New Applications of Weak Donor Atoms to Coordination, Organometallic and Materials Chemistry

Abstract

Non-aqueous solvated transition metal cations are enjoying renewed popularity as precursors for new applications in molecular and materials chemistry. In two related projects, we are engaged in a general investigation of the syntheses, structures and reactivity of new compounds containing nitrile and ether ligands. A major effort is underway to synthesize homoleptic metal-metal bonded acetonitrile cations of second and third row metals for use in coordination and organometallic chemistry, photochemistry and materials chemistry. Dinuclear carboxylate, halide and halide-phosphine complexes are used to synthesize the metal-metal bonded acetonitrile cations [M₂(MeCN)₁₀]⁴⁺ (M = Re, Rh). The unusual partially solvated species [Mo₂ ^IV,IV(μ-F)(MeCN)₈O₂]³⁺ was prepared from MoCl₃(THF)₃ in CH₃CN. Reactions of the bulky ether-phosphine ligand tris(2,4,6-trimethoxyphenyl)phosphine (TMPP) with the dinuclear cation [Rh₂(MeCN)₁₀]⁴⁺ and with acetonitrile cations of 3d metals [M(MeCN)₆]²⁺ (M = Co, Ni) produce bis-phosphine c[odot]mplexes of general formula [M(PR₃)₂] ⁿ⁺ where M = Co²⁺, Ni²⁺, Ni³⁺, Rh²⁺, Rh³⁺. Weakly interacting ether donors on the large phosphine ligand occupy open coordination sites in the solid state. Dissociation of the ether groups in solution is favored, as demonstrated by reactions of Rh(II) and Rh(I) TMPP complexes with CO and CNR. Reversible binding of CO is demonstrated in several systems. Applications of molecules with labile ether or nitrile ligands to the design of sensors, mixed metal oxides and polymers will be outlined.

Key Words:

• weak donor ligands
• homoleptic nitrile complexes
• ether-phosphine ligands
• solvated dinuclear cations
• mononuclear rhodium(II) complexes
• phosphino-phenoxide ligands
• reversible CO chemistry
• polynitrile acceptors
• σ-bonded TCNQ