Neopentyl and trimethylsilylmethyl compounds of rhodium(III) and iridium (III) with ortho-metallated triphenylphosphine. X-Ray crystal structure of [Ir(C6H4PPh2)(CH2SiMe3)(η5-C5Me5)]

Abstract

The compound [RhCl₂(η⁵-C₅Me₅)(PPh₃)] reacts with Li(CH₂SiMe₃) to give the ortho-metallated complex [R[graphic omitted]Ph₂)(CH₂SiMe₃)(η⁵-C₅Me₅)](2), and with Mg(CH₂SiMe₃)Cl in CH₂Cl₂(molar ratio 1:1) to yield [RhCl(CH₂SiMe₃)(η⁵-C₅Me₅)(PPh₃)], (3). Complex (3) is converted by the action of Li(CH₂SiMe₃) into the ortho-metallated compound (2). The reaction of [IrCl₂(η⁵-C₅Me₅)-(PPh₃)] with Mg(CH₂SiMe₃)Cl in CH₂Cl₂ gives [I[graphic omitted]Ph₂)(CH₂SiMe₃)(η⁵-C₅Me₅)], (6), and [lrCl(Me)(η⁵-C₅Me₅)(PPh₃)]. Reaction of [RhCl₂(η⁵-C₅Me₅)(PPh₃)] with Mg(CH₂CMe₃)Cl or Li(CH₂CMe₃) in diethyl ether affords a mixture of [R[graphic omitted]H₂)(η⁵-C₅Me₅)(PPh₃)], [R[graphic omitted]Ph₂)(CH₂CMe₃)(η⁵-C₅Me₅)], and [Rh(η⁵-C₅Me₅)(C₂H₄)(PPh₃)], while reaction in CH₂Cl₂ in equimolar amounts gives [RhCl(CH₂CMe₃)(η⁵-C₅Me₅)(PPh₃)]. Reaction of [lrCl₂(η⁵-C₅Me₅)(PPh₃)] with Mg(CH₂CMe₃)Cl gives [I[graphic omitted]Ph₂)(CH₂CMe₃)(η⁵-C₅Me₅)]. The X-ray crystal structure analysis of compound (6) has been carried out: a= 17.537(7), b= 11.304(4), c= 15.410(7)Å, β= 94.49(1)°, space group P2₁/n, Z= 4, R= 0.0361 for 4114 observed reflections. The ‘piano-stool’ metal co-ordination polyhedron is deformed by ortho-metallation which imposes a 67.0(2)° angle at iridium in the metallacycle, while the other angles, P-Ir-C(17) 89.0(2) and C(17)-Ir-C(36) 89.2(2)°, between the ‘legs’ of the ‘stool’ are near to 90°. The bulky C₅Me₅ ligand (effective cone angle 146°), in approaching the metal, produces large widenings of the other co-ordination polyhedron angles: Cp–Ir–P 137.0(3), Cp–Ir–C(36)(benzene)133.4(3)°, and Cp–Ir–C(17)(silyl)122.6(3)°(Cp = centroid of C₅Me₅). The ortho-metallated ring is nearly planar, (P–Ir–C)⁁(P–C–C) 5.3(3)°, and bent by only 6.6(2)° with respect to the metal-bound benzene ring which maintains its planarity; the only deformation this ring suffers involves the endocyclic angles at the carbon bound to phosphorus which widen to 124.5(5)° and at the ortho carbons which narrow to 115.9(6) and 116.7(5)°.