cis,cis-1,3,5-Tris(diphenylphosphino)cyclohexane (tdppcy). A new tripodal phosphine that forms metal complexes with adamantane-type structures. rystal structure of Ir(tdppcy)Cl3

The novel tridentate phosphine cis,cis-1,3,5-tris(diphenylphosphino)cyclohexane (tdppcy) (3) has been synthesized. Treatment of tdppcy with Mo(C7H8)(CO)3 and Ir(PPh3)2(CO)Cl yields octahedral Mo(tdppcy)(CO)3 (4) and trigonal-bipyramidal Ir(tdppcy)(CO)Cl (5), respectively. Compound 5 is transformed into either Ir(tdppcy)(CO)H (6) or Ir(tdppcy)(CO)(H)2+ (7) by treatment with NaBH4 in refluxing THF. Complex 5 can be oxidized by dichloromethane or Cl2 to the trichloro complex Ir(tdppcy)Cl3 (8), which can be converted into the dihydride Ir(tdppcy)(H)2Cl (9) by treatment with NaBH4 in THF. The dynamic behavior of the highly fluxional pentacoordinate complexes 5 and 6 has been studied by VT31 P{1H} NMR spectroscopy. An X-ray diffraction study has been carried out on 8 ·3CH2Cl2.