Transition metal hydrogen bond

The X-H- M hydrogen bond is analogous to a conventional hydrogen bond and involves an electron-rich transition metal M as the proton acceptor in a 3c-4e interaction. Several criteria that serve to characterize a 3c-4e X-H- M hydrogen bond are as follows  

Two compounds with 3c-4e X-H- M hydrogen bonds are shown in Fig. 11.3.4. The dianion (PtCU) m-[PtCl2(NH2Me)2] 2 consists of two square-planar d8-Pt centers held together by short intermolecular N-H- Pt and N-H- Cl hydrogen bonds H Pt 226.2 pm, H- Cl 231.8 pm. The N-H- Pt bond angle is 167.1°. The presence of the filled Pt dz2 orbital oriented towards 

Molecular structures of compounds with X-H- M hydrogen bond  

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Preliminary investigations show that the principle of oxidative addition can be extended to compounds with transition metal hydrogen bonds. Thus, in the reaction of 1 with hydridopentacarbonylmanganese, the corresponding addition product can be isolated in high yield [29Si NMR 8 = 42.8 ppm, J(SiH) = 157.7 Hz IR v(SiH) = 2200 cnri, v(CO) = 1970, 1955 cnr1] [5],... 

The insertion of carbon dioxide into a transition metal-hydrogen bond may be seen as the first and crucial step in the reduction or fixation of C02. This insertion could proceed in either of two ways to produce a formate complex, either mono- or bi-dentate [(31) or (32), respectively], or to form a metallocarboxylic acid, (33). 

In principle the insertion of C02 into a transition metal hydrogen bond can result in either M-0 or M-C bond formation, i.e., production of metalloformate (4) or metallocarboxylic acid (5) derivatives. Thus far,... 

Pearson, R. G. (1985). The transition-metal-hydrogen bond. Chem. Rev. 85, 41. 

The insertion ofCOj into a transition metal-hydrogen bond produces a formate complex whicii reacts with water yielding formic acid and a transition metal-hydroxy Intermediate. In the presence of hydrogen, the hydroxy complex is reconverted into the primary metal hydride, with concomitant formation of water,... 

The solubility of Na[AlH2(OCH2CHjOCH3)2] in aromatic hydrocarbons makes it unique among the main-group hydride reagents used to form transition-metal hydrogen bonds. It is the reagent of choice for ... 

Although one of the first discovered for transition-metal hydrogen bonds, this method is now seldom used. It gives the (Et3P)2Pt hydridochloride in excellent yield ... 

Table 7-6 shows that transition metal-hydrogen bonds are typically stronger (but not always significantly stronger) than M-C bonds, and both types of bonds... 

This is one of the first specific examples of a ternary transition state for oxidative addition, one of the characteristic reactions of metal radicals as shown generally in Scheme 10.1. In addition, the transition metal-hydrogen bond strength (58 kcal/mol) was determined for H-Co(CN)s2-—one of the first accurate determinations. A... 

Complex hydrides of rhodium, Li4RhH4, and Li4RhH6 have been described (75). They were prepared by treatment of rhodium metal powder with lithium hydride at 600°C. The presence of transition metal-hydrogen bonds in either the latter complexes or those of Weichselfelder has yet to be unequivocally shown. Recent studies using a time-of-flight mass spectrometer have identified TiH4 and chlorohydride derivatives (29). 

The different polarity of transition metal hydrogen bonds is reflected in the hydridic-protonic preference (A// p) scheme developed by Pearson [13]. The basis for is the following gas phase redox equilibrium, in which the protonic and hydridic dissociations of transition metal hydrides are considered. 

Olefin insertions into transition metal-carbon and transition metal-hydrogen bonds are fundamental reactions in homogeneous catalysis. With unsymmetrically substituted olefins, a remarkable regioselectivity is frequently observed, whereby the orientation of the olefin depends on the metal, the ligands, and the olefin itself. Empirical rules of regioselectivity are given, and interpreted on the base of the electronic structure of the reaction partners. 

Jacobsen H, Berke H (2002) Tuning of the transition metal hydrogen bond how do trans ligands influence bond strength and hydridicity J Chem Soc Dalton Trans 3117-3122... 

Included in the published account of the plenary lectures presented at the International Conference on Chemical Thermodynamics held during 1986 is an interesting article on metal-ligand bond energies in organometallic compounds, which includes data on metal carbonyls. Relevant n.m.r. data are to be found in two different sources,and ion-pairing effects on the structures and reactivities of metal carbonyl anions have been described. A timely review of the photochemistry of M-M bonds deals almost exclusively with metal carbonyl derivatives these also feature in articles on transition metal-hydrogen bonds. ... 

Transition metal-hydrogen bonds may be formed directly from hydrogen by addition reactions,... 

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