Cationic transition-metal complexes. Part III. Synthesis and reactions of tetrakis(isocyanide)rhodium tetrafluoroborate complexes

Abstract

Treatment of [Rh(1,5-C₈H₁₂)(MeCN)₂]⁺BF₄^– with Bu^tNC, PrⁱNC, or p-MeOC₆H₄NC affords [Rh(RNC)₄]⁺BF₄^–(R = Bu^t, Prⁱ, or p-MeOC₆H₄). Addition of l₂, Mel, Etl, Prⁿl, Buⁿl, PhCH₂l, or PhCH₂Cl to [Rh(Bu^tNC)₄]⁺BF₄^– affords the octahedral Rh^III species [Rh(Bu^tNC)₄XY]⁺BF₄^–. Trimethyloxonium and nitrosyl tetrafluoroborate react with [Rh(Bu^tNC)₄]⁺BF₄^– to form respectively compounds containing the dications [Rh(Bu^tNC)₄Me]²⁺ and [Rh(Bu^tNC)₄NO]²⁺. Dimethyl- and diethyl-amine, and the primary amines ethyl-, n-propyl-, isopropyl-, n-butyl-, isobutyl-, and cyclohexyl-amine react rapidly with [Rh(Bu^tNC)₄]⁺BF₄^– to form the carbene or amidinium derivatives [Rh(Bu^tNC)₃C(NHBu^t)NR¹R²]⁺BF₄^–(R¹= R²= Me or Et; R¹= H, R²= Et, Prⁿ, Prⁱ, Buⁿ, Buⁱ, or C₆H₁₁). The structure of these compounds is discussed together with their isomerisation by C–N rotation. The carbene complexes undergo oxidative-addition reactions with l₂, Mel, and PhCH₂l to form [Rh(Bu^tNC)₃{C(NHBu^t)-NHR}XY]⁺BF₄^–.