The titanocene silyl hydride complexes [Ti(Cp)2(PMe3)(H)(SiR3)] [SiR3=SiMePhCl (6), SiPh2Cl (7), SiMeCl2 (8), SiCl3 (9)] were prepared by HSiR3 addition to [Ti(Cp)2(PMe3)2] and were studied by NMR and IR spectroscopy, X-ray diffraction (for 6, 8, and 9), and DFT calculations. Spectroscopic and structural data established that these complexes exhibit nonclassical Ti-H-Si-Cl interligand hypervalent interactions. In particular, the observation of silicon-hydride coupling constants J(Si,H) in 6-9 in the range 22-40 Hz, the signs of which we found to be negative for 8 and 9, is conclusive evidence of the presence of a direct Si-H bond. The analogous reaction of [Ti(Cp)2(PMe3)2] with HSi(OEt)3 does not afford the expected classical silyl hydride complex [Ti(Cp)2(PMe3)(H)[Si(OEt)3]], and instead NMR-silent titanium (apparently TiIII) complex(es) and the silane redistribution product Si(OEt)4 are formed. The structural data and DFT calculations for the compounds [Ti(Cp)2(PMe3)(H)(SiR3)] show that the strength of interligand hypervalent interactions in the chlorosilyl complexes decreases as the number of chloro groups on silicon increases. However, in the absence of an Si-bound electron-withdrawing group trans to the Si-H moiety, a silane sigma complex is formed, characterized by a long Ti-Si bond of 2.658 A and short Si-H contact of 1.840 A in the model complex [Ti(Cp)2(PMe3)(H)(SiMe3)]. Both the silane sigma complexes and silyl hydride complexes with interligand hypervalent interactions exhibit bond paths between the silicon and hydride atoms in Atoms in Molecules (AIM) studies. To date a classical titanocene phosphane silyl hydride complex without any Si-H interaction has not been observed, and therefore titanocene silyl hydrides are, depending on the nature of the R groups on Si, either silane sigma complexes or compounds with an interligand hypervalent interaction.
New groups 3 and 4 organometallic and coordination compounds supported by the tetradentate diamino-bis(phenolate) ligands O2 tBuNN‘ and O2 MeNN‘ are reported [H2O2 RNN‘ = (2-C5H4N)CH2N(2-HO-3,5-C6H2R2)2 where R = tBu or Me] along with some comparative studies with the tridentate amino-bis(phenolate) ligand O2 tBuN (H2O2 tBuN = nPrN(2-HO-3,5-C6H2 tBu2)2). Reaction of Na2O2 tBuNN‘ with ScCl3 and pyridine in THF gave monomeric Sc(O2 tBuNN‘)Cl(py) (2), whereas Na2O2 MeNN‘ gave the dimeric phenoxy-bridged Sc2(O2 MeNN‘)2Cl2 (3). Reaction of Na2O2 tBuNN‘ and YCl3 in neat pyridine gave the chloride-bridged, seven-coordinate dimer Y2(O2 tBuNN‘)2(μ-Cl)2(py)2 (4). Reaction of M(CH2SiMe3)3(THF)2 (M = Sc or Y) with H2O2 tBuNN‘ afforded M(O2 tBuNN‘)(CH2SiMe3)(THF). The one-pot reaction of ScCl3 with Na2O2 RNN‘ (R = tBu or Me) and Li[PhC(NSiMe3)2] gave the fluxional benzamidinate derivatives Sc(O2 RNN‘){PhC(NSiMe3)2}. Treatment of Ti(NMe2)4 with H2O2 RNN‘ gave the corresponding Ti(O2 RNN‘)(NMe2)2 (R = tBu (11) or Me); 11 in turn reacts with HS-4-C6H4Me to give Ti(O2 tBuNN‘)(NMe2)(S-4-C6H4Me). One-pot reactions of TiCl4(THF)2 with MeLi (2 equiv) followed by H2O2 RNN‘ affords Ti(O2 RNN‘)Cl2 (R = tBu (9) or Me (10)), which are cleanly methylated with MeMgBr to yield the corresponding Ti(O2 RNN‘)Me2 (R = tBu (14) or Me (15)). The terminal imidotitanium compounds Ti(O2 tBuNN‘)(NR)(py) (R = tBu or 2,6-C6H3Me2) were formed from the respective Ti(NR)Cl2(py)3 reagents and Na2O2 tBuNN‘, and these react with CO2 by imido group transfer to yield the μ-oxo dimer Ti2(O2 tBuNN‘)2(μ-O)2 (18) and RNCO. The related five-coordinate compounds Ti(O2 tBuN)(NR)(py) (R = tBu, 2,6-C6H3Me2 (20) or 2,6-C6H3 iPr2 (21)) were prepared in an analogous manner. These do not give identifiable metal products with CO2. Treatment of the dimethyl compounds 14 or 15 with B(ArF)3 or [CPh3][B(ArF)4] (ArF = C6F5) gave the fluxional, dimeric phenoxy-bridged cations [Ti2(O2 RNN‘)2Me2]2+, which show very sluggish 1-hexene polymerization behavior. The compounds 2, 3, 4, 11, 9, 10, 16, 18, 20, and 21 have been crystallographically characterized.
A family of new organometallic and coordination compounds supported by the diamine−bis(phenolate) ligands O2NN‘Me and O2NN‘tBu are reported [H2O2NN‘R = (2-C5H4N)CH2N(CH2-2-HO-3,5-C6H2R2)2, where R = Me (1a) or tBu (1b)]. Reaction of H2O2NN‘R with sodium hydride in THF gives the corresponding sodium salts Na2O2NN‘R (R = Me (2a) or tBu (2b)). Reaction of H2O2NN‘R with Zr(CH2SiMe3)2Cl2(Et2O)2 gives the cis-dichloride derivatives ZrCl2(O2NN‘R) (R = Me (3a) or tBu (3b)), which exist as two isomers (possessing either C 1 (major) or C s symmetry) in dynamic equilibrium with each other in solution. The compound 3b can also be prepared from Na2O2NN‘tBu and ZrCl4(THF)2, but reaction of Na2O2NN‘Me with either ZrCl4 in benzene or ZrCl4(THF)2 in THF gives mixtures of 3a and the eight-coordinate bis(diamine−bis(phenolate)) complex Zr(O2NN‘Me)2 (4a). The latter can also be prepared from 2 equiv of H2O2NN‘Me and Zr(CH2SiMe3)4. Treatment of Zr(NMe2)4 with H2O2NN‘tBu leads to the bis(dimethylamide) derivative Zr(NMe2)2(O2NN‘tBu) (5b). Similar protonolysis reactions between ZrR‘4 (R‘ = CH2SiMe3, CH2CMe3, or CH2Ph) give the corresponding organometallic alkyl or benzyl compounds ZrR‘2(O2NN‘R) [R‘ = CH2SiMe3 (8a, 8b), CH2CMe3 (9a, 9b), or CH2Ph (10a, 10b); R = Me (suffix a) or tBu (suffix b)]. The dichloride complexes ZrCl2(O2NN‘R) (3a, 3b) are also precursors to new organometallic derivatives, and treatment with LiR‘ (R‘ = Me or CH2SiMe3) or R‘MgCl (R‘ = CH2Ph or C3H5) yields ZrR‘2(O2NN‘R) [R‘ = Me (6a, 6b), η3-C3H5 (7b), CH2SiMe3 (8a, 8b), CH2Ph (10a, 10b)]. The thermally unstable bis(η3-allyl) complex 7b is highly fluxional in solution. Reaction of the dibenzyl compound 10a or 10b with B(C6F5)3 in the presence of THF gives the cationic complexes [Zr(CH2Ph)(THF)(O2NN‘R)]+ as the [PhCH2B(C6F5)3]- salts (11a, 11b). The X-ray crystal structures of the compounds 3a, 3b, 4a, 5b, 6a, 6b, and 10a are described.
The preparation of alkylene-, arylene-, or benzylene-bridged ditin hexachlorides in high yields from the reaction of the corresponding hexacyclohexylated compounds with tin tetrachloride is described. The tetragonal geometry of the tin atom of 1,4-bis(trichlorostannyl)butane in the solid state indicates that no intramolecular or intermolecular interaction involving either end of the molecule exists in this compound. The ditin hexachlorides were successfully transformed in the corresponding hexaalkynides, precursors of hybrid materials.
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