Transition Metal Coordinated Al(X)L₂and Ga(X)L₂Fragments

Abstract

Carbonylmetalate dianions react in thf with the group 13 chlorides X m ECl3 - m (E = Al, Ga; X = Cl, Me, Et, iBu; m = 0, 1) to yield the monoanionic species [(CO) n M−EX m Cl2 - m ]- (M = Fe, Cr, Mo, W; n = 4, 5) as the primary products which could be isolated as solvent free salts after exchange with a non coordinating cation. After addition of a chelating Lewis base, e.g., tmeda, dme, and solvent exchange with dichloromethane the primary products undergo a second salt elimination reaction, yielding the neutral intermetallic systems (CO) n M−Ga[X(L)2] (M = Cr, Mo, W, Fe; n = 4, 5; X = Cl, Me, Et; L2 = tmeda, dme, bipy, tBu-dab, thf2) (1−14) and (CO)5M-Al[X(L)2] (M = Cr, Mo, W; X = Cl, Et, iBu; L2 = tmeda, tmpda) (15−20, 23, 24). The chloro derivatives can be converted to the corresponding hydrido or tetrahydridoboranato species which is exemplarily shown by compounds 21 and 22. In the case of R2GaCl (R = Me, Et; 2 equiv) as starting compounds a ligand exchange reaction, generating GaR3, occurs, before the second salt elimination takes place. The new intermetallic systems were characterized by means of elemental analysis and IR, Raman, NMR, and mass spectroscopy. The complexes (CO)5Cr−Ga[Cl(tmeda)] (2), (CO)5W−Al[Et(tmeda)] (20), and (CO)5W−Al[Cl(tmpda)] (23) are also characterized by single-crystal X-ray diffraction. Compounds 2 and 20 crystallize in the monoclinic space group P21/n, Z = 4. 2: a = 9.059(4) Å, b = 16.084(7) Å, c = 11.835(6) Å, β = 80.6(1)°, V = 1701(1) Å3, and R = 0.037 (R w = 0.118). 20: a = 8.606(2) Å, b = 16.463(6) Å, c = 12.469(4) Å, β = 93.88(2)°, V = 1762(6) Å3, and R = 0.027 (R w = 0.065). Complex 23 crystallizes in the orthorhombic space group Pccn, a = 23.990(6) Å, b = 9.044(3) Å, c = 15.871(4) Å, V = 3445(1) Å3, and R = 0.044 (R w = 0.088). Ab initio quantum chemical calculations at the MP2 level of theory of the model complexes (CO)5W−E[Cl(NH3)2] (E = B, Al, Ga, In, Tl), (CO)5W−Al[H(NH3)2], (CO)5W−AlH, and (CO)5W−AlCl are reported. The group-13 fragments E(R)L2 behave as strong σ-donors with significant acceptor capabilities. The W−E bonds are strong semipolar covalent bonds with large ionic contributions (D e(calc) between 70 and 120 kcal/mol). Only the W−Tl bond is comparatively weak (D e(calc) = 48 kcal/mol).

Coordination Chemistry of Aluminum, Gallium, and Indium at Transition Metals

“…In the lowest electronically excited state an efficient dissociation of the WÀN bond of [(CO) 5 W(py)] takes place. [148] In accordance with the calculated dissociation energies and correcting an earlier note [80] it must be emphasized that the WÀAl bonds do not dissociate thermally. A displacement by other ligands (CO, isocyanides, phosphanes) and a splitting of the fragments EXL 2 can probably only be achieved by using photochemistry.…”

“…[140] In the light of a fast developing chemistry of lowcoordinate centers E, some remarks on the MÀE bonding conditions and the substituent effects seem to be warranted. Quantum chemical DFT calculations have meanwhile been carried out by several groups on the model complexes [(CO) 4 FeÀAlCp], [79,83] [(CO) 5 CrAlCp], [172] [(CO) 4 FeÀGa(h 1 -C 6 H 5 )], [136,140] [(CO) 5 MÀEX], [(CO) 5 MÀEXL 2 ] (E B, Al, Ga, In, Tl; X H, Cl; L NH 3 ) [80] and [L'(CO) 3 Co-GaX 2 L] (X H, Cl; L' PH 3 ). [141] All model complexes were compared to closely related examples, the molecular structures of which were known.…”

“…[80] Let us first turn to the donor-stabilized species (type I). The optimized C S -symmetrical structures of the model complexes agree very well with the X-ray crystallographic data.…”

“…Results of the NBO analysis at the MP2/II-level. [80] was preferred over a covalent view in the sense of complex stabilization of the Cp*Al fragment. Consequently, the carbenoid character of the {Cp*Al} unit does not exist in the complex, it is rather an Al III center.…”

Chromium, Iron and Cobalt Carbonyl Complexes with Gallium Halides: Synthesis and Structures

“…[(CO) 4 [34] [(CO) 4 [8] [Cp(CO) 2 [36] [Cp(CO) 2 FeGaCl 2 (thf)] 231.7(1) 1990 (s), 1995 (s) [37] [Cp(CO) 2 FeGa(R N )(BH 4 )] 237.5 1975 (vs), 1920 (vs) [38] [Fe 2 (CO) 6 {μ-GaSi(SiMe 3 ) 3 } 3 ] 238.18 1964 (s), 1921 (s) [9] [Fe 2 (CO) 6 [40] [{Cp(CO) 2 [30,31] [{Cp(CO) 2 [30,31] [{Cp(CO) 2 [42] [(CO) 4 FeGa(η 1 -C 2 H 3 )(thf)] 2 251.0 - [43] [(CO) 5 CrGaCp*] 240.46 (7) 2052 (s), 982 (s), 1918 (vs), 902 (vs) [8] [(CO) 5 CrGaC 4 H 2 (tBu) 2 P] 239.0(1) 2022 (m), 1936 (sh), 1870 (s) [44] [(CO) 5 CrGaCl(tmeda)] 245.6(1) 2033 (s), 1947 (s), 1900 (vs) [45] [(CO) 5 CrGaCH 3 (tmeda)] 247.9(1) 2013 (vs), 1920 (s), 1844 (vs) [46] [(CO) 5 [45] [(CO) 6 Co 2 (GaCp*) 2 ] 238. 8 2023, 1989, 1953, 1948 [8] [(CO) 6 [12] subhalides with the corresponding metallated silanides.…”