Chemistry of group 5 metallaboranes with heterocyclic thiol ligands: a combined experimental and theoretical study.

Thermolysis of [(Cp*Nb)2(B2H6)2], 1b (Cp* = η5-C5Me5), with 2-mercaptobenzothiazole, C6H4NSCSH (MBT), and 2-mercaptobenzoxazole, C6H4NOCSH (MBO), yielded hydrogen substituted compounds 2 and 3 with a general formula [(Cp*Nb)2(B2H6)(B2H5L)] (2: L = C6H4NSCS and 3: L = C6H4NOCS). A similar reaction of 1b with Ph2Se2 yielded the monosubstituted derivative [(Cp*Nb)2(B2H6){B2H5(PhSe)}], 4. All further efforts towards persubstitution of 1b under various drastic conditions were unfruitful. In parallel, in an effort to find a better synthetic route to the known Ta-aziridine complex [Cp*TaBH(C7H4NS2)CH2S2NC6H4], Cp*TaCl4 was treated with a 2-mercaptobenzothiazolyl-based borate ligand Na[H2B(C6H4NSCS)2]. Surprisingly, the reaction led to the formation of the half-sandwich trichloroaryltantalum(v) complex [Cp*TaCl3{κ2-N,S-C6H4NSCS}], 5, containing a heterocyclic thiol ligand. Using an alternative method complex 5 was isolated in good yield when Cp*TaCl4 was treated with the potassium salt of 2-mercaptobenzothiazole K[C6H4NSCS]. All the compounds were characterized by 1H, 11B{1H}, and 13C{1H} NMR spectroscopy, and their structures were unequivocally established by crystallographic analysis.

Cyclometallation of a germylene ligand by concerted metalation-deprotonation of a methyl group.

The reaction of [CH{(CMe)(2,6-iPr2C6H3N)}2]GeCl with LiN(SiMe3)2 was previously reported, which led to the formation of a hetero-fulvene type germylene, [CH{(CMe)(C[double bond, length as m-dash]CH2)(2,6-iPr2C6H3N)}2]Ge through the deprotonation of the C-H bond from the methyl substituents. In this paper, we attempted the analogous reaction with (Dipp)NCMeCHCOMeGeCl using LiN(SiMe3)2 which gave rise to a metathesis product, (Dipp)NCMeCHCOMeGeN(SiMe3)2 (2). However, the reactions of 2 with [M2Cl2(µ-Cl)2(η5-Cp*)2] (M = Rh and Ir) resulted in cyclometallated Rh and Ir complexes through the activation of the C-H bond from the germylene ligand. The complexes were characterized by single crystal X-ray analysis, which authenticated the presence of Ge-Rh and Ge-Ir bonds. DFT studies have been performed to understand the mechanism.

Synthesis, Structure, Bonding, and Reactivity of Metal Complexes Comprising Diborane(4) and Diborene(2): [{Cp*Mo(CO)2 }2 {µ-η2 :η2 -B2 H4 }] and [{Cp*M(CO)2 }2 B2 H2 M(CO)4 ], M=Mo,W.

The reaction of [(Cp*Mo)2 (µ-Cl)2 B2 H6 ] (1) with CO at room temperature led to the formation of the highly fluxional species [{Cp*Mo(CO)2 }2 {µ-η2 :η2 -B2 H4 }] (2). Compound 2, to the best of our knowledge, is the first example of a bimetallic diborane(4) conforming to a singly bridged Cs structure. Theoretical studies show that 2 mimics the Cotton dimolybdenum-alkyne complex [{CpMo(CO)2 }2 C2 H2 ]. In an attempt to replace two hydrogen atoms of diborane(4) in 2 with a 2e [W(CO)4 ] fragment, [{Cp*Mo(CO)2 }2 B2 H2 W(CO)4 ] (3) was isolated upon treatment with [W(CO)5 ⋅thf]. Compound 3 shows the intriguing presence of [B2 H2 ] with a short B-B length of 1.624(4) Å. We isolated the tungsten analogues of 3, [{Cp*W(CO)2 }2 B2 H2 W(CO)4 ] (4) and [{Cp*W(CO)2 }2 B2 H2 Mo(CO)4 ] (5), which provided direct proof of the existence of the tungsten analogue of 2.

Phenothiazinyl Boranes: A New Class of AIE Luminogens with Mega Stokes Shift, Mechanochromism, and Mechanoluminescence.

Phenothiazines with a dimesityl boron moiety, a new class of aminoboranes with B-N linkage, were synthesized. These aminoboranes exhibited interesting photophysical behavior including aggregation-induced emission (AIE), mechanochromism (MC), mechanoluminescence (ML), and a mega Stokes shift (up to 312 nm in hexane). The solid-state emission of the aminoboranes could be switched reversibly by grinding-fuming processes. Furthermore, the phenothiazine derivative with a bromo and an arylborane group at 3- and 7-positions exhibited bright mechanoluminescence.

Reactivity of [M2 (µ-Cl)2 (cod)2 ] (M=Ir, Rh) and [Ru(Cl)2 (cod)(CH3 CN)2 ] with Na[H2 B(bt)2 ]: Formation of Agostic versus Borate Complexes.

Treatment of [M2 (µ-Cl)2 (cod)2 ] (M=Ir and Rh) with Na[H2 B(bt)2 ] (cod=1,5-cyclooctadiene and bt=2-mercaptobenzothiazolyl) at low temperature led to the formation of dimetallaheterocycles [(Mcod)2 (bt)2 ], 1 and 2 (1: M=Ir and 2: M=Rh) and a borate complex [Rh(cod){κ2 -S,S'-H2 B(bt)2 }], 3. Compounds 1 and 2 are structurally characterized metal analogues of 1,5-cyclooctadiene. Metal-metal bond distances of 3.6195(9) Šin 1 and 3.6749(9) Šin 2 are too long to consider as bonding. In an attempt to generate the Ru analogue of 1 and 2, that is [(Rucod)2 (bt)2 ], we have carried out the reaction of [Ru(Cl)2 (cod)(CH3 CN)2 ] with Na[H2 B(bt)2 ]. Interestingly, the reaction yielded agostic complexes [Ru(cod)L{κ3 -H,S,S'-H2 B(bt)2 }], 4 and 5 (4: L=Cl; 5: L=C7 H4 NS2 ). One of the key differences between 4 and 5 is the presence of different ancillary ligands at the metal center. The natural bond orbital (NBO) analysis of 1 and 2 shows that there is four lone pairs of electrons on each metal center with a significant amount of d character. Furthermore, the electronic structures and the bonding of these complexes have been established on the ground of quantum-chemical calculations. All of the new compounds were characterized by IR, 1 H, 11 B, 13 C NMR spectroscopy, and X-ray crystallographic analysis.

All-metallagermoxane with an adamantanoid cage structure: [(Cp*Ru(CO)2Ge)4(µ-O)6] (Cp* = η(5)-C5Me5).

In an attempt to synthesize a zero valent germanium compound, we have carried out the reaction of [(Cp*RuCO)(GeCl2)]2, 1 with potassium metal that led to the formation of a metallagermoxane [(Cp*Ru(CO)2Ge)4(µ-O)6], 2. Compound 2 is the first example of a tetrametallagermoxane with an exo-{Cp*Ru(CO)2} fragment. DFT calculations were used to examine the key intermediates associated with the formation of 2.

N-Benzoylbenzamidinate complexes of aluminium: highly efficient initiators for the ring-opening polymerization of ε-caprolactone.

A series of aluminium complexes supported by amidinate-based N,O-chelate ligands are synthesized and characterized. While complexes [L(Dipp)AlMe2] () and [L(Ph)AlMe2] () are prepared by treating N-benzoyl-N'-2,6-diisopropylphenylbenzamidine (L(Dipp)H) and N-benzoyl-N'-phenylbenzamidine (L(Ph)H) with a slight excess of 1 equiv. of AlMe3, complexes [(L(Dipp))2AlMe] () and [(L(Ph))3Al] () can be obtained using the ligands and AlMe3 in 2 : 1 and 3 : 1 molar ratios respectively. Complexes have been characterized by (1)H/(13)C NMR spectroscopy and elemental analysis. The molecular structures of complexes , and have also been determined by single crystal X-ray diffraction technique. , and are highly active initiators for the ring opening polymerization (ROP) of ε-caprolactone and produce polycaprolactone with very high molecular weight and narrow molecular weight distribution. These complexes are also active toward the ROP of cyclohexene oxide.