New Types of Constrained Geometry Group 4 Metal Complexes Derived from the Aminomethyldicarbollyl Ligand System:  Synthesis and Structural Characterization of Mono-dicarbollylamino and Bis-dicarbollylamino Group 4 Metal Complexes

Abstract

A series of constrained geometry group 4 metal complexes containing the (N,N′-dimethylaminomethyl) dicarbollyl ligand Dcab N H [nido-7-NHMe 2 (CH 2 )-8-R-7,8-C 2 B 9 H 10 ] (3) was prepared. New types of constrained geometry titanium complexes with the formula (Dcab N )TiCl 2 , [{(η 5 -RC 2 B 9 H 9 )(CH 2 )(η 1 -NMe 2 )}TiCl 2 ] (R ) H, 4a; Me, 4b), were produced by the reaction of the potassium salt of 3 with titanium tetrachloride. The reaction of 3 with Ti(NMe 2 ) 4 in toluene afforded (Dcab N )Ti(NMe 2 ) 2 , [{(η 5 -RC 2 B 9 H 9 )(CH 2 )(η 1 -NMe 2 )}Ti(NMe 2 ) 2 ] (5) (R ) H, a; Me, b), which readily reacted with Me 3 SiCl to yield the corresponding chloride complexes (Dcab N )TiCl 2 (4). However, the reaction of 3 with Zr(NMe 2 ) 4 in toluene afforded (Dcab N )Zr(NMe 2 ) 2 (HNMe 2 ) [{(η 5 -RC 2 B 9 H 9 )(CH 2 )(η 1 -NMe 2 )}Zr(NMe 2 ) 2 (HNMe 2 )] (6) (R ) H, a; Me, b). The structures of the diamido complexes were established by X-ray diffraction studies of 5a and 5b, which authenticated an η 5 ;η 1 -bonding mode derived from the dicarbollylamino ligand functional group. The corresponding bis-chelate complexes, (Dcab N ) 2 Ti (7), were synthesized from the reaction of 4a with an additional dicarbollyl ligand 3a. Bis-chelated complexes (Dcab N ) 2 M (M ) Ti, 7; Zr, 8; Hf, 9) were also formed upon the reaction of 3a with MX 4 (M ) Ti, Zr, Hf) in a 2:1 molar ratio. The NMR spectra revealed that intramolecular M-N coordinations were preserved in solution, resulting in the formation of bis-chelated complexes (Dcab N ) 2 M (7-9). The tetrahedral coordination of the metal center was proven by single-crystal X-ray determination of the complex (Dcab N ) 2 Zr (8). New types of titanium alkoxides, (Dcab N )Ti(O i Pr) 2 (10), were synthesized from the reaction of 3a with Ti(O i Pr) 4 . Sterically less-demanding phenols such as C 6 H 5 OH and 2-MeC 6 H 4 OH replaced the coordinated amido ligands on (Dcab N )Ti(NMe 2 ) 2 (5a) to yield the aryloxy-stabilized CGC complexes (Dcab N )Ti(OPh) 2 (Ph ) C 6 H 5 , 11; 2-Me-C 6 H 4 , 12). The NMR spectra suggested that an intramolecular Ti-N coordination was intact in solution, resulting in a stable piano-stool structure whereby two aryloxy ligands resided in the leg positions. The aryloxy coordinations were further confirmed by single-crystal X-ray diffraction studies on the complexes (Dcab N )Ti(OPh) 2 (Ph ) C 6 H 5 , 11; 2-Me-C 6 H 4 , 12).

New Types of Group 4 and 13 Metal Complexes Stabilized by Homo- or Hetero-Donor Functionalized Dicarbollide Ligands: Syntheses, Characterizations, and Structural Studies of [{η5-C2B9H9(D)}(η1-NMe2CH2)]M(NMe2)2 (D = CH2NMe2, PPh2; M = Ti, Zr) and [(η1-D)(η1-NMe2CH2)C2B9H10]MMe2 (D = CH2

“…In comparison with the parent ligand 3 , the downfield shift was apparent for the methylene protons of NC H 2 and methyl protons of N Me 2 in the side arms of 7 and 8 , appearing at δ 2.93, 4.12 and 2.64, 2.88 for 7 and δ 2.94, 4.10 and 2.64, 2.86 for 8 , respectively. These shifts are consistent with the findings for other intramolecularly coordinated group 4 metal complexes containing methylene spacers, such as (Dcab N )M(NMe 2 ) 2 , (M = Ti, Zr) . Their 13 C NMR spectra were consistent with the results derived from the 1 H NMR spectrum.…”

“…As part of our ongoing efforts to induce π,σ-bonding, a wide variety of pendant donors have been incorporated to the parent dicarbollyl compounds. − Recently, chelating dicarbollide ligands with a nitrogen donor were investigated in the context of the production of π,σ-group 4 metal complexes. − In such ligand systems, the amine or amide donors were found to be the most effective ancillary functionalities to form π,σ-bonds with group 4 metals. Moreover, we recently reported the preparation of π,σ-type group 13 metal complexes, , in which the amine donor was a key ingredient that induced the primary π-interaction with dicarbollide, as shown in Figure .…”

Multinuclear Self-Assembly via a (p-Cymene)ruthenium Unit and ano-Carborane Selenolate Ligand

“…The chemistry of dicarba- closo -dodecaboranes is a fascinating research area, owing to both its unique chemical and thermal stability and its wealth of promising applications in boron neutron capture therapy for cancer (BNCT), catalysis for olefin polymerization, molecular sensing and nonlinear optics (NLO), and so on. It is well-established that o -carborane can be readily converted to closo -C 2 B 10 H 11 − and closo -C 2 B 10 H 10 2− via stepwise deprotonation of the cage C−H protons and to the dicarbollide ion nido -C 2 B 9 H 11 2− by selective removal of one BH vertex .…”

Coordination Ability of 10-EtC(NHPr)=HN-7,8-C2B9H11 in the Reactions with Nickel(II) Phosphine Complexes

“…There are several examples of such stable metal complexes based on nido-carborane with a side substituent coordinated through oxygen or nitrogen [5][6][7][8][13][14][15]. The utility of such bifunctional ligand systems with the nitrogen donor atom in the side chain has been demonstrated by the complexation of [7-Me 2 NCH 2 -7,8-C 2 B 9 H 11 ]with metals such as nickel [16], iron [17], rhuthenium [17], titanium, zirconium, and hafnium [18,19]. In all cases, the intramolecular coordination of the dimethylamino group of the side substituent with the complexing metal was observed.…”