Rhenium Polyhydride Complexes Containing PhP(CH₂CH₂CH₂PCy₂)₂(Cyttp):  Protonation, Insertion, and Ligand Substitution Reactions of ReH₅(Cyttp) and Structural Characterization of ReH₅(Cyttp) and [ReH₄(η²-H₂)(Cyttp)]SbF₆

Abstract

Several new polyhydride complexes of rhenium containing the tridentate phosphine PhP(CH(2)CH(2)CH(2)PCy(2))(2) (Cyttp) were synthesized and characterized by (1)H and (31)P{(1)H} NMR and IR spectroscopy. The solid state structure of the previously reported ReH(5)(Cyttp) (1) was determined by X-ray crystallography. 1 crystallizes in the space group P2(1)/m with the following unit cell parameters: a = 8.582(2) Å, b = 19.690(2) Å, c = 10.800(2) Å, beta = 95.57(1) degrees, and Z = 2. The molecule adopts a classical polyhydride, triangulated dodecahedral structure, with the three phosphorus atoms and one hydrogen atom occupying the B sites, and the remaining hydrogen atoms occupying the A sites. 1 is protonated by HSbF(6) (or HBF(4)) to yield [ReH(4)(eta(2)-H(2))(Cyttp)]SbF(6) (3), which was shown by X-ray diffraction techniques (space group P&onemacr;, unit cell parameters: a = 9.874(2) Å, b = 14.242(4) Å, c = 16.198(2) Å, alpha = 99.12(2) degrees, beta = 98.85(2) degrees, gamma = 109.42(2) degrees, and Z = 2) to contain a nonclassical polyhydride cation with a triangulated dodecahedral structure in the solid. The same structure is suggested in solution by (1)H NMR data (including T(1) measurements). 3 is inert to loss of H(2) and is unaffected by CO, t-BuNC, and P(OMe)(3) at room temperature. In contrast, 1 reacts with a variety of reagents to afford classical tetrahydride complexes which are thought also to possess a triangulated dodecahedral structure, with the hydrogens in the A sites, from spectroscopic evidence. Accordingly, CS(2), p-O(2)NC(6)H(4)NCS, and EtOC(O)NCS (X=C=S) insert into an Re-H bond to yield ReH(4)(SCH=X)(Cyttp) (5-7, respectively). MeI cleaves one Re-H bond to afford ReH(4)I(Cyttp) (8), and [C(7)H(7)]BF(4) abstracts hydride in the presence of MeCN, t-BuNC, CyNC, or P(OMe)(3) (L) to give [ReH(4)L(Cyttp)]BF(4) (9-12, respectively). A related pentahydride, ReH(5)(ttp) (2, ttp = PhP(CH(2)CH(2)CH(2)PPh(2))(2)), also reacts with HSbF(6) to yield [ReH(6)(ttp)]SbF(6) (4), which appears to be a nonclassical polyhydride in solution by T(1) measurements.

Rhenium(VII) polyhydrides supported by chelatingbis-phosphine ligands: DPEphos, xantphos and biphep

“…The weak Re-H stretches in the infra-red spectra for these complexes are all found in the region 1900-2000 cm À1 , well within the range observed for classical polyhydride systems [20]. A correlation between bite-angle and metal-hydride stretch was not readily apparent.…”

“…Since hydrides are intermediates in a number of catalytic reactions, the synthesis and characterization of such complexes can lead to design and development of more efficient catalysts. A thorough understanding of the properties of hydride complexes [18][19][20][21][22] [23]. Hydride complexes can be classified into three structural types, depending upon the strength of the H-H and M-H interactions: non-classical, stretched, and classical (figure 1) [24].…”

Mechanistic studies on reaction of [ReH4(η2-H2)(Cyttp)]+ with ketones to give the hydrido-oxo complex [ReH2(O)(Cyttp)]+ (Cyttp=PhP(CH2CH2CH2PCy2)2)

“…Scheme 2). These patterns and values of 2 J PcPw are consistent with a meridional arrangement of the Cyttp ligand and the presence of a weak ligand opposite P C [15]. A similar 31 P{ 1 H} NMR spectrum was obtained for a heated solution of 1(OTf) in THF, except that the species with the signals at d 19.3 and 18.5 ppm now occurs in significantly higher concentration.…”

“…A complex of the type [ReH 4 (solvent)(Cyttp)]OTf could be isolated pure when solvent = MeCN (Scheme 3), a better ligand than THF. This previously reported compound [15] was characterized spectroscopically as [ReH 4 (MeCN)(Cyttp)]OTf (3(OTf)), with its 19 F{ 1 H} resonance at d À77.3 ppm implicating ionic triflate [16]. Complex 4 was prepared as shown in Scheme 4 and was characterized by 31 P{ 1 H} and 19 F{ 1 H} NMR spectroscopy and elemental analysis (Section 2.3.2).…”

Technetium & Rhenium: Inorganic & Coordination Chemistry

“…In Tcdiphosphonate radiopharmaceuticals, used as bone imaging agents, the metal is believed to be in the +4 oxidation states. 81 The +1 oxidation state in the homoleptic isocyanide complex (22) is expected to be advantageous in terms of the kinetic inertness associated to its low-spin d 6 90 A similar { 188 Re(CO) 3 } + -based chemistry has also been developed. 90 The Tc-nitrido {Tc V ≡N} 2+ core, with the strong π -electron donor nitride ligand, which effectively stabilizes the Tc V oxidation state, is isoelectronic with {Tc V =O} 3+ and is known to form complexes with a variety of chelating ligands, 85 and [ 99m TcN(noet) 2 ] (24) constitutes a new myocardial imaging agent.…”