Zr-X bonds

The broken bonds (boldface = dissociated fragment) BDEs (boldface = recommended data reference in parentheses) Methods (reference in parentheses) References 

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The resulting Zr X bonds can be readily cleaved as shown by the reaction with diphenylchlorophosphane (equation 20). ... 

An x-ray study of the stmcture of Cp2Hf(CO)2 revealed the expected tetrahedral disposition of ligands with OC—Hf—CO and (centroid Cp)—Hf—(centroid Cp) angles of 89.3° and 141°, respectively, and mean bond lengths for both bond types of 0.216 nm (241). The Zr analogue is isomorphous with bond lengths of 0.2187 nm and a OC—Zr—CO bond angle of 89.2° (242). 

Symmetrically equivalent positions -x,-y,z -y,x,z y,-x,z 2.9 Calculate the Zr-O bond lengths in baddeleyite (Zr02), considering only interatomic distances shorter than 300 pm. What is the coordination number of Zr ... 

Cleavage of Zr—C a bonds occurs readily on treatment with H20 or dilute acids, while the Zr—Cp bond usually survives mild protonolysis conditions. The use of D20 or DC1/D20 permits the replacement of Zr with D. Deuterolysis provides a generally reliable method for establishing the presence of Zr—C bonds. Protonolysis or deuterolysis of Zr—Csp bonds proceeds with retention of configuration [97]. In the hydrozirconation of terminal alkynes, deuterium can be introduced at any of the three positions in the vinyl group in a completely regio- and stereoselective manner, as shown in Scheme 1.18. Although relatively little is known about the mechanistic details, the experimental results appear to be consistent with concerted c-bond metathesis (Pattern 13) between C—Zr and H— X bonds. 

An important aspect of the carbomagnesation of six-membered and larger heterocycles is the exclusive intermediacy of metallacyclopentanes, in which the C—Zr bond is formed a to the heterocycle C—X bond (Scheme 6.2). Whether the regioselectivity in the zircona-... 

The reactive nature of compound 22 is illustrated by the series of transformations shown in Scheme 7.12, in which its Zr—C bond reacts selectively with electrophilic reagents to produce a-haloboronates 36—38. Compound 22 also catalyzes the polymerization of styrene. The polymers thus obtained had weight-average molecular masses in the range 75000—100000 with polydispersities of 1.8—2.1. An X-ray analysis of 22 confirmed it to be a four-coordinate Zr complex with two cyclopentadienyl rings, chlorine, and the aliphatic C-l carbon atom as the ligands (Fig. 7.4). 

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