Oligophosphaalkane: X. Disekundäre methylenbisphosphane HPRCH 2PRH; bausteine für cluster mit (μ 2-PR) 2CH 2-, μ 2-PRCH 3- und μ 3-PR-brücken

Abstract

Methylene-bridged disecondary phosphanes HRPCH 2PRH (R = i-Pr, CH 2Ph, Me, t-Bu; Ia–Id) react with excess Fe 2(CO) 9 to give the cluster compounds Fe 3(CO) 9(μ 2-PRCH 2-PRH)(μ-H) (IIIa–IIId) and Fe 3(CO) 9(μ-PR)(μ 2-PRCH 3)(μ-H) (Va–Vd) through cleavage of the PH bond and the PCP skeleton. Pyrolysis of Va, Vb and Vd affords the unsymmetrically substituted bis-μ 3-phosphinidene bridged clusters Fe 3(CO) 9(μ 3-PR)(μ 3-PMe) (VIa, VIb and VId). If Ia or Id is treated with Fe 2(CO) 9 in a 1 2 molar ratio at high temperature, the formation of the binuclear complexes Fe 2(CO) 6(RPCH 2PR) (VIIa, VIId) is accompanied by fragmentation of their PCP backbones. As a result, Fe 2(CO) 6(μ 2-P(i-Pr)H)(μ 2-P(i-Pr)CH 3) (VIII) or VId and Fe 3(CO) 7[(μ 2-P(t-Bu)) 2CH 2](μ 2-P(t-Bu)Me)(μ-H) (IX) with the unusual (μ 2-PR) 2-CH 2 bridge for the Fe 3-triangle are formed. X-Ray structural analysis of Va (triclinic, space group P 1 ) shows an open Fe 3 unit (Fe(1)-Fe(2) 2.774(1), Fe(1)-Fe(3), 2.807(1), Fe(2)-Fe(3) 3.476(1) Å) stabilised by the μ 3-P(i-Pr) and μ 2-P(i-Pr)Me bridges. In cluster IX (monoclinic, space group P2 1/ c), the triangle of iron atoms (Fe(1)-Fe(2) 2.831(1), Fe(1)-Fe(3) 2.806(1), Fe(2)-Fe(3) 2.557(1) Å) is capped by the bifunctional phosphido group (μ 2-P-(t-Bu)) 2CH 2. In addition, the Fe(2)-Fe(3) edge is spanned by the μ 2-P(t-Bu)Me and μ-H species.