Syntheses, structures, and dynamic properties of M(CO)2(η3-C3H5)(en)(X) (M=Mo, W; X=Br, N3, CN) and [(en)(η3-C3H5)(CO)2M(μ-CN)M(CO)2(η3-C3H5)(en)]Br (M=Mo, W)

Abstract

Compounds M(CO) 2 (η 3 -C 3 H 5 )(en)(X) (M = Mo, W; X = Br, N 3 , CN) and [(en)(η 3 -C 3 H 5 )(CO) 2 M( μ -CN)M(CO) 2 (η 3 -C 3 H 5 )(en)]Br (M = Mo, W) were synthesized. In the solid state, M(CO) 2 (η 3 -C 3 H 5 )(en)(X) (M = Mo, W; X = Br, N 3 ) and [(en)(η 3 -C 3 H 5 )(CO) 2 M( μ -CN)M(CO) 2 (η 3 -C 3 H 5 )(en)]Br (M = Mo, W) possess asymmetric endo -forms, however, M(CO) 2 (η 3 -C 3 H 5 )(en)(CN) (M = Mo, W) possess symmetric endo -form. Mononuclear compounds M(CO) 2 (η 3 -C 3 H 5 )(en)(X) (X = Br, M = Mo( 1 ), W( 2 ); X = N 3 , M = Mo( 3 ), W( 4 ); X = CN, M = Mo( 5 ), W( 6 )) and cyanide-bridged bimetallic compounds [(en)(η 3 -C 3 H 5 )(CO) 2 M( μ -CN)M(CO) 2 (η 3 -C 3 H 5 )(en)]Br (M = Mo ( 7 ), W( 8 )) were prepared and characterized. These compounds are fluxional and display broad unresolved proton NMR signals at room temperature. Compounds 1 – 6 were characterized by NMR spectroscopy at −60 °C, which revealed isomers in solution. The major isomers of 1 – 4 adopt an asymmetric endo -conformation, while those of 5 and 6 were both found to possess a symmetric endo -conformation. The single crystal X-ray structures of 1 – 6 are consistent with the structures of the major isomer in solution at low temperature. In contrast to mononuclear terminal cyanide compounds 5 and 6, cyanide-bridged compounds 7 and 8 were found to adopt the asymmetric endo -conformation in the solid state.