Titanium complexes of bis(1°-amido)cyclodiphosph(III)azanes and bis(1°-amido)cyclodiphosph(V)azanes: facial versus lateral coordination †

Abstract

Bis(1Њ-amino)cyclodiphosph()azanes and bis(1Њ-amino)cyclodiphosph()azanes show different coordination preferences with titanium(). The bis(tert-butylamino)cyclodiphosph()azane cis-[Bu t (H)N(Bu t NP) 2 N(H)Bu t ] (1) reacts with TiCl 4 to afford {[(Bu t NP) 2 (NBu t ) 2 ]TiCl 2 } (2), in which the ligand chelates the metal as a diamide, above the heterocycle. Oxidations of 1 with phenyl-or p-tolyl azide yield the cyclodiphosph()azanes cis-[Bu t (H)N(ArN᎐ ᎐ PNBu t ) 2 N(H)Bu t ] (Ar = phenyl (3), p-tolyl (4)). Single-crystal X-ray studies of 3 and 4 reveal structures similar to those of their parent cyclodiphosph()azanes, but with pendent arylimino groups attached to the phosphorus() atoms. When 3 and 4 are allowed to react with TiCl 4 the complexes {[Bu t (H)N(ArN᎐ ᎐ PNBu t ) 2 NBu t ]TiCl 3 } (Ar = phenyl (5), p-tolyl (6)) are isolated. In these compounds the cyclodiphosph()azanes coordinate the metal laterally as monoanionic N-P-N ligands, similar to phosphoranates. An analogous side-on coordination is also found for the dichalcogeno complexes {[Bu t (H)N(E᎐ ᎐ PNBu t ) 2 NBu t ]TiCl 3 } (E = S (9), Se (10)).

Synthesis and Derivatization of the Bis(amido)‐λ3‐cyclodiphosphazanes cis‐[R′(H)NP(μ‐NR)]2, Including a Rare Example, trans‐[tBu(H)N(Se)P(μ‐NCy)]2, Showing Intermolecular Se···H–O Hydrogen Bonding

“…The structure for cis- (15) with the atom numbering scheme is shown in Figure 6. The selected bond angles and bond lengths for 15 are presented in Table 2 www.eurjic.orgable with those of the reported [20] imine derivatives of λ 5 -cyclodiphosphazanes. The P1-N4-P3 bond angle is 141.92°w…”

New Bulky Bis(amino)cyclodiphosph(III)azanes and Their Titanium(IV) Complexes: Synthesis, Structures and Ethene Polymerization Studies

“…In general, the coordination sphere of 11a resembles previously described structures for Ti, Zr and Hf complexes based on the cis-[(tBuNH)(PNtBu)] 2 ligand. [10,11,12] The cyclophosph()azane ring is almost planar and the phenyl rings are almost perpendicular to the P 2 N 2 plane and, hence, leave the metal center relatively open to nucleophilic attack.…”

“…[11] This may be due to NMe 2 substituents donating additional electron density from the sp 2 -hybridized amido nitrogen atoms to the metal center, thereby decreasing the Lewis acidity of the titanium. Four amido nitrogen atoms are in a pseudo-tetrahedral environment around the metal center [N(1)ϪTiϪN(2) and N(5)ϪTiϪN(6) are 111.80 (1)°and 98.66 (2)°respectively] and the amido NϪTi bond lengths vary from 1.884 (4) to 2.020 (3) Å (Table 3).…”

“…The relatively small tert-butyl groups not only leave the titanium center open for activation and polymerization but, at the same time, the catalyst is susceptible to side reactions. Coordination of the Lewis acidic cocatalyst (MAO) to the lone-pair electrons of phosphorus atoms can initiate destruction of the ligand, [11] which could explain the presence of different active centers and could also be one reason for the fast catalyst deactivation. Therefore, bulky aromatic groups attached directly to the amido nitrogen (13؊15) have two roles: they protect the catalytic active center from side reactions and they prevent the phosphorus atoms of the ligand from destructive coordination to MAO.…”

“…[15,16] They have attracted most attention as precursors for hybrid (organic-inorganic) PϪN polymeric materials, [16c] and as ligand precursors for the synthesis of main group element compounds [9] and some, still rare, early transition metal complexes. [10,11,12] They preparation, in good yield, is commonly based on the reaction of cis- (ClPN-tBu) 2 (1) with either lithium amide or an excess of a free amine. [9] We investigated both of these methods to access the new, bulky bis(amino)cyclodiphosph()azanes.…”