HYDROZIRCONATION AND CARBOZIRCONATION OF MULTIPLE-BONDED LOW-COORDINATED PHOSPHORUS SPECIES

Hydrozirconation of phosphaimines RP = NR' (2a-c) (2a, R = N(SiMe3)2, R' = SiMe3; 2b, R = N(SiMe3)(tBu), R' = tBu; 2c, R = tetramethylpiperidino, R' = SiMe3), phosphaalkene (Me3Si)2NP = C(H)SiMe3 (17), or bis(imino)phosphorane (Me3Si)2NP(= NSiMe3)2 (30) by means of Cp2ZrHCl takes place with the formation either of the three-membered rings zirconaazaphosphirane Cp2 activated Zr(Cl)N(R')P(H)R (3a-c) and zirconaphosphirane Cp2 activated Zr(Cl)C(H)(SiMe3)P(H)N(SiMe3)2 (18) or the four-membered ring zirconadiazaphosphetidine Cp2Zr(Cl)N(SiMe3)P(H)[N(SiMe3)2]N(SiMe3) (31). Similarly, carbozirconation of phosphaimine 2a leads to the zirconaazaphosphirane Cp2 activated Zr(Me)N(SiMe3)P(Me)N(SiMe3)2 (7). On the other hand, hydrozirconation of 2a with Cp2ZrH2 or hydrozirconation of the thioiminophosphorane Me3Si(tBu)NP(= S)(= NtBu) (13) gives rise respectively to the acyclic phosphine (Me3Si)2NP(H)NHSiMe3 (6) or to the acyclic phosphine sulfide Me3Si(tBu)NP(S)HN(H)tBu (10b). Addition of Cp2ZrHCl to the chlorophosphaalkene ClP = C(SiMe3)2 (19) affords the diphosphene (Me3Si)2CHP = PCH(SiMe3)2 (20) and the diphosphirane (Me3Si)2CHPC(SiMe3)2PH (21). An easy hydride-chlorine exchange involving Cp2ZrHCl and free or complexed halogenated phosphines is observed and allows obtention of the corresponding P-H phosphines. Ligand exchange occurs when the zirconaphosphirane 18 is treated either with the phosphaimine 2a or the bis(imino)phosphorane 30, leading to the zirconaazaphosphirane 3a or the zirconadiazaphosphetidine 31, respectively. Synthesis of stable cationic cyclic zirconium species, the zirconaazaphosphirane cations [(CH3C = N)Cp2 activated ZrN(SiMe3)P(H)[N(SiMe3)2][X] (15, 16) (15, X = CF3SO3; 16, X = BPh4) or the zirconadiazaphosphetidine cation [CH3C = N)Cp2 activated ZrN(SiMe3)P(H)[N(SiMe3)2]N(SiMe3)][CF3SO3] (38), involving dissociation of a covalent zirconium-oxygen bond, are also reported.