The reactivity of KNHAr reagents (Ar = C(6)H(5), C(6)H(3)Me(2)-2,6, C(6)H(3)(i)Pr(2)-2,6) with lanthanide and yttrium trichlorides has been investigated. With the larger metals Nd and Sm and the smaller 2,6-dimethyl-substituted ligand, the bimetallic dianionic complexes [K(THF)(6)](2)[Ln(&mgr;-NHC(6)H(3)Me(2)-2,6)(NHC(6)H(3)Me(2)-2,6)(3)](2) (Ln: Sm, 1a; Nd, 1b) are isolated as the potassium salts. Under the same reaction conditions YCl(3) forms a bimetallic anion which retains chloride: [K(DME)(2)(THF)(3)][Y(2)(&mgr;-NHC(6)H(3)Me(2)-2,6)(2)(&mgr;-Cl)(NHC(6)H(3)Me(2)-2,6)(4)(THF)(2)], 2. With the larger 2,6-diisopropyl ligands, neutral complexes are isolated in both solvated monometallic and unsolvated bimetallic forms. With Nd, a distorted octahedral trisolvate, Nd(NHC(6)H(3)(i)Pr(2)-2,6)(3)(THF)(3), 3, was obtained, whereas with Yb and Y the trigonal bipyramidal disolvates, Ln(NHC(6)H(3)(i)Pr(2)-2,6)(3)(THF)(2) (Ln: Yb, 4a; Y, 4b), were isolated. THF-free complexes of the NHC(6)H(3)(i)Pr(2)-2,6 ligand are available by reacting the amine NH(2)C(6)H(3)(i)Pr(2)-2,6 with Ln[N(SiMe(3))(2)](3) complexes. By this route, the dimers [Ln(&mgr;-NHC(6)H(3)(i)Pr(2)-2,6)(NHC(6)H(3)(i)Pr(2)-2,6)(2)](2) (Ln: Yb, 5a; Y, 5b) were isolated. The reaction of the unsubstituted arylamido salt KNHC(6)H(5) with NdCl(3) produced an insoluble material which was characterized as [Nd(NHC(6)H(5))(3)(KCl)(3)], 6. 6 reacted with Al(2)Me(6) in hexanes and produced a heteroleptic mixed-metal complex {[Me(2)Al(&mgr;-Me(2))](2)Nd(&mgr;(3)-NC(6)H(5))(&mgr;-Me)AlMe}(2), 7, and the trimeric aluminum arylamido complex [Me(2)Al(&mgr;-NHC(6)H(5))](3), 8. The solvent of crystallization and relevant crystallographic data for the compounds identified by X-ray analysis follow: 1a,THF, 156 K, P2(1)/n, a = 12.985(2) Å, b = 27.122(5) Å, c = 17.935(3) Å, beta = 100.19(1) degrees, V = 6216(1) Å(3), Z = 2, 6148 reflections (I > 3sigma(I)), R(F)() = 7.1%; 1b,THF, 156 K, P2(1)/n, a = 12.998(2) Å, b = 27.058(3) Å, c = 17.962(2) Å, beta = 99.74(1) degrees, V = 6225(1) Å(3), Z = 2; 2,DME/hexanes, P2(1)/n, a = 23.335(2) Å, b = 12.649(1) Å, c = 27.175(3) Å, beta = 96.36(1) degrees, V = 7971(1) Å(3), Z = 4, 2788 reflections (I > 3sigma(I)), R(F)() = 9.5%; 3, THF, P2(1), a = 12.898(1) Å, b = 16.945(1) Å, c = 13.290(1) Å, beta = 118.64(2) degrees, V = 2549.3(3) Å(3), Z = 2, 3414 reflections (I > 3sigma(I)), R(F)() = 4.3%; 4a, hexanes, P2(1), a = 9.718(2) Å, b = 19.119(3) Å, c = 12.640(2) Å, beta = 112.08(1) degrees, V = 2176.3(6) Å(3), Z = 2, 2933 reflections (I > 3sigma(I)), R(F)() = 4.3%; 4b, hexanes, 158 K, a = 9.729(2) Å, b = 19.095(5) Å, c = 12.744(1) Å, beta = 112.11(1) degrees, V = 2193.4(6) Å(3); 5b, hot toluene, 158 K, P2(1), a =19.218(9) Å, b = 9.375(3) Å, c = 19.820(5) Å, beta = 110.25(2) degrees, V = 3350(2)Å(3), Z = 2, 1718 reflections (I > 2sigma (I)), R1 = 9.7%; 7, hexanes, 156 K, P&onemacr;, a = 9.618(3) Å, b = 12.738(4) Å, c = 9.608(3) Å, alpha = 99.32(1) degrees, beta = 108.87(1) degrees, gamma = 94.23(1) degrees, V = 1089.1(6) Å(3), Z = 2, 2976 reflecti...

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A new series of bimetallic triple-decked organometallic sandwich complexes involving Sm(II) can be prepared by reacting [(C5Me4R)Sm(μ-I)(THF)2]2 with 1 equiv of K2C8H8 in toluene to form [(C5Me4R)Sm(THF)]2(μ-η8:η8-C8H8) (R = Me, 1; R = Et, 2). The diglyme ([MeOCH2CH2]2O) adduct of 1, {[(C5Me5)Sm(diglyme)]2(μ-η8:η8-C8H8)}(THF)2 (3) crystallizes from THF with a bridging (C8H8)2- dianion sandwiched between two [(C5Me5)Sm(diglyme)]+ cations with a 137.6° (C5Me5 ring centroid)−Sm−(C8H8 ring centroid) angle. This bent triple-decked metallocene has 2.91(2) Å Sm−C(C5Me5) and 2.96(5) Å Sm−C(C8H8) average distances. 1 and 2 can be desolvated at 30−50 °C under high vacuum over several hours to yield [(C5Me4R)Sm]2(μ-η8:η8-C8H8) (R = Me, 4; R = Et, 5). It was of interest to determine if 4 and 5 had triple-decked metallocene structures with three parallel rings since previously characterized bis(cyclooctatetraenyl) lanthanide and actinide complexes such as uranocene, (C8H8)2U, and [(C8H8)2Ce]- have parallel rings whereas (C5Me5)2Sm is bent. Complex 4 is found to crystallize from toluene with a structure that retains the bent geometry of 3 with 149.3° and 148.9° (C5Me5 ring centroid)−Sm−(C8H8 ring centroid) angles. 5 crystallizes from toluene with a similar bent triple-decked metallocene structure with 157.6° (C5Me5 ring centroid)−Sm−(C8H8 ring centroid) angles. The ethyl groups in 5 are oriented toward the metal center with 3.40 Å Sm···C(CH2 CH3) distances. Complexes 1 and 2 each do two-electron reductions of 1,3,5,7-C8H8 to form (C5Me4R)Sm(C8H8)(THF); 4 and 5 react similarly with 1,3,5,7-C8H8 to form (C5Me4R)Sm(C8H8). A two-electron reduction of C5Me5Cl by 1 generates (C5Me5)Sm(C8H8)(THF) and (C5Me5)2SmCl(THF), a product in which C5Me5Cl has been added to a single (C5Me5)Sm(THF) unit in 1.

The central Se atom is surrounded by six (C5Me5)Sm units in a distorted octahedral arrangement in the title compounds (structure shown on the right). Four pairs of (Se2)2− units, the central Se atom, and two further Se atoms connect the six (C5Me5)Sm units. The complex contains a linear (Se3)4− moiety, which is isoelectronic with the (I3) ion.

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