1 for 4a and 6a and close to 50 kJ mol-1 for 4b, 5, and 6b. These results allow us to propose a likely mechanism for the exchange process that involves the dissociation of the carbonylmetalate anion from the rest of the molecule.