ChemInform Abstract Amide ligands (I) (preparation described) and (III), modified by the presence of the diarylboryl substituents, are used to synthesize low-coordinate metal complexes of unusual structure. X-ray analyses are carried out for (IIIa) (P1, Z=2), (VIa) (Pbca, Z = 8), (VIIIb) (P21/c, Z=4), (Xa), (XI) and (XIIa) (all P1, Z=2). The transition-metal complexes are all high-spin with nominally two-coordinate geometries. However, they all display some deviation from linearity, the strongest N-M-N bending is observed in (VIII). In all the complexes the B-N bond lengths are consistent with π-bonds between boron and nitrogen. The neutral ligands are thus B-N analogues of the alkenyls and behave, for the most part, as one-electron donors. Instead of association through bridging at the nitrogen centers, moderate interactions between the metal and the ipso carbons of the B(Mst)2 groups are found for (VIIIb), (Xb) and (XI), leading to pseudo-square-planar coordination in the first and pseudotetrahedral environment in the latter two cases.

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The synthesis and first structural characterization of crystalline primary and secondary mesitylphosphines PH2Mes (1) and PHMes2 (2) are described. Treatment of 1 and 2 with 1 equiv of n-BuLi affords the solvated lithium phosphides [Li(THF) 3PHMes] (3) and [|Li(OEt2)PMes2)2] (4), which possess previously uncharacterized structural types. A notable feature in the crystal lattice of 1 is the packing of PMes moieties into parallel layers. However, there are no strong interactions between these layers. In 2, the phosphorus center has a pyramidal geometry with bond angles near tetrahedral values. The X-ray crystal structure of 3 shows that it is the first structure of a lithium phosphide with a terminal phosphide group. The pyramidal geometry at phosphorus is in sharp contrast to the planar geometry found for lithium amides. Unlike that of 3, the structure of 4 is dimeric with solvated lithium atoms bridging two [PMes2]" moieties. The central Li2P2 core is essentially planar with the phosphorus centers having distorted tetrahedral geometries. A 3IP NMR study on the degree of solvation between ion pairs in various primary and secondary organophosphide complexes is also reported. Crystallographic data with Mo Ka radiation

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.32)(&mgr;-OH)](2).2C(6)H(6) (12). The structures of 2, 3a, 4, 6, 7, 9a, 10a, 10b, 11, and 12 were determined by X-ray crystallography. The structures of 3a, 9a, 10a, and 10b, are related to 3, 9, and 10, respectively, by partial occupation of chloride or hydride by hydroxide. The compounds were also characterized by (1)H, (13)C, (7)Li, and (27)Al NMR and IR spectroscopy. The major conclusions from the experimental data are that a single ortho terphenyl substituent of the kind reported here are not as effective as the ligand Mes (Mes = 2,4,6-t-Bu(3)C(6)H(2)-) in preventing further coordination and/or aggregation involving the aluminum centers. In effect, one terphenyl ligand is not as successful as a Mes substituent in masking the metal through agostic and/or steric effects.

tion. Complex 2 was prepared by the addition ofa suspension of (Et,NH)BPh, (75.9 nig, 0.18 mmol, from (Et,NH)CI and NaBPh,) in 5 mL of THF to a stirred orange-yellow solution of 1 (90 mg. 0.09 mmol) In 7 mL of THE The reaction was stirred overnight and the solvent was removed by rotary evaporation to leave a dark orange product. This was washed with 5 mL of toluene to remove oily by-products and left a 2: 1 mixture (by NMR spectroscopy of 2 and 3 (1 10 mg). Complex 2 was separated by recrystallization from THF: toluene (4:l).