Crystal structures of four new iridium complexes, each containing a highly flexible carbodiphosphorane PCP pincer ligand.

Compound [Ir(C₈H₁₂)(C₅₁H₄₅P₄)](Cl)₂ or [Ir(cod)(CH(dppm)₂-κ³P,C,P)](Cl)₂ (1a), was obtained from [IrCl(cod)]₂ and the carbodiphosphorane (CDP) salt [CH(dppm)₂]Cl [where cod = cycloocta-1,5-diene and dppm = bis(diphenylphosphino) methane]. Treatment of 1a with thallium(I) trifluoromethanesulfonate [Tl(OTf)] and subsequent crystallization gave complex [Ir(C₈H₁₂)(C₅₁H₄₅P₄)](OTf)₂·CH₃CO₂C₂H₅·CH₂Cl₂ or [Ir(cod)(CH(dppm)₂-κ³P,C,P)](OTf)₂·CH₃CO₂C₂H₅·CH₂Cl₂ (1b) [systematic name: (cycloocta-1,5-diene)(1,1,3,3,5,5,7,7-octaphenyl-1,7-diphospha-3,5-diphosphoniaheptan-4-yl)-iridium(I) bis(trifluoromethanesulfonate)-ethyl acetate-dichloromethane (1/1/1)]. This five-coordinate iridium(I) complex cation adopts a trigonal-bipyramidal geometry with the CDP carbon and one cod double bond in axial sites. Compound 1b represents the first example of a non-meridional coordination of the PCP pincer ligand [CH(dppm)2]+ with a P-Ir-P angle of 98.08 (2)°. Compound 2, [Ir(Cl)₂(H)(C₅₁H₄₄P₄)]·(CH₃)₂CO or [Ir(Cl)₂(H)(C(dppm)₂-κ³P,C,P)]·(CH₃)₂CO [systematic name: dichloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,5λ⁵,7-triphospha-3-phosphoniahept-4-en-4-yl)iridium(III) acetone monosolvate], crystallizes as an acetone monosolvate. It is a six-coordinate Ir^III coordination compound. Here, the PCP pincer ligand is coordinated in a meridional manner; one chlorido ligand is positioned trans to the carbon donor, the remaining two coordination sites being occupied by the second chlorido and a hydrido ligand trans to each other. Complex 3, [Ir(Cl)₂(H)(C₅₁H₄₅P₄)]Cl·5H₂O or [Ir(Cl)₂(H)(CH(dppm)₂-κ³P,C,P)]Cl·5H₂O [systematic name: dichloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,7-diphospha-3,5-diphosphoniaheptan-4-yl)iridium(III) chloride pentahydrate], represents the conjugate CH acid of 2. The ligand [CH(dppm)₂]⁺ is coordinated in a meridional manner. In the cationic six-coordinate Ir^III complex 4, [Ir(Cl)(H)-(CO)(C₅₁H₄₄P₄)]Cl·2CH₃OH·H₂O or [Ir(Cl)(H)(CO)(C(dppm)₂-κ³P,C,P)]Cl^#183;- 2CH₃OH·H₂O [systematic name: carbonylchloridohydrido(1,1,3,3,5,5,7,7-octaphenyl- 1,5λ⁵,7-triphospha-3-phosphoniahept-4-en-4-yl)iridium(III) chloride-methanol-water (1/2/1)], the chlorido ligand is found in the plane defined by the Ir center and the meridional PCP ligand; the H and CO ligands are positioned axially to this plane and trans to each other. [ABSTRACT FROM AUTHOR]