Reactions of trifluoromethyl-phosphine and -arsine with a ruthenium carbonyl cluster: synthesis, characterization and reactivity of cluster derivatives capped by trifluoromethyl-phosphinidene and -arsinidene moieties

Abstract

Reactions of CF₃EH₂ (E = P or As) with [Ru₃(CO)₁₂] under various conditions resulted in the elimination of two hydrogen atoms to afford new trifluoromethyl-phosphinidene and -arsinidene capped ruthenium carbonyl clusters: [Ru₃(CO)₉(µ-H)₂(µ₃-PCF₃)] 1, [Ru₄(CO)₁₃(µ-H)₂(µ₄-PCF₃)] 2, [Ru₄(CO)₁₂(µ-H)₂(µ₃-PCF₃)₂] 3, [Ru₅(CO)₁₅(µ-H)₂(µ₃-PCF₃)₃] 4, [Ru₅(CO)₁₅(µ₄-PCF₃)] 5, [Ru₄(CO)₁₂(µ-H)₂(µ₃-AsCF₃)₂] 6, [Ru₄(CO)₁₃(µ-H)₂(µ₄-AsCF₃)] 7, [Ru₄(CO)₁₃(µ₃-AsCF₃)₂] 8 and [Ru₅(CO)₁₅(µ-H)₂(µ₃-AsCF₃)₃] 9. The structures 2 and 7 contain spiked ruthenium frameworks with a phosphinidene or arsinidene group co-ordinated to all four metal atoms. The molecular structures of 4 and 9 have been shown to contain two-metal and three-metal fragments joined together by three µ₃-phosphinidene (or arsinidene) units. The hydrides in 2 and 7 display similar fluxional behaviour yielding the same values of ΔG ^‡ (= 49 kJ mol^–1). The transformation from 1 to 5, probably via intermediate 2, occurs with increase in nuclearity by the treatment of 1 with [Ru₃(CO)₁₂]. Pathways for the formation of cluster 3 from 2, 9 from [Ru₄(CO)₁₂(µ-H)₂(µ₃-AsCF₃)₂(µ-AsCF₃)] 10, and also 6 from 8 by hydrogenation are discussed.