Tetranuclear carbonylfluorohydroxymanganese(I) clusters, [Mn₄(CO)₃Fx(OH)_4-x]

Abstract

Reactions of Mn(CO)₅X(X = Cl, Br) with TIF or AgF in dichloromethane solution give the cluster species [Mn₄(CO)₁₂F_x(OH)_4-x]. The TlF reactions give predominantly the species with x = 1 and 2 and the AgF reaction the species with x = 2 and 3. The individual species x = 0-4 can be identified in the mass spectrum. The x = 2 product from the AgF abstraction can be separated from the x = 3 one by crystallization over benzene to yield the pure solvate [Mn₄(CO)₁₂F₂(OH)₂],-2C₆H₆. The infrared OH stretch in this compound (3543 cm^-1) shifts to higher frequency (3620 cm^-1) on desolvation (100°C, 0.1 mmHg), confirming OH...π hydrogen bonding to benzene, and explains the purification mechanism. Crystals of the TlF product are cubic, space group Pn3m, with a 11.277(1) Ǻ. The absorption corrected data gave a conventional R value of 0.043 on full- matrix least-squares refinement. This product is predominantly the monofluoride species but the other differently substituted ones form isomorphous crystals. The molecules are cubane-type clusters of Mn(CO)₃ groups at one set of corners interpenetrated with fluoro or hydroxy groups at the other set and exhibit crystallographic symmetry 43m. These interpenetrating tetrahedra have edge length of 3.199(1) and 2.529(3) Ǻ respectively consistent with values expected for limiting non-bonding contacts.