Donor atom substitutions in amidophosphine ligands: Early transition metal complexes of arsine and aryloxide containing ligands

The effects of donor atom substitution in the amidophosphine ligands Ph[P2N2] (where Ph[P2N 2] = PhP(CH2SiMe2NSiMe2CH2) 2PPh) and Ph[NPN] (where [NPN] = PhP(CH2SiMe 2NPh)2 with both stronger and weaker donors is explored through early transition metal coordination chemistry.;The chelating diamidoarsine Ph[NAsN] (where Ph [NAsN] = PhAs(CH2SiMe2NPh)2) can be synthesized as a THF adduct of the lithium salt, Ph[NAsN]Li 2(THF)2. Reaction of the lithium salt with TaMe3Cl 2 affords the five-coordinate alkyl complex Ph[NAsN]TaMe 3. Hydrogenation of Ph[NAsN]TaMe3 does not produce a hydride complex, but instead a modest yield of the protonated ligand precursor Ph[NAsN]H2. Evidence suggests that Ph[NAsN]H2 is produced through hydrogenation of tantalum-amide bonds. Density functional theory calculations carried out on the model complexes 'NAsN'TaMe3 and ('NAsN'Ta)2(mu-H)4 (where 'NAsN' = CH3As(CH2SiH2NCH3) 2) suggest that dissociation of the arsenic donor may play a role in the hydrogenation of the trimethyl complex.;The bis(aryloxy)phosphine ligands R[OPO] (where R[OPO] = RP(3,5-tBu2C 6H2O)2) (R = Ph, iPr) are prepared as dimeric lithium salts (R[OPO]Li2) 2(THF)4, protonated ligand precursors R[OPO]H 2, the dimeric potassium salt (Ph[OPO]K2) 2(THF)6, and trimeric (i Pr[OPO]K2)3(THF)3.;Reaction of [OPO] precursors with group 4 and 5 halides affords Ph[OPO]MCl2(THF) (M = Ti, Zr, Hf) and R[OPO]TaCl 3. Direct alkylations of Ph[OPO]TaCl 3 produce only mixtures of products; however, the methyl complexes Ph[OPO]TaMeCl2, Ph[OPO]TaMe2Cl and Ph[OPO]TaMe3 can be prepared by reaction of Ph[OPO] precursors with TaMe3Cl2. Alkylation and reduction chemistry of the halide complexes is dominated by the formation of bis-ligand complexes, including Ph[OPO]2Ti, likely a result of the reduced steric bulk that is inherent to these metal-ligand systems.;The diamidodiarsine macrocycle Ph[As2N 2] (where Ph[As2N2] = PhAs(CH 2SiMe2NSiMe2CH2)2AsPh) can be synthesized as a 1,4-dioxane adduct of the dilithium salt, Ph[As 2N2]Li2(1,4-dioxane). Reactions of the lithium salt with appropriate metal halides affords the complexes Ph[As 2N2]ZrCl2, Ph[As2N 2]TiCl2 and (Ph[As2N2]Y) 2(mu-Cl)2. The yttrium complex is the first structurally characterized complex containing an yttrium arsenic bond. Attempts to reduce the halide salts in the presence of dinitrogen lead to mixtures of products, and evidence points to the reduction of arsenic within the macrocycle.;Preliminary investigations suggest it may be possible to prepare dinitrogen complexes through reactions with hydrazine and substituted hydrazines, or through ligand exchange with the dinitrogen complex [TaCl3(THF) 2]2(mu-N2).