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Three ŋ4-(C=C-C=O) coordination cobalt(I) complexes 1-3 were synthesized by the reactions of cinnamaldehyde, p-fluorocinnamaldehyde and p-chlorocinnamaldehyde with CoMe(PMe3)4. Complex 4 as ŋ2-(C=C) coordination was prepared by the reaction of chalcone with Co(PMe3)4. The structures of complexes 1-4 were confirmedŋ4-Coordination; ŋ2-Coordination; Cinnamaldehyde; Cobalt by single-crystal X-ray diffraction. Although the reactions didn't undergo C-H bond activation and decarbonylation, the formation of complexes 1-4 deepens our understanding of the reactions between α,β-unsaturated aldehyde or ketone with low-valent central cobalt atom. [ABSTRACT FROM AUTHOR]

The reaction between 2-pyridinetetramethyldisilazane 1 and CoMe(PMe 3 ) 4 led to the formation of the novel bissilyl cobalt(III) hydride CoH((C 5 H 4 N)-N(SiMe 2 ) 2 )(PMe 3 ) 3 ( 2 ) via the cleavage of two Si-H bonds with the elimination of methane. The reaction of phenyltetramethyldisilazane 3 with CoMe(PMe 3 ) 4 could directly provide the hydrido cobalt(III) complex CoH((C 6 H 5 )-N(SiMe 2 ) 2 )(PMe 3 ) 3 4 . Complex 4 is an analogue to complex 2 . This result indicates that a pre-coordination of the nitrogen atom in pyridine to the cobalt center before Si-H bond activation can be excluded in the formation mechanism of 2 . This exclusion is further supported by the in situ 1 H NMR spectra of the reaction mixtures between 2-pyridinetetramethyldisilazane 1 with CoMe(PMe 3 ) 4 in C 6 D 6 in different reaction times. A new bissilyl iron hydride FeH((C 5 H 4 N)-N(SiMe 2 ) 2 )(PMe 3 ) 3 ( 5 ) was obtained through the reaction of Fe(PMe 3 ) 4 with 1 . Complexes 2 , 4 and 5 with two metal-Si bonds are very stable and did not react with MeI, EtBr, acetylacetone, CO or CO 2 . The molecular structures of complexes 2 , 4 and 5 were determined by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]