Syntheses and structural characterisation of [Ir₄(CO)₁₁(η¹-L)] and [Ir₄(CO)₁₀(η¹-L)₂]{L =[Fe(η⁵-P₃C₂Bu^t₂)(η⁵-P₂C₃Bu^t₃)] and [Fe(η⁵-C₅H₅)(η⁵-P₃C₂Bu^t₂)]} and [Ir₄(CO)₁₁{µ-η¹: η¹-[Fe(η⁵-C₅H₅)(η⁵-P₃C₂Bu^t₂)]}Ir₄(CO)₁₁] and its facile conversion to [Ir₄H(CO)₁₀{Fe(η⁵-C₅H₅)[η⁵-P₃C(CMe₂CH₂)CBu^t]}Ir₄(CO)₁₁], via an unusual C–H activation

Abstract

The reactions of NBu4[Ir4(CO)11Br]1 with equivalent amounts of [Fe(η5-P3C2But2)(η5-P2C3But3)] L1 or [Fe(η5-C5H5)(η5-P3C2But2)] L2 in the presence of AgSbF6 gave good yields of [Ir4(CO)11(η1-L)]2a or 2b, besides [Ir4(CO)10(η1-L)2]3a and 3b, respectively, in which the ligands are bound via the PA atom. The solid-state structure of 2b, established by an X-ray analysis, is that of the Td-like isomer, although the low-temperature 31P-{1H} NMR spectrum showed the presence of both C3v- and Td-like isomers in solution. Compound 2a underwent facile conversion to [Ir4(CO)10(µ-η2-L1)]4avia CO loss and further interaction of the adjacent PB atom of L1. Compound 2b reacted with 1 in the presence of AgSbF6 to yield [Ir4(CO)11(µ-η1 : η1-L2)Ir4(CO)11]5b, in which the second Ir4 cluster was ligated via PC, rather than PB, according to NMR spectroscopy. This compound underwent clean conversion into [Ir4H(CO)10{Fe(η5-C5H5)[η5-P3C(CMe2CH2)CBut]}Ir4(CO)11]6b,via CO loss and oxidative addition of a C–H bond of a tert-butyl substituent in the P3C2But2 ring. The molecular structure of 6b was determined by a single crystal X-ray diffraction analysis, which showed that C–H activation occurred on the Ir4 cluster bound via PC.