137916-12-2

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Bridge vs. Terminal Protonation of Isostructural Mo-Pt and W-Pt Heterobimetallic Compounds

Protonation of the complexes (cp=cyclopentadienyl) exhibits an M-dependent site selectivity, with protonation occurring at the metal-metal bond for M=Mo to give (1+) whilst for M=W protonation occurs directly at the tungsten to give a terminal hydrido cation .

Electrophilic additions to phosphido-bridged palladium- and platinum-transition-metal bonds. Synthesis and crystal structure of the heterotetranuclear cluster [{Cp(OC)2W(μ-CO)(μ-PPh2)}{Cp(OC) 2Wμ-AuPPh3(μ-PPh2)}Pt][PF 6]·2THF (Au-Pt, Au-W, 2 W-Pt) (THF = Tetrahydrofuran)

The reactions of a series of phosphido-bridged heterodinuclear complexes with HBF4 in CH2Cl2 afforded the corresponding hydrido-bridged complexes [m(μ-PPh2)(μ-H)Pt(PPh3)2][BF4] (4, m = W(CO)2Cp; 5, m = Mn(CO)4; 6, m = Co(CO)3) and [m(μ-PR2)(μ-H)Pd(PR2H)2][BF4] (13a, m = Cr(CO)2Cp, R = Cy; 14a, m = Mo(CO)2Cp, R = Cy; 14b, m = Mo(CO)2Cp, R = Ph; 15a, m = W(CO)2Cp, R = Cy; 15b, m = W(CO)2Cp, R = Ph; 16a, m = Mn(CO)4, R = Cy; 16b, m = Mn(CO)4, R = Ph; 17a, m = Fe(CO)Cp, R = Cy; 18a, m = Co(CO)3, R = Cy). However, reactions of [m(μ-PCy2)Pd(PCy2H)2] (7a, m = Cr(CO)2Cp; 8a, m = Mo(CO)2Cp; 9a, m = W(CO)2Cp) with HCl in acetone yielded the corresponding chloro complexes [m(μ-PCy2)(μ-H)PdCl(PCy2H)] (19a-21a). It was shown that coordination of the chloride occurs on the labile protonated intermediate. Addition of CuCl to 8b yielded [Cp(OC)2Mo(CuCl)(μ-PPh2)Pd(PPh2H) 2] (22) for which isomers were characterized: 22A in which the CuCl group is terminally bound to Mo and 22B in which this group bridges the Mo-Pd bond. In solution, the latter is in equilibrium with yet another isomer, [Cp(OC)2Mo{μ-Cu(PPh2H)}(μ-PPh 2)PdCl(PPh2H)] (23), which results from a 1,2-mutual exchange between the ligands Cl and PPh2H. The basicity of the phosphido-bridged W-Pt bonds of the trinuclear, bent-chain complex [{Cp(OC)2W(μ-PPh2)}2Pt(CO)] (24) was investigated in reactions with HBF4, HCl, or [AuPPh3]+, which afforded the hydrido complexes 25 and 26 and the heterotetranuclear cluster [{Cp(OC)2W(μ-CO)(μ-PPh2)}{Cp(OC) 2W(μ-AuPPh3)(μ-PPh2)}Pt] [PF6] (27), respectively. The solid-state structure of the tetrahydrofuran solvate of 27 has been determined by a single-crystal X-ray analysis. It crystallizes in the monoclinic space group P21/a with Z = 4 in a unit cell of dimensions a = 30.867 (8) A?, b = 18.855 (4), c = 11.168 (3) A?, and β = 90.46 (1)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares on the basis of 4195 observed reflections to R and Rw values of 0.0684 and 0.0877, respectively. The structure of the cationic part of 27 shows an almost linear W(1)-Pt-W(2) chain [W(1)-Pt-W(2) angle = 170.9 (1)°], with both the W(1)-Pt and W(2)-Pt bonds being doubly bridged. The μ-PPh2 ligands, each bridging a W-Pt bond, are in a quasi trans disposition with respect to the Pt atom [P(1)-Pt-P(2) = 177.7 (3)°]. In addition, the W-Pt bonds are bridged respectively by a AuPPh3 fragment [Au-W(1) = 2.738 (2) and Au-Pt = 2.858 (3) A?] and by a carbonyl ligand, which are also in a quasi trans disposition with respect to the Pt atom [Au-Pt-C(5) = 170.5 (8)°].