Highly Strained Heterometallacycles of Group 4 Metallocenes with Bis(diphenylphosphino)methanide Ligands

A study of the coordination chemistry of different bis(diphenylphosphino)methanide ligands [Ph 2 PC(X)PPh 2 ] (X=H, SiMe 3 ) with Group 4 metallocenes is presented. The paramagnetic complexes [Cp 2 Ti{κ 2 ‐ P , P ‐Ph 2 PC(X)PPh 2 }] (X=H ( 3 a ), X=SiMe 3 ( 3 b )) have been prepared by the reactions of [(Cp 2 TiCl) 2 ] with [Li{C(X)PPh 2 } 2 (thf) 3 ]. Complex 3 b could also be synthesized by reaction of the known titanocene alkyne complex [Cp 2 Ti(η 2 ‐Me 3 SiC 2 SiMe 3 )] with Ph 2 PC(H)(SiMe 3 )PPh 2 ( 2 b ). The heterometallacyclic complex [Cp 2 Zr(H){κ 2 ‐ P , P ‐Ph 2 PC(H)PPh 2 }] ( 4 aH ) has been prepared by reaction of the Schwartz reagent with [Li{C(H)PPh 2 } 2 (thf) 3 ]. Reactions of [Cp 2 HfCl 2 ] with [Li{C(X)PPh 2 } 2 (thf) 3 ] gave the highly strained corresponding metallacycles [Cp 2 M(Cl){κ 2 ‐ P , P ‐Ph 2 PC(X)PPh 2 }] ( 5 aCl and 5 bCl ) in very good yields. Complexes 3 a , 4 aH , and 5 aCl have been characterized by X‐ray crystallography. Complex 3 a has also been characterized by EPR spectroscopy. The structure and bonding of the complexes has been investigated by DFT analysis. Reactions of complexes 4 aH , 5 aCl , and 5 bCl did not give the corresponding more unsaturated heterometallacyclobuta‐2,3‐dienes.