The paramagnetic rhenium complex [NEt4]2[Re(Br)5(NO)] (1) has been used to prepare a series of novel mononitrosyl hydride and dihydrogen rhenium complexes:  [Re(Br)2(NO)(η2-H2)(PR3)2] (R = iPr, 2a; Cy, 2b) and [Re(H)(BH4)(NO)(PR3)2] (R = iPr, 3a; Cy, 3b). The coordinated BH3 of the derivatives 3 can be replaced by the H2 or the NO ligand, thus leading to the tetrahydride and dinitrosyl species [Re(H)4(NO)L2] (R = iPr, 4a; Cy, 4b) or [Re(H)(NO)2(PR3)2] (R = iPr, 5a; Cy, 5b). While [Re(H)4(NO)(PPh3)2] does not seem to be stable, [Re(H)(NO)2(PPh3)2] (5c) has been obtained in a fashion similar to the preparation of 3a,b from the reaction of [Re(H)(BH4)(NO)(PPh3)2] and NOBF4. Detailed investigations of the reactions of 3a,b with NOBF4 have revealed that the compounds initially formed are the isolable BF3 adducts [Re(H)(NO)(NOBF3)(PR3)2] (R = iPr, 6a; Cy, 6b). The source of BF3 is the nitrosonium salt. Dissociation of BF3 from 6a,b takes place in donor solvents such as THF, affording the BF3-free compounds 5a,b, whereas in noncoordinating solvents such as toluene, benzene, or CH2Cl2 only the species 6a,b are observable. Apparently due to an unfavorable position of the dissociation equilibrium, the existence of the complex [Re(H)(NO)(NOBF3)(PPh3)2] could only be made plausible from dynamic NMR spectroscopic observations. Attempts to isolate it failed even from nonpolar solvents. X-ray diffraction studies have been carried out on the complexes [Re(Br)2(NO)(η2-H2)(PiPr3)2] (2a), [Re(H)(BH4)(NO)(PR3)2] (R = iPr, 3a; Ph, 3c), [Re(H)(NO)2(PiPr3)2] (5a), and [Re(H)(NO)(NOBF3)(PiPr3)2] (6a). The hydrogen atoms of the η2-H2 moiety of 2a could not be located in the X-ray diffraction study, but their most probable position in the molecule has been traced by an extensive search based on DFT calculations.

Geometry optimizations as well as frequency calculations for all the reactants, intermediates, products, and transition states were performed at the Density Functional level of theory with the Gaussian03 program package [1] using the hybrid mPW1PW91 functional which includes modified Perdew-Wang exchange and Perdew-Wang 91 correlation, C20 0.212(12) 0.104(7) 0.155(9) -0.102(7) -0.128( 9) 0.125(8) _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag Re1 N1 1.788(3) . yes Re1 N2 1.790(3) . yes Re1 C1 2.127(4) . yes Re1 P1 2.4583(10) . yes Re1 P2 2.4682(10) . yes P1 C6 1.854(4) . yes P1 C9 1.859(4) . yes P1 C3 1.877(4) . yes P2 C12 1.855(4) . yes P2 C15 1.865(5) . yes P2 C18 1.871(4) . yes C1 C2 1.182(6) . yes C2 H2 1.00(6) . yes N1 O1 1.208(4) . yes N2 O2 1.199(4) . yes C3 C5 1.523(5) . yes C3 C4 1.536(6) . yes C3 H3 1.0000 . yes C4 H4A 0.9800 . yes C4 H4B 0.9800 . yes C4 H4C 0.9800 . yes C5 H5A 0.9800 . yes C5 H5B 0.9800 . yes C5 H5C 0.9800 . yes C6 C7 1.530(7) . yes C6 C8 1.531(6) . yes C6 H6 1.0000 . yes C7 H7A 0.9800 . yes C7 H7B 0.9800 . yes C7 H7C 0.9800 . yes C8 H8A 0.9800 . yes C8 H8B 0.9800 . yes C8 H8C 0.9800 . yes C9 C10 1.531(5) . yes C9 C11 1.540(6) . yes C9 H9 1.0000 . yes C10 H10A 0.9800 . yes C10 H10B 0.9800 . yes C10 H10C 0.9800 . yes C11 H11A 0.9800 . yes C11 H11B 0.9800 . yes C11 H11C 0.9800 . yes C12 C14 1.515(8) . yes C12 C13 1.518(7) . yes C12 H12 1.0000 . yes C13 H13A 0.9800 . yes C13 H13B 0.9800 . yes C13 H13C 0.9800 . yes C14 H14A 0.9800 . yes C14 H14B 0.9800 . yes C14 H14C 0.9800 . yes C15 C16 1.532(7) . yes C15 C17 1.536(7) . yes C15 H15 1.0000 . yes C16 H16A 0.9800 . yes C16 H16B 0.9800 . yes C16 H16C 0.9800 . yes C17 H17A 0.9800 . yes C17 H17B 0.9800 . yes C17 H17C 0.9800 . yes C18 C20 1.476(9) . yes C18 C19 1.490(8) . yes C18 H18 1.0000 . yes C19 H19A 0.9800 . yes C19 H19B 0.9800 . yes C19 H19C 0.9800 . yes C20 H20A 0.9800 . yes C20 H20B 0.9800 . yes C20 H20C 0.9800 . yes loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag N1 Re1 N2 120.83(15) . . yes N1 Re1 C1 119.28(16) . . yes N2 Re1 C1 119.86(17) . . yes N1 Re1 P1 94.20(10) . . yes N2 Re1 P1 93.07(11) . . yes C1 Re1 P1 80.89(11) . . yes N1 Re1 P2 94.84(11) . . yes N2 Re1 P2 93.51(11) . . yes C1 Re1 P2 83.26(11) . . yes P1 Re1 P2 164.07(3) . . yes C6 P1 C9 106.8(2) . . yes C6 P1 C3 101.00(19) . . yes C9 P1 C3 104.06(17) . . yes C6 P1 Re1 115.01(14) . . yes C9 P1 Re1...

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The reactions of the nitrile-stabilized complex [Re3(μ-H)3(CO)11(MeCN)] (1) and of the unsaturated complex [Re4(μ-H)4(CO)12] (2) with 2-amino-6-methylpyridine (Hampy), 2-mercaptopyridine (Hmerpy), and 2-hydroxy-6-methylpyridine (Hhympy) have been studied. Complex 1 reacts slowly with Hampy and Hmerpy (refluxing toluene, 5−7 h) to give the binuclear derivatives [Re2(μ-ampy)2(CO)6] (3) and [Re2(μ-merpy)2(CO)6] (4), but no reaction is observed between 1 and Hhympy under analogous conditions. Complex 2 reacts with Hampy and Hmerpy (refluxing 1,2-dichloroethane, 10−20 min) to give the trinuclear anionic derivatives [Re3(μ-H)3(μ3-ampy)(CO)9]- (5) and [Re3(μ-H)3(μ3-merpy)(CO)9]- (6), which have been isolated as pyridinium ([H2ampy]5) or triethylammonium ([HNEt3]5, [HNEt3]6) salts. Under analogous conditions, the reaction of 2 with Hhympy gives an inseparable mixture of compounds. The X-ray structures of [HNEt3]5 and [HNEt3]6 confirm that the three edges of the clusters are spanned by hydride ligands, that the ampy (in 5) and merpy (in 6) are attached to the three Re atoms, and that there are hydrogen-bonding interactions in the solid state between some carbonyl oxygen atoms and the NH fragments of the ampy ligand (in 5) and the triethylammonium cation (in 5 and 6).

The syntheses of a series of bifunctional ligands, in which a cyclopentadienyl and a phosphine group are linked by either a CH2 or a C2H4 fragment (-C5H4(CH2) n PR2; n = 1, 2; R = Me, Ph), are reported, as is that of the related ligand, Li2[Me2C(C5H3CMe2PPh2)2], in which both substituted cyclopentadienyl rings are linked by the CMe2 group. The metallocene dichloride complexes Cp‘2MCl2 (M = Ti, Zr; Cp‘2 = 2C5H4(CH2) n PPh2 (n = 1, 2), Me2C((C5H3)C(Me)2PPh2)2) have also been prepared, and the X-ray structure of (η5-C5H4(CH2)2PPh2)2ZrCl2 (7) has been determined. This complex has the pendent phosphinoalkyl arms close to eclipsed on the two C5H4 groups and bisecting the ZrCl2 angle, but bent in opposite directions away from the ZrCl2 plane. Reaction of 7 and its Ti analogue with (COD)Mo(CO)4 yields the heterobinuclear complexes [(μ-η5:η1-C5H4(CH2)2PPh2)2MCl2Mo(CO)4] (M = Ti, Zr). Structure determinations of these bimetallic complexes show the expected cis arrangement of phosphine moieties at Mo, M−Mo separations of 6.895 Å (M = Ti) and 6.945 Å (M = Zr), and MCl2 moieties aimed at right angles to the M−Mo vectors.