The synthetic chemistry leading to tris(pentamethylcyclopentadienyl)samarium complexes has been examined to determine why some routes fail and to develop routes superior to the first synthesis from (C5Me5)2Sm and 1,3,5,7-cyclooctatetraene (COT). (C5Me5)2Sm(THF) fails as a reagent since (C5Me5)3Sm reacts with any THF present to form the ring-opened product (C5Me5)2Sm[O(CH2)4C5Me5](THF). However, (C5Me5)2Sm(OEt2) reacts cleanly with COT to form (C5Me5)3Sm and (C5Me5)Sm(C8H8). A more efficient synthesis involves the reaction of (C5Me5)2Sm(OEt2) with (C5Me5)2Pb which generates (C5Me5)3Sm in >90% yield. This route has been used to synthesize the more sterically crowded tris(pentaalkylcyclopentadienyl) complex (C5Me4Et)3Sm, which shows that the limit of steric crowding in this class has not yet been realized. X-ray crystallographic study of (C5Me4Et)3Sm revealed a trigonal planar arrangement of ring centroids around samarium with an average Sm−C(C5Me5) distance of 2.834 Å. Two ethyl groups point toward samarium with a minimum Sm−C distance of 3.620(13) Å.

(C(5)Me(5))(2)Sm (2 equiv) reacts with Ph(2)EEPh(2) to give (C(5)Me(5))(2)SmEPh(2) (E: P, 1; As, 2), while (C(5)Me(5))(2)Sm(THF)(2) (2 equiv) reacts with Ph(2)EEPh(2) to give (C(5)Me(5))(2)Sm(EPh(2))(THF) (E: P, 3; As, 4). 3 and 4 are also available from the reactions of 1 and 2 with THF. 3 and 4 undergo further reaction to produce the THF ring-opened products (C(5)Me(5))(2)Sm[O(CH(2))(4)EPh(2)](THF) (E: P, 5; As, 6).(C(5)Me(5))(2)Sm (4 equiv) reacts with Ph(2)EEPh(2) to give the mixed-valent (C(5)Me(5))(2)Sm(&mgr;-EPh(2))Sm(C(5)Me(5))(2) (E: P, 7; As, 8). These compounds are also available from the reaction of 1 and 2 with (C(5)Me(5))(2)Sm. The X-ray crystal structure of 2, crystallized from hexanes (P2(1)/n; a = 26.188(24) Å, b = 9.911(10) Å, c = 23.280(23) Å, beta = 97.150(12) degrees, V = 5995(2) Å(3), D(calcd) = 1.488 Mg/m(3); Z = 8; T = 156 K), revealed, in addition to a conventional seven-coordinate bent metallocene geometry with 2.698 Å Sm-C(C(5)Me(5)) and 2.970 Å Sm-As average distances, two very different Sm-As-C(Ph) angles, 74.2 and 118.7 degrees. As a result, one phenyl group is closer to the metal (2.901 Å minimum Sm-C distance). 4, crystallized from toluene (P2(1)/n; a = 10.713(9) Å, b = 14.143(11) Å, c = 21.620(16) Å, beta = 101.08(6) degrees, V = 3215(4) Å(3), D(calcd) = 1.492 Mg/m(3); Z = 4; T = 163 K), and 6, crystallized from hexanes (P2(1)/n; a = 9.3958(16) Å, b = 22.245(3) Å, c = 17.931(3) Å, beta = 96.497(11) degrees, V = 3724(1) Å(3), D(calcd) = 1.416 Mg/m(3); Z = 4; T = 163 K), have conventional eight-coordinate, bent metallocene structures.

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The reaction of AlMe with 1,3_diphenyltriazene [Hdpt] in toluene gives Al(dpt)3, even when AlMe, is in large excess. The monomeric structure has been established by Xray diffraction. Crystals of Al(dpt)3 are monoclinic, space group C2/c with a = 20.587(3), b = 16.005(3), c = 13.236(3) 8, and b = 119.172(12)", Z = 4, R = 0.067 and R, = 0.083. The aluminium(II1) is coordinated by three chelating triazenido ligands to give a trigonally distorted octahedral geometry. The gallium and indium analogues are also reported.

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