Ming-Chu Cheng

Unusual tripodal ligands. Synthesis of 2,2-bis(diphenylphosphinomethyl)-1-phenylthiopropane and its group VI complexes

Abstract A hybrid tripodal ligand containing phosphorus and sulfur atoms, 2,2-bis(diphenylphosphinomethyl)-1-phenylthiopropane ( P 2 S ), was synthesized and its metal carbonyl complexes ( P 2 S )M(CO) 4 (M = Cr, Mo and W) were prepared. All synthetic intermediates and complexes have been characterized by spectroscopic methods and elemental analysis. The spectroscopic identification of complexes shows that the P 2 S ligand behaves as a bidentate ligand with two phosphorus atoms coordinating to the metal center. The structure was confirmed by a crystal structure study of ( P 2 S )Mo(CO) 4 , which revealed an octahedral coordination around the molybdenum atom, and two cis -coordinated phosphorus donors. The conformation of the six-membered chelate ring is a twisted-boat and the possible reasons for this conformational arrangement are discussed.

Tripodal ligands with mixed donors. Synthesis of 2-diphenylphosphinomethyl-2-phenylthiometryl-1-methoxypropane (PSO) and its transition metal complexes

Abstract A tripodal ligand containing phosphorus, sulphur and oxygen donors has been synthesized and its coordination in chromium(0), molybdenum(0), tungsten(0)

Structural characterization of tripodal phosphine complexes of transition metals. Examples of chair and twisted-boat conformations in six-membered chelate rings

Abstract Complexation of a “hybrid” tripodal ligand 2,2-bis(diphenylphosphinomethyl)-1-methoxypropane ( P 2 O ) with group VI carbonyls, nickel(II) and palladium(II) compounds has been studied. Thus P 2 O reacts with M(CO) 6 , NiCl 2 and PdCl 2 to give ( P 2 O )M(CO) 4 (M = Cr, Mo, W), ( P 2 O )NiCl 2 and ( P 2 O )PdCl 2 , respectively. All the complexes have been characterized by spectroscopy and elemental analysis, and the crystal structures of the complexes of ( P 2 O )Mo(CO) 4 ( 4b ), ( P 2 O )W(CO) 4 ( 4c ) and ( P 2 O )NiCl 2 ( 6 ) have been determined by X-ray diffraction. In all cases, the tripodal ligand behaves solely as a bidentate with two phosphorus donors coordinating to the metal centers. In the examination of the conformations of the six-membered chelate rings, it was found that both 4b and 4c were in the twisted-boat form; whereas 6 was in the chair form. The possible reasons for this conformational difference are discussed.

X-ray structure and spectroscopic properties of platinum(II) complexes of 1,1'-biisoquinoline

Abstract Three plantinum(II) complexes of biq (biq = 1,1′-biisoquinoline), [Pt(biq)Cl2], [Pt(biq)(py)3](ClO4)2 (py = pyridine) and [Pt(biq)(dapy)3](ClO4)2 [dapy = 4-(dimethylamino)pyridine] were prepared. Using 1H NMR spectroscopy and X-ray crystallography, biq in the former complex was found to be bidentate and in the two latter complexes monodentate. Dihedral angles between the two isoquinoline rings were determined to be 35.18° and 41.12° in [Pt(biq)Cl2] and 77.61° in [Pt(biq)(dapy)3](ClO4)2. The crystal structure of [Pt(biq)Cl2] is the first example of η2-μ1 biq complexes with a five-membered chelating ring. Weak intramolecular π-π stacking occurs in the solid phase of [Pt(biq)(dapy)3](ClO4)2.

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.

Structural characterization of[Ru3(CO)10{μ1-gh2-cis-1,2-bis (diphenylphosphino)ethene}]

Abstract The structure of [Ru 3 (CO) 10 (μ 1 -η 2 - c -dpp) = cis -1,2-bis(diphenylphosphino)ethene) has been determined by X-ray crystallography. The crystals are monoclinic, space group P 2 1 / n , with cell dimensions: a = 10.4590(17), b = 24.197(6), c = 14.500(4) A, β = 100.003 (22)° and Z = 4. This structure was refined to give R = 0.031 and R w = 0.028 using 5052 reflections with I > 2σ-( I ) in the range of 2 ≤ 2θ ≤ 50° (Mo Kα). The structure suggested previously to contain a 1,2-bridging c -dpp ligand is now found to contain the ligand in a 1,1-chelating geometry, which is also maintained in solution as indicated by the large downfield 31 P coordination shift. This five-membered chelate ring is not perpendicular as observed for a similar ring in [Ru 3 (CO) 10 (μ 1 -η 2 -bipy)] (bipy = 2,2′-bipyridine) but nearly coplanar with the Ru 3 plane. The synthesis and the structures of [M 3 (CO) 10 ,(LL)] and [M 2 (CO) 6 (LL)] (M  Fe, Ru or Os; LL = chelating c -dpp or bridging 1,2-bis(dimethylarsino)tetrafluorocyclobutene) are compared and a general reaction mechanism from [M 3 (CO) 12 ] to [M 3 (CO) 10 (LL)] and [M 2 (CO) 6 (LL)] is proposed.

Synthesis and structural characterization of some molybdenum carbonyl nitrosyl complexes of diethyldithiocarbamate

Abstract Ten complexes, M ′[ Mo(Et 2 NCS 2 )(CO) 2 (NO)X ] ( M ′ + = PPN + or Et 4 N + ; X − = NCS − ( 1 ), NO 3 − ( 2 ), N 3 − ( 3 ), Br − ( 4 ) or Cl − ( 5 ) and [ Mo(Et 2 NCS 2 )(CO)(NO)L 2 ] ( L 2 = py and CO ( 6 ); dppe ( 7 ); 2 PPh 3 ( 8 ); 2 P(OMe) 3 ( 10 )) , have been prepared. Crystal structures of 1, 3, 4, 6, 7, 8 and 10 were determined from single crystal X-ray data. The structures show clearly that the stronger electron-withdrawing NO, compared with CO, prefers the location trans to the better electron donor such as NCS− in 1, N3− in 3 and Br− in 4, unless some other apparent counteracting factors are also involved. The two bulky phosphine ligands are as expected trans to each other in 8 and 10 and a chelate dppe found in 7. Although the structure of 6 has NO trans to py, the spectral data of 6 (and 7), both in solution and in the solid state, reveal the presence of two different structures. Crystal data: 1, space group P2 1 /n, a = 9.879(2), b = 30.302(3), c = 14.858(4) A , β = 97.00(2)°, Z = 4 ; 3, space group P2 1 /c, a = 16.806(5), b = 16.128(3), c = 18.025(4) A , β = 116.94(2)°, Z = 4 ; 4, space group Ia, a = 14.773(8), b = 8.982(2), c = 17.748(5) A , β = 96.49(5)°, Z = 4 ; 6, space group P2 1 /c, a = 13.499(4), b = 10.033(5), c = 12.962(2) A , β = 91.66(2)°, Z = 4 ; 7, space group P2 1 /n, a = 11.634(3), b = 19.881(4), c = 15.225(4) A , β = 111.10(2)°, Z = 4 ; 8, space group P2 1 /n, a = 11.767(2), b = 18.851(4), c = 19.436(4) A , β = 107.12(2)°, Z = 4 ; 10, space group P2 1 /n, a = 8.732(2), b = 23.98(3), c = 11.303(3) A , β = 97.66(2)°, Z = 4 .

Homonuclear dirhenium complex bridged by CO2: Molecular structure of a rhenium dimer bridged by CO2 and a rhenium chloride complex

Abstract A mononuclear complex (CO) 3 ReL 2 Cl ( 1a ) (L = NH 2 CHMe 2 ) and a dinuclear CO 2 complex (CO) 3 L 2 Re(μ,η 1 ,η 1 -CO 2 )Re(CO) 4 L ( 2 ) are prepared from the reaction of a carbamoyl complex, (CO) 4 ReL(CONHCHMe 2 ) with H 2 O in CHCl 3 . The coupling of a proposed intermediate (CO) 4 LReCOOH with 1a is a viable process for the formation of complex 2 . The structures of (CO) 3 ReL 2 Cl ( 1b ) (L= NH 2 CH 2 CH=CH 2 ) and 2 have been established by X-ray diffraction.

Nitrogen-containing tripodal phosphine ligands

Abstract Two tripodal phosphine ligands, 2,2-bis(diphenylphosphinomethyl)-1-(diethylamino)propane (P2N) and 2,2-bis(diethylaminomethyl)-1-diphenylphosphinopropane (PN2) were synthesized. Palladium(II) and Platinum(II) complexes with these ligands were obtained from the reaction of PdCl2(CH3CN)2 and K2PtCl4 respectively. Complex (P2N)PtCl2 crystallizes in space group Pca21 with a = 21.983(5), b = 11.419(1), c = 14.179(3) A, and the structure was refined to R = 0.039 by using 2826 reflections.

Organotransition-metal complexes of multidentate ligands: XII. Crystal structure of allyl[N,N-bis(pyrazol-1-ylmethyl)aminomethane]dicarbonylchromium(II) hexafluorophosphate; the symmetric orientation of the η3-allyl group with respect to the pyrazole-derived tridentate ligand

Abstract The structure of [Cr(bpam)(CO) 2 (η 3 -allyl)]PF 6 (bpam  N,N -bis(pyrazol-1-ylmethyl)aminomethane) has been determined by X-ray diffraction methods. The crystals are orthorhombic, space group Pbca , with cell dimensions: a = 13.430(3), b = 18.530(4), c = 15.565(3) A and Z = 8. This structure was refined to give R = 0.055 and R w = 0.044 using 1720 reflections with I > 2σ( I ) in the range of 2 ≤ 2θ ≤ 50° (Mo- K α ). As expected previously from NMR studies, the compound named in the title is now confirmed to contain, in the solid state, an η 3 -allyl group symmetric with respect to the nitrogen tridentate ligand, bpam. This symmetric structure is also compared with the unsymmetric structure reported for [Mo(bpam)CO) 2 (η 3 -allyl)]PF 6 and a new five-stage process is proposed for the stereochemically nonrigid behaviour of this compound and of its tungsten analogue in solution at room temperature.