Kom-Bei Shiu

Structures and properties of molybdenum carbonyl complexes containing uninegative nitrogen-tripod ligands derived from heterocyclic compounds including 1-H-pyrazole and 1-H-1,2,4-triazole

The melt reaction between 1-H-1,2,4-triazole (HTz) and NaBPh4 affords Na(PhBTz3) while a similar process between HTz and KBH4 gives K(HBTz3). The uninegative L anion (L  PhBTz3 or HBTz3) reacts with [Mo(CO)6] to give [MoL(CO)3]-. Upon addition of electrophiles, [MoL(CO)2(η3-allyl)], [MoL (CO)2(NO)], [MoL(CO)3Br], and [MoL(CO)3I] are obtained. Two structures have been characterized by X-ray crystallography: [NEt4][Mo(HBPz3)(CO)3], orthorhombic, Pbca, a = 15.832(3), b = 15.799(4), c = 19.388(5) A, Z = 8, R = 0.043, Rw = 0.031 based on 2591 reflections with I > 3.0σ(I; [N(PPh3)2][Mo(HBTz 3)(CO)3], orthorhombic, Pbca, a = 17.815(3), b = 32.017(2), c = 15.331(3) A, Z = 8, R = 0.044, Rw = 0.061 based on 5743 reflections with I > 2.0σ(I). Although comparison of the averaged ν(CO) values reveals the increasing order of the electron donativity as HBBz3− < HBTz3−, PhBTz3− < HBPz′3−, < HBPzp3−, < HBPz′3−, neither structural features nor reactivit ies show an appreciable substituent effect (i.e. HBTz3− vs. HBPz3− and HBTz3− vs. PhBTz3−). Neither is the 5-methyl-group effect for nickel pseudohalides suggested by Trofimenko et al. supported strongly by the solid-state structures of [MoL′(CO)3]− (L′ = HBPz3−, HBPz′3−, or HBPz3−; Pz′ =3,5-dimethylpyrazol-1-yl; Pz = 3-methylpyrazol-1-yl).

Organotransition-metal complexes of multidentate ligands: IX. Synthesis and structure of hydridotris(benzotriazol-l-yl) borate derivatives of the group VI metal carbonyls☆

Potassium hydridotris(benzotriazol-1-yl)borate (KL) reacts with [M(CO)6] (M = Mo, W) to give K[ML(CO)3]. Upon addition of electrophiles, the potassium salts and also [Et4N][ML(CO)3] are converted readily into [ML(CO)3Br], [ML(CO)3I], [ML(C)2(NO)] and [ML(C)2(π-allyl)]. The solid-state structure of [MoL(CO)2-(π-allyl)] has been dtermined by X-ray diffraction, showing that the tridentate ligand (L−) contains more hindered BN bonds and that the metal corrdination occurs at the 2-position of the ring of the benzotirazolyl fragments of the ligand.

Organotransition-metal complexes of multidentate ligands: IV. Facile formation of a heat- and air-stable, 17-electron radical, Tp′ Mo(CO)3, and a sulfur-bridged dimer, [Tp′ Mo(CO)2]2S (Tp′ = hydridotris(3,5-dimethylpyrazol-1-yl)borate)

Abstract A heat- and air-stable, 17-electron (17e) radical, Tp′Mo(CO) 3 , and a sulfur- bridged dimer, [Tp′Mo(CO) 2 ] 2 S (Tp′ = hydridotris(3,5-dimethylpyrazol-1-yl)borate), are obtained from the reaction of Tp′Mo(CO)3 − with Cp 2 Fe + and from that of Tp′Mo(CO) 3 with sulfur, respectively. Success in obtaining the stable Tp′Mo(CO) 3 radical supports the concept that bulky multidentate ligands help to stabilize the 17e organometallic radicals whereas the facile formation of the dimer indicates that sulfurization of the 17e compounds can provide a facile route to metal-sulfur compounds.

Organotransition-metal complexes of multidentate ligands: XIV. Synthesis, structure and behavior in solution of some π-allyldicarbonyl complexes containing the pyrazole-derived bidentate ligands

The π-allyldicarbonyl complexes, [Mo(NN)(CO)2(π-allyl)Br], can be prepared either directly by the allyl bromination of [Mo(NN)(CO)4] (NN = H2CPz2, H2CPz′2, PhHCPz2, PhHCPz′2; Pz = pyrazol-1-yl; Pz′ = 3,5-dimethylpyrazol-1-yl) or [Mo(PhHCPz′2(CO)3] or indirectly by the reaction between [Mo(MeCN)2(CO)2(π-allyl)Br] and NN. The products obtained from [Mo(PhHCpz′2(CO)4] or from [Mo(PhHCPz′2(CO)3] are identical, which supports the mechanism proposed previously for the allyl bromination of substituted metal carbonyl complexes. The single-crystal structure of [Mo(PhHCPz′2)(CO)2(π-ally)Br] has been determined by X-ray diffraction, explaining why the central proton of the allyl group in this complex or [Mo(PhHCOz2(CO)2(π-allyl)Br] is more upfield relative to those of other similar complexes in the 1H NMR spectrum. Furthermore, the unique structural features help to confirm unequivocally the solvent-dependent coordination-stability of the pyrazole-derived bidentate ligands, NN, in [Mo(NN(CO)2(π-allyl)Br].

Synthesis and application of diphenylbis (3,5-dimethylpyrazol-1-yl)methane to form η2-arene complexes of molybdenum

Abstract The neutral nitrogen-bidentate ligand, diphenylbis(3,5-dimethylpyrazol-1-yl)methane, Ph 2 CPz′ 2 , can readily be obtained by the reaction of Ph 2 CCl 2 with excess HPz′ in a mixed-solvent system of toluene and triethylamine. It reacts with [Mo(CO) 6 ] in 1,2-dimethoxyethane to give the η 2 -arene complex, [Mo(Ph 2 CPz′ 2 )(CO) 3 ] ( 1 ). This η 2 -ligation appears to stabilize the coordination of Ph 2 CPz′ 2 in forming [Mo(Ph 2 CPz′ 2 )(CO) 2 (N 2 C 6 H 4 NO 2 - p )][BPh 4 ] ( 2 ) and [Mo(Ph 2 CPz′ 2 )(CO) 2 (N 2 Ph)] [BF 4 ] ( 3 ) from the reaction of 1 with the appropriate diazonium salt but the stabilization seems not strong enough when [Mo{P(OMe) 3 } 3 (CO) 3 ] is formed from the reaction of 1 with P(OMe) 3 . The solid-state structures of 1 and 3 have been determined by X-ray crystallography: 1 -CH 2 Cl 2 , monoclinic, P 2 1 / n , a = 11.814(3), b = 11.7929(12), c = 19.46 0(6) A, β = 95.605(24)°, V = 2698.2(11) A 3 , Z = 4, D calc = 1.530 g/cm 3 , R = 0.044, R w = 0.036 based on 3218 reflections with I > 2σ( I ); 2 ( 3 )-1/2 hexane-1/2 CH 3 OH-1/2 H 2 O-1 CH 2 Cl 2 , monoclinic, C 2/ c , a = 41.766(10), b = 20.518(4), c = 16.784(3) A, β = 101.871(18)°, V = 14076(5) A 3 , Z = 8, D calc = 1.457 g/cm 3 , R = 0.064, R w = 0.059 based on 5865 reflections with I > 2σ( I ). Two independent cations were found in the asymmetric unit of the crystals of 3 . The average distance between the Mo and the two η 2 -ligated carbon atoms is 2.574 A in 1 and 2.581 and 2.608 A in 3 . The unfavourable disposition of the η 2 -phenyl group with respect to the metal centre in 3 and the rigidity of the η 2 -arene ligation excludes the possibility of any appreciable agostic CH → Mo interaction.

Organotransition-metal complexes of multidentate ligands: XVI. On the nature of the sigma-donicity of the saturated nitrogen ligands; chelate-assisted weakening of the α-NH bond: synthesis, and spectral and structural study of [Mo(NN)(CO)4] (NN = saturated nitrogen bidentate ligands)☆

Abstract A series of complexes, [Mo(NN)(CO) 4 ] (NN = saturated nitrogen bidentate ligands), were prepared from [Mo(pip) 2 (CO) 4 ] (pip = piperidine) and NN in CH 2 Cl 2 at 40°C. The structure of [Mo{(PhCH 2 )HNCH 2 CH 2 NMe 2 }(CO) 4 ] was also determined by X-ray crystallography: space group Pbca, a = 14.895(7), b = 11.947(4), c = 19.189(8) A, V = 3415(2) A 3 , Z = 8, d calc = 1.503 g/cm 3 , R = 0.026 and R w = 0.026 based on 1646 reflections with I > 3.0 σ( I ). Both the spectral and structural data of the complexes indicate that the electron-density donating from the ligands comprises not only the lone electron pair of the nitrogen atom but the electron-density deprived from the neighboring groups by the highly electronegative nitrogen atom. These data also show that the more electron density of the α-NH bond relative to that of the α-NR bond (R = alkyl or aryl) is removed upon coordination of the nitrogen donor ligands, apparently explaining why a chelate-assisted oxidative addition of the NH bond occurs more readily than the NR bond through prior coordination and concurrent weakening of the NH bond.

One-Pot Conditional Self-Assembly of Multicopper Metallacycles

The self-assembly of supramolecular metallacycles via the coordination-driven directional bonding approach can be modified to produce some unexpected structural variations. The combination of a flexible ligand-capped dinuclear transition-metal acceptor like [Cu(2)(dppm)(2)(NCMe)(2)]X(2) (1X(2); dppm = Ph(2)PCH(2)PPh(2); X(-) = BF(4)(-), PF(6)(-), or BPh(4)(-)) with monodentate-bidentate donors like 2-, 3-, and 4-pyridylcarboxylates produced oligomeric compounds [{Cu(2)(dppm)(2)}(μ-(2-PyCO(2)))](2)X(2) (2X(2)), [{Cu(2)(dppm)(2)}(μ-(3-PyCO(2)))](2)X(2) (3X(2)), and [{Cu(2)(dppm)(2)}(μ-(4-PyCO(2)))](4)X(4) (4X(4)), respectively, as the thermodynamically stable products in one-pot reactions. However, the modified self-assembly is still subject to steric hindrance. The reaction of complex 1(BF(4))(2) with 6-Me-3-PyCO(2)H did not produce a polygonal dimeric metallacycle but a simple dinuclear complex, [Cu(2)(dppm)(2)(6-Me-3-PyCO(2))](BF(4)) (5(BF(4))). The crystal structures of complexes 2(PF(6))(2), 3(PF(6))(2), 4(BF(4))(4), and 5(BF(4)) were determined using X-ray diffraction.

Syntheses, X-ray structures, and reactions of ruthenium carbonyl complexes containing 1,1-dithiolates

Abstract Treatment of [Ru2(CO)4(MeCN)6][BF4]2 or [Ru2(CO)4(μ-O2CMe)2(MeCN)2] with uni-negative 1,1-dithiolate anions via potassium dimethyldithiocarbamate, sodium diethyldithiocarbamate, potassium tert-butylthioxanthate, and ammonium O,O′-diethylthiophosphate gives both monomeric and dimeric products of cis-[Ru(CO)2(η2-(SS))2] ((SS)−=Me2NCS2− (1), Et2NCS2− (2), tBuSCS2− (3), (EtO)2PS2− (4)) and [Ru(CO)(η2-(Me2NCS2))(μ,η2-Me2NCS2)]2 (5). The lightly stabilized MeCN ligands of [Ru2(CO)4(MeCN)6][BF4]2 are replaced more readily than the bound acetate ligands of [Ru2(CO)4(μ-O2CMe)2(MeCN)2] by thiolates to produce cis-[Ru(CO)2(η2-(SS))2] with less selectivity. Structures 1 and 5 were determined by X-ray crystallography. Although the two chelating dithiolates are cis to each other in 1, the dithiolates are trans to each other in each of the {Ru(CO)(η2-Me2NCS2)2} fragment of 5. The dimeric product 5 can be prepared alternatively from the decarbonylation reaction of 1 with a suitable amount of Me3NO in MeCN. However, the dimer [Ru(CO)(η2-Et2NCS2)(μ,η2-Et2NCS2)]2 (6), prepared from the reaction of 2 with Me3NO, has a structure different from 5. The spectral data of 6 probably indicate that the two chelating dithiolates are cis to each other in one {Ru(CO)(η2-Et2NCS2)2}fragment but trans in the other. Both 5 and 6 react readily at ambient temperature with benzyl isocyanide to yield cis-[Ru(CO)(CNCH2Ph)(η2-(SS))2] ((SS)=Me2NCS2− (7) and Et2NCS2− (8)). A dimerization pathway for cis-[Ru(CO)2(η2-(SS))2] via decabonylation and isomerization is proposed.

Organotransition-metal complexes of multidentate ligands: XVII. Synthesis and characterization of some η3-allylcarbonyl complexes of molybdenum containing dithiocarbamates as the uni-negative sulphur-bidentate ligands: crystal structure of [Mo(η2-S2CNEt2)(CO)-(η3-allyl){η2-bis(diphenylphosphino)methane}]☆

Complexes with a general formula of [Mo{η2-(S,S)}(CO)2(η3-allyl)] ((S,S)− = N,N-diethyldithiocarbamato or pyrrolidine-1-carbodithioato) have been prepared by one of three preparative routes: (1) reaction of the anion, [Mo{η2-(S,S)}(CO)4]− with allyl bromide; (2) reaction of [Mo(η2-H2CPz′2)(CO)2(η3-allyl)Br] (Pz′ = 3,5-dimethylpyrazol-1-yl) with (S,S)−; and (3) the substitution reaction between [Mo(MeCN)2(CO)2(η3-allyl)Br] and (S,S)−. The complexes are probably mononuclear and diamagnetic, based on the relevant spectral data. These complexes can react with pyridine to give [Mo{η2-(S,S)}(CO)2(η3-allyl)(py)] and with the phosphorus-bidentate ligand (P,P) to afford [Mo{η2-(S,S)}(CO)(η3-allyl){η2-(P,P)}] ((P,P) = bis(diphenylphosphino)methane (DPPM) or 1,2-bis(diphenylphosphino)ethane (DPPE)), which can also be prepared from the reaction of [Mo{η2-(P,P)}(CO)2(η3-allyl)Br] with (S,S)−. The new complexes were characterized by element analysis, IR and NMR spectroscopy. The crystal structure of [Mo(η2-S2CNEt2)(CO)(η3-allyl)(η2-DPPM)] was determined to confirm the di-hapticity of (S,S)− and of (P,P) in [Mo{η2-(S,S)}(CO)(η3-allyl){η2-(P,P)}]; space group P21/c, a = 16.028(4), b = 8.867(2), c = 23.459(4) A, β = 93.12(2)°, V = 3329.1(13) A3, Z = 4, Dcalc = 1.392 g/cm3, R = 0.067 and Rw = 0.076 on 3992 reflections with I > 3.0 δ(I).

Syntheses and structures of some coordinatively saturated and unsaturated diruthenium carbonyl complexes

Abstract Reaction of [Ru2(CO)4(μ-DPPM)2(μ-OAc)][PF6] (1) with Et3O+BF4− in MeCN produced coordinatively saturated [Ru2(μ-CO)2(μ-DPPM)2(MeCN)4][BF4]2 (2). Upon addition of an excess amount of a uni-negative anion X− to a solution of 2 in MeCN, a series of neutral, coordinatively unsaturated adducts [Ru2(μ-CO)2(μ-DPPM)2X2] (X−=Cl−, 3a; Br−, 3b; I−, 3c; SH−, 3d; Stol−, 3e; SiPr−, 3f) were readily formed. The reaction of 3a with trimethylamine N-oxide dihydrate produced two isomeric products of [Ru2(CO)2(μ-DPPM)2Cl2(μ-H)(μ-OH)] at a ratio of 4a–4b=2.25. Treatment of 3b and 3c with dimethyl acetylenedicarboxylate produced [Ru2(μ-CO)(μ-DPPM)2(μ-MeO2CCCCO2Me)X2] (X=Br, 5a; I, 5b), whereas treating of 3e and 3f with I2 yielded [Ru2(CO)2(μ-DPPM)2I2(μ-I)(μ-SR)] (R=tol, 6a; iPr, 6b). The structures of 2, 3a, 3c, 3e, 4b, 5a and 6a were determined by X-ray crystallography. The observed RuRu distances are compared and explained in terms of both electronic and steric effects by considering the multiple metalligand (MX) bonding interactions and Alvarezs structural parameters including MMX pyramidal angles and the XMMX torsional angles.