We report here the synthesis of new C,N-chelated chlorostannylenes and germylenes L(3) MCl (M=Sn(1), Ge (2)) and L(4) MCl (M=Sn(3), Ge (4)) containing sterically demanding C,N-chelating ligands L(3, 4) (L(3) =[2,4-di-tBu-6-(Et2 NCH2 )C6 H2 ](-) ; L(4) =[2,4-di-tBu-6-{(C6 H3 -2',6'-iPr2 )N=CH}C6 H2 ](-) ). Reductions of 1-4 yielded three-coordinate C,N-chelated distannynes and digermynes [L(3, 4) M]2 for the first time (5: L(3) , M=Sn, 6: L(3) , M=Ge, 7: L(4) , M=Sn, 8: L(4) , M=Ge). For comparison, the four-coordinate distannyne [L(5) Sn]2 (10) stabilized by N,C,N-chelate L(5) (L(5) =[2,6-{(C6 H3 -2',6'-Me2 )NCH}2 C6 H3 ](-) ) was prepared by the reduction of chlorostannylene L(5) SnCl (9). Hence, we highlight the role of donor-driven stabilization of tetrynes. Compounds 1-10 were characterized by means of elemental analysis, NMR spectroscopy, and in the case of 1, 2, 5-7, and 10, also by single-crystal X-ray diffraction analysis. The bonding situation in either three- or four-coordinate distannynes 5, 7, and 10 was evaluated by DFT calculations. DFT calculations were also used to compare the nature of the metal-metal bond in three-coordinate C,N-chelating distannyne [L(3) Sn]2 (5) and related digermyme [L(3) Ge]2 (6).

Our attempts to synthesize the N→Si intramolecularly coordinated organosilanes Ph2 L(1) SiH (1 a), PhL(1) SiH2 (2 a), Ph2 L(2) SiH (3 a), and PhL(2) SiH2 (4 a) containing a CH=N imine group (in which L(1) is the C,N-chelating ligand {2-[CH=N(C6 H3 -2,6-iPr2)]C6 H4}(-) and L(2) is {2-[CH=N(tBu)]C6 H4}(-)) yielded 1-[2,6-bis(diisopropyl)phenyl]-2,2-diphenyl-1-aza-silole (1), 1-[2,6-bis(diisopropyl)phenyl]-2-phenyl-2-hydrido-1-aza-silole (2), 1-tert-butyl-2,2-diphenyl-1-aza-silole (3), and 1-tert-butyl-2-phenyl-2-hydrido-1-aza-silole (4), respectively. Isolated organosilicon amides 1-4 are an outcome of the spontaneous hydrosilylation of the CH=N imine moiety induced by N→Si intramolecular coordination. Compounds 1-4 were characterized by NMR spectroscopy and X-ray diffraction analysis. The geometries of organosilanes 1 a-4 a and their corresponding hydrosilylated products 1-4 were optimized and fully characterized at the B3LYP/6-31++G(d,p) level of theory. The molecular structure determination of 1-3 suggested the presence of a Si-N double bond. Natural bond orbital (NBO) analysis, however, shows a very strong donor-acceptor interaction between the lone pair of the nitrogen atom and the formal empty p orbital on the silicon and therefore, the calculations show that the Si-N bond is highly polarized pointing to a predominantly zwitterionic Si(+) N(-) bond in 1-4. Since compounds 1-4 are hydrosilylated products of 1 a-4 a, the free energies (ΔG298), enthalpies (ΔH298), and entropies (ΔH298) were computed for the hydrosilylation reaction of 1 a-4 a with both B3LYP and B3LYP-D methods. On the basis of the very negative ΔG298 values, the hydrosilylation reaction is highly exergonic and compounds 1 a-4 a are spontaneously transformed into 1-4 in the absence of a catalyst.

The monomeric tin­(II) hydride L2(H)­Sn·W­(CO)5 (2), where L2 is 2-Et2NCH2-4,6-tBu2-C6H2, was easily transformed to the nonsymmetrical distannyne L1SnSnL2·W­(CO)5 (4), where L1 is 2,6-(Me2NCH2)2C6H3, by an amine elimination reaction with the tin­(II) amide L1SnNEt2 (3), without additional initiators such as N-bases or NHC carbenes. DFT calculations showed that the substitution of an SnH atom by an SnL1 fragment strongly affects the L2SnW­(CO)5 fragment, which accumulates a larger amount of electron density.

A set of neutral and ionic ruthenium arene trichlorostannyl complexes are reported herein. The tin(II) compounds L 1 SnCl {1; L 1 = [2-(CH 2 NEt 2 )-4,6-(tBu) 2 C 6 H 2 ] -} and [L 2 SnCl][SnCl 3 ] {2; L 2 = 2,6-[(CH 3 )C=N(C 6 H 3 -2,6-iPr 2 ) 2 ]C 5 H 3 N} showed a rather different reactivity towards the ruthenium complex [(η 6cymene)RuCl] 2 (η-Cl) 2 . As a consequence, the neutral complex [Ru(η 6 -cymene)(L 1 SnCl)Cl 2 ] (4) and the ionic compound [L 2 SnCl][Ru(η 6 -cymene)(SnCl 3 ) 2 Cl] (8) were isolated. The insertion reaction of 4 with SnCl 2 provided the neutral trimetallic ruthenium complex [Ru(η 6 -cymene)(L 1 SnCl)(SnCl 3 )Cl] (6). Analo- [a]

The synthesis of the C,N-chelated homoleptic organotetrylenes (L 1 ) 2 E (1, E = Sn; 2, E = Pb) and of the tungsten pentacarbonyl complex (L 1 ) 2 SnW(CO) 5 (3), containing the sterically demanding C,N-chelating ligand L2 )N C(Me)}C 6 H 2 (OCH 2 O)] − ) provided either the homoleptic stannylene (L 2 ) 2 Sn (4) or the C,Nchelated chlorostannylene (L 2 )SnCl ( 5). All attempts to convert the latter into the corresponding ditin compound [L 2 Sn] 2 failed, however, and resulted in the isolation of 4 and elemental tin. These attempts also provided the unprecedented complex [2-{(C 6 H 3 -2,6-Pr i 2 )NC(Me)}C 6 H 2 (OCH 2 O)][2-{(C 6 H 3 -2,6-Pr i 2 )NHCH(Me)}C 6 H 2 (OCH 2 O)]Sn (6).

Our attempts to synthesise N→M intramolecularly coordinated diorganometallic hydrides L2MH2 [M=Si (4), Ge (5), Sn (6)] containing the CH=N imine group (in which L is C,N-chelating ligand {2-[(2,6-iPr2C6H3)N=CH]C6 H4}(-)) yielded 1,1'-bis(2,6-diisopropylphenyl)-2,2'-spriobi[benzo[c][1,2]azasilole] (7), 1,1'-bis(2,6-diisopropylphenyl)-2,2'-spriobi[benzo[c][1,2]azagermole] (8) and C,N-chelated homoleptic stannylene L2Sn (10), respectively. Compounds 7 and 8 are an outcome of a spontaneous double hydrometallation of the two CH=N imine moieties induced by N→M intramolecular coordination (M=Si, Ge) in the absence of any catalyst. In contrast, the diorganotin hydride L2SnH2 (6) is redox-unstable and the reduction of the tin centre with the elimination of H2 provided the C,N-chelated homoleptic stannylene L2Sn (10). Compounds 7 and 8 were characterised by NMR spectroscopy and X-ray diffraction analysis. Because the proposed N→M intramolecularly coordinated diorganometallic hydrides L2MH2 [M=Si (4), Ge (5), Sn (6)] revealed two different types of reduction reactions, DFT calculations were performed to gain an insight into the structures and bonding of the non-isolable diorganometallic hydrides as well as the products of their subsequent reactions. Furthermore, the thermodynamic profiles of the different reaction pathways with respect to the central metal atom were also investigated.

α-iminopyridine ligands L1 (2-(CH=N(C6H2-2,4,6-Ph3))C5H4N), L2 (2-(CH=N(C6H2-2,4,6-tBu3))C5H4N) and L3 (1,2-(C5H4N-2-CH=N)2CH2CH2) differing by the steric demand of the substituent on the imine CH=N group and by a number of donating nitrogen atoms...

Studies are focused on the redox potentials of N→Sn coordinated distannnynes {L Sn} (L =1, L =2 and L =3, in which L is [C H -2,6-(Me NCH ) ] , L is [C H -2,4-tBu -6-(Et NCH )] and L is [C H -2,4-tBu -6-(DippN=CH)] ; Dipp=2,6-diisopropylphenyl), containing the tin atom in oxidation state +I. Distannynes 1-3 were used as ligands for transition metals, and complexes [{L Sn} ⋅Fe(CO) ] (4) and [{L Sn} ⋅Fe(CO) ] (5) were prepared. The set of N→Sn coordinated distannynes 1-5 was studied by cyclic voltammetry measurements and the oxidation potentials of tin atoms in 1-5 were determined. The redox potentials are influenced by either ligands L or Sn →Fe coordination. Oxidation reactions of 1-3 were also studied. The reaction of 2 with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) provided mixed organotin oxide {(L SnO)(L )Sn(μ-O)} (6) as a consequence of the instability of the expected {L Sn⋅TEMPO} complex. To support this proposed mechanism, the N→Ge coordinated digermyne {L Ge} (7) was prepared. The reaction of 7 with TEMPO provided the expected complex {L Ge⋅TEMPO} (8).