Reactions of a four-membered Al−N ring, [(Dipp)HNAlMe2]2 (2; Dipp =2,6-diisopropylphenyl), with the aromatic nitriles PhCN, TbpCN (Tbp =4-tert-butylphenyl), DmpCN (Dmp = 2,6-dimethylphenyl), DepCN (DepCN = 2,6-diethylphenyl), and DippCN are reported. 2 reacts with PhCN to give a 1:2 insertion product, the tetrameric aluminum amidinate 3, whereas with TbpCN it gives the 1:1 insertion products 4−6. Under similar conditions, DmpCN, DepCN, and DippCN do not undergo insertion but form simple adducts of alumazene (1), 7a−c and 8a−c (2:1 and 1:1 nitrile/alumazene), in which the nitriles coordinate to Al. Compounds 3−6 and 7a−c have been structurally characterized. 3 is comprised of four four-membered aluminum amidinate rings. 5 features a core made of three Al2N2 and two AlCN2 four-membered rings fused together. The structures of 4 and 6 consist of a dimer of a six-membered Al2CN3 framework. A high-yield synthesis of 3 from N-(Dipp)benzamidine and AlMe3 has also been reported.

Reactions of cyclopentadienyl transition-metal halide complexes [Cp*Mo(CO)Cl], 1, and [CpFe(CO)I], 2, (Cp = CH; Cp* = η-CMe) with borate ligands are reported. Treatment of 1 with [NaBt] (Bt = dihydrobis(2-mercapto-benzothiazolyl)borate) in toluene yielded [Cp*Mo(CO)(CHSN)], 3, and [Cp*Mo(CO)(η-CHCH)], 4, with a selective binding of toluene through C-H activation followed by orthometallation. Note that compound 4 is a structurally characterized toluene-activated molecule in which the metal is in η-coordination mode. Under similar reaction conditions, [NaPy] (Py = dihydrobis(2-mercaptopyridyl)borate) produced only the mercaptopyridyl molybdenum complex [Cp*Mo(CO)(CHSN)], 5, in good yield. On the other hand, when compound 2 was treated individually with [NaBt] (Bt = trihydro(2-mercapto-benzothiazolyl)borate) and [NaPy] in THF, formation of the η-coordinated complexes [CpFe(CO)(CHSN)], 6, and [CpFe(CO)(CHSN)], 7, was observed. The solid-state molecular structures of compounds 3, 4, 6, and 7 have been established by single-crystal X-ray crystallographic analyses.

The complexes [Ag{κ 3 -S,SЈ,H-H 2 B(mbz) 2 }(PR 3 )] x , (1: x = 2, R = Ph; 2: x = 1, R = Cy) (mbz = 2-mercaptobenzothiazolyl) and amidine based dihydro(2-mercaptobenzo-thiazolyl) borates, [HN=C(Ph)-NH(R)-H 2 B(mbz)] (3: R = 2,6-diisopropylphenyl and 4: R = Ph) were synthesized and characterized by various spectroscopic methods and single-crystal X-ray crystallography. Complex [Ag{κ 3 -S,SЈ,H-H 2 B(mbz) 2 }(PPh 3 )] 2 (1) has a dimeric structure in its crystalline state, in which central silver(I) atoms adopt a * Prof. Dr. S. Ghosh E-Mail: sghosh@iitm.ac.in [a] 588 distorted trigonal bipyramid arrangement. In contrast, complex [Ag{κ 3 -S,SЈ,H-H 2 B(mbz) 2 }(PCy 3 )] (2) has a monomeric structure in its crystalline state, in which the central silver(I) atoms adopt a distorted trigonal planar arrangement. Infrared spectroscopy was utilized as a tool for investigating the presence of M···H-B interactions. In addition, density functional theory (DFT) calculations were used to analyse the B-H···[M] bonding interaction in the metal borate complexes. Crystal Data for 1: C 64 H 50 B 2 Ag 2 S 8 N 4 P 2 , M r = 1430.86, triclinic, P1, a = 11.5839(8) Å, b = 11.6836(8) Å, c = 12.2097(9) Å, α = 76.233(6)°, β = 80.921(6)°, γ = 73.582(6)°, V = 1532.3(2) Å 3 , Z = 1, ρ calcd. = 1.551 mg·m -3 , μ = 1.009 mm -1 , F(000) = 724, R 1 = 0.0507, wR 2 = 0.0653, 7252 independent reflections [2θ Յ 58.48°] and 378 parameters, Goodness-of-fit on F 2 = 1.029. Crystal Data for 2: C 32 H 43 BAgS 4 N 2 P, M r = 733.57, monoclinic, P2 1 /n, a = 9.7847(3) Å, b = 25.6692(6) Å, c = 13.9303(4) Å, α = 90°, β = 99.334(3)°, γ = 90°, V = 3452.48(17) Å 3 , Z = 4, ρ calcd. = 1.411 mg·m -3 , μ = 0.897 mm -1 , F(000) = 1520, R 1 = 0.0574, wR 2 = 0.0979, 8391 independent reflections [2θ Յ 58.066°] and 378 parameters, Goodness-of-fit on F 2 = 1.034. Crystal Data for 3: C 26 H 30 BS 2 N 3 , M r = 457.44, monoclinic, P2 1 /n, a = 12.8305(5) Å, b = 14.3085(4) Å, c = 13.9844(4) Å, α = 90°, β = 98.940(3)°, γ = 90°, V = 2536.14(14) Å 3 , Z = 4, ρ calcd. = 1.198 mg·m -3 , μ = 0.228 mm -1 , F(000) = 968, R 1 = 0.1074, wR 2 = 0.1880, 8484 independent reflections [2θ Յ 64.764°] and 310 parameters, Goodness-of-fit on F 2 = 1.106. Crystal Data for 4: C 20 H 18 BS 2 N 3 , M r = 585.61, monoclinic, P2 1 /c, a = 9.9343(10) Å, b = 14.2927(17) Å, c = 23.194(3) Å, α = 90°, β = 92.483(4)°, γ = 90°, V = 3290.2(6) Å 3 , Z = 4, ρ calcd. = 1.182 mg·m -3 , μ = 0.192 mm -593 independent reflections [2θ Յ 50.998°] and 447 parameters, Goodness-of-fit on F 2 = 1.032.Supporting Information (see footnote on the first page of this article): Detailed information about the packing diagram of compounds 3 and 4, spectroscopic data and DFT-computed results for compounds 1, 2, 3 and 4 have been provided in the supporting information.

Reactions of N-monosubstituted amidines of the formula HNC(R)–NH(R′) (R = Ph, 4-tert-butylphenyl, Me; R′ = 2,6-diisopropylphenyl, Ph) with AlMe3 and AlMeCl2 are reported. All the N-(Dipp)amidines (Dipp = 2,6-diisopropylphenyl) react with AlMe3 in a 1:1 ratio to yield tetrameric aluminum amidinates (1, 2, and 3) in good yields. In these compounds, the amidinate ligand chelates to Al while bridging to another Al. However, when N-phenylamidines are employed, tetracyclic (4–9) and pentacyclic (10) Al–N–C heterocycles are formed. In the case of N-phenylbenzamidine, formation of a hexacyclic Al–N–C heterocycle (11) is observed when a slight excess of AlMe3 (1:1.2 equiv) is used. In these compounds, the amidinate ligand coordinates to Al atoms in a bridging fashion. Further, N-(Dipp)acetamidine and N-(Dipp)benzamidine are also treated with AlMeCl2. Whereas N-(Dipp)acetamidine affords an ionic 15-membered aluminum amidinate chain (12), N-(Dipp)benzamidine gives a bicyclic heterocycle (13) and the AlCl3 adduct of N-(Dipp)benzamidine (14). However, from a reaction between N-phenylbenzamidine and AlMeCl2, only the AlCl3 adduct, 15, was isolated. Compounds 3, 4, 6, 8, and 10–15 have been structurally characterized.

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