Synthetic, structural, and reactivity results are presented on neodymium and lanthanum carboxylates that can function as models for diene polymerization catalysts. The neodymium and lanthanum carboxylates {Nd[O 2 CC(CH 3 ) 2 CH 2 CH 3 ] 3 } x (1) and {La[O 2 CC(CH 3 ) 2 CH 2 CH 3 ] 3 } x (2) were synthesized from the lanthanide metal and 2,2-dimethylbutyric acid in the presence of a catalytic amount of HgCl 2 and Hg(OAc) 2 . Nd 2 [O 2 CCH(C 6 H 5 )CH 2 CH 3 ] 6 [HO 2 CCH-(C 6 H 5 )CH 2 CH 3 ] 4 (3) was prepared similarly from neodymium powder and 2-phenylbutyric acid. 1 and 2 crystallize from hot pyridine as the dimeric pyridine adducts Nd 2 [O 2 CC(CH 3 ) 2 -CH 2 CH 3 ] 6 [pyridine] 4 (4) and La 2 [O 2 CC(CH 3 ) 2 CH 2 CH 3 ] 6 [pyridine] 4 (5). 3 crystallizes from hexanes as the carboxylic acid adduct. 1 and 2 react with Et 2 AlCl to form the isolable solids 6 and 7, which react with Al( i Bu) 3 to generate catalytically active systems which polymerize isoprene, ethylene, and styrene. Although crystallization of 6 from THF forms NdCl 3 (THF) 4 (8) and crystallization of 7 from pyridine forms [LaCl 3 (pyridine) 4 ] 2 (9), complexes 6 and 7 are not simply LnCl 3 , since elemental analyses show that they contain aluminum.

The well-defined coordination environment of trivalent [(C5Me5)2Ln]+ complexes has been used to examine the reaction chemistry of the lanthanide carboxylate and R2AlCl (R = Me, Et, iBu) components used in the preparation of lanthanide-based diene polymerization catalysts. Each of the R2AlCl reagents can replace a carboxylate ligand with chloride in reactions with [(C5Me5)2Sm(O2CC6H5)]2, but instead of forming a simple chloride complex like [(C5Me5)2SmCl]3, bimetallic lanthanide aluminum dichloro complexes (C5Me5)2Sm(μ-Cl)2AlR2 are generated by ligand redistribution. These bis(chloride)-bridged complexes are also readily formed from the divalent precursor (C5Me5)2Sm(THF)2 and R2AlCl. However, the analogous reaction between (C5Me5)2Sm(THF)2 and Et3Al gives (C5Me5)2Sm(THF)(μ-η2-Et)AlEt3, which contains the first Ln(III)−(η2-Et) linkage, a coordination mode that differentiates Et from Me. To determine if mixed mono-chloride/alkyl-bridged (C5Me5)2Ln(μ-Cl)(μ-R)AlR2 complexes can be isolated, (C5Me5)2Y(μ-Cl)YCl(C5Me5)2 was reacted with R3Al. These reactions form [(C5Me5)2Y(μ-Cl)(μ-R)AlR2] x complexes, but again there is a differentiation on the basis of R:  the Me complex is a dimer and the others are monomers. (C5Me5)2Y(μ-Cl)2AlR2 complexes were similarly prepared for comparison with the mixed ligand species and for additional Me, Et, and iBu comparisons.

The interaction of the substituted diene monomers isoprene, C 5 H 8 , and myrcene, C 10 H 16 , with a lanthanide was probed by examining their chemistry with (C 5 Me 5 ) 2 Sm. CH 2 dCHC-(Me)dCH 2 reacts with (C 5 Me 5 ) 2 Sm to form the bimetallic [(C 5 Me 5 ) 2 Sm] 2 [µ-η 2 :η 4 -CH 2 CHC-(Me)CH 2 ], 1. Both (C 5 Me 5 ) 2 Sm components in 1 exhibit trivalent metrical parameters. One Sm is oriented toward all four of the dienyl carbon atoms at distances of 2.604(9)-2.799(8) Å, and the other Sm interacts with only two carbons at distances of 2.544(9) and 2.674(9) Å. CH 2 dCHC(dCH 2 )CH 2 CH 2 CHdCMe 2 reacts with (C 5 Me 5 ) 2 Sm to form [(C 5 Me 5 ) 2 Sm] 2 [µ-η 2 : η 4 -CH 2 CHC(CH 2 )CH 2 CH 2 CHCMe 2 ], 2, which is similar in structure to 1. The double bond of the pendant olefinic substituent attached to the diene in myrcene does not coordinate. The structures of 1 and 2 are compared to the (C 5 Me 5 ) 2 Sm/PhCtCPh bimetallic reaction product [(C 5 Me 5 ) 2 Sm] 2 [µ-η 1 :η 1 -PhCCPh], 3, which also contains two (C 5 Me 5 ) 2 Sm units attached to an unsaturated hydrocarbon, but has equivalent trivalent (C 5 Me 5 ) 2 Sm units. Each Sm in 3 interacts with the reduced (PhCtCPh) 2primarily through a 2.52-2.54 Å Sm-C bond, although an ortho phenyl carbon is oriented toward each metal at a distance of >2.96 Å.

The europium hexafluoroacetylacetonate complex Eu(hfac) 3 (diglyme) was synthesized to examine its fluorescence and conversion to a Eu() analog. Reaction of Eu(hfac) 3 (diglyme) with potassium produced the unexpected trivalent product [EuF(hfac) 3 K(diglyme)] 2 . This reduction system was studied further by synthesizing other Ln(hfac) 3 (diglyme) analogs and examining their reactivity with potassium. The Nd, Sm, and Gd analogs of Ln(hfac) 3 (diglyme) also react with potassium to form [LnF(hfac) 3 K(diglyme)] 2 as observed for europium. Reactions of the Eu() precursors, EuI 2 (thf ) 4 and {[Zr 2 (O i Pr) 9 ]Eu(µ-I)} 2 with K(hfac) also form trivalent products, namely Eu(hfac) 3 (diglyme) and [Zr 2 (O i Pr) 9 ]Eu(hfac) 2 .

The use of a new electron‐withdrawing germane, H2Ge[3,5‐(CF3)2C6H3]2 (3), has facilitated the isolation and characterization of three new complexes implicated in the dehydrogenative coupling of bisarylgermanes by Pt0‐phos‐phane complexes. The intermediates include a digermyl species, trans‐[(Et3P)2Pt{GeH(Ar)2}2] (7), a bound digermane showing the first stage of Ge‐Ge catenation, cis‐[(Et3P)2Pt(H){Ge(Ar)2‐GeH(Ar)2}] (8), and the Ge‐H activated form of this product, [(Et3P)2HPtGe(Ar)2‐Ge(Ar)2PtH(PEt3)2] (6). Complexes such as 6 and 8 have not previously been isolated as intermediates in dehydrogenative coupling reactions. An X‐ray crystal structure was determined for complex 6, confirming the cis geometry of the hydrogen and germanium ligands; this provides yet another example of the stability of germyl hydrides towards reductive elimination. A similar cis geometry was observed for complex 8. Performing the dehydrogenative coupling reaction under a CO2 atmosphere failed to yield any products containing trapped germylene species.