Synthesis, Structure, and α-Elimination Chemistry of Hafnocene Triarylstannyl Complexes

Abstract

New hafnocene triarylstannyl complexes were prepared and were shown to undergo clean thermal decompositions via alpha-aryl-elimination to produce the corresponding stannylene and a hafnocene aryl complex. The rate of the decomposition is highly dependent on the nature of the ancillary ligand, with the stabilities of the CpCp*Hf(SnPh(3))X compounds following the order X = NMe(2) > Np (alpha-agostic) > OMe > Cl > Me. Mechanistic information suggests that alpha-aryl-elimination may be viewed as a concerted process involving nucleophilic attack of the migrating aryl group onto the electrophilic metal center.

Dehydrogenative Bond-Forming Catalysis Involving Phosphines

“…Key data to supportstibinidene elimination included a first-order dependence on the stibido complex in the decomposition, negative entropy of activation, and large primary kinetic isotope effect [103]. These features were very similar to those observed forstannylene elimination from highly related stannyl complexes [104][105][106].…”

Group 2 Mediated Dehydrocoupling

“…Notably, a hafnium(IV) triphenylstannyl complex showed analogous reactivity yielding a distannane and hafnium(IV) phenyl complex via an aryl migration, implying that redox inactive cross-metatheses beyond dehydrocoupling may implicate such an α-elimination pathway. 169 Such reactivity has also been observed by Tilley and Waterman for the heaviest Group 15 congener investigated, antimony. Both MesSbH 2 and dmpSbH 2 underwent dehydrocoupling in the presence of a hafnocene(IV) complex to yield the analogous products as observed for arsenic (vide supra).…”

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions

“…The Hf−Sn distances in 6 [2.770(1), 2.781(1) Å] are slightly longer than the bond length found in E (2.7585(11) Å). The Hf−Sn bond lengths in hafnocene derivatives [CpCp*Hf(SnPh 3 ) L], on the other hand, are significantly longer: L=Cl, 2.9650(4); NMe 2 , 2.9694(8); Me, 2.9740(5); OMe, 2.9556(5) Å . The Sn−Sn distances [ 4 : 3.370(1), 5 : 3.526(1), 6 : 3.489(1) Å] in complexes 4 – 6 are longer than typical Sn−Sn single bonds [Ar′H 2 Sn‐SnH 2 Ar“, 2.7449(3)] [Ar′=2,6‐Mes 2 C 6 H 3 , Mes=2,4,6‐trimethylphenyl], however short enough to point towards a minor interaction between both tin atoms .…”

“…Scheme2.Synthesis of the metallocene bis(hydridoorgano-stannylene) complexes 4-6. and 2.7254 (17) . [10h, 16] In the case of the zirconium derivative 5 the ZrÀSn distances [2.795(1), 2.806(1) ]a re comparable with the ZrÀSn bond lengths found in E (2.7942 (10) ), but they are shorter than the values found in B (2.8715 (11) )a nd in the complexC p 2 Zr(SnL 2 ) 2 [2.8230(4)) and 2.8614(4) ;L= 2-{(dimethylamino)methyl}phenyl].…”

“…The HfÀSn bond lengths in hafnocene derivatives [CpCp*Hf(SnPh 3 )L], on the other hand, are significantly longer:L = Cl, 2.9650(4); NMe 2 ,2 .9694(8);M e, 2.9740(5); OMe, 2.9556 (5) . [17] The SnÀSn distances [4: 3.370(1), 5:3 .526(1), 6:3 .489(1) ]i nc omplexes 4-6 are longer than typical SnÀSn single bonds [Ar'H 2 Sn-SnH 2 Ar", 2.7449(3)] [Ar' = 2,6-Mes 2 C 6 H 3 ,M es = 2,4,6-trimethylphenyl],h owever short enough to point towards am inor interaction between both tin atoms. [8c] Coordinationo ft wo stannylenes at metallocene fragments was previously reported in B, F and Cp 2 Zr(SnL 2 ) 2 .T he SnÀSn distances in thesed erivatives are all clearly longer:4 .2364 (B), 3.804 (F-Ti),4 .216 (F-Hf) and 3.559 (Cp 2 Zr(SnL 2 ) 2 ).…”