Synthesis of zirconium complexes that contain the diamidophosphine ligands[(Me3SiNCH2CH2)(2)PPh](2-) or [(RNSiMe2CH2)(2)PPh](2-) (R = t-Bu or 2,6-Me2C6H3)

Anew synthesis of PhP(CH2CH2NH3Cl)(2) is reported that involves the additio n of 2 equiv of butyllithium to a mixture of PhPH2 and 2 equiv of ClCH2CH2( cyclo-NSiMe2CH2CH2SiMe2). The reaction between PhP(CH2CH2NH3Cl)(2) and 4 eq uiv of butyllithium followed by 2 equiv of Me3SiCl then yielded (Me3SiNHCH2 CH2)(2)PPh (H-2[N2P]) quantitatively. Addition of H-2[N2P] to Zr(NMe2)(4) i n pentane gave intermediate [N2P]Zr(NMe2)(2) that was converted without pur ification to white, crystalline [N2P]ZrCl2 in 80% yield overall upon treatm ent with 2 equiv of Me3SiCl. The alkyl complexes that were prepared iriclud e [N2P]Zr(THF)MeCl, [N2P]Zr(i-Bu)Cl, [N2P]ZrMe2, [N2P]Zr(CH2Ph)(2), and [N2 P]Zr(CH3)(CH2Ph). An X-ray diffraction study showed that the basic structur e of [N2P]Zr(CH3)(CH2Ph) is a distorted trigonal bipyramid in which the met hyl group is in the apical position trans to phosphorus and the eta(2)-benz yl group is cis to phosphorus. Compounds of the type PhP(CH2SiMe2NHR)(2) (R = t-Bu or 2,6-Me2C6H3; H-2[R2NPN]) were prepared by treating ClCH2SiMe2Cl with LiNHR to give ClCH2-SiMe2NHR followed by a reaction between PhPH2, ClC H2SiMe2NHR, and butyllithium. Zirconium complexes that were prepared includ e [t-Bu2NPN]ZrMeCl, [Ar2NPN]ZrMeCl, and [Ar2NPN]ZrMe2. An attempted synthes is of [t-Bu2NPN]ZrMe2 led to loss of a tert-butyl group and formation of a dimeric complex containing imido-type bridging nitrogen ligands, as confirm ed in an X-ray study. X-ray studies of [t-Bu2NPN]ZrMeCl and [Ar2NPN]ZrMeCl demonstrate that extensive steric crowding exerted by a tert-butyl group in complexes of this type contributes to the inability to form a simple compl ex such as [PhP(CH2SiMe2N-t-Bu)(2)]ZrMe2.